--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@setfilename gdc.info
+@settitle The GNU D Compiler
+
+@c Merge the standard indexes into a single one.
+@syncodeindex fn cp
+@syncodeindex vr cp
+@syncodeindex ky cp
+@syncodeindex pg cp
+@syncodeindex tp cp
+
+@include gcc-common.texi
+
+@c Copyright years for this manual.
+@set copyrights-d 2006-2022
+
+@copying
+@c man begin COPYRIGHT
+Copyright @copyright{} @value{copyrights-d} Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+A copy of the license is included in the
+@c man end
+section entitled ``GNU Free Documentation License''.
+@ignore
+@c man begin COPYRIGHT
+man page gfdl(7).
+@c man end
+@end ignore
+@end copying
+
+@ifinfo
+@format
+@dircategory Software development
+@direntry
+* gdc: (gdc). A GCC-based compiler for the D language
+@end direntry
+@end format
+
+@insertcopying
+@end ifinfo
+
+@titlepage
+@title The GNU D Compiler
+@versionsubtitle
+@author David Friedman, Iain Buclaw
+
+@page
+@vskip 0pt plus 1filll
+Published by the Free Software Foundation @*
+51 Franklin Street, Fifth Floor@*
+Boston, MA 02110-1301, USA@*
+@sp 1
+@insertcopying
+@end titlepage
+@contents
+@page
+
+@node Top
+@top Introduction
+
+This manual describes how to use @command{gdc}, the GNU compiler for
+the D programming language. This manual is specifically about
+@command{gdc}. For more information about the D programming
+language in general, including language specifications and standard
+package documentation, see @uref{https://dlang.org/}.
+
+@menu
+* Copying:: The GNU General Public License.
+* GNU Free Documentation License::
+ How you can share and copy this manual.
+* Invoking gdc:: How to run gdc.
+* Index:: Index.
+@end menu
+
+
+@include gpl_v3.texi
+
+@include fdl.texi
+
+
+@node Invoking gdc
+@chapter Invoking gdc
+
+@c man title gdc A GCC-based compiler for the D language
+
+@ignore
+@c man begin SYNOPSIS gdc
+gdc [@option{-c}|@option{-S}] [@option{-g}] [@option{-pg}]
+ [@option{-O}@var{level}] [@option{-W}@var{warn}@dots{}]
+ [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
+ [@option{-f}@var{option}@dots{}] [@option{-m}@var{machine-option}@dots{}]
+ [@option{-o} @var{outfile}] [@@@var{file}] @var{infile}@dots{}
+
+Only the most useful options are listed here; see below for the
+remainder.
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7), gcc(1)
+and the Info entries for @file{gdc} and @file{gcc}.
+@c man end
+@end ignore
+
+@c man begin DESCRIPTION gdc
+
+The @command{gdc} command is the GNU compiler for the D language and
+supports many of the same options as @command{gcc}. @xref{Option Summary, ,
+Option Summary, gcc, Using the GNU Compiler Collection (GCC)}.
+This manual only documents the options specific to @command{gdc}.
+
+@c man end
+
+@menu
+* Input and Output files:: Controlling the kind of output:
+ an executable, object files, assembler files,
+* Runtime Options:: Options controlling runtime behavior
+* Directory Options:: Where to find module files
+* Code Generation:: Options controlling the output of gdc
+* Warnings:: Options controlling warnings specific to gdc
+* Linking:: Options influencing the linking step
+* Developer Options:: Options useful for developers of gdc
+@end menu
+
+@c man begin OPTIONS
+
+@node Input and Output files
+@section Input and Output files
+@cindex suffixes for D source
+@cindex D source file suffixes
+
+For any given input file, the file name suffix determines what kind of
+compilation is done. The following kinds of input file names are supported:
+
+@table @gcctabopt
+@item @var{file}.d
+D source files.
+@item @var{file}.dd
+Ddoc source files.
+@item @var{file}.di
+D interface files.
+@end table
+
+You can specify more than one input file on the @command{gdc} command line,
+each being compiled separately in the compilation process. If you specify a
+@code{-o @var{file}} option, all the input files are compiled together,
+producing a single output file, named @var{file}. This is allowed even
+when using @code{-S} or @code{-c}.
+
+@cindex D interface files.
+A D interface file contains only what an import of the module needs,
+rather than the whole implementation of that module. They can be created
+by @command{gdc} from a D source file by using the @code{-H} option.
+When the compiler resolves an import declaration, it searches for matching
+@file{.di} files first, then for @file{.d}.
+
+@cindex Ddoc source files.
+A Ddoc source file contains code in the D macro processor language. It is
+primarily designed for use in producing user documentation from embedded
+comments, with a slight affinity towards HTML generation. If a @file{.d}
+source file starts with the string @code{Ddoc} then it is treated as general
+purpose documentation, not as a D source file.
+
+@node Runtime Options
+@section Runtime Options
+@cindex options, runtime
+
+These options affect the runtime behavior of programs compiled with
+@command{gdc}.
+
+@table @gcctabopt
+
+@item -fall-instantiations
+@cindex @option{-fall-instantiations}
+@cindex @option{-fno-all-instantiations}
+Generate code for all template instantiations. The default template emission
+strategy is to not generate code for declarations that were either
+instantiated speculatively, such as from @code{__traits(compiles, ...)}, or
+that come from an imported module not being compiled.
+
+@item -fno-assert
+@cindex @option{-fassert}
+@cindex @option{-fno-assert}
+Turn off code generation for @code{assert} contracts.
+
+@item -fno-bounds-check
+@cindex @option{-fbounds-check}
+@cindex @option{-fno-bounds-check}
+Turns off array bounds checking for all functions, which can improve
+performance for code that uses arrays extensively. Note that this
+can result in unpredictable behavior if the code in question actually
+does violate array bounds constraints. It is safe to use this option
+if you are sure that your code never throws a @code{RangeError}.
+
+@item -fbounds-check=@var{value}
+@cindex @option{-fbounds-check=}
+An alternative to @option{-fbounds-check} that allows more control
+as to where bounds checking is turned on or off. The following values
+are supported:
+
+@table @samp
+@item on
+Turns on array bounds checking for all functions.
+@item safeonly
+Turns on array bounds checking only for @code{@@safe} functions.
+@item off
+Turns off array bounds checking completely.
+@end table
+
+@item -fno-builtin
+@cindex @option{-fbuiltin}
+@cindex @option{-fno-builtin}
+Don't recognize built-in functions unless they begin with the prefix
+@samp{__builtin_}. By default, the compiler will recognize when a
+function in the @code{core.stdc} package is a built-in function.
+
+@item -fcheckaction=@var{value}
+@cindex @option{-fcheckaction}
+This option controls what code is generated on an assertion, bounds check, or
+final switch failure. The following values are supported:
+
+@table @samp
+@item context
+Throw an @code{AssertError} with extra context information.
+@item halt
+Halt the program execution.
+@item throw
+Throw an @code{AssertError} (the default).
+@end table
+
+@item -fdebug
+@item -fdebug=@var{value}
+@cindex @option{-fdebug}
+@cindex @option{-fno-debug}
+Turn on compilation of conditional @code{debug} code into the program.
+The @option{-fdebug} option itself sets the debug level to @code{1},
+while @option{-fdebug=} enables @code{debug} code that are identified
+by any of the following values:
+
+@table @samp
+@item level
+Sets the debug level to @var{level}, any @code{debug} code <= @var{level}
+is compiled into the program.
+@item ident
+Turns on compilation of any @code{debug} code identified by @var{ident}.
+@end table
+
+@item -fno-druntime
+@cindex @option{-fdruntime}
+@cindex @option{-fno-druntime}
+Implements @uref{https://dlang.org/spec/betterc.html}. Assumes that
+compilation targets an environment without a D runtime library.
+
+This is equivalent to compiling with the following options:
+
+@example
+gdc -nophoboslib -fno-exceptions -fno-moduleinfo -fno-rtti
+@end example
+
+@item -fextern-std=@var{standard}
+@cindex @option{-fextern-std}
+Sets the C++ name mangling compatibility to the version identified by
+@var{standard}. The following values are supported:
+
+@table @samp
+@item c++98
+@item c++03
+Sets @code{__traits(getTargetInfo, "cppStd")} to @code{199711}.
+@item c++11
+Sets @code{__traits(getTargetInfo, "cppStd")} to @code{201103}.
+@item c++14
+Sets @code{__traits(getTargetInfo, "cppStd")} to @code{201402}.
+@item c++17
+Sets @code{__traits(getTargetInfo, "cppStd")} to @code{201703}.
+This is the default.
+@item c++20
+Sets @code{__traits(getTargetInfo, "cppStd")} to @code{202002}.
+@end table
+
+@item -fno-invariants
+@cindex @option{-finvariants}
+@cindex @option{-fno-invariants}
+Turns off code generation for class @code{invariant} contracts.
+
+@item -fmain
+@cindex @option{-fmain}
+Generates a default @code{main()} function when compiling. This is useful when
+unittesting a library, as it enables running the unittests in a library without
+having to manually define an entry-point function. This option does nothing
+when @code{main} is already defined in user code.
+
+@item -fno-moduleinfo
+@cindex @option{-fmoduleinfo}
+@cindex @option{-fno-moduleinfo}
+Turns off generation of the @code{ModuleInfo} and related functions
+that would become unreferenced without it, which may allow linking
+to programs not written in D. Functions that are not be generated
+include module constructors and destructors (@code{static this} and
+@code{static ~this}), @code{unittest} code, and @code{DSO} registry
+functions for dynamically linked code.
+
+@item -fonly=@var{filename}
+@cindex @option{-fonly}
+Tells the compiler to parse and run semantic analysis on all modules
+on the command line, but only generate code for the module specified
+by @var{filename}.
+
+@item -fno-postconditions
+@cindex @option{-fpostconditions}
+@cindex @option{-fno-postconditions}
+Turns off code generation for postcondition @code{out} contracts.
+
+@item -fno-preconditions
+@cindex @option{-fpreconditions}
+@cindex @option{-fno-preconditions}
+Turns off code generation for precondition @code{in} contracts.
+
+@item -fpreview=@var{id}
+@cindex @option{-fpreview}
+Turns on an upcoming D language change identified by @var{id}. The following
+values are supported:
+
+@table @samp
+@item all
+Turns on all upcoming D language features.
+@item dip1000
+Implements @uref{https://github.com/dlang/DIPs/blob/master/DIPs/other/DIP1000.md}
+(Scoped pointers).
+@item dip1008
+Implements @uref{https://github.com/dlang/DIPs/blob/master/DIPs/other/DIP1008.md}
+(Allow exceptions in @code{@@nogc} code).
+@item dip1021
+Implements @uref{https://github.com/dlang/DIPs/blob/master/DIPs/accepted/DIP1021.md}
+(Mutable function arguments).
+@item dip25
+Implements @uref{https://github.com/dlang/DIPs/blob/master/DIPs/archive/DIP25.md}
+(Sealed references).
+@item dtorfields
+Turns on generation for destructing fields of partially constructed objects.
+@item fieldwise
+Turns on generation of struct equality to use field-wise comparisons.
+@item fixaliasthis
+Implements new lookup rules that check the current scope for @code{alias this}
+before searching in upper scopes.
+@item fiximmutableconv
+Disallows unsound immutable conversions that were formerly incorrectly
+permitted.
+@item in
+Implements @code{in} parameters to mean @code{scope const [ref]} and accepts
+rvalues.
+@item inclusiveincontracts
+Implements @code{in} contracts of overridden methods to be a superset of parent
+contract.
+@item intpromote
+Implements C-style integral promotion for unary @code{+}, @code{-} and @code{~}
+expressions.
+@item nosharedaccess
+Turns off and disallows all access to shared memory objects.
+@item rvaluerefparam
+Implements rvalue arguments to @code{ref} parameters.
+@item systemvariables
+Disables access to variables marked @code{@@system} from @code{@@safe} code.
+@end table
+
+@item -frelease
+@cindex @option{-frelease}
+@cindex @option{-fno-release}
+Turns on compiling in release mode, which means not emitting runtime
+checks for contracts and asserts. Array bounds checking is not done
+for @code{@@system} and @code{@@trusted} functions, and assertion
+failures are undefined behavior.
+
+This is equivalent to compiling with the following options:
+
+@example
+gdc -fno-assert -fbounds-check=safe -fno-invariants \
+ -fno-postconditions -fno-preconditions -fno-switch-errors
+@end example
+
+@item -frevert=
+@cindex @option{-frevert}
+Turns off a D language feature identified by @var{id}. The following values
+are supported:
+
+@table @samp
+@item all
+Turns off all revertable D language features.
+@item dip25
+Reverts @uref{https://github.com/dlang/DIPs/blob/master/DIPs/archive/DIP25.md}
+(Sealed references).
+@item dtorfields
+Turns off generation for destructing fields of partially constructed objects.
+@item markdown
+Turns off Markdown replacements in Ddoc comments.
+@end table
+
+@item -fno-rtti
+@cindex @option{-frtti}
+@cindex @option{-fno-rtti}
+Turns off generation of run-time type information for all user defined types.
+Any code that uses features of the language that require access to this
+information will result in an error.
+
+@item -fno-switch-errors
+@cindex @option{-fswitch-errors}
+@cindex @option{-fno-switch-errors}
+This option controls what code is generated when no case is matched
+in a @code{final switch} statement. The default run time behavior
+is to throw a @code{SwitchError}. Turning off @option{-fswitch-errors}
+means that instead the execution of the program is immediately halted.
+
+@item -funittest
+@cindex @option{-funittest}
+@cindex @option{-fno-unittest}
+Turns on compilation of @code{unittest} code, and turns on the
+@code{version(unittest)} identifier. This implies @option{-fassert}.
+
+@item -fversion=@var{value}
+@cindex @option{-fversion}
+Turns on compilation of conditional @code{version} code into the program
+identified by any of the following values:
+
+@table @samp
+@item level
+Sets the version level to @var{level}, any @code{version} code >= @var{level}
+is compiled into the program.
+@item ident
+Turns on compilation of @code{version} code identified by @var{ident}.
+@end table
+
+@item -fno-weak-templates
+@cindex @option{-fweak-templates}
+@cindex @option{-fno-weak-templates}
+Turns off emission of declarations that can be defined in multiple objects as
+weak symbols. The default is to emit all public symbols as weak, unless the
+target lacks support for weak symbols. Disabling this option means that common
+symbols are instead put in COMDAT or become private.
+
+@end table
+
+@node Directory Options
+@section Options for Directory Search
+@cindex directory options
+@cindex options, directory search
+@cindex search path
+
+These options specify directories to search for files, libraries, and
+other parts of the compiler:
+
+@table @gcctabopt
+
+@item -I@var{dir}
+@cindex @option{-I}
+Specify a directory to use when searching for imported modules at
+compile time. Multiple @option{-I} options can be used, and the
+paths are searched in the same order.
+
+@item -J@var{dir}
+@cindex @option{-J}
+Specify a directory to use when searching for files in string imports
+at compile time. This switch is required in order to use
+@code{import(file)} expressions. Multiple @option{-J} options can be
+used, and the paths are searched in the same order.
+
+@item -L@var{dir}
+@cindex @option{-L}
+When linking, specify a library search directory, as with @command{gcc}.
+
+@item -B@var{dir}
+@cindex @option{-B}
+This option specifies where to find the executables, libraries,
+source files, and data files of the compiler itself, as with @command{gcc}.
+
+@item -fmodule-file=@var{module}=@var{spec}
+@cindex @option{-fmodule-file}
+This option manipulates file paths of imported modules, such that if an
+imported module matches all or the leftmost part of @var{module}, the file
+path in @var{spec} is used as the location to search for D sources.
+This is used when the source file path and names are not the same as the
+package and module hierarchy. Consider the following examples:
+
+@example
+gdc test.d -fmodule-file=A.B=foo.d -fmodule-file=C=bar
+@end example
+
+This will tell the compiler to search in all import paths for the source
+file @var{foo.d} when importing @var{A.B}, and the directory @var{bar/}
+when importing @var{C}, as annotated in the following D code:
+
+@example
+module test;
+import A.B; // Matches A.B, searches for foo.d
+import C.D.E; // Matches C, searches for bar/D/E.d
+import A.B.C; // No match, searches for A/B/C.d
+@end example
+
+@item -imultilib @var{dir}
+@cindex @option{-imultilib}
+Use @var{dir} as a subdirectory of the gcc directory containing
+target-specific D sources and interfaces.
+
+@item -iprefix @var{prefix}
+@cindex @option{-iprefix}
+Specify @var{prefix} as the prefix for the gcc directory containing
+target-specific D sources and interfaces. If the @var{prefix} represents
+a directory, you should include the final @code{'/'}.
+
+@item -nostdinc
+@cindex @option{-nostdinc}
+Do not search the standard system directories for D source and interface
+files. Only the directories that have been specified with @option{-I} options
+(and the directory of the current file, if appropriate) are searched.
+
+@end table
+
+@node Code Generation
+@section Code Generation
+@cindex options, code generation
+
+In addition to the many @command{gcc} options controlling code generation,
+@command{gdc} has several options specific to itself.
+
+@table @gcctabopt
+
+@item -H
+@cindex @option{-H}
+Generates D interface files for all modules being compiled. The compiler
+determines the output file based on the name of the input file, removes
+any directory components and suffix, and applies the @file{.di} suffix.
+
+@item -Hd @var{dir}
+@cindex @option{-Hd}
+Same as @option{-H}, but writes interface files to directory @var{dir}.
+This option can be used with @option{-Hf @var{file}} to independently set the
+output file and directory path.
+
+@item -Hf @var{file}
+@cindex @option{-Hf}
+Same as @option{-H} but writes interface files to @var{file}. This option can
+be used with @option{-Hd @var{dir}} to independently set the output file and
+directory path.
+
+@item -M
+@cindex @option{-M}
+Output the module dependencies of all source files being compiled in a
+format suitable for @command{make}. The compiler outputs one
+@command{make} rule containing the object file name for that source file,
+a colon, and the names of all imported files.
+
+@item -MM
+@cindex @option{-MM}
+Like @option{-M} but does not mention imported modules from the D standard
+library package directories.
+
+@item -MF @var{file}
+@cindex @option{-MF}
+When used with @option{-M} or @option{-MM}, specifies a @var{file} to write
+the dependencies to. When used with the driver options @option{-MD} or
+@option{-MMD}, @option{-MF} overrides the default dependency output file.
+
+@item -MG
+@cindex @option{-MG}
+This option is for compatibility with @command{gcc}, and is ignored by the
+compiler.
+
+@item -MP
+@cindex @option{-MP}
+Outputs a phony target for each dependency other than the modules being
+compiled, causing each to depend on nothing.
+
+@item -MT @var{target}
+@cindex @option{-MT}
+Change the @var{target} of the rule emitted by dependency generation
+to be exactly the string you specify. If you want multiple targets,
+you can specify them as a single argument to @option{-MT}, or use
+multiple @option{-MT} options.
+
+@item -MQ @var{target}
+@cindex @option{-MQ}
+Same as @option{-MT}, but it quotes any characters which are special to
+@command{make}.
+
+@item -MD
+@cindex @option{-MD}
+This option is equivalent to @option{-M -MF @var{file}}. The driver
+determines @var{file} by removing any directory components and suffix
+from the input file, and then adding a @file{.deps} suffix.
+
+@item -MMD
+@cindex @option{-MMD}
+Like @option{-MD} but does not mention imported modules from the D standard
+library package directories.
+
+@item -X
+@cindex @option{-X}
+Output information describing the contents of all source files being
+compiled in JSON format to a file. The driver determines @var{file} by
+removing any directory components and suffix from the input file, and then
+adding a @file{.json} suffix.
+
+@item -Xf @var{file}
+@cindex @option{-Xf}
+Same as @option{-X}, but writes all JSON contents to the specified
+@var{file}.
+
+@item -fdoc
+@cindex @option{-fdoc}
+Generates @code{Ddoc} documentation and writes it to a file. The compiler
+determines @var{file} by removing any directory components and suffix
+from the input file, and then adding a @file{.html} suffix.
+
+@item -fdoc-dir=@var{dir}
+@cindex @option{-fdoc-dir}
+Same as @option{-fdoc}, but writes documentation to directory @var{dir}.
+This option can be used with @option{-fdoc-file=@var{file}} to
+independently set the output file and directory path.
+
+@item -fdoc-file=@var{file}
+@cindex @option{-fdoc-file}
+Same as @option{-fdoc}, but writes documentation to @var{file}. This
+option can be used with @option{-fdoc-dir=@var{dir}} to independently
+set the output file and directory path.
+
+@item -fdoc-inc=@var{file}
+@cindex @option{-fdoc-inc}
+Specify @var{file} as a @var{Ddoc} macro file to be read. Multiple
+@option{-fdoc-inc} options can be used, and files are read and processed
+in the same order.
+
+@item -fdump-c++-spec=@var{file}
+For D source files, generate corresponding C++ declarations in @var{file}.
+
+@item -fdump-c++-spec-verbose
+In conjunction with @option{-fdump-c++-spec=} above, add comments for ignored
+declarations in the generated C++ header.
+
+@item -fsave-mixins=@var{file}
+@cindex @option{-fsave-mixins}
+Generates code expanded from D @code{mixin} statements and writes the
+processed sources to @var{file}. This is useful to debug errors in compilation
+and provides source for debuggers to show when requested.
+
+@end table
+
+@node Warnings
+@section Warnings
+@cindex options to control warnings
+@cindex warning messages
+@cindex messages, warning
+@cindex suppressing warnings
+
+Warnings are diagnostic messages that report constructions that
+are not inherently erroneous but that are risky or suggest there
+is likely to be a bug in the program. Unless @option{-Werror} is
+specified, they do not prevent compilation of the program.
+
+@table @gcctabopt
+
+@item -Wall
+@cindex @option{-Wall}
+@cindex @option{-Wno-all}
+Turns on all warnings messages. Warnings are not a defined part of
+the D language, and all constructs for which this may generate a
+warning message are valid code.
+
+@item -Walloca
+@cindex @option{-Walloca}
+This option warns on all uses of "alloca" in the source.
+
+@item -Walloca-larger-than=@var{n}
+@cindex @option{-Walloca-larger-than}
+@cindex @option{-Wno-alloca-larger-than}
+Warn on unbounded uses of alloca, and on bounded uses of alloca
+whose bound can be larger than @var{n} bytes.
+@option{-Wno-alloca-larger-than} disables
+@option{-Walloca-larger-than} warning and is equivalent to
+@option{-Walloca-larger-than=@var{SIZE_MAX}} or larger.
+
+@item -Wcast-result
+@cindex @option{-Wcast-result}
+@cindex @option{-Wno-cast-result}
+Warn about casts that will produce a null or zero result. Currently
+this is only done for casting between an imaginary and non-imaginary
+data type, or casting between a D and C++ class.
+
+@item -Wno-deprecated
+@cindex @option{-Wdeprecated}
+@cindex @option{-Wno-deprecated}
+Do not warn about usage of deprecated features and symbols with
+@code{deprecated} attributes.
+
+@item -Werror
+@cindex @option{-Werror}
+@cindex @option{-Wno-error}
+Turns all warnings into errors.
+
+@item -Wspeculative
+@cindex @option{-Wspeculative}
+@cindex @option{-Wno-speculative}
+List all error messages from speculative compiles, such as
+@code{__traits(compiles, ...)}. This option does not report
+messages as warnings, and these messages therefore never become
+errors when the @option{-Werror} option is also used.
+
+@item -Wtemplates
+@cindex @option{-Wtemplates}
+@cindex @option{-Wno-templates}
+Warn when a template instantiation is encountered. Some coding
+rules disallow templates, and this may be used to enforce that rule.
+
+@item -Wunknown-pragmas
+@cindex @option{-Wunknown-pragmas}
+@cindex @option{-Wno-unknown-pragmas}
+Warn when a @code{pragma()} is encountered that is not understood by
+@command{gdc}. This differs from @option{-fignore-unknown-pragmas}
+where a pragma that is part of the D language, but not implemented by
+the compiler, won't get reported.
+
+@item -Wno-varargs
+@cindex Wvarargs
+@cindex Wno-varargs
+Do not warn upon questionable usage of the macros used to handle variable
+arguments like @code{va_start}.
+
+@item -fignore-unknown-pragmas
+@cindex @option{-fignore-unknown-pragmas}
+@cindex @option{-fno-ignore-unknown-pragmas}
+Turns off errors for unsupported pragmas.
+
+@item -fmax-errors=@var{n}
+@cindex @option{-fmax-errors}
+Limits the maximum number of error messages to @var{n}, at which point
+@command{gdc} bails out rather than attempting to continue processing the
+source code. If @var{n} is 0 (the default), there is no limit on the
+number of error messages produced.
+
+@item -fsyntax-only
+@cindex @option{-fsyntax-only}
+@cindex @option{-fno-syntax-only}
+Check the code for syntax errors, but do not actually compile it. This
+can be used in conjunction with @option{-fdoc} or @option{-H} to generate
+files for each module present on the command-line, but no other output
+file.
+
+@item -ftransition=@var{id}
+@cindex @option{-ftransition}
+Report additional information about D language changes identified by
+@var{id}. The following values are supported:
+
+@table @samp
+@item all
+List information on all D language transitions.
+@item complex
+List all usages of complex or imaginary types.
+@item field
+List all non-mutable fields which occupy an object instance.
+@item in
+List all usages of @code{in} on parameter.
+@item nogc
+List all hidden GC allocations.
+@item templates
+List statistics on template instantiations.
+@item tls
+List all variables going into thread local storage.
+@item vmarkdown
+List instances of Markdown replacements in Ddoc.
+@end table
+
+@end table
+
+@node Linking
+@section Options for Linking
+@cindex options, linking
+@cindex linking, static
+
+These options come into play when the compiler links object files into an
+executable output file. They are meaningless if the compiler is not doing
+a link step.
+
+@table @gcctabopt
+
+@item -defaultlib=@var{libname}
+@cindex @option{-defaultlib=}
+Specify the library to use instead of libphobos when linking. Options
+specifying the linkage of libphobos, such as @option{-static-libphobos}
+or @option{-shared-libphobos}, are ignored.
+
+@item -debuglib=@var{libname}
+@cindex @option{-debuglib=}
+Specify the debug library to use instead of libphobos when linking.
+This option has no effect unless the @option{-g} option was also given
+on the command line. Options specifying the linkage of libphobos, such
+as @option{-static-libphobos} or @option{-shared-libphobos}, are ignored.
+
+@item -nophoboslib
+@cindex @option{-nophoboslib}
+Do not use the Phobos or D runtime library when linking. Options specifying
+the linkage of libphobos, such as @option{-static-libphobos} or
+@option{-shared-libphobos}, are ignored. The standard system libraries are
+used normally, unless @option{-nostdlib} or @option{-nodefaultlibs} is used.
+
+@item -shared-libphobos
+@cindex @option{-shared-libphobos}
+On systems that provide @file{libgphobos} and @file{libgdruntime} as a
+shared and a static library, this option forces the use of the shared
+version. If no shared version was built when the compiler was configured,
+this option has no effect.
+
+@item -static-libphobos
+@cindex @option{-static-libphobos}
+On systems that provide @file{libgphobos} and @file{libgdruntime} as a
+shared and a static library, this option forces the use of the static
+version. If no static version was built when the compiler was configured,
+this option has no effect.
+
+@end table
+
+@node Developer Options
+@section Developer Options
+@cindex developer options
+@cindex debug dump options
+@cindex dump options
+
+This section describes command-line options that are primarily of
+interest to developers or language tooling.
+
+@table @gcctabopt
+
+@item -fdump-d-original
+@cindex @option{-fdump-d-original}
+Output the internal front-end AST after the @code{semantic3} stage.
+This option is only useful for debugging the GNU D compiler itself.
+
+@item -v
+@cindex @option{-v}
+Dump information about the compiler language processing stages as the source
+program is being compiled. This includes listing all modules that are
+processed through the @code{parse}, @code{semantic}, @code{semantic2}, and
+@code{semantic3} stages; all @code{import} modules and their file paths;
+and all @code{function} bodies that are being compiled.
+
+@end table
+
+@c man end
+
+@node Index
+@unnumbered Index
+
+@printindex cp
+
+@bye
--- /dev/null
+@c Copyright (C) 2019-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+@c Contributed by David Malcolm <dmalcolm@redhat.com>.
+
+@node Static Analyzer
+@chapter Static Analyzer
+@cindex analyzer
+@cindex static analysis
+@cindex static analyzer
+
+@menu
+* Analyzer Internals:: Analyzer Internals
+* Debugging the Analyzer:: Useful debugging tips
+@end menu
+
+@node Analyzer Internals
+@section Analyzer Internals
+@cindex analyzer, internals
+@cindex static analyzer, internals
+
+@subsection Overview
+
+The analyzer implementation works on the gimple-SSA representation.
+(I chose this in the hopes of making it easy to work with LTO to
+do whole-program analysis).
+
+The implementation is read-only: it doesn't attempt to change anything,
+just emit warnings.
+
+The gimple representation can be seen using @option{-fdump-ipa-analyzer}.
+@quotation Tip
+If the analyzer ICEs before this is written out, one workaround is to use
+@option{--param=analyzer-bb-explosion-factor=0} to force the analyzer
+to bail out after analyzing the first basic block.
+@end quotation
+
+First, we build a @code{supergraph} which combines the callgraph and all
+of the CFGs into a single directed graph, with both interprocedural and
+intraprocedural edges. The nodes and edges in the supergraph are called
+``supernodes'' and ``superedges'', and often referred to in code as
+@code{snodes} and @code{sedges}. Basic blocks in the CFGs are split at
+interprocedural calls, so there can be more than one supernode per
+basic block. Most statements will be in just one supernode, but a call
+statement can appear in two supernodes: at the end of one for the call,
+and again at the start of another for the return.
+
+The supergraph can be seen using @option{-fdump-analyzer-supergraph}.
+
+We then build an @code{analysis_plan} which walks the callgraph to
+determine which calls might be suitable for being summarized (rather
+than fully explored) and thus in what order to explore the functions.
+
+Next is the heart of the analyzer: we use a worklist to explore state
+within the supergraph, building an "exploded graph".
+Nodes in the exploded graph correspond to <point,@w{ }state> pairs, as in
+ "Precise Interprocedural Dataflow Analysis via Graph Reachability"
+ (Thomas Reps, Susan Horwitz and Mooly Sagiv).
+
+We reuse nodes for <point, state> pairs we've already seen, and avoid
+tracking state too closely, so that (hopefully) we rapidly converge
+on a final exploded graph, and terminate the analysis. We also bail
+out if the number of exploded <end-of-basic-block, state> nodes gets
+larger than a particular multiple of the total number of basic blocks
+(to ensure termination in the face of pathological state-explosion
+cases, or bugs). We also stop exploring a point once we hit a limit
+of states for that point.
+
+We can identify problems directly when processing a <point,@w{ }state>
+instance. For example, if we're finding the successors of
+
+@smallexample
+ <point: before-stmt: "free (ptr);",
+ state: @{"ptr": freed@}>
+@end smallexample
+
+then we can detect a double-free of "ptr". We can then emit a path
+to reach the problem by finding the simplest route through the graph.
+
+Program points in the analysis are much more fine-grained than in the
+CFG and supergraph, with points (and thus potentially exploded nodes)
+for various events, including before individual statements.
+By default the exploded graph merges multiple consecutive statements
+in a supernode into one exploded edge to minimize the size of the
+exploded graph. This can be suppressed via
+@option{-fanalyzer-fine-grained}.
+The fine-grained approach seems to make things simpler and more debuggable
+that other approaches I tried, in that each point is responsible for one
+thing.
+
+Program points in the analysis also have a "call string" identifying the
+stack of callsites below them, so that paths in the exploded graph
+correspond to interprocedurally valid paths: we always return to the
+correct call site, propagating state information accordingly.
+We avoid infinite recursion by stopping the analysis if a callsite
+appears more than @code{analyzer-max-recursion-depth} in a callstring
+(defaulting to 2).
+
+@subsection Graphs
+
+Nodes and edges in the exploded graph are called ``exploded nodes'' and
+``exploded edges'' and often referred to in the code as
+@code{enodes} and @code{eedges} (especially when distinguishing them
+from the @code{snodes} and @code{sedges} in the supergraph).
+
+Each graph numbers its nodes, giving unique identifiers - supernodes
+are referred to throughout dumps in the form @samp{SN': @var{index}} and
+exploded nodes in the form @samp{EN: @var{index}} (e.g. @samp{SN: 2} and
+@samp{EN:29}).
+
+The supergraph can be seen using @option{-fdump-analyzer-supergraph-graph}.
+
+The exploded graph can be seen using @option{-fdump-analyzer-exploded-graph}
+and other dump options. Exploded nodes are color-coded in the .dot output
+based on state-machine states to make it easier to see state changes at
+a glance.
+
+@subsection State Tracking
+
+There's a tension between:
+@itemize @bullet
+@item
+precision of analysis in the straight-line case, vs
+@item
+exponential blow-up in the face of control flow.
+@end itemize
+
+For example, in general, given this CFG:
+
+@smallexample
+ A
+ / \
+ B C
+ \ /
+ D
+ / \
+ E F
+ \ /
+ G
+@end smallexample
+
+we want to avoid differences in state-tracking in B and C from
+leading to blow-up. If we don't prevent state blowup, we end up
+with exponential growth of the exploded graph like this:
+
+@smallexample
+
+ 1:A
+ / \
+ / \
+ / \
+ 2:B 3:C
+ | |
+ 4:D 5:D (2 exploded nodes for D)
+ / \ / \
+ 6:E 7:F 8:E 9:F
+ | | | |
+ 10:G 11:G 12:G 13:G (4 exploded nodes for G)
+
+@end smallexample
+
+Similar issues arise with loops.
+
+To prevent this, we follow various approaches:
+
+@enumerate a
+@item
+state pruning: which tries to discard state that won't be relevant
+later on withing the function.
+This can be disabled via @option{-fno-analyzer-state-purge}.
+
+@item
+state merging. We can try to find the commonality between two
+program_state instances to make a third, simpler program_state.
+We have two strategies here:
+
+ @enumerate
+ @item
+ the worklist keeps new nodes for the same program_point together,
+ and tries to merge them before processing, and thus before they have
+ successors. Hence, in the above, the two nodes for D (4 and 5) reach
+ the front of the worklist together, and we create a node for D with
+ the merger of the incoming states.
+
+ @item
+ try merging with the state of existing enodes for the program_point
+ (which may have already been explored). There will be duplication,
+ but only one set of duplication; subsequent duplicates are more likely
+ to hit the cache. In particular, (hopefully) all merger chains are
+ finite, and so we guarantee termination.
+ This is intended to help with loops: we ought to explore the first
+ iteration, and then have a "subsequent iterations" exploration,
+ which uses a state merged from that of the first, to be more abstract.
+ @end enumerate
+
+We avoid merging pairs of states that have state-machine differences,
+as these are the kinds of differences that are likely to be most
+interesting. So, for example, given:
+
+@smallexample
+ if (condition)
+ ptr = malloc (size);
+ else
+ ptr = local_buf;
+
+ .... do things with 'ptr'
+
+ if (condition)
+ free (ptr);
+
+ ...etc
+@end smallexample
+
+then we end up with an exploded graph that looks like this:
+
+@smallexample
+
+ if (condition)
+ / T \ F
+ --------- ----------
+ / \
+ ptr = malloc (size) ptr = local_buf
+ | |
+ copy of copy of
+ "do things with 'ptr'" "do things with 'ptr'"
+ with ptr: heap-allocated with ptr: stack-allocated
+ | |
+ if (condition) if (condition)
+ | known to be T | known to be F
+ free (ptr); |
+ \ /
+ -----------------------------
+ | ('ptr' is pruned, so states can be merged)
+ etc
+
+@end smallexample
+
+where some duplication has occurred, but only for the places where the
+the different paths are worth exploringly separately.
+
+Merging can be disabled via @option{-fno-analyzer-state-merge}.
+@end enumerate
+
+@subsection Region Model
+
+Part of the state stored at a @code{exploded_node} is a @code{region_model}.
+This is an implementation of the region-based ternary model described in
+@url{https://www.researchgate.net/publication/221430855_A_Memory_Model_for_Static_Analysis_of_C_Programs,
+"A Memory Model for Static Analysis of C Programs"}
+(Zhongxing Xu, Ted Kremenek, and Jian Zhang).
+
+A @code{region_model} encapsulates a representation of the state of
+memory, with a @code{store} recording a binding between @code{region}
+instances, to @code{svalue} instances. The bindings are organized into
+clusters, where regions accessible via well-defined pointer arithmetic
+are in the same cluster. The representation is graph-like because values
+can be pointers to regions. It also stores a constraint_manager,
+capturing relationships between the values.
+
+Because each node in the @code{exploded_graph} has a @code{region_model},
+and each of the latter is graph-like, the @code{exploded_graph} is in some
+ways a graph of graphs.
+
+Here's an example of printing a @code{program_state}, showing the
+@code{region_model} within it, along with state for the @code{malloc}
+state machine.
+
+@smallexample
+(gdb) call debug (*this)
+rmodel:
+stack depth: 1
+ frame (index 0): frame: ‘test’@@1
+clusters within frame: ‘test’@@1
+ cluster for: ptr_3: &HEAP_ALLOCATED_REGION(12)
+m_called_unknown_fn: FALSE
+constraint_manager:
+ equiv classes:
+ constraints:
+malloc:
+ 0x2e89590: &HEAP_ALLOCATED_REGION(12): unchecked ('ptr_3')
+@end smallexample
+
+This is the state at the point of returning from @code{calls_malloc} back
+to @code{test} in the following:
+
+@smallexample
+void *
+calls_malloc (void)
+@{
+ void *result = malloc (1024);
+ return result;
+@}
+
+void test (void)
+@{
+ void *ptr = calls_malloc ();
+ /* etc. */
+@}
+@end smallexample
+
+Within the store, there is the cluster for @code{ptr_3} within the frame
+for @code{test}, where the whole cluster is bound to a pointer value,
+pointing at @code{HEAP_ALLOCATED_REGION(12)}. Additionally, this pointer
+has the @code{unchecked} state for the @code{malloc} state machine
+indicating it hasn't yet been checked against NULL since the allocation
+call.
+
+@subsection Analyzer Paths
+
+We need to explain to the user what the problem is, and to persuade them
+that there really is a problem. Hence having a @code{diagnostic_path}
+isn't just an incidental detail of the analyzer; it's required.
+
+Paths ought to be:
+@itemize @bullet
+@item
+interprocedurally-valid
+@item
+feasible
+@end itemize
+
+Without state-merging, all paths in the exploded graph are feasible
+(in terms of constraints being satisfied).
+With state-merging, paths in the exploded graph can be infeasible.
+
+We collate warnings and only emit them for the simplest path
+e.g. for a bug in a utility function, with lots of routes to calling it,
+we only emit the simplest path (which could be intraprocedural, if
+it can be reproduced without a caller).
+
+We thus want to find the shortest feasible path through the exploded
+graph from the origin to the exploded node at which the diagnostic was
+saved. Unfortunately, if we simply find the shortest such path and
+check if it's feasible we might falsely reject the diagnostic, as there
+might be a longer path that is feasible. Examples include the cases
+where the diagnostic requires us to go at least once around a loop for a
+later condition to be satisfied, or where for a later condition to be
+satisfied we need to enter a suite of code that the simpler path skips.
+
+We attempt to find the shortest feasible path to each diagnostic by
+first constructing a ``trimmed graph'' from the exploded graph,
+containing only those nodes and edges from which there are paths to
+the target node, and using Dijkstra's algorithm to order the trimmed
+nodes by minimal distance to the target.
+
+We then use a worklist to iteratively build a ``feasible graph''
+(actually a tree), capturing the pertinent state along each path, in
+which every path to a ``feasible node'' is feasible by construction,
+restricting ourselves to the trimmed graph to ensure we stay on target,
+and ordering the worklist so that the first feasible path we find to the
+target node is the shortest possible path. Hence we start by trying the
+shortest possible path, but if that fails, we explore progressively
+longer paths, eventually trying iterations through loops. The
+exploration is captured in the feasible_graph, which can be dumped as a
+.dot file via @option{-fdump-analyzer-feasibility} to visualize the
+exploration. The indices of the feasible nodes show the order in which
+they were created. We effectively explore the tree of feasible paths in
+order of shortest path until we either find a feasible path to the
+target node, or hit a limit and give up.
+
+This is something of a brute-force approach, but the trimmed graph
+hopefully keeps the complexity manageable.
+
+This algorithm can be disabled (for debugging purposes) via
+@option{-fno-analyzer-feasibility}, which simply uses the shortest path,
+and notes if it is infeasible.
+
+The above gives us a shortest feasible @code{exploded_path} through the
+@code{exploded_graph} (a list of @code{exploded_edge *}). We use this
+@code{exploded_path} to build a @code{diagnostic_path} (a list of
+@strong{events} for the diagnostic subsystem) - specifically a
+@code{checker_path}.
+
+Having built the @code{checker_path}, we prune it to try to eliminate
+events that aren't relevant, to minimize how much the user has to read.
+
+After pruning, we notify each event in the path of its ID and record the
+IDs of interesting events, allowing for events to refer to other events
+in their descriptions. The @code{pending_diagnostic} class has various
+vfuncs to support emitting more precise descriptions, so that e.g.
+
+@itemize @bullet
+@item
+a deref-of-unchecked-malloc diagnostic might use:
+@smallexample
+ returning possibly-NULL pointer to 'make_obj' from 'allocator'
+@end smallexample
+for a @code{return_event} to make it clearer how the unchecked value moves
+from callee back to caller
+@item
+a double-free diagnostic might use:
+@smallexample
+ second 'free' here; first 'free' was at (3)
+@end smallexample
+and a use-after-free might use
+@smallexample
+ use after 'free' here; memory was freed at (2)
+@end smallexample
+@end itemize
+
+At this point we can emit the diagnostic.
+
+@subsection Limitations
+
+@itemize @bullet
+@item
+Only for C so far
+@item
+The implementation of call summaries is currently very simplistic.
+@item
+Lack of function pointer analysis
+@item
+The constraint-handling code assumes reflexivity in some places
+(that values are equal to themselves), which is not the case for NaN.
+As a simple workaround, constraints on floating-point values are
+currently ignored.
+@item
+There are various other limitations in the region model (grep for TODO/xfail
+in the testsuite).
+@item
+The constraint_manager's implementation of transitivity is currently too
+expensive to enable by default and so must be manually enabled via
+@option{-fanalyzer-transitivity}).
+@item
+The checkers are currently hardcoded and don't allow for user extensibility
+(e.g. adding allocate/release pairs).
+@item
+Although the analyzer's test suite has a proof-of-concept test case for
+LTO, LTO support hasn't had extensive testing. There are various
+lang-specific things in the analyzer that assume C rather than LTO.
+For example, SSA names are printed to the user in ``raw'' form, rather
+than printing the underlying variable name.
+@end itemize
+
+Some ideas for other checkers
+@itemize @bullet
+@item
+File-descriptor-based APIs
+@item
+Linux kernel internal APIs
+@item
+Signal handling
+@end itemize
+
+@node Debugging the Analyzer
+@section Debugging the Analyzer
+@cindex analyzer, debugging
+@cindex static analyzer, debugging
+
+@subsection Special Functions for Debugging the Analyzer
+
+The analyzer recognizes various special functions by name, for use
+in debugging the analyzer. Declarations can be seen in the testsuite
+in @file{analyzer-decls.h}. None of these functions are actually
+implemented.
+
+Add:
+@smallexample
+ __analyzer_break ();
+@end smallexample
+to the source being analyzed to trigger a breakpoint in the analyzer when
+that source is reached. By putting a series of these in the source, it's
+much easier to effectively step through the program state as it's analyzed.
+
+The analyzer handles:
+
+@smallexample
+__analyzer_describe (0, expr);
+@end smallexample
+
+by emitting a warning describing the 2nd argument (which can be of any
+type), at a verbosity level given by the 1st argument. This is for use when
+debugging, and may be of use in DejaGnu tests.
+
+@smallexample
+__analyzer_dump ();
+@end smallexample
+
+will dump the copious information about the analyzer's state each time it
+reaches the call in its traversal of the source.
+
+@smallexample
+extern void __analyzer_dump_capacity (const void *ptr);
+@end smallexample
+
+will emit a warning describing the capacity of the base region of
+the region pointed to by the 1st argument.
+
+@smallexample
+extern void __analyzer_dump_escaped (void);
+@end smallexample
+
+will emit a warning giving the number of decls that have escaped on this
+analysis path, followed by a comma-separated list of their names,
+in alphabetical order.
+
+@smallexample
+__analyzer_dump_path ();
+@end smallexample
+
+will emit a placeholder ``note'' diagnostic with a path to that call site,
+if the analyzer finds a feasible path to it.
+
+The builtin @code{__analyzer_dump_exploded_nodes} will emit a warning
+after analysis containing information on all of the exploded nodes at that
+program point:
+
+@smallexample
+ __analyzer_dump_exploded_nodes (0);
+@end smallexample
+
+will output the number of ``processed'' nodes, and the IDs of
+both ``processed'' and ``merger'' nodes, such as:
+
+@smallexample
+warning: 2 processed enodes: [EN: 56, EN: 58] merger(s): [EN: 54-55, EN: 57, EN: 59]
+@end smallexample
+
+With a non-zero argument
+
+@smallexample
+ __analyzer_dump_exploded_nodes (1);
+@end smallexample
+
+it will also dump all of the states within the ``processed'' nodes.
+
+@smallexample
+ __analyzer_dump_region_model ();
+@end smallexample
+will dump the region_model's state to stderr.
+
+@smallexample
+__analyzer_dump_state ("malloc", ptr);
+@end smallexample
+
+will emit a warning describing the state of the 2nd argument
+(which can be of any type) with respect to the state machine with
+a name matching the 1st argument (which must be a string literal).
+This is for use when debugging, and may be of use in DejaGnu tests.
+
+@smallexample
+__analyzer_eval (expr);
+@end smallexample
+will emit a warning with text "TRUE", FALSE" or "UNKNOWN" based on the
+truthfulness of the argument. This is useful for writing DejaGnu tests.
+
+@smallexample
+__analyzer_get_unknown_ptr ();
+@end smallexample
+will obtain an unknown @code{void *}.
+
+@subsection Other Debugging Techniques
+
+The option @option{-fdump-analyzer-json} will dump both the supergraph
+and the exploded graph in compressed JSON form.
+
+One approach when tracking down where a particular bogus state is
+introduced into the @code{exploded_graph} is to add custom code to
+@code{program_state::validate}.
+
+The debug function @code{region::is_named_decl_p} can be used when debugging,
+such as for assertions and conditional breakpoints. For example, when
+tracking down a bug in handling a decl called @code{yy_buffer_stack}, I
+temporarily added a:
+@smallexample
+ gcc_assert (!m_base_region->is_named_decl_p ("yy_buffer_stack"));
+@end smallexample
+to @code{binding_cluster::mark_as_escaped} to trap a point where
+@code{yy_buffer_stack} was mistakenly being treated as having escaped.
--- /dev/null
+@c Copyright (C) 2012-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc/doc/include/fdl.texi.
+
+@c This file is generated automatically using
+@c gcc/config/avr/gen-avr-mmcu-texi.cc from:
+@c gcc/config/avr/avr-arch.h
+@c gcc/config/avr/avr-devices.cc
+@c gcc/config/avr/avr-mcus.def
+
+@c Please do not edit manually.
+
+@table @code
+
+@item avr2
+``Classic'' devices with up to 8@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{attiny22}, @code{attiny26}, @code{at90s2313}, @code{at90s2323}, @code{at90s2333}, @code{at90s2343}, @code{at90s4414}, @code{at90s4433}, @code{at90s4434}, @code{at90c8534}, @code{at90s8515}, @code{at90s8535}.
+
+@item avr25
+``Classic'' devices with up to 8@tie{}KiB of program memory and with the @code{MOVW} instruction.
+@*@var{mcu}@tie{}= @code{attiny13}, @code{attiny13a}, @code{attiny24}, @code{attiny24a}, @code{attiny25}, @code{attiny261}, @code{attiny261a}, @code{attiny2313}, @code{attiny2313a}, @code{attiny43u}, @code{attiny44}, @code{attiny44a}, @code{attiny45}, @code{attiny48}, @code{attiny441}, @code{attiny461}, @code{attiny461a}, @code{attiny4313}, @code{attiny84}, @code{attiny84a}, @code{attiny85}, @code{attiny87}, @code{attiny88}, @code{attiny828}, @code{attiny841}, @code{attiny861}, @code{attiny861a}, @code{ata5272}, @code{ata6616c}, @code{at86rf401}.
+
+@item avr3
+``Classic'' devices with 16@tie{}KiB up to 64@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{at76c711}, @code{at43usb355}.
+
+@item avr31
+``Classic'' devices with 128@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{atmega103}, @code{at43usb320}.
+
+@item avr35
+``Classic'' devices with 16@tie{}KiB up to 64@tie{}KiB of program memory and with the @code{MOVW} instruction.
+@*@var{mcu}@tie{}= @code{attiny167}, @code{attiny1634}, @code{atmega8u2}, @code{atmega16u2}, @code{atmega32u2}, @code{ata5505}, @code{ata6617c}, @code{ata664251}, @code{at90usb82}, @code{at90usb162}.
+
+@item avr4
+``Enhanced'' devices with up to 8@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{atmega48}, @code{atmega48a}, @code{atmega48p}, @code{atmega48pa}, @code{atmega48pb}, @code{atmega8}, @code{atmega8a}, @code{atmega8hva}, @code{atmega88}, @code{atmega88a}, @code{atmega88p}, @code{atmega88pa}, @code{atmega88pb}, @code{atmega8515}, @code{atmega8535}, @code{ata6285}, @code{ata6286}, @code{ata6289}, @code{ata6612c}, @code{at90pwm1}, @code{at90pwm2}, @code{at90pwm2b}, @code{at90pwm3}, @code{at90pwm3b}, @code{at90pwm81}.
+
+@item avr5
+``Enhanced'' devices with 16@tie{}KiB up to 64@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{atmega16}, @code{atmega16a}, @code{atmega16hva}, @code{atmega16hva2}, @code{atmega16hvb}, @code{atmega16hvbrevb}, @code{atmega16m1}, @code{atmega16u4}, @code{atmega161}, @code{atmega162}, @code{atmega163}, @code{atmega164a}, @code{atmega164p}, @code{atmega164pa}, @code{atmega165}, @code{atmega165a}, @code{atmega165p}, @code{atmega165pa}, @code{atmega168}, @code{atmega168a}, @code{atmega168p}, @code{atmega168pa}, @code{atmega168pb}, @code{atmega169}, @code{atmega169a}, @code{atmega169p}, @code{atmega169pa}, @code{atmega32}, @code{atmega32a}, @code{atmega32c1}, @code{atmega32hvb}, @code{atmega32hvbrevb}, @code{atmega32m1}, @code{atmega32u4}, @code{atmega32u6}, @code{atmega323}, @code{atmega324a}, @code{atmega324p}, @code{atmega324pa}, @code{atmega324pb}, @code{atmega325}, @code{atmega325a}, @code{atmega325p}, @code{atmega325pa}, @code{atmega328}, @code{atmega328p}, @code{atmega328pb}, @code{atmega329}, @code{atmega329a}, @code{atmega329p}, @code{atmega329pa}, @code{atmega3250}, @code{atmega3250a}, @code{atmega3250p}, @code{atmega3250pa}, @code{atmega3290}, @code{atmega3290a}, @code{atmega3290p}, @code{atmega3290pa}, @code{atmega406}, @code{atmega64}, @code{atmega64a}, @code{atmega64c1}, @code{atmega64hve}, @code{atmega64hve2}, @code{atmega64m1}, @code{atmega64rfr2}, @code{atmega640}, @code{atmega644}, @code{atmega644a}, @code{atmega644p}, @code{atmega644pa}, @code{atmega644rfr2}, @code{atmega645}, @code{atmega645a}, @code{atmega645p}, @code{atmega649}, @code{atmega649a}, @code{atmega649p}, @code{atmega6450}, @code{atmega6450a}, @code{atmega6450p}, @code{atmega6490}, @code{atmega6490a}, @code{atmega6490p}, @code{ata5795}, @code{ata5790}, @code{ata5790n}, @code{ata5791}, @code{ata6613c}, @code{ata6614q}, @code{ata5782}, @code{ata5831}, @code{ata8210}, @code{ata8510}, @code{ata5702m322}, @code{at90pwm161}, @code{at90pwm216}, @code{at90pwm316}, @code{at90can32}, @code{at90can64}, @code{at90scr100}, @code{at90usb646}, @code{at90usb647}, @code{at94k}, @code{m3000}.
+
+@item avr51
+``Enhanced'' devices with 128@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{atmega128}, @code{atmega128a}, @code{atmega128rfa1}, @code{atmega128rfr2}, @code{atmega1280}, @code{atmega1281}, @code{atmega1284}, @code{atmega1284p}, @code{atmega1284rfr2}, @code{at90can128}, @code{at90usb1286}, @code{at90usb1287}.
+
+@item avr6
+``Enhanced'' devices with 3-byte PC, i.e.@: with more than 128@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{atmega256rfr2}, @code{atmega2560}, @code{atmega2561}, @code{atmega2564rfr2}.
+
+@item avrxmega2
+``XMEGA'' devices with more than 8@tie{}KiB and up to 64@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{atxmega8e5}, @code{atxmega16a4}, @code{atxmega16a4u}, @code{atxmega16c4}, @code{atxmega16d4}, @code{atxmega16e5}, @code{atxmega32a4}, @code{atxmega32a4u}, @code{atxmega32c3}, @code{atxmega32c4}, @code{atxmega32d3}, @code{atxmega32d4}, @code{atxmega32e5}, @code{avr64da28}, @code{avr64da32}, @code{avr64da48}, @code{avr64da64}, @code{avr64db28}, @code{avr64db32}, @code{avr64db48}, @code{avr64db64}.
+
+@item avrxmega3
+``XMEGA'' devices with up to 64@tie{}KiB of combined program memory and RAM, and with program memory visible in the RAM address space.
+@*@var{mcu}@tie{}= @code{attiny202}, @code{attiny204}, @code{attiny212}, @code{attiny214}, @code{attiny402}, @code{attiny404}, @code{attiny406}, @code{attiny412}, @code{attiny414}, @code{attiny416}, @code{attiny417}, @code{attiny804}, @code{attiny806}, @code{attiny807}, @code{attiny814}, @code{attiny816}, @code{attiny817}, @code{attiny1604}, @code{attiny1606}, @code{attiny1607}, @code{attiny1614}, @code{attiny1616}, @code{attiny1617}, @code{attiny3214}, @code{attiny3216}, @code{attiny3217}, @code{atmega808}, @code{atmega809}, @code{atmega1608}, @code{atmega1609}, @code{atmega3208}, @code{atmega3209}, @code{atmega4808}, @code{atmega4809}, @code{avr32da28}, @code{avr32da32}, @code{avr32da48}, @code{avr32db28}, @code{avr32db32}, @code{avr32db48}.
+
+@item avrxmega4
+``XMEGA'' devices with more than 64@tie{}KiB and up to 128@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{atxmega64a3}, @code{atxmega64a3u}, @code{atxmega64a4u}, @code{atxmega64b1}, @code{atxmega64b3}, @code{atxmega64c3}, @code{atxmega64d3}, @code{atxmega64d4}, @code{avr128da28}, @code{avr128da32}, @code{avr128da48}, @code{avr128da64}, @code{avr128db28}, @code{avr128db32}, @code{avr128db48}, @code{avr128db64}.
+
+@item avrxmega5
+``XMEGA'' devices with more than 64@tie{}KiB and up to 128@tie{}KiB of program memory and more than 64@tie{}KiB of RAM.
+@*@var{mcu}@tie{}= @code{atxmega64a1}, @code{atxmega64a1u}.
+
+@item avrxmega6
+``XMEGA'' devices with more than 128@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{atxmega128a3}, @code{atxmega128a3u}, @code{atxmega128b1}, @code{atxmega128b3}, @code{atxmega128c3}, @code{atxmega128d3}, @code{atxmega128d4}, @code{atxmega192a3}, @code{atxmega192a3u}, @code{atxmega192c3}, @code{atxmega192d3}, @code{atxmega256a3}, @code{atxmega256a3b}, @code{atxmega256a3bu}, @code{atxmega256a3u}, @code{atxmega256c3}, @code{atxmega256d3}, @code{atxmega384c3}, @code{atxmega384d3}.
+
+@item avrxmega7
+``XMEGA'' devices with more than 128@tie{}KiB of program memory and more than 64@tie{}KiB of RAM.
+@*@var{mcu}@tie{}= @code{atxmega128a1}, @code{atxmega128a1u}, @code{atxmega128a4u}.
+
+@item avrtiny
+``TINY'' Tiny core devices with 512@tie{}B up to 4@tie{}KiB of program memory.
+@*@var{mcu}@tie{}= @code{attiny4}, @code{attiny5}, @code{attiny9}, @code{attiny10}, @code{attiny20}, @code{attiny40}.
+
+@item avr1
+This ISA is implemented by the minimal AVR core and supported for assembler only.
+@*@var{mcu}@tie{}= @code{attiny11}, @code{attiny12}, @code{attiny15}, @code{attiny28}, @code{at90s1200}.
+
+@end table
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Bugs
+@chapter Reporting Bugs
+@cindex bugs
+@cindex reporting bugs
+
+Your bug reports play an essential role in making GCC reliable.
+
+When you encounter a problem, the first thing to do is to see if it is
+already known. @xref{Trouble}. If it isn't known, then you should
+report the problem.
+
+@menu
+* Criteria: Bug Criteria. Have you really found a bug?
+* Reporting: Bug Reporting. How to report a bug effectively.
+@end menu
+
+@node Bug Criteria
+@section Have You Found a Bug?
+@cindex bug criteria
+
+If you are not sure whether you have found a bug, here are some guidelines:
+
+@itemize @bullet
+@cindex fatal signal
+@cindex core dump
+@item
+If the compiler gets a fatal signal, for any input whatever, that is a
+compiler bug. Reliable compilers never crash.
+
+@cindex invalid assembly code
+@cindex assembly code, invalid
+@item
+If the compiler produces invalid assembly code, for any input whatever
+(except an @code{asm} statement), that is a compiler bug, unless the
+compiler reports errors (not just warnings) which would ordinarily
+prevent the assembler from being run.
+
+@cindex undefined behavior
+@cindex undefined function value
+@cindex increment operators
+@item
+If the compiler produces valid assembly code that does not correctly
+execute the input source code, that is a compiler bug.
+
+However, you must double-check to make sure, because you may have a
+program whose behavior is undefined, which happened by chance to give
+the desired results with another C or C++ compiler.
+
+For example, in many nonoptimizing compilers, you can write @samp{x;}
+at the end of a function instead of @samp{return x;}, with the same
+results. But the value of the function is undefined if @code{return}
+is omitted; it is not a bug when GCC produces different results.
+
+Problems often result from expressions with two increment operators,
+as in @code{f (*p++, *p++)}. Your previous compiler might have
+interpreted that expression the way you intended; GCC might
+interpret it another way. Neither compiler is wrong. The bug is
+in your code.
+
+After you have localized the error to a single source line, it should
+be easy to check for these things. If your program is correct and
+well defined, you have found a compiler bug.
+
+@item
+If the compiler produces an error message for valid input, that is a
+compiler bug.
+
+@cindex invalid input
+@item
+If the compiler does not produce an error message for invalid input,
+that is a compiler bug. However, you should note that your idea of
+``invalid input'' might be someone else's idea of ``an extension'' or
+``support for traditional practice''.
+
+@item
+If you are an experienced user of one of the languages GCC supports, your
+suggestions for improvement of GCC are welcome in any case.
+@end itemize
+
+@node Bug Reporting
+@section How and Where to Report Bugs
+@cindex compiler bugs, reporting
+
+Bugs should be reported to the bug database at @value{BUGURL}.
--- /dev/null
+@c -*-texinfo-*-
+@c Copyright (C) 2001-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@c ---------------------------------------------------------------------
+@c Control Flow Graph
+@c ---------------------------------------------------------------------
+
+@node Control Flow
+@chapter Control Flow Graph
+@cindex CFG, Control Flow Graph
+@findex basic-block.h
+
+A control flow graph (CFG) is a data structure built on top of the
+intermediate code representation (the RTL or @code{GIMPLE} instruction
+stream) abstracting the control flow behavior of a function that is
+being compiled. The CFG is a directed graph where the vertices
+represent basic blocks and edges represent possible transfer of
+control flow from one basic block to another. The data structures
+used to represent the control flow graph are defined in
+@file{basic-block.h}.
+
+In GCC, the representation of control flow is maintained throughout
+the compilation process, from constructing the CFG early in
+@code{pass_build_cfg} to @code{pass_free_cfg} (see @file{passes.def}).
+The CFG takes various different modes and may undergo extensive
+manipulations, but the graph is always valid between its construction
+and its release. This way, transfer of information such as data flow,
+a measured profile, or the loop tree, can be propagated through the
+passes pipeline, and even from @code{GIMPLE} to @code{RTL}.
+
+Often the CFG may be better viewed as integral part of instruction
+chain, than structure built on the top of it. Updating the compiler's
+intermediate representation for instructions cannot be easily done
+without proper maintenance of the CFG simultaneously.
+
+@menu
+* Basic Blocks:: The definition and representation of basic blocks.
+* Edges:: Types of edges and their representation.
+* Profile information:: Representation of frequencies and probabilities.
+* Maintaining the CFG:: Keeping the control flow graph and up to date.
+* Liveness information:: Using and maintaining liveness information.
+@end menu
+
+
+@node Basic Blocks
+@section Basic Blocks
+
+@cindex basic block
+@findex basic_block
+A basic block is a straight-line sequence of code with only one entry
+point and only one exit. In GCC, basic blocks are represented using
+the @code{basic_block} data type.
+
+@findex ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR
+Special basic blocks represent possible entry and exit points of a
+function. These blocks are called @code{ENTRY_BLOCK_PTR} and
+@code{EXIT_BLOCK_PTR}. These blocks do not contain any code.
+
+@findex BASIC_BLOCK
+The @code{BASIC_BLOCK} array contains all basic blocks in an
+unspecified order. Each @code{basic_block} structure has a field
+that holds a unique integer identifier @code{index} that is the
+index of the block in the @code{BASIC_BLOCK} array.
+The total number of basic blocks in the function is
+@code{n_basic_blocks}. Both the basic block indices and
+the total number of basic blocks may vary during the compilation
+process, as passes reorder, create, duplicate, and destroy basic
+blocks. The index for any block should never be greater than
+@code{last_basic_block}. The indices 0 and 1 are special codes
+reserved for @code{ENTRY_BLOCK} and @code{EXIT_BLOCK}, the
+indices of @code{ENTRY_BLOCK_PTR} and @code{EXIT_BLOCK_PTR}.
+
+@findex next_bb, prev_bb, FOR_EACH_BB, FOR_ALL_BB
+Two pointer members of the @code{basic_block} structure are the
+pointers @code{next_bb} and @code{prev_bb}. These are used to keep
+doubly linked chain of basic blocks in the same order as the
+underlying instruction stream. The chain of basic blocks is updated
+transparently by the provided API for manipulating the CFG@. The macro
+@code{FOR_EACH_BB} can be used to visit all the basic blocks in
+lexicographical order, except @code{ENTRY_BLOCK} and @code{EXIT_BLOCK}.
+The macro @code{FOR_ALL_BB} also visits all basic blocks in
+lexicographical order, including @code{ENTRY_BLOCK} and @code{EXIT_BLOCK}.
+
+@findex post_order_compute, inverted_post_order_compute, walk_dominator_tree
+The functions @code{post_order_compute} and @code{inverted_post_order_compute}
+can be used to compute topological orders of the CFG. The orders are
+stored as vectors of basic block indices. The @code{BASIC_BLOCK} array
+can be used to iterate each basic block by index.
+Dominator traversals are also possible using
+@code{walk_dominator_tree}. Given two basic blocks A and B, block A
+dominates block B if A is @emph{always} executed before B@.
+
+Each @code{basic_block} also contains pointers to the first
+instruction (the @dfn{head}) and the last instruction (the @dfn{tail})
+or @dfn{end} of the instruction stream contained in a basic block. In
+fact, since the @code{basic_block} data type is used to represent
+blocks in both major intermediate representations of GCC (@code{GIMPLE}
+and RTL), there are pointers to the head and end of a basic block for
+both representations, stored in intermediate representation specific
+data in the @code{il} field of @code{struct basic_block_def}.
+
+@findex CODE_LABEL
+@findex NOTE_INSN_BASIC_BLOCK
+For RTL, these pointers are @code{BB_HEAD} and @code{BB_END}.
+
+@cindex insn notes, notes
+@findex NOTE_INSN_BASIC_BLOCK
+In the RTL representation of a function, the instruction stream
+contains not only the ``real'' instructions, but also @dfn{notes}
+or @dfn{insn notes} (to distinguish them from @dfn{reg notes}).
+Any function that moves or duplicates the basic blocks needs
+to take care of updating of these notes. Many of these notes expect
+that the instruction stream consists of linear regions, so updating
+can sometimes be tedious. All types of insn notes are defined
+in @file{insn-notes.def}.
+
+In the RTL function representation, the instructions contained in a
+basic block always follow a @code{NOTE_INSN_BASIC_BLOCK}, but zero
+or more @code{CODE_LABEL} nodes can precede the block note.
+A basic block ends with a control flow instruction or with the last
+instruction before the next @code{CODE_LABEL} or
+@code{NOTE_INSN_BASIC_BLOCK}.
+By definition, a @code{CODE_LABEL} cannot appear in the middle of
+the instruction stream of a basic block.
+
+@findex can_fallthru
+@cindex table jump
+In addition to notes, the jump table vectors are also represented as
+``pseudo-instructions'' inside the insn stream. These vectors never
+appear in the basic block and should always be placed just after the
+table jump instructions referencing them. After removing the
+table-jump it is often difficult to eliminate the code computing the
+address and referencing the vector, so cleaning up these vectors is
+postponed until after liveness analysis. Thus the jump table vectors
+may appear in the insn stream unreferenced and without any purpose.
+Before any edge is made @dfn{fall-thru}, the existence of such
+construct in the way needs to be checked by calling
+@code{can_fallthru} function.
+
+@cindex GIMPLE statement iterators
+For the @code{GIMPLE} representation, the PHI nodes and statements
+contained in a basic block are in a @code{gimple_seq} pointed to by
+the basic block intermediate language specific pointers.
+Abstract containers and iterators are used to access the PHI nodes
+and statements in a basic blocks. These iterators are called
+@dfn{GIMPLE statement iterators} (GSIs). Grep for @code{^gsi}
+in the various @file{gimple-*} and @file{tree-*} files.
+There is a @code{gimple_stmt_iterator} type for iterating over
+all kinds of statement, and a @code{gphi_iterator} subclass for
+iterating over PHI nodes.
+The following snippet will pretty-print all PHI nodes the statements
+of the current function in the GIMPLE representation.
+
+@smallexample
+basic_block bb;
+
+FOR_EACH_BB (bb)
+ @{
+ gphi_iterator pi;
+ gimple_stmt_iterator si;
+
+ for (pi = gsi_start_phis (bb); !gsi_end_p (pi); gsi_next (&pi))
+ @{
+ gphi *phi = pi.phi ();
+ print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
+ @}
+ for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si))
+ @{
+ gimple stmt = gsi_stmt (si);
+ print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
+ @}
+ @}
+@end smallexample
+
+
+@node Edges
+@section Edges
+
+@cindex edge in the flow graph
+@findex edge
+Edges represent possible control flow transfers from the end of some
+basic block A to the head of another basic block B@. We say that A is
+a predecessor of B, and B is a successor of A@. Edges are represented
+in GCC with the @code{edge} data type. Each @code{edge} acts as a
+link between two basic blocks: The @code{src} member of an edge
+points to the predecessor basic block of the @code{dest} basic block.
+The members @code{preds} and @code{succs} of the @code{basic_block} data
+type point to type-safe vectors of edges to the predecessors and
+successors of the block.
+
+@cindex edge iterators
+When walking the edges in an edge vector, @dfn{edge iterators} should
+be used. Edge iterators are constructed using the
+@code{edge_iterator} data structure and several methods are available
+to operate on them:
+
+@ftable @code
+@item ei_start
+This function initializes an @code{edge_iterator} that points to the
+first edge in a vector of edges.
+
+@item ei_last
+This function initializes an @code{edge_iterator} that points to the
+last edge in a vector of edges.
+
+@item ei_end_p
+This predicate is @code{true} if an @code{edge_iterator} represents
+the last edge in an edge vector.
+
+@item ei_one_before_end_p
+This predicate is @code{true} if an @code{edge_iterator} represents
+the second last edge in an edge vector.
+
+@item ei_next
+This function takes a pointer to an @code{edge_iterator} and makes it
+point to the next edge in the sequence.
+
+@item ei_prev
+This function takes a pointer to an @code{edge_iterator} and makes it
+point to the previous edge in the sequence.
+
+@item ei_edge
+This function returns the @code{edge} currently pointed to by an
+@code{edge_iterator}.
+
+@item ei_safe_edge
+This function returns the @code{edge} currently pointed to by an
+@code{edge_iterator}, but returns @code{NULL} if the iterator is
+pointing at the end of the sequence. This function has been provided
+for existing code makes the assumption that a @code{NULL} edge
+indicates the end of the sequence.
+
+@end ftable
+
+The convenience macro @code{FOR_EACH_EDGE} can be used to visit all of
+the edges in a sequence of predecessor or successor edges. It must
+not be used when an element might be removed during the traversal,
+otherwise elements will be missed. Here is an example of how to use
+the macro:
+
+@smallexample
+edge e;
+edge_iterator ei;
+
+FOR_EACH_EDGE (e, ei, bb->succs)
+ @{
+ if (e->flags & EDGE_FALLTHRU)
+ break;
+ @}
+@end smallexample
+
+@findex fall-thru
+There are various reasons why control flow may transfer from one block
+to another. One possibility is that some instruction, for example a
+@code{CODE_LABEL}, in a linearized instruction stream just always
+starts a new basic block. In this case a @dfn{fall-thru} edge links
+the basic block to the first following basic block. But there are
+several other reasons why edges may be created. The @code{flags}
+field of the @code{edge} data type is used to store information
+about the type of edge we are dealing with. Each edge is of one of
+the following types:
+
+@table @emph
+@item jump
+No type flags are set for edges corresponding to jump instructions.
+These edges are used for unconditional or conditional jumps and in
+RTL also for table jumps. They are the easiest to manipulate as they
+may be freely redirected when the flow graph is not in SSA form.
+
+@item fall-thru
+@findex EDGE_FALLTHRU, force_nonfallthru
+Fall-thru edges are present in case where the basic block may continue
+execution to the following one without branching. These edges have
+the @code{EDGE_FALLTHRU} flag set. Unlike other types of edges, these
+edges must come into the basic block immediately following in the
+instruction stream. The function @code{force_nonfallthru} is
+available to insert an unconditional jump in the case that redirection
+is needed. Note that this may require creation of a new basic block.
+
+@item exception handling
+@cindex exception handling
+@findex EDGE_ABNORMAL, EDGE_EH
+Exception handling edges represent possible control transfers from a
+trapping instruction to an exception handler. The definition of
+``trapping'' varies. In C++, only function calls can throw, but for
+Ada exceptions like division by zero or segmentation fault are
+defined and thus each instruction possibly throwing this kind of
+exception needs to be handled as control flow instruction. Exception
+edges have the @code{EDGE_ABNORMAL} and @code{EDGE_EH} flags set.
+
+@findex purge_dead_edges
+When updating the instruction stream it is easy to change possibly
+trapping instruction to non-trapping, by simply removing the exception
+edge. The opposite conversion is difficult, but should not happen
+anyway. The edges can be eliminated via @code{purge_dead_edges} call.
+
+@findex REG_EH_REGION, EDGE_ABNORMAL_CALL
+In the RTL representation, the destination of an exception edge is
+specified by @code{REG_EH_REGION} note attached to the insn.
+In case of a trapping call the @code{EDGE_ABNORMAL_CALL} flag is set
+too. In the @code{GIMPLE} representation, this extra flag is not set.
+
+@findex may_trap_p, tree_could_trap_p
+In the RTL representation, the predicate @code{may_trap_p} may be used
+to check whether instruction still may trap or not. For the tree
+representation, the @code{tree_could_trap_p} predicate is available,
+but this predicate only checks for possible memory traps, as in
+dereferencing an invalid pointer location.
+
+
+@item sibling calls
+@cindex sibling call
+@findex EDGE_ABNORMAL, EDGE_SIBCALL
+Sibling calls or tail calls terminate the function in a non-standard
+way and thus an edge to the exit must be present.
+@code{EDGE_SIBCALL} and @code{EDGE_ABNORMAL} are set in such case.
+These edges only exist in the RTL representation.
+
+@item computed jumps
+@cindex computed jump
+@findex EDGE_ABNORMAL
+Computed jumps contain edges to all labels in the function referenced
+from the code. All those edges have @code{EDGE_ABNORMAL} flag set.
+The edges used to represent computed jumps often cause compile time
+performance problems, since functions consisting of many taken labels
+and many computed jumps may have @emph{very} dense flow graphs, so
+these edges need to be handled with special care. During the earlier
+stages of the compilation process, GCC tries to avoid such dense flow
+graphs by factoring computed jumps. For example, given the following
+series of jumps,
+
+@smallexample
+ goto *x;
+ [ @dots{} ]
+
+ goto *x;
+ [ @dots{} ]
+
+ goto *x;
+ [ @dots{} ]
+@end smallexample
+
+@noindent
+factoring the computed jumps results in the following code sequence
+which has a much simpler flow graph:
+
+@smallexample
+ goto y;
+ [ @dots{} ]
+
+ goto y;
+ [ @dots{} ]
+
+ goto y;
+ [ @dots{} ]
+
+y:
+ goto *x;
+@end smallexample
+
+@findex pass_duplicate_computed_gotos
+However, the classic problem with this transformation is that it has a
+runtime cost in there resulting code: An extra jump. Therefore, the
+computed jumps are un-factored in the later passes of the compiler
+(in the pass called @code{pass_duplicate_computed_gotos}).
+Be aware of that when you work on passes in that area. There have
+been numerous examples already where the compile time for code with
+unfactored computed jumps caused some serious headaches.
+
+@item nonlocal goto handlers
+@cindex nonlocal goto handler
+@findex EDGE_ABNORMAL, EDGE_ABNORMAL_CALL
+GCC allows nested functions to return into caller using a @code{goto}
+to a label passed to as an argument to the callee. The labels passed
+to nested functions contain special code to cleanup after function
+call. Such sections of code are referred to as ``nonlocal goto
+receivers''. If a function contains such nonlocal goto receivers, an
+edge from the call to the label is created with the
+@code{EDGE_ABNORMAL} and @code{EDGE_ABNORMAL_CALL} flags set.
+
+@item function entry points
+@cindex function entry point, alternate function entry point
+@findex LABEL_ALTERNATE_NAME
+By definition, execution of function starts at basic block 0, so there
+is always an edge from the @code{ENTRY_BLOCK_PTR} to basic block 0.
+There is no @code{GIMPLE} representation for alternate entry points at
+this moment. In RTL, alternate entry points are specified by
+@code{CODE_LABEL} with @code{LABEL_ALTERNATE_NAME} defined. This
+feature is currently used for multiple entry point prologues and is
+limited to post-reload passes only. This can be used by back-ends to
+emit alternate prologues for functions called from different contexts.
+In future full support for multiple entry functions defined by Fortran
+90 needs to be implemented.
+
+@item function exits
+In the pre-reload representation a function terminates after the last
+instruction in the insn chain and no explicit return instructions are
+used. This corresponds to the fall-thru edge into exit block. After
+reload, optimal RTL epilogues are used that use explicit (conditional)
+return instructions that are represented by edges with no flags set.
+
+@end table
+
+
+@node Profile information
+@section Profile information
+
+@cindex profile representation
+In many cases a compiler must make a choice whether to trade speed in
+one part of code for speed in another, or to trade code size for code
+speed. In such cases it is useful to know information about how often
+some given block will be executed. That is the purpose for
+maintaining profile within the flow graph.
+GCC can handle profile information obtained through @dfn{profile
+feedback}, but it can also estimate branch probabilities based on
+statics and heuristics.
+
+@cindex profile feedback
+The feedback based profile is produced by compiling the program with
+instrumentation, executing it on a train run and reading the numbers
+of executions of basic blocks and edges back to the compiler while
+re-compiling the program to produce the final executable. This method
+provides very accurate information about where a program spends most
+of its time on the train run. Whether it matches the average run of
+course depends on the choice of train data set, but several studies
+have shown that the behavior of a program usually changes just
+marginally over different data sets.
+
+@cindex Static profile estimation
+@cindex branch prediction
+@findex predict.def
+When profile feedback is not available, the compiler may be asked to
+attempt to predict the behavior of each branch in the program using a
+set of heuristics (see @file{predict.def} for details) and compute
+estimated frequencies of each basic block by propagating the
+probabilities over the graph.
+
+@findex frequency, count, BB_FREQ_BASE
+Each @code{basic_block} contains two integer fields to represent
+profile information: @code{frequency} and @code{count}. The
+@code{frequency} is an estimation how often is basic block executed
+within a function. It is represented as an integer scaled in the
+range from 0 to @code{BB_FREQ_BASE}. The most frequently executed
+basic block in function is initially set to @code{BB_FREQ_BASE} and
+the rest of frequencies are scaled accordingly. During optimization,
+the frequency of the most frequent basic block can both decrease (for
+instance by loop unrolling) or grow (for instance by cross-jumping
+optimization), so scaling sometimes has to be performed multiple
+times.
+
+@findex gcov_type
+The @code{count} contains hard-counted numbers of execution measured
+during training runs and is nonzero only when profile feedback is
+available. This value is represented as the host's widest integer
+(typically a 64 bit integer) of the special type @code{gcov_type}.
+
+Most optimization passes can use only the frequency information of a
+basic block, but a few passes may want to know hard execution counts.
+The frequencies should always match the counts after scaling, however
+during updating of the profile information numerical error may
+accumulate into quite large errors.
+
+@findex REG_BR_PROB_BASE, EDGE_FREQUENCY
+Each edge also contains a branch probability field: an integer in the
+range from 0 to @code{REG_BR_PROB_BASE}. It represents probability of
+passing control from the end of the @code{src} basic block to the
+@code{dest} basic block, i.e.@: the probability that control will flow
+along this edge. The @code{EDGE_FREQUENCY} macro is available to
+compute how frequently a given edge is taken. There is a @code{count}
+field for each edge as well, representing same information as for a
+basic block.
+
+The basic block frequencies are not represented in the instruction
+stream, but in the RTL representation the edge frequencies are
+represented for conditional jumps (via the @code{REG_BR_PROB}
+macro) since they are used when instructions are output to the
+assembly file and the flow graph is no longer maintained.
+
+@cindex reverse probability
+The probability that control flow arrives via a given edge to its
+destination basic block is called @dfn{reverse probability} and is not
+directly represented, but it may be easily computed from frequencies
+of basic blocks.
+
+@findex redirect_edge_and_branch
+Updating profile information is a delicate task that can unfortunately
+not be easily integrated with the CFG manipulation API@. Many of the
+functions and hooks to modify the CFG, such as
+@code{redirect_edge_and_branch}, do not have enough information to
+easily update the profile, so updating it is in the majority of cases
+left up to the caller. It is difficult to uncover bugs in the profile
+updating code, because they manifest themselves only by producing
+worse code, and checking profile consistency is not possible because
+of numeric error accumulation. Hence special attention needs to be
+given to this issue in each pass that modifies the CFG@.
+
+@findex REG_BR_PROB_BASE, BB_FREQ_BASE, count
+It is important to point out that @code{REG_BR_PROB_BASE} and
+@code{BB_FREQ_BASE} are both set low enough to be possible to compute
+second power of any frequency or probability in the flow graph, it is
+not possible to even square the @code{count} field, as modern CPUs are
+fast enough to execute $2^32$ operations quickly.
+
+
+@node Maintaining the CFG
+@section Maintaining the CFG
+@findex cfghooks.h
+
+An important task of each compiler pass is to keep both the control
+flow graph and all profile information up-to-date. Reconstruction of
+the control flow graph after each pass is not an option, since it may be
+very expensive and lost profile information cannot be reconstructed at
+all.
+
+GCC has two major intermediate representations, and both use the
+@code{basic_block} and @code{edge} data types to represent control
+flow. Both representations share as much of the CFG maintenance code
+as possible. For each representation, a set of @dfn{hooks} is defined
+so that each representation can provide its own implementation of CFG
+manipulation routines when necessary. These hooks are defined in
+@file{cfghooks.h}. There are hooks for almost all common CFG
+manipulations, including block splitting and merging, edge redirection
+and creating and deleting basic blocks. These hooks should provide
+everything you need to maintain and manipulate the CFG in both the RTL
+and @code{GIMPLE} representation.
+
+At the moment, the basic block boundaries are maintained transparently
+when modifying instructions, so there rarely is a need to move them
+manually (such as in case someone wants to output instruction outside
+basic block explicitly).
+
+@findex BLOCK_FOR_INSN, gimple_bb
+In the RTL representation, each instruction has a
+@code{BLOCK_FOR_INSN} value that represents pointer to the basic block
+that contains the instruction. In the @code{GIMPLE} representation, the
+function @code{gimple_bb} returns a pointer to the basic block
+containing the queried statement.
+
+@cindex GIMPLE statement iterators
+When changes need to be applied to a function in its @code{GIMPLE}
+representation, @dfn{GIMPLE statement iterators} should be used. These
+iterators provide an integrated abstraction of the flow graph and the
+instruction stream. Block statement iterators are constructed using
+the @code{gimple_stmt_iterator} data structure and several modifiers are
+available, including the following:
+
+@ftable @code
+@item gsi_start
+This function initializes a @code{gimple_stmt_iterator} that points to
+the first non-empty statement in a basic block.
+
+@item gsi_last
+This function initializes a @code{gimple_stmt_iterator} that points to
+the last statement in a basic block.
+
+@item gsi_end_p
+This predicate is @code{true} if a @code{gimple_stmt_iterator}
+represents the end of a basic block.
+
+@item gsi_next
+This function takes a @code{gimple_stmt_iterator} and makes it point to
+its successor.
+
+@item gsi_prev
+This function takes a @code{gimple_stmt_iterator} and makes it point to
+its predecessor.
+
+@item gsi_insert_after
+This function inserts a statement after the @code{gimple_stmt_iterator}
+passed in. The final parameter determines whether the statement
+iterator is updated to point to the newly inserted statement, or left
+pointing to the original statement.
+
+@item gsi_insert_before
+This function inserts a statement before the @code{gimple_stmt_iterator}
+passed in. The final parameter determines whether the statement
+iterator is updated to point to the newly inserted statement, or left
+pointing to the original statement.
+
+@item gsi_remove
+This function removes the @code{gimple_stmt_iterator} passed in and
+rechains the remaining statements in a basic block, if any.
+@end ftable
+
+@findex BB_HEAD, BB_END
+In the RTL representation, the macros @code{BB_HEAD} and @code{BB_END}
+may be used to get the head and end @code{rtx} of a basic block. No
+abstract iterators are defined for traversing the insn chain, but you
+can just use @code{NEXT_INSN} and @code{PREV_INSN} instead. @xref{Insns}.
+
+@findex purge_dead_edges
+Usually a code manipulating pass simplifies the instruction stream and
+the flow of control, possibly eliminating some edges. This may for
+example happen when a conditional jump is replaced with an
+unconditional jump. Updating of edges
+is not transparent and each optimization pass is required to do so
+manually. However only few cases occur in practice. The pass may
+call @code{purge_dead_edges} on a given basic block to remove
+superfluous edges, if any.
+
+@findex redirect_edge_and_branch, redirect_jump
+Another common scenario is redirection of branch instructions, but
+this is best modeled as redirection of edges in the control flow graph
+and thus use of @code{redirect_edge_and_branch} is preferred over more
+low level functions, such as @code{redirect_jump} that operate on RTL
+chain only. The CFG hooks defined in @file{cfghooks.h} should provide
+the complete API required for manipulating and maintaining the CFG@.
+
+@findex split_block
+It is also possible that a pass has to insert control flow instruction
+into the middle of a basic block, thus creating an entry point in the
+middle of the basic block, which is impossible by definition: The
+block must be split to make sure it only has one entry point, i.e.@: the
+head of the basic block. The CFG hook @code{split_block} may be used
+when an instruction in the middle of a basic block has to become the
+target of a jump or branch instruction.
+
+@findex insert_insn_on_edge
+@findex commit_edge_insertions
+@findex gsi_insert_on_edge
+@findex gsi_commit_edge_inserts
+@cindex edge splitting
+For a global optimizer, a common operation is to split edges in the
+flow graph and insert instructions on them. In the RTL
+representation, this can be easily done using the
+@code{insert_insn_on_edge} function that emits an instruction
+``on the edge'', caching it for a later @code{commit_edge_insertions}
+call that will take care of moving the inserted instructions off the
+edge into the instruction stream contained in a basic block. This
+includes the creation of new basic blocks where needed. In the
+@code{GIMPLE} representation, the equivalent functions are
+@code{gsi_insert_on_edge} which inserts a block statement
+iterator on an edge, and @code{gsi_commit_edge_inserts} which flushes
+the instruction to actual instruction stream.
+
+@findex verify_flow_info
+@cindex CFG verification
+While debugging the optimization pass, the @code{verify_flow_info}
+function may be useful to find bugs in the control flow graph updating
+code.
+
+
+@node Liveness information
+@section Liveness information
+@cindex Liveness representation
+Liveness information is useful to determine whether some register is
+``live'' at given point of program, i.e.@: that it contains a value that
+may be used at a later point in the program. This information is
+used, for instance, during register allocation, as the pseudo
+registers only need to be assigned to a unique hard register or to a
+stack slot if they are live. The hard registers and stack slots may
+be freely reused for other values when a register is dead.
+
+Liveness information is available in the back end starting with
+@code{pass_df_initialize} and ending with @code{pass_df_finish}. Three
+flavors of live analysis are available: With @code{LR}, it is possible
+to determine at any point @code{P} in the function if the register may be
+used on some path from @code{P} to the end of the function. With
+@code{UR}, it is possible to determine if there is a path from the
+beginning of the function to @code{P} that defines the variable.
+@code{LIVE} is the intersection of the @code{LR} and @code{UR} and a
+variable is live at @code{P} if there is both an assignment that reaches
+it from the beginning of the function and a use that can be reached on
+some path from @code{P} to the end of the function.
+
+In general @code{LIVE} is the most useful of the three. The macros
+@code{DF_[LR,UR,LIVE]_[IN,OUT]} can be used to access this information.
+The macros take a basic block number and return a bitmap that is indexed
+by the register number. This information is only guaranteed to be up to
+date after calls are made to @code{df_analyze}. See the file
+@code{df-core.cc} for details on using the dataflow.
+
+
+@findex REG_DEAD, REG_UNUSED
+The liveness information is stored partly in the RTL instruction stream
+and partly in the flow graph. Local information is stored in the
+instruction stream: Each instruction may contain @code{REG_DEAD} notes
+representing that the value of a given register is no longer needed, or
+@code{REG_UNUSED} notes representing that the value computed by the
+instruction is never used. The second is useful for instructions
+computing multiple values at once.
+
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Collect2
+@chapter @code{collect2}
+
+GCC uses a utility called @code{collect2} on nearly all systems to arrange
+to call various initialization functions at start time.
+
+The program @code{collect2} works by linking the program once and
+looking through the linker output file for symbols with particular names
+indicating they are constructor functions. If it finds any, it
+creates a new temporary @samp{.c} file containing a table of them,
+compiles it, and links the program a second time including that file.
+
+@findex __main
+@cindex constructors, automatic calls
+The actual calls to the constructors are carried out by a subroutine
+called @code{__main}, which is called (automatically) at the beginning
+of the body of @code{main} (provided @code{main} was compiled with GNU
+CC)@. Calling @code{__main} is necessary, even when compiling C code, to
+allow linking C and C++ object code together. (If you use
+@option{-nostdlib}, you get an unresolved reference to @code{__main},
+since it's defined in the standard GCC library. Include @option{-lgcc} at
+the end of your compiler command line to resolve this reference.)
+
+The program @code{collect2} is installed as @code{ld} in the directory
+where the passes of the compiler are installed. When @code{collect2}
+needs to find the @emph{real} @code{ld}, it tries the following file
+names:
+
+@itemize @bullet
+@item
+a hard coded linker file name, if GCC was configured with the
+@option{--with-ld} option.
+
+@item
+@file{real-ld} in the directories listed in the compiler's search
+directories.
+
+@item
+@file{real-ld} in the directories listed in the environment variable
+@code{PATH}.
+
+@item
+The file specified in the @code{REAL_LD_FILE_NAME} configuration macro,
+if specified.
+
+@item
+@file{ld} in the compiler's search directories, except that
+@code{collect2} will not execute itself recursively.
+
+@item
+@file{ld} in @code{PATH}.
+@end itemize
+
+``The compiler's search directories'' means all the directories where
+@command{gcc} searches for passes of the compiler. This includes
+directories that you specify with @option{-B}.
+
+Cross-compilers search a little differently:
+
+@itemize @bullet
+@item
+@file{real-ld} in the compiler's search directories.
+
+@item
+@file{@var{target}-real-ld} in @code{PATH}.
+
+@item
+The file specified in the @code{REAL_LD_FILE_NAME} configuration macro,
+if specified.
+
+@item
+@file{ld} in the compiler's search directories.
+
+@item
+@file{@var{target}-ld} in @code{PATH}.
+@end itemize
+
+@code{collect2} explicitly avoids running @code{ld} using the file name
+under which @code{collect2} itself was invoked. In fact, it remembers
+up a list of such names---in case one copy of @code{collect2} finds
+another copy (or version) of @code{collect2} installed as @code{ld} in a
+second place in the search path.
+
+@code{collect2} searches for the utilities @code{nm} and @code{strip}
+using the same algorithm as above for @code{ld}.
--- /dev/null
+@c Copyright (C) 2002-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Compatibility
+@chapter Binary Compatibility
+@cindex binary compatibility
+@cindex ABI
+@cindex application binary interface
+
+Binary compatibility encompasses several related concepts:
+
+@table @dfn
+@item application binary interface (ABI)
+The set of runtime conventions followed by all of the tools that deal
+with binary representations of a program, including compilers, assemblers,
+linkers, and language runtime support.
+Some ABIs are formal with a written specification, possibly designed
+by multiple interested parties. Others are simply the way things are
+actually done by a particular set of tools.
+
+@item ABI conformance
+A compiler conforms to an ABI if it generates code that follows all of
+the specifications enumerated by that ABI@.
+A library conforms to an ABI if it is implemented according to that ABI@.
+An application conforms to an ABI if it is built using tools that conform
+to that ABI and does not contain source code that specifically changes
+behavior specified by the ABI@.
+
+@item calling conventions
+Calling conventions are a subset of an ABI that specify of how arguments
+are passed and function results are returned.
+
+@item interoperability
+Different sets of tools are interoperable if they generate files that
+can be used in the same program. The set of tools includes compilers,
+assemblers, linkers, libraries, header files, startup files, and debuggers.
+Binaries produced by different sets of tools are not interoperable unless
+they implement the same ABI@. This applies to different versions of the
+same tools as well as tools from different vendors.
+
+@item intercallability
+Whether a function in a binary built by one set of tools can call a
+function in a binary built by a different set of tools is a subset
+of interoperability.
+
+@item implementation-defined features
+Language standards include lists of implementation-defined features whose
+behavior can vary from one implementation to another. Some of these
+features are normally covered by a platform's ABI and others are not.
+The features that are not covered by an ABI generally affect how a
+program behaves, but not intercallability.
+
+@item compatibility
+Conformance to the same ABI and the same behavior of implementation-defined
+features are both relevant for compatibility.
+@end table
+
+The application binary interface implemented by a C or C++ compiler
+affects code generation and runtime support for:
+
+@itemize @bullet
+@item
+size and alignment of data types
+@item
+layout of structured types
+@item
+calling conventions
+@item
+register usage conventions
+@item
+interfaces for runtime arithmetic support
+@item
+object file formats
+@end itemize
+
+In addition, the application binary interface implemented by a C++ compiler
+affects code generation and runtime support for:
+@itemize @bullet
+@item
+name mangling
+@item
+exception handling
+@item
+invoking constructors and destructors
+@item
+layout, alignment, and padding of classes
+@item
+layout and alignment of virtual tables
+@end itemize
+
+Some GCC compilation options cause the compiler to generate code that
+does not conform to the platform's default ABI@. Other options cause
+different program behavior for implementation-defined features that are
+not covered by an ABI@. These options are provided for consistency with
+other compilers that do not follow the platform's default ABI or the
+usual behavior of implementation-defined features for the platform.
+Be very careful about using such options.
+
+Most platforms have a well-defined ABI that covers C code, but ABIs
+that cover C++ functionality are not yet common.
+
+Starting with GCC 3.2, GCC binary conventions for C++ are based on a
+written, vendor-neutral C++ ABI that was designed to be specific to
+64-bit Itanium but also includes generic specifications that apply to
+any platform.
+This C++ ABI is also implemented by other compiler vendors on some
+platforms, notably GNU/Linux and BSD systems.
+We have tried hard to provide a stable ABI that will be compatible with
+future GCC releases, but it is possible that we will encounter problems
+that make this difficult. Such problems could include different
+interpretations of the C++ ABI by different vendors, bugs in the ABI, or
+bugs in the implementation of the ABI in different compilers.
+GCC's @option{-Wabi} switch warns when G++ generates code that is
+probably not compatible with the C++ ABI@.
+
+The C++ library used with a C++ compiler includes the Standard C++
+Library, with functionality defined in the C++ Standard, plus language
+runtime support. The runtime support is included in a C++ ABI, but there
+is no formal ABI for the Standard C++ Library. Two implementations
+of that library are interoperable if one follows the de-facto ABI of the
+other and if they are both built with the same compiler, or with compilers
+that conform to the same ABI for C++ compiler and runtime support.
+
+When G++ and another C++ compiler conform to the same C++ ABI, but the
+implementations of the Standard C++ Library that they normally use do not
+follow the same ABI for the Standard C++ Library, object files built with
+those compilers can be used in the same program only if they use the same
+C++ library. This requires specifying the location of the C++ library
+header files when invoking the compiler whose usual library is not being
+used. The location of GCC's C++ header files depends on how the GCC
+build was configured, but can be seen by using the G++ @option{-v} option.
+With default configuration options for G++ 3.3 the compile line for a
+different C++ compiler needs to include
+
+@smallexample
+ -I@var{gcc_install_directory}/include/c++/3.3
+@end smallexample
+
+Similarly, compiling code with G++ that must use a C++ library other
+than the GNU C++ library requires specifying the location of the header
+files for that other library.
+
+The most straightforward way to link a program to use a particular
+C++ library is to use a C++ driver that specifies that C++ library by
+default. The @command{g++} driver, for example, tells the linker where
+to find GCC's C++ library (@file{libstdc++}) plus the other libraries
+and startup files it needs, in the proper order.
+
+If a program must use a different C++ library and it's not possible
+to do the final link using a C++ driver that uses that library by default,
+it is necessary to tell @command{g++} the location and name of that
+library. It might also be necessary to specify different startup files
+and other runtime support libraries, and to suppress the use of GCC's
+support libraries with one or more of the options @option{-nostdlib},
+@option{-nostartfiles}, and @option{-nodefaultlibs}.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Configuration Files
+@subsubsection Files Created by @code{configure}
+
+Here we spell out what files will be set up by @file{configure} in the
+@file{gcc} directory. Some other files are created as temporary files
+in the configuration process, and are not used in the subsequent
+build; these are not documented.
+
+@itemize @bullet
+@item
+@file{Makefile} is constructed from @file{Makefile.in}, together with
+the host and target fragments (@pxref{Fragments, , Makefile
+Fragments}) @file{t-@var{target}} and @file{x-@var{host}} from
+@file{config}, if any, and language Makefile fragments
+@file{@var{language}/Make-lang.in}.
+@item
+@file{auto-host.h} contains information about the host machine
+determined by @file{configure}. If the host machine is different from
+the build machine, then @file{auto-build.h} is also created,
+containing such information about the build machine.
+@item
+@file{config.status} is a script that may be run to recreate the
+current configuration.
+@item
+@file{configargs.h} is a header containing details of the arguments
+passed to @file{configure} to configure GCC, and of the thread model
+used.
+@item
+@file{cstamp-h} is used as a timestamp.
+@item
+If a language @file{config-lang.in} file (@pxref{Front End Config, ,
+The Front End @file{config-lang.in} File}) sets @code{outputs}, then
+the files listed in @code{outputs} there are also generated.
+@end itemize
+
+The following configuration headers are created from the Makefile,
+using @file{mkconfig.sh}, rather than directly by @file{configure}.
+@file{config.h}, @file{bconfig.h} and @file{tconfig.h} all contain the
+@file{xm-@var{machine}.h} header, if any, appropriate to the host,
+build and target machines respectively, the configuration headers for
+the target, and some definitions; for the host and build machines,
+these include the autoconfigured headers generated by
+@file{configure}. The other configuration headers are determined by
+@file{config.gcc}. They also contain the typedefs for @code{rtx},
+@code{rtvec} and @code{tree}.
+
+@itemize @bullet
+@item
+@file{config.h}, for use in programs that run on the host machine.
+@item
+@file{bconfig.h}, for use in programs that run on the build machine.
+@item
+@file{tconfig.h}, for use in programs and libraries for the target
+machine.
+@item
+@file{tm_p.h}, which includes the header @file{@var{machine}-protos.h}
+that contains prototypes for functions in the target
+@file{@var{machine}.c} file. The
+@file{@var{machine}-protos.h} header is included after the @file{rtl.h}
+and/or @file{tree.h} would have been included.
+The @file{tm_p.h} also
+includes the header @file{tm-preds.h} which is generated by
+@file{genpreds} program during the build to define the declarations
+and inline functions for the predicate functions.
+@end itemize
--- /dev/null
+@c Copyright (C) 2001-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Configure Terms
+@section Configure Terms and History
+@cindex configure terms
+@cindex canadian
+
+The configure and build process has a long and colorful history, and can
+be confusing to anyone who doesn't know why things are the way they are.
+While there are other documents which describe the configuration process
+in detail, here are a few things that everyone working on GCC should
+know.
+
+There are three system names that the build knows about: the machine you
+are building on (@dfn{build}), the machine that you are building for
+(@dfn{host}), and the machine that GCC will produce code for
+(@dfn{target}). When you configure GCC, you specify these with
+@option{--build=}, @option{--host=}, and @option{--target=}.
+
+Specifying the host without specifying the build should be avoided, as
+@command{configure} may (and once did) assume that the host you specify
+is also the build, which may not be true.
+
+If build, host, and target are all the same, this is called a
+@dfn{native}. If build and host are the same but target is different,
+this is called a @dfn{cross}. If build, host, and target are all
+different this is called a @dfn{canadian} (for obscure reasons dealing
+with Canada's political party and the background of the person working
+on the build at that time). If host and target are the same, but build
+is different, you are using a cross-compiler to build a native for a
+different system. Some people call this a @dfn{host-x-host},
+@dfn{crossed native}, or @dfn{cross-built native}. If build and target
+are the same, but host is different, you are using a cross compiler to
+build a cross compiler that produces code for the machine you're
+building on. This is rare, so there is no common way of describing it.
+There is a proposal to call this a @dfn{crossback}.
+
+If build and host are the same, the GCC you are building will also be
+used to build the target libraries (like @code{libstdc++}). If build and host
+are different, you must have already built and installed a cross
+compiler that will be used to build the target libraries (if you
+configured with @option{--target=foo-bar}, this compiler will be called
+@command{foo-bar-gcc}).
+
+In the case of target libraries, the machine you're building for is the
+machine you specified with @option{--target}. So, build is the machine
+you're building on (no change there), host is the machine you're
+building for (the target libraries are built for the target, so host is
+the target you specified), and target doesn't apply (because you're not
+building a compiler, you're building libraries). The configure/make
+process will adjust these variables as needed. It also sets
+@code{$with_cross_host} to the original @option{--host} value in case you
+need it.
+
+The @code{libiberty} support library is built up to three times: once
+for the host, once for the target (even if they are the same), and once
+for the build if build and host are different. This allows it to be
+used by all programs which are generated in the course of the build
+process.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Contributors
+@unnumbered Contributors to GCC
+@cindex contributors
+
+The GCC project would like to thank its many contributors. Without them the
+project would not have been nearly as successful as it has been. Any omissions
+in this list are accidental. Feel free to contact
+@email{law@@redhat.com} or @email{gerald@@pfeifer.com} if you have been left
+out or some of your contributions are not listed. Please keep this list in
+alphabetical order.
+
+@itemize @bullet
+
+@item
+Analog Devices helped implement the support for complex data types
+and iterators.
+
+@item
+John David Anglin for threading-related fixes and improvements to
+libstdc++-v3, and the HP-UX port.
+
+@item
+James van Artsdalen wrote the code that makes efficient use of
+the Intel 80387 register stack.
+
+@item
+Abramo and Roberto Bagnara for the SysV68 Motorola 3300 Delta Series
+port.
+
+@item
+Alasdair Baird for various bug fixes.
+
+@item
+Giovanni Bajo for analyzing lots of complicated C++ problem reports.
+
+@item
+Peter Barada for his work to improve code generation for new
+ColdFire cores.
+
+@item
+Gerald Baumgartner added the signature extension to the C++ front end.
+
+@item
+Godmar Back for his Java improvements and encouragement.
+
+@item
+Scott Bambrough for help porting the Java compiler.
+
+@item
+Wolfgang Bangerth for processing tons of bug reports.
+
+@item
+Jon Beniston for his Microsoft Windows port of Java and port to Lattice Mico32.
+
+@item
+Daniel Berlin for better DWARF 2 support, faster/better optimizations,
+improved alias analysis, plus migrating GCC to Bugzilla.
+
+@item
+Geoff Berry for his Java object serialization work and various patches.
+
+@item
+David Binderman tests weekly snapshots of GCC trunk against Fedora Rawhide
+for several architectures.
+
+@item
+Laurynas Biveinis for memory management work and DJGPP port fixes.
+
+@item
+Uros Bizjak for the implementation of x87 math built-in functions and
+for various middle end and i386 back end improvements and bug fixes.
+
+@item
+Eric Blake for helping to make GCJ and libgcj conform to the
+specifications.
+
+@item
+Janne Blomqvist for contributions to GNU Fortran.
+
+@item
+Hans-J. Boehm for his garbage collector, IA-64 libffi port, and other
+Java work.
+
+@item
+Segher Boessenkool for helping maintain the PowerPC port and the
+instruction combiner plus various contributions to the middle end.
+
+@item
+Neil Booth for work on cpplib, lang hooks, debug hooks and other
+miscellaneous clean-ups.
+
+@item
+Steven Bosscher for integrating the GNU Fortran front end into GCC and for
+contributing to the tree-ssa branch.
+
+@item
+Eric Botcazou for fixing middle- and backend bugs left and right.
+
+@item
+Per Bothner for his direction via the steering committee and various
+improvements to the infrastructure for supporting new languages. Chill
+front end implementation. Initial implementations of
+cpplib, fix-header, config.guess, libio, and past C++ library (libg++)
+maintainer. Dreaming up, designing and implementing much of GCJ@.
+
+@item
+Devon Bowen helped port GCC to the Tahoe.
+
+@item
+Don Bowman for mips-vxworks contributions.
+
+@item
+James Bowman for the FT32 port.
+
+@item
+Dave Brolley for work on cpplib and Chill.
+
+@item
+Paul Brook for work on the ARM architecture and maintaining GNU Fortran.
+
+@item
+Robert Brown implemented the support for Encore 32000 systems.
+
+@item
+Christian Bruel for improvements to local store elimination.
+
+@item
+Herman A.J. ten Brugge for various fixes.
+
+@item
+Joerg Brunsmann for Java compiler hacking and help with the GCJ FAQ@.
+
+@item
+Joe Buck for his direction via the steering committee from its creation
+to 2013.
+
+@item
+Iain Buclaw for the D frontend.
+
+@item
+Craig Burley for leadership of the G77 Fortran effort.
+
+@item
+Tobias Burnus for contributions to GNU Fortran.
+
+@item
+Stephan Buys for contributing Doxygen notes for libstdc++.
+
+@item
+Paolo Carlini for libstdc++ work: lots of efficiency improvements to
+the C++ strings, streambufs and formatted I/O, hard detective work on
+the frustrating localization issues, and keeping up with the problem reports.
+
+@item
+John Carr for his alias work, SPARC hacking, infrastructure improvements,
+previous contributions to the steering committee, loop optimizations, etc.
+
+@item
+Stephane Carrez for 68HC11 and 68HC12 ports.
+
+@item
+Steve Chamberlain for support for the Renesas SH and H8 processors
+and the PicoJava processor, and for GCJ config fixes.
+
+@item
+Glenn Chambers for help with the GCJ FAQ@.
+
+@item
+John-Marc Chandonia for various libgcj patches.
+
+@item
+Denis Chertykov for contributing and maintaining the AVR port, the first GCC port
+for an 8-bit architecture.
+
+@item
+Kito Cheng for his work on the RISC-V port, including bringing up the test
+suite and maintenance.
+
+@item
+Scott Christley for his Objective-C contributions.
+
+@item
+Eric Christopher for his Java porting help and clean-ups.
+
+@item
+Branko Cibej for more warning contributions.
+
+@item
+The @uref{https://www.gnu.org/software/classpath/,,GNU Classpath project}
+for all of their merged runtime code.
+
+@item
+Nick Clifton for arm, mcore, fr30, v850, m32r, msp430 rx work,
+@option{--help}, and other random hacking.
+
+@item
+Michael Cook for libstdc++ cleanup patches to reduce warnings.
+
+@item
+R. Kelley Cook for making GCC buildable from a read-only directory as
+well as other miscellaneous build process and documentation clean-ups.
+
+@item
+Ralf Corsepius for SH testing and minor bug fixing.
+
+@item
+Fran@,{c}ois-Xavier Coudert for contributions to GNU Fortran.
+
+@item
+Stan Cox for care and feeding of the x86 port and lots of behind
+the scenes hacking.
+
+@item
+Alex Crain provided changes for the 3b1.
+
+@item
+Ian Dall for major improvements to the NS32k port.
+
+@item
+Paul Dale for his work to add uClinux platform support to the
+m68k backend.
+
+@item
+Palmer Dabbelt for his work maintaining the RISC-V port.
+
+@item
+Dario Dariol contributed the four varieties of sample programs
+that print a copy of their source.
+
+@item
+Russell Davidson for fstream and stringstream fixes in libstdc++.
+
+@item
+Bud Davis for work on the G77 and GNU Fortran compilers.
+
+@item
+Mo DeJong for GCJ and libgcj bug fixes.
+
+@item
+Jerry DeLisle for contributions to GNU Fortran.
+
+@item
+DJ Delorie for the DJGPP port, build and libiberty maintenance,
+various bug fixes, and the M32C, MeP, MSP430, and RL78 ports.
+
+@item
+Arnaud Desitter for helping to debug GNU Fortran.
+
+@item
+Gabriel Dos Reis for contributions to G++, contributions and
+maintenance of GCC diagnostics infrastructure, libstdc++-v3,
+including @code{valarray<>}, @code{complex<>}, maintaining the numerics library
+(including that pesky @code{<limits>} :-) and keeping up-to-date anything
+to do with numbers.
+
+@item
+Ulrich Drepper for his work on glibc, testing of GCC using glibc, ISO C99
+support, CFG dumping support, etc., plus support of the C++ runtime
+libraries including for all kinds of C interface issues, contributing and
+maintaining @code{complex<>}, sanity checking and disbursement, configuration
+architecture, libio maintenance, and early math work.
+
+@item
+Fran@,{c}ois Dumont for his work on libstdc++-v3, especially maintaining and
+improving @code{debug-mode} and associative and unordered containers.
+
+@item
+Zdenek Dvorak for a new loop unroller and various fixes.
+
+@item
+Michael Eager for his work on the Xilinx MicroBlaze port.
+
+@item
+Richard Earnshaw for his ongoing work with the ARM@.
+
+@item
+David Edelsohn for his direction via the steering committee, ongoing work
+with the RS6000/PowerPC port, help cleaning up Haifa loop changes,
+doing the entire AIX port of libstdc++ with his bare hands, and for
+ensuring GCC properly keeps working on AIX@.
+
+@item
+Kevin Ediger for the floating point formatting of num_put::do_put in
+libstdc++.
+
+@item
+Phil Edwards for libstdc++ work including configuration hackery,
+documentation maintainer, chief breaker of the web pages, the occasional
+iostream bug fix, and work on shared library symbol versioning.
+
+@item
+Paul Eggert for random hacking all over GCC@.
+
+@item
+Mark Elbrecht for various DJGPP improvements, and for libstdc++
+configuration support for locales and fstream-related fixes.
+
+@item
+Vadim Egorov for libstdc++ fixes in strings, streambufs, and iostreams.
+
+@item
+Christian Ehrhardt for dealing with bug reports.
+
+@item
+Ben Elliston for his work to move the Objective-C runtime into its
+own subdirectory and for his work on autoconf.
+
+@item
+Revital Eres for work on the PowerPC 750CL port.
+
+@item
+Marc Espie for OpenBSD support.
+
+@item
+Doug Evans for much of the global optimization framework, arc, m32r,
+and SPARC work.
+
+@item
+Christopher Faylor for his work on the Cygwin port and for caring and
+feeding the gcc.gnu.org box and saving its users tons of spam.
+
+@item
+Fred Fish for BeOS support and Ada fixes.
+
+@item
+Ivan Fontes Garcia for the Portuguese translation of the GCJ FAQ@.
+
+@item
+Peter Gerwinski for various bug fixes and the Pascal front end.
+
+@item
+Kaveh R.@: Ghazi for his direction via the steering committee, amazing
+work to make @samp{-W -Wall -W* -Werror} useful, and
+testing GCC on a plethora of platforms. Kaveh extends his gratitude to
+the CAIP Center at Rutgers University for providing him with computing
+resources to work on Free Software from the late 1980s to 2010.
+
+@item
+John Gilmore for a donation to the FSF earmarked improving GNU Java.
+
+@item
+Judy Goldberg for c++ contributions.
+
+@item
+Torbjorn Granlund for various fixes and the c-torture testsuite,
+multiply- and divide-by-constant optimization, improved long long
+support, improved leaf function register allocation, and his direction
+via the steering committee.
+
+@item
+Jonny Grant for improvements to @code{collect2's} @option{--help} documentation.
+
+@item
+Anthony Green for his @option{-Os} contributions, the moxie port, and
+Java front end work.
+
+@item
+Stu Grossman for gdb hacking, allowing GCJ developers to debug Java code.
+
+@item
+Michael K. Gschwind contributed the port to the PDP-11.
+
+@item
+Richard Biener for his ongoing middle-end contributions and bug fixes
+and for release management.
+
+@item
+Ron Guilmette implemented the @command{protoize} and @command{unprotoize}
+tools, the support for DWARF 1 symbolic debugging information, and much of
+the support for System V Release 4. He has also worked heavily on the
+Intel 386 and 860 support.
+
+@item
+Sumanth Gundapaneni for contributing the CR16 port.
+
+@item
+Mostafa Hagog for Swing Modulo Scheduling (SMS) and post reload GCSE@.
+
+@item
+Bruno Haible for improvements in the runtime overhead for EH, new
+warnings and assorted bug fixes.
+
+@item
+Andrew Haley for his amazing Java compiler and library efforts.
+
+@item
+Chris Hanson assisted in making GCC work on HP-UX for the 9000 series 300.
+
+@item
+Michael Hayes for various thankless work he's done trying to get
+the c30/c40 ports functional. Lots of loop and unroll improvements and
+fixes.
+
+@item
+Dara Hazeghi for wading through myriads of target-specific bug reports.
+
+@item
+Kate Hedstrom for staking the G77 folks with an initial testsuite.
+
+@item
+Richard Henderson for his ongoing SPARC, alpha, ia32, and ia64 work, loop
+opts, and generally fixing lots of old problems we've ignored for
+years, flow rewrite and lots of further stuff, including reviewing
+tons of patches.
+
+@item
+Aldy Hernandez for working on the PowerPC port, SIMD support, and
+various fixes.
+
+@item
+Nobuyuki Hikichi of Software Research Associates, Tokyo, contributed
+the support for the Sony NEWS machine.
+
+@item
+Kazu Hirata for caring and feeding the Renesas H8/300 port and various fixes.
+
+@item
+Katherine Holcomb for work on GNU Fortran.
+
+@item
+Manfred Hollstein for his ongoing work to keep the m88k alive, lots
+of testing and bug fixing, particularly of GCC configury code.
+
+@item
+Steve Holmgren for MachTen patches.
+
+@item
+Mat Hostetter for work on the TILE-Gx and TILEPro ports.
+
+@item
+Jan Hubicka for his x86 port improvements.
+
+@item
+Falk Hueffner for working on C and optimization bug reports.
+
+@item
+Bernardo Innocenti for his m68k work, including merging of
+ColdFire improvements and uClinux support.
+
+@item
+Christian Iseli for various bug fixes.
+
+@item
+Kamil Iskra for general m68k hacking.
+
+@item
+Lee Iverson for random fixes and MIPS testing.
+
+@item
+Balaji V. Iyer for Cilk+ development and merging.
+
+@item
+Andreas Jaeger for testing and benchmarking of GCC and various bug fixes.
+
+@item
+Martin Jambor for his work on inter-procedural optimizations, the
+switch conversion pass, and scalar replacement of aggregates.
+
+@item
+Jakub Jelinek for his SPARC work and sibling call optimizations as well
+as lots of bug fixes and test cases, and for improving the Java build
+system.
+
+@item
+Janis Johnson for ia64 testing and fixes, her quality improvement
+sidetracks, and web page maintenance.
+
+@item
+Kean Johnston for SCO OpenServer support and various fixes.
+
+@item
+Tim Josling for the sample language treelang based originally on Richard
+Kenner's ``toy'' language.
+
+@item
+Nicolai Josuttis for additional libstdc++ documentation.
+
+@item
+Klaus Kaempf for his ongoing work to make alpha-vms a viable target.
+
+@item
+Steven G. Kargl for work on GNU Fortran.
+
+@item
+David Kashtan of SRI adapted GCC to VMS@.
+
+@item
+Ryszard Kabatek for many, many libstdc++ bug fixes and optimizations of
+strings, especially member functions, and for auto_ptr fixes.
+
+@item
+Geoffrey Keating for his ongoing work to make the PPC work for GNU/Linux
+and his automatic regression tester.
+
+@item
+Brendan Kehoe for his ongoing work with G++ and for a lot of early work
+in just about every part of libstdc++.
+
+@item
+Oliver M. Kellogg of Deutsche Aerospace contributed the port to the
+MIL-STD-1750A@.
+
+@item
+Richard Kenner of the New York University Ultracomputer Research
+Laboratory wrote the machine descriptions for the AMD 29000, the DEC
+Alpha, the IBM RT PC, and the IBM RS/6000 as well as the support for
+instruction attributes. He also made changes to better support RISC
+processors including changes to common subexpression elimination,
+strength reduction, function calling sequence handling, and condition
+code support, in addition to generalizing the code for frame pointer
+elimination and delay slot scheduling. Richard Kenner was also the
+head maintainer of GCC for several years.
+
+@item
+Mumit Khan for various contributions to the Cygwin and Mingw32 ports and
+maintaining binary releases for Microsoft Windows hosts, and for massive libstdc++
+porting work to Cygwin/Mingw32.
+
+@item
+Robin Kirkham for cpu32 support.
+
+@item
+Mark Klein for PA improvements.
+
+@item
+Thomas Koenig for various bug fixes.
+
+@item
+Bruce Korb for the new and improved fixincludes code.
+
+@item
+Benjamin Kosnik for his G++ work and for leading the libstdc++-v3 effort.
+
+@item
+Maxim Kuvyrkov for contributions to the instruction scheduler, the Android
+and m68k/Coldfire ports, and optimizations.
+
+@item
+Charles LaBrec contributed the support for the Integrated Solutions
+68020 system.
+
+@item
+Asher Langton and Mike Kumbera for contributing Cray pointer support
+to GNU Fortran, and for other GNU Fortran improvements.
+
+@item
+Jeff Law for his direction via the steering committee, coordinating the
+entire egcs project and GCC 2.95, rolling out snapshots and releases,
+handling merges from GCC2, reviewing tons of patches that might have
+fallen through the cracks else, and random but extensive hacking.
+
+@item
+Walter Lee for work on the TILE-Gx and TILEPro ports.
+
+@item
+Marc Lehmann for his direction via the steering committee and helping
+with analysis and improvements of x86 performance.
+
+@item
+Victor Leikehman for work on GNU Fortran.
+
+@item
+Ted Lemon wrote parts of the RTL reader and printer.
+
+@item
+Kriang Lerdsuwanakij for C++ improvements including template as template
+parameter support, and many C++ fixes.
+
+@item
+Warren Levy for tremendous work on libgcj (Java Runtime Library) and
+random work on the Java front end.
+
+@item
+Alain Lichnewsky ported GCC to the MIPS CPU@.
+
+@item
+Oskar Liljeblad for hacking on AWT and his many Java bug reports and
+patches.
+
+@item
+Robert Lipe for OpenServer support, new testsuites, testing, etc.
+
+@item
+Chen Liqin for various S+core related fixes/improvement, and for
+maintaining the S+core port.
+
+@item
+Martin Liska for his work on identical code folding, the sanitizers,
+HSA, general bug fixing and for running automated regression testing of GCC
+and reporting numerous bugs.
+
+@item
+Weiwen Liu for testing and various bug fixes.
+
+@item
+Manuel L@'opez-Ib@'a@~nez for improving @option{-Wconversion} and
+many other diagnostics fixes and improvements.
+
+@item
+Dave Love for his ongoing work with the Fortran front end and
+runtime libraries.
+
+@item
+Martin von L@"owis for internal consistency checking infrastructure,
+various C++ improvements including namespace support, and tons of
+assistance with libstdc++/compiler merges.
+
+@item
+H.J. Lu for his previous contributions to the steering committee, many x86
+bug reports, prototype patches, and keeping the GNU/Linux ports working.
+
+@item
+Greg McGary for random fixes and (someday) bounded pointers.
+
+@item
+Andrew MacLeod for his ongoing work in building a real EH system,
+various code generation improvements, work on the global optimizer, etc.
+
+@item
+Vladimir Makarov for hacking some ugly i960 problems, PowerPC hacking
+improvements to compile-time performance, overall knowledge and
+direction in the area of instruction scheduling, design and
+implementation of the automaton based instruction scheduler and
+design and implementation of the integrated and local register allocators.
+
+@item
+David Malcolm for his work on improving GCC diagnostics, JIT, self-tests
+and unit testing.
+
+@item
+Bob Manson for his behind the scenes work on dejagnu.
+
+@item
+John Marino for contributing the DragonFly BSD port.
+
+@item
+Philip Martin for lots of libstdc++ string and vector iterator fixes and
+improvements, and string clean up and testsuites.
+
+@item
+Michael Matz for his work on dominance tree discovery, the x86-64 port,
+link-time optimization framework and general optimization improvements.
+
+@item
+All of the Mauve project contributors for Java test code.
+
+@item
+Bryce McKinlay for numerous GCJ and libgcj fixes and improvements.
+
+@item
+Adam Megacz for his work on the Microsoft Windows port of GCJ@.
+
+@item
+Michael Meissner for LRS framework, ia32, m32r, v850, m88k, MIPS,
+powerpc, haifa, ECOFF debug support, and other assorted hacking.
+
+@item
+Jason Merrill for his direction via the steering committee and leading
+the G++ effort.
+
+@item
+Martin Michlmayr for testing GCC on several architectures using the
+entire Debian archive.
+
+@item
+David Miller for his direction via the steering committee, lots of
+SPARC work, improvements in jump.cc and interfacing with the Linux kernel
+developers.
+
+@item
+Gary Miller ported GCC to Charles River Data Systems machines.
+
+@item
+Alfred Minarik for libstdc++ string and ios bug fixes, and turning the
+entire libstdc++ testsuite namespace-compatible.
+
+@item
+Mark Mitchell for his direction via the steering committee, mountains of
+C++ work, load/store hoisting out of loops, alias analysis improvements,
+ISO C @code{restrict} support, and serving as release manager from 2000
+to 2011.
+
+@item
+Alan Modra for various GNU/Linux bits and testing.
+
+@item
+Toon Moene for his direction via the steering committee, Fortran
+maintenance, and his ongoing work to make us make Fortran run fast.
+
+@item
+Jason Molenda for major help in the care and feeding of all the services
+on the gcc.gnu.org (formerly egcs.cygnus.com) machine---mail, web
+services, ftp services, etc etc. Doing all this work on scrap paper and
+the backs of envelopes would have been@dots{} difficult.
+
+@item
+Catherine Moore for fixing various ugly problems we have sent her
+way, including the haifa bug which was killing the Alpha & PowerPC
+Linux kernels.
+
+@item
+Mike Moreton for his various Java patches.
+
+@item
+David Mosberger-Tang for various Alpha improvements, and for the initial
+IA-64 port.
+
+@item
+Stephen Moshier contributed the floating point emulator that assists in
+cross-compilation and permits support for floating point numbers wider
+than 64 bits and for ISO C99 support.
+
+@item
+Bill Moyer for his behind the scenes work on various issues.
+
+@item
+Philippe De Muyter for his work on the m68k port.
+
+@item
+Joseph S. Myers for his work on the PDP-11 port, format checking and ISO
+C99 support, and continuous emphasis on (and contributions to) documentation.
+
+@item
+Nathan Myers for his work on libstdc++-v3: architecture and authorship
+through the first three snapshots, including implementation of locale
+infrastructure, string, shadow C headers, and the initial project
+documentation (DESIGN, CHECKLIST, and so forth). Later, more work on
+MT-safe string and shadow headers.
+
+@item
+Felix Natter for documentation on porting libstdc++.
+
+@item
+Nathanael Nerode for cleaning up the configuration/build process.
+
+@item
+NeXT, Inc.@: donated the front end that supports the Objective-C
+language.
+
+@item
+Hans-Peter Nilsson for the CRIS and MMIX ports, improvements to the search
+engine setup, various documentation fixes and other small fixes.
+
+@item
+Geoff Noer for his work on getting cygwin native builds working.
+
+@item
+Vegard Nossum for running automated regression testing of GCC and reporting
+numerous bugs.
+
+@item
+Diego Novillo for his work on Tree SSA, OpenMP, SPEC performance
+tracking web pages, GIMPLE tuples, and assorted fixes.
+
+@item
+David O'Brien for the FreeBSD/alpha, FreeBSD/AMD x86-64, FreeBSD/ARM,
+FreeBSD/PowerPC, and FreeBSD/SPARC64 ports and related infrastructure
+improvements.
+
+@item
+Alexandre Oliva for various build infrastructure improvements, scripts and
+amazing testing work, including keeping libtool issues sane and happy.
+
+@item
+Stefan Olsson for work on mt_alloc.
+
+@item
+Melissa O'Neill for various NeXT fixes.
+
+@item
+Rainer Orth for random MIPS work, including improvements to GCC's o32
+ABI support, improvements to dejagnu's MIPS support, Java configuration
+clean-ups and porting work, and maintaining the IRIX, Solaris 2, and
+Tru64 UNIX ports.
+
+@item
+Steven Pemberton for his contribution of @file{enquire} which allowed GCC to
+determine various properties of the floating point unit and generate
+@file{float.h} in older versions of GCC.
+
+@item
+Hartmut Penner for work on the s390 port.
+
+@item
+Paul Petersen wrote the machine description for the Alliant FX/8.
+
+@item
+Alexandre Petit-Bianco for implementing much of the Java compiler and
+continued Java maintainership.
+
+@item
+Matthias Pfaller for major improvements to the NS32k port.
+
+@item
+Gerald Pfeifer for his direction via the steering committee, pointing
+out lots of problems we need to solve, maintenance of the web pages, and
+taking care of documentation maintenance in general.
+
+@item
+Marek Polacek for his work on the C front end, the sanitizers and general
+bug fixing.
+
+@item
+Andrew Pinski for processing bug reports by the dozen.
+
+@item
+Ovidiu Predescu for his work on the Objective-C front end and runtime
+libraries.
+
+@item
+Jerry Quinn for major performance improvements in C++ formatted I/O@.
+
+@item
+Ken Raeburn for various improvements to checker, MIPS ports and various
+cleanups in the compiler.
+
+@item
+Rolf W. Rasmussen for hacking on AWT@.
+
+@item
+David Reese of Sun Microsystems contributed to the Solaris on PowerPC
+port.
+
+@item
+John Regehr for running automated regression testing of GCC and reporting
+numerous bugs.
+
+@item
+Volker Reichelt for running automated regression testing of GCC and reporting
+numerous bugs and for keeping up with the problem reports.
+
+@item
+Joern Rennecke for maintaining the sh port, loop, regmove & reload
+hacking and developing and maintaining the Epiphany port.
+
+@item
+Loren J. Rittle for improvements to libstdc++-v3 including the FreeBSD
+port, threading fixes, thread-related configury changes, critical
+threading documentation, and solutions to really tricky I/O problems,
+as well as keeping GCC properly working on FreeBSD and continuous testing.
+
+@item
+Craig Rodrigues for processing tons of bug reports.
+
+@item
+Ola R@"onnerup for work on mt_alloc.
+
+@item
+Gavin Romig-Koch for lots of behind the scenes MIPS work.
+
+@item
+David Ronis inspired and encouraged Craig to rewrite the G77
+documentation in texinfo format by contributing a first pass at a
+translation of the old @file{g77-0.5.16/f/DOC} file.
+
+@item
+Ken Rose for fixes to GCC's delay slot filling code.
+
+@item
+Ira Rosen for her contributions to the auto-vectorizer.
+
+@item
+Paul Rubin wrote most of the preprocessor.
+
+@item
+P@'etur Run@'olfsson for major performance improvements in C++ formatted I/O and
+large file support in C++ filebuf.
+
+@item
+Chip Salzenberg for libstdc++ patches and improvements to locales, traits,
+Makefiles, libio, libtool hackery, and ``long long'' support.
+
+@item
+Juha Sarlin for improvements to the H8 code generator.
+
+@item
+Greg Satz assisted in making GCC work on HP-UX for the 9000 series 300.
+
+@item
+Roger Sayle for improvements to constant folding and GCC's RTL optimizers
+as well as for fixing numerous bugs.
+
+@item
+Bradley Schatz for his work on the GCJ FAQ@.
+
+@item
+Peter Schauer wrote the code to allow debugging to work on the Alpha.
+
+@item
+William Schelter did most of the work on the Intel 80386 support.
+
+@item
+Tobias Schl@"uter for work on GNU Fortran.
+
+@item
+Bernd Schmidt for various code generation improvements and major
+work in the reload pass, serving as release manager for
+GCC 2.95.3, and work on the Blackfin and C6X ports.
+
+@item
+Peter Schmid for constant testing of libstdc++---especially application
+testing, going above and beyond what was requested for the release
+criteria---and libstdc++ header file tweaks.
+
+@item
+Jason Schroeder for jcf-dump patches.
+
+@item
+Andreas Schwab for his work on the m68k port.
+
+@item
+Lars Segerlund for work on GNU Fortran.
+
+@item
+Dodji Seketeli for numerous C++ bug fixes and debug info improvements.
+
+@item
+Tim Shen for major work on @code{<regex>}.
+
+@item
+Joel Sherrill for his direction via the steering committee, RTEMS
+contributions and RTEMS testing.
+
+@item
+Nathan Sidwell for many C++ fixes/improvements.
+
+@item
+Jeffrey Siegal for helping RMS with the original design of GCC, some
+code which handles the parse tree and RTL data structures, constant
+folding and help with the original VAX & m68k ports.
+
+@item
+Kenny Simpson for prompting libstdc++ fixes due to defect reports from
+the LWG (thereby keeping GCC in line with updates from the ISO)@.
+
+@item
+Franz Sirl for his ongoing work with making the PPC port stable
+for GNU/Linux.
+
+@item
+Andrey Slepuhin for assorted AIX hacking.
+
+@item
+Trevor Smigiel for contributing the SPU port.
+
+@item
+Christopher Smith did the port for Convex machines.
+
+@item
+Danny Smith for his major efforts on the Mingw (and Cygwin) ports.
+Retired from GCC maintainership August 2010, having mentored two
+new maintainers into the role.
+
+@item
+Randy Smith finished the Sun FPA support.
+
+@item
+Ed Smith-Rowland for his continuous work on libstdc++-v3, special functions,
+@code{<random>}, and various improvements to C++11 features.
+
+@item
+Scott Snyder for queue, iterator, istream, and string fixes and libstdc++
+testsuite entries. Also for providing the patch to G77 to add
+rudimentary support for @code{INTEGER*1}, @code{INTEGER*2}, and
+@code{LOGICAL*1}.
+
+@item
+Zdenek Sojka for running automated regression testing of GCC and reporting
+numerous bugs.
+
+@item
+Arseny Solokha for running automated regression testing of GCC and reporting
+numerous bugs.
+
+@item
+Jayant Sonar for contributing the CR16 port.
+
+@item
+Brad Spencer for contributions to the GLIBCPP_FORCE_NEW technique.
+
+@item
+Richard Stallman, for writing the original GCC and launching the GNU project.
+
+@item
+Jan Stein of the Chalmers Computer Society provided support for
+Genix, as well as part of the 32000 machine description.
+
+@item
+Gerhard Steinmetz for running automated regression testing of GCC and reporting
+numerous bugs.
+
+@item
+Nigel Stephens for various mips16 related fixes/improvements.
+
+@item
+Jonathan Stone wrote the machine description for the Pyramid computer.
+
+@item
+Graham Stott for various infrastructure improvements.
+
+@item
+John Stracke for his Java HTTP protocol fixes.
+
+@item
+Mike Stump for his Elxsi port, G++ contributions over the years and more
+recently his vxworks contributions
+
+@item
+Jeff Sturm for Java porting help, bug fixes, and encouragement.
+
+@item
+Zhendong Su for running automated regression testing of GCC and reporting
+numerous bugs.
+
+@item
+Chengnian Sun for running automated regression testing of GCC and reporting
+numerous bugs.
+
+@item
+Shigeya Suzuki for this fixes for the bsdi platforms.
+
+@item
+Ian Lance Taylor for the Go frontend, the initial mips16 and mips64
+support, general configury hacking, fixincludes, etc.
+
+@item
+Holger Teutsch provided the support for the Clipper CPU@.
+
+@item
+Gary Thomas for his ongoing work to make the PPC work for GNU/Linux.
+
+@item
+Paul Thomas for contributions to GNU Fortran.
+
+@item
+Philipp Thomas for random bug fixes throughout the compiler
+
+@item
+Jason Thorpe for thread support in libstdc++ on NetBSD@.
+
+@item
+Kresten Krab Thorup wrote the run time support for the Objective-C
+language and the fantastic Java bytecode interpreter.
+
+@item
+Michael Tiemann for random bug fixes, the first instruction scheduler,
+initial C++ support, function integration, NS32k, SPARC and M88k
+machine description work, delay slot scheduling.
+
+@item
+Andreas Tobler for his work porting libgcj to Darwin.
+
+@item
+Teemu Torma for thread safe exception handling support.
+
+@item
+Leonard Tower wrote parts of the parser, RTL generator, and RTL
+definitions, and of the VAX machine description.
+
+@item
+Daniel Towner and Hariharan Sandanagobalane contributed and
+maintain the picoChip port.
+
+@item
+Tom Tromey for internationalization support and for his many Java
+contributions and libgcj maintainership.
+
+@item
+Lassi Tuura for improvements to config.guess to determine HP processor
+types.
+
+@item
+Petter Urkedal for libstdc++ CXXFLAGS, math, and algorithms fixes.
+
+@item
+Andy Vaught for the design and initial implementation of the GNU Fortran
+front end.
+
+@item
+Brent Verner for work with the libstdc++ cshadow files and their
+associated configure steps.
+
+@item
+Todd Vierling for contributions for NetBSD ports.
+
+@item
+Andrew Waterman for contributing the RISC-V port, as well as maintaining it.
+
+@item
+Jonathan Wakely for contributing libstdc++ Doxygen notes and XHTML
+guidance and maintaining libstdc++.
+
+@item
+Dean Wakerley for converting the install documentation from HTML to texinfo
+in time for GCC 3.0.
+
+@item
+Krister Walfridsson for random bug fixes.
+
+@item
+Feng Wang for contributions to GNU Fortran.
+
+@item
+Stephen M. Webb for time and effort on making libstdc++ shadow files
+work with the tricky Solaris 8+ headers, and for pushing the build-time
+header tree. Also, for starting and driving the @code{<regex>} effort.
+
+@item
+John Wehle for various improvements for the x86 code generator,
+related infrastructure improvements to help x86 code generation,
+value range propagation and other work, WE32k port.
+
+@item
+Ulrich Weigand for work on the s390 port.
+
+@item
+Janus Weil for contributions to GNU Fortran.
+
+@item
+Zack Weinberg for major work on cpplib and various other bug fixes.
+
+@item
+Matt Welsh for help with Linux Threads support in GCJ@.
+
+@item
+Urban Widmark for help fixing java.io.
+
+@item
+Mark Wielaard for new Java library code and his work integrating with
+Classpath.
+
+@item
+Dale Wiles helped port GCC to the Tahoe.
+
+@item
+Bob Wilson from Tensilica, Inc.@: for the Xtensa port.
+
+@item
+Jim Wilson for his direction via the steering committee, tackling hard
+problems in various places that nobody else wanted to work on, strength
+reduction and other loop optimizations.
+
+@item
+Paul Woegerer and Tal Agmon for the CRX port.
+
+@item
+Carlo Wood for various fixes.
+
+@item
+Tom Wood for work on the m88k port.
+
+@item
+Chung-Ju Wu for his work on the Andes NDS32 port.
+
+@item
+Canqun Yang for work on GNU Fortran.
+
+@item
+Masanobu Yuhara of Fujitsu Laboratories implemented the machine
+description for the Tron architecture (specifically, the Gmicro).
+
+@item
+Kevin Zachmann helped port GCC to the Tahoe.
+
+@item
+Ayal Zaks for Swing Modulo Scheduling (SMS).
+
+@item
+Qirun Zhang for running automated regression testing of GCC and reporting
+numerous bugs.
+
+@item
+Xiaoqiang Zhang for work on GNU Fortran.
+
+@item
+Gilles Zunino for help porting Java to Irix.
+
+@end itemize
+
+The following people are recognized for their contributions to GNAT,
+the Ada front end of GCC:
+@itemize @bullet
+@item
+Bernard Banner
+
+@item
+Romain Berrendonner
+
+@item
+Geert Bosch
+
+@item
+Emmanuel Briot
+
+@item
+Joel Brobecker
+
+@item
+Ben Brosgol
+
+@item
+Vincent Celier
+
+@item
+Arnaud Charlet
+
+@item
+Chien Chieng
+
+@item
+Cyrille Comar
+
+@item
+Cyrille Crozes
+
+@item
+Robert Dewar
+
+@item
+Gary Dismukes
+
+@item
+Robert Duff
+
+@item
+Ed Falis
+
+@item
+Ramon Fernandez
+
+@item
+Sam Figueroa
+
+@item
+Vasiliy Fofanov
+
+@item
+Michael Friess
+
+@item
+Franco Gasperoni
+
+@item
+Ted Giering
+
+@item
+Matthew Gingell
+
+@item
+Laurent Guerby
+
+@item
+Jerome Guitton
+
+@item
+Olivier Hainque
+
+@item
+Jerome Hugues
+
+@item
+Hristian Kirtchev
+
+@item
+Jerome Lambourg
+
+@item
+Bruno Leclerc
+
+@item
+Albert Lee
+
+@item
+Sean McNeil
+
+@item
+Javier Miranda
+
+@item
+Laurent Nana
+
+@item
+Pascal Obry
+
+@item
+Dong-Ik Oh
+
+@item
+Laurent Pautet
+
+@item
+Brett Porter
+
+@item
+Thomas Quinot
+
+@item
+Nicolas Roche
+
+@item
+Pat Rogers
+
+@item
+Jose Ruiz
+
+@item
+Douglas Rupp
+
+@item
+Sergey Rybin
+
+@item
+Gail Schenker
+
+@item
+Ed Schonberg
+
+@item
+Nicolas Setton
+
+@item
+Samuel Tardieu
+
+@end itemize
+
+
+The following people are recognized for their contributions of new
+features, bug reports, testing and integration of classpath/libgcj for
+GCC version 4.1:
+@itemize @bullet
+@item
+Lillian Angel for @code{JTree} implementation and lots Free Swing
+additions and bug fixes.
+
+@item
+Wolfgang Baer for @code{GapContent} bug fixes.
+
+@item
+Anthony Balkissoon for @code{JList}, Free Swing 1.5 updates and mouse event
+fixes, lots of Free Swing work including @code{JTable} editing.
+
+@item
+Stuart Ballard for RMI constant fixes.
+
+@item
+Goffredo Baroncelli for @code{HTTPURLConnection} fixes.
+
+@item
+Gary Benson for @code{MessageFormat} fixes.
+
+@item
+Daniel Bonniot for @code{Serialization} fixes.
+
+@item
+Chris Burdess for lots of gnu.xml and http protocol fixes, @code{StAX}
+and @code{DOM xml:id} support.
+
+@item
+Ka-Hing Cheung for @code{TreePath} and @code{TreeSelection} fixes.
+
+@item
+Archie Cobbs for build fixes, VM interface updates,
+@code{URLClassLoader} updates.
+
+@item
+Kelley Cook for build fixes.
+
+@item
+Martin Cordova for Suggestions for better @code{SocketTimeoutException}.
+
+@item
+David Daney for @code{BitSet} bug fixes, @code{HttpURLConnection}
+rewrite and improvements.
+
+@item
+Thomas Fitzsimmons for lots of upgrades to the gtk+ AWT and Cairo 2D
+support. Lots of imageio framework additions, lots of AWT and Free
+Swing bug fixes.
+
+@item
+Jeroen Frijters for @code{ClassLoader} and nio cleanups, serialization fixes,
+better @code{Proxy} support, bug fixes and IKVM integration.
+
+@item
+Santiago Gala for @code{AccessControlContext} fixes.
+
+@item
+Nicolas Geoffray for @code{VMClassLoader} and @code{AccessController}
+improvements.
+
+@item
+David Gilbert for @code{basic} and @code{metal} icon and plaf support
+and lots of documenting, Lots of Free Swing and metal theme
+additions. @code{MetalIconFactory} implementation.
+
+@item
+Anthony Green for @code{MIDI} framework, @code{ALSA} and @code{DSSI}
+providers.
+
+@item
+Andrew Haley for @code{Serialization} and @code{URLClassLoader} fixes,
+gcj build speedups.
+
+@item
+Kim Ho for @code{JFileChooser} implementation.
+
+@item
+Andrew John Hughes for @code{Locale} and net fixes, URI RFC2986
+updates, @code{Serialization} fixes, @code{Properties} XML support and
+generic branch work, VMIntegration guide update.
+
+@item
+Bastiaan Huisman for @code{TimeZone} bug fixing.
+
+@item
+Andreas Jaeger for mprec updates.
+
+@item
+Paul Jenner for better @option{-Werror} support.
+
+@item
+Ito Kazumitsu for @code{NetworkInterface} implementation and updates.
+
+@item
+Roman Kennke for @code{BoxLayout}, @code{GrayFilter} and
+@code{SplitPane}, plus bug fixes all over. Lots of Free Swing work
+including styled text.
+
+@item
+Simon Kitching for @code{String} cleanups and optimization suggestions.
+
+@item
+Michael Koch for configuration fixes, @code{Locale} updates, bug and
+build fixes.
+
+@item
+Guilhem Lavaux for configuration, thread and channel fixes and Kaffe
+integration. JCL native @code{Pointer} updates. Logger bug fixes.
+
+@item
+David Lichteblau for JCL support library global/local reference
+cleanups.
+
+@item
+Aaron Luchko for JDWP updates and documentation fixes.
+
+@item
+Ziga Mahkovec for @code{Graphics2D} upgraded to Cairo 0.5 and new regex
+features.
+
+@item
+Sven de Marothy for BMP imageio support, CSS and @code{TextLayout}
+fixes. @code{GtkImage} rewrite, 2D, awt, free swing and date/time fixes and
+implementing the Qt4 peers.
+
+@item
+Casey Marshall for crypto algorithm fixes, @code{FileChannel} lock,
+@code{SystemLogger} and @code{FileHandler} rotate implementations, NIO
+@code{FileChannel.map} support, security and policy updates.
+
+@item
+Bryce McKinlay for RMI work.
+
+@item
+Audrius Meskauskas for lots of Free Corba, RMI and HTML work plus
+testing and documenting.
+
+@item
+Kalle Olavi Niemitalo for build fixes.
+
+@item
+Rainer Orth for build fixes.
+
+@item
+Andrew Overholt for @code{File} locking fixes.
+
+@item
+Ingo Proetel for @code{Image}, @code{Logger} and @code{URLClassLoader}
+updates.
+
+@item
+Olga Rodimina for @code{MenuSelectionManager} implementation.
+
+@item
+Jan Roehrich for @code{BasicTreeUI} and @code{JTree} fixes.
+
+@item
+Julian Scheid for documentation updates and gjdoc support.
+
+@item
+Christian Schlichtherle for zip fixes and cleanups.
+
+@item
+Robert Schuster for documentation updates and beans fixes,
+@code{TreeNode} enumerations and @code{ActionCommand} and various
+fixes, XML and URL, AWT and Free Swing bug fixes.
+
+@item
+Keith Seitz for lots of JDWP work.
+
+@item
+Christian Thalinger for 64-bit cleanups, Configuration and VM
+interface fixes and @code{CACAO} integration, @code{fdlibm} updates.
+
+@item
+Gael Thomas for @code{VMClassLoader} boot packages support suggestions.
+
+@item
+Andreas Tobler for Darwin and Solaris testing and fixing, @code{Qt4}
+support for Darwin/OS X, @code{Graphics2D} support, @code{gtk+}
+updates.
+
+@item
+Dalibor Topic for better @code{DEBUG} support, build cleanups and
+Kaffe integration. @code{Qt4} build infrastructure, @code{SHA1PRNG}
+and @code{GdkPixbugDecoder} updates.
+
+@item
+Tom Tromey for Eclipse integration, generics work, lots of bug fixes
+and gcj integration including coordinating The Big Merge.
+
+@item
+Mark Wielaard for bug fixes, packaging and release management,
+@code{Clipboard} implementation, system call interrupts and network
+timeouts and @code{GdkPixpufDecoder} fixes.
+
+@end itemize
+
+
+In addition to the above, all of which also contributed time and energy in
+testing GCC, we would like to thank the following for their contributions
+to testing:
+
+@itemize @bullet
+@item
+Michael Abd-El-Malek
+
+@item
+Thomas Arend
+
+@item
+Bonzo Armstrong
+
+@item
+Steven Ashe
+
+@item
+Chris Baldwin
+
+@item
+David Billinghurst
+
+@item
+Jim Blandy
+
+@item
+Stephane Bortzmeyer
+
+@item
+Horst von Brand
+
+@item
+Frank Braun
+
+@item
+Rodney Brown
+
+@item
+Sidney Cadot
+
+@item
+Bradford Castalia
+
+@item
+Robert Clark
+
+@item
+Jonathan Corbet
+
+@item
+Ralph Doncaster
+
+@item
+Richard Emberson
+
+@item
+Levente Farkas
+
+@item
+Graham Fawcett
+
+@item
+Mark Fernyhough
+
+@item
+Robert A. French
+
+@item
+J@"orgen Freyh
+
+@item
+Mark K. Gardner
+
+@item
+Charles-Antoine Gauthier
+
+@item
+Yung Shing Gene
+
+@item
+David Gilbert
+
+@item
+Simon Gornall
+
+@item
+Fred Gray
+
+@item
+John Griffin
+
+@item
+Patrik Hagglund
+
+@item
+Phil Hargett
+
+@item
+Amancio Hasty
+
+@item
+Takafumi Hayashi
+
+@item
+Bryan W. Headley
+
+@item
+Kevin B. Hendricks
+
+@item
+Joep Jansen
+
+@item
+Christian Joensson
+
+@item
+Michel Kern
+
+@item
+David Kidd
+
+@item
+Tobias Kuipers
+
+@item
+Anand Krishnaswamy
+
+@item
+A. O. V. Le Blanc
+
+@item
+llewelly
+
+@item
+Damon Love
+
+@item
+Brad Lucier
+
+@item
+Matthias Klose
+
+@item
+Martin Knoblauch
+
+@item
+Rick Lutowski
+
+@item
+Jesse Macnish
+
+@item
+Stefan Morrell
+
+@item
+Anon A. Mous
+
+@item
+Matthias Mueller
+
+@item
+Pekka Nikander
+
+@item
+Rick Niles
+
+@item
+Jon Olson
+
+@item
+Magnus Persson
+
+@item
+Chris Pollard
+
+@item
+Richard Polton
+
+@item
+Derk Reefman
+
+@item
+David Rees
+
+@item
+Paul Reilly
+
+@item
+Tom Reilly
+
+@item
+Torsten Rueger
+
+@item
+Danny Sadinoff
+
+@item
+Marc Schifer
+
+@item
+Erik Schnetter
+
+@item
+Wayne K. Schroll
+
+@item
+David Schuler
+
+@item
+Vin Shelton
+
+@item
+Tim Souder
+
+@item
+Adam Sulmicki
+
+@item
+Bill Thorson
+
+@item
+George Talbot
+
+@item
+Pedro A. M. Vazquez
+
+@item
+Gregory Warnes
+
+@item
+Ian Watson
+
+@item
+David E. Young
+
+@item
+And many others
+@end itemize
+
+And finally we'd like to thank everyone who uses the compiler, provides
+feedback and generally reminds us why we're doing this work in the first
+place.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Contributing
+@chapter Contributing to GCC Development
+
+If you would like to help pretest GCC releases to assure they work well,
+current development sources are available via Git (see
+@uref{https://gcc.gnu.org/git.html}). Source and binary snapshots are
+also available for FTP; see @uref{https://gcc.gnu.org/snapshots.html}.
+
+If you would like to work on improvements to GCC, please read the
+advice at these URLs:
+
+@smallexample
+@uref{https://gcc.gnu.org/contribute.html}
+@uref{https://gcc.gnu.org/contributewhy.html}
+@end smallexample
+
+@noindent
+for information on how to make useful contributions and avoid
+duplication of effort. Suggested projects are listed at
+@uref{https://gcc.gnu.org/projects/}.
--- /dev/null
+\input texinfo
+@setfilename cpp.info
+@settitle The C Preprocessor
+@setchapternewpage off
+@c @smallbook
+@c @cropmarks
+@c @finalout
+
+@include gcc-common.texi
+
+@copying
+@c man begin COPYRIGHT
+Copyright @copyright{} 1987-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation. A copy of
+the license is included in the
+@c man end
+section entitled ``GNU Free Documentation License''.
+@ignore
+@c man begin COPYRIGHT
+man page gfdl(7).
+@c man end
+@end ignore
+
+@c man begin COPYRIGHT
+This manual contains no Invariant Sections. The Front-Cover Texts are
+(a) (see below), and the Back-Cover Texts are (b) (see below).
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@end copying
+
+@c Create a separate index for command line options.
+@defcodeindex op
+@syncodeindex vr op
+
+@c Used in cppopts.texi and cppenv.texi.
+@set cppmanual
+
+@ifinfo
+@dircategory Software development
+@direntry
+* Cpp: (cpp). The GNU C preprocessor.
+@end direntry
+@end ifinfo
+
+@titlepage
+@title The C Preprocessor
+@versionsubtitle
+@author Richard M. Stallman, Zachary Weinberg
+@page
+@c There is a fill at the bottom of the page, so we need a filll to
+@c override it.
+@vskip 0pt plus 1filll
+@insertcopying
+@end titlepage
+@contents
+@page
+
+@ifnottex
+@node Top
+@top
+The C preprocessor implements the macro language used to transform C,
+C++, and Objective-C programs before they are compiled. It can also be
+useful on its own.
+
+@menu
+* Overview::
+* Header Files::
+* Macros::
+* Conditionals::
+* Diagnostics::
+* Line Control::
+* Pragmas::
+* Other Directives::
+* Preprocessor Output::
+* Traditional Mode::
+* Implementation Details::
+* Invocation::
+* Environment Variables::
+* GNU Free Documentation License::
+* Index of Directives::
+* Option Index::
+* Concept Index::
+
+@detailmenu
+ --- The Detailed Node Listing ---
+
+Overview
+
+* Character sets::
+* Initial processing::
+* Tokenization::
+* The preprocessing language::
+
+Header Files
+
+* Include Syntax::
+* Include Operation::
+* Search Path::
+* Once-Only Headers::
+* Alternatives to Wrapper #ifndef::
+* Computed Includes::
+* Wrapper Headers::
+* System Headers::
+
+Macros
+
+* Object-like Macros::
+* Function-like Macros::
+* Macro Arguments::
+* Stringizing::
+* Concatenation::
+* Variadic Macros::
+* Predefined Macros::
+* Undefining and Redefining Macros::
+* Directives Within Macro Arguments::
+* Macro Pitfalls::
+
+Predefined Macros
+
+* Standard Predefined Macros::
+* Common Predefined Macros::
+* System-specific Predefined Macros::
+* C++ Named Operators::
+
+Macro Pitfalls
+
+* Misnesting::
+* Operator Precedence Problems::
+* Swallowing the Semicolon::
+* Duplication of Side Effects::
+* Self-Referential Macros::
+* Argument Prescan::
+* Newlines in Arguments::
+
+Conditionals
+
+* Conditional Uses::
+* Conditional Syntax::
+* Deleted Code::
+
+Conditional Syntax
+
+* Ifdef::
+* If::
+* Defined::
+* Else::
+* Elif::
+
+Implementation Details
+
+* Implementation-defined behavior::
+* Implementation limits::
+* Obsolete Features::
+
+Obsolete Features
+
+* Obsolete Features::
+
+@end detailmenu
+@end menu
+
+@insertcopying
+@end ifnottex
+
+@node Overview
+@chapter Overview
+@c man begin DESCRIPTION
+The C preprocessor, often known as @dfn{cpp}, is a @dfn{macro processor}
+that is used automatically by the C compiler to transform your program
+before compilation. It is called a macro processor because it allows
+you to define @dfn{macros}, which are brief abbreviations for longer
+constructs.
+
+The C preprocessor is intended to be used only with C, C++, and
+Objective-C source code. In the past, it has been abused as a general
+text processor. It will choke on input which does not obey C's lexical
+rules. For example, apostrophes will be interpreted as the beginning of
+character constants, and cause errors. Also, you cannot rely on it
+preserving characteristics of the input which are not significant to
+C-family languages. If a Makefile is preprocessed, all the hard tabs
+will be removed, and the Makefile will not work.
+
+Having said that, you can often get away with using cpp on things which
+are not C@. Other Algol-ish programming languages are often safe
+(Ada, etc.) So is assembly, with caution. @option{-traditional-cpp}
+mode preserves more white space, and is otherwise more permissive. Many
+of the problems can be avoided by writing C or C++ style comments
+instead of native language comments, and keeping macros simple.
+
+Wherever possible, you should use a preprocessor geared to the language
+you are writing in. Modern versions of the GNU assembler have macro
+facilities. Most high level programming languages have their own
+conditional compilation and inclusion mechanism. If all else fails,
+try a true general text processor, such as GNU M4.
+
+C preprocessors vary in some details. This manual discusses the GNU C
+preprocessor, which provides a small superset of the features of ISO
+Standard C@. In its default mode, the GNU C preprocessor does not do a
+few things required by the standard. These are features which are
+rarely, if ever, used, and may cause surprising changes to the meaning
+of a program which does not expect them. To get strict ISO Standard C,
+you should use the @option{-std=c90}, @option{-std=c99},
+@option{-std=c11} or @option{-std=c17} options, depending
+on which version of the standard you want. To get all the mandatory
+diagnostics, you must also use @option{-pedantic}. @xref{Invocation}.
+
+This manual describes the behavior of the ISO preprocessor. To
+minimize gratuitous differences, where the ISO preprocessor's
+behavior does not conflict with traditional semantics, the
+traditional preprocessor should behave the same way. The various
+differences that do exist are detailed in the section @ref{Traditional
+Mode}.
+
+For clarity, unless noted otherwise, references to @samp{CPP} in this
+manual refer to GNU CPP@.
+@c man end
+
+@menu
+* Character sets::
+* Initial processing::
+* Tokenization::
+* The preprocessing language::
+@end menu
+
+@node Character sets
+@section Character sets
+
+Source code character set processing in C and related languages is
+rather complicated. The C standard discusses two character sets, but
+there are really at least four.
+
+The files input to CPP might be in any character set at all. CPP's
+very first action, before it even looks for line boundaries, is to
+convert the file into the character set it uses for internal
+processing. That set is what the C standard calls the @dfn{source}
+character set. It must be isomorphic with ISO 10646, also known as
+Unicode. CPP uses the UTF-8 encoding of Unicode.
+
+The character sets of the input files are specified using the
+@option{-finput-charset=} option.
+
+All preprocessing work (the subject of the rest of this manual) is
+carried out in the source character set. If you request textual
+output from the preprocessor with the @option{-E} option, it will be
+in UTF-8.
+
+After preprocessing is complete, string and character constants are
+converted again, into the @dfn{execution} character set. This
+character set is under control of the user; the default is UTF-8,
+matching the source character set. Wide string and character
+constants have their own character set, which is not called out
+specifically in the standard. Again, it is under control of the user.
+The default is UTF-16 or UTF-32, whichever fits in the target's
+@code{wchar_t} type, in the target machine's byte
+order.@footnote{UTF-16 does not meet the requirements of the C
+standard for a wide character set, but the choice of 16-bit
+@code{wchar_t} is enshrined in some system ABIs so we cannot fix
+this.} Octal and hexadecimal escape sequences do not undergo
+conversion; @t{'\x12'} has the value 0x12 regardless of the currently
+selected execution character set. All other escapes are replaced by
+the character in the source character set that they represent, then
+converted to the execution character set, just like unescaped
+characters.
+
+In identifiers, characters outside the ASCII range can be specified
+with the @samp{\u} and @samp{\U} escapes or used directly in the input
+encoding. If strict ISO C90 conformance is specified with an option
+such as @option{-std=c90}, or @option{-fno-extended-identifiers} is
+used, then those constructs are not permitted in identifiers.
+
+@node Initial processing
+@section Initial processing
+
+The preprocessor performs a series of textual transformations on its
+input. These happen before all other processing. Conceptually, they
+happen in a rigid order, and the entire file is run through each
+transformation before the next one begins. CPP actually does them
+all at once, for performance reasons. These transformations correspond
+roughly to the first three ``phases of translation'' described in the C
+standard.
+
+@enumerate
+@item
+@cindex line endings
+The input file is read into memory and broken into lines.
+
+Different systems use different conventions to indicate the end of a
+line. GCC accepts the ASCII control sequences @kbd{LF}, @kbd{@w{CR
+LF}} and @kbd{CR} as end-of-line markers. These are the canonical
+sequences used by Unix, DOS and VMS, and the classic Mac OS (before
+OSX) respectively. You may therefore safely copy source code written
+on any of those systems to a different one and use it without
+conversion. (GCC may lose track of the current line number if a file
+doesn't consistently use one convention, as sometimes happens when it
+is edited on computers with different conventions that share a network
+file system.)
+
+If the last line of any input file lacks an end-of-line marker, the end
+of the file is considered to implicitly supply one. The C standard says
+that this condition provokes undefined behavior, so GCC will emit a
+warning message.
+
+@item
+@cindex trigraphs
+@anchor{trigraphs}If trigraphs are enabled, they are replaced by their
+corresponding single characters. By default GCC ignores trigraphs,
+but if you request a strictly conforming mode with the @option{-std}
+option, or you specify the @option{-trigraphs} option, then it
+converts them.
+
+These are nine three-character sequences, all starting with @samp{??},
+that are defined by ISO C to stand for single characters. They permit
+obsolete systems that lack some of C's punctuation to use C@. For
+example, @samp{??/} stands for @samp{\}, so @t{'??/n'} is a character
+constant for a newline.
+
+Trigraphs are not popular and many compilers implement them
+incorrectly. Portable code should not rely on trigraphs being either
+converted or ignored. With @option{-Wtrigraphs} GCC will warn you
+when a trigraph may change the meaning of your program if it were
+converted. @xref{Wtrigraphs}.
+
+In a string constant, you can prevent a sequence of question marks
+from being confused with a trigraph by inserting a backslash between
+the question marks, or by separating the string literal at the
+trigraph and making use of string literal concatenation. @t{"(??\?)"}
+is the string @samp{(???)}, not @samp{(?]}. Traditional C compilers
+do not recognize these idioms.
+
+The nine trigraphs and their replacements are
+
+@smallexample
+Trigraph: ??( ??) ??< ??> ??= ??/ ??' ??! ??-
+Replacement: [ ] @{ @} # \ ^ | ~
+@end smallexample
+
+@item
+@cindex continued lines
+@cindex backslash-newline
+Continued lines are merged into one long line.
+
+A continued line is a line which ends with a backslash, @samp{\}. The
+backslash is removed and the following line is joined with the current
+one. No space is inserted, so you may split a line anywhere, even in
+the middle of a word. (It is generally more readable to split lines
+only at white space.)
+
+The trailing backslash on a continued line is commonly referred to as a
+@dfn{backslash-newline}.
+
+If there is white space between a backslash and the end of a line, that
+is still a continued line. However, as this is usually the result of an
+editing mistake, and many compilers will not accept it as a continued
+line, GCC will warn you about it.
+
+@item
+@cindex comments
+@cindex line comments
+@cindex block comments
+All comments are replaced with single spaces.
+
+There are two kinds of comments. @dfn{Block comments} begin with
+@samp{/*} and continue until the next @samp{*/}. Block comments do not
+nest:
+
+@smallexample
+/* @r{this is} /* @r{one comment} */ @r{text outside comment}
+@end smallexample
+
+@dfn{Line comments} begin with @samp{//} and continue to the end of the
+current line. Line comments do not nest either, but it does not matter,
+because they would end in the same place anyway.
+
+@smallexample
+// @r{this is} // @r{one comment}
+@r{text outside comment}
+@end smallexample
+@end enumerate
+
+It is safe to put line comments inside block comments, or vice versa.
+
+@smallexample
+@group
+/* @r{block comment}
+ // @r{contains line comment}
+ @r{yet more comment}
+ */ @r{outside comment}
+
+// @r{line comment} /* @r{contains block comment} */
+@end group
+@end smallexample
+
+But beware of commenting out one end of a block comment with a line
+comment.
+
+@smallexample
+@group
+ // @r{l.c.} /* @r{block comment begins}
+ @r{oops! this isn't a comment anymore} */
+@end group
+@end smallexample
+
+Comments are not recognized within string literals.
+@t{@w{"/* blah */"}} is the string constant @samp{@w{/* blah */}}, not
+an empty string.
+
+Line comments are not in the 1989 edition of the C standard, but they
+are recognized by GCC as an extension. In C++ and in the 1999 edition
+of the C standard, they are an official part of the language.
+
+Since these transformations happen before all other processing, you can
+split a line mechanically with backslash-newline anywhere. You can
+comment out the end of a line. You can continue a line comment onto the
+next line with backslash-newline. You can even split @samp{/*},
+@samp{*/}, and @samp{//} onto multiple lines with backslash-newline.
+For example:
+
+@smallexample
+@group
+/\
+*
+*/ # /*
+*/ defi\
+ne FO\
+O 10\
+20
+@end group
+@end smallexample
+
+@noindent
+is equivalent to @code{@w{#define FOO 1020}}. All these tricks are
+extremely confusing and should not be used in code intended to be
+readable.
+
+There is no way to prevent a backslash at the end of a line from being
+interpreted as a backslash-newline. This cannot affect any correct
+program, however.
+
+@node Tokenization
+@section Tokenization
+
+@cindex tokens
+@cindex preprocessing tokens
+After the textual transformations are finished, the input file is
+converted into a sequence of @dfn{preprocessing tokens}. These mostly
+correspond to the syntactic tokens used by the C compiler, but there are
+a few differences. White space separates tokens; it is not itself a
+token of any kind. Tokens do not have to be separated by white space,
+but it is often necessary to avoid ambiguities.
+
+When faced with a sequence of characters that has more than one possible
+tokenization, the preprocessor is greedy. It always makes each token,
+starting from the left, as big as possible before moving on to the next
+token. For instance, @code{a+++++b} is interpreted as
+@code{@w{a ++ ++ + b}}, not as @code{@w{a ++ + ++ b}}, even though the
+latter tokenization could be part of a valid C program and the former
+could not.
+
+Once the input file is broken into tokens, the token boundaries never
+change, except when the @samp{##} preprocessing operator is used to paste
+tokens together. @xref{Concatenation}. For example,
+
+@smallexample
+@group
+#define foo() bar
+foo()baz
+ @expansion{} bar baz
+@emph{not}
+ @expansion{} barbaz
+@end group
+@end smallexample
+
+The compiler does not re-tokenize the preprocessor's output. Each
+preprocessing token becomes one compiler token.
+
+@cindex identifiers
+Preprocessing tokens fall into five broad classes: identifiers,
+preprocessing numbers, string literals, punctuators, and other. An
+@dfn{identifier} is the same as an identifier in C: any sequence of
+letters, digits, or underscores, which begins with a letter or
+underscore. Keywords of C have no significance to the preprocessor;
+they are ordinary identifiers. You can define a macro whose name is a
+keyword, for instance. The only identifier which can be considered a
+preprocessing keyword is @code{defined}. @xref{Defined}.
+
+This is mostly true of other languages which use the C preprocessor.
+However, a few of the keywords of C++ are significant even in the
+preprocessor. @xref{C++ Named Operators}.
+
+In the 1999 C standard, identifiers may contain letters which are not
+part of the ``basic source character set'', at the implementation's
+discretion (such as accented Latin letters, Greek letters, or Chinese
+ideograms). This may be done with an extended character set, or the
+@samp{\u} and @samp{\U} escape sequences.
+
+As an extension, GCC treats @samp{$} as a letter. This is for
+compatibility with some systems, such as VMS, where @samp{$} is commonly
+used in system-defined function and object names. @samp{$} is not a
+letter in strictly conforming mode, or if you specify the @option{-$}
+option. @xref{Invocation}.
+
+@cindex numbers
+@cindex preprocessing numbers
+A @dfn{preprocessing number} has a rather bizarre definition. The
+category includes all the normal integer and floating point constants
+one expects of C, but also a number of other things one might not
+initially recognize as a number. Formally, preprocessing numbers begin
+with an optional period, a required decimal digit, and then continue
+with any sequence of letters, digits, underscores, periods, and
+exponents. Exponents are the two-character sequences @samp{e+},
+@samp{e-}, @samp{E+}, @samp{E-}, @samp{p+}, @samp{p-}, @samp{P+}, and
+@samp{P-}. (The exponents that begin with @samp{p} or @samp{P} are
+used for hexadecimal floating-point constants.)
+
+The purpose of this unusual definition is to isolate the preprocessor
+from the full complexity of numeric constants. It does not have to
+distinguish between lexically valid and invalid floating-point numbers,
+which is complicated. The definition also permits you to split an
+identifier at any position and get exactly two tokens, which can then be
+pasted back together with the @samp{##} operator.
+
+It's possible for preprocessing numbers to cause programs to be
+misinterpreted. For example, @code{0xE+12} is a preprocessing number
+which does not translate to any valid numeric constant, therefore a
+syntax error. It does not mean @code{@w{0xE + 12}}, which is what you
+might have intended.
+
+@cindex string literals
+@cindex string constants
+@cindex character constants
+@cindex header file names
+@c the @: prevents makeinfo from turning '' into ".
+@dfn{String literals} are string constants, character constants, and
+header file names (the argument of @samp{#include}).@footnote{The C
+standard uses the term @dfn{string literal} to refer only to what we are
+calling @dfn{string constants}.} String constants and character
+constants are straightforward: @t{"@dots{}"} or @t{'@dots{}'}. In
+either case embedded quotes should be escaped with a backslash:
+@t{'\'@:'} is the character constant for @samp{'}. There is no limit on
+the length of a character constant, but the value of a character
+constant that contains more than one character is
+implementation-defined. @xref{Implementation Details}.
+
+Header file names either look like string constants, @t{"@dots{}"}, or are
+written with angle brackets instead, @t{<@dots{}>}. In either case,
+backslash is an ordinary character. There is no way to escape the
+closing quote or angle bracket. The preprocessor looks for the header
+file in different places depending on which form you use. @xref{Include
+Operation}.
+
+No string literal may extend past the end of a line. You may use continued
+lines instead, or string constant concatenation.
+
+@cindex punctuators
+@cindex digraphs
+@cindex alternative tokens
+@dfn{Punctuators} are all the usual bits of punctuation which are
+meaningful to C and C++. All but three of the punctuation characters in
+ASCII are C punctuators. The exceptions are @samp{@@}, @samp{$}, and
+@samp{`}. In addition, all the two- and three-character operators are
+punctuators. There are also six @dfn{digraphs}, which the C++ standard
+calls @dfn{alternative tokens}, which are merely alternate ways to spell
+other punctuators. This is a second attempt to work around missing
+punctuation in obsolete systems. It has no negative side effects,
+unlike trigraphs, but does not cover as much ground. The digraphs and
+their corresponding normal punctuators are:
+
+@smallexample
+Digraph: <% %> <: :> %: %:%:
+Punctuator: @{ @} [ ] # ##
+@end smallexample
+
+@cindex other tokens
+Any other single byte is considered ``other'' and passed on to the
+preprocessor's output unchanged. The C compiler will almost certainly
+reject source code containing ``other'' tokens. In ASCII, the only
+``other'' characters are @samp{@@}, @samp{$}, @samp{`}, and control
+characters other than NUL (all bits zero). (Note that @samp{$} is
+normally considered a letter.) All bytes with the high bit set
+(numeric range 0x7F--0xFF) that were not succesfully interpreted as
+part of an extended character in the input encoding are also ``other''
+in the present implementation.
+
+NUL is a special case because of the high probability that its
+appearance is accidental, and because it may be invisible to the user
+(many terminals do not display NUL at all). Within comments, NULs are
+silently ignored, just as any other character would be. In running
+text, NUL is considered white space. For example, these two directives
+have the same meaning.
+
+@smallexample
+#define X^@@1
+#define X 1
+@end smallexample
+
+@noindent
+(where @samp{^@@} is ASCII NUL)@. Within string or character constants,
+NULs are preserved. In the latter two cases the preprocessor emits a
+warning message.
+
+@node The preprocessing language
+@section The preprocessing language
+@cindex directives
+@cindex preprocessing directives
+@cindex directive line
+@cindex directive name
+
+After tokenization, the stream of tokens may simply be passed straight
+to the compiler's parser. However, if it contains any operations in the
+@dfn{preprocessing language}, it will be transformed first. This stage
+corresponds roughly to the standard's ``translation phase 4'' and is
+what most people think of as the preprocessor's job.
+
+The preprocessing language consists of @dfn{directives} to be executed
+and @dfn{macros} to be expanded. Its primary capabilities are:
+
+@itemize @bullet
+@item
+Inclusion of header files. These are files of declarations that can be
+substituted into your program.
+
+@item
+Macro expansion. You can define @dfn{macros}, which are abbreviations
+for arbitrary fragments of C code. The preprocessor will replace the
+macros with their definitions throughout the program. Some macros are
+automatically defined for you.
+
+@item
+Conditional compilation. You can include or exclude parts of the
+program according to various conditions.
+
+@item
+Line control. If you use a program to combine or rearrange source files
+into an intermediate file which is then compiled, you can use line
+control to inform the compiler where each source line originally came
+from.
+
+@item
+Diagnostics. You can detect problems at compile time and issue errors
+or warnings.
+@end itemize
+
+There are a few more, less useful, features.
+
+Except for expansion of predefined macros, all these operations are
+triggered with @dfn{preprocessing directives}. Preprocessing directives
+are lines in your program that start with @samp{#}. Whitespace is
+allowed before and after the @samp{#}. The @samp{#} is followed by an
+identifier, the @dfn{directive name}. It specifies the operation to
+perform. Directives are commonly referred to as @samp{#@var{name}}
+where @var{name} is the directive name. For example, @samp{#define} is
+the directive that defines a macro.
+
+The @samp{#} which begins a directive cannot come from a macro
+expansion. Also, the directive name is not macro expanded. Thus, if
+@code{foo} is defined as a macro expanding to @code{define}, that does
+not make @samp{#foo} a valid preprocessing directive.
+
+The set of valid directive names is fixed. Programs cannot define new
+preprocessing directives.
+
+Some directives require arguments; these make up the rest of the
+directive line and must be separated from the directive name by
+whitespace. For example, @samp{#define} must be followed by a macro
+name and the intended expansion of the macro.
+
+A preprocessing directive cannot cover more than one line. The line
+may, however, be continued with backslash-newline, or by a block comment
+which extends past the end of the line. In either case, when the
+directive is processed, the continuations have already been merged with
+the first line to make one long line.
+
+@node Header Files
+@chapter Header Files
+
+@cindex header file
+A header file is a file containing C declarations and macro definitions
+(@pxref{Macros}) to be shared between several source files. You request
+the use of a header file in your program by @dfn{including} it, with the
+C preprocessing directive @samp{#include}.
+
+Header files serve two purposes.
+
+@itemize @bullet
+@item
+@cindex system header files
+System header files declare the interfaces to parts of the operating
+system. You include them in your program to supply the definitions and
+declarations you need to invoke system calls and libraries.
+
+@item
+Your own header files contain declarations for interfaces between the
+source files of your program. Each time you have a group of related
+declarations and macro definitions all or most of which are needed in
+several different source files, it is a good idea to create a header
+file for them.
+@end itemize
+
+Including a header file produces the same results as copying the header
+file into each source file that needs it. Such copying would be
+time-consuming and error-prone. With a header file, the related
+declarations appear in only one place. If they need to be changed, they
+can be changed in one place, and programs that include the header file
+will automatically use the new version when next recompiled. The header
+file eliminates the labor of finding and changing all the copies as well
+as the risk that a failure to find one copy will result in
+inconsistencies within a program.
+
+In C, the usual convention is to give header files names that end with
+@file{.h}. It is most portable to use only letters, digits, dashes, and
+underscores in header file names, and at most one dot.
+
+@menu
+* Include Syntax::
+* Include Operation::
+* Search Path::
+* Once-Only Headers::
+* Alternatives to Wrapper #ifndef::
+* Computed Includes::
+* Wrapper Headers::
+* System Headers::
+@end menu
+
+@node Include Syntax
+@section Include Syntax
+
+@findex #include
+Both user and system header files are included using the preprocessing
+directive @samp{#include}. It has two variants:
+
+@table @code
+@item #include <@var{file}>
+This variant is used for system header files. It searches for a file
+named @var{file} in a standard list of system directories. You can prepend
+directories to this list with the @option{-I} option (@pxref{Invocation}).
+
+@item #include "@var{file}"
+This variant is used for header files of your own program. It
+searches for a file named @var{file} first in the directory containing
+the current file, then in the quote directories and then the same
+directories used for @code{<@var{file}>}. You can prepend directories
+to the list of quote directories with the @option{-iquote} option.
+@end table
+
+The argument of @samp{#include}, whether delimited with quote marks or
+angle brackets, behaves like a string constant in that comments are not
+recognized, and macro names are not expanded. Thus, @code{@w{#include
+<x/*y>}} specifies inclusion of a system header file named @file{x/*y}.
+
+However, if backslashes occur within @var{file}, they are considered
+ordinary text characters, not escape characters. None of the character
+escape sequences appropriate to string constants in C are processed.
+Thus, @code{@w{#include "x\n\\y"}} specifies a filename containing three
+backslashes. (Some systems interpret @samp{\} as a pathname separator.
+All of these also interpret @samp{/} the same way. It is most portable
+to use only @samp{/}.)
+
+It is an error if there is anything (other than comments) on the line
+after the file name.
+
+@node Include Operation
+@section Include Operation
+
+The @samp{#include} directive works by directing the C preprocessor to
+scan the specified file as input before continuing with the rest of the
+current file. The output from the preprocessor contains the output
+already generated, followed by the output resulting from the included
+file, followed by the output that comes from the text after the
+@samp{#include} directive. For example, if you have a header file
+@file{header.h} as follows,
+
+@smallexample
+char *test (void);
+@end smallexample
+
+@noindent
+and a main program called @file{program.c} that uses the header file,
+like this,
+
+@smallexample
+int x;
+#include "header.h"
+
+int
+main (void)
+@{
+ puts (test ());
+@}
+@end smallexample
+
+@noindent
+the compiler will see the same token stream as it would if
+@file{program.c} read
+
+@smallexample
+int x;
+char *test (void);
+
+int
+main (void)
+@{
+ puts (test ());
+@}
+@end smallexample
+
+Included files are not limited to declarations and macro definitions;
+those are merely the typical uses. Any fragment of a C program can be
+included from another file. The include file could even contain the
+beginning of a statement that is concluded in the containing file, or
+the end of a statement that was started in the including file. However,
+an included file must consist of complete tokens. Comments and string
+literals which have not been closed by the end of an included file are
+invalid. For error recovery, they are considered to end at the end of
+the file.
+
+To avoid confusion, it is best if header files contain only complete
+syntactic units---function declarations or definitions, type
+declarations, etc.
+
+The line following the @samp{#include} directive is always treated as a
+separate line by the C preprocessor, even if the included file lacks a
+final newline.
+
+@node Search Path
+@section Search Path
+
+By default, the preprocessor looks for header files included by the quote
+form of the directive @code{@w{#include "@var{file}"}} first relative to
+the directory of the current file, and then in a preconfigured list
+of standard system directories.
+For example, if @file{/usr/include/sys/stat.h} contains
+@code{@w{#include "types.h"}}, GCC looks for @file{types.h} first in
+@file{/usr/include/sys}, then in its usual search path.
+
+For the angle-bracket form @code{@w{#include <@var{file}>}}, the
+preprocessor's default behavior is to look only in the standard system
+directories. The exact search directory list depends on the target
+system, how GCC is configured, and where it is installed. You can
+find the default search directory list for your version of CPP by
+invoking it with the @option{-v} option. For example,
+
+@smallexample
+cpp -v /dev/null -o /dev/null
+@end smallexample
+
+There are a number of command-line options you can use to add
+additional directories to the search path.
+The most commonly-used option is @option{-I@var{dir}}, which causes
+@var{dir} to be searched after the current directory (for the quote
+form of the directive) and ahead of the standard system directories.
+You can specify multiple @option{-I} options on the command line,
+in which case the directories are searched in left-to-right order.
+
+If you need separate control over the search paths for the quote and
+angle-bracket forms of the @samp{#include} directive, you can use the
+@option{-iquote} and/or @option{-isystem} options instead of @option{-I}.
+@xref{Invocation}, for a detailed description of these options, as
+well as others that are less generally useful.
+
+If you specify other options on the command line, such as @option{-I},
+that affect where the preprocessor searches for header files, the
+directory list printed by the @option{-v} option reflects the actual
+search path used by the preprocessor.
+
+Note that you can also prevent the preprocessor from searching any of
+the default system header directories with the @option{-nostdinc}
+option. This is useful when you are compiling an operating system
+kernel or some other program that does not use the standard C library
+facilities, or the standard C library itself.
+
+@node Once-Only Headers
+@section Once-Only Headers
+@cindex repeated inclusion
+@cindex including just once
+@cindex wrapper @code{#ifndef}
+
+If a header file happens to be included twice, the compiler will process
+its contents twice. This is very likely to cause an error, e.g.@: when the
+compiler sees the same structure definition twice. Even if it does not,
+it will certainly waste time.
+
+The standard way to prevent this is to enclose the entire real contents
+of the file in a conditional, like this:
+
+@smallexample
+@group
+/* File foo. */
+#ifndef FILE_FOO_SEEN
+#define FILE_FOO_SEEN
+
+@var{the entire file}
+
+#endif /* !FILE_FOO_SEEN */
+@end group
+@end smallexample
+
+This construct is commonly known as a @dfn{wrapper #ifndef}.
+When the header is included again, the conditional will be false,
+because @code{FILE_FOO_SEEN} is defined. The preprocessor will skip
+over the entire contents of the file, and the compiler will not see it
+twice.
+
+CPP optimizes even further. It remembers when a header file has a
+wrapper @samp{#ifndef}. If a subsequent @samp{#include} specifies that
+header, and the macro in the @samp{#ifndef} is still defined, it does
+not bother to rescan the file at all.
+
+You can put comments outside the wrapper. They will not interfere with
+this optimization.
+
+@cindex controlling macro
+@cindex guard macro
+The macro @code{FILE_FOO_SEEN} is called the @dfn{controlling macro} or
+@dfn{guard macro}. In a user header file, the macro name should not
+begin with @samp{_}. In a system header file, it should begin with
+@samp{__} to avoid conflicts with user programs. In any kind of header
+file, the macro name should contain the name of the file and some
+additional text, to avoid conflicts with other header files.
+
+@node Alternatives to Wrapper #ifndef
+@section Alternatives to Wrapper #ifndef
+
+CPP supports two more ways of indicating that a header file should be
+read only once. Neither one is as portable as a wrapper @samp{#ifndef}
+and we recommend you do not use them in new programs, with the caveat
+that @samp{#import} is standard practice in Objective-C.
+
+@findex #import
+CPP supports a variant of @samp{#include} called @samp{#import} which
+includes a file, but does so at most once. If you use @samp{#import}
+instead of @samp{#include}, then you don't need the conditionals
+inside the header file to prevent multiple inclusion of the contents.
+@samp{#import} is standard in Objective-C, but is considered a
+deprecated extension in C and C++.
+
+@samp{#import} is not a well designed feature. It requires the users of
+a header file to know that it should only be included once. It is much
+better for the header file's implementor to write the file so that users
+don't need to know this. Using a wrapper @samp{#ifndef} accomplishes
+this goal.
+
+In the present implementation, a single use of @samp{#import} will
+prevent the file from ever being read again, by either @samp{#import} or
+@samp{#include}. You should not rely on this; do not use both
+@samp{#import} and @samp{#include} to refer to the same header file.
+
+Another way to prevent a header file from being included more than once
+is with the @samp{#pragma once} directive (@pxref{Pragmas}).
+@samp{#pragma once} does not have the problems that @samp{#import} does,
+but it is not recognized by all preprocessors, so you cannot rely on it
+in a portable program.
+
+@node Computed Includes
+@section Computed Includes
+@cindex computed includes
+@cindex macros in include
+
+Sometimes it is necessary to select one of several different header
+files to be included into your program. They might specify
+configuration parameters to be used on different sorts of operating
+systems, for instance. You could do this with a series of conditionals,
+
+@smallexample
+#if SYSTEM_1
+# include "system_1.h"
+#elif SYSTEM_2
+# include "system_2.h"
+#elif SYSTEM_3
+@dots{}
+#endif
+@end smallexample
+
+That rapidly becomes tedious. Instead, the preprocessor offers the
+ability to use a macro for the header name. This is called a
+@dfn{computed include}. Instead of writing a header name as the direct
+argument of @samp{#include}, you simply put a macro name there instead:
+
+@smallexample
+#define SYSTEM_H "system_1.h"
+@dots{}
+#include SYSTEM_H
+@end smallexample
+
+@noindent
+@code{SYSTEM_H} will be expanded, and the preprocessor will look for
+@file{system_1.h} as if the @samp{#include} had been written that way
+originally. @code{SYSTEM_H} could be defined by your Makefile with a
+@option{-D} option.
+
+You must be careful when you define the macro. @samp{#define} saves
+tokens, not text. The preprocessor has no way of knowing that the macro
+will be used as the argument of @samp{#include}, so it generates
+ordinary tokens, not a header name. This is unlikely to cause problems
+if you use double-quote includes, which are close enough to string
+constants. If you use angle brackets, however, you may have trouble.
+
+The syntax of a computed include is actually a bit more general than the
+above. If the first non-whitespace character after @samp{#include} is
+not @samp{"} or @samp{<}, then the entire line is macro-expanded
+like running text would be.
+
+If the line expands to a single string constant, the contents of that
+string constant are the file to be included. CPP does not re-examine the
+string for embedded quotes, but neither does it process backslash
+escapes in the string. Therefore
+
+@smallexample
+#define HEADER "a\"b"
+#include HEADER
+@end smallexample
+
+@noindent
+looks for a file named @file{a\"b}. CPP searches for the file according
+to the rules for double-quoted includes.
+
+If the line expands to a token stream beginning with a @samp{<} token
+and including a @samp{>} token, then the tokens between the @samp{<} and
+the first @samp{>} are combined to form the filename to be included.
+Any whitespace between tokens is reduced to a single space; then any
+space after the initial @samp{<} is retained, but a trailing space
+before the closing @samp{>} is ignored. CPP searches for the file
+according to the rules for angle-bracket includes.
+
+In either case, if there are any tokens on the line after the file name,
+an error occurs and the directive is not processed. It is also an error
+if the result of expansion does not match either of the two expected
+forms.
+
+These rules are implementation-defined behavior according to the C
+standard. To minimize the risk of different compilers interpreting your
+computed includes differently, we recommend you use only a single
+object-like macro which expands to a string constant. This will also
+minimize confusion for people reading your program.
+
+@node Wrapper Headers
+@section Wrapper Headers
+@cindex wrapper headers
+@cindex overriding a header file
+@findex #include_next
+
+Sometimes it is necessary to adjust the contents of a system-provided
+header file without editing it directly. GCC's @command{fixincludes}
+operation does this, for example. One way to do that would be to create
+a new header file with the same name and insert it in the search path
+before the original header. That works fine as long as you're willing
+to replace the old header entirely. But what if you want to refer to
+the old header from the new one?
+
+You cannot simply include the old header with @samp{#include}. That
+will start from the beginning, and find your new header again. If your
+header is not protected from multiple inclusion (@pxref{Once-Only
+Headers}), it will recurse infinitely and cause a fatal error.
+
+You could include the old header with an absolute pathname:
+@smallexample
+#include "/usr/include/old-header.h"
+@end smallexample
+@noindent
+This works, but is not clean; should the system headers ever move, you
+would have to edit the new headers to match.
+
+There is no way to solve this problem within the C standard, but you can
+use the GNU extension @samp{#include_next}. It means, ``Include the
+@emph{next} file with this name''. This directive works like
+@samp{#include} except in searching for the specified file: it starts
+searching the list of header file directories @emph{after} the directory
+in which the current file was found.
+
+Suppose you specify @option{-I /usr/local/include}, and the list of
+directories to search also includes @file{/usr/include}; and suppose
+both directories contain @file{signal.h}. Ordinary @code{@w{#include
+<signal.h>}} finds the file under @file{/usr/local/include}. If that
+file contains @code{@w{#include_next <signal.h>}}, it starts searching
+after that directory, and finds the file in @file{/usr/include}.
+
+@samp{#include_next} does not distinguish between @code{<@var{file}>}
+and @code{"@var{file}"} inclusion, nor does it check that the file you
+specify has the same name as the current file. It simply looks for the
+file named, starting with the directory in the search path after the one
+where the current file was found.
+
+The use of @samp{#include_next} can lead to great confusion. We
+recommend it be used only when there is no other alternative. In
+particular, it should not be used in the headers belonging to a specific
+program; it should be used only to make global corrections along the
+lines of @command{fixincludes}.
+
+@node System Headers
+@section System Headers
+@cindex system header files
+
+The header files declaring interfaces to the operating system and
+runtime libraries often cannot be written in strictly conforming C@.
+Therefore, GCC gives code found in @dfn{system headers} special
+treatment. All warnings, other than those generated by @samp{#warning}
+(@pxref{Diagnostics}), are suppressed while GCC is processing a system
+header. Macros defined in a system header are immune to a few warnings
+wherever they are expanded. This immunity is granted on an ad-hoc
+basis, when we find that a warning generates lots of false positives
+because of code in macros defined in system headers.
+
+Normally, only the headers found in specific directories are considered
+system headers. These directories are determined when GCC is compiled.
+There are, however, two ways to make normal headers into system headers:
+
+@itemize @bullet
+@item
+Header files found in directories added to the search path with the
+@option{-isystem} and @option{-idirafter} command-line options are
+treated as system headers for the purposes of diagnostics.
+
+@item
+@findex #pragma GCC system_header
+There is also a directive, @code{@w{#pragma GCC system_header}}, which
+tells GCC to consider the rest of the current include file a system
+header, no matter where it was found. Code that comes before the
+@samp{#pragma} in the file is not affected. @code{@w{#pragma GCC
+system_header}} has no effect in the primary source file.
+@end itemize
+
+On some targets, such as RS/6000 AIX, GCC implicitly surrounds all
+system headers with an @samp{extern "C"} block when compiling as C++.
+
+@node Macros
+@chapter Macros
+
+A @dfn{macro} is a fragment of code which has been given a name.
+Whenever the name is used, it is replaced by the contents of the macro.
+There are two kinds of macros. They differ mostly in what they look
+like when they are used. @dfn{Object-like} macros resemble data objects
+when used, @dfn{function-like} macros resemble function calls.
+
+You may define any valid identifier as a macro, even if it is a C
+keyword. The preprocessor does not know anything about keywords. This
+can be useful if you wish to hide a keyword such as @code{const} from an
+older compiler that does not understand it. However, the preprocessor
+operator @code{defined} (@pxref{Defined}) can never be defined as a
+macro, and C++'s named operators (@pxref{C++ Named Operators}) cannot be
+macros when you are compiling C++.
+
+@menu
+* Object-like Macros::
+* Function-like Macros::
+* Macro Arguments::
+* Stringizing::
+* Concatenation::
+* Variadic Macros::
+* Predefined Macros::
+* Undefining and Redefining Macros::
+* Directives Within Macro Arguments::
+* Macro Pitfalls::
+@end menu
+
+@node Object-like Macros
+@section Object-like Macros
+@cindex object-like macro
+@cindex symbolic constants
+@cindex manifest constants
+
+An @dfn{object-like macro} is a simple identifier which will be replaced
+by a code fragment. It is called object-like because it looks like a
+data object in code that uses it. They are most commonly used to give
+symbolic names to numeric constants.
+
+@findex #define
+You create macros with the @samp{#define} directive. @samp{#define} is
+followed by the name of the macro and then the token sequence it should
+be an abbreviation for, which is variously referred to as the macro's
+@dfn{body}, @dfn{expansion} or @dfn{replacement list}. For example,
+
+@smallexample
+#define BUFFER_SIZE 1024
+@end smallexample
+
+@noindent
+defines a macro named @code{BUFFER_SIZE} as an abbreviation for the
+token @code{1024}. If somewhere after this @samp{#define} directive
+there comes a C statement of the form
+
+@smallexample
+foo = (char *) malloc (BUFFER_SIZE);
+@end smallexample
+
+@noindent
+then the C preprocessor will recognize and @dfn{expand} the macro
+@code{BUFFER_SIZE}. The C compiler will see the same tokens as it would
+if you had written
+
+@smallexample
+foo = (char *) malloc (1024);
+@end smallexample
+
+By convention, macro names are written in uppercase. Programs are
+easier to read when it is possible to tell at a glance which names are
+macros.
+
+The macro's body ends at the end of the @samp{#define} line. You may
+continue the definition onto multiple lines, if necessary, using
+backslash-newline. When the macro is expanded, however, it will all
+come out on one line. For example,
+
+@smallexample
+#define NUMBERS 1, \
+ 2, \
+ 3
+int x[] = @{ NUMBERS @};
+ @expansion{} int x[] = @{ 1, 2, 3 @};
+@end smallexample
+
+@noindent
+The most common visible consequence of this is surprising line numbers
+in error messages.
+
+There is no restriction on what can go in a macro body provided it
+decomposes into valid preprocessing tokens. Parentheses need not
+balance, and the body need not resemble valid C code. (If it does not,
+you may get error messages from the C compiler when you use the macro.)
+
+The C preprocessor scans your program sequentially. Macro definitions
+take effect at the place you write them. Therefore, the following input
+to the C preprocessor
+
+@smallexample
+foo = X;
+#define X 4
+bar = X;
+@end smallexample
+
+@noindent
+produces
+
+@smallexample
+foo = X;
+bar = 4;
+@end smallexample
+
+When the preprocessor expands a macro name, the macro's expansion
+replaces the macro invocation, then the expansion is examined for more
+macros to expand. For example,
+
+@smallexample
+@group
+#define TABLESIZE BUFSIZE
+#define BUFSIZE 1024
+TABLESIZE
+ @expansion{} BUFSIZE
+ @expansion{} 1024
+@end group
+@end smallexample
+
+@noindent
+@code{TABLESIZE} is expanded first to produce @code{BUFSIZE}, then that
+macro is expanded to produce the final result, @code{1024}.
+
+Notice that @code{BUFSIZE} was not defined when @code{TABLESIZE} was
+defined. The @samp{#define} for @code{TABLESIZE} uses exactly the
+expansion you specify---in this case, @code{BUFSIZE}---and does not
+check to see whether it too contains macro names. Only when you
+@emph{use} @code{TABLESIZE} is the result of its expansion scanned for
+more macro names.
+
+This makes a difference if you change the definition of @code{BUFSIZE}
+at some point in the source file. @code{TABLESIZE}, defined as shown,
+will always expand using the definition of @code{BUFSIZE} that is
+currently in effect:
+
+@smallexample
+#define BUFSIZE 1020
+#define TABLESIZE BUFSIZE
+#undef BUFSIZE
+#define BUFSIZE 37
+@end smallexample
+
+@noindent
+Now @code{TABLESIZE} expands (in two stages) to @code{37}.
+
+If the expansion of a macro contains its own name, either directly or
+via intermediate macros, it is not expanded again when the expansion is
+examined for more macros. This prevents infinite recursion.
+@xref{Self-Referential Macros}, for the precise details.
+
+@node Function-like Macros
+@section Function-like Macros
+@cindex function-like macros
+
+You can also define macros whose use looks like a function call. These
+are called @dfn{function-like macros}. To define a function-like macro,
+you use the same @samp{#define} directive, but you put a pair of
+parentheses immediately after the macro name. For example,
+
+@smallexample
+#define lang_init() c_init()
+lang_init()
+ @expansion{} c_init()
+@end smallexample
+
+A function-like macro is only expanded if its name appears with a pair
+of parentheses after it. If you write just the name, it is left alone.
+This can be useful when you have a function and a macro of the same
+name, and you wish to use the function sometimes.
+
+@smallexample
+extern void foo(void);
+#define foo() /* @r{optimized inline version} */
+@dots{}
+ foo();
+ funcptr = foo;
+@end smallexample
+
+Here the call to @code{foo()} will use the macro, but the function
+pointer will get the address of the real function. If the macro were to
+be expanded, it would cause a syntax error.
+
+If you put spaces between the macro name and the parentheses in the
+macro definition, that does not define a function-like macro, it defines
+an object-like macro whose expansion happens to begin with a pair of
+parentheses.
+
+@smallexample
+#define lang_init () c_init()
+lang_init()
+ @expansion{} () c_init()()
+@end smallexample
+
+The first two pairs of parentheses in this expansion come from the
+macro. The third is the pair that was originally after the macro
+invocation. Since @code{lang_init} is an object-like macro, it does not
+consume those parentheses.
+
+@node Macro Arguments
+@section Macro Arguments
+@cindex arguments
+@cindex macros with arguments
+@cindex arguments in macro definitions
+
+Function-like macros can take @dfn{arguments}, just like true functions.
+To define a macro that uses arguments, you insert @dfn{parameters}
+between the pair of parentheses in the macro definition that make the
+macro function-like. The parameters must be valid C identifiers,
+separated by commas and optionally whitespace.
+
+To invoke a macro that takes arguments, you write the name of the macro
+followed by a list of @dfn{actual arguments} in parentheses, separated
+by commas. The invocation of the macro need not be restricted to a
+single logical line---it can cross as many lines in the source file as
+you wish. The number of arguments you give must match the number of
+parameters in the macro definition. When the macro is expanded, each
+use of a parameter in its body is replaced by the tokens of the
+corresponding argument. (You need not use all of the parameters in the
+macro body.)
+
+As an example, here is a macro that computes the minimum of two numeric
+values, as it is defined in many C programs, and some uses.
+
+@smallexample
+#define min(X, Y) ((X) < (Y) ? (X) : (Y))
+ x = min(a, b); @expansion{} x = ((a) < (b) ? (a) : (b));
+ y = min(1, 2); @expansion{} y = ((1) < (2) ? (1) : (2));
+ z = min(a + 28, *p); @expansion{} z = ((a + 28) < (*p) ? (a + 28) : (*p));
+@end smallexample
+
+@noindent
+(In this small example you can already see several of the dangers of
+macro arguments. @xref{Macro Pitfalls}, for detailed explanations.)
+
+Leading and trailing whitespace in each argument is dropped, and all
+whitespace between the tokens of an argument is reduced to a single
+space. Parentheses within each argument must balance; a comma within
+such parentheses does not end the argument. However, there is no
+requirement for square brackets or braces to balance, and they do not
+prevent a comma from separating arguments. Thus,
+
+@smallexample
+macro (array[x = y, x + 1])
+@end smallexample
+
+@noindent
+passes two arguments to @code{macro}: @code{array[x = y} and @code{x +
+1]}. If you want to supply @code{array[x = y, x + 1]} as an argument,
+you can write it as @code{array[(x = y, x + 1)]}, which is equivalent C
+code.
+
+All arguments to a macro are completely macro-expanded before they are
+substituted into the macro body. After substitution, the complete text
+is scanned again for macros to expand, including the arguments. This rule
+may seem strange, but it is carefully designed so you need not worry
+about whether any function call is actually a macro invocation. You can
+run into trouble if you try to be too clever, though. @xref{Argument
+Prescan}, for detailed discussion.
+
+For example, @code{min (min (a, b), c)} is first expanded to
+
+@smallexample
+ min (((a) < (b) ? (a) : (b)), (c))
+@end smallexample
+
+@noindent
+and then to
+
+@smallexample
+@group
+((((a) < (b) ? (a) : (b))) < (c)
+ ? (((a) < (b) ? (a) : (b)))
+ : (c))
+@end group
+@end smallexample
+
+@noindent
+(Line breaks shown here for clarity would not actually be generated.)
+
+@cindex empty macro arguments
+You can leave macro arguments empty; this is not an error to the
+preprocessor (but many macros will then expand to invalid code).
+You cannot leave out arguments entirely; if a macro takes two arguments,
+there must be exactly one comma at the top level of its argument list.
+Here are some silly examples using @code{min}:
+
+@smallexample
+min(, b) @expansion{} (( ) < (b) ? ( ) : (b))
+min(a, ) @expansion{} ((a ) < ( ) ? (a ) : ( ))
+min(,) @expansion{} (( ) < ( ) ? ( ) : ( ))
+min((,),) @expansion{} (((,)) < ( ) ? ((,)) : ( ))
+
+min() @error{} macro "min" requires 2 arguments, but only 1 given
+min(,,) @error{} macro "min" passed 3 arguments, but takes just 2
+@end smallexample
+
+Whitespace is not a preprocessing token, so if a macro @code{foo} takes
+one argument, @code{@w{foo ()}} and @code{@w{foo ( )}} both supply it an
+empty argument. Previous GNU preprocessor implementations and
+documentation were incorrect on this point, insisting that a
+function-like macro that takes a single argument be passed a space if an
+empty argument was required.
+
+Macro parameters appearing inside string literals are not replaced by
+their corresponding actual arguments.
+
+@smallexample
+#define foo(x) x, "x"
+foo(bar) @expansion{} bar, "x"
+@end smallexample
+
+@node Stringizing
+@section Stringizing
+@cindex stringizing
+@cindex @samp{#} operator
+
+Sometimes you may want to convert a macro argument into a string
+constant. Parameters are not replaced inside string constants, but you
+can use the @samp{#} preprocessing operator instead. When a macro
+parameter is used with a leading @samp{#}, the preprocessor replaces it
+with the literal text of the actual argument, converted to a string
+constant. Unlike normal parameter replacement, the argument is not
+macro-expanded first. This is called @dfn{stringizing}.
+
+There is no way to combine an argument with surrounding text and
+stringize it all together. Instead, you can write a series of adjacent
+string constants and stringized arguments. The preprocessor
+replaces the stringized arguments with string constants. The C
+compiler then combines all the adjacent string constants into one
+long string.
+
+Here is an example of a macro definition that uses stringizing:
+
+@smallexample
+@group
+#define WARN_IF(EXP) \
+do @{ if (EXP) \
+ fprintf (stderr, "Warning: " #EXP "\n"); @} \
+while (0)
+WARN_IF (x == 0);
+ @expansion{} do @{ if (x == 0)
+ fprintf (stderr, "Warning: " "x == 0" "\n"); @} while (0);
+@end group
+@end smallexample
+
+@noindent
+The argument for @code{EXP} is substituted once, as-is, into the
+@code{if} statement, and once, stringized, into the argument to
+@code{fprintf}. If @code{x} were a macro, it would be expanded in the
+@code{if} statement, but not in the string.
+
+The @code{do} and @code{while (0)} are a kludge to make it possible to
+write @code{WARN_IF (@var{arg});}, which the resemblance of
+@code{WARN_IF} to a function would make C programmers want to do; see
+@ref{Swallowing the Semicolon}.
+
+Stringizing in C involves more than putting double-quote characters
+around the fragment. The preprocessor backslash-escapes the quotes
+surrounding embedded string constants, and all backslashes within string and
+character constants, in order to get a valid C string constant with the
+proper contents. Thus, stringizing @code{@w{p = "foo\n";}} results in
+@t{@w{"p = \"foo\\n\";"}}. However, backslashes that are not inside string
+or character constants are not duplicated: @samp{\n} by itself
+stringizes to @t{"\n"}.
+
+All leading and trailing whitespace in text being stringized is
+ignored. Any sequence of whitespace in the middle of the text is
+converted to a single space in the stringized result. Comments are
+replaced by whitespace long before stringizing happens, so they
+never appear in stringized text.
+
+There is no way to convert a macro argument into a character constant.
+
+If you want to stringize the result of expansion of a macro argument,
+you have to use two levels of macros.
+
+@smallexample
+#define xstr(s) str(s)
+#define str(s) #s
+#define foo 4
+str (foo)
+ @expansion{} "foo"
+xstr (foo)
+ @expansion{} xstr (4)
+ @expansion{} str (4)
+ @expansion{} "4"
+@end smallexample
+
+@code{s} is stringized when it is used in @code{str}, so it is not
+macro-expanded first. But @code{s} is an ordinary argument to
+@code{xstr}, so it is completely macro-expanded before @code{xstr}
+itself is expanded (@pxref{Argument Prescan}). Therefore, by the time
+@code{str} gets to its argument, it has already been macro-expanded.
+
+@node Concatenation
+@section Concatenation
+@cindex concatenation
+@cindex token pasting
+@cindex token concatenation
+@cindex @samp{##} operator
+
+It is often useful to merge two tokens into one while expanding macros.
+This is called @dfn{token pasting} or @dfn{token concatenation}. The
+@samp{##} preprocessing operator performs token pasting. When a macro
+is expanded, the two tokens on either side of each @samp{##} operator
+are combined into a single token, which then replaces the @samp{##} and
+the two original tokens in the macro expansion. Usually both will be
+identifiers, or one will be an identifier and the other a preprocessing
+number. When pasted, they make a longer identifier. This isn't the
+only valid case. It is also possible to concatenate two numbers (or a
+number and a name, such as @code{1.5} and @code{e3}) into a number.
+Also, multi-character operators such as @code{+=} can be formed by
+token pasting.
+
+However, two tokens that don't together form a valid token cannot be
+pasted together. For example, you cannot concatenate @code{x} with
+@code{+} in either order. If you try, the preprocessor issues a warning
+and emits the two tokens. Whether it puts white space between the
+tokens is undefined. It is common to find unnecessary uses of @samp{##}
+in complex macros. If you get this warning, it is likely that you can
+simply remove the @samp{##}.
+
+Both the tokens combined by @samp{##} could come from the macro body,
+but you could just as well write them as one token in the first place.
+Token pasting is most useful when one or both of the tokens comes from a
+macro argument. If either of the tokens next to an @samp{##} is a
+parameter name, it is replaced by its actual argument before @samp{##}
+executes. As with stringizing, the actual argument is not
+macro-expanded first. If the argument is empty, that @samp{##} has no
+effect.
+
+Keep in mind that the C preprocessor converts comments to whitespace
+before macros are even considered. Therefore, you cannot create a
+comment by concatenating @samp{/} and @samp{*}. You can put as much
+whitespace between @samp{##} and its operands as you like, including
+comments, and you can put comments in arguments that will be
+concatenated. However, it is an error if @samp{##} appears at either
+end of a macro body.
+
+Consider a C program that interprets named commands. There probably
+needs to be a table of commands, perhaps an array of structures declared
+as follows:
+
+@smallexample
+@group
+struct command
+@{
+ char *name;
+ void (*function) (void);
+@};
+@end group
+
+@group
+struct command commands[] =
+@{
+ @{ "quit", quit_command @},
+ @{ "help", help_command @},
+ @dots{}
+@};
+@end group
+@end smallexample
+
+It would be cleaner not to have to give each command name twice, once in
+the string constant and once in the function name. A macro which takes the
+name of a command as an argument can make this unnecessary. The string
+constant can be created with stringizing, and the function name by
+concatenating the argument with @samp{_command}. Here is how it is done:
+
+@smallexample
+#define COMMAND(NAME) @{ #NAME, NAME ## _command @}
+
+struct command commands[] =
+@{
+ COMMAND (quit),
+ COMMAND (help),
+ @dots{}
+@};
+@end smallexample
+
+@node Variadic Macros
+@section Variadic Macros
+@cindex variable number of arguments
+@cindex macros with variable arguments
+@cindex variadic macros
+
+A macro can be declared to accept a variable number of arguments much as
+a function can. The syntax for defining the macro is similar to that of
+a function. Here is an example:
+
+@smallexample
+#define eprintf(...) fprintf (stderr, __VA_ARGS__)
+@end smallexample
+
+This kind of macro is called @dfn{variadic}. When the macro is invoked,
+all the tokens in its argument list after the last named argument (this
+macro has none), including any commas, become the @dfn{variable
+argument}. This sequence of tokens replaces the identifier
+@code{@w{__VA_ARGS__}} in the macro body wherever it appears. Thus, we
+have this expansion:
+
+@smallexample
+eprintf ("%s:%d: ", input_file, lineno)
+ @expansion{} fprintf (stderr, "%s:%d: ", input_file, lineno)
+@end smallexample
+
+The variable argument is completely macro-expanded before it is inserted
+into the macro expansion, just like an ordinary argument. You may use
+the @samp{#} and @samp{##} operators to stringize the variable argument
+or to paste its leading or trailing token with another token. (But see
+below for an important special case for @samp{##}.)
+
+If your macro is complicated, you may want a more descriptive name for
+the variable argument than @code{@w{__VA_ARGS__}}. CPP permits
+this, as an extension. You may write an argument name immediately
+before the @samp{...}; that name is used for the variable argument.
+The @code{eprintf} macro above could be written
+
+@smallexample
+#define eprintf(args...) fprintf (stderr, args)
+@end smallexample
+
+@noindent
+using this extension. You cannot use @code{@w{__VA_ARGS__}} and this
+extension in the same macro.
+
+You can have named arguments as well as variable arguments in a variadic
+macro. We could define @code{eprintf} like this, instead:
+
+@smallexample
+#define eprintf(format, ...) fprintf (stderr, format, __VA_ARGS__)
+@end smallexample
+
+@noindent
+This formulation looks more descriptive, but historically it was less
+flexible: you had to supply at least one argument after the format
+string. In standard C, you could not omit the comma separating the
+named argument from the variable arguments. (Note that this
+restriction has been lifted in C++20, and never existed in GNU C; see
+below.)
+
+Furthermore, if you left the variable argument empty, you would have
+gotten a syntax error, because there would have been an extra comma
+after the format string.
+
+@smallexample
+eprintf("success!\n", );
+ @expansion{} fprintf(stderr, "success!\n", );
+@end smallexample
+
+This has been fixed in C++20, and GNU CPP also has a pair of
+extensions which deal with this problem.
+
+First, in GNU CPP, and in C++ beginning in C++20, you are allowed to
+leave the variable argument out entirely:
+
+@smallexample
+eprintf ("success!\n")
+ @expansion{} fprintf(stderr, "success!\n", );
+@end smallexample
+
+@noindent
+Second, C++20 introduces the @code{@w{__VA_OPT__}} function macro.
+This macro may only appear in the definition of a variadic macro. If
+the variable argument has any tokens, then a @code{@w{__VA_OPT__}}
+invocation expands to its argument; but if the variable argument does
+not have any tokens, the @code{@w{__VA_OPT__}} expands to nothing:
+
+@smallexample
+#define eprintf(format, ...) \
+ fprintf (stderr, format __VA_OPT__(,) __VA_ARGS__)
+@end smallexample
+
+@code{@w{__VA_OPT__}} is also available in GNU C and GNU C++.
+
+Historically, GNU CPP has also had another extension to handle the
+trailing comma: the @samp{##} token paste operator has a special
+meaning when placed between a comma and a variable argument. Despite
+the introduction of @code{@w{__VA_OPT__}}, this extension remains
+supported in GNU CPP, for backward compatibility. If you write
+
+@smallexample
+#define eprintf(format, ...) fprintf (stderr, format, ##__VA_ARGS__)
+@end smallexample
+
+@noindent
+and the variable argument is left out when the @code{eprintf} macro is
+used, then the comma before the @samp{##} will be deleted. This does
+@emph{not} happen if you pass an empty argument, nor does it happen if
+the token preceding @samp{##} is anything other than a comma.
+
+@smallexample
+eprintf ("success!\n")
+ @expansion{} fprintf(stderr, "success!\n");
+@end smallexample
+
+@noindent
+The above explanation is ambiguous about the case where the only macro
+parameter is a variable arguments parameter, as it is meaningless to
+try to distinguish whether no argument at all is an empty argument or
+a missing argument.
+CPP retains the comma when conforming to a specific C
+standard. Otherwise the comma is dropped as an extension to the standard.
+
+The C standard
+mandates that the only place the identifier @code{@w{__VA_ARGS__}}
+can appear is in the replacement list of a variadic macro. It may not
+be used as a macro name, macro argument name, or within a different type
+of macro. It may also be forbidden in open text; the standard is
+ambiguous. We recommend you avoid using it except for its defined
+purpose.
+
+Likewise, C++ forbids @code{@w{__VA_OPT__}} anywhere outside the
+replacement list of a variadic macro.
+
+Variadic macros became a standard part of the C language with C99.
+GNU CPP previously supported them
+with a named variable argument
+(@samp{args...}, not @samp{...} and @code{@w{__VA_ARGS__}}), which
+is still supported for backward compatibility.
+
+@node Predefined Macros
+@section Predefined Macros
+
+@cindex predefined macros
+Several object-like macros are predefined; you use them without
+supplying their definitions. They fall into three classes: standard,
+common, and system-specific.
+
+In C++, there is a fourth category, the named operators. They act like
+predefined macros, but you cannot undefine them.
+
+@menu
+* Standard Predefined Macros::
+* Common Predefined Macros::
+* System-specific Predefined Macros::
+* C++ Named Operators::
+@end menu
+
+@node Standard Predefined Macros
+@subsection Standard Predefined Macros
+@cindex standard predefined macros.
+
+The standard predefined macros are specified by the relevant
+language standards, so they are available with all compilers that
+implement those standards. Older compilers may not provide all of
+them. Their names all start with double underscores.
+
+@table @code
+@item __FILE__
+This macro expands to the name of the current input file, in the form of
+a C string constant. This is the path by which the preprocessor opened
+the file, not the short name specified in @samp{#include} or as the
+input file name argument. For example,
+@code{"/usr/local/include/myheader.h"} is a possible expansion of this
+macro.
+
+@item __LINE__
+This macro expands to the current input line number, in the form of a
+decimal integer constant. While we call it a predefined macro, it's
+a pretty strange macro, since its ``definition'' changes with each
+new line of source code.
+@end table
+
+@code{__FILE__} and @code{__LINE__} are useful in generating an error
+message to report an inconsistency detected by the program; the message
+can state the source line at which the inconsistency was detected. For
+example,
+
+@smallexample
+fprintf (stderr, "Internal error: "
+ "negative string length "
+ "%d at %s, line %d.",
+ length, __FILE__, __LINE__);
+@end smallexample
+
+An @samp{#include} directive changes the expansions of @code{__FILE__}
+and @code{__LINE__} to correspond to the included file. At the end of
+that file, when processing resumes on the input file that contained
+the @samp{#include} directive, the expansions of @code{__FILE__} and
+@code{__LINE__} revert to the values they had before the
+@samp{#include} (but @code{__LINE__} is then incremented by one as
+processing moves to the line after the @samp{#include}).
+
+A @samp{#line} directive changes @code{__LINE__}, and may change
+@code{__FILE__} as well. @xref{Line Control}.
+
+C99 introduced @code{__func__}, and GCC has provided @code{__FUNCTION__}
+for a long time. Both of these are strings containing the name of the
+current function (there are slight semantic differences; see the GCC
+manual). Neither of them is a macro; the preprocessor does not know the
+name of the current function. They tend to be useful in conjunction
+with @code{__FILE__} and @code{__LINE__}, though.
+
+@table @code
+
+@item __DATE__
+This macro expands to a string constant that describes the date on which
+the preprocessor is being run. The string constant contains eleven
+characters and looks like @code{@w{"Feb 12 1996"}}. If the day of the
+month is less than 10, it is padded with a space on the left.
+
+If GCC cannot determine the current date, it will emit a warning message
+(once per compilation) and @code{__DATE__} will expand to
+@code{@w{"??? ?? ????"}}.
+
+@item __TIME__
+This macro expands to a string constant that describes the time at
+which the preprocessor is being run. The string constant contains
+eight characters and looks like @code{"23:59:01"}.
+
+If GCC cannot determine the current time, it will emit a warning message
+(once per compilation) and @code{__TIME__} will expand to
+@code{"??:??:??"}.
+
+@item __STDC__
+In normal operation, this macro expands to the constant 1, to signify
+that this compiler conforms to ISO Standard C@. If GNU CPP is used with
+a compiler other than GCC, this is not necessarily true; however, the
+preprocessor always conforms to the standard unless the
+@option{-traditional-cpp} option is used.
+
+This macro is not defined if the @option{-traditional-cpp} option is used.
+
+On some hosts, the system compiler uses a different convention, where
+@code{__STDC__} is normally 0, but is 1 if the user specifies strict
+conformance to the C Standard. CPP follows the host convention when
+processing system header files, but when processing user files
+@code{__STDC__} is always 1. This has been reported to cause problems;
+for instance, some versions of Solaris provide X Windows headers that
+expect @code{__STDC__} to be either undefined or 1. @xref{Invocation}.
+
+@item __STDC_VERSION__
+This macro expands to the C Standard's version number, a long integer
+constant of the form @code{@var{yyyy}@var{mm}L} where @var{yyyy} and
+@var{mm} are the year and month of the Standard version. This signifies
+which version of the C Standard the compiler conforms to. Like
+@code{__STDC__}, this is not necessarily accurate for the entire
+implementation, unless GNU CPP is being used with GCC@.
+
+The value @code{199409L} signifies the 1989 C standard as amended in
+1994, which is the current default; the value @code{199901L} signifies
+the 1999 revision of the C standard; the value @code{201112L}
+signifies the 2011 revision of the C standard; the value
+@code{201710L} signifies the 2017 revision of the C standard (which is
+otherwise identical to the 2011 version apart from correction of
+defects). An unspecified value larger than @code{201710L} is used for
+the experimental @option{-std=c2x} and @option{-std=gnu2x} modes.
+
+This macro is not defined if the @option{-traditional-cpp} option is
+used, nor when compiling C++ or Objective-C@.
+
+@item __STDC_HOSTED__
+This macro is defined, with value 1, if the compiler's target is a
+@dfn{hosted environment}. A hosted environment has the complete
+facilities of the standard C library available.
+
+@item __cplusplus
+This macro is defined when the C++ compiler is in use. You can use
+@code{__cplusplus} to test whether a header is compiled by a C compiler
+or a C++ compiler. This macro is similar to @code{__STDC_VERSION__}, in
+that it expands to a version number. Depending on the language standard
+selected, the value of the macro is
+@code{199711L} for the 1998 C++ standard,
+@code{201103L} for the 2011 C++ standard,
+@code{201402L} for the 2014 C++ standard,
+@code{201703L} for the 2017 C++ standard,
+@code{202002L} for the 2020 C++ standard,
+or an unspecified value strictly larger than @code{202002L} for the
+experimental languages enabled by @option{-std=c++23} and
+@option{-std=gnu++23}.
+
+@item __OBJC__
+This macro is defined, with value 1, when the Objective-C compiler is in
+use. You can use @code{__OBJC__} to test whether a header is compiled
+by a C compiler or an Objective-C compiler.
+
+@item __ASSEMBLER__
+This macro is defined with value 1 when preprocessing assembly
+language.
+
+@end table
+
+@node Common Predefined Macros
+@subsection Common Predefined Macros
+@cindex common predefined macros
+
+The common predefined macros are GNU C extensions. They are available
+with the same meanings regardless of the machine or operating system on
+which you are using GNU C or GNU Fortran. Their names all start with
+double underscores.
+
+@table @code
+
+@item __COUNTER__
+This macro expands to sequential integral values starting from 0. In
+conjunction with the @code{##} operator, this provides a convenient means to
+generate unique identifiers. Care must be taken to ensure that
+@code{__COUNTER__} is not expanded prior to inclusion of precompiled headers
+which use it. Otherwise, the precompiled headers will not be used.
+
+@item __GFORTRAN__
+The GNU Fortran compiler defines this.
+
+@item __GNUC__
+@itemx __GNUC_MINOR__
+@itemx __GNUC_PATCHLEVEL__
+These macros are defined by all GNU compilers that use the C
+preprocessor: C, C++, Objective-C and Fortran. Their values are the major
+version, minor version, and patch level of the compiler, as integer
+constants. For example, GCC version @var{x}.@var{y}.@var{z}
+defines @code{__GNUC__} to @var{x}, @code{__GNUC_MINOR__} to @var{y},
+and @code{__GNUC_PATCHLEVEL__} to @var{z}. These
+macros are also defined if you invoke the preprocessor directly.
+
+If all you need to know is whether or not your program is being compiled
+by GCC, or a non-GCC compiler that claims to accept the GNU C dialects,
+you can simply test @code{__GNUC__}. If you need to write code
+which depends on a specific version, you must be more careful. Each
+time the minor version is increased, the patch level is reset to zero;
+each time the major version is increased, the
+minor version and patch level are reset. If you wish to use the
+predefined macros directly in the conditional, you will need to write it
+like this:
+
+@smallexample
+/* @r{Test for GCC > 3.2.0} */
+#if __GNUC__ > 3 || \
+ (__GNUC__ == 3 && (__GNUC_MINOR__ > 2 || \
+ (__GNUC_MINOR__ == 2 && \
+ __GNUC_PATCHLEVEL__ > 0))
+@end smallexample
+
+@noindent
+Another approach is to use the predefined macros to
+calculate a single number, then compare that against a threshold:
+
+@smallexample
+#define GCC_VERSION (__GNUC__ * 10000 \
+ + __GNUC_MINOR__ * 100 \
+ + __GNUC_PATCHLEVEL__)
+@dots{}
+/* @r{Test for GCC > 3.2.0} */
+#if GCC_VERSION > 30200
+@end smallexample
+
+@noindent
+Many people find this form easier to understand.
+
+@item __GNUG__
+The GNU C++ compiler defines this. Testing it is equivalent to
+testing @code{@w{(__GNUC__ && __cplusplus)}}.
+
+@item __STRICT_ANSI__
+GCC defines this macro if and only if the @option{-ansi} switch, or a
+@option{-std} switch specifying strict conformance to some version of ISO C
+or ISO C++, was specified when GCC was invoked. It is defined to @samp{1}.
+This macro exists primarily to direct GNU libc's header files to use only
+definitions found in standard C.
+
+@item __BASE_FILE__
+This macro expands to the name of the main input file, in the form
+of a C string constant. This is the source file that was specified
+on the command line of the preprocessor or C compiler.
+
+@item __FILE_NAME__
+This macro expands to the basename of the current input file, in the
+form of a C string constant. This is the last path component by which
+the preprocessor opened the file. For example, processing
+@code{"/usr/local/include/myheader.h"} would set this
+macro to @code{"myheader.h"}.
+
+@item __INCLUDE_LEVEL__
+This macro expands to a decimal integer constant that represents the
+depth of nesting in include files. The value of this macro is
+incremented on every @samp{#include} directive and decremented at the
+end of every included file. It starts out at 0, its value within the
+base file specified on the command line.
+
+@item __ELF__
+This macro is defined if the target uses the ELF object format.
+
+@item __VERSION__
+This macro expands to a string constant which describes the version of
+the compiler in use. You should not rely on its contents having any
+particular form, but it can be counted on to contain at least the
+release number.
+
+@item __OPTIMIZE__
+@itemx __OPTIMIZE_SIZE__
+@itemx __NO_INLINE__
+These macros describe the compilation mode. @code{__OPTIMIZE__} is
+defined in all optimizing compilations. @code{__OPTIMIZE_SIZE__} is
+defined if the compiler is optimizing for size, not speed.
+@code{__NO_INLINE__} is defined if no functions will be inlined into
+their callers (when not optimizing, or when inlining has been
+specifically disabled by @option{-fno-inline}).
+
+These macros cause certain GNU header files to provide optimized
+definitions, using macros or inline functions, of system library
+functions. You should not use these macros in any way unless you make
+sure that programs will execute with the same effect whether or not they
+are defined. If they are defined, their value is 1.
+
+@item __GNUC_GNU_INLINE__
+GCC defines this macro if functions declared @code{inline} will be
+handled in GCC's traditional gnu90 mode. Object files will contain
+externally visible definitions of all functions declared @code{inline}
+without @code{extern} or @code{static}. They will not contain any
+definitions of any functions declared @code{extern inline}.
+
+@item __GNUC_STDC_INLINE__
+GCC defines this macro if functions declared @code{inline} will be
+handled according to the ISO C99 or later standards. Object files will contain
+externally visible definitions of all functions declared @code{extern
+inline}. They will not contain definitions of any functions declared
+@code{inline} without @code{extern}.
+
+If this macro is defined, GCC supports the @code{gnu_inline} function
+attribute as a way to always get the gnu90 behavior.
+
+@item __CHAR_UNSIGNED__
+GCC defines this macro if and only if the data type @code{char} is
+unsigned on the target machine. It exists to cause the standard header
+file @file{limits.h} to work correctly. You should not use this macro
+yourself; instead, refer to the standard macros defined in @file{limits.h}.
+
+@item __WCHAR_UNSIGNED__
+Like @code{__CHAR_UNSIGNED__}, this macro is defined if and only if the
+data type @code{wchar_t} is unsigned and the front-end is in C++ mode.
+
+@item __REGISTER_PREFIX__
+This macro expands to a single token (not a string constant) which is
+the prefix applied to CPU register names in assembly language for this
+target. You can use it to write assembly that is usable in multiple
+environments. For example, in the @code{m68k-aout} environment it
+expands to nothing, but in the @code{m68k-coff} environment it expands
+to a single @samp{%}.
+
+@item __USER_LABEL_PREFIX__
+This macro expands to a single token which is the prefix applied to
+user labels (symbols visible to C code) in assembly. For example, in
+the @code{m68k-aout} environment it expands to an @samp{_}, but in the
+@code{m68k-coff} environment it expands to nothing.
+
+This macro will have the correct definition even if
+@option{-f(no-)underscores} is in use, but it will not be correct if
+target-specific options that adjust this prefix are used (e.g.@: the
+OSF/rose @option{-mno-underscores} option).
+
+@item __SIZE_TYPE__
+@itemx __PTRDIFF_TYPE__
+@itemx __WCHAR_TYPE__
+@itemx __WINT_TYPE__
+@itemx __INTMAX_TYPE__
+@itemx __UINTMAX_TYPE__
+@itemx __SIG_ATOMIC_TYPE__
+@itemx __INT8_TYPE__
+@itemx __INT16_TYPE__
+@itemx __INT32_TYPE__
+@itemx __INT64_TYPE__
+@itemx __UINT8_TYPE__
+@itemx __UINT16_TYPE__
+@itemx __UINT32_TYPE__
+@itemx __UINT64_TYPE__
+@itemx __INT_LEAST8_TYPE__
+@itemx __INT_LEAST16_TYPE__
+@itemx __INT_LEAST32_TYPE__
+@itemx __INT_LEAST64_TYPE__
+@itemx __UINT_LEAST8_TYPE__
+@itemx __UINT_LEAST16_TYPE__
+@itemx __UINT_LEAST32_TYPE__
+@itemx __UINT_LEAST64_TYPE__
+@itemx __INT_FAST8_TYPE__
+@itemx __INT_FAST16_TYPE__
+@itemx __INT_FAST32_TYPE__
+@itemx __INT_FAST64_TYPE__
+@itemx __UINT_FAST8_TYPE__
+@itemx __UINT_FAST16_TYPE__
+@itemx __UINT_FAST32_TYPE__
+@itemx __UINT_FAST64_TYPE__
+@itemx __INTPTR_TYPE__
+@itemx __UINTPTR_TYPE__
+These macros are defined to the correct underlying types for the
+@code{size_t}, @code{ptrdiff_t}, @code{wchar_t}, @code{wint_t},
+@code{intmax_t}, @code{uintmax_t}, @code{sig_atomic_t}, @code{int8_t},
+@code{int16_t}, @code{int32_t}, @code{int64_t}, @code{uint8_t},
+@code{uint16_t}, @code{uint32_t}, @code{uint64_t},
+@code{int_least8_t}, @code{int_least16_t}, @code{int_least32_t},
+@code{int_least64_t}, @code{uint_least8_t}, @code{uint_least16_t},
+@code{uint_least32_t}, @code{uint_least64_t}, @code{int_fast8_t},
+@code{int_fast16_t}, @code{int_fast32_t}, @code{int_fast64_t},
+@code{uint_fast8_t}, @code{uint_fast16_t}, @code{uint_fast32_t},
+@code{uint_fast64_t}, @code{intptr_t}, and @code{uintptr_t} typedefs,
+respectively. They exist to make the standard header files
+@file{stddef.h}, @file{stdint.h}, and @file{wchar.h} work correctly.
+You should not use these macros directly; instead, include the
+appropriate headers and use the typedefs. Some of these macros may
+not be defined on particular systems if GCC does not provide a
+@file{stdint.h} header on those systems.
+
+@item __CHAR_BIT__
+Defined to the number of bits used in the representation of the
+@code{char} data type. It exists to make the standard header given
+numerical limits work correctly. You should not use
+this macro directly; instead, include the appropriate headers.
+
+@item __SCHAR_MAX__
+@itemx __WCHAR_MAX__
+@itemx __SHRT_MAX__
+@itemx __INT_MAX__
+@itemx __LONG_MAX__
+@itemx __LONG_LONG_MAX__
+@itemx __WINT_MAX__
+@itemx __SIZE_MAX__
+@itemx __PTRDIFF_MAX__
+@itemx __INTMAX_MAX__
+@itemx __UINTMAX_MAX__
+@itemx __SIG_ATOMIC_MAX__
+@itemx __INT8_MAX__
+@itemx __INT16_MAX__
+@itemx __INT32_MAX__
+@itemx __INT64_MAX__
+@itemx __UINT8_MAX__
+@itemx __UINT16_MAX__
+@itemx __UINT32_MAX__
+@itemx __UINT64_MAX__
+@itemx __INT_LEAST8_MAX__
+@itemx __INT_LEAST16_MAX__
+@itemx __INT_LEAST32_MAX__
+@itemx __INT_LEAST64_MAX__
+@itemx __UINT_LEAST8_MAX__
+@itemx __UINT_LEAST16_MAX__
+@itemx __UINT_LEAST32_MAX__
+@itemx __UINT_LEAST64_MAX__
+@itemx __INT_FAST8_MAX__
+@itemx __INT_FAST16_MAX__
+@itemx __INT_FAST32_MAX__
+@itemx __INT_FAST64_MAX__
+@itemx __UINT_FAST8_MAX__
+@itemx __UINT_FAST16_MAX__
+@itemx __UINT_FAST32_MAX__
+@itemx __UINT_FAST64_MAX__
+@itemx __INTPTR_MAX__
+@itemx __UINTPTR_MAX__
+@itemx __WCHAR_MIN__
+@itemx __WINT_MIN__
+@itemx __SIG_ATOMIC_MIN__
+Defined to the maximum value of the @code{signed char}, @code{wchar_t},
+@code{signed short},
+@code{signed int}, @code{signed long}, @code{signed long long},
+@code{wint_t}, @code{size_t}, @code{ptrdiff_t},
+@code{intmax_t}, @code{uintmax_t}, @code{sig_atomic_t}, @code{int8_t},
+@code{int16_t}, @code{int32_t}, @code{int64_t}, @code{uint8_t},
+@code{uint16_t}, @code{uint32_t}, @code{uint64_t},
+@code{int_least8_t}, @code{int_least16_t}, @code{int_least32_t},
+@code{int_least64_t}, @code{uint_least8_t}, @code{uint_least16_t},
+@code{uint_least32_t}, @code{uint_least64_t}, @code{int_fast8_t},
+@code{int_fast16_t}, @code{int_fast32_t}, @code{int_fast64_t},
+@code{uint_fast8_t}, @code{uint_fast16_t}, @code{uint_fast32_t},
+@code{uint_fast64_t}, @code{intptr_t}, and @code{uintptr_t} types and
+to the minimum value of the @code{wchar_t}, @code{wint_t}, and
+@code{sig_atomic_t} types respectively. They exist to make the
+standard header given numerical limits work correctly. You should not
+use these macros directly; instead, include the appropriate headers.
+Some of these macros may not be defined on particular systems if GCC
+does not provide a @file{stdint.h} header on those systems.
+
+@item __INT8_C
+@itemx __INT16_C
+@itemx __INT32_C
+@itemx __INT64_C
+@itemx __UINT8_C
+@itemx __UINT16_C
+@itemx __UINT32_C
+@itemx __UINT64_C
+@itemx __INTMAX_C
+@itemx __UINTMAX_C
+Defined to implementations of the standard @file{stdint.h} macros with
+the same names without the leading @code{__}. They exist the make the
+implementation of that header work correctly. You should not use
+these macros directly; instead, include the appropriate headers. Some
+of these macros may not be defined on particular systems if GCC does
+not provide a @file{stdint.h} header on those systems.
+
+@item __SCHAR_WIDTH__
+@itemx __SHRT_WIDTH__
+@itemx __INT_WIDTH__
+@itemx __LONG_WIDTH__
+@itemx __LONG_LONG_WIDTH__
+@itemx __PTRDIFF_WIDTH__
+@itemx __SIG_ATOMIC_WIDTH__
+@itemx __SIZE_WIDTH__
+@itemx __WCHAR_WIDTH__
+@itemx __WINT_WIDTH__
+@itemx __INT_LEAST8_WIDTH__
+@itemx __INT_LEAST16_WIDTH__
+@itemx __INT_LEAST32_WIDTH__
+@itemx __INT_LEAST64_WIDTH__
+@itemx __INT_FAST8_WIDTH__
+@itemx __INT_FAST16_WIDTH__
+@itemx __INT_FAST32_WIDTH__
+@itemx __INT_FAST64_WIDTH__
+@itemx __INTPTR_WIDTH__
+@itemx __INTMAX_WIDTH__
+Defined to the bit widths of the corresponding types. They exist to
+make the implementations of @file{limits.h} and @file{stdint.h} behave
+correctly. You should not use these macros directly; instead, include
+the appropriate headers. Some of these macros may not be defined on
+particular systems if GCC does not provide a @file{stdint.h} header on
+those systems.
+
+@item __SIZEOF_INT__
+@itemx __SIZEOF_LONG__
+@itemx __SIZEOF_LONG_LONG__
+@itemx __SIZEOF_SHORT__
+@itemx __SIZEOF_POINTER__
+@itemx __SIZEOF_FLOAT__
+@itemx __SIZEOF_DOUBLE__
+@itemx __SIZEOF_LONG_DOUBLE__
+@itemx __SIZEOF_SIZE_T__
+@itemx __SIZEOF_WCHAR_T__
+@itemx __SIZEOF_WINT_T__
+@itemx __SIZEOF_PTRDIFF_T__
+Defined to the number of bytes of the C standard data types: @code{int},
+@code{long}, @code{long long}, @code{short}, @code{void *}, @code{float},
+@code{double}, @code{long double}, @code{size_t}, @code{wchar_t}, @code{wint_t}
+and @code{ptrdiff_t}.
+
+@item __BYTE_ORDER__
+@itemx __ORDER_LITTLE_ENDIAN__
+@itemx __ORDER_BIG_ENDIAN__
+@itemx __ORDER_PDP_ENDIAN__
+@code{__BYTE_ORDER__} is defined to one of the values
+@code{__ORDER_LITTLE_ENDIAN__}, @code{__ORDER_BIG_ENDIAN__}, or
+@code{__ORDER_PDP_ENDIAN__} to reflect the layout of multi-byte and
+multi-word quantities in memory. If @code{__BYTE_ORDER__} is equal to
+@code{__ORDER_LITTLE_ENDIAN__} or @code{__ORDER_BIG_ENDIAN__}, then
+multi-byte and multi-word quantities are laid out identically: the
+byte (word) at the lowest address is the least significant or most
+significant byte (word) of the quantity, respectively. If
+@code{__BYTE_ORDER__} is equal to @code{__ORDER_PDP_ENDIAN__}, then
+bytes in 16-bit words are laid out in a little-endian fashion, whereas
+the 16-bit subwords of a 32-bit quantity are laid out in big-endian
+fashion.
+
+You should use these macros for testing like this:
+
+@smallexample
+/* @r{Test for a little-endian machine} */
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+@end smallexample
+
+@item __FLOAT_WORD_ORDER__
+@code{__FLOAT_WORD_ORDER__} is defined to one of the values
+@code{__ORDER_LITTLE_ENDIAN__} or @code{__ORDER_BIG_ENDIAN__} to reflect
+the layout of the words of multi-word floating-point quantities.
+
+@item __DEPRECATED
+This macro is defined, with value 1, when compiling a C++ source file
+with warnings about deprecated constructs enabled. These warnings are
+enabled by default, but can be disabled with @option{-Wno-deprecated}.
+
+@item __EXCEPTIONS
+This macro is defined, with value 1, when compiling a C++ source file
+with exceptions enabled. If @option{-fno-exceptions} is used when
+compiling the file, then this macro is not defined.
+
+@item __GXX_RTTI
+This macro is defined, with value 1, when compiling a C++ source file
+with runtime type identification enabled. If @option{-fno-rtti} is
+used when compiling the file, then this macro is not defined.
+
+@item __USING_SJLJ_EXCEPTIONS__
+This macro is defined, with value 1, if the compiler uses the old
+mechanism based on @code{setjmp} and @code{longjmp} for exception
+handling.
+
+@item __GXX_EXPERIMENTAL_CXX0X__
+This macro is defined when compiling a C++ source file with C++11 features
+enabled, i.e., for all C++ language dialects except @option{-std=c++98}
+and @option{-std=gnu++98}. This macro is obsolete, but can be used to
+detect experimental C++0x features in very old versions of GCC. Since
+GCC 4.7.0 the @code{__cplusplus} macro is defined correctly, so most
+code should test @code{__cplusplus >= 201103L} instead of using this
+macro.
+
+@item __GXX_WEAK__
+This macro is defined when compiling a C++ source file. It has the
+value 1 if the compiler will use weak symbols, COMDAT sections, or
+other similar techniques to collapse symbols with ``vague linkage''
+that are defined in multiple translation units. If the compiler will
+not collapse such symbols, this macro is defined with value 0. In
+general, user code should not need to make use of this macro; the
+purpose of this macro is to ease implementation of the C++ runtime
+library provided with G++.
+
+@item __NEXT_RUNTIME__
+This macro is defined, with value 1, if (and only if) the NeXT runtime
+(as in @option{-fnext-runtime}) is in use for Objective-C@. If the GNU
+runtime is used, this macro is not defined, so that you can use this
+macro to determine which runtime (NeXT or GNU) is being used.
+
+@item __LP64__
+@itemx _LP64
+These macros are defined, with value 1, if (and only if) the compilation
+is for a target where @code{long int} and pointer both use 64-bits and
+@code{int} uses 32-bit.
+
+@item __SSP__
+This macro is defined, with value 1, when @option{-fstack-protector} is in
+use.
+
+@item __SSP_ALL__
+This macro is defined, with value 2, when @option{-fstack-protector-all} is
+in use.
+
+@item __SSP_STRONG__
+This macro is defined, with value 3, when @option{-fstack-protector-strong} is
+in use.
+
+@item __SSP_EXPLICIT__
+This macro is defined, with value 4, when @option{-fstack-protector-explicit} is
+in use.
+
+@item __SANITIZE_ADDRESS__
+This macro is defined, with value 1, when @option{-fsanitize=address}
+or @option{-fsanitize=kernel-address} are in use.
+
+@item __SANITIZE_THREAD__
+This macro is defined, with value 1, when @option{-fsanitize=thread} is in use.
+
+@item __TIMESTAMP__
+This macro expands to a string constant that describes the date and time
+of the last modification of the current source file. The string constant
+contains abbreviated day of the week, month, day of the month, time in
+hh:mm:ss form, year and looks like @code{@w{"Sun Sep 16 01:03:52 1973"}}.
+If the day of the month is less than 10, it is padded with a space on the left.
+
+If GCC cannot determine the current date, it will emit a warning message
+(once per compilation) and @code{__TIMESTAMP__} will expand to
+@code{@w{"??? ??? ?? ??:??:?? ????"}}.
+
+@item __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1
+@itemx __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2
+@itemx __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
+@itemx __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8
+@itemx __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16
+These macros are defined when the target processor supports atomic compare
+and swap operations on operands 1, 2, 4, 8 or 16 bytes in length, respectively.
+
+@item __HAVE_SPECULATION_SAFE_VALUE
+This macro is defined with the value 1 to show that this version of GCC
+supports @code{__builtin_speculation_safe_value}.
+
+@item __GCC_HAVE_DWARF2_CFI_ASM
+This macro is defined when the compiler is emitting DWARF CFI directives
+to the assembler. When this is defined, it is possible to emit those same
+directives in inline assembly.
+
+@item __FP_FAST_FMA
+@itemx __FP_FAST_FMAF
+@itemx __FP_FAST_FMAL
+These macros are defined with value 1 if the backend supports the
+@code{fma}, @code{fmaf}, and @code{fmal} builtin functions, so that
+the include file @file{math.h} can define the macros
+@code{FP_FAST_FMA}, @code{FP_FAST_FMAF}, and @code{FP_FAST_FMAL}
+for compatibility with the 1999 C standard.
+
+@item __FP_FAST_FMAF16
+@itemx __FP_FAST_FMAF32
+@itemx __FP_FAST_FMAF64
+@itemx __FP_FAST_FMAF128
+@itemx __FP_FAST_FMAF32X
+@itemx __FP_FAST_FMAF64X
+@itemx __FP_FAST_FMAF128X
+These macros are defined with the value 1 if the backend supports the
+@code{fma} functions using the additional @code{_Float@var{n}} and
+@code{_Float@var{n}x} types that are defined in ISO/IEC TS
+18661-3:2015. The include file @file{math.h} can define the
+@code{FP_FAST_FMAF@var{n}} and @code{FP_FAST_FMAF@var{n}x} macros if
+the user defined @code{__STDC_WANT_IEC_60559_TYPES_EXT__} before
+including @file{math.h}.
+
+@item __GCC_IEC_559
+This macro is defined to indicate the intended level of support for
+IEEE 754 (IEC 60559) floating-point arithmetic. It expands to a
+nonnegative integer value. If 0, it indicates that the combination of
+the compiler configuration and the command-line options is not
+intended to support IEEE 754 arithmetic for @code{float} and
+@code{double} as defined in C99 and C11 Annex F (for example, that the
+standard rounding modes and exceptions are not supported, or that
+optimizations are enabled that conflict with IEEE 754 semantics). If
+1, it indicates that IEEE 754 arithmetic is intended to be supported;
+this does not mean that all relevant language features are supported
+by GCC. If 2 or more, it additionally indicates support for IEEE
+754-2008 (in particular, that the binary encodings for quiet and
+signaling NaNs are as specified in IEEE 754-2008).
+
+This macro does not indicate the default state of command-line options
+that control optimizations that C99 and C11 permit to be controlled by
+standard pragmas, where those standards do not require a particular
+default state. It does not indicate whether optimizations respect
+signaling NaN semantics (the macro for that is
+@code{__SUPPORT_SNAN__}). It does not indicate support for decimal
+floating point or the IEEE 754 binary16 and binary128 types.
+
+@item __GCC_IEC_559_COMPLEX
+This macro is defined to indicate the intended level of support for
+IEEE 754 (IEC 60559) floating-point arithmetic for complex numbers, as
+defined in C99 and C11 Annex G. It expands to a nonnegative integer
+value. If 0, it indicates that the combination of the compiler
+configuration and the command-line options is not intended to support
+Annex G requirements (for example, because @option{-fcx-limited-range}
+was used). If 1 or more, it indicates that it is intended to support
+those requirements; this does not mean that all relevant language
+features are supported by GCC.
+
+@item __NO_MATH_ERRNO__
+This macro is defined if @option{-fno-math-errno} is used, or enabled
+by another option such as @option{-ffast-math} or by default.
+
+@item __RECIPROCAL_MATH__
+This macro is defined if @option{-freciprocal-math} is used, or enabled
+by another option such as @option{-ffast-math} or by default.
+
+@item __NO_SIGNED_ZEROS__
+This macro is defined if @option{-fno-signed-zeros} is used, or enabled
+by another option such as @option{-ffast-math} or by default.
+
+@item __NO_TRAPPING_MATH__
+This macro is defined if @option{-fno-trapping-math} is used.
+
+@item __ASSOCIATIVE_MATH__
+This macro is defined if @option{-fassociative-math} is used, or enabled
+by another option such as @option{-ffast-math} or by default.
+
+@item __ROUNDING_MATH__
+This macro is defined if @option{-frounding-math} is used.
+
+@item __GNUC_EXECUTION_CHARSET_NAME
+@itemx __GNUC_WIDE_EXECUTION_CHARSET_NAME
+These macros are defined to expand to a narrow string literal of
+the name of the narrow and wide compile-time execution character
+set used. It directly reflects the name passed to the options
+@option{-fexec-charset} and @option{-fwide-exec-charset}, or the defaults
+documented for those options (that is, it can expand to something like
+@code{"UTF-8"}). @xref{Invocation}.
+@end table
+
+@node System-specific Predefined Macros
+@subsection System-specific Predefined Macros
+
+@cindex system-specific predefined macros
+@cindex predefined macros, system-specific
+@cindex reserved namespace
+
+The C preprocessor normally predefines several macros that indicate what
+type of system and machine is in use. They are obviously different on
+each target supported by GCC@. This manual, being for all systems and
+machines, cannot tell you what their names are, but you can use
+@command{cpp -dM} to see them all. @xref{Invocation}. All system-specific
+predefined macros expand to a constant value, so you can test them with
+either @samp{#ifdef} or @samp{#if}.
+
+The C standard requires that all system-specific macros be part of the
+@dfn{reserved namespace}. All names which begin with two underscores,
+or an underscore and a capital letter, are reserved for the compiler and
+library to use as they wish. However, historically system-specific
+macros have had names with no special prefix; for instance, it is common
+to find @code{unix} defined on Unix systems. For all such macros, GCC
+provides a parallel macro with two underscores added at the beginning
+and the end. If @code{unix} is defined, @code{__unix__} will be defined
+too. There will never be more than two underscores; the parallel of
+@code{_mips} is @code{__mips__}.
+
+When the @option{-ansi} option, or any @option{-std} option that
+requests strict conformance, is given to the compiler, all the
+system-specific predefined macros outside the reserved namespace are
+suppressed. The parallel macros, inside the reserved namespace, remain
+defined.
+
+We are slowly phasing out all predefined macros which are outside the
+reserved namespace. You should never use them in new programs, and we
+encourage you to correct older code to use the parallel macros whenever
+you find it. We don't recommend you use the system-specific macros that
+are in the reserved namespace, either. It is better in the long run to
+check specifically for features you need, using a tool such as
+@command{autoconf}.
+
+@node C++ Named Operators
+@subsection C++ Named Operators
+@cindex named operators
+@cindex C++ named operators
+@cindex @file{iso646.h}
+
+In C++, there are eleven keywords which are simply alternate spellings
+of operators normally written with punctuation. These keywords are
+treated as such even in the preprocessor. They function as operators in
+@samp{#if}, and they cannot be defined as macros or poisoned. In C, you
+can request that those keywords take their C++ meaning by including
+@file{iso646.h}. That header defines each one as a normal object-like
+macro expanding to the appropriate punctuator.
+
+These are the named operators and their corresponding punctuators:
+
+@multitable {Named Operator} {Punctuator}
+@item Named Operator @tab Punctuator
+@item @code{and} @tab @code{&&}
+@item @code{and_eq} @tab @code{&=}
+@item @code{bitand} @tab @code{&}
+@item @code{bitor} @tab @code{|}
+@item @code{compl} @tab @code{~}
+@item @code{not} @tab @code{!}
+@item @code{not_eq} @tab @code{!=}
+@item @code{or} @tab @code{||}
+@item @code{or_eq} @tab @code{|=}
+@item @code{xor} @tab @code{^}
+@item @code{xor_eq} @tab @code{^=}
+@end multitable
+
+@node Undefining and Redefining Macros
+@section Undefining and Redefining Macros
+@cindex undefining macros
+@cindex redefining macros
+@findex #undef
+
+If a macro ceases to be useful, it may be @dfn{undefined} with the
+@samp{#undef} directive. @samp{#undef} takes a single argument, the
+name of the macro to undefine. You use the bare macro name, even if the
+macro is function-like. It is an error if anything appears on the line
+after the macro name. @samp{#undef} has no effect if the name is not a
+macro.
+
+@smallexample
+#define FOO 4
+x = FOO; @expansion{} x = 4;
+#undef FOO
+x = FOO; @expansion{} x = FOO;
+@end smallexample
+
+Once a macro has been undefined, that identifier may be @dfn{redefined}
+as a macro by a subsequent @samp{#define} directive. The new definition
+need not have any resemblance to the old definition.
+
+However, if an identifier which is currently a macro is redefined, then
+the new definition must be @dfn{effectively the same} as the old one.
+Two macro definitions are effectively the same if:
+@itemize @bullet
+@item Both are the same type of macro (object- or function-like).
+@item All the tokens of the replacement list are the same.
+@item If there are any parameters, they are the same.
+@item Whitespace appears in the same places in both. It need not be
+exactly the same amount of whitespace, though. Remember that comments
+count as whitespace.
+@end itemize
+
+@noindent
+These definitions are effectively the same:
+@smallexample
+#define FOUR (2 + 2)
+#define FOUR (2 + 2)
+#define FOUR (2 /* @r{two} */ + 2)
+@end smallexample
+@noindent
+but these are not:
+@smallexample
+#define FOUR (2 + 2)
+#define FOUR ( 2+2 )
+#define FOUR (2 * 2)
+#define FOUR(score,and,seven,years,ago) (2 + 2)
+@end smallexample
+
+If a macro is redefined with a definition that is not effectively the
+same as the old one, the preprocessor issues a warning and changes the
+macro to use the new definition. If the new definition is effectively
+the same, the redefinition is silently ignored. This allows, for
+instance, two different headers to define a common macro. The
+preprocessor will only complain if the definitions do not match.
+
+@node Directives Within Macro Arguments
+@section Directives Within Macro Arguments
+@cindex macro arguments and directives
+
+Occasionally it is convenient to use preprocessor directives within
+the arguments of a macro. The C and C++ standards declare that
+behavior in these cases is undefined. GNU CPP
+processes arbitrary directives within macro arguments in
+exactly the same way as it would have processed the directive were the
+function-like macro invocation not present.
+
+If, within a macro invocation, that macro is redefined, then the new
+definition takes effect in time for argument pre-expansion, but the
+original definition is still used for argument replacement. Here is a
+pathological example:
+
+@smallexample
+#define f(x) x x
+f (1
+#undef f
+#define f 2
+f)
+@end smallexample
+
+@noindent
+which expands to
+
+@smallexample
+1 2 1 2
+@end smallexample
+
+@noindent
+with the semantics described above.
+
+@node Macro Pitfalls
+@section Macro Pitfalls
+@cindex problems with macros
+@cindex pitfalls of macros
+
+In this section we describe some special rules that apply to macros and
+macro expansion, and point out certain cases in which the rules have
+counter-intuitive consequences that you must watch out for.
+
+@menu
+* Misnesting::
+* Operator Precedence Problems::
+* Swallowing the Semicolon::
+* Duplication of Side Effects::
+* Self-Referential Macros::
+* Argument Prescan::
+* Newlines in Arguments::
+@end menu
+
+@node Misnesting
+@subsection Misnesting
+
+When a macro is called with arguments, the arguments are substituted
+into the macro body and the result is checked, together with the rest of
+the input file, for more macro calls. It is possible to piece together
+a macro call coming partially from the macro body and partially from the
+arguments. For example,
+
+@smallexample
+#define twice(x) (2*(x))
+#define call_with_1(x) x(1)
+call_with_1 (twice)
+ @expansion{} twice(1)
+ @expansion{} (2*(1))
+@end smallexample
+
+Macro definitions do not have to have balanced parentheses. By writing
+an unbalanced open parenthesis in a macro body, it is possible to create
+a macro call that begins inside the macro body but ends outside of it.
+For example,
+
+@smallexample
+#define strange(file) fprintf (file, "%s %d",
+@dots{}
+strange(stderr) p, 35)
+ @expansion{} fprintf (stderr, "%s %d", p, 35)
+@end smallexample
+
+The ability to piece together a macro call can be useful, but the use of
+unbalanced open parentheses in a macro body is just confusing, and
+should be avoided.
+
+@node Operator Precedence Problems
+@subsection Operator Precedence Problems
+@cindex parentheses in macro bodies
+
+You may have noticed that in most of the macro definition examples shown
+above, each occurrence of a macro argument name had parentheses around
+it. In addition, another pair of parentheses usually surround the
+entire macro definition. Here is why it is best to write macros that
+way.
+
+Suppose you define a macro as follows,
+
+@smallexample
+#define ceil_div(x, y) (x + y - 1) / y
+@end smallexample
+
+@noindent
+whose purpose is to divide, rounding up. (One use for this operation is
+to compute how many @code{int} objects are needed to hold a certain
+number of @code{char} objects.) Then suppose it is used as follows:
+
+@smallexample
+a = ceil_div (b & c, sizeof (int));
+ @expansion{} a = (b & c + sizeof (int) - 1) / sizeof (int);
+@end smallexample
+
+@noindent
+This does not do what is intended. The operator-precedence rules of
+C make it equivalent to this:
+
+@smallexample
+a = (b & (c + sizeof (int) - 1)) / sizeof (int);
+@end smallexample
+
+@noindent
+What we want is this:
+
+@smallexample
+a = ((b & c) + sizeof (int) - 1)) / sizeof (int);
+@end smallexample
+
+@noindent
+Defining the macro as
+
+@smallexample
+#define ceil_div(x, y) ((x) + (y) - 1) / (y)
+@end smallexample
+
+@noindent
+provides the desired result.
+
+Unintended grouping can result in another way. Consider @code{sizeof
+ceil_div(1, 2)}. That has the appearance of a C expression that would
+compute the size of the type of @code{ceil_div (1, 2)}, but in fact it
+means something very different. Here is what it expands to:
+
+@smallexample
+sizeof ((1) + (2) - 1) / (2)
+@end smallexample
+
+@noindent
+This would take the size of an integer and divide it by two. The
+precedence rules have put the division outside the @code{sizeof} when it
+was intended to be inside.
+
+Parentheses around the entire macro definition prevent such problems.
+Here, then, is the recommended way to define @code{ceil_div}:
+
+@smallexample
+#define ceil_div(x, y) (((x) + (y) - 1) / (y))
+@end smallexample
+
+@node Swallowing the Semicolon
+@subsection Swallowing the Semicolon
+@cindex semicolons (after macro calls)
+
+Often it is desirable to define a macro that expands into a compound
+statement. Consider, for example, the following macro, that advances a
+pointer (the argument @code{p} says where to find it) across whitespace
+characters:
+
+@smallexample
+#define SKIP_SPACES(p, limit) \
+@{ char *lim = (limit); \
+ while (p < lim) @{ \
+ if (*p++ != ' ') @{ \
+ p--; break; @}@}@}
+@end smallexample
+
+@noindent
+Here backslash-newline is used to split the macro definition, which must
+be a single logical line, so that it resembles the way such code would
+be laid out if not part of a macro definition.
+
+A call to this macro might be @code{SKIP_SPACES (p, lim)}. Strictly
+speaking, the call expands to a compound statement, which is a complete
+statement with no need for a semicolon to end it. However, since it
+looks like a function call, it minimizes confusion if you can use it
+like a function call, writing a semicolon afterward, as in
+@code{SKIP_SPACES (p, lim);}
+
+This can cause trouble before @code{else} statements, because the
+semicolon is actually a null statement. Suppose you write
+
+@smallexample
+if (*p != 0)
+ SKIP_SPACES (p, lim);
+else @dots{}
+@end smallexample
+
+@noindent
+The presence of two statements---the compound statement and a null
+statement---in between the @code{if} condition and the @code{else}
+makes invalid C code.
+
+The definition of the macro @code{SKIP_SPACES} can be altered to solve
+this problem, using a @code{do @dots{} while} statement. Here is how:
+
+@smallexample
+#define SKIP_SPACES(p, limit) \
+do @{ char *lim = (limit); \
+ while (p < lim) @{ \
+ if (*p++ != ' ') @{ \
+ p--; break; @}@}@} \
+while (0)
+@end smallexample
+
+Now @code{SKIP_SPACES (p, lim);} expands into
+
+@smallexample
+do @{@dots{}@} while (0);
+@end smallexample
+
+@noindent
+which is one statement. The loop executes exactly once; most compilers
+generate no extra code for it.
+
+@node Duplication of Side Effects
+@subsection Duplication of Side Effects
+
+@cindex side effects (in macro arguments)
+@cindex unsafe macros
+Many C programs define a macro @code{min}, for ``minimum'', like this:
+
+@smallexample
+#define min(X, Y) ((X) < (Y) ? (X) : (Y))
+@end smallexample
+
+When you use this macro with an argument containing a side effect,
+as shown here,
+
+@smallexample
+next = min (x + y, foo (z));
+@end smallexample
+
+@noindent
+it expands as follows:
+
+@smallexample
+next = ((x + y) < (foo (z)) ? (x + y) : (foo (z)));
+@end smallexample
+
+@noindent
+where @code{x + y} has been substituted for @code{X} and @code{foo (z)}
+for @code{Y}.
+
+The function @code{foo} is used only once in the statement as it appears
+in the program, but the expression @code{foo (z)} has been substituted
+twice into the macro expansion. As a result, @code{foo} might be called
+two times when the statement is executed. If it has side effects or if
+it takes a long time to compute, the results might not be what you
+intended. We say that @code{min} is an @dfn{unsafe} macro.
+
+The best solution to this problem is to define @code{min} in a way that
+computes the value of @code{foo (z)} only once. The C language offers
+no standard way to do this, but it can be done with GNU extensions as
+follows:
+
+@smallexample
+#define min(X, Y) \
+(@{ typeof (X) x_ = (X); \
+ typeof (Y) y_ = (Y); \
+ (x_ < y_) ? x_ : y_; @})
+@end smallexample
+
+The @samp{(@{ @dots{} @})} notation produces a compound statement that
+acts as an expression. Its value is the value of its last statement.
+This permits us to define local variables and assign each argument to
+one. The local variables have underscores after their names to reduce
+the risk of conflict with an identifier of wider scope (it is impossible
+to avoid this entirely). Now each argument is evaluated exactly once.
+
+If you do not wish to use GNU C extensions, the only solution is to be
+careful when @emph{using} the macro @code{min}. For example, you can
+calculate the value of @code{foo (z)}, save it in a variable, and use
+that variable in @code{min}:
+
+@smallexample
+@group
+#define min(X, Y) ((X) < (Y) ? (X) : (Y))
+@dots{}
+@{
+ int tem = foo (z);
+ next = min (x + y, tem);
+@}
+@end group
+@end smallexample
+
+@noindent
+(where we assume that @code{foo} returns type @code{int}).
+
+@node Self-Referential Macros
+@subsection Self-Referential Macros
+@cindex self-reference
+
+A @dfn{self-referential} macro is one whose name appears in its
+definition. Recall that all macro definitions are rescanned for more
+macros to replace. If the self-reference were considered a use of the
+macro, it would produce an infinitely large expansion. To prevent this,
+the self-reference is not considered a macro call. It is passed into
+the preprocessor output unchanged. Consider an example:
+
+@smallexample
+#define foo (4 + foo)
+@end smallexample
+
+@noindent
+where @code{foo} is also a variable in your program.
+
+Following the ordinary rules, each reference to @code{foo} will expand
+into @code{(4 + foo)}; then this will be rescanned and will expand into
+@code{(4 + (4 + foo))}; and so on until the computer runs out of memory.
+
+The self-reference rule cuts this process short after one step, at
+@code{(4 + foo)}. Therefore, this macro definition has the possibly
+useful effect of causing the program to add 4 to the value of @code{foo}
+wherever @code{foo} is referred to.
+
+In most cases, it is a bad idea to take advantage of this feature. A
+person reading the program who sees that @code{foo} is a variable will
+not expect that it is a macro as well. The reader will come across the
+identifier @code{foo} in the program and think its value should be that
+of the variable @code{foo}, whereas in fact the value is four greater.
+
+One common, useful use of self-reference is to create a macro which
+expands to itself. If you write
+
+@smallexample
+#define EPERM EPERM
+@end smallexample
+
+@noindent
+then the macro @code{EPERM} expands to @code{EPERM}. Effectively, it is
+left alone by the preprocessor whenever it's used in running text. You
+can tell that it's a macro with @samp{#ifdef}. You might do this if you
+want to define numeric constants with an @code{enum}, but have
+@samp{#ifdef} be true for each constant.
+
+If a macro @code{x} expands to use a macro @code{y}, and the expansion of
+@code{y} refers to the macro @code{x}, that is an @dfn{indirect
+self-reference} of @code{x}. @code{x} is not expanded in this case
+either. Thus, if we have
+
+@smallexample
+#define x (4 + y)
+#define y (2 * x)
+@end smallexample
+
+@noindent
+then @code{x} and @code{y} expand as follows:
+
+@smallexample
+@group
+x @expansion{} (4 + y)
+ @expansion{} (4 + (2 * x))
+
+y @expansion{} (2 * x)
+ @expansion{} (2 * (4 + y))
+@end group
+@end smallexample
+
+@noindent
+Each macro is expanded when it appears in the definition of the other
+macro, but not when it indirectly appears in its own definition.
+
+@node Argument Prescan
+@subsection Argument Prescan
+@cindex expansion of arguments
+@cindex macro argument expansion
+@cindex prescan of macro arguments
+
+Macro arguments are completely macro-expanded before they are
+substituted into a macro body, unless they are stringized or pasted
+with other tokens. After substitution, the entire macro body, including
+the substituted arguments, is scanned again for macros to be expanded.
+The result is that the arguments are scanned @emph{twice} to expand
+macro calls in them.
+
+Most of the time, this has no effect. If the argument contained any
+macro calls, they are expanded during the first scan. The result
+therefore contains no macro calls, so the second scan does not change
+it. If the argument were substituted as given, with no prescan, the
+single remaining scan would find the same macro calls and produce the
+same results.
+
+You might expect the double scan to change the results when a
+self-referential macro is used in an argument of another macro
+(@pxref{Self-Referential Macros}): the self-referential macro would be
+expanded once in the first scan, and a second time in the second scan.
+However, this is not what happens. The self-references that do not
+expand in the first scan are marked so that they will not expand in the
+second scan either.
+
+You might wonder, ``Why mention the prescan, if it makes no difference?
+And why not skip it and make the preprocessor faster?'' The answer is
+that the prescan does make a difference in three special cases:
+
+@itemize @bullet
+@item
+Nested calls to a macro.
+
+We say that @dfn{nested} calls to a macro occur when a macro's argument
+contains a call to that very macro. For example, if @code{f} is a macro
+that expects one argument, @code{f (f (1))} is a nested pair of calls to
+@code{f}. The desired expansion is made by expanding @code{f (1)} and
+substituting that into the definition of @code{f}. The prescan causes
+the expected result to happen. Without the prescan, @code{f (1)} itself
+would be substituted as an argument, and the inner use of @code{f} would
+appear during the main scan as an indirect self-reference and would not
+be expanded.
+
+@item
+Macros that call other macros that stringize or concatenate.
+
+If an argument is stringized or concatenated, the prescan does not
+occur. If you @emph{want} to expand a macro, then stringize or
+concatenate its expansion, you can do that by causing one macro to call
+another macro that does the stringizing or concatenation. For
+instance, if you have
+
+@smallexample
+#define AFTERX(x) X_ ## x
+#define XAFTERX(x) AFTERX(x)
+#define TABLESIZE 1024
+#define BUFSIZE TABLESIZE
+@end smallexample
+
+then @code{AFTERX(BUFSIZE)} expands to @code{X_BUFSIZE}, and
+@code{XAFTERX(BUFSIZE)} expands to @code{X_1024}. (Not to
+@code{X_TABLESIZE}. Prescan always does a complete expansion.)
+
+@item
+Macros used in arguments, whose expansions contain unshielded commas.
+
+This can cause a macro expanded on the second scan to be called with the
+wrong number of arguments. Here is an example:
+
+@smallexample
+#define foo a,b
+#define bar(x) lose(x)
+#define lose(x) (1 + (x))
+@end smallexample
+
+We would like @code{bar(foo)} to turn into @code{(1 + (foo))}, which
+would then turn into @code{(1 + (a,b))}. Instead, @code{bar(foo)}
+expands into @code{lose(a,b)}, and you get an error because @code{lose}
+requires a single argument. In this case, the problem is easily solved
+by the same parentheses that ought to be used to prevent misnesting of
+arithmetic operations:
+
+@smallexample
+#define foo (a,b)
+@exdent or
+#define bar(x) lose((x))
+@end smallexample
+
+The extra pair of parentheses prevents the comma in @code{foo}'s
+definition from being interpreted as an argument separator.
+
+@end itemize
+
+@node Newlines in Arguments
+@subsection Newlines in Arguments
+@cindex newlines in macro arguments
+
+The invocation of a function-like macro can extend over many logical
+lines. However, in the present implementation, the entire expansion
+comes out on one line. Thus line numbers emitted by the compiler or
+debugger refer to the line the invocation started on, which might be
+different to the line containing the argument causing the problem.
+
+Here is an example illustrating this:
+
+@smallexample
+#define ignore_second_arg(a,b,c) a; c
+
+ignore_second_arg (foo (),
+ ignored (),
+ syntax error);
+@end smallexample
+
+@noindent
+The syntax error triggered by the tokens @code{syntax error} results in
+an error message citing line three---the line of ignore_second_arg---
+even though the problematic code comes from line five.
+
+We consider this a bug, and intend to fix it in the near future.
+
+@node Conditionals
+@chapter Conditionals
+@cindex conditionals
+
+A @dfn{conditional} is a directive that instructs the preprocessor to
+select whether or not to include a chunk of code in the final token
+stream passed to the compiler. Preprocessor conditionals can test
+arithmetic expressions, or whether a name is defined as a macro, or both
+simultaneously using the special @code{defined} operator.
+
+A conditional in the C preprocessor resembles in some ways an @code{if}
+statement in C, but it is important to understand the difference between
+them. The condition in an @code{if} statement is tested during the
+execution of your program. Its purpose is to allow your program to
+behave differently from run to run, depending on the data it is
+operating on. The condition in a preprocessing conditional directive is
+tested when your program is compiled. Its purpose is to allow different
+code to be included in the program depending on the situation at the
+time of compilation.
+
+However, the distinction is becoming less clear. Modern compilers often
+do test @code{if} statements when a program is compiled, if their
+conditions are known not to vary at run time, and eliminate code which
+can never be executed. If you can count on your compiler to do this,
+you may find that your program is more readable if you use @code{if}
+statements with constant conditions (perhaps determined by macros). Of
+course, you can only use this to exclude code, not type definitions or
+other preprocessing directives, and you can only do it if the code
+remains syntactically valid when it is not to be used.
+
+@menu
+* Conditional Uses::
+* Conditional Syntax::
+* Deleted Code::
+@end menu
+
+@node Conditional Uses
+@section Conditional Uses
+
+There are three general reasons to use a conditional.
+
+@itemize @bullet
+@item
+A program may need to use different code depending on the machine or
+operating system it is to run on. In some cases the code for one
+operating system may be erroneous on another operating system; for
+example, it might refer to data types or constants that do not exist on
+the other system. When this happens, it is not enough to avoid
+executing the invalid code. Its mere presence will cause the compiler
+to reject the program. With a preprocessing conditional, the offending
+code can be effectively excised from the program when it is not valid.
+
+@item
+You may want to be able to compile the same source file into two
+different programs. One version might make frequent time-consuming
+consistency checks on its intermediate data, or print the values of
+those data for debugging, and the other not.
+
+@item
+A conditional whose condition is always false is one way to exclude code
+from the program but keep it as a sort of comment for future reference.
+@end itemize
+
+Simple programs that do not need system-specific logic or complex
+debugging hooks generally will not need to use preprocessing
+conditionals.
+
+@node Conditional Syntax
+@section Conditional Syntax
+
+@findex #if
+A conditional in the C preprocessor begins with a @dfn{conditional
+directive}: @samp{#if}, @samp{#ifdef} or @samp{#ifndef}.
+
+@menu
+* Ifdef::
+* If::
+* Defined::
+* Else::
+* Elif::
+* @code{__has_attribute}::
+* @code{__has_cpp_attribute}::
+* @code{__has_c_attribute}::
+* @code{__has_builtin}::
+* @code{__has_include}::
+@end menu
+
+@node Ifdef
+@subsection Ifdef
+@findex #ifdef
+@findex #endif
+
+The simplest sort of conditional is
+
+@smallexample
+@group
+#ifdef @var{MACRO}
+
+@var{controlled text}
+
+#endif /* @var{MACRO} */
+@end group
+@end smallexample
+
+@cindex conditional group
+This block is called a @dfn{conditional group}. @var{controlled text}
+will be included in the output of the preprocessor if and only if
+@var{MACRO} is defined. We say that the conditional @dfn{succeeds} if
+@var{MACRO} is defined, @dfn{fails} if it is not.
+
+The @var{controlled text} inside of a conditional can include
+preprocessing directives. They are executed only if the conditional
+succeeds. You can nest conditional groups inside other conditional
+groups, but they must be completely nested. In other words,
+@samp{#endif} always matches the nearest @samp{#ifdef} (or
+@samp{#ifndef}, or @samp{#if}). Also, you cannot start a conditional
+group in one file and end it in another.
+
+Even if a conditional fails, the @var{controlled text} inside it is
+still run through initial transformations and tokenization. Therefore,
+it must all be lexically valid C@. Normally the only way this matters is
+that all comments and string literals inside a failing conditional group
+must still be properly ended.
+
+The comment following the @samp{#endif} is not required, but it is a
+good practice if there is a lot of @var{controlled text}, because it
+helps people match the @samp{#endif} to the corresponding @samp{#ifdef}.
+Older programs sometimes put @var{MACRO} directly after the
+@samp{#endif} without enclosing it in a comment. This is invalid code
+according to the C standard. CPP accepts it with a warning. It
+never affects which @samp{#ifndef} the @samp{#endif} matches.
+
+@findex #ifndef
+Sometimes you wish to use some code if a macro is @emph{not} defined.
+You can do this by writing @samp{#ifndef} instead of @samp{#ifdef}.
+One common use of @samp{#ifndef} is to include code only the first
+time a header file is included. @xref{Once-Only Headers}.
+
+Macro definitions can vary between compilations for several reasons.
+Here are some samples.
+
+@itemize @bullet
+@item
+Some macros are predefined on each kind of machine
+(@pxref{System-specific Predefined Macros}). This allows you to provide
+code specially tuned for a particular machine.
+
+@item
+System header files define more macros, associated with the features
+they implement. You can test these macros with conditionals to avoid
+using a system feature on a machine where it is not implemented.
+
+@item
+Macros can be defined or undefined with the @option{-D} and @option{-U}
+command-line options when you compile the program. You can arrange to
+compile the same source file into two different programs by choosing a
+macro name to specify which program you want, writing conditionals to
+test whether or how this macro is defined, and then controlling the
+state of the macro with command-line options, perhaps set in the
+Makefile. @xref{Invocation}.
+
+@item
+Your program might have a special header file (often called
+@file{config.h}) that is adjusted when the program is compiled. It can
+define or not define macros depending on the features of the system and
+the desired capabilities of the program. The adjustment can be
+automated by a tool such as @command{autoconf}, or done by hand.
+@end itemize
+
+@node If
+@subsection If
+
+The @samp{#if} directive allows you to test the value of an arithmetic
+expression, rather than the mere existence of one macro. Its syntax is
+
+@smallexample
+@group
+#if @var{expression}
+
+@var{controlled text}
+
+#endif /* @var{expression} */
+@end group
+@end smallexample
+
+@var{expression} is a C expression of integer type, subject to stringent
+restrictions. It may contain
+
+@itemize @bullet
+@item
+Integer constants.
+
+@item
+Character constants, which are interpreted as they would be in normal
+code.
+
+@item
+Arithmetic operators for addition, subtraction, multiplication,
+division, bitwise operations, shifts, comparisons, and logical
+operations (@code{&&} and @code{||}). The latter two obey the usual
+short-circuiting rules of standard C@.
+
+@item
+Macros. All macros in the expression are expanded before actual
+computation of the expression's value begins.
+
+@item
+Uses of the @code{defined} operator, which lets you check whether macros
+are defined in the middle of an @samp{#if}.
+
+@item
+Identifiers that are not macros, which are all considered to be the
+number zero. This allows you to write @code{@w{#if MACRO}} instead of
+@code{@w{#ifdef MACRO}}, if you know that MACRO, when defined, will
+always have a nonzero value. Function-like macros used without their
+function call parentheses are also treated as zero.
+
+In some contexts this shortcut is undesirable. The @option{-Wundef}
+option causes GCC to warn whenever it encounters an identifier which is
+not a macro in an @samp{#if}.
+@end itemize
+
+The preprocessor does not know anything about types in the language.
+Therefore, @code{sizeof} operators are not recognized in @samp{#if}, and
+neither are @code{enum} constants. They will be taken as identifiers
+which are not macros, and replaced by zero. In the case of
+@code{sizeof}, this is likely to cause the expression to be invalid.
+
+The preprocessor calculates the value of @var{expression}. It carries
+out all calculations in the widest integer type known to the compiler;
+on most machines supported by GCC this is 64 bits. This is not the same
+rule as the compiler uses to calculate the value of a constant
+expression, and may give different results in some cases. If the value
+comes out to be nonzero, the @samp{#if} succeeds and the @var{controlled
+text} is included; otherwise it is skipped.
+
+@node Defined
+@subsection Defined
+
+@cindex @code{defined}
+The special operator @code{defined} is used in @samp{#if} and
+@samp{#elif} expressions to test whether a certain name is defined as a
+macro. @code{defined @var{name}} and @code{defined (@var{name})} are
+both expressions whose value is 1 if @var{name} is defined as a macro at
+the current point in the program, and 0 otherwise. Thus, @code{@w{#if
+defined MACRO}} is precisely equivalent to @code{@w{#ifdef MACRO}}.
+
+@code{defined} is useful when you wish to test more than one macro for
+existence at once. For example,
+
+@smallexample
+#if defined (__vax__) || defined (__ns16000__)
+@end smallexample
+
+@noindent
+would succeed if either of the names @code{__vax__} or
+@code{__ns16000__} is defined as a macro.
+
+Conditionals written like this:
+
+@smallexample
+#if defined BUFSIZE && BUFSIZE >= 1024
+@end smallexample
+
+@noindent
+can generally be simplified to just @code{@w{#if BUFSIZE >= 1024}},
+since if @code{BUFSIZE} is not defined, it will be interpreted as having
+the value zero.
+
+If the @code{defined} operator appears as a result of a macro expansion,
+the C standard says the behavior is undefined. GNU cpp treats it as a
+genuine @code{defined} operator and evaluates it normally. It will warn
+wherever your code uses this feature if you use the command-line option
+@option{-Wpedantic}, since other compilers may handle it differently. The
+warning is also enabled by @option{-Wextra}, and can also be enabled
+individually with @option{-Wexpansion-to-defined}.
+
+@node Else
+@subsection Else
+
+@findex #else
+The @samp{#else} directive can be added to a conditional to provide
+alternative text to be used if the condition fails. This is what it
+looks like:
+
+@smallexample
+@group
+#if @var{expression}
+@var{text-if-true}
+#else /* Not @var{expression} */
+@var{text-if-false}
+#endif /* Not @var{expression} */
+@end group
+@end smallexample
+
+@noindent
+If @var{expression} is nonzero, the @var{text-if-true} is included and
+the @var{text-if-false} is skipped. If @var{expression} is zero, the
+opposite happens.
+
+You can use @samp{#else} with @samp{#ifdef} and @samp{#ifndef}, too.
+
+@node Elif
+@subsection Elif
+
+@findex #elif
+One common case of nested conditionals is used to check for more than two
+possible alternatives. For example, you might have
+
+@smallexample
+#if X == 1
+@dots{}
+#else /* X != 1 */
+#if X == 2
+@dots{}
+#else /* X != 2 */
+@dots{}
+#endif /* X != 2 */
+#endif /* X != 1 */
+@end smallexample
+
+Another conditional directive, @samp{#elif}, allows this to be
+abbreviated as follows:
+
+@smallexample
+#if X == 1
+@dots{}
+#elif X == 2
+@dots{}
+#else /* X != 2 and X != 1*/
+@dots{}
+#endif /* X != 2 and X != 1*/
+@end smallexample
+
+@samp{#elif} stands for ``else if''. Like @samp{#else}, it goes in the
+middle of a conditional group and subdivides it; it does not require a
+matching @samp{#endif} of its own. Like @samp{#if}, the @samp{#elif}
+directive includes an expression to be tested. The text following the
+@samp{#elif} is processed only if the original @samp{#if}-condition
+failed and the @samp{#elif} condition succeeds.
+
+More than one @samp{#elif} can go in the same conditional group. Then
+the text after each @samp{#elif} is processed only if the @samp{#elif}
+condition succeeds after the original @samp{#if} and all previous
+@samp{#elif} directives within it have failed.
+
+@samp{#else} is allowed after any number of @samp{#elif} directives, but
+@samp{#elif} may not follow @samp{#else}.
+
+@node @code{__has_attribute}
+@subsection @code{__has_attribute}
+@cindex @code{__has_attribute}
+
+The special operator @code{__has_attribute (@var{operand})} may be used
+in @samp{#if} and @samp{#elif} expressions to test whether the attribute
+referenced by its @var{operand} is recognized by GCC. Using the operator
+in other contexts is not valid. In C code, if compiling for strict
+conformance to standards before C2x, @var{operand} must be
+a valid identifier. Otherwise, @var{operand} may be optionally
+introduced by the @code{@var{attribute-scope}::} prefix.
+The @var{attribute-scope} prefix identifies the ``namespace'' within
+which the attribute is recognized. The scope of GCC attributes is
+@samp{gnu} or @samp{__gnu__}. The @code{__has_attribute} operator by
+itself, without any @var{operand} or parentheses, acts as a predefined
+macro so that support for it can be tested in portable code. Thus,
+the recommended use of the operator is as follows:
+
+@smallexample
+#if defined __has_attribute
+# if __has_attribute (nonnull)
+# define ATTR_NONNULL __attribute__ ((nonnull))
+# endif
+#endif
+@end smallexample
+
+The first @samp{#if} test succeeds only when the operator is supported
+by the version of GCC (or another compiler) being used. Only when that
+test succeeds is it valid to use @code{__has_attribute} as a preprocessor
+operator. As a result, combining the two tests into a single expression as
+shown below would only be valid with a compiler that supports the operator
+but not with others that don't.
+
+@smallexample
+#if defined __has_attribute && __has_attribute (nonnull) /* not portable */
+@dots{}
+#endif
+@end smallexample
+
+@node @code{__has_cpp_attribute}
+@subsection @code{__has_cpp_attribute}
+@cindex @code{__has_cpp_attribute}
+
+The special operator @code{__has_cpp_attribute (@var{operand})} may be used
+in @samp{#if} and @samp{#elif} expressions in C++ code to test whether
+the attribute referenced by its @var{operand} is recognized by GCC.
+@code{__has_cpp_attribute (@var{operand})} is equivalent to
+@code{__has_attribute (@var{operand})} except that when @var{operand}
+designates a supported standard attribute it evaluates to an integer
+constant of the form @code{YYYYMM} indicating the year and month when
+the attribute was first introduced into the C++ standard. For additional
+information including the dates of the introduction of current standard
+attributes, see @w{@uref{https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations/,
+SD-6: SG10 Feature Test Recommendations}}.
+
+@node @code{__has_c_attribute}
+@subsection @code{__has_c_attribute}
+@cindex @code{__has_c_attribute}
+
+The special operator @code{__has_c_attribute (@var{operand})} may be
+used in @samp{#if} and @samp{#elif} expressions in C code to test
+whether the attribute referenced by its @var{operand} is recognized by
+GCC in attributes using the @samp{[[]]} syntax. GNU attributes must
+be specified with the scope @samp{gnu} or @samp{__gnu__} with
+@code{__has_c_attribute}. When @var{operand} designates a supported
+standard attribute it evaluates to an integer constant of the form
+@code{YYYYMM} indicating the year and month when the attribute was
+first introduced into the C standard, or when the syntax of operands
+to the attribute was extended in the C standard.
+
+@node @code{__has_builtin}
+@subsection @code{__has_builtin}
+@cindex @code{__has_builtin}
+
+The special operator @code{__has_builtin (@var{operand})} may be used in
+constant integer contexts and in preprocessor @samp{#if} and @samp{#elif}
+expressions to test whether the symbol named by its @var{operand} is
+recognized as a built-in function by GCC in the current language and
+conformance mode. It evaluates to a constant integer with a nonzero
+value if the argument refers to such a function, and to zero otherwise.
+The operator may also be used in preprocessor @samp{#if} and @samp{#elif}
+expressions. The @code{__has_builtin} operator by itself, without any
+@var{operand} or parentheses, acts as a predefined macro so that support
+for it can be tested in portable code. Thus, the recommended use of
+the operator is as follows:
+
+@smallexample
+#if defined __has_builtin
+# if __has_builtin (__builtin_object_size)
+# define builtin_object_size(ptr) __builtin_object_size (ptr, 2)
+# endif
+#endif
+#ifndef builtin_object_size
+# define builtin_object_size(ptr) ((size_t)-1)
+#endif
+@end smallexample
+
+@node @code{__has_include}
+@subsection @code{__has_include}
+@cindex @code{__has_include}
+
+The special operator @code{__has_include (@var{operand})} may be used in
+@samp{#if} and @samp{#elif} expressions to test whether the header referenced
+by its @var{operand} can be included using the @samp{#include} directive. Using
+the operator in other contexts is not valid. The @var{operand} takes
+the same form as the file in the @samp{#include} directive (@pxref{Include
+Syntax}) and evaluates to a nonzero value if the header can be included and
+to zero otherwise. Note that that the ability to include a header doesn't
+imply that the header doesn't contain invalid constructs or @samp{#error}
+directives that would cause the preprocessor to fail.
+
+The @code{__has_include} operator by itself, without any @var{operand} or
+parentheses, acts as a predefined macro so that support for it can be tested
+in portable code. Thus, the recommended use of the operator is as follows:
+
+@smallexample
+#if defined __has_include
+# if __has_include (<stdatomic.h>)
+# include <stdatomic.h>
+# endif
+#endif
+@end smallexample
+
+The first @samp{#if} test succeeds only when the operator is supported
+by the version of GCC (or another compiler) being used. Only when that
+test succeeds is it valid to use @code{__has_include} as a preprocessor
+operator. As a result, combining the two tests into a single expression
+as shown below would only be valid with a compiler that supports the operator
+but not with others that don't.
+
+@smallexample
+#if defined __has_include && __has_include ("header.h") /* not portable */
+@dots{}
+#endif
+@end smallexample
+
+@node Deleted Code
+@section Deleted Code
+@cindex commenting out code
+
+If you replace or delete a part of the program but want to keep the old
+code around for future reference, you often cannot simply comment it
+out. Block comments do not nest, so the first comment inside the old
+code will end the commenting-out. The probable result is a flood of
+syntax errors.
+
+One way to avoid this problem is to use an always-false conditional
+instead. For instance, put @code{#if 0} before the deleted code and
+@code{#endif} after it. This works even if the code being turned
+off contains conditionals, but they must be entire conditionals
+(balanced @samp{#if} and @samp{#endif}).
+
+Some people use @code{#ifdef notdef} instead. This is risky, because
+@code{notdef} might be accidentally defined as a macro, and then the
+conditional would succeed. @code{#if 0} can be counted on to fail.
+
+Do not use @code{#if 0} for comments which are not C code. Use a real
+comment, instead. The interior of @code{#if 0} must consist of complete
+tokens; in particular, single-quote characters must balance. Comments
+often contain unbalanced single-quote characters (known in English as
+apostrophes). These confuse @code{#if 0}. They don't confuse
+@samp{/*}.
+
+@node Diagnostics
+@chapter Diagnostics
+@cindex diagnostic
+@cindex reporting errors
+@cindex reporting warnings
+
+@findex #error
+The directive @samp{#error} causes the preprocessor to report a fatal
+error. The tokens forming the rest of the line following @samp{#error}
+are used as the error message.
+
+You would use @samp{#error} inside of a conditional that detects a
+combination of parameters which you know the program does not properly
+support. For example, if you know that the program will not run
+properly on a VAX, you might write
+
+@smallexample
+@group
+#ifdef __vax__
+#error "Won't work on VAXen. See comments at get_last_object."
+#endif
+@end group
+@end smallexample
+
+If you have several configuration parameters that must be set up by
+the installation in a consistent way, you can use conditionals to detect
+an inconsistency and report it with @samp{#error}. For example,
+
+@smallexample
+#if !defined(FOO) && defined(BAR)
+#error "BAR requires FOO."
+#endif
+@end smallexample
+
+@findex #warning
+The directive @samp{#warning} is like @samp{#error}, but causes the
+preprocessor to issue a warning and continue preprocessing. The tokens
+following @samp{#warning} are used as the warning message.
+
+You might use @samp{#warning} in obsolete header files, with a message
+directing the user to the header file which should be used instead.
+
+Neither @samp{#error} nor @samp{#warning} macro-expands its argument.
+Internal whitespace sequences are each replaced with a single space.
+The line must consist of complete tokens. It is wisest to make the
+argument of these directives be a single string constant; this avoids
+problems with apostrophes and the like.
+
+@node Line Control
+@chapter Line Control
+@cindex line control
+
+The C preprocessor informs the C compiler of the location in your source
+code where each token came from. Presently, this is just the file name
+and line number. All the tokens resulting from macro expansion are
+reported as having appeared on the line of the source file where the
+outermost macro was used. We intend to be more accurate in the future.
+
+If you write a program which generates source code, such as the
+@command{bison} parser generator, you may want to adjust the preprocessor's
+notion of the current file name and line number by hand. Parts of the
+output from @command{bison} are generated from scratch, other parts come
+from a standard parser file. The rest are copied verbatim from
+@command{bison}'s input. You would like compiler error messages and
+symbolic debuggers to be able to refer to @code{bison}'s input file.
+
+@findex #line
+@command{bison} or any such program can arrange this by writing
+@samp{#line} directives into the output file. @samp{#line} is a
+directive that specifies the original line number and source file name
+for subsequent input in the current preprocessor input file.
+@samp{#line} has three variants:
+
+@table @code
+@item #line @var{linenum}
+@var{linenum} is a non-negative decimal integer constant. It specifies
+the line number which should be reported for the following line of
+input. Subsequent lines are counted from @var{linenum}.
+
+@item #line @var{linenum} @var{filename}
+@var{linenum} is the same as for the first form, and has the same
+effect. In addition, @var{filename} is a string constant. The
+following line and all subsequent lines are reported to come from the
+file it specifies, until something else happens to change that.
+@var{filename} is interpreted according to the normal rules for a string
+constant: backslash escapes are interpreted. This is different from
+@samp{#include}.
+
+@item #line @var{anything else}
+@var{anything else} is checked for macro calls, which are expanded.
+The result should match one of the above two forms.
+@end table
+
+@samp{#line} directives alter the results of the @code{__FILE__} and
+@code{__LINE__} predefined macros from that point on. @xref{Standard
+Predefined Macros}. They do not have any effect on @samp{#include}'s
+idea of the directory containing the current file.
+
+@node Pragmas
+@chapter Pragmas
+
+@cindex pragma directive
+
+The @samp{#pragma} directive is the method specified by the C standard
+for providing additional information to the compiler, beyond what is
+conveyed in the language itself. The forms of this directive
+(commonly known as @dfn{pragmas}) specified by C standard are prefixed with
+@code{STDC}. A C compiler is free to attach any meaning it likes to other
+pragmas. Most GNU-defined, supported pragmas have been given a
+@code{GCC} prefix.
+
+@cindex @code{_Pragma}
+C99 introduced the @code{@w{_Pragma}} operator. This feature addresses a
+major problem with @samp{#pragma}: being a directive, it cannot be
+produced as the result of macro expansion. @code{@w{_Pragma}} is an
+operator, much like @code{sizeof} or @code{defined}, and can be embedded
+in a macro.
+
+Its syntax is @code{@w{_Pragma (@var{string-literal})}}, where
+@var{string-literal} can be either a normal or wide-character string
+literal. It is destringized, by replacing all @samp{\\} with a single
+@samp{\} and all @samp{\"} with a @samp{"}. The result is then
+processed as if it had appeared as the right hand side of a
+@samp{#pragma} directive. For example,
+
+@smallexample
+_Pragma ("GCC dependency \"parse.y\"")
+@end smallexample
+
+@noindent
+has the same effect as @code{#pragma GCC dependency "parse.y"}. The
+same effect could be achieved using macros, for example
+
+@smallexample
+#define DO_PRAGMA(x) _Pragma (#x)
+DO_PRAGMA (GCC dependency "parse.y")
+@end smallexample
+
+The standard is unclear on where a @code{_Pragma} operator can appear.
+The preprocessor does not accept it within a preprocessing conditional
+directive like @samp{#if}. To be safe, you are probably best keeping it
+out of directives other than @samp{#define}, and putting it on a line of
+its own.
+
+This manual documents the pragmas which are meaningful to the
+preprocessor itself. Other pragmas are meaningful to the C or C++
+compilers. They are documented in the GCC manual.
+
+GCC plugins may provide their own pragmas.
+
+@ftable @code
+@item #pragma GCC dependency
+@code{#pragma GCC dependency} allows you to check the relative dates of
+the current file and another file. If the other file is more recent than
+the current file, a warning is issued. This is useful if the current
+file is derived from the other file, and should be regenerated. The
+other file is searched for using the normal include search path.
+Optional trailing text can be used to give more information in the
+warning message.
+
+@smallexample
+#pragma GCC dependency "parse.y"
+#pragma GCC dependency "/usr/include/time.h" rerun fixincludes
+@end smallexample
+
+@item #pragma GCC poison
+Sometimes, there is an identifier that you want to remove completely
+from your program, and make sure that it never creeps back in. To
+enforce this, you can @dfn{poison} the identifier with this pragma.
+@code{#pragma GCC poison} is followed by a list of identifiers to
+poison. If any of those identifiers appears anywhere in the source
+after the directive, it is a hard error. For example,
+
+@smallexample
+#pragma GCC poison printf sprintf fprintf
+sprintf(some_string, "hello");
+@end smallexample
+
+@noindent
+will produce an error.
+
+If a poisoned identifier appears as part of the expansion of a macro
+which was defined before the identifier was poisoned, it will @emph{not}
+cause an error. This lets you poison an identifier without worrying
+about system headers defining macros that use it.
+
+For example,
+
+@smallexample
+#define strrchr rindex
+#pragma GCC poison rindex
+strrchr(some_string, 'h');
+@end smallexample
+
+@noindent
+will not produce an error.
+
+@item #pragma GCC system_header
+This pragma takes no arguments. It causes the rest of the code in the
+current file to be treated as if it came from a system header.
+@xref{System Headers}.
+
+@item #pragma GCC warning
+@itemx #pragma GCC error
+@code{#pragma GCC warning "message"} causes the preprocessor to issue
+a warning diagnostic with the text @samp{message}. The message
+contained in the pragma must be a single string literal. Similarly,
+@code{#pragma GCC error "message"} issues an error message. Unlike
+the @samp{#warning} and @samp{#error} directives, these pragmas can be
+embedded in preprocessor macros using @samp{_Pragma}.
+
+@item #pragma once
+If @code{#pragma once} is seen when scanning a header file, that
+file will never be read again, no matter what. It is a less-portable
+alternative to using @samp{#ifndef} to guard the contents of header files
+against multiple inclusions.
+
+@end ftable
+
+@node Other Directives
+@chapter Other Directives
+
+@findex #ident
+@findex #sccs
+The @samp{#ident} directive takes one argument, a string constant. On
+some systems, that string constant is copied into a special segment of
+the object file. On other systems, the directive is ignored. The
+@samp{#sccs} directive is a synonym for @samp{#ident}.
+
+These directives are not part of the C standard, but they are not
+official GNU extensions either. What historical information we have
+been able to find, suggests they originated with System V@.
+
+@cindex null directive
+The @dfn{null directive} consists of a @samp{#} followed by a newline,
+with only whitespace (including comments) in between. A null directive
+is understood as a preprocessing directive but has no effect on the
+preprocessor output. The primary significance of the existence of the
+null directive is that an input line consisting of just a @samp{#} will
+produce no output, rather than a line of output containing just a
+@samp{#}. Supposedly some old C programs contain such lines.
+
+@node Preprocessor Output
+@chapter Preprocessor Output
+
+When the C preprocessor is used with the C, C++, or Objective-C
+compilers, it is integrated into the compiler and communicates a stream
+of binary tokens directly to the compiler's parser. However, it can
+also be used in the more conventional standalone mode, where it produces
+textual output.
+@c FIXME: Document the library interface.
+
+@cindex output format
+The output from the C preprocessor looks much like the input, except
+that all preprocessing directive lines have been replaced with blank
+lines and all comments with spaces. Long runs of blank lines are
+discarded.
+
+The ISO standard specifies that it is implementation defined whether a
+preprocessor preserves whitespace between tokens, or replaces it with
+e.g.@: a single space. In GNU CPP, whitespace between tokens is collapsed
+to become a single space, with the exception that the first token on a
+non-directive line is preceded with sufficient spaces that it appears in
+the same column in the preprocessed output that it appeared in the
+original source file. This is so the output is easy to read.
+CPP does not insert any
+whitespace where there was none in the original source, except where
+necessary to prevent an accidental token paste.
+
+@cindex linemarkers
+Source file name and line number information is conveyed by lines
+of the form
+
+@smallexample
+# @var{linenum} @var{filename} @var{flags}
+@end smallexample
+
+@noindent
+These are called @dfn{linemarkers}. They are inserted as needed into
+the output (but never within a string or character constant). They mean
+that the following line originated in file @var{filename} at line
+@var{linenum}. @var{filename} will never contain any non-printing
+characters; they are replaced with octal escape sequences.
+
+After the file name comes zero or more flags, which are @samp{1},
+@samp{2}, @samp{3}, or @samp{4}. If there are multiple flags, spaces
+separate them. Here is what the flags mean:
+
+@table @samp
+@item 1
+This indicates the start of a new file.
+@item 2
+This indicates returning to a file (after having included another file).
+@item 3
+This indicates that the following text comes from a system header file,
+so certain warnings should be suppressed.
+@item 4
+This indicates that the following text should be treated as being
+wrapped in an implicit @code{extern "C"} block.
+@c maybe cross reference SYSTEM_IMPLICIT_EXTERN_C
+@end table
+
+As an extension, the preprocessor accepts linemarkers in non-assembler
+input files. They are treated like the corresponding @samp{#line}
+directive, (@pxref{Line Control}), except that trailing flags are
+permitted, and are interpreted with the meanings described above. If
+multiple flags are given, they must be in ascending order.
+
+Some directives may be duplicated in the output of the preprocessor.
+These are @samp{#ident} (always), @samp{#pragma} (only if the
+preprocessor does not handle the pragma itself), and @samp{#define} and
+@samp{#undef} (with certain debugging options). If this happens, the
+@samp{#} of the directive will always be in the first column, and there
+will be no space between the @samp{#} and the directive name. If macro
+expansion happens to generate tokens which might be mistaken for a
+duplicated directive, a space will be inserted between the @samp{#} and
+the directive name.
+
+@node Traditional Mode
+@chapter Traditional Mode
+
+Traditional (pre-standard) C preprocessing is rather different from
+the preprocessing specified by the standard. When the preprocessor
+is invoked with the
+@option{-traditional-cpp} option, it attempts to emulate a traditional
+preprocessor.
+
+This mode is not useful for compiling C code with GCC,
+but is intended for use with non-C preprocessing applications. Thus
+traditional mode semantics are supported only when invoking
+the preprocessor explicitly, and not in the compiler front ends.
+
+The implementation does not correspond precisely to the behavior of
+early pre-standard versions of GCC, nor to any true traditional preprocessor.
+After all, inconsistencies among traditional implementations were a
+major motivation for C standardization. However, we intend that it
+should be compatible with true traditional preprocessors in all ways
+that actually matter.
+
+@menu
+* Traditional lexical analysis::
+* Traditional macros::
+* Traditional miscellany::
+* Traditional warnings::
+@end menu
+
+@node Traditional lexical analysis
+@section Traditional lexical analysis
+
+The traditional preprocessor does not decompose its input into tokens
+the same way a standards-conforming preprocessor does. The input is
+simply treated as a stream of text with minimal internal form.
+
+This implementation does not treat trigraphs (@pxref{trigraphs})
+specially since they were an invention of the standards committee. It
+handles arbitrarily-positioned escaped newlines properly and splices
+the lines as you would expect; many traditional preprocessors did not
+do this.
+
+The form of horizontal whitespace in the input file is preserved in
+the output. In particular, hard tabs remain hard tabs. This can be
+useful if, for example, you are preprocessing a Makefile.
+
+Traditional CPP only recognizes C-style block comments, and treats the
+@samp{/*} sequence as introducing a comment only if it lies outside
+quoted text. Quoted text is introduced by the usual single and double
+quotes, and also by an initial @samp{<} in a @code{#include}
+directive.
+
+Traditionally, comments are completely removed and are not replaced
+with a space. Since a traditional compiler does its own tokenization
+of the output of the preprocessor, this means that comments can
+effectively be used as token paste operators. However, comments
+behave like separators for text handled by the preprocessor itself,
+since it doesn't re-lex its input. For example, in
+
+@smallexample
+#if foo/**/bar
+@end smallexample
+
+@noindent
+@samp{foo} and @samp{bar} are distinct identifiers and expanded
+separately if they happen to be macros. In other words, this
+directive is equivalent to
+
+@smallexample
+#if foo bar
+@end smallexample
+
+@noindent
+rather than
+
+@smallexample
+#if foobar
+@end smallexample
+
+Generally speaking, in traditional mode an opening quote need not have
+a matching closing quote. In particular, a macro may be defined with
+replacement text that contains an unmatched quote. Of course, if you
+attempt to compile preprocessed output containing an unmatched quote
+you will get a syntax error.
+
+However, all preprocessing directives other than @code{#define}
+require matching quotes. For example:
+
+@smallexample
+#define m This macro's fine and has an unmatched quote
+"/* This is not a comment. */
+/* @r{This is a comment. The following #include directive
+ is ill-formed.} */
+#include <stdio.h
+@end smallexample
+
+Just as for the ISO preprocessor, what would be a closing quote can be
+escaped with a backslash to prevent the quoted text from closing.
+
+@node Traditional macros
+@section Traditional macros
+
+The major difference between traditional and ISO macros is that the
+former expand to text rather than to a token sequence. CPP removes
+all leading and trailing horizontal whitespace from a macro's
+replacement text before storing it, but preserves the form of internal
+whitespace.
+
+One consequence is that it is legitimate for the replacement text to
+contain an unmatched quote (@pxref{Traditional lexical analysis}). An
+unclosed string or character constant continues into the text
+following the macro call. Similarly, the text at the end of a macro's
+expansion can run together with the text after the macro invocation to
+produce a single token.
+
+Normally comments are removed from the replacement text after the
+macro is expanded, but if the @option{-CC} option is passed on the
+command-line comments are preserved. (In fact, the current
+implementation removes comments even before saving the macro
+replacement text, but it careful to do it in such a way that the
+observed effect is identical even in the function-like macro case.)
+
+The ISO stringizing operator @samp{#} and token paste operator
+@samp{##} have no special meaning. As explained later, an effect
+similar to these operators can be obtained in a different way. Macro
+names that are embedded in quotes, either from the main file or after
+macro replacement, do not expand.
+
+CPP replaces an unquoted object-like macro name with its replacement
+text, and then rescans it for further macros to replace. Unlike
+standard macro expansion, traditional macro expansion has no provision
+to prevent recursion. If an object-like macro appears unquoted in its
+replacement text, it will be replaced again during the rescan pass,
+and so on @emph{ad infinitum}. GCC detects when it is expanding
+recursive macros, emits an error message, and continues after the
+offending macro invocation.
+
+@smallexample
+#define PLUS +
+#define INC(x) PLUS+x
+INC(foo);
+ @expansion{} ++foo;
+@end smallexample
+
+Function-like macros are similar in form but quite different in
+behavior to their ISO counterparts. Their arguments are contained
+within parentheses, are comma-separated, and can cross physical lines.
+Commas within nested parentheses are not treated as argument
+separators. Similarly, a quote in an argument cannot be left
+unclosed; a following comma or parenthesis that comes before the
+closing quote is treated like any other character. There is no
+facility for handling variadic macros.
+
+This implementation removes all comments from macro arguments, unless
+the @option{-C} option is given. The form of all other horizontal
+whitespace in arguments is preserved, including leading and trailing
+whitespace. In particular
+
+@smallexample
+f( )
+@end smallexample
+
+@noindent
+is treated as an invocation of the macro @samp{f} with a single
+argument consisting of a single space. If you want to invoke a
+function-like macro that takes no arguments, you must not leave any
+whitespace between the parentheses.
+
+If a macro argument crosses a new line, the new line is replaced with
+a space when forming the argument. If the previous line contained an
+unterminated quote, the following line inherits the quoted state.
+
+Traditional preprocessors replace parameters in the replacement text
+with their arguments regardless of whether the parameters are within
+quotes or not. This provides a way to stringize arguments. For
+example
+
+@smallexample
+#define str(x) "x"
+str(/* @r{A comment} */some text )
+ @expansion{} "some text "
+@end smallexample
+
+@noindent
+Note that the comment is removed, but that the trailing space is
+preserved. Here is an example of using a comment to effect token
+pasting.
+
+@smallexample
+#define suffix(x) foo_/**/x
+suffix(bar)
+ @expansion{} foo_bar
+@end smallexample
+
+@node Traditional miscellany
+@section Traditional miscellany
+
+Here are some things to be aware of when using the traditional
+preprocessor.
+
+@itemize @bullet
+@item
+Preprocessing directives are recognized only when their leading
+@samp{#} appears in the first column. There can be no whitespace
+between the beginning of the line and the @samp{#}, but whitespace can
+follow the @samp{#}.
+
+@item
+A true traditional C preprocessor does not recognize @samp{#error} or
+@samp{#pragma}, and may not recognize @samp{#elif}. CPP supports all
+the directives in traditional mode that it supports in ISO mode,
+including extensions, with the exception that the effects of
+@samp{#pragma GCC poison} are undefined.
+
+@item
+__STDC__ is not defined.
+
+@item
+If you use digraphs the behavior is undefined.
+
+@item
+If a line that looks like a directive appears within macro arguments,
+the behavior is undefined.
+
+@end itemize
+
+@node Traditional warnings
+@section Traditional warnings
+You can request warnings about features that did not exist, or worked
+differently, in traditional C with the @option{-Wtraditional} option.
+GCC does not warn about features of ISO C which you must use when you
+are using a conforming compiler, such as the @samp{#} and @samp{##}
+operators.
+
+Presently @option{-Wtraditional} warns about:
+
+@itemize @bullet
+@item
+Macro parameters that appear within string literals in the macro body.
+In traditional C macro replacement takes place within string literals,
+but does not in ISO C@.
+
+@item
+In traditional C, some preprocessor directives did not exist.
+Traditional preprocessors would only consider a line to be a directive
+if the @samp{#} appeared in column 1 on the line. Therefore
+@option{-Wtraditional} warns about directives that traditional C
+understands but would ignore because the @samp{#} does not appear as the
+first character on the line. It also suggests you hide directives like
+@samp{#pragma} not understood by traditional C by indenting them. Some
+traditional implementations would not recognize @samp{#elif}, so it
+suggests avoiding it altogether.
+
+@item
+A function-like macro that appears without an argument list. In some
+traditional preprocessors this was an error. In ISO C it merely means
+that the macro is not expanded.
+
+@item
+The unary plus operator. This did not exist in traditional C@.
+
+@item
+The @samp{U} and @samp{LL} integer constant suffixes, which were not
+available in traditional C@. (Traditional C does support the @samp{L}
+suffix for simple long integer constants.) You are not warned about
+uses of these suffixes in macros defined in system headers. For
+instance, @code{UINT_MAX} may well be defined as @code{4294967295U}, but
+you will not be warned if you use @code{UINT_MAX}.
+
+You can usually avoid the warning, and the related warning about
+constants which are so large that they are unsigned, by writing the
+integer constant in question in hexadecimal, with no U suffix. Take
+care, though, because this gives the wrong result in exotic cases.
+@end itemize
+
+@node Implementation Details
+@chapter Implementation Details
+
+Here we document details of how the preprocessor's implementation
+affects its user-visible behavior. You should try to avoid undue
+reliance on behavior described here, as it is possible that it will
+change subtly in future implementations.
+
+Also documented here are obsolete features still supported by CPP@.
+
+@menu
+* Implementation-defined behavior::
+* Implementation limits::
+* Obsolete Features::
+@end menu
+
+@node Implementation-defined behavior
+@section Implementation-defined behavior
+@cindex implementation-defined behavior
+
+This is how CPP behaves in all the cases which the C standard
+describes as @dfn{implementation-defined}. This term means that the
+implementation is free to do what it likes, but must document its choice
+and stick to it.
+@c FIXME: Check the C++ standard for more implementation-defined stuff.
+
+@itemize @bullet
+@need 1000
+@item The mapping of physical source file multi-byte characters to the
+execution character set.
+
+The input character set can be specified using the
+@option{-finput-charset} option, while the execution character set may
+be controlled using the @option{-fexec-charset} and
+@option{-fwide-exec-charset} options.
+
+@item Identifier characters.
+@anchor{Identifier characters}
+
+The C and C++ standards allow identifiers to be composed of @samp{_}
+and the alphanumeric characters. C++ also allows universal character
+names. C99 and later C standards permit both universal character
+names and implementation-defined characters. In both C and C++ modes,
+GCC accepts in identifiers exactly those extended characters that
+correspond to universal character names permitted by the chosen
+standard.
+
+GCC allows the @samp{$} character in identifiers as an extension for
+most targets. This is true regardless of the @option{std=} switch,
+since this extension cannot conflict with standards-conforming
+programs. When preprocessing assembler, however, dollars are not
+identifier characters by default.
+
+Currently the targets that by default do not permit @samp{$} are AVR,
+IP2K, MMIX, MIPS Irix 3, ARM aout, and PowerPC targets for the AIX
+operating system.
+
+You can override the default with @option{-fdollars-in-identifiers} or
+@option{-fno-dollars-in-identifiers}. @xref{fdollars-in-identifiers}.
+
+@item Non-empty sequences of whitespace characters.
+
+In textual output, each whitespace sequence is collapsed to a single
+space. For aesthetic reasons, the first token on each non-directive
+line of output is preceded with sufficient spaces that it appears in the
+same column as it did in the original source file.
+
+@item The numeric value of character constants in preprocessor expressions.
+
+The preprocessor and compiler interpret character constants in the
+same way; i.e.@: escape sequences such as @samp{\a} are given the
+values they would have on the target machine.
+
+The compiler evaluates a multi-character character constant a character
+at a time, shifting the previous value left by the number of bits per
+target character, and then or-ing in the bit-pattern of the new
+character truncated to the width of a target character. The final
+bit-pattern is given type @code{int}, and is therefore signed,
+regardless of whether single characters are signed or not.
+If there are more
+characters in the constant than would fit in the target @code{int} the
+compiler issues a warning, and the excess leading characters are
+ignored.
+
+For example, @code{'ab'} for a target with an 8-bit @code{char} would be
+interpreted as @w{@samp{(int) ((unsigned char) 'a' * 256 + (unsigned char)
+'b')}}, and @code{'\234a'} as @w{@samp{(int) ((unsigned char) '\234' *
+256 + (unsigned char) 'a')}}.
+
+@item Source file inclusion.
+
+For a discussion on how the preprocessor locates header files,
+@ref{Include Operation}.
+
+@item Interpretation of the filename resulting from a macro-expanded
+@samp{#include} directive.
+
+@xref{Computed Includes}.
+
+@item Treatment of a @samp{#pragma} directive that after macro-expansion
+results in a standard pragma.
+
+No macro expansion occurs on any @samp{#pragma} directive line, so the
+question does not arise.
+
+Note that GCC does not yet implement any of the standard
+pragmas.
+
+@end itemize
+
+@node Implementation limits
+@section Implementation limits
+@cindex implementation limits
+
+CPP has a small number of internal limits. This section lists the
+limits which the C standard requires to be no lower than some minimum,
+and all the others known. It is intended that there should be as few limits
+as possible. If you encounter an undocumented or inconvenient limit,
+please report that as a bug. @xref{Bugs, , Reporting Bugs, gcc, Using
+the GNU Compiler Collection (GCC)}.
+
+Where we say something is limited @dfn{only by available memory}, that
+means that internal data structures impose no intrinsic limit, and space
+is allocated with @code{malloc} or equivalent. The actual limit will
+therefore depend on many things, such as the size of other things
+allocated by the compiler at the same time, the amount of memory
+consumed by other processes on the same computer, etc.
+
+@itemize @bullet
+
+@item Nesting levels of @samp{#include} files.
+
+We impose an arbitrary limit of 200 levels, to avoid runaway recursion.
+The standard requires at least 15 levels.
+
+@item Nesting levels of conditional inclusion.
+
+The C standard mandates this be at least 63. CPP is limited only by
+available memory.
+
+@item Levels of parenthesized expressions within a full expression.
+
+The C standard requires this to be at least 63. In preprocessor
+conditional expressions, it is limited only by available memory.
+
+@item Significant initial characters in an identifier or macro name.
+
+The preprocessor treats all characters as significant. The C standard
+requires only that the first 63 be significant.
+
+@item Number of macros simultaneously defined in a single translation unit.
+
+The standard requires at least 4095 be possible. CPP is limited only
+by available memory.
+
+@item Number of parameters in a macro definition and arguments in a macro call.
+
+We allow @code{USHRT_MAX}, which is no smaller than 65,535. The minimum
+required by the standard is 127.
+
+@item Number of characters on a logical source line.
+
+The C standard requires a minimum of 4096 be permitted. CPP places
+no limits on this, but you may get incorrect column numbers reported in
+diagnostics for lines longer than 65,535 characters.
+
+@item Maximum size of a source file.
+
+The standard does not specify any lower limit on the maximum size of a
+source file. GNU cpp maps files into memory, so it is limited by the
+available address space. This is generally at least two gigabytes.
+Depending on the operating system, the size of physical memory may or
+may not be a limitation.
+
+@end itemize
+
+@node Obsolete Features
+@section Obsolete Features
+
+CPP has some features which are present mainly for compatibility with
+older programs. We discourage their use in new code. In some cases,
+we plan to remove the feature in a future version of GCC@.
+
+@subsection Assertions
+@cindex assertions
+
+@dfn{Assertions} are a deprecated alternative to macros in writing
+conditionals to test what sort of computer or system the compiled
+program will run on. Assertions are usually predefined, but you can
+define them with preprocessing directives or command-line options.
+
+Assertions were intended to provide a more systematic way to describe
+the compiler's target system and we added them for compatibility with
+existing compilers. In practice they are just as unpredictable as the
+system-specific predefined macros. In addition, they are not part of
+any standard, and only a few compilers support them.
+Therefore, the use of assertions is @strong{less} portable than the use
+of system-specific predefined macros. We recommend you do not use them at
+all.
+
+@cindex predicates
+An assertion looks like this:
+
+@smallexample
+#@var{predicate} (@var{answer})
+@end smallexample
+
+@noindent
+@var{predicate} must be a single identifier. @var{answer} can be any
+sequence of tokens; all characters are significant except for leading
+and trailing whitespace, and differences in internal whitespace
+sequences are ignored. (This is similar to the rules governing macro
+redefinition.) Thus, @code{(x + y)} is different from @code{(x+y)} but
+equivalent to @code{@w{( x + y )}}. Parentheses do not nest inside an
+answer.
+
+@cindex testing predicates
+To test an assertion, you write it in an @samp{#if}. For example, this
+conditional succeeds if either @code{vax} or @code{ns16000} has been
+asserted as an answer for @code{machine}.
+
+@smallexample
+#if #machine (vax) || #machine (ns16000)
+@end smallexample
+
+@noindent
+You can test whether @emph{any} answer is asserted for a predicate by
+omitting the answer in the conditional:
+
+@smallexample
+#if #machine
+@end smallexample
+
+@findex #assert
+Assertions are made with the @samp{#assert} directive. Its sole
+argument is the assertion to make, without the leading @samp{#} that
+identifies assertions in conditionals.
+
+@smallexample
+#assert @var{predicate} (@var{answer})
+@end smallexample
+
+@noindent
+You may make several assertions with the same predicate and different
+answers. Subsequent assertions do not override previous ones for the
+same predicate. All the answers for any given predicate are
+simultaneously true.
+
+@cindex assertions, canceling
+@findex #unassert
+Assertions can be canceled with the @samp{#unassert} directive. It
+has the same syntax as @samp{#assert}. In that form it cancels only the
+answer which was specified on the @samp{#unassert} line; other answers
+for that predicate remain true. You can cancel an entire predicate by
+leaving out the answer:
+
+@smallexample
+#unassert @var{predicate}
+@end smallexample
+
+@noindent
+In either form, if no such assertion has been made, @samp{#unassert} has
+no effect.
+
+You can also make or cancel assertions using command-line options.
+@xref{Invocation}.
+
+@node Invocation
+@chapter Invocation
+@cindex invocation
+@cindex command line
+
+Most often when you use the C preprocessor you do not have to invoke it
+explicitly: the C compiler does so automatically. However, the
+preprocessor is sometimes useful on its own. You can invoke the
+preprocessor either with the @command{cpp} command, or via @command{gcc -E}.
+In GCC, the preprocessor is actually integrated with the compiler
+rather than a separate program, and both of these commands invoke
+GCC and tell it to stop after the preprocessing phase.
+
+The @command{cpp} options listed here are also accepted by
+@command{gcc} and have the same meaning. Likewise the @command{cpp}
+command accepts all the usual @command{gcc} driver options, although those
+pertaining to compilation phases after preprocessing are ignored.
+
+Only options specific to preprocessing behavior are documented here.
+Refer to the GCC manual for full documentation of other driver options.
+
+@ignore
+@c man begin SYNOPSIS
+cpp [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
+ [@option{-I}@var{dir}@dots{}] [@option{-iquote}@var{dir}@dots{}]
+ [@option{-M}|@option{-MM}] [@option{-MG}] [@option{-MF} @var{filename}]
+ [@option{-MP}] [@option{-MQ} @var{target}@dots{}]
+ [@option{-MT} @var{target}@dots{}]
+ @var{infile} [[@option{-o}] @var{outfile}]
+
+Only the most useful options are given above; see below for a more
+complete list of preprocessor-specific options.
+In addition, @command{cpp} accepts most @command{gcc} driver options, which
+are not listed here. Refer to the GCC documentation for details.
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7),
+gcc(1), and the Info entries for @file{cpp} and @file{gcc}.
+@c man end
+@end ignore
+
+@c man begin OPTIONS
+The @command{cpp} command expects two file names as arguments, @var{infile} and
+@var{outfile}. The preprocessor reads @var{infile} together with any
+other files it specifies with @samp{#include}. All the output generated
+by the combined input files is written in @var{outfile}.
+
+Either @var{infile} or @var{outfile} may be @option{-}, which as
+@var{infile} means to read from standard input and as @var{outfile}
+means to write to standard output. If either file is omitted, it
+means the same as if @option{-} had been specified for that file.
+You can also use the @option{-o @var{outfile}} option to specify the
+output file.
+
+Unless otherwise noted, or the option ends in @samp{=}, all options
+which take an argument may have that argument appear either immediately
+after the option, or with a space between option and argument:
+@option{-Ifoo} and @option{-I foo} have the same effect.
+
+@cindex grouping options
+@cindex options, grouping
+Many options have multi-letter names; therefore multiple single-letter
+options may @emph{not} be grouped: @option{-dM} is very different from
+@w{@samp{-d -M}}.
+
+@cindex options
+
+@table @gcctabopt
+@include cppopts.texi
+@include cppdiropts.texi
+@include cppwarnopts.texi
+@end table
+@c man end
+
+@node Environment Variables
+@chapter Environment Variables
+@cindex environment variables
+@c man begin ENVIRONMENT
+
+This section describes the environment variables that affect how CPP
+operates. You can use them to specify directories or prefixes to use
+when searching for include files, or to control dependency output.
+
+Note that you can also specify places to search using options such as
+@option{-I}, and control dependency output with options like
+@option{-M} (@pxref{Invocation}). These take precedence over
+environment variables, which in turn take precedence over the
+configuration of GCC@.
+
+@include cppenv.texi
+@c man end
+
+@page
+@include fdl.texi
+
+@page
+@node Index of Directives
+@unnumbered Index of Directives
+@printindex fn
+
+@node Option Index
+@unnumbered Option Index
+@noindent
+CPP's command-line options and environment variables are indexed here
+without any initial @samp{-} or @samp{--}.
+@printindex op
+
+@page
+@node Concept Index
+@unnumbered Concept Index
+@printindex cp
+
+@bye
--- /dev/null
+@c Copyright (C) 1999-2022 Free Software Foundation, Inc.
+@c This is part of the CPP and GCC manuals.
+@c For copying conditions, see the file gcc.texi.
+
+@c ---------------------------------------------------------------------
+@c Options affecting include directory search in the preprocessor
+@c ---------------------------------------------------------------------
+
+@c If this file is included with the flag ``cppmanual'' set, it is
+@c formatted for inclusion in the CPP manual; otherwise the main GCC manual.
+
+@item -I @var{dir}
+@itemx -iquote @var{dir}
+@itemx -isystem @var{dir}
+@itemx -idirafter @var{dir}
+@opindex I
+@opindex iquote
+@opindex isystem
+@opindex idirafter
+Add the directory @var{dir} to the list of directories to be searched
+for header files during preprocessing.
+@ifset cppmanual
+@xref{Search Path}.
+@end ifset
+If @var{dir} begins with @samp{=} or @code{$SYSROOT}, then the @samp{=}
+or @code{$SYSROOT} is replaced by the sysroot prefix; see
+@option{--sysroot} and @option{-isysroot}.
+
+Directories specified with @option{-iquote} apply only to the quote
+form of the directive, @code{@w{#include "@var{file}"}}.
+Directories specified with @option{-I}, @option{-isystem},
+or @option{-idirafter} apply to lookup for both the
+@code{@w{#include "@var{file}"}} and
+@code{@w{#include <@var{file}>}} directives.
+
+You can specify any number or combination of these options on the
+command line to search for header files in several directories.
+The lookup order is as follows:
+
+@enumerate
+@item
+For the quote form of the include directive, the directory of the current
+file is searched first.
+
+@item
+For the quote form of the include directive, the directories specified
+by @option{-iquote} options are searched in left-to-right order,
+as they appear on the command line.
+
+@item
+Directories specified with @option{-I} options are scanned in
+left-to-right order.
+
+@item
+Directories specified with @option{-isystem} options are scanned in
+left-to-right order.
+
+@item
+Standard system directories are scanned.
+
+@item
+Directories specified with @option{-idirafter} options are scanned in
+left-to-right order.
+@end enumerate
+
+You can use @option{-I} to override a system header
+file, substituting your own version, since these directories are
+searched before the standard system header file directories.
+However, you should
+not use this option to add directories that contain vendor-supplied
+system header files; use @option{-isystem} for that.
+
+The @option{-isystem} and @option{-idirafter} options also mark the directory
+as a system directory, so that it gets the same special treatment that
+is applied to the standard system directories.
+@ifset cppmanual
+@xref{System Headers}.
+@end ifset
+
+If a standard system include directory, or a directory specified with
+@option{-isystem}, is also specified with @option{-I}, the @option{-I}
+option is ignored. The directory is still searched but as a
+system directory at its normal position in the system include chain.
+This is to ensure that GCC's procedure to fix buggy system headers and
+the ordering for the @code{#include_next} directive are not inadvertently
+changed.
+If you really need to change the search order for system directories,
+use the @option{-nostdinc} and/or @option{-isystem} options.
+@ifset cppmanual
+@xref{System Headers}.
+@end ifset
+
+@item -I-
+@opindex I-
+Split the include path.
+This option has been deprecated. Please use @option{-iquote} instead for
+@option{-I} directories before the @option{-I-} and remove the @option{-I-}
+option.
+
+Any directories specified with @option{-I}
+options before @option{-I-} are searched only for headers requested with
+@code{@w{#include "@var{file}"}}; they are not searched for
+@code{@w{#include <@var{file}>}}. If additional directories are
+specified with @option{-I} options after the @option{-I-}, those
+directories are searched for all @samp{#include} directives.
+
+In addition, @option{-I-} inhibits the use of the directory of the current
+file directory as the first search directory for @code{@w{#include
+"@var{file}"}}. There is no way to override this effect of @option{-I-}.
+@ifset cppmanual
+@xref{Search Path}.
+@end ifset
+
+@item -iprefix @var{prefix}
+@opindex iprefix
+Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix}
+options. If the prefix represents a directory, you should include the
+final @samp{/}.
+
+@item -iwithprefix @var{dir}
+@itemx -iwithprefixbefore @var{dir}
+@opindex iwithprefix
+@opindex iwithprefixbefore
+Append @var{dir} to the prefix specified previously with
+@option{-iprefix}, and add the resulting directory to the include search
+path. @option{-iwithprefixbefore} puts it in the same place @option{-I}
+would; @option{-iwithprefix} puts it where @option{-idirafter} would.
+
+@item -isysroot @var{dir}
+@opindex isysroot
+This option is like the @option{--sysroot} option, but applies only to
+header files (except for Darwin targets, where it applies to both header
+files and libraries). See the @option{--sysroot} option for more
+information.
+
+@item -imultilib @var{dir}
+@opindex imultilib
+Use @var{dir} as a subdirectory of the directory containing
+target-specific C++ headers.
+
+@item -nostdinc
+@opindex nostdinc
+Do not search the standard system directories for header files.
+Only the directories explicitly specified with @option{-I},
+@option{-iquote}, @option{-isystem}, and/or @option{-idirafter}
+options (and the directory of the current file, if appropriate)
+are searched.
+
+@item -nostdinc++
+@opindex nostdinc++
+Do not search for header files in the C++-specific standard directories,
+but do still search the other standard directories. (This option is
+used when building the C++ library.)
+
--- /dev/null
+@c Copyright (C) 1999-2022 Free Software Foundation, Inc.
+@c This is part of the CPP and GCC manuals.
+@c For copying conditions, see the file gcc.texi.
+
+@c ---------------------------------------------------------------------
+@c Environment variables affecting the preprocessor
+@c ---------------------------------------------------------------------
+
+@c If this file is included with the flag ``cppmanual'' set, it is
+@c formatted for inclusion in the CPP manual; otherwise the main GCC manual.
+
+@vtable @env
+@item CPATH
+@itemx C_INCLUDE_PATH
+@itemx CPLUS_INCLUDE_PATH
+@itemx OBJC_INCLUDE_PATH
+@c Commented out until ObjC++ is part of GCC:
+@c @itemx OBJCPLUS_INCLUDE_PATH
+Each variable's value is a list of directories separated by a special
+character, much like @env{PATH}, in which to look for header files.
+The special character, @code{PATH_SEPARATOR}, is target-dependent and
+determined at GCC build time. For Microsoft Windows-based targets it is a
+semicolon, and for almost all other targets it is a colon.
+
+@env{CPATH} specifies a list of directories to be searched as if
+specified with @option{-I}, but after any paths given with @option{-I}
+options on the command line. This environment variable is used
+regardless of which language is being preprocessed.
+
+The remaining environment variables apply only when preprocessing the
+particular language indicated. Each specifies a list of directories
+to be searched as if specified with @option{-isystem}, but after any
+paths given with @option{-isystem} options on the command line.
+
+In all these variables, an empty element instructs the compiler to
+search its current working directory. Empty elements can appear at the
+beginning or end of a path. For instance, if the value of
+@env{CPATH} is @code{:/special/include}, that has the same
+effect as @samp{@w{-I. -I/special/include}}.
+
+@c man end
+@ifset cppmanual
+See also @ref{Search Path}.
+@end ifset
+@c man begin ENVIRONMENT
+
+@item DEPENDENCIES_OUTPUT
+@cindex dependencies for make as output
+If this variable is set, its value specifies how to output
+dependencies for Make based on the non-system header files processed
+by the compiler. System header files are ignored in the dependency
+output.
+
+The value of @env{DEPENDENCIES_OUTPUT} can be just a file name, in
+which case the Make rules are written to that file, guessing the target
+name from the source file name. Or the value can have the form
+@samp{@var{file} @var{target}}, in which case the rules are written to
+file @var{file} using @var{target} as the target name.
+
+In other words, this environment variable is equivalent to combining
+the options @option{-MM} and @option{-MF}
+@ifset cppmanual
+(@pxref{Invocation}),
+@end ifset
+@ifclear cppmanual
+(@pxref{Preprocessor Options}),
+@end ifclear
+with an optional @option{-MT} switch too.
+
+@item SUNPRO_DEPENDENCIES
+@cindex dependencies for make as output
+This variable is the same as @env{DEPENDENCIES_OUTPUT} (see above),
+except that system header files are not ignored, so it implies
+@option{-M} rather than @option{-MM}. However, the dependence on the
+main input file is omitted.
+@ifset cppmanual
+@xref{Invocation}.
+@end ifset
+@ifclear cppmanual
+@xref{Preprocessor Options}.
+@end ifclear
+
+@item SOURCE_DATE_EPOCH
+If this variable is set, its value specifies a UNIX timestamp to be
+used in replacement of the current date and time in the @code{__DATE__}
+and @code{__TIME__} macros, so that the embedded timestamps become
+reproducible.
+
+The value of @env{SOURCE_DATE_EPOCH} must be a UNIX timestamp,
+defined as the number of seconds (excluding leap seconds) since
+01 Jan 1970 00:00:00 represented in ASCII; identical to the output of
+@code{date +%s} on GNU/Linux and other systems that support the
+@code{%s} extension in the @code{date} command.
+
+The value should be a known timestamp such as the last modification
+time of the source or package and it should be set by the build
+process.
+
+@end vtable
--- /dev/null
+\input texinfo
+@setfilename cppinternals.info
+@settitle The GNU C Preprocessor Internals
+
+@include gcc-common.texi
+
+@ifinfo
+@dircategory Software development
+@direntry
+* Cpplib: (cppinternals). Cpplib internals.
+@end direntry
+@end ifinfo
+
+@c @smallbook
+@c @cropmarks
+@c @finalout
+@setchapternewpage odd
+@ifinfo
+This file documents the internals of the GNU C Preprocessor.
+
+Copyright (C) 2000-2022 Free Software Foundation, Inc.
+
+Permission is granted to make and distribute verbatim copies of
+this manual provided the copyright notice and this permission notice
+are preserved on all copies.
+
+@ignore
+Permission is granted to process this file through Tex and print the
+results, provided the printed document carries copying permission
+notice identical to this one except for the removal of this paragraph
+(this paragraph not being relevant to the printed manual).
+
+@end ignore
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided also that
+the entire resulting derived work is distributed under the terms of a
+permission notice identical to this one.
+
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions.
+@end ifinfo
+
+@titlepage
+@title Cpplib Internals
+@versionsubtitle
+@author Neil Booth
+@page
+@vskip 0pt plus 1filll
+@c man begin COPYRIGHT
+Copyright @copyright{} 2000-2022 Free Software Foundation, Inc.
+
+Permission is granted to make and distribute verbatim copies of
+this manual provided the copyright notice and this permission notice
+are preserved on all copies.
+
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided also that
+the entire resulting derived work is distributed under the terms of a
+permission notice identical to this one.
+
+Permission is granted to copy and distribute translations of this manual
+into another language, under the above conditions for modified versions.
+@c man end
+@end titlepage
+@contents
+@page
+
+@ifnottex
+@node Top
+@top
+@chapter Cpplib---the GNU C Preprocessor
+
+The GNU C preprocessor is
+implemented as a library, @dfn{cpplib}, so it can be easily shared between
+a stand-alone preprocessor, and a preprocessor integrated with the C,
+C++ and Objective-C front ends. It is also available for use by other
+programs, though this is not recommended as its exposed interface has
+not yet reached a point of reasonable stability.
+
+The library has been written to be re-entrant, so that it can be used
+to preprocess many files simultaneously if necessary. It has also been
+written with the preprocessing token as the fundamental unit; the
+preprocessor in previous versions of GCC would operate on text strings
+as the fundamental unit.
+
+This brief manual documents the internals of cpplib, and explains some
+of the tricky issues. It is intended that, along with the comments in
+the source code, a reasonably competent C programmer should be able to
+figure out what the code is doing, and why things have been implemented
+the way they have.
+
+@menu
+* Conventions:: Conventions used in the code.
+* Lexer:: The combined C, C++ and Objective-C Lexer.
+* Hash Nodes:: All identifiers are entered into a hash table.
+* Macro Expansion:: Macro expansion algorithm.
+* Token Spacing:: Spacing and paste avoidance issues.
+* Line Numbering:: Tracking location within files.
+* Guard Macros:: Optimizing header files with guard macros.
+* Files:: File handling.
+* Concept Index:: Index.
+@end menu
+@end ifnottex
+
+@node Conventions
+@unnumbered Conventions
+@cindex interface
+@cindex header files
+
+cpplib has two interfaces---one is exposed internally only, and the
+other is for both internal and external use.
+
+The convention is that functions and types that are exposed to multiple
+files internally are prefixed with @samp{_cpp_}, and are to be found in
+the file @file{internal.h}. Functions and types exposed to external
+clients are in @file{cpplib.h}, and prefixed with @samp{cpp_}. For
+historical reasons this is no longer quite true, but we should strive to
+stick to it.
+
+We are striving to reduce the information exposed in @file{cpplib.h} to the
+bare minimum necessary, and then to keep it there. This makes clear
+exactly what external clients are entitled to assume, and allows us to
+change internals in the future without worrying whether library clients
+are perhaps relying on some kind of undocumented implementation-specific
+behavior.
+
+@node Lexer
+@unnumbered The Lexer
+@cindex lexer
+@cindex newlines
+@cindex escaped newlines
+
+@section Overview
+The lexer is contained in the file @file{lex.cc}. It is a hand-coded
+lexer, and not implemented as a state machine. It can understand C, C++
+and Objective-C source code, and has been extended to allow reasonably
+successful preprocessing of assembly language. The lexer does not make
+an initial pass to strip out trigraphs and escaped newlines, but handles
+them as they are encountered in a single pass of the input file. It
+returns preprocessing tokens individually, not a line at a time.
+
+It is mostly transparent to users of the library, since the library's
+interface for obtaining the next token, @code{cpp_get_token}, takes care
+of lexing new tokens, handling directives, and expanding macros as
+necessary. However, the lexer does expose some functionality so that
+clients of the library can easily spell a given token, such as
+@code{cpp_spell_token} and @code{cpp_token_len}. These functions are
+useful when generating diagnostics, and for emitting the preprocessed
+output.
+
+@section Lexing a token
+Lexing of an individual token is handled by @code{_cpp_lex_direct} and
+its subroutines. In its current form the code is quite complicated,
+with read ahead characters and such-like, since it strives to not step
+back in the character stream in preparation for handling non-ASCII file
+encodings. The current plan is to convert any such files to UTF-8
+before processing them. This complexity is therefore unnecessary and
+will be removed, so I'll not discuss it further here.
+
+The job of @code{_cpp_lex_direct} is simply to lex a token. It is not
+responsible for issues like directive handling, returning lookahead
+tokens directly, multiple-include optimization, or conditional block
+skipping. It necessarily has a minor r@^ole to play in memory
+management of lexed lines. I discuss these issues in a separate section
+(@pxref{Lexing a line}).
+
+The lexer places the token it lexes into storage pointed to by the
+variable @code{cur_token}, and then increments it. This variable is
+important for correct diagnostic positioning. Unless a specific line
+and column are passed to the diagnostic routines, they will examine the
+@code{line} and @code{col} values of the token just before the location
+that @code{cur_token} points to, and use that location to report the
+diagnostic.
+
+The lexer does not consider whitespace to be a token in its own right.
+If whitespace (other than a new line) precedes a token, it sets the
+@code{PREV_WHITE} bit in the token's flags. Each token has its
+@code{line} and @code{col} variables set to the line and column of the
+first character of the token. This line number is the line number in
+the translation unit, and can be converted to a source (file, line) pair
+using the line map code.
+
+The first token on a logical, i.e.@: unescaped, line has the flag
+@code{BOL} set for beginning-of-line. This flag is intended for
+internal use, both to distinguish a @samp{#} that begins a directive
+from one that doesn't, and to generate a call-back to clients that want
+to be notified about the start of every non-directive line with tokens
+on it. Clients cannot reliably determine this for themselves: the first
+token might be a macro, and the tokens of a macro expansion do not have
+the @code{BOL} flag set. The macro expansion may even be empty, and the
+next token on the line certainly won't have the @code{BOL} flag set.
+
+New lines are treated specially; exactly how the lexer handles them is
+context-dependent. The C standard mandates that directives are
+terminated by the first unescaped newline character, even if it appears
+in the middle of a macro expansion. Therefore, if the state variable
+@code{in_directive} is set, the lexer returns a @code{CPP_EOF} token,
+which is normally used to indicate end-of-file, to indicate
+end-of-directive. In a directive a @code{CPP_EOF} token never means
+end-of-file. Conveniently, if the caller was @code{collect_args}, it
+already handles @code{CPP_EOF} as if it were end-of-file, and reports an
+error about an unterminated macro argument list.
+
+The C standard also specifies that a new line in the middle of the
+arguments to a macro is treated as whitespace. This white space is
+important in case the macro argument is stringized. The state variable
+@code{parsing_args} is nonzero when the preprocessor is collecting the
+arguments to a macro call. It is set to 1 when looking for the opening
+parenthesis to a function-like macro, and 2 when collecting the actual
+arguments up to the closing parenthesis, since these two cases need to
+be distinguished sometimes. One such time is here: the lexer sets the
+@code{PREV_WHITE} flag of a token if it meets a new line when
+@code{parsing_args} is set to 2. It doesn't set it if it meets a new
+line when @code{parsing_args} is 1, since then code like
+
+@smallexample
+#define foo() bar
+foo
+baz
+@end smallexample
+
+@noindent would be output with an erroneous space before @samp{baz}:
+
+@smallexample
+foo
+ baz
+@end smallexample
+
+This is a good example of the subtlety of getting token spacing correct
+in the preprocessor; there are plenty of tests in the testsuite for
+corner cases like this.
+
+The lexer is written to treat each of @samp{\r}, @samp{\n}, @samp{\r\n}
+and @samp{\n\r} as a single new line indicator. This allows it to
+transparently preprocess MS-DOS, Macintosh and Unix files without their
+needing to pass through a special filter beforehand.
+
+We also decided to treat a backslash, either @samp{\} or the trigraph
+@samp{??/}, separated from one of the above newline indicators by
+non-comment whitespace only, as intending to escape the newline. It
+tends to be a typing mistake, and cannot reasonably be mistaken for
+anything else in any of the C-family grammars. Since handling it this
+way is not strictly conforming to the ISO standard, the library issues a
+warning wherever it encounters it.
+
+Handling newlines like this is made simpler by doing it in one place
+only. The function @code{handle_newline} takes care of all newline
+characters, and @code{skip_escaped_newlines} takes care of arbitrarily
+long sequences of escaped newlines, deferring to @code{handle_newline}
+to handle the newlines themselves.
+
+The most painful aspect of lexing ISO-standard C and C++ is handling
+trigraphs and backlash-escaped newlines. Trigraphs are processed before
+any interpretation of the meaning of a character is made, and unfortunately
+there is a trigraph representation for a backslash, so it is possible for
+the trigraph @samp{??/} to introduce an escaped newline.
+
+Escaped newlines are tedious because theoretically they can occur
+anywhere---between the @samp{+} and @samp{=} of the @samp{+=} token,
+within the characters of an identifier, and even between the @samp{*}
+and @samp{/} that terminates a comment. Moreover, you cannot be sure
+there is just one---there might be an arbitrarily long sequence of them.
+
+So, for example, the routine that lexes a number, @code{parse_number},
+cannot assume that it can scan forwards until the first non-number
+character and be done with it, because this could be the @samp{\}
+introducing an escaped newline, or the @samp{?} introducing the trigraph
+sequence that represents the @samp{\} of an escaped newline. If it
+encounters a @samp{?} or @samp{\}, it calls @code{skip_escaped_newlines}
+to skip over any potential escaped newlines before checking whether the
+number has been finished.
+
+Similarly code in the main body of @code{_cpp_lex_direct} cannot simply
+check for a @samp{=} after a @samp{+} character to determine whether it
+has a @samp{+=} token; it needs to be prepared for an escaped newline of
+some sort. Such cases use the function @code{get_effective_char}, which
+returns the first character after any intervening escaped newlines.
+
+The lexer needs to keep track of the correct column position, including
+counting tabs as specified by the @option{-ftabstop=} option. This
+should be done even within C-style comments; they can appear in the
+middle of a line, and we want to report diagnostics in the correct
+position for text appearing after the end of the comment.
+
+@anchor{Invalid identifiers}
+Some identifiers, such as @code{__VA_ARGS__} and poisoned identifiers,
+may be invalid and require a diagnostic. However, if they appear in a
+macro expansion we don't want to complain with each use of the macro.
+It is therefore best to catch them during the lexing stage, in
+@code{parse_identifier}. In both cases, whether a diagnostic is needed
+or not is dependent upon the lexer's state. For example, we don't want
+to issue a diagnostic for re-poisoning a poisoned identifier, or for
+using @code{__VA_ARGS__} in the expansion of a variable-argument macro.
+Therefore @code{parse_identifier} makes use of state flags to determine
+whether a diagnostic is appropriate. Since we change state on a
+per-token basis, and don't lex whole lines at a time, this is not a
+problem.
+
+Another place where state flags are used to change behavior is whilst
+lexing header names. Normally, a @samp{<} would be lexed as a single
+token. After a @code{#include} directive, though, it should be lexed as
+a single token as far as the nearest @samp{>} character. Note that we
+don't allow the terminators of header names to be escaped; the first
+@samp{"} or @samp{>} terminates the header name.
+
+Interpretation of some character sequences depends upon whether we are
+lexing C, C++ or Objective-C, and on the revision of the standard in
+force. For example, @samp{::} is a single token in C++, but in C it is
+two separate @samp{:} tokens and almost certainly a syntax error. Such
+cases are handled by @code{_cpp_lex_direct} based upon command-line
+flags stored in the @code{cpp_options} structure.
+
+Once a token has been lexed, it leads an independent existence. The
+spelling of numbers, identifiers and strings is copied to permanent
+storage from the original input buffer, so a token remains valid and
+correct even if its source buffer is freed with @code{_cpp_pop_buffer}.
+The storage holding the spellings of such tokens remains until the
+client program calls cpp_destroy, probably at the end of the translation
+unit.
+
+@anchor{Lexing a line}
+@section Lexing a line
+@cindex token run
+
+When the preprocessor was changed to return pointers to tokens, one
+feature I wanted was some sort of guarantee regarding how long a
+returned pointer remains valid. This is important to the stand-alone
+preprocessor, the future direction of the C family front ends, and even
+to cpplib itself internally.
+
+Occasionally the preprocessor wants to be able to peek ahead in the
+token stream. For example, after the name of a function-like macro, it
+wants to check the next token to see if it is an opening parenthesis.
+Another example is that, after reading the first few tokens of a
+@code{#pragma} directive and not recognizing it as a registered pragma,
+it wants to backtrack and allow the user-defined handler for unknown
+pragmas to access the full @code{#pragma} token stream. The stand-alone
+preprocessor wants to be able to test the current token with the
+previous one to see if a space needs to be inserted to preserve their
+separate tokenization upon re-lexing (paste avoidance), so it needs to
+be sure the pointer to the previous token is still valid. The
+recursive-descent C++ parser wants to be able to perform tentative
+parsing arbitrarily far ahead in the token stream, and then to be able
+to jump back to a prior position in that stream if necessary.
+
+The rule I chose, which is fairly natural, is to arrange that the
+preprocessor lex all tokens on a line consecutively into a token buffer,
+which I call a @dfn{token run}, and when meeting an unescaped new line
+(newlines within comments do not count either), to start lexing back at
+the beginning of the run. Note that we do @emph{not} lex a line of
+tokens at once; if we did that @code{parse_identifier} would not have
+state flags available to warn about invalid identifiers (@pxref{Invalid
+identifiers}).
+
+In other words, accessing tokens that appeared earlier in the current
+line is valid, but since each logical line overwrites the tokens of the
+previous line, tokens from prior lines are unavailable. In particular,
+since a directive only occupies a single logical line, this means that
+the directive handlers like the @code{#pragma} handler can jump around
+in the directive's tokens if necessary.
+
+Two issues remain: what about tokens that arise from macro expansions,
+and what happens when we have a long line that overflows the token run?
+
+Since we promise clients that we preserve the validity of pointers that
+we have already returned for tokens that appeared earlier in the line,
+we cannot reallocate the run. Instead, on overflow it is expanded by
+chaining a new token run on to the end of the existing one.
+
+The tokens forming a macro's replacement list are collected by the
+@code{#define} handler, and placed in storage that is only freed by
+@code{cpp_destroy}. So if a macro is expanded in the line of tokens,
+the pointers to the tokens of its expansion that are returned will always
+remain valid. However, macros are a little trickier than that, since
+they give rise to three sources of fresh tokens. They are the built-in
+macros like @code{__LINE__}, and the @samp{#} and @samp{##} operators
+for stringizing and token pasting. I handled this by allocating
+space for these tokens from the lexer's token run chain. This means
+they automatically receive the same lifetime guarantees as lexed tokens,
+and we don't need to concern ourselves with freeing them.
+
+Lexing into a line of tokens solves some of the token memory management
+issues, but not all. The opening parenthesis after a function-like
+macro name might lie on a different line, and the front ends definitely
+want the ability to look ahead past the end of the current line. So
+cpplib only moves back to the start of the token run at the end of a
+line if the variable @code{keep_tokens} is zero. Line-buffering is
+quite natural for the preprocessor, and as a result the only time cpplib
+needs to increment this variable is whilst looking for the opening
+parenthesis to, and reading the arguments of, a function-like macro. In
+the near future cpplib will export an interface to increment and
+decrement this variable, so that clients can share full control over the
+lifetime of token pointers too.
+
+The routine @code{_cpp_lex_token} handles moving to new token runs,
+calling @code{_cpp_lex_direct} to lex new tokens, or returning
+previously-lexed tokens if we stepped back in the token stream. It also
+checks each token for the @code{BOL} flag, which might indicate a
+directive that needs to be handled, or require a start-of-line call-back
+to be made. @code{_cpp_lex_token} also handles skipping over tokens in
+failed conditional blocks, and invalidates the control macro of the
+multiple-include optimization if a token was successfully lexed outside
+a directive. In other words, its callers do not need to concern
+themselves with such issues.
+
+@node Hash Nodes
+@unnumbered Hash Nodes
+@cindex hash table
+@cindex identifiers
+@cindex macros
+@cindex assertions
+@cindex named operators
+
+When cpplib encounters an ``identifier'', it generates a hash code for
+it and stores it in the hash table. By ``identifier'' we mean tokens
+with type @code{CPP_NAME}; this includes identifiers in the usual C
+sense, as well as keywords, directive names, macro names and so on. For
+example, all of @code{pragma}, @code{int}, @code{foo} and
+@code{__GNUC__} are identifiers and hashed when lexed.
+
+Each node in the hash table contain various information about the
+identifier it represents. For example, its length and type. At any one
+time, each identifier falls into exactly one of three categories:
+
+@itemize @bullet
+@item Macros
+
+These have been declared to be macros, either on the command line or
+with @code{#define}. A few, such as @code{__TIME__} are built-ins
+entered in the hash table during initialization. The hash node for a
+normal macro points to a structure with more information about the
+macro, such as whether it is function-like, how many arguments it takes,
+and its expansion. Built-in macros are flagged as special, and instead
+contain an enum indicating which of the various built-in macros it is.
+
+@item Assertions
+
+Assertions are in a separate namespace to macros. To enforce this, cpp
+actually prepends a @code{#} character before hashing and entering it in
+the hash table. An assertion's node points to a chain of answers to
+that assertion.
+
+@item Void
+
+Everything else falls into this category---an identifier that is not
+currently a macro, or a macro that has since been undefined with
+@code{#undef}.
+
+When preprocessing C++, this category also includes the named operators,
+such as @code{xor}. In expressions these behave like the operators they
+represent, but in contexts where the spelling of a token matters they
+are spelt differently. This spelling distinction is relevant when they
+are operands of the stringizing and pasting macro operators @code{#} and
+@code{##}. Named operator hash nodes are flagged, both to catch the
+spelling distinction and to prevent them from being defined as macros.
+@end itemize
+
+The same identifiers share the same hash node. Since each identifier
+token, after lexing, contains a pointer to its hash node, this is used
+to provide rapid lookup of various information. For example, when
+parsing a @code{#define} statement, CPP flags each argument's identifier
+hash node with the index of that argument. This makes duplicated
+argument checking an O(1) operation for each argument. Similarly, for
+each identifier in the macro's expansion, lookup to see if it is an
+argument, and which argument it is, is also an O(1) operation. Further,
+each directive name, such as @code{endif}, has an associated directive
+enum stored in its hash node, so that directive lookup is also O(1).
+
+@node Macro Expansion
+@unnumbered Macro Expansion Algorithm
+@cindex macro expansion
+
+Macro expansion is a tricky operation, fraught with nasty corner cases
+and situations that render what you thought was a nifty way to
+optimize the preprocessor's expansion algorithm wrong in quite subtle
+ways.
+
+I strongly recommend you have a good grasp of how the C and C++
+standards require macros to be expanded before diving into this
+section, let alone the code!. If you don't have a clear mental
+picture of how things like nested macro expansion, stringizing and
+token pasting are supposed to work, damage to your sanity can quickly
+result.
+
+@section Internal representation of macros
+@cindex macro representation (internal)
+
+The preprocessor stores macro expansions in tokenized form. This
+saves repeated lexing passes during expansion, at the cost of a small
+increase in memory consumption on average. The tokens are stored
+contiguously in memory, so a pointer to the first one and a token
+count is all you need to get the replacement list of a macro.
+
+If the macro is a function-like macro the preprocessor also stores its
+parameters, in the form of an ordered list of pointers to the hash
+table entry of each parameter's identifier. Further, in the macro's
+stored expansion each occurrence of a parameter is replaced with a
+special token of type @code{CPP_MACRO_ARG}. Each such token holds the
+index of the parameter it represents in the parameter list, which
+allows rapid replacement of parameters with their arguments during
+expansion. Despite this optimization it is still necessary to store
+the original parameters to the macro, both for dumping with e.g.,
+@option{-dD}, and to warn about non-trivial macro redefinitions when
+the parameter names have changed.
+
+@section Macro expansion overview
+The preprocessor maintains a @dfn{context stack}, implemented as a
+linked list of @code{cpp_context} structures, which together represent
+the macro expansion state at any one time. The @code{struct
+cpp_reader} member variable @code{context} points to the current top
+of this stack. The top normally holds the unexpanded replacement list
+of the innermost macro under expansion, except when cpplib is about to
+pre-expand an argument, in which case it holds that argument's
+unexpanded tokens.
+
+When there are no macros under expansion, cpplib is in @dfn{base
+context}. All contexts other than the base context contain a
+contiguous list of tokens delimited by a starting and ending token.
+When not in base context, cpplib obtains the next token from the list
+of the top context. If there are no tokens left in the list, it pops
+that context off the stack, and subsequent ones if necessary, until an
+unexhausted context is found or it returns to base context. In base
+context, cpplib reads tokens directly from the lexer.
+
+If it encounters an identifier that is both a macro and enabled for
+expansion, cpplib prepares to push a new context for that macro on the
+stack by calling the routine @code{enter_macro_context}. When this
+routine returns, the new context will contain the unexpanded tokens of
+the replacement list of that macro. In the case of function-like
+macros, @code{enter_macro_context} also replaces any parameters in the
+replacement list, stored as @code{CPP_MACRO_ARG} tokens, with the
+appropriate macro argument. If the standard requires that the
+parameter be replaced with its expanded argument, the argument will
+have been fully macro expanded first.
+
+@code{enter_macro_context} also handles special macros like
+@code{__LINE__}. Although these macros expand to a single token which
+cannot contain any further macros, for reasons of token spacing
+(@pxref{Token Spacing}) and simplicity of implementation, cpplib
+handles these special macros by pushing a context containing just that
+one token.
+
+The final thing that @code{enter_macro_context} does before returning
+is to mark the macro disabled for expansion (except for special macros
+like @code{__TIME__}). The macro is re-enabled when its context is
+later popped from the context stack, as described above. This strict
+ordering ensures that a macro is disabled whilst its expansion is
+being scanned, but that it is @emph{not} disabled whilst any arguments
+to it are being expanded.
+
+@section Scanning the replacement list for macros to expand
+The C standard states that, after any parameters have been replaced
+with their possibly-expanded arguments, the replacement list is
+scanned for nested macros. Further, any identifiers in the
+replacement list that are not expanded during this scan are never
+again eligible for expansion in the future, if the reason they were
+not expanded is that the macro in question was disabled.
+
+Clearly this latter condition can only apply to tokens resulting from
+argument pre-expansion. Other tokens never have an opportunity to be
+re-tested for expansion. It is possible for identifiers that are
+function-like macros to not expand initially but to expand during a
+later scan. This occurs when the identifier is the last token of an
+argument (and therefore originally followed by a comma or a closing
+parenthesis in its macro's argument list), and when it replaces its
+parameter in the macro's replacement list, the subsequent token
+happens to be an opening parenthesis (itself possibly the first token
+of an argument).
+
+It is important to note that when cpplib reads the last token of a
+given context, that context still remains on the stack. Only when
+looking for the @emph{next} token do we pop it off the stack and drop
+to a lower context. This makes backing up by one token easy, but more
+importantly ensures that the macro corresponding to the current
+context is still disabled when we are considering the last token of
+its replacement list for expansion (or indeed expanding it). As an
+example, which illustrates many of the points above, consider
+
+@smallexample
+#define foo(x) bar x
+foo(foo) (2)
+@end smallexample
+
+@noindent which fully expands to @samp{bar foo (2)}. During pre-expansion
+of the argument, @samp{foo} does not expand even though the macro is
+enabled, since it has no following parenthesis [pre-expansion of an
+argument only uses tokens from that argument; it cannot take tokens
+from whatever follows the macro invocation]. This still leaves the
+argument token @samp{foo} eligible for future expansion. Then, when
+re-scanning after argument replacement, the token @samp{foo} is
+rejected for expansion, and marked ineligible for future expansion,
+since the macro is now disabled. It is disabled because the
+replacement list @samp{bar foo} of the macro is still on the context
+stack.
+
+If instead the algorithm looked for an opening parenthesis first and
+then tested whether the macro were disabled it would be subtly wrong.
+In the example above, the replacement list of @samp{foo} would be
+popped in the process of finding the parenthesis, re-enabling
+@samp{foo} and expanding it a second time.
+
+@section Looking for a function-like macro's opening parenthesis
+Function-like macros only expand when immediately followed by a
+parenthesis. To do this cpplib needs to temporarily disable macros
+and read the next token. Unfortunately, because of spacing issues
+(@pxref{Token Spacing}), there can be fake padding tokens in-between,
+and if the next real token is not a parenthesis cpplib needs to be
+able to back up that one token as well as retain the information in
+any intervening padding tokens.
+
+Backing up more than one token when macros are involved is not
+permitted by cpplib, because in general it might involve issues like
+restoring popped contexts onto the context stack, which are too hard.
+Instead, searching for the parenthesis is handled by a special
+function, @code{funlike_invocation_p}, which remembers padding
+information as it reads tokens. If the next real token is not an
+opening parenthesis, it backs up that one token, and then pushes an
+extra context just containing the padding information if necessary.
+
+@section Marking tokens ineligible for future expansion
+As discussed above, cpplib needs a way of marking tokens as
+unexpandable. Since the tokens cpplib handles are read-only once they
+have been lexed, it instead makes a copy of the token and adds the
+flag @code{NO_EXPAND} to the copy.
+
+For efficiency and to simplify memory management by avoiding having to
+remember to free these tokens, they are allocated as temporary tokens
+from the lexer's current token run (@pxref{Lexing a line}) using the
+function @code{_cpp_temp_token}. The tokens are then re-used once the
+current line of tokens has been read in.
+
+This might sound unsafe. However, tokens runs are not re-used at the
+end of a line if it happens to be in the middle of a macro argument
+list, and cpplib only wants to back-up more than one lexer token in
+situations where no macro expansion is involved, so the optimization
+is safe.
+
+@node Token Spacing
+@unnumbered Token Spacing
+@cindex paste avoidance
+@cindex spacing
+@cindex token spacing
+
+First, consider an issue that only concerns the stand-alone
+preprocessor: there needs to be a guarantee that re-reading its preprocessed
+output results in an identical token stream. Without taking special
+measures, this might not be the case because of macro substitution.
+For example:
+
+@smallexample
+#define PLUS +
+#define EMPTY
+#define f(x) =x=
++PLUS -EMPTY- PLUS+ f(=)
+ @expansion{} + + - - + + = = =
+@emph{not}
+ @expansion{} ++ -- ++ ===
+@end smallexample
+
+One solution would be to simply insert a space between all adjacent
+tokens. However, we would like to keep space insertion to a minimum,
+both for aesthetic reasons and because it causes problems for people who
+still try to abuse the preprocessor for things like Fortran source and
+Makefiles.
+
+For now, just notice that when tokens are added (or removed, as shown by
+the @code{EMPTY} example) from the original lexed token stream, we need
+to check for accidental token pasting. We call this @dfn{paste
+avoidance}. Token addition and removal can only occur because of macro
+expansion, but accidental pasting can occur in many places: both before
+and after each macro replacement, each argument replacement, and
+additionally each token created by the @samp{#} and @samp{##} operators.
+
+Look at how the preprocessor gets whitespace output correct
+normally. The @code{cpp_token} structure contains a flags byte, and one
+of those flags is @code{PREV_WHITE}. This is flagged by the lexer, and
+indicates that the token was preceded by whitespace of some form other
+than a new line. The stand-alone preprocessor can use this flag to
+decide whether to insert a space between tokens in the output.
+
+Now consider the result of the following macro expansion:
+
+@smallexample
+#define add(x, y, z) x + y +z;
+sum = add (1,2, 3);
+ @expansion{} sum = 1 + 2 +3;
+@end smallexample
+
+The interesting thing here is that the tokens @samp{1} and @samp{2} are
+output with a preceding space, and @samp{3} is output without a
+preceding space, but when lexed none of these tokens had that property.
+Careful consideration reveals that @samp{1} gets its preceding
+whitespace from the space preceding @samp{add} in the macro invocation,
+@emph{not} replacement list. @samp{2} gets its whitespace from the
+space preceding the parameter @samp{y} in the macro replacement list,
+and @samp{3} has no preceding space because parameter @samp{z} has none
+in the replacement list.
+
+Once lexed, tokens are effectively fixed and cannot be altered, since
+pointers to them might be held in many places, in particular by
+in-progress macro expansions. So instead of modifying the two tokens
+above, the preprocessor inserts a special token, which I call a
+@dfn{padding token}, into the token stream to indicate that spacing of
+the subsequent token is special. The preprocessor inserts padding
+tokens in front of every macro expansion and expanded macro argument.
+These point to a @dfn{source token} from which the subsequent real token
+should inherit its spacing. In the above example, the source tokens are
+@samp{add} in the macro invocation, and @samp{y} and @samp{z} in the
+macro replacement list, respectively.
+
+It is quite easy to get multiple padding tokens in a row, for example if
+a macro's first replacement token expands straight into another macro.
+
+@smallexample
+#define foo bar
+#define bar baz
+[foo]
+ @expansion{} [baz]
+@end smallexample
+
+Here, two padding tokens are generated with sources the @samp{foo} token
+between the brackets, and the @samp{bar} token from foo's replacement
+list, respectively. Clearly the first padding token is the one to
+use, so the output code should contain a rule that the first
+padding token in a sequence is the one that matters.
+
+But what if a macro expansion is left? Adjusting the above
+example slightly:
+
+@smallexample
+#define foo bar
+#define bar EMPTY baz
+#define EMPTY
+[foo] EMPTY;
+ @expansion{} [ baz] ;
+@end smallexample
+
+As shown, now there should be a space before @samp{baz} and the
+semicolon in the output.
+
+The rules we decided above fail for @samp{baz}: we generate three
+padding tokens, one per macro invocation, before the token @samp{baz}.
+We would then have it take its spacing from the first of these, which
+carries source token @samp{foo} with no leading space.
+
+It is vital that cpplib get spacing correct in these examples since any
+of these macro expansions could be stringized, where spacing matters.
+
+So, this demonstrates that not just entering macro and argument
+expansions, but leaving them requires special handling too. I made
+cpplib insert a padding token with a @code{NULL} source token when
+leaving macro expansions, as well as after each replaced argument in a
+macro's replacement list. It also inserts appropriate padding tokens on
+either side of tokens created by the @samp{#} and @samp{##} operators.
+I expanded the rule so that, if we see a padding token with a
+@code{NULL} source token, @emph{and} that source token has no leading
+space, then we behave as if we have seen no padding tokens at all. A
+quick check shows this rule will then get the above example correct as
+well.
+
+Now a relationship with paste avoidance is apparent: we have to be
+careful about paste avoidance in exactly the same locations we have
+padding tokens in order to get white space correct. This makes
+implementation of paste avoidance easy: wherever the stand-alone
+preprocessor is fixing up spacing because of padding tokens, and it
+turns out that no space is needed, it has to take the extra step to
+check that a space is not needed after all to avoid an accidental paste.
+The function @code{cpp_avoid_paste} advises whether a space is required
+between two consecutive tokens. To avoid excessive spacing, it tries
+hard to only require a space if one is likely to be necessary, but for
+reasons of efficiency it is slightly conservative and might recommend a
+space where one is not strictly needed.
+
+@node Line Numbering
+@unnumbered Line numbering
+@cindex line numbers
+
+@section Just which line number anyway?
+
+There are three reasonable requirements a cpplib client might have for
+the line number of a token passed to it:
+
+@itemize @bullet
+@item
+The source line it was lexed on.
+@item
+The line it is output on. This can be different to the line it was
+lexed on if, for example, there are intervening escaped newlines or
+C-style comments. For example:
+
+@smallexample
+foo /* @r{A long
+comment} */ bar \
+baz
+@result{}
+foo bar baz
+@end smallexample
+
+@item
+If the token results from a macro expansion, the line of the macro name,
+or possibly the line of the closing parenthesis in the case of
+function-like macro expansion.
+@end itemize
+
+The @code{cpp_token} structure contains @code{line} and @code{col}
+members. The lexer fills these in with the line and column of the first
+character of the token. Consequently, but maybe unexpectedly, a token
+from the replacement list of a macro expansion carries the location of
+the token within the @code{#define} directive, because cpplib expands a
+macro by returning pointers to the tokens in its replacement list. The
+current implementation of cpplib assigns tokens created from built-in
+macros and the @samp{#} and @samp{##} operators the location of the most
+recently lexed token. This is a because they are allocated from the
+lexer's token runs, and because of the way the diagnostic routines infer
+the appropriate location to report.
+
+The diagnostic routines in cpplib display the location of the most
+recently @emph{lexed} token, unless they are passed a specific line and
+column to report. For diagnostics regarding tokens that arise from
+macro expansions, it might also be helpful for the user to see the
+original location in the macro definition that the token came from.
+Since that is exactly the information each token carries, such an
+enhancement could be made relatively easily in future.
+
+The stand-alone preprocessor faces a similar problem when determining
+the correct line to output the token on: the position attached to a
+token is fairly useless if the token came from a macro expansion. All
+tokens on a logical line should be output on its first physical line, so
+the token's reported location is also wrong if it is part of a physical
+line other than the first.
+
+To solve these issues, cpplib provides a callback that is generated
+whenever it lexes a preprocessing token that starts a new logical line
+other than a directive. It passes this token (which may be a
+@code{CPP_EOF} token indicating the end of the translation unit) to the
+callback routine, which can then use the line and column of this token
+to produce correct output.
+
+@section Representation of line numbers
+
+As mentioned above, cpplib stores with each token the line number that
+it was lexed on. In fact, this number is not the number of the line in
+the source file, but instead bears more resemblance to the number of the
+line in the translation unit.
+
+The preprocessor maintains a monotonic increasing line count, which is
+incremented at every new line character (and also at the end of any
+buffer that does not end in a new line). Since a line number of zero is
+useful to indicate certain special states and conditions, this variable
+starts counting from one.
+
+This variable therefore uniquely enumerates each line in the translation
+unit. With some simple infrastructure, it is straight forward to map
+from this to the original source file and line number pair, saving space
+whenever line number information needs to be saved. The code the
+implements this mapping lies in the files @file{line-map.cc} and
+@file{line-map.h}.
+
+Command-line macros and assertions are implemented by pushing a buffer
+containing the right hand side of an equivalent @code{#define} or
+@code{#assert} directive. Some built-in macros are handled similarly.
+Since these are all processed before the first line of the main input
+file, it will typically have an assigned line closer to twenty than to
+one.
+
+@node Guard Macros
+@unnumbered The Multiple-Include Optimization
+@cindex guard macros
+@cindex controlling macros
+@cindex multiple-include optimization
+
+Header files are often of the form
+
+@smallexample
+#ifndef FOO
+#define FOO
+@dots{}
+#endif
+@end smallexample
+
+@noindent
+to prevent the compiler from processing them more than once. The
+preprocessor notices such header files, so that if the header file
+appears in a subsequent @code{#include} directive and @code{FOO} is
+defined, then it is ignored and it doesn't preprocess or even re-open
+the file a second time. This is referred to as the @dfn{multiple
+include optimization}.
+
+Under what circumstances is such an optimization valid? If the file
+were included a second time, it can only be optimized away if that
+inclusion would result in no tokens to return, and no relevant
+directives to process. Therefore the current implementation imposes
+requirements and makes some allowances as follows:
+
+@enumerate
+@item
+There must be no tokens outside the controlling @code{#if}-@code{#endif}
+pair, but whitespace and comments are permitted.
+
+@item
+There must be no directives outside the controlling directive pair, but
+the @dfn{null directive} (a line containing nothing other than a single
+@samp{#} and possibly whitespace) is permitted.
+
+@item
+The opening directive must be of the form
+
+@smallexample
+#ifndef FOO
+@end smallexample
+
+or
+
+@smallexample
+#if !defined FOO [equivalently, #if !defined(FOO)]
+@end smallexample
+
+@item
+In the second form above, the tokens forming the @code{#if} expression
+must have come directly from the source file---no macro expansion must
+have been involved. This is because macro definitions can change, and
+tracking whether or not a relevant change has been made is not worth the
+implementation cost.
+
+@item
+There can be no @code{#else} or @code{#elif} directives at the outer
+conditional block level, because they would probably contain something
+of interest to a subsequent pass.
+@end enumerate
+
+First, when pushing a new file on the buffer stack,
+@code{_stack_include_file} sets the controlling macro @code{mi_cmacro} to
+@code{NULL}, and sets @code{mi_valid} to @code{true}. This indicates
+that the preprocessor has not yet encountered anything that would
+invalidate the multiple-include optimization. As described in the next
+few paragraphs, these two variables having these values effectively
+indicates top-of-file.
+
+When about to return a token that is not part of a directive,
+@code{_cpp_lex_token} sets @code{mi_valid} to @code{false}. This
+enforces the constraint that tokens outside the controlling conditional
+block invalidate the optimization.
+
+The @code{do_if}, when appropriate, and @code{do_ifndef} directive
+handlers pass the controlling macro to the function
+@code{push_conditional}. cpplib maintains a stack of nested conditional
+blocks, and after processing every opening conditional this function
+pushes an @code{if_stack} structure onto the stack. In this structure
+it records the controlling macro for the block, provided there is one
+and we're at top-of-file (as described above). If an @code{#elif} or
+@code{#else} directive is encountered, the controlling macro for that
+block is cleared to @code{NULL}. Otherwise, it survives until the
+@code{#endif} closing the block, upon which @code{do_endif} sets
+@code{mi_valid} to true and stores the controlling macro in
+@code{mi_cmacro}.
+
+@code{_cpp_handle_directive} clears @code{mi_valid} when processing any
+directive other than an opening conditional and the null directive.
+With this, and requiring top-of-file to record a controlling macro, and
+no @code{#else} or @code{#elif} for it to survive and be copied to
+@code{mi_cmacro} by @code{do_endif}, we have enforced the absence of
+directives outside the main conditional block for the optimization to be
+on.
+
+Note that whilst we are inside the conditional block, @code{mi_valid} is
+likely to be reset to @code{false}, but this does not matter since
+the closing @code{#endif} restores it to @code{true} if appropriate.
+
+Finally, since @code{_cpp_lex_direct} pops the file off the buffer stack
+at @code{EOF} without returning a token, if the @code{#endif} directive
+was not followed by any tokens, @code{mi_valid} is @code{true} and
+@code{_cpp_pop_file_buffer} remembers the controlling macro associated
+with the file. Subsequent calls to @code{stack_include_file} result in
+no buffer being pushed if the controlling macro is defined, effecting
+the optimization.
+
+A quick word on how we handle the
+
+@smallexample
+#if !defined FOO
+@end smallexample
+
+@noindent
+case. @code{_cpp_parse_expr} and @code{parse_defined} take steps to see
+whether the three stages @samp{!}, @samp{defined-expression} and
+@samp{end-of-directive} occur in order in a @code{#if} expression. If
+so, they return the guard macro to @code{do_if} in the variable
+@code{mi_ind_cmacro}, and otherwise set it to @code{NULL}.
+@code{enter_macro_context} sets @code{mi_valid} to false, so if a macro
+was expanded whilst parsing any part of the expression, then the
+top-of-file test in @code{push_conditional} fails and the optimization
+is turned off.
+
+@node Files
+@unnumbered File Handling
+@cindex files
+
+Fairly obviously, the file handling code of cpplib resides in the file
+@file{files.cc}. It takes care of the details of file searching,
+opening, reading and caching, for both the main source file and all the
+headers it recursively includes.
+
+The basic strategy is to minimize the number of system calls. On many
+systems, the basic @code{open ()} and @code{fstat ()} system calls can
+be quite expensive. For every @code{#include}-d file, we need to try
+all the directories in the search path until we find a match. Some
+projects, such as glibc, pass twenty or thirty include paths on the
+command line, so this can rapidly become time consuming.
+
+For a header file we have not encountered before we have little choice
+but to do this. However, it is often the case that the same headers are
+repeatedly included, and in these cases we try to avoid repeating the
+filesystem queries whilst searching for the correct file.
+
+For each file we try to open, we store the constructed path in a splay
+tree. This path first undergoes simplification by the function
+@code{_cpp_simplify_pathname}. For example,
+@file{/usr/include/bits/../foo.h} is simplified to
+@file{/usr/include/foo.h} before we enter it in the splay tree and try
+to @code{open ()} the file. CPP will then find subsequent uses of
+@file{foo.h}, even as @file{/usr/include/foo.h}, in the splay tree and
+save system calls.
+
+Further, it is likely the file contents have also been cached, saving a
+@code{read ()} system call. We don't bother caching the contents of
+header files that are re-inclusion protected, and whose re-inclusion
+macro is defined when we leave the header file for the first time. If
+the host supports it, we try to map suitably large files into memory,
+rather than reading them in directly.
+
+The include paths are internally stored on a null-terminated
+singly-linked list, starting with the @code{"header.h"} directory search
+chain, which then links into the @code{<header.h>} directory chain.
+
+Files included with the @code{<foo.h>} syntax start the lookup directly
+in the second half of this chain. However, files included with the
+@code{"foo.h"} syntax start at the beginning of the chain, but with one
+extra directory prepended. This is the directory of the current file;
+the one containing the @code{#include} directive. Prepending this
+directory on a per-file basis is handled by the function
+@code{search_from}.
+
+Note that a header included with a directory component, such as
+@code{#include "mydir/foo.h"} and opened as
+@file{/usr/local/include/mydir/foo.h}, will have the complete path minus
+the basename @samp{foo.h} as the current directory.
+
+Enough information is stored in the splay tree that CPP can immediately
+tell whether it can skip the header file because of the multiple include
+optimization, whether the file didn't exist or couldn't be opened for
+some reason, or whether the header was flagged not to be re-used, as it
+is with the obsolete @code{#import} directive.
+
+For the benefit of MS-DOS filesystems with an 8.3 filename limitation,
+CPP offers the ability to treat various include file names as aliases
+for the real header files with shorter names. The map from one to the
+other is found in a special file called @samp{header.gcc}, stored in the
+command line (or system) include directories to which the mapping
+applies. This may be higher up the directory tree than the full path to
+the file minus the base name.
+
+@node Concept Index
+@unnumbered Concept Index
+@printindex cp
+
+@bye
--- /dev/null
+@c Copyright (C) 1999-2022 Free Software Foundation, Inc.
+@c This is part of the CPP and GCC manuals.
+@c For copying conditions, see the file gcc.texi.
+
+@c ---------------------------------------------------------------------
+@c Options affecting the preprocessor
+@c ---------------------------------------------------------------------
+
+@c If this file is included with the flag ``cppmanual'' set, it is
+@c formatted for inclusion in the CPP manual; otherwise the main GCC manual.
+
+@item -D @var{name}
+@opindex D
+Predefine @var{name} as a macro, with definition @code{1}.
+
+@item -D @var{name}=@var{definition}
+The contents of @var{definition} are tokenized and processed as if
+they appeared during translation phase three in a @samp{#define}
+directive. In particular, the definition is truncated by
+embedded newline characters.
+
+If you are invoking the preprocessor from a shell or shell-like
+program you may need to use the shell's quoting syntax to protect
+characters such as spaces that have a meaning in the shell syntax.
+
+If you wish to define a function-like macro on the command line, write
+its argument list with surrounding parentheses before the equals sign
+(if any). Parentheses are meaningful to most shells, so you should
+quote the option. With @command{sh} and @command{csh},
+@option{-D'@var{name}(@var{args@dots{}})=@var{definition}'} works.
+
+@option{-D} and @option{-U} options are processed in the order they
+are given on the command line. All @option{-imacros @var{file}} and
+@option{-include @var{file}} options are processed after all
+@option{-D} and @option{-U} options.
+
+@item -U @var{name}
+@opindex U
+Cancel any previous definition of @var{name}, either built in or
+provided with a @option{-D} option.
+
+@item -include @var{file}
+@opindex include
+Process @var{file} as if @code{#include "file"} appeared as the first
+line of the primary source file. However, the first directory searched
+for @var{file} is the preprocessor's working directory @emph{instead of}
+the directory containing the main source file. If not found there, it
+is searched for in the remainder of the @code{#include "@dots{}"} search
+chain as normal.
+
+If multiple @option{-include} options are given, the files are included
+in the order they appear on the command line.
+
+@item -imacros @var{file}
+@opindex imacros
+Exactly like @option{-include}, except that any output produced by
+scanning @var{file} is thrown away. Macros it defines remain defined.
+This allows you to acquire all the macros from a header without also
+processing its declarations.
+
+All files specified by @option{-imacros} are processed before all files
+specified by @option{-include}.
+
+@item -undef
+@opindex undef
+Do not predefine any system-specific or GCC-specific macros. The
+standard predefined macros remain defined.
+@ifset cppmanual
+@xref{Standard Predefined Macros}.
+@end ifset
+
+@item -pthread
+@opindex pthread
+Define additional macros required for using the POSIX threads library.
+You should use this option consistently for both compilation and linking.
+This option is supported on GNU/Linux targets, most other Unix derivatives,
+and also on x86 Cygwin and MinGW targets.
+
+@item -M
+@opindex M
+@cindex @command{make}
+@cindex dependencies, @command{make}
+Instead of outputting the result of preprocessing, output a rule
+suitable for @command{make} describing the dependencies of the main
+source file. The preprocessor outputs one @command{make} rule containing
+the object file name for that source file, a colon, and the names of all
+the included files, including those coming from @option{-include} or
+@option{-imacros} command-line options.
+
+Unless specified explicitly (with @option{-MT} or @option{-MQ}), the
+object file name consists of the name of the source file with any
+suffix replaced with object file suffix and with any leading directory
+parts removed. If there are many included files then the rule is
+split into several lines using @samp{\}-newline. The rule has no
+commands.
+
+This option does not suppress the preprocessor's debug output, such as
+@option{-dM}. To avoid mixing such debug output with the dependency
+rules you should explicitly specify the dependency output file with
+@option{-MF}, or use an environment variable like
+@env{DEPENDENCIES_OUTPUT} (@pxref{Environment Variables}). Debug output
+is still sent to the regular output stream as normal.
+
+Passing @option{-M} to the driver implies @option{-E}, and suppresses
+warnings with an implicit @option{-w}.
+
+@item -MM
+@opindex MM
+Like @option{-M} but do not mention header files that are found in
+system header directories, nor header files that are included,
+directly or indirectly, from such a header.
+
+This implies that the choice of angle brackets or double quotes in an
+@samp{#include} directive does not in itself determine whether that
+header appears in @option{-MM} dependency output.
+
+@anchor{dashMF}
+@item -MF @var{file}
+@opindex MF
+When used with @option{-M} or @option{-MM}, specifies a
+file to write the dependencies to. If no @option{-MF} switch is given
+the preprocessor sends the rules to the same place it would send
+preprocessed output.
+
+When used with the driver options @option{-MD} or @option{-MMD},
+@option{-MF} overrides the default dependency output file.
+
+If @var{file} is @file{-}, then the dependencies are written to @file{stdout}.
+
+@item -MG
+@opindex MG
+In conjunction with an option such as @option{-M} requesting
+dependency generation, @option{-MG} assumes missing header files are
+generated files and adds them to the dependency list without raising
+an error. The dependency filename is taken directly from the
+@code{#include} directive without prepending any path. @option{-MG}
+also suppresses preprocessed output, as a missing header file renders
+this useless.
+
+This feature is used in automatic updating of makefiles.
+
+@item -Mno-modules
+@opindex Mno-modules
+Disable dependency generation for compiled module interfaces.
+
+@item -MP
+@opindex MP
+This option instructs CPP to add a phony target for each dependency
+other than the main file, causing each to depend on nothing. These
+dummy rules work around errors @command{make} gives if you remove header
+files without updating the @file{Makefile} to match.
+
+This is typical output:
+
+@smallexample
+test.o: test.c test.h
+
+test.h:
+@end smallexample
+
+@item -MT @var{target}
+@opindex MT
+
+Change the target of the rule emitted by dependency generation. By
+default CPP takes the name of the main input file, deletes any
+directory components and any file suffix such as @samp{.c}, and
+appends the platform's usual object suffix. The result is the target.
+
+An @option{-MT} option sets the target to be exactly the string you
+specify. If you want multiple targets, you can specify them as a single
+argument to @option{-MT}, or use multiple @option{-MT} options.
+
+For example, @option{@w{-MT '$(objpfx)foo.o'}} might give
+
+@smallexample
+$(objpfx)foo.o: foo.c
+@end smallexample
+
+@item -MQ @var{target}
+@opindex MQ
+
+Same as @option{-MT}, but it quotes any characters which are special to
+Make. @option{@w{-MQ '$(objpfx)foo.o'}} gives
+
+@smallexample
+$$(objpfx)foo.o: foo.c
+@end smallexample
+
+The default target is automatically quoted, as if it were given with
+@option{-MQ}.
+
+@item -MD
+@opindex MD
+@option{-MD} is equivalent to @option{-M -MF @var{file}}, except that
+@option{-E} is not implied. The driver determines @var{file} based on
+whether an @option{-o} option is given. If it is, the driver uses its
+argument but with a suffix of @file{.d}, otherwise it takes the name
+of the input file, removes any directory components and suffix, and
+applies a @file{.d} suffix.
+
+If @option{-MD} is used in conjunction with @option{-E}, any
+@option{-o} switch is understood to specify the dependency output file
+(@pxref{dashMF,,-MF}), but if used without @option{-E}, each @option{-o}
+is understood to specify a target object file.
+
+Since @option{-E} is not implied, @option{-MD} can be used to generate
+a dependency output file as a side effect of the compilation process.
+
+@item -MMD
+@opindex MMD
+Like @option{-MD} except mention only user header files, not system
+header files.
+
+@item -fpreprocessed
+@opindex fpreprocessed
+Indicate to the preprocessor that the input file has already been
+preprocessed. This suppresses things like macro expansion, trigraph
+conversion, escaped newline splicing, and processing of most directives.
+The preprocessor still recognizes and removes comments, so that you can
+pass a file preprocessed with @option{-C} to the compiler without
+problems. In this mode the integrated preprocessor is little more than
+a tokenizer for the front ends.
+
+@option{-fpreprocessed} is implicit if the input file has one of the
+extensions @samp{.i}, @samp{.ii} or @samp{.mi}. These are the
+extensions that GCC uses for preprocessed files created by
+@option{-save-temps}.
+
+@item -fdirectives-only
+@opindex fdirectives-only
+When preprocessing, handle directives, but do not expand macros.
+
+The option's behavior depends on the @option{-E} and @option{-fpreprocessed}
+options.
+
+With @option{-E}, preprocessing is limited to the handling of directives
+such as @code{#define}, @code{#ifdef}, and @code{#error}. Other
+preprocessor operations, such as macro expansion and trigraph
+conversion are not performed. In addition, the @option{-dD} option is
+implicitly enabled.
+
+With @option{-fpreprocessed}, predefinition of command line and most
+builtin macros is disabled. Macros such as @code{__LINE__}, which are
+contextually dependent, are handled normally. This enables compilation of
+files previously preprocessed with @code{-E -fdirectives-only}.
+
+With both @option{-E} and @option{-fpreprocessed}, the rules for
+@option{-fpreprocessed} take precedence. This enables full preprocessing of
+files previously preprocessed with @code{-E -fdirectives-only}.
+
+@item -fdollars-in-identifiers
+@opindex fdollars-in-identifiers
+@anchor{fdollars-in-identifiers}
+Accept @samp{$} in identifiers.
+@ifset cppmanual
+@xref{Identifier characters}.
+@end ifset
+
+@item -fextended-identifiers
+@opindex fextended-identifiers
+Accept universal character names and extended characters in
+identifiers. This option is enabled by default for C99 (and later C
+standard versions) and C++.
+
+@item -fno-canonical-system-headers
+@opindex fno-canonical-system-headers
+When preprocessing, do not shorten system header paths with canonicalization.
+
+@item -fmax-include-depth=@var{depth}
+@opindex fmax-include-depth
+Set the maximum depth of the nested #include. The default is 200.
+
+@item -ftabstop=@var{width}
+@opindex ftabstop
+Set the distance between tab stops. This helps the preprocessor report
+correct column numbers in warnings or errors, even if tabs appear on the
+line. If the value is less than 1 or greater than 100, the option is
+ignored. The default is 8.
+
+@item -ftrack-macro-expansion@r{[}=@var{level}@r{]}
+@opindex ftrack-macro-expansion
+Track locations of tokens across macro expansions. This allows the
+compiler to emit diagnostic about the current macro expansion stack
+when a compilation error occurs in a macro expansion. Using this
+option makes the preprocessor and the compiler consume more
+memory. The @var{level} parameter can be used to choose the level of
+precision of token location tracking thus decreasing the memory
+consumption if necessary. Value @samp{0} of @var{level} de-activates
+this option. Value @samp{1} tracks tokens locations in a
+degraded mode for the sake of minimal memory overhead. In this mode
+all tokens resulting from the expansion of an argument of a
+function-like macro have the same location. Value @samp{2} tracks
+tokens locations completely. This value is the most memory hungry.
+When this option is given no argument, the default parameter value is
+@samp{2}.
+
+Note that @code{-ftrack-macro-expansion=2} is activated by default.
+
+@item -fmacro-prefix-map=@var{old}=@var{new}
+@opindex fmacro-prefix-map
+When preprocessing files residing in directory @file{@var{old}},
+expand the @code{__FILE__} and @code{__BASE_FILE__} macros as if the
+files resided in directory @file{@var{new}} instead. This can be used
+to change an absolute path to a relative path by using @file{.} for
+@var{new} which can result in more reproducible builds that are
+location independent. This option also affects
+@code{__builtin_FILE()} during compilation. See also
+@option{-ffile-prefix-map}.
+
+@item -fexec-charset=@var{charset}
+@opindex fexec-charset
+@cindex character set, execution
+Set the execution character set, used for string and character
+constants. The default is UTF-8. @var{charset} can be any encoding
+supported by the system's @code{iconv} library routine.
+
+@item -fwide-exec-charset=@var{charset}
+@opindex fwide-exec-charset
+@cindex character set, wide execution
+Set the wide execution character set, used for wide string and
+character constants. The default is one of UTF-32BE, UTF-32LE, UTF-16BE,
+or UTF-16LE, whichever corresponds to the width of @code{wchar_t} and the
+big-endian or little-endian byte order being used for code generation. As
+with @option{-fexec-charset}, @var{charset} can be any encoding supported
+by the system's @code{iconv} library routine; however, you will have
+problems with encodings that do not fit exactly in @code{wchar_t}.
+
+@item -finput-charset=@var{charset}
+@opindex finput-charset
+@cindex character set, input
+Set the input character set, used for translation from the character
+set of the input file to the source character set used by GCC@. If the
+locale does not specify, or GCC cannot get this information from the
+locale, the default is UTF-8. This can be overridden by either the locale
+or this command-line option. Currently the command-line option takes
+precedence if there's a conflict. @var{charset} can be any encoding
+supported by the system's @code{iconv} library routine.
+
+@ifclear cppmanual
+@item -fpch-deps
+@opindex fpch-deps
+When using precompiled headers (@pxref{Precompiled Headers}), this flag
+causes the dependency-output flags to also list the files from the
+precompiled header's dependencies. If not specified, only the
+precompiled header are listed and not the files that were used to
+create it, because those files are not consulted when a precompiled
+header is used.
+
+@item -fpch-preprocess
+@opindex fpch-preprocess
+This option allows use of a precompiled header (@pxref{Precompiled
+Headers}) together with @option{-E}. It inserts a special @code{#pragma},
+@code{#pragma GCC pch_preprocess "@var{filename}"} in the output to mark
+the place where the precompiled header was found, and its @var{filename}.
+When @option{-fpreprocessed} is in use, GCC recognizes this @code{#pragma}
+and loads the PCH@.
+
+This option is off by default, because the resulting preprocessed output
+is only really suitable as input to GCC@. It is switched on by
+@option{-save-temps}.
+
+You should not write this @code{#pragma} in your own code, but it is
+safe to edit the filename if the PCH file is available in a different
+location. The filename may be absolute or it may be relative to GCC's
+current directory.
+@end ifclear
+
+@item -fworking-directory
+@opindex fworking-directory
+@opindex fno-working-directory
+Enable generation of linemarkers in the preprocessor output that
+let the compiler know the current working directory at the time of
+preprocessing. When this option is enabled, the preprocessor
+emits, after the initial linemarker, a second linemarker with the
+current working directory followed by two slashes. GCC uses this
+directory, when it's present in the preprocessed input, as the
+directory emitted as the current working directory in some debugging
+information formats. This option is implicitly enabled if debugging
+information is enabled, but this can be inhibited with the negated
+form @option{-fno-working-directory}. If the @option{-P} flag is
+present in the command line, this option has no effect, since no
+@code{#line} directives are emitted whatsoever.
+
+@item -A @var{predicate}=@var{answer}
+@opindex A
+Make an assertion with the predicate @var{predicate} and answer
+@var{answer}. This form is preferred to the older form @option{-A
+@var{predicate}(@var{answer})}, which is still supported, because
+it does not use shell special characters.
+@ifset cppmanual
+@xref{Obsolete Features}.
+@end ifset
+
+@item -A -@var{predicate}=@var{answer}
+Cancel an assertion with the predicate @var{predicate} and answer
+@var{answer}.
+
+@item -C
+@opindex C
+Do not discard comments. All comments are passed through to the output
+file, except for comments in processed directives, which are deleted
+along with the directive.
+
+You should be prepared for side effects when using @option{-C}; it
+causes the preprocessor to treat comments as tokens in their own right.
+For example, comments appearing at the start of what would be a
+directive line have the effect of turning that line into an ordinary
+source line, since the first token on the line is no longer a @samp{#}.
+
+@item -CC
+@opindex CC
+Do not discard comments, including during macro expansion. This is
+like @option{-C}, except that comments contained within macros are
+also passed through to the output file where the macro is expanded.
+
+In addition to the side effects of the @option{-C} option, the
+@option{-CC} option causes all C++-style comments inside a macro
+to be converted to C-style comments. This is to prevent later use
+of that macro from inadvertently commenting out the remainder of
+the source line.
+
+The @option{-CC} option is generally used to support lint comments.
+
+@item -P
+@opindex P
+Inhibit generation of linemarkers in the output from the preprocessor.
+This might be useful when running the preprocessor on something that is
+not C code, and will be sent to a program which might be confused by the
+linemarkers.
+@ifset cppmanual
+@xref{Preprocessor Output}.
+@end ifset
+
+@cindex traditional C language
+@cindex C language, traditional
+@item -traditional
+@itemx -traditional-cpp
+@opindex traditional-cpp
+@opindex traditional
+
+Try to imitate the behavior of pre-standard C preprocessors, as
+opposed to ISO C preprocessors.
+@ifset cppmanual
+@xref{Traditional Mode}.
+@end ifset
+@ifclear cppmanual
+See the GNU CPP manual for details.
+@end ifclear
+
+Note that GCC does not otherwise attempt to emulate a pre-standard
+C compiler, and these options are only supported with the @option{-E}
+switch, or when invoking CPP explicitly.
+
+@item -trigraphs
+@opindex trigraphs
+Support ISO C trigraphs.
+These are three-character sequences, all starting with @samp{??}, that
+are defined by ISO C to stand for single characters. For example,
+@samp{??/} stands for @samp{\}, so @samp{'??/n'} is a character
+constant for a newline.
+@ifset cppmanual
+@xref{Initial processing}.
+@end ifset
+
+@ifclear cppmanual
+The nine trigraphs and their replacements are
+
+@smallexample
+Trigraph: ??( ??) ??< ??> ??= ??/ ??' ??! ??-
+Replacement: [ ] @{ @} # \ ^ | ~
+@end smallexample
+@end ifclear
+
+By default, GCC ignores trigraphs, but in
+standard-conforming modes it converts them. See the @option{-std} and
+@option{-ansi} options.
+
+@item -remap
+@opindex remap
+Enable special code to work around file systems which only permit very
+short file names, such as MS-DOS@.
+
+@item -H
+@opindex H
+Print the name of each header file used, in addition to other normal
+activities. Each name is indented to show how deep in the
+@samp{#include} stack it is. Precompiled header files are also
+printed, even if they are found to be invalid; an invalid precompiled
+header file is printed with @samp{...x} and a valid one with @samp{...!} .
+
+@item -d@var{letters}
+@opindex d
+Says to make debugging dumps during compilation as specified by
+@var{letters}. The flags documented here are those relevant to the
+preprocessor. Other @var{letters} are interpreted
+by the compiler proper, or reserved for future versions of GCC, and so
+are silently ignored. If you specify @var{letters} whose behavior
+conflicts, the result is undefined.
+@ifclear cppmanual
+@xref{Developer Options}, for more information.
+@end ifclear
+
+@table @gcctabopt
+@item -dM
+@opindex dM
+Instead of the normal output, generate a list of @samp{#define}
+directives for all the macros defined during the execution of the
+preprocessor, including predefined macros. This gives you a way of
+finding out what is predefined in your version of the preprocessor.
+Assuming you have no file @file{foo.h}, the command
+
+@smallexample
+touch foo.h; cpp -dM foo.h
+@end smallexample
+
+@noindent
+shows all the predefined macros.
+
+@ifclear cppmanual
+If you use @option{-dM} without the @option{-E} option, @option{-dM} is
+interpreted as a synonym for @option{-fdump-rtl-mach}.
+@xref{Developer Options, , ,gcc}.
+@end ifclear
+
+@item -dD
+@opindex dD
+Like @option{-dM} except in two respects: it does @emph{not} include the
+predefined macros, and it outputs @emph{both} the @samp{#define}
+directives and the result of preprocessing. Both kinds of output go to
+the standard output file.
+
+@item -dN
+@opindex dN
+Like @option{-dD}, but emit only the macro names, not their expansions.
+
+@item -dI
+@opindex dI
+Output @samp{#include} directives in addition to the result of
+preprocessing.
+
+@item -dU
+@opindex dU
+Like @option{-dD} except that only macros that are expanded, or whose
+definedness is tested in preprocessor directives, are output; the
+output is delayed until the use or test of the macro; and
+@samp{#undef} directives are also output for macros tested but
+undefined at the time.
+@end table
+
+@item -fdebug-cpp
+@opindex fdebug-cpp
+This option is only useful for debugging GCC. When used from CPP or with
+@option{-E}, it dumps debugging information about location maps. Every
+token in the output is preceded by the dump of the map its location
+belongs to.
+
+When used from GCC without @option{-E}, this option has no effect.
--- /dev/null
+@c Copyright (C) 1999-2022 Free Software Foundation, Inc.
+@c This is part of the CPP and GCC manuals.
+@c For copying conditions, see the file gcc.texi.
+
+@c ---------------------------------------------------------------------
+@c Options affecting preprocessor warnings
+@c ---------------------------------------------------------------------
+
+@c If this file is included with the flag ``cppmanual'' set, it is
+@c formatted for inclusion in the CPP manual; otherwise the main GCC manual.
+
+@item -Wcomment
+@itemx -Wcomments
+@opindex Wcomment
+@opindex Wcomments
+Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*}
+comment, or whenever a backslash-newline appears in a @samp{//} comment.
+This warning is enabled by @option{-Wall}.
+
+@item -Wtrigraphs
+@opindex Wtrigraphs
+@anchor{Wtrigraphs}
+Warn if any trigraphs are encountered that might change the meaning of
+the program. Trigraphs within comments are not warned about,
+except those that would form escaped newlines.
+
+This option is implied by @option{-Wall}. If @option{-Wall} is not
+given, this option is still enabled unless trigraphs are enabled. To
+get trigraph conversion without warnings, but get the other
+@option{-Wall} warnings, use @samp{-trigraphs -Wall -Wno-trigraphs}.
+
+@item -Wundef
+@opindex Wundef
+@opindex Wno-undef
+Warn if an undefined identifier is evaluated in an @code{#if} directive.
+Such identifiers are replaced with zero.
+
+@item -Wexpansion-to-defined
+@opindex Wexpansion-to-defined
+Warn whenever @samp{defined} is encountered in the expansion of a macro
+(including the case where the macro is expanded by an @samp{#if} directive).
+Such usage is not portable.
+This warning is also enabled by @option{-Wpedantic} and @option{-Wextra}.
+
+@item -Wunused-macros
+@opindex Wunused-macros
+Warn about macros defined in the main file that are unused. A macro
+is @dfn{used} if it is expanded or tested for existence at least once.
+The preprocessor also warns if the macro has not been used at the
+time it is redefined or undefined.
+
+Built-in macros, macros defined on the command line, and macros
+defined in include files are not warned about.
+
+@emph{Note:} If a macro is actually used, but only used in skipped
+conditional blocks, then the preprocessor reports it as unused. To avoid the
+warning in such a case, you might improve the scope of the macro's
+definition by, for example, moving it into the first skipped block.
+Alternatively, you could provide a dummy use with something like:
+
+@smallexample
+#if defined the_macro_causing_the_warning
+#endif
+@end smallexample
+
+@item -Wno-endif-labels
+@opindex Wno-endif-labels
+@opindex Wendif-labels
+Do not warn whenever an @code{#else} or an @code{#endif} are followed by text.
+This sometimes happens in older programs with code of the form
+
+@smallexample
+#if FOO
+@dots{}
+#else FOO
+@dots{}
+#endif FOO
+@end smallexample
+
+@noindent
+The second and third @code{FOO} should be in comments.
+This warning is on by default.
--- /dev/null
+c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node C Extensions
+@chapter Extensions to the C Language Family
+@cindex extensions, C language
+@cindex C language extensions
+
+@opindex pedantic
+GNU C provides several language features not found in ISO standard C@.
+(The @option{-pedantic} option directs GCC to print a warning message if
+any of these features is used.) To test for the availability of these
+features in conditional compilation, check for a predefined macro
+@code{__GNUC__}, which is always defined under GCC@.
+
+These extensions are available in C and Objective-C@. Most of them are
+also available in C++. @xref{C++ Extensions,,Extensions to the
+C++ Language}, for extensions that apply @emph{only} to C++.
+
+Some features that are in ISO C99 but not C90 or C++ are also, as
+extensions, accepted by GCC in C90 mode and in C++.
+
+@menu
+* Statement Exprs:: Putting statements and declarations inside expressions.
+* Local Labels:: Labels local to a block.
+* Labels as Values:: Getting pointers to labels, and computed gotos.
+* Nested Functions:: Nested function in GNU C.
+* Nonlocal Gotos:: Nonlocal gotos.
+* Constructing Calls:: Dispatching a call to another function.
+* Typeof:: @code{typeof}: referring to the type of an expression.
+* Conditionals:: Omitting the middle operand of a @samp{?:} expression.
+* __int128:: 128-bit integers---@code{__int128}.
+* Long Long:: Double-word integers---@code{long long int}.
+* Complex:: Data types for complex numbers.
+* Floating Types:: Additional Floating Types.
+* Half-Precision:: Half-Precision Floating Point.
+* Decimal Float:: Decimal Floating Types.
+* Hex Floats:: Hexadecimal floating-point constants.
+* Fixed-Point:: Fixed-Point Types.
+* Named Address Spaces::Named address spaces.
+* Zero Length:: Zero-length arrays.
+* Empty Structures:: Structures with no members.
+* Variable Length:: Arrays whose length is computed at run time.
+* Variadic Macros:: Macros with a variable number of arguments.
+* Escaped Newlines:: Slightly looser rules for escaped newlines.
+* Subscripting:: Any array can be subscripted, even if not an lvalue.
+* Pointer Arith:: Arithmetic on @code{void}-pointers and function pointers.
+* Variadic Pointer Args:: Pointer arguments to variadic functions.
+* Pointers to Arrays:: Pointers to arrays with qualifiers work as expected.
+* Initializers:: Non-constant initializers.
+* Compound Literals:: Compound literals give structures, unions
+ or arrays as values.
+* Designated Inits:: Labeling elements of initializers.
+* Case Ranges:: `case 1 ... 9' and such.
+* Cast to Union:: Casting to union type from any member of the union.
+* Mixed Labels and Declarations:: Mixing declarations, labels and code.
+* Function Attributes:: Declaring that functions have no side effects,
+ or that they can never return.
+* Variable Attributes:: Specifying attributes of variables.
+* Type Attributes:: Specifying attributes of types.
+* Label Attributes:: Specifying attributes on labels.
+* Enumerator Attributes:: Specifying attributes on enumerators.
+* Statement Attributes:: Specifying attributes on statements.
+* Attribute Syntax:: Formal syntax for attributes.
+* Function Prototypes:: Prototype declarations and old-style definitions.
+* C++ Comments:: C++ comments are recognized.
+* Dollar Signs:: Dollar sign is allowed in identifiers.
+* Character Escapes:: @samp{\e} stands for the character @key{ESC}.
+* Alignment:: Determining the alignment of a function, type or variable.
+* Inline:: Defining inline functions (as fast as macros).
+* Volatiles:: What constitutes an access to a volatile object.
+* Using Assembly Language with C:: Instructions and extensions for interfacing C with assembler.
+* Alternate Keywords:: @code{__const__}, @code{__asm__}, etc., for header files.
+* Incomplete Enums:: @code{enum foo;}, with details to follow.
+* Function Names:: Printable strings which are the name of the current
+ function.
+* Return Address:: Getting the return or frame address of a function.
+* Vector Extensions:: Using vector instructions through built-in functions.
+* Offsetof:: Special syntax for implementing @code{offsetof}.
+* __sync Builtins:: Legacy built-in functions for atomic memory access.
+* __atomic Builtins:: Atomic built-in functions with memory model.
+* Integer Overflow Builtins:: Built-in functions to perform arithmetics and
+ arithmetic overflow checking.
+* x86 specific memory model extensions for transactional memory:: x86 memory models.
+* Object Size Checking:: Built-in functions for limited buffer overflow
+ checking.
+* Other Builtins:: Other built-in functions.
+* Target Builtins:: Built-in functions specific to particular targets.
+* Target Format Checks:: Format checks specific to particular targets.
+* Pragmas:: Pragmas accepted by GCC.
+* Unnamed Fields:: Unnamed struct/union fields within structs/unions.
+* Thread-Local:: Per-thread variables.
+* Binary constants:: Binary constants using the @samp{0b} prefix.
+@end menu
+
+@node Statement Exprs
+@section Statements and Declarations in Expressions
+@cindex statements inside expressions
+@cindex declarations inside expressions
+@cindex expressions containing statements
+@cindex macros, statements in expressions
+
+@c the above section title wrapped and causes an underfull hbox.. i
+@c changed it from "within" to "in". --mew 4feb93
+A compound statement enclosed in parentheses may appear as an expression
+in GNU C@. This allows you to use loops, switches, and local variables
+within an expression.
+
+Recall that a compound statement is a sequence of statements surrounded
+by braces; in this construct, parentheses go around the braces. For
+example:
+
+@smallexample
+(@{ int y = foo (); int z;
+ if (y > 0) z = y;
+ else z = - y;
+ z; @})
+@end smallexample
+
+@noindent
+is a valid (though slightly more complex than necessary) expression
+for the absolute value of @code{foo ()}.
+
+The last thing in the compound statement should be an expression
+followed by a semicolon; the value of this subexpression serves as the
+value of the entire construct. (If you use some other kind of statement
+last within the braces, the construct has type @code{void}, and thus
+effectively no value.)
+
+This feature is especially useful in making macro definitions ``safe'' (so
+that they evaluate each operand exactly once). For example, the
+``maximum'' function is commonly defined as a macro in standard C as
+follows:
+
+@smallexample
+#define max(a,b) ((a) > (b) ? (a) : (b))
+@end smallexample
+
+@noindent
+@cindex side effects, macro argument
+But this definition computes either @var{a} or @var{b} twice, with bad
+results if the operand has side effects. In GNU C, if you know the
+type of the operands (here taken as @code{int}), you can avoid this
+problem by defining the macro as follows:
+
+@smallexample
+#define maxint(a,b) \
+ (@{int _a = (a), _b = (b); _a > _b ? _a : _b; @})
+@end smallexample
+
+Note that introducing variable declarations (as we do in @code{maxint}) can
+cause variable shadowing, so while this example using the @code{max} macro
+produces correct results:
+@smallexample
+int _a = 1, _b = 2, c;
+c = max (_a, _b);
+@end smallexample
+@noindent
+this example using maxint will not:
+@smallexample
+int _a = 1, _b = 2, c;
+c = maxint (_a, _b);
+@end smallexample
+
+This problem may for instance occur when we use this pattern recursively, like
+so:
+
+@smallexample
+#define maxint3(a, b, c) \
+ (@{int _a = (a), _b = (b), _c = (c); maxint (maxint (_a, _b), _c); @})
+@end smallexample
+
+Embedded statements are not allowed in constant expressions, such as
+the value of an enumeration constant, the width of a bit-field, or
+the initial value of a static variable.
+
+If you don't know the type of the operand, you can still do this, but you
+must use @code{typeof} or @code{__auto_type} (@pxref{Typeof}).
+
+In G++, the result value of a statement expression undergoes array and
+function pointer decay, and is returned by value to the enclosing
+expression. For instance, if @code{A} is a class, then
+
+@smallexample
+ A a;
+
+ (@{a;@}).Foo ()
+@end smallexample
+
+@noindent
+constructs a temporary @code{A} object to hold the result of the
+statement expression, and that is used to invoke @code{Foo}.
+Therefore the @code{this} pointer observed by @code{Foo} is not the
+address of @code{a}.
+
+In a statement expression, any temporaries created within a statement
+are destroyed at that statement's end. This makes statement
+expressions inside macros slightly different from function calls. In
+the latter case temporaries introduced during argument evaluation are
+destroyed at the end of the statement that includes the function
+call. In the statement expression case they are destroyed during
+the statement expression. For instance,
+
+@smallexample
+#define macro(a) (@{__typeof__(a) b = (a); b + 3; @})
+template<typename T> T function(T a) @{ T b = a; return b + 3; @}
+
+void foo ()
+@{
+ macro (X ());
+ function (X ());
+@}
+@end smallexample
+
+@noindent
+has different places where temporaries are destroyed. For the
+@code{macro} case, the temporary @code{X} is destroyed just after
+the initialization of @code{b}. In the @code{function} case that
+temporary is destroyed when the function returns.
+
+These considerations mean that it is probably a bad idea to use
+statement expressions of this form in header files that are designed to
+work with C++. (Note that some versions of the GNU C Library contained
+header files using statement expressions that lead to precisely this
+bug.)
+
+Jumping into a statement expression with @code{goto} or using a
+@code{switch} statement outside the statement expression with a
+@code{case} or @code{default} label inside the statement expression is
+not permitted. Jumping into a statement expression with a computed
+@code{goto} (@pxref{Labels as Values}) has undefined behavior.
+Jumping out of a statement expression is permitted, but if the
+statement expression is part of a larger expression then it is
+unspecified which other subexpressions of that expression have been
+evaluated except where the language definition requires certain
+subexpressions to be evaluated before or after the statement
+expression. A @code{break} or @code{continue} statement inside of
+a statement expression used in @code{while}, @code{do} or @code{for}
+loop or @code{switch} statement condition
+or @code{for} statement init or increment expressions jumps to an
+outer loop or @code{switch} statement if any (otherwise it is an error),
+rather than to the loop or @code{switch} statement in whose condition
+or init or increment expression it appears.
+In any case, as with a function call, the evaluation of a
+statement expression is not interleaved with the evaluation of other
+parts of the containing expression. For example,
+
+@smallexample
+ foo (), ((@{ bar1 (); goto a; 0; @}) + bar2 ()), baz();
+@end smallexample
+
+@noindent
+calls @code{foo} and @code{bar1} and does not call @code{baz} but
+may or may not call @code{bar2}. If @code{bar2} is called, it is
+called after @code{foo} and before @code{bar1}.
+
+@node Local Labels
+@section Locally Declared Labels
+@cindex local labels
+@cindex macros, local labels
+
+GCC allows you to declare @dfn{local labels} in any nested block
+scope. A local label is just like an ordinary label, but you can
+only reference it (with a @code{goto} statement, or by taking its
+address) within the block in which it is declared.
+
+A local label declaration looks like this:
+
+@smallexample
+__label__ @var{label};
+@end smallexample
+
+@noindent
+or
+
+@smallexample
+__label__ @var{label1}, @var{label2}, /* @r{@dots{}} */;
+@end smallexample
+
+Local label declarations must come at the beginning of the block,
+before any ordinary declarations or statements.
+
+The label declaration defines the label @emph{name}, but does not define
+the label itself. You must do this in the usual way, with
+@code{@var{label}:}, within the statements of the statement expression.
+
+The local label feature is useful for complex macros. If a macro
+contains nested loops, a @code{goto} can be useful for breaking out of
+them. However, an ordinary label whose scope is the whole function
+cannot be used: if the macro can be expanded several times in one
+function, the label is multiply defined in that function. A
+local label avoids this problem. For example:
+
+@smallexample
+#define SEARCH(value, array, target) \
+do @{ \
+ __label__ found; \
+ typeof (target) _SEARCH_target = (target); \
+ typeof (*(array)) *_SEARCH_array = (array); \
+ int i, j; \
+ int value; \
+ for (i = 0; i < max; i++) \
+ for (j = 0; j < max; j++) \
+ if (_SEARCH_array[i][j] == _SEARCH_target) \
+ @{ (value) = i; goto found; @} \
+ (value) = -1; \
+ found:; \
+@} while (0)
+@end smallexample
+
+This could also be written using a statement expression:
+
+@smallexample
+#define SEARCH(array, target) \
+(@{ \
+ __label__ found; \
+ typeof (target) _SEARCH_target = (target); \
+ typeof (*(array)) *_SEARCH_array = (array); \
+ int i, j; \
+ int value; \
+ for (i = 0; i < max; i++) \
+ for (j = 0; j < max; j++) \
+ if (_SEARCH_array[i][j] == _SEARCH_target) \
+ @{ value = i; goto found; @} \
+ value = -1; \
+ found: \
+ value; \
+@})
+@end smallexample
+
+Local label declarations also make the labels they declare visible to
+nested functions, if there are any. @xref{Nested Functions}, for details.
+
+@node Labels as Values
+@section Labels as Values
+@cindex labels as values
+@cindex computed gotos
+@cindex goto with computed label
+@cindex address of a label
+
+You can get the address of a label defined in the current function
+(or a containing function) with the unary operator @samp{&&}. The
+value has type @code{void *}. This value is a constant and can be used
+wherever a constant of that type is valid. For example:
+
+@smallexample
+void *ptr;
+/* @r{@dots{}} */
+ptr = &&foo;
+@end smallexample
+
+To use these values, you need to be able to jump to one. This is done
+with the computed goto statement@footnote{The analogous feature in
+Fortran is called an assigned goto, but that name seems inappropriate in
+C, where one can do more than simply store label addresses in label
+variables.}, @code{goto *@var{exp};}. For example,
+
+@smallexample
+goto *ptr;
+@end smallexample
+
+@noindent
+Any expression of type @code{void *} is allowed.
+
+One way of using these constants is in initializing a static array that
+serves as a jump table:
+
+@smallexample
+static void *array[] = @{ &&foo, &&bar, &&hack @};
+@end smallexample
+
+@noindent
+Then you can select a label with indexing, like this:
+
+@smallexample
+goto *array[i];
+@end smallexample
+
+@noindent
+Note that this does not check whether the subscript is in bounds---array
+indexing in C never does that.
+
+Such an array of label values serves a purpose much like that of the
+@code{switch} statement. The @code{switch} statement is cleaner, so
+use that rather than an array unless the problem does not fit a
+@code{switch} statement very well.
+
+Another use of label values is in an interpreter for threaded code.
+The labels within the interpreter function can be stored in the
+threaded code for super-fast dispatching.
+
+You may not use this mechanism to jump to code in a different function.
+If you do that, totally unpredictable things happen. The best way to
+avoid this is to store the label address only in automatic variables and
+never pass it as an argument.
+
+An alternate way to write the above example is
+
+@smallexample
+static const int array[] = @{ &&foo - &&foo, &&bar - &&foo,
+ &&hack - &&foo @};
+goto *(&&foo + array[i]);
+@end smallexample
+
+@noindent
+This is more friendly to code living in shared libraries, as it reduces
+the number of dynamic relocations that are needed, and by consequence,
+allows the data to be read-only.
+This alternative with label differences is not supported for the AVR target,
+please use the first approach for AVR programs.
+
+The @code{&&foo} expressions for the same label might have different
+values if the containing function is inlined or cloned. If a program
+relies on them being always the same,
+@code{__attribute__((__noinline__,__noclone__))} should be used to
+prevent inlining and cloning. If @code{&&foo} is used in a static
+variable initializer, inlining and cloning is forbidden.
+
+@node Nested Functions
+@section Nested Functions
+@cindex nested functions
+@cindex downward funargs
+@cindex thunks
+
+A @dfn{nested function} is a function defined inside another function.
+Nested functions are supported as an extension in GNU C, but are not
+supported by GNU C++.
+
+The nested function's name is local to the block where it is defined.
+For example, here we define a nested function named @code{square}, and
+call it twice:
+
+@smallexample
+@group
+foo (double a, double b)
+@{
+ double square (double z) @{ return z * z; @}
+
+ return square (a) + square (b);
+@}
+@end group
+@end smallexample
+
+The nested function can access all the variables of the containing
+function that are visible at the point of its definition. This is
+called @dfn{lexical scoping}. For example, here we show a nested
+function which uses an inherited variable named @code{offset}:
+
+@smallexample
+@group
+bar (int *array, int offset, int size)
+@{
+ int access (int *array, int index)
+ @{ return array[index + offset]; @}
+ int i;
+ /* @r{@dots{}} */
+ for (i = 0; i < size; i++)
+ /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */
+@}
+@end group
+@end smallexample
+
+Nested function definitions are permitted within functions in the places
+where variable definitions are allowed; that is, in any block, mixed
+with the other declarations and statements in the block.
+
+It is possible to call the nested function from outside the scope of its
+name by storing its address or passing the address to another function:
+
+@smallexample
+hack (int *array, int size)
+@{
+ void store (int index, int value)
+ @{ array[index] = value; @}
+
+ intermediate (store, size);
+@}
+@end smallexample
+
+Here, the function @code{intermediate} receives the address of
+@code{store} as an argument. If @code{intermediate} calls @code{store},
+the arguments given to @code{store} are used to store into @code{array}.
+But this technique works only so long as the containing function
+(@code{hack}, in this example) does not exit.
+
+If you try to call the nested function through its address after the
+containing function exits, all hell breaks loose. If you try
+to call it after a containing scope level exits, and if it refers
+to some of the variables that are no longer in scope, you may be lucky,
+but it's not wise to take the risk. If, however, the nested function
+does not refer to anything that has gone out of scope, you should be
+safe.
+
+GCC implements taking the address of a nested function using a technique
+called @dfn{trampolines}. This technique was described in
+@cite{Lexical Closures for C++} (Thomas M. Breuel, USENIX
+C++ Conference Proceedings, October 17-21, 1988).
+
+A nested function can jump to a label inherited from a containing
+function, provided the label is explicitly declared in the containing
+function (@pxref{Local Labels}). Such a jump returns instantly to the
+containing function, exiting the nested function that did the
+@code{goto} and any intermediate functions as well. Here is an example:
+
+@smallexample
+@group
+bar (int *array, int offset, int size)
+@{
+ __label__ failure;
+ int access (int *array, int index)
+ @{
+ if (index > size)
+ goto failure;
+ return array[index + offset];
+ @}
+ int i;
+ /* @r{@dots{}} */
+ for (i = 0; i < size; i++)
+ /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */
+ /* @r{@dots{}} */
+ return 0;
+
+ /* @r{Control comes here from @code{access}
+ if it detects an error.} */
+ failure:
+ return -1;
+@}
+@end group
+@end smallexample
+
+A nested function always has no linkage. Declaring one with
+@code{extern} or @code{static} is erroneous. If you need to declare the nested function
+before its definition, use @code{auto} (which is otherwise meaningless
+for function declarations).
+
+@smallexample
+bar (int *array, int offset, int size)
+@{
+ __label__ failure;
+ auto int access (int *, int);
+ /* @r{@dots{}} */
+ int access (int *array, int index)
+ @{
+ if (index > size)
+ goto failure;
+ return array[index + offset];
+ @}
+ /* @r{@dots{}} */
+@}
+@end smallexample
+
+@node Nonlocal Gotos
+@section Nonlocal Gotos
+@cindex nonlocal gotos
+
+GCC provides the built-in functions @code{__builtin_setjmp} and
+@code{__builtin_longjmp} which are similar to, but not interchangeable
+with, the C library functions @code{setjmp} and @code{longjmp}.
+The built-in versions are used internally by GCC's libraries
+to implement exception handling on some targets. You should use the
+standard C library functions declared in @code{<setjmp.h>} in user code
+instead of the builtins.
+
+The built-in versions of these functions use GCC's normal
+mechanisms to save and restore registers using the stack on function
+entry and exit. The jump buffer argument @var{buf} holds only the
+information needed to restore the stack frame, rather than the entire
+set of saved register values.
+
+An important caveat is that GCC arranges to save and restore only
+those registers known to the specific architecture variant being
+compiled for. This can make @code{__builtin_setjmp} and
+@code{__builtin_longjmp} more efficient than their library
+counterparts in some cases, but it can also cause incorrect and
+mysterious behavior when mixing with code that uses the full register
+set.
+
+You should declare the jump buffer argument @var{buf} to the
+built-in functions as:
+
+@smallexample
+#include <stdint.h>
+intptr_t @var{buf}[5];
+@end smallexample
+
+@deftypefn {Built-in Function} {int} __builtin_setjmp (intptr_t *@var{buf})
+This function saves the current stack context in @var{buf}.
+@code{__builtin_setjmp} returns 0 when returning directly,
+and 1 when returning from @code{__builtin_longjmp} using the same
+@var{buf}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {void} __builtin_longjmp (intptr_t *@var{buf}, int @var{val})
+This function restores the stack context in @var{buf},
+saved by a previous call to @code{__builtin_setjmp}. After
+@code{__builtin_longjmp} is finished, the program resumes execution as
+if the matching @code{__builtin_setjmp} returns the value @var{val},
+which must be 1.
+
+Because @code{__builtin_longjmp} depends on the function return
+mechanism to restore the stack context, it cannot be called
+from the same function calling @code{__builtin_setjmp} to
+initialize @var{buf}. It can only be called from a function called
+(directly or indirectly) from the function calling @code{__builtin_setjmp}.
+@end deftypefn
+
+@node Constructing Calls
+@section Constructing Function Calls
+@cindex constructing calls
+@cindex forwarding calls
+
+Using the built-in functions described below, you can record
+the arguments a function received, and call another function
+with the same arguments, without knowing the number or types
+of the arguments.
+
+You can also record the return value of that function call,
+and later return that value, without knowing what data type
+the function tried to return (as long as your caller expects
+that data type).
+
+However, these built-in functions may interact badly with some
+sophisticated features or other extensions of the language. It
+is, therefore, not recommended to use them outside very simple
+functions acting as mere forwarders for their arguments.
+
+@deftypefn {Built-in Function} {void *} __builtin_apply_args ()
+This built-in function returns a pointer to data
+describing how to perform a call with the same arguments as are passed
+to the current function.
+
+The function saves the arg pointer register, structure value address,
+and all registers that might be used to pass arguments to a function
+into a block of memory allocated on the stack. Then it returns the
+address of that block.
+@end deftypefn
+
+@deftypefn {Built-in Function} {void *} __builtin_apply (void (*@var{function})(), void *@var{arguments}, size_t @var{size})
+This built-in function invokes @var{function}
+with a copy of the parameters described by @var{arguments}
+and @var{size}.
+
+The value of @var{arguments} should be the value returned by
+@code{__builtin_apply_args}. The argument @var{size} specifies the size
+of the stack argument data, in bytes.
+
+This function returns a pointer to data describing
+how to return whatever value is returned by @var{function}. The data
+is saved in a block of memory allocated on the stack.
+
+It is not always simple to compute the proper value for @var{size}. The
+value is used by @code{__builtin_apply} to compute the amount of data
+that should be pushed on the stack and copied from the incoming argument
+area.
+@end deftypefn
+
+@deftypefn {Built-in Function} {void} __builtin_return (void *@var{result})
+This built-in function returns the value described by @var{result} from
+the containing function. You should specify, for @var{result}, a value
+returned by @code{__builtin_apply}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {} __builtin_va_arg_pack ()
+This built-in function represents all anonymous arguments of an inline
+function. It can be used only in inline functions that are always
+inlined, never compiled as a separate function, such as those using
+@code{__attribute__ ((__always_inline__))} or
+@code{__attribute__ ((__gnu_inline__))} extern inline functions.
+It must be only passed as last argument to some other function
+with variable arguments. This is useful for writing small wrapper
+inlines for variable argument functions, when using preprocessor
+macros is undesirable. For example:
+@smallexample
+extern int myprintf (FILE *f, const char *format, ...);
+extern inline __attribute__ ((__gnu_inline__)) int
+myprintf (FILE *f, const char *format, ...)
+@{
+ int r = fprintf (f, "myprintf: ");
+ if (r < 0)
+ return r;
+ int s = fprintf (f, format, __builtin_va_arg_pack ());
+ if (s < 0)
+ return s;
+ return r + s;
+@}
+@end smallexample
+@end deftypefn
+
+@deftypefn {Built-in Function} {size_t} __builtin_va_arg_pack_len ()
+This built-in function returns the number of anonymous arguments of
+an inline function. It can be used only in inline functions that
+are always inlined, never compiled as a separate function, such
+as those using @code{__attribute__ ((__always_inline__))} or
+@code{__attribute__ ((__gnu_inline__))} extern inline functions.
+For example following does link- or run-time checking of open
+arguments for optimized code:
+@smallexample
+#ifdef __OPTIMIZE__
+extern inline __attribute__((__gnu_inline__)) int
+myopen (const char *path, int oflag, ...)
+@{
+ if (__builtin_va_arg_pack_len () > 1)
+ warn_open_too_many_arguments ();
+
+ if (__builtin_constant_p (oflag))
+ @{
+ if ((oflag & O_CREAT) != 0 && __builtin_va_arg_pack_len () < 1)
+ @{
+ warn_open_missing_mode ();
+ return __open_2 (path, oflag);
+ @}
+ return open (path, oflag, __builtin_va_arg_pack ());
+ @}
+
+ if (__builtin_va_arg_pack_len () < 1)
+ return __open_2 (path, oflag);
+
+ return open (path, oflag, __builtin_va_arg_pack ());
+@}
+#endif
+@end smallexample
+@end deftypefn
+
+@node Typeof
+@section Referring to a Type with @code{typeof}
+@findex typeof
+@findex sizeof
+@cindex macros, types of arguments
+
+Another way to refer to the type of an expression is with @code{typeof}.
+The syntax of using of this keyword looks like @code{sizeof}, but the
+construct acts semantically like a type name defined with @code{typedef}.
+
+There are two ways of writing the argument to @code{typeof}: with an
+expression or with a type. Here is an example with an expression:
+
+@smallexample
+typeof (x[0](1))
+@end smallexample
+
+@noindent
+This assumes that @code{x} is an array of pointers to functions;
+the type described is that of the values of the functions.
+
+Here is an example with a typename as the argument:
+
+@smallexample
+typeof (int *)
+@end smallexample
+
+@noindent
+Here the type described is that of pointers to @code{int}.
+
+If you are writing a header file that must work when included in ISO C
+programs, write @code{__typeof__} instead of @code{typeof}.
+@xref{Alternate Keywords}.
+
+A @code{typeof} construct can be used anywhere a typedef name can be
+used. For example, you can use it in a declaration, in a cast, or inside
+of @code{sizeof} or @code{typeof}.
+
+The operand of @code{typeof} is evaluated for its side effects if and
+only if it is an expression of variably modified type or the name of
+such a type.
+
+@code{typeof} is often useful in conjunction with
+statement expressions (@pxref{Statement Exprs}).
+Here is how the two together can
+be used to define a safe ``maximum'' macro which operates on any
+arithmetic type and evaluates each of its arguments exactly once:
+
+@smallexample
+#define max(a,b) \
+ (@{ typeof (a) _a = (a); \
+ typeof (b) _b = (b); \
+ _a > _b ? _a : _b; @})
+@end smallexample
+
+@cindex underscores in variables in macros
+@cindex @samp{_} in variables in macros
+@cindex local variables in macros
+@cindex variables, local, in macros
+@cindex macros, local variables in
+
+The reason for using names that start with underscores for the local
+variables is to avoid conflicts with variable names that occur within the
+expressions that are substituted for @code{a} and @code{b}. Eventually we
+hope to design a new form of declaration syntax that allows you to declare
+variables whose scopes start only after their initializers; this will be a
+more reliable way to prevent such conflicts.
+
+@noindent
+Some more examples of the use of @code{typeof}:
+
+@itemize @bullet
+@item
+This declares @code{y} with the type of what @code{x} points to.
+
+@smallexample
+typeof (*x) y;
+@end smallexample
+
+@item
+This declares @code{y} as an array of such values.
+
+@smallexample
+typeof (*x) y[4];
+@end smallexample
+
+@item
+This declares @code{y} as an array of pointers to characters:
+
+@smallexample
+typeof (typeof (char *)[4]) y;
+@end smallexample
+
+@noindent
+It is equivalent to the following traditional C declaration:
+
+@smallexample
+char *y[4];
+@end smallexample
+
+To see the meaning of the declaration using @code{typeof}, and why it
+might be a useful way to write, rewrite it with these macros:
+
+@smallexample
+#define pointer(T) typeof(T *)
+#define array(T, N) typeof(T [N])
+@end smallexample
+
+@noindent
+Now the declaration can be rewritten this way:
+
+@smallexample
+array (pointer (char), 4) y;
+@end smallexample
+
+@noindent
+Thus, @code{array (pointer (char), 4)} is the type of arrays of 4
+pointers to @code{char}.
+@end itemize
+
+In GNU C, but not GNU C++, you may also declare the type of a variable
+as @code{__auto_type}. In that case, the declaration must declare
+only one variable, whose declarator must just be an identifier, the
+declaration must be initialized, and the type of the variable is
+determined by the initializer; the name of the variable is not in
+scope until after the initializer. (In C++, you should use C++11
+@code{auto} for this purpose.) Using @code{__auto_type}, the
+``maximum'' macro above could be written as:
+
+@smallexample
+#define max(a,b) \
+ (@{ __auto_type _a = (a); \
+ __auto_type _b = (b); \
+ _a > _b ? _a : _b; @})
+@end smallexample
+
+Using @code{__auto_type} instead of @code{typeof} has two advantages:
+
+@itemize @bullet
+@item Each argument to the macro appears only once in the expansion of
+the macro. This prevents the size of the macro expansion growing
+exponentially when calls to such macros are nested inside arguments of
+such macros.
+
+@item If the argument to the macro has variably modified type, it is
+evaluated only once when using @code{__auto_type}, but twice if
+@code{typeof} is used.
+@end itemize
+
+@node Conditionals
+@section Conditionals with Omitted Operands
+@cindex conditional expressions, extensions
+@cindex omitted middle-operands
+@cindex middle-operands, omitted
+@cindex extensions, @code{?:}
+@cindex @code{?:} extensions
+
+The middle operand in a conditional expression may be omitted. Then
+if the first operand is nonzero, its value is the value of the conditional
+expression.
+
+Therefore, the expression
+
+@smallexample
+x ? : y
+@end smallexample
+
+@noindent
+has the value of @code{x} if that is nonzero; otherwise, the value of
+@code{y}.
+
+This example is perfectly equivalent to
+
+@smallexample
+x ? x : y
+@end smallexample
+
+@cindex side effect in @code{?:}
+@cindex @code{?:} side effect
+@noindent
+In this simple case, the ability to omit the middle operand is not
+especially useful. When it becomes useful is when the first operand does,
+or may (if it is a macro argument), contain a side effect. Then repeating
+the operand in the middle would perform the side effect twice. Omitting
+the middle operand uses the value already computed without the undesirable
+effects of recomputing it.
+
+@node __int128
+@section 128-bit Integers
+@cindex @code{__int128} data types
+
+As an extension the integer scalar type @code{__int128} is supported for
+targets which have an integer mode wide enough to hold 128 bits.
+Simply write @code{__int128} for a signed 128-bit integer, or
+@code{unsigned __int128} for an unsigned 128-bit integer. There is no
+support in GCC for expressing an integer constant of type @code{__int128}
+for targets with @code{long long} integer less than 128 bits wide.
+
+@node Long Long
+@section Double-Word Integers
+@cindex @code{long long} data types
+@cindex double-word arithmetic
+@cindex multiprecision arithmetic
+@cindex @code{LL} integer suffix
+@cindex @code{ULL} integer suffix
+
+ISO C99 and ISO C++11 support data types for integers that are at least
+64 bits wide, and as an extension GCC supports them in C90 and C++98 modes.
+Simply write @code{long long int} for a signed integer, or
+@code{unsigned long long int} for an unsigned integer. To make an
+integer constant of type @code{long long int}, add the suffix @samp{LL}
+to the integer. To make an integer constant of type @code{unsigned long
+long int}, add the suffix @samp{ULL} to the integer.
+
+You can use these types in arithmetic like any other integer types.
+Addition, subtraction, and bitwise boolean operations on these types
+are open-coded on all types of machines. Multiplication is open-coded
+if the machine supports a fullword-to-doubleword widening multiply
+instruction. Division and shifts are open-coded only on machines that
+provide special support. The operations that are not open-coded use
+special library routines that come with GCC@.
+
+There may be pitfalls when you use @code{long long} types for function
+arguments without function prototypes. If a function
+expects type @code{int} for its argument, and you pass a value of type
+@code{long long int}, confusion results because the caller and the
+subroutine disagree about the number of bytes for the argument.
+Likewise, if the function expects @code{long long int} and you pass
+@code{int}. The best way to avoid such problems is to use prototypes.
+
+@node Complex
+@section Complex Numbers
+@cindex complex numbers
+@cindex @code{_Complex} keyword
+@cindex @code{__complex__} keyword
+
+ISO C99 supports complex floating data types, and as an extension GCC
+supports them in C90 mode and in C++. GCC also supports complex integer data
+types which are not part of ISO C99. You can declare complex types
+using the keyword @code{_Complex}. As an extension, the older GNU
+keyword @code{__complex__} is also supported.
+
+For example, @samp{_Complex double x;} declares @code{x} as a
+variable whose real part and imaginary part are both of type
+@code{double}. @samp{_Complex short int y;} declares @code{y} to
+have real and imaginary parts of type @code{short int}; this is not
+likely to be useful, but it shows that the set of complex types is
+complete.
+
+To write a constant with a complex data type, use the suffix @samp{i} or
+@samp{j} (either one; they are equivalent). For example, @code{2.5fi}
+has type @code{_Complex float} and @code{3i} has type
+@code{_Complex int}. Such a constant always has a pure imaginary
+value, but you can form any complex value you like by adding one to a
+real constant. This is a GNU extension; if you have an ISO C99
+conforming C library (such as the GNU C Library), and want to construct complex
+constants of floating type, you should include @code{<complex.h>} and
+use the macros @code{I} or @code{_Complex_I} instead.
+
+The ISO C++14 library also defines the @samp{i} suffix, so C++14 code
+that includes the @samp{<complex>} header cannot use @samp{i} for the
+GNU extension. The @samp{j} suffix still has the GNU meaning.
+
+GCC can handle both implicit and explicit casts between the @code{_Complex}
+types and other @code{_Complex} types as casting both the real and imaginary
+parts to the scalar type.
+GCC can handle implicit and explicit casts from a scalar type to a @code{_Complex}
+type and where the imaginary part will be considered zero.
+The C front-end can handle implicit and explicit casts from a @code{_Complex} type
+to a scalar type where the imaginary part will be ignored. In C++ code, this cast
+is considered illformed and G++ will error out.
+
+GCC provides a built-in function @code{__builtin_complex} will can be used to
+construct a complex value.
+
+@cindex @code{__real__} keyword
+@cindex @code{__imag__} keyword
+
+GCC has a few extensions which can be used to extract the real
+and the imaginary part of the complex-valued expression. Note
+these expressions are lvalues if the @var{exp} is an lvalue.
+These expressions operands have the type of a complex type
+which might get prompoted to a complex type from a scalar type.
+E.g. @code{__real__ (int)@var{x}} is the same as casting to
+@code{_Complex int} before @code{__real__} is done.
+
+@multitable @columnfractions .4 .6
+@headitem Expression @tab Description
+@item @code{__real__ @var{exp}}
+@tab Extract the real part of @var{exp}.
+@item @code{__imag__ @var{exp}}
+@tab Extract the imaginary part of @var{exp}.
+@end multitable
+
+For values of floating point, you should use the ISO C99
+functions, declared in @code{<complex.h>} and also provided as
+built-in functions by GCC@.
+
+@multitable @columnfractions .4 .2 .2 .2
+@headitem Expression @tab float @tab double @tab long double
+@item @code{__real__ @var{exp}}
+@tab @code{crealf} @tab @code{creal} @tab @code{creall}
+@item @code{__imag__ @var{exp}}
+@tab @code{cimagf} @tab @code{cimag} @tab @code{cimagl}
+@end multitable
+
+@cindex complex conjugation
+The operator @samp{~} performs complex conjugation when used on a value
+with a complex type. This is a GNU extension; for values of
+floating type, you should use the ISO C99 functions @code{conjf},
+@code{conj} and @code{conjl}, declared in @code{<complex.h>} and also
+provided as built-in functions by GCC@. Note unlike the @code{__real__}
+and @code{__imag__} operators, this operator will not do an implicit cast
+to the complex type because the @samp{~} is already a normal operator.
+
+GCC can allocate complex automatic variables in a noncontiguous
+fashion; it's even possible for the real part to be in a register while
+the imaginary part is on the stack (or vice versa). Only the DWARF
+debug info format can represent this, so use of DWARF is recommended.
+If you are using the stabs debug info format, GCC describes a noncontiguous
+complex variable as if it were two separate variables of noncomplex type.
+If the variable's actual name is @code{foo}, the two fictitious
+variables are named @code{foo$real} and @code{foo$imag}. You can
+examine and set these two fictitious variables with your debugger.
+
+@deftypefn {Built-in Function} @var{type} __builtin_complex (@var{real}, @var{imag})
+
+The built-in function @code{__builtin_complex} is provided for use in
+implementing the ISO C11 macros @code{CMPLXF}, @code{CMPLX} and
+@code{CMPLXL}. @var{real} and @var{imag} must have the same type, a
+real binary floating-point type, and the result has the corresponding
+complex type with real and imaginary parts @var{real} and @var{imag}.
+Unlike @samp{@var{real} + I * @var{imag}}, this works even when
+infinities, NaNs and negative zeros are involved.
+
+@end deftypefn
+
+@node Floating Types
+@section Additional Floating Types
+@cindex additional floating types
+@cindex @code{_Float@var{n}} data types
+@cindex @code{_Float@var{n}x} data types
+@cindex @code{__float80} data type
+@cindex @code{__float128} data type
+@cindex @code{__ibm128} data type
+@cindex @code{w} floating point suffix
+@cindex @code{q} floating point suffix
+@cindex @code{W} floating point suffix
+@cindex @code{Q} floating point suffix
+
+ISO/IEC TS 18661-3:2015 defines C support for additional floating
+types @code{_Float@var{n}} and @code{_Float@var{n}x}, and GCC supports
+these type names; the set of types supported depends on the target
+architecture. These types are not supported when compiling C++.
+Constants with these types use suffixes @code{f@var{n}} or
+@code{F@var{n}} and @code{f@var{n}x} or @code{F@var{n}x}. These type
+names can be used together with @code{_Complex} to declare complex
+types.
+
+As an extension, GNU C and GNU C++ support additional floating
+types, which are not supported by all targets.
+@itemize @bullet
+@item @code{__float128} is available on i386, x86_64, IA-64, and
+hppa HP-UX, as well as on PowerPC GNU/Linux targets that enable
+the vector scalar (VSX) instruction set. @code{__float128} supports
+the 128-bit floating type. On i386, x86_64, PowerPC, and IA-64
+other than HP-UX, @code{__float128} is an alias for @code{_Float128}.
+On hppa and IA-64 HP-UX, @code{__float128} is an alias for @code{long
+double}.
+
+@item @code{__float80} is available on the i386, x86_64, and IA-64
+targets, and supports the 80-bit (@code{XFmode}) floating type. It is
+an alias for the type name @code{_Float64x} on these targets.
+
+@item @code{__ibm128} is available on PowerPC targets, and provides
+access to the IBM extended double format which is the current format
+used for @code{long double}. When @code{long double} transitions to
+@code{__float128} on PowerPC in the future, @code{__ibm128} will remain
+for use in conversions between the two types.
+@end itemize
+
+Support for these additional types includes the arithmetic operators:
+add, subtract, multiply, divide; unary arithmetic operators;
+relational operators; equality operators; and conversions to and from
+integer and other floating types. Use a suffix @samp{w} or @samp{W}
+in a literal constant of type @code{__float80} or type
+@code{__ibm128}. Use a suffix @samp{q} or @samp{Q} for @code{__float128}.
+
+In order to use @code{_Float128}, @code{__float128}, and @code{__ibm128}
+on PowerPC Linux systems, you must use the @option{-mfloat128} option. It is
+expected in future versions of GCC that @code{_Float128} and @code{__float128}
+will be enabled automatically.
+
+The @code{_Float128} type is supported on all systems where
+@code{__float128} is supported or where @code{long double} has the
+IEEE binary128 format. The @code{_Float64x} type is supported on all
+systems where @code{__float128} is supported. The @code{_Float32}
+type is supported on all systems supporting IEEE binary32; the
+@code{_Float64} and @code{_Float32x} types are supported on all systems
+supporting IEEE binary64. The @code{_Float16} type is supported on AArch64
+systems by default, on ARM systems when the IEEE format for 16-bit
+floating-point types is selected with @option{-mfp16-format=ieee} and,
+for both C and C++, on x86 systems with SSE2 enabled. GCC does not currently
+support @code{_Float128x} on any systems.
+
+On the i386, x86_64, IA-64, and HP-UX targets, you can declare complex
+types using the corresponding internal complex type, @code{XCmode} for
+@code{__float80} type and @code{TCmode} for @code{__float128} type:
+
+@smallexample
+typedef _Complex float __attribute__((mode(TC))) _Complex128;
+typedef _Complex float __attribute__((mode(XC))) _Complex80;
+@end smallexample
+
+On the PowerPC Linux VSX targets, you can declare complex types using
+the corresponding internal complex type, @code{KCmode} for
+@code{__float128} type and @code{ICmode} for @code{__ibm128} type:
+
+@smallexample
+typedef _Complex float __attribute__((mode(KC))) _Complex_float128;
+typedef _Complex float __attribute__((mode(IC))) _Complex_ibm128;
+@end smallexample
+
+@node Half-Precision
+@section Half-Precision Floating Point
+@cindex half-precision floating point
+@cindex @code{__fp16} data type
+@cindex @code{__Float16} data type
+
+On ARM and AArch64 targets, GCC supports half-precision (16-bit) floating
+point via the @code{__fp16} type defined in the ARM C Language Extensions.
+On ARM systems, you must enable this type explicitly with the
+@option{-mfp16-format} command-line option in order to use it.
+On x86 targets with SSE2 enabled, GCC supports half-precision (16-bit)
+floating point via the @code{_Float16} type. For C++, x86 provides a builtin
+type named @code{_Float16} which contains same data format as C.
+
+ARM targets support two incompatible representations for half-precision
+floating-point values. You must choose one of the representations and
+use it consistently in your program.
+
+Specifying @option{-mfp16-format=ieee} selects the IEEE 754-2008 format.
+This format can represent normalized values in the range of @math{2^{-14}} to 65504.
+There are 11 bits of significand precision, approximately 3
+decimal digits.
+
+Specifying @option{-mfp16-format=alternative} selects the ARM
+alternative format. This representation is similar to the IEEE
+format, but does not support infinities or NaNs. Instead, the range
+of exponents is extended, so that this format can represent normalized
+values in the range of @math{2^{-14}} to 131008.
+
+The GCC port for AArch64 only supports the IEEE 754-2008 format, and does
+not require use of the @option{-mfp16-format} command-line option.
+
+The @code{__fp16} type may only be used as an argument to intrinsics defined
+in @code{<arm_fp16.h>}, or as a storage format. For purposes of
+arithmetic and other operations, @code{__fp16} values in C or C++
+expressions are automatically promoted to @code{float}.
+
+The ARM target provides hardware support for conversions between
+@code{__fp16} and @code{float} values
+as an extension to VFP and NEON (Advanced SIMD), and from ARMv8-A provides
+hardware support for conversions between @code{__fp16} and @code{double}
+values. GCC generates code using these hardware instructions if you
+compile with options to select an FPU that provides them;
+for example, @option{-mfpu=neon-fp16 -mfloat-abi=softfp},
+in addition to the @option{-mfp16-format} option to select
+a half-precision format.
+
+Language-level support for the @code{__fp16} data type is
+independent of whether GCC generates code using hardware floating-point
+instructions. In cases where hardware support is not specified, GCC
+implements conversions between @code{__fp16} and other types as library
+calls.
+
+It is recommended that portable code use the @code{_Float16} type defined
+by ISO/IEC TS 18661-3:2015. @xref{Floating Types}.
+
+On x86 targets with SSE2 enabled, without @option{-mavx512fp16},
+all operations will be emulated by software emulation and the @code{float}
+instructions. The default behavior for @code{FLT_EVAL_METHOD} is to keep the
+intermediate result of the operation as 32-bit precision. This may lead to
+inconsistent behavior between software emulation and AVX512-FP16 instructions.
+Using @option{-fexcess-precision=16} will force round back after each operation.
+
+Using @option{-mavx512fp16} will generate AVX512-FP16 instructions instead of
+software emulation. The default behavior of @code{FLT_EVAL_METHOD} is to round
+after each operation. The same is true with @option{-fexcess-precision=standard}
+and @option{-mfpmath=sse}. If there is no @option{-mfpmath=sse},
+@option{-fexcess-precision=standard} alone does the same thing as before,
+It is useful for code that does not have @code{_Float16} and runs on the x87
+FPU.
+
+@node Decimal Float
+@section Decimal Floating Types
+@cindex decimal floating types
+@cindex @code{_Decimal32} data type
+@cindex @code{_Decimal64} data type
+@cindex @code{_Decimal128} data type
+@cindex @code{df} integer suffix
+@cindex @code{dd} integer suffix
+@cindex @code{dl} integer suffix
+@cindex @code{DF} integer suffix
+@cindex @code{DD} integer suffix
+@cindex @code{DL} integer suffix
+
+As an extension, GNU C supports decimal floating types as
+defined in the N1312 draft of ISO/IEC WDTR24732. Support for decimal
+floating types in GCC will evolve as the draft technical report changes.
+Calling conventions for any target might also change. Not all targets
+support decimal floating types.
+
+The decimal floating types are @code{_Decimal32}, @code{_Decimal64}, and
+@code{_Decimal128}. They use a radix of ten, unlike the floating types
+@code{float}, @code{double}, and @code{long double} whose radix is not
+specified by the C standard but is usually two.
+
+Support for decimal floating types includes the arithmetic operators
+add, subtract, multiply, divide; unary arithmetic operators;
+relational operators; equality operators; and conversions to and from
+integer and other floating types. Use a suffix @samp{df} or
+@samp{DF} in a literal constant of type @code{_Decimal32}, @samp{dd}
+or @samp{DD} for @code{_Decimal64}, and @samp{dl} or @samp{DL} for
+@code{_Decimal128}.
+
+GCC support of decimal float as specified by the draft technical report
+is incomplete:
+
+@itemize @bullet
+@item
+When the value of a decimal floating type cannot be represented in the
+integer type to which it is being converted, the result is undefined
+rather than the result value specified by the draft technical report.
+
+@item
+GCC does not provide the C library functionality associated with
+@file{math.h}, @file{fenv.h}, @file{stdio.h}, @file{stdlib.h}, and
+@file{wchar.h}, which must come from a separate C library implementation.
+Because of this the GNU C compiler does not define macro
+@code{__STDC_DEC_FP__} to indicate that the implementation conforms to
+the technical report.
+@end itemize
+
+Types @code{_Decimal32}, @code{_Decimal64}, and @code{_Decimal128}
+are supported by the DWARF debug information format.
+
+@node Hex Floats
+@section Hex Floats
+@cindex hex floats
+
+ISO C99 and ISO C++17 support floating-point numbers written not only in
+the usual decimal notation, such as @code{1.55e1}, but also numbers such as
+@code{0x1.fp3} written in hexadecimal format. As a GNU extension, GCC
+supports this in C90 mode (except in some cases when strictly
+conforming) and in C++98, C++11 and C++14 modes. In that format the
+@samp{0x} hex introducer and the @samp{p} or @samp{P} exponent field are
+mandatory. The exponent is a decimal number that indicates the power of
+2 by which the significant part is multiplied. Thus @samp{0x1.f} is
+@tex
+$1 {15\over16}$,
+@end tex
+@ifnottex
+1 15/16,
+@end ifnottex
+@samp{p3} multiplies it by 8, and the value of @code{0x1.fp3}
+is the same as @code{1.55e1}.
+
+Unlike for floating-point numbers in the decimal notation the exponent
+is always required in the hexadecimal notation. Otherwise the compiler
+would not be able to resolve the ambiguity of, e.g., @code{0x1.f}. This
+could mean @code{1.0f} or @code{1.9375} since @samp{f} is also the
+extension for floating-point constants of type @code{float}.
+
+@node Fixed-Point
+@section Fixed-Point Types
+@cindex fixed-point types
+@cindex @code{_Fract} data type
+@cindex @code{_Accum} data type
+@cindex @code{_Sat} data type
+@cindex @code{hr} fixed-suffix
+@cindex @code{r} fixed-suffix
+@cindex @code{lr} fixed-suffix
+@cindex @code{llr} fixed-suffix
+@cindex @code{uhr} fixed-suffix
+@cindex @code{ur} fixed-suffix
+@cindex @code{ulr} fixed-suffix
+@cindex @code{ullr} fixed-suffix
+@cindex @code{hk} fixed-suffix
+@cindex @code{k} fixed-suffix
+@cindex @code{lk} fixed-suffix
+@cindex @code{llk} fixed-suffix
+@cindex @code{uhk} fixed-suffix
+@cindex @code{uk} fixed-suffix
+@cindex @code{ulk} fixed-suffix
+@cindex @code{ullk} fixed-suffix
+@cindex @code{HR} fixed-suffix
+@cindex @code{R} fixed-suffix
+@cindex @code{LR} fixed-suffix
+@cindex @code{LLR} fixed-suffix
+@cindex @code{UHR} fixed-suffix
+@cindex @code{UR} fixed-suffix
+@cindex @code{ULR} fixed-suffix
+@cindex @code{ULLR} fixed-suffix
+@cindex @code{HK} fixed-suffix
+@cindex @code{K} fixed-suffix
+@cindex @code{LK} fixed-suffix
+@cindex @code{LLK} fixed-suffix
+@cindex @code{UHK} fixed-suffix
+@cindex @code{UK} fixed-suffix
+@cindex @code{ULK} fixed-suffix
+@cindex @code{ULLK} fixed-suffix
+
+As an extension, GNU C supports fixed-point types as
+defined in the N1169 draft of ISO/IEC DTR 18037. Support for fixed-point
+types in GCC will evolve as the draft technical report changes.
+Calling conventions for any target might also change. Not all targets
+support fixed-point types.
+
+The fixed-point types are
+@code{short _Fract},
+@code{_Fract},
+@code{long _Fract},
+@code{long long _Fract},
+@code{unsigned short _Fract},
+@code{unsigned _Fract},
+@code{unsigned long _Fract},
+@code{unsigned long long _Fract},
+@code{_Sat short _Fract},
+@code{_Sat _Fract},
+@code{_Sat long _Fract},
+@code{_Sat long long _Fract},
+@code{_Sat unsigned short _Fract},
+@code{_Sat unsigned _Fract},
+@code{_Sat unsigned long _Fract},
+@code{_Sat unsigned long long _Fract},
+@code{short _Accum},
+@code{_Accum},
+@code{long _Accum},
+@code{long long _Accum},
+@code{unsigned short _Accum},
+@code{unsigned _Accum},
+@code{unsigned long _Accum},
+@code{unsigned long long _Accum},
+@code{_Sat short _Accum},
+@code{_Sat _Accum},
+@code{_Sat long _Accum},
+@code{_Sat long long _Accum},
+@code{_Sat unsigned short _Accum},
+@code{_Sat unsigned _Accum},
+@code{_Sat unsigned long _Accum},
+@code{_Sat unsigned long long _Accum}.
+
+Fixed-point data values contain fractional and optional integral parts.
+The format of fixed-point data varies and depends on the target machine.
+
+Support for fixed-point types includes:
+@itemize @bullet
+@item
+prefix and postfix increment and decrement operators (@code{++}, @code{--})
+@item
+unary arithmetic operators (@code{+}, @code{-}, @code{!})
+@item
+binary arithmetic operators (@code{+}, @code{-}, @code{*}, @code{/})
+@item
+binary shift operators (@code{<<}, @code{>>})
+@item
+relational operators (@code{<}, @code{<=}, @code{>=}, @code{>})
+@item
+equality operators (@code{==}, @code{!=})
+@item
+assignment operators (@code{+=}, @code{-=}, @code{*=}, @code{/=},
+@code{<<=}, @code{>>=})
+@item
+conversions to and from integer, floating-point, or fixed-point types
+@end itemize
+
+Use a suffix in a fixed-point literal constant:
+@itemize
+@item @samp{hr} or @samp{HR} for @code{short _Fract} and
+@code{_Sat short _Fract}
+@item @samp{r} or @samp{R} for @code{_Fract} and @code{_Sat _Fract}
+@item @samp{lr} or @samp{LR} for @code{long _Fract} and
+@code{_Sat long _Fract}
+@item @samp{llr} or @samp{LLR} for @code{long long _Fract} and
+@code{_Sat long long _Fract}
+@item @samp{uhr} or @samp{UHR} for @code{unsigned short _Fract} and
+@code{_Sat unsigned short _Fract}
+@item @samp{ur} or @samp{UR} for @code{unsigned _Fract} and
+@code{_Sat unsigned _Fract}
+@item @samp{ulr} or @samp{ULR} for @code{unsigned long _Fract} and
+@code{_Sat unsigned long _Fract}
+@item @samp{ullr} or @samp{ULLR} for @code{unsigned long long _Fract}
+and @code{_Sat unsigned long long _Fract}
+@item @samp{hk} or @samp{HK} for @code{short _Accum} and
+@code{_Sat short _Accum}
+@item @samp{k} or @samp{K} for @code{_Accum} and @code{_Sat _Accum}
+@item @samp{lk} or @samp{LK} for @code{long _Accum} and
+@code{_Sat long _Accum}
+@item @samp{llk} or @samp{LLK} for @code{long long _Accum} and
+@code{_Sat long long _Accum}
+@item @samp{uhk} or @samp{UHK} for @code{unsigned short _Accum} and
+@code{_Sat unsigned short _Accum}
+@item @samp{uk} or @samp{UK} for @code{unsigned _Accum} and
+@code{_Sat unsigned _Accum}
+@item @samp{ulk} or @samp{ULK} for @code{unsigned long _Accum} and
+@code{_Sat unsigned long _Accum}
+@item @samp{ullk} or @samp{ULLK} for @code{unsigned long long _Accum}
+and @code{_Sat unsigned long long _Accum}
+@end itemize
+
+GCC support of fixed-point types as specified by the draft technical report
+is incomplete:
+
+@itemize @bullet
+@item
+Pragmas to control overflow and rounding behaviors are not implemented.
+@end itemize
+
+Fixed-point types are supported by the DWARF debug information format.
+
+@node Named Address Spaces
+@section Named Address Spaces
+@cindex Named Address Spaces
+
+As an extension, GNU C supports named address spaces as
+defined in the N1275 draft of ISO/IEC DTR 18037. Support for named
+address spaces in GCC will evolve as the draft technical report
+changes. Calling conventions for any target might also change. At
+present, only the AVR, M32C, PRU, RL78, and x86 targets support
+address spaces other than the generic address space.
+
+Address space identifiers may be used exactly like any other C type
+qualifier (e.g., @code{const} or @code{volatile}). See the N1275
+document for more details.
+
+@anchor{AVR Named Address Spaces}
+@subsection AVR Named Address Spaces
+
+On the AVR target, there are several address spaces that can be used
+in order to put read-only data into the flash memory and access that
+data by means of the special instructions @code{LPM} or @code{ELPM}
+needed to read from flash.
+
+Devices belonging to @code{avrtiny} and @code{avrxmega3} can access
+flash memory by means of @code{LD*} instructions because the flash
+memory is mapped into the RAM address space. There is @emph{no need}
+for language extensions like @code{__flash} or attribute
+@ref{AVR Variable Attributes,,@code{progmem}}.
+The default linker description files for these devices cater for that
+feature and @code{.rodata} stays in flash: The compiler just generates
+@code{LD*} instructions, and the linker script adds core specific
+offsets to all @code{.rodata} symbols: @code{0x4000} in the case of
+@code{avrtiny} and @code{0x8000} in the case of @code{avrxmega3}.
+See @ref{AVR Options} for a list of respective devices.
+
+For devices not in @code{avrtiny} or @code{avrxmega3},
+any data including read-only data is located in RAM (the generic
+address space) because flash memory is not visible in the RAM address
+space. In order to locate read-only data in flash memory @emph{and}
+to generate the right instructions to access this data without
+using (inline) assembler code, special address spaces are needed.
+
+@table @code
+@item __flash
+@cindex @code{__flash} AVR Named Address Spaces
+The @code{__flash} qualifier locates data in the
+@code{.progmem.data} section. Data is read using the @code{LPM}
+instruction. Pointers to this address space are 16 bits wide.
+
+@item __flash1
+@itemx __flash2
+@itemx __flash3
+@itemx __flash4
+@itemx __flash5
+@cindex @code{__flash1} AVR Named Address Spaces
+@cindex @code{__flash2} AVR Named Address Spaces
+@cindex @code{__flash3} AVR Named Address Spaces
+@cindex @code{__flash4} AVR Named Address Spaces
+@cindex @code{__flash5} AVR Named Address Spaces
+These are 16-bit address spaces locating data in section
+@code{.progmem@var{N}.data} where @var{N} refers to
+address space @code{__flash@var{N}}.
+The compiler sets the @code{RAMPZ} segment register appropriately
+before reading data by means of the @code{ELPM} instruction.
+
+@item __memx
+@cindex @code{__memx} AVR Named Address Spaces
+This is a 24-bit address space that linearizes flash and RAM:
+If the high bit of the address is set, data is read from
+RAM using the lower two bytes as RAM address.
+If the high bit of the address is clear, data is read from flash
+with @code{RAMPZ} set according to the high byte of the address.
+@xref{AVR Built-in Functions,,@code{__builtin_avr_flash_segment}}.
+
+Objects in this address space are located in @code{.progmemx.data}.
+@end table
+
+@b{Example}
+
+@smallexample
+char my_read (const __flash char ** p)
+@{
+ /* p is a pointer to RAM that points to a pointer to flash.
+ The first indirection of p reads that flash pointer
+ from RAM and the second indirection reads a char from this
+ flash address. */
+
+ return **p;
+@}
+
+/* Locate array[] in flash memory */
+const __flash int array[] = @{ 3, 5, 7, 11, 13, 17, 19 @};
+
+int i = 1;
+
+int main (void)
+@{
+ /* Return 17 by reading from flash memory */
+ return array[array[i]];
+@}
+@end smallexample
+
+@noindent
+For each named address space supported by avr-gcc there is an equally
+named but uppercase built-in macro defined.
+The purpose is to facilitate testing if respective address space
+support is available or not:
+
+@smallexample
+#ifdef __FLASH
+const __flash int var = 1;
+
+int read_var (void)
+@{
+ return var;
+@}
+#else
+#include <avr/pgmspace.h> /* From AVR-LibC */
+
+const int var PROGMEM = 1;
+
+int read_var (void)
+@{
+ return (int) pgm_read_word (&var);
+@}
+#endif /* __FLASH */
+@end smallexample
+
+@noindent
+Notice that attribute @ref{AVR Variable Attributes,,@code{progmem}}
+locates data in flash but
+accesses to these data read from generic address space, i.e.@:
+from RAM,
+so that you need special accessors like @code{pgm_read_byte}
+from @w{@uref{http://nongnu.org/avr-libc/user-manual/,AVR-LibC}}
+together with attribute @code{progmem}.
+
+@noindent
+@b{Limitations and caveats}
+
+@itemize
+@item
+Reading across the 64@tie{}KiB section boundary of
+the @code{__flash} or @code{__flash@var{N}} address spaces
+shows undefined behavior. The only address space that
+supports reading across the 64@tie{}KiB flash segment boundaries is
+@code{__memx}.
+
+@item
+If you use one of the @code{__flash@var{N}} address spaces
+you must arrange your linker script to locate the
+@code{.progmem@var{N}.data} sections according to your needs.
+
+@item
+Any data or pointers to the non-generic address spaces must
+be qualified as @code{const}, i.e.@: as read-only data.
+This still applies if the data in one of these address
+spaces like software version number or calibration lookup table are intended to
+be changed after load time by, say, a boot loader. In this case
+the right qualification is @code{const} @code{volatile} so that the compiler
+must not optimize away known values or insert them
+as immediates into operands of instructions.
+
+@item
+The following code initializes a variable @code{pfoo}
+located in static storage with a 24-bit address:
+@smallexample
+extern const __memx char foo;
+const __memx void *pfoo = &foo;
+@end smallexample
+
+@item
+On the reduced Tiny devices like ATtiny40, no address spaces are supported.
+Just use vanilla C / C++ code without overhead as outlined above.
+Attribute @code{progmem} is supported but works differently,
+see @ref{AVR Variable Attributes}.
+
+@end itemize
+
+@subsection M32C Named Address Spaces
+@cindex @code{__far} M32C Named Address Spaces
+
+On the M32C target, with the R8C and M16C CPU variants, variables
+qualified with @code{__far} are accessed using 32-bit addresses in
+order to access memory beyond the first 64@tie{}Ki bytes. If
+@code{__far} is used with the M32CM or M32C CPU variants, it has no
+effect.
+
+@subsection PRU Named Address Spaces
+@cindex @code{__regio_symbol} PRU Named Address Spaces
+
+On the PRU target, variables qualified with @code{__regio_symbol} are
+aliases used to access the special I/O CPU registers. They must be
+declared as @code{extern} because such variables will not be allocated in
+any data memory. They must also be marked as @code{volatile}, and can
+only be 32-bit integer types. The only names those variables can have
+are @code{__R30} and @code{__R31}, representing respectively the
+@code{R30} and @code{R31} special I/O CPU registers. Hence the following
+example is the only valid usage of @code{__regio_symbol}:
+
+@smallexample
+extern volatile __regio_symbol uint32_t __R30;
+extern volatile __regio_symbol uint32_t __R31;
+@end smallexample
+
+@subsection RL78 Named Address Spaces
+@cindex @code{__far} RL78 Named Address Spaces
+
+On the RL78 target, variables qualified with @code{__far} are accessed
+with 32-bit pointers (20-bit addresses) rather than the default 16-bit
+addresses. Non-far variables are assumed to appear in the topmost
+64@tie{}KiB of the address space.
+
+@subsection x86 Named Address Spaces
+@cindex x86 named address spaces
+
+On the x86 target, variables may be declared as being relative
+to the @code{%fs} or @code{%gs} segments.
+
+@table @code
+@item __seg_fs
+@itemx __seg_gs
+@cindex @code{__seg_fs} x86 named address space
+@cindex @code{__seg_gs} x86 named address space
+The object is accessed with the respective segment override prefix.
+
+The respective segment base must be set via some method specific to
+the operating system. Rather than require an expensive system call
+to retrieve the segment base, these address spaces are not considered
+to be subspaces of the generic (flat) address space. This means that
+explicit casts are required to convert pointers between these address
+spaces and the generic address space. In practice the application
+should cast to @code{uintptr_t} and apply the segment base offset
+that it installed previously.
+
+The preprocessor symbols @code{__SEG_FS} and @code{__SEG_GS} are
+defined when these address spaces are supported.
+@end table
+
+@node Zero Length
+@section Arrays of Length Zero
+@cindex arrays of length zero
+@cindex zero-length arrays
+@cindex length-zero arrays
+@cindex flexible array members
+
+Declaring zero-length arrays is allowed in GNU C as an extension.
+A zero-length array can be useful as the last element of a structure
+that is really a header for a variable-length object:
+
+@smallexample
+struct line @{
+ int length;
+ char contents[0];
+@};
+
+struct line *thisline = (struct line *)
+ malloc (sizeof (struct line) + this_length);
+thisline->length = this_length;
+@end smallexample
+
+Although the size of a zero-length array is zero, an array member of
+this kind may increase the size of the enclosing type as a result of tail
+padding. The offset of a zero-length array member from the beginning
+of the enclosing structure is the same as the offset of an array with
+one or more elements of the same type. The alignment of a zero-length
+array is the same as the alignment of its elements.
+
+Declaring zero-length arrays in other contexts, including as interior
+members of structure objects or as non-member objects, is discouraged.
+Accessing elements of zero-length arrays declared in such contexts is
+undefined and may be diagnosed.
+
+In the absence of the zero-length array extension, in ISO C90
+the @code{contents} array in the example above would typically be declared
+to have a single element. Unlike a zero-length array which only contributes
+to the size of the enclosing structure for the purposes of alignment,
+a one-element array always occupies at least as much space as a single
+object of the type. Although using one-element arrays this way is
+discouraged, GCC handles accesses to trailing one-element array members
+analogously to zero-length arrays.
+
+The preferred mechanism to declare variable-length types like
+@code{struct line} above is the ISO C99 @dfn{flexible array member},
+with slightly different syntax and semantics:
+
+@itemize @bullet
+@item
+Flexible array members are written as @code{contents[]} without
+the @code{0}.
+
+@item
+Flexible array members have incomplete type, and so the @code{sizeof}
+operator may not be applied. As a quirk of the original implementation
+of zero-length arrays, @code{sizeof} evaluates to zero.
+
+@item
+Flexible array members may only appear as the last member of a
+@code{struct} that is otherwise non-empty.
+
+@item
+A structure containing a flexible array member, or a union containing
+such a structure (possibly recursively), may not be a member of a
+structure or an element of an array. (However, these uses are
+permitted by GCC as extensions.)
+@end itemize
+
+Non-empty initialization of zero-length
+arrays is treated like any case where there are more initializer
+elements than the array holds, in that a suitable warning about ``excess
+elements in array'' is given, and the excess elements (all of them, in
+this case) are ignored.
+
+GCC allows static initialization of flexible array members.
+This is equivalent to defining a new structure containing the original
+structure followed by an array of sufficient size to contain the data.
+E.g.@: in the following, @code{f1} is constructed as if it were declared
+like @code{f2}.
+
+@smallexample
+struct f1 @{
+ int x; int y[];
+@} f1 = @{ 1, @{ 2, 3, 4 @} @};
+
+struct f2 @{
+ struct f1 f1; int data[3];
+@} f2 = @{ @{ 1 @}, @{ 2, 3, 4 @} @};
+@end smallexample
+
+@noindent
+The convenience of this extension is that @code{f1} has the desired
+type, eliminating the need to consistently refer to @code{f2.f1}.
+
+This has symmetry with normal static arrays, in that an array of
+unknown size is also written with @code{[]}.
+
+Of course, this extension only makes sense if the extra data comes at
+the end of a top-level object, as otherwise we would be overwriting
+data at subsequent offsets. To avoid undue complication and confusion
+with initialization of deeply nested arrays, we simply disallow any
+non-empty initialization except when the structure is the top-level
+object. For example:
+
+@smallexample
+struct foo @{ int x; int y[]; @};
+struct bar @{ struct foo z; @};
+
+struct foo a = @{ 1, @{ 2, 3, 4 @} @}; // @r{Valid.}
+struct bar b = @{ @{ 1, @{ 2, 3, 4 @} @} @}; // @r{Invalid.}
+struct bar c = @{ @{ 1, @{ @} @} @}; // @r{Valid.}
+struct foo d[1] = @{ @{ 1, @{ 2, 3, 4 @} @} @}; // @r{Invalid.}
+@end smallexample
+
+@node Empty Structures
+@section Structures with No Members
+@cindex empty structures
+@cindex zero-size structures
+
+GCC permits a C structure to have no members:
+
+@smallexample
+struct empty @{
+@};
+@end smallexample
+
+The structure has size zero. In C++, empty structures are part
+of the language. G++ treats empty structures as if they had a single
+member of type @code{char}.
+
+@node Variable Length
+@section Arrays of Variable Length
+@cindex variable-length arrays
+@cindex arrays of variable length
+@cindex VLAs
+
+Variable-length automatic arrays are allowed in ISO C99, and as an
+extension GCC accepts them in C90 mode and in C++. These arrays are
+declared like any other automatic arrays, but with a length that is not
+a constant expression. The storage is allocated at the point of
+declaration and deallocated when the block scope containing the declaration
+exits. For
+example:
+
+@smallexample
+FILE *
+concat_fopen (char *s1, char *s2, char *mode)
+@{
+ char str[strlen (s1) + strlen (s2) + 1];
+ strcpy (str, s1);
+ strcat (str, s2);
+ return fopen (str, mode);
+@}
+@end smallexample
+
+@cindex scope of a variable length array
+@cindex variable-length array scope
+@cindex deallocating variable length arrays
+Jumping or breaking out of the scope of the array name deallocates the
+storage. Jumping into the scope is not allowed; you get an error
+message for it.
+
+@cindex variable-length array in a structure
+As an extension, GCC accepts variable-length arrays as a member of
+a structure or a union. For example:
+
+@smallexample
+void
+foo (int n)
+@{
+ struct S @{ int x[n]; @};
+@}
+@end smallexample
+
+@cindex @code{alloca} vs variable-length arrays
+You can use the function @code{alloca} to get an effect much like
+variable-length arrays. The function @code{alloca} is available in
+many other C implementations (but not in all). On the other hand,
+variable-length arrays are more elegant.
+
+There are other differences between these two methods. Space allocated
+with @code{alloca} exists until the containing @emph{function} returns.
+The space for a variable-length array is deallocated as soon as the array
+name's scope ends, unless you also use @code{alloca} in this scope.
+
+You can also use variable-length arrays as arguments to functions:
+
+@smallexample
+struct entry
+tester (int len, char data[len][len])
+@{
+ /* @r{@dots{}} */
+@}
+@end smallexample
+
+The length of an array is computed once when the storage is allocated
+and is remembered for the scope of the array in case you access it with
+@code{sizeof}.
+
+If you want to pass the array first and the length afterward, you can
+use a forward declaration in the parameter list---another GNU extension.
+
+@smallexample
+struct entry
+tester (int len; char data[len][len], int len)
+@{
+ /* @r{@dots{}} */
+@}
+@end smallexample
+
+@cindex parameter forward declaration
+The @samp{int len} before the semicolon is a @dfn{parameter forward
+declaration}, and it serves the purpose of making the name @code{len}
+known when the declaration of @code{data} is parsed.
+
+You can write any number of such parameter forward declarations in the
+parameter list. They can be separated by commas or semicolons, but the
+last one must end with a semicolon, which is followed by the ``real''
+parameter declarations. Each forward declaration must match a ``real''
+declaration in parameter name and data type. ISO C99 does not support
+parameter forward declarations.
+
+@node Variadic Macros
+@section Macros with a Variable Number of Arguments.
+@cindex variable number of arguments
+@cindex macro with variable arguments
+@cindex rest argument (in macro)
+@cindex variadic macros
+
+In the ISO C standard of 1999, a macro can be declared to accept a
+variable number of arguments much as a function can. The syntax for
+defining the macro is similar to that of a function. Here is an
+example:
+
+@smallexample
+#define debug(format, ...) fprintf (stderr, format, __VA_ARGS__)
+@end smallexample
+
+@noindent
+Here @samp{@dots{}} is a @dfn{variable argument}. In the invocation of
+such a macro, it represents the zero or more tokens until the closing
+parenthesis that ends the invocation, including any commas. This set of
+tokens replaces the identifier @code{__VA_ARGS__} in the macro body
+wherever it appears. See the CPP manual for more information.
+
+GCC has long supported variadic macros, and used a different syntax that
+allowed you to give a name to the variable arguments just like any other
+argument. Here is an example:
+
+@smallexample
+#define debug(format, args...) fprintf (stderr, format, args)
+@end smallexample
+
+@noindent
+This is in all ways equivalent to the ISO C example above, but arguably
+more readable and descriptive.
+
+GNU CPP has two further variadic macro extensions, and permits them to
+be used with either of the above forms of macro definition.
+
+In standard C, you are not allowed to leave the variable argument out
+entirely; but you are allowed to pass an empty argument. For example,
+this invocation is invalid in ISO C, because there is no comma after
+the string:
+
+@smallexample
+debug ("A message")
+@end smallexample
+
+GNU CPP permits you to completely omit the variable arguments in this
+way. In the above examples, the compiler would complain, though since
+the expansion of the macro still has the extra comma after the format
+string.
+
+To help solve this problem, CPP behaves specially for variable arguments
+used with the token paste operator, @samp{##}. If instead you write
+
+@smallexample
+#define debug(format, ...) fprintf (stderr, format, ## __VA_ARGS__)
+@end smallexample
+
+@noindent
+and if the variable arguments are omitted or empty, the @samp{##}
+operator causes the preprocessor to remove the comma before it. If you
+do provide some variable arguments in your macro invocation, GNU CPP
+does not complain about the paste operation and instead places the
+variable arguments after the comma. Just like any other pasted macro
+argument, these arguments are not macro expanded.
+
+@node Escaped Newlines
+@section Slightly Looser Rules for Escaped Newlines
+@cindex escaped newlines
+@cindex newlines (escaped)
+
+The preprocessor treatment of escaped newlines is more relaxed
+than that specified by the C90 standard, which requires the newline
+to immediately follow a backslash.
+GCC's implementation allows whitespace in the form
+of spaces, horizontal and vertical tabs, and form feeds between the
+backslash and the subsequent newline. The preprocessor issues a
+warning, but treats it as a valid escaped newline and combines the two
+lines to form a single logical line. This works within comments and
+tokens, as well as between tokens. Comments are @emph{not} treated as
+whitespace for the purposes of this relaxation, since they have not
+yet been replaced with spaces.
+
+@node Subscripting
+@section Non-Lvalue Arrays May Have Subscripts
+@cindex subscripting
+@cindex arrays, non-lvalue
+
+@cindex subscripting and function values
+In ISO C99, arrays that are not lvalues still decay to pointers, and
+may be subscripted, although they may not be modified or used after
+the next sequence point and the unary @samp{&} operator may not be
+applied to them. As an extension, GNU C allows such arrays to be
+subscripted in C90 mode, though otherwise they do not decay to
+pointers outside C99 mode. For example,
+this is valid in GNU C though not valid in C90:
+
+@smallexample
+@group
+struct foo @{int a[4];@};
+
+struct foo f();
+
+bar (int index)
+@{
+ return f().a[index];
+@}
+@end group
+@end smallexample
+
+@node Pointer Arith
+@section Arithmetic on @code{void}- and Function-Pointers
+@cindex void pointers, arithmetic
+@cindex void, size of pointer to
+@cindex function pointers, arithmetic
+@cindex function, size of pointer to
+
+In GNU C, addition and subtraction operations are supported on pointers to
+@code{void} and on pointers to functions. This is done by treating the
+size of a @code{void} or of a function as 1.
+
+A consequence of this is that @code{sizeof} is also allowed on @code{void}
+and on function types, and returns 1.
+
+@opindex Wpointer-arith
+The option @option{-Wpointer-arith} requests a warning if these extensions
+are used.
+
+@node Variadic Pointer Args
+@section Pointer Arguments in Variadic Functions
+@cindex pointer arguments in variadic functions
+@cindex variadic functions, pointer arguments
+
+Standard C requires that pointer types used with @code{va_arg} in
+functions with variable argument lists either must be compatible with
+that of the actual argument, or that one type must be a pointer to
+@code{void} and the other a pointer to a character type. GNU C
+implements the POSIX XSI extension that additionally permits the use
+of @code{va_arg} with a pointer type to receive arguments of any other
+pointer type.
+
+In particular, in GNU C @samp{va_arg (ap, void *)} can safely be used
+to consume an argument of any pointer type.
+
+@node Pointers to Arrays
+@section Pointers to Arrays with Qualifiers Work as Expected
+@cindex pointers to arrays
+@cindex const qualifier
+
+In GNU C, pointers to arrays with qualifiers work similar to pointers
+to other qualified types. For example, a value of type @code{int (*)[5]}
+can be used to initialize a variable of type @code{const int (*)[5]}.
+These types are incompatible in ISO C because the @code{const} qualifier
+is formally attached to the element type of the array and not the
+array itself.
+
+@smallexample
+extern void
+transpose (int N, int M, double out[M][N], const double in[N][M]);
+double x[3][2];
+double y[2][3];
+@r{@dots{}}
+transpose(3, 2, y, x);
+@end smallexample
+
+@node Initializers
+@section Non-Constant Initializers
+@cindex initializers, non-constant
+@cindex non-constant initializers
+
+As in standard C++ and ISO C99, the elements of an aggregate initializer for an
+automatic variable are not required to be constant expressions in GNU C@.
+Here is an example of an initializer with run-time varying elements:
+
+@smallexample
+foo (float f, float g)
+@{
+ float beat_freqs[2] = @{ f-g, f+g @};
+ /* @r{@dots{}} */
+@}
+@end smallexample
+
+@node Compound Literals
+@section Compound Literals
+@cindex constructor expressions
+@cindex initializations in expressions
+@cindex structures, constructor expression
+@cindex expressions, constructor
+@cindex compound literals
+@c The GNU C name for what C99 calls compound literals was "constructor expressions".
+
+A compound literal looks like a cast of a brace-enclosed aggregate
+initializer list. Its value is an object of the type specified in
+the cast, containing the elements specified in the initializer.
+Unlike the result of a cast, a compound literal is an lvalue. ISO
+C99 and later support compound literals. As an extension, GCC
+supports compound literals also in C90 mode and in C++, although
+as explained below, the C++ semantics are somewhat different.
+
+Usually, the specified type of a compound literal is a structure. Assume
+that @code{struct foo} and @code{structure} are declared as shown:
+
+@smallexample
+struct foo @{int a; char b[2];@} structure;
+@end smallexample
+
+@noindent
+Here is an example of constructing a @code{struct foo} with a compound literal:
+
+@smallexample
+structure = ((struct foo) @{x + y, 'a', 0@});
+@end smallexample
+
+@noindent
+This is equivalent to writing the following:
+
+@smallexample
+@{
+ struct foo temp = @{x + y, 'a', 0@};
+ structure = temp;
+@}
+@end smallexample
+
+You can also construct an array, though this is dangerous in C++, as
+explained below. If all the elements of the compound literal are
+(made up of) simple constant expressions suitable for use in
+initializers of objects of static storage duration, then the compound
+literal can be coerced to a pointer to its first element and used in
+such an initializer, as shown here:
+
+@smallexample
+char **foo = (char *[]) @{ "x", "y", "z" @};
+@end smallexample
+
+Compound literals for scalar types and union types are also allowed. In
+the following example the variable @code{i} is initialized to the value
+@code{2}, the result of incrementing the unnamed object created by
+the compound literal.
+
+@smallexample
+int i = ++(int) @{ 1 @};
+@end smallexample
+
+As a GNU extension, GCC allows initialization of objects with static storage
+duration by compound literals (which is not possible in ISO C99 because
+the initializer is not a constant).
+It is handled as if the object were initialized only with the brace-enclosed
+list if the types of the compound literal and the object match.
+The elements of the compound literal must be constant.
+If the object being initialized has array type of unknown size, the size is
+determined by the size of the compound literal.
+
+@smallexample
+static struct foo x = (struct foo) @{1, 'a', 'b'@};
+static int y[] = (int []) @{1, 2, 3@};
+static int z[] = (int [3]) @{1@};
+@end smallexample
+
+@noindent
+The above lines are equivalent to the following:
+@smallexample
+static struct foo x = @{1, 'a', 'b'@};
+static int y[] = @{1, 2, 3@};
+static int z[] = @{1, 0, 0@};
+@end smallexample
+
+In C, a compound literal designates an unnamed object with static or
+automatic storage duration. In C++, a compound literal designates a
+temporary object that only lives until the end of its full-expression.
+As a result, well-defined C code that takes the address of a subobject
+of a compound literal can be undefined in C++, so G++ rejects
+the conversion of a temporary array to a pointer. For instance, if
+the array compound literal example above appeared inside a function,
+any subsequent use of @code{foo} in C++ would have undefined behavior
+because the lifetime of the array ends after the declaration of @code{foo}.
+
+As an optimization, G++ sometimes gives array compound literals longer
+lifetimes: when the array either appears outside a function or has
+a @code{const}-qualified type. If @code{foo} and its initializer had
+elements of type @code{char *const} rather than @code{char *}, or if
+@code{foo} were a global variable, the array would have static storage
+duration. But it is probably safest just to avoid the use of array
+compound literals in C++ code.
+
+@node Designated Inits
+@section Designated Initializers
+@cindex initializers with labeled elements
+@cindex labeled elements in initializers
+@cindex case labels in initializers
+@cindex designated initializers
+
+Standard C90 requires the elements of an initializer to appear in a fixed
+order, the same as the order of the elements in the array or structure
+being initialized.
+
+In ISO C99 you can give the elements in any order, specifying the array
+indices or structure field names they apply to, and GNU C allows this as
+an extension in C90 mode as well. This extension is not
+implemented in GNU C++.
+
+To specify an array index, write
+@samp{[@var{index}] =} before the element value. For example,
+
+@smallexample
+int a[6] = @{ [4] = 29, [2] = 15 @};
+@end smallexample
+
+@noindent
+is equivalent to
+
+@smallexample
+int a[6] = @{ 0, 0, 15, 0, 29, 0 @};
+@end smallexample
+
+@noindent
+The index values must be constant expressions, even if the array being
+initialized is automatic.
+
+An alternative syntax for this that has been obsolete since GCC 2.5 but
+GCC still accepts is to write @samp{[@var{index}]} before the element
+value, with no @samp{=}.
+
+To initialize a range of elements to the same value, write
+@samp{[@var{first} ... @var{last}] = @var{value}}. This is a GNU
+extension. For example,
+
+@smallexample
+int widths[] = @{ [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 @};
+@end smallexample
+
+@noindent
+If the value in it has side effects, the side effects happen only once,
+not for each initialized field by the range initializer.
+
+@noindent
+Note that the length of the array is the highest value specified
+plus one.
+
+In a structure initializer, specify the name of a field to initialize
+with @samp{.@var{fieldname} =} before the element value. For example,
+given the following structure,
+
+@smallexample
+struct point @{ int x, y; @};
+@end smallexample
+
+@noindent
+the following initialization
+
+@smallexample
+struct point p = @{ .y = yvalue, .x = xvalue @};
+@end smallexample
+
+@noindent
+is equivalent to
+
+@smallexample
+struct point p = @{ xvalue, yvalue @};
+@end smallexample
+
+Another syntax that has the same meaning, obsolete since GCC 2.5, is
+@samp{@var{fieldname}:}, as shown here:
+
+@smallexample
+struct point p = @{ y: yvalue, x: xvalue @};
+@end smallexample
+
+Omitted fields are implicitly initialized the same as for objects
+that have static storage duration.
+
+@cindex designators
+The @samp{[@var{index}]} or @samp{.@var{fieldname}} is known as a
+@dfn{designator}. You can also use a designator (or the obsolete colon
+syntax) when initializing a union, to specify which element of the union
+should be used. For example,
+
+@smallexample
+union foo @{ int i; double d; @};
+
+union foo f = @{ .d = 4 @};
+@end smallexample
+
+@noindent
+converts 4 to a @code{double} to store it in the union using
+the second element. By contrast, casting 4 to type @code{union foo}
+stores it into the union as the integer @code{i}, since it is
+an integer. @xref{Cast to Union}.
+
+You can combine this technique of naming elements with ordinary C
+initialization of successive elements. Each initializer element that
+does not have a designator applies to the next consecutive element of the
+array or structure. For example,
+
+@smallexample
+int a[6] = @{ [1] = v1, v2, [4] = v4 @};
+@end smallexample
+
+@noindent
+is equivalent to
+
+@smallexample
+int a[6] = @{ 0, v1, v2, 0, v4, 0 @};
+@end smallexample
+
+Labeling the elements of an array initializer is especially useful
+when the indices are characters or belong to an @code{enum} type.
+For example:
+
+@smallexample
+int whitespace[256]
+ = @{ [' '] = 1, ['\t'] = 1, ['\h'] = 1,
+ ['\f'] = 1, ['\n'] = 1, ['\r'] = 1 @};
+@end smallexample
+
+@cindex designator lists
+You can also write a series of @samp{.@var{fieldname}} and
+@samp{[@var{index}]} designators before an @samp{=} to specify a
+nested subobject to initialize; the list is taken relative to the
+subobject corresponding to the closest surrounding brace pair. For
+example, with the @samp{struct point} declaration above:
+
+@smallexample
+struct point ptarray[10] = @{ [2].y = yv2, [2].x = xv2, [0].x = xv0 @};
+@end smallexample
+
+If the same field is initialized multiple times, or overlapping
+fields of a union are initialized, the value from the last
+initialization is used. When a field of a union is itself a structure,
+the entire structure from the last field initialized is used. If any previous
+initializer has side effect, it is unspecified whether the side effect
+happens or not. Currently, GCC discards the side-effecting
+initializer expressions and issues a warning.
+
+@node Case Ranges
+@section Case Ranges
+@cindex case ranges
+@cindex ranges in case statements
+
+You can specify a range of consecutive values in a single @code{case} label,
+like this:
+
+@smallexample
+case @var{low} ... @var{high}:
+@end smallexample
+
+@noindent
+This has the same effect as the proper number of individual @code{case}
+labels, one for each integer value from @var{low} to @var{high}, inclusive.
+
+This feature is especially useful for ranges of ASCII character codes:
+
+@smallexample
+case 'A' ... 'Z':
+@end smallexample
+
+@strong{Be careful:} Write spaces around the @code{...}, for otherwise
+it may be parsed wrong when you use it with integer values. For example,
+write this:
+
+@smallexample
+case 1 ... 5:
+@end smallexample
+
+@noindent
+rather than this:
+
+@smallexample
+case 1...5:
+@end smallexample
+
+@node Cast to Union
+@section Cast to a Union Type
+@cindex cast to a union
+@cindex union, casting to a
+
+A cast to a union type is a C extension not available in C++. It looks
+just like ordinary casts with the constraint that the type specified is
+a union type. You can specify the type either with the @code{union}
+keyword or with a @code{typedef} name that refers to a union. The result
+of a cast to a union is a temporary rvalue of the union type with a member
+whose type matches that of the operand initialized to the value of
+the operand. The effect of a cast to a union is similar to a compound
+literal except that it yields an rvalue like standard casts do.
+@xref{Compound Literals}.
+
+Expressions that may be cast to the union type are those whose type matches
+at least one of the members of the union. Thus, given the following union
+and variables:
+
+@smallexample
+union foo @{ int i; double d; @};
+int x;
+double y;
+union foo z;
+@end smallexample
+
+@noindent
+both @code{x} and @code{y} can be cast to type @code{union foo} and
+the following assignments
+@smallexample
+ z = (union foo) x;
+ z = (union foo) y;
+@end smallexample
+are shorthand equivalents of these
+@smallexample
+ z = (union foo) @{ .i = x @};
+ z = (union foo) @{ .d = y @};
+@end smallexample
+
+However, @code{(union foo) FLT_MAX;} is not a valid cast because the union
+has no member of type @code{float}.
+
+Using the cast as the right-hand side of an assignment to a variable of
+union type is equivalent to storing in a member of the union with
+the same type
+
+@smallexample
+union foo u;
+/* @r{@dots{}} */
+u = (union foo) x @equiv{} u.i = x
+u = (union foo) y @equiv{} u.d = y
+@end smallexample
+
+You can also use the union cast as a function argument:
+
+@smallexample
+void hack (union foo);
+/* @r{@dots{}} */
+hack ((union foo) x);
+@end smallexample
+
+@node Mixed Labels and Declarations
+@section Mixed Declarations, Labels and Code
+@cindex mixed declarations and code
+@cindex declarations, mixed with code
+@cindex code, mixed with declarations
+
+ISO C99 and ISO C++ allow declarations and code to be freely mixed
+within compound statements. ISO C2X allows labels to be
+placed before declarations and at the end of a compound statement.
+As an extension, GNU C also allows all this in C90 mode. For example,
+you could do:
+
+@smallexample
+int i;
+/* @r{@dots{}} */
+i++;
+int j = i + 2;
+@end smallexample
+
+Each identifier is visible from where it is declared until the end of
+the enclosing block.
+
+@node Function Attributes
+@section Declaring Attributes of Functions
+@cindex function attributes
+@cindex declaring attributes of functions
+@cindex @code{volatile} applied to function
+@cindex @code{const} applied to function
+
+In GNU C and C++, you can use function attributes to specify certain
+function properties that may help the compiler optimize calls or
+check code more carefully for correctness. For example, you
+can use attributes to specify that a function never returns
+(@code{noreturn}), returns a value depending only on the values of
+its arguments (@code{const}), or has @code{printf}-style arguments
+(@code{format}).
+
+You can also use attributes to control memory placement, code
+generation options or call/return conventions within the function
+being annotated. Many of these attributes are target-specific. For
+example, many targets support attributes for defining interrupt
+handler functions, which typically must follow special register usage
+and return conventions. Such attributes are described in the subsection
+for each target. However, a considerable number of attributes are
+supported by most, if not all targets. Those are described in
+the @ref{Common Function Attributes} section.
+
+Function attributes are introduced by the @code{__attribute__} keyword
+in the declaration of a function, followed by an attribute specification
+enclosed in double parentheses. You can specify multiple attributes in
+a declaration by separating them by commas within the double parentheses
+or by immediately following one attribute specification with another.
+@xref{Attribute Syntax}, for the exact rules on attribute syntax and
+placement. Compatible attribute specifications on distinct declarations
+of the same function are merged. An attribute specification that is not
+compatible with attributes already applied to a declaration of the same
+function is ignored with a warning.
+
+Some function attributes take one or more arguments that refer to
+the function's parameters by their positions within the function parameter
+list. Such attribute arguments are referred to as @dfn{positional arguments}.
+Unless specified otherwise, positional arguments that specify properties
+of parameters with pointer types can also specify the same properties of
+the implicit C++ @code{this} argument in non-static member functions, and
+of parameters of reference to a pointer type. For ordinary functions,
+position one refers to the first parameter on the list. In C++ non-static
+member functions, position one refers to the implicit @code{this} pointer.
+The same restrictions and effects apply to function attributes used with
+ordinary functions or C++ member functions.
+
+GCC also supports attributes on
+variable declarations (@pxref{Variable Attributes}),
+labels (@pxref{Label Attributes}),
+enumerators (@pxref{Enumerator Attributes}),
+statements (@pxref{Statement Attributes}),
+types (@pxref{Type Attributes}),
+and on field declarations (for @code{tainted_args}).
+
+There is some overlap between the purposes of attributes and pragmas
+(@pxref{Pragmas,,Pragmas Accepted by GCC}). It has been
+found convenient to use @code{__attribute__} to achieve a natural
+attachment of attributes to their corresponding declarations, whereas
+@code{#pragma} is of use for compatibility with other compilers
+or constructs that do not naturally form part of the grammar.
+
+In addition to the attributes documented here,
+GCC plugins may provide their own attributes.
+
+@menu
+* Common Function Attributes::
+* AArch64 Function Attributes::
+* AMD GCN Function Attributes::
+* ARC Function Attributes::
+* ARM Function Attributes::
+* AVR Function Attributes::
+* Blackfin Function Attributes::
+* BPF Function Attributes::
+* C-SKY Function Attributes::
+* Epiphany Function Attributes::
+* H8/300 Function Attributes::
+* IA-64 Function Attributes::
+* M32C Function Attributes::
+* M32R/D Function Attributes::
+* m68k Function Attributes::
+* MCORE Function Attributes::
+* MeP Function Attributes::
+* MicroBlaze Function Attributes::
+* Microsoft Windows Function Attributes::
+* MIPS Function Attributes::
+* MSP430 Function Attributes::
+* NDS32 Function Attributes::
+* Nios II Function Attributes::
+* Nvidia PTX Function Attributes::
+* PowerPC Function Attributes::
+* RISC-V Function Attributes::
+* RL78 Function Attributes::
+* RX Function Attributes::
+* S/390 Function Attributes::
+* SH Function Attributes::
+* Symbian OS Function Attributes::
+* V850 Function Attributes::
+* Visium Function Attributes::
+* x86 Function Attributes::
+* Xstormy16 Function Attributes::
+@end menu
+
+@node Common Function Attributes
+@subsection Common Function Attributes
+
+The following attributes are supported on most targets.
+
+@table @code
+@c Keep this table alphabetized by attribute name. Treat _ as space.
+
+@item access (@var{access-mode}, @var{ref-index})
+@itemx access (@var{access-mode}, @var{ref-index}, @var{size-index})
+
+The @code{access} attribute enables the detection of invalid or unsafe
+accesses by functions to which they apply or their callers, as well as
+write-only accesses to objects that are never read from. Such accesses
+may be diagnosed by warnings such as @option{-Wstringop-overflow},
+@option{-Wuninitialized}, @option{-Wunused}, and others.
+
+The @code{access} attribute specifies that a function to whose by-reference
+arguments the attribute applies accesses the referenced object according to
+@var{access-mode}. The @var{access-mode} argument is required and must be
+one of four names: @code{read_only}, @code{read_write}, @code{write_only},
+or @code{none}. The remaining two are positional arguments.
+
+The required @var{ref-index} positional argument denotes a function
+argument of pointer (or in C++, reference) type that is subject to
+the access. The same pointer argument can be referenced by at most one
+distinct @code{access} attribute.
+
+The optional @var{size-index} positional argument denotes a function
+argument of integer type that specifies the maximum size of the access.
+The size is the number of elements of the type referenced by @var{ref-index},
+or the number of bytes when the pointer type is @code{void*}. When no
+@var{size-index} argument is specified, the pointer argument must be either
+null or point to a space that is suitably aligned and large for at least one
+object of the referenced type (this implies that a past-the-end pointer is
+not a valid argument). The actual size of the access may be less but it
+must not be more.
+
+The @code{read_only} access mode specifies that the pointer to which it
+applies is used to read the referenced object but not write to it. Unless
+the argument specifying the size of the access denoted by @var{size-index}
+is zero, the referenced object must be initialized. The mode implies
+a stronger guarantee than the @code{const} qualifier which, when cast away
+from a pointer, does not prevent the pointed-to object from being modified.
+Examples of the use of the @code{read_only} access mode is the argument to
+the @code{puts} function, or the second and third arguments to
+the @code{memcpy} function.
+
+@smallexample
+__attribute__ ((access (read_only, 1))) int puts (const char*);
+__attribute__ ((access (read_only, 2, 3))) void* memcpy (void*, const void*, size_t);
+@end smallexample
+
+The @code{read_write} access mode applies to arguments of pointer types
+without the @code{const} qualifier. It specifies that the pointer to which
+it applies is used to both read and write the referenced object. Unless
+the argument specifying the size of the access denoted by @var{size-index}
+is zero, the object referenced by the pointer must be initialized. An example
+of the use of the @code{read_write} access mode is the first argument to
+the @code{strcat} function.
+
+@smallexample
+__attribute__ ((access (read_write, 1), access (read_only, 2))) char* strcat (char*, const char*);
+@end smallexample
+
+The @code{write_only} access mode applies to arguments of pointer types
+without the @code{const} qualifier. It specifies that the pointer to which
+it applies is used to write to the referenced object but not read from it.
+The object referenced by the pointer need not be initialized. An example
+of the use of the @code{write_only} access mode is the first argument to
+the @code{strcpy} function, or the first two arguments to the @code{fgets}
+function.
+
+@smallexample
+__attribute__ ((access (write_only, 1), access (read_only, 2))) char* strcpy (char*, const char*);
+__attribute__ ((access (write_only, 1, 2), access (read_write, 3))) int fgets (char*, int, FILE*);
+@end smallexample
+
+The access mode @code{none} specifies that the pointer to which it applies
+is not used to access the referenced object at all. Unless the pointer is
+null the pointed-to object must exist and have at least the size as denoted
+by the @var{size-index} argument. When the optional @var{size-index}
+argument is omitted for an argument of @code{void*} type the actual pointer
+agument is ignored. The referenced object need not be initialized.
+The mode is intended to be used as a means to help validate the expected
+object size, for example in functions that call @code{__builtin_object_size}.
+@xref{Object Size Checking}.
+
+Note that the @code{access} attribute merely specifies how an object
+referenced by the pointer argument can be accessed; it does not imply that
+an access @strong{will} happen. Also, the @code{access} attribute does not
+imply the attribute @code{nonnull}; it may be appropriate to add both attributes
+at the declaration of a function that unconditionally manipulates a buffer via
+a pointer argument. See the @code{nonnull} attribute for more information and
+caveats.
+
+@item alias ("@var{target}")
+@cindex @code{alias} function attribute
+The @code{alias} attribute causes the declaration to be emitted as an alias
+for another symbol, which must have been previously declared with the same
+type, and for variables, also the same size and alignment. Declaring an alias
+with a different type than the target is undefined and may be diagnosed. As
+an example, the following declarations:
+
+@smallexample
+void __f () @{ /* @r{Do something.} */; @}
+void f () __attribute__ ((weak, alias ("__f")));
+@end smallexample
+
+@noindent
+define @samp{f} to be a weak alias for @samp{__f}. In C++, the mangled name
+for the target must be used. It is an error if @samp{__f} is not defined in
+the same translation unit.
+
+This attribute requires assembler and object file support,
+and may not be available on all targets.
+
+@item aligned
+@itemx aligned (@var{alignment})
+@cindex @code{aligned} function attribute
+The @code{aligned} attribute specifies a minimum alignment for
+the first instruction of the function, measured in bytes. When specified,
+@var{alignment} must be an integer constant power of 2. Specifying no
+@var{alignment} argument implies the ideal alignment for the target.
+The @code{__alignof__} operator can be used to determine what that is
+(@pxref{Alignment}). The attribute has no effect when a definition for
+the function is not provided in the same translation unit.
+
+The attribute cannot be used to decrease the alignment of a function
+previously declared with a more restrictive alignment; only to increase
+it. Attempts to do otherwise are diagnosed. Some targets specify
+a minimum default alignment for functions that is greater than 1. On
+such targets, specifying a less restrictive alignment is silently ignored.
+Using the attribute overrides the effect of the @option{-falign-functions}
+(@pxref{Optimize Options}) option for this function.
+
+Note that the effectiveness of @code{aligned} attributes may be
+limited by inherent limitations in the system linker
+and/or object file format. On some systems, the
+linker is only able to arrange for functions to be aligned up to a
+certain maximum alignment. (For some linkers, the maximum supported
+alignment may be very very small.) See your linker documentation for
+further information.
+
+The @code{aligned} attribute can also be used for variables and fields
+(@pxref{Variable Attributes}.)
+
+@item alloc_align (@var{position})
+@cindex @code{alloc_align} function attribute
+The @code{alloc_align} attribute may be applied to a function that
+returns a pointer and takes at least one argument of an integer or
+enumerated type.
+It indicates that the returned pointer is aligned on a boundary given
+by the function argument at @var{position}. Meaningful alignments are
+powers of 2 greater than one. GCC uses this information to improve
+pointer alignment analysis.
+
+The function parameter denoting the allocated alignment is specified by
+one constant integer argument whose number is the argument of the attribute.
+Argument numbering starts at one.
+
+For instance,
+
+@smallexample
+void* my_memalign (size_t, size_t) __attribute__ ((alloc_align (1)));
+@end smallexample
+
+@noindent
+declares that @code{my_memalign} returns memory with minimum alignment
+given by parameter 1.
+
+@item alloc_size (@var{position})
+@itemx alloc_size (@var{position-1}, @var{position-2})
+@cindex @code{alloc_size} function attribute
+The @code{alloc_size} attribute may be applied to a function that
+returns a pointer and takes at least one argument of an integer or
+enumerated type.
+It indicates that the returned pointer points to memory whose size is
+given by the function argument at @var{position-1}, or by the product
+of the arguments at @var{position-1} and @var{position-2}. Meaningful
+sizes are positive values less than @code{PTRDIFF_MAX}. GCC uses this
+information to improve the results of @code{__builtin_object_size}.
+
+The function parameter(s) denoting the allocated size are specified by
+one or two integer arguments supplied to the attribute. The allocated size
+is either the value of the single function argument specified or the product
+of the two function arguments specified. Argument numbering starts at
+one for ordinary functions, and at two for C++ non-static member functions.
+
+For instance,
+
+@smallexample
+void* my_calloc (size_t, size_t) __attribute__ ((alloc_size (1, 2)));
+void* my_realloc (void*, size_t) __attribute__ ((alloc_size (2)));
+@end smallexample
+
+@noindent
+declares that @code{my_calloc} returns memory of the size given by
+the product of parameter 1 and 2 and that @code{my_realloc} returns memory
+of the size given by parameter 2.
+
+@item always_inline
+@cindex @code{always_inline} function attribute
+Generally, functions are not inlined unless optimization is specified.
+For functions declared inline, this attribute inlines the function
+independent of any restrictions that otherwise apply to inlining.
+Failure to inline such a function is diagnosed as an error.
+Note that if such a function is called indirectly the compiler may
+or may not inline it depending on optimization level and a failure
+to inline an indirect call may or may not be diagnosed.
+
+@item artificial
+@cindex @code{artificial} function attribute
+This attribute is useful for small inline wrappers that if possible
+should appear during debugging as a unit. Depending on the debug
+info format it either means marking the function as artificial
+or using the caller location for all instructions within the inlined
+body.
+
+@item assume_aligned (@var{alignment})
+@itemx assume_aligned (@var{alignment}, @var{offset})
+@cindex @code{assume_aligned} function attribute
+The @code{assume_aligned} attribute may be applied to a function that
+returns a pointer. It indicates that the returned pointer is aligned
+on a boundary given by @var{alignment}. If the attribute has two
+arguments, the second argument is misalignment @var{offset}. Meaningful
+values of @var{alignment} are powers of 2 greater than one. Meaningful
+values of @var{offset} are greater than zero and less than @var{alignment}.
+
+For instance
+
+@smallexample
+void* my_alloc1 (size_t) __attribute__((assume_aligned (16)));
+void* my_alloc2 (size_t) __attribute__((assume_aligned (32, 8)));
+@end smallexample
+
+@noindent
+declares that @code{my_alloc1} returns 16-byte aligned pointers and
+that @code{my_alloc2} returns a pointer whose value modulo 32 is equal
+to 8.
+
+@item cold
+@cindex @code{cold} function attribute
+The @code{cold} attribute on functions is used to inform the compiler that
+the function is unlikely to be executed. The function is optimized for
+size rather than speed and on many targets it is placed into a special
+subsection of the text section so all cold functions appear close together,
+improving code locality of non-cold parts of program. The paths leading
+to calls of cold functions within code are marked as unlikely by the branch
+prediction mechanism. It is thus useful to mark functions used to handle
+unlikely conditions, such as @code{perror}, as cold to improve optimization
+of hot functions that do call marked functions in rare occasions.
+
+When profile feedback is available, via @option{-fprofile-use}, cold functions
+are automatically detected and this attribute is ignored.
+
+@item const
+@cindex @code{const} function attribute
+@cindex functions that have no side effects
+Calls to functions whose return value is not affected by changes to
+the observable state of the program and that have no observable effects
+on such state other than to return a value may lend themselves to
+optimizations such as common subexpression elimination. Declaring such
+functions with the @code{const} attribute allows GCC to avoid emitting
+some calls in repeated invocations of the function with the same argument
+values.
+
+For example,
+
+@smallexample
+int square (int) __attribute__ ((const));
+@end smallexample
+
+@noindent
+tells GCC that subsequent calls to function @code{square} with the same
+argument value can be replaced by the result of the first call regardless
+of the statements in between.
+
+The @code{const} attribute prohibits a function from reading objects
+that affect its return value between successive invocations. However,
+functions declared with the attribute can safely read objects that do
+not change their return value, such as non-volatile constants.
+
+The @code{const} attribute imposes greater restrictions on a function's
+definition than the similar @code{pure} attribute. Declaring the same
+function with both the @code{const} and the @code{pure} attribute is
+diagnosed. Because a const function cannot have any observable side
+effects it does not make sense for it to return @code{void}. Declaring
+such a function is diagnosed.
+
+@cindex pointer arguments
+Note that a function that has pointer arguments and examines the data
+pointed to must @emph{not} be declared @code{const} if the pointed-to
+data might change between successive invocations of the function. In
+general, since a function cannot distinguish data that might change
+from data that cannot, const functions should never take pointer or,
+in C++, reference arguments. Likewise, a function that calls a non-const
+function usually must not be const itself.
+
+@item constructor
+@itemx destructor
+@itemx constructor (@var{priority})
+@itemx destructor (@var{priority})
+@cindex @code{constructor} function attribute
+@cindex @code{destructor} function attribute
+The @code{constructor} attribute causes the function to be called
+automatically before execution enters @code{main ()}. Similarly, the
+@code{destructor} attribute causes the function to be called
+automatically after @code{main ()} completes or @code{exit ()} is
+called. Functions with these attributes are useful for
+initializing data that is used implicitly during the execution of
+the program.
+
+On some targets the attributes also accept an integer argument to
+specify a priority to control the order in which constructor and
+destructor functions are run. A constructor
+with a smaller priority number runs before a constructor with a larger
+priority number; the opposite relationship holds for destructors. Note
+that priorities 0-100 are reserved. So, if you have a constructor that
+allocates a resource and a destructor that deallocates the same
+resource, both functions typically have the same priority. The
+priorities for constructor and destructor functions are the same as
+those specified for namespace-scope C++ objects (@pxref{C++ Attributes}).
+However, at present, the order in which constructors for C++ objects
+with static storage duration and functions decorated with attribute
+@code{constructor} are invoked is unspecified. In mixed declarations,
+attribute @code{init_priority} can be used to impose a specific ordering.
+
+Using the argument forms of the @code{constructor} and @code{destructor}
+attributes on targets where the feature is not supported is rejected with
+an error.
+
+@item copy
+@itemx copy (@var{function})
+@cindex @code{copy} function attribute
+The @code{copy} attribute applies the set of attributes with which
+@var{function} has been declared to the declaration of the function
+to which the attribute is applied. The attribute is designed for
+libraries that define aliases or function resolvers that are expected
+to specify the same set of attributes as their targets. The @code{copy}
+attribute can be used with functions, variables, or types. However,
+the kind of symbol to which the attribute is applied (either function
+or variable) must match the kind of symbol to which the argument refers.
+The @code{copy} attribute copies only syntactic and semantic attributes
+but not attributes that affect a symbol's linkage or visibility such as
+@code{alias}, @code{visibility}, or @code{weak}. The @code{deprecated}
+and @code{target_clones} attribute are also not copied.
+@xref{Common Type Attributes}.
+@xref{Common Variable Attributes}.
+
+For example, the @var{StrongAlias} macro below makes use of the @code{alias}
+and @code{copy} attributes to define an alias named @var{alloc} for function
+@var{allocate} declared with attributes @var{alloc_size}, @var{malloc}, and
+@var{nothrow}. Thanks to the @code{__typeof__} operator the alias has
+the same type as the target function. As a result of the @code{copy}
+attribute the alias also shares the same attributes as the target.
+
+@smallexample
+#define StrongAlias(TargetFunc, AliasDecl) \
+ extern __typeof__ (TargetFunc) AliasDecl \
+ __attribute__ ((alias (#TargetFunc), copy (TargetFunc)));
+
+extern __attribute__ ((alloc_size (1), malloc, nothrow))
+ void* allocate (size_t);
+StrongAlias (allocate, alloc);
+@end smallexample
+
+@item deprecated
+@itemx deprecated (@var{msg})
+@cindex @code{deprecated} function attribute
+The @code{deprecated} attribute results in a warning if the function
+is used anywhere in the source file. This is useful when identifying
+functions that are expected to be removed in a future version of a
+program. The warning also includes the location of the declaration
+of the deprecated function, to enable users to easily find further
+information about why the function is deprecated, or what they should
+do instead. Note that the warnings only occurs for uses:
+
+@smallexample
+int old_fn () __attribute__ ((deprecated));
+int old_fn ();
+int (*fn_ptr)() = old_fn;
+@end smallexample
+
+@noindent
+results in a warning on line 3 but not line 2. The optional @var{msg}
+argument, which must be a string, is printed in the warning if
+present.
+
+The @code{deprecated} attribute can also be used for variables and
+types (@pxref{Variable Attributes}, @pxref{Type Attributes}.)
+
+The message attached to the attribute is affected by the setting of
+the @option{-fmessage-length} option.
+
+@item unavailable
+@itemx unavailable (@var{msg})
+@cindex @code{unavailable} function attribute
+The @code{unavailable} attribute results in an error if the function
+is used anywhere in the source file. This is useful when identifying
+functions that have been removed from a particular variation of an
+interface. Other than emitting an error rather than a warning, the
+@code{unavailable} attribute behaves in the same manner as
+@code{deprecated}.
+
+The @code{unavailable} attribute can also be used for variables and
+types (@pxref{Variable Attributes}, @pxref{Type Attributes}.)
+
+@item error ("@var{message}")
+@itemx warning ("@var{message}")
+@cindex @code{error} function attribute
+@cindex @code{warning} function attribute
+If the @code{error} or @code{warning} attribute
+is used on a function declaration and a call to such a function
+is not eliminated through dead code elimination or other optimizations,
+an error or warning (respectively) that includes @var{message} is diagnosed.
+This is useful
+for compile-time checking, especially together with @code{__builtin_constant_p}
+and inline functions where checking the inline function arguments is not
+possible through @code{extern char [(condition) ? 1 : -1];} tricks.
+
+While it is possible to leave the function undefined and thus invoke
+a link failure (to define the function with
+a message in @code{.gnu.warning*} section),
+when using these attributes the problem is diagnosed
+earlier and with exact location of the call even in presence of inline
+functions or when not emitting debugging information.
+
+@item externally_visible
+@cindex @code{externally_visible} function attribute
+This attribute, attached to a global variable or function, nullifies
+the effect of the @option{-fwhole-program} command-line option, so the
+object remains visible outside the current compilation unit.
+
+If @option{-fwhole-program} is used together with @option{-flto} and
+@command{gold} is used as the linker plugin,
+@code{externally_visible} attributes are automatically added to functions
+(not variable yet due to a current @command{gold} issue)
+that are accessed outside of LTO objects according to resolution file
+produced by @command{gold}.
+For other linkers that cannot generate resolution file,
+explicit @code{externally_visible} attributes are still necessary.
+
+@item fd_arg
+@itemx fd_arg (@var{N})
+@cindex @code{fd_arg} function attribute
+The @code{fd_arg} attribute may be applied to a function that takes an open
+file descriptor at referenced argument @var{N}.
+
+It indicates that the passed filedescriptor must not have been closed.
+Therefore, when the analyzer is enabled with @option{-fanalyzer}, the
+analyzer may emit a @option{-Wanalyzer-fd-use-after-close} diagnostic
+if it detects a code path in which a function with this attribute is
+called with a closed file descriptor.
+
+The attribute also indicates that the file descriptor must have been checked for
+validity before usage. Therefore, analyzer may emit
+@option{-Wanalyzer-fd-use-without-check} diagnostic if it detects a code path in
+which a function with this attribute is called with a file descriptor that has
+not been checked for validity.
+
+@item fd_arg_read
+@itemx fd_arg_read (@var{N})
+@cindex @code{fd_arg_read} function attribute
+The @code{fd_arg_read} is identical to @code{fd_arg}, but with the additional
+requirement that it might read from the file descriptor, and thus, the file
+descriptor must not have been opened as write-only.
+
+The analyzer may emit a @option{-Wanalyzer-access-mode-mismatch}
+diagnostic if it detects a code path in which a function with this
+attribute is called on a file descriptor opened with @code{O_WRONLY}.
+
+@item fd_arg_write
+@itemx fd_arg_write (@var{N})
+@cindex @code{fd_arg_write} function attribute
+The @code{fd_arg_write} is identical to @code{fd_arg_read} except that the
+analyzer may emit a @option{-Wanalyzer-access-mode-mismatch} diagnostic if
+it detects a code path in which a function with this attribute is called on a
+file descriptor opened with @code{O_RDONLY}.
+
+@item flatten
+@cindex @code{flatten} function attribute
+Generally, inlining into a function is limited. For a function marked with
+this attribute, every call inside this function is inlined, if possible.
+Functions declared with attribute @code{noinline} and similar are not
+inlined. Whether the function itself is considered for inlining depends
+on its size and the current inlining parameters.
+
+@item format (@var{archetype}, @var{string-index}, @var{first-to-check})
+@cindex @code{format} function attribute
+@cindex functions with @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style arguments
+@opindex Wformat
+The @code{format} attribute specifies that a function takes @code{printf},
+@code{scanf}, @code{strftime} or @code{strfmon} style arguments that
+should be type-checked against a format string. For example, the
+declaration:
+
+@smallexample
+extern int
+my_printf (void *my_object, const char *my_format, ...)
+ __attribute__ ((format (printf, 2, 3)));
+@end smallexample
+
+@noindent
+causes the compiler to check the arguments in calls to @code{my_printf}
+for consistency with the @code{printf} style format string argument
+@code{my_format}.
+
+The parameter @var{archetype} determines how the format string is
+interpreted, and should be @code{printf}, @code{scanf}, @code{strftime},
+@code{gnu_printf}, @code{gnu_scanf}, @code{gnu_strftime} or
+@code{strfmon}. (You can also use @code{__printf__},
+@code{__scanf__}, @code{__strftime__} or @code{__strfmon__}.) On
+MinGW targets, @code{ms_printf}, @code{ms_scanf}, and
+@code{ms_strftime} are also present.
+@var{archetype} values such as @code{printf} refer to the formats accepted
+by the system's C runtime library,
+while values prefixed with @samp{gnu_} always refer
+to the formats accepted by the GNU C Library. On Microsoft Windows
+targets, values prefixed with @samp{ms_} refer to the formats accepted by the
+@file{msvcrt.dll} library.
+The parameter @var{string-index}
+specifies which argument is the format string argument (starting
+from 1), while @var{first-to-check} is the number of the first
+argument to check against the format string. For functions
+where the arguments are not available to be checked (such as
+@code{vprintf}), specify the third parameter as zero. In this case the
+compiler only checks the format string for consistency. For
+@code{strftime} formats, the third parameter is required to be zero.
+Since non-static C++ methods have an implicit @code{this} argument, the
+arguments of such methods should be counted from two, not one, when
+giving values for @var{string-index} and @var{first-to-check}.
+
+In the example above, the format string (@code{my_format}) is the second
+argument of the function @code{my_print}, and the arguments to check
+start with the third argument, so the correct parameters for the format
+attribute are 2 and 3.
+
+@opindex ffreestanding
+@opindex fno-builtin
+The @code{format} attribute allows you to identify your own functions
+that take format strings as arguments, so that GCC can check the
+calls to these functions for errors. The compiler always (unless
+@option{-ffreestanding} or @option{-fno-builtin} is used) checks formats
+for the standard library functions @code{printf}, @code{fprintf},
+@code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime},
+@code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such
+warnings are requested (using @option{-Wformat}), so there is no need to
+modify the header file @file{stdio.h}. In C99 mode, the functions
+@code{snprintf}, @code{vsnprintf}, @code{vscanf}, @code{vfscanf} and
+@code{vsscanf} are also checked. Except in strictly conforming C
+standard modes, the X/Open function @code{strfmon} is also checked as
+are @code{printf_unlocked} and @code{fprintf_unlocked}.
+@xref{C Dialect Options,,Options Controlling C Dialect}.
+
+For Objective-C dialects, @code{NSString} (or @code{__NSString__}) is
+recognized in the same context. Declarations including these format attributes
+are parsed for correct syntax, however the result of checking of such format
+strings is not yet defined, and is not carried out by this version of the
+compiler.
+
+The target may also provide additional types of format checks.
+@xref{Target Format Checks,,Format Checks Specific to Particular
+Target Machines}.
+
+@item format_arg (@var{string-index})
+@cindex @code{format_arg} function attribute
+@opindex Wformat-nonliteral
+The @code{format_arg} attribute specifies that a function takes one or
+more format strings for a @code{printf}, @code{scanf}, @code{strftime} or
+@code{strfmon} style function and modifies it (for example, to translate
+it into another language), so the result can be passed to a
+@code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style
+function (with the remaining arguments to the format function the same
+as they would have been for the unmodified string). Multiple
+@code{format_arg} attributes may be applied to the same function, each
+designating a distinct parameter as a format string. For example, the
+declaration:
+
+@smallexample
+extern char *
+my_dgettext (char *my_domain, const char *my_format)
+ __attribute__ ((format_arg (2)));
+@end smallexample
+
+@noindent
+causes the compiler to check the arguments in calls to a @code{printf},
+@code{scanf}, @code{strftime} or @code{strfmon} type function, whose
+format string argument is a call to the @code{my_dgettext} function, for
+consistency with the format string argument @code{my_format}. If the
+@code{format_arg} attribute had not been specified, all the compiler
+could tell in such calls to format functions would be that the format
+string argument is not constant; this would generate a warning when
+@option{-Wformat-nonliteral} is used, but the calls could not be checked
+without the attribute.
+
+In calls to a function declared with more than one @code{format_arg}
+attribute, each with a distinct argument value, the corresponding
+actual function arguments are checked against all format strings
+designated by the attributes. This capability is designed to support
+the GNU @code{ngettext} family of functions.
+
+The parameter @var{string-index} specifies which argument is the format
+string argument (starting from one). Since non-static C++ methods have
+an implicit @code{this} argument, the arguments of such methods should
+be counted from two.
+
+The @code{format_arg} attribute allows you to identify your own
+functions that modify format strings, so that GCC can check the
+calls to @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon}
+type function whose operands are a call to one of your own function.
+The compiler always treats @code{gettext}, @code{dgettext}, and
+@code{dcgettext} in this manner except when strict ISO C support is
+requested by @option{-ansi} or an appropriate @option{-std} option, or
+@option{-ffreestanding} or @option{-fno-builtin}
+is used. @xref{C Dialect Options,,Options
+Controlling C Dialect}.
+
+For Objective-C dialects, the @code{format-arg} attribute may refer to an
+@code{NSString} reference for compatibility with the @code{format} attribute
+above.
+
+The target may also allow additional types in @code{format-arg} attributes.
+@xref{Target Format Checks,,Format Checks Specific to Particular
+Target Machines}.
+
+@item gnu_inline
+@cindex @code{gnu_inline} function attribute
+This attribute should be used with a function that is also declared
+with the @code{inline} keyword. It directs GCC to treat the function
+as if it were defined in gnu90 mode even when compiling in C99 or
+gnu99 mode.
+
+If the function is declared @code{extern}, then this definition of the
+function is used only for inlining. In no case is the function
+compiled as a standalone function, not even if you take its address
+explicitly. Such an address becomes an external reference, as if you
+had only declared the function, and had not defined it. This has
+almost the effect of a macro. The way to use this is to put a
+function definition in a header file with this attribute, and put
+another copy of the function, without @code{extern}, in a library
+file. The definition in the header file causes most calls to the
+function to be inlined. If any uses of the function remain, they
+refer to the single copy in the library. Note that the two
+definitions of the functions need not be precisely the same, although
+if they do not have the same effect your program may behave oddly.
+
+In C, if the function is neither @code{extern} nor @code{static}, then
+the function is compiled as a standalone function, as well as being
+inlined where possible.
+
+This is how GCC traditionally handled functions declared
+@code{inline}. Since ISO C99 specifies a different semantics for
+@code{inline}, this function attribute is provided as a transition
+measure and as a useful feature in its own right. This attribute is
+available in GCC 4.1.3 and later. It is available if either of the
+preprocessor macros @code{__GNUC_GNU_INLINE__} or
+@code{__GNUC_STDC_INLINE__} are defined. @xref{Inline,,An Inline
+Function is As Fast As a Macro}.
+
+In C++, this attribute does not depend on @code{extern} in any way,
+but it still requires the @code{inline} keyword to enable its special
+behavior.
+
+@item hot
+@cindex @code{hot} function attribute
+The @code{hot} attribute on a function is used to inform the compiler that
+the function is a hot spot of the compiled program. The function is
+optimized more aggressively and on many targets it is placed into a special
+subsection of the text section so all hot functions appear close together,
+improving locality.
+
+When profile feedback is available, via @option{-fprofile-use}, hot functions
+are automatically detected and this attribute is ignored.
+
+@item ifunc ("@var{resolver}")
+@cindex @code{ifunc} function attribute
+@cindex indirect functions
+@cindex functions that are dynamically resolved
+The @code{ifunc} attribute is used to mark a function as an indirect
+function using the STT_GNU_IFUNC symbol type extension to the ELF
+standard. This allows the resolution of the symbol value to be
+determined dynamically at load time, and an optimized version of the
+routine to be selected for the particular processor or other system
+characteristics determined then. To use this attribute, first define
+the implementation functions available, and a resolver function that
+returns a pointer to the selected implementation function. The
+implementation functions' declarations must match the API of the
+function being implemented. The resolver should be declared to
+be a function taking no arguments and returning a pointer to
+a function of the same type as the implementation. For example:
+
+@smallexample
+void *my_memcpy (void *dst, const void *src, size_t len)
+@{
+ @dots{}
+ return dst;
+@}
+
+static void * (*resolve_memcpy (void))(void *, const void *, size_t)
+@{
+ return my_memcpy; // we will just always select this routine
+@}
+@end smallexample
+
+@noindent
+The exported header file declaring the function the user calls would
+contain:
+
+@smallexample
+extern void *memcpy (void *, const void *, size_t);
+@end smallexample
+
+@noindent
+allowing the user to call @code{memcpy} as a regular function, unaware of
+the actual implementation. Finally, the indirect function needs to be
+defined in the same translation unit as the resolver function:
+
+@smallexample
+void *memcpy (void *, const void *, size_t)
+ __attribute__ ((ifunc ("resolve_memcpy")));
+@end smallexample
+
+In C++, the @code{ifunc} attribute takes a string that is the mangled name
+of the resolver function. A C++ resolver for a non-static member function
+of class @code{C} should be declared to return a pointer to a non-member
+function taking pointer to @code{C} as the first argument, followed by
+the same arguments as of the implementation function. G++ checks
+the signatures of the two functions and issues
+a @option{-Wattribute-alias} warning for mismatches. To suppress a warning
+for the necessary cast from a pointer to the implementation member function
+to the type of the corresponding non-member function use
+the @option{-Wno-pmf-conversions} option. For example:
+
+@smallexample
+class S
+@{
+private:
+ int debug_impl (int);
+ int optimized_impl (int);
+
+ typedef int Func (S*, int);
+
+ static Func* resolver ();
+public:
+
+ int interface (int);
+@};
+
+int S::debug_impl (int) @{ /* @r{@dots{}} */ @}
+int S::optimized_impl (int) @{ /* @r{@dots{}} */ @}
+
+S::Func* S::resolver ()
+@{
+ int (S::*pimpl) (int)
+ = getenv ("DEBUG") ? &S::debug_impl : &S::optimized_impl;
+
+ // Cast triggers -Wno-pmf-conversions.
+ return reinterpret_cast<Func*>(pimpl);
+@}
+
+int S::interface (int) __attribute__ ((ifunc ("_ZN1S8resolverEv")));
+@end smallexample
+
+Indirect functions cannot be weak. Binutils version 2.20.1 or higher
+and GNU C Library version 2.11.1 are required to use this feature.
+
+@item interrupt
+@itemx interrupt_handler
+Many GCC back ends support attributes to indicate that a function is
+an interrupt handler, which tells the compiler to generate function
+entry and exit sequences that differ from those from regular
+functions. The exact syntax and behavior are target-specific;
+refer to the following subsections for details.
+
+@item leaf
+@cindex @code{leaf} function attribute
+Calls to external functions with this attribute must return to the
+current compilation unit only by return or by exception handling. In
+particular, a leaf function is not allowed to invoke callback functions
+passed to it from the current compilation unit, directly call functions
+exported by the unit, or @code{longjmp} into the unit. Leaf functions
+might still call functions from other compilation units and thus they
+are not necessarily leaf in the sense that they contain no function
+calls at all.
+
+The attribute is intended for library functions to improve dataflow
+analysis. The compiler takes the hint that any data not escaping the
+current compilation unit cannot be used or modified by the leaf
+function. For example, the @code{sin} function is a leaf function, but
+@code{qsort} is not.
+
+Note that leaf functions might indirectly run a signal handler defined
+in the current compilation unit that uses static variables. Similarly,
+when lazy symbol resolution is in effect, leaf functions might invoke
+indirect functions whose resolver function or implementation function is
+defined in the current compilation unit and uses static variables. There
+is no standard-compliant way to write such a signal handler, resolver
+function, or implementation function, and the best that you can do is to
+remove the @code{leaf} attribute or mark all such static variables
+@code{volatile}. Lastly, for ELF-based systems that support symbol
+interposition, care should be taken that functions defined in the
+current compilation unit do not unexpectedly interpose other symbols
+based on the defined standards mode and defined feature test macros;
+otherwise an inadvertent callback would be added.
+
+The attribute has no effect on functions defined within the current
+compilation unit. This is to allow easy merging of multiple compilation
+units into one, for example, by using the link-time optimization. For
+this reason the attribute is not allowed on types to annotate indirect
+calls.
+
+@item malloc
+@item malloc (@var{deallocator})
+@item malloc (@var{deallocator}, @var{ptr-index})
+@cindex @code{malloc} function attribute
+@cindex functions that behave like malloc
+Attribute @code{malloc} indicates that a function is @code{malloc}-like,
+i.e., that the pointer @var{P} returned by the function cannot alias any
+other pointer valid when the function returns, and moreover no
+pointers to valid objects occur in any storage addressed by @var{P}. In
+addition, the GCC predicts that a function with the attribute returns
+non-null in most cases.
+
+Independently, the form of the attribute with one or two arguments
+associates @code{deallocator} as a suitable deallocation function for
+pointers returned from the @code{malloc}-like function. @var{ptr-index}
+denotes the positional argument to which when the pointer is passed in
+calls to @code{deallocator} has the effect of deallocating it.
+
+Using the attribute with no arguments is designed to improve optimization
+by relying on the aliasing property it implies. Functions like @code{malloc}
+and @code{calloc} have this property because they return a pointer to
+uninitialized or zeroed-out, newly obtained storage. However, functions
+like @code{realloc} do not have this property, as they may return pointers
+to storage containing pointers to existing objects. Additionally, since
+all such functions are assumed to return null only infrequently, callers
+can be optimized based on that assumption.
+
+Associating a function with a @var{deallocator} helps detect calls to
+mismatched allocation and deallocation functions and diagnose them under
+the control of options such as @option{-Wmismatched-dealloc}. It also
+makes it possible to diagnose attempts to deallocate objects that were not
+allocated dynamically, by @option{-Wfree-nonheap-object}. To indicate
+that an allocation function both satisifies the nonaliasing property and
+has a deallocator associated with it, both the plain form of the attribute
+and the one with the @var{deallocator} argument must be used. The same
+function can be both an allocator and a deallocator. Since inlining one
+of the associated functions but not the other could result in apparent
+mismatches, this form of attribute @code{malloc} is not accepted on inline
+functions. For the same reason, using the attribute prevents both
+the allocation and deallocation functions from being expanded inline.
+
+For example, besides stating that the functions return pointers that do
+not alias any others, the following declarations make @code{fclose}
+a suitable deallocator for pointers returned from all functions except
+@code{popen}, and @code{pclose} as the only suitable deallocator for
+pointers returned from @code{popen}. The deallocator functions must
+be declared before they can be referenced in the attribute.
+
+@smallexample
+int fclose (FILE*);
+int pclose (FILE*);
+
+__attribute__ ((malloc, malloc (fclose, 1)))
+ FILE* fdopen (int, const char*);
+__attribute__ ((malloc, malloc (fclose, 1)))
+ FILE* fopen (const char*, const char*);
+__attribute__ ((malloc, malloc (fclose, 1)))
+ FILE* fmemopen(void *, size_t, const char *);
+__attribute__ ((malloc, malloc (pclose, 1)))
+ FILE* popen (const char*, const char*);
+__attribute__ ((malloc, malloc (fclose, 1)))
+ FILE* tmpfile (void);
+@end smallexample
+
+The warnings guarded by @option{-fanalyzer} respect allocation and
+deallocation pairs marked with the @code{malloc}. In particular:
+
+@itemize @bullet
+
+@item
+The analyzer will emit a @option{-Wanalyzer-mismatching-deallocation}
+diagnostic if there is an execution path in which the result of an
+allocation call is passed to a different deallocator.
+
+@item
+The analyzer will emit a @option{-Wanalyzer-double-free}
+diagnostic if there is an execution path in which a value is passed
+more than once to a deallocation call.
+
+@item
+The analyzer will consider the possibility that an allocation function
+could fail and return NULL. It will emit
+@option{-Wanalyzer-possible-null-dereference} and
+@option{-Wanalyzer-possible-null-argument} diagnostics if there are
+execution paths in which an unchecked result of an allocation call is
+dereferenced or passed to a function requiring a non-null argument.
+If the allocator always returns non-null, use
+@code{__attribute__ ((returns_nonnull))} to suppress these warnings.
+For example:
+@smallexample
+char *xstrdup (const char *)
+ __attribute__((malloc (free), returns_nonnull));
+@end smallexample
+
+@item
+The analyzer will emit a @option{-Wanalyzer-use-after-free}
+diagnostic if there is an execution path in which the memory passed
+by pointer to a deallocation call is used after the deallocation.
+
+@item
+The analyzer will emit a @option{-Wanalyzer-malloc-leak} diagnostic if
+there is an execution path in which the result of an allocation call
+is leaked (without being passed to the deallocation function).
+
+@item
+The analyzer will emit a @option{-Wanalyzer-free-of-non-heap} diagnostic
+if a deallocation function is used on a global or on-stack variable.
+
+@end itemize
+
+The analyzer assumes that deallocators can gracefully handle the @code{NULL}
+pointer. If this is not the case, the deallocator can be marked with
+@code{__attribute__((nonnull))} so that @option{-fanalyzer} can emit
+a @option{-Wanalyzer-possible-null-argument} diagnostic for code paths
+in which the deallocator is called with NULL.
+
+@item no_icf
+@cindex @code{no_icf} function attribute
+This function attribute prevents a functions from being merged with another
+semantically equivalent function.
+
+@item no_instrument_function
+@cindex @code{no_instrument_function} function attribute
+@opindex finstrument-functions
+@opindex p
+@opindex pg
+If any of @option{-finstrument-functions}, @option{-p}, or @option{-pg} are
+given, profiling function calls are
+generated at entry and exit of most user-compiled functions.
+Functions with this attribute are not so instrumented.
+
+@item no_profile_instrument_function
+@cindex @code{no_profile_instrument_function} function attribute
+The @code{no_profile_instrument_function} attribute on functions is used
+to inform the compiler that it should not process any profile feedback based
+optimization code instrumentation.
+
+@item no_reorder
+@cindex @code{no_reorder} function attribute
+Do not reorder functions or variables marked @code{no_reorder}
+against each other or top level assembler statements the executable.
+The actual order in the program will depend on the linker command
+line. Static variables marked like this are also not removed.
+This has a similar effect
+as the @option{-fno-toplevel-reorder} option, but only applies to the
+marked symbols.
+
+@item no_sanitize ("@var{sanitize_option}")
+@cindex @code{no_sanitize} function attribute
+The @code{no_sanitize} attribute on functions is used
+to inform the compiler that it should not do sanitization of any option
+mentioned in @var{sanitize_option}. A list of values acceptable by
+the @option{-fsanitize} option can be provided.
+
+@smallexample
+void __attribute__ ((no_sanitize ("alignment", "object-size")))
+f () @{ /* @r{Do something.} */; @}
+void __attribute__ ((no_sanitize ("alignment,object-size")))
+g () @{ /* @r{Do something.} */; @}
+@end smallexample
+
+@item no_sanitize_address
+@itemx no_address_safety_analysis
+@cindex @code{no_sanitize_address} function attribute
+The @code{no_sanitize_address} attribute on functions is used
+to inform the compiler that it should not instrument memory accesses
+in the function when compiling with the @option{-fsanitize=address} option.
+The @code{no_address_safety_analysis} is a deprecated alias of the
+@code{no_sanitize_address} attribute, new code should use
+@code{no_sanitize_address}.
+
+@item no_sanitize_thread
+@cindex @code{no_sanitize_thread} function attribute
+The @code{no_sanitize_thread} attribute on functions is used
+to inform the compiler that it should not instrument memory accesses
+in the function when compiling with the @option{-fsanitize=thread} option.
+
+@item no_sanitize_undefined
+@cindex @code{no_sanitize_undefined} function attribute
+The @code{no_sanitize_undefined} attribute on functions is used
+to inform the compiler that it should not check for undefined behavior
+in the function when compiling with the @option{-fsanitize=undefined} option.
+
+@item no_sanitize_coverage
+@cindex @code{no_sanitize_coverage} function attribute
+The @code{no_sanitize_coverage} attribute on functions is used
+to inform the compiler that it should not do coverage-guided
+fuzzing code instrumentation (@option{-fsanitize-coverage}).
+
+@item no_split_stack
+@cindex @code{no_split_stack} function attribute
+@opindex fsplit-stack
+If @option{-fsplit-stack} is given, functions have a small
+prologue which decides whether to split the stack. Functions with the
+@code{no_split_stack} attribute do not have that prologue, and thus
+may run with only a small amount of stack space available.
+
+@item no_stack_limit
+@cindex @code{no_stack_limit} function attribute
+This attribute locally overrides the @option{-fstack-limit-register}
+and @option{-fstack-limit-symbol} command-line options; it has the effect
+of disabling stack limit checking in the function it applies to.
+
+@item noclone
+@cindex @code{noclone} function attribute
+This function attribute prevents a function from being considered for
+cloning---a mechanism that produces specialized copies of functions
+and which is (currently) performed by interprocedural constant
+propagation.
+
+@item noinline
+@cindex @code{noinline} function attribute
+This function attribute prevents a function from being considered for
+inlining.
+@c Don't enumerate the optimizations by name here; we try to be
+@c future-compatible with this mechanism.
+If the function does not have side effects, there are optimizations
+other than inlining that cause function calls to be optimized away,
+although the function call is live. To keep such calls from being
+optimized away, put
+@smallexample
+asm ("");
+@end smallexample
+
+@noindent
+(@pxref{Extended Asm}) in the called function, to serve as a special
+side effect.
+
+@item noipa
+@cindex @code{noipa} function attribute
+Disable interprocedural optimizations between the function with this
+attribute and its callers, as if the body of the function is not available
+when optimizing callers and the callers are unavailable when optimizing
+the body. This attribute implies @code{noinline}, @code{noclone} and
+@code{no_icf} attributes. However, this attribute is not equivalent
+to a combination of other attributes, because its purpose is to suppress
+existing and future optimizations employing interprocedural analysis,
+including those that do not have an attribute suitable for disabling
+them individually. This attribute is supported mainly for the purpose
+of testing the compiler.
+
+@item nonnull
+@itemx nonnull (@var{arg-index}, @dots{})
+@cindex @code{nonnull} function attribute
+@cindex functions with non-null pointer arguments
+The @code{nonnull} attribute may be applied to a function that takes at
+least one argument of a pointer type. It indicates that the referenced
+arguments must be non-null pointers. For instance, the declaration:
+
+@smallexample
+extern void *
+my_memcpy (void *dest, const void *src, size_t len)
+ __attribute__((nonnull (1, 2)));
+@end smallexample
+
+@noindent
+informs the compiler that, in calls to @code{my_memcpy}, arguments
+@var{dest} and @var{src} must be non-null.
+
+The attribute has an effect both on functions calls and function definitions.
+
+For function calls:
+@itemize @bullet
+@item If the compiler determines that a null pointer is
+passed in an argument slot marked as non-null, and the
+@option{-Wnonnull} option is enabled, a warning is issued.
+@xref{Warning Options}.
+@item The @option{-fisolate-erroneous-paths-attribute} option can be
+specified to have GCC transform calls with null arguments to non-null
+functions into traps. @xref{Optimize Options}.
+@item The compiler may also perform optimizations based on the
+knowledge that certain function arguments cannot be null. These
+optimizations can be disabled by the
+@option{-fno-delete-null-pointer-checks} option. @xref{Optimize Options}.
+@end itemize
+
+For function definitions:
+@itemize @bullet
+@item If the compiler determines that a function parameter that is
+marked with nonnull is compared with null, and
+@option{-Wnonnull-compare} option is enabled, a warning is issued.
+@xref{Warning Options}.
+@item The compiler may also perform optimizations based on the
+knowledge that @code{nonnul} parameters cannot be null. This can
+currently not be disabled other than by removing the nonnull
+attribute.
+@end itemize
+
+If no @var{arg-index} is given to the @code{nonnull} attribute,
+all pointer arguments are marked as non-null. To illustrate, the
+following declaration is equivalent to the previous example:
+
+@smallexample
+extern void *
+my_memcpy (void *dest, const void *src, size_t len)
+ __attribute__((nonnull));
+@end smallexample
+
+@item noplt
+@cindex @code{noplt} function attribute
+The @code{noplt} attribute is the counterpart to option @option{-fno-plt}.
+Calls to functions marked with this attribute in position-independent code
+do not use the PLT.
+
+@smallexample
+@group
+/* Externally defined function foo. */
+int foo () __attribute__ ((noplt));
+
+int
+main (/* @r{@dots{}} */)
+@{
+ /* @r{@dots{}} */
+ foo ();
+ /* @r{@dots{}} */
+@}
+@end group
+@end smallexample
+
+The @code{noplt} attribute on function @code{foo}
+tells the compiler to assume that
+the function @code{foo} is externally defined and that the call to
+@code{foo} must avoid the PLT
+in position-independent code.
+
+In position-dependent code, a few targets also convert calls to
+functions that are marked to not use the PLT to use the GOT instead.
+
+@item noreturn
+@cindex @code{noreturn} function attribute
+@cindex functions that never return
+A few standard library functions, such as @code{abort} and @code{exit},
+cannot return. GCC knows this automatically. Some programs define
+their own functions that never return. You can declare them
+@code{noreturn} to tell the compiler this fact. For example,
+
+@smallexample
+@group
+void fatal () __attribute__ ((noreturn));
+
+void
+fatal (/* @r{@dots{}} */)
+@{
+ /* @r{@dots{}} */ /* @r{Print error message.} */ /* @r{@dots{}} */
+ exit (1);
+@}
+@end group
+@end smallexample
+
+The @code{noreturn} keyword tells the compiler to assume that
+@code{fatal} cannot return. It can then optimize without regard to what
+would happen if @code{fatal} ever did return. This makes slightly
+better code. More importantly, it helps avoid spurious warnings of
+uninitialized variables.
+
+The @code{noreturn} keyword does not affect the exceptional path when that
+applies: a @code{noreturn}-marked function may still return to the caller
+by throwing an exception or calling @code{longjmp}.
+
+In order to preserve backtraces, GCC will never turn calls to
+@code{noreturn} functions into tail calls.
+
+Do not assume that registers saved by the calling function are
+restored before calling the @code{noreturn} function.
+
+It does not make sense for a @code{noreturn} function to have a return
+type other than @code{void}.
+
+@item nothrow
+@cindex @code{nothrow} function attribute
+The @code{nothrow} attribute is used to inform the compiler that a
+function cannot throw an exception. For example, most functions in
+the standard C library can be guaranteed not to throw an exception
+with the notable exceptions of @code{qsort} and @code{bsearch} that
+take function pointer arguments.
+
+@item optimize (@var{level}, @dots{})
+@item optimize (@var{string}, @dots{})
+@cindex @code{optimize} function attribute
+The @code{optimize} attribute is used to specify that a function is to
+be compiled with different optimization options than specified on the
+command line. The optimize attribute arguments of a function behave
+behave as if appended to the command-line.
+
+Valid arguments are constant non-negative integers and
+strings. Each numeric argument specifies an optimization @var{level}.
+Each @var{string} argument consists of one or more comma-separated
+substrings. Each substring that begins with the letter @code{O} refers
+to an optimization option such as @option{-O0} or @option{-Os}. Other
+substrings are taken as suffixes to the @code{-f} prefix jointly
+forming the name of an optimization option. @xref{Optimize Options}.
+
+@samp{#pragma GCC optimize} can be used to set optimization options
+for more than one function. @xref{Function Specific Option Pragmas},
+for details about the pragma.
+
+Providing multiple strings as arguments separated by commas to specify
+multiple options is equivalent to separating the option suffixes with
+a comma (@samp{,}) within a single string. Spaces are not permitted
+within the strings.
+
+Not every optimization option that starts with the @var{-f} prefix
+specified by the attribute necessarily has an effect on the function.
+The @code{optimize} attribute should be used for debugging purposes only.
+It is not suitable in production code.
+
+@item patchable_function_entry
+@cindex @code{patchable_function_entry} function attribute
+@cindex extra NOP instructions at the function entry point
+In case the target's text segment can be made writable at run time by
+any means, padding the function entry with a number of NOPs can be
+used to provide a universal tool for instrumentation.
+
+The @code{patchable_function_entry} function attribute can be used to
+change the number of NOPs to any desired value. The two-value syntax
+is the same as for the command-line switch
+@option{-fpatchable-function-entry=N,M}, generating @var{N} NOPs, with
+the function entry point before the @var{M}th NOP instruction.
+@var{M} defaults to 0 if omitted e.g.@: function entry point is before
+the first NOP.
+
+If patchable function entries are enabled globally using the command-line
+option @option{-fpatchable-function-entry=N,M}, then you must disable
+instrumentation on all functions that are part of the instrumentation
+framework with the attribute @code{patchable_function_entry (0)}
+to prevent recursion.
+
+@item pure
+@cindex @code{pure} function attribute
+@cindex functions that have no side effects
+
+Calls to functions that have no observable effects on the state of
+the program other than to return a value may lend themselves to optimizations
+such as common subexpression elimination. Declaring such functions with
+the @code{pure} attribute allows GCC to avoid emitting some calls in repeated
+invocations of the function with the same argument values.
+
+The @code{pure} attribute prohibits a function from modifying the state
+of the program that is observable by means other than inspecting
+the function's return value. However, functions declared with the @code{pure}
+attribute can safely read any non-volatile objects, and modify the value of
+objects in a way that does not affect their return value or the observable
+state of the program.
+
+For example,
+
+@smallexample
+int hash (char *) __attribute__ ((pure));
+@end smallexample
+
+@noindent
+tells GCC that subsequent calls to the function @code{hash} with the same
+string can be replaced by the result of the first call provided the state
+of the program observable by @code{hash}, including the contents of the array
+itself, does not change in between. Even though @code{hash} takes a non-const
+pointer argument it must not modify the array it points to, or any other object
+whose value the rest of the program may depend on. However, the caller may
+safely change the contents of the array between successive calls to
+the function (doing so disables the optimization). The restriction also
+applies to member objects referenced by the @code{this} pointer in C++
+non-static member functions.
+
+Some common examples of pure functions are @code{strlen} or @code{memcmp}.
+Interesting non-pure functions are functions with infinite loops or those
+depending on volatile memory or other system resource, that may change between
+consecutive calls (such as the standard C @code{feof} function in
+a multithreading environment).
+
+The @code{pure} attribute imposes similar but looser restrictions on
+a function's definition than the @code{const} attribute: @code{pure}
+allows the function to read any non-volatile memory, even if it changes
+in between successive invocations of the function. Declaring the same
+function with both the @code{pure} and the @code{const} attribute is
+diagnosed. Because a pure function cannot have any observable side
+effects it does not make sense for such a function to return @code{void}.
+Declaring such a function is diagnosed.
+
+@item returns_nonnull
+@cindex @code{returns_nonnull} function attribute
+The @code{returns_nonnull} attribute specifies that the function
+return value should be a non-null pointer. For instance, the declaration:
+
+@smallexample
+extern void *
+mymalloc (size_t len) __attribute__((returns_nonnull));
+@end smallexample
+
+@noindent
+lets the compiler optimize callers based on the knowledge
+that the return value will never be null.
+
+@item returns_twice
+@cindex @code{returns_twice} function attribute
+@cindex functions that return more than once
+The @code{returns_twice} attribute tells the compiler that a function may
+return more than one time. The compiler ensures that all registers
+are dead before calling such a function and emits a warning about
+the variables that may be clobbered after the second return from the
+function. Examples of such functions are @code{setjmp} and @code{vfork}.
+The @code{longjmp}-like counterpart of such function, if any, might need
+to be marked with the @code{noreturn} attribute.
+
+@item section ("@var{section-name}")
+@cindex @code{section} function attribute
+@cindex functions in arbitrary sections
+Normally, the compiler places the code it generates in the @code{text} section.
+Sometimes, however, you need additional sections, or you need certain
+particular functions to appear in special sections. The @code{section}
+attribute specifies that a function lives in a particular section.
+For example, the declaration:
+
+@smallexample
+extern void foobar (void) __attribute__ ((section ("bar")));
+@end smallexample
+
+@noindent
+puts the function @code{foobar} in the @code{bar} section.
+
+Some file formats do not support arbitrary sections so the @code{section}
+attribute is not available on all platforms.
+If you need to map the entire contents of a module to a particular
+section, consider using the facilities of the linker instead.
+
+@item sentinel
+@itemx sentinel (@var{position})
+@cindex @code{sentinel} function attribute
+This function attribute indicates that an argument in a call to the function
+is expected to be an explicit @code{NULL}. The attribute is only valid on
+variadic functions. By default, the sentinel is expected to be the last
+argument of the function call. If the optional @var{position} argument
+is specified to the attribute, the sentinel must be located at
+@var{position} counting backwards from the end of the argument list.
+
+@smallexample
+__attribute__ ((sentinel))
+is equivalent to
+__attribute__ ((sentinel(0)))
+@end smallexample
+
+The attribute is automatically set with a position of 0 for the built-in
+functions @code{execl} and @code{execlp}. The built-in function
+@code{execle} has the attribute set with a position of 1.
+
+A valid @code{NULL} in this context is defined as zero with any object
+pointer type. If your system defines the @code{NULL} macro with
+an integer type then you need to add an explicit cast. During
+installation GCC replaces the system @code{<stddef.h>} header with
+a copy that redefines NULL appropriately.
+
+The warnings for missing or incorrect sentinels are enabled with
+@option{-Wformat}.
+
+@item simd
+@itemx simd("@var{mask}")
+@cindex @code{simd} function attribute
+This attribute enables creation of one or more function versions that
+can process multiple arguments using SIMD instructions from a
+single invocation. Specifying this attribute allows compiler to
+assume that such versions are available at link time (provided
+in the same or another translation unit). Generated versions are
+target-dependent and described in the corresponding Vector ABI document. For
+x86_64 target this document can be found
+@w{@uref{https://sourceware.org/glibc/wiki/libmvec?action=AttachFile&do=view&target=VectorABI.txt,here}}.
+
+The optional argument @var{mask} may have the value
+@code{notinbranch} or @code{inbranch},
+and instructs the compiler to generate non-masked or masked
+clones correspondingly. By default, all clones are generated.
+
+If the attribute is specified and @code{#pragma omp declare simd} is
+present on a declaration and the @option{-fopenmp} or @option{-fopenmp-simd}
+switch is specified, then the attribute is ignored.
+
+@item stack_protect
+@cindex @code{stack_protect} function attribute
+This attribute adds stack protection code to the function if
+flags @option{-fstack-protector}, @option{-fstack-protector-strong}
+or @option{-fstack-protector-explicit} are set.
+
+@item no_stack_protector
+@cindex @code{no_stack_protector} function attribute
+This attribute prevents stack protection code for the function.
+
+@item target (@var{string}, @dots{})
+@cindex @code{target} function attribute
+Multiple target back ends implement the @code{target} attribute
+to specify that a function is to
+be compiled with different target options than specified on the
+command line. The original target command-line options are ignored.
+One or more strings can be provided as arguments.
+Each string consists of one or more comma-separated suffixes to
+the @code{-m} prefix jointly forming the name of a machine-dependent
+option. @xref{Submodel Options,,Machine-Dependent Options}.
+
+The @code{target} attribute can be used for instance to have a function
+compiled with a different ISA (instruction set architecture) than the
+default. @samp{#pragma GCC target} can be used to specify target-specific
+options for more than one function. @xref{Function Specific Option Pragmas},
+for details about the pragma.
+
+For instance, on an x86, you could declare one function with the
+@code{target("sse4.1,arch=core2")} attribute and another with
+@code{target("sse4a,arch=amdfam10")}. This is equivalent to
+compiling the first function with @option{-msse4.1} and
+@option{-march=core2} options, and the second function with
+@option{-msse4a} and @option{-march=amdfam10} options. It is up to you
+to make sure that a function is only invoked on a machine that
+supports the particular ISA it is compiled for (for example by using
+@code{cpuid} on x86 to determine what feature bits and architecture
+family are used).
+
+@smallexample
+int core2_func (void) __attribute__ ((__target__ ("arch=core2")));
+int sse3_func (void) __attribute__ ((__target__ ("sse3")));
+@end smallexample
+
+Providing multiple strings as arguments separated by commas to specify
+multiple options is equivalent to separating the option suffixes with
+a comma (@samp{,}) within a single string. Spaces are not permitted
+within the strings.
+
+The options supported are specific to each target; refer to @ref{x86
+Function Attributes}, @ref{PowerPC Function Attributes},
+@ref{ARM Function Attributes}, @ref{AArch64 Function Attributes},
+@ref{Nios II Function Attributes}, and @ref{S/390 Function Attributes}
+for details.
+
+@item symver ("@var{name2}@@@var{nodename}")
+@cindex @code{symver} function attribute
+On ELF targets this attribute creates a symbol version. The @var{name2} part
+of the parameter is the actual name of the symbol by which it will be
+externally referenced. The @code{nodename} portion should be the name of a
+node specified in the version script supplied to the linker when building a
+shared library. Versioned symbol must be defined and must be exported with
+default visibility.
+
+@smallexample
+__attribute__ ((__symver__ ("foo@@VERS_1"))) int
+foo_v1 (void)
+@{
+@}
+@end smallexample
+
+Will produce a @code{.symver foo_v1, foo@@VERS_1} directive in the assembler
+output.
+
+One can also define multiple version for a given symbol
+(starting from binutils 2.35).
+
+@smallexample
+__attribute__ ((__symver__ ("foo@@VERS_2"), __symver__ ("foo@@VERS_3")))
+int symver_foo_v1 (void)
+@{
+@}
+@end smallexample
+
+This example creates a symbol name @code{symver_foo_v1}
+which will be version @code{VERS_2} and @code{VERS_3} of @code{foo}.
+
+If you have an older release of binutils, then symbol alias needs to
+be used:
+
+@smallexample
+__attribute__ ((__symver__ ("foo@@VERS_2")))
+int foo_v1 (void)
+@{
+ return 0;
+@}
+
+__attribute__ ((__symver__ ("foo@@VERS_3")))
+__attribute__ ((alias ("foo_v1")))
+int symver_foo_v1 (void);
+@end smallexample
+
+Finally if the parameter is @code{"@var{name2}@@@@@var{nodename}"} then in
+addition to creating a symbol version (as if
+@code{"@var{name2}@@@var{nodename}"} was used) the version will be also used
+to resolve @var{name2} by the linker.
+
+@item tainted_args
+@cindex @code{tainted_args} function attribute
+The @code{tainted_args} attribute is used to specify that a function is called
+in a way that requires sanitization of its arguments, such as a system
+call in an operating system kernel. Such a function can be considered part
+of the ``attack surface'' of the program. The attribute can be used both
+on function declarations, and on field declarations containing function
+pointers. In the latter case, any function used as an initializer of
+such a callback field will be treated as being called with tainted
+arguments.
+
+The analyzer will pay particular attention to such functions when both
+@option{-fanalyzer} and @option{-fanalyzer-checker=taint} are supplied,
+potentially issuing warnings guarded by
+@option{-Wanalyzer-tainted-allocation-size},
+@option{-Wanalyzer-tainted-array-index},
+@option{-Wanalyzer-tainted-divisor},
+@option{-Wanalyzer-tainted-offset},
+and @option{-Wanalyzer-tainted-size}.
+
+@item target_clones (@var{options})
+@cindex @code{target_clones} function attribute
+The @code{target_clones} attribute is used to specify that a function
+be cloned into multiple versions compiled with different target options
+than specified on the command line. The supported options and restrictions
+are the same as for @code{target} attribute.
+
+For instance, on an x86, you could compile a function with
+@code{target_clones("sse4.1,avx")}. GCC creates two function clones,
+one compiled with @option{-msse4.1} and another with @option{-mavx}.
+
+On a PowerPC, you can compile a function with
+@code{target_clones("cpu=power9,default")}. GCC will create two
+function clones, one compiled with @option{-mcpu=power9} and another
+with the default options. GCC must be configured to use GLIBC 2.23 or
+newer in order to use the @code{target_clones} attribute.
+
+It also creates a resolver function (see
+the @code{ifunc} attribute above) that dynamically selects a clone
+suitable for current architecture. The resolver is created only if there
+is a usage of a function with @code{target_clones} attribute.
+
+Note that any subsequent call of a function without @code{target_clone}
+from a @code{target_clone} caller will not lead to copying
+(target clone) of the called function.
+If you want to enforce such behaviour,
+we recommend declaring the calling function with the @code{flatten} attribute?
+
+@item unused
+@cindex @code{unused} function attribute
+This attribute, attached to a function, means that the function is meant
+to be possibly unused. GCC does not produce a warning for this
+function.
+
+@item used
+@cindex @code{used} function attribute
+This attribute, attached to a function, means that code must be emitted
+for the function even if it appears that the function is not referenced.
+This is useful, for example, when the function is referenced only in
+inline assembly.
+
+When applied to a member function of a C++ class template, the
+attribute also means that the function is instantiated if the
+class itself is instantiated.
+
+@item retain
+@cindex @code{retain} function attribute
+For ELF targets that support the GNU or FreeBSD OSABIs, this attribute
+will save the function from linker garbage collection. To support
+this behavior, functions that have not been placed in specific sections
+(e.g. by the @code{section} attribute, or the @code{-ffunction-sections}
+option), will be placed in new, unique sections.
+
+This additional functionality requires Binutils version 2.36 or later.
+
+@item visibility ("@var{visibility_type}")
+@cindex @code{visibility} function attribute
+This attribute affects the linkage of the declaration to which it is attached.
+It can be applied to variables (@pxref{Common Variable Attributes}) and types
+(@pxref{Common Type Attributes}) as well as functions.
+
+There are four supported @var{visibility_type} values: default,
+hidden, protected or internal visibility.
+
+@smallexample
+void __attribute__ ((visibility ("protected")))
+f () @{ /* @r{Do something.} */; @}
+int i __attribute__ ((visibility ("hidden")));
+@end smallexample
+
+The possible values of @var{visibility_type} correspond to the
+visibility settings in the ELF gABI.
+
+@table @code
+@c keep this list of visibilities in alphabetical order.
+
+@item default
+Default visibility is the normal case for the object file format.
+This value is available for the visibility attribute to override other
+options that may change the assumed visibility of entities.
+
+On ELF, default visibility means that the declaration is visible to other
+modules and, in shared libraries, means that the declared entity may be
+overridden.
+
+On Darwin, default visibility means that the declaration is visible to
+other modules.
+
+Default visibility corresponds to ``external linkage'' in the language.
+
+@item hidden
+Hidden visibility indicates that the entity declared has a new
+form of linkage, which we call ``hidden linkage''. Two
+declarations of an object with hidden linkage refer to the same object
+if they are in the same shared object.
+
+@item internal
+Internal visibility is like hidden visibility, but with additional
+processor specific semantics. Unless otherwise specified by the
+psABI, GCC defines internal visibility to mean that a function is
+@emph{never} called from another module. Compare this with hidden
+functions which, while they cannot be referenced directly by other
+modules, can be referenced indirectly via function pointers. By
+indicating that a function cannot be called from outside the module,
+GCC may for instance omit the load of a PIC register since it is known
+that the calling function loaded the correct value.
+
+@item protected
+Protected visibility is like default visibility except that it
+indicates that references within the defining module bind to the
+definition in that module. That is, the declared entity cannot be
+overridden by another module.
+
+@end table
+
+All visibilities are supported on many, but not all, ELF targets
+(supported when the assembler supports the @samp{.visibility}
+pseudo-op). Default visibility is supported everywhere. Hidden
+visibility is supported on Darwin targets.
+
+The visibility attribute should be applied only to declarations that
+would otherwise have external linkage. The attribute should be applied
+consistently, so that the same entity should not be declared with
+different settings of the attribute.
+
+In C++, the visibility attribute applies to types as well as functions
+and objects, because in C++ types have linkage. A class must not have
+greater visibility than its non-static data member types and bases,
+and class members default to the visibility of their class. Also, a
+declaration without explicit visibility is limited to the visibility
+of its type.
+
+In C++, you can mark member functions and static member variables of a
+class with the visibility attribute. This is useful if you know a
+particular method or static member variable should only be used from
+one shared object; then you can mark it hidden while the rest of the
+class has default visibility. Care must be taken to avoid breaking
+the One Definition Rule; for example, it is usually not useful to mark
+an inline method as hidden without marking the whole class as hidden.
+
+A C++ namespace declaration can also have the visibility attribute.
+
+@smallexample
+namespace nspace1 __attribute__ ((visibility ("protected")))
+@{ /* @r{Do something.} */; @}
+@end smallexample
+
+This attribute applies only to the particular namespace body, not to
+other definitions of the same namespace; it is equivalent to using
+@samp{#pragma GCC visibility} before and after the namespace
+definition (@pxref{Visibility Pragmas}).
+
+In C++, if a template argument has limited visibility, this
+restriction is implicitly propagated to the template instantiation.
+Otherwise, template instantiations and specializations default to the
+visibility of their template.
+
+If both the template and enclosing class have explicit visibility, the
+visibility from the template is used.
+
+@item warn_unused_result
+@cindex @code{warn_unused_result} function attribute
+The @code{warn_unused_result} attribute causes a warning to be emitted
+if a caller of the function with this attribute does not use its
+return value. This is useful for functions where not checking
+the result is either a security problem or always a bug, such as
+@code{realloc}.
+
+@smallexample
+int fn () __attribute__ ((warn_unused_result));
+int foo ()
+@{
+ if (fn () < 0) return -1;
+ fn ();
+ return 0;
+@}
+@end smallexample
+
+@noindent
+results in warning on line 5.
+
+@item weak
+@cindex @code{weak} function attribute
+The @code{weak} attribute causes a declaration of an external symbol
+to be emitted as a weak symbol rather than a global. This is primarily
+useful in defining library functions that can be overridden in user code,
+though it can also be used with non-function declarations. The overriding
+symbol must have the same type as the weak symbol. In addition, if it
+designates a variable it must also have the same size and alignment as
+the weak symbol. Weak symbols are supported for ELF targets, and also
+for a.out targets when using the GNU assembler and linker.
+
+@item weakref
+@itemx weakref ("@var{target}")
+@cindex @code{weakref} function attribute
+The @code{weakref} attribute marks a declaration as a weak reference.
+Without arguments, it should be accompanied by an @code{alias} attribute
+naming the target symbol. Alternatively, @var{target} may be given as
+an argument to @code{weakref} itself, naming the target definition of
+the alias. The @var{target} must have the same type as the declaration.
+In addition, if it designates a variable it must also have the same size
+and alignment as the declaration. In either form of the declaration
+@code{weakref} implicitly marks the declared symbol as @code{weak}. Without
+a @var{target} given as an argument to @code{weakref} or to @code{alias},
+@code{weakref} is equivalent to @code{weak} (in that case the declaration
+may be @code{extern}).
+
+@smallexample
+/* Given the declaration: */
+extern int y (void);
+
+/* the following... */
+static int x (void) __attribute__ ((weakref ("y")));
+
+/* is equivalent to... */
+static int x (void) __attribute__ ((weakref, alias ("y")));
+
+/* or, alternatively, to... */
+static int x (void) __attribute__ ((weakref));
+static int x (void) __attribute__ ((alias ("y")));
+@end smallexample
+
+A weak reference is an alias that does not by itself require a
+definition to be given for the target symbol. If the target symbol is
+only referenced through weak references, then it becomes a @code{weak}
+undefined symbol. If it is directly referenced, however, then such
+strong references prevail, and a definition is required for the
+symbol, not necessarily in the same translation unit.
+
+The effect is equivalent to moving all references to the alias to a
+separate translation unit, renaming the alias to the aliased symbol,
+declaring it as weak, compiling the two separate translation units and
+performing a link with relocatable output (i.e.@: @code{ld -r}) on them.
+
+A declaration to which @code{weakref} is attached and that is associated
+with a named @code{target} must be @code{static}.
+
+@item zero_call_used_regs ("@var{choice}")
+@cindex @code{zero_call_used_regs} function attribute
+
+The @code{zero_call_used_regs} attribute causes the compiler to zero
+a subset of all call-used registers@footnote{A ``call-used'' register
+is a register whose contents can be changed by a function call;
+therefore, a caller cannot assume that the register has the same contents
+on return from the function as it had before calling the function. Such
+registers are also called ``call-clobbered'', ``caller-saved'', or
+``volatile''.} at function return.
+This is used to increase program security by either mitigating
+Return-Oriented Programming (ROP) attacks or preventing information leakage
+through registers.
+
+In order to satisfy users with different security needs and control the
+run-time overhead at the same time, the @var{choice} parameter provides a
+flexible way to choose the subset of the call-used registers to be zeroed.
+The three basic values of @var{choice} are:
+
+@itemize @bullet
+@item
+@samp{skip} doesn't zero any call-used registers.
+
+@item
+@samp{used} only zeros call-used registers that are used in the function.
+A ``used'' register is one whose content has been set or referenced in
+the function.
+
+@item
+@samp{all} zeros all call-used registers.
+@end itemize
+
+In addition to these three basic choices, it is possible to modify
+@samp{used} or @samp{all} as follows:
+
+@itemize @bullet
+@item
+Adding @samp{-gpr} restricts the zeroing to general-purpose registers.
+
+@item
+Adding @samp{-arg} restricts the zeroing to registers that can sometimes
+be used to pass function arguments. This includes all argument registers
+defined by the platform's calling conversion, regardless of whether the
+function uses those registers for function arguments or not.
+@end itemize
+
+The modifiers can be used individually or together. If they are used
+together, they must appear in the order above.
+
+The full list of @var{choice}s is therefore:
+
+@table @code
+@item skip
+doesn't zero any call-used register.
+
+@item used
+only zeros call-used registers that are used in the function.
+
+@item used-gpr
+only zeros call-used general purpose registers that are used in the function.
+
+@item used-arg
+only zeros call-used registers that are used in the function and pass arguments.
+
+@item used-gpr-arg
+only zeros call-used general purpose registers that are used in the function
+and pass arguments.
+
+@item all
+zeros all call-used registers.
+
+@item all-gpr
+zeros all call-used general purpose registers.
+
+@item all-arg
+zeros all call-used registers that pass arguments.
+
+@item all-gpr-arg
+zeros all call-used general purpose registers that pass
+arguments.
+@end table
+
+Of this list, @samp{used-arg}, @samp{used-gpr-arg}, @samp{all-arg},
+and @samp{all-gpr-arg} are mainly used for ROP mitigation.
+
+The default for the attribute is controlled by @option{-fzero-call-used-regs}.
+@end table
+
+@c This is the end of the target-independent attribute table
+
+@node AArch64 Function Attributes
+@subsection AArch64 Function Attributes
+
+The following target-specific function attributes are available for the
+AArch64 target. For the most part, these options mirror the behavior of
+similar command-line options (@pxref{AArch64 Options}), but on a
+per-function basis.
+
+@table @code
+@item general-regs-only
+@cindex @code{general-regs-only} function attribute, AArch64
+Indicates that no floating-point or Advanced SIMD registers should be
+used when generating code for this function. If the function explicitly
+uses floating-point code, then the compiler gives an error. This is
+the same behavior as that of the command-line option
+@option{-mgeneral-regs-only}.
+
+@item fix-cortex-a53-835769
+@cindex @code{fix-cortex-a53-835769} function attribute, AArch64
+Indicates that the workaround for the Cortex-A53 erratum 835769 should be
+applied to this function. To explicitly disable the workaround for this
+function specify the negated form: @code{no-fix-cortex-a53-835769}.
+This corresponds to the behavior of the command line options
+@option{-mfix-cortex-a53-835769} and @option{-mno-fix-cortex-a53-835769}.
+
+@item cmodel=
+@cindex @code{cmodel=} function attribute, AArch64
+Indicates that code should be generated for a particular code model for
+this function. The behavior and permissible arguments are the same as
+for the command line option @option{-mcmodel=}.
+
+@item strict-align
+@itemx no-strict-align
+@cindex @code{strict-align} function attribute, AArch64
+@code{strict-align} indicates that the compiler should not assume that unaligned
+memory references are handled by the system. To allow the compiler to assume
+that aligned memory references are handled by the system, the inverse attribute
+@code{no-strict-align} can be specified. The behavior is same as for the
+command-line option @option{-mstrict-align} and @option{-mno-strict-align}.
+
+@item omit-leaf-frame-pointer
+@cindex @code{omit-leaf-frame-pointer} function attribute, AArch64
+Indicates that the frame pointer should be omitted for a leaf function call.
+To keep the frame pointer, the inverse attribute
+@code{no-omit-leaf-frame-pointer} can be specified. These attributes have
+the same behavior as the command-line options @option{-momit-leaf-frame-pointer}
+and @option{-mno-omit-leaf-frame-pointer}.
+
+@item tls-dialect=
+@cindex @code{tls-dialect=} function attribute, AArch64
+Specifies the TLS dialect to use for this function. The behavior and
+permissible arguments are the same as for the command-line option
+@option{-mtls-dialect=}.
+
+@item arch=
+@cindex @code{arch=} function attribute, AArch64
+Specifies the architecture version and architectural extensions to use
+for this function. The behavior and permissible arguments are the same as
+for the @option{-march=} command-line option.
+
+@item tune=
+@cindex @code{tune=} function attribute, AArch64
+Specifies the core for which to tune the performance of this function.
+The behavior and permissible arguments are the same as for the @option{-mtune=}
+command-line option.
+
+@item cpu=
+@cindex @code{cpu=} function attribute, AArch64
+Specifies the core for which to tune the performance of this function and also
+whose architectural features to use. The behavior and valid arguments are the
+same as for the @option{-mcpu=} command-line option.
+
+@item sign-return-address
+@cindex @code{sign-return-address} function attribute, AArch64
+Select the function scope on which return address signing will be applied. The
+behavior and permissible arguments are the same as for the command-line option
+@option{-msign-return-address=}. The default value is @code{none}. This
+attribute is deprecated. The @code{branch-protection} attribute should
+be used instead.
+
+@item branch-protection
+@cindex @code{branch-protection} function attribute, AArch64
+Select the function scope on which branch protection will be applied. The
+behavior and permissible arguments are the same as for the command-line option
+@option{-mbranch-protection=}. The default value is @code{none}.
+
+@item outline-atomics
+@cindex @code{outline-atomics} function attribute, AArch64
+Enable or disable calls to out-of-line helpers to implement atomic operations.
+This corresponds to the behavior of the command line options
+@option{-moutline-atomics} and @option{-mno-outline-atomics}.
+
+@end table
+
+The above target attributes can be specified as follows:
+
+@smallexample
+__attribute__((target("@var{attr-string}")))
+int
+f (int a)
+@{
+ return a + 5;
+@}
+@end smallexample
+
+where @code{@var{attr-string}} is one of the attribute strings specified above.
+
+Additionally, the architectural extension string may be specified on its
+own. This can be used to turn on and off particular architectural extensions
+without having to specify a particular architecture version or core. Example:
+
+@smallexample
+__attribute__((target("+crc+nocrypto")))
+int
+foo (int a)
+@{
+ return a + 5;
+@}
+@end smallexample
+
+In this example @code{target("+crc+nocrypto")} enables the @code{crc}
+extension and disables the @code{crypto} extension for the function @code{foo}
+without modifying an existing @option{-march=} or @option{-mcpu} option.
+
+Multiple target function attributes can be specified by separating them with
+a comma. For example:
+@smallexample
+__attribute__((target("arch=armv8-a+crc+crypto,tune=cortex-a53")))
+int
+foo (int a)
+@{
+ return a + 5;
+@}
+@end smallexample
+
+is valid and compiles function @code{foo} for ARMv8-A with @code{crc}
+and @code{crypto} extensions and tunes it for @code{cortex-a53}.
+
+@subsubsection Inlining rules
+Specifying target attributes on individual functions or performing link-time
+optimization across translation units compiled with different target options
+can affect function inlining rules:
+
+In particular, a caller function can inline a callee function only if the
+architectural features available to the callee are a subset of the features
+available to the caller.
+For example: A function @code{foo} compiled with @option{-march=armv8-a+crc},
+or tagged with the equivalent @code{arch=armv8-a+crc} attribute,
+can inline a function @code{bar} compiled with @option{-march=armv8-a+nocrc}
+because the all the architectural features that function @code{bar} requires
+are available to function @code{foo}. Conversely, function @code{bar} cannot
+inline function @code{foo}.
+
+Additionally inlining a function compiled with @option{-mstrict-align} into a
+function compiled without @code{-mstrict-align} is not allowed.
+However, inlining a function compiled without @option{-mstrict-align} into a
+function compiled with @option{-mstrict-align} is allowed.
+
+Note that CPU tuning options and attributes such as the @option{-mcpu=},
+@option{-mtune=} do not inhibit inlining unless the CPU specified by the
+@option{-mcpu=} option or the @code{cpu=} attribute conflicts with the
+architectural feature rules specified above.
+
+@node AMD GCN Function Attributes
+@subsection AMD GCN Function Attributes
+
+These function attributes are supported by the AMD GCN back end:
+
+@table @code
+@item amdgpu_hsa_kernel
+@cindex @code{amdgpu_hsa_kernel} function attribute, AMD GCN
+This attribute indicates that the corresponding function should be compiled as
+a kernel function, that is an entry point that can be invoked from the host
+via the HSA runtime library. By default functions are only callable only from
+other GCN functions.
+
+This attribute is implicitly applied to any function named @code{main}, using
+default parameters.
+
+Kernel functions may return an integer value, which will be written to a
+conventional place within the HSA "kernargs" region.
+
+The attribute parameters configure what values are passed into the kernel
+function by the GPU drivers, via the initial register state. Some values are
+used by the compiler, and therefore forced on. Enabling other options may
+break assumptions in the compiler and/or run-time libraries.
+
+@table @code
+@item private_segment_buffer
+Set @code{enable_sgpr_private_segment_buffer} flag. Always on (required to
+locate the stack).
+
+@item dispatch_ptr
+Set @code{enable_sgpr_dispatch_ptr} flag. Always on (required to locate the
+launch dimensions).
+
+@item queue_ptr
+Set @code{enable_sgpr_queue_ptr} flag. Always on (required to convert address
+spaces).
+
+@item kernarg_segment_ptr
+Set @code{enable_sgpr_kernarg_segment_ptr} flag. Always on (required to
+locate the kernel arguments, "kernargs").
+
+@item dispatch_id
+Set @code{enable_sgpr_dispatch_id} flag.
+
+@item flat_scratch_init
+Set @code{enable_sgpr_flat_scratch_init} flag.
+
+@item private_segment_size
+Set @code{enable_sgpr_private_segment_size} flag.
+
+@item grid_workgroup_count_X
+Set @code{enable_sgpr_grid_workgroup_count_x} flag. Always on (required to
+use OpenACC/OpenMP).
+
+@item grid_workgroup_count_Y
+Set @code{enable_sgpr_grid_workgroup_count_y} flag.
+
+@item grid_workgroup_count_Z
+Set @code{enable_sgpr_grid_workgroup_count_z} flag.
+
+@item workgroup_id_X
+Set @code{enable_sgpr_workgroup_id_x} flag.
+
+@item workgroup_id_Y
+Set @code{enable_sgpr_workgroup_id_y} flag.
+
+@item workgroup_id_Z
+Set @code{enable_sgpr_workgroup_id_z} flag.
+
+@item workgroup_info
+Set @code{enable_sgpr_workgroup_info} flag.
+
+@item private_segment_wave_offset
+Set @code{enable_sgpr_private_segment_wave_byte_offset} flag. Always on
+(required to locate the stack).
+
+@item work_item_id_X
+Set @code{enable_vgpr_workitem_id} parameter. Always on (can't be disabled).
+
+@item work_item_id_Y
+Set @code{enable_vgpr_workitem_id} parameter. Always on (required to enable
+vectorization.)
+
+@item work_item_id_Z
+Set @code{enable_vgpr_workitem_id} parameter. Always on (required to use
+OpenACC/OpenMP).
+
+@end table
+@end table
+
+@node ARC Function Attributes
+@subsection ARC Function Attributes
+
+These function attributes are supported by the ARC back end:
+
+@table @code
+@item interrupt
+@cindex @code{interrupt} function attribute, ARC
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+
+On the ARC, you must specify the kind of interrupt to be handled
+in a parameter to the interrupt attribute like this:
+
+@smallexample
+void f () __attribute__ ((interrupt ("ilink1")));
+@end smallexample
+
+Permissible values for this parameter are: @w{@code{ilink1}} and
+@w{@code{ilink2}} for ARCv1 architecture, and @w{@code{ilink}} and
+@w{@code{firq}} for ARCv2 architecture.
+
+@item long_call
+@itemx medium_call
+@itemx short_call
+@cindex @code{long_call} function attribute, ARC
+@cindex @code{medium_call} function attribute, ARC
+@cindex @code{short_call} function attribute, ARC
+@cindex indirect calls, ARC
+These attributes specify how a particular function is called.
+These attributes override the
+@option{-mlong-calls} and @option{-mmedium-calls} (@pxref{ARC Options})
+command-line switches and @code{#pragma long_calls} settings.
+
+For ARC, a function marked with the @code{long_call} attribute is
+always called using register-indirect jump-and-link instructions,
+thereby enabling the called function to be placed anywhere within the
+32-bit address space. A function marked with the @code{medium_call}
+attribute will always be close enough to be called with an unconditional
+branch-and-link instruction, which has a 25-bit offset from
+the call site. A function marked with the @code{short_call}
+attribute will always be close enough to be called with a conditional
+branch-and-link instruction, which has a 21-bit offset from
+the call site.
+
+@item jli_always
+@cindex @code{jli_always} function attribute, ARC
+Forces a particular function to be called using @code{jli}
+instruction. The @code{jli} instruction makes use of a table stored
+into @code{.jlitab} section, which holds the location of the functions
+which are addressed using this instruction.
+
+@item jli_fixed
+@cindex @code{jli_fixed} function attribute, ARC
+Identical like the above one, but the location of the function in the
+@code{jli} table is known and given as an attribute parameter.
+
+@item secure_call
+@cindex @code{secure_call} function attribute, ARC
+This attribute allows one to mark secure-code functions that are
+callable from normal mode. The location of the secure call function
+into the @code{sjli} table needs to be passed as argument.
+
+@item naked
+@cindex @code{naked} function attribute, ARC
+This attribute allows the compiler to construct the requisite function
+declaration, while allowing the body of the function to be assembly
+code. The specified function will not have prologue/epilogue
+sequences generated by the compiler. Only basic @code{asm} statements
+can safely be included in naked functions (@pxref{Basic Asm}). While
+using extended @code{asm} or a mixture of basic @code{asm} and C code
+may appear to work, they cannot be depended upon to work reliably and
+are not supported.
+
+@end table
+
+@node ARM Function Attributes
+@subsection ARM Function Attributes
+
+These function attributes are supported for ARM targets:
+
+@table @code
+
+@item general-regs-only
+@cindex @code{general-regs-only} function attribute, ARM
+Indicates that no floating-point or Advanced SIMD registers should be
+used when generating code for this function. If the function explicitly
+uses floating-point code, then the compiler gives an error. This is
+the same behavior as that of the command-line option
+@option{-mgeneral-regs-only}.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, ARM
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+
+You can specify the kind of interrupt to be handled by
+adding an optional parameter to the interrupt attribute like this:
+
+@smallexample
+void f () __attribute__ ((interrupt ("IRQ")));
+@end smallexample
+
+@noindent
+Permissible values for this parameter are: @code{IRQ}, @code{FIQ},
+@code{SWI}, @code{ABORT} and @code{UNDEF}.
+
+On ARMv7-M the interrupt type is ignored, and the attribute means the function
+may be called with a word-aligned stack pointer.
+
+@item isr
+@cindex @code{isr} function attribute, ARM
+Use this attribute on ARM to write Interrupt Service Routines. This is an
+alias to the @code{interrupt} attribute above.
+
+@item long_call
+@itemx short_call
+@cindex @code{long_call} function attribute, ARM
+@cindex @code{short_call} function attribute, ARM
+@cindex indirect calls, ARM
+These attributes specify how a particular function is called.
+These attributes override the
+@option{-mlong-calls} (@pxref{ARM Options})
+command-line switch and @code{#pragma long_calls} settings. For ARM, the
+@code{long_call} attribute indicates that the function might be far
+away from the call site and require a different (more expensive)
+calling sequence. The @code{short_call} attribute always places
+the offset to the function from the call site into the @samp{BL}
+instruction directly.
+
+@item naked
+@cindex @code{naked} function attribute, ARM
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+
+@item pcs
+@cindex @code{pcs} function attribute, ARM
+
+The @code{pcs} attribute can be used to control the calling convention
+used for a function on ARM. The attribute takes an argument that specifies
+the calling convention to use.
+
+When compiling using the AAPCS ABI (or a variant of it) then valid
+values for the argument are @code{"aapcs"} and @code{"aapcs-vfp"}. In
+order to use a variant other than @code{"aapcs"} then the compiler must
+be permitted to use the appropriate co-processor registers (i.e., the
+VFP registers must be available in order to use @code{"aapcs-vfp"}).
+For example,
+
+@smallexample
+/* Argument passed in r0, and result returned in r0+r1. */
+double f2d (float) __attribute__((pcs("aapcs")));
+@end smallexample
+
+Variadic functions always use the @code{"aapcs"} calling convention and
+the compiler rejects attempts to specify an alternative.
+
+@item target (@var{options})
+@cindex @code{target} function attribute
+As discussed in @ref{Common Function Attributes}, this attribute
+allows specification of target-specific compilation options.
+
+On ARM, the following options are allowed:
+
+@table @samp
+@item thumb
+@cindex @code{target("thumb")} function attribute, ARM
+Force code generation in the Thumb (T16/T32) ISA, depending on the
+architecture level.
+
+@item arm
+@cindex @code{target("arm")} function attribute, ARM
+Force code generation in the ARM (A32) ISA.
+
+Functions from different modes can be inlined in the caller's mode.
+
+@item fpu=
+@cindex @code{target("fpu=")} function attribute, ARM
+Specifies the fpu for which to tune the performance of this function.
+The behavior and permissible arguments are the same as for the @option{-mfpu=}
+command-line option.
+
+@item arch=
+@cindex @code{arch=} function attribute, ARM
+Specifies the architecture version and architectural extensions to use
+for this function. The behavior and permissible arguments are the same as
+for the @option{-march=} command-line option.
+
+The above target attributes can be specified as follows:
+
+@smallexample
+__attribute__((target("arch=armv8-a+crc")))
+int
+f (int a)
+@{
+ return a + 5;
+@}
+@end smallexample
+
+Additionally, the architectural extension string may be specified on its
+own. This can be used to turn on and off particular architectural extensions
+without having to specify a particular architecture version or core. Example:
+
+@smallexample
+__attribute__((target("+crc+nocrypto")))
+int
+foo (int a)
+@{
+ return a + 5;
+@}
+@end smallexample
+
+In this example @code{target("+crc+nocrypto")} enables the @code{crc}
+extension and disables the @code{crypto} extension for the function @code{foo}
+without modifying an existing @option{-march=} or @option{-mcpu} option.
+
+@end table
+
+@end table
+
+@node AVR Function Attributes
+@subsection AVR Function Attributes
+
+These function attributes are supported by the AVR back end:
+
+@table @code
+@item interrupt
+@cindex @code{interrupt} function attribute, AVR
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+
+On the AVR, the hardware globally disables interrupts when an
+interrupt is executed. The first instruction of an interrupt handler
+declared with this attribute is a @code{SEI} instruction to
+re-enable interrupts. See also the @code{signal} function attribute
+that does not insert a @code{SEI} instruction. If both @code{signal} and
+@code{interrupt} are specified for the same function, @code{signal}
+is silently ignored.
+
+@item naked
+@cindex @code{naked} function attribute, AVR
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+
+@item no_gccisr
+@cindex @code{no_gccisr} function attribute, AVR
+Do not use @code{__gcc_isr} pseudo instructions in a function with
+the @code{interrupt} or @code{signal} attribute aka. interrupt
+service routine (ISR).
+Use this attribute if the preamble of the ISR prologue should always read
+@example
+push __zero_reg__
+push __tmp_reg__
+in __tmp_reg__, __SREG__
+push __tmp_reg__
+clr __zero_reg__
+@end example
+and accordingly for the postamble of the epilogue --- no matter whether
+the mentioned registers are actually used in the ISR or not.
+Situations where you might want to use this attribute include:
+@itemize @bullet
+@item
+Code that (effectively) clobbers bits of @code{SREG} other than the
+@code{I}-flag by writing to the memory location of @code{SREG}.
+@item
+Code that uses inline assembler to jump to a different function which
+expects (parts of) the prologue code as outlined above to be present.
+@end itemize
+To disable @code{__gcc_isr} generation for the whole compilation unit,
+there is option @option{-mno-gas-isr-prologues}, @pxref{AVR Options}.
+
+@item OS_main
+@itemx OS_task
+@cindex @code{OS_main} function attribute, AVR
+@cindex @code{OS_task} function attribute, AVR
+On AVR, functions with the @code{OS_main} or @code{OS_task} attribute
+do not save/restore any call-saved register in their prologue/epilogue.
+
+The @code{OS_main} attribute can be used when there @emph{is
+guarantee} that interrupts are disabled at the time when the function
+is entered. This saves resources when the stack pointer has to be
+changed to set up a frame for local variables.
+
+The @code{OS_task} attribute can be used when there is @emph{no
+guarantee} that interrupts are disabled at that time when the function
+is entered like for, e@.g@. task functions in a multi-threading operating
+system. In that case, changing the stack pointer register is
+guarded by save/clear/restore of the global interrupt enable flag.
+
+The differences to the @code{naked} function attribute are:
+@itemize @bullet
+@item @code{naked} functions do not have a return instruction whereas
+@code{OS_main} and @code{OS_task} functions have a @code{RET} or
+@code{RETI} return instruction.
+@item @code{naked} functions do not set up a frame for local variables
+or a frame pointer whereas @code{OS_main} and @code{OS_task} do this
+as needed.
+@end itemize
+
+@item signal
+@cindex @code{signal} function attribute, AVR
+Use this attribute on the AVR to indicate that the specified
+function is an interrupt handler. The compiler generates function
+entry and exit sequences suitable for use in an interrupt handler when this
+attribute is present.
+
+See also the @code{interrupt} function attribute.
+
+The AVR hardware globally disables interrupts when an interrupt is executed.
+Interrupt handler functions defined with the @code{signal} attribute
+do not re-enable interrupts. It is save to enable interrupts in a
+@code{signal} handler. This ``save'' only applies to the code
+generated by the compiler and not to the IRQ layout of the
+application which is responsibility of the application.
+
+If both @code{signal} and @code{interrupt} are specified for the same
+function, @code{signal} is silently ignored.
+@end table
+
+@node Blackfin Function Attributes
+@subsection Blackfin Function Attributes
+
+These function attributes are supported by the Blackfin back end:
+
+@table @code
+
+@item exception_handler
+@cindex @code{exception_handler} function attribute
+@cindex exception handler functions, Blackfin
+Use this attribute on the Blackfin to indicate that the specified function
+is an exception handler. The compiler generates function entry and
+exit sequences suitable for use in an exception handler when this
+attribute is present.
+
+@item interrupt_handler
+@cindex @code{interrupt_handler} function attribute, Blackfin
+Use this attribute to
+indicate that the specified function is an interrupt handler. The compiler
+generates function entry and exit sequences suitable for use in an
+interrupt handler when this attribute is present.
+
+@item kspisusp
+@cindex @code{kspisusp} function attribute, Blackfin
+@cindex User stack pointer in interrupts on the Blackfin
+When used together with @code{interrupt_handler}, @code{exception_handler}
+or @code{nmi_handler}, code is generated to load the stack pointer
+from the USP register in the function prologue.
+
+@item l1_text
+@cindex @code{l1_text} function attribute, Blackfin
+This attribute specifies a function to be placed into L1 Instruction
+SRAM@. The function is put into a specific section named @code{.l1.text}.
+With @option{-mfdpic}, function calls with a such function as the callee
+or caller uses inlined PLT.
+
+@item l2
+@cindex @code{l2} function attribute, Blackfin
+This attribute specifies a function to be placed into L2
+SRAM. The function is put into a specific section named
+@code{.l2.text}. With @option{-mfdpic}, callers of such functions use
+an inlined PLT.
+
+@item longcall
+@itemx shortcall
+@cindex indirect calls, Blackfin
+@cindex @code{longcall} function attribute, Blackfin
+@cindex @code{shortcall} function attribute, Blackfin
+The @code{longcall} attribute
+indicates that the function might be far away from the call site and
+require a different (more expensive) calling sequence. The
+@code{shortcall} attribute indicates that the function is always close
+enough for the shorter calling sequence to be used. These attributes
+override the @option{-mlongcall} switch.
+
+@item nesting
+@cindex @code{nesting} function attribute, Blackfin
+@cindex Allow nesting in an interrupt handler on the Blackfin processor
+Use this attribute together with @code{interrupt_handler},
+@code{exception_handler} or @code{nmi_handler} to indicate that the function
+entry code should enable nested interrupts or exceptions.
+
+@item nmi_handler
+@cindex @code{nmi_handler} function attribute, Blackfin
+@cindex NMI handler functions on the Blackfin processor
+Use this attribute on the Blackfin to indicate that the specified function
+is an NMI handler. The compiler generates function entry and
+exit sequences suitable for use in an NMI handler when this
+attribute is present.
+
+@item saveall
+@cindex @code{saveall} function attribute, Blackfin
+@cindex save all registers on the Blackfin
+Use this attribute to indicate that
+all registers except the stack pointer should be saved in the prologue
+regardless of whether they are used or not.
+@end table
+
+@node BPF Function Attributes
+@subsection BPF Function Attributes
+
+These function attributes are supported by the BPF back end:
+
+@table @code
+@item kernel_helper
+@cindex @code{kernel helper}, function attribute, BPF
+use this attribute to indicate the specified function declaration is a
+kernel helper. The helper function is passed as an argument to the
+attribute. Example:
+
+@smallexample
+int bpf_probe_read (void *dst, int size, const void *unsafe_ptr)
+ __attribute__ ((kernel_helper (4)));
+@end smallexample
+@end table
+
+@node C-SKY Function Attributes
+@subsection C-SKY Function Attributes
+
+These function attributes are supported by the C-SKY back end:
+
+@table @code
+@item interrupt
+@itemx isr
+@cindex @code{interrupt} function attribute, C-SKY
+@cindex @code{isr} function attribute, C-SKY
+Use these attributes to indicate that the specified function
+is an interrupt handler.
+The compiler generates function entry and exit sequences suitable for
+use in an interrupt handler when either of these attributes are present.
+
+Use of these options requires the @option{-mistack} command-line option
+to enable support for the necessary interrupt stack instructions. They
+are ignored with a warning otherwise. @xref{C-SKY Options}.
+
+@item naked
+@cindex @code{naked} function attribute, C-SKY
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+@end table
+
+
+@node Epiphany Function Attributes
+@subsection Epiphany Function Attributes
+
+These function attributes are supported by the Epiphany back end:
+
+@table @code
+@item disinterrupt
+@cindex @code{disinterrupt} function attribute, Epiphany
+This attribute causes the compiler to emit
+instructions to disable interrupts for the duration of the given
+function.
+
+@item forwarder_section
+@cindex @code{forwarder_section} function attribute, Epiphany
+This attribute modifies the behavior of an interrupt handler.
+The interrupt handler may be in external memory which cannot be
+reached by a branch instruction, so generate a local memory trampoline
+to transfer control. The single parameter identifies the section where
+the trampoline is placed.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, Epiphany
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present. It may also generate
+a special section with code to initialize the interrupt vector table.
+
+On Epiphany targets one or more optional parameters can be added like this:
+
+@smallexample
+void __attribute__ ((interrupt ("dma0, dma1"))) universal_dma_handler ();
+@end smallexample
+
+Permissible values for these parameters are: @w{@code{reset}},
+@w{@code{software_exception}}, @w{@code{page_miss}},
+@w{@code{timer0}}, @w{@code{timer1}}, @w{@code{message}},
+@w{@code{dma0}}, @w{@code{dma1}}, @w{@code{wand}} and @w{@code{swi}}.
+Multiple parameters indicate that multiple entries in the interrupt
+vector table should be initialized for this function, i.e.@: for each
+parameter @w{@var{name}}, a jump to the function is emitted in
+the section @w{ivt_entry_@var{name}}. The parameter(s) may be omitted
+entirely, in which case no interrupt vector table entry is provided.
+
+Note that interrupts are enabled inside the function
+unless the @code{disinterrupt} attribute is also specified.
+
+The following examples are all valid uses of these attributes on
+Epiphany targets:
+@smallexample
+void __attribute__ ((interrupt)) universal_handler ();
+void __attribute__ ((interrupt ("dma1"))) dma1_handler ();
+void __attribute__ ((interrupt ("dma0, dma1")))
+ universal_dma_handler ();
+void __attribute__ ((interrupt ("timer0"), disinterrupt))
+ fast_timer_handler ();
+void __attribute__ ((interrupt ("dma0, dma1"),
+ forwarder_section ("tramp")))
+ external_dma_handler ();
+@end smallexample
+
+@item long_call
+@itemx short_call
+@cindex @code{long_call} function attribute, Epiphany
+@cindex @code{short_call} function attribute, Epiphany
+@cindex indirect calls, Epiphany
+These attributes specify how a particular function is called.
+These attributes override the
+@option{-mlong-calls} (@pxref{Adapteva Epiphany Options})
+command-line switch and @code{#pragma long_calls} settings.
+@end table
+
+
+@node H8/300 Function Attributes
+@subsection H8/300 Function Attributes
+
+These function attributes are available for H8/300 targets:
+
+@table @code
+@item function_vector
+@cindex @code{function_vector} function attribute, H8/300
+Use this attribute on the H8/300, H8/300H, and H8S to indicate
+that the specified function should be called through the function vector.
+Calling a function through the function vector reduces code size; however,
+the function vector has a limited size (maximum 128 entries on the H8/300
+and 64 entries on the H8/300H and H8S)
+and shares space with the interrupt vector.
+
+@item interrupt_handler
+@cindex @code{interrupt_handler} function attribute, H8/300
+Use this attribute on the H8/300, H8/300H, and H8S to
+indicate that the specified function is an interrupt handler. The compiler
+generates function entry and exit sequences suitable for use in an
+interrupt handler when this attribute is present.
+
+@item saveall
+@cindex @code{saveall} function attribute, H8/300
+@cindex save all registers on the H8/300, H8/300H, and H8S
+Use this attribute on the H8/300, H8/300H, and H8S to indicate that
+all registers except the stack pointer should be saved in the prologue
+regardless of whether they are used or not.
+@end table
+
+@node IA-64 Function Attributes
+@subsection IA-64 Function Attributes
+
+These function attributes are supported on IA-64 targets:
+
+@table @code
+@item syscall_linkage
+@cindex @code{syscall_linkage} function attribute, IA-64
+This attribute is used to modify the IA-64 calling convention by marking
+all input registers as live at all function exits. This makes it possible
+to restart a system call after an interrupt without having to save/restore
+the input registers. This also prevents kernel data from leaking into
+application code.
+
+@item version_id
+@cindex @code{version_id} function attribute, IA-64
+This IA-64 HP-UX attribute, attached to a global variable or function, renames a
+symbol to contain a version string, thus allowing for function level
+versioning. HP-UX system header files may use function level versioning
+for some system calls.
+
+@smallexample
+extern int foo () __attribute__((version_id ("20040821")));
+@end smallexample
+
+@noindent
+Calls to @code{foo} are mapped to calls to @code{foo@{20040821@}}.
+@end table
+
+@node M32C Function Attributes
+@subsection M32C Function Attributes
+
+These function attributes are supported by the M32C back end:
+
+@table @code
+@item bank_switch
+@cindex @code{bank_switch} function attribute, M32C
+When added to an interrupt handler with the M32C port, causes the
+prologue and epilogue to use bank switching to preserve the registers
+rather than saving them on the stack.
+
+@item fast_interrupt
+@cindex @code{fast_interrupt} function attribute, M32C
+Use this attribute on the M32C port to indicate that the specified
+function is a fast interrupt handler. This is just like the
+@code{interrupt} attribute, except that @code{freit} is used to return
+instead of @code{reit}.
+
+@item function_vector
+@cindex @code{function_vector} function attribute, M16C/M32C
+On M16C/M32C targets, the @code{function_vector} attribute declares a
+special page subroutine call function. Use of this attribute reduces
+the code size by 2 bytes for each call generated to the
+subroutine. The argument to the attribute is the vector number entry
+from the special page vector table which contains the 16 low-order
+bits of the subroutine's entry address. Each vector table has special
+page number (18 to 255) that is used in @code{jsrs} instructions.
+Jump addresses of the routines are generated by adding 0x0F0000 (in
+case of M16C targets) or 0xFF0000 (in case of M32C targets), to the
+2-byte addresses set in the vector table. Therefore you need to ensure
+that all the special page vector routines should get mapped within the
+address range 0x0F0000 to 0x0FFFFF (for M16C) and 0xFF0000 to 0xFFFFFF
+(for M32C).
+
+In the following example 2 bytes are saved for each call to
+function @code{foo}.
+
+@smallexample
+void foo (void) __attribute__((function_vector(0x18)));
+void foo (void)
+@{
+@}
+
+void bar (void)
+@{
+ foo();
+@}
+@end smallexample
+
+If functions are defined in one file and are called in another file,
+then be sure to write this declaration in both files.
+
+This attribute is ignored for R8C target.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, M32C
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+@end table
+
+@node M32R/D Function Attributes
+@subsection M32R/D Function Attributes
+
+These function attributes are supported by the M32R/D back end:
+
+@table @code
+@item interrupt
+@cindex @code{interrupt} function attribute, M32R/D
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+
+@item model (@var{model-name})
+@cindex @code{model} function attribute, M32R/D
+@cindex function addressability on the M32R/D
+
+On the M32R/D, use this attribute to set the addressability of an
+object, and of the code generated for a function. The identifier
+@var{model-name} is one of @code{small}, @code{medium}, or
+@code{large}, representing each of the code models.
+
+Small model objects live in the lower 16MB of memory (so that their
+addresses can be loaded with the @code{ld24} instruction), and are
+callable with the @code{bl} instruction.
+
+Medium model objects may live anywhere in the 32-bit address space (the
+compiler generates @code{seth/add3} instructions to load their addresses),
+and are callable with the @code{bl} instruction.
+
+Large model objects may live anywhere in the 32-bit address space (the
+compiler generates @code{seth/add3} instructions to load their addresses),
+and may not be reachable with the @code{bl} instruction (the compiler
+generates the much slower @code{seth/add3/jl} instruction sequence).
+@end table
+
+@node m68k Function Attributes
+@subsection m68k Function Attributes
+
+These function attributes are supported by the m68k back end:
+
+@table @code
+@item interrupt
+@itemx interrupt_handler
+@cindex @code{interrupt} function attribute, m68k
+@cindex @code{interrupt_handler} function attribute, m68k
+Use this attribute to
+indicate that the specified function is an interrupt handler. The compiler
+generates function entry and exit sequences suitable for use in an
+interrupt handler when this attribute is present. Either name may be used.
+
+@item interrupt_thread
+@cindex @code{interrupt_thread} function attribute, fido
+Use this attribute on fido, a subarchitecture of the m68k, to indicate
+that the specified function is an interrupt handler that is designed
+to run as a thread. The compiler omits generate prologue/epilogue
+sequences and replaces the return instruction with a @code{sleep}
+instruction. This attribute is available only on fido.
+@end table
+
+@node MCORE Function Attributes
+@subsection MCORE Function Attributes
+
+These function attributes are supported by the MCORE back end:
+
+@table @code
+@item naked
+@cindex @code{naked} function attribute, MCORE
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+@end table
+
+@node MeP Function Attributes
+@subsection MeP Function Attributes
+
+These function attributes are supported by the MeP back end:
+
+@table @code
+@item disinterrupt
+@cindex @code{disinterrupt} function attribute, MeP
+On MeP targets, this attribute causes the compiler to emit
+instructions to disable interrupts for the duration of the given
+function.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, MeP
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+
+@item near
+@cindex @code{near} function attribute, MeP
+This attribute causes the compiler to assume the called
+function is close enough to use the normal calling convention,
+overriding the @option{-mtf} command-line option.
+
+@item far
+@cindex @code{far} function attribute, MeP
+On MeP targets this causes the compiler to use a calling convention
+that assumes the called function is too far away for the built-in
+addressing modes.
+
+@item vliw
+@cindex @code{vliw} function attribute, MeP
+The @code{vliw} attribute tells the compiler to emit
+instructions in VLIW mode instead of core mode. Note that this
+attribute is not allowed unless a VLIW coprocessor has been configured
+and enabled through command-line options.
+@end table
+
+@node MicroBlaze Function Attributes
+@subsection MicroBlaze Function Attributes
+
+These function attributes are supported on MicroBlaze targets:
+
+@table @code
+@item save_volatiles
+@cindex @code{save_volatiles} function attribute, MicroBlaze
+Use this attribute to indicate that the function is
+an interrupt handler. All volatile registers (in addition to non-volatile
+registers) are saved in the function prologue. If the function is a leaf
+function, only volatiles used by the function are saved. A normal function
+return is generated instead of a return from interrupt.
+
+@item break_handler
+@cindex @code{break_handler} function attribute, MicroBlaze
+@cindex break handler functions
+Use this attribute to indicate that
+the specified function is a break handler. The compiler generates function
+entry and exit sequences suitable for use in an break handler when this
+attribute is present. The return from @code{break_handler} is done through
+the @code{rtbd} instead of @code{rtsd}.
+
+@smallexample
+void f () __attribute__ ((break_handler));
+@end smallexample
+
+@item interrupt_handler
+@itemx fast_interrupt
+@cindex @code{interrupt_handler} function attribute, MicroBlaze
+@cindex @code{fast_interrupt} function attribute, MicroBlaze
+These attributes indicate that the specified function is an interrupt
+handler. Use the @code{fast_interrupt} attribute to indicate handlers
+used in low-latency interrupt mode, and @code{interrupt_handler} for
+interrupts that do not use low-latency handlers. In both cases, GCC
+emits appropriate prologue code and generates a return from the handler
+using @code{rtid} instead of @code{rtsd}.
+@end table
+
+@node Microsoft Windows Function Attributes
+@subsection Microsoft Windows Function Attributes
+
+The following attributes are available on Microsoft Windows and Symbian OS
+targets.
+
+@table @code
+@item dllexport
+@cindex @code{dllexport} function attribute
+@cindex @code{__declspec(dllexport)}
+On Microsoft Windows targets and Symbian OS targets the
+@code{dllexport} attribute causes the compiler to provide a global
+pointer to a pointer in a DLL, so that it can be referenced with the
+@code{dllimport} attribute. On Microsoft Windows targets, the pointer
+name is formed by combining @code{_imp__} and the function or variable
+name.
+
+You can use @code{__declspec(dllexport)} as a synonym for
+@code{__attribute__ ((dllexport))} for compatibility with other
+compilers.
+
+On systems that support the @code{visibility} attribute, this
+attribute also implies ``default'' visibility. It is an error to
+explicitly specify any other visibility.
+
+GCC's default behavior is to emit all inline functions with the
+@code{dllexport} attribute. Since this can cause object file-size bloat,
+you can use @option{-fno-keep-inline-dllexport}, which tells GCC to
+ignore the attribute for inlined functions unless the
+@option{-fkeep-inline-functions} flag is used instead.
+
+The attribute is ignored for undefined symbols.
+
+When applied to C++ classes, the attribute marks defined non-inlined
+member functions and static data members as exports. Static consts
+initialized in-class are not marked unless they are also defined
+out-of-class.
+
+For Microsoft Windows targets there are alternative methods for
+including the symbol in the DLL's export table such as using a
+@file{.def} file with an @code{EXPORTS} section or, with GNU ld, using
+the @option{--export-all} linker flag.
+
+@item dllimport
+@cindex @code{dllimport} function attribute
+@cindex @code{__declspec(dllimport)}
+On Microsoft Windows and Symbian OS targets, the @code{dllimport}
+attribute causes the compiler to reference a function or variable via
+a global pointer to a pointer that is set up by the DLL exporting the
+symbol. The attribute implies @code{extern}. On Microsoft Windows
+targets, the pointer name is formed by combining @code{_imp__} and the
+function or variable name.
+
+You can use @code{__declspec(dllimport)} as a synonym for
+@code{__attribute__ ((dllimport))} for compatibility with other
+compilers.
+
+On systems that support the @code{visibility} attribute, this
+attribute also implies ``default'' visibility. It is an error to
+explicitly specify any other visibility.
+
+Currently, the attribute is ignored for inlined functions. If the
+attribute is applied to a symbol @emph{definition}, an error is reported.
+If a symbol previously declared @code{dllimport} is later defined, the
+attribute is ignored in subsequent references, and a warning is emitted.
+The attribute is also overridden by a subsequent declaration as
+@code{dllexport}.
+
+When applied to C++ classes, the attribute marks non-inlined
+member functions and static data members as imports. However, the
+attribute is ignored for virtual methods to allow creation of vtables
+using thunks.
+
+On the SH Symbian OS target the @code{dllimport} attribute also has
+another affect---it can cause the vtable and run-time type information
+for a class to be exported. This happens when the class has a
+dllimported constructor or a non-inline, non-pure virtual function
+and, for either of those two conditions, the class also has an inline
+constructor or destructor and has a key function that is defined in
+the current translation unit.
+
+For Microsoft Windows targets the use of the @code{dllimport}
+attribute on functions is not necessary, but provides a small
+performance benefit by eliminating a thunk in the DLL@. The use of the
+@code{dllimport} attribute on imported variables can be avoided by passing the
+@option{--enable-auto-import} switch to the GNU linker. As with
+functions, using the attribute for a variable eliminates a thunk in
+the DLL@.
+
+One drawback to using this attribute is that a pointer to a
+@emph{variable} marked as @code{dllimport} cannot be used as a constant
+address. However, a pointer to a @emph{function} with the
+@code{dllimport} attribute can be used as a constant initializer; in
+this case, the address of a stub function in the import lib is
+referenced. On Microsoft Windows targets, the attribute can be disabled
+for functions by setting the @option{-mnop-fun-dllimport} flag.
+@end table
+
+@node MIPS Function Attributes
+@subsection MIPS Function Attributes
+
+These function attributes are supported by the MIPS back end:
+
+@table @code
+@item interrupt
+@cindex @code{interrupt} function attribute, MIPS
+Use this attribute to indicate that the specified function is an interrupt
+handler. The compiler generates function entry and exit sequences suitable
+for use in an interrupt handler when this attribute is present.
+An optional argument is supported for the interrupt attribute which allows
+the interrupt mode to be described. By default GCC assumes the external
+interrupt controller (EIC) mode is in use, this can be explicitly set using
+@code{eic}. When interrupts are non-masked then the requested Interrupt
+Priority Level (IPL) is copied to the current IPL which has the effect of only
+enabling higher priority interrupts. To use vectored interrupt mode use
+the argument @code{vector=[sw0|sw1|hw0|hw1|hw2|hw3|hw4|hw5]}, this will change
+the behavior of the non-masked interrupt support and GCC will arrange to mask
+all interrupts from sw0 up to and including the specified interrupt vector.
+
+You can use the following attributes to modify the behavior
+of an interrupt handler:
+@table @code
+@item use_shadow_register_set
+@cindex @code{use_shadow_register_set} function attribute, MIPS
+Assume that the handler uses a shadow register set, instead of
+the main general-purpose registers. An optional argument @code{intstack} is
+supported to indicate that the shadow register set contains a valid stack
+pointer.
+
+@item keep_interrupts_masked
+@cindex @code{keep_interrupts_masked} function attribute, MIPS
+Keep interrupts masked for the whole function. Without this attribute,
+GCC tries to reenable interrupts for as much of the function as it can.
+
+@item use_debug_exception_return
+@cindex @code{use_debug_exception_return} function attribute, MIPS
+Return using the @code{deret} instruction. Interrupt handlers that don't
+have this attribute return using @code{eret} instead.
+@end table
+
+You can use any combination of these attributes, as shown below:
+@smallexample
+void __attribute__ ((interrupt)) v0 ();
+void __attribute__ ((interrupt, use_shadow_register_set)) v1 ();
+void __attribute__ ((interrupt, keep_interrupts_masked)) v2 ();
+void __attribute__ ((interrupt, use_debug_exception_return)) v3 ();
+void __attribute__ ((interrupt, use_shadow_register_set,
+ keep_interrupts_masked)) v4 ();
+void __attribute__ ((interrupt, use_shadow_register_set,
+ use_debug_exception_return)) v5 ();
+void __attribute__ ((interrupt, keep_interrupts_masked,
+ use_debug_exception_return)) v6 ();
+void __attribute__ ((interrupt, use_shadow_register_set,
+ keep_interrupts_masked,
+ use_debug_exception_return)) v7 ();
+void __attribute__ ((interrupt("eic"))) v8 ();
+void __attribute__ ((interrupt("vector=hw3"))) v9 ();
+@end smallexample
+
+@item long_call
+@itemx short_call
+@itemx near
+@itemx far
+@cindex indirect calls, MIPS
+@cindex @code{long_call} function attribute, MIPS
+@cindex @code{short_call} function attribute, MIPS
+@cindex @code{near} function attribute, MIPS
+@cindex @code{far} function attribute, MIPS
+These attributes specify how a particular function is called on MIPS@.
+The attributes override the @option{-mlong-calls} (@pxref{MIPS Options})
+command-line switch. The @code{long_call} and @code{far} attributes are
+synonyms, and cause the compiler to always call
+the function by first loading its address into a register, and then using
+the contents of that register. The @code{short_call} and @code{near}
+attributes are synonyms, and have the opposite
+effect; they specify that non-PIC calls should be made using the more
+efficient @code{jal} instruction.
+
+@item mips16
+@itemx nomips16
+@cindex @code{mips16} function attribute, MIPS
+@cindex @code{nomips16} function attribute, MIPS
+
+On MIPS targets, you can use the @code{mips16} and @code{nomips16}
+function attributes to locally select or turn off MIPS16 code generation.
+A function with the @code{mips16} attribute is emitted as MIPS16 code,
+while MIPS16 code generation is disabled for functions with the
+@code{nomips16} attribute. These attributes override the
+@option{-mips16} and @option{-mno-mips16} options on the command line
+(@pxref{MIPS Options}).
+
+When compiling files containing mixed MIPS16 and non-MIPS16 code, the
+preprocessor symbol @code{__mips16} reflects the setting on the command line,
+not that within individual functions. Mixed MIPS16 and non-MIPS16 code
+may interact badly with some GCC extensions such as @code{__builtin_apply}
+(@pxref{Constructing Calls}).
+
+@item micromips, MIPS
+@itemx nomicromips, MIPS
+@cindex @code{micromips} function attribute
+@cindex @code{nomicromips} function attribute
+
+On MIPS targets, you can use the @code{micromips} and @code{nomicromips}
+function attributes to locally select or turn off microMIPS code generation.
+A function with the @code{micromips} attribute is emitted as microMIPS code,
+while microMIPS code generation is disabled for functions with the
+@code{nomicromips} attribute. These attributes override the
+@option{-mmicromips} and @option{-mno-micromips} options on the command line
+(@pxref{MIPS Options}).
+
+When compiling files containing mixed microMIPS and non-microMIPS code, the
+preprocessor symbol @code{__mips_micromips} reflects the setting on the
+command line,
+not that within individual functions. Mixed microMIPS and non-microMIPS code
+may interact badly with some GCC extensions such as @code{__builtin_apply}
+(@pxref{Constructing Calls}).
+
+@item nocompression
+@cindex @code{nocompression} function attribute, MIPS
+On MIPS targets, you can use the @code{nocompression} function attribute
+to locally turn off MIPS16 and microMIPS code generation. This attribute
+overrides the @option{-mips16} and @option{-mmicromips} options on the
+command line (@pxref{MIPS Options}).
+@end table
+
+@node MSP430 Function Attributes
+@subsection MSP430 Function Attributes
+
+These function attributes are supported by the MSP430 back end:
+
+@table @code
+@item critical
+@cindex @code{critical} function attribute, MSP430
+Critical functions disable interrupts upon entry and restore the
+previous interrupt state upon exit. Critical functions cannot also
+have the @code{naked}, @code{reentrant} or @code{interrupt} attributes.
+
+The MSP430 hardware ensures that interrupts are disabled on entry to
+@code{interrupt} functions, and restores the previous interrupt state
+on exit. The @code{critical} attribute is therefore redundant on
+@code{interrupt} functions.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, MSP430
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+
+You can provide an argument to the interrupt
+attribute which specifies a name or number. If the argument is a
+number it indicates the slot in the interrupt vector table (0 - 31) to
+which this handler should be assigned. If the argument is a name it
+is treated as a symbolic name for the vector slot. These names should
+match up with appropriate entries in the linker script. By default
+the names @code{watchdog} for vector 26, @code{nmi} for vector 30 and
+@code{reset} for vector 31 are recognized.
+
+@item naked
+@cindex @code{naked} function attribute, MSP430
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+
+@item reentrant
+@cindex @code{reentrant} function attribute, MSP430
+Reentrant functions disable interrupts upon entry and enable them
+upon exit. Reentrant functions cannot also have the @code{naked}
+or @code{critical} attributes. They can have the @code{interrupt}
+attribute.
+
+@item wakeup
+@cindex @code{wakeup} function attribute, MSP430
+This attribute only applies to interrupt functions. It is silently
+ignored if applied to a non-interrupt function. A wakeup interrupt
+function will rouse the processor from any low-power state that it
+might be in when the function exits.
+
+@item lower
+@itemx upper
+@itemx either
+@cindex @code{lower} function attribute, MSP430
+@cindex @code{upper} function attribute, MSP430
+@cindex @code{either} function attribute, MSP430
+On the MSP430 target these attributes can be used to specify whether
+the function or variable should be placed into low memory, high
+memory, or the placement should be left to the linker to decide. The
+attributes are only significant if compiling for the MSP430X
+architecture in the large memory model.
+
+The attributes work in conjunction with a linker script that has been
+augmented to specify where to place sections with a @code{.lower} and
+a @code{.upper} prefix. So, for example, as well as placing the
+@code{.data} section, the script also specifies the placement of a
+@code{.lower.data} and a @code{.upper.data} section. The intention
+is that @code{lower} sections are placed into a small but easier to
+access memory region and the upper sections are placed into a larger, but
+slower to access, region.
+
+The @code{either} attribute is special. It tells the linker to place
+the object into the corresponding @code{lower} section if there is
+room for it. If there is insufficient room then the object is placed
+into the corresponding @code{upper} section instead. Note that the
+placement algorithm is not very sophisticated. It does not attempt to
+find an optimal packing of the @code{lower} sections. It just makes
+one pass over the objects and does the best that it can. Using the
+@option{-ffunction-sections} and @option{-fdata-sections} command-line
+options can help the packing, however, since they produce smaller,
+easier to pack regions.
+@end table
+
+@node NDS32 Function Attributes
+@subsection NDS32 Function Attributes
+
+These function attributes are supported by the NDS32 back end:
+
+@table @code
+@item exception
+@cindex @code{exception} function attribute
+@cindex exception handler functions, NDS32
+Use this attribute on the NDS32 target to indicate that the specified function
+is an exception handler. The compiler will generate corresponding sections
+for use in an exception handler.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, NDS32
+On NDS32 target, this attribute indicates that the specified function
+is an interrupt handler. The compiler generates corresponding sections
+for use in an interrupt handler. You can use the following attributes
+to modify the behavior:
+@table @code
+@item nested
+@cindex @code{nested} function attribute, NDS32
+This interrupt service routine is interruptible.
+@item not_nested
+@cindex @code{not_nested} function attribute, NDS32
+This interrupt service routine is not interruptible.
+@item nested_ready
+@cindex @code{nested_ready} function attribute, NDS32
+This interrupt service routine is interruptible after @code{PSW.GIE}
+(global interrupt enable) is set. This allows interrupt service routine to
+finish some short critical code before enabling interrupts.
+@item save_all
+@cindex @code{save_all} function attribute, NDS32
+The system will help save all registers into stack before entering
+interrupt handler.
+@item partial_save
+@cindex @code{partial_save} function attribute, NDS32
+The system will help save caller registers into stack before entering
+interrupt handler.
+@end table
+
+@item naked
+@cindex @code{naked} function attribute, NDS32
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+
+@item reset
+@cindex @code{reset} function attribute, NDS32
+@cindex reset handler functions
+Use this attribute on the NDS32 target to indicate that the specified function
+is a reset handler. The compiler will generate corresponding sections
+for use in a reset handler. You can use the following attributes
+to provide extra exception handling:
+@table @code
+@item nmi
+@cindex @code{nmi} function attribute, NDS32
+Provide a user-defined function to handle NMI exception.
+@item warm
+@cindex @code{warm} function attribute, NDS32
+Provide a user-defined function to handle warm reset exception.
+@end table
+@end table
+
+@node Nios II Function Attributes
+@subsection Nios II Function Attributes
+
+These function attributes are supported by the Nios II back end:
+
+@table @code
+@item target (@var{options})
+@cindex @code{target} function attribute
+As discussed in @ref{Common Function Attributes}, this attribute
+allows specification of target-specific compilation options.
+
+When compiling for Nios II, the following options are allowed:
+
+@table @samp
+@item custom-@var{insn}=@var{N}
+@itemx no-custom-@var{insn}
+@cindex @code{target("custom-@var{insn}=@var{N}")} function attribute, Nios II
+@cindex @code{target("no-custom-@var{insn}")} function attribute, Nios II
+Each @samp{custom-@var{insn}=@var{N}} attribute locally enables use of a
+custom instruction with encoding @var{N} when generating code that uses
+@var{insn}. Similarly, @samp{no-custom-@var{insn}} locally inhibits use of
+the custom instruction @var{insn}.
+These target attributes correspond to the
+@option{-mcustom-@var{insn}=@var{N}} and @option{-mno-custom-@var{insn}}
+command-line options, and support the same set of @var{insn} keywords.
+@xref{Nios II Options}, for more information.
+
+@item custom-fpu-cfg=@var{name}
+@cindex @code{target("custom-fpu-cfg=@var{name}")} function attribute, Nios II
+This attribute corresponds to the @option{-mcustom-fpu-cfg=@var{name}}
+command-line option, to select a predefined set of custom instructions
+named @var{name}.
+@xref{Nios II Options}, for more information.
+@end table
+@end table
+
+@node Nvidia PTX Function Attributes
+@subsection Nvidia PTX Function Attributes
+
+These function attributes are supported by the Nvidia PTX back end:
+
+@table @code
+@item kernel
+@cindex @code{kernel} attribute, Nvidia PTX
+This attribute indicates that the corresponding function should be compiled
+as a kernel function, which can be invoked from the host via the CUDA RT
+library.
+By default functions are only callable only from other PTX functions.
+
+Kernel functions must have @code{void} return type.
+@end table
+
+@node PowerPC Function Attributes
+@subsection PowerPC Function Attributes
+
+These function attributes are supported by the PowerPC back end:
+
+@table @code
+@item longcall
+@itemx shortcall
+@cindex indirect calls, PowerPC
+@cindex @code{longcall} function attribute, PowerPC
+@cindex @code{shortcall} function attribute, PowerPC
+The @code{longcall} attribute
+indicates that the function might be far away from the call site and
+require a different (more expensive) calling sequence. The
+@code{shortcall} attribute indicates that the function is always close
+enough for the shorter calling sequence to be used. These attributes
+override both the @option{-mlongcall} switch and
+the @code{#pragma longcall} setting.
+
+@xref{RS/6000 and PowerPC Options}, for more information on whether long
+calls are necessary.
+
+@item target (@var{options})
+@cindex @code{target} function attribute
+As discussed in @ref{Common Function Attributes}, this attribute
+allows specification of target-specific compilation options.
+
+On the PowerPC, the following options are allowed:
+
+@table @samp
+@item altivec
+@itemx no-altivec
+@cindex @code{target("altivec")} function attribute, PowerPC
+Generate code that uses (does not use) AltiVec instructions. In
+32-bit code, you cannot enable AltiVec instructions unless
+@option{-mabi=altivec} is used on the command line.
+
+@item cmpb
+@itemx no-cmpb
+@cindex @code{target("cmpb")} function attribute, PowerPC
+Generate code that uses (does not use) the compare bytes instruction
+implemented on the POWER6 processor and other processors that support
+the PowerPC V2.05 architecture.
+
+@item dlmzb
+@itemx no-dlmzb
+@cindex @code{target("dlmzb")} function attribute, PowerPC
+Generate code that uses (does not use) the string-search @samp{dlmzb}
+instruction on the IBM 405, 440, 464 and 476 processors. This instruction is
+generated by default when targeting those processors.
+
+@item fprnd
+@itemx no-fprnd
+@cindex @code{target("fprnd")} function attribute, PowerPC
+Generate code that uses (does not use) the FP round to integer
+instructions implemented on the POWER5+ processor and other processors
+that support the PowerPC V2.03 architecture.
+
+@item hard-dfp
+@itemx no-hard-dfp
+@cindex @code{target("hard-dfp")} function attribute, PowerPC
+Generate code that uses (does not use) the decimal floating-point
+instructions implemented on some POWER processors.
+
+@item isel
+@itemx no-isel
+@cindex @code{target("isel")} function attribute, PowerPC
+Generate code that uses (does not use) ISEL instruction.
+
+@item mfcrf
+@itemx no-mfcrf
+@cindex @code{target("mfcrf")} function attribute, PowerPC
+Generate code that uses (does not use) the move from condition
+register field instruction implemented on the POWER4 processor and
+other processors that support the PowerPC V2.01 architecture.
+
+@item mulhw
+@itemx no-mulhw
+@cindex @code{target("mulhw")} function attribute, PowerPC
+Generate code that uses (does not use) the half-word multiply and
+multiply-accumulate instructions on the IBM 405, 440, 464 and 476 processors.
+These instructions are generated by default when targeting those
+processors.
+
+@item multiple
+@itemx no-multiple
+@cindex @code{target("multiple")} function attribute, PowerPC
+Generate code that uses (does not use) the load multiple word
+instructions and the store multiple word instructions.
+
+@item update
+@itemx no-update
+@cindex @code{target("update")} function attribute, PowerPC
+Generate code that uses (does not use) the load or store instructions
+that update the base register to the address of the calculated memory
+location.
+
+@item popcntb
+@itemx no-popcntb
+@cindex @code{target("popcntb")} function attribute, PowerPC
+Generate code that uses (does not use) the popcount and double-precision
+FP reciprocal estimate instruction implemented on the POWER5
+processor and other processors that support the PowerPC V2.02
+architecture.
+
+@item popcntd
+@itemx no-popcntd
+@cindex @code{target("popcntd")} function attribute, PowerPC
+Generate code that uses (does not use) the popcount instruction
+implemented on the POWER7 processor and other processors that support
+the PowerPC V2.06 architecture.
+
+@item powerpc-gfxopt
+@itemx no-powerpc-gfxopt
+@cindex @code{target("powerpc-gfxopt")} function attribute, PowerPC
+Generate code that uses (does not use) the optional PowerPC
+architecture instructions in the Graphics group, including
+floating-point select.
+
+@item powerpc-gpopt
+@itemx no-powerpc-gpopt
+@cindex @code{target("powerpc-gpopt")} function attribute, PowerPC
+Generate code that uses (does not use) the optional PowerPC
+architecture instructions in the General Purpose group, including
+floating-point square root.
+
+@item recip-precision
+@itemx no-recip-precision
+@cindex @code{target("recip-precision")} function attribute, PowerPC
+Assume (do not assume) that the reciprocal estimate instructions
+provide higher-precision estimates than is mandated by the PowerPC
+ABI.
+
+@item string
+@itemx no-string
+@cindex @code{target("string")} function attribute, PowerPC
+Generate code that uses (does not use) the load string instructions
+and the store string word instructions to save multiple registers and
+do small block moves.
+
+@item vsx
+@itemx no-vsx
+@cindex @code{target("vsx")} function attribute, PowerPC
+Generate code that uses (does not use) vector/scalar (VSX)
+instructions, and also enable the use of built-in functions that allow
+more direct access to the VSX instruction set. In 32-bit code, you
+cannot enable VSX or AltiVec instructions unless
+@option{-mabi=altivec} is used on the command line.
+
+@item friz
+@itemx no-friz
+@cindex @code{target("friz")} function attribute, PowerPC
+Generate (do not generate) the @code{friz} instruction when the
+@option{-funsafe-math-optimizations} option is used to optimize
+rounding a floating-point value to 64-bit integer and back to floating
+point. The @code{friz} instruction does not return the same value if
+the floating-point number is too large to fit in an integer.
+
+@item avoid-indexed-addresses
+@itemx no-avoid-indexed-addresses
+@cindex @code{target("avoid-indexed-addresses")} function attribute, PowerPC
+Generate code that tries to avoid (not avoid) the use of indexed load
+or store instructions.
+
+@item paired
+@itemx no-paired
+@cindex @code{target("paired")} function attribute, PowerPC
+Generate code that uses (does not use) the generation of PAIRED simd
+instructions.
+
+@item longcall
+@itemx no-longcall
+@cindex @code{target("longcall")} function attribute, PowerPC
+Generate code that assumes (does not assume) that all calls are far
+away so that a longer more expensive calling sequence is required.
+
+@item cpu=@var{CPU}
+@cindex @code{target("cpu=@var{CPU}")} function attribute, PowerPC
+Specify the architecture to generate code for when compiling the
+function. If you select the @code{target("cpu=power7")} attribute when
+generating 32-bit code, VSX and AltiVec instructions are not generated
+unless you use the @option{-mabi=altivec} option on the command line.
+
+@item tune=@var{TUNE}
+@cindex @code{target("tune=@var{TUNE}")} function attribute, PowerPC
+Specify the architecture to tune for when compiling the function. If
+you do not specify the @code{target("tune=@var{TUNE}")} attribute and
+you do specify the @code{target("cpu=@var{CPU}")} attribute,
+compilation tunes for the @var{CPU} architecture, and not the
+default tuning specified on the command line.
+@end table
+
+On the PowerPC, the inliner does not inline a
+function that has different target options than the caller, unless the
+callee has a subset of the target options of the caller.
+@end table
+
+@node RISC-V Function Attributes
+@subsection RISC-V Function Attributes
+
+These function attributes are supported by the RISC-V back end:
+
+@table @code
+@item naked
+@cindex @code{naked} function attribute, RISC-V
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, RISC-V
+Use this attribute to indicate that the specified function is an interrupt
+handler. The compiler generates function entry and exit sequences suitable
+for use in an interrupt handler when this attribute is present.
+
+You can specify the kind of interrupt to be handled by adding an optional
+parameter to the interrupt attribute like this:
+
+@smallexample
+void f (void) __attribute__ ((interrupt ("user")));
+@end smallexample
+
+Permissible values for this parameter are @code{user}, @code{supervisor},
+and @code{machine}. If there is no parameter, then it defaults to
+@code{machine}.
+@end table
+
+@node RL78 Function Attributes
+@subsection RL78 Function Attributes
+
+These function attributes are supported by the RL78 back end:
+
+@table @code
+@item interrupt
+@itemx brk_interrupt
+@cindex @code{interrupt} function attribute, RL78
+@cindex @code{brk_interrupt} function attribute, RL78
+These attributes indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+
+Use @code{brk_interrupt} instead of @code{interrupt} for
+handlers intended to be used with the @code{BRK} opcode (i.e.@: those
+that must end with @code{RETB} instead of @code{RETI}).
+
+@item naked
+@cindex @code{naked} function attribute, RL78
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+@end table
+
+@node RX Function Attributes
+@subsection RX Function Attributes
+
+These function attributes are supported by the RX back end:
+
+@table @code
+@item fast_interrupt
+@cindex @code{fast_interrupt} function attribute, RX
+Use this attribute on the RX port to indicate that the specified
+function is a fast interrupt handler. This is just like the
+@code{interrupt} attribute, except that @code{freit} is used to return
+instead of @code{reit}.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, RX
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+
+On RX and RL78 targets, you may specify one or more vector numbers as arguments
+to the attribute, as well as naming an alternate table name.
+Parameters are handled sequentially, so one handler can be assigned to
+multiple entries in multiple tables. One may also pass the magic
+string @code{"$default"} which causes the function to be used for any
+unfilled slots in the current table.
+
+This example shows a simple assignment of a function to one vector in
+the default table (note that preprocessor macros may be used for
+chip-specific symbolic vector names):
+@smallexample
+void __attribute__ ((interrupt (5))) txd1_handler ();
+@end smallexample
+
+This example assigns a function to two slots in the default table
+(using preprocessor macros defined elsewhere) and makes it the default
+for the @code{dct} table:
+@smallexample
+void __attribute__ ((interrupt (RXD1_VECT,RXD2_VECT,"dct","$default")))
+ txd1_handler ();
+@end smallexample
+
+@item naked
+@cindex @code{naked} function attribute, RX
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+
+@item vector
+@cindex @code{vector} function attribute, RX
+This RX attribute is similar to the @code{interrupt} attribute, including its
+parameters, but does not make the function an interrupt-handler type
+function (i.e.@: it retains the normal C function calling ABI). See the
+@code{interrupt} attribute for a description of its arguments.
+@end table
+
+@node S/390 Function Attributes
+@subsection S/390 Function Attributes
+
+These function attributes are supported on the S/390:
+
+@table @code
+@item hotpatch (@var{halfwords-before-function-label},@var{halfwords-after-function-label})
+@cindex @code{hotpatch} function attribute, S/390
+
+On S/390 System z targets, you can use this function attribute to
+make GCC generate a ``hot-patching'' function prologue. If the
+@option{-mhotpatch=} command-line option is used at the same time,
+the @code{hotpatch} attribute takes precedence. The first of the
+two arguments specifies the number of halfwords to be added before
+the function label. A second argument can be used to specify the
+number of halfwords to be added after the function label. For
+both arguments the maximum allowed value is 1000000.
+
+If both arguments are zero, hotpatching is disabled.
+
+@item target (@var{options})
+@cindex @code{target} function attribute
+As discussed in @ref{Common Function Attributes}, this attribute
+allows specification of target-specific compilation options.
+
+On S/390, the following options are supported:
+
+@table @samp
+@item arch=
+@item tune=
+@item stack-guard=
+@item stack-size=
+@item branch-cost=
+@item warn-framesize=
+@item backchain
+@itemx no-backchain
+@item hard-dfp
+@itemx no-hard-dfp
+@item hard-float
+@itemx soft-float
+@item htm
+@itemx no-htm
+@item vx
+@itemx no-vx
+@item packed-stack
+@itemx no-packed-stack
+@item small-exec
+@itemx no-small-exec
+@item mvcle
+@itemx no-mvcle
+@item warn-dynamicstack
+@itemx no-warn-dynamicstack
+@end table
+
+The options work exactly like the S/390 specific command line
+options (without the prefix @option{-m}) except that they do not
+change any feature macros. For example,
+
+@smallexample
+@code{target("no-vx")}
+@end smallexample
+
+does not undefine the @code{__VEC__} macro.
+@end table
+
+@node SH Function Attributes
+@subsection SH Function Attributes
+
+These function attributes are supported on the SH family of processors:
+
+@table @code
+@item function_vector
+@cindex @code{function_vector} function attribute, SH
+@cindex calling functions through the function vector on SH2A
+On SH2A targets, this attribute declares a function to be called using the
+TBR relative addressing mode. The argument to this attribute is the entry
+number of the same function in a vector table containing all the TBR
+relative addressable functions. For correct operation the TBR must be setup
+accordingly to point to the start of the vector table before any functions with
+this attribute are invoked. Usually a good place to do the initialization is
+the startup routine. The TBR relative vector table can have at max 256 function
+entries. The jumps to these functions are generated using a SH2A specific,
+non delayed branch instruction JSR/N @@(disp8,TBR). You must use GAS and GLD
+from GNU binutils version 2.7 or later for this attribute to work correctly.
+
+In an application, for a function being called once, this attribute
+saves at least 8 bytes of code; and if other successive calls are being
+made to the same function, it saves 2 bytes of code per each of these
+calls.
+
+@item interrupt_handler
+@cindex @code{interrupt_handler} function attribute, SH
+Use this attribute to
+indicate that the specified function is an interrupt handler. The compiler
+generates function entry and exit sequences suitable for use in an
+interrupt handler when this attribute is present.
+
+@item nosave_low_regs
+@cindex @code{nosave_low_regs} function attribute, SH
+Use this attribute on SH targets to indicate that an @code{interrupt_handler}
+function should not save and restore registers R0..R7. This can be used on SH3*
+and SH4* targets that have a second R0..R7 register bank for non-reentrant
+interrupt handlers.
+
+@item renesas
+@cindex @code{renesas} function attribute, SH
+On SH targets this attribute specifies that the function or struct follows the
+Renesas ABI.
+
+@item resbank
+@cindex @code{resbank} function attribute, SH
+On the SH2A target, this attribute enables the high-speed register
+saving and restoration using a register bank for @code{interrupt_handler}
+routines. Saving to the bank is performed automatically after the CPU
+accepts an interrupt that uses a register bank.
+
+The nineteen 32-bit registers comprising general register R0 to R14,
+control register GBR, and system registers MACH, MACL, and PR and the
+vector table address offset are saved into a register bank. Register
+banks are stacked in first-in last-out (FILO) sequence. Restoration
+from the bank is executed by issuing a RESBANK instruction.
+
+@item sp_switch
+@cindex @code{sp_switch} function attribute, SH
+Use this attribute on the SH to indicate an @code{interrupt_handler}
+function should switch to an alternate stack. It expects a string
+argument that names a global variable holding the address of the
+alternate stack.
+
+@smallexample
+void *alt_stack;
+void f () __attribute__ ((interrupt_handler,
+ sp_switch ("alt_stack")));
+@end smallexample
+
+@item trap_exit
+@cindex @code{trap_exit} function attribute, SH
+Use this attribute on the SH for an @code{interrupt_handler} to return using
+@code{trapa} instead of @code{rte}. This attribute expects an integer
+argument specifying the trap number to be used.
+
+@item trapa_handler
+@cindex @code{trapa_handler} function attribute, SH
+On SH targets this function attribute is similar to @code{interrupt_handler}
+but it does not save and restore all registers.
+@end table
+
+@node Symbian OS Function Attributes
+@subsection Symbian OS Function Attributes
+
+@xref{Microsoft Windows Function Attributes}, for discussion of the
+@code{dllexport} and @code{dllimport} attributes.
+
+@node V850 Function Attributes
+@subsection V850 Function Attributes
+
+The V850 back end supports these function attributes:
+
+@table @code
+@item interrupt
+@itemx interrupt_handler
+@cindex @code{interrupt} function attribute, V850
+@cindex @code{interrupt_handler} function attribute, V850
+Use these attributes to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when either attribute is present.
+@end table
+
+@node Visium Function Attributes
+@subsection Visium Function Attributes
+
+These function attributes are supported by the Visium back end:
+
+@table @code
+@item interrupt
+@cindex @code{interrupt} function attribute, Visium
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+@end table
+
+@node x86 Function Attributes
+@subsection x86 Function Attributes
+
+These function attributes are supported by the x86 back end:
+
+@table @code
+@item cdecl
+@cindex @code{cdecl} function attribute, x86-32
+@cindex functions that pop the argument stack on x86-32
+@opindex mrtd
+On the x86-32 targets, the @code{cdecl} attribute causes the compiler to
+assume that the calling function pops off the stack space used to
+pass arguments. This is
+useful to override the effects of the @option{-mrtd} switch.
+
+@item fastcall
+@cindex @code{fastcall} function attribute, x86-32
+@cindex functions that pop the argument stack on x86-32
+On x86-32 targets, the @code{fastcall} attribute causes the compiler to
+pass the first argument (if of integral type) in the register ECX and
+the second argument (if of integral type) in the register EDX@. Subsequent
+and other typed arguments are passed on the stack. The called function
+pops the arguments off the stack. If the number of arguments is variable all
+arguments are pushed on the stack.
+
+@item thiscall
+@cindex @code{thiscall} function attribute, x86-32
+@cindex functions that pop the argument stack on x86-32
+On x86-32 targets, the @code{thiscall} attribute causes the compiler to
+pass the first argument (if of integral type) in the register ECX.
+Subsequent and other typed arguments are passed on the stack. The called
+function pops the arguments off the stack.
+If the number of arguments is variable all arguments are pushed on the
+stack.
+The @code{thiscall} attribute is intended for C++ non-static member functions.
+As a GCC extension, this calling convention can be used for C functions
+and for static member methods.
+
+@item ms_abi
+@itemx sysv_abi
+@cindex @code{ms_abi} function attribute, x86
+@cindex @code{sysv_abi} function attribute, x86
+
+On 32-bit and 64-bit x86 targets, you can use an ABI attribute
+to indicate which calling convention should be used for a function. The
+@code{ms_abi} attribute tells the compiler to use the Microsoft ABI,
+while the @code{sysv_abi} attribute tells the compiler to use the System V
+ELF ABI, which is used on GNU/Linux and other systems. The default is to use
+the Microsoft ABI when targeting Windows. On all other systems, the default
+is the System V ELF ABI.
+
+Note, the @code{ms_abi} attribute for Microsoft Windows 64-bit targets currently
+requires the @option{-maccumulate-outgoing-args} option.
+
+@item callee_pop_aggregate_return (@var{number})
+@cindex @code{callee_pop_aggregate_return} function attribute, x86
+
+On x86-32 targets, you can use this attribute to control how
+aggregates are returned in memory. If the caller is responsible for
+popping the hidden pointer together with the rest of the arguments, specify
+@var{number} equal to zero. If callee is responsible for popping the
+hidden pointer, specify @var{number} equal to one.
+
+The default x86-32 ABI assumes that the callee pops the
+stack for hidden pointer. However, on x86-32 Microsoft Windows targets,
+the compiler assumes that the
+caller pops the stack for hidden pointer.
+
+@item ms_hook_prologue
+@cindex @code{ms_hook_prologue} function attribute, x86
+
+On 32-bit and 64-bit x86 targets, you can use
+this function attribute to make GCC generate the ``hot-patching'' function
+prologue used in Win32 API functions in Microsoft Windows XP Service Pack 2
+and newer.
+
+@item naked
+@cindex @code{naked} function attribute, x86
+This attribute allows the compiler to construct the
+requisite function declaration, while allowing the body of the
+function to be assembly code. The specified function will not have
+prologue/epilogue sequences generated by the compiler. Only basic
+@code{asm} statements can safely be included in naked functions
+(@pxref{Basic Asm}). While using extended @code{asm} or a mixture of
+basic @code{asm} and C code may appear to work, they cannot be
+depended upon to work reliably and are not supported.
+
+@item regparm (@var{number})
+@cindex @code{regparm} function attribute, x86
+@cindex functions that are passed arguments in registers on x86-32
+On x86-32 targets, the @code{regparm} attribute causes the compiler to
+pass arguments number one to @var{number} if they are of integral type
+in registers EAX, EDX, and ECX instead of on the stack. Functions that
+take a variable number of arguments continue to be passed all of their
+arguments on the stack.
+
+Beware that on some ELF systems this attribute is unsuitable for
+global functions in shared libraries with lazy binding (which is the
+default). Lazy binding sends the first call via resolving code in
+the loader, which might assume EAX, EDX and ECX can be clobbered, as
+per the standard calling conventions. Solaris 8 is affected by this.
+Systems with the GNU C Library version 2.1 or higher
+and FreeBSD are believed to be
+safe since the loaders there save EAX, EDX and ECX. (Lazy binding can be
+disabled with the linker or the loader if desired, to avoid the
+problem.)
+
+@item sseregparm
+@cindex @code{sseregparm} function attribute, x86
+On x86-32 targets with SSE support, the @code{sseregparm} attribute
+causes the compiler to pass up to 3 floating-point arguments in
+SSE registers instead of on the stack. Functions that take a
+variable number of arguments continue to pass all of their
+floating-point arguments on the stack.
+
+@item force_align_arg_pointer
+@cindex @code{force_align_arg_pointer} function attribute, x86
+On x86 targets, the @code{force_align_arg_pointer} attribute may be
+applied to individual function definitions, generating an alternate
+prologue and epilogue that realigns the run-time stack if necessary.
+This supports mixing legacy codes that run with a 4-byte aligned stack
+with modern codes that keep a 16-byte stack for SSE compatibility.
+
+@item stdcall
+@cindex @code{stdcall} function attribute, x86-32
+@cindex functions that pop the argument stack on x86-32
+On x86-32 targets, the @code{stdcall} attribute causes the compiler to
+assume that the called function pops off the stack space used to
+pass arguments, unless it takes a variable number of arguments.
+
+@item no_caller_saved_registers
+@cindex @code{no_caller_saved_registers} function attribute, x86
+Use this attribute to indicate that the specified function has no
+caller-saved registers. That is, all registers are callee-saved. For
+example, this attribute can be used for a function called from an
+interrupt handler. The compiler generates proper function entry and
+exit sequences to save and restore any modified registers, except for
+the EFLAGS register. Since GCC doesn't preserve SSE, MMX nor x87
+states, the GCC option @option{-mgeneral-regs-only} should be used to
+compile functions with @code{no_caller_saved_registers} attribute.
+
+@item interrupt
+@cindex @code{interrupt} function attribute, x86
+Use this attribute to indicate that the specified function is an
+interrupt handler or an exception handler (depending on parameters passed
+to the function, explained further). The compiler generates function
+entry and exit sequences suitable for use in an interrupt handler when
+this attribute is present. The @code{IRET} instruction, instead of the
+@code{RET} instruction, is used to return from interrupt handlers. All
+registers, except for the EFLAGS register which is restored by the
+@code{IRET} instruction, are preserved by the compiler. Since GCC
+doesn't preserve SSE, MMX nor x87 states, the GCC option
+@option{-mgeneral-regs-only} should be used to compile interrupt and
+exception handlers.
+
+Any interruptible-without-stack-switch code must be compiled with
+@option{-mno-red-zone} since interrupt handlers can and will, because
+of the hardware design, touch the red zone.
+
+An interrupt handler must be declared with a mandatory pointer
+argument:
+
+@smallexample
+struct interrupt_frame;
+
+__attribute__ ((interrupt))
+void
+f (struct interrupt_frame *frame)
+@{
+@}
+@end smallexample
+
+@noindent
+and you must define @code{struct interrupt_frame} as described in the
+processor's manual.
+
+Exception handlers differ from interrupt handlers because the system
+pushes an error code on the stack. An exception handler declaration is
+similar to that for an interrupt handler, but with a different mandatory
+function signature. The compiler arranges to pop the error code off the
+stack before the @code{IRET} instruction.
+
+@smallexample
+#ifdef __x86_64__
+typedef unsigned long long int uword_t;
+#else
+typedef unsigned int uword_t;
+#endif
+
+struct interrupt_frame;
+
+__attribute__ ((interrupt))
+void
+f (struct interrupt_frame *frame, uword_t error_code)
+@{
+ ...
+@}
+@end smallexample
+
+Exception handlers should only be used for exceptions that push an error
+code; you should use an interrupt handler in other cases. The system
+will crash if the wrong kind of handler is used.
+
+@item target (@var{options})
+@cindex @code{target} function attribute
+As discussed in @ref{Common Function Attributes}, this attribute
+allows specification of target-specific compilation options.
+
+On the x86, the following options are allowed:
+@table @samp
+@item 3dnow
+@itemx no-3dnow
+@cindex @code{target("3dnow")} function attribute, x86
+Enable/disable the generation of the 3DNow!@: instructions.
+
+@item 3dnowa
+@itemx no-3dnowa
+@cindex @code{target("3dnowa")} function attribute, x86
+Enable/disable the generation of the enhanced 3DNow!@: instructions.
+
+@item abm
+@itemx no-abm
+@cindex @code{target("abm")} function attribute, x86
+Enable/disable the generation of the advanced bit instructions.
+
+@item adx
+@itemx no-adx
+@cindex @code{target("adx")} function attribute, x86
+Enable/disable the generation of the ADX instructions.
+
+@item aes
+@itemx no-aes
+@cindex @code{target("aes")} function attribute, x86
+Enable/disable the generation of the AES instructions.
+
+@item avx
+@itemx no-avx
+@cindex @code{target("avx")} function attribute, x86
+Enable/disable the generation of the AVX instructions.
+
+@item avx2
+@itemx no-avx2
+@cindex @code{target("avx2")} function attribute, x86
+Enable/disable the generation of the AVX2 instructions.
+
+@item avx5124fmaps
+@itemx no-avx5124fmaps
+@cindex @code{target("avx5124fmaps")} function attribute, x86
+Enable/disable the generation of the AVX5124FMAPS instructions.
+
+@item avx5124vnniw
+@itemx no-avx5124vnniw
+@cindex @code{target("avx5124vnniw")} function attribute, x86
+Enable/disable the generation of the AVX5124VNNIW instructions.
+
+@item avx512bitalg
+@itemx no-avx512bitalg
+@cindex @code{target("avx512bitalg")} function attribute, x86
+Enable/disable the generation of the AVX512BITALG instructions.
+
+@item avx512bw
+@itemx no-avx512bw
+@cindex @code{target("avx512bw")} function attribute, x86
+Enable/disable the generation of the AVX512BW instructions.
+
+@item avx512cd
+@itemx no-avx512cd
+@cindex @code{target("avx512cd")} function attribute, x86
+Enable/disable the generation of the AVX512CD instructions.
+
+@item avx512dq
+@itemx no-avx512dq
+@cindex @code{target("avx512dq")} function attribute, x86
+Enable/disable the generation of the AVX512DQ instructions.
+
+@item avx512er
+@itemx no-avx512er
+@cindex @code{target("avx512er")} function attribute, x86
+Enable/disable the generation of the AVX512ER instructions.
+
+@item avx512f
+@itemx no-avx512f
+@cindex @code{target("avx512f")} function attribute, x86
+Enable/disable the generation of the AVX512F instructions.
+
+@item avx512ifma
+@itemx no-avx512ifma
+@cindex @code{target("avx512ifma")} function attribute, x86
+Enable/disable the generation of the AVX512IFMA instructions.
+
+@item avx512pf
+@itemx no-avx512pf
+@cindex @code{target("avx512pf")} function attribute, x86
+Enable/disable the generation of the AVX512PF instructions.
+
+@item avx512vbmi
+@itemx no-avx512vbmi
+@cindex @code{target("avx512vbmi")} function attribute, x86
+Enable/disable the generation of the AVX512VBMI instructions.
+
+@item avx512vbmi2
+@itemx no-avx512vbmi2
+@cindex @code{target("avx512vbmi2")} function attribute, x86
+Enable/disable the generation of the AVX512VBMI2 instructions.
+
+@item avx512vl
+@itemx no-avx512vl
+@cindex @code{target("avx512vl")} function attribute, x86
+Enable/disable the generation of the AVX512VL instructions.
+
+@item avx512vnni
+@itemx no-avx512vnni
+@cindex @code{target("avx512vnni")} function attribute, x86
+Enable/disable the generation of the AVX512VNNI instructions.
+
+@item avx512vpopcntdq
+@itemx no-avx512vpopcntdq
+@cindex @code{target("avx512vpopcntdq")} function attribute, x86
+Enable/disable the generation of the AVX512VPOPCNTDQ instructions.
+
+@item bmi
+@itemx no-bmi
+@cindex @code{target("bmi")} function attribute, x86
+Enable/disable the generation of the BMI instructions.
+
+@item bmi2
+@itemx no-bmi2
+@cindex @code{target("bmi2")} function attribute, x86
+Enable/disable the generation of the BMI2 instructions.
+
+@item cldemote
+@itemx no-cldemote
+@cindex @code{target("cldemote")} function attribute, x86
+Enable/disable the generation of the CLDEMOTE instructions.
+
+@item clflushopt
+@itemx no-clflushopt
+@cindex @code{target("clflushopt")} function attribute, x86
+Enable/disable the generation of the CLFLUSHOPT instructions.
+
+@item clwb
+@itemx no-clwb
+@cindex @code{target("clwb")} function attribute, x86
+Enable/disable the generation of the CLWB instructions.
+
+@item clzero
+@itemx no-clzero
+@cindex @code{target("clzero")} function attribute, x86
+Enable/disable the generation of the CLZERO instructions.
+
+@item crc32
+@itemx no-crc32
+@cindex @code{target("crc32")} function attribute, x86
+Enable/disable the generation of the CRC32 instructions.
+
+@item cx16
+@itemx no-cx16
+@cindex @code{target("cx16")} function attribute, x86
+Enable/disable the generation of the CMPXCHG16B instructions.
+
+@item default
+@cindex @code{target("default")} function attribute, x86
+@xref{Function Multiversioning}, where it is used to specify the
+default function version.
+
+@item f16c
+@itemx no-f16c
+@cindex @code{target("f16c")} function attribute, x86
+Enable/disable the generation of the F16C instructions.
+
+@item fma
+@itemx no-fma
+@cindex @code{target("fma")} function attribute, x86
+Enable/disable the generation of the FMA instructions.
+
+@item fma4
+@itemx no-fma4
+@cindex @code{target("fma4")} function attribute, x86
+Enable/disable the generation of the FMA4 instructions.
+
+@item fsgsbase
+@itemx no-fsgsbase
+@cindex @code{target("fsgsbase")} function attribute, x86
+Enable/disable the generation of the FSGSBASE instructions.
+
+@item fxsr
+@itemx no-fxsr
+@cindex @code{target("fxsr")} function attribute, x86
+Enable/disable the generation of the FXSR instructions.
+
+@item gfni
+@itemx no-gfni
+@cindex @code{target("gfni")} function attribute, x86
+Enable/disable the generation of the GFNI instructions.
+
+@item hle
+@itemx no-hle
+@cindex @code{target("hle")} function attribute, x86
+Enable/disable the generation of the HLE instruction prefixes.
+
+@item lwp
+@itemx no-lwp
+@cindex @code{target("lwp")} function attribute, x86
+Enable/disable the generation of the LWP instructions.
+
+@item lzcnt
+@itemx no-lzcnt
+@cindex @code{target("lzcnt")} function attribute, x86
+Enable/disable the generation of the LZCNT instructions.
+
+@item mmx
+@itemx no-mmx
+@cindex @code{target("mmx")} function attribute, x86
+Enable/disable the generation of the MMX instructions.
+
+@item movbe
+@itemx no-movbe
+@cindex @code{target("movbe")} function attribute, x86
+Enable/disable the generation of the MOVBE instructions.
+
+@item movdir64b
+@itemx no-movdir64b
+@cindex @code{target("movdir64b")} function attribute, x86
+Enable/disable the generation of the MOVDIR64B instructions.
+
+@item movdiri
+@itemx no-movdiri
+@cindex @code{target("movdiri")} function attribute, x86
+Enable/disable the generation of the MOVDIRI instructions.
+
+@item mwait
+@itemx no-mwait
+@cindex @code{target("mwait")} function attribute, x86
+Enable/disable the generation of the MWAIT and MONITOR instructions.
+
+@item mwaitx
+@itemx no-mwaitx
+@cindex @code{target("mwaitx")} function attribute, x86
+Enable/disable the generation of the MWAITX instructions.
+
+@item pclmul
+@itemx no-pclmul
+@cindex @code{target("pclmul")} function attribute, x86
+Enable/disable the generation of the PCLMUL instructions.
+
+@item pconfig
+@itemx no-pconfig
+@cindex @code{target("pconfig")} function attribute, x86
+Enable/disable the generation of the PCONFIG instructions.
+
+@item pku
+@itemx no-pku
+@cindex @code{target("pku")} function attribute, x86
+Enable/disable the generation of the PKU instructions.
+
+@item popcnt
+@itemx no-popcnt
+@cindex @code{target("popcnt")} function attribute, x86
+Enable/disable the generation of the POPCNT instruction.
+
+@item prefetchwt1
+@itemx no-prefetchwt1
+@cindex @code{target("prefetchwt1")} function attribute, x86
+Enable/disable the generation of the PREFETCHWT1 instructions.
+
+@item prfchw
+@itemx no-prfchw
+@cindex @code{target("prfchw")} function attribute, x86
+Enable/disable the generation of the PREFETCHW instruction.
+
+@item ptwrite
+@itemx no-ptwrite
+@cindex @code{target("ptwrite")} function attribute, x86
+Enable/disable the generation of the PTWRITE instructions.
+
+@item rdpid
+@itemx no-rdpid
+@cindex @code{target("rdpid")} function attribute, x86
+Enable/disable the generation of the RDPID instructions.
+
+@item rdrnd
+@itemx no-rdrnd
+@cindex @code{target("rdrnd")} function attribute, x86
+Enable/disable the generation of the RDRND instructions.
+
+@item rdseed
+@itemx no-rdseed
+@cindex @code{target("rdseed")} function attribute, x86
+Enable/disable the generation of the RDSEED instructions.
+
+@item rtm
+@itemx no-rtm
+@cindex @code{target("rtm")} function attribute, x86
+Enable/disable the generation of the RTM instructions.
+
+@item sahf
+@itemx no-sahf
+@cindex @code{target("sahf")} function attribute, x86
+Enable/disable the generation of the SAHF instructions.
+
+@item sgx
+@itemx no-sgx
+@cindex @code{target("sgx")} function attribute, x86
+Enable/disable the generation of the SGX instructions.
+
+@item sha
+@itemx no-sha
+@cindex @code{target("sha")} function attribute, x86
+Enable/disable the generation of the SHA instructions.
+
+@item shstk
+@itemx no-shstk
+@cindex @code{target("shstk")} function attribute, x86
+Enable/disable the shadow stack built-in functions from CET.
+
+@item sse
+@itemx no-sse
+@cindex @code{target("sse")} function attribute, x86
+Enable/disable the generation of the SSE instructions.
+
+@item sse2
+@itemx no-sse2
+@cindex @code{target("sse2")} function attribute, x86
+Enable/disable the generation of the SSE2 instructions.
+
+@item sse3
+@itemx no-sse3
+@cindex @code{target("sse3")} function attribute, x86
+Enable/disable the generation of the SSE3 instructions.
+
+@item sse4
+@itemx no-sse4
+@cindex @code{target("sse4")} function attribute, x86
+Enable/disable the generation of the SSE4 instructions (both SSE4.1
+and SSE4.2).
+
+@item sse4.1
+@itemx no-sse4.1
+@cindex @code{target("sse4.1")} function attribute, x86
+Enable/disable the generation of the SSE4.1 instructions.
+
+@item sse4.2
+@itemx no-sse4.2
+@cindex @code{target("sse4.2")} function attribute, x86
+Enable/disable the generation of the SSE4.2 instructions.
+
+@item sse4a
+@itemx no-sse4a
+@cindex @code{target("sse4a")} function attribute, x86
+Enable/disable the generation of the SSE4A instructions.
+
+@item ssse3
+@itemx no-ssse3
+@cindex @code{target("ssse3")} function attribute, x86
+Enable/disable the generation of the SSSE3 instructions.
+
+@item tbm
+@itemx no-tbm
+@cindex @code{target("tbm")} function attribute, x86
+Enable/disable the generation of the TBM instructions.
+
+@item vaes
+@itemx no-vaes
+@cindex @code{target("vaes")} function attribute, x86
+Enable/disable the generation of the VAES instructions.
+
+@item vpclmulqdq
+@itemx no-vpclmulqdq
+@cindex @code{target("vpclmulqdq")} function attribute, x86
+Enable/disable the generation of the VPCLMULQDQ instructions.
+
+@item waitpkg
+@itemx no-waitpkg
+@cindex @code{target("waitpkg")} function attribute, x86
+Enable/disable the generation of the WAITPKG instructions.
+
+@item wbnoinvd
+@itemx no-wbnoinvd
+@cindex @code{target("wbnoinvd")} function attribute, x86
+Enable/disable the generation of the WBNOINVD instructions.
+
+@item xop
+@itemx no-xop
+@cindex @code{target("xop")} function attribute, x86
+Enable/disable the generation of the XOP instructions.
+
+@item xsave
+@itemx no-xsave
+@cindex @code{target("xsave")} function attribute, x86
+Enable/disable the generation of the XSAVE instructions.
+
+@item xsavec
+@itemx no-xsavec
+@cindex @code{target("xsavec")} function attribute, x86
+Enable/disable the generation of the XSAVEC instructions.
+
+@item xsaveopt
+@itemx no-xsaveopt
+@cindex @code{target("xsaveopt")} function attribute, x86
+Enable/disable the generation of the XSAVEOPT instructions.
+
+@item xsaves
+@itemx no-xsaves
+@cindex @code{target("xsaves")} function attribute, x86
+Enable/disable the generation of the XSAVES instructions.
+
+@item amx-tile
+@itemx no-amx-tile
+@cindex @code{target("amx-tile")} function attribute, x86
+Enable/disable the generation of the AMX-TILE instructions.
+
+@item amx-int8
+@itemx no-amx-int8
+@cindex @code{target("amx-int8")} function attribute, x86
+Enable/disable the generation of the AMX-INT8 instructions.
+
+@item amx-bf16
+@itemx no-amx-bf16
+@cindex @code{target("amx-bf16")} function attribute, x86
+Enable/disable the generation of the AMX-BF16 instructions.
+
+@item uintr
+@itemx no-uintr
+@cindex @code{target("uintr")} function attribute, x86
+Enable/disable the generation of the UINTR instructions.
+
+@item hreset
+@itemx no-hreset
+@cindex @code{target("hreset")} function attribute, x86
+Enable/disable the generation of the HRESET instruction.
+
+@item kl
+@itemx no-kl
+@cindex @code{target("kl")} function attribute, x86
+Enable/disable the generation of the KEYLOCKER instructions.
+
+@item widekl
+@itemx no-widekl
+@cindex @code{target("widekl")} function attribute, x86
+Enable/disable the generation of the WIDEKL instructions.
+
+@item avxvnni
+@itemx no-avxvnni
+@cindex @code{target("avxvnni")} function attribute, x86
+Enable/disable the generation of the AVXVNNI instructions.
+
+@item avxifma
+@itemx no-avxifma
+@cindex @code{target("avxifma")} function attribute, x86
+Enable/disable the generation of the AVXIFMA instructions.
+
+@item avxvnniint8
+@itemx no-avxvnniint8
+@cindex @code{target("avxvnniint8")} function attribute, x86
+Enable/disable the generation of the AVXVNNIINT8 instructions.
+
+@item avxneconvert
+@itemx no-avxneconvert
+@cindex @code{target("avxneconvert")} function attribute, x86
+Enable/disable the generation of the AVXNECONVERT instructions.
+
+@item cmpccxadd
+@itemx no-cmpccxadd
+@cindex @code{target("cmpccxadd")} function attribute, x86
+Enable/disable the generation of the CMPccXADD instructions.
+
+@item amx-fp16
+@itemx no-amx-fp16
+@cindex @code{target("amx-fp16")} function attribute, x86
+Enable/disable the generation of the AMX-FP16 instructions.
+
+@item prefetchi
+@itemx no-prefetchi
+@cindex @code{target("prefetchi")} function attribute, x86
+Enable/disable the generation of the PREFETCHI instructions.
+
+@item raoint
+@itemx no-raoint
+@cindex @code{target("raoint")} function attribute, x86
+Enable/disable the generation of the RAOINT instructions.
+
+@item cld
+@itemx no-cld
+@cindex @code{target("cld")} function attribute, x86
+Enable/disable the generation of the CLD before string moves.
+
+@item fancy-math-387
+@itemx no-fancy-math-387
+@cindex @code{target("fancy-math-387")} function attribute, x86
+Enable/disable the generation of the @code{sin}, @code{cos}, and
+@code{sqrt} instructions on the 387 floating-point unit.
+
+@item ieee-fp
+@itemx no-ieee-fp
+@cindex @code{target("ieee-fp")} function attribute, x86
+Enable/disable the generation of floating point that depends on IEEE arithmetic.
+
+@item inline-all-stringops
+@itemx no-inline-all-stringops
+@cindex @code{target("inline-all-stringops")} function attribute, x86
+Enable/disable inlining of string operations.
+
+@item inline-stringops-dynamically
+@itemx no-inline-stringops-dynamically
+@cindex @code{target("inline-stringops-dynamically")} function attribute, x86
+Enable/disable the generation of the inline code to do small string
+operations and calling the library routines for large operations.
+
+@item align-stringops
+@itemx no-align-stringops
+@cindex @code{target("align-stringops")} function attribute, x86
+Do/do not align destination of inlined string operations.
+
+@item recip
+@itemx no-recip
+@cindex @code{target("recip")} function attribute, x86
+Enable/disable the generation of RCPSS, RCPPS, RSQRTSS and RSQRTPS
+instructions followed an additional Newton-Raphson step instead of
+doing a floating-point division.
+
+@item general-regs-only
+@cindex @code{target("general-regs-only")} function attribute, x86
+Generate code which uses only the general registers.
+
+@item arch=@var{ARCH}
+@cindex @code{target("arch=@var{ARCH}")} function attribute, x86
+Specify the architecture to generate code for in compiling the function.
+
+@item tune=@var{TUNE}
+@cindex @code{target("tune=@var{TUNE}")} function attribute, x86
+Specify the architecture to tune for in compiling the function.
+
+@item fpmath=@var{FPMATH}
+@cindex @code{target("fpmath=@var{FPMATH}")} function attribute, x86
+Specify which floating-point unit to use. You must specify the
+@code{target("fpmath=sse,387")} option as
+@code{target("fpmath=sse+387")} because the comma would separate
+different options.
+
+@item prefer-vector-width=@var{OPT}
+@cindex @code{prefer-vector-width} function attribute, x86
+On x86 targets, the @code{prefer-vector-width} attribute informs the
+compiler to use @var{OPT}-bit vector width in instructions
+instead of the default on the selected platform.
+
+Valid @var{OPT} values are:
+
+@table @samp
+@item none
+No extra limitations applied to GCC other than defined by the selected platform.
+
+@item 128
+Prefer 128-bit vector width for instructions.
+
+@item 256
+Prefer 256-bit vector width for instructions.
+
+@item 512
+Prefer 512-bit vector width for instructions.
+@end table
+
+On the x86, the inliner does not inline a
+function that has different target options than the caller, unless the
+callee has a subset of the target options of the caller. For example
+a function declared with @code{target("sse3")} can inline a function
+with @code{target("sse2")}, since @code{-msse3} implies @code{-msse2}.
+@end table
+
+@item indirect_branch("@var{choice}")
+@cindex @code{indirect_branch} function attribute, x86
+On x86 targets, the @code{indirect_branch} attribute causes the compiler
+to convert indirect call and jump with @var{choice}. @samp{keep}
+keeps indirect call and jump unmodified. @samp{thunk} converts indirect
+call and jump to call and return thunk. @samp{thunk-inline} converts
+indirect call and jump to inlined call and return thunk.
+@samp{thunk-extern} converts indirect call and jump to external call
+and return thunk provided in a separate object file.
+
+@item function_return("@var{choice}")
+@cindex @code{function_return} function attribute, x86
+On x86 targets, the @code{function_return} attribute causes the compiler
+to convert function return with @var{choice}. @samp{keep} keeps function
+return unmodified. @samp{thunk} converts function return to call and
+return thunk. @samp{thunk-inline} converts function return to inlined
+call and return thunk. @samp{thunk-extern} converts function return to
+external call and return thunk provided in a separate object file.
+
+@item nocf_check
+@cindex @code{nocf_check} function attribute
+The @code{nocf_check} attribute on a function is used to inform the
+compiler that the function's prologue should not be instrumented when
+compiled with the @option{-fcf-protection=branch} option. The
+compiler assumes that the function's address is a valid target for a
+control-flow transfer.
+
+The @code{nocf_check} attribute on a type of pointer to function is
+used to inform the compiler that a call through the pointer should
+not be instrumented when compiled with the
+@option{-fcf-protection=branch} option. The compiler assumes
+that the function's address from the pointer is a valid target for
+a control-flow transfer. A direct function call through a function
+name is assumed to be a safe call thus direct calls are not
+instrumented by the compiler.
+
+The @code{nocf_check} attribute is applied to an object's type.
+In case of assignment of a function address or a function pointer to
+another pointer, the attribute is not carried over from the right-hand
+object's type; the type of left-hand object stays unchanged. The
+compiler checks for @code{nocf_check} attribute mismatch and reports
+a warning in case of mismatch.
+
+@smallexample
+@{
+int foo (void) __attribute__(nocf_check);
+void (*foo1)(void) __attribute__(nocf_check);
+void (*foo2)(void);
+
+/* foo's address is assumed to be valid. */
+int
+foo (void)
+
+ /* This call site is not checked for control-flow
+ validity. */
+ (*foo1)();
+
+ /* A warning is issued about attribute mismatch. */
+ foo1 = foo2;
+
+ /* This call site is still not checked. */
+ (*foo1)();
+
+ /* This call site is checked. */
+ (*foo2)();
+
+ /* A warning is issued about attribute mismatch. */
+ foo2 = foo1;
+
+ /* This call site is still checked. */
+ (*foo2)();
+
+ return 0;
+@}
+@end smallexample
+
+@item cf_check
+@cindex @code{cf_check} function attribute, x86
+
+The @code{cf_check} attribute on a function is used to inform the
+compiler that ENDBR instruction should be placed at the function
+entry when @option{-fcf-protection=branch} is enabled.
+
+@item indirect_return
+@cindex @code{indirect_return} function attribute, x86
+
+The @code{indirect_return} attribute can be applied to a function,
+as well as variable or type of function pointer to inform the
+compiler that the function may return via indirect branch.
+
+@item fentry_name("@var{name}")
+@cindex @code{fentry_name} function attribute, x86
+On x86 targets, the @code{fentry_name} attribute sets the function to
+call on function entry when function instrumentation is enabled
+with @option{-pg -mfentry}. When @var{name} is nop then a 5 byte
+nop sequence is generated.
+
+@item fentry_section("@var{name}")
+@cindex @code{fentry_section} function attribute, x86
+On x86 targets, the @code{fentry_section} attribute sets the name
+of the section to record function entry instrumentation calls in when
+enabled with @option{-pg -mrecord-mcount}
+
+@item nodirect_extern_access
+@cindex @code{nodirect_extern_access} function attribute
+@opindex mno-direct-extern-access
+This attribute, attached to a global variable or function, is the
+counterpart to option @option{-mno-direct-extern-access}.
+
+@end table
+
+@node Xstormy16 Function Attributes
+@subsection Xstormy16 Function Attributes
+
+These function attributes are supported by the Xstormy16 back end:
+
+@table @code
+@item interrupt
+@cindex @code{interrupt} function attribute, Xstormy16
+Use this attribute to indicate
+that the specified function is an interrupt handler. The compiler generates
+function entry and exit sequences suitable for use in an interrupt handler
+when this attribute is present.
+@end table
+
+@node Variable Attributes
+@section Specifying Attributes of Variables
+@cindex attribute of variables
+@cindex variable attributes
+
+The keyword @code{__attribute__} allows you to specify special properties
+of variables, function parameters, or structure, union, and, in C++, class
+members. This @code{__attribute__} keyword is followed by an attribute
+specification enclosed in double parentheses. Some attributes are currently
+defined generically for variables. Other attributes are defined for
+variables on particular target systems. Other attributes are available
+for functions (@pxref{Function Attributes}), labels (@pxref{Label Attributes}),
+enumerators (@pxref{Enumerator Attributes}), statements
+(@pxref{Statement Attributes}), and for types (@pxref{Type Attributes}).
+Other front ends might define more attributes
+(@pxref{C++ Extensions,,Extensions to the C++ Language}).
+
+@xref{Attribute Syntax}, for details of the exact syntax for using
+attributes.
+
+@menu
+* Common Variable Attributes::
+* ARC Variable Attributes::
+* AVR Variable Attributes::
+* Blackfin Variable Attributes::
+* H8/300 Variable Attributes::
+* IA-64 Variable Attributes::
+* LoongArch Variable Attributes::
+* M32R/D Variable Attributes::
+* MeP Variable Attributes::
+* Microsoft Windows Variable Attributes::
+* MSP430 Variable Attributes::
+* Nvidia PTX Variable Attributes::
+* PowerPC Variable Attributes::
+* RL78 Variable Attributes::
+* V850 Variable Attributes::
+* x86 Variable Attributes::
+* Xstormy16 Variable Attributes::
+@end menu
+
+@node Common Variable Attributes
+@subsection Common Variable Attributes
+
+The following attributes are supported on most targets.
+
+@table @code
+
+@item alias ("@var{target}")
+@cindex @code{alias} variable attribute
+The @code{alias} variable attribute causes the declaration to be emitted
+as an alias for another symbol known as an @dfn{alias target}. Except
+for top-level qualifiers the alias target must have the same type as
+the alias. For instance, the following
+
+@smallexample
+int var_target;
+extern int __attribute__ ((alias ("var_target"))) var_alias;
+@end smallexample
+
+@noindent
+defines @code{var_alias} to be an alias for the @code{var_target} variable.
+
+It is an error if the alias target is not defined in the same translation
+unit as the alias.
+
+Note that in the absence of the attribute GCC assumes that distinct
+declarations with external linkage denote distinct objects. Using both
+the alias and the alias target to access the same object is undefined
+in a translation unit without a declaration of the alias with the attribute.
+
+This attribute requires assembler and object file support, and may not be
+available on all targets.
+
+@cindex @code{aligned} variable attribute
+@item aligned
+@itemx aligned (@var{alignment})
+The @code{aligned} attribute specifies a minimum alignment for the variable
+or structure field, measured in bytes. When specified, @var{alignment} must
+be an integer constant power of 2. Specifying no @var{alignment} argument
+implies the maximum alignment for the target, which is often, but by no
+means always, 8 or 16 bytes.
+
+For example, the declaration:
+
+@smallexample
+int x __attribute__ ((aligned (16))) = 0;
+@end smallexample
+
+@noindent
+causes the compiler to allocate the global variable @code{x} on a
+16-byte boundary. On a 68040, this could be used in conjunction with
+an @code{asm} expression to access the @code{move16} instruction which
+requires 16-byte aligned operands.
+
+You can also specify the alignment of structure fields. For example, to
+create a double-word aligned @code{int} pair, you could write:
+
+@smallexample
+struct foo @{ int x[2] __attribute__ ((aligned (8))); @};
+@end smallexample
+
+@noindent
+This is an alternative to creating a union with a @code{double} member,
+which forces the union to be double-word aligned.
+
+As in the preceding examples, you can explicitly specify the alignment
+(in bytes) that you wish the compiler to use for a given variable or
+structure field. Alternatively, you can leave out the alignment factor
+and just ask the compiler to align a variable or field to the
+default alignment for the target architecture you are compiling for.
+The default alignment is sufficient for all scalar types, but may not be
+enough for all vector types on a target that supports vector operations.
+The default alignment is fixed for a particular target ABI.
+
+GCC also provides a target specific macro @code{__BIGGEST_ALIGNMENT__},
+which is the largest alignment ever used for any data type on the
+target machine you are compiling for. For example, you could write:
+
+@smallexample
+short array[3] __attribute__ ((aligned (__BIGGEST_ALIGNMENT__)));
+@end smallexample
+
+The compiler automatically sets the alignment for the declared
+variable or field to @code{__BIGGEST_ALIGNMENT__}. Doing this can
+often make copy operations more efficient, because the compiler can
+use whatever instructions copy the biggest chunks of memory when
+performing copies to or from the variables or fields that you have
+aligned this way. Note that the value of @code{__BIGGEST_ALIGNMENT__}
+may change depending on command-line options.
+
+When used on a struct, or struct member, the @code{aligned} attribute can
+only increase the alignment; in order to decrease it, the @code{packed}
+attribute must be specified as well. When used as part of a typedef, the
+@code{aligned} attribute can both increase and decrease alignment, and
+specifying the @code{packed} attribute generates a warning.
+
+Note that the effectiveness of @code{aligned} attributes for static
+variables may be limited by inherent limitations in the system linker
+and/or object file format. On some systems, the linker is
+only able to arrange for variables to be aligned up to a certain maximum
+alignment. (For some linkers, the maximum supported alignment may
+be very very small.) If your linker is only able to align variables
+up to a maximum of 8-byte alignment, then specifying @code{aligned(16)}
+in an @code{__attribute__} still only provides you with 8-byte
+alignment. See your linker documentation for further information.
+
+Stack variables are not affected by linker restrictions; GCC can properly
+align them on any target.
+
+The @code{aligned} attribute can also be used for functions
+(@pxref{Common Function Attributes}.)
+
+@cindex @code{warn_if_not_aligned} variable attribute
+@item warn_if_not_aligned (@var{alignment})
+This attribute specifies a threshold for the structure field, measured
+in bytes. If the structure field is aligned below the threshold, a
+warning will be issued. For example, the declaration:
+
+@smallexample
+struct foo
+@{
+ int i1;
+ int i2;
+ unsigned long long x __attribute__ ((warn_if_not_aligned (16)));
+@};
+@end smallexample
+
+@noindent
+causes the compiler to issue an warning on @code{struct foo}, like
+@samp{warning: alignment 8 of 'struct foo' is less than 16}.
+The compiler also issues a warning, like @samp{warning: 'x' offset
+8 in 'struct foo' isn't aligned to 16}, when the structure field has
+the misaligned offset:
+
+@smallexample
+struct __attribute__ ((aligned (16))) foo
+@{
+ int i1;
+ int i2;
+ unsigned long long x __attribute__ ((warn_if_not_aligned (16)));
+@};
+@end smallexample
+
+This warning can be disabled by @option{-Wno-if-not-aligned}.
+The @code{warn_if_not_aligned} attribute can also be used for types
+(@pxref{Common Type Attributes}.)
+
+@cindex @code{strict_flex_array} variable attribute
+@item strict_flex_array (@var{level})
+The @code{strict_flex_array} attribute should be attached to the trailing
+array field of a structure. It controls when to treat the trailing array
+field of a structure as a flexible array member for the purposes of accessing
+the elements of such an array.
+@var{level} must be an integer betwen 0 to 3.
+
+@var{level}=0 is the least strict level, all trailing arrays of structures
+are treated as flexible array members. @var{level}=3 is the strictest level,
+only when the trailing array is declared as a flexible array member per C99
+standard onwards (@samp{[]}), it is treated as a flexible array member.
+
+There are two more levels in between 0 and 3, which are provided to support
+older codes that use GCC zero-length array extension (@samp{[0]}) or one-element
+array as flexible array members (@samp{[1]}):
+When @var{level} is 1, the trailing array is treated as a flexible array member
+when it is declared as either @samp{[]}, @samp{[0]}, or @samp{[1]};
+When @var{level} is 2, the trailing array is treated as a flexible array member
+when it is declared as either @samp{[]}, or @samp{[0]}.
+
+This attribute can be used with or without the @option{-fstrict-flex-arrays}.
+When both the attribute and the option present at the same time, the level of
+the strictness for the specific trailing array field is determined by the
+attribute.
+
+@item alloc_size (@var{position})
+@itemx alloc_size (@var{position-1}, @var{position-2})
+@cindex @code{alloc_size} variable attribute
+The @code{alloc_size} variable attribute may be applied to the declaration
+of a pointer to a function that returns a pointer and takes at least one
+argument of an integer type. It indicates that the returned pointer points
+to an object whose size is given by the function argument at @var{position},
+or by the product of the arguments at @var{position-1} and @var{position-2}.
+Meaningful sizes are positive values less than @code{PTRDIFF_MAX}. Other
+sizes are diagnosed when detected. GCC uses this information to improve
+the results of @code{__builtin_object_size}.
+
+For instance, the following declarations
+
+@smallexample
+typedef __attribute__ ((alloc_size (1, 2))) void*
+ (*calloc_ptr) (size_t, size_t);
+typedef __attribute__ ((alloc_size (1))) void*
+ (*malloc_ptr) (size_t);
+@end smallexample
+
+@noindent
+specify that @code{calloc_ptr} is a pointer of a function that, like
+the standard C function @code{calloc}, returns an object whose size
+is given by the product of arguments 1 and 2, and similarly, that
+@code{malloc_ptr}, like the standard C function @code{malloc},
+returns an object whose size is given by argument 1 to the function.
+
+@item cleanup (@var{cleanup_function})
+@cindex @code{cleanup} variable attribute
+The @code{cleanup} attribute runs a function when the variable goes
+out of scope. This attribute can only be applied to auto function
+scope variables; it may not be applied to parameters or variables
+with static storage duration. The function must take one parameter,
+a pointer to a type compatible with the variable. The return value
+of the function (if any) is ignored.
+
+If @option{-fexceptions} is enabled, then @var{cleanup_function}
+is run during the stack unwinding that happens during the
+processing of the exception. Note that the @code{cleanup} attribute
+does not allow the exception to be caught, only to perform an action.
+It is undefined what happens if @var{cleanup_function} does not
+return normally.
+
+@item common
+@itemx nocommon
+@cindex @code{common} variable attribute
+@cindex @code{nocommon} variable attribute
+@opindex fcommon
+@opindex fno-common
+The @code{common} attribute requests GCC to place a variable in
+``common'' storage. The @code{nocommon} attribute requests the
+opposite---to allocate space for it directly.
+
+These attributes override the default chosen by the
+@option{-fno-common} and @option{-fcommon} flags respectively.
+
+@item copy
+@itemx copy (@var{variable})
+@cindex @code{copy} variable attribute
+The @code{copy} attribute applies the set of attributes with which
+@var{variable} has been declared to the declaration of the variable
+to which the attribute is applied. The attribute is designed for
+libraries that define aliases that are expected to specify the same
+set of attributes as the aliased symbols. The @code{copy} attribute
+can be used with variables, functions or types. However, the kind
+of symbol to which the attribute is applied (either varible or
+function) must match the kind of symbol to which the argument refers.
+The @code{copy} attribute copies only syntactic and semantic attributes
+but not attributes that affect a symbol's linkage or visibility such as
+@code{alias}, @code{visibility}, or @code{weak}. The @code{deprecated}
+attribute is also not copied. @xref{Common Function Attributes}.
+@xref{Common Type Attributes}.
+
+@item deprecated
+@itemx deprecated (@var{msg})
+@cindex @code{deprecated} variable attribute
+The @code{deprecated} attribute results in a warning if the variable
+is used anywhere in the source file. This is useful when identifying
+variables that are expected to be removed in a future version of a
+program. The warning also includes the location of the declaration
+of the deprecated variable, to enable users to easily find further
+information about why the variable is deprecated, or what they should
+do instead. Note that the warning only occurs for uses:
+
+@smallexample
+extern int old_var __attribute__ ((deprecated));
+extern int old_var;
+int new_fn () @{ return old_var; @}
+@end smallexample
+
+@noindent
+results in a warning on line 3 but not line 2. The optional @var{msg}
+argument, which must be a string, is printed in the warning if
+present.
+
+The @code{deprecated} attribute can also be used for functions and
+types (@pxref{Common Function Attributes},
+@pxref{Common Type Attributes}).
+
+The message attached to the attribute is affected by the setting of
+the @option{-fmessage-length} option.
+
+@item unavailable
+@itemx unavailable (@var{msg})
+@cindex @code{unavailable} variable attribute
+The @code{unavailable} attribute indicates that the variable so marked
+is not available, if it is used anywhere in the source file. It behaves
+in the same manner as the @code{deprecated} attribute except that the
+compiler will emit an error rather than a warning.
+
+It is expected that items marked as @code{deprecated} will eventually be
+withdrawn from interfaces, and then become unavailable. This attribute
+allows for marking them appropriately.
+
+The @code{unavailable} attribute can also be used for functions and
+types (@pxref{Common Function Attributes},
+@pxref{Common Type Attributes}).
+
+@item mode (@var{mode})
+@cindex @code{mode} variable attribute
+This attribute specifies the data type for the declaration---whichever
+type corresponds to the mode @var{mode}. This in effect lets you
+request an integer or floating-point type according to its width.
+
+@xref{Machine Modes,,, gccint, GNU Compiler Collection (GCC) Internals},
+for a list of the possible keywords for @var{mode}.
+You may also specify a mode of @code{byte} or @code{__byte__} to
+indicate the mode corresponding to a one-byte integer, @code{word} or
+@code{__word__} for the mode of a one-word integer, and @code{pointer}
+or @code{__pointer__} for the mode used to represent pointers.
+
+@item nonstring
+@cindex @code{nonstring} variable attribute
+The @code{nonstring} variable attribute specifies that an object or member
+declaration with type array of @code{char}, @code{signed char}, or
+@code{unsigned char}, or pointer to such a type is intended to store
+character arrays that do not necessarily contain a terminating @code{NUL}.
+This is useful in detecting uses of such arrays or pointers with functions
+that expect @code{NUL}-terminated strings, and to avoid warnings when such
+an array or pointer is used as an argument to a bounded string manipulation
+function such as @code{strncpy}. For example, without the attribute, GCC
+will issue a warning for the @code{strncpy} call below because it may
+truncate the copy without appending the terminating @code{NUL} character.
+Using the attribute makes it possible to suppress the warning. However,
+when the array is declared with the attribute the call to @code{strlen} is
+diagnosed because when the array doesn't contain a @code{NUL}-terminated
+string the call is undefined. To copy, compare, of search non-string
+character arrays use the @code{memcpy}, @code{memcmp}, @code{memchr},
+and other functions that operate on arrays of bytes. In addition,
+calling @code{strnlen} and @code{strndup} with such arrays is safe
+provided a suitable bound is specified, and not diagnosed.
+
+@smallexample
+struct Data
+@{
+ char name [32] __attribute__ ((nonstring));
+@};
+
+int f (struct Data *pd, const char *s)
+@{
+ strncpy (pd->name, s, sizeof pd->name);
+ @dots{}
+ return strlen (pd->name); // unsafe, gets a warning
+@}
+@end smallexample
+
+@item packed
+@cindex @code{packed} variable attribute
+The @code{packed} attribute specifies that a structure member should have
+the smallest possible alignment---one bit for a bit-field and one byte
+otherwise, unless a larger value is specified with the @code{aligned}
+attribute. The attribute does not apply to non-member objects.
+
+For example in the structure below, the member array @code{x} is packed
+so that it immediately follows @code{a} with no intervening padding:
+
+@smallexample
+struct foo
+@{
+ char a;
+ int x[2] __attribute__ ((packed));
+@};
+@end smallexample
+
+@emph{Note:} The 4.1, 4.2 and 4.3 series of GCC ignore the
+@code{packed} attribute on bit-fields of type @code{char}. This has
+been fixed in GCC 4.4 but the change can lead to differences in the
+structure layout. See the documentation of
+@option{-Wpacked-bitfield-compat} for more information.
+
+@item section ("@var{section-name}")
+@cindex @code{section} variable attribute
+Normally, the compiler places the objects it generates in sections like
+@code{data} and @code{bss}. Sometimes, however, you need additional sections,
+or you need certain particular variables to appear in special sections,
+for example to map to special hardware. The @code{section}
+attribute specifies that a variable (or function) lives in a particular
+section. For example, this small program uses several specific section names:
+
+@smallexample
+struct duart a __attribute__ ((section ("DUART_A"))) = @{ 0 @};
+struct duart b __attribute__ ((section ("DUART_B"))) = @{ 0 @};
+char stack[10000] __attribute__ ((section ("STACK"))) = @{ 0 @};
+int init_data __attribute__ ((section ("INITDATA")));
+
+main()
+@{
+ /* @r{Initialize stack pointer} */
+ init_sp (stack + sizeof (stack));
+
+ /* @r{Initialize initialized data} */
+ memcpy (&init_data, &data, &edata - &data);
+
+ /* @r{Turn on the serial ports} */
+ init_duart (&a);
+ init_duart (&b);
+@}
+@end smallexample
+
+@noindent
+Use the @code{section} attribute with
+@emph{global} variables and not @emph{local} variables,
+as shown in the example.
+
+You may use the @code{section} attribute with initialized or
+uninitialized global variables but the linker requires
+each object be defined once, with the exception that uninitialized
+variables tentatively go in the @code{common} (or @code{bss}) section
+and can be multiply ``defined''. Using the @code{section} attribute
+changes what section the variable goes into and may cause the
+linker to issue an error if an uninitialized variable has multiple
+definitions. You can force a variable to be initialized with the
+@option{-fno-common} flag or the @code{nocommon} attribute.
+
+Some file formats do not support arbitrary sections so the @code{section}
+attribute is not available on all platforms.
+If you need to map the entire contents of a module to a particular
+section, consider using the facilities of the linker instead.
+
+@item tls_model ("@var{tls_model}")
+@cindex @code{tls_model} variable attribute
+The @code{tls_model} attribute sets thread-local storage model
+(@pxref{Thread-Local}) of a particular @code{__thread} variable,
+overriding @option{-ftls-model=} command-line switch on a per-variable
+basis.
+The @var{tls_model} argument should be one of @code{global-dynamic},
+@code{local-dynamic}, @code{initial-exec} or @code{local-exec}.
+
+Not all targets support this attribute.
+
+@item unused
+@cindex @code{unused} variable attribute
+This attribute, attached to a variable or structure field, means that
+the variable or field is meant to be possibly unused. GCC does not
+produce a warning for this variable or field.
+
+@item used
+@cindex @code{used} variable attribute
+This attribute, attached to a variable with static storage, means that
+the variable must be emitted even if it appears that the variable is not
+referenced.
+
+When applied to a static data member of a C++ class template, the
+attribute also means that the member is instantiated if the
+class itself is instantiated.
+
+@item retain
+@cindex @code{retain} variable attribute
+For ELF targets that support the GNU or FreeBSD OSABIs, this attribute
+will save the variable from linker garbage collection. To support
+this behavior, variables that have not been placed in specific sections
+(e.g. by the @code{section} attribute, or the @code{-fdata-sections} option),
+will be placed in new, unique sections.
+
+This additional functionality requires Binutils version 2.36 or later.
+
+@item uninitialized
+@cindex @code{uninitialized} variable attribute
+This attribute, attached to a variable with automatic storage, means that
+the variable should not be automatically initialized by the compiler when
+the option @code{-ftrivial-auto-var-init} presents.
+
+With the option @code{-ftrivial-auto-var-init}, all the automatic variables
+that do not have explicit initializers will be initialized by the compiler.
+These additional compiler initializations might incur run-time overhead,
+sometimes dramatically. This attribute can be used to mark some variables
+to be excluded from such automatical initialization in order to reduce runtime
+overhead.
+
+This attribute has no effect when the option @code{-ftrivial-auto-var-init}
+does not present.
+
+@item vector_size (@var{bytes})
+@cindex @code{vector_size} variable attribute
+This attribute specifies the vector size for the type of the declared
+variable, measured in bytes. The type to which it applies is known as
+the @dfn{base type}. The @var{bytes} argument must be a positive
+power-of-two multiple of the base type size. For example, the declaration:
+
+@smallexample
+int foo __attribute__ ((vector_size (16)));
+@end smallexample
+
+@noindent
+causes the compiler to set the mode for @code{foo}, to be 16 bytes,
+divided into @code{int} sized units. Assuming a 32-bit @code{int},
+@code{foo}'s type is a vector of four units of four bytes each, and
+the corresponding mode of @code{foo} is @code{V4SI}.
+@xref{Vector Extensions}, for details of manipulating vector variables.
+
+This attribute is only applicable to integral and floating scalars,
+although arrays, pointers, and function return values are allowed in
+conjunction with this construct.
+
+Aggregates with this attribute are invalid, even if they are of the same
+size as a corresponding scalar. For example, the declaration:
+
+@smallexample
+struct S @{ int a; @};
+struct S __attribute__ ((vector_size (16))) foo;
+@end smallexample
+
+@noindent
+is invalid even if the size of the structure is the same as the size of
+the @code{int}.
+
+@item visibility ("@var{visibility_type}")
+@cindex @code{visibility} variable attribute
+This attribute affects the linkage of the declaration to which it is attached.
+The @code{visibility} attribute is described in
+@ref{Common Function Attributes}.
+
+@item weak
+@cindex @code{weak} variable attribute
+The @code{weak} attribute is described in
+@ref{Common Function Attributes}.
+
+@item noinit
+@cindex @code{noinit} variable attribute
+Any data with the @code{noinit} attribute will not be initialized by
+the C runtime startup code, or the program loader. Not initializing
+data in this way can reduce program startup times.
+
+This attribute is specific to ELF targets and relies on the linker
+script to place sections with the @code{.noinit} prefix in the right
+location.
+
+@item persistent
+@cindex @code{persistent} variable attribute
+Any data with the @code{persistent} attribute will not be initialized by
+the C runtime startup code, but will be initialized by the program
+loader. This enables the value of the variable to @samp{persist}
+between processor resets.
+
+This attribute is specific to ELF targets and relies on the linker
+script to place the sections with the @code{.persistent} prefix in the
+right location. Specifically, some type of non-volatile, writeable
+memory is required.
+
+@item objc_nullability (@var{nullability kind}) @r{(Objective-C and Objective-C++ only)}
+@cindex @code{objc_nullability} variable attribute
+This attribute applies to pointer variables only. It allows marking the
+pointer with one of four possible values describing the conditions under
+which the pointer might have a @code{nil} value. In most cases, the
+attribute is intended to be an internal representation for property and
+method nullability (specified by language keywords); it is not recommended
+to use it directly.
+
+When @var{nullability kind} is @code{"unspecified"} or @code{0}, nothing is
+known about the conditions in which the pointer might be @code{nil}. Making
+this state specific serves to avoid false positives in diagnostics.
+
+When @var{nullability kind} is @code{"nonnull"} or @code{1}, the pointer has
+no meaning if it is @code{nil} and thus the compiler is free to emit
+diagnostics if it can be determined that the value will be @code{nil}.
+
+When @var{nullability kind} is @code{"nullable"} or @code{2}, the pointer might
+be @code{nil} and carry meaning as such.
+
+When @var{nullability kind} is @code{"resettable"} or @code{3} (used only in
+the context of property attribute lists) this describes the case in which a
+property setter may take the value @code{nil} (which perhaps causes the
+property to be reset in some manner to a default) but for which the property
+getter will never validly return @code{nil}.
+
+@end table
+
+@node ARC Variable Attributes
+@subsection ARC Variable Attributes
+
+@table @code
+@item aux
+@cindex @code{aux} variable attribute, ARC
+The @code{aux} attribute is used to directly access the ARC's
+auxiliary register space from C. The auxilirary register number is
+given via attribute argument.
+
+@end table
+
+@node AVR Variable Attributes
+@subsection AVR Variable Attributes
+
+@table @code
+@item progmem
+@cindex @code{progmem} variable attribute, AVR
+The @code{progmem} attribute is used on the AVR to place read-only
+data in the non-volatile program memory (flash). The @code{progmem}
+attribute accomplishes this by putting respective variables into a
+section whose name starts with @code{.progmem}.
+
+This attribute works similar to the @code{section} attribute
+but adds additional checking.
+
+@table @asis
+@item @bullet{} Ordinary AVR cores with 32 general purpose registers:
+@code{progmem} affects the location
+of the data but not how this data is accessed.
+In order to read data located with the @code{progmem} attribute
+(inline) assembler must be used.
+@smallexample
+/* Use custom macros from @w{@uref{http://nongnu.org/avr-libc/user-manual/,AVR-LibC}} */
+#include <avr/pgmspace.h>
+
+/* Locate var in flash memory */
+const int var[2] PROGMEM = @{ 1, 2 @};
+
+int read_var (int i)
+@{
+ /* Access var[] by accessor macro from avr/pgmspace.h */
+ return (int) pgm_read_word (& var[i]);
+@}
+@end smallexample
+
+AVR is a Harvard architecture processor and data and read-only data
+normally resides in the data memory (RAM).
+
+See also the @ref{AVR Named Address Spaces} section for
+an alternate way to locate and access data in flash memory.
+
+@item @bullet{} AVR cores with flash memory visible in the RAM address range:
+On such devices, there is no need for attribute @code{progmem} or
+@ref{AVR Named Address Spaces,,@code{__flash}} qualifier at all.
+Just use standard C / C++. The compiler will generate @code{LD*}
+instructions. As flash memory is visible in the RAM address range,
+and the default linker script does @emph{not} locate @code{.rodata} in
+RAM, no special features are needed in order not to waste RAM for
+read-only data or to read from flash. You might even get slightly better
+performance by
+avoiding @code{progmem} and @code{__flash}. This applies to devices from
+families @code{avrtiny} and @code{avrxmega3}, see @ref{AVR Options} for
+an overview.
+
+@item @bullet{} Reduced AVR Tiny cores like ATtiny40:
+The compiler adds @code{0x4000}
+to the addresses of objects and declarations in @code{progmem} and locates
+the objects in flash memory, namely in section @code{.progmem.data}.
+The offset is needed because the flash memory is visible in the RAM
+address space starting at address @code{0x4000}.
+
+Data in @code{progmem} can be accessed by means of ordinary C@tie{}code,
+no special functions or macros are needed.
+
+@smallexample
+/* var is located in flash memory */
+extern const int var[2] __attribute__((progmem));
+
+int read_var (int i)
+@{
+ return var[i];
+@}
+@end smallexample
+
+Please notice that on these devices, there is no need for @code{progmem}
+at all.
+
+@end table
+
+@item io
+@itemx io (@var{addr})
+@cindex @code{io} variable attribute, AVR
+Variables with the @code{io} attribute are used to address
+memory-mapped peripherals in the io address range.
+If an address is specified, the variable
+is assigned that address, and the value is interpreted as an
+address in the data address space.
+Example:
+
+@smallexample
+volatile int porta __attribute__((io (0x22)));
+@end smallexample
+
+The address specified in the address in the data address range.
+
+Otherwise, the variable it is not assigned an address, but the
+compiler will still use in/out instructions where applicable,
+assuming some other module assigns an address in the io address range.
+Example:
+
+@smallexample
+extern volatile int porta __attribute__((io));
+@end smallexample
+
+@item io_low
+@itemx io_low (@var{addr})
+@cindex @code{io_low} variable attribute, AVR
+This is like the @code{io} attribute, but additionally it informs the
+compiler that the object lies in the lower half of the I/O area,
+allowing the use of @code{cbi}, @code{sbi}, @code{sbic} and @code{sbis}
+instructions.
+
+@item address
+@itemx address (@var{addr})
+@cindex @code{address} variable attribute, AVR
+Variables with the @code{address} attribute are used to address
+memory-mapped peripherals that may lie outside the io address range.
+
+@smallexample
+volatile int porta __attribute__((address (0x600)));
+@end smallexample
+
+@item absdata
+@cindex @code{absdata} variable attribute, AVR
+Variables in static storage and with the @code{absdata} attribute can
+be accessed by the @code{LDS} and @code{STS} instructions which take
+absolute addresses.
+
+@itemize @bullet
+@item
+This attribute is only supported for the reduced AVR Tiny core
+like ATtiny40.
+
+@item
+You must make sure that respective data is located in the
+address range @code{0x40}@dots{}@code{0xbf} accessible by
+@code{LDS} and @code{STS}. One way to achieve this as an
+appropriate linker description file.
+
+@item
+If the location does not fit the address range of @code{LDS}
+and @code{STS}, there is currently (Binutils 2.26) just an unspecific
+warning like
+@quotation
+@code{module.cc:(.text+0x1c): warning: internal error: out of range error}
+@end quotation
+
+@end itemize
+
+See also the @option{-mabsdata} @ref{AVR Options,command-line option}.
+
+@end table
+
+@node Blackfin Variable Attributes
+@subsection Blackfin Variable Attributes
+
+Three attributes are currently defined for the Blackfin.
+
+@table @code
+@item l1_data
+@itemx l1_data_A
+@itemx l1_data_B
+@cindex @code{l1_data} variable attribute, Blackfin
+@cindex @code{l1_data_A} variable attribute, Blackfin
+@cindex @code{l1_data_B} variable attribute, Blackfin
+Use these attributes on the Blackfin to place the variable into L1 Data SRAM.
+Variables with @code{l1_data} attribute are put into the specific section
+named @code{.l1.data}. Those with @code{l1_data_A} attribute are put into
+the specific section named @code{.l1.data.A}. Those with @code{l1_data_B}
+attribute are put into the specific section named @code{.l1.data.B}.
+
+@item l2
+@cindex @code{l2} variable attribute, Blackfin
+Use this attribute on the Blackfin to place the variable into L2 SRAM.
+Variables with @code{l2} attribute are put into the specific section
+named @code{.l2.data}.
+@end table
+
+@node H8/300 Variable Attributes
+@subsection H8/300 Variable Attributes
+
+These variable attributes are available for H8/300 targets:
+
+@table @code
+@item eightbit_data
+@cindex @code{eightbit_data} variable attribute, H8/300
+@cindex eight-bit data on the H8/300, H8/300H, and H8S
+Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified
+variable should be placed into the eight-bit data section.
+The compiler generates more efficient code for certain operations
+on data in the eight-bit data area. Note the eight-bit data area is limited to
+256 bytes of data.
+
+You must use GAS and GLD from GNU binutils version 2.7 or later for
+this attribute to work correctly.
+
+@item tiny_data
+@cindex @code{tiny_data} variable attribute, H8/300
+@cindex tiny data section on the H8/300H and H8S
+Use this attribute on the H8/300H and H8S to indicate that the specified
+variable should be placed into the tiny data section.
+The compiler generates more efficient code for loads and stores
+on data in the tiny data section. Note the tiny data area is limited to
+slightly under 32KB of data.
+
+@end table
+
+@node IA-64 Variable Attributes
+@subsection IA-64 Variable Attributes
+
+The IA-64 back end supports the following variable attribute:
+
+@table @code
+@item model (@var{model-name})
+@cindex @code{model} variable attribute, IA-64
+
+On IA-64, use this attribute to set the addressability of an object.
+At present, the only supported identifier for @var{model-name} is
+@code{small}, indicating addressability via ``small'' (22-bit)
+addresses (so that their addresses can be loaded with the @code{addl}
+instruction). Caveat: such addressing is by definition not position
+independent and hence this attribute must not be used for objects
+defined by shared libraries.
+
+@end table
+
+@node LoongArch Variable Attributes
+@subsection LoongArch Variable Attributes
+
+One attribute is currently defined for the LoongArch.
+
+@table @code
+@item model("@var{name}")
+@cindex @code{model} variable attribute, LoongArch
+Use this attribute on the LoongArch to use a different code model for
+addressing this variable, than the code model specified by the global
+@option{-mcmodel} option. This attribute is mostly useful if a
+@code{section} attribute and/or a linker script will locate this object
+specially. Currently the only supported values of @var{name} are
+@code{normal} and @code{extreme}.
+@end table
+
+@node M32R/D Variable Attributes
+@subsection M32R/D Variable Attributes
+
+One attribute is currently defined for the M32R/D@.
+
+@table @code
+@item model (@var{model-name})
+@cindex @code{model-name} variable attribute, M32R/D
+@cindex variable addressability on the M32R/D
+Use this attribute on the M32R/D to set the addressability of an object.
+The identifier @var{model-name} is one of @code{small}, @code{medium},
+or @code{large}, representing each of the code models.
+
+Small model objects live in the lower 16MB of memory (so that their
+addresses can be loaded with the @code{ld24} instruction).
+
+Medium and large model objects may live anywhere in the 32-bit address space
+(the compiler generates @code{seth/add3} instructions to load their
+addresses).
+@end table
+
+@node MeP Variable Attributes
+@subsection MeP Variable Attributes
+
+The MeP target has a number of addressing modes and busses. The
+@code{near} space spans the standard memory space's first 16 megabytes
+(24 bits). The @code{far} space spans the entire 32-bit memory space.
+The @code{based} space is a 128-byte region in the memory space that
+is addressed relative to the @code{$tp} register. The @code{tiny}
+space is a 65536-byte region relative to the @code{$gp} register. In
+addition to these memory regions, the MeP target has a separate 16-bit
+control bus which is specified with @code{cb} attributes.
+
+@table @code
+
+@item based
+@cindex @code{based} variable attribute, MeP
+Any variable with the @code{based} attribute is assigned to the
+@code{.based} section, and is accessed with relative to the
+@code{$tp} register.
+
+@item tiny
+@cindex @code{tiny} variable attribute, MeP
+Likewise, the @code{tiny} attribute assigned variables to the
+@code{.tiny} section, relative to the @code{$gp} register.
+
+@item near
+@cindex @code{near} variable attribute, MeP
+Variables with the @code{near} attribute are assumed to have addresses
+that fit in a 24-bit addressing mode. This is the default for large
+variables (@code{-mtiny=4} is the default) but this attribute can
+override @code{-mtiny=} for small variables, or override @code{-ml}.
+
+@item far
+@cindex @code{far} variable attribute, MeP
+Variables with the @code{far} attribute are addressed using a full
+32-bit address. Since this covers the entire memory space, this
+allows modules to make no assumptions about where variables might be
+stored.
+
+@item io
+@cindex @code{io} variable attribute, MeP
+@itemx io (@var{addr})
+Variables with the @code{io} attribute are used to address
+memory-mapped peripherals. If an address is specified, the variable
+is assigned that address, else it is not assigned an address (it is
+assumed some other module assigns an address). Example:
+
+@smallexample
+int timer_count __attribute__((io(0x123)));
+@end smallexample
+
+@item cb
+@itemx cb (@var{addr})
+@cindex @code{cb} variable attribute, MeP
+Variables with the @code{cb} attribute are used to access the control
+bus, using special instructions. @code{addr} indicates the control bus
+address. Example:
+
+@smallexample
+int cpu_clock __attribute__((cb(0x123)));
+@end smallexample
+
+@end table
+
+@node Microsoft Windows Variable Attributes
+@subsection Microsoft Windows Variable Attributes
+
+You can use these attributes on Microsoft Windows targets.
+@ref{x86 Variable Attributes} for additional Windows compatibility
+attributes available on all x86 targets.
+
+@table @code
+@item dllimport
+@itemx dllexport
+@cindex @code{dllimport} variable attribute
+@cindex @code{dllexport} variable attribute
+The @code{dllimport} and @code{dllexport} attributes are described in
+@ref{Microsoft Windows Function Attributes}.
+
+@item selectany
+@cindex @code{selectany} variable attribute
+The @code{selectany} attribute causes an initialized global variable to
+have link-once semantics. When multiple definitions of the variable are
+encountered by the linker, the first is selected and the remainder are
+discarded. Following usage by the Microsoft compiler, the linker is told
+@emph{not} to warn about size or content differences of the multiple
+definitions.
+
+Although the primary usage of this attribute is for POD types, the
+attribute can also be applied to global C++ objects that are initialized
+by a constructor. In this case, the static initialization and destruction
+code for the object is emitted in each translation defining the object,
+but the calls to the constructor and destructor are protected by a
+link-once guard variable.
+
+The @code{selectany} attribute is only available on Microsoft Windows
+targets. You can use @code{__declspec (selectany)} as a synonym for
+@code{__attribute__ ((selectany))} for compatibility with other
+compilers.
+
+@item shared
+@cindex @code{shared} variable attribute
+On Microsoft Windows, in addition to putting variable definitions in a named
+section, the section can also be shared among all running copies of an
+executable or DLL@. For example, this small program defines shared data
+by putting it in a named section @code{shared} and marking the section
+shareable:
+
+@smallexample
+int foo __attribute__((section ("shared"), shared)) = 0;
+
+int
+main()
+@{
+ /* @r{Read and write foo. All running
+ copies see the same value.} */
+ return 0;
+@}
+@end smallexample
+
+@noindent
+You may only use the @code{shared} attribute along with @code{section}
+attribute with a fully-initialized global definition because of the way
+linkers work. See @code{section} attribute for more information.
+
+The @code{shared} attribute is only available on Microsoft Windows@.
+
+@end table
+
+@node MSP430 Variable Attributes
+@subsection MSP430 Variable Attributes
+
+@table @code
+@item upper
+@itemx either
+@cindex @code{upper} variable attribute, MSP430
+@cindex @code{either} variable attribute, MSP430
+These attributes are the same as the MSP430 function attributes of the
+same name (@pxref{MSP430 Function Attributes}).
+
+@item lower
+@cindex @code{lower} variable attribute, MSP430
+This option behaves mostly the same as the MSP430 function attribute of the
+same name (@pxref{MSP430 Function Attributes}), but it has some additional
+functionality.
+
+If @option{-mdata-region=}@{@code{upper,either,none}@} has been passed, or
+the @code{section} attribute is applied to a variable, the compiler will
+generate 430X instructions to handle it. This is because the compiler has
+to assume that the variable could get placed in the upper memory region
+(above address 0xFFFF). Marking the variable with the @code{lower} attribute
+informs the compiler that the variable will be placed in lower memory so it
+is safe to use 430 instructions to handle it.
+
+In the case of the @code{section} attribute, the section name given
+will be used, and the @code{.lower} prefix will not be added.
+
+@end table
+
+@node Nvidia PTX Variable Attributes
+@subsection Nvidia PTX Variable Attributes
+
+These variable attributes are supported by the Nvidia PTX back end:
+
+@table @code
+@item shared
+@cindex @code{shared} attribute, Nvidia PTX
+Use this attribute to place a variable in the @code{.shared} memory space.
+This memory space is private to each cooperative thread array; only threads
+within one thread block refer to the same instance of the variable.
+The runtime does not initialize variables in this memory space.
+@end table
+
+@node PowerPC Variable Attributes
+@subsection PowerPC Variable Attributes
+
+Three attributes currently are defined for PowerPC configurations:
+@code{altivec}, @code{ms_struct} and @code{gcc_struct}.
+
+@cindex @code{ms_struct} variable attribute, PowerPC
+@cindex @code{gcc_struct} variable attribute, PowerPC
+For full documentation of the struct attributes please see the
+documentation in @ref{x86 Variable Attributes}.
+
+@cindex @code{altivec} variable attribute, PowerPC
+For documentation of @code{altivec} attribute please see the
+documentation in @ref{PowerPC Type Attributes}.
+
+@node RL78 Variable Attributes
+@subsection RL78 Variable Attributes
+
+@cindex @code{saddr} variable attribute, RL78
+The RL78 back end supports the @code{saddr} variable attribute. This
+specifies placement of the corresponding variable in the SADDR area,
+which can be accessed more efficiently than the default memory region.
+
+@node V850 Variable Attributes
+@subsection V850 Variable Attributes
+
+These variable attributes are supported by the V850 back end:
+
+@table @code
+
+@item sda
+@cindex @code{sda} variable attribute, V850
+Use this attribute to explicitly place a variable in the small data area,
+which can hold up to 64 kilobytes.
+
+@item tda
+@cindex @code{tda} variable attribute, V850
+Use this attribute to explicitly place a variable in the tiny data area,
+which can hold up to 256 bytes in total.
+
+@item zda
+@cindex @code{zda} variable attribute, V850
+Use this attribute to explicitly place a variable in the first 32 kilobytes
+of memory.
+@end table
+
+@node x86 Variable Attributes
+@subsection x86 Variable Attributes
+
+Two attributes are currently defined for x86 configurations:
+@code{ms_struct} and @code{gcc_struct}.
+
+@table @code
+@item ms_struct
+@itemx gcc_struct
+@cindex @code{ms_struct} variable attribute, x86
+@cindex @code{gcc_struct} variable attribute, x86
+
+If @code{packed} is used on a structure, or if bit-fields are used,
+it may be that the Microsoft ABI lays out the structure differently
+than the way GCC normally does. Particularly when moving packed
+data between functions compiled with GCC and the native Microsoft compiler
+(either via function call or as data in a file), it may be necessary to access
+either format.
+
+The @code{ms_struct} and @code{gcc_struct} attributes correspond
+to the @option{-mms-bitfields} and @option{-mno-ms-bitfields}
+command-line options, respectively;
+see @ref{x86 Options}, for details of how structure layout is affected.
+@xref{x86 Type Attributes}, for information about the corresponding
+attributes on types.
+
+@end table
+
+@node Xstormy16 Variable Attributes
+@subsection Xstormy16 Variable Attributes
+
+One attribute is currently defined for xstormy16 configurations:
+@code{below100}.
+
+@table @code
+@item below100
+@cindex @code{below100} variable attribute, Xstormy16
+
+If a variable has the @code{below100} attribute (@code{BELOW100} is
+allowed also), GCC places the variable in the first 0x100 bytes of
+memory and use special opcodes to access it. Such variables are
+placed in either the @code{.bss_below100} section or the
+@code{.data_below100} section.
+
+@end table
+
+@node Type Attributes
+@section Specifying Attributes of Types
+@cindex attribute of types
+@cindex type attributes
+
+The keyword @code{__attribute__} allows you to specify various special
+properties of types. Some type attributes apply only to structure and
+union types, and in C++, also class types, while others can apply to
+any type defined via a @code{typedef} declaration. Unless otherwise
+specified, the same restrictions and effects apply to attributes regardless
+of whether a type is a trivial structure or a C++ class with user-defined
+constructors, destructors, or a copy assignment.
+
+Other attributes are defined for functions (@pxref{Function Attributes}),
+labels (@pxref{Label Attributes}), enumerators (@pxref{Enumerator
+Attributes}), statements (@pxref{Statement Attributes}), and for variables
+(@pxref{Variable Attributes}).
+
+The @code{__attribute__} keyword is followed by an attribute specification
+enclosed in double parentheses.
+
+You may specify type attributes in an enum, struct or union type
+declaration or definition by placing them immediately after the
+@code{struct}, @code{union} or @code{enum} keyword. You can also place
+them just past the closing curly brace of the definition, but this is less
+preferred because logically the type should be fully defined at
+the closing brace.
+
+You can also include type attributes in a @code{typedef} declaration.
+@xref{Attribute Syntax}, for details of the exact syntax for using
+attributes.
+
+@menu
+* Common Type Attributes::
+* ARC Type Attributes::
+* ARM Type Attributes::
+* BPF Type Attributes::
+* MeP Type Attributes::
+* PowerPC Type Attributes::
+* x86 Type Attributes::
+@end menu
+
+@node Common Type Attributes
+@subsection Common Type Attributes
+
+The following type attributes are supported on most targets.
+
+@table @code
+@cindex @code{aligned} type attribute
+@item aligned
+@itemx aligned (@var{alignment})
+The @code{aligned} attribute specifies a minimum alignment (in bytes) for
+variables of the specified type. When specified, @var{alignment} must be
+a power of 2. Specifying no @var{alignment} argument implies the maximum
+alignment for the target, which is often, but by no means always, 8 or 16
+bytes. For example, the declarations:
+
+@smallexample
+struct __attribute__ ((aligned (8))) S @{ short f[3]; @};
+typedef int more_aligned_int __attribute__ ((aligned (8)));
+@end smallexample
+
+@noindent
+force the compiler to ensure (as far as it can) that each variable whose
+type is @code{struct S} or @code{more_aligned_int} is allocated and
+aligned @emph{at least} on a 8-byte boundary. On a SPARC, having all
+variables of type @code{struct S} aligned to 8-byte boundaries allows
+the compiler to use the @code{ldd} and @code{std} (doubleword load and
+store) instructions when copying one variable of type @code{struct S} to
+another, thus improving run-time efficiency.
+
+Note that the alignment of any given @code{struct} or @code{union} type
+is required by the ISO C standard to be at least a perfect multiple of
+the lowest common multiple of the alignments of all of the members of
+the @code{struct} or @code{union} in question. This means that you @emph{can}
+effectively adjust the alignment of a @code{struct} or @code{union}
+type by attaching an @code{aligned} attribute to any one of the members
+of such a type, but the notation illustrated in the example above is a
+more obvious, intuitive, and readable way to request the compiler to
+adjust the alignment of an entire @code{struct} or @code{union} type.
+
+As in the preceding example, you can explicitly specify the alignment
+(in bytes) that you wish the compiler to use for a given @code{struct}
+or @code{union} type. Alternatively, you can leave out the alignment factor
+and just ask the compiler to align a type to the maximum
+useful alignment for the target machine you are compiling for. For
+example, you could write:
+
+@smallexample
+struct __attribute__ ((aligned)) S @{ short f[3]; @};
+@end smallexample
+
+Whenever you leave out the alignment factor in an @code{aligned}
+attribute specification, the compiler automatically sets the alignment
+for the type to the largest alignment that is ever used for any data
+type on the target machine you are compiling for. Doing this can often
+make copy operations more efficient, because the compiler can use
+whatever instructions copy the biggest chunks of memory when performing
+copies to or from the variables that have types that you have aligned
+this way.
+
+In the example above, if the size of each @code{short} is 2 bytes, then
+the size of the entire @code{struct S} type is 6 bytes. The smallest
+power of two that is greater than or equal to that is 8, so the
+compiler sets the alignment for the entire @code{struct S} type to 8
+bytes.
+
+Note that although you can ask the compiler to select a time-efficient
+alignment for a given type and then declare only individual stand-alone
+objects of that type, the compiler's ability to select a time-efficient
+alignment is primarily useful only when you plan to create arrays of
+variables having the relevant (efficiently aligned) type. If you
+declare or use arrays of variables of an efficiently-aligned type, then
+it is likely that your program also does pointer arithmetic (or
+subscripting, which amounts to the same thing) on pointers to the
+relevant type, and the code that the compiler generates for these
+pointer arithmetic operations is often more efficient for
+efficiently-aligned types than for other types.
+
+Note that the effectiveness of @code{aligned} attributes may be limited
+by inherent limitations in your linker. On many systems, the linker is
+only able to arrange for variables to be aligned up to a certain maximum
+alignment. (For some linkers, the maximum supported alignment may
+be very very small.) If your linker is only able to align variables
+up to a maximum of 8-byte alignment, then specifying @code{aligned (16)}
+in an @code{__attribute__} still only provides you with 8-byte
+alignment. See your linker documentation for further information.
+
+When used on a struct, or struct member, the @code{aligned} attribute can
+only increase the alignment; in order to decrease it, the @code{packed}
+attribute must be specified as well. When used as part of a typedef, the
+@code{aligned} attribute can both increase and decrease alignment, and
+specifying the @code{packed} attribute generates a warning.
+
+@cindex @code{warn_if_not_aligned} type attribute
+@item warn_if_not_aligned (@var{alignment})
+This attribute specifies a threshold for the structure field, measured
+in bytes. If the structure field is aligned below the threshold, a
+warning will be issued. For example, the declaration:
+
+@smallexample
+typedef unsigned long long __u64
+ __attribute__((aligned (4), warn_if_not_aligned (8)));
+
+struct foo
+@{
+ int i1;
+ int i2;
+ __u64 x;
+@};
+@end smallexample
+
+@noindent
+causes the compiler to issue an warning on @code{struct foo}, like
+@samp{warning: alignment 4 of 'struct foo' is less than 8}.
+It is used to define @code{struct foo} in such a way that
+@code{struct foo} has the same layout and the structure field @code{x}
+has the same alignment when @code{__u64} is aligned at either 4 or
+8 bytes. Align @code{struct foo} to 8 bytes:
+
+@smallexample
+struct __attribute__ ((aligned (8))) foo
+@{
+ int i1;
+ int i2;
+ __u64 x;
+@};
+@end smallexample
+
+@noindent
+silences the warning. The compiler also issues a warning, like
+@samp{warning: 'x' offset 12 in 'struct foo' isn't aligned to 8},
+when the structure field has the misaligned offset:
+
+@smallexample
+struct __attribute__ ((aligned (8))) foo
+@{
+ int i1;
+ int i2;
+ int i3;
+ __u64 x;
+@};
+@end smallexample
+
+This warning can be disabled by @option{-Wno-if-not-aligned}.
+
+@item alloc_size (@var{position})
+@itemx alloc_size (@var{position-1}, @var{position-2})
+@cindex @code{alloc_size} type attribute
+The @code{alloc_size} type attribute may be applied to the definition
+of a type of a function that returns a pointer and takes at least one
+argument of an integer type. It indicates that the returned pointer
+points to an object whose size is given by the function argument at
+@var{position-1}, or by the product of the arguments at @var{position-1}
+and @var{position-2}. Meaningful sizes are positive values less than
+@code{PTRDIFF_MAX}. Other sizes are disagnosed when detected. GCC uses
+this information to improve the results of @code{__builtin_object_size}.
+
+For instance, the following declarations
+
+@smallexample
+typedef __attribute__ ((alloc_size (1, 2))) void*
+ calloc_type (size_t, size_t);
+typedef __attribute__ ((alloc_size (1))) void*
+ malloc_type (size_t);
+@end smallexample
+
+@noindent
+specify that @code{calloc_type} is a type of a function that, like
+the standard C function @code{calloc}, returns an object whose size
+is given by the product of arguments 1 and 2, and that
+@code{malloc_type}, like the standard C function @code{malloc},
+returns an object whose size is given by argument 1 to the function.
+
+@item copy
+@itemx copy (@var{expression})
+@cindex @code{copy} type attribute
+The @code{copy} attribute applies the set of attributes with which
+the type of the @var{expression} has been declared to the declaration
+of the type to which the attribute is applied. The attribute is
+designed for libraries that define aliases that are expected to
+specify the same set of attributes as the aliased symbols.
+The @code{copy} attribute can be used with types, variables, or
+functions. However, the kind of symbol to which the attribute is
+applied (either varible or function) must match the kind of symbol
+to which the argument refers.
+The @code{copy} attribute copies only syntactic and semantic attributes
+but not attributes that affect a symbol's linkage or visibility such as
+@code{alias}, @code{visibility}, or @code{weak}. The @code{deprecated}
+attribute is also not copied. @xref{Common Function Attributes}.
+@xref{Common Variable Attributes}.
+
+For example, suppose @code{struct A} below is defined in some third
+party library header to have the alignment requirement @code{N} and
+to force a warning whenever a variable of the type is not so aligned
+due to attribute @code{packed}. Specifying the @code{copy} attribute
+on the definition on the unrelated @code{struct B} has the effect of
+copying all relevant attributes from the type referenced by the pointer
+expression to @code{struct B}.
+
+@smallexample
+struct __attribute__ ((aligned (N), warn_if_not_aligned (N)))
+A @{ /* @r{@dots{}} */ @};
+struct __attribute__ ((copy ( (struct A *)0)) B @{ /* @r{@dots{}} */ @};
+@end smallexample
+
+@item deprecated
+@itemx deprecated (@var{msg})
+@cindex @code{deprecated} type attribute
+The @code{deprecated} attribute results in a warning if the type
+is used anywhere in the source file. This is useful when identifying
+types that are expected to be removed in a future version of a program.
+If possible, the warning also includes the location of the declaration
+of the deprecated type, to enable users to easily find further
+information about why the type is deprecated, or what they should do
+instead. Note that the warnings only occur for uses and then only
+if the type is being applied to an identifier that itself is not being
+declared as deprecated.
+
+@smallexample
+typedef int T1 __attribute__ ((deprecated));
+T1 x;
+typedef T1 T2;
+T2 y;
+typedef T1 T3 __attribute__ ((deprecated));
+T3 z __attribute__ ((deprecated));
+@end smallexample
+
+@noindent
+results in a warning on line 2 and 3 but not lines 4, 5, or 6. No
+warning is issued for line 4 because T2 is not explicitly
+deprecated. Line 5 has no warning because T3 is explicitly
+deprecated. Similarly for line 6. The optional @var{msg}
+argument, which must be a string, is printed in the warning if
+present. Control characters in the string will be replaced with
+escape sequences, and if the @option{-fmessage-length} option is set
+to 0 (its default value) then any newline characters will be ignored.
+
+The @code{deprecated} attribute can also be used for functions and
+variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.)
+
+The message attached to the attribute is affected by the setting of
+the @option{-fmessage-length} option.
+
+@item unavailable
+@itemx unavailable (@var{msg})
+@cindex @code{unavailable} type attribute
+The @code{unavailable} attribute behaves in the same manner as the
+@code{deprecated} one, but emits an error rather than a warning. It is
+used to indicate that a (perhaps previously @code{deprecated}) type is
+no longer usable.
+
+The @code{unavailable} attribute can also be used for functions and
+variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.)
+
+@item designated_init
+@cindex @code{designated_init} type attribute
+This attribute may only be applied to structure types. It indicates
+that any initialization of an object of this type must use designated
+initializers rather than positional initializers. The intent of this
+attribute is to allow the programmer to indicate that a structure's
+layout may change, and that therefore relying on positional
+initialization will result in future breakage.
+
+GCC emits warnings based on this attribute by default; use
+@option{-Wno-designated-init} to suppress them.
+
+@item may_alias
+@cindex @code{may_alias} type attribute
+Accesses through pointers to types with this attribute are not subject
+to type-based alias analysis, but are instead assumed to be able to alias
+any other type of objects.
+In the context of section 6.5 paragraph 7 of the C99 standard,
+an lvalue expression
+dereferencing such a pointer is treated like having a character type.
+See @option{-fstrict-aliasing} for more information on aliasing issues.
+This extension exists to support some vector APIs, in which pointers to
+one vector type are permitted to alias pointers to a different vector type.
+
+Note that an object of a type with this attribute does not have any
+special semantics.
+
+Example of use:
+
+@smallexample
+typedef short __attribute__ ((__may_alias__)) short_a;
+
+int
+main (void)
+@{
+ int a = 0x12345678;
+ short_a *b = (short_a *) &a;
+
+ b[1] = 0;
+
+ if (a == 0x12345678)
+ abort();
+
+ exit(0);
+@}
+@end smallexample
+
+@noindent
+If you replaced @code{short_a} with @code{short} in the variable
+declaration, the above program would abort when compiled with
+@option{-fstrict-aliasing}, which is on by default at @option{-O2} or
+above.
+
+@item mode (@var{mode})
+@cindex @code{mode} type attribute
+This attribute specifies the data type for the declaration---whichever
+type corresponds to the mode @var{mode}. This in effect lets you
+request an integer or floating-point type according to its width.
+
+@xref{Machine Modes,,, gccint, GNU Compiler Collection (GCC) Internals},
+for a list of the possible keywords for @var{mode}.
+You may also specify a mode of @code{byte} or @code{__byte__} to
+indicate the mode corresponding to a one-byte integer, @code{word} or
+@code{__word__} for the mode of a one-word integer, and @code{pointer}
+or @code{__pointer__} for the mode used to represent pointers.
+
+@item packed
+@cindex @code{packed} type attribute
+This attribute, attached to a @code{struct}, @code{union}, or C++ @code{class}
+type definition, specifies that each of its members (other than zero-width
+bit-fields) is placed to minimize the memory required. This is equivalent
+to specifying the @code{packed} attribute on each of the members.
+
+@opindex fshort-enums
+When attached to an @code{enum} definition, the @code{packed} attribute
+indicates that the smallest integral type should be used.
+Specifying the @option{-fshort-enums} flag on the command line
+is equivalent to specifying the @code{packed}
+attribute on all @code{enum} definitions.
+
+In the following example @code{struct my_packed_struct}'s members are
+packed closely together, but the internal layout of its @code{s} member
+is not packed---to do that, @code{struct my_unpacked_struct} needs to
+be packed too.
+
+@smallexample
+struct my_unpacked_struct
+ @{
+ char c;
+ int i;
+ @};
+
+struct __attribute__ ((__packed__)) my_packed_struct
+ @{
+ char c;
+ int i;
+ struct my_unpacked_struct s;
+ @};
+@end smallexample
+
+You may only specify the @code{packed} attribute on the definition
+of an @code{enum}, @code{struct}, @code{union}, or @code{class},
+not on a @code{typedef} that does not also define the enumerated type,
+structure, union, or class.
+
+@item scalar_storage_order ("@var{endianness}")
+@cindex @code{scalar_storage_order} type attribute
+When attached to a @code{union} or a @code{struct}, this attribute sets
+the storage order, aka endianness, of the scalar fields of the type, as
+well as the array fields whose component is scalar. The supported
+endiannesses are @code{big-endian} and @code{little-endian}. The attribute
+has no effects on fields which are themselves a @code{union}, a @code{struct}
+or an array whose component is a @code{union} or a @code{struct}, and it is
+possible for these fields to have a different scalar storage order than the
+enclosing type.
+
+Note that neither pointer nor vector fields are considered scalar fields in
+this context, so the attribute has no effects on these fields.
+
+This attribute is supported only for targets that use a uniform default
+scalar storage order (fortunately, most of them), i.e.@: targets that store
+the scalars either all in big-endian or all in little-endian.
+
+Additional restrictions are enforced for types with the reverse scalar
+storage order with regard to the scalar storage order of the target:
+
+@itemize
+@item Taking the address of a scalar field of a @code{union} or a
+@code{struct} with reverse scalar storage order is not permitted and yields
+an error.
+@item Taking the address of an array field, whose component is scalar, of
+a @code{union} or a @code{struct} with reverse scalar storage order is
+permitted but yields a warning, unless @option{-Wno-scalar-storage-order}
+is specified.
+@item Taking the address of a @code{union} or a @code{struct} with reverse
+scalar storage order is permitted.
+@end itemize
+
+These restrictions exist because the storage order attribute is lost when
+the address of a scalar or the address of an array with scalar component is
+taken, so storing indirectly through this address generally does not work.
+The second case is nevertheless allowed to be able to perform a block copy
+from or to the array.
+
+Moreover, the use of type punning or aliasing to toggle the storage order
+is not supported; that is to say, if a given scalar object can be accessed
+through distinct types that assign a different storage order to it, then the
+behavior is undefined.
+
+@item transparent_union
+@cindex @code{transparent_union} type attribute
+
+This attribute, attached to a @code{union} type definition, indicates
+that any function parameter having that union type causes calls to that
+function to be treated in a special way.
+
+First, the argument corresponding to a transparent union type can be of
+any type in the union; no cast is required. Also, if the union contains
+a pointer type, the corresponding argument can be a null pointer
+constant or a void pointer expression; and if the union contains a void
+pointer type, the corresponding argument can be any pointer expression.
+If the union member type is a pointer, qualifiers like @code{const} on
+the referenced type must be respected, just as with normal pointer
+conversions.
+
+Second, the argument is passed to the function using the calling
+conventions of the first member of the transparent union, not the calling
+conventions of the union itself. All members of the union must have the
+same machine representation; this is necessary for this argument passing
+to work properly.
+
+Transparent unions are designed for library functions that have multiple
+interfaces for compatibility reasons. For example, suppose the
+@code{wait} function must accept either a value of type @code{int *} to
+comply with POSIX, or a value of type @code{union wait *} to comply with
+the 4.1BSD interface. If @code{wait}'s parameter were @code{void *},
+@code{wait} would accept both kinds of arguments, but it would also
+accept any other pointer type and this would make argument type checking
+less useful. Instead, @code{<sys/wait.h>} might define the interface
+as follows:
+
+@smallexample
+typedef union __attribute__ ((__transparent_union__))
+ @{
+ int *__ip;
+ union wait *__up;
+ @} wait_status_ptr_t;
+
+pid_t wait (wait_status_ptr_t);
+@end smallexample
+
+@noindent
+This interface allows either @code{int *} or @code{union wait *}
+arguments to be passed, using the @code{int *} calling convention.
+The program can call @code{wait} with arguments of either type:
+
+@smallexample
+int w1 () @{ int w; return wait (&w); @}
+int w2 () @{ union wait w; return wait (&w); @}
+@end smallexample
+
+@noindent
+With this interface, @code{wait}'s implementation might look like this:
+
+@smallexample
+pid_t wait (wait_status_ptr_t p)
+@{
+ return waitpid (-1, p.__ip, 0);
+@}
+@end smallexample
+
+@item unused
+@cindex @code{unused} type attribute
+When attached to a type (including a @code{union} or a @code{struct}),
+this attribute means that variables of that type are meant to appear
+possibly unused. GCC does not produce a warning for any variables of
+that type, even if the variable appears to do nothing. This is often
+the case with lock or thread classes, which are usually defined and then
+not referenced, but contain constructors and destructors that have
+nontrivial bookkeeping functions.
+
+@item vector_size (@var{bytes})
+@cindex @code{vector_size} type attribute
+This attribute specifies the vector size for the type, measured in bytes.
+The type to which it applies is known as the @dfn{base type}. The @var{bytes}
+argument must be a positive power-of-two multiple of the base type size. For
+example, the following declarations:
+
+@smallexample
+typedef __attribute__ ((vector_size (32))) int int_vec32_t ;
+typedef __attribute__ ((vector_size (32))) int* int_vec32_ptr_t;
+typedef __attribute__ ((vector_size (32))) int int_vec32_arr3_t[3];
+@end smallexample
+
+@noindent
+define @code{int_vec32_t} to be a 32-byte vector type composed of @code{int}
+sized units. With @code{int} having a size of 4 bytes, the type defines
+a vector of eight units, four bytes each. The mode of variables of type
+@code{int_vec32_t} is @code{V8SI}. @code{int_vec32_ptr_t} is then defined
+to be a pointer to such a vector type, and @code{int_vec32_arr3_t} to be
+an array of three such vectors. @xref{Vector Extensions}, for details of
+manipulating objects of vector types.
+
+This attribute is only applicable to integral and floating scalar types.
+In function declarations the attribute applies to the function return
+type.
+
+For example, the following:
+@smallexample
+__attribute__ ((vector_size (16))) float get_flt_vec16 (void);
+@end smallexample
+declares @code{get_flt_vec16} to be a function returning a 16-byte vector
+with the base type @code{float}.
+
+@item visibility
+@cindex @code{visibility} type attribute
+In C++, attribute visibility (@pxref{Function Attributes}) can also be
+applied to class, struct, union and enum types. Unlike other type
+attributes, the attribute must appear between the initial keyword and
+the name of the type; it cannot appear after the body of the type.
+
+Note that the type visibility is applied to vague linkage entities
+associated with the class (vtable, typeinfo node, etc.). In
+particular, if a class is thrown as an exception in one shared object
+and caught in another, the class must have default visibility.
+Otherwise the two shared objects are unable to use the same
+typeinfo node and exception handling will break.
+
+@item objc_root_class @r{(Objective-C and Objective-C++ only)}
+@cindex @code{objc_root_class} type attribute
+This attribute marks a class as being a root class, and thus allows
+the compiler to elide any warnings about a missing superclass and to
+make additional checks for mandatory methods as needed.
+
+@end table
+
+To specify multiple attributes, separate them by commas within the
+double parentheses: for example, @samp{__attribute__ ((aligned (16),
+packed))}.
+
+@node ARC Type Attributes
+@subsection ARC Type Attributes
+
+@cindex @code{uncached} type attribute, ARC
+Declaring objects with @code{uncached} allows you to exclude
+data-cache participation in load and store operations on those objects
+without involving the additional semantic implications of
+@code{volatile}. The @code{.di} instruction suffix is used for all
+loads and stores of data declared @code{uncached}.
+
+@node ARM Type Attributes
+@subsection ARM Type Attributes
+
+@cindex @code{notshared} type attribute, ARM
+On those ARM targets that support @code{dllimport} (such as Symbian
+OS), you can use the @code{notshared} attribute to indicate that the
+virtual table and other similar data for a class should not be
+exported from a DLL@. For example:
+
+@smallexample
+class __declspec(notshared) C @{
+public:
+ __declspec(dllimport) C();
+ virtual void f();
+@}
+
+__declspec(dllexport)
+C::C() @{@}
+@end smallexample
+
+@noindent
+In this code, @code{C::C} is exported from the current DLL, but the
+virtual table for @code{C} is not exported. (You can use
+@code{__attribute__} instead of @code{__declspec} if you prefer, but
+most Symbian OS code uses @code{__declspec}.)
+
+@node BPF Type Attributes
+@subsection BPF Type Attributes
+
+@cindex @code{preserve_access_index} type attribute, BPF
+BPF Compile Once - Run Everywhere (CO-RE) support. When attached to a
+@code{struct} or @code{union} type definition, indicates that CO-RE
+relocation information should be generated for any access to a variable
+of that type. The behavior is equivalent to the programmer manually
+wrapping every such access with @code{__builtin_preserve_access_index}.
+
+
+@node MeP Type Attributes
+@subsection MeP Type Attributes
+
+@cindex @code{based} type attribute, MeP
+@cindex @code{tiny} type attribute, MeP
+@cindex @code{near} type attribute, MeP
+@cindex @code{far} type attribute, MeP
+Many of the MeP variable attributes may be applied to types as well.
+Specifically, the @code{based}, @code{tiny}, @code{near}, and
+@code{far} attributes may be applied to either. The @code{io} and
+@code{cb} attributes may not be applied to types.
+
+@node PowerPC Type Attributes
+@subsection PowerPC Type Attributes
+
+Three attributes currently are defined for PowerPC configurations:
+@code{altivec}, @code{ms_struct} and @code{gcc_struct}.
+
+@cindex @code{ms_struct} type attribute, PowerPC
+@cindex @code{gcc_struct} type attribute, PowerPC
+For full documentation of the @code{ms_struct} and @code{gcc_struct}
+attributes please see the documentation in @ref{x86 Type Attributes}.
+
+@cindex @code{altivec} type attribute, PowerPC
+The @code{altivec} attribute allows one to declare AltiVec vector data
+types supported by the AltiVec Programming Interface Manual. The
+attribute requires an argument to specify one of three vector types:
+@code{vector__}, @code{pixel__} (always followed by unsigned short),
+and @code{bool__} (always followed by unsigned).
+
+@smallexample
+__attribute__((altivec(vector__)))
+__attribute__((altivec(pixel__))) unsigned short
+__attribute__((altivec(bool__))) unsigned
+@end smallexample
+
+These attributes mainly are intended to support the @code{__vector},
+@code{__pixel}, and @code{__bool} AltiVec keywords.
+
+@node x86 Type Attributes
+@subsection x86 Type Attributes
+
+Two attributes are currently defined for x86 configurations:
+@code{ms_struct} and @code{gcc_struct}.
+
+@table @code
+
+@item ms_struct
+@itemx gcc_struct
+@cindex @code{ms_struct} type attribute, x86
+@cindex @code{gcc_struct} type attribute, x86
+
+If @code{packed} is used on a structure, or if bit-fields are used
+it may be that the Microsoft ABI packs them differently
+than GCC normally packs them. Particularly when moving packed
+data between functions compiled with GCC and the native Microsoft compiler
+(either via function call or as data in a file), it may be necessary to access
+either format.
+
+The @code{ms_struct} and @code{gcc_struct} attributes correspond
+to the @option{-mms-bitfields} and @option{-mno-ms-bitfields}
+command-line options, respectively;
+see @ref{x86 Options}, for details of how structure layout is affected.
+@xref{x86 Variable Attributes}, for information about the corresponding
+attributes on variables.
+
+@end table
+
+@node Label Attributes
+@section Label Attributes
+@cindex Label Attributes
+
+GCC allows attributes to be set on C labels. @xref{Attribute Syntax}, for
+details of the exact syntax for using attributes. Other attributes are
+available for functions (@pxref{Function Attributes}), variables
+(@pxref{Variable Attributes}), enumerators (@pxref{Enumerator Attributes}),
+statements (@pxref{Statement Attributes}), and for types
+(@pxref{Type Attributes}). A label attribute followed
+by a declaration appertains to the label and not the declaration.
+
+This example uses the @code{cold} label attribute to indicate the
+@code{ErrorHandling} branch is unlikely to be taken and that the
+@code{ErrorHandling} label is unused:
+
+@smallexample
+
+ asm goto ("some asm" : : : : NoError);
+
+/* This branch (the fall-through from the asm) is less commonly used */
+ErrorHandling:
+ __attribute__((cold, unused)); /* Semi-colon is required here */
+ printf("error\n");
+ return 0;
+
+NoError:
+ printf("no error\n");
+ return 1;
+@end smallexample
+
+@table @code
+@item unused
+@cindex @code{unused} label attribute
+This feature is intended for program-generated code that may contain
+unused labels, but which is compiled with @option{-Wall}. It is
+not normally appropriate to use in it human-written code, though it
+could be useful in cases where the code that jumps to the label is
+contained within an @code{#ifdef} conditional.
+
+@item hot
+@cindex @code{hot} label attribute
+The @code{hot} attribute on a label is used to inform the compiler that
+the path following the label is more likely than paths that are not so
+annotated. This attribute is used in cases where @code{__builtin_expect}
+cannot be used, for instance with computed goto or @code{asm goto}.
+
+@item cold
+@cindex @code{cold} label attribute
+The @code{cold} attribute on labels is used to inform the compiler that
+the path following the label is unlikely to be executed. This attribute
+is used in cases where @code{__builtin_expect} cannot be used, for instance
+with computed goto or @code{asm goto}.
+
+@end table
+
+@node Enumerator Attributes
+@section Enumerator Attributes
+@cindex Enumerator Attributes
+
+GCC allows attributes to be set on enumerators. @xref{Attribute Syntax}, for
+details of the exact syntax for using attributes. Other attributes are
+available for functions (@pxref{Function Attributes}), variables
+(@pxref{Variable Attributes}), labels (@pxref{Label Attributes}), statements
+(@pxref{Statement Attributes}), and for types (@pxref{Type Attributes}).
+
+This example uses the @code{deprecated} enumerator attribute to indicate the
+@code{oldval} enumerator is deprecated:
+
+@smallexample
+enum E @{
+ oldval __attribute__((deprecated)),
+ newval
+@};
+
+int
+fn (void)
+@{
+ return oldval;
+@}
+@end smallexample
+
+@table @code
+@item deprecated
+@cindex @code{deprecated} enumerator attribute
+The @code{deprecated} attribute results in a warning if the enumerator
+is used anywhere in the source file. This is useful when identifying
+enumerators that are expected to be removed in a future version of a
+program. The warning also includes the location of the declaration
+of the deprecated enumerator, to enable users to easily find further
+information about why the enumerator is deprecated, or what they should
+do instead. Note that the warnings only occurs for uses.
+
+@item unavailable
+@cindex @code{unavailable} enumerator attribute
+The @code{unavailable} attribute results in an error if the enumerator
+is used anywhere in the source file. In other respects it behaves in the
+same manner as the @code{deprecated} attribute.
+
+@end table
+
+@node Statement Attributes
+@section Statement Attributes
+@cindex Statement Attributes
+
+GCC allows attributes to be set on null statements. @xref{Attribute Syntax},
+for details of the exact syntax for using attributes. Other attributes are
+available for functions (@pxref{Function Attributes}), variables
+(@pxref{Variable Attributes}), labels (@pxref{Label Attributes}), enumerators
+(@pxref{Enumerator Attributes}), and for types (@pxref{Type Attributes}).
+
+@table @code
+@item fallthrough
+@cindex @code{fallthrough} statement attribute
+The @code{fallthrough} attribute with a null statement serves as a
+fallthrough statement. It hints to the compiler that a statement
+that falls through to another case label, or user-defined label
+in a switch statement is intentional and thus the
+@option{-Wimplicit-fallthrough} warning must not trigger. The
+fallthrough attribute may appear at most once in each attribute
+list, and may not be mixed with other attributes. It can only
+be used in a switch statement (the compiler will issue an error
+otherwise), after a preceding statement and before a logically
+succeeding case label, or user-defined label.
+
+This example uses the @code{fallthrough} statement attribute to indicate that
+the @option{-Wimplicit-fallthrough} warning should not be emitted:
+
+@smallexample
+switch (cond)
+ @{
+ case 1:
+ bar (1);
+ __attribute__((fallthrough));
+ case 2:
+ @dots{}
+ @}
+@end smallexample
+
+@item assume
+@cindex @code{assume} statement attribute
+The @code{assume} attribute with a null statement serves as portable
+assumption. It should have a single argument, a conditional expression,
+which is not evaluated. If the argument would evaluate to true
+at the point where it appears, it has no effect, otherwise there
+is undefined behavior. This is a GNU variant of the ISO C++23
+standard @code{assume} attribute, but it can be used in any version of
+both C and C++.
+
+@smallexample
+int
+foo (int x, int y)
+@{
+ __attribute__((assume(x == 42)));
+ __attribute__((assume(++y == 43)));
+ return x + y;
+@}
+@end smallexample
+
+@code{y} is not actually incremented and the compiler can but does not
+have to optimize it to just @code{return 42 + 42;}.
+
+@end table
+
+@node Attribute Syntax
+@section Attribute Syntax
+@cindex attribute syntax
+
+This section describes the syntax with which @code{__attribute__} may be
+used, and the constructs to which attribute specifiers bind, for the C
+language. Some details may vary for C++ and Objective-C@. Because of
+infelicities in the grammar for attributes, some forms described here
+may not be successfully parsed in all cases.
+
+There are some problems with the semantics of attributes in C++. For
+example, there are no manglings for attributes, although they may affect
+code generation, so problems may arise when attributed types are used in
+conjunction with templates or overloading. Similarly, @code{typeid}
+does not distinguish between types with different attributes. Support
+for attributes in C++ may be restricted in future to attributes on
+declarations only, but not on nested declarators.
+
+@xref{Function Attributes}, for details of the semantics of attributes
+applying to functions. @xref{Variable Attributes}, for details of the
+semantics of attributes applying to variables. @xref{Type Attributes},
+for details of the semantics of attributes applying to structure, union
+and enumerated types.
+@xref{Label Attributes}, for details of the semantics of attributes
+applying to labels.
+@xref{Enumerator Attributes}, for details of the semantics of attributes
+applying to enumerators.
+@xref{Statement Attributes}, for details of the semantics of attributes
+applying to statements.
+
+An @dfn{attribute specifier} is of the form
+@code{__attribute__ ((@var{attribute-list}))}. An @dfn{attribute list}
+is a possibly empty comma-separated sequence of @dfn{attributes}, where
+each attribute is one of the following:
+
+@itemize @bullet
+@item
+Empty. Empty attributes are ignored.
+
+@item
+An attribute name
+(which may be an identifier such as @code{unused}, or a reserved
+word such as @code{const}).
+
+@item
+An attribute name followed by a parenthesized list of
+parameters for the attribute.
+These parameters take one of the following forms:
+
+@itemize @bullet
+@item
+An identifier. For example, @code{mode} attributes use this form.
+
+@item
+An identifier followed by a comma and a non-empty comma-separated list
+of expressions. For example, @code{format} attributes use this form.
+
+@item
+A possibly empty comma-separated list of expressions. For example,
+@code{format_arg} attributes use this form with the list being a single
+integer constant expression, and @code{alias} attributes use this form
+with the list being a single string constant.
+@end itemize
+@end itemize
+
+An @dfn{attribute specifier list} is a sequence of one or more attribute
+specifiers, not separated by any other tokens.
+
+You may optionally specify attribute names with @samp{__}
+preceding and following the name.
+This allows you to use them in header files without
+being concerned about a possible macro of the same name. For example,
+you may use the attribute name @code{__noreturn__} instead of @code{noreturn}.
+
+
+@subsubheading Label Attributes
+
+In GNU C, an attribute specifier list may appear after the colon following a
+label, other than a @code{case} or @code{default} label. GNU C++ only permits
+attributes on labels if the attribute specifier is immediately
+followed by a semicolon (i.e., the label applies to an empty
+statement). If the semicolon is missing, C++ label attributes are
+ambiguous, as it is permissible for a declaration, which could begin
+with an attribute list, to be labelled in C++. Declarations cannot be
+labelled in C90 or C99, so the ambiguity does not arise there.
+
+@subsubheading Enumerator Attributes
+
+In GNU C, an attribute specifier list may appear as part of an enumerator.
+The attribute goes after the enumeration constant, before @code{=}, if
+present. The optional attribute in the enumerator appertains to the
+enumeration constant. It is not possible to place the attribute after
+the constant expression, if present.
+
+@subsubheading Statement Attributes
+In GNU C, an attribute specifier list may appear as part of a null
+statement. The attribute goes before the semicolon.
+
+@subsubheading Type Attributes
+
+An attribute specifier list may appear as part of a @code{struct},
+@code{union} or @code{enum} specifier. It may go either immediately
+after the @code{struct}, @code{union} or @code{enum} keyword, or after
+the closing brace. The former syntax is preferred.
+Where attribute specifiers follow the closing brace, they are considered
+to relate to the structure, union or enumerated type defined, not to any
+enclosing declaration the type specifier appears in, and the type
+defined is not complete until after the attribute specifiers.
+@c Otherwise, there would be the following problems: a shift/reduce
+@c conflict between attributes binding the struct/union/enum and
+@c binding to the list of specifiers/qualifiers; and "aligned"
+@c attributes could use sizeof for the structure, but the size could be
+@c changed later by "packed" attributes.
+
+
+@subsubheading All other attributes
+
+Otherwise, an attribute specifier appears as part of a declaration,
+counting declarations of unnamed parameters and type names, and relates
+to that declaration (which may be nested in another declaration, for
+example in the case of a parameter declaration), or to a particular declarator
+within a declaration. Where an
+attribute specifier is applied to a parameter declared as a function or
+an array, it should apply to the function or array rather than the
+pointer to which the parameter is implicitly converted, but this is not
+yet correctly implemented.
+
+Any list of specifiers and qualifiers at the start of a declaration may
+contain attribute specifiers, whether or not such a list may in that
+context contain storage class specifiers. (Some attributes, however,
+are essentially in the nature of storage class specifiers, and only make
+sense where storage class specifiers may be used; for example,
+@code{section}.) There is one necessary limitation to this syntax: the
+first old-style parameter declaration in a function definition cannot
+begin with an attribute specifier, because such an attribute applies to
+the function instead by syntax described below (which, however, is not
+yet implemented in this case). In some other cases, attribute
+specifiers are permitted by this grammar but not yet supported by the
+compiler. All attribute specifiers in this place relate to the
+declaration as a whole. In the obsolescent usage where a type of
+@code{int} is implied by the absence of type specifiers, such a list of
+specifiers and qualifiers may be an attribute specifier list with no
+other specifiers or qualifiers.
+
+At present, the first parameter in a function prototype must have some
+type specifier that is not an attribute specifier; this resolves an
+ambiguity in the interpretation of @code{void f(int
+(__attribute__((foo)) x))}, but is subject to change. At present, if
+the parentheses of a function declarator contain only attributes then
+those attributes are ignored, rather than yielding an error or warning
+or implying a single parameter of type int, but this is subject to
+change.
+
+An attribute specifier list may appear immediately before a declarator
+(other than the first) in a comma-separated list of declarators in a
+declaration of more than one identifier using a single list of
+specifiers and qualifiers. Such attribute specifiers apply
+only to the identifier before whose declarator they appear. For
+example, in
+
+@smallexample
+__attribute__((noreturn)) void d0 (void),
+ __attribute__((format(printf, 1, 2))) d1 (const char *, ...),
+ d2 (void);
+@end smallexample
+
+@noindent
+the @code{noreturn} attribute applies to all the functions
+declared; the @code{format} attribute only applies to @code{d1}.
+
+An attribute specifier list may appear immediately before the comma,
+@code{=} or semicolon terminating the declaration of an identifier other
+than a function definition. Such attribute specifiers apply
+to the declared object or function. Where an
+assembler name for an object or function is specified (@pxref{Asm
+Labels}), the attribute must follow the @code{asm}
+specification.
+
+An attribute specifier list may, in future, be permitted to appear after
+the declarator in a function definition (before any old-style parameter
+declarations or the function body).
+
+Attribute specifiers may be mixed with type qualifiers appearing inside
+the @code{[]} of a parameter array declarator, in the C99 construct by
+which such qualifiers are applied to the pointer to which the array is
+implicitly converted. Such attribute specifiers apply to the pointer,
+not to the array, but at present this is not implemented and they are
+ignored.
+
+An attribute specifier list may appear at the start of a nested
+declarator. At present, there are some limitations in this usage: the
+attributes correctly apply to the declarator, but for most individual
+attributes the semantics this implies are not implemented.
+When attribute specifiers follow the @code{*} of a pointer
+declarator, they may be mixed with any type qualifiers present.
+The following describes the formal semantics of this syntax. It makes the
+most sense if you are familiar with the formal specification of
+declarators in the ISO C standard.
+
+Consider (as in C99 subclause 6.7.5 paragraph 4) a declaration @code{T
+D1}, where @code{T} contains declaration specifiers that specify a type
+@var{Type} (such as @code{int}) and @code{D1} is a declarator that
+contains an identifier @var{ident}. The type specified for @var{ident}
+for derived declarators whose type does not include an attribute
+specifier is as in the ISO C standard.
+
+If @code{D1} has the form @code{( @var{attribute-specifier-list} D )},
+and the declaration @code{T D} specifies the type
+``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then
+@code{T D1} specifies the type ``@var{derived-declarator-type-list}
+@var{attribute-specifier-list} @var{Type}'' for @var{ident}.
+
+If @code{D1} has the form @code{*
+@var{type-qualifier-and-attribute-specifier-list} D}, and the
+declaration @code{T D} specifies the type
+``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then
+@code{T D1} specifies the type ``@var{derived-declarator-type-list}
+@var{type-qualifier-and-attribute-specifier-list} pointer to @var{Type}'' for
+@var{ident}.
+
+For example,
+
+@smallexample
+void (__attribute__((noreturn)) ****f) (void);
+@end smallexample
+
+@noindent
+specifies the type ``pointer to pointer to pointer to pointer to
+non-returning function returning @code{void}''. As another example,
+
+@smallexample
+char *__attribute__((aligned(8))) *f;
+@end smallexample
+
+@noindent
+specifies the type ``pointer to 8-byte-aligned pointer to @code{char}''.
+Note again that this does not work with most attributes; for example,
+the usage of @samp{aligned} and @samp{noreturn} attributes given above
+is not yet supported.
+
+For compatibility with existing code written for compiler versions that
+did not implement attributes on nested declarators, some laxity is
+allowed in the placing of attributes. If an attribute that only applies
+to types is applied to a declaration, it is treated as applying to
+the type of that declaration. If an attribute that only applies to
+declarations is applied to the type of a declaration, it is treated
+as applying to that declaration; and, for compatibility with code
+placing the attributes immediately before the identifier declared, such
+an attribute applied to a function return type is treated as
+applying to the function type, and such an attribute applied to an array
+element type is treated as applying to the array type. If an
+attribute that only applies to function types is applied to a
+pointer-to-function type, it is treated as applying to the pointer
+target type; if such an attribute is applied to a function return type
+that is not a pointer-to-function type, it is treated as applying
+to the function type.
+
+@node Function Prototypes
+@section Prototypes and Old-Style Function Definitions
+@cindex function prototype declarations
+@cindex old-style function definitions
+@cindex promotion of formal parameters
+
+GNU C extends ISO C to allow a function prototype to override a later
+old-style non-prototype definition. Consider the following example:
+
+@smallexample
+/* @r{Use prototypes unless the compiler is old-fashioned.} */
+#ifdef __STDC__
+#define P(x) x
+#else
+#define P(x) ()
+#endif
+
+/* @r{Prototype function declaration.} */
+int isroot P((uid_t));
+
+/* @r{Old-style function definition.} */
+int
+isroot (x) /* @r{??? lossage here ???} */
+ uid_t x;
+@{
+ return x == 0;
+@}
+@end smallexample
+
+Suppose the type @code{uid_t} happens to be @code{short}. ISO C does
+not allow this example, because subword arguments in old-style
+non-prototype definitions are promoted. Therefore in this example the
+function definition's argument is really an @code{int}, which does not
+match the prototype argument type of @code{short}.
+
+This restriction of ISO C makes it hard to write code that is portable
+to traditional C compilers, because the programmer does not know
+whether the @code{uid_t} type is @code{short}, @code{int}, or
+@code{long}. Therefore, in cases like these GNU C allows a prototype
+to override a later old-style definition. More precisely, in GNU C, a
+function prototype argument type overrides the argument type specified
+by a later old-style definition if the former type is the same as the
+latter type before promotion. Thus in GNU C the above example is
+equivalent to the following:
+
+@smallexample
+int isroot (uid_t);
+
+int
+isroot (uid_t x)
+@{
+ return x == 0;
+@}
+@end smallexample
+
+@noindent
+GNU C++ does not support old-style function definitions, so this
+extension is irrelevant.
+
+@node C++ Comments
+@section C++ Style Comments
+@cindex @code{//}
+@cindex C++ comments
+@cindex comments, C++ style
+
+In GNU C, you may use C++ style comments, which start with @samp{//} and
+continue until the end of the line. Many other C implementations allow
+such comments, and they are included in the 1999 C standard. However,
+C++ style comments are not recognized if you specify an @option{-std}
+option specifying a version of ISO C before C99, or @option{-ansi}
+(equivalent to @option{-std=c90}).
+
+@node Dollar Signs
+@section Dollar Signs in Identifier Names
+@cindex $
+@cindex dollar signs in identifier names
+@cindex identifier names, dollar signs in
+
+In GNU C, you may normally use dollar signs in identifier names.
+This is because many traditional C implementations allow such identifiers.
+However, dollar signs in identifiers are not supported on a few target
+machines, typically because the target assembler does not allow them.
+
+@node Character Escapes
+@section The Character @key{ESC} in Constants
+
+You can use the sequence @samp{\e} in a string or character constant to
+stand for the ASCII character @key{ESC}.
+
+@node Alignment
+@section Determining the Alignment of Functions, Types or Variables
+@cindex alignment
+@cindex type alignment
+@cindex variable alignment
+
+The keyword @code{__alignof__} determines the alignment requirement of
+a function, object, or a type, or the minimum alignment usually required
+by a type. Its syntax is just like @code{sizeof} and C11 @code{_Alignof}.
+
+For example, if the target machine requires a @code{double} value to be
+aligned on an 8-byte boundary, then @code{__alignof__ (double)} is 8.
+This is true on many RISC machines. On more traditional machine
+designs, @code{__alignof__ (double)} is 4 or even 2.
+
+Some machines never actually require alignment; they allow references to any
+data type even at an odd address. For these machines, @code{__alignof__}
+reports the smallest alignment that GCC gives the data type, usually as
+mandated by the target ABI.
+
+If the operand of @code{__alignof__} is an lvalue rather than a type,
+its value is the required alignment for its type, taking into account
+any minimum alignment specified by attribute @code{aligned}
+(@pxref{Common Variable Attributes}). For example, after this
+declaration:
+
+@smallexample
+struct foo @{ int x; char y; @} foo1;
+@end smallexample
+
+@noindent
+the value of @code{__alignof__ (foo1.y)} is 1, even though its actual
+alignment is probably 2 or 4, the same as @code{__alignof__ (int)}.
+It is an error to ask for the alignment of an incomplete type other
+than @code{void}.
+
+If the operand of the @code{__alignof__} expression is a function,
+the expression evaluates to the alignment of the function which may
+be specified by attribute @code{aligned} (@pxref{Common Function Attributes}).
+
+@node Inline
+@section An Inline Function is As Fast As a Macro
+@cindex inline functions
+@cindex integrating function code
+@cindex open coding
+@cindex macros, inline alternative
+
+By declaring a function inline, you can direct GCC to make
+calls to that function faster. One way GCC can achieve this is to
+integrate that function's code into the code for its callers. This
+makes execution faster by eliminating the function-call overhead; in
+addition, if any of the actual argument values are constant, their
+known values may permit simplifications at compile time so that not
+all of the inline function's code needs to be included. The effect on
+code size is less predictable; object code may be larger or smaller
+with function inlining, depending on the particular case. You can
+also direct GCC to try to integrate all ``simple enough'' functions
+into their callers with the option @option{-finline-functions}.
+
+GCC implements three different semantics of declaring a function
+inline. One is available with @option{-std=gnu89} or
+@option{-fgnu89-inline} or when @code{gnu_inline} attribute is present
+on all inline declarations, another when
+@option{-std=c99},
+@option{-std=gnu99} or an option for a later C version is used
+(without @option{-fgnu89-inline}), and the third
+is used when compiling C++.
+
+To declare a function inline, use the @code{inline} keyword in its
+declaration, like this:
+
+@smallexample
+static inline int
+inc (int *a)
+@{
+ return (*a)++;
+@}
+@end smallexample
+
+If you are writing a header file to be included in ISO C90 programs, write
+@code{__inline__} instead of @code{inline}. @xref{Alternate Keywords}.
+
+The three types of inlining behave similarly in two important cases:
+when the @code{inline} keyword is used on a @code{static} function,
+like the example above, and when a function is first declared without
+using the @code{inline} keyword and then is defined with
+@code{inline}, like this:
+
+@smallexample
+extern int inc (int *a);
+inline int
+inc (int *a)
+@{
+ return (*a)++;
+@}
+@end smallexample
+
+In both of these common cases, the program behaves the same as if you
+had not used the @code{inline} keyword, except for its speed.
+
+@cindex inline functions, omission of
+@opindex fkeep-inline-functions
+When a function is both inline and @code{static}, if all calls to the
+function are integrated into the caller, and the function's address is
+never used, then the function's own assembler code is never referenced.
+In this case, GCC does not actually output assembler code for the
+function, unless you specify the option @option{-fkeep-inline-functions}.
+If there is a nonintegrated call, then the function is compiled to
+assembler code as usual. The function must also be compiled as usual if
+the program refers to its address, because that cannot be inlined.
+
+@opindex Winline
+Note that certain usages in a function definition can make it unsuitable
+for inline substitution. Among these usages are: variadic functions,
+use of @code{alloca}, use of computed goto (@pxref{Labels as Values}),
+use of nonlocal goto, use of nested functions, use of @code{setjmp}, use
+of @code{__builtin_longjmp} and use of @code{__builtin_return} or
+@code{__builtin_apply_args}. Using @option{-Winline} warns when a
+function marked @code{inline} could not be substituted, and gives the
+reason for the failure.
+
+@cindex automatic @code{inline} for C++ member fns
+@cindex @code{inline} automatic for C++ member fns
+@cindex member fns, automatically @code{inline}
+@cindex C++ member fns, automatically @code{inline}
+@opindex fno-default-inline
+As required by ISO C++, GCC considers member functions defined within
+the body of a class to be marked inline even if they are
+not explicitly declared with the @code{inline} keyword. You can
+override this with @option{-fno-default-inline}; @pxref{C++ Dialect
+Options,,Options Controlling C++ Dialect}.
+
+GCC does not inline any functions when not optimizing unless you specify
+the @samp{always_inline} attribute for the function, like this:
+
+@smallexample
+/* @r{Prototype.} */
+inline void foo (const char) __attribute__((always_inline));
+@end smallexample
+
+The remainder of this section is specific to GNU C90 inlining.
+
+@cindex non-static inline function
+When an inline function is not @code{static}, then the compiler must assume
+that there may be calls from other source files; since a global symbol can
+be defined only once in any program, the function must not be defined in
+the other source files, so the calls therein cannot be integrated.
+Therefore, a non-@code{static} inline function is always compiled on its
+own in the usual fashion.
+
+If you specify both @code{inline} and @code{extern} in the function
+definition, then the definition is used only for inlining. In no case
+is the function compiled on its own, not even if you refer to its
+address explicitly. Such an address becomes an external reference, as
+if you had only declared the function, and had not defined it.
+
+This combination of @code{inline} and @code{extern} has almost the
+effect of a macro. The way to use it is to put a function definition in
+a header file with these keywords, and put another copy of the
+definition (lacking @code{inline} and @code{extern}) in a library file.
+The definition in the header file causes most calls to the function
+to be inlined. If any uses of the function remain, they refer to
+the single copy in the library.
+
+@node Volatiles
+@section When is a Volatile Object Accessed?
+@cindex accessing volatiles
+@cindex volatile read
+@cindex volatile write
+@cindex volatile access
+
+C has the concept of volatile objects. These are normally accessed by
+pointers and used for accessing hardware or inter-thread
+communication. The standard encourages compilers to refrain from
+optimizations concerning accesses to volatile objects, but leaves it
+implementation defined as to what constitutes a volatile access. The
+minimum requirement is that at a sequence point all previous accesses
+to volatile objects have stabilized and no subsequent accesses have
+occurred. Thus an implementation is free to reorder and combine
+volatile accesses that occur between sequence points, but cannot do
+so for accesses across a sequence point. The use of volatile does
+not allow you to violate the restriction on updating objects multiple
+times between two sequence points.
+
+Accesses to non-volatile objects are not ordered with respect to
+volatile accesses. You cannot use a volatile object as a memory
+barrier to order a sequence of writes to non-volatile memory. For
+instance:
+
+@smallexample
+int *ptr = @var{something};
+volatile int vobj;
+*ptr = @var{something};
+vobj = 1;
+@end smallexample
+
+@noindent
+Unless @var{*ptr} and @var{vobj} can be aliased, it is not guaranteed
+that the write to @var{*ptr} occurs by the time the update
+of @var{vobj} happens. If you need this guarantee, you must use
+a stronger memory barrier such as:
+
+@smallexample
+int *ptr = @var{something};
+volatile int vobj;
+*ptr = @var{something};
+asm volatile ("" : : : "memory");
+vobj = 1;
+@end smallexample
+
+A scalar volatile object is read when it is accessed in a void context:
+
+@smallexample
+volatile int *src = @var{somevalue};
+*src;
+@end smallexample
+
+Such expressions are rvalues, and GCC implements this as a
+read of the volatile object being pointed to.
+
+Assignments are also expressions and have an rvalue. However when
+assigning to a scalar volatile, the volatile object is not reread,
+regardless of whether the assignment expression's rvalue is used or
+not. If the assignment's rvalue is used, the value is that assigned
+to the volatile object. For instance, there is no read of @var{vobj}
+in all the following cases:
+
+@smallexample
+int obj;
+volatile int vobj;
+vobj = @var{something};
+obj = vobj = @var{something};
+obj ? vobj = @var{onething} : vobj = @var{anotherthing};
+obj = (@var{something}, vobj = @var{anotherthing});
+@end smallexample
+
+If you need to read the volatile object after an assignment has
+occurred, you must use a separate expression with an intervening
+sequence point.
+
+As bit-fields are not individually addressable, volatile bit-fields may
+be implicitly read when written to, or when adjacent bit-fields are
+accessed. Bit-field operations may be optimized such that adjacent
+bit-fields are only partially accessed, if they straddle a storage unit
+boundary. For these reasons it is unwise to use volatile bit-fields to
+access hardware.
+
+@node Using Assembly Language with C
+@section How to Use Inline Assembly Language in C Code
+@cindex @code{asm} keyword
+@cindex assembly language in C
+@cindex inline assembly language
+@cindex mixing assembly language and C
+
+The @code{asm} keyword allows you to embed assembler instructions
+within C code. GCC provides two forms of inline @code{asm}
+statements. A @dfn{basic @code{asm}} statement is one with no
+operands (@pxref{Basic Asm}), while an @dfn{extended @code{asm}}
+statement (@pxref{Extended Asm}) includes one or more operands.
+The extended form is preferred for mixing C and assembly language
+within a function, but to include assembly language at
+top level you must use basic @code{asm}.
+
+You can also use the @code{asm} keyword to override the assembler name
+for a C symbol, or to place a C variable in a specific register.
+
+@menu
+* Basic Asm:: Inline assembler without operands.
+* Extended Asm:: Inline assembler with operands.
+* Constraints:: Constraints for @code{asm} operands
+* Asm Labels:: Specifying the assembler name to use for a C symbol.
+* Explicit Register Variables:: Defining variables residing in specified
+ registers.
+* Size of an asm:: How GCC calculates the size of an @code{asm} block.
+@end menu
+
+@node Basic Asm
+@subsection Basic Asm --- Assembler Instructions Without Operands
+@cindex basic @code{asm}
+@cindex assembly language in C, basic
+
+A basic @code{asm} statement has the following syntax:
+
+@example
+asm @var{asm-qualifiers} ( @var{AssemblerInstructions} )
+@end example
+
+For the C language, the @code{asm} keyword is a GNU extension.
+When writing C code that can be compiled with @option{-ansi} and the
+@option{-std} options that select C dialects without GNU extensions, use
+@code{__asm__} instead of @code{asm} (@pxref{Alternate Keywords}). For
+the C++ language, @code{asm} is a standard keyword, but @code{__asm__}
+can be used for code compiled with @option{-fno-asm}.
+
+@subsubheading Qualifiers
+@table @code
+@item volatile
+The optional @code{volatile} qualifier has no effect.
+All basic @code{asm} blocks are implicitly volatile.
+
+@item inline
+If you use the @code{inline} qualifier, then for inlining purposes the size
+of the @code{asm} statement is taken as the smallest size possible (@pxref{Size
+of an asm}).
+@end table
+
+@subsubheading Parameters
+@table @var
+
+@item AssemblerInstructions
+This is a literal string that specifies the assembler code. The string can
+contain any instructions recognized by the assembler, including directives.
+GCC does not parse the assembler instructions themselves and
+does not know what they mean or even whether they are valid assembler input.
+
+You may place multiple assembler instructions together in a single @code{asm}
+string, separated by the characters normally used in assembly code for the
+system. A combination that works in most places is a newline to break the
+line, plus a tab character (written as @samp{\n\t}).
+Some assemblers allow semicolons as a line separator. However,
+note that some assembler dialects use semicolons to start a comment.
+@end table
+
+@subsubheading Remarks
+Using extended @code{asm} (@pxref{Extended Asm}) typically produces
+smaller, safer, and more efficient code, and in most cases it is a
+better solution than basic @code{asm}. However, there are two
+situations where only basic @code{asm} can be used:
+
+@itemize @bullet
+@item
+Extended @code{asm} statements have to be inside a C
+function, so to write inline assembly language at file scope (``top-level''),
+outside of C functions, you must use basic @code{asm}.
+You can use this technique to emit assembler directives,
+define assembly language macros that can be invoked elsewhere in the file,
+or write entire functions in assembly language.
+Basic @code{asm} statements outside of functions may not use any
+qualifiers.
+
+@item
+Functions declared
+with the @code{naked} attribute also require basic @code{asm}
+(@pxref{Function Attributes}).
+@end itemize
+
+Safely accessing C data and calling functions from basic @code{asm} is more
+complex than it may appear. To access C data, it is better to use extended
+@code{asm}.
+
+Do not expect a sequence of @code{asm} statements to remain perfectly
+consecutive after compilation. If certain instructions need to remain
+consecutive in the output, put them in a single multi-instruction @code{asm}
+statement. Note that GCC's optimizers can move @code{asm} statements
+relative to other code, including across jumps.
+
+@code{asm} statements may not perform jumps into other @code{asm} statements.
+GCC does not know about these jumps, and therefore cannot take
+account of them when deciding how to optimize. Jumps from @code{asm} to C
+labels are only supported in extended @code{asm}.
+
+Under certain circumstances, GCC may duplicate (or remove duplicates of) your
+assembly code when optimizing. This can lead to unexpected duplicate
+symbol errors during compilation if your assembly code defines symbols or
+labels.
+
+@strong{Warning:} The C standards do not specify semantics for @code{asm},
+making it a potential source of incompatibilities between compilers. These
+incompatibilities may not produce compiler warnings/errors.
+
+GCC does not parse basic @code{asm}'s @var{AssemblerInstructions}, which
+means there is no way to communicate to the compiler what is happening
+inside them. GCC has no visibility of symbols in the @code{asm} and may
+discard them as unreferenced. It also does not know about side effects of
+the assembler code, such as modifications to memory or registers. Unlike
+some compilers, GCC assumes that no changes to general purpose registers
+occur. This assumption may change in a future release.
+
+To avoid complications from future changes to the semantics and the
+compatibility issues between compilers, consider replacing basic @code{asm}
+with extended @code{asm}. See
+@uref{https://gcc.gnu.org/wiki/ConvertBasicAsmToExtended, How to convert
+from basic asm to extended asm} for information about how to perform this
+conversion.
+
+The compiler copies the assembler instructions in a basic @code{asm}
+verbatim to the assembly language output file, without
+processing dialects or any of the @samp{%} operators that are available with
+extended @code{asm}. This results in minor differences between basic
+@code{asm} strings and extended @code{asm} templates. For example, to refer to
+registers you might use @samp{%eax} in basic @code{asm} and
+@samp{%%eax} in extended @code{asm}.
+
+On targets such as x86 that support multiple assembler dialects,
+all basic @code{asm} blocks use the assembler dialect specified by the
+@option{-masm} command-line option (@pxref{x86 Options}).
+Basic @code{asm} provides no
+mechanism to provide different assembler strings for different dialects.
+
+For basic @code{asm} with non-empty assembler string GCC assumes
+the assembler block does not change any general purpose registers,
+but it may read or write any globally accessible variable.
+
+Here is an example of basic @code{asm} for i386:
+
+@example
+/* Note that this code will not compile with -masm=intel */
+#define DebugBreak() asm("int $3")
+@end example
+
+@node Extended Asm
+@subsection Extended Asm - Assembler Instructions with C Expression Operands
+@cindex extended @code{asm}
+@cindex assembly language in C, extended
+
+With extended @code{asm} you can read and write C variables from
+assembler and perform jumps from assembler code to C labels.
+Extended @code{asm} syntax uses colons (@samp{:}) to delimit
+the operand parameters after the assembler template:
+
+@example
+asm @var{asm-qualifiers} ( @var{AssemblerTemplate}
+ : @var{OutputOperands}
+ @r{[} : @var{InputOperands}
+ @r{[} : @var{Clobbers} @r{]} @r{]})
+
+asm @var{asm-qualifiers} ( @var{AssemblerTemplate}
+ : @var{OutputOperands}
+ : @var{InputOperands}
+ : @var{Clobbers}
+ : @var{GotoLabels})
+@end example
+where in the last form, @var{asm-qualifiers} contains @code{goto} (and in the
+first form, not).
+
+The @code{asm} keyword is a GNU extension.
+When writing code that can be compiled with @option{-ansi} and the
+various @option{-std} options, use @code{__asm__} instead of
+@code{asm} (@pxref{Alternate Keywords}).
+
+@subsubheading Qualifiers
+@table @code
+
+@item volatile
+The typical use of extended @code{asm} statements is to manipulate input
+values to produce output values. However, your @code{asm} statements may
+also produce side effects. If so, you may need to use the @code{volatile}
+qualifier to disable certain optimizations. @xref{Volatile}.
+
+@item inline
+If you use the @code{inline} qualifier, then for inlining purposes the size
+of the @code{asm} statement is taken as the smallest size possible
+(@pxref{Size of an asm}).
+
+@item goto
+This qualifier informs the compiler that the @code{asm} statement may
+perform a jump to one of the labels listed in the @var{GotoLabels}.
+@xref{GotoLabels}.
+@end table
+
+@subsubheading Parameters
+@table @var
+@item AssemblerTemplate
+This is a literal string that is the template for the assembler code. It is a
+combination of fixed text and tokens that refer to the input, output,
+and goto parameters. @xref{AssemblerTemplate}.
+
+@item OutputOperands
+A comma-separated list of the C variables modified by the instructions in the
+@var{AssemblerTemplate}. An empty list is permitted. @xref{OutputOperands}.
+
+@item InputOperands
+A comma-separated list of C expressions read by the instructions in the
+@var{AssemblerTemplate}. An empty list is permitted. @xref{InputOperands}.
+
+@item Clobbers
+A comma-separated list of registers or other values changed by the
+@var{AssemblerTemplate}, beyond those listed as outputs.
+An empty list is permitted. @xref{Clobbers and Scratch Registers}.
+
+@item GotoLabels
+When you are using the @code{goto} form of @code{asm}, this section contains
+the list of all C labels to which the code in the
+@var{AssemblerTemplate} may jump.
+@xref{GotoLabels}.
+
+@code{asm} statements may not perform jumps into other @code{asm} statements,
+only to the listed @var{GotoLabels}.
+GCC's optimizers do not know about other jumps; therefore they cannot take
+account of them when deciding how to optimize.
+@end table
+
+The total number of input + output + goto operands is limited to 30.
+
+@subsubheading Remarks
+The @code{asm} statement allows you to include assembly instructions directly
+within C code. This may help you to maximize performance in time-sensitive
+code or to access assembly instructions that are not readily available to C
+programs.
+
+Note that extended @code{asm} statements must be inside a function. Only
+basic @code{asm} may be outside functions (@pxref{Basic Asm}).
+Functions declared with the @code{naked} attribute also require basic
+@code{asm} (@pxref{Function Attributes}).
+
+While the uses of @code{asm} are many and varied, it may help to think of an
+@code{asm} statement as a series of low-level instructions that convert input
+parameters to output parameters. So a simple (if not particularly useful)
+example for i386 using @code{asm} might look like this:
+
+@example
+int src = 1;
+int dst;
+
+asm ("mov %1, %0\n\t"
+ "add $1, %0"
+ : "=r" (dst)
+ : "r" (src));
+
+printf("%d\n", dst);
+@end example
+
+This code copies @code{src} to @code{dst} and add 1 to @code{dst}.
+
+@anchor{Volatile}
+@subsubsection Volatile
+@cindex volatile @code{asm}
+@cindex @code{asm} volatile
+
+GCC's optimizers sometimes discard @code{asm} statements if they determine
+there is no need for the output variables. Also, the optimizers may move
+code out of loops if they believe that the code will always return the same
+result (i.e.@: none of its input values change between calls). Using the
+@code{volatile} qualifier disables these optimizations. @code{asm} statements
+that have no output operands and @code{asm goto} statements,
+are implicitly volatile.
+
+This i386 code demonstrates a case that does not use (or require) the
+@code{volatile} qualifier. If it is performing assertion checking, this code
+uses @code{asm} to perform the validation. Otherwise, @code{dwRes} is
+unreferenced by any code. As a result, the optimizers can discard the
+@code{asm} statement, which in turn removes the need for the entire
+@code{DoCheck} routine. By omitting the @code{volatile} qualifier when it
+isn't needed you allow the optimizers to produce the most efficient code
+possible.
+
+@example
+void DoCheck(uint32_t dwSomeValue)
+@{
+ uint32_t dwRes;
+
+ // Assumes dwSomeValue is not zero.
+ asm ("bsfl %1,%0"
+ : "=r" (dwRes)
+ : "r" (dwSomeValue)
+ : "cc");
+
+ assert(dwRes > 3);
+@}
+@end example
+
+The next example shows a case where the optimizers can recognize that the input
+(@code{dwSomeValue}) never changes during the execution of the function and can
+therefore move the @code{asm} outside the loop to produce more efficient code.
+Again, using the @code{volatile} qualifier disables this type of optimization.
+
+@example
+void do_print(uint32_t dwSomeValue)
+@{
+ uint32_t dwRes;
+
+ for (uint32_t x=0; x < 5; x++)
+ @{
+ // Assumes dwSomeValue is not zero.
+ asm ("bsfl %1,%0"
+ : "=r" (dwRes)
+ : "r" (dwSomeValue)
+ : "cc");
+
+ printf("%u: %u %u\n", x, dwSomeValue, dwRes);
+ @}
+@}
+@end example
+
+The following example demonstrates a case where you need to use the
+@code{volatile} qualifier.
+It uses the x86 @code{rdtsc} instruction, which reads
+the computer's time-stamp counter. Without the @code{volatile} qualifier,
+the optimizers might assume that the @code{asm} block will always return the
+same value and therefore optimize away the second call.
+
+@example
+uint64_t msr;
+
+asm volatile ( "rdtsc\n\t" // Returns the time in EDX:EAX.
+ "shl $32, %%rdx\n\t" // Shift the upper bits left.
+ "or %%rdx, %0" // 'Or' in the lower bits.
+ : "=a" (msr)
+ :
+ : "rdx");
+
+printf("msr: %llx\n", msr);
+
+// Do other work...
+
+// Reprint the timestamp
+asm volatile ( "rdtsc\n\t" // Returns the time in EDX:EAX.
+ "shl $32, %%rdx\n\t" // Shift the upper bits left.
+ "or %%rdx, %0" // 'Or' in the lower bits.
+ : "=a" (msr)
+ :
+ : "rdx");
+
+printf("msr: %llx\n", msr);
+@end example
+
+GCC's optimizers do not treat this code like the non-volatile code in the
+earlier examples. They do not move it out of loops or omit it on the
+assumption that the result from a previous call is still valid.
+
+Note that the compiler can move even @code{volatile asm} instructions relative
+to other code, including across jump instructions. For example, on many
+targets there is a system register that controls the rounding mode of
+floating-point operations. Setting it with a @code{volatile asm} statement,
+as in the following PowerPC example, does not work reliably.
+
+@example
+asm volatile("mtfsf 255, %0" : : "f" (fpenv));
+sum = x + y;
+@end example
+
+The compiler may move the addition back before the @code{volatile asm}
+statement. To make it work as expected, add an artificial dependency to
+the @code{asm} by referencing a variable in the subsequent code, for
+example:
+
+@example
+asm volatile ("mtfsf 255,%1" : "=X" (sum) : "f" (fpenv));
+sum = x + y;
+@end example
+
+Under certain circumstances, GCC may duplicate (or remove duplicates of) your
+assembly code when optimizing. This can lead to unexpected duplicate symbol
+errors during compilation if your @code{asm} code defines symbols or labels.
+Using @samp{%=}
+(@pxref{AssemblerTemplate}) may help resolve this problem.
+
+@anchor{AssemblerTemplate}
+@subsubsection Assembler Template
+@cindex @code{asm} assembler template
+
+An assembler template is a literal string containing assembler instructions.
+The compiler replaces tokens in the template that refer
+to inputs, outputs, and goto labels,
+and then outputs the resulting string to the assembler. The
+string can contain any instructions recognized by the assembler, including
+directives. GCC does not parse the assembler instructions
+themselves and does not know what they mean or even whether they are valid
+assembler input. However, it does count the statements
+(@pxref{Size of an asm}).
+
+You may place multiple assembler instructions together in a single @code{asm}
+string, separated by the characters normally used in assembly code for the
+system. A combination that works in most places is a newline to break the
+line, plus a tab character to move to the instruction field (written as
+@samp{\n\t}).
+Some assemblers allow semicolons as a line separator. However, note
+that some assembler dialects use semicolons to start a comment.
+
+Do not expect a sequence of @code{asm} statements to remain perfectly
+consecutive after compilation, even when you are using the @code{volatile}
+qualifier. If certain instructions need to remain consecutive in the output,
+put them in a single multi-instruction @code{asm} statement.
+
+Accessing data from C programs without using input/output operands (such as
+by using global symbols directly from the assembler template) may not work as
+expected. Similarly, calling functions directly from an assembler template
+requires a detailed understanding of the target assembler and ABI.
+
+Since GCC does not parse the assembler template,
+it has no visibility of any
+symbols it references. This may result in GCC discarding those symbols as
+unreferenced unless they are also listed as input, output, or goto operands.
+
+@subsubheading Special format strings
+
+In addition to the tokens described by the input, output, and goto operands,
+these tokens have special meanings in the assembler template:
+
+@table @samp
+@item %%
+Outputs a single @samp{%} into the assembler code.
+
+@item %=
+Outputs a number that is unique to each instance of the @code{asm}
+statement in the entire compilation. This option is useful when creating local
+labels and referring to them multiple times in a single template that
+generates multiple assembler instructions.
+
+@item %@{
+@itemx %|
+@itemx %@}
+Outputs @samp{@{}, @samp{|}, and @samp{@}} characters (respectively)
+into the assembler code. When unescaped, these characters have special
+meaning to indicate multiple assembler dialects, as described below.
+@end table
+
+@subsubheading Multiple assembler dialects in @code{asm} templates
+
+On targets such as x86, GCC supports multiple assembler dialects.
+The @option{-masm} option controls which dialect GCC uses as its
+default for inline assembler. The target-specific documentation for the
+@option{-masm} option contains the list of supported dialects, as well as the
+default dialect if the option is not specified. This information may be
+important to understand, since assembler code that works correctly when
+compiled using one dialect will likely fail if compiled using another.
+@xref{x86 Options}.
+
+If your code needs to support multiple assembler dialects (for example, if
+you are writing public headers that need to support a variety of compilation
+options), use constructs of this form:
+
+@example
+@{ dialect0 | dialect1 | dialect2... @}
+@end example
+
+This construct outputs @code{dialect0}
+when using dialect #0 to compile the code,
+@code{dialect1} for dialect #1, etc. If there are fewer alternatives within the
+braces than the number of dialects the compiler supports, the construct
+outputs nothing.
+
+For example, if an x86 compiler supports two dialects
+(@samp{att}, @samp{intel}), an
+assembler template such as this:
+
+@example
+"bt@{l %[Offset],%[Base] | %[Base],%[Offset]@}; jc %l2"
+@end example
+
+@noindent
+is equivalent to one of
+
+@example
+"btl %[Offset],%[Base] ; jc %l2" @r{/* att dialect */}
+"bt %[Base],%[Offset]; jc %l2" @r{/* intel dialect */}
+@end example
+
+Using that same compiler, this code:
+
+@example
+"xchg@{l@}\t@{%%@}ebx, %1"
+@end example
+
+@noindent
+corresponds to either
+
+@example
+"xchgl\t%%ebx, %1" @r{/* att dialect */}
+"xchg\tebx, %1" @r{/* intel dialect */}
+@end example
+
+There is no support for nesting dialect alternatives.
+
+@anchor{OutputOperands}
+@subsubsection Output Operands
+@cindex @code{asm} output operands
+
+An @code{asm} statement has zero or more output operands indicating the names
+of C variables modified by the assembler code.
+
+In this i386 example, @code{old} (referred to in the template string as
+@code{%0}) and @code{*Base} (as @code{%1}) are outputs and @code{Offset}
+(@code{%2}) is an input:
+
+@example
+bool old;
+
+__asm__ ("btsl %2,%1\n\t" // Turn on zero-based bit #Offset in Base.
+ "sbb %0,%0" // Use the CF to calculate old.
+ : "=r" (old), "+rm" (*Base)
+ : "Ir" (Offset)
+ : "cc");
+
+return old;
+@end example
+
+Operands are separated by commas. Each operand has this format:
+
+@example
+@r{[} [@var{asmSymbolicName}] @r{]} @var{constraint} (@var{cvariablename})
+@end example
+
+@table @var
+@item asmSymbolicName
+Specifies a symbolic name for the operand.
+Reference the name in the assembler template
+by enclosing it in square brackets
+(i.e.@: @samp{%[Value]}). The scope of the name is the @code{asm} statement
+that contains the definition. Any valid C variable name is acceptable,
+including names already defined in the surrounding code. No two operands
+within the same @code{asm} statement can use the same symbolic name.
+
+When not using an @var{asmSymbolicName}, use the (zero-based) position
+of the operand
+in the list of operands in the assembler template. For example if there are
+three output operands, use @samp{%0} in the template to refer to the first,
+@samp{%1} for the second, and @samp{%2} for the third.
+
+@item constraint
+A string constant specifying constraints on the placement of the operand;
+@xref{Constraints}, for details.
+
+Output constraints must begin with either @samp{=} (a variable overwriting an
+existing value) or @samp{+} (when reading and writing). When using
+@samp{=}, do not assume the location contains the existing value
+on entry to the @code{asm}, except
+when the operand is tied to an input; @pxref{InputOperands,,Input Operands}.
+
+After the prefix, there must be one or more additional constraints
+(@pxref{Constraints}) that describe where the value resides. Common
+constraints include @samp{r} for register and @samp{m} for memory.
+When you list more than one possible location (for example, @code{"=rm"}),
+the compiler chooses the most efficient one based on the current context.
+If you list as many alternates as the @code{asm} statement allows, you permit
+the optimizers to produce the best possible code.
+If you must use a specific register, but your Machine Constraints do not
+provide sufficient control to select the specific register you want,
+local register variables may provide a solution (@pxref{Local Register
+Variables}).
+
+@item cvariablename
+Specifies a C lvalue expression to hold the output, typically a variable name.
+The enclosing parentheses are a required part of the syntax.
+
+@end table
+
+When the compiler selects the registers to use to
+represent the output operands, it does not use any of the clobbered registers
+(@pxref{Clobbers and Scratch Registers}).
+
+Output operand expressions must be lvalues. The compiler cannot check whether
+the operands have data types that are reasonable for the instruction being
+executed. For output expressions that are not directly addressable (for
+example a bit-field), the constraint must allow a register. In that case, GCC
+uses the register as the output of the @code{asm}, and then stores that
+register into the output.
+
+Operands using the @samp{+} constraint modifier count as two operands
+(that is, both as input and output) towards the total maximum of 30 operands
+per @code{asm} statement.
+
+Use the @samp{&} constraint modifier (@pxref{Modifiers}) on all output
+operands that must not overlap an input. Otherwise,
+GCC may allocate the output operand in the same register as an unrelated
+input operand, on the assumption that the assembler code consumes its
+inputs before producing outputs. This assumption may be false if the assembler
+code actually consists of more than one instruction.
+
+The same problem can occur if one output parameter (@var{a}) allows a register
+constraint and another output parameter (@var{b}) allows a memory constraint.
+The code generated by GCC to access the memory address in @var{b} can contain
+registers which @emph{might} be shared by @var{a}, and GCC considers those
+registers to be inputs to the asm. As above, GCC assumes that such input
+registers are consumed before any outputs are written. This assumption may
+result in incorrect behavior if the @code{asm} statement writes to @var{a}
+before using
+@var{b}. Combining the @samp{&} modifier with the register constraint on @var{a}
+ensures that modifying @var{a} does not affect the address referenced by
+@var{b}. Otherwise, the location of @var{b}
+is undefined if @var{a} is modified before using @var{b}.
+
+@code{asm} supports operand modifiers on operands (for example @samp{%k2}
+instead of simply @samp{%2}). Typically these qualifiers are hardware
+dependent. The list of supported modifiers for x86 is found at
+@ref{x86Operandmodifiers,x86 Operand modifiers}.
+
+If the C code that follows the @code{asm} makes no use of any of the output
+operands, use @code{volatile} for the @code{asm} statement to prevent the
+optimizers from discarding the @code{asm} statement as unneeded
+(see @ref{Volatile}).
+
+This code makes no use of the optional @var{asmSymbolicName}. Therefore it
+references the first output operand as @code{%0} (were there a second, it
+would be @code{%1}, etc). The number of the first input operand is one greater
+than that of the last output operand. In this i386 example, that makes
+@code{Mask} referenced as @code{%1}:
+
+@example
+uint32_t Mask = 1234;
+uint32_t Index;
+
+ asm ("bsfl %1, %0"
+ : "=r" (Index)
+ : "r" (Mask)
+ : "cc");
+@end example
+
+That code overwrites the variable @code{Index} (@samp{=}),
+placing the value in a register (@samp{r}).
+Using the generic @samp{r} constraint instead of a constraint for a specific
+register allows the compiler to pick the register to use, which can result
+in more efficient code. This may not be possible if an assembler instruction
+requires a specific register.
+
+The following i386 example uses the @var{asmSymbolicName} syntax.
+It produces the
+same result as the code above, but some may consider it more readable or more
+maintainable since reordering index numbers is not necessary when adding or
+removing operands. The names @code{aIndex} and @code{aMask}
+are only used in this example to emphasize which
+names get used where.
+It is acceptable to reuse the names @code{Index} and @code{Mask}.
+
+@example
+uint32_t Mask = 1234;
+uint32_t Index;
+
+ asm ("bsfl %[aMask], %[aIndex]"
+ : [aIndex] "=r" (Index)
+ : [aMask] "r" (Mask)
+ : "cc");
+@end example
+
+Here are some more examples of output operands.
+
+@example
+uint32_t c = 1;
+uint32_t d;
+uint32_t *e = &c;
+
+asm ("mov %[e], %[d]"
+ : [d] "=rm" (d)
+ : [e] "rm" (*e));
+@end example
+
+Here, @code{d} may either be in a register or in memory. Since the compiler
+might already have the current value of the @code{uint32_t} location
+pointed to by @code{e}
+in a register, you can enable it to choose the best location
+for @code{d} by specifying both constraints.
+
+@anchor{FlagOutputOperands}
+@subsubsection Flag Output Operands
+@cindex @code{asm} flag output operands
+
+Some targets have a special register that holds the ``flags'' for the
+result of an operation or comparison. Normally, the contents of that
+register are either unmodifed by the asm, or the @code{asm} statement is
+considered to clobber the contents.
+
+On some targets, a special form of output operand exists by which
+conditions in the flags register may be outputs of the asm. The set of
+conditions supported are target specific, but the general rule is that
+the output variable must be a scalar integer, and the value is boolean.
+When supported, the target defines the preprocessor symbol
+@code{__GCC_ASM_FLAG_OUTPUTS__}.
+
+Because of the special nature of the flag output operands, the constraint
+may not include alternatives.
+
+Most often, the target has only one flags register, and thus is an implied
+operand of many instructions. In this case, the operand should not be
+referenced within the assembler template via @code{%0} etc, as there's
+no corresponding text in the assembly language.
+
+@table @asis
+@item ARM
+@itemx AArch64
+The flag output constraints for the ARM family are of the form
+@samp{=@@cc@var{cond}} where @var{cond} is one of the standard
+conditions defined in the ARM ARM for @code{ConditionHolds}.
+
+@table @code
+@item eq
+Z flag set, or equal
+@item ne
+Z flag clear or not equal
+@item cs
+@itemx hs
+C flag set or unsigned greater than equal
+@item cc
+@itemx lo
+C flag clear or unsigned less than
+@item mi
+N flag set or ``minus''
+@item pl
+N flag clear or ``plus''
+@item vs
+V flag set or signed overflow
+@item vc
+V flag clear
+@item hi
+unsigned greater than
+@item ls
+unsigned less than equal
+@item ge
+signed greater than equal
+@item lt
+signed less than
+@item gt
+signed greater than
+@item le
+signed less than equal
+@end table
+
+The flag output constraints are not supported in thumb1 mode.
+
+@item x86 family
+The flag output constraints for the x86 family are of the form
+@samp{=@@cc@var{cond}} where @var{cond} is one of the standard
+conditions defined in the ISA manual for @code{j@var{cc}} or
+@code{set@var{cc}}.
+
+@table @code
+@item a
+``above'' or unsigned greater than
+@item ae
+``above or equal'' or unsigned greater than or equal
+@item b
+``below'' or unsigned less than
+@item be
+``below or equal'' or unsigned less than or equal
+@item c
+carry flag set
+@item e
+@itemx z
+``equal'' or zero flag set
+@item g
+signed greater than
+@item ge
+signed greater than or equal
+@item l
+signed less than
+@item le
+signed less than or equal
+@item o
+overflow flag set
+@item p
+parity flag set
+@item s
+sign flag set
+@item na
+@itemx nae
+@itemx nb
+@itemx nbe
+@itemx nc
+@itemx ne
+@itemx ng
+@itemx nge
+@itemx nl
+@itemx nle
+@itemx no
+@itemx np
+@itemx ns
+@itemx nz
+``not'' @var{flag}, or inverted versions of those above
+@end table
+
+@end table
+
+@anchor{InputOperands}
+@subsubsection Input Operands
+@cindex @code{asm} input operands
+@cindex @code{asm} expressions
+
+Input operands make values from C variables and expressions available to the
+assembly code.
+
+Operands are separated by commas. Each operand has this format:
+
+@example
+@r{[} [@var{asmSymbolicName}] @r{]} @var{constraint} (@var{cexpression})
+@end example
+
+@table @var
+@item asmSymbolicName
+Specifies a symbolic name for the operand.
+Reference the name in the assembler template
+by enclosing it in square brackets
+(i.e.@: @samp{%[Value]}). The scope of the name is the @code{asm} statement
+that contains the definition. Any valid C variable name is acceptable,
+including names already defined in the surrounding code. No two operands
+within the same @code{asm} statement can use the same symbolic name.
+
+When not using an @var{asmSymbolicName}, use the (zero-based) position
+of the operand
+in the list of operands in the assembler template. For example if there are
+two output operands and three inputs,
+use @samp{%2} in the template to refer to the first input operand,
+@samp{%3} for the second, and @samp{%4} for the third.
+
+@item constraint
+A string constant specifying constraints on the placement of the operand;
+@xref{Constraints}, for details.
+
+Input constraint strings may not begin with either @samp{=} or @samp{+}.
+When you list more than one possible location (for example, @samp{"irm"}),
+the compiler chooses the most efficient one based on the current context.
+If you must use a specific register, but your Machine Constraints do not
+provide sufficient control to select the specific register you want,
+local register variables may provide a solution (@pxref{Local Register
+Variables}).
+
+Input constraints can also be digits (for example, @code{"0"}). This indicates
+that the specified input must be in the same place as the output constraint
+at the (zero-based) index in the output constraint list.
+When using @var{asmSymbolicName} syntax for the output operands,
+you may use these names (enclosed in brackets @samp{[]}) instead of digits.
+
+@item cexpression
+This is the C variable or expression being passed to the @code{asm} statement
+as input. The enclosing parentheses are a required part of the syntax.
+
+@end table
+
+When the compiler selects the registers to use to represent the input
+operands, it does not use any of the clobbered registers
+(@pxref{Clobbers and Scratch Registers}).
+
+If there are no output operands but there are input operands, place two
+consecutive colons where the output operands would go:
+
+@example
+__asm__ ("some instructions"
+ : /* No outputs. */
+ : "r" (Offset / 8));
+@end example
+
+@strong{Warning:} Do @emph{not} modify the contents of input-only operands
+(except for inputs tied to outputs). The compiler assumes that on exit from
+the @code{asm} statement these operands contain the same values as they
+had before executing the statement.
+It is @emph{not} possible to use clobbers
+to inform the compiler that the values in these inputs are changing. One
+common work-around is to tie the changing input variable to an output variable
+that never gets used. Note, however, that if the code that follows the
+@code{asm} statement makes no use of any of the output operands, the GCC
+optimizers may discard the @code{asm} statement as unneeded
+(see @ref{Volatile}).
+
+@code{asm} supports operand modifiers on operands (for example @samp{%k2}
+instead of simply @samp{%2}). Typically these qualifiers are hardware
+dependent. The list of supported modifiers for x86 is found at
+@ref{x86Operandmodifiers,x86 Operand modifiers}.
+
+In this example using the fictitious @code{combine} instruction, the
+constraint @code{"0"} for input operand 1 says that it must occupy the same
+location as output operand 0. Only input operands may use numbers in
+constraints, and they must each refer to an output operand. Only a number (or
+the symbolic assembler name) in the constraint can guarantee that one operand
+is in the same place as another. The mere fact that @code{foo} is the value of
+both operands is not enough to guarantee that they are in the same place in
+the generated assembler code.
+
+@example
+asm ("combine %2, %0"
+ : "=r" (foo)
+ : "0" (foo), "g" (bar));
+@end example
+
+Here is an example using symbolic names.
+
+@example
+asm ("cmoveq %1, %2, %[result]"
+ : [result] "=r"(result)
+ : "r" (test), "r" (new), "[result]" (old));
+@end example
+
+@anchor{Clobbers and Scratch Registers}
+@subsubsection Clobbers and Scratch Registers
+@cindex @code{asm} clobbers
+@cindex @code{asm} scratch registers
+
+While the compiler is aware of changes to entries listed in the output
+operands, the inline @code{asm} code may modify more than just the outputs. For
+example, calculations may require additional registers, or the processor may
+overwrite a register as a side effect of a particular assembler instruction.
+In order to inform the compiler of these changes, list them in the clobber
+list. Clobber list items are either register names or the special clobbers
+(listed below). Each clobber list item is a string constant
+enclosed in double quotes and separated by commas.
+
+Clobber descriptions may not in any way overlap with an input or output
+operand. For example, you may not have an operand describing a register class
+with one member when listing that register in the clobber list. Variables
+declared to live in specific registers (@pxref{Explicit Register
+Variables}) and used
+as @code{asm} input or output operands must have no part mentioned in the
+clobber description. In particular, there is no way to specify that input
+operands get modified without also specifying them as output operands.
+
+When the compiler selects which registers to use to represent input and output
+operands, it does not use any of the clobbered registers. As a result,
+clobbered registers are available for any use in the assembler code.
+
+Another restriction is that the clobber list should not contain the
+stack pointer register. This is because the compiler requires the
+value of the stack pointer to be the same after an @code{asm}
+statement as it was on entry to the statement. However, previous
+versions of GCC did not enforce this rule and allowed the stack
+pointer to appear in the list, with unclear semantics. This behavior
+is deprecated and listing the stack pointer may become an error in
+future versions of GCC@.
+
+Here is a realistic example for the VAX showing the use of clobbered
+registers:
+
+@example
+asm volatile ("movc3 %0, %1, %2"
+ : /* No outputs. */
+ : "g" (from), "g" (to), "g" (count)
+ : "r0", "r1", "r2", "r3", "r4", "r5", "memory");
+@end example
+
+Also, there are two special clobber arguments:
+
+@table @code
+@item "cc"
+The @code{"cc"} clobber indicates that the assembler code modifies the flags
+register. On some machines, GCC represents the condition codes as a specific
+hardware register; @code{"cc"} serves to name this register.
+On other machines, condition code handling is different,
+and specifying @code{"cc"} has no effect. But
+it is valid no matter what the target.
+
+@item "memory"
+The @code{"memory"} clobber tells the compiler that the assembly code
+performs memory
+reads or writes to items other than those listed in the input and output
+operands (for example, accessing the memory pointed to by one of the input
+parameters). To ensure memory contains correct values, GCC may need to flush
+specific register values to memory before executing the @code{asm}. Further,
+the compiler does not assume that any values read from memory before an
+@code{asm} remain unchanged after that @code{asm}; it reloads them as
+needed.
+Using the @code{"memory"} clobber effectively forms a read/write
+memory barrier for the compiler.
+
+Note that this clobber does not prevent the @emph{processor} from doing
+speculative reads past the @code{asm} statement. To prevent that, you need
+processor-specific fence instructions.
+
+@end table
+
+Flushing registers to memory has performance implications and may be
+an issue for time-sensitive code. You can provide better information
+to GCC to avoid this, as shown in the following examples. At a
+minimum, aliasing rules allow GCC to know what memory @emph{doesn't}
+need to be flushed.
+
+Here is a fictitious sum of squares instruction, that takes two
+pointers to floating point values in memory and produces a floating
+point register output.
+Notice that @code{x}, and @code{y} both appear twice in the @code{asm}
+parameters, once to specify memory accessed, and once to specify a
+base register used by the @code{asm}. You won't normally be wasting a
+register by doing this as GCC can use the same register for both
+purposes. However, it would be foolish to use both @code{%1} and
+@code{%3} for @code{x} in this @code{asm} and expect them to be the
+same. In fact, @code{%3} may well not be a register. It might be a
+symbolic memory reference to the object pointed to by @code{x}.
+
+@smallexample
+asm ("sumsq %0, %1, %2"
+ : "+f" (result)
+ : "r" (x), "r" (y), "m" (*x), "m" (*y));
+@end smallexample
+
+Here is a fictitious @code{*z++ = *x++ * *y++} instruction.
+Notice that the @code{x}, @code{y} and @code{z} pointer registers
+must be specified as input/output because the @code{asm} modifies
+them.
+
+@smallexample
+asm ("vecmul %0, %1, %2"
+ : "+r" (z), "+r" (x), "+r" (y), "=m" (*z)
+ : "m" (*x), "m" (*y));
+@end smallexample
+
+An x86 example where the string memory argument is of unknown length.
+
+@smallexample
+asm("repne scasb"
+ : "=c" (count), "+D" (p)
+ : "m" (*(const char (*)[]) p), "0" (-1), "a" (0));
+@end smallexample
+
+If you know the above will only be reading a ten byte array then you
+could instead use a memory input like:
+@code{"m" (*(const char (*)[10]) p)}.
+
+Here is an example of a PowerPC vector scale implemented in assembly,
+complete with vector and condition code clobbers, and some initialized
+offset registers that are unchanged by the @code{asm}.
+
+@smallexample
+void
+dscal (size_t n, double *x, double alpha)
+@{
+ asm ("/* lots of asm here */"
+ : "+m" (*(double (*)[n]) x), "+&r" (n), "+b" (x)
+ : "d" (alpha), "b" (32), "b" (48), "b" (64),
+ "b" (80), "b" (96), "b" (112)
+ : "cr0",
+ "vs32","vs33","vs34","vs35","vs36","vs37","vs38","vs39",
+ "vs40","vs41","vs42","vs43","vs44","vs45","vs46","vs47");
+@}
+@end smallexample
+
+Rather than allocating fixed registers via clobbers to provide scratch
+registers for an @code{asm} statement, an alternative is to define a
+variable and make it an early-clobber output as with @code{a2} and
+@code{a3} in the example below. This gives the compiler register
+allocator more freedom. You can also define a variable and make it an
+output tied to an input as with @code{a0} and @code{a1}, tied
+respectively to @code{ap} and @code{lda}. Of course, with tied
+outputs your @code{asm} can't use the input value after modifying the
+output register since they are one and the same register. What's
+more, if you omit the early-clobber on the output, it is possible that
+GCC might allocate the same register to another of the inputs if GCC
+could prove they had the same value on entry to the @code{asm}. This
+is why @code{a1} has an early-clobber. Its tied input, @code{lda}
+might conceivably be known to have the value 16 and without an
+early-clobber share the same register as @code{%11}. On the other
+hand, @code{ap} can't be the same as any of the other inputs, so an
+early-clobber on @code{a0} is not needed. It is also not desirable in
+this case. An early-clobber on @code{a0} would cause GCC to allocate
+a separate register for the @code{"m" (*(const double (*)[]) ap)}
+input. Note that tying an input to an output is the way to set up an
+initialized temporary register modified by an @code{asm} statement.
+An input not tied to an output is assumed by GCC to be unchanged, for
+example @code{"b" (16)} below sets up @code{%11} to 16, and GCC might
+use that register in following code if the value 16 happened to be
+needed. You can even use a normal @code{asm} output for a scratch if
+all inputs that might share the same register are consumed before the
+scratch is used. The VSX registers clobbered by the @code{asm}
+statement could have used this technique except for GCC's limit on the
+number of @code{asm} parameters.
+
+@smallexample
+static void
+dgemv_kernel_4x4 (long n, const double *ap, long lda,
+ const double *x, double *y, double alpha)
+@{
+ double *a0;
+ double *a1;
+ double *a2;
+ double *a3;
+
+ __asm__
+ (
+ /* lots of asm here */
+ "#n=%1 ap=%8=%12 lda=%13 x=%7=%10 y=%0=%2 alpha=%9 o16=%11\n"
+ "#a0=%3 a1=%4 a2=%5 a3=%6"
+ :
+ "+m" (*(double (*)[n]) y),
+ "+&r" (n), // 1
+ "+b" (y), // 2
+ "=b" (a0), // 3
+ "=&b" (a1), // 4
+ "=&b" (a2), // 5
+ "=&b" (a3) // 6
+ :
+ "m" (*(const double (*)[n]) x),
+ "m" (*(const double (*)[]) ap),
+ "d" (alpha), // 9
+ "r" (x), // 10
+ "b" (16), // 11
+ "3" (ap), // 12
+ "4" (lda) // 13
+ :
+ "cr0",
+ "vs32","vs33","vs34","vs35","vs36","vs37",
+ "vs40","vs41","vs42","vs43","vs44","vs45","vs46","vs47"
+ );
+@}
+@end smallexample
+
+@anchor{GotoLabels}
+@subsubsection Goto Labels
+@cindex @code{asm} goto labels
+
+@code{asm goto} allows assembly code to jump to one or more C labels. The
+@var{GotoLabels} section in an @code{asm goto} statement contains
+a comma-separated
+list of all C labels to which the assembler code may jump. GCC assumes that
+@code{asm} execution falls through to the next statement (if this is not the
+case, consider using the @code{__builtin_unreachable} intrinsic after the
+@code{asm} statement). Optimization of @code{asm goto} may be improved by
+using the @code{hot} and @code{cold} label attributes (@pxref{Label
+Attributes}).
+
+If the assembler code does modify anything, use the @code{"memory"} clobber
+to force the
+optimizers to flush all register values to memory and reload them if
+necessary after the @code{asm} statement.
+
+Also note that an @code{asm goto} statement is always implicitly
+considered volatile.
+
+Be careful when you set output operands inside @code{asm goto} only on
+some possible control flow paths. If you don't set up the output on
+given path and never use it on this path, it is okay. Otherwise, you
+should use @samp{+} constraint modifier meaning that the operand is
+input and output one. With this modifier you will have the correct
+values on all possible paths from the @code{asm goto}.
+
+To reference a label in the assembler template, prefix it with
+@samp{%l} (lowercase @samp{L}) followed by its (zero-based) position
+in @var{GotoLabels} plus the number of input and output operands.
+Output operand with constraint modifier @samp{+} is counted as two
+operands because it is considered as one output and one input operand.
+For example, if the @code{asm} has three inputs, one output operand
+with constraint modifier @samp{+} and one output operand with
+constraint modifier @samp{=} and references two labels, refer to the
+first label as @samp{%l6} and the second as @samp{%l7}).
+
+Alternately, you can reference labels using the actual C label name
+enclosed in brackets. For example, to reference a label named
+@code{carry}, you can use @samp{%l[carry]}. The label must still be
+listed in the @var{GotoLabels} section when using this approach. It
+is better to use the named references for labels as in this case you
+can avoid counting input and output operands and special treatment of
+output operands with constraint modifier @samp{+}.
+
+Here is an example of @code{asm goto} for i386:
+
+@example
+asm goto (
+ "btl %1, %0\n\t"
+ "jc %l2"
+ : /* No outputs. */
+ : "r" (p1), "r" (p2)
+ : "cc"
+ : carry);
+
+return 0;
+
+carry:
+return 1;
+@end example
+
+The following example shows an @code{asm goto} that uses a memory clobber.
+
+@example
+int frob(int x)
+@{
+ int y;
+ asm goto ("frob %%r5, %1; jc %l[error]; mov (%2), %%r5"
+ : /* No outputs. */
+ : "r"(x), "r"(&y)
+ : "r5", "memory"
+ : error);
+ return y;
+error:
+ return -1;
+@}
+@end example
+
+The following example shows an @code{asm goto} that uses an output.
+
+@example
+int foo(int count)
+@{
+ asm goto ("dec %0; jb %l[stop]"
+ : "+r" (count)
+ :
+ :
+ : stop);
+ return count;
+stop:
+ return 0;
+@}
+@end example
+
+The following artificial example shows an @code{asm goto} that sets
+up an output only on one path inside the @code{asm goto}. Usage of
+constraint modifier @code{=} instead of @code{+} would be wrong as
+@code{factor} is used on all paths from the @code{asm goto}.
+
+@example
+int foo(int inp)
+@{
+ int factor = 0;
+ asm goto ("cmp %1, 10; jb %l[lab]; mov 2, %0"
+ : "+r" (factor)
+ : "r" (inp)
+ :
+ : lab);
+lab:
+ return inp * factor; /* return 2 * inp or 0 if inp < 10 */
+@}
+@end example
+
+@anchor{x86Operandmodifiers}
+@subsubsection x86 Operand Modifiers
+
+References to input, output, and goto operands in the assembler template
+of extended @code{asm} statements can use
+modifiers to affect the way the operands are formatted in
+the code output to the assembler. For example, the
+following code uses the @samp{h} and @samp{b} modifiers for x86:
+
+@example
+uint16_t num;
+asm volatile ("xchg %h0, %b0" : "+a" (num) );
+@end example
+
+@noindent
+These modifiers generate this assembler code:
+
+@example
+xchg %ah, %al
+@end example
+
+The rest of this discussion uses the following code for illustrative purposes.
+
+@example
+int main()
+@{
+ int iInt = 1;
+
+top:
+
+ asm volatile goto ("some assembler instructions here"
+ : /* No outputs. */
+ : "q" (iInt), "X" (sizeof(unsigned char) + 1), "i" (42)
+ : /* No clobbers. */
+ : top);
+@}
+@end example
+
+With no modifiers, this is what the output from the operands would be
+for the @samp{att} and @samp{intel} dialects of assembler:
+
+@multitable {Operand} {$.L2} {OFFSET FLAT:.L2}
+@headitem Operand @tab @samp{att} @tab @samp{intel}
+@item @code{%0}
+@tab @code{%eax}
+@tab @code{eax}
+@item @code{%1}
+@tab @code{$2}
+@tab @code{2}
+@item @code{%3}
+@tab @code{$.L3}
+@tab @code{OFFSET FLAT:.L3}
+@item @code{%4}
+@tab @code{$8}
+@tab @code{8}
+@item @code{%5}
+@tab @code{%xmm0}
+@tab @code{xmm0}
+@item @code{%7}
+@tab @code{$0}
+@tab @code{0}
+@end multitable
+
+The table below shows the list of supported modifiers and their effects.
+
+@multitable {Modifier} {Print the opcode suffix for the size of th} {Operand} {@samp{att}} {@samp{intel}}
+@headitem Modifier @tab Description @tab Operand @tab @samp{att} @tab @samp{intel}
+@item @code{A}
+@tab Print an absolute memory reference.
+@tab @code{%A0}
+@tab @code{*%rax}
+@tab @code{rax}
+@item @code{b}
+@tab Print the QImode name of the register.
+@tab @code{%b0}
+@tab @code{%al}
+@tab @code{al}
+@item @code{B}
+@tab print the opcode suffix of b.
+@tab @code{%B0}
+@tab @code{b}
+@tab
+@item @code{c}
+@tab Require a constant operand and print the constant expression with no punctuation.
+@tab @code{%c1}
+@tab @code{2}
+@tab @code{2}
+@item @code{d}
+@tab print duplicated register operand for AVX instruction.
+@tab @code{%d5}
+@tab @code{%xmm0, %xmm0}
+@tab @code{xmm0, xmm0}
+@item @code{E}
+@tab Print the address in Double Integer (DImode) mode (8 bytes) when the target is 64-bit.
+Otherwise mode is unspecified (VOIDmode).
+@tab @code{%E1}
+@tab @code{%(rax)}
+@tab @code{[rax]}
+@item @code{g}
+@tab Print the V16SFmode name of the register.
+@tab @code{%g0}
+@tab @code{%zmm0}
+@tab @code{zmm0}
+@item @code{h}
+@tab Print the QImode name for a ``high'' register.
+@tab @code{%h0}
+@tab @code{%ah}
+@tab @code{ah}
+@item @code{H}
+@tab Add 8 bytes to an offsettable memory reference. Useful when accessing the
+high 8 bytes of SSE values. For a memref in (%rax), it generates
+@tab @code{%H0}
+@tab @code{8(%rax)}
+@tab @code{8[rax]}
+@item @code{k}
+@tab Print the SImode name of the register.
+@tab @code{%k0}
+@tab @code{%eax}
+@tab @code{eax}
+@item @code{l}
+@tab Print the label name with no punctuation.
+@tab @code{%l3}
+@tab @code{.L3}
+@tab @code{.L3}
+@item @code{L}
+@tab print the opcode suffix of l.
+@tab @code{%L0}
+@tab @code{l}
+@tab
+@item @code{N}
+@tab print maskz.
+@tab @code{%N7}
+@tab @code{@{z@}}
+@tab @code{@{z@}}
+@item @code{p}
+@tab Print raw symbol name (without syntax-specific prefixes).
+@tab @code{%p2}
+@tab @code{42}
+@tab @code{42}
+@item @code{P}
+@tab If used for a function, print the PLT suffix and generate PIC code.
+For example, emit @code{foo@@PLT} instead of 'foo' for the function
+foo(). If used for a constant, drop all syntax-specific prefixes and
+issue the bare constant. See @code{p} above.
+@item @code{q}
+@tab Print the DImode name of the register.
+@tab @code{%q0}
+@tab @code{%rax}
+@tab @code{rax}
+@item @code{Q}
+@tab print the opcode suffix of q.
+@tab @code{%Q0}
+@tab @code{q}
+@tab
+@item @code{R}
+@tab print embedded rounding and sae.
+@tab @code{%R4}
+@tab @code{@{rn-sae@}, }
+@tab @code{, @{rn-sae@}}
+@item @code{r}
+@tab print only sae.
+@tab @code{%r4}
+@tab @code{@{sae@}, }
+@tab @code{, @{sae@}}
+@item @code{s}
+@tab print a shift double count, followed by the assemblers argument
+delimiterprint the opcode suffix of s.
+@tab @code{%s1}
+@tab @code{$2, }
+@tab @code{2, }
+@item @code{S}
+@tab print the opcode suffix of s.
+@tab @code{%S0}
+@tab @code{s}
+@tab
+@item @code{t}
+@tab print the V8SFmode name of the register.
+@tab @code{%t5}
+@tab @code{%ymm0}
+@tab @code{ymm0}
+@item @code{T}
+@tab print the opcode suffix of t.
+@tab @code{%T0}
+@tab @code{t}
+@tab
+@item @code{V}
+@tab print naked full integer register name without %.
+@tab @code{%V0}
+@tab @code{eax}
+@tab @code{eax}
+@item @code{w}
+@tab Print the HImode name of the register.
+@tab @code{%w0}
+@tab @code{%ax}
+@tab @code{ax}
+@item @code{W}
+@tab print the opcode suffix of w.
+@tab @code{%W0}
+@tab @code{w}
+@tab
+@item @code{x}
+@tab print the V4SFmode name of the register.
+@tab @code{%x5}
+@tab @code{%xmm0}
+@tab @code{xmm0}
+@item @code{y}
+@tab print "st(0)" instead of "st" as a register.
+@tab @code{%y6}
+@tab @code{%st(0)}
+@tab @code{st(0)}
+@item @code{z}
+@tab Print the opcode suffix for the size of the current integer operand (one of @code{b}/@code{w}/@code{l}/@code{q}).
+@tab @code{%z0}
+@tab @code{l}
+@tab
+@item @code{Z}
+@tab Like @code{z}, with special suffixes for x87 instructions.
+@end multitable
+
+
+@anchor{x86floatingpointasmoperands}
+@subsubsection x86 Floating-Point @code{asm} Operands
+
+On x86 targets, there are several rules on the usage of stack-like registers
+in the operands of an @code{asm}. These rules apply only to the operands
+that are stack-like registers:
+
+@enumerate
+@item
+Given a set of input registers that die in an @code{asm}, it is
+necessary to know which are implicitly popped by the @code{asm}, and
+which must be explicitly popped by GCC@.
+
+An input register that is implicitly popped by the @code{asm} must be
+explicitly clobbered, unless it is constrained to match an
+output operand.
+
+@item
+For any input register that is implicitly popped by an @code{asm}, it is
+necessary to know how to adjust the stack to compensate for the pop.
+If any non-popped input is closer to the top of the reg-stack than
+the implicitly popped register, it would not be possible to know what the
+stack looked like---it's not clear how the rest of the stack ``slides
+up''.
+
+All implicitly popped input registers must be closer to the top of
+the reg-stack than any input that is not implicitly popped.
+
+It is possible that if an input dies in an @code{asm}, the compiler might
+use the input register for an output reload. Consider this example:
+
+@smallexample
+asm ("foo" : "=t" (a) : "f" (b));
+@end smallexample
+
+@noindent
+This code says that input @code{b} is not popped by the @code{asm}, and that
+the @code{asm} pushes a result onto the reg-stack, i.e., the stack is one
+deeper after the @code{asm} than it was before. But, it is possible that
+reload may think that it can use the same register for both the input and
+the output.
+
+To prevent this from happening,
+if any input operand uses the @samp{f} constraint, all output register
+constraints must use the @samp{&} early-clobber modifier.
+
+The example above is correctly written as:
+
+@smallexample
+asm ("foo" : "=&t" (a) : "f" (b));
+@end smallexample
+
+@item
+Some operands need to be in particular places on the stack. All
+output operands fall in this category---GCC has no other way to
+know which registers the outputs appear in unless you indicate
+this in the constraints.
+
+Output operands must specifically indicate which register an output
+appears in after an @code{asm}. @samp{=f} is not allowed: the operand
+constraints must select a class with a single register.
+
+@item
+Output operands may not be ``inserted'' between existing stack registers.
+Since no 387 opcode uses a read/write operand, all output operands
+are dead before the @code{asm}, and are pushed by the @code{asm}.
+It makes no sense to push anywhere but the top of the reg-stack.
+
+Output operands must start at the top of the reg-stack: output
+operands may not ``skip'' a register.
+
+@item
+Some @code{asm} statements may need extra stack space for internal
+calculations. This can be guaranteed by clobbering stack registers
+unrelated to the inputs and outputs.
+
+@end enumerate
+
+This @code{asm}
+takes one input, which is internally popped, and produces two outputs.
+
+@smallexample
+asm ("fsincos" : "=t" (cos), "=u" (sin) : "0" (inp));
+@end smallexample
+
+@noindent
+This @code{asm} takes two inputs, which are popped by the @code{fyl2xp1} opcode,
+and replaces them with one output. The @code{st(1)} clobber is necessary
+for the compiler to know that @code{fyl2xp1} pops both inputs.
+
+@smallexample
+asm ("fyl2xp1" : "=t" (result) : "0" (x), "u" (y) : "st(1)");
+@end smallexample
+
+@anchor{msp430Operandmodifiers}
+@subsubsection MSP430 Operand Modifiers
+
+The list below describes the supported modifiers and their effects for MSP430.
+
+@multitable @columnfractions .10 .90
+@headitem Modifier @tab Description
+@item @code{A} @tab Select low 16-bits of the constant/register/memory operand.
+@item @code{B} @tab Select high 16-bits of the constant/register/memory
+operand.
+@item @code{C} @tab Select bits 32-47 of the constant/register/memory operand.
+@item @code{D} @tab Select bits 48-63 of the constant/register/memory operand.
+@item @code{H} @tab Equivalent to @code{B} (for backwards compatibility).
+@item @code{I} @tab Print the inverse (logical @code{NOT}) of the constant
+value.
+@item @code{J} @tab Print an integer without a @code{#} prefix.
+@item @code{L} @tab Equivalent to @code{A} (for backwards compatibility).
+@item @code{O} @tab Offset of the current frame from the top of the stack.
+@item @code{Q} @tab Use the @code{A} instruction postfix.
+@item @code{R} @tab Inverse of condition code, for unsigned comparisons.
+@item @code{W} @tab Subtract 16 from the constant value.
+@item @code{X} @tab Use the @code{X} instruction postfix.
+@item @code{Y} @tab Subtract 4 from the constant value.
+@item @code{Z} @tab Subtract 1 from the constant value.
+@item @code{b} @tab Append @code{.B}, @code{.W} or @code{.A} to the
+instruction, depending on the mode.
+@item @code{d} @tab Offset 1 byte of a memory reference or constant value.
+@item @code{e} @tab Offset 3 bytes of a memory reference or constant value.
+@item @code{f} @tab Offset 5 bytes of a memory reference or constant value.
+@item @code{g} @tab Offset 7 bytes of a memory reference or constant value.
+@item @code{p} @tab Print the value of 2, raised to the power of the given
+constant. Used to select the specified bit position.
+@item @code{r} @tab Inverse of condition code, for signed comparisons.
+@item @code{x} @tab Equivialent to @code{X}, but only for pointers.
+@end multitable
+
+@lowersections
+@include md.texi
+@raisesections
+
+@node Asm Labels
+@subsection Controlling Names Used in Assembler Code
+@cindex assembler names for identifiers
+@cindex names used in assembler code
+@cindex identifiers, names in assembler code
+
+You can specify the name to be used in the assembler code for a C
+function or variable by writing the @code{asm} (or @code{__asm__})
+keyword after the declarator.
+It is up to you to make sure that the assembler names you choose do not
+conflict with any other assembler symbols, or reference registers.
+
+@subsubheading Assembler names for data
+
+This sample shows how to specify the assembler name for data:
+
+@smallexample
+int foo asm ("myfoo") = 2;
+@end smallexample
+
+@noindent
+This specifies that the name to be used for the variable @code{foo} in
+the assembler code should be @samp{myfoo} rather than the usual
+@samp{_foo}.
+
+On systems where an underscore is normally prepended to the name of a C
+variable, this feature allows you to define names for the
+linker that do not start with an underscore.
+
+GCC does not support using this feature with a non-static local variable
+since such variables do not have assembler names. If you are
+trying to put the variable in a particular register, see
+@ref{Explicit Register Variables}.
+
+@subsubheading Assembler names for functions
+
+To specify the assembler name for functions, write a declaration for the
+function before its definition and put @code{asm} there, like this:
+
+@smallexample
+int func (int x, int y) asm ("MYFUNC");
+
+int func (int x, int y)
+@{
+ /* @r{@dots{}} */
+@end smallexample
+
+@noindent
+This specifies that the name to be used for the function @code{func} in
+the assembler code should be @code{MYFUNC}.
+
+@node Explicit Register Variables
+@subsection Variables in Specified Registers
+@anchor{Explicit Reg Vars}
+@cindex explicit register variables
+@cindex variables in specified registers
+@cindex specified registers
+
+GNU C allows you to associate specific hardware registers with C
+variables. In almost all cases, allowing the compiler to assign
+registers produces the best code. However under certain unusual
+circumstances, more precise control over the variable storage is
+required.
+
+Both global and local variables can be associated with a register. The
+consequences of performing this association are very different between
+the two, as explained in the sections below.
+
+@menu
+* Global Register Variables:: Variables declared at global scope.
+* Local Register Variables:: Variables declared within a function.
+@end menu
+
+@node Global Register Variables
+@subsubsection Defining Global Register Variables
+@anchor{Global Reg Vars}
+@cindex global register variables
+@cindex registers, global variables in
+@cindex registers, global allocation
+
+You can define a global register variable and associate it with a specified
+register like this:
+
+@smallexample
+register int *foo asm ("r12");
+@end smallexample
+
+@noindent
+Here @code{r12} is the name of the register that should be used. Note that
+this is the same syntax used for defining local register variables, but for
+a global variable the declaration appears outside a function. The
+@code{register} keyword is required, and cannot be combined with
+@code{static}. The register name must be a valid register name for the
+target platform.
+
+Do not use type qualifiers such as @code{const} and @code{volatile}, as
+the outcome may be contrary to expectations. In particular, using the
+@code{volatile} qualifier does not fully prevent the compiler from
+optimizing accesses to the register.
+
+Registers are a scarce resource on most systems and allowing the
+compiler to manage their usage usually results in the best code. However,
+under special circumstances it can make sense to reserve some globally.
+For example this may be useful in programs such as programming language
+interpreters that have a couple of global variables that are accessed
+very often.
+
+After defining a global register variable, for the current compilation
+unit:
+
+@itemize @bullet
+@item If the register is a call-saved register, call ABI is affected:
+the register will not be restored in function epilogue sequences after
+the variable has been assigned. Therefore, functions cannot safely
+return to callers that assume standard ABI.
+@item Conversely, if the register is a call-clobbered register, making
+calls to functions that use standard ABI may lose contents of the variable.
+Such calls may be created by the compiler even if none are evident in
+the original program, for example when libgcc functions are used to
+make up for unavailable instructions.
+@item Accesses to the variable may be optimized as usual and the register
+remains available for allocation and use in any computations, provided that
+observable values of the variable are not affected.
+@item If the variable is referenced in inline assembly, the type of access
+must be provided to the compiler via constraints (@pxref{Constraints}).
+Accesses from basic asms are not supported.
+@end itemize
+
+Note that these points @emph{only} apply to code that is compiled with the
+definition. The behavior of code that is merely linked in (for example
+code from libraries) is not affected.
+
+If you want to recompile source files that do not actually use your global
+register variable so they do not use the specified register for any other
+purpose, you need not actually add the global register declaration to
+their source code. It suffices to specify the compiler option
+@option{-ffixed-@var{reg}} (@pxref{Code Gen Options}) to reserve the
+register.
+
+@subsubheading Declaring the variable
+
+Global register variables cannot have initial values, because an
+executable file has no means to supply initial contents for a register.
+
+When selecting a register, choose one that is normally saved and
+restored by function calls on your machine. This ensures that code
+which is unaware of this reservation (such as library routines) will
+restore it before returning.
+
+On machines with register windows, be sure to choose a global
+register that is not affected magically by the function call mechanism.
+
+@subsubheading Using the variable
+
+@cindex @code{qsort}, and global register variables
+When calling routines that are not aware of the reservation, be
+cautious if those routines call back into code which uses them. As an
+example, if you call the system library version of @code{qsort}, it may
+clobber your registers during execution, but (if you have selected
+appropriate registers) it will restore them before returning. However
+it will @emph{not} restore them before calling @code{qsort}'s comparison
+function. As a result, global values will not reliably be available to
+the comparison function unless the @code{qsort} function itself is rebuilt.
+
+Similarly, it is not safe to access the global register variables from signal
+handlers or from more than one thread of control. Unless you recompile
+them specially for the task at hand, the system library routines may
+temporarily use the register for other things. Furthermore, since the register
+is not reserved exclusively for the variable, accessing it from handlers of
+asynchronous signals may observe unrelated temporary values residing in the
+register.
+
+@cindex register variable after @code{longjmp}
+@cindex global register after @code{longjmp}
+@cindex value after @code{longjmp}
+@findex longjmp
+@findex setjmp
+On most machines, @code{longjmp} restores to each global register
+variable the value it had at the time of the @code{setjmp}. On some
+machines, however, @code{longjmp} does not change the value of global
+register variables. To be portable, the function that called @code{setjmp}
+should make other arrangements to save the values of the global register
+variables, and to restore them in a @code{longjmp}. This way, the same
+thing happens regardless of what @code{longjmp} does.
+
+@node Local Register Variables
+@subsubsection Specifying Registers for Local Variables
+@anchor{Local Reg Vars}
+@cindex local variables, specifying registers
+@cindex specifying registers for local variables
+@cindex registers for local variables
+
+You can define a local register variable and associate it with a specified
+register like this:
+
+@smallexample
+register int *foo asm ("r12");
+@end smallexample
+
+@noindent
+Here @code{r12} is the name of the register that should be used. Note
+that this is the same syntax used for defining global register variables,
+but for a local variable the declaration appears within a function. The
+@code{register} keyword is required, and cannot be combined with
+@code{static}. The register name must be a valid register name for the
+target platform.
+
+Do not use type qualifiers such as @code{const} and @code{volatile}, as
+the outcome may be contrary to expectations. In particular, when the
+@code{const} qualifier is used, the compiler may substitute the
+variable with its initializer in @code{asm} statements, which may cause
+the corresponding operand to appear in a different register.
+
+As with global register variables, it is recommended that you choose
+a register that is normally saved and restored by function calls on your
+machine, so that calls to library routines will not clobber it.
+
+The only supported use for this feature is to specify registers
+for input and output operands when calling Extended @code{asm}
+(@pxref{Extended Asm}). This may be necessary if the constraints for a
+particular machine don't provide sufficient control to select the desired
+register. To force an operand into a register, create a local variable
+and specify the register name after the variable's declaration. Then use
+the local variable for the @code{asm} operand and specify any constraint
+letter that matches the register:
+
+@smallexample
+register int *p1 asm ("r0") = @dots{};
+register int *p2 asm ("r1") = @dots{};
+register int *result asm ("r0");
+asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2));
+@end smallexample
+
+@emph{Warning:} In the above example, be aware that a register (for example
+@code{r0}) can be call-clobbered by subsequent code, including function
+calls and library calls for arithmetic operators on other variables (for
+example the initialization of @code{p2}). In this case, use temporary
+variables for expressions between the register assignments:
+
+@smallexample
+int t1 = @dots{};
+register int *p1 asm ("r0") = @dots{};
+register int *p2 asm ("r1") = t1;
+register int *result asm ("r0");
+asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2));
+@end smallexample
+
+Defining a register variable does not reserve the register. Other than
+when invoking the Extended @code{asm}, the contents of the specified
+register are not guaranteed. For this reason, the following uses
+are explicitly @emph{not} supported. If they appear to work, it is only
+happenstance, and may stop working as intended due to (seemingly)
+unrelated changes in surrounding code, or even minor changes in the
+optimization of a future version of gcc:
+
+@itemize @bullet
+@item Passing parameters to or from Basic @code{asm}
+@item Passing parameters to or from Extended @code{asm} without using input
+or output operands.
+@item Passing parameters to or from routines written in assembler (or
+other languages) using non-standard calling conventions.
+@end itemize
+
+Some developers use Local Register Variables in an attempt to improve
+gcc's allocation of registers, especially in large functions. In this
+case the register name is essentially a hint to the register allocator.
+While in some instances this can generate better code, improvements are
+subject to the whims of the allocator/optimizers. Since there are no
+guarantees that your improvements won't be lost, this usage of Local
+Register Variables is discouraged.
+
+On the MIPS platform, there is related use for local register variables
+with slightly different characteristics (@pxref{MIPS Coprocessors,,
+Defining coprocessor specifics for MIPS targets, gccint,
+GNU Compiler Collection (GCC) Internals}).
+
+@node Size of an asm
+@subsection Size of an @code{asm}
+
+Some targets require that GCC track the size of each instruction used
+in order to generate correct code. Because the final length of the
+code produced by an @code{asm} statement is only known by the
+assembler, GCC must make an estimate as to how big it will be. It
+does this by counting the number of instructions in the pattern of the
+@code{asm} and multiplying that by the length of the longest
+instruction supported by that processor. (When working out the number
+of instructions, it assumes that any occurrence of a newline or of
+whatever statement separator character is supported by the assembler ---
+typically @samp{;} --- indicates the end of an instruction.)
+
+Normally, GCC's estimate is adequate to ensure that correct
+code is generated, but it is possible to confuse the compiler if you use
+pseudo instructions or assembler macros that expand into multiple real
+instructions, or if you use assembler directives that expand to more
+space in the object file than is needed for a single instruction.
+If this happens then the assembler may produce a diagnostic saying that
+a label is unreachable.
+
+@cindex @code{asm inline}
+This size is also used for inlining decisions. If you use @code{asm inline}
+instead of just @code{asm}, then for inlining purposes the size of the asm
+is taken as the minimum size, ignoring how many instructions GCC thinks it is.
+
+@node Alternate Keywords
+@section Alternate Keywords
+@cindex alternate keywords
+@cindex keywords, alternate
+
+@option{-ansi} and the various @option{-std} options disable certain
+keywords. This causes trouble when you want to use GNU C extensions, or
+a general-purpose header file that should be usable by all programs,
+including ISO C programs. The keywords @code{asm}, @code{typeof} and
+@code{inline} are not available in programs compiled with
+@option{-ansi} or @option{-std} (although @code{inline} can be used in a
+program compiled with @option{-std=c99} or a later standard). The
+ISO C99 keyword
+@code{restrict} is only available when @option{-std=gnu99} (which will
+eventually be the default) or @option{-std=c99} (or the equivalent
+@option{-std=iso9899:1999}), or an option for a later standard
+version, is used.
+
+The way to solve these problems is to put @samp{__} at the beginning and
+end of each problematical keyword. For example, use @code{__asm__}
+instead of @code{asm}, and @code{__inline__} instead of @code{inline}.
+
+Other C compilers won't accept these alternative keywords; if you want to
+compile with another compiler, you can define the alternate keywords as
+macros to replace them with the customary keywords. It looks like this:
+
+@smallexample
+#ifndef __GNUC__
+#define __asm__ asm
+#endif
+@end smallexample
+
+@findex __extension__
+@opindex pedantic
+@option{-pedantic} and other options cause warnings for many GNU C extensions.
+You can
+prevent such warnings within one expression by writing
+@code{__extension__} before the expression. @code{__extension__} has no
+effect aside from this.
+
+@node Incomplete Enums
+@section Incomplete @code{enum} Types
+
+You can define an @code{enum} tag without specifying its possible values.
+This results in an incomplete type, much like what you get if you write
+@code{struct foo} without describing the elements. A later declaration
+that does specify the possible values completes the type.
+
+You cannot allocate variables or storage using the type while it is
+incomplete. However, you can work with pointers to that type.
+
+This extension may not be very useful, but it makes the handling of
+@code{enum} more consistent with the way @code{struct} and @code{union}
+are handled.
+
+This extension is not supported by GNU C++.
+
+@node Function Names
+@section Function Names as Strings
+@cindex @code{__func__} identifier
+@cindex @code{__FUNCTION__} identifier
+@cindex @code{__PRETTY_FUNCTION__} identifier
+
+GCC provides three magic constants that hold the name of the current
+function as a string. In C++11 and later modes, all three are treated
+as constant expressions and can be used in @code{constexpr} constexts.
+The first of these constants is @code{__func__}, which is part of
+the C99 standard:
+
+The identifier @code{__func__} is implicitly declared by the translator
+as if, immediately following the opening brace of each function
+definition, the declaration
+
+@smallexample
+static const char __func__[] = "function-name";
+@end smallexample
+
+@noindent
+appeared, where function-name is the name of the lexically-enclosing
+function. This name is the unadorned name of the function. As an
+extension, at file (or, in C++, namespace scope), @code{__func__}
+evaluates to the empty string.
+
+@code{__FUNCTION__} is another name for @code{__func__}, provided for
+backward compatibility with old versions of GCC.
+
+In C, @code{__PRETTY_FUNCTION__} is yet another name for
+@code{__func__}, except that at file scope (or, in C++, namespace scope),
+it evaluates to the string @code{"top level"}. In addition, in C++,
+@code{__PRETTY_FUNCTION__} contains the signature of the function as
+well as its bare name. For example, this program:
+
+@smallexample
+extern "C" int printf (const char *, ...);
+
+class a @{
+ public:
+ void sub (int i)
+ @{
+ printf ("__FUNCTION__ = %s\n", __FUNCTION__);
+ printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__);
+ @}
+@};
+
+int
+main (void)
+@{
+ a ax;
+ ax.sub (0);
+ return 0;
+@}
+@end smallexample
+
+@noindent
+gives this output:
+
+@smallexample
+__FUNCTION__ = sub
+__PRETTY_FUNCTION__ = void a::sub(int)
+@end smallexample
+
+These identifiers are variables, not preprocessor macros, and may not
+be used to initialize @code{char} arrays or be concatenated with string
+literals.
+
+@node Return Address
+@section Getting the Return or Frame Address of a Function
+
+These functions may be used to get information about the callers of a
+function.
+
+@deftypefn {Built-in Function} {void *} __builtin_return_address (unsigned int @var{level})
+This function returns the return address of the current function, or of
+one of its callers. The @var{level} argument is number of frames to
+scan up the call stack. A value of @code{0} yields the return address
+of the current function, a value of @code{1} yields the return address
+of the caller of the current function, and so forth. When inlining
+the expected behavior is that the function returns the address of
+the function that is returned to. To work around this behavior use
+the @code{noinline} function attribute.
+
+The @var{level} argument must be a constant integer.
+
+On some machines it may be impossible to determine the return address of
+any function other than the current one; in such cases, or when the top
+of the stack has been reached, this function returns an unspecified
+value. In addition, @code{__builtin_frame_address} may be used
+to determine if the top of the stack has been reached.
+
+Additional post-processing of the returned value may be needed, see
+@code{__builtin_extract_return_addr}.
+
+The stored representation of the return address in memory may be different
+from the address returned by @code{__builtin_return_address}. For example,
+on AArch64 the stored address may be mangled with return address signing
+whereas the address returned by @code{__builtin_return_address} is not.
+
+Calling this function with a nonzero argument can have unpredictable
+effects, including crashing the calling program. As a result, calls
+that are considered unsafe are diagnosed when the @option{-Wframe-address}
+option is in effect. Such calls should only be made in debugging
+situations.
+
+On targets where code addresses are representable as @code{void *},
+@smallexample
+void *addr = __builtin_extract_return_addr (__builtin_return_address (0));
+@end smallexample
+gives the code address where the current function would return. For example,
+such an address may be used with @code{dladdr} or other interfaces that work
+with code addresses.
+@end deftypefn
+
+@deftypefn {Built-in Function} {void *} __builtin_extract_return_addr (void *@var{addr})
+The address as returned by @code{__builtin_return_address} may have to be fed
+through this function to get the actual encoded address. For example, on the
+31-bit S/390 platform the highest bit has to be masked out, or on SPARC
+platforms an offset has to be added for the true next instruction to be
+executed.
+
+If no fixup is needed, this function simply passes through @var{addr}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {void *} __builtin_frob_return_addr (void *@var{addr})
+This function does the reverse of @code{__builtin_extract_return_addr}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {void *} __builtin_frame_address (unsigned int @var{level})
+This function is similar to @code{__builtin_return_address}, but it
+returns the address of the function frame rather than the return address
+of the function. Calling @code{__builtin_frame_address} with a value of
+@code{0} yields the frame address of the current function, a value of
+@code{1} yields the frame address of the caller of the current function,
+and so forth.
+
+The frame is the area on the stack that holds local variables and saved
+registers. The frame address is normally the address of the first word
+pushed on to the stack by the function. However, the exact definition
+depends upon the processor and the calling convention. If the processor
+has a dedicated frame pointer register, and the function has a frame,
+then @code{__builtin_frame_address} returns the value of the frame
+pointer register.
+
+On some machines it may be impossible to determine the frame address of
+any function other than the current one; in such cases, or when the top
+of the stack has been reached, this function returns @code{0} if
+the first frame pointer is properly initialized by the startup code.
+
+Calling this function with a nonzero argument can have unpredictable
+effects, including crashing the calling program. As a result, calls
+that are considered unsafe are diagnosed when the @option{-Wframe-address}
+option is in effect. Such calls should only be made in debugging
+situations.
+@end deftypefn
+
+@node Vector Extensions
+@section Using Vector Instructions through Built-in Functions
+
+On some targets, the instruction set contains SIMD vector instructions which
+operate on multiple values contained in one large register at the same time.
+For example, on the x86 the MMX, 3DNow!@: and SSE extensions can be used
+this way.
+
+The first step in using these extensions is to provide the necessary data
+types. This should be done using an appropriate @code{typedef}:
+
+@smallexample
+typedef int v4si __attribute__ ((vector_size (16)));
+@end smallexample
+
+@noindent
+The @code{int} type specifies the @dfn{base type}, while the attribute specifies
+the vector size for the variable, measured in bytes. For example, the
+declaration above causes the compiler to set the mode for the @code{v4si}
+type to be 16 bytes wide and divided into @code{int} sized units. For
+a 32-bit @code{int} this means a vector of 4 units of 4 bytes, and the
+corresponding mode of @code{foo} is @acronym{V4SI}.
+
+The @code{vector_size} attribute is only applicable to integral and
+floating scalars, although arrays, pointers, and function return values
+are allowed in conjunction with this construct. Only sizes that are
+positive power-of-two multiples of the base type size are currently allowed.
+
+All the basic integer types can be used as base types, both as signed
+and as unsigned: @code{char}, @code{short}, @code{int}, @code{long},
+@code{long long}. In addition, @code{float} and @code{double} can be
+used to build floating-point vector types.
+
+Specifying a combination that is not valid for the current architecture
+causes GCC to synthesize the instructions using a narrower mode.
+For example, if you specify a variable of type @code{V4SI} and your
+architecture does not allow for this specific SIMD type, GCC
+produces code that uses 4 @code{SIs}.
+
+The types defined in this manner can be used with a subset of normal C
+operations. Currently, GCC allows using the following operators
+on these types: @code{+, -, *, /, unary minus, ^, |, &, ~, %}@.
+
+The operations behave like C++ @code{valarrays}. Addition is defined as
+the addition of the corresponding elements of the operands. For
+example, in the code below, each of the 4 elements in @var{a} is
+added to the corresponding 4 elements in @var{b} and the resulting
+vector is stored in @var{c}.
+
+@smallexample
+typedef int v4si __attribute__ ((vector_size (16)));
+
+v4si a, b, c;
+
+c = a + b;
+@end smallexample
+
+Subtraction, multiplication, division, and the logical operations
+operate in a similar manner. Likewise, the result of using the unary
+minus or complement operators on a vector type is a vector whose
+elements are the negative or complemented values of the corresponding
+elements in the operand.
+
+It is possible to use shifting operators @code{<<}, @code{>>} on
+integer-type vectors. The operation is defined as following: @code{@{a0,
+a1, @dots{}, an@} >> @{b0, b1, @dots{}, bn@} == @{a0 >> b0, a1 >> b1,
+@dots{}, an >> bn@}}@. Vector operands must have the same number of
+elements.
+
+For convenience, it is allowed to use a binary vector operation
+where one operand is a scalar. In that case the compiler transforms
+the scalar operand into a vector where each element is the scalar from
+the operation. The transformation happens only if the scalar could be
+safely converted to the vector-element type.
+Consider the following code.
+
+@smallexample
+typedef int v4si __attribute__ ((vector_size (16)));
+
+v4si a, b, c;
+long l;
+
+a = b + 1; /* a = b + @{1,1,1,1@}; */
+a = 2 * b; /* a = @{2,2,2,2@} * b; */
+
+a = l + a; /* Error, cannot convert long to int. */
+@end smallexample
+
+Vectors can be subscripted as if the vector were an array with
+the same number of elements and base type. Out of bound accesses
+invoke undefined behavior at run time. Warnings for out of bound
+accesses for vector subscription can be enabled with
+@option{-Warray-bounds}.
+
+Vector comparison is supported with standard comparison
+operators: @code{==, !=, <, <=, >, >=}. Comparison operands can be
+vector expressions of integer-type or real-type. Comparison between
+integer-type vectors and real-type vectors are not supported. The
+result of the comparison is a vector of the same width and number of
+elements as the comparison operands with a signed integral element
+type.
+
+Vectors are compared element-wise producing 0 when comparison is false
+and -1 (constant of the appropriate type where all bits are set)
+otherwise. Consider the following example.
+
+@smallexample
+typedef int v4si __attribute__ ((vector_size (16)));
+
+v4si a = @{1,2,3,4@};
+v4si b = @{3,2,1,4@};
+v4si c;
+
+c = a > b; /* The result would be @{0, 0,-1, 0@} */
+c = a == b; /* The result would be @{0,-1, 0,-1@} */
+@end smallexample
+
+In C++, the ternary operator @code{?:} is available. @code{a?b:c}, where
+@code{b} and @code{c} are vectors of the same type and @code{a} is an
+integer vector with the same number of elements of the same size as @code{b}
+and @code{c}, computes all three arguments and creates a vector
+@code{@{a[0]?b[0]:c[0], a[1]?b[1]:c[1], @dots{}@}}. Note that unlike in
+OpenCL, @code{a} is thus interpreted as @code{a != 0} and not @code{a < 0}.
+As in the case of binary operations, this syntax is also accepted when
+one of @code{b} or @code{c} is a scalar that is then transformed into a
+vector. If both @code{b} and @code{c} are scalars and the type of
+@code{true?b:c} has the same size as the element type of @code{a}, then
+@code{b} and @code{c} are converted to a vector type whose elements have
+this type and with the same number of elements as @code{a}.
+
+In C++, the logic operators @code{!, &&, ||} are available for vectors.
+@code{!v} is equivalent to @code{v == 0}, @code{a && b} is equivalent to
+@code{a!=0 & b!=0} and @code{a || b} is equivalent to @code{a!=0 | b!=0}.
+For mixed operations between a scalar @code{s} and a vector @code{v},
+@code{s && v} is equivalent to @code{s?v!=0:0} (the evaluation is
+short-circuit) and @code{v && s} is equivalent to @code{v!=0 & (s?-1:0)}.
+
+@findex __builtin_shuffle
+Vector shuffling is available using functions
+@code{__builtin_shuffle (vec, mask)} and
+@code{__builtin_shuffle (vec0, vec1, mask)}.
+Both functions construct a permutation of elements from one or two
+vectors and return a vector of the same type as the input vector(s).
+The @var{mask} is an integral vector with the same width (@var{W})
+and element count (@var{N}) as the output vector.
+
+The elements of the input vectors are numbered in memory ordering of
+@var{vec0} beginning at 0 and @var{vec1} beginning at @var{N}. The
+elements of @var{mask} are considered modulo @var{N} in the single-operand
+case and modulo @math{2*@var{N}} in the two-operand case.
+
+Consider the following example,
+
+@smallexample
+typedef int v4si __attribute__ ((vector_size (16)));
+
+v4si a = @{1,2,3,4@};
+v4si b = @{5,6,7,8@};
+v4si mask1 = @{0,1,1,3@};
+v4si mask2 = @{0,4,2,5@};
+v4si res;
+
+res = __builtin_shuffle (a, mask1); /* res is @{1,2,2,4@} */
+res = __builtin_shuffle (a, b, mask2); /* res is @{1,5,3,6@} */
+@end smallexample
+
+Note that @code{__builtin_shuffle} is intentionally semantically
+compatible with the OpenCL @code{shuffle} and @code{shuffle2} functions.
+
+You can declare variables and use them in function calls and returns, as
+well as in assignments and some casts. You can specify a vector type as
+a return type for a function. Vector types can also be used as function
+arguments. It is possible to cast from one vector type to another,
+provided they are of the same size (in fact, you can also cast vectors
+to and from other datatypes of the same size).
+
+You cannot operate between vectors of different lengths or different
+signedness without a cast.
+
+@findex __builtin_shufflevector
+Vector shuffling is available using the
+@code{__builtin_shufflevector (vec1, vec2, index...)}
+function. @var{vec1} and @var{vec2} must be expressions with
+vector type with a compatible element type. The result of
+@code{__builtin_shufflevector} is a vector with the same element type
+as @var{vec1} and @var{vec2} but that has an element count equal to
+the number of indices specified.
+
+The @var{index} arguments are a list of integers that specify the
+elements indices of the first two vectors that should be extracted and
+returned in a new vector. These element indices are numbered sequentially
+starting with the first vector, continuing into the second vector.
+An index of -1 can be used to indicate that the corresponding element in
+the returned vector is a don't care and can be freely chosen to optimized
+the generated code sequence performing the shuffle operation.
+
+Consider the following example,
+@smallexample
+typedef int v4si __attribute__ ((vector_size (16)));
+typedef int v8si __attribute__ ((vector_size (32)));
+
+v8si a = @{1,-2,3,-4,5,-6,7,-8@};
+v4si b = __builtin_shufflevector (a, a, 0, 2, 4, 6); /* b is @{1,3,5,7@} */
+v4si c = @{-2,-4,-6,-8@};
+v8si d = __builtin_shufflevector (c, b, 4, 0, 5, 1, 6, 2, 7, 3); /* d is a */
+@end smallexample
+
+@findex __builtin_convertvector
+Vector conversion is available using the
+@code{__builtin_convertvector (vec, vectype)}
+function. @var{vec} must be an expression with integral or floating
+vector type and @var{vectype} an integral or floating vector type with the
+same number of elements. The result has @var{vectype} type and value of
+a C cast of every element of @var{vec} to the element type of @var{vectype}.
+
+Consider the following example,
+@smallexample
+typedef int v4si __attribute__ ((vector_size (16)));
+typedef float v4sf __attribute__ ((vector_size (16)));
+typedef double v4df __attribute__ ((vector_size (32)));
+typedef unsigned long long v4di __attribute__ ((vector_size (32)));
+
+v4si a = @{1,-2,3,-4@};
+v4sf b = @{1.5f,-2.5f,3.f,7.f@};
+v4di c = @{1ULL,5ULL,0ULL,10ULL@};
+v4sf d = __builtin_convertvector (a, v4sf); /* d is @{1.f,-2.f,3.f,-4.f@} */
+/* Equivalent of:
+ v4sf d = @{ (float)a[0], (float)a[1], (float)a[2], (float)a[3] @}; */
+v4df e = __builtin_convertvector (a, v4df); /* e is @{1.,-2.,3.,-4.@} */
+v4df f = __builtin_convertvector (b, v4df); /* f is @{1.5,-2.5,3.,7.@} */
+v4si g = __builtin_convertvector (f, v4si); /* g is @{1,-2,3,7@} */
+v4si h = __builtin_convertvector (c, v4si); /* h is @{1,5,0,10@} */
+@end smallexample
+
+@cindex vector types, using with x86 intrinsics
+Sometimes it is desirable to write code using a mix of generic vector
+operations (for clarity) and machine-specific vector intrinsics (to
+access vector instructions that are not exposed via generic built-ins).
+On x86, intrinsic functions for integer vectors typically use the same
+vector type @code{__m128i} irrespective of how they interpret the vector,
+making it necessary to cast their arguments and return values from/to
+other vector types. In C, you can make use of a @code{union} type:
+@c In C++ such type punning via a union is not allowed by the language
+@smallexample
+#include <immintrin.h>
+
+typedef unsigned char u8x16 __attribute__ ((vector_size (16)));
+typedef unsigned int u32x4 __attribute__ ((vector_size (16)));
+
+typedef union @{
+ __m128i mm;
+ u8x16 u8;
+ u32x4 u32;
+@} v128;
+@end smallexample
+
+@noindent
+for variables that can be used with both built-in operators and x86
+intrinsics:
+
+@smallexample
+v128 x, y = @{ 0 @};
+memcpy (&x, ptr, sizeof x);
+y.u8 += 0x80;
+x.mm = _mm_adds_epu8 (x.mm, y.mm);
+x.u32 &= 0xffffff;
+
+/* Instead of a variable, a compound literal may be used to pass the
+ return value of an intrinsic call to a function expecting the union: */
+v128 foo (v128);
+x = foo ((v128) @{_mm_adds_epu8 (x.mm, y.mm)@});
+@c This could be done implicitly with __attribute__((transparent_union)),
+@c but GCC does not accept it for unions of vector types (PR 88955).
+@end smallexample
+
+@node Offsetof
+@section Support for @code{offsetof}
+@findex __builtin_offsetof
+
+GCC implements for both C and C++ a syntactic extension to implement
+the @code{offsetof} macro.
+
+@smallexample
+primary:
+ "__builtin_offsetof" "(" @code{typename} "," offsetof_member_designator ")"
+
+offsetof_member_designator:
+ @code{identifier}
+ | offsetof_member_designator "." @code{identifier}
+ | offsetof_member_designator "[" @code{expr} "]"
+@end smallexample
+
+This extension is sufficient such that
+
+@smallexample
+#define offsetof(@var{type}, @var{member}) __builtin_offsetof (@var{type}, @var{member})
+@end smallexample
+
+@noindent
+is a suitable definition of the @code{offsetof} macro. In C++, @var{type}
+may be dependent. In either case, @var{member} may consist of a single
+identifier, or a sequence of member accesses and array references.
+
+@node __sync Builtins
+@section Legacy @code{__sync} Built-in Functions for Atomic Memory Access
+
+The following built-in functions
+are intended to be compatible with those described
+in the @cite{Intel Itanium Processor-specific Application Binary Interface},
+section 7.4. As such, they depart from normal GCC practice by not using
+the @samp{__builtin_} prefix and also by being overloaded so that they
+work on multiple types.
+
+The definition given in the Intel documentation allows only for the use of
+the types @code{int}, @code{long}, @code{long long} or their unsigned
+counterparts. GCC allows any scalar type that is 1, 2, 4 or 8 bytes in
+size other than the C type @code{_Bool} or the C++ type @code{bool}.
+Operations on pointer arguments are performed as if the operands were
+of the @code{uintptr_t} type. That is, they are not scaled by the size
+of the type to which the pointer points.
+
+These functions are implemented in terms of the @samp{__atomic}
+builtins (@pxref{__atomic Builtins}). They should not be used for new
+code which should use the @samp{__atomic} builtins instead.
+
+Not all operations are supported by all target processors. If a particular
+operation cannot be implemented on the target processor, a warning is
+generated and a call to an external function is generated. The external
+function carries the same name as the built-in version,
+with an additional suffix
+@samp{_@var{n}} where @var{n} is the size of the data type.
+
+@c ??? Should we have a mechanism to suppress this warning? This is almost
+@c useful for implementing the operation under the control of an external
+@c mutex.
+
+In most cases, these built-in functions are considered a @dfn{full barrier}.
+That is,
+no memory operand is moved across the operation, either forward or
+backward. Further, instructions are issued as necessary to prevent the
+processor from speculating loads across the operation and from queuing stores
+after the operation.
+
+All of the routines are described in the Intel documentation to take
+``an optional list of variables protected by the memory barrier''. It's
+not clear what is meant by that; it could mean that @emph{only} the
+listed variables are protected, or it could mean a list of additional
+variables to be protected. The list is ignored by GCC which treats it as
+empty. GCC interprets an empty list as meaning that all globally
+accessible variables should be protected.
+
+@table @code
+@item @var{type} __sync_fetch_and_add (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_fetch_and_sub (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_fetch_and_or (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_fetch_and_and (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_fetch_and_xor (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_fetch_and_nand (@var{type} *ptr, @var{type} value, ...)
+@findex __sync_fetch_and_add
+@findex __sync_fetch_and_sub
+@findex __sync_fetch_and_or
+@findex __sync_fetch_and_and
+@findex __sync_fetch_and_xor
+@findex __sync_fetch_and_nand
+These built-in functions perform the operation suggested by the name, and
+returns the value that had previously been in memory. That is, operations
+on integer operands have the following semantics. Operations on pointer
+arguments are performed as if the operands were of the @code{uintptr_t}
+type. That is, they are not scaled by the size of the type to which
+the pointer points.
+
+@smallexample
+@{ tmp = *ptr; *ptr @var{op}= value; return tmp; @}
+@{ tmp = *ptr; *ptr = ~(tmp & value); return tmp; @} // nand
+@end smallexample
+
+The object pointed to by the first argument must be of integer or pointer
+type. It must not be a boolean type.
+
+@emph{Note:} GCC 4.4 and later implement @code{__sync_fetch_and_nand}
+as @code{*ptr = ~(tmp & value)} instead of @code{*ptr = ~tmp & value}.
+
+@item @var{type} __sync_add_and_fetch (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_sub_and_fetch (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_or_and_fetch (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_and_and_fetch (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_xor_and_fetch (@var{type} *ptr, @var{type} value, ...)
+@itemx @var{type} __sync_nand_and_fetch (@var{type} *ptr, @var{type} value, ...)
+@findex __sync_add_and_fetch
+@findex __sync_sub_and_fetch
+@findex __sync_or_and_fetch
+@findex __sync_and_and_fetch
+@findex __sync_xor_and_fetch
+@findex __sync_nand_and_fetch
+These built-in functions perform the operation suggested by the name, and
+return the new value. That is, operations on integer operands have
+the following semantics. Operations on pointer operands are performed as
+if the operand's type were @code{uintptr_t}.
+
+@smallexample
+@{ *ptr @var{op}= value; return *ptr; @}
+@{ *ptr = ~(*ptr & value); return *ptr; @} // nand
+@end smallexample
+
+The same constraints on arguments apply as for the corresponding
+@code{__sync_op_and_fetch} built-in functions.
+
+@emph{Note:} GCC 4.4 and later implement @code{__sync_nand_and_fetch}
+as @code{*ptr = ~(*ptr & value)} instead of
+@code{*ptr = ~*ptr & value}.
+
+@item bool __sync_bool_compare_and_swap (@var{type} *ptr, @var{type} oldval, @var{type} newval, ...)
+@itemx @var{type} __sync_val_compare_and_swap (@var{type} *ptr, @var{type} oldval, @var{type} newval, ...)
+@findex __sync_bool_compare_and_swap
+@findex __sync_val_compare_and_swap
+These built-in functions perform an atomic compare and swap.
+That is, if the current
+value of @code{*@var{ptr}} is @var{oldval}, then write @var{newval} into
+@code{*@var{ptr}}.
+
+The ``bool'' version returns @code{true} if the comparison is successful and
+@var{newval} is written. The ``val'' version returns the contents
+of @code{*@var{ptr}} before the operation.
+
+@item __sync_synchronize (...)
+@findex __sync_synchronize
+This built-in function issues a full memory barrier.
+
+@item @var{type} __sync_lock_test_and_set (@var{type} *ptr, @var{type} value, ...)
+@findex __sync_lock_test_and_set
+This built-in function, as described by Intel, is not a traditional test-and-set
+operation, but rather an atomic exchange operation. It writes @var{value}
+into @code{*@var{ptr}}, and returns the previous contents of
+@code{*@var{ptr}}.
+
+Many targets have only minimal support for such locks, and do not support
+a full exchange operation. In this case, a target may support reduced
+functionality here by which the @emph{only} valid value to store is the
+immediate constant 1. The exact value actually stored in @code{*@var{ptr}}
+is implementation defined.
+
+This built-in function is not a full barrier,
+but rather an @dfn{acquire barrier}.
+This means that references after the operation cannot move to (or be
+speculated to) before the operation, but previous memory stores may not
+be globally visible yet, and previous memory loads may not yet be
+satisfied.
+
+@item void __sync_lock_release (@var{type} *ptr, ...)
+@findex __sync_lock_release
+This built-in function releases the lock acquired by
+@code{__sync_lock_test_and_set}.
+Normally this means writing the constant 0 to @code{*@var{ptr}}.
+
+This built-in function is not a full barrier,
+but rather a @dfn{release barrier}.
+This means that all previous memory stores are globally visible, and all
+previous memory loads have been satisfied, but following memory reads
+are not prevented from being speculated to before the barrier.
+@end table
+
+@node __atomic Builtins
+@section Built-in Functions for Memory Model Aware Atomic Operations
+
+The following built-in functions approximately match the requirements
+for the C++11 memory model. They are all
+identified by being prefixed with @samp{__atomic} and most are
+overloaded so that they work with multiple types.
+
+These functions are intended to replace the legacy @samp{__sync}
+builtins. The main difference is that the memory order that is requested
+is a parameter to the functions. New code should always use the
+@samp{__atomic} builtins rather than the @samp{__sync} builtins.
+
+Note that the @samp{__atomic} builtins assume that programs will
+conform to the C++11 memory model. In particular, they assume
+that programs are free of data races. See the C++11 standard for
+detailed requirements.
+
+The @samp{__atomic} builtins can be used with any integral scalar or
+pointer type that is 1, 2, 4, or 8 bytes in length. 16-byte integral
+types are also allowed if @samp{__int128} (@pxref{__int128}) is
+supported by the architecture.
+
+The four non-arithmetic functions (load, store, exchange, and
+compare_exchange) all have a generic version as well. This generic
+version works on any data type. It uses the lock-free built-in function
+if the specific data type size makes that possible; otherwise, an
+external call is left to be resolved at run time. This external call is
+the same format with the addition of a @samp{size_t} parameter inserted
+as the first parameter indicating the size of the object being pointed to.
+All objects must be the same size.
+
+There are 6 different memory orders that can be specified. These map
+to the C++11 memory orders with the same names, see the C++11 standard
+or the @uref{https://gcc.gnu.org/wiki/Atomic/GCCMM/AtomicSync,GCC wiki
+on atomic synchronization} for detailed definitions. Individual
+targets may also support additional memory orders for use on specific
+architectures. Refer to the target documentation for details of
+these.
+
+An atomic operation can both constrain code motion and
+be mapped to hardware instructions for synchronization between threads
+(e.g., a fence). To which extent this happens is controlled by the
+memory orders, which are listed here in approximately ascending order of
+strength. The description of each memory order is only meant to roughly
+illustrate the effects and is not a specification; see the C++11
+memory model for precise semantics.
+
+@table @code
+@item __ATOMIC_RELAXED
+Implies no inter-thread ordering constraints.
+@item __ATOMIC_CONSUME
+This is currently implemented using the stronger @code{__ATOMIC_ACQUIRE}
+memory order because of a deficiency in C++11's semantics for
+@code{memory_order_consume}.
+@item __ATOMIC_ACQUIRE
+Creates an inter-thread happens-before constraint from the release (or
+stronger) semantic store to this acquire load. Can prevent hoisting
+of code to before the operation.
+@item __ATOMIC_RELEASE
+Creates an inter-thread happens-before constraint to acquire (or stronger)
+semantic loads that read from this release store. Can prevent sinking
+of code to after the operation.
+@item __ATOMIC_ACQ_REL
+Combines the effects of both @code{__ATOMIC_ACQUIRE} and
+@code{__ATOMIC_RELEASE}.
+@item __ATOMIC_SEQ_CST
+Enforces total ordering with all other @code{__ATOMIC_SEQ_CST} operations.
+@end table
+
+Note that in the C++11 memory model, @emph{fences} (e.g.,
+@samp{__atomic_thread_fence}) take effect in combination with other
+atomic operations on specific memory locations (e.g., atomic loads);
+operations on specific memory locations do not necessarily affect other
+operations in the same way.
+
+Target architectures are encouraged to provide their own patterns for
+each of the atomic built-in functions. If no target is provided, the original
+non-memory model set of @samp{__sync} atomic built-in functions are
+used, along with any required synchronization fences surrounding it in
+order to achieve the proper behavior. Execution in this case is subject
+to the same restrictions as those built-in functions.
+
+If there is no pattern or mechanism to provide a lock-free instruction
+sequence, a call is made to an external routine with the same parameters
+to be resolved at run time.
+
+When implementing patterns for these built-in functions, the memory order
+parameter can be ignored as long as the pattern implements the most
+restrictive @code{__ATOMIC_SEQ_CST} memory order. Any of the other memory
+orders execute correctly with this memory order but they may not execute as
+efficiently as they could with a more appropriate implementation of the
+relaxed requirements.
+
+Note that the C++11 standard allows for the memory order parameter to be
+determined at run time rather than at compile time. These built-in
+functions map any run-time value to @code{__ATOMIC_SEQ_CST} rather
+than invoke a runtime library call or inline a switch statement. This is
+standard compliant, safe, and the simplest approach for now.
+
+The memory order parameter is a signed int, but only the lower 16 bits are
+reserved for the memory order. The remainder of the signed int is reserved
+for target use and should be 0. Use of the predefined atomic values
+ensures proper usage.
+
+@deftypefn {Built-in Function} @var{type} __atomic_load_n (@var{type} *ptr, int memorder)
+This built-in function implements an atomic load operation. It returns the
+contents of @code{*@var{ptr}}.
+
+The valid memory order variants are
+@code{__ATOMIC_RELAXED}, @code{__ATOMIC_SEQ_CST}, @code{__ATOMIC_ACQUIRE},
+and @code{__ATOMIC_CONSUME}.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void __atomic_load (@var{type} *ptr, @var{type} *ret, int memorder)
+This is the generic version of an atomic load. It returns the
+contents of @code{*@var{ptr}} in @code{*@var{ret}}.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void __atomic_store_n (@var{type} *ptr, @var{type} val, int memorder)
+This built-in function implements an atomic store operation. It writes
+@code{@var{val}} into @code{*@var{ptr}}.
+
+The valid memory order variants are
+@code{__ATOMIC_RELAXED}, @code{__ATOMIC_SEQ_CST}, and @code{__ATOMIC_RELEASE}.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void __atomic_store (@var{type} *ptr, @var{type} *val, int memorder)
+This is the generic version of an atomic store. It stores the value
+of @code{*@var{val}} into @code{*@var{ptr}}.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __atomic_exchange_n (@var{type} *ptr, @var{type} val, int memorder)
+This built-in function implements an atomic exchange operation. It writes
+@var{val} into @code{*@var{ptr}}, and returns the previous contents of
+@code{*@var{ptr}}.
+
+All memory order variants are valid.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void __atomic_exchange (@var{type} *ptr, @var{type} *val, @var{type} *ret, int memorder)
+This is the generic version of an atomic exchange. It stores the
+contents of @code{*@var{val}} into @code{*@var{ptr}}. The original value
+of @code{*@var{ptr}} is copied into @code{*@var{ret}}.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __atomic_compare_exchange_n (@var{type} *ptr, @var{type} *expected, @var{type} desired, bool weak, int success_memorder, int failure_memorder)
+This built-in function implements an atomic compare and exchange operation.
+This compares the contents of @code{*@var{ptr}} with the contents of
+@code{*@var{expected}}. If equal, the operation is a @emph{read-modify-write}
+operation that writes @var{desired} into @code{*@var{ptr}}. If they are not
+equal, the operation is a @emph{read} and the current contents of
+@code{*@var{ptr}} are written into @code{*@var{expected}}. @var{weak} is @code{true}
+for weak compare_exchange, which may fail spuriously, and @code{false} for
+the strong variation, which never fails spuriously. Many targets
+only offer the strong variation and ignore the parameter. When in doubt, use
+the strong variation.
+
+If @var{desired} is written into @code{*@var{ptr}} then @code{true} is returned
+and memory is affected according to the
+memory order specified by @var{success_memorder}. There are no
+restrictions on what memory order can be used here.
+
+Otherwise, @code{false} is returned and memory is affected according
+to @var{failure_memorder}. This memory order cannot be
+@code{__ATOMIC_RELEASE} nor @code{__ATOMIC_ACQ_REL}. It also cannot be a
+stronger order than that specified by @var{success_memorder}.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __atomic_compare_exchange (@var{type} *ptr, @var{type} *expected, @var{type} *desired, bool weak, int success_memorder, int failure_memorder)
+This built-in function implements the generic version of
+@code{__atomic_compare_exchange}. The function is virtually identical to
+@code{__atomic_compare_exchange_n}, except the desired value is also a
+pointer.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __atomic_add_fetch (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_sub_fetch (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_and_fetch (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_xor_fetch (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_or_fetch (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_nand_fetch (@var{type} *ptr, @var{type} val, int memorder)
+These built-in functions perform the operation suggested by the name, and
+return the result of the operation. Operations on pointer arguments are
+performed as if the operands were of the @code{uintptr_t} type. That is,
+they are not scaled by the size of the type to which the pointer points.
+
+@smallexample
+@{ *ptr @var{op}= val; return *ptr; @}
+@{ *ptr = ~(*ptr & val); return *ptr; @} // nand
+@end smallexample
+
+The object pointed to by the first argument must be of integer or pointer
+type. It must not be a boolean type. All memory orders are valid.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __atomic_fetch_add (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_fetch_sub (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_fetch_and (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_fetch_xor (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_fetch_or (@var{type} *ptr, @var{type} val, int memorder)
+@deftypefnx {Built-in Function} @var{type} __atomic_fetch_nand (@var{type} *ptr, @var{type} val, int memorder)
+These built-in functions perform the operation suggested by the name, and
+return the value that had previously been in @code{*@var{ptr}}. Operations
+on pointer arguments are performed as if the operands were of
+the @code{uintptr_t} type. That is, they are not scaled by the size of
+the type to which the pointer points.
+
+@smallexample
+@{ tmp = *ptr; *ptr @var{op}= val; return tmp; @}
+@{ tmp = *ptr; *ptr = ~(*ptr & val); return tmp; @} // nand
+@end smallexample
+
+The same constraints on arguments apply as for the corresponding
+@code{__atomic_op_fetch} built-in functions. All memory orders are valid.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __atomic_test_and_set (void *ptr, int memorder)
+
+This built-in function performs an atomic test-and-set operation on
+the byte at @code{*@var{ptr}}. The byte is set to some implementation
+defined nonzero ``set'' value and the return value is @code{true} if and only
+if the previous contents were ``set''.
+It should be only used for operands of type @code{bool} or @code{char}. For
+other types only part of the value may be set.
+
+All memory orders are valid.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void __atomic_clear (bool *ptr, int memorder)
+
+This built-in function performs an atomic clear operation on
+@code{*@var{ptr}}. After the operation, @code{*@var{ptr}} contains 0.
+It should be only used for operands of type @code{bool} or @code{char} and
+in conjunction with @code{__atomic_test_and_set}.
+For other types it may only clear partially. If the type is not @code{bool}
+prefer using @code{__atomic_store}.
+
+The valid memory order variants are
+@code{__ATOMIC_RELAXED}, @code{__ATOMIC_SEQ_CST}, and
+@code{__ATOMIC_RELEASE}.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void __atomic_thread_fence (int memorder)
+
+This built-in function acts as a synchronization fence between threads
+based on the specified memory order.
+
+All memory orders are valid.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void __atomic_signal_fence (int memorder)
+
+This built-in function acts as a synchronization fence between a thread
+and signal handlers based in the same thread.
+
+All memory orders are valid.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __atomic_always_lock_free (size_t size, void *ptr)
+
+This built-in function returns @code{true} if objects of @var{size} bytes always
+generate lock-free atomic instructions for the target architecture.
+@var{size} must resolve to a compile-time constant and the result also
+resolves to a compile-time constant.
+
+@var{ptr} is an optional pointer to the object that may be used to determine
+alignment. A value of 0 indicates typical alignment should be used. The
+compiler may also ignore this parameter.
+
+@smallexample
+if (__atomic_always_lock_free (sizeof (long long), 0))
+@end smallexample
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __atomic_is_lock_free (size_t size, void *ptr)
+
+This built-in function returns @code{true} if objects of @var{size} bytes always
+generate lock-free atomic instructions for the target architecture. If
+the built-in function is not known to be lock-free, a call is made to a
+runtime routine named @code{__atomic_is_lock_free}.
+
+@var{ptr} is an optional pointer to the object that may be used to determine
+alignment. A value of 0 indicates typical alignment should be used. The
+compiler may also ignore this parameter.
+@end deftypefn
+
+@node Integer Overflow Builtins
+@section Built-in Functions to Perform Arithmetic with Overflow Checking
+
+The following built-in functions allow performing simple arithmetic operations
+together with checking whether the operations overflowed.
+
+@deftypefn {Built-in Function} bool __builtin_add_overflow (@var{type1} a, @var{type2} b, @var{type3} *res)
+@deftypefnx {Built-in Function} bool __builtin_sadd_overflow (int a, int b, int *res)
+@deftypefnx {Built-in Function} bool __builtin_saddl_overflow (long int a, long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_saddll_overflow (long long int a, long long int b, long long int *res)
+@deftypefnx {Built-in Function} bool __builtin_uadd_overflow (unsigned int a, unsigned int b, unsigned int *res)
+@deftypefnx {Built-in Function} bool __builtin_uaddl_overflow (unsigned long int a, unsigned long int b, unsigned long int *res)
+@deftypefnx {Built-in Function} bool __builtin_uaddll_overflow (unsigned long long int a, unsigned long long int b, unsigned long long int *res)
+
+These built-in functions promote the first two operands into infinite precision signed
+type and perform addition on those promoted operands. The result is then
+cast to the type the third pointer argument points to and stored there.
+If the stored result is equal to the infinite precision result, the built-in
+functions return @code{false}, otherwise they return @code{true}. As the addition is
+performed in infinite signed precision, these built-in functions have fully defined
+behavior for all argument values.
+
+The first built-in function allows arbitrary integral types for operands and
+the result type must be pointer to some integral type other than enumerated or
+boolean type, the rest of the built-in functions have explicit integer types.
+
+The compiler will attempt to use hardware instructions to implement
+these built-in functions where possible, like conditional jump on overflow
+after addition, conditional jump on carry etc.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __builtin_sub_overflow (@var{type1} a, @var{type2} b, @var{type3} *res)
+@deftypefnx {Built-in Function} bool __builtin_ssub_overflow (int a, int b, int *res)
+@deftypefnx {Built-in Function} bool __builtin_ssubl_overflow (long int a, long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_ssubll_overflow (long long int a, long long int b, long long int *res)
+@deftypefnx {Built-in Function} bool __builtin_usub_overflow (unsigned int a, unsigned int b, unsigned int *res)
+@deftypefnx {Built-in Function} bool __builtin_usubl_overflow (unsigned long int a, unsigned long int b, unsigned long int *res)
+@deftypefnx {Built-in Function} bool __builtin_usubll_overflow (unsigned long long int a, unsigned long long int b, unsigned long long int *res)
+
+These built-in functions are similar to the add overflow checking built-in
+functions above, except they perform subtraction, subtract the second argument
+from the first one, instead of addition.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __builtin_mul_overflow (@var{type1} a, @var{type2} b, @var{type3} *res)
+@deftypefnx {Built-in Function} bool __builtin_smul_overflow (int a, int b, int *res)
+@deftypefnx {Built-in Function} bool __builtin_smull_overflow (long int a, long int b, long int *res)
+@deftypefnx {Built-in Function} bool __builtin_smulll_overflow (long long int a, long long int b, long long int *res)
+@deftypefnx {Built-in Function} bool __builtin_umul_overflow (unsigned int a, unsigned int b, unsigned int *res)
+@deftypefnx {Built-in Function} bool __builtin_umull_overflow (unsigned long int a, unsigned long int b, unsigned long int *res)
+@deftypefnx {Built-in Function} bool __builtin_umulll_overflow (unsigned long long int a, unsigned long long int b, unsigned long long int *res)
+
+These built-in functions are similar to the add overflow checking built-in
+functions above, except they perform multiplication, instead of addition.
+
+@end deftypefn
+
+The following built-in functions allow checking if simple arithmetic operation
+would overflow.
+
+@deftypefn {Built-in Function} bool __builtin_add_overflow_p (@var{type1} a, @var{type2} b, @var{type3} c)
+@deftypefnx {Built-in Function} bool __builtin_sub_overflow_p (@var{type1} a, @var{type2} b, @var{type3} c)
+@deftypefnx {Built-in Function} bool __builtin_mul_overflow_p (@var{type1} a, @var{type2} b, @var{type3} c)
+
+These built-in functions are similar to @code{__builtin_add_overflow},
+@code{__builtin_sub_overflow}, or @code{__builtin_mul_overflow}, except that
+they don't store the result of the arithmetic operation anywhere and the
+last argument is not a pointer, but some expression with integral type other
+than enumerated or boolean type.
+
+The built-in functions promote the first two operands into infinite precision signed type
+and perform addition on those promoted operands. The result is then
+cast to the type of the third argument. If the cast result is equal to the infinite
+precision result, the built-in functions return @code{false}, otherwise they return @code{true}.
+The value of the third argument is ignored, just the side effects in the third argument
+are evaluated, and no integral argument promotions are performed on the last argument.
+If the third argument is a bit-field, the type used for the result cast has the
+precision and signedness of the given bit-field, rather than precision and signedness
+of the underlying type.
+
+For example, the following macro can be used to portably check, at
+compile-time, whether or not adding two constant integers will overflow,
+and perform the addition only when it is known to be safe and not to trigger
+a @option{-Woverflow} warning.
+
+@smallexample
+#define INT_ADD_OVERFLOW_P(a, b) \
+ __builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0)
+
+enum @{
+ A = INT_MAX, B = 3,
+ C = INT_ADD_OVERFLOW_P (A, B) ? 0 : A + B,
+ D = __builtin_add_overflow_p (1, SCHAR_MAX, (signed char) 0)
+@};
+@end smallexample
+
+The compiler will attempt to use hardware instructions to implement
+these built-in functions where possible, like conditional jump on overflow
+after addition, conditional jump on carry etc.
+
+@end deftypefn
+
+@node x86 specific memory model extensions for transactional memory
+@section x86-Specific Memory Model Extensions for Transactional Memory
+
+The x86 architecture supports additional memory ordering flags
+to mark critical sections for hardware lock elision.
+These must be specified in addition to an existing memory order to
+atomic intrinsics.
+
+@table @code
+@item __ATOMIC_HLE_ACQUIRE
+Start lock elision on a lock variable.
+Memory order must be @code{__ATOMIC_ACQUIRE} or stronger.
+@item __ATOMIC_HLE_RELEASE
+End lock elision on a lock variable.
+Memory order must be @code{__ATOMIC_RELEASE} or stronger.
+@end table
+
+When a lock acquire fails, it is required for good performance to abort
+the transaction quickly. This can be done with a @code{_mm_pause}.
+
+@smallexample
+#include <immintrin.h> // For _mm_pause
+
+int lockvar;
+
+/* Acquire lock with lock elision */
+while (__atomic_exchange_n(&lockvar, 1, __ATOMIC_ACQUIRE|__ATOMIC_HLE_ACQUIRE))
+ _mm_pause(); /* Abort failed transaction */
+...
+/* Free lock with lock elision */
+__atomic_store_n(&lockvar, 0, __ATOMIC_RELEASE|__ATOMIC_HLE_RELEASE);
+@end smallexample
+
+@node Object Size Checking
+@section Object Size Checking Built-in Functions
+@findex __builtin_object_size
+@findex __builtin_dynamic_object_size
+@findex __builtin___memcpy_chk
+@findex __builtin___mempcpy_chk
+@findex __builtin___memmove_chk
+@findex __builtin___memset_chk
+@findex __builtin___strcpy_chk
+@findex __builtin___stpcpy_chk
+@findex __builtin___strncpy_chk
+@findex __builtin___strcat_chk
+@findex __builtin___strncat_chk
+@findex __builtin___sprintf_chk
+@findex __builtin___snprintf_chk
+@findex __builtin___vsprintf_chk
+@findex __builtin___vsnprintf_chk
+@findex __builtin___printf_chk
+@findex __builtin___vprintf_chk
+@findex __builtin___fprintf_chk
+@findex __builtin___vfprintf_chk
+
+GCC implements a limited buffer overflow protection mechanism that can
+prevent some buffer overflow attacks by determining the sizes of objects
+into which data is about to be written and preventing the writes when
+the size isn't sufficient. The built-in functions described below yield
+the best results when used together and when optimization is enabled.
+For example, to detect object sizes across function boundaries or to
+follow pointer assignments through non-trivial control flow they rely
+on various optimization passes enabled with @option{-O2}. However, to
+a limited extent, they can be used without optimization as well.
+
+@deftypefn {Built-in Function} {size_t} __builtin_object_size (const void * @var{ptr}, int @var{type})
+is a built-in construct that returns a constant number of bytes from
+@var{ptr} to the end of the object @var{ptr} pointer points to
+(if known at compile time). To determine the sizes of dynamically allocated
+objects the function relies on the allocation functions called to obtain
+the storage to be declared with the @code{alloc_size} attribute (@pxref{Common
+Function Attributes}). @code{__builtin_object_size} never evaluates
+its arguments for side effects. If there are any side effects in them, it
+returns @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0}
+for @var{type} 2 or 3. If there are multiple objects @var{ptr} can
+point to and all of them are known at compile time, the returned number
+is the maximum of remaining byte counts in those objects if @var{type} & 2 is
+0 and minimum if nonzero. If it is not possible to determine which objects
+@var{ptr} points to at compile time, @code{__builtin_object_size} should
+return @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0}
+for @var{type} 2 or 3.
+
+@var{type} is an integer constant from 0 to 3. If the least significant
+bit is clear, objects are whole variables, if it is set, a closest
+surrounding subobject is considered the object a pointer points to.
+The second bit determines if maximum or minimum of remaining bytes
+is computed.
+
+@smallexample
+struct V @{ char buf1[10]; int b; char buf2[10]; @} var;
+char *p = &var.buf1[1], *q = &var.b;
+
+/* Here the object p points to is var. */
+assert (__builtin_object_size (p, 0) == sizeof (var) - 1);
+/* The subobject p points to is var.buf1. */
+assert (__builtin_object_size (p, 1) == sizeof (var.buf1) - 1);
+/* The object q points to is var. */
+assert (__builtin_object_size (q, 0)
+ == (char *) (&var + 1) - (char *) &var.b);
+/* The subobject q points to is var.b. */
+assert (__builtin_object_size (q, 1) == sizeof (var.b));
+@end smallexample
+@end deftypefn
+
+@deftypefn {Built-in Function} {size_t} __builtin_dynamic_object_size (const void * @var{ptr}, int @var{type})
+is similar to @code{__builtin_object_size} in that it returns a number of bytes
+from @var{ptr} to the end of the object @var{ptr} pointer points to, except
+that the size returned may not be a constant. This results in successful
+evaluation of object size estimates in a wider range of use cases and can be
+more precise than @code{__builtin_object_size}, but it incurs a performance
+penalty since it may add a runtime overhead on size computation. Semantics of
+@var{type} as well as return values in case it is not possible to determine
+which objects @var{ptr} points to at compile time are the same as in the case
+of @code{__builtin_object_size}.
+@end deftypefn
+
+There are built-in functions added for many common string operation
+functions, e.g., for @code{memcpy} @code{__builtin___memcpy_chk}
+built-in is provided. This built-in has an additional last argument,
+which is the number of bytes remaining in the object the @var{dest}
+argument points to or @code{(size_t) -1} if the size is not known.
+
+The built-in functions are optimized into the normal string functions
+like @code{memcpy} if the last argument is @code{(size_t) -1} or if
+it is known at compile time that the destination object will not
+be overflowed. If the compiler can determine at compile time that the
+object will always be overflowed, it issues a warning.
+
+The intended use can be e.g.@:
+
+@smallexample
+#undef memcpy
+#define bos0(dest) __builtin_object_size (dest, 0)
+#define memcpy(dest, src, n) \
+ __builtin___memcpy_chk (dest, src, n, bos0 (dest))
+
+char *volatile p;
+char buf[10];
+/* It is unknown what object p points to, so this is optimized
+ into plain memcpy - no checking is possible. */
+memcpy (p, "abcde", n);
+/* Destination is known and length too. It is known at compile
+ time there will be no overflow. */
+memcpy (&buf[5], "abcde", 5);
+/* Destination is known, but the length is not known at compile time.
+ This will result in __memcpy_chk call that can check for overflow
+ at run time. */
+memcpy (&buf[5], "abcde", n);
+/* Destination is known and it is known at compile time there will
+ be overflow. There will be a warning and __memcpy_chk call that
+ will abort the program at run time. */
+memcpy (&buf[6], "abcde", 5);
+@end smallexample
+
+Such built-in functions are provided for @code{memcpy}, @code{mempcpy},
+@code{memmove}, @code{memset}, @code{strcpy}, @code{stpcpy}, @code{strncpy},
+@code{strcat} and @code{strncat}.
+
+There are also checking built-in functions for formatted output functions.
+@smallexample
+int __builtin___sprintf_chk (char *s, int flag, size_t os, const char *fmt, ...);
+int __builtin___snprintf_chk (char *s, size_t maxlen, int flag, size_t os,
+ const char *fmt, ...);
+int __builtin___vsprintf_chk (char *s, int flag, size_t os, const char *fmt,
+ va_list ap);
+int __builtin___vsnprintf_chk (char *s, size_t maxlen, int flag, size_t os,
+ const char *fmt, va_list ap);
+@end smallexample
+
+The added @var{flag} argument is passed unchanged to @code{__sprintf_chk}
+etc.@: functions and can contain implementation specific flags on what
+additional security measures the checking function might take, such as
+handling @code{%n} differently.
+
+The @var{os} argument is the object size @var{s} points to, like in the
+other built-in functions. There is a small difference in the behavior
+though, if @var{os} is @code{(size_t) -1}, the built-in functions are
+optimized into the non-checking functions only if @var{flag} is 0, otherwise
+the checking function is called with @var{os} argument set to
+@code{(size_t) -1}.
+
+In addition to this, there are checking built-in functions
+@code{__builtin___printf_chk}, @code{__builtin___vprintf_chk},
+@code{__builtin___fprintf_chk} and @code{__builtin___vfprintf_chk}.
+These have just one additional argument, @var{flag}, right before
+format string @var{fmt}. If the compiler is able to optimize them to
+@code{fputc} etc.@: functions, it does, otherwise the checking function
+is called and the @var{flag} argument passed to it.
+
+@node Other Builtins
+@section Other Built-in Functions Provided by GCC
+@cindex built-in functions
+@findex __builtin_alloca
+@findex __builtin_alloca_with_align
+@findex __builtin_alloca_with_align_and_max
+@findex __builtin_call_with_static_chain
+@findex __builtin_extend_pointer
+@findex __builtin_fpclassify
+@findex __builtin_has_attribute
+@findex __builtin_isfinite
+@findex __builtin_isnormal
+@findex __builtin_isgreater
+@findex __builtin_isgreaterequal
+@findex __builtin_isinf_sign
+@findex __builtin_isless
+@findex __builtin_islessequal
+@findex __builtin_islessgreater
+@findex __builtin_issignaling
+@findex __builtin_isunordered
+@findex __builtin_object_size
+@findex __builtin_powi
+@findex __builtin_powif
+@findex __builtin_powil
+@findex __builtin_speculation_safe_value
+@findex _Exit
+@findex _exit
+@findex abort
+@findex abs
+@findex acos
+@findex acosf
+@findex acosh
+@findex acoshf
+@findex acoshl
+@findex acosl
+@findex alloca
+@findex asin
+@findex asinf
+@findex asinh
+@findex asinhf
+@findex asinhl
+@findex asinl
+@findex atan
+@findex atan2
+@findex atan2f
+@findex atan2l
+@findex atanf
+@findex atanh
+@findex atanhf
+@findex atanhl
+@findex atanl
+@findex bcmp
+@findex bzero
+@findex cabs
+@findex cabsf
+@findex cabsl
+@findex cacos
+@findex cacosf
+@findex cacosh
+@findex cacoshf
+@findex cacoshl
+@findex cacosl
+@findex calloc
+@findex carg
+@findex cargf
+@findex cargl
+@findex casin
+@findex casinf
+@findex casinh
+@findex casinhf
+@findex casinhl
+@findex casinl
+@findex catan
+@findex catanf
+@findex catanh
+@findex catanhf
+@findex catanhl
+@findex catanl
+@findex cbrt
+@findex cbrtf
+@findex cbrtl
+@findex ccos
+@findex ccosf
+@findex ccosh
+@findex ccoshf
+@findex ccoshl
+@findex ccosl
+@findex ceil
+@findex ceilf
+@findex ceill
+@findex cexp
+@findex cexpf
+@findex cexpl
+@findex cimag
+@findex cimagf
+@findex cimagl
+@findex clog
+@findex clogf
+@findex clogl
+@findex clog10
+@findex clog10f
+@findex clog10l
+@findex conj
+@findex conjf
+@findex conjl
+@findex copysign
+@findex copysignf
+@findex copysignl
+@findex cos
+@findex cosf
+@findex cosh
+@findex coshf
+@findex coshl
+@findex cosl
+@findex cpow
+@findex cpowf
+@findex cpowl
+@findex cproj
+@findex cprojf
+@findex cprojl
+@findex creal
+@findex crealf
+@findex creall
+@findex csin
+@findex csinf
+@findex csinh
+@findex csinhf
+@findex csinhl
+@findex csinl
+@findex csqrt
+@findex csqrtf
+@findex csqrtl
+@findex ctan
+@findex ctanf
+@findex ctanh
+@findex ctanhf
+@findex ctanhl
+@findex ctanl
+@findex dcgettext
+@findex dgettext
+@findex drem
+@findex dremf
+@findex dreml
+@findex erf
+@findex erfc
+@findex erfcf
+@findex erfcl
+@findex erff
+@findex erfl
+@findex exit
+@findex exp
+@findex exp10
+@findex exp10f
+@findex exp10l
+@findex exp2
+@findex exp2f
+@findex exp2l
+@findex expf
+@findex expl
+@findex expm1
+@findex expm1f
+@findex expm1l
+@findex fabs
+@findex fabsf
+@findex fabsl
+@findex fdim
+@findex fdimf
+@findex fdiml
+@findex ffs
+@findex floor
+@findex floorf
+@findex floorl
+@findex fma
+@findex fmaf
+@findex fmal
+@findex fmax
+@findex fmaxf
+@findex fmaxl
+@findex fmin
+@findex fminf
+@findex fminl
+@findex fmod
+@findex fmodf
+@findex fmodl
+@findex fprintf
+@findex fprintf_unlocked
+@findex fputs
+@findex fputs_unlocked
+@findex free
+@findex frexp
+@findex frexpf
+@findex frexpl
+@findex fscanf
+@findex gamma
+@findex gammaf
+@findex gammal
+@findex gamma_r
+@findex gammaf_r
+@findex gammal_r
+@findex gettext
+@findex hypot
+@findex hypotf
+@findex hypotl
+@findex ilogb
+@findex ilogbf
+@findex ilogbl
+@findex imaxabs
+@findex index
+@findex isalnum
+@findex isalpha
+@findex isascii
+@findex isblank
+@findex iscntrl
+@findex isdigit
+@findex isgraph
+@findex islower
+@findex isprint
+@findex ispunct
+@findex isspace
+@findex isupper
+@findex iswalnum
+@findex iswalpha
+@findex iswblank
+@findex iswcntrl
+@findex iswdigit
+@findex iswgraph
+@findex iswlower
+@findex iswprint
+@findex iswpunct
+@findex iswspace
+@findex iswupper
+@findex iswxdigit
+@findex isxdigit
+@findex j0
+@findex j0f
+@findex j0l
+@findex j1
+@findex j1f
+@findex j1l
+@findex jn
+@findex jnf
+@findex jnl
+@findex labs
+@findex ldexp
+@findex ldexpf
+@findex ldexpl
+@findex lgamma
+@findex lgammaf
+@findex lgammal
+@findex lgamma_r
+@findex lgammaf_r
+@findex lgammal_r
+@findex llabs
+@findex llrint
+@findex llrintf
+@findex llrintl
+@findex llround
+@findex llroundf
+@findex llroundl
+@findex log
+@findex log10
+@findex log10f
+@findex log10l
+@findex log1p
+@findex log1pf
+@findex log1pl
+@findex log2
+@findex log2f
+@findex log2l
+@findex logb
+@findex logbf
+@findex logbl
+@findex logf
+@findex logl
+@findex lrint
+@findex lrintf
+@findex lrintl
+@findex lround
+@findex lroundf
+@findex lroundl
+@findex malloc
+@findex memchr
+@findex memcmp
+@findex memcpy
+@findex mempcpy
+@findex memset
+@findex modf
+@findex modff
+@findex modfl
+@findex nearbyint
+@findex nearbyintf
+@findex nearbyintl
+@findex nextafter
+@findex nextafterf
+@findex nextafterl
+@findex nexttoward
+@findex nexttowardf
+@findex nexttowardl
+@findex pow
+@findex pow10
+@findex pow10f
+@findex pow10l
+@findex powf
+@findex powl
+@findex printf
+@findex printf_unlocked
+@findex putchar
+@findex puts
+@findex realloc
+@findex remainder
+@findex remainderf
+@findex remainderl
+@findex remquo
+@findex remquof
+@findex remquol
+@findex rindex
+@findex rint
+@findex rintf
+@findex rintl
+@findex round
+@findex roundf
+@findex roundl
+@findex scalb
+@findex scalbf
+@findex scalbl
+@findex scalbln
+@findex scalblnf
+@findex scalblnf
+@findex scalbn
+@findex scalbnf
+@findex scanfnl
+@findex signbit
+@findex signbitf
+@findex signbitl
+@findex signbitd32
+@findex signbitd64
+@findex signbitd128
+@findex significand
+@findex significandf
+@findex significandl
+@findex sin
+@findex sincos
+@findex sincosf
+@findex sincosl
+@findex sinf
+@findex sinh
+@findex sinhf
+@findex sinhl
+@findex sinl
+@findex snprintf
+@findex sprintf
+@findex sqrt
+@findex sqrtf
+@findex sqrtl
+@findex sscanf
+@findex stpcpy
+@findex stpncpy
+@findex strcasecmp
+@findex strcat
+@findex strchr
+@findex strcmp
+@findex strcpy
+@findex strcspn
+@findex strdup
+@findex strfmon
+@findex strftime
+@findex strlen
+@findex strncasecmp
+@findex strncat
+@findex strncmp
+@findex strncpy
+@findex strndup
+@findex strnlen
+@findex strpbrk
+@findex strrchr
+@findex strspn
+@findex strstr
+@findex tan
+@findex tanf
+@findex tanh
+@findex tanhf
+@findex tanhl
+@findex tanl
+@findex tgamma
+@findex tgammaf
+@findex tgammal
+@findex toascii
+@findex tolower
+@findex toupper
+@findex towlower
+@findex towupper
+@findex trunc
+@findex truncf
+@findex truncl
+@findex vfprintf
+@findex vfscanf
+@findex vprintf
+@findex vscanf
+@findex vsnprintf
+@findex vsprintf
+@findex vsscanf
+@findex y0
+@findex y0f
+@findex y0l
+@findex y1
+@findex y1f
+@findex y1l
+@findex yn
+@findex ynf
+@findex ynl
+
+GCC provides a large number of built-in functions other than the ones
+mentioned above. Some of these are for internal use in the processing
+of exceptions or variable-length argument lists and are not
+documented here because they may change from time to time; we do not
+recommend general use of these functions.
+
+The remaining functions are provided for optimization purposes.
+
+With the exception of built-ins that have library equivalents such as
+the standard C library functions discussed below, or that expand to
+library calls, GCC built-in functions are always expanded inline and
+thus do not have corresponding entry points and their address cannot
+be obtained. Attempting to use them in an expression other than
+a function call results in a compile-time error.
+
+@opindex fno-builtin
+GCC includes built-in versions of many of the functions in the standard
+C library. These functions come in two forms: one whose names start with
+the @code{__builtin_} prefix, and the other without. Both forms have the
+same type (including prototype), the same address (when their address is
+taken), and the same meaning as the C library functions even if you specify
+the @option{-fno-builtin} option @pxref{C Dialect Options}). Many of these
+functions are only optimized in certain cases; if they are not optimized in
+a particular case, a call to the library function is emitted.
+
+@opindex ansi
+@opindex std
+Outside strict ISO C mode (@option{-ansi}, @option{-std=c90},
+@option{-std=c99} or @option{-std=c11}), the functions
+@code{_exit}, @code{alloca}, @code{bcmp}, @code{bzero},
+@code{dcgettext}, @code{dgettext}, @code{dremf}, @code{dreml},
+@code{drem}, @code{exp10f}, @code{exp10l}, @code{exp10}, @code{ffsll},
+@code{ffsl}, @code{ffs}, @code{fprintf_unlocked},
+@code{fputs_unlocked}, @code{gammaf}, @code{gammal}, @code{gamma},
+@code{gammaf_r}, @code{gammal_r}, @code{gamma_r}, @code{gettext},
+@code{index}, @code{isascii}, @code{j0f}, @code{j0l}, @code{j0},
+@code{j1f}, @code{j1l}, @code{j1}, @code{jnf}, @code{jnl}, @code{jn},
+@code{lgammaf_r}, @code{lgammal_r}, @code{lgamma_r}, @code{mempcpy},
+@code{pow10f}, @code{pow10l}, @code{pow10}, @code{printf_unlocked},
+@code{rindex}, @code{roundeven}, @code{roundevenf}, @code{roundevenl},
+@code{scalbf}, @code{scalbl}, @code{scalb},
+@code{signbit}, @code{signbitf}, @code{signbitl}, @code{signbitd32},
+@code{signbitd64}, @code{signbitd128}, @code{significandf},
+@code{significandl}, @code{significand}, @code{sincosf},
+@code{sincosl}, @code{sincos}, @code{stpcpy}, @code{stpncpy},
+@code{strcasecmp}, @code{strdup}, @code{strfmon}, @code{strncasecmp},
+@code{strndup}, @code{strnlen}, @code{toascii}, @code{y0f}, @code{y0l},
+@code{y0}, @code{y1f}, @code{y1l}, @code{y1}, @code{ynf}, @code{ynl} and
+@code{yn}
+may be handled as built-in functions.
+All these functions have corresponding versions
+prefixed with @code{__builtin_}, which may be used even in strict C90
+mode.
+
+The ISO C99 functions
+@code{_Exit}, @code{acoshf}, @code{acoshl}, @code{acosh}, @code{asinhf},
+@code{asinhl}, @code{asinh}, @code{atanhf}, @code{atanhl}, @code{atanh},
+@code{cabsf}, @code{cabsl}, @code{cabs}, @code{cacosf}, @code{cacoshf},
+@code{cacoshl}, @code{cacosh}, @code{cacosl}, @code{cacos},
+@code{cargf}, @code{cargl}, @code{carg}, @code{casinf}, @code{casinhf},
+@code{casinhl}, @code{casinh}, @code{casinl}, @code{casin},
+@code{catanf}, @code{catanhf}, @code{catanhl}, @code{catanh},
+@code{catanl}, @code{catan}, @code{cbrtf}, @code{cbrtl}, @code{cbrt},
+@code{ccosf}, @code{ccoshf}, @code{ccoshl}, @code{ccosh}, @code{ccosl},
+@code{ccos}, @code{cexpf}, @code{cexpl}, @code{cexp}, @code{cimagf},
+@code{cimagl}, @code{cimag}, @code{clogf}, @code{clogl}, @code{clog},
+@code{conjf}, @code{conjl}, @code{conj}, @code{copysignf}, @code{copysignl},
+@code{copysign}, @code{cpowf}, @code{cpowl}, @code{cpow}, @code{cprojf},
+@code{cprojl}, @code{cproj}, @code{crealf}, @code{creall}, @code{creal},
+@code{csinf}, @code{csinhf}, @code{csinhl}, @code{csinh}, @code{csinl},
+@code{csin}, @code{csqrtf}, @code{csqrtl}, @code{csqrt}, @code{ctanf},
+@code{ctanhf}, @code{ctanhl}, @code{ctanh}, @code{ctanl}, @code{ctan},
+@code{erfcf}, @code{erfcl}, @code{erfc}, @code{erff}, @code{erfl},
+@code{erf}, @code{exp2f}, @code{exp2l}, @code{exp2}, @code{expm1f},
+@code{expm1l}, @code{expm1}, @code{fdimf}, @code{fdiml}, @code{fdim},
+@code{fmaf}, @code{fmal}, @code{fmaxf}, @code{fmaxl}, @code{fmax},
+@code{fma}, @code{fminf}, @code{fminl}, @code{fmin}, @code{hypotf},
+@code{hypotl}, @code{hypot}, @code{ilogbf}, @code{ilogbl}, @code{ilogb},
+@code{imaxabs}, @code{isblank}, @code{iswblank}, @code{lgammaf},
+@code{lgammal}, @code{lgamma}, @code{llabs}, @code{llrintf}, @code{llrintl},
+@code{llrint}, @code{llroundf}, @code{llroundl}, @code{llround},
+@code{log1pf}, @code{log1pl}, @code{log1p}, @code{log2f}, @code{log2l},
+@code{log2}, @code{logbf}, @code{logbl}, @code{logb}, @code{lrintf},
+@code{lrintl}, @code{lrint}, @code{lroundf}, @code{lroundl},
+@code{lround}, @code{nearbyintf}, @code{nearbyintl}, @code{nearbyint},
+@code{nextafterf}, @code{nextafterl}, @code{nextafter},
+@code{nexttowardf}, @code{nexttowardl}, @code{nexttoward},
+@code{remainderf}, @code{remainderl}, @code{remainder}, @code{remquof},
+@code{remquol}, @code{remquo}, @code{rintf}, @code{rintl}, @code{rint},
+@code{roundf}, @code{roundl}, @code{round}, @code{scalblnf},
+@code{scalblnl}, @code{scalbln}, @code{scalbnf}, @code{scalbnl},
+@code{scalbn}, @code{snprintf}, @code{tgammaf}, @code{tgammal},
+@code{tgamma}, @code{truncf}, @code{truncl}, @code{trunc},
+@code{vfscanf}, @code{vscanf}, @code{vsnprintf} and @code{vsscanf}
+are handled as built-in functions
+except in strict ISO C90 mode (@option{-ansi} or @option{-std=c90}).
+
+There are also built-in versions of the ISO C99 functions
+@code{acosf}, @code{acosl}, @code{asinf}, @code{asinl}, @code{atan2f},
+@code{atan2l}, @code{atanf}, @code{atanl}, @code{ceilf}, @code{ceill},
+@code{cosf}, @code{coshf}, @code{coshl}, @code{cosl}, @code{expf},
+@code{expl}, @code{fabsf}, @code{fabsl}, @code{floorf}, @code{floorl},
+@code{fmodf}, @code{fmodl}, @code{frexpf}, @code{frexpl}, @code{ldexpf},
+@code{ldexpl}, @code{log10f}, @code{log10l}, @code{logf}, @code{logl},
+@code{modfl}, @code{modff}, @code{powf}, @code{powl}, @code{sinf},
+@code{sinhf}, @code{sinhl}, @code{sinl}, @code{sqrtf}, @code{sqrtl},
+@code{tanf}, @code{tanhf}, @code{tanhl} and @code{tanl}
+that are recognized in any mode since ISO C90 reserves these names for
+the purpose to which ISO C99 puts them. All these functions have
+corresponding versions prefixed with @code{__builtin_}.
+
+There are also built-in functions @code{__builtin_fabsf@var{n}},
+@code{__builtin_fabsf@var{n}x}, @code{__builtin_copysignf@var{n}} and
+@code{__builtin_copysignf@var{n}x}, corresponding to the TS 18661-3
+functions @code{fabsf@var{n}}, @code{fabsf@var{n}x},
+@code{copysignf@var{n}} and @code{copysignf@var{n}x}, for supported
+types @code{_Float@var{n}} and @code{_Float@var{n}x}.
+
+There are also GNU extension functions @code{clog10}, @code{clog10f} and
+@code{clog10l} which names are reserved by ISO C99 for future use.
+All these functions have versions prefixed with @code{__builtin_}.
+
+The ISO C94 functions
+@code{iswalnum}, @code{iswalpha}, @code{iswcntrl}, @code{iswdigit},
+@code{iswgraph}, @code{iswlower}, @code{iswprint}, @code{iswpunct},
+@code{iswspace}, @code{iswupper}, @code{iswxdigit}, @code{towlower} and
+@code{towupper}
+are handled as built-in functions
+except in strict ISO C90 mode (@option{-ansi} or @option{-std=c90}).
+
+The ISO C90 functions
+@code{abort}, @code{abs}, @code{acos}, @code{asin}, @code{atan2},
+@code{atan}, @code{calloc}, @code{ceil}, @code{cosh}, @code{cos},
+@code{exit}, @code{exp}, @code{fabs}, @code{floor}, @code{fmod},
+@code{fprintf}, @code{fputs}, @code{free}, @code{frexp}, @code{fscanf},
+@code{isalnum}, @code{isalpha}, @code{iscntrl}, @code{isdigit},
+@code{isgraph}, @code{islower}, @code{isprint}, @code{ispunct},
+@code{isspace}, @code{isupper}, @code{isxdigit}, @code{tolower},
+@code{toupper}, @code{labs}, @code{ldexp}, @code{log10}, @code{log},
+@code{malloc}, @code{memchr}, @code{memcmp}, @code{memcpy},
+@code{memset}, @code{modf}, @code{pow}, @code{printf}, @code{putchar},
+@code{puts}, @code{realloc}, @code{scanf}, @code{sinh}, @code{sin},
+@code{snprintf}, @code{sprintf}, @code{sqrt}, @code{sscanf}, @code{strcat},
+@code{strchr}, @code{strcmp}, @code{strcpy}, @code{strcspn},
+@code{strlen}, @code{strncat}, @code{strncmp}, @code{strncpy},
+@code{strpbrk}, @code{strrchr}, @code{strspn}, @code{strstr},
+@code{tanh}, @code{tan}, @code{vfprintf}, @code{vprintf} and @code{vsprintf}
+are all recognized as built-in functions unless
+@option{-fno-builtin} is specified (or @option{-fno-builtin-@var{function}}
+is specified for an individual function). All of these functions have
+corresponding versions prefixed with @code{__builtin_}.
+
+GCC provides built-in versions of the ISO C99 floating-point comparison
+macros that avoid raising exceptions for unordered operands. They have
+the same names as the standard macros ( @code{isgreater},
+@code{isgreaterequal}, @code{isless}, @code{islessequal},
+@code{islessgreater}, and @code{isunordered}) , with @code{__builtin_}
+prefixed. We intend for a library implementor to be able to simply
+@code{#define} each standard macro to its built-in equivalent.
+In the same fashion, GCC provides @code{fpclassify}, @code{isfinite},
+@code{isinf_sign}, @code{isnormal} and @code{signbit} built-ins used with
+@code{__builtin_} prefixed. The @code{isinf} and @code{isnan}
+built-in functions appear both with and without the @code{__builtin_} prefix.
+With @code{-ffinite-math-only} option the @code{isinf} and @code{isnan}
+built-in functions will always return 0.
+
+GCC provides built-in versions of the ISO C99 floating-point rounding and
+exceptions handling functions @code{fegetround}, @code{feclearexcept} and
+@code{feraiseexcept}. They may not be available for all targets, and because
+they need close interaction with libc internal values, they may not be available
+for all target libcs, but in all cases they will gracefully fallback to libc
+calls. These built-in functions appear both with and without the
+@code{__builtin_} prefix.
+
+@deftypefn {Built-in Function} void *__builtin_alloca (size_t size)
+The @code{__builtin_alloca} function must be called at block scope.
+The function allocates an object @var{size} bytes large on the stack
+of the calling function. The object is aligned on the default stack
+alignment boundary for the target determined by the
+@code{__BIGGEST_ALIGNMENT__} macro. The @code{__builtin_alloca}
+function returns a pointer to the first byte of the allocated object.
+The lifetime of the allocated object ends just before the calling
+function returns to its caller. This is so even when
+@code{__builtin_alloca} is called within a nested block.
+
+For example, the following function allocates eight objects of @code{n}
+bytes each on the stack, storing a pointer to each in consecutive elements
+of the array @code{a}. It then passes the array to function @code{g}
+which can safely use the storage pointed to by each of the array elements.
+
+@smallexample
+void f (unsigned n)
+@{
+ void *a [8];
+ for (int i = 0; i != 8; ++i)
+ a [i] = __builtin_alloca (n);
+
+ g (a, n); // @r{safe}
+@}
+@end smallexample
+
+Since the @code{__builtin_alloca} function doesn't validate its argument
+it is the responsibility of its caller to make sure the argument doesn't
+cause it to exceed the stack size limit.
+The @code{__builtin_alloca} function is provided to make it possible to
+allocate on the stack arrays of bytes with an upper bound that may be
+computed at run time. Since C99 Variable Length Arrays offer
+similar functionality under a portable, more convenient, and safer
+interface they are recommended instead, in both C99 and C++ programs
+where GCC provides them as an extension.
+@xref{Variable Length}, for details.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void *__builtin_alloca_with_align (size_t size, size_t alignment)
+The @code{__builtin_alloca_with_align} function must be called at block
+scope. The function allocates an object @var{size} bytes large on
+the stack of the calling function. The allocated object is aligned on
+the boundary specified by the argument @var{alignment} whose unit is given
+in bits (not bytes). The @var{size} argument must be positive and not
+exceed the stack size limit. The @var{alignment} argument must be a constant
+integer expression that evaluates to a power of 2 greater than or equal to
+@code{CHAR_BIT} and less than some unspecified maximum. Invocations
+with other values are rejected with an error indicating the valid bounds.
+The function returns a pointer to the first byte of the allocated object.
+The lifetime of the allocated object ends at the end of the block in which
+the function was called. The allocated storage is released no later than
+just before the calling function returns to its caller, but may be released
+at the end of the block in which the function was called.
+
+For example, in the following function the call to @code{g} is unsafe
+because when @code{overalign} is non-zero, the space allocated by
+@code{__builtin_alloca_with_align} may have been released at the end
+of the @code{if} statement in which it was called.
+
+@smallexample
+void f (unsigned n, bool overalign)
+@{
+ void *p;
+ if (overalign)
+ p = __builtin_alloca_with_align (n, 64 /* bits */);
+ else
+ p = __builtin_alloc (n);
+
+ g (p, n); // @r{unsafe}
+@}
+@end smallexample
+
+Since the @code{__builtin_alloca_with_align} function doesn't validate its
+@var{size} argument it is the responsibility of its caller to make sure
+the argument doesn't cause it to exceed the stack size limit.
+The @code{__builtin_alloca_with_align} function is provided to make
+it possible to allocate on the stack overaligned arrays of bytes with
+an upper bound that may be computed at run time. Since C99
+Variable Length Arrays offer the same functionality under
+a portable, more convenient, and safer interface they are recommended
+instead, in both C99 and C++ programs where GCC provides them as
+an extension. @xref{Variable Length}, for details.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void *__builtin_alloca_with_align_and_max (size_t size, size_t alignment, size_t max_size)
+Similar to @code{__builtin_alloca_with_align} but takes an extra argument
+specifying an upper bound for @var{size} in case its value cannot be computed
+at compile time, for use by @option{-fstack-usage}, @option{-Wstack-usage}
+and @option{-Walloca-larger-than}. @var{max_size} must be a constant integer
+expression, it has no effect on code generation and no attempt is made to
+check its compatibility with @var{size}.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __builtin_has_attribute (@var{type-or-expression}, @var{attribute})
+The @code{__builtin_has_attribute} function evaluates to an integer constant
+expression equal to @code{true} if the symbol or type referenced by
+the @var{type-or-expression} argument has been declared with
+the @var{attribute} referenced by the second argument. For
+an @var{type-or-expression} argument that does not reference a symbol,
+since attributes do not apply to expressions the built-in consider
+the type of the argument. Neither argument is evaluated.
+The @var{type-or-expression} argument is subject to the same
+restrictions as the argument to @code{typeof} (@pxref{Typeof}). The
+@var{attribute} argument is an attribute name optionally followed by
+a comma-separated list of arguments enclosed in parentheses. Both forms
+of attribute names---with and without double leading and trailing
+underscores---are recognized. @xref{Attribute Syntax}, for details.
+When no attribute arguments are specified for an attribute that expects
+one or more arguments the function returns @code{true} if
+@var{type-or-expression} has been declared with the attribute regardless
+of the attribute argument values. Arguments provided for an attribute
+that expects some are validated and matched up to the provided number.
+The function returns @code{true} if all provided arguments match. For
+example, the first call to the function below evaluates to @code{true}
+because @code{x} is declared with the @code{aligned} attribute but
+the second call evaluates to @code{false} because @code{x} is declared
+@code{aligned (8)} and not @code{aligned (4)}.
+
+@smallexample
+__attribute__ ((aligned (8))) int x;
+_Static_assert (__builtin_has_attribute (x, aligned), "aligned");
+_Static_assert (!__builtin_has_attribute (x, aligned (4)), "aligned (4)");
+@end smallexample
+
+Due to a limitation the @code{__builtin_has_attribute} function returns
+@code{false} for the @code{mode} attribute even if the type or variable
+referenced by the @var{type-or-expression} argument was declared with one.
+The function is also not supported with labels, and in C with enumerators.
+
+Note that unlike the @code{__has_attribute} preprocessor operator which
+is suitable for use in @code{#if} preprocessing directives
+@code{__builtin_has_attribute} is an intrinsic function that is not
+recognized in such contexts.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __builtin_speculation_safe_value (@var{type} val, @var{type} failval)
+
+This built-in function can be used to help mitigate against unsafe
+speculative execution. @var{type} may be any integral type or any
+pointer type.
+
+@enumerate
+@item
+If the CPU is not speculatively executing the code, then @var{val}
+is returned.
+@item
+If the CPU is executing speculatively then either:
+@itemize
+@item
+The function may cause execution to pause until it is known that the
+code is no-longer being executed speculatively (in which case
+@var{val} can be returned, as above); or
+@item
+The function may use target-dependent speculation tracking state to cause
+@var{failval} to be returned when it is known that speculative
+execution has incorrectly predicted a conditional branch operation.
+@end itemize
+@end enumerate
+
+The second argument, @var{failval}, is optional and defaults to zero
+if omitted.
+
+GCC defines the preprocessor macro
+@code{__HAVE_BUILTIN_SPECULATION_SAFE_VALUE} for targets that have been
+updated to support this builtin.
+
+The built-in function can be used where a variable appears to be used in a
+safe way, but the CPU, due to speculative execution may temporarily ignore
+the bounds checks. Consider, for example, the following function:
+
+@smallexample
+int array[500];
+int f (unsigned untrusted_index)
+@{
+ if (untrusted_index < 500)
+ return array[untrusted_index];
+ return 0;
+@}
+@end smallexample
+
+If the function is called repeatedly with @code{untrusted_index} less
+than the limit of 500, then a branch predictor will learn that the
+block of code that returns a value stored in @code{array} will be
+executed. If the function is subsequently called with an
+out-of-range value it will still try to execute that block of code
+first until the CPU determines that the prediction was incorrect
+(the CPU will unwind any incorrect operations at that point).
+However, depending on how the result of the function is used, it might be
+possible to leave traces in the cache that can reveal what was stored
+at the out-of-bounds location. The built-in function can be used to
+provide some protection against leaking data in this way by changing
+the code to:
+
+@smallexample
+int array[500];
+int f (unsigned untrusted_index)
+@{
+ if (untrusted_index < 500)
+ return array[__builtin_speculation_safe_value (untrusted_index)];
+ return 0;
+@}
+@end smallexample
+
+The built-in function will either cause execution to stall until the
+conditional branch has been fully resolved, or it may permit
+speculative execution to continue, but using 0 instead of
+@code{untrusted_value} if that exceeds the limit.
+
+If accessing any memory location is potentially unsafe when speculative
+execution is incorrect, then the code can be rewritten as
+
+@smallexample
+int array[500];
+int f (unsigned untrusted_index)
+@{
+ if (untrusted_index < 500)
+ return *__builtin_speculation_safe_value (&array[untrusted_index], NULL);
+ return 0;
+@}
+@end smallexample
+
+which will cause a @code{NULL} pointer to be used for the unsafe case.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_types_compatible_p (@var{type1}, @var{type2})
+
+You can use the built-in function @code{__builtin_types_compatible_p} to
+determine whether two types are the same.
+
+This built-in function returns 1 if the unqualified versions of the
+types @var{type1} and @var{type2} (which are types, not expressions) are
+compatible, 0 otherwise. The result of this built-in function can be
+used in integer constant expressions.
+
+This built-in function ignores top level qualifiers (e.g., @code{const},
+@code{volatile}). For example, @code{int} is equivalent to @code{const
+int}.
+
+The type @code{int[]} and @code{int[5]} are compatible. On the other
+hand, @code{int} and @code{char *} are not compatible, even if the size
+of their types, on the particular architecture are the same. Also, the
+amount of pointer indirection is taken into account when determining
+similarity. Consequently, @code{short *} is not similar to
+@code{short **}. Furthermore, two types that are typedefed are
+considered compatible if their underlying types are compatible.
+
+An @code{enum} type is not considered to be compatible with another
+@code{enum} type even if both are compatible with the same integer
+type; this is what the C standard specifies.
+For example, @code{enum @{foo, bar@}} is not similar to
+@code{enum @{hot, dog@}}.
+
+You typically use this function in code whose execution varies
+depending on the arguments' types. For example:
+
+@smallexample
+#define foo(x) \
+ (@{ \
+ typeof (x) tmp = (x); \
+ if (__builtin_types_compatible_p (typeof (x), long double)) \
+ tmp = foo_long_double (tmp); \
+ else if (__builtin_types_compatible_p (typeof (x), double)) \
+ tmp = foo_double (tmp); \
+ else if (__builtin_types_compatible_p (typeof (x), float)) \
+ tmp = foo_float (tmp); \
+ else \
+ abort (); \
+ tmp; \
+ @})
+@end smallexample
+
+@emph{Note:} This construct is only available for C@.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __builtin_call_with_static_chain (@var{call_exp}, @var{pointer_exp})
+
+The @var{call_exp} expression must be a function call, and the
+@var{pointer_exp} expression must be a pointer. The @var{pointer_exp}
+is passed to the function call in the target's static chain location.
+The result of builtin is the result of the function call.
+
+@emph{Note:} This builtin is only available for C@.
+This builtin can be used to call Go closures from C.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __builtin_choose_expr (@var{const_exp}, @var{exp1}, @var{exp2})
+
+You can use the built-in function @code{__builtin_choose_expr} to
+evaluate code depending on the value of a constant expression. This
+built-in function returns @var{exp1} if @var{const_exp}, which is an
+integer constant expression, is nonzero. Otherwise it returns @var{exp2}.
+
+This built-in function is analogous to the @samp{? :} operator in C,
+except that the expression returned has its type unaltered by promotion
+rules. Also, the built-in function does not evaluate the expression
+that is not chosen. For example, if @var{const_exp} evaluates to @code{true},
+@var{exp2} is not evaluated even if it has side effects.
+
+This built-in function can return an lvalue if the chosen argument is an
+lvalue.
+
+If @var{exp1} is returned, the return type is the same as @var{exp1}'s
+type. Similarly, if @var{exp2} is returned, its return type is the same
+as @var{exp2}.
+
+Example:
+
+@smallexample
+#define foo(x) \
+ __builtin_choose_expr ( \
+ __builtin_types_compatible_p (typeof (x), double), \
+ foo_double (x), \
+ __builtin_choose_expr ( \
+ __builtin_types_compatible_p (typeof (x), float), \
+ foo_float (x), \
+ /* @r{The void expression results in a compile-time error} \
+ @r{when assigning the result to something.} */ \
+ (void)0))
+@end smallexample
+
+@emph{Note:} This construct is only available for C@. Furthermore, the
+unused expression (@var{exp1} or @var{exp2} depending on the value of
+@var{const_exp}) may still generate syntax errors. This may change in
+future revisions.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __builtin_tgmath (@var{functions}, @var{arguments})
+
+The built-in function @code{__builtin_tgmath}, available only for C
+and Objective-C, calls a function determined according to the rules of
+@code{<tgmath.h>} macros. It is intended to be used in
+implementations of that header, so that expansions of macros from that
+header only expand each of their arguments once, to avoid problems
+when calls to such macros are nested inside the arguments of other
+calls to such macros; in addition, it results in better diagnostics
+for invalid calls to @code{<tgmath.h>} macros than implementations
+using other GNU C language features. For example, the @code{pow}
+type-generic macro might be defined as:
+
+@smallexample
+#define pow(a, b) __builtin_tgmath (powf, pow, powl, \
+ cpowf, cpow, cpowl, a, b)
+@end smallexample
+
+The arguments to @code{__builtin_tgmath} are at least two pointers to
+functions, followed by the arguments to the type-generic macro (which
+will be passed as arguments to the selected function). All the
+pointers to functions must be pointers to prototyped functions, none
+of which may have variable arguments, and all of which must have the
+same number of parameters; the number of parameters of the first
+function determines how many arguments to @code{__builtin_tgmath} are
+interpreted as function pointers, and how many as the arguments to the
+called function.
+
+The types of the specified functions must all be different, but
+related to each other in the same way as a set of functions that may
+be selected between by a macro in @code{<tgmath.h>}. This means that
+the functions are parameterized by a floating-point type @var{t},
+different for each such function. The function return types may all
+be the same type, or they may be @var{t} for each function, or they
+may be the real type corresponding to @var{t} for each function (if
+some of the types @var{t} are complex). Likewise, for each parameter
+position, the type of the parameter in that position may always be the
+same type, or may be @var{t} for each function (this case must apply
+for at least one parameter position), or may be the real type
+corresponding to @var{t} for each function.
+
+The standard rules for @code{<tgmath.h>} macros are used to find a
+common type @var{u} from the types of the arguments for parameters
+whose types vary between the functions; complex integer types (a GNU
+extension) are treated like @code{_Complex double} for this purpose
+(or @code{_Complex _Float64} if all the function return types are the
+same @code{_Float@var{n}} or @code{_Float@var{n}x} type).
+If the function return types vary, or are all the same integer type,
+the function called is the one for which @var{t} is @var{u}, and it is
+an error if there is no such function. If the function return types
+are all the same floating-point type, the type-generic macro is taken
+to be one of those from TS 18661 that rounds the result to a narrower
+type; if there is a function for which @var{t} is @var{u}, it is
+called, and otherwise the first function, if any, for which @var{t}
+has at least the range and precision of @var{u} is called, and it is
+an error if there is no such function.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_constant_p (@var{exp})
+You can use the built-in function @code{__builtin_constant_p} to
+determine if a value is known to be constant at compile time and hence
+that GCC can perform constant-folding on expressions involving that
+value. The argument of the function is the value to test. The function
+returns the integer 1 if the argument is known to be a compile-time
+constant and 0 if it is not known to be a compile-time constant. A
+return of 0 does not indicate that the value is @emph{not} a constant,
+but merely that GCC cannot prove it is a constant with the specified
+value of the @option{-O} option.
+
+You typically use this function in an embedded application where
+memory is a critical resource. If you have some complex calculation,
+you may want it to be folded if it involves constants, but need to call
+a function if it does not. For example:
+
+@smallexample
+#define Scale_Value(X) \
+ (__builtin_constant_p (X) \
+ ? ((X) * SCALE + OFFSET) : Scale (X))
+@end smallexample
+
+You may use this built-in function in either a macro or an inline
+function. However, if you use it in an inlined function and pass an
+argument of the function as the argument to the built-in, GCC
+never returns 1 when you call the inline function with a string constant
+or compound literal (@pxref{Compound Literals}) and does not return 1
+when you pass a constant numeric value to the inline function unless you
+specify the @option{-O} option.
+
+You may also use @code{__builtin_constant_p} in initializers for static
+data. For instance, you can write
+
+@smallexample
+static const int table[] = @{
+ __builtin_constant_p (EXPRESSION) ? (EXPRESSION) : -1,
+ /* @r{@dots{}} */
+@};
+@end smallexample
+
+@noindent
+This is an acceptable initializer even if @var{EXPRESSION} is not a
+constant expression, including the case where
+@code{__builtin_constant_p} returns 1 because @var{EXPRESSION} can be
+folded to a constant but @var{EXPRESSION} contains operands that are
+not otherwise permitted in a static initializer (for example,
+@code{0 && foo ()}). GCC must be more conservative about evaluating the
+built-in in this case, because it has no opportunity to perform
+optimization.
+@end deftypefn
+
+@deftypefn {Built-in Function} bool __builtin_is_constant_evaluated (void)
+The @code{__builtin_is_constant_evaluated} function is available only
+in C++. The built-in is intended to be used by implementations of
+the @code{std::is_constant_evaluated} C++ function. Programs should make
+use of the latter function rather than invoking the built-in directly.
+
+The main use case of the built-in is to determine whether a @code{constexpr}
+function is being called in a @code{constexpr} context. A call to
+the function evaluates to a core constant expression with the value
+@code{true} if and only if it occurs within the evaluation of an expression
+or conversion that is manifestly constant-evaluated as defined in the C++
+standard. Manifestly constant-evaluated contexts include constant-expressions,
+the conditions of @code{constexpr if} statements, constraint-expressions, and
+initializers of variables usable in constant expressions. For more details
+refer to the latest revision of the C++ standard.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_clear_padding (@var{ptr})
+The built-in function @code{__builtin_clear_padding} function clears
+padding bits inside of the object representation of object pointed by
+@var{ptr}, which has to be a pointer. The value representation of the
+object is not affected. The type of the object is assumed to be the type
+the pointer points to. Inside of a union, the only cleared bits are
+bits that are padding bits for all the union members.
+
+This built-in-function is useful if the padding bits of an object might
+have intederminate values and the object representation needs to be
+bitwise compared to some other object, for example for atomic operations.
+
+For C++, @var{ptr} argument type should be pointer to trivially-copyable
+type, unless the argument is address of a variable or parameter, because
+otherwise it isn't known if the type isn't just a base class whose padding
+bits are reused or laid out differently in a derived class.
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __builtin_bit_cast (@var{type}, @var{arg})
+The @code{__builtin_bit_cast} function is available only
+in C++. The built-in is intended to be used by implementations of
+the @code{std::bit_cast} C++ template function. Programs should make
+use of the latter function rather than invoking the built-in directly.
+
+This built-in function allows reinterpreting the bits of the @var{arg}
+argument as if it had type @var{type}. @var{type} and the type of the
+@var{arg} argument need to be trivially copyable types with the same size.
+When manifestly constant-evaluated, it performs extra diagnostics required
+for @code{std::bit_cast} and returns a constant expression if @var{arg}
+is a constant expression. For more details
+refer to the latest revision of the C++ standard.
+@end deftypefn
+
+@deftypefn {Built-in Function} long __builtin_expect (long @var{exp}, long @var{c})
+@opindex fprofile-arcs
+You may use @code{__builtin_expect} to provide the compiler with
+branch prediction information. In general, you should prefer to
+use actual profile feedback for this (@option{-fprofile-arcs}), as
+programmers are notoriously bad at predicting how their programs
+actually perform. However, there are applications in which this
+data is hard to collect.
+
+The return value is the value of @var{exp}, which should be an integral
+expression. The semantics of the built-in are that it is expected that
+@var{exp} == @var{c}. For example:
+
+@smallexample
+if (__builtin_expect (x, 0))
+ foo ();
+@end smallexample
+
+@noindent
+indicates that we do not expect to call @code{foo}, since
+we expect @code{x} to be zero. Since you are limited to integral
+expressions for @var{exp}, you should use constructions such as
+
+@smallexample
+if (__builtin_expect (ptr != NULL, 1))
+ foo (*ptr);
+@end smallexample
+
+@noindent
+when testing pointer or floating-point values.
+
+For the purposes of branch prediction optimizations, the probability that
+a @code{__builtin_expect} expression is @code{true} is controlled by GCC's
+@code{builtin-expect-probability} parameter, which defaults to 90%.
+
+You can also use @code{__builtin_expect_with_probability} to explicitly
+assign a probability value to individual expressions. If the built-in
+is used in a loop construct, the provided probability will influence
+the expected number of iterations made by loop optimizations.
+@end deftypefn
+
+@deftypefn {Built-in Function} long __builtin_expect_with_probability
+(long @var{exp}, long @var{c}, double @var{probability})
+
+This function has the same semantics as @code{__builtin_expect},
+but the caller provides the expected probability that @var{exp} == @var{c}.
+The last argument, @var{probability}, is a floating-point value in the
+range 0.0 to 1.0, inclusive. The @var{probability} argument must be
+constant floating-point expression.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_trap (void)
+This function causes the program to exit abnormally. GCC implements
+this function by using a target-dependent mechanism (such as
+intentionally executing an illegal instruction) or by calling
+@code{abort}. The mechanism used may vary from release to release so
+you should not rely on any particular implementation.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_unreachable (void)
+If control flow reaches the point of the @code{__builtin_unreachable},
+the program is undefined. It is useful in situations where the
+compiler cannot deduce the unreachability of the code.
+
+One such case is immediately following an @code{asm} statement that
+either never terminates, or one that transfers control elsewhere
+and never returns. In this example, without the
+@code{__builtin_unreachable}, GCC issues a warning that control
+reaches the end of a non-void function. It also generates code
+to return after the @code{asm}.
+
+@smallexample
+int f (int c, int v)
+@{
+ if (c)
+ @{
+ return v;
+ @}
+ else
+ @{
+ asm("jmp error_handler");
+ __builtin_unreachable ();
+ @}
+@}
+@end smallexample
+
+@noindent
+Because the @code{asm} statement unconditionally transfers control out
+of the function, control never reaches the end of the function
+body. The @code{__builtin_unreachable} is in fact unreachable and
+communicates this fact to the compiler.
+
+Another use for @code{__builtin_unreachable} is following a call a
+function that never returns but that is not declared
+@code{__attribute__((noreturn))}, as in this example:
+
+@smallexample
+void function_that_never_returns (void);
+
+int g (int c)
+@{
+ if (c)
+ @{
+ return 1;
+ @}
+ else
+ @{
+ function_that_never_returns ();
+ __builtin_unreachable ();
+ @}
+@}
+@end smallexample
+
+@end deftypefn
+
+@deftypefn {Built-in Function} @var{type} __builtin_assoc_barrier (@var{type} @var{expr})
+This built-in inhibits re-association of the floating-point expression
+@var{expr} with expressions consuming the return value of the built-in. The
+expression @var{expr} itself can be reordered, and the whole expression
+@var{expr} can be reordered with operands after the barrier. The barrier is
+only relevant when @code{-fassociative-math} is active, since otherwise
+floating-point is not treated as associative.
+
+@smallexample
+float x0 = a + b - b;
+float x1 = __builtin_assoc_barrier(a + b) - b;
+@end smallexample
+
+@noindent
+means that, with @code{-fassociative-math}, @code{x0} can be optimized to
+@code{x0 = a} but @code{x1} cannot.
+@end deftypefn
+
+@deftypefn {Built-in Function} {void *} __builtin_assume_aligned (const void *@var{exp}, size_t @var{align}, ...)
+This function returns its first argument, and allows the compiler
+to assume that the returned pointer is at least @var{align} bytes
+aligned. This built-in can have either two or three arguments,
+if it has three, the third argument should have integer type, and
+if it is nonzero means misalignment offset. For example:
+
+@smallexample
+void *x = __builtin_assume_aligned (arg, 16);
+@end smallexample
+
+@noindent
+means that the compiler can assume @code{x}, set to @code{arg}, is at least
+16-byte aligned, while:
+
+@smallexample
+void *x = __builtin_assume_aligned (arg, 32, 8);
+@end smallexample
+
+@noindent
+means that the compiler can assume for @code{x}, set to @code{arg}, that
+@code{(char *) x - 8} is 32-byte aligned.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_LINE ()
+This function is the equivalent of the preprocessor @code{__LINE__}
+macro and returns a constant integer expression that evaluates to
+the line number of the invocation of the built-in. When used as a C++
+default argument for a function @var{F}, it returns the line number
+of the call to @var{F}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {const char *} __builtin_FUNCTION ()
+This function is the equivalent of the @code{__FUNCTION__} symbol
+and returns an address constant pointing to the name of the function
+from which the built-in was invoked, or the empty string if
+the invocation is not at function scope. When used as a C++ default
+argument for a function @var{F}, it returns the name of @var{F}'s
+caller or the empty string if the call was not made at function
+scope.
+@end deftypefn
+
+@deftypefn {Built-in Function} {const char *} __builtin_FILE ()
+This function is the equivalent of the preprocessor @code{__FILE__}
+macro and returns an address constant pointing to the file name
+containing the invocation of the built-in, or the empty string if
+the invocation is not at function scope. When used as a C++ default
+argument for a function @var{F}, it returns the file name of the call
+to @var{F} or the empty string if the call was not made at function
+scope.
+
+For example, in the following, each call to function @code{foo} will
+print a line similar to @code{"file.c:123: foo: message"} with the name
+of the file and the line number of the @code{printf} call, the name of
+the function @code{foo}, followed by the word @code{message}.
+
+@smallexample
+const char*
+function (const char *func = __builtin_FUNCTION ())
+@{
+ return func;
+@}
+
+void foo (void)
+@{
+ printf ("%s:%i: %s: message\n", file (), line (), function ());
+@}
+@end smallexample
+
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin___clear_cache (void *@var{begin}, void *@var{end})
+This function is used to flush the processor's instruction cache for
+the region of memory between @var{begin} inclusive and @var{end}
+exclusive. Some targets require that the instruction cache be
+flushed, after modifying memory containing code, in order to obtain
+deterministic behavior.
+
+If the target does not require instruction cache flushes,
+@code{__builtin___clear_cache} has no effect. Otherwise either
+instructions are emitted in-line to clear the instruction cache or a
+call to the @code{__clear_cache} function in libgcc is made.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_prefetch (const void *@var{addr}, ...)
+This function is used to minimize cache-miss latency by moving data into
+a cache before it is accessed.
+You can insert calls to @code{__builtin_prefetch} into code for which
+you know addresses of data in memory that is likely to be accessed soon.
+If the target supports them, data prefetch instructions are generated.
+If the prefetch is done early enough before the access then the data will
+be in the cache by the time it is accessed.
+
+The value of @var{addr} is the address of the memory to prefetch.
+There are two optional arguments, @var{rw} and @var{locality}.
+The value of @var{rw} is a compile-time constant one or zero; one
+means that the prefetch is preparing for a write to the memory address
+and zero, the default, means that the prefetch is preparing for a read.
+The value @var{locality} must be a compile-time constant integer between
+zero and three. A value of zero means that the data has no temporal
+locality, so it need not be left in the cache after the access. A value
+of three means that the data has a high degree of temporal locality and
+should be left in all levels of cache possible. Values of one and two
+mean, respectively, a low or moderate degree of temporal locality. The
+default is three.
+
+@smallexample
+for (i = 0; i < n; i++)
+ @{
+ a[i] = a[i] + b[i];
+ __builtin_prefetch (&a[i+j], 1, 1);
+ __builtin_prefetch (&b[i+j], 0, 1);
+ /* @r{@dots{}} */
+ @}
+@end smallexample
+
+Data prefetch does not generate faults if @var{addr} is invalid, but
+the address expression itself must be valid. For example, a prefetch
+of @code{p->next} does not fault if @code{p->next} is not a valid
+address, but evaluation faults if @code{p} is not a valid address.
+
+If the target does not support data prefetch, the address expression
+is evaluated if it includes side effects but no other code is generated
+and GCC does not issue a warning.
+@end deftypefn
+
+@deftypefn {Built-in Function}{size_t} __builtin_object_size (const void * @var{ptr}, int @var{type})
+Returns the size of an object pointed to by @var{ptr}. @xref{Object Size
+Checking}, for a detailed description of the function.
+@end deftypefn
+
+@deftypefn {Built-in Function} double __builtin_huge_val (void)
+Returns a positive infinity, if supported by the floating-point format,
+else @code{DBL_MAX}. This function is suitable for implementing the
+ISO C macro @code{HUGE_VAL}.
+@end deftypefn
+
+@deftypefn {Built-in Function} float __builtin_huge_valf (void)
+Similar to @code{__builtin_huge_val}, except the return type is @code{float}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {long double} __builtin_huge_vall (void)
+Similar to @code{__builtin_huge_val}, except the return
+type is @code{long double}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Float@var{n} __builtin_huge_valf@var{n} (void)
+Similar to @code{__builtin_huge_val}, except the return type is
+@code{_Float@var{n}}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Float@var{n}x __builtin_huge_valf@var{n}x (void)
+Similar to @code{__builtin_huge_val}, except the return type is
+@code{_Float@var{n}x}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_fpclassify (int, int, int, int, int, ...)
+This built-in implements the C99 fpclassify functionality. The first
+five int arguments should be the target library's notion of the
+possible FP classes and are used for return values. They must be
+constant values and they must appear in this order: @code{FP_NAN},
+@code{FP_INFINITE}, @code{FP_NORMAL}, @code{FP_SUBNORMAL} and
+@code{FP_ZERO}. The ellipsis is for exactly one floating-point value
+to classify. GCC treats the last argument as type-generic, which
+means it does not do default promotion from float to double.
+@end deftypefn
+
+@deftypefn {Built-in Function} double __builtin_inf (void)
+Similar to @code{__builtin_huge_val}, except a warning is generated
+if the target floating-point format does not support infinities.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal32 __builtin_infd32 (void)
+Similar to @code{__builtin_inf}, except the return type is @code{_Decimal32}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal64 __builtin_infd64 (void)
+Similar to @code{__builtin_inf}, except the return type is @code{_Decimal64}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal128 __builtin_infd128 (void)
+Similar to @code{__builtin_inf}, except the return type is @code{_Decimal128}.
+@end deftypefn
+
+@deftypefn {Built-in Function} float __builtin_inff (void)
+Similar to @code{__builtin_inf}, except the return type is @code{float}.
+This function is suitable for implementing the ISO C99 macro @code{INFINITY}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {long double} __builtin_infl (void)
+Similar to @code{__builtin_inf}, except the return
+type is @code{long double}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Float@var{n} __builtin_inff@var{n} (void)
+Similar to @code{__builtin_inf}, except the return
+type is @code{_Float@var{n}}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Float@var{n} __builtin_inff@var{n}x (void)
+Similar to @code{__builtin_inf}, except the return
+type is @code{_Float@var{n}x}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_isinf_sign (...)
+Similar to @code{isinf}, except the return value is -1 for
+an argument of @code{-Inf} and 1 for an argument of @code{+Inf}.
+Note while the parameter list is an
+ellipsis, this function only accepts exactly one floating-point
+argument. GCC treats this parameter as type-generic, which means it
+does not do default promotion from float to double.
+@end deftypefn
+
+@deftypefn {Built-in Function} double __builtin_nan (const char *str)
+This is an implementation of the ISO C99 function @code{nan}.
+
+Since ISO C99 defines this function in terms of @code{strtod}, which we
+do not implement, a description of the parsing is in order. The string
+is parsed as by @code{strtol}; that is, the base is recognized by
+leading @samp{0} or @samp{0x} prefixes. The number parsed is placed
+in the significand such that the least significant bit of the number
+is at the least significant bit of the significand. The number is
+truncated to fit the significand field provided. The significand is
+forced to be a quiet NaN@.
+
+This function, if given a string literal all of which would have been
+consumed by @code{strtol}, is evaluated early enough that it is considered a
+compile-time constant.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal32 __builtin_nand32 (const char *str)
+Similar to @code{__builtin_nan}, except the return type is @code{_Decimal32}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal64 __builtin_nand64 (const char *str)
+Similar to @code{__builtin_nan}, except the return type is @code{_Decimal64}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal128 __builtin_nand128 (const char *str)
+Similar to @code{__builtin_nan}, except the return type is @code{_Decimal128}.
+@end deftypefn
+
+@deftypefn {Built-in Function} float __builtin_nanf (const char *str)
+Similar to @code{__builtin_nan}, except the return type is @code{float}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {long double} __builtin_nanl (const char *str)
+Similar to @code{__builtin_nan}, except the return type is @code{long double}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Float@var{n} __builtin_nanf@var{n} (const char *str)
+Similar to @code{__builtin_nan}, except the return type is
+@code{_Float@var{n}}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Float@var{n}x __builtin_nanf@var{n}x (const char *str)
+Similar to @code{__builtin_nan}, except the return type is
+@code{_Float@var{n}x}.
+@end deftypefn
+
+@deftypefn {Built-in Function} double __builtin_nans (const char *str)
+Similar to @code{__builtin_nan}, except the significand is forced
+to be a signaling NaN@. The @code{nans} function is proposed by
+@uref{http://www.open-std.org/jtc1/sc22/wg14/www/docs/n965.htm,,WG14 N965}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal32 __builtin_nansd32 (const char *str)
+Similar to @code{__builtin_nans}, except the return type is @code{_Decimal32}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal64 __builtin_nansd64 (const char *str)
+Similar to @code{__builtin_nans}, except the return type is @code{_Decimal64}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Decimal128 __builtin_nansd128 (const char *str)
+Similar to @code{__builtin_nans}, except the return type is @code{_Decimal128}.
+@end deftypefn
+
+@deftypefn {Built-in Function} float __builtin_nansf (const char *str)
+Similar to @code{__builtin_nans}, except the return type is @code{float}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {long double} __builtin_nansl (const char *str)
+Similar to @code{__builtin_nans}, except the return type is @code{long double}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Float@var{n} __builtin_nansf@var{n} (const char *str)
+Similar to @code{__builtin_nans}, except the return type is
+@code{_Float@var{n}}.
+@end deftypefn
+
+@deftypefn {Built-in Function} _Float@var{n}x __builtin_nansf@var{n}x (const char *str)
+Similar to @code{__builtin_nans}, except the return type is
+@code{_Float@var{n}x}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_issignaling (...)
+Return non-zero if the argument is a signaling NaN and zero otherwise.
+Note while the parameter list is an
+ellipsis, this function only accepts exactly one floating-point
+argument. GCC treats this parameter as type-generic, which means it
+does not do default promotion from float to double.
+This built-in function can work even without the non-default
+@code{-fsignaling-nans} option, although if a signaling NaN is computed,
+stored or passed as argument to some function other than this built-in
+in the current translation unit, it is safer to use @code{-fsignaling-nans}.
+With @code{-ffinite-math-only} option this built-in function will always
+return 0.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ffs (int x)
+Returns one plus the index of the least significant 1-bit of @var{x}, or
+if @var{x} is zero, returns zero.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clz (unsigned int x)
+Returns the number of leading 0-bits in @var{x}, starting at the most
+significant bit position. If @var{x} is 0, the result is undefined.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ctz (unsigned int x)
+Returns the number of trailing 0-bits in @var{x}, starting at the least
+significant bit position. If @var{x} is 0, the result is undefined.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clrsb (int x)
+Returns the number of leading redundant sign bits in @var{x}, i.e.@: the
+number of bits following the most significant bit that are identical
+to it. There are no special cases for 0 or other values.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_popcount (unsigned int x)
+Returns the number of 1-bits in @var{x}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_parity (unsigned int x)
+Returns the parity of @var{x}, i.e.@: the number of 1-bits in @var{x}
+modulo 2.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ffsl (long)
+Similar to @code{__builtin_ffs}, except the argument type is
+@code{long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clzl (unsigned long)
+Similar to @code{__builtin_clz}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ctzl (unsigned long)
+Similar to @code{__builtin_ctz}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clrsbl (long)
+Similar to @code{__builtin_clrsb}, except the argument type is
+@code{long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_popcountl (unsigned long)
+Similar to @code{__builtin_popcount}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_parityl (unsigned long)
+Similar to @code{__builtin_parity}, except the argument type is
+@code{unsigned long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ffsll (long long)
+Similar to @code{__builtin_ffs}, except the argument type is
+@code{long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clzll (unsigned long long)
+Similar to @code{__builtin_clz}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_ctzll (unsigned long long)
+Similar to @code{__builtin_ctz}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_clrsbll (long long)
+Similar to @code{__builtin_clrsb}, except the argument type is
+@code{long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_popcountll (unsigned long long)
+Similar to @code{__builtin_popcount}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_parityll (unsigned long long)
+Similar to @code{__builtin_parity}, except the argument type is
+@code{unsigned long long}.
+@end deftypefn
+
+@deftypefn {Built-in Function} double __builtin_powi (double, int)
+Returns the first argument raised to the power of the second. Unlike the
+@code{pow} function no guarantees about precision and rounding are made.
+@end deftypefn
+
+@deftypefn {Built-in Function} float __builtin_powif (float, int)
+Similar to @code{__builtin_powi}, except the argument and return types
+are @code{float}.
+@end deftypefn
+
+@deftypefn {Built-in Function} {long double} __builtin_powil (long double, int)
+Similar to @code{__builtin_powi}, except the argument and return types
+are @code{long double}.
+@end deftypefn
+
+@deftypefn {Built-in Function} uint16_t __builtin_bswap16 (uint16_t x)
+Returns @var{x} with the order of the bytes reversed; for example,
+@code{0xaabb} becomes @code{0xbbaa}. Byte here always means
+exactly 8 bits.
+@end deftypefn
+
+@deftypefn {Built-in Function} uint32_t __builtin_bswap32 (uint32_t x)
+Similar to @code{__builtin_bswap16}, except the argument and return types
+are 32-bit.
+@end deftypefn
+
+@deftypefn {Built-in Function} uint64_t __builtin_bswap64 (uint64_t x)
+Similar to @code{__builtin_bswap32}, except the argument and return types
+are 64-bit.
+@end deftypefn
+
+@deftypefn {Built-in Function} uint128_t __builtin_bswap128 (uint128_t x)
+Similar to @code{__builtin_bswap64}, except the argument and return types
+are 128-bit. Only supported on targets when 128-bit types are supported.
+@end deftypefn
+
+
+@deftypefn {Built-in Function} Pmode __builtin_extend_pointer (void * x)
+On targets where the user visible pointer size is smaller than the size
+of an actual hardware address this function returns the extended user
+pointer. Targets where this is true included ILP32 mode on x86_64 or
+Aarch64. This function is mainly useful when writing inline assembly
+code.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_goacc_parlevel_id (int x)
+Returns the openacc gang, worker or vector id depending on whether @var{x} is
+0, 1 or 2.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_goacc_parlevel_size (int x)
+Returns the openacc gang, worker or vector size depending on whether @var{x} is
+0, 1 or 2.
+@end deftypefn
+
+@node Target Builtins
+@section Built-in Functions Specific to Particular Target Machines
+
+On some target machines, GCC supports many built-in functions specific
+to those machines. Generally these generate calls to specific machine
+instructions, but allow the compiler to schedule those calls.
+
+@menu
+* AArch64 Built-in Functions::
+* Alpha Built-in Functions::
+* Altera Nios II Built-in Functions::
+* ARC Built-in Functions::
+* ARC SIMD Built-in Functions::
+* ARM iWMMXt Built-in Functions::
+* ARM C Language Extensions (ACLE)::
+* ARM Floating Point Status and Control Intrinsics::
+* ARM ARMv8-M Security Extensions::
+* AVR Built-in Functions::
+* Blackfin Built-in Functions::
+* BPF Built-in Functions::
+* FR-V Built-in Functions::
+* MIPS DSP Built-in Functions::
+* MIPS Paired-Single Support::
+* MIPS Loongson Built-in Functions::
+* MIPS SIMD Architecture (MSA) Support::
+* Other MIPS Built-in Functions::
+* MSP430 Built-in Functions::
+* NDS32 Built-in Functions::
+* picoChip Built-in Functions::
+* Basic PowerPC Built-in Functions::
+* PowerPC AltiVec/VSX Built-in Functions::
+* PowerPC Hardware Transactional Memory Built-in Functions::
+* PowerPC Atomic Memory Operation Functions::
+* PowerPC Matrix-Multiply Assist Built-in Functions::
+* PRU Built-in Functions::
+* RISC-V Built-in Functions::
+* RX Built-in Functions::
+* S/390 System z Built-in Functions::
+* SH Built-in Functions::
+* SPARC VIS Built-in Functions::
+* TI C6X Built-in Functions::
+* x86 Built-in Functions::
+* x86 transactional memory intrinsics::
+* x86 control-flow protection intrinsics::
+@end menu
+
+@node AArch64 Built-in Functions
+@subsection AArch64 Built-in Functions
+
+These built-in functions are available for the AArch64 family of
+processors.
+@smallexample
+unsigned int __builtin_aarch64_get_fpcr ();
+void __builtin_aarch64_set_fpcr (unsigned int);
+unsigned int __builtin_aarch64_get_fpsr ();
+void __builtin_aarch64_set_fpsr (unsigned int);
+
+unsigned long long __builtin_aarch64_get_fpcr64 ();
+void __builtin_aarch64_set_fpcr64 (unsigned long long);
+unsigned long long __builtin_aarch64_get_fpsr64 ();
+void __builtin_aarch64_set_fpsr64 (unsigned long long);
+@end smallexample
+
+@node Alpha Built-in Functions
+@subsection Alpha Built-in Functions
+
+These built-in functions are available for the Alpha family of
+processors, depending on the command-line switches used.
+
+The following built-in functions are always available. They
+all generate the machine instruction that is part of the name.
+
+@smallexample
+long __builtin_alpha_implver (void);
+long __builtin_alpha_rpcc (void);
+long __builtin_alpha_amask (long);
+long __builtin_alpha_cmpbge (long, long);
+long __builtin_alpha_extbl (long, long);
+long __builtin_alpha_extwl (long, long);
+long __builtin_alpha_extll (long, long);
+long __builtin_alpha_extql (long, long);
+long __builtin_alpha_extwh (long, long);
+long __builtin_alpha_extlh (long, long);
+long __builtin_alpha_extqh (long, long);
+long __builtin_alpha_insbl (long, long);
+long __builtin_alpha_inswl (long, long);
+long __builtin_alpha_insll (long, long);
+long __builtin_alpha_insql (long, long);
+long __builtin_alpha_inswh (long, long);
+long __builtin_alpha_inslh (long, long);
+long __builtin_alpha_insqh (long, long);
+long __builtin_alpha_mskbl (long, long);
+long __builtin_alpha_mskwl (long, long);
+long __builtin_alpha_mskll (long, long);
+long __builtin_alpha_mskql (long, long);
+long __builtin_alpha_mskwh (long, long);
+long __builtin_alpha_msklh (long, long);
+long __builtin_alpha_mskqh (long, long);
+long __builtin_alpha_umulh (long, long);
+long __builtin_alpha_zap (long, long);
+long __builtin_alpha_zapnot (long, long);
+@end smallexample
+
+The following built-in functions are always with @option{-mmax}
+or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{pca56} or
+later. They all generate the machine instruction that is part
+of the name.
+
+@smallexample
+long __builtin_alpha_pklb (long);
+long __builtin_alpha_pkwb (long);
+long __builtin_alpha_unpkbl (long);
+long __builtin_alpha_unpkbw (long);
+long __builtin_alpha_minub8 (long, long);
+long __builtin_alpha_minsb8 (long, long);
+long __builtin_alpha_minuw4 (long, long);
+long __builtin_alpha_minsw4 (long, long);
+long __builtin_alpha_maxub8 (long, long);
+long __builtin_alpha_maxsb8 (long, long);
+long __builtin_alpha_maxuw4 (long, long);
+long __builtin_alpha_maxsw4 (long, long);
+long __builtin_alpha_perr (long, long);
+@end smallexample
+
+The following built-in functions are always with @option{-mcix}
+or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{ev67} or
+later. They all generate the machine instruction that is part
+of the name.
+
+@smallexample
+long __builtin_alpha_cttz (long);
+long __builtin_alpha_ctlz (long);
+long __builtin_alpha_ctpop (long);
+@end smallexample
+
+The following built-in functions are available on systems that use the OSF/1
+PALcode. Normally they invoke the @code{rduniq} and @code{wruniq}
+PAL calls, but when invoked with @option{-mtls-kernel}, they invoke
+@code{rdval} and @code{wrval}.
+
+@smallexample
+void *__builtin_thread_pointer (void);
+void __builtin_set_thread_pointer (void *);
+@end smallexample
+
+@node Altera Nios II Built-in Functions
+@subsection Altera Nios II Built-in Functions
+
+These built-in functions are available for the Altera Nios II
+family of processors.
+
+The following built-in functions are always available. They
+all generate the machine instruction that is part of the name.
+
+@example
+int __builtin_ldbio (volatile const void *);
+int __builtin_ldbuio (volatile const void *);
+int __builtin_ldhio (volatile const void *);
+int __builtin_ldhuio (volatile const void *);
+int __builtin_ldwio (volatile const void *);
+void __builtin_stbio (volatile void *, int);
+void __builtin_sthio (volatile void *, int);
+void __builtin_stwio (volatile void *, int);
+void __builtin_sync (void);
+int __builtin_rdctl (int);
+int __builtin_rdprs (int, int);
+void __builtin_wrctl (int, int);
+void __builtin_flushd (volatile void *);
+void __builtin_flushda (volatile void *);
+int __builtin_wrpie (int);
+void __builtin_eni (int);
+int __builtin_ldex (volatile const void *);
+int __builtin_stex (volatile void *, int);
+int __builtin_ldsex (volatile const void *);
+int __builtin_stsex (volatile void *, int);
+@end example
+
+The following built-in functions are always available. They
+all generate a Nios II Custom Instruction. The name of the
+function represents the types that the function takes and
+returns. The letter before the @code{n} is the return type
+or void if absent. The @code{n} represents the first parameter
+to all the custom instructions, the custom instruction number.
+The two letters after the @code{n} represent the up to two
+parameters to the function.
+
+The letters represent the following data types:
+@table @code
+@item <no letter>
+@code{void} for return type and no parameter for parameter types.
+
+@item i
+@code{int} for return type and parameter type
+
+@item f
+@code{float} for return type and parameter type
+
+@item p
+@code{void *} for return type and parameter type
+
+@end table
+
+And the function names are:
+@example
+void __builtin_custom_n (void);
+void __builtin_custom_ni (int);
+void __builtin_custom_nf (float);
+void __builtin_custom_np (void *);
+void __builtin_custom_nii (int, int);
+void __builtin_custom_nif (int, float);
+void __builtin_custom_nip (int, void *);
+void __builtin_custom_nfi (float, int);
+void __builtin_custom_nff (float, float);
+void __builtin_custom_nfp (float, void *);
+void __builtin_custom_npi (void *, int);
+void __builtin_custom_npf (void *, float);
+void __builtin_custom_npp (void *, void *);
+int __builtin_custom_in (void);
+int __builtin_custom_ini (int);
+int __builtin_custom_inf (float);
+int __builtin_custom_inp (void *);
+int __builtin_custom_inii (int, int);
+int __builtin_custom_inif (int, float);
+int __builtin_custom_inip (int, void *);
+int __builtin_custom_infi (float, int);
+int __builtin_custom_inff (float, float);
+int __builtin_custom_infp (float, void *);
+int __builtin_custom_inpi (void *, int);
+int __builtin_custom_inpf (void *, float);
+int __builtin_custom_inpp (void *, void *);
+float __builtin_custom_fn (void);
+float __builtin_custom_fni (int);
+float __builtin_custom_fnf (float);
+float __builtin_custom_fnp (void *);
+float __builtin_custom_fnii (int, int);
+float __builtin_custom_fnif (int, float);
+float __builtin_custom_fnip (int, void *);
+float __builtin_custom_fnfi (float, int);
+float __builtin_custom_fnff (float, float);
+float __builtin_custom_fnfp (float, void *);
+float __builtin_custom_fnpi (void *, int);
+float __builtin_custom_fnpf (void *, float);
+float __builtin_custom_fnpp (void *, void *);
+void * __builtin_custom_pn (void);
+void * __builtin_custom_pni (int);
+void * __builtin_custom_pnf (float);
+void * __builtin_custom_pnp (void *);
+void * __builtin_custom_pnii (int, int);
+void * __builtin_custom_pnif (int, float);
+void * __builtin_custom_pnip (int, void *);
+void * __builtin_custom_pnfi (float, int);
+void * __builtin_custom_pnff (float, float);
+void * __builtin_custom_pnfp (float, void *);
+void * __builtin_custom_pnpi (void *, int);
+void * __builtin_custom_pnpf (void *, float);
+void * __builtin_custom_pnpp (void *, void *);
+@end example
+
+@node ARC Built-in Functions
+@subsection ARC Built-in Functions
+
+The following built-in functions are provided for ARC targets. The
+built-ins generate the corresponding assembly instructions. In the
+examples given below, the generated code often requires an operand or
+result to be in a register. Where necessary further code will be
+generated to ensure this is true, but for brevity this is not
+described in each case.
+
+@emph{Note:} Using a built-in to generate an instruction not supported
+by a target may cause problems. At present the compiler is not
+guaranteed to detect such misuse, and as a result an internal compiler
+error may be generated.
+
+@deftypefn {Built-in Function} int __builtin_arc_aligned (void *@var{val}, int @var{alignval})
+Return 1 if @var{val} is known to have the byte alignment given
+by @var{alignval}, otherwise return 0.
+Note that this is different from
+@smallexample
+__alignof__(*(char *)@var{val}) >= alignval
+@end smallexample
+because __alignof__ sees only the type of the dereference, whereas
+__builtin_arc_align uses alignment information from the pointer
+as well as from the pointed-to type.
+The information available will depend on optimization level.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_brk (void)
+Generates
+@example
+brk
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} {unsigned int} __builtin_arc_core_read (unsigned int @var{regno})
+The operand is the number of a register to be read. Generates:
+@example
+mov @var{dest}, r@var{regno}
+@end example
+where the value in @var{dest} will be the result returned from the
+built-in.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_core_write (unsigned int @var{regno}, unsigned int @var{val})
+The first operand is the number of a register to be written, the
+second operand is a compile time constant to write into that
+register. Generates:
+@example
+mov r@var{regno}, @var{val}
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_arc_divaw (int @var{a}, int @var{b})
+Only available if either @option{-mcpu=ARC700} or @option{-meA} is set.
+Generates:
+@example
+divaw @var{dest}, @var{a}, @var{b}
+@end example
+where the value in @var{dest} will be the result returned from the
+built-in.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_flag (unsigned int @var{a})
+Generates
+@example
+flag @var{a}
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} {unsigned int} __builtin_arc_lr (unsigned int @var{auxr})
+The operand, @var{auxv}, is the address of an auxiliary register and
+must be a compile time constant. Generates:
+@example
+lr @var{dest}, [@var{auxr}]
+@end example
+Where the value in @var{dest} will be the result returned from the
+built-in.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_mul64 (int @var{a}, int @var{b})
+Only available with @option{-mmul64}. Generates:
+@example
+mul64 @var{a}, @var{b}
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_mulu64 (unsigned int @var{a}, unsigned int @var{b})
+Only available with @option{-mmul64}. Generates:
+@example
+mulu64 @var{a}, @var{b}
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_nop (void)
+Generates:
+@example
+nop
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_arc_norm (int @var{src})
+Only valid if the @samp{norm} instruction is available through the
+@option{-mnorm} option or by default with @option{-mcpu=ARC700}.
+Generates:
+@example
+norm @var{dest}, @var{src}
+@end example
+Where the value in @var{dest} will be the result returned from the
+built-in.
+@end deftypefn
+
+@deftypefn {Built-in Function} {short int} __builtin_arc_normw (short int @var{src})
+Only valid if the @samp{normw} instruction is available through the
+@option{-mnorm} option or by default with @option{-mcpu=ARC700}.
+Generates:
+@example
+normw @var{dest}, @var{src}
+@end example
+Where the value in @var{dest} will be the result returned from the
+built-in.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_rtie (void)
+Generates:
+@example
+rtie
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_sleep (int @var{a}
+Generates:
+@example
+sleep @var{a}
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_sr (unsigned int @var{val}, unsigned int @var{auxr})
+The first argument, @var{val}, is a compile time constant to be
+written to the register, the second argument, @var{auxr}, is the
+address of an auxiliary register. Generates:
+@example
+sr @var{val}, [@var{auxr}]
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_arc_swap (int @var{src})
+Only valid with @option{-mswap}. Generates:
+@example
+swap @var{dest}, @var{src}
+@end example
+Where the value in @var{dest} will be the result returned from the
+built-in.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_swi (void)
+Generates:
+@example
+swi
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_sync (void)
+Only available with @option{-mcpu=ARC700}. Generates:
+@example
+sync
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_trap_s (unsigned int @var{c})
+Only available with @option{-mcpu=ARC700}. Generates:
+@example
+trap_s @var{c}
+@end example
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_arc_unimp_s (void)
+Only available with @option{-mcpu=ARC700}. Generates:
+@example
+unimp_s
+@end example
+@end deftypefn
+
+The instructions generated by the following builtins are not
+considered as candidates for scheduling. They are not moved around by
+the compiler during scheduling, and thus can be expected to appear
+where they are put in the C code:
+@example
+__builtin_arc_brk()
+__builtin_arc_core_read()
+__builtin_arc_core_write()
+__builtin_arc_flag()
+__builtin_arc_lr()
+__builtin_arc_sleep()
+__builtin_arc_sr()
+__builtin_arc_swi()
+@end example
+
+@node ARC SIMD Built-in Functions
+@subsection ARC SIMD Built-in Functions
+
+SIMD builtins provided by the compiler can be used to generate the
+vector instructions. This section describes the available builtins
+and their usage in programs. With the @option{-msimd} option, the
+compiler provides 128-bit vector types, which can be specified using
+the @code{vector_size} attribute. The header file @file{arc-simd.h}
+can be included to use the following predefined types:
+@example
+typedef int __v4si __attribute__((vector_size(16)));
+typedef short __v8hi __attribute__((vector_size(16)));
+@end example
+
+These types can be used to define 128-bit variables. The built-in
+functions listed in the following section can be used on these
+variables to generate the vector operations.
+
+For all builtins, @code{__builtin_arc_@var{someinsn}}, the header file
+@file{arc-simd.h} also provides equivalent macros called
+@code{_@var{someinsn}} that can be used for programming ease and
+improved readability. The following macros for DMA control are also
+provided:
+@example
+#define _setup_dma_in_channel_reg _vdiwr
+#define _setup_dma_out_channel_reg _vdowr
+@end example
+
+The following is a complete list of all the SIMD built-ins provided
+for ARC, grouped by calling signature.
+
+The following take two @code{__v8hi} arguments and return a
+@code{__v8hi} result:
+@example
+__v8hi __builtin_arc_vaddaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vaddw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vand (__v8hi, __v8hi);
+__v8hi __builtin_arc_vandaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vavb (__v8hi, __v8hi);
+__v8hi __builtin_arc_vavrb (__v8hi, __v8hi);
+__v8hi __builtin_arc_vbic (__v8hi, __v8hi);
+__v8hi __builtin_arc_vbicaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vdifaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vdifw (__v8hi, __v8hi);
+__v8hi __builtin_arc_veqw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vh264f (__v8hi, __v8hi);
+__v8hi __builtin_arc_vh264ft (__v8hi, __v8hi);
+__v8hi __builtin_arc_vh264fw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vlew (__v8hi, __v8hi);
+__v8hi __builtin_arc_vltw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmaxaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmaxw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vminaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vminw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr1aw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr1w (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr2aw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr2w (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr3aw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr3w (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr4aw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr4w (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr5aw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr5w (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr6aw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr6w (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr7aw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmr7w (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmrb (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmulaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmulfaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmulfw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vmulw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vnew (__v8hi, __v8hi);
+__v8hi __builtin_arc_vor (__v8hi, __v8hi);
+__v8hi __builtin_arc_vsubaw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vsubw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vsummw (__v8hi, __v8hi);
+__v8hi __builtin_arc_vvc1f (__v8hi, __v8hi);
+__v8hi __builtin_arc_vvc1ft (__v8hi, __v8hi);
+__v8hi __builtin_arc_vxor (__v8hi, __v8hi);
+__v8hi __builtin_arc_vxoraw (__v8hi, __v8hi);
+@end example
+
+The following take one @code{__v8hi} and one @code{int} argument and return a
+@code{__v8hi} result:
+
+@example
+__v8hi __builtin_arc_vbaddw (__v8hi, int);
+__v8hi __builtin_arc_vbmaxw (__v8hi, int);
+__v8hi __builtin_arc_vbminw (__v8hi, int);
+__v8hi __builtin_arc_vbmulaw (__v8hi, int);
+__v8hi __builtin_arc_vbmulfw (__v8hi, int);
+__v8hi __builtin_arc_vbmulw (__v8hi, int);
+__v8hi __builtin_arc_vbrsubw (__v8hi, int);
+__v8hi __builtin_arc_vbsubw (__v8hi, int);
+@end example
+
+The following take one @code{__v8hi} argument and one @code{int} argument which
+must be a 3-bit compile time constant indicating a register number
+I0-I7. They return a @code{__v8hi} result.
+@example
+__v8hi __builtin_arc_vasrw (__v8hi, const int);
+__v8hi __builtin_arc_vsr8 (__v8hi, const int);
+__v8hi __builtin_arc_vsr8aw (__v8hi, const int);
+@end example
+
+The following take one @code{__v8hi} argument and one @code{int}
+argument which must be a 6-bit compile time constant. They return a
+@code{__v8hi} result.
+@example
+__v8hi __builtin_arc_vasrpwbi (__v8hi, const int);
+__v8hi __builtin_arc_vasrrpwbi (__v8hi, const int);
+__v8hi __builtin_arc_vasrrwi (__v8hi, const int);
+__v8hi __builtin_arc_vasrsrwi (__v8hi, const int);
+__v8hi __builtin_arc_vasrwi (__v8hi, const int);
+__v8hi __builtin_arc_vsr8awi (__v8hi, const int);
+__v8hi __builtin_arc_vsr8i (__v8hi, const int);
+@end example
+
+The following take one @code{__v8hi} argument and one @code{int} argument which
+must be a 8-bit compile time constant. They return a @code{__v8hi}
+result.
+@example
+__v8hi __builtin_arc_vd6tapf (__v8hi, const int);
+__v8hi __builtin_arc_vmvaw (__v8hi, const int);
+__v8hi __builtin_arc_vmvw (__v8hi, const int);
+__v8hi __builtin_arc_vmvzw (__v8hi, const int);
+@end example
+
+The following take two @code{int} arguments, the second of which which
+must be a 8-bit compile time constant. They return a @code{__v8hi}
+result:
+@example
+__v8hi __builtin_arc_vmovaw (int, const int);
+__v8hi __builtin_arc_vmovw (int, const int);
+__v8hi __builtin_arc_vmovzw (int, const int);
+@end example
+
+The following take a single @code{__v8hi} argument and return a
+@code{__v8hi} result:
+@example
+__v8hi __builtin_arc_vabsaw (__v8hi);
+__v8hi __builtin_arc_vabsw (__v8hi);
+__v8hi __builtin_arc_vaddsuw (__v8hi);
+__v8hi __builtin_arc_vexch1 (__v8hi);
+__v8hi __builtin_arc_vexch2 (__v8hi);
+__v8hi __builtin_arc_vexch4 (__v8hi);
+__v8hi __builtin_arc_vsignw (__v8hi);
+__v8hi __builtin_arc_vupbaw (__v8hi);
+__v8hi __builtin_arc_vupbw (__v8hi);
+__v8hi __builtin_arc_vupsbaw (__v8hi);
+__v8hi __builtin_arc_vupsbw (__v8hi);
+@end example
+
+The following take two @code{int} arguments and return no result:
+@example
+void __builtin_arc_vdirun (int, int);
+void __builtin_arc_vdorun (int, int);
+@end example
+
+The following take two @code{int} arguments and return no result. The
+first argument must a 3-bit compile time constant indicating one of
+the DR0-DR7 DMA setup channels:
+@example
+void __builtin_arc_vdiwr (const int, int);
+void __builtin_arc_vdowr (const int, int);
+@end example
+
+The following take an @code{int} argument and return no result:
+@example
+void __builtin_arc_vendrec (int);
+void __builtin_arc_vrec (int);
+void __builtin_arc_vrecrun (int);
+void __builtin_arc_vrun (int);
+@end example
+
+The following take a @code{__v8hi} argument and two @code{int}
+arguments and return a @code{__v8hi} result. The second argument must
+be a 3-bit compile time constants, indicating one the registers I0-I7,
+and the third argument must be an 8-bit compile time constant.
+
+@emph{Note:} Although the equivalent hardware instructions do not take
+an SIMD register as an operand, these builtins overwrite the relevant
+bits of the @code{__v8hi} register provided as the first argument with
+the value loaded from the @code{[Ib, u8]} location in the SDM.
+
+@example
+__v8hi __builtin_arc_vld32 (__v8hi, const int, const int);
+__v8hi __builtin_arc_vld32wh (__v8hi, const int, const int);
+__v8hi __builtin_arc_vld32wl (__v8hi, const int, const int);
+__v8hi __builtin_arc_vld64 (__v8hi, const int, const int);
+@end example
+
+The following take two @code{int} arguments and return a @code{__v8hi}
+result. The first argument must be a 3-bit compile time constants,
+indicating one the registers I0-I7, and the second argument must be an
+8-bit compile time constant.
+
+@example
+__v8hi __builtin_arc_vld128 (const int, const int);
+__v8hi __builtin_arc_vld64w (const int, const int);
+@end example
+
+The following take a @code{__v8hi} argument and two @code{int}
+arguments and return no result. The second argument must be a 3-bit
+compile time constants, indicating one the registers I0-I7, and the
+third argument must be an 8-bit compile time constant.
+
+@example
+void __builtin_arc_vst128 (__v8hi, const int, const int);
+void __builtin_arc_vst64 (__v8hi, const int, const int);
+@end example
+
+The following take a @code{__v8hi} argument and three @code{int}
+arguments and return no result. The second argument must be a 3-bit
+compile-time constant, identifying the 16-bit sub-register to be
+stored, the third argument must be a 3-bit compile time constants,
+indicating one the registers I0-I7, and the fourth argument must be an
+8-bit compile time constant.
+
+@example
+void __builtin_arc_vst16_n (__v8hi, const int, const int, const int);
+void __builtin_arc_vst32_n (__v8hi, const int, const int, const int);
+@end example
+
+@node ARM iWMMXt Built-in Functions
+@subsection ARM iWMMXt Built-in Functions
+
+These built-in functions are available for the ARM family of
+processors when the @option{-mcpu=iwmmxt} switch is used:
+
+@smallexample
+typedef int v2si __attribute__ ((vector_size (8)));
+typedef short v4hi __attribute__ ((vector_size (8)));
+typedef char v8qi __attribute__ ((vector_size (8)));
+
+int __builtin_arm_getwcgr0 (void);
+void __builtin_arm_setwcgr0 (int);
+int __builtin_arm_getwcgr1 (void);
+void __builtin_arm_setwcgr1 (int);
+int __builtin_arm_getwcgr2 (void);
+void __builtin_arm_setwcgr2 (int);
+int __builtin_arm_getwcgr3 (void);
+void __builtin_arm_setwcgr3 (int);
+int __builtin_arm_textrmsb (v8qi, int);
+int __builtin_arm_textrmsh (v4hi, int);
+int __builtin_arm_textrmsw (v2si, int);
+int __builtin_arm_textrmub (v8qi, int);
+int __builtin_arm_textrmuh (v4hi, int);
+int __builtin_arm_textrmuw (v2si, int);
+v8qi __builtin_arm_tinsrb (v8qi, int, int);
+v4hi __builtin_arm_tinsrh (v4hi, int, int);
+v2si __builtin_arm_tinsrw (v2si, int, int);
+long long __builtin_arm_tmia (long long, int, int);
+long long __builtin_arm_tmiabb (long long, int, int);
+long long __builtin_arm_tmiabt (long long, int, int);
+long long __builtin_arm_tmiaph (long long, int, int);
+long long __builtin_arm_tmiatb (long long, int, int);
+long long __builtin_arm_tmiatt (long long, int, int);
+int __builtin_arm_tmovmskb (v8qi);
+int __builtin_arm_tmovmskh (v4hi);
+int __builtin_arm_tmovmskw (v2si);
+long long __builtin_arm_waccb (v8qi);
+long long __builtin_arm_wacch (v4hi);
+long long __builtin_arm_waccw (v2si);
+v8qi __builtin_arm_waddb (v8qi, v8qi);
+v8qi __builtin_arm_waddbss (v8qi, v8qi);
+v8qi __builtin_arm_waddbus (v8qi, v8qi);
+v4hi __builtin_arm_waddh (v4hi, v4hi);
+v4hi __builtin_arm_waddhss (v4hi, v4hi);
+v4hi __builtin_arm_waddhus (v4hi, v4hi);
+v2si __builtin_arm_waddw (v2si, v2si);
+v2si __builtin_arm_waddwss (v2si, v2si);
+v2si __builtin_arm_waddwus (v2si, v2si);
+v8qi __builtin_arm_walign (v8qi, v8qi, int);
+long long __builtin_arm_wand(long long, long long);
+long long __builtin_arm_wandn (long long, long long);
+v8qi __builtin_arm_wavg2b (v8qi, v8qi);
+v8qi __builtin_arm_wavg2br (v8qi, v8qi);
+v4hi __builtin_arm_wavg2h (v4hi, v4hi);
+v4hi __builtin_arm_wavg2hr (v4hi, v4hi);
+v8qi __builtin_arm_wcmpeqb (v8qi, v8qi);
+v4hi __builtin_arm_wcmpeqh (v4hi, v4hi);
+v2si __builtin_arm_wcmpeqw (v2si, v2si);
+v8qi __builtin_arm_wcmpgtsb (v8qi, v8qi);
+v4hi __builtin_arm_wcmpgtsh (v4hi, v4hi);
+v2si __builtin_arm_wcmpgtsw (v2si, v2si);
+v8qi __builtin_arm_wcmpgtub (v8qi, v8qi);
+v4hi __builtin_arm_wcmpgtuh (v4hi, v4hi);
+v2si __builtin_arm_wcmpgtuw (v2si, v2si);
+long long __builtin_arm_wmacs (long long, v4hi, v4hi);
+long long __builtin_arm_wmacsz (v4hi, v4hi);
+long long __builtin_arm_wmacu (long long, v4hi, v4hi);
+long long __builtin_arm_wmacuz (v4hi, v4hi);
+v4hi __builtin_arm_wmadds (v4hi, v4hi);
+v4hi __builtin_arm_wmaddu (v4hi, v4hi);
+v8qi __builtin_arm_wmaxsb (v8qi, v8qi);
+v4hi __builtin_arm_wmaxsh (v4hi, v4hi);
+v2si __builtin_arm_wmaxsw (v2si, v2si);
+v8qi __builtin_arm_wmaxub (v8qi, v8qi);
+v4hi __builtin_arm_wmaxuh (v4hi, v4hi);
+v2si __builtin_arm_wmaxuw (v2si, v2si);
+v8qi __builtin_arm_wminsb (v8qi, v8qi);
+v4hi __builtin_arm_wminsh (v4hi, v4hi);
+v2si __builtin_arm_wminsw (v2si, v2si);
+v8qi __builtin_arm_wminub (v8qi, v8qi);
+v4hi __builtin_arm_wminuh (v4hi, v4hi);
+v2si __builtin_arm_wminuw (v2si, v2si);
+v4hi __builtin_arm_wmulsm (v4hi, v4hi);
+v4hi __builtin_arm_wmulul (v4hi, v4hi);
+v4hi __builtin_arm_wmulum (v4hi, v4hi);
+long long __builtin_arm_wor (long long, long long);
+v2si __builtin_arm_wpackdss (long long, long long);
+v2si __builtin_arm_wpackdus (long long, long long);
+v8qi __builtin_arm_wpackhss (v4hi, v4hi);
+v8qi __builtin_arm_wpackhus (v4hi, v4hi);
+v4hi __builtin_arm_wpackwss (v2si, v2si);
+v4hi __builtin_arm_wpackwus (v2si, v2si);
+long long __builtin_arm_wrord (long long, long long);
+long long __builtin_arm_wrordi (long long, int);
+v4hi __builtin_arm_wrorh (v4hi, long long);
+v4hi __builtin_arm_wrorhi (v4hi, int);
+v2si __builtin_arm_wrorw (v2si, long long);
+v2si __builtin_arm_wrorwi (v2si, int);
+v2si __builtin_arm_wsadb (v2si, v8qi, v8qi);
+v2si __builtin_arm_wsadbz (v8qi, v8qi);
+v2si __builtin_arm_wsadh (v2si, v4hi, v4hi);
+v2si __builtin_arm_wsadhz (v4hi, v4hi);
+v4hi __builtin_arm_wshufh (v4hi, int);
+long long __builtin_arm_wslld (long long, long long);
+long long __builtin_arm_wslldi (long long, int);
+v4hi __builtin_arm_wsllh (v4hi, long long);
+v4hi __builtin_arm_wsllhi (v4hi, int);
+v2si __builtin_arm_wsllw (v2si, long long);
+v2si __builtin_arm_wsllwi (v2si, int);
+long long __builtin_arm_wsrad (long long, long long);
+long long __builtin_arm_wsradi (long long, int);
+v4hi __builtin_arm_wsrah (v4hi, long long);
+v4hi __builtin_arm_wsrahi (v4hi, int);
+v2si __builtin_arm_wsraw (v2si, long long);
+v2si __builtin_arm_wsrawi (v2si, int);
+long long __builtin_arm_wsrld (long long, long long);
+long long __builtin_arm_wsrldi (long long, int);
+v4hi __builtin_arm_wsrlh (v4hi, long long);
+v4hi __builtin_arm_wsrlhi (v4hi, int);
+v2si __builtin_arm_wsrlw (v2si, long long);
+v2si __builtin_arm_wsrlwi (v2si, int);
+v8qi __builtin_arm_wsubb (v8qi, v8qi);
+v8qi __builtin_arm_wsubbss (v8qi, v8qi);
+v8qi __builtin_arm_wsubbus (v8qi, v8qi);
+v4hi __builtin_arm_wsubh (v4hi, v4hi);
+v4hi __builtin_arm_wsubhss (v4hi, v4hi);
+v4hi __builtin_arm_wsubhus (v4hi, v4hi);
+v2si __builtin_arm_wsubw (v2si, v2si);
+v2si __builtin_arm_wsubwss (v2si, v2si);
+v2si __builtin_arm_wsubwus (v2si, v2si);
+v4hi __builtin_arm_wunpckehsb (v8qi);
+v2si __builtin_arm_wunpckehsh (v4hi);
+long long __builtin_arm_wunpckehsw (v2si);
+v4hi __builtin_arm_wunpckehub (v8qi);
+v2si __builtin_arm_wunpckehuh (v4hi);
+long long __builtin_arm_wunpckehuw (v2si);
+v4hi __builtin_arm_wunpckelsb (v8qi);
+v2si __builtin_arm_wunpckelsh (v4hi);
+long long __builtin_arm_wunpckelsw (v2si);
+v4hi __builtin_arm_wunpckelub (v8qi);
+v2si __builtin_arm_wunpckeluh (v4hi);
+long long __builtin_arm_wunpckeluw (v2si);
+v8qi __builtin_arm_wunpckihb (v8qi, v8qi);
+v4hi __builtin_arm_wunpckihh (v4hi, v4hi);
+v2si __builtin_arm_wunpckihw (v2si, v2si);
+v8qi __builtin_arm_wunpckilb (v8qi, v8qi);
+v4hi __builtin_arm_wunpckilh (v4hi, v4hi);
+v2si __builtin_arm_wunpckilw (v2si, v2si);
+long long __builtin_arm_wxor (long long, long long);
+long long __builtin_arm_wzero ();
+@end smallexample
+
+
+@node ARM C Language Extensions (ACLE)
+@subsection ARM C Language Extensions (ACLE)
+
+GCC implements extensions for C as described in the ARM C Language
+Extensions (ACLE) specification, which can be found at
+@uref{https://developer.arm.com/documentation/ihi0053/latest/}.
+
+As a part of ACLE, GCC implements extensions for Advanced SIMD as described in
+the ARM C Language Extensions Specification. The complete list of Advanced SIMD
+intrinsics can be found at
+@uref{https://developer.arm.com/documentation/ihi0073/latest/}.
+The built-in intrinsics for the Advanced SIMD extension are available when
+NEON is enabled.
+
+Currently, ARM and AArch64 back ends do not support ACLE 2.0 fully. Both
+back ends support CRC32 intrinsics and the ARM back end supports the
+Coprocessor intrinsics, all from @file{arm_acle.h}. The ARM back end's 16-bit
+floating-point Advanced SIMD intrinsics currently comply to ACLE v1.1.
+AArch64's back end does not have support for 16-bit floating point Advanced SIMD
+intrinsics yet.
+
+See @ref{ARM Options} and @ref{AArch64 Options} for more information on the
+availability of extensions.
+
+@node ARM Floating Point Status and Control Intrinsics
+@subsection ARM Floating Point Status and Control Intrinsics
+
+These built-in functions are available for the ARM family of
+processors with floating-point unit.
+
+@smallexample
+unsigned int __builtin_arm_get_fpscr ();
+void __builtin_arm_set_fpscr (unsigned int);
+@end smallexample
+
+@node ARM ARMv8-M Security Extensions
+@subsection ARM ARMv8-M Security Extensions
+
+GCC implements the ARMv8-M Security Extensions as described in the ARMv8-M
+Security Extensions: Requirements on Development Tools Engineering
+Specification, which can be found at
+@uref{https://developer.arm.com/documentation/ecm0359818/latest/}.
+
+As part of the Security Extensions GCC implements two new function attributes:
+@code{cmse_nonsecure_entry} and @code{cmse_nonsecure_call}.
+
+As part of the Security Extensions GCC implements the intrinsics below. FPTR
+is used here to mean any function pointer type.
+
+@smallexample
+cmse_address_info_t cmse_TT (void *);
+cmse_address_info_t cmse_TT_fptr (FPTR);
+cmse_address_info_t cmse_TTT (void *);
+cmse_address_info_t cmse_TTT_fptr (FPTR);
+cmse_address_info_t cmse_TTA (void *);
+cmse_address_info_t cmse_TTA_fptr (FPTR);
+cmse_address_info_t cmse_TTAT (void *);
+cmse_address_info_t cmse_TTAT_fptr (FPTR);
+void * cmse_check_address_range (void *, size_t, int);
+typeof(p) cmse_nsfptr_create (FPTR p);
+intptr_t cmse_is_nsfptr (FPTR);
+int cmse_nonsecure_caller (void);
+@end smallexample
+
+@node AVR Built-in Functions
+@subsection AVR Built-in Functions
+
+For each built-in function for AVR, there is an equally named,
+uppercase built-in macro defined. That way users can easily query if
+or if not a specific built-in is implemented or not. For example, if
+@code{__builtin_avr_nop} is available the macro
+@code{__BUILTIN_AVR_NOP} is defined to @code{1} and undefined otherwise.
+
+@table @code
+
+@item void __builtin_avr_nop (void)
+@itemx void __builtin_avr_sei (void)
+@itemx void __builtin_avr_cli (void)
+@itemx void __builtin_avr_sleep (void)
+@itemx void __builtin_avr_wdr (void)
+@itemx unsigned char __builtin_avr_swap (unsigned char)
+@itemx unsigned int __builtin_avr_fmul (unsigned char, unsigned char)
+@itemx int __builtin_avr_fmuls (char, char)
+@itemx int __builtin_avr_fmulsu (char, unsigned char)
+These built-in functions map to the respective machine
+instruction, i.e.@: @code{nop}, @code{sei}, @code{cli}, @code{sleep},
+@code{wdr}, @code{swap}, @code{fmul}, @code{fmuls}
+resp. @code{fmulsu}. The three @code{fmul*} built-ins are implemented
+as library call if no hardware multiplier is available.
+
+@item void __builtin_avr_delay_cycles (unsigned long ticks)
+Delay execution for @var{ticks} cycles. Note that this
+built-in does not take into account the effect of interrupts that
+might increase delay time. @var{ticks} must be a compile-time
+integer constant; delays with a variable number of cycles are not supported.
+
+@item char __builtin_avr_flash_segment (const __memx void*)
+This built-in takes a byte address to the 24-bit
+@ref{AVR Named Address Spaces,address space} @code{__memx} and returns
+the number of the flash segment (the 64 KiB chunk) where the address
+points to. Counting starts at @code{0}.
+If the address does not point to flash memory, return @code{-1}.
+
+@item uint8_t __builtin_avr_insert_bits (uint32_t map, uint8_t bits, uint8_t val)
+Insert bits from @var{bits} into @var{val} and return the resulting
+value. The nibbles of @var{map} determine how the insertion is
+performed: Let @var{X} be the @var{n}-th nibble of @var{map}
+@enumerate
+@item If @var{X} is @code{0xf},
+then the @var{n}-th bit of @var{val} is returned unaltered.
+
+@item If X is in the range 0@dots{}7,
+then the @var{n}-th result bit is set to the @var{X}-th bit of @var{bits}
+
+@item If X is in the range 8@dots{}@code{0xe},
+then the @var{n}-th result bit is undefined.
+@end enumerate
+
+@noindent
+One typical use case for this built-in is adjusting input and
+output values to non-contiguous port layouts. Some examples:
+
+@smallexample
+// same as val, bits is unused
+__builtin_avr_insert_bits (0xffffffff, bits, val);
+@end smallexample
+
+@smallexample
+// same as bits, val is unused
+__builtin_avr_insert_bits (0x76543210, bits, val);
+@end smallexample
+
+@smallexample
+// same as rotating bits by 4
+__builtin_avr_insert_bits (0x32107654, bits, 0);
+@end smallexample
+
+@smallexample
+// high nibble of result is the high nibble of val
+// low nibble of result is the low nibble of bits
+__builtin_avr_insert_bits (0xffff3210, bits, val);
+@end smallexample
+
+@smallexample
+// reverse the bit order of bits
+__builtin_avr_insert_bits (0x01234567, bits, 0);
+@end smallexample
+
+@item void __builtin_avr_nops (unsigned count)
+Insert @var{count} @code{NOP} instructions.
+The number of instructions must be a compile-time integer constant.
+
+@end table
+
+@noindent
+There are many more AVR-specific built-in functions that are used to
+implement the ISO/IEC TR 18037 ``Embedded C'' fixed-point functions of
+section 7.18a.6. You don't need to use these built-ins directly.
+Instead, use the declarations as supplied by the @code{stdfix.h} header
+with GNU-C99:
+
+@smallexample
+#include <stdfix.h>
+
+// Re-interpret the bit representation of unsigned 16-bit
+// integer @var{uval} as Q-format 0.16 value.
+unsigned fract get_bits (uint_ur_t uval)
+@{
+ return urbits (uval);
+@}
+@end smallexample
+
+@node Blackfin Built-in Functions
+@subsection Blackfin Built-in Functions
+
+Currently, there are two Blackfin-specific built-in functions. These are
+used for generating @code{CSYNC} and @code{SSYNC} machine insns without
+using inline assembly; by using these built-in functions the compiler can
+automatically add workarounds for hardware errata involving these
+instructions. These functions are named as follows:
+
+@smallexample
+void __builtin_bfin_csync (void);
+void __builtin_bfin_ssync (void);
+@end smallexample
+
+@node BPF Built-in Functions
+@subsection BPF Built-in Functions
+
+The following built-in functions are available for eBPF targets.
+
+@deftypefn {Built-in Function} unsigned long long __builtin_bpf_load_byte (unsigned long long @var{offset})
+Load a byte from the @code{struct sk_buff} packet data pointed by the register @code{%r6} and return it.
+@end deftypefn
+
+@deftypefn {Built-in Function} unsigned long long __builtin_bpf_load_half (unsigned long long @var{offset})
+Load 16-bits from the @code{struct sk_buff} packet data pointed by the register @code{%r6} and return it.
+@end deftypefn
+
+@deftypefn {Built-in Function} unsigned long long __builtin_bpf_load_word (unsigned long long @var{offset})
+Load 32-bits from the @code{struct sk_buff} packet data pointed by the register @code{%r6} and return it.
+@end deftypefn
+
+@deftypefn {Built-in Function} void * __builtin_preserve_access_index (@var{expr})
+BPF Compile Once-Run Everywhere (CO-RE) support. Instruct GCC to generate CO-RE relocation records for any accesses to aggregate data structures (struct, union, array types) in @var{expr}. This builtin is otherwise transparent, the return value is whatever @var{expr} evaluates to. It is also overloaded: @var{expr} may be of any type (not necessarily a pointer), the return type is the same. Has no effect if @code{-mco-re} is not in effect (either specified or implied).
+@end deftypefn
+
+@deftypefn {Built-in Function} unsigned int __builtin_preserve_field_info (@var{expr}, unsigned int @var{kind})
+BPF Compile Once-Run Everywhere (CO-RE) support. This builtin is used to
+extract information to aid in struct/union relocations. @var{expr} is
+an access to a field of a struct or union. Depending on @var{kind}, different
+information is returned to the program. A CO-RE relocation for the access in
+@var{expr} with kind @var{kind} is recorded if @code{-mco-re} is in effect.
+
+The following values are supported for @var{kind}:
+@table @var
+@item FIELD_BYTE_OFFSET = 0
+The returned value is the offset, in bytes, of the field from the
+beginning of the containing structure. For bitfields, the byte offset
+of the containing word.
+
+@item FIELD_BYTE_SIZE = 1
+The returned value is the size, in bytes, of the field. For bitfields,
+the size in bytes of the containing word.
+
+@item FIELD_EXISTENCE = 2
+The returned value is 1 if the field exists, 0 otherwise. Always 1 at
+compile time.
+
+@item FIELD_SIGNEDNESS = 3
+The returned value is 1 if the field is signed, 0 otherwise.
+
+@item FIELD_LSHIFT_U64 = 4
+@itemx FIELD_RSHIFT_U64 = 5
+The returned value is the number of bits of left- or right-shifting
+respectively needed in order to recover the original value of the field,
+after it has been loaded by a read of FIELD_BYTE_SIZE bytes into an
+unsigned 64-bit value. Primarily useful for reading bitfield values
+from structures which may change between kernel versions.
+
+@end table
+
+Note that the return value is a constant which is known at
+compile-time. If the field has a variable offset then
+FIELD_BYTE_OFFSET, FIELD_LSHIFT_U64 and FIELD_RSHIFT_U64 are not
+supported. Similarly, if the field has a variable size then
+FIELD_BYTE_SIZE, FIELD_LSHIFT_U64 and FIELD_RSHIFT_U64 are not
+supported.
+
+For example, __builtin_preserve_field_info can be used to reliably
+extract bitfield values from a structure which may change between
+kernel versions:
+
+@example
+struct S
+@{
+ short a;
+ int x:7;
+ int y:5;
+@};
+
+int
+read_y (struct S *arg)
+@{
+ unsigned long long val;
+ unsigned int offset = __builtin_preserve_field_info (arg->y, FIELD_BYTE_OFFSET);
+ unsigned int size = __builtin_presrve_field_info (arg->y, FIELD_BYTE_SIZE);
+
+ /* Read size bytes from arg + offset into val. */
+ bpf_probe_read (&val, size, arg + offset);
+
+ val <<= __builtin_preserve_field_info (arg->y, FIELD_LSHIFT_U64);
+
+ if (__builtin_preserve_field_info (arg->y, FIELD_SIGNEDNESS))
+ val = ((long long) val >> __builtin_preserve_field_info (arg->y, FIELD_RSHIFT_U64));
+ else
+ val >>= __builtin_preserve_field_info (arg->y, FIELD_RSHIFT_U64);
+
+ return val;
+@}
+
+@end example
+@end deftypefn
+
+@node FR-V Built-in Functions
+@subsection FR-V Built-in Functions
+
+GCC provides many FR-V-specific built-in functions. In general,
+these functions are intended to be compatible with those described
+by @cite{FR-V Family, Softune C/C++ Compiler Manual (V6), Fujitsu
+Semiconductor}. The two exceptions are @code{__MDUNPACKH} and
+@code{__MBTOHE}, the GCC forms of which pass 128-bit values by
+pointer rather than by value.
+
+Most of the functions are named after specific FR-V instructions.
+Such functions are said to be ``directly mapped'' and are summarized
+here in tabular form.
+
+@menu
+* Argument Types::
+* Directly-mapped Integer Functions::
+* Directly-mapped Media Functions::
+* Raw read/write Functions::
+* Other Built-in Functions::
+@end menu
+
+@node Argument Types
+@subsubsection Argument Types
+
+The arguments to the built-in functions can be divided into three groups:
+register numbers, compile-time constants and run-time values. In order
+to make this classification clear at a glance, the arguments and return
+values are given the following pseudo types:
+
+@multitable @columnfractions .20 .30 .15 .35
+@headitem Pseudo type @tab Real C type @tab Constant? @tab Description
+@item @code{uh} @tab @code{unsigned short} @tab No @tab an unsigned halfword
+@item @code{uw1} @tab @code{unsigned int} @tab No @tab an unsigned word
+@item @code{sw1} @tab @code{int} @tab No @tab a signed word
+@item @code{uw2} @tab @code{unsigned long long} @tab No
+@tab an unsigned doubleword
+@item @code{sw2} @tab @code{long long} @tab No @tab a signed doubleword
+@item @code{const} @tab @code{int} @tab Yes @tab an integer constant
+@item @code{acc} @tab @code{int} @tab Yes @tab an ACC register number
+@item @code{iacc} @tab @code{int} @tab Yes @tab an IACC register number
+@end multitable
+
+These pseudo types are not defined by GCC, they are simply a notational
+convenience used in this manual.
+
+Arguments of type @code{uh}, @code{uw1}, @code{sw1}, @code{uw2}
+and @code{sw2} are evaluated at run time. They correspond to
+register operands in the underlying FR-V instructions.
+
+@code{const} arguments represent immediate operands in the underlying
+FR-V instructions. They must be compile-time constants.
+
+@code{acc} arguments are evaluated at compile time and specify the number
+of an accumulator register. For example, an @code{acc} argument of 2
+selects the ACC2 register.
+
+@code{iacc} arguments are similar to @code{acc} arguments but specify the
+number of an IACC register. See @pxref{Other Built-in Functions}
+for more details.
+
+@node Directly-mapped Integer Functions
+@subsubsection Directly-Mapped Integer Functions
+
+The functions listed below map directly to FR-V I-type instructions.
+
+@multitable @columnfractions .45 .32 .23
+@headitem Function prototype @tab Example usage @tab Assembly output
+@item @code{sw1 __ADDSS (sw1, sw1)}
+@tab @code{@var{c} = __ADDSS (@var{a}, @var{b})}
+@tab @code{ADDSS @var{a},@var{b},@var{c}}
+@item @code{sw1 __SCAN (sw1, sw1)}
+@tab @code{@var{c} = __SCAN (@var{a}, @var{b})}
+@tab @code{SCAN @var{a},@var{b},@var{c}}
+@item @code{sw1 __SCUTSS (sw1)}
+@tab @code{@var{b} = __SCUTSS (@var{a})}
+@tab @code{SCUTSS @var{a},@var{b}}
+@item @code{sw1 __SLASS (sw1, sw1)}
+@tab @code{@var{c} = __SLASS (@var{a}, @var{b})}
+@tab @code{SLASS @var{a},@var{b},@var{c}}
+@item @code{void __SMASS (sw1, sw1)}
+@tab @code{__SMASS (@var{a}, @var{b})}
+@tab @code{SMASS @var{a},@var{b}}
+@item @code{void __SMSSS (sw1, sw1)}
+@tab @code{__SMSSS (@var{a}, @var{b})}
+@tab @code{SMSSS @var{a},@var{b}}
+@item @code{void __SMU (sw1, sw1)}
+@tab @code{__SMU (@var{a}, @var{b})}
+@tab @code{SMU @var{a},@var{b}}
+@item @code{sw2 __SMUL (sw1, sw1)}
+@tab @code{@var{c} = __SMUL (@var{a}, @var{b})}
+@tab @code{SMUL @var{a},@var{b},@var{c}}
+@item @code{sw1 __SUBSS (sw1, sw1)}
+@tab @code{@var{c} = __SUBSS (@var{a}, @var{b})}
+@tab @code{SUBSS @var{a},@var{b},@var{c}}
+@item @code{uw2 __UMUL (uw1, uw1)}
+@tab @code{@var{c} = __UMUL (@var{a}, @var{b})}
+@tab @code{UMUL @var{a},@var{b},@var{c}}
+@end multitable
+
+@node Directly-mapped Media Functions
+@subsubsection Directly-Mapped Media Functions
+
+The functions listed below map directly to FR-V M-type instructions.
+
+@multitable @columnfractions .45 .32 .23
+@headitem Function prototype @tab Example usage @tab Assembly output
+@item @code{uw1 __MABSHS (sw1)}
+@tab @code{@var{b} = __MABSHS (@var{a})}
+@tab @code{MABSHS @var{a},@var{b}}
+@item @code{void __MADDACCS (acc, acc)}
+@tab @code{__MADDACCS (@var{b}, @var{a})}
+@tab @code{MADDACCS @var{a},@var{b}}
+@item @code{sw1 __MADDHSS (sw1, sw1)}
+@tab @code{@var{c} = __MADDHSS (@var{a}, @var{b})}
+@tab @code{MADDHSS @var{a},@var{b},@var{c}}
+@item @code{uw1 __MADDHUS (uw1, uw1)}
+@tab @code{@var{c} = __MADDHUS (@var{a}, @var{b})}
+@tab @code{MADDHUS @var{a},@var{b},@var{c}}
+@item @code{uw1 __MAND (uw1, uw1)}
+@tab @code{@var{c} = __MAND (@var{a}, @var{b})}
+@tab @code{MAND @var{a},@var{b},@var{c}}
+@item @code{void __MASACCS (acc, acc)}
+@tab @code{__MASACCS (@var{b}, @var{a})}
+@tab @code{MASACCS @var{a},@var{b}}
+@item @code{uw1 __MAVEH (uw1, uw1)}
+@tab @code{@var{c} = __MAVEH (@var{a}, @var{b})}
+@tab @code{MAVEH @var{a},@var{b},@var{c}}
+@item @code{uw2 __MBTOH (uw1)}
+@tab @code{@var{b} = __MBTOH (@var{a})}
+@tab @code{MBTOH @var{a},@var{b}}
+@item @code{void __MBTOHE (uw1 *, uw1)}
+@tab @code{__MBTOHE (&@var{b}, @var{a})}
+@tab @code{MBTOHE @var{a},@var{b}}
+@item @code{void __MCLRACC (acc)}
+@tab @code{__MCLRACC (@var{a})}
+@tab @code{MCLRACC @var{a}}
+@item @code{void __MCLRACCA (void)}
+@tab @code{__MCLRACCA ()}
+@tab @code{MCLRACCA}
+@item @code{uw1 __Mcop1 (uw1, uw1)}
+@tab @code{@var{c} = __Mcop1 (@var{a}, @var{b})}
+@tab @code{Mcop1 @var{a},@var{b},@var{c}}
+@item @code{uw1 __Mcop2 (uw1, uw1)}
+@tab @code{@var{c} = __Mcop2 (@var{a}, @var{b})}
+@tab @code{Mcop2 @var{a},@var{b},@var{c}}
+@item @code{uw1 __MCPLHI (uw2, const)}
+@tab @code{@var{c} = __MCPLHI (@var{a}, @var{b})}
+@tab @code{MCPLHI @var{a},#@var{b},@var{c}}
+@item @code{uw1 __MCPLI (uw2, const)}
+@tab @code{@var{c} = __MCPLI (@var{a}, @var{b})}
+@tab @code{MCPLI @var{a},#@var{b},@var{c}}
+@item @code{void __MCPXIS (acc, sw1, sw1)}
+@tab @code{__MCPXIS (@var{c}, @var{a}, @var{b})}
+@tab @code{MCPXIS @var{a},@var{b},@var{c}}
+@item @code{void __MCPXIU (acc, uw1, uw1)}
+@tab @code{__MCPXIU (@var{c}, @var{a}, @var{b})}
+@tab @code{MCPXIU @var{a},@var{b},@var{c}}
+@item @code{void __MCPXRS (acc, sw1, sw1)}
+@tab @code{__MCPXRS (@var{c}, @var{a}, @var{b})}
+@tab @code{MCPXRS @var{a},@var{b},@var{c}}
+@item @code{void __MCPXRU (acc, uw1, uw1)}
+@tab @code{__MCPXRU (@var{c}, @var{a}, @var{b})}
+@tab @code{MCPXRU @var{a},@var{b},@var{c}}
+@item @code{uw1 __MCUT (acc, uw1)}
+@tab @code{@var{c} = __MCUT (@var{a}, @var{b})}
+@tab @code{MCUT @var{a},@var{b},@var{c}}
+@item @code{uw1 __MCUTSS (acc, sw1)}
+@tab @code{@var{c} = __MCUTSS (@var{a}, @var{b})}
+@tab @code{MCUTSS @var{a},@var{b},@var{c}}
+@item @code{void __MDADDACCS (acc, acc)}
+@tab @code{__MDADDACCS (@var{b}, @var{a})}
+@tab @code{MDADDACCS @var{a},@var{b}}
+@item @code{void __MDASACCS (acc, acc)}
+@tab @code{__MDASACCS (@var{b}, @var{a})}
+@tab @code{MDASACCS @var{a},@var{b}}
+@item @code{uw2 __MDCUTSSI (acc, const)}
+@tab @code{@var{c} = __MDCUTSSI (@var{a}, @var{b})}
+@tab @code{MDCUTSSI @var{a},#@var{b},@var{c}}
+@item @code{uw2 __MDPACKH (uw2, uw2)}
+@tab @code{@var{c} = __MDPACKH (@var{a}, @var{b})}
+@tab @code{MDPACKH @var{a},@var{b},@var{c}}
+@item @code{uw2 __MDROTLI (uw2, const)}
+@tab @code{@var{c} = __MDROTLI (@var{a}, @var{b})}
+@tab @code{MDROTLI @var{a},#@var{b},@var{c}}
+@item @code{void __MDSUBACCS (acc, acc)}
+@tab @code{__MDSUBACCS (@var{b}, @var{a})}
+@tab @code{MDSUBACCS @var{a},@var{b}}
+@item @code{void __MDUNPACKH (uw1 *, uw2)}
+@tab @code{__MDUNPACKH (&@var{b}, @var{a})}
+@tab @code{MDUNPACKH @var{a},@var{b}}
+@item @code{uw2 __MEXPDHD (uw1, const)}
+@tab @code{@var{c} = __MEXPDHD (@var{a}, @var{b})}
+@tab @code{MEXPDHD @var{a},#@var{b},@var{c}}
+@item @code{uw1 __MEXPDHW (uw1, const)}
+@tab @code{@var{c} = __MEXPDHW (@var{a}, @var{b})}
+@tab @code{MEXPDHW @var{a},#@var{b},@var{c}}
+@item @code{uw1 __MHDSETH (uw1, const)}
+@tab @code{@var{c} = __MHDSETH (@var{a}, @var{b})}
+@tab @code{MHDSETH @var{a},#@var{b},@var{c}}
+@item @code{sw1 __MHDSETS (const)}
+@tab @code{@var{b} = __MHDSETS (@var{a})}
+@tab @code{MHDSETS #@var{a},@var{b}}
+@item @code{uw1 __MHSETHIH (uw1, const)}
+@tab @code{@var{b} = __MHSETHIH (@var{b}, @var{a})}
+@tab @code{MHSETHIH #@var{a},@var{b}}
+@item @code{sw1 __MHSETHIS (sw1, const)}
+@tab @code{@var{b} = __MHSETHIS (@var{b}, @var{a})}
+@tab @code{MHSETHIS #@var{a},@var{b}}
+@item @code{uw1 __MHSETLOH (uw1, const)}
+@tab @code{@var{b} = __MHSETLOH (@var{b}, @var{a})}
+@tab @code{MHSETLOH #@var{a},@var{b}}
+@item @code{sw1 __MHSETLOS (sw1, const)}
+@tab @code{@var{b} = __MHSETLOS (@var{b}, @var{a})}
+@tab @code{MHSETLOS #@var{a},@var{b}}
+@item @code{uw1 __MHTOB (uw2)}
+@tab @code{@var{b} = __MHTOB (@var{a})}
+@tab @code{MHTOB @var{a},@var{b}}
+@item @code{void __MMACHS (acc, sw1, sw1)}
+@tab @code{__MMACHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MMACHS @var{a},@var{b},@var{c}}
+@item @code{void __MMACHU (acc, uw1, uw1)}
+@tab @code{__MMACHU (@var{c}, @var{a}, @var{b})}
+@tab @code{MMACHU @var{a},@var{b},@var{c}}
+@item @code{void __MMRDHS (acc, sw1, sw1)}
+@tab @code{__MMRDHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MMRDHS @var{a},@var{b},@var{c}}
+@item @code{void __MMRDHU (acc, uw1, uw1)}
+@tab @code{__MMRDHU (@var{c}, @var{a}, @var{b})}
+@tab @code{MMRDHU @var{a},@var{b},@var{c}}
+@item @code{void __MMULHS (acc, sw1, sw1)}
+@tab @code{__MMULHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MMULHS @var{a},@var{b},@var{c}}
+@item @code{void __MMULHU (acc, uw1, uw1)}
+@tab @code{__MMULHU (@var{c}, @var{a}, @var{b})}
+@tab @code{MMULHU @var{a},@var{b},@var{c}}
+@item @code{void __MMULXHS (acc, sw1, sw1)}
+@tab @code{__MMULXHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MMULXHS @var{a},@var{b},@var{c}}
+@item @code{void __MMULXHU (acc, uw1, uw1)}
+@tab @code{__MMULXHU (@var{c}, @var{a}, @var{b})}
+@tab @code{MMULXHU @var{a},@var{b},@var{c}}
+@item @code{uw1 __MNOT (uw1)}
+@tab @code{@var{b} = __MNOT (@var{a})}
+@tab @code{MNOT @var{a},@var{b}}
+@item @code{uw1 __MOR (uw1, uw1)}
+@tab @code{@var{c} = __MOR (@var{a}, @var{b})}
+@tab @code{MOR @var{a},@var{b},@var{c}}
+@item @code{uw1 __MPACKH (uh, uh)}
+@tab @code{@var{c} = __MPACKH (@var{a}, @var{b})}
+@tab @code{MPACKH @var{a},@var{b},@var{c}}
+@item @code{sw2 __MQADDHSS (sw2, sw2)}
+@tab @code{@var{c} = __MQADDHSS (@var{a}, @var{b})}
+@tab @code{MQADDHSS @var{a},@var{b},@var{c}}
+@item @code{uw2 __MQADDHUS (uw2, uw2)}
+@tab @code{@var{c} = __MQADDHUS (@var{a}, @var{b})}
+@tab @code{MQADDHUS @var{a},@var{b},@var{c}}
+@item @code{void __MQCPXIS (acc, sw2, sw2)}
+@tab @code{__MQCPXIS (@var{c}, @var{a}, @var{b})}
+@tab @code{MQCPXIS @var{a},@var{b},@var{c}}
+@item @code{void __MQCPXIU (acc, uw2, uw2)}
+@tab @code{__MQCPXIU (@var{c}, @var{a}, @var{b})}
+@tab @code{MQCPXIU @var{a},@var{b},@var{c}}
+@item @code{void __MQCPXRS (acc, sw2, sw2)}
+@tab @code{__MQCPXRS (@var{c}, @var{a}, @var{b})}
+@tab @code{MQCPXRS @var{a},@var{b},@var{c}}
+@item @code{void __MQCPXRU (acc, uw2, uw2)}
+@tab @code{__MQCPXRU (@var{c}, @var{a}, @var{b})}
+@tab @code{MQCPXRU @var{a},@var{b},@var{c}}
+@item @code{sw2 __MQLCLRHS (sw2, sw2)}
+@tab @code{@var{c} = __MQLCLRHS (@var{a}, @var{b})}
+@tab @code{MQLCLRHS @var{a},@var{b},@var{c}}
+@item @code{sw2 __MQLMTHS (sw2, sw2)}
+@tab @code{@var{c} = __MQLMTHS (@var{a}, @var{b})}
+@tab @code{MQLMTHS @var{a},@var{b},@var{c}}
+@item @code{void __MQMACHS (acc, sw2, sw2)}
+@tab @code{__MQMACHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MQMACHS @var{a},@var{b},@var{c}}
+@item @code{void __MQMACHU (acc, uw2, uw2)}
+@tab @code{__MQMACHU (@var{c}, @var{a}, @var{b})}
+@tab @code{MQMACHU @var{a},@var{b},@var{c}}
+@item @code{void __MQMACXHS (acc, sw2, sw2)}
+@tab @code{__MQMACXHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MQMACXHS @var{a},@var{b},@var{c}}
+@item @code{void __MQMULHS (acc, sw2, sw2)}
+@tab @code{__MQMULHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MQMULHS @var{a},@var{b},@var{c}}
+@item @code{void __MQMULHU (acc, uw2, uw2)}
+@tab @code{__MQMULHU (@var{c}, @var{a}, @var{b})}
+@tab @code{MQMULHU @var{a},@var{b},@var{c}}
+@item @code{void __MQMULXHS (acc, sw2, sw2)}
+@tab @code{__MQMULXHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MQMULXHS @var{a},@var{b},@var{c}}
+@item @code{void __MQMULXHU (acc, uw2, uw2)}
+@tab @code{__MQMULXHU (@var{c}, @var{a}, @var{b})}
+@tab @code{MQMULXHU @var{a},@var{b},@var{c}}
+@item @code{sw2 __MQSATHS (sw2, sw2)}
+@tab @code{@var{c} = __MQSATHS (@var{a}, @var{b})}
+@tab @code{MQSATHS @var{a},@var{b},@var{c}}
+@item @code{uw2 __MQSLLHI (uw2, int)}
+@tab @code{@var{c} = __MQSLLHI (@var{a}, @var{b})}
+@tab @code{MQSLLHI @var{a},@var{b},@var{c}}
+@item @code{sw2 __MQSRAHI (sw2, int)}
+@tab @code{@var{c} = __MQSRAHI (@var{a}, @var{b})}
+@tab @code{MQSRAHI @var{a},@var{b},@var{c}}
+@item @code{sw2 __MQSUBHSS (sw2, sw2)}
+@tab @code{@var{c} = __MQSUBHSS (@var{a}, @var{b})}
+@tab @code{MQSUBHSS @var{a},@var{b},@var{c}}
+@item @code{uw2 __MQSUBHUS (uw2, uw2)}
+@tab @code{@var{c} = __MQSUBHUS (@var{a}, @var{b})}
+@tab @code{MQSUBHUS @var{a},@var{b},@var{c}}
+@item @code{void __MQXMACHS (acc, sw2, sw2)}
+@tab @code{__MQXMACHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MQXMACHS @var{a},@var{b},@var{c}}
+@item @code{void __MQXMACXHS (acc, sw2, sw2)}
+@tab @code{__MQXMACXHS (@var{c}, @var{a}, @var{b})}
+@tab @code{MQXMACXHS @var{a},@var{b},@var{c}}
+@item @code{uw1 __MRDACC (acc)}
+@tab @code{@var{b} = __MRDACC (@var{a})}
+@tab @code{MRDACC @var{a},@var{b}}
+@item @code{uw1 __MRDACCG (acc)}
+@tab @code{@var{b} = __MRDACCG (@var{a})}
+@tab @code{MRDACCG @var{a},@var{b}}
+@item @code{uw1 __MROTLI (uw1, const)}
+@tab @code{@var{c} = __MROTLI (@var{a}, @var{b})}
+@tab @code{MROTLI @var{a},#@var{b},@var{c}}
+@item @code{uw1 __MROTRI (uw1, const)}
+@tab @code{@var{c} = __MROTRI (@var{a}, @var{b})}
+@tab @code{MROTRI @var{a},#@var{b},@var{c}}
+@item @code{sw1 __MSATHS (sw1, sw1)}
+@tab @code{@var{c} = __MSATHS (@var{a}, @var{b})}
+@tab @code{MSATHS @var{a},@var{b},@var{c}}
+@item @code{uw1 __MSATHU (uw1, uw1)}
+@tab @code{@var{c} = __MSATHU (@var{a}, @var{b})}
+@tab @code{MSATHU @var{a},@var{b},@var{c}}
+@item @code{uw1 __MSLLHI (uw1, const)}
+@tab @code{@var{c} = __MSLLHI (@var{a}, @var{b})}
+@tab @code{MSLLHI @var{a},#@var{b},@var{c}}
+@item @code{sw1 __MSRAHI (sw1, const)}
+@tab @code{@var{c} = __MSRAHI (@var{a}, @var{b})}
+@tab @code{MSRAHI @var{a},#@var{b},@var{c}}
+@item @code{uw1 __MSRLHI (uw1, const)}
+@tab @code{@var{c} = __MSRLHI (@var{a}, @var{b})}
+@tab @code{MSRLHI @var{a},#@var{b},@var{c}}
+@item @code{void __MSUBACCS (acc, acc)}
+@tab @code{__MSUBACCS (@var{b}, @var{a})}
+@tab @code{MSUBACCS @var{a},@var{b}}
+@item @code{sw1 __MSUBHSS (sw1, sw1)}
+@tab @code{@var{c} = __MSUBHSS (@var{a}, @var{b})}
+@tab @code{MSUBHSS @var{a},@var{b},@var{c}}
+@item @code{uw1 __MSUBHUS (uw1, uw1)}
+@tab @code{@var{c} = __MSUBHUS (@var{a}, @var{b})}
+@tab @code{MSUBHUS @var{a},@var{b},@var{c}}
+@item @code{void __MTRAP (void)}
+@tab @code{__MTRAP ()}
+@tab @code{MTRAP}
+@item @code{uw2 __MUNPACKH (uw1)}
+@tab @code{@var{b} = __MUNPACKH (@var{a})}
+@tab @code{MUNPACKH @var{a},@var{b}}
+@item @code{uw1 __MWCUT (uw2, uw1)}
+@tab @code{@var{c} = __MWCUT (@var{a}, @var{b})}
+@tab @code{MWCUT @var{a},@var{b},@var{c}}
+@item @code{void __MWTACC (acc, uw1)}
+@tab @code{__MWTACC (@var{b}, @var{a})}
+@tab @code{MWTACC @var{a},@var{b}}
+@item @code{void __MWTACCG (acc, uw1)}
+@tab @code{__MWTACCG (@var{b}, @var{a})}
+@tab @code{MWTACCG @var{a},@var{b}}
+@item @code{uw1 __MXOR (uw1, uw1)}
+@tab @code{@var{c} = __MXOR (@var{a}, @var{b})}
+@tab @code{MXOR @var{a},@var{b},@var{c}}
+@end multitable
+
+@node Raw read/write Functions
+@subsubsection Raw Read/Write Functions
+
+This sections describes built-in functions related to read and write
+instructions to access memory. These functions generate
+@code{membar} instructions to flush the I/O load and stores where
+appropriate, as described in Fujitsu's manual described above.
+
+@table @code
+
+@item unsigned char __builtin_read8 (void *@var{data})
+@item unsigned short __builtin_read16 (void *@var{data})
+@item unsigned long __builtin_read32 (void *@var{data})
+@item unsigned long long __builtin_read64 (void *@var{data})
+
+@item void __builtin_write8 (void *@var{data}, unsigned char @var{datum})
+@item void __builtin_write16 (void *@var{data}, unsigned short @var{datum})
+@item void __builtin_write32 (void *@var{data}, unsigned long @var{datum})
+@item void __builtin_write64 (void *@var{data}, unsigned long long @var{datum})
+@end table
+
+@node Other Built-in Functions
+@subsubsection Other Built-in Functions
+
+This section describes built-in functions that are not named after
+a specific FR-V instruction.
+
+@table @code
+@item sw2 __IACCreadll (iacc @var{reg})
+Return the full 64-bit value of IACC0@. The @var{reg} argument is reserved
+for future expansion and must be 0.
+
+@item sw1 __IACCreadl (iacc @var{reg})
+Return the value of IACC0H if @var{reg} is 0 and IACC0L if @var{reg} is 1.
+Other values of @var{reg} are rejected as invalid.
+
+@item void __IACCsetll (iacc @var{reg}, sw2 @var{x})
+Set the full 64-bit value of IACC0 to @var{x}. The @var{reg} argument
+is reserved for future expansion and must be 0.
+
+@item void __IACCsetl (iacc @var{reg}, sw1 @var{x})
+Set IACC0H to @var{x} if @var{reg} is 0 and IACC0L to @var{x} if @var{reg}
+is 1. Other values of @var{reg} are rejected as invalid.
+
+@item void __data_prefetch0 (const void *@var{x})
+Use the @code{dcpl} instruction to load the contents of address @var{x}
+into the data cache.
+
+@item void __data_prefetch (const void *@var{x})
+Use the @code{nldub} instruction to load the contents of address @var{x}
+into the data cache. The instruction is issued in slot I1@.
+@end table
+
+@node MIPS DSP Built-in Functions
+@subsection MIPS DSP Built-in Functions
+
+The MIPS DSP Application-Specific Extension (ASE) includes new
+instructions that are designed to improve the performance of DSP and
+media applications. It provides instructions that operate on packed
+8-bit/16-bit integer data, Q7, Q15 and Q31 fractional data.
+
+GCC supports MIPS DSP operations using both the generic
+vector extensions (@pxref{Vector Extensions}) and a collection of
+MIPS-specific built-in functions. Both kinds of support are
+enabled by the @option{-mdsp} command-line option.
+
+Revision 2 of the ASE was introduced in the second half of 2006.
+This revision adds extra instructions to the original ASE, but is
+otherwise backwards-compatible with it. You can select revision 2
+using the command-line option @option{-mdspr2}; this option implies
+@option{-mdsp}.
+
+The SCOUNT and POS bits of the DSP control register are global. The
+WRDSP, EXTPDP, EXTPDPV and MTHLIP instructions modify the SCOUNT and
+POS bits. During optimization, the compiler does not delete these
+instructions and it does not delete calls to functions containing
+these instructions.
+
+At present, GCC only provides support for operations on 32-bit
+vectors. The vector type associated with 8-bit integer data is
+usually called @code{v4i8}, the vector type associated with Q7
+is usually called @code{v4q7}, the vector type associated with 16-bit
+integer data is usually called @code{v2i16}, and the vector type
+associated with Q15 is usually called @code{v2q15}. They can be
+defined in C as follows:
+
+@smallexample
+typedef signed char v4i8 __attribute__ ((vector_size(4)));
+typedef signed char v4q7 __attribute__ ((vector_size(4)));
+typedef short v2i16 __attribute__ ((vector_size(4)));
+typedef short v2q15 __attribute__ ((vector_size(4)));
+@end smallexample
+
+@code{v4i8}, @code{v4q7}, @code{v2i16} and @code{v2q15} values are
+initialized in the same way as aggregates. For example:
+
+@smallexample
+v4i8 a = @{1, 2, 3, 4@};
+v4i8 b;
+b = (v4i8) @{5, 6, 7, 8@};
+
+v2q15 c = @{0x0fcb, 0x3a75@};
+v2q15 d;
+d = (v2q15) @{0.1234 * 0x1.0p15, 0.4567 * 0x1.0p15@};
+@end smallexample
+
+@emph{Note:} The CPU's endianness determines the order in which values
+are packed. On little-endian targets, the first value is the least
+significant and the last value is the most significant. The opposite
+order applies to big-endian targets. For example, the code above
+sets the lowest byte of @code{a} to @code{1} on little-endian targets
+and @code{4} on big-endian targets.
+
+@emph{Note:} Q7, Q15 and Q31 values must be initialized with their integer
+representation. As shown in this example, the integer representation
+of a Q7 value can be obtained by multiplying the fractional value by
+@code{0x1.0p7}. The equivalent for Q15 values is to multiply by
+@code{0x1.0p15}. The equivalent for Q31 values is to multiply by
+@code{0x1.0p31}.
+
+The table below lists the @code{v4i8} and @code{v2q15} operations for which
+hardware support exists. @code{a} and @code{b} are @code{v4i8} values,
+and @code{c} and @code{d} are @code{v2q15} values.
+
+@multitable @columnfractions .50 .50
+@headitem C code @tab MIPS instruction
+@item @code{a + b} @tab @code{addu.qb}
+@item @code{c + d} @tab @code{addq.ph}
+@item @code{a - b} @tab @code{subu.qb}
+@item @code{c - d} @tab @code{subq.ph}
+@end multitable
+
+The table below lists the @code{v2i16} operation for which
+hardware support exists for the DSP ASE REV 2. @code{e} and @code{f} are
+@code{v2i16} values.
+
+@multitable @columnfractions .50 .50
+@headitem C code @tab MIPS instruction
+@item @code{e * f} @tab @code{mul.ph}
+@end multitable
+
+It is easier to describe the DSP built-in functions if we first define
+the following types:
+
+@smallexample
+typedef int q31;
+typedef int i32;
+typedef unsigned int ui32;
+typedef long long a64;
+@end smallexample
+
+@code{q31} and @code{i32} are actually the same as @code{int}, but we
+use @code{q31} to indicate a Q31 fractional value and @code{i32} to
+indicate a 32-bit integer value. Similarly, @code{a64} is the same as
+@code{long long}, but we use @code{a64} to indicate values that are
+placed in one of the four DSP accumulators (@code{$ac0},
+@code{$ac1}, @code{$ac2} or @code{$ac3}).
+
+Also, some built-in functions prefer or require immediate numbers as
+parameters, because the corresponding DSP instructions accept both immediate
+numbers and register operands, or accept immediate numbers only. The
+immediate parameters are listed as follows.
+
+@smallexample
+imm0_3: 0 to 3.
+imm0_7: 0 to 7.
+imm0_15: 0 to 15.
+imm0_31: 0 to 31.
+imm0_63: 0 to 63.
+imm0_255: 0 to 255.
+imm_n32_31: -32 to 31.
+imm_n512_511: -512 to 511.
+@end smallexample
+
+The following built-in functions map directly to a particular MIPS DSP
+instruction. Please refer to the architecture specification
+for details on what each instruction does.
+
+@smallexample
+v2q15 __builtin_mips_addq_ph (v2q15, v2q15);
+v2q15 __builtin_mips_addq_s_ph (v2q15, v2q15);
+q31 __builtin_mips_addq_s_w (q31, q31);
+v4i8 __builtin_mips_addu_qb (v4i8, v4i8);
+v4i8 __builtin_mips_addu_s_qb (v4i8, v4i8);
+v2q15 __builtin_mips_subq_ph (v2q15, v2q15);
+v2q15 __builtin_mips_subq_s_ph (v2q15, v2q15);
+q31 __builtin_mips_subq_s_w (q31, q31);
+v4i8 __builtin_mips_subu_qb (v4i8, v4i8);
+v4i8 __builtin_mips_subu_s_qb (v4i8, v4i8);
+i32 __builtin_mips_addsc (i32, i32);
+i32 __builtin_mips_addwc (i32, i32);
+i32 __builtin_mips_modsub (i32, i32);
+i32 __builtin_mips_raddu_w_qb (v4i8);
+v2q15 __builtin_mips_absq_s_ph (v2q15);
+q31 __builtin_mips_absq_s_w (q31);
+v4i8 __builtin_mips_precrq_qb_ph (v2q15, v2q15);
+v2q15 __builtin_mips_precrq_ph_w (q31, q31);
+v2q15 __builtin_mips_precrq_rs_ph_w (q31, q31);
+v4i8 __builtin_mips_precrqu_s_qb_ph (v2q15, v2q15);
+q31 __builtin_mips_preceq_w_phl (v2q15);
+q31 __builtin_mips_preceq_w_phr (v2q15);
+v2q15 __builtin_mips_precequ_ph_qbl (v4i8);
+v2q15 __builtin_mips_precequ_ph_qbr (v4i8);
+v2q15 __builtin_mips_precequ_ph_qbla (v4i8);
+v2q15 __builtin_mips_precequ_ph_qbra (v4i8);
+v2q15 __builtin_mips_preceu_ph_qbl (v4i8);
+v2q15 __builtin_mips_preceu_ph_qbr (v4i8);
+v2q15 __builtin_mips_preceu_ph_qbla (v4i8);
+v2q15 __builtin_mips_preceu_ph_qbra (v4i8);
+v4i8 __builtin_mips_shll_qb (v4i8, imm0_7);
+v4i8 __builtin_mips_shll_qb (v4i8, i32);
+v2q15 __builtin_mips_shll_ph (v2q15, imm0_15);
+v2q15 __builtin_mips_shll_ph (v2q15, i32);
+v2q15 __builtin_mips_shll_s_ph (v2q15, imm0_15);
+v2q15 __builtin_mips_shll_s_ph (v2q15, i32);
+q31 __builtin_mips_shll_s_w (q31, imm0_31);
+q31 __builtin_mips_shll_s_w (q31, i32);
+v4i8 __builtin_mips_shrl_qb (v4i8, imm0_7);
+v4i8 __builtin_mips_shrl_qb (v4i8, i32);
+v2q15 __builtin_mips_shra_ph (v2q15, imm0_15);
+v2q15 __builtin_mips_shra_ph (v2q15, i32);
+v2q15 __builtin_mips_shra_r_ph (v2q15, imm0_15);
+v2q15 __builtin_mips_shra_r_ph (v2q15, i32);
+q31 __builtin_mips_shra_r_w (q31, imm0_31);
+q31 __builtin_mips_shra_r_w (q31, i32);
+v2q15 __builtin_mips_muleu_s_ph_qbl (v4i8, v2q15);
+v2q15 __builtin_mips_muleu_s_ph_qbr (v4i8, v2q15);
+v2q15 __builtin_mips_mulq_rs_ph (v2q15, v2q15);
+q31 __builtin_mips_muleq_s_w_phl (v2q15, v2q15);
+q31 __builtin_mips_muleq_s_w_phr (v2q15, v2q15);
+a64 __builtin_mips_dpau_h_qbl (a64, v4i8, v4i8);
+a64 __builtin_mips_dpau_h_qbr (a64, v4i8, v4i8);
+a64 __builtin_mips_dpsu_h_qbl (a64, v4i8, v4i8);
+a64 __builtin_mips_dpsu_h_qbr (a64, v4i8, v4i8);
+a64 __builtin_mips_dpaq_s_w_ph (a64, v2q15, v2q15);
+a64 __builtin_mips_dpaq_sa_l_w (a64, q31, q31);
+a64 __builtin_mips_dpsq_s_w_ph (a64, v2q15, v2q15);
+a64 __builtin_mips_dpsq_sa_l_w (a64, q31, q31);
+a64 __builtin_mips_mulsaq_s_w_ph (a64, v2q15, v2q15);
+a64 __builtin_mips_maq_s_w_phl (a64, v2q15, v2q15);
+a64 __builtin_mips_maq_s_w_phr (a64, v2q15, v2q15);
+a64 __builtin_mips_maq_sa_w_phl (a64, v2q15, v2q15);
+a64 __builtin_mips_maq_sa_w_phr (a64, v2q15, v2q15);
+i32 __builtin_mips_bitrev (i32);
+i32 __builtin_mips_insv (i32, i32);
+v4i8 __builtin_mips_repl_qb (imm0_255);
+v4i8 __builtin_mips_repl_qb (i32);
+v2q15 __builtin_mips_repl_ph (imm_n512_511);
+v2q15 __builtin_mips_repl_ph (i32);
+void __builtin_mips_cmpu_eq_qb (v4i8, v4i8);
+void __builtin_mips_cmpu_lt_qb (v4i8, v4i8);
+void __builtin_mips_cmpu_le_qb (v4i8, v4i8);
+i32 __builtin_mips_cmpgu_eq_qb (v4i8, v4i8);
+i32 __builtin_mips_cmpgu_lt_qb (v4i8, v4i8);
+i32 __builtin_mips_cmpgu_le_qb (v4i8, v4i8);
+void __builtin_mips_cmp_eq_ph (v2q15, v2q15);
+void __builtin_mips_cmp_lt_ph (v2q15, v2q15);
+void __builtin_mips_cmp_le_ph (v2q15, v2q15);
+v4i8 __builtin_mips_pick_qb (v4i8, v4i8);
+v2q15 __builtin_mips_pick_ph (v2q15, v2q15);
+v2q15 __builtin_mips_packrl_ph (v2q15, v2q15);
+i32 __builtin_mips_extr_w (a64, imm0_31);
+i32 __builtin_mips_extr_w (a64, i32);
+i32 __builtin_mips_extr_r_w (a64, imm0_31);
+i32 __builtin_mips_extr_s_h (a64, i32);
+i32 __builtin_mips_extr_rs_w (a64, imm0_31);
+i32 __builtin_mips_extr_rs_w (a64, i32);
+i32 __builtin_mips_extr_s_h (a64, imm0_31);
+i32 __builtin_mips_extr_r_w (a64, i32);
+i32 __builtin_mips_extp (a64, imm0_31);
+i32 __builtin_mips_extp (a64, i32);
+i32 __builtin_mips_extpdp (a64, imm0_31);
+i32 __builtin_mips_extpdp (a64, i32);
+a64 __builtin_mips_shilo (a64, imm_n32_31);
+a64 __builtin_mips_shilo (a64, i32);
+a64 __builtin_mips_mthlip (a64, i32);
+void __builtin_mips_wrdsp (i32, imm0_63);
+i32 __builtin_mips_rddsp (imm0_63);
+i32 __builtin_mips_lbux (void *, i32);
+i32 __builtin_mips_lhx (void *, i32);
+i32 __builtin_mips_lwx (void *, i32);
+a64 __builtin_mips_ldx (void *, i32); /* MIPS64 only */
+i32 __builtin_mips_bposge32 (void);
+a64 __builtin_mips_madd (a64, i32, i32);
+a64 __builtin_mips_maddu (a64, ui32, ui32);
+a64 __builtin_mips_msub (a64, i32, i32);
+a64 __builtin_mips_msubu (a64, ui32, ui32);
+a64 __builtin_mips_mult (i32, i32);
+a64 __builtin_mips_multu (ui32, ui32);
+@end smallexample
+
+The following built-in functions map directly to a particular MIPS DSP REV 2
+instruction. Please refer to the architecture specification
+for details on what each instruction does.
+
+@smallexample
+v4q7 __builtin_mips_absq_s_qb (v4q7);
+v2i16 __builtin_mips_addu_ph (v2i16, v2i16);
+v2i16 __builtin_mips_addu_s_ph (v2i16, v2i16);
+v4i8 __builtin_mips_adduh_qb (v4i8, v4i8);
+v4i8 __builtin_mips_adduh_r_qb (v4i8, v4i8);
+i32 __builtin_mips_append (i32, i32, imm0_31);
+i32 __builtin_mips_balign (i32, i32, imm0_3);
+i32 __builtin_mips_cmpgdu_eq_qb (v4i8, v4i8);
+i32 __builtin_mips_cmpgdu_lt_qb (v4i8, v4i8);
+i32 __builtin_mips_cmpgdu_le_qb (v4i8, v4i8);
+a64 __builtin_mips_dpa_w_ph (a64, v2i16, v2i16);
+a64 __builtin_mips_dps_w_ph (a64, v2i16, v2i16);
+v2i16 __builtin_mips_mul_ph (v2i16, v2i16);
+v2i16 __builtin_mips_mul_s_ph (v2i16, v2i16);
+q31 __builtin_mips_mulq_rs_w (q31, q31);
+v2q15 __builtin_mips_mulq_s_ph (v2q15, v2q15);
+q31 __builtin_mips_mulq_s_w (q31, q31);
+a64 __builtin_mips_mulsa_w_ph (a64, v2i16, v2i16);
+v4i8 __builtin_mips_precr_qb_ph (v2i16, v2i16);
+v2i16 __builtin_mips_precr_sra_ph_w (i32, i32, imm0_31);
+v2i16 __builtin_mips_precr_sra_r_ph_w (i32, i32, imm0_31);
+i32 __builtin_mips_prepend (i32, i32, imm0_31);
+v4i8 __builtin_mips_shra_qb (v4i8, imm0_7);
+v4i8 __builtin_mips_shra_r_qb (v4i8, imm0_7);
+v4i8 __builtin_mips_shra_qb (v4i8, i32);
+v4i8 __builtin_mips_shra_r_qb (v4i8, i32);
+v2i16 __builtin_mips_shrl_ph (v2i16, imm0_15);
+v2i16 __builtin_mips_shrl_ph (v2i16, i32);
+v2i16 __builtin_mips_subu_ph (v2i16, v2i16);
+v2i16 __builtin_mips_subu_s_ph (v2i16, v2i16);
+v4i8 __builtin_mips_subuh_qb (v4i8, v4i8);
+v4i8 __builtin_mips_subuh_r_qb (v4i8, v4i8);
+v2q15 __builtin_mips_addqh_ph (v2q15, v2q15);
+v2q15 __builtin_mips_addqh_r_ph (v2q15, v2q15);
+q31 __builtin_mips_addqh_w (q31, q31);
+q31 __builtin_mips_addqh_r_w (q31, q31);
+v2q15 __builtin_mips_subqh_ph (v2q15, v2q15);
+v2q15 __builtin_mips_subqh_r_ph (v2q15, v2q15);
+q31 __builtin_mips_subqh_w (q31, q31);
+q31 __builtin_mips_subqh_r_w (q31, q31);
+a64 __builtin_mips_dpax_w_ph (a64, v2i16, v2i16);
+a64 __builtin_mips_dpsx_w_ph (a64, v2i16, v2i16);
+a64 __builtin_mips_dpaqx_s_w_ph (a64, v2q15, v2q15);
+a64 __builtin_mips_dpaqx_sa_w_ph (a64, v2q15, v2q15);
+a64 __builtin_mips_dpsqx_s_w_ph (a64, v2q15, v2q15);
+a64 __builtin_mips_dpsqx_sa_w_ph (a64, v2q15, v2q15);
+@end smallexample
+
+
+@node MIPS Paired-Single Support
+@subsection MIPS Paired-Single Support
+
+The MIPS64 architecture includes a number of instructions that
+operate on pairs of single-precision floating-point values.
+Each pair is packed into a 64-bit floating-point register,
+with one element being designated the ``upper half'' and
+the other being designated the ``lower half''.
+
+GCC supports paired-single operations using both the generic
+vector extensions (@pxref{Vector Extensions}) and a collection of
+MIPS-specific built-in functions. Both kinds of support are
+enabled by the @option{-mpaired-single} command-line option.
+
+The vector type associated with paired-single values is usually
+called @code{v2sf}. It can be defined in C as follows:
+
+@smallexample
+typedef float v2sf __attribute__ ((vector_size (8)));
+@end smallexample
+
+@code{v2sf} values are initialized in the same way as aggregates.
+For example:
+
+@smallexample
+v2sf a = @{1.5, 9.1@};
+v2sf b;
+float e, f;
+b = (v2sf) @{e, f@};
+@end smallexample
+
+@emph{Note:} The CPU's endianness determines which value is stored in
+the upper half of a register and which value is stored in the lower half.
+On little-endian targets, the first value is the lower one and the second
+value is the upper one. The opposite order applies to big-endian targets.
+For example, the code above sets the lower half of @code{a} to
+@code{1.5} on little-endian targets and @code{9.1} on big-endian targets.
+
+@node MIPS Loongson Built-in Functions
+@subsection MIPS Loongson Built-in Functions
+
+GCC provides intrinsics to access the SIMD instructions provided by the
+ST Microelectronics Loongson-2E and -2F processors. These intrinsics,
+available after inclusion of the @code{loongson.h} header file,
+operate on the following 64-bit vector types:
+
+@itemize
+@item @code{uint8x8_t}, a vector of eight unsigned 8-bit integers;
+@item @code{uint16x4_t}, a vector of four unsigned 16-bit integers;
+@item @code{uint32x2_t}, a vector of two unsigned 32-bit integers;
+@item @code{int8x8_t}, a vector of eight signed 8-bit integers;
+@item @code{int16x4_t}, a vector of four signed 16-bit integers;
+@item @code{int32x2_t}, a vector of two signed 32-bit integers.
+@end itemize
+
+The intrinsics provided are listed below; each is named after the
+machine instruction to which it corresponds, with suffixes added as
+appropriate to distinguish intrinsics that expand to the same machine
+instruction yet have different argument types. Refer to the architecture
+documentation for a description of the functionality of each
+instruction.
+
+@smallexample
+int16x4_t packsswh (int32x2_t s, int32x2_t t);
+int8x8_t packsshb (int16x4_t s, int16x4_t t);
+uint8x8_t packushb (uint16x4_t s, uint16x4_t t);
+uint32x2_t paddw_u (uint32x2_t s, uint32x2_t t);
+uint16x4_t paddh_u (uint16x4_t s, uint16x4_t t);
+uint8x8_t paddb_u (uint8x8_t s, uint8x8_t t);
+int32x2_t paddw_s (int32x2_t s, int32x2_t t);
+int16x4_t paddh_s (int16x4_t s, int16x4_t t);
+int8x8_t paddb_s (int8x8_t s, int8x8_t t);
+uint64_t paddd_u (uint64_t s, uint64_t t);
+int64_t paddd_s (int64_t s, int64_t t);
+int16x4_t paddsh (int16x4_t s, int16x4_t t);
+int8x8_t paddsb (int8x8_t s, int8x8_t t);
+uint16x4_t paddush (uint16x4_t s, uint16x4_t t);
+uint8x8_t paddusb (uint8x8_t s, uint8x8_t t);
+uint64_t pandn_ud (uint64_t s, uint64_t t);
+uint32x2_t pandn_uw (uint32x2_t s, uint32x2_t t);
+uint16x4_t pandn_uh (uint16x4_t s, uint16x4_t t);
+uint8x8_t pandn_ub (uint8x8_t s, uint8x8_t t);
+int64_t pandn_sd (int64_t s, int64_t t);
+int32x2_t pandn_sw (int32x2_t s, int32x2_t t);
+int16x4_t pandn_sh (int16x4_t s, int16x4_t t);
+int8x8_t pandn_sb (int8x8_t s, int8x8_t t);
+uint16x4_t pavgh (uint16x4_t s, uint16x4_t t);
+uint8x8_t pavgb (uint8x8_t s, uint8x8_t t);
+uint32x2_t pcmpeqw_u (uint32x2_t s, uint32x2_t t);
+uint16x4_t pcmpeqh_u (uint16x4_t s, uint16x4_t t);
+uint8x8_t pcmpeqb_u (uint8x8_t s, uint8x8_t t);
+int32x2_t pcmpeqw_s (int32x2_t s, int32x2_t t);
+int16x4_t pcmpeqh_s (int16x4_t s, int16x4_t t);
+int8x8_t pcmpeqb_s (int8x8_t s, int8x8_t t);
+uint32x2_t pcmpgtw_u (uint32x2_t s, uint32x2_t t);
+uint16x4_t pcmpgth_u (uint16x4_t s, uint16x4_t t);
+uint8x8_t pcmpgtb_u (uint8x8_t s, uint8x8_t t);
+int32x2_t pcmpgtw_s (int32x2_t s, int32x2_t t);
+int16x4_t pcmpgth_s (int16x4_t s, int16x4_t t);
+int8x8_t pcmpgtb_s (int8x8_t s, int8x8_t t);
+uint16x4_t pextrh_u (uint16x4_t s, int field);
+int16x4_t pextrh_s (int16x4_t s, int field);
+uint16x4_t pinsrh_0_u (uint16x4_t s, uint16x4_t t);
+uint16x4_t pinsrh_1_u (uint16x4_t s, uint16x4_t t);
+uint16x4_t pinsrh_2_u (uint16x4_t s, uint16x4_t t);
+uint16x4_t pinsrh_3_u (uint16x4_t s, uint16x4_t t);
+int16x4_t pinsrh_0_s (int16x4_t s, int16x4_t t);
+int16x4_t pinsrh_1_s (int16x4_t s, int16x4_t t);
+int16x4_t pinsrh_2_s (int16x4_t s, int16x4_t t);
+int16x4_t pinsrh_3_s (int16x4_t s, int16x4_t t);
+int32x2_t pmaddhw (int16x4_t s, int16x4_t t);
+int16x4_t pmaxsh (int16x4_t s, int16x4_t t);
+uint8x8_t pmaxub (uint8x8_t s, uint8x8_t t);
+int16x4_t pminsh (int16x4_t s, int16x4_t t);
+uint8x8_t pminub (uint8x8_t s, uint8x8_t t);
+uint8x8_t pmovmskb_u (uint8x8_t s);
+int8x8_t pmovmskb_s (int8x8_t s);
+uint16x4_t pmulhuh (uint16x4_t s, uint16x4_t t);
+int16x4_t pmulhh (int16x4_t s, int16x4_t t);
+int16x4_t pmullh (int16x4_t s, int16x4_t t);
+int64_t pmuluw (uint32x2_t s, uint32x2_t t);
+uint8x8_t pasubub (uint8x8_t s, uint8x8_t t);
+uint16x4_t biadd (uint8x8_t s);
+uint16x4_t psadbh (uint8x8_t s, uint8x8_t t);
+uint16x4_t pshufh_u (uint16x4_t dest, uint16x4_t s, uint8_t order);
+int16x4_t pshufh_s (int16x4_t dest, int16x4_t s, uint8_t order);
+uint16x4_t psllh_u (uint16x4_t s, uint8_t amount);
+int16x4_t psllh_s (int16x4_t s, uint8_t amount);
+uint32x2_t psllw_u (uint32x2_t s, uint8_t amount);
+int32x2_t psllw_s (int32x2_t s, uint8_t amount);
+uint16x4_t psrlh_u (uint16x4_t s, uint8_t amount);
+int16x4_t psrlh_s (int16x4_t s, uint8_t amount);
+uint32x2_t psrlw_u (uint32x2_t s, uint8_t amount);
+int32x2_t psrlw_s (int32x2_t s, uint8_t amount);
+uint16x4_t psrah_u (uint16x4_t s, uint8_t amount);
+int16x4_t psrah_s (int16x4_t s, uint8_t amount);
+uint32x2_t psraw_u (uint32x2_t s, uint8_t amount);
+int32x2_t psraw_s (int32x2_t s, uint8_t amount);
+uint32x2_t psubw_u (uint32x2_t s, uint32x2_t t);
+uint16x4_t psubh_u (uint16x4_t s, uint16x4_t t);
+uint8x8_t psubb_u (uint8x8_t s, uint8x8_t t);
+int32x2_t psubw_s (int32x2_t s, int32x2_t t);
+int16x4_t psubh_s (int16x4_t s, int16x4_t t);
+int8x8_t psubb_s (int8x8_t s, int8x8_t t);
+uint64_t psubd_u (uint64_t s, uint64_t t);
+int64_t psubd_s (int64_t s, int64_t t);
+int16x4_t psubsh (int16x4_t s, int16x4_t t);
+int8x8_t psubsb (int8x8_t s, int8x8_t t);
+uint16x4_t psubush (uint16x4_t s, uint16x4_t t);
+uint8x8_t psubusb (uint8x8_t s, uint8x8_t t);
+uint32x2_t punpckhwd_u (uint32x2_t s, uint32x2_t t);
+uint16x4_t punpckhhw_u (uint16x4_t s, uint16x4_t t);
+uint8x8_t punpckhbh_u (uint8x8_t s, uint8x8_t t);
+int32x2_t punpckhwd_s (int32x2_t s, int32x2_t t);
+int16x4_t punpckhhw_s (int16x4_t s, int16x4_t t);
+int8x8_t punpckhbh_s (int8x8_t s, int8x8_t t);
+uint32x2_t punpcklwd_u (uint32x2_t s, uint32x2_t t);
+uint16x4_t punpcklhw_u (uint16x4_t s, uint16x4_t t);
+uint8x8_t punpcklbh_u (uint8x8_t s, uint8x8_t t);
+int32x2_t punpcklwd_s (int32x2_t s, int32x2_t t);
+int16x4_t punpcklhw_s (int16x4_t s, int16x4_t t);
+int8x8_t punpcklbh_s (int8x8_t s, int8x8_t t);
+@end smallexample
+
+@menu
+* Paired-Single Arithmetic::
+* Paired-Single Built-in Functions::
+* MIPS-3D Built-in Functions::
+@end menu
+
+@node Paired-Single Arithmetic
+@subsubsection Paired-Single Arithmetic
+
+The table below lists the @code{v2sf} operations for which hardware
+support exists. @code{a}, @code{b} and @code{c} are @code{v2sf}
+values and @code{x} is an integral value.
+
+@multitable @columnfractions .50 .50
+@headitem C code @tab MIPS instruction
+@item @code{a + b} @tab @code{add.ps}
+@item @code{a - b} @tab @code{sub.ps}
+@item @code{-a} @tab @code{neg.ps}
+@item @code{a * b} @tab @code{mul.ps}
+@item @code{a * b + c} @tab @code{madd.ps}
+@item @code{a * b - c} @tab @code{msub.ps}
+@item @code{-(a * b + c)} @tab @code{nmadd.ps}
+@item @code{-(a * b - c)} @tab @code{nmsub.ps}
+@item @code{x ? a : b} @tab @code{movn.ps}/@code{movz.ps}
+@end multitable
+
+Note that the multiply-accumulate instructions can be disabled
+using the command-line option @code{-mno-fused-madd}.
+
+@node Paired-Single Built-in Functions
+@subsubsection Paired-Single Built-in Functions
+
+The following paired-single functions map directly to a particular
+MIPS instruction. Please refer to the architecture specification
+for details on what each instruction does.
+
+@table @code
+@item v2sf __builtin_mips_pll_ps (v2sf, v2sf)
+Pair lower lower (@code{pll.ps}).
+
+@item v2sf __builtin_mips_pul_ps (v2sf, v2sf)
+Pair upper lower (@code{pul.ps}).
+
+@item v2sf __builtin_mips_plu_ps (v2sf, v2sf)
+Pair lower upper (@code{plu.ps}).
+
+@item v2sf __builtin_mips_puu_ps (v2sf, v2sf)
+Pair upper upper (@code{puu.ps}).
+
+@item v2sf __builtin_mips_cvt_ps_s (float, float)
+Convert pair to paired single (@code{cvt.ps.s}).
+
+@item float __builtin_mips_cvt_s_pl (v2sf)
+Convert pair lower to single (@code{cvt.s.pl}).
+
+@item float __builtin_mips_cvt_s_pu (v2sf)
+Convert pair upper to single (@code{cvt.s.pu}).
+
+@item v2sf __builtin_mips_abs_ps (v2sf)
+Absolute value (@code{abs.ps}).
+
+@item v2sf __builtin_mips_alnv_ps (v2sf, v2sf, int)
+Align variable (@code{alnv.ps}).
+
+@emph{Note:} The value of the third parameter must be 0 or 4
+modulo 8, otherwise the result is unpredictable. Please read the
+instruction description for details.
+@end table
+
+The following multi-instruction functions are also available.
+In each case, @var{cond} can be any of the 16 floating-point conditions:
+@code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult},
+@code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq}, @code{ngl},
+@code{lt}, @code{nge}, @code{le} or @code{ngt}.
+
+@table @code
+@item v2sf __builtin_mips_movt_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
+@itemx v2sf __builtin_mips_movf_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
+Conditional move based on floating-point comparison (@code{c.@var{cond}.ps},
+@code{movt.ps}/@code{movf.ps}).
+
+The @code{movt} functions return the value @var{x} computed by:
+
+@smallexample
+c.@var{cond}.ps @var{cc},@var{a},@var{b}
+mov.ps @var{x},@var{c}
+movt.ps @var{x},@var{d},@var{cc}
+@end smallexample
+
+The @code{movf} functions are similar but use @code{movf.ps} instead
+of @code{movt.ps}.
+
+@item int __builtin_mips_upper_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
+@itemx int __builtin_mips_lower_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
+Comparison of two paired-single values (@code{c.@var{cond}.ps},
+@code{bc1t}/@code{bc1f}).
+
+These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps}
+and return either the upper or lower half of the result. For example:
+
+@smallexample
+v2sf a, b;
+if (__builtin_mips_upper_c_eq_ps (a, b))
+ upper_halves_are_equal ();
+else
+ upper_halves_are_unequal ();
+
+if (__builtin_mips_lower_c_eq_ps (a, b))
+ lower_halves_are_equal ();
+else
+ lower_halves_are_unequal ();
+@end smallexample
+@end table
+
+@node MIPS-3D Built-in Functions
+@subsubsection MIPS-3D Built-in Functions
+
+The MIPS-3D Application-Specific Extension (ASE) includes additional
+paired-single instructions that are designed to improve the performance
+of 3D graphics operations. Support for these instructions is controlled
+by the @option{-mips3d} command-line option.
+
+The functions listed below map directly to a particular MIPS-3D
+instruction. Please refer to the architecture specification for
+more details on what each instruction does.
+
+@table @code
+@item v2sf __builtin_mips_addr_ps (v2sf, v2sf)
+Reduction add (@code{addr.ps}).
+
+@item v2sf __builtin_mips_mulr_ps (v2sf, v2sf)
+Reduction multiply (@code{mulr.ps}).
+
+@item v2sf __builtin_mips_cvt_pw_ps (v2sf)
+Convert paired single to paired word (@code{cvt.pw.ps}).
+
+@item v2sf __builtin_mips_cvt_ps_pw (v2sf)
+Convert paired word to paired single (@code{cvt.ps.pw}).
+
+@item float __builtin_mips_recip1_s (float)
+@itemx double __builtin_mips_recip1_d (double)
+@itemx v2sf __builtin_mips_recip1_ps (v2sf)
+Reduced-precision reciprocal (sequence step 1) (@code{recip1.@var{fmt}}).
+
+@item float __builtin_mips_recip2_s (float, float)
+@itemx double __builtin_mips_recip2_d (double, double)
+@itemx v2sf __builtin_mips_recip2_ps (v2sf, v2sf)
+Reduced-precision reciprocal (sequence step 2) (@code{recip2.@var{fmt}}).
+
+@item float __builtin_mips_rsqrt1_s (float)
+@itemx double __builtin_mips_rsqrt1_d (double)
+@itemx v2sf __builtin_mips_rsqrt1_ps (v2sf)
+Reduced-precision reciprocal square root (sequence step 1)
+(@code{rsqrt1.@var{fmt}}).
+
+@item float __builtin_mips_rsqrt2_s (float, float)
+@itemx double __builtin_mips_rsqrt2_d (double, double)
+@itemx v2sf __builtin_mips_rsqrt2_ps (v2sf, v2sf)
+Reduced-precision reciprocal square root (sequence step 2)
+(@code{rsqrt2.@var{fmt}}).
+@end table
+
+The following multi-instruction functions are also available.
+In each case, @var{cond} can be any of the 16 floating-point conditions:
+@code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult},
+@code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq},
+@code{ngl}, @code{lt}, @code{nge}, @code{le} or @code{ngt}.
+
+@table @code
+@item int __builtin_mips_cabs_@var{cond}_s (float @var{a}, float @var{b})
+@itemx int __builtin_mips_cabs_@var{cond}_d (double @var{a}, double @var{b})
+Absolute comparison of two scalar values (@code{cabs.@var{cond}.@var{fmt}},
+@code{bc1t}/@code{bc1f}).
+
+These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.s}
+or @code{cabs.@var{cond}.d} and return the result as a boolean value.
+For example:
+
+@smallexample
+float a, b;
+if (__builtin_mips_cabs_eq_s (a, b))
+ true ();
+else
+ false ();
+@end smallexample
+
+@item int __builtin_mips_upper_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
+@itemx int __builtin_mips_lower_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
+Absolute comparison of two paired-single values (@code{cabs.@var{cond}.ps},
+@code{bc1t}/@code{bc1f}).
+
+These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.ps}
+and return either the upper or lower half of the result. For example:
+
+@smallexample
+v2sf a, b;
+if (__builtin_mips_upper_cabs_eq_ps (a, b))
+ upper_halves_are_equal ();
+else
+ upper_halves_are_unequal ();
+
+if (__builtin_mips_lower_cabs_eq_ps (a, b))
+ lower_halves_are_equal ();
+else
+ lower_halves_are_unequal ();
+@end smallexample
+
+@item v2sf __builtin_mips_movt_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
+@itemx v2sf __builtin_mips_movf_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
+Conditional move based on absolute comparison (@code{cabs.@var{cond}.ps},
+@code{movt.ps}/@code{movf.ps}).
+
+The @code{movt} functions return the value @var{x} computed by:
+
+@smallexample
+cabs.@var{cond}.ps @var{cc},@var{a},@var{b}
+mov.ps @var{x},@var{c}
+movt.ps @var{x},@var{d},@var{cc}
+@end smallexample
+
+The @code{movf} functions are similar but use @code{movf.ps} instead
+of @code{movt.ps}.
+
+@item int __builtin_mips_any_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
+@itemx int __builtin_mips_all_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
+@itemx int __builtin_mips_any_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
+@itemx int __builtin_mips_all_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b})
+Comparison of two paired-single values
+(@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps},
+@code{bc1any2t}/@code{bc1any2f}).
+
+These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps}
+or @code{cabs.@var{cond}.ps}. The @code{any} forms return @code{true} if either
+result is @code{true} and the @code{all} forms return @code{true} if both results are @code{true}.
+For example:
+
+@smallexample
+v2sf a, b;
+if (__builtin_mips_any_c_eq_ps (a, b))
+ one_is_true ();
+else
+ both_are_false ();
+
+if (__builtin_mips_all_c_eq_ps (a, b))
+ both_are_true ();
+else
+ one_is_false ();
+@end smallexample
+
+@item int __builtin_mips_any_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
+@itemx int __builtin_mips_all_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
+@itemx int __builtin_mips_any_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
+@itemx int __builtin_mips_all_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d})
+Comparison of four paired-single values
+(@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps},
+@code{bc1any4t}/@code{bc1any4f}).
+
+These functions use @code{c.@var{cond}.ps} or @code{cabs.@var{cond}.ps}
+to compare @var{a} with @var{b} and to compare @var{c} with @var{d}.
+The @code{any} forms return @code{true} if any of the four results are @code{true}
+and the @code{all} forms return @code{true} if all four results are @code{true}.
+For example:
+
+@smallexample
+v2sf a, b, c, d;
+if (__builtin_mips_any_c_eq_4s (a, b, c, d))
+ some_are_true ();
+else
+ all_are_false ();
+
+if (__builtin_mips_all_c_eq_4s (a, b, c, d))
+ all_are_true ();
+else
+ some_are_false ();
+@end smallexample
+@end table
+
+@node MIPS SIMD Architecture (MSA) Support
+@subsection MIPS SIMD Architecture (MSA) Support
+
+@menu
+* MIPS SIMD Architecture Built-in Functions::
+@end menu
+
+GCC provides intrinsics to access the SIMD instructions provided by the
+MSA MIPS SIMD Architecture. The interface is made available by including
+@code{<msa.h>} and using @option{-mmsa -mhard-float -mfp64 -mnan=2008}.
+For each @code{__builtin_msa_*}, there is a shortened name of the intrinsic,
+@code{__msa_*}.
+
+MSA implements 128-bit wide vector registers, operating on 8-, 16-, 32- and
+64-bit integer, 16- and 32-bit fixed-point, or 32- and 64-bit floating point
+data elements. The following vectors typedefs are included in @code{msa.h}:
+@itemize
+@item @code{v16i8}, a vector of sixteen signed 8-bit integers;
+@item @code{v16u8}, a vector of sixteen unsigned 8-bit integers;
+@item @code{v8i16}, a vector of eight signed 16-bit integers;
+@item @code{v8u16}, a vector of eight unsigned 16-bit integers;
+@item @code{v4i32}, a vector of four signed 32-bit integers;
+@item @code{v4u32}, a vector of four unsigned 32-bit integers;
+@item @code{v2i64}, a vector of two signed 64-bit integers;
+@item @code{v2u64}, a vector of two unsigned 64-bit integers;
+@item @code{v4f32}, a vector of four 32-bit floats;
+@item @code{v2f64}, a vector of two 64-bit doubles.
+@end itemize
+
+Instructions and corresponding built-ins may have additional restrictions and/or
+input/output values manipulated:
+@itemize
+@item @code{imm0_1}, an integer literal in range 0 to 1;
+@item @code{imm0_3}, an integer literal in range 0 to 3;
+@item @code{imm0_7}, an integer literal in range 0 to 7;
+@item @code{imm0_15}, an integer literal in range 0 to 15;
+@item @code{imm0_31}, an integer literal in range 0 to 31;
+@item @code{imm0_63}, an integer literal in range 0 to 63;
+@item @code{imm0_255}, an integer literal in range 0 to 255;
+@item @code{imm_n16_15}, an integer literal in range -16 to 15;
+@item @code{imm_n512_511}, an integer literal in range -512 to 511;
+@item @code{imm_n1024_1022}, an integer literal in range -512 to 511 left
+shifted by 1 bit, i.e., -1024, -1022, @dots{}, 1020, 1022;
+@item @code{imm_n2048_2044}, an integer literal in range -512 to 511 left
+shifted by 2 bits, i.e., -2048, -2044, @dots{}, 2040, 2044;
+@item @code{imm_n4096_4088}, an integer literal in range -512 to 511 left
+shifted by 3 bits, i.e., -4096, -4088, @dots{}, 4080, 4088;
+@item @code{imm1_4}, an integer literal in range 1 to 4;
+@item @code{i32, i64, u32, u64, f32, f64}, defined as follows:
+@end itemize
+
+@smallexample
+@{
+typedef int i32;
+#if __LONG_MAX__ == __LONG_LONG_MAX__
+typedef long i64;
+#else
+typedef long long i64;
+#endif
+
+typedef unsigned int u32;
+#if __LONG_MAX__ == __LONG_LONG_MAX__
+typedef unsigned long u64;
+#else
+typedef unsigned long long u64;
+#endif
+
+typedef double f64;
+typedef float f32;
+@}
+@end smallexample
+
+@node MIPS SIMD Architecture Built-in Functions
+@subsubsection MIPS SIMD Architecture Built-in Functions
+
+The intrinsics provided are listed below; each is named after the
+machine instruction.
+
+@smallexample
+v16i8 __builtin_msa_add_a_b (v16i8, v16i8);
+v8i16 __builtin_msa_add_a_h (v8i16, v8i16);
+v4i32 __builtin_msa_add_a_w (v4i32, v4i32);
+v2i64 __builtin_msa_add_a_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_adds_a_b (v16i8, v16i8);
+v8i16 __builtin_msa_adds_a_h (v8i16, v8i16);
+v4i32 __builtin_msa_adds_a_w (v4i32, v4i32);
+v2i64 __builtin_msa_adds_a_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_adds_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_adds_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_adds_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_adds_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_adds_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_adds_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_adds_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_adds_u_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_addv_b (v16i8, v16i8);
+v8i16 __builtin_msa_addv_h (v8i16, v8i16);
+v4i32 __builtin_msa_addv_w (v4i32, v4i32);
+v2i64 __builtin_msa_addv_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_addvi_b (v16i8, imm0_31);
+v8i16 __builtin_msa_addvi_h (v8i16, imm0_31);
+v4i32 __builtin_msa_addvi_w (v4i32, imm0_31);
+v2i64 __builtin_msa_addvi_d (v2i64, imm0_31);
+
+v16u8 __builtin_msa_and_v (v16u8, v16u8);
+
+v16u8 __builtin_msa_andi_b (v16u8, imm0_255);
+
+v16i8 __builtin_msa_asub_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_asub_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_asub_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_asub_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_asub_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_asub_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_asub_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_asub_u_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_ave_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_ave_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_ave_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_ave_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_ave_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_ave_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_ave_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_ave_u_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_aver_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_aver_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_aver_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_aver_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_aver_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_aver_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_aver_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_aver_u_d (v2u64, v2u64);
+
+v16u8 __builtin_msa_bclr_b (v16u8, v16u8);
+v8u16 __builtin_msa_bclr_h (v8u16, v8u16);
+v4u32 __builtin_msa_bclr_w (v4u32, v4u32);
+v2u64 __builtin_msa_bclr_d (v2u64, v2u64);
+
+v16u8 __builtin_msa_bclri_b (v16u8, imm0_7);
+v8u16 __builtin_msa_bclri_h (v8u16, imm0_15);
+v4u32 __builtin_msa_bclri_w (v4u32, imm0_31);
+v2u64 __builtin_msa_bclri_d (v2u64, imm0_63);
+
+v16u8 __builtin_msa_binsl_b (v16u8, v16u8, v16u8);
+v8u16 __builtin_msa_binsl_h (v8u16, v8u16, v8u16);
+v4u32 __builtin_msa_binsl_w (v4u32, v4u32, v4u32);
+v2u64 __builtin_msa_binsl_d (v2u64, v2u64, v2u64);
+
+v16u8 __builtin_msa_binsli_b (v16u8, v16u8, imm0_7);
+v8u16 __builtin_msa_binsli_h (v8u16, v8u16, imm0_15);
+v4u32 __builtin_msa_binsli_w (v4u32, v4u32, imm0_31);
+v2u64 __builtin_msa_binsli_d (v2u64, v2u64, imm0_63);
+
+v16u8 __builtin_msa_binsr_b (v16u8, v16u8, v16u8);
+v8u16 __builtin_msa_binsr_h (v8u16, v8u16, v8u16);
+v4u32 __builtin_msa_binsr_w (v4u32, v4u32, v4u32);
+v2u64 __builtin_msa_binsr_d (v2u64, v2u64, v2u64);
+
+v16u8 __builtin_msa_binsri_b (v16u8, v16u8, imm0_7);
+v8u16 __builtin_msa_binsri_h (v8u16, v8u16, imm0_15);
+v4u32 __builtin_msa_binsri_w (v4u32, v4u32, imm0_31);
+v2u64 __builtin_msa_binsri_d (v2u64, v2u64, imm0_63);
+
+v16u8 __builtin_msa_bmnz_v (v16u8, v16u8, v16u8);
+
+v16u8 __builtin_msa_bmnzi_b (v16u8, v16u8, imm0_255);
+
+v16u8 __builtin_msa_bmz_v (v16u8, v16u8, v16u8);
+
+v16u8 __builtin_msa_bmzi_b (v16u8, v16u8, imm0_255);
+
+v16u8 __builtin_msa_bneg_b (v16u8, v16u8);
+v8u16 __builtin_msa_bneg_h (v8u16, v8u16);
+v4u32 __builtin_msa_bneg_w (v4u32, v4u32);
+v2u64 __builtin_msa_bneg_d (v2u64, v2u64);
+
+v16u8 __builtin_msa_bnegi_b (v16u8, imm0_7);
+v8u16 __builtin_msa_bnegi_h (v8u16, imm0_15);
+v4u32 __builtin_msa_bnegi_w (v4u32, imm0_31);
+v2u64 __builtin_msa_bnegi_d (v2u64, imm0_63);
+
+i32 __builtin_msa_bnz_b (v16u8);
+i32 __builtin_msa_bnz_h (v8u16);
+i32 __builtin_msa_bnz_w (v4u32);
+i32 __builtin_msa_bnz_d (v2u64);
+
+i32 __builtin_msa_bnz_v (v16u8);
+
+v16u8 __builtin_msa_bsel_v (v16u8, v16u8, v16u8);
+
+v16u8 __builtin_msa_bseli_b (v16u8, v16u8, imm0_255);
+
+v16u8 __builtin_msa_bset_b (v16u8, v16u8);
+v8u16 __builtin_msa_bset_h (v8u16, v8u16);
+v4u32 __builtin_msa_bset_w (v4u32, v4u32);
+v2u64 __builtin_msa_bset_d (v2u64, v2u64);
+
+v16u8 __builtin_msa_bseti_b (v16u8, imm0_7);
+v8u16 __builtin_msa_bseti_h (v8u16, imm0_15);
+v4u32 __builtin_msa_bseti_w (v4u32, imm0_31);
+v2u64 __builtin_msa_bseti_d (v2u64, imm0_63);
+
+i32 __builtin_msa_bz_b (v16u8);
+i32 __builtin_msa_bz_h (v8u16);
+i32 __builtin_msa_bz_w (v4u32);
+i32 __builtin_msa_bz_d (v2u64);
+
+i32 __builtin_msa_bz_v (v16u8);
+
+v16i8 __builtin_msa_ceq_b (v16i8, v16i8);
+v8i16 __builtin_msa_ceq_h (v8i16, v8i16);
+v4i32 __builtin_msa_ceq_w (v4i32, v4i32);
+v2i64 __builtin_msa_ceq_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_ceqi_b (v16i8, imm_n16_15);
+v8i16 __builtin_msa_ceqi_h (v8i16, imm_n16_15);
+v4i32 __builtin_msa_ceqi_w (v4i32, imm_n16_15);
+v2i64 __builtin_msa_ceqi_d (v2i64, imm_n16_15);
+
+i32 __builtin_msa_cfcmsa (imm0_31);
+
+v16i8 __builtin_msa_cle_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_cle_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_cle_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_cle_s_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_cle_u_b (v16u8, v16u8);
+v8i16 __builtin_msa_cle_u_h (v8u16, v8u16);
+v4i32 __builtin_msa_cle_u_w (v4u32, v4u32);
+v2i64 __builtin_msa_cle_u_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_clei_s_b (v16i8, imm_n16_15);
+v8i16 __builtin_msa_clei_s_h (v8i16, imm_n16_15);
+v4i32 __builtin_msa_clei_s_w (v4i32, imm_n16_15);
+v2i64 __builtin_msa_clei_s_d (v2i64, imm_n16_15);
+
+v16i8 __builtin_msa_clei_u_b (v16u8, imm0_31);
+v8i16 __builtin_msa_clei_u_h (v8u16, imm0_31);
+v4i32 __builtin_msa_clei_u_w (v4u32, imm0_31);
+v2i64 __builtin_msa_clei_u_d (v2u64, imm0_31);
+
+v16i8 __builtin_msa_clt_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_clt_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_clt_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_clt_s_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_clt_u_b (v16u8, v16u8);
+v8i16 __builtin_msa_clt_u_h (v8u16, v8u16);
+v4i32 __builtin_msa_clt_u_w (v4u32, v4u32);
+v2i64 __builtin_msa_clt_u_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_clti_s_b (v16i8, imm_n16_15);
+v8i16 __builtin_msa_clti_s_h (v8i16, imm_n16_15);
+v4i32 __builtin_msa_clti_s_w (v4i32, imm_n16_15);
+v2i64 __builtin_msa_clti_s_d (v2i64, imm_n16_15);
+
+v16i8 __builtin_msa_clti_u_b (v16u8, imm0_31);
+v8i16 __builtin_msa_clti_u_h (v8u16, imm0_31);
+v4i32 __builtin_msa_clti_u_w (v4u32, imm0_31);
+v2i64 __builtin_msa_clti_u_d (v2u64, imm0_31);
+
+i32 __builtin_msa_copy_s_b (v16i8, imm0_15);
+i32 __builtin_msa_copy_s_h (v8i16, imm0_7);
+i32 __builtin_msa_copy_s_w (v4i32, imm0_3);
+i64 __builtin_msa_copy_s_d (v2i64, imm0_1);
+
+u32 __builtin_msa_copy_u_b (v16i8, imm0_15);
+u32 __builtin_msa_copy_u_h (v8i16, imm0_7);
+u32 __builtin_msa_copy_u_w (v4i32, imm0_3);
+u64 __builtin_msa_copy_u_d (v2i64, imm0_1);
+
+void __builtin_msa_ctcmsa (imm0_31, i32);
+
+v16i8 __builtin_msa_div_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_div_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_div_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_div_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_div_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_div_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_div_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_div_u_d (v2u64, v2u64);
+
+v8i16 __builtin_msa_dotp_s_h (v16i8, v16i8);
+v4i32 __builtin_msa_dotp_s_w (v8i16, v8i16);
+v2i64 __builtin_msa_dotp_s_d (v4i32, v4i32);
+
+v8u16 __builtin_msa_dotp_u_h (v16u8, v16u8);
+v4u32 __builtin_msa_dotp_u_w (v8u16, v8u16);
+v2u64 __builtin_msa_dotp_u_d (v4u32, v4u32);
+
+v8i16 __builtin_msa_dpadd_s_h (v8i16, v16i8, v16i8);
+v4i32 __builtin_msa_dpadd_s_w (v4i32, v8i16, v8i16);
+v2i64 __builtin_msa_dpadd_s_d (v2i64, v4i32, v4i32);
+
+v8u16 __builtin_msa_dpadd_u_h (v8u16, v16u8, v16u8);
+v4u32 __builtin_msa_dpadd_u_w (v4u32, v8u16, v8u16);
+v2u64 __builtin_msa_dpadd_u_d (v2u64, v4u32, v4u32);
+
+v8i16 __builtin_msa_dpsub_s_h (v8i16, v16i8, v16i8);
+v4i32 __builtin_msa_dpsub_s_w (v4i32, v8i16, v8i16);
+v2i64 __builtin_msa_dpsub_s_d (v2i64, v4i32, v4i32);
+
+v8i16 __builtin_msa_dpsub_u_h (v8i16, v16u8, v16u8);
+v4i32 __builtin_msa_dpsub_u_w (v4i32, v8u16, v8u16);
+v2i64 __builtin_msa_dpsub_u_d (v2i64, v4u32, v4u32);
+
+v4f32 __builtin_msa_fadd_w (v4f32, v4f32);
+v2f64 __builtin_msa_fadd_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fcaf_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcaf_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fceq_w (v4f32, v4f32);
+v2i64 __builtin_msa_fceq_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fclass_w (v4f32);
+v2i64 __builtin_msa_fclass_d (v2f64);
+
+v4i32 __builtin_msa_fcle_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcle_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fclt_w (v4f32, v4f32);
+v2i64 __builtin_msa_fclt_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fcne_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcne_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fcor_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcor_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fcueq_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcueq_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fcule_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcule_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fcult_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcult_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fcun_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcun_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fcune_w (v4f32, v4f32);
+v2i64 __builtin_msa_fcune_d (v2f64, v2f64);
+
+v4f32 __builtin_msa_fdiv_w (v4f32, v4f32);
+v2f64 __builtin_msa_fdiv_d (v2f64, v2f64);
+
+v8i16 __builtin_msa_fexdo_h (v4f32, v4f32);
+v4f32 __builtin_msa_fexdo_w (v2f64, v2f64);
+
+v4f32 __builtin_msa_fexp2_w (v4f32, v4i32);
+v2f64 __builtin_msa_fexp2_d (v2f64, v2i64);
+
+v4f32 __builtin_msa_fexupl_w (v8i16);
+v2f64 __builtin_msa_fexupl_d (v4f32);
+
+v4f32 __builtin_msa_fexupr_w (v8i16);
+v2f64 __builtin_msa_fexupr_d (v4f32);
+
+v4f32 __builtin_msa_ffint_s_w (v4i32);
+v2f64 __builtin_msa_ffint_s_d (v2i64);
+
+v4f32 __builtin_msa_ffint_u_w (v4u32);
+v2f64 __builtin_msa_ffint_u_d (v2u64);
+
+v4f32 __builtin_msa_ffql_w (v8i16);
+v2f64 __builtin_msa_ffql_d (v4i32);
+
+v4f32 __builtin_msa_ffqr_w (v8i16);
+v2f64 __builtin_msa_ffqr_d (v4i32);
+
+v16i8 __builtin_msa_fill_b (i32);
+v8i16 __builtin_msa_fill_h (i32);
+v4i32 __builtin_msa_fill_w (i32);
+v2i64 __builtin_msa_fill_d (i64);
+
+v4f32 __builtin_msa_flog2_w (v4f32);
+v2f64 __builtin_msa_flog2_d (v2f64);
+
+v4f32 __builtin_msa_fmadd_w (v4f32, v4f32, v4f32);
+v2f64 __builtin_msa_fmadd_d (v2f64, v2f64, v2f64);
+
+v4f32 __builtin_msa_fmax_w (v4f32, v4f32);
+v2f64 __builtin_msa_fmax_d (v2f64, v2f64);
+
+v4f32 __builtin_msa_fmax_a_w (v4f32, v4f32);
+v2f64 __builtin_msa_fmax_a_d (v2f64, v2f64);
+
+v4f32 __builtin_msa_fmin_w (v4f32, v4f32);
+v2f64 __builtin_msa_fmin_d (v2f64, v2f64);
+
+v4f32 __builtin_msa_fmin_a_w (v4f32, v4f32);
+v2f64 __builtin_msa_fmin_a_d (v2f64, v2f64);
+
+v4f32 __builtin_msa_fmsub_w (v4f32, v4f32, v4f32);
+v2f64 __builtin_msa_fmsub_d (v2f64, v2f64, v2f64);
+
+v4f32 __builtin_msa_fmul_w (v4f32, v4f32);
+v2f64 __builtin_msa_fmul_d (v2f64, v2f64);
+
+v4f32 __builtin_msa_frint_w (v4f32);
+v2f64 __builtin_msa_frint_d (v2f64);
+
+v4f32 __builtin_msa_frcp_w (v4f32);
+v2f64 __builtin_msa_frcp_d (v2f64);
+
+v4f32 __builtin_msa_frsqrt_w (v4f32);
+v2f64 __builtin_msa_frsqrt_d (v2f64);
+
+v4i32 __builtin_msa_fsaf_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsaf_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fseq_w (v4f32, v4f32);
+v2i64 __builtin_msa_fseq_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fsle_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsle_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fslt_w (v4f32, v4f32);
+v2i64 __builtin_msa_fslt_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fsne_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsne_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fsor_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsor_d (v2f64, v2f64);
+
+v4f32 __builtin_msa_fsqrt_w (v4f32);
+v2f64 __builtin_msa_fsqrt_d (v2f64);
+
+v4f32 __builtin_msa_fsub_w (v4f32, v4f32);
+v2f64 __builtin_msa_fsub_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fsueq_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsueq_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fsule_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsule_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fsult_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsult_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fsun_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsun_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_fsune_w (v4f32, v4f32);
+v2i64 __builtin_msa_fsune_d (v2f64, v2f64);
+
+v4i32 __builtin_msa_ftint_s_w (v4f32);
+v2i64 __builtin_msa_ftint_s_d (v2f64);
+
+v4u32 __builtin_msa_ftint_u_w (v4f32);
+v2u64 __builtin_msa_ftint_u_d (v2f64);
+
+v8i16 __builtin_msa_ftq_h (v4f32, v4f32);
+v4i32 __builtin_msa_ftq_w (v2f64, v2f64);
+
+v4i32 __builtin_msa_ftrunc_s_w (v4f32);
+v2i64 __builtin_msa_ftrunc_s_d (v2f64);
+
+v4u32 __builtin_msa_ftrunc_u_w (v4f32);
+v2u64 __builtin_msa_ftrunc_u_d (v2f64);
+
+v8i16 __builtin_msa_hadd_s_h (v16i8, v16i8);
+v4i32 __builtin_msa_hadd_s_w (v8i16, v8i16);
+v2i64 __builtin_msa_hadd_s_d (v4i32, v4i32);
+
+v8u16 __builtin_msa_hadd_u_h (v16u8, v16u8);
+v4u32 __builtin_msa_hadd_u_w (v8u16, v8u16);
+v2u64 __builtin_msa_hadd_u_d (v4u32, v4u32);
+
+v8i16 __builtin_msa_hsub_s_h (v16i8, v16i8);
+v4i32 __builtin_msa_hsub_s_w (v8i16, v8i16);
+v2i64 __builtin_msa_hsub_s_d (v4i32, v4i32);
+
+v8i16 __builtin_msa_hsub_u_h (v16u8, v16u8);
+v4i32 __builtin_msa_hsub_u_w (v8u16, v8u16);
+v2i64 __builtin_msa_hsub_u_d (v4u32, v4u32);
+
+v16i8 __builtin_msa_ilvev_b (v16i8, v16i8);
+v8i16 __builtin_msa_ilvev_h (v8i16, v8i16);
+v4i32 __builtin_msa_ilvev_w (v4i32, v4i32);
+v2i64 __builtin_msa_ilvev_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_ilvl_b (v16i8, v16i8);
+v8i16 __builtin_msa_ilvl_h (v8i16, v8i16);
+v4i32 __builtin_msa_ilvl_w (v4i32, v4i32);
+v2i64 __builtin_msa_ilvl_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_ilvod_b (v16i8, v16i8);
+v8i16 __builtin_msa_ilvod_h (v8i16, v8i16);
+v4i32 __builtin_msa_ilvod_w (v4i32, v4i32);
+v2i64 __builtin_msa_ilvod_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_ilvr_b (v16i8, v16i8);
+v8i16 __builtin_msa_ilvr_h (v8i16, v8i16);
+v4i32 __builtin_msa_ilvr_w (v4i32, v4i32);
+v2i64 __builtin_msa_ilvr_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_insert_b (v16i8, imm0_15, i32);
+v8i16 __builtin_msa_insert_h (v8i16, imm0_7, i32);
+v4i32 __builtin_msa_insert_w (v4i32, imm0_3, i32);
+v2i64 __builtin_msa_insert_d (v2i64, imm0_1, i64);
+
+v16i8 __builtin_msa_insve_b (v16i8, imm0_15, v16i8);
+v8i16 __builtin_msa_insve_h (v8i16, imm0_7, v8i16);
+v4i32 __builtin_msa_insve_w (v4i32, imm0_3, v4i32);
+v2i64 __builtin_msa_insve_d (v2i64, imm0_1, v2i64);
+
+v16i8 __builtin_msa_ld_b (const void *, imm_n512_511);
+v8i16 __builtin_msa_ld_h (const void *, imm_n1024_1022);
+v4i32 __builtin_msa_ld_w (const void *, imm_n2048_2044);
+v2i64 __builtin_msa_ld_d (const void *, imm_n4096_4088);
+
+v16i8 __builtin_msa_ldi_b (imm_n512_511);
+v8i16 __builtin_msa_ldi_h (imm_n512_511);
+v4i32 __builtin_msa_ldi_w (imm_n512_511);
+v2i64 __builtin_msa_ldi_d (imm_n512_511);
+
+v8i16 __builtin_msa_madd_q_h (v8i16, v8i16, v8i16);
+v4i32 __builtin_msa_madd_q_w (v4i32, v4i32, v4i32);
+
+v8i16 __builtin_msa_maddr_q_h (v8i16, v8i16, v8i16);
+v4i32 __builtin_msa_maddr_q_w (v4i32, v4i32, v4i32);
+
+v16i8 __builtin_msa_maddv_b (v16i8, v16i8, v16i8);
+v8i16 __builtin_msa_maddv_h (v8i16, v8i16, v8i16);
+v4i32 __builtin_msa_maddv_w (v4i32, v4i32, v4i32);
+v2i64 __builtin_msa_maddv_d (v2i64, v2i64, v2i64);
+
+v16i8 __builtin_msa_max_a_b (v16i8, v16i8);
+v8i16 __builtin_msa_max_a_h (v8i16, v8i16);
+v4i32 __builtin_msa_max_a_w (v4i32, v4i32);
+v2i64 __builtin_msa_max_a_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_max_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_max_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_max_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_max_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_max_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_max_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_max_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_max_u_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_maxi_s_b (v16i8, imm_n16_15);
+v8i16 __builtin_msa_maxi_s_h (v8i16, imm_n16_15);
+v4i32 __builtin_msa_maxi_s_w (v4i32, imm_n16_15);
+v2i64 __builtin_msa_maxi_s_d (v2i64, imm_n16_15);
+
+v16u8 __builtin_msa_maxi_u_b (v16u8, imm0_31);
+v8u16 __builtin_msa_maxi_u_h (v8u16, imm0_31);
+v4u32 __builtin_msa_maxi_u_w (v4u32, imm0_31);
+v2u64 __builtin_msa_maxi_u_d (v2u64, imm0_31);
+
+v16i8 __builtin_msa_min_a_b (v16i8, v16i8);
+v8i16 __builtin_msa_min_a_h (v8i16, v8i16);
+v4i32 __builtin_msa_min_a_w (v4i32, v4i32);
+v2i64 __builtin_msa_min_a_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_min_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_min_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_min_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_min_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_min_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_min_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_min_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_min_u_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_mini_s_b (v16i8, imm_n16_15);
+v8i16 __builtin_msa_mini_s_h (v8i16, imm_n16_15);
+v4i32 __builtin_msa_mini_s_w (v4i32, imm_n16_15);
+v2i64 __builtin_msa_mini_s_d (v2i64, imm_n16_15);
+
+v16u8 __builtin_msa_mini_u_b (v16u8, imm0_31);
+v8u16 __builtin_msa_mini_u_h (v8u16, imm0_31);
+v4u32 __builtin_msa_mini_u_w (v4u32, imm0_31);
+v2u64 __builtin_msa_mini_u_d (v2u64, imm0_31);
+
+v16i8 __builtin_msa_mod_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_mod_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_mod_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_mod_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_mod_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_mod_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_mod_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_mod_u_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_move_v (v16i8);
+
+v8i16 __builtin_msa_msub_q_h (v8i16, v8i16, v8i16);
+v4i32 __builtin_msa_msub_q_w (v4i32, v4i32, v4i32);
+
+v8i16 __builtin_msa_msubr_q_h (v8i16, v8i16, v8i16);
+v4i32 __builtin_msa_msubr_q_w (v4i32, v4i32, v4i32);
+
+v16i8 __builtin_msa_msubv_b (v16i8, v16i8, v16i8);
+v8i16 __builtin_msa_msubv_h (v8i16, v8i16, v8i16);
+v4i32 __builtin_msa_msubv_w (v4i32, v4i32, v4i32);
+v2i64 __builtin_msa_msubv_d (v2i64, v2i64, v2i64);
+
+v8i16 __builtin_msa_mul_q_h (v8i16, v8i16);
+v4i32 __builtin_msa_mul_q_w (v4i32, v4i32);
+
+v8i16 __builtin_msa_mulr_q_h (v8i16, v8i16);
+v4i32 __builtin_msa_mulr_q_w (v4i32, v4i32);
+
+v16i8 __builtin_msa_mulv_b (v16i8, v16i8);
+v8i16 __builtin_msa_mulv_h (v8i16, v8i16);
+v4i32 __builtin_msa_mulv_w (v4i32, v4i32);
+v2i64 __builtin_msa_mulv_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_nloc_b (v16i8);
+v8i16 __builtin_msa_nloc_h (v8i16);
+v4i32 __builtin_msa_nloc_w (v4i32);
+v2i64 __builtin_msa_nloc_d (v2i64);
+
+v16i8 __builtin_msa_nlzc_b (v16i8);
+v8i16 __builtin_msa_nlzc_h (v8i16);
+v4i32 __builtin_msa_nlzc_w (v4i32);
+v2i64 __builtin_msa_nlzc_d (v2i64);
+
+v16u8 __builtin_msa_nor_v (v16u8, v16u8);
+
+v16u8 __builtin_msa_nori_b (v16u8, imm0_255);
+
+v16u8 __builtin_msa_or_v (v16u8, v16u8);
+
+v16u8 __builtin_msa_ori_b (v16u8, imm0_255);
+
+v16i8 __builtin_msa_pckev_b (v16i8, v16i8);
+v8i16 __builtin_msa_pckev_h (v8i16, v8i16);
+v4i32 __builtin_msa_pckev_w (v4i32, v4i32);
+v2i64 __builtin_msa_pckev_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_pckod_b (v16i8, v16i8);
+v8i16 __builtin_msa_pckod_h (v8i16, v8i16);
+v4i32 __builtin_msa_pckod_w (v4i32, v4i32);
+v2i64 __builtin_msa_pckod_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_pcnt_b (v16i8);
+v8i16 __builtin_msa_pcnt_h (v8i16);
+v4i32 __builtin_msa_pcnt_w (v4i32);
+v2i64 __builtin_msa_pcnt_d (v2i64);
+
+v16i8 __builtin_msa_sat_s_b (v16i8, imm0_7);
+v8i16 __builtin_msa_sat_s_h (v8i16, imm0_15);
+v4i32 __builtin_msa_sat_s_w (v4i32, imm0_31);
+v2i64 __builtin_msa_sat_s_d (v2i64, imm0_63);
+
+v16u8 __builtin_msa_sat_u_b (v16u8, imm0_7);
+v8u16 __builtin_msa_sat_u_h (v8u16, imm0_15);
+v4u32 __builtin_msa_sat_u_w (v4u32, imm0_31);
+v2u64 __builtin_msa_sat_u_d (v2u64, imm0_63);
+
+v16i8 __builtin_msa_shf_b (v16i8, imm0_255);
+v8i16 __builtin_msa_shf_h (v8i16, imm0_255);
+v4i32 __builtin_msa_shf_w (v4i32, imm0_255);
+
+v16i8 __builtin_msa_sld_b (v16i8, v16i8, i32);
+v8i16 __builtin_msa_sld_h (v8i16, v8i16, i32);
+v4i32 __builtin_msa_sld_w (v4i32, v4i32, i32);
+v2i64 __builtin_msa_sld_d (v2i64, v2i64, i32);
+
+v16i8 __builtin_msa_sldi_b (v16i8, v16i8, imm0_15);
+v8i16 __builtin_msa_sldi_h (v8i16, v8i16, imm0_7);
+v4i32 __builtin_msa_sldi_w (v4i32, v4i32, imm0_3);
+v2i64 __builtin_msa_sldi_d (v2i64, v2i64, imm0_1);
+
+v16i8 __builtin_msa_sll_b (v16i8, v16i8);
+v8i16 __builtin_msa_sll_h (v8i16, v8i16);
+v4i32 __builtin_msa_sll_w (v4i32, v4i32);
+v2i64 __builtin_msa_sll_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_slli_b (v16i8, imm0_7);
+v8i16 __builtin_msa_slli_h (v8i16, imm0_15);
+v4i32 __builtin_msa_slli_w (v4i32, imm0_31);
+v2i64 __builtin_msa_slli_d (v2i64, imm0_63);
+
+v16i8 __builtin_msa_splat_b (v16i8, i32);
+v8i16 __builtin_msa_splat_h (v8i16, i32);
+v4i32 __builtin_msa_splat_w (v4i32, i32);
+v2i64 __builtin_msa_splat_d (v2i64, i32);
+
+v16i8 __builtin_msa_splati_b (v16i8, imm0_15);
+v8i16 __builtin_msa_splati_h (v8i16, imm0_7);
+v4i32 __builtin_msa_splati_w (v4i32, imm0_3);
+v2i64 __builtin_msa_splati_d (v2i64, imm0_1);
+
+v16i8 __builtin_msa_sra_b (v16i8, v16i8);
+v8i16 __builtin_msa_sra_h (v8i16, v8i16);
+v4i32 __builtin_msa_sra_w (v4i32, v4i32);
+v2i64 __builtin_msa_sra_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_srai_b (v16i8, imm0_7);
+v8i16 __builtin_msa_srai_h (v8i16, imm0_15);
+v4i32 __builtin_msa_srai_w (v4i32, imm0_31);
+v2i64 __builtin_msa_srai_d (v2i64, imm0_63);
+
+v16i8 __builtin_msa_srar_b (v16i8, v16i8);
+v8i16 __builtin_msa_srar_h (v8i16, v8i16);
+v4i32 __builtin_msa_srar_w (v4i32, v4i32);
+v2i64 __builtin_msa_srar_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_srari_b (v16i8, imm0_7);
+v8i16 __builtin_msa_srari_h (v8i16, imm0_15);
+v4i32 __builtin_msa_srari_w (v4i32, imm0_31);
+v2i64 __builtin_msa_srari_d (v2i64, imm0_63);
+
+v16i8 __builtin_msa_srl_b (v16i8, v16i8);
+v8i16 __builtin_msa_srl_h (v8i16, v8i16);
+v4i32 __builtin_msa_srl_w (v4i32, v4i32);
+v2i64 __builtin_msa_srl_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_srli_b (v16i8, imm0_7);
+v8i16 __builtin_msa_srli_h (v8i16, imm0_15);
+v4i32 __builtin_msa_srli_w (v4i32, imm0_31);
+v2i64 __builtin_msa_srli_d (v2i64, imm0_63);
+
+v16i8 __builtin_msa_srlr_b (v16i8, v16i8);
+v8i16 __builtin_msa_srlr_h (v8i16, v8i16);
+v4i32 __builtin_msa_srlr_w (v4i32, v4i32);
+v2i64 __builtin_msa_srlr_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_srlri_b (v16i8, imm0_7);
+v8i16 __builtin_msa_srlri_h (v8i16, imm0_15);
+v4i32 __builtin_msa_srlri_w (v4i32, imm0_31);
+v2i64 __builtin_msa_srlri_d (v2i64, imm0_63);
+
+void __builtin_msa_st_b (v16i8, void *, imm_n512_511);
+void __builtin_msa_st_h (v8i16, void *, imm_n1024_1022);
+void __builtin_msa_st_w (v4i32, void *, imm_n2048_2044);
+void __builtin_msa_st_d (v2i64, void *, imm_n4096_4088);
+
+v16i8 __builtin_msa_subs_s_b (v16i8, v16i8);
+v8i16 __builtin_msa_subs_s_h (v8i16, v8i16);
+v4i32 __builtin_msa_subs_s_w (v4i32, v4i32);
+v2i64 __builtin_msa_subs_s_d (v2i64, v2i64);
+
+v16u8 __builtin_msa_subs_u_b (v16u8, v16u8);
+v8u16 __builtin_msa_subs_u_h (v8u16, v8u16);
+v4u32 __builtin_msa_subs_u_w (v4u32, v4u32);
+v2u64 __builtin_msa_subs_u_d (v2u64, v2u64);
+
+v16u8 __builtin_msa_subsus_u_b (v16u8, v16i8);
+v8u16 __builtin_msa_subsus_u_h (v8u16, v8i16);
+v4u32 __builtin_msa_subsus_u_w (v4u32, v4i32);
+v2u64 __builtin_msa_subsus_u_d (v2u64, v2i64);
+
+v16i8 __builtin_msa_subsuu_s_b (v16u8, v16u8);
+v8i16 __builtin_msa_subsuu_s_h (v8u16, v8u16);
+v4i32 __builtin_msa_subsuu_s_w (v4u32, v4u32);
+v2i64 __builtin_msa_subsuu_s_d (v2u64, v2u64);
+
+v16i8 __builtin_msa_subv_b (v16i8, v16i8);
+v8i16 __builtin_msa_subv_h (v8i16, v8i16);
+v4i32 __builtin_msa_subv_w (v4i32, v4i32);
+v2i64 __builtin_msa_subv_d (v2i64, v2i64);
+
+v16i8 __builtin_msa_subvi_b (v16i8, imm0_31);
+v8i16 __builtin_msa_subvi_h (v8i16, imm0_31);
+v4i32 __builtin_msa_subvi_w (v4i32, imm0_31);
+v2i64 __builtin_msa_subvi_d (v2i64, imm0_31);
+
+v16i8 __builtin_msa_vshf_b (v16i8, v16i8, v16i8);
+v8i16 __builtin_msa_vshf_h (v8i16, v8i16, v8i16);
+v4i32 __builtin_msa_vshf_w (v4i32, v4i32, v4i32);
+v2i64 __builtin_msa_vshf_d (v2i64, v2i64, v2i64);
+
+v16u8 __builtin_msa_xor_v (v16u8, v16u8);
+
+v16u8 __builtin_msa_xori_b (v16u8, imm0_255);
+@end smallexample
+
+@node Other MIPS Built-in Functions
+@subsection Other MIPS Built-in Functions
+
+GCC provides other MIPS-specific built-in functions:
+
+@table @code
+@item void __builtin_mips_cache (int @var{op}, const volatile void *@var{addr})
+Insert a @samp{cache} instruction with operands @var{op} and @var{addr}.
+GCC defines the preprocessor macro @code{___GCC_HAVE_BUILTIN_MIPS_CACHE}
+when this function is available.
+
+@item unsigned int __builtin_mips_get_fcsr (void)
+@itemx void __builtin_mips_set_fcsr (unsigned int @var{value})
+Get and set the contents of the floating-point control and status register
+(FPU control register 31). These functions are only available in hard-float
+code but can be called in both MIPS16 and non-MIPS16 contexts.
+
+@code{__builtin_mips_set_fcsr} can be used to change any bit of the
+register except the condition codes, which GCC assumes are preserved.
+@end table
+
+@node MSP430 Built-in Functions
+@subsection MSP430 Built-in Functions
+
+GCC provides a couple of special builtin functions to aid in the
+writing of interrupt handlers in C.
+
+@table @code
+@item __bic_SR_register_on_exit (int @var{mask})
+This clears the indicated bits in the saved copy of the status register
+currently residing on the stack. This only works inside interrupt
+handlers and the changes to the status register will only take affect
+once the handler returns.
+
+@item __bis_SR_register_on_exit (int @var{mask})
+This sets the indicated bits in the saved copy of the status register
+currently residing on the stack. This only works inside interrupt
+handlers and the changes to the status register will only take affect
+once the handler returns.
+
+@item __delay_cycles (long long @var{cycles})
+This inserts an instruction sequence that takes exactly @var{cycles}
+cycles (between 0 and about 17E9) to complete. The inserted sequence
+may use jumps, loops, or no-ops, and does not interfere with any other
+instructions. Note that @var{cycles} must be a compile-time constant
+integer - that is, you must pass a number, not a variable that may be
+optimized to a constant later. The number of cycles delayed by this
+builtin is exact.
+@end table
+
+@node NDS32 Built-in Functions
+@subsection NDS32 Built-in Functions
+
+These built-in functions are available for the NDS32 target:
+
+@deftypefn {Built-in Function} void __builtin_nds32_isync (int *@var{addr})
+Insert an ISYNC instruction into the instruction stream where
+@var{addr} is an instruction address for serialization.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_nds32_isb (void)
+Insert an ISB instruction into the instruction stream.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_nds32_mfsr (int @var{sr})
+Return the content of a system register which is mapped by @var{sr}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_nds32_mfusr (int @var{usr})
+Return the content of a user space register which is mapped by @var{usr}.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_nds32_mtsr (int @var{value}, int @var{sr})
+Move the @var{value} to a system register which is mapped by @var{sr}.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_nds32_mtusr (int @var{value}, int @var{usr})
+Move the @var{value} to a user space register which is mapped by @var{usr}.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_nds32_setgie_en (void)
+Enable global interrupt.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_nds32_setgie_dis (void)
+Disable global interrupt.
+@end deftypefn
+
+@node picoChip Built-in Functions
+@subsection picoChip Built-in Functions
+
+GCC provides an interface to selected machine instructions from the
+picoChip instruction set.
+
+@table @code
+@item int __builtin_sbc (int @var{value})
+Sign bit count. Return the number of consecutive bits in @var{value}
+that have the same value as the sign bit. The result is the number of
+leading sign bits minus one, giving the number of redundant sign bits in
+@var{value}.
+
+@item int __builtin_byteswap (int @var{value})
+Byte swap. Return the result of swapping the upper and lower bytes of
+@var{value}.
+
+@item int __builtin_brev (int @var{value})
+Bit reversal. Return the result of reversing the bits in
+@var{value}. Bit 15 is swapped with bit 0, bit 14 is swapped with bit 1,
+and so on.
+
+@item int __builtin_adds (int @var{x}, int @var{y})
+Saturating addition. Return the result of adding @var{x} and @var{y},
+storing the value 32767 if the result overflows.
+
+@item int __builtin_subs (int @var{x}, int @var{y})
+Saturating subtraction. Return the result of subtracting @var{y} from
+@var{x}, storing the value @minus{}32768 if the result overflows.
+
+@item void __builtin_halt (void)
+Halt. The processor stops execution. This built-in is useful for
+implementing assertions.
+
+@end table
+
+@node Basic PowerPC Built-in Functions
+@subsection Basic PowerPC Built-in Functions
+
+@menu
+* Basic PowerPC Built-in Functions Available on all Configurations::
+* Basic PowerPC Built-in Functions Available on ISA 2.05::
+* Basic PowerPC Built-in Functions Available on ISA 2.06::
+* Basic PowerPC Built-in Functions Available on ISA 2.07::
+* Basic PowerPC Built-in Functions Available on ISA 3.0::
+* Basic PowerPC Built-in Functions Available on ISA 3.1::
+@end menu
+
+This section describes PowerPC built-in functions that do not require
+the inclusion of any special header files to declare prototypes or
+provide macro definitions. The sections that follow describe
+additional PowerPC built-in functions.
+
+@node Basic PowerPC Built-in Functions Available on all Configurations
+@subsubsection Basic PowerPC Built-in Functions Available on all Configurations
+
+@deftypefn {Built-in Function} void __builtin_cpu_init (void)
+This function is a @code{nop} on the PowerPC platform and is included solely
+to maintain API compatibility with the x86 builtins.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_cpu_is (const char *@var{cpuname})
+This function returns a value of @code{1} if the run-time CPU is of type
+@var{cpuname} and returns @code{0} otherwise
+
+The @code{__builtin_cpu_is} function requires GLIBC 2.23 or newer
+which exports the hardware capability bits. GCC defines the macro
+@code{__BUILTIN_CPU_SUPPORTS__} if the @code{__builtin_cpu_supports}
+built-in function is fully supported.
+
+If GCC was configured to use a GLIBC before 2.23, the built-in
+function @code{__builtin_cpu_is} always returns a 0 and the compiler
+issues a warning.
+
+The following CPU names can be detected:
+
+@table @samp
+@item power10
+IBM POWER10 Server CPU.
+@item power9
+IBM POWER9 Server CPU.
+@item power8
+IBM POWER8 Server CPU.
+@item power7
+IBM POWER7 Server CPU.
+@item power6x
+IBM POWER6 Server CPU (RAW mode).
+@item power6
+IBM POWER6 Server CPU (Architected mode).
+@item power5+
+IBM POWER5+ Server CPU.
+@item power5
+IBM POWER5 Server CPU.
+@item ppc970
+IBM 970 Server CPU (ie, Apple G5).
+@item power4
+IBM POWER4 Server CPU.
+@item ppca2
+IBM A2 64-bit Embedded CPU
+@item ppc476
+IBM PowerPC 476FP 32-bit Embedded CPU.
+@item ppc464
+IBM PowerPC 464 32-bit Embedded CPU.
+@item ppc440
+PowerPC 440 32-bit Embedded CPU.
+@item ppc405
+PowerPC 405 32-bit Embedded CPU.
+@item ppc-cell-be
+IBM PowerPC Cell Broadband Engine Architecture CPU.
+@end table
+
+Here is an example:
+@smallexample
+#ifdef __BUILTIN_CPU_SUPPORTS__
+ if (__builtin_cpu_is ("power8"))
+ @{
+ do_power8 (); // POWER8 specific implementation.
+ @}
+ else
+#endif
+ @{
+ do_generic (); // Generic implementation.
+ @}
+@end smallexample
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_cpu_supports (const char *@var{feature})
+This function returns a value of @code{1} if the run-time CPU supports the HWCAP
+feature @var{feature} and returns @code{0} otherwise.
+
+The @code{__builtin_cpu_supports} function requires GLIBC 2.23 or
+newer which exports the hardware capability bits. GCC defines the
+macro @code{__BUILTIN_CPU_SUPPORTS__} if the
+@code{__builtin_cpu_supports} built-in function is fully supported.
+
+If GCC was configured to use a GLIBC before 2.23, the built-in
+function @code{__builtin_cpu_supports} always returns a 0 and the
+compiler issues a warning.
+
+The following features can be
+detected:
+
+@table @samp
+@item 4xxmac
+4xx CPU has a Multiply Accumulator.
+@item altivec
+CPU has a SIMD/Vector Unit.
+@item arch_2_05
+CPU supports ISA 2.05 (eg, POWER6)
+@item arch_2_06
+CPU supports ISA 2.06 (eg, POWER7)
+@item arch_2_07
+CPU supports ISA 2.07 (eg, POWER8)
+@item arch_3_00
+CPU supports ISA 3.0 (eg, POWER9)
+@item arch_3_1
+CPU supports ISA 3.1 (eg, POWER10)
+@item archpmu
+CPU supports the set of compatible performance monitoring events.
+@item booke
+CPU supports the Embedded ISA category.
+@item cellbe
+CPU has a CELL broadband engine.
+@item darn
+CPU supports the @code{darn} (deliver a random number) instruction.
+@item dfp
+CPU has a decimal floating point unit.
+@item dscr
+CPU supports the data stream control register.
+@item ebb
+CPU supports event base branching.
+@item efpdouble
+CPU has a SPE double precision floating point unit.
+@item efpsingle
+CPU has a SPE single precision floating point unit.
+@item fpu
+CPU has a floating point unit.
+@item htm
+CPU has hardware transaction memory instructions.
+@item htm-nosc
+Kernel aborts hardware transactions when a syscall is made.
+@item htm-no-suspend
+CPU supports hardware transaction memory but does not support the
+@code{tsuspend.} instruction.
+@item ic_snoop
+CPU supports icache snooping capabilities.
+@item ieee128
+CPU supports 128-bit IEEE binary floating point instructions.
+@item isel
+CPU supports the integer select instruction.
+@item mma
+CPU supports the matrix-multiply assist instructions.
+@item mmu
+CPU has a memory management unit.
+@item notb
+CPU does not have a timebase (eg, 601 and 403gx).
+@item pa6t
+CPU supports the PA Semi 6T CORE ISA.
+@item power4
+CPU supports ISA 2.00 (eg, POWER4)
+@item power5
+CPU supports ISA 2.02 (eg, POWER5)
+@item power5+
+CPU supports ISA 2.03 (eg, POWER5+)
+@item power6x
+CPU supports ISA 2.05 (eg, POWER6) extended opcodes mffgpr and mftgpr.
+@item ppc32
+CPU supports 32-bit mode execution.
+@item ppc601
+CPU supports the old POWER ISA (eg, 601)
+@item ppc64
+CPU supports 64-bit mode execution.
+@item ppcle
+CPU supports a little-endian mode that uses address swizzling.
+@item scv
+Kernel supports system call vectored.
+@item smt
+CPU support simultaneous multi-threading.
+@item spe
+CPU has a signal processing extension unit.
+@item tar
+CPU supports the target address register.
+@item true_le
+CPU supports true little-endian mode.
+@item ucache
+CPU has unified I/D cache.
+@item vcrypto
+CPU supports the vector cryptography instructions.
+@item vsx
+CPU supports the vector-scalar extension.
+@end table
+
+Here is an example:
+@smallexample
+#ifdef __BUILTIN_CPU_SUPPORTS__
+ if (__builtin_cpu_supports ("fpu"))
+ @{
+ asm("fadd %0,%1,%2" : "=d"(dst) : "d"(src1), "d"(src2));
+ @}
+ else
+#endif
+ @{
+ dst = __fadd (src1, src2); // Software FP addition function.
+ @}
+@end smallexample
+@end deftypefn
+
+The following built-in functions are also available on all PowerPC
+processors:
+@smallexample
+uint64_t __builtin_ppc_get_timebase ();
+unsigned long __builtin_ppc_mftb ();
+double __builtin_unpack_ibm128 (__ibm128, int);
+__ibm128 __builtin_pack_ibm128 (double, double);
+double __builtin_mffs (void);
+void __builtin_mtfsf (const int, double);
+void __builtin_mtfsb0 (const int);
+void __builtin_mtfsb1 (const int);
+void __builtin_set_fpscr_rn (int);
+@end smallexample
+
+The @code{__builtin_ppc_get_timebase} and @code{__builtin_ppc_mftb}
+functions generate instructions to read the Time Base Register. The
+@code{__builtin_ppc_get_timebase} function may generate multiple
+instructions and always returns the 64 bits of the Time Base Register.
+The @code{__builtin_ppc_mftb} function always generates one instruction and
+returns the Time Base Register value as an unsigned long, throwing away
+the most significant word on 32-bit environments. The @code{__builtin_mffs}
+return the value of the FPSCR register. Note, ISA 3.0 supports the
+@code{__builtin_mffsl()} which permits software to read the control and
+non-sticky status bits in the FSPCR without the higher latency associated with
+accessing the sticky status bits. The @code{__builtin_mtfsf} takes a constant
+8-bit integer field mask and a double precision floating point argument
+and generates the @code{mtfsf} (extended mnemonic) instruction to write new
+values to selected fields of the FPSCR. The
+@code{__builtin_mtfsb0} and @code{__builtin_mtfsb1} take the bit to change
+as an argument. The valid bit range is between 0 and 31. The builtins map to
+the @code{mtfsb0} and @code{mtfsb1} instructions which take the argument and
+add 32. Hence these instructions only modify the FPSCR[32:63] bits by
+changing the specified bit to a zero or one respectively. The
+@code{__builtin_set_fpscr_rn} builtin allows changing both of the floating
+point rounding mode bits. The argument is a 2-bit value. The argument can
+either be a @code{const int} or stored in a variable. The builtin uses
+the ISA 3.0
+instruction @code{mffscrn} if available, otherwise it reads the FPSCR, masks
+the current rounding mode bits out and OR's in the new value.
+
+@node Basic PowerPC Built-in Functions Available on ISA 2.05
+@subsubsection Basic PowerPC Built-in Functions Available on ISA 2.05
+
+The basic built-in functions described in this section are
+available on the PowerPC family of processors starting with ISA 2.05
+or later. Unless specific options are explicitly disabled on the
+command line, specifying option @option{-mcpu=power6} has the effect of
+enabling the @option{-mpowerpc64}, @option{-mpowerpc-gpopt},
+@option{-mpowerpc-gfxopt}, @option{-mmfcrf}, @option{-mpopcntb},
+@option{-mfprnd}, @option{-mcmpb}, @option{-mhard-dfp}, and
+@option{-mrecip-precision} options. Specify the
+@option{-maltivec} option explicitly in
+combination with the above options if desired.
+
+The following functions require option @option{-mcmpb}.
+@smallexample
+unsigned long long __builtin_cmpb (unsigned long long int, unsigned long long int);
+unsigned int __builtin_cmpb (unsigned int, unsigned int);
+@end smallexample
+
+The @code{__builtin_cmpb} function
+performs a byte-wise compare on the contents of its two arguments,
+returning the result of the byte-wise comparison as the returned
+value. For each byte comparison, the corresponding byte of the return
+value holds 0xff if the input bytes are equal and 0 if the input bytes
+are not equal. If either of the arguments to this built-in function
+is wider than 32 bits, the function call expands into the form that
+expects @code{unsigned long long int} arguments
+which is only available on 64-bit targets.
+
+The following built-in functions are available
+when hardware decimal floating point
+(@option{-mhard-dfp}) is available:
+@smallexample
+void __builtin_set_fpscr_drn(int);
+_Decimal64 __builtin_ddedpd (int, _Decimal64);
+_Decimal128 __builtin_ddedpdq (int, _Decimal128);
+_Decimal64 __builtin_denbcd (int, _Decimal64);
+_Decimal128 __builtin_denbcdq (int, _Decimal128);
+_Decimal64 __builtin_diex (long long, _Decimal64);
+_Decimal128 _builtin_diexq (long long, _Decimal128);
+_Decimal64 __builtin_dscli (_Decimal64, int);
+_Decimal128 __builtin_dscliq (_Decimal128, int);
+_Decimal64 __builtin_dscri (_Decimal64, int);
+_Decimal128 __builtin_dscriq (_Decimal128, int);
+long long __builtin_dxex (_Decimal64);
+long long __builtin_dxexq (_Decimal128);
+_Decimal128 __builtin_pack_dec128 (unsigned long long, unsigned long long);
+unsigned long long __builtin_unpack_dec128 (_Decimal128, int);
+
+The @code{__builtin_set_fpscr_drn} builtin allows changing the three decimal
+floating point rounding mode bits. The argument is a 3-bit value. The
+argument can either be a @code{const int} or the value can be stored in
+a variable.
+The builtin uses the ISA 3.0 instruction @code{mffscdrn} if available.
+Otherwise the builtin reads the FPSCR, masks the current decimal rounding
+mode bits out and OR's in the new value.
+
+@end smallexample
+
+The following functions require @option{-mhard-float},
+@option{-mpowerpc-gfxopt}, and @option{-mpopcntb} options.
+
+@smallexample
+double __builtin_recipdiv (double, double);
+float __builtin_recipdivf (float, float);
+double __builtin_rsqrt (double);
+float __builtin_rsqrtf (float);
+@end smallexample
+
+The @code{vec_rsqrt}, @code{__builtin_rsqrt}, and
+@code{__builtin_rsqrtf} functions generate multiple instructions to
+implement the reciprocal sqrt functionality using reciprocal sqrt
+estimate instructions.
+
+The @code{__builtin_recipdiv}, and @code{__builtin_recipdivf}
+functions generate multiple instructions to implement division using
+the reciprocal estimate instructions.
+
+The following functions require @option{-mhard-float} and
+@option{-mmultiple} options.
+
+The @code{__builtin_unpack_longdouble} function takes a
+@code{long double} argument and a compile time constant of 0 or 1. If
+the constant is 0, the first @code{double} within the
+@code{long double} is returned, otherwise the second @code{double}
+is returned. The @code{__builtin_unpack_longdouble} function is only
+available if @code{long double} uses the IBM extended double
+representation.
+
+The @code{__builtin_pack_longdouble} function takes two @code{double}
+arguments and returns a @code{long double} value that combines the two
+arguments. The @code{__builtin_pack_longdouble} function is only
+available if @code{long double} uses the IBM extended double
+representation.
+
+The @code{__builtin_unpack_ibm128} function takes a @code{__ibm128}
+argument and a compile time constant of 0 or 1. If the constant is 0,
+the first @code{double} within the @code{__ibm128} is returned,
+otherwise the second @code{double} is returned.
+
+The @code{__builtin_pack_ibm128} function takes two @code{double}
+arguments and returns a @code{__ibm128} value that combines the two
+arguments.
+
+Additional built-in functions are available for the 64-bit PowerPC
+family of processors, for efficient use of 128-bit floating point
+(@code{__float128}) values.
+
+@node Basic PowerPC Built-in Functions Available on ISA 2.06
+@subsubsection Basic PowerPC Built-in Functions Available on ISA 2.06
+
+The basic built-in functions described in this section are
+available on the PowerPC family of processors starting with ISA 2.05
+or later. Unless specific options are explicitly disabled on the
+command line, specifying option @option{-mcpu=power7} has the effect of
+enabling all the same options as for @option{-mcpu=power6} in
+addition to the @option{-maltivec}, @option{-mpopcntd}, and
+@option{-mvsx} options.
+
+The following basic built-in functions require @option{-mpopcntd}:
+@smallexample
+unsigned int __builtin_addg6s (unsigned int, unsigned int);
+long long __builtin_bpermd (long long, long long);
+unsigned int __builtin_cbcdtd (unsigned int);
+unsigned int __builtin_cdtbcd (unsigned int);
+long long __builtin_divde (long long, long long);
+unsigned long long __builtin_divdeu (unsigned long long, unsigned long long);
+int __builtin_divwe (int, int);
+unsigned int __builtin_divweu (unsigned int, unsigned int);
+vector __int128 __builtin_pack_vector_int128 (long long, long long);
+void __builtin_rs6000_speculation_barrier (void);
+long long __builtin_unpack_vector_int128 (vector __int128, signed char);
+@end smallexample
+
+Of these, the @code{__builtin_divde} and @code{__builtin_divdeu} functions
+require a 64-bit environment.
+
+The following basic built-in functions, which are also supported on
+x86 targets, require @option{-mfloat128}.
+@smallexample
+__float128 __builtin_fabsq (__float128);
+__float128 __builtin_copysignq (__float128, __float128);
+__float128 __builtin_infq (void);
+__float128 __builtin_huge_valq (void);
+__float128 __builtin_nanq (void);
+__float128 __builtin_nansq (void);
+
+__float128 __builtin_sqrtf128 (__float128);
+__float128 __builtin_fmaf128 (__float128, __float128, __float128);
+@end smallexample
+
+@node Basic PowerPC Built-in Functions Available on ISA 2.07
+@subsubsection Basic PowerPC Built-in Functions Available on ISA 2.07
+
+The basic built-in functions described in this section are
+available on the PowerPC family of processors starting with ISA 2.07
+or later. Unless specific options are explicitly disabled on the
+command line, specifying option @option{-mcpu=power8} has the effect of
+enabling all the same options as for @option{-mcpu=power7} in
+addition to the @option{-mpower8-fusion}, @option{-mpower8-vector},
+@option{-mcrypto}, @option{-mhtm}, @option{-mquad-memory}, and
+@option{-mquad-memory-atomic} options.
+
+This section intentionally empty.
+
+@node Basic PowerPC Built-in Functions Available on ISA 3.0
+@subsubsection Basic PowerPC Built-in Functions Available on ISA 3.0
+
+The basic built-in functions described in this section are
+available on the PowerPC family of processors starting with ISA 3.0
+or later. Unless specific options are explicitly disabled on the
+command line, specifying option @option{-mcpu=power9} has the effect of
+enabling all the same options as for @option{-mcpu=power8} in
+addition to the @option{-misel} option.
+
+The following built-in functions are available on Linux 64-bit systems
+that use the ISA 3.0 instruction set (@option{-mcpu=power9}):
+
+@table @code
+@item __float128 __builtin_addf128_round_to_odd (__float128, __float128)
+Perform a 128-bit IEEE floating point add using round to odd as the
+rounding mode.
+@findex __builtin_addf128_round_to_odd
+
+@item __float128 __builtin_subf128_round_to_odd (__float128, __float128)
+Perform a 128-bit IEEE floating point subtract using round to odd as
+the rounding mode.
+@findex __builtin_subf128_round_to_odd
+
+@item __float128 __builtin_mulf128_round_to_odd (__float128, __float128)
+Perform a 128-bit IEEE floating point multiply using round to odd as
+the rounding mode.
+@findex __builtin_mulf128_round_to_odd
+
+@item __float128 __builtin_divf128_round_to_odd (__float128, __float128)
+Perform a 128-bit IEEE floating point divide using round to odd as
+the rounding mode.
+@findex __builtin_divf128_round_to_odd
+
+@item __float128 __builtin_sqrtf128_round_to_odd (__float128)
+Perform a 128-bit IEEE floating point square root using round to odd
+as the rounding mode.
+@findex __builtin_sqrtf128_round_to_odd
+
+@item __float128 __builtin_fmaf128_round_to_odd (__float128, __float128, __float128)
+Perform a 128-bit IEEE floating point fused multiply and add operation
+using round to odd as the rounding mode.
+@findex __builtin_fmaf128_round_to_odd
+
+@item double __builtin_truncf128_round_to_odd (__float128)
+Convert a 128-bit IEEE floating point value to @code{double} using
+round to odd as the rounding mode.
+@findex __builtin_truncf128_round_to_odd
+@end table
+
+The following additional built-in functions are also available for the
+PowerPC family of processors, starting with ISA 3.0 or later:
+@smallexample
+long long __builtin_darn (void);
+long long __builtin_darn_raw (void);
+int __builtin_darn_32 (void);
+@end smallexample
+
+The @code{__builtin_darn} and @code{__builtin_darn_raw}
+functions require a
+64-bit environment supporting ISA 3.0 or later.
+The @code{__builtin_darn} function provides a 64-bit conditioned
+random number. The @code{__builtin_darn_raw} function provides a
+64-bit raw random number. The @code{__builtin_darn_32} function
+provides a 32-bit conditioned random number.
+
+The following additional built-in functions are also available for the
+PowerPC family of processors, starting with ISA 3.0 or later:
+
+@smallexample
+int __builtin_byte_in_set (unsigned char u, unsigned long long set);
+int __builtin_byte_in_range (unsigned char u, unsigned int range);
+int __builtin_byte_in_either_range (unsigned char u, unsigned int ranges);
+
+int __builtin_dfp_dtstsfi_lt (unsigned int comparison, _Decimal64 value);
+int __builtin_dfp_dtstsfi_lt (unsigned int comparison, _Decimal128 value);
+int __builtin_dfp_dtstsfi_lt_dd (unsigned int comparison, _Decimal64 value);
+int __builtin_dfp_dtstsfi_lt_td (unsigned int comparison, _Decimal128 value);
+
+int __builtin_dfp_dtstsfi_gt (unsigned int comparison, _Decimal64 value);
+int __builtin_dfp_dtstsfi_gt (unsigned int comparison, _Decimal128 value);
+int __builtin_dfp_dtstsfi_gt_dd (unsigned int comparison, _Decimal64 value);
+int __builtin_dfp_dtstsfi_gt_td (unsigned int comparison, _Decimal128 value);
+
+int __builtin_dfp_dtstsfi_eq (unsigned int comparison, _Decimal64 value);
+int __builtin_dfp_dtstsfi_eq (unsigned int comparison, _Decimal128 value);
+int __builtin_dfp_dtstsfi_eq_dd (unsigned int comparison, _Decimal64 value);
+int __builtin_dfp_dtstsfi_eq_td (unsigned int comparison, _Decimal128 value);
+
+int __builtin_dfp_dtstsfi_ov (unsigned int comparison, _Decimal64 value);
+int __builtin_dfp_dtstsfi_ov (unsigned int comparison, _Decimal128 value);
+int __builtin_dfp_dtstsfi_ov_dd (unsigned int comparison, _Decimal64 value);
+int __builtin_dfp_dtstsfi_ov_td (unsigned int comparison, _Decimal128 value);
+
+double __builtin_mffsl(void);
+
+@end smallexample
+The @code{__builtin_byte_in_set} function requires a
+64-bit environment supporting ISA 3.0 or later. This function returns
+a non-zero value if and only if its @code{u} argument exactly equals one of
+the eight bytes contained within its 64-bit @code{set} argument.
+
+The @code{__builtin_byte_in_range} and
+@code{__builtin_byte_in_either_range} require an environment
+supporting ISA 3.0 or later. For these two functions, the
+@code{range} argument is encoded as 4 bytes, organized as
+@code{hi_1:lo_1:hi_2:lo_2}.
+The @code{__builtin_byte_in_range} function returns a
+non-zero value if and only if its @code{u} argument is within the
+range bounded between @code{lo_2} and @code{hi_2} inclusive.
+The @code{__builtin_byte_in_either_range} function returns non-zero if
+and only if its @code{u} argument is within either the range bounded
+between @code{lo_1} and @code{hi_1} inclusive or the range bounded
+between @code{lo_2} and @code{hi_2} inclusive.
+
+The @code{__builtin_dfp_dtstsfi_lt} function returns a non-zero value
+if and only if the number of signficant digits of its @code{value} argument
+is less than its @code{comparison} argument. The
+@code{__builtin_dfp_dtstsfi_lt_dd} and
+@code{__builtin_dfp_dtstsfi_lt_td} functions behave similarly, but
+require that the type of the @code{value} argument be
+@code{__Decimal64} and @code{__Decimal128} respectively.
+
+The @code{__builtin_dfp_dtstsfi_gt} function returns a non-zero value
+if and only if the number of signficant digits of its @code{value} argument
+is greater than its @code{comparison} argument. The
+@code{__builtin_dfp_dtstsfi_gt_dd} and
+@code{__builtin_dfp_dtstsfi_gt_td} functions behave similarly, but
+require that the type of the @code{value} argument be
+@code{__Decimal64} and @code{__Decimal128} respectively.
+
+The @code{__builtin_dfp_dtstsfi_eq} function returns a non-zero value
+if and only if the number of signficant digits of its @code{value} argument
+equals its @code{comparison} argument. The
+@code{__builtin_dfp_dtstsfi_eq_dd} and
+@code{__builtin_dfp_dtstsfi_eq_td} functions behave similarly, but
+require that the type of the @code{value} argument be
+@code{__Decimal64} and @code{__Decimal128} respectively.
+
+The @code{__builtin_dfp_dtstsfi_ov} function returns a non-zero value
+if and only if its @code{value} argument has an undefined number of
+significant digits, such as when @code{value} is an encoding of @code{NaN}.
+The @code{__builtin_dfp_dtstsfi_ov_dd} and
+@code{__builtin_dfp_dtstsfi_ov_td} functions behave similarly, but
+require that the type of the @code{value} argument be
+@code{__Decimal64} and @code{__Decimal128} respectively.
+
+The @code{__builtin_mffsl} uses the ISA 3.0 @code{mffsl} instruction to read
+the FPSCR. The instruction is a lower latency version of the @code{mffs}
+instruction. If the @code{mffsl} instruction is not available, then the
+builtin uses the older @code{mffs} instruction to read the FPSCR.
+
+@node Basic PowerPC Built-in Functions Available on ISA 3.1
+@subsubsection Basic PowerPC Built-in Functions Available on ISA 3.1
+
+The basic built-in functions described in this section are
+available on the PowerPC family of processors starting with ISA 3.1.
+Unless specific options are explicitly disabled on the
+command line, specifying option @option{-mcpu=power10} has the effect of
+enabling all the same options as for @option{-mcpu=power9}.
+
+The following built-in functions are available on Linux 64-bit systems
+that use a future architecture instruction set (@option{-mcpu=power10}):
+
+@smallexample
+@exdent unsigned long long
+@exdent __builtin_cfuged (unsigned long long, unsigned long long)
+@end smallexample
+Perform a 64-bit centrifuge operation, as if implemented by the
+@code{cfuged} instruction.
+@findex __builtin_cfuged
+
+@smallexample
+@exdent unsigned long long
+@exdent __builtin_cntlzdm (unsigned long long, unsigned long long)
+@end smallexample
+Perform a 64-bit count leading zeros operation under mask, as if
+implemented by the @code{cntlzdm} instruction.
+@findex __builtin_cntlzdm
+
+@smallexample
+@exdent unsigned long long
+@exdent __builtin_cnttzdm (unsigned long long, unsigned long long)
+@end smallexample
+Perform a 64-bit count trailing zeros operation under mask, as if
+implemented by the @code{cnttzdm} instruction.
+@findex __builtin_cnttzdm
+
+@smallexample
+@exdent unsigned long long
+@exdent __builtin_pdepd (unsigned long long, unsigned long long)
+@end smallexample
+Perform a 64-bit parallel bits deposit operation, as if implemented by the
+@code{pdepd} instruction.
+@findex __builtin_pdepd
+
+@smallexample
+@exdent unsigned long long
+@exdent __builtin_pextd (unsigned long long, unsigned long long)
+@end smallexample
+Perform a 64-bit parallel bits extract operation, as if implemented by the
+@code{pextd} instruction.
+@findex __builtin_pextd
+
+@smallexample
+@exdent vector signed __int128 vsx_xl_sext (signed long long, signed char *)
+
+@exdent vector signed __int128 vsx_xl_sext (signed long long, signed short *)
+
+@exdent vector signed __int128 vsx_xl_sext (signed long long, signed int *)
+
+@exdent vector signed __int128 vsx_xl_sext (signed long long, signed long long *)
+
+@exdent vector unsigned __int128 vsx_xl_zext (signed long long, unsigned char *)
+
+@exdent vector unsigned __int128 vsx_xl_zext (signed long long, unsigned short *)
+
+@exdent vector unsigned __int128 vsx_xl_zext (signed long long, unsigned int *)
+
+@exdent vector unsigned __int128 vsx_xl_zext (signed long long, unsigned long long *)
+@end smallexample
+
+Load (and sign extend) to an __int128 vector, as if implemented by the ISA 3.1
+@code{lxvrbx}, @code{lxvrhx}, @code{lxvrwx}, and @code{lxvrdx} instructions.
+@findex vsx_xl_sext
+@findex vsx_xl_zext
+
+@smallexample
+@exdent void vec_xst_trunc (vector signed __int128, signed long long, signed char *)
+
+@exdent void vec_xst_trunc (vector signed __int128, signed long long, signed short *)
+
+@exdent void vec_xst_trunc (vector signed __int128, signed long long, signed int *)
+
+@exdent void vec_xst_trunc (vector signed __int128, signed long long, signed long long *)
+
+@exdent void vec_xst_trunc (vector unsigned __int128, signed long long, unsigned char *)
+
+@exdent void vec_xst_trunc (vector unsigned __int128, signed long long, unsigned short *)
+
+@exdent void vec_xst_trunc (vector unsigned __int128, signed long long, unsigned int *)
+
+@exdent void vec_xst_trunc (vector unsigned __int128, signed long long, unsigned long long *)
+@end smallexample
+
+Truncate and store the rightmost element of a vector, as if implemented by the
+ISA 3.1 @code{stxvrbx}, @code{stxvrhx}, @code{stxvrwx}, and @code{stxvrdx}
+instructions.
+@findex vec_xst_trunc
+
+@node PowerPC AltiVec/VSX Built-in Functions
+@subsection PowerPC AltiVec/VSX Built-in Functions
+
+GCC provides an interface for the PowerPC family of processors to access
+the AltiVec operations described in Motorola's AltiVec Programming
+Interface Manual. The interface is made available by including
+@code{<altivec.h>} and using @option{-maltivec} and
+@option{-mabi=altivec}. The interface supports the following vector
+types.
+
+@smallexample
+vector unsigned char
+vector signed char
+vector bool char
+
+vector unsigned short
+vector signed short
+vector bool short
+vector pixel
+
+vector unsigned int
+vector signed int
+vector bool int
+vector float
+@end smallexample
+
+GCC's implementation of the high-level language interface available from
+C and C++ code differs from Motorola's documentation in several ways.
+
+@itemize @bullet
+
+@item
+A vector constant is a list of constant expressions within curly braces.
+
+@item
+A vector initializer requires no cast if the vector constant is of the
+same type as the variable it is initializing.
+
+@item
+If @code{signed} or @code{unsigned} is omitted, the signedness of the
+vector type is the default signedness of the base type. The default
+varies depending on the operating system, so a portable program should
+always specify the signedness.
+
+@item
+Compiling with @option{-maltivec} adds keywords @code{__vector},
+@code{vector}, @code{__pixel}, @code{pixel}, @code{__bool} and
+@code{bool}. When compiling ISO C, the context-sensitive substitution
+of the keywords @code{vector}, @code{pixel} and @code{bool} is
+disabled. To use them, you must include @code{<altivec.h>} instead.
+
+@item
+GCC allows using a @code{typedef} name as the type specifier for a
+vector type, but only under the following circumstances:
+
+@itemize @bullet
+
+@item
+When using @code{__vector} instead of @code{vector}; for example,
+
+@smallexample
+typedef signed short int16;
+__vector int16 data;
+@end smallexample
+
+@item
+When using @code{vector} in keyword-and-predefine mode; for example,
+
+@smallexample
+typedef signed short int16;
+vector int16 data;
+@end smallexample
+
+Note that keyword-and-predefine mode is enabled by disabling GNU
+extensions (e.g., by using @code{-std=c11}) and including
+@code{<altivec.h>}.
+@end itemize
+
+@item
+For C, overloaded functions are implemented with macros so the following
+does not work:
+
+@smallexample
+ vec_add ((vector signed int)@{1, 2, 3, 4@}, foo);
+@end smallexample
+
+@noindent
+Since @code{vec_add} is a macro, the vector constant in the example
+is treated as four separate arguments. Wrap the entire argument in
+parentheses for this to work.
+@end itemize
+
+@emph{Note:} Only the @code{<altivec.h>} interface is supported.
+Internally, GCC uses built-in functions to achieve the functionality in
+the aforementioned header file, but they are not supported and are
+subject to change without notice.
+
+GCC complies with the Power Vector Intrinsic Programming Reference (PVIPR),
+which may be found at
+@uref{https://openpowerfoundation.org/?resource_lib=power-vector-intrinsic-programming-reference}.
+Chapter 4 of this document fully documents the vector API interfaces
+that must be
+provided by compliant compilers. Programmers should preferentially use
+the interfaces described therein. However, historically GCC has provided
+additional interfaces for access to vector instructions. These are
+briefly described below. Where the PVIPR provides a portable interface,
+other functions in GCC that provide the same capabilities should be
+considered deprecated.
+
+The PVIPR documents the following overloaded functions:
+
+@multitable @columnfractions 0.33 0.33 0.33
+
+@item @code{vec_abs}
+@tab @code{vec_absd}
+@tab @code{vec_abss}
+@item @code{vec_add}
+@tab @code{vec_addc}
+@tab @code{vec_adde}
+@item @code{vec_addec}
+@tab @code{vec_adds}
+@tab @code{vec_all_eq}
+@item @code{vec_all_ge}
+@tab @code{vec_all_gt}
+@tab @code{vec_all_in}
+@item @code{vec_all_le}
+@tab @code{vec_all_lt}
+@tab @code{vec_all_nan}
+@item @code{vec_all_ne}
+@tab @code{vec_all_nge}
+@tab @code{vec_all_ngt}
+@item @code{vec_all_nle}
+@tab @code{vec_all_nlt}
+@tab @code{vec_all_numeric}
+@item @code{vec_and}
+@tab @code{vec_andc}
+@tab @code{vec_any_eq}
+@item @code{vec_any_ge}
+@tab @code{vec_any_gt}
+@tab @code{vec_any_le}
+@item @code{vec_any_lt}
+@tab @code{vec_any_nan}
+@tab @code{vec_any_ne}
+@item @code{vec_any_nge}
+@tab @code{vec_any_ngt}
+@tab @code{vec_any_nle}
+@item @code{vec_any_nlt}
+@tab @code{vec_any_numeric}
+@tab @code{vec_any_out}
+@item @code{vec_avg}
+@tab @code{vec_bperm}
+@tab @code{vec_ceil}
+@item @code{vec_cipher_be}
+@tab @code{vec_cipherlast_be}
+@tab @code{vec_cmpb}
+@item @code{vec_cmpeq}
+@tab @code{vec_cmpge}
+@tab @code{vec_cmpgt}
+@item @code{vec_cmple}
+@tab @code{vec_cmplt}
+@tab @code{vec_cmpne}
+@item @code{vec_cmpnez}
+@tab @code{vec_cntlz}
+@tab @code{vec_cntlz_lsbb}
+@item @code{vec_cnttz}
+@tab @code{vec_cnttz_lsbb}
+@tab @code{vec_cpsgn}
+@item @code{vec_ctf}
+@tab @code{vec_cts}
+@tab @code{vec_ctu}
+@item @code{vec_div}
+@tab @code{vec_double}
+@tab @code{vec_doublee}
+@item @code{vec_doubleh}
+@tab @code{vec_doublel}
+@tab @code{vec_doubleo}
+@item @code{vec_eqv}
+@tab @code{vec_expte}
+@tab @code{vec_extract}
+@item @code{vec_extract_exp}
+@tab @code{vec_extract_fp32_from_shorth}
+@tab @code{vec_extract_fp32_from_shortl}
+@item @code{vec_extract_sig}
+@tab @code{vec_extract_4b}
+@tab @code{vec_first_match_index}
+@item @code{vec_first_match_or_eos_index}
+@tab @code{vec_first_mismatch_index}
+@tab @code{vec_first_mismatch_or_eos_index}
+@item @code{vec_float}
+@tab @code{vec_float2}
+@tab @code{vec_floate}
+@item @code{vec_floato}
+@tab @code{vec_floor}
+@tab @code{vec_gb}
+@item @code{vec_insert}
+@tab @code{vec_insert_exp}
+@tab @code{vec_insert4b}
+@item @code{vec_ld}
+@tab @code{vec_lde}
+@tab @code{vec_ldl}
+@item @code{vec_loge}
+@tab @code{vec_madd}
+@tab @code{vec_madds}
+@item @code{vec_max}
+@tab @code{vec_mergee}
+@tab @code{vec_mergeh}
+@item @code{vec_mergel}
+@tab @code{vec_mergeo}
+@tab @code{vec_mfvscr}
+@item @code{vec_min}
+@tab @code{vec_mradds}
+@tab @code{vec_msub}
+@item @code{vec_msum}
+@tab @code{vec_msums}
+@tab @code{vec_mtvscr}
+@item @code{vec_mul}
+@tab @code{vec_mule}
+@tab @code{vec_mulo}
+@item @code{vec_nabs}
+@tab @code{vec_nand}
+@tab @code{vec_ncipher_be}
+@item @code{vec_ncipherlast_be}
+@tab @code{vec_nearbyint}
+@tab @code{vec_neg}
+@item @code{vec_nmadd}
+@tab @code{vec_nmsub}
+@tab @code{vec_nor}
+@item @code{vec_or}
+@tab @code{vec_orc}
+@tab @code{vec_pack}
+@item @code{vec_pack_to_short_fp32}
+@tab @code{vec_packpx}
+@tab @code{vec_packs}
+@item @code{vec_packsu}
+@tab @code{vec_parity_lsbb}
+@tab @code{vec_perm}
+@item @code{vec_permxor}
+@tab @code{vec_pmsum_be}
+@tab @code{vec_popcnt}
+@item @code{vec_re}
+@tab @code{vec_recipdiv}
+@tab @code{vec_revb}
+@item @code{vec_reve}
+@tab @code{vec_rint}
+@tab @code{vec_rl}
+@item @code{vec_rlmi}
+@tab @code{vec_rlnm}
+@tab @code{vec_round}
+@item @code{vec_rsqrt}
+@tab @code{vec_rsqrte}
+@tab @code{vec_sbox_be}
+@item @code{vec_sel}
+@tab @code{vec_shasigma_be}
+@tab @code{vec_signed}
+@item @code{vec_signed2}
+@tab @code{vec_signede}
+@tab @code{vec_signedo}
+@item @code{vec_sl}
+@tab @code{vec_sld}
+@tab @code{vec_sldw}
+@item @code{vec_sll}
+@tab @code{vec_slo}
+@tab @code{vec_slv}
+@item @code{vec_splat}
+@tab @code{vec_splat_s8}
+@tab @code{vec_splat_s16}
+@item @code{vec_splat_s32}
+@tab @code{vec_splat_u8}
+@tab @code{vec_splat_u16}
+@item @code{vec_splat_u32}
+@tab @code{vec_splats}
+@tab @code{vec_sqrt}
+@item @code{vec_sr}
+@tab @code{vec_sra}
+@tab @code{vec_srl}
+@item @code{vec_sro}
+@tab @code{vec_srv}
+@tab @code{vec_st}
+@item @code{vec_ste}
+@tab @code{vec_stl}
+@tab @code{vec_sub}
+@item @code{vec_subc}
+@tab @code{vec_sube}
+@tab @code{vec_subec}
+@item @code{vec_subs}
+@tab @code{vec_sum2s}
+@tab @code{vec_sum4s}
+@item @code{vec_sums}
+@tab @code{vec_test_data_class}
+@tab @code{vec_trunc}
+@item @code{vec_unpackh}
+@tab @code{vec_unpackl}
+@tab @code{vec_unsigned}
+@item @code{vec_unsigned2}
+@tab @code{vec_unsignede}
+@tab @code{vec_unsignedo}
+@item @code{vec_xl}
+@tab @code{vec_xl_be}
+@tab @code{vec_xl_len}
+@item @code{vec_xl_len_r}
+@tab @code{vec_xor}
+@tab @code{vec_xst}
+@item @code{vec_xst_be}
+@tab @code{vec_xst_len}
+@tab @code{vec_xst_len_r}
+
+@end multitable
+
+@menu
+* PowerPC AltiVec Built-in Functions on ISA 2.05::
+* PowerPC AltiVec Built-in Functions Available on ISA 2.06::
+* PowerPC AltiVec Built-in Functions Available on ISA 2.07::
+* PowerPC AltiVec Built-in Functions Available on ISA 3.0::
+* PowerPC AltiVec Built-in Functions Available on ISA 3.1::
+@end menu
+
+@node PowerPC AltiVec Built-in Functions on ISA 2.05
+@subsubsection PowerPC AltiVec Built-in Functions on ISA 2.05
+
+The following interfaces are supported for the generic and specific
+AltiVec operations and the AltiVec predicates. In cases where there
+is a direct mapping between generic and specific operations, only the
+generic names are shown here, although the specific operations can also
+be used.
+
+Arguments that are documented as @code{const int} require literal
+integral values within the range required for that operation.
+
+Only functions excluded from the PVIPR are listed here.
+
+@smallexample
+void vec_dss (const int);
+
+void vec_dssall (void);
+
+void vec_dst (const vector unsigned char *, int, const int);
+void vec_dst (const vector signed char *, int, const int);
+void vec_dst (const vector bool char *, int, const int);
+void vec_dst (const vector unsigned short *, int, const int);
+void vec_dst (const vector signed short *, int, const int);
+void vec_dst (const vector bool short *, int, const int);
+void vec_dst (const vector pixel *, int, const int);
+void vec_dst (const vector unsigned int *, int, const int);
+void vec_dst (const vector signed int *, int, const int);
+void vec_dst (const vector bool int *, int, const int);
+void vec_dst (const vector float *, int, const int);
+void vec_dst (const unsigned char *, int, const int);
+void vec_dst (const signed char *, int, const int);
+void vec_dst (const unsigned short *, int, const int);
+void vec_dst (const short *, int, const int);
+void vec_dst (const unsigned int *, int, const int);
+void vec_dst (const int *, int, const int);
+void vec_dst (const float *, int, const int);
+
+void vec_dstst (const vector unsigned char *, int, const int);
+void vec_dstst (const vector signed char *, int, const int);
+void vec_dstst (const vector bool char *, int, const int);
+void vec_dstst (const vector unsigned short *, int, const int);
+void vec_dstst (const vector signed short *, int, const int);
+void vec_dstst (const vector bool short *, int, const int);
+void vec_dstst (const vector pixel *, int, const int);
+void vec_dstst (const vector unsigned int *, int, const int);
+void vec_dstst (const vector signed int *, int, const int);
+void vec_dstst (const vector bool int *, int, const int);
+void vec_dstst (const vector float *, int, const int);
+void vec_dstst (const unsigned char *, int, const int);
+void vec_dstst (const signed char *, int, const int);
+void vec_dstst (const unsigned short *, int, const int);
+void vec_dstst (const short *, int, const int);
+void vec_dstst (const unsigned int *, int, const int);
+void vec_dstst (const int *, int, const int);
+void vec_dstst (const unsigned long *, int, const int);
+void vec_dstst (const long *, int, const int);
+void vec_dstst (const float *, int, const int);
+
+void vec_dststt (const vector unsigned char *, int, const int);
+void vec_dststt (const vector signed char *, int, const int);
+void vec_dststt (const vector bool char *, int, const int);
+void vec_dststt (const vector unsigned short *, int, const int);
+void vec_dststt (const vector signed short *, int, const int);
+void vec_dststt (const vector bool short *, int, const int);
+void vec_dststt (const vector pixel *, int, const int);
+void vec_dststt (const vector unsigned int *, int, const int);
+void vec_dststt (const vector signed int *, int, const int);
+void vec_dststt (const vector bool int *, int, const int);
+void vec_dststt (const vector float *, int, const int);
+void vec_dststt (const unsigned char *, int, const int);
+void vec_dststt (const signed char *, int, const int);
+void vec_dststt (const unsigned short *, int, const int);
+void vec_dststt (const short *, int, const int);
+void vec_dststt (const unsigned int *, int, const int);
+void vec_dststt (const int *, int, const int);
+void vec_dststt (const float *, int, const int);
+
+void vec_dstt (const vector unsigned char *, int, const int);
+void vec_dstt (const vector signed char *, int, const int);
+void vec_dstt (const vector bool char *, int, const int);
+void vec_dstt (const vector unsigned short *, int, const int);
+void vec_dstt (const vector signed short *, int, const int);
+void vec_dstt (const vector bool short *, int, const int);
+void vec_dstt (const vector pixel *, int, const int);
+void vec_dstt (const vector unsigned int *, int, const int);
+void vec_dstt (const vector signed int *, int, const int);
+void vec_dstt (const vector bool int *, int, const int);
+void vec_dstt (const vector float *, int, const int);
+void vec_dstt (const unsigned char *, int, const int);
+void vec_dstt (const signed char *, int, const int);
+void vec_dstt (const unsigned short *, int, const int);
+void vec_dstt (const short *, int, const int);
+void vec_dstt (const unsigned int *, int, const int);
+void vec_dstt (const int *, int, const int);
+void vec_dstt (const float *, int, const int);
+
+vector signed char vec_lvebx (int, char *);
+vector unsigned char vec_lvebx (int, unsigned char *);
+
+vector signed short vec_lvehx (int, short *);
+vector unsigned short vec_lvehx (int, unsigned short *);
+
+vector float vec_lvewx (int, float *);
+vector signed int vec_lvewx (int, int *);
+vector unsigned int vec_lvewx (int, unsigned int *);
+
+vector unsigned char vec_lvsl (int, const unsigned char *);
+vector unsigned char vec_lvsl (int, const signed char *);
+vector unsigned char vec_lvsl (int, const unsigned short *);
+vector unsigned char vec_lvsl (int, const short *);
+vector unsigned char vec_lvsl (int, const unsigned int *);
+vector unsigned char vec_lvsl (int, const int *);
+vector unsigned char vec_lvsl (int, const float *);
+
+vector unsigned char vec_lvsr (int, const unsigned char *);
+vector unsigned char vec_lvsr (int, const signed char *);
+vector unsigned char vec_lvsr (int, const unsigned short *);
+vector unsigned char vec_lvsr (int, const short *);
+vector unsigned char vec_lvsr (int, const unsigned int *);
+vector unsigned char vec_lvsr (int, const int *);
+vector unsigned char vec_lvsr (int, const float *);
+
+void vec_stvebx (vector signed char, int, signed char *);
+void vec_stvebx (vector unsigned char, int, unsigned char *);
+void vec_stvebx (vector bool char, int, signed char *);
+void vec_stvebx (vector bool char, int, unsigned char *);
+
+void vec_stvehx (vector signed short, int, short *);
+void vec_stvehx (vector unsigned short, int, unsigned short *);
+void vec_stvehx (vector bool short, int, short *);
+void vec_stvehx (vector bool short, int, unsigned short *);
+
+void vec_stvewx (vector float, int, float *);
+void vec_stvewx (vector signed int, int, int *);
+void vec_stvewx (vector unsigned int, int, unsigned int *);
+void vec_stvewx (vector bool int, int, int *);
+void vec_stvewx (vector bool int, int, unsigned int *);
+
+vector float vec_vaddfp (vector float, vector float);
+
+vector signed char vec_vaddsbs (vector bool char, vector signed char);
+vector signed char vec_vaddsbs (vector signed char, vector bool char);
+vector signed char vec_vaddsbs (vector signed char, vector signed char);
+
+vector signed short vec_vaddshs (vector bool short, vector signed short);
+vector signed short vec_vaddshs (vector signed short, vector bool short);
+vector signed short vec_vaddshs (vector signed short, vector signed short);
+
+vector signed int vec_vaddsws (vector bool int, vector signed int);
+vector signed int vec_vaddsws (vector signed int, vector bool int);
+vector signed int vec_vaddsws (vector signed int, vector signed int);
+
+vector signed char vec_vaddubm (vector bool char, vector signed char);
+vector signed char vec_vaddubm (vector signed char, vector bool char);
+vector signed char vec_vaddubm (vector signed char, vector signed char);
+vector unsigned char vec_vaddubm (vector bool char, vector unsigned char);
+vector unsigned char vec_vaddubm (vector unsigned char, vector bool char);
+vector unsigned char vec_vaddubm (vector unsigned char, vector unsigned char);
+
+vector unsigned char vec_vaddubs (vector bool char, vector unsigned char);
+vector unsigned char vec_vaddubs (vector unsigned char, vector bool char);
+vector unsigned char vec_vaddubs (vector unsigned char, vector unsigned char);
+
+vector signed short vec_vadduhm (vector bool short, vector signed short);
+vector signed short vec_vadduhm (vector signed short, vector bool short);
+vector signed short vec_vadduhm (vector signed short, vector signed short);
+vector unsigned short vec_vadduhm (vector bool short, vector unsigned short);
+vector unsigned short vec_vadduhm (vector unsigned short, vector bool short);
+vector unsigned short vec_vadduhm (vector unsigned short, vector unsigned short);
+
+vector unsigned short vec_vadduhs (vector bool short, vector unsigned short);
+vector unsigned short vec_vadduhs (vector unsigned short, vector bool short);
+vector unsigned short vec_vadduhs (vector unsigned short, vector unsigned short);
+
+vector signed int vec_vadduwm (vector bool int, vector signed int);
+vector signed int vec_vadduwm (vector signed int, vector bool int);
+vector signed int vec_vadduwm (vector signed int, vector signed int);
+vector unsigned int vec_vadduwm (vector bool int, vector unsigned int);
+vector unsigned int vec_vadduwm (vector unsigned int, vector bool int);
+vector unsigned int vec_vadduwm (vector unsigned int, vector unsigned int);
+
+vector unsigned int vec_vadduws (vector bool int, vector unsigned int);
+vector unsigned int vec_vadduws (vector unsigned int, vector bool int);
+vector unsigned int vec_vadduws (vector unsigned int, vector unsigned int);
+
+vector signed char vec_vavgsb (vector signed char, vector signed char);
+
+vector signed short vec_vavgsh (vector signed short, vector signed short);
+
+vector signed int vec_vavgsw (vector signed int, vector signed int);
+
+vector unsigned char vec_vavgub (vector unsigned char, vector unsigned char);
+
+vector unsigned short vec_vavguh (vector unsigned short, vector unsigned short);
+
+vector unsigned int vec_vavguw (vector unsigned int, vector unsigned int);
+
+vector float vec_vcfsx (vector signed int, const int);
+
+vector float vec_vcfux (vector unsigned int, const int);
+
+vector bool int vec_vcmpeqfp (vector float, vector float);
+
+vector bool char vec_vcmpequb (vector signed char, vector signed char);
+vector bool char vec_vcmpequb (vector unsigned char, vector unsigned char);
+
+vector bool short vec_vcmpequh (vector signed short, vector signed short);
+vector bool short vec_vcmpequh (vector unsigned short, vector unsigned short);
+
+vector bool int vec_vcmpequw (vector signed int, vector signed int);
+vector bool int vec_vcmpequw (vector unsigned int, vector unsigned int);
+
+vector bool int vec_vcmpgtfp (vector float, vector float);
+
+vector bool char vec_vcmpgtsb (vector signed char, vector signed char);
+
+vector bool short vec_vcmpgtsh (vector signed short, vector signed short);
+
+vector bool int vec_vcmpgtsw (vector signed int, vector signed int);
+
+vector bool char vec_vcmpgtub (vector unsigned char, vector unsigned char);
+
+vector bool short vec_vcmpgtuh (vector unsigned short, vector unsigned short);
+
+vector bool int vec_vcmpgtuw (vector unsigned int, vector unsigned int);
+
+vector float vec_vmaxfp (vector float, vector float);
+
+vector signed char vec_vmaxsb (vector bool char, vector signed char);
+vector signed char vec_vmaxsb (vector signed char, vector bool char);
+vector signed char vec_vmaxsb (vector signed char, vector signed char);
+
+vector signed short vec_vmaxsh (vector bool short, vector signed short);
+vector signed short vec_vmaxsh (vector signed short, vector bool short);
+vector signed short vec_vmaxsh (vector signed short, vector signed short);
+
+vector signed int vec_vmaxsw (vector bool int, vector signed int);
+vector signed int vec_vmaxsw (vector signed int, vector bool int);
+vector signed int vec_vmaxsw (vector signed int, vector signed int);
+
+vector unsigned char vec_vmaxub (vector bool char, vector unsigned char);
+vector unsigned char vec_vmaxub (vector unsigned char, vector bool char);
+vector unsigned char vec_vmaxub (vector unsigned char, vector unsigned char);
+
+vector unsigned short vec_vmaxuh (vector bool short, vector unsigned short);
+vector unsigned short vec_vmaxuh (vector unsigned short, vector bool short);
+vector unsigned short vec_vmaxuh (vector unsigned short, vector unsigned short);
+
+vector unsigned int vec_vmaxuw (vector bool int, vector unsigned int);
+vector unsigned int vec_vmaxuw (vector unsigned int, vector bool int);
+vector unsigned int vec_vmaxuw (vector unsigned int, vector unsigned int);
+
+vector float vec_vminfp (vector float, vector float);
+
+vector signed char vec_vminsb (vector bool char, vector signed char);
+vector signed char vec_vminsb (vector signed char, vector bool char);
+vector signed char vec_vminsb (vector signed char, vector signed char);
+
+vector signed short vec_vminsh (vector bool short, vector signed short);
+vector signed short vec_vminsh (vector signed short, vector bool short);
+vector signed short vec_vminsh (vector signed short, vector signed short);
+
+vector signed int vec_vminsw (vector bool int, vector signed int);
+vector signed int vec_vminsw (vector signed int, vector bool int);
+vector signed int vec_vminsw (vector signed int, vector signed int);
+
+vector unsigned char vec_vminub (vector bool char, vector unsigned char);
+vector unsigned char vec_vminub (vector unsigned char, vector bool char);
+vector unsigned char vec_vminub (vector unsigned char, vector unsigned char);
+
+vector unsigned short vec_vminuh (vector bool short, vector unsigned short);
+vector unsigned short vec_vminuh (vector unsigned short, vector bool short);
+vector unsigned short vec_vminuh (vector unsigned short, vector unsigned short);
+
+vector unsigned int vec_vminuw (vector bool int, vector unsigned int);
+vector unsigned int vec_vminuw (vector unsigned int, vector bool int);
+vector unsigned int vec_vminuw (vector unsigned int, vector unsigned int);
+
+vector bool char vec_vmrghb (vector bool char, vector bool char);
+vector signed char vec_vmrghb (vector signed char, vector signed char);
+vector unsigned char vec_vmrghb (vector unsigned char, vector unsigned char);
+
+vector bool short vec_vmrghh (vector bool short, vector bool short);
+vector signed short vec_vmrghh (vector signed short, vector signed short);
+vector unsigned short vec_vmrghh (vector unsigned short, vector unsigned short);
+vector pixel vec_vmrghh (vector pixel, vector pixel);
+
+vector float vec_vmrghw (vector float, vector float);
+vector bool int vec_vmrghw (vector bool int, vector bool int);
+vector signed int vec_vmrghw (vector signed int, vector signed int);
+vector unsigned int vec_vmrghw (vector unsigned int, vector unsigned int);
+
+vector bool char vec_vmrglb (vector bool char, vector bool char);
+vector signed char vec_vmrglb (vector signed char, vector signed char);
+vector unsigned char vec_vmrglb (vector unsigned char, vector unsigned char);
+
+vector bool short vec_vmrglh (vector bool short, vector bool short);
+vector signed short vec_vmrglh (vector signed short, vector signed short);
+vector unsigned short vec_vmrglh (vector unsigned short, vector unsigned short);
+vector pixel vec_vmrglh (vector pixel, vector pixel);
+
+vector float vec_vmrglw (vector float, vector float);
+vector signed int vec_vmrglw (vector signed int, vector signed int);
+vector unsigned int vec_vmrglw (vector unsigned int, vector unsigned int);
+vector bool int vec_vmrglw (vector bool int, vector bool int);
+
+vector signed int vec_vmsummbm (vector signed char, vector unsigned char,
+ vector signed int);
+
+vector signed int vec_vmsumshm (vector signed short, vector signed short,
+ vector signed int);
+
+vector signed int vec_vmsumshs (vector signed short, vector signed short,
+ vector signed int);
+
+vector unsigned int vec_vmsumubm (vector unsigned char, vector unsigned char,
+ vector unsigned int);
+
+vector unsigned int vec_vmsumuhm (vector unsigned short, vector unsigned short,
+ vector unsigned int);
+
+vector unsigned int vec_vmsumuhs (vector unsigned short, vector unsigned short,
+ vector unsigned int);
+
+vector signed short vec_vmulesb (vector signed char, vector signed char);
+
+vector signed int vec_vmulesh (vector signed short, vector signed short);
+
+vector unsigned short vec_vmuleub (vector unsigned char, vector unsigned char);
+
+vector unsigned int vec_vmuleuh (vector unsigned short, vector unsigned short);
+
+vector signed short vec_vmulosb (vector signed char, vector signed char);
+
+vector signed int vec_vmulosh (vector signed short, vector signed short);
+
+vector unsigned short vec_vmuloub (vector unsigned char, vector unsigned char);
+
+vector unsigned int vec_vmulouh (vector unsigned short, vector unsigned short);
+
+vector signed char vec_vpkshss (vector signed short, vector signed short);
+
+vector unsigned char vec_vpkshus (vector signed short, vector signed short);
+
+vector signed short vec_vpkswss (vector signed int, vector signed int);
+
+vector unsigned short vec_vpkswus (vector signed int, vector signed int);
+
+vector bool char vec_vpkuhum (vector bool short, vector bool short);
+vector signed char vec_vpkuhum (vector signed short, vector signed short);
+vector unsigned char vec_vpkuhum (vector unsigned short, vector unsigned short);
+
+vector unsigned char vec_vpkuhus (vector unsigned short, vector unsigned short);
+
+vector bool short vec_vpkuwum (vector bool int, vector bool int);
+vector signed short vec_vpkuwum (vector signed int, vector signed int);
+vector unsigned short vec_vpkuwum (vector unsigned int, vector unsigned int);
+
+vector unsigned short vec_vpkuwus (vector unsigned int, vector unsigned int);
+
+vector signed char vec_vrlb (vector signed char, vector unsigned char);
+vector unsigned char vec_vrlb (vector unsigned char, vector unsigned char);
+
+vector signed short vec_vrlh (vector signed short, vector unsigned short);
+vector unsigned short vec_vrlh (vector unsigned short, vector unsigned short);
+
+vector signed int vec_vrlw (vector signed int, vector unsigned int);
+vector unsigned int vec_vrlw (vector unsigned int, vector unsigned int);
+
+vector signed char vec_vslb (vector signed char, vector unsigned char);
+vector unsigned char vec_vslb (vector unsigned char, vector unsigned char);
+
+vector signed short vec_vslh (vector signed short, vector unsigned short);
+vector unsigned short vec_vslh (vector unsigned short, vector unsigned short);
+
+vector signed int vec_vslw (vector signed int, vector unsigned int);
+vector unsigned int vec_vslw (vector unsigned int, vector unsigned int);
+
+vector signed char vec_vspltb (vector signed char, const int);
+vector unsigned char vec_vspltb (vector unsigned char, const int);
+vector bool char vec_vspltb (vector bool char, const int);
+
+vector bool short vec_vsplth (vector bool short, const int);
+vector signed short vec_vsplth (vector signed short, const int);
+vector unsigned short vec_vsplth (vector unsigned short, const int);
+vector pixel vec_vsplth (vector pixel, const int);
+
+vector float vec_vspltw (vector float, const int);
+vector signed int vec_vspltw (vector signed int, const int);
+vector unsigned int vec_vspltw (vector unsigned int, const int);
+vector bool int vec_vspltw (vector bool int, const int);
+
+vector signed char vec_vsrab (vector signed char, vector unsigned char);
+vector unsigned char vec_vsrab (vector unsigned char, vector unsigned char);
+
+vector signed short vec_vsrah (vector signed short, vector unsigned short);
+vector unsigned short vec_vsrah (vector unsigned short, vector unsigned short);
+
+vector signed int vec_vsraw (vector signed int, vector unsigned int);
+vector unsigned int vec_vsraw (vector unsigned int, vector unsigned int);
+
+vector signed char vec_vsrb (vector signed char, vector unsigned char);
+vector unsigned char vec_vsrb (vector unsigned char, vector unsigned char);
+
+vector signed short vec_vsrh (vector signed short, vector unsigned short);
+vector unsigned short vec_vsrh (vector unsigned short, vector unsigned short);
+
+vector signed int vec_vsrw (vector signed int, vector unsigned int);
+vector unsigned int vec_vsrw (vector unsigned int, vector unsigned int);
+
+vector float vec_vsubfp (vector float, vector float);
+
+vector signed char vec_vsubsbs (vector bool char, vector signed char);
+vector signed char vec_vsubsbs (vector signed char, vector bool char);
+vector signed char vec_vsubsbs (vector signed char, vector signed char);
+
+vector signed short vec_vsubshs (vector bool short, vector signed short);
+vector signed short vec_vsubshs (vector signed short, vector bool short);
+vector signed short vec_vsubshs (vector signed short, vector signed short);
+
+vector signed int vec_vsubsws (vector bool int, vector signed int);
+vector signed int vec_vsubsws (vector signed int, vector bool int);
+vector signed int vec_vsubsws (vector signed int, vector signed int);
+
+vector signed char vec_vsububm (vector bool char, vector signed char);
+vector signed char vec_vsububm (vector signed char, vector bool char);
+vector signed char vec_vsububm (vector signed char, vector signed char);
+vector unsigned char vec_vsububm (vector bool char, vector unsigned char);
+vector unsigned char vec_vsububm (vector unsigned char, vector bool char);
+vector unsigned char vec_vsububm (vector unsigned char, vector unsigned char);
+
+vector unsigned char vec_vsububs (vector bool char, vector unsigned char);
+vector unsigned char vec_vsububs (vector unsigned char, vector bool char);
+vector unsigned char vec_vsububs (vector unsigned char, vector unsigned char);
+
+vector signed short vec_vsubuhm (vector bool short, vector signed short);
+vector signed short vec_vsubuhm (vector signed short, vector bool short);
+vector signed short vec_vsubuhm (vector signed short, vector signed short);
+vector unsigned short vec_vsubuhm (vector bool short, vector unsigned short);
+vector unsigned short vec_vsubuhm (vector unsigned short, vector bool short);
+vector unsigned short vec_vsubuhm (vector unsigned short, vector unsigned short);
+
+vector unsigned short vec_vsubuhs (vector bool short, vector unsigned short);
+vector unsigned short vec_vsubuhs (vector unsigned short, vector bool short);
+vector unsigned short vec_vsubuhs (vector unsigned short, vector unsigned short);
+
+vector signed int vec_vsubuwm (vector bool int, vector signed int);
+vector signed int vec_vsubuwm (vector signed int, vector bool int);
+vector signed int vec_vsubuwm (vector signed int, vector signed int);
+vector unsigned int vec_vsubuwm (vector bool int, vector unsigned int);
+vector unsigned int vec_vsubuwm (vector unsigned int, vector bool int);
+vector unsigned int vec_vsubuwm (vector unsigned int, vector unsigned int);
+
+vector unsigned int vec_vsubuws (vector bool int, vector unsigned int);
+vector unsigned int vec_vsubuws (vector unsigned int, vector bool int);
+vector unsigned int vec_vsubuws (vector unsigned int, vector unsigned int);
+
+vector signed int vec_vsum4sbs (vector signed char, vector signed int);
+
+vector signed int vec_vsum4shs (vector signed short, vector signed int);
+
+vector unsigned int vec_vsum4ubs (vector unsigned char, vector unsigned int);
+
+vector unsigned int vec_vupkhpx (vector pixel);
+
+vector bool short vec_vupkhsb (vector bool char);
+vector signed short vec_vupkhsb (vector signed char);
+
+vector bool int vec_vupkhsh (vector bool short);
+vector signed int vec_vupkhsh (vector signed short);
+
+vector unsigned int vec_vupklpx (vector pixel);
+
+vector bool short vec_vupklsb (vector bool char);
+vector signed short vec_vupklsb (vector signed char);
+
+vector bool int vec_vupklsh (vector bool short);
+vector signed int vec_vupklsh (vector signed short);
+@end smallexample
+
+@node PowerPC AltiVec Built-in Functions Available on ISA 2.06
+@subsubsection PowerPC AltiVec Built-in Functions Available on ISA 2.06
+
+The AltiVec built-in functions described in this section are
+available on the PowerPC family of processors starting with ISA 2.06
+or later. These are normally enabled by adding @option{-mvsx} to the
+command line.
+
+When @option{-mvsx} is used, the following additional vector types are
+implemented.
+
+@smallexample
+vector unsigned __int128
+vector signed __int128
+vector unsigned long long int
+vector signed long long int
+vector double
+@end smallexample
+
+The long long types are only implemented for 64-bit code generation.
+
+Only functions excluded from the PVIPR are listed here.
+
+@smallexample
+void vec_dst (const unsigned long *, int, const int);
+void vec_dst (const long *, int, const int);
+
+void vec_dststt (const unsigned long *, int, const int);
+void vec_dststt (const long *, int, const int);
+
+void vec_dstt (const unsigned long *, int, const int);
+void vec_dstt (const long *, int, const int);
+
+vector unsigned char vec_lvsl (int, const unsigned long *);
+vector unsigned char vec_lvsl (int, const long *);
+
+vector unsigned char vec_lvsr (int, const unsigned long *);
+vector unsigned char vec_lvsr (int, const long *);
+
+vector unsigned char vec_lvsl (int, const double *);
+vector unsigned char vec_lvsr (int, const double *);
+
+vector double vec_vsx_ld (int, const vector double *);
+vector double vec_vsx_ld (int, const double *);
+vector float vec_vsx_ld (int, const vector float *);
+vector float vec_vsx_ld (int, const float *);
+vector bool int vec_vsx_ld (int, const vector bool int *);
+vector signed int vec_vsx_ld (int, const vector signed int *);
+vector signed int vec_vsx_ld (int, const int *);
+vector signed int vec_vsx_ld (int, const long *);
+vector unsigned int vec_vsx_ld (int, const vector unsigned int *);
+vector unsigned int vec_vsx_ld (int, const unsigned int *);
+vector unsigned int vec_vsx_ld (int, const unsigned long *);
+vector bool short vec_vsx_ld (int, const vector bool short *);
+vector pixel vec_vsx_ld (int, const vector pixel *);
+vector signed short vec_vsx_ld (int, const vector signed short *);
+vector signed short vec_vsx_ld (int, const short *);
+vector unsigned short vec_vsx_ld (int, const vector unsigned short *);
+vector unsigned short vec_vsx_ld (int, const unsigned short *);
+vector bool char vec_vsx_ld (int, const vector bool char *);
+vector signed char vec_vsx_ld (int, const vector signed char *);
+vector signed char vec_vsx_ld (int, const signed char *);
+vector unsigned char vec_vsx_ld (int, const vector unsigned char *);
+vector unsigned char vec_vsx_ld (int, const unsigned char *);
+
+void vec_vsx_st (vector double, int, vector double *);
+void vec_vsx_st (vector double, int, double *);
+void vec_vsx_st (vector float, int, vector float *);
+void vec_vsx_st (vector float, int, float *);
+void vec_vsx_st (vector signed int, int, vector signed int *);
+void vec_vsx_st (vector signed int, int, int *);
+void vec_vsx_st (vector unsigned int, int, vector unsigned int *);
+void vec_vsx_st (vector unsigned int, int, unsigned int *);
+void vec_vsx_st (vector bool int, int, vector bool int *);
+void vec_vsx_st (vector bool int, int, unsigned int *);
+void vec_vsx_st (vector bool int, int, int *);
+void vec_vsx_st (vector signed short, int, vector signed short *);
+void vec_vsx_st (vector signed short, int, short *);
+void vec_vsx_st (vector unsigned short, int, vector unsigned short *);
+void vec_vsx_st (vector unsigned short, int, unsigned short *);
+void vec_vsx_st (vector bool short, int, vector bool short *);
+void vec_vsx_st (vector bool short, int, unsigned short *);
+void vec_vsx_st (vector pixel, int, vector pixel *);
+void vec_vsx_st (vector pixel, int, unsigned short *);
+void vec_vsx_st (vector pixel, int, short *);
+void vec_vsx_st (vector bool short, int, short *);
+void vec_vsx_st (vector signed char, int, vector signed char *);
+void vec_vsx_st (vector signed char, int, signed char *);
+void vec_vsx_st (vector unsigned char, int, vector unsigned char *);
+void vec_vsx_st (vector unsigned char, int, unsigned char *);
+void vec_vsx_st (vector bool char, int, vector bool char *);
+void vec_vsx_st (vector bool char, int, unsigned char *);
+void vec_vsx_st (vector bool char, int, signed char *);
+
+vector double vec_xxpermdi (vector double, vector double, const int);
+vector float vec_xxpermdi (vector float, vector float, const int);
+vector long long vec_xxpermdi (vector long long, vector long long, const int);
+vector unsigned long long vec_xxpermdi (vector unsigned long long,
+ vector unsigned long long, const int);
+vector int vec_xxpermdi (vector int, vector int, const int);
+vector unsigned int vec_xxpermdi (vector unsigned int,
+ vector unsigned int, const int);
+vector short vec_xxpermdi (vector short, vector short, const int);
+vector unsigned short vec_xxpermdi (vector unsigned short,
+ vector unsigned short, const int);
+vector signed char vec_xxpermdi (vector signed char, vector signed char,
+ const int);
+vector unsigned char vec_xxpermdi (vector unsigned char,
+ vector unsigned char, const int);
+
+vector double vec_xxsldi (vector double, vector double, int);
+vector float vec_xxsldi (vector float, vector float, int);
+vector long long vec_xxsldi (vector long long, vector long long, int);
+vector unsigned long long vec_xxsldi (vector unsigned long long,
+ vector unsigned long long, int);
+vector int vec_xxsldi (vector int, vector int, int);
+vector unsigned int vec_xxsldi (vector unsigned int, vector unsigned int, int);
+vector short vec_xxsldi (vector short, vector short, int);
+vector unsigned short vec_xxsldi (vector unsigned short,
+ vector unsigned short, int);
+vector signed char vec_xxsldi (vector signed char, vector signed char, int);
+vector unsigned char vec_xxsldi (vector unsigned char,
+ vector unsigned char, int);
+@end smallexample
+
+Note that the @samp{vec_ld} and @samp{vec_st} built-in functions always
+generate the AltiVec @samp{LVX} and @samp{STVX} instructions even
+if the VSX instruction set is available. The @samp{vec_vsx_ld} and
+@samp{vec_vsx_st} built-in functions always generate the VSX @samp{LXVD2X},
+@samp{LXVW4X}, @samp{STXVD2X}, and @samp{STXVW4X} instructions.
+
+@node PowerPC AltiVec Built-in Functions Available on ISA 2.07
+@subsubsection PowerPC AltiVec Built-in Functions Available on ISA 2.07
+
+If the ISA 2.07 additions to the vector/scalar (power8-vector)
+instruction set are available, the following additional functions are
+available for both 32-bit and 64-bit targets. For 64-bit targets, you
+can use @var{vector long} instead of @var{vector long long},
+@var{vector bool long} instead of @var{vector bool long long}, and
+@var{vector unsigned long} instead of @var{vector unsigned long long}.
+
+Only functions excluded from the PVIPR are listed here.
+
+@smallexample
+vector long long vec_vaddudm (vector long long, vector long long);
+vector long long vec_vaddudm (vector bool long long, vector long long);
+vector long long vec_vaddudm (vector long long, vector bool long long);
+vector unsigned long long vec_vaddudm (vector unsigned long long,
+ vector unsigned long long);
+vector unsigned long long vec_vaddudm (vector bool unsigned long long,
+ vector unsigned long long);
+vector unsigned long long vec_vaddudm (vector unsigned long long,
+ vector bool unsigned long long);
+
+vector long long vec_vclz (vector long long);
+vector unsigned long long vec_vclz (vector unsigned long long);
+vector int vec_vclz (vector int);
+vector unsigned int vec_vclz (vector int);
+vector short vec_vclz (vector short);
+vector unsigned short vec_vclz (vector unsigned short);
+vector signed char vec_vclz (vector signed char);
+vector unsigned char vec_vclz (vector unsigned char);
+
+vector signed char vec_vclzb (vector signed char);
+vector unsigned char vec_vclzb (vector unsigned char);
+
+vector long long vec_vclzd (vector long long);
+vector unsigned long long vec_vclzd (vector unsigned long long);
+
+vector short vec_vclzh (vector short);
+vector unsigned short vec_vclzh (vector unsigned short);
+
+vector int vec_vclzw (vector int);
+vector unsigned int vec_vclzw (vector int);
+
+vector signed char vec_vgbbd (vector signed char);
+vector unsigned char vec_vgbbd (vector unsigned char);
+
+vector long long vec_vmaxsd (vector long long, vector long long);
+
+vector unsigned long long vec_vmaxud (vector unsigned long long,
+ unsigned vector long long);
+
+vector long long vec_vminsd (vector long long, vector long long);
+
+vector unsigned long long vec_vminud (vector long long, vector long long);
+
+vector int vec_vpksdss (vector long long, vector long long);
+vector unsigned int vec_vpksdss (vector long long, vector long long);
+
+vector unsigned int vec_vpkudus (vector unsigned long long,
+ vector unsigned long long);
+
+vector int vec_vpkudum (vector long long, vector long long);
+vector unsigned int vec_vpkudum (vector unsigned long long,
+ vector unsigned long long);
+vector bool int vec_vpkudum (vector bool long long, vector bool long long);
+
+vector long long vec_vpopcnt (vector long long);
+vector unsigned long long vec_vpopcnt (vector unsigned long long);
+vector int vec_vpopcnt (vector int);
+vector unsigned int vec_vpopcnt (vector int);
+vector short vec_vpopcnt (vector short);
+vector unsigned short vec_vpopcnt (vector unsigned short);
+vector signed char vec_vpopcnt (vector signed char);
+vector unsigned char vec_vpopcnt (vector unsigned char);
+
+vector signed char vec_vpopcntb (vector signed char);
+vector unsigned char vec_vpopcntb (vector unsigned char);
+
+vector long long vec_vpopcntd (vector long long);
+vector unsigned long long vec_vpopcntd (vector unsigned long long);
+
+vector short vec_vpopcnth (vector short);
+vector unsigned short vec_vpopcnth (vector unsigned short);
+
+vector int vec_vpopcntw (vector int);
+vector unsigned int vec_vpopcntw (vector int);
+
+vector long long vec_vrld (vector long long, vector unsigned long long);
+vector unsigned long long vec_vrld (vector unsigned long long,
+ vector unsigned long long);
+
+vector long long vec_vsld (vector long long, vector unsigned long long);
+vector long long vec_vsld (vector unsigned long long,
+ vector unsigned long long);
+
+vector long long vec_vsrad (vector long long, vector unsigned long long);
+vector unsigned long long vec_vsrad (vector unsigned long long,
+ vector unsigned long long);
+
+vector long long vec_vsrd (vector long long, vector unsigned long long);
+vector unsigned long long char vec_vsrd (vector unsigned long long,
+ vector unsigned long long);
+
+vector long long vec_vsubudm (vector long long, vector long long);
+vector long long vec_vsubudm (vector bool long long, vector long long);
+vector long long vec_vsubudm (vector long long, vector bool long long);
+vector unsigned long long vec_vsubudm (vector unsigned long long,
+ vector unsigned long long);
+vector unsigned long long vec_vsubudm (vector bool long long,
+ vector unsigned long long);
+vector unsigned long long vec_vsubudm (vector unsigned long long,
+ vector bool long long);
+
+vector long long vec_vupkhsw (vector int);
+vector unsigned long long vec_vupkhsw (vector unsigned int);
+
+vector long long vec_vupklsw (vector int);
+vector unsigned long long vec_vupklsw (vector int);
+@end smallexample
+
+If the ISA 2.07 additions to the vector/scalar (power8-vector)
+instruction set are available, the following additional functions are
+available for 64-bit targets. New vector types
+(@var{vector __int128} and @var{vector __uint128}) are available
+to hold the @var{__int128} and @var{__uint128} types to use these
+builtins.
+
+The normal vector extract, and set operations work on
+@var{vector __int128} and @var{vector __uint128} types,
+but the index value must be 0.
+
+Only functions excluded from the PVIPR are listed here.
+
+@smallexample
+vector __int128 vec_vaddcuq (vector __int128, vector __int128);
+vector __uint128 vec_vaddcuq (vector __uint128, vector __uint128);
+
+vector __int128 vec_vadduqm (vector __int128, vector __int128);
+vector __uint128 vec_vadduqm (vector __uint128, vector __uint128);
+
+vector __int128 vec_vaddecuq (vector __int128, vector __int128,
+ vector __int128);
+vector __uint128 vec_vaddecuq (vector __uint128, vector __uint128,
+ vector __uint128);
+
+vector __int128 vec_vaddeuqm (vector __int128, vector __int128,
+ vector __int128);
+vector __uint128 vec_vaddeuqm (vector __uint128, vector __uint128,
+ vector __uint128);
+
+vector __int128 vec_vsubecuq (vector __int128, vector __int128,
+ vector __int128);
+vector __uint128 vec_vsubecuq (vector __uint128, vector __uint128,
+ vector __uint128);
+
+vector __int128 vec_vsubeuqm (vector __int128, vector __int128,
+ vector __int128);
+vector __uint128 vec_vsubeuqm (vector __uint128, vector __uint128,
+ vector __uint128);
+
+vector __int128 vec_vsubcuq (vector __int128, vector __int128);
+vector __uint128 vec_vsubcuq (vector __uint128, vector __uint128);
+
+__int128 vec_vsubuqm (__int128, __int128);
+__uint128 vec_vsubuqm (__uint128, __uint128);
+
+vector __int128 __builtin_bcdadd (vector __int128, vector __int128, const int);
+vector unsigned char __builtin_bcdadd (vector unsigned char, vector unsigned char,
+ const int);
+int __builtin_bcdadd_lt (vector __int128, vector __int128, const int);
+int __builtin_bcdadd_lt (vector unsigned char, vector unsigned char, const int);
+int __builtin_bcdadd_eq (vector __int128, vector __int128, const int);
+int __builtin_bcdadd_eq (vector unsigned char, vector unsigned char, const int);
+int __builtin_bcdadd_gt (vector __int128, vector __int128, const int);
+int __builtin_bcdadd_gt (vector unsigned char, vector unsigned char, const int);
+int __builtin_bcdadd_ov (vector __int128, vector __int128, const int);
+int __builtin_bcdadd_ov (vector unsigned char, vector unsigned char, const int);
+
+vector __int128 __builtin_bcdsub (vector __int128, vector __int128, const int);
+vector unsigned char __builtin_bcdsub (vector unsigned char, vector unsigned char,
+ const int);
+int __builtin_bcdsub_lt (vector __int128, vector __int128, const int);
+int __builtin_bcdsub_lt (vector unsigned char, vector unsigned char, const int);
+int __builtin_bcdsub_eq (vector __int128, vector __int128, const int);
+int __builtin_bcdsub_eq (vector unsigned char, vector unsigned char, const int);
+int __builtin_bcdsub_gt (vector __int128, vector __int128, const int);
+int __builtin_bcdsub_gt (vector unsigned char, vector unsigned char, const int);
+int __builtin_bcdsub_ov (vector __int128, vector __int128, const int);
+int __builtin_bcdsub_ov (vector unsigned char, vector unsigned char, const int);
+@end smallexample
+
+@node PowerPC AltiVec Built-in Functions Available on ISA 3.0
+@subsubsection PowerPC AltiVec Built-in Functions Available on ISA 3.0
+
+The following additional built-in functions are also available for the
+PowerPC family of processors, starting with ISA 3.0
+(@option{-mcpu=power9}) or later.
+
+Only instructions excluded from the PVIPR are listed here.
+
+@smallexample
+unsigned int scalar_extract_exp (double source);
+unsigned long long int scalar_extract_exp (__ieee128 source);
+
+unsigned long long int scalar_extract_sig (double source);
+unsigned __int128 scalar_extract_sig (__ieee128 source);
+
+double scalar_insert_exp (unsigned long long int significand,
+ unsigned long long int exponent);
+double scalar_insert_exp (double significand, unsigned long long int exponent);
+
+ieee_128 scalar_insert_exp (unsigned __int128 significand,
+ unsigned long long int exponent);
+ieee_128 scalar_insert_exp (ieee_128 significand, unsigned long long int exponent);
+
+int scalar_cmp_exp_gt (double arg1, double arg2);
+int scalar_cmp_exp_lt (double arg1, double arg2);
+int scalar_cmp_exp_eq (double arg1, double arg2);
+int scalar_cmp_exp_unordered (double arg1, double arg2);
+
+bool scalar_test_data_class (float source, const int condition);
+bool scalar_test_data_class (double source, const int condition);
+bool scalar_test_data_class (__ieee128 source, const int condition);
+
+bool scalar_test_neg (float source);
+bool scalar_test_neg (double source);
+bool scalar_test_neg (__ieee128 source);
+@end smallexample
+
+The @code{scalar_extract_exp} and @code{scalar_extract_sig}
+functions require a 64-bit environment supporting ISA 3.0 or later.
+The @code{scalar_extract_exp} and @code{scalar_extract_sig} built-in
+functions return the significand and the biased exponent value
+respectively of their @code{source} arguments.
+When supplied with a 64-bit @code{source} argument, the
+result returned by @code{scalar_extract_sig} has
+the @code{0x0010000000000000} bit set if the
+function's @code{source} argument is in normalized form.
+Otherwise, this bit is set to 0.
+When supplied with a 128-bit @code{source} argument, the
+@code{0x00010000000000000000000000000000} bit of the result is
+treated similarly.
+Note that the sign of the significand is not represented in the result
+returned from the @code{scalar_extract_sig} function. Use the
+@code{scalar_test_neg} function to test the sign of its @code{double}
+argument.
+
+The @code{scalar_insert_exp}
+functions require a 64-bit environment supporting ISA 3.0 or later.
+When supplied with a 64-bit first argument, the
+@code{scalar_insert_exp} built-in function returns a double-precision
+floating point value that is constructed by assembling the values of its
+@code{significand} and @code{exponent} arguments. The sign of the
+result is copied from the most significant bit of the
+@code{significand} argument. The significand and exponent components
+of the result are composed of the least significant 11 bits of the
+@code{exponent} argument and the least significant 52 bits of the
+@code{significand} argument respectively.
+
+When supplied with a 128-bit first argument, the
+@code{scalar_insert_exp} built-in function returns a quad-precision
+ieee floating point value. The sign bit of the result is copied from
+the most significant bit of the @code{significand} argument.
+The significand and exponent components of the result are composed of
+the least significant 15 bits of the @code{exponent} argument and the
+least significant 112 bits of the @code{significand} argument respectively.
+
+The @code{scalar_cmp_exp_gt}, @code{scalar_cmp_exp_lt},
+@code{scalar_cmp_exp_eq}, and @code{scalar_cmp_exp_unordered} built-in
+functions return a non-zero value if @code{arg1} is greater than, less
+than, equal to, or not comparable to @code{arg2} respectively. The
+arguments are not comparable if one or the other equals NaN (not a
+number).
+
+The @code{scalar_test_data_class} built-in function returns 1
+if any of the condition tests enabled by the value of the
+@code{condition} variable are true, and 0 otherwise. The
+@code{condition} argument must be a compile-time constant integer with
+value not exceeding 127. The
+@code{condition} argument is encoded as a bitmask with each bit
+enabling the testing of a different condition, as characterized by the
+following:
+@smallexample
+0x40 Test for NaN
+0x20 Test for +Infinity
+0x10 Test for -Infinity
+0x08 Test for +Zero
+0x04 Test for -Zero
+0x02 Test for +Denormal
+0x01 Test for -Denormal
+@end smallexample
+
+The @code{scalar_test_neg} built-in function returns 1 if its
+@code{source} argument holds a negative value, 0 otherwise.
+
+The following built-in functions are also available for the PowerPC family
+of processors, starting with ISA 3.0 or later
+(@option{-mcpu=power9}). These string functions are described
+separately in order to group the descriptions closer to the function
+prototypes.
+
+Only functions excluded from the PVIPR are listed here.
+
+@smallexample
+int vec_all_nez (vector signed char, vector signed char);
+int vec_all_nez (vector unsigned char, vector unsigned char);
+int vec_all_nez (vector signed short, vector signed short);
+int vec_all_nez (vector unsigned short, vector unsigned short);
+int vec_all_nez (vector signed int, vector signed int);
+int vec_all_nez (vector unsigned int, vector unsigned int);
+
+int vec_any_eqz (vector signed char, vector signed char);
+int vec_any_eqz (vector unsigned char, vector unsigned char);
+int vec_any_eqz (vector signed short, vector signed short);
+int vec_any_eqz (vector unsigned short, vector unsigned short);
+int vec_any_eqz (vector signed int, vector signed int);
+int vec_any_eqz (vector unsigned int, vector unsigned int);
+
+signed char vec_xlx (unsigned int index, vector signed char data);
+unsigned char vec_xlx (unsigned int index, vector unsigned char data);
+signed short vec_xlx (unsigned int index, vector signed short data);
+unsigned short vec_xlx (unsigned int index, vector unsigned short data);
+signed int vec_xlx (unsigned int index, vector signed int data);
+unsigned int vec_xlx (unsigned int index, vector unsigned int data);
+float vec_xlx (unsigned int index, vector float data);
+
+signed char vec_xrx (unsigned int index, vector signed char data);
+unsigned char vec_xrx (unsigned int index, vector unsigned char data);
+signed short vec_xrx (unsigned int index, vector signed short data);
+unsigned short vec_xrx (unsigned int index, vector unsigned short data);
+signed int vec_xrx (unsigned int index, vector signed int data);
+unsigned int vec_xrx (unsigned int index, vector unsigned int data);
+float vec_xrx (unsigned int index, vector float data);
+@end smallexample
+
+The @code{vec_all_nez}, @code{vec_any_eqz}, and @code{vec_cmpnez}
+perform pairwise comparisons between the elements at the same
+positions within their two vector arguments.
+The @code{vec_all_nez} function returns a
+non-zero value if and only if all pairwise comparisons are not
+equal and no element of either vector argument contains a zero.
+The @code{vec_any_eqz} function returns a
+non-zero value if and only if at least one pairwise comparison is equal
+or if at least one element of either vector argument contains a zero.
+The @code{vec_cmpnez} function returns a vector of the same type as
+its two arguments, within which each element consists of all ones to
+denote that either the corresponding elements of the incoming arguments are
+not equal or that at least one of the corresponding elements contains
+zero. Otherwise, the element of the returned vector contains all zeros.
+
+The @code{vec_xlx} and @code{vec_xrx} functions extract the single
+element selected by the @code{index} argument from the vector
+represented by the @code{data} argument. The @code{index} argument
+always specifies a byte offset, regardless of the size of the vector
+element. With @code{vec_xlx}, @code{index} is the offset of the first
+byte of the element to be extracted. With @code{vec_xrx}, @code{index}
+represents the last byte of the element to be extracted, measured
+from the right end of the vector. In other words, the last byte of
+the element to be extracted is found at position @code{(15 - index)}.
+There is no requirement that @code{index} be a multiple of the vector
+element size. However, if the size of the vector element added to
+@code{index} is greater than 15, the content of the returned value is
+undefined.
+
+The following functions are also available if the ISA 3.0 instruction
+set additions (@option{-mcpu=power9}) are available.
+
+Only functions excluded from the PVIPR are listed here.
+
+@smallexample
+vector long long vec_vctz (vector long long);
+vector unsigned long long vec_vctz (vector unsigned long long);
+vector int vec_vctz (vector int);
+vector unsigned int vec_vctz (vector int);
+vector short vec_vctz (vector short);
+vector unsigned short vec_vctz (vector unsigned short);
+vector signed char vec_vctz (vector signed char);
+vector unsigned char vec_vctz (vector unsigned char);
+
+vector signed char vec_vctzb (vector signed char);
+vector unsigned char vec_vctzb (vector unsigned char);
+
+vector long long vec_vctzd (vector long long);
+vector unsigned long long vec_vctzd (vector unsigned long long);
+
+vector short vec_vctzh (vector short);
+vector unsigned short vec_vctzh (vector unsigned short);
+
+vector int vec_vctzw (vector int);
+vector unsigned int vec_vctzw (vector int);
+
+vector int vec_vprtyb (vector int);
+vector unsigned int vec_vprtyb (vector unsigned int);
+vector long long vec_vprtyb (vector long long);
+vector unsigned long long vec_vprtyb (vector unsigned long long);
+
+vector int vec_vprtybw (vector int);
+vector unsigned int vec_vprtybw (vector unsigned int);
+
+vector long long vec_vprtybd (vector long long);
+vector unsigned long long vec_vprtybd (vector unsigned long long);
+@end smallexample
+
+On 64-bit targets, if the ISA 3.0 additions (@option{-mcpu=power9})
+are available:
+
+@smallexample
+vector long vec_vprtyb (vector long);
+vector unsigned long vec_vprtyb (vector unsigned long);
+vector __int128 vec_vprtyb (vector __int128);
+vector __uint128 vec_vprtyb (vector __uint128);
+
+vector long vec_vprtybd (vector long);
+vector unsigned long vec_vprtybd (vector unsigned long);
+
+vector __int128 vec_vprtybq (vector __int128);
+vector __uint128 vec_vprtybd (vector __uint128);
+@end smallexample
+
+The following built-in functions are available for the PowerPC family
+of processors, starting with ISA 3.0 or later (@option{-mcpu=power9}).
+
+Only functions excluded from the PVIPR are listed here.
+
+@smallexample
+__vector unsigned char
+vec_absdb (__vector unsigned char arg1, __vector unsigned char arg2);
+__vector unsigned short
+vec_absdh (__vector unsigned short arg1, __vector unsigned short arg2);
+__vector unsigned int
+vec_absdw (__vector unsigned int arg1, __vector unsigned int arg2);
+@end smallexample
+
+The @code{vec_absd}, @code{vec_absdb}, @code{vec_absdh}, and
+@code{vec_absdw} built-in functions each computes the absolute
+differences of the pairs of vector elements supplied in its two vector
+arguments, placing the absolute differences into the corresponding
+elements of the vector result.
+
+The following built-in functions are available for the PowerPC family
+of processors, starting with ISA 3.0 or later (@option{-mcpu=power9}):
+@smallexample
+vector unsigned int vec_vrlnm (vector unsigned int, vector unsigned int);
+vector unsigned long long vec_vrlnm (vector unsigned long long,
+ vector unsigned long long);
+@end smallexample
+
+The result of @code{vec_vrlnm} is obtained by rotating each element
+of the first argument vector left and ANDing it with a mask. The
+second argument vector contains the mask beginning in bits 11:15,
+the mask end in bits 19:23, and the shift count in bits 27:31,
+of each element.
+
+If the cryptographic instructions are enabled (@option{-mcrypto} or
+@option{-mcpu=power8}), the following builtins are enabled.
+
+Only functions excluded from the PVIPR are listed here.
+
+@smallexample
+vector unsigned long long __builtin_crypto_vsbox (vector unsigned long long);
+
+vector unsigned long long __builtin_crypto_vcipher (vector unsigned long long,
+ vector unsigned long long);
+
+vector unsigned long long __builtin_crypto_vcipherlast
+ (vector unsigned long long,
+ vector unsigned long long);
+
+vector unsigned long long __builtin_crypto_vncipher (vector unsigned long long,
+ vector unsigned long long);
+
+vector unsigned long long __builtin_crypto_vncipherlast (vector unsigned long long,
+ vector unsigned long long);
+
+vector unsigned char __builtin_crypto_vpermxor (vector unsigned char,
+ vector unsigned char,
+ vector unsigned char);
+
+vector unsigned short __builtin_crypto_vpermxor (vector unsigned short,
+ vector unsigned short,
+ vector unsigned short);
+
+vector unsigned int __builtin_crypto_vpermxor (vector unsigned int,
+ vector unsigned int,
+ vector unsigned int);
+
+vector unsigned long long __builtin_crypto_vpermxor (vector unsigned long long,
+ vector unsigned long long,
+ vector unsigned long long);
+
+vector unsigned char __builtin_crypto_vpmsumb (vector unsigned char,
+ vector unsigned char);
+
+vector unsigned short __builtin_crypto_vpmsumh (vector unsigned short,
+ vector unsigned short);
+
+vector unsigned int __builtin_crypto_vpmsumw (vector unsigned int,
+ vector unsigned int);
+
+vector unsigned long long __builtin_crypto_vpmsumd (vector unsigned long long,
+ vector unsigned long long);
+
+vector unsigned long long __builtin_crypto_vshasigmad (vector unsigned long long,
+ int, int);
+
+vector unsigned int __builtin_crypto_vshasigmaw (vector unsigned int, int, int);
+@end smallexample
+
+The second argument to @var{__builtin_crypto_vshasigmad} and
+@var{__builtin_crypto_vshasigmaw} must be a constant
+integer that is 0 or 1. The third argument to these built-in functions
+must be a constant integer in the range of 0 to 15.
+
+The following sign extension builtins are provided:
+
+@smallexample
+vector signed int vec_signexti (vector signed char a);
+vector signed long long vec_signextll (vector signed char a);
+vector signed int vec_signexti (vector signed short a);
+vector signed long long vec_signextll (vector signed short a);
+vector signed long long vec_signextll (vector signed int a);
+vector signed long long vec_signextq (vector signed long long a);
+@end smallexample
+
+Each element of the result is produced by sign-extending the element of the
+input vector that would fall in the least significant portion of the result
+element. For example, a sign-extension of a vector signed char to a vector
+signed long long will sign extend the rightmost byte of each doubleword.
+
+@node PowerPC AltiVec Built-in Functions Available on ISA 3.1
+@subsubsection PowerPC AltiVec Built-in Functions Available on ISA 3.1
+
+The following additional built-in functions are also available for the
+PowerPC family of processors, starting with ISA 3.1 (@option{-mcpu=power10}):
+
+
+@smallexample
+@exdent vector unsigned long long int
+@exdent vec_cfuge (vector unsigned long long int, vector unsigned long long int);
+@end smallexample
+Perform a vector centrifuge operation, as if implemented by the
+@code{vcfuged} instruction.
+@findex vec_cfuge
+
+@smallexample
+@exdent vector unsigned long long int
+@exdent vec_cntlzm (vector unsigned long long int, vector unsigned long long int);
+@end smallexample
+Perform a vector count leading zeros under bit mask operation, as if
+implemented by the @code{vclzdm} instruction.
+@findex vec_cntlzm
+
+@smallexample
+@exdent vector unsigned long long int
+@exdent vec_cnttzm (vector unsigned long long int, vector unsigned long long int);
+@end smallexample
+Perform a vector count trailing zeros under bit mask operation, as if
+implemented by the @code{vctzdm} instruction.
+@findex vec_cnttzm
+
+@smallexample
+@exdent vector signed char
+@exdent vec_clrl (vector signed char a, unsigned int n);
+@exdent vector unsigned char
+@exdent vec_clrl (vector unsigned char a, unsigned int n);
+@end smallexample
+Clear the left-most @code{(16 - n)} bytes of vector argument @code{a}, as if
+implemented by the @code{vclrlb} instruction on a big-endian target
+and by the @code{vclrrb} instruction on a little-endian target. A
+value of @code{n} that is greater than 16 is treated as if it equaled 16.
+@findex vec_clrl
+
+@smallexample
+@exdent vector signed char
+@exdent vec_clrr (vector signed char a, unsigned int n);
+@exdent vector unsigned char
+@exdent vec_clrr (vector unsigned char a, unsigned int n);
+@end smallexample
+Clear the right-most @code{(16 - n)} bytes of vector argument @code{a}, as if
+implemented by the @code{vclrrb} instruction on a big-endian target
+and by the @code{vclrlb} instruction on a little-endian target. A
+value of @code{n} that is greater than 16 is treated as if it equaled 16.
+@findex vec_clrr
+
+@smallexample
+@exdent vector unsigned long long int
+@exdent vec_gnb (vector unsigned __int128, const unsigned char);
+@end smallexample
+Perform a 128-bit vector gather operation, as if implemented by the
+@code{vgnb} instruction. The second argument must be a literal
+integer value between 2 and 7 inclusive.
+@findex vec_gnb
+
+
+Vector Extract
+
+@smallexample
+@exdent vector unsigned long long int
+@exdent vec_extractl (vector unsigned char, vector unsigned char, unsigned int);
+@exdent vector unsigned long long int
+@exdent vec_extractl (vector unsigned short, vector unsigned short, unsigned int);
+@exdent vector unsigned long long int
+@exdent vec_extractl (vector unsigned int, vector unsigned int, unsigned int);
+@exdent vector unsigned long long int
+@exdent vec_extractl (vector unsigned long long, vector unsigned long long, unsigned int);
+@end smallexample
+Extract an element from two concatenated vectors starting at the given byte index
+in natural-endian order, and place it zero-extended in doubleword 1 of the result
+according to natural element order. If the byte index is out of range for the
+data type, the intrinsic will be rejected.
+For little-endian, this output will match the placement by the hardware
+instruction, i.e., dword[0] in RTL notation. For big-endian, an additional
+instruction is needed to move it from the "left" doubleword to the "right" one.
+For little-endian, semantics matching the @code{vextdubvrx},
+@code{vextduhvrx}, @code{vextduwvrx} instruction will be generated, while for
+big-endian, semantics matching the @code{vextdubvlx}, @code{vextduhvlx},
+@code{vextduwvlx} instructions
+will be generated. Note that some fairly anomalous results can be generated if
+the byte index is not aligned on an element boundary for the element being
+extracted. This is a limitation of the bi-endian vector programming model is
+consistent with the limitation on @code{vec_perm}.
+@findex vec_extractl
+
+@smallexample
+@exdent vector unsigned long long int
+@exdent vec_extracth (vector unsigned char, vector unsigned char, unsigned int);
+@exdent vector unsigned long long int
+@exdent vec_extracth (vector unsigned short, vector unsigned short,
+unsigned int);
+@exdent vector unsigned long long int
+@exdent vec_extracth (vector unsigned int, vector unsigned int, unsigned int);
+@exdent vector unsigned long long int
+@exdent vec_extracth (vector unsigned long long, vector unsigned long long,
+unsigned int);
+@end smallexample
+Extract an element from two concatenated vectors starting at the given byte
+index. The index is based on big endian order for a little endian system.
+Similarly, the index is based on little endian order for a big endian system.
+The extraced elements are zero-extended and put in doubleword 1
+according to natural element order. If the byte index is out of range for the
+data type, the intrinsic will be rejected. For little-endian, this output
+will match the placement by the hardware instruction (vextdubvrx, vextduhvrx,
+vextduwvrx, vextddvrx) i.e., dword[0] in RTL
+notation. For big-endian, an additional instruction is needed to move it
+from the "left" doubleword to the "right" one. For little-endian, semantics
+matching the @code{vextdubvlx}, @code{vextduhvlx}, @code{vextduwvlx}
+instructions will be generated, while for big-endian, semantics matching the
+@code{vextdubvrx}, @code{vextduhvrx}, @code{vextduwvrx} instructions will
+be generated. Note that some fairly anomalous
+results can be generated if the byte index is not aligned on the
+element boundary for the element being extracted. This is a
+limitation of the bi-endian vector programming model consistent with the
+limitation on @code{vec_perm}.
+@findex vec_extracth
+@smallexample
+@exdent vector unsigned long long int
+@exdent vec_pdep (vector unsigned long long int, vector unsigned long long int);
+@end smallexample
+Perform a vector parallel bits deposit operation, as if implemented by
+the @code{vpdepd} instruction.
+@findex vec_pdep
+
+Vector Insert
+
+@smallexample
+@exdent vector unsigned char
+@exdent vec_insertl (unsigned char, vector unsigned char, unsigned int);
+@exdent vector unsigned short
+@exdent vec_insertl (unsigned short, vector unsigned short, unsigned int);
+@exdent vector unsigned int
+@exdent vec_insertl (unsigned int, vector unsigned int, unsigned int);
+@exdent vector unsigned long long
+@exdent vec_insertl (unsigned long long, vector unsigned long long,
+unsigned int);
+@exdent vector unsigned char
+@exdent vec_insertl (vector unsigned char, vector unsigned char, unsigned int;
+@exdent vector unsigned short
+@exdent vec_insertl (vector unsigned short, vector unsigned short,
+unsigned int);
+@exdent vector unsigned int
+@exdent vec_insertl (vector unsigned int, vector unsigned int, unsigned int);
+@end smallexample
+
+Let src be the first argument, when the first argument is a scalar, or the
+rightmost element of the left doubleword of the first argument, when the first
+argument is a vector. Insert the source into the destination at the position
+given by the third argument, using natural element order in the second
+argument. The rest of the second argument is unchanged. If the byte
+index is greater than 14 for halfwords, greater than 12 for words, or
+greater than 8 for doublewords the result is undefined. For little-endian,
+the generated code will be semantically equivalent to @code{vins[bhwd]rx}
+instructions. Similarly for big-endian it will be semantically equivalent
+to @code{vins[bhwd]lx}. Note that some fairly anomalous results can be
+generated if the byte index is not aligned on an element boundary for the
+type of element being inserted.
+@findex vec_insertl
+
+@smallexample
+@exdent vector unsigned char
+@exdent vec_inserth (unsigned char, vector unsigned char, unsigned int);
+@exdent vector unsigned short
+@exdent vec_inserth (unsigned short, vector unsigned short, unsigned int);
+@exdent vector unsigned int
+@exdent vec_inserth (unsigned int, vector unsigned int, unsigned int);
+@exdent vector unsigned long long
+@exdent vec_inserth (unsigned long long, vector unsigned long long,
+unsigned int);
+@exdent vector unsigned char
+@exdent vec_inserth (vector unsigned char, vector unsigned char, unsigned int);
+@exdent vector unsigned short
+@exdent vec_inserth (vector unsigned short, vector unsigned short,
+unsigned int);
+@exdent vector unsigned int
+@exdent vec_inserth (vector unsigned int, vector unsigned int, unsigned int);
+@end smallexample
+
+Let src be the first argument, when the first argument is a scalar, or the
+rightmost element of the first argument, when the first argument is a vector.
+Insert src into the second argument at the position identified by the third
+argument, using opposite element order in the second argument, and leaving the
+rest of the second argument unchanged. If the byte index is greater than 14
+for halfwords, 12 for words, or 8 for doublewords, the intrinsic will be
+rejected. Note that the underlying hardware instruction uses the same register
+for the second argument and the result.
+For little-endian, the code generation will be semantically equivalent to
+@code{vins[bhwd]lx}, while for big-endian it will be semantically equivalent to
+@code{vins[bhwd]rx}.
+Note that some fairly anomalous results can be generated if the byte index is
+not aligned on an element boundary for the sort of element being inserted.
+@findex vec_inserth
+
+Vector Replace Element
+@smallexample
+@exdent vector signed int vec_replace_elt (vector signed int, signed int,
+const int);
+@exdent vector unsigned int vec_replace_elt (vector unsigned int,
+unsigned int, const int);
+@exdent vector float vec_replace_elt (vector float, float, const int);
+@exdent vector signed long long vec_replace_elt (vector signed long long,
+signed long long, const int);
+@exdent vector unsigned long long vec_replace_elt (vector unsigned long long,
+unsigned long long, const int);
+@exdent vector double rec_replace_elt (vector double, double, const int);
+@end smallexample
+The third argument (constrained to [0,3]) identifies the natural-endian
+element number of the first argument that will be replaced by the second
+argument to produce the result. The other elements of the first argument will
+remain unchanged in the result.
+
+If it's desirable to insert a word at an unaligned position, use
+vec_replace_unaligned instead.
+
+@findex vec_replace_element
+
+Vector Replace Unaligned
+@smallexample
+@exdent vector unsigned char vec_replace_unaligned (vector unsigned char,
+signed int, const int);
+@exdent vector unsigned char vec_replace_unaligned (vector unsigned char,
+unsigned int, const int);
+@exdent vector unsigned char vec_replace_unaligned (vector unsigned char,
+float, const int);
+@exdent vector unsigned char vec_replace_unaligned (vector unsigned char,
+signed long long, const int);
+@exdent vector unsigned char vec_replace_unaligned (vector unsigned char,
+unsigned long long, const int);
+@exdent vector unsigned char vec_replace_unaligned (vector unsigned char,
+double, const int);
+@end smallexample
+
+The second argument replaces a portion of the first argument to produce the
+result, with the rest of the first argument unchanged in the result. The
+third argument identifies the byte index (using left-to-right, or big-endian
+order) where the high-order byte of the second argument will be placed, with
+the remaining bytes of the second argument placed naturally "to the right"
+of the high-order byte.
+
+The programmer is responsible for understanding the endianness issues involved
+with the first argument and the result.
+@findex vec_replace_unaligned
+
+Vector Shift Left Double Bit Immediate
+@smallexample
+@exdent vector signed char vec_sldb (vector signed char, vector signed char,
+const unsigned int);
+@exdent vector unsigned char vec_sldb (vector unsigned char,
+vector unsigned char, const unsigned int);
+@exdent vector signed short vec_sldb (vector signed short, vector signed short,
+const unsigned int);
+@exdent vector unsigned short vec_sldb (vector unsigned short,
+vector unsigned short, const unsigned int);
+@exdent vector signed int vec_sldb (vector signed int, vector signed int,
+const unsigned int);
+@exdent vector unsigned int vec_sldb (vector unsigned int, vector unsigned int,
+const unsigned int);
+@exdent vector signed long long vec_sldb (vector signed long long,
+vector signed long long, const unsigned int);
+@exdent vector unsigned long long vec_sldb (vector unsigned long long,
+vector unsigned long long, const unsigned int);
+@end smallexample
+
+Shift the combined input vectors left by the amount specified by the low-order
+three bits of the third argument, and return the leftmost remaining 128 bits.
+Code using this instruction must be endian-aware.
+
+@findex vec_sldb
+
+Vector Shift Right Double Bit Immediate
+
+@smallexample
+@exdent vector signed char vec_srdb (vector signed char, vector signed char,
+const unsigned int);
+@exdent vector unsigned char vec_srdb (vector unsigned char, vector unsigned char,
+const unsigned int);
+@exdent vector signed short vec_srdb (vector signed short, vector signed short,
+const unsigned int);
+@exdent vector unsigned short vec_srdb (vector unsigned short, vector unsigned short,
+const unsigned int);
+@exdent vector signed int vec_srdb (vector signed int, vector signed int,
+const unsigned int);
+@exdent vector unsigned int vec_srdb (vector unsigned int, vector unsigned int,
+const unsigned int);
+@exdent vector signed long long vec_srdb (vector signed long long,
+vector signed long long, const unsigned int);
+@exdent vector unsigned long long vec_srdb (vector unsigned long long,
+vector unsigned long long, const unsigned int);
+@end smallexample
+
+Shift the combined input vectors right by the amount specified by the low-order
+three bits of the third argument, and return the remaining 128 bits. Code
+using this built-in must be endian-aware.
+
+@findex vec_srdb
+
+Vector Splat
+
+@smallexample
+@exdent vector signed int vec_splati (const signed int);
+@exdent vector float vec_splati (const float);
+@end smallexample
+
+Splat a 32-bit immediate into a vector of words.
+
+@findex vec_splati
+
+@smallexample
+@exdent vector double vec_splatid (const float);
+@end smallexample
+
+Convert a single precision floating-point value to double-precision and splat
+the result to a vector of double-precision floats.
+
+@findex vec_splatid
+
+@smallexample
+@exdent vector signed int vec_splati_ins (vector signed int,
+const unsigned int, const signed int);
+@exdent vector unsigned int vec_splati_ins (vector unsigned int,
+const unsigned int, const unsigned int);
+@exdent vector float vec_splati_ins (vector float, const unsigned int,
+const float);
+@end smallexample
+
+Argument 2 must be either 0 or 1. Splat the value of argument 3 into the word
+identified by argument 2 of each doubleword of argument 1 and return the
+result. The other words of argument 1 are unchanged.
+
+@findex vec_splati_ins
+
+Vector Blend Variable
+
+@smallexample
+@exdent vector signed char vec_blendv (vector signed char, vector signed char,
+vector unsigned char);
+@exdent vector unsigned char vec_blendv (vector unsigned char,
+vector unsigned char, vector unsigned char);
+@exdent vector signed short vec_blendv (vector signed short,
+vector signed short, vector unsigned short);
+@exdent vector unsigned short vec_blendv (vector unsigned short,
+vector unsigned short, vector unsigned short);
+@exdent vector signed int vec_blendv (vector signed int, vector signed int,
+vector unsigned int);
+@exdent vector unsigned int vec_blendv (vector unsigned int,
+vector unsigned int, vector unsigned int);
+@exdent vector signed long long vec_blendv (vector signed long long,
+vector signed long long, vector unsigned long long);
+@exdent vector unsigned long long vec_blendv (vector unsigned long long,
+vector unsigned long long, vector unsigned long long);
+@exdent vector float vec_blendv (vector float, vector float,
+vector unsigned int);
+@exdent vector double vec_blendv (vector double, vector double,
+vector unsigned long long);
+@end smallexample
+
+Blend the first and second argument vectors according to the sign bits of the
+corresponding elements of the third argument vector. This is similar to the
+@code{vsel} and @code{xxsel} instructions but for bigger elements.
+
+@findex vec_blendv
+
+Vector Permute Extended
+
+@smallexample
+@exdent vector signed char vec_permx (vector signed char, vector signed char,
+vector unsigned char, const int);
+@exdent vector unsigned char vec_permx (vector unsigned char,
+vector unsigned char, vector unsigned char, const int);
+@exdent vector signed short vec_permx (vector signed short,
+vector signed short, vector unsigned char, const int);
+@exdent vector unsigned short vec_permx (vector unsigned short,
+vector unsigned short, vector unsigned char, const int);
+@exdent vector signed int vec_permx (vector signed int, vector signed int,
+vector unsigned char, const int);
+@exdent vector unsigned int vec_permx (vector unsigned int,
+vector unsigned int, vector unsigned char, const int);
+@exdent vector signed long long vec_permx (vector signed long long,
+vector signed long long, vector unsigned char, const int);
+@exdent vector unsigned long long vec_permx (vector unsigned long long,
+vector unsigned long long, vector unsigned char, const int);
+@exdent vector float (vector float, vector float, vector unsigned char,
+const int);
+@exdent vector double (vector double, vector double, vector unsigned char,
+const int);
+@end smallexample
+
+Perform a partial permute of the first two arguments, which form a 32-byte
+section of an emulated vector up to 256 bytes wide, using the partial permute
+control vector in the third argument. The fourth argument (constrained to
+values of 0-7) identifies which 32-byte section of the emulated vector is
+contained in the first two arguments.
+@findex vec_permx
+
+@smallexample
+@exdent vector unsigned long long int
+@exdent vec_pext (vector unsigned long long int, vector unsigned long long int);
+@end smallexample
+Perform a vector parallel bit extract operation, as if implemented by
+the @code{vpextd} instruction.
+@findex vec_pext
+
+@smallexample
+@exdent vector unsigned char vec_stril (vector unsigned char);
+@exdent vector signed char vec_stril (vector signed char);
+@exdent vector unsigned short vec_stril (vector unsigned short);
+@exdent vector signed short vec_stril (vector signed short);
+@end smallexample
+Isolate the left-most non-zero elements of the incoming vector argument,
+replacing all elements to the right of the left-most zero element
+found within the argument with zero. The typical implementation uses
+the @code{vstribl} or @code{vstrihl} instruction on big-endian targets
+and uses the @code{vstribr} or @code{vstrihr} instruction on
+little-endian targets.
+@findex vec_stril
+
+@smallexample
+@exdent int vec_stril_p (vector unsigned char);
+@exdent int vec_stril_p (vector signed char);
+@exdent int short vec_stril_p (vector unsigned short);
+@exdent int vec_stril_p (vector signed short);
+@end smallexample
+Return a non-zero value if and only if the argument contains a zero
+element. The typical implementation uses
+the @code{vstribl.} or @code{vstrihl.} instruction on big-endian targets
+and uses the @code{vstribr.} or @code{vstrihr.} instruction on
+little-endian targets. Choose this built-in to check for presence of
+zero element if the same argument is also passed to @code{vec_stril}.
+@findex vec_stril_p
+
+@smallexample
+@exdent vector unsigned char vec_strir (vector unsigned char);
+@exdent vector signed char vec_strir (vector signed char);
+@exdent vector unsigned short vec_strir (vector unsigned short);
+@exdent vector signed short vec_strir (vector signed short);
+@end smallexample
+Isolate the right-most non-zero elements of the incoming vector argument,
+replacing all elements to the left of the right-most zero element
+found within the argument with zero. The typical implementation uses
+the @code{vstribr} or @code{vstrihr} instruction on big-endian targets
+and uses the @code{vstribl} or @code{vstrihl} instruction on
+little-endian targets.
+@findex vec_strir
+
+@smallexample
+@exdent int vec_strir_p (vector unsigned char);
+@exdent int vec_strir_p (vector signed char);
+@exdent int short vec_strir_p (vector unsigned short);
+@exdent int vec_strir_p (vector signed short);
+@end smallexample
+Return a non-zero value if and only if the argument contains a zero
+element. The typical implementation uses
+the @code{vstribr.} or @code{vstrihr.} instruction on big-endian targets
+and uses the @code{vstribl.} or @code{vstrihl.} instruction on
+little-endian targets. Choose this built-in to check for presence of
+zero element if the same argument is also passed to @code{vec_strir}.
+@findex vec_strir_p
+
+@smallexample
+@exdent vector unsigned char
+@exdent vec_ternarylogic (vector unsigned char, vector unsigned char,
+ vector unsigned char, const unsigned int);
+@exdent vector unsigned short
+@exdent vec_ternarylogic (vector unsigned short, vector unsigned short,
+ vector unsigned short, const unsigned int);
+@exdent vector unsigned int
+@exdent vec_ternarylogic (vector unsigned int, vector unsigned int,
+ vector unsigned int, const unsigned int);
+@exdent vector unsigned long long int
+@exdent vec_ternarylogic (vector unsigned long long int, vector unsigned long long int,
+ vector unsigned long long int, const unsigned int);
+@exdent vector unsigned __int128
+@exdent vec_ternarylogic (vector unsigned __int128, vector unsigned __int128,
+ vector unsigned __int128, const unsigned int);
+@end smallexample
+Perform a 128-bit vector evaluate operation, as if implemented by the
+@code{xxeval} instruction. The fourth argument must be a literal
+integer value between 0 and 255 inclusive.
+@findex vec_ternarylogic
+
+@smallexample
+@exdent vector unsigned char vec_genpcvm (vector unsigned char, const int);
+@exdent vector unsigned short vec_genpcvm (vector unsigned short, const int);
+@exdent vector unsigned int vec_genpcvm (vector unsigned int, const int);
+@exdent vector unsigned int vec_genpcvm (vector unsigned long long int,
+ const int);
+@end smallexample
+
+Vector Integer Multiply/Divide/Modulo
+
+@smallexample
+@exdent vector signed int
+@exdent vec_mulh (vector signed int a, vector signed int b);
+@exdent vector unsigned int
+@exdent vec_mulh (vector unsigned int a, vector unsigned int b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 3, do the following. The integer
+value in word element @code{i} of a is multiplied by the integer value in word
+element @code{i} of b. The high-order 32 bits of the 64-bit product are placed
+into word element @code{i} of the vector returned.
+
+@smallexample
+@exdent vector signed long long
+@exdent vec_mulh (vector signed long long a, vector signed long long b);
+@exdent vector unsigned long long
+@exdent vec_mulh (vector unsigned long long a, vector unsigned long long b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 1, do the following. The integer
+value in doubleword element @code{i} of a is multiplied by the integer value in
+doubleword element @code{i} of b. The high-order 64 bits of the 128-bit product
+are placed into doubleword element @code{i} of the vector returned.
+
+@smallexample
+@exdent vector unsigned long long
+@exdent vec_mul (vector unsigned long long a, vector unsigned long long b);
+@exdent vector signed long long
+@exdent vec_mul (vector signed long long a, vector signed long long b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 1, do the following. The integer
+value in doubleword element @code{i} of a is multiplied by the integer value in
+doubleword element @code{i} of b. The low-order 64 bits of the 128-bit product
+are placed into doubleword element @code{i} of the vector returned.
+
+@smallexample
+@exdent vector signed int
+@exdent vec_div (vector signed int a, vector signed int b);
+@exdent vector unsigned int
+@exdent vec_div (vector unsigned int a, vector unsigned int b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 3, do the following. The integer in
+word element @code{i} of a is divided by the integer in word element @code{i}
+of b. The unique integer quotient is placed into the word element @code{i} of
+the vector returned. If an attempt is made to perform any of the divisions
+<anything> ÷ 0 then the quotient is undefined.
+
+@smallexample
+@exdent vector signed long long
+@exdent vec_div (vector signed long long a, vector signed long long b);
+@exdent vector unsigned long long
+@exdent vec_div (vector unsigned long long a, vector unsigned long long b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 1, do the following. The integer in
+doubleword element @code{i} of a is divided by the integer in doubleword
+element @code{i} of b. The unique integer quotient is placed into the
+doubleword element @code{i} of the vector returned. If an attempt is made to
+perform any of the divisions 0x8000_0000_0000_0000 ÷ -1 or <anything> ÷ 0 then
+the quotient is undefined.
+
+@smallexample
+@exdent vector signed int
+@exdent vec_dive (vector signed int a, vector signed int b);
+@exdent vector unsigned int
+@exdent vec_dive (vector unsigned int a, vector unsigned int b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 3, do the following. The integer in
+word element @code{i} of a is shifted left by 32 bits, then divided by the
+integer in word element @code{i} of b. The unique integer quotient is placed
+into the word element @code{i} of the vector returned. If the quotient cannot
+be represented in 32 bits, or if an attempt is made to perform any of the
+divisions <anything> ÷ 0 then the quotient is undefined.
+
+@smallexample
+@exdent vector signed long long
+@exdent vec_dive (vector signed long long a, vector signed long long b);
+@exdent vector unsigned long long
+@exdent vec_dive (vector unsigned long long a, vector unsigned long long b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 1, do the following. The integer in
+doubleword element @code{i} of a is shifted left by 64 bits, then divided by
+the integer in doubleword element @code{i} of b. The unique integer quotient is
+placed into the doubleword element @code{i} of the vector returned. If the
+quotient cannot be represented in 64 bits, or if an attempt is made to perform
+<anything> ÷ 0 then the quotient is undefined.
+
+@smallexample
+@exdent vector signed int
+@exdent vec_mod (vector signed int a, vector signed int b);
+@exdent vector unsigned int
+@exdent vec_mod (vector unsigned int a, vector unsigned int b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 3, do the following. The integer in
+word element @code{i} of a is divided by the integer in word element @code{i}
+of b. The unique integer remainder is placed into the word element @code{i} of
+the vector returned. If an attempt is made to perform any of the divisions
+0x8000_0000 ÷ -1 or <anything> ÷ 0 then the remainder is undefined.
+
+@smallexample
+@exdent vector signed long long
+@exdent vec_mod (vector signed long long a, vector signed long long b);
+@exdent vector unsigned long long
+@exdent vec_mod (vector unsigned long long a, vector unsigned long long b);
+@end smallexample
+
+For each integer value @code{i} from 0 to 1, do the following. The integer in
+doubleword element @code{i} of a is divided by the integer in doubleword
+element @code{i} of b. The unique integer remainder is placed into the
+doubleword element @code{i} of the vector returned. If an attempt is made to
+perform <anything> ÷ 0 then the remainder is undefined.
+
+Generate PCV from specified Mask size, as if implemented by the
+@code{xxgenpcvbm}, @code{xxgenpcvhm}, @code{xxgenpcvwm} instructions, where
+immediate value is either 0, 1, 2 or 3.
+@findex vec_genpcvm
+
+@smallexample
+@exdent vector unsigned __int128 vec_rl (vector unsigned __int128 A,
+ vector unsigned __int128 B);
+@exdent vector signed __int128 vec_rl (vector signed __int128 A,
+ vector unsigned __int128 B);
+@end smallexample
+
+Result value: Each element of R is obtained by rotating the corresponding element
+of A left by the number of bits specified by the corresponding element of B.
+
+
+@smallexample
+@exdent vector unsigned __int128 vec_rlmi (vector unsigned __int128,
+ vector unsigned __int128,
+ vector unsigned __int128);
+@exdent vector signed __int128 vec_rlmi (vector signed __int128,
+ vector signed __int128,
+ vector unsigned __int128);
+@end smallexample
+
+Returns the result of rotating the first input and inserting it under mask
+into the second input. The first bit in the mask, the last bit in the mask are
+obtained from the two 7-bit fields bits [108:115] and bits [117:123]
+respectively of the second input. The shift is obtained from the third input
+in the 7-bit field [125:131] where all bits counted from zero at the left.
+
+@smallexample
+@exdent vector unsigned __int128 vec_rlnm (vector unsigned __int128,
+ vector unsigned __int128,
+ vector unsigned __int128);
+@exdent vector signed __int128 vec_rlnm (vector signed __int128,
+ vector unsigned __int128,
+ vector unsigned __int128);
+@end smallexample
+
+Returns the result of rotating the first input and ANDing it with a mask. The
+first bit in the mask and the last bit in the mask are obtained from the two
+7-bit fields bits [117:123] and bits [125:131] respectively of the second
+input. The shift is obtained from the third input in the 7-bit field bits
+[125:131] where all bits counted from zero at the left.
+
+@smallexample
+@exdent vector unsigned __int128 vec_sl(vector unsigned __int128 A, vector unsigned __int128 B);
+@exdent vector signed __int128 vec_sl(vector signed __int128 A, vector unsigned __int128 B);
+@end smallexample
+
+Result value: Each element of R is obtained by shifting the corresponding element of
+A left by the number of bits specified by the corresponding element of B.
+
+@smallexample
+@exdent vector unsigned __int128 vec_sr(vector unsigned __int128 A, vector unsigned __int128 B);
+@exdent vector signed __int128 vec_sr(vector signed __int128 A, vector unsigned __int128 B);
+@end smallexample
+
+Result value: Each element of R is obtained by shifting the corresponding element of
+A right by the number of bits specified by the corresponding element of B.
+
+@smallexample
+@exdent vector unsigned __int128 vec_sra(vector unsigned __int128 A, vector unsigned __int128 B);
+@exdent vector signed __int128 vec_sra(vector signed __int128 A, vector unsigned __int128 B);
+@end smallexample
+
+Result value: Each element of R is obtained by arithmetic shifting the corresponding
+element of A right by the number of bits specified by the corresponding element of B.
+
+@smallexample
+@exdent vector unsigned __int128 vec_mule (vector unsigned long long,
+ vector unsigned long long);
+@exdent vector signed __int128 vec_mule (vector signed long long,
+ vector signed long long);
+@end smallexample
+
+Returns a vector containing a 128-bit integer result of multiplying the even
+doubleword elements of the two inputs.
+
+@smallexample
+@exdent vector unsigned __int128 vec_mulo (vector unsigned long long,
+ vector unsigned long long);
+@exdent vector signed __int128 vec_mulo (vector signed long long,
+ vector signed long long);
+@end smallexample
+
+Returns a vector containing a 128-bit integer result of multiplying the odd
+doubleword elements of the two inputs.
+
+@smallexample
+@exdent vector unsigned __int128 vec_div (vector unsigned __int128,
+ vector unsigned __int128);
+@exdent vector signed __int128 vec_div (vector signed __int128,
+ vector signed __int128);
+@end smallexample
+
+Returns the result of dividing the first operand by the second operand. An
+attempt to divide any value by zero or to divide the most negative signed
+128-bit integer by negative one results in an undefined value.
+
+@smallexample
+@exdent vector unsigned __int128 vec_dive (vector unsigned __int128,
+ vector unsigned __int128);
+@exdent vector signed __int128 vec_dive (vector signed __int128,
+ vector signed __int128);
+@end smallexample
+
+The result is produced by shifting the first input left by 128 bits and
+dividing by the second. If an attempt is made to divide by zero or the result
+is larger than 128 bits, the result is undefined.
+
+@smallexample
+@exdent vector unsigned __int128 vec_mod (vector unsigned __int128,
+ vector unsigned __int128);
+@exdent vector signed __int128 vec_mod (vector signed __int128,
+ vector signed __int128);
+@end smallexample
+
+The result is the modulo result of dividing the first input by the second
+input.
+
+The following builtins perform 128-bit vector comparisons. The
+@code{vec_all_xx}, @code{vec_any_xx}, and @code{vec_cmpxx}, where @code{xx} is
+one of the operations @code{eq, ne, gt, lt, ge, le} perform pairwise
+comparisons between the elements at the same positions within their two vector
+arguments. The @code{vec_all_xx}function returns a non-zero value if and only
+if all pairwise comparisons are true. The @code{vec_any_xx} function returns
+a non-zero value if and only if at least one pairwise comparison is true. The
+@code{vec_cmpxx}function returns a vector of the same type as its two
+arguments, within which each element consists of all ones to denote that
+specified logical comparison of the corresponding elements was true.
+Otherwise, the element of the returned vector contains all zeros.
+
+@smallexample
+vector bool __int128 vec_cmpeq (vector signed __int128, vector signed __int128);
+vector bool __int128 vec_cmpeq (vector unsigned __int128, vector unsigned __int128);
+vector bool __int128 vec_cmpne (vector signed __int128, vector signed __int128);
+vector bool __int128 vec_cmpne (vector unsigned __int128, vector unsigned __int128);
+vector bool __int128 vec_cmpgt (vector signed __int128, vector signed __int128);
+vector bool __int128 vec_cmpgt (vector unsigned __int128, vector unsigned __int128);
+vector bool __int128 vec_cmplt (vector signed __int128, vector signed __int128);
+vector bool __int128 vec_cmplt (vector unsigned __int128, vector unsigned __int128);
+vector bool __int128 vec_cmpge (vector signed __int128, vector signed __int128);
+vector bool __int128 vec_cmpge (vector unsigned __int128, vector unsigned __int128);
+vector bool __int128 vec_cmple (vector signed __int128, vector signed __int128);
+vector bool __int128 vec_cmple (vector unsigned __int128, vector unsigned __int128);
+
+int vec_all_eq (vector signed __int128, vector signed __int128);
+int vec_all_eq (vector unsigned __int128, vector unsigned __int128);
+int vec_all_ne (vector signed __int128, vector signed __int128);
+int vec_all_ne (vector unsigned __int128, vector unsigned __int128);
+int vec_all_gt (vector signed __int128, vector signed __int128);
+int vec_all_gt (vector unsigned __int128, vector unsigned __int128);
+int vec_all_lt (vector signed __int128, vector signed __int128);
+int vec_all_lt (vector unsigned __int128, vector unsigned __int128);
+int vec_all_ge (vector signed __int128, vector signed __int128);
+int vec_all_ge (vector unsigned __int128, vector unsigned __int128);
+int vec_all_le (vector signed __int128, vector signed __int128);
+int vec_all_le (vector unsigned __int128, vector unsigned __int128);
+
+int vec_any_eq (vector signed __int128, vector signed __int128);
+int vec_any_eq (vector unsigned __int128, vector unsigned __int128);
+int vec_any_ne (vector signed __int128, vector signed __int128);
+int vec_any_ne (vector unsigned __int128, vector unsigned __int128);
+int vec_any_gt (vector signed __int128, vector signed __int128);
+int vec_any_gt (vector unsigned __int128, vector unsigned __int128);
+int vec_any_lt (vector signed __int128, vector signed __int128);
+int vec_any_lt (vector unsigned __int128, vector unsigned __int128);
+int vec_any_ge (vector signed __int128, vector signed __int128);
+int vec_any_ge (vector unsigned __int128, vector unsigned __int128);
+int vec_any_le (vector signed __int128, vector signed __int128);
+int vec_any_le (vector unsigned __int128, vector unsigned __int128);
+@end smallexample
+
+
+@node PowerPC Hardware Transactional Memory Built-in Functions
+@subsection PowerPC Hardware Transactional Memory Built-in Functions
+GCC provides two interfaces for accessing the Hardware Transactional
+Memory (HTM) instructions available on some of the PowerPC family
+of processors (eg, POWER8). The two interfaces come in a low level
+interface, consisting of built-in functions specific to PowerPC and a
+higher level interface consisting of inline functions that are common
+between PowerPC and S/390.
+
+@subsubsection PowerPC HTM Low Level Built-in Functions
+
+The following low level built-in functions are available with
+@option{-mhtm} or @option{-mcpu=CPU} where CPU is `power8' or later.
+They all generate the machine instruction that is part of the name.
+
+The HTM builtins (with the exception of @code{__builtin_tbegin}) return
+the full 4-bit condition register value set by their associated hardware
+instruction. The header file @code{htmintrin.h} defines some macros that can
+be used to decipher the return value. The @code{__builtin_tbegin} builtin
+returns a simple @code{true} or @code{false} value depending on whether a transaction was
+successfully started or not. The arguments of the builtins match exactly the
+type and order of the associated hardware instruction's operands, except for
+the @code{__builtin_tcheck} builtin, which does not take any input arguments.
+Refer to the ISA manual for a description of each instruction's operands.
+
+@smallexample
+unsigned int __builtin_tbegin (unsigned int);
+unsigned int __builtin_tend (unsigned int);
+
+unsigned int __builtin_tabort (unsigned int);
+unsigned int __builtin_tabortdc (unsigned int, unsigned int, unsigned int);
+unsigned int __builtin_tabortdci (unsigned int, unsigned int, int);
+unsigned int __builtin_tabortwc (unsigned int, unsigned int, unsigned int);
+unsigned int __builtin_tabortwci (unsigned int, unsigned int, int);
+
+unsigned int __builtin_tcheck (void);
+unsigned int __builtin_treclaim (unsigned int);
+unsigned int __builtin_trechkpt (void);
+unsigned int __builtin_tsr (unsigned int);
+@end smallexample
+
+In addition to the above HTM built-ins, we have added built-ins for
+some common extended mnemonics of the HTM instructions:
+
+@smallexample
+unsigned int __builtin_tendall (void);
+unsigned int __builtin_tresume (void);
+unsigned int __builtin_tsuspend (void);
+@end smallexample
+
+Note that the semantics of the above HTM builtins are required to mimic
+the locking semantics used for critical sections. Builtins that are used
+to create a new transaction or restart a suspended transaction must have
+lock acquisition like semantics while those builtins that end or suspend a
+transaction must have lock release like semantics. Specifically, this must
+mimic lock semantics as specified by C++11, for example: Lock acquisition is
+as-if an execution of __atomic_exchange_n(&globallock,1,__ATOMIC_ACQUIRE)
+that returns 0, and lock release is as-if an execution of
+__atomic_store(&globallock,0,__ATOMIC_RELEASE), with globallock being an
+implicit implementation-defined lock used for all transactions. The HTM
+instructions associated with with the builtins inherently provide the
+correct acquisition and release hardware barriers required. However,
+the compiler must also be prohibited from moving loads and stores across
+the builtins in a way that would violate their semantics. This has been
+accomplished by adding memory barriers to the associated HTM instructions
+(which is a conservative approach to provide acquire and release semantics).
+Earlier versions of the compiler did not treat the HTM instructions as
+memory barriers. A @code{__TM_FENCE__} macro has been added, which can
+be used to determine whether the current compiler treats HTM instructions
+as memory barriers or not. This allows the user to explicitly add memory
+barriers to their code when using an older version of the compiler.
+
+The following set of built-in functions are available to gain access
+to the HTM specific special purpose registers.
+
+@smallexample
+unsigned long __builtin_get_texasr (void);
+unsigned long __builtin_get_texasru (void);
+unsigned long __builtin_get_tfhar (void);
+unsigned long __builtin_get_tfiar (void);
+
+void __builtin_set_texasr (unsigned long);
+void __builtin_set_texasru (unsigned long);
+void __builtin_set_tfhar (unsigned long);
+void __builtin_set_tfiar (unsigned long);
+@end smallexample
+
+Example usage of these low level built-in functions may look like:
+
+@smallexample
+#include <htmintrin.h>
+
+int num_retries = 10;
+
+while (1)
+ @{
+ if (__builtin_tbegin (0))
+ @{
+ /* Transaction State Initiated. */
+ if (is_locked (lock))
+ __builtin_tabort (0);
+ ... transaction code...
+ __builtin_tend (0);
+ break;
+ @}
+ else
+ @{
+ /* Transaction State Failed. Use locks if the transaction
+ failure is "persistent" or we've tried too many times. */
+ if (num_retries-- <= 0
+ || _TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))
+ @{
+ acquire_lock (lock);
+ ... non transactional fallback path...
+ release_lock (lock);
+ break;
+ @}
+ @}
+ @}
+@end smallexample
+
+One final built-in function has been added that returns the value of
+the 2-bit Transaction State field of the Machine Status Register (MSR)
+as stored in @code{CR0}.
+
+@smallexample
+unsigned long __builtin_ttest (void)
+@end smallexample
+
+This built-in can be used to determine the current transaction state
+using the following code example:
+
+@smallexample
+#include <htmintrin.h>
+
+unsigned char tx_state = _HTM_STATE (__builtin_ttest ());
+
+if (tx_state == _HTM_TRANSACTIONAL)
+ @{
+ /* Code to use in transactional state. */
+ @}
+else if (tx_state == _HTM_NONTRANSACTIONAL)
+ @{
+ /* Code to use in non-transactional state. */
+ @}
+else if (tx_state == _HTM_SUSPENDED)
+ @{
+ /* Code to use in transaction suspended state. */
+ @}
+@end smallexample
+
+@subsubsection PowerPC HTM High Level Inline Functions
+
+The following high level HTM interface is made available by including
+@code{<htmxlintrin.h>} and using @option{-mhtm} or @option{-mcpu=CPU}
+where CPU is `power8' or later. This interface is common between PowerPC
+and S/390, allowing users to write one HTM source implementation that
+can be compiled and executed on either system.
+
+@smallexample
+long __TM_simple_begin (void);
+long __TM_begin (void* const TM_buff);
+long __TM_end (void);
+void __TM_abort (void);
+void __TM_named_abort (unsigned char const code);
+void __TM_resume (void);
+void __TM_suspend (void);
+
+long __TM_is_user_abort (void* const TM_buff);
+long __TM_is_named_user_abort (void* const TM_buff, unsigned char *code);
+long __TM_is_illegal (void* const TM_buff);
+long __TM_is_footprint_exceeded (void* const TM_buff);
+long __TM_nesting_depth (void* const TM_buff);
+long __TM_is_nested_too_deep(void* const TM_buff);
+long __TM_is_conflict(void* const TM_buff);
+long __TM_is_failure_persistent(void* const TM_buff);
+long __TM_failure_address(void* const TM_buff);
+long long __TM_failure_code(void* const TM_buff);
+@end smallexample
+
+Using these common set of HTM inline functions, we can create
+a more portable version of the HTM example in the previous
+section that will work on either PowerPC or S/390:
+
+@smallexample
+#include <htmxlintrin.h>
+
+int num_retries = 10;
+TM_buff_type TM_buff;
+
+while (1)
+ @{
+ if (__TM_begin (TM_buff) == _HTM_TBEGIN_STARTED)
+ @{
+ /* Transaction State Initiated. */
+ if (is_locked (lock))
+ __TM_abort ();
+ ... transaction code...
+ __TM_end ();
+ break;
+ @}
+ else
+ @{
+ /* Transaction State Failed. Use locks if the transaction
+ failure is "persistent" or we've tried too many times. */
+ if (num_retries-- <= 0
+ || __TM_is_failure_persistent (TM_buff))
+ @{
+ acquire_lock (lock);
+ ... non transactional fallback path...
+ release_lock (lock);
+ break;
+ @}
+ @}
+ @}
+@end smallexample
+
+@node PowerPC Atomic Memory Operation Functions
+@subsection PowerPC Atomic Memory Operation Functions
+ISA 3.0 of the PowerPC added new atomic memory operation (amo)
+instructions. GCC provides support for these instructions in 64-bit
+environments. All of the functions are declared in the include file
+@code{amo.h}.
+
+The functions supported are:
+
+@smallexample
+#include <amo.h>
+
+uint32_t amo_lwat_add (uint32_t *, uint32_t);
+uint32_t amo_lwat_xor (uint32_t *, uint32_t);
+uint32_t amo_lwat_ior (uint32_t *, uint32_t);
+uint32_t amo_lwat_and (uint32_t *, uint32_t);
+uint32_t amo_lwat_umax (uint32_t *, uint32_t);
+uint32_t amo_lwat_umin (uint32_t *, uint32_t);
+uint32_t amo_lwat_swap (uint32_t *, uint32_t);
+
+int32_t amo_lwat_sadd (int32_t *, int32_t);
+int32_t amo_lwat_smax (int32_t *, int32_t);
+int32_t amo_lwat_smin (int32_t *, int32_t);
+int32_t amo_lwat_sswap (int32_t *, int32_t);
+
+uint64_t amo_ldat_add (uint64_t *, uint64_t);
+uint64_t amo_ldat_xor (uint64_t *, uint64_t);
+uint64_t amo_ldat_ior (uint64_t *, uint64_t);
+uint64_t amo_ldat_and (uint64_t *, uint64_t);
+uint64_t amo_ldat_umax (uint64_t *, uint64_t);
+uint64_t amo_ldat_umin (uint64_t *, uint64_t);
+uint64_t amo_ldat_swap (uint64_t *, uint64_t);
+
+int64_t amo_ldat_sadd (int64_t *, int64_t);
+int64_t amo_ldat_smax (int64_t *, int64_t);
+int64_t amo_ldat_smin (int64_t *, int64_t);
+int64_t amo_ldat_sswap (int64_t *, int64_t);
+
+void amo_stwat_add (uint32_t *, uint32_t);
+void amo_stwat_xor (uint32_t *, uint32_t);
+void amo_stwat_ior (uint32_t *, uint32_t);
+void amo_stwat_and (uint32_t *, uint32_t);
+void amo_stwat_umax (uint32_t *, uint32_t);
+void amo_stwat_umin (uint32_t *, uint32_t);
+
+void amo_stwat_sadd (int32_t *, int32_t);
+void amo_stwat_smax (int32_t *, int32_t);
+void amo_stwat_smin (int32_t *, int32_t);
+
+void amo_stdat_add (uint64_t *, uint64_t);
+void amo_stdat_xor (uint64_t *, uint64_t);
+void amo_stdat_ior (uint64_t *, uint64_t);
+void amo_stdat_and (uint64_t *, uint64_t);
+void amo_stdat_umax (uint64_t *, uint64_t);
+void amo_stdat_umin (uint64_t *, uint64_t);
+
+void amo_stdat_sadd (int64_t *, int64_t);
+void amo_stdat_smax (int64_t *, int64_t);
+void amo_stdat_smin (int64_t *, int64_t);
+@end smallexample
+
+@node PowerPC Matrix-Multiply Assist Built-in Functions
+@subsection PowerPC Matrix-Multiply Assist Built-in Functions
+ISA 3.1 of the PowerPC added new Matrix-Multiply Assist (MMA) instructions.
+GCC provides support for these instructions through the following built-in
+functions which are enabled with the @code{-mmma} option. The vec_t type
+below is defined to be a normal vector unsigned char type. The uint2, uint4
+and uint8 parameters are 2-bit, 4-bit and 8-bit unsigned integer constants
+respectively. The compiler will verify that they are constants and that
+their values are within range.
+
+The built-in functions supported are:
+
+@smallexample
+void __builtin_mma_xvi4ger8 (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvi8ger4 (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvi16ger2 (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvi16ger2s (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf16ger2 (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvbf16ger2 (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf32ger (__vector_quad *, vec_t, vec_t);
+
+void __builtin_mma_xvi4ger8pp (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvi8ger4pp (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvi8ger4spp(__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvi16ger2pp (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvi16ger2spp (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf16ger2pp (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf16ger2pn (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf16ger2np (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf16ger2nn (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvbf16ger2pp (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvbf16ger2pn (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvbf16ger2np (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvbf16ger2nn (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf32gerpp (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf32gerpn (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf32gernp (__vector_quad *, vec_t, vec_t);
+void __builtin_mma_xvf32gernn (__vector_quad *, vec_t, vec_t);
+
+void __builtin_mma_pmxvi4ger8 (__vector_quad *, vec_t, vec_t, uint4, uint4, uint8);
+void __builtin_mma_pmxvi4ger8pp (__vector_quad *, vec_t, vec_t, uint4, uint4, uint8);
+
+void __builtin_mma_pmxvi8ger4 (__vector_quad *, vec_t, vec_t, uint4, uint4, uint4);
+void __builtin_mma_pmxvi8ger4pp (__vector_quad *, vec_t, vec_t, uint4, uint4, uint4);
+void __builtin_mma_pmxvi8ger4spp(__vector_quad *, vec_t, vec_t, uint4, uint4, uint4);
+
+void __builtin_mma_pmxvi16ger2 (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvi16ger2s (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvf16ger2 (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvbf16ger2 (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+
+void __builtin_mma_pmxvi16ger2pp (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvi16ger2spp (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvf16ger2pp (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvf16ger2pn (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvf16ger2np (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvf16ger2nn (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvbf16ger2pp (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvbf16ger2pn (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvbf16ger2np (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+void __builtin_mma_pmxvbf16ger2nn (__vector_quad *, vec_t, vec_t, uint4, uint4, uint2);
+
+void __builtin_mma_pmxvf32ger (__vector_quad *, vec_t, vec_t, uint4, uint4);
+void __builtin_mma_pmxvf32gerpp (__vector_quad *, vec_t, vec_t, uint4, uint4);
+void __builtin_mma_pmxvf32gerpn (__vector_quad *, vec_t, vec_t, uint4, uint4);
+void __builtin_mma_pmxvf32gernp (__vector_quad *, vec_t, vec_t, uint4, uint4);
+void __builtin_mma_pmxvf32gernn (__vector_quad *, vec_t, vec_t, uint4, uint4);
+
+void __builtin_mma_xvf64ger (__vector_quad *, __vector_pair, vec_t);
+void __builtin_mma_xvf64gerpp (__vector_quad *, __vector_pair, vec_t);
+void __builtin_mma_xvf64gerpn (__vector_quad *, __vector_pair, vec_t);
+void __builtin_mma_xvf64gernp (__vector_quad *, __vector_pair, vec_t);
+void __builtin_mma_xvf64gernn (__vector_quad *, __vector_pair, vec_t);
+
+void __builtin_mma_pmxvf64ger (__vector_quad *, __vector_pair, vec_t, uint4, uint2);
+void __builtin_mma_pmxvf64gerpp (__vector_quad *, __vector_pair, vec_t, uint4, uint2);
+void __builtin_mma_pmxvf64gerpn (__vector_quad *, __vector_pair, vec_t, uint4, uint2);
+void __builtin_mma_pmxvf64gernp (__vector_quad *, __vector_pair, vec_t, uint4, uint2);
+void __builtin_mma_pmxvf64gernn (__vector_quad *, __vector_pair, vec_t, uint4, uint2);
+
+void __builtin_mma_xxmtacc (__vector_quad *);
+void __builtin_mma_xxmfacc (__vector_quad *);
+void __builtin_mma_xxsetaccz (__vector_quad *);
+
+void __builtin_mma_build_acc (__vector_quad *, vec_t, vec_t, vec_t, vec_t);
+void __builtin_mma_disassemble_acc (void *, __vector_quad *);
+
+void __builtin_vsx_build_pair (__vector_pair *, vec_t, vec_t);
+void __builtin_vsx_disassemble_pair (void *, __vector_pair *);
+
+vec_t __builtin_vsx_xvcvspbf16 (vec_t);
+vec_t __builtin_vsx_xvcvbf16spn (vec_t);
+
+__vector_pair __builtin_vsx_lxvp (size_t, __vector_pair *);
+void __builtin_vsx_stxvp (__vector_pair, size_t, __vector_pair *);
+@end smallexample
+
+@node PRU Built-in Functions
+@subsection PRU Built-in Functions
+
+GCC provides a couple of special builtin functions to aid in utilizing
+special PRU instructions.
+
+The built-in functions supported are:
+
+@table @code
+@item __delay_cycles (long long @var{cycles})
+This inserts an instruction sequence that takes exactly @var{cycles}
+cycles (between 0 and 0xffffffff) to complete. The inserted sequence
+may use jumps, loops, or no-ops, and does not interfere with any other
+instructions. Note that @var{cycles} must be a compile-time constant
+integer - that is, you must pass a number, not a variable that may be
+optimized to a constant later. The number of cycles delayed by this
+builtin is exact.
+
+@item __halt (void)
+This inserts a HALT instruction to stop processor execution.
+
+@item unsigned int __lmbd (unsigned int @var{wordval}, unsigned int @var{bitval})
+This inserts LMBD instruction to calculate the left-most bit with value
+@var{bitval} in value @var{wordval}. Only the least significant bit
+of @var{bitval} is taken into account.
+@end table
+
+@node RISC-V Built-in Functions
+@subsection RISC-V Built-in Functions
+
+These built-in functions are available for the RISC-V family of
+processors.
+
+@deftypefn {Built-in Function} {void *} __builtin_thread_pointer (void)
+Returns the value that is currently set in the @samp{tp} register.
+@end deftypefn
+
+@node RX Built-in Functions
+@subsection RX Built-in Functions
+GCC supports some of the RX instructions which cannot be expressed in
+the C programming language via the use of built-in functions. The
+following functions are supported:
+
+@deftypefn {Built-in Function} void __builtin_rx_brk (void)
+Generates the @code{brk} machine instruction.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_clrpsw (int)
+Generates the @code{clrpsw} machine instruction to clear the specified
+bit in the processor status word.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_int (int)
+Generates the @code{int} machine instruction to generate an interrupt
+with the specified value.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_machi (int, int)
+Generates the @code{machi} machine instruction to add the result of
+multiplying the top 16 bits of the two arguments into the
+accumulator.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_maclo (int, int)
+Generates the @code{maclo} machine instruction to add the result of
+multiplying the bottom 16 bits of the two arguments into the
+accumulator.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_mulhi (int, int)
+Generates the @code{mulhi} machine instruction to place the result of
+multiplying the top 16 bits of the two arguments into the
+accumulator.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_mullo (int, int)
+Generates the @code{mullo} machine instruction to place the result of
+multiplying the bottom 16 bits of the two arguments into the
+accumulator.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_rx_mvfachi (void)
+Generates the @code{mvfachi} machine instruction to read the top
+32 bits of the accumulator.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_rx_mvfacmi (void)
+Generates the @code{mvfacmi} machine instruction to read the middle
+32 bits of the accumulator.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_rx_mvfc (int)
+Generates the @code{mvfc} machine instruction which reads the control
+register specified in its argument and returns its value.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_mvtachi (int)
+Generates the @code{mvtachi} machine instruction to set the top
+32 bits of the accumulator.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_mvtaclo (int)
+Generates the @code{mvtaclo} machine instruction to set the bottom
+32 bits of the accumulator.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_mvtc (int reg, int val)
+Generates the @code{mvtc} machine instruction which sets control
+register number @code{reg} to @code{val}.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_mvtipl (int)
+Generates the @code{mvtipl} machine instruction set the interrupt
+priority level.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_racw (int)
+Generates the @code{racw} machine instruction to round the accumulator
+according to the specified mode.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_rx_revw (int)
+Generates the @code{revw} machine instruction which swaps the bytes in
+the argument so that bits 0--7 now occupy bits 8--15 and vice versa,
+and also bits 16--23 occupy bits 24--31 and vice versa.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_rmpa (void)
+Generates the @code{rmpa} machine instruction which initiates a
+repeated multiply and accumulate sequence.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_round (float)
+Generates the @code{round} machine instruction which returns the
+floating-point argument rounded according to the current rounding mode
+set in the floating-point status word register.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_rx_sat (int)
+Generates the @code{sat} machine instruction which returns the
+saturated value of the argument.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_setpsw (int)
+Generates the @code{setpsw} machine instruction to set the specified
+bit in the processor status word.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_rx_wait (void)
+Generates the @code{wait} machine instruction.
+@end deftypefn
+
+@node S/390 System z Built-in Functions
+@subsection S/390 System z Built-in Functions
+@deftypefn {Built-in Function} int __builtin_tbegin (void*)
+Generates the @code{tbegin} machine instruction starting a
+non-constrained hardware transaction. If the parameter is non-NULL the
+memory area is used to store the transaction diagnostic buffer and
+will be passed as first operand to @code{tbegin}. This buffer can be
+defined using the @code{struct __htm_tdb} C struct defined in
+@code{htmintrin.h} and must reside on a double-word boundary. The
+second tbegin operand is set to @code{0xff0c}. This enables
+save/restore of all GPRs and disables aborts for FPR and AR
+manipulations inside the transaction body. The condition code set by
+the tbegin instruction is returned as integer value. The tbegin
+instruction by definition overwrites the content of all FPRs. The
+compiler will generate code which saves and restores the FPRs. For
+soft-float code it is recommended to used the @code{*_nofloat}
+variant. In order to prevent a TDB from being written it is required
+to pass a constant zero value as parameter. Passing a zero value
+through a variable is not sufficient. Although modifications of
+access registers inside the transaction will not trigger an
+transaction abort it is not supported to actually modify them. Access
+registers do not get saved when entering a transaction. They will have
+undefined state when reaching the abort code.
+@end deftypefn
+
+Macros for the possible return codes of tbegin are defined in the
+@code{htmintrin.h} header file:
+
+@table @code
+@item _HTM_TBEGIN_STARTED
+@code{tbegin} has been executed as part of normal processing. The
+transaction body is supposed to be executed.
+@item _HTM_TBEGIN_INDETERMINATE
+The transaction was aborted due to an indeterminate condition which
+might be persistent.
+@item _HTM_TBEGIN_TRANSIENT
+The transaction aborted due to a transient failure. The transaction
+should be re-executed in that case.
+@item _HTM_TBEGIN_PERSISTENT
+The transaction aborted due to a persistent failure. Re-execution
+under same circumstances will not be productive.
+@end table
+
+@defmac _HTM_FIRST_USER_ABORT_CODE
+The @code{_HTM_FIRST_USER_ABORT_CODE} defined in @code{htmintrin.h}
+specifies the first abort code which can be used for
+@code{__builtin_tabort}. Values below this threshold are reserved for
+machine use.
+@end defmac
+
+@deftp {Data type} {struct __htm_tdb}
+The @code{struct __htm_tdb} defined in @code{htmintrin.h} describes
+the structure of the transaction diagnostic block as specified in the
+Principles of Operation manual chapter 5-91.
+@end deftp
+
+@deftypefn {Built-in Function} int __builtin_tbegin_nofloat (void*)
+Same as @code{__builtin_tbegin} but without FPR saves and restores.
+Using this variant in code making use of FPRs will leave the FPRs in
+undefined state when entering the transaction abort handler code.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_tbegin_retry (void*, int)
+In addition to @code{__builtin_tbegin} a loop for transient failures
+is generated. If tbegin returns a condition code of 2 the transaction
+will be retried as often as specified in the second argument. The
+perform processor assist instruction is used to tell the CPU about the
+number of fails so far.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_tbegin_retry_nofloat (void*, int)
+Same as @code{__builtin_tbegin_retry} but without FPR saves and
+restores. Using this variant in code making use of FPRs will leave
+the FPRs in undefined state when entering the transaction abort
+handler code.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_tbeginc (void)
+Generates the @code{tbeginc} machine instruction starting a constrained
+hardware transaction. The second operand is set to @code{0xff08}.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_tend (void)
+Generates the @code{tend} machine instruction finishing a transaction
+and making the changes visible to other threads. The condition code
+generated by tend is returned as integer value.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_tabort (int)
+Generates the @code{tabort} machine instruction with the specified
+abort code. Abort codes from 0 through 255 are reserved and will
+result in an error message.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_tx_assist (int)
+Generates the @code{ppa rX,rY,1} machine instruction. Where the
+integer parameter is loaded into rX and a value of zero is loaded into
+rY. The integer parameter specifies the number of times the
+transaction repeatedly aborted.
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_tx_nesting_depth (void)
+Generates the @code{etnd} machine instruction. The current nesting
+depth is returned as integer value. For a nesting depth of 0 the code
+is not executed as part of an transaction.
+@end deftypefn
+
+@deftypefn {Built-in Function} void __builtin_non_tx_store (uint64_t *, uint64_t)
+
+Generates the @code{ntstg} machine instruction. The second argument
+is written to the first arguments location. The store operation will
+not be rolled-back in case of an transaction abort.
+@end deftypefn
+
+@node SH Built-in Functions
+@subsection SH Built-in Functions
+The following built-in functions are supported on the SH1, SH2, SH3 and SH4
+families of processors:
+
+@deftypefn {Built-in Function} {void} __builtin_set_thread_pointer (void *@var{ptr})
+Sets the @samp{GBR} register to the specified value @var{ptr}. This is usually
+used by system code that manages threads and execution contexts. The compiler
+normally does not generate code that modifies the contents of @samp{GBR} and
+thus the value is preserved across function calls. Changing the @samp{GBR}
+value in user code must be done with caution, since the compiler might use
+@samp{GBR} in order to access thread local variables.
+
+@end deftypefn
+
+@deftypefn {Built-in Function} {void *} __builtin_thread_pointer (void)
+Returns the value that is currently set in the @samp{GBR} register.
+Memory loads and stores that use the thread pointer as a base address are
+turned into @samp{GBR} based displacement loads and stores, if possible.
+For example:
+@smallexample
+struct my_tcb
+@{
+ int a, b, c, d, e;
+@};
+
+int get_tcb_value (void)
+@{
+ // Generate @samp{mov.l @@(8,gbr),r0} instruction
+ return ((my_tcb*)__builtin_thread_pointer ())->c;
+@}
+
+@end smallexample
+@end deftypefn
+
+@deftypefn {Built-in Function} {unsigned int} __builtin_sh_get_fpscr (void)
+Returns the value that is currently set in the @samp{FPSCR} register.
+@end deftypefn
+
+@deftypefn {Built-in Function} {void} __builtin_sh_set_fpscr (unsigned int @var{val})
+Sets the @samp{FPSCR} register to the specified value @var{val}, while
+preserving the current values of the FR, SZ and PR bits.
+@end deftypefn
+
+@node SPARC VIS Built-in Functions
+@subsection SPARC VIS Built-in Functions
+
+GCC supports SIMD operations on the SPARC using both the generic vector
+extensions (@pxref{Vector Extensions}) as well as built-in functions for
+the SPARC Visual Instruction Set (VIS). When you use the @option{-mvis}
+switch, the VIS extension is exposed as the following built-in functions:
+
+@smallexample
+typedef int v1si __attribute__ ((vector_size (4)));
+typedef int v2si __attribute__ ((vector_size (8)));
+typedef short v4hi __attribute__ ((vector_size (8)));
+typedef short v2hi __attribute__ ((vector_size (4)));
+typedef unsigned char v8qi __attribute__ ((vector_size (8)));
+typedef unsigned char v4qi __attribute__ ((vector_size (4)));
+
+void __builtin_vis_write_gsr (int64_t);
+int64_t __builtin_vis_read_gsr (void);
+
+void * __builtin_vis_alignaddr (void *, long);
+void * __builtin_vis_alignaddrl (void *, long);
+int64_t __builtin_vis_faligndatadi (int64_t, int64_t);
+v2si __builtin_vis_faligndatav2si (v2si, v2si);
+v4hi __builtin_vis_faligndatav4hi (v4si, v4si);
+v8qi __builtin_vis_faligndatav8qi (v8qi, v8qi);
+
+v4hi __builtin_vis_fexpand (v4qi);
+
+v4hi __builtin_vis_fmul8x16 (v4qi, v4hi);
+v4hi __builtin_vis_fmul8x16au (v4qi, v2hi);
+v4hi __builtin_vis_fmul8x16al (v4qi, v2hi);
+v4hi __builtin_vis_fmul8sux16 (v8qi, v4hi);
+v4hi __builtin_vis_fmul8ulx16 (v8qi, v4hi);
+v2si __builtin_vis_fmuld8sux16 (v4qi, v2hi);
+v2si __builtin_vis_fmuld8ulx16 (v4qi, v2hi);
+
+v4qi __builtin_vis_fpack16 (v4hi);
+v8qi __builtin_vis_fpack32 (v2si, v8qi);
+v2hi __builtin_vis_fpackfix (v2si);
+v8qi __builtin_vis_fpmerge (v4qi, v4qi);
+
+int64_t __builtin_vis_pdist (v8qi, v8qi, int64_t);
+
+long __builtin_vis_edge8 (void *, void *);
+long __builtin_vis_edge8l (void *, void *);
+long __builtin_vis_edge16 (void *, void *);
+long __builtin_vis_edge16l (void *, void *);
+long __builtin_vis_edge32 (void *, void *);
+long __builtin_vis_edge32l (void *, void *);
+
+long __builtin_vis_fcmple16 (v4hi, v4hi);
+long __builtin_vis_fcmple32 (v2si, v2si);
+long __builtin_vis_fcmpne16 (v4hi, v4hi);
+long __builtin_vis_fcmpne32 (v2si, v2si);
+long __builtin_vis_fcmpgt16 (v4hi, v4hi);
+long __builtin_vis_fcmpgt32 (v2si, v2si);
+long __builtin_vis_fcmpeq16 (v4hi, v4hi);
+long __builtin_vis_fcmpeq32 (v2si, v2si);
+
+v4hi __builtin_vis_fpadd16 (v4hi, v4hi);
+v2hi __builtin_vis_fpadd16s (v2hi, v2hi);
+v2si __builtin_vis_fpadd32 (v2si, v2si);
+v1si __builtin_vis_fpadd32s (v1si, v1si);
+v4hi __builtin_vis_fpsub16 (v4hi, v4hi);
+v2hi __builtin_vis_fpsub16s (v2hi, v2hi);
+v2si __builtin_vis_fpsub32 (v2si, v2si);
+v1si __builtin_vis_fpsub32s (v1si, v1si);
+
+long __builtin_vis_array8 (long, long);
+long __builtin_vis_array16 (long, long);
+long __builtin_vis_array32 (long, long);
+@end smallexample
+
+When you use the @option{-mvis2} switch, the VIS version 2.0 built-in
+functions also become available:
+
+@smallexample
+long __builtin_vis_bmask (long, long);
+int64_t __builtin_vis_bshuffledi (int64_t, int64_t);
+v2si __builtin_vis_bshufflev2si (v2si, v2si);
+v4hi __builtin_vis_bshufflev2si (v4hi, v4hi);
+v8qi __builtin_vis_bshufflev2si (v8qi, v8qi);
+
+long __builtin_vis_edge8n (void *, void *);
+long __builtin_vis_edge8ln (void *, void *);
+long __builtin_vis_edge16n (void *, void *);
+long __builtin_vis_edge16ln (void *, void *);
+long __builtin_vis_edge32n (void *, void *);
+long __builtin_vis_edge32ln (void *, void *);
+@end smallexample
+
+When you use the @option{-mvis3} switch, the VIS version 3.0 built-in
+functions also become available:
+
+@smallexample
+void __builtin_vis_cmask8 (long);
+void __builtin_vis_cmask16 (long);
+void __builtin_vis_cmask32 (long);
+
+v4hi __builtin_vis_fchksm16 (v4hi, v4hi);
+
+v4hi __builtin_vis_fsll16 (v4hi, v4hi);
+v4hi __builtin_vis_fslas16 (v4hi, v4hi);
+v4hi __builtin_vis_fsrl16 (v4hi, v4hi);
+v4hi __builtin_vis_fsra16 (v4hi, v4hi);
+v2si __builtin_vis_fsll16 (v2si, v2si);
+v2si __builtin_vis_fslas16 (v2si, v2si);
+v2si __builtin_vis_fsrl16 (v2si, v2si);
+v2si __builtin_vis_fsra16 (v2si, v2si);
+
+long __builtin_vis_pdistn (v8qi, v8qi);
+
+v4hi __builtin_vis_fmean16 (v4hi, v4hi);
+
+int64_t __builtin_vis_fpadd64 (int64_t, int64_t);
+int64_t __builtin_vis_fpsub64 (int64_t, int64_t);
+
+v4hi __builtin_vis_fpadds16 (v4hi, v4hi);
+v2hi __builtin_vis_fpadds16s (v2hi, v2hi);
+v4hi __builtin_vis_fpsubs16 (v4hi, v4hi);
+v2hi __builtin_vis_fpsubs16s (v2hi, v2hi);
+v2si __builtin_vis_fpadds32 (v2si, v2si);
+v1si __builtin_vis_fpadds32s (v1si, v1si);
+v2si __builtin_vis_fpsubs32 (v2si, v2si);
+v1si __builtin_vis_fpsubs32s (v1si, v1si);
+
+long __builtin_vis_fucmple8 (v8qi, v8qi);
+long __builtin_vis_fucmpne8 (v8qi, v8qi);
+long __builtin_vis_fucmpgt8 (v8qi, v8qi);
+long __builtin_vis_fucmpeq8 (v8qi, v8qi);
+
+float __builtin_vis_fhadds (float, float);
+double __builtin_vis_fhaddd (double, double);
+float __builtin_vis_fhsubs (float, float);
+double __builtin_vis_fhsubd (double, double);
+float __builtin_vis_fnhadds (float, float);
+double __builtin_vis_fnhaddd (double, double);
+
+int64_t __builtin_vis_umulxhi (int64_t, int64_t);
+int64_t __builtin_vis_xmulx (int64_t, int64_t);
+int64_t __builtin_vis_xmulxhi (int64_t, int64_t);
+@end smallexample
+
+When you use the @option{-mvis4} switch, the VIS version 4.0 built-in
+functions also become available:
+
+@smallexample
+v8qi __builtin_vis_fpadd8 (v8qi, v8qi);
+v8qi __builtin_vis_fpadds8 (v8qi, v8qi);
+v8qi __builtin_vis_fpaddus8 (v8qi, v8qi);
+v4hi __builtin_vis_fpaddus16 (v4hi, v4hi);
+
+v8qi __builtin_vis_fpsub8 (v8qi, v8qi);
+v8qi __builtin_vis_fpsubs8 (v8qi, v8qi);
+v8qi __builtin_vis_fpsubus8 (v8qi, v8qi);
+v4hi __builtin_vis_fpsubus16 (v4hi, v4hi);
+
+long __builtin_vis_fpcmple8 (v8qi, v8qi);
+long __builtin_vis_fpcmpgt8 (v8qi, v8qi);
+long __builtin_vis_fpcmpule16 (v4hi, v4hi);
+long __builtin_vis_fpcmpugt16 (v4hi, v4hi);
+long __builtin_vis_fpcmpule32 (v2si, v2si);
+long __builtin_vis_fpcmpugt32 (v2si, v2si);
+
+v8qi __builtin_vis_fpmax8 (v8qi, v8qi);
+v4hi __builtin_vis_fpmax16 (v4hi, v4hi);
+v2si __builtin_vis_fpmax32 (v2si, v2si);
+
+v8qi __builtin_vis_fpmaxu8 (v8qi, v8qi);
+v4hi __builtin_vis_fpmaxu16 (v4hi, v4hi);
+v2si __builtin_vis_fpmaxu32 (v2si, v2si);
+
+v8qi __builtin_vis_fpmin8 (v8qi, v8qi);
+v4hi __builtin_vis_fpmin16 (v4hi, v4hi);
+v2si __builtin_vis_fpmin32 (v2si, v2si);
+
+v8qi __builtin_vis_fpminu8 (v8qi, v8qi);
+v4hi __builtin_vis_fpminu16 (v4hi, v4hi);
+v2si __builtin_vis_fpminu32 (v2si, v2si);
+@end smallexample
+
+When you use the @option{-mvis4b} switch, the VIS version 4.0B
+built-in functions also become available:
+
+@smallexample
+v8qi __builtin_vis_dictunpack8 (double, int);
+v4hi __builtin_vis_dictunpack16 (double, int);
+v2si __builtin_vis_dictunpack32 (double, int);
+
+long __builtin_vis_fpcmple8shl (v8qi, v8qi, int);
+long __builtin_vis_fpcmpgt8shl (v8qi, v8qi, int);
+long __builtin_vis_fpcmpeq8shl (v8qi, v8qi, int);
+long __builtin_vis_fpcmpne8shl (v8qi, v8qi, int);
+
+long __builtin_vis_fpcmple16shl (v4hi, v4hi, int);
+long __builtin_vis_fpcmpgt16shl (v4hi, v4hi, int);
+long __builtin_vis_fpcmpeq16shl (v4hi, v4hi, int);
+long __builtin_vis_fpcmpne16shl (v4hi, v4hi, int);
+
+long __builtin_vis_fpcmple32shl (v2si, v2si, int);
+long __builtin_vis_fpcmpgt32shl (v2si, v2si, int);
+long __builtin_vis_fpcmpeq32shl (v2si, v2si, int);
+long __builtin_vis_fpcmpne32shl (v2si, v2si, int);
+
+long __builtin_vis_fpcmpule8shl (v8qi, v8qi, int);
+long __builtin_vis_fpcmpugt8shl (v8qi, v8qi, int);
+long __builtin_vis_fpcmpule16shl (v4hi, v4hi, int);
+long __builtin_vis_fpcmpugt16shl (v4hi, v4hi, int);
+long __builtin_vis_fpcmpule32shl (v2si, v2si, int);
+long __builtin_vis_fpcmpugt32shl (v2si, v2si, int);
+
+long __builtin_vis_fpcmpde8shl (v8qi, v8qi, int);
+long __builtin_vis_fpcmpde16shl (v4hi, v4hi, int);
+long __builtin_vis_fpcmpde32shl (v2si, v2si, int);
+
+long __builtin_vis_fpcmpur8shl (v8qi, v8qi, int);
+long __builtin_vis_fpcmpur16shl (v4hi, v4hi, int);
+long __builtin_vis_fpcmpur32shl (v2si, v2si, int);
+@end smallexample
+
+@node TI C6X Built-in Functions
+@subsection TI C6X Built-in Functions
+
+GCC provides intrinsics to access certain instructions of the TI C6X
+processors. These intrinsics, listed below, are available after
+inclusion of the @code{c6x_intrinsics.h} header file. They map directly
+to C6X instructions.
+
+@smallexample
+int _sadd (int, int);
+int _ssub (int, int);
+int _sadd2 (int, int);
+int _ssub2 (int, int);
+long long _mpy2 (int, int);
+long long _smpy2 (int, int);
+int _add4 (int, int);
+int _sub4 (int, int);
+int _saddu4 (int, int);
+
+int _smpy (int, int);
+int _smpyh (int, int);
+int _smpyhl (int, int);
+int _smpylh (int, int);
+
+int _sshl (int, int);
+int _subc (int, int);
+
+int _avg2 (int, int);
+int _avgu4 (int, int);
+
+int _clrr (int, int);
+int _extr (int, int);
+int _extru (int, int);
+int _abs (int);
+int _abs2 (int);
+@end smallexample
+
+@node x86 Built-in Functions
+@subsection x86 Built-in Functions
+
+These built-in functions are available for the x86-32 and x86-64 family
+of computers, depending on the command-line switches used.
+
+If you specify command-line switches such as @option{-msse},
+the compiler could use the extended instruction sets even if the built-ins
+are not used explicitly in the program. For this reason, applications
+that perform run-time CPU detection must compile separate files for each
+supported architecture, using the appropriate flags. In particular,
+the file containing the CPU detection code should be compiled without
+these options.
+
+The following machine modes are available for use with MMX built-in functions
+(@pxref{Vector Extensions}): @code{V2SI} for a vector of two 32-bit integers,
+@code{V4HI} for a vector of four 16-bit integers, and @code{V8QI} for a
+vector of eight 8-bit integers. Some of the built-in functions operate on
+MMX registers as a whole 64-bit entity, these use @code{V1DI} as their mode.
+
+If 3DNow!@: extensions are enabled, @code{V2SF} is used as a mode for a vector
+of two 32-bit floating-point values.
+
+If SSE extensions are enabled, @code{V4SF} is used for a vector of four 32-bit
+floating-point values. Some instructions use a vector of four 32-bit
+integers, these use @code{V4SI}. Finally, some instructions operate on an
+entire vector register, interpreting it as a 128-bit integer, these use mode
+@code{TI}.
+
+The x86-32 and x86-64 family of processors use additional built-in
+functions for efficient use of @code{TF} (@code{__float128}) 128-bit
+floating point and @code{TC} 128-bit complex floating-point values.
+
+The following floating-point built-in functions are always available. All
+of them implement the function that is part of the name.
+
+@smallexample
+__float128 __builtin_fabsq (__float128)
+__float128 __builtin_copysignq (__float128, __float128)
+@end smallexample
+
+The following built-in functions are always available.
+
+@table @code
+@item __float128 __builtin_infq (void)
+Similar to @code{__builtin_inf}, except the return type is @code{__float128}.
+@findex __builtin_infq
+
+@item __float128 __builtin_huge_valq (void)
+Similar to @code{__builtin_huge_val}, except the return type is @code{__float128}.
+@findex __builtin_huge_valq
+
+@item __float128 __builtin_nanq (void)
+Similar to @code{__builtin_nan}, except the return type is @code{__float128}.
+@findex __builtin_nanq
+
+@item __float128 __builtin_nansq (void)
+Similar to @code{__builtin_nans}, except the return type is @code{__float128}.
+@findex __builtin_nansq
+@end table
+
+The following built-in function is always available.
+
+@table @code
+@item void __builtin_ia32_pause (void)
+Generates the @code{pause} machine instruction with a compiler memory
+barrier.
+@end table
+
+The following built-in functions are always available and can be used to
+check the target platform type.
+
+@deftypefn {Built-in Function} void __builtin_cpu_init (void)
+This function runs the CPU detection code to check the type of CPU and the
+features supported. This built-in function needs to be invoked along with the built-in functions
+to check CPU type and features, @code{__builtin_cpu_is} and
+@code{__builtin_cpu_supports}, only when used in a function that is
+executed before any constructors are called. The CPU detection code is
+automatically executed in a very high priority constructor.
+
+For example, this function has to be used in @code{ifunc} resolvers that
+check for CPU type using the built-in functions @code{__builtin_cpu_is}
+and @code{__builtin_cpu_supports}, or in constructors on targets that
+don't support constructor priority.
+@smallexample
+
+static void (*resolve_memcpy (void)) (void)
+@{
+ // ifunc resolvers fire before constructors, explicitly call the init
+ // function.
+ __builtin_cpu_init ();
+ if (__builtin_cpu_supports ("ssse3"))
+ return ssse3_memcpy; // super fast memcpy with ssse3 instructions.
+ else
+ return default_memcpy;
+@}
+
+void *memcpy (void *, const void *, size_t)
+ __attribute__ ((ifunc ("resolve_memcpy")));
+@end smallexample
+
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_cpu_is (const char *@var{cpuname})
+This function returns a positive integer if the run-time CPU
+is of type @var{cpuname}
+and returns @code{0} otherwise. The following CPU names can be detected:
+
+@table @samp
+@item amd
+AMD CPU.
+
+@item intel
+Intel CPU.
+
+@item atom
+Intel Atom CPU.
+
+@item slm
+Intel Silvermont CPU.
+
+@item core2
+Intel Core 2 CPU.
+
+@item corei7
+Intel Core i7 CPU.
+
+@item nehalem
+Intel Core i7 Nehalem CPU.
+
+@item westmere
+Intel Core i7 Westmere CPU.
+
+@item sandybridge
+Intel Core i7 Sandy Bridge CPU.
+
+@item ivybridge
+Intel Core i7 Ivy Bridge CPU.
+
+@item haswell
+Intel Core i7 Haswell CPU.
+
+@item broadwell
+Intel Core i7 Broadwell CPU.
+
+@item skylake
+Intel Core i7 Skylake CPU.
+
+@item skylake-avx512
+Intel Core i7 Skylake AVX512 CPU.
+
+@item cannonlake
+Intel Core i7 Cannon Lake CPU.
+
+@item icelake-client
+Intel Core i7 Ice Lake Client CPU.
+
+@item icelake-server
+Intel Core i7 Ice Lake Server CPU.
+
+@item cascadelake
+Intel Core i7 Cascadelake CPU.
+
+@item tigerlake
+Intel Core i7 Tigerlake CPU.
+
+@item cooperlake
+Intel Core i7 Cooperlake CPU.
+
+@item sapphirerapids
+Intel Core i7 sapphirerapids CPU.
+
+@item alderlake
+Intel Core i7 Alderlake CPU.
+
+@item rocketlake
+Intel Core i7 Rocketlake CPU.
+
+@item graniterapids
+Intel Core i7 graniterapids CPU.
+
+@item bonnell
+Intel Atom Bonnell CPU.
+
+@item silvermont
+Intel Atom Silvermont CPU.
+
+@item goldmont
+Intel Atom Goldmont CPU.
+
+@item goldmont-plus
+Intel Atom Goldmont Plus CPU.
+
+@item tremont
+Intel Atom Tremont CPU.
+
+@item sierraforest
+Intel Atom Sierra Forest CPU.
+
+@item grandridge
+Intel Atom Grand Ridge CPU.
+
+@item knl
+Intel Knights Landing CPU.
+
+@item knm
+Intel Knights Mill CPU.
+
+@item lujiazui
+ZHAOXIN lujiazui CPU.
+
+@item amdfam10h
+AMD Family 10h CPU.
+
+@item barcelona
+AMD Family 10h Barcelona CPU.
+
+@item shanghai
+AMD Family 10h Shanghai CPU.
+
+@item istanbul
+AMD Family 10h Istanbul CPU.
+
+@item btver1
+AMD Family 14h CPU.
+
+@item amdfam15h
+AMD Family 15h CPU.
+
+@item bdver1
+AMD Family 15h Bulldozer version 1.
+
+@item bdver2
+AMD Family 15h Bulldozer version 2.
+
+@item bdver3
+AMD Family 15h Bulldozer version 3.
+
+@item bdver4
+AMD Family 15h Bulldozer version 4.
+
+@item btver2
+AMD Family 16h CPU.
+
+@item amdfam17h
+AMD Family 17h CPU.
+
+@item znver1
+AMD Family 17h Zen version 1.
+
+@item znver2
+AMD Family 17h Zen version 2.
+
+@item amdfam19h
+AMD Family 19h CPU.
+
+@item znver3
+AMD Family 19h Zen version 3.
+
+@item znver4
+AMD Family 19h Zen version 4.
+
+@item x86-64
+Baseline x86-64 microarchitecture level (as defined in x86-64 psABI).
+
+@item x86-64-v2
+x86-64-v2 microarchitecture level.
+
+@item x86-64-v3
+x86-64-v3 microarchitecture level.
+
+@item x86-64-v4
+x86-64-v4 microarchitecture level.
+@end table
+
+Here is an example:
+@smallexample
+if (__builtin_cpu_is ("corei7"))
+ @{
+ do_corei7 (); // Core i7 specific implementation.
+ @}
+else
+ @{
+ do_generic (); // Generic implementation.
+ @}
+@end smallexample
+@end deftypefn
+
+@deftypefn {Built-in Function} int __builtin_cpu_supports (const char *@var{feature})
+This function returns a positive integer if the run-time CPU
+supports @var{feature}
+and returns @code{0} otherwise. The following features can be detected:
+
+@table @samp
+@item cmov
+CMOV instruction.
+@item mmx
+MMX instructions.
+@item popcnt
+POPCNT instruction.
+@item sse
+SSE instructions.
+@item sse2
+SSE2 instructions.
+@item sse3
+SSE3 instructions.
+@item ssse3
+SSSE3 instructions.
+@item sse4.1
+SSE4.1 instructions.
+@item sse4.2
+SSE4.2 instructions.
+@item avx
+AVX instructions.
+@item avx2
+AVX2 instructions.
+@item sse4a
+SSE4A instructions.
+@item fma4
+FMA4 instructions.
+@item xop
+XOP instructions.
+@item fma
+FMA instructions.
+@item avx512f
+AVX512F instructions.
+@item bmi
+BMI instructions.
+@item bmi2
+BMI2 instructions.
+@item aes
+AES instructions.
+@item pclmul
+PCLMUL instructions.
+@item avx512vl
+AVX512VL instructions.
+@item avx512bw
+AVX512BW instructions.
+@item avx512dq
+AVX512DQ instructions.
+@item avx512cd
+AVX512CD instructions.
+@item avx512er
+AVX512ER instructions.
+@item avx512pf
+AVX512PF instructions.
+@item avx512vbmi
+AVX512VBMI instructions.
+@item avx512ifma
+AVX512IFMA instructions.
+@item avx5124vnniw
+AVX5124VNNIW instructions.
+@item avx5124fmaps
+AVX5124FMAPS instructions.
+@item avx512vpopcntdq
+AVX512VPOPCNTDQ instructions.
+@item avx512vbmi2
+AVX512VBMI2 instructions.
+@item gfni
+GFNI instructions.
+@item vpclmulqdq
+VPCLMULQDQ instructions.
+@item avx512vnni
+AVX512VNNI instructions.
+@item avx512bitalg
+AVX512BITALG instructions.
+@end table
+
+Here is an example:
+@smallexample
+if (__builtin_cpu_supports ("popcnt"))
+ @{
+ asm("popcnt %1,%0" : "=r"(count) : "rm"(n) : "cc");
+ @}
+else
+ @{
+ count = generic_countbits (n); //generic implementation.
+ @}
+@end smallexample
+@end deftypefn
+
+The following built-in functions are made available by @option{-mmmx}.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+v8qi __builtin_ia32_paddb (v8qi, v8qi);
+v4hi __builtin_ia32_paddw (v4hi, v4hi);
+v2si __builtin_ia32_paddd (v2si, v2si);
+v8qi __builtin_ia32_psubb (v8qi, v8qi);
+v4hi __builtin_ia32_psubw (v4hi, v4hi);
+v2si __builtin_ia32_psubd (v2si, v2si);
+v8qi __builtin_ia32_paddsb (v8qi, v8qi);
+v4hi __builtin_ia32_paddsw (v4hi, v4hi);
+v8qi __builtin_ia32_psubsb (v8qi, v8qi);
+v4hi __builtin_ia32_psubsw (v4hi, v4hi);
+v8qi __builtin_ia32_paddusb (v8qi, v8qi);
+v4hi __builtin_ia32_paddusw (v4hi, v4hi);
+v8qi __builtin_ia32_psubusb (v8qi, v8qi);
+v4hi __builtin_ia32_psubusw (v4hi, v4hi);
+v4hi __builtin_ia32_pmullw (v4hi, v4hi);
+v4hi __builtin_ia32_pmulhw (v4hi, v4hi);
+di __builtin_ia32_pand (di, di);
+di __builtin_ia32_pandn (di,di);
+di __builtin_ia32_por (di, di);
+di __builtin_ia32_pxor (di, di);
+v8qi __builtin_ia32_pcmpeqb (v8qi, v8qi);
+v4hi __builtin_ia32_pcmpeqw (v4hi, v4hi);
+v2si __builtin_ia32_pcmpeqd (v2si, v2si);
+v8qi __builtin_ia32_pcmpgtb (v8qi, v8qi);
+v4hi __builtin_ia32_pcmpgtw (v4hi, v4hi);
+v2si __builtin_ia32_pcmpgtd (v2si, v2si);
+v8qi __builtin_ia32_punpckhbw (v8qi, v8qi);
+v4hi __builtin_ia32_punpckhwd (v4hi, v4hi);
+v2si __builtin_ia32_punpckhdq (v2si, v2si);
+v8qi __builtin_ia32_punpcklbw (v8qi, v8qi);
+v4hi __builtin_ia32_punpcklwd (v4hi, v4hi);
+v2si __builtin_ia32_punpckldq (v2si, v2si);
+v8qi __builtin_ia32_packsswb (v4hi, v4hi);
+v4hi __builtin_ia32_packssdw (v2si, v2si);
+v8qi __builtin_ia32_packuswb (v4hi, v4hi);
+
+v4hi __builtin_ia32_psllw (v4hi, v4hi);
+v2si __builtin_ia32_pslld (v2si, v2si);
+v1di __builtin_ia32_psllq (v1di, v1di);
+v4hi __builtin_ia32_psrlw (v4hi, v4hi);
+v2si __builtin_ia32_psrld (v2si, v2si);
+v1di __builtin_ia32_psrlq (v1di, v1di);
+v4hi __builtin_ia32_psraw (v4hi, v4hi);
+v2si __builtin_ia32_psrad (v2si, v2si);
+v4hi __builtin_ia32_psllwi (v4hi, int);
+v2si __builtin_ia32_pslldi (v2si, int);
+v1di __builtin_ia32_psllqi (v1di, int);
+v4hi __builtin_ia32_psrlwi (v4hi, int);
+v2si __builtin_ia32_psrldi (v2si, int);
+v1di __builtin_ia32_psrlqi (v1di, int);
+v4hi __builtin_ia32_psrawi (v4hi, int);
+v2si __builtin_ia32_psradi (v2si, int);
+@end smallexample
+
+The following built-in functions are made available either with
+@option{-msse}, or with @option{-m3dnowa}. All of them generate
+the machine instruction that is part of the name.
+
+@smallexample
+v4hi __builtin_ia32_pmulhuw (v4hi, v4hi);
+v8qi __builtin_ia32_pavgb (v8qi, v8qi);
+v4hi __builtin_ia32_pavgw (v4hi, v4hi);
+v1di __builtin_ia32_psadbw (v8qi, v8qi);
+v8qi __builtin_ia32_pmaxub (v8qi, v8qi);
+v4hi __builtin_ia32_pmaxsw (v4hi, v4hi);
+v8qi __builtin_ia32_pminub (v8qi, v8qi);
+v4hi __builtin_ia32_pminsw (v4hi, v4hi);
+int __builtin_ia32_pmovmskb (v8qi);
+void __builtin_ia32_maskmovq (v8qi, v8qi, char *);
+void __builtin_ia32_movntq (di *, di);
+void __builtin_ia32_sfence (void);
+@end smallexample
+
+The following built-in functions are available when @option{-msse} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+int __builtin_ia32_comieq (v4sf, v4sf);
+int __builtin_ia32_comineq (v4sf, v4sf);
+int __builtin_ia32_comilt (v4sf, v4sf);
+int __builtin_ia32_comile (v4sf, v4sf);
+int __builtin_ia32_comigt (v4sf, v4sf);
+int __builtin_ia32_comige (v4sf, v4sf);
+int __builtin_ia32_ucomieq (v4sf, v4sf);
+int __builtin_ia32_ucomineq (v4sf, v4sf);
+int __builtin_ia32_ucomilt (v4sf, v4sf);
+int __builtin_ia32_ucomile (v4sf, v4sf);
+int __builtin_ia32_ucomigt (v4sf, v4sf);
+int __builtin_ia32_ucomige (v4sf, v4sf);
+v4sf __builtin_ia32_addps (v4sf, v4sf);
+v4sf __builtin_ia32_subps (v4sf, v4sf);
+v4sf __builtin_ia32_mulps (v4sf, v4sf);
+v4sf __builtin_ia32_divps (v4sf, v4sf);
+v4sf __builtin_ia32_addss (v4sf, v4sf);
+v4sf __builtin_ia32_subss (v4sf, v4sf);
+v4sf __builtin_ia32_mulss (v4sf, v4sf);
+v4sf __builtin_ia32_divss (v4sf, v4sf);
+v4sf __builtin_ia32_cmpeqps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpltps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpleps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpgtps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpgeps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpunordps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpneqps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpnltps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpnleps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpngtps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpngeps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpordps (v4sf, v4sf);
+v4sf __builtin_ia32_cmpeqss (v4sf, v4sf);
+v4sf __builtin_ia32_cmpltss (v4sf, v4sf);
+v4sf __builtin_ia32_cmpless (v4sf, v4sf);
+v4sf __builtin_ia32_cmpunordss (v4sf, v4sf);
+v4sf __builtin_ia32_cmpneqss (v4sf, v4sf);
+v4sf __builtin_ia32_cmpnltss (v4sf, v4sf);
+v4sf __builtin_ia32_cmpnless (v4sf, v4sf);
+v4sf __builtin_ia32_cmpordss (v4sf, v4sf);
+v4sf __builtin_ia32_maxps (v4sf, v4sf);
+v4sf __builtin_ia32_maxss (v4sf, v4sf);
+v4sf __builtin_ia32_minps (v4sf, v4sf);
+v4sf __builtin_ia32_minss (v4sf, v4sf);
+v4sf __builtin_ia32_andps (v4sf, v4sf);
+v4sf __builtin_ia32_andnps (v4sf, v4sf);
+v4sf __builtin_ia32_orps (v4sf, v4sf);
+v4sf __builtin_ia32_xorps (v4sf, v4sf);
+v4sf __builtin_ia32_movss (v4sf, v4sf);
+v4sf __builtin_ia32_movhlps (v4sf, v4sf);
+v4sf __builtin_ia32_movlhps (v4sf, v4sf);
+v4sf __builtin_ia32_unpckhps (v4sf, v4sf);
+v4sf __builtin_ia32_unpcklps (v4sf, v4sf);
+v4sf __builtin_ia32_cvtpi2ps (v4sf, v2si);
+v4sf __builtin_ia32_cvtsi2ss (v4sf, int);
+v2si __builtin_ia32_cvtps2pi (v4sf);
+int __builtin_ia32_cvtss2si (v4sf);
+v2si __builtin_ia32_cvttps2pi (v4sf);
+int __builtin_ia32_cvttss2si (v4sf);
+v4sf __builtin_ia32_rcpps (v4sf);
+v4sf __builtin_ia32_rsqrtps (v4sf);
+v4sf __builtin_ia32_sqrtps (v4sf);
+v4sf __builtin_ia32_rcpss (v4sf);
+v4sf __builtin_ia32_rsqrtss (v4sf);
+v4sf __builtin_ia32_sqrtss (v4sf);
+v4sf __builtin_ia32_shufps (v4sf, v4sf, int);
+void __builtin_ia32_movntps (float *, v4sf);
+int __builtin_ia32_movmskps (v4sf);
+@end smallexample
+
+The following built-in functions are available when @option{-msse} is used.
+
+@table @code
+@item v4sf __builtin_ia32_loadups (float *)
+Generates the @code{movups} machine instruction as a load from memory.
+@item void __builtin_ia32_storeups (float *, v4sf)
+Generates the @code{movups} machine instruction as a store to memory.
+@item v4sf __builtin_ia32_loadss (float *)
+Generates the @code{movss} machine instruction as a load from memory.
+@item v4sf __builtin_ia32_loadhps (v4sf, const v2sf *)
+Generates the @code{movhps} machine instruction as a load from memory.
+@item v4sf __builtin_ia32_loadlps (v4sf, const v2sf *)
+Generates the @code{movlps} machine instruction as a load from memory
+@item void __builtin_ia32_storehps (v2sf *, v4sf)
+Generates the @code{movhps} machine instruction as a store to memory.
+@item void __builtin_ia32_storelps (v2sf *, v4sf)
+Generates the @code{movlps} machine instruction as a store to memory.
+@end table
+
+The following built-in functions are available when @option{-msse2} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+int __builtin_ia32_comisdeq (v2df, v2df);
+int __builtin_ia32_comisdlt (v2df, v2df);
+int __builtin_ia32_comisdle (v2df, v2df);
+int __builtin_ia32_comisdgt (v2df, v2df);
+int __builtin_ia32_comisdge (v2df, v2df);
+int __builtin_ia32_comisdneq (v2df, v2df);
+int __builtin_ia32_ucomisdeq (v2df, v2df);
+int __builtin_ia32_ucomisdlt (v2df, v2df);
+int __builtin_ia32_ucomisdle (v2df, v2df);
+int __builtin_ia32_ucomisdgt (v2df, v2df);
+int __builtin_ia32_ucomisdge (v2df, v2df);
+int __builtin_ia32_ucomisdneq (v2df, v2df);
+v2df __builtin_ia32_cmpeqpd (v2df, v2df);
+v2df __builtin_ia32_cmpltpd (v2df, v2df);
+v2df __builtin_ia32_cmplepd (v2df, v2df);
+v2df __builtin_ia32_cmpgtpd (v2df, v2df);
+v2df __builtin_ia32_cmpgepd (v2df, v2df);
+v2df __builtin_ia32_cmpunordpd (v2df, v2df);
+v2df __builtin_ia32_cmpneqpd (v2df, v2df);
+v2df __builtin_ia32_cmpnltpd (v2df, v2df);
+v2df __builtin_ia32_cmpnlepd (v2df, v2df);
+v2df __builtin_ia32_cmpngtpd (v2df, v2df);
+v2df __builtin_ia32_cmpngepd (v2df, v2df);
+v2df __builtin_ia32_cmpordpd (v2df, v2df);
+v2df __builtin_ia32_cmpeqsd (v2df, v2df);
+v2df __builtin_ia32_cmpltsd (v2df, v2df);
+v2df __builtin_ia32_cmplesd (v2df, v2df);
+v2df __builtin_ia32_cmpunordsd (v2df, v2df);
+v2df __builtin_ia32_cmpneqsd (v2df, v2df);
+v2df __builtin_ia32_cmpnltsd (v2df, v2df);
+v2df __builtin_ia32_cmpnlesd (v2df, v2df);
+v2df __builtin_ia32_cmpordsd (v2df, v2df);
+v2di __builtin_ia32_paddq (v2di, v2di);
+v2di __builtin_ia32_psubq (v2di, v2di);
+v2df __builtin_ia32_addpd (v2df, v2df);
+v2df __builtin_ia32_subpd (v2df, v2df);
+v2df __builtin_ia32_mulpd (v2df, v2df);
+v2df __builtin_ia32_divpd (v2df, v2df);
+v2df __builtin_ia32_addsd (v2df, v2df);
+v2df __builtin_ia32_subsd (v2df, v2df);
+v2df __builtin_ia32_mulsd (v2df, v2df);
+v2df __builtin_ia32_divsd (v2df, v2df);
+v2df __builtin_ia32_minpd (v2df, v2df);
+v2df __builtin_ia32_maxpd (v2df, v2df);
+v2df __builtin_ia32_minsd (v2df, v2df);
+v2df __builtin_ia32_maxsd (v2df, v2df);
+v2df __builtin_ia32_andpd (v2df, v2df);
+v2df __builtin_ia32_andnpd (v2df, v2df);
+v2df __builtin_ia32_orpd (v2df, v2df);
+v2df __builtin_ia32_xorpd (v2df, v2df);
+v2df __builtin_ia32_movsd (v2df, v2df);
+v2df __builtin_ia32_unpckhpd (v2df, v2df);
+v2df __builtin_ia32_unpcklpd (v2df, v2df);
+v16qi __builtin_ia32_paddb128 (v16qi, v16qi);
+v8hi __builtin_ia32_paddw128 (v8hi, v8hi);
+v4si __builtin_ia32_paddd128 (v4si, v4si);
+v2di __builtin_ia32_paddq128 (v2di, v2di);
+v16qi __builtin_ia32_psubb128 (v16qi, v16qi);
+v8hi __builtin_ia32_psubw128 (v8hi, v8hi);
+v4si __builtin_ia32_psubd128 (v4si, v4si);
+v2di __builtin_ia32_psubq128 (v2di, v2di);
+v8hi __builtin_ia32_pmullw128 (v8hi, v8hi);
+v8hi __builtin_ia32_pmulhw128 (v8hi, v8hi);
+v2di __builtin_ia32_pand128 (v2di, v2di);
+v2di __builtin_ia32_pandn128 (v2di, v2di);
+v2di __builtin_ia32_por128 (v2di, v2di);
+v2di __builtin_ia32_pxor128 (v2di, v2di);
+v16qi __builtin_ia32_pavgb128 (v16qi, v16qi);
+v8hi __builtin_ia32_pavgw128 (v8hi, v8hi);
+v16qi __builtin_ia32_pcmpeqb128 (v16qi, v16qi);
+v8hi __builtin_ia32_pcmpeqw128 (v8hi, v8hi);
+v4si __builtin_ia32_pcmpeqd128 (v4si, v4si);
+v16qi __builtin_ia32_pcmpgtb128 (v16qi, v16qi);
+v8hi __builtin_ia32_pcmpgtw128 (v8hi, v8hi);
+v4si __builtin_ia32_pcmpgtd128 (v4si, v4si);
+v16qi __builtin_ia32_pmaxub128 (v16qi, v16qi);
+v8hi __builtin_ia32_pmaxsw128 (v8hi, v8hi);
+v16qi __builtin_ia32_pminub128 (v16qi, v16qi);
+v8hi __builtin_ia32_pminsw128 (v8hi, v8hi);
+v16qi __builtin_ia32_punpckhbw128 (v16qi, v16qi);
+v8hi __builtin_ia32_punpckhwd128 (v8hi, v8hi);
+v4si __builtin_ia32_punpckhdq128 (v4si, v4si);
+v2di __builtin_ia32_punpckhqdq128 (v2di, v2di);
+v16qi __builtin_ia32_punpcklbw128 (v16qi, v16qi);
+v8hi __builtin_ia32_punpcklwd128 (v8hi, v8hi);
+v4si __builtin_ia32_punpckldq128 (v4si, v4si);
+v2di __builtin_ia32_punpcklqdq128 (v2di, v2di);
+v16qi __builtin_ia32_packsswb128 (v8hi, v8hi);
+v8hi __builtin_ia32_packssdw128 (v4si, v4si);
+v16qi __builtin_ia32_packuswb128 (v8hi, v8hi);
+v8hi __builtin_ia32_pmulhuw128 (v8hi, v8hi);
+void __builtin_ia32_maskmovdqu (v16qi, v16qi);
+v2df __builtin_ia32_loadupd (double *);
+void __builtin_ia32_storeupd (double *, v2df);
+v2df __builtin_ia32_loadhpd (v2df, double const *);
+v2df __builtin_ia32_loadlpd (v2df, double const *);
+int __builtin_ia32_movmskpd (v2df);
+int __builtin_ia32_pmovmskb128 (v16qi);
+void __builtin_ia32_movnti (int *, int);
+void __builtin_ia32_movnti64 (long long int *, long long int);
+void __builtin_ia32_movntpd (double *, v2df);
+void __builtin_ia32_movntdq (v2df *, v2df);
+v4si __builtin_ia32_pshufd (v4si, int);
+v8hi __builtin_ia32_pshuflw (v8hi, int);
+v8hi __builtin_ia32_pshufhw (v8hi, int);
+v2di __builtin_ia32_psadbw128 (v16qi, v16qi);
+v2df __builtin_ia32_sqrtpd (v2df);
+v2df __builtin_ia32_sqrtsd (v2df);
+v2df __builtin_ia32_shufpd (v2df, v2df, int);
+v2df __builtin_ia32_cvtdq2pd (v4si);
+v4sf __builtin_ia32_cvtdq2ps (v4si);
+v4si __builtin_ia32_cvtpd2dq (v2df);
+v2si __builtin_ia32_cvtpd2pi (v2df);
+v4sf __builtin_ia32_cvtpd2ps (v2df);
+v4si __builtin_ia32_cvttpd2dq (v2df);
+v2si __builtin_ia32_cvttpd2pi (v2df);
+v2df __builtin_ia32_cvtpi2pd (v2si);
+int __builtin_ia32_cvtsd2si (v2df);
+int __builtin_ia32_cvttsd2si (v2df);
+long long __builtin_ia32_cvtsd2si64 (v2df);
+long long __builtin_ia32_cvttsd2si64 (v2df);
+v4si __builtin_ia32_cvtps2dq (v4sf);
+v2df __builtin_ia32_cvtps2pd (v4sf);
+v4si __builtin_ia32_cvttps2dq (v4sf);
+v2df __builtin_ia32_cvtsi2sd (v2df, int);
+v2df __builtin_ia32_cvtsi642sd (v2df, long long);
+v4sf __builtin_ia32_cvtsd2ss (v4sf, v2df);
+v2df __builtin_ia32_cvtss2sd (v2df, v4sf);
+void __builtin_ia32_clflush (const void *);
+void __builtin_ia32_lfence (void);
+void __builtin_ia32_mfence (void);
+v16qi __builtin_ia32_loaddqu (const char *);
+void __builtin_ia32_storedqu (char *, v16qi);
+v1di __builtin_ia32_pmuludq (v2si, v2si);
+v2di __builtin_ia32_pmuludq128 (v4si, v4si);
+v8hi __builtin_ia32_psllw128 (v8hi, v8hi);
+v4si __builtin_ia32_pslld128 (v4si, v4si);
+v2di __builtin_ia32_psllq128 (v2di, v2di);
+v8hi __builtin_ia32_psrlw128 (v8hi, v8hi);
+v4si __builtin_ia32_psrld128 (v4si, v4si);
+v2di __builtin_ia32_psrlq128 (v2di, v2di);
+v8hi __builtin_ia32_psraw128 (v8hi, v8hi);
+v4si __builtin_ia32_psrad128 (v4si, v4si);
+v2di __builtin_ia32_pslldqi128 (v2di, int);
+v8hi __builtin_ia32_psllwi128 (v8hi, int);
+v4si __builtin_ia32_pslldi128 (v4si, int);
+v2di __builtin_ia32_psllqi128 (v2di, int);
+v2di __builtin_ia32_psrldqi128 (v2di, int);
+v8hi __builtin_ia32_psrlwi128 (v8hi, int);
+v4si __builtin_ia32_psrldi128 (v4si, int);
+v2di __builtin_ia32_psrlqi128 (v2di, int);
+v8hi __builtin_ia32_psrawi128 (v8hi, int);
+v4si __builtin_ia32_psradi128 (v4si, int);
+v4si __builtin_ia32_pmaddwd128 (v8hi, v8hi);
+v2di __builtin_ia32_movq128 (v2di);
+@end smallexample
+
+The following built-in functions are available when @option{-msse3} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+v2df __builtin_ia32_addsubpd (v2df, v2df);
+v4sf __builtin_ia32_addsubps (v4sf, v4sf);
+v2df __builtin_ia32_haddpd (v2df, v2df);
+v4sf __builtin_ia32_haddps (v4sf, v4sf);
+v2df __builtin_ia32_hsubpd (v2df, v2df);
+v4sf __builtin_ia32_hsubps (v4sf, v4sf);
+v16qi __builtin_ia32_lddqu (char const *);
+void __builtin_ia32_monitor (void *, unsigned int, unsigned int);
+v4sf __builtin_ia32_movshdup (v4sf);
+v4sf __builtin_ia32_movsldup (v4sf);
+void __builtin_ia32_mwait (unsigned int, unsigned int);
+@end smallexample
+
+The following built-in functions are available when @option{-mssse3} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+v2si __builtin_ia32_phaddd (v2si, v2si);
+v4hi __builtin_ia32_phaddw (v4hi, v4hi);
+v4hi __builtin_ia32_phaddsw (v4hi, v4hi);
+v2si __builtin_ia32_phsubd (v2si, v2si);
+v4hi __builtin_ia32_phsubw (v4hi, v4hi);
+v4hi __builtin_ia32_phsubsw (v4hi, v4hi);
+v4hi __builtin_ia32_pmaddubsw (v8qi, v8qi);
+v4hi __builtin_ia32_pmulhrsw (v4hi, v4hi);
+v8qi __builtin_ia32_pshufb (v8qi, v8qi);
+v8qi __builtin_ia32_psignb (v8qi, v8qi);
+v2si __builtin_ia32_psignd (v2si, v2si);
+v4hi __builtin_ia32_psignw (v4hi, v4hi);
+v1di __builtin_ia32_palignr (v1di, v1di, int);
+v8qi __builtin_ia32_pabsb (v8qi);
+v2si __builtin_ia32_pabsd (v2si);
+v4hi __builtin_ia32_pabsw (v4hi);
+@end smallexample
+
+The following built-in functions are available when @option{-mssse3} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+v4si __builtin_ia32_phaddd128 (v4si, v4si);
+v8hi __builtin_ia32_phaddw128 (v8hi, v8hi);
+v8hi __builtin_ia32_phaddsw128 (v8hi, v8hi);
+v4si __builtin_ia32_phsubd128 (v4si, v4si);
+v8hi __builtin_ia32_phsubw128 (v8hi, v8hi);
+v8hi __builtin_ia32_phsubsw128 (v8hi, v8hi);
+v8hi __builtin_ia32_pmaddubsw128 (v16qi, v16qi);
+v8hi __builtin_ia32_pmulhrsw128 (v8hi, v8hi);
+v16qi __builtin_ia32_pshufb128 (v16qi, v16qi);
+v16qi __builtin_ia32_psignb128 (v16qi, v16qi);
+v4si __builtin_ia32_psignd128 (v4si, v4si);
+v8hi __builtin_ia32_psignw128 (v8hi, v8hi);
+v2di __builtin_ia32_palignr128 (v2di, v2di, int);
+v16qi __builtin_ia32_pabsb128 (v16qi);
+v4si __builtin_ia32_pabsd128 (v4si);
+v8hi __builtin_ia32_pabsw128 (v8hi);
+@end smallexample
+
+The following built-in functions are available when @option{-msse4.1} is
+used. All of them generate the machine instruction that is part of the
+name.
+
+@smallexample
+v2df __builtin_ia32_blendpd (v2df, v2df, const int);
+v4sf __builtin_ia32_blendps (v4sf, v4sf, const int);
+v2df __builtin_ia32_blendvpd (v2df, v2df, v2df);
+v4sf __builtin_ia32_blendvps (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_dppd (v2df, v2df, const int);
+v4sf __builtin_ia32_dpps (v4sf, v4sf, const int);
+v4sf __builtin_ia32_insertps128 (v4sf, v4sf, const int);
+v2di __builtin_ia32_movntdqa (v2di *);
+v16qi __builtin_ia32_mpsadbw128 (v16qi, v16qi, const int);
+v8hi __builtin_ia32_packusdw128 (v4si, v4si);
+v16qi __builtin_ia32_pblendvb128 (v16qi, v16qi, v16qi);
+v8hi __builtin_ia32_pblendw128 (v8hi, v8hi, const int);
+v2di __builtin_ia32_pcmpeqq (v2di, v2di);
+v8hi __builtin_ia32_phminposuw128 (v8hi);
+v16qi __builtin_ia32_pmaxsb128 (v16qi, v16qi);
+v4si __builtin_ia32_pmaxsd128 (v4si, v4si);
+v4si __builtin_ia32_pmaxud128 (v4si, v4si);
+v8hi __builtin_ia32_pmaxuw128 (v8hi, v8hi);
+v16qi __builtin_ia32_pminsb128 (v16qi, v16qi);
+v4si __builtin_ia32_pminsd128 (v4si, v4si);
+v4si __builtin_ia32_pminud128 (v4si, v4si);
+v8hi __builtin_ia32_pminuw128 (v8hi, v8hi);
+v4si __builtin_ia32_pmovsxbd128 (v16qi);
+v2di __builtin_ia32_pmovsxbq128 (v16qi);
+v8hi __builtin_ia32_pmovsxbw128 (v16qi);
+v2di __builtin_ia32_pmovsxdq128 (v4si);
+v4si __builtin_ia32_pmovsxwd128 (v8hi);
+v2di __builtin_ia32_pmovsxwq128 (v8hi);
+v4si __builtin_ia32_pmovzxbd128 (v16qi);
+v2di __builtin_ia32_pmovzxbq128 (v16qi);
+v8hi __builtin_ia32_pmovzxbw128 (v16qi);
+v2di __builtin_ia32_pmovzxdq128 (v4si);
+v4si __builtin_ia32_pmovzxwd128 (v8hi);
+v2di __builtin_ia32_pmovzxwq128 (v8hi);
+v2di __builtin_ia32_pmuldq128 (v4si, v4si);
+v4si __builtin_ia32_pmulld128 (v4si, v4si);
+int __builtin_ia32_ptestc128 (v2di, v2di);
+int __builtin_ia32_ptestnzc128 (v2di, v2di);
+int __builtin_ia32_ptestz128 (v2di, v2di);
+v2df __builtin_ia32_roundpd (v2df, const int);
+v4sf __builtin_ia32_roundps (v4sf, const int);
+v2df __builtin_ia32_roundsd (v2df, v2df, const int);
+v4sf __builtin_ia32_roundss (v4sf, v4sf, const int);
+@end smallexample
+
+The following built-in functions are available when @option{-msse4.1} is
+used.
+
+@table @code
+@item v4sf __builtin_ia32_vec_set_v4sf (v4sf, float, const int)
+Generates the @code{insertps} machine instruction.
+@item int __builtin_ia32_vec_ext_v16qi (v16qi, const int)
+Generates the @code{pextrb} machine instruction.
+@item v16qi __builtin_ia32_vec_set_v16qi (v16qi, int, const int)
+Generates the @code{pinsrb} machine instruction.
+@item v4si __builtin_ia32_vec_set_v4si (v4si, int, const int)
+Generates the @code{pinsrd} machine instruction.
+@item v2di __builtin_ia32_vec_set_v2di (v2di, long long, const int)
+Generates the @code{pinsrq} machine instruction in 64bit mode.
+@end table
+
+The following built-in functions are changed to generate new SSE4.1
+instructions when @option{-msse4.1} is used.
+
+@table @code
+@item float __builtin_ia32_vec_ext_v4sf (v4sf, const int)
+Generates the @code{extractps} machine instruction.
+@item int __builtin_ia32_vec_ext_v4si (v4si, const int)
+Generates the @code{pextrd} machine instruction.
+@item long long __builtin_ia32_vec_ext_v2di (v2di, const int)
+Generates the @code{pextrq} machine instruction in 64bit mode.
+@end table
+
+The following built-in functions are available when @option{-msse4.2} is
+used. All of them generate the machine instruction that is part of the
+name.
+
+@smallexample
+v16qi __builtin_ia32_pcmpestrm128 (v16qi, int, v16qi, int, const int);
+int __builtin_ia32_pcmpestri128 (v16qi, int, v16qi, int, const int);
+int __builtin_ia32_pcmpestria128 (v16qi, int, v16qi, int, const int);
+int __builtin_ia32_pcmpestric128 (v16qi, int, v16qi, int, const int);
+int __builtin_ia32_pcmpestrio128 (v16qi, int, v16qi, int, const int);
+int __builtin_ia32_pcmpestris128 (v16qi, int, v16qi, int, const int);
+int __builtin_ia32_pcmpestriz128 (v16qi, int, v16qi, int, const int);
+v16qi __builtin_ia32_pcmpistrm128 (v16qi, v16qi, const int);
+int __builtin_ia32_pcmpistri128 (v16qi, v16qi, const int);
+int __builtin_ia32_pcmpistria128 (v16qi, v16qi, const int);
+int __builtin_ia32_pcmpistric128 (v16qi, v16qi, const int);
+int __builtin_ia32_pcmpistrio128 (v16qi, v16qi, const int);
+int __builtin_ia32_pcmpistris128 (v16qi, v16qi, const int);
+int __builtin_ia32_pcmpistriz128 (v16qi, v16qi, const int);
+v2di __builtin_ia32_pcmpgtq (v2di, v2di);
+@end smallexample
+
+The following built-in functions are available when @option{-msse4.2} is
+used.
+
+@table @code
+@item unsigned int __builtin_ia32_crc32qi (unsigned int, unsigned char)
+Generates the @code{crc32b} machine instruction.
+@item unsigned int __builtin_ia32_crc32hi (unsigned int, unsigned short)
+Generates the @code{crc32w} machine instruction.
+@item unsigned int __builtin_ia32_crc32si (unsigned int, unsigned int)
+Generates the @code{crc32l} machine instruction.
+@item unsigned long long __builtin_ia32_crc32di (unsigned long long, unsigned long long)
+Generates the @code{crc32q} machine instruction.
+@end table
+
+The following built-in functions are changed to generate new SSE4.2
+instructions when @option{-msse4.2} is used.
+
+@table @code
+@item int __builtin_popcount (unsigned int)
+Generates the @code{popcntl} machine instruction.
+@item int __builtin_popcountl (unsigned long)
+Generates the @code{popcntl} or @code{popcntq} machine instruction,
+depending on the size of @code{unsigned long}.
+@item int __builtin_popcountll (unsigned long long)
+Generates the @code{popcntq} machine instruction.
+@end table
+
+The following built-in functions are available when @option{-mavx} is
+used. All of them generate the machine instruction that is part of the
+name.
+
+@smallexample
+v4df __builtin_ia32_addpd256 (v4df,v4df);
+v8sf __builtin_ia32_addps256 (v8sf,v8sf);
+v4df __builtin_ia32_addsubpd256 (v4df,v4df);
+v8sf __builtin_ia32_addsubps256 (v8sf,v8sf);
+v4df __builtin_ia32_andnpd256 (v4df,v4df);
+v8sf __builtin_ia32_andnps256 (v8sf,v8sf);
+v4df __builtin_ia32_andpd256 (v4df,v4df);
+v8sf __builtin_ia32_andps256 (v8sf,v8sf);
+v4df __builtin_ia32_blendpd256 (v4df,v4df,int);
+v8sf __builtin_ia32_blendps256 (v8sf,v8sf,int);
+v4df __builtin_ia32_blendvpd256 (v4df,v4df,v4df);
+v8sf __builtin_ia32_blendvps256 (v8sf,v8sf,v8sf);
+v2df __builtin_ia32_cmppd (v2df,v2df,int);
+v4df __builtin_ia32_cmppd256 (v4df,v4df,int);
+v4sf __builtin_ia32_cmpps (v4sf,v4sf,int);
+v8sf __builtin_ia32_cmpps256 (v8sf,v8sf,int);
+v2df __builtin_ia32_cmpsd (v2df,v2df,int);
+v4sf __builtin_ia32_cmpss (v4sf,v4sf,int);
+v4df __builtin_ia32_cvtdq2pd256 (v4si);
+v8sf __builtin_ia32_cvtdq2ps256 (v8si);
+v4si __builtin_ia32_cvtpd2dq256 (v4df);
+v4sf __builtin_ia32_cvtpd2ps256 (v4df);
+v8si __builtin_ia32_cvtps2dq256 (v8sf);
+v4df __builtin_ia32_cvtps2pd256 (v4sf);
+v4si __builtin_ia32_cvttpd2dq256 (v4df);
+v8si __builtin_ia32_cvttps2dq256 (v8sf);
+v4df __builtin_ia32_divpd256 (v4df,v4df);
+v8sf __builtin_ia32_divps256 (v8sf,v8sf);
+v8sf __builtin_ia32_dpps256 (v8sf,v8sf,int);
+v4df __builtin_ia32_haddpd256 (v4df,v4df);
+v8sf __builtin_ia32_haddps256 (v8sf,v8sf);
+v4df __builtin_ia32_hsubpd256 (v4df,v4df);
+v8sf __builtin_ia32_hsubps256 (v8sf,v8sf);
+v32qi __builtin_ia32_lddqu256 (pcchar);
+v32qi __builtin_ia32_loaddqu256 (pcchar);
+v4df __builtin_ia32_loadupd256 (pcdouble);
+v8sf __builtin_ia32_loadups256 (pcfloat);
+v2df __builtin_ia32_maskloadpd (pcv2df,v2df);
+v4df __builtin_ia32_maskloadpd256 (pcv4df,v4df);
+v4sf __builtin_ia32_maskloadps (pcv4sf,v4sf);
+v8sf __builtin_ia32_maskloadps256 (pcv8sf,v8sf);
+void __builtin_ia32_maskstorepd (pv2df,v2df,v2df);
+void __builtin_ia32_maskstorepd256 (pv4df,v4df,v4df);
+void __builtin_ia32_maskstoreps (pv4sf,v4sf,v4sf);
+void __builtin_ia32_maskstoreps256 (pv8sf,v8sf,v8sf);
+v4df __builtin_ia32_maxpd256 (v4df,v4df);
+v8sf __builtin_ia32_maxps256 (v8sf,v8sf);
+v4df __builtin_ia32_minpd256 (v4df,v4df);
+v8sf __builtin_ia32_minps256 (v8sf,v8sf);
+v4df __builtin_ia32_movddup256 (v4df);
+int __builtin_ia32_movmskpd256 (v4df);
+int __builtin_ia32_movmskps256 (v8sf);
+v8sf __builtin_ia32_movshdup256 (v8sf);
+v8sf __builtin_ia32_movsldup256 (v8sf);
+v4df __builtin_ia32_mulpd256 (v4df,v4df);
+v8sf __builtin_ia32_mulps256 (v8sf,v8sf);
+v4df __builtin_ia32_orpd256 (v4df,v4df);
+v8sf __builtin_ia32_orps256 (v8sf,v8sf);
+v2df __builtin_ia32_pd_pd256 (v4df);
+v4df __builtin_ia32_pd256_pd (v2df);
+v4sf __builtin_ia32_ps_ps256 (v8sf);
+v8sf __builtin_ia32_ps256_ps (v4sf);
+int __builtin_ia32_ptestc256 (v4di,v4di,ptest);
+int __builtin_ia32_ptestnzc256 (v4di,v4di,ptest);
+int __builtin_ia32_ptestz256 (v4di,v4di,ptest);
+v8sf __builtin_ia32_rcpps256 (v8sf);
+v4df __builtin_ia32_roundpd256 (v4df,int);
+v8sf __builtin_ia32_roundps256 (v8sf,int);
+v8sf __builtin_ia32_rsqrtps_nr256 (v8sf);
+v8sf __builtin_ia32_rsqrtps256 (v8sf);
+v4df __builtin_ia32_shufpd256 (v4df,v4df,int);
+v8sf __builtin_ia32_shufps256 (v8sf,v8sf,int);
+v4si __builtin_ia32_si_si256 (v8si);
+v8si __builtin_ia32_si256_si (v4si);
+v4df __builtin_ia32_sqrtpd256 (v4df);
+v8sf __builtin_ia32_sqrtps_nr256 (v8sf);
+v8sf __builtin_ia32_sqrtps256 (v8sf);
+void __builtin_ia32_storedqu256 (pchar,v32qi);
+void __builtin_ia32_storeupd256 (pdouble,v4df);
+void __builtin_ia32_storeups256 (pfloat,v8sf);
+v4df __builtin_ia32_subpd256 (v4df,v4df);
+v8sf __builtin_ia32_subps256 (v8sf,v8sf);
+v4df __builtin_ia32_unpckhpd256 (v4df,v4df);
+v8sf __builtin_ia32_unpckhps256 (v8sf,v8sf);
+v4df __builtin_ia32_unpcklpd256 (v4df,v4df);
+v8sf __builtin_ia32_unpcklps256 (v8sf,v8sf);
+v4df __builtin_ia32_vbroadcastf128_pd256 (pcv2df);
+v8sf __builtin_ia32_vbroadcastf128_ps256 (pcv4sf);
+v4df __builtin_ia32_vbroadcastsd256 (pcdouble);
+v4sf __builtin_ia32_vbroadcastss (pcfloat);
+v8sf __builtin_ia32_vbroadcastss256 (pcfloat);
+v2df __builtin_ia32_vextractf128_pd256 (v4df,int);
+v4sf __builtin_ia32_vextractf128_ps256 (v8sf,int);
+v4si __builtin_ia32_vextractf128_si256 (v8si,int);
+v4df __builtin_ia32_vinsertf128_pd256 (v4df,v2df,int);
+v8sf __builtin_ia32_vinsertf128_ps256 (v8sf,v4sf,int);
+v8si __builtin_ia32_vinsertf128_si256 (v8si,v4si,int);
+v4df __builtin_ia32_vperm2f128_pd256 (v4df,v4df,int);
+v8sf __builtin_ia32_vperm2f128_ps256 (v8sf,v8sf,int);
+v8si __builtin_ia32_vperm2f128_si256 (v8si,v8si,int);
+v2df __builtin_ia32_vpermil2pd (v2df,v2df,v2di,int);
+v4df __builtin_ia32_vpermil2pd256 (v4df,v4df,v4di,int);
+v4sf __builtin_ia32_vpermil2ps (v4sf,v4sf,v4si,int);
+v8sf __builtin_ia32_vpermil2ps256 (v8sf,v8sf,v8si,int);
+v2df __builtin_ia32_vpermilpd (v2df,int);
+v4df __builtin_ia32_vpermilpd256 (v4df,int);
+v4sf __builtin_ia32_vpermilps (v4sf,int);
+v8sf __builtin_ia32_vpermilps256 (v8sf,int);
+v2df __builtin_ia32_vpermilvarpd (v2df,v2di);
+v4df __builtin_ia32_vpermilvarpd256 (v4df,v4di);
+v4sf __builtin_ia32_vpermilvarps (v4sf,v4si);
+v8sf __builtin_ia32_vpermilvarps256 (v8sf,v8si);
+int __builtin_ia32_vtestcpd (v2df,v2df,ptest);
+int __builtin_ia32_vtestcpd256 (v4df,v4df,ptest);
+int __builtin_ia32_vtestcps (v4sf,v4sf,ptest);
+int __builtin_ia32_vtestcps256 (v8sf,v8sf,ptest);
+int __builtin_ia32_vtestnzcpd (v2df,v2df,ptest);
+int __builtin_ia32_vtestnzcpd256 (v4df,v4df,ptest);
+int __builtin_ia32_vtestnzcps (v4sf,v4sf,ptest);
+int __builtin_ia32_vtestnzcps256 (v8sf,v8sf,ptest);
+int __builtin_ia32_vtestzpd (v2df,v2df,ptest);
+int __builtin_ia32_vtestzpd256 (v4df,v4df,ptest);
+int __builtin_ia32_vtestzps (v4sf,v4sf,ptest);
+int __builtin_ia32_vtestzps256 (v8sf,v8sf,ptest);
+void __builtin_ia32_vzeroall (void);
+void __builtin_ia32_vzeroupper (void);
+v4df __builtin_ia32_xorpd256 (v4df,v4df);
+v8sf __builtin_ia32_xorps256 (v8sf,v8sf);
+@end smallexample
+
+The following built-in functions are available when @option{-mavx2} is
+used. All of them generate the machine instruction that is part of the
+name.
+
+@smallexample
+v32qi __builtin_ia32_mpsadbw256 (v32qi,v32qi,int);
+v32qi __builtin_ia32_pabsb256 (v32qi);
+v16hi __builtin_ia32_pabsw256 (v16hi);
+v8si __builtin_ia32_pabsd256 (v8si);
+v16hi __builtin_ia32_packssdw256 (v8si,v8si);
+v32qi __builtin_ia32_packsswb256 (v16hi,v16hi);
+v16hi __builtin_ia32_packusdw256 (v8si,v8si);
+v32qi __builtin_ia32_packuswb256 (v16hi,v16hi);
+v32qi __builtin_ia32_paddb256 (v32qi,v32qi);
+v16hi __builtin_ia32_paddw256 (v16hi,v16hi);
+v8si __builtin_ia32_paddd256 (v8si,v8si);
+v4di __builtin_ia32_paddq256 (v4di,v4di);
+v32qi __builtin_ia32_paddsb256 (v32qi,v32qi);
+v16hi __builtin_ia32_paddsw256 (v16hi,v16hi);
+v32qi __builtin_ia32_paddusb256 (v32qi,v32qi);
+v16hi __builtin_ia32_paddusw256 (v16hi,v16hi);
+v4di __builtin_ia32_palignr256 (v4di,v4di,int);
+v4di __builtin_ia32_andsi256 (v4di,v4di);
+v4di __builtin_ia32_andnotsi256 (v4di,v4di);
+v32qi __builtin_ia32_pavgb256 (v32qi,v32qi);
+v16hi __builtin_ia32_pavgw256 (v16hi,v16hi);
+v32qi __builtin_ia32_pblendvb256 (v32qi,v32qi,v32qi);
+v16hi __builtin_ia32_pblendw256 (v16hi,v16hi,int);
+v32qi __builtin_ia32_pcmpeqb256 (v32qi,v32qi);
+v16hi __builtin_ia32_pcmpeqw256 (v16hi,v16hi);
+v8si __builtin_ia32_pcmpeqd256 (c8si,v8si);
+v4di __builtin_ia32_pcmpeqq256 (v4di,v4di);
+v32qi __builtin_ia32_pcmpgtb256 (v32qi,v32qi);
+v16hi __builtin_ia32_pcmpgtw256 (16hi,v16hi);
+v8si __builtin_ia32_pcmpgtd256 (v8si,v8si);
+v4di __builtin_ia32_pcmpgtq256 (v4di,v4di);
+v16hi __builtin_ia32_phaddw256 (v16hi,v16hi);
+v8si __builtin_ia32_phaddd256 (v8si,v8si);
+v16hi __builtin_ia32_phaddsw256 (v16hi,v16hi);
+v16hi __builtin_ia32_phsubw256 (v16hi,v16hi);
+v8si __builtin_ia32_phsubd256 (v8si,v8si);
+v16hi __builtin_ia32_phsubsw256 (v16hi,v16hi);
+v32qi __builtin_ia32_pmaddubsw256 (v32qi,v32qi);
+v16hi __builtin_ia32_pmaddwd256 (v16hi,v16hi);
+v32qi __builtin_ia32_pmaxsb256 (v32qi,v32qi);
+v16hi __builtin_ia32_pmaxsw256 (v16hi,v16hi);
+v8si __builtin_ia32_pmaxsd256 (v8si,v8si);
+v32qi __builtin_ia32_pmaxub256 (v32qi,v32qi);
+v16hi __builtin_ia32_pmaxuw256 (v16hi,v16hi);
+v8si __builtin_ia32_pmaxud256 (v8si,v8si);
+v32qi __builtin_ia32_pminsb256 (v32qi,v32qi);
+v16hi __builtin_ia32_pminsw256 (v16hi,v16hi);
+v8si __builtin_ia32_pminsd256 (v8si,v8si);
+v32qi __builtin_ia32_pminub256 (v32qi,v32qi);
+v16hi __builtin_ia32_pminuw256 (v16hi,v16hi);
+v8si __builtin_ia32_pminud256 (v8si,v8si);
+int __builtin_ia32_pmovmskb256 (v32qi);
+v16hi __builtin_ia32_pmovsxbw256 (v16qi);
+v8si __builtin_ia32_pmovsxbd256 (v16qi);
+v4di __builtin_ia32_pmovsxbq256 (v16qi);
+v8si __builtin_ia32_pmovsxwd256 (v8hi);
+v4di __builtin_ia32_pmovsxwq256 (v8hi);
+v4di __builtin_ia32_pmovsxdq256 (v4si);
+v16hi __builtin_ia32_pmovzxbw256 (v16qi);
+v8si __builtin_ia32_pmovzxbd256 (v16qi);
+v4di __builtin_ia32_pmovzxbq256 (v16qi);
+v8si __builtin_ia32_pmovzxwd256 (v8hi);
+v4di __builtin_ia32_pmovzxwq256 (v8hi);
+v4di __builtin_ia32_pmovzxdq256 (v4si);
+v4di __builtin_ia32_pmuldq256 (v8si,v8si);
+v16hi __builtin_ia32_pmulhrsw256 (v16hi, v16hi);
+v16hi __builtin_ia32_pmulhuw256 (v16hi,v16hi);
+v16hi __builtin_ia32_pmulhw256 (v16hi,v16hi);
+v16hi __builtin_ia32_pmullw256 (v16hi,v16hi);
+v8si __builtin_ia32_pmulld256 (v8si,v8si);
+v4di __builtin_ia32_pmuludq256 (v8si,v8si);
+v4di __builtin_ia32_por256 (v4di,v4di);
+v16hi __builtin_ia32_psadbw256 (v32qi,v32qi);
+v32qi __builtin_ia32_pshufb256 (v32qi,v32qi);
+v8si __builtin_ia32_pshufd256 (v8si,int);
+v16hi __builtin_ia32_pshufhw256 (v16hi,int);
+v16hi __builtin_ia32_pshuflw256 (v16hi,int);
+v32qi __builtin_ia32_psignb256 (v32qi,v32qi);
+v16hi __builtin_ia32_psignw256 (v16hi,v16hi);
+v8si __builtin_ia32_psignd256 (v8si,v8si);
+v4di __builtin_ia32_pslldqi256 (v4di,int);
+v16hi __builtin_ia32_psllwi256 (16hi,int);
+v16hi __builtin_ia32_psllw256(v16hi,v8hi);
+v8si __builtin_ia32_pslldi256 (v8si,int);
+v8si __builtin_ia32_pslld256(v8si,v4si);
+v4di __builtin_ia32_psllqi256 (v4di,int);
+v4di __builtin_ia32_psllq256(v4di,v2di);
+v16hi __builtin_ia32_psrawi256 (v16hi,int);
+v16hi __builtin_ia32_psraw256 (v16hi,v8hi);
+v8si __builtin_ia32_psradi256 (v8si,int);
+v8si __builtin_ia32_psrad256 (v8si,v4si);
+v4di __builtin_ia32_psrldqi256 (v4di, int);
+v16hi __builtin_ia32_psrlwi256 (v16hi,int);
+v16hi __builtin_ia32_psrlw256 (v16hi,v8hi);
+v8si __builtin_ia32_psrldi256 (v8si,int);
+v8si __builtin_ia32_psrld256 (v8si,v4si);
+v4di __builtin_ia32_psrlqi256 (v4di,int);
+v4di __builtin_ia32_psrlq256(v4di,v2di);
+v32qi __builtin_ia32_psubb256 (v32qi,v32qi);
+v32hi __builtin_ia32_psubw256 (v16hi,v16hi);
+v8si __builtin_ia32_psubd256 (v8si,v8si);
+v4di __builtin_ia32_psubq256 (v4di,v4di);
+v32qi __builtin_ia32_psubsb256 (v32qi,v32qi);
+v16hi __builtin_ia32_psubsw256 (v16hi,v16hi);
+v32qi __builtin_ia32_psubusb256 (v32qi,v32qi);
+v16hi __builtin_ia32_psubusw256 (v16hi,v16hi);
+v32qi __builtin_ia32_punpckhbw256 (v32qi,v32qi);
+v16hi __builtin_ia32_punpckhwd256 (v16hi,v16hi);
+v8si __builtin_ia32_punpckhdq256 (v8si,v8si);
+v4di __builtin_ia32_punpckhqdq256 (v4di,v4di);
+v32qi __builtin_ia32_punpcklbw256 (v32qi,v32qi);
+v16hi __builtin_ia32_punpcklwd256 (v16hi,v16hi);
+v8si __builtin_ia32_punpckldq256 (v8si,v8si);
+v4di __builtin_ia32_punpcklqdq256 (v4di,v4di);
+v4di __builtin_ia32_pxor256 (v4di,v4di);
+v4di __builtin_ia32_movntdqa256 (pv4di);
+v4sf __builtin_ia32_vbroadcastss_ps (v4sf);
+v8sf __builtin_ia32_vbroadcastss_ps256 (v4sf);
+v4df __builtin_ia32_vbroadcastsd_pd256 (v2df);
+v4di __builtin_ia32_vbroadcastsi256 (v2di);
+v4si __builtin_ia32_pblendd128 (v4si,v4si);
+v8si __builtin_ia32_pblendd256 (v8si,v8si);
+v32qi __builtin_ia32_pbroadcastb256 (v16qi);
+v16hi __builtin_ia32_pbroadcastw256 (v8hi);
+v8si __builtin_ia32_pbroadcastd256 (v4si);
+v4di __builtin_ia32_pbroadcastq256 (v2di);
+v16qi __builtin_ia32_pbroadcastb128 (v16qi);
+v8hi __builtin_ia32_pbroadcastw128 (v8hi);
+v4si __builtin_ia32_pbroadcastd128 (v4si);
+v2di __builtin_ia32_pbroadcastq128 (v2di);
+v8si __builtin_ia32_permvarsi256 (v8si,v8si);
+v4df __builtin_ia32_permdf256 (v4df,int);
+v8sf __builtin_ia32_permvarsf256 (v8sf,v8sf);
+v4di __builtin_ia32_permdi256 (v4di,int);
+v4di __builtin_ia32_permti256 (v4di,v4di,int);
+v4di __builtin_ia32_extract128i256 (v4di,int);
+v4di __builtin_ia32_insert128i256 (v4di,v2di,int);
+v8si __builtin_ia32_maskloadd256 (pcv8si,v8si);
+v4di __builtin_ia32_maskloadq256 (pcv4di,v4di);
+v4si __builtin_ia32_maskloadd (pcv4si,v4si);
+v2di __builtin_ia32_maskloadq (pcv2di,v2di);
+void __builtin_ia32_maskstored256 (pv8si,v8si,v8si);
+void __builtin_ia32_maskstoreq256 (pv4di,v4di,v4di);
+void __builtin_ia32_maskstored (pv4si,v4si,v4si);
+void __builtin_ia32_maskstoreq (pv2di,v2di,v2di);
+v8si __builtin_ia32_psllv8si (v8si,v8si);
+v4si __builtin_ia32_psllv4si (v4si,v4si);
+v4di __builtin_ia32_psllv4di (v4di,v4di);
+v2di __builtin_ia32_psllv2di (v2di,v2di);
+v8si __builtin_ia32_psrav8si (v8si,v8si);
+v4si __builtin_ia32_psrav4si (v4si,v4si);
+v8si __builtin_ia32_psrlv8si (v8si,v8si);
+v4si __builtin_ia32_psrlv4si (v4si,v4si);
+v4di __builtin_ia32_psrlv4di (v4di,v4di);
+v2di __builtin_ia32_psrlv2di (v2di,v2di);
+v2df __builtin_ia32_gathersiv2df (v2df, pcdouble,v4si,v2df,int);
+v4df __builtin_ia32_gathersiv4df (v4df, pcdouble,v4si,v4df,int);
+v2df __builtin_ia32_gatherdiv2df (v2df, pcdouble,v2di,v2df,int);
+v4df __builtin_ia32_gatherdiv4df (v4df, pcdouble,v4di,v4df,int);
+v4sf __builtin_ia32_gathersiv4sf (v4sf, pcfloat,v4si,v4sf,int);
+v8sf __builtin_ia32_gathersiv8sf (v8sf, pcfloat,v8si,v8sf,int);
+v4sf __builtin_ia32_gatherdiv4sf (v4sf, pcfloat,v2di,v4sf,int);
+v4sf __builtin_ia32_gatherdiv4sf256 (v4sf, pcfloat,v4di,v4sf,int);
+v2di __builtin_ia32_gathersiv2di (v2di, pcint64,v4si,v2di,int);
+v4di __builtin_ia32_gathersiv4di (v4di, pcint64,v4si,v4di,int);
+v2di __builtin_ia32_gatherdiv2di (v2di, pcint64,v2di,v2di,int);
+v4di __builtin_ia32_gatherdiv4di (v4di, pcint64,v4di,v4di,int);
+v4si __builtin_ia32_gathersiv4si (v4si, pcint,v4si,v4si,int);
+v8si __builtin_ia32_gathersiv8si (v8si, pcint,v8si,v8si,int);
+v4si __builtin_ia32_gatherdiv4si (v4si, pcint,v2di,v4si,int);
+v4si __builtin_ia32_gatherdiv4si256 (v4si, pcint,v4di,v4si,int);
+@end smallexample
+
+The following built-in functions are available when @option{-maes} is
+used. All of them generate the machine instruction that is part of the
+name.
+
+@smallexample
+v2di __builtin_ia32_aesenc128 (v2di, v2di);
+v2di __builtin_ia32_aesenclast128 (v2di, v2di);
+v2di __builtin_ia32_aesdec128 (v2di, v2di);
+v2di __builtin_ia32_aesdeclast128 (v2di, v2di);
+v2di __builtin_ia32_aeskeygenassist128 (v2di, const int);
+v2di __builtin_ia32_aesimc128 (v2di);
+@end smallexample
+
+The following built-in function is available when @option{-mpclmul} is
+used.
+
+@table @code
+@item v2di __builtin_ia32_pclmulqdq128 (v2di, v2di, const int)
+Generates the @code{pclmulqdq} machine instruction.
+@end table
+
+The following built-in function is available when @option{-mfsgsbase} is
+used. All of them generate the machine instruction that is part of the
+name.
+
+@smallexample
+unsigned int __builtin_ia32_rdfsbase32 (void);
+unsigned long long __builtin_ia32_rdfsbase64 (void);
+unsigned int __builtin_ia32_rdgsbase32 (void);
+unsigned long long __builtin_ia32_rdgsbase64 (void);
+void _writefsbase_u32 (unsigned int);
+void _writefsbase_u64 (unsigned long long);
+void _writegsbase_u32 (unsigned int);
+void _writegsbase_u64 (unsigned long long);
+@end smallexample
+
+The following built-in function is available when @option{-mrdrnd} is
+used. All of them generate the machine instruction that is part of the
+name.
+
+@smallexample
+unsigned int __builtin_ia32_rdrand16_step (unsigned short *);
+unsigned int __builtin_ia32_rdrand32_step (unsigned int *);
+unsigned int __builtin_ia32_rdrand64_step (unsigned long long *);
+@end smallexample
+
+The following built-in function is available when @option{-mptwrite} is
+used. All of them generate the machine instruction that is part of the
+name.
+
+@smallexample
+void __builtin_ia32_ptwrite32 (unsigned);
+void __builtin_ia32_ptwrite64 (unsigned long long);
+@end smallexample
+
+The following built-in functions are available when @option{-msse4a} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+void __builtin_ia32_movntsd (double *, v2df);
+void __builtin_ia32_movntss (float *, v4sf);
+v2di __builtin_ia32_extrq (v2di, v16qi);
+v2di __builtin_ia32_extrqi (v2di, const unsigned int, const unsigned int);
+v2di __builtin_ia32_insertq (v2di, v2di);
+v2di __builtin_ia32_insertqi (v2di, v2di, const unsigned int, const unsigned int);
+@end smallexample
+
+The following built-in functions are available when @option{-mxop} is used.
+@smallexample
+v2df __builtin_ia32_vfrczpd (v2df);
+v4sf __builtin_ia32_vfrczps (v4sf);
+v2df __builtin_ia32_vfrczsd (v2df);
+v4sf __builtin_ia32_vfrczss (v4sf);
+v4df __builtin_ia32_vfrczpd256 (v4df);
+v8sf __builtin_ia32_vfrczps256 (v8sf);
+v2di __builtin_ia32_vpcmov (v2di, v2di, v2di);
+v2di __builtin_ia32_vpcmov_v2di (v2di, v2di, v2di);
+v4si __builtin_ia32_vpcmov_v4si (v4si, v4si, v4si);
+v8hi __builtin_ia32_vpcmov_v8hi (v8hi, v8hi, v8hi);
+v16qi __builtin_ia32_vpcmov_v16qi (v16qi, v16qi, v16qi);
+v2df __builtin_ia32_vpcmov_v2df (v2df, v2df, v2df);
+v4sf __builtin_ia32_vpcmov_v4sf (v4sf, v4sf, v4sf);
+v4di __builtin_ia32_vpcmov_v4di256 (v4di, v4di, v4di);
+v8si __builtin_ia32_vpcmov_v8si256 (v8si, v8si, v8si);
+v16hi __builtin_ia32_vpcmov_v16hi256 (v16hi, v16hi, v16hi);
+v32qi __builtin_ia32_vpcmov_v32qi256 (v32qi, v32qi, v32qi);
+v4df __builtin_ia32_vpcmov_v4df256 (v4df, v4df, v4df);
+v8sf __builtin_ia32_vpcmov_v8sf256 (v8sf, v8sf, v8sf);
+v16qi __builtin_ia32_vpcomeqb (v16qi, v16qi);
+v8hi __builtin_ia32_vpcomeqw (v8hi, v8hi);
+v4si __builtin_ia32_vpcomeqd (v4si, v4si);
+v2di __builtin_ia32_vpcomeqq (v2di, v2di);
+v16qi __builtin_ia32_vpcomequb (v16qi, v16qi);
+v4si __builtin_ia32_vpcomequd (v4si, v4si);
+v2di __builtin_ia32_vpcomequq (v2di, v2di);
+v8hi __builtin_ia32_vpcomequw (v8hi, v8hi);
+v8hi __builtin_ia32_vpcomeqw (v8hi, v8hi);
+v16qi __builtin_ia32_vpcomfalseb (v16qi, v16qi);
+v4si __builtin_ia32_vpcomfalsed (v4si, v4si);
+v2di __builtin_ia32_vpcomfalseq (v2di, v2di);
+v16qi __builtin_ia32_vpcomfalseub (v16qi, v16qi);
+v4si __builtin_ia32_vpcomfalseud (v4si, v4si);
+v2di __builtin_ia32_vpcomfalseuq (v2di, v2di);
+v8hi __builtin_ia32_vpcomfalseuw (v8hi, v8hi);
+v8hi __builtin_ia32_vpcomfalsew (v8hi, v8hi);
+v16qi __builtin_ia32_vpcomgeb (v16qi, v16qi);
+v4si __builtin_ia32_vpcomged (v4si, v4si);
+v2di __builtin_ia32_vpcomgeq (v2di, v2di);
+v16qi __builtin_ia32_vpcomgeub (v16qi, v16qi);
+v4si __builtin_ia32_vpcomgeud (v4si, v4si);
+v2di __builtin_ia32_vpcomgeuq (v2di, v2di);
+v8hi __builtin_ia32_vpcomgeuw (v8hi, v8hi);
+v8hi __builtin_ia32_vpcomgew (v8hi, v8hi);
+v16qi __builtin_ia32_vpcomgtb (v16qi, v16qi);
+v4si __builtin_ia32_vpcomgtd (v4si, v4si);
+v2di __builtin_ia32_vpcomgtq (v2di, v2di);
+v16qi __builtin_ia32_vpcomgtub (v16qi, v16qi);
+v4si __builtin_ia32_vpcomgtud (v4si, v4si);
+v2di __builtin_ia32_vpcomgtuq (v2di, v2di);
+v8hi __builtin_ia32_vpcomgtuw (v8hi, v8hi);
+v8hi __builtin_ia32_vpcomgtw (v8hi, v8hi);
+v16qi __builtin_ia32_vpcomleb (v16qi, v16qi);
+v4si __builtin_ia32_vpcomled (v4si, v4si);
+v2di __builtin_ia32_vpcomleq (v2di, v2di);
+v16qi __builtin_ia32_vpcomleub (v16qi, v16qi);
+v4si __builtin_ia32_vpcomleud (v4si, v4si);
+v2di __builtin_ia32_vpcomleuq (v2di, v2di);
+v8hi __builtin_ia32_vpcomleuw (v8hi, v8hi);
+v8hi __builtin_ia32_vpcomlew (v8hi, v8hi);
+v16qi __builtin_ia32_vpcomltb (v16qi, v16qi);
+v4si __builtin_ia32_vpcomltd (v4si, v4si);
+v2di __builtin_ia32_vpcomltq (v2di, v2di);
+v16qi __builtin_ia32_vpcomltub (v16qi, v16qi);
+v4si __builtin_ia32_vpcomltud (v4si, v4si);
+v2di __builtin_ia32_vpcomltuq (v2di, v2di);
+v8hi __builtin_ia32_vpcomltuw (v8hi, v8hi);
+v8hi __builtin_ia32_vpcomltw (v8hi, v8hi);
+v16qi __builtin_ia32_vpcomneb (v16qi, v16qi);
+v4si __builtin_ia32_vpcomned (v4si, v4si);
+v2di __builtin_ia32_vpcomneq (v2di, v2di);
+v16qi __builtin_ia32_vpcomneub (v16qi, v16qi);
+v4si __builtin_ia32_vpcomneud (v4si, v4si);
+v2di __builtin_ia32_vpcomneuq (v2di, v2di);
+v8hi __builtin_ia32_vpcomneuw (v8hi, v8hi);
+v8hi __builtin_ia32_vpcomnew (v8hi, v8hi);
+v16qi __builtin_ia32_vpcomtrueb (v16qi, v16qi);
+v4si __builtin_ia32_vpcomtrued (v4si, v4si);
+v2di __builtin_ia32_vpcomtrueq (v2di, v2di);
+v16qi __builtin_ia32_vpcomtrueub (v16qi, v16qi);
+v4si __builtin_ia32_vpcomtrueud (v4si, v4si);
+v2di __builtin_ia32_vpcomtrueuq (v2di, v2di);
+v8hi __builtin_ia32_vpcomtrueuw (v8hi, v8hi);
+v8hi __builtin_ia32_vpcomtruew (v8hi, v8hi);
+v4si __builtin_ia32_vphaddbd (v16qi);
+v2di __builtin_ia32_vphaddbq (v16qi);
+v8hi __builtin_ia32_vphaddbw (v16qi);
+v2di __builtin_ia32_vphadddq (v4si);
+v4si __builtin_ia32_vphaddubd (v16qi);
+v2di __builtin_ia32_vphaddubq (v16qi);
+v8hi __builtin_ia32_vphaddubw (v16qi);
+v2di __builtin_ia32_vphaddudq (v4si);
+v4si __builtin_ia32_vphadduwd (v8hi);
+v2di __builtin_ia32_vphadduwq (v8hi);
+v4si __builtin_ia32_vphaddwd (v8hi);
+v2di __builtin_ia32_vphaddwq (v8hi);
+v8hi __builtin_ia32_vphsubbw (v16qi);
+v2di __builtin_ia32_vphsubdq (v4si);
+v4si __builtin_ia32_vphsubwd (v8hi);
+v4si __builtin_ia32_vpmacsdd (v4si, v4si, v4si);
+v2di __builtin_ia32_vpmacsdqh (v4si, v4si, v2di);
+v2di __builtin_ia32_vpmacsdql (v4si, v4si, v2di);
+v4si __builtin_ia32_vpmacssdd (v4si, v4si, v4si);
+v2di __builtin_ia32_vpmacssdqh (v4si, v4si, v2di);
+v2di __builtin_ia32_vpmacssdql (v4si, v4si, v2di);
+v4si __builtin_ia32_vpmacsswd (v8hi, v8hi, v4si);
+v8hi __builtin_ia32_vpmacssww (v8hi, v8hi, v8hi);
+v4si __builtin_ia32_vpmacswd (v8hi, v8hi, v4si);
+v8hi __builtin_ia32_vpmacsww (v8hi, v8hi, v8hi);
+v4si __builtin_ia32_vpmadcsswd (v8hi, v8hi, v4si);
+v4si __builtin_ia32_vpmadcswd (v8hi, v8hi, v4si);
+v16qi __builtin_ia32_vpperm (v16qi, v16qi, v16qi);
+v16qi __builtin_ia32_vprotb (v16qi, v16qi);
+v4si __builtin_ia32_vprotd (v4si, v4si);
+v2di __builtin_ia32_vprotq (v2di, v2di);
+v8hi __builtin_ia32_vprotw (v8hi, v8hi);
+v16qi __builtin_ia32_vpshab (v16qi, v16qi);
+v4si __builtin_ia32_vpshad (v4si, v4si);
+v2di __builtin_ia32_vpshaq (v2di, v2di);
+v8hi __builtin_ia32_vpshaw (v8hi, v8hi);
+v16qi __builtin_ia32_vpshlb (v16qi, v16qi);
+v4si __builtin_ia32_vpshld (v4si, v4si);
+v2di __builtin_ia32_vpshlq (v2di, v2di);
+v8hi __builtin_ia32_vpshlw (v8hi, v8hi);
+@end smallexample
+
+The following built-in functions are available when @option{-mfma4} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+v2df __builtin_ia32_vfmaddpd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfmaddps (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfmaddsd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfmaddss (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfmsubpd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfmsubps (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfmsubsd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfmsubss (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfnmaddpd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfnmaddps (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfnmaddsd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfnmaddss (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfnmsubpd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfnmsubps (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfnmsubsd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfnmsubss (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfmaddsubpd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfmaddsubps (v4sf, v4sf, v4sf);
+v2df __builtin_ia32_vfmsubaddpd (v2df, v2df, v2df);
+v4sf __builtin_ia32_vfmsubaddps (v4sf, v4sf, v4sf);
+v4df __builtin_ia32_vfmaddpd256 (v4df, v4df, v4df);
+v8sf __builtin_ia32_vfmaddps256 (v8sf, v8sf, v8sf);
+v4df __builtin_ia32_vfmsubpd256 (v4df, v4df, v4df);
+v8sf __builtin_ia32_vfmsubps256 (v8sf, v8sf, v8sf);
+v4df __builtin_ia32_vfnmaddpd256 (v4df, v4df, v4df);
+v8sf __builtin_ia32_vfnmaddps256 (v8sf, v8sf, v8sf);
+v4df __builtin_ia32_vfnmsubpd256 (v4df, v4df, v4df);
+v8sf __builtin_ia32_vfnmsubps256 (v8sf, v8sf, v8sf);
+v4df __builtin_ia32_vfmaddsubpd256 (v4df, v4df, v4df);
+v8sf __builtin_ia32_vfmaddsubps256 (v8sf, v8sf, v8sf);
+v4df __builtin_ia32_vfmsubaddpd256 (v4df, v4df, v4df);
+v8sf __builtin_ia32_vfmsubaddps256 (v8sf, v8sf, v8sf);
+
+@end smallexample
+
+The following built-in functions are available when @option{-mlwp} is used.
+
+@smallexample
+void __builtin_ia32_llwpcb16 (void *);
+void __builtin_ia32_llwpcb32 (void *);
+void __builtin_ia32_llwpcb64 (void *);
+void * __builtin_ia32_llwpcb16 (void);
+void * __builtin_ia32_llwpcb32 (void);
+void * __builtin_ia32_llwpcb64 (void);
+void __builtin_ia32_lwpval16 (unsigned short, unsigned int, unsigned short);
+void __builtin_ia32_lwpval32 (unsigned int, unsigned int, unsigned int);
+void __builtin_ia32_lwpval64 (unsigned __int64, unsigned int, unsigned int);
+unsigned char __builtin_ia32_lwpins16 (unsigned short, unsigned int, unsigned short);
+unsigned char __builtin_ia32_lwpins32 (unsigned int, unsigned int, unsigned int);
+unsigned char __builtin_ia32_lwpins64 (unsigned __int64, unsigned int, unsigned int);
+@end smallexample
+
+The following built-in functions are available when @option{-mbmi} is used.
+All of them generate the machine instruction that is part of the name.
+@smallexample
+unsigned int __builtin_ia32_bextr_u32(unsigned int, unsigned int);
+unsigned long long __builtin_ia32_bextr_u64 (unsigned long long, unsigned long long);
+@end smallexample
+
+The following built-in functions are available when @option{-mbmi2} is used.
+All of them generate the machine instruction that is part of the name.
+@smallexample
+unsigned int _bzhi_u32 (unsigned int, unsigned int);
+unsigned int _pdep_u32 (unsigned int, unsigned int);
+unsigned int _pext_u32 (unsigned int, unsigned int);
+unsigned long long _bzhi_u64 (unsigned long long, unsigned long long);
+unsigned long long _pdep_u64 (unsigned long long, unsigned long long);
+unsigned long long _pext_u64 (unsigned long long, unsigned long long);
+@end smallexample
+
+The following built-in functions are available when @option{-mlzcnt} is used.
+All of them generate the machine instruction that is part of the name.
+@smallexample
+unsigned short __builtin_ia32_lzcnt_u16(unsigned short);
+unsigned int __builtin_ia32_lzcnt_u32(unsigned int);
+unsigned long long __builtin_ia32_lzcnt_u64 (unsigned long long);
+@end smallexample
+
+The following built-in functions are available when @option{-mfxsr} is used.
+All of them generate the machine instruction that is part of the name.
+@smallexample
+void __builtin_ia32_fxsave (void *);
+void __builtin_ia32_fxrstor (void *);
+void __builtin_ia32_fxsave64 (void *);
+void __builtin_ia32_fxrstor64 (void *);
+@end smallexample
+
+The following built-in functions are available when @option{-mxsave} is used.
+All of them generate the machine instruction that is part of the name.
+@smallexample
+void __builtin_ia32_xsave (void *, long long);
+void __builtin_ia32_xrstor (void *, long long);
+void __builtin_ia32_xsave64 (void *, long long);
+void __builtin_ia32_xrstor64 (void *, long long);
+@end smallexample
+
+The following built-in functions are available when @option{-mxsaveopt} is used.
+All of them generate the machine instruction that is part of the name.
+@smallexample
+void __builtin_ia32_xsaveopt (void *, long long);
+void __builtin_ia32_xsaveopt64 (void *, long long);
+@end smallexample
+
+The following built-in functions are available when @option{-mtbm} is used.
+Both of them generate the immediate form of the bextr machine instruction.
+@smallexample
+unsigned int __builtin_ia32_bextri_u32 (unsigned int,
+ const unsigned int);
+unsigned long long __builtin_ia32_bextri_u64 (unsigned long long,
+ const unsigned long long);
+@end smallexample
+
+
+The following built-in functions are available when @option{-m3dnow} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+void __builtin_ia32_femms (void);
+v8qi __builtin_ia32_pavgusb (v8qi, v8qi);
+v2si __builtin_ia32_pf2id (v2sf);
+v2sf __builtin_ia32_pfacc (v2sf, v2sf);
+v2sf __builtin_ia32_pfadd (v2sf, v2sf);
+v2si __builtin_ia32_pfcmpeq (v2sf, v2sf);
+v2si __builtin_ia32_pfcmpge (v2sf, v2sf);
+v2si __builtin_ia32_pfcmpgt (v2sf, v2sf);
+v2sf __builtin_ia32_pfmax (v2sf, v2sf);
+v2sf __builtin_ia32_pfmin (v2sf, v2sf);
+v2sf __builtin_ia32_pfmul (v2sf, v2sf);
+v2sf __builtin_ia32_pfrcp (v2sf);
+v2sf __builtin_ia32_pfrcpit1 (v2sf, v2sf);
+v2sf __builtin_ia32_pfrcpit2 (v2sf, v2sf);
+v2sf __builtin_ia32_pfrsqrt (v2sf);
+v2sf __builtin_ia32_pfsub (v2sf, v2sf);
+v2sf __builtin_ia32_pfsubr (v2sf, v2sf);
+v2sf __builtin_ia32_pi2fd (v2si);
+v4hi __builtin_ia32_pmulhrw (v4hi, v4hi);
+@end smallexample
+
+The following built-in functions are available when @option{-m3dnowa} is used.
+All of them generate the machine instruction that is part of the name.
+
+@smallexample
+v2si __builtin_ia32_pf2iw (v2sf);
+v2sf __builtin_ia32_pfnacc (v2sf, v2sf);
+v2sf __builtin_ia32_pfpnacc (v2sf, v2sf);
+v2sf __builtin_ia32_pi2fw (v2si);
+v2sf __builtin_ia32_pswapdsf (v2sf);
+v2si __builtin_ia32_pswapdsi (v2si);
+@end smallexample
+
+The following built-in functions are available when @option{-mrtm} is used
+They are used for restricted transactional memory. These are the internal
+low level functions. Normally the functions in
+@ref{x86 transactional memory intrinsics} should be used instead.
+
+@smallexample
+int __builtin_ia32_xbegin ();
+void __builtin_ia32_xend ();
+void __builtin_ia32_xabort (status);
+int __builtin_ia32_xtest ();
+@end smallexample
+
+The following built-in functions are available when @option{-mmwaitx} is used.
+All of them generate the machine instruction that is part of the name.
+@smallexample
+void __builtin_ia32_monitorx (void *, unsigned int, unsigned int);
+void __builtin_ia32_mwaitx (unsigned int, unsigned int, unsigned int);
+@end smallexample
+
+The following built-in functions are available when @option{-mclzero} is used.
+All of them generate the machine instruction that is part of the name.
+@smallexample
+void __builtin_i32_clzero (void *);
+@end smallexample
+
+The following built-in functions are available when @option{-mpku} is used.
+They generate reads and writes to PKRU.
+@smallexample
+void __builtin_ia32_wrpkru (unsigned int);
+unsigned int __builtin_ia32_rdpkru ();
+@end smallexample
+
+The following built-in functions are available when
+@option{-mshstk} option is used. They support shadow stack
+machine instructions from Intel Control-flow Enforcement Technology (CET).
+Each built-in function generates the machine instruction that is part
+of the function's name. These are the internal low-level functions.
+Normally the functions in @ref{x86 control-flow protection intrinsics}
+should be used instead.
+
+@smallexample
+unsigned int __builtin_ia32_rdsspd (void);
+unsigned long long __builtin_ia32_rdsspq (void);
+void __builtin_ia32_incsspd (unsigned int);
+void __builtin_ia32_incsspq (unsigned long long);
+void __builtin_ia32_saveprevssp(void);
+void __builtin_ia32_rstorssp(void *);
+void __builtin_ia32_wrssd(unsigned int, void *);
+void __builtin_ia32_wrssq(unsigned long long, void *);
+void __builtin_ia32_wrussd(unsigned int, void *);
+void __builtin_ia32_wrussq(unsigned long long, void *);
+void __builtin_ia32_setssbsy(void);
+void __builtin_ia32_clrssbsy(void *);
+@end smallexample
+
+@node x86 transactional memory intrinsics
+@subsection x86 Transactional Memory Intrinsics
+
+These hardware transactional memory intrinsics for x86 allow you to use
+memory transactions with RTM (Restricted Transactional Memory).
+This support is enabled with the @option{-mrtm} option.
+For using HLE (Hardware Lock Elision) see
+@ref{x86 specific memory model extensions for transactional memory} instead.
+
+A memory transaction commits all changes to memory in an atomic way,
+as visible to other threads. If the transaction fails it is rolled back
+and all side effects discarded.
+
+Generally there is no guarantee that a memory transaction ever succeeds
+and suitable fallback code always needs to be supplied.
+
+@deftypefn {RTM Function} {unsigned} _xbegin ()
+Start a RTM (Restricted Transactional Memory) transaction.
+Returns @code{_XBEGIN_STARTED} when the transaction
+started successfully (note this is not 0, so the constant has to be
+explicitly tested).
+
+If the transaction aborts, all side effects
+are undone and an abort code encoded as a bit mask is returned.
+The following macros are defined:
+
+@table @code
+@item _XABORT_EXPLICIT
+Transaction was explicitly aborted with @code{_xabort}. The parameter passed
+to @code{_xabort} is available with @code{_XABORT_CODE(status)}.
+@item _XABORT_RETRY
+Transaction retry is possible.
+@item _XABORT_CONFLICT
+Transaction abort due to a memory conflict with another thread.
+@item _XABORT_CAPACITY
+Transaction abort due to the transaction using too much memory.
+@item _XABORT_DEBUG
+Transaction abort due to a debug trap.
+@item _XABORT_NESTED
+Transaction abort in an inner nested transaction.
+@end table
+
+There is no guarantee
+any transaction ever succeeds, so there always needs to be a valid
+fallback path.
+@end deftypefn
+
+@deftypefn {RTM Function} {void} _xend ()
+Commit the current transaction. When no transaction is active this faults.
+All memory side effects of the transaction become visible
+to other threads in an atomic manner.
+@end deftypefn
+
+@deftypefn {RTM Function} {int} _xtest ()
+Return a nonzero value if a transaction is currently active, otherwise 0.
+@end deftypefn
+
+@deftypefn {RTM Function} {void} _xabort (status)
+Abort the current transaction. When no transaction is active this is a no-op.
+The @var{status} is an 8-bit constant; its value is encoded in the return
+value from @code{_xbegin}.
+@end deftypefn
+
+Here is an example showing handling for @code{_XABORT_RETRY}
+and a fallback path for other failures:
+
+@smallexample
+#include <immintrin.h>
+
+int n_tries, max_tries;
+unsigned status = _XABORT_EXPLICIT;
+...
+
+for (n_tries = 0; n_tries < max_tries; n_tries++)
+ @{
+ status = _xbegin ();
+ if (status == _XBEGIN_STARTED || !(status & _XABORT_RETRY))
+ break;
+ @}
+if (status == _XBEGIN_STARTED)
+ @{
+ ... transaction code...
+ _xend ();
+ @}
+else
+ @{
+ ... non-transactional fallback path...
+ @}
+@end smallexample
+
+@noindent
+Note that, in most cases, the transactional and non-transactional code
+must synchronize together to ensure consistency.
+
+@node x86 control-flow protection intrinsics
+@subsection x86 Control-Flow Protection Intrinsics
+
+@deftypefn {CET Function} {ret_type} _get_ssp (void)
+Get the current value of shadow stack pointer if shadow stack support
+from Intel CET is enabled in the hardware or @code{0} otherwise.
+The @code{ret_type} is @code{unsigned long long} for 64-bit targets
+and @code{unsigned int} for 32-bit targets.
+@end deftypefn
+
+@deftypefn {CET Function} void _inc_ssp (unsigned int)
+Increment the current shadow stack pointer by the size specified by the
+function argument. The argument is masked to a byte value for security
+reasons, so to increment by more than 255 bytes you must call the function
+multiple times.
+@end deftypefn
+
+The shadow stack unwind code looks like:
+
+@smallexample
+#include <immintrin.h>
+
+/* Unwind the shadow stack for EH. */
+#define _Unwind_Frames_Extra(x) \
+ do \
+ @{ \
+ _Unwind_Word ssp = _get_ssp (); \
+ if (ssp != 0) \
+ @{ \
+ _Unwind_Word tmp = (x); \
+ while (tmp > 255) \
+ @{ \
+ _inc_ssp (tmp); \
+ tmp -= 255; \
+ @} \
+ _inc_ssp (tmp); \
+ @} \
+ @} \
+ while (0)
+@end smallexample
+
+@noindent
+This code runs unconditionally on all 64-bit processors. For 32-bit
+processors the code runs on those that support multi-byte NOP instructions.
+
+@node Target Format Checks
+@section Format Checks Specific to Particular Target Machines
+
+For some target machines, GCC supports additional options to the
+format attribute
+(@pxref{Function Attributes,,Declaring Attributes of Functions}).
+
+@menu
+* Solaris Format Checks::
+* Darwin Format Checks::
+@end menu
+
+@node Solaris Format Checks
+@subsection Solaris Format Checks
+
+Solaris targets support the @code{cmn_err} (or @code{__cmn_err__}) format
+check. @code{cmn_err} accepts a subset of the standard @code{printf}
+conversions, and the two-argument @code{%b} conversion for displaying
+bit-fields. See the Solaris man page for @code{cmn_err} for more information.
+
+@node Darwin Format Checks
+@subsection Darwin Format Checks
+
+In addition to the full set of format archetypes (attribute format style
+arguments such as @code{printf}, @code{scanf}, @code{strftime}, and
+@code{strfmon}), Darwin targets also support the @code{CFString} (or
+@code{__CFString__}) archetype in the @code{format} attribute.
+Declarations with this archetype are parsed for correct syntax
+and argument types. However, parsing of the format string itself and
+validating arguments against it in calls to such functions is currently
+not performed.
+
+Additionally, @code{CFStringRefs} (defined by the @code{CoreFoundation} headers) may
+also be used as format arguments. Note that the relevant headers are only likely to be
+available on Darwin (OSX) installations. On such installations, the XCode and system
+documentation provide descriptions of @code{CFString}, @code{CFStringRefs} and
+associated functions.
+
+@node Pragmas
+@section Pragmas Accepted by GCC
+@cindex pragmas
+@cindex @code{#pragma}
+
+GCC supports several types of pragmas, primarily in order to compile
+code originally written for other compilers. Note that in general
+we do not recommend the use of pragmas; @xref{Function Attributes},
+for further explanation.
+
+The GNU C preprocessor recognizes several pragmas in addition to the
+compiler pragmas documented here. Refer to the CPP manual for more
+information.
+
+@menu
+* AArch64 Pragmas::
+* ARM Pragmas::
+* M32C Pragmas::
+* MeP Pragmas::
+* PRU Pragmas::
+* RS/6000 and PowerPC Pragmas::
+* S/390 Pragmas::
+* Darwin Pragmas::
+* Solaris Pragmas::
+* Symbol-Renaming Pragmas::
+* Structure-Layout Pragmas::
+* Weak Pragmas::
+* Diagnostic Pragmas::
+* Visibility Pragmas::
+* Push/Pop Macro Pragmas::
+* Function Specific Option Pragmas::
+* Loop-Specific Pragmas::
+@end menu
+
+@node AArch64 Pragmas
+@subsection AArch64 Pragmas
+
+The pragmas defined by the AArch64 target correspond to the AArch64
+target function attributes. They can be specified as below:
+@smallexample
+#pragma GCC target("string")
+@end smallexample
+
+where @code{@var{string}} can be any string accepted as an AArch64 target
+attribute. @xref{AArch64 Function Attributes}, for more details
+on the permissible values of @code{string}.
+
+@node ARM Pragmas
+@subsection ARM Pragmas
+
+The ARM target defines pragmas for controlling the default addition of
+@code{long_call} and @code{short_call} attributes to functions.
+@xref{Function Attributes}, for information about the effects of these
+attributes.
+
+@table @code
+@item long_calls
+@cindex pragma, long_calls
+Set all subsequent functions to have the @code{long_call} attribute.
+
+@item no_long_calls
+@cindex pragma, no_long_calls
+Set all subsequent functions to have the @code{short_call} attribute.
+
+@item long_calls_off
+@cindex pragma, long_calls_off
+Do not affect the @code{long_call} or @code{short_call} attributes of
+subsequent functions.
+@end table
+
+@node M32C Pragmas
+@subsection M32C Pragmas
+
+@table @code
+@item GCC memregs @var{number}
+@cindex pragma, memregs
+Overrides the command-line option @code{-memregs=} for the current
+file. Use with care! This pragma must be before any function in the
+file, and mixing different memregs values in different objects may
+make them incompatible. This pragma is useful when a
+performance-critical function uses a memreg for temporary values,
+as it may allow you to reduce the number of memregs used.
+
+@item ADDRESS @var{name} @var{address}
+@cindex pragma, address
+For any declared symbols matching @var{name}, this does three things
+to that symbol: it forces the symbol to be located at the given
+address (a number), it forces the symbol to be volatile, and it
+changes the symbol's scope to be static. This pragma exists for
+compatibility with other compilers, but note that the common
+@code{1234H} numeric syntax is not supported (use @code{0x1234}
+instead). Example:
+
+@smallexample
+#pragma ADDRESS port3 0x103
+char port3;
+@end smallexample
+
+@end table
+
+@node MeP Pragmas
+@subsection MeP Pragmas
+
+@table @code
+
+@item custom io_volatile (on|off)
+@cindex pragma, custom io_volatile
+Overrides the command-line option @code{-mio-volatile} for the current
+file. Note that for compatibility with future GCC releases, this
+option should only be used once before any @code{io} variables in each
+file.
+
+@item GCC coprocessor available @var{registers}
+@cindex pragma, coprocessor available
+Specifies which coprocessor registers are available to the register
+allocator. @var{registers} may be a single register, register range
+separated by ellipses, or comma-separated list of those. Example:
+
+@smallexample
+#pragma GCC coprocessor available $c0...$c10, $c28
+@end smallexample
+
+@item GCC coprocessor call_saved @var{registers}
+@cindex pragma, coprocessor call_saved
+Specifies which coprocessor registers are to be saved and restored by
+any function using them. @var{registers} may be a single register,
+register range separated by ellipses, or comma-separated list of
+those. Example:
+
+@smallexample
+#pragma GCC coprocessor call_saved $c4...$c6, $c31
+@end smallexample
+
+@item GCC coprocessor subclass '(A|B|C|D)' = @var{registers}
+@cindex pragma, coprocessor subclass
+Creates and defines a register class. These register classes can be
+used by inline @code{asm} constructs. @var{registers} may be a single
+register, register range separated by ellipses, or comma-separated
+list of those. Example:
+
+@smallexample
+#pragma GCC coprocessor subclass 'B' = $c2, $c4, $c6
+
+asm ("cpfoo %0" : "=B" (x));
+@end smallexample
+
+@item GCC disinterrupt @var{name} , @var{name} @dots{}
+@cindex pragma, disinterrupt
+For the named functions, the compiler adds code to disable interrupts
+for the duration of those functions. If any functions so named
+are not encountered in the source, a warning is emitted that the pragma is
+not used. Examples:
+
+@smallexample
+#pragma disinterrupt foo
+#pragma disinterrupt bar, grill
+int foo () @{ @dots{} @}
+@end smallexample
+
+@item GCC call @var{name} , @var{name} @dots{}
+@cindex pragma, call
+For the named functions, the compiler always uses a register-indirect
+call model when calling the named functions. Examples:
+
+@smallexample
+extern int foo ();
+#pragma call foo
+@end smallexample
+
+@end table
+
+@node PRU Pragmas
+@subsection PRU Pragmas
+
+@table @code
+
+@item ctable_entry @var{index} @var{constant_address}
+@cindex pragma, ctable_entry
+Specifies that the PRU CTABLE entry given by @var{index} has the value
+@var{constant_address}. This enables GCC to emit LBCO/SBCO instructions
+when the load/store address is known and can be addressed with some CTABLE
+entry. For example:
+
+@smallexample
+/* will compile to "sbco Rx, 2, 0x10, 4" */
+#pragma ctable_entry 2 0x4802a000
+*(unsigned int *)0x4802a010 = val;
+@end smallexample
+
+@end table
+
+@node RS/6000 and PowerPC Pragmas
+@subsection RS/6000 and PowerPC Pragmas
+
+The RS/6000 and PowerPC targets define one pragma for controlling
+whether or not the @code{longcall} attribute is added to function
+declarations by default. This pragma overrides the @option{-mlongcall}
+option, but not the @code{longcall} and @code{shortcall} attributes.
+@xref{RS/6000 and PowerPC Options}, for more information about when long
+calls are and are not necessary.
+
+@table @code
+@item longcall (1)
+@cindex pragma, longcall
+Apply the @code{longcall} attribute to all subsequent function
+declarations.
+
+@item longcall (0)
+Do not apply the @code{longcall} attribute to subsequent function
+declarations.
+@end table
+
+@c Describe h8300 pragmas here.
+@c Describe sh pragmas here.
+@c Describe v850 pragmas here.
+
+@node S/390 Pragmas
+@subsection S/390 Pragmas
+
+The pragmas defined by the S/390 target correspond to the S/390
+target function attributes and some the additional options:
+
+@table @samp
+@item zvector
+@itemx no-zvector
+@end table
+
+Note that options of the pragma, unlike options of the target
+attribute, do change the value of preprocessor macros like
+@code{__VEC__}. They can be specified as below:
+
+@smallexample
+#pragma GCC target("string[,string]...")
+#pragma GCC target("string"[,"string"]...)
+@end smallexample
+
+@node Darwin Pragmas
+@subsection Darwin Pragmas
+
+The following pragmas are available for all architectures running the
+Darwin operating system. These are useful for compatibility with other
+Mac OS compilers.
+
+@table @code
+@item mark @var{tokens}@dots{}
+@cindex pragma, mark
+This pragma is accepted, but has no effect.
+
+@item options align=@var{alignment}
+@cindex pragma, options align
+This pragma sets the alignment of fields in structures. The values of
+@var{alignment} may be @code{mac68k}, to emulate m68k alignment, or
+@code{power}, to emulate PowerPC alignment. Uses of this pragma nest
+properly; to restore the previous setting, use @code{reset} for the
+@var{alignment}.
+
+@item segment @var{tokens}@dots{}
+@cindex pragma, segment
+This pragma is accepted, but has no effect.
+
+@item unused (@var{var} [, @var{var}]@dots{})
+@cindex pragma, unused
+This pragma declares variables to be possibly unused. GCC does not
+produce warnings for the listed variables. The effect is similar to
+that of the @code{unused} attribute, except that this pragma may appear
+anywhere within the variables' scopes.
+@end table
+
+@node Solaris Pragmas
+@subsection Solaris Pragmas
+
+The Solaris target supports @code{#pragma redefine_extname}
+(@pxref{Symbol-Renaming Pragmas}). It also supports additional
+@code{#pragma} directives for compatibility with the system compiler.
+
+@table @code
+@item align @var{alignment} (@var{variable} [, @var{variable}]...)
+@cindex pragma, align
+
+Increase the minimum alignment of each @var{variable} to @var{alignment}.
+This is the same as GCC's @code{aligned} attribute @pxref{Variable
+Attributes}). Macro expansion occurs on the arguments to this pragma
+when compiling C and Objective-C@. It does not currently occur when
+compiling C++, but this is a bug which may be fixed in a future
+release.
+
+@item fini (@var{function} [, @var{function}]...)
+@cindex pragma, fini
+
+This pragma causes each listed @var{function} to be called after
+main, or during shared module unloading, by adding a call to the
+@code{.fini} section.
+
+@item init (@var{function} [, @var{function}]...)
+@cindex pragma, init
+
+This pragma causes each listed @var{function} to be called during
+initialization (before @code{main}) or during shared module loading, by
+adding a call to the @code{.init} section.
+
+@end table
+
+@node Symbol-Renaming Pragmas
+@subsection Symbol-Renaming Pragmas
+
+GCC supports a @code{#pragma} directive that changes the name used in
+assembly for a given declaration. While this pragma is supported on all
+platforms, it is intended primarily to provide compatibility with the
+Solaris system headers. This effect can also be achieved using the asm
+labels extension (@pxref{Asm Labels}).
+
+@table @code
+@item redefine_extname @var{oldname} @var{newname}
+@cindex pragma, redefine_extname
+
+This pragma gives the C function @var{oldname} the assembly symbol
+@var{newname}. The preprocessor macro @code{__PRAGMA_REDEFINE_EXTNAME}
+is defined if this pragma is available (currently on all platforms).
+@end table
+
+This pragma and the @code{asm} labels extension interact in a complicated
+manner. Here are some corner cases you may want to be aware of:
+
+@enumerate
+@item This pragma silently applies only to declarations with external
+linkage. The @code{asm} label feature does not have this restriction.
+
+@item In C++, this pragma silently applies only to declarations with
+``C'' linkage. Again, @code{asm} labels do not have this restriction.
+
+@item If either of the ways of changing the assembly name of a
+declaration are applied to a declaration whose assembly name has
+already been determined (either by a previous use of one of these
+features, or because the compiler needed the assembly name in order to
+generate code), and the new name is different, a warning issues and
+the name does not change.
+
+@item The @var{oldname} used by @code{#pragma redefine_extname} is
+always the C-language name.
+@end enumerate
+
+@node Structure-Layout Pragmas
+@subsection Structure-Layout Pragmas
+
+For compatibility with Microsoft Windows compilers, GCC supports a
+set of @code{#pragma} directives that change the maximum alignment of
+members of structures (other than zero-width bit-fields), unions, and
+classes subsequently defined. The @var{n} value below always is required
+to be a small power of two and specifies the new alignment in bytes.
+
+@enumerate
+@item @code{#pragma pack(@var{n})} simply sets the new alignment.
+@item @code{#pragma pack()} sets the alignment to the one that was in
+effect when compilation started (see also command-line option
+@option{-fpack-struct[=@var{n}]} @pxref{Code Gen Options}).
+@item @code{#pragma pack(push[,@var{n}])} pushes the current alignment
+setting on an internal stack and then optionally sets the new alignment.
+@item @code{#pragma pack(pop)} restores the alignment setting to the one
+saved at the top of the internal stack (and removes that stack entry).
+Note that @code{#pragma pack([@var{n}])} does not influence this internal
+stack; thus it is possible to have @code{#pragma pack(push)} followed by
+multiple @code{#pragma pack(@var{n})} instances and finalized by a single
+@code{#pragma pack(pop)}.
+@end enumerate
+
+Some targets, e.g.@: x86 and PowerPC, support the @code{#pragma ms_struct}
+directive which lays out structures and unions subsequently defined as the
+documented @code{__attribute__ ((ms_struct))}.
+
+@enumerate
+@item @code{#pragma ms_struct on} turns on the Microsoft layout.
+@item @code{#pragma ms_struct off} turns off the Microsoft layout.
+@item @code{#pragma ms_struct reset} goes back to the default layout.
+@end enumerate
+
+Most targets also support the @code{#pragma scalar_storage_order} directive
+which lays out structures and unions subsequently defined as the documented
+@code{__attribute__ ((scalar_storage_order))}.
+
+@enumerate
+@item @code{#pragma scalar_storage_order big-endian} sets the storage order
+of the scalar fields to big-endian.
+@item @code{#pragma scalar_storage_order little-endian} sets the storage order
+of the scalar fields to little-endian.
+@item @code{#pragma scalar_storage_order default} goes back to the endianness
+that was in effect when compilation started (see also command-line option
+@option{-fsso-struct=@var{endianness}} @pxref{C Dialect Options}).
+@end enumerate
+
+@node Weak Pragmas
+@subsection Weak Pragmas
+
+For compatibility with SVR4, GCC supports a set of @code{#pragma}
+directives for declaring symbols to be weak, and defining weak
+aliases.
+
+@table @code
+@item #pragma weak @var{symbol}
+@cindex pragma, weak
+This pragma declares @var{symbol} to be weak, as if the declaration
+had the attribute of the same name. The pragma may appear before
+or after the declaration of @var{symbol}. It is not an error for
+@var{symbol} to never be defined at all.
+
+@item #pragma weak @var{symbol1} = @var{symbol2}
+This pragma declares @var{symbol1} to be a weak alias of @var{symbol2}.
+It is an error if @var{symbol2} is not defined in the current
+translation unit.
+@end table
+
+@node Diagnostic Pragmas
+@subsection Diagnostic Pragmas
+
+GCC allows the user to selectively enable or disable certain types of
+diagnostics, and change the kind of the diagnostic. For example, a
+project's policy might require that all sources compile with
+@option{-Werror} but certain files might have exceptions allowing
+specific types of warnings. Or, a project might selectively enable
+diagnostics and treat them as errors depending on which preprocessor
+macros are defined.
+
+@table @code
+@item #pragma GCC diagnostic @var{kind} @var{option}
+@cindex pragma, diagnostic
+
+Modifies the disposition of a diagnostic. Note that not all
+diagnostics are modifiable; at the moment only warnings (normally
+controlled by @samp{-W@dots{}}) can be controlled, and not all of them.
+Use @option{-fdiagnostics-show-option} to determine which diagnostics
+are controllable and which option controls them.
+
+@var{kind} is @samp{error} to treat this diagnostic as an error,
+@samp{warning} to treat it like a warning (even if @option{-Werror} is
+in effect), or @samp{ignored} if the diagnostic is to be ignored.
+@var{option} is a double quoted string that matches the command-line
+option.
+
+@smallexample
+#pragma GCC diagnostic warning "-Wformat"
+#pragma GCC diagnostic error "-Wformat"
+#pragma GCC diagnostic ignored "-Wformat"
+@end smallexample
+
+Note that these pragmas override any command-line options. GCC keeps
+track of the location of each pragma, and issues diagnostics according
+to the state as of that point in the source file. Thus, pragmas occurring
+after a line do not affect diagnostics caused by that line.
+
+@item #pragma GCC diagnostic push
+@itemx #pragma GCC diagnostic pop
+
+Causes GCC to remember the state of the diagnostics as of each
+@code{push}, and restore to that point at each @code{pop}. If a
+@code{pop} has no matching @code{push}, the command-line options are
+restored.
+
+@smallexample
+#pragma GCC diagnostic error "-Wuninitialized"
+ foo(a); /* error is given for this one */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wuninitialized"
+ foo(b); /* no diagnostic for this one */
+#pragma GCC diagnostic pop
+ foo(c); /* error is given for this one */
+#pragma GCC diagnostic pop
+ foo(d); /* depends on command-line options */
+@end smallexample
+
+@item #pragma GCC diagnostic ignored_attributes
+
+Similarly to @option{-Wno-attributes=}, this pragma allows users to suppress
+warnings about unknown scoped attributes (in C++11 and C2X). For example,
+@code{#pragma GCC diagnostic ignored_attributes "vendor::attr"} disables
+warning about the following declaration:
+
+@smallexample
+[[vendor::attr]] void f();
+@end smallexample
+
+whereas @code{#pragma GCC diagnostic ignored_attributes "vendor::"} prevents
+warning about both of these declarations:
+
+@smallexample
+[[vendor::safe]] void f();
+[[vendor::unsafe]] void f2();
+@end smallexample
+
+@end table
+
+GCC also offers a simple mechanism for printing messages during
+compilation.
+
+@table @code
+@item #pragma message @var{string}
+@cindex pragma, diagnostic
+
+Prints @var{string} as a compiler message on compilation. The message
+is informational only, and is neither a compilation warning nor an
+error. Newlines can be included in the string by using the @samp{\n}
+escape sequence.
+
+@smallexample
+#pragma message "Compiling " __FILE__ "..."
+@end smallexample
+
+@var{string} may be parenthesized, and is printed with location
+information. For example,
+
+@smallexample
+#define DO_PRAGMA(x) _Pragma (#x)
+#define TODO(x) DO_PRAGMA(message ("TODO - " #x))
+
+TODO(Remember to fix this)
+@end smallexample
+
+@noindent
+prints @samp{/tmp/file.c:4: note: #pragma message:
+TODO - Remember to fix this}.
+
+@item #pragma GCC error @var{message}
+@cindex pragma, diagnostic
+Generates an error message. This pragma @emph{is} considered to
+indicate an error in the compilation, and it will be treated as such.
+
+Newlines can be included in the string by using the @samp{\n}
+escape sequence. They will be displayed as newlines even if the
+@option{-fmessage-length} option is set to zero.
+
+The error is only generated if the pragma is present in the code after
+pre-processing has been completed. It does not matter however if the
+code containing the pragma is unreachable:
+
+@smallexample
+#if 0
+#pragma GCC error "this error is not seen"
+#endif
+void foo (void)
+@{
+ return;
+#pragma GCC error "this error is seen"
+@}
+@end smallexample
+
+@item #pragma GCC warning @var{message}
+@cindex pragma, diagnostic
+This is just like @samp{pragma GCC error} except that a warning
+message is issued instead of an error message. Unless
+@option{-Werror} is in effect, in which case this pragma will generate
+an error as well.
+
+@end table
+
+@node Visibility Pragmas
+@subsection Visibility Pragmas
+
+@table @code
+@item #pragma GCC visibility push(@var{visibility})
+@itemx #pragma GCC visibility pop
+@cindex pragma, visibility
+
+This pragma allows the user to set the visibility for multiple
+declarations without having to give each a visibility attribute
+(@pxref{Function Attributes}).
+
+In C++, @samp{#pragma GCC visibility} affects only namespace-scope
+declarations. Class members and template specializations are not
+affected; if you want to override the visibility for a particular
+member or instantiation, you must use an attribute.
+
+@end table
+
+
+@node Push/Pop Macro Pragmas
+@subsection Push/Pop Macro Pragmas
+
+For compatibility with Microsoft Windows compilers, GCC supports
+@samp{#pragma push_macro(@var{"macro_name"})}
+and @samp{#pragma pop_macro(@var{"macro_name"})}.
+
+@table @code
+@item #pragma push_macro(@var{"macro_name"})
+@cindex pragma, push_macro
+This pragma saves the value of the macro named as @var{macro_name} to
+the top of the stack for this macro.
+
+@item #pragma pop_macro(@var{"macro_name"})
+@cindex pragma, pop_macro
+This pragma sets the value of the macro named as @var{macro_name} to
+the value on top of the stack for this macro. If the stack for
+@var{macro_name} is empty, the value of the macro remains unchanged.
+@end table
+
+For example:
+
+@smallexample
+#define X 1
+#pragma push_macro("X")
+#undef X
+#define X -1
+#pragma pop_macro("X")
+int x [X];
+@end smallexample
+
+@noindent
+In this example, the definition of X as 1 is saved by @code{#pragma
+push_macro} and restored by @code{#pragma pop_macro}.
+
+@node Function Specific Option Pragmas
+@subsection Function Specific Option Pragmas
+
+@table @code
+@item #pragma GCC target (@var{string}, @dots{})
+@cindex pragma GCC target
+
+This pragma allows you to set target-specific options for functions
+defined later in the source file. One or more strings can be
+specified. Each function that is defined after this point is treated
+as if it had been declared with one @code{target(}@var{string}@code{)}
+attribute for each @var{string} argument. The parentheses around
+the strings in the pragma are optional. @xref{Function Attributes},
+for more information about the @code{target} attribute and the attribute
+syntax.
+
+The @code{#pragma GCC target} pragma is presently implemented for
+x86, ARM, AArch64, PowerPC, S/390, and Nios II targets only.
+
+@item #pragma GCC optimize (@var{string}, @dots{})
+@cindex pragma GCC optimize
+
+This pragma allows you to set global optimization options for functions
+defined later in the source file. One or more strings can be
+specified. Each function that is defined after this point is treated
+as if it had been declared with one @code{optimize(}@var{string}@code{)}
+attribute for each @var{string} argument. The parentheses around
+the strings in the pragma are optional. @xref{Function Attributes},
+for more information about the @code{optimize} attribute and the attribute
+syntax.
+
+@item #pragma GCC push_options
+@itemx #pragma GCC pop_options
+@cindex pragma GCC push_options
+@cindex pragma GCC pop_options
+
+These pragmas maintain a stack of the current target and optimization
+options. It is intended for include files where you temporarily want
+to switch to using a different @samp{#pragma GCC target} or
+@samp{#pragma GCC optimize} and then to pop back to the previous
+options.
+
+@item #pragma GCC reset_options
+@cindex pragma GCC reset_options
+
+This pragma clears the current @code{#pragma GCC target} and
+@code{#pragma GCC optimize} to use the default switches as specified
+on the command line.
+
+@end table
+
+@node Loop-Specific Pragmas
+@subsection Loop-Specific Pragmas
+
+@table @code
+@item #pragma GCC ivdep
+@cindex pragma GCC ivdep
+
+With this pragma, the programmer asserts that there are no loop-carried
+dependencies which would prevent consecutive iterations of
+the following loop from executing concurrently with SIMD
+(single instruction multiple data) instructions.
+
+For example, the compiler can only unconditionally vectorize the following
+loop with the pragma:
+
+@smallexample
+void foo (int n, int *a, int *b, int *c)
+@{
+ int i, j;
+#pragma GCC ivdep
+ for (i = 0; i < n; ++i)
+ a[i] = b[i] + c[i];
+@}
+@end smallexample
+
+@noindent
+In this example, using the @code{restrict} qualifier had the same
+effect. In the following example, that would not be possible. Assume
+@math{k < -m} or @math{k >= m}. Only with the pragma, the compiler knows
+that it can unconditionally vectorize the following loop:
+
+@smallexample
+void ignore_vec_dep (int *a, int k, int c, int m)
+@{
+#pragma GCC ivdep
+ for (int i = 0; i < m; i++)
+ a[i] = a[i + k] * c;
+@}
+@end smallexample
+
+@item #pragma GCC unroll @var{n}
+@cindex pragma GCC unroll @var{n}
+
+You can use this pragma to control how many times a loop should be unrolled.
+It must be placed immediately before a @code{for}, @code{while} or @code{do}
+loop or a @code{#pragma GCC ivdep}, and applies only to the loop that follows.
+@var{n} is an integer constant expression specifying the unrolling factor.
+The values of @math{0} and @math{1} block any unrolling of the loop.
+
+@end table
+
+@node Unnamed Fields
+@section Unnamed Structure and Union Fields
+@cindex @code{struct}
+@cindex @code{union}
+
+As permitted by ISO C11 and for compatibility with other compilers,
+GCC allows you to define
+a structure or union that contains, as fields, structures and unions
+without names. For example:
+
+@smallexample
+struct @{
+ int a;
+ union @{
+ int b;
+ float c;
+ @};
+ int d;
+@} foo;
+@end smallexample
+
+@noindent
+In this example, you are able to access members of the unnamed
+union with code like @samp{foo.b}. Note that only unnamed structs and
+unions are allowed, you may not have, for example, an unnamed
+@code{int}.
+
+You must never create such structures that cause ambiguous field definitions.
+For example, in this structure:
+
+@smallexample
+struct @{
+ int a;
+ struct @{
+ int a;
+ @};
+@} foo;
+@end smallexample
+
+@noindent
+it is ambiguous which @code{a} is being referred to with @samp{foo.a}.
+The compiler gives errors for such constructs.
+
+@opindex fms-extensions
+Unless @option{-fms-extensions} is used, the unnamed field must be a
+structure or union definition without a tag (for example, @samp{struct
+@{ int a; @};}). If @option{-fms-extensions} is used, the field may
+also be a definition with a tag such as @samp{struct foo @{ int a;
+@};}, a reference to a previously defined structure or union such as
+@samp{struct foo;}, or a reference to a @code{typedef} name for a
+previously defined structure or union type.
+
+@opindex fplan9-extensions
+The option @option{-fplan9-extensions} enables
+@option{-fms-extensions} as well as two other extensions. First, a
+pointer to a structure is automatically converted to a pointer to an
+anonymous field for assignments and function calls. For example:
+
+@smallexample
+struct s1 @{ int a; @};
+struct s2 @{ struct s1; @};
+extern void f1 (struct s1 *);
+void f2 (struct s2 *p) @{ f1 (p); @}
+@end smallexample
+
+@noindent
+In the call to @code{f1} inside @code{f2}, the pointer @code{p} is
+converted into a pointer to the anonymous field.
+
+Second, when the type of an anonymous field is a @code{typedef} for a
+@code{struct} or @code{union}, code may refer to the field using the
+name of the @code{typedef}.
+
+@smallexample
+typedef struct @{ int a; @} s1;
+struct s2 @{ s1; @};
+s1 f1 (struct s2 *p) @{ return p->s1; @}
+@end smallexample
+
+These usages are only permitted when they are not ambiguous.
+
+@node Thread-Local
+@section Thread-Local Storage
+@cindex Thread-Local Storage
+@cindex @acronym{TLS}
+@cindex @code{__thread}
+
+Thread-local storage (@acronym{TLS}) is a mechanism by which variables
+are allocated such that there is one instance of the variable per extant
+thread. The runtime model GCC uses to implement this originates
+in the IA-64 processor-specific ABI, but has since been migrated
+to other processors as well. It requires significant support from
+the linker (@command{ld}), dynamic linker (@command{ld.so}), and
+system libraries (@file{libc.so} and @file{libpthread.so}), so it
+is not available everywhere.
+
+At the user level, the extension is visible with a new storage
+class keyword: @code{__thread}. For example:
+
+@smallexample
+__thread int i;
+extern __thread struct state s;
+static __thread char *p;
+@end smallexample
+
+The @code{__thread} specifier may be used alone, with the @code{extern}
+or @code{static} specifiers, but with no other storage class specifier.
+When used with @code{extern} or @code{static}, @code{__thread} must appear
+immediately after the other storage class specifier.
+
+The @code{__thread} specifier may be applied to any global, file-scoped
+static, function-scoped static, or static data member of a class. It may
+not be applied to block-scoped automatic or non-static data member.
+
+When the address-of operator is applied to a thread-local variable, it is
+evaluated at run time and returns the address of the current thread's
+instance of that variable. An address so obtained may be used by any
+thread. When a thread terminates, any pointers to thread-local variables
+in that thread become invalid.
+
+No static initialization may refer to the address of a thread-local variable.
+
+In C++, if an initializer is present for a thread-local variable, it must
+be a @var{constant-expression}, as defined in 5.19.2 of the ANSI/ISO C++
+standard.
+
+See @uref{https://www.akkadia.org/drepper/tls.pdf,
+ELF Handling For Thread-Local Storage} for a detailed explanation of
+the four thread-local storage addressing models, and how the runtime
+is expected to function.
+
+@menu
+* C99 Thread-Local Edits::
+* C++98 Thread-Local Edits::
+@end menu
+
+@node C99 Thread-Local Edits
+@subsection ISO/IEC 9899:1999 Edits for Thread-Local Storage
+
+The following are a set of changes to ISO/IEC 9899:1999 (aka C99)
+that document the exact semantics of the language extension.
+
+@itemize @bullet
+@item
+@cite{5.1.2 Execution environments}
+
+Add new text after paragraph 1
+
+@quotation
+Within either execution environment, a @dfn{thread} is a flow of
+control within a program. It is implementation defined whether
+or not there may be more than one thread associated with a program.
+It is implementation defined how threads beyond the first are
+created, the name and type of the function called at thread
+startup, and how threads may be terminated. However, objects
+with thread storage duration shall be initialized before thread
+startup.
+@end quotation
+
+@item
+@cite{6.2.4 Storage durations of objects}
+
+Add new text before paragraph 3
+
+@quotation
+An object whose identifier is declared with the storage-class
+specifier @w{@code{__thread}} has @dfn{thread storage duration}.
+Its lifetime is the entire execution of the thread, and its
+stored value is initialized only once, prior to thread startup.
+@end quotation
+
+@item
+@cite{6.4.1 Keywords}
+
+Add @code{__thread}.
+
+@item
+@cite{6.7.1 Storage-class specifiers}
+
+Add @code{__thread} to the list of storage class specifiers in
+paragraph 1.
+
+Change paragraph 2 to
+
+@quotation
+With the exception of @code{__thread}, at most one storage-class
+specifier may be given [@dots{}]. The @code{__thread} specifier may
+be used alone, or immediately following @code{extern} or
+@code{static}.
+@end quotation
+
+Add new text after paragraph 6
+
+@quotation
+The declaration of an identifier for a variable that has
+block scope that specifies @code{__thread} shall also
+specify either @code{extern} or @code{static}.
+
+The @code{__thread} specifier shall be used only with
+variables.
+@end quotation
+@end itemize
+
+@node C++98 Thread-Local Edits
+@subsection ISO/IEC 14882:1998 Edits for Thread-Local Storage
+
+The following are a set of changes to ISO/IEC 14882:1998 (aka C++98)
+that document the exact semantics of the language extension.
+
+@itemize @bullet
+@item
+@b{[intro.execution]}
+
+New text after paragraph 4
+
+@quotation
+A @dfn{thread} is a flow of control within the abstract machine.
+It is implementation defined whether or not there may be more than
+one thread.
+@end quotation
+
+New text after paragraph 7
+
+@quotation
+It is unspecified whether additional action must be taken to
+ensure when and whether side effects are visible to other threads.
+@end quotation
+
+@item
+@b{[lex.key]}
+
+Add @code{__thread}.
+
+@item
+@b{[basic.start.main]}
+
+Add after paragraph 5
+
+@quotation
+The thread that begins execution at the @code{main} function is called
+the @dfn{main thread}. It is implementation defined how functions
+beginning threads other than the main thread are designated or typed.
+A function so designated, as well as the @code{main} function, is called
+a @dfn{thread startup function}. It is implementation defined what
+happens if a thread startup function returns. It is implementation
+defined what happens to other threads when any thread calls @code{exit}.
+@end quotation
+
+@item
+@b{[basic.start.init]}
+
+Add after paragraph 4
+
+@quotation
+The storage for an object of thread storage duration shall be
+statically initialized before the first statement of the thread startup
+function. An object of thread storage duration shall not require
+dynamic initialization.
+@end quotation
+
+@item
+@b{[basic.start.term]}
+
+Add after paragraph 3
+
+@quotation
+The type of an object with thread storage duration shall not have a
+non-trivial destructor, nor shall it be an array type whose elements
+(directly or indirectly) have non-trivial destructors.
+@end quotation
+
+@item
+@b{[basic.stc]}
+
+Add ``thread storage duration'' to the list in paragraph 1.
+
+Change paragraph 2
+
+@quotation
+Thread, static, and automatic storage durations are associated with
+objects introduced by declarations [@dots{}].
+@end quotation
+
+Add @code{__thread} to the list of specifiers in paragraph 3.
+
+@item
+@b{[basic.stc.thread]}
+
+New section before @b{[basic.stc.static]}
+
+@quotation
+The keyword @code{__thread} applied to a non-local object gives the
+object thread storage duration.
+
+A local variable or class data member declared both @code{static}
+and @code{__thread} gives the variable or member thread storage
+duration.
+@end quotation
+
+@item
+@b{[basic.stc.static]}
+
+Change paragraph 1
+
+@quotation
+All objects that have neither thread storage duration, dynamic
+storage duration nor are local [@dots{}].
+@end quotation
+
+@item
+@b{[dcl.stc]}
+
+Add @code{__thread} to the list in paragraph 1.
+
+Change paragraph 1
+
+@quotation
+With the exception of @code{__thread}, at most one
+@var{storage-class-specifier} shall appear in a given
+@var{decl-specifier-seq}. The @code{__thread} specifier may
+be used alone, or immediately following the @code{extern} or
+@code{static} specifiers. [@dots{}]
+@end quotation
+
+Add after paragraph 5
+
+@quotation
+The @code{__thread} specifier can be applied only to the names of objects
+and to anonymous unions.
+@end quotation
+
+@item
+@b{[class.mem]}
+
+Add after paragraph 6
+
+@quotation
+Non-@code{static} members shall not be @code{__thread}.
+@end quotation
+@end itemize
+
+@node Binary constants
+@section Binary Constants using the @samp{0b} Prefix
+@cindex Binary constants using the @samp{0b} prefix
+
+Integer constants can be written as binary constants, consisting of a
+sequence of @samp{0} and @samp{1} digits, prefixed by @samp{0b} or
+@samp{0B}. This is particularly useful in environments that operate a
+lot on the bit level (like microcontrollers).
+
+The following statements are identical:
+
+@smallexample
+i = 42;
+i = 0x2a;
+i = 052;
+i = 0b101010;
+@end smallexample
+
+The type of these constants follows the same rules as for octal or
+hexadecimal integer constants, so suffixes like @samp{L} or @samp{UL}
+can be applied.
+
+@node C++ Extensions
+@chapter Extensions to the C++ Language
+@cindex extensions, C++ language
+@cindex C++ language extensions
+
+The GNU compiler provides these extensions to the C++ language (and you
+can also use most of the C language extensions in your C++ programs). If you
+want to write code that checks whether these features are available, you can
+test for the GNU compiler the same way as for C programs: check for a
+predefined macro @code{__GNUC__}. You can also use @code{__GNUG__} to
+test specifically for GNU C++ (@pxref{Common Predefined Macros,,
+Predefined Macros,cpp,The GNU C Preprocessor}).
+
+@menu
+* C++ Volatiles:: What constitutes an access to a volatile object.
+* Restricted Pointers:: C99 restricted pointers and references.
+* Vague Linkage:: Where G++ puts inlines, vtables and such.
+* C++ Interface:: You can use a single C++ header file for both
+ declarations and definitions.
+* Template Instantiation:: Methods for ensuring that exactly one copy of
+ each needed template instantiation is emitted.
+* Bound member functions:: You can extract a function pointer to the
+ method denoted by a @samp{->*} or @samp{.*} expression.
+* C++ Attributes:: Variable, function, and type attributes for C++ only.
+* Function Multiversioning:: Declaring multiple function versions.
+* Type Traits:: Compiler support for type traits.
+* C++ Concepts:: Improved support for generic programming.
+* Deprecated Features:: Things will disappear from G++.
+* Backwards Compatibility:: Compatibilities with earlier definitions of C++.
+@end menu
+
+@node C++ Volatiles
+@section When is a Volatile C++ Object Accessed?
+@cindex accessing volatiles
+@cindex volatile read
+@cindex volatile write
+@cindex volatile access
+
+The C++ standard differs from the C standard in its treatment of
+volatile objects. It fails to specify what constitutes a volatile
+access, except to say that C++ should behave in a similar manner to C
+with respect to volatiles, where possible. However, the different
+lvalueness of expressions between C and C++ complicate the behavior.
+G++ behaves the same as GCC for volatile access, @xref{C
+Extensions,,Volatiles}, for a description of GCC's behavior.
+
+The C and C++ language specifications differ when an object is
+accessed in a void context:
+
+@smallexample
+volatile int *src = @var{somevalue};
+*src;
+@end smallexample
+
+The C++ standard specifies that such expressions do not undergo lvalue
+to rvalue conversion, and that the type of the dereferenced object may
+be incomplete. The C++ standard does not specify explicitly that it
+is lvalue to rvalue conversion that is responsible for causing an
+access. There is reason to believe that it is, because otherwise
+certain simple expressions become undefined. However, because it
+would surprise most programmers, G++ treats dereferencing a pointer to
+volatile object of complete type as GCC would do for an equivalent
+type in C@. When the object has incomplete type, G++ issues a
+warning; if you wish to force an error, you must force a conversion to
+rvalue with, for instance, a static cast.
+
+When using a reference to volatile, G++ does not treat equivalent
+expressions as accesses to volatiles, but instead issues a warning that
+no volatile is accessed. The rationale for this is that otherwise it
+becomes difficult to determine where volatile access occur, and not
+possible to ignore the return value from functions returning volatile
+references. Again, if you wish to force a read, cast the reference to
+an rvalue.
+
+G++ implements the same behavior as GCC does when assigning to a
+volatile object---there is no reread of the assigned-to object, the
+assigned rvalue is reused. Note that in C++ assignment expressions
+are lvalues, and if used as an lvalue, the volatile object is
+referred to. For instance, @var{vref} refers to @var{vobj}, as
+expected, in the following example:
+
+@smallexample
+volatile int vobj;
+volatile int &vref = vobj = @var{something};
+@end smallexample
+
+@node Restricted Pointers
+@section Restricting Pointer Aliasing
+@cindex restricted pointers
+@cindex restricted references
+@cindex restricted this pointer
+
+As with the C front end, G++ understands the C99 feature of restricted pointers,
+specified with the @code{__restrict__}, or @code{__restrict} type
+qualifier. Because you cannot compile C++ by specifying the @option{-std=c99}
+language flag, @code{restrict} is not a keyword in C++.
+
+In addition to allowing restricted pointers, you can specify restricted
+references, which indicate that the reference is not aliased in the local
+context.
+
+@smallexample
+void fn (int *__restrict__ rptr, int &__restrict__ rref)
+@{
+ /* @r{@dots{}} */
+@}
+@end smallexample
+
+@noindent
+In the body of @code{fn}, @var{rptr} points to an unaliased integer and
+@var{rref} refers to a (different) unaliased integer.
+
+You may also specify whether a member function's @var{this} pointer is
+unaliased by using @code{__restrict__} as a member function qualifier.
+
+@smallexample
+void T::fn () __restrict__
+@{
+ /* @r{@dots{}} */
+@}
+@end smallexample
+
+@noindent
+Within the body of @code{T::fn}, @var{this} has the effective
+definition @code{T *__restrict__ const this}. Notice that the
+interpretation of a @code{__restrict__} member function qualifier is
+different to that of @code{const} or @code{volatile} qualifier, in that it
+is applied to the pointer rather than the object. This is consistent with
+other compilers that implement restricted pointers.
+
+As with all outermost parameter qualifiers, @code{__restrict__} is
+ignored in function definition matching. This means you only need to
+specify @code{__restrict__} in a function definition, rather than
+in a function prototype as well.
+
+@node Vague Linkage
+@section Vague Linkage
+@cindex vague linkage
+
+There are several constructs in C++ that require space in the object
+file but are not clearly tied to a single translation unit. We say that
+these constructs have ``vague linkage''. Typically such constructs are
+emitted wherever they are needed, though sometimes we can be more
+clever.
+
+@table @asis
+@item Inline Functions
+Inline functions are typically defined in a header file which can be
+included in many different compilations. Hopefully they can usually be
+inlined, but sometimes an out-of-line copy is necessary, if the address
+of the function is taken or if inlining fails. In general, we emit an
+out-of-line copy in all translation units where one is needed. As an
+exception, we only emit inline virtual functions with the vtable, since
+it always requires a copy.
+
+Local static variables and string constants used in an inline function
+are also considered to have vague linkage, since they must be shared
+between all inlined and out-of-line instances of the function.
+
+@item VTables
+@cindex vtable
+C++ virtual functions are implemented in most compilers using a lookup
+table, known as a vtable. The vtable contains pointers to the virtual
+functions provided by a class, and each object of the class contains a
+pointer to its vtable (or vtables, in some multiple-inheritance
+situations). If the class declares any non-inline, non-pure virtual
+functions, the first one is chosen as the ``key method'' for the class,
+and the vtable is only emitted in the translation unit where the key
+method is defined.
+
+@emph{Note:} If the chosen key method is later defined as inline, the
+vtable is still emitted in every translation unit that defines it.
+Make sure that any inline virtuals are declared inline in the class
+body, even if they are not defined there.
+
+@item @code{type_info} objects
+@cindex @code{type_info}
+@cindex RTTI
+C++ requires information about types to be written out in order to
+implement @samp{dynamic_cast}, @samp{typeid} and exception handling.
+For polymorphic classes (classes with virtual functions), the @samp{type_info}
+object is written out along with the vtable so that @samp{dynamic_cast}
+can determine the dynamic type of a class object at run time. For all
+other types, we write out the @samp{type_info} object when it is used: when
+applying @samp{typeid} to an expression, throwing an object, or
+referring to a type in a catch clause or exception specification.
+
+@item Template Instantiations
+Most everything in this section also applies to template instantiations,
+but there are other options as well.
+@xref{Template Instantiation,,Where's the Template?}.
+
+@end table
+
+When used with GNU ld version 2.8 or later on an ELF system such as
+GNU/Linux or Solaris 2, or on Microsoft Windows, duplicate copies of
+these constructs will be discarded at link time. This is known as
+COMDAT support.
+
+On targets that don't support COMDAT, but do support weak symbols, GCC
+uses them. This way one copy overrides all the others, but
+the unused copies still take up space in the executable.
+
+For targets that do not support either COMDAT or weak symbols,
+most entities with vague linkage are emitted as local symbols to
+avoid duplicate definition errors from the linker. This does not happen
+for local statics in inlines, however, as having multiple copies
+almost certainly breaks things.
+
+@xref{C++ Interface,,Declarations and Definitions in One Header}, for
+another way to control placement of these constructs.
+
+@node C++ Interface
+@section C++ Interface and Implementation Pragmas
+
+@cindex interface and implementation headers, C++
+@cindex C++ interface and implementation headers
+@cindex pragmas, interface and implementation
+
+@code{#pragma interface} and @code{#pragma implementation} provide the
+user with a way of explicitly directing the compiler to emit entities
+with vague linkage (and debugging information) in a particular
+translation unit.
+
+@emph{Note:} These @code{#pragma}s have been superceded as of GCC 2.7.2
+by COMDAT support and the ``key method'' heuristic
+mentioned in @ref{Vague Linkage}. Using them can actually cause your
+program to grow due to unnecessary out-of-line copies of inline
+functions.
+
+@table @code
+@item #pragma interface
+@itemx #pragma interface "@var{subdir}/@var{objects}.h"
+@kindex #pragma interface
+Use this directive in @emph{header files} that define object classes, to save
+space in most of the object files that use those classes. Normally,
+local copies of certain information (backup copies of inline member
+functions, debugging information, and the internal tables that implement
+virtual functions) must be kept in each object file that includes class
+definitions. You can use this pragma to avoid such duplication. When a
+header file containing @samp{#pragma interface} is included in a
+compilation, this auxiliary information is not generated (unless
+the main input source file itself uses @samp{#pragma implementation}).
+Instead, the object files contain references to be resolved at link
+time.
+
+The second form of this directive is useful for the case where you have
+multiple headers with the same name in different directories. If you
+use this form, you must specify the same string to @samp{#pragma
+implementation}.
+
+@item #pragma implementation
+@itemx #pragma implementation "@var{objects}.h"
+@kindex #pragma implementation
+Use this pragma in a @emph{main input file}, when you want full output from
+included header files to be generated (and made globally visible). The
+included header file, in turn, should use @samp{#pragma interface}.
+Backup copies of inline member functions, debugging information, and the
+internal tables used to implement virtual functions are all generated in
+implementation files.
+
+@cindex implied @code{#pragma implementation}
+@cindex @code{#pragma implementation}, implied
+@cindex naming convention, implementation headers
+If you use @samp{#pragma implementation} with no argument, it applies to
+an include file with the same basename@footnote{A file's @dfn{basename}
+is the name stripped of all leading path information and of trailing
+suffixes, such as @samp{.h} or @samp{.C} or @samp{.cc}.} as your source
+file. For example, in @file{allclass.cc}, giving just
+@samp{#pragma implementation}
+by itself is equivalent to @samp{#pragma implementation "allclass.h"}.
+
+Use the string argument if you want a single implementation file to
+include code from multiple header files. (You must also use
+@samp{#include} to include the header file; @samp{#pragma
+implementation} only specifies how to use the file---it doesn't actually
+include it.)
+
+There is no way to split up the contents of a single header file into
+multiple implementation files.
+@end table
+
+@cindex inlining and C++ pragmas
+@cindex C++ pragmas, effect on inlining
+@cindex pragmas in C++, effect on inlining
+@samp{#pragma implementation} and @samp{#pragma interface} also have an
+effect on function inlining.
+
+If you define a class in a header file marked with @samp{#pragma
+interface}, the effect on an inline function defined in that class is
+similar to an explicit @code{extern} declaration---the compiler emits
+no code at all to define an independent version of the function. Its
+definition is used only for inlining with its callers.
+
+@opindex fno-implement-inlines
+Conversely, when you include the same header file in a main source file
+that declares it as @samp{#pragma implementation}, the compiler emits
+code for the function itself; this defines a version of the function
+that can be found via pointers (or by callers compiled without
+inlining). If all calls to the function can be inlined, you can avoid
+emitting the function by compiling with @option{-fno-implement-inlines}.
+If any calls are not inlined, you will get linker errors.
+
+@node Template Instantiation
+@section Where's the Template?
+@cindex template instantiation
+
+C++ templates were the first language feature to require more
+intelligence from the environment than was traditionally found on a UNIX
+system. Somehow the compiler and linker have to make sure that each
+template instance occurs exactly once in the executable if it is needed,
+and not at all otherwise. There are two basic approaches to this
+problem, which are referred to as the Borland model and the Cfront model.
+
+@table @asis
+@item Borland model
+Borland C++ solved the template instantiation problem by adding the code
+equivalent of common blocks to their linker; the compiler emits template
+instances in each translation unit that uses them, and the linker
+collapses them together. The advantage of this model is that the linker
+only has to consider the object files themselves; there is no external
+complexity to worry about. The disadvantage is that compilation time
+is increased because the template code is being compiled repeatedly.
+Code written for this model tends to include definitions of all
+templates in the header file, since they must be seen to be
+instantiated.
+
+@item Cfront model
+The AT&T C++ translator, Cfront, solved the template instantiation
+problem by creating the notion of a template repository, an
+automatically maintained place where template instances are stored. A
+more modern version of the repository works as follows: As individual
+object files are built, the compiler places any template definitions and
+instantiations encountered in the repository. At link time, the link
+wrapper adds in the objects in the repository and compiles any needed
+instances that were not previously emitted. The advantages of this
+model are more optimal compilation speed and the ability to use the
+system linker; to implement the Borland model a compiler vendor also
+needs to replace the linker. The disadvantages are vastly increased
+complexity, and thus potential for error; for some code this can be
+just as transparent, but in practice it can been very difficult to build
+multiple programs in one directory and one program in multiple
+directories. Code written for this model tends to separate definitions
+of non-inline member templates into a separate file, which should be
+compiled separately.
+@end table
+
+G++ implements the Borland model on targets where the linker supports it,
+including ELF targets (such as GNU/Linux), Mac OS X and Microsoft Windows.
+Otherwise G++ implements neither automatic model.
+
+You have the following options for dealing with template instantiations:
+
+@enumerate
+@item
+Do nothing. Code written for the Borland model works fine, but
+each translation unit contains instances of each of the templates it
+uses. The duplicate instances will be discarded by the linker, but in
+a large program, this can lead to an unacceptable amount of code
+duplication in object files or shared libraries.
+
+Duplicate instances of a template can be avoided by defining an explicit
+instantiation in one object file, and preventing the compiler from doing
+implicit instantiations in any other object files by using an explicit
+instantiation declaration, using the @code{extern template} syntax:
+
+@smallexample
+extern template int max (int, int);
+@end smallexample
+
+This syntax is defined in the C++ 2011 standard, but has been supported by
+G++ and other compilers since well before 2011.
+
+Explicit instantiations can be used for the largest or most frequently
+duplicated instances, without having to know exactly which other instances
+are used in the rest of the program. You can scatter the explicit
+instantiations throughout your program, perhaps putting them in the
+translation units where the instances are used or the translation units
+that define the templates themselves; you can put all of the explicit
+instantiations you need into one big file; or you can create small files
+like
+
+@smallexample
+#include "Foo.h"
+#include "Foo.cc"
+
+template class Foo<int>;
+template ostream& operator <<
+ (ostream&, const Foo<int>&);
+@end smallexample
+
+@noindent
+for each of the instances you need, and create a template instantiation
+library from those.
+
+This is the simplest option, but also offers flexibility and
+fine-grained control when necessary. It is also the most portable
+alternative and programs using this approach will work with most modern
+compilers.
+
+@item
+@opindex fno-implicit-templates
+Compile your code with @option{-fno-implicit-templates} to disable the
+implicit generation of template instances, and explicitly instantiate
+all the ones you use. This approach requires more knowledge of exactly
+which instances you need than do the others, but it's less
+mysterious and allows greater control if you want to ensure that only
+the intended instances are used.
+
+If you are using Cfront-model code, you can probably get away with not
+using @option{-fno-implicit-templates} when compiling files that don't
+@samp{#include} the member template definitions.
+
+If you use one big file to do the instantiations, you may want to
+compile it without @option{-fno-implicit-templates} so you get all of the
+instances required by your explicit instantiations (but not by any
+other files) without having to specify them as well.
+
+In addition to forward declaration of explicit instantiations
+(with @code{extern}), G++ has extended the template instantiation
+syntax to support instantiation of the compiler support data for a
+template class (i.e.@: the vtable) without instantiating any of its
+members (with @code{inline}), and instantiation of only the static data
+members of a template class, without the support data or member
+functions (with @code{static}):
+
+@smallexample
+inline template class Foo<int>;
+static template class Foo<int>;
+@end smallexample
+@end enumerate
+
+@node Bound member functions
+@section Extracting the Function Pointer from a Bound Pointer to Member Function
+@cindex pmf
+@cindex pointer to member function
+@cindex bound pointer to member function
+
+In C++, pointer to member functions (PMFs) are implemented using a wide
+pointer of sorts to handle all the possible call mechanisms; the PMF
+needs to store information about how to adjust the @samp{this} pointer,
+and if the function pointed to is virtual, where to find the vtable, and
+where in the vtable to look for the member function. If you are using
+PMFs in an inner loop, you should really reconsider that decision. If
+that is not an option, you can extract the pointer to the function that
+would be called for a given object/PMF pair and call it directly inside
+the inner loop, to save a bit of time.
+
+Note that you still pay the penalty for the call through a
+function pointer; on most modern architectures, such a call defeats the
+branch prediction features of the CPU@. This is also true of normal
+virtual function calls.
+
+The syntax for this extension is
+
+@smallexample
+extern A a;
+extern int (A::*fp)();
+typedef int (*fptr)(A *);
+
+fptr p = (fptr)(a.*fp);
+@end smallexample
+
+For PMF constants (i.e.@: expressions of the form @samp{&Klasse::Member}),
+no object is needed to obtain the address of the function. They can be
+converted to function pointers directly:
+
+@smallexample
+fptr p1 = (fptr)(&A::foo);
+@end smallexample
+
+@opindex Wno-pmf-conversions
+You must specify @option{-Wno-pmf-conversions} to use this extension.
+
+@node C++ Attributes
+@section C++-Specific Variable, Function, and Type Attributes
+
+Some attributes only make sense for C++ programs.
+
+@table @code
+@item abi_tag ("@var{tag}", ...)
+@cindex @code{abi_tag} function attribute
+@cindex @code{abi_tag} variable attribute
+@cindex @code{abi_tag} type attribute
+The @code{abi_tag} attribute can be applied to a function, variable, or class
+declaration. It modifies the mangled name of the entity to
+incorporate the tag name, in order to distinguish the function or
+class from an earlier version with a different ABI; perhaps the class
+has changed size, or the function has a different return type that is
+not encoded in the mangled name.
+
+The attribute can also be applied to an inline namespace, but does not
+affect the mangled name of the namespace; in this case it is only used
+for @option{-Wabi-tag} warnings and automatic tagging of functions and
+variables. Tagging inline namespaces is generally preferable to
+tagging individual declarations, but the latter is sometimes
+necessary, such as when only certain members of a class need to be
+tagged.
+
+The argument can be a list of strings of arbitrary length. The
+strings are sorted on output, so the order of the list is
+unimportant.
+
+A redeclaration of an entity must not add new ABI tags,
+since doing so would change the mangled name.
+
+The ABI tags apply to a name, so all instantiations and
+specializations of a template have the same tags. The attribute will
+be ignored if applied to an explicit specialization or instantiation.
+
+The @option{-Wabi-tag} flag enables a warning about a class which does
+not have all the ABI tags used by its subobjects and virtual functions; for users with code
+that needs to coexist with an earlier ABI, using this option can help
+to find all affected types that need to be tagged.
+
+When a type involving an ABI tag is used as the type of a variable or
+return type of a function where that tag is not already present in the
+signature of the function, the tag is automatically applied to the
+variable or function. @option{-Wabi-tag} also warns about this
+situation; this warning can be avoided by explicitly tagging the
+variable or function or moving it into a tagged inline namespace.
+
+@item init_priority (@var{priority})
+@cindex @code{init_priority} variable attribute
+
+In Standard C++, objects defined at namespace scope are guaranteed to be
+initialized in an order in strict accordance with that of their definitions
+@emph{in a given translation unit}. No guarantee is made for initializations
+across translation units. However, GNU C++ allows users to control the
+order of initialization of objects defined at namespace scope with the
+@code{init_priority} attribute by specifying a relative @var{priority},
+a constant integral expression currently bounded between 101 and 65535
+inclusive. Lower numbers indicate a higher priority.
+
+In the following example, @code{A} would normally be created before
+@code{B}, but the @code{init_priority} attribute reverses that order:
+
+@smallexample
+Some_Class A __attribute__ ((init_priority (2000)));
+Some_Class B __attribute__ ((init_priority (543)));
+@end smallexample
+
+@noindent
+Note that the particular values of @var{priority} do not matter; only their
+relative ordering.
+
+@item warn_unused
+@cindex @code{warn_unused} type attribute
+
+For C++ types with non-trivial constructors and/or destructors it is
+impossible for the compiler to determine whether a variable of this
+type is truly unused if it is not referenced. This type attribute
+informs the compiler that variables of this type should be warned
+about if they appear to be unused, just like variables of fundamental
+types.
+
+This attribute is appropriate for types which just represent a value,
+such as @code{std::string}; it is not appropriate for types which
+control a resource, such as @code{std::lock_guard}.
+
+This attribute is also accepted in C, but it is unnecessary because C
+does not have constructors or destructors.
+
+@end table
+
+@node Function Multiversioning
+@section Function Multiversioning
+@cindex function versions
+
+With the GNU C++ front end, for x86 targets, you may specify multiple
+versions of a function, where each function is specialized for a
+specific target feature. At runtime, the appropriate version of the
+function is automatically executed depending on the characteristics of
+the execution platform. Here is an example.
+
+@smallexample
+__attribute__ ((target ("default")))
+int foo ()
+@{
+ // The default version of foo.
+ return 0;
+@}
+
+__attribute__ ((target ("sse4.2")))
+int foo ()
+@{
+ // foo version for SSE4.2
+ return 1;
+@}
+
+__attribute__ ((target ("arch=atom")))
+int foo ()
+@{
+ // foo version for the Intel ATOM processor
+ return 2;
+@}
+
+__attribute__ ((target ("arch=amdfam10")))
+int foo ()
+@{
+ // foo version for the AMD Family 0x10 processors.
+ return 3;
+@}
+
+int main ()
+@{
+ int (*p)() = &foo;
+ assert ((*p) () == foo ());
+ return 0;
+@}
+@end smallexample
+
+In the above example, four versions of function foo are created. The
+first version of foo with the target attribute "default" is the default
+version. This version gets executed when no other target specific
+version qualifies for execution on a particular platform. A new version
+of foo is created by using the same function signature but with a
+different target string. Function foo is called or a pointer to it is
+taken just like a regular function. GCC takes care of doing the
+dispatching to call the right version at runtime. Refer to the
+@uref{https://gcc.gnu.org/wiki/FunctionMultiVersioning, GCC wiki on
+Function Multiversioning} for more details.
+
+@node Type Traits
+@section Type Traits
+
+The C++ front end implements syntactic extensions that allow
+compile-time determination of
+various characteristics of a type (or of a
+pair of types).
+
+@table @code
+@item __has_nothrow_assign (type)
+If @code{type} is @code{const}-qualified or is a reference type then
+the trait is @code{false}. Otherwise if @code{__has_trivial_assign (type)}
+is @code{true} then the trait is @code{true}, else if @code{type} is
+a cv-qualified class or union type with copy assignment operators that are
+known not to throw an exception then the trait is @code{true}, else it is
+@code{false}.
+Requires: @code{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+
+@item __has_nothrow_copy (type)
+If @code{__has_trivial_copy (type)} is @code{true} then the trait is
+@code{true}, else if @code{type} is a cv-qualified class or union type
+with copy constructors that are known not to throw an exception then
+the trait is @code{true}, else it is @code{false}.
+Requires: @code{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+
+@item __has_nothrow_constructor (type)
+If @code{__has_trivial_constructor (type)} is @code{true} then the trait
+is @code{true}, else if @code{type} is a cv class or union type (or array
+thereof) with a default constructor that is known not to throw an
+exception then the trait is @code{true}, else it is @code{false}.
+Requires: @code{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+
+@item __has_trivial_assign (type)
+If @code{type} is @code{const}- qualified or is a reference type then
+the trait is @code{false}. Otherwise if @code{__is_trivial (type)} is
+@code{true} then the trait is @code{true}, else if @code{type} is
+a cv-qualified class or union type with a trivial copy assignment
+([class.copy]) then the trait is @code{true}, else it is @code{false}.
+Requires: @code{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+
+@item __has_trivial_copy (type)
+If @code{__is_trivial (type)} is @code{true} or @code{type} is a reference
+type then the trait is @code{true}, else if @code{type} is a cv class
+or union type with a trivial copy constructor ([class.copy]) then the trait
+is @code{true}, else it is @code{false}. Requires: @code{type} shall be
+a complete type, (possibly cv-qualified) @code{void}, or an array of unknown
+bound.
+
+@item __has_trivial_constructor (type)
+If @code{__is_trivial (type)} is @code{true} then the trait is @code{true},
+else if @code{type} is a cv-qualified class or union type (or array thereof)
+with a trivial default constructor ([class.ctor]) then the trait is @code{true},
+else it is @code{false}.
+Requires: @code{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+
+@item __has_trivial_destructor (type)
+If @code{__is_trivial (type)} is @code{true} or @code{type} is a reference type
+then the trait is @code{true}, else if @code{type} is a cv class or union
+type (or array thereof) with a trivial destructor ([class.dtor]) then
+the trait is @code{true}, else it is @code{false}.
+Requires: @code{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+
+@item __has_virtual_destructor (type)
+If @code{type} is a class type with a virtual destructor
+([class.dtor]) then the trait is @code{true}, else it is @code{false}.
+Requires: If @code{type} is a non-union class type, it shall be a complete type.
+
+@item __is_abstract (type)
+If @code{type} is an abstract class ([class.abstract]) then the trait
+is @code{true}, else it is @code{false}.
+Requires: If @code{type} is a non-union class type, it shall be a complete type.
+
+@item __is_aggregate (type)
+If @code{type} is an aggregate type ([dcl.init.aggr]) the trait is
+@code{true}, else it is @code{false}.
+Requires: If @code{type} is a class type, it shall be a complete type.
+
+@item __is_base_of (base_type, derived_type)
+If @code{base_type} is a base class of @code{derived_type}
+([class.derived]) then the trait is @code{true}, otherwise it is @code{false}.
+Top-level cv-qualifications of @code{base_type} and
+@code{derived_type} are ignored. For the purposes of this trait, a
+class type is considered is own base.
+Requires: if @code{__is_class (base_type)} and @code{__is_class (derived_type)}
+are @code{true} and @code{base_type} and @code{derived_type} are not the same
+type (disregarding cv-qualifiers), @code{derived_type} shall be a complete
+type. A diagnostic is produced if this requirement is not met.
+
+@item __is_class (type)
+If @code{type} is a cv-qualified class type, and not a union type
+([basic.compound]) the trait is @code{true}, else it is @code{false}.
+
+@item __is_empty (type)
+If @code{__is_class (type)} is @code{false} then the trait is @code{false}.
+Otherwise @code{type} is considered empty if and only if: @code{type}
+has no non-static data members, or all non-static data members, if
+any, are bit-fields of length 0, and @code{type} has no virtual
+members, and @code{type} has no virtual base classes, and @code{type}
+has no base classes @code{base_type} for which
+@code{__is_empty (base_type)} is @code{false}.
+Requires: If @code{type} is a non-union class type, it shall be a complete type.
+
+@item __is_enum (type)
+If @code{type} is a cv enumeration type ([basic.compound]) the trait is
+@code{true}, else it is @code{false}.
+
+@item __is_final (type)
+If @code{type} is a class or union type marked @code{final}, then the trait
+is @code{true}, else it is @code{false}.
+Requires: If @code{type} is a class type, it shall be a complete type.
+
+@item __is_literal_type (type)
+If @code{type} is a literal type ([basic.types]) the trait is
+@code{true}, else it is @code{false}.
+Requires: @code{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+
+@item __is_pod (type)
+If @code{type} is a cv POD type ([basic.types]) then the trait is @code{true},
+else it is @code{false}.
+Requires: @code{type} shall be a complete type, (possibly cv-qualified)
+@code{void}, or an array of unknown bound.
+
+@item __is_polymorphic (type)
+If @code{type} is a polymorphic class ([class.virtual]) then the trait
+is @code{true}, else it is @code{false}.
+Requires: If @code{type} is a non-union class type, it shall be a complete type.
+
+@item __is_standard_layout (type)
+If @code{type} is a standard-layout type ([basic.types]) the trait is
+@code{true}, else it is @code{false}.
+Requires: @code{type} shall be a complete type, an array of complete types,
+or (possibly cv-qualified) @code{void}.
+
+@item __is_trivial (type)
+If @code{type} is a trivial type ([basic.types]) the trait is
+@code{true}, else it is @code{false}.
+Requires: @code{type} shall be a complete type, an array of complete types,
+or (possibly cv-qualified) @code{void}.
+
+@item __is_union (type)
+If @code{type} is a cv union type ([basic.compound]) the trait is
+@code{true}, else it is @code{false}.
+
+@item __underlying_type (type)
+The underlying type of @code{type}.
+Requires: @code{type} shall be an enumeration type ([dcl.enum]).
+
+@item __integer_pack (length)
+When used as the pattern of a pack expansion within a template
+definition, expands to a template argument pack containing integers
+from @code{0} to @code{length-1}. This is provided for efficient
+implementation of @code{std::make_integer_sequence}.
+
+@end table
+
+
+@node C++ Concepts
+@section C++ Concepts
+
+C++ concepts provide much-improved support for generic programming. In
+particular, they allow the specification of constraints on template arguments.
+The constraints are used to extend the usual overloading and partial
+specialization capabilities of the language, allowing generic data structures
+and algorithms to be ``refined'' based on their properties rather than their
+type names.
+
+The following keywords are reserved for concepts.
+
+@table @code
+@item assumes
+States an expression as an assumption, and if possible, verifies that the
+assumption is valid. For example, @code{assume(n > 0)}.
+
+@item axiom
+Introduces an axiom definition. Axioms introduce requirements on values.
+
+@item forall
+Introduces a universally quantified object in an axiom. For example,
+@code{forall (int n) n + 0 == n}).
+
+@item concept
+Introduces a concept definition. Concepts are sets of syntactic and semantic
+requirements on types and their values.
+
+@item requires
+Introduces constraints on template arguments or requirements for a member
+function of a class template.
+
+@end table
+
+The front end also exposes a number of internal mechanism that can be used
+to simplify the writing of type traits. Note that some of these traits are
+likely to be removed in the future.
+
+@table @code
+@item __is_same (type1, type2)
+A binary type trait: @code{true} whenever the type arguments are the same.
+
+@end table
+
+
+@node Deprecated Features
+@section Deprecated Features
+
+In the past, the GNU C++ compiler was extended to experiment with new
+features, at a time when the C++ language was still evolving. Now that
+the C++ standard is complete, some of those features are superseded by
+superior alternatives. Using the old features might cause a warning in
+some cases that the feature will be dropped in the future. In other
+cases, the feature might be gone already.
+
+G++ allows a virtual function returning @samp{void *} to be overridden
+by one returning a different pointer type. This extension to the
+covariant return type rules is now deprecated and will be removed from a
+future version.
+
+The use of default arguments in function pointers, function typedefs
+and other places where they are not permitted by the standard is
+deprecated and will be removed from a future version of G++.
+
+G++ allows floating-point literals to appear in integral constant expressions,
+e.g.@: @samp{ enum E @{ e = int(2.2 * 3.7) @} }
+This extension is deprecated and will be removed from a future version.
+
+G++ allows static data members of const floating-point type to be declared
+with an initializer in a class definition. The standard only allows
+initializers for static members of const integral types and const
+enumeration types so this extension has been deprecated and will be removed
+from a future version.
+
+G++ allows attributes to follow a parenthesized direct initializer,
+e.g.@: @samp{ int f (0) __attribute__ ((something)); } This extension
+has been ignored since G++ 3.3 and is deprecated.
+
+G++ allows anonymous structs and unions to have members that are not
+public non-static data members (i.e.@: fields). These extensions are
+deprecated.
+
+@node Backwards Compatibility
+@section Backwards Compatibility
+@cindex Backwards Compatibility
+@cindex ARM [Annotated C++ Reference Manual]
+
+Now that there is a definitive ISO standard C++, G++ has a specification
+to adhere to. The C++ language evolved over time, and features that
+used to be acceptable in previous drafts of the standard, such as the ARM
+[Annotated C++ Reference Manual], are no longer accepted. In order to allow
+compilation of C++ written to such drafts, G++ contains some backwards
+compatibilities. @emph{All such backwards compatibility features are
+liable to disappear in future versions of G++.} They should be considered
+deprecated. @xref{Deprecated Features}.
+
+@table @code
+
+@item Implicit C language
+Old C system header files did not contain an @code{extern "C" @{@dots{}@}}
+scope to set the language. On such systems, all system header files are
+implicitly scoped inside a C language scope. Such headers must
+correctly prototype function argument types, there is no leeway for
+@code{()} to indicate an unspecified set of arguments.
+
+@end table
+
+@c LocalWords: emph deftypefn builtin ARCv2EM SIMD builtins msimd
+@c LocalWords: typedef v4si v8hi DMA dma vdiwr vdowr
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Fragments
+@chapter Makefile Fragments
+@cindex makefile fragment
+
+When you configure GCC using the @file{configure} script, it will
+construct the file @file{Makefile} from the template file
+@file{Makefile.in}. When it does this, it can incorporate makefile
+fragments from the @file{config} directory. These are used to set
+Makefile parameters that are not amenable to being calculated by
+autoconf. The list of fragments to incorporate is set by
+@file{config.gcc} (and occasionally @file{config.build}
+and @file{config.host}); @xref{System Config}.
+
+Fragments are named either @file{t-@var{target}} or @file{x-@var{host}},
+depending on whether they are relevant to configuring GCC to produce
+code for a particular target, or to configuring GCC to run on a
+particular host. Here @var{target} and @var{host} are mnemonics
+which usually have some relationship to the canonical system name, but
+no formal connection.
+
+If these files do not exist, it means nothing needs to be added for a
+given target or host. Most targets need a few @file{t-@var{target}}
+fragments, but needing @file{x-@var{host}} fragments is rare.
+
+@menu
+* Target Fragment:: Writing @file{t-@var{target}} files.
+* Host Fragment:: Writing @file{x-@var{host}} files.
+@end menu
+
+@node Target Fragment
+@section Target Makefile Fragments
+@cindex target makefile fragment
+@cindex @file{t-@var{target}}
+
+Target makefile fragments can set these Makefile variables.
+
+@table @code
+@findex LIBGCC2_CFLAGS
+@item LIBGCC2_CFLAGS
+Compiler flags to use when compiling @file{libgcc2.c}.
+
+@findex LIB2FUNCS_EXTRA
+@item LIB2FUNCS_EXTRA
+A list of source file names to be compiled or assembled and inserted
+into @file{libgcc.a}.
+
+@findex CRTSTUFF_T_CFLAGS
+@item CRTSTUFF_T_CFLAGS
+Special flags used when compiling @file{crtstuff.c}.
+@xref{Initialization}.
+
+@findex CRTSTUFF_T_CFLAGS_S
+@item CRTSTUFF_T_CFLAGS_S
+Special flags used when compiling @file{crtstuff.c} for shared
+linking. Used if you use @file{crtbeginS.o} and @file{crtendS.o}
+in @code{EXTRA-PARTS}.
+@xref{Initialization}.
+
+@findex MULTILIB_OPTIONS
+@item MULTILIB_OPTIONS
+For some targets, invoking GCC in different ways produces objects
+that cannot be linked together. For example, for some targets GCC
+produces both big and little endian code. For these targets, you must
+arrange for multiple versions of @file{libgcc.a} to be compiled, one for
+each set of incompatible options. When GCC invokes the linker, it
+arranges to link in the right version of @file{libgcc.a}, based on
+the command line options used.
+
+The @code{MULTILIB_OPTIONS} macro lists the set of options for which
+special versions of @file{libgcc.a} must be built. Write options that
+are mutually incompatible side by side, separated by a slash. Write
+options that may be used together separated by a space. The build
+procedure will build all combinations of compatible options.
+
+For example, if you set @code{MULTILIB_OPTIONS} to @samp{m68000/m68020
+msoft-float}, @file{Makefile} will build special versions of
+@file{libgcc.a} using the following sets of options: @option{-m68000},
+@option{-m68020}, @option{-msoft-float}, @samp{-m68000 -msoft-float}, and
+@samp{-m68020 -msoft-float}.
+
+@findex MULTILIB_DIRNAMES
+@item MULTILIB_DIRNAMES
+If @code{MULTILIB_OPTIONS} is used, this variable specifies the
+directory names that should be used to hold the various libraries.
+Write one element in @code{MULTILIB_DIRNAMES} for each element in
+@code{MULTILIB_OPTIONS}. If @code{MULTILIB_DIRNAMES} is not used, the
+default value will be @code{MULTILIB_OPTIONS}, with all slashes treated
+as spaces.
+
+@code{MULTILIB_DIRNAMES} describes the multilib directories using GCC
+conventions and is applied to directories that are part of the GCC
+installation. When multilib-enabled, the compiler will add a
+subdirectory of the form @var{prefix}/@var{multilib} before each
+directory in the search path for libraries and crt files.
+
+For example, if @code{MULTILIB_OPTIONS} is set to @samp{m68000/m68020
+msoft-float}, then the default value of @code{MULTILIB_DIRNAMES} is
+@samp{m68000 m68020 msoft-float}. You may specify a different value if
+you desire a different set of directory names.
+
+@findex MULTILIB_MATCHES
+@item MULTILIB_MATCHES
+Sometimes the same option may be written in two different ways. If an
+option is listed in @code{MULTILIB_OPTIONS}, GCC needs to know about
+any synonyms. In that case, set @code{MULTILIB_MATCHES} to a list of
+items of the form @samp{option=option} to describe all relevant
+synonyms. For example, @samp{m68000=mc68000 m68020=mc68020}.
+
+@findex MULTILIB_EXCEPTIONS
+@item MULTILIB_EXCEPTIONS
+Sometimes when there are multiple sets of @code{MULTILIB_OPTIONS} being
+specified, there are combinations that should not be built. In that
+case, set @code{MULTILIB_EXCEPTIONS} to be all of the switch exceptions
+in shell case syntax that should not be built.
+
+For example the ARM processor cannot execute both hardware floating
+point instructions and the reduced size THUMB instructions at the same
+time, so there is no need to build libraries with both of these
+options enabled. Therefore @code{MULTILIB_EXCEPTIONS} is set to:
+@smallexample
+*mthumb/*mhard-float*
+@end smallexample
+
+@findex MULTILIB_REQUIRED
+@item MULTILIB_REQUIRED
+Sometimes when there are only a few combinations are required, it would
+be a big effort to come up with a @code{MULTILIB_EXCEPTIONS} list to
+cover all undesired ones. In such a case, just listing all the required
+combinations in @code{MULTILIB_REQUIRED} would be more straightforward.
+
+The way to specify the entries in @code{MULTILIB_REQUIRED} is same with
+the way used for @code{MULTILIB_EXCEPTIONS}, only this time what are
+required will be specified. Suppose there are multiple sets of
+@code{MULTILIB_OPTIONS} and only two combinations are required, one
+for ARMv7-M and one for ARMv7-R with hard floating-point ABI and FPU, the
+@code{MULTILIB_REQUIRED} can be set to:
+@smallexample
+@code{MULTILIB_REQUIRED} = mthumb/march=armv7-m
+@code{MULTILIB_REQUIRED} += march=armv7-r/mfloat-abi=hard/mfpu=vfpv3-d16
+@end smallexample
+
+The @code{MULTILIB_REQUIRED} can be used together with
+@code{MULTILIB_EXCEPTIONS}. The option combinations generated from
+@code{MULTILIB_OPTIONS} will be filtered by @code{MULTILIB_EXCEPTIONS}
+and then by @code{MULTILIB_REQUIRED}.
+
+@findex MULTILIB_REUSE
+@item MULTILIB_REUSE
+Sometimes it is desirable to reuse one existing multilib for different
+sets of options. Such kind of reuse can minimize the number of multilib
+variants. And for some targets it is better to reuse an existing multilib
+than to fall back to default multilib when there is no corresponding multilib.
+This can be done by adding reuse rules to @code{MULTILIB_REUSE}.
+
+A reuse rule is comprised of two parts connected by equality sign. The left
+part is the option set used to build multilib and the right part is the option
+set that will reuse this multilib. Both parts should only use options
+specified in @code{MULTILIB_OPTIONS} and the equality signs found in options
+name should be replaced with periods. An explicit period in the rule can be
+escaped by preceding it with a backslash. The order of options in the left
+part matters and should be same with those specified in
+@code{MULTILIB_REQUIRED} or aligned with the order in @code{MULTILIB_OPTIONS}.
+There is no such limitation for options in the right part as we don't build
+multilib from them.
+
+@code{MULTILIB_REUSE} is different from @code{MULTILIB_MATCHES} in that it
+sets up relations between two option sets rather than two options. Here is an
+example to demo how we reuse libraries built in Thumb mode for applications built
+in ARM mode:
+@smallexample
+@code{MULTILIB_REUSE} = mthumb/march.armv7-r=marm/march.armv7-r
+@end smallexample
+
+Before the advent of @code{MULTILIB_REUSE}, GCC select multilib by comparing command
+line options with options used to build multilib. The @code{MULTILIB_REUSE} is
+complementary to that way. Only when the original comparison matches nothing it will
+work to see if it is OK to reuse some existing multilib.
+
+@findex MULTILIB_EXTRA_OPTS
+@item MULTILIB_EXTRA_OPTS
+Sometimes it is desirable that when building multiple versions of
+@file{libgcc.a} certain options should always be passed on to the
+compiler. In that case, set @code{MULTILIB_EXTRA_OPTS} to be the list
+of options to be used for all builds. If you set this, you should
+probably set @code{CRTSTUFF_T_CFLAGS} to a dash followed by it.
+
+@findex MULTILIB_OSDIRNAMES
+@item MULTILIB_OSDIRNAMES
+If @code{MULTILIB_OPTIONS} is used, this variable specifies
+a list of subdirectory names, that are used to modify the search
+path depending on the chosen multilib. Unlike @code{MULTILIB_DIRNAMES},
+@code{MULTILIB_OSDIRNAMES} describes the multilib directories using
+operating systems conventions, and is applied to the directories such as
+@code{lib} or those in the @env{LIBRARY_PATH} environment variable.
+The format is either the same as of
+@code{MULTILIB_DIRNAMES}, or a set of mappings. When it is the same
+as @code{MULTILIB_DIRNAMES}, it describes the multilib directories
+using operating system conventions, rather than GCC conventions. When it is a set
+of mappings of the form @var{gccdir}=@var{osdir}, the left side gives
+the GCC convention and the right gives the equivalent OS defined
+location. If the @var{osdir} part begins with a @samp{!},
+GCC will not search in the non-multilib directory and use
+exclusively the multilib directory. Otherwise, the compiler will
+examine the search path for libraries and crt files twice; the first
+time it will add @var{multilib} to each directory in the search path,
+the second it will not.
+
+For configurations that support both multilib and multiarch,
+@code{MULTILIB_OSDIRNAMES} also encodes the multiarch name, thus
+subsuming @code{MULTIARCH_DIRNAME}. The multiarch name is appended to
+each directory name, separated by a colon (e.g.@:
+@samp{../lib32:i386-linux-gnu}).
+
+Each multiarch subdirectory will be searched before the corresponding OS
+multilib directory, for example @samp{/lib/i386-linux-gnu} before
+@samp{/lib/../lib32}. The multiarch name will also be used to modify the
+system header search path, as explained for @code{MULTIARCH_DIRNAME}.
+
+@findex MULTIARCH_DIRNAME
+@item MULTIARCH_DIRNAME
+This variable specifies the multiarch name for configurations that are
+multiarch-enabled but not multilibbed configurations.
+
+The multiarch name is used to augment the search path for libraries, crt
+files and system header files with additional locations. The compiler
+will add a multiarch subdirectory of the form
+@var{prefix}/@var{multiarch} before each directory in the library and
+crt search path. It will also add two directories
+@code{LOCAL_INCLUDE_DIR}/@var{multiarch} and
+@code{NATIVE_SYSTEM_HEADER_DIR}/@var{multiarch}) to the system header
+search path, respectively before @code{LOCAL_INCLUDE_DIR} and
+@code{NATIVE_SYSTEM_HEADER_DIR}.
+
+@code{MULTIARCH_DIRNAME} is not used for configurations that support
+both multilib and multiarch. In that case, multiarch names are encoded
+in @code{MULTILIB_OSDIRNAMES} instead.
+
+More documentation about multiarch can be found at
+@uref{https://wiki.debian.org/Multiarch}.
+
+@findex SPECS
+@item SPECS
+Unfortunately, setting @code{MULTILIB_EXTRA_OPTS} is not enough, since
+it does not affect the build of target libraries, at least not the
+build of the default multilib. One possible work-around is to use
+@code{DRIVER_SELF_SPECS} to bring options from the @file{specs} file
+as if they had been passed in the compiler driver command line.
+However, you don't want to be adding these options after the toolchain
+is installed, so you can instead tweak the @file{specs} file that will
+be used during the toolchain build, while you still install the
+original, built-in @file{specs}. The trick is to set @code{SPECS} to
+some other filename (say @file{specs.install}), that will then be
+created out of the built-in specs, and introduce a @file{Makefile}
+rule to generate the @file{specs} file that's going to be used at
+build time out of your @file{specs.install}.
+
+@item T_CFLAGS
+These are extra flags to pass to the C compiler. They are used both
+when building GCC, and when compiling things with the just-built GCC@.
+This variable is deprecated and should not be used.
+@end table
+
+@node Host Fragment
+@section Host Makefile Fragments
+@cindex host makefile fragment
+@cindex @file{x-@var{host}}
+
+The use of @file{x-@var{host}} fragments is discouraged. You should only
+use it for makefile dependencies.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node G++ and GCC
+@chapter Programming Languages Supported by GCC
+
+@cindex GCC
+@cindex GNU Compiler Collection
+@cindex GNU C Compiler
+@cindex Ada
+@cindex D
+@cindex Fortran
+@cindex Go
+@cindex Objective-C
+@cindex Objective-C++
+GCC stands for ``GNU Compiler Collection''. GCC is an integrated
+distribution of compilers for several major programming languages. These
+languages currently include C, C++, Objective-C, Objective-C++,
+Fortran, Ada, D, and Go.
+
+The abbreviation @dfn{GCC} has multiple meanings in common use. The
+current official meaning is ``GNU Compiler Collection'', which refers
+generically to the complete suite of tools. The name historically stood
+for ``GNU C Compiler'', and this usage is still common when the emphasis
+is on compiling C programs. Finally, the name is also used when speaking
+of the @dfn{language-independent} component of GCC: code shared among the
+compilers for all supported languages.
+
+The language-independent component of GCC includes the majority of the
+optimizers, as well as the ``back ends'' that generate machine code for
+various processors.
+
+@cindex COBOL
+@cindex Mercury
+The part of a compiler that is specific to a particular language is
+called the ``front end''. In addition to the front ends that are
+integrated components of GCC, there are several other front ends that
+are maintained separately. These support languages such as
+Mercury, and COBOL@. To use these, they must be built together with
+GCC proper.
+
+@cindex C++
+@cindex G++
+@cindex Ada
+@cindex GNAT
+Most of the compilers for languages other than C have their own names.
+The C++ compiler is G++, the Ada compiler is GNAT, and so on. When we
+talk about compiling one of those languages, we might refer to that
+compiler by its own name, or as GCC@. Either is correct.
+
+@cindex compiler compared to C++ preprocessor
+@cindex intermediate C version, nonexistent
+@cindex C intermediate output, nonexistent
+Historically, compilers for many languages, including C++ and Fortran,
+have been implemented as ``preprocessors'' which emit another high
+level language such as C@. None of the compilers included in GCC are
+implemented this way; they all generate machine code directly. This
+sort of preprocessor should not be confused with the @dfn{C
+preprocessor}, which is an integral feature of the C, C++, Objective-C
+and Objective-C++ languages.
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@c %**start of header
+@setfilename gcc.info
+@c INTERNALS is used by md.texi to determine whether to include the
+@c whole of that file, in the internals manual, or only the part
+@c dealing with constraints, in the user manual.
+@clear INTERNALS
+
+@c NOTE: checks/things to do:
+@c
+@c -have bob do a search in all seven files for "mew" (ideally --mew,
+@c but i may have forgotten the occasional "--"..).
+@c Just checked... all have `--'! Bob 22Jul96
+@c Use this to search: grep -n '\-\-mew' *.texi
+@c -item/itemx, text after all (sub/sub)section titles, etc..
+@c -consider putting the lists of options on pp 17--> etc in columns or
+@c some such.
+@c -overfulls. do a search for "mew" in the files, and you will see
+@c overfulls that i noted but could not deal with.
+@c -have to add text: beginning of chapter 8
+
+@c
+@c anything else? --mew 10feb93
+
+@include gcc-common.texi
+
+@settitle Using the GNU Compiler Collection (GCC)
+
+@c Create a separate index for command line options.
+@defcodeindex op
+@c Merge the standard indexes into a single one.
+@syncodeindex fn cp
+@syncodeindex vr cp
+@syncodeindex ky cp
+@syncodeindex pg cp
+@syncodeindex tp cp
+
+@paragraphindent 1
+
+@c %**end of header
+
+@copying
+Copyright @copyright{} 1988-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``Funding Free Software'', the Front-Cover
+Texts being (a) (see below), and with the Back-Cover Texts being (b)
+(see below). A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@end copying
+@ifnottex
+@dircategory Software development
+@direntry
+* gcc: (gcc). The GNU Compiler Collection.
+* g++: (gcc). The GNU C++ compiler.
+* gcov: (gcc) Gcov. @command{gcov}---a test coverage program.
+* gcov-tool: (gcc) Gcov-tool. @command{gcov-tool}---an offline gcda profile processing program.
+* gcov-dump: (gcc) Gcov-dump. @command{gcov-dump}---an offline gcda and gcno profile dump tool.
+* lto-dump: (gcc) lto-dump. @command{lto-dump}---Tool for
+dumping LTO object files.
+@end direntry
+This file documents the use of the GNU compilers.
+@sp 1
+@insertcopying
+@sp 1
+@end ifnottex
+
+@setchapternewpage odd
+@titlepage
+@title Using the GNU Compiler Collection
+@versionsubtitle
+@author Richard M. Stallman and the @sc{GCC} Developer Community
+@page
+@vskip 0pt plus 1filll
+Published by:
+@multitable @columnfractions 0.5 0.5
+@item GNU Press
+@tab Website: @uref{http://www.gnupress.org}
+@item a division of the
+@tab General: @email{press@@gnu.org}
+@item Free Software Foundation
+@tab Orders: @email{sales@@gnu.org}
+@item 51 Franklin Street, Fifth Floor
+@tab Tel 617-542-5942
+@item Boston, MA 02110-1301 USA
+@tab Fax 617-542-2652
+@end multitable
+@sp 2
+@ifset FSFPRINT
+@c Update this ISBN when printing a new edition.
+@acronym{ISBN} 1-882114-39-6
+
+Cover art by Gary M. Torrisi. Cover design by Jonathan Richard.
+@end ifset
+@ifclear FSFPRINT
+Last printed October 2003 for GCC 3.3.1.@*
+Printed copies are available for $45 each.
+@end ifclear
+@sp 1
+@insertcopying
+@end titlepage
+@summarycontents
+@contents
+@page
+
+@node Top, G++ and GCC
+@top Introduction
+@cindex introduction
+
+This manual documents how to use the GNU compilers,
+as well as their features and incompatibilities, and how to report
+bugs. It corresponds to the compilers
+@ifset VERSION_PACKAGE
+@value{VERSION_PACKAGE}
+@end ifset
+version @value{version-GCC}.
+The internals of the GNU compilers, including how to port them to new
+targets and some information about how to write front ends for new
+languages, are documented in a separate manual. @xref{Top,,
+Introduction, gccint, GNU Compiler Collection (GCC) Internals}.
+
+@menu
+* G++ and GCC:: You can compile C or C++ programs.
+* Standards:: Language standards supported by GCC.
+* Invoking GCC:: Command options supported by @samp{gcc}.
+* C Implementation:: How GCC implements the ISO C specification.
+* C++ Implementation:: How GCC implements the ISO C++ specification.
+* C Extensions:: GNU extensions to the C language family.
+* C++ Extensions:: GNU extensions to the C++ language.
+* Objective-C:: GNU Objective-C runtime features.
+* Compatibility:: Binary Compatibility
+* Gcov:: @command{gcov}---a test coverage program.
+* Gcov-tool:: @command{gcov-tool}---an offline gcda profile processing program.
+* Gcov-dump:: @command{gcov-dump}---an offline gcda and gcno profile dump tool.
+* lto-dump:: @command{lto-dump}---Tool for dumping LTO
+object files.
+* Trouble:: If you have trouble using GCC.
+* Bugs:: How, why and where to report bugs.
+* Service:: How To Get Help with GCC
+* Contributing:: How to contribute to testing and developing GCC.
+
+* Funding:: How to help assure funding for free software.
+* GNU Project:: The GNU Project and GNU/Linux.
+
+* Copying:: GNU General Public License says
+ how you can copy and share GCC.
+* GNU Free Documentation License:: How you can copy and share this manual.
+* Contributors:: People who have contributed to GCC.
+
+* Option Index:: Index to command line options.
+* Keyword Index:: Index of concepts and symbol names.
+@end menu
+
+@include frontends.texi
+@include standards.texi
+@include invoke.texi
+@include implement-c.texi
+@include implement-cxx.texi
+@include extend.texi
+@include objc.texi
+@include compat.texi
+@include gcov.texi
+@include gcov-tool.texi
+@include gcov-dump.texi
+@include lto-dump.texi
+@include trouble.texi
+@include bugreport.texi
+@include service.texi
+@include contribute.texi
+
+@include funding.texi
+@include gnu.texi
+@include gpl_v3.texi
+
+@c ---------------------------------------------------------------------
+@c GFDL
+@c ---------------------------------------------------------------------
+
+@include fdl.texi
+
+@include contrib.texi
+
+@c ---------------------------------------------------------------------
+@c Indexes
+@c ---------------------------------------------------------------------
+
+@node Option Index
+@unnumbered Option Index
+
+GCC's command line options are indexed here without any initial @samp{-}
+or @samp{--}. Where an option has both positive and negative forms
+(such as @option{-f@var{option}} and @option{-fno-@var{option}}),
+relevant entries in the manual are indexed under the most appropriate
+form; it may sometimes be useful to look up both forms.
+
+@printindex op
+
+@node Keyword Index
+@unnumbered Keyword Index
+
+@printindex cp
+
+@c ---------------------------------------------------------------------
+@c Epilogue
+@c ---------------------------------------------------------------------
+
+@bye
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@c %**start of header
+@setfilename gccint.info
+@c INTERNALS is used by md.texi to determine whether to include the
+@c whole of that file, in the internals manual, or only the part
+@c dealing with constraints, in the user manual.
+@set INTERNALS
+
+@c See miscellaneous notes in gcc.texi on checks/things to do.
+
+@include gcc-common.texi
+
+@settitle GNU Compiler Collection (GCC) Internals
+
+@c Create a separate index for command line options.
+@defcodeindex op
+@c Merge the standard indexes into a single one.
+@syncodeindex fn cp
+@syncodeindex vr cp
+@syncodeindex ky cp
+@syncodeindex pg cp
+@syncodeindex tp cp
+
+@paragraphindent 1
+
+@c %**end of header
+
+@copying
+Copyright @copyright{} 1988-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``Funding Free Software'', the Front-Cover
+Texts being (a) (see below), and with the Back-Cover Texts being (b)
+(see below). A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@end copying
+@ifnottex
+@dircategory Software development
+@direntry
+* gccint: (gccint). Internals of the GNU Compiler Collection.
+@end direntry
+This file documents the internals of the GNU compilers.
+@sp 1
+@insertcopying
+@sp 1
+@end ifnottex
+
+@setchapternewpage odd
+@titlepage
+@title GNU Compiler Collection Internals
+@versionsubtitle
+@author Richard M. Stallman and the @sc{GCC} Developer Community
+@page
+@vskip 0pt plus 1filll
+@insertcopying
+@end titlepage
+@summarycontents
+@contents
+@page
+
+@node Top, Contributing
+@top Introduction
+@cindex introduction
+
+This manual documents the internals of the GNU compilers, including
+how to port them to new targets and some information about how to
+write front ends for new languages. It corresponds to the compilers
+@ifset VERSION_PACKAGE
+@value{VERSION_PACKAGE}
+@end ifset
+version @value{version-GCC}. The use of the GNU compilers is documented in a
+separate manual. @xref{Top,, Introduction, gcc, Using the GNU
+Compiler Collection (GCC)}.
+
+This manual is mainly a reference manual rather than a tutorial. It
+discusses how to contribute to GCC (@pxref{Contributing}), the
+characteristics of the machines supported by GCC as hosts and targets
+(@pxref{Portability}), how GCC relates to the ABIs on such systems
+(@pxref{Interface}), and the characteristics of the languages for
+which GCC front ends are written (@pxref{Languages}). It then
+describes the GCC source tree structure and build system, some of the
+interfaces to GCC front ends, and how support for a target system is
+implemented in GCC@.
+
+Additional tutorial information is linked to from
+@uref{https://gcc.gnu.org/readings.html}.
+
+@menu
+* Contributing:: How to contribute to testing and developing GCC.
+* Portability:: Goals of GCC's portability features.
+* Interface:: Function-call interface of GCC output.
+* Libgcc:: Low-level runtime library used by GCC.
+* Languages:: Languages for which GCC front ends are written.
+* Source Tree:: GCC source tree structure and build system.
+* Testsuites:: GCC testsuites.
+* Options:: Option specification files.
+* Passes:: Order of passes, what they do, and what each file is for.
+* poly_int:: Representation of runtime sizes and offsets.
+* GENERIC:: Language-independent representation generated by Front Ends
+* GIMPLE:: Tuple representation used by Tree SSA optimizers
+* Tree SSA:: Analysis and optimization of GIMPLE
+* RTL:: Machine-dependent low-level intermediate representation.
+* Control Flow:: Maintaining and manipulating the control flow graph.
+* Loop Analysis and Representation:: Analysis and representation of loops
+* Machine Desc:: How to write machine description instruction patterns.
+* Target Macros:: How to write the machine description C macros and functions.
+* Host Config:: Writing the @file{xm-@var{machine}.h} file.
+* Fragments:: Writing the @file{t-@var{target}} and @file{x-@var{host}} files.
+* Collect2:: How @code{collect2} works; how it finds @code{ld}.
+* Header Dirs:: Understanding the standard header file directories.
+* Type Information:: GCC's memory management; generating type information.
+* Plugins:: Extending the compiler with plugins.
+* LTO:: Using Link-Time Optimization.
+
+* Match and Simplify:: How to write expression simplification patterns for GIMPLE and GENERIC
+* Static Analyzer:: Working with the static analyzer.
+* User Experience Guidelines:: Guidelines for implementing diagnostics and options.
+* Funding:: How to help assure funding for free software.
+* GNU Project:: The GNU Project and GNU/Linux.
+
+* Copying:: GNU General Public License says
+ how you can copy and share GCC.
+* GNU Free Documentation License:: How you can copy and share this manual.
+* Contributors:: People who have contributed to GCC.
+
+* Option Index:: Index to command line options.
+* Concept Index:: Index of concepts and symbol names.
+@end menu
+
+@include contribute.texi
+@include portability.texi
+@include interface.texi
+@include libgcc.texi
+@include languages.texi
+@include sourcebuild.texi
+@include options.texi
+@include passes.texi
+@include poly-int.texi
+@include generic.texi
+@include gimple.texi
+@include tree-ssa.texi
+@include rtl.texi
+@include cfg.texi
+@include loop.texi
+@include md.texi
+@include tm.texi
+@include hostconfig.texi
+@include fragments.texi
+@include collect2.texi
+@include headerdirs.texi
+@include gty.texi
+@include plugins.texi
+@include lto.texi
+@include match-and-simplify.texi
+@include analyzer.texi
+@include ux.texi
+
+@include funding.texi
+@include gnu.texi
+@include gpl_v3.texi
+
+@c ---------------------------------------------------------------------
+@c GFDL
+@c ---------------------------------------------------------------------
+
+@include fdl.texi
+
+@include contrib.texi
+
+@c ---------------------------------------------------------------------
+@c Indexes
+@c ---------------------------------------------------------------------
+
+@node Option Index
+@unnumbered Option Index
+
+GCC's command line options are indexed here without any initial @samp{-}
+or @samp{--}. Where an option has both positive and negative forms
+(such as @option{-f@var{option}} and @option{-fno-@var{option}}),
+relevant entries in the manual are indexed under the most appropriate
+form; it may sometimes be useful to look up both forms.
+
+@printindex op
+
+@node Concept Index
+@unnumbered Concept Index
+
+@printindex cp
+
+@c ---------------------------------------------------------------------
+@c Epilogue
+@c ---------------------------------------------------------------------
+
+@bye
--- /dev/null
+@c Copyright (C) 2017-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@ignore
+@c man begin COPYRIGHT
+Copyright @copyright{} 2017-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``GNU General Public License'' and ``Funding
+Free Software'', the Front-Cover texts being (a) (see below), and with
+the Back-Cover Texts being (b) (see below). A copy of the license is
+included in the gfdl(7) man page.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@c Set file name and title for the man page.
+@setfilename gcov-dump
+@settitle offline gcda and gcno profile dump tool
+@end ignore
+
+@node Gcov-dump
+@chapter @command{gcov-dump}---an Offline Gcda and Gcno Profile Dump Tool
+
+@menu
+* Gcov-dump Intro:: Introduction to gcov-dump.
+* Invoking Gcov-dump:: How to use gcov-dump.
+@end menu
+
+@node Gcov-dump Intro
+@section Introduction to @command{gcov-dump}
+@c man begin DESCRIPTION
+
+@command{gcov-dump} is a tool you can use in conjunction with GCC to
+dump content of gcda and gcno profile files offline.
+
+@c man end
+
+@node Invoking Gcov-dump
+@section Invoking @command{gcov-dump}
+
+@smallexample
+Usage: gcov-dump @r{[}@var{OPTION}@r{]} ... @var{gcovfiles}
+@end smallexample
+
+@command{gcov-dump} accepts the following options:
+
+@ignore
+@c man begin SYNOPSIS
+gcov-dump [@option{-v}|@option{--version}]
+ [@option{-h}|@option{--help}]
+ [@option{-l}|@option{--long}]
+ [@option{-p}|@option{--positions}]
+ [@option{-r}|@option{--raw}]
+ [@option{-s}|@option{--stable}]
+ @var{gcovfiles}
+@c man end
+@end ignore
+
+@c man begin OPTIONS
+@table @gcctabopt
+@item -h
+@itemx --help
+Display help about using @command{gcov-dump} (on the standard output), and
+exit without doing any further processing.
+
+@item -l
+@itemx --long
+Dump content of records.
+
+@item -p
+@itemx --positions
+Dump positions of records.
+
+@item -r
+@itemx --raw
+Print content records in raw format.
+
+@item -s
+@itemx --stable
+Print content in stable format usable for comparison.
+
+@item -v
+@itemx --version
+Display the @command{gcov-dump} version number (on the standard output),
+and exit without doing any further processing.
+@end table
+
+@c man end
--- /dev/null
+@c Copyright (C) 2014-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@ignore
+@c man begin COPYRIGHT
+Copyright @copyright{} 2014-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``GNU General Public License'' and ``Funding
+Free Software'', the Front-Cover texts being (a) (see below), and with
+the Back-Cover Texts being (b) (see below). A copy of the license is
+included in the gfdl(7) man page.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@c Set file name and title for the man page.
+@setfilename gcov-tool
+@settitle offline gcda profile processing tool
+@end ignore
+
+@node Gcov-tool
+@chapter @command{gcov-tool}---an Offline Gcda Profile Processing Tool
+
+@command{gcov-tool} is a tool you can use in conjunction with GCC to
+manipulate or process gcda profile files offline.
+
+@menu
+* Gcov-tool Intro:: Introduction to gcov-tool.
+* Invoking Gcov-tool:: How to use gcov-tool.
+@end menu
+
+@node Gcov-tool Intro
+@section Introduction to @command{gcov-tool}
+@c man begin DESCRIPTION
+
+@command{gcov-tool} is an offline tool to process gcc's gcda profile files.
+
+Current gcov-tool supports the following functionalities:
+
+@itemize @bullet
+@item
+merge two sets of profiles with weights.
+
+@item
+read a stream of profiles with associated filenames and merge it with a set of
+profiles with weights.
+
+@item
+read one set of profile and rewrite profile contents. One can scale or
+normalize the count values.
+@end itemize
+
+Examples of the use cases for this tool are:
+@itemize @bullet
+@item
+Collect the profiles for different set of inputs, and use this tool to merge
+them. One can specify the weight to factor in the relative importance of
+each input.
+
+@item
+Collect profiles from target systems without a filesystem (freestanding
+environments). Merge the collected profiles with associated profiles
+present on the host system. One can specify the weight to factor in the
+relative importance of each input.
+
+@item
+Rewrite the profile after removing a subset of the gcda files, while maintaining
+the consistency of the summary and the histogram.
+
+@item
+It can also be used to debug or libgcov code as the tools shares the majority
+code as the runtime library.
+@end itemize
+
+Note that for the merging operation, this profile generated offline may
+contain slight different values from the online merged profile. Here are
+a list of typical differences:
+
+@itemize @bullet
+@item
+histogram difference: This offline tool recomputes the histogram after merging
+the counters. The resulting histogram, therefore, is precise. The online
+merging does not have this capability -- the histogram is merged from two
+histograms and the result is an approximation.
+
+@item
+summary checksum difference: Summary checksum uses a CRC32 operation. The value
+depends on the link list order of gcov-info objects. This order is different in
+gcov-tool from that in the online merge. It's expected to have different
+summary checksums. It does not really matter as the compiler does not use this
+checksum anywhere.
+
+@item
+value profile counter values difference: Some counter values for value profile
+are runtime dependent, like heap addresses. It's normal to see some difference
+in these kind of counters.
+@end itemize
+
+@c man end
+
+@node Invoking Gcov-tool
+@section Invoking @command{gcov-tool}
+
+@smallexample
+gcov-tool @r{[}@var{global-options}@r{]} SUB_COMMAND @r{[}@var{sub_command-options}@r{]} @var{profile_dir}
+@end smallexample
+
+@command{gcov-tool} accepts the following options:
+
+@ignore
+@c man begin SYNOPSIS
+gcov-tool [@option{-v}|@option{--version}] [@option{-h}|@option{--help}]
+
+gcov-tool merge [merge-options] @var{directory1} @var{directory2}
+ [@option{-o}|@option{--output} @var{directory}]
+ [@option{-v}|@option{--verbose}]
+ [@option{-w}|@option{--weight} @var{w1,w2}]
+
+gcov-tool merge-stream [merge-stream-options] [@var{file}]
+ [@option{-v}|@option{--verbose}]
+ [@option{-w}|@option{--weight} @var{w1,w2}]
+
+gcov-tool rewrite [rewrite-options] @var{directory}
+ [@option{-n}|@option{--normalize} @var{long_long_value}]
+ [@option{-o}|@option{--output} @var{directory}]
+ [@option{-s}|@option{--scale} @var{float_or_simple-frac_value}]
+ [@option{-v}|@option{--verbose}]
+
+gcov-tool overlap [overlap-options] @var{directory1} @var{directory2}
+ [@option{-f}|@option{--function}]
+ [@option{-F}|@option{--fullname}]
+ [@option{-h}|@option{--hotonly}]
+ [@option{-o}|@option{--object}]
+ [@option{-t}|@option{--hot_threshold}] @var{float}
+ [@option{-v}|@option{--verbose}]
+
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7), gcc(1), gcov(1) and the Info entry for
+@file{gcc}.
+@c man end
+@end ignore
+
+@c man begin OPTIONS
+@table @gcctabopt
+@item -h
+@itemx --help
+Display help about using @command{gcov-tool} (on the standard output), and
+exit without doing any further processing.
+
+@item -v
+@itemx --version
+Display the @command{gcov-tool} version number (on the standard output),
+and exit without doing any further processing.
+
+@item merge
+Merge two profile directories.
+@table @gcctabopt
+
+@item -o @var{directory}
+@itemx --output @var{directory}
+Set the output profile directory. Default output directory name is
+@var{merged_profile}.
+
+@item -v
+@itemx --verbose
+Set the verbose mode.
+
+@item -w @var{w1},@var{w2}
+@itemx --weight @var{w1},@var{w2}
+Set the merge weights of the @var{directory1} and @var{directory2},
+respectively. The default weights are 1 for both.
+@end table
+
+@item merge-stream
+Collect profiles with associated filenames from a @emph{gcfn} and @emph{gcda}
+data stream. Read the stream from the file specified by @var{file} or from
+@file{stdin}. Merge the profiles with associated profiles in the host
+filesystem. Apply the optional weights while merging profiles.
+
+For the generation of a @emph{gcfn} and @emph{gcda} data stream on the target
+system, please have a look at the @code{__gcov_filename_to_gcfn()} and
+@code{__gcov_info_to_gcda()} functions declared in @code{#include <gcov.h>}.
+@table @gcctabopt
+
+@item -v
+@itemx --verbose
+Set the verbose mode.
+
+@item -w @var{w1},@var{w2}
+@itemx --weight @var{w1},@var{w2}
+Set the merge weights of the profiles from the @emph{gcfn} and @emph{gcda} data
+stream and the associated profiles in the host filesystem, respectively. The
+default weights are 1 for both.
+@end table
+
+@item rewrite
+Read the specified profile directory and rewrite to a new directory.
+@table @gcctabopt
+
+@item -n @var{long_long_value}
+@itemx --normalize <long_long_value>
+Normalize the profile. The specified value is the max counter value
+in the new profile.
+
+@item -o @var{directory}
+@itemx --output @var{directory}
+Set the output profile directory. Default output name is @var{rewrite_profile}.
+
+@item -s @var{float_or_simple-frac_value}
+@itemx --scale @var{float_or_simple-frac_value}
+Scale the profile counters. The specified value can be in floating point value,
+or simple fraction value form, such 1, 2, 2/3, and 5/3.
+
+@item -v
+@itemx --verbose
+Set the verbose mode.
+@end table
+
+@item overlap
+Compute the overlap score between the two specified profile directories.
+The overlap score is computed based on the arc profiles. It is defined as
+the sum of min (p1_counter[i] / p1_sum_all, p2_counter[i] / p2_sum_all),
+for all arc counter i, where p1_counter[i] and p2_counter[i] are two
+matched counters and p1_sum_all and p2_sum_all are the sum of counter
+values in profile 1 and profile 2, respectively.
+
+@table @gcctabopt
+@item -f
+@itemx --function
+Print function level overlap score.
+
+@item -F
+@itemx --fullname
+Print full gcda filename.
+
+@item -h
+@itemx --hotonly
+Only print info for hot objects/functions.
+
+@item -o
+@itemx --object
+Print object level overlap score.
+
+@item -t @var{float}
+@itemx --hot_threshold <float>
+Set the threshold for hot counter value.
+
+@item -v
+@itemx --verbose
+Set the verbose mode.
+@end table
+
+@end table
+
+@c man end
--- /dev/null
+@c Copyright (C) 1996-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@ignore
+@c man begin COPYRIGHT
+Copyright @copyright{} 1996-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``GNU General Public License'' and ``Funding
+Free Software'', the Front-Cover texts being (a) (see below), and with
+the Back-Cover Texts being (b) (see below). A copy of the license is
+included in the gfdl(7) man page.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@c Set file name and title for the man page.
+@setfilename gcov
+@settitle coverage testing tool
+@end ignore
+
+@node Gcov
+@chapter @command{gcov}---a Test Coverage Program
+
+@command{gcov} is a tool you can use in conjunction with GCC to
+test code coverage in your programs.
+
+@menu
+* Gcov Intro:: Introduction to gcov.
+* Invoking Gcov:: How to use gcov.
+* Gcov and Optimization:: Using gcov with GCC optimization.
+* Gcov Data Files:: The files used by gcov.
+* Cross-profiling:: Data file relocation.
+* Freestanding Environments:: How to use profiling and test
+ coverage in freestanding environments.
+@end menu
+
+@node Gcov Intro
+@section Introduction to @command{gcov}
+@c man begin DESCRIPTION
+
+@command{gcov} is a test coverage program. Use it in concert with GCC
+to analyze your programs to help create more efficient, faster running
+code and to discover untested parts of your program. You can use
+@command{gcov} as a profiling tool to help discover where your
+optimization efforts will best affect your code. You can also use
+@command{gcov} along with the other profiling tool, @command{gprof}, to
+assess which parts of your code use the greatest amount of computing
+time.
+
+Profiling tools help you analyze your code's performance. Using a
+profiler such as @command{gcov} or @command{gprof}, you can find out some
+basic performance statistics, such as:
+
+@itemize @bullet
+@item
+how often each line of code executes
+
+@item
+what lines of code are actually executed
+
+@item
+how much computing time each section of code uses
+@end itemize
+
+Once you know these things about how your code works when compiled, you
+can look at each module to see which modules should be optimized.
+@command{gcov} helps you determine where to work on optimization.
+
+Software developers also use coverage testing in concert with
+testsuites, to make sure software is actually good enough for a release.
+Testsuites can verify that a program works as expected; a coverage
+program tests to see how much of the program is exercised by the
+testsuite. Developers can then determine what kinds of test cases need
+to be added to the testsuites to create both better testing and a better
+final product.
+
+You should compile your code without optimization if you plan to use
+@command{gcov} because the optimization, by combining some lines of code
+into one function, may not give you as much information as you need to
+look for `hot spots' where the code is using a great deal of computer
+time. Likewise, because @command{gcov} accumulates statistics by line (at
+the lowest resolution), it works best with a programming style that
+places only one statement on each line. If you use complicated macros
+that expand to loops or to other control structures, the statistics are
+less helpful---they only report on the line where the macro call
+appears. If your complex macros behave like functions, you can replace
+them with inline functions to solve this problem.
+
+@command{gcov} creates a logfile called @file{@var{sourcefile}.gcov} which
+indicates how many times each line of a source file @file{@var{sourcefile}.c}
+has executed. You can use these logfiles along with @command{gprof} to aid
+in fine-tuning the performance of your programs. @command{gprof} gives
+timing information you can use along with the information you get from
+@command{gcov}.
+
+@command{gcov} works only on code compiled with GCC@. It is not
+compatible with any other profiling or test coverage mechanism.
+
+@c man end
+
+@node Invoking Gcov
+@section Invoking @command{gcov}
+
+@smallexample
+gcov @r{[}@var{options}@r{]} @var{files}
+@end smallexample
+
+@command{gcov} accepts the following options:
+
+@ignore
+@c man begin SYNOPSIS
+gcov [@option{-v}|@option{--version}] [@option{-h}|@option{--help}]
+ [@option{-a}|@option{--all-blocks}]
+ [@option{-b}|@option{--branch-probabilities}]
+ [@option{-c}|@option{--branch-counts}]
+ [@option{-d}|@option{--display-progress}]
+ [@option{-f}|@option{--function-summaries}]
+ [@option{-j}|@option{--json-format}]
+ [@option{-H}|@option{--human-readable}]
+ [@option{-k}|@option{--use-colors}]
+ [@option{-l}|@option{--long-file-names}]
+ [@option{-m}|@option{--demangled-names}]
+ [@option{-n}|@option{--no-output}]
+ [@option{-o}|@option{--object-directory} @var{directory|file}]
+ [@option{-p}|@option{--preserve-paths}]
+ [@option{-q}|@option{--use-hotness-colors}]
+ [@option{-r}|@option{--relative-only}]
+ [@option{-s}|@option{--source-prefix} @var{directory}]
+ [@option{-t}|@option{--stdout}]
+ [@option{-u}|@option{--unconditional-branches}]
+ [@option{-x}|@option{--hash-filenames}]
+ @var{files}
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7), gcc(1) and the Info entry for @file{gcc}.
+@c man end
+@end ignore
+
+@c man begin OPTIONS
+@table @gcctabopt
+
+@item -a
+@itemx --all-blocks
+Write individual execution counts for every basic block. Normally gcov
+outputs execution counts only for the main blocks of a line. With this
+option you can determine if blocks within a single line are not being
+executed.
+
+@item -b
+@itemx --branch-probabilities
+Write branch frequencies to the output file, and write branch summary
+info to the standard output. This option allows you to see how often
+each branch in your program was taken. Unconditional branches will not
+be shown, unless the @option{-u} option is given.
+
+@item -c
+@itemx --branch-counts
+Write branch frequencies as the number of branches taken, rather than
+the percentage of branches taken.
+
+@item -d
+@itemx --display-progress
+Display the progress on the standard output.
+
+@item -f
+@itemx --function-summaries
+Output summaries for each function in addition to the file level summary.
+
+@item -h
+@itemx --help
+Display help about using @command{gcov} (on the standard output), and
+exit without doing any further processing.
+
+@item -j
+@itemx --json-format
+Output gcov file in an easy-to-parse JSON intermediate format
+which does not require source code for generation. The JSON
+file is compressed with gzip compression algorithm
+and the files have @file{.gcov.json.gz} extension.
+
+Structure of the JSON is following:
+
+@smallexample
+@{
+ "current_working_directory": "foo/bar",
+ "data_file": "a.out",
+ "format_version": "1",
+ "gcc_version": "11.1.1 20210510"
+ "files": ["$file"]
+@}
+@end smallexample
+
+Fields of the root element have following semantics:
+
+@itemize @bullet
+@item
+@var{current_working_directory}: working directory where
+a compilation unit was compiled
+
+@item
+@var{data_file}: name of the data file (GCDA)
+
+@item
+@var{format_version}: semantic version of the format
+
+@item
+@var{gcc_version}: version of the GCC compiler
+@end itemize
+
+Each @var{file} has the following form:
+
+@smallexample
+@{
+ "file": "a.c",
+ "functions": ["$function"],
+ "lines": ["$line"]
+@}
+@end smallexample
+
+Fields of the @var{file} element have following semantics:
+
+@itemize @bullet
+@item
+@var{file_name}: name of the source file
+@end itemize
+
+Each @var{function} has the following form:
+
+@smallexample
+@{
+ "blocks": 2,
+ "blocks_executed": 2,
+ "demangled_name": "foo",
+ "end_column": 1,
+ "end_line": 4,
+ "execution_count": 1,
+ "name": "foo",
+ "start_column": 5,
+ "start_line": 1
+@}
+@end smallexample
+
+Fields of the @var{function} element have following semantics:
+
+@itemize @bullet
+@item
+@var{blocks}: number of blocks that are in the function
+
+@item
+@var{blocks_executed}: number of executed blocks of the function
+
+@item
+@var{demangled_name}: demangled name of the function
+
+@item
+@var{end_column}: column in the source file where the function ends
+
+@item
+@var{end_line}: line in the source file where the function ends
+
+@item
+@var{execution_count}: number of executions of the function
+
+@item
+@var{name}: name of the function
+
+@item
+@var{start_column}: column in the source file where the function begins
+
+@item
+@var{start_line}: line in the source file where the function begins
+@end itemize
+
+Note that line numbers and column numbers number from 1. In the current
+implementation, @var{start_line} and @var{start_column} do not include
+any template parameters and the leading return type but that
+this is likely to be fixed in the future.
+
+Each @var{line} has the following form:
+
+@smallexample
+@{
+ "branches": ["$branch"],
+ "count": 2,
+ "line_number": 15,
+ "unexecuted_block": false,
+ "function_name": "foo",
+@}
+@end smallexample
+
+Branches are present only with @var{-b} option.
+Fields of the @var{line} element have following semantics:
+
+@itemize @bullet
+@item
+@var{count}: number of executions of the line
+
+@item
+@var{line_number}: line number
+
+@item
+@var{unexecuted_block}: flag whether the line contains an unexecuted block
+(not all statements on the line are executed)
+
+@item
+@var{function_name}: a name of a function this @var{line} belongs to
+(for a line with an inlined statements can be not set)
+@end itemize
+
+Each @var{branch} has the following form:
+
+@smallexample
+@{
+ "count": 11,
+ "fallthrough": true,
+ "throw": false
+@}
+@end smallexample
+
+Fields of the @var{branch} element have following semantics:
+
+@itemize @bullet
+@item
+@var{count}: number of executions of the branch
+
+@item
+@var{fallthrough}: true when the branch is a fall through branch
+
+@item
+@var{throw}: true when the branch is an exceptional branch
+@end itemize
+
+@item -H
+@itemx --human-readable
+Write counts in human readable format (like 24.6k).
+
+@item -k
+@itemx --use-colors
+
+Use colors for lines of code that have zero coverage. We use red color for
+non-exceptional lines and cyan for exceptional. Same colors are used for
+basic blocks with @option{-a} option.
+
+@item -l
+@itemx --long-file-names
+Create long file names for included source files. For example, if the
+header file @file{x.h} contains code, and was included in the file
+@file{a.c}, then running @command{gcov} on the file @file{a.c} will
+produce an output file called @file{a.c##x.h.gcov} instead of
+@file{x.h.gcov}. This can be useful if @file{x.h} is included in
+multiple source files and you want to see the individual
+contributions. If you use the @samp{-p} option, both the including
+and included file names will be complete path names.
+
+@item -m
+@itemx --demangled-names
+Display demangled function names in output. The default is to show
+mangled function names.
+
+@item -n
+@itemx --no-output
+Do not create the @command{gcov} output file.
+
+@item -o @var{directory|file}
+@itemx --object-directory @var{directory}
+@itemx --object-file @var{file}
+Specify either the directory containing the gcov data files, or the
+object path name. The @file{.gcno}, and
+@file{.gcda} data files are searched for using this option. If a directory
+is specified, the data files are in that directory and named after the
+input file name, without its extension. If a file is specified here,
+the data files are named after that file, without its extension.
+
+@item -p
+@itemx --preserve-paths
+Preserve complete path information in the names of generated
+@file{.gcov} files. Without this option, just the filename component is
+used. With this option, all directories are used, with @samp{/} characters
+translated to @samp{#} characters, @file{.} directory components
+removed and unremoveable @file{..}
+components renamed to @samp{^}. This is useful if sourcefiles are in several
+different directories.
+
+@item -q
+@itemx --use-hotness-colors
+
+Emit perf-like colored output for hot lines. Legend of the color scale
+is printed at the very beginning of the output file.
+
+@item -r
+@itemx --relative-only
+Only output information about source files with a relative pathname
+(after source prefix elision). Absolute paths are usually system
+header files and coverage of any inline functions therein is normally
+uninteresting.
+
+@item -s @var{directory}
+@itemx --source-prefix @var{directory}
+A prefix for source file names to remove when generating the output
+coverage files. This option is useful when building in a separate
+directory, and the pathname to the source directory is not wanted when
+determining the output file names. Note that this prefix detection is
+applied before determining whether the source file is absolute.
+
+@item -t
+@itemx --stdout
+Output to standard output instead of output files.
+
+@item -u
+@itemx --unconditional-branches
+When branch probabilities are given, include those of unconditional branches.
+Unconditional branches are normally not interesting.
+
+@item -v
+@itemx --version
+Display the @command{gcov} version number (on the standard output),
+and exit without doing any further processing.
+
+@item -w
+@itemx --verbose
+Print verbose informations related to basic blocks and arcs.
+
+@item -x
+@itemx --hash-filenames
+When using @var{--preserve-paths},
+gcov uses the full pathname of the source files to create
+an output filename. This can lead to long filenames that can overflow
+filesystem limits. This option creates names of the form
+@file{@var{source-file}##@var{md5}.gcov},
+where the @var{source-file} component is the final filename part and
+the @var{md5} component is calculated from the full mangled name that
+would have been used otherwise. The option is an alternative
+to the @var{--preserve-paths} on systems which have a filesystem limit.
+
+@end table
+
+@command{gcov} should be run with the current directory the same as that
+when you invoked the compiler. Otherwise it will not be able to locate
+the source files. @command{gcov} produces files called
+@file{@var{mangledname}.gcov} in the current directory. These contain
+the coverage information of the source file they correspond to.
+One @file{.gcov} file is produced for each source (or header) file
+containing code,
+which was compiled to produce the data files. The @var{mangledname} part
+of the output file name is usually simply the source file name, but can
+be something more complicated if the @samp{-l} or @samp{-p} options are
+given. Refer to those options for details.
+
+If you invoke @command{gcov} with multiple input files, the
+contributions from each input file are summed. Typically you would
+invoke it with the same list of files as the final link of your executable.
+
+The @file{.gcov} files contain the @samp{:} separated fields along with
+program source code. The format is
+
+@smallexample
+@var{execution_count}:@var{line_number}:@var{source line text}
+@end smallexample
+
+Additional block information may succeed each line, when requested by
+command line option. The @var{execution_count} is @samp{-} for lines
+containing no code. Unexecuted lines are marked @samp{#####} or
+@samp{=====}, depending on whether they are reachable by
+non-exceptional paths or only exceptional paths such as C++ exception
+handlers, respectively. Given the @samp{-a} option, unexecuted blocks are
+marked @samp{$$$$$} or @samp{%%%%%}, depending on whether a basic block
+is reachable via non-exceptional or exceptional paths.
+Executed basic blocks having a statement with zero @var{execution_count}
+end with @samp{*} character and are colored with magenta color with
+the @option{-k} option. This functionality is not supported in Ada.
+
+Note that GCC can completely remove the bodies of functions that are
+not needed -- for instance if they are inlined everywhere. Such functions
+are marked with @samp{-}, which can be confusing.
+Use the @option{-fkeep-inline-functions} and @option{-fkeep-static-functions}
+options to retain these functions and
+allow gcov to properly show their @var{execution_count}.
+
+Some lines of information at the start have @var{line_number} of zero.
+These preamble lines are of the form
+
+@smallexample
+-:0:@var{tag}:@var{value}
+@end smallexample
+
+The ordering and number of these preamble lines will be augmented as
+@command{gcov} development progresses --- do not rely on them remaining
+unchanged. Use @var{tag} to locate a particular preamble line.
+
+The additional block information is of the form
+
+@smallexample
+@var{tag} @var{information}
+@end smallexample
+
+The @var{information} is human readable, but designed to be simple
+enough for machine parsing too.
+
+When printing percentages, 0% and 100% are only printed when the values
+are @emph{exactly} 0% and 100% respectively. Other values which would
+conventionally be rounded to 0% or 100% are instead printed as the
+nearest non-boundary value.
+
+When using @command{gcov}, you must first compile your program
+with a special GCC option @samp{--coverage}.
+This tells the compiler to generate additional information needed by
+gcov (basically a flow graph of the program) and also includes
+additional code in the object files for generating the extra profiling
+information needed by gcov. These additional files are placed in the
+directory where the object file is located.
+
+Running the program will cause profile output to be generated. For each
+source file compiled with @option{-fprofile-arcs}, an accompanying
+@file{.gcda} file will be placed in the object file directory.
+
+Running @command{gcov} with your program's source file names as arguments
+will now produce a listing of the code along with frequency of execution
+for each line. For example, if your program is called @file{tmp.cpp}, this
+is what you see when you use the basic @command{gcov} facility:
+
+@smallexample
+$ g++ --coverage tmp.cpp -c
+$ g++ --coverage tmp.o
+$ a.out
+$ gcov tmp.cpp -m
+File 'tmp.cpp'
+Lines executed:92.86% of 14
+Creating 'tmp.cpp.gcov'
+@end smallexample
+
+The file @file{tmp.cpp.gcov} contains output from @command{gcov}.
+Here is a sample:
+
+@smallexample
+ -: 0:Source:tmp.cpp
+ -: 0:Working directory:/home/gcc/testcase
+ -: 0:Graph:tmp.gcno
+ -: 0:Data:tmp.gcda
+ -: 0:Runs:1
+ -: 0:Programs:1
+ -: 1:#include <stdio.h>
+ -: 2:
+ -: 3:template<class T>
+ -: 4:class Foo
+ -: 5:@{
+ -: 6: public:
+ 1*: 7: Foo(): b (1000) @{@}
+------------------
+Foo<char>::Foo():
+ #####: 7: Foo(): b (1000) @{@}
+------------------
+Foo<int>::Foo():
+ 1: 7: Foo(): b (1000) @{@}
+------------------
+ 2*: 8: void inc () @{ b++; @}
+------------------
+Foo<char>::inc():
+ #####: 8: void inc () @{ b++; @}
+------------------
+Foo<int>::inc():
+ 2: 8: void inc () @{ b++; @}
+------------------
+ -: 9:
+ -: 10: private:
+ -: 11: int b;
+ -: 12:@};
+ -: 13:
+ -: 14:template class Foo<int>;
+ -: 15:template class Foo<char>;
+ -: 16:
+ -: 17:int
+ 1: 18:main (void)
+ -: 19:@{
+ -: 20: int i, total;
+ 1: 21: Foo<int> counter;
+ -: 22:
+ 1: 23: counter.inc();
+ 1: 24: counter.inc();
+ 1: 25: total = 0;
+ -: 26:
+ 11: 27: for (i = 0; i < 10; i++)
+ 10: 28: total += i;
+ -: 29:
+ 1*: 30: int v = total > 100 ? 1 : 2;
+ -: 31:
+ 1: 32: if (total != 45)
+ #####: 33: printf ("Failure\n");
+ -: 34: else
+ 1: 35: printf ("Success\n");
+ 1: 36: return 0;
+ -: 37:@}
+@end smallexample
+
+Note that line 7 is shown in the report multiple times. First occurrence
+presents total number of execution of the line and the next two belong
+to instances of class Foo constructors. As you can also see, line 30 contains
+some unexecuted basic blocks and thus execution count has asterisk symbol.
+
+When you use the @option{-a} option, you will get individual block
+counts, and the output looks like this:
+
+@smallexample
+ -: 0:Source:tmp.cpp
+ -: 0:Working directory:/home/gcc/testcase
+ -: 0:Graph:tmp.gcno
+ -: 0:Data:tmp.gcda
+ -: 0:Runs:1
+ -: 0:Programs:1
+ -: 1:#include <stdio.h>
+ -: 2:
+ -: 3:template<class T>
+ -: 4:class Foo
+ -: 5:@{
+ -: 6: public:
+ 1*: 7: Foo(): b (1000) @{@}
+------------------
+Foo<char>::Foo():
+ #####: 7: Foo(): b (1000) @{@}
+------------------
+Foo<int>::Foo():
+ 1: 7: Foo(): b (1000) @{@}
+------------------
+ 2*: 8: void inc () @{ b++; @}
+------------------
+Foo<char>::inc():
+ #####: 8: void inc () @{ b++; @}
+------------------
+Foo<int>::inc():
+ 2: 8: void inc () @{ b++; @}
+------------------
+ -: 9:
+ -: 10: private:
+ -: 11: int b;
+ -: 12:@};
+ -: 13:
+ -: 14:template class Foo<int>;
+ -: 15:template class Foo<char>;
+ -: 16:
+ -: 17:int
+ 1: 18:main (void)
+ -: 19:@{
+ -: 20: int i, total;
+ 1: 21: Foo<int> counter;
+ 1: 21-block 0
+ -: 22:
+ 1: 23: counter.inc();
+ 1: 23-block 0
+ 1: 24: counter.inc();
+ 1: 24-block 0
+ 1: 25: total = 0;
+ -: 26:
+ 11: 27: for (i = 0; i < 10; i++)
+ 1: 27-block 0
+ 11: 27-block 1
+ 10: 28: total += i;
+ 10: 28-block 0
+ -: 29:
+ 1*: 30: int v = total > 100 ? 1 : 2;
+ 1: 30-block 0
+ %%%%%: 30-block 1
+ 1: 30-block 2
+ -: 31:
+ 1: 32: if (total != 45)
+ 1: 32-block 0
+ #####: 33: printf ("Failure\n");
+ %%%%%: 33-block 0
+ -: 34: else
+ 1: 35: printf ("Success\n");
+ 1: 35-block 0
+ 1: 36: return 0;
+ 1: 36-block 0
+ -: 37:@}
+@end smallexample
+
+In this mode, each basic block is only shown on one line -- the last
+line of the block. A multi-line block will only contribute to the
+execution count of that last line, and other lines will not be shown
+to contain code, unless previous blocks end on those lines.
+The total execution count of a line is shown and subsequent lines show
+the execution counts for individual blocks that end on that line. After each
+block, the branch and call counts of the block will be shown, if the
+@option{-b} option is given.
+
+Because of the way GCC instruments calls, a call count can be shown
+after a line with no individual blocks.
+As you can see, line 33 contains a basic block that was not executed.
+
+@need 450
+When you use the @option{-b} option, your output looks like this:
+
+@smallexample
+ -: 0:Source:tmp.cpp
+ -: 0:Working directory:/home/gcc/testcase
+ -: 0:Graph:tmp.gcno
+ -: 0:Data:tmp.gcda
+ -: 0:Runs:1
+ -: 0:Programs:1
+ -: 1:#include <stdio.h>
+ -: 2:
+ -: 3:template<class T>
+ -: 4:class Foo
+ -: 5:@{
+ -: 6: public:
+ 1*: 7: Foo(): b (1000) @{@}
+------------------
+Foo<char>::Foo():
+function Foo<char>::Foo() called 0 returned 0% blocks executed 0%
+ #####: 7: Foo(): b (1000) @{@}
+------------------
+Foo<int>::Foo():
+function Foo<int>::Foo() called 1 returned 100% blocks executed 100%
+ 1: 7: Foo(): b (1000) @{@}
+------------------
+ 2*: 8: void inc () @{ b++; @}
+------------------
+Foo<char>::inc():
+function Foo<char>::inc() called 0 returned 0% blocks executed 0%
+ #####: 8: void inc () @{ b++; @}
+------------------
+Foo<int>::inc():
+function Foo<int>::inc() called 2 returned 100% blocks executed 100%
+ 2: 8: void inc () @{ b++; @}
+------------------
+ -: 9:
+ -: 10: private:
+ -: 11: int b;
+ -: 12:@};
+ -: 13:
+ -: 14:template class Foo<int>;
+ -: 15:template class Foo<char>;
+ -: 16:
+ -: 17:int
+function main called 1 returned 100% blocks executed 81%
+ 1: 18:main (void)
+ -: 19:@{
+ -: 20: int i, total;
+ 1: 21: Foo<int> counter;
+call 0 returned 100%
+branch 1 taken 100% (fallthrough)
+branch 2 taken 0% (throw)
+ -: 22:
+ 1: 23: counter.inc();
+call 0 returned 100%
+branch 1 taken 100% (fallthrough)
+branch 2 taken 0% (throw)
+ 1: 24: counter.inc();
+call 0 returned 100%
+branch 1 taken 100% (fallthrough)
+branch 2 taken 0% (throw)
+ 1: 25: total = 0;
+ -: 26:
+ 11: 27: for (i = 0; i < 10; i++)
+branch 0 taken 91% (fallthrough)
+branch 1 taken 9%
+ 10: 28: total += i;
+ -: 29:
+ 1*: 30: int v = total > 100 ? 1 : 2;
+branch 0 taken 0% (fallthrough)
+branch 1 taken 100%
+ -: 31:
+ 1: 32: if (total != 45)
+branch 0 taken 0% (fallthrough)
+branch 1 taken 100%
+ #####: 33: printf ("Failure\n");
+call 0 never executed
+branch 1 never executed
+branch 2 never executed
+ -: 34: else
+ 1: 35: printf ("Success\n");
+call 0 returned 100%
+branch 1 taken 100% (fallthrough)
+branch 2 taken 0% (throw)
+ 1: 36: return 0;
+ -: 37:@}
+@end smallexample
+
+For each function, a line is printed showing how many times the function
+is called, how many times it returns and what percentage of the
+function's blocks were executed.
+
+For each basic block, a line is printed after the last line of the basic
+block describing the branch or call that ends the basic block. There can
+be multiple branches and calls listed for a single source line if there
+are multiple basic blocks that end on that line. In this case, the
+branches and calls are each given a number. There is no simple way to map
+these branches and calls back to source constructs. In general, though,
+the lowest numbered branch or call will correspond to the leftmost construct
+on the source line.
+
+For a branch, if it was executed at least once, then a percentage
+indicating the number of times the branch was taken divided by the
+number of times the branch was executed will be printed. Otherwise, the
+message ``never executed'' is printed.
+
+For a call, if it was executed at least once, then a percentage
+indicating the number of times the call returned divided by the number
+of times the call was executed will be printed. This will usually be
+100%, but may be less for functions that call @code{exit} or @code{longjmp},
+and thus may not return every time they are called.
+
+The execution counts are cumulative. If the example program were
+executed again without removing the @file{.gcda} file, the count for the
+number of times each line in the source was executed would be added to
+the results of the previous run(s). This is potentially useful in
+several ways. For example, it could be used to accumulate data over a
+number of program runs as part of a test verification suite, or to
+provide more accurate long-term information over a large number of
+program runs.
+
+The data in the @file{.gcda} files is saved immediately before the program
+exits. For each source file compiled with @option{-fprofile-arcs}, the
+profiling code first attempts to read in an existing @file{.gcda} file; if
+the file doesn't match the executable (differing number of basic block
+counts) it will ignore the contents of the file. It then adds in the
+new execution counts and finally writes the data to the file.
+
+@node Gcov and Optimization
+@section Using @command{gcov} with GCC Optimization
+
+If you plan to use @command{gcov} to help optimize your code, you must
+first compile your program with a special GCC option
+@samp{--coverage}. Aside from that, you can use any
+other GCC options; but if you want to prove that every single line
+in your program was executed, you should not compile with optimization
+at the same time. On some machines the optimizer can eliminate some
+simple code lines by combining them with other lines. For example, code
+like this:
+
+@smallexample
+if (a != b)
+ c = 1;
+else
+ c = 0;
+@end smallexample
+
+@noindent
+can be compiled into one instruction on some machines. In this case,
+there is no way for @command{gcov} to calculate separate execution counts
+for each line because there isn't separate code for each line. Hence
+the @command{gcov} output looks like this if you compiled the program with
+optimization:
+
+@smallexample
+ 100: 12:if (a != b)
+ 100: 13: c = 1;
+ 100: 14:else
+ 100: 15: c = 0;
+@end smallexample
+
+The output shows that this block of code, combined by optimization,
+executed 100 times. In one sense this result is correct, because there
+was only one instruction representing all four of these lines. However,
+the output does not indicate how many times the result was 0 and how
+many times the result was 1.
+
+Inlineable functions can create unexpected line counts. Line counts are
+shown for the source code of the inlineable function, but what is shown
+depends on where the function is inlined, or if it is not inlined at all.
+
+If the function is not inlined, the compiler must emit an out of line
+copy of the function, in any object file that needs it. If
+@file{fileA.o} and @file{fileB.o} both contain out of line bodies of a
+particular inlineable function, they will also both contain coverage
+counts for that function. When @file{fileA.o} and @file{fileB.o} are
+linked together, the linker will, on many systems, select one of those
+out of line bodies for all calls to that function, and remove or ignore
+the other. Unfortunately, it will not remove the coverage counters for
+the unused function body. Hence when instrumented, all but one use of
+that function will show zero counts.
+
+If the function is inlined in several places, the block structure in
+each location might not be the same. For instance, a condition might
+now be calculable at compile time in some instances. Because the
+coverage of all the uses of the inline function will be shown for the
+same source lines, the line counts themselves might seem inconsistent.
+
+Long-running applications can use the @code{__gcov_reset} and @code{__gcov_dump}
+facilities to restrict profile collection to the program region of
+interest. Calling @code{__gcov_reset(void)} will clear all run-time profile
+counters to zero, and calling @code{__gcov_dump(void)} will cause the profile
+information collected at that point to be dumped to @file{.gcda} output files.
+Instrumented applications use a static destructor with priority 99
+to invoke the @code{__gcov_dump} function. Thus @code{__gcov_dump}
+is executed after all user defined static destructors,
+as well as handlers registered with @code{atexit}.
+
+If an executable loads a dynamic shared object via dlopen functionality,
+@option{-Wl,--dynamic-list-data} is needed to dump all profile data.
+
+Profiling run-time library reports various errors related to profile
+manipulation and profile saving. Errors are printed into standard error output
+or @samp{GCOV_ERROR_FILE} file, if environment variable is used.
+In order to terminate immediately after an errors occurs
+set @samp{GCOV_EXIT_AT_ERROR} environment variable.
+That can help users to find profile clashing which leads
+to a misleading profile.
+
+@c man end
+
+@node Gcov Data Files
+@section Brief Description of @command{gcov} Data Files
+
+@command{gcov} uses two files for profiling. The names of these files
+are derived from the original @emph{object} file by substituting the
+file suffix with either @file{.gcno}, or @file{.gcda}. The files
+contain coverage and profile data stored in a platform-independent format.
+The @file{.gcno} files are placed in the same directory as the object
+file. By default, the @file{.gcda} files are also stored in the same
+directory as the object file, but the GCC @option{-fprofile-dir} option
+may be used to store the @file{.gcda} files in a separate directory.
+
+The @file{.gcno} notes file is generated when the source file is compiled
+with the GCC @option{-ftest-coverage} option. It contains information to
+reconstruct the basic block graphs and assign source line numbers to
+blocks.
+
+The @file{.gcda} count data file is generated when a program containing
+object files built with the GCC @option{-fprofile-arcs} option is executed.
+A separate @file{.gcda} file is created for each object file compiled with
+this option. It contains arc transition counts, value profile counts, and
+some summary information.
+
+It is not recommended to access the coverage files directly.
+Consumers should use the intermediate format that is provided
+by @command{gcov} tool via @option{--json-format} option.
+
+@node Cross-profiling
+@section Data File Relocation to Support Cross-Profiling
+
+Running the program will cause profile output to be generated. For each
+source file compiled with @option{-fprofile-arcs}, an accompanying @file{.gcda}
+file will be placed in the object file directory. That implicitly requires
+running the program on the same system as it was built or having the same
+absolute directory structure on the target system. The program will try
+to create the needed directory structure, if it is not already present.
+
+To support cross-profiling, a program compiled with @option{-fprofile-arcs}
+can relocate the data files based on two environment variables:
+
+@itemize @bullet
+@item
+GCOV_PREFIX contains the prefix to add to the absolute paths
+in the object file. Prefix can be absolute, or relative. The
+default is no prefix.
+
+@item
+GCOV_PREFIX_STRIP indicates the how many initial directory names to strip off
+the hardwired absolute paths. Default value is 0.
+
+@emph{Note:} If GCOV_PREFIX_STRIP is set without GCOV_PREFIX is undefined,
+ then a relative path is made out of the hardwired absolute paths.
+@end itemize
+
+For example, if the object file @file{/user/build/foo.o} was built with
+@option{-fprofile-arcs}, the final executable will try to create the data file
+@file{/user/build/foo.gcda} when running on the target system. This will
+fail if the corresponding directory does not exist and it is unable to create
+it. This can be overcome by, for example, setting the environment as
+@samp{GCOV_PREFIX=/target/run} and @samp{GCOV_PREFIX_STRIP=1}. Such a
+setting will name the data file @file{/target/run/build/foo.gcda}.
+
+You must move the data files to the expected directory tree in order to
+use them for profile directed optimizations (@option{-fprofile-use}), or to
+use the @command{gcov} tool.
+
+@node Freestanding Environments
+@section Profiling and Test Coverage in Freestanding Environments
+
+In case your application runs in a hosted environment such as GNU/Linux, then
+this section is likely not relevant to you. This section is intended for
+application developers targeting freestanding environments (for example
+embedded systems) with limited resources. In particular, systems or test cases
+which do not support constructors/destructors or the C library file I/O. In
+this section, the @dfn{target system} runs your application instrumented for
+profiling or test coverage. You develop and analyze your application on the
+@dfn{host system}. We now provide an overview how profiling and test coverage
+can be obtained in this scenario followed by a tutorial which can be exercised
+on the host system. Finally, some system initialization caveats are listed.
+
+@subsection Overview
+
+For an application instrumented for profiling or test coverage, the compiler
+generates some global data structures which are updated by instrumentation code
+while the application runs. These data structures are called the @dfn{gcov
+information}. Normally, when the application exits, the gcov information is
+stored to @file{.gcda} files. There is one file per translation unit
+instrumented for profiling or test coverage. The function
+@code{__gcov_exit()}, which stores the gcov information to a file, is called by
+a global destructor function for each translation unit instrumented for
+profiling or test coverage. It runs at process exit. In a global constructor
+function, the @code{__gcov_init()} function is called to register the gcov
+information of a translation unit in a global list. In some situations, this
+procedure does not work. Firstly, if you want to profile the global
+constructor or exit processing of an operating system, the compiler generated
+functions may conflict with the test objectives. Secondly, you may want to
+test early parts of the system initialization or abnormal program behaviour
+which do not allow a global constructor or exit processing. Thirdly, you need
+a filesystem to store the files.
+
+The @option{-fprofile-info-section} GCC option enables you to use profiling and
+test coverage in freestanding environments. This option disables the use of
+global constructors and destructors for the gcov information. Instead, a
+pointer to the gcov information is stored in a special linker input section for
+each translation unit which is compiled with this option. By default, the
+section name is @code{.gcov_info}. The gcov information is statically
+initialized. The pointers to the gcov information from all translation units
+of an executable can be collected by the linker in a contiguous memory block.
+For the GNU linker, the below linker script output section definition can be
+used to achieve this:
+
+@smallexample
+ .gcov_info :
+ @{
+ PROVIDE (__gcov_info_start = .);
+ KEEP (*(.gcov_info))
+ PROVIDE (__gcov_info_end = .);
+ @}
+@end smallexample
+
+The linker will provide two global symbols, @code{__gcov_info_start} and
+@code{__gcov_info_end}, which define the start and end of the array of pointers
+to gcov information blocks, respectively. The @code{KEEP ()} directive is
+required to prevent a garbage collection of the pointers. They are not
+directly referenced by anything in the executable. The section may be placed
+in a read-only memory area.
+
+In order to transfer the profiling and test coverage data from the target to
+the host system, the application has to provide a function to produce a
+reliable in order byte stream from the target to the host. The byte stream may
+be compressed and encoded using error detection and correction codes to meet
+application-specific requirements. The GCC provided @file{libgcov} target
+library provides two functions, @code{__gcov_info_to_gcda()} and
+@code{__gcov_filename_to_gcfn()}, to generate a byte stream from a gcov
+information bock. The functions are declared in @code{#include <gcov.h>}. The
+byte stream can be deserialized by the @command{merge-stream} subcommand of the
+@command{gcov-tool} to create or update @file{.gcda} files in the host
+filesystem for the instrumented application.
+
+@subsection Tutorial
+
+This tutorial should be exercised on the host system. We will build a program
+instrumented for test coverage. The program runs an application and dumps the
+gcov information to @file{stderr} encoded as a printable character stream. The
+application simply decodes such character streams from @file{stdin} and writes
+the decoded character stream to @file{stdout} (warning: this is binary data).
+The decoded character stream is consumed by the @command{merge-stream}
+subcommand of the @command{gcov-tool} to create or update the @file{.gcda}
+files.
+
+To get started, create an empty directory. Change into the new directory.
+Then you will create the following three files in this directory
+
+@enumerate
+@item
+@file{app.h} - a header file included by @file{app.c} and @file{main.c},
+
+@item
+@file{app.c} - a source file which contains an example application, and
+
+@item
+@file{main.c} - a source file which contains the program main function and code
+to dump the gcov information.
+@end enumerate
+
+Firstly, create the header file @file{app.h} with the following content:
+
+@smallexample
+static const unsigned char a = 'a';
+
+static inline unsigned char *
+encode (unsigned char c, unsigned char buf[2])
+@{
+ buf[0] = c % 16 + a;
+ buf[1] = (c / 16) % 16 + a;
+ return buf;
+@}
+
+extern void application (void);
+@end smallexample
+
+Secondly, create the source file @file{app.c} with the following content:
+
+@smallexample
+#include "app.h"
+
+#include <stdio.h>
+
+/* The application reads a character stream encoded by encode() from stdin,
+ decodes it, and writes the decoded characters to stdout. Characters other
+ than the 16 characters 'a' to 'p' are ignored. */
+
+static int can_decode (unsigned char c)
+@{
+ return (unsigned char)(c - a) < 16;
+@}
+
+void
+application (void)
+@{
+ int first = 1;
+ int i;
+ unsigned char c;
+
+ while ((i = fgetc (stdin)) != EOF)
+ @{
+ unsigned char x = (unsigned char)i;
+
+ if (can_decode (x))
+ @{
+ if (first)
+ c = x - a;
+ else
+ fputc (c + 16 * (x - a), stdout);
+ first = !first;
+ @}
+ else
+ first = 1;
+ @}
+@}
+@end smallexample
+
+Thirdly, create the source file @file{main.c} with the following content:
+
+@smallexample
+#include "app.h"
+
+#include <gcov.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/* The start and end symbols are provided by the linker script. We use the
+ array notation to avoid issues with a potential small-data area. */
+
+extern const struct gcov_info *const __gcov_info_start[];
+extern const struct gcov_info *const __gcov_info_end[];
+
+/* This function shall produce a reliable in order byte stream to transfer the
+ gcov information from the target to the host system. */
+
+static void
+dump (const void *d, unsigned n, void *arg)
+@{
+ (void)arg;
+ const unsigned char *c = d;
+ unsigned char buf[2];
+
+ for (unsigned i = 0; i < n; ++i)
+ fwrite (encode (c[i], buf), sizeof (buf), 1, stderr);
+@}
+
+/* The filename is serialized to a gcfn data stream by the
+ __gcov_filename_to_gcfn() function. The gcfn data is used by the
+ "merge-stream" subcommand of the "gcov-tool" to figure out the filename
+ associated with the gcov information. */
+
+static void
+filename (const char *f, void *arg)
+@{
+ __gcov_filename_to_gcfn (f, dump, arg);
+@}
+
+/* The __gcov_info_to_gcda() function may have to allocate memory under
+ certain conditions. Simply try it out if it is needed for your application
+ or not. */
+
+static void *
+allocate (unsigned length, void *arg)
+@{
+ (void)arg;
+ return malloc (length);
+@}
+
+/* Dump the gcov information of all translation units. */
+
+static void
+dump_gcov_info (void)
+@{
+ const struct gcov_info *const *info = __gcov_info_start;
+ const struct gcov_info *const *end = __gcov_info_end;
+
+ /* Obfuscate variable to prevent compiler optimizations. */
+ __asm__ ("" : "+r" (info));
+
+ while (info != end)
+ @{
+ void *arg = NULL;
+ __gcov_info_to_gcda (*info, filename, dump, allocate, arg);
+ fputc ('\n', stderr);
+ ++info;
+ @}
+@}
+
+/* The main() function just runs the application and then dumps the gcov
+ information to stderr. */
+
+int
+main (void)
+@{
+ application ();
+ dump_gcov_info ();
+ return 0;
+@}
+@end smallexample
+
+If we compile @file{app.c} with test coverage and no extra profiling options,
+then a global constructor (@code{_sub_I_00100_0} here, it may have a different
+name in your environment) and destructor (@code{_sub_D_00100_1}) is used to
+register and dump the gcov information, respectively. We also see undefined
+references to @code{__gcov_init} and @code{__gcov_exit}:
+
+@smallexample
+$ gcc --coverage -c app.c
+$ nm app.o
+0000000000000000 r a
+0000000000000030 T application
+0000000000000000 t can_decode
+ U fgetc
+ U fputc
+0000000000000000 b __gcov0.application
+0000000000000038 b __gcov0.can_decode
+0000000000000000 d __gcov_.application
+00000000000000c0 d __gcov_.can_decode
+ U __gcov_exit
+ U __gcov_init
+ U __gcov_merge_add
+ U stdin
+ U stdout
+0000000000000161 t _sub_D_00100_1
+0000000000000151 t _sub_I_00100_0
+@end smallexample
+
+Compile @file{app.c} and @file{main.c} with test coverage and
+@option{-fprofile-info-section}. Now, a read-only pointer size object is
+present in the @code{.gcov_info} section and there are no undefined references
+to @code{__gcov_init} and @code{__gcov_exit}:
+
+@smallexample
+$ gcc --coverage -fprofile-info-section -c main.c
+$ gcc --coverage -fprofile-info-section -c app.c
+$ objdump -h app.o
+
+app.o: file format elf64-x86-64
+
+Sections:
+Idx Name Size VMA LMA File off Algn
+ 0 .text 00000151 0000000000000000 0000000000000000 00000040 2**0
+ CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
+ 1 .data 00000100 0000000000000000 0000000000000000 000001a0 2**5
+ CONTENTS, ALLOC, LOAD, RELOC, DATA
+ 2 .bss 00000040 0000000000000000 0000000000000000 000002a0 2**5
+ ALLOC
+ 3 .rodata 0000003c 0000000000000000 0000000000000000 000002a0 2**3
+ CONTENTS, ALLOC, LOAD, READONLY, DATA
+ 4 .gcov_info 00000008 0000000000000000 0000000000000000 000002e0 2**3
+ CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
+ 5 .comment 0000004e 0000000000000000 0000000000000000 000002e8 2**0
+ CONTENTS, READONLY
+ 6 .note.GNU-stack 00000000 0000000000000000 0000000000000000 00000336 2**0
+ CONTENTS, READONLY
+ 7 .eh_frame 00000058 0000000000000000 0000000000000000 00000338 2**3
+ CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
+@end smallexample
+
+We have to customize the program link procedure so that all the
+@code{.gcov_info} linker input sections are placed in a contiguous memory block
+with a begin and end symbol. Firstly, get the default linker script using the
+following commands (we assume a GNU linker):
+
+@smallexample
+$ ld --verbose | sed '1,/^===/d' | sed '/^===/d' > linkcmds
+@end smallexample
+
+Secondly, open the file @file{linkcmds} with a text editor and place the linker
+output section definition from the overview after the @code{.rodata} section
+definition. Link the program executable using the customized linker script:
+
+@smallexample
+$ gcc --coverage main.o app.o -T linkcmds -Wl,-Map,app.map
+@end smallexample
+
+In the linker map file @file{app.map}, we see that the linker placed the
+read-only pointer size objects of our objects files @file{main.o} and
+@file{app.o} into a contiguous memory block and provided the symbols
+@code{__gcov_info_start} and @code{__gcov_info_end}:
+
+@smallexample
+$ grep -C 1 "\.gcov_info" app.map
+
+.gcov_info 0x0000000000403ac0 0x10
+ 0x0000000000403ac0 PROVIDE (__gcov_info_start = .)
+ *(.gcov_info)
+ .gcov_info 0x0000000000403ac0 0x8 main.o
+ .gcov_info 0x0000000000403ac8 0x8 app.o
+ 0x0000000000403ad0 PROVIDE (__gcov_info_end = .)
+@end smallexample
+
+Make sure no @file{.gcda} files are present. Run the program with nothing to
+decode and dump @file{stderr} to the file @file{gcda-0.txt} (first run). Run
+the program to decode @file{gcda-0.txt} and send it to the @command{gcov-tool}
+using the @command{merge-stream} subcommand to create the @file{.gcda} files
+(second run). Run @command{gcov} to produce a report for @file{app.c}. We see
+that the first run with nothing to decode results in a partially covered
+application:
+
+@smallexample
+$ rm -f app.gcda main.gcda
+$ echo "" | ./a.out 2>gcda-0.txt
+$ ./a.out <gcda-0.txt 2>gcda-1.txt | gcov-tool merge-stream
+$ gcov -bc app.c
+File 'app.c'
+Lines executed:69.23% of 13
+Branches executed:66.67% of 6
+Taken at least once:50.00% of 6
+Calls executed:66.67% of 3
+Creating 'app.c.gcov'
+
+Lines executed:69.23% of 13
+@end smallexample
+
+Run the program to decode @file{gcda-1.txt} and send it to the
+@command{gcov-tool} using the @command{merge-stream} subcommand to update the
+@file{.gcda} files. Run @command{gcov} to produce a report for @file{app.c}.
+Since the second run decoded the gcov information of the first run, we have now
+a fully covered application:
+
+@smallexample
+$ ./a.out <gcda-1.txt 2>gcda-2.txt | gcov-tool merge-stream
+$ gcov -bc app.c
+File 'app.c'
+Lines executed:100.00% of 13
+Branches executed:100.00% of 6
+Taken at least once:100.00% of 6
+Calls executed:100.00% of 3
+Creating 'app.c.gcov'
+
+Lines executed:100.00% of 13
+@end smallexample
+
+@subsection System Initialization Caveats
+
+The gcov information of a translation unit consists of several global data
+structures. For example, the instrumented code may update program flow graph
+edge counters in a zero-initialized data structure. It is safe to run
+instrumented code before the zero-initialized data is cleared to zero. The
+coverage information obtained before the zero-initialized data is cleared to
+zero is unusable. Dumping the gcov information using
+@code{__gcov_info_to_gcda()} before the zero-initialized data is cleared to
+zero or the initialized data is loaded, is undefined behaviour. Clearing the
+zero-initialized data to zero through a function instrumented for profiling or
+test coverage is undefined behaviour, since it may produce inconsistent program
+flow graph edge counters for example.
--- /dev/null
+@c Copyright (C) 2004-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@c ---------------------------------------------------------------------
+@c GENERIC
+@c ---------------------------------------------------------------------
+
+@node GENERIC
+@chapter GENERIC
+@cindex GENERIC
+
+The purpose of GENERIC is simply to provide a
+language-independent way of representing an entire function in
+trees. To this end, it was necessary to add a few new tree codes
+to the back end, but almost everything was already there. If you
+can express it with the codes in @code{gcc/tree.def}, it's
+GENERIC@.
+
+Early on, there was a great deal of debate about how to think
+about statements in a tree IL@. In GENERIC, a statement is
+defined as any expression whose value, if any, is ignored. A
+statement will always have @code{TREE_SIDE_EFFECTS} set (or it
+will be discarded), but a non-statement expression may also have
+side effects. A @code{CALL_EXPR}, for instance.
+
+It would be possible for some local optimizations to work on the
+GENERIC form of a function; indeed, the adapted tree inliner
+works fine on GENERIC, but the current compiler performs inlining
+after lowering to GIMPLE (a restricted form described in the next
+section). Indeed, currently the frontends perform this lowering
+before handing off to @code{tree_rest_of_compilation}, but this
+seems inelegant.
+
+@menu
+* Deficiencies:: Topics not yet covered in this document.
+* Tree overview:: All about @code{tree}s.
+* Types:: Fundamental and aggregate types.
+* Declarations:: Type declarations and variables.
+* Attributes:: Declaration and type attributes.
+* Expressions: Expression trees. Operating on data.
+* Statements:: Control flow and related trees.
+* Functions:: Function bodies, linkage, and other aspects.
+* Language-dependent trees:: Topics and trees specific to language front ends.
+* C and C++ Trees:: Trees specific to C and C++.
+@end menu
+
+@c ---------------------------------------------------------------------
+@c Deficiencies
+@c ---------------------------------------------------------------------
+
+@node Deficiencies
+@section Deficiencies
+
+@c The spelling of "incomplet" and "incorrekt" below is intentional.
+There are many places in which this document is incomplet and incorrekt.
+It is, as of yet, only @emph{preliminary} documentation.
+
+@c ---------------------------------------------------------------------
+@c Overview
+@c ---------------------------------------------------------------------
+
+@node Tree overview
+@section Overview
+@cindex tree
+@findex TREE_CODE
+
+The central data structure used by the internal representation is the
+@code{tree}. These nodes, while all of the C type @code{tree}, are of
+many varieties. A @code{tree} is a pointer type, but the object to
+which it points may be of a variety of types. From this point forward,
+we will refer to trees in ordinary type, rather than in @code{this
+font}, except when talking about the actual C type @code{tree}.
+
+You can tell what kind of node a particular tree is by using the
+@code{TREE_CODE} macro. Many, many macros take trees as input and
+return trees as output. However, most macros require a certain kind of
+tree node as input. In other words, there is a type-system for trees,
+but it is not reflected in the C type-system.
+
+For safety, it is useful to configure GCC with @option{--enable-checking}.
+Although this results in a significant performance penalty (since all
+tree types are checked at run-time), and is therefore inappropriate in a
+release version, it is extremely helpful during the development process.
+
+Many macros behave as predicates. Many, although not all, of these
+predicates end in @samp{_P}. Do not rely on the result type of these
+macros being of any particular type. You may, however, rely on the fact
+that the type can be compared to @code{0}, so that statements like
+@smallexample
+if (TEST_P (t) && !TEST_P (y))
+ x = 1;
+@end smallexample
+@noindent
+and
+@smallexample
+int i = (TEST_P (t) != 0);
+@end smallexample
+@noindent
+are legal. Macros that return @code{int} values now may be changed to
+return @code{tree} values, or other pointers in the future. Even those
+that continue to return @code{int} may return multiple nonzero codes
+where previously they returned only zero and one. Therefore, you should
+not write code like
+@smallexample
+if (TEST_P (t) == 1)
+@end smallexample
+@noindent
+as this code is not guaranteed to work correctly in the future.
+
+You should not take the address of values returned by the macros or
+functions described here. In particular, no guarantee is given that the
+values are lvalues.
+
+In general, the names of macros are all in uppercase, while the names of
+functions are entirely in lowercase. There are rare exceptions to this
+rule. You should assume that any macro or function whose name is made
+up entirely of uppercase letters may evaluate its arguments more than
+once. You may assume that a macro or function whose name is made up
+entirely of lowercase letters will evaluate its arguments only once.
+
+The @code{error_mark_node} is a special tree. Its tree code is
+@code{ERROR_MARK}, but since there is only ever one node with that code,
+the usual practice is to compare the tree against
+@code{error_mark_node}. (This test is just a test for pointer
+equality.) If an error has occurred during front-end processing the
+flag @code{errorcount} will be set. If the front end has encountered
+code it cannot handle, it will issue a message to the user and set
+@code{sorrycount}. When these flags are set, any macro or function
+which normally returns a tree of a particular kind may instead return
+the @code{error_mark_node}. Thus, if you intend to do any processing of
+erroneous code, you must be prepared to deal with the
+@code{error_mark_node}.
+
+Occasionally, a particular tree slot (like an operand to an expression,
+or a particular field in a declaration) will be referred to as
+``reserved for the back end''. These slots are used to store RTL when
+the tree is converted to RTL for use by the GCC back end. However, if
+that process is not taking place (e.g., if the front end is being hooked
+up to an intelligent editor), then those slots may be used by the
+back end presently in use.
+
+If you encounter situations that do not match this documentation, such
+as tree nodes of types not mentioned here, or macros documented to
+return entities of a particular kind that instead return entities of
+some different kind, you have found a bug, either in the front end or in
+the documentation. Please report these bugs as you would any other
+bug.
+
+@menu
+* Macros and Functions::Macros and functions that can be used with all trees.
+* Identifiers:: The names of things.
+* Containers:: Lists and vectors.
+@end menu
+
+@c ---------------------------------------------------------------------
+@c Trees
+@c ---------------------------------------------------------------------
+
+@node Macros and Functions
+@subsection Trees
+@cindex tree
+@findex TREE_CHAIN
+@findex TREE_TYPE
+
+All GENERIC trees have two fields in common. First, @code{TREE_CHAIN}
+is a pointer that can be used as a singly-linked list to other trees.
+The other is @code{TREE_TYPE}. Many trees store the type of an
+expression or declaration in this field.
+
+These are some other functions for handling trees:
+
+@ftable @code
+
+@item tree_size
+Return the number of bytes a tree takes.
+
+@item build0
+@itemx build1
+@itemx build2
+@itemx build3
+@itemx build4
+@itemx build5
+@itemx build6
+
+These functions build a tree and supply values to put in each
+parameter. The basic signature is @samp{@w{code, type, [operands]}}.
+@code{code} is the @code{TREE_CODE}, and @code{type} is a tree
+representing the @code{TREE_TYPE}. These are followed by the
+operands, each of which is also a tree.
+
+@end ftable
+
+
+@c ---------------------------------------------------------------------
+@c Identifiers
+@c ---------------------------------------------------------------------
+
+@node Identifiers
+@subsection Identifiers
+@cindex identifier
+@cindex name
+@tindex IDENTIFIER_NODE
+
+An @code{IDENTIFIER_NODE} represents a slightly more general concept
+than the standard C or C++ concept of identifier. In particular, an
+@code{IDENTIFIER_NODE} may contain a @samp{$}, or other extraordinary
+characters.
+
+There are never two distinct @code{IDENTIFIER_NODE}s representing the
+same identifier. Therefore, you may use pointer equality to compare
+@code{IDENTIFIER_NODE}s, rather than using a routine like
+@code{strcmp}. Use @code{get_identifier} to obtain the unique
+@code{IDENTIFIER_NODE} for a supplied string.
+
+You can use the following macros to access identifiers:
+@ftable @code
+@item IDENTIFIER_POINTER
+The string represented by the identifier, represented as a
+@code{char*}. This string is always @code{NUL}-terminated, and contains
+no embedded @code{NUL} characters.
+
+@item IDENTIFIER_LENGTH
+The length of the string returned by @code{IDENTIFIER_POINTER}, not
+including the trailing @code{NUL}. This value of
+@code{IDENTIFIER_LENGTH (x)} is always the same as @code{strlen
+(IDENTIFIER_POINTER (x))}.
+
+@item IDENTIFIER_OPNAME_P
+This predicate holds if the identifier represents the name of an
+overloaded operator. In this case, you should not depend on the
+contents of either the @code{IDENTIFIER_POINTER} or the
+@code{IDENTIFIER_LENGTH}.
+
+@item IDENTIFIER_TYPENAME_P
+This predicate holds if the identifier represents the name of a
+user-defined conversion operator. In this case, the @code{TREE_TYPE} of
+the @code{IDENTIFIER_NODE} holds the type to which the conversion
+operator converts.
+
+@end ftable
+
+@c ---------------------------------------------------------------------
+@c Containers
+@c ---------------------------------------------------------------------
+
+@node Containers
+@subsection Containers
+@cindex container
+@cindex list
+@cindex vector
+@tindex TREE_LIST
+@tindex TREE_VEC
+@findex TREE_PURPOSE
+@findex TREE_VALUE
+@findex TREE_VEC_LENGTH
+@findex TREE_VEC_ELT
+
+Two common container data structures can be represented directly with
+tree nodes. A @code{TREE_LIST} is a singly linked list containing two
+trees per node. These are the @code{TREE_PURPOSE} and @code{TREE_VALUE}
+of each node. (Often, the @code{TREE_PURPOSE} contains some kind of
+tag, or additional information, while the @code{TREE_VALUE} contains the
+majority of the payload. In other cases, the @code{TREE_PURPOSE} is
+simply @code{NULL_TREE}, while in still others both the
+@code{TREE_PURPOSE} and @code{TREE_VALUE} are of equal stature.) Given
+one @code{TREE_LIST} node, the next node is found by following the
+@code{TREE_CHAIN}. If the @code{TREE_CHAIN} is @code{NULL_TREE}, then
+you have reached the end of the list.
+
+A @code{TREE_VEC} is a simple vector. The @code{TREE_VEC_LENGTH} is an
+integer (not a tree) giving the number of nodes in the vector. The
+nodes themselves are accessed using the @code{TREE_VEC_ELT} macro, which
+takes two arguments. The first is the @code{TREE_VEC} in question; the
+second is an integer indicating which element in the vector is desired.
+The elements are indexed from zero.
+
+@c ---------------------------------------------------------------------
+@c Types
+@c ---------------------------------------------------------------------
+
+@node Types
+@section Types
+@cindex type
+@cindex pointer
+@cindex reference
+@cindex fundamental type
+@cindex array
+@tindex VOID_TYPE
+@tindex INTEGER_TYPE
+@tindex TYPE_MIN_VALUE
+@tindex TYPE_MAX_VALUE
+@tindex REAL_TYPE
+@tindex FIXED_POINT_TYPE
+@tindex COMPLEX_TYPE
+@tindex ENUMERAL_TYPE
+@tindex BOOLEAN_TYPE
+@tindex POINTER_TYPE
+@tindex REFERENCE_TYPE
+@tindex FUNCTION_TYPE
+@tindex METHOD_TYPE
+@tindex ARRAY_TYPE
+@tindex RECORD_TYPE
+@tindex UNION_TYPE
+@tindex OPAQUE_TYPE
+@tindex UNKNOWN_TYPE
+@tindex OFFSET_TYPE
+@findex TYPE_UNQUALIFIED
+@findex TYPE_QUAL_CONST
+@findex TYPE_QUAL_VOLATILE
+@findex TYPE_QUAL_RESTRICT
+@findex TYPE_MAIN_VARIANT
+@cindex qualified type
+@findex TYPE_SIZE
+@findex TYPE_ALIGN
+@findex TYPE_PRECISION
+@findex TYPE_ARG_TYPES
+@findex TYPE_METHOD_BASETYPE
+@findex TYPE_OFFSET_BASETYPE
+@findex TREE_TYPE
+@findex TYPE_CONTEXT
+@findex TYPE_NAME
+@findex TYPENAME_TYPE_FULLNAME
+@findex TYPE_FIELDS
+@findex TYPE_CANONICAL
+@findex TYPE_STRUCTURAL_EQUALITY_P
+@findex SET_TYPE_STRUCTURAL_EQUALITY
+
+All types have corresponding tree nodes. However, you should not assume
+that there is exactly one tree node corresponding to each type. There
+are often multiple nodes corresponding to the same type.
+
+For the most part, different kinds of types have different tree codes.
+(For example, pointer types use a @code{POINTER_TYPE} code while arrays
+use an @code{ARRAY_TYPE} code.) However, pointers to member functions
+use the @code{RECORD_TYPE} code. Therefore, when writing a
+@code{switch} statement that depends on the code associated with a
+particular type, you should take care to handle pointers to member
+functions under the @code{RECORD_TYPE} case label.
+
+The following functions and macros deal with cv-qualification of types:
+@ftable @code
+@item TYPE_MAIN_VARIANT
+This macro returns the unqualified version of a type. It may be applied
+to an unqualified type, but it is not always the identity function in
+that case.
+@end ftable
+
+A few other macros and functions are usable with all types:
+@ftable @code
+@item TYPE_SIZE
+The number of bits required to represent the type, represented as an
+@code{INTEGER_CST}. For an incomplete type, @code{TYPE_SIZE} will be
+@code{NULL_TREE}.
+
+@item TYPE_ALIGN
+The alignment of the type, in bits, represented as an @code{int}.
+
+@item TYPE_NAME
+This macro returns a declaration (in the form of a @code{TYPE_DECL}) for
+the type. (Note this macro does @emph{not} return an
+@code{IDENTIFIER_NODE}, as you might expect, given its name!) You can
+look at the @code{DECL_NAME} of the @code{TYPE_DECL} to obtain the
+actual name of the type. The @code{TYPE_NAME} will be @code{NULL_TREE}
+for a type that is not a built-in type, the result of a typedef, or a
+named class type.
+
+@item TYPE_CANONICAL
+This macro returns the ``canonical'' type for the given type
+node. Canonical types are used to improve performance in the C++ and
+Objective-C++ front ends by allowing efficient comparison between two
+type nodes in @code{same_type_p}: if the @code{TYPE_CANONICAL} values
+of the types are equal, the types are equivalent; otherwise, the types
+are not equivalent. The notion of equivalence for canonical types is
+the same as the notion of type equivalence in the language itself. For
+instance,
+
+When @code{TYPE_CANONICAL} is @code{NULL_TREE}, there is no canonical
+type for the given type node. In this case, comparison between this
+type and any other type requires the compiler to perform a deep,
+``structural'' comparison to see if the two type nodes have the same
+form and properties.
+
+The canonical type for a node is always the most fundamental type in
+the equivalence class of types. For instance, @code{int} is its own
+canonical type. A typedef @code{I} of @code{int} will have @code{int}
+as its canonical type. Similarly, @code{I*}@ and a typedef @code{IP}@
+(defined to @code{I*}) will has @code{int*} as their canonical
+type. When building a new type node, be sure to set
+@code{TYPE_CANONICAL} to the appropriate canonical type. If the new
+type is a compound type (built from other types), and any of those
+other types require structural equality, use
+@code{SET_TYPE_STRUCTURAL_EQUALITY} to ensure that the new type also
+requires structural equality. Finally, if for some reason you cannot
+guarantee that @code{TYPE_CANONICAL} will point to the canonical type,
+use @code{SET_TYPE_STRUCTURAL_EQUALITY} to make sure that the new
+type--and any type constructed based on it--requires structural
+equality. If you suspect that the canonical type system is
+miscomparing types, pass @code{--param verify-canonical-types=1} to
+the compiler or configure with @code{--enable-checking} to force the
+compiler to verify its canonical-type comparisons against the
+structural comparisons; the compiler will then print any warnings if
+the canonical types miscompare.
+
+@item TYPE_STRUCTURAL_EQUALITY_P
+This predicate holds when the node requires structural equality
+checks, e.g., when @code{TYPE_CANONICAL} is @code{NULL_TREE}.
+
+@item SET_TYPE_STRUCTURAL_EQUALITY
+This macro states that the type node it is given requires structural
+equality checks, e.g., it sets @code{TYPE_CANONICAL} to
+@code{NULL_TREE}.
+
+@item same_type_p
+This predicate takes two types as input, and holds if they are the same
+type. For example, if one type is a @code{typedef} for the other, or
+both are @code{typedef}s for the same type. This predicate also holds if
+the two trees given as input are simply copies of one another; i.e.,
+there is no difference between them at the source level, but, for
+whatever reason, a duplicate has been made in the representation. You
+should never use @code{==} (pointer equality) to compare types; always
+use @code{same_type_p} instead.
+@end ftable
+
+Detailed below are the various kinds of types, and the macros that can
+be used to access them. Although other kinds of types are used
+elsewhere in G++, the types described here are the only ones that you
+will encounter while examining the intermediate representation.
+
+@table @code
+@item VOID_TYPE
+Used to represent the @code{void} type.
+
+@item INTEGER_TYPE
+Used to represent the various integral types, including @code{char},
+@code{short}, @code{int}, @code{long}, and @code{long long}. This code
+is not used for enumeration types, nor for the @code{bool} type.
+The @code{TYPE_PRECISION} is the number of bits used in
+the representation, represented as an @code{unsigned int}. (Note that
+in the general case this is not the same value as @code{TYPE_SIZE};
+suppose that there were a 24-bit integer type, but that alignment
+requirements for the ABI required 32-bit alignment. Then,
+@code{TYPE_SIZE} would be an @code{INTEGER_CST} for 32, while
+@code{TYPE_PRECISION} would be 24.) The integer type is unsigned if
+@code{TYPE_UNSIGNED} holds; otherwise, it is signed.
+
+The @code{TYPE_MIN_VALUE} is an @code{INTEGER_CST} for the smallest
+integer that may be represented by this type. Similarly, the
+@code{TYPE_MAX_VALUE} is an @code{INTEGER_CST} for the largest integer
+that may be represented by this type.
+
+@item REAL_TYPE
+Used to represent the @code{float}, @code{double}, and @code{long
+double} types. The number of bits in the floating-point representation
+is given by @code{TYPE_PRECISION}, as in the @code{INTEGER_TYPE} case.
+
+@item FIXED_POINT_TYPE
+Used to represent the @code{short _Fract}, @code{_Fract}, @code{long
+_Fract}, @code{long long _Fract}, @code{short _Accum}, @code{_Accum},
+@code{long _Accum}, and @code{long long _Accum} types. The number of bits
+in the fixed-point representation is given by @code{TYPE_PRECISION},
+as in the @code{INTEGER_TYPE} case. There may be padding bits, fractional
+bits and integral bits. The number of fractional bits is given by
+@code{TYPE_FBIT}, and the number of integral bits is given by @code{TYPE_IBIT}.
+The fixed-point type is unsigned if @code{TYPE_UNSIGNED} holds; otherwise,
+it is signed.
+The fixed-point type is saturating if @code{TYPE_SATURATING} holds; otherwise,
+it is not saturating.
+
+@item COMPLEX_TYPE
+Used to represent GCC built-in @code{__complex__} data types. The
+@code{TREE_TYPE} is the type of the real and imaginary parts.
+
+@item ENUMERAL_TYPE
+Used to represent an enumeration type. The @code{TYPE_PRECISION} gives
+(as an @code{int}), the number of bits used to represent the type. If
+there are no negative enumeration constants, @code{TYPE_UNSIGNED} will
+hold. The minimum and maximum enumeration constants may be obtained
+with @code{TYPE_MIN_VALUE} and @code{TYPE_MAX_VALUE}, respectively; each
+of these macros returns an @code{INTEGER_CST}.
+
+The actual enumeration constants themselves may be obtained by looking
+at the @code{TYPE_VALUES}. This macro will return a @code{TREE_LIST},
+containing the constants. The @code{TREE_PURPOSE} of each node will be
+an @code{IDENTIFIER_NODE} giving the name of the constant; the
+@code{TREE_VALUE} will be an @code{INTEGER_CST} giving the value
+assigned to that constant. These constants will appear in the order in
+which they were declared. The @code{TREE_TYPE} of each of these
+constants will be the type of enumeration type itself.
+
+@item OPAQUE_TYPE
+Used for things that have a @code{MODE_OPAQUE} mode class in the
+backend. Opaque types have a size and precision, and can be held in
+memory or registers. They are used when we do not want the compiler to
+make assumptions about the availability of other operations as would
+happen with integer types.
+
+@item BOOLEAN_TYPE
+Used to represent the @code{bool} type.
+
+@item POINTER_TYPE
+Used to represent pointer types, and pointer to data member types. The
+@code{TREE_TYPE} gives the type to which this type points.
+
+@item REFERENCE_TYPE
+Used to represent reference types. The @code{TREE_TYPE} gives the type
+to which this type refers.
+
+@item FUNCTION_TYPE
+Used to represent the type of non-member functions and of static member
+functions. The @code{TREE_TYPE} gives the return type of the function.
+The @code{TYPE_ARG_TYPES} are a @code{TREE_LIST} of the argument types.
+The @code{TREE_VALUE} of each node in this list is the type of the
+corresponding argument; the @code{TREE_PURPOSE} is an expression for the
+default argument value, if any. If the last node in the list is
+@code{void_list_node} (a @code{TREE_LIST} node whose @code{TREE_VALUE}
+is the @code{void_type_node}), then functions of this type do not take
+variable arguments. Otherwise, they do take a variable number of
+arguments.
+
+Note that in C (but not in C++) a function declared like @code{void f()}
+is an unprototyped function taking a variable number of arguments; the
+@code{TYPE_ARG_TYPES} of such a function will be @code{NULL}.
+
+@item METHOD_TYPE
+Used to represent the type of a non-static member function. Like a
+@code{FUNCTION_TYPE}, the return type is given by the @code{TREE_TYPE}.
+The type of @code{*this}, i.e., the class of which functions of this
+type are a member, is given by the @code{TYPE_METHOD_BASETYPE}. The
+@code{TYPE_ARG_TYPES} is the parameter list, as for a
+@code{FUNCTION_TYPE}, and includes the @code{this} argument.
+
+@item ARRAY_TYPE
+Used to represent array types. The @code{TREE_TYPE} gives the type of
+the elements in the array. If the array-bound is present in the type,
+the @code{TYPE_DOMAIN} is an @code{INTEGER_TYPE} whose
+@code{TYPE_MIN_VALUE} and @code{TYPE_MAX_VALUE} will be the lower and
+upper bounds of the array, respectively. The @code{TYPE_MIN_VALUE} will
+always be an @code{INTEGER_CST} for zero, while the
+@code{TYPE_MAX_VALUE} will be one less than the number of elements in
+the array, i.e., the highest value which may be used to index an element
+in the array.
+
+@item RECORD_TYPE
+Used to represent @code{struct} and @code{class} types, as well as
+pointers to member functions and similar constructs in other languages.
+@code{TYPE_FIELDS} contains the items contained in this type, each of
+which can be a @code{FIELD_DECL}, @code{VAR_DECL}, @code{CONST_DECL}, or
+@code{TYPE_DECL}. You may not make any assumptions about the ordering
+of the fields in the type or whether one or more of them overlap.
+
+@item UNION_TYPE
+Used to represent @code{union} types. Similar to @code{RECORD_TYPE}
+except that all @code{FIELD_DECL} nodes in @code{TYPE_FIELD} start at
+bit position zero.
+
+@item QUAL_UNION_TYPE
+Used to represent part of a variant record in Ada. Similar to
+@code{UNION_TYPE} except that each @code{FIELD_DECL} has a
+@code{DECL_QUALIFIER} field, which contains a boolean expression that
+indicates whether the field is present in the object. The type will only
+have one field, so each field's @code{DECL_QUALIFIER} is only evaluated
+if none of the expressions in the previous fields in @code{TYPE_FIELDS}
+are nonzero. Normally these expressions will reference a field in the
+outer object using a @code{PLACEHOLDER_EXPR}.
+
+@item LANG_TYPE
+This node is used to represent a language-specific type. The front
+end must handle it.
+
+@item OFFSET_TYPE
+This node is used to represent a pointer-to-data member. For a data
+member @code{X::m} the @code{TYPE_OFFSET_BASETYPE} is @code{X} and the
+@code{TREE_TYPE} is the type of @code{m}.
+
+@end table
+
+There are variables whose values represent some of the basic types.
+These include:
+@table @code
+@item void_type_node
+A node for @code{void}.
+
+@item integer_type_node
+A node for @code{int}.
+
+@item unsigned_type_node.
+A node for @code{unsigned int}.
+
+@item char_type_node.
+A node for @code{char}.
+@end table
+@noindent
+It may sometimes be useful to compare one of these variables with a type
+in hand, using @code{same_type_p}.
+
+@c ---------------------------------------------------------------------
+@c Declarations
+@c ---------------------------------------------------------------------
+
+@node Declarations
+@section Declarations
+@cindex declaration
+@cindex variable
+@cindex type declaration
+@tindex LABEL_DECL
+@tindex CONST_DECL
+@tindex TYPE_DECL
+@tindex VAR_DECL
+@tindex PARM_DECL
+@tindex DEBUG_EXPR_DECL
+@tindex FIELD_DECL
+@tindex NAMESPACE_DECL
+@tindex RESULT_DECL
+@tindex TEMPLATE_DECL
+@tindex THUNK_DECL
+@findex THUNK_DELTA
+@findex DECL_INITIAL
+@findex DECL_SIZE
+@findex DECL_ALIGN
+@findex DECL_EXTERNAL
+
+This section covers the various kinds of declarations that appear in the
+internal representation, except for declarations of functions
+(represented by @code{FUNCTION_DECL} nodes), which are described in
+@ref{Functions}.
+
+@menu
+* Working with declarations:: Macros and functions that work on
+declarations.
+* Internal structure:: How declaration nodes are represented.
+@end menu
+
+@node Working with declarations
+@subsection Working with declarations
+
+Some macros can be used with any kind of declaration. These include:
+@ftable @code
+@item DECL_NAME
+This macro returns an @code{IDENTIFIER_NODE} giving the name of the
+entity.
+
+@item TREE_TYPE
+This macro returns the type of the entity declared.
+
+@item EXPR_FILENAME
+This macro returns the name of the file in which the entity was
+declared, as a @code{char*}. For an entity declared implicitly by the
+compiler (like @code{__builtin_memcpy}), this will be the string
+@code{"<internal>"}.
+
+@item EXPR_LINENO
+This macro returns the line number at which the entity was declared, as
+an @code{int}.
+
+@item DECL_ARTIFICIAL
+This predicate holds if the declaration was implicitly generated by the
+compiler. For example, this predicate will hold of an implicitly
+declared member function, or of the @code{TYPE_DECL} implicitly
+generated for a class type. Recall that in C++ code like:
+@smallexample
+struct S @{@};
+@end smallexample
+@noindent
+is roughly equivalent to C code like:
+@smallexample
+struct S @{@};
+typedef struct S S;
+@end smallexample
+The implicitly generated @code{typedef} declaration is represented by a
+@code{TYPE_DECL} for which @code{DECL_ARTIFICIAL} holds.
+
+@end ftable
+
+The various kinds of declarations include:
+@table @code
+@item LABEL_DECL
+These nodes are used to represent labels in function bodies. For more
+information, see @ref{Functions}. These nodes only appear in block
+scopes.
+
+@item CONST_DECL
+These nodes are used to represent enumeration constants. The value of
+the constant is given by @code{DECL_INITIAL} which will be an
+@code{INTEGER_CST} with the same type as the @code{TREE_TYPE} of the
+@code{CONST_DECL}, i.e., an @code{ENUMERAL_TYPE}.
+
+@item RESULT_DECL
+These nodes represent the value returned by a function. When a value is
+assigned to a @code{RESULT_DECL}, that indicates that the value should
+be returned, via bitwise copy, by the function. You can use
+@code{DECL_SIZE} and @code{DECL_ALIGN} on a @code{RESULT_DECL}, just as
+with a @code{VAR_DECL}.
+
+@item TYPE_DECL
+These nodes represent @code{typedef} declarations. The @code{TREE_TYPE}
+is the type declared to have the name given by @code{DECL_NAME}. In
+some cases, there is no associated name.
+
+@item VAR_DECL
+These nodes represent variables with namespace or block scope, as well
+as static data members. The @code{DECL_SIZE} and @code{DECL_ALIGN} are
+analogous to @code{TYPE_SIZE} and @code{TYPE_ALIGN}. For a declaration,
+you should always use the @code{DECL_SIZE} and @code{DECL_ALIGN} rather
+than the @code{TYPE_SIZE} and @code{TYPE_ALIGN} given by the
+@code{TREE_TYPE}, since special attributes may have been applied to the
+variable to give it a particular size and alignment. You may use the
+predicates @code{DECL_THIS_STATIC} or @code{DECL_THIS_EXTERN} to test
+whether the storage class specifiers @code{static} or @code{extern} were
+used to declare a variable.
+
+If this variable is initialized (but does not require a constructor),
+the @code{DECL_INITIAL} will be an expression for the initializer. The
+initializer should be evaluated, and a bitwise copy into the variable
+performed. If the @code{DECL_INITIAL} is the @code{error_mark_node},
+there is an initializer, but it is given by an explicit statement later
+in the code; no bitwise copy is required.
+
+GCC provides an extension that allows either automatic variables, or
+global variables, to be placed in particular registers. This extension
+is being used for a particular @code{VAR_DECL} if @code{DECL_REGISTER}
+holds for the @code{VAR_DECL}, and if @code{DECL_ASSEMBLER_NAME} is not
+equal to @code{DECL_NAME}. In that case, @code{DECL_ASSEMBLER_NAME} is
+the name of the register into which the variable will be placed.
+
+@item PARM_DECL
+Used to represent a parameter to a function. Treat these nodes
+similarly to @code{VAR_DECL} nodes. These nodes only appear in the
+@code{DECL_ARGUMENTS} for a @code{FUNCTION_DECL}.
+
+The @code{DECL_ARG_TYPE} for a @code{PARM_DECL} is the type that will
+actually be used when a value is passed to this function. It may be a
+wider type than the @code{TREE_TYPE} of the parameter; for example, the
+ordinary type might be @code{short} while the @code{DECL_ARG_TYPE} is
+@code{int}.
+
+@item DEBUG_EXPR_DECL
+Used to represent an anonymous debug-information temporary created to
+hold an expression as it is optimized away, so that its value can be
+referenced in debug bind statements.
+
+@item FIELD_DECL
+These nodes represent non-static data members. The @code{DECL_SIZE} and
+@code{DECL_ALIGN} behave as for @code{VAR_DECL} nodes.
+The position of the field within the parent record is specified by a
+combination of three attributes. @code{DECL_FIELD_OFFSET} is the position,
+counting in bytes, of the @code{DECL_OFFSET_ALIGN}-bit sized word containing
+the bit of the field closest to the beginning of the structure.
+@code{DECL_FIELD_BIT_OFFSET} is the bit offset of the first bit of the field
+within this word; this may be nonzero even for fields that are not bit-fields,
+since @code{DECL_OFFSET_ALIGN} may be greater than the natural alignment
+of the field's type.
+
+If @code{DECL_C_BIT_FIELD} holds, this field is a bit-field. In a bit-field,
+@code{DECL_BIT_FIELD_TYPE} also contains the type that was originally
+specified for it, while DECL_TYPE may be a modified type with lesser precision,
+according to the size of the bit field.
+
+@item NAMESPACE_DECL
+Namespaces provide a name hierarchy for other declarations. They
+appear in the @code{DECL_CONTEXT} of other @code{_DECL} nodes.
+
+@end table
+
+@node Internal structure
+@subsection Internal structure
+
+@code{DECL} nodes are represented internally as a hierarchy of
+structures.
+
+@menu
+* Current structure hierarchy:: The current DECL node structure
+hierarchy.
+* Adding new DECL node types:: How to add a new DECL node to a
+frontend.
+@end menu
+
+@node Current structure hierarchy
+@subsubsection Current structure hierarchy
+
+@table @code
+
+@item struct tree_decl_minimal
+This is the minimal structure to inherit from in order for common
+@code{DECL} macros to work. The fields it contains are a unique ID,
+source location, context, and name.
+
+@item struct tree_decl_common
+This structure inherits from @code{struct tree_decl_minimal}. It
+contains fields that most @code{DECL} nodes need, such as a field to
+store alignment, machine mode, size, and attributes.
+
+@item struct tree_field_decl
+This structure inherits from @code{struct tree_decl_common}. It is
+used to represent @code{FIELD_DECL}.
+
+@item struct tree_label_decl
+This structure inherits from @code{struct tree_decl_common}. It is
+used to represent @code{LABEL_DECL}.
+
+@item struct tree_translation_unit_decl
+This structure inherits from @code{struct tree_decl_common}. It is
+used to represent @code{TRANSLATION_UNIT_DECL}.
+
+@item struct tree_decl_with_rtl
+This structure inherits from @code{struct tree_decl_common}. It
+contains a field to store the low-level RTL associated with a
+@code{DECL} node.
+
+@item struct tree_result_decl
+This structure inherits from @code{struct tree_decl_with_rtl}. It is
+used to represent @code{RESULT_DECL}.
+
+@item struct tree_const_decl
+This structure inherits from @code{struct tree_decl_with_rtl}. It is
+used to represent @code{CONST_DECL}.
+
+@item struct tree_parm_decl
+This structure inherits from @code{struct tree_decl_with_rtl}. It is
+used to represent @code{PARM_DECL}.
+
+@item struct tree_decl_with_vis
+This structure inherits from @code{struct tree_decl_with_rtl}. It
+contains fields necessary to store visibility information, as well as
+a section name and assembler name.
+
+@item struct tree_var_decl
+This structure inherits from @code{struct tree_decl_with_vis}. It is
+used to represent @code{VAR_DECL}.
+
+@item struct tree_function_decl
+This structure inherits from @code{struct tree_decl_with_vis}. It is
+used to represent @code{FUNCTION_DECL}.
+
+@end table
+@node Adding new DECL node types
+@subsubsection Adding new DECL node types
+
+Adding a new @code{DECL} tree consists of the following steps
+
+@table @asis
+
+@item Add a new tree code for the @code{DECL} node
+For language specific @code{DECL} nodes, there is a @file{.def} file
+in each frontend directory where the tree code should be added.
+For @code{DECL} nodes that are part of the middle-end, the code should
+be added to @file{tree.def}.
+
+@item Create a new structure type for the @code{DECL} node
+These structures should inherit from one of the existing structures in
+the language hierarchy by using that structure as the first member.
+
+@smallexample
+struct tree_foo_decl
+@{
+ struct tree_decl_with_vis common;
+@}
+@end smallexample
+
+Would create a structure name @code{tree_foo_decl} that inherits from
+@code{struct tree_decl_with_vis}.
+
+For language specific @code{DECL} nodes, this new structure type
+should go in the appropriate @file{.h} file.
+For @code{DECL} nodes that are part of the middle-end, the structure
+type should go in @file{tree.h}.
+
+@item Add a member to the tree structure enumerator for the node
+For garbage collection and dynamic checking purposes, each @code{DECL}
+node structure type is required to have a unique enumerator value
+specified with it.
+For language specific @code{DECL} nodes, this new enumerator value
+should go in the appropriate @file{.def} file.
+For @code{DECL} nodes that are part of the middle-end, the enumerator
+values are specified in @file{treestruct.def}.
+
+@item Update @code{union tree_node}
+In order to make your new structure type usable, it must be added to
+@code{union tree_node}.
+For language specific @code{DECL} nodes, a new entry should be added
+to the appropriate @file{.h} file of the form
+@smallexample
+ struct tree_foo_decl GTY ((tag ("TS_VAR_DECL"))) foo_decl;
+@end smallexample
+For @code{DECL} nodes that are part of the middle-end, the additional
+member goes directly into @code{union tree_node} in @file{tree.h}.
+
+@item Update dynamic checking info
+In order to be able to check whether accessing a named portion of
+@code{union tree_node} is legal, and whether a certain @code{DECL} node
+contains one of the enumerated @code{DECL} node structures in the
+hierarchy, a simple lookup table is used.
+This lookup table needs to be kept up to date with the tree structure
+hierarchy, or else checking and containment macros will fail
+inappropriately.
+
+For language specific @code{DECL} nodes, there is an @code{init_ts}
+function in an appropriate @file{.c} file, which initializes the lookup
+table.
+Code setting up the table for new @code{DECL} nodes should be added
+there.
+For each @code{DECL} tree code and enumerator value representing a
+member of the inheritance hierarchy, the table should contain 1 if
+that tree code inherits (directly or indirectly) from that member.
+Thus, a @code{FOO_DECL} node derived from @code{struct decl_with_rtl},
+and enumerator value @code{TS_FOO_DECL}, would be set up as follows
+@smallexample
+tree_contains_struct[FOO_DECL][TS_FOO_DECL] = 1;
+tree_contains_struct[FOO_DECL][TS_DECL_WRTL] = 1;
+tree_contains_struct[FOO_DECL][TS_DECL_COMMON] = 1;
+tree_contains_struct[FOO_DECL][TS_DECL_MINIMAL] = 1;
+@end smallexample
+
+For @code{DECL} nodes that are part of the middle-end, the setup code
+goes into @file{tree.cc}.
+
+@item Add macros to access any new fields and flags
+
+Each added field or flag should have a macro that is used to access
+it, that performs appropriate checking to ensure only the right type of
+@code{DECL} nodes access the field.
+
+These macros generally take the following form
+@smallexample
+#define FOO_DECL_FIELDNAME(NODE) FOO_DECL_CHECK(NODE)->foo_decl.fieldname
+@end smallexample
+However, if the structure is simply a base class for further
+structures, something like the following should be used
+@smallexample
+#define BASE_STRUCT_CHECK(T) CONTAINS_STRUCT_CHECK(T, TS_BASE_STRUCT)
+#define BASE_STRUCT_FIELDNAME(NODE) \
+ (BASE_STRUCT_CHECK(NODE)->base_struct.fieldname
+@end smallexample
+
+Reading them from the generated @file{all-tree.def} file (which in
+turn includes all the @file{tree.def} files), @file{gencheck.cc} is
+used during GCC's build to generate the @code{*_CHECK} macros for all
+tree codes.
+
+@end table
+
+
+@c ---------------------------------------------------------------------
+@c Attributes
+@c ---------------------------------------------------------------------
+@node Attributes
+@section Attributes in trees
+@cindex attributes
+
+Attributes, as specified using the @code{__attribute__} keyword, are
+represented internally as a @code{TREE_LIST}. The @code{TREE_PURPOSE}
+is the name of the attribute, as an @code{IDENTIFIER_NODE}. The
+@code{TREE_VALUE} is a @code{TREE_LIST} of the arguments of the
+attribute, if any, or @code{NULL_TREE} if there are no arguments; the
+arguments are stored as the @code{TREE_VALUE} of successive entries in
+the list, and may be identifiers or expressions. The @code{TREE_CHAIN}
+of the attribute is the next attribute in a list of attributes applying
+to the same declaration or type, or @code{NULL_TREE} if there are no
+further attributes in the list.
+
+Attributes may be attached to declarations and to types; these
+attributes may be accessed with the following macros. All attributes
+are stored in this way, and many also cause other changes to the
+declaration or type or to other internal compiler data structures.
+
+@deftypefn {Tree Macro} tree DECL_ATTRIBUTES (tree @var{decl})
+This macro returns the attributes on the declaration @var{decl}.
+@end deftypefn
+
+@deftypefn {Tree Macro} tree TYPE_ATTRIBUTES (tree @var{type})
+This macro returns the attributes on the type @var{type}.
+@end deftypefn
+
+
+@c ---------------------------------------------------------------------
+@c Expressions
+@c ---------------------------------------------------------------------
+
+@node Expression trees
+@section Expressions
+@cindex expression
+@findex TREE_TYPE
+@findex TREE_OPERAND
+
+The internal representation for expressions is for the most part quite
+straightforward. However, there are a few facts that one must bear in
+mind. In particular, the expression ``tree'' is actually a directed
+acyclic graph. (For example there may be many references to the integer
+constant zero throughout the source program; many of these will be
+represented by the same expression node.) You should not rely on
+certain kinds of node being shared, nor should you rely on certain kinds of
+nodes being unshared.
+
+The following macros can be used with all expression nodes:
+
+@ftable @code
+@item TREE_TYPE
+Returns the type of the expression. This value may not be precisely the
+same type that would be given the expression in the original program.
+@end ftable
+
+In what follows, some nodes that one might expect to always have type
+@code{bool} are documented to have either integral or boolean type. At
+some point in the future, the C front end may also make use of this same
+intermediate representation, and at this point these nodes will
+certainly have integral type. The previous sentence is not meant to
+imply that the C++ front end does not or will not give these nodes
+integral type.
+
+Below, we list the various kinds of expression nodes. Except where
+noted otherwise, the operands to an expression are accessed using the
+@code{TREE_OPERAND} macro. For example, to access the first operand to
+a binary plus expression @code{expr}, use:
+
+@smallexample
+TREE_OPERAND (expr, 0)
+@end smallexample
+@noindent
+
+As this example indicates, the operands are zero-indexed.
+
+
+@menu
+* Constants: Constant expressions.
+* Storage References::
+* Unary and Binary Expressions::
+* Vectors::
+@end menu
+
+@node Constant expressions
+@subsection Constant expressions
+@tindex INTEGER_CST
+@findex tree_int_cst_lt
+@findex tree_int_cst_equal
+@tindex tree_fits_uhwi_p
+@tindex tree_fits_shwi_p
+@tindex tree_to_uhwi
+@tindex tree_to_shwi
+@tindex TREE_INT_CST_NUNITS
+@tindex TREE_INT_CST_ELT
+@tindex TREE_INT_CST_LOW
+@tindex REAL_CST
+@tindex FIXED_CST
+@tindex COMPLEX_CST
+@tindex VECTOR_CST
+@tindex STRING_CST
+@tindex POLY_INT_CST
+@findex TREE_STRING_LENGTH
+@findex TREE_STRING_POINTER
+
+The table below begins with constants, moves on to unary expressions,
+then proceeds to binary expressions, and concludes with various other
+kinds of expressions:
+
+@table @code
+@item INTEGER_CST
+These nodes represent integer constants. Note that the type of these
+constants is obtained with @code{TREE_TYPE}; they are not always of type
+@code{int}. In particular, @code{char} constants are represented with
+@code{INTEGER_CST} nodes. The value of the integer constant @code{e} is
+represented in an array of HOST_WIDE_INT. There are enough elements
+in the array to represent the value without taking extra elements for
+redundant 0s or -1. The number of elements used to represent @code{e}
+is available via @code{TREE_INT_CST_NUNITS}. Element @code{i} can be
+extracted by using @code{TREE_INT_CST_ELT (e, i)}.
+@code{TREE_INT_CST_LOW} is a shorthand for @code{TREE_INT_CST_ELT (e, 0)}.
+
+The functions @code{tree_fits_shwi_p} and @code{tree_fits_uhwi_p}
+can be used to tell if the value is small enough to fit in a
+signed HOST_WIDE_INT or an unsigned HOST_WIDE_INT respectively.
+The value can then be extracted using @code{tree_to_shwi} and
+@code{tree_to_uhwi}.
+
+@item REAL_CST
+
+FIXME: Talk about how to obtain representations of this constant, do
+comparisons, and so forth.
+
+@item FIXED_CST
+
+These nodes represent fixed-point constants. The type of these constants
+is obtained with @code{TREE_TYPE}. @code{TREE_FIXED_CST_PTR} points to
+a @code{struct fixed_value}; @code{TREE_FIXED_CST} returns the structure
+itself. @code{struct fixed_value} contains @code{data} with the size of two
+@code{HOST_BITS_PER_WIDE_INT} and @code{mode} as the associated fixed-point
+machine mode for @code{data}.
+
+@item COMPLEX_CST
+These nodes are used to represent complex number constants, that is a
+@code{__complex__} whose parts are constant nodes. The
+@code{TREE_REALPART} and @code{TREE_IMAGPART} return the real and the
+imaginary parts respectively.
+
+@item VECTOR_CST
+These nodes are used to represent vector constants. Each vector
+constant @var{v} is treated as a specific instance of an arbitrary-length
+sequence that itself contains @samp{VECTOR_CST_NPATTERNS (@var{v})}
+interleaved patterns. Each pattern has the form:
+
+@smallexample
+@{ @var{base0}, @var{base1}, @var{base1} + @var{step}, @var{base1} + @var{step} * 2, @dots{} @}
+@end smallexample
+
+The first three elements in each pattern are enough to determine the
+values of the other elements. However, if all @var{step}s are zero,
+only the first two elements are needed. If in addition each @var{base1}
+is equal to the corresponding @var{base0}, only the first element in
+each pattern is needed. The number of encoded elements per pattern
+is given by @samp{VECTOR_CST_NELTS_PER_PATTERN (@var{v})}.
+
+For example, the constant:
+
+@smallexample
+@{ 0, 1, 2, 6, 3, 8, 4, 10, 5, 12, 6, 14, 7, 16, 8, 18 @}
+@end smallexample
+
+is interpreted as an interleaving of the sequences:
+
+@smallexample
+@{ 0, 2, 3, 4, 5, 6, 7, 8 @}
+@{ 1, 6, 8, 10, 12, 14, 16, 18 @}
+@end smallexample
+
+where the sequences are represented by the following patterns:
+
+@smallexample
+@var{base0} == 0, @var{base1} == 2, @var{step} == 1
+@var{base0} == 1, @var{base1} == 6, @var{step} == 2
+@end smallexample
+
+In this case:
+
+@smallexample
+VECTOR_CST_NPATTERNS (@var{v}) == 2
+VECTOR_CST_NELTS_PER_PATTERN (@var{v}) == 3
+@end smallexample
+
+The vector is therefore encoded using the first 6 elements
+(@samp{@{ 0, 1, 2, 6, 3, 8 @}}), with the remaining 10 elements
+being implicit extensions of them.
+
+Sometimes this scheme can create two possible encodings of the same
+vector. For example @{ 0, 1 @} could be seen as two patterns with
+one element each or one pattern with two elements (@var{base0} and
+@var{base1}). The canonical encoding is always the one with the
+fewest patterns or (if both encodings have the same number of
+petterns) the one with the fewest encoded elements.
+
+@samp{vector_cst_encoding_nelts (@var{v})} gives the total number of
+encoded elements in @var{v}, which is 6 in the example above.
+@code{VECTOR_CST_ENCODED_ELTS (@var{v})} gives a pointer to the elements
+encoded in @var{v} and @code{VECTOR_CST_ENCODED_ELT (@var{v}, @var{i})}
+accesses the value of encoded element @var{i}.
+
+@samp{VECTOR_CST_DUPLICATE_P (@var{v})} is true if @var{v} simply contains
+repeated instances of @samp{VECTOR_CST_NPATTERNS (@var{v})} values. This is
+a shorthand for testing @samp{VECTOR_CST_NELTS_PER_PATTERN (@var{v}) == 1}.
+
+@samp{VECTOR_CST_STEPPED_P (@var{v})} is true if at least one
+pattern in @var{v} has a nonzero step. This is a shorthand for
+testing @samp{VECTOR_CST_NELTS_PER_PATTERN (@var{v}) == 3}.
+
+The utility function @code{vector_cst_elt} gives the value of an
+arbitrary index as a @code{tree}. @code{vector_cst_int_elt} gives
+the same value as a @code{wide_int}.
+
+@item STRING_CST
+These nodes represent string-constants. The @code{TREE_STRING_LENGTH}
+returns the length of the string, as an @code{int}. The
+@code{TREE_STRING_POINTER} is a @code{char*} containing the string
+itself. The string may not be @code{NUL}-terminated, and it may contain
+embedded @code{NUL} characters. Therefore, the
+@code{TREE_STRING_LENGTH} includes the trailing @code{NUL} if it is
+present.
+
+For wide string constants, the @code{TREE_STRING_LENGTH} is the number
+of bytes in the string, and the @code{TREE_STRING_POINTER}
+points to an array of the bytes of the string, as represented on the
+target system (that is, as integers in the target endianness). Wide and
+non-wide string constants are distinguished only by the @code{TREE_TYPE}
+of the @code{STRING_CST}.
+
+FIXME: The formats of string constants are not well-defined when the
+target system bytes are not the same width as host system bytes.
+
+@item POLY_INT_CST
+These nodes represent invariants that depend on some target-specific
+runtime parameters. They consist of @code{NUM_POLY_INT_COEFFS}
+coefficients, with the first coefficient being the constant term and
+the others being multipliers that are applied to the runtime parameters.
+
+@code{POLY_INT_CST_ELT (@var{x}, @var{i})} references coefficient number
+@var{i} of @code{POLY_INT_CST} node @var{x}. Each coefficient is an
+@code{INTEGER_CST}.
+
+@end table
+
+@node Storage References
+@subsection References to storage
+@tindex ADDR_EXPR
+@tindex INDIRECT_REF
+@tindex MEM_REF
+@tindex ARRAY_REF
+@tindex ARRAY_RANGE_REF
+@tindex TARGET_MEM_REF
+@tindex COMPONENT_REF
+
+@table @code
+@item ARRAY_REF
+These nodes represent array accesses. The first operand is the array;
+the second is the index. To calculate the address of the memory
+accessed, you must scale the index by the size of the type of the array
+elements. The type of these expressions must be the type of a component of
+the array. The third and fourth operands are used after gimplification
+to represent the lower bound and component size but should not be used
+directly; call @code{array_ref_low_bound} and @code{array_ref_element_size}
+instead.
+
+@item ARRAY_RANGE_REF
+These nodes represent access to a range (or ``slice'') of an array. The
+operands are the same as that for @code{ARRAY_REF} and have the same
+meanings. The type of these expressions must be an array whose component
+type is the same as that of the first operand. The range of that array
+type determines the amount of data these expressions access.
+
+@item COMPONENT_REF
+These nodes represent non-static data member accesses. The first
+operand is the object (rather than a pointer to it); the second operand
+is the @code{FIELD_DECL} for the data member. The third operand represents
+the byte offset of the field, but should not be used directly; call
+@code{component_ref_field_offset} instead.
+
+@item ADDR_EXPR
+These nodes are used to represent the address of an object. (These
+expressions will always have pointer or reference type.) The operand may
+be another expression, or it may be a declaration.
+
+As an extension, GCC allows users to take the address of a label. In
+this case, the operand of the @code{ADDR_EXPR} will be a
+@code{LABEL_DECL}. The type of such an expression is @code{void*}.
+
+If the object addressed is not an lvalue, a temporary is created, and
+the address of the temporary is used.
+
+@item INDIRECT_REF
+These nodes are used to represent the object pointed to by a pointer.
+The operand is the pointer being dereferenced; it will always have
+pointer or reference type.
+
+@item MEM_REF
+These nodes are used to represent the object pointed to by a pointer
+offset by a constant.
+The first operand is the pointer being dereferenced; it will always have
+pointer or reference type. The second operand is a pointer constant
+serving as constant offset applied to the pointer being dereferenced
+with its type specifying the type to be used for type-based alias analysis.
+The type of the node specifies the alignment of the access.
+
+@item TARGET_MEM_REF
+These nodes represent memory accesses whose address directly map to
+an addressing mode of the target architecture. The first argument
+is @code{TMR_BASE} and is a pointer to the object being accessed.
+The second argument is @code{TMR_OFFSET} which is a pointer constant
+with dual purpose serving both as constant offset and holder of
+the type used for type-based alias analysis. The first two operands
+have exactly the same semantics as @code{MEM_REF}. The third
+and fourth operand are @code{TMR_INDEX} and @code{TMR_STEP} where
+the former is an integer and the latter an integer constant. The
+fifth and last operand is @code{TMR_INDEX2} which is an alternate
+non-constant offset. Any of the third to last operands may be
+@code{NULL} if the corresponding component does not appear in
+the address, but @code{TMR_INDEX} and @code{TMR_STEP} shall be
+always supplied in pair. The Address of the @code{TARGET_MEM_REF}
+is determined in the following way.
+
+@smallexample
+TMR_BASE + TMR_OFFSET + TMR_INDEX * TMR_STEP + TMR_INDEX2
+@end smallexample
+
+The type of the node specifies the alignment of the access.
+
+@end table
+
+@node Unary and Binary Expressions
+@subsection Unary and Binary Expressions
+@tindex NEGATE_EXPR
+@tindex ABS_EXPR
+@tindex ABSU_EXPR
+@tindex BIT_NOT_EXPR
+@tindex TRUTH_NOT_EXPR
+@tindex PREDECREMENT_EXPR
+@tindex PREINCREMENT_EXPR
+@tindex POSTDECREMENT_EXPR
+@tindex POSTINCREMENT_EXPR
+@tindex FIX_TRUNC_EXPR
+@tindex FLOAT_EXPR
+@tindex COMPLEX_EXPR
+@tindex CONJ_EXPR
+@tindex REALPART_EXPR
+@tindex IMAGPART_EXPR
+@tindex NON_LVALUE_EXPR
+@tindex NOP_EXPR
+@tindex CONVERT_EXPR
+@tindex FIXED_CONVERT_EXPR
+@tindex THROW_EXPR
+@tindex LSHIFT_EXPR
+@tindex RSHIFT_EXPR
+@tindex BIT_IOR_EXPR
+@tindex BIT_XOR_EXPR
+@tindex BIT_AND_EXPR
+@tindex TRUTH_ANDIF_EXPR
+@tindex TRUTH_ORIF_EXPR
+@tindex TRUTH_AND_EXPR
+@tindex TRUTH_OR_EXPR
+@tindex TRUTH_XOR_EXPR
+@tindex POINTER_PLUS_EXPR
+@tindex POINTER_DIFF_EXPR
+@tindex PLUS_EXPR
+@tindex MINUS_EXPR
+@tindex MULT_EXPR
+@tindex WIDEN_MULT_EXPR
+@tindex MULT_HIGHPART_EXPR
+@tindex RDIV_EXPR
+@tindex TRUNC_DIV_EXPR
+@tindex FLOOR_DIV_EXPR
+@tindex CEIL_DIV_EXPR
+@tindex ROUND_DIV_EXPR
+@tindex TRUNC_MOD_EXPR
+@tindex FLOOR_MOD_EXPR
+@tindex CEIL_MOD_EXPR
+@tindex ROUND_MOD_EXPR
+@tindex EXACT_DIV_EXPR
+@tindex LT_EXPR
+@tindex LE_EXPR
+@tindex GT_EXPR
+@tindex GE_EXPR
+@tindex EQ_EXPR
+@tindex NE_EXPR
+@tindex ORDERED_EXPR
+@tindex UNORDERED_EXPR
+@tindex UNLT_EXPR
+@tindex UNLE_EXPR
+@tindex UNGT_EXPR
+@tindex UNGE_EXPR
+@tindex UNEQ_EXPR
+@tindex LTGT_EXPR
+@tindex MODIFY_EXPR
+@tindex INIT_EXPR
+@tindex COMPOUND_EXPR
+@tindex COND_EXPR
+@tindex CALL_EXPR
+@tindex STMT_EXPR
+@tindex BIND_EXPR
+@tindex LOOP_EXPR
+@tindex EXIT_EXPR
+@tindex CLEANUP_POINT_EXPR
+@tindex CONSTRUCTOR
+@tindex COMPOUND_LITERAL_EXPR
+@tindex SAVE_EXPR
+@tindex TARGET_EXPR
+@tindex VA_ARG_EXPR
+@tindex ANNOTATE_EXPR
+
+@table @code
+@item NEGATE_EXPR
+These nodes represent unary negation of the single operand, for both
+integer and floating-point types. The type of negation can be
+determined by looking at the type of the expression.
+
+The behavior of this operation on signed arithmetic overflow is
+controlled by the @code{flag_wrapv} and @code{flag_trapv} variables.
+
+@item ABS_EXPR
+These nodes represent the absolute value of the single operand, for
+both integer and floating-point types. This is typically used to
+implement the @code{abs}, @code{labs} and @code{llabs} builtins for
+integer types, and the @code{fabs}, @code{fabsf} and @code{fabsl}
+builtins for floating point types. The type of abs operation can
+be determined by looking at the type of the expression.
+
+This node is not used for complex types. To represent the modulus
+or complex abs of a complex value, use the @code{BUILT_IN_CABS},
+@code{BUILT_IN_CABSF} or @code{BUILT_IN_CABSL} builtins, as used
+to implement the C99 @code{cabs}, @code{cabsf} and @code{cabsl}
+built-in functions.
+
+@item ABSU_EXPR
+These nodes represent the absolute value of the single operand in
+equivalent unsigned type such that @code{ABSU_EXPR} of @code{TYPE_MIN}
+is well defined.
+
+@item BIT_NOT_EXPR
+These nodes represent bitwise complement, and will always have integral
+type. The only operand is the value to be complemented.
+
+@item TRUTH_NOT_EXPR
+These nodes represent logical negation, and will always have integral
+(or boolean) type. The operand is the value being negated. The type
+of the operand and that of the result are always of @code{BOOLEAN_TYPE}
+or @code{INTEGER_TYPE}.
+
+@item PREDECREMENT_EXPR
+@itemx PREINCREMENT_EXPR
+@itemx POSTDECREMENT_EXPR
+@itemx POSTINCREMENT_EXPR
+These nodes represent increment and decrement expressions. The value of
+the single operand is computed, and the operand incremented or
+decremented. In the case of @code{PREDECREMENT_EXPR} and
+@code{PREINCREMENT_EXPR}, the value of the expression is the value
+resulting after the increment or decrement; in the case of
+@code{POSTDECREMENT_EXPR} and @code{POSTINCREMENT_EXPR} is the value
+before the increment or decrement occurs. The type of the operand, like
+that of the result, will be either integral, boolean, or floating-point.
+
+@item FIX_TRUNC_EXPR
+These nodes represent conversion of a floating-point value to an
+integer. The single operand will have a floating-point type, while
+the complete expression will have an integral (or boolean) type. The
+operand is rounded towards zero.
+
+@item FLOAT_EXPR
+These nodes represent conversion of an integral (or boolean) value to a
+floating-point value. The single operand will have integral type, while
+the complete expression will have a floating-point type.
+
+FIXME: How is the operand supposed to be rounded? Is this dependent on
+@option{-mieee}?
+
+@item COMPLEX_EXPR
+These nodes are used to represent complex numbers constructed from two
+expressions of the same (integer or real) type. The first operand is the
+real part and the second operand is the imaginary part.
+
+@item CONJ_EXPR
+These nodes represent the conjugate of their operand.
+
+@item REALPART_EXPR
+@itemx IMAGPART_EXPR
+These nodes represent respectively the real and the imaginary parts
+of complex numbers (their sole argument).
+
+@item NON_LVALUE_EXPR
+These nodes indicate that their one and only operand is not an lvalue.
+A back end can treat these identically to the single operand.
+
+@item NOP_EXPR
+These nodes are used to represent conversions that do not require any
+code-generation. For example, conversion of a @code{char*} to an
+@code{int*} does not require any code be generated; such a conversion is
+represented by a @code{NOP_EXPR}. The single operand is the expression
+to be converted. The conversion from a pointer to a reference is also
+represented with a @code{NOP_EXPR}.
+
+@item CONVERT_EXPR
+These nodes are similar to @code{NOP_EXPR}s, but are used in those
+situations where code may need to be generated. For example, if an
+@code{int*} is converted to an @code{int} code may need to be generated
+on some platforms. These nodes are never used for C++-specific
+conversions, like conversions between pointers to different classes in
+an inheritance hierarchy. Any adjustments that need to be made in such
+cases are always indicated explicitly. Similarly, a user-defined
+conversion is never represented by a @code{CONVERT_EXPR}; instead, the
+function calls are made explicit.
+
+@item FIXED_CONVERT_EXPR
+These nodes are used to represent conversions that involve fixed-point
+values. For example, from a fixed-point value to another fixed-point value,
+from an integer to a fixed-point value, from a fixed-point value to an
+integer, from a floating-point value to a fixed-point value, or from
+a fixed-point value to a floating-point value.
+
+@item LSHIFT_EXPR
+@itemx RSHIFT_EXPR
+These nodes represent left and right shifts, respectively. The first
+operand is the value to shift; it will always be of integral type. The
+second operand is an expression for the number of bits by which to
+shift. Right shift should be treated as arithmetic, i.e., the
+high-order bits should be zero-filled when the expression has unsigned
+type and filled with the sign bit when the expression has signed type.
+Note that the result is undefined if the second operand is larger
+than or equal to the first operand's type size. Unlike most nodes, these
+can have a vector as first operand and a scalar as second operand.
+
+
+@item BIT_IOR_EXPR
+@itemx BIT_XOR_EXPR
+@itemx BIT_AND_EXPR
+These nodes represent bitwise inclusive or, bitwise exclusive or, and
+bitwise and, respectively. Both operands will always have integral
+type.
+
+@item TRUTH_ANDIF_EXPR
+@itemx TRUTH_ORIF_EXPR
+These nodes represent logical ``and'' and logical ``or'', respectively.
+These operators are not strict; i.e., the second operand is evaluated
+only if the value of the expression is not determined by evaluation of
+the first operand. The type of the operands and that of the result are
+always of @code{BOOLEAN_TYPE} or @code{INTEGER_TYPE}.
+
+@item TRUTH_AND_EXPR
+@itemx TRUTH_OR_EXPR
+@itemx TRUTH_XOR_EXPR
+These nodes represent logical and, logical or, and logical exclusive or.
+They are strict; both arguments are always evaluated. There are no
+corresponding operators in C or C++, but the front end will sometimes
+generate these expressions anyhow, if it can tell that strictness does
+not matter. The type of the operands and that of the result are
+always of @code{BOOLEAN_TYPE} or @code{INTEGER_TYPE}.
+
+@item POINTER_PLUS_EXPR
+This node represents pointer arithmetic. The first operand is always
+a pointer/reference type. The second operand is always an unsigned
+integer type compatible with sizetype. This and POINTER_DIFF_EXPR are
+the only binary arithmetic operators that can operate on pointer types.
+
+@item POINTER_DIFF_EXPR
+This node represents pointer subtraction. The two operands always
+have pointer/reference type. It returns a signed integer of the same
+precision as the pointers. The behavior is undefined if the difference
+of the two pointers, seen as infinite precision non-negative integers,
+does not fit in the result type. The result does not depend on the
+pointer type, it is not divided by the size of the pointed-to type.
+
+@item PLUS_EXPR
+@itemx MINUS_EXPR
+@itemx MULT_EXPR
+These nodes represent various binary arithmetic operations.
+Respectively, these operations are addition, subtraction (of the second
+operand from the first) and multiplication. Their operands may have
+either integral or floating type, but there will never be case in which
+one operand is of floating type and the other is of integral type.
+
+The behavior of these operations on signed arithmetic overflow is
+controlled by the @code{flag_wrapv} and @code{flag_trapv} variables.
+
+@item WIDEN_MULT_EXPR
+This node represents a widening multiplication. The operands have
+integral types with same @var{b} bits of precision, producing an
+integral type result with at least @math{2@var{b}} bits of precision.
+The behaviour is equivalent to extending both operands, possibly of
+different signedness, to the result type, then multiplying them.
+
+@item MULT_HIGHPART_EXPR
+This node represents the ``high-part'' of a widening multiplication.
+For an integral type with @var{b} bits of precision, the result is
+the most significant @var{b} bits of the full @math{2@var{b}} product.
+Both operands must have the same precision and same signedness.
+
+@item RDIV_EXPR
+This node represents a floating point division operation.
+
+@item TRUNC_DIV_EXPR
+@itemx FLOOR_DIV_EXPR
+@itemx CEIL_DIV_EXPR
+@itemx ROUND_DIV_EXPR
+These nodes represent integer division operations that return an integer
+result. @code{TRUNC_DIV_EXPR} rounds towards zero, @code{FLOOR_DIV_EXPR}
+rounds towards negative infinity, @code{CEIL_DIV_EXPR} rounds towards
+positive infinity and @code{ROUND_DIV_EXPR} rounds to the closest integer.
+Integer division in C and C++ is truncating, i.e.@: @code{TRUNC_DIV_EXPR}.
+
+The behavior of these operations on signed arithmetic overflow, when
+dividing the minimum signed integer by minus one, is controlled by the
+@code{flag_wrapv} and @code{flag_trapv} variables.
+
+@item TRUNC_MOD_EXPR
+@itemx FLOOR_MOD_EXPR
+@itemx CEIL_MOD_EXPR
+@itemx ROUND_MOD_EXPR
+These nodes represent the integer remainder or modulus operation.
+The integer modulus of two operands @code{a} and @code{b} is
+defined as @code{a - (a/b)*b} where the division calculated using
+the corresponding division operator. Hence for @code{TRUNC_MOD_EXPR}
+this definition assumes division using truncation towards zero, i.e.@:
+@code{TRUNC_DIV_EXPR}. Integer remainder in C and C++ uses truncating
+division, i.e.@: @code{TRUNC_MOD_EXPR}.
+
+@item EXACT_DIV_EXPR
+The @code{EXACT_DIV_EXPR} code is used to represent integer divisions where
+the numerator is known to be an exact multiple of the denominator. This
+allows the backend to choose between the faster of @code{TRUNC_DIV_EXPR},
+@code{CEIL_DIV_EXPR} and @code{FLOOR_DIV_EXPR} for the current target.
+
+@item LT_EXPR
+@itemx LE_EXPR
+@itemx GT_EXPR
+@itemx GE_EXPR
+@itemx LTGT_EXPR
+@itemx EQ_EXPR
+@itemx NE_EXPR
+These nodes represent the less than, less than or equal to, greater than,
+greater than or equal to, less or greater than, equal, and not equal
+comparison operators. The first and second operands will either be both
+of integral type, both of floating type or both of vector type, except for
+LTGT_EXPR where they will only be both of floating type. The result type
+of these expressions will always be of integral, boolean or signed integral
+vector type. These operations return the result type's zero value for false,
+the result type's one value for true, and a vector whose elements are zero
+(false) or minus one (true) for vectors.
+
+For floating point comparisons, if we honor IEEE NaNs and either operand
+is NaN, then @code{NE_EXPR} always returns true and the remaining operators
+always return false. On some targets, comparisons against an IEEE NaN,
+other than equality and inequality, may generate a floating-point exception.
+
+@item ORDERED_EXPR
+@itemx UNORDERED_EXPR
+These nodes represent non-trapping ordered and unordered comparison
+operators. These operations take two floating point operands and
+determine whether they are ordered or unordered relative to each other.
+If either operand is an IEEE NaN, their comparison is defined to be
+unordered, otherwise the comparison is defined to be ordered. The
+result type of these expressions will always be of integral or boolean
+type. These operations return the result type's zero value for false,
+and the result type's one value for true.
+
+@item UNLT_EXPR
+@itemx UNLE_EXPR
+@itemx UNGT_EXPR
+@itemx UNGE_EXPR
+@itemx UNEQ_EXPR
+These nodes represent the unordered comparison operators.
+These operations take two floating point operands and determine whether
+the operands are unordered or are less than, less than or equal to,
+greater than, greater than or equal to, or equal respectively. For
+example, @code{UNLT_EXPR} returns true if either operand is an IEEE
+NaN or the first operand is less than the second. All these operations
+are guaranteed not to generate a floating point exception. The result
+type of these expressions will always be of integral or boolean type.
+These operations return the result type's zero value for false,
+and the result type's one value for true.
+
+@item MODIFY_EXPR
+These nodes represent assignment. The left-hand side is the first
+operand; the right-hand side is the second operand. The left-hand side
+will be a @code{VAR_DECL}, @code{INDIRECT_REF}, @code{COMPONENT_REF}, or
+other lvalue.
+
+These nodes are used to represent not only assignment with @samp{=} but
+also compound assignments (like @samp{+=}), by reduction to @samp{=}
+assignment. In other words, the representation for @samp{i += 3} looks
+just like that for @samp{i = i + 3}.
+
+@item INIT_EXPR
+These nodes are just like @code{MODIFY_EXPR}, but are used only when a
+variable is initialized, rather than assigned to subsequently. This
+means that we can assume that the target of the initialization is not
+used in computing its own value; any reference to the lhs in computing
+the rhs is undefined.
+
+@item COMPOUND_EXPR
+These nodes represent comma-expressions. The first operand is an
+expression whose value is computed and thrown away prior to the
+evaluation of the second operand. The value of the entire expression is
+the value of the second operand.
+
+@item COND_EXPR
+These nodes represent @code{?:} expressions. The first operand
+is of boolean or integral type. If it evaluates to a nonzero value,
+the second operand should be evaluated, and returned as the value of the
+expression. Otherwise, the third operand is evaluated, and returned as
+the value of the expression.
+
+The second operand must have the same type as the entire expression,
+unless it unconditionally throws an exception or calls a noreturn
+function, in which case it should have void type. The same constraints
+apply to the third operand. This allows array bounds checks to be
+represented conveniently as @code{(i >= 0 && i < 10) ? i : abort()}.
+
+As a GNU extension, the C language front-ends allow the second
+operand of the @code{?:} operator may be omitted in the source.
+For example, @code{x ? : 3} is equivalent to @code{x ? x : 3},
+assuming that @code{x} is an expression without side effects.
+In the tree representation, however, the second operand is always
+present, possibly protected by @code{SAVE_EXPR} if the first
+argument does cause side effects.
+
+@item CALL_EXPR
+These nodes are used to represent calls to functions, including
+non-static member functions. @code{CALL_EXPR}s are implemented as
+expression nodes with a variable number of operands. Rather than using
+@code{TREE_OPERAND} to extract them, it is preferable to use the
+specialized accessor macros and functions that operate specifically on
+@code{CALL_EXPR} nodes.
+
+@code{CALL_EXPR_FN} returns a pointer to the
+function to call; it is always an expression whose type is a
+@code{POINTER_TYPE}.
+
+The number of arguments to the call is returned by @code{call_expr_nargs},
+while the arguments themselves can be accessed with the @code{CALL_EXPR_ARG}
+macro. The arguments are zero-indexed and numbered left-to-right.
+You can iterate over the arguments using @code{FOR_EACH_CALL_EXPR_ARG}, as in:
+
+@smallexample
+tree call, arg;
+call_expr_arg_iterator iter;
+FOR_EACH_CALL_EXPR_ARG (arg, iter, call)
+ /* arg is bound to successive arguments of call. */
+ @dots{};
+@end smallexample
+
+For non-static
+member functions, there will be an operand corresponding to the
+@code{this} pointer. There will always be expressions corresponding to
+all of the arguments, even if the function is declared with default
+arguments and some arguments are not explicitly provided at the call
+sites.
+
+@code{CALL_EXPR}s also have a @code{CALL_EXPR_STATIC_CHAIN} operand that
+is used to implement nested functions. This operand is otherwise null.
+
+@item CLEANUP_POINT_EXPR
+These nodes represent full-expressions. The single operand is an
+expression to evaluate. Any destructor calls engendered by the creation
+of temporaries during the evaluation of that expression should be
+performed immediately after the expression is evaluated.
+
+@item CONSTRUCTOR
+These nodes represent the brace-enclosed initializers for a structure or an
+array. They contain a sequence of component values made out of a vector of
+constructor_elt, which is a (@code{INDEX}, @code{VALUE}) pair.
+
+If the @code{TREE_TYPE} of the @code{CONSTRUCTOR} is a @code{RECORD_TYPE},
+@code{UNION_TYPE} or @code{QUAL_UNION_TYPE} then the @code{INDEX} of each
+node in the sequence will be a @code{FIELD_DECL} and the @code{VALUE} will
+be the expression used to initialize that field.
+
+If the @code{TREE_TYPE} of the @code{CONSTRUCTOR} is an @code{ARRAY_TYPE},
+then the @code{INDEX} of each node in the sequence will be an
+@code{INTEGER_CST} or a @code{RANGE_EXPR} of two @code{INTEGER_CST}s.
+A single @code{INTEGER_CST} indicates which element of the array is being
+assigned to. A @code{RANGE_EXPR} indicates an inclusive range of elements
+to initialize. In both cases the @code{VALUE} is the corresponding
+initializer. It is re-evaluated for each element of a
+@code{RANGE_EXPR}. If the @code{INDEX} is @code{NULL_TREE}, then
+the initializer is for the next available array element.
+
+In the front end, you should not depend on the fields appearing in any
+particular order. However, in the middle end, fields must appear in
+declaration order. You should not assume that all fields will be
+represented. Unrepresented fields will be cleared (zeroed), unless the
+CONSTRUCTOR_NO_CLEARING flag is set, in which case their value becomes
+undefined.
+
+@item COMPOUND_LITERAL_EXPR
+@findex COMPOUND_LITERAL_EXPR_DECL_EXPR
+@findex COMPOUND_LITERAL_EXPR_DECL
+These nodes represent ISO C99 compound literals. The
+@code{COMPOUND_LITERAL_EXPR_DECL_EXPR} is a @code{DECL_EXPR}
+containing an anonymous @code{VAR_DECL} for
+the unnamed object represented by the compound literal; the
+@code{DECL_INITIAL} of that @code{VAR_DECL} is a @code{CONSTRUCTOR}
+representing the brace-enclosed list of initializers in the compound
+literal. That anonymous @code{VAR_DECL} can also be accessed directly
+by the @code{COMPOUND_LITERAL_EXPR_DECL} macro.
+
+@item SAVE_EXPR
+
+A @code{SAVE_EXPR} represents an expression (possibly involving
+side effects) that is used more than once. The side effects should
+occur only the first time the expression is evaluated. Subsequent uses
+should just reuse the computed value. The first operand to the
+@code{SAVE_EXPR} is the expression to evaluate. The side effects should
+be executed where the @code{SAVE_EXPR} is first encountered in a
+depth-first preorder traversal of the expression tree.
+
+@item TARGET_EXPR
+A @code{TARGET_EXPR} represents a temporary object. The first operand
+is a @code{VAR_DECL} for the temporary variable. The second operand is
+the initializer for the temporary. The initializer is evaluated and,
+if non-void, copied (bitwise) into the temporary. If the initializer
+is void, that means that it will perform the initialization itself.
+
+Often, a @code{TARGET_EXPR} occurs on the right-hand side of an
+assignment, or as the second operand to a comma-expression which is
+itself the right-hand side of an assignment, etc. In this case, we say
+that the @code{TARGET_EXPR} is ``normal''; otherwise, we say it is
+``orphaned''. For a normal @code{TARGET_EXPR} the temporary variable
+should be treated as an alias for the left-hand side of the assignment,
+rather than as a new temporary variable.
+
+The third operand to the @code{TARGET_EXPR}, if present, is a
+cleanup-expression (i.e., destructor call) for the temporary. If this
+expression is orphaned, then this expression must be executed when the
+statement containing this expression is complete. These cleanups must
+always be executed in the order opposite to that in which they were
+encountered. Note that if a temporary is created on one branch of a
+conditional operator (i.e., in the second or third operand to a
+@code{COND_EXPR}), the cleanup must be run only if that branch is
+actually executed.
+
+@item VA_ARG_EXPR
+This node is used to implement support for the C/C++ variable argument-list
+mechanism. It represents expressions like @code{va_arg (ap, type)}.
+Its @code{TREE_TYPE} yields the tree representation for @code{type} and
+its sole argument yields the representation for @code{ap}.
+
+@item ANNOTATE_EXPR
+This node is used to attach markers to an expression. The first operand
+is the annotated expression, the second is an @code{INTEGER_CST} with
+a value from @code{enum annot_expr_kind}, the third is an @code{INTEGER_CST}.
+@end table
+
+
+@node Vectors
+@subsection Vectors
+@tindex VEC_DUPLICATE_EXPR
+@tindex VEC_SERIES_EXPR
+@tindex VEC_LSHIFT_EXPR
+@tindex VEC_RSHIFT_EXPR
+@tindex VEC_WIDEN_MULT_HI_EXPR
+@tindex VEC_WIDEN_MULT_LO_EXPR
+@tindex VEC_WIDEN_PLUS_HI_EXPR
+@tindex VEC_WIDEN_PLUS_LO_EXPR
+@tindex VEC_WIDEN_MINUS_HI_EXPR
+@tindex VEC_WIDEN_MINUS_LO_EXPR
+@tindex VEC_UNPACK_HI_EXPR
+@tindex VEC_UNPACK_LO_EXPR
+@tindex VEC_UNPACK_FLOAT_HI_EXPR
+@tindex VEC_UNPACK_FLOAT_LO_EXPR
+@tindex VEC_UNPACK_FIX_TRUNC_HI_EXPR
+@tindex VEC_UNPACK_FIX_TRUNC_LO_EXPR
+@tindex VEC_PACK_TRUNC_EXPR
+@tindex VEC_PACK_SAT_EXPR
+@tindex VEC_PACK_FIX_TRUNC_EXPR
+@tindex VEC_PACK_FLOAT_EXPR
+@tindex VEC_COND_EXPR
+@tindex SAD_EXPR
+
+@table @code
+@item VEC_DUPLICATE_EXPR
+This node has a single operand and represents a vector in which every
+element is equal to that operand.
+
+@item VEC_SERIES_EXPR
+This node represents a vector formed from a scalar base and step,
+given as the first and second operands respectively. Element @var{i}
+of the result is equal to @samp{@var{base} + @var{i}*@var{step}}.
+
+This node is restricted to integral types, in order to avoid
+specifying the rounding behavior for floating-point types.
+
+@item VEC_LSHIFT_EXPR
+@itemx VEC_RSHIFT_EXPR
+These nodes represent whole vector left and right shifts, respectively.
+The first operand is the vector to shift; it will always be of vector type.
+The second operand is an expression for the number of bits by which to
+shift. Note that the result is undefined if the second operand is larger
+than or equal to the first operand's type size.
+
+@item VEC_WIDEN_MULT_HI_EXPR
+@itemx VEC_WIDEN_MULT_LO_EXPR
+These nodes represent widening vector multiplication of the high and low
+parts of the two input vectors, respectively. Their operands are vectors
+that contain the same number of elements (@code{N}) of the same integral type.
+The result is a vector that contains half as many elements, of an integral type
+whose size is twice as wide. In the case of @code{VEC_WIDEN_MULT_HI_EXPR} the
+high @code{N/2} elements of the two vector are multiplied to produce the
+vector of @code{N/2} products. In the case of @code{VEC_WIDEN_MULT_LO_EXPR} the
+low @code{N/2} elements of the two vector are multiplied to produce the
+vector of @code{N/2} products.
+
+@item VEC_WIDEN_PLUS_HI_EXPR
+@itemx VEC_WIDEN_PLUS_LO_EXPR
+These nodes represent widening vector addition of the high and low parts of
+the two input vectors, respectively. Their operands are vectors that contain
+the same number of elements (@code{N}) of the same integral type. The result
+is a vector that contains half as many elements, of an integral type whose size
+is twice as wide. In the case of @code{VEC_WIDEN_PLUS_HI_EXPR} the high
+@code{N/2} elements of the two vectors are added to produce the vector of
+@code{N/2} products. In the case of @code{VEC_WIDEN_PLUS_LO_EXPR} the low
+@code{N/2} elements of the two vectors are added to produce the vector of
+@code{N/2} products.
+
+@item VEC_WIDEN_MINUS_HI_EXPR
+@itemx VEC_WIDEN_MINUS_LO_EXPR
+These nodes represent widening vector subtraction of the high and low parts of
+the two input vectors, respectively. Their operands are vectors that contain
+the same number of elements (@code{N}) of the same integral type. The high/low
+elements of the second vector are subtracted from the high/low elements of the
+first. The result is a vector that contains half as many elements, of an
+integral type whose size is twice as wide. In the case of
+@code{VEC_WIDEN_MINUS_HI_EXPR} the high @code{N/2} elements of the second
+vector are subtracted from the high @code{N/2} of the first to produce the
+vector of @code{N/2} products. In the case of
+@code{VEC_WIDEN_MINUS_LO_EXPR} the low @code{N/2} elements of the second
+vector are subtracted from the low @code{N/2} of the first to produce the
+vector of @code{N/2} products.
+
+@item VEC_UNPACK_HI_EXPR
+@itemx VEC_UNPACK_LO_EXPR
+These nodes represent unpacking of the high and low parts of the input vector,
+respectively. The single operand is a vector that contains @code{N} elements
+of the same integral or floating point type. The result is a vector
+that contains half as many elements, of an integral or floating point type
+whose size is twice as wide. In the case of @code{VEC_UNPACK_HI_EXPR} the
+high @code{N/2} elements of the vector are extracted and widened (promoted).
+In the case of @code{VEC_UNPACK_LO_EXPR} the low @code{N/2} elements of the
+vector are extracted and widened (promoted).
+
+@item VEC_UNPACK_FLOAT_HI_EXPR
+@itemx VEC_UNPACK_FLOAT_LO_EXPR
+These nodes represent unpacking of the high and low parts of the input vector,
+where the values are converted from fixed point to floating point. The
+single operand is a vector that contains @code{N} elements of the same
+integral type. The result is a vector that contains half as many elements
+of a floating point type whose size is twice as wide. In the case of
+@code{VEC_UNPACK_FLOAT_HI_EXPR} the high @code{N/2} elements of the vector are
+extracted, converted and widened. In the case of @code{VEC_UNPACK_FLOAT_LO_EXPR}
+the low @code{N/2} elements of the vector are extracted, converted and widened.
+
+@item VEC_UNPACK_FIX_TRUNC_HI_EXPR
+@itemx VEC_UNPACK_FIX_TRUNC_LO_EXPR
+These nodes represent unpacking of the high and low parts of the input vector,
+where the values are truncated from floating point to fixed point. The
+single operand is a vector that contains @code{N} elements of the same
+floating point type. The result is a vector that contains half as many
+elements of an integral type whose size is twice as wide. In the case of
+@code{VEC_UNPACK_FIX_TRUNC_HI_EXPR} the high @code{N/2} elements of the
+vector are extracted and converted with truncation. In the case of
+@code{VEC_UNPACK_FIX_TRUNC_LO_EXPR} the low @code{N/2} elements of the
+vector are extracted and converted with truncation.
+
+@item VEC_PACK_TRUNC_EXPR
+This node represents packing of truncated elements of the two input vectors
+into the output vector. Input operands are vectors that contain the same
+number of elements of the same integral or floating point type. The result
+is a vector that contains twice as many elements of an integral or floating
+point type whose size is half as wide. The elements of the two vectors are
+demoted and merged (concatenated) to form the output vector.
+
+@item VEC_PACK_SAT_EXPR
+This node represents packing of elements of the two input vectors into the
+output vector using saturation. Input operands are vectors that contain
+the same number of elements of the same integral type. The result is a
+vector that contains twice as many elements of an integral type whose size
+is half as wide. The elements of the two vectors are demoted and merged
+(concatenated) to form the output vector.
+
+@item VEC_PACK_FIX_TRUNC_EXPR
+This node represents packing of elements of the two input vectors into the
+output vector, where the values are converted from floating point
+to fixed point. Input operands are vectors that contain the same number
+of elements of a floating point type. The result is a vector that contains
+twice as many elements of an integral type whose size is half as wide. The
+elements of the two vectors are merged (concatenated) to form the output
+vector.
+
+@item VEC_PACK_FLOAT_EXPR
+This node represents packing of elements of the two input vectors into the
+output vector, where the values are converted from fixed point to floating
+point. Input operands are vectors that contain the same number of elements
+of an integral type. The result is a vector that contains twice as many
+elements of floating point type whose size is half as wide. The elements of
+the two vectors are merged (concatenated) to form the output vector.
+
+@item VEC_COND_EXPR
+These nodes represent @code{?:} expressions. The three operands must be
+vectors of the same size and number of elements. The second and third
+operands must have the same type as the entire expression. The first
+operand is of signed integral vector type. If an element of the first
+operand evaluates to a zero value, the corresponding element of the
+result is taken from the third operand. If it evaluates to a minus one
+value, it is taken from the second operand. It should never evaluate to
+any other value currently, but optimizations should not rely on that
+property. In contrast with a @code{COND_EXPR}, all operands are always
+evaluated.
+
+@item SAD_EXPR
+This node represents the Sum of Absolute Differences operation. The three
+operands must be vectors of integral types. The first and second operand
+must have the same type. The size of the vector element of the third
+operand must be at lease twice of the size of the vector element of the
+first and second one. The SAD is calculated between the first and second
+operands, added to the third operand, and returned.
+
+@end table
+
+
+@c ---------------------------------------------------------------------
+@c Statements
+@c ---------------------------------------------------------------------
+
+@node Statements
+@section Statements
+@cindex Statements
+
+Most statements in GIMPLE are assignment statements, represented by
+@code{GIMPLE_ASSIGN}. No other C expressions can appear at statement level;
+a reference to a volatile object is converted into a
+@code{GIMPLE_ASSIGN}.
+
+There are also several varieties of complex statements.
+
+@menu
+* Basic Statements::
+* Blocks::
+* Statement Sequences::
+* Empty Statements::
+* Jumps::
+* Cleanups::
+* OpenMP::
+* OpenACC::
+@end menu
+
+@node Basic Statements
+@subsection Basic Statements
+@cindex Basic Statements
+
+@table @code
+@item ASM_EXPR
+
+Used to represent an inline assembly statement. For an inline assembly
+statement like:
+@smallexample
+asm ("mov x, y");
+@end smallexample
+The @code{ASM_STRING} macro will return a @code{STRING_CST} node for
+@code{"mov x, y"}. If the original statement made use of the
+extended-assembly syntax, then @code{ASM_OUTPUTS},
+@code{ASM_INPUTS}, and @code{ASM_CLOBBERS} will be the outputs, inputs,
+and clobbers for the statement, represented as @code{STRING_CST} nodes.
+The extended-assembly syntax looks like:
+@smallexample
+asm ("fsinx %1,%0" : "=f" (result) : "f" (angle));
+@end smallexample
+The first string is the @code{ASM_STRING}, containing the instruction
+template. The next two strings are the output and inputs, respectively;
+this statement has no clobbers. As this example indicates, ``plain''
+assembly statements are merely a special case of extended assembly
+statements; they have no cv-qualifiers, outputs, inputs, or clobbers.
+All of the strings will be @code{NUL}-terminated, and will contain no
+embedded @code{NUL}-characters.
+
+If the assembly statement is declared @code{volatile}, or if the
+statement was not an extended assembly statement, and is therefore
+implicitly volatile, then the predicate @code{ASM_VOLATILE_P} will hold
+of the @code{ASM_EXPR}.
+
+@item DECL_EXPR
+
+Used to represent a local declaration. The @code{DECL_EXPR_DECL} macro
+can be used to obtain the entity declared. This declaration may be a
+@code{LABEL_DECL}, indicating that the label declared is a local label.
+(As an extension, GCC allows the declaration of labels with scope.) In
+C, this declaration may be a @code{FUNCTION_DECL}, indicating the
+use of the GCC nested function extension. For more information,
+@pxref{Functions}.
+
+@item LABEL_EXPR
+
+Used to represent a label. The @code{LABEL_DECL} declared by this
+statement can be obtained with the @code{LABEL_EXPR_LABEL} macro. The
+@code{IDENTIFIER_NODE} giving the name of the label can be obtained from
+the @code{LABEL_DECL} with @code{DECL_NAME}.
+
+@item GOTO_EXPR
+
+Used to represent a @code{goto} statement. The @code{GOTO_DESTINATION} will
+usually be a @code{LABEL_DECL}. However, if the ``computed goto'' extension
+has been used, the @code{GOTO_DESTINATION} will be an arbitrary expression
+indicating the destination. This expression will always have pointer type.
+
+@item RETURN_EXPR
+
+Used to represent a @code{return} statement. Operand 0 represents the
+value to return. It should either be the @code{RESULT_DECL} for the
+containing function, or a @code{MODIFY_EXPR} or @code{INIT_EXPR}
+setting the function's @code{RESULT_DECL}. It will be
+@code{NULL_TREE} if the statement was just
+@smallexample
+return;
+@end smallexample
+
+@item LOOP_EXPR
+These nodes represent ``infinite'' loops. The @code{LOOP_EXPR_BODY}
+represents the body of the loop. It should be executed forever, unless
+an @code{EXIT_EXPR} is encountered.
+
+@item EXIT_EXPR
+These nodes represent conditional exits from the nearest enclosing
+@code{LOOP_EXPR}. The single operand is the condition; if it is
+nonzero, then the loop should be exited. An @code{EXIT_EXPR} will only
+appear within a @code{LOOP_EXPR}.
+
+@item SWITCH_EXPR
+
+Used to represent a @code{switch} statement. The @code{SWITCH_COND}
+is the expression on which the switch is occurring. The
+@code{SWITCH_BODY} is the body of the switch statement.
+@code{SWITCH_ALL_CASES_P} is true if the switch includes a default
+label or the case label ranges cover all possible values of the
+condition expression.
+
+Note that @code{TREE_TYPE} for a @code{SWITCH_EXPR} represents the
+original type of switch expression as given in the source, before any
+compiler conversions, instead of the type of the switch expression
+itself (which is not meaningful).
+
+@item CASE_LABEL_EXPR
+
+Use to represent a @code{case} label, range of @code{case} labels, or a
+@code{default} label. If @code{CASE_LOW} is @code{NULL_TREE}, then this is a
+@code{default} label. Otherwise, if @code{CASE_HIGH} is @code{NULL_TREE}, then
+this is an ordinary @code{case} label. In this case, @code{CASE_LOW} is
+an expression giving the value of the label. Both @code{CASE_LOW} and
+@code{CASE_HIGH} are @code{INTEGER_CST} nodes. These values will have
+the same type as the condition expression in the switch statement.
+
+Otherwise, if both @code{CASE_LOW} and @code{CASE_HIGH} are defined, the
+statement is a range of case labels. Such statements originate with the
+extension that allows users to write things of the form:
+@smallexample
+case 2 ... 5:
+@end smallexample
+The first value will be @code{CASE_LOW}, while the second will be
+@code{CASE_HIGH}.
+
+@item DEBUG_BEGIN_STMT
+
+Marks the beginning of a source statement, for purposes of debug
+information generation.
+
+@end table
+
+
+@node Blocks
+@subsection Blocks
+@cindex Blocks
+
+Block scopes and the variables they declare in GENERIC are
+expressed using the @code{BIND_EXPR} code, which in previous
+versions of GCC was primarily used for the C statement-expression
+extension.
+
+Variables in a block are collected into @code{BIND_EXPR_VARS} in
+declaration order through their @code{TREE_CHAIN} field. Any runtime
+initialization is moved out of @code{DECL_INITIAL} and into a
+statement in the controlled block. When gimplifying from C or C++,
+this initialization replaces the @code{DECL_STMT}. These variables
+will never require cleanups. The scope of these variables is just the
+body
+
+Variable-length arrays (VLAs) complicate this process, as their size
+often refers to variables initialized earlier in the block and their
+initialization involves an explicit stack allocation. To handle this,
+we add an indirection and replace them with a pointer to stack space
+allocated by means of @code{alloca}. In most cases, we also arrange
+for this space to be reclaimed when the enclosing @code{BIND_EXPR} is
+exited, the exception to this being when there is an explicit call to
+@code{alloca} in the source code, in which case the stack is left
+depressed on exit of the @code{BIND_EXPR}.
+
+A C++ program will usually contain more @code{BIND_EXPR}s than
+there are syntactic blocks in the source code, since several C++
+constructs have implicit scopes associated with them. On the
+other hand, although the C++ front end uses pseudo-scopes to
+handle cleanups for objects with destructors, these don't
+translate into the GIMPLE form; multiple declarations at the same
+level use the same @code{BIND_EXPR}.
+
+@node Statement Sequences
+@subsection Statement Sequences
+@cindex Statement Sequences
+
+Multiple statements at the same nesting level are collected into
+a @code{STATEMENT_LIST}. Statement lists are modified and
+traversed using the interface in @samp{tree-iterator.h}.
+
+@node Empty Statements
+@subsection Empty Statements
+@cindex Empty Statements
+
+Whenever possible, statements with no effect are discarded. But
+if they are nested within another construct which cannot be
+discarded for some reason, they are instead replaced with an
+empty statement, generated by @code{build_empty_stmt}.
+Initially, all empty statements were shared, after the pattern of
+the Java front end, but this caused a lot of trouble in practice.
+
+An empty statement is represented as @code{(void)0}.
+
+@node Jumps
+@subsection Jumps
+@cindex Jumps
+
+Other jumps are expressed by either @code{GOTO_EXPR} or
+@code{RETURN_EXPR}.
+
+The operand of a @code{GOTO_EXPR} must be either a label or a
+variable containing the address to jump to.
+
+The operand of a @code{RETURN_EXPR} is either @code{NULL_TREE},
+@code{RESULT_DECL}, or a @code{MODIFY_EXPR} which sets the return
+value. It would be nice to move the @code{MODIFY_EXPR} into a
+separate statement, but the special return semantics in
+@code{expand_return} make that difficult. It may still happen in
+the future, perhaps by moving most of that logic into
+@code{expand_assignment}.
+
+@node Cleanups
+@subsection Cleanups
+@cindex Cleanups
+
+Destructors for local C++ objects and similar dynamic cleanups are
+represented in GIMPLE by a @code{TRY_FINALLY_EXPR}.
+@code{TRY_FINALLY_EXPR} has two operands, both of which are a sequence
+of statements to execute. The first sequence is executed. When it
+completes the second sequence is executed.
+
+The first sequence may complete in the following ways:
+
+@enumerate
+
+@item Execute the last statement in the sequence and fall off the
+end.
+
+@item Execute a goto statement (@code{GOTO_EXPR}) to an ordinary
+label outside the sequence.
+
+@item Execute a return statement (@code{RETURN_EXPR}).
+
+@item Throw an exception. This is currently not explicitly represented in
+GIMPLE.
+
+@end enumerate
+
+The second sequence is not executed if the first sequence completes by
+calling @code{setjmp} or @code{exit} or any other function that does
+not return. The second sequence is also not executed if the first
+sequence completes via a non-local goto or a computed goto (in general
+the compiler does not know whether such a goto statement exits the
+first sequence or not, so we assume that it doesn't).
+
+After the second sequence is executed, if it completes normally by
+falling off the end, execution continues wherever the first sequence
+would have continued, by falling off the end, or doing a goto, etc.
+
+If the second sequence is an @code{EH_ELSE_EXPR} selector, then the
+sequence in its first operand is used when the first sequence completes
+normally, and that in its second operand is used for exceptional
+cleanups, i.e., when an exception propagates out of the first sequence.
+
+@code{TRY_FINALLY_EXPR} complicates the flow graph, since the cleanup
+needs to appear on every edge out of the controlled block; this
+reduces the freedom to move code across these edges. Therefore, the
+EH lowering pass which runs before most of the optimization passes
+eliminates these expressions by explicitly adding the cleanup to each
+edge. Rethrowing the exception is represented using @code{RESX_EXPR}.
+
+@node OpenMP
+@subsection OpenMP
+@tindex OMP_PARALLEL
+@tindex OMP_FOR
+@tindex OMP_SECTIONS
+@tindex OMP_SINGLE
+@tindex OMP_SECTION
+@tindex OMP_MASTER
+@tindex OMP_ORDERED
+@tindex OMP_CRITICAL
+@tindex OMP_RETURN
+@tindex OMP_CONTINUE
+@tindex OMP_ATOMIC
+@tindex OMP_CLAUSE
+
+All the statements starting with @code{OMP_} represent directives and
+clauses used by the OpenMP API @w{@uref{https://www.openmp.org}}.
+
+@table @code
+@item OMP_PARALLEL
+
+Represents @code{#pragma omp parallel [clause1 @dots{} clauseN]}. It
+has four operands:
+
+Operand @code{OMP_PARALLEL_BODY} is valid while in GENERIC and
+High GIMPLE forms. It contains the body of code to be executed
+by all the threads. During GIMPLE lowering, this operand becomes
+@code{NULL} and the body is emitted linearly after
+@code{OMP_PARALLEL}.
+
+Operand @code{OMP_PARALLEL_CLAUSES} is the list of clauses
+associated with the directive.
+
+Operand @code{OMP_PARALLEL_FN} is created by
+@code{pass_lower_omp}, it contains the @code{FUNCTION_DECL}
+for the function that will contain the body of the parallel
+region.
+
+Operand @code{OMP_PARALLEL_DATA_ARG} is also created by
+@code{pass_lower_omp}. If there are shared variables to be
+communicated to the children threads, this operand will contain
+the @code{VAR_DECL} that contains all the shared values and
+variables.
+
+@item OMP_FOR
+
+Represents @code{#pragma omp for [clause1 @dots{} clauseN]}. It has
+six operands:
+
+Operand @code{OMP_FOR_BODY} contains the loop body.
+
+Operand @code{OMP_FOR_CLAUSES} is the list of clauses
+associated with the directive.
+
+Operand @code{OMP_FOR_INIT} is the loop initialization code of
+the form @code{VAR = N1}.
+
+Operand @code{OMP_FOR_COND} is the loop conditional expression
+of the form @code{VAR @{<,>,<=,>=@} N2}.
+
+Operand @code{OMP_FOR_INCR} is the loop index increment of the
+form @code{VAR @{+=,-=@} INCR}.
+
+Operand @code{OMP_FOR_PRE_BODY} contains side effect code from
+operands @code{OMP_FOR_INIT}, @code{OMP_FOR_COND} and
+@code{OMP_FOR_INC}. These side effects are part of the
+@code{OMP_FOR} block but must be evaluated before the start of
+loop body.
+
+The loop index variable @code{VAR} must be a signed integer variable,
+which is implicitly private to each thread. Bounds
+@code{N1} and @code{N2} and the increment expression
+@code{INCR} are required to be loop invariant integer
+expressions that are evaluated without any synchronization. The
+evaluation order, frequency of evaluation and side effects are
+unspecified by the standard.
+
+@item OMP_SECTIONS
+
+Represents @code{#pragma omp sections [clause1 @dots{} clauseN]}.
+
+Operand @code{OMP_SECTIONS_BODY} contains the sections body,
+which in turn contains a set of @code{OMP_SECTION} nodes for
+each of the concurrent sections delimited by @code{#pragma omp
+section}.
+
+Operand @code{OMP_SECTIONS_CLAUSES} is the list of clauses
+associated with the directive.
+
+@item OMP_SECTION
+
+Section delimiter for @code{OMP_SECTIONS}.
+
+@item OMP_SINGLE
+
+Represents @code{#pragma omp single}.
+
+Operand @code{OMP_SINGLE_BODY} contains the body of code to be
+executed by a single thread.
+
+Operand @code{OMP_SINGLE_CLAUSES} is the list of clauses
+associated with the directive.
+
+@item OMP_MASTER
+
+Represents @code{#pragma omp master}.
+
+Operand @code{OMP_MASTER_BODY} contains the body of code to be
+executed by the master thread.
+
+@item OMP_ORDERED
+
+Represents @code{#pragma omp ordered}.
+
+Operand @code{OMP_ORDERED_BODY} contains the body of code to be
+executed in the sequential order dictated by the loop index
+variable.
+
+@item OMP_CRITICAL
+
+Represents @code{#pragma omp critical [name]}.
+
+Operand @code{OMP_CRITICAL_BODY} is the critical section.
+
+Operand @code{OMP_CRITICAL_NAME} is an optional identifier to
+label the critical section.
+
+@item OMP_RETURN
+
+This does not represent any OpenMP directive, it is an artificial
+marker to indicate the end of the body of an OpenMP@. It is used
+by the flow graph (@code{tree-cfg.cc}) and OpenMP region
+building code (@code{omp-low.cc}).
+
+@item OMP_CONTINUE
+
+Similarly, this instruction does not represent an OpenMP
+directive, it is used by @code{OMP_FOR} (and similar codes) as well as
+@code{OMP_SECTIONS} to mark the place where the code needs to
+loop to the next iteration, or the next section, respectively.
+
+In some cases, @code{OMP_CONTINUE} is placed right before
+@code{OMP_RETURN}. But if there are cleanups that need to
+occur right after the looping body, it will be emitted between
+@code{OMP_CONTINUE} and @code{OMP_RETURN}.
+
+@item OMP_ATOMIC
+
+Represents @code{#pragma omp atomic}.
+
+Operand 0 is the address at which the atomic operation is to be
+performed.
+
+Operand 1 is the expression to evaluate. The gimplifier tries
+three alternative code generation strategies. Whenever possible,
+an atomic update built-in is used. If that fails, a
+compare-and-swap loop is attempted. If that also fails, a
+regular critical section around the expression is used.
+
+@item OMP_CLAUSE
+
+Represents clauses associated with one of the @code{OMP_} directives.
+Clauses are represented by separate subcodes defined in
+@file{tree.h}. Clauses codes can be one of:
+@code{OMP_CLAUSE_PRIVATE}, @code{OMP_CLAUSE_SHARED},
+@code{OMP_CLAUSE_FIRSTPRIVATE},
+@code{OMP_CLAUSE_LASTPRIVATE}, @code{OMP_CLAUSE_COPYIN},
+@code{OMP_CLAUSE_COPYPRIVATE}, @code{OMP_CLAUSE_IF},
+@code{OMP_CLAUSE_NUM_THREADS}, @code{OMP_CLAUSE_SCHEDULE},
+@code{OMP_CLAUSE_NOWAIT}, @code{OMP_CLAUSE_ORDERED},
+@code{OMP_CLAUSE_DEFAULT}, @code{OMP_CLAUSE_REDUCTION},
+@code{OMP_CLAUSE_COLLAPSE}, @code{OMP_CLAUSE_UNTIED},
+@code{OMP_CLAUSE_FINAL}, and @code{OMP_CLAUSE_MERGEABLE}. Each code
+represents the corresponding OpenMP clause.
+
+Clauses associated with the same directive are chained together
+via @code{OMP_CLAUSE_CHAIN}. Those clauses that accept a list
+of variables are restricted to exactly one, accessed with
+@code{OMP_CLAUSE_VAR}. Therefore, multiple variables under the
+same clause @code{C} need to be represented as multiple @code{C} clauses
+chained together. This facilitates adding new clauses during
+compilation.
+
+@end table
+
+@node OpenACC
+@subsection OpenACC
+@tindex OACC_CACHE
+@tindex OACC_DATA
+@tindex OACC_DECLARE
+@tindex OACC_ENTER_DATA
+@tindex OACC_EXIT_DATA
+@tindex OACC_HOST_DATA
+@tindex OACC_KERNELS
+@tindex OACC_LOOP
+@tindex OACC_PARALLEL
+@tindex OACC_SERIAL
+@tindex OACC_UPDATE
+
+All the statements starting with @code{OACC_} represent directives and
+clauses used by the OpenACC API @w{@uref{https://www.openacc.org}}.
+
+@table @code
+@item OACC_CACHE
+
+Represents @code{#pragma acc cache (var @dots{})}.
+
+@item OACC_DATA
+
+Represents @code{#pragma acc data [clause1 @dots{} clauseN]}.
+
+@item OACC_DECLARE
+
+Represents @code{#pragma acc declare [clause1 @dots{} clauseN]}.
+
+@item OACC_ENTER_DATA
+
+Represents @code{#pragma acc enter data [clause1 @dots{} clauseN]}.
+
+@item OACC_EXIT_DATA
+
+Represents @code{#pragma acc exit data [clause1 @dots{} clauseN]}.
+
+@item OACC_HOST_DATA
+
+Represents @code{#pragma acc host_data [clause1 @dots{} clauseN]}.
+
+@item OACC_KERNELS
+
+Represents @code{#pragma acc kernels [clause1 @dots{} clauseN]}.
+
+@item OACC_LOOP
+
+Represents @code{#pragma acc loop [clause1 @dots{} clauseN]}.
+
+See the description of the @code{OMP_FOR} code.
+
+@item OACC_PARALLEL
+
+Represents @code{#pragma acc parallel [clause1 @dots{} clauseN]}.
+
+@item OACC_SERIAL
+
+Represents @code{#pragma acc serial [clause1 @dots{} clauseN]}.
+
+@item OACC_UPDATE
+
+Represents @code{#pragma acc update [clause1 @dots{} clauseN]}.
+
+@end table
+
+@c ---------------------------------------------------------------------
+@c Functions
+@c ---------------------------------------------------------------------
+
+@node Functions
+@section Functions
+@cindex function
+@tindex FUNCTION_DECL
+
+A function is represented by a @code{FUNCTION_DECL} node. It stores
+the basic pieces of the function such as body, parameters, and return
+type as well as information on the surrounding context, visibility,
+and linkage.
+
+@menu
+* Function Basics:: Function names, body, and parameters.
+* Function Properties:: Context, linkage, etc.
+@end menu
+
+@c ---------------------------------------------------------------------
+@c Function Basics
+@c ---------------------------------------------------------------------
+
+@node Function Basics
+@subsection Function Basics
+@findex DECL_NAME
+@findex DECL_ASSEMBLER_NAME
+@findex TREE_PUBLIC
+@findex DECL_ARTIFICIAL
+@findex DECL_FUNCTION_SPECIFIC_TARGET
+@findex DECL_FUNCTION_SPECIFIC_OPTIMIZATION
+
+A function has four core parts: the name, the parameters, the result,
+and the body. The following macros and functions access these parts
+of a @code{FUNCTION_DECL} as well as other basic features:
+@ftable @code
+@item DECL_NAME
+This macro returns the unqualified name of the function, as an
+@code{IDENTIFIER_NODE}. For an instantiation of a function template,
+the @code{DECL_NAME} is the unqualified name of the template, not
+something like @code{f<int>}. The value of @code{DECL_NAME} is
+undefined when used on a constructor, destructor, overloaded operator,
+or type-conversion operator, or any function that is implicitly
+generated by the compiler. See below for macros that can be used to
+distinguish these cases.
+
+@item DECL_ASSEMBLER_NAME
+This macro returns the mangled name of the function, also an
+@code{IDENTIFIER_NODE}. This name does not contain leading underscores
+on systems that prefix all identifiers with underscores. The mangled
+name is computed in the same way on all platforms; if special processing
+is required to deal with the object file format used on a particular
+platform, it is the responsibility of the back end to perform those
+modifications. (Of course, the back end should not modify
+@code{DECL_ASSEMBLER_NAME} itself.)
+
+Using @code{DECL_ASSEMBLER_NAME} will cause additional memory to be
+allocated (for the mangled name of the entity) so it should be used
+only when emitting assembly code. It should not be used within the
+optimizers to determine whether or not two declarations are the same,
+even though some of the existing optimizers do use it in that way.
+These uses will be removed over time.
+
+@item DECL_ARGUMENTS
+This macro returns the @code{PARM_DECL} for the first argument to the
+function. Subsequent @code{PARM_DECL} nodes can be obtained by
+following the @code{TREE_CHAIN} links.
+
+@item DECL_RESULT
+This macro returns the @code{RESULT_DECL} for the function.
+
+@item DECL_SAVED_TREE
+This macro returns the complete body of the function.
+
+@item TREE_TYPE
+This macro returns the @code{FUNCTION_TYPE} or @code{METHOD_TYPE} for
+the function.
+
+@item DECL_INITIAL
+A function that has a definition in the current translation unit will
+have a non-@code{NULL} @code{DECL_INITIAL}. However, back ends should not make
+use of the particular value given by @code{DECL_INITIAL}.
+
+It should contain a tree of @code{BLOCK} nodes that mirrors the scopes
+that variables are bound in the function. Each block contains a list
+of decls declared in a basic block, a pointer to a chain of blocks at
+the next lower scope level, then a pointer to the next block at the
+same level and a backpointer to the parent @code{BLOCK} or
+@code{FUNCTION_DECL}. So given a function as follows:
+
+@smallexample
+void foo()
+@{
+ int a;
+ @{
+ int b;
+ @}
+ int c;
+@}
+@end smallexample
+
+you would get the following:
+
+@smallexample
+tree foo = FUNCTION_DECL;
+tree decl_a = VAR_DECL;
+tree decl_b = VAR_DECL;
+tree decl_c = VAR_DECL;
+tree block_a = BLOCK;
+tree block_b = BLOCK;
+tree block_c = BLOCK;
+BLOCK_VARS(block_a) = decl_a;
+BLOCK_SUBBLOCKS(block_a) = block_b;
+BLOCK_CHAIN(block_a) = block_c;
+BLOCK_SUPERCONTEXT(block_a) = foo;
+BLOCK_VARS(block_b) = decl_b;
+BLOCK_SUPERCONTEXT(block_b) = block_a;
+BLOCK_VARS(block_c) = decl_c;
+BLOCK_SUPERCONTEXT(block_c) = foo;
+DECL_INITIAL(foo) = block_a;
+@end smallexample
+
+@end ftable
+
+@c ---------------------------------------------------------------------
+@c Function Properties
+@c ---------------------------------------------------------------------
+
+@node Function Properties
+@subsection Function Properties
+@cindex function properties
+@cindex statements
+
+To determine the scope of a function, you can use the
+@code{DECL_CONTEXT} macro. This macro will return the class
+(either a @code{RECORD_TYPE} or a @code{UNION_TYPE}) or namespace (a
+@code{NAMESPACE_DECL}) of which the function is a member. For a virtual
+function, this macro returns the class in which the function was
+actually defined, not the base class in which the virtual declaration
+occurred.
+
+In C, the @code{DECL_CONTEXT} for a function maybe another function.
+This representation indicates that the GNU nested function extension
+is in use. For details on the semantics of nested functions, see the
+GCC Manual. The nested function can refer to local variables in its
+containing function. Such references are not explicitly marked in the
+tree structure; back ends must look at the @code{DECL_CONTEXT} for the
+referenced @code{VAR_DECL}. If the @code{DECL_CONTEXT} for the
+referenced @code{VAR_DECL} is not the same as the function currently
+being processed, and neither @code{DECL_EXTERNAL} nor
+@code{TREE_STATIC} hold, then the reference is to a local variable in
+a containing function, and the back end must take appropriate action.
+
+@ftable @code
+@item DECL_EXTERNAL
+This predicate holds if the function is undefined.
+
+@item TREE_PUBLIC
+This predicate holds if the function has external linkage.
+
+@item TREE_STATIC
+This predicate holds if the function has been defined.
+
+@item TREE_THIS_VOLATILE
+This predicate holds if the function does not return normally.
+
+@item TREE_READONLY
+This predicate holds if the function can only read its arguments.
+
+@item DECL_PURE_P
+This predicate holds if the function can only read its arguments, but
+may also read global memory.
+
+@item DECL_VIRTUAL_P
+This predicate holds if the function is virtual.
+
+@item DECL_ARTIFICIAL
+This macro holds if the function was implicitly generated by the
+compiler, rather than explicitly declared. In addition to implicitly
+generated class member functions, this macro holds for the special
+functions created to implement static initialization and destruction, to
+compute run-time type information, and so forth.
+
+@item DECL_FUNCTION_SPECIFIC_TARGET
+This macro returns a tree node that holds the target options that are
+to be used to compile this particular function or @code{NULL_TREE} if
+the function is to be compiled with the target options specified on
+the command line.
+
+@item DECL_FUNCTION_SPECIFIC_OPTIMIZATION
+This macro returns a tree node that holds the optimization options
+that are to be used to compile this particular function or
+@code{NULL_TREE} if the function is to be compiled with the
+optimization options specified on the command line.
+
+@end ftable
+
+@c ---------------------------------------------------------------------
+@c Language-dependent trees
+@c ---------------------------------------------------------------------
+
+@node Language-dependent trees
+@section Language-dependent trees
+@cindex language-dependent trees
+
+Front ends may wish to keep some state associated with various GENERIC
+trees while parsing. To support this, trees provide a set of flags
+that may be used by the front end. They are accessed using
+@code{TREE_LANG_FLAG_n} where @samp{n} is currently 0 through 6.
+
+If necessary, a front end can use some language-dependent tree
+codes in its GENERIC representation, so long as it provides a
+hook for converting them to GIMPLE and doesn't expect them to
+work with any (hypothetical) optimizers that run before the
+conversion to GIMPLE@. The intermediate representation used while
+parsing C and C++ looks very little like GENERIC, but the C and
+C++ gimplifier hooks are perfectly happy to take it as input and
+spit out GIMPLE@.
+
+
+
+@node C and C++ Trees
+@section C and C++ Trees
+
+This section documents the internal representation used by GCC to
+represent C and C++ source programs. When presented with a C or C++
+source program, GCC parses the program, performs semantic analysis
+(including the generation of error messages), and then produces the
+internal representation described here. This representation contains a
+complete representation for the entire translation unit provided as
+input to the front end. This representation is then typically processed
+by a code-generator in order to produce machine code, but could also be
+used in the creation of source browsers, intelligent editors, automatic
+documentation generators, interpreters, and any other programs needing
+the ability to process C or C++ code.
+
+This section explains the internal representation. In particular, it
+documents the internal representation for C and C++ source
+constructs, and the macros, functions, and variables that can be used to
+access these constructs. The C++ representation is largely a superset
+of the representation used in the C front end. There is only one
+construct used in C that does not appear in the C++ front end and that
+is the GNU ``nested function'' extension. Many of the macros documented
+here do not apply in C because the corresponding language constructs do
+not appear in C@.
+
+The C and C++ front ends generate a mix of GENERIC trees and ones
+specific to C and C++. These language-specific trees are higher-level
+constructs than the ones in GENERIC to make the parser's job easier.
+This section describes those trees that aren't part of GENERIC as well
+as aspects of GENERIC trees that are treated in a language-specific
+manner.
+
+If you are developing a ``back end'', be it is a code-generator or some
+other tool, that uses this representation, you may occasionally find
+that you need to ask questions not easily answered by the functions and
+macros available here. If that situation occurs, it is quite likely
+that GCC already supports the functionality you desire, but that the
+interface is simply not documented here. In that case, you should ask
+the GCC maintainers (via mail to @email{gcc@@gcc.gnu.org}) about
+documenting the functionality you require. Similarly, if you find
+yourself writing functions that do not deal directly with your back end,
+but instead might be useful to other people using the GCC front end, you
+should submit your patches for inclusion in GCC@.
+
+@menu
+* Types for C++:: Fundamental and aggregate types.
+* Namespaces:: Namespaces.
+* Classes:: Classes.
+* Functions for C++:: Overloading and accessors for C++.
+* Statements for C and C++:: Statements specific to C and C++.
+* C++ Expressions:: From @code{typeid} to @code{throw}.
+@end menu
+
+@node Types for C++
+@subsection Types for C++
+@tindex UNKNOWN_TYPE
+@tindex TYPENAME_TYPE
+@tindex TYPEOF_TYPE
+@findex cp_type_quals
+@findex TYPE_UNQUALIFIED
+@findex TYPE_QUAL_CONST
+@findex TYPE_QUAL_VOLATILE
+@findex TYPE_QUAL_RESTRICT
+@findex TYPE_MAIN_VARIANT
+@cindex qualified type
+@findex TYPE_SIZE
+@findex TYPE_ALIGN
+@findex TYPE_PRECISION
+@findex TYPE_ARG_TYPES
+@findex TYPE_METHOD_BASETYPE
+@findex TYPE_PTRDATAMEM_P
+@findex TYPE_OFFSET_BASETYPE
+@findex TREE_TYPE
+@findex TYPE_CONTEXT
+@findex TYPE_NAME
+@findex TYPENAME_TYPE_FULLNAME
+@findex TYPE_FIELDS
+@findex TYPE_PTROBV_P
+
+In C++, an array type is not qualified; rather the type of the array
+elements is qualified. This situation is reflected in the intermediate
+representation. The macros described here will always examine the
+qualification of the underlying element type when applied to an array
+type. (If the element type is itself an array, then the recursion
+continues until a non-array type is found, and the qualification of this
+type is examined.) So, for example, @code{CP_TYPE_CONST_P} will hold of
+the type @code{const int ()[7]}, denoting an array of seven @code{int}s.
+
+The following functions and macros deal with cv-qualification of types:
+@ftable @code
+@item cp_type_quals
+This function returns the set of type qualifiers applied to this type.
+This value is @code{TYPE_UNQUALIFIED} if no qualifiers have been
+applied. The @code{TYPE_QUAL_CONST} bit is set if the type is
+@code{const}-qualified. The @code{TYPE_QUAL_VOLATILE} bit is set if the
+type is @code{volatile}-qualified. The @code{TYPE_QUAL_RESTRICT} bit is
+set if the type is @code{restrict}-qualified.
+
+@item CP_TYPE_CONST_P
+This macro holds if the type is @code{const}-qualified.
+
+@item CP_TYPE_VOLATILE_P
+This macro holds if the type is @code{volatile}-qualified.
+
+@item CP_TYPE_RESTRICT_P
+This macro holds if the type is @code{restrict}-qualified.
+
+@item CP_TYPE_CONST_NON_VOLATILE_P
+This predicate holds for a type that is @code{const}-qualified, but
+@emph{not} @code{volatile}-qualified; other cv-qualifiers are ignored as
+well: only the @code{const}-ness is tested.
+
+@end ftable
+
+A few other macros and functions are usable with all types:
+@ftable @code
+@item TYPE_SIZE
+The number of bits required to represent the type, represented as an
+@code{INTEGER_CST}. For an incomplete type, @code{TYPE_SIZE} will be
+@code{NULL_TREE}.
+
+@item TYPE_ALIGN
+The alignment of the type, in bits, represented as an @code{int}.
+
+@item TYPE_NAME
+This macro returns a declaration (in the form of a @code{TYPE_DECL}) for
+the type. (Note this macro does @emph{not} return an
+@code{IDENTIFIER_NODE}, as you might expect, given its name!) You can
+look at the @code{DECL_NAME} of the @code{TYPE_DECL} to obtain the
+actual name of the type. The @code{TYPE_NAME} will be @code{NULL_TREE}
+for a type that is not a built-in type, the result of a typedef, or a
+named class type.
+
+@item CP_INTEGRAL_TYPE
+This predicate holds if the type is an integral type. Notice that in
+C++, enumerations are @emph{not} integral types.
+
+@item ARITHMETIC_TYPE_P
+This predicate holds if the type is an integral type (in the C++ sense)
+or a floating point type.
+
+@item CLASS_TYPE_P
+This predicate holds for a class-type.
+
+@item TYPE_BUILT_IN
+This predicate holds for a built-in type.
+
+@item TYPE_PTRDATAMEM_P
+This predicate holds if the type is a pointer to data member.
+
+@item TYPE_PTR_P
+This predicate holds if the type is a pointer type, and the pointee is
+not a data member.
+
+@item TYPE_PTRFN_P
+This predicate holds for a pointer to function type.
+
+@item TYPE_PTROB_P
+This predicate holds for a pointer to object type. Note however that it
+does not hold for the generic pointer to object type @code{void *}. You
+may use @code{TYPE_PTROBV_P} to test for a pointer to object type as
+well as @code{void *}.
+
+@end ftable
+
+The table below describes types specific to C and C++ as well as
+language-dependent info about GENERIC types.
+
+@table @code
+
+@item POINTER_TYPE
+Used to represent pointer types, and pointer to data member types. If
+@code{TREE_TYPE}
+is a pointer to data member type, then @code{TYPE_PTRDATAMEM_P} will hold.
+For a pointer to data member type of the form @samp{T X::*},
+@code{TYPE_PTRMEM_CLASS_TYPE} will be the type @code{X}, while
+@code{TYPE_PTRMEM_POINTED_TO_TYPE} will be the type @code{T}.
+
+@item RECORD_TYPE
+Used to represent @code{struct} and @code{class} types in C and C++. If
+@code{TYPE_PTRMEMFUNC_P} holds, then this type is a pointer-to-member
+type. In that case, the @code{TYPE_PTRMEMFUNC_FN_TYPE} is a
+@code{POINTER_TYPE} pointing to a @code{METHOD_TYPE}. The
+@code{METHOD_TYPE} is the type of a function pointed to by the
+pointer-to-member function. If @code{TYPE_PTRMEMFUNC_P} does not hold,
+this type is a class type. For more information, @pxref{Classes}.
+
+@item UNKNOWN_TYPE
+This node is used to represent a type the knowledge of which is
+insufficient for a sound processing.
+
+@item TYPENAME_TYPE
+Used to represent a construct of the form @code{typename T::A}. The
+@code{TYPE_CONTEXT} is @code{T}; the @code{TYPE_NAME} is an
+@code{IDENTIFIER_NODE} for @code{A}. If the type is specified via a
+template-id, then @code{TYPENAME_TYPE_FULLNAME} yields a
+@code{TEMPLATE_ID_EXPR}. The @code{TREE_TYPE} is non-@code{NULL} if the
+node is implicitly generated in support for the implicit typename
+extension; in which case the @code{TREE_TYPE} is a type node for the
+base-class.
+
+@item TYPEOF_TYPE
+Used to represent the @code{__typeof__} extension. The
+@code{TYPE_FIELDS} is the expression the type of which is being
+represented.
+
+@end table
+
+
+@c ---------------------------------------------------------------------
+@c Namespaces
+@c ---------------------------------------------------------------------
+
+@node Namespaces
+@subsection Namespaces
+@cindex namespace, scope
+@tindex NAMESPACE_DECL
+
+The root of the entire intermediate representation is the variable
+@code{global_namespace}. This is the namespace specified with @code{::}
+in C++ source code. All other namespaces, types, variables, functions,
+and so forth can be found starting with this namespace.
+
+However, except for the fact that it is distinguished as the root of the
+representation, the global namespace is no different from any other
+namespace. Thus, in what follows, we describe namespaces generally,
+rather than the global namespace in particular.
+
+A namespace is represented by a @code{NAMESPACE_DECL} node.
+
+The following macros and functions can be used on a @code{NAMESPACE_DECL}:
+
+@ftable @code
+@item DECL_NAME
+This macro is used to obtain the @code{IDENTIFIER_NODE} corresponding to
+the unqualified name of the name of the namespace (@pxref{Identifiers}).
+The name of the global namespace is @samp{::}, even though in C++ the
+global namespace is unnamed. However, you should use comparison with
+@code{global_namespace}, rather than @code{DECL_NAME} to determine
+whether or not a namespace is the global one. An unnamed namespace
+will have a @code{DECL_NAME} equal to @code{anonymous_namespace_name}.
+Within a single translation unit, all unnamed namespaces will have the
+same name.
+
+@item DECL_CONTEXT
+This macro returns the enclosing namespace. The @code{DECL_CONTEXT} for
+the @code{global_namespace} is @code{NULL_TREE}.
+
+@item DECL_NAMESPACE_ALIAS
+If this declaration is for a namespace alias, then
+@code{DECL_NAMESPACE_ALIAS} is the namespace for which this one is an
+alias.
+
+Do not attempt to use @code{cp_namespace_decls} for a namespace which is
+an alias. Instead, follow @code{DECL_NAMESPACE_ALIAS} links until you
+reach an ordinary, non-alias, namespace, and call
+@code{cp_namespace_decls} there.
+
+@item DECL_NAMESPACE_STD_P
+This predicate holds if the namespace is the special @code{::std}
+namespace.
+
+@item cp_namespace_decls
+This function will return the declarations contained in the namespace,
+including types, overloaded functions, other namespaces, and so forth.
+If there are no declarations, this function will return
+@code{NULL_TREE}. The declarations are connected through their
+@code{TREE_CHAIN} fields.
+
+Although most entries on this list will be declarations,
+@code{TREE_LIST} nodes may also appear. In this case, the
+@code{TREE_VALUE} will be an @code{OVERLOAD}. The value of the
+@code{TREE_PURPOSE} is unspecified; back ends should ignore this value.
+As with the other kinds of declarations returned by
+@code{cp_namespace_decls}, the @code{TREE_CHAIN} will point to the next
+declaration in this list.
+
+For more information on the kinds of declarations that can occur on this
+list, @xref{Declarations}. Some declarations will not appear on this
+list. In particular, no @code{FIELD_DECL}, @code{LABEL_DECL}, or
+@code{PARM_DECL} nodes will appear here.
+
+This function cannot be used with namespaces that have
+@code{DECL_NAMESPACE_ALIAS} set.
+
+@end ftable
+
+@c ---------------------------------------------------------------------
+@c Classes
+@c ---------------------------------------------------------------------
+
+@node Classes
+@subsection Classes
+@cindex class, scope
+@tindex RECORD_TYPE
+@tindex UNION_TYPE
+@findex CLASSTYPE_DECLARED_CLASS
+@findex TYPE_BINFO
+@findex BINFO_TYPE
+@findex TYPE_FIELDS
+@findex TYPE_VFIELD
+
+Besides namespaces, the other high-level scoping construct in C++ is the
+class. (Throughout this manual the term @dfn{class} is used to mean the
+types referred to in the ANSI/ISO C++ Standard as classes; these include
+types defined with the @code{class}, @code{struct}, and @code{union}
+keywords.)
+
+A class type is represented by either a @code{RECORD_TYPE} or a
+@code{UNION_TYPE}. A class declared with the @code{union} tag is
+represented by a @code{UNION_TYPE}, while classes declared with either
+the @code{struct} or the @code{class} tag are represented by
+@code{RECORD_TYPE}s. You can use the @code{CLASSTYPE_DECLARED_CLASS}
+macro to discern whether or not a particular type is a @code{class} as
+opposed to a @code{struct}. This macro will be true only for classes
+declared with the @code{class} tag.
+
+Almost all members are available on the @code{TYPE_FIELDS}
+list. Given one member, the next can be found by following the
+@code{TREE_CHAIN}. You should not depend in any way on the order in
+which fields appear on this list. All nodes on this list will be
+@samp{DECL} nodes. A @code{FIELD_DECL} is used to represent a non-static
+data member, a @code{VAR_DECL} is used to represent a static data
+member, and a @code{TYPE_DECL} is used to represent a type. Note that
+the @code{CONST_DECL} for an enumeration constant will appear on this
+list, if the enumeration type was declared in the class. (Of course,
+the @code{TYPE_DECL} for the enumeration type will appear here as well.)
+There are no entries for base classes on this list. In particular,
+there is no @code{FIELD_DECL} for the ``base-class portion'' of an
+object. If a function member is overloaded, each of the overloaded
+functions appears; no @code{OVERLOAD} nodes appear on the @code{TYPE_FIELDS}
+list. Implicitly declared functions (including default constructors,
+copy constructors, assignment operators, and destructors) will appear on
+this list as well.
+
+The @code{TYPE_VFIELD} is a compiler-generated field used to point to
+virtual function tables. It may or may not appear on the
+@code{TYPE_FIELDS} list. However, back ends should handle the
+@code{TYPE_VFIELD} just like all the entries on the @code{TYPE_FIELDS}
+list.
+
+Every class has an associated @dfn{binfo}, which can be obtained with
+@code{TYPE_BINFO}. Binfos are used to represent base-classes. The
+binfo given by @code{TYPE_BINFO} is the degenerate case, whereby every
+class is considered to be its own base-class. The base binfos for a
+particular binfo are held in a vector, whose length is obtained with
+@code{BINFO_N_BASE_BINFOS}. The base binfos themselves are obtained
+with @code{BINFO_BASE_BINFO} and @code{BINFO_BASE_ITERATE}. To add a
+new binfo, use @code{BINFO_BASE_APPEND}. The vector of base binfos can
+be obtained with @code{BINFO_BASE_BINFOS}, but normally you do not need
+to use that. The class type associated with a binfo is given by
+@code{BINFO_TYPE}. It is not always the case that @code{BINFO_TYPE
+(TYPE_BINFO (x))}, because of typedefs and qualified types. Neither is
+it the case that @code{TYPE_BINFO (BINFO_TYPE (y))} is the same binfo as
+@code{y}. The reason is that if @code{y} is a binfo representing a
+base-class @code{B} of a derived class @code{D}, then @code{BINFO_TYPE
+(y)} will be @code{B}, and @code{TYPE_BINFO (BINFO_TYPE (y))} will be
+@code{B} as its own base-class, rather than as a base-class of @code{D}.
+
+The access to a base type can be found with @code{BINFO_BASE_ACCESS}.
+This will produce @code{access_public_node}, @code{access_private_node}
+or @code{access_protected_node}. If bases are always public,
+@code{BINFO_BASE_ACCESSES} may be @code{NULL}.
+
+@code{BINFO_VIRTUAL_P} is used to specify whether the binfo is inherited
+virtually or not. The other flags, @code{BINFO_FLAG_0} to
+@code{BINFO_FLAG_6}, can be used for language specific use.
+
+The following macros can be used on a tree node representing a class-type.
+
+@ftable @code
+@item LOCAL_CLASS_P
+This predicate holds if the class is local class @emph{i.e.}@: declared
+inside a function body.
+
+@item TYPE_POLYMORPHIC_P
+This predicate holds if the class has at least one virtual function
+(declared or inherited).
+
+@item TYPE_HAS_DEFAULT_CONSTRUCTOR
+This predicate holds whenever its argument represents a class-type with
+default constructor.
+
+@item CLASSTYPE_HAS_MUTABLE
+@itemx TYPE_HAS_MUTABLE_P
+These predicates hold for a class-type having a mutable data member.
+
+@item CLASSTYPE_NON_POD_P
+This predicate holds only for class-types that are not PODs.
+
+@item TYPE_HAS_NEW_OPERATOR
+This predicate holds for a class-type that defines
+@code{operator new}.
+
+@item TYPE_HAS_ARRAY_NEW_OPERATOR
+This predicate holds for a class-type for which
+@code{operator new[]} is defined.
+
+@item TYPE_OVERLOADS_CALL_EXPR
+This predicate holds for class-type for which the function call
+@code{operator()} is overloaded.
+
+@item TYPE_OVERLOADS_ARRAY_REF
+This predicate holds for a class-type that overloads
+@code{operator[]}
+
+@item TYPE_OVERLOADS_ARROW
+This predicate holds for a class-type for which @code{operator->} is
+overloaded.
+
+@end ftable
+
+@node Functions for C++
+@subsection Functions for C++
+@cindex function
+@tindex FUNCTION_DECL
+@tindex OVERLOAD
+@findex OVL_CURRENT
+@findex OVL_NEXT
+
+A function is represented by a @code{FUNCTION_DECL} node. A set of
+overloaded functions is sometimes represented by an @code{OVERLOAD} node.
+
+An @code{OVERLOAD} node is not a declaration, so none of the
+@samp{DECL_} macros should be used on an @code{OVERLOAD}. An
+@code{OVERLOAD} node is similar to a @code{TREE_LIST}. Use
+@code{OVL_CURRENT} to get the function associated with an
+@code{OVERLOAD} node; use @code{OVL_NEXT} to get the next
+@code{OVERLOAD} node in the list of overloaded functions. The macros
+@code{OVL_CURRENT} and @code{OVL_NEXT} are actually polymorphic; you can
+use them to work with @code{FUNCTION_DECL} nodes as well as with
+overloads. In the case of a @code{FUNCTION_DECL}, @code{OVL_CURRENT}
+will always return the function itself, and @code{OVL_NEXT} will always
+be @code{NULL_TREE}.
+
+To determine the scope of a function, you can use the
+@code{DECL_CONTEXT} macro. This macro will return the class
+(either a @code{RECORD_TYPE} or a @code{UNION_TYPE}) or namespace (a
+@code{NAMESPACE_DECL}) of which the function is a member. For a virtual
+function, this macro returns the class in which the function was
+actually defined, not the base class in which the virtual declaration
+occurred.
+
+If a friend function is defined in a class scope, the
+@code{DECL_FRIEND_CONTEXT} macro can be used to determine the class in
+which it was defined. For example, in
+@smallexample
+class C @{ friend void f() @{@} @};
+@end smallexample
+@noindent
+the @code{DECL_CONTEXT} for @code{f} will be the
+@code{global_namespace}, but the @code{DECL_FRIEND_CONTEXT} will be the
+@code{RECORD_TYPE} for @code{C}.
+
+
+The following macros and functions can be used on a @code{FUNCTION_DECL}:
+@ftable @code
+@item DECL_MAIN_P
+This predicate holds for a function that is the program entry point
+@code{::code}.
+
+@item DECL_LOCAL_FUNCTION_P
+This predicate holds if the function was declared at block scope, even
+though it has a global scope.
+
+@item DECL_ANTICIPATED
+This predicate holds if the function is a built-in function but its
+prototype is not yet explicitly declared.
+
+@item DECL_EXTERN_C_FUNCTION_P
+This predicate holds if the function is declared as an
+`@code{extern "C"}' function.
+
+@item DECL_LINKONCE_P
+This macro holds if multiple copies of this function may be emitted in
+various translation units. It is the responsibility of the linker to
+merge the various copies. Template instantiations are the most common
+example of functions for which @code{DECL_LINKONCE_P} holds; G++
+instantiates needed templates in all translation units which require them,
+and then relies on the linker to remove duplicate instantiations.
+
+FIXME: This macro is not yet implemented.
+
+@item DECL_FUNCTION_MEMBER_P
+This macro holds if the function is a member of a class, rather than a
+member of a namespace.
+
+@item DECL_STATIC_FUNCTION_P
+This predicate holds if the function a static member function.
+
+@item DECL_NONSTATIC_MEMBER_FUNCTION_P
+This macro holds for a non-static member function.
+
+@item DECL_CONST_MEMFUNC_P
+This predicate holds for a @code{const}-member function.
+
+@item DECL_VOLATILE_MEMFUNC_P
+This predicate holds for a @code{volatile}-member function.
+
+@item DECL_CONSTRUCTOR_P
+This macro holds if the function is a constructor.
+
+@item DECL_NONCONVERTING_P
+This predicate holds if the constructor is a non-converting constructor.
+
+@item DECL_COMPLETE_CONSTRUCTOR_P
+This predicate holds for a function which is a constructor for an object
+of a complete type.
+
+@item DECL_BASE_CONSTRUCTOR_P
+This predicate holds for a function which is a constructor for a base
+class sub-object.
+
+@item DECL_COPY_CONSTRUCTOR_P
+This predicate holds for a function which is a copy-constructor.
+
+@item DECL_DESTRUCTOR_P
+This macro holds if the function is a destructor.
+
+@item DECL_COMPLETE_DESTRUCTOR_P
+This predicate holds if the function is the destructor for an object a
+complete type.
+
+@item DECL_OVERLOADED_OPERATOR_P
+This macro holds if the function is an overloaded operator.
+
+@item DECL_CONV_FN_P
+This macro holds if the function is a type-conversion operator.
+
+@item DECL_GLOBAL_CTOR_P
+This predicate holds if the function is a file-scope initialization
+function.
+
+@item DECL_GLOBAL_DTOR_P
+This predicate holds if the function is a file-scope finalization
+function.
+
+@item DECL_THUNK_P
+This predicate holds if the function is a thunk.
+
+These functions represent stub code that adjusts the @code{this} pointer
+and then jumps to another function. When the jumped-to function
+returns, control is transferred directly to the caller, without
+returning to the thunk. The first parameter to the thunk is always the
+@code{this} pointer; the thunk should add @code{THUNK_DELTA} to this
+value. (The @code{THUNK_DELTA} is an @code{int}, not an
+@code{INTEGER_CST}.)
+
+Then, if @code{THUNK_VCALL_OFFSET} (an @code{INTEGER_CST}) is nonzero
+the adjusted @code{this} pointer must be adjusted again. The complete
+calculation is given by the following pseudo-code:
+
+@smallexample
+this += THUNK_DELTA
+if (THUNK_VCALL_OFFSET)
+ this += (*((ptrdiff_t **) this))[THUNK_VCALL_OFFSET]
+@end smallexample
+
+Finally, the thunk should jump to the location given
+by @code{DECL_INITIAL}; this will always be an expression for the
+address of a function.
+
+@item DECL_NON_THUNK_FUNCTION_P
+This predicate holds if the function is @emph{not} a thunk function.
+
+@item GLOBAL_INIT_PRIORITY
+If either @code{DECL_GLOBAL_CTOR_P} or @code{DECL_GLOBAL_DTOR_P} holds,
+then this gives the initialization priority for the function. The
+linker will arrange that all functions for which
+@code{DECL_GLOBAL_CTOR_P} holds are run in increasing order of priority
+before @code{main} is called. When the program exits, all functions for
+which @code{DECL_GLOBAL_DTOR_P} holds are run in the reverse order.
+
+@item TYPE_RAISES_EXCEPTIONS
+This macro returns the list of exceptions that a (member-)function can
+raise. The returned list, if non @code{NULL}, is comprised of nodes
+whose @code{TREE_VALUE} represents a type.
+
+@item TYPE_NOTHROW_P
+This predicate holds when the exception-specification of its arguments
+is of the form `@code{()}'.
+
+@item DECL_ARRAY_DELETE_OPERATOR_P
+This predicate holds if the function an overloaded
+@code{operator delete[]}.
+
+@end ftable
+
+@c ---------------------------------------------------------------------
+@c Function Bodies
+@c ---------------------------------------------------------------------
+
+@node Statements for C and C++
+@subsection Statements for C and C++
+@cindex statements
+@tindex BREAK_STMT
+@tindex CLEANUP_STMT
+@findex CLEANUP_DECL
+@findex CLEANUP_EXPR
+@tindex CONTINUE_STMT
+@tindex DECL_STMT
+@findex DECL_STMT_DECL
+@tindex DO_STMT
+@findex DO_BODY
+@findex DO_COND
+@tindex EMPTY_CLASS_EXPR
+@tindex EXPR_STMT
+@findex EXPR_STMT_EXPR
+@tindex FOR_STMT
+@findex FOR_INIT_STMT
+@findex FOR_COND
+@findex FOR_EXPR
+@findex FOR_BODY
+@tindex HANDLER
+@tindex IF_STMT
+@findex IF_COND
+@findex THEN_CLAUSE
+@findex ELSE_CLAUSE
+@tindex RETURN_STMT
+@findex RETURN_EXPR
+@tindex SUBOBJECT
+@findex SUBOBJECT_CLEANUP
+@tindex SWITCH_STMT
+@findex SWITCH_COND
+@findex SWITCH_BODY
+@tindex TRY_BLOCK
+@findex TRY_STMTS
+@findex TRY_HANDLERS
+@findex HANDLER_PARMS
+@findex HANDLER_BODY
+@findex USING_STMT
+@tindex WHILE_STMT
+@findex WHILE_BODY
+@findex WHILE_COND
+
+A function that has a definition in the current translation unit has
+a non-@code{NULL} @code{DECL_INITIAL}. However, back ends should not make
+use of the particular value given by @code{DECL_INITIAL}.
+
+The @code{DECL_SAVED_TREE} gives the complete body of the
+function.
+
+There are tree nodes corresponding to all of the source-level
+statement constructs, used within the C and C++ frontends. These are
+enumerated here, together with a list of the various macros that can
+be used to obtain information about them. There are a few macros that
+can be used with all statements:
+
+@ftable @code
+@item STMT_IS_FULL_EXPR_P
+In C++, statements normally constitute ``full expressions''; temporaries
+created during a statement are destroyed when the statement is complete.
+However, G++ sometimes represents expressions by statements; these
+statements will not have @code{STMT_IS_FULL_EXPR_P} set. Temporaries
+created during such statements should be destroyed when the innermost
+enclosing statement with @code{STMT_IS_FULL_EXPR_P} set is exited.
+
+@end ftable
+
+Here is the list of the various statement nodes, and the macros used to
+access them. This documentation describes the use of these nodes in
+non-template functions (including instantiations of template functions).
+In template functions, the same nodes are used, but sometimes in
+slightly different ways.
+
+Many of the statements have substatements. For example, a @code{while}
+loop has a body, which is itself a statement. If the substatement
+is @code{NULL_TREE}, it is considered equivalent to a statement
+consisting of a single @code{;}, i.e., an expression statement in which
+the expression has been omitted. A substatement may in fact be a list
+of statements, connected via their @code{TREE_CHAIN}s. So, you should
+always process the statement tree by looping over substatements, like
+this:
+@smallexample
+void process_stmt (stmt)
+ tree stmt;
+@{
+ while (stmt)
+ @{
+ switch (TREE_CODE (stmt))
+ @{
+ case IF_STMT:
+ process_stmt (THEN_CLAUSE (stmt));
+ /* @r{More processing here.} */
+ break;
+
+ @dots{}
+ @}
+
+ stmt = TREE_CHAIN (stmt);
+ @}
+@}
+@end smallexample
+In other words, while the @code{then} clause of an @code{if} statement
+in C++ can be only one statement (although that one statement may be a
+compound statement), the intermediate representation sometimes uses
+several statements chained together.
+
+@table @code
+@item BREAK_STMT
+
+Used to represent a @code{break} statement. There are no additional
+fields.
+
+@item CLEANUP_STMT
+
+Used to represent an action that should take place upon exit from the
+enclosing scope. Typically, these actions are calls to destructors for
+local objects, but back ends cannot rely on this fact. If these nodes
+are in fact representing such destructors, @code{CLEANUP_DECL} will be
+the @code{VAR_DECL} destroyed. Otherwise, @code{CLEANUP_DECL} will be
+@code{NULL_TREE}. In any case, the @code{CLEANUP_EXPR} is the
+expression to execute. The cleanups executed on exit from a scope
+should be run in the reverse order of the order in which the associated
+@code{CLEANUP_STMT}s were encountered.
+
+@item CONTINUE_STMT
+
+Used to represent a @code{continue} statement. There are no additional
+fields.
+
+@item CTOR_STMT
+
+Used to mark the beginning (if @code{CTOR_BEGIN_P} holds) or end (if
+@code{CTOR_END_P} holds of the main body of a constructor. See also
+@code{SUBOBJECT} for more information on how to use these nodes.
+
+@item DO_STMT
+
+Used to represent a @code{do} loop. The body of the loop is given by
+@code{DO_BODY} while the termination condition for the loop is given by
+@code{DO_COND}. The condition for a @code{do}-statement is always an
+expression.
+
+@item EMPTY_CLASS_EXPR
+
+Used to represent a temporary object of a class with no data whose
+address is never taken. (All such objects are interchangeable.) The
+@code{TREE_TYPE} represents the type of the object.
+
+@item EXPR_STMT
+
+Used to represent an expression statement. Use @code{EXPR_STMT_EXPR} to
+obtain the expression.
+
+@item FOR_STMT
+
+Used to represent a @code{for} statement. The @code{FOR_INIT_STMT} is
+the initialization statement for the loop. The @code{FOR_COND} is the
+termination condition. The @code{FOR_EXPR} is the expression executed
+right before the @code{FOR_COND} on each loop iteration; often, this
+expression increments a counter. The body of the loop is given by
+@code{FOR_BODY}. @code{FOR_SCOPE} holds the scope of the @code{for}
+statement (used in the C++ front end only). Note that
+@code{FOR_INIT_STMT} and @code{FOR_BODY} return statements, while
+@code{FOR_COND} and @code{FOR_EXPR} return expressions.
+
+@item HANDLER
+
+Used to represent a C++ @code{catch} block. The @code{HANDLER_TYPE}
+is the type of exception that will be caught by this handler; it is
+equal (by pointer equality) to @code{NULL} if this handler is for all
+types. @code{HANDLER_PARMS} is the @code{DECL_STMT} for the catch
+parameter, and @code{HANDLER_BODY} is the code for the block itself.
+
+@item IF_STMT
+
+Used to represent an @code{if} statement. The @code{IF_COND} is the
+expression.
+
+If the condition is a @code{TREE_LIST}, then the @code{TREE_PURPOSE} is
+a statement (usually a @code{DECL_STMT}). Each time the condition is
+evaluated, the statement should be executed. Then, the
+@code{TREE_VALUE} should be used as the conditional expression itself.
+This representation is used to handle C++ code like this:
+
+@smallexample
+if (int i = 7) @dots{}
+@end smallexample
+
+where there is a new local variable (or variables) declared within the
+condition.
+
+The @code{THEN_CLAUSE} represents the statement given by the @code{then}
+condition, while the @code{ELSE_CLAUSE} represents the statement given
+by the @code{else} condition.
+
+C++ distinguishes between this and @code{COND_EXPR} for handling templates.
+
+@item SUBOBJECT
+
+In a constructor, these nodes are used to mark the point at which a
+subobject of @code{this} is fully constructed. If, after this point, an
+exception is thrown before a @code{CTOR_STMT} with @code{CTOR_END_P} set
+is encountered, the @code{SUBOBJECT_CLEANUP} must be executed. The
+cleanups must be executed in the reverse order in which they appear.
+
+@item SWITCH_STMT
+
+Used to represent a @code{switch} statement. The @code{SWITCH_STMT_COND}
+is the expression on which the switch is occurring. See the documentation
+for an @code{IF_STMT} for more information on the representation used
+for the condition. The @code{SWITCH_STMT_BODY} is the body of the switch
+statement. The @code{SWITCH_STMT_TYPE} is the original type of switch
+expression as given in the source, before any compiler conversions.
+The @code{SWITCH_STMT_SCOPE} is the statement scope (used in the
+C++ front end only).
+
+There are also two boolean flags used with @code{SWITCH_STMT}.
+@code{SWITCH_STMT_ALL_CASES_P} is true if the switch includes a default label
+or the case label ranges cover all possible values of the condition
+expression. @code{SWITCH_STMT_NO_BREAK_P} is true if there are no
+@code{break} statements in the switch.
+
+@item TRY_BLOCK
+Used to represent a @code{try} block. The body of the try block is
+given by @code{TRY_STMTS}. Each of the catch blocks is a @code{HANDLER}
+node. The first handler is given by @code{TRY_HANDLERS}. Subsequent
+handlers are obtained by following the @code{TREE_CHAIN} link from one
+handler to the next. The body of the handler is given by
+@code{HANDLER_BODY}.
+
+If @code{CLEANUP_P} holds of the @code{TRY_BLOCK}, then the
+@code{TRY_HANDLERS} will not be a @code{HANDLER} node. Instead, it will
+be an expression that should be executed if an exception is thrown in
+the try block. It must rethrow the exception after executing that code.
+And, if an exception is thrown while the expression is executing,
+@code{terminate} must be called.
+
+@item USING_STMT
+Used to represent a @code{using} directive. The namespace is given by
+@code{USING_STMT_NAMESPACE}, which will be a NAMESPACE_DECL@. This node
+is needed inside template functions, to implement using directives
+during instantiation.
+
+@item WHILE_STMT
+
+Used to represent a @code{while} loop. The @code{WHILE_COND} is the
+termination condition for the loop. See the documentation for an
+@code{IF_STMT} for more information on the representation used for the
+condition.
+
+The @code{WHILE_BODY} is the body of the loop.
+
+@end table
+
+@node C++ Expressions
+@subsection C++ Expressions
+
+This section describes expressions specific to the C and C++ front
+ends.
+
+@table @code
+@item TYPEID_EXPR
+
+Used to represent a @code{typeid} expression.
+
+@item NEW_EXPR
+@itemx VEC_NEW_EXPR
+
+Used to represent a call to @code{new} and @code{new[]} respectively.
+
+@item DELETE_EXPR
+@itemx VEC_DELETE_EXPR
+
+Used to represent a call to @code{delete} and @code{delete[]} respectively.
+
+@item MEMBER_REF
+
+Represents a reference to a member of a class.
+
+@item THROW_EXPR
+
+Represents an instance of @code{throw} in the program. Operand 0,
+which is the expression to throw, may be @code{NULL_TREE}.
+
+
+@item AGGR_INIT_EXPR
+An @code{AGGR_INIT_EXPR} represents the initialization as the return
+value of a function call, or as the result of a constructor. An
+@code{AGGR_INIT_EXPR} will only appear as a full-expression, or as the
+second operand of a @code{TARGET_EXPR}. @code{AGGR_INIT_EXPR}s have
+a representation similar to that of @code{CALL_EXPR}s. You can use
+the @code{AGGR_INIT_EXPR_FN} and @code{AGGR_INIT_EXPR_ARG} macros to access
+the function to call and the arguments to pass.
+
+If @code{AGGR_INIT_VIA_CTOR_P} holds of the @code{AGGR_INIT_EXPR}, then
+the initialization is via a constructor call. The address of the
+@code{AGGR_INIT_EXPR_SLOT} operand, which is always a @code{VAR_DECL},
+is taken, and this value replaces the first argument in the argument
+list.
+
+In either case, the expression is void.
+
+
+@end table
--- /dev/null
+@c Copyright (C) 2008-2022 Free Software Foundation, Inc.
+@c Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node GIMPLE
+@chapter GIMPLE
+@cindex GIMPLE
+
+GIMPLE is a three-address representation derived from GENERIC by
+breaking down GENERIC expressions into tuples of no more than 3
+operands (with some exceptions like function calls). GIMPLE was
+heavily influenced by the SIMPLE IL used by the McCAT compiler
+project at McGill University, though we have made some different
+choices. For one thing, SIMPLE doesn't support @code{goto}.
+
+Temporaries are introduced to hold intermediate values needed to
+compute complex expressions. Additionally, all the control
+structures used in GENERIC are lowered into conditional jumps,
+lexical scopes are removed and exception regions are converted
+into an on the side exception region tree.
+
+The compiler pass which converts GENERIC into GIMPLE is referred to as
+the @samp{gimplifier}. The gimplifier works recursively, generating
+GIMPLE tuples out of the original GENERIC expressions.
+
+One of the early implementation strategies used for the GIMPLE
+representation was to use the same internal data structures used
+by front ends to represent parse trees. This simplified
+implementation because we could leverage existing functionality
+and interfaces. However, GIMPLE is a much more restrictive
+representation than abstract syntax trees (AST), therefore it
+does not require the full structural complexity provided by the
+main tree data structure.
+
+The GENERIC representation of a function is stored in the
+@code{DECL_SAVED_TREE} field of the associated @code{FUNCTION_DECL}
+tree node. It is converted to GIMPLE by a call to
+@code{gimplify_function_tree}.
+
+If a front end wants to include language-specific tree codes in the tree
+representation which it provides to the back end, it must provide a
+definition of @code{LANG_HOOKS_GIMPLIFY_EXPR} which knows how to
+convert the front end trees to GIMPLE@. Usually such a hook will involve
+much of the same code for expanding front end trees to RTL@. This function
+can return fully lowered GIMPLE, or it can return GENERIC trees and let the
+main gimplifier lower them the rest of the way; this is often simpler.
+GIMPLE that is not fully lowered is known as ``High GIMPLE'' and
+consists of the IL before the pass @code{pass_lower_cf}. High GIMPLE
+contains some container statements like lexical scopes
+(represented by @code{GIMPLE_BIND}) and nested expressions (e.g.,
+@code{GIMPLE_TRY}), while ``Low GIMPLE'' exposes all of the
+implicit jumps for control and exception expressions directly in
+the IL and EH region trees.
+
+The C and C++ front ends currently convert directly from front end
+trees to GIMPLE, and hand that off to the back end rather than first
+converting to GENERIC@. Their gimplifier hooks know about all the
+@code{_STMT} nodes and how to convert them to GENERIC forms. There
+was some work done on a genericization pass which would run first, but
+the existence of @code{STMT_EXPR} meant that in order to convert all
+of the C statements into GENERIC equivalents would involve walking the
+entire tree anyway, so it was simpler to lower all the way. This
+might change in the future if someone writes an optimization pass
+which would work better with higher-level trees, but currently the
+optimizers all expect GIMPLE@.
+
+You can request to dump a C-like representation of the GIMPLE form
+with the flag @option{-fdump-tree-gimple}.
+
+@menu
+* Tuple representation::
+* Class hierarchy of GIMPLE statements::
+* GIMPLE instruction set::
+* GIMPLE Exception Handling::
+* Temporaries::
+* Operands::
+* Manipulating GIMPLE statements::
+* Tuple specific accessors::
+* GIMPLE sequences::
+* Sequence iterators::
+* Adding a new GIMPLE statement code::
+* Statement and operand traversals::
+@end menu
+
+@node Tuple representation
+@section Tuple representation
+@cindex tuples
+
+GIMPLE instructions are tuples of variable size divided in two
+groups: a header describing the instruction and its locations,
+and a variable length body with all the operands. Tuples are
+organized into a hierarchy with 3 main classes of tuples.
+
+@subsection @code{gimple} (gsbase)
+@cindex gimple
+
+This is the root of the hierarchy, it holds basic information
+needed by most GIMPLE statements. There are some fields that
+may not be relevant to every GIMPLE statement, but those were
+moved into the base structure to take advantage of holes left by
+other fields (thus making the structure more compact). The
+structure takes 4 words (32 bytes) on 64 bit hosts:
+
+@multitable {@code{references_memory_p}} {Size (bits)}
+@item Field @tab Size (bits)
+@item @code{code} @tab 8
+@item @code{subcode} @tab 16
+@item @code{no_warning} @tab 1
+@item @code{visited} @tab 1
+@item @code{nontemporal_move} @tab 1
+@item @code{plf} @tab 2
+@item @code{modified} @tab 1
+@item @code{has_volatile_ops} @tab 1
+@item @code{references_memory_p} @tab 1
+@item @code{uid} @tab 32
+@item @code{location} @tab 32
+@item @code{num_ops} @tab 32
+@item @code{bb} @tab 64
+@item @code{block} @tab 63
+@item Total size @tab 32 bytes
+@end multitable
+
+@itemize @bullet
+@item @code{code}
+Main identifier for a GIMPLE instruction.
+
+@item @code{subcode}
+Used to distinguish different variants of the same basic
+instruction or provide flags applicable to a given code. The
+@code{subcode} flags field has different uses depending on the code of
+the instruction, but mostly it distinguishes instructions of the
+same family. The most prominent use of this field is in
+assignments, where subcode indicates the operation done on the
+RHS of the assignment. For example, a = b + c is encoded as
+@code{GIMPLE_ASSIGN <PLUS_EXPR, a, b, c>}.
+
+@item @code{no_warning}
+Bitflag to indicate whether a warning has already been issued on
+this statement.
+
+@item @code{visited}
+General purpose ``visited'' marker. Set and cleared by each pass
+when needed.
+
+@item @code{nontemporal_move}
+Bitflag used in assignments that represent non-temporal moves.
+Although this bitflag is only used in assignments, it was moved
+into the base to take advantage of the bit holes left by the
+previous fields.
+
+@item @code{plf}
+Pass Local Flags. This 2-bit mask can be used as general purpose
+markers by any pass. Passes are responsible for clearing and
+setting these two flags accordingly.
+
+@item @code{modified}
+Bitflag to indicate whether the statement has been modified.
+Used mainly by the operand scanner to determine when to re-scan a
+statement for operands.
+
+@item @code{has_volatile_ops}
+Bitflag to indicate whether this statement contains operands that
+have been marked volatile.
+
+@item @code{references_memory_p}
+Bitflag to indicate whether this statement contains memory
+references (i.e., its operands are either global variables, or
+pointer dereferences or anything that must reside in memory).
+
+@item @code{uid}
+This is an unsigned integer used by passes that want to assign
+IDs to every statement. These IDs must be assigned and used by
+each pass.
+
+@item @code{location}
+This is a @code{location_t} identifier to specify source code
+location for this statement. It is inherited from the front
+end.
+
+@item @code{num_ops}
+Number of operands that this statement has. This specifies the
+size of the operand vector embedded in the tuple. Only used in
+some tuples, but it is declared in the base tuple to take
+advantage of the 32-bit hole left by the previous fields.
+
+@item @code{bb}
+Basic block holding the instruction.
+
+@item @code{block}
+Lexical block holding this statement. Also used for debug
+information generation.
+@end itemize
+
+@subsection @code{gimple_statement_with_ops}
+@cindex gimple_statement_with_ops
+
+This tuple is actually split in two:
+@code{gimple_statement_with_ops_base} and
+@code{gimple_statement_with_ops}. This is needed to accommodate the
+way the operand vector is allocated. The operand vector is
+defined to be an array of 1 element. So, to allocate a dynamic
+number of operands, the memory allocator (@code{gimple_alloc}) simply
+allocates enough memory to hold the structure itself plus @code{N
+- 1} operands which run ``off the end'' of the structure. For
+example, to allocate space for a tuple with 3 operands,
+@code{gimple_alloc} reserves @code{sizeof (struct
+gimple_statement_with_ops) + 2 * sizeof (tree)} bytes.
+
+On the other hand, several fields in this tuple need to be shared
+with the @code{gimple_statement_with_memory_ops} tuple. So, these
+common fields are placed in @code{gimple_statement_with_ops_base} which
+is then inherited from the other two tuples.
+
+
+@multitable {@code{def_ops}} {48 + 8 * @code{num_ops} bytes}
+@item @code{gsbase} @tab 256
+@item @code{def_ops} @tab 64
+@item @code{use_ops} @tab 64
+@item @code{op} @tab @code{num_ops} * 64
+@item Total size @tab 48 + 8 * @code{num_ops} bytes
+@end multitable
+
+@itemize @bullet
+@item @code{gsbase}
+Inherited from @code{struct gimple}.
+
+@item @code{def_ops}
+Array of pointers into the operand array indicating all the slots that
+contain a variable written-to by the statement. This array is
+also used for immediate use chaining. Note that it would be
+possible to not rely on this array, but the changes required to
+implement this are pretty invasive.
+
+@item @code{use_ops}
+Similar to @code{def_ops} but for variables read by the statement.
+
+@item @code{op}
+Array of trees with @code{num_ops} slots.
+@end itemize
+
+@subsection @code{gimple_statement_with_memory_ops}
+
+This tuple is essentially identical to @code{gimple_statement_with_ops},
+except that it contains 4 additional fields to hold vectors
+related memory stores and loads. Similar to the previous case,
+the structure is split in two to accommodate for the operand
+vector (@code{gimple_statement_with_memory_ops_base} and
+@code{gimple_statement_with_memory_ops}).
+
+
+@multitable {@code{vdef_ops}} {80 + 8 * @code{num_ops} bytes}
+@item Field @tab Size (bits)
+@item @code{gsbase} @tab 256
+@item @code{def_ops} @tab 64
+@item @code{use_ops} @tab 64
+@item @code{vdef_ops} @tab 64
+@item @code{vuse_ops} @tab 64
+@item @code{stores} @tab 64
+@item @code{loads} @tab 64
+@item @code{op} @tab @code{num_ops} * 64
+@item Total size @tab 80 + 8 * @code{num_ops} bytes
+@end multitable
+
+@itemize @bullet
+@item @code{vdef_ops}
+Similar to @code{def_ops} but for @code{VDEF} operators. There is
+one entry per memory symbol written by this statement. This is
+used to maintain the memory SSA use-def and def-def chains.
+
+@item @code{vuse_ops}
+Similar to @code{use_ops} but for @code{VUSE} operators. There is
+one entry per memory symbol loaded by this statement. This is
+used to maintain the memory SSA use-def chains.
+
+@item @code{stores}
+Bitset with all the UIDs for the symbols written-to by the
+statement. This is different than @code{vdef_ops} in that all the
+affected symbols are mentioned in this set. If memory
+partitioning is enabled, the @code{vdef_ops} vector will refer to memory
+partitions. Furthermore, no SSA information is stored in this
+set.
+
+@item @code{loads}
+Similar to @code{stores}, but for memory loads. (Note that there
+is some amount of redundancy here, it should be possible to
+reduce memory utilization further by removing these sets).
+@end itemize
+
+All the other tuples are defined in terms of these three basic
+ones. Each tuple will add some fields.
+
+
+@node Class hierarchy of GIMPLE statements
+@section Class hierarchy of GIMPLE statements
+@cindex GIMPLE class hierarchy
+
+The following diagram shows the C++ inheritance hierarchy of statement
+kinds, along with their relationships to @code{GSS_} values (layouts) and
+@code{GIMPLE_} values (codes):
+
+@smallexample
+ gimple
+ | layout: GSS_BASE
+ | used for 4 codes: GIMPLE_ERROR_MARK
+ | GIMPLE_NOP
+ | GIMPLE_OMP_SECTIONS_SWITCH
+ | GIMPLE_PREDICT
+ |
+ + gimple_statement_with_ops_base
+ | | (no GSS layout)
+ | |
+ | + gimple_statement_with_ops
+ | | | layout: GSS_WITH_OPS
+ | | |
+ | | + gcond
+ | | | code: GIMPLE_COND
+ | | |
+ | | + gdebug
+ | | | code: GIMPLE_DEBUG
+ | | |
+ | | + ggoto
+ | | | code: GIMPLE_GOTO
+ | | |
+ | | + glabel
+ | | | code: GIMPLE_LABEL
+ | | |
+ | | + gswitch
+ | | code: GIMPLE_SWITCH
+ | |
+ | + gimple_statement_with_memory_ops_base
+ | | layout: GSS_WITH_MEM_OPS_BASE
+ | |
+ | + gimple_statement_with_memory_ops
+ | | | layout: GSS_WITH_MEM_OPS
+ | | |
+ | | + gassign
+ | | | code GIMPLE_ASSIGN
+ | | |
+ | | + greturn
+ | | code GIMPLE_RETURN
+ | |
+ | + gcall
+ | | layout: GSS_CALL, code: GIMPLE_CALL
+ | |
+ | + gasm
+ | | layout: GSS_ASM, code: GIMPLE_ASM
+ | |
+ | + gtransaction
+ | layout: GSS_TRANSACTION, code: GIMPLE_TRANSACTION
+ |
+ + gimple_statement_omp
+ | | layout: GSS_OMP. Used for code GIMPLE_OMP_SECTION
+ | |
+ | + gomp_critical
+ | | layout: GSS_OMP_CRITICAL, code: GIMPLE_OMP_CRITICAL
+ | |
+ | + gomp_for
+ | | layout: GSS_OMP_FOR, code: GIMPLE_OMP_FOR
+ | |
+ | + gomp_parallel_layout
+ | | | layout: GSS_OMP_PARALLEL_LAYOUT
+ | | |
+ | | + gimple_statement_omp_taskreg
+ | | | |
+ | | | + gomp_parallel
+ | | | | code: GIMPLE_OMP_PARALLEL
+ | | | |
+ | | | + gomp_task
+ | | | code: GIMPLE_OMP_TASK
+ | | |
+ | | + gimple_statement_omp_target
+ | | code: GIMPLE_OMP_TARGET
+ | |
+ | + gomp_sections
+ | | layout: GSS_OMP_SECTIONS, code: GIMPLE_OMP_SECTIONS
+ | |
+ | + gimple_statement_omp_single_layout
+ | | layout: GSS_OMP_SINGLE_LAYOUT
+ | |
+ | + gomp_single
+ | | code: GIMPLE_OMP_SINGLE
+ | |
+ | + gomp_teams
+ | code: GIMPLE_OMP_TEAMS
+ |
+ + gbind
+ | layout: GSS_BIND, code: GIMPLE_BIND
+ |
+ + gcatch
+ | layout: GSS_CATCH, code: GIMPLE_CATCH
+ |
+ + geh_filter
+ | layout: GSS_EH_FILTER, code: GIMPLE_EH_FILTER
+ |
+ + geh_else
+ | layout: GSS_EH_ELSE, code: GIMPLE_EH_ELSE
+ |
+ + geh_mnt
+ | layout: GSS_EH_MNT, code: GIMPLE_EH_MUST_NOT_THROW
+ |
+ + gphi
+ | layout: GSS_PHI, code: GIMPLE_PHI
+ |
+ + gimple_statement_eh_ctrl
+ | | layout: GSS_EH_CTRL
+ | |
+ | + gresx
+ | | code: GIMPLE_RESX
+ | |
+ | + geh_dispatch
+ | code: GIMPLE_EH_DISPATCH
+ |
+ + gtry
+ | layout: GSS_TRY, code: GIMPLE_TRY
+ |
+ + gimple_statement_wce
+ | layout: GSS_WCE, code: GIMPLE_WITH_CLEANUP_EXPR
+ |
+ + gomp_continue
+ | layout: GSS_OMP_CONTINUE, code: GIMPLE_OMP_CONTINUE
+ |
+ + gomp_atomic_load
+ | layout: GSS_OMP_ATOMIC_LOAD, code: GIMPLE_OMP_ATOMIC_LOAD
+ |
+ + gimple_statement_omp_atomic_store_layout
+ | layout: GSS_OMP_ATOMIC_STORE_LAYOUT,
+ | code: GIMPLE_OMP_ATOMIC_STORE
+ |
+ + gomp_atomic_store
+ | code: GIMPLE_OMP_ATOMIC_STORE
+ |
+ + gomp_return
+ code: GIMPLE_OMP_RETURN
+@end smallexample
+
+
+@node GIMPLE instruction set
+@section GIMPLE instruction set
+@cindex GIMPLE instruction set
+
+The following table briefly describes the GIMPLE instruction set.
+
+@multitable {@code{GIMPLE_OMP_SECTIONS_SWITCH}} {High GIMPLE} {Low GIMPLE}
+@item Instruction @tab High GIMPLE @tab Low GIMPLE
+@item @code{GIMPLE_ASM} @tab x @tab x
+@item @code{GIMPLE_ASSIGN} @tab x @tab x
+@item @code{GIMPLE_BIND} @tab x @tab
+@item @code{GIMPLE_CALL} @tab x @tab x
+@item @code{GIMPLE_CATCH} @tab x @tab
+@item @code{GIMPLE_COND} @tab x @tab x
+@item @code{GIMPLE_DEBUG} @tab x @tab x
+@item @code{GIMPLE_EH_FILTER} @tab x @tab
+@item @code{GIMPLE_GOTO} @tab x @tab x
+@item @code{GIMPLE_LABEL} @tab x @tab x
+@item @code{GIMPLE_NOP} @tab x @tab x
+@item @code{GIMPLE_OMP_ATOMIC_LOAD} @tab x @tab x
+@item @code{GIMPLE_OMP_ATOMIC_STORE} @tab x @tab x
+@item @code{GIMPLE_OMP_CONTINUE} @tab x @tab x
+@item @code{GIMPLE_OMP_CRITICAL} @tab x @tab x
+@item @code{GIMPLE_OMP_FOR} @tab x @tab x
+@item @code{GIMPLE_OMP_MASTER} @tab x @tab x
+@item @code{GIMPLE_OMP_ORDERED} @tab x @tab x
+@item @code{GIMPLE_OMP_PARALLEL} @tab x @tab x
+@item @code{GIMPLE_OMP_RETURN} @tab x @tab x
+@item @code{GIMPLE_OMP_SECTION} @tab x @tab x
+@item @code{GIMPLE_OMP_SECTIONS} @tab x @tab x
+@item @code{GIMPLE_OMP_SECTIONS_SWITCH} @tab x @tab x
+@item @code{GIMPLE_OMP_SINGLE} @tab x @tab x
+@item @code{GIMPLE_PHI} @tab @tab x
+@item @code{GIMPLE_RESX} @tab @tab x
+@item @code{GIMPLE_RETURN} @tab x @tab x
+@item @code{GIMPLE_SWITCH} @tab x @tab x
+@item @code{GIMPLE_TRY} @tab x @tab
+@end multitable
+
+@node GIMPLE Exception Handling
+@section Exception Handling
+@cindex GIMPLE Exception Handling
+
+Other exception handling constructs are represented using
+@code{GIMPLE_TRY_CATCH}. @code{GIMPLE_TRY_CATCH} has two operands. The
+first operand is a sequence of statements to execute. If executing
+these statements does not throw an exception, then the second operand
+is ignored. Otherwise, if an exception is thrown, then the second
+operand of the @code{GIMPLE_TRY_CATCH} is checked. The second
+operand may have the following forms:
+
+@enumerate
+
+@item A sequence of statements to execute. When an exception occurs,
+these statements are executed, and then the exception is rethrown.
+
+@item A sequence of @code{GIMPLE_CATCH} statements. Each
+@code{GIMPLE_CATCH} has a list of applicable exception types and
+handler code. If the thrown exception matches one of the caught
+types, the associated handler code is executed. If the handler
+code falls off the bottom, execution continues after the original
+@code{GIMPLE_TRY_CATCH}.
+
+@item A @code{GIMPLE_EH_FILTER} statement. This has a list of
+permitted exception types, and code to handle a match failure. If the
+thrown exception does not match one of the allowed types, the
+associated match failure code is executed. If the thrown exception
+does match, it continues unwinding the stack looking for the next
+handler.
+
+@end enumerate
+
+Currently throwing an exception is not directly represented in
+GIMPLE, since it is implemented by calling a function. At some
+point in the future we will want to add some way to express that
+the call will throw an exception of a known type.
+
+Just before running the optimizers, the compiler lowers the
+high-level EH constructs above into a set of @samp{goto}s, magic
+labels, and EH regions. Continuing to unwind at the end of a
+cleanup is represented with a @code{GIMPLE_RESX}.
+
+
+@node Temporaries
+@section Temporaries
+@cindex Temporaries
+
+When gimplification encounters a subexpression that is too
+complex, it creates a new temporary variable to hold the value of
+the subexpression, and adds a new statement to initialize it
+before the current statement. These special temporaries are known
+as @samp{expression temporaries}, and are allocated using
+@code{get_formal_tmp_var}. The compiler tries to always evaluate
+identical expressions into the same temporary, to simplify
+elimination of redundant calculations.
+
+We can only use expression temporaries when we know that it will
+not be reevaluated before its value is used, and that it will not
+be otherwise modified@footnote{These restrictions are derived
+from those in Morgan 4.8.}. Other temporaries can be allocated
+using @code{get_initialized_tmp_var} or @code{create_tmp_var}.
+
+Currently, an expression like @code{a = b + 5} is not reduced any
+further. We tried converting it to something like
+@smallexample
+T1 = b + 5;
+a = T1;
+@end smallexample
+but this bloated the representation for minimal benefit. However, a
+variable which must live in memory cannot appear in an expression; its
+value is explicitly loaded into a temporary first. Similarly, storing
+the value of an expression to a memory variable goes through a
+temporary.
+
+@node Operands
+@section Operands
+@cindex Operands
+
+In general, expressions in GIMPLE consist of an operation and the
+appropriate number of simple operands; these operands must either be a
+GIMPLE rvalue (@code{is_gimple_val}), i.e.@: a constant or a register
+variable. More complex operands are factored out into temporaries, so
+that
+@smallexample
+a = b + c + d
+@end smallexample
+becomes
+@smallexample
+T1 = b + c;
+a = T1 + d;
+@end smallexample
+
+The same rule holds for arguments to a @code{GIMPLE_CALL}.
+
+The target of an assignment is usually a variable, but can also be a
+@code{MEM_REF} or a compound lvalue as described below.
+
+@menu
+* Compound Expressions::
+* Compound Lvalues::
+* Conditional Expressions::
+* Logical Operators::
+@end menu
+
+@node Compound Expressions
+@subsection Compound Expressions
+@cindex Compound Expressions
+
+The left-hand side of a C comma expression is simply moved into a separate
+statement.
+
+@node Compound Lvalues
+@subsection Compound Lvalues
+@cindex Compound Lvalues
+
+Currently compound lvalues involving array and structure field references
+are not broken down; an expression like @code{a.b[2] = 42} is not reduced
+any further (though complex array subscripts are). This restriction is a
+workaround for limitations in later optimizers; if we were to convert this
+to
+
+@smallexample
+T1 = &a.b;
+T1[2] = 42;
+@end smallexample
+
+alias analysis would not remember that the reference to @code{T1[2]} came
+by way of @code{a.b}, so it would think that the assignment could alias
+another member of @code{a}; this broke @code{struct-alias-1.c}. Future
+optimizer improvements may make this limitation unnecessary.
+
+@node Conditional Expressions
+@subsection Conditional Expressions
+@cindex Conditional Expressions
+
+A C @code{?:} expression is converted into an @code{if} statement with
+each branch assigning to the same temporary. So,
+
+@smallexample
+a = b ? c : d;
+@end smallexample
+becomes
+@smallexample
+if (b == 1)
+ T1 = c;
+else
+ T1 = d;
+a = T1;
+@end smallexample
+
+The GIMPLE level if-conversion pass re-introduces @code{?:}
+expression, if appropriate. It is used to vectorize loops with
+conditions using vector conditional operations.
+
+Note that in GIMPLE, @code{if} statements are represented using
+@code{GIMPLE_COND}, as described below.
+
+@node Logical Operators
+@subsection Logical Operators
+@cindex Logical Operators
+
+Except when they appear in the condition operand of a
+@code{GIMPLE_COND}, logical `and' and `or' operators are simplified
+as follows: @code{a = b && c} becomes
+
+@smallexample
+T1 = (bool)b;
+if (T1 == true)
+ T1 = (bool)c;
+a = T1;
+@end smallexample
+
+Note that @code{T1} in this example cannot be an expression temporary,
+because it has two different assignments.
+
+@subsection Manipulating operands
+
+All gimple operands are of type @code{tree}. But only certain
+types of trees are allowed to be used as operand tuples. Basic
+validation is controlled by the function
+@code{get_gimple_rhs_class}, which given a tree code, returns an
+@code{enum} with the following values of type @code{enum
+gimple_rhs_class}
+
+@itemize @bullet
+@item @code{GIMPLE_INVALID_RHS}
+The tree cannot be used as a GIMPLE operand.
+
+@item @code{GIMPLE_TERNARY_RHS}
+The tree is a valid GIMPLE ternary operation.
+
+@item @code{GIMPLE_BINARY_RHS}
+The tree is a valid GIMPLE binary operation.
+
+@item @code{GIMPLE_UNARY_RHS}
+The tree is a valid GIMPLE unary operation.
+
+@item @code{GIMPLE_SINGLE_RHS}
+The tree is a single object, that cannot be split into simpler
+operands (for instance, @code{SSA_NAME}, @code{VAR_DECL}, @code{COMPONENT_REF}, etc).
+
+This operand class also acts as an escape hatch for tree nodes
+that may be flattened out into the operand vector, but would need
+more than two slots on the RHS. For instance, a @code{COND_EXPR}
+expression of the form @code{(a op b) ? x : y} could be flattened
+out on the operand vector using 4 slots, but it would also
+require additional processing to distinguish @code{c = a op b}
+from @code{c = a op b ? x : y}. Something similar occurs with
+@code{ASSERT_EXPR}. In time, these special case tree
+expressions should be flattened into the operand vector.
+@end itemize
+
+For tree nodes in the categories @code{GIMPLE_TERNARY_RHS},
+@code{GIMPLE_BINARY_RHS} and @code{GIMPLE_UNARY_RHS}, they cannot be
+stored inside tuples directly. They first need to be flattened and
+separated into individual components. For instance, given the GENERIC
+expression
+
+@smallexample
+a = b + c
+@end smallexample
+
+its tree representation is:
+
+@smallexample
+MODIFY_EXPR <VAR_DECL <a>, PLUS_EXPR <VAR_DECL <b>, VAR_DECL <c>>>
+@end smallexample
+
+In this case, the GIMPLE form for this statement is logically
+identical to its GENERIC form but in GIMPLE, the @code{PLUS_EXPR}
+on the RHS of the assignment is not represented as a tree,
+instead the two operands are taken out of the @code{PLUS_EXPR} sub-tree
+and flattened into the GIMPLE tuple as follows:
+
+@smallexample
+GIMPLE_ASSIGN <PLUS_EXPR, VAR_DECL <a>, VAR_DECL <b>, VAR_DECL <c>>
+@end smallexample
+
+@subsection Operand vector allocation
+
+The operand vector is stored at the bottom of the three tuple
+structures that accept operands. This means, that depending on
+the code of a given statement, its operand vector will be at
+different offsets from the base of the structure. To access
+tuple operands use the following accessors
+
+@deftypefn {GIMPLE function} unsigned gimple_num_ops (gimple g)
+Returns the number of operands in statement G.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_op (gimple g, unsigned i)
+Returns operand @code{I} from statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_ops (gimple g)
+Returns a pointer into the operand vector for statement @code{G}. This
+is computed using an internal table called @code{gimple_ops_offset_}[].
+This table is indexed by the gimple code of @code{G}.
+
+When the compiler is built, this table is filled-in using the
+sizes of the structures used by each statement code defined in
+gimple.def. Since the operand vector is at the bottom of the
+structure, for a gimple code @code{C} the offset is computed as sizeof
+(struct-of @code{C}) - sizeof (tree).
+
+This mechanism adds one memory indirection to every access when
+using @code{gimple_op}(), if this becomes a bottleneck, a pass can
+choose to memoize the result from @code{gimple_ops}() and use that to
+access the operands.
+@end deftypefn
+
+@subsection Operand validation
+
+When adding a new operand to a gimple statement, the operand will
+be validated according to what each tuple accepts in its operand
+vector. These predicates are called by the
+@code{gimple_@var{name}_set_...()}. Each tuple will use one of the
+following predicates (Note, this list is not exhaustive):
+
+@deftypefn {GIMPLE function} bool is_gimple_val (tree t)
+Returns true if t is a "GIMPLE value", which are all the
+non-addressable stack variables (variables for which
+@code{is_gimple_reg} returns true) and constants (expressions for which
+@code{is_gimple_min_invariant} returns true).
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_addressable (tree t)
+Returns true if t is a symbol or memory reference whose address
+can be taken.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_asm_val (tree t)
+Similar to @code{is_gimple_val} but it also accepts hard registers.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_call_addr (tree t)
+Return true if t is a valid expression to use as the function
+called by a @code{GIMPLE_CALL}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_mem_ref_addr (tree t)
+Return true if t is a valid expression to use as first operand
+of a @code{MEM_REF} expression.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_constant (tree t)
+Return true if t is a valid gimple constant.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_min_invariant (tree t)
+Return true if t is a valid minimal invariant. This is different
+from constants, in that the specific value of t may not be known
+at compile time, but it is known that it doesn't change (e.g.,
+the address of a function local variable).
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_ip_invariant (tree t)
+Return true if t is an interprocedural invariant. This means that t
+is a valid invariant in all functions (e.g.@: it can be an address of a
+global variable but not of a local one).
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_ip_invariant_address (tree t)
+Return true if t is an @code{ADDR_EXPR} that does not change once the
+program is running (and which is valid in all functions).
+@end deftypefn
+
+
+@subsection Statement validation
+
+@deftypefn {GIMPLE function} bool is_gimple_assign (gimple g)
+Return true if the code of g is @code{GIMPLE_ASSIGN}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_call (gimple g)
+Return true if the code of g is @code{GIMPLE_CALL}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_debug (gimple g)
+Return true if the code of g is @code{GIMPLE_DEBUG}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_assign_cast_p (const_gimple g)
+Return true if g is a @code{GIMPLE_ASSIGN} that performs a type cast
+operation.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_debug_bind_p (gimple g)
+Return true if g is a @code{GIMPLE_DEBUG} that binds the value of an
+expression to a variable.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool is_gimple_omp (gimple g)
+Return true if g is any of the OpenMP codes.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_debug_begin_stmt_p (gimple g)
+Return true if g is a @code{GIMPLE_DEBUG} that marks the beginning of
+a source statement.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_debug_inline_entry_p (gimple g)
+Return true if g is a @code{GIMPLE_DEBUG} that marks the entry
+point of an inlined function.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_debug_nonbind_marker_p (gimple g)
+Return true if g is a @code{GIMPLE_DEBUG} that marks a program location,
+without any variable binding.
+@end deftypefn
+
+@node Manipulating GIMPLE statements
+@section Manipulating GIMPLE statements
+@cindex Manipulating GIMPLE statements
+
+This section documents all the functions available to handle each
+of the GIMPLE instructions.
+
+@subsection Common accessors
+The following are common accessors for gimple statements.
+
+@deftypefn {GIMPLE function} {enum gimple_code} gimple_code (gimple g)
+Return the code for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} basic_block gimple_bb (gimple g)
+Return the basic block to which statement @code{G} belongs to.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_block (gimple g)
+Return the lexical scope block holding statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {enum tree_code} gimple_expr_code (gimple stmt)
+Return the tree code for the expression computed by @code{STMT}. This
+is only meaningful for @code{GIMPLE_CALL}, @code{GIMPLE_ASSIGN} and
+@code{GIMPLE_COND}. If @code{STMT} is @code{GIMPLE_CALL}, it will return @code{CALL_EXPR}.
+For @code{GIMPLE_COND}, it returns the code of the comparison predicate.
+For @code{GIMPLE_ASSIGN} it returns the code of the operation performed
+by the @code{RHS} of the assignment.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_block (gimple g, tree block)
+Set the lexical scope block of @code{G} to @code{BLOCK}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} location_t gimple_locus (gimple g)
+Return locus information for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_locus (gimple g, location_t locus)
+Set locus information for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_locus_empty_p (gimple g)
+Return true if @code{G} does not have locus information.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_no_warning_p (gimple stmt)
+Return true if no warnings should be emitted for statement @code{STMT}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_visited (gimple stmt, bool visited_p)
+Set the visited status on statement @code{STMT} to @code{VISITED_P}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_visited_p (gimple stmt)
+Return the visited status on statement @code{STMT}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_plf (gimple stmt, enum plf_mask plf, bool val_p)
+Set pass local flag @code{PLF} on statement @code{STMT} to @code{VAL_P}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {unsigned int} gimple_plf (gimple stmt, enum plf_mask plf)
+Return the value of pass local flag @code{PLF} on statement @code{STMT}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_has_ops (gimple g)
+Return true if statement @code{G} has register or memory operands.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_has_mem_ops (gimple g)
+Return true if statement @code{G} has memory operands.
+@end deftypefn
+
+@deftypefn {GIMPLE function} unsigned gimple_num_ops (gimple g)
+Return the number of operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_ops (gimple g)
+Return the array of operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_op (gimple g, unsigned i)
+Return operand @code{I} for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_op_ptr (gimple g, unsigned i)
+Return a pointer to operand @code{I} for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_op (gimple g, unsigned i, tree op)
+Set operand @code{I} of statement @code{G} to @code{OP}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bitmap gimple_addresses_taken (gimple stmt)
+Return the set of symbols that have had their address taken by
+@code{STMT}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {struct def_optype_d *} gimple_def_ops (gimple g)
+Return the set of @code{DEF} operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_def_ops (gimple g, struct def_optype_d *def)
+Set @code{DEF} to be the set of @code{DEF} operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {struct use_optype_d *} gimple_use_ops (gimple g)
+Return the set of @code{USE} operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_use_ops (gimple g, struct use_optype_d *use)
+Set @code{USE} to be the set of @code{USE} operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {struct voptype_d *} gimple_vuse_ops (gimple g)
+Return the set of @code{VUSE} operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_vuse_ops (gimple g, struct voptype_d *ops)
+Set @code{OPS} to be the set of @code{VUSE} operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {struct voptype_d *} gimple_vdef_ops (gimple g)
+Return the set of @code{VDEF} operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_vdef_ops (gimple g, struct voptype_d *ops)
+Set @code{OPS} to be the set of @code{VDEF} operands for statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bitmap gimple_loaded_syms (gimple g)
+Return the set of symbols loaded by statement @code{G}. Each element of
+the set is the @code{DECL_UID} of the corresponding symbol.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bitmap gimple_stored_syms (gimple g)
+Return the set of symbols stored by statement @code{G}. Each element of
+the set is the @code{DECL_UID} of the corresponding symbol.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_modified_p (gimple g)
+Return true if statement @code{G} has operands and the modified field
+has been set.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_has_volatile_ops (gimple stmt)
+Return true if statement @code{STMT} contains volatile operands.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_set_has_volatile_ops (gimple stmt, bool volatilep)
+Return true if statement @code{STMT} contains volatile operands.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void update_stmt (gimple s)
+Mark statement @code{S} as modified, and update it.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void update_stmt_if_modified (gimple s)
+Update statement @code{S} if it has been marked modified.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple gimple_copy (gimple stmt)
+Return a deep copy of statement @code{STMT}.
+@end deftypefn
+
+@node Tuple specific accessors
+@section Tuple specific accessors
+@cindex Tuple specific accessors
+
+@menu
+* @code{GIMPLE_ASM}::
+* @code{GIMPLE_ASSIGN}::
+* @code{GIMPLE_BIND}::
+* @code{GIMPLE_CALL}::
+* @code{GIMPLE_CATCH}::
+* @code{GIMPLE_COND}::
+* @code{GIMPLE_DEBUG}::
+* @code{GIMPLE_EH_FILTER}::
+* @code{GIMPLE_LABEL}::
+* @code{GIMPLE_GOTO}::
+* @code{GIMPLE_NOP}::
+* @code{GIMPLE_OMP_ATOMIC_LOAD}::
+* @code{GIMPLE_OMP_ATOMIC_STORE}::
+* @code{GIMPLE_OMP_CONTINUE}::
+* @code{GIMPLE_OMP_CRITICAL}::
+* @code{GIMPLE_OMP_FOR}::
+* @code{GIMPLE_OMP_MASTER}::
+* @code{GIMPLE_OMP_ORDERED}::
+* @code{GIMPLE_OMP_PARALLEL}::
+* @code{GIMPLE_OMP_RETURN}::
+* @code{GIMPLE_OMP_SECTION}::
+* @code{GIMPLE_OMP_SECTIONS}::
+* @code{GIMPLE_OMP_SINGLE}::
+* @code{GIMPLE_PHI}::
+* @code{GIMPLE_RESX}::
+* @code{GIMPLE_RETURN}::
+* @code{GIMPLE_SWITCH}::
+* @code{GIMPLE_TRY}::
+* @code{GIMPLE_WITH_CLEANUP_EXPR}::
+@end menu
+
+
+@node @code{GIMPLE_ASM}
+@subsection @code{GIMPLE_ASM}
+@cindex @code{GIMPLE_ASM}
+
+@deftypefn {GIMPLE function} gasm *gimple_build_asm_vec ( @
+const char *string, vec<tree, va_gc> *inputs, @
+vec<tree, va_gc> *outputs, vec<tree, va_gc> *clobbers, @
+vec<tree, va_gc> *labels)
+Build a @code{GIMPLE_ASM} statement. This statement is used for
+building in-line assembly constructs. @code{STRING} is the assembly
+code. @code{INPUTS}, @code{OUTPUTS}, @code{CLOBBERS} and @code{LABELS}
+are the inputs, outputs, clobbered registers and labels.
+@end deftypefn
+
+@deftypefn {GIMPLE function} unsigned gimple_asm_ninputs (const gasm *g)
+Return the number of input operands for @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} unsigned gimple_asm_noutputs (const gasm *g)
+Return the number of output operands for @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} unsigned gimple_asm_nclobbers (const gasm *g)
+Return the number of clobber operands for @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_asm_input_op (const gasm *g, @
+unsigned index)
+Return input operand @code{INDEX} of @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_asm_set_input_op (gasm *g, @
+unsigned index, tree in_op)
+Set @code{IN_OP} to be input operand @code{INDEX} in @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_asm_output_op (const gasm *g, @
+unsigned index)
+Return output operand @code{INDEX} of @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_asm_set_output_op (gasm *g, @
+unsigned index, tree out_op)
+Set @code{OUT_OP} to be output operand @code{INDEX} in @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_asm_clobber_op (const gasm *g, @
+unsigned index)
+Return clobber operand @code{INDEX} of @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_asm_set_clobber_op (gasm *g, @
+unsigned index, tree clobber_op)
+Set @code{CLOBBER_OP} to be clobber operand @code{INDEX} in @code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {const char *} gimple_asm_string (const gasm *g)
+Return the string representing the assembly instruction in
+@code{GIMPLE_ASM} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_asm_volatile_p (const gasm *g)
+Return true if @code{G} is an asm statement marked volatile.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_asm_set_volatile (gasm *g, @
+bool volatile_p)
+Mark asm statement @code{G} as volatile or non-volatile based on
+@code{VOLATILE_P}.
+@end deftypefn
+
+@node @code{GIMPLE_ASSIGN}
+@subsection @code{GIMPLE_ASSIGN}
+@cindex @code{GIMPLE_ASSIGN}
+
+@deftypefn {GIMPLE function} gassign *gimple_build_assign (tree lhs, tree rhs)
+Build a @code{GIMPLE_ASSIGN} statement. The left-hand side is an lvalue
+passed in lhs. The right-hand side can be either a unary or
+binary tree expression. The expression tree rhs will be
+flattened and its operands assigned to the corresponding operand
+slots in the new statement. This function is useful when you
+already have a tree expression that you want to convert into a
+tuple. However, try to avoid building expression trees for the
+sole purpose of calling this function. If you already have the
+operands in separate trees, it is better to use
+@code{gimple_build_assign} with @code{enum tree_code} argument and separate
+arguments for each operand.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gassign *gimple_build_assign @
+(tree lhs, enum tree_code subcode, tree op1, tree op2, tree op3)
+This function is similar to two operand @code{gimple_build_assign},
+but is used to build a @code{GIMPLE_ASSIGN} statement when the operands of the
+right-hand side of the assignment are already split into
+different operands.
+
+The left-hand side is an lvalue passed in lhs. Subcode is the
+@code{tree_code} for the right-hand side of the assignment. Op1, op2 and op3
+are the operands.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gassign *gimple_build_assign @
+(tree lhs, enum tree_code subcode, tree op1, tree op2)
+Like the above 5 operand @code{gimple_build_assign}, but with the last
+argument @code{NULL} - this overload should not be used for
+@code{GIMPLE_TERNARY_RHS} assignments.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gassign *gimple_build_assign @
+(tree lhs, enum tree_code subcode, tree op1)
+Like the above 4 operand @code{gimple_build_assign}, but with the last
+argument @code{NULL} - this overload should be used only for
+@code{GIMPLE_UNARY_RHS} and @code{GIMPLE_SINGLE_RHS} assignments.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple gimplify_assign (tree dst, tree src, gimple_seq *seq_p)
+Build a new @code{GIMPLE_ASSIGN} tuple and append it to the end of
+@code{*SEQ_P}.
+@end deftypefn
+
+@code{DST}/@code{SRC} are the destination and source respectively. You can
+pass ungimplified trees in @code{DST} or @code{SRC}, in which
+case they will be converted to a gimple operand if necessary.
+
+This function returns the newly created @code{GIMPLE_ASSIGN} tuple.
+
+@deftypefn {GIMPLE function} {enum tree_code} gimple_assign_rhs_code (gimple g)
+Return the code of the expression computed on the @code{RHS} of
+assignment statement @code{G}.
+@end deftypefn
+
+
+@deftypefn {GIMPLE function} {enum gimple_rhs_class} gimple_assign_rhs_class (gimple g)
+Return the gimple rhs class of the code for the expression
+computed on the rhs of assignment statement @code{G}. This will never
+return @code{GIMPLE_INVALID_RHS}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_assign_lhs (gimple g)
+Return the @code{LHS} of assignment statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_assign_lhs_ptr (gimple g)
+Return a pointer to the @code{LHS} of assignment statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_assign_rhs1 (gimple g)
+Return the first operand on the @code{RHS} of assignment statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_assign_rhs1_ptr (gimple g)
+Return the address of the first operand on the @code{RHS} of assignment
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_assign_rhs2 (gimple g)
+Return the second operand on the @code{RHS} of assignment statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_assign_rhs2_ptr (gimple g)
+Return the address of the second operand on the @code{RHS} of assignment
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_assign_rhs3 (gimple g)
+Return the third operand on the @code{RHS} of assignment statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_assign_rhs3_ptr (gimple g)
+Return the address of the third operand on the @code{RHS} of assignment
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_assign_set_lhs (gimple g, tree lhs)
+Set @code{LHS} to be the @code{LHS} operand of assignment statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_assign_set_rhs1 (gimple g, tree rhs)
+Set @code{RHS} to be the first operand on the @code{RHS} of assignment
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_assign_set_rhs2 (gimple g, tree rhs)
+Set @code{RHS} to be the second operand on the @code{RHS} of assignment
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_assign_set_rhs3 (gimple g, tree rhs)
+Set @code{RHS} to be the third operand on the @code{RHS} of assignment
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_assign_cast_p (const_gimple s)
+Return true if @code{S} is a type-cast assignment.
+@end deftypefn
+
+
+@node @code{GIMPLE_BIND}
+@subsection @code{GIMPLE_BIND}
+@cindex @code{GIMPLE_BIND}
+
+@deftypefn {GIMPLE function} gbind *gimple_build_bind (tree vars, @
+gimple_seq body)
+Build a @code{GIMPLE_BIND} statement with a list of variables in @code{VARS}
+and a body of statements in sequence @code{BODY}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_bind_vars (const gbind *g)
+Return the variables declared in the @code{GIMPLE_BIND} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_bind_set_vars (gbind *g, tree vars)
+Set @code{VARS} to be the set of variables declared in the @code{GIMPLE_BIND}
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_bind_append_vars (gbind *g, tree vars)
+Append @code{VARS} to the set of variables declared in the @code{GIMPLE_BIND}
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_bind_body (gbind *g)
+Return the GIMPLE sequence contained in the @code{GIMPLE_BIND} statement
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_bind_set_body (gbind *g, @
+gimple_seq seq)
+Set @code{SEQ} to be sequence contained in the @code{GIMPLE_BIND} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_bind_add_stmt (gbind *gs, gimple stmt)
+Append a statement to the end of a @code{GIMPLE_BIND}'s body.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_bind_add_seq (gbind *gs, @
+gimple_seq seq)
+Append a sequence of statements to the end of a @code{GIMPLE_BIND}'s
+body.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_bind_block (const gbind *g)
+Return the @code{TREE_BLOCK} node associated with @code{GIMPLE_BIND} statement
+@code{G}. This is analogous to the @code{BIND_EXPR_BLOCK} field in trees.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_bind_set_block (gbind *g, tree block)
+Set @code{BLOCK} to be the @code{TREE_BLOCK} node associated with @code{GIMPLE_BIND}
+statement @code{G}.
+@end deftypefn
+
+
+@node @code{GIMPLE_CALL}
+@subsection @code{GIMPLE_CALL}
+@cindex @code{GIMPLE_CALL}
+
+@deftypefn {GIMPLE function} gcall *gimple_build_call (tree fn, @
+unsigned nargs, ...)
+Build a @code{GIMPLE_CALL} statement to function @code{FN}. The argument @code{FN}
+must be either a @code{FUNCTION_DECL} or a gimple call address as
+determined by @code{is_gimple_call_addr}. @code{NARGS} are the number of
+arguments. The rest of the arguments follow the argument @code{NARGS},
+and must be trees that are valid as rvalues in gimple (i.e., each
+operand is validated with @code{is_gimple_operand}).
+@end deftypefn
+
+
+@deftypefn {GIMPLE function} gcall *gimple_build_call_from_tree (tree call_expr, @
+tree fnptrtype)
+Build a @code{GIMPLE_CALL} from a @code{CALL_EXPR} node. The arguments
+and the function are taken from the expression directly. The type of the
+@code{GIMPLE_CALL} is set from the second parameter passed by a caller.
+This routine assumes that @code{call_expr} is already in GIMPLE form.
+That is, its operands are GIMPLE values and the function call needs no further
+simplification. All the call flags in @code{call_expr} are copied over
+to the new @code{GIMPLE_CALL}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gcall *gimple_build_call_vec (tree fn, @
+@code{vec<tree>} args)
+Identical to @code{gimple_build_call} but the arguments are stored in a
+@code{vec<tree>}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_call_lhs (gimple g)
+Return the @code{LHS} of call statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_call_lhs_ptr (gimple g)
+Return a pointer to the @code{LHS} of call statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_call_set_lhs (gimple g, tree lhs)
+Set @code{LHS} to be the @code{LHS} operand of call statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_call_fn (gimple g)
+Return the tree node representing the function called by call
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_call_set_fn (gcall *g, tree fn)
+Set @code{FN} to be the function called by call statement @code{G}. This has
+to be a gimple value specifying the address of the called
+function.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_call_fndecl (gimple g)
+If a given @code{GIMPLE_CALL}'s callee is a @code{FUNCTION_DECL}, return it.
+Otherwise return @code{NULL}. This function is analogous to
+@code{get_callee_fndecl} in @code{GENERIC}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_call_set_fndecl (gimple g, tree fndecl)
+Set the called function to @code{FNDECL}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_call_return_type (const gcall *g)
+Return the type returned by call statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_call_chain (gimple g)
+Return the static chain for call statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_call_set_chain (gcall *g, tree chain)
+Set @code{CHAIN} to be the static chain for call statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} unsigned gimple_call_num_args (gimple g)
+Return the number of arguments used by call statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_call_arg (gimple g, unsigned index)
+Return the argument at position @code{INDEX} for call statement @code{G}. The
+first argument is 0.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_call_arg_ptr (gimple g, unsigned index)
+Return a pointer to the argument at position @code{INDEX} for call
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_call_set_arg (gimple g, unsigned index, tree arg)
+Set @code{ARG} to be the argument at position @code{INDEX} for call statement
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_call_set_tail (gcall *s)
+Mark call statement @code{S} as being a tail call (i.e., a call just
+before the exit of a function). These calls are candidate for
+tail call optimization.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_call_tail_p (gcall *s)
+Return true if @code{GIMPLE_CALL} @code{S} is marked as a tail call.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_call_noreturn_p (gimple s)
+Return true if @code{S} is a noreturn call.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple gimple_call_copy_skip_args (gcall *stmt, @
+bitmap args_to_skip)
+Build a @code{GIMPLE_CALL} identical to @code{STMT} but skipping the arguments
+in the positions marked by the set @code{ARGS_TO_SKIP}.
+@end deftypefn
+
+
+@node @code{GIMPLE_CATCH}
+@subsection @code{GIMPLE_CATCH}
+@cindex @code{GIMPLE_CATCH}
+
+@deftypefn {GIMPLE function} gcatch *gimple_build_catch (tree types, @
+gimple_seq handler)
+Build a @code{GIMPLE_CATCH} statement. @code{TYPES} are the tree types this
+catch handles. @code{HANDLER} is a sequence of statements with the code
+for the handler.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_catch_types (const gcatch *g)
+Return the types handled by @code{GIMPLE_CATCH} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_catch_types_ptr (gcatch *g)
+Return a pointer to the types handled by @code{GIMPLE_CATCH} statement
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_catch_handler (gcatch *g)
+Return the GIMPLE sequence representing the body of the handler
+of @code{GIMPLE_CATCH} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_catch_set_types (gcatch *g, tree t)
+Set @code{T} to be the set of types handled by @code{GIMPLE_CATCH} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_catch_set_handler (gcatch *g, @
+gimple_seq handler)
+Set @code{HANDLER} to be the body of @code{GIMPLE_CATCH} @code{G}.
+@end deftypefn
+
+
+@node @code{GIMPLE_COND}
+@subsection @code{GIMPLE_COND}
+@cindex @code{GIMPLE_COND}
+
+@deftypefn {GIMPLE function} gcond *gimple_build_cond ( @
+enum tree_code pred_code, tree lhs, tree rhs, tree t_label, tree f_label)
+Build a @code{GIMPLE_COND} statement. @code{A} @code{GIMPLE_COND} statement compares
+@code{LHS} and @code{RHS} and if the condition in @code{PRED_CODE} is true, jump to
+the label in @code{t_label}, otherwise jump to the label in @code{f_label}.
+@code{PRED_CODE} are relational operator tree codes like @code{EQ_EXPR},
+@code{LT_EXPR}, @code{LE_EXPR}, @code{NE_EXPR}, etc.
+@end deftypefn
+
+
+@deftypefn {GIMPLE function} gcond *gimple_build_cond_from_tree (tree cond, @
+tree t_label, tree f_label)
+Build a @code{GIMPLE_COND} statement from the conditional expression
+tree @code{COND}. @code{T_LABEL} and @code{F_LABEL} are as in @code{gimple_build_cond}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {enum tree_code} gimple_cond_code (gimple g)
+Return the code of the predicate computed by conditional
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_cond_set_code (gcond *g, @
+enum tree_code code)
+Set @code{CODE} to be the predicate code for the conditional statement
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_cond_lhs (gimple g)
+Return the @code{LHS} of the predicate computed by conditional statement
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_cond_set_lhs (gcond *g, tree lhs)
+Set @code{LHS} to be the @code{LHS} operand of the predicate computed by
+conditional statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_cond_rhs (gimple g)
+Return the @code{RHS} operand of the predicate computed by conditional
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_cond_set_rhs (gcond *g, tree rhs)
+Set @code{RHS} to be the @code{RHS} operand of the predicate computed by
+conditional statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_cond_true_label (const gcond *g)
+Return the label used by conditional statement @code{G} when its
+predicate evaluates to true.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_cond_set_true_label (gcond *g, tree label)
+Set @code{LABEL} to be the label used by conditional statement @code{G} when
+its predicate evaluates to true.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_cond_set_false_label (gcond *g, tree label)
+Set @code{LABEL} to be the label used by conditional statement @code{G} when
+its predicate evaluates to false.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_cond_false_label (const gcond *g)
+Return the label used by conditional statement @code{G} when its
+predicate evaluates to false.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_cond_make_false (gcond *g)
+Set the conditional @code{COND_STMT} to be of the form 'if (1 == 0)'.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_cond_make_true (gcond *g)
+Set the conditional @code{COND_STMT} to be of the form 'if (1 == 1)'.
+@end deftypefn
+
+@node @code{GIMPLE_DEBUG}
+@subsection @code{GIMPLE_DEBUG}
+@cindex @code{GIMPLE_DEBUG}
+@cindex @code{GIMPLE_DEBUG_BIND}
+@cindex @code{GIMPLE_DEBUG_BEGIN_STMT}
+@cindex @code{GIMPLE_DEBUG_INLINE_ENTRY}
+
+@deftypefn {GIMPLE function} gdebug *gimple_build_debug_bind (tree var, @
+tree value, gimple stmt)
+Build a @code{GIMPLE_DEBUG} statement with @code{GIMPLE_DEBUG_BIND}
+@code{subcode}. The effect of this statement is to tell debug
+information generation machinery that the value of user variable
+@code{var} is given by @code{value} at that point, and to remain with
+that value until @code{var} runs out of scope, a
+dynamically-subsequent debug bind statement overrides the binding, or
+conflicting values reach a control flow merge point. Even if
+components of the @code{value} expression change afterwards, the
+variable is supposed to retain the same value, though not necessarily
+the same location.
+
+It is expected that @code{var} be most often a tree for automatic user
+variables (@code{VAR_DECL} or @code{PARM_DECL}) that satisfy the
+requirements for gimple registers, but it may also be a tree for a
+scalarized component of a user variable (@code{ARRAY_REF},
+@code{COMPONENT_REF}), or a debug temporary (@code{DEBUG_EXPR_DECL}).
+
+As for @code{value}, it can be an arbitrary tree expression, but it is
+recommended that it be in a suitable form for a gimple assignment
+@code{RHS}. It is not expected that user variables that could appear
+as @code{var} ever appear in @code{value}, because in the latter we'd
+have their @code{SSA_NAME}s instead, but even if they were not in SSA
+form, user variables appearing in @code{value} are to be regarded as
+part of the executable code space, whereas those in @code{var} are to
+be regarded as part of the source code space. There is no way to
+refer to the value bound to a user variable within a @code{value}
+expression.
+
+If @code{value} is @code{GIMPLE_DEBUG_BIND_NOVALUE}, debug information
+generation machinery is informed that the variable @code{var} is
+unbound, i.e., that its value is indeterminate, which sometimes means
+it is really unavailable, and other times that the compiler could not
+keep track of it.
+
+Block and location information for the newly-created stmt are
+taken from @code{stmt}, if given.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_debug_bind_get_var (gimple stmt)
+Return the user variable @var{var} that is bound at @code{stmt}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_debug_bind_get_value (gimple stmt)
+Return the value expression that is bound to a user variable at
+@code{stmt}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_debug_bind_get_value_ptr (gimple stmt)
+Return a pointer to the value expression that is bound to a user
+variable at @code{stmt}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_debug_bind_set_var (gimple stmt, tree var)
+Modify the user variable bound at @code{stmt} to @var{var}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_debug_bind_set_value (gimple stmt, tree var)
+Modify the value bound to the user variable bound at @code{stmt} to
+@var{value}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_debug_bind_reset_value (gimple stmt)
+Modify the value bound to the user variable bound at @code{stmt} so
+that the variable becomes unbound.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_debug_bind_has_value_p (gimple stmt)
+Return @code{TRUE} if @code{stmt} binds a user variable to a value,
+and @code{FALSE} if it unbinds the variable.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple gimple_build_debug_begin_stmt (tree block, location_t location)
+Build a @code{GIMPLE_DEBUG} statement with
+@code{GIMPLE_DEBUG_BEGIN_STMT} @code{subcode}. The effect of this
+statement is to tell debug information generation machinery that the
+user statement at the given @code{location} and @code{block} starts at
+the point at which the statement is inserted. The intent is that side
+effects (e.g.@: variable bindings) of all prior user statements are
+observable, and that none of the side effects of subsequent user
+statements are.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple gimple_build_debug_inline_entry (tree block, location_t location)
+Build a @code{GIMPLE_DEBUG} statement with
+@code{GIMPLE_DEBUG_INLINE_ENTRY} @code{subcode}. The effect of this
+statement is to tell debug information generation machinery that a
+function call at @code{location} underwent inline substitution, that
+@code{block} is the enclosing lexical block created for the
+substitution, and that at the point of the program in which the stmt is
+inserted, all parameters for the inlined function are bound to the
+respective arguments, and none of the side effects of its stmts are
+observable.
+@end deftypefn
+
+@node @code{GIMPLE_EH_FILTER}
+@subsection @code{GIMPLE_EH_FILTER}
+@cindex @code{GIMPLE_EH_FILTER}
+
+@deftypefn {GIMPLE function} geh_filter *gimple_build_eh_filter (tree types, @
+gimple_seq failure)
+Build a @code{GIMPLE_EH_FILTER} statement. @code{TYPES} are the filter's
+types. @code{FAILURE} is a sequence with the filter's failure action.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_eh_filter_types (gimple g)
+Return the types handled by @code{GIMPLE_EH_FILTER} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_eh_filter_types_ptr (gimple g)
+Return a pointer to the types handled by @code{GIMPLE_EH_FILTER}
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_eh_filter_failure (gimple g)
+Return the sequence of statement to execute when @code{GIMPLE_EH_FILTER}
+statement fails.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_eh_filter_set_types (geh_filter *g, @
+tree types)
+Set @code{TYPES} to be the set of types handled by @code{GIMPLE_EH_FILTER} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_eh_filter_set_failure (geh_filter *g, @
+gimple_seq failure)
+Set @code{FAILURE} to be the sequence of statements to execute on
+failure for @code{GIMPLE_EH_FILTER} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_eh_must_not_throw_fndecl ( @
+geh_mnt *eh_mnt_stmt)
+Get the function decl to be called by the MUST_NOT_THROW region.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_eh_must_not_throw_set_fndecl ( @
+geh_mnt *eh_mnt_stmt, tree decl)
+Set the function decl to be called by GS to DECL.
+@end deftypefn
+
+
+@node @code{GIMPLE_LABEL}
+@subsection @code{GIMPLE_LABEL}
+@cindex @code{GIMPLE_LABEL}
+
+@deftypefn {GIMPLE function} glabel *gimple_build_label (tree label)
+Build a @code{GIMPLE_LABEL} statement with corresponding to the tree
+label, @code{LABEL}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_label_label (const glabel *g)
+Return the @code{LABEL_DECL} node used by @code{GIMPLE_LABEL} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_label_set_label (glabel *g, tree label)
+Set @code{LABEL} to be the @code{LABEL_DECL} node used by @code{GIMPLE_LABEL}
+statement @code{G}.
+@end deftypefn
+
+@node @code{GIMPLE_GOTO}
+@subsection @code{GIMPLE_GOTO}
+@cindex @code{GIMPLE_GOTO}
+
+@deftypefn {GIMPLE function} ggoto *gimple_build_goto (tree dest)
+Build a @code{GIMPLE_GOTO} statement to label @code{DEST}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_goto_dest (gimple g)
+Return the destination of the unconditional jump @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_goto_set_dest (ggoto *g, tree dest)
+Set @code{DEST} to be the destination of the unconditional jump @code{G}.
+@end deftypefn
+
+
+@node @code{GIMPLE_NOP}
+@subsection @code{GIMPLE_NOP}
+@cindex @code{GIMPLE_NOP}
+
+@deftypefn {GIMPLE function} gimple gimple_build_nop (void)
+Build a @code{GIMPLE_NOP} statement.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_nop_p (gimple g)
+Returns @code{TRUE} if statement @code{G} is a @code{GIMPLE_NOP}.
+@end deftypefn
+
+@node @code{GIMPLE_OMP_ATOMIC_LOAD}
+@subsection @code{GIMPLE_OMP_ATOMIC_LOAD}
+@cindex @code{GIMPLE_OMP_ATOMIC_LOAD}
+
+@deftypefn {GIMPLE function} gomp_atomic_load *gimple_build_omp_atomic_load ( @
+tree lhs, tree rhs)
+Build a @code{GIMPLE_OMP_ATOMIC_LOAD} statement. @code{LHS} is the left-hand
+side of the assignment. @code{RHS} is the right-hand side of the
+assignment.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_atomic_load_set_lhs ( @
+gomp_atomic_load *g, tree lhs)
+Set the @code{LHS} of an atomic load.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_atomic_load_lhs ( @
+const gomp_atomic_load *g)
+Get the @code{LHS} of an atomic load.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_atomic_load_set_rhs ( @
+gomp_atomic_load *g, tree rhs)
+Set the @code{RHS} of an atomic set.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_atomic_load_rhs ( @
+const gomp_atomic_load *g)
+Get the @code{RHS} of an atomic set.
+@end deftypefn
+
+
+@node @code{GIMPLE_OMP_ATOMIC_STORE}
+@subsection @code{GIMPLE_OMP_ATOMIC_STORE}
+@cindex @code{GIMPLE_OMP_ATOMIC_STORE}
+
+@deftypefn {GIMPLE function} gomp_atomic_store *gimple_build_omp_atomic_store ( @
+tree val)
+Build a @code{GIMPLE_OMP_ATOMIC_STORE} statement. @code{VAL} is the value to be
+stored.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_atomic_store_set_val ( @
+gomp_atomic_store *g, tree val)
+Set the value being stored in an atomic store.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_atomic_store_val ( @
+const gomp_atomic_store *g)
+Return the value being stored in an atomic store.
+@end deftypefn
+
+@node @code{GIMPLE_OMP_CONTINUE}
+@subsection @code{GIMPLE_OMP_CONTINUE}
+@cindex @code{GIMPLE_OMP_CONTINUE}
+
+@deftypefn {GIMPLE function} gomp_continue *gimple_build_omp_continue ( @
+tree control_def, tree control_use)
+Build a @code{GIMPLE_OMP_CONTINUE} statement. @code{CONTROL_DEF} is the
+definition of the control variable. @code{CONTROL_USE} is the use of
+the control variable.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_continue_control_def ( @
+const gomp_continue *s)
+Return the definition of the control variable on a
+@code{GIMPLE_OMP_CONTINUE} in @code{S}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_continue_control_def_ptr ( @
+gomp_continue *s)
+Same as above, but return the pointer.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_continue_set_control_def ( @
+gomp_continue *s)
+Set the control variable definition for a @code{GIMPLE_OMP_CONTINUE}
+statement in @code{S}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_continue_control_use ( @
+const gomp_continue *s)
+Return the use of the control variable on a @code{GIMPLE_OMP_CONTINUE}
+in @code{S}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_continue_control_use_ptr ( @
+gomp_continue *s)
+Same as above, but return the pointer.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_continue_set_control_use ( @
+gomp_continue *s)
+Set the control variable use for a @code{GIMPLE_OMP_CONTINUE} statement
+in @code{S}.
+@end deftypefn
+
+
+@node @code{GIMPLE_OMP_CRITICAL}
+@subsection @code{GIMPLE_OMP_CRITICAL}
+@cindex @code{GIMPLE_OMP_CRITICAL}
+
+@deftypefn {GIMPLE function} gomp_critical *gimple_build_omp_critical ( @
+gimple_seq body, tree name)
+Build a @code{GIMPLE_OMP_CRITICAL} statement. @code{BODY} is the sequence of
+statements for which only one thread can execute. @code{NAME} is an
+optional identifier for this critical block.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_critical_name ( @
+const gomp_critical *g)
+Return the name associated with @code{OMP_CRITICAL} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_critical_name_ptr ( @
+gomp_critical *g)
+Return a pointer to the name associated with @code{OMP} critical
+statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_critical_set_name ( @
+gomp_critical *g, tree name)
+Set @code{NAME} to be the name associated with @code{OMP} critical statement @code{G}.
+@end deftypefn
+
+@node @code{GIMPLE_OMP_FOR}
+@subsection @code{GIMPLE_OMP_FOR}
+@cindex @code{GIMPLE_OMP_FOR}
+
+@deftypefn {GIMPLE function} gomp_for *gimple_build_omp_for (gimple_seq body, @
+tree clauses, tree index, tree initial, tree final, tree incr, @
+gimple_seq pre_body, enum tree_code omp_for_cond)
+Build a @code{GIMPLE_OMP_FOR} statement. @code{BODY} is sequence of statements
+inside the for loop. @code{CLAUSES}, are any of the loop
+construct's clauses. @code{PRE_BODY} is the
+sequence of statements that are loop invariant. @code{INDEX} is the
+index variable. @code{INITIAL} is the initial value of @code{INDEX}. @code{FINAL} is
+final value of @code{INDEX}. OMP_FOR_COND is the predicate used to
+compare @code{INDEX} and @code{FINAL}. @code{INCR} is the increment expression.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_for_clauses (gimple g)
+Return the clauses associated with @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_for_clauses_ptr (gimple g)
+Return a pointer to the @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_for_set_clauses (gimple g, tree clauses)
+Set @code{CLAUSES} to be the list of clauses associated with @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_for_index (gimple g)
+Return the index variable for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_for_index_ptr (gimple g)
+Return a pointer to the index variable for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_for_set_index (gimple g, tree index)
+Set @code{INDEX} to be the index variable for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_for_initial (gimple g)
+Return the initial value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_for_initial_ptr (gimple g)
+Return a pointer to the initial value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_for_set_initial (gimple g, tree initial)
+Set @code{INITIAL} to be the initial value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_for_final (gimple g)
+Return the final value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_for_final_ptr (gimple g)
+turn a pointer to the final value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_for_set_final (gimple g, tree final)
+Set @code{FINAL} to be the final value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_for_incr (gimple g)
+Return the increment value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_for_incr_ptr (gimple g)
+Return a pointer to the increment value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_for_set_incr (gimple g, tree incr)
+Set @code{INCR} to be the increment value for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_omp_for_pre_body (gimple g)
+Return the sequence of statements to execute before the @code{OMP_FOR}
+statement @code{G} starts.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_for_set_pre_body (gimple g, gimple_seq pre_body)
+Set @code{PRE_BODY} to be the sequence of statements to execute before
+the @code{OMP_FOR} statement @code{G} starts.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_for_set_cond (gimple g, enum tree_code cond)
+Set @code{COND} to be the condition code for @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {enum tree_code} gimple_omp_for_cond (gimple g)
+Return the condition code associated with @code{OMP_FOR} @code{G}.
+@end deftypefn
+
+
+@node @code{GIMPLE_OMP_MASTER}
+@subsection @code{GIMPLE_OMP_MASTER}
+@cindex @code{GIMPLE_OMP_MASTER}
+
+@deftypefn {GIMPLE function} gimple gimple_build_omp_master (gimple_seq body)
+Build a @code{GIMPLE_OMP_MASTER} statement. @code{BODY} is the sequence of
+statements to be executed by just the master.
+@end deftypefn
+
+
+@node @code{GIMPLE_OMP_ORDERED}
+@subsection @code{GIMPLE_OMP_ORDERED}
+@cindex @code{GIMPLE_OMP_ORDERED}
+
+@deftypefn {GIMPLE function} gimple gimple_build_omp_ordered (gimple_seq body)
+Build a @code{GIMPLE_OMP_ORDERED} statement.
+
+@code{BODY} is the sequence of statements inside a loop that will
+executed in sequence.
+@end deftypefn
+
+@node @code{GIMPLE_OMP_PARALLEL}
+@subsection @code{GIMPLE_OMP_PARALLEL}
+@cindex @code{GIMPLE_OMP_PARALLEL}
+
+@deftypefn {GIMPLE function} gomp_parallel *gimple_build_omp_parallel (@
+gimple_seq body, tree clauses, tree child_fn, tree data_arg)
+Build a @code{GIMPLE_OMP_PARALLEL} statement.
+
+@code{BODY} is sequence of statements which are executed in parallel.
+@code{CLAUSES}, are the @code{OMP} parallel construct's clauses. @code{CHILD_FN} is
+the function created for the parallel threads to execute.
+@code{DATA_ARG} are the shared data argument(s).
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_omp_parallel_combined_p (gimple g)
+Return true if @code{OMP} parallel statement @code{G} has the
+@code{GF_OMP_PARALLEL_COMBINED} flag set.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_parallel_set_combined_p (gimple g)
+Set the @code{GF_OMP_PARALLEL_COMBINED} field in @code{OMP} parallel statement
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_omp_body (gimple g)
+Return the body for the @code{OMP} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_set_body (gimple g, gimple_seq body)
+Set @code{BODY} to be the body for the @code{OMP} statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_parallel_clauses (gimple g)
+Return the clauses associated with @code{OMP_PARALLEL} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_parallel_clauses_ptr ( @
+gomp_parallel *g)
+Return a pointer to the clauses associated with @code{OMP_PARALLEL} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_parallel_set_clauses ( @
+gomp_parallel *g, tree clauses)
+Set @code{CLAUSES} to be the list of clauses associated with
+@code{OMP_PARALLEL} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_parallel_child_fn ( @
+const gomp_parallel *g)
+Return the child function used to hold the body of @code{OMP_PARALLEL}
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_parallel_child_fn_ptr ( @
+gomp_parallel *g)
+Return a pointer to the child function used to hold the body of
+@code{OMP_PARALLEL} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_parallel_set_child_fn ( @
+gomp_parallel *g, tree child_fn)
+Set @code{CHILD_FN} to be the child function for @code{OMP_PARALLEL} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_parallel_data_arg ( @
+const gomp_parallel *g)
+Return the artificial argument used to send variables and values
+from the parent to the children threads in @code{OMP_PARALLEL} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_parallel_data_arg_ptr ( @
+gomp_parallel *g)
+Return a pointer to the data argument for @code{OMP_PARALLEL} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_parallel_set_data_arg ( @
+gomp_parallel *g, tree data_arg)
+Set @code{DATA_ARG} to be the data argument for @code{OMP_PARALLEL} @code{G}.
+@end deftypefn
+
+
+@node @code{GIMPLE_OMP_RETURN}
+@subsection @code{GIMPLE_OMP_RETURN}
+@cindex @code{GIMPLE_OMP_RETURN}
+
+@deftypefn {GIMPLE function} gimple gimple_build_omp_return (bool wait_p)
+Build a @code{GIMPLE_OMP_RETURN} statement. @code{WAIT_P} is true if this is a
+non-waiting return.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_return_set_nowait (gimple s)
+Set the nowait flag on @code{GIMPLE_OMP_RETURN} statement @code{S}.
+@end deftypefn
+
+
+@deftypefn {GIMPLE function} bool gimple_omp_return_nowait_p (gimple g)
+Return true if @code{OMP} return statement @code{G} has the
+@code{GF_OMP_RETURN_NOWAIT} flag set.
+@end deftypefn
+
+@node @code{GIMPLE_OMP_SECTION}
+@subsection @code{GIMPLE_OMP_SECTION}
+@cindex @code{GIMPLE_OMP_SECTION}
+
+@deftypefn {GIMPLE function} gimple gimple_build_omp_section (gimple_seq body)
+Build a @code{GIMPLE_OMP_SECTION} statement for a sections statement.
+
+@code{BODY} is the sequence of statements in the section.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_omp_section_last_p (gimple g)
+Return true if @code{OMP} section statement @code{G} has the
+@code{GF_OMP_SECTION_LAST} flag set.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_section_set_last (gimple g)
+Set the @code{GF_OMP_SECTION_LAST} flag on @code{G}.
+@end deftypefn
+
+@node @code{GIMPLE_OMP_SECTIONS}
+@subsection @code{GIMPLE_OMP_SECTIONS}
+@cindex @code{GIMPLE_OMP_SECTIONS}
+
+@deftypefn {GIMPLE function} gomp_sections *gimple_build_omp_sections ( @
+gimple_seq body, tree clauses)
+Build a @code{GIMPLE_OMP_SECTIONS} statement. @code{BODY} is a sequence of
+section statements. @code{CLAUSES} are any of the @code{OMP} sections
+construct's clauses: private, firstprivate, lastprivate,
+reduction, and nowait.
+@end deftypefn
+
+
+@deftypefn {GIMPLE function} gimple gimple_build_omp_sections_switch (void)
+Build a @code{GIMPLE_OMP_SECTIONS_SWITCH} statement.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_sections_control (gimple g)
+Return the control variable associated with the
+@code{GIMPLE_OMP_SECTIONS} in @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_sections_control_ptr (gimple g)
+Return a pointer to the clauses associated with the
+@code{GIMPLE_OMP_SECTIONS} in @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_sections_set_control (gimple g, tree control)
+Set @code{CONTROL} to be the set of clauses associated with the
+@code{GIMPLE_OMP_SECTIONS} in @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_sections_clauses (gimple g)
+Return the clauses associated with @code{OMP_SECTIONS} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_sections_clauses_ptr (gimple g)
+Return a pointer to the clauses associated with @code{OMP_SECTIONS} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_sections_set_clauses (gimple g, tree clauses)
+Set @code{CLAUSES} to be the set of clauses associated with @code{OMP_SECTIONS}
+@code{G}.
+@end deftypefn
+
+
+@node @code{GIMPLE_OMP_SINGLE}
+@subsection @code{GIMPLE_OMP_SINGLE}
+@cindex @code{GIMPLE_OMP_SINGLE}
+
+@deftypefn {GIMPLE function} gomp_single *gimple_build_omp_single ( @
+gimple_seq body, tree clauses)
+Build a @code{GIMPLE_OMP_SINGLE} statement. @code{BODY} is the sequence of
+statements that will be executed once. @code{CLAUSES} are any of the
+@code{OMP} single construct's clauses: private, firstprivate,
+copyprivate, nowait.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_omp_single_clauses (gimple g)
+Return the clauses associated with @code{OMP_SINGLE} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_omp_single_clauses_ptr (gimple g)
+Return a pointer to the clauses associated with @code{OMP_SINGLE} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_omp_single_set_clauses ( @
+gomp_single *g, tree clauses)
+Set @code{CLAUSES} to be the clauses associated with @code{OMP_SINGLE} @code{G}.
+@end deftypefn
+
+
+@node @code{GIMPLE_PHI}
+@subsection @code{GIMPLE_PHI}
+@cindex @code{GIMPLE_PHI}
+
+@deftypefn {GIMPLE function} unsigned gimple_phi_capacity (gimple g)
+Return the maximum number of arguments supported by @code{GIMPLE_PHI} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} unsigned gimple_phi_num_args (gimple g)
+Return the number of arguments in @code{GIMPLE_PHI} @code{G}. This must always
+be exactly the number of incoming edges for the basic block
+holding @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_phi_result (gimple g)
+Return the @code{SSA} name created by @code{GIMPLE_PHI} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {tree *} gimple_phi_result_ptr (gimple g)
+Return a pointer to the @code{SSA} name created by @code{GIMPLE_PHI} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_phi_set_result (gphi *g, tree result)
+Set @code{RESULT} to be the @code{SSA} name created by @code{GIMPLE_PHI} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {struct phi_arg_d *} gimple_phi_arg (gimple g, index)
+Return the @code{PHI} argument corresponding to incoming edge @code{INDEX} for
+@code{GIMPLE_PHI} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_phi_set_arg (gphi *g, index, @
+struct phi_arg_d * phiarg)
+Set @code{PHIARG} to be the argument corresponding to incoming edge
+@code{INDEX} for @code{GIMPLE_PHI} @code{G}.
+@end deftypefn
+
+@node @code{GIMPLE_RESX}
+@subsection @code{GIMPLE_RESX}
+@cindex @code{GIMPLE_RESX}
+
+@deftypefn {GIMPLE function} gresx *gimple_build_resx (int region)
+Build a @code{GIMPLE_RESX} statement which is a statement. This
+statement is a placeholder for _Unwind_Resume before we know if a
+function call or a branch is needed. @code{REGION} is the exception
+region from which control is flowing.
+@end deftypefn
+
+@deftypefn {GIMPLE function} int gimple_resx_region (const gresx *g)
+Return the region number for @code{GIMPLE_RESX} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_resx_set_region (gresx *g, int region)
+Set @code{REGION} to be the region number for @code{GIMPLE_RESX} @code{G}.
+@end deftypefn
+
+@node @code{GIMPLE_RETURN}
+@subsection @code{GIMPLE_RETURN}
+@cindex @code{GIMPLE_RETURN}
+
+@deftypefn {GIMPLE function} greturn *gimple_build_return (tree retval)
+Build a @code{GIMPLE_RETURN} statement whose return value is retval.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_return_retval (const greturn *g)
+Return the return value for @code{GIMPLE_RETURN} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_return_set_retval (greturn *g, @
+tree retval)
+Set @code{RETVAL} to be the return value for @code{GIMPLE_RETURN} @code{G}.
+@end deftypefn
+
+@node @code{GIMPLE_SWITCH}
+@subsection @code{GIMPLE_SWITCH}
+@cindex @code{GIMPLE_SWITCH}
+
+@deftypefn {GIMPLE function} gswitch *gimple_build_switch (tree index, @
+tree default_label, @code{vec}<tree> *args)
+Build a @code{GIMPLE_SWITCH} statement. @code{INDEX} is the index variable
+to switch on, and @code{DEFAULT_LABEL} represents the default label.
+@code{ARGS} is a vector of @code{CASE_LABEL_EXPR} trees that contain the
+non-default case labels. Each label is a tree of code @code{CASE_LABEL_EXPR}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} unsigned gimple_switch_num_labels ( @
+const gswitch *g)
+Return the number of labels associated with the switch statement
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_switch_set_num_labels (gswitch *g, @
+unsigned nlabels)
+Set @code{NLABELS} to be the number of labels for the switch statement
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_switch_index (const gswitch *g)
+Return the index variable used by the switch statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_switch_set_index (gswitch *g, @
+tree index)
+Set @code{INDEX} to be the index variable for switch statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_switch_label (const gswitch *g, @
+unsigned index)
+Return the label numbered @code{INDEX}. The default label is 0, followed
+by any labels in a switch statement.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_switch_set_label (gswitch *g, @
+unsigned index, tree label)
+Set the label number @code{INDEX} to @code{LABEL}. 0 is always the default
+label.
+@end deftypefn
+
+@deftypefn {GIMPLE function} tree gimple_switch_default_label ( @
+const gswitch *g)
+Return the default label for a switch statement.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_switch_set_default_label (gswitch *g, @
+tree label)
+Set the default label for a switch statement.
+@end deftypefn
+
+
+@node @code{GIMPLE_TRY}
+@subsection @code{GIMPLE_TRY}
+@cindex @code{GIMPLE_TRY}
+
+@deftypefn {GIMPLE function} gtry *gimple_build_try (gimple_seq eval, @
+gimple_seq cleanup, unsigned int kind)
+Build a @code{GIMPLE_TRY} statement. @code{EVAL} is a sequence with the
+expression to evaluate. @code{CLEANUP} is a sequence of statements to
+run at clean-up time. @code{KIND} is the enumeration value
+@code{GIMPLE_TRY_CATCH} if this statement denotes a try/catch construct
+or @code{GIMPLE_TRY_FINALLY} if this statement denotes a try/finally
+construct.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {enum gimple_try_flags} gimple_try_kind (gimple g)
+Return the kind of try block represented by @code{GIMPLE_TRY} @code{G}. This is
+either @code{GIMPLE_TRY_CATCH} or @code{GIMPLE_TRY_FINALLY}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_try_catch_is_cleanup (gimple g)
+Return the @code{GIMPLE_TRY_CATCH_IS_CLEANUP} flag.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_try_eval (gimple g)
+Return the sequence of statements used as the body for @code{GIMPLE_TRY}
+@code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_try_cleanup (gimple g)
+Return the sequence of statements used as the cleanup body for
+@code{GIMPLE_TRY} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_try_set_catch_is_cleanup (gimple g, @
+bool catch_is_cleanup)
+Set the @code{GIMPLE_TRY_CATCH_IS_CLEANUP} flag.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_try_set_eval (gtry *g, gimple_seq eval)
+Set @code{EVAL} to be the sequence of statements to use as the body for
+@code{GIMPLE_TRY} @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_try_set_cleanup (gtry *g, @
+gimple_seq cleanup)
+Set @code{CLEANUP} to be the sequence of statements to use as the
+cleanup body for @code{GIMPLE_TRY} @code{G}.
+@end deftypefn
+
+@node @code{GIMPLE_WITH_CLEANUP_EXPR}
+@subsection @code{GIMPLE_WITH_CLEANUP_EXPR}
+@cindex @code{GIMPLE_WITH_CLEANUP_EXPR}
+
+@deftypefn {GIMPLE function} gimple gimple_build_wce (gimple_seq cleanup)
+Build a @code{GIMPLE_WITH_CLEANUP_EXPR} statement. @code{CLEANUP} is the
+clean-up expression.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_wce_cleanup (gimple g)
+Return the cleanup sequence for cleanup statement @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_wce_set_cleanup (gimple g, gimple_seq cleanup)
+Set @code{CLEANUP} to be the cleanup sequence for @code{G}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_wce_cleanup_eh_only (gimple g)
+Return the @code{CLEANUP_EH_ONLY} flag for a @code{WCE} tuple.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_wce_set_cleanup_eh_only (gimple g, bool eh_only_p)
+Set the @code{CLEANUP_EH_ONLY} flag for a @code{WCE} tuple.
+@end deftypefn
+
+
+@node GIMPLE sequences
+@section GIMPLE sequences
+@cindex GIMPLE sequences
+
+GIMPLE sequences are the tuple equivalent of @code{STATEMENT_LIST}'s
+used in @code{GENERIC}. They are used to chain statements together, and
+when used in conjunction with sequence iterators, provide a
+framework for iterating through statements.
+
+GIMPLE sequences are of type struct @code{gimple_sequence}, but are more
+commonly passed by reference to functions dealing with sequences.
+The type for a sequence pointer is @code{gimple_seq} which is the same
+as struct @code{gimple_sequence} *. When declaring a local sequence,
+you can define a local variable of type struct @code{gimple_sequence}.
+When declaring a sequence allocated on the garbage collected
+heap, use the function @code{gimple_seq_alloc} documented below.
+
+There are convenience functions for iterating through sequences
+in the section entitled Sequence Iterators.
+
+Below is a list of functions to manipulate and query sequences.
+
+@deftypefn {GIMPLE function} void gimple_seq_add_stmt (gimple_seq *seq, gimple g)
+Link a gimple statement to the end of the sequence *@code{SEQ} if @code{G} is
+not @code{NULL}. If *@code{SEQ} is @code{NULL}, allocate a sequence before linking.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_seq_add_seq (gimple_seq *dest, gimple_seq src)
+Append sequence @code{SRC} to the end of sequence *@code{DEST} if @code{SRC} is not
+@code{NULL}. If *@code{DEST} is @code{NULL}, allocate a new sequence before
+appending.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_seq_deep_copy (gimple_seq src)
+Perform a deep copy of sequence @code{SRC} and return the result.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_seq_reverse (gimple_seq seq)
+Reverse the order of the statements in the sequence @code{SEQ}. Return
+@code{SEQ}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple gimple_seq_first (gimple_seq s)
+Return the first statement in sequence @code{S}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple gimple_seq_last (gimple_seq s)
+Return the last statement in sequence @code{S}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_seq_set_last (gimple_seq s, gimple last)
+Set the last statement in sequence @code{S} to the statement in @code{LAST}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_seq_set_first (gimple_seq s, gimple first)
+Set the first statement in sequence @code{S} to the statement in @code{FIRST}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_seq_init (gimple_seq s)
+Initialize sequence @code{S} to an empty sequence.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gimple_seq_alloc (void)
+Allocate a new sequence in the garbage collected store and return
+it.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gimple_seq_copy (gimple_seq dest, gimple_seq src)
+Copy the sequence @code{SRC} into the sequence @code{DEST}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_seq_empty_p (gimple_seq s)
+Return true if the sequence @code{S} is empty.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq bb_seq (basic_block bb)
+Returns the sequence of statements in @code{BB}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void set_bb_seq (basic_block bb, gimple_seq seq)
+Sets the sequence of statements in @code{BB} to @code{SEQ}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gimple_seq_singleton_p (gimple_seq seq)
+Determine whether @code{SEQ} contains exactly one statement.
+@end deftypefn
+
+@node Sequence iterators
+@section Sequence iterators
+@cindex Sequence iterators
+
+Sequence iterators are convenience constructs for iterating
+through statements in a sequence. Given a sequence @code{SEQ}, here is
+a typical use of gimple sequence iterators:
+
+@smallexample
+gimple_stmt_iterator gsi;
+
+for (gsi = gsi_start (seq); !gsi_end_p (gsi); gsi_next (&gsi))
+ @{
+ gimple g = gsi_stmt (gsi);
+ /* Do something with gimple statement @code{G}. */
+ @}
+@end smallexample
+
+Backward iterations are possible:
+
+@smallexample
+ for (gsi = gsi_last (seq); !gsi_end_p (gsi); gsi_prev (&gsi))
+@end smallexample
+
+Forward and backward iterations on basic blocks are possible with
+@code{gsi_start_bb} and @code{gsi_last_bb}.
+
+In the documentation below we sometimes refer to enum
+@code{gsi_iterator_update}. The valid options for this enumeration are:
+
+@itemize @bullet
+@item @code{GSI_NEW_STMT}
+Only valid when a single statement is added. Move the iterator to it.
+
+@item @code{GSI_SAME_STMT}
+Leave the iterator at the same statement.
+
+@item @code{GSI_CONTINUE_LINKING}
+Move iterator to whatever position is suitable for linking other
+statements in the same direction.
+@end itemize
+
+Below is a list of the functions used to manipulate and use
+statement iterators.
+
+@deftypefn {GIMPLE function} gimple_stmt_iterator gsi_start (gimple_seq seq)
+Return a new iterator pointing to the sequence @code{SEQ}'s first
+statement. If @code{SEQ} is empty, the iterator's basic block is @code{NULL}.
+Use @code{gsi_start_bb} instead when the iterator needs to always have
+the correct basic block set.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_stmt_iterator gsi_start_bb (basic_block bb)
+Return a new iterator pointing to the first statement in basic
+block @code{BB}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_stmt_iterator gsi_last (gimple_seq seq)
+Return a new iterator initially pointing to the last statement of
+sequence @code{SEQ}. If @code{SEQ} is empty, the iterator's basic block is
+@code{NULL}. Use @code{gsi_last_bb} instead when the iterator needs to always
+have the correct basic block set.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_stmt_iterator gsi_last_bb (basic_block bb)
+Return a new iterator pointing to the last statement in basic
+block @code{BB}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gsi_end_p (gimple_stmt_iterator i)
+Return @code{TRUE} if at the end of @code{I}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} bool gsi_one_before_end_p (gimple_stmt_iterator i)
+Return @code{TRUE} if we're one statement before the end of @code{I}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_next (gimple_stmt_iterator *i)
+Advance the iterator to the next gimple statement.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_prev (gimple_stmt_iterator *i)
+Advance the iterator to the previous gimple statement.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple gsi_stmt (gimple_stmt_iterator i)
+Return the current stmt.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_stmt_iterator gsi_after_labels (basic_block bb)
+Return a block statement iterator that points to the first
+non-label statement in block @code{BB}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} {gimple *} gsi_stmt_ptr (gimple_stmt_iterator *i)
+Return a pointer to the current stmt.
+@end deftypefn
+
+@deftypefn {GIMPLE function} basic_block gsi_bb (gimple_stmt_iterator i)
+Return the basic block associated with this iterator.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gsi_seq (gimple_stmt_iterator i)
+Return the sequence associated with this iterator.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_remove (gimple_stmt_iterator *i, bool remove_eh_info)
+Remove the current stmt from the sequence. The iterator is
+updated to point to the next statement. When @code{REMOVE_EH_INFO} is
+true we remove the statement pointed to by iterator @code{I} from the @code{EH}
+tables. Otherwise we do not modify the @code{EH} tables. Generally,
+@code{REMOVE_EH_INFO} should be true when the statement is going to be
+removed from the @code{IL} and not reinserted elsewhere.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_link_seq_before (gimple_stmt_iterator *i, gimple_seq seq, enum gsi_iterator_update mode)
+Links the sequence of statements @code{SEQ} before the statement pointed
+by iterator @code{I}. @code{MODE} indicates what to do with the iterator
+after insertion (see @code{enum gsi_iterator_update} above).
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_link_before (gimple_stmt_iterator *i, gimple g, enum gsi_iterator_update mode)
+Links statement @code{G} before the statement pointed-to by iterator @code{I}.
+Updates iterator @code{I} according to @code{MODE}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_link_seq_after (gimple_stmt_iterator *i, @
+gimple_seq seq, enum gsi_iterator_update mode)
+Links sequence @code{SEQ} after the statement pointed-to by iterator @code{I}.
+@code{MODE} is as in @code{gsi_insert_after}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_link_after (gimple_stmt_iterator *i, @
+gimple g, enum gsi_iterator_update mode)
+Links statement @code{G} after the statement pointed-to by iterator @code{I}.
+@code{MODE} is as in @code{gsi_insert_after}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gsi_split_seq_after (gimple_stmt_iterator i)
+Move all statements in the sequence after @code{I} to a new sequence.
+Return this new sequence.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_seq gsi_split_seq_before (gimple_stmt_iterator *i)
+Move all statements in the sequence before @code{I} to a new sequence.
+Return this new sequence.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_replace (gimple_stmt_iterator *i, @
+gimple stmt, bool update_eh_info)
+Replace the statement pointed-to by @code{I} to @code{STMT}. If @code{UPDATE_EH_INFO}
+is true, the exception handling information of the original
+statement is moved to the new statement.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_insert_before (gimple_stmt_iterator *i, @
+gimple stmt, enum gsi_iterator_update mode)
+Insert statement @code{STMT} before the statement pointed-to by iterator
+@code{I}, update @code{STMT}'s basic block and scan it for new operands. @code{MODE}
+specifies how to update iterator @code{I} after insertion (see enum
+@code{gsi_iterator_update}).
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_insert_seq_before (gimple_stmt_iterator *i, @
+gimple_seq seq, enum gsi_iterator_update mode)
+Like @code{gsi_insert_before}, but for all the statements in @code{SEQ}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_insert_after (gimple_stmt_iterator *i, @
+gimple stmt, enum gsi_iterator_update mode)
+Insert statement @code{STMT} after the statement pointed-to by iterator
+@code{I}, update @code{STMT}'s basic block and scan it for new operands. @code{MODE}
+specifies how to update iterator @code{I} after insertion (see enum
+@code{gsi_iterator_update}).
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_insert_seq_after (gimple_stmt_iterator *i, @
+gimple_seq seq, enum gsi_iterator_update mode)
+Like @code{gsi_insert_after}, but for all the statements in @code{SEQ}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} gimple_stmt_iterator gsi_for_stmt (gimple stmt)
+Finds iterator for @code{STMT}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_move_after (gimple_stmt_iterator *from, @
+gimple_stmt_iterator *to)
+Move the statement at @code{FROM} so it comes right after the statement
+at @code{TO}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_move_before (gimple_stmt_iterator *from, @
+gimple_stmt_iterator *to)
+Move the statement at @code{FROM} so it comes right before the statement
+at @code{TO}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_move_to_bb_end (gimple_stmt_iterator *from, @
+basic_block bb)
+Move the statement at @code{FROM} to the end of basic block @code{BB}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_insert_on_edge (edge e, gimple stmt)
+Add @code{STMT} to the pending list of edge @code{E}. No actual insertion is
+made until a call to @code{gsi_commit_edge_inserts}() is made.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_insert_seq_on_edge (edge e, gimple_seq seq)
+Add the sequence of statements in @code{SEQ} to the pending list of edge
+@code{E}. No actual insertion is made until a call to
+@code{gsi_commit_edge_inserts}() is made.
+@end deftypefn
+
+@deftypefn {GIMPLE function} basic_block gsi_insert_on_edge_immediate (edge e, gimple stmt)
+Similar to @code{gsi_insert_on_edge}+@code{gsi_commit_edge_inserts}. If a new
+block has to be created, it is returned.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_commit_one_edge_insert (edge e, basic_block *new_bb)
+Commit insertions pending at edge @code{E}. If a new block is created,
+set @code{NEW_BB} to this block, otherwise set it to @code{NULL}.
+@end deftypefn
+
+@deftypefn {GIMPLE function} void gsi_commit_edge_inserts (void)
+This routine will commit all pending edge insertions, creating
+any new basic blocks which are necessary.
+@end deftypefn
+
+
+@node Adding a new GIMPLE statement code
+@section Adding a new GIMPLE statement code
+@cindex Adding a new GIMPLE statement code
+
+The first step in adding a new GIMPLE statement code, is
+modifying the file @code{gimple.def}, which contains all the GIMPLE
+codes. Then you must add a corresponding gimple subclass
+located in @code{gimple.h}. This in turn, will require you to add a
+corresponding @code{GTY} tag in @code{gsstruct.def}, and code to handle
+this tag in @code{gss_for_code} which is located in @code{gimple.cc}.
+
+In order for the garbage collector to know the size of the
+structure you created in @code{gimple.h}, you need to add a case to
+handle your new GIMPLE statement in @code{gimple_size} which is located
+in @code{gimple.cc}.
+
+You will probably want to create a function to build the new
+gimple statement in @code{gimple.cc}. The function should be called
+@code{gimple_build_@var{new-tuple-name}}, and should return the new tuple
+as a pointer to the appropriate gimple subclass.
+
+If your new statement requires accessors for any members or
+operands it may have, put simple inline accessors in
+@code{gimple.h} and any non-trivial accessors in @code{gimple.cc} with a
+corresponding prototype in @code{gimple.h}.
+
+You should add the new statement subclass to the class hierarchy diagram
+in @code{gimple.texi}.
+
+
+@node Statement and operand traversals
+@section Statement and operand traversals
+@cindex Statement and operand traversals
+
+There are two functions available for walking statements and
+sequences: @code{walk_gimple_stmt} and @code{walk_gimple_seq},
+accordingly, and a third function for walking the operands in a
+statement: @code{walk_gimple_op}.
+
+@deftypefn {GIMPLE function} tree walk_gimple_stmt (gimple_stmt_iterator *gsi, @
+ walk_stmt_fn callback_stmt, walk_tree_fn callback_op, struct walk_stmt_info *wi)
+This function is used to walk the current statement in @code{GSI},
+optionally using traversal state stored in @code{WI}. If @code{WI} is @code{NULL}, no
+state is kept during the traversal.
+
+The callback @code{CALLBACK_STMT} is called. If @code{CALLBACK_STMT} returns
+true, it means that the callback function has handled all the
+operands of the statement and it is not necessary to walk its
+operands.
+
+If @code{CALLBACK_STMT} is @code{NULL} or it returns false, @code{CALLBACK_OP} is
+called on each operand of the statement via @code{walk_gimple_op}. If
+@code{walk_gimple_op} returns non-@code{NULL} for any operand, the remaining
+operands are not scanned.
+
+The return value is that returned by the last call to
+@code{walk_gimple_op}, or @code{NULL_TREE} if no @code{CALLBACK_OP} is specified.
+@end deftypefn
+
+
+@deftypefn {GIMPLE function} tree walk_gimple_op (gimple stmt, @
+ walk_tree_fn callback_op, struct walk_stmt_info *wi)
+Use this function to walk the operands of statement @code{STMT}. Every
+operand is walked via @code{walk_tree} with optional state information
+in @code{WI}.
+
+@code{CALLBACK_OP} is called on each operand of @code{STMT} via @code{walk_tree}.
+Additional parameters to @code{walk_tree} must be stored in @code{WI}. For
+each operand @code{OP}, @code{walk_tree} is called as:
+
+@smallexample
+walk_tree (&@code{OP}, @code{CALLBACK_OP}, @code{WI}, @code{PSET})
+@end smallexample
+
+If @code{CALLBACK_OP} returns non-@code{NULL} for an operand, the remaining
+operands are not scanned. The return value is that returned by
+the last call to @code{walk_tree}, or @code{NULL_TREE} if no @code{CALLBACK_OP} is
+specified.
+@end deftypefn
+
+
+@deftypefn {GIMPLE function} tree walk_gimple_seq (gimple_seq seq, @
+ walk_stmt_fn callback_stmt, walk_tree_fn callback_op, struct walk_stmt_info *wi)
+This function walks all the statements in the sequence @code{SEQ}
+calling @code{walk_gimple_stmt} on each one. @code{WI} is as in
+@code{walk_gimple_stmt}. If @code{walk_gimple_stmt} returns non-@code{NULL}, the walk
+is stopped and the value returned. Otherwise, all the statements
+are walked and @code{NULL_TREE} returned.
+@end deftypefn
--- /dev/null
+@c Copyright (C) 2001 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node GNU Project
+@unnumbered The GNU Project and GNU/Linux
+
+The GNU Project was launched in 1984 to develop a complete Unix-like
+operating system which is free software: the GNU system. (GNU is a
+recursive acronym for ``GNU's Not Unix''; it is pronounced
+``guh-NEW''@.) Variants of the GNU operating system, which use the
+kernel Linux, are now widely used; though these systems are often
+referred to as ``Linux'', they are more accurately called GNU/Linux
+systems.
+
+For more information, see:
+@smallexample
+@uref{https://www.gnu.org/}
+@uref{https://www.gnu.org/gnu/linux-and-gnu.html}
+@end smallexample
--- /dev/null
+@c Copyright (C) 2002-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Type Information
+@chapter Memory Management and Type Information
+@cindex GGC
+@findex GTY
+
+GCC uses some fairly sophisticated memory management techniques, which
+involve determining information about GCC's data structures from GCC's
+source code and using this information to perform garbage collection and
+implement precompiled headers.
+
+A full C++ parser would be too complicated for this task, so a limited
+subset of C++ is interpreted and special markers are used to determine
+what parts of the source to look at. All @code{struct}, @code{union}
+and @code{template} structure declarations that define data structures
+that are allocated under control of the garbage collector must be
+marked. All global variables that hold pointers to garbage-collected
+memory must also be marked. Finally, all global variables that need
+to be saved and restored by a precompiled header must be marked. (The
+precompiled header mechanism can only save static variables if they're
+scalar. Complex data structures must be allocated in garbage-collected
+memory to be saved in a precompiled header.)
+
+The full format of a marker is
+@smallexample
+GTY (([@var{option}] [(@var{param})], [@var{option}] [(@var{param})] @dots{}))
+@end smallexample
+@noindent
+but in most cases no options are needed. The outer double parentheses
+are still necessary, though: @code{GTY(())}. Markers can appear:
+
+@itemize @bullet
+@item
+In a structure definition, before the open brace;
+@item
+In a global variable declaration, after the keyword @code{static} or
+@code{extern}; and
+@item
+In a structure field definition, before the name of the field.
+@end itemize
+
+Here are some examples of marking simple data structures and globals.
+
+@smallexample
+struct GTY(()) @var{tag}
+@{
+ @var{fields}@dots{}
+@};
+
+typedef struct GTY(()) @var{tag}
+@{
+ @var{fields}@dots{}
+@} *@var{typename};
+
+static GTY(()) struct @var{tag} *@var{list}; /* @r{points to GC memory} */
+static GTY(()) int @var{counter}; /* @r{save counter in a PCH} */
+@end smallexample
+
+The parser understands simple typedefs such as
+@code{typedef struct @var{tag} *@var{name};} and
+@code{typedef int @var{name};}.
+These don't need to be marked.
+
+However, in combination with GTY, avoid using typedefs such as
+@code{typedef int_hash<@dots{}> @var{name};}
+for these generate infinite-recursion code.
+See @uref{https://gcc.gnu.org/PR103157,PR103157}.
+Instead, you may use
+@code{struct @var{name} : int_hash<@dots{}> @{@};},
+for example.
+
+Since @code{gengtype}'s understanding of C++ is limited, there are
+several constructs and declarations that are not supported inside
+classes/structures marked for automatic GC code generation. The
+following C++ constructs produce a @code{gengtype} error on
+structures/classes marked for automatic GC code generation:
+
+@itemize @bullet
+@item
+Type definitions inside classes/structures are not supported.
+@item
+Enumerations inside classes/structures are not supported.
+@end itemize
+
+If you have a class or structure using any of the above constructs,
+you need to mark that class as @code{GTY ((user))} and provide your
+own marking routines (see section @ref{User GC} for details).
+
+It is always valid to include function definitions inside classes.
+Those are always ignored by @code{gengtype}, as it only cares about
+data members.
+
+@menu
+* GTY Options:: What goes inside a @code{GTY(())}.
+* Inheritance and GTY:: Adding GTY to a class hierarchy.
+* User GC:: Adding user-provided GC marking routines.
+* GGC Roots:: Making global variables GGC roots.
+* Files:: How the generated files work.
+* Invoking the garbage collector:: How to invoke the garbage collector.
+* Troubleshooting:: When something does not work as expected.
+@end menu
+
+@node GTY Options
+@section The Inside of a @code{GTY(())}
+
+Sometimes the C code is not enough to fully describe the type
+structure. Extra information can be provided with @code{GTY} options
+and additional markers. Some options take a parameter, which may be
+either a string or a type name, depending on the parameter. If an
+option takes no parameter, it is acceptable either to omit the
+parameter entirely, or to provide an empty string as a parameter. For
+example, @code{@w{GTY ((skip))}} and @code{@w{GTY ((skip ("")))}} are
+equivalent.
+
+When the parameter is a string, often it is a fragment of C code. Four
+special escapes may be used in these strings, to refer to pieces of
+the data structure being marked:
+
+@cindex % in GTY option
+@table @code
+@item %h
+The current structure.
+@item %1
+The structure that immediately contains the current structure.
+@item %0
+The outermost structure that contains the current structure.
+@item %a
+A partial expression of the form @code{[i1][i2]@dots{}} that indexes
+the array item currently being marked.
+@end table
+
+For instance, suppose that you have a structure of the form
+@smallexample
+struct A @{
+ @dots{}
+@};
+struct B @{
+ struct A foo[12];
+@};
+@end smallexample
+@noindent
+and @code{b} is a variable of type @code{struct B}. When marking
+@samp{b.foo[11]}, @code{%h} would expand to @samp{b.foo[11]},
+@code{%0} and @code{%1} would both expand to @samp{b}, and @code{%a}
+would expand to @samp{[11]}.
+
+As in ordinary C, adjacent strings will be concatenated; this is
+helpful when you have a complicated expression.
+@smallexample
+@group
+GTY ((chain_next ("TREE_CODE (&%h.generic) == INTEGER_TYPE"
+ " ? TYPE_NEXT_VARIANT (&%h.generic)"
+ " : TREE_CHAIN (&%h.generic)")))
+@end group
+@end smallexample
+
+The available options are:
+
+@table @code
+@findex length
+@item length ("@var{expression}")
+
+There are two places the type machinery will need to be explicitly told
+the length of an array of non-atomic objects. The first case is when a
+structure ends in a variable-length array, like this:
+@smallexample
+struct GTY(()) rtvec_def @{
+ int num_elem; /* @r{number of elements} */
+ rtx GTY ((length ("%h.num_elem"))) elem[1];
+@};
+@end smallexample
+
+In this case, the @code{length} option is used to override the specified
+array length (which should usually be @code{1}). The parameter of the
+option is a fragment of C code that calculates the length.
+
+The second case is when a structure or a global variable contains a
+pointer to an array, like this:
+@smallexample
+struct gimple_omp_for_iter * GTY((length ("%h.collapse"))) iter;
+@end smallexample
+In this case, @code{iter} has been allocated by writing something like
+@smallexample
+ x->iter = ggc_alloc_cleared_vec_gimple_omp_for_iter (collapse);
+@end smallexample
+and the @code{collapse} provides the length of the field.
+
+This second use of @code{length} also works on global variables, like:
+@verbatim
+static GTY((length("reg_known_value_size"))) rtx *reg_known_value;
+@end verbatim
+
+Note that the @code{length} option is only meant for use with arrays of
+non-atomic objects, that is, objects that contain pointers pointing to
+other GTY-managed objects. For other GC-allocated arrays and strings
+you should use @code{atomic} or @code{string_length}.
+
+@findex string_length
+@item string_length ("@var{expression}")
+
+In order to simplify production of PCH, a structure member that is a plain
+array of bytes (an optionally @code{const} and/or @code{unsigned} @code{char
+*}) is treated specially by the infrastructure. Even if such an array has not
+been allocated in GC-controlled memory, it will still be written properly into
+a PCH. The machinery responsible for this needs to know the length of the
+data; by default, the length is determined by calling @code{strlen} on the
+pointer. The @code{string_length} option specifies an alternate way to
+determine the length, such as by inspecting another struct member:
+
+@smallexample
+struct GTY(()) non_terminated_string @{
+ size_t sz;
+ const char * GTY((string_length ("%h.sz"))) data;
+@};
+@end smallexample
+
+@findex skip
+@item skip
+
+If @code{skip} is applied to a field, the type machinery will ignore it.
+This is somewhat dangerous; the only safe use is in a union when one
+field really isn't ever used.
+
+@findex callback
+@item callback
+
+@code{callback} should be applied to fields with pointer to function type
+and causes the field to be ignored similarly to @code{skip}, except when
+writing PCH and the field is non-NULL it will remember the field's address
+for relocation purposes if the process writing PCH has different load base
+from a process reading PCH.
+
+@findex for_user
+@item for_user
+
+Use this to mark types that need to be marked by user gc routines, but are not
+refered to in a template argument. So if you have some user gc type T1 and a
+non user gc type T2 you can give T2 the for_user option so that the marking
+functions for T1 can call non mangled functions to mark T2.
+
+@findex desc
+@findex tag
+@findex default
+@item desc ("@var{expression}")
+@itemx tag ("@var{constant}")
+@itemx default
+
+The type machinery needs to be told which field of a @code{union} is
+currently active. This is done by giving each field a constant
+@code{tag} value, and then specifying a discriminator using @code{desc}.
+The value of the expression given by @code{desc} is compared against
+each @code{tag} value, each of which should be different. If no
+@code{tag} is matched, the field marked with @code{default} is used if
+there is one, otherwise no field in the union will be marked.
+
+In the @code{desc} option, the ``current structure'' is the union that
+it discriminates. Use @code{%1} to mean the structure containing it.
+There are no escapes available to the @code{tag} option, since it is a
+constant.
+
+For example,
+@smallexample
+struct GTY(()) tree_binding
+@{
+ struct tree_common common;
+ union tree_binding_u @{
+ tree GTY ((tag ("0"))) scope;
+ struct cp_binding_level * GTY ((tag ("1"))) level;
+ @} GTY ((desc ("BINDING_HAS_LEVEL_P ((tree)&%0)"))) xscope;
+ tree value;
+@};
+@end smallexample
+
+In this example, the value of BINDING_HAS_LEVEL_P when applied to a
+@code{struct tree_binding *} is presumed to be 0 or 1. If 1, the type
+mechanism will treat the field @code{level} as being present and if 0,
+will treat the field @code{scope} as being present.
+
+The @code{desc} and @code{tag} options can also be used for inheritance
+to denote which subclass an instance is. See @ref{Inheritance and GTY}
+for more information.
+
+@findex cache
+@item cache
+
+When the @code{cache} option is applied to a global variable gt_cleare_cache is
+called on that variable between the mark and sweep phases of garbage
+collection. The gt_clear_cache function is free to mark blocks as used, or to
+clear pointers in the variable.
+
+@findex deletable
+@item deletable
+
+@code{deletable}, when applied to a global variable, indicates that when
+garbage collection runs, there's no need to mark anything pointed to
+by this variable, it can just be set to @code{NULL} instead. This is used
+to keep a list of free structures around for re-use.
+
+@findex maybe_undef
+@item maybe_undef
+
+When applied to a field, @code{maybe_undef} indicates that it's OK if
+the structure that this fields points to is never defined, so long as
+this field is always @code{NULL}. This is used to avoid requiring
+backends to define certain optional structures. It doesn't work with
+language frontends.
+
+@findex nested_ptr
+@item nested_ptr (@var{type}, "@var{to expression}", "@var{from expression}")
+
+The type machinery expects all pointers to point to the start of an
+object. Sometimes for abstraction purposes it's convenient to have
+a pointer which points inside an object. So long as it's possible to
+convert the original object to and from the pointer, such pointers
+can still be used. @var{type} is the type of the original object,
+the @var{to expression} returns the pointer given the original object,
+and the @var{from expression} returns the original object given
+the pointer. The pointer will be available using the @code{%h}
+escape.
+
+@findex chain_next
+@findex chain_prev
+@findex chain_circular
+@item chain_next ("@var{expression}")
+@itemx chain_prev ("@var{expression}")
+@itemx chain_circular ("@var{expression}")
+
+It's helpful for the type machinery to know if objects are often
+chained together in long lists; this lets it generate code that uses
+less stack space by iterating along the list instead of recursing down
+it. @code{chain_next} is an expression for the next item in the list,
+@code{chain_prev} is an expression for the previous item. For singly
+linked lists, use only @code{chain_next}; for doubly linked lists, use
+both. The machinery requires that taking the next item of the
+previous item gives the original item. @code{chain_circular} is similar
+to @code{chain_next}, but can be used for circular single linked lists.
+
+@findex reorder
+@item reorder ("@var{function name}")
+
+Some data structures depend on the relative ordering of pointers. If
+the precompiled header machinery needs to change that ordering, it
+will call the function referenced by the @code{reorder} option, before
+changing the pointers in the object that's pointed to by the field the
+option applies to. The function must take four arguments, with the
+signature @samp{@w{void *, void *, gt_pointer_operator, void *}}.
+The first parameter is a pointer to the structure that contains the
+object being updated, or the object itself if there is no containing
+structure. The second parameter is a cookie that should be ignored.
+The third parameter is a routine that, given a pointer, will update it
+to its correct new value. The fourth parameter is a cookie that must
+be passed to the second parameter.
+
+PCH cannot handle data structures that depend on the absolute values
+of pointers. @code{reorder} functions can be expensive. When
+possible, it is better to depend on properties of the data, like an ID
+number or the hash of a string instead.
+
+@findex atomic
+@item atomic
+
+The @code{atomic} option can only be used with pointers. It informs
+the GC machinery that the memory that the pointer points to does not
+contain any pointers, and hence it should be treated by the GC and PCH
+machinery as an ``atomic'' block of memory that does not need to be
+examined when scanning memory for pointers. In particular, the
+machinery will not scan that memory for pointers to mark them as
+reachable (when marking pointers for GC) or to relocate them (when
+writing a PCH file).
+
+The @code{atomic} option differs from the @code{skip} option.
+@code{atomic} keeps the memory under Garbage Collection, but makes the
+GC ignore the contents of the memory. @code{skip} is more drastic in
+that it causes the pointer and the memory to be completely ignored by
+the Garbage Collector. So, memory marked as @code{atomic} is
+automatically freed when no longer reachable, while memory marked as
+@code{skip} is not.
+
+The @code{atomic} option must be used with great care, because all
+sorts of problem can occur if used incorrectly, that is, if the memory
+the pointer points to does actually contain a pointer.
+
+Here is an example of how to use it:
+@smallexample
+struct GTY(()) my_struct @{
+ int number_of_elements;
+ unsigned int * GTY ((atomic)) elements;
+@};
+@end smallexample
+In this case, @code{elements} is a pointer under GC, and the memory it
+points to needs to be allocated using the Garbage Collector, and will
+be freed automatically by the Garbage Collector when it is no longer
+referenced. But the memory that the pointer points to is an array of
+@code{unsigned int} elements, and the GC must not try to scan it to
+find pointers to mark or relocate, which is why it is marked with the
+@code{atomic} option.
+
+Note that, currently, global variables cannot be marked with
+@code{atomic}; only fields of a struct can. This is a known
+limitation. It would be useful to be able to mark global pointers
+with @code{atomic} to make the PCH machinery aware of them so that
+they are saved and restored correctly to PCH files.
+
+@findex special
+@item special ("@var{name}")
+
+The @code{special} option is used to mark types that have to be dealt
+with by special case machinery. The parameter is the name of the
+special case. See @file{gengtype.cc} for further details. Avoid
+adding new special cases unless there is no other alternative.
+
+@findex user
+@item user
+
+The @code{user} option indicates that the code to mark structure
+fields is completely handled by user-provided routines. See section
+@ref{User GC} for details on what functions need to be provided.
+@end table
+
+@node Inheritance and GTY
+@section Support for inheritance
+gengtype has some support for simple class hierarchies. You can use
+this to have gengtype autogenerate marking routines, provided:
+
+@itemize @bullet
+@item
+There must be a concrete base class, with a discriminator expression
+that can be used to identify which subclass an instance is.
+@item
+Only single inheritance is used.
+@item
+None of the classes within the hierarchy are templates.
+@end itemize
+
+If your class hierarchy does not fit in this pattern, you must use
+@ref{User GC} instead.
+
+The base class and its discriminator must be identified using the ``desc''
+option. Each concrete subclass must use the ``tag'' option to identify
+which value of the discriminator it corresponds to.
+
+Every class in the hierarchy must have a @code{GTY(())} marker, as
+gengtype will only attempt to parse classes that have such a marker
+@footnote{Classes lacking such a marker will not be identified as being
+part of the hierarchy, and so the marking routines will not handle them,
+leading to a assertion failure within the marking routines due to an
+unknown tag value (assuming that assertions are enabled).}.
+
+@smallexample
+class GTY((desc("%h.kind"), tag("0"))) example_base
+@{
+public:
+ int kind;
+ tree a;
+@};
+
+class GTY((tag("1"))) some_subclass : public example_base
+@{
+public:
+ tree b;
+@};
+
+class GTY((tag("2"))) some_other_subclass : public example_base
+@{
+public:
+ tree c;
+@};
+@end smallexample
+
+The generated marking routines for the above will contain a ``switch''
+on ``kind'', visiting all appropriate fields. For example, if kind is
+2, it will cast to ``some_other_subclass'' and visit fields a, b, and c.
+
+@node User GC
+@section Support for user-provided GC marking routines
+@cindex user gc
+The garbage collector supports types for which no automatic marking
+code is generated. For these types, the user is required to provide
+three functions: one to act as a marker for garbage collection, and
+two functions to act as marker and pointer walker for pre-compiled
+headers.
+
+Given a structure @code{struct GTY((user)) my_struct}, the following functions
+should be defined to mark @code{my_struct}:
+
+@smallexample
+void gt_ggc_mx (my_struct *p)
+@{
+ /* This marks field 'fld'. */
+ gt_ggc_mx (p->fld);
+@}
+
+void gt_pch_nx (my_struct *p)
+@{
+ /* This marks field 'fld'. */
+ gt_pch_nx (tp->fld);
+@}
+
+void gt_pch_nx (my_struct *p, gt_pointer_operator op, void *cookie)
+@{
+ /* For every field 'fld', call the given pointer operator. */
+ op (&(tp->fld), NULL, cookie);
+@}
+@end smallexample
+
+In general, each marker @code{M} should call @code{M} for every
+pointer field in the structure. Fields that are not allocated in GC
+or are not pointers must be ignored.
+
+For embedded lists (e.g., structures with a @code{next} or @code{prev}
+pointer), the marker must follow the chain and mark every element in
+it.
+
+Note that the rules for the pointer walker @code{gt_pch_nx (my_struct
+*, gt_pointer_operator, void *)} are slightly different. In this
+case, the operation @code{op} must be applied to the @emph{address} of
+every pointer field.
+
+@subsection User-provided marking routines for template types
+When a template type @code{TP} is marked with @code{GTY}, all
+instances of that type are considered user-provided types. This means
+that the individual instances of @code{TP} do not need to be marked
+with @code{GTY}. The user needs to provide template functions to mark
+all the fields of the type.
+
+The following code snippets represent all the functions that need to
+be provided. Note that type @code{TP} may reference to more than one
+type. In these snippets, there is only one type @code{T}, but there
+could be more.
+
+@smallexample
+template<typename T>
+void gt_ggc_mx (TP<T> *tp)
+@{
+ extern void gt_ggc_mx (T&);
+
+ /* This marks field 'fld' of type 'T'. */
+ gt_ggc_mx (tp->fld);
+@}
+
+template<typename T>
+void gt_pch_nx (TP<T> *tp)
+@{
+ extern void gt_pch_nx (T&);
+
+ /* This marks field 'fld' of type 'T'. */
+ gt_pch_nx (tp->fld);
+@}
+
+template<typename T>
+void gt_pch_nx (TP<T *> *tp, gt_pointer_operator op, void *cookie)
+@{
+ /* For every field 'fld' of 'tp' with type 'T *', call the given
+ pointer operator. */
+ op (&(tp->fld), NULL, cookie);
+@}
+
+template<typename T>
+void gt_pch_nx (TP<T> *tp, gt_pointer_operator, void *cookie)
+@{
+ extern void gt_pch_nx (T *, gt_pointer_operator, void *);
+
+ /* For every field 'fld' of 'tp' with type 'T', call the pointer
+ walker for all the fields of T. */
+ gt_pch_nx (&(tp->fld), op, cookie);
+@}
+@end smallexample
+
+Support for user-defined types is currently limited. The following
+restrictions apply:
+
+@enumerate
+@item Type @code{TP} and all the argument types @code{T} must be
+marked with @code{GTY}.
+
+@item Type @code{TP} can only have type names in its argument list.
+
+@item The pointer walker functions are different for @code{TP<T>} and
+@code{TP<T *>}. In the case of @code{TP<T>}, references to
+@code{T} must be handled by calling @code{gt_pch_nx} (which
+will, in turn, walk all the pointers inside fields of @code{T}).
+In the case of @code{TP<T *>}, references to @code{T *} must be
+handled by calling the @code{op} function on the address of the
+pointer (see the code snippets above).
+@end enumerate
+
+@node GGC Roots
+@section Marking Roots for the Garbage Collector
+@cindex roots, marking
+@cindex marking roots
+
+In addition to keeping track of types, the type machinery also locates
+the global variables (@dfn{roots}) that the garbage collector starts
+at. Roots must be declared using one of the following syntaxes:
+
+@itemize @bullet
+@item
+@code{extern GTY(([@var{options}])) @var{type} @var{name};}
+@item
+@code{static GTY(([@var{options}])) @var{type} @var{name};}
+@end itemize
+@noindent
+The syntax
+@itemize @bullet
+@item
+@code{GTY(([@var{options}])) @var{type} @var{name};}
+@end itemize
+@noindent
+is @emph{not} accepted. There should be an @code{extern} declaration
+of such a variable in a header somewhere---mark that, not the
+definition. Or, if the variable is only used in one file, make it
+@code{static}.
+
+@node Files
+@section Source Files Containing Type Information
+@cindex generated files
+@cindex files, generated
+
+Whenever you add @code{GTY} markers to a source file that previously
+had none, or create a new source file containing @code{GTY} markers,
+there are three things you need to do:
+
+@enumerate
+@item
+You need to add the file to the list of source files the type
+machinery scans. There are four cases:
+
+@enumerate a
+@item
+For a back-end file, this is usually done
+automatically; if not, you should add it to @code{target_gtfiles} in
+the appropriate port's entries in @file{config.gcc}.
+
+@item
+For files shared by all front ends, add the filename to the
+@code{GTFILES} variable in @file{Makefile.in}.
+
+@item
+For files that are part of one front end, add the filename to the
+@code{gtfiles} variable defined in the appropriate
+@file{config-lang.in}.
+Headers should appear before non-headers in this list.
+
+@item
+For files that are part of some but not all front ends, add the
+filename to the @code{gtfiles} variable of @emph{all} the front ends
+that use it.
+@end enumerate
+
+@item
+If the file was a header file, you'll need to check that it's included
+in the right place to be visible to the generated files. For a back-end
+header file, this should be done automatically. For a front-end header
+file, it needs to be included by the same file that includes
+@file{gtype-@var{lang}.h}. For other header files, it needs to be
+included in @file{gtype-desc.cc}, which is a generated file, so add it to
+@code{ifiles} in @code{open_base_file} in @file{gengtype.cc}.
+
+For source files that aren't header files, the machinery will generate a
+header file that should be included in the source file you just changed.
+The file will be called @file{gt-@var{path}.h} where @var{path} is the
+pathname relative to the @file{gcc} directory with slashes replaced by
+@verb{|-|}, so for example the header file to be included in
+@file{cp/parser.cc} is called @file{gt-cp-parser.h}. The
+generated header file should be included after everything else in the
+source file.
+
+@end enumerate
+
+For language frontends, there is another file that needs to be included
+somewhere. It will be called @file{gtype-@var{lang}.h}, where
+@var{lang} is the name of the subdirectory the language is contained in.
+
+Plugins can add additional root tables. Run the @code{gengtype}
+utility in plugin mode as @code{gengtype -P pluginout.h @var{source-dir}
+@var{file-list} @var{plugin*.c}} with your plugin files
+@var{plugin*.c} using @code{GTY} to generate the @var{pluginout.h} file.
+The GCC build tree is needed to be present in that mode.
+
+
+@node Invoking the garbage collector
+@section How to invoke the garbage collector
+@cindex garbage collector, invocation
+@findex ggc_collect
+
+The GCC garbage collector GGC is only invoked explicitly. In contrast
+with many other garbage collectors, it is not implicitly invoked by
+allocation routines when a lot of memory has been consumed. So the
+only way to have GGC reclaim storage is to call the @code{ggc_collect}
+function explicitly.
+With @var{mode} @code{GGC_COLLECT_FORCE} or otherwise (default
+@code{GGC_COLLECT_HEURISTIC}) when the internal heuristic decides to
+collect, this call is potentially an expensive operation, as it may
+have to scan the entire heap. Beware that local variables (on the GCC
+call stack) are not followed by such an invocation (as many other
+garbage collectors do): you should reference all your data from static
+or external @code{GTY}-ed variables, and it is advised to call
+@code{ggc_collect} with a shallow call stack. The GGC is an exact mark
+and sweep garbage collector (so it does not scan the call stack for
+pointers). In practice GCC passes don't often call @code{ggc_collect}
+themselves, because it is called by the pass manager between passes.
+
+At the time of the @code{ggc_collect} call all pointers in the GC-marked
+structures must be valid or @code{NULL}. In practice this means that
+there should not be uninitialized pointer fields in the structures even
+if your code never reads or writes those fields at a particular
+instance. One way to ensure this is to use cleared versions of
+allocators unless all the fields are initialized manually immediately
+after allocation.
+
+@node Troubleshooting
+@section Troubleshooting the garbage collector
+@cindex garbage collector, troubleshooting
+
+With the current garbage collector implementation, most issues should
+show up as GCC compilation errors. Some of the most commonly
+encountered issues are described below.
+
+@itemize @bullet
+@item Gengtype does not produce allocators for a @code{GTY}-marked type.
+Gengtype checks if there is at least one possible path from GC roots to
+at least one instance of each type before outputting allocators. If
+there is no such path, the @code{GTY} markers will be ignored and no
+allocators will be output. Solve this by making sure that there exists
+at least one such path. If creating it is unfeasible or raises a ``code
+smell'', consider if you really must use GC for allocating such type.
+
+@item Link-time errors about undefined @code{gt_ggc_r_foo_bar} and
+similarly-named symbols. Check if your @file{foo_bar} source file has
+@code{#include "gt-foo_bar.h"} as its very last line.
+
+@end itemize
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Header Dirs
+@chapter Standard Header File Directories
+
+@code{GCC_INCLUDE_DIR} means the same thing for native and cross. It is
+where GCC stores its private include files, and also where GCC
+stores the fixed include files. A cross compiled GCC runs
+@code{fixincludes} on the header files in @file{$(tooldir)/include}.
+(If the cross compilation header files need to be fixed, they must be
+installed before GCC is built. If the cross compilation header files
+are already suitable for GCC, nothing special need be done).
+
+@code{GPLUSPLUS_INCLUDE_DIR} means the same thing for native and cross. It
+is where @command{g++} looks first for header files. The C++ library
+installs only target independent header files in that directory.
+
+@code{LOCAL_INCLUDE_DIR} is used only by native compilers. GCC
+doesn't install anything there. It is normally
+@file{/usr/local/include}. This is where local additions to a packaged
+system should place header files.
+
+@code{CROSS_INCLUDE_DIR} is used only by cross compilers. GCC
+doesn't install anything there.
+
+@code{TOOL_INCLUDE_DIR} is used for both native and cross compilers. It
+is the place for other packages to install header files that GCC will
+use. For a cross-compiler, this is the equivalent of
+@file{/usr/include}. When you build a cross-compiler,
+@code{fixincludes} processes any header files in this directory.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gccint.texi.
+
+@node Host Config
+@chapter Host Configuration
+@cindex host configuration
+
+Most details about the machine and system on which the compiler is
+actually running are detected by the @command{configure} script. Some
+things are impossible for @command{configure} to detect; these are
+described in two ways, either by macros defined in a file named
+@file{xm-@var{machine}.h} or by hook functions in the file specified
+by the @var{out_host_hook_obj} variable in @file{config.gcc}. (The
+intention is that very few hosts will need a header file but nearly
+every fully supported host will need to override some hooks.)
+
+If you need to define only a few macros, and they have simple
+definitions, consider using the @code{xm_defines} variable in your
+@file{config.gcc} entry instead of creating a host configuration
+header. @xref{System Config}.
+
+@menu
+* Host Common:: Things every host probably needs implemented.
+* Filesystem:: Your host cannot have the letter `a' in filenames?
+* Host Misc:: Rare configuration options for hosts.
+@end menu
+
+@node Host Common
+@section Host Common
+@cindex host hooks
+@cindex host functions
+
+Some things are just not portable, even between similar operating systems,
+and are too difficult for autoconf to detect. They get implemented using
+hook functions in the file specified by the @var{host_hook_obj}
+variable in @file{config.gcc}.
+
+@deftypefn {Host Hook} void HOST_HOOKS_EXTRA_SIGNALS (void)
+This host hook is used to set up handling for extra signals. The most
+common thing to do in this hook is to detect stack overflow.
+@end deftypefn
+
+@deftypefn {Host Hook} {void *} HOST_HOOKS_GT_PCH_GET_ADDRESS (size_t @
+ @var{size}, int @var{fd})
+This host hook returns the address of some space that is likely to be
+free in some subsequent invocation of the compiler. We intend to load
+the PCH data at this address such that the data need not be relocated.
+The area should be able to hold @var{size} bytes. If the host uses
+@code{mmap}, @var{fd} is an open file descriptor that can be used for
+probing.
+@end deftypefn
+
+@deftypefn {Host Hook} int HOST_HOOKS_GT_PCH_USE_ADDRESS (void * @var{address}, @
+ size_t @var{size}, int @var{fd}, size_t @var{offset})
+This host hook is called when a PCH file is about to be loaded.
+We want to load @var{size} bytes from @var{fd} at @var{offset}
+into memory at @var{address}. The given address will be the result of
+a previous invocation of @code{HOST_HOOKS_GT_PCH_GET_ADDRESS}.
+Return @minus{}1 if we couldn't allocate @var{size} bytes at @var{address}.
+Return 0 if the memory is allocated but the data is not loaded. Return 1
+if the hook has performed everything.
+
+If the implementation uses reserved address space, free any reserved
+space beyond @var{size}, regardless of the return value. If no PCH will
+be loaded, this hook may be called with @var{size} zero, in which case
+all reserved address space should be freed.
+
+Do not try to handle values of @var{address} that could not have been
+returned by this executable; just return @minus{}1. Such values usually
+indicate an out-of-date PCH file (built by some other GCC executable),
+and such a PCH file won't work.
+@end deftypefn
+
+@deftypefn {Host Hook} size_t HOST_HOOKS_GT_PCH_ALLOC_GRANULARITY (void);
+This host hook returns the alignment required for allocating virtual
+memory. Usually this is the same as getpagesize, but on some hosts the
+alignment for reserving memory differs from the pagesize for committing
+memory.
+@end deftypefn
+
+@node Filesystem
+@section Host Filesystem
+@cindex configuration file
+@cindex @file{xm-@var{machine}.h}
+
+GCC needs to know a number of things about the semantics of the host
+machine's filesystem. Filesystems with Unix and MS-DOS semantics are
+automatically detected. For other systems, you can define the
+following macros in @file{xm-@var{machine}.h}.
+
+@ftable @code
+@item HAVE_DOS_BASED_FILE_SYSTEM
+This macro is automatically defined by @file{system.h} if the host
+file system obeys the semantics defined by MS-DOS instead of Unix.
+DOS file systems are case insensitive, file specifications may begin
+with a drive letter, and both forward slash and backslash (@samp{/}
+and @samp{\}) are directory separators.
+
+@item DIR_SEPARATOR
+@itemx DIR_SEPARATOR_2
+If defined, these macros expand to character constants specifying
+separators for directory names within a file specification.
+@file{system.h} will automatically give them appropriate values on
+Unix and MS-DOS file systems. If your file system is neither of
+these, define one or both appropriately in @file{xm-@var{machine}.h}.
+
+However, operating systems like VMS, where constructing a pathname is
+more complicated than just stringing together directory names
+separated by a special character, should not define either of these
+macros.
+
+@item PATH_SEPARATOR
+If defined, this macro should expand to a character constant
+specifying the separator for elements of search paths. The default
+value is a colon (@samp{:}). DOS-based systems usually, but not
+always, use semicolon (@samp{;}).
+
+@item VMS
+Define this macro if the host system is VMS@.
+
+@item HOST_OBJECT_SUFFIX
+Define this macro to be a C string representing the suffix for object
+files on your host machine. If you do not define this macro, GCC will
+use @samp{.o} as the suffix for object files.
+
+@item HOST_EXECUTABLE_SUFFIX
+Define this macro to be a C string representing the suffix for
+executable files on your host machine. If you do not define this macro,
+GCC will use the null string as the suffix for executable files.
+
+@item HOST_BIT_BUCKET
+A pathname defined by the host operating system, which can be opened as
+a file and written to, but all the information written is discarded.
+This is commonly known as a @dfn{bit bucket} or @dfn{null device}. If
+you do not define this macro, GCC will use @samp{/dev/null} as the bit
+bucket. If the host does not support a bit bucket, define this macro to
+an invalid filename.
+
+@item UPDATE_PATH_HOST_CANONICALIZE (@var{path})
+If defined, a C statement (sans semicolon) that performs host-dependent
+canonicalization when a path used in a compilation driver or
+preprocessor is canonicalized. @var{path} is a malloc-ed path to be
+canonicalized. If the C statement does canonicalize @var{path} into a
+different buffer, the old path should be freed and the new buffer should
+have been allocated with malloc.
+
+@item DUMPFILE_FORMAT
+Define this macro to be a C string representing the format to use for
+constructing the index part of debugging dump file names. The resultant
+string must fit in fifteen bytes. The full filename will be the
+concatenation of: the prefix of the assembler file name, the string
+resulting from applying this format to an index number, and a string
+unique to each dump file kind, e.g.@: @samp{rtl}.
+
+If you do not define this macro, GCC will use @samp{.%02d.}. You should
+define this macro if using the default will create an invalid file name.
+
+@item DELETE_IF_ORDINARY
+Define this macro to be a C statement (sans semicolon) that performs
+host-dependent removal of ordinary temp files in the compilation driver.
+
+If you do not define this macro, GCC will use the default version. You
+should define this macro if the default version does not reliably remove
+the temp file as, for example, on VMS which allows multiple versions
+of a file.
+
+@item HOST_LACKS_INODE_NUMBERS
+Define this macro if the host filesystem does not report meaningful inode
+numbers in struct stat.
+@end ftable
+
+@node Host Misc
+@section Host Misc
+@cindex configuration file
+@cindex @file{xm-@var{machine}.h}
+
+@ftable @code
+@item FATAL_EXIT_CODE
+A C expression for the status code to be returned when the compiler
+exits after serious errors. The default is the system-provided macro
+@samp{EXIT_FAILURE}, or @samp{1} if the system doesn't define that
+macro. Define this macro only if these defaults are incorrect.
+
+@item SUCCESS_EXIT_CODE
+A C expression for the status code to be returned when the compiler
+exits without serious errors. (Warnings are not serious errors.) The
+default is the system-provided macro @samp{EXIT_SUCCESS}, or @samp{0} if
+the system doesn't define that macro. Define this macro only if these
+defaults are incorrect.
+
+@item USE_C_ALLOCA
+Define this macro if GCC should use the C implementation of @code{alloca}
+provided by @file{libiberty.a}. This only affects how some parts of the
+compiler itself allocate memory. It does not change code generation.
+
+When GCC is built with a compiler other than itself, the C @code{alloca}
+is always used. This is because most other implementations have serious
+bugs. You should define this macro only on a system where no
+stack-based @code{alloca} can possibly work. For instance, if a system
+has a small limit on the size of the stack, GCC's builtin @code{alloca}
+will not work reliably.
+
+@item COLLECT2_HOST_INITIALIZATION
+If defined, a C statement (sans semicolon) that performs host-dependent
+initialization when @code{collect2} is being initialized.
+
+@item GCC_DRIVER_HOST_INITIALIZATION
+If defined, a C statement (sans semicolon) that performs host-dependent
+initialization when a compilation driver is being initialized.
+
+@item HOST_LONG_LONG_FORMAT
+If defined, the string used to indicate an argument of type @code{long
+long} to functions like @code{printf}. The default value is
+@code{"ll"}.
+
+@item HOST_LONG_FORMAT
+If defined, the string used to indicate an argument of type @code{long}
+to functions like @code{printf}. The default value is @code{"l"}.
+
+@item HOST_PTR_PRINTF
+If defined, the string used to indicate an argument of type @code{void *}
+to functions like @code{printf}. The default value is @code{"%p"}.
+@end ftable
+
+In addition, if @command{configure} generates an incorrect definition of
+any of the macros in @file{auto-host.h}, you can override that
+definition in a host configuration header. If you need to do this,
+first see if it is possible to fix @command{configure}.
--- /dev/null
+@c Copyright (C) 2001-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node C Implementation
+@chapter C Implementation-Defined Behavior
+@cindex implementation-defined behavior, C language
+
+A conforming implementation of ISO C is required to document its
+choice of behavior in each of the areas that are designated
+``implementation defined''. The following lists all such areas,
+along with the section numbers from the ISO/IEC 9899:1990, ISO/IEC
+9899:1999 and ISO/IEC 9899:2011 standards. Some areas are only
+implementation-defined in one version of the standard.
+
+Some choices depend on the externally determined ABI for the platform
+(including standard character encodings) which GCC follows; these are
+listed as ``determined by ABI'' below. @xref{Compatibility, , Binary
+Compatibility}, and @uref{https://gcc.gnu.org/readings.html}. Some
+choices are documented in the preprocessor manual.
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}. Some choices are made by the
+library and operating system (or other environment when compiling for
+a freestanding environment); refer to their documentation for details.
+
+@menu
+* Translation implementation::
+* Environment implementation::
+* Identifiers implementation::
+* Characters implementation::
+* Integers implementation::
+* Floating point implementation::
+* Arrays and pointers implementation::
+* Hints implementation::
+* Structures unions enumerations and bit-fields implementation::
+* Qualifiers implementation::
+* Declarators implementation::
+* Statements implementation::
+* Preprocessing directives implementation::
+* Library functions implementation::
+* Architecture implementation::
+* Locale-specific behavior implementation::
+@end menu
+
+@node Translation implementation
+@section Translation
+
+@itemize @bullet
+@item
+@cite{How a diagnostic is identified (C90 3.7, C99 and C11 3.10, C90,
+C99 and C11 5.1.1.3).}
+
+Diagnostics consist of all the output sent to stderr by GCC@.
+
+@item
+@cite{Whether each nonempty sequence of white-space characters other than
+new-line is retained or replaced by one space character in translation
+phase 3 (C90, C99 and C11 5.1.1.2).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.
+
+@end itemize
+
+@node Environment implementation
+@section Environment
+
+The behavior of most of these points are dependent on the implementation
+of the C library, and are not defined by GCC itself.
+
+@itemize @bullet
+@item
+@cite{The mapping between physical source file multibyte characters
+and the source character set in translation phase 1 (C90, C99 and C11
+5.1.1.2).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.
+
+@end itemize
+
+@node Identifiers implementation
+@section Identifiers
+
+@itemize @bullet
+@item
+@cite{Which additional multibyte characters may appear in identifiers
+and their correspondence to universal character names (C99 and C11 6.4.2).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.
+
+@item
+@cite{The number of significant initial characters in an identifier
+(C90 6.1.2, C90, C99 and C11 5.2.4.1, C99 and C11 6.4.2).}
+
+For internal names, all characters are significant. For external names,
+the number of significant characters are defined by the linker; for
+almost all targets, all characters are significant.
+
+@item
+@cite{Whether case distinctions are significant in an identifier with
+external linkage (C90 6.1.2).}
+
+This is a property of the linker. C99 and C11 require that case distinctions
+are always significant in identifiers with external linkage and
+systems without this property are not supported by GCC@.
+
+@end itemize
+
+@node Characters implementation
+@section Characters
+
+@itemize @bullet
+@item
+@cite{The number of bits in a byte (C90 3.4, C99 and C11 3.6).}
+
+Determined by ABI@.
+
+@item
+@cite{The values of the members of the execution character set (C90,
+C99 and C11 5.2.1).}
+
+Determined by ABI@.
+
+@item
+@cite{The unique value of the member of the execution character set produced
+for each of the standard alphabetic escape sequences (C90, C99 and C11
+5.2.2).}
+
+Determined by ABI@.
+
+@item
+@cite{The value of a @code{char} object into which has been stored any
+character other than a member of the basic execution character set
+(C90 6.1.2.5, C99 and C11 6.2.5).}
+
+Determined by ABI@.
+
+@item
+@cite{Which of @code{signed char} or @code{unsigned char} has the same
+range, representation, and behavior as ``plain'' @code{char} (C90
+6.1.2.5, C90 6.2.1.1, C99 and C11 6.2.5, C99 and C11 6.3.1.1).}
+
+@opindex fsigned-char
+@opindex funsigned-char
+Determined by ABI@. The options @option{-funsigned-char} and
+@option{-fsigned-char} change the default. @xref{C Dialect Options, ,
+Options Controlling C Dialect}.
+
+@item
+@cite{The mapping of members of the source character set (in character
+constants and string literals) to members of the execution character
+set (C90 6.1.3.4, C99 and C11 6.4.4.4, C90, C99 and C11 5.1.1.2).}
+
+Determined by ABI@.
+
+@item
+@cite{The value of an integer character constant containing more than one
+character or containing a character or escape sequence that does not map
+to a single-byte execution character (C90 6.1.3.4, C99 and C11 6.4.4.4).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.
+
+@item
+@cite{The value of a wide character constant containing more than one
+multibyte character or a single multibyte character that maps to
+multiple members of the extended execution character set, or
+containing a multibyte character or escape sequence not represented in
+the extended execution character set (C90 6.1.3.4, C99 and C11
+6.4.4.4).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.
+
+@item
+@cite{The current locale used to convert a wide character constant consisting
+of a single multibyte character that maps to a member of the extended
+execution character set into a corresponding wide character code (C90
+6.1.3.4, C99 and C11 6.4.4.4).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.
+
+@item
+@cite{Whether differently-prefixed wide string literal tokens can be
+concatenated and, if so, the treatment of the resulting multibyte
+character sequence (C11 6.4.5).}
+
+Such tokens may not be concatenated.
+
+@item
+@cite{The current locale used to convert a wide string literal into
+corresponding wide character codes (C90 6.1.4, C99 and C11 6.4.5).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.
+
+@item
+@cite{The value of a string literal containing a multibyte character or escape
+sequence not represented in the execution character set (C90 6.1.4,
+C99 and C11 6.4.5).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}.
+
+@item
+@cite{The encoding of any of @code{wchar_t}, @code{char16_t}, and
+@code{char32_t} where the corresponding standard encoding macro
+(@code{__STDC_ISO_10646__}, @code{__STDC_UTF_16__}, or
+@code{__STDC_UTF_32__}) is not defined (C11 6.10.8.2).}
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}. @code{char16_t} and
+@code{char32_t} literals are always encoded in UTF-16 and UTF-32
+respectively.
+
+@end itemize
+
+@node Integers implementation
+@section Integers
+
+@itemize @bullet
+@item
+@cite{Any extended integer types that exist in the implementation (C99
+and C11 6.2.5).}
+
+GCC does not support any extended integer types.
+@c The __mode__ attribute might create types of precisions not
+@c otherwise supported, but the syntax isn't right for use everywhere
+@c the standard type names might be used. Predefined typedefs should
+@c be used if any extended integer types are to be defined. The
+@c __int128_t and __uint128_t typedefs are not extended integer types
+@c as they are generally longer than the ABI-specified intmax_t.
+
+@item
+@cite{Whether signed integer types are represented using sign and magnitude,
+two's complement, or one's complement, and whether the extraordinary value
+is a trap representation or an ordinary value (C99 and C11 6.2.6.2).}
+
+GCC supports only two's complement integer types, and all bit patterns
+are ordinary values.
+
+@item
+@cite{The rank of any extended integer type relative to another extended
+integer type with the same precision (C99 and C11 6.3.1.1).}
+
+GCC does not support any extended integer types.
+@c If it did, there would only be one of each precision and signedness.
+
+@item
+@cite{The result of, or the signal raised by, converting an integer to a
+signed integer type when the value cannot be represented in an object of
+that type (C90 6.2.1.2, C99 and C11 6.3.1.3).}
+
+For conversion to a type of width @math{N}, the value is reduced
+modulo @math{2^N} to be within range of the type; no signal is raised.
+
+@item
+@cite{The results of some bitwise operations on signed integers (C90
+6.3, C99 and C11 6.5).}
+
+Bitwise operators act on the representation of the value including
+both the sign and value bits, where the sign bit is considered
+immediately above the highest-value value bit. Signed @samp{>>} acts
+on negative numbers by sign extension.
+
+As an extension to the C language, GCC does not use the latitude given in
+C99 and C11 only to treat certain aspects of signed @samp{<<} as undefined.
+However, @option{-fsanitize=shift} (and @option{-fsanitize=undefined}) will
+diagnose such cases. They are also diagnosed where constant
+expressions are required.
+
+@item
+@cite{The sign of the remainder on integer division (C90 6.3.5).}
+
+GCC always follows the C99 and C11 requirement that the result of division is
+truncated towards zero.
+
+@end itemize
+
+@node Floating point implementation
+@section Floating Point
+
+@itemize @bullet
+@item
+@cite{The accuracy of the floating-point operations and of the library
+functions in @code{<math.h>} and @code{<complex.h>} that return floating-point
+results (C90, C99 and C11 5.2.4.2.2).}
+
+The accuracy is unknown.
+
+@item
+@cite{The rounding behaviors characterized by non-standard values
+of @code{FLT_ROUNDS} @gol
+(C90, C99 and C11 5.2.4.2.2).}
+
+GCC does not use such values.
+
+@item
+@cite{The evaluation methods characterized by non-standard negative
+values of @code{FLT_EVAL_METHOD} (C99 and C11 5.2.4.2.2).}
+
+GCC does not use such values.
+
+@item
+@cite{The direction of rounding when an integer is converted to a
+floating-point number that cannot exactly represent the original
+value (C90 6.2.1.3, C99 and C11 6.3.1.4).}
+
+C99 Annex F is followed.
+
+@item
+@cite{The direction of rounding when a floating-point number is
+converted to a narrower floating-point number (C90 6.2.1.4, C99 and C11
+6.3.1.5).}
+
+C99 Annex F is followed.
+
+@item
+@cite{How the nearest representable value or the larger or smaller
+representable value immediately adjacent to the nearest representable
+value is chosen for certain floating constants (C90 6.1.3.1, C99 and C11
+6.4.4.2).}
+
+C99 Annex F is followed.
+
+@item
+@cite{Whether and how floating expressions are contracted when not
+disallowed by the @code{FP_CONTRACT} pragma (C99 and C11 6.5).}
+
+Expressions are currently only contracted if @option{-ffp-contract=fast},
+@option{-funsafe-math-optimizations} or @option{-ffast-math} are used.
+This is subject to change.
+
+@item
+@cite{The default state for the @code{FENV_ACCESS} pragma (C99 and C11
+7.6.1).}
+
+This pragma is not implemented, but the default is to ``off'' unless
+@option{-frounding-math} is used and @option{-fno-trapping-math} is not
+in which case it is ``on''.
+
+@item
+@cite{Additional floating-point exceptions, rounding modes, environments,
+and classifications, and their macro names (C99 and C11 7.6, C99 and
+C11 7.12).}
+
+This is dependent on the implementation of the C library, and is not
+defined by GCC itself.
+
+@item
+@cite{The default state for the @code{FP_CONTRACT} pragma (C99 and C11
+7.12.2).}
+
+This pragma is not implemented. Expressions are currently only
+contracted if @option{-ffp-contract=fast},
+@option{-funsafe-math-optimizations} or @option{-ffast-math} are used.
+This is subject to change.
+
+@item
+@cite{Whether the ``inexact'' floating-point exception can be raised
+when the rounded result actually does equal the mathematical result
+in an IEC 60559 conformant implementation (C99 F.9).}
+
+This is dependent on the implementation of the C library, and is not
+defined by GCC itself.
+
+@item
+@cite{Whether the ``underflow'' (and ``inexact'') floating-point
+exception can be raised when a result is tiny but not inexact in an
+IEC 60559 conformant implementation (C99 F.9).}
+
+This is dependent on the implementation of the C library, and is not
+defined by GCC itself.
+
+@end itemize
+
+@node Arrays and pointers implementation
+@section Arrays and Pointers
+
+@itemize @bullet
+@item
+@cite{The result of converting a pointer to an integer or
+vice versa (C90 6.3.4, C99 and C11 6.3.2.3).}
+
+A cast from pointer to integer discards most-significant bits if the
+pointer representation is larger than the integer type,
+sign-extends@footnote{Future versions of GCC may zero-extend, or use
+a target-defined @code{ptr_extend} pattern. Do not rely on sign extension.}
+if the pointer representation is smaller than the integer type, otherwise
+the bits are unchanged.
+@c ??? We've always claimed that pointers were unsigned entities.
+@c Shouldn't we therefore be doing zero-extension? If so, the bug
+@c is in convert_to_integer, where we call type_for_size and request
+@c a signed integral type. On the other hand, it might be most useful
+@c for the target if we extend according to POINTERS_EXTEND_UNSIGNED.
+
+A cast from integer to pointer discards most-significant bits if the
+pointer representation is smaller than the integer type, extends according
+to the signedness of the integer type if the pointer representation
+is larger than the integer type, otherwise the bits are unchanged.
+
+When casting from pointer to integer and back again, the resulting
+pointer must reference the same object as the original pointer, otherwise
+the behavior is undefined. That is, one may not use integer arithmetic to
+avoid the undefined behavior of pointer arithmetic as proscribed in
+C99 and C11 6.5.6/8.
+
+@item
+@cite{The size of the result of subtracting two pointers to elements
+of the same array (C90 6.3.6, C99 and C11 6.5.6).}
+
+The value is as specified in the standard and the type is determined
+by the ABI@.
+
+@end itemize
+
+@node Hints implementation
+@section Hints
+
+@itemize @bullet
+@item
+@cite{The extent to which suggestions made by using the @code{register}
+storage-class specifier are effective (C90 6.5.1, C99 and C11 6.7.1).}
+
+The @code{register} specifier affects code generation only in these ways:
+
+@itemize @bullet
+@item
+When used as part of the register variable extension, see
+@ref{Explicit Register Variables}.
+
+@item
+When @option{-O0} is in use, the compiler allocates distinct stack
+memory for all variables that do not have the @code{register}
+storage-class specifier; if @code{register} is specified, the variable
+may have a shorter lifespan than the code would indicate and may never
+be placed in memory.
+
+@item
+On some rare x86 targets, @code{setjmp} doesn't save the registers in
+all circumstances. In those cases, GCC doesn't allocate any variables
+in registers unless they are marked @code{register}.
+
+@end itemize
+
+@item
+@cite{The extent to which suggestions made by using the inline function
+specifier are effective (C99 and C11 6.7.4).}
+
+GCC will not inline any functions if the @option{-fno-inline} option is
+used or if @option{-O0} is used. Otherwise, GCC may still be unable to
+inline a function for many reasons; the @option{-Winline} option may be
+used to determine if a function has not been inlined and why not.
+
+@end itemize
+
+@node Structures unions enumerations and bit-fields implementation
+@section Structures, Unions, Enumerations, and Bit-Fields
+
+@itemize @bullet
+@item
+@cite{A member of a union object is accessed using a member of a
+different type (C90 6.3.2.3).}
+
+The relevant bytes of the representation of the object are treated as
+an object of the type used for the access. @xref{Type-punning}. This
+may be a trap representation.
+
+@item
+@cite{Whether a ``plain'' @code{int} bit-field is treated as a
+@code{signed int} bit-field or as an @code{unsigned int} bit-field
+(C90 6.5.2, C90 6.5.2.1, C99 and C11 6.7.2, C99 and C11 6.7.2.1).}
+
+@opindex funsigned-bitfields
+By default it is treated as @code{signed int} but this may be changed
+by the @option{-funsigned-bitfields} option.
+
+@item
+@cite{Allowable bit-field types other than @code{_Bool}, @code{signed int},
+and @code{unsigned int} (C99 and C11 6.7.2.1).}
+
+Other integer types, such as @code{long int}, and enumerated types are
+permitted even in strictly conforming mode.
+
+@item
+@cite{Whether atomic types are permitted for bit-fields (C11 6.7.2.1).}
+
+Atomic types are not permitted for bit-fields.
+
+@item
+@cite{Whether a bit-field can straddle a storage-unit boundary (C90
+6.5.2.1, C99 and C11 6.7.2.1).}
+
+Determined by ABI@.
+
+@item
+@cite{The order of allocation of bit-fields within a unit (C90
+6.5.2.1, C99 and C11 6.7.2.1).}
+
+Determined by ABI@.
+
+@item
+@cite{The alignment of non-bit-field members of structures (C90
+6.5.2.1, C99 and C11 6.7.2.1).}
+
+Determined by ABI@.
+
+@item
+@cite{The integer type compatible with each enumerated type (C90
+6.5.2.2, C99 and C11 6.7.2.2).}
+
+@opindex fshort-enums
+Normally, the type is @code{unsigned int} if there are no negative
+values in the enumeration, otherwise @code{int}. If
+@option{-fshort-enums} is specified, then if there are negative values
+it is the first of @code{signed char}, @code{short} and @code{int}
+that can represent all the values, otherwise it is the first of
+@code{unsigned char}, @code{unsigned short} and @code{unsigned int}
+that can represent all the values.
+@c On a few unusual targets with 64-bit int, this doesn't agree with
+@c the code and one of the types accessed via mode attributes (which
+@c are not currently considered extended integer types) may be used.
+@c If these types are made extended integer types, it would still be
+@c the case that -fshort-enums stops the implementation from
+@c conforming to C90 on those targets.
+
+On some targets, @option{-fshort-enums} is the default; this is
+determined by the ABI@.
+
+@end itemize
+
+@node Qualifiers implementation
+@section Qualifiers
+
+@itemize @bullet
+@item
+@cite{What constitutes an access to an object that has volatile-qualified
+type (C90 6.5.3, C99 and C11 6.7.3).}
+
+Such an object is normally accessed by pointers and used for accessing
+hardware. In most expressions, it is intuitively obvious what is a read
+and what is a write. For example
+
+@smallexample
+volatile int *dst = @var{somevalue};
+volatile int *src = @var{someothervalue};
+*dst = *src;
+@end smallexample
+
+@noindent
+will cause a read of the volatile object pointed to by @var{src} and store the
+value into the volatile object pointed to by @var{dst}. There is no
+guarantee that these reads and writes are atomic, especially for objects
+larger than @code{int}.
+
+However, if the volatile storage is not being modified, and the value of
+the volatile storage is not used, then the situation is less obvious.
+For example
+
+@smallexample
+volatile int *src = @var{somevalue};
+*src;
+@end smallexample
+
+According to the C standard, such an expression is an rvalue whose type
+is the unqualified version of its original type, i.e.@: @code{int}. Whether
+GCC interprets this as a read of the volatile object being pointed to or
+only as a request to evaluate the expression for its side effects depends
+on this type.
+
+If it is a scalar type, or on most targets an aggregate type whose only
+member object is of a scalar type, or a union type whose member objects
+are of scalar types, the expression is interpreted by GCC as a read of
+the volatile object; in the other cases, the expression is only evaluated
+for its side effects.
+
+When an object of an aggregate type, with the same size and alignment as a
+scalar type @code{S}, is the subject of a volatile access by an assignment
+expression or an atomic function, the access to it is performed as if the
+object's declared type were @code{volatile S}.
+
+@end itemize
+
+@node Declarators implementation
+@section Declarators
+
+@itemize @bullet
+@item
+@cite{The maximum number of declarators that may modify an arithmetic,
+structure or union type (C90 6.5.4).}
+
+GCC is only limited by available memory.
+
+@end itemize
+
+@node Statements implementation
+@section Statements
+
+@itemize @bullet
+@item
+@cite{The maximum number of @code{case} values in a @code{switch}
+statement (C90 6.6.4.2).}
+
+GCC is only limited by available memory.
+
+@end itemize
+
+@node Preprocessing directives implementation
+@section Preprocessing Directives
+
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}, for details of these aspects of
+implementation-defined behavior.
+
+@itemize @bullet
+@item
+@cite{The locations within @code{#pragma} directives where header name
+preprocessing tokens are recognized (C11 6.4, C11 6.4.7).}
+
+@item
+@cite{How sequences in both forms of header names are mapped to headers
+or external source file names (C90 6.1.7, C99 and C11 6.4.7).}
+
+@item
+@cite{Whether the value of a character constant in a constant expression
+that controls conditional inclusion matches the value of the same character
+constant in the execution character set (C90 6.8.1, C99 and C11 6.10.1).}
+
+@item
+@cite{Whether the value of a single-character character constant in a
+constant expression that controls conditional inclusion may have a
+negative value (C90 6.8.1, C99 and C11 6.10.1).}
+
+@item
+@cite{The places that are searched for an included @samp{<>} delimited
+header, and how the places are specified or the header is
+identified (C90 6.8.2, C99 and C11 6.10.2).}
+
+@item
+@cite{How the named source file is searched for in an included @samp{""}
+delimited header (C90 6.8.2, C99 and C11 6.10.2).}
+
+@item
+@cite{The method by which preprocessing tokens (possibly resulting from
+macro expansion) in a @code{#include} directive are combined into a header
+name (C90 6.8.2, C99 and C11 6.10.2).}
+
+@item
+@cite{The nesting limit for @code{#include} processing (C90 6.8.2, C99
+and C11 6.10.2).}
+
+@item
+@cite{Whether the @samp{#} operator inserts a @samp{\} character before
+the @samp{\} character that begins a universal character name in a
+character constant or string literal (C99 and C11 6.10.3.2).}
+
+@item
+@cite{The behavior on each recognized non-@code{STDC #pragma}
+directive (C90 6.8.6, C99 and C11 6.10.6).}
+
+@xref{Pragmas, , Pragmas, cpp, The C Preprocessor}, for details of
+pragmas accepted by GCC on all targets. @xref{Pragmas, , Pragmas
+Accepted by GCC}, for details of target-specific pragmas.
+
+@item
+@cite{The definitions for @code{__DATE__} and @code{__TIME__} when
+respectively, the date and time of translation are not available (C90
+6.8.8, C99 6.10.8, C11 6.10.8.1).}
+
+@end itemize
+
+@node Library functions implementation
+@section Library Functions
+
+The behavior of most of these points are dependent on the implementation
+of the C library, and are not defined by GCC itself.
+
+@itemize @bullet
+@item
+@cite{The null pointer constant to which the macro @code{NULL} expands
+(C90 7.1.6, C99 7.17, C11 7.19).}
+
+In @code{<stddef.h>}, @code{NULL} expands to @code{((void *)0)}. GCC
+does not provide the other headers which define @code{NULL} and some
+library implementations may use other definitions in those headers.
+
+@end itemize
+
+@node Architecture implementation
+@section Architecture
+
+@itemize @bullet
+@item
+@cite{The values or expressions assigned to the macros specified in the
+headers @code{<float.h>}, @code{<limits.h>}, and @code{<stdint.h>}
+(C90, C99 and C11 5.2.4.2, C99 7.18.2, C99 7.18.3, C11 7.20.2, C11 7.20.3).}
+
+Determined by ABI@.
+
+@item
+@cite{The result of attempting to indirectly access an object with
+automatic or thread storage duration from a thread other than the one
+with which it is associated (C11 6.2.4).}
+
+Such accesses are supported, subject to the same requirements for
+synchronization for concurrent accesses as for concurrent accesses to
+any object.
+
+@item
+@cite{The number, order, and encoding of bytes in any object
+(when not explicitly specified in this International Standard) (C99
+and C11 6.2.6.1).}
+
+Determined by ABI@.
+
+@item
+@cite{Whether any extended alignments are supported and the contexts
+in which they are supported (C11 6.2.8).}
+
+Extended alignments up to @math{2^{28}} (bytes) are supported for
+objects of automatic storage duration. Alignments supported for
+objects of static and thread storage duration are determined by the
+ABI.
+
+@item
+@cite{Valid alignment values other than those returned by an _Alignof
+expression for fundamental types, if any (C11 6.2.8).}
+
+Valid alignments are powers of 2 up to and including @math{2^{28}}.
+
+@item
+@cite{The value of the result of the @code{sizeof} and @code{_Alignof}
+operators (C90 6.3.3.4, C99 and C11 6.5.3.4).}
+
+Determined by ABI@.
+
+@end itemize
+
+@node Locale-specific behavior implementation
+@section Locale-Specific Behavior
+
+The behavior of these points are dependent on the implementation
+of the C library, and are not defined by GCC itself.
--- /dev/null
+@c Copyright (C) 2009-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node C++ Implementation
+@chapter C++ Implementation-Defined Behavior
+@cindex implementation-defined behavior, C++ language
+
+A conforming implementation of ISO C++ is required to document its
+choice of behavior in each of the areas that are designated
+``implementation defined''. The following lists all such areas,
+along with the section numbers from the ISO/IEC 14882:1998 and ISO/IEC
+14882:2003 standards. Some areas are only implementation-defined in
+one version of the standard.
+
+Some choices depend on the externally determined ABI for the platform
+(including standard character encodings) which GCC follows; these are
+listed as ``determined by ABI'' below. @xref{Compatibility, , Binary
+Compatibility}, and @uref{https://gcc.gnu.org/readings.html}. Some
+choices are documented in the preprocessor manual.
+@xref{Implementation-defined behavior, , Implementation-defined
+behavior, cpp, The C Preprocessor}. Some choices are documented in
+the corresponding document for the C language. @xref{C
+Implementation}. Some choices are made by the library and operating
+system (or other environment when compiling for a freestanding
+environment); refer to their documentation for details.
+
+@menu
+* Conditionally-supported behavior::
+* Exception handling::
+@end menu
+
+@node Conditionally-supported behavior
+@section Conditionally-Supported Behavior
+
+@cite{Each implementation shall include documentation that identifies
+all conditionally-supported constructs that it does not support (C++0x
+1.4).}
+
+@itemize @bullet
+@item
+@cite{Whether an argument of class type with a non-trivial copy
+constructor or destructor can be passed to ... (C++0x 5.2.2).}
+
+Such argument passing is supported, using the same
+pass-by-invisible-reference approach used for normal function
+arguments of such types.
+
+@end itemize
+
+@node Exception handling
+@section Exception Handling
+
+@itemize @bullet
+@item
+@cite{In the situation where no matching handler is found, it is
+implementation-defined whether or not the stack is unwound before
+std::terminate() is called (C++98 15.5.1).}
+
+The stack is not unwound before std::terminate is called.
+
+@end itemize
--- /dev/null
+@ignore
+@c Set file name and title for man page.
+@setfilename gfdl
+@settitle GNU Free Documentation License
+@c man begin SEEALSO
+gpl(7), fsf-funding(7).
+@c man end
+@c man begin COPYRIGHT
+Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+@uref{https://fsf.org/}
+
+Everyone is permitted to copy and distribute verbatim copies
+of this license document, but changing it is not allowed.
+@c This file is intended to be included within another document,
+@c hence no sectioning command or @node.
+@c man end
+@end ignore
+@c Special handling for inclusion in the install manual.
+@ifset gfdlhtml
+@ifnothtml
+@comment node-name, next, previous, up
+@node GNU Free Documentation License, Concept Index, Specific, Top
+@end ifnothtml
+@html
+<h1 align="center">Installing GCC: GNU Free Documentation License</h1>
+@end html
+@ifnothtml
+@unnumbered GNU Free Documentation License
+@end ifnothtml
+@end ifset
+@c man begin DESCRIPTION
+@ifclear gfdlhtml
+@comment For some cases, this default @node/@unnumbered is not applicable and
+@comment causes warnings. In those cases, the including file can set
+@comment nodefaultgnufreedocumentationlicensenode and provide it's own version.
+@comment F.i., when this file is included in an @raisesections context, the
+@comment including file can use an @unnumberedsec.
+@ifclear nodefaultgnufreedocumentationlicensenode
+@node GNU Free Documentation License
+@unnumbered GNU Free Documentation License
+@end ifclear
+@end ifclear
+
+@cindex FDL, GNU Free Documentation License
+@center Version 1.3, 3 November 2008
+
+@display
+Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+@uref{https://fsf.org/}
+
+Everyone is permitted to copy and distribute verbatim copies
+of this license document, but changing it is not allowed.
+@end display
+
+@enumerate 0
+@item
+PREAMBLE
+
+The purpose of this License is to make a manual, textbook, or other
+functional and useful document @dfn{free} in the sense of freedom: to
+assure everyone the effective freedom to copy and redistribute it,
+with or without modifying it, either commercially or noncommercially.
+Secondarily, this License preserves for the author and publisher a way
+to get credit for their work, while not being considered responsible
+for modifications made by others.
+
+This License is a kind of ``copyleft'', which means that derivative
+works of the document must themselves be free in the same sense. It
+complements the GNU General Public License, which is a copyleft
+license designed for free software.
+
+We have designed this License in order to use it for manuals for free
+software, because free software needs free documentation: a free
+program should come with manuals providing the same freedoms that the
+software does. But this License is not limited to software manuals;
+it can be used for any textual work, regardless of subject matter or
+whether it is published as a printed book. We recommend this License
+principally for works whose purpose is instruction or reference.
+
+@item
+APPLICABILITY AND DEFINITIONS
+
+This License applies to any manual or other work, in any medium, that
+contains a notice placed by the copyright holder saying it can be
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+licensee, and is addressed as ``you''. You accept the license if you
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+A ``Modified Version'' of the Document means any work containing the
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+
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+The ``Cover Texts'' are certain short passages of text that are listed,
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+
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+output purposes only.
+
+The ``Title Page'' means, for a printed book, the title page itself,
+plus such following pages as are needed to hold, legibly, the material
+this License requires to appear in the title page. For works in
+formats which do not have any title page as such, ``Title Page'' means
+the text near the most prominent appearance of the work's title,
+preceding the beginning of the body of the text.
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+The ``publisher'' means any person or entity that distributes copies
+of the Document to the public.
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+A section ``Entitled XYZ'' means a named subunit of the Document whose
+title either is precisely XYZ or contains XYZ in parentheses following
+text that translates XYZ in another language. (Here XYZ stands for a
+specific section name mentioned below, such as ``Acknowledgements'',
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+of such a section when you modify the Document means that it remains a
+section ``Entitled XYZ'' according to this definition.
+
+The Document may include Warranty Disclaimers next to the notice which
+states that this License applies to the Document. These Warranty
+Disclaimers are considered to be included by reference in this
+License, but only as regards disclaiming warranties: any other
+implication that these Warranty Disclaimers may have is void and has
+no effect on the meaning of this License.
+
+@item
+VERBATIM COPYING
+
+You may copy and distribute the Document in any medium, either
+commercially or noncommercially, provided that this License, the
+copyright notices, and the license notice saying this License applies
+to the Document are reproduced in all copies, and that you add no other
+conditions whatsoever to those of this License. You may not use
+technical measures to obstruct or control the reading or further
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+compensation in exchange for copies. If you distribute a large enough
+number of copies you must also follow the conditions in section 3.
+
+You may also lend copies, under the same conditions stated above, and
+you may publicly display copies.
+
+@item
+COPYING IN QUANTITY
+
+If you publish printed copies (or copies in media that commonly have
+printed covers) of the Document, numbering more than 100, and the
+Document's license notice requires Cover Texts, you must enclose the
+copies in covers that carry, clearly and legibly, all these Cover
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+as verbatim copying in other respects.
+
+If the required texts for either cover are too voluminous to fit
+legibly, you should put the first ones listed (as many as fit
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+
+If you publish or distribute Opaque copies of the Document numbering
+more than 100, you must either include a machine-readable Transparent
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+a computer-network location from which the general network-using
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+
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+
+@item
+MODIFICATIONS
+
+You may copy and distribute a Modified Version of the Document under
+the conditions of sections 2 and 3 above, provided that you release
+the Modified Version under precisely this License, with the Modified
+Version filling the role of the Document, thus licensing distribution
+and modification of the Modified Version to whoever possesses a copy
+of it. In addition, you must do these things in the Modified Version:
+
+@enumerate A
+@item
+Use in the Title Page (and on the covers, if any) a title distinct
+from that of the Document, and from those of previous versions
+(which should, if there were any, be listed in the History section
+of the Document). You may use the same title as a previous version
+if the original publisher of that version gives permission.
+
+@item
+List on the Title Page, as authors, one or more persons or entities
+responsible for authorship of the modifications in the Modified
+Version, together with at least five of the principal authors of the
+Document (all of its principal authors, if it has fewer than five),
+unless they release you from this requirement.
+
+@item
+State on the Title page the name of the publisher of the
+Modified Version, as the publisher.
+
+@item
+Preserve all the copyright notices of the Document.
+
+@item
+Add an appropriate copyright notice for your modifications
+adjacent to the other copyright notices.
+
+@item
+Include, immediately after the copyright notices, a license notice
+giving the public permission to use the Modified Version under the
+terms of this License, in the form shown in the Addendum below.
+
+@item
+Preserve in that license notice the full lists of Invariant Sections
+and required Cover Texts given in the Document's license notice.
+
+@item
+Include an unaltered copy of this License.
+
+@item
+Preserve the section Entitled ``History'', Preserve its Title, and add
+to it an item stating at least the title, year, new authors, and
+publisher of the Modified Version as given on the Title Page. If
+there is no section Entitled ``History'' in the Document, create one
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+given on its Title Page, then add an item describing the Modified
+Version as stated in the previous sentence.
+
+@item
+Preserve the network location, if any, given in the Document for
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+publisher of the version it refers to gives permission.
+
+@item
+For any section Entitled ``Acknowledgements'' or ``Dedications'', Preserve
+the Title of the section, and preserve in the section all the
+substance and tone of each of the contributor acknowledgements and/or
+dedications given therein.
+
+@item
+Preserve all the Invariant Sections of the Document,
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+
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+Delete any section Entitled ``Endorsements''. Such a section
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+
+@item
+Do not retitle any existing section to be Entitled ``Endorsements'' or
+to conflict in title with any Invariant Section.
+
+@item
+Preserve any Warranty Disclaimers.
+@end enumerate
+
+If the Modified Version includes new front-matter sections or
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+
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+nothing but endorsements of your Modified Version by various
+parties---for example, statements of peer review or that the text has
+been approved by an organization as the authoritative definition of a
+standard.
+
+You may add a passage of up to five words as a Front-Cover Text, and a
+passage of up to 25 words as a Back-Cover Text, to the end of the list
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+permission from the previous publisher that added the old one.
+
+The author(s) and publisher(s) of the Document do not by this License
+give permission to use their names for publicity for or to assert or
+imply endorsement of any Modified Version.
+
+@item
+COMBINING DOCUMENTS
+
+You may combine the Document with other documents released under this
+License, under the terms defined in section 4 above for modified
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+Invariant Sections of all of the original documents, unmodified, and
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+sections Entitled ``Endorsements.''
+
+@item
+COLLECTIONS OF DOCUMENTS
+
+You may make a collection consisting of the Document and other documents
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+
+@item
+AGGREGATION WITH INDEPENDENT WORKS
+
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+
+@item
+TRANSLATION
+
+Translation is considered a kind of modification, so you may
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+title.
+
+@item
+TERMINATION
+
+You may not copy, modify, sublicense, or distribute the Document
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+
+@item
+FUTURE REVISIONS OF THIS LICENSE
+
+The Free Software Foundation may publish new, revised versions
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+Document.
+
+@item
+RELICENSING
+
+``Massive Multiauthor Collaboration Site'' (or ``MMC Site'') means any
+World Wide Web server that publishes copyrightable works and also
+provides prominent facilities for anybody to edit those works. A
+public wiki that anybody can edit is an example of such a server. A
+``Massive Multiauthor Collaboration'' (or ``MMC'') contained in the
+site means any set of copyrightable works thus published on the MMC
+site.
+
+``CC-BY-SA'' means the Creative Commons Attribution-Share Alike 3.0
+license published by Creative Commons Corporation, a not-for-profit
+corporation with a principal place of business in San Francisco,
+California, as well as future copyleft versions of that license
+published by that same organization.
+
+``Incorporate'' means to publish or republish a Document, in whole or
+in part, as part of another Document.
+
+An MMC is ``eligible for relicensing'' if it is licensed under this
+License, and if all works that were first published under this License
+somewhere other than this MMC, and subsequently incorporated in whole
+or in part into the MMC, (1) had no cover texts or invariant sections,
+and (2) were thus incorporated prior to November 1, 2008.
+
+The operator of an MMC Site may republish an MMC contained in the site
+under CC-BY-SA on the same site at any time before August 1, 2009,
+provided the MMC is eligible for relicensing.
+
+@end enumerate
+
+@page
+@unnumberedsec ADDENDUM: How to use this License for your documents
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and
+license notices just after the title page:
+
+@smallexample
+@group
+ Copyright (C) @var{year} @var{your name}.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+ Texts. A copy of the license is included in the section entitled ``GNU
+ Free Documentation License''.
+@end group
+@end smallexample
+
+If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
+replace the ``with...Texts.'' line with this:
+
+@smallexample
+@group
+ with the Invariant Sections being @var{list their titles}, with
+ the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
+ being @var{list}.
+@end group
+@end smallexample
+
+If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of
+free software license, such as the GNU General Public License,
+to permit their use in free software.
+
+@c Local Variables:
+@c ispell-local-pdict: "ispell-dict"
+@c End:
+
+@c man end
--- /dev/null
+@ignore
+@c Set file name and title for man page.
+@setfilename fsf-funding
+@settitle Funding Free Software
+@c man begin SEEALSO
+gpl(7), gfdl(7).
+@c man end
+@end ignore
+@node Funding
+@c man begin DESCRIPTION
+@unnumbered Funding Free Software
+
+If you want to have more free software a few years from now, it makes
+sense for you to help encourage people to contribute funds for its
+development. The most effective approach known is to encourage
+commercial redistributors to donate.
+
+Users of free software systems can boost the pace of development by
+encouraging for-a-fee distributors to donate part of their selling price
+to free software developers---the Free Software Foundation, and others.
+
+The way to convince distributors to do this is to demand it and expect
+it from them. So when you compare distributors, judge them partly by
+how much they give to free software development. Show distributors
+they must compete to be the one who gives the most.
+
+To make this approach work, you must insist on numbers that you can
+compare, such as, ``We will donate ten dollars to the Frobnitz project
+for each disk sold.'' Don't be satisfied with a vague promise, such as
+``A portion of the profits are donated,'' since it doesn't give a basis
+for comparison.
+
+Even a precise fraction ``of the profits from this disk'' is not very
+meaningful, since creative accounting and unrelated business decisions
+can greatly alter what fraction of the sales price counts as profit.
+If the price you pay is $50, ten percent of the profit is probably
+less than a dollar; it might be a few cents, or nothing at all.
+
+Some redistributors do development work themselves. This is useful too;
+but to keep everyone honest, you need to inquire how much they do, and
+what kind. Some kinds of development make much more long-term
+difference than others. For example, maintaining a separate version of
+a program contributes very little; maintaining the standard version of a
+program for the whole community contributes much. Easy new ports
+contribute little, since someone else would surely do them; difficult
+ports such as adding a new CPU to the GNU Compiler Collection contribute more;
+major new features or packages contribute the most.
+
+By establishing the idea that supporting further development is ``the
+proper thing to do'' when distributing free software for a fee, we can
+assure a steady flow of resources into making more free software.
+@c man end
+
+@display
+@c man begin COPYRIGHT
+Copyright @copyright{} 1994 Free Software Foundation, Inc.
+Verbatim copying and redistribution of this section is permitted
+without royalty; alteration is not permitted.
+@c man end
+@end display
--- /dev/null
+@c Copyright (C) 2001-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@c Version number and development mode.
+@c version-GCC is @set to the base GCC version number.
+@c DEVELOPMENT is @set for an in-development version, @clear for a
+@c release version (corresponding to ``experimental''/anything else
+@c in gcc/DEV-PHASE).
+
+@include gcc-vers.texi
+
+@c Common macros to support generating man pages:
+
+@macro gcctabopt{body}
+@code{\body\}
+@end macro
+@macro gccoptlist{body}
+@smallexample
+\body\
+@end smallexample
+@end macro
+@c Makeinfo handles the above macro OK, TeX needs manual line breaks;
+@c they get lost at some point in handling the macro. But if @macro is
+@c used here rather than @alias, it produces double line breaks.
+@iftex
+@alias gol = *
+@end iftex
+@ifnottex
+@macro gol
+@end macro
+@end ifnottex
+
+@c For FSF printing, define FSFPRINT. Also update the ISBN and last
+@c printing date for the manual being printed.
+@c @set FSFPRINT
+@ifset FSFPRINT
+@smallbook
+@finalout
+@c Cause even numbered pages to be printed on the left hand side of
+@c the page and odd numbered pages to be printed on the right hand
+@c side of the page. Using this, you can print on both sides of a
+@c sheet of paper and have the text on the same part of the sheet.
+
+@c The text on right hand pages is pushed towards the right hand
+@c margin and the text on left hand pages is pushed toward the left
+@c hand margin.
+@c (To provide the reverse effect, set bindingoffset to -0.75in.)
+@tex
+\global\bindingoffset=0.75in
+\global\normaloffset =0.75in
+@end tex
+@end ifset
+
+@c Macro to generate a "For the N.N.N version" subtitle on the title
+@c page of TeX documentation. This macro should be used in the
+@c titlepage environment after the title and any other subtitles have
+@c been placed, and before any authors are placed.
+@macro versionsubtitle
+@ifclear DEVELOPMENT
+@subtitle For @sc{gcc} version @value{version-GCC}
+@end ifclear
+@ifset DEVELOPMENT
+@subtitle For @sc{gcc} version @value{version-GCC} (pre-release)
+@end ifset
+@ifset VERSION_PACKAGE
+@sp 1
+@subtitle @value{VERSION_PACKAGE}
+@end ifset
+@c Even if there are no authors, the second titlepage line should be
+@c forced to the bottom of the page.
+@vskip 0pt plus 1filll
+@end macro
--- /dev/null
+@ignore
+@c Set file name and title for man page.
+@setfilename gpl
+@settitle GNU General Public License
+@c man begin SEEALSO
+gfdl(7), fsf-funding(7).
+@c man end
+@c man begin COPYRIGHT
+Copyright @copyright{} 2007 Free Software Foundation, Inc.
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+@c man end
+@end ignore
+@node Copying
+@c man begin DESCRIPTION
+@unnumbered GNU General Public License
+@center Version 3, 29 June 2007
+
+@c This file is intended to be included in another file.
+
+@display
+Copyright @copyright{} 2007 Free Software Foundation, Inc. @url{https://fsf.org/}
+
+Everyone is permitted to copy and distribute verbatim copies of this
+license document, but changing it is not allowed.
+@end display
+
+@heading Preamble
+
+The GNU General Public License is a free, copyleft license for
+software and other kinds of works.
+
+The licenses for most software and other practical works are designed
+to take away your freedom to share and change the works. By contrast,
+the GNU General Public License is intended to guarantee your freedom
+to share and change all versions of a program--to make sure it remains
+free software for all its users. We, the Free Software Foundation,
+use the GNU General Public License for most of our software; it
+applies also to any other work released this way by its authors. You
+can apply it to your programs, too.
+
+When we speak of free software, we are referring to freedom, not
+price. Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+them if you wish), that you receive source code or can get it if you
+want it, that you can change the software or use pieces of it in new
+free programs, and that you know you can do these things.
+
+To protect your rights, we need to prevent others from denying you
+these rights or asking you to surrender the rights. Therefore, you
+have certain responsibilities if you distribute copies of the
+software, or if you modify it: responsibilities to respect the freedom
+of others.
+
+For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must pass on to the recipients the same
+freedoms that you received. You must make sure that they, too,
+receive or can get the source code. And you must show them these
+terms so they know their rights.
+
+Developers that use the GNU GPL protect your rights with two steps:
+(1) assert copyright on the software, and (2) offer you this License
+giving you legal permission to copy, distribute and/or modify it.
+
+For the developers' and authors' protection, the GPL clearly explains
+that there is no warranty for this free software. For both users' and
+authors' sake, the GPL requires that modified versions be marked as
+changed, so that their problems will not be attributed erroneously to
+authors of previous versions.
+
+Some devices are designed to deny users access to install or run
+modified versions of the software inside them, although the
+manufacturer can do so. This is fundamentally incompatible with the
+aim of protecting users' freedom to change the software. The
+systematic pattern of such abuse occurs in the area of products for
+individuals to use, which is precisely where it is most unacceptable.
+Therefore, we have designed this version of the GPL to prohibit the
+practice for those products. If such problems arise substantially in
+other domains, we stand ready to extend this provision to those
+domains in future versions of the GPL, as needed to protect the
+freedom of users.
+
+Finally, every program is threatened constantly by software patents.
+States should not allow patents to restrict development and use of
+software on general-purpose computers, but in those that do, we wish
+to avoid the special danger that patents applied to a free program
+could make it effectively proprietary. To prevent this, the GPL
+assures that patents cannot be used to render the program non-free.
+
+The precise terms and conditions for copying, distribution and
+modification follow.
+
+@heading TERMS AND CONDITIONS
+
+@enumerate 0
+@item Definitions.
+
+``This License'' refers to version 3 of the GNU General Public License.
+
+``Copyright'' also means copyright-like laws that apply to other kinds
+of works, such as semiconductor masks.
+
+``The Program'' refers to any copyrightable work licensed under this
+License. Each licensee is addressed as ``you''. ``Licensees'' and
+``recipients'' may be individuals or organizations.
+
+To ``modify'' a work means to copy from or adapt all or part of the work
+in a fashion requiring copyright permission, other than the making of
+an exact copy. The resulting work is called a ``modified version'' of
+the earlier work or a work ``based on'' the earlier work.
+
+A ``covered work'' means either the unmodified Program or a work based
+on the Program.
+
+To ``propagate'' a work means to do anything with it that, without
+permission, would make you directly or secondarily liable for
+infringement under applicable copyright law, except executing it on a
+computer or modifying a private copy. Propagation includes copying,
+distribution (with or without modification), making available to the
+public, and in some countries other activities as well.
+
+To ``convey'' a work means any kind of propagation that enables other
+parties to make or receive copies. Mere interaction with a user
+through a computer network, with no transfer of a copy, is not
+conveying.
+
+An interactive user interface displays ``Appropriate Legal Notices'' to
+the extent that it includes a convenient and prominently visible
+feature that (1) displays an appropriate copyright notice, and (2)
+tells the user that there is no warranty for the work (except to the
+extent that warranties are provided), that licensees may convey the
+work under this License, and how to view a copy of this License. If
+the interface presents a list of user commands or options, such as a
+menu, a prominent item in the list meets this criterion.
+
+@item Source Code.
+
+The ``source code'' for a work means the preferred form of the work for
+making modifications to it. ``Object code'' means any non-source form
+of a work.
+
+A ``Standard Interface'' means an interface that either is an official
+standard defined by a recognized standards body, or, in the case of
+interfaces specified for a particular programming language, one that
+is widely used among developers working in that language.
+
+The ``System Libraries'' of an executable work include anything, other
+than the work as a whole, that (a) is included in the normal form of
+packaging a Major Component, but which is not part of that Major
+Component, and (b) serves only to enable use of the work with that
+Major Component, or to implement a Standard Interface for which an
+implementation is available to the public in source code form. A
+``Major Component'', in this context, means a major essential component
+(kernel, window system, and so on) of the specific operating system
+(if any) on which the executable work runs, or a compiler used to
+produce the work, or an object code interpreter used to run it.
+
+The ``Corresponding Source'' for a work in object code form means all
+the source code needed to generate, install, and (for an executable
+work) run the object code and to modify the work, including scripts to
+control those activities. However, it does not include the work's
+System Libraries, or general-purpose tools or generally available free
+programs which are used unmodified in performing those activities but
+which are not part of the work. For example, Corresponding Source
+includes interface definition files associated with source files for
+the work, and the source code for shared libraries and dynamically
+linked subprograms that the work is specifically designed to require,
+such as by intimate data communication or control flow between those
+subprograms and other parts of the work.
+
+The Corresponding Source need not include anything that users can
+regenerate automatically from other parts of the Corresponding Source.
+
+The Corresponding Source for a work in source code form is that same
+work.
+
+@item Basic Permissions.
+
+All rights granted under this License are granted for the term of
+copyright on the Program, and are irrevocable provided the stated
+conditions are met. This License explicitly affirms your unlimited
+permission to run the unmodified Program. The output from running a
+covered work is covered by this License only if the output, given its
+content, constitutes a covered work. This License acknowledges your
+rights of fair use or other equivalent, as provided by copyright law.
+
+You may make, run and propagate covered works that you do not convey,
+without conditions so long as your license otherwise remains in force.
+You may convey covered works to others for the sole purpose of having
+them make modifications exclusively for you, or provide you with
+facilities for running those works, provided that you comply with the
+terms of this License in conveying all material for which you do not
+control copyright. Those thus making or running the covered works for
+you must do so exclusively on your behalf, under your direction and
+control, on terms that prohibit them from making any copies of your
+copyrighted material outside their relationship with you.
+
+Conveying under any other circumstances is permitted solely under the
+conditions stated below. Sublicensing is not allowed; section 10
+makes it unnecessary.
+
+@item Protecting Users' Legal Rights From Anti-Circumvention Law.
+
+No covered work shall be deemed part of an effective technological
+measure under any applicable law fulfilling obligations under article
+11 of the WIPO copyright treaty adopted on 20 December 1996, or
+similar laws prohibiting or restricting circumvention of such
+measures.
+
+When you convey a covered work, you waive any legal power to forbid
+circumvention of technological measures to the extent such
+circumvention is effected by exercising rights under this License with
+respect to the covered work, and you disclaim any intention to limit
+operation or modification of the work as a means of enforcing, against
+the work's users, your or third parties' legal rights to forbid
+circumvention of technological measures.
+
+@item Conveying Verbatim Copies.
+
+You may convey verbatim copies of the Program's source code as you
+receive it, in any medium, provided that you conspicuously and
+appropriately publish on each copy an appropriate copyright notice;
+keep intact all notices stating that this License and any
+non-permissive terms added in accord with section 7 apply to the code;
+keep intact all notices of the absence of any warranty; and give all
+recipients a copy of this License along with the Program.
+
+You may charge any price or no price for each copy that you convey,
+and you may offer support or warranty protection for a fee.
+
+@item Conveying Modified Source Versions.
+
+You may convey a work based on the Program, or the modifications to
+produce it from the Program, in the form of source code under the
+terms of section 4, provided that you also meet all of these
+conditions:
+
+@enumerate a
+@item
+The work must carry prominent notices stating that you modified it,
+and giving a relevant date.
+
+@item
+The work must carry prominent notices stating that it is released
+under this License and any conditions added under section 7. This
+requirement modifies the requirement in section 4 to ``keep intact all
+notices''.
+
+@item
+You must license the entire work, as a whole, under this License to
+anyone who comes into possession of a copy. This License will
+therefore apply, along with any applicable section 7 additional terms,
+to the whole of the work, and all its parts, regardless of how they
+are packaged. This License gives no permission to license the work in
+any other way, but it does not invalidate such permission if you have
+separately received it.
+
+@item
+If the work has interactive user interfaces, each must display
+Appropriate Legal Notices; however, if the Program has interactive
+interfaces that do not display Appropriate Legal Notices, your work
+need not make them do so.
+@end enumerate
+
+A compilation of a covered work with other separate and independent
+works, which are not by their nature extensions of the covered work,
+and which are not combined with it such as to form a larger program,
+in or on a volume of a storage or distribution medium, is called an
+``aggregate'' if the compilation and its resulting copyright are not
+used to limit the access or legal rights of the compilation's users
+beyond what the individual works permit. Inclusion of a covered work
+in an aggregate does not cause this License to apply to the other
+parts of the aggregate.
+
+@item Conveying Non-Source Forms.
+
+You may convey a covered work in object code form under the terms of
+sections 4 and 5, provided that you also convey the machine-readable
+Corresponding Source under the terms of this License, in one of these
+ways:
+
+@enumerate a
+@item
+Convey the object code in, or embodied in, a physical product
+(including a physical distribution medium), accompanied by the
+Corresponding Source fixed on a durable physical medium customarily
+used for software interchange.
+
+@item
+Convey the object code in, or embodied in, a physical product
+(including a physical distribution medium), accompanied by a written
+offer, valid for at least three years and valid for as long as you
+offer spare parts or customer support for that product model, to give
+anyone who possesses the object code either (1) a copy of the
+Corresponding Source for all the software in the product that is
+covered by this License, on a durable physical medium customarily used
+for software interchange, for a price no more than your reasonable
+cost of physically performing this conveying of source, or (2) access
+to copy the Corresponding Source from a network server at no charge.
+
+@item
+Convey individual copies of the object code with a copy of the written
+offer to provide the Corresponding Source. This alternative is
+allowed only occasionally and noncommercially, and only if you
+received the object code with such an offer, in accord with subsection
+6b.
+
+@item
+Convey the object code by offering access from a designated place
+(gratis or for a charge), and offer equivalent access to the
+Corresponding Source in the same way through the same place at no
+further charge. You need not require recipients to copy the
+Corresponding Source along with the object code. If the place to copy
+the object code is a network server, the Corresponding Source may be
+on a different server (operated by you or a third party) that supports
+equivalent copying facilities, provided you maintain clear directions
+next to the object code saying where to find the Corresponding Source.
+Regardless of what server hosts the Corresponding Source, you remain
+obligated to ensure that it is available for as long as needed to
+satisfy these requirements.
+
+@item
+Convey the object code using peer-to-peer transmission, provided you
+inform other peers where the object code and Corresponding Source of
+the work are being offered to the general public at no charge under
+subsection 6d.
+
+@end enumerate
+
+A separable portion of the object code, whose source code is excluded
+from the Corresponding Source as a System Library, need not be
+included in conveying the object code work.
+
+A ``User Product'' is either (1) a ``consumer product'', which means any
+tangible personal property which is normally used for personal,
+family, or household purposes, or (2) anything designed or sold for
+incorporation into a dwelling. In determining whether a product is a
+consumer product, doubtful cases shall be resolved in favor of
+coverage. For a particular product received by a particular user,
+``normally used'' refers to a typical or common use of that class of
+product, regardless of the status of the particular user or of the way
+in which the particular user actually uses, or expects or is expected
+to use, the product. A product is a consumer product regardless of
+whether the product has substantial commercial, industrial or
+non-consumer uses, unless such uses represent the only significant
+mode of use of the product.
+
+``Installation Information'' for a User Product means any methods,
+procedures, authorization keys, or other information required to
+install and execute modified versions of a covered work in that User
+Product from a modified version of its Corresponding Source. The
+information must suffice to ensure that the continued functioning of
+the modified object code is in no case prevented or interfered with
+solely because modification has been made.
+
+If you convey an object code work under this section in, or with, or
+specifically for use in, a User Product, and the conveying occurs as
+part of a transaction in which the right of possession and use of the
+User Product is transferred to the recipient in perpetuity or for a
+fixed term (regardless of how the transaction is characterized), the
+Corresponding Source conveyed under this section must be accompanied
+by the Installation Information. But this requirement does not apply
+if neither you nor any third party retains the ability to install
+modified object code on the User Product (for example, the work has
+been installed in ROM).
+
+The requirement to provide Installation Information does not include a
+requirement to continue to provide support service, warranty, or
+updates for a work that has been modified or installed by the
+recipient, or for the User Product in which it has been modified or
+installed. Access to a network may be denied when the modification
+itself materially and adversely affects the operation of the network
+or violates the rules and protocols for communication across the
+network.
+
+Corresponding Source conveyed, and Installation Information provided,
+in accord with this section must be in a format that is publicly
+documented (and with an implementation available to the public in
+source code form), and must require no special password or key for
+unpacking, reading or copying.
+
+@item Additional Terms.
+
+``Additional permissions'' are terms that supplement the terms of this
+License by making exceptions from one or more of its conditions.
+Additional permissions that are applicable to the entire Program shall
+be treated as though they were included in this License, to the extent
+that they are valid under applicable law. If additional permissions
+apply only to part of the Program, that part may be used separately
+under those permissions, but the entire Program remains governed by
+this License without regard to the additional permissions.
+
+When you convey a copy of a covered work, you may at your option
+remove any additional permissions from that copy, or from any part of
+it. (Additional permissions may be written to require their own
+removal in certain cases when you modify the work.) You may place
+additional permissions on material, added by you to a covered work,
+for which you have or can give appropriate copyright permission.
+
+Notwithstanding any other provision of this License, for material you
+add to a covered work, you may (if authorized by the copyright holders
+of that material) supplement the terms of this License with terms:
+
+@enumerate a
+@item
+Disclaiming warranty or limiting liability differently from the terms
+of sections 15 and 16 of this License; or
+
+@item
+Requiring preservation of specified reasonable legal notices or author
+attributions in that material or in the Appropriate Legal Notices
+displayed by works containing it; or
+
+@item
+Prohibiting misrepresentation of the origin of that material, or
+requiring that modified versions of such material be marked in
+reasonable ways as different from the original version; or
+
+@item
+Limiting the use for publicity purposes of names of licensors or
+authors of the material; or
+
+@item
+Declining to grant rights under trademark law for use of some trade
+names, trademarks, or service marks; or
+
+@item
+Requiring indemnification of licensors and authors of that material by
+anyone who conveys the material (or modified versions of it) with
+contractual assumptions of liability to the recipient, for any
+liability that these contractual assumptions directly impose on those
+licensors and authors.
+@end enumerate
+
+All other non-permissive additional terms are considered ``further
+restrictions'' within the meaning of section 10. If the Program as you
+received it, or any part of it, contains a notice stating that it is
+governed by this License along with a term that is a further
+restriction, you may remove that term. If a license document contains
+a further restriction but permits relicensing or conveying under this
+License, you may add to a covered work material governed by the terms
+of that license document, provided that the further restriction does
+not survive such relicensing or conveying.
+
+If you add terms to a covered work in accord with this section, you
+must place, in the relevant source files, a statement of the
+additional terms that apply to those files, or a notice indicating
+where to find the applicable terms.
+
+Additional terms, permissive or non-permissive, may be stated in the
+form of a separately written license, or stated as exceptions; the
+above requirements apply either way.
+
+@item Termination.
+
+You may not propagate or modify a covered work except as expressly
+provided under this License. Any attempt otherwise to propagate or
+modify it is void, and will automatically terminate your rights under
+this License (including any patent licenses granted under the third
+paragraph of section 11).
+
+However, if you cease all violation of this License, then your license
+from a particular copyright holder is reinstated (a) provisionally,
+unless and until the copyright holder explicitly and finally
+terminates your license, and (b) permanently, if the copyright holder
+fails to notify you of the violation by some reasonable means prior to
+60 days after the cessation.
+
+Moreover, your license from a particular copyright holder is
+reinstated permanently if the copyright holder notifies you of the
+violation by some reasonable means, this is the first time you have
+received notice of violation of this License (for any work) from that
+copyright holder, and you cure the violation prior to 30 days after
+your receipt of the notice.
+
+Termination of your rights under this section does not terminate the
+licenses of parties who have received copies or rights from you under
+this License. If your rights have been terminated and not permanently
+reinstated, you do not qualify to receive new licenses for the same
+material under section 10.
+
+@item Acceptance Not Required for Having Copies.
+
+You are not required to accept this License in order to receive or run
+a copy of the Program. Ancillary propagation of a covered work
+occurring solely as a consequence of using peer-to-peer transmission
+to receive a copy likewise does not require acceptance. However,
+nothing other than this License grants you permission to propagate or
+modify any covered work. These actions infringe copyright if you do
+not accept this License. Therefore, by modifying or propagating a
+covered work, you indicate your acceptance of this License to do so.
+
+@item Automatic Licensing of Downstream Recipients.
+
+Each time you convey a covered work, the recipient automatically
+receives a license from the original licensors, to run, modify and
+propagate that work, subject to this License. You are not responsible
+for enforcing compliance by third parties with this License.
+
+An ``entity transaction'' is a transaction transferring control of an
+organization, or substantially all assets of one, or subdividing an
+organization, or merging organizations. If propagation of a covered
+work results from an entity transaction, each party to that
+transaction who receives a copy of the work also receives whatever
+licenses to the work the party's predecessor in interest had or could
+give under the previous paragraph, plus a right to possession of the
+Corresponding Source of the work from the predecessor in interest, if
+the predecessor has it or can get it with reasonable efforts.
+
+You may not impose any further restrictions on the exercise of the
+rights granted or affirmed under this License. For example, you may
+not impose a license fee, royalty, or other charge for exercise of
+rights granted under this License, and you may not initiate litigation
+(including a cross-claim or counterclaim in a lawsuit) alleging that
+any patent claim is infringed by making, using, selling, offering for
+sale, or importing the Program or any portion of it.
+
+@item Patents.
+
+A ``contributor'' is a copyright holder who authorizes use under this
+License of the Program or a work on which the Program is based. The
+work thus licensed is called the contributor's ``contributor version''.
+
+A contributor's ``essential patent claims'' are all patent claims owned
+or controlled by the contributor, whether already acquired or
+hereafter acquired, that would be infringed by some manner, permitted
+by this License, of making, using, or selling its contributor version,
+but do not include claims that would be infringed only as a
+consequence of further modification of the contributor version. For
+purposes of this definition, ``control'' includes the right to grant
+patent sublicenses in a manner consistent with the requirements of
+this License.
+
+Each contributor grants you a non-exclusive, worldwide, royalty-free
+patent license under the contributor's essential patent claims, to
+make, use, sell, offer for sale, import and otherwise run, modify and
+propagate the contents of its contributor version.
+
+In the following three paragraphs, a ``patent license'' is any express
+agreement or commitment, however denominated, not to enforce a patent
+(such as an express permission to practice a patent or covenant not to
+sue for patent infringement). To ``grant'' such a patent license to a
+party means to make such an agreement or commitment not to enforce a
+patent against the party.
+
+If you convey a covered work, knowingly relying on a patent license,
+and the Corresponding Source of the work is not available for anyone
+to copy, free of charge and under the terms of this License, through a
+publicly available network server or other readily accessible means,
+then you must either (1) cause the Corresponding Source to be so
+available, or (2) arrange to deprive yourself of the benefit of the
+patent license for this particular work, or (3) arrange, in a manner
+consistent with the requirements of this License, to extend the patent
+license to downstream recipients. ``Knowingly relying'' means you have
+actual knowledge that, but for the patent license, your conveying the
+covered work in a country, or your recipient's use of the covered work
+in a country, would infringe one or more identifiable patents in that
+country that you have reason to believe are valid.
+
+If, pursuant to or in connection with a single transaction or
+arrangement, you convey, or propagate by procuring conveyance of, a
+covered work, and grant a patent license to some of the parties
+receiving the covered work authorizing them to use, propagate, modify
+or convey a specific copy of the covered work, then the patent license
+you grant is automatically extended to all recipients of the covered
+work and works based on it.
+
+A patent license is ``discriminatory'' if it does not include within the
+scope of its coverage, prohibits the exercise of, or is conditioned on
+the non-exercise of one or more of the rights that are specifically
+granted under this License. You may not convey a covered work if you
+are a party to an arrangement with a third party that is in the
+business of distributing software, under which you make payment to the
+third party based on the extent of your activity of conveying the
+work, and under which the third party grants, to any of the parties
+who would receive the covered work from you, a discriminatory patent
+license (a) in connection with copies of the covered work conveyed by
+you (or copies made from those copies), or (b) primarily for and in
+connection with specific products or compilations that contain the
+covered work, unless you entered into that arrangement, or that patent
+license was granted, prior to 28 March 2007.
+
+Nothing in this License shall be construed as excluding or limiting
+any implied license or other defenses to infringement that may
+otherwise be available to you under applicable patent law.
+
+@item No Surrender of Others' Freedom.
+
+If conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License. If you cannot convey
+a covered work so as to satisfy simultaneously your obligations under
+this License and any other pertinent obligations, then as a
+consequence you may not convey it at all. For example, if you agree
+to terms that obligate you to collect a royalty for further conveying
+from those to whom you convey the Program, the only way you could
+satisfy both those terms and this License would be to refrain entirely
+from conveying the Program.
+
+@item Use with the GNU Affero General Public License.
+
+Notwithstanding any other provision of this License, you have
+permission to link or combine any covered work with a work licensed
+under version 3 of the GNU Affero General Public License into a single
+combined work, and to convey the resulting work. The terms of this
+License will continue to apply to the part which is the covered work,
+but the special requirements of the GNU Affero General Public License,
+section 13, concerning interaction through a network will apply to the
+combination as such.
+
+@item Revised Versions of this License.
+
+The Free Software Foundation may publish revised and/or new versions
+of the GNU General Public License from time to time. Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns.
+
+Each version is given a distinguishing version number. If the Program
+specifies that a certain numbered version of the GNU General Public
+License ``or any later version'' applies to it, you have the option of
+following the terms and conditions either of that numbered version or
+of any later version published by the Free Software Foundation. If
+the Program does not specify a version number of the GNU General
+Public License, you may choose any version ever published by the Free
+Software Foundation.
+
+If the Program specifies that a proxy can decide which future versions
+of the GNU General Public License can be used, that proxy's public
+statement of acceptance of a version permanently authorizes you to
+choose that version for the Program.
+
+Later license versions may give you additional or different
+permissions. However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+@item Disclaimer of Warranty.
+
+THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM ``AS IS'' WITHOUT
+WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND
+PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE
+DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
+CORRECTION.
+
+@item Limitation of Liability.
+
+IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR
+CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES
+ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT
+NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR
+LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM
+TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER
+PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
+
+@item Interpretation of Sections 15 and 16.
+
+If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+@end enumerate
+
+@heading END OF TERMS AND CONDITIONS
+
+@heading How to Apply These Terms to Your New Programs
+
+If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these
+terms.
+
+To do so, attach the following notices to the program. It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the ``copyright'' line and a pointer to where the full notice is found.
+
+@smallexample
+@var{one line to give the program's name and a brief idea of what it does.}
+Copyright (C) @var{year} @var{name of author}
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at
+your option) any later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see @url{https://www.gnu.org/licenses/}.
+@end smallexample
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+@smallexample
+@var{program} Copyright (C) @var{year} @var{name of author}
+This program comes with ABSOLUTELY NO WARRANTY; for details type @samp{show w}.
+This is free software, and you are welcome to redistribute it
+under certain conditions; type @samp{show c} for details.
+@end smallexample
+
+The hypothetical commands @samp{show w} and @samp{show c} should show
+the appropriate parts of the General Public License. Of course, your
+program's commands might be different; for a GUI interface, you would
+use an ``about box''.
+
+You should also get your employer (if you work as a programmer) or school,
+if any, to sign a ``copyright disclaimer'' for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+@url{https://www.gnu.org/licenses/}.
+
+The GNU General Public License does not permit incorporating your
+program into proprietary programs. If your program is a subroutine
+library, you may consider it more useful to permit linking proprietary
+applications with the library. If this is what you want to do, use
+the GNU Lesser General Public License instead of this License. But
+first, please read @url{https://www.gnu.org/licenses/why-not-lgpl.html}.
+@c man end
--- /dev/null
+\input texinfo.tex @c -*-texinfo-*-
+@c @ifnothtml
+@c %**start of header
+@setfilename gccinstall.info
+@setchapternewpage odd
+@c %**end of header
+@c @end ifnothtml
+
+@include gcc-common.texi
+
+@c Specify title for specific html page
+@ifset indexhtml
+@settitle Installing GCC
+@end ifset
+@ifset specifichtml
+@settitle Host/Target specific installation notes for GCC
+@end ifset
+@ifset prerequisiteshtml
+@settitle Prerequisites for GCC
+@end ifset
+@ifset downloadhtml
+@settitle Downloading GCC
+@end ifset
+@ifset configurehtml
+@settitle Installing GCC: Configuration
+@end ifset
+@ifset buildhtml
+@settitle Installing GCC: Building
+@end ifset
+@ifset testhtml
+@settitle Installing GCC: Testing
+@end ifset
+@ifset finalinstallhtml
+@settitle Installing GCC: Final installation
+@end ifset
+@ifset binarieshtml
+@settitle Installing GCC: Binaries
+@end ifset
+@ifset gfdlhtml
+@settitle Installing GCC: GNU Free Documentation License
+@end ifset
+
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c *** Converted to texinfo by Dean Wakerley, dean@wakerley.com
+
+@c IMPORTANT: whenever you modify this file, run `install.texi2html' to
+@c test the generation of HTML documents for the gcc.gnu.org web pages.
+@c
+@c Do not use @footnote{} in this file as it breaks install.texi2html!
+
+@c Include everything if we're not making html
+@ifnothtml
+@set indexhtml
+@set specifichtml
+@set prerequisiteshtml
+@set downloadhtml
+@set configurehtml
+@set buildhtml
+@set testhtml
+@set finalinstallhtml
+@set binarieshtml
+@set gfdlhtml
+@end ifnothtml
+
+@c Part 2 Summary Description and Copyright
+@copying
+Copyright @copyright{} 1988-2022 Free Software Foundation, Inc.
+@sp 1
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, the Front-Cover texts being (a) (see below), and
+with the Back-Cover Texts being (b) (see below). A copy of the
+license is included in the section entitled ``@uref{./gfdl.html,,GNU
+Free Documentation License}''.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@end copying
+@ifinfo
+@insertcopying
+@end ifinfo
+@dircategory Software development
+@direntry
+* gccinstall: (gccinstall). Installing the GNU Compiler Collection.
+@end direntry
+
+@c Part 3 Titlepage and Copyright
+@titlepage
+@title Installing GCC
+@versionsubtitle
+
+@c The following two commands start the copyright page.
+@page
+@vskip 0pt plus 1filll
+@insertcopying
+@end titlepage
+
+@c Part 4 Top node, Master Menu, and/or Table of Contents
+@ifinfo
+@node Top, , , (dir)
+@comment node-name, next, Previous, up
+
+@menu
+* Installing GCC:: This document describes the generic installation
+ procedure for GCC as well as detailing some target
+ specific installation instructions.
+
+* Specific:: Host/target specific installation notes for GCC.
+* Binaries:: Where to get pre-compiled binaries.
+
+* GNU Free Documentation License:: How you can copy and share this manual.
+* Concept Index:: This index has two entries.
+@end menu
+@end ifinfo
+
+@iftex
+@contents
+@end iftex
+
+@c Part 5 The Body of the Document
+@c ***Installing GCC**********************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Installing GCC, Binaries, , Top
+@end ifnothtml
+@ifset indexhtml
+@ifnothtml
+@chapter Installing GCC
+@end ifnothtml
+
+The latest version of this document is always available at
+@uref{https://gcc.gnu.org/install/,,https://gcc.gnu.org/install/}.
+It refers to the current development sources, instructions for
+specific released versions are included with the sources.
+
+This document describes the generic installation procedure for GCC as well
+as detailing some target specific installation instructions.
+
+GCC includes several components that previously were separate distributions
+with their own installation instructions. This document supersedes all
+package-specific installation instructions.
+
+@emph{Before} starting the build/install procedure please check the
+@ifnothtml
+@ref{Specific, host/target specific installation notes}.
+@end ifnothtml
+@ifhtml
+@uref{specific.html,,host/target specific installation notes}.
+@end ifhtml
+We recommend you browse the entire generic installation instructions before
+you proceed.
+
+Lists of successful builds for released versions of GCC are
+available at @uref{https://gcc.gnu.org/buildstat.html}.
+These lists are updated as new information becomes available.
+
+The installation procedure itself is broken into five steps.
+
+@ifinfo
+@menu
+* Prerequisites::
+* Downloading the source::
+* Configuration::
+* Building::
+* Testing:: (optional)
+* Final install::
+@end menu
+@end ifinfo
+@ifhtml
+@enumerate
+@item
+@uref{prerequisites.html,,Prerequisites}
+@item
+@uref{download.html,,Downloading the source}
+@item
+@uref{configure.html,,Configuration}
+@item
+@uref{build.html,,Building}
+@item
+@uref{test.html,,Testing} (optional)
+@item
+@uref{finalinstall.html,,Final install}
+@end enumerate
+@end ifhtml
+
+Please note that GCC does not support @samp{make uninstall} and probably
+won't do so in the near future as this would open a can of worms. Instead,
+we suggest that you install GCC into a directory of its own and simply
+remove that directory when you do not need that specific version of GCC
+any longer, and, if shared libraries are installed there as well, no
+more binaries exist that use them.
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+
+@insertcopying
+@end ifhtml
+@end ifset
+
+@c ***Prerequisites**************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Prerequisites, Downloading the source, , Installing GCC
+@end ifnothtml
+@ifset prerequisiteshtml
+@ifnothtml
+@chapter Prerequisites
+@end ifnothtml
+@cindex Prerequisites
+
+GCC requires that various tools and packages be available for use in the
+build procedure. Modifying GCC sources requires additional tools
+described below.
+
+@heading Tools/packages necessary for building GCC
+@table @asis
+@item ISO C++11 compiler
+Necessary to bootstrap GCC.
+
+Versions of GCC prior to 11 also allow bootstrapping with an ISO C++98
+compiler, versions of GCC prior to 4.8 also allow bootstrapping with a
+ISO C89 compiler, and versions of GCC prior to 3.4 also allow
+bootstrapping with a traditional (K&R) C compiler.
+
+To build all languages in a cross-compiler or other configuration where
+3-stage bootstrap is not performed, you need to start with an existing
+GCC binary (version 4.8 or later) because source code for language
+frontends other than C might use GCC extensions.
+
+@item C standard library and headers
+
+In order to build GCC, the C standard library and headers must be present
+for all target variants for which target libraries will be built (and not
+only the variant of the host C++ compiler).
+
+This affects the popular @samp{x86_64-pc-linux-gnu} platform (among
+other multilib targets), for which 64-bit (@samp{x86_64}) and 32-bit
+(@samp{i386}) libc headers are usually packaged separately. If you do a
+build of a native compiler on @samp{x86_64-pc-linux-gnu}, make sure you
+either have the 32-bit libc developer package properly installed (the exact
+name of the package depends on your distro) or you must build GCC as a
+64-bit only compiler by configuring with the option
+@option{--disable-multilib}. Otherwise, you may encounter an error such as
+@samp{fatal error: gnu/stubs-32.h: No such file}
+
+@item @anchor{GNAT-prerequisite}GNAT
+
+In order to build GNAT, the Ada compiler, you need a working GNAT
+compiler (GCC version 5.1 or later).
+
+This includes GNAT tools such as @command{gnatmake} and
+@command{gnatlink}, since the Ada front end is written in Ada and
+uses some GNAT-specific extensions.
+
+In order to build a cross compiler, it is strongly recommended to install
+the new compiler as native first, and then use it to build the cross
+compiler. Other native compiler versions may work but this is not guaranteed and
+will typically fail with hard to understand compilation errors during the
+build.
+
+Similarly, it is strongly recommended to use an older version of GNAT to build
+GNAT. More recent versions of GNAT than the version built are not guaranteed
+to work and will often fail during the build with compilation errors.
+
+Note that @command{configure} does not test whether the GNAT installation works
+and has a sufficiently recent version; if too old a GNAT version is
+installed and @option{--enable-languages=ada} is used, the build will fail.
+
+@env{ADA_INCLUDE_PATH} and @env{ADA_OBJECT_PATH} environment variables
+must not be set when building the Ada compiler, the Ada tools, or the
+Ada runtime libraries. You can check that your build environment is clean
+by verifying that @samp{gnatls -v} lists only one explicit path in each
+section.
+
+@item @anchor{GDC-prerequisite}GDC
+
+In order to build GDC, the D compiler, you need a working GDC
+compiler (GCC version 9.1 or later) and D runtime library,
+@samp{libphobos}, as the D front end is written in D.
+
+Versions of GDC prior to 12 can be built with an ISO C++11 compiler, which can
+then be installed and used to bootstrap newer versions of the D front end.
+
+It is strongly recommended to use an older version of GDC to build GDC. More
+recent versions of GDC than the version built are not guaranteed to work and
+will often fail during the build with compilation errors relating to
+deprecations or removed features.
+
+Note that @command{configure} does not test whether the GDC installation works
+and has a sufficiently recent version. Though the implementation of the D
+front end does not make use of any GDC-specific extensions, or novel features
+of the D language, if too old a GDC version is installed and
+@option{--enable-languages=d} is used, the build will fail.
+
+On some targets, @samp{libphobos} isn't enabled by default, but compiles
+and works if @option{--enable-libphobos} is used. Specifics are
+documented for affected targets.
+
+@item A ``working'' POSIX compatible shell, or GNU bash
+
+Necessary when running @command{configure} because some
+@command{/bin/sh} shells have bugs and may crash when configuring the
+target libraries. In other cases, @command{/bin/sh} or @command{ksh}
+have disastrous corner-case performance problems. This
+can cause target @command{configure} runs to literally take days to
+complete in some cases.
+
+So on some platforms @command{/bin/ksh} is sufficient, on others it
+isn't. See the host/target specific instructions for your platform, or
+use @command{bash} to be sure. Then set @env{CONFIG_SHELL} in your
+environment to your ``good'' shell prior to running
+@command{configure}/@command{make}.
+
+@command{zsh} is not a fully compliant POSIX shell and will not
+work when configuring GCC@.
+
+@item A POSIX or SVR4 awk
+
+Necessary for creating some of the generated source files for GCC@.
+If in doubt, use a recent GNU awk version, as some of the older ones
+are broken. GNU awk version 3.1.5 is known to work.
+
+@item GNU binutils
+
+Necessary in some circumstances, optional in others. See the
+host/target specific instructions for your platform for the exact
+requirements.
+
+Note binutils 2.35 or newer is required for LTO to work correctly
+with GNU libtool that includes doing a bootstrap with LTO enabled.
+
+@item gzip version 1.2.4 (or later) or
+@itemx bzip2 version 1.0.2 (or later)
+
+Necessary to uncompress GCC @command{tar} files when source code is
+obtained via HTTPS mirror sites.
+
+@item GNU make version 3.80 (or later)
+
+You must have GNU make installed to build GCC@.
+
+@item GNU tar version 1.14 (or later)
+
+Necessary (only on some platforms) to untar the source code. Many
+systems' @command{tar} programs will also work, only try GNU
+@command{tar} if you have problems.
+
+@item Perl version between 5.6.1 and 5.6.24
+
+Necessary when targeting Darwin, building @samp{libstdc++},
+and not using @option{--disable-symvers}.
+Necessary when targeting Solaris 2 with Solaris @command{ld} and not using
+@option{--disable-symvers}.
+
+Necessary when regenerating @file{Makefile} dependencies in libiberty.
+Necessary when regenerating @file{libiberty/functions.texi}.
+Necessary when generating manpages from Texinfo manuals.
+Used by various scripts to generate some files included in the source
+repository (mainly Unicode-related and rarely changing) from source
+tables.
+
+Used by @command{automake}.
+
+@end table
+
+Several support libraries are necessary to build GCC, some are required,
+others optional. While any sufficiently new version of required tools
+usually work, library requirements are generally stricter. Newer
+versions may work in some cases, but it's safer to use the exact
+versions documented. We appreciate bug reports about problems with
+newer versions, though. If your OS vendor provides packages for the
+support libraries then using those packages may be the simplest way to
+install the libraries.
+
+@table @asis
+@item GNU Multiple Precision Library (GMP) version 4.3.2 (or later)
+
+Necessary to build GCC@. If a GMP source distribution is found in a
+subdirectory of your GCC sources named @file{gmp}, it will be built
+together with GCC. Alternatively, if GMP is already installed but it
+is not in your library search path, you will have to configure with the
+@option{--with-gmp} configure option. See also @option{--with-gmp-lib}
+and @option{--with-gmp-include}.
+The in-tree build is only supported with the GMP version that
+download_prerequisites installs.
+
+@item MPFR Library version 3.1.0 (or later)
+
+Necessary to build GCC@. It can be downloaded from
+@uref{https://www.mpfr.org}. If an MPFR source distribution is found
+in a subdirectory of your GCC sources named @file{mpfr}, it will be
+built together with GCC. Alternatively, if MPFR is already installed
+but it is not in your default library search path, the
+@option{--with-mpfr} configure option should be used. See also
+@option{--with-mpfr-lib} and @option{--with-mpfr-include}.
+The in-tree build is only supported with the MPFR version that
+download_prerequisites installs.
+
+@item MPC Library version 1.0.1 (or later)
+
+Necessary to build GCC@. It can be downloaded from
+@uref{https://www.multiprecision.org/mpc/}. If an MPC source distribution
+is found in a subdirectory of your GCC sources named @file{mpc}, it
+will be built together with GCC. Alternatively, if MPC is already
+installed but it is not in your default library search path, the
+@option{--with-mpc} configure option should be used. See also
+@option{--with-mpc-lib} and @option{--with-mpc-include}.
+The in-tree build is only supported with the MPC version that
+download_prerequisites installs.
+
+@item isl Library version 0.15 or later.
+
+Necessary to build GCC with the Graphite loop optimizations.
+It can be downloaded from @uref{https://gcc.gnu.org/pub/gcc/infrastructure/}.
+If an isl source distribution is found
+in a subdirectory of your GCC sources named @file{isl}, it will be
+built together with GCC. Alternatively, the @option{--with-isl} configure
+option should be used if isl is not installed in your default library
+search path.
+
+@item zstd Library.
+
+Necessary to build GCC with zstd compression used for LTO bytecode.
+The library is searched in your default library patch search.
+Alternatively, the @option{--with-zstd} configure option should be used.
+
+@end table
+
+@heading Tools/packages necessary for modifying GCC
+@table @asis
+@item autoconf version 2.69
+@itemx GNU m4 version 1.4.6 (or later)
+
+Necessary when modifying @file{configure.ac}, @file{aclocal.m4}, etc.@:
+to regenerate @file{configure} and @file{config.in} files.
+
+@item automake version 1.15.1
+
+Necessary when modifying a @file{Makefile.am} file to regenerate its
+associated @file{Makefile.in}.
+
+Much of GCC does not use automake, so directly edit the @file{Makefile.in}
+file. Specifically this applies to the @file{gcc}, @file{intl},
+@file{libcpp}, @file{libiberty}, @file{libobjc} directories as well
+as any of their subdirectories.
+
+For directories that use automake, GCC requires the latest release in
+the 1.15 series, which is currently 1.15.1. When regenerating a directory
+to a newer version, please update all the directories using an older 1.15
+to the latest released version.
+
+@item gettext version 0.14.5 (or later)
+
+Needed to regenerate @file{gcc.pot}.
+
+@item gperf version 2.7.2 (or later)
+
+Necessary when modifying @command{gperf} input files, e.g.@:
+@file{gcc/cp/cfns.gperf} to regenerate its associated header file, e.g.@:
+@file{gcc/cp/cfns.h}.
+
+@item DejaGnu version 1.5.3 (or later)
+@itemx Expect
+@itemx Tcl
+@c Once Tcl 8.5 or higher is required, remove any obsolete
+@c compatibility workarounds:
+@c git grep 'compatibility with earlier Tcl releases'
+
+Necessary to run the GCC testsuite; see the section on testing for
+details.
+
+@item autogen version 5.5.4 (or later) and
+@itemx guile version 1.4.1 (or later)
+
+Necessary to regenerate @file{fixinc/fixincl.x} from
+@file{fixinc/inclhack.def} and @file{fixinc/*.tpl}.
+
+Necessary to run @samp{make check} for @file{fixinc}.
+
+Necessary to regenerate the top level @file{Makefile.in} file from
+@file{Makefile.tpl} and @file{Makefile.def}.
+
+@item Flex version 2.5.4 (or later)
+
+Necessary when modifying @file{*.l} files.
+
+Necessary to build GCC during development because the generated output
+files are not included in the version-controlled source repository.
+They are included in releases.
+
+@item Texinfo version 4.7 (or later)
+
+Necessary for running @command{makeinfo} when modifying @file{*.texi}
+files to test your changes.
+
+Necessary for running @command{make dvi} or @command{make pdf} to
+create printable documentation in DVI or PDF format. Texinfo version
+4.8 or later is required for @command{make pdf}.
+
+Necessary to build GCC documentation during development because the
+generated output files are not included in the repository. They are
+included in releases.
+
+@item @TeX{} (any working version)
+
+Necessary for running @command{texi2dvi} and @command{texi2pdf}, which
+are used when running @command{make dvi} or @command{make pdf} to create
+DVI or PDF files, respectively.
+
+@item Sphinx version 1.0 (or later)
+
+Necessary to regenerate @file{jit/docs/_build/texinfo} from the @file{.rst}
+files in the directories below @file{jit/docs}.
+
+@item git (any version)
+@itemx SSH (any version)
+
+Necessary to access the source repository. Public releases and weekly
+snapshots of the development sources are also available via HTTPS@.
+
+@item GNU diffutils version 2.7 (or later)
+
+Useful when submitting patches for the GCC source code.
+
+@item patch version 2.5.4 (or later)
+
+Necessary when applying patches, created with @command{diff}, to one's
+own sources.
+
+@end table
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***Downloading the source**************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Downloading the source, Configuration, Prerequisites, Installing GCC
+@end ifnothtml
+@ifset downloadhtml
+@ifnothtml
+@chapter Downloading GCC
+@end ifnothtml
+@cindex Downloading GCC
+@cindex Downloading the Source
+
+GCC is distributed via @uref{https://gcc.gnu.org/git.html,,git} and via
+HTTPS as tarballs compressed with @command{gzip} or @command{bzip2}.
+
+Please refer to the @uref{https://gcc.gnu.org/releases.html,,releases web page}
+for information on how to obtain GCC@.
+
+The source distribution includes the C, C++, Objective-C, Fortran,
+and Ada (in the case of GCC 3.1 and later) compilers, as well as
+runtime libraries for C++, Objective-C, and Fortran.
+For previous versions these were downloadable as separate components such
+as the core GCC distribution, which included the C language front end and
+shared components, and language-specific distributions including the
+language front end and the language runtime (where appropriate).
+
+If you also intend to build binutils (either to upgrade an existing
+installation or for use in place of the corresponding tools of your
+OS), unpack the binutils distribution either in the same directory or
+a separate one. In the latter case, add symbolic links to any
+components of the binutils you intend to build alongside the compiler
+(@file{bfd}, @file{binutils}, @file{gas}, @file{gprof}, @file{ld},
+@file{opcodes}, @dots{}) to the directory containing the GCC sources.
+
+Likewise the GMP, MPFR and MPC libraries can be automatically built
+together with GCC. You may simply run the
+@command{contrib/download_prerequisites} script in the GCC source directory
+to set up everything.
+Otherwise unpack the GMP, MPFR and/or MPC source
+distributions in the directory containing the GCC sources and rename
+their directories to @file{gmp}, @file{mpfr} and @file{mpc},
+respectively (or use symbolic links with the same name).
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***Configuration***********************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Configuration, Building, Downloading the source, Installing GCC
+@end ifnothtml
+@ifset configurehtml
+@ifnothtml
+@chapter Installing GCC: Configuration
+@end ifnothtml
+@cindex Configuration
+@cindex Installing GCC: Configuration
+
+Like most GNU software, GCC must be configured before it can be built.
+This document describes the recommended configuration procedure
+for both native and cross targets.
+
+We use @var{srcdir} to refer to the toplevel source directory for
+GCC; we use @var{objdir} to refer to the toplevel build/object directory.
+
+If you obtained the sources by cloning the repository, @var{srcdir}
+must refer to the top @file{gcc} directory, the one where the
+@file{MAINTAINERS} file can be found, and not its @file{gcc}
+subdirectory, otherwise the build will fail.
+
+If either @var{srcdir} or @var{objdir} is located on an automounted NFS
+file system, the shell's built-in @command{pwd} command will return
+temporary pathnames. Using these can lead to various sorts of build
+problems. To avoid this issue, set the @env{PWDCMD} environment
+variable to an automounter-aware @command{pwd} command, e.g.,
+@command{pawd} or @samp{amq -w}, during the configuration and build
+phases.
+
+First, we @strong{highly} recommend that GCC be built into a
+separate directory from the sources which does @strong{not} reside
+within the source tree. This is how we generally build GCC; building
+where @var{srcdir} == @var{objdir} should still work, but doesn't
+get extensive testing; building where @var{objdir} is a subdirectory
+of @var{srcdir} is unsupported.
+
+If you have previously built GCC in the same directory for a
+different target machine, do @samp{make distclean} to delete all files
+that might be invalid. One of the files this deletes is @file{Makefile};
+if @samp{make distclean} complains that @file{Makefile} does not exist
+or issues a message like ``don't know how to make distclean'' it probably
+means that the directory is already suitably clean. However, with the
+recommended method of building in a separate @var{objdir}, you should
+simply use a different @var{objdir} for each target.
+
+Second, when configuring a native system, either @command{cc} or
+@command{gcc} must be in your path or you must set @env{CC} in
+your environment before running configure. Otherwise the configuration
+scripts may fail.
+
+@ignore
+Note that the bootstrap compiler and the resulting GCC must be link
+compatible, else the bootstrap will fail with linker errors about
+incompatible object file formats. Several multilibed targets are
+affected by this requirement, see
+@ifnothtml
+@ref{Specific, host/target specific installation notes}.
+@end ifnothtml
+@ifhtml
+@uref{specific.html,,host/target specific installation notes}.
+@end ifhtml
+@end ignore
+
+To configure GCC:
+
+@smallexample
+% mkdir @var{objdir}
+% cd @var{objdir}
+% @var{srcdir}/configure [@var{options}] [@var{target}]
+@end smallexample
+
+@heading Distributor options
+
+If you will be distributing binary versions of GCC, with modifications
+to the source code, you should use the options described in this
+section to make clear that your version contains modifications.
+
+@table @code
+@item --with-pkgversion=@var{version}
+Specify a string that identifies your package. You may wish
+to include a build number or build date. This version string will be
+included in the output of @command{gcc --version}. This suffix does
+not replace the default version string, only the @samp{GCC} part.
+
+The default value is @samp{GCC}.
+
+@item --with-bugurl=@var{url}
+Specify the URL that users should visit if they wish to report a bug.
+You are of course welcome to forward bugs reported to you to the FSF,
+if you determine that they are not bugs in your modifications.
+
+The default value refers to the FSF's GCC bug tracker.
+
+@item --with-documentation-root-url=@var{url}
+Specify the URL root that contains GCC option documentation. The @var{url}
+should end with a @code{/} character.
+
+The default value is @uref{https://gcc.gnu.org/onlinedocs/,,https://gcc.gnu.org/onlinedocs/}.
+
+@item --with-changes-root-url=@var{url}
+Specify the URL root that contains information about changes in GCC
+releases like @code{gcc-@var{version}/changes.html}.
+The @var{url} should end with a @code{/} character.
+
+The default value is @uref{https://gcc.gnu.org/,,https://gcc.gnu.org/}.
+
+@end table
+
+@heading Host, Build and Target specification
+
+Specify the host, build and target machine configurations. You do this
+when you run the @file{configure} script.
+
+The @dfn{build} machine is the system which you are using, the
+@dfn{host} machine is the system where you want to run the resulting
+compiler (normally the build machine), and the @dfn{target} machine is
+the system for which you want the compiler to generate code.
+
+If you are building a compiler to produce code for the machine it runs
+on (a native compiler), you normally do not need to specify any operands
+to @file{configure}; it will try to guess the type of machine you are on
+and use that as the build, host and target machines. So you don't need
+to specify a configuration when building a native compiler unless
+@file{configure} cannot figure out what your configuration is or guesses
+wrong.
+
+In those cases, specify the build machine's @dfn{configuration name}
+with the @option{--host} option; the host and target will default to be
+the same as the host machine.
+
+Here is an example:
+
+@smallexample
+./configure --host=x86_64-pc-linux-gnu
+@end smallexample
+
+A configuration name may be canonical or it may be more or less
+abbreviated (@file{config.sub} script produces canonical versions).
+
+A canonical configuration name has three parts, separated by dashes.
+It looks like this: @samp{@var{cpu}-@var{company}-@var{system}}.
+
+Here are the possible CPU types:
+
+@quotation
+aarch64, aarch64_be, alpha, alpha64, amdgcn, arc, arceb, arm, armeb, avr, bfin,
+bpf, cris, csky, epiphany, fido, fr30, frv, ft32, h8300, hppa, hppa2.0,
+hppa64, i486, i686, ia64, iq2000, lm32, loongarch64, m32c, m32r, m32rle, m68k,
+mcore, microblaze, microblazeel, mips, mips64, mips64el, mips64octeon,
+mips64orion, mips64vr, mipsel, mipsisa32, mipsisa32r2, mipsisa64, mipsisa64r2,
+mipsisa64r2el, mipsisa64sb1, mipsisa64sr71k, mipstx39, mmix, mn10300, moxie,
+msp430, nds32be, nds32le, nios2, nvptx, or1k, pdp11, powerpc, powerpc64,
+powerpc64le, powerpcle, pru, riscv32, riscv32be, riscv64, riscv64be, rl78, rx,
+s390, s390x, sh, shle, sparc, sparc64, tic6x, v850,
+v850e, v850e1, vax, visium, x86_64, xstormy16, xtensa
+@end quotation
+
+Here is a list of system types:
+
+@quotation
+aix@var{version}, amdhsa, aout, cygwin, darwin@var{version},
+eabi, eabialtivec, eabisim, eabisimaltivec, elf, elf32,
+elfbare, elfoabi, freebsd@var{version}, gnu, hpux, hpux@var{version},
+kfreebsd-gnu, kopensolaris-gnu, linux-androideabi, linux-gnu,
+linux-gnu_altivec, linux-musl, linux-uclibc, lynxos, mingw32, mingw32crt,
+mmixware, msdosdjgpp, netbsd, netbsdelf@var{version}, nto-qnx, openbsd,
+rtems, solaris@var{version}, symbianelf, tpf, uclinux, uclinux_eabi, vms,
+vxworks, vxworksae, vxworksmils
+@end quotation
+
+@heading Options specification
+
+Use @var{options} to override several configure time options for
+GCC@. A list of supported @var{options} follows; @samp{configure
+--help} may list other options, but those not listed below may not
+work and should not normally be used.
+
+Note that each @option{--enable} option has a corresponding
+@option{--disable} option and that each @option{--with} option has a
+corresponding @option{--without} option.
+
+@table @code
+@item --prefix=@var{dirname}
+Specify the toplevel installation
+directory. This is the recommended way to install the tools into a directory
+other than the default. The toplevel installation directory defaults to
+@file{/usr/local}.
+
+We @strong{highly} recommend against @var{dirname} being the same or a
+subdirectory of @var{objdir} or vice versa. If specifying a directory
+beneath a user's home directory tree, some shells will not expand
+@var{dirname} correctly if it contains the @samp{~} metacharacter; use
+@env{$HOME} instead.
+
+The following standard @command{autoconf} options are supported. Normally you
+should not need to use these options.
+@table @code
+@item --exec-prefix=@var{dirname}
+Specify the toplevel installation directory for architecture-dependent
+files. The default is @file{@var{prefix}}.
+
+@item --bindir=@var{dirname}
+Specify the installation directory for the executables called by users
+(such as @command{gcc} and @command{g++}). The default is
+@file{@var{exec-prefix}/bin}.
+
+@item --libdir=@var{dirname}
+Specify the installation directory for object code libraries and
+internal data files of GCC@. The default is @file{@var{exec-prefix}/lib}.
+
+@item --libexecdir=@var{dirname}
+Specify the installation directory for internal executables of GCC@.
+The default is @file{@var{exec-prefix}/libexec}.
+
+@item --with-slibdir=@var{dirname}
+Specify the installation directory for the shared libgcc library. The
+default is @file{@var{libdir}}.
+
+@item --datarootdir=@var{dirname}
+Specify the root of the directory tree for read-only architecture-independent
+data files referenced by GCC@. The default is @file{@var{prefix}/share}.
+
+@item --infodir=@var{dirname}
+Specify the installation directory for documentation in info format.
+The default is @file{@var{datarootdir}/info}.
+
+@item --datadir=@var{dirname}
+Specify the installation directory for some architecture-independent
+data files referenced by GCC@. The default is @file{@var{datarootdir}}.
+
+@item --docdir=@var{dirname}
+Specify the installation directory for documentation files (other
+than Info) for GCC@. The default is @file{@var{datarootdir}/doc}.
+
+@item --htmldir=@var{dirname}
+Specify the installation directory for HTML documentation files.
+The default is @file{@var{docdir}}.
+
+@item --pdfdir=@var{dirname}
+Specify the installation directory for PDF documentation files.
+The default is @file{@var{docdir}}.
+
+@item --mandir=@var{dirname}
+Specify the installation directory for manual pages. The default is
+@file{@var{datarootdir}/man}. (Note that the manual pages are only extracts
+from the full GCC manuals, which are provided in Texinfo format. The manpages
+are derived by an automatic conversion process from parts of the full
+manual.)
+
+@item --with-gxx-include-dir=@var{dirname}
+Specify
+the installation directory for G++ header files. The default depends
+on other configuration options, and differs between cross and native
+configurations.
+
+@item --with-specs=@var{specs}
+Specify additional command line driver SPECS.
+This can be useful if you need to turn on a non-standard feature by
+default without modifying the compiler's source code, for instance
+@option{--with-specs=%@{!fcommon:%@{!fno-common:-fno-common@}@}}.
+@ifnothtml
+@xref{Spec Files,, Specifying subprocesses and the switches to pass to them,
+gcc, Using the GNU Compiler Collection (GCC)},
+@end ifnothtml
+@ifhtml
+See ``Spec Files'' in the main manual
+@end ifhtml
+
+@end table
+
+@item --program-prefix=@var{prefix}
+GCC supports some transformations of the names of its programs when
+installing them. This option prepends @var{prefix} to the names of
+programs to install in @var{bindir} (see above). For example, specifying
+@option{--program-prefix=foo-} would result in @samp{gcc}
+being installed as @file{/usr/local/bin/foo-gcc}.
+
+@item --program-suffix=@var{suffix}
+Appends @var{suffix} to the names of programs to install in @var{bindir}
+(see above). For example, specifying @option{--program-suffix=-3.1}
+would result in @samp{gcc} being installed as
+@file{/usr/local/bin/gcc-3.1}.
+
+@item --program-transform-name=@var{pattern}
+Applies the @samp{sed} script @var{pattern} to be applied to the names
+of programs to install in @var{bindir} (see above). @var{pattern} has to
+consist of one or more basic @samp{sed} editing commands, separated by
+semicolons. For example, if you want the @samp{gcc} program name to be
+transformed to the installed program @file{/usr/local/bin/myowngcc} and
+the @samp{g++} program name to be transformed to
+@file{/usr/local/bin/gspecial++} without changing other program names,
+you could use the pattern
+@option{--program-transform-name='s/^gcc$/myowngcc/; s/^g++$/gspecial++/'}
+to achieve this effect.
+
+All three options can be combined and used together, resulting in more
+complex conversion patterns. As a basic rule, @var{prefix} (and
+@var{suffix}) are prepended (appended) before further transformations
+can happen with a special transformation script @var{pattern}.
+
+As currently implemented, this option only takes effect for native
+builds; cross compiler binaries' names are not transformed even when a
+transformation is explicitly asked for by one of these options.
+
+For native builds, some of the installed programs are also installed
+with the target alias in front of their name, as in
+@samp{i686-pc-linux-gnu-gcc}. All of the above transformations happen
+before the target alias is prepended to the name---so, specifying
+@option{--program-prefix=foo-} and @option{program-suffix=-3.1}, the
+resulting binary would be installed as
+@file{/usr/local/bin/i686-pc-linux-gnu-foo-gcc-3.1}.
+
+As a last shortcoming, none of the installed Ada programs are
+transformed yet, which will be fixed in some time.
+
+@item --with-local-prefix=@var{dirname}
+Specify the
+installation directory for local include files. The default is
+@file{/usr/local}. Specify this option if you want the compiler to
+search directory @file{@var{dirname}/include} for locally installed
+header files @emph{instead} of @file{/usr/local/include}.
+
+You should specify @option{--with-local-prefix} @strong{only} if your
+site has a different convention (not @file{/usr/local}) for where to put
+site-specific files.
+
+The default value for @option{--with-local-prefix} is @file{/usr/local}
+regardless of the value of @option{--prefix}. Specifying
+@option{--prefix} has no effect on which directory GCC searches for
+local header files. This may seem counterintuitive, but actually it is
+logical.
+
+The purpose of @option{--prefix} is to specify where to @emph{install
+GCC}. The local header files in @file{/usr/local/include}---if you put
+any in that directory---are not part of GCC@. They are part of other
+programs---perhaps many others. (GCC installs its own header files in
+another directory which is based on the @option{--prefix} value.)
+
+Both the local-prefix include directory and the GCC-prefix include
+directory are part of GCC's ``system include'' directories. Although these
+two directories are not fixed, they need to be searched in the proper
+order for the correct processing of the include_next directive. The
+local-prefix include directory is searched before the GCC-prefix
+include directory. Another characteristic of system include directories
+is that pedantic warnings are turned off for headers in these directories.
+
+Some autoconf macros add @option{-I @var{directory}} options to the
+compiler command line, to ensure that directories containing installed
+packages' headers are searched. When @var{directory} is one of GCC's
+system include directories, GCC will ignore the option so that system
+directories continue to be processed in the correct order. This
+may result in a search order different from what was specified but the
+directory will still be searched.
+
+GCC automatically searches for ordinary libraries using
+@env{GCC_EXEC_PREFIX}. Thus, when the same installation prefix is
+used for both GCC and packages, GCC will automatically search for
+both headers and libraries. This provides a configuration that is
+easy to use. GCC behaves in a manner similar to that when it is
+installed as a system compiler in @file{/usr}.
+
+Sites that need to install multiple versions of GCC may not want to
+use the above simple configuration. It is possible to use the
+@option{--program-prefix}, @option{--program-suffix} and
+@option{--program-transform-name} options to install multiple versions
+into a single directory, but it may be simpler to use different prefixes
+and the @option{--with-local-prefix} option to specify the location of the
+site-specific files for each version. It will then be necessary for
+users to specify explicitly the location of local site libraries
+(e.g., with @env{LIBRARY_PATH}).
+
+The same value can be used for both @option{--with-local-prefix} and
+@option{--prefix} provided it is not @file{/usr}. This can be used
+to avoid the default search of @file{/usr/local/include}.
+
+@strong{Do not} specify @file{/usr} as the @option{--with-local-prefix}!
+The directory you use for @option{--with-local-prefix} @strong{must not}
+contain any of the system's standard header files. If it did contain
+them, certain programs would be miscompiled (including GNU Emacs, on
+certain targets), because this would override and nullify the header
+file corrections made by the @command{fixincludes} script.
+
+Indications are that people who use this option use it based on mistaken
+ideas of what it is for. People use it as if it specified where to
+install part of GCC@. Perhaps they make this assumption because
+installing GCC creates the directory.
+
+@item --with-gcc-major-version-only
+Specifies that GCC should use only the major number rather than
+@var{major}.@var{minor}.@var{patchlevel} in filesystem paths.
+
+@item --with-native-system-header-dir=@var{dirname}
+Specifies that @var{dirname} is the directory that contains native system
+header files, rather than @file{/usr/include}. This option is most useful
+if you are creating a compiler that should be isolated from the system
+as much as possible. It is most commonly used with the
+@option{--with-sysroot} option and will cause GCC to search
+@var{dirname} inside the system root specified by that option.
+
+@item --enable-shared[=@var{package}[,@dots{}]]
+Build shared versions of libraries, if shared libraries are supported on
+the target platform. Unlike GCC 2.95.x and earlier, shared libraries
+are enabled by default on all platforms that support shared libraries.
+
+If a list of packages is given as an argument, build shared libraries
+only for the listed packages. For other packages, only static libraries
+will be built. Package names currently recognized in the GCC tree are
+@samp{libgcc} (also known as @samp{gcc}), @samp{libstdc++} (not
+@samp{libstdc++-v3}), @samp{libffi}, @samp{zlib}, @samp{boehm-gc},
+@samp{ada}, @samp{libada}, @samp{libgo}, @samp{libobjc}, and @samp{libphobos}.
+Note @samp{libiberty} does not support shared libraries at all.
+
+Use @option{--disable-shared} to build only static libraries. Note that
+@option{--disable-shared} does not accept a list of package names as
+argument, only @option{--enable-shared} does.
+
+Contrast with @option{--enable-host-shared}, which affects @emph{host}
+code.
+
+@item --enable-host-shared
+Specify that the @emph{host} code should be built into position-independent
+machine code (with -fPIC), allowing it to be used within shared libraries,
+but yielding a slightly slower compiler.
+
+This option is required when building the libgccjit.so library.
+
+Contrast with @option{--enable-shared}, which affects @emph{target}
+libraries.
+
+@item @anchor{with-gnu-as}--with-gnu-as
+Specify that the compiler should assume that the
+assembler it finds is the GNU assembler. However, this does not modify
+the rules to find an assembler and will result in confusion if the
+assembler found is not actually the GNU assembler. (Confusion may also
+result if the compiler finds the GNU assembler but has not been
+configured with @option{--with-gnu-as}.) If you have more than one
+assembler installed on your system, you may want to use this option in
+connection with @option{--with-as=@var{pathname}} or
+@option{--with-build-time-tools=@var{pathname}}.
+
+The following systems are the only ones where it makes a difference
+whether you use the GNU assembler. On any other system,
+@option{--with-gnu-as} has no effect.
+
+@itemize @bullet
+@item @samp{hppa1.0-@var{any}-@var{any}}
+@item @samp{hppa1.1-@var{any}-@var{any}}
+@item @samp{sparc-sun-solaris2.@var{any}}
+@item @samp{sparc64-@var{any}-solaris2.@var{any}}
+@end itemize
+
+@item @anchor{with-as}--with-as=@var{pathname}
+Specify that the compiler should use the assembler pointed to by
+@var{pathname}, rather than the one found by the standard rules to find
+an assembler, which are:
+@itemize @bullet
+@item
+Unless GCC is being built with a cross compiler, check the
+@file{@var{libexec}/gcc/@var{target}/@var{version}} directory.
+@var{libexec} defaults to @file{@var{exec-prefix}/libexec};
+@var{exec-prefix} defaults to @var{prefix}, which
+defaults to @file{/usr/local} unless overridden by the
+@option{--prefix=@var{pathname}} switch described above. @var{target}
+is the target system triple, such as @samp{sparc-sun-solaris2.7}, and
+@var{version} denotes the GCC version, such as 3.0.
+
+@item
+If the target system is the same that you are building on, check
+operating system specific directories (e.g.@: @file{/usr/ccs/bin} on
+Solaris 2).
+
+@item
+Check in the @env{PATH} for a tool whose name is prefixed by the
+target system triple.
+
+@item
+Check in the @env{PATH} for a tool whose name is not prefixed by the
+target system triple, if the host and target system triple are
+the same (in other words, we use a host tool if it can be used for
+the target as well).
+@end itemize
+
+You may want to use @option{--with-as} if no assembler
+is installed in the directories listed above, or if you have multiple
+assemblers installed and want to choose one that is not found by the
+above rules.
+
+@item @anchor{with-gnu-ld}--with-gnu-ld
+Same as @uref{#with-gnu-as,,@option{--with-gnu-as}}
+but for the linker.
+
+@item --with-ld=@var{pathname}
+Same as @uref{#with-as,,@option{--with-as}}
+but for the linker.
+
+@item --with-dsymutil=@var{pathname}
+Same as @uref{#with-as,,@option{--with-as}}
+but for the debug linker (only used on Darwin platforms so far).
+
+@item --with-tls=@var{dialect}
+Specify the default TLS dialect, for systems were there is a choice.
+For ARM targets, possible values for @var{dialect} are @code{gnu} or
+@code{gnu2}, which select between the original GNU dialect and the GNU TLS
+descriptor-based dialect.
+
+@item --enable-multiarch
+Specify whether to enable or disable multiarch support. The default is
+to check for glibc start files in a multiarch location, and enable it
+if the files are found. The auto detection is enabled for native builds,
+and for cross builds configured with @option{--with-sysroot}, and without
+@option{--with-native-system-header-dir}.
+More documentation about multiarch can be found at
+@uref{https://wiki.debian.org/Multiarch}.
+
+@item --enable-sjlj-exceptions
+Force use of the @code{setjmp}/@code{longjmp}-based scheme for exceptions.
+@samp{configure} ordinarily picks the correct value based on the platform.
+Only use this option if you are sure you need a different setting.
+
+@item --enable-vtable-verify
+Specify whether to enable or disable the vtable verification feature.
+Enabling this feature causes libstdc++ to be built with its virtual calls
+in verifiable mode. This means that, when linked with libvtv, every
+virtual call in libstdc++ will verify the vtable pointer through which the
+call will be made before actually making the call. If not linked with libvtv,
+the verifier will call stub functions (in libstdc++ itself) and do nothing.
+If vtable verification is disabled, then libstdc++ is not built with its
+virtual calls in verifiable mode at all. However the libvtv library will
+still be built (see @option{--disable-libvtv} to turn off building libvtv).
+@option{--disable-vtable-verify} is the default.
+
+@item --disable-gcov
+Specify that the run-time library used for coverage analysis
+and associated host tools should not be built.
+
+@item --disable-multilib
+Specify that multiple target
+libraries to support different target variants, calling
+conventions, etc.@: should not be built. The default is to build a
+predefined set of them.
+
+Some targets provide finer-grained control over which multilibs are built
+(e.g., @option{--disable-softfloat}):
+@table @code
+@item arm-*-*
+fpu, 26bit, underscore, interwork, biendian, nofmult.
+
+@item m68*-*-*
+softfloat, m68881, m68000, m68020.
+
+@item mips*-*-*
+single-float, biendian, softfloat.
+
+@item msp430-*-*
+no-exceptions
+
+@item powerpc*-*-*, rs6000*-*-*
+aix64, pthread, softfloat, powercpu, powerpccpu, powerpcos, biendian,
+sysv, aix.
+
+@end table
+
+@item --with-multilib-list=@var{list}
+@itemx --without-multilib-list
+Specify what multilibs to build. @var{list} is a comma separated list of
+values, possibly consisting of a single value. Currently only implemented
+for aarch64*-*-*, arm*-*-*, loongarch64-*-*, riscv*-*-*, sh*-*-* and
+x86-64-*-linux*. The accepted values and meaning for each target is given
+below.
+
+@table @code
+@item aarch64*-*-*
+@var{list} is a comma separated list of @code{ilp32}, and @code{lp64}
+to enable ILP32 and LP64 run-time libraries, respectively. If
+@var{list} is empty, then there will be no multilibs and only the
+default run-time library will be built. If @var{list} is
+@code{default} or --with-multilib-list= is not specified, then the
+default set of libraries is selected based on the value of
+@option{--target}.
+
+@item arm*-*-*
+@var{list} is a comma separated list of @code{aprofile} and
+@code{rmprofile} to build multilibs for A or R and M architecture
+profiles respectively. Note that, due to some limitation of the current
+multilib framework, using the combined @code{aprofile,rmprofile}
+multilibs selects in some cases a less optimal multilib than when using
+the multilib profile for the architecture targetted. The special value
+@code{default} is also accepted and is equivalent to omitting the
+option, i.e., only the default run-time library will be enabled.
+
+@var{list} may instead contain @code{@@name}, to use the multilib
+configuration Makefile fragment @file{name} in @file{gcc/config/arm} in
+the source tree (it is part of the corresponding sources, after all).
+It is recommended, but not required, that files used for this purpose to
+be named starting with @file{t-ml-}, to make their intended purpose
+self-evident, in line with GCC conventions. Such files enable custom,
+user-chosen multilib lists to be configured. Whether multiple such
+files can be used together depends on the contents of the supplied
+files. See @file{gcc/config/arm/t-multilib} and its supplementary
+@file{gcc/config/arm/t-*profile} files for an example of what such
+Makefile fragments might look like for this version of GCC. The macros
+expected to be defined in these fragments are not stable across GCC
+releases, so make sure they define the @code{MULTILIB}-related macros
+expected by the version of GCC you are building.
+@ifnothtml
+@xref{Target Fragment,, Target Makefile Fragments, gccint, GNU Compiler
+Collection (GCC) Internals}.
+@end ifnothtml
+@ifhtml
+See ``Target Makefile Fragments'' in the internals manual.
+@end ifhtml
+
+The table below gives the combination of ISAs, architectures, FPUs and
+floating-point ABIs for which multilibs are built for each predefined
+profile. The union of these options is considered when specifying both
+@code{aprofile} and @code{rmprofile}.
+
+@multitable @columnfractions .15 .28 .30
+@item Option @tab aprofile @tab rmprofile
+@item ISAs
+@tab @code{-marm} and @code{-mthumb}
+@tab @code{-mthumb}
+@item Architectures@*@*@*@*@*@*
+@tab default architecture@*
+@code{-march=armv7-a}@*
+@code{-march=armv7ve}@*
+@code{-march=armv8-a}@*@*@*
+@tab default architecture@*
+@code{-march=armv6s-m}@*
+@code{-march=armv7-m}@*
+@code{-march=armv7e-m}@*
+@code{-march=armv8-m.base}@*
+@code{-march=armv8-m.main}@*
+@code{-march=armv7}
+@item FPUs@*@*@*@*@*
+@tab none@*
+@code{-mfpu=vfpv3-d16}@*
+@code{-mfpu=neon}@*
+@code{-mfpu=vfpv4-d16}@*
+@code{-mfpu=neon-vfpv4}@*
+@code{-mfpu=neon-fp-armv8}
+@tab none@*
+@code{-mfpu=vfpv3-d16}@*
+@code{-mfpu=fpv4-sp-d16}@*
+@code{-mfpu=fpv5-sp-d16}@*
+@code{-mfpu=fpv5-d16}@*
+@item floating-point@/ ABIs@*@*
+@tab @code{-mfloat-abi=soft}@*
+@code{-mfloat-abi=softfp}@*
+@code{-mfloat-abi=hard}
+@tab @code{-mfloat-abi=soft}@*
+@code{-mfloat-abi=softfp}@*
+@code{-mfloat-abi=hard}
+@end multitable
+
+@item loongarch*-*-*
+@var{list} is a comma-separated list of the following ABI identifiers:
+@code{lp64d[/base]} @code{lp64f[/base]} @code{lp64d[/base]}, where the
+@code{/base} suffix may be omitted, to enable their respective run-time
+libraries. If @var{list} is empty or @code{default},
+or if @option{--with-multilib-list} is not specified, then the default ABI
+as specified by @option{--with-abi} or implied by @option{--target} is selected.
+
+@item riscv*-*-*
+@var{list} is a single ABI name. The target architecture must be either
+@code{rv32gc} or @code{rv64gc}. This will build a single multilib for the
+specified architecture and ABI pair. If @code{--with-multilib-list} is not
+given, then a default set of multilibs is selected based on the value of
+@option{--target}. This is usually a large set of multilibs.
+
+@item sh*-*-*
+@var{list} is a comma separated list of CPU names. These must be of the
+form @code{sh*} or @code{m*} (in which case they match the compiler option
+for that processor). The list should not contain any endian options -
+these are handled by @option{--with-endian}.
+
+If @var{list} is empty, then there will be no multilibs for extra
+processors. The multilib for the secondary endian remains enabled.
+
+As a special case, if an entry in the list starts with a @code{!}
+(exclamation point), then it is added to the list of excluded multilibs.
+Entries of this sort should be compatible with @samp{MULTILIB_EXCLUDES}
+(once the leading @code{!} has been stripped).
+
+If @option{--with-multilib-list} is not given, then a default set of
+multilibs is selected based on the value of @option{--target}. This is
+usually the complete set of libraries, but some targets imply a more
+specialized subset.
+
+Example 1: to configure a compiler for SH4A only, but supporting both
+endians, with little endian being the default:
+@smallexample
+--with-cpu=sh4a --with-endian=little,big --with-multilib-list=
+@end smallexample
+
+Example 2: to configure a compiler for both SH4A and SH4AL-DSP, but with
+only little endian SH4AL:
+@smallexample
+--with-cpu=sh4a --with-endian=little,big \
+--with-multilib-list=sh4al,!mb/m4al
+@end smallexample
+
+@item x86-64-*-linux*
+@var{list} is a comma separated list of @code{m32}, @code{m64} and
+@code{mx32} to enable 32-bit, 64-bit and x32 run-time libraries,
+respectively. If @var{list} is empty, then there will be no multilibs
+and only the default run-time library will be enabled.
+
+If @option{--with-multilib-list} is not given, then only 32-bit and
+64-bit run-time libraries will be enabled.
+@end table
+
+@item --with-multilib-generator=@var{config}
+Specify what multilibs to build. @var{config} is a semicolon separated list of
+values, possibly consisting of a single value. Currently only implemented
+for riscv*-*-elf*. The accepted values and meanings are given below.
+
+
+Every config is constructed with four components: architecture string, ABI,
+reuse rule with architecture string and reuse rule with sub-extension.
+
+Example 1: Add multi-lib suppport for rv32i with ilp32.
+@smallexample
+rv32i-ilp32--
+@end smallexample
+
+Example 2: Add multi-lib suppport for rv32i with ilp32 and rv32imafd with ilp32.
+@smallexample
+rv32i-ilp32--;rv32imafd-ilp32--
+@end smallexample
+
+Example 3: Add multi-lib suppport for rv32i with ilp32; rv32im with ilp32 and
+rv32ic with ilp32 will reuse this multi-lib set.
+@smallexample
+rv32i-ilp32-rv32im-c
+@end smallexample
+
+Example 4: Add multi-lib suppport for rv64ima with lp64; rv64imaf with lp64,
+rv64imac with lp64 and rv64imafc with lp64 will reuse this multi-lib set.
+@smallexample
+rv64ima-lp64--f,c,fc
+@end smallexample
+
+@option{--with-multilib-generator} have an optional configuration argument
+@option{--cmodel=val} for code model, this option will expand with other
+config options, @var{val} is a comma separated list of possible code model,
+currently we support medlow and medany.
+
+Example 5: Add multi-lib suppport for rv64ima with lp64; rv64ima with lp64 and
+medlow code model
+@smallexample
+rv64ima-lp64--;--cmodel=medlow
+@end smallexample
+
+Example 6: Add multi-lib suppport for rv64ima with lp64; rv64ima with lp64 and
+medlow code model; rv64ima with lp64 and medany code model
+@smallexample
+rv64ima-lp64--;--cmodel=medlow,medany
+@end smallexample
+
+@item --with-endian=@var{endians}
+Specify what endians to use.
+Currently only implemented for sh*-*-*.
+
+@var{endians} may be one of the following:
+@table @code
+@item big
+Use big endian exclusively.
+@item little
+Use little endian exclusively.
+@item big,little
+Use big endian by default. Provide a multilib for little endian.
+@item little,big
+Use little endian by default. Provide a multilib for big endian.
+@end table
+
+@item --enable-threads
+Specify that the target
+supports threads. This affects the Objective-C compiler and runtime
+library, and exception handling for other languages like C++.
+On some systems, this is the default.
+
+In general, the best (and, in many cases, the only known) threading
+model available will be configured for use. Beware that on some
+systems, GCC has not been taught what threading models are generally
+available for the system. In this case, @option{--enable-threads} is an
+alias for @option{--enable-threads=single}.
+
+@item --disable-threads
+Specify that threading support should be disabled for the system.
+This is an alias for @option{--enable-threads=single}.
+
+@item --enable-threads=@var{lib}
+Specify that
+@var{lib} is the thread support library. This affects the Objective-C
+compiler and runtime library, and exception handling for other languages
+like C++. The possibilities for @var{lib} are:
+
+@table @code
+@item aix
+AIX thread support.
+@item dce
+DCE thread support.
+@item lynx
+LynxOS thread support.
+@item mipssde
+MIPS SDE thread support.
+@item no
+This is an alias for @samp{single}.
+@item posix
+Generic POSIX/Unix98 thread support.
+@item rtems
+RTEMS thread support.
+@item single
+Disable thread support, should work for all platforms.
+@item tpf
+TPF thread support.
+@item vxworks
+VxWorks thread support.
+@item win32
+Microsoft Win32 API thread support.
+@end table
+
+@item --enable-tls
+Specify that the target supports TLS (Thread Local Storage). Usually
+configure can correctly determine if TLS is supported. In cases where
+it guesses incorrectly, TLS can be explicitly enabled or disabled with
+@option{--enable-tls} or @option{--disable-tls}. This can happen if
+the assembler supports TLS but the C library does not, or if the
+assumptions made by the configure test are incorrect.
+
+@item --disable-tls
+Specify that the target does not support TLS.
+This is an alias for @option{--enable-tls=no}.
+
+@item --disable-tm-clone-registry
+Disable TM clone registry in libgcc. It is enabled in libgcc by default.
+This option helps to reduce code size for embedded targets which do
+not use transactional memory.
+
+@item --with-cpu=@var{cpu}
+@itemx --with-cpu-32=@var{cpu}
+@itemx --with-cpu-64=@var{cpu}
+Specify which cpu variant the compiler should generate code for by default.
+@var{cpu} will be used as the default value of the @option{-mcpu=} switch.
+This option is only supported on some targets, including ARC, ARM, i386, M68k,
+PowerPC, and SPARC@. It is mandatory for ARC@. The @option{--with-cpu-32} and
+@option{--with-cpu-64} options specify separate default CPUs for
+32-bit and 64-bit modes; these options are only supported for aarch64, i386,
+x86-64, PowerPC, and SPARC@.
+
+@item --with-schedule=@var{cpu}
+@itemx --with-arch=@var{cpu}
+@itemx --with-arch-32=@var{cpu}
+@itemx --with-arch-64=@var{cpu}
+@itemx --with-tune=@var{cpu}
+@itemx --with-tune-32=@var{cpu}
+@itemx --with-tune-64=@var{cpu}
+@itemx --with-abi=@var{abi}
+@itemx --with-fpu=@var{type}
+@itemx --with-float=@var{type}
+These configure options provide default values for the @option{-mschedule=},
+@option{-march=}, @option{-mtune=}, @option{-mabi=}, and @option{-mfpu=}
+options and for @option{-mhard-float} or @option{-msoft-float}. As with
+@option{--with-cpu}, which switches will be accepted and acceptable values
+of the arguments depend on the target.
+
+@item --with-mode=@var{mode}
+Specify if the compiler should default to @option{-marm} or @option{-mthumb}.
+This option is only supported on ARM targets.
+
+@item --with-stack-offset=@var{num}
+This option sets the default for the -mstack-offset=@var{num} option,
+and will thus generally also control the setting of this option for
+libraries. This option is only supported on Epiphany targets.
+
+@item --with-fpmath=@var{isa}
+This options sets @option{-mfpmath=sse} by default and specifies the default
+ISA for floating-point arithmetics. You can select either @samp{sse} which
+enables @option{-msse2} or @samp{avx} which enables @option{-mavx} by default.
+This option is only supported on i386 and x86-64 targets.
+
+@item --with-fp-32=@var{mode}
+On MIPS targets, set the default value for the @option{-mfp} option when using
+the o32 ABI. The possibilities for @var{mode} are:
+@table @code
+@item 32
+Use the o32 FP32 ABI extension, as with the @option{-mfp32} command-line
+option.
+@item xx
+Use the o32 FPXX ABI extension, as with the @option{-mfpxx} command-line
+option.
+@item 64
+Use the o32 FP64 ABI extension, as with the @option{-mfp64} command-line
+option.
+@end table
+In the absence of this configuration option the default is to use the o32
+FP32 ABI extension.
+
+@item --with-odd-spreg-32
+On MIPS targets, set the @option{-modd-spreg} option by default when using
+the o32 ABI.
+
+@item --without-odd-spreg-32
+On MIPS targets, set the @option{-mno-odd-spreg} option by default when using
+the o32 ABI. This is normally used in conjunction with
+@option{--with-fp-32=64} in order to target the o32 FP64A ABI extension.
+
+@item --with-nan=@var{encoding}
+On MIPS targets, set the default encoding convention to use for the
+special not-a-number (NaN) IEEE 754 floating-point data. The
+possibilities for @var{encoding} are:
+@table @code
+@item legacy
+Use the legacy encoding, as with the @option{-mnan=legacy} command-line
+option.
+@item 2008
+Use the 754-2008 encoding, as with the @option{-mnan=2008} command-line
+option.
+@end table
+To use this configuration option you must have an assembler version
+installed that supports the @option{-mnan=} command-line option too.
+In the absence of this configuration option the default convention is
+the legacy encoding, as when neither of the @option{-mnan=2008} and
+@option{-mnan=legacy} command-line options has been used.
+
+@item --with-divide=@var{type}
+Specify how the compiler should generate code for checking for
+division by zero. This option is only supported on the MIPS target.
+The possibilities for @var{type} are:
+@table @code
+@item traps
+Division by zero checks use conditional traps (this is the default on
+systems that support conditional traps).
+@item breaks
+Division by zero checks use the break instruction.
+@end table
+
+@item --with-compact-branches=@var{policy}
+Specify how the compiler should generate branch instructions.
+This option is only supported on the MIPS target.
+The possibilities for @var{type} are:
+@table @code
+@item optimal
+Cause a delay slot branch to be used if one is available in the
+current ISA and the delay slot is successfully filled. If the delay slot
+is not filled, a compact branch will be chosen if one is available.
+@item never
+Ensures that compact branch instructions will never be generated.
+@item always
+Ensures that a compact branch instruction will be generated if available.
+If a compact branch instruction is not available,
+a delay slot form of the branch will be used instead.
+This option is supported from MIPS Release 6 onwards.
+For pre-R6/microMIPS/MIPS16, this option is just same as never/optimal.
+@end table
+
+@c If you make --with-llsc the default for additional targets,
+@c update the --with-llsc description in the MIPS section below.
+
+@item --with-llsc
+On MIPS targets, make @option{-mllsc} the default when no
+@option{-mno-llsc} option is passed. This is the default for
+Linux-based targets, as the kernel will emulate them if the ISA does
+not provide them.
+
+@item --without-llsc
+On MIPS targets, make @option{-mno-llsc} the default when no
+@option{-mllsc} option is passed.
+
+@item --with-synci
+On MIPS targets, make @option{-msynci} the default when no
+@option{-mno-synci} option is passed.
+
+@item --without-synci
+On MIPS targets, make @option{-mno-synci} the default when no
+@option{-msynci} option is passed. This is the default.
+
+@item --with-lxc1-sxc1
+On MIPS targets, make @option{-mlxc1-sxc1} the default when no
+@option{-mno-lxc1-sxc1} option is passed. This is the default.
+
+@item --without-lxc1-sxc1
+On MIPS targets, make @option{-mno-lxc1-sxc1} the default when no
+@option{-mlxc1-sxc1} option is passed. The indexed load/store
+instructions are not directly a problem but can lead to unexpected
+behaviour when deployed in an application intended for a 32-bit address
+space but run on a 64-bit processor. The issue is seen because all
+known MIPS 64-bit Linux kernels execute o32 and n32 applications
+with 64-bit addressing enabled which affects the overflow behaviour
+of the indexed addressing mode. GCC will assume that ordinary
+32-bit arithmetic overflow behaviour is the same whether performed
+as an @code{addu} instruction or as part of the address calculation
+in @code{lwxc1} type instructions. This assumption holds true in a
+pure 32-bit environment and can hold true in a 64-bit environment if
+the address space is accurately set to be 32-bit for o32 and n32.
+
+@item --with-madd4
+On MIPS targets, make @option{-mmadd4} the default when no
+@option{-mno-madd4} option is passed. This is the default.
+
+@item --without-madd4
+On MIPS targets, make @option{-mno-madd4} the default when no
+@option{-mmadd4} option is passed. The @code{madd4} instruction
+family can be problematic when targeting a combination of cores that
+implement these instructions differently. There are two known cores
+that implement these as fused operations instead of unfused (where
+unfused is normally expected). Disabling these instructions is the
+only way to ensure compatible code is generated; this will incur
+a performance penalty.
+
+@item --with-mips-plt
+On MIPS targets, make use of copy relocations and PLTs.
+These features are extensions to the traditional
+SVR4-based MIPS ABIs and require support from GNU binutils
+and the runtime C library.
+
+@item --with-stack-clash-protection-guard-size=@var{size}
+On certain targets this option sets the default stack clash protection guard
+size as a power of two in bytes. On AArch64 @var{size} is required to be either
+12 (4KB) or 16 (64KB).
+
+@item --with-isa-spec=@var{ISA-spec-string}
+On RISC-V targets specify the default version of the RISC-V Unprivileged
+(formerly User-Level) ISA specification to produce code conforming to.
+The possibilities for @var{ISA-spec-string} are:
+@table @code
+@item 2.2
+Produce code conforming to version 2.2.
+@item 20190608
+Produce code conforming to version 20190608.
+@item 20191213
+Produce code conforming to version 20191213.
+@end table
+In the absence of this configuration option the default version is 20191213.
+
+@item --enable-__cxa_atexit
+Define if you want to use __cxa_atexit, rather than atexit, to
+register C++ destructors for local statics and global objects.
+This is essential for fully standards-compliant handling of
+destructors, but requires __cxa_atexit in libc. This option is currently
+only available on systems with GNU libc. When enabled, this will cause
+@option{-fuse-cxa-atexit} to be passed by default.
+
+@item --enable-gnu-indirect-function
+Define if you want to enable the @code{ifunc} attribute. This option is
+currently only available on systems with GNU libc on certain targets.
+
+@item --enable-target-optspace
+Specify that target
+libraries should be optimized for code space instead of code speed.
+This is the default for the m32r platform.
+
+@item --with-cpp-install-dir=@var{dirname}
+Specify that the user visible @command{cpp} program should be installed
+in @file{@var{prefix}/@var{dirname}/cpp}, in addition to @var{bindir}.
+
+@item --enable-comdat
+Enable COMDAT group support. This is primarily used to override the
+automatically detected value.
+
+@item --enable-initfini-array
+Force the use of sections @code{.init_array} and @code{.fini_array}
+(instead of @code{.init} and @code{.fini}) for constructors and
+destructors. Option @option{--disable-initfini-array} has the
+opposite effect. If neither option is specified, the configure script
+will try to guess whether the @code{.init_array} and
+@code{.fini_array} sections are supported and, if they are, use them.
+
+@item --enable-link-mutex
+When building GCC, use a mutex to avoid linking the compilers for
+multiple languages at the same time, to avoid thrashing on build
+systems with limited free memory. The default is not to use such a mutex.
+
+@item --enable-link-serialization
+When building GCC, use make dependencies to serialize linking the compilers for
+multiple languages, to avoid thrashing on build
+systems with limited free memory. The default is not to add such
+dependencies and thus with parallel make potentially link different
+compilers concurrently. If the argument is a positive integer, allow
+that number of concurrent link processes for the large binaries.
+
+@item --enable-maintainer-mode
+The build rules that regenerate the Autoconf and Automake output files as
+well as the GCC master message catalog @file{gcc.pot} are normally
+disabled. This is because it can only be rebuilt if the complete source
+tree is present. If you have changed the sources and want to rebuild the
+catalog, configuring with @option{--enable-maintainer-mode} will enable
+this. Note that you need a recent version of the @code{gettext} tools
+to do so.
+
+@item --disable-bootstrap
+For a native build, the default configuration is to perform
+a 3-stage bootstrap of the compiler when @samp{make} is invoked,
+testing that GCC can compile itself correctly. If you want to disable
+this process, you can configure with @option{--disable-bootstrap}.
+
+@item --enable-bootstrap
+In special cases, you may want to perform a 3-stage build
+even if the target and host triplets are different.
+This is possible when the host can run code compiled for
+the target (e.g.@: host is i686-linux, target is i486-linux).
+Starting from GCC 4.2, to do this you have to configure explicitly
+with @option{--enable-bootstrap}.
+
+@item --enable-generated-files-in-srcdir
+Neither the .c and .h files that are generated from Bison and flex nor the
+info manuals and man pages that are built from the .texi files are present
+in the repository development tree. When building GCC from that development tree,
+or from one of our snapshots, those generated files are placed in your
+build directory, which allows for the source to be in a readonly
+directory.
+
+If you configure with @option{--enable-generated-files-in-srcdir} then those
+generated files will go into the source directory. This is mainly intended
+for generating release or prerelease tarballs of the GCC sources, since it
+is not a requirement that the users of source releases to have flex, Bison,
+or makeinfo.
+
+@item --enable-version-specific-runtime-libs
+Specify
+that runtime libraries should be installed in the compiler specific
+subdirectory (@file{@var{libdir}/gcc}) rather than the usual places. In
+addition, @samp{libstdc++}'s include files will be installed into
+@file{@var{libdir}} unless you overruled it by using
+@option{--with-gxx-include-dir=@var{dirname}}. Using this option is
+particularly useful if you intend to use several versions of GCC in
+parallel. The default is @samp{yes} for @samp{libada}, and @samp{no} for
+the remaining libraries.
+
+@item @anchor{WithAixSoname}--with-aix-soname=@samp{aix}, @samp{svr4} or @samp{both}
+Traditional AIX shared library versioning (versioned @code{Shared Object}
+files as members of unversioned @code{Archive Library} files named
+@samp{lib.a}) causes numerous headaches for package managers. However,
+@code{Import Files} as members of @code{Archive Library} files allow for
+@strong{filename-based versioning} of shared libraries as seen on Linux/SVR4,
+where this is called the "SONAME". But as they prevent static linking,
+@code{Import Files} may be used with @code{Runtime Linking} only, where the
+linker does search for @samp{libNAME.so} before @samp{libNAME.a} library
+filenames with the @samp{-lNAME} linker flag.
+
+@anchor{AixLdCommand}For detailed information please refer to the AIX
+@uref{https://www.ibm.com/support/knowledgecenter/search/%22the%20ld%20command%2C%20also%20called%20the%20linkage%20editor%20or%20binder%22,,ld
+Command} reference.
+
+As long as shared library creation is enabled, upon:
+@table @code
+@item --with-aix-soname=aix
+@item --with-aix-soname=both
+ A (traditional AIX) @code{Shared Archive Library} file is created:
+ @itemize @bullet
+ @item using the @samp{libNAME.a} filename scheme
+ @item with the @code{Shared Object} file as archive member named
+ @samp{libNAME.so.V} (except for @samp{libgcc_s}, where the @code{Shared
+ Object} file is named @samp{shr.o} for backwards compatibility), which
+ @itemize @minus
+ @item is used for runtime loading from inside the @samp{libNAME.a} file
+ @item is used for dynamic loading via
+ @code{dlopen("libNAME.a(libNAME.so.V)", RTLD_MEMBER)}
+ @item is used for shared linking
+ @item is used for static linking, so no separate @code{Static Archive
+ Library} file is needed
+ @end itemize
+ @end itemize
+@item --with-aix-soname=both
+@item --with-aix-soname=svr4
+ A (second) @code{Shared Archive Library} file is created:
+ @itemize @bullet
+ @item using the @samp{libNAME.so.V} filename scheme
+ @item with the @code{Shared Object} file as archive member named
+ @samp{shr.o}, which
+ @itemize @minus
+ @item is created with the @code{-G linker flag}
+ @item has the @code{F_LOADONLY} flag set
+ @item is used for runtime loading from inside the @samp{libNAME.so.V} file
+ @item is used for dynamic loading via @code{dlopen("libNAME.so.V(shr.o)",
+ RTLD_MEMBER)}
+ @end itemize
+ @item with the @code{Import File} as archive member named @samp{shr.imp},
+ which
+ @itemize @minus
+ @item refers to @samp{libNAME.so.V(shr.o)} as the "SONAME", to be recorded
+ in the @code{Loader Section} of subsequent binaries
+ @item indicates whether @samp{libNAME.so.V(shr.o)} is 32 or 64 bit
+ @item lists all the public symbols exported by @samp{lib.so.V(shr.o)},
+ eventually decorated with the @code{@samp{weak} Keyword}
+ @item is necessary for shared linking against @samp{lib.so.V(shr.o)}
+ @end itemize
+ @end itemize
+ A symbolic link using the @samp{libNAME.so} filename scheme is created:
+ @itemize @bullet
+ @item pointing to the @samp{libNAME.so.V} @code{Shared Archive Library} file
+ @item to permit the @code{ld Command} to find @samp{lib.so.V(shr.imp)} via
+ the @samp{-lNAME} argument (requires @code{Runtime Linking} to be enabled)
+ @item to permit dynamic loading of @samp{lib.so.V(shr.o)} without the need
+ to specify the version number via @code{dlopen("libNAME.so(shr.o)",
+ RTLD_MEMBER)}
+ @end itemize
+@end table
+
+As long as static library creation is enabled, upon:
+@table @code
+@item --with-aix-soname=svr4
+ A @code{Static Archive Library} is created:
+ @itemize @bullet
+ @item using the @samp{libNAME.a} filename scheme
+ @item with all the @code{Static Object} files as archive members, which
+ @itemize @minus
+ @item are used for static linking
+ @end itemize
+ @end itemize
+@end table
+
+While the aix-soname=@samp{svr4} option does not create @code{Shared Object}
+files as members of unversioned @code{Archive Library} files any more, package
+managers still are responsible to
+@uref{./specific.html#TransferAixShobj,,transfer} @code{Shared Object} files
+found as member of a previously installed unversioned @code{Archive Library}
+file into the newly installed @code{Archive Library} file with the same
+filename.
+
+@emph{WARNING:} Creating @code{Shared Object} files with @code{Runtime Linking}
+enabled may bloat the TOC, eventually leading to @code{TOC overflow} errors,
+requiring the use of either the @option{-Wl,-bbigtoc} linker flag (seen to
+break with the @code{GDB} debugger) or some of the TOC-related compiler flags,
+@ifnothtml
+@xref{RS/6000 and PowerPC Options,, RS/6000 and PowerPC Options, gcc,
+Using the GNU Compiler Collection (GCC)}.
+@end ifnothtml
+@ifhtml
+see ``RS/6000 and PowerPC Options'' in the main manual.
+@end ifhtml
+
+@option{--with-aix-soname} is currently supported by @samp{libgcc_s} only, so
+this option is still experimental and not for normal use yet.
+
+Default is the traditional behavior @option{--with-aix-soname=@samp{aix}}.
+
+@item --enable-languages=@var{lang1},@var{lang2},@dots{}
+Specify that only a particular subset of compilers and
+their runtime libraries should be built. For a list of valid values for
+@var{langN} you can issue the following command in the
+@file{gcc} directory of your GCC source tree:@*
+@smallexample
+grep ^language= */config-lang.in
+@end smallexample
+Currently, you can use any of the following:
+@code{all}, @code{default}, @code{ada}, @code{c}, @code{c++}, @code{d},
+@code{fortran}, @code{go}, @code{jit}, @code{lto}, @code{objc}, @code{obj-c++}.
+Building the Ada compiler has special requirements, see below.
+If you do not pass this flag, or specify the option @code{default}, then the
+default languages available in the @file{gcc} sub-tree will be configured.
+Ada, D, Go, Jit, and Objective-C++ are not default languages. LTO is not a
+default language, but is built by default because @option{--enable-lto} is
+enabled by default. The other languages are default languages. If
+@code{all} is specified, then all available languages are built. An
+exception is @code{jit} language, which requires
+@option{--enable-host-shared} to be included with @code{all}.
+
+@item --enable-stage1-languages=@var{lang1},@var{lang2},@dots{}
+Specify that a particular subset of compilers and their runtime
+libraries should be built with the system C compiler during stage 1 of
+the bootstrap process, rather than only in later stages with the
+bootstrapped C compiler. The list of valid values is the same as for
+@option{--enable-languages}, and the option @code{all} will select all
+of the languages enabled by @option{--enable-languages}. This option is
+primarily useful for GCC development; for instance, when a development
+version of the compiler cannot bootstrap due to compiler bugs, or when
+one is debugging front ends other than the C front end. When this
+option is used, one can then build the target libraries for the
+specified languages with the stage-1 compiler by using @command{make
+stage1-bubble all-target}, or run the testsuite on the stage-1 compiler
+for the specified languages using @command{make stage1-start check-gcc}.
+
+@item --disable-libada
+Specify that the run-time libraries and tools used by GNAT should not
+be built. This can be useful for debugging, or for compatibility with
+previous Ada build procedures, when it was required to explicitly
+do a @samp{make -C gcc gnatlib_and_tools}.
+
+@item --disable-libsanitizer
+Specify that the run-time libraries for the various sanitizers should
+not be built.
+
+@item --disable-libssp
+Specify that the run-time libraries for stack smashing protection
+should not be built or linked against. On many targets library support
+is provided by the C library instead.
+
+@item --disable-libquadmath
+Specify that the GCC quad-precision math library should not be built.
+On some systems, the library is required to be linkable when building
+the Fortran front end, unless @option{--disable-libquadmath-support}
+is used.
+
+@item --disable-libquadmath-support
+Specify that the Fortran front end and @code{libgfortran} do not add
+support for @code{libquadmath} on systems supporting it.
+
+@item --disable-libgomp
+Specify that the GNU Offloading and Multi Processing Runtime Library
+should not be built.
+
+@item --disable-libvtv
+Specify that the run-time libraries used by vtable verification
+should not be built.
+
+@item --with-dwarf2
+Specify that the compiler should
+use DWARF 2 debugging information as the default.
+
+@item --with-advance-toolchain=@var{at}
+On 64-bit PowerPC Linux systems, configure the compiler to use the
+header files, library files, and the dynamic linker from the Advance
+Toolchain release @var{at} instead of the default versions that are
+provided by the Linux distribution. In general, this option is
+intended for the developers of GCC, and it is not intended for general
+use.
+
+@item --enable-targets=all
+@itemx --enable-targets=@var{target_list}
+Some GCC targets, e.g.@: powerpc64-linux, build bi-arch compilers.
+These are compilers that are able to generate either 64-bit or 32-bit
+code. Typically, the corresponding 32-bit target, e.g.@:
+powerpc-linux for powerpc64-linux, only generates 32-bit code. This
+option enables the 32-bit target to be a bi-arch compiler, which is
+useful when you want a bi-arch compiler that defaults to 32-bit, and
+you are building a bi-arch or multi-arch binutils in a combined tree.
+On mips-linux, this will build a tri-arch compiler (ABI o32/n32/64),
+defaulted to o32.
+Currently, this option only affects sparc-linux, powerpc-linux, x86-linux,
+mips-linux and s390-linux.
+
+@item --enable-default-pie
+Turn on @option{-fPIE} and @option{-pie} by default.
+
+@item --enable-secureplt
+This option enables @option{-msecure-plt} by default for powerpc-linux.
+@ifnothtml
+@xref{RS/6000 and PowerPC Options,, RS/6000 and PowerPC Options, gcc,
+Using the GNU Compiler Collection (GCC)},
+@end ifnothtml
+@ifhtml
+See ``RS/6000 and PowerPC Options'' in the main manual
+@end ifhtml
+
+@item --enable-default-ssp
+Turn on @option{-fstack-protector-strong} by default.
+
+@item --enable-cld
+This option enables @option{-mcld} by default for 32-bit x86 targets.
+@ifnothtml
+@xref{i386 and x86-64 Options,, i386 and x86-64 Options, gcc,
+Using the GNU Compiler Collection (GCC)},
+@end ifnothtml
+@ifhtml
+See ``i386 and x86-64 Options'' in the main manual
+@end ifhtml
+
+@item --enable-large-address-aware
+The @option{--enable-large-address-aware} option arranges for MinGW
+executables to be linked using the @option{--large-address-aware}
+option, that enables the use of more than 2GB of memory. If GCC is
+configured with this option, its effects can be reversed by passing the
+@option{-Wl,--disable-large-address-aware} option to the so-configured
+compiler driver.
+
+@item --enable-win32-registry
+@itemx --enable-win32-registry=@var{key}
+@itemx --disable-win32-registry
+The @option{--enable-win32-registry} option enables Microsoft Windows-hosted GCC
+to look up installations paths in the registry using the following key:
+
+@smallexample
+@code{HKEY_LOCAL_MACHINE\SOFTWARE\Free Software Foundation\@var{key}}
+@end smallexample
+
+@var{key} defaults to GCC version number, and can be overridden by the
+@option{--enable-win32-registry=@var{key}} option. Vendors and distributors
+who use custom installers are encouraged to provide a different key,
+perhaps one comprised of vendor name and GCC version number, to
+avoid conflict with existing installations. This feature is enabled
+by default, and can be disabled by @option{--disable-win32-registry}
+option. This option has no effect on the other hosts.
+
+@item --nfp
+Specify that the machine does not have a floating point unit. This
+option only applies to @samp{m68k-sun-sunos@var{n}}. On any other
+system, @option{--nfp} has no effect.
+
+@item --enable-werror
+@itemx --disable-werror
+@itemx --enable-werror=yes
+@itemx --enable-werror=no
+When you specify this option, it controls whether certain files in the
+compiler are built with @option{-Werror} in bootstrap stage2 and later.
+If you don't specify it, @option{-Werror} is turned on for the main
+development trunk. However it defaults to off for release branches and
+final releases. The specific files which get @option{-Werror} are
+controlled by the Makefiles.
+
+@item --enable-checking
+@itemx --disable-checking
+@itemx --enable-checking=@var{list}
+This option controls performing internal consistency checks in the compiler.
+It does not change the generated code, but adds error checking of the
+requested complexity. This slows down the compiler and may only work
+properly if you are building the compiler with GCC@.
+
+When the option is not specified, the active set of checks depends on context.
+Namely, bootstrap stage 1 defaults to @samp{--enable-checking=yes}, builds
+from release branches or release archives default to
+@samp{--enable-checking=release}, and otherwise
+@samp{--enable-checking=yes,extra} is used. When the option is
+specified without a @var{list}, the result is the same as
+@samp{--enable-checking=yes}. Likewise, @samp{--disable-checking} is
+equivalent to @samp{--enable-checking=no}.
+
+The categories of checks available in @var{list} are @samp{yes} (most common
+checks @samp{assert,misc,gc,gimple,rtlflag,runtime,tree,types}), @samp{no}
+(no checks at all), @samp{all} (all but @samp{valgrind}), @samp{release}
+(cheapest checks @samp{assert,runtime}) or @samp{none} (same as @samp{no}).
+@samp{release} checks are always on and to disable them
+@samp{--disable-checking} or @samp{--enable-checking=no[,<other checks>]}
+must be explicitly requested. Disabling assertions makes the compiler and
+runtime slightly faster but increases the risk of undetected internal errors
+causing wrong code to be generated.
+
+Individual checks can be enabled with these flags: @samp{assert}, @samp{df},
+@samp{extra}, @samp{fold}, @samp{gc}, @samp{gcac}, @samp{gimple},
+@samp{misc}, @samp{rtl}, @samp{rtlflag}, @samp{runtime}, @samp{tree},
+@samp{types} and @samp{valgrind}. @samp{extra} extends @samp{misc}
+checking with extra checks that might affect code generation and should
+therefore not differ between stage1 and later stages in bootstrap.
+
+The @samp{valgrind} check requires the external @command{valgrind} simulator,
+available from @uref{https://valgrind.org}. The @samp{rtl} checks are
+expensive and the @samp{df}, @samp{gcac} and @samp{valgrind} checks are very
+expensive.
+
+@item --disable-stage1-checking
+@itemx --enable-stage1-checking
+@itemx --enable-stage1-checking=@var{list}
+This option affects only bootstrap build. If no @option{--enable-checking}
+option is specified the stage1 compiler is built with @samp{yes} checking
+enabled, otherwise the stage1 checking flags are the same as specified by
+@option{--enable-checking}. To build the stage1 compiler with
+different checking options use @option{--enable-stage1-checking}.
+The list of checking options is the same as for @option{--enable-checking}.
+If your system is too slow or too small to bootstrap a released compiler
+with checking for stage1 enabled, you can use @samp{--disable-stage1-checking}
+to disable checking for the stage1 compiler.
+
+@item --enable-coverage
+@itemx --enable-coverage=@var{level}
+With this option, the compiler is built to collect self coverage
+information, every time it is run. This is for internal development
+purposes, and only works when the compiler is being built with gcc. The
+@var{level} argument controls whether the compiler is built optimized or
+not, values are @samp{opt} and @samp{noopt}. For coverage analysis you
+want to disable optimization, for performance analysis you want to
+enable optimization. When coverage is enabled, the default level is
+without optimization.
+
+@item --enable-gather-detailed-mem-stats
+When this option is specified more detailed information on memory
+allocation is gathered. This information is printed when using
+@option{-fmem-report}.
+
+@item --enable-valgrind-annotations
+Mark selected memory related operations in the compiler when run under
+valgrind to suppress false positives.
+
+@item --enable-nls
+@itemx --disable-nls
+The @option{--enable-nls} option enables Native Language Support (NLS),
+which lets GCC output diagnostics in languages other than American
+English. Native Language Support is enabled by default if not doing a
+canadian cross build. The @option{--disable-nls} option disables NLS@.
+
+@item --with-included-gettext
+If NLS is enabled, the @option{--with-included-gettext} option causes the build
+procedure to prefer its copy of GNU @command{gettext}.
+
+@item --with-catgets
+If NLS is enabled, and if the host lacks @code{gettext} but has the
+inferior @code{catgets} interface, the GCC build procedure normally
+ignores @code{catgets} and instead uses GCC's copy of the GNU
+@code{gettext} library. The @option{--with-catgets} option causes the
+build procedure to use the host's @code{catgets} in this situation.
+
+@item --with-libiconv-prefix=@var{dir}
+Search for libiconv header files in @file{@var{dir}/include} and
+libiconv library files in @file{@var{dir}/lib}.
+
+@item --enable-obsolete
+Enable configuration for an obsoleted system. If you attempt to
+configure GCC for a system (build, host, or target) which has been
+obsoleted, and you do not specify this flag, configure will halt with an
+error message.
+
+All support for systems which have been obsoleted in one release of GCC
+is removed entirely in the next major release, unless someone steps
+forward to maintain the port.
+
+@item --enable-decimal-float
+@itemx --enable-decimal-float=yes
+@itemx --enable-decimal-float=no
+@itemx --enable-decimal-float=bid
+@itemx --enable-decimal-float=dpd
+@itemx --disable-decimal-float
+Enable (or disable) support for the C decimal floating point extension
+that is in the IEEE 754-2008 standard. This is enabled by default only
+on PowerPC, i386, and x86_64 GNU/Linux systems. Other systems may also
+support it, but require the user to specifically enable it. You can
+optionally control which decimal floating point format is used (either
+@samp{bid} or @samp{dpd}). The @samp{bid} (binary integer decimal)
+format is default on i386 and x86_64 systems, and the @samp{dpd}
+(densely packed decimal) format is default on PowerPC systems.
+
+@item --enable-fixed-point
+@itemx --disable-fixed-point
+Enable (or disable) support for C fixed-point arithmetic.
+This option is enabled by default for some targets (such as MIPS) which
+have hardware-support for fixed-point operations. On other targets, you
+may enable this option manually.
+
+@item --with-long-double-128
+Specify if @code{long double} type should be 128-bit by default on selected
+GNU/Linux architectures. If using @code{--without-long-double-128},
+@code{long double} will be by default 64-bit, the same as @code{double} type.
+When neither of these configure options are used, the default will be
+128-bit @code{long double} when built against GNU C Library 2.4 and later,
+64-bit @code{long double} otherwise.
+
+@item --with-long-double-format=ibm
+@itemx --with-long-double-format=ieee
+Specify whether @code{long double} uses the IBM extended double format
+or the IEEE 128-bit floating point format on PowerPC Linux systems.
+This configuration switch will only work on little endian PowerPC
+Linux systems and on big endian 64-bit systems where the default cpu
+is at least power7 (i.e.@: @option{--with-cpu=power7},
+@option{--with-cpu=power8}, or @option{--with-cpu=power9} is used).
+
+If you use the @option{--with-long-double-64} configuration option,
+the @option{--with-long-double-format=ibm} and
+@option{--with-long-double-format=ieee} options are ignored.
+
+The default @code{long double} format is to use IBM extended double.
+Until all of the libraries are converted to use IEEE 128-bit floating
+point, it is not recommended to use
+@option{--with-long-double-format=ieee}.
+
+@item --enable-fdpic
+On SH Linux systems, generate ELF FDPIC code.
+
+@item --with-gmp=@var{pathname}
+@itemx --with-gmp-include=@var{pathname}
+@itemx --with-gmp-lib=@var{pathname}
+@itemx --with-mpfr=@var{pathname}
+@itemx --with-mpfr-include=@var{pathname}
+@itemx --with-mpfr-lib=@var{pathname}
+@itemx --with-mpc=@var{pathname}
+@itemx --with-mpc-include=@var{pathname}
+@itemx --with-mpc-lib=@var{pathname}
+If you want to build GCC but do not have the GMP library, the MPFR
+library and/or the MPC library installed in a standard location and
+do not have their sources present in the GCC source tree then you
+can explicitly specify the directory where they are installed
+(@samp{--with-gmp=@var{gmpinstalldir}},
+@samp{--with-mpfr=@/@var{mpfrinstalldir}},
+@samp{--with-mpc=@/@var{mpcinstalldir}}). The
+@option{--with-gmp=@/@var{gmpinstalldir}} option is shorthand for
+@option{--with-gmp-lib=@/@var{gmpinstalldir}/lib} and
+@option{--with-gmp-include=@/@var{gmpinstalldir}/include}. Likewise the
+@option{--with-mpfr=@/@var{mpfrinstalldir}} option is shorthand for
+@option{--with-mpfr-lib=@/@var{mpfrinstalldir}/lib} and
+@option{--with-mpfr-include=@/@var{mpfrinstalldir}/include}, also the
+@option{--with-mpc=@/@var{mpcinstalldir}} option is shorthand for
+@option{--with-mpc-lib=@/@var{mpcinstalldir}/lib} and
+@option{--with-mpc-include=@/@var{mpcinstalldir}/include}. If these
+shorthand assumptions are not correct, you can use the explicit
+include and lib options directly. You might also need to ensure the
+shared libraries can be found by the dynamic linker when building and
+using GCC, for example by setting the runtime shared library path
+variable (@env{LD_LIBRARY_PATH} on GNU/Linux and Solaris systems).
+
+These flags are applicable to the host platform only. When building
+a cross compiler, they will not be used to configure target libraries.
+
+@item --with-isl=@var{pathname}
+@itemx --with-isl-include=@var{pathname}
+@itemx --with-isl-lib=@var{pathname}
+If you do not have the isl library installed in a standard location and you
+want to build GCC, you can explicitly specify the directory where it is
+installed (@samp{--with-isl=@/@var{islinstalldir}}). The
+@option{--with-isl=@/@var{islinstalldir}} option is shorthand for
+@option{--with-isl-lib=@/@var{islinstalldir}/lib} and
+@option{--with-isl-include=@/@var{islinstalldir}/include}. If this
+shorthand assumption is not correct, you can use the explicit
+include and lib options directly.
+
+These flags are applicable to the host platform only. When building
+a cross compiler, they will not be used to configure target libraries.
+
+@item --with-stage1-ldflags=@var{flags}
+This option may be used to set linker flags to be used when linking
+stage 1 of GCC. These are also used when linking GCC if configured with
+@option{--disable-bootstrap}. If @option{--with-stage1-libs} is not set to a
+value, then the default is @samp{-static-libstdc++ -static-libgcc}, if
+supported.
+
+@item --with-stage1-libs=@var{libs}
+This option may be used to set libraries to be used when linking stage 1
+of GCC. These are also used when linking GCC if configured with
+@option{--disable-bootstrap}.
+
+@item --with-boot-ldflags=@var{flags}
+This option may be used to set linker flags to be used when linking
+stage 2 and later when bootstrapping GCC. If --with-boot-libs
+is not is set to a value, then the default is
+@samp{-static-libstdc++ -static-libgcc}.
+
+@item --with-boot-libs=@var{libs}
+This option may be used to set libraries to be used when linking stage 2
+and later when bootstrapping GCC.
+
+@item --with-debug-prefix-map=@var{map}
+Convert source directory names using @option{-fdebug-prefix-map} when
+building runtime libraries. @samp{@var{map}} is a space-separated
+list of maps of the form @samp{@var{old}=@var{new}}.
+
+@item --enable-linker-build-id
+Tells GCC to pass @option{--build-id} option to the linker for all final
+links (links performed without the @option{-r} or @option{--relocatable}
+option), if the linker supports it. If you specify
+@option{--enable-linker-build-id}, but your linker does not
+support @option{--build-id} option, a warning is issued and the
+@option{--enable-linker-build-id} option is ignored. The default is off.
+
+@item --with-linker-hash-style=@var{choice}
+Tells GCC to pass @option{--hash-style=@var{choice}} option to the
+linker for all final links. @var{choice} can be one of
+@samp{sysv}, @samp{gnu}, and @samp{both} where @samp{sysv} is the default.
+
+@item --enable-gnu-unique-object
+@itemx --disable-gnu-unique-object
+Tells GCC to use the gnu_unique_object relocation for C++ template
+static data members and inline function local statics. Enabled by
+default for a toolchain with an assembler that accepts it and
+GLIBC 2.11 or above, otherwise disabled.
+
+@item --with-diagnostics-color=@var{choice}
+Tells GCC to use @var{choice} as the default for @option{-fdiagnostics-color=}
+option (if not used explicitly on the command line). @var{choice}
+can be one of @samp{never}, @samp{auto}, @samp{always}, and @samp{auto-if-env}
+where @samp{auto} is the default. @samp{auto-if-env} makes
+@option{-fdiagnostics-color=auto} the default if @env{GCC_COLORS}
+is present and non-empty in the environment of the compiler, and
+@option{-fdiagnostics-color=never} otherwise.
+
+@item --with-diagnostics-urls=@var{choice}
+Tells GCC to use @var{choice} as the default for @option{-fdiagnostics-urls=}
+option (if not used explicitly on the command line). @var{choice}
+can be one of @samp{never}, @samp{auto}, @samp{always}, and @samp{auto-if-env}
+where @samp{auto} is the default. @samp{auto-if-env} makes
+@option{-fdiagnostics-urls=auto} the default if @env{GCC_URLS}
+or @env{TERM_URLS} is present and non-empty in the environment of the
+compiler, and @option{-fdiagnostics-urls=never} otherwise.
+
+@item --enable-lto
+@itemx --disable-lto
+Enable support for link-time optimization (LTO). This is enabled by
+default, and may be disabled using @option{--disable-lto}.
+
+@item --enable-linker-plugin-configure-flags=FLAGS
+@itemx --enable-linker-plugin-flags=FLAGS
+By default, linker plugins (such as the LTO plugin) are built for the
+host system architecture. For the case that the linker has a
+different (but run-time compatible) architecture, these flags can be
+specified to build plugins that are compatible to the linker. For
+example, if you are building GCC for a 64-bit x86_64
+(@samp{x86_64-pc-linux-gnu}) host system, but have a 32-bit x86
+GNU/Linux (@samp{i686-pc-linux-gnu}) linker executable (which is
+executable on the former system), you can configure GCC as follows for
+getting compatible linker plugins:
+
+@smallexample
+% @var{srcdir}/configure \
+ --host=x86_64-pc-linux-gnu \
+ --enable-linker-plugin-configure-flags=--host=i686-pc-linux-gnu \
+ --enable-linker-plugin-flags='CC=gcc\ -m32\ -Wl,-rpath,[...]/i686-pc-linux-gnu/lib'
+@end smallexample
+
+@item --with-plugin-ld=@var{pathname}
+Enable an alternate linker to be used at link-time optimization (LTO)
+link time when @option{-fuse-linker-plugin} is enabled.
+This linker should have plugin support such as gold starting with
+version 2.20 or GNU ld starting with version 2.21.
+See @option{-fuse-linker-plugin} for details.
+
+@item --enable-canonical-system-headers
+@itemx --disable-canonical-system-headers
+Enable system header path canonicalization for @file{libcpp}. This can
+produce shorter header file paths in diagnostics and dependency output
+files, but these changed header paths may conflict with some compilation
+environments. Enabled by default, and may be disabled using
+@option{--disable-canonical-system-headers}.
+
+@item --with-glibc-version=@var{major}.@var{minor}
+Tell GCC that when the GNU C Library (glibc) is used on the target it
+will be version @var{major}.@var{minor} or later. Normally this can
+be detected from the C library's header files, but this option may be
+needed when bootstrapping a cross toolchain without the header files
+available for building the initial bootstrap compiler.
+
+If GCC is configured with some multilibs that use glibc and some that
+do not, this option applies only to the multilibs that use glibc.
+However, such configurations may not work well as not all the relevant
+configuration in GCC is on a per-multilib basis.
+
+@item --enable-as-accelerator-for=@var{target}
+Build as offload target compiler. Specify offload host triple by @var{target}.
+
+@item --enable-offload-targets=@var{target1}[=@var{path1}],@dots{},@var{targetN}[=@var{pathN}]
+Enable offloading to targets @var{target1}, @dots{}, @var{targetN}.
+Offload compilers are expected to be already installed. Default search
+path for them is @file{@var{exec-prefix}}, but it can be changed by
+specifying paths @var{path1}, @dots{}, @var{pathN}.
+
+@smallexample
+% @var{srcdir}/configure \
+ --enable-offload-targets=amdgcn-amdhsa,nvptx-none
+@end smallexample
+
+@item --enable-offload-defaulted
+
+Tell GCC that configured but not installed offload compilers and libgomp
+plugins are silently ignored. Useful for distribution compilers where
+those are in separate optional packages and where the presence or absence
+of those optional packages should determine the actual supported offloading
+target set rather than the GCC configure-time selection.
+
+@item --enable-cet
+@itemx --disable-cet
+Enable building target run-time libraries with control-flow
+instrumentation, see @option{-fcf-protection} option. When
+@code{--enable-cet} is specified target libraries are configured
+to add @option{-fcf-protection} and, if needed, other target
+specific options to a set of building options.
+
+@code{--enable-cet=auto} is default. CET is enabled on Linux/x86 if
+target binutils supports @code{Intel CET} instructions and disabled
+otherwise. In this case, the target libraries are configured to get
+additional @option{-fcf-protection} option.
+
+@item --with-riscv-attribute=@samp{yes}, @samp{no} or @samp{default}
+Generate RISC-V attribute by default, in order to record extra build
+information in object.
+
+The option is disabled by default. It is enabled on RISC-V/ELF (bare-metal)
+target if target binutils supported.
+
+@item --enable-s390-excess-float-precision
+@itemx --disable-s390-excess-float-precision
+On s390(x) targets, enable treatment of float expressions with double precision
+when in standards-compliant mode (e.g., when @code{--std=c99} or
+@code{-fexcess-precision=standard} are given).
+
+For a native build and cross compiles that have target headers, the option's
+default is derived from glibc's behavior. When glibc clamps float_t to double,
+GCC follows and enables the option. For other cross compiles, the default is
+disabled.
+
+@item --with-zstd=@var{pathname}
+@itemx --with-zstd-include=@var{pathname}
+@itemx --with-zstd-lib=@var{pathname}
+If you do not have the @code{zstd} library installed in a standard
+location and you want to build GCC, you can explicitly specify the
+directory where it is installed (@samp{--with-zstd=@/@var{zstdinstalldir}}).
+The @option{--with-zstd=@/@var{zstdinstalldir}} option is shorthand for
+@option{--with-zstd-lib=@/@var{zstdinstalldir}/lib} and
+@option{--with-zstd-include=@/@var{zstdinstalldir}/include}. If this
+shorthand assumption is not correct, you can use the explicit
+include and lib options directly.
+
+These flags are applicable to the host platform only. When building
+a cross compiler, they will not be used to configure target libraries.
+@end table
+
+@subheading Cross-Compiler-Specific Options
+The following options only apply to building cross compilers.
+
+@table @code
+@item --with-toolexeclibdir=@var{dir}
+Specify the installation directory for libraries built with a cross compiler.
+The default is @option{$@{gcc_tooldir@}/lib}.
+
+@item --with-sysroot
+@itemx --with-sysroot=@var{dir}
+Tells GCC to consider @var{dir} as the root of a tree that contains
+(a subset of) the root filesystem of the target operating system.
+Target system headers, libraries and run-time object files will be
+searched for in there. More specifically, this acts as if
+@option{--sysroot=@var{dir}} was added to the default options of the built
+compiler. The specified directory is not copied into the
+install tree, unlike the options @option{--with-headers} and
+@option{--with-libs} that this option obsoletes. The default value,
+in case @option{--with-sysroot} is not given an argument, is
+@option{$@{gcc_tooldir@}/sys-root}. If the specified directory is a
+subdirectory of @option{$@{exec_prefix@}}, then it will be found relative to
+the GCC binaries if the installation tree is moved.
+
+This option affects the system root for the compiler used to build
+target libraries (which runs on the build system) and the compiler newly
+installed with @code{make install}; it does not affect the compiler which is
+used to build GCC itself.
+
+If you specify the @option{--with-native-system-header-dir=@var{dirname}}
+option then the compiler will search that directory within @var{dirname} for
+native system headers rather than the default @file{/usr/include}.
+
+@item --with-build-sysroot
+@itemx --with-build-sysroot=@var{dir}
+Tells GCC to consider @var{dir} as the system root (see
+@option{--with-sysroot}) while building target libraries, instead of
+the directory specified with @option{--with-sysroot}. This option is
+only useful when you are already using @option{--with-sysroot}. You
+can use @option{--with-build-sysroot} when you are configuring with
+@option{--prefix} set to a directory that is different from the one in
+which you are installing GCC and your target libraries.
+
+This option affects the system root for the compiler used to build
+target libraries (which runs on the build system); it does not affect
+the compiler which is used to build GCC itself.
+
+If you specify the @option{--with-native-system-header-dir=@var{dirname}}
+option then the compiler will search that directory within @var{dirname} for
+native system headers rather than the default @file{/usr/include}.
+
+@item --with-headers
+@itemx --with-headers=@var{dir}
+Deprecated in favor of @option{--with-sysroot}.
+Specifies that target headers are available when building a cross compiler.
+The @var{dir} argument specifies a directory which has the target include
+files. These include files will be copied into the @file{gcc} install
+directory. @emph{This option with the @var{dir} argument is required} when
+building a cross compiler, if @file{@var{prefix}/@var{target}/sys-include}
+doesn't pre-exist. If @file{@var{prefix}/@var{target}/sys-include} does
+pre-exist, the @var{dir} argument may be omitted. @command{fixincludes}
+will be run on these files to make them compatible with GCC@.
+
+@item --without-headers
+Tells GCC not use any target headers from a libc when building a cross
+compiler. When crossing to GNU/Linux, you need the headers so GCC
+can build the exception handling for libgcc.
+
+@item --with-libs
+@itemx --with-libs="@var{dir1} @var{dir2} @dots{} @var{dirN}"
+Deprecated in favor of @option{--with-sysroot}.
+Specifies a list of directories which contain the target runtime
+libraries. These libraries will be copied into the @file{gcc} install
+directory. If the directory list is omitted, this option has no
+effect.
+
+@item --with-newlib
+Specifies that @samp{newlib} is
+being used as the target C library. This causes @code{__eprintf} to be
+omitted from @file{libgcc.a} on the assumption that it will be provided by
+@samp{newlib}.
+
+@html
+<a name="avr"></a>
+@end html
+@item --with-avrlibc
+Only supported for the AVR target. Specifies that @samp{AVR-Libc} is
+being used as the target C@tie{} library. This causes float support
+functions like @code{__addsf3} to be omitted from @file{libgcc.a} on
+the assumption that it will be provided by @file{libm.a}. For more
+technical details, cf. @uref{https://gcc.gnu.org/PR54461,,PR54461}.
+It is not supported for
+RTEMS configurations, which currently use newlib. The option is
+supported since version 4.7.2 and is the default in 4.8.0 and newer.
+
+@item --with-double=@{32|64|32,64|64,32@}
+@itemx --with-long-double=@{32|64|32,64|64,32|double@}
+Only supported for the AVR target since version@tie{}10.
+Specify the default layout available for the C/C++ @samp{double}
+and @samp{long double} type, respectively. The following rules apply:
+@itemize
+@item
+The first value after the @samp{=} specifies the default layout (in bits)
+of the type and also the default for the @option{-mdouble=} resp.
+@option{-mlong-double=} compiler option.
+@item
+If more than one value is specified, respective multilib variants are
+available, and @option{-mdouble=} resp. @option{-mlong-double=} acts
+as a multilib option.
+@item
+If @option{--with-long-double=double} is specified, @samp{double} and
+@samp{long double} will have the same layout.
+@item
+The defaults are @option{--with-long-double=64,32} and
+@option{--with-double=32,64}. The default @samp{double} layout imposed by
+the latter is compatible with older versions of the compiler that implement
+@samp{double} as a 32-bit type, which does not comply to the language standard.
+@end itemize
+Not all combinations of @option{--with-double=} and
+@option{--with-long-double=} are valid. For example, the combination
+@option{--with-double=32,64} @option{--with-long-double=32} will be
+rejected because the first option specifies the availability of
+multilibs for @samp{double}, whereas the second option implies
+that @samp{long double} --- and hence also @samp{double} --- is always
+32@tie{}bits wide.
+
+@item --with-double-comparison=@{tristate|bool|libf7@}
+Only supported for the AVR target since version@tie{}10.
+Specify what result format is returned by library functions that
+compare 64-bit floating point values (@code{DFmode}).
+The GCC default is @samp{tristate}. If the floating point
+implementation returns a boolean instead, set it to @samp{bool}.
+
+@item --with-libf7=@{libgcc|math|math-symbols|no@}
+Only supported for the AVR target since version@tie{}10.
+Specify to which degree code from LibF7 is included in libgcc.
+LibF7 is an ad-hoc, AVR-specific, 64-bit floating point emulation
+written in C and (inline) assembly. @samp{libgcc} adds support
+for functions that one would usually expect in libgcc like double addition,
+double comparisons and double conversions. @samp{math} also adds routines
+that one would expect in @file{libm.a}, but with @code{__} (two underscores)
+prepended to the symbol names as specified by @file{math.h}.
+@samp{math-symbols} also defines weak aliases for the functions
+declared in @file{math.h}. However, @code{--with-libf7} won't
+install no @file{math.h} header file whatsoever, this file must come
+from elsewhere. This option sets @option{--with-double-comparison}
+to @samp{bool}.
+
+@item --with-nds32-lib=@var{library}
+Specifies that @var{library} setting is used for building @file{libgcc.a}.
+Currently, the valid @var{library} is @samp{newlib} or @samp{mculib}.
+This option is only supported for the NDS32 target.
+
+@item --with-build-time-tools=@var{dir}
+Specifies where to find the set of target tools (assembler, linker, etc.)
+that will be used while building GCC itself. This option can be useful
+if the directory layouts are different between the system you are building
+GCC on, and the system where you will deploy it.
+
+For example, on an @samp{ia64-hp-hpux} system, you may have the GNU
+assembler and linker in @file{/usr/bin}, and the native tools in a
+different path, and build a toolchain that expects to find the
+native tools in @file{/usr/bin}.
+
+When you use this option, you should ensure that @var{dir} includes
+@command{ar}, @command{as}, @command{ld}, @command{nm},
+@command{ranlib} and @command{strip} if necessary, and possibly
+@command{objdump}. Otherwise, GCC may use an inconsistent set of
+tools.
+@end table
+
+@subsubheading Overriding @command{configure} test results
+
+Sometimes, it might be necessary to override the result of some
+@command{configure} test, for example in order to ease porting to a new
+system or work around a bug in a test. The toplevel @command{configure}
+script provides three variables for this:
+
+@table @code
+
+@item build_configargs
+@cindex @code{build_configargs}
+The contents of this variable is passed to all build @command{configure}
+scripts.
+
+@item host_configargs
+@cindex @code{host_configargs}
+The contents of this variable is passed to all host @command{configure}
+scripts.
+
+@item target_configargs
+@cindex @code{target_configargs}
+The contents of this variable is passed to all target @command{configure}
+scripts.
+
+@end table
+
+In order to avoid shell and @command{make} quoting issues for complex
+overrides, you can pass a setting for @env{CONFIG_SITE} and set
+variables in the site file.
+
+@subheading Objective-C-Specific Options
+
+The following options apply to the build of the Objective-C runtime library.
+
+@table @code
+@item --enable-objc-gc
+Specify that an additional variant of the GNU Objective-C runtime library
+is built, using an external build of the Boehm-Demers-Weiser garbage
+collector (@uref{https://www.hboehm.info/gc/}). This library needs to be
+available for each multilib variant, unless configured with
+@option{--enable-objc-gc=@samp{auto}} in which case the build of the
+additional runtime library is skipped when not available and the build
+continues.
+
+@item --with-target-bdw-gc=@var{list}
+@itemx --with-target-bdw-gc-include=@var{list}
+@itemx --with-target-bdw-gc-lib=@var{list}
+Specify search directories for the garbage collector header files and
+libraries. @var{list} is a comma separated list of key value pairs of the
+form @samp{@var{multilibdir}=@var{path}}, where the default multilib key
+is named as @samp{.} (dot), or is omitted (e.g.@:
+@samp{--with-target-bdw-gc=/opt/bdw-gc,32=/opt-bdw-gc32}).
+
+The options @option{--with-target-bdw-gc-include} and
+@option{--with-target-bdw-gc-lib} must always be specified together
+for each multilib variant and they take precedence over
+@option{--with-target-bdw-gc}. If @option{--with-target-bdw-gc-include}
+is missing values for a multilib, then the value for the default
+multilib is used (e.g.@: @samp{--with-target-bdw-gc-include=/opt/bdw-gc/include}
+@samp{--with-target-bdw-gc-lib=/opt/bdw-gc/lib64,32=/opt-bdw-gc/lib32}).
+If none of these options are specified, the library is assumed in
+default locations.
+@end table
+
+@subheading D-Specific Options
+
+The following options apply to the build of the D runtime library.
+
+@table @code
+@item --enable-libphobos-checking
+@itemx --disable-libphobos-checking
+@itemx --enable-libphobos-checking=@var{list}
+This option controls whether run-time checks and contracts are compiled into
+the D runtime library. When the option is not specified, the library is built
+with @samp{release} checking. When the option is specified without a
+@var{list}, the result is the same as @samp{--enable-libphobos-checking=yes}.
+Likewise, @samp{--disable-libphobos-checking} is equivalent to
+@samp{--enable-libphobos-checking=no}.
+
+The categories of checks available in @var{list} are @samp{yes} (compiles
+libphobos with @option{-fno-release}), @samp{no} (compiles libphobos with
+@option{-frelease}), @samp{all} (same as @samp{yes}), @samp{none} or
+@samp{release} (same as @samp{no}).
+
+Individual checks available in @var{list} are @samp{assert} (compiles libphobos
+with an extra option @option{-fassert}).
+
+@item --with-libphobos-druntime-only
+@itemx --with-libphobos-druntime-only=@var{choice}
+Specify whether to build only the core D runtime library (druntime), or both
+the core and standard library (phobos) into libphobos. This is useful for
+targets that have full support in druntime, but no or incomplete support
+in phobos. @var{choice} can be one of @samp{auto}, @samp{yes}, and @samp{no}
+where @samp{auto} is the default.
+
+When the option is not specified, the default choice @samp{auto} means that it
+is inferred whether the target has support for the phobos standard library.
+When the option is specified without a @var{choice}, the result is the same as
+@samp{--with-libphobos-druntime-only=yes}.
+
+@item --with-target-system-zlib
+Use installed @samp{zlib} rather than that included with GCC@. This needs
+to be available for each multilib variant, unless configured with
+@option{--with-target-system-zlib=@samp{auto}} in which case the GCC@ included
+@samp{zlib} is only used when the system installed library is not available.
+@end table
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***Building****************************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Building, Testing, Configuration, Installing GCC
+@end ifnothtml
+@ifset buildhtml
+@ifnothtml
+@chapter Building
+@end ifnothtml
+@cindex Installing GCC: Building
+
+Now that GCC is configured, you are ready to build the compiler and
+runtime libraries.
+
+Some commands executed when making the compiler may fail (return a
+nonzero status) and be ignored by @command{make}. These failures, which
+are often due to files that were not found, are expected, and can safely
+be ignored.
+
+It is normal to have compiler warnings when compiling certain files.
+Unless you are a GCC developer, you can generally ignore these warnings
+unless they cause compilation to fail. Developers should attempt to fix
+any warnings encountered, however they can temporarily continue past
+warnings-as-errors by specifying the configure flag
+@option{--disable-werror}.
+
+On certain old systems, defining certain environment variables such as
+@env{CC} can interfere with the functioning of @command{make}.
+
+If you encounter seemingly strange errors when trying to build the
+compiler in a directory other than the source directory, it could be
+because you have previously configured the compiler in the source
+directory. Make sure you have done all the necessary preparations.
+
+If you build GCC on a BSD system using a directory stored in an old System
+V file system, problems may occur in running @command{fixincludes} if the
+System V file system doesn't support symbolic links. These problems
+result in a failure to fix the declaration of @code{size_t} in
+@file{sys/types.h}. If you find that @code{size_t} is a signed type and
+that type mismatches occur, this could be the cause.
+
+The solution is not to use such a directory for building GCC@.
+
+Similarly, when building from the source repository or snapshots, or if you modify
+@file{*.l} files, you need the Flex lexical analyzer generator
+installed. If you do not modify @file{*.l} files, releases contain
+the Flex-generated files and you do not need Flex installed to build
+them. There is still one Flex-based lexical analyzer (part of the
+build machinery, not of GCC itself) that is used even if you only
+build the C front end.
+
+When building from the source repository or snapshots, or if you modify Texinfo
+documentation, you need version 4.7 or later of Texinfo installed if you
+want Info documentation to be regenerated. Releases contain Info
+documentation pre-built for the unmodified documentation in the release.
+
+@section Building a native compiler
+
+For a native build, the default configuration is to perform
+a 3-stage bootstrap of the compiler when @samp{make} is invoked.
+This will build the entire GCC system and ensure that it compiles
+itself correctly. It can be disabled with the @option{--disable-bootstrap}
+parameter to @samp{configure}, but bootstrapping is suggested because
+the compiler will be tested more completely and could also have
+better performance.
+
+The bootstrapping process will complete the following steps:
+
+@itemize @bullet
+@item
+Build tools necessary to build the compiler.
+
+@item
+Perform a 3-stage bootstrap of the compiler. This includes building
+three times the target tools for use by the compiler such as binutils
+(bfd, binutils, gas, gprof, ld, and opcodes) if they have been
+individually linked or moved into the top level GCC source tree before
+configuring.
+
+@item
+Perform a comparison test of the stage2 and stage3 compilers.
+
+@item
+Build runtime libraries using the stage3 compiler from the previous step.
+
+@end itemize
+
+If you are short on disk space you might consider @samp{make
+bootstrap-lean} instead. The sequence of compilation is the
+same described above, but object files from the stage1 and
+stage2 of the 3-stage bootstrap of the compiler are deleted as
+soon as they are no longer needed.
+
+If you wish to use non-default GCC flags when compiling the stage2
+and stage3 compilers, set @code{BOOT_CFLAGS} on the command line when
+doing @samp{make}. For example, if you want to save additional space
+during the bootstrap and in the final installation as well, you can
+build the compiler binaries without debugging information as in the
+following example. This will save roughly 40% of disk space both for
+the bootstrap and the final installation. (Libraries will still contain
+debugging information.)
+
+@smallexample
+make BOOT_CFLAGS='-O' bootstrap
+@end smallexample
+
+You can place non-default optimization flags into @code{BOOT_CFLAGS}; they
+are less well tested here than the default of @samp{-g -O2}, but should
+still work. In a few cases, you may find that you need to specify special
+flags such as @option{-msoft-float} here to complete the bootstrap; or,
+if the native compiler miscompiles the stage1 compiler, you may need
+to work around this, by choosing @code{BOOT_CFLAGS} to avoid the parts
+of the stage1 compiler that were miscompiled, or by using @samp{make
+bootstrap4} to increase the number of stages of bootstrap.
+
+@code{BOOT_CFLAGS} does not apply to bootstrapped target libraries.
+Since these are always compiled with the compiler currently being
+bootstrapped, you can use @code{CFLAGS_FOR_TARGET} to modify their
+compilation flags, as for non-bootstrapped target libraries.
+Again, if the native compiler miscompiles the stage1 compiler, you may
+need to work around this by avoiding non-working parts of the stage1
+compiler. Use @code{STAGE1_TFLAGS} to this end.
+
+If you used the flag @option{--enable-languages=@dots{}} to restrict
+the compilers to be built, only those you've actually enabled will be
+built. This will of course only build those runtime libraries, for
+which the particular compiler has been built. Please note,
+that re-defining @env{LANGUAGES} when calling @samp{make}
+@strong{does not} work anymore!
+
+If the comparison of stage2 and stage3 fails, this normally indicates
+that the stage2 compiler has compiled GCC incorrectly, and is therefore
+a potentially serious bug which you should investigate and report. (On
+a few systems, meaningful comparison of object files is impossible; they
+always appear ``different''. If you encounter this problem, you will
+need to disable comparison in the @file{Makefile}.)
+
+If you do not want to bootstrap your compiler, you can configure with
+@option{--disable-bootstrap}. In particular cases, you may want to
+bootstrap your compiler even if the target system is not the same as
+the one you are building on: for example, you could build a
+@code{powerpc-unknown-linux-gnu} toolchain on a
+@code{powerpc64-unknown-linux-gnu} host. In this case, pass
+@option{--enable-bootstrap} to the configure script.
+
+@code{BUILD_CONFIG} can be used to bring in additional customization
+to the build. It can be set to a whitespace-separated list of names.
+For each such @code{NAME}, top-level @file{config/@code{NAME}.mk} will
+be included by the top-level @file{Makefile}, bringing in any settings
+it contains. The default @code{BUILD_CONFIG} can be set using the
+configure option @option{--with-build-config=@code{NAME}...}. Some
+examples of supported build configurations are:
+
+@table @asis
+@item @samp{bootstrap-O1}
+Removes any @option{-O}-started option from @code{BOOT_CFLAGS}, and adds
+@option{-O1} to it. @samp{BUILD_CONFIG=bootstrap-O1} is equivalent to
+@samp{BOOT_CFLAGS='-g -O1'}.
+
+@item @samp{bootstrap-O3}
+@itemx @samp{bootstrap-Og}
+Analogous to @code{bootstrap-O1}.
+
+@item @samp{bootstrap-lto}
+Enables Link-Time Optimization for host tools during bootstrapping.
+@samp{BUILD_CONFIG=bootstrap-lto} is equivalent to adding
+@option{-flto} to @samp{BOOT_CFLAGS}. This option assumes that the host
+supports the linker plugin (e.g.@: GNU ld version 2.21 or later or GNU gold
+version 2.21 or later).
+
+@item @samp{bootstrap-lto-noplugin}
+This option is similar to @code{bootstrap-lto}, but is intended for
+hosts that do not support the linker plugin. Without the linker plugin
+static libraries are not compiled with link-time optimizations. Since
+the GCC middle end and back end are in @file{libbackend.a} this means
+that only the front end is actually LTO optimized.
+
+@item @samp{bootstrap-lto-lean}
+This option is similar to @code{bootstrap-lto}, but is intended for
+faster build by only using LTO in the final bootstrap stage.
+With @samp{make profiledbootstrap} the LTO frontend
+is trained only on generator files.
+
+@item @samp{bootstrap-debug}
+Verifies that the compiler generates the same executable code, whether
+or not it is asked to emit debug information. To this end, this
+option builds stage2 host programs without debug information, and uses
+@file{contrib/compare-debug} to compare them with the stripped stage3
+object files. If @code{BOOT_CFLAGS} is overridden so as to not enable
+debug information, stage2 will have it, and stage3 won't. This option
+is enabled by default when GCC bootstrapping is enabled, if
+@code{strip} can turn object files compiled with and without debug
+info into identical object files. In addition to better test
+coverage, this option makes default bootstraps faster and leaner.
+
+@item @samp{bootstrap-debug-big}
+Rather than comparing stripped object files, as in
+@code{bootstrap-debug}, this option saves internal compiler dumps
+during stage2 and stage3 and compares them as well, which helps catch
+additional potential problems, but at a great cost in terms of disk
+space. It can be specified in addition to @samp{bootstrap-debug}.
+
+@item @samp{bootstrap-debug-lean}
+This option saves disk space compared with @code{bootstrap-debug-big},
+but at the expense of some recompilation. Instead of saving the dumps
+of stage2 and stage3 until the final compare, it uses
+@option{-fcompare-debug} to generate, compare and remove the dumps
+during stage3, repeating the compilation that already took place in
+stage2, whose dumps were not saved.
+
+@item @samp{bootstrap-debug-lib}
+This option tests executable code invariance over debug information
+generation on target libraries, just like @code{bootstrap-debug-lean}
+tests it on host programs. It builds stage3 libraries with
+@option{-fcompare-debug}, and it can be used along with any of the
+@code{bootstrap-debug} options above.
+
+There aren't @code{-lean} or @code{-big} counterparts to this option
+because most libraries are only build in stage3, so bootstrap compares
+would not get significant coverage. Moreover, the few libraries built
+in stage2 are used in stage3 host programs, so we wouldn't want to
+compile stage2 libraries with different options for comparison purposes.
+
+@item @samp{bootstrap-debug-ckovw}
+Arranges for error messages to be issued if the compiler built on any
+stage is run without the option @option{-fcompare-debug}. This is
+useful to verify the full @option{-fcompare-debug} testing coverage. It
+must be used along with @code{bootstrap-debug-lean} and
+@code{bootstrap-debug-lib}.
+
+@item @samp{bootstrap-cet}
+This option enables Intel CET for host tools during bootstrapping.
+@samp{BUILD_CONFIG=bootstrap-cet} is equivalent to adding
+@option{-fcf-protection} to @samp{BOOT_CFLAGS}. This option
+assumes that the host supports Intel CET (e.g.@: GNU assembler version
+2.30 or later).
+
+@item @samp{bootstrap-time}
+Arranges for the run time of each program started by the GCC driver,
+built in any stage, to be logged to @file{time.log}, in the top level of
+the build tree.
+
+@item @samp{bootstrap-asan}
+Compiles GCC itself using Address Sanitization in order to catch invalid memory
+accesses within the GCC code.
+
+@item @samp{bootstrap-hwasan}
+Compiles GCC itself using HWAddress Sanitization in order to catch invalid
+memory accesses within the GCC code. This option is only available on AArch64
+systems that are running Linux kernel version 5.4 or later.
+
+@end table
+
+@section Building a cross compiler
+
+When building a cross compiler, it is not generally possible to do a
+3-stage bootstrap of the compiler. This makes for an interesting problem
+as parts of GCC can only be built with GCC@.
+
+To build a cross compiler, we recommend first building and installing a
+native compiler. You can then use the native GCC compiler to build the
+cross compiler. The installed native compiler needs to be GCC version
+2.95 or later.
+
+Assuming you have already installed a native copy of GCC and configured
+your cross compiler, issue the command @command{make}, which performs the
+following steps:
+
+@itemize @bullet
+@item
+Build host tools necessary to build the compiler.
+
+@item
+Build target tools for use by the compiler such as binutils (bfd,
+binutils, gas, gprof, ld, and opcodes)
+if they have been individually linked or moved into the top level GCC source
+tree before configuring.
+
+@item
+Build the compiler (single stage only).
+
+@item
+Build runtime libraries using the compiler from the previous step.
+@end itemize
+
+Note that if an error occurs in any step the make process will exit.
+
+If you are not building GNU binutils in the same source tree as GCC,
+you will need a cross-assembler and cross-linker installed before
+configuring GCC@. Put them in the directory
+@file{@var{prefix}/@var{target}/bin}. Here is a table of the tools
+you should put in this directory:
+
+@table @file
+@item as
+This should be the cross-assembler.
+
+@item ld
+This should be the cross-linker.
+
+@item ar
+This should be the cross-archiver: a program which can manipulate
+archive files (linker libraries) in the target machine's format.
+
+@item ranlib
+This should be a program to construct a symbol table in an archive file.
+@end table
+
+The installation of GCC will find these programs in that directory,
+and copy or link them to the proper place to for the cross-compiler to
+find them when run later.
+
+The easiest way to provide these files is to build the Binutils package.
+Configure it with the same @option{--host} and @option{--target}
+options that you use for configuring GCC, then build and install
+them. They install their executables automatically into the proper
+directory. Alas, they do not support all the targets that GCC
+supports.
+
+If you are not building a C library in the same source tree as GCC,
+you should also provide the target libraries and headers before
+configuring GCC, specifying the directories with
+@option{--with-sysroot} or @option{--with-headers} and
+@option{--with-libs}. Many targets also require ``start files'' such
+as @file{crt0.o} and
+@file{crtn.o} which are linked into each executable. There may be several
+alternatives for @file{crt0.o}, for use with profiling or other
+compilation options. Check your target's definition of
+@code{STARTFILE_SPEC} to find out what start files it uses.
+
+@section Building in parallel
+
+GNU Make 3.80 and above, which is necessary to build GCC, support
+building in parallel. To activate this, you can use @samp{make -j 2}
+instead of @samp{make}. You can also specify a bigger number, and
+in most cases using a value greater than the number of processors in
+your machine will result in fewer and shorter I/O latency hits, thus
+improving overall throughput; this is especially true for slow drives
+and network filesystems.
+
+@section Building the Ada compiler
+
+@ifnothtml
+@ref{GNAT-prerequisite}.
+@end ifnothtml
+@ifhtml
+@uref{prerequisites.html#GNAT-prerequisite,,GNAT prerequisites}.
+@end ifhtml
+
+@section Building the D compiler
+
+@ifnothtml
+@ref{GDC-prerequisite}.
+@end ifnothtml
+@ifhtml
+@uref{prerequisites.html#GDC-prerequisite,,GDC prerequisites}.
+@end ifhtml
+
+@section Building with profile feedback
+
+It is possible to use profile feedback to optimize the compiler itself. This
+should result in a faster compiler binary. Experiments done on x86 using gcc
+3.3 showed approximately 7 percent speedup on compiling C programs. To
+bootstrap the compiler with profile feedback, use @code{make profiledbootstrap}.
+
+When @samp{make profiledbootstrap} is run, it will first build a @code{stage1}
+compiler. This compiler is used to build a @code{stageprofile} compiler
+instrumented to collect execution counts of instruction and branch
+probabilities. Training run is done by building @code{stagetrain}
+compiler. Finally a @code{stagefeedback} compiler is built
+using the information collected.
+
+Unlike standard bootstrap, several additional restrictions apply. The
+compiler used to build @code{stage1} needs to support a 64-bit integral type.
+It is recommended to only use GCC for this.
+
+On Linux/x86_64 hosts with some restrictions (no virtualization) it is
+also possible to do autofdo build with @samp{make
+autoprofiledback}. This uses Linux perf to sample branches in the
+binary and then rebuild it with feedback derived from the profile.
+Linux perf and the @code{autofdo} toolkit needs to be installed for
+this.
+
+Only the profile from the current build is used, so when an error
+occurs it is recommended to clean before restarting. Otherwise
+the code quality may be much worse.
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***Testing*****************************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Testing, Final install, Building, Installing GCC
+@end ifnothtml
+@ifset testhtml
+@ifnothtml
+@chapter Installing GCC: Testing
+@end ifnothtml
+@cindex Testing
+@cindex Installing GCC: Testing
+@cindex Testsuite
+
+Before you install GCC, we encourage you to run the testsuites and to
+compare your results with results from a similar configuration that have
+been submitted to the
+@uref{https://gcc.gnu.org/ml/gcc-testresults/,,gcc-testresults mailing list}.
+Some of these archived results are linked from the build status lists
+at @uref{https://gcc.gnu.org/buildstat.html}, although not everyone who
+reports a successful build runs the testsuites and submits the results.
+This step is optional and may require you to download additional software,
+but it can give you confidence in your new GCC installation or point out
+problems before you install and start using your new GCC@.
+
+First, you must have @uref{download.html,,downloaded the testsuites}.
+These are part of the full distribution, but if you downloaded the
+``core'' compiler plus any front ends, you must download the testsuites
+separately.
+
+Second, you must have the testing tools installed. This includes
+@uref{https://www.gnu.org/software/dejagnu/,,DejaGnu}, Tcl, and Expect;
+the DejaGnu site has links to these.
+Some optional tests also require Python3 and pytest module.
+
+If the directories where @command{runtest} and @command{expect} were
+installed are not in the @env{PATH}, you may need to set the following
+environment variables appropriately, as in the following example (which
+assumes that DejaGnu has been installed under @file{/usr/local}):
+
+@smallexample
+TCL_LIBRARY = /usr/local/share/tcl8.0
+DEJAGNULIBS = /usr/local/share/dejagnu
+@end smallexample
+
+(On systems such as Cygwin, these paths are required to be actual
+paths, not mounts or links; presumably this is due to some lack of
+portability in the DejaGnu code.)
+
+
+Finally, you can run the testsuite (which may take a long time):
+@smallexample
+cd @var{objdir}; make -k check
+@end smallexample
+
+This will test various components of GCC, such as compiler
+front ends and runtime libraries. While running the testsuite, DejaGnu
+might emit some harmless messages resembling
+@samp{WARNING: Couldn't find the global config file.} or
+@samp{WARNING: Couldn't find tool init file} that can be ignored.
+
+If you are testing a cross-compiler, you may want to run the testsuite
+on a simulator as described at @uref{https://gcc.gnu.org/simtest-howto.html}.
+
+@section How can you run the testsuite on selected tests?
+
+In order to run sets of tests selectively, there are targets
+@samp{make check-gcc} and language specific @samp{make check-c},
+@samp{make check-c++}, @samp{make check-d} @samp{make check-fortran},
+@samp{make check-ada}, @samp{make check-objc}, @samp{make check-obj-c++},
+@samp{make check-lto}
+in the @file{gcc} subdirectory of the object directory. You can also
+just run @samp{make check} in a subdirectory of the object directory.
+
+
+A more selective way to just run all @command{gcc} execute tests in the
+testsuite is to use
+
+@smallexample
+make check-gcc RUNTESTFLAGS="execute.exp @var{other-options}"
+@end smallexample
+
+Likewise, in order to run only the @command{g++} ``old-deja'' tests in
+the testsuite with filenames matching @samp{9805*}, you would use
+
+@smallexample
+make check-g++ RUNTESTFLAGS="old-deja.exp=9805* @var{other-options}"
+@end smallexample
+
+The file-matching expression following @var{filename}@command{.exp=} is treated
+as a series of whitespace-delimited glob expressions so that multiple patterns
+may be passed, although any whitespace must either be escaped or surrounded by
+single quotes if multiple expressions are desired. For example,
+
+@smallexample
+make check-g++ RUNTESTFLAGS="old-deja.exp=9805*\ virtual2.c @var{other-options}"
+make check-g++ RUNTESTFLAGS="'old-deja.exp=9805* virtual2.c' @var{other-options}"
+@end smallexample
+
+The @file{*.exp} files are located in the testsuite directories of the GCC
+source, the most important ones being @file{compile.exp},
+@file{execute.exp}, @file{dg.exp} and @file{old-deja.exp}.
+To get a list of the possible @file{*.exp} files, pipe the
+output of @samp{make check} into a file and look at the
+@samp{Running @dots{} .exp} lines.
+
+@section Passing options and running multiple testsuites
+
+You can pass multiple options to the testsuite using the
+@samp{--target_board} option of DejaGNU, either passed as part of
+@samp{RUNTESTFLAGS}, or directly to @command{runtest} if you prefer to
+work outside the makefiles. For example,
+
+@smallexample
+make check-g++ RUNTESTFLAGS="--target_board=unix/-O3/-fmerge-constants"
+@end smallexample
+
+will run the standard @command{g++} testsuites (``unix'' is the target name
+for a standard native testsuite situation), passing
+@samp{-O3 -fmerge-constants} to the compiler on every test, i.e.,
+slashes separate options.
+
+You can run the testsuites multiple times using combinations of options
+with a syntax similar to the brace expansion of popular shells:
+
+@smallexample
+@dots{}"--target_board=arm-sim\@{-mhard-float,-msoft-float\@}\@{-O1,-O2,-O3,\@}"
+@end smallexample
+
+(Note the empty option caused by the trailing comma in the final group.)
+The following will run each testsuite eight times using the @samp{arm-sim}
+target, as if you had specified all possible combinations yourself:
+
+@smallexample
+--target_board='arm-sim/-mhard-float/-O1 \
+ arm-sim/-mhard-float/-O2 \
+ arm-sim/-mhard-float/-O3 \
+ arm-sim/-mhard-float \
+ arm-sim/-msoft-float/-O1 \
+ arm-sim/-msoft-float/-O2 \
+ arm-sim/-msoft-float/-O3 \
+ arm-sim/-msoft-float'
+@end smallexample
+
+They can be combined as many times as you wish, in arbitrary ways. This
+list:
+
+@smallexample
+@dots{}"--target_board=unix/-Wextra\@{-O3,-fno-strength\@}\@{-fomit-frame,\@}"
+@end smallexample
+
+will generate four combinations, all involving @samp{-Wextra}.
+
+The disadvantage to this method is that the testsuites are run in serial,
+which is a waste on multiprocessor systems. For users with GNU Make and
+a shell which performs brace expansion, you can run the testsuites in
+parallel by having the shell perform the combinations and @command{make}
+do the parallel runs. Instead of using @samp{--target_board}, use a
+special makefile target:
+
+@smallexample
+make -j@var{N} check-@var{testsuite}//@var{test-target}/@var{option1}/@var{option2}/@dots{}
+@end smallexample
+
+For example,
+
+@smallexample
+make -j3 check-gcc//sh-hms-sim/@{-m1,-m2,-m3,-m3e,-m4@}/@{,-nofpu@}
+@end smallexample
+
+will run three concurrent ``make-gcc'' testsuites, eventually testing all
+ten combinations as described above. Note that this is currently only
+supported in the @file{gcc} subdirectory. (To see how this works, try
+typing @command{echo} before the example given here.)
+
+
+@section How to interpret test results
+
+The result of running the testsuite are various @file{*.sum} and @file{*.log}
+files in the testsuite subdirectories. The @file{*.log} files contain a
+detailed log of the compiler invocations and the corresponding
+results, the @file{*.sum} files summarize the results. These summaries
+contain status codes for all tests:
+
+@itemize @bullet
+@item
+PASS: the test passed as expected
+@item
+XPASS: the test unexpectedly passed
+@item
+FAIL: the test unexpectedly failed
+@item
+XFAIL: the test failed as expected
+@item
+UNSUPPORTED: the test is not supported on this platform
+@item
+ERROR: the testsuite detected an error
+@item
+WARNING: the testsuite detected a possible problem
+@end itemize
+
+It is normal for some tests to report unexpected failures. At the
+current time the testing harness does not allow fine grained control
+over whether or not a test is expected to fail. This problem should
+be fixed in future releases.
+
+
+@section Submitting test results
+
+If you want to report the results to the GCC project, use the
+@file{contrib/test_summary} shell script. Start it in the @var{objdir} with
+
+@smallexample
+@var{srcdir}/contrib/test_summary -p your_commentary.txt \
+ -m gcc-testresults@@gcc.gnu.org |sh
+@end smallexample
+
+This script uses the @command{Mail} program to send the results, so
+make sure it is in your @env{PATH}. The file @file{your_commentary.txt} is
+prepended to the testsuite summary and should contain any special
+remarks you have on your results or your build environment. Please
+do not edit the testsuite result block or the subject line, as these
+messages may be automatically processed.
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***Final install***********************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Final install, , Testing, Installing GCC
+@end ifnothtml
+@ifset finalinstallhtml
+@ifnothtml
+@chapter Installing GCC: Final installation
+@end ifnothtml
+
+Now that GCC has been built (and optionally tested), you can install it with
+@smallexample
+cd @var{objdir} && make install
+@end smallexample
+
+We strongly recommend to install into a target directory where there is
+no previous version of GCC present. Also, the GNAT runtime should not
+be stripped, as this would break certain features of the debugger that
+depend on this debugging information (catching Ada exceptions for
+instance).
+
+That step completes the installation of GCC; user level binaries can
+be found in @file{@var{prefix}/bin} where @var{prefix} is the value
+you specified with the @option{--prefix} to configure (or
+@file{/usr/local} by default). (If you specified @option{--bindir},
+that directory will be used instead; otherwise, if you specified
+@option{--exec-prefix}, @file{@var{exec-prefix}/bin} will be used.)
+Headers for the C++ library are installed in
+@file{@var{prefix}/include}; libraries in @file{@var{libdir}}
+(normally @file{@var{prefix}/lib}); internal parts of the compiler in
+@file{@var{libdir}/gcc} and @file{@var{libexecdir}/gcc}; documentation
+in info format in @file{@var{infodir}} (normally
+@file{@var{prefix}/info}).
+
+When installing cross-compilers, GCC's executables
+are not only installed into @file{@var{bindir}}, that
+is, @file{@var{exec-prefix}/bin}, but additionally into
+@file{@var{exec-prefix}/@var{target-alias}/bin}, if that directory
+exists. Typically, such @dfn{tooldirs} hold target-specific
+binutils, including assembler and linker.
+
+Installation into a temporary staging area or into a @command{chroot}
+jail can be achieved with the command
+
+@smallexample
+make DESTDIR=@var{path-to-rootdir} install
+@end smallexample
+
+@noindent
+where @var{path-to-rootdir} is the absolute path of
+a directory relative to which all installation paths will be
+interpreted. Note that the directory specified by @code{DESTDIR}
+need not exist yet; it will be created if necessary.
+
+There is a subtle point with tooldirs and @code{DESTDIR}:
+If you relocate a cross-compiler installation with
+e.g.@: @samp{DESTDIR=@var{rootdir}}, then the directory
+@file{@var{rootdir}/@var{exec-prefix}/@var{target-alias}/bin} will
+be filled with duplicated GCC executables only if it already exists,
+it will not be created otherwise. This is regarded as a feature,
+not as a bug, because it gives slightly more control to the packagers
+using the @code{DESTDIR} feature.
+
+You can install stripped programs and libraries with
+
+@smallexample
+make install-strip
+@end smallexample
+
+If you are bootstrapping a released version of GCC then please
+quickly review the build status page for your release, available from
+@uref{https://gcc.gnu.org/buildstat.html}.
+If your system is not listed for the version of GCC that you built,
+send a note to
+@email{gcc@@gcc.gnu.org} indicating
+that you successfully built and installed GCC@.
+Include the following information:
+
+@itemize @bullet
+@item
+Output from running @file{@var{srcdir}/config.guess}. Do not send
+that file itself, just the one-line output from running it.
+
+@item
+The output of @samp{gcc -v} for your newly installed @command{gcc}.
+This tells us which version of GCC you built and the options you passed to
+configure.
+
+@item
+Whether you enabled all languages or a subset of them. If you used a
+full distribution then this information is part of the configure
+options in the output of @samp{gcc -v}, but if you downloaded the
+``core'' compiler plus additional front ends then it isn't apparent
+which ones you built unless you tell us about it.
+
+@item
+If the build was for GNU/Linux, also include:
+@itemize @bullet
+@item
+The distribution name and version (e.g., Red Hat 7.1 or Debian 2.2.3);
+this information should be available from @file{/etc/issue}.
+
+@item
+The version of the Linux kernel, available from @samp{uname --version}
+or @samp{uname -a}.
+
+@item
+The version of glibc you used; for RPM-based systems like Red Hat,
+Mandrake, and SuSE type @samp{rpm -q glibc} to get the glibc version,
+and on systems like Debian and Progeny use @samp{dpkg -l libc6}.
+@end itemize
+For other systems, you can include similar information if you think it is
+relevant.
+
+@item
+Any other information that you think would be useful to people building
+GCC on the same configuration. The new entry in the build status list
+will include a link to the archived copy of your message.
+@end itemize
+
+We'd also like to know if the
+@ifnothtml
+@ref{Specific, host/target specific installation notes}
+@end ifnothtml
+@ifhtml
+@uref{specific.html,,host/target specific installation notes}
+@end ifhtml
+didn't include your host/target information or if that information is
+incomplete or out of date. Send a note to
+@email{gcc@@gcc.gnu.org} detailing how the information should be changed.
+
+If you find a bug, please report it following the
+@uref{../bugs/,,bug reporting guidelines}.
+
+If you want to print the GCC manuals, do @samp{cd @var{objdir}; make
+dvi}. You will need to have @command{texi2dvi} (version at least 4.7)
+and @TeX{} installed. This creates a number of @file{.dvi} files in
+subdirectories of @file{@var{objdir}}; these may be converted for
+printing with programs such as @command{dvips}. Alternately, by using
+@samp{make pdf} in place of @samp{make dvi}, you can create documentation
+in the form of @file{.pdf} files; this requires @command{texi2pdf}, which
+is included with Texinfo version 4.8 and later. You can also
+@uref{https://shop.fsf.org/,,buy printed manuals from the
+Free Software Foundation}, though such manuals may not be for the most
+recent version of GCC@.
+
+If you would like to generate online HTML documentation, do @samp{cd
+@var{objdir}; make html} and HTML will be generated for the gcc manuals in
+@file{@var{objdir}/gcc/HTML}.
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***Binaries****************************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Binaries, Specific, Installing GCC, Top
+@end ifnothtml
+@ifset binarieshtml
+@ifnothtml
+@chapter Installing GCC: Binaries
+@end ifnothtml
+@cindex Binaries
+@cindex Installing GCC: Binaries
+
+We are often asked about pre-compiled versions of GCC@. While we cannot
+provide these for all platforms, below you'll find links to binaries for
+various platforms where creating them by yourself is not easy due to various
+reasons.
+
+Please note that we did not create these binaries, nor do we
+support them. If you have any problems installing them, please
+contact their makers.
+
+@itemize
+@item
+AIX:
+@itemize
+@item
+@uref{http://www.perzl.org/aix/,,AIX Open Source Packages (AIX5L AIX 6.1
+AIX 7.1)}.
+@end itemize
+
+@item
+DOS---@uref{http://www.delorie.com/djgpp/,,DJGPP}.
+
+@item
+HP-UX:
+@itemize
+@item
+@uref{http://hpux.connect.org.uk/,,HP-UX Porting Center};
+@end itemize
+
+@item
+Solaris 2 (SPARC, Intel):
+@itemize
+@item
+@uref{https://www.opencsw.org/,,OpenCSW}
+@end itemize
+
+@item
+macOS:
+@itemize
+@item
+The @uref{https://brew.sh,,Homebrew} package manager;
+@item
+@uref{https://www.macports.org,,MacPorts}.
+@end itemize
+
+@item
+Microsoft Windows:
+@itemize
+@item
+The @uref{https://sourceware.org/cygwin/,,Cygwin} project;
+@item
+The @uref{https://osdn.net/projects/mingw/,,MinGW} and
+@uref{https://www.mingw-w64.org/,,mingw-w64} projects.
+@end itemize
+
+@item
+@uref{http://www.openpkg.org/,,OpenPKG} offers binaries for quite a
+number of platforms.
+
+@item
+The @uref{https://gcc.gnu.org/wiki/GFortranBinaries,,GFortran Wiki} has
+links to GNU Fortran binaries for several platforms.
+@end itemize
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***Specific****************************************************************
+@ifnothtml
+@comment node-name, next, previous, up
+@node Specific, GNU Free Documentation License, Binaries, Top
+@end ifnothtml
+@ifset specifichtml
+@ifnothtml
+@chapter Host/target specific installation notes for GCC
+@end ifnothtml
+@cindex Specific
+@cindex Specific installation notes
+@cindex Target specific installation
+@cindex Host specific installation
+@cindex Target specific installation notes
+
+Please read this document carefully @emph{before} installing the
+GNU Compiler Collection on your machine.
+
+Note that this list of install notes is @emph{not} a list of supported
+hosts or targets. Not all supported hosts and targets are listed
+here, only the ones that require host-specific or target-specific
+information have to.
+
+@ifhtml
+@itemize
+@item
+@uref{#aarch64-x-x,,aarch64*-*-*}
+@item
+@uref{#alpha-x-x,,alpha*-*-*}
+@item
+@uref{#amdgcn-x-amdhsa,,amdgcn-*-amdhsa}
+@item
+@uref{#amd64-x-solaris2,,amd64-*-solaris2*}
+@item
+@uref{#arc-x-elf32,,arc-*-elf32}
+@item
+@uref{#arc-linux-uclibc,,arc-linux-uclibc}
+@item
+@uref{#arm-x-eabi,,arm-*-eabi}
+@item
+@uref{#avr,,avr}
+@item
+@uref{#bfin,,Blackfin}
+@item
+@uref{#cris,,cris}
+@item
+@uref{#dos,,DOS}
+@item
+@uref{#epiphany-x-elf,,epiphany-*-elf}
+@item
+@uref{#ft32-x-elf,,ft32-*-elf}
+@item
+@uref{#x-x-freebsd,,*-*-freebsd*}
+@item
+@uref{#h8300-hms,,h8300-hms}
+@item
+@uref{#hppa-hp-hpux,,hppa*-hp-hpux*}
+@item
+@uref{#hppa-hp-hpux10,,hppa*-hp-hpux10}
+@item
+@uref{#hppa-hp-hpux11,,hppa*-hp-hpux11}
+@item
+@uref{#x-x-linux-gnu,,*-*-linux-gnu}
+@item
+@uref{#ix86-x-linux,,i?86-*-linux*}
+@item
+@uref{#ix86-x-solaris2,,i?86-*-solaris2*}
+@item
+@uref{#ia64-x-linux,,ia64-*-linux}
+@item
+@uref{#ia64-x-hpux,,ia64-*-hpux*}
+@item
+@uref{#x-ibm-aix,,*-ibm-aix*}
+@item
+@uref{#iq2000-x-elf,,iq2000-*-elf}
+@item
+@uref{#loongarch,,loongarch}
+@item
+@uref{#lm32-x-elf,,lm32-*-elf}
+@item
+@uref{#lm32-x-uclinux,,lm32-*-uclinux}
+@item
+@uref{#m32c-x-elf,,m32c-*-elf}
+@item
+@uref{#m32r-x-elf,,m32r-*-elf}
+@item
+@uref{#m68k-x-x,,m68k-*-*}
+@item
+@uref{#m68k-x-uclinux,,m68k-*-uclinux}
+@item
+@uref{#microblaze-x-elf,,microblaze-*-elf}
+@item
+@uref{#mips-x-x,,mips-*-*}
+@item
+@uref{#moxie-x-elf,,moxie-*-elf}
+@item
+@uref{#msp430-x-elf,,msp430-*-elf}
+@item
+@uref{#nds32le-x-elf,,nds32le-*-elf}
+@item
+@uref{#nds32be-x-elf,,nds32be-*-elf}
+@item
+@uref{#nvptx-x-none,,nvptx-*-none}
+@item
+@uref{#or1k-x-elf,,or1k-*-elf}
+@item
+@uref{#or1k-x-linux,,or1k-*-linux}
+@item
+@uref{#powerpc-x-x,,powerpc*-*-*}
+@item
+@uref{#powerpc-x-darwin,,powerpc-*-darwin*}
+@item
+@uref{#powerpc-x-elf,,powerpc-*-elf}
+@item
+@uref{#powerpc-x-linux-gnu,,powerpc*-*-linux-gnu*}
+@item
+@uref{#powerpc-x-netbsd,,powerpc-*-netbsd*}
+@item
+@uref{#powerpc-x-eabisim,,powerpc-*-eabisim}
+@item
+@uref{#powerpc-x-eabi,,powerpc-*-eabi}
+@item
+@uref{#powerpcle-x-elf,,powerpcle-*-elf}
+@item
+@uref{#powerpcle-x-eabisim,,powerpcle-*-eabisim}
+@item
+@uref{#powerpcle-x-eabi,,powerpcle-*-eabi}
+@item
+@uref{#riscv32-x-elf,,riscv32-*-elf}
+@item
+@uref{#riscv32-x-linux,,riscv32-*-linux}
+@item
+@uref{#riscv64-x-elf,,riscv64-*-elf}
+@item
+@uref{#riscv64-x-linux,,riscv64-*-linux}
+@item
+@uref{#rl78-x-elf,,rl78-*-elf}
+@item
+@uref{#rx-x-elf,,rx-*-elf}
+@item
+@uref{#s390-x-linux,,s390-*-linux*}
+@item
+@uref{#s390x-x-linux,,s390x-*-linux*}
+@item
+@uref{#s390x-ibm-tpf,,s390x-ibm-tpf*}
+@item
+@uref{#x-x-solaris2,,*-*-solaris2*}
+@item
+@uref{#sparc-x-x,,sparc*-*-*}
+@item
+@uref{#sparc-sun-solaris2,,sparc-sun-solaris2*}
+@item
+@uref{#sparc-x-linux,,sparc-*-linux*}
+@item
+@uref{#sparc64-x-solaris2,,sparc64-*-solaris2*}
+@item
+@uref{#sparcv9-x-solaris2,,sparcv9-*-solaris2*}
+@item
+@uref{#c6x-x-x,,c6x-*-*}
+@item
+@uref{#visium-x-elf, visium-*-elf}
+@item
+@uref{#x-x-vxworks,,*-*-vxworks*}
+@item
+@uref{#x86-64-x-x,,x86_64-*-*, amd64-*-*}
+@item
+@uref{#x86-64-x-solaris2,,x86_64-*-solaris2*}
+@item
+@uref{#xtensa-x-elf,,xtensa*-*-elf}
+@item
+@uref{#xtensa-x-linux,,xtensa*-*-linux*}
+@item
+@uref{#windows,,Microsoft Windows}
+@item
+@uref{#x-x-cygwin,,*-*-cygwin}
+@item
+@uref{#x-x-mingw32,,*-*-mingw32}
+@item
+@uref{#os2,,OS/2}
+@item
+@uref{#older,,Older systems}
+@end itemize
+
+@itemize
+@item
+@uref{#elf,,all ELF targets} (SVR4, Solaris 2, etc.)
+@end itemize
+@end ifhtml
+
+
+@html
+<!-- -------- host/target specific issues start here ---------------- -->
+<hr />
+@end html
+@anchor{aarch64-x-x}
+@heading aarch64*-*-*
+Binutils pre 2.24 does not have support for selecting @option{-mabi} and
+does not support ILP32. If it is used to build GCC 4.9 or later, GCC will
+not support option @option{-mabi=ilp32}.
+
+To enable a workaround for the Cortex-A53 erratum number 835769 by default
+(for all CPUs regardless of -mcpu option given) at configure time use the
+@option{--enable-fix-cortex-a53-835769} option. This will enable the fix by
+default and can be explicitly disabled during compilation by passing the
+@option{-mno-fix-cortex-a53-835769} option. Conversely,
+@option{--disable-fix-cortex-a53-835769} will disable the workaround by
+default. The workaround is disabled by default if neither of
+@option{--enable-fix-cortex-a53-835769} or
+@option{--disable-fix-cortex-a53-835769} is given at configure time.
+
+To enable a workaround for the Cortex-A53 erratum number 843419 by default
+(for all CPUs regardless of -mcpu option given) at configure time use the
+@option{--enable-fix-cortex-a53-843419} option. This workaround is applied at
+link time. Enabling the workaround will cause GCC to pass the relevant option
+to the linker. It can be explicitly disabled during compilation by passing the
+@option{-mno-fix-cortex-a53-843419} option. Conversely,
+@option{--disable-fix-cortex-a53-843419} will disable the workaround by default.
+The workaround is disabled by default if neither of
+@option{--enable-fix-cortex-a53-843419} or
+@option{--disable-fix-cortex-a53-843419} is given at configure time.
+
+To enable Branch Target Identification Mechanism and Return Address Signing by
+default at configure time use the @option{--enable-standard-branch-protection}
+option. This is equivalent to having @option{-mbranch-protection=standard}
+during compilation. This can be explicitly disabled during compilation by
+passing the @option{-mbranch-protection=none} option which turns off all
+types of branch protections. Conversely,
+@option{--disable-standard-branch-protection} will disable both the
+protections by default. This mechanism is turned off by default if neither
+of the options are given at configure time.
+
+@html
+<hr />
+@end html
+@anchor{alpha-x-x}
+@heading alpha*-*-*
+This section contains general configuration information for all
+Alpha-based platforms using ELF@. In addition to reading this
+section, please read all other sections that match your target.
+
+@html
+<hr />
+@end html
+@anchor{amd64-x-solaris2}
+@heading amd64-*-solaris2*
+This is a synonym for @samp{x86_64-*-solaris2*}.
+
+@html
+<hr />
+@end html
+@anchor{amdgcn-x-amdhsa}
+@heading amdgcn-*-amdhsa
+AMD GCN GPU target.
+
+Instead of GNU Binutils, you will need to install LLVM 13.0.1, or later, and copy
+@file{bin/llvm-mc} to @file{amdgcn-amdhsa/bin/as},
+@file{bin/lld} to @file{amdgcn-amdhsa/bin/ld},
+@file{bin/llvm-nm} to @file{amdgcn-amdhsa/bin/nm}, and
+@file{bin/llvm-ar} to both @file{bin/amdgcn-amdhsa-ar} and
+@file{bin/amdgcn-amdhsa-ranlib}.
+
+Use Newlib (3.2.0, or newer).
+
+To run the binaries, install the HSA Runtime from the
+@uref{https://rocm.github.io,,ROCm Platform}, and use
+@file{libexec/gcc/amdhsa-amdhsa/@var{version}/gcn-run} to launch them
+on the GPU.
+
+@html
+<hr />
+@end html
+@anchor{arc-x-elf32}
+@heading arc-*-elf32
+
+Use @samp{configure --target=arc-elf32 --with-cpu=@var{cpu} --enable-languages="c,c++"}
+to configure GCC, with @var{cpu} being one of @samp{arc600}, @samp{arc601},
+or @samp{arc700}@.
+
+@html
+<hr />
+@end html
+@anchor{arc-linux-uclibc}
+@heading arc-linux-uclibc
+
+Use @samp{configure --target=arc-linux-uclibc --with-cpu=arc700 --enable-languages="c,c++"} to configure GCC@.
+
+@html
+<hr />
+@end html
+@anchor{arm-x-eabi}
+@heading arm-*-eabi
+ARM-family processors.
+
+Building the Ada frontend commonly fails (an infinite loop executing
+@code{xsinfo}) if the host compiler is GNAT 4.8. Host compilers built from the
+GNAT 4.6, 4.9 or 5 release branches are known to succeed.
+
+@html
+<hr />
+@end html
+@anchor{avr}
+@heading avr
+ATMEL AVR-family micro controllers. These are used in embedded
+applications. There are no standard Unix configurations.
+@ifnothtml
+@xref{AVR Options,, AVR Options, gcc, Using the GNU Compiler
+Collection (GCC)},
+@end ifnothtml
+@ifhtml
+See ``AVR Options'' in the main manual
+@end ifhtml
+for the list of supported MCU types.
+
+Use @samp{configure --target=avr --enable-languages="c"} to configure GCC@.
+
+Further installation notes and other useful information about AVR tools
+can also be obtained from:
+
+@itemize @bullet
+@item
+@uref{http://www.nongnu.org/avr/,,http://www.nongnu.org/avr/}
+@item
+@uref{http://www.amelek.gda.pl/avr/,,http://www.amelek.gda.pl/avr/}
+@end itemize
+
+The following error:
+@smallexample
+Error: register required
+@end smallexample
+
+indicates that you should upgrade to a newer version of the binutils.
+
+@html
+<hr />
+@end html
+@anchor{bfin}
+@heading Blackfin
+The Blackfin processor, an Analog Devices DSP.
+@ifnothtml
+@xref{Blackfin Options,, Blackfin Options, gcc, Using the GNU Compiler
+Collection (GCC)},
+@end ifnothtml
+@ifhtml
+See ``Blackfin Options'' in the main manual
+@end ifhtml
+
+More information, and a version of binutils with support for this processor,
+are available at @uref{https://sourceforge.net/projects/adi-toolchain/}.
+
+@html
+<hr />
+@end html
+@anchor{cris}
+@heading CRIS
+CRIS is a CPU architecture in Axis Communications systems-on-a-chip, for
+example the ETRAX series. These are used in embedded applications.
+
+@ifnothtml
+@xref{CRIS Options,, CRIS Options, gcc, Using the GNU Compiler
+Collection (GCC)},
+@end ifnothtml
+@ifhtml
+See ``CRIS Options'' in the main manual
+@end ifhtml
+for a list of CRIS-specific options.
+
+Use @samp{configure --target=cris-elf} to configure GCC@ for building
+a cross-compiler for CRIS.
+@html
+<hr />
+@end html
+@anchor{dos}
+@heading DOS
+Please have a look at the @uref{binaries.html,,binaries page}.
+
+You cannot install GCC by itself on MSDOS; it will not compile under
+any MSDOS compiler except itself. You need to get the complete
+compilation package DJGPP, which includes binaries as well as sources,
+and includes all the necessary compilation tools and libraries.
+
+@html
+<hr />
+@end html
+@anchor{epiphany-x-elf}
+@heading epiphany-*-elf
+Adapteva Epiphany.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{x-x-freebsd}
+@heading *-*-freebsd*
+In order to better utilize FreeBSD base system functionality and match
+the configuration of the system compiler, GCC 4.5 and above as well as
+GCC 4.4 past 2010-06-20 leverage SSP support in libc (which is present
+on FreeBSD 7 or later) and the use of @code{__cxa_atexit} by default
+(on FreeBSD 6 or later). The use of @code{dl_iterate_phdr} inside
+@file{libgcc_s.so.1} and boehm-gc (on FreeBSD 7 or later) is enabled
+by GCC 4.5 and above.
+
+We support FreeBSD using the ELF file format with DWARF 2 debugging
+for all CPU architectures. There are
+no known issues with mixing object files and libraries with different
+debugging formats. Otherwise, this release of GCC should now match
+more of the configuration used in the stock FreeBSD configuration of
+GCC@. In particular, @option{--enable-threads} is now configured by
+default. However, as a general user, do not attempt to replace the
+system compiler with this release. Known to bootstrap and check with
+good results on FreeBSD 7.2-STABLE@. In the past, known to bootstrap
+and check with good results on FreeBSD 3.0, 3.4, 4.0, 4.2, 4.3, 4.4,
+4.5, 4.8, 4.9 and 5-CURRENT@.
+
+The version of binutils installed in @file{/usr/bin} probably works
+with this release of GCC@. Bootstrapping against the latest GNU
+binutils and/or the version found in @file{/usr/ports/devel/binutils} has
+been known to enable additional features and improve overall testsuite
+results. However, it is currently known that boehm-gc may not configure
+properly on FreeBSD prior to the FreeBSD 7.0 release with GNU binutils
+after 2.16.1.
+
+@html
+<hr />
+@end html
+@anchor{ft32-x-elf}
+@heading ft32-*-elf
+The FT32 processor.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{h8300-hms}
+@heading h8300-hms
+Renesas H8/300 series of processors.
+
+Please have a look at the @uref{binaries.html,,binaries page}.
+
+The calling convention and structure layout has changed in release 2.6.
+All code must be recompiled. The calling convention now passes the
+first three arguments in function calls in registers. Structures are no
+longer a multiple of 2 bytes.
+
+@html
+<hr />
+@end html
+@anchor{hppa-hp-hpux}
+@heading hppa*-hp-hpux*
+Support for HP-UX version 9 and older was discontinued in GCC 3.4.
+
+We require using gas/binutils on all hppa platforms. Version 2.19 or
+later is recommended.
+
+It may be helpful to configure GCC with the
+@uref{./configure.html#with-gnu-as,,@option{--with-gnu-as}} and
+@option{--with-as=@dots{}} options to ensure that GCC can find GAS@.
+
+The HP assembler should not be used with GCC. It is rarely tested and may
+not work. It shouldn't be used with any languages other than C due to its
+many limitations.
+
+Specifically, @option{-g} does not work (HP-UX uses a peculiar debugging
+format which GCC does not know about). It also inserts timestamps
+into each object file it creates, causing the 3-stage comparison test to
+fail during a bootstrap. You should be able to continue by saying
+@samp{make all-host all-target} after getting the failure from @samp{make}.
+
+Various GCC features are not supported. For example, it does not support weak
+symbols or alias definitions. As a result, explicit template instantiations
+are required when using C++. This makes it difficult if not impossible to
+build many C++ applications.
+
+There are two default scheduling models for instructions. These are
+PROCESSOR_7100LC and PROCESSOR_8000. They are selected from the pa-risc
+architecture specified for the target machine when configuring.
+PROCESSOR_8000 is the default. PROCESSOR_7100LC is selected when
+the target is a @samp{hppa1*} machine.
+
+The PROCESSOR_8000 model is not well suited to older processors. Thus,
+it is important to completely specify the machine architecture when
+configuring if you want a model other than PROCESSOR_8000. The macro
+TARGET_SCHED_DEFAULT can be defined in BOOT_CFLAGS if a different
+default scheduling model is desired.
+
+As of GCC 4.0, GCC uses the UNIX 95 namespace for HP-UX 10.10
+through 11.00, and the UNIX 98 namespace for HP-UX 11.11 and later.
+This namespace change might cause problems when bootstrapping with
+an earlier version of GCC or the HP compiler as essentially the same
+namespace is required for an entire build. This problem can be avoided
+in a number of ways. With HP cc, @env{UNIX_STD} can be set to @samp{95}
+or @samp{98}. Another way is to add an appropriate set of predefines
+to @env{CC}. The description for the @option{munix=} option contains
+a list of the predefines used with each standard.
+
+More specific information to @samp{hppa*-hp-hpux*} targets follows.
+
+@html
+<hr />
+@end html
+@anchor{hppa-hp-hpux10}
+@heading hppa*-hp-hpux10
+For hpux10.20, we @emph{highly} recommend you pick up the latest sed patch
+@code{PHCO_19798} from HP@.
+
+The C++ ABI has changed incompatibly in GCC 4.0. COMDAT subspaces are
+used for one-only code and data. This resolves many of the previous
+problems in using C++ on this target. However, the ABI is not compatible
+with the one implemented under HP-UX 11 using secondary definitions.
+
+@html
+<hr />
+@end html
+@anchor{hppa-hp-hpux11}
+@heading hppa*-hp-hpux11
+GCC 3.0 and up support HP-UX 11. GCC 2.95.x is not supported and cannot
+be used to compile GCC 3.0 and up.
+
+The libffi library haven't been ported to 64-bit HP-UX@ and doesn't build.
+
+Refer to @uref{binaries.html,,binaries} for information about obtaining
+precompiled GCC binaries for HP-UX@. Precompiled binaries must be obtained
+to build the Ada language as it cannot be bootstrapped using C@. Ada is
+only available for the 32-bit PA-RISC runtime.
+
+Starting with GCC 3.4 an ISO C compiler is required to bootstrap. The
+bundled compiler supports only traditional C; you will need either HP's
+unbundled compiler, or a binary distribution of GCC@.
+
+It is possible to build GCC 3.3 starting with the bundled HP compiler,
+but the process requires several steps. GCC 3.3 can then be used to
+build later versions.
+
+There are several possible approaches to building the distribution.
+Binutils can be built first using the HP tools. Then, the GCC
+distribution can be built. The second approach is to build GCC
+first using the HP tools, then build binutils, then rebuild GCC@.
+There have been problems with various binary distributions, so it
+is best not to start from a binary distribution.
+
+On 64-bit capable systems, there are two distinct targets. Different
+installation prefixes must be used if both are to be installed on
+the same system. The @samp{hppa[1-2]*-hp-hpux11*} target generates code
+for the 32-bit PA-RISC runtime architecture and uses the HP linker.
+The @samp{hppa64-hp-hpux11*} target generates 64-bit code for the
+PA-RISC 2.0 architecture.
+
+The script config.guess now selects the target type based on the compiler
+detected during configuration. You must define @env{PATH} or @env{CC} so
+that configure finds an appropriate compiler for the initial bootstrap.
+When @env{CC} is used, the definition should contain the options that are
+needed whenever @env{CC} is used.
+
+Specifically, options that determine the runtime architecture must be
+in @env{CC} to correctly select the target for the build. It is also
+convenient to place many other compiler options in @env{CC}. For example,
+@env{CC="cc -Ac +DA2.0W -Wp,-H16376 -D_CLASSIC_TYPES -D_HPUX_SOURCE"}
+can be used to bootstrap the GCC 3.3 branch with the HP compiler in
+64-bit K&R/bundled mode. The @option{+DA2.0W} option will result in
+the automatic selection of the @samp{hppa64-hp-hpux11*} target. The
+macro definition table of cpp needs to be increased for a successful
+build with the HP compiler. _CLASSIC_TYPES and _HPUX_SOURCE need to
+be defined when building with the bundled compiler, or when using the
+@option{-Ac} option. These defines aren't necessary with @option{-Ae}.
+
+It is best to explicitly configure the @samp{hppa64-hp-hpux11*} target
+with the @option{--with-ld=@dots{}} option. This overrides the standard
+search for ld. The two linkers supported on this target require different
+commands. The default linker is determined during configuration. As a
+result, it's not possible to switch linkers in the middle of a GCC build.
+This has been reported to sometimes occur in unified builds of binutils
+and GCC@.
+
+A recent linker patch must be installed for the correct operation of
+GCC 3.3 and later. @code{PHSS_26559} and @code{PHSS_24304} are the
+oldest linker patches that are known to work. They are for HP-UX
+11.00 and 11.11, respectively. @code{PHSS_24303}, the companion to
+@code{PHSS_24304}, might be usable but it hasn't been tested. These
+patches have been superseded. Consult the HP patch database to obtain
+the currently recommended linker patch for your system.
+
+The patches are necessary for the support of weak symbols on the
+32-bit port, and for the running of initializers and finalizers. Weak
+symbols are implemented using SOM secondary definition symbols. Prior
+to HP-UX 11, there are bugs in the linker support for secondary symbols.
+The patches correct a problem of linker core dumps creating shared
+libraries containing secondary symbols, as well as various other
+linking issues involving secondary symbols.
+
+GCC 3.3 uses the ELF DT_INIT_ARRAY and DT_FINI_ARRAY capabilities to
+run initializers and finalizers on the 64-bit port. The 32-bit port
+uses the linker @option{+init} and @option{+fini} options for the same
+purpose. The patches correct various problems with the +init/+fini
+options, including program core dumps. Binutils 2.14 corrects a
+problem on the 64-bit port resulting from HP's non-standard use of
+the .init and .fini sections for array initializers and finalizers.
+
+Although the HP and GNU linkers are both supported for the
+@samp{hppa64-hp-hpux11*} target, it is strongly recommended that the
+HP linker be used for link editing on this target.
+
+At this time, the GNU linker does not support the creation of long
+branch stubs. As a result, it cannot successfully link binaries
+containing branch offsets larger than 8 megabytes. In addition,
+there are problems linking shared libraries, linking executables
+with @option{-static}, and with dwarf2 unwind and exception support.
+It also doesn't provide stubs for internal calls to global functions
+in shared libraries, so these calls cannot be overloaded.
+
+The HP dynamic loader does not support GNU symbol versioning, so symbol
+versioning is not supported. It may be necessary to disable symbol
+versioning with @option{--disable-symvers} when using GNU ld.
+
+POSIX threads are the default. The optional DCE thread library is not
+supported, so @option{--enable-threads=dce} does not work.
+
+@html
+<hr />
+@end html
+@anchor{x-x-linux-gnu}
+@heading *-*-linux-gnu
+The @code{.init_array} and @code{.fini_array} sections are enabled
+unconditionally which requires at least glibc 2.1 and binutils 2.12.
+
+Versions of libstdc++-v3 starting with 3.2.1 require bug fixes present
+in glibc 2.2.5 and later. More information is available in the
+libstdc++-v3 documentation.
+
+@html
+<hr />
+@end html
+@anchor{ix86-x-linux}
+@heading i?86-*-linux*
+As of GCC 3.3, binutils 2.13.1 or later is required for this platform.
+See @uref{https://gcc.gnu.org/PR10877,,bug 10877} for more information.
+
+If you receive Signal 11 errors when building on GNU/Linux, then it is
+possible you have a hardware problem. Further information on this can be
+found on @uref{https://www.bitwizard.nl/sig11/,,www.bitwizard.nl}.
+
+@html
+<hr />
+@end html
+@anchor{ix86-x-solaris2}
+@heading i?86-*-solaris2*
+Use this for Solaris 11.3 or later on x86 and x86-64 systems. Starting
+with GCC 4.7, there is also a 64-bit @samp{amd64-*-solaris2*} or
+@samp{x86_64-*-solaris2*} configuration that corresponds to
+@samp{sparcv9-sun-solaris2*}.
+
+It is recommended that you configure GCC to use the GNU assembler. The
+versions included in Solaris 11.3, from GNU binutils 2.23.1 or
+newer (available as @file{/usr/bin/gas} and
+@file{/usr/gnu/bin/as}), work fine. The current version, from GNU
+binutils 2.34, is known to work. Recent versions of the Solaris assembler in
+@file{/usr/bin/as} work almost as well, though.
+
+For linking, the Solaris linker is preferred. If you want to use the GNU
+linker instead, the version in Solaris 11.3, from GNU binutils 2.23.1 or
+newer (in @file{/usr/gnu/bin/ld} and @file{/usr/bin/gld}), works,
+as does the latest version, from GNU binutils 2.34.
+
+To use GNU @command{as}, configure with the options
+@option{--with-gnu-as --with-as=@//usr/@/gnu/@/bin/@/as}. It may be necessary
+to configure with @option{--without-gnu-ld --with-ld=@//usr/@/ccs/@/bin/@/ld} to
+guarantee use of Solaris @command{ld}.
+@c FIXME: why --without-gnu-ld --with-ld?
+
+@html
+<hr />
+@end html
+@anchor{ia64-x-linux}
+@heading ia64-*-linux
+IA-64 processor (also known as IPF, or Itanium Processor Family)
+running GNU/Linux.
+
+If you are using the installed system libunwind library with
+@option{--with-system-libunwind}, then you must use libunwind 0.98 or
+later.
+
+@html
+<hr />
+@end html
+@anchor{ia64-x-hpux}
+@heading ia64-*-hpux*
+Building GCC on this target requires the GNU Assembler. The bundled HP
+assembler will not work. To prevent GCC from using the wrong assembler,
+the option @option{--with-gnu-as} may be necessary.
+
+The GCC libunwind library has not been ported to HPUX@. This means that for
+GCC versions 3.2.3 and earlier, @option{--enable-libunwind-exceptions}
+is required to build GCC@. For GCC 3.3 and later, this is the default.
+For gcc 3.4.3 and later, @option{--enable-libunwind-exceptions} is
+removed and the system libunwind library will always be used.
+
+@html
+<hr />
+<!-- rs6000-ibm-aix*, powerpc-ibm-aix* -->
+@end html
+@anchor{x-ibm-aix}
+@heading *-ibm-aix*
+Support for AIX version 3 and older was discontinued in GCC 3.4.
+Support for AIX version 4.2 and older was discontinued in GCC 4.5.
+
+``out of memory'' bootstrap failures may indicate a problem with
+process resource limits (ulimit). Hard limits are configured in the
+@file{/etc/security/limits} system configuration file.
+
+GCC 4.9 and above require a C++ compiler for bootstrap. IBM VAC++ / xlC
+cannot bootstrap GCC. xlc can bootstrap an older version of GCC and
+G++ can bootstrap recent releases of GCC.
+
+GCC can bootstrap with recent versions of IBM XLC, but bootstrapping
+with an earlier release of GCC is recommended. Bootstrapping with XLC
+requires a larger data segment, which can be enabled through the
+@var{LDR_CNTRL} environment variable, e.g.,
+
+@smallexample
+% LDR_CNTRL=MAXDATA=0x50000000
+% export LDR_CNTRL
+@end smallexample
+
+One can start with a pre-compiled version of GCC to build from
+sources. One may delete GCC's ``fixed'' header files when starting
+with a version of GCC built for an earlier release of AIX.
+
+To speed up the configuration phases of bootstrapping and installing GCC,
+one may use GNU Bash instead of AIX @command{/bin/sh}, e.g.,
+
+@smallexample
+% CONFIG_SHELL=/opt/freeware/bin/bash
+% export CONFIG_SHELL
+@end smallexample
+
+and then proceed as described in @uref{build.html,,the build
+instructions}, where we strongly recommend specifying an absolute path
+to invoke @var{srcdir}/configure.
+
+Because GCC on AIX is built as a 32-bit executable by default,
+(although it can generate 64-bit programs) the GMP and MPFR libraries
+required by gfortran must be 32-bit libraries. Building GMP and MPFR
+as static archive libraries works better than shared libraries.
+
+Errors involving @code{alloca} when building GCC generally are due
+to an incorrect definition of @code{CC} in the Makefile or mixing files
+compiled with the native C compiler and GCC@. During the stage1 phase of
+the build, the native AIX compiler @strong{must} be invoked as @command{cc}
+(not @command{xlc}). Once @command{configure} has been informed of
+@command{xlc}, one needs to use @samp{make distclean} to remove the
+configure cache files and ensure that @env{CC} environment variable
+does not provide a definition that will confuse @command{configure}.
+If this error occurs during stage2 or later, then the problem most likely
+is the version of Make (see above).
+
+The native @command{as} and @command{ld} are recommended for
+bootstrapping on AIX@. The GNU Assembler, GNU Linker, and GNU
+Binutils version 2.20 is the minimum level that supports bootstrap on
+AIX 5@. The GNU Assembler has not been updated to support AIX 6@ or
+AIX 7. The native AIX tools do interoperate with GCC@.
+
+AIX 7.1 added partial support for DWARF debugging, but full support
+requires AIX 7.1 TL03 SP7 that supports additional DWARF sections and
+fixes a bug in the assembler. AIX 7.1 TL03 SP5 distributed a version
+of libm.a missing important symbols; a fix for IV77796 will be
+included in SP6.
+
+AIX 5.3 TL10, AIX 6.1 TL05 and AIX 7.1 TL00 introduced an AIX
+assembler change that sometimes produces corrupt assembly files
+causing AIX linker errors. The bug breaks GCC bootstrap on AIX and
+can cause compilation failures with existing GCC installations. An
+AIX iFix for AIX 5.3 is available (APAR IZ98385 for AIX 5.3 TL10, APAR
+IZ98477 for AIX 5.3 TL11 and IZ98134 for AIX 5.3 TL12). AIX 5.3 TL11 SP8,
+AIX 5.3 TL12 SP5, AIX 6.1 TL04 SP11, AIX 6.1 TL05 SP7, AIX 6.1 TL06 SP6,
+AIX 6.1 TL07 and AIX 7.1 TL01 should include the fix.
+
+Building @file{libstdc++.a} requires a fix for an AIX Assembler bug
+APAR IY26685 (AIX 4.3) or APAR IY25528 (AIX 5.1). It also requires a
+fix for another AIX Assembler bug and a co-dependent AIX Archiver fix
+referenced as APAR IY53606 (AIX 5.2) or as APAR IY54774 (AIX 5.1)
+
+@anchor{TransferAixShobj}
+@samp{libstdc++} in GCC 3.4 increments the major version number of the
+shared object and GCC installation places the @file{libstdc++.a}
+shared library in a common location which will overwrite the and GCC
+3.3 version of the shared library. Applications either need to be
+re-linked against the new shared library or the GCC 3.1 and GCC 3.3
+versions of the @samp{libstdc++} shared object needs to be available
+to the AIX runtime loader. The GCC 3.1 @samp{libstdc++.so.4}, if
+present, and GCC 3.3 @samp{libstdc++.so.5} shared objects can be
+installed for runtime dynamic loading using the following steps to set
+the @samp{F_LOADONLY} flag in the shared object for @emph{each}
+multilib @file{libstdc++.a} installed:
+
+Extract the shared objects from the currently installed
+@file{libstdc++.a} archive:
+@smallexample
+% ar -x libstdc++.a libstdc++.so.4 libstdc++.so.5
+@end smallexample
+
+Enable the @samp{F_LOADONLY} flag so that the shared object will be
+available for runtime dynamic loading, but not linking:
+@smallexample
+% strip -e libstdc++.so.4 libstdc++.so.5
+@end smallexample
+
+Archive the runtime-only shared object in the GCC 3.4
+@file{libstdc++.a} archive:
+@smallexample
+% ar -q libstdc++.a libstdc++.so.4 libstdc++.so.5
+@end smallexample
+
+Eventually, the
+@uref{./configure.html#WithAixSoname,,@option{--with-aix-soname=svr4}}
+configure option may drop the need for this procedure for libraries that
+support it.
+
+Linking executables and shared libraries may produce warnings of
+duplicate symbols. The assembly files generated by GCC for AIX always
+have included multiple symbol definitions for certain global variable
+and function declarations in the original program. The warnings should
+not prevent the linker from producing a correct library or runnable
+executable.
+
+AIX 4.3 utilizes a ``large format'' archive to support both 32-bit and
+64-bit object modules. The routines provided in AIX 4.3.0 and AIX 4.3.1
+to parse archive libraries did not handle the new format correctly.
+These routines are used by GCC and result in error messages during
+linking such as ``not a COFF file''. The version of the routines shipped
+with AIX 4.3.1 should work for a 32-bit environment. The @option{-g}
+option of the archive command may be used to create archives of 32-bit
+objects using the original ``small format''. A correct version of the
+routines is shipped with AIX 4.3.2 and above.
+
+Some versions of the AIX binder (linker) can fail with a relocation
+overflow severe error when the @option{-bbigtoc} option is used to link
+GCC-produced object files into an executable that overflows the TOC@. A fix
+for APAR IX75823 (OVERFLOW DURING LINK WHEN USING GCC AND -BBIGTOC) is
+available from IBM Customer Support and from its
+@uref{https://techsupport.services.ibm.com/,,techsupport.services.ibm.com}
+website as PTF U455193.
+
+The AIX 4.3.2.1 linker (bos.rte.bind_cmds Level 4.3.2.1) will dump core
+with a segmentation fault when invoked by any version of GCC@. A fix for
+APAR IX87327 is available from IBM Customer Support and from its
+@uref{https://techsupport.services.ibm.com/,,techsupport.services.ibm.com}
+website as PTF U461879. This fix is incorporated in AIX 4.3.3 and above.
+
+The initial assembler shipped with AIX 4.3.0 generates incorrect object
+files. A fix for APAR IX74254 (64BIT DISASSEMBLED OUTPUT FROM COMPILER FAILS
+TO ASSEMBLE/BIND) is available from IBM Customer Support and from its
+@uref{https://techsupport.services.ibm.com/,,techsupport.services.ibm.com}
+website as PTF U453956. This fix is incorporated in AIX 4.3.1 and above.
+
+AIX provides National Language Support (NLS)@. Compilers and assemblers
+use NLS to support locale-specific representations of various data
+formats including floating-point numbers (e.g., @samp{.} vs @samp{,} for
+separating decimal fractions). There have been problems reported where
+GCC does not produce the same floating-point formats that the assembler
+expects. If one encounters this problem, set the @env{LANG}
+environment variable to @samp{C} or @samp{En_US}.
+
+A default can be specified with the @option{-mcpu=@var{cpu_type}}
+switch and using the configure option @option{--with-cpu-@var{cpu_type}}.
+
+@html
+<hr />
+@end html
+@anchor{iq2000-x-elf}
+@heading iq2000-*-elf
+Vitesse IQ2000 processors. These are used in embedded
+applications. There are no standard Unix configurations.
+
+@html
+<hr />
+@end html
+@anchor{lm32-x-elf}
+@heading lm32-*-elf
+Lattice Mico32 processor.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{lm32-x-uclinux}
+@heading lm32-*-uclinux
+Lattice Mico32 processor.
+This configuration is intended for embedded systems running uClinux.
+
+@html
+<hr />
+@end html
+@anchor{loongarch}
+@heading LoongArch
+LoongArch processor.
+The following LoongArch targets are available:
+@table @code
+@item loongarch64-linux-gnu*
+LoongArch processor running GNU/Linux. This target triplet may be coupled
+with a small set of possible suffixes to identify their default ABI type:
+@table @code
+@item f64
+Uses @code{lp64d/base} ABI by default.
+@item f32
+Uses @code{lp64f/base} ABI by default.
+@item sf
+Uses @code{lp64s/base} ABI by default.
+@end table
+
+@item loongarch64-linux-gnu
+Same as @code{loongarch64-linux-gnuf64}, but may be used with
+@option{--with-abi=*} to configure the default ABI type.
+@end table
+
+More information about LoongArch can be found at
+@uref{https://github.com/loongson/LoongArch-Documentation}.
+
+@html
+<hr />
+@end html
+@anchor{m32c-x-elf}
+@heading m32c-*-elf
+Renesas M32C processor.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{m32r-x-elf}
+@heading m32r-*-elf
+Renesas M32R processor.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{m68k-x-x}
+@heading m68k-*-*
+By default,
+@samp{m68k-*-elf*}, @samp{m68k-*-rtems}, @samp{m68k-*-uclinux} and
+@samp{m68k-*-linux}
+build libraries for both M680x0 and ColdFire processors. If you only
+need the M680x0 libraries, you can omit the ColdFire ones by passing
+@option{--with-arch=m68k} to @command{configure}. Alternatively, you
+can omit the M680x0 libraries by passing @option{--with-arch=cf} to
+@command{configure}. These targets default to 5206 or 5475 code as
+appropriate for the target system when
+configured with @option{--with-arch=cf} and 68020 code otherwise.
+
+The @samp{m68k-*-netbsd} and
+@samp{m68k-*-openbsd} targets also support the @option{--with-arch}
+option. They will generate ColdFire CFV4e code when configured with
+@option{--with-arch=cf} and 68020 code otherwise.
+
+You can override the default processors listed above by configuring
+with @option{--with-cpu=@var{target}}. This @var{target} can either
+be a @option{-mcpu} argument or one of the following values:
+@samp{m68000}, @samp{m68010}, @samp{m68020}, @samp{m68030},
+@samp{m68040}, @samp{m68060}, @samp{m68020-40} and @samp{m68020-60}.
+
+GCC requires at least binutils version 2.17 on these targets.
+
+@html
+<hr />
+@end html
+@anchor{m68k-x-uclinux}
+@heading m68k-*-uclinux
+GCC 4.3 changed the uClinux configuration so that it uses the
+@samp{m68k-linux-gnu} ABI rather than the @samp{m68k-elf} ABI.
+It also added improved support for C++ and flat shared libraries,
+both of which were ABI changes.
+
+@html
+<hr />
+@end html
+@anchor{microblaze-x-elf}
+@heading microblaze-*-elf
+Xilinx MicroBlaze processor.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{mips-x-x}
+@heading mips-*-*
+If on a MIPS system you get an error message saying ``does not have gp
+sections for all it's [sic] sectons [sic]'', don't worry about it. This
+happens whenever you use GAS with the MIPS linker, but there is not
+really anything wrong, and it is okay to use the output file. You can
+stop such warnings by installing the GNU linker.
+
+It would be nice to extend GAS to produce the gp tables, but they are
+optional, and there should not be a warning about their absence.
+
+The libstdc++ atomic locking routines for MIPS targets requires MIPS II
+and later. A patch went in just after the GCC 3.3 release to
+make @samp{mips*-*-*} use the generic implementation instead. You can also
+configure for @samp{mipsel-elf} as a workaround. The
+@samp{mips*-*-linux*} target continues to use the MIPS II routines. More
+work on this is expected in future releases.
+
+@c If you make --with-llsc the default for another target, please also
+@c update the description of the --with-llsc option.
+
+The built-in @code{__sync_*} functions are available on MIPS II and
+later systems and others that support the @samp{ll}, @samp{sc} and
+@samp{sync} instructions. This can be overridden by passing
+@option{--with-llsc} or @option{--without-llsc} when configuring GCC.
+Since the Linux kernel emulates these instructions if they are
+missing, the default for @samp{mips*-*-linux*} targets is
+@option{--with-llsc}. The @option{--with-llsc} and
+@option{--without-llsc} configure options may be overridden at compile
+time by passing the @option{-mllsc} or @option{-mno-llsc} options to
+the compiler.
+
+MIPS systems check for division by zero (unless
+@option{-mno-check-zero-division} is passed to the compiler) by
+generating either a conditional trap or a break instruction. Using
+trap results in smaller code, but is only supported on MIPS II and
+later. Also, some versions of the Linux kernel have a bug that
+prevents trap from generating the proper signal (@code{SIGFPE}). To enable
+the use of break, use the @option{--with-divide=breaks}
+@command{configure} option when configuring GCC@. The default is to
+use traps on systems that support them.
+
+@html
+<hr />
+@end html
+@anchor{moxie-x-elf}
+@heading moxie-*-elf
+The moxie processor.
+
+@html
+<hr />
+@end html
+@anchor{msp430-x-elf}
+@heading msp430-*-elf*
+TI MSP430 processor.
+This configuration is intended for embedded systems.
+
+@samp{msp430-*-elf} is the standard configuration with most GCC
+features enabled by default.
+
+@samp{msp430-*-elfbare} is tuned for a bare-metal environment, and disables
+features related to shared libraries and other functionality not used for
+this device. This reduces code and data usage of the GCC libraries, resulting
+in a minimal run-time environment by default.
+
+Features disabled by default include:
+@itemize
+@item transactional memory
+@item __cxa_atexit
+@end itemize
+
+@html
+<hr />
+@end html
+@anchor{nds32le-x-elf}
+@heading nds32le-*-elf
+Andes NDS32 target in little endian mode.
+
+@html
+<hr />
+@end html
+@anchor{nds32be-x-elf}
+@heading nds32be-*-elf
+Andes NDS32 target in big endian mode.
+
+@html
+<hr />
+@end html
+@anchor{nvptx-x-none}
+@heading nvptx-*-none
+Nvidia PTX target.
+
+Instead of GNU binutils, you will need to install
+@uref{https://github.com/MentorEmbedded/nvptx-tools/,,nvptx-tools}.
+Tell GCC where to find it:
+@option{--with-build-time-tools=[install-nvptx-tools]/nvptx-none/bin}.
+
+You will need newlib 3.1.0 or later. It can be
+automatically built together with GCC@. For this, add a symbolic link
+to nvptx-newlib's @file{newlib} directory to the directory containing
+the GCC sources.
+
+Use the @option{--disable-sjlj-exceptions} and
+@option{--enable-newlib-io-long-long} options when configuring.
+
+The @option{--with-arch} option may be specified to override the
+default value for the @option{-march} option, and to also build
+corresponding target libraries.
+The default is @option{--with-arch=sm_30}.
+
+For example, if @option{--with-arch=sm_70} is specified,
+@option{-march=sm_30} and @option{-march=sm_70} target libraries are
+built, and code generation defaults to @option{-march=sm_70}.
+
+@html
+<hr />
+@end html
+@anchor{or1k-x-elf}
+@heading or1k-*-elf
+The OpenRISC 1000 32-bit processor with delay slots.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{or1k-x-linux}
+@heading or1k-*-linux
+The OpenRISC 1000 32-bit processor with delay slots.
+
+@html
+<hr />
+@end html
+@anchor{powerpc-x-x}
+@heading powerpc-*-*
+You can specify a default version for the @option{-mcpu=@var{cpu_type}}
+switch by using the configure option @option{--with-cpu-@var{cpu_type}}.
+
+You will need GNU binutils 2.20 or newer.
+
+@html
+<hr />
+@end html
+@anchor{powerpc-x-darwin}
+@heading powerpc-*-darwin*
+PowerPC running Darwin (Mac OS X kernel).
+
+Pre-installed versions of Mac OS X may not include any developer tools,
+meaning that you will not be able to build GCC from source. Tool
+binaries are available at
+@uref{https://opensource.apple.com}.
+
+This version of GCC requires at least cctools-590.36. The
+cctools-590.36 package referenced from
+@uref{https://gcc.gnu.org/ml/gcc/2006-03/msg00507.html} will not work
+on systems older than 10.3.9 (aka darwin7.9.0).
+
+@html
+<hr />
+@end html
+@anchor{powerpc-x-elf}
+@heading powerpc-*-elf
+PowerPC system in big endian mode, running System V.4.
+
+@html
+<hr />
+@end html
+@anchor{powerpc-x-linux-gnu}
+@heading powerpc*-*-linux-gnu*
+PowerPC system in big endian mode running Linux.
+
+@html
+<hr />
+@end html
+@anchor{powerpc-x-netbsd}
+@heading powerpc-*-netbsd*
+PowerPC system in big endian mode running NetBSD@.
+
+@html
+<hr />
+@end html
+@anchor{powerpc-x-eabisim}
+@heading powerpc-*-eabisim
+Embedded PowerPC system in big endian mode for use in running under the
+PSIM simulator.
+
+@html
+<hr />
+@end html
+@anchor{powerpc-x-eabi}
+@heading powerpc-*-eabi
+Embedded PowerPC system in big endian mode.
+
+@html
+<hr />
+@end html
+@anchor{powerpcle-x-elf}
+@heading powerpcle-*-elf
+PowerPC system in little endian mode, running System V.4.
+
+@html
+<hr />
+@end html
+@anchor{powerpcle-x-eabisim}
+@heading powerpcle-*-eabisim
+Embedded PowerPC system in little endian mode for use in running under
+the PSIM simulator.
+
+@html
+<hr />
+@end html
+@anchor{powerpcle-x-eabi}
+@heading powerpcle-*-eabi
+Embedded PowerPC system in little endian mode.
+
+@html
+<hr />
+@end html
+@anchor{rl78-x-elf}
+@heading rl78-*-elf
+The Renesas RL78 processor.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{riscv32-x-elf}
+@heading riscv32-*-elf
+The RISC-V RV32 instruction set.
+This configuration is intended for embedded systems.
+This (and all other RISC-V) targets require the binutils 2.30 release.
+
+@html
+<hr />
+@end html
+@anchor{riscv32-x-linux}
+@heading riscv32-*-linux
+The RISC-V RV32 instruction set running GNU/Linux.
+This (and all other RISC-V) targets require the binutils 2.30 release.
+
+@html
+<hr />
+@end html
+@anchor{riscv64-x-elf}
+@heading riscv64-*-elf
+The RISC-V RV64 instruction set.
+This configuration is intended for embedded systems.
+This (and all other RISC-V) targets require the binutils 2.30 release.
+
+@html
+<hr />
+@end html
+@anchor{riscv64-x-linux}
+@heading riscv64-*-linux
+The RISC-V RV64 instruction set running GNU/Linux.
+This (and all other RISC-V) targets require the binutils 2.30 release.
+
+@html
+<hr />
+@end html
+@anchor{rx-x-elf}
+@heading rx-*-elf
+The Renesas RX processor.
+
+@html
+<hr />
+@end html
+@anchor{s390-x-linux}
+@heading s390-*-linux*
+S/390 system running GNU/Linux for S/390@.
+
+@html
+<hr />
+@end html
+@anchor{s390x-x-linux}
+@heading s390x-*-linux*
+zSeries system (64-bit) running GNU/Linux for zSeries@.
+
+@html
+<hr />
+@end html
+@anchor{s390x-ibm-tpf}
+@heading s390x-ibm-tpf*
+zSeries system (64-bit) running TPF@. This platform is
+supported as cross-compilation target only.
+
+@html
+<hr />
+@end html
+@c Please use Solaris 2 to refer to all release of Solaris, starting
+@c with 2.0 until 2.6, 7, 8, etc. Solaris 1 was a marketing name for
+@c SunOS 4 releases which we don't use to avoid confusion. Solaris
+@c alone is too unspecific and must be avoided.
+@anchor{x-x-solaris2}
+@heading *-*-solaris2*
+Support for Solaris 10 has been removed in GCC 10. Support for Solaris
+9 has been removed in GCC 5. Support for Solaris 8 has been removed in
+GCC 4.8. Support for Solaris 7 has been removed in GCC 4.6.
+
+Solaris 11.3 provides GCC 4.5.2, 4.7.3, and 4.8.2 as
+@command{/usr/gcc/4.5/bin/gcc} or similar. Newer Solaris versions
+provide one or more of GCC 5, 7, and 9. Alternatively,
+you can install a pre-built GCC to bootstrap and install GCC. See the
+@uref{binaries.html,,binaries page} for details.
+
+The Solaris 2 @command{/bin/sh} will often fail to configure
+@samp{libstdc++-v3}. We therefore recommend using the
+following initial sequence of commands
+
+@smallexample
+% CONFIG_SHELL=/bin/ksh
+% export CONFIG_SHELL
+@end smallexample
+
+@noindent
+and proceed as described in @uref{configure.html,,the configure instructions}.
+In addition we strongly recommend specifying an absolute path to invoke
+@command{@var{srcdir}/configure}.
+
+In Solaris 11, you need to check for @code{system/header},
+@code{system/linker}, and @code{developer/assembler} packages.
+
+Trying to use the linker and other tools in
+@file{/usr/ucb} to install GCC has been observed to cause trouble.
+For example, the linker may hang indefinitely. The fix is to remove
+@file{/usr/ucb} from your @env{PATH}.
+
+The build process works more smoothly with the legacy Solaris tools so, if you
+have @file{/usr/xpg4/bin} in your @env{PATH}, we recommend that you place
+@file{/usr/bin} before @file{/usr/xpg4/bin} for the duration of the build.
+
+We recommend the use of the Solaris assembler or the GNU assembler, in
+conjunction with the Solaris linker. The GNU @command{as}
+versions included in Solaris 11.3,
+from GNU binutils 2.23.1 or newer (in @file{/usr/bin/gas} and
+@file{/usr/gnu/bin/as}), are known to work.
+The current version, from GNU binutils 2.34,
+is known to work as well. Note that your mileage may vary
+if you use a combination of the GNU tools and the Solaris tools: while the
+combination GNU @command{as} + Solaris @command{ld} should reasonably work,
+the reverse combination Solaris @command{as} + GNU @command{ld} may fail to
+build or cause memory corruption at runtime in some cases for C++ programs.
+@c FIXME: still?
+GNU @command{ld} usually works as well. Again, the current
+version (2.34) is known to work, but generally lacks platform specific
+features, so better stay with Solaris @command{ld}. To use the LTO linker
+plugin (@option{-fuse-linker-plugin}) with GNU @command{ld}, GNU
+binutils @emph{must} be configured with @option{--enable-largefile}.
+
+To enable symbol versioning in @samp{libstdc++} with the Solaris linker,
+you need to have any version of GNU @command{c++filt}, which is part of
+GNU binutils. @samp{libstdc++} symbol versioning will be disabled if no
+appropriate version is found. Solaris @command{c++filt} from the Solaris
+Studio compilers does @emph{not} work.
+
+In order to build the GNU D compiler, GDC, a working @samp{libphobos} is
+needed. That library wasn't built by default in GCC 9--11 on SPARC, or
+on x86 when the Solaris assembler is used, but can be enabled by
+configuring with @option{--enable-libphobos}. Also, GDC 9.4.0 is
+required on x86, while GDC 9.3.0 is known to work on SPARC.
+
+The versions of the GNU Multiple Precision Library (GMP), the MPFR
+library and the MPC library bundled with Solaris 11.3 and later are
+usually recent enough to match GCC's requirements. There are two
+caveats:
+
+@itemize @bullet
+@item
+While the version of the GMP library in Solaris 11.3 works with GCC, you
+need to configure with @option{--with-gmp-include=/usr/include/gmp}.
+
+@item
+The version of the MPFR libary included in Solaris 11.3 is too old; you
+need to provide a more recent one.
+
+@end itemize
+
+@html
+<hr />
+@end html
+@anchor{sparc-x-x}
+@heading sparc*-*-*
+This section contains general configuration information for all
+SPARC-based platforms. In addition to reading this section, please
+read all other sections that match your target.
+
+Newer versions of the GNU Multiple Precision Library (GMP), the MPFR
+library and the MPC library are known to be miscompiled by earlier
+versions of GCC on these platforms. We therefore recommend the use
+of the exact versions of these libraries listed as minimal versions
+in @uref{prerequisites.html,,the prerequisites}.
+
+@html
+<hr />
+@end html
+@anchor{sparc-sun-solaris2}
+@heading sparc-sun-solaris2*
+When GCC is configured to use GNU binutils 2.14 or later, the binaries
+produced are smaller than the ones produced using Solaris native tools;
+this difference is quite significant for binaries containing debugging
+information.
+
+Starting with Solaris 7, the operating system is capable of executing
+64-bit SPARC V9 binaries. GCC 3.1 and later properly supports
+this; the @option{-m64} option enables 64-bit code generation.
+However, if all you want is code tuned for the UltraSPARC CPU, you
+should try the @option{-mtune=ultrasparc} option instead, which produces
+code that, unlike full 64-bit code, can still run on non-UltraSPARC
+machines.
+
+When configuring the GNU Multiple Precision Library (GMP), the MPFR
+library or the MPC library on a Solaris 7 or later system, the canonical
+target triplet must be specified as the @command{build} parameter on the
+configure line. This target triplet can be obtained by invoking @command{./config.guess} in the toplevel source directory of GCC (and
+not that of GMP or MPFR or MPC). For example on a Solaris 11 system:
+
+@smallexample
+% ./configure --build=sparc-sun-solaris2.11 --prefix=xxx
+@end smallexample
+
+@html
+<hr />
+@end html
+@anchor{sparc-x-linux}
+@heading sparc-*-linux*
+
+@html
+<hr />
+@end html
+@anchor{sparc64-x-solaris2}
+@heading sparc64-*-solaris2*
+When configuring a 64-bit-default GCC on Solaris/SPARC, you must use a
+build compiler that generates 64-bit code, either by default or by
+specifying @samp{CC='gcc -m64' CXX='gcc-m64'} to @command{configure}.
+Additionally, you @emph{must} pass @option{--build=sparc64-sun-solaris2.11}
+or @option{--build=sparcv9-sun-solaris2.11} because @file{config.guess}
+misdetects this situation, which can cause build failures.
+
+When configuring the GNU Multiple Precision Library (GMP), the MPFR
+library or the MPC library, the canonical target triplet must be specified
+as the @command{build} parameter on the configure line. For example
+on a Solaris 11 system:
+
+@smallexample
+% ./configure --build=sparc64-sun-solaris2.11 --prefix=xxx
+@end smallexample
+
+@html
+<hr />
+@end html
+@anchor{sparcv9-x-solaris2}
+@heading sparcv9-*-solaris2*
+This is a synonym for @samp{sparc64-*-solaris2*}.
+
+@html
+<hr />
+@end html
+@anchor{c6x-x-x}
+@heading c6x-*-*
+The C6X family of processors. This port requires binutils-2.22 or newer.
+
+@html
+<hr />
+@end html
+@anchor{visium-x-elf}
+@heading visium-*-elf
+CDS VISIUMcore processor.
+This configuration is intended for embedded systems.
+
+@html
+<hr />
+@end html
+@anchor{x-x-vxworks}
+@heading *-*-vxworks*
+Support for VxWorks is in flux. At present GCC supports @emph{only} the
+very recent VxWorks 5.5 (aka Tornado 2.2) release, and only on PowerPC@.
+We welcome patches for other architectures supported by VxWorks 5.5.
+Support for VxWorks AE would also be welcome; we believe this is merely
+a matter of writing an appropriate ``configlette'' (see below). We are
+not interested in supporting older, a.out or COFF-based, versions of
+VxWorks in GCC 3.
+
+VxWorks comes with an older version of GCC installed in
+@file{@var{$WIND_BASE}/host}; we recommend you do not overwrite it.
+Choose an installation @var{prefix} entirely outside @var{$WIND_BASE}.
+Before running @command{configure}, create the directories @file{@var{prefix}}
+and @file{@var{prefix}/bin}. Link or copy the appropriate assembler,
+linker, etc.@: into @file{@var{prefix}/bin}, and set your @var{PATH} to
+include that directory while running both @command{configure} and
+@command{make}.
+
+You must give @command{configure} the
+@option{--with-headers=@var{$WIND_BASE}/target/h} switch so that it can
+find the VxWorks system headers. Since VxWorks is a cross compilation
+target only, you must also specify @option{--target=@var{target}}.
+@command{configure} will attempt to create the directory
+@file{@var{prefix}/@var{target}/sys-include} and copy files into it;
+make sure the user running @command{configure} has sufficient privilege
+to do so.
+
+GCC's exception handling runtime requires a special ``configlette''
+module, @file{contrib/gthr_supp_vxw_5x.c}. Follow the instructions in
+that file to add the module to your kernel build. (Future versions of
+VxWorks will incorporate this module.)
+
+@html
+<hr />
+@end html
+@anchor{x86-64-x-x}
+@heading x86_64-*-*, amd64-*-*
+GCC supports the x86-64 architecture implemented by the AMD64 processor
+(amd64-*-* is an alias for x86_64-*-*) on GNU/Linux, FreeBSD and NetBSD@.
+On GNU/Linux the default is a bi-arch compiler which is able to generate
+both 64-bit x86-64 and 32-bit x86 code (via the @option{-m32} switch).
+
+@html
+<hr />
+@end html
+@anchor{x86-64-x-solaris2}
+@heading x86_64-*-solaris2*
+GCC also supports the x86-64 architecture implemented by the AMD64
+processor (@samp{amd64-*-*} is an alias for @samp{x86_64-*-*}) on
+Solaris 10 or later. Unlike other systems, without special options a
+bi-arch compiler is built which generates 32-bit code by default, but
+can generate 64-bit x86-64 code with the @option{-m64} switch. Since
+GCC 4.7, there is also a configuration that defaults to 64-bit code, but
+can generate 32-bit code with @option{-m32}. To configure and build
+this way, you have to provide all support libraries like @file{libgmp}
+as 64-bit code, configure with @option{--target=x86_64-pc-solaris2.11}
+and @samp{CC=gcc -m64}.
+
+@html
+<hr />
+@end html
+@anchor{xtensa-x-elf}
+@heading xtensa*-*-elf
+This target is intended for embedded Xtensa systems using the
+@samp{newlib} C library. It uses ELF but does not support shared
+objects. Designed-defined instructions specified via the
+Tensilica Instruction Extension (TIE) language are only supported
+through inline assembly.
+
+The Xtensa configuration information must be specified prior to
+building GCC@. The @file{include/xtensa-config.h} header
+file contains the configuration information. If you created your
+own Xtensa configuration with the Xtensa Processor Generator, the
+downloaded files include a customized copy of this header file,
+which you can use to replace the default header file.
+
+@html
+<hr />
+@end html
+@anchor{xtensa-x-linux}
+@heading xtensa*-*-linux*
+This target is for Xtensa systems running GNU/Linux. It supports ELF
+shared objects and the GNU C library (glibc). It also generates
+position-independent code (PIC) regardless of whether the
+@option{-fpic} or @option{-fPIC} options are used. In other
+respects, this target is the same as the
+@uref{#xtensa*-*-elf,,@samp{xtensa*-*-elf}} target.
+
+@html
+<hr />
+@end html
+@anchor{windows}
+@heading Microsoft Windows
+
+@subheading Intel 16-bit versions
+The 16-bit versions of Microsoft Windows, such as Windows 3.1, are not
+supported.
+
+However, the 32-bit port has limited support for Microsoft
+Windows 3.11 in the Win32s environment, as a target only. See below.
+
+@subheading Intel 32-bit versions
+The 32-bit versions of Windows, including Windows 95, Windows NT, Windows
+XP, and Windows Vista, are supported by several different target
+platforms. These targets differ in which Windows subsystem they target
+and which C libraries are used.
+
+@itemize
+@item Cygwin @uref{#x-x-cygwin,,*-*-cygwin}: Cygwin provides a user-space
+Linux API emulation layer in the Win32 subsystem.
+@item MinGW @uref{#x-x-mingw32,,*-*-mingw32}: MinGW is a native GCC port for
+the Win32 subsystem that provides a subset of POSIX.
+@item MKS i386-pc-mks: NuTCracker from MKS. See
+@uref{https://www.mkssoftware.com} for more information.
+@end itemize
+
+@subheading Intel 64-bit versions
+GCC contains support for x86-64 using the mingw-w64
+runtime library, available from @uref{https://www.mingw-w64.org/downloads/}.
+This library should be used with the target triple x86_64-pc-mingw32.
+
+@subheading Windows CE
+Windows CE is supported as a target only on Hitachi
+SuperH (sh-wince-pe), and MIPS (mips-wince-pe).
+
+@subheading Other Windows Platforms
+GCC no longer supports Windows NT on the Alpha or PowerPC.
+
+GCC no longer supports the Windows POSIX subsystem. However, it does
+support the Interix subsystem. See above.
+
+Old target names including *-*-winnt and *-*-windowsnt are no longer used.
+
+PW32 (i386-pc-pw32) support was never completed, and the project seems to
+be inactive. See @uref{http://pw32.sourceforge.net/} for more information.
+
+UWIN support has been removed due to a lack of maintenance.
+
+@html
+<hr />
+@end html
+@anchor{x-x-cygwin}
+@heading *-*-cygwin
+Ports of GCC are included with the
+@uref{http://www.cygwin.com/,,Cygwin environment}.
+
+GCC will build under Cygwin without modification; it does not build
+with Microsoft's C++ compiler and there are no plans to make it do so.
+
+The Cygwin native compiler can be configured to target any 32-bit x86
+cpu architecture desired; the default is i686-pc-cygwin. It should be
+used with as up-to-date a version of binutils as possible; use either
+the latest official GNU binutils release in the Cygwin distribution,
+or version 2.20 or above if building your own.
+
+@html
+<hr />
+@end html
+@anchor{x-x-mingw32}
+@heading *-*-mingw32
+GCC will build with and support only MinGW runtime 3.12 and later.
+Earlier versions of headers are incompatible with the new default semantics
+of @code{extern inline} in @code{-std=c99} and @code{-std=gnu99} modes.
+
+To support emitting DWARF debugging info you need to use GNU binutils
+version 2.16 or above containing support for the @code{.secrel32}
+assembler pseudo-op.
+
+@html
+<hr />
+@end html
+@anchor{older}
+@heading Older systems
+GCC contains support files for many older (1980s and early
+1990s) Unix variants. For the most part, support for these systems
+has not been deliberately removed, but it has not been maintained for
+several years and may suffer from bitrot.
+
+Starting with GCC 3.1, each release has a list of ``obsoleted'' systems.
+Support for these systems is still present in that release, but
+@command{configure} will fail unless the @option{--enable-obsolete}
+option is given. Unless a maintainer steps forward, support for these
+systems will be removed from the next release of GCC@.
+
+Support for old systems as hosts for GCC can cause problems if the
+workarounds for compiler, library and operating system bugs affect the
+cleanliness or maintainability of the rest of GCC@. In some cases, to
+bring GCC up on such a system, if still possible with current GCC, may
+require first installing an old version of GCC which did work on that
+system, and using it to compile a more recent GCC, to avoid bugs in the
+vendor compiler. Old releases of GCC 1 and GCC 2 are available in the
+@file{old-releases} directory on the @uref{../mirrors.html,,GCC mirror
+sites}. Header bugs may generally be avoided using
+@command{fixincludes}, but bugs or deficiencies in libraries and the
+operating system may still cause problems.
+
+Support for older systems as targets for cross-compilation is less
+problematic than support for them as hosts for GCC; if an enthusiast
+wishes to make such a target work again (including resurrecting any of
+the targets that never worked with GCC 2, starting from the last
+version before they were removed), patches
+@uref{../contribute.html,,following the usual requirements} would be
+likely to be accepted, since they should not affect the support for more
+modern targets.
+
+For some systems, old versions of GNU binutils may also be useful,
+and are available from @file{pub/binutils/old-releases} on
+@uref{https://sourceware.org/mirrors.html,,sourceware.org mirror sites}.
+
+Some of the information on specific systems above relates to
+such older systems, but much of the information
+about GCC on such systems (which may no longer be applicable to
+current GCC) is to be found in the GCC texinfo manual.
+
+@html
+<hr />
+@end html
+@anchor{elf}
+@heading all ELF targets (SVR4, Solaris 2, etc.)
+C++ support is significantly better on ELF targets if you use the
+@uref{./configure.html#with-gnu-ld,,GNU linker}; duplicate copies of
+inlines, vtables and template instantiations will be discarded
+automatically.
+
+
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***GFDL********************************************************************
+@ifset gfdlhtml
+@include fdl.texi
+@html
+<hr />
+<p>
+@end html
+@ifhtml
+@uref{./index.html,,Return to the GCC Installation page}
+@end ifhtml
+@end ifset
+
+@c ***************************************************************************
+@c Part 6 The End of the Document
+@ifinfo
+@comment node-name, next, previous, up
+@node Concept Index, , GNU Free Documentation License, Top
+@end ifinfo
+
+@ifinfo
+@unnumbered Concept Index
+
+@printindex cp
+
+@contents
+@end ifinfo
+@bye
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Interface
+@chapter Interfacing to GCC Output
+@cindex interfacing to GCC output
+@cindex run-time conventions
+@cindex function call conventions
+@cindex conventions, run-time
+
+GCC is normally configured to use the same function calling convention
+normally in use on the target system. This is done with the
+machine-description macros described (@pxref{Target Macros}).
+
+@cindex unions, returning
+@cindex structures, returning
+@cindex returning structures and unions
+However, returning of structure and union values is done differently on
+some target machines. As a result, functions compiled with PCC
+returning such types cannot be called from code compiled with GCC,
+and vice versa. This does not cause trouble often because few Unix
+library routines return structures or unions.
+
+GCC code returns structures and unions that are 1, 2, 4 or 8 bytes
+long in the same registers used for @code{int} or @code{double} return
+values. (GCC typically allocates variables of such types in
+registers also.) Structures and unions of other sizes are returned by
+storing them into an address passed by the caller (usually in a
+register). The target hook @code{TARGET_STRUCT_VALUE_RTX}
+tells GCC where to pass this address.
+
+By contrast, PCC on most target machines returns structures and unions
+of any size by copying the data into an area of static storage, and then
+returning the address of that storage as if it were a pointer value.
+The caller must copy the data from that memory area to the place where
+the value is wanted. This is slower than the method used by GCC, and
+fails to be reentrant.
+
+On some target machines, such as RISC machines and the 80386, the
+standard system convention is to pass to the subroutine the address of
+where to return the value. On these machines, GCC has been
+configured to be compatible with the standard compiler, when this method
+is used. It may not be compatible for structures of 1, 2, 4 or 8 bytes.
+
+@cindex argument passing
+@cindex passing arguments
+GCC uses the system's standard convention for passing arguments. On
+some machines, the first few arguments are passed in registers; in
+others, all are passed on the stack. It would be possible to use
+registers for argument passing on any machine, and this would probably
+result in a significant speedup. But the result would be complete
+incompatibility with code that follows the standard convention. So this
+change is practical only if you are switching to GCC as the sole C
+compiler for the system. We may implement register argument passing on
+certain machines once we have a complete GNU system so that we can
+compile the libraries with GCC@.
+
+On some machines (particularly the SPARC), certain types of arguments
+are passed ``by invisible reference''. This means that the value is
+stored in memory, and the address of the memory location is passed to
+the subroutine.
+
+@cindex @code{longjmp} and automatic variables
+If you use @code{longjmp}, beware of automatic variables. ISO C says that
+automatic variables that are not declared @code{volatile} have undefined
+values after a @code{longjmp}. And this is all GCC promises to do,
+because it is very difficult to restore register variables correctly, and
+one of GCC's features is that it can put variables in registers without
+your asking it to.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@ignore
+@c man begin INCLUDE
+@include gcc-vers.texi
+@c man end
+
+@c man begin COPYRIGHT
+Copyright @copyright{} 1988-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``GNU General Public License'' and ``Funding
+Free Software'', the Front-Cover texts being (a) (see below), and with
+the Back-Cover Texts being (b) (see below). A copy of the license is
+included in the gfdl(7) man page.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@c Set file name and title for the man page.
+@setfilename gcc
+@settitle GNU project C and C++ compiler
+@c man begin SYNOPSIS
+gcc [@option{-c}|@option{-S}|@option{-E}] [@option{-std=}@var{standard}]
+ [@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
+ [@option{-W}@var{warn}@dots{}] [@option{-Wpedantic}]
+ [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
+ [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
+ [@option{-f}@var{option}@dots{}] [@option{-m}@var{machine-option}@dots{}]
+ [@option{-o} @var{outfile}] [@@@var{file}] @var{infile}@dots{}
+
+Only the most useful options are listed here; see below for the
+remainder. @command{g++} accepts mostly the same options as @command{gcc}.
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7),
+cpp(1), gcov(1), as(1), ld(1), gdb(1)
+and the Info entries for @file{gcc}, @file{cpp}, @file{as},
+@file{ld}, @file{binutils} and @file{gdb}.
+@c man end
+@c man begin BUGS
+For instructions on reporting bugs, see
+@w{@value{BUGURL}}.
+@c man end
+@c man begin AUTHOR
+See the Info entry for @command{gcc}, or
+@w{@uref{https://gcc.gnu.org/onlinedocs/gcc/Contributors.html}},
+for contributors to GCC@.
+@c man end
+@end ignore
+
+@node Invoking GCC
+@chapter GCC Command Options
+@cindex GCC command options
+@cindex command options
+@cindex options, GCC command
+
+@c man begin DESCRIPTION
+When you invoke GCC, it normally does preprocessing, compilation,
+assembly and linking. The ``overall options'' allow you to stop this
+process at an intermediate stage. For example, the @option{-c} option
+says not to run the linker. Then the output consists of object files
+output by the assembler.
+@xref{Overall Options,,Options Controlling the Kind of Output}.
+
+Other options are passed on to one or more stages of processing. Some options
+control the preprocessor and others the compiler itself. Yet other
+options control the assembler and linker; most of these are not
+documented here, since you rarely need to use any of them.
+
+@cindex C compilation options
+Most of the command-line options that you can use with GCC are useful
+for C programs; when an option is only useful with another language
+(usually C++), the explanation says so explicitly. If the description
+for a particular option does not mention a source language, you can use
+that option with all supported languages.
+
+@cindex cross compiling
+@cindex specifying machine version
+@cindex specifying compiler version and target machine
+@cindex compiler version, specifying
+@cindex target machine, specifying
+The usual way to run GCC is to run the executable called @command{gcc}, or
+@command{@var{machine}-gcc} when cross-compiling, or
+@command{@var{machine}-gcc-@var{version}} to run a specific version of GCC.
+When you compile C++ programs, you should invoke GCC as @command{g++}
+instead. @xref{Invoking G++,,Compiling C++ Programs},
+for information about the differences in behavior between @command{gcc}
+and @command{g++} when compiling C++ programs.
+
+@cindex grouping options
+@cindex options, grouping
+The @command{gcc} program accepts options and file names as operands. Many
+options have multi-letter names; therefore multiple single-letter options
+may @emph{not} be grouped: @option{-dv} is very different from @w{@samp{-d
+-v}}.
+
+@cindex order of options
+@cindex options, order
+You can mix options and other arguments. For the most part, the order
+you use doesn't matter. Order does matter when you use several
+options of the same kind; for example, if you specify @option{-L} more
+than once, the directories are searched in the order specified. Also,
+the placement of the @option{-l} option is significant.
+
+Many options have long names starting with @samp{-f} or with
+@samp{-W}---for example,
+@option{-fmove-loop-invariants}, @option{-Wformat} and so on. Most of
+these have both positive and negative forms; the negative form of
+@option{-ffoo} is @option{-fno-foo}. This manual documents
+only one of these two forms, whichever one is not the default.
+
+Some options take one or more arguments typically separated either
+by a space or by the equals sign (@samp{=}) from the option name.
+Unless documented otherwise, an argument can be either numeric or
+a string. Numeric arguments must typically be small unsigned decimal
+or hexadecimal integers. Hexadecimal arguments must begin with
+the @samp{0x} prefix. Arguments to options that specify a size
+threshold of some sort may be arbitrarily large decimal or hexadecimal
+integers followed by a byte size suffix designating a multiple of bytes
+such as @code{kB} and @code{KiB} for kilobyte and kibibyte, respectively,
+@code{MB} and @code{MiB} for megabyte and mebibyte, @code{GB} and
+@code{GiB} for gigabyte and gigibyte, and so on. Such arguments are
+designated by @var{byte-size} in the following text. Refer to the NIST,
+IEC, and other relevant national and international standards for the full
+listing and explanation of the binary and decimal byte size prefixes.
+
+@c man end
+
+@xref{Option Index}, for an index to GCC's options.
+
+@menu
+* Option Summary:: Brief list of all options, without explanations.
+* Overall Options:: Controlling the kind of output:
+ an executable, object files, assembler files,
+ or preprocessed source.
+* Invoking G++:: Compiling C++ programs.
+* C Dialect Options:: Controlling the variant of C language compiled.
+* C++ Dialect Options:: Variations on C++.
+* Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C
+ and Objective-C++.
+* Diagnostic Message Formatting Options:: Controlling how diagnostics should
+ be formatted.
+* Warning Options:: How picky should the compiler be?
+* Static Analyzer Options:: More expensive warnings.
+* Debugging Options:: Producing debuggable code.
+* Optimize Options:: How much optimization?
+* Instrumentation Options:: Enabling profiling and extra run-time error checking.
+* Preprocessor Options:: Controlling header files and macro definitions.
+ Also, getting dependency information for Make.
+* Assembler Options:: Passing options to the assembler.
+* Link Options:: Specifying libraries and so on.
+* Directory Options:: Where to find header files and libraries.
+ Where to find the compiler executable files.
+* Code Gen Options:: Specifying conventions for function calls, data layout
+ and register usage.
+* Developer Options:: Printing GCC configuration info, statistics, and
+ debugging dumps.
+* Submodel Options:: Target-specific options, such as compiling for a
+ specific processor variant.
+* Spec Files:: How to pass switches to sub-processes.
+* Environment Variables:: Env vars that affect GCC.
+* Precompiled Headers:: Compiling a header once, and using it many times.
+* C++ Modules:: Experimental C++20 module system.
+@end menu
+
+@c man begin OPTIONS
+
+@node Option Summary
+@section Option Summary
+
+Here is a summary of all the options, grouped by type. Explanations are
+in the following sections.
+
+@table @emph
+@item Overall Options
+@xref{Overall Options,,Options Controlling the Kind of Output}.
+@gccoptlist{-c -S -E -o @var{file} @gol
+-dumpbase @var{dumpbase} -dumpbase-ext @var{auxdropsuf} @gol
+-dumpdir @var{dumppfx} -x @var{language} @gol
+-v -### --help@r{[}=@var{class}@r{[},@dots{}@r{]]} --target-help --version @gol
+-pass-exit-codes -pipe -specs=@var{file} -wrapper @gol
+@@@var{file} -ffile-prefix-map=@var{old}=@var{new} @gol
+-fplugin=@var{file} -fplugin-arg-@var{name}=@var{arg} @gol
+-fdump-ada-spec@r{[}-slim@r{]} -fada-spec-parent=@var{unit} -fdump-go-spec=@var{file}}
+
+@item C Language Options
+@xref{C Dialect Options,,Options Controlling C Dialect}.
+@gccoptlist{-ansi -std=@var{standard} -aux-info @var{filename} @gol
+-fno-asm @gol
+-fno-builtin -fno-builtin-@var{function} -fcond-mismatch @gol
+-ffreestanding -fgimple -fgnu-tm -fgnu89-inline -fhosted @gol
+-flax-vector-conversions -fms-extensions @gol
+-foffload=@var{arg} -foffload-options=@var{arg} @gol
+-fopenacc -fopenacc-dim=@var{geom} @gol
+-fopenmp -fopenmp-simd @gol
+-fpermitted-flt-eval-methods=@var{standard} @gol
+-fplan9-extensions -fsigned-bitfields -funsigned-bitfields @gol
+-fsigned-char -funsigned-char -fstrict-flex-arrays[=@var{n}] @gol
+-fsso-struct=@var{endianness}}
+
+@item C++ Language Options
+@xref{C++ Dialect Options,,Options Controlling C++ Dialect}.
+@gccoptlist{-fabi-version=@var{n} -fno-access-control @gol
+-faligned-new=@var{n} -fargs-in-order=@var{n} -fchar8_t -fcheck-new @gol
+-fconstexpr-depth=@var{n} -fconstexpr-cache-depth=@var{n} @gol
+-fconstexpr-loop-limit=@var{n} -fconstexpr-ops-limit=@var{n} @gol
+-fno-elide-constructors @gol
+-fno-enforce-eh-specs @gol
+-fno-gnu-keywords @gol
+-fno-implicit-templates @gol
+-fno-implicit-inline-templates @gol
+-fno-implement-inlines @gol
+-fmodule-header@r{[}=@var{kind}@r{]} -fmodule-only -fmodules-ts @gol
+-fmodule-implicit-inline @gol
+-fno-module-lazy @gol
+-fmodule-mapper=@var{specification} @gol
+-fmodule-version-ignore @gol
+-fms-extensions @gol
+-fnew-inheriting-ctors @gol
+-fnew-ttp-matching @gol
+-fno-nonansi-builtins -fnothrow-opt -fno-operator-names @gol
+-fno-optional-diags -fpermissive @gol
+-fno-pretty-templates @gol
+-fno-rtti -fsized-deallocation @gol
+-ftemplate-backtrace-limit=@var{n} @gol
+-ftemplate-depth=@var{n} @gol
+-fno-threadsafe-statics -fuse-cxa-atexit @gol
+-fno-weak -nostdinc++ @gol
+-fvisibility-inlines-hidden @gol
+-fvisibility-ms-compat @gol
+-fext-numeric-literals @gol
+-flang-info-include-translate@r{[}=@var{header}@r{]} @gol
+-flang-info-include-translate-not @gol
+-flang-info-module-cmi@r{[}=@var{module}@r{]} @gol
+-stdlib=@var{libstdc++,libc++} @gol
+-Wabi-tag -Wcatch-value -Wcatch-value=@var{n} @gol
+-Wno-class-conversion -Wclass-memaccess @gol
+-Wcomma-subscript -Wconditionally-supported @gol
+-Wno-conversion-null -Wctad-maybe-unsupported @gol
+-Wctor-dtor-privacy -Wdangling-reference @gol
+-Wno-delete-incomplete @gol
+-Wdelete-non-virtual-dtor -Wno-deprecated-array-compare @gol
+-Wdeprecated-copy -Wdeprecated-copy-dtor @gol
+-Wno-deprecated-enum-enum-conversion -Wno-deprecated-enum-float-conversion @gol
+-Weffc++ -Wno-exceptions -Wextra-semi -Wno-inaccessible-base @gol
+-Wno-inherited-variadic-ctor -Wno-init-list-lifetime @gol
+-Winvalid-imported-macros @gol
+-Wno-invalid-offsetof -Wno-literal-suffix @gol
+-Wmismatched-new-delete -Wmismatched-tags @gol
+-Wmultiple-inheritance -Wnamespaces -Wnarrowing @gol
+-Wnoexcept -Wnoexcept-type -Wnon-virtual-dtor @gol
+-Wpessimizing-move -Wno-placement-new -Wplacement-new=@var{n} @gol
+-Wrange-loop-construct -Wredundant-move -Wredundant-tags @gol
+-Wreorder -Wregister @gol
+-Wstrict-null-sentinel -Wno-subobject-linkage -Wtemplates @gol
+-Wno-non-template-friend -Wold-style-cast @gol
+-Woverloaded-virtual -Wno-pmf-conversions -Wself-move -Wsign-promo @gol
+-Wsized-deallocation -Wsuggest-final-methods @gol
+-Wsuggest-final-types -Wsuggest-override @gol
+-Wno-terminate -Wuseless-cast -Wno-vexing-parse @gol
+-Wvirtual-inheritance @gol
+-Wno-virtual-move-assign -Wvolatile -Wzero-as-null-pointer-constant}
+
+@item Objective-C and Objective-C++ Language Options
+@xref{Objective-C and Objective-C++ Dialect Options,,Options Controlling
+Objective-C and Objective-C++ Dialects}.
+@gccoptlist{-fconstant-string-class=@var{class-name} @gol
+-fgnu-runtime -fnext-runtime @gol
+-fno-nil-receivers @gol
+-fobjc-abi-version=@var{n} @gol
+-fobjc-call-cxx-cdtors @gol
+-fobjc-direct-dispatch @gol
+-fobjc-exceptions @gol
+-fobjc-gc @gol
+-fobjc-nilcheck @gol
+-fobjc-std=objc1 @gol
+-fno-local-ivars @gol
+-fivar-visibility=@r{[}public@r{|}protected@r{|}private@r{|}package@r{]} @gol
+-freplace-objc-classes @gol
+-fzero-link @gol
+-gen-decls @gol
+-Wassign-intercept -Wno-property-assign-default @gol
+-Wno-protocol -Wobjc-root-class -Wselector @gol
+-Wstrict-selector-match @gol
+-Wundeclared-selector}
+
+@item Diagnostic Message Formatting Options
+@xref{Diagnostic Message Formatting Options,,Options to Control Diagnostic Messages Formatting}.
+@gccoptlist{-fmessage-length=@var{n} @gol
+-fdiagnostics-plain-output @gol
+-fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]} @gol
+-fdiagnostics-color=@r{[}auto@r{|}never@r{|}always@r{]} @gol
+-fdiagnostics-urls=@r{[}auto@r{|}never@r{|}always@r{]} @gol
+-fdiagnostics-format=@r{[}text@r{|}sarif-stderr@r{|}sarif-file@r{|}json@r{|}json-stderr@r{|}json-file@r{]} @gol
+-fno-diagnostics-show-option -fno-diagnostics-show-caret @gol
+-fno-diagnostics-show-labels -fno-diagnostics-show-line-numbers @gol
+-fno-diagnostics-show-cwe @gol
+-fno-diagnostics-show-rule @gol
+-fdiagnostics-minimum-margin-width=@var{width} @gol
+-fdiagnostics-parseable-fixits -fdiagnostics-generate-patch @gol
+-fdiagnostics-show-template-tree -fno-elide-type @gol
+-fdiagnostics-path-format=@r{[}none@r{|}separate-events@r{|}inline-events@r{]} @gol
+-fdiagnostics-show-path-depths @gol
+-fno-show-column @gol
+-fdiagnostics-column-unit=@r{[}display@r{|}byte@r{]} @gol
+-fdiagnostics-column-origin=@var{origin} @gol
+-fdiagnostics-escape-format=@r{[}unicode@r{|}bytes@r{]}}
+
+@item Warning Options
+@xref{Warning Options,,Options to Request or Suppress Warnings}.
+@gccoptlist{-fsyntax-only -fmax-errors=@var{n} -Wpedantic @gol
+-pedantic-errors @gol
+-w -Wextra -Wall -Wabi=@var{n} @gol
+-Waddress -Wno-address-of-packed-member -Waggregate-return @gol
+-Walloc-size-larger-than=@var{byte-size} -Walloc-zero @gol
+-Walloca -Walloca-larger-than=@var{byte-size} @gol
+-Wno-aggressive-loop-optimizations @gol
+-Warith-conversion @gol
+-Warray-bounds -Warray-bounds=@var{n} -Warray-compare @gol
+-Wno-attributes -Wattribute-alias=@var{n} -Wno-attribute-alias @gol
+-Wno-attribute-warning @gol
+-Wbidi-chars=@r{[}none@r{|}unpaired@r{|}any@r{|}ucn@r{]} @gol
+-Wbool-compare -Wbool-operation @gol
+-Wno-builtin-declaration-mismatch @gol
+-Wno-builtin-macro-redefined -Wc90-c99-compat -Wc99-c11-compat @gol
+-Wc11-c2x-compat @gol
+-Wc++-compat -Wc++11-compat -Wc++14-compat -Wc++17-compat @gol
+-Wc++20-compat @gol
+-Wno-c++11-extensions -Wno-c++14-extensions -Wno-c++17-extensions @gol
+-Wno-c++20-extensions -Wno-c++23-extensions @gol
+-Wcast-align -Wcast-align=strict -Wcast-function-type -Wcast-qual @gol
+-Wchar-subscripts @gol
+-Wclobbered -Wcomment @gol
+-Wconversion -Wno-coverage-mismatch -Wno-cpp @gol
+-Wdangling-else -Wdangling-pointer -Wdangling-pointer=@var{n} @gol
+-Wdate-time @gol
+-Wno-deprecated -Wno-deprecated-declarations -Wno-designated-init @gol
+-Wdisabled-optimization @gol
+-Wno-discarded-array-qualifiers -Wno-discarded-qualifiers @gol
+-Wno-div-by-zero -Wdouble-promotion @gol
+-Wduplicated-branches -Wduplicated-cond @gol
+-Wempty-body -Wno-endif-labels -Wenum-compare -Wenum-conversion @gol
+-Wenum-int-mismatch @gol
+-Werror -Werror=* -Wexpansion-to-defined -Wfatal-errors @gol
+-Wfloat-conversion -Wfloat-equal -Wformat -Wformat=2 @gol
+-Wno-format-contains-nul -Wno-format-extra-args @gol
+-Wformat-nonliteral -Wformat-overflow=@var{n} @gol
+-Wformat-security -Wformat-signedness -Wformat-truncation=@var{n} @gol
+-Wformat-y2k -Wframe-address @gol
+-Wframe-larger-than=@var{byte-size} -Wno-free-nonheap-object @gol
+-Wno-if-not-aligned -Wno-ignored-attributes @gol
+-Wignored-qualifiers -Wno-incompatible-pointer-types @gol
+-Wimplicit -Wimplicit-fallthrough -Wimplicit-fallthrough=@var{n} @gol
+-Wno-implicit-function-declaration -Wno-implicit-int @gol
+-Winfinite-recursion @gol
+-Winit-self -Winline -Wno-int-conversion -Wint-in-bool-context @gol
+-Wno-int-to-pointer-cast -Wno-invalid-memory-model @gol
+-Winvalid-pch -Winvalid-utf8 -Wno-unicode -Wjump-misses-init @gol
+-Wlarger-than=@var{byte-size} -Wlogical-not-parentheses -Wlogical-op @gol
+-Wlong-long -Wno-lto-type-mismatch -Wmain -Wmaybe-uninitialized @gol
+-Wmemset-elt-size -Wmemset-transposed-args @gol
+-Wmisleading-indentation -Wmissing-attributes -Wmissing-braces @gol
+-Wmissing-field-initializers -Wmissing-format-attribute @gol
+-Wmissing-include-dirs -Wmissing-noreturn -Wno-missing-profile @gol
+-Wno-multichar -Wmultistatement-macros -Wnonnull -Wnonnull-compare @gol
+-Wnormalized=@r{[}none@r{|}id@r{|}nfc@r{|}nfkc@r{]} @gol
+-Wnull-dereference -Wno-odr @gol
+-Wopenacc-parallelism @gol
+-Wopenmp-simd @gol
+-Wno-overflow -Woverlength-strings -Wno-override-init-side-effects @gol
+-Wpacked -Wno-packed-bitfield-compat -Wpacked-not-aligned -Wpadded @gol
+-Wparentheses -Wno-pedantic-ms-format @gol
+-Wpointer-arith -Wno-pointer-compare -Wno-pointer-to-int-cast @gol
+-Wno-pragmas -Wno-prio-ctor-dtor -Wredundant-decls @gol
+-Wrestrict -Wno-return-local-addr -Wreturn-type @gol
+-Wno-scalar-storage-order -Wsequence-point @gol
+-Wshadow -Wshadow=global -Wshadow=local -Wshadow=compatible-local @gol
+-Wno-shadow-ivar @gol
+-Wno-shift-count-negative -Wno-shift-count-overflow -Wshift-negative-value @gol
+-Wno-shift-overflow -Wshift-overflow=@var{n} @gol
+-Wsign-compare -Wsign-conversion @gol
+-Wno-sizeof-array-argument @gol
+-Wsizeof-array-div @gol
+-Wsizeof-pointer-div -Wsizeof-pointer-memaccess @gol
+-Wstack-protector -Wstack-usage=@var{byte-size} -Wstrict-aliasing @gol
+-Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=@var{n} @gol
+-Wstring-compare @gol
+-Wno-stringop-overflow -Wno-stringop-overread @gol
+-Wno-stringop-truncation @gol
+-Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{|}malloc@r{]} @gol
+-Wswitch -Wno-switch-bool -Wswitch-default -Wswitch-enum @gol
+-Wno-switch-outside-range -Wno-switch-unreachable -Wsync-nand @gol
+-Wsystem-headers -Wtautological-compare -Wtrampolines -Wtrigraphs @gol
+-Wtrivial-auto-var-init -Wtsan -Wtype-limits -Wundef @gol
+-Wuninitialized -Wunknown-pragmas @gol
+-Wunsuffixed-float-constants -Wunused @gol
+-Wunused-but-set-parameter -Wunused-but-set-variable @gol
+-Wunused-const-variable -Wunused-const-variable=@var{n} @gol
+-Wunused-function -Wunused-label -Wunused-local-typedefs @gol
+-Wunused-macros @gol
+-Wunused-parameter -Wno-unused-result @gol
+-Wunused-value -Wunused-variable @gol
+-Wno-varargs -Wvariadic-macros @gol
+-Wvector-operation-performance @gol
+-Wvla -Wvla-larger-than=@var{byte-size} -Wno-vla-larger-than @gol
+-Wvolatile-register-var -Wwrite-strings @gol
+-Wxor-used-as-pow @gol
+-Wzero-length-bounds}
+
+@item Static Analyzer Options
+@gccoptlist{
+-fanalyzer @gol
+-fanalyzer-call-summaries @gol
+-fanalyzer-checker=@var{name} @gol
+-fno-analyzer-feasibility @gol
+-fanalyzer-fine-grained @gol
+-fno-analyzer-state-merge @gol
+-fno-analyzer-state-purge @gol
+-fanalyzer-transitivity @gol
+-fno-analyzer-undo-inlining @gol
+-fanalyzer-verbose-edges @gol
+-fanalyzer-verbose-state-changes @gol
+-fanalyzer-verbosity=@var{level} @gol
+-fdump-analyzer @gol
+-fdump-analyzer-callgraph @gol
+-fdump-analyzer-exploded-graph @gol
+-fdump-analyzer-exploded-nodes @gol
+-fdump-analyzer-exploded-nodes-2 @gol
+-fdump-analyzer-exploded-nodes-3 @gol
+-fdump-analyzer-exploded-paths @gol
+-fdump-analyzer-feasibility @gol
+-fdump-analyzer-json @gol
+-fdump-analyzer-state-purge @gol
+-fdump-analyzer-stderr @gol
+-fdump-analyzer-supergraph @gol
+-fdump-analyzer-untracked @gol
+-Wno-analyzer-double-fclose @gol
+-Wno-analyzer-double-free @gol
+-Wno-analyzer-exposure-through-output-file @gol
+-Wno-analyzer-exposure-through-uninit-copy @gol
+-Wno-analyzer-fd-access-mode-mismatch @gol
+-Wno-analyzer-fd-double-close @gol
+-Wno-analyzer-fd-leak @gol
+-Wno-analyzer-fd-use-after-close @gol
+-Wno-analyzer-fd-use-without-check @gol
+-Wno-analyzer-file-leak @gol
+-Wno-analyzer-free-of-non-heap @gol
+-Wno-analyzer-imprecise-fp-arithmetic @gol
+-Wno-analyzer-jump-through-null @gol
+-Wno-analyzer-malloc-leak @gol
+-Wno-analyzer-mismatching-deallocation @gol
+-Wno-analyzer-null-argument @gol
+-Wno-analyzer-null-dereference @gol
+-Wno-analyzer-out-of-bounds @gol
+-Wno-analyzer-possible-null-argument @gol
+-Wno-analyzer-possible-null-dereference @gol
+-Wno-analyzer-putenv-of-auto-var @gol
+-Wno-analyzer-shift-count-negative @gol
+-Wno-analyzer-shift-count-overflow @gol
+-Wno-analyzer-stale-setjmp-buffer @gol
+-Wno-analyzer-tainted-allocation-size @gol
+-Wno-analyzer-tainted-array-index @gol
+-Wno-analyzer-tainted-divisor @gol
+-Wno-analyzer-tainted-offset @gol
+-Wno-analyzer-tainted-size @gol
+-Wanalyzer-too-complex @gol
+-Wno-analyzer-unsafe-call-within-signal-handler @gol
+-Wno-analyzer-use-after-free @gol
+-Wno-analyzer-use-of-pointer-in-stale-stack-frame @gol
+-Wno-analyzer-use-of-uninitialized-value @gol
+-Wno-analyzer-va-arg-type-mismatch @gol
+-Wno-analyzer-va-list-exhausted @gol
+-Wno-analyzer-va-list-leak @gol
+-Wno-analyzer-va-list-use-after-va-end @gol
+-Wno-analyzer-write-to-const @gol
+-Wno-analyzer-write-to-string-literal @gol
+}
+
+@item C and Objective-C-only Warning Options
+@gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol
+-Wmissing-parameter-type -Wmissing-prototypes -Wnested-externs @gol
+-Wold-style-declaration -Wold-style-definition @gol
+-Wstrict-prototypes -Wtraditional -Wtraditional-conversion @gol
+-Wdeclaration-after-statement -Wpointer-sign}
+
+@item Debugging Options
+@xref{Debugging Options,,Options for Debugging Your Program}.
+@gccoptlist{-g -g@var{level} -gdwarf -gdwarf-@var{version} @gol
+-gbtf -gctf -gctf@var{level} @gol
+-ggdb -grecord-gcc-switches -gno-record-gcc-switches @gol
+-gstrict-dwarf -gno-strict-dwarf @gol
+-gas-loc-support -gno-as-loc-support @gol
+-gas-locview-support -gno-as-locview-support @gol
+-gcolumn-info -gno-column-info -gdwarf32 -gdwarf64 @gol
+-gstatement-frontiers -gno-statement-frontiers @gol
+-gvariable-location-views -gno-variable-location-views @gol
+-ginternal-reset-location-views -gno-internal-reset-location-views @gol
+-ginline-points -gno-inline-points @gol
+-gvms -gz@r{[}=@var{type}@r{]} @gol
+-gsplit-dwarf -gdescribe-dies -gno-describe-dies @gol
+-fdebug-prefix-map=@var{old}=@var{new} -fdebug-types-section @gol
+-fno-eliminate-unused-debug-types @gol
+-femit-struct-debug-baseonly -femit-struct-debug-reduced @gol
+-femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]} @gol
+-fno-eliminate-unused-debug-symbols -femit-class-debug-always @gol
+-fno-merge-debug-strings -fno-dwarf2-cfi-asm @gol
+-fvar-tracking -fvar-tracking-assignments}
+
+@item Optimization Options
+@xref{Optimize Options,,Options that Control Optimization}.
+@gccoptlist{-faggressive-loop-optimizations @gol
+-falign-functions[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
+-falign-jumps[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
+-falign-labels[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
+-falign-loops[=@var{n}[:@var{m}:[@var{n2}[:@var{m2}]]]] @gol
+-fno-allocation-dce -fallow-store-data-races @gol
+-fassociative-math -fauto-profile -fauto-profile[=@var{path}] @gol
+-fauto-inc-dec -fbranch-probabilities @gol
+-fcaller-saves @gol
+-fcombine-stack-adjustments -fconserve-stack @gol
+-fcompare-elim -fcprop-registers -fcrossjumping @gol
+-fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules @gol
+-fcx-limited-range @gol
+-fdata-sections -fdce -fdelayed-branch @gol
+-fdelete-null-pointer-checks -fdevirtualize -fdevirtualize-speculatively @gol
+-fdevirtualize-at-ltrans -fdse @gol
+-fearly-inlining -fipa-sra -fexpensive-optimizations -ffat-lto-objects @gol
+-ffast-math -ffinite-math-only -ffloat-store -fexcess-precision=@var{style} @gol
+-ffinite-loops @gol
+-fforward-propagate -ffp-contract=@var{style} -ffunction-sections @gol
+-fgcse -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity @gol
+-fgcse-sm -fhoist-adjacent-loads -fif-conversion @gol
+-fif-conversion2 -findirect-inlining @gol
+-finline-functions -finline-functions-called-once -finline-limit=@var{n} @gol
+-finline-small-functions -fipa-modref -fipa-cp -fipa-cp-clone @gol
+-fipa-bit-cp -fipa-vrp -fipa-pta -fipa-profile -fipa-pure-const @gol
+-fipa-reference -fipa-reference-addressable @gol
+-fipa-stack-alignment -fipa-icf -fira-algorithm=@var{algorithm} @gol
+-flive-patching=@var{level} @gol
+-fira-region=@var{region} -fira-hoist-pressure @gol
+-fira-loop-pressure -fno-ira-share-save-slots @gol
+-fno-ira-share-spill-slots @gol
+-fisolate-erroneous-paths-dereference -fisolate-erroneous-paths-attribute @gol
+-fivopts -fkeep-inline-functions -fkeep-static-functions @gol
+-fkeep-static-consts -flimit-function-alignment -flive-range-shrinkage @gol
+-floop-block -floop-interchange -floop-strip-mine @gol
+-floop-unroll-and-jam -floop-nest-optimize @gol
+-floop-parallelize-all -flra-remat -flto -flto-compression-level @gol
+-flto-partition=@var{alg} -fmerge-all-constants @gol
+-fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves @gol
+-fmove-loop-invariants -fmove-loop-stores -fno-branch-count-reg @gol
+-fno-defer-pop -fno-fp-int-builtin-inexact -fno-function-cse @gol
+-fno-guess-branch-probability -fno-inline -fno-math-errno -fno-peephole @gol
+-fno-peephole2 -fno-printf-return-value -fno-sched-interblock @gol
+-fno-sched-spec -fno-signed-zeros @gol
+-fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol
+-fomit-frame-pointer -foptimize-sibling-calls @gol
+-fpartial-inlining -fpeel-loops -fpredictive-commoning @gol
+-fprefetch-loop-arrays @gol
+-fprofile-correction @gol
+-fprofile-use -fprofile-use=@var{path} -fprofile-partial-training @gol
+-fprofile-values -fprofile-reorder-functions @gol
+-freciprocal-math -free -frename-registers -freorder-blocks @gol
+-freorder-blocks-algorithm=@var{algorithm} @gol
+-freorder-blocks-and-partition -freorder-functions @gol
+-frerun-cse-after-loop -freschedule-modulo-scheduled-loops @gol
+-frounding-math -fsave-optimization-record @gol
+-fsched2-use-superblocks -fsched-pressure @gol
+-fsched-spec-load -fsched-spec-load-dangerous @gol
+-fsched-stalled-insns-dep[=@var{n}] -fsched-stalled-insns[=@var{n}] @gol
+-fsched-group-heuristic -fsched-critical-path-heuristic @gol
+-fsched-spec-insn-heuristic -fsched-rank-heuristic @gol
+-fsched-last-insn-heuristic -fsched-dep-count-heuristic @gol
+-fschedule-fusion @gol
+-fschedule-insns -fschedule-insns2 -fsection-anchors @gol
+-fselective-scheduling -fselective-scheduling2 @gol
+-fsel-sched-pipelining -fsel-sched-pipelining-outer-loops @gol
+-fsemantic-interposition -fshrink-wrap -fshrink-wrap-separate @gol
+-fsignaling-nans @gol
+-fsingle-precision-constant -fsplit-ivs-in-unroller -fsplit-loops@gol
+-fsplit-paths @gol
+-fsplit-wide-types -fsplit-wide-types-early -fssa-backprop -fssa-phiopt @gol
+-fstdarg-opt -fstore-merging -fstrict-aliasing -fipa-strict-aliasing @gol
+-fthread-jumps -ftracer -ftree-bit-ccp @gol
+-ftree-builtin-call-dce -ftree-ccp -ftree-ch @gol
+-ftree-coalesce-vars -ftree-copy-prop -ftree-dce -ftree-dominator-opts @gol
+-ftree-dse -ftree-forwprop -ftree-fre -fcode-hoisting @gol
+-ftree-loop-if-convert -ftree-loop-im @gol
+-ftree-phiprop -ftree-loop-distribution -ftree-loop-distribute-patterns @gol
+-ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize @gol
+-ftree-loop-vectorize @gol
+-ftree-parallelize-loops=@var{n} -ftree-pre -ftree-partial-pre -ftree-pta @gol
+-ftree-reassoc -ftree-scev-cprop -ftree-sink -ftree-slsr -ftree-sra @gol
+-ftree-switch-conversion -ftree-tail-merge @gol
+-ftree-ter -ftree-vectorize -ftree-vrp -ftrivial-auto-var-init @gol
+-funconstrained-commons -funit-at-a-time -funroll-all-loops @gol
+-funroll-loops -funsafe-math-optimizations -funswitch-loops @gol
+-fipa-ra -fvariable-expansion-in-unroller -fvect-cost-model -fvpt @gol
+-fweb -fwhole-program -fwpa -fuse-linker-plugin -fzero-call-used-regs @gol
+--param @var{name}=@var{value}
+-O -O0 -O1 -O2 -O3 -Os -Ofast -Og -Oz}
+
+@item Program Instrumentation Options
+@xref{Instrumentation Options,,Program Instrumentation Options}.
+@gccoptlist{-p -pg -fprofile-arcs --coverage -ftest-coverage @gol
+-fprofile-abs-path @gol
+-fprofile-dir=@var{path} -fprofile-generate -fprofile-generate=@var{path} @gol
+-fprofile-info-section -fprofile-info-section=@var{name} @gol
+-fprofile-note=@var{path} -fprofile-prefix-path=@var{path} @gol
+-fprofile-update=@var{method} -fprofile-filter-files=@var{regex} @gol
+-fprofile-exclude-files=@var{regex} @gol
+-fprofile-reproducible=@r{[}multithreaded@r{|}parallel-runs@r{|}serial@r{]} @gol
+-fsanitize=@var{style} -fsanitize-recover -fsanitize-recover=@var{style} @gol
+-fsanitize-trap -fsanitize-trap=@var{style} @gol
+-fasan-shadow-offset=@var{number} -fsanitize-sections=@var{s1},@var{s2},... @gol
+-fsanitize-undefined-trap-on-error -fbounds-check @gol
+-fcf-protection=@r{[}full@r{|}branch@r{|}return@r{|}none@r{|}check@r{]} @gol
+-fharden-compares -fharden-conditional-branches @gol
+-fstack-protector -fstack-protector-all -fstack-protector-strong @gol
+-fstack-protector-explicit -fstack-check @gol
+-fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol
+-fno-stack-limit -fsplit-stack @gol
+-fvtable-verify=@r{[}std@r{|}preinit@r{|}none@r{]} @gol
+-fvtv-counts -fvtv-debug @gol
+-finstrument-functions -finstrument-functions-once @gol
+-finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{} @gol
+-finstrument-functions-exclude-file-list=@var{file},@var{file},@dots{}} @gol
+-fprofile-prefix-map=@var{old}=@var{new}
+
+@item Preprocessor Options
+@xref{Preprocessor Options,,Options Controlling the Preprocessor}.
+@gccoptlist{-A@var{question}=@var{answer} @gol
+-A-@var{question}@r{[}=@var{answer}@r{]} @gol
+-C -CC -D@var{macro}@r{[}=@var{defn}@r{]} @gol
+-dD -dI -dM -dN -dU @gol
+-fdebug-cpp -fdirectives-only -fdollars-in-identifiers @gol
+-fexec-charset=@var{charset} -fextended-identifiers @gol
+-finput-charset=@var{charset} -flarge-source-files @gol
+-fmacro-prefix-map=@var{old}=@var{new} -fmax-include-depth=@var{depth} @gol
+-fno-canonical-system-headers -fpch-deps -fpch-preprocess @gol
+-fpreprocessed -ftabstop=@var{width} -ftrack-macro-expansion @gol
+-fwide-exec-charset=@var{charset} -fworking-directory @gol
+-H -imacros @var{file} -include @var{file} @gol
+-M -MD -MF -MG -MM -MMD -MP -MQ -MT -Mno-modules @gol
+-no-integrated-cpp -P -pthread -remap @gol
+-traditional -traditional-cpp -trigraphs @gol
+-U@var{macro} -undef @gol
+-Wp,@var{option} -Xpreprocessor @var{option}}
+
+@item Assembler Options
+@xref{Assembler Options,,Passing Options to the Assembler}.
+@gccoptlist{-Wa,@var{option} -Xassembler @var{option}}
+
+@item Linker Options
+@xref{Link Options,,Options for Linking}.
+@gccoptlist{@var{object-file-name} -fuse-ld=@var{linker} -l@var{library} @gol
+-nostartfiles -nodefaultlibs -nolibc -nostdlib -nostdlib++ @gol
+-e @var{entry} --entry=@var{entry} @gol
+-pie -pthread -r -rdynamic @gol
+-s -static -static-pie -static-libgcc -static-libstdc++ @gol
+-static-libasan -static-libtsan -static-liblsan -static-libubsan @gol
+-shared -shared-libgcc -symbolic @gol
+-T @var{script} -Wl,@var{option} -Xlinker @var{option} @gol
+-u @var{symbol} -z @var{keyword}}
+
+@item Directory Options
+@xref{Directory Options,,Options for Directory Search}.
+@gccoptlist{-B@var{prefix} -I@var{dir} -I- @gol
+-idirafter @var{dir} @gol
+-imacros @var{file} -imultilib @var{dir} @gol
+-iplugindir=@var{dir} -iprefix @var{file} @gol
+-iquote @var{dir} -isysroot @var{dir} -isystem @var{dir} @gol
+-iwithprefix @var{dir} -iwithprefixbefore @var{dir} @gol
+-L@var{dir} -no-canonical-prefixes --no-sysroot-suffix @gol
+-nostdinc -nostdinc++ --sysroot=@var{dir}}
+
+@item Code Generation Options
+@xref{Code Gen Options,,Options for Code Generation Conventions}.
+@gccoptlist{-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol
+-ffixed-@var{reg} -fexceptions @gol
+-fnon-call-exceptions -fdelete-dead-exceptions -funwind-tables @gol
+-fasynchronous-unwind-tables @gol
+-fno-gnu-unique @gol
+-finhibit-size-directive -fcommon -fno-ident @gol
+-fpcc-struct-return -fpic -fPIC -fpie -fPIE -fno-plt @gol
+-fno-jump-tables -fno-bit-tests @gol
+-frecord-gcc-switches @gol
+-freg-struct-return -fshort-enums -fshort-wchar @gol
+-fverbose-asm -fpack-struct[=@var{n}] @gol
+-fleading-underscore -ftls-model=@var{model} @gol
+-fstack-reuse=@var{reuse_level} @gol
+-ftrampolines -ftrapv -fwrapv @gol
+-fvisibility=@r{[}default@r{|}internal@r{|}hidden@r{|}protected@r{]} @gol
+-fstrict-volatile-bitfields -fsync-libcalls}
+
+@item Developer Options
+@xref{Developer Options,,GCC Developer Options}.
+@gccoptlist{-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol
+-dumpfullversion -fcallgraph-info@r{[}=su,da@r{]}
+-fchecking -fchecking=@var{n}
+-fdbg-cnt-list @gol -fdbg-cnt=@var{counter-value-list} @gol
+-fdisable-ipa-@var{pass_name} @gol
+-fdisable-rtl-@var{pass_name} @gol
+-fdisable-rtl-@var{pass-name}=@var{range-list} @gol
+-fdisable-tree-@var{pass_name} @gol
+-fdisable-tree-@var{pass-name}=@var{range-list} @gol
+-fdump-debug -fdump-earlydebug @gol
+-fdump-noaddr -fdump-unnumbered -fdump-unnumbered-links @gol
+-fdump-final-insns@r{[}=@var{file}@r{]} @gol
+-fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline @gol
+-fdump-lang-all @gol
+-fdump-lang-@var{switch} @gol
+-fdump-lang-@var{switch}-@var{options} @gol
+-fdump-lang-@var{switch}-@var{options}=@var{filename} @gol
+-fdump-passes @gol
+-fdump-rtl-@var{pass} -fdump-rtl-@var{pass}=@var{filename} @gol
+-fdump-statistics @gol
+-fdump-tree-all @gol
+-fdump-tree-@var{switch} @gol
+-fdump-tree-@var{switch}-@var{options} @gol
+-fdump-tree-@var{switch}-@var{options}=@var{filename} @gol
+-fcompare-debug@r{[}=@var{opts}@r{]} -fcompare-debug-second @gol
+-fenable-@var{kind}-@var{pass} @gol
+-fenable-@var{kind}-@var{pass}=@var{range-list} @gol
+-fira-verbose=@var{n} @gol
+-flto-report -flto-report-wpa -fmem-report-wpa @gol
+-fmem-report -fpre-ipa-mem-report -fpost-ipa-mem-report @gol
+-fopt-info -fopt-info-@var{options}@r{[}=@var{file}@r{]} @gol
+-fmultiflags -fprofile-report @gol
+-frandom-seed=@var{string} -fsched-verbose=@var{n} @gol
+-fsel-sched-verbose -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose @gol
+-fstats -fstack-usage -ftime-report -ftime-report-details @gol
+-fvar-tracking-assignments-toggle -gtoggle @gol
+-print-file-name=@var{library} -print-libgcc-file-name @gol
+-print-multi-directory -print-multi-lib -print-multi-os-directory @gol
+-print-prog-name=@var{program} -print-search-dirs -Q @gol
+-print-sysroot -print-sysroot-headers-suffix @gol
+-save-temps -save-temps=cwd -save-temps=obj -time@r{[}=@var{file}@r{]}}
+
+@item Machine-Dependent Options
+@xref{Submodel Options,,Machine-Dependent Options}.
+@c This list is ordered alphanumerically by subsection name.
+@c Try and put the significant identifier (CPU or system) first,
+@c so users have a clue at guessing where the ones they want will be.
+
+@emph{AArch64 Options}
+@gccoptlist{-mabi=@var{name} -mbig-endian -mlittle-endian @gol
+-mgeneral-regs-only @gol
+-mcmodel=tiny -mcmodel=small -mcmodel=large @gol
+-mstrict-align -mno-strict-align @gol
+-momit-leaf-frame-pointer @gol
+-mtls-dialect=desc -mtls-dialect=traditional @gol
+-mtls-size=@var{size} @gol
+-mfix-cortex-a53-835769 -mfix-cortex-a53-843419 @gol
+-mlow-precision-recip-sqrt -mlow-precision-sqrt -mlow-precision-div @gol
+-mpc-relative-literal-loads @gol
+-msign-return-address=@var{scope} @gol
+-mbranch-protection=@var{none}|@var{standard}|@var{pac-ret}[+@var{leaf}
++@var{b-key}]|@var{bti} @gol
+-mharden-sls=@var{opts} @gol
+-march=@var{name} -mcpu=@var{name} -mtune=@var{name} @gol
+-moverride=@var{string} -mverbose-cost-dump @gol
+-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{sysreg} @gol
+-mstack-protector-guard-offset=@var{offset} -mtrack-speculation @gol
+-moutline-atomics }
+
+@emph{Adapteva Epiphany Options}
+@gccoptlist{-mhalf-reg-file -mprefer-short-insn-regs @gol
+-mbranch-cost=@var{num} -mcmove -mnops=@var{num} -msoft-cmpsf @gol
+-msplit-lohi -mpost-inc -mpost-modify -mstack-offset=@var{num} @gol
+-mround-nearest -mlong-calls -mshort-calls -msmall16 @gol
+-mfp-mode=@var{mode} -mvect-double -max-vect-align=@var{num} @gol
+-msplit-vecmove-early -m1reg-@var{reg}}
+
+@emph{AMD GCN Options}
+@gccoptlist{-march=@var{gpu} -mtune=@var{gpu} -mstack-size=@var{bytes}}
+
+@emph{ARC Options}
+@gccoptlist{-mbarrel-shifter -mjli-always @gol
+-mcpu=@var{cpu} -mA6 -mARC600 -mA7 -mARC700 @gol
+-mdpfp -mdpfp-compact -mdpfp-fast -mno-dpfp-lrsr @gol
+-mea -mno-mpy -mmul32x16 -mmul64 -matomic @gol
+-mnorm -mspfp -mspfp-compact -mspfp-fast -msimd -msoft-float -mswap @gol
+-mcrc -mdsp-packa -mdvbf -mlock -mmac-d16 -mmac-24 -mrtsc -mswape @gol
+-mtelephony -mxy -misize -mannotate-align -marclinux -marclinux_prof @gol
+-mlong-calls -mmedium-calls -msdata -mirq-ctrl-saved @gol
+-mrgf-banked-regs -mlpc-width=@var{width} -G @var{num} @gol
+-mvolatile-cache -mtp-regno=@var{regno} @gol
+-malign-call -mauto-modify-reg -mbbit-peephole -mno-brcc @gol
+-mcase-vector-pcrel -mcompact-casesi -mno-cond-exec -mearly-cbranchsi @gol
+-mexpand-adddi -mindexed-loads -mlra -mlra-priority-none @gol
+-mlra-priority-compact -mlra-priority-noncompact -mmillicode @gol
+-mmixed-code -mq-class -mRcq -mRcw -msize-level=@var{level} @gol
+-mtune=@var{cpu} -mmultcost=@var{num} -mcode-density-frame @gol
+-munalign-prob-threshold=@var{probability} -mmpy-option=@var{multo} @gol
+-mdiv-rem -mcode-density -mll64 -mfpu=@var{fpu} -mrf16 -mbranch-index}
+
+@emph{ARM Options}
+@gccoptlist{-mapcs-frame -mno-apcs-frame @gol
+-mabi=@var{name} @gol
+-mapcs-stack-check -mno-apcs-stack-check @gol
+-mapcs-reentrant -mno-apcs-reentrant @gol
+-mgeneral-regs-only @gol
+-msched-prolog -mno-sched-prolog @gol
+-mlittle-endian -mbig-endian @gol
+-mbe8 -mbe32 @gol
+-mfloat-abi=@var{name} @gol
+-mfp16-format=@var{name}
+-mthumb-interwork -mno-thumb-interwork @gol
+-mcpu=@var{name} -march=@var{name} -mfpu=@var{name} @gol
+-mtune=@var{name} -mprint-tune-info @gol
+-mstructure-size-boundary=@var{n} @gol
+-mabort-on-noreturn @gol
+-mlong-calls -mno-long-calls @gol
+-msingle-pic-base -mno-single-pic-base @gol
+-mpic-register=@var{reg} @gol
+-mnop-fun-dllimport @gol
+-mpoke-function-name @gol
+-mthumb -marm -mflip-thumb @gol
+-mtpcs-frame -mtpcs-leaf-frame @gol
+-mcaller-super-interworking -mcallee-super-interworking @gol
+-mtp=@var{name} -mtls-dialect=@var{dialect} @gol
+-mword-relocations @gol
+-mfix-cortex-m3-ldrd @gol
+-mfix-cortex-a57-aes-1742098 @gol
+-mfix-cortex-a72-aes-1655431 @gol
+-munaligned-access @gol
+-mneon-for-64bits @gol
+-mslow-flash-data @gol
+-masm-syntax-unified @gol
+-mrestrict-it @gol
+-mverbose-cost-dump @gol
+-mpure-code @gol
+-mcmse @gol
+-mfix-cmse-cve-2021-35465 @gol
+-mstack-protector-guard=@var{guard} -mstack-protector-guard-offset=@var{offset} @gol
+-mfdpic}
+
+@emph{AVR Options}
+@gccoptlist{-mmcu=@var{mcu} -mabsdata -maccumulate-args @gol
+-mbranch-cost=@var{cost} @gol
+-mcall-prologues -mgas-isr-prologues -mint8 @gol
+-mdouble=@var{bits} -mlong-double=@var{bits} @gol
+-mn_flash=@var{size} -mno-interrupts @gol
+-mmain-is-OS_task -mrelax -mrmw -mstrict-X -mtiny-stack @gol
+-mfract-convert-truncate @gol
+-mshort-calls -nodevicelib -nodevicespecs @gol
+-Waddr-space-convert -Wmisspelled-isr}
+
+@emph{Blackfin Options}
+@gccoptlist{-mcpu=@var{cpu}@r{[}-@var{sirevision}@r{]} @gol
+-msim -momit-leaf-frame-pointer -mno-omit-leaf-frame-pointer @gol
+-mspecld-anomaly -mno-specld-anomaly -mcsync-anomaly -mno-csync-anomaly @gol
+-mlow-64k -mno-low64k -mstack-check-l1 -mid-shared-library @gol
+-mno-id-shared-library -mshared-library-id=@var{n} @gol
+-mleaf-id-shared-library -mno-leaf-id-shared-library @gol
+-msep-data -mno-sep-data -mlong-calls -mno-long-calls @gol
+-mfast-fp -minline-plt -mmulticore -mcorea -mcoreb -msdram @gol
+-micplb}
+
+@emph{C6X Options}
+@gccoptlist{-mbig-endian -mlittle-endian -march=@var{cpu} @gol
+-msim -msdata=@var{sdata-type}}
+
+@emph{CRIS Options}
+@gccoptlist{-mcpu=@var{cpu} -march=@var{cpu}
+-mtune=@var{cpu} -mmax-stack-frame=@var{n} @gol
+-metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol
+-mstack-align -mdata-align -mconst-align @gol
+-m32-bit -m16-bit -m8-bit -mno-prologue-epilogue @gol
+-melf -maout -sim -sim2 @gol
+-mmul-bug-workaround -mno-mul-bug-workaround}
+
+@emph{C-SKY Options}
+@gccoptlist{-march=@var{arch} -mcpu=@var{cpu} @gol
+-mbig-endian -EB -mlittle-endian -EL @gol
+-mhard-float -msoft-float -mfpu=@var{fpu} -mdouble-float -mfdivdu @gol
+-mfloat-abi=@var{name} @gol
+-melrw -mistack -mmp -mcp -mcache -msecurity -mtrust @gol
+-mdsp -medsp -mvdsp @gol
+-mdiv -msmart -mhigh-registers -manchor @gol
+-mpushpop -mmultiple-stld -mconstpool -mstack-size -mccrt @gol
+-mbranch-cost=@var{n} -mcse-cc -msched-prolog -msim}
+
+@emph{Darwin Options}
+@gccoptlist{-all_load -allowable_client -arch -arch_errors_fatal @gol
+-arch_only -bind_at_load -bundle -bundle_loader @gol
+-client_name -compatibility_version -current_version @gol
+-dead_strip @gol
+-dependency-file -dylib_file -dylinker_install_name @gol
+-dynamic -dynamiclib -exported_symbols_list @gol
+-filelist -flat_namespace -force_cpusubtype_ALL @gol
+-force_flat_namespace -headerpad_max_install_names @gol
+-iframework @gol
+-image_base -init -install_name -keep_private_externs @gol
+-multi_module -multiply_defined -multiply_defined_unused @gol
+-noall_load -no_dead_strip_inits_and_terms @gol
+-nofixprebinding -nomultidefs -noprebind -noseglinkedit @gol
+-pagezero_size -prebind -prebind_all_twolevel_modules @gol
+-private_bundle -read_only_relocs -sectalign @gol
+-sectobjectsymbols -whyload -seg1addr @gol
+-sectcreate -sectobjectsymbols -sectorder @gol
+-segaddr -segs_read_only_addr -segs_read_write_addr @gol
+-seg_addr_table -seg_addr_table_filename -seglinkedit @gol
+-segprot -segs_read_only_addr -segs_read_write_addr @gol
+-single_module -static -sub_library -sub_umbrella @gol
+-twolevel_namespace -umbrella -undefined @gol
+-unexported_symbols_list -weak_reference_mismatches @gol
+-whatsloaded -F -gused -gfull -mmacosx-version-min=@var{version} @gol
+-mkernel -mone-byte-bool}
+
+@emph{DEC Alpha Options}
+@gccoptlist{-mno-fp-regs -msoft-float @gol
+-mieee -mieee-with-inexact -mieee-conformant @gol
+-mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol
+-mtrap-precision=@var{mode} -mbuild-constants @gol
+-mcpu=@var{cpu-type} -mtune=@var{cpu-type} @gol
+-mbwx -mmax -mfix -mcix @gol
+-mfloat-vax -mfloat-ieee @gol
+-mexplicit-relocs -msmall-data -mlarge-data @gol
+-msmall-text -mlarge-text @gol
+-mmemory-latency=@var{time}}
+
+@emph{eBPF Options}
+@gccoptlist{-mbig-endian -mlittle-endian -mkernel=@var{version}
+-mframe-limit=@var{bytes} -mxbpf -mco-re -mno-co-re
+-mjmpext -mjmp32 -malu32 -mcpu=@var{version}}
+
+@emph{FR30 Options}
+@gccoptlist{-msmall-model -mno-lsim}
+
+@emph{FT32 Options}
+@gccoptlist{-msim -mlra -mnodiv -mft32b -mcompress -mnopm}
+
+@emph{FRV Options}
+@gccoptlist{-mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 @gol
+-mhard-float -msoft-float @gol
+-malloc-cc -mfixed-cc -mdword -mno-dword @gol
+-mdouble -mno-double @gol
+-mmedia -mno-media -mmuladd -mno-muladd @gol
+-mfdpic -minline-plt -mgprel-ro -multilib-library-pic @gol
+-mlinked-fp -mlong-calls -malign-labels @gol
+-mlibrary-pic -macc-4 -macc-8 @gol
+-mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move @gol
+-moptimize-membar -mno-optimize-membar @gol
+-mscc -mno-scc -mcond-exec -mno-cond-exec @gol
+-mvliw-branch -mno-vliw-branch @gol
+-mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec @gol
+-mno-nested-cond-exec -mtomcat-stats @gol
+-mTLS -mtls @gol
+-mcpu=@var{cpu}}
+
+@emph{GNU/Linux Options}
+@gccoptlist{-mglibc -muclibc -mmusl -mbionic -mandroid @gol
+-tno-android-cc -tno-android-ld}
+
+@emph{H8/300 Options}
+@gccoptlist{-mrelax -mh -ms -mn -mexr -mno-exr -mint32 -malign-300}
+
+@emph{HPPA Options}
+@gccoptlist{-march=@var{architecture-type} @gol
+-mcaller-copies -mdisable-fpregs -mdisable-indexing @gol
+-mfast-indirect-calls -mgas -mgnu-ld -mhp-ld @gol
+-mfixed-range=@var{register-range} @gol
+-mjump-in-delay -mlinker-opt -mlong-calls @gol
+-mlong-load-store -mno-disable-fpregs @gol
+-mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol
+-mno-jump-in-delay -mno-long-load-store @gol
+-mno-portable-runtime -mno-soft-float @gol
+-mno-space-regs -msoft-float -mpa-risc-1-0 @gol
+-mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol
+-mschedule=@var{cpu-type} -mspace-regs -msio -mwsio @gol
+-munix=@var{unix-std} -nolibdld -static -threads}
+
+@emph{IA-64 Options}
+@gccoptlist{-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol
+-mvolatile-asm-stop -mregister-names -msdata -mno-sdata @gol
+-mconstant-gp -mauto-pic -mfused-madd @gol
+-minline-float-divide-min-latency @gol
+-minline-float-divide-max-throughput @gol
+-mno-inline-float-divide @gol
+-minline-int-divide-min-latency @gol
+-minline-int-divide-max-throughput @gol
+-mno-inline-int-divide @gol
+-minline-sqrt-min-latency -minline-sqrt-max-throughput @gol
+-mno-inline-sqrt @gol
+-mdwarf2-asm -mearly-stop-bits @gol
+-mfixed-range=@var{register-range} -mtls-size=@var{tls-size} @gol
+-mtune=@var{cpu-type} -milp32 -mlp64 @gol
+-msched-br-data-spec -msched-ar-data-spec -msched-control-spec @gol
+-msched-br-in-data-spec -msched-ar-in-data-spec -msched-in-control-spec @gol
+-msched-spec-ldc -msched-spec-control-ldc @gol
+-msched-prefer-non-data-spec-insns -msched-prefer-non-control-spec-insns @gol
+-msched-stop-bits-after-every-cycle -msched-count-spec-in-critical-path @gol
+-msel-sched-dont-check-control-spec -msched-fp-mem-deps-zero-cost @gol
+-msched-max-memory-insns-hard-limit -msched-max-memory-insns=@var{max-insns}}
+
+@emph{LM32 Options}
+@gccoptlist{-mbarrel-shift-enabled -mdivide-enabled -mmultiply-enabled @gol
+-msign-extend-enabled -muser-enabled}
+
+@emph{LoongArch Options}
+@gccoptlist{-march=@var{cpu-type} -mtune=@var{cpu-type} -mabi=@var{base-abi-type} @gol
+-mfpu=@var{fpu-type} -msoft-float -msingle-float -mdouble-float @gol
+-mbranch-cost=@var{n} -mcheck-zero-division -mno-check-zero-division @gol
+-mcond-move-int -mno-cond-move-int @gol
+-mcond-move-float -mno-cond-move-float @gol
+-memcpy -mno-memcpy -mstrict-align -mno-strict-align @gol
+-mmax-inline-memcpy-size=@var{n} @gol
+-mexplicit-relocs -mno-explicit-relocs @gol
+-mdirect-extern-access -mno-direct-extern-access @gol
+-mcmodel=@var{code-model}}
+
+@emph{M32R/D Options}
+@gccoptlist{-m32r2 -m32rx -m32r @gol
+-mdebug @gol
+-malign-loops -mno-align-loops @gol
+-missue-rate=@var{number} @gol
+-mbranch-cost=@var{number} @gol
+-mmodel=@var{code-size-model-type} @gol
+-msdata=@var{sdata-type} @gol
+-mno-flush-func -mflush-func=@var{name} @gol
+-mno-flush-trap -mflush-trap=@var{number} @gol
+-G @var{num}}
+
+@emph{M32C Options}
+@gccoptlist{-mcpu=@var{cpu} -msim -memregs=@var{number}}
+
+@emph{M680x0 Options}
+@gccoptlist{-march=@var{arch} -mcpu=@var{cpu} -mtune=@var{tune} @gol
+-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol
+-m68060 -mcpu32 -m5200 -m5206e -m528x -m5307 -m5407 @gol
+-mcfv4e -mbitfield -mno-bitfield -mc68000 -mc68020 @gol
+-mnobitfield -mrtd -mno-rtd -mdiv -mno-div -mshort @gol
+-mno-short -mhard-float -m68881 -msoft-float -mpcrel @gol
+-malign-int -mstrict-align -msep-data -mno-sep-data @gol
+-mshared-library-id=n -mid-shared-library -mno-id-shared-library @gol
+-mxgot -mno-xgot -mlong-jump-table-offsets}
+
+@emph{MCore Options}
+@gccoptlist{-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol
+-mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol
+-m4byte-functions -mno-4byte-functions -mcallgraph-data @gol
+-mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol
+-mlittle-endian -mbig-endian -m210 -m340 -mstack-increment}
+
+@emph{MeP Options}
+@gccoptlist{-mabsdiff -mall-opts -maverage -mbased=@var{n} -mbitops @gol
+-mc=@var{n} -mclip -mconfig=@var{name} -mcop -mcop32 -mcop64 -mivc2 @gol
+-mdc -mdiv -meb -mel -mio-volatile -ml -mleadz -mm -mminmax @gol
+-mmult -mno-opts -mrepeat -ms -msatur -msdram -msim -msimnovec -mtf @gol
+-mtiny=@var{n}}
+
+@emph{MicroBlaze Options}
+@gccoptlist{-msoft-float -mhard-float -msmall-divides -mcpu=@var{cpu} @gol
+-mmemcpy -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift @gol
+-mxl-pattern-compare -mxl-stack-check -mxl-gp-opt -mno-clearbss @gol
+-mxl-multiply-high -mxl-float-convert -mxl-float-sqrt @gol
+-mbig-endian -mlittle-endian -mxl-reorder -mxl-mode-@var{app-model} @gol
+-mpic-data-is-text-relative}
+
+@emph{MIPS Options}
+@gccoptlist{-EL -EB -march=@var{arch} -mtune=@var{arch} @gol
+-mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 -mips32r3 -mips32r5 @gol
+-mips32r6 -mips64 -mips64r2 -mips64r3 -mips64r5 -mips64r6 @gol
+-mips16 -mno-mips16 -mflip-mips16 @gol
+-minterlink-compressed -mno-interlink-compressed @gol
+-minterlink-mips16 -mno-interlink-mips16 @gol
+-mabi=@var{abi} -mabicalls -mno-abicalls @gol
+-mshared -mno-shared -mplt -mno-plt -mxgot -mno-xgot @gol
+-mgp32 -mgp64 -mfp32 -mfpxx -mfp64 -mhard-float -msoft-float @gol
+-mno-float -msingle-float -mdouble-float @gol
+-modd-spreg -mno-odd-spreg @gol
+-mabs=@var{mode} -mnan=@var{encoding} @gol
+-mdsp -mno-dsp -mdspr2 -mno-dspr2 @gol
+-mmcu -mmno-mcu @gol
+-meva -mno-eva @gol
+-mvirt -mno-virt @gol
+-mxpa -mno-xpa @gol
+-mcrc -mno-crc @gol
+-mginv -mno-ginv @gol
+-mmicromips -mno-micromips @gol
+-mmsa -mno-msa @gol
+-mloongson-mmi -mno-loongson-mmi @gol
+-mloongson-ext -mno-loongson-ext @gol
+-mloongson-ext2 -mno-loongson-ext2 @gol
+-mfpu=@var{fpu-type} @gol
+-msmartmips -mno-smartmips @gol
+-mpaired-single -mno-paired-single -mdmx -mno-mdmx @gol
+-mips3d -mno-mips3d -mmt -mno-mt -mllsc -mno-llsc @gol
+-mlong64 -mlong32 -msym32 -mno-sym32 @gol
+-G@var{num} -mlocal-sdata -mno-local-sdata @gol
+-mextern-sdata -mno-extern-sdata -mgpopt -mno-gopt @gol
+-membedded-data -mno-embedded-data @gol
+-muninit-const-in-rodata -mno-uninit-const-in-rodata @gol
+-mcode-readable=@var{setting} @gol
+-msplit-addresses -mno-split-addresses @gol
+-mexplicit-relocs -mno-explicit-relocs @gol
+-mcheck-zero-division -mno-check-zero-division @gol
+-mdivide-traps -mdivide-breaks @gol
+-mload-store-pairs -mno-load-store-pairs @gol
+-munaligned-access -mno-unaligned-access @gol
+-mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol
+-mmad -mno-mad -mimadd -mno-imadd -mfused-madd -mno-fused-madd -nocpp @gol
+-mfix-24k -mno-fix-24k @gol
+-mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 @gol
+-mfix-r5900 -mno-fix-r5900 @gol
+-mfix-r10000 -mno-fix-r10000 -mfix-rm7000 -mno-fix-rm7000 @gol
+-mfix-vr4120 -mno-fix-vr4120 @gol
+-mfix-vr4130 -mno-fix-vr4130 -mfix-sb1 -mno-fix-sb1 @gol
+-mflush-func=@var{func} -mno-flush-func @gol
+-mbranch-cost=@var{num} -mbranch-likely -mno-branch-likely @gol
+-mcompact-branches=@var{policy} @gol
+-mfp-exceptions -mno-fp-exceptions @gol
+-mvr4130-align -mno-vr4130-align -msynci -mno-synci @gol
+-mlxc1-sxc1 -mno-lxc1-sxc1 -mmadd4 -mno-madd4 @gol
+-mrelax-pic-calls -mno-relax-pic-calls -mmcount-ra-address @gol
+-mframe-header-opt -mno-frame-header-opt}
+
+@emph{MMIX Options}
+@gccoptlist{-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu @gol
+-mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols @gol
+-melf -mbranch-predict -mno-branch-predict -mbase-addresses @gol
+-mno-base-addresses -msingle-exit -mno-single-exit}
+
+@emph{MN10300 Options}
+@gccoptlist{-mmult-bug -mno-mult-bug @gol
+-mno-am33 -mam33 -mam33-2 -mam34 @gol
+-mtune=@var{cpu-type} @gol
+-mreturn-pointer-on-d0 @gol
+-mno-crt0 -mrelax -mliw -msetlb}
+
+@emph{Moxie Options}
+@gccoptlist{-meb -mel -mmul.x -mno-crt0}
+
+@emph{MSP430 Options}
+@gccoptlist{-msim -masm-hex -mmcu= -mcpu= -mlarge -msmall -mrelax @gol
+-mwarn-mcu @gol
+-mcode-region= -mdata-region= @gol
+-msilicon-errata= -msilicon-errata-warn= @gol
+-mhwmult= -minrt -mtiny-printf -mmax-inline-shift=}
+
+@emph{NDS32 Options}
+@gccoptlist{-mbig-endian -mlittle-endian @gol
+-mreduced-regs -mfull-regs @gol
+-mcmov -mno-cmov @gol
+-mext-perf -mno-ext-perf @gol
+-mext-perf2 -mno-ext-perf2 @gol
+-mext-string -mno-ext-string @gol
+-mv3push -mno-v3push @gol
+-m16bit -mno-16bit @gol
+-misr-vector-size=@var{num} @gol
+-mcache-block-size=@var{num} @gol
+-march=@var{arch} @gol
+-mcmodel=@var{code-model} @gol
+-mctor-dtor -mrelax}
+
+@emph{Nios II Options}
+@gccoptlist{-G @var{num} -mgpopt=@var{option} -mgpopt -mno-gpopt @gol
+-mgprel-sec=@var{regexp} -mr0rel-sec=@var{regexp} @gol
+-mel -meb @gol
+-mno-bypass-cache -mbypass-cache @gol
+-mno-cache-volatile -mcache-volatile @gol
+-mno-fast-sw-div -mfast-sw-div @gol
+-mhw-mul -mno-hw-mul -mhw-mulx -mno-hw-mulx -mno-hw-div -mhw-div @gol
+-mcustom-@var{insn}=@var{N} -mno-custom-@var{insn} @gol
+-mcustom-fpu-cfg=@var{name} @gol
+-mhal -msmallc -msys-crt0=@var{name} -msys-lib=@var{name} @gol
+-march=@var{arch} -mbmx -mno-bmx -mcdx -mno-cdx}
+
+@emph{Nvidia PTX Options}
+@gccoptlist{-m64 -mmainkernel -moptimize}
+
+@emph{OpenRISC Options}
+@gccoptlist{-mboard=@var{name} -mnewlib -mhard-mul -mhard-div @gol
+-msoft-mul -msoft-div @gol
+-msoft-float -mhard-float -mdouble-float -munordered-float @gol
+-mcmov -mror -mrori -msext -msfimm -mshftimm @gol
+-mcmodel=@var{code-model}}
+
+@emph{PDP-11 Options}
+@gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol
+-mint32 -mno-int16 -mint16 -mno-int32 @gol
+-msplit -munix-asm -mdec-asm -mgnu-asm -mlra}
+
+@emph{picoChip Options}
+@gccoptlist{-mae=@var{ae_type} -mvliw-lookahead=@var{N} @gol
+-msymbol-as-address -mno-inefficient-warnings}
+
+@emph{PowerPC Options}
+See RS/6000 and PowerPC Options.
+
+@emph{PRU Options}
+@gccoptlist{-mmcu=@var{mcu} -minrt -mno-relax -mloop @gol
+-mabi=@var{variant} @gol}
+
+@emph{RISC-V Options}
+@gccoptlist{-mbranch-cost=@var{N-instruction} @gol
+-mplt -mno-plt @gol
+-mabi=@var{ABI-string} @gol
+-mfdiv -mno-fdiv @gol
+-mdiv -mno-div @gol
+-misa-spec=@var{ISA-spec-string} @gol
+-march=@var{ISA-string} @gol
+-mtune=@var{processor-string} @gol
+-mpreferred-stack-boundary=@var{num} @gol
+-msmall-data-limit=@var{N-bytes} @gol
+-msave-restore -mno-save-restore @gol
+-mshorten-memrefs -mno-shorten-memrefs @gol
+-mstrict-align -mno-strict-align @gol
+-mcmodel=medlow -mcmodel=medany @gol
+-mexplicit-relocs -mno-explicit-relocs @gol
+-mrelax -mno-relax @gol
+-mriscv-attribute -mno-riscv-attribute @gol
+-malign-data=@var{type} @gol
+-mbig-endian -mlittle-endian @gol
+-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{reg} @gol
+-mstack-protector-guard-offset=@var{offset}}
+-mcsr-check -mno-csr-check @gol
+
+@emph{RL78 Options}
+@gccoptlist{-msim -mmul=none -mmul=g13 -mmul=g14 -mallregs @gol
+-mcpu=g10 -mcpu=g13 -mcpu=g14 -mg10 -mg13 -mg14 @gol
+-m64bit-doubles -m32bit-doubles -msave-mduc-in-interrupts}
+
+@emph{RS/6000 and PowerPC Options}
+@gccoptlist{-mcpu=@var{cpu-type} @gol
+-mtune=@var{cpu-type} @gol
+-mcmodel=@var{code-model} @gol
+-mpowerpc64 @gol
+-maltivec -mno-altivec @gol
+-mpowerpc-gpopt -mno-powerpc-gpopt @gol
+-mpowerpc-gfxopt -mno-powerpc-gfxopt @gol
+-mmfcrf -mno-mfcrf -mpopcntb -mno-popcntb -mpopcntd -mno-popcntd @gol
+-mfprnd -mno-fprnd @gol
+-mcmpb -mno-cmpb -mhard-dfp -mno-hard-dfp @gol
+-mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc @gol
+-m64 -m32 -mxl-compat -mno-xl-compat -mpe @gol
+-malign-power -malign-natural @gol
+-msoft-float -mhard-float -mmultiple -mno-multiple @gol
+-mupdate -mno-update @gol
+-mavoid-indexed-addresses -mno-avoid-indexed-addresses @gol
+-mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol
+-mstrict-align -mno-strict-align -mrelocatable @gol
+-mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol
+-mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol
+-mdynamic-no-pic -mswdiv -msingle-pic-base @gol
+-mprioritize-restricted-insns=@var{priority} @gol
+-msched-costly-dep=@var{dependence_type} @gol
+-minsert-sched-nops=@var{scheme} @gol
+-mcall-aixdesc -mcall-eabi -mcall-freebsd @gol
+-mcall-linux -mcall-netbsd -mcall-openbsd @gol
+-mcall-sysv -mcall-sysv-eabi -mcall-sysv-noeabi @gol
+-mtraceback=@var{traceback_type} @gol
+-maix-struct-return -msvr4-struct-return @gol
+-mabi=@var{abi-type} -msecure-plt -mbss-plt @gol
+-mlongcall -mno-longcall -mpltseq -mno-pltseq @gol
+-mblock-move-inline-limit=@var{num} @gol
+-mblock-compare-inline-limit=@var{num} @gol
+-mblock-compare-inline-loop-limit=@var{num} @gol
+-mno-block-ops-unaligned-vsx @gol
+-mstring-compare-inline-limit=@var{num} @gol
+-misel -mno-isel @gol
+-mvrsave -mno-vrsave @gol
+-mmulhw -mno-mulhw @gol
+-mdlmzb -mno-dlmzb @gol
+-mprototype -mno-prototype @gol
+-msim -mmvme -mads -myellowknife -memb -msdata @gol
+-msdata=@var{opt} -mreadonly-in-sdata -mvxworks -G @var{num} @gol
+-mrecip -mrecip=@var{opt} -mno-recip -mrecip-precision @gol
+-mno-recip-precision @gol
+-mveclibabi=@var{type} -mfriz -mno-friz @gol
+-mpointers-to-nested-functions -mno-pointers-to-nested-functions @gol
+-msave-toc-indirect -mno-save-toc-indirect @gol
+-mpower8-fusion -mno-mpower8-fusion -mpower8-vector -mno-power8-vector @gol
+-mcrypto -mno-crypto -mhtm -mno-htm @gol
+-mquad-memory -mno-quad-memory @gol
+-mquad-memory-atomic -mno-quad-memory-atomic @gol
+-mcompat-align-parm -mno-compat-align-parm @gol
+-mfloat128 -mno-float128 -mfloat128-hardware -mno-float128-hardware @gol
+-mgnu-attribute -mno-gnu-attribute @gol
+-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{reg} @gol
+-mstack-protector-guard-offset=@var{offset} -mprefixed -mno-prefixed @gol
+-mpcrel -mno-pcrel -mmma -mno-mmma -mrop-protect -mno-rop-protect @gol
+-mprivileged -mno-privileged}
+
+@emph{RX Options}
+@gccoptlist{-m64bit-doubles -m32bit-doubles -fpu -nofpu@gol
+-mcpu=@gol
+-mbig-endian-data -mlittle-endian-data @gol
+-msmall-data @gol
+-msim -mno-sim@gol
+-mas100-syntax -mno-as100-syntax@gol
+-mrelax@gol
+-mmax-constant-size=@gol
+-mint-register=@gol
+-mpid@gol
+-mallow-string-insns -mno-allow-string-insns@gol
+-mjsr@gol
+-mno-warn-multiple-fast-interrupts@gol
+-msave-acc-in-interrupts}
+
+@emph{S/390 and zSeries Options}
+@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol
+-mhard-float -msoft-float -mhard-dfp -mno-hard-dfp @gol
+-mlong-double-64 -mlong-double-128 @gol
+-mbackchain -mno-backchain -mpacked-stack -mno-packed-stack @gol
+-msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol
+-m64 -m31 -mdebug -mno-debug -mesa -mzarch @gol
+-mhtm -mvx -mzvector @gol
+-mtpf-trace -mno-tpf-trace -mtpf-trace-skip -mno-tpf-trace-skip @gol
+-mfused-madd -mno-fused-madd @gol
+-mwarn-framesize -mwarn-dynamicstack -mstack-size -mstack-guard @gol
+-mhotpatch=@var{halfwords},@var{halfwords}}
+
+@emph{Score Options}
+@gccoptlist{-meb -mel @gol
+-mnhwloop @gol
+-muls @gol
+-mmac @gol
+-mscore5 -mscore5u -mscore7 -mscore7d}
+
+@emph{SH Options}
+@gccoptlist{-m1 -m2 -m2e @gol
+-m2a-nofpu -m2a-single-only -m2a-single -m2a @gol
+-m3 -m3e @gol
+-m4-nofpu -m4-single-only -m4-single -m4 @gol
+-m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al @gol
+-mb -ml -mdalign -mrelax @gol
+-mbigtable -mfmovd -mrenesas -mno-renesas -mnomacsave @gol
+-mieee -mno-ieee -mbitops -misize -minline-ic_invalidate -mpadstruct @gol
+-mprefergot -musermode -multcost=@var{number} -mdiv=@var{strategy} @gol
+-mdivsi3_libfunc=@var{name} -mfixed-range=@var{register-range} @gol
+-maccumulate-outgoing-args @gol
+-matomic-model=@var{atomic-model} @gol
+-mbranch-cost=@var{num} -mzdcbranch -mno-zdcbranch @gol
+-mcbranch-force-delay-slot @gol
+-mfused-madd -mno-fused-madd -mfsca -mno-fsca -mfsrra -mno-fsrra @gol
+-mpretend-cmove -mtas}
+
+@emph{Solaris 2 Options}
+@gccoptlist{-mclear-hwcap -mno-clear-hwcap -mimpure-text -mno-impure-text @gol
+-pthreads}
+
+@emph{SPARC Options}
+@gccoptlist{-mcpu=@var{cpu-type} @gol
+-mtune=@var{cpu-type} @gol
+-mcmodel=@var{code-model} @gol
+-mmemory-model=@var{mem-model} @gol
+-m32 -m64 -mapp-regs -mno-app-regs @gol
+-mfaster-structs -mno-faster-structs -mflat -mno-flat @gol
+-mfpu -mno-fpu -mhard-float -msoft-float @gol
+-mhard-quad-float -msoft-quad-float @gol
+-mstack-bias -mno-stack-bias @gol
+-mstd-struct-return -mno-std-struct-return @gol
+-munaligned-doubles -mno-unaligned-doubles @gol
+-muser-mode -mno-user-mode @gol
+-mv8plus -mno-v8plus -mvis -mno-vis @gol
+-mvis2 -mno-vis2 -mvis3 -mno-vis3 @gol
+-mvis4 -mno-vis4 -mvis4b -mno-vis4b @gol
+-mcbcond -mno-cbcond -mfmaf -mno-fmaf -mfsmuld -mno-fsmuld @gol
+-mpopc -mno-popc -msubxc -mno-subxc @gol
+-mfix-at697f -mfix-ut699 -mfix-ut700 -mfix-gr712rc @gol
+-mlra -mno-lra}
+
+@emph{System V Options}
+@gccoptlist{-Qy -Qn -YP,@var{paths} -Ym,@var{dir}}
+
+@emph{V850 Options}
+@gccoptlist{-mlong-calls -mno-long-calls -mep -mno-ep @gol
+-mprolog-function -mno-prolog-function -mspace @gol
+-mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol
+-mapp-regs -mno-app-regs @gol
+-mdisable-callt -mno-disable-callt @gol
+-mv850e2v3 -mv850e2 -mv850e1 -mv850es @gol
+-mv850e -mv850 -mv850e3v5 @gol
+-mloop @gol
+-mrelax @gol
+-mlong-jumps @gol
+-msoft-float @gol
+-mhard-float @gol
+-mgcc-abi @gol
+-mrh850-abi @gol
+-mbig-switch}
+
+@emph{VAX Options}
+@gccoptlist{-mg -mgnu -munix -mlra}
+
+@emph{Visium Options}
+@gccoptlist{-mdebug -msim -mfpu -mno-fpu -mhard-float -msoft-float @gol
+-mcpu=@var{cpu-type} -mtune=@var{cpu-type} -msv-mode -muser-mode}
+
+@emph{VMS Options}
+@gccoptlist{-mvms-return-codes -mdebug-main=@var{prefix} -mmalloc64 @gol
+-mpointer-size=@var{size}}
+
+@emph{VxWorks Options}
+@gccoptlist{-mrtp -non-static -Bstatic -Bdynamic @gol
+-Xbind-lazy -Xbind-now}
+
+@emph{x86 Options}
+@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol
+-mtune-ctrl=@var{feature-list} -mdump-tune-features -mno-default @gol
+-mfpmath=@var{unit} @gol
+-masm=@var{dialect} -mno-fancy-math-387 @gol
+-mno-fp-ret-in-387 -m80387 -mhard-float -msoft-float @gol
+-mno-wide-multiply -mrtd -malign-double @gol
+-mpreferred-stack-boundary=@var{num} @gol
+-mincoming-stack-boundary=@var{num} @gol
+-mcld -mcx16 -msahf -mmovbe -mcrc32 -mmwait @gol
+-mrecip -mrecip=@var{opt} @gol
+-mvzeroupper -mprefer-avx128 -mprefer-vector-width=@var{opt} @gol
+-mmove-max=@var{bits} -mstore-max=@var{bits} @gol
+-mmmx -msse -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -mavx @gol
+-mavx2 -mavx512f -mavx512pf -mavx512er -mavx512cd -mavx512vl @gol
+-mavx512bw -mavx512dq -mavx512ifma -mavx512vbmi -msha -maes @gol
+-mpclmul -mfsgsbase -mrdrnd -mf16c -mfma -mpconfig -mwbnoinvd @gol
+-mptwrite -mprefetchwt1 -mclflushopt -mclwb -mxsavec -mxsaves @gol
+-msse4a -m3dnow -m3dnowa -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop @gol
+-madx -mlzcnt -mbmi2 -mfxsr -mxsave -mxsaveopt -mrtm -mhle -mlwp @gol
+-mmwaitx -mclzero -mpku -mthreads -mgfni -mvaes -mwaitpkg @gol
+-mshstk -mmanual-endbr -mcet-switch -mforce-indirect-call @gol
+-mavx512vbmi2 -mavx512bf16 -menqcmd @gol
+-mvpclmulqdq -mavx512bitalg -mmovdiri -mmovdir64b -mavx512vpopcntdq @gol
+-mavx5124fmaps -mavx512vnni -mavx5124vnniw -mprfchw -mrdpid @gol
+-mrdseed -msgx -mavx512vp2intersect -mserialize -mtsxldtrk@gol
+-mamx-tile -mamx-int8 -mamx-bf16 -muintr -mhreset -mavxvnni@gol
+-mavx512fp16 -mavxifma -mavxvnniint8 -mavxneconvert -mcmpccxadd -mamx-fp16 @gol
+-mprefetchi -mraoint @gol
+-mcldemote -mms-bitfields -mno-align-stringops -minline-all-stringops @gol
+-minline-stringops-dynamically -mstringop-strategy=@var{alg} @gol
+-mkl -mwidekl @gol
+-mmemcpy-strategy=@var{strategy} -mmemset-strategy=@var{strategy} @gol
+-mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol
+-m96bit-long-double -mlong-double-64 -mlong-double-80 -mlong-double-128 @gol
+-mregparm=@var{num} -msseregparm @gol
+-mveclibabi=@var{type} -mvect8-ret-in-mem @gol
+-mpc32 -mpc64 -mpc80 -mstackrealign @gol
+-momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol
+-mcmodel=@var{code-model} -mabi=@var{name} -maddress-mode=@var{mode} @gol
+-m32 -m64 -mx32 -m16 -miamcu -mlarge-data-threshold=@var{num} @gol
+-msse2avx -mfentry -mrecord-mcount -mnop-mcount -m8bit-idiv @gol
+-minstrument-return=@var{type} -mfentry-name=@var{name} -mfentry-section=@var{name} @gol
+-mavx256-split-unaligned-load -mavx256-split-unaligned-store @gol
+-malign-data=@var{type} -mstack-protector-guard=@var{guard} @gol
+-mstack-protector-guard-reg=@var{reg} @gol
+-mstack-protector-guard-offset=@var{offset} @gol
+-mstack-protector-guard-symbol=@var{symbol} @gol
+-mgeneral-regs-only -mcall-ms2sysv-xlogues -mrelax-cmpxchg-loop @gol
+-mindirect-branch=@var{choice} -mfunction-return=@var{choice} @gol
+-mindirect-branch-register -mharden-sls=@var{choice} @gol
+-mindirect-branch-cs-prefix -mneeded -mno-direct-extern-access}
+
+@emph{x86 Windows Options}
+@gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll @gol
+-mnop-fun-dllimport -mthread @gol
+-municode -mwin32 -mwindows -fno-set-stack-executable}
+
+@emph{Xstormy16 Options}
+@gccoptlist{-msim}
+
+@emph{Xtensa Options}
+@gccoptlist{-mconst16 -mno-const16 @gol
+-mfused-madd -mno-fused-madd @gol
+-mforce-no-pic @gol
+-mserialize-volatile -mno-serialize-volatile @gol
+-mtext-section-literals -mno-text-section-literals @gol
+-mauto-litpools -mno-auto-litpools @gol
+-mtarget-align -mno-target-align @gol
+-mlongcalls -mno-longcalls @gol
+-mabi=@var{abi-type} @gol
+-mextra-l32r-costs=@var{cycles}}
+
+@emph{zSeries Options}
+See S/390 and zSeries Options.
+@end table
+
+
+@node Overall Options
+@section Options Controlling the Kind of Output
+
+Compilation can involve up to four stages: preprocessing, compilation
+proper, assembly and linking, always in that order. GCC is capable of
+preprocessing and compiling several files either into several
+assembler input files, or into one assembler input file; then each
+assembler input file produces an object file, and linking combines all
+the object files (those newly compiled, and those specified as input)
+into an executable file.
+
+@cindex file name suffix
+For any given input file, the file name suffix determines what kind of
+compilation is done:
+
+@table @gcctabopt
+@item @var{file}.c
+C source code that must be preprocessed.
+
+@item @var{file}.i
+C source code that should not be preprocessed.
+
+@item @var{file}.ii
+C++ source code that should not be preprocessed.
+
+@item @var{file}.m
+Objective-C source code. Note that you must link with the @file{libobjc}
+library to make an Objective-C program work.
+
+@item @var{file}.mi
+Objective-C source code that should not be preprocessed.
+
+@item @var{file}.mm
+@itemx @var{file}.M
+Objective-C++ source code. Note that you must link with the @file{libobjc}
+library to make an Objective-C++ program work. Note that @samp{.M} refers
+to a literal capital M@.
+
+@item @var{file}.mii
+Objective-C++ source code that should not be preprocessed.
+
+@item @var{file}.h
+C, C++, Objective-C or Objective-C++ header file to be turned into a
+precompiled header (default), or C, C++ header file to be turned into an
+Ada spec (via the @option{-fdump-ada-spec} switch).
+
+@item @var{file}.cc
+@itemx @var{file}.cp
+@itemx @var{file}.cxx
+@itemx @var{file}.cpp
+@itemx @var{file}.CPP
+@itemx @var{file}.c++
+@itemx @var{file}.C
+C++ source code that must be preprocessed. Note that in @samp{.cxx},
+the last two letters must both be literally @samp{x}. Likewise,
+@samp{.C} refers to a literal capital C@.
+
+@item @var{file}.mm
+@itemx @var{file}.M
+Objective-C++ source code that must be preprocessed.
+
+@item @var{file}.mii
+Objective-C++ source code that should not be preprocessed.
+
+@item @var{file}.hh
+@itemx @var{file}.H
+@itemx @var{file}.hp
+@itemx @var{file}.hxx
+@itemx @var{file}.hpp
+@itemx @var{file}.HPP
+@itemx @var{file}.h++
+@itemx @var{file}.tcc
+C++ header file to be turned into a precompiled header or Ada spec.
+
+@item @var{file}.f
+@itemx @var{file}.for
+@itemx @var{file}.ftn
+Fixed form Fortran source code that should not be preprocessed.
+
+@item @var{file}.F
+@itemx @var{file}.FOR
+@itemx @var{file}.fpp
+@itemx @var{file}.FPP
+@itemx @var{file}.FTN
+Fixed form Fortran source code that must be preprocessed (with the traditional
+preprocessor).
+
+@item @var{file}.f90
+@itemx @var{file}.f95
+@itemx @var{file}.f03
+@itemx @var{file}.f08
+Free form Fortran source code that should not be preprocessed.
+
+@item @var{file}.F90
+@itemx @var{file}.F95
+@itemx @var{file}.F03
+@itemx @var{file}.F08
+Free form Fortran source code that must be preprocessed (with the
+traditional preprocessor).
+
+@item @var{file}.go
+Go source code.
+
+@item @var{file}.d
+D source code.
+
+@item @var{file}.di
+D interface file.
+
+@item @var{file}.dd
+D documentation code (Ddoc).
+
+@item @var{file}.ads
+Ada source code file that contains a library unit declaration (a
+declaration of a package, subprogram, or generic, or a generic
+instantiation), or a library unit renaming declaration (a package,
+generic, or subprogram renaming declaration). Such files are also
+called @dfn{specs}.
+
+@item @var{file}.adb
+Ada source code file containing a library unit body (a subprogram or
+package body). Such files are also called @dfn{bodies}.
+
+@c GCC also knows about some suffixes for languages not yet included:
+@c Ratfor:
+@c @var{file}.r
+
+@item @var{file}.s
+Assembler code.
+
+@item @var{file}.S
+@itemx @var{file}.sx
+Assembler code that must be preprocessed.
+
+@item @var{other}
+An object file to be fed straight into linking.
+Any file name with no recognized suffix is treated this way.
+@end table
+
+@opindex x
+You can specify the input language explicitly with the @option{-x} option:
+
+@table @gcctabopt
+@item -x @var{language}
+Specify explicitly the @var{language} for the following input files
+(rather than letting the compiler choose a default based on the file
+name suffix). This option applies to all following input files until
+the next @option{-x} option. Possible values for @var{language} are:
+@smallexample
+c c-header cpp-output
+c++ c++-header c++-system-header c++-user-header c++-cpp-output
+objective-c objective-c-header objective-c-cpp-output
+objective-c++ objective-c++-header objective-c++-cpp-output
+assembler assembler-with-cpp
+ada
+d
+f77 f77-cpp-input f95 f95-cpp-input
+go
+@end smallexample
+
+@item -x none
+Turn off any specification of a language, so that subsequent files are
+handled according to their file name suffixes (as they are if @option{-x}
+has not been used at all).
+@end table
+
+If you only want some of the stages of compilation, you can use
+@option{-x} (or filename suffixes) to tell @command{gcc} where to start, and
+one of the options @option{-c}, @option{-S}, or @option{-E} to say where
+@command{gcc} is to stop. Note that some combinations (for example,
+@samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all.
+
+@table @gcctabopt
+@item -c
+@opindex c
+Compile or assemble the source files, but do not link. The linking
+stage simply is not done. The ultimate output is in the form of an
+object file for each source file.
+
+By default, the object file name for a source file is made by replacing
+the suffix @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}.
+
+Unrecognized input files, not requiring compilation or assembly, are
+ignored.
+
+@item -S
+@opindex S
+Stop after the stage of compilation proper; do not assemble. The output
+is in the form of an assembler code file for each non-assembler input
+file specified.
+
+By default, the assembler file name for a source file is made by
+replacing the suffix @samp{.c}, @samp{.i}, etc., with @samp{.s}.
+
+Input files that don't require compilation are ignored.
+
+@item -E
+@opindex E
+Stop after the preprocessing stage; do not run the compiler proper. The
+output is in the form of preprocessed source code, which is sent to the
+standard output.
+
+Input files that don't require preprocessing are ignored.
+
+@cindex output file option
+@item -o @var{file}
+@opindex o
+Place the primary output in file @var{file}. This applies to whatever
+sort of output is being produced, whether it be an executable file, an
+object file, an assembler file or preprocessed C code.
+
+If @option{-o} is not specified, the default is to put an executable
+file in @file{a.out}, the object file for
+@file{@var{source}.@var{suffix}} in @file{@var{source}.o}, its
+assembler file in @file{@var{source}.s}, a precompiled header file in
+@file{@var{source}.@var{suffix}.gch}, and all preprocessed C source on
+standard output.
+
+Though @option{-o} names only the primary output, it also affects the
+naming of auxiliary and dump outputs. See the examples below. Unless
+overridden, both auxiliary outputs and dump outputs are placed in the
+same directory as the primary output. In auxiliary outputs, the suffix
+of the input file is replaced with that of the auxiliary output file
+type; in dump outputs, the suffix of the dump file is appended to the
+input file suffix. In compilation commands, the base name of both
+auxiliary and dump outputs is that of the primary output; in compile and
+link commands, the primary output name, minus the executable suffix, is
+combined with the input file name. If both share the same base name,
+disregarding the suffix, the result of the combination is that base
+name, otherwise, they are concatenated, separated by a dash.
+
+@smallexample
+gcc -c foo.c ...
+@end smallexample
+
+will use @file{foo.o} as the primary output, and place aux outputs and
+dumps next to it, e.g., aux file @file{foo.dwo} for
+@option{-gsplit-dwarf}, and dump file @file{foo.c.???r.final} for
+@option{-fdump-rtl-final}.
+
+If a non-linker output file is explicitly specified, aux and dump files
+by default take the same base name:
+
+@smallexample
+gcc -c foo.c -o dir/foobar.o ...
+@end smallexample
+
+will name aux outputs @file{dir/foobar.*} and dump outputs
+@file{dir/foobar.c.*}.
+
+A linker output will instead prefix aux and dump outputs:
+
+@smallexample
+gcc foo.c bar.c -o dir/foobar ...
+@end smallexample
+
+will generally name aux outputs @file{dir/foobar-foo.*} and
+@file{dir/foobar-bar.*}, and dump outputs @file{dir/foobar-foo.c.*} and
+@file{dir/foobar-bar.c.*}.
+
+The one exception to the above is when the executable shares the base
+name with the single input:
+
+@smallexample
+gcc foo.c -o dir/foo ...
+@end smallexample
+
+in which case aux outputs are named @file{dir/foo.*} and dump outputs
+named @file{dir/foo.c.*}.
+
+The location and the names of auxiliary and dump outputs can be adjusted
+by the options @option{-dumpbase}, @option{-dumpbase-ext},
+@option{-dumpdir}, @option{-save-temps=cwd}, and
+@option{-save-temps=obj}.
+
+
+@item -dumpbase @var{dumpbase}
+@opindex dumpbase
+This option sets the base name for auxiliary and dump output files. It
+does not affect the name of the primary output file. Intermediate
+outputs, when preserved, are not regarded as primary outputs, but as
+auxiliary outputs:
+
+@smallexample
+gcc -save-temps -S foo.c
+@end smallexample
+
+saves the (no longer) temporary preprocessed file in @file{foo.i}, and
+then compiles to the (implied) output file @file{foo.s}, whereas:
+
+@smallexample
+gcc -save-temps -dumpbase save-foo -c foo.c
+@end smallexample
+
+preprocesses to in @file{save-foo.i}, compiles to @file{save-foo.s} (now
+an intermediate, thus auxiliary output), and then assembles to the
+(implied) output file @file{foo.o}.
+
+Absent this option, dump and aux files take their names from the input
+file, or from the (non-linker) output file, if one is explicitly
+specified: dump output files (e.g. those requested by @option{-fdump-*}
+options) with the input name suffix, and aux output files (those
+requested by other non-dump options, e.g. @code{-save-temps},
+@code{-gsplit-dwarf}, @code{-fcallgraph-info}) without it.
+
+Similar suffix differentiation of dump and aux outputs can be attained
+for explicitly-given @option{-dumpbase basename.suf} by also specifying
+@option{-dumpbase-ext .suf}.
+
+If @var{dumpbase} is explicitly specified with any directory component,
+any @var{dumppfx} specification (e.g. @option{-dumpdir} or
+@option{-save-temps=*}) is ignored, and instead of appending to it,
+@var{dumpbase} fully overrides it:
+
+@smallexample
+gcc foo.c -c -o dir/foo.o -dumpbase alt/foo \
+ -dumpdir pfx- -save-temps=cwd ...
+@end smallexample
+
+creates auxiliary and dump outputs named @file{alt/foo.*}, disregarding
+@file{dir/} in @option{-o}, the @file{./} prefix implied by
+@option{-save-temps=cwd}, and @file{pfx-} in @option{-dumpdir}.
+
+When @option{-dumpbase} is specified in a command that compiles multiple
+inputs, or that compiles and then links, it may be combined with
+@var{dumppfx}, as specified under @option{-dumpdir}. Then, each input
+file is compiled using the combined @var{dumppfx}, and default values
+for @var{dumpbase} and @var{auxdropsuf} are computed for each input
+file:
+
+@smallexample
+gcc foo.c bar.c -c -dumpbase main ...
+@end smallexample
+
+creates @file{foo.o} and @file{bar.o} as primary outputs, and avoids
+overwriting the auxiliary and dump outputs by using the @var{dumpbase}
+as a prefix, creating auxiliary and dump outputs named @file{main-foo.*}
+and @file{main-bar.*}.
+
+An empty string specified as @var{dumpbase} avoids the influence of the
+output basename in the naming of auxiliary and dump outputs during
+compilation, computing default values :
+
+@smallexample
+gcc -c foo.c -o dir/foobar.o -dumpbase '' ...
+@end smallexample
+
+will name aux outputs @file{dir/foo.*} and dump outputs
+@file{dir/foo.c.*}. Note how their basenames are taken from the input
+name, but the directory still defaults to that of the output.
+
+The empty-string dumpbase does not prevent the use of the output
+basename for outputs during linking:
+
+@smallexample
+gcc foo.c bar.c -o dir/foobar -dumpbase '' -flto ...
+@end smallexample
+
+The compilation of the source files will name auxiliary outputs
+@file{dir/foo.*} and @file{dir/bar.*}, and dump outputs
+@file{dir/foo.c.*} and @file{dir/bar.c.*}. LTO recompilation during
+linking will use @file{dir/foobar.} as the prefix for dumps and
+auxiliary files.
+
+
+@item -dumpbase-ext @var{auxdropsuf}
+@opindex dumpbase-ext
+When forming the name of an auxiliary (but not a dump) output file, drop
+trailing @var{auxdropsuf} from @var{dumpbase} before appending any
+suffixes. If not specified, this option defaults to the suffix of a
+default @var{dumpbase}, i.e., the suffix of the input file when
+@option{-dumpbase} is not present in the command line, or @var{dumpbase}
+is combined with @var{dumppfx}.
+
+@smallexample
+gcc foo.c -c -o dir/foo.o -dumpbase x-foo.c -dumpbase-ext .c ...
+@end smallexample
+
+creates @file{dir/foo.o} as the main output, and generates auxiliary
+outputs in @file{dir/x-foo.*}, taking the location of the primary
+output, and dropping the @file{.c} suffix from the @var{dumpbase}. Dump
+outputs retain the suffix: @file{dir/x-foo.c.*}.
+
+This option is disregarded if it does not match the suffix of a
+specified @var{dumpbase}, except as an alternative to the executable
+suffix when appending the linker output base name to @var{dumppfx}, as
+specified below:
+
+@smallexample
+gcc foo.c bar.c -o main.out -dumpbase-ext .out ...
+@end smallexample
+
+creates @file{main.out} as the primary output, and avoids overwriting
+the auxiliary and dump outputs by using the executable name minus
+@var{auxdropsuf} as a prefix, creating auxiliary outputs named
+@file{main-foo.*} and @file{main-bar.*} and dump outputs named
+@file{main-foo.c.*} and @file{main-bar.c.*}.
+
+
+@item -dumpdir @var{dumppfx}
+@opindex dumpdir
+When forming the name of an auxiliary or dump output file, use
+@var{dumppfx} as a prefix:
+
+@smallexample
+gcc -dumpdir pfx- -c foo.c ...
+@end smallexample
+
+creates @file{foo.o} as the primary output, and auxiliary outputs named
+@file{pfx-foo.*}, combining the given @var{dumppfx} with the default
+@var{dumpbase} derived from the default primary output, derived in turn
+from the input name. Dump outputs also take the input name suffix:
+@file{pfx-foo.c.*}.
+
+If @var{dumppfx} is to be used as a directory name, it must end with a
+directory separator:
+
+@smallexample
+gcc -dumpdir dir/ -c foo.c -o obj/bar.o ...
+@end smallexample
+
+creates @file{obj/bar.o} as the primary output, and auxiliary outputs
+named @file{dir/bar.*}, combining the given @var{dumppfx} with the
+default @var{dumpbase} derived from the primary output name. Dump
+outputs also take the input name suffix: @file{dir/bar.c.*}.
+
+It defaults to the location of the output file, unless the output
+file is a special file like @code{/dev/null}. Options
+@option{-save-temps=cwd} and @option{-save-temps=obj} override this
+default, just like an explicit @option{-dumpdir} option. In case
+multiple such options are given, the last one prevails:
+
+@smallexample
+gcc -dumpdir pfx- -c foo.c -save-temps=obj ...
+@end smallexample
+
+outputs @file{foo.o}, with auxiliary outputs named @file{foo.*} because
+@option{-save-temps=*} overrides the @var{dumppfx} given by the earlier
+@option{-dumpdir} option. It does not matter that @option{=obj} is the
+default for @option{-save-temps}, nor that the output directory is
+implicitly the current directory. Dump outputs are named
+@file{foo.c.*}.
+
+When compiling from multiple input files, if @option{-dumpbase} is
+specified, @var{dumpbase}, minus a @var{auxdropsuf} suffix, and a dash
+are appended to (or override, if containing any directory components) an
+explicit or defaulted @var{dumppfx}, so that each of the multiple
+compilations gets differently-named aux and dump outputs.
+
+@smallexample
+gcc foo.c bar.c -c -dumpdir dir/pfx- -dumpbase main ...
+@end smallexample
+
+outputs auxiliary dumps to @file{dir/pfx-main-foo.*} and
+@file{dir/pfx-main-bar.*}, appending @var{dumpbase}- to @var{dumppfx}.
+Dump outputs retain the input file suffix: @file{dir/pfx-main-foo.c.*}
+and @file{dir/pfx-main-bar.c.*}, respectively. Contrast with the
+single-input compilation:
+
+@smallexample
+gcc foo.c -c -dumpdir dir/pfx- -dumpbase main ...
+@end smallexample
+
+that, applying @option{-dumpbase} to a single source, does not compute
+and append a separate @var{dumpbase} per input file. Its auxiliary and
+dump outputs go in @file{dir/pfx-main.*}.
+
+When compiling and then linking from multiple input files, a defaulted
+or explicitly specified @var{dumppfx} also undergoes the @var{dumpbase}-
+transformation above (e.g. the compilation of @file{foo.c} and
+@file{bar.c} above, but without @option{-c}). If neither
+@option{-dumpdir} nor @option{-dumpbase} are given, the linker output
+base name, minus @var{auxdropsuf}, if specified, or the executable
+suffix otherwise, plus a dash is appended to the default @var{dumppfx}
+instead. Note, however, that unlike earlier cases of linking:
+
+@smallexample
+gcc foo.c bar.c -dumpdir dir/pfx- -o main ...
+@end smallexample
+
+does not append the output name @file{main} to @var{dumppfx}, because
+@option{-dumpdir} is explicitly specified. The goal is that the
+explicitly-specified @var{dumppfx} may contain the specified output name
+as part of the prefix, if desired; only an explicitly-specified
+@option{-dumpbase} would be combined with it, in order to avoid simply
+discarding a meaningful option.
+
+When compiling and then linking from a single input file, the linker
+output base name will only be appended to the default @var{dumppfx} as
+above if it does not share the base name with the single input file
+name. This has been covered in single-input linking cases above, but
+not with an explicit @option{-dumpdir} that inhibits the combination,
+even if overridden by @option{-save-temps=*}:
+
+@smallexample
+gcc foo.c -dumpdir alt/pfx- -o dir/main.exe -save-temps=cwd ...
+@end smallexample
+
+Auxiliary outputs are named @file{foo.*}, and dump outputs
+@file{foo.c.*}, in the current working directory as ultimately requested
+by @option{-save-temps=cwd}.
+
+Summing it all up for an intuitive though slightly imprecise data flow:
+the primary output name is broken into a directory part and a basename
+part; @var{dumppfx} is set to the former, unless overridden by
+@option{-dumpdir} or @option{-save-temps=*}, and @var{dumpbase} is set
+to the latter, unless overriden by @option{-dumpbase}. If there are
+multiple inputs or linking, this @var{dumpbase} may be combined with
+@var{dumppfx} and taken from each input file. Auxiliary output names
+for each input are formed by combining @var{dumppfx}, @var{dumpbase}
+minus suffix, and the auxiliary output suffix; dump output names are
+only different in that the suffix from @var{dumpbase} is retained.
+
+When it comes to auxiliary and dump outputs created during LTO
+recompilation, a combination of @var{dumppfx} and @var{dumpbase}, as
+given or as derived from the linker output name but not from inputs,
+even in cases in which this combination would not otherwise be used as
+such, is passed down with a trailing period replacing the compiler-added
+dash, if any, as a @option{-dumpdir} option to @command{lto-wrapper};
+being involved in linking, this program does not normally get any
+@option{-dumpbase} and @option{-dumpbase-ext}, and it ignores them.
+
+When running sub-compilers, @command{lto-wrapper} appends LTO stage
+names to the received @var{dumppfx}, ensures it contains a directory
+component so that it overrides any @option{-dumpdir}, and passes that as
+@option{-dumpbase} to sub-compilers.
+
+@item -v
+@opindex v
+Print (on standard error output) the commands executed to run the stages
+of compilation. Also print the version number of the compiler driver
+program and of the preprocessor and the compiler proper.
+
+@item -###
+@opindex ###
+Like @option{-v} except the commands are not executed and arguments
+are quoted unless they contain only alphanumeric characters or @code{./-_}.
+This is useful for shell scripts to capture the driver-generated command lines.
+
+@item --help
+@opindex help
+Print (on the standard output) a description of the command-line options
+understood by @command{gcc}. If the @option{-v} option is also specified
+then @option{--help} is also passed on to the various processes
+invoked by @command{gcc}, so that they can display the command-line options
+they accept. If the @option{-Wextra} option has also been specified
+(prior to the @option{--help} option), then command-line options that
+have no documentation associated with them are also displayed.
+
+@item --target-help
+@opindex target-help
+Print (on the standard output) a description of target-specific command-line
+options for each tool. For some targets extra target-specific
+information may also be printed.
+
+@item --help=@{@var{class}@r{|[}^@r{]}@var{qualifier}@}@r{[},@dots{}@r{]}
+Print (on the standard output) a description of the command-line
+options understood by the compiler that fit into all specified classes
+and qualifiers. These are the supported classes:
+
+@table @asis
+@item @samp{optimizers}
+Display all of the optimization options supported by the
+compiler.
+
+@item @samp{warnings}
+Display all of the options controlling warning messages
+produced by the compiler.
+
+@item @samp{target}
+Display target-specific options. Unlike the
+@option{--target-help} option however, target-specific options of the
+linker and assembler are not displayed. This is because those
+tools do not currently support the extended @option{--help=} syntax.
+
+@item @samp{params}
+Display the values recognized by the @option{--param}
+option.
+
+@item @var{language}
+Display the options supported for @var{language}, where
+@var{language} is the name of one of the languages supported in this
+version of GCC@. If an option is supported by all languages, one needs
+to select @samp{common} class.
+
+@item @samp{common}
+Display the options that are common to all languages.
+@end table
+
+These are the supported qualifiers:
+
+@table @asis
+@item @samp{undocumented}
+Display only those options that are undocumented.
+
+@item @samp{joined}
+Display options taking an argument that appears after an equal
+sign in the same continuous piece of text, such as:
+@samp{--help=target}.
+
+@item @samp{separate}
+Display options taking an argument that appears as a separate word
+following the original option, such as: @samp{-o output-file}.
+@end table
+
+Thus for example to display all the undocumented target-specific
+switches supported by the compiler, use:
+
+@smallexample
+--help=target,undocumented
+@end smallexample
+
+The sense of a qualifier can be inverted by prefixing it with the
+@samp{^} character, so for example to display all binary warning
+options (i.e., ones that are either on or off and that do not take an
+argument) that have a description, use:
+
+@smallexample
+--help=warnings,^joined,^undocumented
+@end smallexample
+
+The argument to @option{--help=} should not consist solely of inverted
+qualifiers.
+
+Combining several classes is possible, although this usually
+restricts the output so much that there is nothing to display. One
+case where it does work, however, is when one of the classes is
+@var{target}. For example, to display all the target-specific
+optimization options, use:
+
+@smallexample
+--help=target,optimizers
+@end smallexample
+
+The @option{--help=} option can be repeated on the command line. Each
+successive use displays its requested class of options, skipping
+those that have already been displayed. If @option{--help} is also
+specified anywhere on the command line then this takes precedence
+over any @option{--help=} option.
+
+If the @option{-Q} option appears on the command line before the
+@option{--help=} option, then the descriptive text displayed by
+@option{--help=} is changed. Instead of describing the displayed
+options, an indication is given as to whether the option is enabled,
+disabled or set to a specific value (assuming that the compiler
+knows this at the point where the @option{--help=} option is used).
+
+Here is a truncated example from the ARM port of @command{gcc}:
+
+@smallexample
+ % gcc -Q -mabi=2 --help=target -c
+ The following options are target specific:
+ -mabi= 2
+ -mabort-on-noreturn [disabled]
+ -mapcs [disabled]
+@end smallexample
+
+The output is sensitive to the effects of previous command-line
+options, so for example it is possible to find out which optimizations
+are enabled at @option{-O2} by using:
+
+@smallexample
+-Q -O2 --help=optimizers
+@end smallexample
+
+Alternatively you can discover which binary optimizations are enabled
+by @option{-O3} by using:
+
+@smallexample
+gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
+gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
+diff /tmp/O2-opts /tmp/O3-opts | grep enabled
+@end smallexample
+
+@item --version
+@opindex version
+Display the version number and copyrights of the invoked GCC@.
+
+@item -pass-exit-codes
+@opindex pass-exit-codes
+Normally the @command{gcc} program exits with the code of 1 if any
+phase of the compiler returns a non-success return code. If you specify
+@option{-pass-exit-codes}, the @command{gcc} program instead returns with
+the numerically highest error produced by any phase returning an error
+indication. The C, C++, and Fortran front ends return 4 if an internal
+compiler error is encountered.
+
+@item -pipe
+@opindex pipe
+Use pipes rather than temporary files for communication between the
+various stages of compilation. This fails to work on some systems where
+the assembler is unable to read from a pipe; but the GNU assembler has
+no trouble.
+
+@item -specs=@var{file}
+@opindex specs
+Process @var{file} after the compiler reads in the standard @file{specs}
+file, in order to override the defaults which the @command{gcc} driver
+program uses when determining what switches to pass to @command{cc1},
+@command{cc1plus}, @command{as}, @command{ld}, etc. More than one
+@option{-specs=@var{file}} can be specified on the command line, and they
+are processed in order, from left to right. @xref{Spec Files}, for
+information about the format of the @var{file}.
+
+@item -wrapper
+@opindex wrapper
+Invoke all subcommands under a wrapper program. The name of the
+wrapper program and its parameters are passed as a comma separated
+list.
+
+@smallexample
+gcc -c t.c -wrapper gdb,--args
+@end smallexample
+
+@noindent
+This invokes all subprograms of @command{gcc} under
+@samp{gdb --args}, thus the invocation of @command{cc1} is
+@samp{gdb --args cc1 @dots{}}.
+
+@item -ffile-prefix-map=@var{old}=@var{new}
+@opindex ffile-prefix-map
+When compiling files residing in directory @file{@var{old}}, record
+any references to them in the result of the compilation as if the
+files resided in directory @file{@var{new}} instead. Specifying this
+option is equivalent to specifying all the individual
+@option{-f*-prefix-map} options. This can be used to make reproducible
+builds that are location independent. See also
+@option{-fmacro-prefix-map}, @option{-fdebug-prefix-map} and
+@option{-fprofile-prefix-map}.
+
+@item -fplugin=@var{name}.so
+@opindex fplugin
+Load the plugin code in file @var{name}.so, assumed to be a
+shared object to be dlopen'd by the compiler. The base name of
+the shared object file is used to identify the plugin for the
+purposes of argument parsing (See
+@option{-fplugin-arg-@var{name}-@var{key}=@var{value}} below).
+Each plugin should define the callback functions specified in the
+Plugins API.
+
+@item -fplugin-arg-@var{name}-@var{key}=@var{value}
+@opindex fplugin-arg
+Define an argument called @var{key} with a value of @var{value}
+for the plugin called @var{name}.
+
+@item -fdump-ada-spec@r{[}-slim@r{]}
+@opindex fdump-ada-spec
+For C and C++ source and include files, generate corresponding Ada specs.
+@xref{Generating Ada Bindings for C and C++ headers,,, gnat_ugn,
+GNAT User's Guide}, which provides detailed documentation on this feature.
+
+@item -fada-spec-parent=@var{unit}
+@opindex fada-spec-parent
+In conjunction with @option{-fdump-ada-spec@r{[}-slim@r{]}} above, generate
+Ada specs as child units of parent @var{unit}.
+
+@item -fdump-go-spec=@var{file}
+@opindex fdump-go-spec
+For input files in any language, generate corresponding Go
+declarations in @var{file}. This generates Go @code{const},
+@code{type}, @code{var}, and @code{func} declarations which may be a
+useful way to start writing a Go interface to code written in some
+other language.
+
+@include @value{srcdir}/../libiberty/at-file.texi
+@end table
+
+@node Invoking G++
+@section Compiling C++ Programs
+
+@cindex suffixes for C++ source
+@cindex C++ source file suffixes
+C++ source files conventionally use one of the suffixes @samp{.C},
+@samp{.cc}, @samp{.cpp}, @samp{.CPP}, @samp{.c++}, @samp{.cp}, or
+@samp{.cxx}; C++ header files often use @samp{.hh}, @samp{.hpp},
+@samp{.H}, or (for shared template code) @samp{.tcc}; and
+preprocessed C++ files use the suffix @samp{.ii}. GCC recognizes
+files with these names and compiles them as C++ programs even if you
+call the compiler the same way as for compiling C programs (usually
+with the name @command{gcc}).
+
+@findex g++
+@findex c++
+However, the use of @command{gcc} does not add the C++ library.
+@command{g++} is a program that calls GCC and automatically specifies linking
+against the C++ library. It treats @samp{.c},
+@samp{.h} and @samp{.i} files as C++ source files instead of C source
+files unless @option{-x} is used. This program is also useful when
+precompiling a C header file with a @samp{.h} extension for use in C++
+compilations. On many systems, @command{g++} is also installed with
+the name @command{c++}.
+
+@cindex invoking @command{g++}
+When you compile C++ programs, you may specify many of the same
+command-line options that you use for compiling programs in any
+language; or command-line options meaningful for C and related
+languages; or options that are meaningful only for C++ programs.
+@xref{C Dialect Options,,Options Controlling C Dialect}, for
+explanations of options for languages related to C@.
+@xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for
+explanations of options that are meaningful only for C++ programs.
+
+@node C Dialect Options
+@section Options Controlling C Dialect
+@cindex dialect options
+@cindex language dialect options
+@cindex options, dialect
+
+The following options control the dialect of C (or languages derived
+from C, such as C++, Objective-C and Objective-C++) that the compiler
+accepts:
+
+@table @gcctabopt
+@cindex ANSI support
+@cindex ISO support
+@item -ansi
+@opindex ansi
+In C mode, this is equivalent to @option{-std=c90}. In C++ mode, it is
+equivalent to @option{-std=c++98}.
+
+This turns off certain features of GCC that are incompatible with ISO
+C90 (when compiling C code), or of standard C++ (when compiling C++ code),
+such as the @code{asm} and @code{typeof} keywords, and
+predefined macros such as @code{unix} and @code{vax} that identify the
+type of system you are using. It also enables the undesirable and
+rarely used ISO trigraph feature. For the C compiler,
+it disables recognition of C++ style @samp{//} comments as well as
+the @code{inline} keyword.
+
+The alternate keywords @code{__asm__}, @code{__extension__},
+@code{__inline__} and @code{__typeof__} continue to work despite
+@option{-ansi}. You would not want to use them in an ISO C program, of
+course, but it is useful to put them in header files that might be included
+in compilations done with @option{-ansi}. Alternate predefined macros
+such as @code{__unix__} and @code{__vax__} are also available, with or
+without @option{-ansi}.
+
+The @option{-ansi} option does not cause non-ISO programs to be
+rejected gratuitously. For that, @option{-Wpedantic} is required in
+addition to @option{-ansi}. @xref{Warning Options}.
+
+The macro @code{__STRICT_ANSI__} is predefined when the @option{-ansi}
+option is used. Some header files may notice this macro and refrain
+from declaring certain functions or defining certain macros that the
+ISO standard doesn't call for; this is to avoid interfering with any
+programs that might use these names for other things.
+
+Functions that are normally built in but do not have semantics
+defined by ISO C (such as @code{alloca} and @code{ffs}) are not built-in
+functions when @option{-ansi} is used. @xref{Other Builtins,,Other
+built-in functions provided by GCC}, for details of the functions
+affected.
+
+@item -std=
+@opindex std
+Determine the language standard. @xref{Standards,,Language Standards
+Supported by GCC}, for details of these standard versions. This option
+is currently only supported when compiling C or C++.
+
+The compiler can accept several base standards, such as @samp{c90} or
+@samp{c++98}, and GNU dialects of those standards, such as
+@samp{gnu90} or @samp{gnu++98}. When a base standard is specified, the
+compiler accepts all programs following that standard plus those
+using GNU extensions that do not contradict it. For example,
+@option{-std=c90} turns off certain features of GCC that are
+incompatible with ISO C90, such as the @code{asm} and @code{typeof}
+keywords, but not other GNU extensions that do not have a meaning in
+ISO C90, such as omitting the middle term of a @code{?:}
+expression. On the other hand, when a GNU dialect of a standard is
+specified, all features supported by the compiler are enabled, even when
+those features change the meaning of the base standard. As a result, some
+strict-conforming programs may be rejected. The particular standard
+is used by @option{-Wpedantic} to identify which features are GNU
+extensions given that version of the standard. For example
+@option{-std=gnu90 -Wpedantic} warns about C++ style @samp{//}
+comments, while @option{-std=gnu99 -Wpedantic} does not.
+
+A value for this option must be provided; possible values are
+
+@table @samp
+@item c90
+@itemx c89
+@itemx iso9899:1990
+Support all ISO C90 programs (certain GNU extensions that conflict
+with ISO C90 are disabled). Same as @option{-ansi} for C code.
+
+@item iso9899:199409
+ISO C90 as modified in amendment 1.
+
+@item c99
+@itemx c9x
+@itemx iso9899:1999
+@itemx iso9899:199x
+ISO C99. This standard is substantially completely supported, modulo
+bugs and floating-point issues
+(mainly but not entirely relating to optional C99 features from
+Annexes F and G). See
+@w{@uref{https://gcc.gnu.org/c99status.html}} for more information. The
+names @samp{c9x} and @samp{iso9899:199x} are deprecated.
+
+@item c11
+@itemx c1x
+@itemx iso9899:2011
+ISO C11, the 2011 revision of the ISO C standard. This standard is
+substantially completely supported, modulo bugs, floating-point issues
+(mainly but not entirely relating to optional C11 features from
+Annexes F and G) and the optional Annexes K (Bounds-checking
+interfaces) and L (Analyzability). The name @samp{c1x} is deprecated.
+
+@item c17
+@itemx c18
+@itemx iso9899:2017
+@itemx iso9899:2018
+ISO C17, the 2017 revision of the ISO C standard
+(published in 2018). This standard is
+same as C11 except for corrections of defects (all of which are also
+applied with @option{-std=c11}) and a new value of
+@code{__STDC_VERSION__}, and so is supported to the same extent as C11.
+
+@item c2x
+The next version of the ISO C standard, still under development. The
+support for this version is experimental and incomplete.
+
+@item gnu90
+@itemx gnu89
+GNU dialect of ISO C90 (including some C99 features).
+
+@item gnu99
+@itemx gnu9x
+GNU dialect of ISO C99. The name @samp{gnu9x} is deprecated.
+
+@item gnu11
+@itemx gnu1x
+GNU dialect of ISO C11.
+The name @samp{gnu1x} is deprecated.
+
+@item gnu17
+@itemx gnu18
+GNU dialect of ISO C17. This is the default for C code.
+
+@item gnu2x
+The next version of the ISO C standard, still under development, plus
+GNU extensions. The support for this version is experimental and
+incomplete.
+
+@item c++98
+@itemx c++03
+The 1998 ISO C++ standard plus the 2003 technical corrigendum and some
+additional defect reports. Same as @option{-ansi} for C++ code.
+
+@item gnu++98
+@itemx gnu++03
+GNU dialect of @option{-std=c++98}.
+
+@item c++11
+@itemx c++0x
+The 2011 ISO C++ standard plus amendments.
+The name @samp{c++0x} is deprecated.
+
+@item gnu++11
+@itemx gnu++0x
+GNU dialect of @option{-std=c++11}.
+The name @samp{gnu++0x} is deprecated.
+
+@item c++14
+@itemx c++1y
+The 2014 ISO C++ standard plus amendments.
+The name @samp{c++1y} is deprecated.
+
+@item gnu++14
+@itemx gnu++1y
+GNU dialect of @option{-std=c++14}.
+The name @samp{gnu++1y} is deprecated.
+
+@item c++17
+@itemx c++1z
+The 2017 ISO C++ standard plus amendments.
+The name @samp{c++1z} is deprecated.
+
+@item gnu++17
+@itemx gnu++1z
+GNU dialect of @option{-std=c++17}.
+This is the default for C++ code.
+The name @samp{gnu++1z} is deprecated.
+
+@item c++20
+@itemx c++2a
+The 2020 ISO C++ standard plus amendments.
+Support is experimental, and could change in incompatible ways in
+future releases.
+The name @samp{c++2a} is deprecated.
+
+@item gnu++20
+@itemx gnu++2a
+GNU dialect of @option{-std=c++20}.
+Support is experimental, and could change in incompatible ways in
+future releases.
+The name @samp{gnu++2a} is deprecated.
+
+@item c++2b
+@itemx c++23
+The next revision of the ISO C++ standard, planned for
+2023. Support is highly experimental, and will almost certainly
+change in incompatible ways in future releases.
+
+@item gnu++2b
+@itemx gnu++23
+GNU dialect of @option{-std=c++2b}. Support is highly experimental,
+and will almost certainly change in incompatible ways in future
+releases.
+@end table
+
+@item -aux-info @var{filename}
+@opindex aux-info
+Output to the given filename prototyped declarations for all functions
+declared and/or defined in a translation unit, including those in header
+files. This option is silently ignored in any language other than C@.
+
+Besides declarations, the file indicates, in comments, the origin of
+each declaration (source file and line), whether the declaration was
+implicit, prototyped or unprototyped (@samp{I}, @samp{N} for new or
+@samp{O} for old, respectively, in the first character after the line
+number and the colon), and whether it came from a declaration or a
+definition (@samp{C} or @samp{F}, respectively, in the following
+character). In the case of function definitions, a K&R-style list of
+arguments followed by their declarations is also provided, inside
+comments, after the declaration.
+
+@item -fno-asm
+@opindex fno-asm
+@opindex fasm
+Do not recognize @code{asm}, @code{inline} or @code{typeof} as a
+keyword, so that code can use these words as identifiers. You can use
+the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__}
+instead. In C, @option{-ansi} implies @option{-fno-asm}.
+
+In C++, @code{inline} is a standard keyword and is not affected by
+this switch. You may want to use the @option{-fno-gnu-keywords} flag
+instead, which disables @code{typeof} but not @code{asm} and
+@code{inline}. In C99 mode (@option{-std=c99} or @option{-std=gnu99}),
+this switch only affects the @code{asm} and @code{typeof} keywords,
+since @code{inline} is a standard keyword in ISO C99. In C2X mode
+(@option{-std=c2x} or @option{-std=gnu2x}), this switch only affects
+the @code{asm} keyword, since @code{typeof} is a standard keyword in
+ISO C2X.
+
+@item -fno-builtin
+@itemx -fno-builtin-@var{function}
+@opindex fno-builtin
+@opindex fbuiltin
+@cindex built-in functions
+Don't recognize built-in functions that do not begin with
+@samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in
+functions provided by GCC}, for details of the functions affected,
+including those which are not built-in functions when @option{-ansi} or
+@option{-std} options for strict ISO C conformance are used because they
+do not have an ISO standard meaning.
+
+GCC normally generates special code to handle certain built-in functions
+more efficiently; for instance, calls to @code{alloca} may become single
+instructions which adjust the stack directly, and calls to @code{memcpy}
+may become inline copy loops. The resulting code is often both smaller
+and faster, but since the function calls no longer appear as such, you
+cannot set a breakpoint on those calls, nor can you change the behavior
+of the functions by linking with a different library. In addition,
+when a function is recognized as a built-in function, GCC may use
+information about that function to warn about problems with calls to
+that function, or to generate more efficient code, even if the
+resulting code still contains calls to that function. For example,
+warnings are given with @option{-Wformat} for bad calls to
+@code{printf} when @code{printf} is built in and @code{strlen} is
+known not to modify global memory.
+
+With the @option{-fno-builtin-@var{function}} option
+only the built-in function @var{function} is
+disabled. @var{function} must not begin with @samp{__builtin_}. If a
+function is named that is not built-in in this version of GCC, this
+option is ignored. There is no corresponding
+@option{-fbuiltin-@var{function}} option; if you wish to enable
+built-in functions selectively when using @option{-fno-builtin} or
+@option{-ffreestanding}, you may define macros such as:
+
+@smallexample
+#define abs(n) __builtin_abs ((n))
+#define strcpy(d, s) __builtin_strcpy ((d), (s))
+@end smallexample
+
+@item -fcond-mismatch
+@opindex fcond-mismatch
+Allow conditional expressions with mismatched types in the second and
+third arguments. The value of such an expression is void. This option
+is not supported for C++.
+
+@item -ffreestanding
+@opindex ffreestanding
+@cindex hosted environment
+
+Assert that compilation targets a freestanding environment. This
+implies @option{-fno-builtin}. A freestanding environment
+is one in which the standard library may not exist, and program startup may
+not necessarily be at @code{main}. The most obvious example is an OS kernel.
+This is equivalent to @option{-fno-hosted}.
+
+@xref{Standards,,Language Standards Supported by GCC}, for details of
+freestanding and hosted environments.
+
+@item -fgimple
+@opindex fgimple
+
+Enable parsing of function definitions marked with @code{__GIMPLE}.
+This is an experimental feature that allows unit testing of GIMPLE
+passes.
+
+@item -fgnu-tm
+@opindex fgnu-tm
+When the option @option{-fgnu-tm} is specified, the compiler
+generates code for the Linux variant of Intel's current Transactional
+Memory ABI specification document (Revision 1.1, May 6 2009). This is
+an experimental feature whose interface may change in future versions
+of GCC, as the official specification changes. Please note that not
+all architectures are supported for this feature.
+
+For more information on GCC's support for transactional memory,
+@xref{Enabling libitm,,The GNU Transactional Memory Library,libitm,GNU
+Transactional Memory Library}.
+
+Note that the transactional memory feature is not supported with
+non-call exceptions (@option{-fnon-call-exceptions}).
+
+@item -fgnu89-inline
+@opindex fgnu89-inline
+The option @option{-fgnu89-inline} tells GCC to use the traditional
+GNU semantics for @code{inline} functions when in C99 mode.
+@xref{Inline,,An Inline Function is As Fast As a Macro}.
+Using this option is roughly equivalent to adding the
+@code{gnu_inline} function attribute to all inline functions
+(@pxref{Function Attributes}).
+
+The option @option{-fno-gnu89-inline} explicitly tells GCC to use the
+C99 semantics for @code{inline} when in C99 or gnu99 mode (i.e., it
+specifies the default behavior).
+This option is not supported in @option{-std=c90} or
+@option{-std=gnu90} mode.
+
+The preprocessor macros @code{__GNUC_GNU_INLINE__} and
+@code{__GNUC_STDC_INLINE__} may be used to check which semantics are
+in effect for @code{inline} functions. @xref{Common Predefined
+Macros,,,cpp,The C Preprocessor}.
+
+@item -fhosted
+@opindex fhosted
+@cindex hosted environment
+
+Assert that compilation targets a hosted environment. This implies
+@option{-fbuiltin}. A hosted environment is one in which the
+entire standard library is available, and in which @code{main} has a return
+type of @code{int}. Examples are nearly everything except a kernel.
+This is equivalent to @option{-fno-freestanding}.
+
+@item -flax-vector-conversions
+@opindex flax-vector-conversions
+Allow implicit conversions between vectors with differing numbers of
+elements and/or incompatible element types. This option should not be
+used for new code.
+
+@item -fms-extensions
+@opindex fms-extensions
+Accept some non-standard constructs used in Microsoft header files.
+
+In C++ code, this allows member names in structures to be similar
+to previous types declarations.
+
+@smallexample
+typedef int UOW;
+struct ABC @{
+ UOW UOW;
+@};
+@end smallexample
+
+Some cases of unnamed fields in structures and unions are only
+accepted with this option. @xref{Unnamed Fields,,Unnamed struct/union
+fields within structs/unions}, for details.
+
+Note that this option is off for all targets except for x86
+targets using ms-abi.
+
+@item -foffload=disable
+@itemx -foffload=default
+@itemx -foffload=@var{target-list}
+@opindex foffload
+@cindex Offloading targets
+@cindex OpenACC offloading targets
+@cindex OpenMP offloading targets
+Specify for which OpenMP and OpenACC offload targets code should be generated.
+The default behavior, equivalent to @option{-foffload=default}, is to generate
+code for all supported offload targets. The @option{-foffload=disable} form
+generates code only for the host fallback, while
+@option{-foffload=@var{target-list}} generates code only for the specified
+comma-separated list of offload targets.
+
+Offload targets are specified in GCC's internal target-triplet format. You can
+run the compiler with @option{-v} to show the list of configured offload targets
+under @code{OFFLOAD_TARGET_NAMES}.
+
+@item -foffload-options=@var{options}
+@itemx -foffload-options=@var{target-triplet-list}=@var{options}
+@opindex foffload-options
+@cindex Offloading options
+@cindex OpenACC offloading options
+@cindex OpenMP offloading options
+
+With @option{-foffload-options=@var{options}}, GCC passes the specified
+@var{options} to the compilers for all enabled offloading targets. You can
+specify options that apply only to a specific target or targets by using
+the @option{-foffload-options=@var{target-list}=@var{options}} form. The
+@var{target-list} is a comma-separated list in the same format as for the
+@option{-foffload=} option.
+
+Typical command lines are
+
+@smallexample
+-foffload-options=-lgfortran -foffload-options=-lm
+-foffload-options="-lgfortran -lm" -foffload-options=nvptx-none=-latomic
+-foffload-options=amdgcn-amdhsa=-march=gfx906 -foffload-options=-lm
+@end smallexample
+
+@item -fopenacc
+@opindex fopenacc
+@cindex OpenACC accelerator programming
+Enable handling of OpenACC directives @code{#pragma acc} in C/C++ and
+@code{!$acc} in Fortran. When @option{-fopenacc} is specified, the
+compiler generates accelerated code according to the OpenACC Application
+Programming Interface v2.6 @w{@uref{https://www.openacc.org}}. This option
+implies @option{-pthread}, and thus is only supported on targets that
+have support for @option{-pthread}.
+
+@item -fopenacc-dim=@var{geom}
+@opindex fopenacc-dim
+@cindex OpenACC accelerator programming
+Specify default compute dimensions for parallel offload regions that do
+not explicitly specify. The @var{geom} value is a triple of
+':'-separated sizes, in order 'gang', 'worker' and, 'vector'. A size
+can be omitted, to use a target-specific default value.
+
+@item -fopenmp
+@opindex fopenmp
+@cindex OpenMP parallel
+Enable handling of OpenMP directives @code{#pragma omp} in C/C++,
+@code{[[omp::directive(...)]]} and @code{[[omp::sequence(...)]]} in C++ and
+@code{!$omp} in Fortran. When @option{-fopenmp} is specified, the
+compiler generates parallel code according to the OpenMP Application
+Program Interface v4.5 @w{@uref{https://www.openmp.org}}. This option
+implies @option{-pthread}, and thus is only supported on targets that
+have support for @option{-pthread}. @option{-fopenmp} implies
+@option{-fopenmp-simd}.
+
+@item -fopenmp-simd
+@opindex fopenmp-simd
+@cindex OpenMP SIMD
+@cindex SIMD
+Enable handling of OpenMP's @code{simd}, @code{declare simd},
+@code{declare reduction}, @code{assume}, @code{ordered}, @code{scan},
+@code{loop} directives and combined or composite directives with
+@code{simd} as constituent with @code{#pragma omp} in C/C++,
+@code{[[omp::directive(...)]]} and @code{[[omp::sequence(...)]]} in C++
+and @code{!$omp} in Fortran. Other OpenMP directives are ignored.
+
+@item -fpermitted-flt-eval-methods=@var{style}
+@opindex fpermitted-flt-eval-methods
+@opindex fpermitted-flt-eval-methods=c11
+@opindex fpermitted-flt-eval-methods=ts-18661-3
+ISO/IEC TS 18661-3 defines new permissible values for
+@code{FLT_EVAL_METHOD} that indicate that operations and constants with
+a semantic type that is an interchange or extended format should be
+evaluated to the precision and range of that type. These new values are
+a superset of those permitted under C99/C11, which does not specify the
+meaning of other positive values of @code{FLT_EVAL_METHOD}. As such, code
+conforming to C11 may not have been written expecting the possibility of
+the new values.
+
+@option{-fpermitted-flt-eval-methods} specifies whether the compiler
+should allow only the values of @code{FLT_EVAL_METHOD} specified in C99/C11,
+or the extended set of values specified in ISO/IEC TS 18661-3.
+
+@var{style} is either @code{c11} or @code{ts-18661-3} as appropriate.
+
+The default when in a standards compliant mode (@option{-std=c11} or similar)
+is @option{-fpermitted-flt-eval-methods=c11}. The default when in a GNU
+dialect (@option{-std=gnu11} or similar) is
+@option{-fpermitted-flt-eval-methods=ts-18661-3}.
+
+@item -fplan9-extensions
+@opindex fplan9-extensions
+Accept some non-standard constructs used in Plan 9 code.
+
+This enables @option{-fms-extensions}, permits passing pointers to
+structures with anonymous fields to functions that expect pointers to
+elements of the type of the field, and permits referring to anonymous
+fields declared using a typedef. @xref{Unnamed Fields,,Unnamed
+struct/union fields within structs/unions}, for details. This is only
+supported for C, not C++.
+
+@item -fsigned-bitfields
+@itemx -funsigned-bitfields
+@itemx -fno-signed-bitfields
+@itemx -fno-unsigned-bitfields
+@opindex fsigned-bitfields
+@opindex funsigned-bitfields
+@opindex fno-signed-bitfields
+@opindex fno-unsigned-bitfields
+These options control whether a bit-field is signed or unsigned, when the
+declaration does not use either @code{signed} or @code{unsigned}. By
+default, such a bit-field is signed, because this is consistent: the
+basic integer types such as @code{int} are signed types.
+
+@item -fsigned-char
+@opindex fsigned-char
+Let the type @code{char} be signed, like @code{signed char}.
+
+Note that this is equivalent to @option{-fno-unsigned-char}, which is
+the negative form of @option{-funsigned-char}. Likewise, the option
+@option{-fno-signed-char} is equivalent to @option{-funsigned-char}.
+
+@item -funsigned-char
+@opindex funsigned-char
+Let the type @code{char} be unsigned, like @code{unsigned char}.
+
+Each kind of machine has a default for what @code{char} should
+be. It is either like @code{unsigned char} by default or like
+@code{signed char} by default.
+
+Ideally, a portable program should always use @code{signed char} or
+@code{unsigned char} when it depends on the signedness of an object.
+But many programs have been written to use plain @code{char} and
+expect it to be signed, or expect it to be unsigned, depending on the
+machines they were written for. This option, and its inverse, let you
+make such a program work with the opposite default.
+
+The type @code{char} is always a distinct type from each of
+@code{signed char} or @code{unsigned char}, even though its behavior
+is always just like one of those two.
+
+@item -fstrict-flex-arrays
+@opindex fstrict-flex-arrays
+@opindex fno-strict-flex-arrays
+Control when to treat the trailing array of a structure as a flexible array
+member for the purpose of accessing the elements of such an array.
+The positive form is equivalent to @option{-fstrict-flex-arrays=3}, which is the
+strictest. A trailing array is treated as a flexible array member only when it
+is declared as a flexible array member per C99 standard onwards.
+The negative form is equivalent to @option{-fstrict-flex-arrays=0}, which is the
+least strict. All trailing arrays of structures are treated as flexible array
+members.
+
+@item -fstrict-flex-arrays=@var{level}
+@opindex fstrict-flex-arrays=@var{level}
+Control when to treat the trailing array of a structure as a flexible array
+member for the purpose of accessing the elements of such an array. The value
+of @var{level} controls the level of strictness.
+
+The possible values of @var{level} are the same as for the
+@code{strict_flex_array} attribute (@pxref{Variable Attributes}).
+
+You can control this behavior for a specific trailing array field of a
+structure by using the variable attribute @code{strict_flex_array} attribute
+(@pxref{Variable Attributes}).
+
+@item -fsso-struct=@var{endianness}
+@opindex fsso-struct
+Set the default scalar storage order of structures and unions to the
+specified endianness. The accepted values are @samp{big-endian},
+@samp{little-endian} and @samp{native} for the native endianness of
+the target (the default). This option is not supported for C++.
+
+@strong{Warning:} the @option{-fsso-struct} switch causes GCC to generate
+code that is not binary compatible with code generated without it if the
+specified endianness is not the native endianness of the target.
+@end table
+
+@node C++ Dialect Options
+@section Options Controlling C++ Dialect
+
+@cindex compiler options, C++
+@cindex C++ options, command-line
+@cindex options, C++
+This section describes the command-line options that are only meaningful
+for C++ programs. You can also use most of the GNU compiler options
+regardless of what language your program is in. For example, you
+might compile a file @file{firstClass.C} like this:
+
+@smallexample
+g++ -g -fstrict-enums -O -c firstClass.C
+@end smallexample
+
+@noindent
+In this example, only @option{-fstrict-enums} is an option meant
+only for C++ programs; you can use the other options with any
+language supported by GCC@.
+
+Some options for compiling C programs, such as @option{-std}, are also
+relevant for C++ programs.
+@xref{C Dialect Options,,Options Controlling C Dialect}.
+
+Here is a list of options that are @emph{only} for compiling C++ programs:
+
+@table @gcctabopt
+
+@item -fabi-version=@var{n}
+@opindex fabi-version
+Use version @var{n} of the C++ ABI@. The default is version 0.
+
+Version 0 refers to the version conforming most closely to
+the C++ ABI specification. Therefore, the ABI obtained using version 0
+will change in different versions of G++ as ABI bugs are fixed.
+
+Version 1 is the version of the C++ ABI that first appeared in G++ 3.2.
+
+Version 2 is the version of the C++ ABI that first appeared in G++
+3.4, and was the default through G++ 4.9.
+
+Version 3 corrects an error in mangling a constant address as a
+template argument.
+
+Version 4, which first appeared in G++ 4.5, implements a standard
+mangling for vector types.
+
+Version 5, which first appeared in G++ 4.6, corrects the mangling of
+attribute const/volatile on function pointer types, decltype of a
+plain decl, and use of a function parameter in the declaration of
+another parameter.
+
+Version 6, which first appeared in G++ 4.7, corrects the promotion
+behavior of C++11 scoped enums and the mangling of template argument
+packs, const/static_cast, prefix ++ and --, and a class scope function
+used as a template argument.
+
+Version 7, which first appeared in G++ 4.8, that treats nullptr_t as a
+builtin type and corrects the mangling of lambdas in default argument
+scope.
+
+Version 8, which first appeared in G++ 4.9, corrects the substitution
+behavior of function types with function-cv-qualifiers.
+
+Version 9, which first appeared in G++ 5.2, corrects the alignment of
+@code{nullptr_t}.
+
+Version 10, which first appeared in G++ 6.1, adds mangling of
+attributes that affect type identity, such as ia32 calling convention
+attributes (e.g.@: @samp{stdcall}).
+
+Version 11, which first appeared in G++ 7, corrects the mangling of
+sizeof... expressions and operator names. For multiple entities with
+the same name within a function, that are declared in different scopes,
+the mangling now changes starting with the twelfth occurrence. It also
+implies @option{-fnew-inheriting-ctors}.
+
+Version 12, which first appeared in G++ 8, corrects the calling
+conventions for empty classes on the x86_64 target and for classes
+with only deleted copy/move constructors. It accidentally changes the
+calling convention for classes with a deleted copy constructor and a
+trivial move constructor.
+
+Version 13, which first appeared in G++ 8.2, fixes the accidental
+change in version 12.
+
+Version 14, which first appeared in G++ 10, corrects the mangling of
+the nullptr expression.
+
+Version 15, which first appeared in G++ 10.3, corrects G++ 10 ABI
+tag regression.
+
+Version 16, which first appeared in G++ 11, changes the mangling of
+@code{__alignof__} to be distinct from that of @code{alignof}, and
+dependent operator names.
+
+Version 17, which first appeared in G++ 12, fixes layout of classes
+that inherit from aggregate classes with default member initializers
+in C++14 and up.
+
+Version 18, which first appeard in G++ 13, fixes manglings of lambdas
+that have additional context.
+
+See also @option{-Wabi}.
+
+@item -fabi-compat-version=@var{n}
+@opindex fabi-compat-version
+On targets that support strong aliases, G++
+works around mangling changes by creating an alias with the correct
+mangled name when defining a symbol with an incorrect mangled name.
+This switch specifies which ABI version to use for the alias.
+
+With @option{-fabi-version=0} (the default), this defaults to 13 (GCC 8.2
+compatibility). If another ABI version is explicitly selected, this
+defaults to 0. For compatibility with GCC versions 3.2 through 4.9,
+use @option{-fabi-compat-version=2}.
+
+If this option is not provided but @option{-Wabi=@var{n}} is, that
+version is used for compatibility aliases. If this option is provided
+along with @option{-Wabi} (without the version), the version from this
+option is used for the warning.
+
+@item -fno-access-control
+@opindex fno-access-control
+@opindex faccess-control
+Turn off all access checking. This switch is mainly useful for working
+around bugs in the access control code.
+
+@item -faligned-new
+@opindex faligned-new
+Enable support for C++17 @code{new} of types that require more
+alignment than @code{void* ::operator new(std::size_t)} provides. A
+numeric argument such as @code{-faligned-new=32} can be used to
+specify how much alignment (in bytes) is provided by that function,
+but few users will need to override the default of
+@code{alignof(std::max_align_t)}.
+
+This flag is enabled by default for @option{-std=c++17}.
+
+@item -fchar8_t
+@itemx -fno-char8_t
+@opindex fchar8_t
+@opindex fno-char8_t
+Enable support for @code{char8_t} as adopted for C++20. This includes
+the addition of a new @code{char8_t} fundamental type, changes to the
+types of UTF-8 string and character literals, new signatures for
+user-defined literals, associated standard library updates, and new
+@code{__cpp_char8_t} and @code{__cpp_lib_char8_t} feature test macros.
+
+This option enables functions to be overloaded for ordinary and UTF-8
+strings:
+
+@smallexample
+int f(const char *); // #1
+int f(const char8_t *); // #2
+int v1 = f("text"); // Calls #1
+int v2 = f(u8"text"); // Calls #2
+@end smallexample
+
+@noindent
+and introduces new signatures for user-defined literals:
+
+@smallexample
+int operator""_udl1(char8_t);
+int v3 = u8'x'_udl1;
+int operator""_udl2(const char8_t*, std::size_t);
+int v4 = u8"text"_udl2;
+template<typename T, T...> int operator""_udl3();
+int v5 = u8"text"_udl3;
+@end smallexample
+
+@noindent
+The change to the types of UTF-8 string and character literals introduces
+incompatibilities with ISO C++11 and later standards. For example, the
+following code is well-formed under ISO C++11, but is ill-formed when
+@option{-fchar8_t} is specified.
+
+@smallexample
+char ca[] = u8"xx"; // error: char-array initialized from wide
+ // string
+const char *cp = u8"xx";// error: invalid conversion from
+ // `const char8_t*' to `const char*'
+int f(const char*);
+auto v = f(u8"xx"); // error: invalid conversion from
+ // `const char8_t*' to `const char*'
+std::string s@{u8"xx"@}; // error: no matching function for call to
+ // `std::basic_string<char>::basic_string()'
+using namespace std::literals;
+s = u8"xx"s; // error: conversion from
+ // `basic_string<char8_t>' to non-scalar
+ // type `basic_string<char>' requested
+@end smallexample
+
+@item -fcheck-new
+@opindex fcheck-new
+Check that the pointer returned by @code{operator new} is non-null
+before attempting to modify the storage allocated. This check is
+normally unnecessary because the C++ standard specifies that
+@code{operator new} only returns @code{0} if it is declared
+@code{throw()}, in which case the compiler always checks the
+return value even without this option. In all other cases, when
+@code{operator new} has a non-empty exception specification, memory
+exhaustion is signalled by throwing @code{std::bad_alloc}. See also
+@samp{new (nothrow)}.
+
+@item -fconcepts
+@itemx -fconcepts-ts
+@opindex fconcepts
+@opindex fconcepts-ts
+Enable support for the C++ Concepts feature for constraining template
+arguments. With @option{-std=c++20} and above, Concepts are part of
+the language standard, so @option{-fconcepts} defaults to on.
+
+Some constructs that were allowed by the earlier C++ Extensions for
+Concepts Technical Specification, ISO 19217 (2015), but didn't make it
+into the standard, can additionally be enabled by
+@option{-fconcepts-ts}.
+
+@item -fconstexpr-depth=@var{n}
+@opindex fconstexpr-depth
+Set the maximum nested evaluation depth for C++11 constexpr functions
+to @var{n}. A limit is needed to detect endless recursion during
+constant expression evaluation. The minimum specified by the standard
+is 512.
+
+@item -fconstexpr-cache-depth=@var{n}
+@opindex fconstexpr-cache-depth
+Set the maximum level of nested evaluation depth for C++11 constexpr
+functions that will be cached to @var{n}. This is a heuristic that
+trades off compilation speed (when the cache avoids repeated
+calculations) against memory consumption (when the cache grows very
+large from highly recursive evaluations). The default is 8. Very few
+users are likely to want to adjust it, but if your code does heavy
+constexpr calculations you might want to experiment to find which
+value works best for you.
+
+@item -fconstexpr-fp-except
+@opindex fconstexpr-fp-except
+Annex F of the C standard specifies that IEC559 floating point
+exceptions encountered at compile time should not stop compilation.
+C++ compilers have historically not followed this guidance, instead
+treating floating point division by zero as non-constant even though
+it has a well defined value. This flag tells the compiler to give
+Annex F priority over other rules saying that a particular operation
+is undefined.
+
+@smallexample
+constexpr float inf = 1./0.; // OK with -fconstexpr-fp-except
+@end smallexample
+
+@item -fconstexpr-loop-limit=@var{n}
+@opindex fconstexpr-loop-limit
+Set the maximum number of iterations for a loop in C++14 constexpr functions
+to @var{n}. A limit is needed to detect infinite loops during
+constant expression evaluation. The default is 262144 (1<<18).
+
+@item -fconstexpr-ops-limit=@var{n}
+@opindex fconstexpr-ops-limit
+Set the maximum number of operations during a single constexpr evaluation.
+Even when number of iterations of a single loop is limited with the above limit,
+if there are several nested loops and each of them has many iterations but still
+smaller than the above limit, or if in a body of some loop or even outside
+of a loop too many expressions need to be evaluated, the resulting constexpr
+evaluation might take too long.
+The default is 33554432 (1<<25).
+
+@item -fcoroutines
+@opindex fcoroutines
+Enable support for the C++ coroutines extension (experimental).
+
+@item -fno-elide-constructors
+@opindex fno-elide-constructors
+@opindex felide-constructors
+The C++ standard allows an implementation to omit creating a temporary
+that is only used to initialize another object of the same type.
+Specifying this option disables that optimization, and forces G++ to
+call the copy constructor in all cases. This option also causes G++
+to call trivial member functions which otherwise would be expanded inline.
+
+In C++17, the compiler is required to omit these temporaries, but this
+option still affects trivial member functions.
+
+@item -fno-enforce-eh-specs
+@opindex fno-enforce-eh-specs
+@opindex fenforce-eh-specs
+Don't generate code to check for violation of exception specifications
+at run time. This option violates the C++ standard, but may be useful
+for reducing code size in production builds, much like defining
+@code{NDEBUG}. This does not give user code permission to throw
+exceptions in violation of the exception specifications; the compiler
+still optimizes based on the specifications, so throwing an
+unexpected exception results in undefined behavior at run time.
+
+@item -fextern-tls-init
+@itemx -fno-extern-tls-init
+@opindex fextern-tls-init
+@opindex fno-extern-tls-init
+The C++11 and OpenMP standards allow @code{thread_local} and
+@code{threadprivate} variables to have dynamic (runtime)
+initialization. To support this, any use of such a variable goes
+through a wrapper function that performs any necessary initialization.
+When the use and definition of the variable are in the same
+translation unit, this overhead can be optimized away, but when the
+use is in a different translation unit there is significant overhead
+even if the variable doesn't actually need dynamic initialization. If
+the programmer can be sure that no use of the variable in a
+non-defining TU needs to trigger dynamic initialization (either
+because the variable is statically initialized, or a use of the
+variable in the defining TU will be executed before any uses in
+another TU), they can avoid this overhead with the
+@option{-fno-extern-tls-init} option.
+
+On targets that support symbol aliases, the default is
+@option{-fextern-tls-init}. On targets that do not support symbol
+aliases, the default is @option{-fno-extern-tls-init}.
+
+@item -ffold-simple-inlines
+@itemx -fno-fold-simple-inlines
+@opindex ffold-simple-inlines
+@opindex fno-fold-simple-inlines
+Permit the C++ frontend to fold calls to @code{std::move}, @code{std::forward},
+@code{std::addressof} and @code{std::as_const}. In contrast to inlining, this
+means no debug information will be generated for such calls. Since these
+functions are rarely interesting to debug, this flag is enabled by default
+unless @option{-fno-inline} is active.
+
+@item -fno-gnu-keywords
+@opindex fno-gnu-keywords
+@opindex fgnu-keywords
+Do not recognize @code{typeof} as a keyword, so that code can use this
+word as an identifier. You can use the keyword @code{__typeof__} instead.
+This option is implied by the strict ISO C++ dialects: @option{-ansi},
+@option{-std=c++98}, @option{-std=c++11}, etc.
+
+@item -fimplicit-constexpr
+@opindex fimplicit-constexpr
+Make inline functions implicitly constexpr, if they satisfy the
+requirements for a constexpr function. This option can be used in
+C++14 mode or later. This can result in initialization changing from
+dynamic to static and other optimizations.
+
+@item -fno-implicit-templates
+@opindex fno-implicit-templates
+@opindex fimplicit-templates
+Never emit code for non-inline templates that are instantiated
+implicitly (i.e.@: by use); only emit code for explicit instantiations.
+If you use this option, you must take care to structure your code to
+include all the necessary explicit instantiations to avoid getting
+undefined symbols at link time.
+@xref{Template Instantiation}, for more information.
+
+@item -fno-implicit-inline-templates
+@opindex fno-implicit-inline-templates
+@opindex fimplicit-inline-templates
+Don't emit code for implicit instantiations of inline templates, either.
+The default is to handle inlines differently so that compiles with and
+without optimization need the same set of explicit instantiations.
+
+@item -fno-implement-inlines
+@opindex fno-implement-inlines
+@opindex fimplement-inlines
+To save space, do not emit out-of-line copies of inline functions
+controlled by @code{#pragma implementation}. This causes linker
+errors if these functions are not inlined everywhere they are called.
+
+@item -fmodules-ts
+@itemx -fno-modules-ts
+@opindex fmodules-ts
+@opindex fno-modules-ts
+Enable support for C++20 modules (@pxref{C++ Modules}). The
+@option{-fno-modules-ts} is usually not needed, as that is the
+default. Even though this is a C++20 feature, it is not currently
+implicitly enabled by selecting that standard version.
+
+@item -fmodule-header
+@itemx -fmodule-header=user
+@itemx -fmodule-header=system
+@opindex fmodule-header
+Compile a header file to create an importable header unit.
+
+@item -fmodule-implicit-inline
+@opindex fmodule-implicit-inline
+Member functions defined in their class definitions are not implicitly
+inline for modular code. This is different to traditional C++
+behavior, for good reasons. However, it may result in a difficulty
+during code porting. This option makes such function definitions
+implicitly inline. It does however generate an ABI incompatibility,
+so you must use it everywhere or nowhere. (Such definitions outside
+of a named module remain implicitly inline, regardless.)
+
+@item -fno-module-lazy
+@opindex fno-module-lazy
+@opindex fmodule-lazy
+Disable lazy module importing and module mapper creation.
+
+@item -fmodule-mapper=@r{[}@var{hostname}@r{]}:@var{port}@r{[}?@var{ident}@r{]}
+@itemx -fmodule-mapper=|@var{program}@r{[}?@var{ident}@r{]} @var{args...}
+@itemx -fmodule-mapper==@var{socket}@r{[}?@var{ident}@r{]}
+@itemx -fmodule-mapper=<>@r{[}@var{inout}@r{]}@r{[}?@var{ident}@r{]}
+@itemx -fmodule-mapper=<@var{in}>@var{out}@r{[}?@var{ident}@r{]}
+@itemx -fmodule-mapper=@var{file}@r{[}?@var{ident}@r{]}
+@vindex CXX_MODULE_MAPPER @r{environment variable}
+@opindex fmodule-mapper
+An oracle to query for module name to filename mappings. If
+unspecified the @env{CXX_MODULE_MAPPER} environment variable is used,
+and if that is unset, an in-process default is provided.
+
+@item -fmodule-only
+@opindex fmodule-only
+Only emit the Compiled Module Interface, inhibiting any object file.
+
+@item -fms-extensions
+@opindex fms-extensions
+Disable Wpedantic warnings about constructs used in MFC, such as implicit
+int and getting a pointer to member function via non-standard syntax.
+
+@item -fnew-inheriting-ctors
+@opindex fnew-inheriting-ctors
+Enable the P0136 adjustment to the semantics of C++11 constructor
+inheritance. This is part of C++17 but also considered to be a Defect
+Report against C++11 and C++14. This flag is enabled by default
+unless @option{-fabi-version=10} or lower is specified.
+
+@item -fnew-ttp-matching
+@opindex fnew-ttp-matching
+Enable the P0522 resolution to Core issue 150, template template
+parameters and default arguments: this allows a template with default
+template arguments as an argument for a template template parameter
+with fewer template parameters. This flag is enabled by default for
+@option{-std=c++17}.
+
+@item -fno-nonansi-builtins
+@opindex fno-nonansi-builtins
+@opindex fnonansi-builtins
+Disable built-in declarations of functions that are not mandated by
+ANSI/ISO C@. These include @code{ffs}, @code{alloca}, @code{_exit},
+@code{index}, @code{bzero}, @code{conjf}, and other related functions.
+
+@item -fnothrow-opt
+@opindex fnothrow-opt
+Treat a @code{throw()} exception specification as if it were a
+@code{noexcept} specification to reduce or eliminate the text size
+overhead relative to a function with no exception specification. If
+the function has local variables of types with non-trivial
+destructors, the exception specification actually makes the
+function smaller because the EH cleanups for those variables can be
+optimized away. The semantic effect is that an exception thrown out of
+a function with such an exception specification results in a call
+to @code{terminate} rather than @code{unexpected}.
+
+@item -fno-operator-names
+@opindex fno-operator-names
+@opindex foperator-names
+Do not treat the operator name keywords @code{and}, @code{bitand},
+@code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as
+synonyms as keywords.
+
+@item -fno-optional-diags
+@opindex fno-optional-diags
+@opindex foptional-diags
+Disable diagnostics that the standard says a compiler does not need to
+issue. Currently, the only such diagnostic issued by G++ is the one for
+a name having multiple meanings within a class.
+
+@item -fpermissive
+@opindex fpermissive
+Downgrade some diagnostics about nonconformant code from errors to
+warnings. Thus, using @option{-fpermissive} allows some
+nonconforming code to compile.
+
+@item -fno-pretty-templates
+@opindex fno-pretty-templates
+@opindex fpretty-templates
+When an error message refers to a specialization of a function
+template, the compiler normally prints the signature of the
+template followed by the template arguments and any typedefs or
+typenames in the signature (e.g.@: @code{void f(T) [with T = int]}
+rather than @code{void f(int)}) so that it's clear which template is
+involved. When an error message refers to a specialization of a class
+template, the compiler omits any template arguments that match
+the default template arguments for that template. If either of these
+behaviors make it harder to understand the error message rather than
+easier, you can use @option{-fno-pretty-templates} to disable them.
+
+@item -fno-rtti
+@opindex fno-rtti
+@opindex frtti
+Disable generation of information about every class with virtual
+functions for use by the C++ run-time type identification features
+(@code{dynamic_cast} and @code{typeid}). If you don't use those parts
+of the language, you can save some space by using this flag. Note that
+exception handling uses the same information, but G++ generates it as
+needed. The @code{dynamic_cast} operator can still be used for casts that
+do not require run-time type information, i.e.@: casts to @code{void *} or to
+unambiguous base classes.
+
+Mixing code compiled with @option{-frtti} with that compiled with
+@option{-fno-rtti} may not work. For example, programs may
+fail to link if a class compiled with @option{-fno-rtti} is used as a base
+for a class compiled with @option{-frtti}.
+
+@item -fsized-deallocation
+@opindex fsized-deallocation
+Enable the built-in global declarations
+@smallexample
+void operator delete (void *, std::size_t) noexcept;
+void operator delete[] (void *, std::size_t) noexcept;
+@end smallexample
+as introduced in C++14. This is useful for user-defined replacement
+deallocation functions that, for example, use the size of the object
+to make deallocation faster. Enabled by default under
+@option{-std=c++14} and above. The flag @option{-Wsized-deallocation}
+warns about places that might want to add a definition.
+
+@item -fstrict-enums
+@opindex fstrict-enums
+Allow the compiler to optimize using the assumption that a value of
+enumerated type can only be one of the values of the enumeration (as
+defined in the C++ standard; basically, a value that can be
+represented in the minimum number of bits needed to represent all the
+enumerators). This assumption may not be valid if the program uses a
+cast to convert an arbitrary integer value to the enumerated type.
+
+@item -fstrong-eval-order
+@opindex fstrong-eval-order
+Evaluate member access, array subscripting, and shift expressions in
+left-to-right order, and evaluate assignment in right-to-left order,
+as adopted for C++17. Enabled by default with @option{-std=c++17}.
+@option{-fstrong-eval-order=some} enables just the ordering of member
+access and shift expressions, and is the default without
+@option{-std=c++17}.
+
+@item -ftemplate-backtrace-limit=@var{n}
+@opindex ftemplate-backtrace-limit
+Set the maximum number of template instantiation notes for a single
+warning or error to @var{n}. The default value is 10.
+
+@item -ftemplate-depth=@var{n}
+@opindex ftemplate-depth
+Set the maximum instantiation depth for template classes to @var{n}.
+A limit on the template instantiation depth is needed to detect
+endless recursions during template class instantiation. ANSI/ISO C++
+conforming programs must not rely on a maximum depth greater than 17
+(changed to 1024 in C++11). The default value is 900, as the compiler
+can run out of stack space before hitting 1024 in some situations.
+
+@item -fno-threadsafe-statics
+@opindex fno-threadsafe-statics
+@opindex fthreadsafe-statics
+Do not emit the extra code to use the routines specified in the C++
+ABI for thread-safe initialization of local statics. You can use this
+option to reduce code size slightly in code that doesn't need to be
+thread-safe.
+
+@item -fuse-cxa-atexit
+@opindex fuse-cxa-atexit
+Register destructors for objects with static storage duration with the
+@code{__cxa_atexit} function rather than the @code{atexit} function.
+This option is required for fully standards-compliant handling of static
+destructors, but only works if your C library supports
+@code{__cxa_atexit}.
+
+@item -fno-use-cxa-get-exception-ptr
+@opindex fno-use-cxa-get-exception-ptr
+@opindex fuse-cxa-get-exception-ptr
+Don't use the @code{__cxa_get_exception_ptr} runtime routine. This
+causes @code{std::uncaught_exception} to be incorrect, but is necessary
+if the runtime routine is not available.
+
+@item -fvisibility-inlines-hidden
+@opindex fvisibility-inlines-hidden
+This switch declares that the user does not attempt to compare
+pointers to inline functions or methods where the addresses of the two functions
+are taken in different shared objects.
+
+The effect of this is that GCC may, effectively, mark inline methods with
+@code{__attribute__ ((visibility ("hidden")))} so that they do not
+appear in the export table of a DSO and do not require a PLT indirection
+when used within the DSO@. Enabling this option can have a dramatic effect
+on load and link times of a DSO as it massively reduces the size of the
+dynamic export table when the library makes heavy use of templates.
+
+The behavior of this switch is not quite the same as marking the
+methods as hidden directly, because it does not affect static variables
+local to the function or cause the compiler to deduce that
+the function is defined in only one shared object.
+
+You may mark a method as having a visibility explicitly to negate the
+effect of the switch for that method. For example, if you do want to
+compare pointers to a particular inline method, you might mark it as
+having default visibility. Marking the enclosing class with explicit
+visibility has no effect.
+
+Explicitly instantiated inline methods are unaffected by this option
+as their linkage might otherwise cross a shared library boundary.
+@xref{Template Instantiation}.
+
+@item -fvisibility-ms-compat
+@opindex fvisibility-ms-compat
+This flag attempts to use visibility settings to make GCC's C++
+linkage model compatible with that of Microsoft Visual Studio.
+
+The flag makes these changes to GCC's linkage model:
+
+@enumerate
+@item
+It sets the default visibility to @code{hidden}, like
+@option{-fvisibility=hidden}.
+
+@item
+Types, but not their members, are not hidden by default.
+
+@item
+The One Definition Rule is relaxed for types without explicit
+visibility specifications that are defined in more than one
+shared object: those declarations are permitted if they are
+permitted when this option is not used.
+@end enumerate
+
+In new code it is better to use @option{-fvisibility=hidden} and
+export those classes that are intended to be externally visible.
+Unfortunately it is possible for code to rely, perhaps accidentally,
+on the Visual Studio behavior.
+
+Among the consequences of these changes are that static data members
+of the same type with the same name but defined in different shared
+objects are different, so changing one does not change the other;
+and that pointers to function members defined in different shared
+objects may not compare equal. When this flag is given, it is a
+violation of the ODR to define types with the same name differently.
+
+@item -fno-weak
+@opindex fno-weak
+@opindex fweak
+Do not use weak symbol support, even if it is provided by the linker.
+By default, G++ uses weak symbols if they are available. This
+option exists only for testing, and should not be used by end-users;
+it results in inferior code and has no benefits. This option may
+be removed in a future release of G++.
+
+@item -fext-numeric-literals @r{(C++ and Objective-C++ only)}
+@opindex fext-numeric-literals
+@opindex fno-ext-numeric-literals
+Accept imaginary, fixed-point, or machine-defined
+literal number suffixes as GNU extensions.
+When this option is turned off these suffixes are treated
+as C++11 user-defined literal numeric suffixes.
+This is on by default for all pre-C++11 dialects and all GNU dialects:
+@option{-std=c++98}, @option{-std=gnu++98}, @option{-std=gnu++11},
+@option{-std=gnu++14}.
+This option is off by default
+for ISO C++11 onwards (@option{-std=c++11}, ...).
+
+@item -nostdinc++
+@opindex nostdinc++
+Do not search for header files in the standard directories specific to
+C++, but do still search the other standard directories. (This option
+is used when building the C++ library.)
+
+@item -flang-info-include-translate
+@itemx -flang-info-include-translate-not
+@itemx -flang-info-include-translate=@var{header}
+@opindex flang-info-include-translate
+@opindex flang-info-include-translate-not
+Inform of include translation events. The first will note accepted
+include translations, the second will note declined include
+translations. The @var{header} form will inform of include
+translations relating to that specific header. If @var{header} is of
+the form @code{"user"} or @code{<system>} it will be resolved to a
+specific user or system header using the include path.
+
+@item -flang-info-module-cmi
+@itemx -flang-info-module-cmi=@var{module}
+@opindex flang-info-module-cmi
+Inform of Compiled Module Interface pathnames. The first will note
+all read CMI pathnames. The @var{module} form will not reading a
+specific module's CMI. @var{module} may be a named module or a
+header-unit (the latter indicated by either being a pathname containing
+directory separators or enclosed in @code{<>} or @code{""}).
+
+@item -stdlib=@var{libstdc++,libc++}
+@opindex stdlib
+When G++ is configured to support this option, it allows specification of
+alternate C++ runtime libraries. Two options are available: @var{libstdc++}
+(the default, native C++ runtime for G++) and @var{libc++} which is the
+C++ runtime installed on some operating systems (e.g. Darwin versions from
+Darwin11 onwards). The option switches G++ to use the headers from the
+specified library and to emit @code{-lstdc++} or @code{-lc++} respectively,
+when a C++ runtime is required for linking.
+@end table
+
+In addition, these warning options have meanings only for C++ programs:
+
+@table @gcctabopt
+@item -Wabi-tag @r{(C++ and Objective-C++ only)}
+@opindex Wabi-tag
+Warn when a type with an ABI tag is used in a context that does not
+have that ABI tag. See @ref{C++ Attributes} for more information
+about ABI tags.
+
+@item -Wcomma-subscript @r{(C++ and Objective-C++ only)}
+@opindex Wcomma-subscript
+@opindex Wno-comma-subscript
+Warn about uses of a comma expression within a subscripting expression.
+This usage was deprecated in C++20 and is going to be removed in C++23.
+However, a comma expression wrapped in @code{( )} is not deprecated. Example:
+
+@smallexample
+@group
+void f(int *a, int b, int c) @{
+ a[b,c]; // deprecated in C++20, invalid in C++23
+ a[(b,c)]; // OK
+@}
+@end group
+@end smallexample
+
+In C++23 it is valid to have comma separated expressions in a subscript
+when an overloaded subscript operator is found and supports the right
+number and types of arguments. G++ will accept the formerly valid syntax
+for code that is not valid in C++23 but used to be valid but deprecated
+in C++20 with a pedantic warning that can be disabled with
+@option{-Wno-comma-subscript}.
+
+Enabled by default with @option{-std=c++20} unless @option{-Wno-deprecated},
+and with @option{-std=c++23} regardless of @option{-Wno-deprecated}.
+
+@item -Wctad-maybe-unsupported @r{(C++ and Objective-C++ only)}
+@opindex Wctad-maybe-unsupported
+@opindex Wno-ctad-maybe-unsupported
+Warn when performing class template argument deduction (CTAD) on a type with
+no explicitly written deduction guides. This warning will point out cases
+where CTAD succeeded only because the compiler synthesized the implicit
+deduction guides, which might not be what the programmer intended. Certain
+style guides allow CTAD only on types that specifically "opt-in"; i.e., on
+types that are designed to support CTAD. This warning can be suppressed with
+the following pattern:
+
+@smallexample
+struct allow_ctad_t; // any name works
+template <typename T> struct S @{
+ S(T) @{ @}
+@};
+S(allow_ctad_t) -> S<void>; // guide with incomplete parameter type will never be considered
+@end smallexample
+
+@item -Wctor-dtor-privacy @r{(C++ and Objective-C++ only)}
+@opindex Wctor-dtor-privacy
+@opindex Wno-ctor-dtor-privacy
+Warn when a class seems unusable because all the constructors or
+destructors in that class are private, and it has neither friends nor
+public static member functions. Also warn if there are no non-private
+methods, and there's at least one private member function that isn't
+a constructor or destructor.
+
+@item -Wdangling-reference @r{(C++ and Objective-C++ only)}
+@opindex Wdangling-reference
+@opindex Wno-dangling-reference
+Warn when a reference is bound to a temporary whose lifetime has ended.
+For example:
+
+@smallexample
+int n = 1;
+const int& r = std::max(n - 1, n + 1); // r is dangling
+@end smallexample
+
+In the example above, two temporaries are created, one for each
+argument, and a reference to one of the temporaries is returned.
+However, both temporaries are destroyed at the end of the full
+expression, so the reference @code{r} is dangling. This warning
+also detects dangling references in member initializer lists:
+
+@smallexample
+const int& f(const int& i) @{ return i; @}
+struct S @{
+ const int &r; // r is dangling
+ S() : r(f(10)) @{ @}
+@};
+@end smallexample
+
+Member functions are checked as well, but only their object argument:
+
+@smallexample
+struct S @{
+ const S& self () @{ return *this; @}
+@};
+const S& s = S().self(); // s is dangling
+@end smallexample
+
+Certain functions are safe in this respect, for example @code{std::use_facet}:
+they take and return a reference, but they don't return one of its arguments,
+which can fool the warning. Such functions can be excluded from the warning
+by wrapping them in a @code{#pragma}:
+
+@smallexample
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdangling-reference"
+const T& foo (const T&) @{ @dots{} @}
+#pragma GCC diagnostic pop
+@end smallexample
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wdelete-non-virtual-dtor @r{(C++ and Objective-C++ only)}
+@opindex Wdelete-non-virtual-dtor
+@opindex Wno-delete-non-virtual-dtor
+Warn when @code{delete} is used to destroy an instance of a class that
+has virtual functions and non-virtual destructor. It is unsafe to delete
+an instance of a derived class through a pointer to a base class if the
+base class does not have a virtual destructor. This warning is enabled
+by @option{-Wall}.
+
+@item -Wdeprecated-copy @r{(C++ and Objective-C++ only)}
+@opindex Wdeprecated-copy
+@opindex Wno-deprecated-copy
+Warn that the implicit declaration of a copy constructor or copy
+assignment operator is deprecated if the class has a user-provided
+copy constructor or copy assignment operator, in C++11 and up. This
+warning is enabled by @option{-Wextra}. With
+@option{-Wdeprecated-copy-dtor}, also deprecate if the class has a
+user-provided destructor.
+
+@item -Wno-deprecated-enum-enum-conversion @r{(C++ and Objective-C++ only)}
+@opindex Wdeprecated-enum-enum-conversion
+@opindex Wno-deprecated-enum-enum-conversion
+Disable the warning about the case when the usual arithmetic conversions
+are applied on operands where one is of enumeration type and the other is
+of a different enumeration type. This conversion was deprecated in C++20.
+For example:
+
+@smallexample
+enum E1 @{ e @};
+enum E2 @{ f @};
+int k = f - e;
+@end smallexample
+
+@option{-Wdeprecated-enum-enum-conversion} is enabled by default with
+@option{-std=c++20}. In pre-C++20 dialects, this warning can be enabled
+by @option{-Wenum-conversion}.
+
+@item -Wno-deprecated-enum-float-conversion @r{(C++ and Objective-C++ only)}
+@opindex Wdeprecated-enum-float-conversion
+@opindex Wno-deprecated-enum-float-conversion
+Disable the warning about the case when the usual arithmetic conversions
+are applied on operands where one is of enumeration type and the other is
+of a floating-point type. This conversion was deprecated in C++20. For
+example:
+
+@smallexample
+enum E1 @{ e @};
+enum E2 @{ f @};
+bool b = e <= 3.7;
+@end smallexample
+
+@option{-Wdeprecated-enum-float-conversion} is enabled by default with
+@option{-std=c++20}. In pre-C++20 dialects, this warning can be enabled
+by @option{-Wenum-conversion}.
+
+@item -Wno-init-list-lifetime @r{(C++ and Objective-C++ only)}
+@opindex Winit-list-lifetime
+@opindex Wno-init-list-lifetime
+Do not warn about uses of @code{std::initializer_list} that are likely
+to result in dangling pointers. Since the underlying array for an
+@code{initializer_list} is handled like a normal C++ temporary object,
+it is easy to inadvertently keep a pointer to the array past the end
+of the array's lifetime. For example:
+
+@itemize @bullet
+@item
+If a function returns a temporary @code{initializer_list}, or a local
+@code{initializer_list} variable, the array's lifetime ends at the end
+of the return statement, so the value returned has a dangling pointer.
+
+@item
+If a new-expression creates an @code{initializer_list}, the array only
+lives until the end of the enclosing full-expression, so the
+@code{initializer_list} in the heap has a dangling pointer.
+
+@item
+When an @code{initializer_list} variable is assigned from a
+brace-enclosed initializer list, the temporary array created for the
+right side of the assignment only lives until the end of the
+full-expression, so at the next statement the @code{initializer_list}
+variable has a dangling pointer.
+
+@smallexample
+// li's initial underlying array lives as long as li
+std::initializer_list<int> li = @{ 1,2,3 @};
+// assignment changes li to point to a temporary array
+li = @{ 4, 5 @};
+// now the temporary is gone and li has a dangling pointer
+int i = li.begin()[0] // undefined behavior
+@end smallexample
+
+@item
+When a list constructor stores the @code{begin} pointer from the
+@code{initializer_list} argument, this doesn't extend the lifetime of
+the array, so if a class variable is constructed from a temporary
+@code{initializer_list}, the pointer is left dangling by the end of
+the variable declaration statement.
+
+@end itemize
+
+@item -Winvalid-imported-macros
+@opindex Winvalid-imported-macros
+@opindex Wno-invalid-imported-macros
+Verify all imported macro definitions are valid at the end of
+compilation. This is not enabled by default, as it requires
+additional processing to determine. It may be useful when preparing
+sets of header-units to ensure consistent macros.
+
+@item -Wno-literal-suffix @r{(C++ and Objective-C++ only)}
+@opindex Wliteral-suffix
+@opindex Wno-literal-suffix
+Do not warn when a string or character literal is followed by a
+ud-suffix which does not begin with an underscore. As a conforming
+extension, GCC treats such suffixes as separate preprocessing tokens
+in order to maintain backwards compatibility with code that uses
+formatting macros from @code{<inttypes.h>}. For example:
+
+@smallexample
+#define __STDC_FORMAT_MACROS
+#include <inttypes.h>
+#include <stdio.h>
+
+int main() @{
+ int64_t i64 = 123;
+ printf("My int64: %" PRId64"\n", i64);
+@}
+@end smallexample
+
+In this case, @code{PRId64} is treated as a separate preprocessing token.
+
+This option also controls warnings when a user-defined literal
+operator is declared with a literal suffix identifier that doesn't
+begin with an underscore. Literal suffix identifiers that don't begin
+with an underscore are reserved for future standardization.
+
+These warnings are enabled by default.
+
+@item -Wno-narrowing @r{(C++ and Objective-C++ only)}
+@opindex Wnarrowing
+@opindex Wno-narrowing
+For C++11 and later standards, narrowing conversions are diagnosed by default,
+as required by the standard. A narrowing conversion from a constant produces
+an error, and a narrowing conversion from a non-constant produces a warning,
+but @option{-Wno-narrowing} suppresses the diagnostic.
+Note that this does not affect the meaning of well-formed code;
+narrowing conversions are still considered ill-formed in SFINAE contexts.
+
+With @option{-Wnarrowing} in C++98, warn when a narrowing
+conversion prohibited by C++11 occurs within
+@samp{@{ @}}, e.g.
+
+@smallexample
+int i = @{ 2.2 @}; // error: narrowing from double to int
+@end smallexample
+
+This flag is included in @option{-Wall} and @option{-Wc++11-compat}.
+
+@item -Wnoexcept @r{(C++ and Objective-C++ only)}
+@opindex Wnoexcept
+@opindex Wno-noexcept
+Warn when a noexcept-expression evaluates to false because of a call
+to a function that does not have a non-throwing exception
+specification (i.e. @code{throw()} or @code{noexcept}) but is known by
+the compiler to never throw an exception.
+
+@item -Wnoexcept-type @r{(C++ and Objective-C++ only)}
+@opindex Wnoexcept-type
+@opindex Wno-noexcept-type
+Warn if the C++17 feature making @code{noexcept} part of a function
+type changes the mangled name of a symbol relative to C++14. Enabled
+by @option{-Wabi} and @option{-Wc++17-compat}.
+
+As an example:
+
+@smallexample
+template <class T> void f(T t) @{ t(); @};
+void g() noexcept;
+void h() @{ f(g); @}
+@end smallexample
+
+@noindent
+In C++14, @code{f} calls @code{f<void(*)()>}, but in
+C++17 it calls @code{f<void(*)()noexcept>}.
+
+@item -Wclass-memaccess @r{(C++ and Objective-C++ only)}
+@opindex Wclass-memaccess
+@opindex Wno-class-memaccess
+Warn when the destination of a call to a raw memory function such as
+@code{memset} or @code{memcpy} is an object of class type, and when writing
+into such an object might bypass the class non-trivial or deleted constructor
+or copy assignment, violate const-correctness or encapsulation, or corrupt
+virtual table pointers. Modifying the representation of such objects may
+violate invariants maintained by member functions of the class. For example,
+the call to @code{memset} below is undefined because it modifies a non-trivial
+class object and is, therefore, diagnosed. The safe way to either initialize
+or clear the storage of objects of such types is by using the appropriate
+constructor or assignment operator, if one is available.
+@smallexample
+std::string str = "abc";
+memset (&str, 0, sizeof str);
+@end smallexample
+The @option{-Wclass-memaccess} option is enabled by @option{-Wall}.
+Explicitly casting the pointer to the class object to @code{void *} or
+to a type that can be safely accessed by the raw memory function suppresses
+the warning.
+
+@item -Wnon-virtual-dtor @r{(C++ and Objective-C++ only)}
+@opindex Wnon-virtual-dtor
+@opindex Wno-non-virtual-dtor
+Warn when a class has virtual functions and an accessible non-virtual
+destructor itself or in an accessible polymorphic base class, in which
+case it is possible but unsafe to delete an instance of a derived
+class through a pointer to the class itself or base class. This
+warning is automatically enabled if @option{-Weffc++} is specified.
+
+@item -Wregister @r{(C++ and Objective-C++ only)}
+@opindex Wregister
+@opindex Wno-register
+Warn on uses of the @code{register} storage class specifier, except
+when it is part of the GNU @ref{Explicit Register Variables} extension.
+The use of the @code{register} keyword as storage class specifier has
+been deprecated in C++11 and removed in C++17.
+Enabled by default with @option{-std=c++17}.
+
+@item -Wreorder @r{(C++ and Objective-C++ only)}
+@opindex Wreorder
+@opindex Wno-reorder
+@cindex reordering, warning
+@cindex warning for reordering of member initializers
+Warn when the order of member initializers given in the code does not
+match the order in which they must be executed. For instance:
+
+@smallexample
+struct A @{
+ int i;
+ int j;
+ A(): j (0), i (1) @{ @}
+@};
+@end smallexample
+
+@noindent
+The compiler rearranges the member initializers for @code{i}
+and @code{j} to match the declaration order of the members, emitting
+a warning to that effect. This warning is enabled by @option{-Wall}.
+
+@item -Wno-pessimizing-move @r{(C++ and Objective-C++ only)}
+@opindex Wpessimizing-move
+@opindex Wno-pessimizing-move
+This warning warns when a call to @code{std::move} prevents copy
+elision. A typical scenario when copy elision can occur is when returning in
+a function with a class return type, when the expression being returned is the
+name of a non-volatile automatic object, and is not a function parameter, and
+has the same type as the function return type.
+
+@smallexample
+struct T @{
+@dots{}
+@};
+T fn()
+@{
+ T t;
+ @dots{}
+ return std::move (t);
+@}
+@end smallexample
+
+But in this example, the @code{std::move} call prevents copy elision.
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wno-redundant-move @r{(C++ and Objective-C++ only)}
+@opindex Wredundant-move
+@opindex Wno-redundant-move
+This warning warns about redundant calls to @code{std::move}; that is, when
+a move operation would have been performed even without the @code{std::move}
+call. This happens because the compiler is forced to treat the object as if
+it were an rvalue in certain situations such as returning a local variable,
+where copy elision isn't applicable. Consider:
+
+@smallexample
+struct T @{
+@dots{}
+@};
+T fn(T t)
+@{
+ @dots{}
+ return std::move (t);
+@}
+@end smallexample
+
+Here, the @code{std::move} call is redundant. Because G++ implements Core
+Issue 1579, another example is:
+
+@smallexample
+struct T @{ // convertible to U
+@dots{}
+@};
+struct U @{
+@dots{}
+@};
+U fn()
+@{
+ T t;
+ @dots{}
+ return std::move (t);
+@}
+@end smallexample
+In this example, copy elision isn't applicable because the type of the
+expression being returned and the function return type differ, yet G++
+treats the return value as if it were designated by an rvalue.
+
+This warning is enabled by @option{-Wextra}.
+
+@item -Wrange-loop-construct @r{(C++ and Objective-C++ only)}
+@opindex Wrange-loop-construct
+@opindex Wno-range-loop-construct
+This warning warns when a C++ range-based for-loop is creating an unnecessary
+copy. This can happen when the range declaration is not a reference, but
+probably should be. For example:
+
+@smallexample
+struct S @{ char arr[128]; @};
+void fn () @{
+ S arr[5];
+ for (const auto x : arr) @{ @dots{} @}
+@}
+@end smallexample
+
+It does not warn when the type being copied is a trivially-copyable type whose
+size is less than 64 bytes.
+
+This warning also warns when a loop variable in a range-based for-loop is
+initialized with a value of a different type resulting in a copy. For example:
+
+@smallexample
+void fn() @{
+ int arr[10];
+ for (const double &x : arr) @{ @dots{} @}
+@}
+@end smallexample
+
+In the example above, in every iteration of the loop a temporary value of
+type @code{double} is created and destroyed, to which the reference
+@code{const double &} is bound.
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wredundant-tags @r{(C++ and Objective-C++ only)}
+@opindex Wredundant-tags
+@opindex Wno-redundant-tags
+Warn about redundant class-key and enum-key in references to class types
+and enumerated types in contexts where the key can be eliminated without
+causing an ambiguity. For example:
+
+@smallexample
+struct foo;
+struct foo *p; // warn that keyword struct can be eliminated
+@end smallexample
+
+@noindent
+On the other hand, in this example there is no warning:
+
+@smallexample
+struct foo;
+void foo (); // "hides" struct foo
+void bar (struct foo&); // no warning, keyword struct is necessary
+@end smallexample
+
+@item -Wno-subobject-linkage @r{(C++ and Objective-C++ only)}
+@opindex Wsubobject-linkage
+@opindex Wno-subobject-linkage
+Do not warn
+if a class type has a base or a field whose type uses the anonymous
+namespace or depends on a type with no linkage. If a type A depends on
+a type B with no or internal linkage, defining it in multiple
+translation units would be an ODR violation because the meaning of B
+is different in each translation unit. If A only appears in a single
+translation unit, the best way to silence the warning is to give it
+internal linkage by putting it in an anonymous namespace as well. The
+compiler doesn't give this warning for types defined in the main .C
+file, as those are unlikely to have multiple definitions.
+@option{-Wsubobject-linkage} is enabled by default.
+
+@item -Weffc++ @r{(C++ and Objective-C++ only)}
+@opindex Weffc++
+@opindex Wno-effc++
+Warn about violations of the following style guidelines from Scott Meyers'
+@cite{Effective C++} series of books:
+
+@itemize @bullet
+@item
+Define a copy constructor and an assignment operator for classes
+with dynamically-allocated memory.
+
+@item
+Prefer initialization to assignment in constructors.
+
+@item
+Have @code{operator=} return a reference to @code{*this}.
+
+@item
+Don't try to return a reference when you must return an object.
+
+@item
+Distinguish between prefix and postfix forms of increment and
+decrement operators.
+
+@item
+Never overload @code{&&}, @code{||}, or @code{,}.
+
+@end itemize
+
+This option also enables @option{-Wnon-virtual-dtor}, which is also
+one of the effective C++ recommendations. However, the check is
+extended to warn about the lack of virtual destructor in accessible
+non-polymorphic bases classes too.
+
+When selecting this option, be aware that the standard library
+headers do not obey all of these guidelines; use @samp{grep -v}
+to filter out those warnings.
+
+@item -Wno-exceptions @r{(C++ and Objective-C++ only)}
+@opindex Wexceptions
+@opindex Wno-exceptions
+Disable the warning about the case when an exception handler is shadowed by
+another handler, which can point out a wrong ordering of exception handlers.
+
+@item -Wstrict-null-sentinel @r{(C++ and Objective-C++ only)}
+@opindex Wstrict-null-sentinel
+@opindex Wno-strict-null-sentinel
+Warn about the use of an uncasted @code{NULL} as sentinel. When
+compiling only with GCC this is a valid sentinel, as @code{NULL} is defined
+to @code{__null}. Although it is a null pointer constant rather than a
+null pointer, it is guaranteed to be of the same size as a pointer.
+But this use is not portable across different compilers.
+
+@item -Wno-non-template-friend @r{(C++ and Objective-C++ only)}
+@opindex Wno-non-template-friend
+@opindex Wnon-template-friend
+Disable warnings when non-template friend functions are declared
+within a template. In very old versions of GCC that predate implementation
+of the ISO standard, declarations such as
+@samp{friend int foo(int)}, where the name of the friend is an unqualified-id,
+could be interpreted as a particular specialization of a template
+function; the warning exists to diagnose compatibility problems,
+and is enabled by default.
+
+@item -Wold-style-cast @r{(C++ and Objective-C++ only)}
+@opindex Wold-style-cast
+@opindex Wno-old-style-cast
+Warn if an old-style (C-style) cast to a non-void type is used within
+a C++ program. The new-style casts (@code{dynamic_cast},
+@code{static_cast}, @code{reinterpret_cast}, and @code{const_cast}) are
+less vulnerable to unintended effects and much easier to search for.
+
+@item -Woverloaded-virtual @r{(C++ and Objective-C++ only)}
+@itemx -Woverloaded-virtual=@var{n}
+@opindex Woverloaded-virtual
+@opindex Wno-overloaded-virtual
+@cindex overloaded virtual function, warning
+@cindex warning for overloaded virtual function
+Warn when a function declaration hides virtual functions from a
+base class. For example, in:
+
+@smallexample
+struct A @{
+ virtual void f();
+@};
+
+struct B: public A @{
+ void f(int); // does not override
+@};
+@end smallexample
+
+the @code{A} class version of @code{f} is hidden in @code{B}, and code
+like:
+
+@smallexample
+B* b;
+b->f();
+@end smallexample
+
+@noindent
+fails to compile.
+
+The optional level suffix controls the behavior when all the
+declarations in the derived class override virtual functions in the
+base class, even if not all of the base functions are overridden:
+
+@smallexample
+struct C @{
+ virtual void f();
+ virtual void f(int);
+@};
+
+struct D: public C @{
+ void f(int); // does override
+@}
+@end smallexample
+
+This pattern is less likely to be a mistake; if D is only used
+virtually, the user might have decided that the base class semantics
+for some of the overloads are fine.
+
+At level 1, this case does not warn; at level 2, it does.
+@option{-Woverloaded-virtual} by itself selects level 2. Level 1 is
+included in @option{-Wall}.
+
+@item -Wno-pmf-conversions @r{(C++ and Objective-C++ only)}
+@opindex Wno-pmf-conversions
+@opindex Wpmf-conversions
+Disable the diagnostic for converting a bound pointer to member function
+to a plain pointer.
+
+@item -Wsign-promo @r{(C++ and Objective-C++ only)}
+@opindex Wsign-promo
+@opindex Wno-sign-promo
+Warn when overload resolution chooses a promotion from unsigned or
+enumerated type to a signed type, over a conversion to an unsigned type of
+the same size. Previous versions of G++ tried to preserve
+unsignedness, but the standard mandates the current behavior.
+
+@item -Wtemplates @r{(C++ and Objective-C++ only)}
+@opindex Wtemplates
+@opindex Wno-templates
+Warn when a primary template declaration is encountered. Some coding
+rules disallow templates, and this may be used to enforce that rule.
+The warning is inactive inside a system header file, such as the STL, so
+one can still use the STL. One may also instantiate or specialize
+templates.
+
+@item -Wmismatched-new-delete @r{(C++ and Objective-C++ only)}
+@opindex Wmismatched-new-delete
+@opindex Wno-mismatched-new-delete
+Warn for mismatches between calls to @code{operator new} or @code{operator
+delete} and the corresponding call to the allocation or deallocation function.
+This includes invocations of C++ @code{operator delete} with pointers
+returned from either mismatched forms of @code{operator new}, or from other
+functions that allocate objects for which the @code{operator delete} isn't
+a suitable deallocator, as well as calls to other deallocation functions
+with pointers returned from @code{operator new} for which the deallocation
+function isn't suitable.
+
+For example, the @code{delete} expression in the function below is diagnosed
+because it doesn't match the array form of the @code{new} expression
+the pointer argument was returned from. Similarly, the call to @code{free}
+is also diagnosed.
+
+@smallexample
+void f ()
+@{
+ int *a = new int[n];
+ delete a; // warning: mismatch in array forms of expressions
+
+ char *p = new char[n];
+ free (p); // warning: mismatch between new and free
+@}
+@end smallexample
+
+The related option @option{-Wmismatched-dealloc} diagnoses mismatches
+involving allocation and deallocation functions other than @code{operator
+new} and @code{operator delete}.
+
+@option{-Wmismatched-new-delete} is included in @option{-Wall}.
+
+@item -Wmismatched-tags @r{(C++ and Objective-C++ only)}
+@opindex Wmismatched-tags
+@opindex Wno-mismatched-tags
+Warn for declarations of structs, classes, and class templates and their
+specializations with a class-key that does not match either the definition
+or the first declaration if no definition is provided.
+
+For example, the declaration of @code{struct Object} in the argument list
+of @code{draw} triggers the warning. To avoid it, either remove the redundant
+class-key @code{struct} or replace it with @code{class} to match its definition.
+@smallexample
+class Object @{
+public:
+ virtual ~Object () = 0;
+@};
+void draw (struct Object*);
+@end smallexample
+
+It is not wrong to declare a class with the class-key @code{struct} as
+the example above shows. The @option{-Wmismatched-tags} option is intended
+to help achieve a consistent style of class declarations. In code that is
+intended to be portable to Windows-based compilers the warning helps prevent
+unresolved references due to the difference in the mangling of symbols
+declared with different class-keys. The option can be used either on its
+own or in conjunction with @option{-Wredundant-tags}.
+
+@item -Wmultiple-inheritance @r{(C++ and Objective-C++ only)}
+@opindex Wmultiple-inheritance
+@opindex Wno-multiple-inheritance
+Warn when a class is defined with multiple direct base classes. Some
+coding rules disallow multiple inheritance, and this may be used to
+enforce that rule. The warning is inactive inside a system header file,
+such as the STL, so one can still use the STL. One may also define
+classes that indirectly use multiple inheritance.
+
+@item -Wvirtual-inheritance
+@opindex Wvirtual-inheritance
+@opindex Wno-virtual-inheritance
+Warn when a class is defined with a virtual direct base class. Some
+coding rules disallow multiple inheritance, and this may be used to
+enforce that rule. The warning is inactive inside a system header file,
+such as the STL, so one can still use the STL. One may also define
+classes that indirectly use virtual inheritance.
+
+@item -Wno-virtual-move-assign
+@opindex Wvirtual-move-assign
+@opindex Wno-virtual-move-assign
+Suppress warnings about inheriting from a virtual base with a
+non-trivial C++11 move assignment operator. This is dangerous because
+if the virtual base is reachable along more than one path, it is
+moved multiple times, which can mean both objects end up in the
+moved-from state. If the move assignment operator is written to avoid
+moving from a moved-from object, this warning can be disabled.
+
+@item -Wnamespaces
+@opindex Wnamespaces
+@opindex Wno-namespaces
+Warn when a namespace definition is opened. Some coding rules disallow
+namespaces, and this may be used to enforce that rule. The warning is
+inactive inside a system header file, such as the STL, so one can still
+use the STL. One may also use using directives and qualified names.
+
+@item -Wno-terminate @r{(C++ and Objective-C++ only)}
+@opindex Wterminate
+@opindex Wno-terminate
+Disable the warning about a throw-expression that will immediately
+result in a call to @code{terminate}.
+
+@item -Wno-vexing-parse @r{(C++ and Objective-C++ only)}
+@opindex Wvexing-parse
+@opindex Wno-vexing-parse
+Warn about the most vexing parse syntactic ambiguity. This warns about
+the cases when a declaration looks like a variable definition, but the
+C++ language requires it to be interpreted as a function declaration.
+For instance:
+
+@smallexample
+void f(double a) @{
+ int i(); // extern int i (void);
+ int n(int(a)); // extern int n (int);
+@}
+@end smallexample
+
+Another example:
+
+@smallexample
+struct S @{ S(int); @};
+void f(double a) @{
+ S x(int(a)); // extern struct S x (int);
+ S y(int()); // extern struct S y (int (*) (void));
+ S z(); // extern struct S z (void);
+@}
+@end smallexample
+
+The warning will suggest options how to deal with such an ambiguity; e.g.,
+it can suggest removing the parentheses or using braces instead.
+
+This warning is enabled by default.
+
+@item -Wno-class-conversion @r{(C++ and Objective-C++ only)}
+@opindex Wno-class-conversion
+@opindex Wclass-conversion
+Do not warn when a conversion function converts an
+object to the same type, to a base class of that type, or to void; such
+a conversion function will never be called.
+
+@item -Wvolatile @r{(C++ and Objective-C++ only)}
+@opindex Wvolatile
+@opindex Wno-volatile
+Warn about deprecated uses of the @code{volatile} qualifier. This includes
+postfix and prefix @code{++} and @code{--} expressions of
+@code{volatile}-qualified types, using simple assignments where the left
+operand is a @code{volatile}-qualified non-class type for their value,
+compound assignments where the left operand is a @code{volatile}-qualified
+non-class type, @code{volatile}-qualified function return type,
+@code{volatile}-qualified parameter type, and structured bindings of a
+@code{volatile}-qualified type. This usage was deprecated in C++20.
+
+Enabled by default with @option{-std=c++20}.
+
+@item -Wzero-as-null-pointer-constant @r{(C++ and Objective-C++ only)}
+@opindex Wzero-as-null-pointer-constant
+@opindex Wno-zero-as-null-pointer-constant
+Warn when a literal @samp{0} is used as null pointer constant. This can
+be useful to facilitate the conversion to @code{nullptr} in C++11.
+
+@item -Waligned-new
+@opindex Waligned-new
+@opindex Wno-aligned-new
+Warn about a new-expression of a type that requires greater alignment
+than the @code{alignof(std::max_align_t)} but uses an allocation
+function without an explicit alignment parameter. This option is
+enabled by @option{-Wall}.
+
+Normally this only warns about global allocation functions, but
+@option{-Waligned-new=all} also warns about class member allocation
+functions.
+
+@item -Wno-placement-new
+@itemx -Wplacement-new=@var{n}
+@opindex Wplacement-new
+@opindex Wno-placement-new
+Warn about placement new expressions with undefined behavior, such as
+constructing an object in a buffer that is smaller than the type of
+the object. For example, the placement new expression below is diagnosed
+because it attempts to construct an array of 64 integers in a buffer only
+64 bytes large.
+@smallexample
+char buf [64];
+new (buf) int[64];
+@end smallexample
+This warning is enabled by default.
+
+@table @gcctabopt
+@item -Wplacement-new=1
+This is the default warning level of @option{-Wplacement-new}. At this
+level the warning is not issued for some strictly undefined constructs that
+GCC allows as extensions for compatibility with legacy code. For example,
+the following @code{new} expression is not diagnosed at this level even
+though it has undefined behavior according to the C++ standard because
+it writes past the end of the one-element array.
+@smallexample
+struct S @{ int n, a[1]; @};
+S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]);
+new (s->a)int [32]();
+@end smallexample
+
+@item -Wplacement-new=2
+At this level, in addition to diagnosing all the same constructs as at level
+1, a diagnostic is also issued for placement new expressions that construct
+an object in the last member of structure whose type is an array of a single
+element and whose size is less than the size of the object being constructed.
+While the previous example would be diagnosed, the following construct makes
+use of the flexible member array extension to avoid the warning at level 2.
+@smallexample
+struct S @{ int n, a[]; @};
+S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]);
+new (s->a)int [32]();
+@end smallexample
+
+@end table
+
+@item -Wcatch-value
+@itemx -Wcatch-value=@var{n} @r{(C++ and Objective-C++ only)}
+@opindex Wcatch-value
+@opindex Wno-catch-value
+Warn about catch handlers that do not catch via reference.
+With @option{-Wcatch-value=1} (or @option{-Wcatch-value} for short)
+warn about polymorphic class types that are caught by value.
+With @option{-Wcatch-value=2} warn about all class types that are caught
+by value. With @option{-Wcatch-value=3} warn about all types that are
+not caught by reference. @option{-Wcatch-value} is enabled by @option{-Wall}.
+
+@item -Wconditionally-supported @r{(C++ and Objective-C++ only)}
+@opindex Wconditionally-supported
+@opindex Wno-conditionally-supported
+Warn for conditionally-supported (C++11 [intro.defs]) constructs.
+
+@item -Wno-delete-incomplete @r{(C++ and Objective-C++ only)}
+@opindex Wdelete-incomplete
+@opindex Wno-delete-incomplete
+Do not warn when deleting a pointer to incomplete type, which may cause
+undefined behavior at runtime. This warning is enabled by default.
+
+@item -Wextra-semi @r{(C++, Objective-C++ only)}
+@opindex Wextra-semi
+@opindex Wno-extra-semi
+Warn about redundant semicolons after in-class function definitions.
+
+@item -Wno-inaccessible-base @r{(C++, Objective-C++ only)}
+@opindex Winaccessible-base
+@opindex Wno-inaccessible-base
+This option controls warnings
+when a base class is inaccessible in a class derived from it due to
+ambiguity. The warning is enabled by default.
+Note that the warning for ambiguous virtual
+bases is enabled by the @option{-Wextra} option.
+@smallexample
+@group
+struct A @{ int a; @};
+
+struct B : A @{ @};
+
+struct C : B, A @{ @};
+@end group
+@end smallexample
+
+@item -Wno-inherited-variadic-ctor
+@opindex Winherited-variadic-ctor
+@opindex Wno-inherited-variadic-ctor
+Suppress warnings about use of C++11 inheriting constructors when the
+base class inherited from has a C variadic constructor; the warning is
+on by default because the ellipsis is not inherited.
+
+@item -Wno-invalid-offsetof @r{(C++ and Objective-C++ only)}
+@opindex Wno-invalid-offsetof
+@opindex Winvalid-offsetof
+Suppress warnings from applying the @code{offsetof} macro to a non-POD
+type. According to the 2014 ISO C++ standard, applying @code{offsetof}
+to a non-standard-layout type is undefined. In existing C++ implementations,
+however, @code{offsetof} typically gives meaningful results.
+This flag is for users who are aware that they are
+writing nonportable code and who have deliberately chosen to ignore the
+warning about it.
+
+The restrictions on @code{offsetof} may be relaxed in a future version
+of the C++ standard.
+
+@item -Wsized-deallocation @r{(C++ and Objective-C++ only)}
+@opindex Wsized-deallocation
+@opindex Wno-sized-deallocation
+Warn about a definition of an unsized deallocation function
+@smallexample
+void operator delete (void *) noexcept;
+void operator delete[] (void *) noexcept;
+@end smallexample
+without a definition of the corresponding sized deallocation function
+@smallexample
+void operator delete (void *, std::size_t) noexcept;
+void operator delete[] (void *, std::size_t) noexcept;
+@end smallexample
+or vice versa. Enabled by @option{-Wextra} along with
+@option{-fsized-deallocation}.
+
+@item -Wsuggest-final-types
+@opindex Wno-suggest-final-types
+@opindex Wsuggest-final-types
+Warn about types with virtual methods where code quality would be improved
+if the type were declared with the C++11 @code{final} specifier,
+or, if possible,
+declared in an anonymous namespace. This allows GCC to more aggressively
+devirtualize the polymorphic calls. This warning is more effective with
+link-time optimization,
+where the information about the class hierarchy graph is
+more complete.
+
+@item -Wsuggest-final-methods
+@opindex Wno-suggest-final-methods
+@opindex Wsuggest-final-methods
+Warn about virtual methods where code quality would be improved if the method
+were declared with the C++11 @code{final} specifier,
+or, if possible, its type were
+declared in an anonymous namespace or with the @code{final} specifier.
+This warning is
+more effective with link-time optimization, where the information about the
+class hierarchy graph is more complete. It is recommended to first consider
+suggestions of @option{-Wsuggest-final-types} and then rebuild with new
+annotations.
+
+@item -Wsuggest-override
+@opindex Wsuggest-override
+@opindex Wno-suggest-override
+Warn about overriding virtual functions that are not marked with the
+@code{override} keyword.
+
+@item -Wuse-after-free
+@itemx -Wuse-after-free=@var{n}
+@opindex Wuse-after-free
+@opindex Wno-use-after-free
+Warn about uses of pointers to dynamically allocated objects that have
+been rendered indeterminate by a call to a deallocation function.
+The warning is enabled at all optimization levels but may yield different
+results with optimization than without.
+
+@table @gcctabopt
+@item -Wuse-after-free=1
+At level 1 the warning attempts to diagnose only unconditional uses
+of pointers made indeterminate by a deallocation call or a successful
+call to @code{realloc}, regardless of whether or not the call resulted
+in an actual reallocatio of memory. This includes double-@code{free}
+calls as well as uses in arithmetic and relational expressions. Although
+undefined, uses of indeterminate pointers in equality (or inequality)
+expressions are not diagnosed at this level.
+@item -Wuse-after-free=2
+At level 2, in addition to unconditional uses, the warning also diagnoses
+conditional uses of pointers made indeterminate by a deallocation call.
+As at level 2, uses in equality (or inequality) expressions are not
+diagnosed. For example, the second call to @code{free} in the following
+function is diagnosed at this level:
+@smallexample
+struct A @{ int refcount; void *data; @};
+
+void release (struct A *p)
+@{
+ int refcount = --p->refcount;
+ free (p);
+ if (refcount == 0)
+ free (p->data); // warning: p may be used after free
+@}
+@end smallexample
+@item -Wuse-after-free=3
+At level 3, the warning also diagnoses uses of indeterminate pointers in
+equality expressions. All uses of indeterminate pointers are undefined
+but equality tests sometimes appear after calls to @code{realloc} as
+an attempt to determine whether the call resulted in relocating the object
+to a different address. They are diagnosed at a separate level to aid
+legacy code gradually transition to safe alternatives. For example,
+the equality test in the function below is diagnosed at this level:
+@smallexample
+void adjust_pointers (int**, int);
+
+void grow (int **p, int n)
+@{
+ int **q = (int**)realloc (p, n *= 2);
+ if (q == p)
+ return;
+ adjust_pointers ((int**)q, n);
+@}
+@end smallexample
+To avoid the warning at this level, store offsets into allocated memory
+instead of pointers. This approach obviates needing to adjust the stored
+pointers after reallocation.
+@end table
+
+@option{-Wuse-after-free=2} is included in @option{-Wall}.
+
+@item -Wuseless-cast @r{(C++ and Objective-C++ only)}
+@opindex Wuseless-cast
+@opindex Wno-useless-cast
+Warn when an expression is cast to its own type. This warning does not
+occur when a class object is converted to a non-reference type as that
+is a way to create a temporary:
+
+@smallexample
+struct S @{ @};
+void g (S&&);
+void f (S&& arg)
+@{
+ g (S(arg)); // make arg prvalue so that it can bind to S&&
+@}
+@end smallexample
+
+@item -Wno-conversion-null @r{(C++ and Objective-C++ only)}
+@opindex Wconversion-null
+@opindex Wno-conversion-null
+Do not warn for conversions between @code{NULL} and non-pointer
+types. @option{-Wconversion-null} is enabled by default.
+
+@end table
+
+@node Objective-C and Objective-C++ Dialect Options
+@section Options Controlling Objective-C and Objective-C++ Dialects
+
+@cindex compiler options, Objective-C and Objective-C++
+@cindex Objective-C and Objective-C++ options, command-line
+@cindex options, Objective-C and Objective-C++
+(NOTE: This manual does not describe the Objective-C and Objective-C++
+languages themselves. @xref{Standards,,Language Standards
+Supported by GCC}, for references.)
+
+This section describes the command-line options that are only meaningful
+for Objective-C and Objective-C++ programs. You can also use most of
+the language-independent GNU compiler options.
+For example, you might compile a file @file{some_class.m} like this:
+
+@smallexample
+gcc -g -fgnu-runtime -O -c some_class.m
+@end smallexample
+
+@noindent
+In this example, @option{-fgnu-runtime} is an option meant only for
+Objective-C and Objective-C++ programs; you can use the other options with
+any language supported by GCC@.
+
+Note that since Objective-C is an extension of the C language, Objective-C
+compilations may also use options specific to the C front-end (e.g.,
+@option{-Wtraditional}). Similarly, Objective-C++ compilations may use
+C++-specific options (e.g., @option{-Wabi}).
+
+Here is a list of options that are @emph{only} for compiling Objective-C
+and Objective-C++ programs:
+
+@table @gcctabopt
+@item -fconstant-string-class=@var{class-name}
+@opindex fconstant-string-class
+Use @var{class-name} as the name of the class to instantiate for each
+literal string specified with the syntax @code{@@"@dots{}"}. The default
+class name is @code{NXConstantString} if the GNU runtime is being used, and
+@code{NSConstantString} if the NeXT runtime is being used (see below). The
+@option{-fconstant-cfstrings} option, if also present, overrides the
+@option{-fconstant-string-class} setting and cause @code{@@"@dots{}"} literals
+to be laid out as constant CoreFoundation strings.
+
+@item -fgnu-runtime
+@opindex fgnu-runtime
+Generate object code compatible with the standard GNU Objective-C
+runtime. This is the default for most types of systems.
+
+@item -fnext-runtime
+@opindex fnext-runtime
+Generate output compatible with the NeXT runtime. This is the default
+for NeXT-based systems, including Darwin and Mac OS X@. The macro
+@code{__NEXT_RUNTIME__} is predefined if (and only if) this option is
+used.
+
+@item -fno-nil-receivers
+@opindex fno-nil-receivers
+@opindex fnil-receivers
+Assume that all Objective-C message dispatches (@code{[receiver
+message:arg]}) in this translation unit ensure that the receiver is
+not @code{nil}. This allows for more efficient entry points in the
+runtime to be used. This option is only available in conjunction with
+the NeXT runtime and ABI version 0 or 1.
+
+@item -fobjc-abi-version=@var{n}
+@opindex fobjc-abi-version
+Use version @var{n} of the Objective-C ABI for the selected runtime.
+This option is currently supported only for the NeXT runtime. In that
+case, Version 0 is the traditional (32-bit) ABI without support for
+properties and other Objective-C 2.0 additions. Version 1 is the
+traditional (32-bit) ABI with support for properties and other
+Objective-C 2.0 additions. Version 2 is the modern (64-bit) ABI. If
+nothing is specified, the default is Version 0 on 32-bit target
+machines, and Version 2 on 64-bit target machines.
+
+@item -fobjc-call-cxx-cdtors
+@opindex fobjc-call-cxx-cdtors
+For each Objective-C class, check if any of its instance variables is a
+C++ object with a non-trivial default constructor. If so, synthesize a
+special @code{- (id) .cxx_construct} instance method which runs
+non-trivial default constructors on any such instance variables, in order,
+and then return @code{self}. Similarly, check if any instance variable
+is a C++ object with a non-trivial destructor, and if so, synthesize a
+special @code{- (void) .cxx_destruct} method which runs
+all such default destructors, in reverse order.
+
+The @code{- (id) .cxx_construct} and @code{- (void) .cxx_destruct}
+methods thusly generated only operate on instance variables
+declared in the current Objective-C class, and not those inherited
+from superclasses. It is the responsibility of the Objective-C
+runtime to invoke all such methods in an object's inheritance
+hierarchy. The @code{- (id) .cxx_construct} methods are invoked
+by the runtime immediately after a new object instance is allocated;
+the @code{- (void) .cxx_destruct} methods are invoked immediately
+before the runtime deallocates an object instance.
+
+As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has
+support for invoking the @code{- (id) .cxx_construct} and
+@code{- (void) .cxx_destruct} methods.
+
+@item -fobjc-direct-dispatch
+@opindex fobjc-direct-dispatch
+Allow fast jumps to the message dispatcher. On Darwin this is
+accomplished via the comm page.
+
+@item -fobjc-exceptions
+@opindex fobjc-exceptions
+Enable syntactic support for structured exception handling in
+Objective-C, similar to what is offered by C++. This option
+is required to use the Objective-C keywords @code{@@try},
+@code{@@throw}, @code{@@catch}, @code{@@finally} and
+@code{@@synchronized}. This option is available with both the GNU
+runtime and the NeXT runtime (but not available in conjunction with
+the NeXT runtime on Mac OS X 10.2 and earlier).
+
+@item -fobjc-gc
+@opindex fobjc-gc
+Enable garbage collection (GC) in Objective-C and Objective-C++
+programs. This option is only available with the NeXT runtime; the
+GNU runtime has a different garbage collection implementation that
+does not require special compiler flags.
+
+@item -fobjc-nilcheck
+@opindex fobjc-nilcheck
+For the NeXT runtime with version 2 of the ABI, check for a nil
+receiver in method invocations before doing the actual method call.
+This is the default and can be disabled using
+@option{-fno-objc-nilcheck}. Class methods and super calls are never
+checked for nil in this way no matter what this flag is set to.
+Currently this flag does nothing when the GNU runtime, or an older
+version of the NeXT runtime ABI, is used.
+
+@item -fobjc-std=objc1
+@opindex fobjc-std
+Conform to the language syntax of Objective-C 1.0, the language
+recognized by GCC 4.0. This only affects the Objective-C additions to
+the C/C++ language; it does not affect conformance to C/C++ standards,
+which is controlled by the separate C/C++ dialect option flags. When
+this option is used with the Objective-C or Objective-C++ compiler,
+any Objective-C syntax that is not recognized by GCC 4.0 is rejected.
+This is useful if you need to make sure that your Objective-C code can
+be compiled with older versions of GCC@.
+
+@item -freplace-objc-classes
+@opindex freplace-objc-classes
+Emit a special marker instructing @command{ld(1)} not to statically link in
+the resulting object file, and allow @command{dyld(1)} to load it in at
+run time instead. This is used in conjunction with the Fix-and-Continue
+debugging mode, where the object file in question may be recompiled and
+dynamically reloaded in the course of program execution, without the need
+to restart the program itself. Currently, Fix-and-Continue functionality
+is only available in conjunction with the NeXT runtime on Mac OS X 10.3
+and later.
+
+@item -fzero-link
+@opindex fzero-link
+When compiling for the NeXT runtime, the compiler ordinarily replaces calls
+to @code{objc_getClass("@dots{}")} (when the name of the class is known at
+compile time) with static class references that get initialized at load time,
+which improves run-time performance. Specifying the @option{-fzero-link} flag
+suppresses this behavior and causes calls to @code{objc_getClass("@dots{}")}
+to be retained. This is useful in Zero-Link debugging mode, since it allows
+for individual class implementations to be modified during program execution.
+The GNU runtime currently always retains calls to @code{objc_get_class("@dots{}")}
+regardless of command-line options.
+
+@item -fno-local-ivars
+@opindex fno-local-ivars
+@opindex flocal-ivars
+By default instance variables in Objective-C can be accessed as if
+they were local variables from within the methods of the class they're
+declared in. This can lead to shadowing between instance variables
+and other variables declared either locally inside a class method or
+globally with the same name. Specifying the @option{-fno-local-ivars}
+flag disables this behavior thus avoiding variable shadowing issues.
+
+@item -fivar-visibility=@r{[}public@r{|}protected@r{|}private@r{|}package@r{]}
+@opindex fivar-visibility
+Set the default instance variable visibility to the specified option
+so that instance variables declared outside the scope of any access
+modifier directives default to the specified visibility.
+
+@item -gen-decls
+@opindex gen-decls
+Dump interface declarations for all classes seen in the source file to a
+file named @file{@var{sourcename}.decl}.
+
+@item -Wassign-intercept @r{(Objective-C and Objective-C++ only)}
+@opindex Wassign-intercept
+@opindex Wno-assign-intercept
+Warn whenever an Objective-C assignment is being intercepted by the
+garbage collector.
+
+@item -Wno-property-assign-default @r{(Objective-C and Objective-C++ only)}
+@opindex Wproperty-assign-default
+@opindex Wno-property-assign-default
+Do not warn if a property for an Objective-C object has no assign
+semantics specified.
+
+@item -Wno-protocol @r{(Objective-C and Objective-C++ only)}
+@opindex Wno-protocol
+@opindex Wprotocol
+If a class is declared to implement a protocol, a warning is issued for
+every method in the protocol that is not implemented by the class. The
+default behavior is to issue a warning for every method not explicitly
+implemented in the class, even if a method implementation is inherited
+from the superclass. If you use the @option{-Wno-protocol} option, then
+methods inherited from the superclass are considered to be implemented,
+and no warning is issued for them.
+
+@item -Wobjc-root-class @r{(Objective-C and Objective-C++ only)}
+@opindex Wobjc-root-class
+Warn if a class interface lacks a superclass. Most classes will inherit
+from @code{NSObject} (or @code{Object}) for example. When declaring
+classes intended to be root classes, the warning can be suppressed by
+marking their interfaces with @code{__attribute__((objc_root_class))}.
+
+@item -Wselector @r{(Objective-C and Objective-C++ only)}
+@opindex Wselector
+@opindex Wno-selector
+Warn if multiple methods of different types for the same selector are
+found during compilation. The check is performed on the list of methods
+in the final stage of compilation. Additionally, a check is performed
+for each selector appearing in a @code{@@selector(@dots{})}
+expression, and a corresponding method for that selector has been found
+during compilation. Because these checks scan the method table only at
+the end of compilation, these warnings are not produced if the final
+stage of compilation is not reached, for example because an error is
+found during compilation, or because the @option{-fsyntax-only} option is
+being used.
+
+@item -Wstrict-selector-match @r{(Objective-C and Objective-C++ only)}
+@opindex Wstrict-selector-match
+@opindex Wno-strict-selector-match
+Warn if multiple methods with differing argument and/or return types are
+found for a given selector when attempting to send a message using this
+selector to a receiver of type @code{id} or @code{Class}. When this flag
+is off (which is the default behavior), the compiler omits such warnings
+if any differences found are confined to types that share the same size
+and alignment.
+
+@item -Wundeclared-selector @r{(Objective-C and Objective-C++ only)}
+@opindex Wundeclared-selector
+@opindex Wno-undeclared-selector
+Warn if a @code{@@selector(@dots{})} expression referring to an
+undeclared selector is found. A selector is considered undeclared if no
+method with that name has been declared before the
+@code{@@selector(@dots{})} expression, either explicitly in an
+@code{@@interface} or @code{@@protocol} declaration, or implicitly in
+an @code{@@implementation} section. This option always performs its
+checks as soon as a @code{@@selector(@dots{})} expression is found,
+while @option{-Wselector} only performs its checks in the final stage of
+compilation. This also enforces the coding style convention
+that methods and selectors must be declared before being used.
+
+@item -print-objc-runtime-info
+@opindex print-objc-runtime-info
+Generate C header describing the largest structure that is passed by
+value, if any.
+
+@end table
+
+@node Diagnostic Message Formatting Options
+@section Options to Control Diagnostic Messages Formatting
+@cindex options to control diagnostics formatting
+@cindex diagnostic messages
+@cindex message formatting
+
+Traditionally, diagnostic messages have been formatted irrespective of
+the output device's aspect (e.g.@: its width, @dots{}). You can use the
+options described below
+to control the formatting algorithm for diagnostic messages,
+e.g.@: how many characters per line, how often source location
+information should be reported. Note that some language front ends may not
+honor these options.
+
+@table @gcctabopt
+@item -fmessage-length=@var{n}
+@opindex fmessage-length
+Try to format error messages so that they fit on lines of about
+@var{n} characters. If @var{n} is zero, then no line-wrapping is
+done; each error message appears on a single line. This is the
+default for all front ends.
+
+Note - this option also affects the display of the @samp{#error} and
+@samp{#warning} pre-processor directives, and the @samp{deprecated}
+function/type/variable attribute. It does not however affect the
+@samp{pragma GCC warning} and @samp{pragma GCC error} pragmas.
+
+@item -fdiagnostics-plain-output
+This option requests that diagnostic output look as plain as possible, which
+may be useful when running @command{dejagnu} or other utilities that need to
+parse diagnostics output and prefer that it remain more stable over time.
+@option{-fdiagnostics-plain-output} is currently equivalent to the following
+options:
+@gccoptlist{-fno-diagnostics-show-caret @gol
+-fno-diagnostics-show-line-numbers @gol
+-fdiagnostics-color=never @gol
+-fdiagnostics-urls=never @gol
+-fdiagnostics-path-format=separate-events}
+In the future, if GCC changes the default appearance of its diagnostics, the
+corresponding option to disable the new behavior will be added to this list.
+
+@item -fdiagnostics-show-location=once
+@opindex fdiagnostics-show-location
+Only meaningful in line-wrapping mode. Instructs the diagnostic messages
+reporter to emit source location information @emph{once}; that is, in
+case the message is too long to fit on a single physical line and has to
+be wrapped, the source location won't be emitted (as prefix) again,
+over and over, in subsequent continuation lines. This is the default
+behavior.
+
+@item -fdiagnostics-show-location=every-line
+Only meaningful in line-wrapping mode. Instructs the diagnostic
+messages reporter to emit the same source location information (as
+prefix) for physical lines that result from the process of breaking
+a message which is too long to fit on a single line.
+
+@item -fdiagnostics-color[=@var{WHEN}]
+@itemx -fno-diagnostics-color
+@opindex fdiagnostics-color
+@cindex highlight, color
+@vindex GCC_COLORS @r{environment variable}
+Use color in diagnostics. @var{WHEN} is @samp{never}, @samp{always},
+or @samp{auto}. The default depends on how the compiler has been configured,
+it can be any of the above @var{WHEN} options or also @samp{never}
+if @env{GCC_COLORS} environment variable isn't present in the environment,
+and @samp{auto} otherwise.
+@samp{auto} makes GCC use color only when the standard error is a terminal,
+and when not executing in an emacs shell.
+The forms @option{-fdiagnostics-color} and @option{-fno-diagnostics-color} are
+aliases for @option{-fdiagnostics-color=always} and
+@option{-fdiagnostics-color=never}, respectively.
+
+The colors are defined by the environment variable @env{GCC_COLORS}.
+Its value is a colon-separated list of capabilities and Select Graphic
+Rendition (SGR) substrings. SGR commands are interpreted by the
+terminal or terminal emulator. (See the section in the documentation
+of your text terminal for permitted values and their meanings as
+character attributes.) These substring values are integers in decimal
+representation and can be concatenated with semicolons.
+Common values to concatenate include
+@samp{1} for bold,
+@samp{4} for underline,
+@samp{5} for blink,
+@samp{7} for inverse,
+@samp{39} for default foreground color,
+@samp{30} to @samp{37} for foreground colors,
+@samp{90} to @samp{97} for 16-color mode foreground colors,
+@samp{38;5;0} to @samp{38;5;255}
+for 88-color and 256-color modes foreground colors,
+@samp{49} for default background color,
+@samp{40} to @samp{47} for background colors,
+@samp{100} to @samp{107} for 16-color mode background colors,
+and @samp{48;5;0} to @samp{48;5;255}
+for 88-color and 256-color modes background colors.
+
+The default @env{GCC_COLORS} is
+@smallexample
+error=01;31:warning=01;35:note=01;36:range1=32:range2=34:locus=01:\
+quote=01:path=01;36:fixit-insert=32:fixit-delete=31:\
+diff-filename=01:diff-hunk=32:diff-delete=31:diff-insert=32:\
+type-diff=01;32:fnname=01;32:targs=35
+@end smallexample
+@noindent
+where @samp{01;31} is bold red, @samp{01;35} is bold magenta,
+@samp{01;36} is bold cyan, @samp{32} is green, @samp{34} is blue,
+@samp{01} is bold, and @samp{31} is red.
+Setting @env{GCC_COLORS} to the empty string disables colors.
+Supported capabilities are as follows.
+
+@table @code
+@item error=
+@vindex error GCC_COLORS @r{capability}
+SGR substring for error: markers.
+
+@item warning=
+@vindex warning GCC_COLORS @r{capability}
+SGR substring for warning: markers.
+
+@item note=
+@vindex note GCC_COLORS @r{capability}
+SGR substring for note: markers.
+
+@item path=
+@vindex path GCC_COLORS @r{capability}
+SGR substring for colorizing paths of control-flow events as printed
+via @option{-fdiagnostics-path-format=}, such as the identifiers of
+individual events and lines indicating interprocedural calls and returns.
+
+@item range1=
+@vindex range1 GCC_COLORS @r{capability}
+SGR substring for first additional range.
+
+@item range2=
+@vindex range2 GCC_COLORS @r{capability}
+SGR substring for second additional range.
+
+@item locus=
+@vindex locus GCC_COLORS @r{capability}
+SGR substring for location information, @samp{file:line} or
+@samp{file:line:column} etc.
+
+@item quote=
+@vindex quote GCC_COLORS @r{capability}
+SGR substring for information printed within quotes.
+
+@item fnname=
+@vindex fnname GCC_COLORS @r{capability}
+SGR substring for names of C++ functions.
+
+@item targs=
+@vindex targs GCC_COLORS @r{capability}
+SGR substring for C++ function template parameter bindings.
+
+@item fixit-insert=
+@vindex fixit-insert GCC_COLORS @r{capability}
+SGR substring for fix-it hints suggesting text to
+be inserted or replaced.
+
+@item fixit-delete=
+@vindex fixit-delete GCC_COLORS @r{capability}
+SGR substring for fix-it hints suggesting text to
+be deleted.
+
+@item diff-filename=
+@vindex diff-filename GCC_COLORS @r{capability}
+SGR substring for filename headers within generated patches.
+
+@item diff-hunk=
+@vindex diff-hunk GCC_COLORS @r{capability}
+SGR substring for the starts of hunks within generated patches.
+
+@item diff-delete=
+@vindex diff-delete GCC_COLORS @r{capability}
+SGR substring for deleted lines within generated patches.
+
+@item diff-insert=
+@vindex diff-insert GCC_COLORS @r{capability}
+SGR substring for inserted lines within generated patches.
+
+@item type-diff=
+@vindex type-diff GCC_COLORS @r{capability}
+SGR substring for highlighting mismatching types within template
+arguments in the C++ frontend.
+@end table
+
+@item -fdiagnostics-urls[=@var{WHEN}]
+@opindex fdiagnostics-urls
+@cindex urls
+@vindex GCC_URLS @r{environment variable}
+@vindex TERM_URLS @r{environment variable}
+Use escape sequences to embed URLs in diagnostics. For example, when
+@option{-fdiagnostics-show-option} emits text showing the command-line
+option controlling a diagnostic, embed a URL for documentation of that
+option.
+
+@var{WHEN} is @samp{never}, @samp{always}, or @samp{auto}.
+@samp{auto} makes GCC use URL escape sequences only when the standard error
+is a terminal, and when not executing in an emacs shell or any graphical
+terminal which is known to be incompatible with this feature, see below.
+
+The default depends on how the compiler has been configured.
+It can be any of the above @var{WHEN} options.
+
+GCC can also be configured (via the
+@option{--with-diagnostics-urls=auto-if-env} configure-time option)
+so that the default is affected by environment variables.
+Under such a configuration, GCC defaults to using @samp{auto}
+if either @env{GCC_URLS} or @env{TERM_URLS} environment variables are
+present and non-empty in the environment of the compiler, or @samp{never}
+if neither are.
+
+However, even with @option{-fdiagnostics-urls=always} the behavior is
+dependent on those environment variables:
+If @env{GCC_URLS} is set to empty or @samp{no}, do not embed URLs in
+diagnostics. If set to @samp{st}, URLs use ST escape sequences.
+If set to @samp{bel}, the default, URLs use BEL escape sequences.
+Any other non-empty value enables the feature.
+If @env{GCC_URLS} is not set, use @env{TERM_URLS} as a fallback.
+Note: ST is an ANSI escape sequence, string terminator @samp{ESC \},
+BEL is an ASCII character, CTRL-G that usually sounds like a beep.
+
+At this time GCC tries to detect also a few terminals that are known to
+not implement the URL feature, and have bugs or at least had bugs in
+some versions that are still in use, where the URL escapes are likely
+to misbehave, i.e. print garbage on the screen.
+That list is currently xfce4-terminal, certain known to be buggy
+gnome-terminal versions, the linux console, and mingw.
+This check can be skipped with the @option{-fdiagnostics-urls=always}.
+
+@item -fno-diagnostics-show-option
+@opindex fno-diagnostics-show-option
+@opindex fdiagnostics-show-option
+By default, each diagnostic emitted includes text indicating the
+command-line option that directly controls the diagnostic (if such an
+option is known to the diagnostic machinery). Specifying the
+@option{-fno-diagnostics-show-option} flag suppresses that behavior.
+
+@item -fno-diagnostics-show-caret
+@opindex fno-diagnostics-show-caret
+@opindex fdiagnostics-show-caret
+By default, each diagnostic emitted includes the original source line
+and a caret @samp{^} indicating the column. This option suppresses this
+information. The source line is truncated to @var{n} characters, if
+the @option{-fmessage-length=n} option is given. When the output is done
+to the terminal, the width is limited to the width given by the
+@env{COLUMNS} environment variable or, if not set, to the terminal width.
+
+@item -fno-diagnostics-show-labels
+@opindex fno-diagnostics-show-labels
+@opindex fdiagnostics-show-labels
+By default, when printing source code (via @option{-fdiagnostics-show-caret}),
+diagnostics can label ranges of source code with pertinent information, such
+as the types of expressions:
+
+@smallexample
+ printf ("foo %s bar", long_i + long_j);
+ ~^ ~~~~~~~~~~~~~~~
+ | |
+ char * long int
+@end smallexample
+
+This option suppresses the printing of these labels (in the example above,
+the vertical bars and the ``char *'' and ``long int'' text).
+
+@item -fno-diagnostics-show-cwe
+@opindex fno-diagnostics-show-cwe
+@opindex fdiagnostics-show-cwe
+Diagnostic messages can optionally have an associated
+@uref{https://cwe.mitre.org/index.html, CWE} identifier.
+GCC itself only provides such metadata for some of the @option{-fanalyzer}
+diagnostics. GCC plugins may also provide diagnostics with such metadata.
+By default, if this information is present, it will be printed with
+the diagnostic. This option suppresses the printing of this metadata.
+
+@item -fno-diagnostics-show-rules
+@opindex fno-diagnostics-show-rules
+@opindex fdiagnostics-show-rules
+Diagnostic messages can optionally have rules associated with them, such
+as from a coding standard, or a specification.
+GCC itself does not do this for any of its diagnostics, but plugins may do so.
+By default, if this information is present, it will be printed with
+the diagnostic. This option suppresses the printing of this metadata.
+
+@item -fno-diagnostics-show-line-numbers
+@opindex fno-diagnostics-show-line-numbers
+@opindex fdiagnostics-show-line-numbers
+By default, when printing source code (via @option{-fdiagnostics-show-caret}),
+a left margin is printed, showing line numbers. This option suppresses this
+left margin.
+
+@item -fdiagnostics-minimum-margin-width=@var{width}
+@opindex fdiagnostics-minimum-margin-width
+This option controls the minimum width of the left margin printed by
+@option{-fdiagnostics-show-line-numbers}. It defaults to 6.
+
+@item -fdiagnostics-parseable-fixits
+@opindex fdiagnostics-parseable-fixits
+Emit fix-it hints in a machine-parseable format, suitable for consumption
+by IDEs. For each fix-it, a line will be printed after the relevant
+diagnostic, starting with the string ``fix-it:''. For example:
+
+@smallexample
+fix-it:"test.c":@{45:3-45:21@}:"gtk_widget_show_all"
+@end smallexample
+
+The location is expressed as a half-open range, expressed as a count of
+bytes, starting at byte 1 for the initial column. In the above example,
+bytes 3 through 20 of line 45 of ``test.c'' are to be replaced with the
+given string:
+
+@smallexample
+00000000011111111112222222222
+12345678901234567890123456789
+ gtk_widget_showall (dlg);
+ ^^^^^^^^^^^^^^^^^^
+ gtk_widget_show_all
+@end smallexample
+
+The filename and replacement string escape backslash as ``\\", tab as ``\t'',
+newline as ``\n'', double quotes as ``\"'', non-printable characters as octal
+(e.g. vertical tab as ``\013'').
+
+An empty replacement string indicates that the given range is to be removed.
+An empty range (e.g. ``45:3-45:3'') indicates that the string is to
+be inserted at the given position.
+
+@item -fdiagnostics-generate-patch
+@opindex fdiagnostics-generate-patch
+Print fix-it hints to stderr in unified diff format, after any diagnostics
+are printed. For example:
+
+@smallexample
+--- test.c
++++ test.c
+@@ -42,5 +42,5 @@
+
+ void show_cb(GtkDialog *dlg)
+ @{
+- gtk_widget_showall(dlg);
++ gtk_widget_show_all(dlg);
+ @}
+
+@end smallexample
+
+The diff may or may not be colorized, following the same rules
+as for diagnostics (see @option{-fdiagnostics-color}).
+
+@item -fdiagnostics-show-template-tree
+@opindex fdiagnostics-show-template-tree
+
+In the C++ frontend, when printing diagnostics showing mismatching
+template types, such as:
+
+@smallexample
+ could not convert 'std::map<int, std::vector<double> >()'
+ from 'map<[...],vector<double>>' to 'map<[...],vector<float>>
+@end smallexample
+
+the @option{-fdiagnostics-show-template-tree} flag enables printing a
+tree-like structure showing the common and differing parts of the types,
+such as:
+
+@smallexample
+ map<
+ [...],
+ vector<
+ [double != float]>>
+@end smallexample
+
+The parts that differ are highlighted with color (``double'' and
+``float'' in this case).
+
+@item -fno-elide-type
+@opindex fno-elide-type
+@opindex felide-type
+By default when the C++ frontend prints diagnostics showing mismatching
+template types, common parts of the types are printed as ``[...]'' to
+simplify the error message. For example:
+
+@smallexample
+ could not convert 'std::map<int, std::vector<double> >()'
+ from 'map<[...],vector<double>>' to 'map<[...],vector<float>>
+@end smallexample
+
+Specifying the @option{-fno-elide-type} flag suppresses that behavior.
+This flag also affects the output of the
+@option{-fdiagnostics-show-template-tree} flag.
+
+@item -fdiagnostics-path-format=@var{KIND}
+@opindex fdiagnostics-path-format
+Specify how to print paths of control-flow events for diagnostics that
+have such a path associated with them.
+
+@var{KIND} is @samp{none}, @samp{separate-events}, or @samp{inline-events},
+the default.
+
+@samp{none} means to not print diagnostic paths.
+
+@samp{separate-events} means to print a separate ``note'' diagnostic for
+each event within the diagnostic. For example:
+
+@smallexample
+test.c:29:5: error: passing NULL as argument 1 to 'PyList_Append' which requires a non-NULL parameter
+test.c:25:10: note: (1) when 'PyList_New' fails, returning NULL
+test.c:27:3: note: (2) when 'i < count'
+test.c:29:5: note: (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
+@end smallexample
+
+@samp{inline-events} means to print the events ``inline'' within the source
+code. This view attempts to consolidate the events into runs of
+sufficiently-close events, printing them as labelled ranges within the source.
+
+For example, the same events as above might be printed as:
+
+@smallexample
+ 'test': events 1-3
+ |
+ | 25 | list = PyList_New(0);
+ | | ^~~~~~~~~~~~~
+ | | |
+ | | (1) when 'PyList_New' fails, returning NULL
+ | 26 |
+ | 27 | for (i = 0; i < count; i++) @{
+ | | ~~~
+ | | |
+ | | (2) when 'i < count'
+ | 28 | item = PyLong_FromLong(random());
+ | 29 | PyList_Append(list, item);
+ | | ~~~~~~~~~~~~~~~~~~~~~~~~~
+ | | |
+ | | (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
+ |
+@end smallexample
+
+Interprocedural control flow is shown by grouping the events by stack frame,
+and using indentation to show how stack frames are nested, pushed, and popped.
+
+For example:
+
+@smallexample
+ 'test': events 1-2
+ |
+ | 133 | @{
+ | | ^
+ | | |
+ | | (1) entering 'test'
+ | 134 | boxed_int *obj = make_boxed_int (i);
+ | | ~~~~~~~~~~~~~~~~~~
+ | | |
+ | | (2) calling 'make_boxed_int'
+ |
+ +--> 'make_boxed_int': events 3-4
+ |
+ | 120 | @{
+ | | ^
+ | | |
+ | | (3) entering 'make_boxed_int'
+ | 121 | boxed_int *result = (boxed_int *)wrapped_malloc (sizeof (boxed_int));
+ | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ | | |
+ | | (4) calling 'wrapped_malloc'
+ |
+ +--> 'wrapped_malloc': events 5-6
+ |
+ | 7 | @{
+ | | ^
+ | | |
+ | | (5) entering 'wrapped_malloc'
+ | 8 | return malloc (size);
+ | | ~~~~~~~~~~~~~
+ | | |
+ | | (6) calling 'malloc'
+ |
+ <-------------+
+ |
+ 'test': event 7
+ |
+ | 138 | free_boxed_int (obj);
+ | | ^~~~~~~~~~~~~~~~~~~~
+ | | |
+ | | (7) calling 'free_boxed_int'
+ |
+(etc)
+@end smallexample
+
+@item -fdiagnostics-show-path-depths
+@opindex fdiagnostics-show-path-depths
+This option provides additional information when printing control-flow paths
+associated with a diagnostic.
+
+If this is option is provided then the stack depth will be printed for
+each run of events within @option{-fdiagnostics-path-format=inline-events}.
+If provided with @option{-fdiagnostics-path-format=separate-events}, then
+the stack depth and function declaration will be appended when printing
+each event.
+
+This is intended for use by GCC developers and plugin developers when
+debugging diagnostics that report interprocedural control flow.
+
+@item -fno-show-column
+@opindex fno-show-column
+@opindex fshow-column
+Do not print column numbers in diagnostics. This may be necessary if
+diagnostics are being scanned by a program that does not understand the
+column numbers, such as @command{dejagnu}.
+
+@item -fdiagnostics-column-unit=@var{UNIT}
+@opindex fdiagnostics-column-unit
+Select the units for the column number. This affects traditional diagnostics
+(in the absence of @option{-fno-show-column}), as well as JSON format
+diagnostics if requested.
+
+The default @var{UNIT}, @samp{display}, considers the number of display
+columns occupied by each character. This may be larger than the number
+of bytes required to encode the character, in the case of tab
+characters, or it may be smaller, in the case of multibyte characters.
+For example, the character ``GREEK SMALL LETTER PI (U+03C0)'' occupies one
+display column, and its UTF-8 encoding requires two bytes; the character
+``SLIGHTLY SMILING FACE (U+1F642)'' occupies two display columns, and
+its UTF-8 encoding requires four bytes.
+
+Setting @var{UNIT} to @samp{byte} changes the column number to the raw byte
+count in all cases, as was traditionally output by GCC prior to version 11.1.0.
+
+@item -fdiagnostics-column-origin=@var{ORIGIN}
+@opindex fdiagnostics-column-origin
+Select the origin for column numbers, i.e. the column number assigned to the
+first column. The default value of 1 corresponds to traditional GCC
+behavior and to the GNU style guide. Some utilities may perform better with an
+origin of 0; any non-negative value may be specified.
+
+@item -fdiagnostics-escape-format=@var{FORMAT}
+@opindex fdiagnostics-escape-format
+When GCC prints pertinent source lines for a diagnostic it normally attempts
+to print the source bytes directly. However, some diagnostics relate to encoding
+issues in the source file, such as malformed UTF-8, or issues with Unicode
+normalization. These diagnostics are flagged so that GCC will escape bytes
+that are not printable ASCII when printing their pertinent source lines.
+
+This option controls how such bytes should be escaped.
+
+The default @var{FORMAT}, @samp{unicode} displays Unicode characters that
+are not printable ASCII in the form @samp{<U+XXXX>}, and bytes that do not
+correspond to a Unicode character validly-encoded in UTF-8-encoded will be
+displayed as hexadecimal in the form @samp{<XX>}.
+
+For example, a source line containing the string @samp{before} followed by the
+Unicode character U+03C0 (``GREEK SMALL LETTER PI'', with UTF-8 encoding
+0xCF 0x80) followed by the byte 0xBF (a stray UTF-8 trailing byte), followed by
+the string @samp{after} will be printed for such a diagnostic as:
+
+@smallexample
+ before<U+03C0><BF>after
+@end smallexample
+
+Setting @var{FORMAT} to @samp{bytes} will display all non-printable-ASCII bytes
+in the form @samp{<XX>}, thus showing the underlying encoding of non-ASCII
+Unicode characters. For the example above, the following will be printed:
+
+@smallexample
+ before<CF><80><BF>after
+@end smallexample
+
+@item -fdiagnostics-format=@var{FORMAT}
+@opindex fdiagnostics-format
+Select a different format for printing diagnostics.
+@var{FORMAT} is @samp{text}, @samp{sarif-stderr}, @samp{sarif-file},
+@samp{json}, @samp{json-stderr}, or @samp{json-file}.
+
+The default is @samp{text}.
+
+The @samp{sarif-stderr} and @samp{sarif-file} formats both emit
+diagnostics in SARIF Version 2.1.0 format, either to stderr, or to a file
+named @file{@var{source}.sarif}, respectively.
+
+The @samp{json} format is a synonym for @samp{json-stderr}.
+The @samp{json-stderr} and @samp{json-file} formats are identical, apart from
+where the JSON is emitted to - with the former, the JSON is emitted to stderr,
+whereas with @samp{json-file} it is written to @file{@var{source}.gcc.json}.
+
+The emitted JSON consists of a top-level JSON array containing JSON objects
+representing the diagnostics. The JSON is emitted as one line, without
+formatting; the examples below have been formatted for clarity.
+
+Diagnostics can have child diagnostics. For example, this error and note:
+
+@smallexample
+misleading-indentation.c:15:3: warning: this 'if' clause does not
+ guard... [-Wmisleading-indentation]
+ 15 | if (flag)
+ | ^~
+misleading-indentation.c:17:5: note: ...this statement, but the latter
+ is misleadingly indented as if it were guarded by the 'if'
+ 17 | y = 2;
+ | ^
+@end smallexample
+
+@noindent
+might be printed in JSON form (after formatting) like this:
+
+@smallexample
+[
+ @{
+ "kind": "warning",
+ "locations": [
+ @{
+ "caret": @{
+ "display-column": 3,
+ "byte-column": 3,
+ "column": 3,
+ "file": "misleading-indentation.c",
+ "line": 15
+ @},
+ "finish": @{
+ "display-column": 4,
+ "byte-column": 4,
+ "column": 4,
+ "file": "misleading-indentation.c",
+ "line": 15
+ @}
+ @}
+ ],
+ "message": "this \u2018if\u2019 clause does not guard...",
+ "option": "-Wmisleading-indentation",
+ "option_url": "https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmisleading-indentation",
+ "children": [
+ @{
+ "kind": "note",
+ "locations": [
+ @{
+ "caret": @{
+ "display-column": 5,
+ "byte-column": 5,
+ "column": 5,
+ "file": "misleading-indentation.c",
+ "line": 17
+ @}
+ @}
+ ],
+ "escape-source": false,
+ "message": "...this statement, but the latter is @dots{}"
+ @}
+ ]
+ "escape-source": false,
+ "column-origin": 1,
+ @}
+]
+@end smallexample
+
+@noindent
+where the @code{note} is a child of the @code{warning}.
+
+A diagnostic has a @code{kind}. If this is @code{warning}, then there is
+an @code{option} key describing the command-line option controlling the
+warning.
+
+A diagnostic can contain zero or more locations. Each location has an
+optional @code{label} string and up to three positions within it: a
+@code{caret} position and optional @code{start} and @code{finish} positions.
+A position is described by a @code{file} name, a @code{line} number, and
+three numbers indicating a column position:
+@itemize @bullet
+
+@item
+@code{display-column} counts display columns, accounting for tabs and
+multibyte characters.
+
+@item
+@code{byte-column} counts raw bytes.
+
+@item
+@code{column} is equal to one of
+the previous two, as dictated by the @option{-fdiagnostics-column-unit}
+option.
+
+@end itemize
+All three columns are relative to the origin specified by
+@option{-fdiagnostics-column-origin}, which is typically equal to 1 but may
+be set, for instance, to 0 for compatibility with other utilities that
+number columns from 0. The column origin is recorded in the JSON output in
+the @code{column-origin} tag. In the remaining examples below, the extra
+column number outputs have been omitted for brevity.
+
+For example, this error:
+
+@smallexample
+bad-binary-ops.c:64:23: error: invalid operands to binary + (have 'S' @{aka
+ 'struct s'@} and 'T' @{aka 'struct t'@})
+ 64 | return callee_4a () + callee_4b ();
+ | ~~~~~~~~~~~~ ^ ~~~~~~~~~~~~
+ | | |
+ | | T @{aka struct t@}
+ | S @{aka struct s@}
+@end smallexample
+
+@noindent
+has three locations. Its primary location is at the ``+'' token at column
+23. It has two secondary locations, describing the left and right-hand sides
+of the expression, which have labels. It might be printed in JSON form as:
+
+@smallexample
+ @{
+ "children": [],
+ "kind": "error",
+ "locations": [
+ @{
+ "caret": @{
+ "column": 23, "file": "bad-binary-ops.c", "line": 64
+ @}
+ @},
+ @{
+ "caret": @{
+ "column": 10, "file": "bad-binary-ops.c", "line": 64
+ @},
+ "finish": @{
+ "column": 21, "file": "bad-binary-ops.c", "line": 64
+ @},
+ "label": "S @{aka struct s@}"
+ @},
+ @{
+ "caret": @{
+ "column": 25, "file": "bad-binary-ops.c", "line": 64
+ @},
+ "finish": @{
+ "column": 36, "file": "bad-binary-ops.c", "line": 64
+ @},
+ "label": "T @{aka struct t@}"
+ @}
+ ],
+ "escape-source": false,
+ "message": "invalid operands to binary + @dots{}"
+ @}
+@end smallexample
+
+If a diagnostic contains fix-it hints, it has a @code{fixits} array,
+consisting of half-open intervals, similar to the output of
+@option{-fdiagnostics-parseable-fixits}. For example, this diagnostic
+with a replacement fix-it hint:
+
+@smallexample
+demo.c:8:15: error: 'struct s' has no member named 'colour'; did you
+ mean 'color'?
+ 8 | return ptr->colour;
+ | ^~~~~~
+ | color
+@end smallexample
+
+@noindent
+might be printed in JSON form as:
+
+@smallexample
+ @{
+ "children": [],
+ "fixits": [
+ @{
+ "next": @{
+ "column": 21,
+ "file": "demo.c",
+ "line": 8
+ @},
+ "start": @{
+ "column": 15,
+ "file": "demo.c",
+ "line": 8
+ @},
+ "string": "color"
+ @}
+ ],
+ "kind": "error",
+ "locations": [
+ @{
+ "caret": @{
+ "column": 15,
+ "file": "demo.c",
+ "line": 8
+ @},
+ "finish": @{
+ "column": 20,
+ "file": "demo.c",
+ "line": 8
+ @}
+ @}
+ ],
+ "escape-source": false,
+ "message": "\u2018struct s\u2019 has no member named @dots{}"
+ @}
+@end smallexample
+
+@noindent
+where the fix-it hint suggests replacing the text from @code{start} up
+to but not including @code{next} with @code{string}'s value. Deletions
+are expressed via an empty value for @code{string}, insertions by
+having @code{start} equal @code{next}.
+
+If the diagnostic has a path of control-flow events associated with it,
+it has a @code{path} array of objects representing the events. Each
+event object has a @code{description} string, a @code{location} object,
+along with a @code{function} string and a @code{depth} number for
+representing interprocedural paths. The @code{function} represents the
+current function at that event, and the @code{depth} represents the
+stack depth relative to some baseline: the higher, the more frames are
+within the stack.
+
+For example, the intraprocedural example shown for
+@option{-fdiagnostics-path-format=} might have this JSON for its path:
+
+@smallexample
+ "path": [
+ @{
+ "depth": 0,
+ "description": "when 'PyList_New' fails, returning NULL",
+ "function": "test",
+ "location": @{
+ "column": 10,
+ "file": "test.c",
+ "line": 25
+ @}
+ @},
+ @{
+ "depth": 0,
+ "description": "when 'i < count'",
+ "function": "test",
+ "location": @{
+ "column": 3,
+ "file": "test.c",
+ "line": 27
+ @}
+ @},
+ @{
+ "depth": 0,
+ "description": "when calling 'PyList_Append', passing NULL from (1) as argument 1",
+ "function": "test",
+ "location": @{
+ "column": 5,
+ "file": "test.c",
+ "line": 29
+ @}
+ @}
+ ]
+@end smallexample
+
+Diagnostics have a boolean attribute @code{escape-source}, hinting whether
+non-ASCII bytes should be escaped when printing the pertinent lines of
+source code (@code{true} for diagnostics involving source encoding issues).
+
+@end table
+
+@node Warning Options
+@section Options to Request or Suppress Warnings
+@cindex options to control warnings
+@cindex warning messages
+@cindex messages, warning
+@cindex suppressing warnings
+
+Warnings are diagnostic messages that report constructions that
+are not inherently erroneous but that are risky or suggest there
+may have been an error.
+
+The following language-independent options do not enable specific
+warnings but control the kinds of diagnostics produced by GCC@.
+
+@table @gcctabopt
+@cindex syntax checking
+@item -fsyntax-only
+@opindex fsyntax-only
+Check the code for syntax errors, but don't do anything beyond that.
+
+@item -fmax-errors=@var{n}
+@opindex fmax-errors
+Limits the maximum number of error messages to @var{n}, at which point
+GCC bails out rather than attempting to continue processing the source
+code. If @var{n} is 0 (the default), there is no limit on the number
+of error messages produced. If @option{-Wfatal-errors} is also
+specified, then @option{-Wfatal-errors} takes precedence over this
+option.
+
+@item -w
+@opindex w
+Inhibit all warning messages.
+
+@item -Werror
+@opindex Werror
+@opindex Wno-error
+Make all warnings into errors.
+
+@item -Werror=
+@opindex Werror=
+@opindex Wno-error=
+Make the specified warning into an error. The specifier for a warning
+is appended; for example @option{-Werror=switch} turns the warnings
+controlled by @option{-Wswitch} into errors. This switch takes a
+negative form, to be used to negate @option{-Werror} for specific
+warnings; for example @option{-Wno-error=switch} makes
+@option{-Wswitch} warnings not be errors, even when @option{-Werror}
+is in effect.
+
+The warning message for each controllable warning includes the
+option that controls the warning. That option can then be used with
+@option{-Werror=} and @option{-Wno-error=} as described above.
+(Printing of the option in the warning message can be disabled using the
+@option{-fno-diagnostics-show-option} flag.)
+
+Note that specifying @option{-Werror=}@var{foo} automatically implies
+@option{-W}@var{foo}. However, @option{-Wno-error=}@var{foo} does not
+imply anything.
+
+@item -Wfatal-errors
+@opindex Wfatal-errors
+@opindex Wno-fatal-errors
+This option causes the compiler to abort compilation on the first error
+occurred rather than trying to keep going and printing further error
+messages.
+
+@end table
+
+You can request many specific warnings with options beginning with
+@samp{-W}, for example @option{-Wimplicit} to request warnings on
+implicit declarations. Each of these specific warning options also
+has a negative form beginning @samp{-Wno-} to turn off warnings; for
+example, @option{-Wno-implicit}. This manual lists only one of the
+two forms, whichever is not the default. For further
+language-specific options also refer to @ref{C++ Dialect Options} and
+@ref{Objective-C and Objective-C++ Dialect Options}.
+Additional warnings can be produced by enabling the static analyzer;
+@xref{Static Analyzer Options}.
+
+Some options, such as @option{-Wall} and @option{-Wextra}, turn on other
+options, such as @option{-Wunused}, which may turn on further options,
+such as @option{-Wunused-value}. The combined effect of positive and
+negative forms is that more specific options have priority over less
+specific ones, independently of their position in the command-line. For
+options of the same specificity, the last one takes effect. Options
+enabled or disabled via pragmas (@pxref{Diagnostic Pragmas}) take effect
+as if they appeared at the end of the command-line.
+
+When an unrecognized warning option is requested (e.g.,
+@option{-Wunknown-warning}), GCC emits a diagnostic stating
+that the option is not recognized. However, if the @option{-Wno-} form
+is used, the behavior is slightly different: no diagnostic is
+produced for @option{-Wno-unknown-warning} unless other diagnostics
+are being produced. This allows the use of new @option{-Wno-} options
+with old compilers, but if something goes wrong, the compiler
+warns that an unrecognized option is present.
+
+The effectiveness of some warnings depends on optimizations also being
+enabled. For example @option{-Wsuggest-final-types} is more effective
+with link-time optimization and some instances of other warnings may
+not be issued at all unless optimization is enabled. While optimization
+in general improves the efficacy of control and data flow sensitive
+warnings, in some cases it may also cause false positives.
+
+@table @gcctabopt
+@item -Wpedantic
+@itemx -pedantic
+@opindex pedantic
+@opindex Wpedantic
+@opindex Wno-pedantic
+Issue all the warnings demanded by strict ISO C and ISO C++;
+reject all programs that use forbidden extensions, and some other
+programs that do not follow ISO C and ISO C++. For ISO C, follows the
+version of the ISO C standard specified by any @option{-std} option used.
+
+Valid ISO C and ISO C++ programs should compile properly with or without
+this option (though a rare few require @option{-ansi} or a
+@option{-std} option specifying the required version of ISO C)@. However,
+without this option, certain GNU extensions and traditional C and C++
+features are supported as well. With this option, they are rejected.
+
+@option{-Wpedantic} does not cause warning messages for use of the
+alternate keywords whose names begin and end with @samp{__}. This alternate
+format can also be used to disable warnings for non-ISO @samp{__intN} types,
+i.e. @samp{__intN__}.
+Pedantic warnings are also disabled in the expression that follows
+@code{__extension__}. However, only system header files should use
+these escape routes; application programs should avoid them.
+@xref{Alternate Keywords}.
+
+Some users try to use @option{-Wpedantic} to check programs for strict ISO
+C conformance. They soon find that it does not do quite what they want:
+it finds some non-ISO practices, but not all---only those for which
+ISO C @emph{requires} a diagnostic, and some others for which
+diagnostics have been added.
+
+A feature to report any failure to conform to ISO C might be useful in
+some instances, but would require considerable additional work and would
+be quite different from @option{-Wpedantic}. We don't have plans to
+support such a feature in the near future.
+
+Where the standard specified with @option{-std} represents a GNU
+extended dialect of C, such as @samp{gnu90} or @samp{gnu99}, there is a
+corresponding @dfn{base standard}, the version of ISO C on which the GNU
+extended dialect is based. Warnings from @option{-Wpedantic} are given
+where they are required by the base standard. (It does not make sense
+for such warnings to be given only for features not in the specified GNU
+C dialect, since by definition the GNU dialects of C include all
+features the compiler supports with the given option, and there would be
+nothing to warn about.)
+
+@item -pedantic-errors
+@opindex pedantic-errors
+Give an error whenever the @dfn{base standard} (see @option{-Wpedantic})
+requires a diagnostic, in some cases where there is undefined behavior
+at compile-time and in some other cases that do not prevent compilation
+of programs that are valid according to the standard. This is not
+equivalent to @option{-Werror=pedantic}, since there are errors enabled
+by this option and not enabled by the latter and vice versa.
+
+@item -Wall
+@opindex Wall
+@opindex Wno-all
+This enables all the warnings about constructions that some users
+consider questionable, and that are easy to avoid (or modify to
+prevent the warning), even in conjunction with macros. This also
+enables some language-specific warnings described in @ref{C++ Dialect
+Options} and @ref{Objective-C and Objective-C++ Dialect Options}.
+
+@option{-Wall} turns on the following warning flags:
+
+@gccoptlist{-Waddress @gol
+-Warray-bounds=1 @r{(only with} @option{-O2}@r{)} @gol
+-Warray-compare @gol
+-Warray-parameter=2 @r{(C and Objective-C only)} @gol
+-Wbool-compare @gol
+-Wbool-operation @gol
+-Wc++11-compat -Wc++14-compat @gol
+-Wcatch-value @r{(C++ and Objective-C++ only)} @gol
+-Wchar-subscripts @gol
+-Wcomment @gol
+-Wdangling-pointer=2 @gol
+-Wduplicate-decl-specifier @r{(C and Objective-C only)} @gol
+-Wenum-compare @r{(in C/ObjC; this is on by default in C++)} @gol
+-Wenum-int-mismatch @r{(C and Objective-C only)} @gol
+-Wformat @gol
+-Wformat-overflow @gol
+-Wformat-truncation @gol
+-Wint-in-bool-context @gol
+-Wimplicit @r{(C and Objective-C only)} @gol
+-Wimplicit-int @r{(C and Objective-C only)} @gol
+-Wimplicit-function-declaration @r{(C and Objective-C only)} @gol
+-Winit-self @r{(only for C++)} @gol
+-Wlogical-not-parentheses @gol
+-Wmain @r{(only for C/ObjC and unless} @option{-ffreestanding}@r{)} @gol
+-Wmaybe-uninitialized @gol
+-Wmemset-elt-size @gol
+-Wmemset-transposed-args @gol
+-Wmisleading-indentation @r{(only for C/C++)} @gol
+-Wmismatched-dealloc @gol
+-Wmismatched-new-delete @r{(only for C/C++)} @gol
+-Wmissing-attributes @gol
+-Wmissing-braces @r{(only for C/ObjC)} @gol
+-Wmultistatement-macros @gol
+-Wnarrowing @r{(only for C++)} @gol
+-Wnonnull @gol
+-Wnonnull-compare @gol
+-Wopenmp-simd @gol
+-Wparentheses @gol
+-Wpessimizing-move @r{(only for C++)} @gol
+-Wpointer-sign @gol
+-Wrange-loop-construct @r{(only for C++)} @gol
+-Wreorder @gol
+-Wrestrict @gol
+-Wreturn-type @gol
+-Wself-move @r{(only for C++)} @gol
+-Wsequence-point @gol
+-Wsign-compare @r{(only in C++)} @gol
+-Wsizeof-array-div @gol
+-Wsizeof-pointer-div @gol
+-Wsizeof-pointer-memaccess @gol
+-Wstrict-aliasing @gol
+-Wstrict-overflow=1 @gol
+-Wswitch @gol
+-Wtautological-compare @gol
+-Wtrigraphs @gol
+-Wuninitialized @gol
+-Wunknown-pragmas @gol
+-Wunused-function @gol
+-Wunused-label @gol
+-Wunused-value @gol
+-Wunused-variable @gol
+-Wuse-after-free=3 @gol
+-Wvla-parameter @r{(C and Objective-C only)} @gol
+-Wvolatile-register-var @gol
+-Wzero-length-bounds}
+
+Note that some warning flags are not implied by @option{-Wall}. Some of
+them warn about constructions that users generally do not consider
+questionable, but which occasionally you might wish to check for;
+others warn about constructions that are necessary or hard to avoid in
+some cases, and there is no simple way to modify the code to suppress
+the warning. Some of them are enabled by @option{-Wextra} but many of
+them must be enabled individually.
+
+@item -Wextra
+@opindex W
+@opindex Wextra
+@opindex Wno-extra
+This enables some extra warning flags that are not enabled by
+@option{-Wall}. (This option used to be called @option{-W}. The older
+name is still supported, but the newer name is more descriptive.)
+
+@gccoptlist{-Wclobbered @gol
+-Wcast-function-type @gol
+-Wdeprecated-copy @r{(C++ only)} @gol
+-Wempty-body @gol
+-Wenum-conversion @r{(C only)} @gol
+-Wignored-qualifiers @gol
+-Wimplicit-fallthrough=3 @gol
+-Wmissing-field-initializers @gol
+-Wmissing-parameter-type @r{(C only)} @gol
+-Wold-style-declaration @r{(C only)} @gol
+-Woverride-init @gol
+-Wsign-compare @r{(C only)} @gol
+-Wstring-compare @gol
+-Wredundant-move @r{(only for C++)} @gol
+-Wtype-limits @gol
+-Wuninitialized @gol
+-Wshift-negative-value @r{(in C++11 to C++17 and in C99 and newer)} @gol
+-Wunused-parameter @r{(only with} @option{-Wunused} @r{or} @option{-Wall}@r{)} @gol
+-Wunused-but-set-parameter @r{(only with} @option{-Wunused} @r{or} @option{-Wall}@r{)}}
+
+
+The option @option{-Wextra} also prints warning messages for the
+following cases:
+
+@itemize @bullet
+
+@item
+A pointer is compared against integer zero with @code{<}, @code{<=},
+@code{>}, or @code{>=}.
+
+@item
+(C++ only) An enumerator and a non-enumerator both appear in a
+conditional expression.
+
+@item
+(C++ only) Ambiguous virtual bases.
+
+@item
+(C++ only) Subscripting an array that has been declared @code{register}.
+
+@item
+(C++ only) Taking the address of a variable that has been declared
+@code{register}.
+
+@item
+(C++ only) A base class is not initialized in the copy constructor
+of a derived class.
+
+@end itemize
+
+@item -Wabi @r{(C, Objective-C, C++ and Objective-C++ only)}
+@opindex Wabi
+@opindex Wno-abi
+
+Warn about code affected by ABI changes. This includes code that may
+not be compatible with the vendor-neutral C++ ABI as well as the psABI
+for the particular target.
+
+Since G++ now defaults to updating the ABI with each major release,
+normally @option{-Wabi} warns only about C++ ABI compatibility
+problems if there is a check added later in a release series for an
+ABI issue discovered since the initial release. @option{-Wabi} warns
+about more things if an older ABI version is selected (with
+@option{-fabi-version=@var{n}}).
+
+@option{-Wabi} can also be used with an explicit version number to
+warn about C++ ABI compatibility with a particular @option{-fabi-version}
+level, e.g.@: @option{-Wabi=2} to warn about changes relative to
+@option{-fabi-version=2}.
+
+If an explicit version number is provided and
+@option{-fabi-compat-version} is not specified, the version number
+from this option is used for compatibility aliases. If no explicit
+version number is provided with this option, but
+@option{-fabi-compat-version} is specified, that version number is
+used for C++ ABI warnings.
+
+Although an effort has been made to warn about
+all such cases, there are probably some cases that are not warned about,
+even though G++ is generating incompatible code. There may also be
+cases where warnings are emitted even though the code that is generated
+is compatible.
+
+You should rewrite your code to avoid these warnings if you are
+concerned about the fact that code generated by G++ may not be binary
+compatible with code generated by other compilers.
+
+Known incompatibilities in @option{-fabi-version=2} (which was the
+default from GCC 3.4 to 4.9) include:
+
+@itemize @bullet
+
+@item
+A template with a non-type template parameter of reference type was
+mangled incorrectly:
+@smallexample
+extern int N;
+template <int &> struct S @{@};
+void n (S<N>) @{2@}
+@end smallexample
+
+This was fixed in @option{-fabi-version=3}.
+
+@item
+SIMD vector types declared using @code{__attribute ((vector_size))} were
+mangled in a non-standard way that does not allow for overloading of
+functions taking vectors of different sizes.
+
+The mangling was changed in @option{-fabi-version=4}.
+
+@item
+@code{__attribute ((const))} and @code{noreturn} were mangled as type
+qualifiers, and @code{decltype} of a plain declaration was folded away.
+
+These mangling issues were fixed in @option{-fabi-version=5}.
+
+@item
+Scoped enumerators passed as arguments to a variadic function are
+promoted like unscoped enumerators, causing @code{va_arg} to complain.
+On most targets this does not actually affect the parameter passing
+ABI, as there is no way to pass an argument smaller than @code{int}.
+
+Also, the ABI changed the mangling of template argument packs,
+@code{const_cast}, @code{static_cast}, prefix increment/decrement, and
+a class scope function used as a template argument.
+
+These issues were corrected in @option{-fabi-version=6}.
+
+@item
+Lambdas in default argument scope were mangled incorrectly, and the
+ABI changed the mangling of @code{nullptr_t}.
+
+These issues were corrected in @option{-fabi-version=7}.
+
+@item
+When mangling a function type with function-cv-qualifiers, the
+un-qualified function type was incorrectly treated as a substitution
+candidate.
+
+This was fixed in @option{-fabi-version=8}, the default for GCC 5.1.
+
+@item
+@code{decltype(nullptr)} incorrectly had an alignment of 1, leading to
+unaligned accesses. Note that this did not affect the ABI of a
+function with a @code{nullptr_t} parameter, as parameters have a
+minimum alignment.
+
+This was fixed in @option{-fabi-version=9}, the default for GCC 5.2.
+
+@item
+Target-specific attributes that affect the identity of a type, such as
+ia32 calling conventions on a function type (stdcall, regparm, etc.),
+did not affect the mangled name, leading to name collisions when
+function pointers were used as template arguments.
+
+This was fixed in @option{-fabi-version=10}, the default for GCC 6.1.
+
+@end itemize
+
+This option also enables warnings about psABI-related changes.
+The known psABI changes at this point include:
+
+@itemize @bullet
+
+@item
+For SysV/x86-64, unions with @code{long double} members are
+passed in memory as specified in psABI. Prior to GCC 4.4, this was not
+the case. For example:
+
+@smallexample
+union U @{
+ long double ld;
+ int i;
+@};
+@end smallexample
+
+@noindent
+@code{union U} is now always passed in memory.
+
+@end itemize
+
+@item -Wchar-subscripts
+@opindex Wchar-subscripts
+@opindex Wno-char-subscripts
+Warn if an array subscript has type @code{char}. This is a common cause
+of error, as programmers often forget that this type is signed on some
+machines.
+This warning is enabled by @option{-Wall}.
+
+@item -Wno-coverage-mismatch
+@opindex Wno-coverage-mismatch
+@opindex Wcoverage-mismatch
+Warn if feedback profiles do not match when using the
+@option{-fprofile-use} option.
+If a source file is changed between compiling with @option{-fprofile-generate}
+and with @option{-fprofile-use}, the files with the profile feedback can fail
+to match the source file and GCC cannot use the profile feedback
+information. By default, this warning is enabled and is treated as an
+error. @option{-Wno-coverage-mismatch} can be used to disable the
+warning or @option{-Wno-error=coverage-mismatch} can be used to
+disable the error. Disabling the error for this warning can result in
+poorly optimized code and is useful only in the
+case of very minor changes such as bug fixes to an existing code-base.
+Completely disabling the warning is not recommended.
+
+@item -Wno-coverage-invalid-line-number
+@opindex Wno-coverage-invalid-line-number
+@opindex Wcoverage-invalid-line-number
+Warn in case a function ends earlier than it begins due
+to an invalid linenum macros. The warning is emitted only
+with @option{--coverage} enabled.
+
+By default, this warning is enabled and is treated as an
+error. @option{-Wno-coverage-invalid-line-number} can be used to disable the
+warning or @option{-Wno-error=coverage-invalid-line-number} can be used to
+disable the error.
+
+@item -Wno-cpp @r{(C, Objective-C, C++, Objective-C++ and Fortran only)}
+@opindex Wno-cpp
+@opindex Wcpp
+Suppress warning messages emitted by @code{#warning} directives.
+
+@item -Wdouble-promotion @r{(C, C++, Objective-C and Objective-C++ only)}
+@opindex Wdouble-promotion
+@opindex Wno-double-promotion
+Give a warning when a value of type @code{float} is implicitly
+promoted to @code{double}. CPUs with a 32-bit ``single-precision''
+floating-point unit implement @code{float} in hardware, but emulate
+@code{double} in software. On such a machine, doing computations
+using @code{double} values is much more expensive because of the
+overhead required for software emulation.
+
+It is easy to accidentally do computations with @code{double} because
+floating-point literals are implicitly of type @code{double}. For
+example, in:
+@smallexample
+@group
+float area(float radius)
+@{
+ return 3.14159 * radius * radius;
+@}
+@end group
+@end smallexample
+the compiler performs the entire computation with @code{double}
+because the floating-point literal is a @code{double}.
+
+@item -Wduplicate-decl-specifier @r{(C and Objective-C only)}
+@opindex Wduplicate-decl-specifier
+@opindex Wno-duplicate-decl-specifier
+Warn if a declaration has duplicate @code{const}, @code{volatile},
+@code{restrict} or @code{_Atomic} specifier. This warning is enabled by
+@option{-Wall}.
+
+@item -Wformat
+@itemx -Wformat=@var{n}
+@opindex Wformat
+@opindex Wno-format
+@opindex ffreestanding
+@opindex fno-builtin
+@opindex Wformat=
+Check calls to @code{printf} and @code{scanf}, etc., to make sure that
+the arguments supplied have types appropriate to the format string
+specified, and that the conversions specified in the format string make
+sense. This includes standard functions, and others specified by format
+attributes (@pxref{Function Attributes}), in the @code{printf},
+@code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension,
+not in the C standard) families (or other target-specific families).
+Which functions are checked without format attributes having been
+specified depends on the standard version selected, and such checks of
+functions without the attribute specified are disabled by
+@option{-ffreestanding} or @option{-fno-builtin}.
+
+The formats are checked against the format features supported by GNU
+libc version 2.2. These include all ISO C90 and C99 features, as well
+as features from the Single Unix Specification and some BSD and GNU
+extensions. Other library implementations may not support all these
+features; GCC does not support warning about features that go beyond a
+particular library's limitations. However, if @option{-Wpedantic} is used
+with @option{-Wformat}, warnings are given about format features not
+in the selected standard version (but not for @code{strfmon} formats,
+since those are not in any version of the C standard). @xref{C Dialect
+Options,,Options Controlling C Dialect}.
+
+@table @gcctabopt
+@item -Wformat=1
+@itemx -Wformat
+@opindex Wformat
+@opindex Wformat=1
+Option @option{-Wformat} is equivalent to @option{-Wformat=1}, and
+@option{-Wno-format} is equivalent to @option{-Wformat=0}. Since
+@option{-Wformat} also checks for null format arguments for several
+functions, @option{-Wformat} also implies @option{-Wnonnull}. Some
+aspects of this level of format checking can be disabled by the
+options: @option{-Wno-format-contains-nul},
+@option{-Wno-format-extra-args}, and @option{-Wno-format-zero-length}.
+@option{-Wformat} is enabled by @option{-Wall}.
+
+@item -Wformat=2
+@opindex Wformat=2
+Enable @option{-Wformat} plus additional format checks. Currently
+equivalent to @option{-Wformat -Wformat-nonliteral -Wformat-security
+-Wformat-y2k}.
+@end table
+
+@item -Wno-format-contains-nul
+@opindex Wno-format-contains-nul
+@opindex Wformat-contains-nul
+If @option{-Wformat} is specified, do not warn about format strings that
+contain NUL bytes.
+
+@item -Wno-format-extra-args
+@opindex Wno-format-extra-args
+@opindex Wformat-extra-args
+If @option{-Wformat} is specified, do not warn about excess arguments to a
+@code{printf} or @code{scanf} format function. The C standard specifies
+that such arguments are ignored.
+
+Where the unused arguments lie between used arguments that are
+specified with @samp{$} operand number specifications, normally
+warnings are still given, since the implementation could not know what
+type to pass to @code{va_arg} to skip the unused arguments. However,
+in the case of @code{scanf} formats, this option suppresses the
+warning if the unused arguments are all pointers, since the Single
+Unix Specification says that such unused arguments are allowed.
+
+@item -Wformat-overflow
+@itemx -Wformat-overflow=@var{level}
+@opindex Wformat-overflow
+@opindex Wno-format-overflow
+Warn about calls to formatted input/output functions such as @code{sprintf}
+and @code{vsprintf} that might overflow the destination buffer. When the
+exact number of bytes written by a format directive cannot be determined
+at compile-time it is estimated based on heuristics that depend on the
+@var{level} argument and on optimization. While enabling optimization
+will in most cases improve the accuracy of the warning, it may also
+result in false positives.
+
+@table @gcctabopt
+@item -Wformat-overflow
+@itemx -Wformat-overflow=1
+@opindex Wformat-overflow
+@opindex Wno-format-overflow
+Level @var{1} of @option{-Wformat-overflow} enabled by @option{-Wformat}
+employs a conservative approach that warns only about calls that most
+likely overflow the buffer. At this level, numeric arguments to format
+directives with unknown values are assumed to have the value of one, and
+strings of unknown length to be empty. Numeric arguments that are known
+to be bounded to a subrange of their type, or string arguments whose output
+is bounded either by their directive's precision or by a finite set of
+string literals, are assumed to take on the value within the range that
+results in the most bytes on output. For example, the call to @code{sprintf}
+below is diagnosed because even with both @var{a} and @var{b} equal to zero,
+the terminating NUL character (@code{'\0'}) appended by the function
+to the destination buffer will be written past its end. Increasing
+the size of the buffer by a single byte is sufficient to avoid the
+warning, though it may not be sufficient to avoid the overflow.
+
+@smallexample
+void f (int a, int b)
+@{
+ char buf [13];
+ sprintf (buf, "a = %i, b = %i\n", a, b);
+@}
+@end smallexample
+
+@item -Wformat-overflow=2
+Level @var{2} warns also about calls that might overflow the destination
+buffer given an argument of sufficient length or magnitude. At level
+@var{2}, unknown numeric arguments are assumed to have the minimum
+representable value for signed types with a precision greater than 1, and
+the maximum representable value otherwise. Unknown string arguments whose
+length cannot be assumed to be bounded either by the directive's precision,
+or by a finite set of string literals they may evaluate to, or the character
+array they may point to, are assumed to be 1 character long.
+
+At level @var{2}, the call in the example above is again diagnosed, but
+this time because with @var{a} equal to a 32-bit @code{INT_MIN} the first
+@code{%i} directive will write some of its digits beyond the end of
+the destination buffer. To make the call safe regardless of the values
+of the two variables, the size of the destination buffer must be increased
+to at least 34 bytes. GCC includes the minimum size of the buffer in
+an informational note following the warning.
+
+An alternative to increasing the size of the destination buffer is to
+constrain the range of formatted values. The maximum length of string
+arguments can be bounded by specifying the precision in the format
+directive. When numeric arguments of format directives can be assumed
+to be bounded by less than the precision of their type, choosing
+an appropriate length modifier to the format specifier will reduce
+the required buffer size. For example, if @var{a} and @var{b} in the
+example above can be assumed to be within the precision of
+the @code{short int} type then using either the @code{%hi} format
+directive or casting the argument to @code{short} reduces the maximum
+required size of the buffer to 24 bytes.
+
+@smallexample
+void f (int a, int b)
+@{
+ char buf [23];
+ sprintf (buf, "a = %hi, b = %i\n", a, (short)b);
+@}
+@end smallexample
+@end table
+
+@item -Wno-format-zero-length
+@opindex Wno-format-zero-length
+@opindex Wformat-zero-length
+If @option{-Wformat} is specified, do not warn about zero-length formats.
+The C standard specifies that zero-length formats are allowed.
+
+@item -Wformat-nonliteral
+@opindex Wformat-nonliteral
+@opindex Wno-format-nonliteral
+If @option{-Wformat} is specified, also warn if the format string is not a
+string literal and so cannot be checked, unless the format function
+takes its format arguments as a @code{va_list}.
+
+@item -Wformat-security
+@opindex Wformat-security
+@opindex Wno-format-security
+If @option{-Wformat} is specified, also warn about uses of format
+functions that represent possible security problems. At present, this
+warns about calls to @code{printf} and @code{scanf} functions where the
+format string is not a string literal and there are no format arguments,
+as in @code{printf (foo);}. This may be a security hole if the format
+string came from untrusted input and contains @samp{%n}. (This is
+currently a subset of what @option{-Wformat-nonliteral} warns about, but
+in future warnings may be added to @option{-Wformat-security} that are not
+included in @option{-Wformat-nonliteral}.)
+
+@item -Wformat-signedness
+@opindex Wformat-signedness
+@opindex Wno-format-signedness
+If @option{-Wformat} is specified, also warn if the format string
+requires an unsigned argument and the argument is signed and vice versa.
+
+@item -Wformat-truncation
+@itemx -Wformat-truncation=@var{level}
+@opindex Wformat-truncation
+@opindex Wno-format-truncation
+Warn about calls to formatted input/output functions such as @code{snprintf}
+and @code{vsnprintf} that might result in output truncation. When the exact
+number of bytes written by a format directive cannot be determined at
+compile-time it is estimated based on heuristics that depend on
+the @var{level} argument and on optimization. While enabling optimization
+will in most cases improve the accuracy of the warning, it may also result
+in false positives. Except as noted otherwise, the option uses the same
+logic @option{-Wformat-overflow}.
+
+@table @gcctabopt
+@item -Wformat-truncation
+@itemx -Wformat-truncation=1
+@opindex Wformat-truncation
+@opindex Wno-format-truncation
+Level @var{1} of @option{-Wformat-truncation} enabled by @option{-Wformat}
+employs a conservative approach that warns only about calls to bounded
+functions whose return value is unused and that will most likely result
+in output truncation.
+
+@item -Wformat-truncation=2
+Level @var{2} warns also about calls to bounded functions whose return
+value is used and that might result in truncation given an argument of
+sufficient length or magnitude.
+@end table
+
+@item -Wformat-y2k
+@opindex Wformat-y2k
+@opindex Wno-format-y2k
+If @option{-Wformat} is specified, also warn about @code{strftime}
+formats that may yield only a two-digit year.
+
+@item -Wnonnull
+@opindex Wnonnull
+@opindex Wno-nonnull
+Warn about passing a null pointer for arguments marked as
+requiring a non-null value by the @code{nonnull} function attribute.
+
+@option{-Wnonnull} is included in @option{-Wall} and @option{-Wformat}. It
+can be disabled with the @option{-Wno-nonnull} option.
+
+@item -Wnonnull-compare
+@opindex Wnonnull-compare
+@opindex Wno-nonnull-compare
+Warn when comparing an argument marked with the @code{nonnull}
+function attribute against null inside the function.
+
+@option{-Wnonnull-compare} is included in @option{-Wall}. It
+can be disabled with the @option{-Wno-nonnull-compare} option.
+
+@item -Wnull-dereference
+@opindex Wnull-dereference
+@opindex Wno-null-dereference
+Warn if the compiler detects paths that trigger erroneous or
+undefined behavior due to dereferencing a null pointer. This option
+is only active when @option{-fdelete-null-pointer-checks} is active,
+which is enabled by optimizations in most targets. The precision of
+the warnings depends on the optimization options used.
+
+@item -Winfinite-recursion
+@opindex Winfinite-recursion
+@opindex Wno-infinite-recursion
+Warn about infinitely recursive calls. The warning is effective at all
+optimization levels but requires optimization in order to detect infinite
+recursion in calls between two or more functions.
+@option{-Winfinite-recursion} is included in @option{-Wall}.
+
+@item -Winit-self @r{(C, C++, Objective-C and Objective-C++ only)}
+@opindex Winit-self
+@opindex Wno-init-self
+Warn about uninitialized variables that are initialized with themselves.
+Note this option can only be used with the @option{-Wuninitialized} option.
+
+For example, GCC warns about @code{i} being uninitialized in the
+following snippet only when @option{-Winit-self} has been specified:
+@smallexample
+@group
+int f()
+@{
+ int i = i;
+ return i;
+@}
+@end group
+@end smallexample
+
+This warning is enabled by @option{-Wall} in C++.
+
+@item -Wno-implicit-int @r{(C and Objective-C only)}
+@opindex Wimplicit-int
+@opindex Wno-implicit-int
+This option controls warnings when a declaration does not specify a type.
+This warning is enabled by default in C99 and later dialects of C,
+and also by @option{-Wall}.
+
+@item -Wno-implicit-function-declaration @r{(C and Objective-C only)}
+@opindex Wimplicit-function-declaration
+@opindex Wno-implicit-function-declaration
+This option controls warnings when a function is used before being declared.
+This warning is enabled by default in C99 and later dialects of C,
+and also by @option{-Wall}.
+The warning is made into an error by @option{-pedantic-errors}.
+
+@item -Wimplicit @r{(C and Objective-C only)}
+@opindex Wimplicit
+@opindex Wno-implicit
+Same as @option{-Wimplicit-int} and @option{-Wimplicit-function-declaration}.
+This warning is enabled by @option{-Wall}.
+
+@item -Wimplicit-fallthrough
+@opindex Wimplicit-fallthrough
+@opindex Wno-implicit-fallthrough
+@option{-Wimplicit-fallthrough} is the same as @option{-Wimplicit-fallthrough=3}
+and @option{-Wno-implicit-fallthrough} is the same as
+@option{-Wimplicit-fallthrough=0}.
+
+@item -Wimplicit-fallthrough=@var{n}
+@opindex Wimplicit-fallthrough=
+Warn when a switch case falls through. For example:
+
+@smallexample
+@group
+switch (cond)
+ @{
+ case 1:
+ a = 1;
+ break;
+ case 2:
+ a = 2;
+ case 3:
+ a = 3;
+ break;
+ @}
+@end group
+@end smallexample
+
+This warning does not warn when the last statement of a case cannot
+fall through, e.g. when there is a return statement or a call to function
+declared with the noreturn attribute. @option{-Wimplicit-fallthrough=}
+also takes into account control flow statements, such as ifs, and only
+warns when appropriate. E.g.@:
+
+@smallexample
+@group
+switch (cond)
+ @{
+ case 1:
+ if (i > 3) @{
+ bar (5);
+ break;
+ @} else if (i < 1) @{
+ bar (0);
+ @} else
+ return;
+ default:
+ @dots{}
+ @}
+@end group
+@end smallexample
+
+Since there are occasions where a switch case fall through is desirable,
+GCC provides an attribute, @code{__attribute__ ((fallthrough))}, that is
+to be used along with a null statement to suppress this warning that
+would normally occur:
+
+@smallexample
+@group
+switch (cond)
+ @{
+ case 1:
+ bar (0);
+ __attribute__ ((fallthrough));
+ default:
+ @dots{}
+ @}
+@end group
+@end smallexample
+
+C++17 provides a standard way to suppress the @option{-Wimplicit-fallthrough}
+warning using @code{[[fallthrough]];} instead of the GNU attribute. In C++11
+or C++14 users can use @code{[[gnu::fallthrough]];}, which is a GNU extension.
+Instead of these attributes, it is also possible to add a fallthrough comment
+to silence the warning. The whole body of the C or C++ style comment should
+match the given regular expressions listed below. The option argument @var{n}
+specifies what kind of comments are accepted:
+
+@itemize @bullet
+
+@item @option{-Wimplicit-fallthrough=0} disables the warning altogether.
+
+@item @option{-Wimplicit-fallthrough=1} matches @code{.*} regular
+expression, any comment is used as fallthrough comment.
+
+@item @option{-Wimplicit-fallthrough=2} case insensitively matches
+@code{.*falls?[ \t-]*thr(ough|u).*} regular expression.
+
+@item @option{-Wimplicit-fallthrough=3} case sensitively matches one of the
+following regular expressions:
+
+@itemize @bullet
+
+@item @code{-fallthrough}
+
+@item @code{@@fallthrough@@}
+
+@item @code{lint -fallthrough[ \t]*}
+
+@item @code{[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?@*FALL(S | |-)?THR(OUGH|U)[ \t.!]*(-[^\n\r]*)?}
+
+@item @code{[ \t.!]*(Else,? |Intentional(ly)? )?@*Fall((s | |-)[Tt]|t)hr(ough|u)[ \t.!]*(-[^\n\r]*)?}
+
+@item @code{[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?@*fall(s | |-)?thr(ough|u)[ \t.!]*(-[^\n\r]*)?}
+
+@end itemize
+
+@item @option{-Wimplicit-fallthrough=4} case sensitively matches one of the
+following regular expressions:
+
+@itemize @bullet
+
+@item @code{-fallthrough}
+
+@item @code{@@fallthrough@@}
+
+@item @code{lint -fallthrough[ \t]*}
+
+@item @code{[ \t]*FALLTHR(OUGH|U)[ \t]*}
+
+@end itemize
+
+@item @option{-Wimplicit-fallthrough=5} doesn't recognize any comments as
+fallthrough comments, only attributes disable the warning.
+
+@end itemize
+
+The comment needs to be followed after optional whitespace and other comments
+by @code{case} or @code{default} keywords or by a user label that precedes some
+@code{case} or @code{default} label.
+
+@smallexample
+@group
+switch (cond)
+ @{
+ case 1:
+ bar (0);
+ /* FALLTHRU */
+ default:
+ @dots{}
+ @}
+@end group
+@end smallexample
+
+The @option{-Wimplicit-fallthrough=3} warning is enabled by @option{-Wextra}.
+
+@item -Wno-if-not-aligned @r{(C, C++, Objective-C and Objective-C++ only)}
+@opindex Wif-not-aligned
+@opindex Wno-if-not-aligned
+Control if warnings triggered by the @code{warn_if_not_aligned} attribute
+should be issued. These warnings are enabled by default.
+
+@item -Wignored-qualifiers @r{(C and C++ only)}
+@opindex Wignored-qualifiers
+@opindex Wno-ignored-qualifiers
+Warn if the return type of a function has a type qualifier
+such as @code{const}. For ISO C such a type qualifier has no effect,
+since the value returned by a function is not an lvalue.
+For C++, the warning is only emitted for scalar types or @code{void}.
+ISO C prohibits qualified @code{void} return types on function
+definitions, so such return types always receive a warning
+even without this option.
+
+This warning is also enabled by @option{-Wextra}.
+
+@item -Wno-ignored-attributes @r{(C and C++ only)}
+@opindex Wignored-attributes
+@opindex Wno-ignored-attributes
+This option controls warnings when an attribute is ignored.
+This is different from the
+@option{-Wattributes} option in that it warns whenever the compiler decides
+to drop an attribute, not that the attribute is either unknown, used in a
+wrong place, etc. This warning is enabled by default.
+
+@item -Wmain
+@opindex Wmain
+@opindex Wno-main
+Warn if the type of @code{main} is suspicious. @code{main} should be
+a function with external linkage, returning int, taking either zero
+arguments, two, or three arguments of appropriate types. This warning
+is enabled by default in C++ and is enabled by either @option{-Wall}
+or @option{-Wpedantic}.
+
+@item -Wmisleading-indentation @r{(C and C++ only)}
+@opindex Wmisleading-indentation
+@opindex Wno-misleading-indentation
+Warn when the indentation of the code does not reflect the block structure.
+Specifically, a warning is issued for @code{if}, @code{else}, @code{while}, and
+@code{for} clauses with a guarded statement that does not use braces,
+followed by an unguarded statement with the same indentation.
+
+In the following example, the call to ``bar'' is misleadingly indented as
+if it were guarded by the ``if'' conditional.
+
+@smallexample
+ if (some_condition ())
+ foo ();
+ bar (); /* Gotcha: this is not guarded by the "if". */
+@end smallexample
+
+In the case of mixed tabs and spaces, the warning uses the
+@option{-ftabstop=} option to determine if the statements line up
+(defaulting to 8).
+
+The warning is not issued for code involving multiline preprocessor logic
+such as the following example.
+
+@smallexample
+ if (flagA)
+ foo (0);
+#if SOME_CONDITION_THAT_DOES_NOT_HOLD
+ if (flagB)
+#endif
+ foo (1);
+@end smallexample
+
+The warning is not issued after a @code{#line} directive, since this
+typically indicates autogenerated code, and no assumptions can be made
+about the layout of the file that the directive references.
+
+This warning is enabled by @option{-Wall} in C and C++.
+
+@item -Wmissing-attributes
+@opindex Wmissing-attributes
+@opindex Wno-missing-attributes
+Warn when a declaration of a function is missing one or more attributes
+that a related function is declared with and whose absence may adversely
+affect the correctness or efficiency of generated code. For example,
+the warning is issued for declarations of aliases that use attributes
+to specify less restrictive requirements than those of their targets.
+This typically represents a potential optimization opportunity.
+By contrast, the @option{-Wattribute-alias=2} option controls warnings
+issued when the alias is more restrictive than the target, which could
+lead to incorrect code generation.
+Attributes considered include @code{alloc_align}, @code{alloc_size},
+@code{cold}, @code{const}, @code{hot}, @code{leaf}, @code{malloc},
+@code{nonnull}, @code{noreturn}, @code{nothrow}, @code{pure},
+@code{returns_nonnull}, and @code{returns_twice}.
+
+In C++, the warning is issued when an explicit specialization of a primary
+template declared with attribute @code{alloc_align}, @code{alloc_size},
+@code{assume_aligned}, @code{format}, @code{format_arg}, @code{malloc},
+or @code{nonnull} is declared without it. Attributes @code{deprecated},
+@code{error}, and @code{warning} suppress the warning.
+(@pxref{Function Attributes}).
+
+You can use the @code{copy} attribute to apply the same
+set of attributes to a declaration as that on another declaration without
+explicitly enumerating the attributes. This attribute can be applied
+to declarations of functions (@pxref{Common Function Attributes}),
+variables (@pxref{Common Variable Attributes}), or types
+(@pxref{Common Type Attributes}).
+
+@option{-Wmissing-attributes} is enabled by @option{-Wall}.
+
+For example, since the declaration of the primary function template
+below makes use of both attribute @code{malloc} and @code{alloc_size}
+the declaration of the explicit specialization of the template is
+diagnosed because it is missing one of the attributes.
+
+@smallexample
+template <class T>
+T* __attribute__ ((malloc, alloc_size (1)))
+allocate (size_t);
+
+template <>
+void* __attribute__ ((malloc)) // missing alloc_size
+allocate<void> (size_t);
+@end smallexample
+
+@item -Wmissing-braces
+@opindex Wmissing-braces
+@opindex Wno-missing-braces
+Warn if an aggregate or union initializer is not fully bracketed. In
+the following example, the initializer for @code{a} is not fully
+bracketed, but that for @code{b} is fully bracketed.
+
+@smallexample
+int a[2][2] = @{ 0, 1, 2, 3 @};
+int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @};
+@end smallexample
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wmissing-include-dirs @r{(C, C++, Objective-C, Objective-C++ and Fortran only)}
+@opindex Wmissing-include-dirs
+@opindex Wno-missing-include-dirs
+Warn if a user-supplied include directory does not exist. This opions is disabled
+by default for C, C++, Objective-C and Objective-C++. For Fortran, it is partially
+enabled by default by warning for -I and -J, only.
+
+@item -Wno-missing-profile
+@opindex Wmissing-profile
+@opindex Wno-missing-profile
+This option controls warnings if feedback profiles are missing when using the
+@option{-fprofile-use} option.
+This option diagnoses those cases where a new function or a new file is added
+between compiling with @option{-fprofile-generate} and with
+@option{-fprofile-use}, without regenerating the profiles.
+In these cases, the profile feedback data files do not contain any
+profile feedback information for
+the newly added function or file respectively. Also, in the case when profile
+count data (.gcda) files are removed, GCC cannot use any profile feedback
+information. In all these cases, warnings are issued to inform you that a
+profile generation step is due.
+Ignoring the warning can result in poorly optimized code.
+@option{-Wno-missing-profile} can be used to
+disable the warning, but this is not recommended and should be done only
+when non-existent profile data is justified.
+
+@item -Wmismatched-dealloc
+@opindex Wmismatched-dealloc
+@opindex Wno-mismatched-dealloc
+
+Warn for calls to deallocation functions with pointer arguments returned
+from from allocations functions for which the former isn't a suitable
+deallocator. A pair of functions can be associated as matching allocators
+and deallocators by use of attribute @code{malloc}. Unless disabled by
+the @option{-fno-builtin} option the standard functions @code{calloc},
+@code{malloc}, @code{realloc}, and @code{free}, as well as the corresponding
+forms of C++ @code{operator new} and @code{operator delete} are implicitly
+associated as matching allocators and deallocators. In the following
+example @code{mydealloc} is the deallocator for pointers returned from
+@code{myalloc}.
+
+@smallexample
+void mydealloc (void*);
+
+__attribute__ ((malloc (mydealloc, 1))) void*
+myalloc (size_t);
+
+void f (void)
+@{
+ void *p = myalloc (32);
+ // @dots{}use p@dots{}
+ free (p); // warning: not a matching deallocator for myalloc
+ mydealloc (p); // ok
+@}
+@end smallexample
+
+In C++, the related option @option{-Wmismatched-new-delete} diagnoses
+mismatches involving either @code{operator new} or @code{operator delete}.
+
+Option @option{-Wmismatched-dealloc} is included in @option{-Wall}.
+
+@item -Wmultistatement-macros
+@opindex Wmultistatement-macros
+@opindex Wno-multistatement-macros
+Warn about unsafe multiple statement macros that appear to be guarded
+by a clause such as @code{if}, @code{else}, @code{for}, @code{switch}, or
+@code{while}, in which only the first statement is actually guarded after
+the macro is expanded.
+
+For example:
+
+@smallexample
+#define DOIT x++; y++
+if (c)
+ DOIT;
+@end smallexample
+
+will increment @code{y} unconditionally, not just when @code{c} holds.
+The can usually be fixed by wrapping the macro in a do-while loop:
+@smallexample
+#define DOIT do @{ x++; y++; @} while (0)
+if (c)
+ DOIT;
+@end smallexample
+
+This warning is enabled by @option{-Wall} in C and C++.
+
+@item -Wparentheses
+@opindex Wparentheses
+@opindex Wno-parentheses
+Warn if parentheses are omitted in certain contexts, such
+as when there is an assignment in a context where a truth value
+is expected, or when operators are nested whose precedence people
+often get confused about.
+
+Also warn if a comparison like @code{x<=y<=z} appears; this is
+equivalent to @code{(x<=y ? 1 : 0) <= z}, which is a different
+interpretation from that of ordinary mathematical notation.
+
+Also warn for dangerous uses of the GNU extension to
+@code{?:} with omitted middle operand. When the condition
+in the @code{?}: operator is a boolean expression, the omitted value is
+always 1. Often programmers expect it to be a value computed
+inside the conditional expression instead.
+
+For C++ this also warns for some cases of unnecessary parentheses in
+declarations, which can indicate an attempt at a function call instead
+of a declaration:
+@smallexample
+@{
+ // Declares a local variable called mymutex.
+ std::unique_lock<std::mutex> (mymutex);
+ // User meant std::unique_lock<std::mutex> lock (mymutex);
+@}
+@end smallexample
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wno-self-move @r{(C++ and Objective-C++ only)}
+@opindex Wself-move
+@opindex Wno-self-move
+This warning warns when a value is moved to itself with @code{std::move}.
+Such a @code{std::move} typically has no effect.
+
+@smallexample
+struct T @{
+@dots{}
+@};
+void fn()
+@{
+ T t;
+ @dots{}
+ t = std::move (t);
+@}
+@end smallexample
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wsequence-point
+@opindex Wsequence-point
+@opindex Wno-sequence-point
+Warn about code that may have undefined semantics because of violations
+of sequence point rules in the C and C++ standards.
+
+The C and C++ standards define the order in which expressions in a C/C++
+program are evaluated in terms of @dfn{sequence points}, which represent
+a partial ordering between the execution of parts of the program: those
+executed before the sequence point, and those executed after it. These
+occur after the evaluation of a full expression (one which is not part
+of a larger expression), after the evaluation of the first operand of a
+@code{&&}, @code{||}, @code{? :} or @code{,} (comma) operator, before a
+function is called (but after the evaluation of its arguments and the
+expression denoting the called function), and in certain other places.
+Other than as expressed by the sequence point rules, the order of
+evaluation of subexpressions of an expression is not specified. All
+these rules describe only a partial order rather than a total order,
+since, for example, if two functions are called within one expression
+with no sequence point between them, the order in which the functions
+are called is not specified. However, the standards committee have
+ruled that function calls do not overlap.
+
+It is not specified when between sequence points modifications to the
+values of objects take effect. Programs whose behavior depends on this
+have undefined behavior; the C and C++ standards specify that ``Between
+the previous and next sequence point an object shall have its stored
+value modified at most once by the evaluation of an expression.
+Furthermore, the prior value shall be read only to determine the value
+to be stored.''. If a program breaks these rules, the results on any
+particular implementation are entirely unpredictable.
+
+Examples of code with undefined behavior are @code{a = a++;}, @code{a[n]
+= b[n++]} and @code{a[i++] = i;}. Some more complicated cases are not
+diagnosed by this option, and it may give an occasional false positive
+result, but in general it has been found fairly effective at detecting
+this sort of problem in programs.
+
+The C++17 standard will define the order of evaluation of operands in
+more cases: in particular it requires that the right-hand side of an
+assignment be evaluated before the left-hand side, so the above
+examples are no longer undefined. But this option will still warn
+about them, to help people avoid writing code that is undefined in C
+and earlier revisions of C++.
+
+The standard is worded confusingly, therefore there is some debate
+over the precise meaning of the sequence point rules in subtle cases.
+Links to discussions of the problem, including proposed formal
+definitions, may be found on the GCC readings page, at
+@uref{https://gcc.gnu.org/@/readings.html}.
+
+This warning is enabled by @option{-Wall} for C and C++.
+
+@item -Wno-return-local-addr
+@opindex Wno-return-local-addr
+@opindex Wreturn-local-addr
+Do not warn about returning a pointer (or in C++, a reference) to a
+variable that goes out of scope after the function returns.
+
+@item -Wreturn-type
+@opindex Wreturn-type
+@opindex Wno-return-type
+Warn whenever a function is defined with a return type that defaults
+to @code{int}. Also warn about any @code{return} statement with no
+return value in a function whose return type is not @code{void}
+(falling off the end of the function body is considered returning
+without a value).
+
+For C only, warn about a @code{return} statement with an expression in a
+function whose return type is @code{void}, unless the expression type is
+also @code{void}. As a GNU extension, the latter case is accepted
+without a warning unless @option{-Wpedantic} is used. Attempting
+to use the return value of a non-@code{void} function other than @code{main}
+that flows off the end by reaching the closing curly brace that terminates
+the function is undefined.
+
+Unlike in C, in C++, flowing off the end of a non-@code{void} function other
+than @code{main} results in undefined behavior even when the value of
+the function is not used.
+
+This warning is enabled by default in C++ and by @option{-Wall} otherwise.
+
+@item -Wno-shift-count-negative
+@opindex Wshift-count-negative
+@opindex Wno-shift-count-negative
+Controls warnings if a shift count is negative.
+This warning is enabled by default.
+
+@item -Wno-shift-count-overflow
+@opindex Wshift-count-overflow
+@opindex Wno-shift-count-overflow
+Controls warnings if a shift count is greater than or equal to the bit width
+of the type. This warning is enabled by default.
+
+@item -Wshift-negative-value
+@opindex Wshift-negative-value
+@opindex Wno-shift-negative-value
+Warn if left shifting a negative value. This warning is enabled by
+@option{-Wextra} in C99 (and newer) and C++11 to C++17 modes.
+
+@item -Wno-shift-overflow
+@itemx -Wshift-overflow=@var{n}
+@opindex Wshift-overflow
+@opindex Wno-shift-overflow
+These options control warnings about left shift overflows.
+
+@table @gcctabopt
+@item -Wshift-overflow=1
+This is the warning level of @option{-Wshift-overflow} and is enabled
+by default in C99 and C++11 modes (and newer). This warning level does
+not warn about left-shifting 1 into the sign bit. (However, in C, such
+an overflow is still rejected in contexts where an integer constant expression
+is required.) No warning is emitted in C++20 mode (and newer), as signed left
+shifts always wrap.
+
+@item -Wshift-overflow=2
+This warning level also warns about left-shifting 1 into the sign bit,
+unless C++14 mode (or newer) is active.
+@end table
+
+@item -Wswitch
+@opindex Wswitch
+@opindex Wno-switch
+Warn whenever a @code{switch} statement has an index of enumerated type
+and lacks a @code{case} for one or more of the named codes of that
+enumeration. (The presence of a @code{default} label prevents this
+warning.) @code{case} labels outside the enumeration range also
+provoke warnings when this option is used (even if there is a
+@code{default} label).
+This warning is enabled by @option{-Wall}.
+
+@item -Wswitch-default
+@opindex Wswitch-default
+@opindex Wno-switch-default
+Warn whenever a @code{switch} statement does not have a @code{default}
+case.
+
+@item -Wswitch-enum
+@opindex Wswitch-enum
+@opindex Wno-switch-enum
+Warn whenever a @code{switch} statement has an index of enumerated type
+and lacks a @code{case} for one or more of the named codes of that
+enumeration. @code{case} labels outside the enumeration range also
+provoke warnings when this option is used. The only difference
+between @option{-Wswitch} and this option is that this option gives a
+warning about an omitted enumeration code even if there is a
+@code{default} label.
+
+@item -Wno-switch-bool
+@opindex Wswitch-bool
+@opindex Wno-switch-bool
+Do not warn when a @code{switch} statement has an index of boolean type
+and the case values are outside the range of a boolean type.
+It is possible to suppress this warning by casting the controlling
+expression to a type other than @code{bool}. For example:
+@smallexample
+@group
+switch ((int) (a == 4))
+ @{
+ @dots{}
+ @}
+@end group
+@end smallexample
+This warning is enabled by default for C and C++ programs.
+
+@item -Wno-switch-outside-range
+@opindex Wswitch-outside-range
+@opindex Wno-switch-outside-range
+This option controls warnings when a @code{switch} case has a value
+that is outside of its
+respective type range. This warning is enabled by default for
+C and C++ programs.
+
+@item -Wno-switch-unreachable
+@opindex Wswitch-unreachable
+@opindex Wno-switch-unreachable
+Do not warn when a @code{switch} statement contains statements between the
+controlling expression and the first case label, which will never be
+executed. For example:
+@smallexample
+@group
+switch (cond)
+ @{
+ i = 15;
+ @dots{}
+ case 5:
+ @dots{}
+ @}
+@end group
+@end smallexample
+@option{-Wswitch-unreachable} does not warn if the statement between the
+controlling expression and the first case label is just a declaration:
+@smallexample
+@group
+switch (cond)
+ @{
+ int i;
+ @dots{}
+ case 5:
+ i = 5;
+ @dots{}
+ @}
+@end group
+@end smallexample
+This warning is enabled by default for C and C++ programs.
+
+@item -Wsync-nand @r{(C and C++ only)}
+@opindex Wsync-nand
+@opindex Wno-sync-nand
+Warn when @code{__sync_fetch_and_nand} and @code{__sync_nand_and_fetch}
+built-in functions are used. These functions changed semantics in GCC 4.4.
+
+@item -Wtrivial-auto-var-init
+@opindex Wtrivial-auto-var-init
+@opindex Wno-trivial-auto-var-init
+Warn when @code{-ftrivial-auto-var-init} cannot initialize the automatic
+variable. A common situation is an automatic variable that is declared
+between the controlling expression and the first case label of a @code{switch}
+statement.
+
+@item -Wunused-but-set-parameter
+@opindex Wunused-but-set-parameter
+@opindex Wno-unused-but-set-parameter
+Warn whenever a function parameter is assigned to, but otherwise unused
+(aside from its declaration).
+
+To suppress this warning use the @code{unused} attribute
+(@pxref{Variable Attributes}).
+
+This warning is also enabled by @option{-Wunused} together with
+@option{-Wextra}.
+
+@item -Wunused-but-set-variable
+@opindex Wunused-but-set-variable
+@opindex Wno-unused-but-set-variable
+Warn whenever a local variable is assigned to, but otherwise unused
+(aside from its declaration).
+This warning is enabled by @option{-Wall}.
+
+To suppress this warning use the @code{unused} attribute
+(@pxref{Variable Attributes}).
+
+This warning is also enabled by @option{-Wunused}, which is enabled
+by @option{-Wall}.
+
+@item -Wunused-function
+@opindex Wunused-function
+@opindex Wno-unused-function
+Warn whenever a static function is declared but not defined or a
+non-inline static function is unused.
+This warning is enabled by @option{-Wall}.
+
+@item -Wunused-label
+@opindex Wunused-label
+@opindex Wno-unused-label
+Warn whenever a label is declared but not used.
+This warning is enabled by @option{-Wall}.
+
+To suppress this warning use the @code{unused} attribute
+(@pxref{Variable Attributes}).
+
+@item -Wunused-local-typedefs @r{(C, Objective-C, C++ and Objective-C++ only)}
+@opindex Wunused-local-typedefs
+@opindex Wno-unused-local-typedefs
+Warn when a typedef locally defined in a function is not used.
+This warning is enabled by @option{-Wall}.
+
+@item -Wunused-parameter
+@opindex Wunused-parameter
+@opindex Wno-unused-parameter
+Warn whenever a function parameter is unused aside from its declaration.
+
+To suppress this warning use the @code{unused} attribute
+(@pxref{Variable Attributes}).
+
+@item -Wno-unused-result
+@opindex Wunused-result
+@opindex Wno-unused-result
+Do not warn if a caller of a function marked with attribute
+@code{warn_unused_result} (@pxref{Function Attributes}) does not use
+its return value. The default is @option{-Wunused-result}.
+
+@item -Wunused-variable
+@opindex Wunused-variable
+@opindex Wno-unused-variable
+Warn whenever a local or static variable is unused aside from its
+declaration. This option implies @option{-Wunused-const-variable=1} for C,
+but not for C++. This warning is enabled by @option{-Wall}.
+
+To suppress this warning use the @code{unused} attribute
+(@pxref{Variable Attributes}).
+
+@item -Wunused-const-variable
+@itemx -Wunused-const-variable=@var{n}
+@opindex Wunused-const-variable
+@opindex Wno-unused-const-variable
+Warn whenever a constant static variable is unused aside from its declaration.
+@option{-Wunused-const-variable=1} is enabled by @option{-Wunused-variable}
+for C, but not for C++. In C this declares variable storage, but in C++ this
+is not an error since const variables take the place of @code{#define}s.
+
+To suppress this warning use the @code{unused} attribute
+(@pxref{Variable Attributes}).
+
+@table @gcctabopt
+@item -Wunused-const-variable=1
+This is the warning level that is enabled by @option{-Wunused-variable} for
+C. It warns only about unused static const variables defined in the main
+compilation unit, but not about static const variables declared in any
+header included.
+
+@item -Wunused-const-variable=2
+This warning level also warns for unused constant static variables in
+headers (excluding system headers). This is the warning level of
+@option{-Wunused-const-variable} and must be explicitly requested since
+in C++ this isn't an error and in C it might be harder to clean up all
+headers included.
+@end table
+
+@item -Wunused-value
+@opindex Wunused-value
+@opindex Wno-unused-value
+Warn whenever a statement computes a result that is explicitly not
+used. To suppress this warning cast the unused expression to
+@code{void}. This includes an expression-statement or the left-hand
+side of a comma expression that contains no side effects. For example,
+an expression such as @code{x[i,j]} causes a warning, while
+@code{x[(void)i,j]} does not.
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wunused
+@opindex Wunused
+@opindex Wno-unused
+All the above @option{-Wunused} options combined.
+
+In order to get a warning about an unused function parameter, you must
+either specify @option{-Wextra -Wunused} (note that @option{-Wall} implies
+@option{-Wunused}), or separately specify @option{-Wunused-parameter}.
+
+@item -Wuninitialized
+@opindex Wuninitialized
+@opindex Wno-uninitialized
+Warn if an object with automatic or allocated storage duration is used
+without having been initialized. In C++, also warn if a non-static
+reference or non-static @code{const} member appears in a class without
+constructors.
+
+In addition, passing a pointer (or in C++, a reference) to an uninitialized
+object to a @code{const}-qualified argument of a built-in function known to
+read the object is also diagnosed by this warning.
+(@option{-Wmaybe-uninitialized} is issued for ordinary functions.)
+
+If you want to warn about code that uses the uninitialized value of the
+variable in its own initializer, use the @option{-Winit-self} option.
+
+These warnings occur for individual uninitialized elements of
+structure, union or array variables as well as for variables that are
+uninitialized as a whole. They do not occur for variables or elements
+declared @code{volatile}. Because these warnings depend on
+optimization, the exact variables or elements for which there are
+warnings depend on the precise optimization options and version of GCC
+used.
+
+Note that there may be no warning about a variable that is used only
+to compute a value that itself is never used, because such
+computations may be deleted by data flow analysis before the warnings
+are printed.
+
+In C++, this warning also warns about using uninitialized objects in
+member-initializer-lists. For example, GCC warns about @code{b} being
+uninitialized in the following snippet:
+
+@smallexample
+struct A @{
+ int a;
+ int b;
+ A() : a(b) @{ @}
+@};
+@end smallexample
+
+@item -Wno-invalid-memory-model
+@opindex Winvalid-memory-model
+@opindex Wno-invalid-memory-model
+This option controls warnings
+for invocations of @ref{__atomic Builtins}, @ref{__sync Builtins},
+and the C11 atomic generic functions with a memory consistency argument
+that is either invalid for the operation or outside the range of values
+of the @code{memory_order} enumeration. For example, since the
+@code{__atomic_store} and @code{__atomic_store_n} built-ins are only
+defined for the relaxed, release, and sequentially consistent memory
+orders the following code is diagnosed:
+
+@smallexample
+void store (int *i)
+@{
+ __atomic_store_n (i, 0, memory_order_consume);
+@}
+@end smallexample
+
+@option{-Winvalid-memory-model} is enabled by default.
+
+@item -Wmaybe-uninitialized
+@opindex Wmaybe-uninitialized
+@opindex Wno-maybe-uninitialized
+For an object with automatic or allocated storage duration, if there exists
+a path from the function entry to a use of the object that is initialized,
+but there exist some other paths for which the object is not initialized,
+the compiler emits a warning if it cannot prove the uninitialized paths
+are not executed at run time.
+
+In addition, passing a pointer (or in C++, a reference) to an uninitialized
+object to a @code{const}-qualified function argument is also diagnosed by
+this warning. (@option{-Wuninitialized} is issued for built-in functions
+known to read the object.) Annotating the function with attribute
+@code{access (none)} indicates that the argument isn't used to access
+the object and avoids the warning (@pxref{Common Function Attributes}).
+
+These warnings are only possible in optimizing compilation, because otherwise
+GCC does not keep track of the state of variables.
+
+These warnings are made optional because GCC may not be able to determine when
+the code is correct in spite of appearing to have an error. Here is one
+example of how this can happen:
+
+@smallexample
+@group
+@{
+ int x;
+ switch (y)
+ @{
+ case 1: x = 1;
+ break;
+ case 2: x = 4;
+ break;
+ case 3: x = 5;
+ @}
+ foo (x);
+@}
+@end group
+@end smallexample
+
+@noindent
+If the value of @code{y} is always 1, 2 or 3, then @code{x} is
+always initialized, but GCC doesn't know this. To suppress the
+warning, you need to provide a default case with assert(0) or
+similar code.
+
+@cindex @code{longjmp} warnings
+This option also warns when a non-volatile automatic variable might be
+changed by a call to @code{longjmp}.
+The compiler sees only the calls to @code{setjmp}. It cannot know
+where @code{longjmp} will be called; in fact, a signal handler could
+call it at any point in the code. As a result, you may get a warning
+even when there is in fact no problem because @code{longjmp} cannot
+in fact be called at the place that would cause a problem.
+
+Some spurious warnings can be avoided if you declare all the functions
+you use that never return as @code{noreturn}. @xref{Function
+Attributes}.
+
+This warning is enabled by @option{-Wall} or @option{-Wextra}.
+
+@item -Wunknown-pragmas
+@opindex Wunknown-pragmas
+@opindex Wno-unknown-pragmas
+@cindex warning for unknown pragmas
+@cindex unknown pragmas, warning
+@cindex pragmas, warning of unknown
+Warn when a @code{#pragma} directive is encountered that is not understood by
+GCC@. If this command-line option is used, warnings are even issued
+for unknown pragmas in system header files. This is not the case if
+the warnings are only enabled by the @option{-Wall} command-line option.
+
+@item -Wno-pragmas
+@opindex Wno-pragmas
+@opindex Wpragmas
+Do not warn about misuses of pragmas, such as incorrect parameters,
+invalid syntax, or conflicts between pragmas. See also
+@option{-Wunknown-pragmas}.
+
+@item -Wno-prio-ctor-dtor
+@opindex Wno-prio-ctor-dtor
+@opindex Wprio-ctor-dtor
+Do not warn if a priority from 0 to 100 is used for constructor or destructor.
+The use of constructor and destructor attributes allow you to assign a
+priority to the constructor/destructor to control its order of execution
+before @code{main} is called or after it returns. The priority values must be
+greater than 100 as the compiler reserves priority values between 0--100 for
+the implementation.
+
+@item -Wstrict-aliasing
+@opindex Wstrict-aliasing
+@opindex Wno-strict-aliasing
+This option is only active when @option{-fstrict-aliasing} is active.
+It warns about code that might break the strict aliasing rules that the
+compiler is using for optimization. The warning does not catch all
+cases, but does attempt to catch the more common pitfalls. It is
+included in @option{-Wall}.
+It is equivalent to @option{-Wstrict-aliasing=3}
+
+@item -Wstrict-aliasing=n
+@opindex Wstrict-aliasing=n
+This option is only active when @option{-fstrict-aliasing} is active.
+It warns about code that might break the strict aliasing rules that the
+compiler is using for optimization.
+Higher levels correspond to higher accuracy (fewer false positives).
+Higher levels also correspond to more effort, similar to the way @option{-O}
+works.
+@option{-Wstrict-aliasing} is equivalent to @option{-Wstrict-aliasing=3}.
+
+Level 1: Most aggressive, quick, least accurate.
+Possibly useful when higher levels
+do not warn but @option{-fstrict-aliasing} still breaks the code, as it has very few
+false negatives. However, it has many false positives.
+Warns for all pointer conversions between possibly incompatible types,
+even if never dereferenced. Runs in the front end only.
+
+Level 2: Aggressive, quick, not too precise.
+May still have many false positives (not as many as level 1 though),
+and few false negatives (but possibly more than level 1).
+Unlike level 1, it only warns when an address is taken. Warns about
+incomplete types. Runs in the front end only.
+
+Level 3 (default for @option{-Wstrict-aliasing}):
+Should have very few false positives and few false
+negatives. Slightly slower than levels 1 or 2 when optimization is enabled.
+Takes care of the common pun+dereference pattern in the front end:
+@code{*(int*)&some_float}.
+If optimization is enabled, it also runs in the back end, where it deals
+with multiple statement cases using flow-sensitive points-to information.
+Only warns when the converted pointer is dereferenced.
+Does not warn about incomplete types.
+
+@item -Wstrict-overflow
+@itemx -Wstrict-overflow=@var{n}
+@opindex Wstrict-overflow
+@opindex Wno-strict-overflow
+This option is only active when signed overflow is undefined.
+It warns about cases where the compiler optimizes based on the
+assumption that signed overflow does not occur. Note that it does not
+warn about all cases where the code might overflow: it only warns
+about cases where the compiler implements some optimization. Thus
+this warning depends on the optimization level.
+
+An optimization that assumes that signed overflow does not occur is
+perfectly safe if the values of the variables involved are such that
+overflow never does, in fact, occur. Therefore this warning can
+easily give a false positive: a warning about code that is not
+actually a problem. To help focus on important issues, several
+warning levels are defined. No warnings are issued for the use of
+undefined signed overflow when estimating how many iterations a loop
+requires, in particular when determining whether a loop will be
+executed at all.
+
+@table @gcctabopt
+@item -Wstrict-overflow=1
+Warn about cases that are both questionable and easy to avoid. For
+example the compiler simplifies
+@code{x + 1 > x} to @code{1}. This level of
+@option{-Wstrict-overflow} is enabled by @option{-Wall}; higher levels
+are not, and must be explicitly requested.
+
+@item -Wstrict-overflow=2
+Also warn about other cases where a comparison is simplified to a
+constant. For example: @code{abs (x) >= 0}. This can only be
+simplified when signed integer overflow is undefined, because
+@code{abs (INT_MIN)} overflows to @code{INT_MIN}, which is less than
+zero. @option{-Wstrict-overflow} (with no level) is the same as
+@option{-Wstrict-overflow=2}.
+
+@item -Wstrict-overflow=3
+Also warn about other cases where a comparison is simplified. For
+example: @code{x + 1 > 1} is simplified to @code{x > 0}.
+
+@item -Wstrict-overflow=4
+Also warn about other simplifications not covered by the above cases.
+For example: @code{(x * 10) / 5} is simplified to @code{x * 2}.
+
+@item -Wstrict-overflow=5
+Also warn about cases where the compiler reduces the magnitude of a
+constant involved in a comparison. For example: @code{x + 2 > y} is
+simplified to @code{x + 1 >= y}. This is reported only at the
+highest warning level because this simplification applies to many
+comparisons, so this warning level gives a very large number of
+false positives.
+@end table
+
+@item -Wstring-compare
+@opindex Wstring-compare
+@opindex Wno-string-compare
+Warn for calls to @code{strcmp} and @code{strncmp} whose result is
+determined to be either zero or non-zero in tests for such equality
+owing to the length of one argument being greater than the size of
+the array the other argument is stored in (or the bound in the case
+of @code{strncmp}). Such calls could be mistakes. For example,
+the call to @code{strcmp} below is diagnosed because its result is
+necessarily non-zero irrespective of the contents of the array @code{a}.
+
+@smallexample
+extern char a[4];
+void f (char *d)
+@{
+ strcpy (d, "string");
+ @dots{}
+ if (0 == strcmp (a, d)) // cannot be true
+ puts ("a and d are the same");
+@}
+@end smallexample
+
+@option{-Wstring-compare} is enabled by @option{-Wextra}.
+
+@item -Wno-stringop-overflow
+@item -Wstringop-overflow
+@itemx -Wstringop-overflow=@var{type}
+@opindex Wstringop-overflow
+@opindex Wno-stringop-overflow
+Warn for calls to string manipulation functions such as @code{memcpy} and
+@code{strcpy} that are determined to overflow the destination buffer. The
+optional argument is one greater than the type of Object Size Checking to
+perform to determine the size of the destination. @xref{Object Size Checking}.
+The argument is meaningful only for functions that operate on character arrays
+but not for raw memory functions like @code{memcpy} which always make use
+of Object Size type-0. The option also warns for calls that specify a size
+in excess of the largest possible object or at most @code{SIZE_MAX / 2} bytes.
+The option produces the best results with optimization enabled but can detect
+a small subset of simple buffer overflows even without optimization in
+calls to the GCC built-in functions like @code{__builtin_memcpy} that
+correspond to the standard functions. In any case, the option warns about
+just a subset of buffer overflows detected by the corresponding overflow
+checking built-ins. For example, the option issues a warning for
+the @code{strcpy} call below because it copies at least 5 characters
+(the string @code{"blue"} including the terminating NUL) into the buffer
+of size 4.
+
+@smallexample
+enum Color @{ blue, purple, yellow @};
+const char* f (enum Color clr)
+@{
+ static char buf [4];
+ const char *str;
+ switch (clr)
+ @{
+ case blue: str = "blue"; break;
+ case purple: str = "purple"; break;
+ case yellow: str = "yellow"; break;
+ @}
+
+ return strcpy (buf, str); // warning here
+@}
+@end smallexample
+
+Option @option{-Wstringop-overflow=2} is enabled by default.
+
+@table @gcctabopt
+@item -Wstringop-overflow
+@itemx -Wstringop-overflow=1
+@opindex Wstringop-overflow
+@opindex Wno-stringop-overflow
+The @option{-Wstringop-overflow=1} option uses type-zero Object Size Checking
+to determine the sizes of destination objects. At this setting the option
+does not warn for writes past the end of subobjects of larger objects accessed
+by pointers unless the size of the largest surrounding object is known. When
+the destination may be one of several objects it is assumed to be the largest
+one of them. On Linux systems, when optimization is enabled at this setting
+the option warns for the same code as when the @code{_FORTIFY_SOURCE} macro
+is defined to a non-zero value.
+
+@item -Wstringop-overflow=2
+The @option{-Wstringop-overflow=2} option uses type-one Object Size Checking
+to determine the sizes of destination objects. At this setting the option
+warns about overflows when writing to members of the largest complete
+objects whose exact size is known. However, it does not warn for excessive
+writes to the same members of unknown objects referenced by pointers since
+they may point to arrays containing unknown numbers of elements. This is
+the default setting of the option.
+
+@item -Wstringop-overflow=3
+The @option{-Wstringop-overflow=3} option uses type-two Object Size Checking
+to determine the sizes of destination objects. At this setting the option
+warns about overflowing the smallest object or data member. This is the
+most restrictive setting of the option that may result in warnings for safe
+code.
+
+@item -Wstringop-overflow=4
+The @option{-Wstringop-overflow=4} option uses type-three Object Size Checking
+to determine the sizes of destination objects. At this setting the option
+warns about overflowing any data members, and when the destination is
+one of several objects it uses the size of the largest of them to decide
+whether to issue a warning. Similarly to @option{-Wstringop-overflow=3} this
+setting of the option may result in warnings for benign code.
+@end table
+
+@item -Wno-stringop-overread
+@opindex Wstringop-overread
+@opindex Wno-stringop-overread
+Warn for calls to string manipulation functions such as @code{memchr}, or
+@code{strcpy} that are determined to read past the end of the source
+sequence.
+
+Option @option{-Wstringop-overread} is enabled by default.
+
+@item -Wno-stringop-truncation
+@opindex Wstringop-truncation
+@opindex Wno-stringop-truncation
+Do not warn for calls to bounded string manipulation functions
+such as @code{strncat},
+@code{strncpy}, and @code{stpncpy} that may either truncate the copied string
+or leave the destination unchanged.
+
+In the following example, the call to @code{strncat} specifies a bound that
+is less than the length of the source string. As a result, the copy of
+the source will be truncated and so the call is diagnosed. To avoid the
+warning use @code{bufsize - strlen (buf) - 1)} as the bound.
+
+@smallexample
+void append (char *buf, size_t bufsize)
+@{
+ strncat (buf, ".txt", 3);
+@}
+@end smallexample
+
+As another example, the following call to @code{strncpy} results in copying
+to @code{d} just the characters preceding the terminating NUL, without
+appending the NUL to the end. Assuming the result of @code{strncpy} is
+necessarily a NUL-terminated string is a common mistake, and so the call
+is diagnosed. To avoid the warning when the result is not expected to be
+NUL-terminated, call @code{memcpy} instead.
+
+@smallexample
+void copy (char *d, const char *s)
+@{
+ strncpy (d, s, strlen (s));
+@}
+@end smallexample
+
+In the following example, the call to @code{strncpy} specifies the size
+of the destination buffer as the bound. If the length of the source
+string is equal to or greater than this size the result of the copy will
+not be NUL-terminated. Therefore, the call is also diagnosed. To avoid
+the warning, specify @code{sizeof buf - 1} as the bound and set the last
+element of the buffer to @code{NUL}.
+
+@smallexample
+void copy (const char *s)
+@{
+ char buf[80];
+ strncpy (buf, s, sizeof buf);
+ @dots{}
+@}
+@end smallexample
+
+In situations where a character array is intended to store a sequence
+of bytes with no terminating @code{NUL} such an array may be annotated
+with attribute @code{nonstring} to avoid this warning. Such arrays,
+however, are not suitable arguments to functions that expect
+@code{NUL}-terminated strings. To help detect accidental misuses of
+such arrays GCC issues warnings unless it can prove that the use is
+safe. @xref{Common Variable Attributes}.
+
+@item -Wsuggest-attribute=@r{[}pure@r{|}const@r{|}noreturn@r{|}format@r{|}cold@r{|}malloc@r{]}
+@opindex Wsuggest-attribute=
+@opindex Wno-suggest-attribute=
+Warn for cases where adding an attribute may be beneficial. The
+attributes currently supported are listed below.
+
+@table @gcctabopt
+@item -Wsuggest-attribute=pure
+@itemx -Wsuggest-attribute=const
+@itemx -Wsuggest-attribute=noreturn
+@itemx -Wmissing-noreturn
+@itemx -Wsuggest-attribute=malloc
+@opindex Wsuggest-attribute=pure
+@opindex Wno-suggest-attribute=pure
+@opindex Wsuggest-attribute=const
+@opindex Wno-suggest-attribute=const
+@opindex Wsuggest-attribute=noreturn
+@opindex Wno-suggest-attribute=noreturn
+@opindex Wmissing-noreturn
+@opindex Wno-missing-noreturn
+@opindex Wsuggest-attribute=malloc
+@opindex Wno-suggest-attribute=malloc
+
+Warn about functions that might be candidates for attributes
+@code{pure}, @code{const} or @code{noreturn} or @code{malloc}. The compiler
+only warns for functions visible in other compilation units or (in the case of
+@code{pure} and @code{const}) if it cannot prove that the function returns
+normally. A function returns normally if it doesn't contain an infinite loop or
+return abnormally by throwing, calling @code{abort} or trapping. This analysis
+requires option @option{-fipa-pure-const}, which is enabled by default at
+@option{-O} and higher. Higher optimization levels improve the accuracy
+of the analysis.
+
+@item -Wsuggest-attribute=format
+@itemx -Wmissing-format-attribute
+@opindex Wsuggest-attribute=format
+@opindex Wmissing-format-attribute
+@opindex Wno-suggest-attribute=format
+@opindex Wno-missing-format-attribute
+@opindex Wformat
+@opindex Wno-format
+
+Warn about function pointers that might be candidates for @code{format}
+attributes. Note these are only possible candidates, not absolute ones.
+GCC guesses that function pointers with @code{format} attributes that
+are used in assignment, initialization, parameter passing or return
+statements should have a corresponding @code{format} attribute in the
+resulting type. I.e.@: the left-hand side of the assignment or
+initialization, the type of the parameter variable, or the return type
+of the containing function respectively should also have a @code{format}
+attribute to avoid the warning.
+
+GCC also warns about function definitions that might be
+candidates for @code{format} attributes. Again, these are only
+possible candidates. GCC guesses that @code{format} attributes
+might be appropriate for any function that calls a function like
+@code{vprintf} or @code{vscanf}, but this might not always be the
+case, and some functions for which @code{format} attributes are
+appropriate may not be detected.
+
+@item -Wsuggest-attribute=cold
+@opindex Wsuggest-attribute=cold
+@opindex Wno-suggest-attribute=cold
+
+Warn about functions that might be candidates for @code{cold} attribute. This
+is based on static detection and generally only warns about functions which
+always leads to a call to another @code{cold} function such as wrappers of
+C++ @code{throw} or fatal error reporting functions leading to @code{abort}.
+@end table
+
+@item -Walloc-zero
+@opindex Wno-alloc-zero
+@opindex Walloc-zero
+Warn about calls to allocation functions decorated with attribute
+@code{alloc_size} that specify zero bytes, including those to the built-in
+forms of the functions @code{aligned_alloc}, @code{alloca}, @code{calloc},
+@code{malloc}, and @code{realloc}. Because the behavior of these functions
+when called with a zero size differs among implementations (and in the case
+of @code{realloc} has been deprecated) relying on it may result in subtle
+portability bugs and should be avoided.
+
+@item -Walloc-size-larger-than=@var{byte-size}
+@opindex Walloc-size-larger-than=
+@opindex Wno-alloc-size-larger-than
+Warn about calls to functions decorated with attribute @code{alloc_size}
+that attempt to allocate objects larger than the specified number of bytes,
+or where the result of the size computation in an integer type with infinite
+precision would exceed the value of @samp{PTRDIFF_MAX} on the target.
+@option{-Walloc-size-larger-than=}@samp{PTRDIFF_MAX} is enabled by default.
+Warnings controlled by the option can be disabled either by specifying
+@var{byte-size} of @samp{SIZE_MAX} or more or by
+@option{-Wno-alloc-size-larger-than}.
+@xref{Function Attributes}.
+
+@item -Wno-alloc-size-larger-than
+@opindex Wno-alloc-size-larger-than
+Disable @option{-Walloc-size-larger-than=} warnings. The option is
+equivalent to @option{-Walloc-size-larger-than=}@samp{SIZE_MAX} or
+larger.
+
+@item -Walloca
+@opindex Wno-alloca
+@opindex Walloca
+This option warns on all uses of @code{alloca} in the source.
+
+@item -Walloca-larger-than=@var{byte-size}
+@opindex Walloca-larger-than=
+@opindex Wno-alloca-larger-than
+This option warns on calls to @code{alloca} with an integer argument whose
+value is either zero, or that is not bounded by a controlling predicate
+that limits its value to at most @var{byte-size}. It also warns for calls
+to @code{alloca} where the bound value is unknown. Arguments of non-integer
+types are considered unbounded even if they appear to be constrained to
+the expected range.
+
+For example, a bounded case of @code{alloca} could be:
+
+@smallexample
+void func (size_t n)
+@{
+ void *p;
+ if (n <= 1000)
+ p = alloca (n);
+ else
+ p = malloc (n);
+ f (p);
+@}
+@end smallexample
+
+In the above example, passing @code{-Walloca-larger-than=1000} would not
+issue a warning because the call to @code{alloca} is known to be at most
+1000 bytes. However, if @code{-Walloca-larger-than=500} were passed,
+the compiler would emit a warning.
+
+Unbounded uses, on the other hand, are uses of @code{alloca} with no
+controlling predicate constraining its integer argument. For example:
+
+@smallexample
+void func ()
+@{
+ void *p = alloca (n);
+ f (p);
+@}
+@end smallexample
+
+If @code{-Walloca-larger-than=500} were passed, the above would trigger
+a warning, but this time because of the lack of bounds checking.
+
+Note, that even seemingly correct code involving signed integers could
+cause a warning:
+
+@smallexample
+void func (signed int n)
+@{
+ if (n < 500)
+ @{
+ p = alloca (n);
+ f (p);
+ @}
+@}
+@end smallexample
+
+In the above example, @var{n} could be negative, causing a larger than
+expected argument to be implicitly cast into the @code{alloca} call.
+
+This option also warns when @code{alloca} is used in a loop.
+
+@option{-Walloca-larger-than=}@samp{PTRDIFF_MAX} is enabled by default
+but is usually only effective when @option{-ftree-vrp} is active (default
+for @option{-O2} and above).
+
+See also @option{-Wvla-larger-than=}@samp{byte-size}.
+
+@item -Wno-alloca-larger-than
+@opindex Wno-alloca-larger-than
+Disable @option{-Walloca-larger-than=} warnings. The option is
+equivalent to @option{-Walloca-larger-than=}@samp{SIZE_MAX} or larger.
+
+@item -Warith-conversion
+@opindex Warith-conversion
+@opindex Wno-arith-conversion
+Do warn about implicit conversions from arithmetic operations even
+when conversion of the operands to the same type cannot change their
+values. This affects warnings from @option{-Wconversion},
+@option{-Wfloat-conversion}, and @option{-Wsign-conversion}.
+
+@smallexample
+@group
+void f (char c, int i)
+@{
+ c = c + i; // warns with @option{-Wconversion}
+ c = c + 1; // only warns with @option{-Warith-conversion}
+@}
+@end group
+@end smallexample
+
+@item -Warray-bounds
+@itemx -Warray-bounds=@var{n}
+@opindex Wno-array-bounds
+@opindex Warray-bounds
+Warn about out of bounds subscripts or offsets into arrays. This warning
+is enabled by @option{-Wall}. It is more effective when @option{-ftree-vrp}
+is active (the default for @option{-O2} and above) but a subset of instances
+are issued even without optimization.
+
+@table @gcctabopt
+@item -Warray-bounds=1
+This is the default warning level of @option{-Warray-bounds} and is enabled
+by @option{-Wall}; higher levels are not, and must be explicitly requested.
+
+@item -Warray-bounds=2
+This warning level also warns about out of bounds accesses to trailing
+struct members of one-element array types (@pxref{Zero Length}) and about
+the intermediate results of pointer arithmetic that may yield out of bounds
+values. This warning level may give a larger number of false positives and
+is deactivated by default.
+@end table
+
+@item -Warray-compare
+@opindex Warray-compare
+@opindex Wno-array-compare
+Warn about equality and relational comparisons between two operands of array
+type. This comparison was deprecated in C++20. For example:
+
+@smallexample
+int arr1[5];
+int arr2[5];
+bool same = arr1 == arr2;
+@end smallexample
+
+@option{-Warray-compare} is enabled by @option{-Wall}.
+
+@item -Warray-parameter
+@itemx -Warray-parameter=@var{n}
+@opindex Wno-array-parameter
+Warn about redeclarations of functions involving arguments of array or
+pointer types of inconsistent kinds or forms, and enable the detection
+of out-of-bounds accesses to such parameters by warnings such as
+@option{-Warray-bounds}.
+
+If the first function declaration uses the array form the bound specified
+in the array is assumed to be the minimum number of elements expected to
+be provided in calls to the function and the maximum number of elements
+accessed by it. Failing to provide arguments of sufficient size or accessing
+more than the maximum number of elements may be diagnosed by warnings such
+as @option{-Warray-bounds}. At level 1 the warning diagnoses inconsistencies
+involving array parameters declared using the @code{T[static N]} form.
+
+For example, the warning triggers for the following redeclarations because
+the first one allows an array of any size to be passed to @code{f} while
+the second one with the keyword @code{static} specifies that the array
+argument must have at least four elements.
+
+@smallexample
+void f (int[static 4]);
+void f (int[]); // warning (inconsistent array form)
+
+void g (void)
+@{
+ int *p = (int *)malloc (4);
+ f (p); // warning (array too small)
+ @dots{}
+@}
+@end smallexample
+
+At level 2 the warning also triggers for redeclarations involving any other
+inconsistency in array or pointer argument forms denoting array sizes.
+Pointers and arrays of unspecified bound are considered equivalent and do
+not trigger a warning.
+
+@smallexample
+void g (int*);
+void g (int[]); // no warning
+void g (int[8]); // warning (inconsistent array bound)
+@end smallexample
+
+@option{-Warray-parameter=2} is included in @option{-Wall}. The
+@option{-Wvla-parameter} option triggers warnings for similar inconsistencies
+involving Variable Length Array arguments.
+
+@item -Wattribute-alias=@var{n}
+@itemx -Wno-attribute-alias
+@opindex Wattribute-alias
+@opindex Wno-attribute-alias
+Warn about declarations using the @code{alias} and similar attributes whose
+target is incompatible with the type of the alias.
+@xref{Function Attributes,,Declaring Attributes of Functions}.
+
+@table @gcctabopt
+@item -Wattribute-alias=1
+The default warning level of the @option{-Wattribute-alias} option diagnoses
+incompatibilities between the type of the alias declaration and that of its
+target. Such incompatibilities are typically indicative of bugs.
+
+@item -Wattribute-alias=2
+
+At this level @option{-Wattribute-alias} also diagnoses cases where
+the attributes of the alias declaration are more restrictive than the
+attributes applied to its target. These mismatches can potentially
+result in incorrect code generation. In other cases they may be
+benign and could be resolved simply by adding the missing attribute to
+the target. For comparison, see the @option{-Wmissing-attributes}
+option, which controls diagnostics when the alias declaration is less
+restrictive than the target, rather than more restrictive.
+
+Attributes considered include @code{alloc_align}, @code{alloc_size},
+@code{cold}, @code{const}, @code{hot}, @code{leaf}, @code{malloc},
+@code{nonnull}, @code{noreturn}, @code{nothrow}, @code{pure},
+@code{returns_nonnull}, and @code{returns_twice}.
+@end table
+
+@option{-Wattribute-alias} is equivalent to @option{-Wattribute-alias=1}.
+This is the default. You can disable these warnings with either
+@option{-Wno-attribute-alias} or @option{-Wattribute-alias=0}.
+
+@item -Wbidi-chars=@r{[}none@r{|}unpaired@r{|}any@r{|}ucn@r{]}
+@opindex Wbidi-chars=
+@opindex Wbidi-chars
+@opindex Wno-bidi-chars
+Warn about possibly misleading UTF-8 bidirectional control characters in
+comments, string literals, character constants, and identifiers. Such
+characters can change left-to-right writing direction into right-to-left
+(and vice versa), which can cause confusion between the logical order and
+visual order. This may be dangerous; for instance, it may seem that a piece
+of code is not commented out, whereas it in fact is.
+
+There are three levels of warning supported by GCC@. The default is
+@option{-Wbidi-chars=unpaired}, which warns about improperly terminated
+bidi contexts. @option{-Wbidi-chars=none} turns the warning off.
+@option{-Wbidi-chars=any} warns about any use of bidirectional control
+characters.
+
+By default, this warning does not warn about UCNs. It is, however, possible
+to turn on such checking by using @option{-Wbidi-chars=unpaired,ucn} or
+@option{-Wbidi-chars=any,ucn}. Using @option{-Wbidi-chars=ucn} is valid,
+and is equivalent to @option{-Wbidi-chars=unpaired,ucn}, if no previous
+@option{-Wbidi-chars=any} was specified.
+
+@item -Wbool-compare
+@opindex Wno-bool-compare
+@opindex Wbool-compare
+Warn about boolean expression compared with an integer value different from
+@code{true}/@code{false}. For instance, the following comparison is
+always false:
+@smallexample
+int n = 5;
+@dots{}
+if ((n > 1) == 2) @{ @dots{} @}
+@end smallexample
+This warning is enabled by @option{-Wall}.
+
+@item -Wbool-operation
+@opindex Wno-bool-operation
+@opindex Wbool-operation
+Warn about suspicious operations on expressions of a boolean type. For
+instance, bitwise negation of a boolean is very likely a bug in the program.
+For C, this warning also warns about incrementing or decrementing a boolean,
+which rarely makes sense. (In C++, decrementing a boolean is always invalid.
+Incrementing a boolean is invalid in C++17, and deprecated otherwise.)
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wduplicated-branches
+@opindex Wno-duplicated-branches
+@opindex Wduplicated-branches
+Warn when an if-else has identical branches. This warning detects cases like
+@smallexample
+if (p != NULL)
+ return 0;
+else
+ return 0;
+@end smallexample
+It doesn't warn when both branches contain just a null statement. This warning
+also warn for conditional operators:
+@smallexample
+ int i = x ? *p : *p;
+@end smallexample
+
+@item -Wduplicated-cond
+@opindex Wno-duplicated-cond
+@opindex Wduplicated-cond
+Warn about duplicated conditions in an if-else-if chain. For instance,
+warn for the following code:
+@smallexample
+if (p->q != NULL) @{ @dots{} @}
+else if (p->q != NULL) @{ @dots{} @}
+@end smallexample
+
+@item -Wframe-address
+@opindex Wno-frame-address
+@opindex Wframe-address
+Warn when the @samp{__builtin_frame_address} or @samp{__builtin_return_address}
+is called with an argument greater than 0. Such calls may return indeterminate
+values or crash the program. The warning is included in @option{-Wall}.
+
+@item -Wno-discarded-qualifiers @r{(C and Objective-C only)}
+@opindex Wno-discarded-qualifiers
+@opindex Wdiscarded-qualifiers
+Do not warn if type qualifiers on pointers are being discarded.
+Typically, the compiler warns if a @code{const char *} variable is
+passed to a function that takes a @code{char *} parameter. This option
+can be used to suppress such a warning.
+
+@item -Wno-discarded-array-qualifiers @r{(C and Objective-C only)}
+@opindex Wno-discarded-array-qualifiers
+@opindex Wdiscarded-array-qualifiers
+Do not warn if type qualifiers on arrays which are pointer targets
+are being discarded. Typically, the compiler warns if a
+@code{const int (*)[]} variable is passed to a function that
+takes a @code{int (*)[]} parameter. This option can be used to
+suppress such a warning.
+
+@item -Wno-incompatible-pointer-types @r{(C and Objective-C only)}
+@opindex Wno-incompatible-pointer-types
+@opindex Wincompatible-pointer-types
+Do not warn when there is a conversion between pointers that have incompatible
+types. This warning is for cases not covered by @option{-Wno-pointer-sign},
+which warns for pointer argument passing or assignment with different
+signedness.
+
+@item -Wno-int-conversion @r{(C and Objective-C only)}
+@opindex Wno-int-conversion
+@opindex Wint-conversion
+Do not warn about incompatible integer to pointer and pointer to integer
+conversions. This warning is about implicit conversions; for explicit
+conversions the warnings @option{-Wno-int-to-pointer-cast} and
+@option{-Wno-pointer-to-int-cast} may be used.
+
+@item -Wzero-length-bounds
+@opindex Wzero-length-bounds
+@opindex Wzero-length-bounds
+Warn about accesses to elements of zero-length array members that might
+overlap other members of the same object. Declaring interior zero-length
+arrays is discouraged because accesses to them are undefined. See
+@xref{Zero Length}.
+
+For example, the first two stores in function @code{bad} are diagnosed
+because the array elements overlap the subsequent members @code{b} and
+@code{c}. The third store is diagnosed by @option{-Warray-bounds}
+because it is beyond the bounds of the enclosing object.
+
+@smallexample
+struct X @{ int a[0]; int b, c; @};
+struct X x;
+
+void bad (void)
+@{
+ x.a[0] = 0; // -Wzero-length-bounds
+ x.a[1] = 1; // -Wzero-length-bounds
+ x.a[2] = 2; // -Warray-bounds
+@}
+@end smallexample
+
+Option @option{-Wzero-length-bounds} is enabled by @option{-Warray-bounds}.
+
+@item -Wno-div-by-zero
+@opindex Wno-div-by-zero
+@opindex Wdiv-by-zero
+Do not warn about compile-time integer division by zero. Floating-point
+division by zero is not warned about, as it can be a legitimate way of
+obtaining infinities and NaNs.
+
+@item -Wsystem-headers
+@opindex Wsystem-headers
+@opindex Wno-system-headers
+@cindex warnings from system headers
+@cindex system headers, warnings from
+Print warning messages for constructs found in system header files.
+Warnings from system headers are normally suppressed, on the assumption
+that they usually do not indicate real problems and would only make the
+compiler output harder to read. Using this command-line option tells
+GCC to emit warnings from system headers as if they occurred in user
+code. However, note that using @option{-Wall} in conjunction with this
+option does @emph{not} warn about unknown pragmas in system
+headers---for that, @option{-Wunknown-pragmas} must also be used.
+
+@item -Wtautological-compare
+@opindex Wtautological-compare
+@opindex Wno-tautological-compare
+Warn if a self-comparison always evaluates to true or false. This
+warning detects various mistakes such as:
+@smallexample
+int i = 1;
+@dots{}
+if (i > i) @{ @dots{} @}
+@end smallexample
+
+This warning also warns about bitwise comparisons that always evaluate
+to true or false, for instance:
+@smallexample
+if ((a & 16) == 10) @{ @dots{} @}
+@end smallexample
+will always be false.
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wtrampolines
+@opindex Wtrampolines
+@opindex Wno-trampolines
+Warn about trampolines generated for pointers to nested functions.
+A trampoline is a small piece of data or code that is created at run
+time on the stack when the address of a nested function is taken, and is
+used to call the nested function indirectly. For some targets, it is
+made up of data only and thus requires no special treatment. But, for
+most targets, it is made up of code and thus requires the stack to be
+made executable in order for the program to work properly.
+
+@item -Wfloat-equal
+@opindex Wfloat-equal
+@opindex Wno-float-equal
+Warn if floating-point values are used in equality comparisons.
+
+The idea behind this is that sometimes it is convenient (for the
+programmer) to consider floating-point values as approximations to
+infinitely precise real numbers. If you are doing this, then you need
+to compute (by analyzing the code, or in some other way) the maximum or
+likely maximum error that the computation introduces, and allow for it
+when performing comparisons (and when producing output, but that's a
+different problem). In particular, instead of testing for equality, you
+should check to see whether the two values have ranges that overlap; and
+this is done with the relational operators, so equality comparisons are
+probably mistaken.
+
+@item -Wtraditional @r{(C and Objective-C only)}
+@opindex Wtraditional
+@opindex Wno-traditional
+Warn about certain constructs that behave differently in traditional and
+ISO C@. Also warn about ISO C constructs that have no traditional C
+equivalent, and/or problematic constructs that should be avoided.
+
+@itemize @bullet
+@item
+Macro parameters that appear within string literals in the macro body.
+In traditional C macro replacement takes place within string literals,
+but in ISO C it does not.
+
+@item
+In traditional C, some preprocessor directives did not exist.
+Traditional preprocessors only considered a line to be a directive
+if the @samp{#} appeared in column 1 on the line. Therefore
+@option{-Wtraditional} warns about directives that traditional C
+understands but ignores because the @samp{#} does not appear as the
+first character on the line. It also suggests you hide directives like
+@code{#pragma} not understood by traditional C by indenting them. Some
+traditional implementations do not recognize @code{#elif}, so this option
+suggests avoiding it altogether.
+
+@item
+A function-like macro that appears without arguments.
+
+@item
+The unary plus operator.
+
+@item
+The @samp{U} integer constant suffix, or the @samp{F} or @samp{L} floating-point
+constant suffixes. (Traditional C does support the @samp{L} suffix on integer
+constants.) Note, these suffixes appear in macros defined in the system
+headers of most modern systems, e.g.@: the @samp{_MIN}/@samp{_MAX} macros in @code{<limits.h>}.
+Use of these macros in user code might normally lead to spurious
+warnings, however GCC's integrated preprocessor has enough context to
+avoid warning in these cases.
+
+@item
+A function declared external in one block and then used after the end of
+the block.
+
+@item
+A @code{switch} statement has an operand of type @code{long}.
+
+@item
+A non-@code{static} function declaration follows a @code{static} one.
+This construct is not accepted by some traditional C compilers.
+
+@item
+The ISO type of an integer constant has a different width or
+signedness from its traditional type. This warning is only issued if
+the base of the constant is ten. I.e.@: hexadecimal or octal values, which
+typically represent bit patterns, are not warned about.
+
+@item
+Usage of ISO string concatenation is detected.
+
+@item
+Initialization of automatic aggregates.
+
+@item
+Identifier conflicts with labels. Traditional C lacks a separate
+namespace for labels.
+
+@item
+Initialization of unions. If the initializer is zero, the warning is
+omitted. This is done under the assumption that the zero initializer in
+user code appears conditioned on e.g.@: @code{__STDC__} to avoid missing
+initializer warnings and relies on default initialization to zero in the
+traditional C case.
+
+@item
+Conversions by prototypes between fixed/floating-point values and vice
+versa. The absence of these prototypes when compiling with traditional
+C causes serious problems. This is a subset of the possible
+conversion warnings; for the full set use @option{-Wtraditional-conversion}.
+
+@item
+Use of ISO C style function definitions. This warning intentionally is
+@emph{not} issued for prototype declarations or variadic functions
+because these ISO C features appear in your code when using
+libiberty's traditional C compatibility macros, @code{PARAMS} and
+@code{VPARAMS}. This warning is also bypassed for nested functions
+because that feature is already a GCC extension and thus not relevant to
+traditional C compatibility.
+@end itemize
+
+@item -Wtraditional-conversion @r{(C and Objective-C only)}
+@opindex Wtraditional-conversion
+@opindex Wno-traditional-conversion
+Warn if a prototype causes a type conversion that is different from what
+would happen to the same argument in the absence of a prototype. This
+includes conversions of fixed point to floating and vice versa, and
+conversions changing the width or signedness of a fixed-point argument
+except when the same as the default promotion.
+
+@item -Wdeclaration-after-statement @r{(C and Objective-C only)}
+@opindex Wdeclaration-after-statement
+@opindex Wno-declaration-after-statement
+Warn when a declaration is found after a statement in a block. This
+construct, known from C++, was introduced with ISO C99 and is by default
+allowed in GCC@. It is not supported by ISO C90. @xref{Mixed Labels and Declarations}.
+
+@item -Wshadow
+@opindex Wshadow
+@opindex Wno-shadow
+Warn whenever a local variable or type declaration shadows another
+variable, parameter, type, class member (in C++), or instance variable
+(in Objective-C) or whenever a built-in function is shadowed. Note
+that in C++, the compiler warns if a local variable shadows an
+explicit typedef, but not if it shadows a struct/class/enum.
+If this warning is enabled, it includes also all instances of
+local shadowing. This means that @option{-Wno-shadow=local}
+and @option{-Wno-shadow=compatible-local} are ignored when
+@option{-Wshadow} is used.
+Same as @option{-Wshadow=global}.
+
+@item -Wno-shadow-ivar @r{(Objective-C only)}
+@opindex Wno-shadow-ivar
+@opindex Wshadow-ivar
+Do not warn whenever a local variable shadows an instance variable in an
+Objective-C method.
+
+@item -Wshadow=global
+@opindex Wshadow=global
+Warn for any shadowing.
+Same as @option{-Wshadow}.
+
+@item -Wshadow=local
+@opindex Wshadow=local
+Warn when a local variable shadows another local variable or parameter.
+
+@item -Wshadow=compatible-local
+@opindex Wshadow=compatible-local
+Warn when a local variable shadows another local variable or parameter
+whose type is compatible with that of the shadowing variable. In C++,
+type compatibility here means the type of the shadowing variable can be
+converted to that of the shadowed variable. The creation of this flag
+(in addition to @option{-Wshadow=local}) is based on the idea that when
+a local variable shadows another one of incompatible type, it is most
+likely intentional, not a bug or typo, as shown in the following example:
+
+@smallexample
+@group
+for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i)
+@{
+ for (int i = 0; i < N; ++i)
+ @{
+ ...
+ @}
+ ...
+@}
+@end group
+@end smallexample
+
+Since the two variable @code{i} in the example above have incompatible types,
+enabling only @option{-Wshadow=compatible-local} does not emit a warning.
+Because their types are incompatible, if a programmer accidentally uses one
+in place of the other, type checking is expected to catch that and emit an
+error or warning. Use of this flag instead of @option{-Wshadow=local} can
+possibly reduce the number of warnings triggered by intentional shadowing.
+Note that this also means that shadowing @code{const char *i} by
+@code{char *i} does not emit a warning.
+
+This warning is also enabled by @option{-Wshadow=local}.
+
+@item -Wlarger-than=@var{byte-size}
+@opindex Wlarger-than=
+@opindex Wlarger-than-@var{byte-size}
+Warn whenever an object is defined whose size exceeds @var{byte-size}.
+@option{-Wlarger-than=}@samp{PTRDIFF_MAX} is enabled by default.
+Warnings controlled by the option can be disabled either by specifying
+@var{byte-size} of @samp{SIZE_MAX} or more or by @option{-Wno-larger-than}.
+
+Also warn for calls to bounded functions such as @code{memchr} or
+@code{strnlen} that specify a bound greater than the largest possible
+object, which is @samp{PTRDIFF_MAX} bytes by default. These warnings
+can only be disabled by @option{-Wno-larger-than}.
+
+@item -Wno-larger-than
+@opindex Wno-larger-than
+Disable @option{-Wlarger-than=} warnings. The option is equivalent
+to @option{-Wlarger-than=}@samp{SIZE_MAX} or larger.
+
+@item -Wframe-larger-than=@var{byte-size}
+@opindex Wframe-larger-than=
+@opindex Wno-frame-larger-than
+Warn if the size of a function frame exceeds @var{byte-size}.
+The computation done to determine the stack frame size is approximate
+and not conservative.
+The actual requirements may be somewhat greater than @var{byte-size}
+even if you do not get a warning. In addition, any space allocated
+via @code{alloca}, variable-length arrays, or related constructs
+is not included by the compiler when determining
+whether or not to issue a warning.
+@option{-Wframe-larger-than=}@samp{PTRDIFF_MAX} is enabled by default.
+Warnings controlled by the option can be disabled either by specifying
+@var{byte-size} of @samp{SIZE_MAX} or more or by
+@option{-Wno-frame-larger-than}.
+
+@item -Wno-frame-larger-than
+@opindex Wno-frame-larger-than
+Disable @option{-Wframe-larger-than=} warnings. The option is equivalent
+to @option{-Wframe-larger-than=}@samp{SIZE_MAX} or larger.
+
+@item -Wfree-nonheap-object
+@opindex Wfree-nonheap-object
+@opindex Wno-free-nonheap-object
+Warn when attempting to deallocate an object that was either not allocated
+on the heap, or by using a pointer that was not returned from a prior call
+to the corresponding allocation function. For example, because the call
+to @code{stpcpy} returns a pointer to the terminating nul character and
+not to the beginning of the object, the call to @code{free} below is
+diagnosed.
+
+@smallexample
+void f (char *p)
+@{
+ p = stpcpy (p, "abc");
+ // ...
+ free (p); // warning
+@}
+@end smallexample
+
+@option{-Wfree-nonheap-object} is included in @option{-Wall}.
+
+@item -Wstack-usage=@var{byte-size}
+@opindex Wstack-usage
+@opindex Wno-stack-usage
+Warn if the stack usage of a function might exceed @var{byte-size}.
+The computation done to determine the stack usage is conservative.
+Any space allocated via @code{alloca}, variable-length arrays, or related
+constructs is included by the compiler when determining whether or not to
+issue a warning.
+
+The message is in keeping with the output of @option{-fstack-usage}.
+
+@itemize
+@item
+If the stack usage is fully static but exceeds the specified amount, it's:
+
+@smallexample
+ warning: stack usage is 1120 bytes
+@end smallexample
+@item
+If the stack usage is (partly) dynamic but bounded, it's:
+
+@smallexample
+ warning: stack usage might be 1648 bytes
+@end smallexample
+@item
+If the stack usage is (partly) dynamic and not bounded, it's:
+
+@smallexample
+ warning: stack usage might be unbounded
+@end smallexample
+@end itemize
+
+@option{-Wstack-usage=}@samp{PTRDIFF_MAX} is enabled by default.
+Warnings controlled by the option can be disabled either by specifying
+@var{byte-size} of @samp{SIZE_MAX} or more or by
+@option{-Wno-stack-usage}.
+
+@item -Wno-stack-usage
+@opindex Wno-stack-usage
+Disable @option{-Wstack-usage=} warnings. The option is equivalent
+to @option{-Wstack-usage=}@samp{SIZE_MAX} or larger.
+
+@item -Wunsafe-loop-optimizations
+@opindex Wunsafe-loop-optimizations
+@opindex Wno-unsafe-loop-optimizations
+Warn if the loop cannot be optimized because the compiler cannot
+assume anything on the bounds of the loop indices. With
+@option{-funsafe-loop-optimizations} warn if the compiler makes
+such assumptions.
+
+@item -Wno-pedantic-ms-format @r{(MinGW targets only)}
+@opindex Wno-pedantic-ms-format
+@opindex Wpedantic-ms-format
+When used in combination with @option{-Wformat}
+and @option{-pedantic} without GNU extensions, this option
+disables the warnings about non-ISO @code{printf} / @code{scanf} format
+width specifiers @code{I32}, @code{I64}, and @code{I} used on Windows targets,
+which depend on the MS runtime.
+
+@item -Wpointer-arith
+@opindex Wpointer-arith
+@opindex Wno-pointer-arith
+Warn about anything that depends on the ``size of'' a function type or
+of @code{void}. GNU C assigns these types a size of 1, for
+convenience in calculations with @code{void *} pointers and pointers
+to functions. In C++, warn also when an arithmetic operation involves
+@code{NULL}. This warning is also enabled by @option{-Wpedantic}.
+
+@item -Wno-pointer-compare
+@opindex Wpointer-compare
+@opindex Wno-pointer-compare
+Do not warn if a pointer is compared with a zero character constant.
+This usually
+means that the pointer was meant to be dereferenced. For example:
+
+@smallexample
+const char *p = foo ();
+if (p == '\0')
+ return 42;
+@end smallexample
+
+Note that the code above is invalid in C++11.
+
+This warning is enabled by default.
+
+@item -Wtsan
+@opindex Wtsan
+@opindex Wno-tsan
+Warn about unsupported features in ThreadSanitizer.
+
+ThreadSanitizer does not support @code{std::atomic_thread_fence} and
+can report false positives.
+
+This warning is enabled by default.
+
+@item -Wtype-limits
+@opindex Wtype-limits
+@opindex Wno-type-limits
+Warn if a comparison is always true or always false due to the limited
+range of the data type, but do not warn for constant expressions. For
+example, warn if an unsigned variable is compared against zero with
+@code{<} or @code{>=}. This warning is also enabled by
+@option{-Wextra}.
+
+@item -Wabsolute-value @r{(C and Objective-C only)}
+@opindex Wabsolute-value
+@opindex Wno-absolute-value
+Warn for calls to standard functions that compute the absolute value
+of an argument when a more appropriate standard function is available.
+For example, calling @code{abs(3.14)} triggers the warning because the
+appropriate function to call to compute the absolute value of a double
+argument is @code{fabs}. The option also triggers warnings when the
+argument in a call to such a function has an unsigned type. This
+warning can be suppressed with an explicit type cast and it is also
+enabled by @option{-Wextra}.
+
+@include cppwarnopts.texi
+
+@item -Wbad-function-cast @r{(C and Objective-C only)}
+@opindex Wbad-function-cast
+@opindex Wno-bad-function-cast
+Warn when a function call is cast to a non-matching type.
+For example, warn if a call to a function returning an integer type
+is cast to a pointer type.
+
+@item -Wc90-c99-compat @r{(C and Objective-C only)}
+@opindex Wc90-c99-compat
+@opindex Wno-c90-c99-compat
+Warn about features not present in ISO C90, but present in ISO C99.
+For instance, warn about use of variable length arrays, @code{long long}
+type, @code{bool} type, compound literals, designated initializers, and so
+on. This option is independent of the standards mode. Warnings are disabled
+in the expression that follows @code{__extension__}.
+
+@item -Wc99-c11-compat @r{(C and Objective-C only)}
+@opindex Wc99-c11-compat
+@opindex Wno-c99-c11-compat
+Warn about features not present in ISO C99, but present in ISO C11.
+For instance, warn about use of anonymous structures and unions,
+@code{_Atomic} type qualifier, @code{_Thread_local} storage-class specifier,
+@code{_Alignas} specifier, @code{Alignof} operator, @code{_Generic} keyword,
+and so on. This option is independent of the standards mode. Warnings are
+disabled in the expression that follows @code{__extension__}.
+
+@item -Wc11-c2x-compat @r{(C and Objective-C only)}
+@opindex Wc11-c2x-compat
+@opindex Wno-c11-c2x-compat
+Warn about features not present in ISO C11, but present in ISO C2X.
+For instance, warn about omitting the string in @code{_Static_assert},
+use of @samp{[[]]} syntax for attributes, use of decimal
+floating-point types, and so on. This option is independent of the
+standards mode. Warnings are disabled in the expression that follows
+@code{__extension__}.
+
+@item -Wc++-compat @r{(C and Objective-C only)}
+@opindex Wc++-compat
+@opindex Wno-c++-compat
+Warn about ISO C constructs that are outside of the common subset of
+ISO C and ISO C++, e.g.@: request for implicit conversion from
+@code{void *} to a pointer to non-@code{void} type.
+
+@item -Wc++11-compat @r{(C++ and Objective-C++ only)}
+@opindex Wc++11-compat
+@opindex Wno-c++11-compat
+Warn about C++ constructs whose meaning differs between ISO C++ 1998
+and ISO C++ 2011, e.g., identifiers in ISO C++ 1998 that are keywords
+in ISO C++ 2011. This warning turns on @option{-Wnarrowing} and is
+enabled by @option{-Wall}.
+
+@item -Wc++14-compat @r{(C++ and Objective-C++ only)}
+@opindex Wc++14-compat
+@opindex Wno-c++14-compat
+Warn about C++ constructs whose meaning differs between ISO C++ 2011
+and ISO C++ 2014. This warning is enabled by @option{-Wall}.
+
+@item -Wc++17-compat @r{(C++ and Objective-C++ only)}
+@opindex Wc++17-compat
+@opindex Wno-c++17-compat
+Warn about C++ constructs whose meaning differs between ISO C++ 2014
+and ISO C++ 2017. This warning is enabled by @option{-Wall}.
+
+@item -Wc++20-compat @r{(C++ and Objective-C++ only)}
+@opindex Wc++20-compat
+@opindex Wno-c++20-compat
+Warn about C++ constructs whose meaning differs between ISO C++ 2017
+and ISO C++ 2020. This warning is enabled by @option{-Wall}.
+
+@item -Wno-c++11-extensions @r{(C++ and Objective-C++ only)}
+@opindex Wc++11-extensions
+@opindex Wno-c++11-extensions
+Do not warn about C++11 constructs in code being compiled using
+an older C++ standard. Even without this option, some C++11 constructs
+will only be diagnosed if @option{-Wpedantic} is used.
+
+@item -Wno-c++14-extensions @r{(C++ and Objective-C++ only)}
+@opindex Wc++14-extensions
+@opindex Wno-c++14-extensions
+Do not warn about C++14 constructs in code being compiled using
+an older C++ standard. Even without this option, some C++14 constructs
+will only be diagnosed if @option{-Wpedantic} is used.
+
+@item -Wno-c++17-extensions @r{(C++ and Objective-C++ only)}
+@opindex Wc++17-extensions
+@opindex Wno-c++17-extensions
+Do not warn about C++17 constructs in code being compiled using
+an older C++ standard. Even without this option, some C++17 constructs
+will only be diagnosed if @option{-Wpedantic} is used.
+
+@item -Wno-c++20-extensions @r{(C++ and Objective-C++ only)}
+@opindex Wc++20-extensions
+@opindex Wno-c++20-extensions
+Do not warn about C++20 constructs in code being compiled using
+an older C++ standard. Even without this option, some C++20 constructs
+will only be diagnosed if @option{-Wpedantic} is used.
+
+@item -Wno-c++23-extensions @r{(C++ and Objective-C++ only)}
+@opindex Wc++23-extensions
+@opindex Wno-c++23-extensions
+Do not warn about C++23 constructs in code being compiled using
+an older C++ standard. Even without this option, some C++23 constructs
+will only be diagnosed if @option{-Wpedantic} is used.
+
+@item -Wcast-qual
+@opindex Wcast-qual
+@opindex Wno-cast-qual
+Warn whenever a pointer is cast so as to remove a type qualifier from
+the target type. For example, warn if a @code{const char *} is cast
+to an ordinary @code{char *}.
+
+Also warn when making a cast that introduces a type qualifier in an
+unsafe way. For example, casting @code{char **} to @code{const char **}
+is unsafe, as in this example:
+
+@smallexample
+ /* p is char ** value. */
+ const char **q = (const char **) p;
+ /* Assignment of readonly string to const char * is OK. */
+ *q = "string";
+ /* Now char** pointer points to read-only memory. */
+ **p = 'b';
+@end smallexample
+
+@item -Wcast-align
+@opindex Wcast-align
+@opindex Wno-cast-align
+Warn whenever a pointer is cast such that the required alignment of the
+target is increased. For example, warn if a @code{char *} is cast to
+an @code{int *} on machines where integers can only be accessed at
+two- or four-byte boundaries.
+
+@item -Wcast-align=strict
+@opindex Wcast-align=strict
+Warn whenever a pointer is cast such that the required alignment of the
+target is increased. For example, warn if a @code{char *} is cast to
+an @code{int *} regardless of the target machine.
+
+@item -Wcast-function-type
+@opindex Wcast-function-type
+@opindex Wno-cast-function-type
+Warn when a function pointer is cast to an incompatible function pointer.
+In a cast involving function types with a variable argument list only
+the types of initial arguments that are provided are considered.
+Any parameter of pointer-type matches any other pointer-type. Any benign
+differences in integral types are ignored, like @code{int} vs.@: @code{long}
+on ILP32 targets. Likewise type qualifiers are ignored. The function
+type @code{void (*) (void)} is special and matches everything, which can
+be used to suppress this warning.
+In a cast involving pointer to member types this warning warns whenever
+the type cast is changing the pointer to member type.
+This warning is enabled by @option{-Wextra}.
+
+@item -Wwrite-strings
+@opindex Wwrite-strings
+@opindex Wno-write-strings
+When compiling C, give string constants the type @code{const
+char[@var{length}]} so that copying the address of one into a
+non-@code{const} @code{char *} pointer produces a warning. These
+warnings help you find at compile time code that can try to write
+into a string constant, but only if you have been very careful about
+using @code{const} in declarations and prototypes. Otherwise, it is
+just a nuisance. This is why we did not make @option{-Wall} request
+these warnings.
+
+When compiling C++, warn about the deprecated conversion from string
+literals to @code{char *}. This warning is enabled by default for C++
+programs.
+
+@item -Wclobbered
+@opindex Wclobbered
+@opindex Wno-clobbered
+Warn for variables that might be changed by @code{longjmp} or
+@code{vfork}. This warning is also enabled by @option{-Wextra}.
+
+@item -Wconversion
+@opindex Wconversion
+@opindex Wno-conversion
+Warn for implicit conversions that may alter a value. This includes
+conversions between real and integer, like @code{abs (x)} when
+@code{x} is @code{double}; conversions between signed and unsigned,
+like @code{unsigned ui = -1}; and conversions to smaller types, like
+@code{sqrtf (M_PI)}. Do not warn for explicit casts like @code{abs
+((int) x)} and @code{ui = (unsigned) -1}, or if the value is not
+changed by the conversion like in @code{abs (2.0)}. Warnings about
+conversions between signed and unsigned integers can be disabled by
+using @option{-Wno-sign-conversion}.
+
+For C++, also warn for confusing overload resolution for user-defined
+conversions; and conversions that never use a type conversion
+operator: conversions to @code{void}, the same type, a base class or a
+reference to them. Warnings about conversions between signed and
+unsigned integers are disabled by default in C++ unless
+@option{-Wsign-conversion} is explicitly enabled.
+
+Warnings about conversion from arithmetic on a small type back to that
+type are only given with @option{-Warith-conversion}.
+
+@item -Wdangling-else
+@opindex Wdangling-else
+@opindex Wno-dangling-else
+Warn about constructions where there may be confusion to which
+@code{if} statement an @code{else} branch belongs. Here is an example of
+such a case:
+
+@smallexample
+@group
+@{
+ if (a)
+ if (b)
+ foo ();
+ else
+ bar ();
+@}
+@end group
+@end smallexample
+
+In C/C++, every @code{else} branch belongs to the innermost possible
+@code{if} statement, which in this example is @code{if (b)}. This is
+often not what the programmer expected, as illustrated in the above
+example by indentation the programmer chose. When there is the
+potential for this confusion, GCC issues a warning when this flag
+is specified. To eliminate the warning, add explicit braces around
+the innermost @code{if} statement so there is no way the @code{else}
+can belong to the enclosing @code{if}. The resulting code
+looks like this:
+
+@smallexample
+@group
+@{
+ if (a)
+ @{
+ if (b)
+ foo ();
+ else
+ bar ();
+ @}
+@}
+@end group
+@end smallexample
+
+This warning is enabled by @option{-Wparentheses}.
+
+@item -Wdangling-pointer
+@itemx -Wdangling-pointer=@var{n}
+@opindex Wdangling-pointer
+@opindex Wno-dangling-pointer
+Warn about uses of pointers (or C++ references) to objects with automatic
+storage duration after their lifetime has ended. This includes local
+variables declared in nested blocks, compound literals and other unnamed
+temporary objects. In addition, warn about storing the address of such
+objects in escaped pointers. The warning is enabled at all optimization
+levels but may yield different results with optimization than without.
+
+@table @gcctabopt
+@item -Wdangling-pointer=1
+At level 1 the warning diagnoses only unconditional uses of dangling pointers.
+For example
+@smallexample
+int f (int c1, int c2, x)
+@{
+ char *p = strchr ((char[])@{ c1, c2 @}, c3);
+ return p ? *p : 'x'; // warning: dangling pointer to a compound literal
+@}
+@end smallexample
+In the following function the store of the address of the local variable
+@code{x} in the escaped pointer @code{*p} also triggers the warning.
+@smallexample
+void g (int **p)
+@{
+ int x = 7;
+ *p = &x; // warning: storing the address of a local variable in *p
+@}
+@end smallexample
+
+@item -Wdangling-pointer=2
+At level 2, in addition to unconditional uses the warning also diagnoses
+conditional uses of dangling pointers.
+
+For example, because the array @var{a} in the following function is out of
+scope when the pointer @var{s} that was set to point is used, the warning
+triggers at this level.
+
+@smallexample
+void f (char *s)
+@{
+ if (!s)
+ @{
+ char a[12] = "tmpname";
+ s = a;
+ @}
+ strcat (s, ".tmp"); // warning: dangling pointer to a may be used
+ ...
+@}
+@end smallexample
+@end table
+
+@option{-Wdangling-pointer=2} is included in @option{-Wall}.
+
+@item -Wdate-time
+@opindex Wdate-time
+@opindex Wno-date-time
+Warn when macros @code{__TIME__}, @code{__DATE__} or @code{__TIMESTAMP__}
+are encountered as they might prevent bit-wise-identical reproducible
+compilations.
+
+@item -Wempty-body
+@opindex Wempty-body
+@opindex Wno-empty-body
+Warn if an empty body occurs in an @code{if}, @code{else} or @code{do
+while} statement. This warning is also enabled by @option{-Wextra}.
+
+@item -Wno-endif-labels
+@opindex Wendif-labels
+@opindex Wno-endif-labels
+Do not warn about stray tokens after @code{#else} and @code{#endif}.
+
+@item -Wenum-compare
+@opindex Wenum-compare
+@opindex Wno-enum-compare
+Warn about a comparison between values of different enumerated types.
+In C++ enumerated type mismatches in conditional expressions are also
+diagnosed and the warning is enabled by default. In C this warning is
+enabled by @option{-Wall}.
+
+@item -Wenum-conversion
+@opindex Wenum-conversion
+@opindex Wno-enum-conversion
+Warn when a value of enumerated type is implicitly converted to a
+different enumerated type. This warning is enabled by @option{-Wextra}
+in C@.
+
+@item -Wenum-int-mismatch @r{(C and Objective-C only)}
+@opindex Wenum-int-mismatch
+@opindex Wno-enum-int-mismatch
+Warn about mismatches between an enumerated type and an integer type in
+declarations. For example:
+
+@smallexample
+enum E @{ l = -1, z = 0, g = 1 @};
+int foo(void);
+enum E foo(void);
+@end smallexample
+
+In C, an enumerated type is compatible with @code{char}, a signed
+integer type, or an unsigned integer type. However, since the choice
+of the underlying type of an enumerated type is implementation-defined,
+such mismatches may cause portability issues. In C++, such mismatches
+are an error. In C, this warning is enabled by @option{-Wall} and
+@option{-Wc++-compat}.
+
+@item -Wjump-misses-init @r{(C, Objective-C only)}
+@opindex Wjump-misses-init
+@opindex Wno-jump-misses-init
+Warn if a @code{goto} statement or a @code{switch} statement jumps
+forward across the initialization of a variable, or jumps backward to a
+label after the variable has been initialized. This only warns about
+variables that are initialized when they are declared. This warning is
+only supported for C and Objective-C; in C++ this sort of branch is an
+error in any case.
+
+@option{-Wjump-misses-init} is included in @option{-Wc++-compat}. It
+can be disabled with the @option{-Wno-jump-misses-init} option.
+
+@item -Wsign-compare
+@opindex Wsign-compare
+@opindex Wno-sign-compare
+@cindex warning for comparison of signed and unsigned values
+@cindex comparison of signed and unsigned values, warning
+@cindex signed and unsigned values, comparison warning
+Warn when a comparison between signed and unsigned values could produce
+an incorrect result when the signed value is converted to unsigned.
+In C++, this warning is also enabled by @option{-Wall}. In C, it is
+also enabled by @option{-Wextra}.
+
+@item -Wsign-conversion
+@opindex Wsign-conversion
+@opindex Wno-sign-conversion
+Warn for implicit conversions that may change the sign of an integer
+value, like assigning a signed integer expression to an unsigned
+integer variable. An explicit cast silences the warning. In C, this
+option is enabled also by @option{-Wconversion}.
+
+@item -Wfloat-conversion
+@opindex Wfloat-conversion
+@opindex Wno-float-conversion
+Warn for implicit conversions that reduce the precision of a real value.
+This includes conversions from real to integer, and from higher precision
+real to lower precision real values. This option is also enabled by
+@option{-Wconversion}.
+
+@item -Wno-scalar-storage-order
+@opindex Wno-scalar-storage-order
+@opindex Wscalar-storage-order
+Do not warn on suspicious constructs involving reverse scalar storage order.
+
+@item -Wsizeof-array-div
+@opindex Wsizeof-array-div
+@opindex Wno-sizeof-array-div
+Warn about divisions of two sizeof operators when the first one is applied
+to an array and the divisor does not equal the size of the array element.
+In such a case, the computation will not yield the number of elements in the
+array, which is likely what the user intended. This warning warns e.g. about
+@smallexample
+int fn ()
+@{
+ int arr[10];
+ return sizeof (arr) / sizeof (short);
+@}
+@end smallexample
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wsizeof-pointer-div
+@opindex Wsizeof-pointer-div
+@opindex Wno-sizeof-pointer-div
+Warn for suspicious divisions of two sizeof expressions that divide
+the pointer size by the element size, which is the usual way to compute
+the array size but won't work out correctly with pointers. This warning
+warns e.g.@: about @code{sizeof (ptr) / sizeof (ptr[0])} if @code{ptr} is
+not an array, but a pointer. This warning is enabled by @option{-Wall}.
+
+@item -Wsizeof-pointer-memaccess
+@opindex Wsizeof-pointer-memaccess
+@opindex Wno-sizeof-pointer-memaccess
+Warn for suspicious length parameters to certain string and memory built-in
+functions if the argument uses @code{sizeof}. This warning triggers for
+example for @code{memset (ptr, 0, sizeof (ptr));} if @code{ptr} is not
+an array, but a pointer, and suggests a possible fix, or about
+@code{memcpy (&foo, ptr, sizeof (&foo));}. @option{-Wsizeof-pointer-memaccess}
+also warns about calls to bounded string copy functions like @code{strncat}
+or @code{strncpy} that specify as the bound a @code{sizeof} expression of
+the source array. For example, in the following function the call to
+@code{strncat} specifies the size of the source string as the bound. That
+is almost certainly a mistake and so the call is diagnosed.
+@smallexample
+void make_file (const char *name)
+@{
+ char path[PATH_MAX];
+ strncpy (path, name, sizeof path - 1);
+ strncat (path, ".text", sizeof ".text");
+ @dots{}
+@}
+@end smallexample
+
+The @option{-Wsizeof-pointer-memaccess} option is enabled by @option{-Wall}.
+
+@item -Wno-sizeof-array-argument
+@opindex Wsizeof-array-argument
+@opindex Wno-sizeof-array-argument
+Do not warn when the @code{sizeof} operator is applied to a parameter that is
+declared as an array in a function definition. This warning is enabled by
+default for C and C++ programs.
+
+@item -Wmemset-elt-size
+@opindex Wmemset-elt-size
+@opindex Wno-memset-elt-size
+Warn for suspicious calls to the @code{memset} built-in function, if the
+first argument references an array, and the third argument is a number
+equal to the number of elements, but not equal to the size of the array
+in memory. This indicates that the user has omitted a multiplication by
+the element size. This warning is enabled by @option{-Wall}.
+
+@item -Wmemset-transposed-args
+@opindex Wmemset-transposed-args
+@opindex Wno-memset-transposed-args
+Warn for suspicious calls to the @code{memset} built-in function where
+the second argument is not zero and the third argument is zero. For
+example, the call @code{memset (buf, sizeof buf, 0)} is diagnosed because
+@code{memset (buf, 0, sizeof buf)} was meant instead. The diagnostic
+is only emitted if the third argument is a literal zero. Otherwise, if
+it is an expression that is folded to zero, or a cast of zero to some
+type, it is far less likely that the arguments have been mistakenly
+transposed and no warning is emitted. This warning is enabled
+by @option{-Wall}.
+
+@item -Waddress
+@opindex Waddress
+@opindex Wno-address
+Warn about suspicious uses of address expressions. These include comparing
+the address of a function or a declared object to the null pointer constant
+such as in
+@smallexample
+void f (void);
+void g (void)
+@{
+ if (!f) // warning: expression evaluates to false
+ abort ();
+@}
+@end smallexample
+comparisons of a pointer to a string literal, such as in
+@smallexample
+void f (const char *x)
+@{
+ if (x == "abc") // warning: expression evaluates to false
+ puts ("equal");
+@}
+@end smallexample
+and tests of the results of pointer addition or subtraction for equality
+to null, such as in
+@smallexample
+void f (const int *p, int i)
+@{
+ return p + i == NULL;
+@}
+@end smallexample
+Such uses typically indicate a programmer error: the address of most
+functions and objects necessarily evaluates to true (the exception are
+weak symbols), so their use in a conditional might indicate missing
+parentheses in a function call or a missing dereference in an array
+expression. The subset of the warning for object pointers can be
+suppressed by casting the pointer operand to an integer type such
+as @code{intptr_t} or @code{uintptr_t}.
+Comparisons against string literals result in unspecified behavior
+and are not portable, and suggest the intent was to call @code{strcmp}.
+The warning is suppressed if the suspicious expression is the result
+of macro expansion.
+@option{-Waddress} warning is enabled by @option{-Wall}.
+
+@item -Wno-address-of-packed-member
+@opindex Waddress-of-packed-member
+@opindex Wno-address-of-packed-member
+Do not warn when the address of packed member of struct or union is taken,
+which usually results in an unaligned pointer value. This is
+enabled by default.
+
+@item -Wlogical-op
+@opindex Wlogical-op
+@opindex Wno-logical-op
+Warn about suspicious uses of logical operators in expressions.
+This includes using logical operators in contexts where a
+bit-wise operator is likely to be expected. Also warns when
+the operands of a logical operator are the same:
+@smallexample
+extern int a;
+if (a < 0 && a < 0) @{ @dots{} @}
+@end smallexample
+
+@item -Wlogical-not-parentheses
+@opindex Wlogical-not-parentheses
+@opindex Wno-logical-not-parentheses
+Warn about logical not used on the left hand side operand of a comparison.
+This option does not warn if the right operand is considered to be a boolean
+expression. Its purpose is to detect suspicious code like the following:
+@smallexample
+int a;
+@dots{}
+if (!a > 1) @{ @dots{} @}
+@end smallexample
+
+It is possible to suppress the warning by wrapping the LHS into
+parentheses:
+@smallexample
+if ((!a) > 1) @{ @dots{} @}
+@end smallexample
+
+This warning is enabled by @option{-Wall}.
+
+@item -Waggregate-return
+@opindex Waggregate-return
+@opindex Wno-aggregate-return
+Warn if any functions that return structures or unions are defined or
+called. (In languages where you can return an array, this also elicits
+a warning.)
+
+@item -Wno-aggressive-loop-optimizations
+@opindex Wno-aggressive-loop-optimizations
+@opindex Waggressive-loop-optimizations
+Warn if in a loop with constant number of iterations the compiler detects
+undefined behavior in some statement during one or more of the iterations.
+
+@item -Wno-attributes
+@opindex Wno-attributes
+@opindex Wattributes
+Do not warn if an unexpected @code{__attribute__} is used, such as
+unrecognized attributes, function attributes applied to variables,
+etc. This does not stop errors for incorrect use of supported
+attributes.
+
+Additionally, using @option{-Wno-attributes=}, it is possible to suppress
+warnings about unknown scoped attributes (in C++11 and C2X). For example,
+@option{-Wno-attributes=vendor::attr} disables warning about the following
+declaration:
+
+@smallexample
+[[vendor::attr]] void f();
+@end smallexample
+
+It is also possible to disable warning about all attributes in a namespace
+using @option{-Wno-attributes=vendor::} which prevents warning about both
+of these declarations:
+
+@smallexample
+[[vendor::safe]] void f();
+[[vendor::unsafe]] void f2();
+@end smallexample
+
+Note that @option{-Wno-attributes=} does not imply @option{-Wno-attributes}.
+
+@item -Wno-builtin-declaration-mismatch
+@opindex Wno-builtin-declaration-mismatch
+@opindex Wbuiltin-declaration-mismatch
+Warn if a built-in function is declared with an incompatible signature
+or as a non-function, or when a built-in function declared with a type
+that does not include a prototype is called with arguments whose promoted
+types do not match those expected by the function. When @option{-Wextra}
+is specified, also warn when a built-in function that takes arguments is
+declared without a prototype. The @option{-Wbuiltin-declaration-mismatch}
+warning is enabled by default. To avoid the warning include the appropriate
+header to bring the prototypes of built-in functions into scope.
+
+For example, the call to @code{memset} below is diagnosed by the warning
+because the function expects a value of type @code{size_t} as its argument
+but the type of @code{32} is @code{int}. With @option{-Wextra},
+the declaration of the function is diagnosed as well.
+@smallexample
+extern void* memset ();
+void f (void *d)
+@{
+ memset (d, '\0', 32);
+@}
+@end smallexample
+
+@item -Wno-builtin-macro-redefined
+@opindex Wno-builtin-macro-redefined
+@opindex Wbuiltin-macro-redefined
+Do not warn if certain built-in macros are redefined. This suppresses
+warnings for redefinition of @code{__TIMESTAMP__}, @code{__TIME__},
+@code{__DATE__}, @code{__FILE__}, and @code{__BASE_FILE__}.
+
+@item -Wstrict-prototypes @r{(C and Objective-C only)}
+@opindex Wstrict-prototypes
+@opindex Wno-strict-prototypes
+Warn if a function is declared or defined without specifying the
+argument types. (An old-style function definition is permitted without
+a warning if preceded by a declaration that specifies the argument
+types.)
+
+@item -Wold-style-declaration @r{(C and Objective-C only)}
+@opindex Wold-style-declaration
+@opindex Wno-old-style-declaration
+Warn for obsolescent usages, according to the C Standard, in a
+declaration. For example, warn if storage-class specifiers like
+@code{static} are not the first things in a declaration. This warning
+is also enabled by @option{-Wextra}.
+
+@item -Wold-style-definition @r{(C and Objective-C only)}
+@opindex Wold-style-definition
+@opindex Wno-old-style-definition
+Warn if an old-style function definition is used. A warning is given
+even if there is a previous prototype. A definition using @samp{()}
+is not considered an old-style definition in C2X mode, because it is
+equivalent to @samp{(void)} in that case, but is considered an
+old-style definition for older standards.
+
+@item -Wmissing-parameter-type @r{(C and Objective-C only)}
+@opindex Wmissing-parameter-type
+@opindex Wno-missing-parameter-type
+A function parameter is declared without a type specifier in K&R-style
+functions:
+
+@smallexample
+void foo(bar) @{ @}
+@end smallexample
+
+This warning is also enabled by @option{-Wextra}.
+
+@item -Wmissing-prototypes @r{(C and Objective-C only)}
+@opindex Wmissing-prototypes
+@opindex Wno-missing-prototypes
+Warn if a global function is defined without a previous prototype
+declaration. This warning is issued even if the definition itself
+provides a prototype. Use this option to detect global functions
+that do not have a matching prototype declaration in a header file.
+This option is not valid for C++ because all function declarations
+provide prototypes and a non-matching declaration declares an
+overload rather than conflict with an earlier declaration.
+Use @option{-Wmissing-declarations} to detect missing declarations in C++.
+
+@item -Wmissing-declarations
+@opindex Wmissing-declarations
+@opindex Wno-missing-declarations
+Warn if a global function is defined without a previous declaration.
+Do so even if the definition itself provides a prototype.
+Use this option to detect global functions that are not declared in
+header files. In C, no warnings are issued for functions with previous
+non-prototype declarations; use @option{-Wmissing-prototypes} to detect
+missing prototypes. In C++, no warnings are issued for function templates,
+or for inline functions, or for functions in anonymous namespaces.
+
+@item -Wmissing-field-initializers
+@opindex Wmissing-field-initializers
+@opindex Wno-missing-field-initializers
+@opindex W
+@opindex Wextra
+@opindex Wno-extra
+Warn if a structure's initializer has some fields missing. For
+example, the following code causes such a warning, because
+@code{x.h} is implicitly zero:
+
+@smallexample
+struct s @{ int f, g, h; @};
+struct s x = @{ 3, 4 @};
+@end smallexample
+
+This option does not warn about designated initializers, so the following
+modification does not trigger a warning:
+
+@smallexample
+struct s @{ int f, g, h; @};
+struct s x = @{ .f = 3, .g = 4 @};
+@end smallexample
+
+In C this option does not warn about the universal zero initializer
+@samp{@{ 0 @}}:
+
+@smallexample
+struct s @{ int f, g, h; @};
+struct s x = @{ 0 @};
+@end smallexample
+
+Likewise, in C++ this option does not warn about the empty @{ @}
+initializer, for example:
+
+@smallexample
+struct s @{ int f, g, h; @};
+s x = @{ @};
+@end smallexample
+
+This warning is included in @option{-Wextra}. To get other @option{-Wextra}
+warnings without this one, use @option{-Wextra -Wno-missing-field-initializers}.
+
+@item -Wno-missing-requires
+@opindex Wmissing-requires
+@opindex Wno-missing-requires
+
+By default, the compiler warns about a concept-id appearing as a C++20 simple-requirement:
+
+@smallexample
+bool satisfied = requires @{ C<T> @};
+@end smallexample
+
+Here @samp{satisfied} will be true if @samp{C<T>} is a valid
+expression, which it is for all T. Presumably the user meant to write
+
+@smallexample
+bool satisfied = requires @{ requires C<T> @};
+@end smallexample
+
+so @samp{satisfied} is only true if concept @samp{C} is satisfied for
+type @samp{T}.
+
+This warning can be disabled with @option{-Wno-missing-requires}.
+
+@item -Wno-missing-template-keyword
+@opindex Wmissing-template-keyword
+@opindex Wno-missing-template-keyword
+
+The member access tokens ., -> and :: must be followed by the @code{template}
+keyword if the parent object is dependent and the member being named is a
+template.
+
+@smallexample
+template <class X>
+void DoStuff (X x)
+@{
+ x.template DoSomeOtherStuff<X>(); // Good.
+ x.DoMoreStuff<X>(); // Warning, x is dependent.
+@}
+@end smallexample
+
+In rare cases it is possible to get false positives. To silence this, wrap
+the expression in parentheses. For example, the following is treated as a
+template, even where m and N are integers:
+
+@smallexample
+void NotATemplate (my_class t)
+@{
+ int N = 5;
+
+ bool test = t.m < N > (0); // Treated as a template.
+ test = (t.m < N) > (0); // Same meaning, but not treated as a template.
+@}
+@end smallexample
+
+This warning can be disabled with @option{-Wno-missing-template-keyword}.
+
+@item -Wno-multichar
+@opindex Wno-multichar
+@opindex Wmultichar
+Do not warn if a multicharacter constant (@samp{'FOOF'}) is used.
+Usually they indicate a typo in the user's code, as they have
+implementation-defined values, and should not be used in portable code.
+
+@item -Wnormalized=@r{[}none@r{|}id@r{|}nfc@r{|}nfkc@r{]}
+@opindex Wnormalized=
+@opindex Wnormalized
+@opindex Wno-normalized
+@cindex NFC
+@cindex NFKC
+@cindex character set, input normalization
+In ISO C and ISO C++, two identifiers are different if they are
+different sequences of characters. However, sometimes when characters
+outside the basic ASCII character set are used, you can have two
+different character sequences that look the same. To avoid confusion,
+the ISO 10646 standard sets out some @dfn{normalization rules} which
+when applied ensure that two sequences that look the same are turned into
+the same sequence. GCC can warn you if you are using identifiers that
+have not been normalized; this option controls that warning.
+
+There are four levels of warning supported by GCC@. The default is
+@option{-Wnormalized=nfc}, which warns about any identifier that is
+not in the ISO 10646 ``C'' normalized form, @dfn{NFC}. NFC is the
+recommended form for most uses. It is equivalent to
+@option{-Wnormalized}.
+
+Unfortunately, there are some characters allowed in identifiers by
+ISO C and ISO C++ that, when turned into NFC, are not allowed in
+identifiers. That is, there's no way to use these symbols in portable
+ISO C or C++ and have all your identifiers in NFC@.
+@option{-Wnormalized=id} suppresses the warning for these characters.
+It is hoped that future versions of the standards involved will correct
+this, which is why this option is not the default.
+
+You can switch the warning off for all characters by writing
+@option{-Wnormalized=none} or @option{-Wno-normalized}. You should
+only do this if you are using some other normalization scheme (like
+``D''), because otherwise you can easily create bugs that are
+literally impossible to see.
+
+Some characters in ISO 10646 have distinct meanings but look identical
+in some fonts or display methodologies, especially once formatting has
+been applied. For instance @code{\u207F}, ``SUPERSCRIPT LATIN SMALL
+LETTER N'', displays just like a regular @code{n} that has been
+placed in a superscript. ISO 10646 defines the @dfn{NFKC}
+normalization scheme to convert all these into a standard form as
+well, and GCC warns if your code is not in NFKC if you use
+@option{-Wnormalized=nfkc}. This warning is comparable to warning
+about every identifier that contains the letter O because it might be
+confused with the digit 0, and so is not the default, but may be
+useful as a local coding convention if the programming environment
+cannot be fixed to display these characters distinctly.
+
+@item -Wno-attribute-warning
+@opindex Wno-attribute-warning
+@opindex Wattribute-warning
+Do not warn about usage of functions (@pxref{Function Attributes})
+declared with @code{warning} attribute. By default, this warning is
+enabled. @option{-Wno-attribute-warning} can be used to disable the
+warning or @option{-Wno-error=attribute-warning} can be used to
+disable the error when compiled with @option{-Werror} flag.
+
+@item -Wno-deprecated
+@opindex Wno-deprecated
+@opindex Wdeprecated
+Do not warn about usage of deprecated features. @xref{Deprecated Features}.
+
+@item -Wno-deprecated-declarations
+@opindex Wno-deprecated-declarations
+@opindex Wdeprecated-declarations
+Do not warn about uses of functions (@pxref{Function Attributes}),
+variables (@pxref{Variable Attributes}), and types (@pxref{Type
+Attributes}) marked as deprecated by using the @code{deprecated}
+attribute.
+
+@item -Wno-overflow
+@opindex Wno-overflow
+@opindex Woverflow
+Do not warn about compile-time overflow in constant expressions.
+
+@item -Wno-odr
+@opindex Wno-odr
+@opindex Wodr
+Warn about One Definition Rule violations during link-time optimization.
+Enabled by default.
+
+@item -Wopenacc-parallelism
+@opindex Wopenacc-parallelism
+@opindex Wno-openacc-parallelism
+@cindex OpenACC accelerator programming
+Warn about potentially suboptimal choices related to OpenACC parallelism.
+
+@item -Wopenmp-simd
+@opindex Wopenmp-simd
+@opindex Wno-openmp-simd
+Warn if the vectorizer cost model overrides the OpenMP
+simd directive set by user. The @option{-fsimd-cost-model=unlimited}
+option can be used to relax the cost model.
+
+@item -Woverride-init @r{(C and Objective-C only)}
+@opindex Woverride-init
+@opindex Wno-override-init
+@opindex W
+@opindex Wextra
+@opindex Wno-extra
+Warn if an initialized field without side effects is overridden when
+using designated initializers (@pxref{Designated Inits, , Designated
+Initializers}).
+
+This warning is included in @option{-Wextra}. To get other
+@option{-Wextra} warnings without this one, use @option{-Wextra
+-Wno-override-init}.
+
+@item -Wno-override-init-side-effects @r{(C and Objective-C only)}
+@opindex Woverride-init-side-effects
+@opindex Wno-override-init-side-effects
+Do not warn if an initialized field with side effects is overridden when
+using designated initializers (@pxref{Designated Inits, , Designated
+Initializers}). This warning is enabled by default.
+
+@item -Wpacked
+@opindex Wpacked
+@opindex Wno-packed
+Warn if a structure is given the packed attribute, but the packed
+attribute has no effect on the layout or size of the structure.
+Such structures may be mis-aligned for little benefit. For
+instance, in this code, the variable @code{f.x} in @code{struct bar}
+is misaligned even though @code{struct bar} does not itself
+have the packed attribute:
+
+@smallexample
+@group
+struct foo @{
+ int x;
+ char a, b, c, d;
+@} __attribute__((packed));
+struct bar @{
+ char z;
+ struct foo f;
+@};
+@end group
+@end smallexample
+
+@item -Wnopacked-bitfield-compat
+@opindex Wpacked-bitfield-compat
+@opindex Wno-packed-bitfield-compat
+The 4.1, 4.2 and 4.3 series of GCC ignore the @code{packed} attribute
+on bit-fields of type @code{char}. This was fixed in GCC 4.4 but
+the change can lead to differences in the structure layout. GCC
+informs you when the offset of such a field has changed in GCC 4.4.
+For example there is no longer a 4-bit padding between field @code{a}
+and @code{b} in this structure:
+
+@smallexample
+struct foo
+@{
+ char a:4;
+ char b:8;
+@} __attribute__ ((packed));
+@end smallexample
+
+This warning is enabled by default. Use
+@option{-Wno-packed-bitfield-compat} to disable this warning.
+
+@item -Wpacked-not-aligned @r{(C, C++, Objective-C and Objective-C++ only)}
+@opindex Wpacked-not-aligned
+@opindex Wno-packed-not-aligned
+Warn if a structure field with explicitly specified alignment in a
+packed struct or union is misaligned. For example, a warning will
+be issued on @code{struct S}, like, @code{warning: alignment 1 of
+'struct S' is less than 8}, in this code:
+
+@smallexample
+@group
+struct __attribute__ ((aligned (8))) S8 @{ char a[8]; @};
+struct __attribute__ ((packed)) S @{
+ struct S8 s8;
+@};
+@end group
+@end smallexample
+
+This warning is enabled by @option{-Wall}.
+
+@item -Wpadded
+@opindex Wpadded
+@opindex Wno-padded
+Warn if padding is included in a structure, either to align an element
+of the structure or to align the whole structure. Sometimes when this
+happens it is possible to rearrange the fields of the structure to
+reduce the padding and so make the structure smaller.
+
+@item -Wredundant-decls
+@opindex Wredundant-decls
+@opindex Wno-redundant-decls
+Warn if anything is declared more than once in the same scope, even in
+cases where multiple declaration is valid and changes nothing.
+
+@item -Wrestrict
+@opindex Wrestrict
+@opindex Wno-restrict
+Warn when an object referenced by a @code{restrict}-qualified parameter
+(or, in C++, a @code{__restrict}-qualified parameter) is aliased by another
+argument, or when copies between such objects overlap. For example,
+the call to the @code{strcpy} function below attempts to truncate the string
+by replacing its initial characters with the last four. However, because
+the call writes the terminating NUL into @code{a[4]}, the copies overlap and
+the call is diagnosed.
+
+@smallexample
+void foo (void)
+@{
+ char a[] = "abcd1234";
+ strcpy (a, a + 4);
+ @dots{}
+@}
+@end smallexample
+The @option{-Wrestrict} option detects some instances of simple overlap
+even without optimization but works best at @option{-O2} and above. It
+is included in @option{-Wall}.
+
+@item -Wnested-externs @r{(C and Objective-C only)}
+@opindex Wnested-externs
+@opindex Wno-nested-externs
+Warn if an @code{extern} declaration is encountered within a function.
+
+@item -Winline
+@opindex Winline
+@opindex Wno-inline
+Warn if a function that is declared as inline cannot be inlined.
+Even with this option, the compiler does not warn about failures to
+inline functions declared in system headers.
+
+The compiler uses a variety of heuristics to determine whether or not
+to inline a function. For example, the compiler takes into account
+the size of the function being inlined and the amount of inlining
+that has already been done in the current function. Therefore,
+seemingly insignificant changes in the source program can cause the
+warnings produced by @option{-Winline} to appear or disappear.
+
+@item -Winterference-size
+@opindex Winterference-size
+Warn about use of C++17 @code{std::hardware_destructive_interference_size}
+without specifying its value with @option{--param destructive-interference-size}.
+Also warn about questionable values for that option.
+
+This variable is intended to be used for controlling class layout, to
+avoid false sharing in concurrent code:
+
+@smallexample
+struct independent_fields @{
+ alignas(std::hardware_destructive_interference_size) std::atomic<int> one;
+ alignas(std::hardware_destructive_interference_size) std::atomic<int> two;
+@};
+@end smallexample
+
+Here @samp{one} and @samp{two} are intended to be far enough apart
+that stores to one won't require accesses to the other to reload the
+cache line.
+
+By default, @option{--param destructive-interference-size} and
+@option{--param constructive-interference-size} are set based on the
+current @option{-mtune} option, typically to the L1 cache line size
+for the particular target CPU, sometimes to a range if tuning for a
+generic target. So all translation units that depend on ABI
+compatibility for the use of these variables must be compiled with
+the same @option{-mtune} (or @option{-mcpu}).
+
+If ABI stability is important, such as if the use is in a header for a
+library, you should probably not use the hardware interference size
+variables at all. Alternatively, you can force a particular value
+with @option{--param}.
+
+If you are confident that your use of the variable does not affect ABI
+outside a single build of your project, you can turn off the warning
+with @option{-Wno-interference-size}.
+
+@item -Wint-in-bool-context
+@opindex Wint-in-bool-context
+@opindex Wno-int-in-bool-context
+Warn for suspicious use of integer values where boolean values are expected,
+such as conditional expressions (?:) using non-boolean integer constants in
+boolean context, like @code{if (a <= b ? 2 : 3)}. Or left shifting of signed
+integers in boolean context, like @code{for (a = 0; 1 << a; a++);}. Likewise
+for all kinds of multiplications regardless of the data type.
+This warning is enabled by @option{-Wall}.
+
+@item -Wno-int-to-pointer-cast
+@opindex Wno-int-to-pointer-cast
+@opindex Wint-to-pointer-cast
+Suppress warnings from casts to pointer type of an integer of a
+different size. In C++, casting to a pointer type of smaller size is
+an error. @option{Wint-to-pointer-cast} is enabled by default.
+
+
+@item -Wno-pointer-to-int-cast @r{(C and Objective-C only)}
+@opindex Wno-pointer-to-int-cast
+@opindex Wpointer-to-int-cast
+Suppress warnings from casts from a pointer to an integer type of a
+different size.
+
+@item -Winvalid-pch
+@opindex Winvalid-pch
+@opindex Wno-invalid-pch
+Warn if a precompiled header (@pxref{Precompiled Headers}) is found in
+the search path but cannot be used.
+
+@item -Winvalid-utf8
+@opindex Winvalid-utf8
+@opindex Wno-invalid-utf8
+Warn if an invalid UTF-8 character is found.
+This warning is on by default for C++23 if @option{-finput-charset=UTF-8}
+is used and turned into error with @option{-pedantic-errors}.
+
+@item -Wno-unicode
+@opindex Wunicode
+@opindex Wno-unicode
+Don't diagnose invalid forms of delimited or named escape sequences which are
+treated as separate tokens. @option{Wunicode} is enabled by default.
+
+@item -Wlong-long
+@opindex Wlong-long
+@opindex Wno-long-long
+Warn if @code{long long} type is used. This is enabled by either
+@option{-Wpedantic} or @option{-Wtraditional} in ISO C90 and C++98
+modes. To inhibit the warning messages, use @option{-Wno-long-long}.
+
+@item -Wvariadic-macros
+@opindex Wvariadic-macros
+@opindex Wno-variadic-macros
+Warn if variadic macros are used in ISO C90 mode, or if the GNU
+alternate syntax is used in ISO C99 mode. This is enabled by either
+@option{-Wpedantic} or @option{-Wtraditional}. To inhibit the warning
+messages, use @option{-Wno-variadic-macros}.
+
+@item -Wno-varargs
+@opindex Wvarargs
+@opindex Wno-varargs
+Do not warn upon questionable usage of the macros used to handle variable
+arguments like @code{va_start}. These warnings are enabled by default.
+
+@item -Wvector-operation-performance
+@opindex Wvector-operation-performance
+@opindex Wno-vector-operation-performance
+Warn if vector operation is not implemented via SIMD capabilities of the
+architecture. Mainly useful for the performance tuning.
+Vector operation can be implemented @code{piecewise}, which means that the
+scalar operation is performed on every vector element;
+@code{in parallel}, which means that the vector operation is implemented
+using scalars of wider type, which normally is more performance efficient;
+and @code{as a single scalar}, which means that vector fits into a
+scalar type.
+
+@item -Wvla
+@opindex Wvla
+@opindex Wno-vla
+Warn if a variable-length array is used in the code.
+@option{-Wno-vla} prevents the @option{-Wpedantic} warning of
+the variable-length array.
+
+@item -Wvla-larger-than=@var{byte-size}
+@opindex Wvla-larger-than=
+@opindex Wno-vla-larger-than
+If this option is used, the compiler warns for declarations of
+variable-length arrays whose size is either unbounded, or bounded
+by an argument that allows the array size to exceed @var{byte-size}
+bytes. This is similar to how @option{-Walloca-larger-than=}@var{byte-size}
+works, but with variable-length arrays.
+
+Note that GCC may optimize small variable-length arrays of a known
+value into plain arrays, so this warning may not get triggered for
+such arrays.
+
+@option{-Wvla-larger-than=}@samp{PTRDIFF_MAX} is enabled by default but
+is typically only effective when @option{-ftree-vrp} is active (default
+for @option{-O2} and above).
+
+See also @option{-Walloca-larger-than=@var{byte-size}}.
+
+@item -Wno-vla-larger-than
+@opindex Wno-vla-larger-than
+Disable @option{-Wvla-larger-than=} warnings. The option is equivalent
+to @option{-Wvla-larger-than=}@samp{SIZE_MAX} or larger.
+
+@item -Wvla-parameter
+@opindex Wno-vla-parameter
+Warn about redeclarations of functions involving arguments of Variable
+Length Array types of inconsistent kinds or forms, and enable the detection
+of out-of-bounds accesses to such parameters by warnings such as
+@option{-Warray-bounds}.
+
+If the first function declaration uses the VLA form the bound specified
+in the array is assumed to be the minimum number of elements expected to
+be provided in calls to the function and the maximum number of elements
+accessed by it. Failing to provide arguments of sufficient size or
+accessing more than the maximum number of elements may be diagnosed.
+
+For example, the warning triggers for the following redeclarations because
+the first one allows an array of any size to be passed to @code{f} while
+the second one specifies that the array argument must have at least @code{n}
+elements. In addition, calling @code{f} with the associated VLA bound
+parameter in excess of the actual VLA bound triggers a warning as well.
+
+@smallexample
+void f (int n, int[n]);
+void f (int, int[]); // warning: argument 2 previously declared as a VLA
+
+void g (int n)
+@{
+ if (n > 4)
+ return;
+ int a[n];
+ f (sizeof a, a); // warning: access to a by f may be out of bounds
+ @dots{}
+@}
+
+@end smallexample
+
+@option{-Wvla-parameter} is included in @option{-Wall}. The
+@option{-Warray-parameter} option triggers warnings for similar problems
+involving ordinary array arguments.
+
+@item -Wvolatile-register-var
+@opindex Wvolatile-register-var
+@opindex Wno-volatile-register-var
+Warn if a register variable is declared volatile. The volatile
+modifier does not inhibit all optimizations that may eliminate reads
+and/or writes to register variables. This warning is enabled by
+@option{-Wall}.
+
+@item -Wxor-used-as-pow @r{(C, C++, Objective-C and Objective-C++ only)}
+@opindex Wxor-used-as-pow
+@opindex Wno-xor-used-as-pow
+Warn about uses of @code{^}, the exclusive or operator, where it appears
+the user meant exponentiation. Specifically, the warning occurs when the
+left-hand side is the decimal constant 2 or 10 and the right-hand side
+is also a decimal constant.
+
+In C and C++, @code{^} means exclusive or, whereas in some other languages
+(e.g. TeX and some versions of BASIC) it means exponentiation.
+
+This warning is enabled by default. It can be silenced by converting one
+of the operands to hexadecimal.
+
+@item -Wdisabled-optimization
+@opindex Wdisabled-optimization
+@opindex Wno-disabled-optimization
+Warn if a requested optimization pass is disabled. This warning does
+not generally indicate that there is anything wrong with your code; it
+merely indicates that GCC's optimizers are unable to handle the code
+effectively. Often, the problem is that your code is too big or too
+complex; GCC refuses to optimize programs when the optimization
+itself is likely to take inordinate amounts of time.
+
+@item -Wpointer-sign @r{(C and Objective-C only)}
+@opindex Wpointer-sign
+@opindex Wno-pointer-sign
+Warn for pointer argument passing or assignment with different signedness.
+This option is only supported for C and Objective-C@. It is implied by
+@option{-Wall} and by @option{-Wpedantic}, which can be disabled with
+@option{-Wno-pointer-sign}.
+
+@item -Wstack-protector
+@opindex Wstack-protector
+@opindex Wno-stack-protector
+This option is only active when @option{-fstack-protector} is active. It
+warns about functions that are not protected against stack smashing.
+
+@item -Woverlength-strings
+@opindex Woverlength-strings
+@opindex Wno-overlength-strings
+Warn about string constants that are longer than the ``minimum
+maximum'' length specified in the C standard. Modern compilers
+generally allow string constants that are much longer than the
+standard's minimum limit, but very portable programs should avoid
+using longer strings.
+
+The limit applies @emph{after} string constant concatenation, and does
+not count the trailing NUL@. In C90, the limit was 509 characters; in
+C99, it was raised to 4095. C++98 does not specify a normative
+minimum maximum, so we do not diagnose overlength strings in C++@.
+
+This option is implied by @option{-Wpedantic}, and can be disabled with
+@option{-Wno-overlength-strings}.
+
+@item -Wunsuffixed-float-constants @r{(C and Objective-C only)}
+@opindex Wunsuffixed-float-constants
+@opindex Wno-unsuffixed-float-constants
+
+Issue a warning for any floating constant that does not have
+a suffix. When used together with @option{-Wsystem-headers} it
+warns about such constants in system header files. This can be useful
+when preparing code to use with the @code{FLOAT_CONST_DECIMAL64} pragma
+from the decimal floating-point extension to C99.
+
+@item -Wno-lto-type-mismatch
+@opindex Wlto-type-mismatch
+@opindex Wno-lto-type-mismatch
+
+During the link-time optimization, do not warn about type mismatches in
+global declarations from different compilation units.
+Requires @option{-flto} to be enabled. Enabled by default.
+
+@item -Wno-designated-init @r{(C and Objective-C only)}
+@opindex Wdesignated-init
+@opindex Wno-designated-init
+Suppress warnings when a positional initializer is used to initialize
+a structure that has been marked with the @code{designated_init}
+attribute.
+
+@end table
+
+@node Static Analyzer Options
+@section Options That Control Static Analysis
+
+@table @gcctabopt
+@item -fanalyzer
+@opindex analyzer
+@opindex fanalyzer
+@opindex fno-analyzer
+This option enables an static analysis of program flow which looks
+for ``interesting'' interprocedural paths through the
+code, and issues warnings for problems found on them.
+
+This analysis is much more expensive than other GCC warnings.
+
+Enabling this option effectively enables the following warnings:
+
+@gccoptlist{ @gol
+-Wanalyzer-allocation-size @gol
+-Wanalyzer-double-fclose @gol
+-Wanalyzer-double-free @gol
+-Wanalyzer-exposure-through-output-file @gol
+-Wanalyzer-exposure-through-uninit-copy @gol
+-Wanalyzer-fd-access-mode-mismatch @gol
+-Wanalyzer-fd-double-close @gol
+-Wanalyzer-fd-leak @gol
+-Wanalyzer-fd-use-after-close @gol
+-Wanalyzer-fd-use-without-check @gol
+-Wanalyzer-file-leak @gol
+-Wanalyzer-free-of-non-heap @gol
+-Wanalyzer-imprecise-fp-arithmetic @gol
+-Wanalyzer-jump-through-null @gol
+-Wanalyzer-malloc-leak @gol
+-Wanalyzer-mismatching-deallocation @gol
+-Wanalyzer-null-argument @gol
+-Wanalyzer-null-dereference @gol
+-Wanalyzer-out-of-bounds @gol
+-Wanalyzer-possible-null-argument @gol
+-Wanalyzer-possible-null-dereference @gol
+-Wanalyzer-putenv-of-auto-var @gol
+-Wanalyzer-shift-count-negative @gol
+-Wanalyzer-shift-count-overflow @gol
+-Wanalyzer-stale-setjmp-buffer @gol
+-Wanalyzer-unsafe-call-within-signal-handler @gol
+-Wanalyzer-use-after-free @gol
+-Wanalyzer-use-of-pointer-in-stale-stack-frame @gol
+-Wanalyzer-use-of-uninitialized-value @gol
+-Wanalyzer-va-arg-type-mismatch @gol
+-Wanalyzer-va-list-exhausted @gol
+-Wanalyzer-va-list-leak @gol
+-Wanalyzer-va-list-use-after-va-end @gol
+-Wanalyzer-write-to-const @gol
+-Wanalyzer-write-to-string-literal @gol
+}
+@ignore
+-Wanalyzer-tainted-allocation-size @gol
+-Wanalyzer-tainted-array-index @gol
+-Wanalyzer-tainted-divisor @gol
+-Wanalyzer-tainted-offset @gol
+-Wanalyzer-tainted-size @gol
+@end ignore
+
+This option is only available if GCC was configured with analyzer
+support enabled.
+
+@item -Wanalyzer-too-complex
+@opindex Wanalyzer-too-complex
+@opindex Wno-analyzer-too-complex
+If @option{-fanalyzer} is enabled, the analyzer uses various heuristics
+to attempt to explore the control flow and data flow in the program,
+but these can be defeated by sufficiently complicated code.
+
+By default, the analysis silently stops if the code is too
+complicated for the analyzer to fully explore and it reaches an internal
+limit. The @option{-Wanalyzer-too-complex} option warns if this occurs.
+
+@item -Wno-analyzer-allocation-size
+@opindex Wanalyzer-allocation-size
+@opindex Wno-analyzer-allocation-size
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-allocation-size}
+to disable it.
+
+This diagnostic warns for paths through the code in which a pointer to
+a buffer is assigned to point at a buffer with a size that is not a
+multiple of @code{sizeof (*pointer)}.
+
+See @uref{https://cwe.mitre.org/data/definitions/131.html, CWE-131: Incorrect Calculation of Buffer Size}.
+
+@item -Wno-analyzer-double-fclose
+@opindex Wanalyzer-double-fclose
+@opindex Wno-analyzer-double-fclose
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-double-fclose} to disable it.
+
+This diagnostic warns for paths through the code in which a @code{FILE *}
+can have @code{fclose} called on it more than once.
+
+See @uref{https://cwe.mitre.org/data/definitions/1341.html, CWE-1341: Multiple Releases of Same Resource or Handle}.
+
+@item -Wno-analyzer-double-free
+@opindex Wanalyzer-double-free
+@opindex Wno-analyzer-double-free
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-double-free} to disable it.
+
+This diagnostic warns for paths through the code in which a pointer
+can have a deallocator called on it more than once, either @code{free},
+or a deallocator referenced by attribute @code{malloc}.
+
+See @uref{https://cwe.mitre.org/data/definitions/415.html, CWE-415: Double Free}.
+
+@item -Wno-analyzer-exposure-through-output-file
+@opindex Wanalyzer-exposure-through-output-file
+@opindex Wno-analyzer-exposure-through-output-file
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-exposure-through-output-file}
+to disable it.
+
+This diagnostic warns for paths through the code in which a
+security-sensitive value is written to an output file
+(such as writing a password to a log file).
+
+See @uref{https://cwe.mitre.org/data/definitions/532.html, CWE-532: Information Exposure Through Log Files}.
+
+@item -Wanalyzer-exposure-through-uninit-copy
+@opindex Wanalyzer-exposure-through-uninit-copy
+@opindex Wno-analyzer-exposure-through-uninit-copy
+This warning requires both @option{-fanalyzer} and the use of a plugin
+to specify a function that copies across a ``trust boundary''. Use
+@option{-Wno-analyzer-exposure-through-uninit-copy} to disable it.
+
+This diagnostic warns for ``infoleaks'' - paths through the code in which
+uninitialized values are copied across a security boundary
+(such as code within an OS kernel that copies a partially-initialized
+struct on the stack to user space).
+
+See @uref{https://cwe.mitre.org/data/definitions/200.html, CWE-200: Exposure of Sensitive Information to an Unauthorized Actor}.
+
+@item -Wno-analyzer-fd-access-mode-mismatch
+@opindex Wanalyzer-fd-access-mode-mismatch
+@opindex Wno-analyzer-fd-access-mode-mismatch
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-fd-access-mode-mismatch}
+to disable it.
+
+This diagnostic warns for paths through code in which a
+@code{read} on a write-only file descriptor is attempted, or vice versa.
+
+This diagnostic also warns for code paths in a which a function with attribute
+@code{fd_arg_read (N)} is called with a file descriptor opened with
+@code{O_WRONLY} at referenced argument @code{N} or a function with attribute
+@code{fd_arg_write (N)} is called with a file descriptor opened with
+@code{O_RDONLY} at referenced argument @var{N}.
+
+@item -Wno-analyzer-fd-double-close
+@opindex Wanalyzer-fd-double-close
+@opindex Wno-analyzer-fd-double-close
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-fd-double-close}
+to disable it.
+
+This diagnostic warns for paths through code in which a
+file descriptor can be closed more than once.
+
+See @uref{https://cwe.mitre.org/data/definitions/1341.html, CWE-1341: Multiple Releases of Same Resource or Handle}.
+
+@item -Wno-analyzer-fd-leak
+@opindex Wanalyzer-fd-leak
+@opindex Wno-analyzer-fd-leak
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-fd-leak}
+to disable it.
+
+This diagnostic warns for paths through code in which an
+open file descriptor is leaked.
+
+See @uref{https://cwe.mitre.org/data/definitions/775.html, CWE-775: Missing Release of File Descriptor or Handle after Effective Lifetime}.
+
+@item -Wno-analyzer-fd-use-after-close
+@opindex Wanalyzer-fd-use-after-close
+@opindex Wno-analyzer-fd-use-after-close
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-fd-use-after-close}
+to disable it.
+
+This diagnostic warns for paths through code in which a
+read or write is called on a closed file descriptor.
+
+This diagnostic also warns for paths through code in which
+a function with attribute @code{fd_arg (N)} or @code{fd_arg_read (N)}
+or @code{fd_arg_write (N)} is called with a closed file descriptor at
+referenced argument @code{N}.
+
+@item -Wno-analyzer-fd-use-without-check
+@opindex Wanalyzer-fd-use-without-check
+@opindex Wno-analyzer-fd-use-without-check
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-fd-use-without-check}
+to disable it.
+
+This diagnostic warns for paths through code in which a
+file descriptor is used without being checked for validity.
+
+This diagnostic also warns for paths through code in which
+a function with attribute @code{fd_arg (N)} or @code{fd_arg_read (N)}
+or @code{fd_arg_write (N)} is called with a file descriptor, at referenced
+argument @code{N}, without being checked for validity.
+
+@item -Wno-analyzer-file-leak
+@opindex Wanalyzer-file-leak
+@opindex Wno-analyzer-file-leak
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-file-leak}
+to disable it.
+
+This diagnostic warns for paths through the code in which a
+@code{<stdio.h>} @code{FILE *} stream object is leaked.
+
+See @uref{https://cwe.mitre.org/data/definitions/775.html, CWE-775: Missing Release of File Descriptor or Handle after Effective Lifetime}.
+
+@item -Wno-analyzer-free-of-non-heap
+@opindex Wanalyzer-free-of-non-heap
+@opindex Wno-analyzer-free-of-non-heap
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-free-of-non-heap}
+to disable it.
+
+This diagnostic warns for paths through the code in which @code{free}
+is called on a non-heap pointer (e.g. an on-stack buffer, or a global).
+
+See @uref{https://cwe.mitre.org/data/definitions/590.html, CWE-590: Free of Memory not on the Heap}.
+
+@item -Wno-analyzer-imprecise-fp-arithmetic
+@opindex Wanalyzer-imprecise-fp-arithmetic
+@opindex Wno-analyzer-imprecise-fp-arithmetic
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-imprecise-fp-arithmetic}
+to disable it.
+
+This diagnostic warns for paths through the code in which floating-point
+arithmetic is used in locations where precise computation is needed. This
+diagnostic only warns on use of floating-point operands inside the
+calculation of an allocation size at the moment.
+
+@item -Wno-analyzer-jump-through-null
+@opindex Wanalyzer-jump-through-null
+@opindex Wno-analyzer-jump-through-null
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-jump-through-null}
+to disable it.
+
+This diagnostic warns for paths through the code in which a @code{NULL}
+function pointer is called.
+
+@item -Wno-analyzer-malloc-leak
+@opindex Wanalyzer-malloc-leak
+@opindex Wno-analyzer-malloc-leak
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-malloc-leak}
+to disable it.
+
+This diagnostic warns for paths through the code in which a
+pointer allocated via an allocator is leaked: either @code{malloc},
+or a function marked with attribute @code{malloc}.
+
+See @uref{https://cwe.mitre.org/data/definitions/401.html, CWE-401: Missing Release of Memory after Effective Lifetime}.
+
+@item -Wno-analyzer-mismatching-deallocation
+@opindex Wanalyzer-mismatching-deallocation
+@opindex Wno-analyzer-mismatching-deallocation
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-mismatching-deallocation}
+to disable it.
+
+This diagnostic warns for paths through the code in which the
+wrong deallocation function is called on a pointer value, based on
+which function was used to allocate the pointer value. The diagnostic
+will warn about mismatches between @code{free}, scalar @code{delete}
+and vector @code{delete[]}, and those marked as allocator/deallocator
+pairs using attribute @code{malloc}.
+
+See @uref{https://cwe.mitre.org/data/definitions/762.html, CWE-762: Mismatched Memory Management Routines}.
+
+@item -Wno-analyzer-out-of-bounds
+@opindex Wanalyzer-out-of-bounds
+@opindex Wno-analyzer-out-of-bounds
+This warning requires @option{-fanalyzer} to enable it; use
+@option{-Wno-analyzer-out-of-bounds} to disable it.
+
+This diagnostic warns for path through the code in which a buffer is
+definitely read or written out-of-bounds. The diagnostic applies for
+cases where the analyzer is able to determine a constant offset and for
+accesses past the end of a buffer, also a constant capacity. Further,
+the diagnostic does limited checking for accesses past the end when the
+offset as well as the capacity is symbolic.
+
+See @uref{https://cwe.mitre.org/data/definitions/119.html, CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer}.
+
+@item -Wno-analyzer-possible-null-argument
+@opindex Wanalyzer-possible-null-argument
+@opindex Wno-analyzer-possible-null-argument
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-possible-null-argument} to disable it.
+
+This diagnostic warns for paths through the code in which a
+possibly-NULL value is passed to a function argument marked
+with @code{__attribute__((nonnull))} as requiring a non-NULL
+value.
+
+See @uref{https://cwe.mitre.org/data/definitions/690.html, CWE-690: Unchecked Return Value to NULL Pointer Dereference}.
+
+@item -Wno-analyzer-possible-null-dereference
+@opindex Wanalyzer-possible-null-dereference
+@opindex Wno-analyzer-possible-null-dereference
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-possible-null-dereference} to disable it.
+
+This diagnostic warns for paths through the code in which a
+possibly-NULL value is dereferenced.
+
+See @uref{https://cwe.mitre.org/data/definitions/690.html, CWE-690: Unchecked Return Value to NULL Pointer Dereference}.
+
+@item -Wno-analyzer-null-argument
+@opindex Wanalyzer-null-argument
+@opindex Wno-analyzer-null-argument
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-null-argument} to disable it.
+
+This diagnostic warns for paths through the code in which a
+value known to be NULL is passed to a function argument marked
+with @code{__attribute__((nonnull))} as requiring a non-NULL
+value.
+
+See @uref{https://cwe.mitre.org/data/definitions/476.html, CWE-476: NULL Pointer Dereference}.
+
+@item -Wno-analyzer-null-dereference
+@opindex Wanalyzer-null-dereference
+@opindex Wno-analyzer-null-dereference
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-null-dereference} to disable it.
+
+This diagnostic warns for paths through the code in which a
+value known to be NULL is dereferenced.
+
+See @uref{https://cwe.mitre.org/data/definitions/476.html, CWE-476: NULL Pointer Dereference}.
+
+@item -Wno-analyzer-putenv-of-auto-var
+@opindex Wanalyzer-putenv-of-auto-var
+@opindex Wno-analyzer-putenv-of-auto-var
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-putenv-of-auto-var} to disable it.
+
+This diagnostic warns for paths through the code in which a
+call to @code{putenv} is passed a pointer to an automatic variable
+or an on-stack buffer.
+
+See @uref{https://wiki.sei.cmu.edu/confluence/x/6NYxBQ, POS34-C. Do not call putenv() with a pointer to an automatic variable as the argument}.
+
+@item -Wno-analyzer-shift-count-negative
+@opindex Wanalyzer-shift-count-negative
+@opindex Wno-analyzer-shift-count-negative
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-shift-count-negative} to disable it.
+
+This diagnostic warns for paths through the code in which a
+shift is attempted with a negative count. It is analogous to
+the @option{-Wshift-count-negative} diagnostic implemented in
+the C/C++ front ends, but is implemented based on analyzing
+interprocedural paths, rather than merely parsing the syntax tree.
+However, the analyzer does not prioritize detection of such paths, so
+false negatives are more likely relative to other warnings.
+
+@item -Wno-analyzer-shift-count-overflow
+@opindex Wanalyzer-shift-count-overflow
+@opindex Wno-analyzer-shift-count-overflow
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-shift-count-overflow} to disable it.
+
+This diagnostic warns for paths through the code in which a
+shift is attempted with a count greater than or equal to the
+precision of the operand's type. It is analogous to
+the @option{-Wshift-count-overflow} diagnostic implemented in
+the C/C++ front ends, but is implemented based on analyzing
+interprocedural paths, rather than merely parsing the syntax tree.
+However, the analyzer does not prioritize detection of such paths, so
+false negatives are more likely relative to other warnings.
+
+@item -Wno-analyzer-stale-setjmp-buffer
+@opindex Wanalyzer-stale-setjmp-buffer
+@opindex Wno-analyzer-stale-setjmp-buffer
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-stale-setjmp-buffer} to disable it.
+
+This diagnostic warns for paths through the code in which
+@code{longjmp} is called to rewind to a @code{jmp_buf} relating
+to a @code{setjmp} call in a function that has returned.
+
+When @code{setjmp} is called on a @code{jmp_buf} to record a rewind
+location, it records the stack frame. The stack frame becomes invalid
+when the function containing the @code{setjmp} call returns. Attempting
+to rewind to it via @code{longjmp} would reference a stack frame that
+no longer exists, and likely lead to a crash (or worse).
+
+@item -Wno-analyzer-tainted-allocation-size
+@opindex Wanalyzer-tainted-allocation-size
+@opindex Wno-analyzer-tainted-allocation-size
+This warning requires both @option{-fanalyzer} and
+@option{-fanalyzer-checker=taint} to enable it;
+use @option{-Wno-analyzer-tainted-allocation-size} to disable it.
+
+This diagnostic warns for paths through the code in which a value
+that could be under an attacker's control is used as the size
+of an allocation without being sanitized, so that an attacker could
+inject an excessively large allocation and potentially cause a denial
+of service attack.
+
+See @uref{https://cwe.mitre.org/data/definitions/789.html, CWE-789: Memory Allocation with Excessive Size Value}.
+
+@item -Wno-analyzer-tainted-array-index
+@opindex Wanalyzer-tainted-array-index
+@opindex Wno-analyzer-tainted-array-index
+This warning requires both @option{-fanalyzer} and
+@option{-fanalyzer-checker=taint} to enable it;
+use @option{-Wno-analyzer-tainted-array-index} to disable it.
+
+This diagnostic warns for paths through the code in which a value
+that could be under an attacker's control is used as the index
+of an array access without being sanitized, so that an attacker
+could inject an out-of-bounds access.
+
+See @uref{https://cwe.mitre.org/data/definitions/129.html, CWE-129: Improper Validation of Array Index}.
+
+@item -Wno-analyzer-tainted-divisor
+@opindex Wanalyzer-tainted-divisor
+@opindex Wno-analyzer-tainted-divisor
+This warning requires both @option{-fanalyzer} and
+@option{-fanalyzer-checker=taint} to enable it;
+use @option{-Wno-analyzer-tainted-divisor} to disable it.
+
+This diagnostic warns for paths through the code in which a value
+that could be under an attacker's control is used as the divisor
+in a division or modulus operation without being sanitized, so that
+an attacker could inject a division-by-zero.
+
+See @uref{https://cwe.mitre.org/data/definitions/369.html, CWE-369: Divide By Zero}.
+
+@item -Wno-analyzer-tainted-offset
+@opindex Wanalyzer-tainted-offset
+@opindex Wno-analyzer-tainted-offset
+This warning requires both @option{-fanalyzer} and
+@option{-fanalyzer-checker=taint} to enable it;
+use @option{-Wno-analyzer-tainted-offset} to disable it.
+
+This diagnostic warns for paths through the code in which a value
+that could be under an attacker's control is used as a pointer offset
+without being sanitized, so that an attacker could inject an out-of-bounds
+access.
+
+See @uref{https://cwe.mitre.org/data/definitions/823.html, CWE-823: Use of Out-of-range Pointer Offset}.
+
+@item -Wno-analyzer-tainted-size
+@opindex Wanalyzer-tainted-size
+@opindex Wno-analyzer-tainted-size
+This warning requires both @option{-fanalyzer} and
+@option{-fanalyzer-checker=taint} to enable it;
+use @option{-Wno-analyzer-tainted-size} to disable it.
+
+This diagnostic warns for paths through the code in which a value
+that could be under an attacker's control is used as the size of
+an operation such as @code{memset} without being sanitized, so that an
+attacker could inject an out-of-bounds access.
+
+See @uref{https://cwe.mitre.org/data/definitions/129.html, CWE-129: Improper Validation of Array Index}.
+
+@item -Wno-analyzer-unsafe-call-within-signal-handler
+@opindex Wanalyzer-unsafe-call-within-signal-handler
+@opindex Wno-analyzer-unsafe-call-within-signal-handler
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-unsafe-call-within-signal-handler} to disable it.
+
+This diagnostic warns for paths through the code in which a
+function known to be async-signal-unsafe (such as @code{fprintf}) is
+called from a signal handler.
+
+See @uref{https://cwe.mitre.org/data/definitions/479.html, CWE-479: Signal Handler Use of a Non-reentrant Function}.
+
+@item -Wno-analyzer-use-after-free
+@opindex Wanalyzer-use-after-free
+@opindex Wno-analyzer-use-after-free
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-use-after-free} to disable it.
+
+This diagnostic warns for paths through the code in which a
+pointer is used after a deallocator is called on it: either @code{free},
+or a deallocator referenced by attribute @code{malloc}.
+
+See @uref{https://cwe.mitre.org/data/definitions/416.html, CWE-416: Use After Free}.
+
+@item -Wno-analyzer-use-of-pointer-in-stale-stack-frame
+@opindex Wanalyzer-use-of-pointer-in-stale-stack-frame
+@opindex Wno-analyzer-use-of-pointer-in-stale-stack-frame
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-use-of-pointer-in-stale-stack-frame}
+to disable it.
+
+This diagnostic warns for paths through the code in which a pointer
+is dereferenced that points to a variable in a stale stack frame.
+
+@item -Wno-analyzer-va-arg-type-mismatch
+@opindex Wanalyzer-va-arg-type-mismatch
+@opindex Wno-analyzer-va-arg-type-mismatch
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-va-arg-type-mismatch}
+to disable it.
+
+This diagnostic warns for interprocedural paths through the code for which
+the analyzer detects an attempt to use @code{va_arg} to extract a value
+passed to a variadic call, but uses a type that does not match that of
+the expression passed to the call.
+
+See @uref{https://cwe.mitre.org/data/definitions/686.html, CWE-686: Function Call With Incorrect Argument Type}.
+
+@item -Wno-analyzer-va-list-exhausted
+@opindex Wanalyzer-va-list-exhausted
+@opindex Wno-analyzer-va-list-exhausted
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-va-list-exhausted}
+to disable it.
+
+This diagnostic warns for interprocedural paths through the code for which
+the analyzer detects an attempt to use @code{va_arg} to access the next
+value passed to a variadic call, but all of the values in the
+@code{va_list} have already been consumed.
+
+See @uref{https://cwe.mitre.org/data/definitions/685.html, CWE-685: Function Call With Incorrect Number of Arguments}.
+
+@item -Wno-analyzer-va-list-leak
+@opindex Wanalyzer-va-list-leak
+@opindex Wno-analyzer-va-list-leak
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-va-list-leak}
+to disable it.
+
+This diagnostic warns for interprocedural paths through the code for which
+the analyzer detects that @code{va_start} or @code{va_copy} has been called
+on a @code{va_list} without a corresponding call to @code{va_end}.
+
+@item -Wno-analyzer-va-list-use-after-va-end
+@opindex Wanalyzer-va-list-use-after-va-end
+@opindex Wno-analyzer-va-list-use-after-va-end
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-va-list-use-after-va-end}
+to disable it.
+
+This diagnostic warns for interprocedural paths through the code for which
+the analyzer detects an attempt to use a @code{va_list} after
+@code{va_end} has been called on it.
+@code{va_list}.
+
+@item -Wno-analyzer-write-to-const
+@opindex Wanalyzer-write-to-const
+@opindex Wno-analyzer-write-to-const
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-write-to-const}
+to disable it.
+
+This diagnostic warns for paths through the code in which the analyzer
+detects an attempt to write through a pointer to a @code{const} object.
+However, the analyzer does not prioritize detection of such paths, so
+false negatives are more likely relative to other warnings.
+
+@item -Wno-analyzer-write-to-string-literal
+@opindex Wanalyzer-write-to-string-literal
+@opindex Wno-analyzer-write-to-string-literal
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-write-to-string-literal}
+to disable it.
+
+This diagnostic warns for paths through the code in which the analyzer
+detects an attempt to write through a pointer to a string literal.
+However, the analyzer does not prioritize detection of such paths, so
+false negatives are more likely relative to other warnings.
+
+@item -Wno-analyzer-use-of-uninitialized-value
+@opindex Wanalyzer-use-of-uninitialized-value
+@opindex Wno-analyzer-use-of-uninitialized-value
+This warning requires @option{-fanalyzer}, which enables it; use
+@option{-Wno-analyzer-use-of-uninitialized-value} to disable it.
+
+This diagnostic warns for paths through the code in which an uninitialized
+value is used.
+
+See @uref{https://cwe.mitre.org/data/definitions/457.html, CWE-457: Use of Uninitialized Variable}.
+
+@end table
+
+The analyzer has hardcoded knowledge about the behavior of the following
+memory-management functions:
+
+@itemize @bullet
+@item @code{alloca}
+@item The built-in functions @code{__builtin_alloc},
+@code{__builtin_alloc_with_align}, @item @code{__builtin_calloc},
+@code{__builtin_free}, @code{__builtin_malloc}, @code{__builtin_memcpy},
+@code{__builtin_memcpy_chk}, @code{__builtin_memset},
+@code{__builtin_memset_chk}, @code{__builtin_realloc},
+@code{__builtin_stack_restore}, and @code{__builtin_stack_save}
+@item @code{calloc}
+@item @code{free}
+@item @code{malloc}
+@item @code{memset}
+@item @code{operator delete}
+@item @code{operator delete []}
+@item @code{operator new}
+@item @code{operator new []}
+@item @code{realloc}
+@item @code{strdup}
+@item @code{strndup}
+@end itemize
+
+of the following functions for working with file descriptors:
+
+@itemize @bullet
+@item @code{open}
+@item @code{close}
+@item @code{creat}
+@item @code{dup}, @code{dup2} and @code{dup3}
+@item @code{pipe}, and @code{pipe2}
+@item @code{read}
+@item @code{write}
+@end itemize
+
+of the following functions for working with @code{<stdio.h>} streams:
+@itemize @bullet
+@item The built-in functions @code{__builtin_fprintf},
+@code{__builtin_fprintf_unlocked}, @code{__builtin_fputc},
+@code{__builtin_fputc_unlocked}, @code{__builtin_fputs},
+@code{__builtin_fputs_unlocked}, @code{__builtin_fwrite},
+@code{__builtin_fwrite_unlocked}, @code{__builtin_printf},
+@code{__builtin_printf_unlocked}, @code{__builtin_putc},
+@code{__builtin_putchar}, @code{__builtin_putchar_unlocked},
+@code{__builtin_putc_unlocked}, @code{__builtin_puts},
+@code{__builtin_puts_unlocked}, @code{__builtin_vfprintf}, and
+@code{__builtin_vprintf}
+@item @code{fopen}
+@item @code{fclose}
+@item @code{fgets}
+@item @code{fgets_unlocked}
+@item @code{fread}
+@item @code{getchar}
+@item @code{fprintf}
+@item @code{printf}
+@item @code{fwrite}
+@end itemize
+
+and of the following functions:
+
+@itemize @bullet
+@item The built-in functions @code{__builtin_expect},
+@code{__builtin_expect_with_probability}, @code{__builtin_strchr},
+@code{__builtin_strcpy}, @code{__builtin_strcpy_chk},
+@code{__builtin_strlen}, @code{__builtin_va_copy}, and
+@code{__builtin_va_start}
+@item The GNU extensions @code{error} and @code{error_at_line}
+@item @code{getpass}
+@item @code{longjmp}
+@item @code{putenv}
+@item @code{setjmp}
+@item @code{siglongjmp}
+@item @code{signal}
+@item @code{sigsetjmp}
+@item @code{strchr}
+@item @code{strlen}
+@end itemize
+
+In addition, various functions with an @code{__analyzer_} prefix have
+special meaning to the analyzer, described in the GCC Internals manual.
+
+Pertinent parameters for controlling the exploration are:
+@option{--param analyzer-bb-explosion-factor=@var{value}},
+@option{--param analyzer-max-enodes-per-program-point=@var{value}},
+@option{--param analyzer-max-recursion-depth=@var{value}}, and
+@option{--param analyzer-min-snodes-for-call-summary=@var{value}}.
+
+The following options control the analyzer.
+
+@table @gcctabopt
+
+@item -fanalyzer-call-summaries
+@opindex fanalyzer-call-summaries
+@opindex fno-analyzer-call-summaries
+Simplify interprocedural analysis by computing the effect of certain calls,
+rather than exploring all paths through the function from callsite to each
+possible return.
+
+If enabled, call summaries are only used for functions with more than one
+call site, and that are sufficiently complicated (as per
+@option{--param analyzer-min-snodes-for-call-summary=@var{value}}).
+
+@item -fanalyzer-checker=@var{name}
+@opindex fanalyzer-checker
+Restrict the analyzer to run just the named checker, and enable it.
+
+Some checkers are disabled by default (even with @option{-fanalyzer}),
+such as the @code{taint} checker that implements
+@option{-Wanalyzer-tainted-array-index}, and this option is required
+to enable them.
+
+@emph{Note:} currently, @option{-fanalyzer-checker=taint} disables the
+following warnings from @option{-fanalyzer}:
+
+@gccoptlist{ @gol
+-Wanalyzer-double-fclose @gol
+-Wanalyzer-double-free @gol
+-Wanalyzer-exposure-through-output-file @gol
+-Wanalyzer-fd-access-mode-mismatch @gol
+-Wanalyzer-fd-double-close @gol
+-Wanalyzer-fd-leak @gol
+-Wanalyzer-fd-use-after-close @gol
+-Wanalyzer-fd-use-without-check @gol
+-Wanalyzer-file-leak @gol
+-Wanalyzer-free-of-non-heap @gol
+-Wanalyzer-malloc-leak @gol
+-Wanalyzer-mismatching-deallocation @gol
+-Wanalyzer-null-argument @gol
+-Wanalyzer-null-dereference @gol
+-Wanalyzer-possible-null-argument @gol
+-Wanalyzer-possible-null-dereference @gol
+-Wanalyzer-unsafe-call-within-signal-handler @gol
+-Wanalyzer-use-after-free @gol
+-Wanalyzer-va-list-leak @gol
+-Wanalyzer-va-list-use-after-va-end @gol
+}
+
+@item -fno-analyzer-feasibility
+@opindex fanalyzer-feasibility
+@opindex fno-analyzer-feasibility
+This option is intended for analyzer developers.
+
+By default the analyzer verifies that there is a feasible control flow path
+for each diagnostic it emits: that the conditions that hold are not mutually
+exclusive. Diagnostics for which no feasible path can be found are rejected.
+This filtering can be suppressed with @option{-fno-analyzer-feasibility}, for
+debugging issues in this code.
+
+@item -fanalyzer-fine-grained
+@opindex fanalyzer-fine-grained
+@opindex fno-analyzer-fine-grained
+This option is intended for analyzer developers.
+
+Internally the analyzer builds an ``exploded graph'' that combines
+control flow graphs with data flow information.
+
+By default, an edge in this graph can contain the effects of a run
+of multiple statements within a basic block. With
+@option{-fanalyzer-fine-grained}, each statement gets its own edge.
+
+@item -fanalyzer-show-duplicate-count
+@opindex fanalyzer-show-duplicate-count
+@opindex fno-analyzer-show-duplicate-count
+This option is intended for analyzer developers: if multiple diagnostics
+have been detected as being duplicates of each other, it emits a note when
+reporting the best diagnostic, giving the number of additional diagnostics
+that were suppressed by the deduplication logic.
+
+@item -fno-analyzer-state-merge
+@opindex fanalyzer-state-merge
+@opindex fno-analyzer-state-merge
+This option is intended for analyzer developers.
+
+By default the analyzer attempts to simplify analysis by merging
+sufficiently similar states at each program point as it builds its
+``exploded graph''. With @option{-fno-analyzer-state-merge} this
+merging can be suppressed, for debugging state-handling issues.
+
+@item -fno-analyzer-state-purge
+@opindex fanalyzer-state-purge
+@opindex fno-analyzer-state-purge
+This option is intended for analyzer developers.
+
+By default the analyzer attempts to simplify analysis by purging
+aspects of state at a program point that appear to no longer be relevant
+e.g. the values of locals that aren't accessed later in the function
+and which aren't relevant to leak analysis.
+
+With @option{-fno-analyzer-state-purge} this purging of state can
+be suppressed, for debugging state-handling issues.
+
+@item -fanalyzer-transitivity
+@opindex fanalyzer-transitivity
+@opindex fno-analyzer-transitivity
+This option enables transitivity of constraints within the analyzer.
+
+@item -fno-analyzer-undo-inlining
+@opindex fanalyzer-undo-inlining
+@opindex fno-analyzer-undo-inlining
+This option is intended for analyzer developers.
+
+@option{-fanalyzer} runs relatively late compared to other code analysis
+tools, and some optimizations have already been applied to the code. In
+particular function inlining may have occurred, leading to the
+interprocedural execution paths emitted by the analyzer containing
+function frames that don't correspond to those in the original source
+code.
+
+By default the analyzer attempts to reconstruct the original function
+frames, and to emit events showing the inlined calls.
+
+With @option{-fno-analyzer-undo-inlining} this attempt to reconstruct
+the original frame information can be be disabled, which may be of help
+when debugging issues in the analyzer.
+
+@item -fanalyzer-verbose-edges
+This option is intended for analyzer developers. It enables more
+verbose, lower-level detail in the descriptions of control flow
+within diagnostic paths.
+
+@item -fanalyzer-verbose-state-changes
+This option is intended for analyzer developers. It enables more
+verbose, lower-level detail in the descriptions of events relating
+to state machines within diagnostic paths.
+
+@item -fanalyzer-verbosity=@var{level}
+This option controls the complexity of the control flow paths that are
+emitted for analyzer diagnostics.
+
+The @var{level} can be one of:
+
+@table @samp
+@item 0
+At this level, interprocedural call and return events are displayed,
+along with the most pertinent state-change events relating to
+a diagnostic. For example, for a double-@code{free} diagnostic,
+both calls to @code{free} will be shown.
+
+@item 1
+As per the previous level, but also show events for the entry
+to each function.
+
+@item 2
+As per the previous level, but also show events relating to
+control flow that are significant to triggering the issue
+(e.g. ``true path taken'' at a conditional).
+
+This level is the default.
+
+@item 3
+As per the previous level, but show all control flow events, not
+just significant ones.
+
+@item 4
+This level is intended for analyzer developers; it adds various
+other events intended for debugging the analyzer.
+
+@end table
+
+@item -fdump-analyzer
+@opindex fdump-analyzer
+Dump internal details about what the analyzer is doing to
+@file{@var{file}.analyzer.txt}.
+This option is overridden by @option{-fdump-analyzer-stderr}.
+
+@item -fdump-analyzer-stderr
+@opindex fdump-analyzer-stderr
+Dump internal details about what the analyzer is doing to stderr.
+This option overrides @option{-fdump-analyzer}.
+
+@item -fdump-analyzer-callgraph
+@opindex fdump-analyzer-callgraph
+Dump a representation of the call graph suitable for viewing with
+GraphViz to @file{@var{file}.callgraph.dot}.
+
+@item -fdump-analyzer-exploded-graph
+@opindex fdump-analyzer-exploded-graph
+Dump a representation of the ``exploded graph'' suitable for viewing with
+GraphViz to @file{@var{file}.eg.dot}.
+Nodes are color-coded based on state-machine states to emphasize
+state changes.
+
+@item -fdump-analyzer-exploded-nodes
+@opindex dump-analyzer-exploded-nodes
+Emit diagnostics showing where nodes in the ``exploded graph'' are
+in relation to the program source.
+
+@item -fdump-analyzer-exploded-nodes-2
+@opindex dump-analyzer-exploded-nodes-2
+Dump a textual representation of the ``exploded graph'' to
+@file{@var{file}.eg.txt}.
+
+@item -fdump-analyzer-exploded-nodes-3
+@opindex dump-analyzer-exploded-nodes-3
+Dump a textual representation of the ``exploded graph'' to
+one dump file per node, to @file{@var{file}.eg-@var{id}.txt}.
+This is typically a large number of dump files.
+
+@item -fdump-analyzer-exploded-paths
+@opindex fdump-analyzer-exploded-paths
+Dump a textual representation of the ``exploded path'' for each
+diagnostic to @file{@var{file}.@var{idx}.@var{kind}.epath.txt}.
+
+@item -fdump-analyzer-feasibility
+@opindex dump-analyzer-feasibility
+Dump internal details about the analyzer's search for feasible paths.
+The details are written in a form suitable for viewing with GraphViz
+to filenames of the form @file{@var{file}.*.fg.dot},
+@file{@var{file}.*.tg.dot}, and @file{@var{file}.*.fpath.txt}.
+
+@item -fdump-analyzer-json
+@opindex fdump-analyzer-json
+Dump a compressed JSON representation of analyzer internals to
+@file{@var{file}.analyzer.json.gz}. The precise format is subject
+to change.
+
+@item -fdump-analyzer-state-purge
+@opindex fdump-analyzer-state-purge
+As per @option{-fdump-analyzer-supergraph}, dump a representation of the
+``supergraph'' suitable for viewing with GraphViz, but annotate the
+graph with information on what state will be purged at each node.
+The graph is written to @file{@var{file}.state-purge.dot}.
+
+@item -fdump-analyzer-supergraph
+@opindex fdump-analyzer-supergraph
+Dump representations of the ``supergraph'' suitable for viewing with
+GraphViz to @file{@var{file}.supergraph.dot} and to
+@file{@var{file}.supergraph-eg.dot}. These show all of the
+control flow graphs in the program, with interprocedural edges for
+calls and returns. The second dump contains annotations showing nodes
+in the ``exploded graph'' and diagnostics associated with them.
+
+@item -fdump-analyzer-untracked
+@opindex fdump-analyzer-untracked
+Emit custom warnings with internal details intended for analyzer developers.
+
+@end table
+
+@node Debugging Options
+@section Options for Debugging Your Program
+@cindex options, debugging
+@cindex debugging information options
+
+To tell GCC to emit extra information for use by a debugger, in almost
+all cases you need only to add @option{-g} to your other options. Some debug
+formats can co-exist (like DWARF with CTF) when each of them is enabled
+explicitly by adding the respective command line option to your other options.
+
+GCC allows you to use @option{-g} with
+@option{-O}. The shortcuts taken by optimized code may occasionally
+be surprising: some variables you declared may not exist
+at all; flow of control may briefly move where you did not expect it;
+some statements may not be executed because they compute constant
+results or their values are already at hand; some statements may
+execute in different places because they have been moved out of loops.
+Nevertheless it is possible to debug optimized output. This makes
+it reasonable to use the optimizer for programs that might have bugs.
+
+If you are not using some other optimization option, consider
+using @option{-Og} (@pxref{Optimize Options}) with @option{-g}.
+With no @option{-O} option at all, some compiler passes that collect
+information useful for debugging do not run at all, so that
+@option{-Og} may result in a better debugging experience.
+
+@table @gcctabopt
+@item -g
+@opindex g
+Produce debugging information in the operating system's native format
+(stabs, COFF, XCOFF, or DWARF)@. GDB can work with this debugging
+information.
+
+On most systems that use stabs format, @option{-g} enables use of extra
+debugging information that only GDB can use; this extra information
+makes debugging work better in GDB but probably makes other debuggers
+crash or refuse to read the program. If you want to control for certain whether
+to generate the extra information, use @option{-gvms} (see below).
+
+@item -ggdb
+@opindex ggdb
+Produce debugging information for use by GDB@. This means to use the
+most expressive format available (DWARF, stabs, or the native format
+if neither of those are supported), including GDB extensions if at all
+possible.
+
+@item -gdwarf
+@itemx -gdwarf-@var{version}
+@opindex gdwarf
+Produce debugging information in DWARF format (if that is supported).
+The value of @var{version} may be either 2, 3, 4 or 5; the default
+version for most targets is 5 (with the exception of VxWorks, TPF and
+Darwin/Mac OS X, which default to version 2, and AIX, which defaults
+to version 4).
+
+Note that with DWARF Version 2, some ports require and always
+use some non-conflicting DWARF 3 extensions in the unwind tables.
+
+Version 4 may require GDB 7.0 and @option{-fvar-tracking-assignments}
+for maximum benefit. Version 5 requires GDB 8.0 or higher.
+
+GCC no longer supports DWARF Version 1, which is substantially
+different than Version 2 and later. For historical reasons, some
+other DWARF-related options such as
+@option{-fno-dwarf2-cfi-asm}) retain a reference to DWARF Version 2
+in their names, but apply to all currently-supported versions of DWARF.
+
+@item -gbtf
+@opindex gbtf
+Request BTF debug information. BTF is the default debugging format for the
+eBPF target. On other targets, like x86, BTF debug information can be
+generated along with DWARF debug information when both of the debug formats are
+enabled explicitly via their respective command line options.
+
+@item -gctf
+@itemx -gctf@var{level}
+@opindex gctf
+Request CTF debug information and use level to specify how much CTF debug
+information should be produced. If @option{-gctf} is specified
+without a value for level, the default level of CTF debug information is 2.
+
+CTF debug information can be generated along with DWARF debug information when
+both of the debug formats are enabled explicitly via their respective command
+line options.
+
+Level 0 produces no CTF debug information at all. Thus, @option{-gctf0}
+negates @option{-gctf}.
+
+Level 1 produces CTF information for tracebacks only. This includes callsite
+information, but does not include type information.
+
+Level 2 produces type information for entities (functions, data objects etc.)
+at file-scope or global-scope only.
+
+@item -gvms
+@opindex gvms
+Produce debugging information in Alpha/VMS debug format (if that is
+supported). This is the format used by DEBUG on Alpha/VMS systems.
+
+@item -g@var{level}
+@itemx -ggdb@var{level}
+@itemx -gvms@var{level}
+Request debugging information and also use @var{level} to specify how
+much information. The default level is 2.
+
+Level 0 produces no debug information at all. Thus, @option{-g0} negates
+@option{-g}.
+
+Level 1 produces minimal information, enough for making backtraces in
+parts of the program that you don't plan to debug. This includes
+descriptions of functions and external variables, and line number
+tables, but no information about local variables.
+
+Level 3 includes extra information, such as all the macro definitions
+present in the program. Some debuggers support macro expansion when
+you use @option{-g3}.
+
+If you use multiple @option{-g} options, with or without level numbers,
+the last such option is the one that is effective.
+
+@option{-gdwarf} does not accept a concatenated debug level, to avoid
+confusion with @option{-gdwarf-@var{level}}.
+Instead use an additional @option{-g@var{level}} option to change the
+debug level for DWARF.
+
+@item -fno-eliminate-unused-debug-symbols
+@opindex feliminate-unused-debug-symbols
+@opindex fno-eliminate-unused-debug-symbols
+By default, no debug information is produced for symbols that are not actually
+used. Use this option if you want debug information for all symbols.
+
+@item -femit-class-debug-always
+@opindex femit-class-debug-always
+Instead of emitting debugging information for a C++ class in only one
+object file, emit it in all object files using the class. This option
+should be used only with debuggers that are unable to handle the way GCC
+normally emits debugging information for classes because using this
+option increases the size of debugging information by as much as a
+factor of two.
+
+@item -fno-merge-debug-strings
+@opindex fmerge-debug-strings
+@opindex fno-merge-debug-strings
+Direct the linker to not merge together strings in the debugging
+information that are identical in different object files. Merging is
+not supported by all assemblers or linkers. Merging decreases the size
+of the debug information in the output file at the cost of increasing
+link processing time. Merging is enabled by default.
+
+@item -fdebug-prefix-map=@var{old}=@var{new}
+@opindex fdebug-prefix-map
+When compiling files residing in directory @file{@var{old}}, record
+debugging information describing them as if the files resided in
+directory @file{@var{new}} instead. This can be used to replace a
+build-time path with an install-time path in the debug info. It can
+also be used to change an absolute path to a relative path by using
+@file{.} for @var{new}. This can give more reproducible builds, which
+are location independent, but may require an extra command to tell GDB
+where to find the source files. See also @option{-ffile-prefix-map}.
+
+@item -fvar-tracking
+@opindex fvar-tracking
+Run variable tracking pass. It computes where variables are stored at each
+position in code. Better debugging information is then generated
+(if the debugging information format supports this information).
+
+It is enabled by default when compiling with optimization (@option{-Os},
+@option{-O}, @option{-O2}, @dots{}), debugging information (@option{-g}) and
+the debug info format supports it.
+
+@item -fvar-tracking-assignments
+@opindex fvar-tracking-assignments
+@opindex fno-var-tracking-assignments
+Annotate assignments to user variables early in the compilation and
+attempt to carry the annotations over throughout the compilation all the
+way to the end, in an attempt to improve debug information while
+optimizing. Use of @option{-gdwarf-4} is recommended along with it.
+
+It can be enabled even if var-tracking is disabled, in which case
+annotations are created and maintained, but discarded at the end.
+By default, this flag is enabled together with @option{-fvar-tracking},
+except when selective scheduling is enabled.
+
+@item -gsplit-dwarf
+@opindex gsplit-dwarf
+If DWARF debugging information is enabled, separate as much debugging
+information as possible into a separate output file with the extension
+@file{.dwo}. This option allows the build system to avoid linking files with
+debug information. To be useful, this option requires a debugger capable of
+reading @file{.dwo} files.
+
+@item -gdwarf32
+@itemx -gdwarf64
+@opindex gdwarf32
+@opindex gdwarf64
+If DWARF debugging information is enabled, the @option{-gdwarf32} selects
+the 32-bit DWARF format and the @option{-gdwarf64} selects the 64-bit
+DWARF format. The default is target specific, on most targets it is
+@option{-gdwarf32} though. The 32-bit DWARF format is smaller, but
+can't support more than 2GiB of debug information in any of the DWARF
+debug information sections. The 64-bit DWARF format allows larger debug
+information and might not be well supported by all consumers yet.
+
+@item -gdescribe-dies
+@opindex gdescribe-dies
+Add description attributes to some DWARF DIEs that have no name attribute,
+such as artificial variables, external references and call site
+parameter DIEs.
+
+@item -gpubnames
+@opindex gpubnames
+Generate DWARF @code{.debug_pubnames} and @code{.debug_pubtypes} sections.
+
+@item -ggnu-pubnames
+@opindex ggnu-pubnames
+Generate @code{.debug_pubnames} and @code{.debug_pubtypes} sections in a format
+suitable for conversion into a GDB@ index. This option is only useful
+with a linker that can produce GDB@ index version 7.
+
+@item -fdebug-types-section
+@opindex fdebug-types-section
+@opindex fno-debug-types-section
+When using DWARF Version 4 or higher, type DIEs can be put into
+their own @code{.debug_types} section instead of making them part of the
+@code{.debug_info} section. It is more efficient to put them in a separate
+comdat section since the linker can then remove duplicates.
+But not all DWARF consumers support @code{.debug_types} sections yet
+and on some objects @code{.debug_types} produces larger instead of smaller
+debugging information.
+
+@item -grecord-gcc-switches
+@itemx -gno-record-gcc-switches
+@opindex grecord-gcc-switches
+@opindex gno-record-gcc-switches
+This switch causes the command-line options used to invoke the
+compiler that may affect code generation to be appended to the
+DW_AT_producer attribute in DWARF debugging information. The options
+are concatenated with spaces separating them from each other and from
+the compiler version.
+It is enabled by default.
+See also @option{-frecord-gcc-switches} for another
+way of storing compiler options into the object file.
+
+@item -gstrict-dwarf
+@opindex gstrict-dwarf
+Disallow using extensions of later DWARF standard version than selected
+with @option{-gdwarf-@var{version}}. On most targets using non-conflicting
+DWARF extensions from later standard versions is allowed.
+
+@item -gno-strict-dwarf
+@opindex gno-strict-dwarf
+Allow using extensions of later DWARF standard version than selected with
+@option{-gdwarf-@var{version}}.
+
+@item -gas-loc-support
+@opindex gas-loc-support
+Inform the compiler that the assembler supports @code{.loc} directives.
+It may then use them for the assembler to generate DWARF2+ line number
+tables.
+
+This is generally desirable, because assembler-generated line-number
+tables are a lot more compact than those the compiler can generate
+itself.
+
+This option will be enabled by default if, at GCC configure time, the
+assembler was found to support such directives.
+
+@item -gno-as-loc-support
+@opindex gno-as-loc-support
+Force GCC to generate DWARF2+ line number tables internally, if DWARF2+
+line number tables are to be generated.
+
+@item -gas-locview-support
+@opindex gas-locview-support
+Inform the compiler that the assembler supports @code{view} assignment
+and reset assertion checking in @code{.loc} directives.
+
+This option will be enabled by default if, at GCC configure time, the
+assembler was found to support them.
+
+@item -gno-as-locview-support
+Force GCC to assign view numbers internally, if
+@option{-gvariable-location-views} are explicitly requested.
+
+@item -gcolumn-info
+@itemx -gno-column-info
+@opindex gcolumn-info
+@opindex gno-column-info
+Emit location column information into DWARF debugging information, rather
+than just file and line.
+This option is enabled by default.
+
+@item -gstatement-frontiers
+@itemx -gno-statement-frontiers
+@opindex gstatement-frontiers
+@opindex gno-statement-frontiers
+This option causes GCC to create markers in the internal representation
+at the beginning of statements, and to keep them roughly in place
+throughout compilation, using them to guide the output of @code{is_stmt}
+markers in the line number table. This is enabled by default when
+compiling with optimization (@option{-Os}, @option{-O1}, @option{-O2},
+@dots{}), and outputting DWARF 2 debug information at the normal level.
+
+@item -gvariable-location-views
+@itemx -gvariable-location-views=incompat5
+@itemx -gno-variable-location-views
+@opindex gvariable-location-views
+@opindex gvariable-location-views=incompat5
+@opindex gno-variable-location-views
+Augment variable location lists with progressive view numbers implied
+from the line number table. This enables debug information consumers to
+inspect state at certain points of the program, even if no instructions
+associated with the corresponding source locations are present at that
+point. If the assembler lacks support for view numbers in line number
+tables, this will cause the compiler to emit the line number table,
+which generally makes them somewhat less compact. The augmented line
+number tables and location lists are fully backward-compatible, so they
+can be consumed by debug information consumers that are not aware of
+these augmentations, but they won't derive any benefit from them either.
+
+This is enabled by default when outputting DWARF 2 debug information at
+the normal level, as long as there is assembler support,
+@option{-fvar-tracking-assignments} is enabled and
+@option{-gstrict-dwarf} is not. When assembler support is not
+available, this may still be enabled, but it will force GCC to output
+internal line number tables, and if
+@option{-ginternal-reset-location-views} is not enabled, that will most
+certainly lead to silently mismatching location views.
+
+There is a proposed representation for view numbers that is not backward
+compatible with the location list format introduced in DWARF 5, that can
+be enabled with @option{-gvariable-location-views=incompat5}. This
+option may be removed in the future, is only provided as a reference
+implementation of the proposed representation. Debug information
+consumers are not expected to support this extended format, and they
+would be rendered unable to decode location lists using it.
+
+@item -ginternal-reset-location-views
+@itemx -gno-internal-reset-location-views
+@opindex ginternal-reset-location-views
+@opindex gno-internal-reset-location-views
+Attempt to determine location views that can be omitted from location
+view lists. This requires the compiler to have very accurate insn
+length estimates, which isn't always the case, and it may cause
+incorrect view lists to be generated silently when using an assembler
+that does not support location view lists. The GNU assembler will flag
+any such error as a @code{view number mismatch}. This is only enabled
+on ports that define a reliable estimation function.
+
+@item -ginline-points
+@itemx -gno-inline-points
+@opindex ginline-points
+@opindex gno-inline-points
+Generate extended debug information for inlined functions. Location
+view tracking markers are inserted at inlined entry points, so that
+address and view numbers can be computed and output in debug
+information. This can be enabled independently of location views, in
+which case the view numbers won't be output, but it can only be enabled
+along with statement frontiers, and it is only enabled by default if
+location views are enabled.
+
+@item -gz@r{[}=@var{type}@r{]}
+@opindex gz
+Produce compressed debug sections in DWARF format, if that is supported.
+If @var{type} is not given, the default type depends on the capabilities
+of the assembler and linker used. @var{type} may be one of
+@samp{none} (don't compress debug sections), or @samp{zlib} (use zlib
+compression in ELF gABI format). If the linker doesn't support writing
+compressed debug sections, the option is rejected. Otherwise, if the
+assembler does not support them, @option{-gz} is silently ignored when
+producing object files.
+
+@item -femit-struct-debug-baseonly
+@opindex femit-struct-debug-baseonly
+Emit debug information for struct-like types
+only when the base name of the compilation source file
+matches the base name of file in which the struct is defined.
+
+This option substantially reduces the size of debugging information,
+but at significant potential loss in type information to the debugger.
+See @option{-femit-struct-debug-reduced} for a less aggressive option.
+See @option{-femit-struct-debug-detailed} for more detailed control.
+
+This option works only with DWARF debug output.
+
+@item -femit-struct-debug-reduced
+@opindex femit-struct-debug-reduced
+Emit debug information for struct-like types
+only when the base name of the compilation source file
+matches the base name of file in which the type is defined,
+unless the struct is a template or defined in a system header.
+
+This option significantly reduces the size of debugging information,
+with some potential loss in type information to the debugger.
+See @option{-femit-struct-debug-baseonly} for a more aggressive option.
+See @option{-femit-struct-debug-detailed} for more detailed control.
+
+This option works only with DWARF debug output.
+
+@item -femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]}
+@opindex femit-struct-debug-detailed
+Specify the struct-like types
+for which the compiler generates debug information.
+The intent is to reduce duplicate struct debug information
+between different object files within the same program.
+
+This option is a detailed version of
+@option{-femit-struct-debug-reduced} and @option{-femit-struct-debug-baseonly},
+which serves for most needs.
+
+A specification has the syntax@*
+[@samp{dir:}|@samp{ind:}][@samp{ord:}|@samp{gen:}](@samp{any}|@samp{sys}|@samp{base}|@samp{none})
+
+The optional first word limits the specification to
+structs that are used directly (@samp{dir:}) or used indirectly (@samp{ind:}).
+A struct type is used directly when it is the type of a variable, member.
+Indirect uses arise through pointers to structs.
+That is, when use of an incomplete struct is valid, the use is indirect.
+An example is
+@samp{struct one direct; struct two * indirect;}.
+
+The optional second word limits the specification to
+ordinary structs (@samp{ord:}) or generic structs (@samp{gen:}).
+Generic structs are a bit complicated to explain.
+For C++, these are non-explicit specializations of template classes,
+or non-template classes within the above.
+Other programming languages have generics,
+but @option{-femit-struct-debug-detailed} does not yet implement them.
+
+The third word specifies the source files for those
+structs for which the compiler should emit debug information.
+The values @samp{none} and @samp{any} have the normal meaning.
+The value @samp{base} means that
+the base of name of the file in which the type declaration appears
+must match the base of the name of the main compilation file.
+In practice, this means that when compiling @file{foo.c}, debug information
+is generated for types declared in that file and @file{foo.h},
+but not other header files.
+The value @samp{sys} means those types satisfying @samp{base}
+or declared in system or compiler headers.
+
+You may need to experiment to determine the best settings for your application.
+
+The default is @option{-femit-struct-debug-detailed=all}.
+
+This option works only with DWARF debug output.
+
+@item -fno-dwarf2-cfi-asm
+@opindex fdwarf2-cfi-asm
+@opindex fno-dwarf2-cfi-asm
+Emit DWARF unwind info as compiler generated @code{.eh_frame} section
+instead of using GAS @code{.cfi_*} directives.
+
+@item -fno-eliminate-unused-debug-types
+@opindex feliminate-unused-debug-types
+@opindex fno-eliminate-unused-debug-types
+Normally, when producing DWARF output, GCC avoids producing debug symbol
+output for types that are nowhere used in the source file being compiled.
+Sometimes it is useful to have GCC emit debugging
+information for all types declared in a compilation
+unit, regardless of whether or not they are actually used
+in that compilation unit, for example
+if, in the debugger, you want to cast a value to a type that is
+not actually used in your program (but is declared). More often,
+however, this results in a significant amount of wasted space.
+@end table
+
+@node Optimize Options
+@section Options That Control Optimization
+@cindex optimize options
+@cindex options, optimization
+
+These options control various sorts of optimizations.
+
+Without any optimization option, the compiler's goal is to reduce the
+cost of compilation and to make debugging produce the expected
+results. Statements are independent: if you stop the program with a
+breakpoint between statements, you can then assign a new value to any
+variable or change the program counter to any other statement in the
+function and get exactly the results you expect from the source
+code.
+
+Turning on optimization flags makes the compiler attempt to improve
+the performance and/or code size at the expense of compilation time
+and possibly the ability to debug the program.
+
+The compiler performs optimization based on the knowledge it has of the
+program. Compiling multiple files at once to a single output file mode allows
+the compiler to use information gained from all of the files when compiling
+each of them.
+
+Not all optimizations are controlled directly by a flag. Only
+optimizations that have a flag are listed in this section.
+
+Most optimizations are completely disabled at @option{-O0} or if an
+@option{-O} level is not set on the command line, even if individual
+optimization flags are specified. Similarly, @option{-Og} suppresses
+many optimization passes.
+
+Depending on the target and how GCC was configured, a slightly different
+set of optimizations may be enabled at each @option{-O} level than
+those listed here. You can invoke GCC with @option{-Q --help=optimizers}
+to find out the exact set of optimizations that are enabled at each level.
+@xref{Overall Options}, for examples.
+
+@table @gcctabopt
+@item -O
+@itemx -O1
+@opindex O
+@opindex O1
+Optimize. Optimizing compilation takes somewhat more time, and a lot
+more memory for a large function.
+
+With @option{-O}, the compiler tries to reduce code size and execution
+time, without performing any optimizations that take a great deal of
+compilation time.
+
+@c Note that in addition to the default_options_table list in opts.cc,
+@c several optimization flags default to true but control optimization
+@c passes that are explicitly disabled at -O0.
+
+@option{-O} turns on the following optimization flags:
+
+@c Please keep the following list alphabetized.
+@gccoptlist{-fauto-inc-dec @gol
+-fbranch-count-reg @gol
+-fcombine-stack-adjustments @gol
+-fcompare-elim @gol
+-fcprop-registers @gol
+-fdce @gol
+-fdefer-pop @gol
+-fdelayed-branch @gol
+-fdse @gol
+-fforward-propagate @gol
+-fguess-branch-probability @gol
+-fif-conversion @gol
+-fif-conversion2 @gol
+-finline-functions-called-once @gol
+-fipa-modref @gol
+-fipa-profile @gol
+-fipa-pure-const @gol
+-fipa-reference @gol
+-fipa-reference-addressable @gol
+-fmerge-constants @gol
+-fmove-loop-invariants @gol
+-fmove-loop-stores@gol
+-fomit-frame-pointer @gol
+-freorder-blocks @gol
+-fshrink-wrap @gol
+-fshrink-wrap-separate @gol
+-fsplit-wide-types @gol
+-fssa-backprop @gol
+-fssa-phiopt @gol
+-ftree-bit-ccp @gol
+-ftree-ccp @gol
+-ftree-ch @gol
+-ftree-coalesce-vars @gol
+-ftree-copy-prop @gol
+-ftree-dce @gol
+-ftree-dominator-opts @gol
+-ftree-dse @gol
+-ftree-forwprop @gol
+-ftree-fre @gol
+-ftree-phiprop @gol
+-ftree-pta @gol
+-ftree-scev-cprop @gol
+-ftree-sink @gol
+-ftree-slsr @gol
+-ftree-sra @gol
+-ftree-ter @gol
+-funit-at-a-time}
+
+@item -O2
+@opindex O2
+Optimize even more. GCC performs nearly all supported optimizations
+that do not involve a space-speed tradeoff.
+As compared to @option{-O}, this option increases both compilation time
+and the performance of the generated code.
+
+@option{-O2} turns on all optimization flags specified by @option{-O1}. It
+also turns on the following optimization flags:
+
+@c Please keep the following list alphabetized!
+@gccoptlist{-falign-functions -falign-jumps @gol
+-falign-labels -falign-loops @gol
+-fcaller-saves @gol
+-fcode-hoisting @gol
+-fcrossjumping @gol
+-fcse-follow-jumps -fcse-skip-blocks @gol
+-fdelete-null-pointer-checks @gol
+-fdevirtualize -fdevirtualize-speculatively @gol
+-fexpensive-optimizations @gol
+-ffinite-loops @gol
+-fgcse -fgcse-lm @gol
+-fhoist-adjacent-loads @gol
+-finline-functions @gol
+-finline-small-functions @gol
+-findirect-inlining @gol
+-fipa-bit-cp -fipa-cp -fipa-icf @gol
+-fipa-ra -fipa-sra -fipa-vrp @gol
+-fisolate-erroneous-paths-dereference @gol
+-flra-remat @gol
+-foptimize-sibling-calls @gol
+-foptimize-strlen @gol
+-fpartial-inlining @gol
+-fpeephole2 @gol
+-freorder-blocks-algorithm=stc @gol
+-freorder-blocks-and-partition -freorder-functions @gol
+-frerun-cse-after-loop @gol
+-fschedule-insns -fschedule-insns2 @gol
+-fsched-interblock -fsched-spec @gol
+-fstore-merging @gol
+-fstrict-aliasing @gol
+-fthread-jumps @gol
+-ftree-builtin-call-dce @gol
+-ftree-loop-vectorize @gol
+-ftree-pre @gol
+-ftree-slp-vectorize @gol
+-ftree-switch-conversion -ftree-tail-merge @gol
+-ftree-vrp @gol
+-fvect-cost-model=very-cheap}
+
+Please note the warning under @option{-fgcse} about
+invoking @option{-O2} on programs that use computed gotos.
+
+@item -O3
+@opindex O3
+Optimize yet more. @option{-O3} turns on all optimizations specified
+by @option{-O2} and also turns on the following optimization flags:
+
+@c Please keep the following list alphabetized!
+@gccoptlist{-fgcse-after-reload @gol
+-fipa-cp-clone
+-floop-interchange @gol
+-floop-unroll-and-jam @gol
+-fpeel-loops @gol
+-fpredictive-commoning @gol
+-fsplit-loops @gol
+-fsplit-paths @gol
+-ftree-loop-distribution @gol
+-ftree-partial-pre @gol
+-funswitch-loops @gol
+-fvect-cost-model=dynamic @gol
+-fversion-loops-for-strides}
+
+@item -O0
+@opindex O0
+Reduce compilation time and make debugging produce the expected
+results. This is the default.
+
+@item -Os
+@opindex Os
+Optimize for size. @option{-Os} enables all @option{-O2} optimizations
+except those that often increase code size:
+
+@gccoptlist{-falign-functions -falign-jumps @gol
+-falign-labels -falign-loops @gol
+-fprefetch-loop-arrays -freorder-blocks-algorithm=stc}
+
+It also enables @option{-finline-functions}, causes the compiler to tune for
+code size rather than execution speed, and performs further optimizations
+designed to reduce code size.
+
+@item -Ofast
+@opindex Ofast
+Disregard strict standards compliance. @option{-Ofast} enables all
+@option{-O3} optimizations. It also enables optimizations that are not
+valid for all standard-compliant programs.
+It turns on @option{-ffast-math}, @option{-fallow-store-data-races}
+and the Fortran-specific @option{-fstack-arrays}, unless
+@option{-fmax-stack-var-size} is specified, and @option{-fno-protect-parens}.
+It turns off @option{-fsemantic-interposition}.
+
+@item -Og
+@opindex Og
+Optimize debugging experience. @option{-Og} should be the optimization
+level of choice for the standard edit-compile-debug cycle, offering
+a reasonable level of optimization while maintaining fast compilation
+and a good debugging experience. It is a better choice than @option{-O0}
+for producing debuggable code because some compiler passes
+that collect debug information are disabled at @option{-O0}.
+
+Like @option{-O0}, @option{-Og} completely disables a number of
+optimization passes so that individual options controlling them have
+no effect. Otherwise @option{-Og} enables all @option{-O1}
+optimization flags except for those that may interfere with debugging:
+
+@gccoptlist{-fbranch-count-reg -fdelayed-branch @gol
+-fdse -fif-conversion -fif-conversion2 @gol
+-finline-functions-called-once @gol
+-fmove-loop-invariants -fmove-loop-stores -fssa-phiopt @gol
+-ftree-bit-ccp -ftree-dse -ftree-pta -ftree-sra}
+
+@item -Oz
+@opindex Oz
+Optimize aggressively for size rather than speed. This may increase
+the number of instructions executed if those instructions require
+fewer bytes to encode. @option{-Oz} behaves similarly to @option{-Os}
+including enabling most @option{-O2} optimizations.
+
+@end table
+
+If you use multiple @option{-O} options, with or without level numbers,
+the last such option is the one that is effective.
+
+Options of the form @option{-f@var{flag}} specify machine-independent
+flags. Most flags have both positive and negative forms; the negative
+form of @option{-ffoo} is @option{-fno-foo}. In the table
+below, only one of the forms is listed---the one you typically
+use. You can figure out the other form by either removing @samp{no-}
+or adding it.
+
+The following options control specific optimizations. They are either
+activated by @option{-O} options or are related to ones that are. You
+can use the following flags in the rare cases when ``fine-tuning'' of
+optimizations to be performed is desired.
+
+@table @gcctabopt
+@item -fno-defer-pop
+@opindex fno-defer-pop
+@opindex fdefer-pop
+For machines that must pop arguments after a function call, always pop
+the arguments as soon as each function returns.
+At levels @option{-O1} and higher, @option{-fdefer-pop} is the default;
+this allows the compiler to let arguments accumulate on the stack for several
+function calls and pop them all at once.
+
+@item -fforward-propagate
+@opindex fforward-propagate
+Perform a forward propagation pass on RTL@. The pass tries to combine two
+instructions and checks if the result can be simplified. If loop unrolling
+is active, two passes are performed and the second is scheduled after
+loop unrolling.
+
+This option is enabled by default at optimization levels @option{-O1},
+@option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -ffp-contract=@var{style}
+@opindex ffp-contract
+@option{-ffp-contract=off} disables floating-point expression contraction.
+@option{-ffp-contract=fast} enables floating-point expression contraction
+such as forming of fused multiply-add operations if the target has
+native support for them.
+@option{-ffp-contract=on} enables floating-point expression contraction
+if allowed by the language standard. This is currently not implemented
+and treated equal to @option{-ffp-contract=off}.
+
+The default is @option{-ffp-contract=fast}.
+
+@item -fomit-frame-pointer
+@opindex fomit-frame-pointer
+Omit the frame pointer in functions that don't need one. This avoids the
+instructions to save, set up and restore the frame pointer; on many targets
+it also makes an extra register available.
+
+On some targets this flag has no effect because the standard calling sequence
+always uses a frame pointer, so it cannot be omitted.
+
+Note that @option{-fno-omit-frame-pointer} doesn't guarantee the frame pointer
+is used in all functions. Several targets always omit the frame pointer in
+leaf functions.
+
+Enabled by default at @option{-O1} and higher.
+
+@item -foptimize-sibling-calls
+@opindex foptimize-sibling-calls
+Optimize sibling and tail recursive calls.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -foptimize-strlen
+@opindex foptimize-strlen
+Optimize various standard C string functions (e.g.@: @code{strlen},
+@code{strchr} or @code{strcpy}) and
+their @code{_FORTIFY_SOURCE} counterparts into faster alternatives.
+
+Enabled at levels @option{-O2}, @option{-O3}.
+
+@item -fno-inline
+@opindex fno-inline
+@opindex finline
+Do not expand any functions inline apart from those marked with
+the @code{always_inline} attribute. This is the default when not
+optimizing.
+
+Single functions can be exempted from inlining by marking them
+with the @code{noinline} attribute.
+
+@item -finline-small-functions
+@opindex finline-small-functions
+Integrate functions into their callers when their body is smaller than expected
+function call code (so overall size of program gets smaller). The compiler
+heuristically decides which functions are simple enough to be worth integrating
+in this way. This inlining applies to all functions, even those not declared
+inline.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -findirect-inlining
+@opindex findirect-inlining
+Inline also indirect calls that are discovered to be known at compile
+time thanks to previous inlining. This option has any effect only
+when inlining itself is turned on by the @option{-finline-functions}
+or @option{-finline-small-functions} options.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -finline-functions
+@opindex finline-functions
+Consider all functions for inlining, even if they are not declared inline.
+The compiler heuristically decides which functions are worth integrating
+in this way.
+
+If all calls to a given function are integrated, and the function is
+declared @code{static}, then the function is normally not output as
+assembler code in its own right.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. Also enabled
+by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -finline-functions-called-once
+@opindex finline-functions-called-once
+Consider all @code{static} functions called once for inlining into their
+caller even if they are not marked @code{inline}. If a call to a given
+function is integrated, then the function is not output as assembler code
+in its own right.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3} and @option{-Os},
+but not @option{-Og}.
+
+@item -fearly-inlining
+@opindex fearly-inlining
+Inline functions marked by @code{always_inline} and functions whose body seems
+smaller than the function call overhead early before doing
+@option{-fprofile-generate} instrumentation and real inlining pass. Doing so
+makes profiling significantly cheaper and usually inlining faster on programs
+having large chains of nested wrapper functions.
+
+Enabled by default.
+
+@item -fipa-sra
+@opindex fipa-sra
+Perform interprocedural scalar replacement of aggregates, removal of
+unused parameters and replacement of parameters passed by reference
+by parameters passed by value.
+
+Enabled at levels @option{-O2}, @option{-O3} and @option{-Os}.
+
+@item -finline-limit=@var{n}
+@opindex finline-limit
+By default, GCC limits the size of functions that can be inlined. This flag
+allows coarse control of this limit. @var{n} is the size of functions that
+can be inlined in number of pseudo instructions.
+
+Inlining is actually controlled by a number of parameters, which may be
+specified individually by using @option{--param @var{name}=@var{value}}.
+The @option{-finline-limit=@var{n}} option sets some of these parameters
+as follows:
+
+@table @gcctabopt
+@item max-inline-insns-single
+is set to @var{n}/2.
+@item max-inline-insns-auto
+is set to @var{n}/2.
+@end table
+
+See below for a documentation of the individual
+parameters controlling inlining and for the defaults of these parameters.
+
+@emph{Note:} there may be no value to @option{-finline-limit} that results
+in default behavior.
+
+@emph{Note:} pseudo instruction represents, in this particular context, an
+abstract measurement of function's size. In no way does it represent a count
+of assembly instructions and as such its exact meaning might change from one
+release to an another.
+
+@item -fno-keep-inline-dllexport
+@opindex fno-keep-inline-dllexport
+@opindex fkeep-inline-dllexport
+This is a more fine-grained version of @option{-fkeep-inline-functions},
+which applies only to functions that are declared using the @code{dllexport}
+attribute or declspec. @xref{Function Attributes,,Declaring Attributes of
+Functions}.
+
+@item -fkeep-inline-functions
+@opindex fkeep-inline-functions
+In C, emit @code{static} functions that are declared @code{inline}
+into the object file, even if the function has been inlined into all
+of its callers. This switch does not affect functions using the
+@code{extern inline} extension in GNU C90@. In C++, emit any and all
+inline functions into the object file.
+
+@item -fkeep-static-functions
+@opindex fkeep-static-functions
+Emit @code{static} functions into the object file, even if the function
+is never used.
+
+@item -fkeep-static-consts
+@opindex fkeep-static-consts
+Emit variables declared @code{static const} when optimization isn't turned
+on, even if the variables aren't referenced.
+
+GCC enables this option by default. If you want to force the compiler to
+check if a variable is referenced, regardless of whether or not
+optimization is turned on, use the @option{-fno-keep-static-consts} option.
+
+@item -fmerge-constants
+@opindex fmerge-constants
+Attempt to merge identical constants (string constants and floating-point
+constants) across compilation units.
+
+This option is the default for optimized compilation if the assembler and
+linker support it. Use @option{-fno-merge-constants} to inhibit this
+behavior.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fmerge-all-constants
+@opindex fmerge-all-constants
+Attempt to merge identical constants and identical variables.
+
+This option implies @option{-fmerge-constants}. In addition to
+@option{-fmerge-constants} this considers e.g.@: even constant initialized
+arrays or initialized constant variables with integral or floating-point
+types. Languages like C or C++ require each variable, including multiple
+instances of the same variable in recursive calls, to have distinct locations,
+so using this option results in non-conforming
+behavior.
+
+@item -fmodulo-sched
+@opindex fmodulo-sched
+Perform swing modulo scheduling immediately before the first scheduling
+pass. This pass looks at innermost loops and reorders their
+instructions by overlapping different iterations.
+
+@item -fmodulo-sched-allow-regmoves
+@opindex fmodulo-sched-allow-regmoves
+Perform more aggressive SMS-based modulo scheduling with register moves
+allowed. By setting this flag certain anti-dependences edges are
+deleted, which triggers the generation of reg-moves based on the
+life-range analysis. This option is effective only with
+@option{-fmodulo-sched} enabled.
+
+@item -fno-branch-count-reg
+@opindex fno-branch-count-reg
+@opindex fbranch-count-reg
+Disable the optimization pass that scans for opportunities to use
+``decrement and branch'' instructions on a count register instead of
+instruction sequences that decrement a register, compare it against zero, and
+then branch based upon the result. This option is only meaningful on
+architectures that support such instructions, which include x86, PowerPC,
+IA-64 and S/390. Note that the @option{-fno-branch-count-reg} option
+doesn't remove the decrement and branch instructions from the generated
+instruction stream introduced by other optimization passes.
+
+The default is @option{-fbranch-count-reg} at @option{-O1} and higher,
+except for @option{-Og}.
+
+@item -fno-function-cse
+@opindex fno-function-cse
+@opindex ffunction-cse
+Do not put function addresses in registers; make each instruction that
+calls a constant function contain the function's address explicitly.
+
+This option results in less efficient code, but some strange hacks
+that alter the assembler output may be confused by the optimizations
+performed when this option is not used.
+
+The default is @option{-ffunction-cse}
+
+@item -fno-zero-initialized-in-bss
+@opindex fno-zero-initialized-in-bss
+@opindex fzero-initialized-in-bss
+If the target supports a BSS section, GCC by default puts variables that
+are initialized to zero into BSS@. This can save space in the resulting
+code.
+
+This option turns off this behavior because some programs explicitly
+rely on variables going to the data section---e.g., so that the
+resulting executable can find the beginning of that section and/or make
+assumptions based on that.
+
+The default is @option{-fzero-initialized-in-bss}.
+
+@item -fthread-jumps
+@opindex fthread-jumps
+Perform optimizations that check to see if a jump branches to a
+location where another comparison subsumed by the first is found. If
+so, the first branch is redirected to either the destination of the
+second branch or a point immediately following it, depending on whether
+the condition is known to be true or false.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fsplit-wide-types
+@opindex fsplit-wide-types
+When using a type that occupies multiple registers, such as @code{long
+long} on a 32-bit system, split the registers apart and allocate them
+independently. This normally generates better code for those types,
+but may make debugging more difficult.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3},
+@option{-Os}.
+
+@item -fsplit-wide-types-early
+@opindex fsplit-wide-types-early
+Fully split wide types early, instead of very late.
+This option has no effect unless @option{-fsplit-wide-types} is turned on.
+
+This is the default on some targets.
+
+@item -fcse-follow-jumps
+@opindex fcse-follow-jumps
+In common subexpression elimination (CSE), scan through jump instructions
+when the target of the jump is not reached by any other path. For
+example, when CSE encounters an @code{if} statement with an
+@code{else} clause, CSE follows the jump when the condition
+tested is false.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fcse-skip-blocks
+@opindex fcse-skip-blocks
+This is similar to @option{-fcse-follow-jumps}, but causes CSE to
+follow jumps that conditionally skip over blocks. When CSE
+encounters a simple @code{if} statement with no else clause,
+@option{-fcse-skip-blocks} causes CSE to follow the jump around the
+body of the @code{if}.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -frerun-cse-after-loop
+@opindex frerun-cse-after-loop
+Re-run common subexpression elimination after loop optimizations are
+performed.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fgcse
+@opindex fgcse
+Perform a global common subexpression elimination pass.
+This pass also performs global constant and copy propagation.
+
+@emph{Note:} When compiling a program using computed gotos, a GCC
+extension, you may get better run-time performance if you disable
+the global common subexpression elimination pass by adding
+@option{-fno-gcse} to the command line.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fgcse-lm
+@opindex fgcse-lm
+When @option{-fgcse-lm} is enabled, global common subexpression elimination
+attempts to move loads that are only killed by stores into themselves. This
+allows a loop containing a load/store sequence to be changed to a load outside
+the loop, and a copy/store within the loop.
+
+Enabled by default when @option{-fgcse} is enabled.
+
+@item -fgcse-sm
+@opindex fgcse-sm
+When @option{-fgcse-sm} is enabled, a store motion pass is run after
+global common subexpression elimination. This pass attempts to move
+stores out of loops. When used in conjunction with @option{-fgcse-lm},
+loops containing a load/store sequence can be changed to a load before
+the loop and a store after the loop.
+
+Not enabled at any optimization level.
+
+@item -fgcse-las
+@opindex fgcse-las
+When @option{-fgcse-las} is enabled, the global common subexpression
+elimination pass eliminates redundant loads that come after stores to the
+same memory location (both partial and full redundancies).
+
+Not enabled at any optimization level.
+
+@item -fgcse-after-reload
+@opindex fgcse-after-reload
+When @option{-fgcse-after-reload} is enabled, a redundant load elimination
+pass is performed after reload. The purpose of this pass is to clean up
+redundant spilling.
+
+Enabled by @option{-O3}, @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -faggressive-loop-optimizations
+@opindex faggressive-loop-optimizations
+This option tells the loop optimizer to use language constraints to
+derive bounds for the number of iterations of a loop. This assumes that
+loop code does not invoke undefined behavior by for example causing signed
+integer overflows or out-of-bound array accesses. The bounds for the
+number of iterations of a loop are used to guide loop unrolling and peeling
+and loop exit test optimizations.
+This option is enabled by default.
+
+@item -funconstrained-commons
+@opindex funconstrained-commons
+This option tells the compiler that variables declared in common blocks
+(e.g.@: Fortran) may later be overridden with longer trailing arrays. This
+prevents certain optimizations that depend on knowing the array bounds.
+
+@item -fcrossjumping
+@opindex fcrossjumping
+Perform cross-jumping transformation.
+This transformation unifies equivalent code and saves code size. The
+resulting code may or may not perform better than without cross-jumping.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fauto-inc-dec
+@opindex fauto-inc-dec
+Combine increments or decrements of addresses with memory accesses.
+This pass is always skipped on architectures that do not have
+instructions to support this. Enabled by default at @option{-O1} and
+higher on architectures that support this.
+
+@item -fdce
+@opindex fdce
+Perform dead code elimination (DCE) on RTL@.
+Enabled by default at @option{-O1} and higher.
+
+@item -fdse
+@opindex fdse
+Perform dead store elimination (DSE) on RTL@.
+Enabled by default at @option{-O1} and higher.
+
+@item -fif-conversion
+@opindex fif-conversion
+Attempt to transform conditional jumps into branch-less equivalents. This
+includes use of conditional moves, min, max, set flags and abs instructions, and
+some tricks doable by standard arithmetics. The use of conditional execution
+on chips where it is available is controlled by @option{-fif-conversion2}.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os}, but
+not with @option{-Og}.
+
+@item -fif-conversion2
+@opindex fif-conversion2
+Use conditional execution (where available) to transform conditional jumps into
+branch-less equivalents.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os}, but
+not with @option{-Og}.
+
+@item -fdeclone-ctor-dtor
+@opindex fdeclone-ctor-dtor
+The C++ ABI requires multiple entry points for constructors and
+destructors: one for a base subobject, one for a complete object, and
+one for a virtual destructor that calls operator delete afterwards.
+For a hierarchy with virtual bases, the base and complete variants are
+clones, which means two copies of the function. With this option, the
+base and complete variants are changed to be thunks that call a common
+implementation.
+
+Enabled by @option{-Os}.
+
+@item -fdelete-null-pointer-checks
+@opindex fdelete-null-pointer-checks
+Assume that programs cannot safely dereference null pointers, and that
+no code or data element resides at address zero.
+This option enables simple constant
+folding optimizations at all optimization levels. In addition, other
+optimization passes in GCC use this flag to control global dataflow
+analyses that eliminate useless checks for null pointers; these assume
+that a memory access to address zero always results in a trap, so
+that if a pointer is checked after it has already been dereferenced,
+it cannot be null.
+
+Note however that in some environments this assumption is not true.
+Use @option{-fno-delete-null-pointer-checks} to disable this optimization
+for programs that depend on that behavior.
+
+This option is enabled by default on most targets. On Nios II ELF, it
+defaults to off. On AVR and MSP430, this option is completely disabled.
+
+Passes that use the dataflow information
+are enabled independently at different optimization levels.
+
+@item -fdevirtualize
+@opindex fdevirtualize
+Attempt to convert calls to virtual functions to direct calls. This
+is done both within a procedure and interprocedurally as part of
+indirect inlining (@option{-findirect-inlining}) and interprocedural constant
+propagation (@option{-fipa-cp}).
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fdevirtualize-speculatively
+@opindex fdevirtualize-speculatively
+Attempt to convert calls to virtual functions to speculative direct calls.
+Based on the analysis of the type inheritance graph, determine for a given call
+the set of likely targets. If the set is small, preferably of size 1, change
+the call into a conditional deciding between direct and indirect calls. The
+speculative calls enable more optimizations, such as inlining. When they seem
+useless after further optimization, they are converted back into original form.
+
+@item -fdevirtualize-at-ltrans
+@opindex fdevirtualize-at-ltrans
+Stream extra information needed for aggressive devirtualization when running
+the link-time optimizer in local transformation mode.
+This option enables more devirtualization but
+significantly increases the size of streamed data. For this reason it is
+disabled by default.
+
+@item -fexpensive-optimizations
+@opindex fexpensive-optimizations
+Perform a number of minor optimizations that are relatively expensive.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -free
+@opindex free
+Attempt to remove redundant extension instructions. This is especially
+helpful for the x86-64 architecture, which implicitly zero-extends in 64-bit
+registers after writing to their lower 32-bit half.
+
+Enabled for Alpha, AArch64 and x86 at levels @option{-O2},
+@option{-O3}, @option{-Os}.
+
+@item -fno-lifetime-dse
+@opindex fno-lifetime-dse
+@opindex flifetime-dse
+In C++ the value of an object is only affected by changes within its
+lifetime: when the constructor begins, the object has an indeterminate
+value, and any changes during the lifetime of the object are dead when
+the object is destroyed. Normally dead store elimination will take
+advantage of this; if your code relies on the value of the object
+storage persisting beyond the lifetime of the object, you can use this
+flag to disable this optimization. To preserve stores before the
+constructor starts (e.g.@: because your operator new clears the object
+storage) but still treat the object as dead after the destructor, you
+can use @option{-flifetime-dse=1}. The default behavior can be
+explicitly selected with @option{-flifetime-dse=2}.
+@option{-flifetime-dse=0} is equivalent to @option{-fno-lifetime-dse}.
+
+@item -flive-range-shrinkage
+@opindex flive-range-shrinkage
+Attempt to decrease register pressure through register live range
+shrinkage. This is helpful for fast processors with small or moderate
+size register sets.
+
+@item -fira-algorithm=@var{algorithm}
+@opindex fira-algorithm
+Use the specified coloring algorithm for the integrated register
+allocator. The @var{algorithm} argument can be @samp{priority}, which
+specifies Chow's priority coloring, or @samp{CB}, which specifies
+Chaitin-Briggs coloring. Chaitin-Briggs coloring is not implemented
+for all architectures, but for those targets that do support it, it is
+the default because it generates better code.
+
+@item -fira-region=@var{region}
+@opindex fira-region
+Use specified regions for the integrated register allocator. The
+@var{region} argument should be one of the following:
+
+@table @samp
+
+@item all
+Use all loops as register allocation regions.
+This can give the best results for machines with a small and/or
+irregular register set.
+
+@item mixed
+Use all loops except for loops with small register pressure
+as the regions. This value usually gives
+the best results in most cases and for most architectures,
+and is enabled by default when compiling with optimization for speed
+(@option{-O}, @option{-O2}, @dots{}).
+
+@item one
+Use all functions as a single region.
+This typically results in the smallest code size, and is enabled by default for
+@option{-Os} or @option{-O0}.
+
+@end table
+
+@item -fira-hoist-pressure
+@opindex fira-hoist-pressure
+Use IRA to evaluate register pressure in the code hoisting pass for
+decisions to hoist expressions. This option usually results in smaller
+code, but it can slow the compiler down.
+
+This option is enabled at level @option{-Os} for all targets.
+
+@item -fira-loop-pressure
+@opindex fira-loop-pressure
+Use IRA to evaluate register pressure in loops for decisions to move
+loop invariants. This option usually results in generation
+of faster and smaller code on machines with large register files (>= 32
+registers), but it can slow the compiler down.
+
+This option is enabled at level @option{-O3} for some targets.
+
+@item -fno-ira-share-save-slots
+@opindex fno-ira-share-save-slots
+@opindex fira-share-save-slots
+Disable sharing of stack slots used for saving call-used hard
+registers living through a call. Each hard register gets a
+separate stack slot, and as a result function stack frames are
+larger.
+
+@item -fno-ira-share-spill-slots
+@opindex fno-ira-share-spill-slots
+@opindex fira-share-spill-slots
+Disable sharing of stack slots allocated for pseudo-registers. Each
+pseudo-register that does not get a hard register gets a separate
+stack slot, and as a result function stack frames are larger.
+
+@item -flra-remat
+@opindex flra-remat
+Enable CFG-sensitive rematerialization in LRA. Instead of loading
+values of spilled pseudos, LRA tries to rematerialize (recalculate)
+values if it is profitable.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fdelayed-branch
+@opindex fdelayed-branch
+If supported for the target machine, attempt to reorder instructions
+to exploit instruction slots available after delayed branch
+instructions.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os},
+but not at @option{-Og}.
+
+@item -fschedule-insns
+@opindex fschedule-insns
+If supported for the target machine, attempt to reorder instructions to
+eliminate execution stalls due to required data being unavailable. This
+helps machines that have slow floating point or memory load instructions
+by allowing other instructions to be issued until the result of the load
+or floating-point instruction is required.
+
+Enabled at levels @option{-O2}, @option{-O3}.
+
+@item -fschedule-insns2
+@opindex fschedule-insns2
+Similar to @option{-fschedule-insns}, but requests an additional pass of
+instruction scheduling after register allocation has been done. This is
+especially useful on machines with a relatively small number of
+registers and where memory load instructions take more than one cycle.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fno-sched-interblock
+@opindex fno-sched-interblock
+@opindex fsched-interblock
+Disable instruction scheduling across basic blocks, which
+is normally enabled when scheduling before register allocation, i.e.@:
+with @option{-fschedule-insns} or at @option{-O2} or higher.
+
+@item -fno-sched-spec
+@opindex fno-sched-spec
+@opindex fsched-spec
+Disable speculative motion of non-load instructions, which
+is normally enabled when scheduling before register allocation, i.e.@:
+with @option{-fschedule-insns} or at @option{-O2} or higher.
+
+@item -fsched-pressure
+@opindex fsched-pressure
+Enable register pressure sensitive insn scheduling before register
+allocation. This only makes sense when scheduling before register
+allocation is enabled, i.e.@: with @option{-fschedule-insns} or at
+@option{-O2} or higher. Usage of this option can improve the
+generated code and decrease its size by preventing register pressure
+increase above the number of available hard registers and subsequent
+spills in register allocation.
+
+@item -fsched-spec-load
+@opindex fsched-spec-load
+Allow speculative motion of some load instructions. This only makes
+sense when scheduling before register allocation, i.e.@: with
+@option{-fschedule-insns} or at @option{-O2} or higher.
+
+@item -fsched-spec-load-dangerous
+@opindex fsched-spec-load-dangerous
+Allow speculative motion of more load instructions. This only makes
+sense when scheduling before register allocation, i.e.@: with
+@option{-fschedule-insns} or at @option{-O2} or higher.
+
+@item -fsched-stalled-insns
+@itemx -fsched-stalled-insns=@var{n}
+@opindex fsched-stalled-insns
+Define how many insns (if any) can be moved prematurely from the queue
+of stalled insns into the ready list during the second scheduling pass.
+@option{-fno-sched-stalled-insns} means that no insns are moved
+prematurely, @option{-fsched-stalled-insns=0} means there is no limit
+on how many queued insns can be moved prematurely.
+@option{-fsched-stalled-insns} without a value is equivalent to
+@option{-fsched-stalled-insns=1}.
+
+@item -fsched-stalled-insns-dep
+@itemx -fsched-stalled-insns-dep=@var{n}
+@opindex fsched-stalled-insns-dep
+Define how many insn groups (cycles) are examined for a dependency
+on a stalled insn that is a candidate for premature removal from the queue
+of stalled insns. This has an effect only during the second scheduling pass,
+and only if @option{-fsched-stalled-insns} is used.
+@option{-fno-sched-stalled-insns-dep} is equivalent to
+@option{-fsched-stalled-insns-dep=0}.
+@option{-fsched-stalled-insns-dep} without a value is equivalent to
+@option{-fsched-stalled-insns-dep=1}.
+
+@item -fsched2-use-superblocks
+@opindex fsched2-use-superblocks
+When scheduling after register allocation, use superblock scheduling.
+This allows motion across basic block boundaries,
+resulting in faster schedules. This option is experimental, as not all machine
+descriptions used by GCC model the CPU closely enough to avoid unreliable
+results from the algorithm.
+
+This only makes sense when scheduling after register allocation, i.e.@: with
+@option{-fschedule-insns2} or at @option{-O2} or higher.
+
+@item -fsched-group-heuristic
+@opindex fsched-group-heuristic
+Enable the group heuristic in the scheduler. This heuristic favors
+the instruction that belongs to a schedule group. This is enabled
+by default when scheduling is enabled, i.e.@: with @option{-fschedule-insns}
+or @option{-fschedule-insns2} or at @option{-O2} or higher.
+
+@item -fsched-critical-path-heuristic
+@opindex fsched-critical-path-heuristic
+Enable the critical-path heuristic in the scheduler. This heuristic favors
+instructions on the critical path. This is enabled by default when
+scheduling is enabled, i.e.@: with @option{-fschedule-insns}
+or @option{-fschedule-insns2} or at @option{-O2} or higher.
+
+@item -fsched-spec-insn-heuristic
+@opindex fsched-spec-insn-heuristic
+Enable the speculative instruction heuristic in the scheduler. This
+heuristic favors speculative instructions with greater dependency weakness.
+This is enabled by default when scheduling is enabled, i.e.@:
+with @option{-fschedule-insns} or @option{-fschedule-insns2}
+or at @option{-O2} or higher.
+
+@item -fsched-rank-heuristic
+@opindex fsched-rank-heuristic
+Enable the rank heuristic in the scheduler. This heuristic favors
+the instruction belonging to a basic block with greater size or frequency.
+This is enabled by default when scheduling is enabled, i.e.@:
+with @option{-fschedule-insns} or @option{-fschedule-insns2} or
+at @option{-O2} or higher.
+
+@item -fsched-last-insn-heuristic
+@opindex fsched-last-insn-heuristic
+Enable the last-instruction heuristic in the scheduler. This heuristic
+favors the instruction that is less dependent on the last instruction
+scheduled. This is enabled by default when scheduling is enabled,
+i.e.@: with @option{-fschedule-insns} or @option{-fschedule-insns2} or
+at @option{-O2} or higher.
+
+@item -fsched-dep-count-heuristic
+@opindex fsched-dep-count-heuristic
+Enable the dependent-count heuristic in the scheduler. This heuristic
+favors the instruction that has more instructions depending on it.
+This is enabled by default when scheduling is enabled, i.e.@:
+with @option{-fschedule-insns} or @option{-fschedule-insns2} or
+at @option{-O2} or higher.
+
+@item -freschedule-modulo-scheduled-loops
+@opindex freschedule-modulo-scheduled-loops
+Modulo scheduling is performed before traditional scheduling. If a loop
+is modulo scheduled, later scheduling passes may change its schedule.
+Use this option to control that behavior.
+
+@item -fselective-scheduling
+@opindex fselective-scheduling
+Schedule instructions using selective scheduling algorithm. Selective
+scheduling runs instead of the first scheduler pass.
+
+@item -fselective-scheduling2
+@opindex fselective-scheduling2
+Schedule instructions using selective scheduling algorithm. Selective
+scheduling runs instead of the second scheduler pass.
+
+@item -fsel-sched-pipelining
+@opindex fsel-sched-pipelining
+Enable software pipelining of innermost loops during selective scheduling.
+This option has no effect unless one of @option{-fselective-scheduling} or
+@option{-fselective-scheduling2} is turned on.
+
+@item -fsel-sched-pipelining-outer-loops
+@opindex fsel-sched-pipelining-outer-loops
+When pipelining loops during selective scheduling, also pipeline outer loops.
+This option has no effect unless @option{-fsel-sched-pipelining} is turned on.
+
+@item -fsemantic-interposition
+@opindex fsemantic-interposition
+Some object formats, like ELF, allow interposing of symbols by the
+dynamic linker.
+This means that for symbols exported from the DSO, the compiler cannot perform
+interprocedural propagation, inlining and other optimizations in anticipation
+that the function or variable in question may change. While this feature is
+useful, for example, to rewrite memory allocation functions by a debugging
+implementation, it is expensive in the terms of code quality.
+With @option{-fno-semantic-interposition} the compiler assumes that
+if interposition happens for functions the overwriting function will have
+precisely the same semantics (and side effects).
+Similarly if interposition happens
+for variables, the constructor of the variable will be the same. The flag
+has no effect for functions explicitly declared inline
+(where it is never allowed for interposition to change semantics)
+and for symbols explicitly declared weak.
+
+@item -fshrink-wrap
+@opindex fshrink-wrap
+Emit function prologues only before parts of the function that need it,
+rather than at the top of the function. This flag is enabled by default at
+@option{-O} and higher.
+
+@item -fshrink-wrap-separate
+@opindex fshrink-wrap-separate
+Shrink-wrap separate parts of the prologue and epilogue separately, so that
+those parts are only executed when needed.
+This option is on by default, but has no effect unless @option{-fshrink-wrap}
+is also turned on and the target supports this.
+
+@item -fcaller-saves
+@opindex fcaller-saves
+Enable allocation of values to registers that are clobbered by
+function calls, by emitting extra instructions to save and restore the
+registers around such calls. Such allocation is done only when it
+seems to result in better code.
+
+This option is always enabled by default on certain machines, usually
+those which have no call-preserved registers to use instead.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fcombine-stack-adjustments
+@opindex fcombine-stack-adjustments
+Tracks stack adjustments (pushes and pops) and stack memory references
+and then tries to find ways to combine them.
+
+Enabled by default at @option{-O1} and higher.
+
+@item -fipa-ra
+@opindex fipa-ra
+Use caller save registers for allocation if those registers are not used by
+any called function. In that case it is not necessary to save and restore
+them around calls. This is only possible if called functions are part of
+same compilation unit as current function and they are compiled before it.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, however the option
+is disabled if generated code will be instrumented for profiling
+(@option{-p}, or @option{-pg}) or if callee's register usage cannot be known
+exactly (this happens on targets that do not expose prologues
+and epilogues in RTL).
+
+@item -fconserve-stack
+@opindex fconserve-stack
+Attempt to minimize stack usage. The compiler attempts to use less
+stack space, even if that makes the program slower. This option
+implies setting the @option{large-stack-frame} parameter to 100
+and the @option{large-stack-frame-growth} parameter to 400.
+
+@item -ftree-reassoc
+@opindex ftree-reassoc
+Perform reassociation on trees. This flag is enabled by default
+at @option{-O1} and higher.
+
+@item -fcode-hoisting
+@opindex fcode-hoisting
+Perform code hoisting. Code hoisting tries to move the
+evaluation of expressions executed on all paths to the function exit
+as early as possible. This is especially useful as a code size
+optimization, but it often helps for code speed as well.
+This flag is enabled by default at @option{-O2} and higher.
+
+@item -ftree-pre
+@opindex ftree-pre
+Perform partial redundancy elimination (PRE) on trees. This flag is
+enabled by default at @option{-O2} and @option{-O3}.
+
+@item -ftree-partial-pre
+@opindex ftree-partial-pre
+Make partial redundancy elimination (PRE) more aggressive. This flag is
+enabled by default at @option{-O3}.
+
+@item -ftree-forwprop
+@opindex ftree-forwprop
+Perform forward propagation on trees. This flag is enabled by default
+at @option{-O1} and higher.
+
+@item -ftree-fre
+@opindex ftree-fre
+Perform full redundancy elimination (FRE) on trees. The difference
+between FRE and PRE is that FRE only considers expressions
+that are computed on all paths leading to the redundant computation.
+This analysis is faster than PRE, though it exposes fewer redundancies.
+This flag is enabled by default at @option{-O1} and higher.
+
+@item -ftree-phiprop
+@opindex ftree-phiprop
+Perform hoisting of loads from conditional pointers on trees. This
+pass is enabled by default at @option{-O1} and higher.
+
+@item -fhoist-adjacent-loads
+@opindex fhoist-adjacent-loads
+Speculatively hoist loads from both branches of an if-then-else if the
+loads are from adjacent locations in the same structure and the target
+architecture has a conditional move instruction. This flag is enabled
+by default at @option{-O2} and higher.
+
+@item -ftree-copy-prop
+@opindex ftree-copy-prop
+Perform copy propagation on trees. This pass eliminates unnecessary
+copy operations. This flag is enabled by default at @option{-O1} and
+higher.
+
+@item -fipa-pure-const
+@opindex fipa-pure-const
+Discover which functions are pure or constant.
+Enabled by default at @option{-O1} and higher.
+
+@item -fipa-reference
+@opindex fipa-reference
+Discover which static variables do not escape the
+compilation unit.
+Enabled by default at @option{-O1} and higher.
+
+@item -fipa-reference-addressable
+@opindex fipa-reference-addressable
+Discover read-only, write-only and non-addressable static variables.
+Enabled by default at @option{-O1} and higher.
+
+@item -fipa-stack-alignment
+@opindex fipa-stack-alignment
+Reduce stack alignment on call sites if possible.
+Enabled by default.
+
+@item -fipa-pta
+@opindex fipa-pta
+Perform interprocedural pointer analysis and interprocedural modification
+and reference analysis. This option can cause excessive memory and
+compile-time usage on large compilation units. It is not enabled by
+default at any optimization level.
+
+@item -fipa-profile
+@opindex fipa-profile
+Perform interprocedural profile propagation. The functions called only from
+cold functions are marked as cold. Also functions executed once (such as
+@code{cold}, @code{noreturn}, static constructors or destructors) are
+identified. Cold functions and loop less parts of functions executed once are
+then optimized for size.
+Enabled by default at @option{-O1} and higher.
+
+@item -fipa-modref
+@opindex fipa-modref
+Perform interprocedural mod/ref analysis. This optimization analyzes the side
+effects of functions (memory locations that are modified or referenced) and
+enables better optimization across the function call boundary. This flag is
+enabled by default at @option{-O1} and higher.
+
+@item -fipa-cp
+@opindex fipa-cp
+Perform interprocedural constant propagation.
+This optimization analyzes the program to determine when values passed
+to functions are constants and then optimizes accordingly.
+This optimization can substantially increase performance
+if the application has constants passed to functions.
+This flag is enabled by default at @option{-O2}, @option{-Os} and @option{-O3}.
+It is also enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -fipa-cp-clone
+@opindex fipa-cp-clone
+Perform function cloning to make interprocedural constant propagation stronger.
+When enabled, interprocedural constant propagation performs function cloning
+when externally visible function can be called with constant arguments.
+Because this optimization can create multiple copies of functions,
+it may significantly increase code size
+(see @option{--param ipa-cp-unit-growth=@var{value}}).
+This flag is enabled by default at @option{-O3}.
+It is also enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -fipa-bit-cp
+@opindex fipa-bit-cp
+When enabled, perform interprocedural bitwise constant
+propagation. This flag is enabled by default at @option{-O2} and
+by @option{-fprofile-use} and @option{-fauto-profile}.
+It requires that @option{-fipa-cp} is enabled.
+
+@item -fipa-vrp
+@opindex fipa-vrp
+When enabled, perform interprocedural propagation of value
+ranges. This flag is enabled by default at @option{-O2}. It requires
+that @option{-fipa-cp} is enabled.
+
+@item -fipa-icf
+@opindex fipa-icf
+Perform Identical Code Folding for functions and read-only variables.
+The optimization reduces code size and may disturb unwind stacks by replacing
+a function by equivalent one with a different name. The optimization works
+more effectively with link-time optimization enabled.
+
+Although the behavior is similar to the Gold Linker's ICF optimization, GCC ICF
+works on different levels and thus the optimizations are not same - there are
+equivalences that are found only by GCC and equivalences found only by Gold.
+
+This flag is enabled by default at @option{-O2} and @option{-Os}.
+
+@item -flive-patching=@var{level}
+@opindex flive-patching
+Control GCC's optimizations to produce output suitable for live-patching.
+
+If the compiler's optimization uses a function's body or information extracted
+from its body to optimize/change another function, the latter is called an
+impacted function of the former. If a function is patched, its impacted
+functions should be patched too.
+
+The impacted functions are determined by the compiler's interprocedural
+optimizations. For example, a caller is impacted when inlining a function
+into its caller,
+cloning a function and changing its caller to call this new clone,
+or extracting a function's pureness/constness information to optimize
+its direct or indirect callers, etc.
+
+Usually, the more IPA optimizations enabled, the larger the number of
+impacted functions for each function. In order to control the number of
+impacted functions and more easily compute the list of impacted function,
+IPA optimizations can be partially enabled at two different levels.
+
+The @var{level} argument should be one of the following:
+
+@table @samp
+
+@item inline-clone
+
+Only enable inlining and cloning optimizations, which includes inlining,
+cloning, interprocedural scalar replacement of aggregates and partial inlining.
+As a result, when patching a function, all its callers and its clones'
+callers are impacted, therefore need to be patched as well.
+
+@option{-flive-patching=inline-clone} disables the following optimization flags:
+@gccoptlist{-fwhole-program -fipa-pta -fipa-reference -fipa-ra @gol
+-fipa-icf -fipa-icf-functions -fipa-icf-variables @gol
+-fipa-bit-cp -fipa-vrp -fipa-pure-const -fipa-reference-addressable @gol
+-fipa-stack-alignment -fipa-modref}
+
+@item inline-only-static
+
+Only enable inlining of static functions.
+As a result, when patching a static function, all its callers are impacted
+and so need to be patched as well.
+
+In addition to all the flags that @option{-flive-patching=inline-clone}
+disables,
+@option{-flive-patching=inline-only-static} disables the following additional
+optimization flags:
+@gccoptlist{-fipa-cp-clone -fipa-sra -fpartial-inlining -fipa-cp}
+
+@end table
+
+When @option{-flive-patching} is specified without any value, the default value
+is @var{inline-clone}.
+
+This flag is disabled by default.
+
+Note that @option{-flive-patching} is not supported with link-time optimization
+(@option{-flto}).
+
+@item -fisolate-erroneous-paths-dereference
+@opindex fisolate-erroneous-paths-dereference
+Detect paths that trigger erroneous or undefined behavior due to
+dereferencing a null pointer. Isolate those paths from the main control
+flow and turn the statement with erroneous or undefined behavior into a trap.
+This flag is enabled by default at @option{-O2} and higher and depends on
+@option{-fdelete-null-pointer-checks} also being enabled.
+
+@item -fisolate-erroneous-paths-attribute
+@opindex fisolate-erroneous-paths-attribute
+Detect paths that trigger erroneous or undefined behavior due to a null value
+being used in a way forbidden by a @code{returns_nonnull} or @code{nonnull}
+attribute. Isolate those paths from the main control flow and turn the
+statement with erroneous or undefined behavior into a trap. This is not
+currently enabled, but may be enabled by @option{-O2} in the future.
+
+@item -ftree-sink
+@opindex ftree-sink
+Perform forward store motion on trees. This flag is
+enabled by default at @option{-O1} and higher.
+
+@item -ftree-bit-ccp
+@opindex ftree-bit-ccp
+Perform sparse conditional bit constant propagation on trees and propagate
+pointer alignment information.
+This pass only operates on local scalar variables and is enabled by default
+at @option{-O1} and higher, except for @option{-Og}.
+It requires that @option{-ftree-ccp} is enabled.
+
+@item -ftree-ccp
+@opindex ftree-ccp
+Perform sparse conditional constant propagation (CCP) on trees. This
+pass only operates on local scalar variables and is enabled by default
+at @option{-O1} and higher.
+
+@item -fssa-backprop
+@opindex fssa-backprop
+Propagate information about uses of a value up the definition chain
+in order to simplify the definitions. For example, this pass strips
+sign operations if the sign of a value never matters. The flag is
+enabled by default at @option{-O1} and higher.
+
+@item -fssa-phiopt
+@opindex fssa-phiopt
+Perform pattern matching on SSA PHI nodes to optimize conditional
+code. This pass is enabled by default at @option{-O1} and higher,
+except for @option{-Og}.
+
+@item -ftree-switch-conversion
+@opindex ftree-switch-conversion
+Perform conversion of simple initializations in a switch to
+initializations from a scalar array. This flag is enabled by default
+at @option{-O2} and higher.
+
+@item -ftree-tail-merge
+@opindex ftree-tail-merge
+Look for identical code sequences. When found, replace one with a jump to the
+other. This optimization is known as tail merging or cross jumping. This flag
+is enabled by default at @option{-O2} and higher. The compilation time
+in this pass can
+be limited using @option{max-tail-merge-comparisons} parameter and
+@option{max-tail-merge-iterations} parameter.
+
+@item -ftree-dce
+@opindex ftree-dce
+Perform dead code elimination (DCE) on trees. This flag is enabled by
+default at @option{-O1} and higher.
+
+@item -ftree-builtin-call-dce
+@opindex ftree-builtin-call-dce
+Perform conditional dead code elimination (DCE) for calls to built-in functions
+that may set @code{errno} but are otherwise free of side effects. This flag is
+enabled by default at @option{-O2} and higher if @option{-Os} is not also
+specified.
+
+@item -ffinite-loops
+@opindex ffinite-loops
+@opindex fno-finite-loops
+Assume that a loop with an exit will eventually take the exit and not loop
+indefinitely. This allows the compiler to remove loops that otherwise have
+no side-effects, not considering eventual endless looping as such.
+
+This option is enabled by default at @option{-O2} for C++ with -std=c++11
+or higher.
+
+@item -ftree-dominator-opts
+@opindex ftree-dominator-opts
+Perform a variety of simple scalar cleanups (constant/copy
+propagation, redundancy elimination, range propagation and expression
+simplification) based on a dominator tree traversal. This also
+performs jump threading (to reduce jumps to jumps). This flag is
+enabled by default at @option{-O1} and higher.
+
+@item -ftree-dse
+@opindex ftree-dse
+Perform dead store elimination (DSE) on trees. A dead store is a store into
+a memory location that is later overwritten by another store without
+any intervening loads. In this case the earlier store can be deleted. This
+flag is enabled by default at @option{-O1} and higher.
+
+@item -ftree-ch
+@opindex ftree-ch
+Perform loop header copying on trees. This is beneficial since it increases
+effectiveness of code motion optimizations. It also saves one jump. This flag
+is enabled by default at @option{-O1} and higher. It is not enabled
+for @option{-Os}, since it usually increases code size.
+
+@item -ftree-loop-optimize
+@opindex ftree-loop-optimize
+Perform loop optimizations on trees. This flag is enabled by default
+at @option{-O1} and higher.
+
+@item -ftree-loop-linear
+@itemx -floop-strip-mine
+@itemx -floop-block
+@opindex ftree-loop-linear
+@opindex floop-strip-mine
+@opindex floop-block
+Perform loop nest optimizations. Same as
+@option{-floop-nest-optimize}. To use this code transformation, GCC has
+to be configured with @option{--with-isl} to enable the Graphite loop
+transformation infrastructure.
+
+@item -fgraphite-identity
+@opindex fgraphite-identity
+Enable the identity transformation for graphite. For every SCoP we generate
+the polyhedral representation and transform it back to gimple. Using
+@option{-fgraphite-identity} we can check the costs or benefits of the
+GIMPLE -> GRAPHITE -> GIMPLE transformation. Some minimal optimizations
+are also performed by the code generator isl, like index splitting and
+dead code elimination in loops.
+
+@item -floop-nest-optimize
+@opindex floop-nest-optimize
+Enable the isl based loop nest optimizer. This is a generic loop nest
+optimizer based on the Pluto optimization algorithms. It calculates a loop
+structure optimized for data-locality and parallelism. This option
+is experimental.
+
+@item -floop-parallelize-all
+@opindex floop-parallelize-all
+Use the Graphite data dependence analysis to identify loops that can
+be parallelized. Parallelize all the loops that can be analyzed to
+not contain loop carried dependences without checking that it is
+profitable to parallelize the loops.
+
+@item -ftree-coalesce-vars
+@opindex ftree-coalesce-vars
+While transforming the program out of the SSA representation, attempt to
+reduce copying by coalescing versions of different user-defined
+variables, instead of just compiler temporaries. This may severely
+limit the ability to debug an optimized program compiled with
+@option{-fno-var-tracking-assignments}. In the negated form, this flag
+prevents SSA coalescing of user variables. This option is enabled by
+default if optimization is enabled, and it does very little otherwise.
+
+@item -ftree-loop-if-convert
+@opindex ftree-loop-if-convert
+Attempt to transform conditional jumps in the innermost loops to
+branch-less equivalents. The intent is to remove control-flow from
+the innermost loops in order to improve the ability of the
+vectorization pass to handle these loops. This is enabled by default
+if vectorization is enabled.
+
+@item -ftree-loop-distribution
+@opindex ftree-loop-distribution
+Perform loop distribution. This flag can improve cache performance on
+big loop bodies and allow further loop optimizations, like
+parallelization or vectorization, to take place. For example, the loop
+@smallexample
+DO I = 1, N
+ A(I) = B(I) + C
+ D(I) = E(I) * F
+ENDDO
+@end smallexample
+is transformed to
+@smallexample
+DO I = 1, N
+ A(I) = B(I) + C
+ENDDO
+DO I = 1, N
+ D(I) = E(I) * F
+ENDDO
+@end smallexample
+This flag is enabled by default at @option{-O3}.
+It is also enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -ftree-loop-distribute-patterns
+@opindex ftree-loop-distribute-patterns
+Perform loop distribution of patterns that can be code generated with
+calls to a library. This flag is enabled by default at @option{-O2} and
+higher, and by @option{-fprofile-use} and @option{-fauto-profile}.
+
+This pass distributes the initialization loops and generates a call to
+memset zero. For example, the loop
+@smallexample
+DO I = 1, N
+ A(I) = 0
+ B(I) = A(I) + I
+ENDDO
+@end smallexample
+is transformed to
+@smallexample
+DO I = 1, N
+ A(I) = 0
+ENDDO
+DO I = 1, N
+ B(I) = A(I) + I
+ENDDO
+@end smallexample
+and the initialization loop is transformed into a call to memset zero.
+This flag is enabled by default at @option{-O3}.
+It is also enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -floop-interchange
+@opindex floop-interchange
+Perform loop interchange outside of graphite. This flag can improve cache
+performance on loop nest and allow further loop optimizations, like
+vectorization, to take place. For example, the loop
+@smallexample
+for (int i = 0; i < N; i++)
+ for (int j = 0; j < N; j++)
+ for (int k = 0; k < N; k++)
+ c[i][j] = c[i][j] + a[i][k]*b[k][j];
+@end smallexample
+is transformed to
+@smallexample
+for (int i = 0; i < N; i++)
+ for (int k = 0; k < N; k++)
+ for (int j = 0; j < N; j++)
+ c[i][j] = c[i][j] + a[i][k]*b[k][j];
+@end smallexample
+This flag is enabled by default at @option{-O3}.
+It is also enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -floop-unroll-and-jam
+@opindex floop-unroll-and-jam
+Apply unroll and jam transformations on feasible loops. In a loop
+nest this unrolls the outer loop by some factor and fuses the resulting
+multiple inner loops. This flag is enabled by default at @option{-O3}.
+It is also enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -ftree-loop-im
+@opindex ftree-loop-im
+Perform loop invariant motion on trees. This pass moves only invariants that
+are hard to handle at RTL level (function calls, operations that expand to
+nontrivial sequences of insns). With @option{-funswitch-loops} it also moves
+operands of conditions that are invariant out of the loop, so that we can use
+just trivial invariantness analysis in loop unswitching. The pass also includes
+store motion.
+
+@item -ftree-loop-ivcanon
+@opindex ftree-loop-ivcanon
+Create a canonical counter for number of iterations in loops for which
+determining number of iterations requires complicated analysis. Later
+optimizations then may determine the number easily. Useful especially
+in connection with unrolling.
+
+@item -ftree-scev-cprop
+@opindex ftree-scev-cprop
+Perform final value replacement. If a variable is modified in a loop
+in such a way that its value when exiting the loop can be determined using
+only its initial value and the number of loop iterations, replace uses of
+the final value by such a computation, provided it is sufficiently cheap.
+This reduces data dependencies and may allow further simplifications.
+Enabled by default at @option{-O1} and higher.
+
+@item -fivopts
+@opindex fivopts
+Perform induction variable optimizations (strength reduction, induction
+variable merging and induction variable elimination) on trees.
+
+@item -ftree-parallelize-loops=n
+@opindex ftree-parallelize-loops
+Parallelize loops, i.e., split their iteration space to run in n threads.
+This is only possible for loops whose iterations are independent
+and can be arbitrarily reordered. The optimization is only
+profitable on multiprocessor machines, for loops that are CPU-intensive,
+rather than constrained e.g.@: by memory bandwidth. This option
+implies @option{-pthread}, and thus is only supported on targets
+that have support for @option{-pthread}.
+
+@item -ftree-pta
+@opindex ftree-pta
+Perform function-local points-to analysis on trees. This flag is
+enabled by default at @option{-O1} and higher, except for @option{-Og}.
+
+@item -ftree-sra
+@opindex ftree-sra
+Perform scalar replacement of aggregates. This pass replaces structure
+references with scalars to prevent committing structures to memory too
+early. This flag is enabled by default at @option{-O1} and higher,
+except for @option{-Og}.
+
+@item -fstore-merging
+@opindex fstore-merging
+Perform merging of narrow stores to consecutive memory addresses. This pass
+merges contiguous stores of immediate values narrower than a word into fewer
+wider stores to reduce the number of instructions. This is enabled by default
+at @option{-O2} and higher as well as @option{-Os}.
+
+@item -ftree-ter
+@opindex ftree-ter
+Perform temporary expression replacement during the SSA->normal phase. Single
+use/single def temporaries are replaced at their use location with their
+defining expression. This results in non-GIMPLE code, but gives the expanders
+much more complex trees to work on resulting in better RTL generation. This is
+enabled by default at @option{-O1} and higher.
+
+@item -ftree-slsr
+@opindex ftree-slsr
+Perform straight-line strength reduction on trees. This recognizes related
+expressions involving multiplications and replaces them by less expensive
+calculations when possible. This is enabled by default at @option{-O1} and
+higher.
+
+@item -ftree-vectorize
+@opindex ftree-vectorize
+Perform vectorization on trees. This flag enables @option{-ftree-loop-vectorize}
+and @option{-ftree-slp-vectorize} if not explicitly specified.
+
+@item -ftree-loop-vectorize
+@opindex ftree-loop-vectorize
+Perform loop vectorization on trees. This flag is enabled by default at
+@option{-O2} and by @option{-ftree-vectorize}, @option{-fprofile-use},
+and @option{-fauto-profile}.
+
+@item -ftree-slp-vectorize
+@opindex ftree-slp-vectorize
+Perform basic block vectorization on trees. This flag is enabled by default at
+@option{-O2} and by @option{-ftree-vectorize}, @option{-fprofile-use},
+and @option{-fauto-profile}.
+
+@item -ftrivial-auto-var-init=@var{choice}
+@opindex ftrivial-auto-var-init
+Initialize automatic variables with either a pattern or with zeroes to increase
+the security and predictability of a program by preventing uninitialized memory
+disclosure and use.
+GCC still considers an automatic variable that doesn't have an explicit
+initializer as uninitialized, @option{-Wuninitialized} and
+@option{-Wanalyzer-use-of-uninitialized-value} will still report
+warning messages on such automatic variables.
+With this option, GCC will also initialize any padding of automatic variables
+that have structure or union types to zeroes.
+However, the current implementation cannot initialize automatic variables that
+are declared between the controlling expression and the first case of a
+@code{switch} statement. Using @option{-Wtrivial-auto-var-init} to report all
+such cases.
+
+The three values of @var{choice} are:
+
+@itemize @bullet
+@item
+@samp{uninitialized} doesn't initialize any automatic variables.
+This is C and C++'s default.
+
+@item
+@samp{pattern} Initialize automatic variables with values which will likely
+transform logic bugs into crashes down the line, are easily recognized in a
+crash dump and without being values that programmers can rely on for useful
+program semantics.
+The current value is byte-repeatable pattern with byte "0xFE".
+The values used for pattern initialization might be changed in the future.
+
+@item
+@samp{zero} Initialize automatic variables with zeroes.
+@end itemize
+
+The default is @samp{uninitialized}.
+
+You can control this behavior for a specific variable by using the variable
+attribute @code{uninitialized} (@pxref{Variable Attributes}).
+
+@item -fvect-cost-model=@var{model}
+@opindex fvect-cost-model
+Alter the cost model used for vectorization. The @var{model} argument
+should be one of @samp{unlimited}, @samp{dynamic}, @samp{cheap} or
+@samp{very-cheap}.
+With the @samp{unlimited} model the vectorized code-path is assumed
+to be profitable while with the @samp{dynamic} model a runtime check
+guards the vectorized code-path to enable it only for iteration
+counts that will likely execute faster than when executing the original
+scalar loop. The @samp{cheap} model disables vectorization of
+loops where doing so would be cost prohibitive for example due to
+required runtime checks for data dependence or alignment but otherwise
+is equal to the @samp{dynamic} model. The @samp{very-cheap} model only
+allows vectorization if the vector code would entirely replace the
+scalar code that is being vectorized. For example, if each iteration
+of a vectorized loop would only be able to handle exactly four iterations
+of the scalar loop, the @samp{very-cheap} model would only allow
+vectorization if the scalar iteration count is known to be a multiple
+of four.
+
+The default cost model depends on other optimization flags and is
+either @samp{dynamic} or @samp{cheap}.
+
+@item -fsimd-cost-model=@var{model}
+@opindex fsimd-cost-model
+Alter the cost model used for vectorization of loops marked with the OpenMP
+simd directive. The @var{model} argument should be one of
+@samp{unlimited}, @samp{dynamic}, @samp{cheap}. All values of @var{model}
+have the same meaning as described in @option{-fvect-cost-model} and by
+default a cost model defined with @option{-fvect-cost-model} is used.
+
+@item -ftree-vrp
+@opindex ftree-vrp
+Perform Value Range Propagation on trees. This is similar to the
+constant propagation pass, but instead of values, ranges of values are
+propagated. This allows the optimizers to remove unnecessary range
+checks like array bound checks and null pointer checks. This is
+enabled by default at @option{-O2} and higher. Null pointer check
+elimination is only done if @option{-fdelete-null-pointer-checks} is
+enabled.
+
+@item -fsplit-paths
+@opindex fsplit-paths
+Split paths leading to loop backedges. This can improve dead code
+elimination and common subexpression elimination. This is enabled by
+default at @option{-O3} and above.
+
+@item -fsplit-ivs-in-unroller
+@opindex fsplit-ivs-in-unroller
+Enables expression of values of induction variables in later iterations
+of the unrolled loop using the value in the first iteration. This breaks
+long dependency chains, thus improving efficiency of the scheduling passes.
+
+A combination of @option{-fweb} and CSE is often sufficient to obtain the
+same effect. However, that is not reliable in cases where the loop body
+is more complicated than a single basic block. It also does not work at all
+on some architectures due to restrictions in the CSE pass.
+
+This optimization is enabled by default.
+
+@item -fvariable-expansion-in-unroller
+@opindex fvariable-expansion-in-unroller
+With this option, the compiler creates multiple copies of some
+local variables when unrolling a loop, which can result in superior code.
+
+This optimization is enabled by default for PowerPC targets, but disabled
+by default otherwise.
+
+@item -fpartial-inlining
+@opindex fpartial-inlining
+Inline parts of functions. This option has any effect only
+when inlining itself is turned on by the @option{-finline-functions}
+or @option{-finline-small-functions} options.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fpredictive-commoning
+@opindex fpredictive-commoning
+Perform predictive commoning optimization, i.e., reusing computations
+(especially memory loads and stores) performed in previous
+iterations of loops.
+
+This option is enabled at level @option{-O3}.
+It is also enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -fprefetch-loop-arrays
+@opindex fprefetch-loop-arrays
+If supported by the target machine, generate instructions to prefetch
+memory to improve the performance of loops that access large arrays.
+
+This option may generate better or worse code; results are highly
+dependent on the structure of loops within the source code.
+
+Disabled at level @option{-Os}.
+
+@item -fno-printf-return-value
+@opindex fno-printf-return-value
+@opindex fprintf-return-value
+Do not substitute constants for known return value of formatted output
+functions such as @code{sprintf}, @code{snprintf}, @code{vsprintf}, and
+@code{vsnprintf} (but not @code{printf} of @code{fprintf}). This
+transformation allows GCC to optimize or even eliminate branches based
+on the known return value of these functions called with arguments that
+are either constant, or whose values are known to be in a range that
+makes determining the exact return value possible. For example, when
+@option{-fprintf-return-value} is in effect, both the branch and the
+body of the @code{if} statement (but not the call to @code{snprint})
+can be optimized away when @code{i} is a 32-bit or smaller integer
+because the return value is guaranteed to be at most 8.
+
+@smallexample
+char buf[9];
+if (snprintf (buf, "%08x", i) >= sizeof buf)
+ @dots{}
+@end smallexample
+
+The @option{-fprintf-return-value} option relies on other optimizations
+and yields best results with @option{-O2} and above. It works in tandem
+with the @option{-Wformat-overflow} and @option{-Wformat-truncation}
+options. The @option{-fprintf-return-value} option is enabled by default.
+
+@item -fno-peephole
+@itemx -fno-peephole2
+@opindex fno-peephole
+@opindex fpeephole
+@opindex fno-peephole2
+@opindex fpeephole2
+Disable any machine-specific peephole optimizations. The difference
+between @option{-fno-peephole} and @option{-fno-peephole2} is in how they
+are implemented in the compiler; some targets use one, some use the
+other, a few use both.
+
+@option{-fpeephole} is enabled by default.
+@option{-fpeephole2} enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fno-guess-branch-probability
+@opindex fno-guess-branch-probability
+@opindex fguess-branch-probability
+Do not guess branch probabilities using heuristics.
+
+GCC uses heuristics to guess branch probabilities if they are
+not provided by profiling feedback (@option{-fprofile-arcs}). These
+heuristics are based on the control flow graph. If some branch probabilities
+are specified by @code{__builtin_expect}, then the heuristics are
+used to guess branch probabilities for the rest of the control flow graph,
+taking the @code{__builtin_expect} info into account. The interactions
+between the heuristics and @code{__builtin_expect} can be complex, and in
+some cases, it may be useful to disable the heuristics so that the effects
+of @code{__builtin_expect} are easier to understand.
+
+It is also possible to specify expected probability of the expression
+with @code{__builtin_expect_with_probability} built-in function.
+
+The default is @option{-fguess-branch-probability} at levels
+@option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -freorder-blocks
+@opindex freorder-blocks
+Reorder basic blocks in the compiled function in order to reduce number of
+taken branches and improve code locality.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -freorder-blocks-algorithm=@var{algorithm}
+@opindex freorder-blocks-algorithm
+Use the specified algorithm for basic block reordering. The
+@var{algorithm} argument can be @samp{simple}, which does not increase
+code size (except sometimes due to secondary effects like alignment),
+or @samp{stc}, the ``software trace cache'' algorithm, which tries to
+put all often executed code together, minimizing the number of branches
+executed by making extra copies of code.
+
+The default is @samp{simple} at levels @option{-O1}, @option{-Os}, and
+@samp{stc} at levels @option{-O2}, @option{-O3}.
+
+@item -freorder-blocks-and-partition
+@opindex freorder-blocks-and-partition
+In addition to reordering basic blocks in the compiled function, in order
+to reduce number of taken branches, partitions hot and cold basic blocks
+into separate sections of the assembly and @file{.o} files, to improve
+paging and cache locality performance.
+
+This optimization is automatically turned off in the presence of
+exception handling or unwind tables (on targets using setjump/longjump or target specific scheme), for linkonce sections, for functions with a user-defined
+section attribute and on any architecture that does not support named
+sections. When @option{-fsplit-stack} is used this option is not
+enabled by default (to avoid linker errors), but may be enabled
+explicitly (if using a working linker).
+
+Enabled for x86 at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -freorder-functions
+@opindex freorder-functions
+Reorder functions in the object file in order to
+improve code locality. This is implemented by using special
+subsections @code{.text.hot} for most frequently executed functions and
+@code{.text.unlikely} for unlikely executed functions. Reordering is done by
+the linker so object file format must support named sections and linker must
+place them in a reasonable way.
+
+This option isn't effective unless you either provide profile feedback
+(see @option{-fprofile-arcs} for details) or manually annotate functions with
+@code{hot} or @code{cold} attributes (@pxref{Common Function Attributes}).
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fstrict-aliasing
+@opindex fstrict-aliasing
+Allow the compiler to assume the strictest aliasing rules applicable to
+the language being compiled. For C (and C++), this activates
+optimizations based on the type of expressions. In particular, an
+object of one type is assumed never to reside at the same address as an
+object of a different type, unless the types are almost the same. For
+example, an @code{unsigned int} can alias an @code{int}, but not a
+@code{void*} or a @code{double}. A character type may alias any other
+type.
+
+@anchor{Type-punning}Pay special attention to code like this:
+@smallexample
+union a_union @{
+ int i;
+ double d;
+@};
+
+int f() @{
+ union a_union t;
+ t.d = 3.0;
+ return t.i;
+@}
+@end smallexample
+The practice of reading from a different union member than the one most
+recently written to (called ``type-punning'') is common. Even with
+@option{-fstrict-aliasing}, type-punning is allowed, provided the memory
+is accessed through the union type. So, the code above works as
+expected. @xref{Structures unions enumerations and bit-fields
+implementation}. However, this code might not:
+@smallexample
+int f() @{
+ union a_union t;
+ int* ip;
+ t.d = 3.0;
+ ip = &t.i;
+ return *ip;
+@}
+@end smallexample
+
+Similarly, access by taking the address, casting the resulting pointer
+and dereferencing the result has undefined behavior, even if the cast
+uses a union type, e.g.:
+@smallexample
+int f() @{
+ double d = 3.0;
+ return ((union a_union *) &d)->i;
+@}
+@end smallexample
+
+The @option{-fstrict-aliasing} option is enabled at levels
+@option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fipa-strict-aliasing
+@opindex fipa-strict-aliasing
+Controls whether rules of @option{-fstrict-aliasing} are applied across
+function boundaries. Note that if multiple functions gets inlined into a
+single function the memory accesses are no longer considered to be crossing a
+function boundary.
+
+The @option{-fipa-strict-aliasing} option is enabled by default and is
+effective only in combination with @option{-fstrict-aliasing}.
+
+@item -falign-functions
+@itemx -falign-functions=@var{n}
+@itemx -falign-functions=@var{n}:@var{m}
+@itemx -falign-functions=@var{n}:@var{m}:@var{n2}
+@itemx -falign-functions=@var{n}:@var{m}:@var{n2}:@var{m2}
+@opindex falign-functions
+Align the start of functions to the next power-of-two greater than or
+equal to @var{n}, skipping up to @var{m}-1 bytes. This ensures that at
+least the first @var{m} bytes of the function can be fetched by the CPU
+without crossing an @var{n}-byte alignment boundary.
+
+If @var{m} is not specified, it defaults to @var{n}.
+
+Examples: @option{-falign-functions=32} aligns functions to the next
+32-byte boundary, @option{-falign-functions=24} aligns to the next
+32-byte boundary only if this can be done by skipping 23 bytes or less,
+@option{-falign-functions=32:7} aligns to the next
+32-byte boundary only if this can be done by skipping 6 bytes or less.
+
+The second pair of @var{n2}:@var{m2} values allows you to specify
+a secondary alignment: @option{-falign-functions=64:7:32:3} aligns to
+the next 64-byte boundary if this can be done by skipping 6 bytes or less,
+otherwise aligns to the next 32-byte boundary if this can be done
+by skipping 2 bytes or less.
+If @var{m2} is not specified, it defaults to @var{n2}.
+
+Some assemblers only support this flag when @var{n} is a power of two;
+in that case, it is rounded up.
+
+@option{-fno-align-functions} and @option{-falign-functions=1} are
+equivalent and mean that functions are not aligned.
+
+If @var{n} is not specified or is zero, use a machine-dependent default.
+The maximum allowed @var{n} option value is 65536.
+
+Enabled at levels @option{-O2}, @option{-O3}.
+
+@item -flimit-function-alignment
+If this option is enabled, the compiler tries to avoid unnecessarily
+overaligning functions. It attempts to instruct the assembler to align
+by the amount specified by @option{-falign-functions}, but not to
+skip more bytes than the size of the function.
+
+@item -falign-labels
+@itemx -falign-labels=@var{n}
+@itemx -falign-labels=@var{n}:@var{m}
+@itemx -falign-labels=@var{n}:@var{m}:@var{n2}
+@itemx -falign-labels=@var{n}:@var{m}:@var{n2}:@var{m2}
+@opindex falign-labels
+Align all branch targets to a power-of-two boundary.
+
+Parameters of this option are analogous to the @option{-falign-functions} option.
+@option{-fno-align-labels} and @option{-falign-labels=1} are
+equivalent and mean that labels are not aligned.
+
+If @option{-falign-loops} or @option{-falign-jumps} are applicable and
+are greater than this value, then their values are used instead.
+
+If @var{n} is not specified or is zero, use a machine-dependent default
+which is very likely to be @samp{1}, meaning no alignment.
+The maximum allowed @var{n} option value is 65536.
+
+Enabled at levels @option{-O2}, @option{-O3}.
+
+@item -falign-loops
+@itemx -falign-loops=@var{n}
+@itemx -falign-loops=@var{n}:@var{m}
+@itemx -falign-loops=@var{n}:@var{m}:@var{n2}
+@itemx -falign-loops=@var{n}:@var{m}:@var{n2}:@var{m2}
+@opindex falign-loops
+Align loops to a power-of-two boundary. If the loops are executed
+many times, this makes up for any execution of the dummy padding
+instructions.
+
+If @option{-falign-labels} is greater than this value, then its value
+is used instead.
+
+Parameters of this option are analogous to the @option{-falign-functions} option.
+@option{-fno-align-loops} and @option{-falign-loops=1} are
+equivalent and mean that loops are not aligned.
+The maximum allowed @var{n} option value is 65536.
+
+If @var{n} is not specified or is zero, use a machine-dependent default.
+
+Enabled at levels @option{-O2}, @option{-O3}.
+
+@item -falign-jumps
+@itemx -falign-jumps=@var{n}
+@itemx -falign-jumps=@var{n}:@var{m}
+@itemx -falign-jumps=@var{n}:@var{m}:@var{n2}
+@itemx -falign-jumps=@var{n}:@var{m}:@var{n2}:@var{m2}
+@opindex falign-jumps
+Align branch targets to a power-of-two boundary, for branch targets
+where the targets can only be reached by jumping. In this case,
+no dummy operations need be executed.
+
+If @option{-falign-labels} is greater than this value, then its value
+is used instead.
+
+Parameters of this option are analogous to the @option{-falign-functions} option.
+@option{-fno-align-jumps} and @option{-falign-jumps=1} are
+equivalent and mean that loops are not aligned.
+
+If @var{n} is not specified or is zero, use a machine-dependent default.
+The maximum allowed @var{n} option value is 65536.
+
+Enabled at levels @option{-O2}, @option{-O3}.
+
+@item -fno-allocation-dce
+@opindex fno-allocation-dce
+Do not remove unused C++ allocations in dead code elimination.
+
+@item -fallow-store-data-races
+@opindex fallow-store-data-races
+Allow the compiler to perform optimizations that may introduce new data races
+on stores, without proving that the variable cannot be concurrently accessed
+by other threads. Does not affect optimization of local data. It is safe to
+use this option if it is known that global data will not be accessed by
+multiple threads.
+
+Examples of optimizations enabled by @option{-fallow-store-data-races} include
+hoisting or if-conversions that may cause a value that was already in memory
+to be re-written with that same value. Such re-writing is safe in a single
+threaded context but may be unsafe in a multi-threaded context. Note that on
+some processors, if-conversions may be required in order to enable
+vectorization.
+
+Enabled at level @option{-Ofast}.
+
+@item -funit-at-a-time
+@opindex funit-at-a-time
+This option is left for compatibility reasons. @option{-funit-at-a-time}
+has no effect, while @option{-fno-unit-at-a-time} implies
+@option{-fno-toplevel-reorder} and @option{-fno-section-anchors}.
+
+Enabled by default.
+
+@item -fno-toplevel-reorder
+@opindex fno-toplevel-reorder
+@opindex ftoplevel-reorder
+Do not reorder top-level functions, variables, and @code{asm}
+statements. Output them in the same order that they appear in the
+input file. When this option is used, unreferenced static variables
+are not removed. This option is intended to support existing code
+that relies on a particular ordering. For new code, it is better to
+use attributes when possible.
+
+@option{-ftoplevel-reorder} is the default at @option{-O1} and higher, and
+also at @option{-O0} if @option{-fsection-anchors} is explicitly requested.
+Additionally @option{-fno-toplevel-reorder} implies
+@option{-fno-section-anchors}.
+
+@item -funreachable-traps
+@opindex funreachable-traps
+With this option, the compiler turns calls to
+@code{__builtin_unreachable} into traps, instead of using them for
+optimization. This also affects any such calls implicitly generated
+by the compiler.
+
+This option has the same effect as @option{-fsanitize=unreachable
+-fsanitize-trap=unreachable}, but does not affect the values of those
+options. If @option{-fsanitize=unreachable} is enabled, that option
+takes priority over this one.
+
+This option is enabled by default at @option{-O0} and @option{-Og}.
+
+@item -fweb
+@opindex fweb
+Constructs webs as commonly used for register allocation purposes and assign
+each web individual pseudo register. This allows the register allocation pass
+to operate on pseudos directly, but also strengthens several other optimization
+passes, such as CSE, loop optimizer and trivial dead code remover. It can,
+however, make debugging impossible, since variables no longer stay in a
+``home register''.
+
+Enabled by default with @option{-funroll-loops}.
+
+@item -fwhole-program
+@opindex fwhole-program
+Assume that the current compilation unit represents the whole program being
+compiled. All public functions and variables with the exception of @code{main}
+and those merged by attribute @code{externally_visible} become static functions
+and in effect are optimized more aggressively by interprocedural optimizers.
+
+This option should not be used in combination with @option{-flto}.
+Instead relying on a linker plugin should provide safer and more precise
+information.
+
+@item -flto[=@var{n}]
+@opindex flto
+This option runs the standard link-time optimizer. When invoked
+with source code, it generates GIMPLE (one of GCC's internal
+representations) and writes it to special ELF sections in the object
+file. When the object files are linked together, all the function
+bodies are read from these ELF sections and instantiated as if they
+had been part of the same translation unit.
+
+To use the link-time optimizer, @option{-flto} and optimization
+options should be specified at compile time and during the final link.
+It is recommended that you compile all the files participating in the
+same link with the same options and also specify those options at
+link time.
+For example:
+
+@smallexample
+gcc -c -O2 -flto foo.c
+gcc -c -O2 -flto bar.c
+gcc -o myprog -flto -O2 foo.o bar.o
+@end smallexample
+
+The first two invocations to GCC save a bytecode representation
+of GIMPLE into special ELF sections inside @file{foo.o} and
+@file{bar.o}. The final invocation reads the GIMPLE bytecode from
+@file{foo.o} and @file{bar.o}, merges the two files into a single
+internal image, and compiles the result as usual. Since both
+@file{foo.o} and @file{bar.o} are merged into a single image, this
+causes all the interprocedural analyses and optimizations in GCC to
+work across the two files as if they were a single one. This means,
+for example, that the inliner is able to inline functions in
+@file{bar.o} into functions in @file{foo.o} and vice-versa.
+
+Another (simpler) way to enable link-time optimization is:
+
+@smallexample
+gcc -o myprog -flto -O2 foo.c bar.c
+@end smallexample
+
+The above generates bytecode for @file{foo.c} and @file{bar.c},
+merges them together into a single GIMPLE representation and optimizes
+them as usual to produce @file{myprog}.
+
+The important thing to keep in mind is that to enable link-time
+optimizations you need to use the GCC driver to perform the link step.
+GCC automatically performs link-time optimization if any of the
+objects involved were compiled with the @option{-flto} command-line option.
+You can always override
+the automatic decision to do link-time optimization
+by passing @option{-fno-lto} to the link command.
+
+To make whole program optimization effective, it is necessary to make
+certain whole program assumptions. The compiler needs to know
+what functions and variables can be accessed by libraries and runtime
+outside of the link-time optimized unit. When supported by the linker,
+the linker plugin (see @option{-fuse-linker-plugin}) passes information
+to the compiler about used and externally visible symbols. When
+the linker plugin is not available, @option{-fwhole-program} should be
+used to allow the compiler to make these assumptions, which leads
+to more aggressive optimization decisions.
+
+When a file is compiled with @option{-flto} without
+@option{-fuse-linker-plugin}, the generated object file is larger than
+a regular object file because it contains GIMPLE bytecodes and the usual
+final code (see @option{-ffat-lto-objects}). This means that
+object files with LTO information can be linked as normal object
+files; if @option{-fno-lto} is passed to the linker, no
+interprocedural optimizations are applied. Note that when
+@option{-fno-fat-lto-objects} is enabled the compile stage is faster
+but you cannot perform a regular, non-LTO link on them.
+
+When producing the final binary, GCC only
+applies link-time optimizations to those files that contain bytecode.
+Therefore, you can mix and match object files and libraries with
+GIMPLE bytecodes and final object code. GCC automatically selects
+which files to optimize in LTO mode and which files to link without
+further processing.
+
+Generally, options specified at link time override those
+specified at compile time, although in some cases GCC attempts to infer
+link-time options from the settings used to compile the input files.
+
+If you do not specify an optimization level option @option{-O} at
+link time, then GCC uses the highest optimization level
+used when compiling the object files. Note that it is generally
+ineffective to specify an optimization level option only at link time and
+not at compile time, for two reasons. First, compiling without
+optimization suppresses compiler passes that gather information
+needed for effective optimization at link time. Second, some early
+optimization passes can be performed only at compile time and
+not at link time.
+
+There are some code generation flags preserved by GCC when
+generating bytecodes, as they need to be used during the final link.
+Currently, the following options and their settings are taken from
+the first object file that explicitly specifies them:
+@option{-fcommon}, @option{-fexceptions}, @option{-fnon-call-exceptions},
+@option{-fgnu-tm} and all the @option{-m} target flags.
+
+The following options @option{-fPIC}, @option{-fpic}, @option{-fpie} and
+@option{-fPIE} are combined based on the following scheme:
+
+@smallexample
+@option{-fPIC} + @option{-fpic} = @option{-fpic}
+@option{-fPIC} + @option{-fno-pic} = @option{-fno-pic}
+@option{-fpic/-fPIC} + (no option) = (no option)
+@option{-fPIC} + @option{-fPIE} = @option{-fPIE}
+@option{-fpic} + @option{-fPIE} = @option{-fpie}
+@option{-fPIC/-fpic} + @option{-fpie} = @option{-fpie}
+@end smallexample
+
+Certain ABI-changing flags are required to match in all compilation units,
+and trying to override this at link time with a conflicting value
+is ignored. This includes options such as @option{-freg-struct-return}
+and @option{-fpcc-struct-return}.
+
+Other options such as @option{-ffp-contract}, @option{-fno-strict-overflow},
+@option{-fwrapv}, @option{-fno-trapv} or @option{-fno-strict-aliasing}
+are passed through to the link stage and merged conservatively for
+conflicting translation units. Specifically
+@option{-fno-strict-overflow}, @option{-fwrapv} and @option{-fno-trapv} take
+precedence; and for example @option{-ffp-contract=off} takes precedence
+over @option{-ffp-contract=fast}. You can override them at link time.
+
+Diagnostic options such as @option{-Wstringop-overflow} are passed
+through to the link stage and their setting matches that of the
+compile-step at function granularity. Note that this matters only
+for diagnostics emitted during optimization. Note that code
+transforms such as inlining can lead to warnings being enabled
+or disabled for regions if code not consistent with the setting
+at compile time.
+
+When you need to pass options to the assembler via @option{-Wa} or
+@option{-Xassembler} make sure to either compile such translation
+units with @option{-fno-lto} or consistently use the same assembler
+options on all translation units. You can alternatively also
+specify assembler options at LTO link time.
+
+To enable debug info generation you need to supply @option{-g} at
+compile time. If any of the input files at link time were built
+with debug info generation enabled the link will enable debug info
+generation as well. Any elaborate debug info settings
+like the dwarf level @option{-gdwarf-5} need to be explicitly repeated
+at the linker command line and mixing different settings in different
+translation units is discouraged.
+
+If LTO encounters objects with C linkage declared with incompatible
+types in separate translation units to be linked together (undefined
+behavior according to ISO C99 6.2.7), a non-fatal diagnostic may be
+issued. The behavior is still undefined at run time. Similar
+diagnostics may be raised for other languages.
+
+Another feature of LTO is that it is possible to apply interprocedural
+optimizations on files written in different languages:
+
+@smallexample
+gcc -c -flto foo.c
+g++ -c -flto bar.cc
+gfortran -c -flto baz.f90
+g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran
+@end smallexample
+
+Notice that the final link is done with @command{g++} to get the C++
+runtime libraries and @option{-lgfortran} is added to get the Fortran
+runtime libraries. In general, when mixing languages in LTO mode, you
+should use the same link command options as when mixing languages in a
+regular (non-LTO) compilation.
+
+If object files containing GIMPLE bytecode are stored in a library archive, say
+@file{libfoo.a}, it is possible to extract and use them in an LTO link if you
+are using a linker with plugin support. To create static libraries suitable
+for LTO, use @command{gcc-ar} and @command{gcc-ranlib} instead of @command{ar}
+and @command{ranlib};
+to show the symbols of object files with GIMPLE bytecode, use
+@command{gcc-nm}. Those commands require that @command{ar}, @command{ranlib}
+and @command{nm} have been compiled with plugin support. At link time, use the
+flag @option{-fuse-linker-plugin} to ensure that the library participates in
+the LTO optimization process:
+
+@smallexample
+gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo
+@end smallexample
+
+With the linker plugin enabled, the linker extracts the needed
+GIMPLE files from @file{libfoo.a} and passes them on to the running GCC
+to make them part of the aggregated GIMPLE image to be optimized.
+
+If you are not using a linker with plugin support and/or do not
+enable the linker plugin, then the objects inside @file{libfoo.a}
+are extracted and linked as usual, but they do not participate
+in the LTO optimization process. In order to make a static library suitable
+for both LTO optimization and usual linkage, compile its object files with
+@option{-flto} @option{-ffat-lto-objects}.
+
+Link-time optimizations do not require the presence of the whole program to
+operate. If the program does not require any symbols to be exported, it is
+possible to combine @option{-flto} and @option{-fwhole-program} to allow
+the interprocedural optimizers to use more aggressive assumptions which may
+lead to improved optimization opportunities.
+Use of @option{-fwhole-program} is not needed when linker plugin is
+active (see @option{-fuse-linker-plugin}).
+
+The current implementation of LTO makes no
+attempt to generate bytecode that is portable between different
+types of hosts. The bytecode files are versioned and there is a
+strict version check, so bytecode files generated in one version of
+GCC do not work with an older or newer version of GCC.
+
+Link-time optimization does not work well with generation of debugging
+information on systems other than those using a combination of ELF and
+DWARF.
+
+If you specify the optional @var{n}, the optimization and code
+generation done at link time is executed in parallel using @var{n}
+parallel jobs by utilizing an installed @command{make} program. The
+environment variable @env{MAKE} may be used to override the program
+used.
+
+You can also specify @option{-flto=jobserver} to use GNU make's
+job server mode to determine the number of parallel jobs. This
+is useful when the Makefile calling GCC is already executing in parallel.
+You must prepend a @samp{+} to the command recipe in the parent Makefile
+for this to work. This option likely only works if @env{MAKE} is
+GNU make. Even without the option value, GCC tries to automatically
+detect a running GNU make's job server.
+
+Use @option{-flto=auto} to use GNU make's job server, if available,
+or otherwise fall back to autodetection of the number of CPU threads
+present in your system.
+
+@item -flto-partition=@var{alg}
+@opindex flto-partition
+Specify the partitioning algorithm used by the link-time optimizer.
+The value is either @samp{1to1} to specify a partitioning mirroring
+the original source files or @samp{balanced} to specify partitioning
+into equally sized chunks (whenever possible) or @samp{max} to create
+new partition for every symbol where possible. Specifying @samp{none}
+as an algorithm disables partitioning and streaming completely.
+The default value is @samp{balanced}. While @samp{1to1} can be used
+as an workaround for various code ordering issues, the @samp{max}
+partitioning is intended for internal testing only.
+The value @samp{one} specifies that exactly one partition should be
+used while the value @samp{none} bypasses partitioning and executes
+the link-time optimization step directly from the WPA phase.
+
+@item -flto-compression-level=@var{n}
+@opindex flto-compression-level
+This option specifies the level of compression used for intermediate
+language written to LTO object files, and is only meaningful in
+conjunction with LTO mode (@option{-flto}). GCC currently supports two
+LTO compression algorithms. For zstd, valid values are 0 (no compression)
+to 19 (maximum compression), while zlib supports values from 0 to 9.
+Values outside this range are clamped to either minimum or maximum
+of the supported values. If the option is not given,
+a default balanced compression setting is used.
+
+@item -fuse-linker-plugin
+@opindex fuse-linker-plugin
+Enables the use of a linker plugin during link-time optimization. This
+option relies on plugin support in the linker, which is available in gold
+or in GNU ld 2.21 or newer.
+
+This option enables the extraction of object files with GIMPLE bytecode out
+of library archives. This improves the quality of optimization by exposing
+more code to the link-time optimizer. This information specifies what
+symbols can be accessed externally (by non-LTO object or during dynamic
+linking). Resulting code quality improvements on binaries (and shared
+libraries that use hidden visibility) are similar to @option{-fwhole-program}.
+See @option{-flto} for a description of the effect of this flag and how to
+use it.
+
+This option is enabled by default when LTO support in GCC is enabled
+and GCC was configured for use with
+a linker supporting plugins (GNU ld 2.21 or newer or gold).
+
+@item -ffat-lto-objects
+@opindex ffat-lto-objects
+Fat LTO objects are object files that contain both the intermediate language
+and the object code. This makes them usable for both LTO linking and normal
+linking. This option is effective only when compiling with @option{-flto}
+and is ignored at link time.
+
+@option{-fno-fat-lto-objects} improves compilation time over plain LTO, but
+requires the complete toolchain to be aware of LTO. It requires a linker with
+linker plugin support for basic functionality. Additionally,
+@command{nm}, @command{ar} and @command{ranlib}
+need to support linker plugins to allow a full-featured build environment
+(capable of building static libraries etc). GCC provides the @command{gcc-ar},
+@command{gcc-nm}, @command{gcc-ranlib} wrappers to pass the right options
+to these tools. With non fat LTO makefiles need to be modified to use them.
+
+Note that modern binutils provide plugin auto-load mechanism.
+Installing the linker plugin into @file{$libdir/bfd-plugins} has the same
+effect as usage of the command wrappers (@command{gcc-ar}, @command{gcc-nm} and
+@command{gcc-ranlib}).
+
+The default is @option{-fno-fat-lto-objects} on targets with linker plugin
+support.
+
+@item -fcompare-elim
+@opindex fcompare-elim
+After register allocation and post-register allocation instruction splitting,
+identify arithmetic instructions that compute processor flags similar to a
+comparison operation based on that arithmetic. If possible, eliminate the
+explicit comparison operation.
+
+This pass only applies to certain targets that cannot explicitly represent
+the comparison operation before register allocation is complete.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fcprop-registers
+@opindex fcprop-registers
+After register allocation and post-register allocation instruction splitting,
+perform a copy-propagation pass to try to reduce scheduling dependencies
+and occasionally eliminate the copy.
+
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -fprofile-correction
+@opindex fprofile-correction
+Profiles collected using an instrumented binary for multi-threaded programs may
+be inconsistent due to missed counter updates. When this option is specified,
+GCC uses heuristics to correct or smooth out such inconsistencies. By
+default, GCC emits an error message when an inconsistent profile is detected.
+
+This option is enabled by @option{-fauto-profile}.
+
+@item -fprofile-partial-training
+@opindex fprofile-partial-training
+With @code{-fprofile-use} all portions of programs not executed during train
+run are optimized agressively for size rather than speed. In some cases it is
+not practical to train all possible hot paths in the program. (For
+example, program may contain functions specific for a given hardware and
+trianing may not cover all hardware configurations program is run on.) With
+@code{-fprofile-partial-training} profile feedback will be ignored for all
+functions not executed during the train run leading them to be optimized as if
+they were compiled without profile feedback. This leads to better performance
+when train run is not representative but also leads to significantly bigger
+code.
+
+@item -fprofile-use
+@itemx -fprofile-use=@var{path}
+@opindex fprofile-use
+Enable profile feedback-directed optimizations,
+and the following optimizations, many of which
+are generally profitable only with profile feedback available:
+
+@gccoptlist{-fbranch-probabilities -fprofile-values @gol
+-funroll-loops -fpeel-loops -ftracer -fvpt @gol
+-finline-functions -fipa-cp -fipa-cp-clone -fipa-bit-cp @gol
+-fpredictive-commoning -fsplit-loops -funswitch-loops @gol
+-fgcse-after-reload -ftree-loop-vectorize -ftree-slp-vectorize @gol
+-fvect-cost-model=dynamic -ftree-loop-distribute-patterns @gol
+-fprofile-reorder-functions}
+
+Before you can use this option, you must first generate profiling information.
+@xref{Instrumentation Options}, for information about the
+@option{-fprofile-generate} option.
+
+By default, GCC emits an error message if the feedback profiles do not
+match the source code. This error can be turned into a warning by using
+@option{-Wno-error=coverage-mismatch}. Note this may result in poorly
+optimized code. Additionally, by default, GCC also emits a warning message if
+the feedback profiles do not exist (see @option{-Wmissing-profile}).
+
+If @var{path} is specified, GCC looks at the @var{path} to find
+the profile feedback data files. See @option{-fprofile-dir}.
+
+@item -fauto-profile
+@itemx -fauto-profile=@var{path}
+@opindex fauto-profile
+Enable sampling-based feedback-directed optimizations,
+and the following optimizations,
+many of which are generally profitable only with profile feedback available:
+
+@gccoptlist{-fbranch-probabilities -fprofile-values @gol
+-funroll-loops -fpeel-loops -ftracer -fvpt @gol
+-finline-functions -fipa-cp -fipa-cp-clone -fipa-bit-cp @gol
+-fpredictive-commoning -fsplit-loops -funswitch-loops @gol
+-fgcse-after-reload -ftree-loop-vectorize -ftree-slp-vectorize @gol
+-fvect-cost-model=dynamic -ftree-loop-distribute-patterns @gol
+-fprofile-correction}
+
+@var{path} is the name of a file containing AutoFDO profile information.
+If omitted, it defaults to @file{fbdata.afdo} in the current directory.
+
+Producing an AutoFDO profile data file requires running your program
+with the @command{perf} utility on a supported GNU/Linux target system.
+For more information, see @uref{https://perf.wiki.kernel.org/}.
+
+E.g.
+@smallexample
+perf record -e br_inst_retired:near_taken -b -o perf.data \
+ -- your_program
+@end smallexample
+
+Then use the @command{create_gcov} tool to convert the raw profile data
+to a format that can be used by GCC.@ You must also supply the
+unstripped binary for your program to this tool.
+See @uref{https://github.com/google/autofdo}.
+
+E.g.
+@smallexample
+create_gcov --binary=your_program.unstripped --profile=perf.data \
+ --gcov=profile.afdo
+@end smallexample
+@end table
+
+The following options control compiler behavior regarding floating-point
+arithmetic. These options trade off between speed and
+correctness. All must be specifically enabled.
+
+@table @gcctabopt
+@item -ffloat-store
+@opindex ffloat-store
+Do not store floating-point variables in registers, and inhibit other
+options that might change whether a floating-point value is taken from a
+register or memory.
+
+@cindex floating-point precision
+This option prevents undesirable excess precision on machines such as
+the 68000 where the floating registers (of the 68881) keep more
+precision than a @code{double} is supposed to have. Similarly for the
+x86 architecture. For most programs, the excess precision does only
+good, but a few programs rely on the precise definition of IEEE floating
+point. Use @option{-ffloat-store} for such programs, after modifying
+them to store all pertinent intermediate computations into variables.
+
+@item -fexcess-precision=@var{style}
+@opindex fexcess-precision
+This option allows further control over excess precision on machines
+where floating-point operations occur in a format with more precision or
+range than the IEEE standard and interchange floating-point types. By
+default, @option{-fexcess-precision=fast} is in effect; this means that
+operations may be carried out in a wider precision than the types specified
+in the source if that would result in faster code, and it is unpredictable
+when rounding to the types specified in the source code takes place.
+When compiling C or C++, if @option{-fexcess-precision=standard} is specified
+then excess precision follows the rules specified in ISO C99 or C++; in particular,
+both casts and assignments cause values to be rounded to their
+semantic types (whereas @option{-ffloat-store} only affects
+assignments). This option is enabled by default for C or C++ if a strict
+conformance option such as @option{-std=c99} or @option{-std=c++17} is used.
+@option{-ffast-math} enables @option{-fexcess-precision=fast} by default
+regardless of whether a strict conformance option is used.
+
+@opindex mfpmath
+@option{-fexcess-precision=standard} is not implemented for languages
+other than C or C++. On the x86, it has no effect if @option{-mfpmath=sse}
+or @option{-mfpmath=sse+387} is specified; in the former case, IEEE
+semantics apply without excess precision, and in the latter, rounding
+is unpredictable.
+
+@item -ffast-math
+@opindex ffast-math
+Sets the options @option{-fno-math-errno}, @option{-funsafe-math-optimizations},
+@option{-ffinite-math-only}, @option{-fno-rounding-math},
+@option{-fno-signaling-nans}, @option{-fcx-limited-range} and
+@option{-fexcess-precision=fast}.
+
+This option causes the preprocessor macro @code{__FAST_MATH__} to be defined.
+
+This option is not turned on by any @option{-O} option besides
+@option{-Ofast} since it can result in incorrect output for programs
+that depend on an exact implementation of IEEE or ISO rules/specifications
+for math functions. It may, however, yield faster code for programs
+that do not require the guarantees of these specifications.
+
+@item -fno-math-errno
+@opindex fno-math-errno
+@opindex fmath-errno
+Do not set @code{errno} after calling math functions that are executed
+with a single instruction, e.g., @code{sqrt}. A program that relies on
+IEEE exceptions for math error handling may want to use this flag
+for speed while maintaining IEEE arithmetic compatibility.
+
+This option is not turned on by any @option{-O} option since
+it can result in incorrect output for programs that depend on
+an exact implementation of IEEE or ISO rules/specifications for
+math functions. It may, however, yield faster code for programs
+that do not require the guarantees of these specifications.
+
+The default is @option{-fmath-errno}.
+
+On Darwin systems, the math library never sets @code{errno}. There is
+therefore no reason for the compiler to consider the possibility that
+it might, and @option{-fno-math-errno} is the default.
+
+@item -funsafe-math-optimizations
+@opindex funsafe-math-optimizations
+
+Allow optimizations for floating-point arithmetic that (a) assume
+that arguments and results are valid and (b) may violate IEEE or
+ANSI standards. When used at link time, it may include libraries
+or startup files that change the default FPU control word or other
+similar optimizations.
+
+This option is not turned on by any @option{-O} option since
+it can result in incorrect output for programs that depend on
+an exact implementation of IEEE or ISO rules/specifications for
+math functions. It may, however, yield faster code for programs
+that do not require the guarantees of these specifications.
+Enables @option{-fno-signed-zeros}, @option{-fno-trapping-math},
+@option{-fassociative-math} and @option{-freciprocal-math}.
+
+The default is @option{-fno-unsafe-math-optimizations}.
+
+@item -fassociative-math
+@opindex fassociative-math
+
+Allow re-association of operands in series of floating-point operations.
+This violates the ISO C and C++ language standard by possibly changing
+computation result. NOTE: re-ordering may change the sign of zero as
+well as ignore NaNs and inhibit or create underflow or overflow (and
+thus cannot be used on code that relies on rounding behavior like
+@code{(x + 2**52) - 2**52}. May also reorder floating-point comparisons
+and thus may not be used when ordered comparisons are required.
+This option requires that both @option{-fno-signed-zeros} and
+@option{-fno-trapping-math} be in effect. Moreover, it doesn't make
+much sense with @option{-frounding-math}. For Fortran the option
+is automatically enabled when both @option{-fno-signed-zeros} and
+@option{-fno-trapping-math} are in effect.
+
+The default is @option{-fno-associative-math}.
+
+@item -freciprocal-math
+@opindex freciprocal-math
+
+Allow the reciprocal of a value to be used instead of dividing by
+the value if this enables optimizations. For example @code{x / y}
+can be replaced with @code{x * (1/y)}, which is useful if @code{(1/y)}
+is subject to common subexpression elimination. Note that this loses
+precision and increases the number of flops operating on the value.
+
+The default is @option{-fno-reciprocal-math}.
+
+@item -ffinite-math-only
+@opindex ffinite-math-only
+Allow optimizations for floating-point arithmetic that assume
+that arguments and results are not NaNs or +-Infs.
+
+This option is not turned on by any @option{-O} option since
+it can result in incorrect output for programs that depend on
+an exact implementation of IEEE or ISO rules/specifications for
+math functions. It may, however, yield faster code for programs
+that do not require the guarantees of these specifications.
+
+The default is @option{-fno-finite-math-only}.
+
+@item -fno-signed-zeros
+@opindex fno-signed-zeros
+@opindex fsigned-zeros
+Allow optimizations for floating-point arithmetic that ignore the
+signedness of zero. IEEE arithmetic specifies the behavior of
+distinct +0.0 and @minus{}0.0 values, which then prohibits simplification
+of expressions such as x+0.0 or 0.0*x (even with @option{-ffinite-math-only}).
+This option implies that the sign of a zero result isn't significant.
+
+The default is @option{-fsigned-zeros}.
+
+@item -fno-trapping-math
+@opindex fno-trapping-math
+@opindex ftrapping-math
+Compile code assuming that floating-point operations cannot generate
+user-visible traps. These traps include division by zero, overflow,
+underflow, inexact result and invalid operation. This option requires
+that @option{-fno-signaling-nans} be in effect. Setting this option may
+allow faster code if one relies on ``non-stop'' IEEE arithmetic, for example.
+
+This option should never be turned on by any @option{-O} option since
+it can result in incorrect output for programs that depend on
+an exact implementation of IEEE or ISO rules/specifications for
+math functions.
+
+The default is @option{-ftrapping-math}.
+
+Future versions of GCC may provide finer control of this setting
+using C99's @code{FENV_ACCESS} pragma. This command-line option
+will be used along with @option{-frounding-math} to specify the
+default state for @code{FENV_ACCESS}.
+
+@item -frounding-math
+@opindex frounding-math
+Disable transformations and optimizations that assume default floating-point
+rounding behavior. This is round-to-zero for all floating point
+to integer conversions, and round-to-nearest for all other arithmetic
+truncations. This option should be specified for programs that change
+the FP rounding mode dynamically, or that may be executed with a
+non-default rounding mode. This option disables constant folding of
+floating-point expressions at compile time (which may be affected by
+rounding mode) and arithmetic transformations that are unsafe in the
+presence of sign-dependent rounding modes.
+
+The default is @option{-fno-rounding-math}.
+
+This option is experimental and does not currently guarantee to
+disable all GCC optimizations that are affected by rounding mode.
+Future versions of GCC may provide finer control of this setting
+using C99's @code{FENV_ACCESS} pragma. This command-line option
+will be used along with @option{-ftrapping-math} to specify the
+default state for @code{FENV_ACCESS}.
+
+@item -fsignaling-nans
+@opindex fsignaling-nans
+Compile code assuming that IEEE signaling NaNs may generate user-visible
+traps during floating-point operations. Setting this option disables
+optimizations that may change the number of exceptions visible with
+signaling NaNs. This option implies @option{-ftrapping-math}.
+
+This option causes the preprocessor macro @code{__SUPPORT_SNAN__} to
+be defined.
+
+The default is @option{-fno-signaling-nans}.
+
+This option is experimental and does not currently guarantee to
+disable all GCC optimizations that affect signaling NaN behavior.
+
+@item -fno-fp-int-builtin-inexact
+@opindex fno-fp-int-builtin-inexact
+@opindex ffp-int-builtin-inexact
+Do not allow the built-in functions @code{ceil}, @code{floor},
+@code{round} and @code{trunc}, and their @code{float} and @code{long
+double} variants, to generate code that raises the ``inexact''
+floating-point exception for noninteger arguments. ISO C99 and C11
+allow these functions to raise the ``inexact'' exception, but ISO/IEC
+TS 18661-1:2014, the C bindings to IEEE 754-2008, as integrated into
+ISO C2X, does not allow these functions to do so.
+
+The default is @option{-ffp-int-builtin-inexact}, allowing the
+exception to be raised, unless C2X or a later C standard is selected.
+This option does nothing unless @option{-ftrapping-math} is in effect.
+
+Even if @option{-fno-fp-int-builtin-inexact} is used, if the functions
+generate a call to a library function then the ``inexact'' exception
+may be raised if the library implementation does not follow TS 18661.
+
+@item -fsingle-precision-constant
+@opindex fsingle-precision-constant
+Treat floating-point constants as single precision instead of
+implicitly converting them to double-precision constants.
+
+@item -fcx-limited-range
+@opindex fcx-limited-range
+When enabled, this option states that a range reduction step is not
+needed when performing complex division. Also, there is no checking
+whether the result of a complex multiplication or division is @code{NaN
++ I*NaN}, with an attempt to rescue the situation in that case. The
+default is @option{-fno-cx-limited-range}, but is enabled by
+@option{-ffast-math}.
+
+This option controls the default setting of the ISO C99
+@code{CX_LIMITED_RANGE} pragma. Nevertheless, the option applies to
+all languages.
+
+@item -fcx-fortran-rules
+@opindex fcx-fortran-rules
+Complex multiplication and division follow Fortran rules. Range
+reduction is done as part of complex division, but there is no checking
+whether the result of a complex multiplication or division is @code{NaN
++ I*NaN}, with an attempt to rescue the situation in that case.
+
+The default is @option{-fno-cx-fortran-rules}.
+
+@end table
+
+The following options control optimizations that may improve
+performance, but are not enabled by any @option{-O} options. This
+section includes experimental options that may produce broken code.
+
+@table @gcctabopt
+@item -fbranch-probabilities
+@opindex fbranch-probabilities
+After running a program compiled with @option{-fprofile-arcs}
+(@pxref{Instrumentation Options}),
+you can compile it a second time using
+@option{-fbranch-probabilities}, to improve optimizations based on
+the number of times each branch was taken. When a program
+compiled with @option{-fprofile-arcs} exits, it saves arc execution
+counts to a file called @file{@var{sourcename}.gcda} for each source
+file. The information in this data file is very dependent on the
+structure of the generated code, so you must use the same source code
+and the same optimization options for both compilations.
+See details about the file naming in @option{-fprofile-arcs}.
+
+With @option{-fbranch-probabilities}, GCC puts a
+@samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}.
+These can be used to improve optimization. Currently, they are only
+used in one place: in @file{reorg.cc}, instead of guessing which path a
+branch is most likely to take, the @samp{REG_BR_PROB} values are used to
+exactly determine which path is taken more often.
+
+Enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -fprofile-values
+@opindex fprofile-values
+If combined with @option{-fprofile-arcs}, it adds code so that some
+data about values of expressions in the program is gathered.
+
+With @option{-fbranch-probabilities}, it reads back the data gathered
+from profiling values of expressions for usage in optimizations.
+
+Enabled by @option{-fprofile-generate}, @option{-fprofile-use}, and
+@option{-fauto-profile}.
+
+@item -fprofile-reorder-functions
+@opindex fprofile-reorder-functions
+Function reordering based on profile instrumentation collects
+first time of execution of a function and orders these functions
+in ascending order.
+
+Enabled with @option{-fprofile-use}.
+
+@item -fvpt
+@opindex fvpt
+If combined with @option{-fprofile-arcs}, this option instructs the compiler
+to add code to gather information about values of expressions.
+
+With @option{-fbranch-probabilities}, it reads back the data gathered
+and actually performs the optimizations based on them.
+Currently the optimizations include specialization of division operations
+using the knowledge about the value of the denominator.
+
+Enabled with @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -frename-registers
+@opindex frename-registers
+Attempt to avoid false dependencies in scheduled code by making use
+of registers left over after register allocation. This optimization
+most benefits processors with lots of registers. Depending on the
+debug information format adopted by the target, however, it can
+make debugging impossible, since variables no longer stay in
+a ``home register''.
+
+Enabled by default with @option{-funroll-loops}.
+
+@item -fschedule-fusion
+@opindex fschedule-fusion
+Performs a target dependent pass over the instruction stream to schedule
+instructions of same type together because target machine can execute them
+more efficiently if they are adjacent to each other in the instruction flow.
+
+Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+
+@item -ftracer
+@opindex ftracer
+Perform tail duplication to enlarge superblock size. This transformation
+simplifies the control flow of the function allowing other optimizations to do
+a better job.
+
+Enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -funroll-loops
+@opindex funroll-loops
+Unroll loops whose number of iterations can be determined at compile time or
+upon entry to the loop. @option{-funroll-loops} implies
+@option{-frerun-cse-after-loop}, @option{-fweb} and @option{-frename-registers}.
+It also turns on complete loop peeling (i.e.@: complete removal of loops with
+a small constant number of iterations). This option makes code larger, and may
+or may not make it run faster.
+
+Enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -funroll-all-loops
+@opindex funroll-all-loops
+Unroll all loops, even if their number of iterations is uncertain when
+the loop is entered. This usually makes programs run more slowly.
+@option{-funroll-all-loops} implies the same options as
+@option{-funroll-loops}.
+
+@item -fpeel-loops
+@opindex fpeel-loops
+Peels loops for which there is enough information that they do not
+roll much (from profile feedback or static analysis). It also turns on
+complete loop peeling (i.e.@: complete removal of loops with small constant
+number of iterations).
+
+Enabled by @option{-O3}, @option{-fprofile-use}, and @option{-fauto-profile}.
+
+@item -fmove-loop-invariants
+@opindex fmove-loop-invariants
+Enables the loop invariant motion pass in the RTL loop optimizer. Enabled
+at level @option{-O1} and higher, except for @option{-Og}.
+
+@item -fmove-loop-stores
+@opindex fmove-loop-stores
+Enables the loop store motion pass in the GIMPLE loop optimizer. This
+moves invariant stores to after the end of the loop in exchange for
+carrying the stored value in a register across the iteration.
+Note for this option to have an effect @option{-ftree-loop-im} has to
+be enabled as well. Enabled at level @option{-O1} and higher, except
+for @option{-Og}.
+
+@item -fsplit-loops
+@opindex fsplit-loops
+Split a loop into two if it contains a condition that's always true
+for one side of the iteration space and false for the other.
+
+Enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -funswitch-loops
+@opindex funswitch-loops
+Move branches with loop invariant conditions out of the loop, with duplicates
+of the loop on both branches (modified according to result of the condition).
+
+Enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -fversion-loops-for-strides
+@opindex fversion-loops-for-strides
+If a loop iterates over an array with a variable stride, create another
+version of the loop that assumes the stride is always one. For example:
+
+@smallexample
+for (int i = 0; i < n; ++i)
+ x[i * stride] = @dots{};
+@end smallexample
+
+becomes:
+
+@smallexample
+if (stride == 1)
+ for (int i = 0; i < n; ++i)
+ x[i] = @dots{};
+else
+ for (int i = 0; i < n; ++i)
+ x[i * stride] = @dots{};
+@end smallexample
+
+This is particularly useful for assumed-shape arrays in Fortran where
+(for example) it allows better vectorization assuming contiguous accesses.
+This flag is enabled by default at @option{-O3}.
+It is also enabled by @option{-fprofile-use} and @option{-fauto-profile}.
+
+@item -ffunction-sections
+@itemx -fdata-sections
+@opindex ffunction-sections
+@opindex fdata-sections
+Place each function or data item into its own section in the output
+file if the target supports arbitrary sections. The name of the
+function or the name of the data item determines the section's name
+in the output file.
+
+Use these options on systems where the linker can perform optimizations to
+improve locality of reference in the instruction space. Most systems using the
+ELF object format have linkers with such optimizations. On AIX, the linker
+rearranges sections (CSECTs) based on the call graph. The performance impact
+varies.
+
+Together with a linker garbage collection (linker @option{--gc-sections}
+option) these options may lead to smaller statically-linked executables (after
+stripping).
+
+On ELF/DWARF systems these options do not degenerate the quality of the debug
+information. There could be issues with other object files/debug info formats.
+
+Only use these options when there are significant benefits from doing so. When
+you specify these options, the assembler and linker create larger object and
+executable files and are also slower. These options affect code generation.
+They prevent optimizations by the compiler and assembler using relative
+locations inside a translation unit since the locations are unknown until
+link time. An example of such an optimization is relaxing calls to short call
+instructions.
+
+@item -fstdarg-opt
+@opindex fstdarg-opt
+Optimize the prologue of variadic argument functions with respect to usage of
+those arguments.
+
+@item -fsection-anchors
+@opindex fsection-anchors
+Try to reduce the number of symbolic address calculations by using
+shared ``anchor'' symbols to address nearby objects. This transformation
+can help to reduce the number of GOT entries and GOT accesses on some
+targets.
+
+For example, the implementation of the following function @code{foo}:
+
+@smallexample
+static int a, b, c;
+int foo (void) @{ return a + b + c; @}
+@end smallexample
+
+@noindent
+usually calculates the addresses of all three variables, but if you
+compile it with @option{-fsection-anchors}, it accesses the variables
+from a common anchor point instead. The effect is similar to the
+following pseudocode (which isn't valid C):
+
+@smallexample
+int foo (void)
+@{
+ register int *xr = &x;
+ return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
+@}
+@end smallexample
+
+Not all targets support this option.
+
+@item -fzero-call-used-regs=@var{choice}
+@opindex fzero-call-used-regs
+Zero call-used registers at function return to increase program
+security by either mitigating Return-Oriented Programming (ROP)
+attacks or preventing information leakage through registers.
+
+The possible values of @var{choice} are the same as for the
+@code{zero_call_used_regs} attribute (@pxref{Function Attributes}).
+The default is @samp{skip}.
+
+You can control this behavior for a specific function by using the function
+attribute @code{zero_call_used_regs} (@pxref{Function Attributes}).
+
+@item --param @var{name}=@var{value}
+@opindex param
+In some places, GCC uses various constants to control the amount of
+optimization that is done. For example, GCC does not inline functions
+that contain more than a certain number of instructions. You can
+control some of these constants on the command line using the
+@option{--param} option.
+
+The names of specific parameters, and the meaning of the values, are
+tied to the internals of the compiler, and are subject to change
+without notice in future releases.
+
+In order to get minimal, maximal and default value of a parameter,
+one can use @option{--help=param -Q} options.
+
+In each case, the @var{value} is an integer. The following choices
+of @var{name} are recognized for all targets:
+
+@table @gcctabopt
+@item predictable-branch-outcome
+When branch is predicted to be taken with probability lower than this threshold
+(in percent), then it is considered well predictable.
+
+@item max-rtl-if-conversion-insns
+RTL if-conversion tries to remove conditional branches around a block and
+replace them with conditionally executed instructions. This parameter
+gives the maximum number of instructions in a block which should be
+considered for if-conversion. The compiler will
+also use other heuristics to decide whether if-conversion is likely to be
+profitable.
+
+@item max-rtl-if-conversion-predictable-cost
+RTL if-conversion will try to remove conditional branches around a block
+and replace them with conditionally executed instructions. These parameters
+give the maximum permissible cost for the sequence that would be generated
+by if-conversion depending on whether the branch is statically determined
+to be predictable or not. The units for this parameter are the same as
+those for the GCC internal seq_cost metric. The compiler will try to
+provide a reasonable default for this parameter using the BRANCH_COST
+target macro.
+
+@item max-crossjump-edges
+The maximum number of incoming edges to consider for cross-jumping.
+The algorithm used by @option{-fcrossjumping} is @math{O(N^2)} in
+the number of edges incoming to each block. Increasing values mean
+more aggressive optimization, making the compilation time increase with
+probably small improvement in executable size.
+
+@item min-crossjump-insns
+The minimum number of instructions that must be matched at the end
+of two blocks before cross-jumping is performed on them. This
+value is ignored in the case where all instructions in the block being
+cross-jumped from are matched.
+
+@item max-grow-copy-bb-insns
+The maximum code size expansion factor when copying basic blocks
+instead of jumping. The expansion is relative to a jump instruction.
+
+@item max-goto-duplication-insns
+The maximum number of instructions to duplicate to a block that jumps
+to a computed goto. To avoid @math{O(N^2)} behavior in a number of
+passes, GCC factors computed gotos early in the compilation process,
+and unfactors them as late as possible. Only computed jumps at the
+end of a basic blocks with no more than max-goto-duplication-insns are
+unfactored.
+
+@item max-delay-slot-insn-search
+The maximum number of instructions to consider when looking for an
+instruction to fill a delay slot. If more than this arbitrary number of
+instructions are searched, the time savings from filling the delay slot
+are minimal, so stop searching. Increasing values mean more
+aggressive optimization, making the compilation time increase with probably
+small improvement in execution time.
+
+@item max-delay-slot-live-search
+When trying to fill delay slots, the maximum number of instructions to
+consider when searching for a block with valid live register
+information. Increasing this arbitrarily chosen value means more
+aggressive optimization, increasing the compilation time. This parameter
+should be removed when the delay slot code is rewritten to maintain the
+control-flow graph.
+
+@item max-gcse-memory
+The approximate maximum amount of memory in @code{kB} that can be allocated in
+order to perform the global common subexpression elimination
+optimization. If more memory than specified is required, the
+optimization is not done.
+
+@item max-gcse-insertion-ratio
+If the ratio of expression insertions to deletions is larger than this value
+for any expression, then RTL PRE inserts or removes the expression and thus
+leaves partially redundant computations in the instruction stream.
+
+@item max-pending-list-length
+The maximum number of pending dependencies scheduling allows
+before flushing the current state and starting over. Large functions
+with few branches or calls can create excessively large lists which
+needlessly consume memory and resources.
+
+@item max-modulo-backtrack-attempts
+The maximum number of backtrack attempts the scheduler should make
+when modulo scheduling a loop. Larger values can exponentially increase
+compilation time.
+
+@item max-inline-functions-called-once-loop-depth
+Maximal loop depth of a call considered by inline heuristics that tries to
+inline all functions called once.
+
+@item max-inline-functions-called-once-insns
+Maximal estimated size of functions produced while inlining functions called
+once.
+
+@item max-inline-insns-single
+Several parameters control the tree inliner used in GCC@. This number sets the
+maximum number of instructions (counted in GCC's internal representation) in a
+single function that the tree inliner considers for inlining. This only
+affects functions declared inline and methods implemented in a class
+declaration (C++).
+
+
+@item max-inline-insns-auto
+When you use @option{-finline-functions} (included in @option{-O3}),
+a lot of functions that would otherwise not be considered for inlining
+by the compiler are investigated. To those functions, a different
+(more restrictive) limit compared to functions declared inline can
+be applied (@option{--param max-inline-insns-auto}).
+
+@item max-inline-insns-small
+This is bound applied to calls which are considered relevant with
+@option{-finline-small-functions}.
+
+@item max-inline-insns-size
+This is bound applied to calls which are optimized for size. Small growth
+may be desirable to anticipate optimization oppurtunities exposed by inlining.
+
+@item uninlined-function-insns
+Number of instructions accounted by inliner for function overhead such as
+function prologue and epilogue.
+
+@item uninlined-function-time
+Extra time accounted by inliner for function overhead such as time needed to
+execute function prologue and epilogue.
+
+@item inline-heuristics-hint-percent
+The scale (in percents) applied to @option{inline-insns-single},
+@option{inline-insns-single-O2}, @option{inline-insns-auto}
+when inline heuristics hints that inlining is
+very profitable (will enable later optimizations).
+
+@item uninlined-thunk-insns
+@item uninlined-thunk-time
+Same as @option{--param uninlined-function-insns} and
+@option{--param uninlined-function-time} but applied to function thunks.
+
+@item inline-min-speedup
+When estimated performance improvement of caller + callee runtime exceeds this
+threshold (in percent), the function can be inlined regardless of the limit on
+@option{--param max-inline-insns-single} and @option{--param
+max-inline-insns-auto}.
+
+@item large-function-insns
+The limit specifying really large functions. For functions larger than this
+limit after inlining, inlining is constrained by
+@option{--param large-function-growth}. This parameter is useful primarily
+to avoid extreme compilation time caused by non-linear algorithms used by the
+back end.
+
+@item large-function-growth
+Specifies maximal growth of large function caused by inlining in percents.
+For example, parameter value 100 limits large function growth to 2.0 times
+the original size.
+
+@item large-unit-insns
+The limit specifying large translation unit. Growth caused by inlining of
+units larger than this limit is limited by @option{--param inline-unit-growth}.
+For small units this might be too tight.
+For example, consider a unit consisting of function A
+that is inline and B that just calls A three times. If B is small relative to
+A, the growth of unit is 300\% and yet such inlining is very sane. For very
+large units consisting of small inlineable functions, however, the overall unit
+growth limit is needed to avoid exponential explosion of code size. Thus for
+smaller units, the size is increased to @option{--param large-unit-insns}
+before applying @option{--param inline-unit-growth}.
+
+@item lazy-modules
+Maximum number of concurrently open C++ module files when lazy loading.
+
+@item inline-unit-growth
+Specifies maximal overall growth of the compilation unit caused by inlining.
+For example, parameter value 20 limits unit growth to 1.2 times the original
+size. Cold functions (either marked cold via an attribute or by profile
+feedback) are not accounted into the unit size.
+
+@item ipa-cp-unit-growth
+Specifies maximal overall growth of the compilation unit caused by
+interprocedural constant propagation. For example, parameter value 10 limits
+unit growth to 1.1 times the original size.
+
+@item ipa-cp-large-unit-insns
+The size of translation unit that IPA-CP pass considers large.
+
+@item large-stack-frame
+The limit specifying large stack frames. While inlining the algorithm is trying
+to not grow past this limit too much.
+
+@item large-stack-frame-growth
+Specifies maximal growth of large stack frames caused by inlining in percents.
+For example, parameter value 1000 limits large stack frame growth to 11 times
+the original size.
+
+@item max-inline-insns-recursive
+@itemx max-inline-insns-recursive-auto
+Specifies the maximum number of instructions an out-of-line copy of a
+self-recursive inline
+function can grow into by performing recursive inlining.
+
+@option{--param max-inline-insns-recursive} applies to functions
+declared inline.
+For functions not declared inline, recursive inlining
+happens only when @option{-finline-functions} (included in @option{-O3}) is
+enabled; @option{--param max-inline-insns-recursive-auto} applies instead.
+
+@item max-inline-recursive-depth
+@itemx max-inline-recursive-depth-auto
+Specifies the maximum recursion depth used for recursive inlining.
+
+@option{--param max-inline-recursive-depth} applies to functions
+declared inline. For functions not declared inline, recursive inlining
+happens only when @option{-finline-functions} (included in @option{-O3}) is
+enabled; @option{--param max-inline-recursive-depth-auto} applies instead.
+
+@item min-inline-recursive-probability
+Recursive inlining is profitable only for function having deep recursion
+in average and can hurt for function having little recursion depth by
+increasing the prologue size or complexity of function body to other
+optimizers.
+
+When profile feedback is available (see @option{-fprofile-generate}) the actual
+recursion depth can be guessed from the probability that function recurses
+via a given call expression. This parameter limits inlining only to call
+expressions whose probability exceeds the given threshold (in percents).
+
+@item early-inlining-insns
+Specify growth that the early inliner can make. In effect it increases
+the amount of inlining for code having a large abstraction penalty.
+
+@item max-early-inliner-iterations
+Limit of iterations of the early inliner. This basically bounds
+the number of nested indirect calls the early inliner can resolve.
+Deeper chains are still handled by late inlining.
+
+@item comdat-sharing-probability
+Probability (in percent) that C++ inline function with comdat visibility
+are shared across multiple compilation units.
+
+@item modref-max-bases
+@item modref-max-refs
+@item modref-max-accesses
+Specifies the maximal number of base pointers, references and accesses stored
+for a single function by mod/ref analysis.
+
+@item modref-max-tests
+Specifies the maxmal number of tests alias oracle can perform to disambiguate
+memory locations using the mod/ref information. This parameter ought to be
+bigger than @option{--param modref-max-bases} and @option{--param
+modref-max-refs}.
+
+@item modref-max-depth
+Specifies the maximum depth of DFS walk used by modref escape analysis.
+Setting to 0 disables the analysis completely.
+
+@item modref-max-escape-points
+Specifies the maximum number of escape points tracked by modref per SSA-name.
+
+@item modref-max-adjustments
+Specifies the maximum number the access range is enlarged during modref dataflow
+analysis.
+
+@item profile-func-internal-id
+A parameter to control whether to use function internal id in profile
+database lookup. If the value is 0, the compiler uses an id that
+is based on function assembler name and filename, which makes old profile
+data more tolerant to source changes such as function reordering etc.
+
+@item min-vect-loop-bound
+The minimum number of iterations under which loops are not vectorized
+when @option{-ftree-vectorize} is used. The number of iterations after
+vectorization needs to be greater than the value specified by this option
+to allow vectorization.
+
+@item gcse-cost-distance-ratio
+Scaling factor in calculation of maximum distance an expression
+can be moved by GCSE optimizations. This is currently supported only in the
+code hoisting pass. The bigger the ratio, the more aggressive code hoisting
+is with simple expressions, i.e., the expressions that have cost
+less than @option{gcse-unrestricted-cost}. Specifying 0 disables
+hoisting of simple expressions.
+
+@item gcse-unrestricted-cost
+Cost, roughly measured as the cost of a single typical machine
+instruction, at which GCSE optimizations do not constrain
+the distance an expression can travel. This is currently
+supported only in the code hoisting pass. The lesser the cost,
+the more aggressive code hoisting is. Specifying 0
+allows all expressions to travel unrestricted distances.
+
+@item max-hoist-depth
+The depth of search in the dominator tree for expressions to hoist.
+This is used to avoid quadratic behavior in hoisting algorithm.
+The value of 0 does not limit on the search, but may slow down compilation
+of huge functions.
+
+@item max-tail-merge-comparisons
+The maximum amount of similar bbs to compare a bb with. This is used to
+avoid quadratic behavior in tree tail merging.
+
+@item max-tail-merge-iterations
+The maximum amount of iterations of the pass over the function. This is used to
+limit compilation time in tree tail merging.
+
+@item store-merging-allow-unaligned
+Allow the store merging pass to introduce unaligned stores if it is legal to
+do so.
+
+@item max-stores-to-merge
+The maximum number of stores to attempt to merge into wider stores in the store
+merging pass.
+
+@item max-store-chains-to-track
+The maximum number of store chains to track at the same time in the attempt
+to merge them into wider stores in the store merging pass.
+
+@item max-stores-to-track
+The maximum number of stores to track at the same time in the attemt to
+to merge them into wider stores in the store merging pass.
+
+@item max-unrolled-insns
+The maximum number of instructions that a loop may have to be unrolled.
+If a loop is unrolled, this parameter also determines how many times
+the loop code is unrolled.
+
+@item max-average-unrolled-insns
+The maximum number of instructions biased by probabilities of their execution
+that a loop may have to be unrolled. If a loop is unrolled,
+this parameter also determines how many times the loop code is unrolled.
+
+@item max-unroll-times
+The maximum number of unrollings of a single loop.
+
+@item max-peeled-insns
+The maximum number of instructions that a loop may have to be peeled.
+If a loop is peeled, this parameter also determines how many times
+the loop code is peeled.
+
+@item max-peel-times
+The maximum number of peelings of a single loop.
+
+@item max-peel-branches
+The maximum number of branches on the hot path through the peeled sequence.
+
+@item max-completely-peeled-insns
+The maximum number of insns of a completely peeled loop.
+
+@item max-completely-peel-times
+The maximum number of iterations of a loop to be suitable for complete peeling.
+
+@item max-completely-peel-loop-nest-depth
+The maximum depth of a loop nest suitable for complete peeling.
+
+@item max-unswitch-insns
+The maximum number of insns of an unswitched loop.
+
+@item lim-expensive
+The minimum cost of an expensive expression in the loop invariant motion.
+
+@item min-loop-cond-split-prob
+When FDO profile information is available, @option{min-loop-cond-split-prob}
+specifies minimum threshold for probability of semi-invariant condition
+statement to trigger loop split.
+
+@item iv-consider-all-candidates-bound
+Bound on number of candidates for induction variables, below which
+all candidates are considered for each use in induction variable
+optimizations. If there are more candidates than this,
+only the most relevant ones are considered to avoid quadratic time complexity.
+
+@item iv-max-considered-uses
+The induction variable optimizations give up on loops that contain more
+induction variable uses.
+
+@item iv-always-prune-cand-set-bound
+If the number of candidates in the set is smaller than this value,
+always try to remove unnecessary ivs from the set
+when adding a new one.
+
+@item avg-loop-niter
+Average number of iterations of a loop.
+
+@item dse-max-object-size
+Maximum size (in bytes) of objects tracked bytewise by dead store elimination.
+Larger values may result in larger compilation times.
+
+@item dse-max-alias-queries-per-store
+Maximum number of queries into the alias oracle per store.
+Larger values result in larger compilation times and may result in more
+removed dead stores.
+
+@item scev-max-expr-size
+Bound on size of expressions used in the scalar evolutions analyzer.
+Large expressions slow the analyzer.
+
+@item scev-max-expr-complexity
+Bound on the complexity of the expressions in the scalar evolutions analyzer.
+Complex expressions slow the analyzer.
+
+@item max-tree-if-conversion-phi-args
+Maximum number of arguments in a PHI supported by TREE if conversion
+unless the loop is marked with simd pragma.
+
+@item vect-max-layout-candidates
+The maximum number of possible vector layouts (such as permutations)
+to consider when optimizing to-be-vectorized code.
+
+@item vect-max-version-for-alignment-checks
+The maximum number of run-time checks that can be performed when
+doing loop versioning for alignment in the vectorizer.
+
+@item vect-max-version-for-alias-checks
+The maximum number of run-time checks that can be performed when
+doing loop versioning for alias in the vectorizer.
+
+@item vect-max-peeling-for-alignment
+The maximum number of loop peels to enhance access alignment
+for vectorizer. Value -1 means no limit.
+
+@item max-iterations-to-track
+The maximum number of iterations of a loop the brute-force algorithm
+for analysis of the number of iterations of the loop tries to evaluate.
+
+@item hot-bb-count-fraction
+The denominator n of fraction 1/n of the maximal execution count of a
+basic block in the entire program that a basic block needs to at least
+have in order to be considered hot. The default is 10000, which means
+that a basic block is considered hot if its execution count is greater
+than 1/10000 of the maximal execution count. 0 means that it is never
+considered hot. Used in non-LTO mode.
+
+@item hot-bb-count-ws-permille
+The number of most executed permilles, ranging from 0 to 1000, of the
+profiled execution of the entire program to which the execution count
+of a basic block must be part of in order to be considered hot. The
+default is 990, which means that a basic block is considered hot if
+its execution count contributes to the upper 990 permilles, or 99.0%,
+of the profiled execution of the entire program. 0 means that it is
+never considered hot. Used in LTO mode.
+
+@item hot-bb-frequency-fraction
+The denominator n of fraction 1/n of the execution frequency of the
+entry block of a function that a basic block of this function needs
+to at least have in order to be considered hot. The default is 1000,
+which means that a basic block is considered hot in a function if it
+is executed more frequently than 1/1000 of the frequency of the entry
+block of the function. 0 means that it is never considered hot.
+
+@item unlikely-bb-count-fraction
+The denominator n of fraction 1/n of the number of profiled runs of
+the entire program below which the execution count of a basic block
+must be in order for the basic block to be considered unlikely executed.
+The default is 20, which means that a basic block is considered unlikely
+executed if it is executed in fewer than 1/20, or 5%, of the runs of
+the program. 0 means that it is always considered unlikely executed.
+
+@item max-predicted-iterations
+The maximum number of loop iterations we predict statically. This is useful
+in cases where a function contains a single loop with known bound and
+another loop with unknown bound.
+The known number of iterations is predicted correctly, while
+the unknown number of iterations average to roughly 10. This means that the
+loop without bounds appears artificially cold relative to the other one.
+
+@item builtin-expect-probability
+Control the probability of the expression having the specified value. This
+parameter takes a percentage (i.e.@: 0 ... 100) as input.
+
+@item builtin-string-cmp-inline-length
+The maximum length of a constant string for a builtin string cmp call
+eligible for inlining.
+
+@item align-threshold
+
+Select fraction of the maximal frequency of executions of a basic block in
+a function to align the basic block.
+
+@item align-loop-iterations
+
+A loop expected to iterate at least the selected number of iterations is
+aligned.
+
+@item tracer-dynamic-coverage
+@itemx tracer-dynamic-coverage-feedback
+
+This value is used to limit superblock formation once the given percentage of
+executed instructions is covered. This limits unnecessary code size
+expansion.
+
+The @option{tracer-dynamic-coverage-feedback} parameter
+is used only when profile
+feedback is available. The real profiles (as opposed to statically estimated
+ones) are much less balanced allowing the threshold to be larger value.
+
+@item tracer-max-code-growth
+Stop tail duplication once code growth has reached given percentage. This is
+a rather artificial limit, as most of the duplicates are eliminated later in
+cross jumping, so it may be set to much higher values than is the desired code
+growth.
+
+@item tracer-min-branch-ratio
+
+Stop reverse growth when the reverse probability of best edge is less than this
+threshold (in percent).
+
+@item tracer-min-branch-probability
+@itemx tracer-min-branch-probability-feedback
+
+Stop forward growth if the best edge has probability lower than this
+threshold.
+
+Similarly to @option{tracer-dynamic-coverage} two parameters are
+provided. @option{tracer-min-branch-probability-feedback} is used for
+compilation with profile feedback and @option{tracer-min-branch-probability}
+compilation without. The value for compilation with profile feedback
+needs to be more conservative (higher) in order to make tracer
+effective.
+
+@item stack-clash-protection-guard-size
+Specify the size of the operating system provided stack guard as
+2 raised to @var{num} bytes. Higher values may reduce the
+number of explicit probes, but a value larger than the operating system
+provided guard will leave code vulnerable to stack clash style attacks.
+
+@item stack-clash-protection-probe-interval
+Stack clash protection involves probing stack space as it is allocated. This
+param controls the maximum distance between probes into the stack as 2 raised
+to @var{num} bytes. Higher values may reduce the number of explicit probes, but a value
+larger than the operating system provided guard will leave code vulnerable to
+stack clash style attacks.
+
+@item max-cse-path-length
+
+The maximum number of basic blocks on path that CSE considers.
+
+@item max-cse-insns
+The maximum number of instructions CSE processes before flushing.
+
+@item ggc-min-expand
+
+GCC uses a garbage collector to manage its own memory allocation. This
+parameter specifies the minimum percentage by which the garbage
+collector's heap should be allowed to expand between collections.
+Tuning this may improve compilation speed; it has no effect on code
+generation.
+
+The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when
+RAM >= 1GB@. If @code{getrlimit} is available, the notion of ``RAM'' is
+the smallest of actual RAM and @code{RLIMIT_DATA} or @code{RLIMIT_AS}. If
+GCC is not able to calculate RAM on a particular platform, the lower
+bound of 30% is used. Setting this parameter and
+@option{ggc-min-heapsize} to zero causes a full collection to occur at
+every opportunity. This is extremely slow, but can be useful for
+debugging.
+
+@item ggc-min-heapsize
+
+Minimum size of the garbage collector's heap before it begins bothering
+to collect garbage. The first collection occurs after the heap expands
+by @option{ggc-min-expand}% beyond @option{ggc-min-heapsize}. Again,
+tuning this may improve compilation speed, and has no effect on code
+generation.
+
+The default is the smaller of RAM/8, RLIMIT_RSS, or a limit that
+tries to ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded, but
+with a lower bound of 4096 (four megabytes) and an upper bound of
+131072 (128 megabytes). If GCC is not able to calculate RAM on a
+particular platform, the lower bound is used. Setting this parameter
+very large effectively disables garbage collection. Setting this
+parameter and @option{ggc-min-expand} to zero causes a full collection
+to occur at every opportunity.
+
+@item max-reload-search-insns
+The maximum number of instruction reload should look backward for equivalent
+register. Increasing values mean more aggressive optimization, making the
+compilation time increase with probably slightly better performance.
+
+@item max-cselib-memory-locations
+The maximum number of memory locations cselib should take into account.
+Increasing values mean more aggressive optimization, making the compilation time
+increase with probably slightly better performance.
+
+@item max-sched-ready-insns
+The maximum number of instructions ready to be issued the scheduler should
+consider at any given time during the first scheduling pass. Increasing
+values mean more thorough searches, making the compilation time increase
+with probably little benefit.
+
+@item max-sched-region-blocks
+The maximum number of blocks in a region to be considered for
+interblock scheduling.
+
+@item max-pipeline-region-blocks
+The maximum number of blocks in a region to be considered for
+pipelining in the selective scheduler.
+
+@item max-sched-region-insns
+The maximum number of insns in a region to be considered for
+interblock scheduling.
+
+@item max-pipeline-region-insns
+The maximum number of insns in a region to be considered for
+pipelining in the selective scheduler.
+
+@item min-spec-prob
+The minimum probability (in percents) of reaching a source block
+for interblock speculative scheduling.
+
+@item max-sched-extend-regions-iters
+The maximum number of iterations through CFG to extend regions.
+A value of 0 disables region extensions.
+
+@item max-sched-insn-conflict-delay
+The maximum conflict delay for an insn to be considered for speculative motion.
+
+@item sched-spec-prob-cutoff
+The minimal probability of speculation success (in percents), so that
+speculative insns are scheduled.
+
+@item sched-state-edge-prob-cutoff
+The minimum probability an edge must have for the scheduler to save its
+state across it.
+
+@item sched-mem-true-dep-cost
+Minimal distance (in CPU cycles) between store and load targeting same
+memory locations.
+
+@item selsched-max-lookahead
+The maximum size of the lookahead window of selective scheduling. It is a
+depth of search for available instructions.
+
+@item selsched-max-sched-times
+The maximum number of times that an instruction is scheduled during
+selective scheduling. This is the limit on the number of iterations
+through which the instruction may be pipelined.
+
+@item selsched-insns-to-rename
+The maximum number of best instructions in the ready list that are considered
+for renaming in the selective scheduler.
+
+@item sms-min-sc
+The minimum value of stage count that swing modulo scheduler
+generates.
+
+@item max-last-value-rtl
+The maximum size measured as number of RTLs that can be recorded in an expression
+in combiner for a pseudo register as last known value of that register.
+
+@item max-combine-insns
+The maximum number of instructions the RTL combiner tries to combine.
+
+@item integer-share-limit
+Small integer constants can use a shared data structure, reducing the
+compiler's memory usage and increasing its speed. This sets the maximum
+value of a shared integer constant.
+
+@item ssp-buffer-size
+The minimum size of buffers (i.e.@: arrays) that receive stack smashing
+protection when @option{-fstack-protector} is used.
+
+@item min-size-for-stack-sharing
+The minimum size of variables taking part in stack slot sharing when not
+optimizing.
+
+@item max-jump-thread-duplication-stmts
+Maximum number of statements allowed in a block that needs to be
+duplicated when threading jumps.
+
+@item max-jump-thread-paths
+The maximum number of paths to consider when searching for jump threading
+opportunities. When arriving at a block, incoming edges are only considered
+if the number of paths to be searched so far multiplied by the number of
+incoming edges does not exhaust the specified maximum number of paths to
+consider.
+
+@item max-fields-for-field-sensitive
+Maximum number of fields in a structure treated in
+a field sensitive manner during pointer analysis.
+
+@item prefetch-latency
+Estimate on average number of instructions that are executed before
+prefetch finishes. The distance prefetched ahead is proportional
+to this constant. Increasing this number may also lead to less
+streams being prefetched (see @option{simultaneous-prefetches}).
+
+@item simultaneous-prefetches
+Maximum number of prefetches that can run at the same time.
+
+@item l1-cache-line-size
+The size of cache line in L1 data cache, in bytes.
+
+@item l1-cache-size
+The size of L1 data cache, in kilobytes.
+
+@item l2-cache-size
+The size of L2 data cache, in kilobytes.
+
+@item prefetch-dynamic-strides
+Whether the loop array prefetch pass should issue software prefetch hints
+for strides that are non-constant. In some cases this may be
+beneficial, though the fact the stride is non-constant may make it
+hard to predict when there is clear benefit to issuing these hints.
+
+Set to 1 if the prefetch hints should be issued for non-constant
+strides. Set to 0 if prefetch hints should be issued only for strides that
+are known to be constant and below @option{prefetch-minimum-stride}.
+
+@item prefetch-minimum-stride
+Minimum constant stride, in bytes, to start using prefetch hints for. If
+the stride is less than this threshold, prefetch hints will not be issued.
+
+This setting is useful for processors that have hardware prefetchers, in
+which case there may be conflicts between the hardware prefetchers and
+the software prefetchers. If the hardware prefetchers have a maximum
+stride they can handle, it should be used here to improve the use of
+software prefetchers.
+
+A value of -1 means we don't have a threshold and therefore
+prefetch hints can be issued for any constant stride.
+
+This setting is only useful for strides that are known and constant.
+
+@item destructive-interference-size
+@item constructive-interference-size
+The values for the C++17 variables
+@code{std::hardware_destructive_interference_size} and
+@code{std::hardware_constructive_interference_size}. The destructive
+interference size is the minimum recommended offset between two
+independent concurrently-accessed objects; the constructive
+interference size is the maximum recommended size of contiguous memory
+accessed together. Typically both will be the size of an L1 cache
+line for the target, in bytes. For a generic target covering a range of L1
+cache line sizes, typically the constructive interference size will be
+the small end of the range and the destructive size will be the large
+end.
+
+The destructive interference size is intended to be used for layout,
+and thus has ABI impact. The default value is not expected to be
+stable, and on some targets varies with @option{-mtune}, so use of
+this variable in a context where ABI stability is important, such as
+the public interface of a library, is strongly discouraged; if it is
+used in that context, users can stabilize the value using this
+option.
+
+The constructive interference size is less sensitive, as it is
+typically only used in a @samp{static_assert} to make sure that a type
+fits within a cache line.
+
+See also @option{-Winterference-size}.
+
+@item loop-interchange-max-num-stmts
+The maximum number of stmts in a loop to be interchanged.
+
+@item loop-interchange-stride-ratio
+The minimum ratio between stride of two loops for interchange to be profitable.
+
+@item min-insn-to-prefetch-ratio
+The minimum ratio between the number of instructions and the
+number of prefetches to enable prefetching in a loop.
+
+@item prefetch-min-insn-to-mem-ratio
+The minimum ratio between the number of instructions and the
+number of memory references to enable prefetching in a loop.
+
+@item use-canonical-types
+Whether the compiler should use the ``canonical'' type system.
+Should always be 1, which uses a more efficient internal
+mechanism for comparing types in C++ and Objective-C++. However, if
+bugs in the canonical type system are causing compilation failures,
+set this value to 0 to disable canonical types.
+
+@item switch-conversion-max-branch-ratio
+Switch initialization conversion refuses to create arrays that are
+bigger than @option{switch-conversion-max-branch-ratio} times the number of
+branches in the switch.
+
+@item max-partial-antic-length
+Maximum length of the partial antic set computed during the tree
+partial redundancy elimination optimization (@option{-ftree-pre}) when
+optimizing at @option{-O3} and above. For some sorts of source code
+the enhanced partial redundancy elimination optimization can run away,
+consuming all of the memory available on the host machine. This
+parameter sets a limit on the length of the sets that are computed,
+which prevents the runaway behavior. Setting a value of 0 for
+this parameter allows an unlimited set length.
+
+@item rpo-vn-max-loop-depth
+Maximum loop depth that is value-numbered optimistically.
+When the limit hits the innermost
+@var{rpo-vn-max-loop-depth} loops and the outermost loop in the
+loop nest are value-numbered optimistically and the remaining ones not.
+
+@item sccvn-max-alias-queries-per-access
+Maximum number of alias-oracle queries we perform when looking for
+redundancies for loads and stores. If this limit is hit the search
+is aborted and the load or store is not considered redundant. The
+number of queries is algorithmically limited to the number of
+stores on all paths from the load to the function entry.
+
+@item ira-max-loops-num
+IRA uses regional register allocation by default. If a function
+contains more loops than the number given by this parameter, only at most
+the given number of the most frequently-executed loops form regions
+for regional register allocation.
+
+@item ira-max-conflict-table-size
+Although IRA uses a sophisticated algorithm to compress the conflict
+table, the table can still require excessive amounts of memory for
+huge functions. If the conflict table for a function could be more
+than the size in MB given by this parameter, the register allocator
+instead uses a faster, simpler, and lower-quality
+algorithm that does not require building a pseudo-register conflict table.
+
+@item ira-loop-reserved-regs
+IRA can be used to evaluate more accurate register pressure in loops
+for decisions to move loop invariants (see @option{-O3}). The number
+of available registers reserved for some other purposes is given
+by this parameter. Default of the parameter
+is the best found from numerous experiments.
+
+@item ira-consider-dup-in-all-alts
+Make IRA to consider matching constraint (duplicated operand number)
+heavily in all available alternatives for preferred register class.
+If it is set as zero, it means IRA only respects the matching
+constraint when it's in the only available alternative with an
+appropriate register class. Otherwise, it means IRA will check all
+available alternatives for preferred register class even if it has
+found some choice with an appropriate register class and respect the
+found qualified matching constraint.
+
+@item lra-inheritance-ebb-probability-cutoff
+LRA tries to reuse values reloaded in registers in subsequent insns.
+This optimization is called inheritance. EBB is used as a region to
+do this optimization. The parameter defines a minimal fall-through
+edge probability in percentage used to add BB to inheritance EBB in
+LRA. The default value was chosen
+from numerous runs of SPEC2000 on x86-64.
+
+@item loop-invariant-max-bbs-in-loop
+Loop invariant motion can be very expensive, both in compilation time and
+in amount of needed compile-time memory, with very large loops. Loops
+with more basic blocks than this parameter won't have loop invariant
+motion optimization performed on them.
+
+@item loop-max-datarefs-for-datadeps
+Building data dependencies is expensive for very large loops. This
+parameter limits the number of data references in loops that are
+considered for data dependence analysis. These large loops are no
+handled by the optimizations using loop data dependencies.
+
+@item max-vartrack-size
+Sets a maximum number of hash table slots to use during variable
+tracking dataflow analysis of any function. If this limit is exceeded
+with variable tracking at assignments enabled, analysis for that
+function is retried without it, after removing all debug insns from
+the function. If the limit is exceeded even without debug insns, var
+tracking analysis is completely disabled for the function. Setting
+the parameter to zero makes it unlimited.
+
+@item max-vartrack-expr-depth
+Sets a maximum number of recursion levels when attempting to map
+variable names or debug temporaries to value expressions. This trades
+compilation time for more complete debug information. If this is set too
+low, value expressions that are available and could be represented in
+debug information may end up not being used; setting this higher may
+enable the compiler to find more complex debug expressions, but compile
+time and memory use may grow.
+
+@item max-debug-marker-count
+Sets a threshold on the number of debug markers (e.g.@: begin stmt
+markers) to avoid complexity explosion at inlining or expanding to RTL.
+If a function has more such gimple stmts than the set limit, such stmts
+will be dropped from the inlined copy of a function, and from its RTL
+expansion.
+
+@item min-nondebug-insn-uid
+Use uids starting at this parameter for nondebug insns. The range below
+the parameter is reserved exclusively for debug insns created by
+@option{-fvar-tracking-assignments}, but debug insns may get
+(non-overlapping) uids above it if the reserved range is exhausted.
+
+@item ipa-sra-ptr-growth-factor
+IPA-SRA replaces a pointer to an aggregate with one or more new
+parameters only when their cumulative size is less or equal to
+@option{ipa-sra-ptr-growth-factor} times the size of the original
+pointer parameter.
+
+@item ipa-sra-max-replacements
+Maximum pieces of an aggregate that IPA-SRA tracks. As a
+consequence, it is also the maximum number of replacements of a formal
+parameter.
+
+@item sra-max-scalarization-size-Ospeed
+@itemx sra-max-scalarization-size-Osize
+The two Scalar Reduction of Aggregates passes (SRA and IPA-SRA) aim to
+replace scalar parts of aggregates with uses of independent scalar
+variables. These parameters control the maximum size, in storage units,
+of aggregate which is considered for replacement when compiling for
+speed
+(@option{sra-max-scalarization-size-Ospeed}) or size
+(@option{sra-max-scalarization-size-Osize}) respectively.
+
+@item sra-max-propagations
+The maximum number of artificial accesses that Scalar Replacement of
+Aggregates (SRA) will track, per one local variable, in order to
+facilitate copy propagation.
+
+@item tm-max-aggregate-size
+When making copies of thread-local variables in a transaction, this
+parameter specifies the size in bytes after which variables are
+saved with the logging functions as opposed to save/restore code
+sequence pairs. This option only applies when using
+@option{-fgnu-tm}.
+
+@item graphite-max-nb-scop-params
+To avoid exponential effects in the Graphite loop transforms, the
+number of parameters in a Static Control Part (SCoP) is bounded.
+A value of zero can be used to lift
+the bound. A variable whose value is unknown at compilation time and
+defined outside a SCoP is a parameter of the SCoP.
+
+@item loop-block-tile-size
+Loop blocking or strip mining transforms, enabled with
+@option{-floop-block} or @option{-floop-strip-mine}, strip mine each
+loop in the loop nest by a given number of iterations. The strip
+length can be changed using the @option{loop-block-tile-size}
+parameter.
+
+@item ipa-jump-function-lookups
+Specifies number of statements visited during jump function offset discovery.
+
+@item ipa-cp-value-list-size
+IPA-CP attempts to track all possible values and types passed to a function's
+parameter in order to propagate them and perform devirtualization.
+@option{ipa-cp-value-list-size} is the maximum number of values and types it
+stores per one formal parameter of a function.
+
+@item ipa-cp-eval-threshold
+IPA-CP calculates its own score of cloning profitability heuristics
+and performs those cloning opportunities with scores that exceed
+@option{ipa-cp-eval-threshold}.
+
+@item ipa-cp-max-recursive-depth
+Maximum depth of recursive cloning for self-recursive function.
+
+@item ipa-cp-min-recursive-probability
+Recursive cloning only when the probability of call being executed exceeds
+the parameter.
+
+@item ipa-cp-profile-count-base
+When using @option{-fprofile-use} option, IPA-CP will consider the measured
+execution count of a call graph edge at this percentage position in their
+histogram as the basis for its heuristics calculation.
+
+@item ipa-cp-recursive-freq-factor
+The number of times interprocedural copy propagation expects recursive
+functions to call themselves.
+
+@item ipa-cp-recursion-penalty
+Percentage penalty the recursive functions will receive when they
+are evaluated for cloning.
+
+@item ipa-cp-single-call-penalty
+Percentage penalty functions containing a single call to another
+function will receive when they are evaluated for cloning.
+
+@item ipa-max-agg-items
+IPA-CP is also capable to propagate a number of scalar values passed
+in an aggregate. @option{ipa-max-agg-items} controls the maximum
+number of such values per one parameter.
+
+@item ipa-cp-loop-hint-bonus
+When IPA-CP determines that a cloning candidate would make the number
+of iterations of a loop known, it adds a bonus of
+@option{ipa-cp-loop-hint-bonus} to the profitability score of
+the candidate.
+
+@item ipa-max-loop-predicates
+The maximum number of different predicates IPA will use to describe when
+loops in a function have known properties.
+
+@item ipa-max-aa-steps
+During its analysis of function bodies, IPA-CP employs alias analysis
+in order to track values pointed to by function parameters. In order
+not spend too much time analyzing huge functions, it gives up and
+consider all memory clobbered after examining
+@option{ipa-max-aa-steps} statements modifying memory.
+
+@item ipa-max-switch-predicate-bounds
+Maximal number of boundary endpoints of case ranges of switch statement.
+For switch exceeding this limit, IPA-CP will not construct cloning cost
+predicate, which is used to estimate cloning benefit, for default case
+of the switch statement.
+
+@item ipa-max-param-expr-ops
+IPA-CP will analyze conditional statement that references some function
+parameter to estimate benefit for cloning upon certain constant value.
+But if number of operations in a parameter expression exceeds
+@option{ipa-max-param-expr-ops}, the expression is treated as complicated
+one, and is not handled by IPA analysis.
+
+@item lto-partitions
+Specify desired number of partitions produced during WHOPR compilation.
+The number of partitions should exceed the number of CPUs used for compilation.
+
+@item lto-min-partition
+Size of minimal partition for WHOPR (in estimated instructions).
+This prevents expenses of splitting very small programs into too many
+partitions.
+
+@item lto-max-partition
+Size of max partition for WHOPR (in estimated instructions).
+to provide an upper bound for individual size of partition.
+Meant to be used only with balanced partitioning.
+
+@item lto-max-streaming-parallelism
+Maximal number of parallel processes used for LTO streaming.
+
+@item cxx-max-namespaces-for-diagnostic-help
+The maximum number of namespaces to consult for suggestions when C++
+name lookup fails for an identifier.
+
+@item sink-frequency-threshold
+The maximum relative execution frequency (in percents) of the target block
+relative to a statement's original block to allow statement sinking of a
+statement. Larger numbers result in more aggressive statement sinking.
+A small positive adjustment is applied for
+statements with memory operands as those are even more profitable so sink.
+
+@item max-stores-to-sink
+The maximum number of conditional store pairs that can be sunk. Set to 0
+if either vectorization (@option{-ftree-vectorize}) or if-conversion
+(@option{-ftree-loop-if-convert}) is disabled.
+
+@item case-values-threshold
+The smallest number of different values for which it is best to use a
+jump-table instead of a tree of conditional branches. If the value is
+0, use the default for the machine.
+
+@item jump-table-max-growth-ratio-for-size
+The maximum code size growth ratio when expanding
+into a jump table (in percent). The parameter is used when
+optimizing for size.
+
+@item jump-table-max-growth-ratio-for-speed
+The maximum code size growth ratio when expanding
+into a jump table (in percent). The parameter is used when
+optimizing for speed.
+
+@item tree-reassoc-width
+Set the maximum number of instructions executed in parallel in
+reassociated tree. This parameter overrides target dependent
+heuristics used by default if has non zero value.
+
+@item sched-pressure-algorithm
+Choose between the two available implementations of
+@option{-fsched-pressure}. Algorithm 1 is the original implementation
+and is the more likely to prevent instructions from being reordered.
+Algorithm 2 was designed to be a compromise between the relatively
+conservative approach taken by algorithm 1 and the rather aggressive
+approach taken by the default scheduler. It relies more heavily on
+having a regular register file and accurate register pressure classes.
+See @file{haifa-sched.cc} in the GCC sources for more details.
+
+The default choice depends on the target.
+
+@item max-slsr-cand-scan
+Set the maximum number of existing candidates that are considered when
+seeking a basis for a new straight-line strength reduction candidate.
+
+@item asan-globals
+Enable buffer overflow detection for global objects. This kind
+of protection is enabled by default if you are using
+@option{-fsanitize=address} option.
+To disable global objects protection use @option{--param asan-globals=0}.
+
+@item asan-stack
+Enable buffer overflow detection for stack objects. This kind of
+protection is enabled by default when using @option{-fsanitize=address}.
+To disable stack protection use @option{--param asan-stack=0} option.
+
+@item asan-instrument-reads
+Enable buffer overflow detection for memory reads. This kind of
+protection is enabled by default when using @option{-fsanitize=address}.
+To disable memory reads protection use
+@option{--param asan-instrument-reads=0}.
+
+@item asan-instrument-writes
+Enable buffer overflow detection for memory writes. This kind of
+protection is enabled by default when using @option{-fsanitize=address}.
+To disable memory writes protection use
+@option{--param asan-instrument-writes=0} option.
+
+@item asan-memintrin
+Enable detection for built-in functions. This kind of protection
+is enabled by default when using @option{-fsanitize=address}.
+To disable built-in functions protection use
+@option{--param asan-memintrin=0}.
+
+@item asan-use-after-return
+Enable detection of use-after-return. This kind of protection
+is enabled by default when using the @option{-fsanitize=address} option.
+To disable it use @option{--param asan-use-after-return=0}.
+
+Note: By default the check is disabled at run time. To enable it,
+add @code{detect_stack_use_after_return=1} to the environment variable
+@env{ASAN_OPTIONS}.
+
+@item asan-instrumentation-with-call-threshold
+If number of memory accesses in function being instrumented
+is greater or equal to this number, use callbacks instead of inline checks.
+E.g. to disable inline code use
+@option{--param asan-instrumentation-with-call-threshold=0}.
+
+@item hwasan-instrument-stack
+Enable hwasan instrumentation of statically sized stack-allocated variables.
+This kind of instrumentation is enabled by default when using
+@option{-fsanitize=hwaddress} and disabled by default when using
+@option{-fsanitize=kernel-hwaddress}.
+To disable stack instrumentation use
+@option{--param hwasan-instrument-stack=0}, and to enable it use
+@option{--param hwasan-instrument-stack=1}.
+
+@item hwasan-random-frame-tag
+When using stack instrumentation, decide tags for stack variables using a
+deterministic sequence beginning at a random tag for each frame. With this
+parameter unset tags are chosen using the same sequence but beginning from 1.
+This is enabled by default for @option{-fsanitize=hwaddress} and unavailable
+for @option{-fsanitize=kernel-hwaddress}.
+To disable it use @option{--param hwasan-random-frame-tag=0}.
+
+@item hwasan-instrument-allocas
+Enable hwasan instrumentation of dynamically sized stack-allocated variables.
+This kind of instrumentation is enabled by default when using
+@option{-fsanitize=hwaddress} and disabled by default when using
+@option{-fsanitize=kernel-hwaddress}.
+To disable instrumentation of such variables use
+@option{--param hwasan-instrument-allocas=0}, and to enable it use
+@option{--param hwasan-instrument-allocas=1}.
+
+@item hwasan-instrument-reads
+Enable hwasan checks on memory reads. Instrumentation of reads is enabled by
+default for both @option{-fsanitize=hwaddress} and
+@option{-fsanitize=kernel-hwaddress}.
+To disable checking memory reads use
+@option{--param hwasan-instrument-reads=0}.
+
+@item hwasan-instrument-writes
+Enable hwasan checks on memory writes. Instrumentation of writes is enabled by
+default for both @option{-fsanitize=hwaddress} and
+@option{-fsanitize=kernel-hwaddress}.
+To disable checking memory writes use
+@option{--param hwasan-instrument-writes=0}.
+
+@item hwasan-instrument-mem-intrinsics
+Enable hwasan instrumentation of builtin functions. Instrumentation of these
+builtin functions is enabled by default for both @option{-fsanitize=hwaddress}
+and @option{-fsanitize=kernel-hwaddress}.
+To disable instrumentation of builtin functions use
+@option{--param hwasan-instrument-mem-intrinsics=0}.
+
+@item use-after-scope-direct-emission-threshold
+If the size of a local variable in bytes is smaller or equal to this
+number, directly poison (or unpoison) shadow memory instead of using
+run-time callbacks.
+
+@item tsan-distinguish-volatile
+Emit special instrumentation for accesses to volatiles.
+
+@item tsan-instrument-func-entry-exit
+Emit instrumentation calls to __tsan_func_entry() and __tsan_func_exit().
+
+@item max-fsm-thread-path-insns
+Maximum number of instructions to copy when duplicating blocks on a
+finite state automaton jump thread path.
+
+@item threader-debug
+threader-debug=[none|all] Enables verbose dumping of the threader solver.
+
+@item parloops-chunk-size
+Chunk size of omp schedule for loops parallelized by parloops.
+
+@item parloops-schedule
+Schedule type of omp schedule for loops parallelized by parloops (static,
+dynamic, guided, auto, runtime).
+
+@item parloops-min-per-thread
+The minimum number of iterations per thread of an innermost parallelized
+loop for which the parallelized variant is preferred over the single threaded
+one. Note that for a parallelized loop nest the
+minimum number of iterations of the outermost loop per thread is two.
+
+@item max-ssa-name-query-depth
+Maximum depth of recursion when querying properties of SSA names in things
+like fold routines. One level of recursion corresponds to following a
+use-def chain.
+
+@item max-speculative-devirt-maydefs
+The maximum number of may-defs we analyze when looking for a must-def
+specifying the dynamic type of an object that invokes a virtual call
+we may be able to devirtualize speculatively.
+
+@item max-vrp-switch-assertions
+The maximum number of assertions to add along the default edge of a switch
+statement during VRP.
+
+@item evrp-sparse-threshold
+Maximum number of basic blocks before EVRP uses a sparse cache.
+
+@item vrp1-mode
+Specifies the mode VRP pass 1 should operate in.
+
+@item vrp2-mode
+Specifies the mode VRP pass 2 should operate in.
+
+@item ranger-debug
+Specifies the type of debug output to be issued for ranges.
+
+@item evrp-switch-limit
+Specifies the maximum number of switch cases before EVRP ignores a switch.
+
+@item unroll-jam-min-percent
+The minimum percentage of memory references that must be optimized
+away for the unroll-and-jam transformation to be considered profitable.
+
+@item unroll-jam-max-unroll
+The maximum number of times the outer loop should be unrolled by
+the unroll-and-jam transformation.
+
+@item max-rtl-if-conversion-unpredictable-cost
+Maximum permissible cost for the sequence that would be generated
+by the RTL if-conversion pass for a branch that is considered unpredictable.
+
+@item max-variable-expansions-in-unroller
+If @option{-fvariable-expansion-in-unroller} is used, the maximum number
+of times that an individual variable will be expanded during loop unrolling.
+
+@item partial-inlining-entry-probability
+Maximum probability of the entry BB of split region
+(in percent relative to entry BB of the function)
+to make partial inlining happen.
+
+@item max-tracked-strlens
+Maximum number of strings for which strlen optimization pass will
+track string lengths.
+
+@item gcse-after-reload-partial-fraction
+The threshold ratio for performing partial redundancy
+elimination after reload.
+
+@item gcse-after-reload-critical-fraction
+The threshold ratio of critical edges execution count that
+permit performing redundancy elimination after reload.
+
+@item max-loop-header-insns
+The maximum number of insns in loop header duplicated
+by the copy loop headers pass.
+
+@item vect-epilogues-nomask
+Enable loop epilogue vectorization using smaller vector size.
+
+@item vect-partial-vector-usage
+Controls when the loop vectorizer considers using partial vector loads
+and stores as an alternative to falling back to scalar code. 0 stops
+the vectorizer from ever using partial vector loads and stores. 1 allows
+partial vector loads and stores if vectorization removes the need for the
+code to iterate. 2 allows partial vector loads and stores in all loops.
+The parameter only has an effect on targets that support partial
+vector loads and stores.
+
+@item vect-inner-loop-cost-factor
+The maximum factor which the loop vectorizer applies to the cost of statements
+in an inner loop relative to the loop being vectorized. The factor applied
+is the maximum of the estimated number of iterations of the inner loop and
+this parameter. The default value of this parameter is 50.
+
+@item vect-induction-float
+Enable loop vectorization of floating point inductions.
+
+@item avoid-fma-max-bits
+Maximum number of bits for which we avoid creating FMAs.
+
+@item sms-loop-average-count-threshold
+A threshold on the average loop count considered by the swing modulo scheduler.
+
+@item sms-dfa-history
+The number of cycles the swing modulo scheduler considers when checking
+conflicts using DFA.
+
+@item graphite-allow-codegen-errors
+Whether codegen errors should be ICEs when @option{-fchecking}.
+
+@item sms-max-ii-factor
+A factor for tuning the upper bound that swing modulo scheduler
+uses for scheduling a loop.
+
+@item lra-max-considered-reload-pseudos
+The max number of reload pseudos which are considered during
+spilling a non-reload pseudo.
+
+@item max-pow-sqrt-depth
+Maximum depth of sqrt chains to use when synthesizing exponentiation
+by a real constant.
+
+@item max-dse-active-local-stores
+Maximum number of active local stores in RTL dead store elimination.
+
+@item asan-instrument-allocas
+Enable asan allocas/VLAs protection.
+
+@item max-iterations-computation-cost
+Bound on the cost of an expression to compute the number of iterations.
+
+@item max-isl-operations
+Maximum number of isl operations, 0 means unlimited.
+
+@item graphite-max-arrays-per-scop
+Maximum number of arrays per scop.
+
+@item max-vartrack-reverse-op-size
+Max. size of loc list for which reverse ops should be added.
+
+@item fsm-scale-path-stmts
+Scale factor to apply to the number of statements in a threading path
+when comparing to the number of (scaled) blocks.
+
+@item uninit-control-dep-attempts
+Maximum number of nested calls to search for control dependencies
+during uninitialized variable analysis.
+
+@item fsm-scale-path-blocks
+Scale factor to apply to the number of blocks in a threading path
+when comparing to the number of (scaled) statements.
+
+@item sched-autopref-queue-depth
+Hardware autoprefetcher scheduler model control flag.
+Number of lookahead cycles the model looks into; at '
+' only enable instruction sorting heuristic.
+
+@item loop-versioning-max-inner-insns
+The maximum number of instructions that an inner loop can have
+before the loop versioning pass considers it too big to copy.
+
+@item loop-versioning-max-outer-insns
+The maximum number of instructions that an outer loop can have
+before the loop versioning pass considers it too big to copy,
+discounting any instructions in inner loops that directly benefit
+from versioning.
+
+@item ssa-name-def-chain-limit
+The maximum number of SSA_NAME assignments to follow in determining
+a property of a variable such as its value. This limits the number
+of iterations or recursive calls GCC performs when optimizing certain
+statements or when determining their validity prior to issuing
+diagnostics.
+
+@item store-merging-max-size
+Maximum size of a single store merging region in bytes.
+
+@item hash-table-verification-limit
+The number of elements for which hash table verification is done
+for each searched element.
+
+@item max-find-base-term-values
+Maximum number of VALUEs handled during a single find_base_term call.
+
+@item analyzer-max-enodes-per-program-point
+The maximum number of exploded nodes per program point within
+the analyzer, before terminating analysis of that point.
+
+@item analyzer-max-constraints
+The maximum number of constraints per state.
+
+@item analyzer-min-snodes-for-call-summary
+The minimum number of supernodes within a function for the
+analyzer to consider summarizing its effects at call sites.
+
+@item analyzer-max-enodes-for-full-dump
+The maximum depth of exploded nodes that should appear in a dot dump
+before switching to a less verbose format.
+
+@item analyzer-max-recursion-depth
+The maximum number of times a callsite can appear in a call stack
+within the analyzer, before terminating analysis of a call that would
+recurse deeper.
+
+@item analyzer-max-svalue-depth
+The maximum depth of a symbolic value, before approximating
+the value as unknown.
+
+@item analyzer-max-infeasible-edges
+The maximum number of infeasible edges to reject before declaring
+a diagnostic as infeasible.
+
+@item gimple-fe-computed-hot-bb-threshold
+The number of executions of a basic block which is considered hot.
+The parameter is used only in GIMPLE FE.
+
+@item analyzer-bb-explosion-factor
+The maximum number of 'after supernode' exploded nodes within the analyzer
+per supernode, before terminating analysis.
+
+@item ranger-logical-depth
+Maximum depth of logical expression evaluation ranger will look through
+when evaluating outgoing edge ranges.
+
+@item relation-block-limit
+Maximum number of relations the oracle will register in a basic block.
+
+@item min-pagesize
+Minimum page size for warning purposes.
+
+@item openacc-kernels
+Specify mode of OpenACC `kernels' constructs handling.
+With @option{--param=openacc-kernels=decompose}, OpenACC `kernels'
+constructs are decomposed into parts, a sequence of compute
+constructs, each then handled individually.
+This is work in progress.
+With @option{--param=openacc-kernels=parloops}, OpenACC `kernels'
+constructs are handled by the @samp{parloops} pass, en bloc.
+This is the current default.
+
+@item openacc-privatization
+Specify mode of OpenACC privatization diagnostics for
+@option{-fopt-info-omp-note} and applicable
+@option{-fdump-tree-*-details}.
+With @option{--param=openacc-privatization=quiet}, don't diagnose.
+This is the current default.
+With @option{--param=openacc-privatization=noisy}, do diagnose.
+
+@end table
+
+The following choices of @var{name} are available on AArch64 targets:
+
+@table @gcctabopt
+@item aarch64-sve-compare-costs
+When vectorizing for SVE, consider using ``unpacked'' vectors for
+smaller elements and use the cost model to pick the cheapest approach.
+Also use the cost model to choose between SVE and Advanced SIMD vectorization.
+
+Using unpacked vectors includes storing smaller elements in larger
+containers and accessing elements with extending loads and truncating
+stores.
+
+@item aarch64-float-recp-precision
+The number of Newton iterations for calculating the reciprocal for float type.
+The precision of division is proportional to this param when division
+approximation is enabled. The default value is 1.
+
+@item aarch64-double-recp-precision
+The number of Newton iterations for calculating the reciprocal for double type.
+The precision of division is propotional to this param when division
+approximation is enabled. The default value is 2.
+
+@item aarch64-autovec-preference
+Force an ISA selection strategy for auto-vectorization. Accepts values from
+0 to 4, inclusive.
+@table @samp
+@item 0
+Use the default heuristics.
+@item 1
+Use only Advanced SIMD for auto-vectorization.
+@item 2
+Use only SVE for auto-vectorization.
+@item 3
+Use both Advanced SIMD and SVE. Prefer Advanced SIMD when the costs are
+deemed equal.
+@item 4
+Use both Advanced SIMD and SVE. Prefer SVE when the costs are deemed equal.
+@end table
+The default value is 0.
+
+@item aarch64-loop-vect-issue-rate-niters
+The tuning for some AArch64 CPUs tries to take both latencies and issue
+rates into account when deciding whether a loop should be vectorized
+using SVE, vectorized using Advanced SIMD, or not vectorized at all.
+If this parameter is set to @var{n}, GCC will not use this heuristic
+for loops that are known to execute in fewer than @var{n} Advanced
+SIMD iterations.
+
+@item aarch64-vect-unroll-limit
+The vectorizer will use available tuning information to determine whether it
+would be beneficial to unroll the main vectorized loop and by how much. This
+parameter set's the upper bound of how much the vectorizer will unroll the main
+loop. The default value is four.
+
+@end table
+
+The following choices of @var{name} are available on i386 and x86_64 targets:
+
+@table @gcctabopt
+@item x86-stlf-window-ninsns
+Instructions number above which STFL stall penalty can be compensated.
+
+@end table
+
+@end table
+
+@node Instrumentation Options
+@section Program Instrumentation Options
+@cindex instrumentation options
+@cindex program instrumentation options
+@cindex run-time error checking options
+@cindex profiling options
+@cindex options, program instrumentation
+@cindex options, run-time error checking
+@cindex options, profiling
+
+GCC supports a number of command-line options that control adding
+run-time instrumentation to the code it normally generates.
+For example, one purpose of instrumentation is collect profiling
+statistics for use in finding program hot spots, code coverage
+analysis, or profile-guided optimizations.
+Another class of program instrumentation is adding run-time checking
+to detect programming errors like invalid pointer
+dereferences or out-of-bounds array accesses, as well as deliberately
+hostile attacks such as stack smashing or C++ vtable hijacking.
+There is also a general hook which can be used to implement other
+forms of tracing or function-level instrumentation for debug or
+program analysis purposes.
+
+@table @gcctabopt
+@cindex @command{prof}
+@cindex @command{gprof}
+@item -p
+@itemx -pg
+@opindex p
+@opindex pg
+Generate extra code to write profile information suitable for the
+analysis program @command{prof} (for @option{-p}) or @command{gprof}
+(for @option{-pg}). You must use this option when compiling
+the source files you want data about, and you must also use it when
+linking.
+
+You can use the function attribute @code{no_instrument_function} to
+suppress profiling of individual functions when compiling with these options.
+@xref{Common Function Attributes}.
+
+@item -fprofile-arcs
+@opindex fprofile-arcs
+Add code so that program flow @dfn{arcs} are instrumented. During
+execution the program records how many times each branch and call is
+executed and how many times it is taken or returns. On targets that support
+constructors with priority support, profiling properly handles constructors,
+destructors and C++ constructors (and destructors) of classes which are used
+as a type of a global variable.
+
+When the compiled
+program exits it saves this data to a file called
+@file{@var{auxname}.gcda} for each source file. The data may be used for
+profile-directed optimizations (@option{-fbranch-probabilities}), or for
+test coverage analysis (@option{-ftest-coverage}). Each object file's
+@var{auxname} is generated from the name of the output file, if
+explicitly specified and it is not the final executable, otherwise it is
+the basename of the source file. In both cases any suffix is removed
+(e.g.@: @file{foo.gcda} for input file @file{dir/foo.c}, or
+@file{dir/foo.gcda} for output file specified as @option{-o dir/foo.o}).
+
+Note that if a command line directly links source files, the corresponding
+@var{.gcda} files will be prefixed with the unsuffixed name of the output file.
+E.g. @code{gcc a.c b.c -o binary} would generate @file{binary-a.gcda} and
+@file{binary-b.gcda} files.
+
+@xref{Cross-profiling}.
+
+@cindex @command{gcov}
+@item --coverage
+@opindex coverage
+
+This option is used to compile and link code instrumented for coverage
+analysis. The option is a synonym for @option{-fprofile-arcs}
+@option{-ftest-coverage} (when compiling) and @option{-lgcov} (when
+linking). See the documentation for those options for more details.
+
+@itemize
+
+@item
+Compile the source files with @option{-fprofile-arcs} plus optimization
+and code generation options. For test coverage analysis, use the
+additional @option{-ftest-coverage} option. You do not need to profile
+every source file in a program.
+
+@item
+Compile the source files additionally with @option{-fprofile-abs-path}
+to create absolute path names in the @file{.gcno} files. This allows
+@command{gcov} to find the correct sources in projects where compilations
+occur with different working directories.
+
+@item
+Link your object files with @option{-lgcov} or @option{-fprofile-arcs}
+(the latter implies the former).
+
+@item
+Run the program on a representative workload to generate the arc profile
+information. This may be repeated any number of times. You can run
+concurrent instances of your program, and provided that the file system
+supports locking, the data files will be correctly updated. Unless
+a strict ISO C dialect option is in effect, @code{fork} calls are
+detected and correctly handled without double counting.
+
+Moreover, an object file can be recompiled multiple times
+and the corresponding @file{.gcda} file merges as long as
+the source file and the compiler options are unchanged.
+
+@item
+For profile-directed optimizations, compile the source files again with
+the same optimization and code generation options plus
+@option{-fbranch-probabilities} (@pxref{Optimize Options,,Options that
+Control Optimization}).
+
+@item
+For test coverage analysis, use @command{gcov} to produce human readable
+information from the @file{.gcno} and @file{.gcda} files. Refer to the
+@command{gcov} documentation for further information.
+
+@end itemize
+
+With @option{-fprofile-arcs}, for each function of your program GCC
+creates a program flow graph, then finds a spanning tree for the graph.
+Only arcs that are not on the spanning tree have to be instrumented: the
+compiler adds code to count the number of times that these arcs are
+executed. When an arc is the only exit or only entrance to a block, the
+instrumentation code can be added to the block; otherwise, a new basic
+block must be created to hold the instrumentation code.
+
+@need 2000
+@item -ftest-coverage
+@opindex ftest-coverage
+Produce a notes file that the @command{gcov} code-coverage utility
+(@pxref{Gcov,, @command{gcov}---a Test Coverage Program}) can use to
+show program coverage. Each source file's note file is called
+@file{@var{auxname}.gcno}. Refer to the @option{-fprofile-arcs} option
+above for a description of @var{auxname} and instructions on how to
+generate test coverage data. Coverage data matches the source files
+more closely if you do not optimize.
+
+@item -fprofile-abs-path
+@opindex fprofile-abs-path
+Automatically convert relative source file names to absolute path names
+in the @file{.gcno} files. This allows @command{gcov} to find the correct
+sources in projects where compilations occur with different working
+directories.
+
+@item -fprofile-dir=@var{path}
+@opindex fprofile-dir
+
+Set the directory to search for the profile data files in to @var{path}.
+This option affects only the profile data generated by
+@option{-fprofile-generate}, @option{-ftest-coverage}, @option{-fprofile-arcs}
+and used by @option{-fprofile-use} and @option{-fbranch-probabilities}
+and its related options. Both absolute and relative paths can be used.
+By default, GCC uses the current directory as @var{path}, thus the
+profile data file appears in the same directory as the object file.
+In order to prevent the file name clashing, if the object file name is
+not an absolute path, we mangle the absolute path of the
+@file{@var{sourcename}.gcda} file and use it as the file name of a
+@file{.gcda} file. See details about the file naming in @option{-fprofile-arcs}.
+See similar option @option{-fprofile-note}.
+
+When an executable is run in a massive parallel environment, it is recommended
+to save profile to different folders. That can be done with variables
+in @var{path} that are exported during run-time:
+
+@table @gcctabopt
+
+@item %p
+process ID.
+
+@item %q@{VAR@}
+value of environment variable @var{VAR}
+
+@end table
+
+@item -fprofile-generate
+@itemx -fprofile-generate=@var{path}
+@opindex fprofile-generate
+
+Enable options usually used for instrumenting application to produce
+profile useful for later recompilation with profile feedback based
+optimization. You must use @option{-fprofile-generate} both when
+compiling and when linking your program.
+
+The following options are enabled:
+@option{-fprofile-arcs}, @option{-fprofile-values},
+@option{-finline-functions}, and @option{-fipa-bit-cp}.
+
+If @var{path} is specified, GCC looks at the @var{path} to find
+the profile feedback data files. See @option{-fprofile-dir}.
+
+To optimize the program based on the collected profile information, use
+@option{-fprofile-use}. @xref{Optimize Options}, for more information.
+
+@item -fprofile-info-section
+@itemx -fprofile-info-section=@var{name}
+@opindex fprofile-info-section
+
+Register the profile information in the specified section instead of using a
+constructor/destructor. The section name is @var{name} if it is specified,
+otherwise the section name defaults to @code{.gcov_info}. A pointer to the
+profile information generated by @option{-fprofile-arcs} is placed in the
+specified section for each translation unit. This option disables the profile
+information registration through a constructor and it disables the profile
+information processing through a destructor. This option is not intended to be
+used in hosted environments such as GNU/Linux. It targets freestanding
+environments (for example embedded systems) with limited resources which do not
+support constructors/destructors or the C library file I/O.
+
+The linker could collect the input sections in a continuous memory block and
+define start and end symbols. A GNU linker script example which defines a
+linker output section follows:
+
+@smallexample
+ .gcov_info :
+ @{
+ PROVIDE (__gcov_info_start = .);
+ KEEP (*(.gcov_info))
+ PROVIDE (__gcov_info_end = .);
+ @}
+@end smallexample
+
+The program could dump the profiling information registered in this linker set
+for example like this:
+
+@smallexample
+#include <gcov.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+extern const struct gcov_info *const __gcov_info_start[];
+extern const struct gcov_info *const __gcov_info_end[];
+
+static void
+dump (const void *d, unsigned n, void *arg)
+@{
+ const unsigned char *c = d;
+
+ for (unsigned i = 0; i < n; ++i)
+ printf ("%02x", c[i]);
+@}
+
+static void
+filename (const char *f, void *arg)
+@{
+ __gcov_filename_to_gcfn (f, dump, arg );
+@}
+
+static void *
+allocate (unsigned length, void *arg)
+@{
+ return malloc (length);
+@}
+
+static void
+dump_gcov_info (void)
+@{
+ const struct gcov_info *const *info = __gcov_info_start;
+ const struct gcov_info *const *end = __gcov_info_end;
+
+ /* Obfuscate variable to prevent compiler optimizations. */
+ __asm__ ("" : "+r" (info));
+
+ while (info != end)
+ @{
+ void *arg = NULL;
+ __gcov_info_to_gcda (*info, filename, dump, allocate, arg);
+ putchar ('\n');
+ ++info;
+ @}
+@}
+
+int
+main (void)
+@{
+ dump_gcov_info ();
+ return 0;
+@}
+@end smallexample
+
+The @command{merge-stream} subcommand of @command{gcov-tool} may be used to
+deserialize the data stream generated by the @code{__gcov_filename_to_gcfn} and
+@code{__gcov_info_to_gcda} functions and merge the profile information into
+@file{.gcda} files on the host filesystem.
+
+@item -fprofile-note=@var{path}
+@opindex fprofile-note
+
+If @var{path} is specified, GCC saves @file{.gcno} file into @var{path}
+location. If you combine the option with multiple source files,
+the @file{.gcno} file will be overwritten.
+
+@item -fprofile-prefix-path=@var{path}
+@opindex fprofile-prefix-path
+
+This option can be used in combination with
+@option{profile-generate=}@var{profile_dir} and
+@option{profile-use=}@var{profile_dir} to inform GCC where is the base
+directory of built source tree. By default @var{profile_dir} will contain
+files with mangled absolute paths of all object files in the built project.
+This is not desirable when directory used to build the instrumented binary
+differs from the directory used to build the binary optimized with profile
+feedback because the profile data will not be found during the optimized build.
+In such setups @option{-fprofile-prefix-path=}@var{path} with @var{path}
+pointing to the base directory of the build can be used to strip the irrelevant
+part of the path and keep all file names relative to the main build directory.
+
+@item -fprofile-prefix-map=@var{old}=@var{new}
+@opindex fprofile-prefix-map
+When compiling files residing in directory @file{@var{old}}, record
+profiling information (with @option{--coverage})
+describing them as if the files resided in
+directory @file{@var{new}} instead.
+See also @option{-ffile-prefix-map}.
+
+@item -fprofile-update=@var{method}
+@opindex fprofile-update
+
+Alter the update method for an application instrumented for profile
+feedback based optimization. The @var{method} argument should be one of
+@samp{single}, @samp{atomic} or @samp{prefer-atomic}.
+The first one is useful for single-threaded applications,
+while the second one prevents profile corruption by emitting thread-safe code.
+
+@strong{Warning:} When an application does not properly join all threads
+(or creates an detached thread), a profile file can be still corrupted.
+
+Using @samp{prefer-atomic} would be transformed either to @samp{atomic},
+when supported by a target, or to @samp{single} otherwise. The GCC driver
+automatically selects @samp{prefer-atomic} when @option{-pthread}
+is present in the command line.
+
+@item -fprofile-filter-files=@var{regex}
+@opindex fprofile-filter-files
+
+Instrument only functions from files whose name matches
+any of the regular expressions (separated by semi-colons).
+
+For example, @option{-fprofile-filter-files=main\.c;module.*\.c} will instrument
+only @file{main.c} and all C files starting with 'module'.
+
+@item -fprofile-exclude-files=@var{regex}
+@opindex fprofile-exclude-files
+
+Instrument only functions from files whose name does not match
+any of the regular expressions (separated by semi-colons).
+
+For example, @option{-fprofile-exclude-files=/usr/.*} will prevent instrumentation
+of all files that are located in the @file{/usr/} folder.
+
+@item -fprofile-reproducible=@r{[}multithreaded@r{|}parallel-runs@r{|}serial@r{]}
+@opindex fprofile-reproducible
+Control level of reproducibility of profile gathered by
+@code{-fprofile-generate}. This makes it possible to rebuild program
+with same outcome which is useful, for example, for distribution
+packages.
+
+With @option{-fprofile-reproducible=serial} the profile gathered by
+@option{-fprofile-generate} is reproducible provided the trained program
+behaves the same at each invocation of the train run, it is not
+multi-threaded and profile data streaming is always done in the same
+order. Note that profile streaming happens at the end of program run but
+also before @code{fork} function is invoked.
+
+Note that it is quite common that execution counts of some part of
+programs depends, for example, on length of temporary file names or
+memory space randomization (that may affect hash-table collision rate).
+Such non-reproducible part of programs may be annotated by
+@code{no_instrument_function} function attribute. @command{gcov-dump} with
+@option{-l} can be used to dump gathered data and verify that they are
+indeed reproducible.
+
+With @option{-fprofile-reproducible=parallel-runs} collected profile
+stays reproducible regardless the order of streaming of the data into
+gcda files. This setting makes it possible to run multiple instances of
+instrumented program in parallel (such as with @code{make -j}). This
+reduces quality of gathered data, in particular of indirect call
+profiling.
+
+@item -fsanitize=address
+@opindex fsanitize=address
+Enable AddressSanitizer, a fast memory error detector.
+Memory access instructions are instrumented to detect
+out-of-bounds and use-after-free bugs.
+The option enables @option{-fsanitize-address-use-after-scope}.
+See @uref{https://github.com/google/sanitizers/wiki/AddressSanitizer} for
+more details. The run-time behavior can be influenced using the
+@env{ASAN_OPTIONS} environment variable. When set to @code{help=1},
+the available options are shown at startup of the instrumented program. See
+@url{https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags}
+for a list of supported options.
+The option cannot be combined with @option{-fsanitize=thread} or
+@option{-fsanitize=hwaddress}. Note that the only target
+@option{-fsanitize=hwaddress} is currently supported on is AArch64.
+
+@item -fsanitize=kernel-address
+@opindex fsanitize=kernel-address
+Enable AddressSanitizer for Linux kernel.
+See @uref{https://github.com/google/kasan} for more details.
+
+@item -fsanitize=hwaddress
+@opindex fsanitize=hwaddress
+Enable Hardware-assisted AddressSanitizer, which uses a hardware ability to
+ignore the top byte of a pointer to allow the detection of memory errors with
+a low memory overhead.
+Memory access instructions are instrumented to detect out-of-bounds and
+use-after-free bugs.
+The option enables @option{-fsanitize-address-use-after-scope}.
+See
+@uref{https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html}
+for more details. The run-time behavior can be influenced using the
+@env{HWASAN_OPTIONS} environment variable. When set to @code{help=1},
+the available options are shown at startup of the instrumented program.
+The option cannot be combined with @option{-fsanitize=thread} or
+@option{-fsanitize=address}, and is currently only available on AArch64.
+
+@item -fsanitize=kernel-hwaddress
+@opindex fsanitize=kernel-hwaddress
+Enable Hardware-assisted AddressSanitizer for compilation of the Linux kernel.
+Similar to @option{-fsanitize=kernel-address} but using an alternate
+instrumentation method, and similar to @option{-fsanitize=hwaddress} but with
+instrumentation differences necessary for compiling the Linux kernel.
+These differences are to avoid hwasan library initialization calls and to
+account for the stack pointer having a different value in its top byte.
+
+@emph{Note:} This option has different defaults to the @option{-fsanitize=hwaddress}.
+Instrumenting the stack and alloca calls are not on by default but are still
+possible by specifying the command-line options
+@option{--param hwasan-instrument-stack=1} and
+@option{--param hwasan-instrument-allocas=1} respectively. Using a random frame
+tag is not implemented for kernel instrumentation.
+
+@item -fsanitize=pointer-compare
+@opindex fsanitize=pointer-compare
+Instrument comparison operation (<, <=, >, >=) with pointer operands.
+The option must be combined with either @option{-fsanitize=kernel-address} or
+@option{-fsanitize=address}
+The option cannot be combined with @option{-fsanitize=thread}.
+Note: By default the check is disabled at run time. To enable it,
+add @code{detect_invalid_pointer_pairs=2} to the environment variable
+@env{ASAN_OPTIONS}. Using @code{detect_invalid_pointer_pairs=1} detects
+invalid operation only when both pointers are non-null.
+
+@item -fsanitize=pointer-subtract
+@opindex fsanitize=pointer-subtract
+Instrument subtraction with pointer operands.
+The option must be combined with either @option{-fsanitize=kernel-address} or
+@option{-fsanitize=address}
+The option cannot be combined with @option{-fsanitize=thread}.
+Note: By default the check is disabled at run time. To enable it,
+add @code{detect_invalid_pointer_pairs=2} to the environment variable
+@env{ASAN_OPTIONS}. Using @code{detect_invalid_pointer_pairs=1} detects
+invalid operation only when both pointers are non-null.
+
+@item -fsanitize=shadow-call-stack
+@opindex fsanitize=shadow-call-stack
+Enable ShadowCallStack, a security enhancement mechanism used to protect
+programs against return address overwrites (e.g. stack buffer overflows.)
+It works by saving a function's return address to a separately allocated
+shadow call stack in the function prologue and restoring the return address
+from the shadow call stack in the function epilogue. Instrumentation only
+occurs in functions that need to save the return address to the stack.
+
+Currently it only supports the aarch64 platform. It is specifically
+designed for linux kernels that enable the CONFIG_SHADOW_CALL_STACK option.
+For the user space programs, runtime support is not currently provided
+in libc and libgcc. Users who want to use this feature in user space need
+to provide their own support for the runtime. It should be noted that
+this may cause the ABI rules to be broken.
+
+On aarch64, the instrumentation makes use of the platform register @code{x18}.
+This generally means that any code that may run on the same thread as code
+compiled with ShadowCallStack must be compiled with the flag
+@option{-ffixed-x18}, otherwise functions compiled without
+@option{-ffixed-x18} might clobber @code{x18} and so corrupt the shadow
+stack pointer.
+
+Also, because there is no userspace runtime support, code compiled with
+ShadowCallStack cannot use exception handling. Use @option{-fno-exceptions}
+to turn off exceptions.
+
+See @uref{https://clang.llvm.org/docs/ShadowCallStack.html} for more
+details.
+
+@item -fsanitize=thread
+@opindex fsanitize=thread
+Enable ThreadSanitizer, a fast data race detector.
+Memory access instructions are instrumented to detect
+data race bugs. See @uref{https://github.com/google/sanitizers/wiki#threadsanitizer} for more
+details. The run-time behavior can be influenced using the @env{TSAN_OPTIONS}
+environment variable; see
+@url{https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags} for a list of
+supported options.
+The option cannot be combined with @option{-fsanitize=address},
+@option{-fsanitize=leak}.
+
+Note that sanitized atomic builtins cannot throw exceptions when
+operating on invalid memory addresses with non-call exceptions
+(@option{-fnon-call-exceptions}).
+
+@item -fsanitize=leak
+@opindex fsanitize=leak
+Enable LeakSanitizer, a memory leak detector.
+This option only matters for linking of executables and
+the executable is linked against a library that overrides @code{malloc}
+and other allocator functions. See
+@uref{https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer} for more
+details. The run-time behavior can be influenced using the
+@env{LSAN_OPTIONS} environment variable.
+The option cannot be combined with @option{-fsanitize=thread}.
+
+@item -fsanitize=undefined
+@opindex fsanitize=undefined
+Enable UndefinedBehaviorSanitizer, a fast undefined behavior detector.
+Various computations are instrumented to detect undefined behavior
+at runtime. See @uref{https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html} for more details. The run-time behavior can be influenced using the
+@env{UBSAN_OPTIONS} environment variable. Current suboptions are:
+
+@table @gcctabopt
+
+@item -fsanitize=shift
+@opindex fsanitize=shift
+This option enables checking that the result of a shift operation is
+not undefined. Note that what exactly is considered undefined differs
+slightly between C and C++, as well as between ISO C90 and C99, etc.
+This option has two suboptions, @option{-fsanitize=shift-base} and
+@option{-fsanitize=shift-exponent}.
+
+@item -fsanitize=shift-exponent
+@opindex fsanitize=shift-exponent
+This option enables checking that the second argument of a shift operation
+is not negative and is smaller than the precision of the promoted first
+argument.
+
+@item -fsanitize=shift-base
+@opindex fsanitize=shift-base
+If the second argument of a shift operation is within range, check that the
+result of a shift operation is not undefined. Note that what exactly is
+considered undefined differs slightly between C and C++, as well as between
+ISO C90 and C99, etc.
+
+@item -fsanitize=integer-divide-by-zero
+@opindex fsanitize=integer-divide-by-zero
+Detect integer division by zero.
+
+@item -fsanitize=unreachable
+@opindex fsanitize=unreachable
+With this option, the compiler turns the @code{__builtin_unreachable}
+call into a diagnostics message call instead. When reaching the
+@code{__builtin_unreachable} call, the behavior is undefined.
+
+@item -fsanitize=vla-bound
+@opindex fsanitize=vla-bound
+This option instructs the compiler to check that the size of a variable
+length array is positive.
+
+@item -fsanitize=null
+@opindex fsanitize=null
+This option enables pointer checking. Particularly, the application
+built with this option turned on will issue an error message when it
+tries to dereference a NULL pointer, or if a reference (possibly an
+rvalue reference) is bound to a NULL pointer, or if a method is invoked
+on an object pointed by a NULL pointer.
+
+@item -fsanitize=return
+@opindex fsanitize=return
+This option enables return statement checking. Programs
+built with this option turned on will issue an error message
+when the end of a non-void function is reached without actually
+returning a value. This option works in C++ only.
+
+@item -fsanitize=signed-integer-overflow
+@opindex fsanitize=signed-integer-overflow
+This option enables signed integer overflow checking. We check that
+the result of @code{+}, @code{*}, and both unary and binary @code{-}
+does not overflow in the signed arithmetics. This also detects
+@code{INT_MIN / -1} signed division. Note, integer promotion
+rules must be taken into account. That is, the following is not an
+overflow:
+@smallexample
+signed char a = SCHAR_MAX;
+a++;
+@end smallexample
+
+@item -fsanitize=bounds
+@opindex fsanitize=bounds
+This option enables instrumentation of array bounds. Various out of bounds
+accesses are detected. Flexible array members, flexible array member-like
+arrays, and initializers of variables with static storage are not instrumented.
+
+@item -fsanitize=bounds-strict
+@opindex fsanitize=bounds-strict
+This option enables strict instrumentation of array bounds. Most out of bounds
+accesses are detected, including flexible array members and flexible array
+member-like arrays. Initializers of variables with static storage are not
+instrumented.
+
+@item -fsanitize=alignment
+@opindex fsanitize=alignment
+
+This option enables checking of alignment of pointers when they are
+dereferenced, or when a reference is bound to insufficiently aligned target,
+or when a method or constructor is invoked on insufficiently aligned object.
+
+@item -fsanitize=object-size
+@opindex fsanitize=object-size
+This option enables instrumentation of memory references using the
+@code{__builtin_object_size} function. Various out of bounds pointer
+accesses are detected.
+
+@item -fsanitize=float-divide-by-zero
+@opindex fsanitize=float-divide-by-zero
+Detect floating-point division by zero. Unlike other similar options,
+@option{-fsanitize=float-divide-by-zero} is not enabled by
+@option{-fsanitize=undefined}, since floating-point division by zero can
+be a legitimate way of obtaining infinities and NaNs.
+
+@item -fsanitize=float-cast-overflow
+@opindex fsanitize=float-cast-overflow
+This option enables floating-point type to integer conversion checking.
+We check that the result of the conversion does not overflow.
+Unlike other similar options, @option{-fsanitize=float-cast-overflow} is
+not enabled by @option{-fsanitize=undefined}.
+This option does not work well with @code{FE_INVALID} exceptions enabled.
+
+@item -fsanitize=nonnull-attribute
+@opindex fsanitize=nonnull-attribute
+
+This option enables instrumentation of calls, checking whether null values
+are not passed to arguments marked as requiring a non-null value by the
+@code{nonnull} function attribute.
+
+@item -fsanitize=returns-nonnull-attribute
+@opindex fsanitize=returns-nonnull-attribute
+
+This option enables instrumentation of return statements in functions
+marked with @code{returns_nonnull} function attribute, to detect returning
+of null values from such functions.
+
+@item -fsanitize=bool
+@opindex fsanitize=bool
+
+This option enables instrumentation of loads from bool. If a value other
+than 0/1 is loaded, a run-time error is issued.
+
+@item -fsanitize=enum
+@opindex fsanitize=enum
+
+This option enables instrumentation of loads from an enum type. If
+a value outside the range of values for the enum type is loaded,
+a run-time error is issued.
+
+@item -fsanitize=vptr
+@opindex fsanitize=vptr
+
+This option enables instrumentation of C++ member function calls, member
+accesses and some conversions between pointers to base and derived classes,
+to verify the referenced object has the correct dynamic type.
+
+@item -fsanitize=pointer-overflow
+@opindex fsanitize=pointer-overflow
+
+This option enables instrumentation of pointer arithmetics. If the pointer
+arithmetics overflows, a run-time error is issued.
+
+@item -fsanitize=builtin
+@opindex fsanitize=builtin
+
+This option enables instrumentation of arguments to selected builtin
+functions. If an invalid value is passed to such arguments, a run-time
+error is issued. E.g.@ passing 0 as the argument to @code{__builtin_ctz}
+or @code{__builtin_clz} invokes undefined behavior and is diagnosed
+by this option.
+
+@end table
+
+Note that sanitizers tend to increase the rate of false positive
+warnings, most notably those around @option{-Wmaybe-uninitialized}.
+We recommend against combining @option{-Werror} and [the use of]
+sanitizers.
+
+While @option{-ftrapv} causes traps for signed overflows to be emitted,
+@option{-fsanitize=undefined} gives a diagnostic message.
+This currently works only for the C family of languages.
+
+@item -fno-sanitize=all
+@opindex fno-sanitize=all
+
+This option disables all previously enabled sanitizers.
+@option{-fsanitize=all} is not allowed, as some sanitizers cannot be used
+together.
+
+@item -fasan-shadow-offset=@var{number}
+@opindex fasan-shadow-offset
+This option forces GCC to use custom shadow offset in AddressSanitizer checks.
+It is useful for experimenting with different shadow memory layouts in
+Kernel AddressSanitizer.
+
+@item -fsanitize-sections=@var{s1},@var{s2},...
+@opindex fsanitize-sections
+Sanitize global variables in selected user-defined sections. @var{si} may
+contain wildcards.
+
+@item -fsanitize-recover@r{[}=@var{opts}@r{]}
+@opindex fsanitize-recover
+@opindex fno-sanitize-recover
+@option{-fsanitize-recover=} controls error recovery mode for sanitizers
+mentioned in comma-separated list of @var{opts}. Enabling this option
+for a sanitizer component causes it to attempt to continue
+running the program as if no error happened. This means multiple
+runtime errors can be reported in a single program run, and the exit
+code of the program may indicate success even when errors
+have been reported. The @option{-fno-sanitize-recover=} option
+can be used to alter
+this behavior: only the first detected error is reported
+and program then exits with a non-zero exit code.
+
+Currently this feature only works for @option{-fsanitize=undefined} (and its suboptions
+except for @option{-fsanitize=unreachable} and @option{-fsanitize=return}),
+@option{-fsanitize=float-cast-overflow}, @option{-fsanitize=float-divide-by-zero},
+@option{-fsanitize=bounds-strict},
+@option{-fsanitize=kernel-address} and @option{-fsanitize=address}.
+For these sanitizers error recovery is turned on by default,
+except @option{-fsanitize=address}, for which this feature is experimental.
+@option{-fsanitize-recover=all} and @option{-fno-sanitize-recover=all} is also
+accepted, the former enables recovery for all sanitizers that support it,
+the latter disables recovery for all sanitizers that support it.
+
+Even if a recovery mode is turned on the compiler side, it needs to be also
+enabled on the runtime library side, otherwise the failures are still fatal.
+The runtime library defaults to @code{halt_on_error=0} for
+ThreadSanitizer and UndefinedBehaviorSanitizer, while default value for
+AddressSanitizer is @code{halt_on_error=1}. This can be overridden through
+setting the @code{halt_on_error} flag in the corresponding environment variable.
+
+Syntax without an explicit @var{opts} parameter is deprecated. It is
+equivalent to specifying an @var{opts} list of:
+
+@smallexample
+undefined,float-cast-overflow,float-divide-by-zero,bounds-strict
+@end smallexample
+
+@item -fsanitize-address-use-after-scope
+@opindex fsanitize-address-use-after-scope
+Enable sanitization of local variables to detect use-after-scope bugs.
+The option sets @option{-fstack-reuse} to @samp{none}.
+
+@item -fsanitize-trap@r{[}=@var{opts}@r{]}
+@opindex fsanitize-trap
+@opindex fno-sanitize-trap
+The @option{-fsanitize-trap=} option instructs the compiler to
+report for sanitizers mentioned in comma-separated list of @var{opts}
+undefined behavior using @code{__builtin_trap} rather than a @code{libubsan}
+library routine. If this option is enabled for certain sanitizer,
+it takes precedence over the @option{-fsanitizer-recover=} for that
+sanitizer, @code{__builtin_trap} will be emitted and be fatal regardless
+of whether recovery is enabled or disabled using @option{-fsanitize-recover=}.
+
+The advantage of this is that the @code{libubsan} library is not needed
+and is not linked in, so this is usable even in freestanding environments.
+
+Currently this feature works with @option{-fsanitize=undefined} (and its suboptions
+except for @option{-fsanitize=vptr}), @option{-fsanitize=float-cast-overflow},
+@option{-fsanitize=float-divide-by-zero} and
+@option{-fsanitize=bounds-strict}. @code{-fsanitize-trap=all} can be also
+specified, which enables it for @code{undefined} suboptions,
+@option{-fsanitize=float-cast-overflow},
+@option{-fsanitize=float-divide-by-zero} and
+@option{-fsanitize=bounds-strict}.
+If @code{-fsanitize-trap=undefined} or @code{-fsanitize-trap=all} is used
+and @code{-fsanitize=vptr} is enabled on the command line, the
+instrumentation is silently ignored as the instrumentation always needs
+@code{libubsan} support, @option{-fsanitize-trap=vptr} is not allowed.
+
+@item -fsanitize-undefined-trap-on-error
+@opindex fsanitize-undefined-trap-on-error
+The @option{-fsanitize-undefined-trap-on-error} option is deprecated
+equivalent of @option{-fsanitize-trap=all}.
+
+@item -fsanitize-coverage=trace-pc
+@opindex fsanitize-coverage=trace-pc
+Enable coverage-guided fuzzing code instrumentation.
+Inserts a call to @code{__sanitizer_cov_trace_pc} into every basic block.
+
+@item -fsanitize-coverage=trace-cmp
+@opindex fsanitize-coverage=trace-cmp
+Enable dataflow guided fuzzing code instrumentation.
+Inserts a call to @code{__sanitizer_cov_trace_cmp1},
+@code{__sanitizer_cov_trace_cmp2}, @code{__sanitizer_cov_trace_cmp4} or
+@code{__sanitizer_cov_trace_cmp8} for integral comparison with both operands
+variable or @code{__sanitizer_cov_trace_const_cmp1},
+@code{__sanitizer_cov_trace_const_cmp2},
+@code{__sanitizer_cov_trace_const_cmp4} or
+@code{__sanitizer_cov_trace_const_cmp8} for integral comparison with one
+operand constant, @code{__sanitizer_cov_trace_cmpf} or
+@code{__sanitizer_cov_trace_cmpd} for float or double comparisons and
+@code{__sanitizer_cov_trace_switch} for switch statements.
+
+@item -fcf-protection=@r{[}full@r{|}branch@r{|}return@r{|}none@r{|}check@r{]}
+@opindex fcf-protection
+Enable code instrumentation of control-flow transfers to increase
+program security by checking that target addresses of control-flow
+transfer instructions (such as indirect function call, function return,
+indirect jump) are valid. This prevents diverting the flow of control
+to an unexpected target. This is intended to protect against such
+threats as Return-oriented Programming (ROP), and similarly
+call/jmp-oriented programming (COP/JOP).
+
+The value @code{branch} tells the compiler to implement checking of
+validity of control-flow transfer at the point of indirect branch
+instructions, i.e.@: call/jmp instructions. The value @code{return}
+implements checking of validity at the point of returning from a
+function. The value @code{full} is an alias for specifying both
+@code{branch} and @code{return}. The value @code{none} turns off
+instrumentation.
+
+The value @code{check} is used for the final link with link-time
+optimization (LTO). An error is issued if LTO object files are
+compiled with different @option{-fcf-protection} values. The
+value @code{check} is ignored at the compile time.
+
+The macro @code{__CET__} is defined when @option{-fcf-protection} is
+used. The first bit of @code{__CET__} is set to 1 for the value
+@code{branch} and the second bit of @code{__CET__} is set to 1 for
+the @code{return}.
+
+You can also use the @code{nocf_check} attribute to identify
+which functions and calls should be skipped from instrumentation
+(@pxref{Function Attributes}).
+
+Currently the x86 GNU/Linux target provides an implementation based
+on Intel Control-flow Enforcement Technology (CET) which works for
+i686 processor or newer.
+
+@item -fharden-compares
+@opindex fharden-compares
+For every logical test that survives gimple optimizations and is
+@emph{not} the condition in a conditional branch (for example,
+conditions tested for conditional moves, or to store in boolean
+variables), emit extra code to compute and verify the reversed
+condition, and to call @code{__builtin_trap} if the results do not
+match. Use with @samp{-fharden-conditional-branches} to cover all
+conditionals.
+
+@item -fharden-conditional-branches
+@opindex fharden-conditional-branches
+For every non-vectorized conditional branch that survives gimple
+optimizations, emit extra code to compute and verify the reversed
+condition, and to call @code{__builtin_trap} if the result is
+unexpected. Use with @samp{-fharden-compares} to cover all
+conditionals.
+
+@item -fstack-protector
+@opindex fstack-protector
+Emit extra code to check for buffer overflows, such as stack smashing
+attacks. This is done by adding a guard variable to functions with
+vulnerable objects. This includes functions that call @code{alloca}, and
+functions with buffers larger than or equal to 8 bytes. The guards are
+initialized when a function is entered and then checked when the function
+exits. If a guard check fails, an error message is printed and the program
+exits. Only variables that are actually allocated on the stack are
+considered, optimized away variables or variables allocated in registers
+don't count.
+
+@item -fstack-protector-all
+@opindex fstack-protector-all
+Like @option{-fstack-protector} except that all functions are protected.
+
+@item -fstack-protector-strong
+@opindex fstack-protector-strong
+Like @option{-fstack-protector} but includes additional functions to
+be protected --- those that have local array definitions, or have
+references to local frame addresses. Only variables that are actually
+allocated on the stack are considered, optimized away variables or variables
+allocated in registers don't count.
+
+@item -fstack-protector-explicit
+@opindex fstack-protector-explicit
+Like @option{-fstack-protector} but only protects those functions which
+have the @code{stack_protect} attribute.
+
+@item -fstack-check
+@opindex fstack-check
+Generate code to verify that you do not go beyond the boundary of the
+stack. You should specify this flag if you are running in an
+environment with multiple threads, but you only rarely need to specify it in
+a single-threaded environment since stack overflow is automatically
+detected on nearly all systems if there is only one stack.
+
+Note that this switch does not actually cause checking to be done; the
+operating system or the language runtime must do that. The switch causes
+generation of code to ensure that they see the stack being extended.
+
+You can additionally specify a string parameter: @samp{no} means no
+checking, @samp{generic} means force the use of old-style checking,
+@samp{specific} means use the best checking method and is equivalent
+to bare @option{-fstack-check}.
+
+Old-style checking is a generic mechanism that requires no specific
+target support in the compiler but comes with the following drawbacks:
+
+@enumerate
+@item
+Modified allocation strategy for large objects: they are always
+allocated dynamically if their size exceeds a fixed threshold. Note this
+may change the semantics of some code.
+
+@item
+Fixed limit on the size of the static frame of functions: when it is
+topped by a particular function, stack checking is not reliable and
+a warning is issued by the compiler.
+
+@item
+Inefficiency: because of both the modified allocation strategy and the
+generic implementation, code performance is hampered.
+@end enumerate
+
+Note that old-style stack checking is also the fallback method for
+@samp{specific} if no target support has been added in the compiler.
+
+@samp{-fstack-check=} is designed for Ada's needs to detect infinite recursion
+and stack overflows. @samp{specific} is an excellent choice when compiling
+Ada code. It is not generally sufficient to protect against stack-clash
+attacks. To protect against those you want @samp{-fstack-clash-protection}.
+
+@item -fstack-clash-protection
+@opindex fstack-clash-protection
+Generate code to prevent stack clash style attacks. When this option is
+enabled, the compiler will only allocate one page of stack space at a time
+and each page is accessed immediately after allocation. Thus, it prevents
+allocations from jumping over any stack guard page provided by the
+operating system.
+
+Most targets do not fully support stack clash protection. However, on
+those targets @option{-fstack-clash-protection} will protect dynamic stack
+allocations. @option{-fstack-clash-protection} may also provide limited
+protection for static stack allocations if the target supports
+@option{-fstack-check=specific}.
+
+@item -fstack-limit-register=@var{reg}
+@itemx -fstack-limit-symbol=@var{sym}
+@itemx -fno-stack-limit
+@opindex fstack-limit-register
+@opindex fstack-limit-symbol
+@opindex fno-stack-limit
+Generate code to ensure that the stack does not grow beyond a certain value,
+either the value of a register or the address of a symbol. If a larger
+stack is required, a signal is raised at run time. For most targets,
+the signal is raised before the stack overruns the boundary, so
+it is possible to catch the signal without taking special precautions.
+
+For instance, if the stack starts at absolute address @samp{0x80000000}
+and grows downwards, you can use the flags
+@option{-fstack-limit-symbol=__stack_limit} and
+@option{-Wl,--defsym,__stack_limit=0x7ffe0000} to enforce a stack limit
+of 128KB@. Note that this may only work with the GNU linker.
+
+You can locally override stack limit checking by using the
+@code{no_stack_limit} function attribute (@pxref{Function Attributes}).
+
+@item -fsplit-stack
+@opindex fsplit-stack
+Generate code to automatically split the stack before it overflows.
+The resulting program has a discontiguous stack which can only
+overflow if the program is unable to allocate any more memory. This
+is most useful when running threaded programs, as it is no longer
+necessary to calculate a good stack size to use for each thread. This
+is currently only implemented for the x86 targets running
+GNU/Linux.
+
+When code compiled with @option{-fsplit-stack} calls code compiled
+without @option{-fsplit-stack}, there may not be much stack space
+available for the latter code to run. If compiling all code,
+including library code, with @option{-fsplit-stack} is not an option,
+then the linker can fix up these calls so that the code compiled
+without @option{-fsplit-stack} always has a large stack. Support for
+this is implemented in the gold linker in GNU binutils release 2.21
+and later.
+
+@item -fvtable-verify=@r{[}std@r{|}preinit@r{|}none@r{]}
+@opindex fvtable-verify
+This option is only available when compiling C++ code.
+It turns on (or off, if using @option{-fvtable-verify=none}) the security
+feature that verifies at run time, for every virtual call, that
+the vtable pointer through which the call is made is valid for the type of
+the object, and has not been corrupted or overwritten. If an invalid vtable
+pointer is detected at run time, an error is reported and execution of the
+program is immediately halted.
+
+This option causes run-time data structures to be built at program startup,
+which are used for verifying the vtable pointers.
+The options @samp{std} and @samp{preinit}
+control the timing of when these data structures are built. In both cases the
+data structures are built before execution reaches @code{main}. Using
+@option{-fvtable-verify=std} causes the data structures to be built after
+shared libraries have been loaded and initialized.
+@option{-fvtable-verify=preinit} causes them to be built before shared
+libraries have been loaded and initialized.
+
+If this option appears multiple times in the command line with different
+values specified, @samp{none} takes highest priority over both @samp{std} and
+@samp{preinit}; @samp{preinit} takes priority over @samp{std}.
+
+@item -fvtv-debug
+@opindex fvtv-debug
+When used in conjunction with @option{-fvtable-verify=std} or
+@option{-fvtable-verify=preinit}, causes debug versions of the
+runtime functions for the vtable verification feature to be called.
+This flag also causes the compiler to log information about which
+vtable pointers it finds for each class.
+This information is written to a file named @file{vtv_set_ptr_data.log}
+in the directory named by the environment variable @env{VTV_LOGS_DIR}
+if that is defined or the current working directory otherwise.
+
+Note: This feature @emph{appends} data to the log file. If you want a fresh log
+file, be sure to delete any existing one.
+
+@item -fvtv-counts
+@opindex fvtv-counts
+This is a debugging flag. When used in conjunction with
+@option{-fvtable-verify=std} or @option{-fvtable-verify=preinit}, this
+causes the compiler to keep track of the total number of virtual calls
+it encounters and the number of verifications it inserts. It also
+counts the number of calls to certain run-time library functions
+that it inserts and logs this information for each compilation unit.
+The compiler writes this information to a file named
+@file{vtv_count_data.log} in the directory named by the environment
+variable @env{VTV_LOGS_DIR} if that is defined or the current working
+directory otherwise. It also counts the size of the vtable pointer sets
+for each class, and writes this information to @file{vtv_class_set_sizes.log}
+in the same directory.
+
+Note: This feature @emph{appends} data to the log files. To get fresh log
+files, be sure to delete any existing ones.
+
+@item -finstrument-functions
+@opindex finstrument-functions
+Generate instrumentation calls for entry and exit to functions. Just
+after function entry and just before function exit, the following
+profiling functions are called with the address of the current
+function and its call site. (On some platforms,
+@code{__builtin_return_address} does not work beyond the current
+function, so the call site information may not be available to the
+profiling functions otherwise.)
+
+@smallexample
+void __cyg_profile_func_enter (void *this_fn,
+ void *call_site);
+void __cyg_profile_func_exit (void *this_fn,
+ void *call_site);
+@end smallexample
+
+The first argument is the address of the start of the current function,
+which may be looked up exactly in the symbol table.
+
+This instrumentation is also done for functions expanded inline in other
+functions. The profiling calls indicate where, conceptually, the
+inline function is entered and exited. This means that addressable
+versions of such functions must be available. If all your uses of a
+function are expanded inline, this may mean an additional expansion of
+code size. If you use @code{extern inline} in your C code, an
+addressable version of such functions must be provided. (This is
+normally the case anyway, but if you get lucky and the optimizer always
+expands the functions inline, you might have gotten away without
+providing static copies.)
+
+A function may be given the attribute @code{no_instrument_function}, in
+which case this instrumentation is not done. This can be used, for
+example, for the profiling functions listed above, high-priority
+interrupt routines, and any functions from which the profiling functions
+cannot safely be called (perhaps signal handlers, if the profiling
+routines generate output or allocate memory).
+@xref{Common Function Attributes}.
+
+@item -finstrument-functions-once
+@opindex -finstrument-functions-once
+This is similar to @option{-finstrument-functions}, but the profiling
+functions are called only once per instrumented function, i.e. the first
+profiling function is called after the first entry into the instrumented
+function and the second profiling function is called before the exit
+corresponding to this first entry.
+
+The definition of @code{once} for the purpose of this option is a little
+vague because the implementation is not protected against data races.
+As a result, the implementation only guarantees that the profiling
+functions are called at @emph{least} once per process and at @emph{most}
+once per thread, but the calls are always paired, that is to say, if a
+thread calls the first function, then it will call the second function,
+unless it never reaches the exit of the instrumented function.
+
+@item -finstrument-functions-exclude-file-list=@var{file},@var{file},@dots{}
+@opindex finstrument-functions-exclude-file-list
+
+Set the list of functions that are excluded from instrumentation (see
+the description of @option{-finstrument-functions}). If the file that
+contains a function definition matches with one of @var{file}, then
+that function is not instrumented. The match is done on substrings:
+if the @var{file} parameter is a substring of the file name, it is
+considered to be a match.
+
+For example:
+
+@smallexample
+-finstrument-functions-exclude-file-list=/bits/stl,include/sys
+@end smallexample
+
+@noindent
+excludes any inline function defined in files whose pathnames
+contain @file{/bits/stl} or @file{include/sys}.
+
+If, for some reason, you want to include letter @samp{,} in one of
+@var{sym}, write @samp{\,}. For example,
+@option{-finstrument-functions-exclude-file-list='\,\,tmp'}
+(note the single quote surrounding the option).
+
+@item -finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{}
+@opindex finstrument-functions-exclude-function-list
+
+This is similar to @option{-finstrument-functions-exclude-file-list},
+but this option sets the list of function names to be excluded from
+instrumentation. The function name to be matched is its user-visible
+name, such as @code{vector<int> blah(const vector<int> &)}, not the
+internal mangled name (e.g., @code{_Z4blahRSt6vectorIiSaIiEE}). The
+match is done on substrings: if the @var{sym} parameter is a substring
+of the function name, it is considered to be a match. For C99 and C++
+extended identifiers, the function name must be given in UTF-8, not
+using universal character names.
+
+@item -fpatchable-function-entry=@var{N}[,@var{M}]
+@opindex fpatchable-function-entry
+Generate @var{N} NOPs right at the beginning
+of each function, with the function entry point before the @var{M}th NOP.
+If @var{M} is omitted, it defaults to @code{0} so the
+function entry points to the address just at the first NOP.
+The NOP instructions reserve extra space which can be used to patch in
+any desired instrumentation at run time, provided that the code segment
+is writable. The amount of space is controllable indirectly via
+the number of NOPs; the NOP instruction used corresponds to the instruction
+emitted by the internal GCC back-end interface @code{gen_nop}. This behavior
+is target-specific and may also depend on the architecture variant and/or
+other compilation options.
+
+For run-time identification, the starting addresses of these areas,
+which correspond to their respective function entries minus @var{M},
+are additionally collected in the @code{__patchable_function_entries}
+section of the resulting binary.
+
+Note that the value of @code{__attribute__ ((patchable_function_entry
+(N,M)))} takes precedence over command-line option
+@option{-fpatchable-function-entry=N,M}. This can be used to increase
+the area size or to remove it completely on a single function.
+If @code{N=0}, no pad location is recorded.
+
+The NOP instructions are inserted at---and maybe before, depending on
+@var{M}---the function entry address, even before the prologue. On
+PowerPC with the ELFv2 ABI, for a function with dual entry points,
+the local entry point is this function entry address.
+
+The maximum value of @var{N} and @var{M} is 65535. On PowerPC with the
+ELFv2 ABI, for a function with dual entry points, the supported values
+for @var{M} are 0, 2, 6 and 14.
+@end table
+
+
+@node Preprocessor Options
+@section Options Controlling the Preprocessor
+@cindex preprocessor options
+@cindex options, preprocessor
+
+These options control the C preprocessor, which is run on each C source
+file before actual compilation.
+
+If you use the @option{-E} option, nothing is done except preprocessing.
+Some of these options make sense only together with @option{-E} because
+they cause the preprocessor output to be unsuitable for actual
+compilation.
+
+In addition to the options listed here, there are a number of options
+to control search paths for include files documented in
+@ref{Directory Options}.
+Options to control preprocessor diagnostics are listed in
+@ref{Warning Options}.
+
+@table @gcctabopt
+@include cppopts.texi
+
+@item -Wp,@var{option}
+@opindex Wp
+You can use @option{-Wp,@var{option}} to bypass the compiler driver
+and pass @var{option} directly through to the preprocessor. If
+@var{option} contains commas, it is split into multiple options at the
+commas. However, many options are modified, translated or interpreted
+by the compiler driver before being passed to the preprocessor, and
+@option{-Wp} forcibly bypasses this phase. The preprocessor's direct
+interface is undocumented and subject to change, so whenever possible
+you should avoid using @option{-Wp} and let the driver handle the
+options instead.
+
+@item -Xpreprocessor @var{option}
+@opindex Xpreprocessor
+Pass @var{option} as an option to the preprocessor. You can use this to
+supply system-specific preprocessor options that GCC does not
+recognize.
+
+If you want to pass an option that takes an argument, you must use
+@option{-Xpreprocessor} twice, once for the option and once for the argument.
+
+@item -no-integrated-cpp
+@opindex no-integrated-cpp
+Perform preprocessing as a separate pass before compilation.
+By default, GCC performs preprocessing as an integrated part of
+input tokenization and parsing.
+If this option is provided, the appropriate language front end
+(@command{cc1}, @command{cc1plus}, or @command{cc1obj} for C, C++,
+and Objective-C, respectively) is instead invoked twice,
+once for preprocessing only and once for actual compilation
+of the preprocessed input.
+This option may be useful in conjunction with the @option{-B} or
+@option{-wrapper} options to specify an alternate preprocessor or
+perform additional processing of the program source between
+normal preprocessing and compilation.
+
+@item -flarge-source-files
+@opindex flarge-source-files
+Adjust GCC to expect large source files, at the expense of slower
+compilation and higher memory usage.
+
+Specifically, GCC normally tracks both column numbers and line numbers
+within source files and it normally prints both of these numbers in
+diagnostics. However, once it has processed a certain number of source
+lines, it stops tracking column numbers and only tracks line numbers.
+This means that diagnostics for later lines do not include column numbers.
+It also means that options like @option{-Wmisleading-indentation} cease to work
+at that point, although the compiler prints a note if this happens.
+Passing @option{-flarge-source-files} significantly increases the number
+of source lines that GCC can process before it stops tracking columns.
+
+@end table
+
+@node Assembler Options
+@section Passing Options to the Assembler
+
+@c prevent bad page break with this line
+You can pass options to the assembler.
+
+@table @gcctabopt
+@item -Wa,@var{option}
+@opindex Wa
+Pass @var{option} as an option to the assembler. If @var{option}
+contains commas, it is split into multiple options at the commas.
+
+@item -Xassembler @var{option}
+@opindex Xassembler
+Pass @var{option} as an option to the assembler. You can use this to
+supply system-specific assembler options that GCC does not
+recognize.
+
+If you want to pass an option that takes an argument, you must use
+@option{-Xassembler} twice, once for the option and once for the argument.
+
+@end table
+
+@node Link Options
+@section Options for Linking
+@cindex link options
+@cindex options, linking
+
+These options come into play when the compiler links object files into
+an executable output file. They are meaningless if the compiler is
+not doing a link step.
+
+@table @gcctabopt
+@cindex file names
+@item @var{object-file-name}
+A file name that does not end in a special recognized suffix is
+considered to name an object file or library. (Object files are
+distinguished from libraries by the linker according to the file
+contents.) If linking is done, these object files are used as input
+to the linker.
+
+@item -c
+@itemx -S
+@itemx -E
+@opindex c
+@opindex S
+@opindex E
+If any of these options is used, then the linker is not run, and
+object file names should not be used as arguments. @xref{Overall
+Options}.
+
+@item -flinker-output=@var{type}
+@opindex flinker-output
+This option controls code generation of the link-time optimizer. By
+default the linker output is automatically determined by the linker
+plugin. For debugging the compiler and if incremental linking with a
+non-LTO object file is desired, it may be useful to control the type
+manually.
+
+If @var{type} is @samp{exec}, code generation produces a static
+binary. In this case @option{-fpic} and @option{-fpie} are both
+disabled.
+
+If @var{type} is @samp{dyn}, code generation produces a shared
+library. In this case @option{-fpic} or @option{-fPIC} is preserved,
+but not enabled automatically. This allows to build shared libraries
+without position-independent code on architectures where this is
+possible, i.e.@: on x86.
+
+If @var{type} is @samp{pie}, code generation produces an @option{-fpie}
+executable. This results in similar optimizations as @samp{exec}
+except that @option{-fpie} is not disabled if specified at compilation
+time.
+
+If @var{type} is @samp{rel}, the compiler assumes that incremental linking is
+done. The sections containing intermediate code for link-time optimization are
+merged, pre-optimized, and output to the resulting object file. In addition, if
+@option{-ffat-lto-objects} is specified, binary code is produced for future
+non-LTO linking. The object file produced by incremental linking is smaller
+than a static library produced from the same object files. At link time the
+result of incremental linking also loads faster than a static
+library assuming that the majority of objects in the library are used.
+
+Finally @samp{nolto-rel} configures the compiler for incremental linking where
+code generation is forced, a final binary is produced, and the intermediate
+code for later link-time optimization is stripped. When multiple object files
+are linked together the resulting code is better optimized than with
+link-time optimizations disabled (for example, cross-module inlining
+happens), but most of benefits of whole program optimizations are lost.
+
+During the incremental link (by @option{-r}) the linker plugin defaults to
+@option{rel}. With current interfaces to GNU Binutils it is however not
+possible to incrementally link LTO objects and non-LTO objects into a single
+mixed object file. If any of object files in incremental link cannot
+be used for link-time optimization, the linker plugin issues a warning and
+uses @samp{nolto-rel}. To maintain whole program optimization, it is
+recommended to link such objects into static library instead. Alternatively it
+is possible to use H.J. Lu's binutils with support for mixed objects.
+
+@item -fuse-ld=bfd
+@opindex fuse-ld=bfd
+Use the @command{bfd} linker instead of the default linker.
+
+@item -fuse-ld=gold
+@opindex fuse-ld=gold
+Use the @command{gold} linker instead of the default linker.
+
+@item -fuse-ld=lld
+@opindex fuse-ld=lld
+Use the LLVM @command{lld} linker instead of the default linker.
+
+@item -fuse-ld=mold
+@opindex fuse-ld=mold
+Use the Modern Linker (@command{mold}) instead of the default linker.
+
+@cindex Libraries
+@item -l@var{library}
+@itemx -l @var{library}
+@opindex l
+Search the library named @var{library} when linking. (The second
+alternative with the library as a separate argument is only for
+POSIX compliance and is not recommended.)
+
+The @option{-l} option is passed directly to the linker by GCC. Refer
+to your linker documentation for exact details. The general
+description below applies to the GNU linker.
+
+The linker searches a standard list of directories for the library.
+The directories searched include several standard system directories
+plus any that you specify with @option{-L}.
+
+Static libraries are archives of object files, and have file names
+like @file{lib@var{library}.a}. Some targets also support shared
+libraries, which typically have names like @file{lib@var{library}.so}.
+If both static and shared libraries are found, the linker gives
+preference to linking with the shared library unless the
+@option{-static} option is used.
+
+It makes a difference where in the command you write this option; the
+linker searches and processes libraries and object files in the order they
+are specified. Thus, @samp{foo.o -lz bar.o} searches library @samp{z}
+after file @file{foo.o} but before @file{bar.o}. If @file{bar.o} refers
+to functions in @samp{z}, those functions may not be loaded.
+
+@item -lobjc
+@opindex lobjc
+You need this special case of the @option{-l} option in order to
+link an Objective-C or Objective-C++ program.
+
+@item -nostartfiles
+@opindex nostartfiles
+Do not use the standard system startup files when linking.
+The standard system libraries are used normally, unless @option{-nostdlib},
+@option{-nolibc}, or @option{-nodefaultlibs} is used.
+
+@item -nodefaultlibs
+@opindex nodefaultlibs
+Do not use the standard system libraries when linking.
+Only the libraries you specify are passed to the linker, and options
+specifying linkage of the system libraries, such as @option{-static-libgcc}
+or @option{-shared-libgcc}, are ignored.
+The standard startup files are used normally, unless @option{-nostartfiles}
+is used.
+
+The compiler may generate calls to @code{memcmp},
+@code{memset}, @code{memcpy} and @code{memmove}.
+These entries are usually resolved by entries in
+libc. These entry points should be supplied through some other
+mechanism when this option is specified.
+
+@item -nolibc
+@opindex nolibc
+Do not use the C library or system libraries tightly coupled with it when
+linking. Still link with the startup files, @file{libgcc} or toolchain
+provided language support libraries such as @file{libgnat}, @file{libgfortran}
+or @file{libstdc++} unless options preventing their inclusion are used as
+well. This typically removes @option{-lc} from the link command line, as well
+as system libraries that normally go with it and become meaningless when
+absence of a C library is assumed, for example @option{-lpthread} or
+@option{-lm} in some configurations. This is intended for bare-board
+targets when there is indeed no C library available.
+
+@item -nostdlib
+@opindex nostdlib
+Do not use the standard system startup files or libraries when linking.
+No startup files and only the libraries you specify are passed to
+the linker, and options specifying linkage of the system libraries, such as
+@option{-static-libgcc} or @option{-shared-libgcc}, are ignored.
+
+The compiler may generate calls to @code{memcmp}, @code{memset},
+@code{memcpy} and @code{memmove}.
+These entries are usually resolved by entries in
+libc. These entry points should be supplied through some other
+mechanism when this option is specified.
+
+@cindex @option{-lgcc}, use with @option{-nostdlib}
+@cindex @option{-nostdlib} and unresolved references
+@cindex unresolved references and @option{-nostdlib}
+@cindex @option{-lgcc}, use with @option{-nodefaultlibs}
+@cindex @option{-nodefaultlibs} and unresolved references
+@cindex unresolved references and @option{-nodefaultlibs}
+One of the standard libraries bypassed by @option{-nostdlib} and
+@option{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines
+which GCC uses to overcome shortcomings of particular machines, or special
+needs for some languages.
+(@xref{Interface,,Interfacing to GCC Output,gccint,GNU Compiler
+Collection (GCC) Internals},
+for more discussion of @file{libgcc.a}.)
+In most cases, you need @file{libgcc.a} even when you want to avoid
+other standard libraries. In other words, when you specify @option{-nostdlib}
+or @option{-nodefaultlibs} you should usually specify @option{-lgcc} as well.
+This ensures that you have no unresolved references to internal GCC
+library subroutines.
+(An example of such an internal subroutine is @code{__main}, used to ensure C++
+constructors are called; @pxref{Collect2,,@code{collect2}, gccint,
+GNU Compiler Collection (GCC) Internals}.)
+
+@item -nostdlib++
+@opindex nostdlib++
+Do not implicitly link with standard C++ libraries.
+
+@item -e @var{entry}
+@itemx --entry=@var{entry}
+@opindex e
+@opindex entry
+
+Specify that the program entry point is @var{entry}. The argument is
+interpreted by the linker; the GNU linker accepts either a symbol name
+or an address.
+
+@item -pie
+@opindex pie
+Produce a dynamically linked position independent executable on targets
+that support it. For predictable results, you must also specify the same
+set of options used for compilation (@option{-fpie}, @option{-fPIE},
+or model suboptions) when you specify this linker option.
+
+@item -no-pie
+@opindex no-pie
+Don't produce a dynamically linked position independent executable.
+
+@item -static-pie
+@opindex static-pie
+Produce a static position independent executable on targets that support
+it. A static position independent executable is similar to a static
+executable, but can be loaded at any address without a dynamic linker.
+For predictable results, you must also specify the same set of options
+used for compilation (@option{-fpie}, @option{-fPIE}, or model
+suboptions) when you specify this linker option.
+
+@item -pthread
+@opindex pthread
+Link with the POSIX threads library. This option is supported on
+GNU/Linux targets, most other Unix derivatives, and also on
+x86 Cygwin and MinGW targets. On some targets this option also sets
+flags for the preprocessor, so it should be used consistently for both
+compilation and linking.
+
+@item -r
+@opindex r
+Produce a relocatable object as output. This is also known as partial
+linking.
+
+@item -rdynamic
+@opindex rdynamic
+Pass the flag @option{-export-dynamic} to the ELF linker, on targets
+that support it. This instructs the linker to add all symbols, not
+only used ones, to the dynamic symbol table. This option is needed
+for some uses of @code{dlopen} or to allow obtaining backtraces
+from within a program.
+
+@item -s
+@opindex s
+Remove all symbol table and relocation information from the executable.
+
+@item -static
+@opindex static
+On systems that support dynamic linking, this overrides @option{-pie}
+and prevents linking with the shared libraries. On other systems, this
+option has no effect.
+
+@item -shared
+@opindex shared
+Produce a shared object which can then be linked with other objects to
+form an executable. Not all systems support this option. For predictable
+results, you must also specify the same set of options used for compilation
+(@option{-fpic}, @option{-fPIC}, or model suboptions) when
+you specify this linker option.@footnote{On some systems, @samp{gcc -shared}
+needs to build supplementary stub code for constructors to work. On
+multi-libbed systems, @samp{gcc -shared} must select the correct support
+libraries to link against. Failing to supply the correct flags may lead
+to subtle defects. Supplying them in cases where they are not necessary
+is innocuous.}
+
+@item -shared-libgcc
+@itemx -static-libgcc
+@opindex shared-libgcc
+@opindex static-libgcc
+On systems that provide @file{libgcc} as a shared library, these options
+force the use of either the shared or static version, respectively.
+If no shared version of @file{libgcc} was built when the compiler was
+configured, these options have no effect.
+
+There are several situations in which an application should use the
+shared @file{libgcc} instead of the static version. The most common
+of these is when the application wishes to throw and catch exceptions
+across different shared libraries. In that case, each of the libraries
+as well as the application itself should use the shared @file{libgcc}.
+
+Therefore, the G++ driver automatically adds @option{-shared-libgcc}
+whenever you build a shared library or a main executable, because C++
+programs typically use exceptions, so this is the right thing to do.
+
+If, instead, you use the GCC driver to create shared libraries, you may
+find that they are not always linked with the shared @file{libgcc}.
+If GCC finds, at its configuration time, that you have a non-GNU linker
+or a GNU linker that does not support option @option{--eh-frame-hdr},
+it links the shared version of @file{libgcc} into shared libraries
+by default. Otherwise, it takes advantage of the linker and optimizes
+away the linking with the shared version of @file{libgcc}, linking with
+the static version of libgcc by default. This allows exceptions to
+propagate through such shared libraries, without incurring relocation
+costs at library load time.
+
+However, if a library or main executable is supposed to throw or catch
+exceptions, you must link it using the G++ driver, or using the option
+@option{-shared-libgcc}, such that it is linked with the shared
+@file{libgcc}.
+
+@item -static-libasan
+@opindex static-libasan
+When the @option{-fsanitize=address} option is used to link a program,
+the GCC driver automatically links against @option{libasan}. If
+@file{libasan} is available as a shared library, and the @option{-static}
+option is not used, then this links against the shared version of
+@file{libasan}. The @option{-static-libasan} option directs the GCC
+driver to link @file{libasan} statically, without necessarily linking
+other libraries statically.
+
+@item -static-libtsan
+@opindex static-libtsan
+When the @option{-fsanitize=thread} option is used to link a program,
+the GCC driver automatically links against @option{libtsan}. If
+@file{libtsan} is available as a shared library, and the @option{-static}
+option is not used, then this links against the shared version of
+@file{libtsan}. The @option{-static-libtsan} option directs the GCC
+driver to link @file{libtsan} statically, without necessarily linking
+other libraries statically.
+
+@item -static-liblsan
+@opindex static-liblsan
+When the @option{-fsanitize=leak} option is used to link a program,
+the GCC driver automatically links against @option{liblsan}. If
+@file{liblsan} is available as a shared library, and the @option{-static}
+option is not used, then this links against the shared version of
+@file{liblsan}. The @option{-static-liblsan} option directs the GCC
+driver to link @file{liblsan} statically, without necessarily linking
+other libraries statically.
+
+@item -static-libubsan
+@opindex static-libubsan
+When the @option{-fsanitize=undefined} option is used to link a program,
+the GCC driver automatically links against @option{libubsan}. If
+@file{libubsan} is available as a shared library, and the @option{-static}
+option is not used, then this links against the shared version of
+@file{libubsan}. The @option{-static-libubsan} option directs the GCC
+driver to link @file{libubsan} statically, without necessarily linking
+other libraries statically.
+
+@item -static-libstdc++
+@opindex static-libstdc++
+When the @command{g++} program is used to link a C++ program, it
+normally automatically links against @option{libstdc++}. If
+@file{libstdc++} is available as a shared library, and the
+@option{-static} option is not used, then this links against the
+shared version of @file{libstdc++}. That is normally fine. However, it
+is sometimes useful to freeze the version of @file{libstdc++} used by
+the program without going all the way to a fully static link. The
+@option{-static-libstdc++} option directs the @command{g++} driver to
+link @file{libstdc++} statically, without necessarily linking other
+libraries statically.
+
+@item -symbolic
+@opindex symbolic
+Bind references to global symbols when building a shared object. Warn
+about any unresolved references (unless overridden by the link editor
+option @option{-Xlinker -z -Xlinker defs}). Only a few systems support
+this option.
+
+@item -T @var{script}
+@opindex T
+@cindex linker script
+Use @var{script} as the linker script. This option is supported by most
+systems using the GNU linker. On some targets, such as bare-board
+targets without an operating system, the @option{-T} option may be required
+when linking to avoid references to undefined symbols.
+
+@item -Xlinker @var{option}
+@opindex Xlinker
+Pass @var{option} as an option to the linker. You can use this to
+supply system-specific linker options that GCC does not recognize.
+
+If you want to pass an option that takes a separate argument, you must use
+@option{-Xlinker} twice, once for the option and once for the argument.
+For example, to pass @option{-assert definitions}, you must write
+@option{-Xlinker -assert -Xlinker definitions}. It does not work to write
+@option{-Xlinker "-assert definitions"}, because this passes the entire
+string as a single argument, which is not what the linker expects.
+
+When using the GNU linker, it is usually more convenient to pass
+arguments to linker options using the @option{@var{option}=@var{value}}
+syntax than as separate arguments. For example, you can specify
+@option{-Xlinker -Map=output.map} rather than
+@option{-Xlinker -Map -Xlinker output.map}. Other linkers may not support
+this syntax for command-line options.
+
+@item -Wl,@var{option}
+@opindex Wl
+Pass @var{option} as an option to the linker. If @var{option} contains
+commas, it is split into multiple options at the commas. You can use this
+syntax to pass an argument to the option.
+For example, @option{-Wl,-Map,output.map} passes @option{-Map output.map} to the
+linker. When using the GNU linker, you can also get the same effect with
+@option{-Wl,-Map=output.map}.
+
+@item -u @var{symbol}
+@opindex u
+Pretend the symbol @var{symbol} is undefined, to force linking of
+library modules to define it. You can use @option{-u} multiple times with
+different symbols to force loading of additional library modules.
+
+@item -z @var{keyword}
+@opindex z
+@option{-z} is passed directly on to the linker along with the keyword
+@var{keyword}. See the section in the documentation of your linker for
+permitted values and their meanings.
+@end table
+
+@node Directory Options
+@section Options for Directory Search
+@cindex directory options
+@cindex options, directory search
+@cindex search path
+
+These options specify directories to search for header files, for
+libraries and for parts of the compiler:
+
+@table @gcctabopt
+@include cppdiropts.texi
+
+@item -iplugindir=@var{dir}
+@opindex iplugindir=
+Set the directory to search for plugins that are passed
+by @option{-fplugin=@var{name}} instead of
+@option{-fplugin=@var{path}/@var{name}.so}. This option is not meant
+to be used by the user, but only passed by the driver.
+
+@item -L@var{dir}
+@opindex L
+Add directory @var{dir} to the list of directories to be searched
+for @option{-l}.
+
+@item -B@var{prefix}
+@opindex B
+This option specifies where to find the executables, libraries,
+include files, and data files of the compiler itself.
+
+The compiler driver program runs one or more of the subprograms
+@command{cpp}, @command{cc1}, @command{as} and @command{ld}. It tries
+@var{prefix} as a prefix for each program it tries to run, both with and
+without @samp{@var{machine}/@var{version}/} for the corresponding target
+machine and compiler version.
+
+For each subprogram to be run, the compiler driver first tries the
+@option{-B} prefix, if any. If that name is not found, or if @option{-B}
+is not specified, the driver tries two standard prefixes,
+@file{/usr/lib/gcc/} and @file{/usr/local/lib/gcc/}. If neither of
+those results in a file name that is found, the unmodified program
+name is searched for using the directories specified in your
+@env{PATH} environment variable.
+
+The compiler checks to see if the path provided by @option{-B}
+refers to a directory, and if necessary it adds a directory
+separator character at the end of the path.
+
+@option{-B} prefixes that effectively specify directory names also apply
+to libraries in the linker, because the compiler translates these
+options into @option{-L} options for the linker. They also apply to
+include files in the preprocessor, because the compiler translates these
+options into @option{-isystem} options for the preprocessor. In this case,
+the compiler appends @samp{include} to the prefix.
+
+The runtime support file @file{libgcc.a} can also be searched for using
+the @option{-B} prefix, if needed. If it is not found there, the two
+standard prefixes above are tried, and that is all. The file is left
+out of the link if it is not found by those means.
+
+Another way to specify a prefix much like the @option{-B} prefix is to use
+the environment variable @env{GCC_EXEC_PREFIX}. @xref{Environment
+Variables}.
+
+As a special kludge, if the path provided by @option{-B} is
+@file{[dir/]stage@var{N}/}, where @var{N} is a number in the range 0 to
+9, then it is replaced by @file{[dir/]include}. This is to help
+with boot-strapping the compiler.
+
+@item -no-canonical-prefixes
+@opindex no-canonical-prefixes
+Do not expand any symbolic links, resolve references to @samp{/../}
+or @samp{/./}, or make the path absolute when generating a relative
+prefix.
+
+@item --sysroot=@var{dir}
+@opindex sysroot
+Use @var{dir} as the logical root directory for headers and libraries.
+For example, if the compiler normally searches for headers in
+@file{/usr/include} and libraries in @file{/usr/lib}, it instead
+searches @file{@var{dir}/usr/include} and @file{@var{dir}/usr/lib}.
+
+If you use both this option and the @option{-isysroot} option, then
+the @option{--sysroot} option applies to libraries, but the
+@option{-isysroot} option applies to header files.
+
+The GNU linker (beginning with version 2.16) has the necessary support
+for this option. If your linker does not support this option, the
+header file aspect of @option{--sysroot} still works, but the
+library aspect does not.
+
+@item --no-sysroot-suffix
+@opindex no-sysroot-suffix
+For some targets, a suffix is added to the root directory specified
+with @option{--sysroot}, depending on the other options used, so that
+headers may for example be found in
+@file{@var{dir}/@var{suffix}/usr/include} instead of
+@file{@var{dir}/usr/include}. This option disables the addition of
+such a suffix.
+
+@end table
+
+@node Code Gen Options
+@section Options for Code Generation Conventions
+@cindex code generation conventions
+@cindex options, code generation
+@cindex run-time options
+
+These machine-independent options control the interface conventions
+used in code generation.
+
+Most of them have both positive and negative forms; the negative form
+of @option{-ffoo} is @option{-fno-foo}. In the table below, only
+one of the forms is listed---the one that is not the default. You
+can figure out the other form by either removing @samp{no-} or adding
+it.
+
+@table @gcctabopt
+@item -fstack-reuse=@var{reuse-level}
+@opindex fstack_reuse
+This option controls stack space reuse for user declared local/auto variables
+and compiler generated temporaries. @var{reuse_level} can be @samp{all},
+@samp{named_vars}, or @samp{none}. @samp{all} enables stack reuse for all
+local variables and temporaries, @samp{named_vars} enables the reuse only for
+user defined local variables with names, and @samp{none} disables stack reuse
+completely. The default value is @samp{all}. The option is needed when the
+program extends the lifetime of a scoped local variable or a compiler generated
+temporary beyond the end point defined by the language. When a lifetime of
+a variable ends, and if the variable lives in memory, the optimizing compiler
+has the freedom to reuse its stack space with other temporaries or scoped
+local variables whose live range does not overlap with it. Legacy code extending
+local lifetime is likely to break with the stack reuse optimization.
+
+For example,
+
+@smallexample
+ int *p;
+ @{
+ int local1;
+
+ p = &local1;
+ local1 = 10;
+ ....
+ @}
+ @{
+ int local2;
+ local2 = 20;
+ ...
+ @}
+
+ if (*p == 10) // out of scope use of local1
+ @{
+
+ @}
+@end smallexample
+
+Another example:
+@smallexample
+
+ struct A
+ @{
+ A(int k) : i(k), j(k) @{ @}
+ int i;
+ int j;
+ @};
+
+ A *ap;
+
+ void foo(const A& ar)
+ @{
+ ap = &ar;
+ @}
+
+ void bar()
+ @{
+ foo(A(10)); // temp object's lifetime ends when foo returns
+
+ @{
+ A a(20);
+ ....
+ @}
+ ap->i+= 10; // ap references out of scope temp whose space
+ // is reused with a. What is the value of ap->i?
+ @}
+
+@end smallexample
+
+The lifetime of a compiler generated temporary is well defined by the C++
+standard. When a lifetime of a temporary ends, and if the temporary lives
+in memory, the optimizing compiler has the freedom to reuse its stack
+space with other temporaries or scoped local variables whose live range
+does not overlap with it. However some of the legacy code relies on
+the behavior of older compilers in which temporaries' stack space is
+not reused, the aggressive stack reuse can lead to runtime errors. This
+option is used to control the temporary stack reuse optimization.
+
+@item -ftrapv
+@opindex ftrapv
+This option generates traps for signed overflow on addition, subtraction,
+multiplication operations.
+The options @option{-ftrapv} and @option{-fwrapv} override each other, so using
+@option{-ftrapv} @option{-fwrapv} on the command-line results in
+@option{-fwrapv} being effective. Note that only active options override, so
+using @option{-ftrapv} @option{-fwrapv} @option{-fno-wrapv} on the command-line
+results in @option{-ftrapv} being effective.
+
+@item -fwrapv
+@opindex fwrapv
+This option instructs the compiler to assume that signed arithmetic
+overflow of addition, subtraction and multiplication wraps around
+using twos-complement representation. This flag enables some optimizations
+and disables others.
+The options @option{-ftrapv} and @option{-fwrapv} override each other, so using
+@option{-ftrapv} @option{-fwrapv} on the command-line results in
+@option{-fwrapv} being effective. Note that only active options override, so
+using @option{-ftrapv} @option{-fwrapv} @option{-fno-wrapv} on the command-line
+results in @option{-ftrapv} being effective.
+
+@item -fwrapv-pointer
+@opindex fwrapv-pointer
+This option instructs the compiler to assume that pointer arithmetic
+overflow on addition and subtraction wraps around using twos-complement
+representation. This flag disables some optimizations which assume
+pointer overflow is invalid.
+
+@item -fstrict-overflow
+@opindex fstrict-overflow
+This option implies @option{-fno-wrapv} @option{-fno-wrapv-pointer} and when
+negated implies @option{-fwrapv} @option{-fwrapv-pointer}.
+
+@item -fexceptions
+@opindex fexceptions
+Enable exception handling. Generates extra code needed to propagate
+exceptions. For some targets, this implies GCC generates frame
+unwind information for all functions, which can produce significant data
+size overhead, although it does not affect execution. If you do not
+specify this option, GCC enables it by default for languages like
+C++ that normally require exception handling, and disables it for
+languages like C that do not normally require it. However, you may need
+to enable this option when compiling C code that needs to interoperate
+properly with exception handlers written in C++. You may also wish to
+disable this option if you are compiling older C++ programs that don't
+use exception handling.
+
+@item -fnon-call-exceptions
+@opindex fnon-call-exceptions
+Generate code that allows trapping instructions to throw exceptions.
+Note that this requires platform-specific runtime support that does
+not exist everywhere. Moreover, it only allows @emph{trapping}
+instructions to throw exceptions, i.e.@: memory references or floating-point
+instructions. It does not allow exceptions to be thrown from
+arbitrary signal handlers such as @code{SIGALRM}. This enables
+@option{-fexceptions}.
+
+@item -fdelete-dead-exceptions
+@opindex fdelete-dead-exceptions
+Consider that instructions that may throw exceptions but don't otherwise
+contribute to the execution of the program can be optimized away.
+This does not affect calls to functions except those with the
+@code{pure} or @code{const} attributes.
+This option is enabled by default for the Ada and C++ compilers, as permitted by
+the language specifications.
+Optimization passes that cause dead exceptions to be removed are enabled independently at different optimization levels.
+
+@item -funwind-tables
+@opindex funwind-tables
+Similar to @option{-fexceptions}, except that it just generates any needed
+static data, but does not affect the generated code in any other way.
+You normally do not need to enable this option; instead, a language processor
+that needs this handling enables it on your behalf.
+
+@item -fasynchronous-unwind-tables
+@opindex fasynchronous-unwind-tables
+Generate unwind table in DWARF format, if supported by target machine. The
+table is exact at each instruction boundary, so it can be used for stack
+unwinding from asynchronous events (such as debugger or garbage collector).
+
+@item -fno-gnu-unique
+@opindex fno-gnu-unique
+@opindex fgnu-unique
+On systems with recent GNU assembler and C library, the C++ compiler
+uses the @code{STB_GNU_UNIQUE} binding to make sure that definitions
+of template static data members and static local variables in inline
+functions are unique even in the presence of @code{RTLD_LOCAL}; this
+is necessary to avoid problems with a library used by two different
+@code{RTLD_LOCAL} plugins depending on a definition in one of them and
+therefore disagreeing with the other one about the binding of the
+symbol. But this causes @code{dlclose} to be ignored for affected
+DSOs; if your program relies on reinitialization of a DSO via
+@code{dlclose} and @code{dlopen}, you can use
+@option{-fno-gnu-unique}.
+
+@item -fpcc-struct-return
+@opindex fpcc-struct-return
+Return ``short'' @code{struct} and @code{union} values in memory like
+longer ones, rather than in registers. This convention is less
+efficient, but it has the advantage of allowing intercallability between
+GCC-compiled files and files compiled with other compilers, particularly
+the Portable C Compiler (pcc).
+
+The precise convention for returning structures in memory depends
+on the target configuration macros.
+
+Short structures and unions are those whose size and alignment match
+that of some integer type.
+
+@strong{Warning:} code compiled with the @option{-fpcc-struct-return}
+switch is not binary compatible with code compiled with the
+@option{-freg-struct-return} switch.
+Use it to conform to a non-default application binary interface.
+
+@item -freg-struct-return
+@opindex freg-struct-return
+Return @code{struct} and @code{union} values in registers when possible.
+This is more efficient for small structures than
+@option{-fpcc-struct-return}.
+
+If you specify neither @option{-fpcc-struct-return} nor
+@option{-freg-struct-return}, GCC defaults to whichever convention is
+standard for the target. If there is no standard convention, GCC
+defaults to @option{-fpcc-struct-return}, except on targets where GCC is
+the principal compiler. In those cases, we can choose the standard, and
+we chose the more efficient register return alternative.
+
+@strong{Warning:} code compiled with the @option{-freg-struct-return}
+switch is not binary compatible with code compiled with the
+@option{-fpcc-struct-return} switch.
+Use it to conform to a non-default application binary interface.
+
+@item -fshort-enums
+@opindex fshort-enums
+Allocate to an @code{enum} type only as many bytes as it needs for the
+declared range of possible values. Specifically, the @code{enum} type
+is equivalent to the smallest integer type that has enough room.
+
+@strong{Warning:} the @option{-fshort-enums} switch causes GCC to generate
+code that is not binary compatible with code generated without that switch.
+Use it to conform to a non-default application binary interface.
+
+@item -fshort-wchar
+@opindex fshort-wchar
+Override the underlying type for @code{wchar_t} to be @code{short
+unsigned int} instead of the default for the target. This option is
+useful for building programs to run under WINE@.
+
+@strong{Warning:} the @option{-fshort-wchar} switch causes GCC to generate
+code that is not binary compatible with code generated without that switch.
+Use it to conform to a non-default application binary interface.
+
+@item -fcommon
+@opindex fcommon
+@opindex fno-common
+@cindex tentative definitions
+In C code, this option controls the placement of global variables
+defined without an initializer, known as @dfn{tentative definitions}
+in the C standard. Tentative definitions are distinct from declarations
+of a variable with the @code{extern} keyword, which do not allocate storage.
+
+The default is @option{-fno-common}, which specifies that the compiler places
+uninitialized global variables in the BSS section of the object file.
+This inhibits the merging of tentative definitions by the linker so you get a
+multiple-definition error if the same variable is accidentally defined in more
+than one compilation unit.
+
+The @option{-fcommon} places uninitialized global variables in a common block.
+This allows the linker to resolve all tentative definitions of the same variable
+in different compilation units to the same object, or to a non-tentative
+definition. This behavior is inconsistent with C++, and on many targets implies
+a speed and code size penalty on global variable references. It is mainly
+useful to enable legacy code to link without errors.
+
+@item -fno-ident
+@opindex fno-ident
+@opindex fident
+Ignore the @code{#ident} directive.
+
+@item -finhibit-size-directive
+@opindex finhibit-size-directive
+Don't output a @code{.size} assembler directive, or anything else that
+would cause trouble if the function is split in the middle, and the
+two halves are placed at locations far apart in memory. This option is
+used when compiling @file{crtstuff.c}; you should not need to use it
+for anything else.
+
+@item -fverbose-asm
+@opindex fverbose-asm
+Put extra commentary information in the generated assembly code to
+make it more readable. This option is generally only of use to those
+who actually need to read the generated assembly code (perhaps while
+debugging the compiler itself).
+
+@option{-fno-verbose-asm}, the default, causes the
+extra information to be omitted and is useful when comparing two assembler
+files.
+
+The added comments include:
+
+@itemize @bullet
+
+@item
+information on the compiler version and command-line options,
+
+@item
+the source code lines associated with the assembly instructions,
+in the form FILENAME:LINENUMBER:CONTENT OF LINE,
+
+@item
+hints on which high-level expressions correspond to
+the various assembly instruction operands.
+
+@end itemize
+
+For example, given this C source file:
+
+@smallexample
+int test (int n)
+@{
+ int i;
+ int total = 0;
+
+ for (i = 0; i < n; i++)
+ total += i * i;
+
+ return total;
+@}
+@end smallexample
+
+compiling to (x86_64) assembly via @option{-S} and emitting the result
+direct to stdout via @option{-o} @option{-}
+
+@smallexample
+gcc -S test.c -fverbose-asm -Os -o -
+@end smallexample
+
+gives output similar to this:
+
+@smallexample
+ .file "test.c"
+# GNU C11 (GCC) version 7.0.0 20160809 (experimental) (x86_64-pc-linux-gnu)
+ [...snip...]
+# options passed:
+ [...snip...]
+
+ .text
+ .globl test
+ .type test, @@function
+test:
+.LFB0:
+ .cfi_startproc
+# test.c:4: int total = 0;
+ xorl %eax, %eax # <retval>
+# test.c:6: for (i = 0; i < n; i++)
+ xorl %edx, %edx # i
+.L2:
+# test.c:6: for (i = 0; i < n; i++)
+ cmpl %edi, %edx # n, i
+ jge .L5 #,
+# test.c:7: total += i * i;
+ movl %edx, %ecx # i, tmp92
+ imull %edx, %ecx # i, tmp92
+# test.c:6: for (i = 0; i < n; i++)
+ incl %edx # i
+# test.c:7: total += i * i;
+ addl %ecx, %eax # tmp92, <retval>
+ jmp .L2 #
+.L5:
+# test.c:10: @}
+ ret
+ .cfi_endproc
+.LFE0:
+ .size test, .-test
+ .ident "GCC: (GNU) 7.0.0 20160809 (experimental)"
+ .section .note.GNU-stack,"",@@progbits
+@end smallexample
+
+The comments are intended for humans rather than machines and hence the
+precise format of the comments is subject to change.
+
+@item -frecord-gcc-switches
+@opindex frecord-gcc-switches
+This switch causes the command line used to invoke the
+compiler to be recorded into the object file that is being created.
+This switch is only implemented on some targets and the exact format
+of the recording is target and binary file format dependent, but it
+usually takes the form of a section containing ASCII text. This
+switch is related to the @option{-fverbose-asm} switch, but that
+switch only records information in the assembler output file as
+comments, so it never reaches the object file.
+See also @option{-grecord-gcc-switches} for another
+way of storing compiler options into the object file.
+
+@item -fpic
+@opindex fpic
+@cindex global offset table
+@cindex PIC
+Generate position-independent code (PIC) suitable for use in a shared
+library, if supported for the target machine. Such code accesses all
+constant addresses through a global offset table (GOT)@. The dynamic
+loader resolves the GOT entries when the program starts (the dynamic
+loader is not part of GCC; it is part of the operating system). If
+the GOT size for the linked executable exceeds a machine-specific
+maximum size, you get an error message from the linker indicating that
+@option{-fpic} does not work; in that case, recompile with @option{-fPIC}
+instead. (These maximums are 8k on the SPARC, 28k on AArch64 and 32k
+on the m68k and RS/6000. The x86 has no such limit.)
+
+Position-independent code requires special support, and therefore works
+only on certain machines. For the x86, GCC supports PIC for System V
+but not for the Sun 386i. Code generated for the IBM RS/6000 is always
+position-independent.
+
+When this flag is set, the macros @code{__pic__} and @code{__PIC__}
+are defined to 1.
+
+@item -fPIC
+@opindex fPIC
+If supported for the target machine, emit position-independent code,
+suitable for dynamic linking and avoiding any limit on the size of the
+global offset table. This option makes a difference on AArch64, m68k,
+PowerPC and SPARC@.
+
+Position-independent code requires special support, and therefore works
+only on certain machines.
+
+When this flag is set, the macros @code{__pic__} and @code{__PIC__}
+are defined to 2.
+
+@item -fpie
+@itemx -fPIE
+@opindex fpie
+@opindex fPIE
+These options are similar to @option{-fpic} and @option{-fPIC}, but the
+generated position-independent code can be only linked into executables.
+Usually these options are used to compile code that will be linked using
+the @option{-pie} GCC option.
+
+@option{-fpie} and @option{-fPIE} both define the macros
+@code{__pie__} and @code{__PIE__}. The macros have the value 1
+for @option{-fpie} and 2 for @option{-fPIE}.
+
+@item -fno-plt
+@opindex fno-plt
+@opindex fplt
+Do not use the PLT for external function calls in position-independent code.
+Instead, load the callee address at call sites from the GOT and branch to it.
+This leads to more efficient code by eliminating PLT stubs and exposing
+GOT loads to optimizations. On architectures such as 32-bit x86 where
+PLT stubs expect the GOT pointer in a specific register, this gives more
+register allocation freedom to the compiler.
+Lazy binding requires use of the PLT;
+with @option{-fno-plt} all external symbols are resolved at load time.
+
+Alternatively, the function attribute @code{noplt} can be used to avoid calls
+through the PLT for specific external functions.
+
+In position-dependent code, a few targets also convert calls to
+functions that are marked to not use the PLT to use the GOT instead.
+
+@item -fno-jump-tables
+@opindex fno-jump-tables
+@opindex fjump-tables
+Do not use jump tables for switch statements even where it would be
+more efficient than other code generation strategies. This option is
+of use in conjunction with @option{-fpic} or @option{-fPIC} for
+building code that forms part of a dynamic linker and cannot
+reference the address of a jump table. On some targets, jump tables
+do not require a GOT and this option is not needed.
+
+@item -fno-bit-tests
+@opindex fno-bit-tests
+@opindex fbit-tests
+Do not use bit tests for switch statements even where it would be
+more efficient than other code generation strategies.
+
+@item -ffixed-@var{reg}
+@opindex ffixed
+Treat the register named @var{reg} as a fixed register; generated code
+should never refer to it (except perhaps as a stack pointer, frame
+pointer or in some other fixed role).
+
+@var{reg} must be the name of a register. The register names accepted
+are machine-specific and are defined in the @code{REGISTER_NAMES}
+macro in the machine description macro file.
+
+This flag does not have a negative form, because it specifies a
+three-way choice.
+
+@item -fcall-used-@var{reg}
+@opindex fcall-used
+Treat the register named @var{reg} as an allocable register that is
+clobbered by function calls. It may be allocated for temporaries or
+variables that do not live across a call. Functions compiled this way
+do not save and restore the register @var{reg}.
+
+It is an error to use this flag with the frame pointer or stack pointer.
+Use of this flag for other registers that have fixed pervasive roles in
+the machine's execution model produces disastrous results.
+
+This flag does not have a negative form, because it specifies a
+three-way choice.
+
+@item -fcall-saved-@var{reg}
+@opindex fcall-saved
+Treat the register named @var{reg} as an allocable register saved by
+functions. It may be allocated even for temporaries or variables that
+live across a call. Functions compiled this way save and restore
+the register @var{reg} if they use it.
+
+It is an error to use this flag with the frame pointer or stack pointer.
+Use of this flag for other registers that have fixed pervasive roles in
+the machine's execution model produces disastrous results.
+
+A different sort of disaster results from the use of this flag for
+a register in which function values may be returned.
+
+This flag does not have a negative form, because it specifies a
+three-way choice.
+
+@item -fpack-struct[=@var{n}]
+@opindex fpack-struct
+Without a value specified, pack all structure members together without
+holes. When a value is specified (which must be a small power of two), pack
+structure members according to this value, representing the maximum
+alignment (that is, objects with default alignment requirements larger than
+this are output potentially unaligned at the next fitting location.
+
+@strong{Warning:} the @option{-fpack-struct} switch causes GCC to generate
+code that is not binary compatible with code generated without that switch.
+Additionally, it makes the code suboptimal.
+Use it to conform to a non-default application binary interface.
+
+@item -fleading-underscore
+@opindex fleading-underscore
+This option and its counterpart, @option{-fno-leading-underscore}, forcibly
+change the way C symbols are represented in the object file. One use
+is to help link with legacy assembly code.
+
+@strong{Warning:} the @option{-fleading-underscore} switch causes GCC to
+generate code that is not binary compatible with code generated without that
+switch. Use it to conform to a non-default application binary interface.
+Not all targets provide complete support for this switch.
+
+@item -ftls-model=@var{model}
+@opindex ftls-model
+Alter the thread-local storage model to be used (@pxref{Thread-Local}).
+The @var{model} argument should be one of @samp{global-dynamic},
+@samp{local-dynamic}, @samp{initial-exec} or @samp{local-exec}.
+Note that the choice is subject to optimization: the compiler may use
+a more efficient model for symbols not visible outside of the translation
+unit, or if @option{-fpic} is not given on the command line.
+
+The default without @option{-fpic} is @samp{initial-exec}; with
+@option{-fpic} the default is @samp{global-dynamic}.
+
+@item -ftrampolines
+@opindex ftrampolines
+For targets that normally need trampolines for nested functions, always
+generate them instead of using descriptors. Otherwise, for targets that
+do not need them, like for example HP-PA or IA-64, do nothing.
+
+A trampoline is a small piece of code that is created at run time on the
+stack when the address of a nested function is taken, and is used to call
+the nested function indirectly. Therefore, it requires the stack to be
+made executable in order for the program to work properly.
+
+@option{-fno-trampolines} is enabled by default on a language by language
+basis to let the compiler avoid generating them, if it computes that this
+is safe, and replace them with descriptors. Descriptors are made up of data
+only, but the generated code must be prepared to deal with them. As of this
+writing, @option{-fno-trampolines} is enabled by default only for Ada.
+
+Moreover, code compiled with @option{-ftrampolines} and code compiled with
+@option{-fno-trampolines} are not binary compatible if nested functions are
+present. This option must therefore be used on a program-wide basis and be
+manipulated with extreme care.
+
+For languages other than Ada, the @code{-ftrampolines} and
+@code{-fno-trampolines} options currently have no effect, and
+trampolines are always generated on platforms that need them
+for nested functions.
+
+@item -fvisibility=@r{[}default@r{|}internal@r{|}hidden@r{|}protected@r{]}
+@opindex fvisibility
+Set the default ELF image symbol visibility to the specified option---all
+symbols are marked with this unless overridden within the code.
+Using this feature can very substantially improve linking and
+load times of shared object libraries, produce more optimized
+code, provide near-perfect API export and prevent symbol clashes.
+It is @strong{strongly} recommended that you use this in any shared objects
+you distribute.
+
+Despite the nomenclature, @samp{default} always means public; i.e.,
+available to be linked against from outside the shared object.
+@samp{protected} and @samp{internal} are pretty useless in real-world
+usage so the only other commonly used option is @samp{hidden}.
+The default if @option{-fvisibility} isn't specified is
+@samp{default}, i.e., make every symbol public.
+
+A good explanation of the benefits offered by ensuring ELF
+symbols have the correct visibility is given by ``How To Write
+Shared Libraries'' by Ulrich Drepper (which can be found at
+@w{@uref{https://www.akkadia.org/drepper/}})---however a superior
+solution made possible by this option to marking things hidden when
+the default is public is to make the default hidden and mark things
+public. This is the norm with DLLs on Windows and with @option{-fvisibility=hidden}
+and @code{__attribute__ ((visibility("default")))} instead of
+@code{__declspec(dllexport)} you get almost identical semantics with
+identical syntax. This is a great boon to those working with
+cross-platform projects.
+
+For those adding visibility support to existing code, you may find
+@code{#pragma GCC visibility} of use. This works by you enclosing
+the declarations you wish to set visibility for with (for example)
+@code{#pragma GCC visibility push(hidden)} and
+@code{#pragma GCC visibility pop}.
+Bear in mind that symbol visibility should be viewed @strong{as
+part of the API interface contract} and thus all new code should
+always specify visibility when it is not the default; i.e., declarations
+only for use within the local DSO should @strong{always} be marked explicitly
+as hidden as so to avoid PLT indirection overheads---making this
+abundantly clear also aids readability and self-documentation of the code.
+Note that due to ISO C++ specification requirements, @code{operator new} and
+@code{operator delete} must always be of default visibility.
+
+Be aware that headers from outside your project, in particular system
+headers and headers from any other library you use, may not be
+expecting to be compiled with visibility other than the default. You
+may need to explicitly say @code{#pragma GCC visibility push(default)}
+before including any such headers.
+
+@code{extern} declarations are not affected by @option{-fvisibility}, so
+a lot of code can be recompiled with @option{-fvisibility=hidden} with
+no modifications. However, this means that calls to @code{extern}
+functions with no explicit visibility use the PLT, so it is more
+effective to use @code{__attribute ((visibility))} and/or
+@code{#pragma GCC visibility} to tell the compiler which @code{extern}
+declarations should be treated as hidden.
+
+Note that @option{-fvisibility} does affect C++ vague linkage
+entities. This means that, for instance, an exception class that is
+be thrown between DSOs must be explicitly marked with default
+visibility so that the @samp{type_info} nodes are unified between
+the DSOs.
+
+An overview of these techniques, their benefits and how to use them
+is at @uref{https://gcc.gnu.org/@/wiki/@/Visibility}.
+
+@item -fstrict-volatile-bitfields
+@opindex fstrict-volatile-bitfields
+This option should be used if accesses to volatile bit-fields (or other
+structure fields, although the compiler usually honors those types
+anyway) should use a single access of the width of the
+field's type, aligned to a natural alignment if possible. For
+example, targets with memory-mapped peripheral registers might require
+all such accesses to be 16 bits wide; with this flag you can
+declare all peripheral bit-fields as @code{unsigned short} (assuming short
+is 16 bits on these targets) to force GCC to use 16-bit accesses
+instead of, perhaps, a more efficient 32-bit access.
+
+If this option is disabled, the compiler uses the most efficient
+instruction. In the previous example, that might be a 32-bit load
+instruction, even though that accesses bytes that do not contain
+any portion of the bit-field, or memory-mapped registers unrelated to
+the one being updated.
+
+In some cases, such as when the @code{packed} attribute is applied to a
+structure field, it may not be possible to access the field with a single
+read or write that is correctly aligned for the target machine. In this
+case GCC falls back to generating multiple accesses rather than code that
+will fault or truncate the result at run time.
+
+Note: Due to restrictions of the C/C++11 memory model, write accesses are
+not allowed to touch non bit-field members. It is therefore recommended
+to define all bits of the field's type as bit-field members.
+
+The default value of this option is determined by the application binary
+interface for the target processor.
+
+@item -fsync-libcalls
+@opindex fsync-libcalls
+This option controls whether any out-of-line instance of the @code{__sync}
+family of functions may be used to implement the C++11 @code{__atomic}
+family of functions.
+
+The default value of this option is enabled, thus the only useful form
+of the option is @option{-fno-sync-libcalls}. This option is used in
+the implementation of the @file{libatomic} runtime library.
+
+@end table
+
+@node Developer Options
+@section GCC Developer Options
+@cindex developer options
+@cindex debugging GCC
+@cindex debug dump options
+@cindex dump options
+@cindex compilation statistics
+
+This section describes command-line options that are primarily of
+interest to GCC developers, including options to support compiler
+testing and investigation of compiler bugs and compile-time
+performance problems. This includes options that produce debug dumps
+at various points in the compilation; that print statistics such as
+memory use and execution time; and that print information about GCC's
+configuration, such as where it searches for libraries. You should
+rarely need to use any of these options for ordinary compilation and
+linking tasks.
+
+Many developer options that cause GCC to dump output to a file take an
+optional @samp{=@var{filename}} suffix. You can specify @samp{stdout}
+or @samp{-} to dump to standard output, and @samp{stderr} for standard
+error.
+
+If @samp{=@var{filename}} is omitted, a default dump file name is
+constructed by concatenating the base dump file name, a pass number,
+phase letter, and pass name. The base dump file name is the name of
+output file produced by the compiler if explicitly specified and not
+an executable; otherwise it is the source file name.
+The pass number is determined by the order passes are registered with
+the compiler's pass manager.
+This is generally the same as the order of execution, but passes
+registered by plugins, target-specific passes, or passes that are
+otherwise registered late are numbered higher than the pass named
+@samp{final}, even if they are executed earlier. The phase letter is
+one of @samp{i} (inter-procedural analysis), @samp{l}
+(language-specific), @samp{r} (RTL), or @samp{t} (tree).
+The files are created in the directory of the output file.
+
+@table @gcctabopt
+
+@item -fcallgraph-info
+@itemx -fcallgraph-info=@var{MARKERS}
+@opindex fcallgraph-info
+Makes the compiler output callgraph information for the program, on a
+per-object-file basis. The information is generated in the common VCG
+format. It can be decorated with additional, per-node and/or per-edge
+information, if a list of comma-separated markers is additionally
+specified. When the @code{su} marker is specified, the callgraph is
+decorated with stack usage information; it is equivalent to
+@option{-fstack-usage}. When the @code{da} marker is specified, the
+callgraph is decorated with information about dynamically allocated
+objects.
+
+When compiling with @option{-flto}, no callgraph information is output
+along with the object file. At LTO link time, @option{-fcallgraph-info}
+may generate multiple callgraph information files next to intermediate
+LTO output files.
+
+@item -d@var{letters}
+@itemx -fdump-rtl-@var{pass}
+@itemx -fdump-rtl-@var{pass}=@var{filename}
+@opindex d
+@opindex fdump-rtl-@var{pass}
+Says to make debugging dumps during compilation at times specified by
+@var{letters}. This is used for debugging the RTL-based passes of the
+compiler.
+
+Some @option{-d@var{letters}} switches have different meaning when
+@option{-E} is used for preprocessing. @xref{Preprocessor Options},
+for information about preprocessor-specific dump options.
+
+Debug dumps can be enabled with a @option{-fdump-rtl} switch or some
+@option{-d} option @var{letters}. Here are the possible
+letters for use in @var{pass} and @var{letters}, and their meanings:
+
+@table @gcctabopt
+
+@item -fdump-rtl-alignments
+@opindex fdump-rtl-alignments
+Dump after branch alignments have been computed.
+
+@item -fdump-rtl-asmcons
+@opindex fdump-rtl-asmcons
+Dump after fixing rtl statements that have unsatisfied in/out constraints.
+
+@item -fdump-rtl-auto_inc_dec
+@opindex fdump-rtl-auto_inc_dec
+Dump after auto-inc-dec discovery. This pass is only run on
+architectures that have auto inc or auto dec instructions.
+
+@item -fdump-rtl-barriers
+@opindex fdump-rtl-barriers
+Dump after cleaning up the barrier instructions.
+
+@item -fdump-rtl-bbpart
+@opindex fdump-rtl-bbpart
+Dump after partitioning hot and cold basic blocks.
+
+@item -fdump-rtl-bbro
+@opindex fdump-rtl-bbro
+Dump after block reordering.
+
+@item -fdump-rtl-btl1
+@itemx -fdump-rtl-btl2
+@opindex fdump-rtl-btl2
+@opindex fdump-rtl-btl2
+@option{-fdump-rtl-btl1} and @option{-fdump-rtl-btl2} enable dumping
+after the two branch
+target load optimization passes.
+
+@item -fdump-rtl-bypass
+@opindex fdump-rtl-bypass
+Dump after jump bypassing and control flow optimizations.
+
+@item -fdump-rtl-combine
+@opindex fdump-rtl-combine
+Dump after the RTL instruction combination pass.
+
+@item -fdump-rtl-compgotos
+@opindex fdump-rtl-compgotos
+Dump after duplicating the computed gotos.
+
+@item -fdump-rtl-ce1
+@itemx -fdump-rtl-ce2
+@itemx -fdump-rtl-ce3
+@opindex fdump-rtl-ce1
+@opindex fdump-rtl-ce2
+@opindex fdump-rtl-ce3
+@option{-fdump-rtl-ce1}, @option{-fdump-rtl-ce2}, and
+@option{-fdump-rtl-ce3} enable dumping after the three
+if conversion passes.
+
+@item -fdump-rtl-cprop_hardreg
+@opindex fdump-rtl-cprop_hardreg
+Dump after hard register copy propagation.
+
+@item -fdump-rtl-csa
+@opindex fdump-rtl-csa
+Dump after combining stack adjustments.
+
+@item -fdump-rtl-cse1
+@itemx -fdump-rtl-cse2
+@opindex fdump-rtl-cse1
+@opindex fdump-rtl-cse2
+@option{-fdump-rtl-cse1} and @option{-fdump-rtl-cse2} enable dumping after
+the two common subexpression elimination passes.
+
+@item -fdump-rtl-dce
+@opindex fdump-rtl-dce
+Dump after the standalone dead code elimination passes.
+
+@item -fdump-rtl-dbr
+@opindex fdump-rtl-dbr
+Dump after delayed branch scheduling.
+
+@item -fdump-rtl-dce1
+@itemx -fdump-rtl-dce2
+@opindex fdump-rtl-dce1
+@opindex fdump-rtl-dce2
+@option{-fdump-rtl-dce1} and @option{-fdump-rtl-dce2} enable dumping after
+the two dead store elimination passes.
+
+@item -fdump-rtl-eh
+@opindex fdump-rtl-eh
+Dump after finalization of EH handling code.
+
+@item -fdump-rtl-eh_ranges
+@opindex fdump-rtl-eh_ranges
+Dump after conversion of EH handling range regions.
+
+@item -fdump-rtl-expand
+@opindex fdump-rtl-expand
+Dump after RTL generation.
+
+@item -fdump-rtl-fwprop1
+@itemx -fdump-rtl-fwprop2
+@opindex fdump-rtl-fwprop1
+@opindex fdump-rtl-fwprop2
+@option{-fdump-rtl-fwprop1} and @option{-fdump-rtl-fwprop2} enable
+dumping after the two forward propagation passes.
+
+@item -fdump-rtl-gcse1
+@itemx -fdump-rtl-gcse2
+@opindex fdump-rtl-gcse1
+@opindex fdump-rtl-gcse2
+@option{-fdump-rtl-gcse1} and @option{-fdump-rtl-gcse2} enable dumping
+after global common subexpression elimination.
+
+@item -fdump-rtl-init-regs
+@opindex fdump-rtl-init-regs
+Dump after the initialization of the registers.
+
+@item -fdump-rtl-initvals
+@opindex fdump-rtl-initvals
+Dump after the computation of the initial value sets.
+
+@item -fdump-rtl-into_cfglayout
+@opindex fdump-rtl-into_cfglayout
+Dump after converting to cfglayout mode.
+
+@item -fdump-rtl-ira
+@opindex fdump-rtl-ira
+Dump after iterated register allocation.
+
+@item -fdump-rtl-jump
+@opindex fdump-rtl-jump
+Dump after the second jump optimization.
+
+@item -fdump-rtl-loop2
+@opindex fdump-rtl-loop2
+@option{-fdump-rtl-loop2} enables dumping after the rtl
+loop optimization passes.
+
+@item -fdump-rtl-mach
+@opindex fdump-rtl-mach
+Dump after performing the machine dependent reorganization pass, if that
+pass exists.
+
+@item -fdump-rtl-mode_sw
+@opindex fdump-rtl-mode_sw
+Dump after removing redundant mode switches.
+
+@item -fdump-rtl-rnreg
+@opindex fdump-rtl-rnreg
+Dump after register renumbering.
+
+@item -fdump-rtl-outof_cfglayout
+@opindex fdump-rtl-outof_cfglayout
+Dump after converting from cfglayout mode.
+
+@item -fdump-rtl-peephole2
+@opindex fdump-rtl-peephole2
+Dump after the peephole pass.
+
+@item -fdump-rtl-postreload
+@opindex fdump-rtl-postreload
+Dump after post-reload optimizations.
+
+@item -fdump-rtl-pro_and_epilogue
+@opindex fdump-rtl-pro_and_epilogue
+Dump after generating the function prologues and epilogues.
+
+@item -fdump-rtl-sched1
+@itemx -fdump-rtl-sched2
+@opindex fdump-rtl-sched1
+@opindex fdump-rtl-sched2
+@option{-fdump-rtl-sched1} and @option{-fdump-rtl-sched2} enable dumping
+after the basic block scheduling passes.
+
+@item -fdump-rtl-ree
+@opindex fdump-rtl-ree
+Dump after sign/zero extension elimination.
+
+@item -fdump-rtl-seqabstr
+@opindex fdump-rtl-seqabstr
+Dump after common sequence discovery.
+
+@item -fdump-rtl-shorten
+@opindex fdump-rtl-shorten
+Dump after shortening branches.
+
+@item -fdump-rtl-sibling
+@opindex fdump-rtl-sibling
+Dump after sibling call optimizations.
+
+@item -fdump-rtl-split1
+@itemx -fdump-rtl-split2
+@itemx -fdump-rtl-split3
+@itemx -fdump-rtl-split4
+@itemx -fdump-rtl-split5
+@opindex fdump-rtl-split1
+@opindex fdump-rtl-split2
+@opindex fdump-rtl-split3
+@opindex fdump-rtl-split4
+@opindex fdump-rtl-split5
+These options enable dumping after five rounds of
+instruction splitting.
+
+@item -fdump-rtl-sms
+@opindex fdump-rtl-sms
+Dump after modulo scheduling. This pass is only run on some
+architectures.
+
+@item -fdump-rtl-stack
+@opindex fdump-rtl-stack
+Dump after conversion from GCC's ``flat register file'' registers to the
+x87's stack-like registers. This pass is only run on x86 variants.
+
+@item -fdump-rtl-subreg1
+@itemx -fdump-rtl-subreg2
+@opindex fdump-rtl-subreg1
+@opindex fdump-rtl-subreg2
+@option{-fdump-rtl-subreg1} and @option{-fdump-rtl-subreg2} enable dumping after
+the two subreg expansion passes.
+
+@item -fdump-rtl-unshare
+@opindex fdump-rtl-unshare
+Dump after all rtl has been unshared.
+
+@item -fdump-rtl-vartrack
+@opindex fdump-rtl-vartrack
+Dump after variable tracking.
+
+@item -fdump-rtl-vregs
+@opindex fdump-rtl-vregs
+Dump after converting virtual registers to hard registers.
+
+@item -fdump-rtl-web
+@opindex fdump-rtl-web
+Dump after live range splitting.
+
+@item -fdump-rtl-regclass
+@itemx -fdump-rtl-subregs_of_mode_init
+@itemx -fdump-rtl-subregs_of_mode_finish
+@itemx -fdump-rtl-dfinit
+@itemx -fdump-rtl-dfinish
+@opindex fdump-rtl-regclass
+@opindex fdump-rtl-subregs_of_mode_init
+@opindex fdump-rtl-subregs_of_mode_finish
+@opindex fdump-rtl-dfinit
+@opindex fdump-rtl-dfinish
+These dumps are defined but always produce empty files.
+
+@item -da
+@itemx -fdump-rtl-all
+@opindex da
+@opindex fdump-rtl-all
+Produce all the dumps listed above.
+
+@item -dA
+@opindex dA
+Annotate the assembler output with miscellaneous debugging information.
+
+@item -dD
+@opindex dD
+Dump all macro definitions, at the end of preprocessing, in addition to
+normal output.
+
+@item -dH
+@opindex dH
+Produce a core dump whenever an error occurs.
+
+@item -dp
+@opindex dp
+Annotate the assembler output with a comment indicating which
+pattern and alternative is used. The length and cost of each instruction are
+also printed.
+
+@item -dP
+@opindex dP
+Dump the RTL in the assembler output as a comment before each instruction.
+Also turns on @option{-dp} annotation.
+
+@item -dx
+@opindex dx
+Just generate RTL for a function instead of compiling it. Usually used
+with @option{-fdump-rtl-expand}.
+@end table
+
+@item -fdump-debug
+@opindex fdump-debug
+Dump debugging information generated during the debug
+generation phase.
+
+@item -fdump-earlydebug
+@opindex fdump-earlydebug
+Dump debugging information generated during the early debug
+generation phase.
+
+@item -fdump-noaddr
+@opindex fdump-noaddr
+When doing debugging dumps, suppress address output. This makes it more
+feasible to use diff on debugging dumps for compiler invocations with
+different compiler binaries and/or different
+text / bss / data / heap / stack / dso start locations.
+
+@item -freport-bug
+@opindex freport-bug
+Collect and dump debug information into a temporary file if an
+internal compiler error (ICE) occurs.
+
+@item -fdump-unnumbered
+@opindex fdump-unnumbered
+When doing debugging dumps, suppress instruction numbers and address output.
+This makes it more feasible to use diff on debugging dumps for compiler
+invocations with different options, in particular with and without
+@option{-g}.
+
+@item -fdump-unnumbered-links
+@opindex fdump-unnumbered-links
+When doing debugging dumps (see @option{-d} option above), suppress
+instruction numbers for the links to the previous and next instructions
+in a sequence.
+
+@item -fdump-ipa-@var{switch}
+@itemx -fdump-ipa-@var{switch}-@var{options}
+@opindex fdump-ipa
+Control the dumping at various stages of inter-procedural analysis
+language tree to a file. The file name is generated by appending a
+switch specific suffix to the source file name, and the file is created
+in the same directory as the output file. The following dumps are
+possible:
+
+@table @samp
+@item all
+Enables all inter-procedural analysis dumps.
+
+@item cgraph
+Dumps information about call-graph optimization, unused function removal,
+and inlining decisions.
+
+@item inline
+Dump after function inlining.
+
+@end table
+
+Additionally, the options @option{-optimized}, @option{-missed},
+@option{-note}, and @option{-all} can be provided, with the same meaning
+as for @option{-fopt-info}, defaulting to @option{-optimized}.
+
+For example, @option{-fdump-ipa-inline-optimized-missed} will emit
+information on callsites that were inlined, along with callsites
+that were not inlined.
+
+By default, the dump will contain messages about successful
+optimizations (equivalent to @option{-optimized}) together with
+low-level details about the analysis.
+
+@item -fdump-lang
+@opindex fdump-lang
+Dump language-specific information. The file name is made by appending
+@file{.lang} to the source file name.
+
+@item -fdump-lang-all
+@itemx -fdump-lang-@var{switch}
+@itemx -fdump-lang-@var{switch}-@var{options}
+@itemx -fdump-lang-@var{switch}-@var{options}=@var{filename}
+@opindex fdump-lang-all
+@opindex fdump-lang
+Control the dumping of language-specific information. The @var{options}
+and @var{filename} portions behave as described in the
+@option{-fdump-tree} option. The following @var{switch} values are
+accepted:
+
+@table @samp
+@item all
+
+Enable all language-specific dumps.
+
+@item class
+Dump class hierarchy information. Virtual table information is emitted
+unless '@option{slim}' is specified. This option is applicable to C++ only.
+
+@item module
+Dump module information. Options @option{lineno} (locations),
+@option{graph} (reachability), @option{blocks} (clusters),
+@option{uid} (serialization), @option{alias} (mergeable),
+@option{asmname} (Elrond), @option{eh} (mapper) & @option{vops}
+(macros) may provide additional information. This option is
+applicable to C++ only.
+
+@item raw
+Dump the raw internal tree data. This option is applicable to C++ only.
+
+@end table
+
+@item -fdump-passes
+@opindex fdump-passes
+Print on @file{stderr} the list of optimization passes that are turned
+on and off by the current command-line options.
+
+@item -fdump-statistics-@var{option}
+@opindex fdump-statistics
+Enable and control dumping of pass statistics in a separate file. The
+file name is generated by appending a suffix ending in
+@samp{.statistics} to the source file name, and the file is created in
+the same directory as the output file. If the @samp{-@var{option}}
+form is used, @samp{-stats} causes counters to be summed over the
+whole compilation unit while @samp{-details} dumps every event as
+the passes generate them. The default with no option is to sum
+counters for each function compiled.
+
+@item -fdump-tree-all
+@itemx -fdump-tree-@var{switch}
+@itemx -fdump-tree-@var{switch}-@var{options}
+@itemx -fdump-tree-@var{switch}-@var{options}=@var{filename}
+@opindex fdump-tree-all
+@opindex fdump-tree
+Control the dumping at various stages of processing the intermediate
+language tree to a file. If the @samp{-@var{options}}
+form is used, @var{options} is a list of @samp{-} separated options
+which control the details of the dump. Not all options are applicable
+to all dumps; those that are not meaningful are ignored. The
+following options are available
+
+@table @samp
+@item address
+Print the address of each node. Usually this is not meaningful as it
+changes according to the environment and source file. Its primary use
+is for tying up a dump file with a debug environment.
+@item asmname
+If @code{DECL_ASSEMBLER_NAME} has been set for a given decl, use that
+in the dump instead of @code{DECL_NAME}. Its primary use is ease of
+use working backward from mangled names in the assembly file.
+@item slim
+When dumping front-end intermediate representations, inhibit dumping
+of members of a scope or body of a function merely because that scope
+has been reached. Only dump such items when they are directly reachable
+by some other path.
+
+When dumping pretty-printed trees, this option inhibits dumping the
+bodies of control structures.
+
+When dumping RTL, print the RTL in slim (condensed) form instead of
+the default LISP-like representation.
+@item raw
+Print a raw representation of the tree. By default, trees are
+pretty-printed into a C-like representation.
+@item details
+Enable more detailed dumps (not honored by every dump option). Also
+include information from the optimization passes.
+@item stats
+Enable dumping various statistics about the pass (not honored by every dump
+option).
+@item blocks
+Enable showing basic block boundaries (disabled in raw dumps).
+@item graph
+For each of the other indicated dump files (@option{-fdump-rtl-@var{pass}}),
+dump a representation of the control flow graph suitable for viewing with
+GraphViz to @file{@var{file}.@var{passid}.@var{pass}.dot}. Each function in
+the file is pretty-printed as a subgraph, so that GraphViz can render them
+all in a single plot.
+
+This option currently only works for RTL dumps, and the RTL is always
+dumped in slim form.
+@item vops
+Enable showing virtual operands for every statement.
+@item lineno
+Enable showing line numbers for statements.
+@item uid
+Enable showing the unique ID (@code{DECL_UID}) for each variable.
+@item verbose
+Enable showing the tree dump for each statement.
+@item eh
+Enable showing the EH region number holding each statement.
+@item scev
+Enable showing scalar evolution analysis details.
+@item optimized
+Enable showing optimization information (only available in certain
+passes).
+@item missed
+Enable showing missed optimization information (only available in certain
+passes).
+@item note
+Enable other detailed optimization information (only available in
+certain passes).
+@item all
+Turn on all options, except @option{raw}, @option{slim}, @option{verbose}
+and @option{lineno}.
+@item optall
+Turn on all optimization options, i.e., @option{optimized},
+@option{missed}, and @option{note}.
+@end table
+
+To determine what tree dumps are available or find the dump for a pass
+of interest follow the steps below.
+
+@enumerate
+@item
+Invoke GCC with @option{-fdump-passes} and in the @file{stderr} output
+look for a code that corresponds to the pass you are interested in.
+For example, the codes @code{tree-evrp}, @code{tree-vrp1}, and
+@code{tree-vrp2} correspond to the three Value Range Propagation passes.
+The number at the end distinguishes distinct invocations of the same pass.
+@item
+To enable the creation of the dump file, append the pass code to
+the @option{-fdump-} option prefix and invoke GCC with it. For example,
+to enable the dump from the Early Value Range Propagation pass, invoke
+GCC with the @option{-fdump-tree-evrp} option. Optionally, you may
+specify the name of the dump file. If you don't specify one, GCC
+creates as described below.
+@item
+Find the pass dump in a file whose name is composed of three components
+separated by a period: the name of the source file GCC was invoked to
+compile, a numeric suffix indicating the pass number followed by the
+letter @samp{t} for tree passes (and the letter @samp{r} for RTL passes),
+and finally the pass code. For example, the Early VRP pass dump might
+be in a file named @file{myfile.c.038t.evrp} in the current working
+directory. Note that the numeric codes are not stable and may change
+from one version of GCC to another.
+@end enumerate
+
+@item -fopt-info
+@itemx -fopt-info-@var{options}
+@itemx -fopt-info-@var{options}=@var{filename}
+@opindex fopt-info
+Controls optimization dumps from various optimization passes. If the
+@samp{-@var{options}} form is used, @var{options} is a list of
+@samp{-} separated option keywords to select the dump details and
+optimizations.
+
+The @var{options} can be divided into three groups:
+@enumerate
+@item
+options describing what kinds of messages should be emitted,
+@item
+options describing the verbosity of the dump, and
+@item
+options describing which optimizations should be included.
+@end enumerate
+The options from each group can be freely mixed as they are
+non-overlapping. However, in case of any conflicts,
+the later options override the earlier options on the command
+line.
+
+The following options control which kinds of messages should be emitted:
+
+@table @samp
+@item optimized
+Print information when an optimization is successfully applied. It is
+up to a pass to decide which information is relevant. For example, the
+vectorizer passes print the source location of loops which are
+successfully vectorized.
+@item missed
+Print information about missed optimizations. Individual passes
+control which information to include in the output.
+@item note
+Print verbose information about optimizations, such as certain
+transformations, more detailed messages about decisions etc.
+@item all
+Print detailed optimization information. This includes
+@samp{optimized}, @samp{missed}, and @samp{note}.
+@end table
+
+The following option controls the dump verbosity:
+
+@table @samp
+@item internals
+By default, only ``high-level'' messages are emitted. This option enables
+additional, more detailed, messages, which are likely to only be of interest
+to GCC developers.
+@end table
+
+One or more of the following option keywords can be used to describe a
+group of optimizations:
+
+@table @samp
+@item ipa
+Enable dumps from all interprocedural optimizations.
+@item loop
+Enable dumps from all loop optimizations.
+@item inline
+Enable dumps from all inlining optimizations.
+@item omp
+Enable dumps from all OMP (Offloading and Multi Processing) optimizations.
+@item vec
+Enable dumps from all vectorization optimizations.
+@item optall
+Enable dumps from all optimizations. This is a superset of
+the optimization groups listed above.
+@end table
+
+If @var{options} is
+omitted, it defaults to @samp{optimized-optall}, which means to dump messages
+about successful optimizations from all the passes, omitting messages
+that are treated as ``internals''.
+
+If the @var{filename} is provided, then the dumps from all the
+applicable optimizations are concatenated into the @var{filename}.
+Otherwise the dump is output onto @file{stderr}. Though multiple
+@option{-fopt-info} options are accepted, only one of them can include
+a @var{filename}. If other filenames are provided then all but the
+first such option are ignored.
+
+Note that the output @var{filename} is overwritten
+in case of multiple translation units. If a combined output from
+multiple translation units is desired, @file{stderr} should be used
+instead.
+
+In the following example, the optimization info is output to
+@file{stderr}:
+
+@smallexample
+gcc -O3 -fopt-info
+@end smallexample
+
+This example:
+@smallexample
+gcc -O3 -fopt-info-missed=missed.all
+@end smallexample
+
+@noindent
+outputs missed optimization report from all the passes into
+@file{missed.all}, and this one:
+
+@smallexample
+gcc -O2 -ftree-vectorize -fopt-info-vec-missed
+@end smallexample
+
+@noindent
+prints information about missed optimization opportunities from
+vectorization passes on @file{stderr}.
+Note that @option{-fopt-info-vec-missed} is equivalent to
+@option{-fopt-info-missed-vec}. The order of the optimization group
+names and message types listed after @option{-fopt-info} does not matter.
+
+As another example,
+@smallexample
+gcc -O3 -fopt-info-inline-optimized-missed=inline.txt
+@end smallexample
+
+@noindent
+outputs information about missed optimizations as well as
+optimized locations from all the inlining passes into
+@file{inline.txt}.
+
+Finally, consider:
+
+@smallexample
+gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt
+@end smallexample
+
+@noindent
+Here the two output filenames @file{vec.miss} and @file{loop.opt} are
+in conflict since only one output file is allowed. In this case, only
+the first option takes effect and the subsequent options are
+ignored. Thus only @file{vec.miss} is produced which contains
+dumps from the vectorizer about missed opportunities.
+
+@item -fsave-optimization-record
+@opindex fsave-optimization-record
+Write a SRCFILE.opt-record.json.gz file detailing what optimizations
+were performed, for those optimizations that support @option{-fopt-info}.
+
+This option is experimental and the format of the data within the
+compressed JSON file is subject to change.
+
+It is roughly equivalent to a machine-readable version of
+@option{-fopt-info-all}, as a collection of messages with source file,
+line number and column number, with the following additional data for
+each message:
+
+@itemize @bullet
+
+@item
+the execution count of the code being optimized, along with metadata about
+whether this was from actual profile data, or just an estimate, allowing
+consumers to prioritize messages by code hotness,
+
+@item
+the function name of the code being optimized, where applicable,
+
+@item
+the ``inlining chain'' for the code being optimized, so that when
+a function is inlined into several different places (which might
+themselves be inlined), the reader can distinguish between the copies,
+
+@item
+objects identifying those parts of the message that refer to expressions,
+statements or symbol-table nodes, which of these categories they are, and,
+when available, their source code location,
+
+@item
+the GCC pass that emitted the message, and
+
+@item
+the location in GCC's own code from which the message was emitted
+
+@end itemize
+
+Additionally, some messages are logically nested within other
+messages, reflecting implementation details of the optimization
+passes.
+
+@item -fsched-verbose=@var{n}
+@opindex fsched-verbose
+On targets that use instruction scheduling, this option controls the
+amount of debugging output the scheduler prints to the dump files.
+
+For @var{n} greater than zero, @option{-fsched-verbose} outputs the
+same information as @option{-fdump-rtl-sched1} and @option{-fdump-rtl-sched2}.
+For @var{n} greater than one, it also output basic block probabilities,
+detailed ready list information and unit/insn info. For @var{n} greater
+than two, it includes RTL at abort point, control-flow and regions info.
+And for @var{n} over four, @option{-fsched-verbose} also includes
+dependence info.
+
+
+
+@item -fenable-@var{kind}-@var{pass}
+@itemx -fdisable-@var{kind}-@var{pass}=@var{range-list}
+@opindex fdisable-
+@opindex fenable-
+
+This is a set of options that are used to explicitly disable/enable
+optimization passes. These options are intended for use for debugging GCC.
+Compiler users should use regular options for enabling/disabling
+passes instead.
+
+@table @gcctabopt
+
+@item -fdisable-ipa-@var{pass}
+Disable IPA pass @var{pass}. @var{pass} is the pass name. If the same pass is
+statically invoked in the compiler multiple times, the pass name should be
+appended with a sequential number starting from 1.
+
+@item -fdisable-rtl-@var{pass}
+@itemx -fdisable-rtl-@var{pass}=@var{range-list}
+Disable RTL pass @var{pass}. @var{pass} is the pass name. If the same pass is
+statically invoked in the compiler multiple times, the pass name should be
+appended with a sequential number starting from 1. @var{range-list} is a
+comma-separated list of function ranges or assembler names. Each range is a number
+pair separated by a colon. The range is inclusive in both ends. If the range
+is trivial, the number pair can be simplified as a single number. If the
+function's call graph node's @var{uid} falls within one of the specified ranges,
+the @var{pass} is disabled for that function. The @var{uid} is shown in the
+function header of a dump file, and the pass names can be dumped by using
+option @option{-fdump-passes}.
+
+@item -fdisable-tree-@var{pass}
+@itemx -fdisable-tree-@var{pass}=@var{range-list}
+Disable tree pass @var{pass}. See @option{-fdisable-rtl} for the description of
+option arguments.
+
+@item -fenable-ipa-@var{pass}
+Enable IPA pass @var{pass}. @var{pass} is the pass name. If the same pass is
+statically invoked in the compiler multiple times, the pass name should be
+appended with a sequential number starting from 1.
+
+@item -fenable-rtl-@var{pass}
+@itemx -fenable-rtl-@var{pass}=@var{range-list}
+Enable RTL pass @var{pass}. See @option{-fdisable-rtl} for option argument
+description and examples.
+
+@item -fenable-tree-@var{pass}
+@itemx -fenable-tree-@var{pass}=@var{range-list}
+Enable tree pass @var{pass}. See @option{-fdisable-rtl} for the description
+of option arguments.
+
+@end table
+
+Here are some examples showing uses of these options.
+
+@smallexample
+
+# disable ccp1 for all functions
+ -fdisable-tree-ccp1
+# disable complete unroll for function whose cgraph node uid is 1
+ -fenable-tree-cunroll=1
+# disable gcse2 for functions at the following ranges [1,1],
+# [300,400], and [400,1000]
+# disable gcse2 for functions foo and foo2
+ -fdisable-rtl-gcse2=foo,foo2
+# disable early inlining
+ -fdisable-tree-einline
+# disable ipa inlining
+ -fdisable-ipa-inline
+# enable tree full unroll
+ -fenable-tree-unroll
+
+@end smallexample
+
+@item -fchecking
+@itemx -fchecking=@var{n}
+@opindex fchecking
+@opindex fno-checking
+Enable internal consistency checking. The default depends on
+the compiler configuration. @option{-fchecking=2} enables further
+internal consistency checking that might affect code generation.
+
+@item -frandom-seed=@var{string}
+@opindex frandom-seed
+This option provides a seed that GCC uses in place of
+random numbers in generating certain symbol names
+that have to be different in every compiled file. It is also used to
+place unique stamps in coverage data files and the object files that
+produce them. You can use the @option{-frandom-seed} option to produce
+reproducibly identical object files.
+
+The @var{string} can either be a number (decimal, octal or hex) or an
+arbitrary string (in which case it's converted to a number by
+computing CRC32).
+
+The @var{string} should be different for every file you compile.
+
+@item -save-temps
+@opindex save-temps
+Store the usual ``temporary'' intermediate files permanently; name them
+as auxiliary output files, as specified described under
+@option{-dumpbase} and @option{-dumpdir}.
+
+When used in combination with the @option{-x} command-line option,
+@option{-save-temps} is sensible enough to avoid overwriting an
+input source file with the same extension as an intermediate file.
+The corresponding intermediate file may be obtained by renaming the
+source file before using @option{-save-temps}.
+
+@item -save-temps=cwd
+@opindex save-temps=cwd
+Equivalent to @option{-save-temps -dumpdir ./}.
+
+@item -save-temps=obj
+@opindex save-temps=obj
+Equivalent to @option{-save-temps -dumpdir @file{outdir/}}, where
+@file{outdir/} is the directory of the output file specified after the
+@option{-o} option, including any directory separators. If the
+@option{-o} option is not used, the @option{-save-temps=obj} switch
+behaves like @option{-save-temps=cwd}.
+
+@item -time@r{[}=@var{file}@r{]}
+@opindex time
+Report the CPU time taken by each subprocess in the compilation
+sequence. For C source files, this is the compiler proper and assembler
+(plus the linker if linking is done).
+
+Without the specification of an output file, the output looks like this:
+
+@smallexample
+# cc1 0.12 0.01
+# as 0.00 0.01
+@end smallexample
+
+The first number on each line is the ``user time'', that is time spent
+executing the program itself. The second number is ``system time'',
+time spent executing operating system routines on behalf of the program.
+Both numbers are in seconds.
+
+With the specification of an output file, the output is appended to the
+named file, and it looks like this:
+
+@smallexample
+0.12 0.01 cc1 @var{options}
+0.00 0.01 as @var{options}
+@end smallexample
+
+The ``user time'' and the ``system time'' are moved before the program
+name, and the options passed to the program are displayed, so that one
+can later tell what file was being compiled, and with which options.
+
+@item -fdump-final-insns@r{[}=@var{file}@r{]}
+@opindex fdump-final-insns
+Dump the final internal representation (RTL) to @var{file}. If the
+optional argument is omitted (or if @var{file} is @code{.}), the name
+of the dump file is determined by appending @code{.gkd} to the
+dump base name, see @option{-dumpbase}.
+
+@item -fcompare-debug@r{[}=@var{opts}@r{]}
+@opindex fcompare-debug
+@opindex fno-compare-debug
+If no error occurs during compilation, run the compiler a second time,
+adding @var{opts} and @option{-fcompare-debug-second} to the arguments
+passed to the second compilation. Dump the final internal
+representation in both compilations, and print an error if they differ.
+
+If the equal sign is omitted, the default @option{-gtoggle} is used.
+
+The environment variable @env{GCC_COMPARE_DEBUG}, if defined, non-empty
+and nonzero, implicitly enables @option{-fcompare-debug}. If
+@env{GCC_COMPARE_DEBUG} is defined to a string starting with a dash,
+then it is used for @var{opts}, otherwise the default @option{-gtoggle}
+is used.
+
+@option{-fcompare-debug=}, with the equal sign but without @var{opts},
+is equivalent to @option{-fno-compare-debug}, which disables the dumping
+of the final representation and the second compilation, preventing even
+@env{GCC_COMPARE_DEBUG} from taking effect.
+
+To verify full coverage during @option{-fcompare-debug} testing, set
+@env{GCC_COMPARE_DEBUG} to say @option{-fcompare-debug-not-overridden},
+which GCC rejects as an invalid option in any actual compilation
+(rather than preprocessing, assembly or linking). To get just a
+warning, setting @env{GCC_COMPARE_DEBUG} to @samp{-w%n-fcompare-debug
+not overridden} will do.
+
+@item -fcompare-debug-second
+@opindex fcompare-debug-second
+This option is implicitly passed to the compiler for the second
+compilation requested by @option{-fcompare-debug}, along with options to
+silence warnings, and omitting other options that would cause the compiler
+to produce output to files or to standard output as a side effect. Dump
+files and preserved temporary files are renamed so as to contain the
+@code{.gk} additional extension during the second compilation, to avoid
+overwriting those generated by the first.
+
+When this option is passed to the compiler driver, it causes the
+@emph{first} compilation to be skipped, which makes it useful for little
+other than debugging the compiler proper.
+
+@item -gtoggle
+@opindex gtoggle
+Turn off generation of debug info, if leaving out this option
+generates it, or turn it on at level 2 otherwise. The position of this
+argument in the command line does not matter; it takes effect after all
+other options are processed, and it does so only once, no matter how
+many times it is given. This is mainly intended to be used with
+@option{-fcompare-debug}.
+
+@item -fvar-tracking-assignments-toggle
+@opindex fvar-tracking-assignments-toggle
+@opindex fno-var-tracking-assignments-toggle
+Toggle @option{-fvar-tracking-assignments}, in the same way that
+@option{-gtoggle} toggles @option{-g}.
+
+@item -Q
+@opindex Q
+Makes the compiler print out each function name as it is compiled, and
+print some statistics about each pass when it finishes.
+
+@item -ftime-report
+@opindex ftime-report
+Makes the compiler print some statistics about the time consumed by each
+pass when it finishes.
+
+@item -ftime-report-details
+@opindex ftime-report-details
+Record the time consumed by infrastructure parts separately for each pass.
+
+@item -fira-verbose=@var{n}
+@opindex fira-verbose
+Control the verbosity of the dump file for the integrated register allocator.
+The default value is 5. If the value @var{n} is greater or equal to 10,
+the dump output is sent to stderr using the same format as @var{n} minus 10.
+
+@item -flto-report
+@opindex flto-report
+Prints a report with internal details on the workings of the link-time
+optimizer. The contents of this report vary from version to version.
+It is meant to be useful to GCC developers when processing object
+files in LTO mode (via @option{-flto}).
+
+Disabled by default.
+
+@item -flto-report-wpa
+@opindex flto-report-wpa
+Like @option{-flto-report}, but only print for the WPA phase of link-time
+optimization.
+
+@item -fmem-report
+@opindex fmem-report
+Makes the compiler print some statistics about permanent memory
+allocation when it finishes.
+
+@item -fmem-report-wpa
+@opindex fmem-report-wpa
+Makes the compiler print some statistics about permanent memory
+allocation for the WPA phase only.
+
+@item -fpre-ipa-mem-report
+@opindex fpre-ipa-mem-report
+@item -fpost-ipa-mem-report
+@opindex fpost-ipa-mem-report
+Makes the compiler print some statistics about permanent memory
+allocation before or after interprocedural optimization.
+
+@item -fmultiflags
+@opindex fmultiflags
+This option enables multilib-aware @code{TFLAGS} to be used to build
+target libraries with options different from those the compiler is
+configured to use by default, through the use of specs (@xref{Spec
+Files}) set up by compiler internals, by the target, or by builders at
+configure time.
+
+Like @code{TFLAGS}, this allows the target libraries to be built for
+portable baseline environments, while the compiler defaults to more
+demanding ones. That's useful because users can easily override the
+defaults the compiler is configured to use to build their own programs,
+if the defaults are not ideal for their target environment, whereas
+rebuilding the runtime libraries is usually not as easy or desirable.
+
+Unlike @code{TFLAGS}, the use of specs enables different flags to be
+selected for different multilibs. The way to accomplish that is to
+build with @samp{make TFLAGS=-fmultiflags}, after configuring
+@samp{--with-specs=%@{fmultiflags:...@}}.
+
+This option is discarded by the driver once it's done processing driver
+self spec.
+
+It is also useful to check that @code{TFLAGS} are being used to build
+all target libraries, by configuring a non-bootstrap compiler
+@samp{--with-specs='%@{!fmultiflags:%emissing TFLAGS@}'} and building
+the compiler and target libraries.
+
+@item -fprofile-report
+@opindex fprofile-report
+Makes the compiler print some statistics about consistency of the
+(estimated) profile and effect of individual passes.
+
+@item -fstack-usage
+@opindex fstack-usage
+Makes the compiler output stack usage information for the program, on a
+per-function basis. The filename for the dump is made by appending
+@file{.su} to the @var{auxname}. @var{auxname} is generated from the name of
+the output file, if explicitly specified and it is not an executable,
+otherwise it is the basename of the source file. An entry is made up
+of three fields:
+
+@itemize
+@item
+The name of the function.
+@item
+A number of bytes.
+@item
+One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
+@end itemize
+
+The qualifier @code{static} means that the function manipulates the stack
+statically: a fixed number of bytes are allocated for the frame on function
+entry and released on function exit; no stack adjustments are otherwise made
+in the function. The second field is this fixed number of bytes.
+
+The qualifier @code{dynamic} means that the function manipulates the stack
+dynamically: in addition to the static allocation described above, stack
+adjustments are made in the body of the function, for example to push/pop
+arguments around function calls. If the qualifier @code{bounded} is also
+present, the amount of these adjustments is bounded at compile time and
+the second field is an upper bound of the total amount of stack used by
+the function. If it is not present, the amount of these adjustments is
+not bounded at compile time and the second field only represents the
+bounded part.
+
+@item -fstats
+@opindex fstats
+Emit statistics about front-end processing at the end of the compilation.
+This option is supported only by the C++ front end, and
+the information is generally only useful to the G++ development team.
+
+@item -fdbg-cnt-list
+@opindex fdbg-cnt-list
+Print the name and the counter upper bound for all debug counters.
+
+
+@item -fdbg-cnt=@var{counter-value-list}
+@opindex fdbg-cnt
+Set the internal debug counter lower and upper bound. @var{counter-value-list}
+is a comma-separated list of @var{name}:@var{lower_bound1}-@var{upper_bound1}
+[:@var{lower_bound2}-@var{upper_bound2}...] tuples which sets
+the name of the counter and list of closed intervals.
+The @var{lower_bound} is optional and is zero
+initialized if not set.
+For example, with @option{-fdbg-cnt=dce:2-4:10-11,tail_call:10},
+@code{dbg_cnt(dce)} returns true only for second, third, fourth, tenth and
+eleventh invocation.
+For @code{dbg_cnt(tail_call)} true is returned for first 10 invocations.
+
+@item -print-file-name=@var{library}
+@opindex print-file-name
+Print the full absolute name of the library file @var{library} that
+would be used when linking---and don't do anything else. With this
+option, GCC does not compile or link anything; it just prints the
+file name.
+
+@item -print-multi-directory
+@opindex print-multi-directory
+Print the directory name corresponding to the multilib selected by any
+other switches present in the command line. This directory is supposed
+to exist in @env{GCC_EXEC_PREFIX}.
+
+@item -print-multi-lib
+@opindex print-multi-lib
+Print the mapping from multilib directory names to compiler switches
+that enable them. The directory name is separated from the switches by
+@samp{;}, and each switch starts with an @samp{@@} instead of the
+@samp{-}, without spaces between multiple switches. This is supposed to
+ease shell processing.
+
+@item -print-multi-os-directory
+@opindex print-multi-os-directory
+Print the path to OS libraries for the selected
+multilib, relative to some @file{lib} subdirectory. If OS libraries are
+present in the @file{lib} subdirectory and no multilibs are used, this is
+usually just @file{.}, if OS libraries are present in @file{lib@var{suffix}}
+sibling directories this prints e.g.@: @file{../lib64}, @file{../lib} or
+@file{../lib32}, or if OS libraries are present in @file{lib/@var{subdir}}
+subdirectories it prints e.g.@: @file{amd64}, @file{sparcv9} or @file{ev6}.
+
+@item -print-multiarch
+@opindex print-multiarch
+Print the path to OS libraries for the selected multiarch,
+relative to some @file{lib} subdirectory.
+
+@item -print-prog-name=@var{program}
+@opindex print-prog-name
+Like @option{-print-file-name}, but searches for a program such as @command{cpp}.
+
+@item -print-libgcc-file-name
+@opindex print-libgcc-file-name
+Same as @option{-print-file-name=libgcc.a}.
+
+This is useful when you use @option{-nostdlib} or @option{-nodefaultlibs}
+but you do want to link with @file{libgcc.a}. You can do:
+
+@smallexample
+gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name`
+@end smallexample
+
+@item -print-search-dirs
+@opindex print-search-dirs
+Print the name of the configured installation directory and a list of
+program and library directories @command{gcc} searches---and don't do anything else.
+
+This is useful when @command{gcc} prints the error message
+@samp{installation problem, cannot exec cpp0: No such file or directory}.
+To resolve this you either need to put @file{cpp0} and the other compiler
+components where @command{gcc} expects to find them, or you can set the environment
+variable @env{GCC_EXEC_PREFIX} to the directory where you installed them.
+Don't forget the trailing @samp{/}.
+@xref{Environment Variables}.
+
+@item -print-sysroot
+@opindex print-sysroot
+Print the target sysroot directory that is used during
+compilation. This is the target sysroot specified either at configure
+time or using the @option{--sysroot} option, possibly with an extra
+suffix that depends on compilation options. If no target sysroot is
+specified, the option prints nothing.
+
+@item -print-sysroot-headers-suffix
+@opindex print-sysroot-headers-suffix
+Print the suffix added to the target sysroot when searching for
+headers, or give an error if the compiler is not configured with such
+a suffix---and don't do anything else.
+
+@item -dumpmachine
+@opindex dumpmachine
+Print the compiler's target machine (for example,
+@samp{i686-pc-linux-gnu})---and don't do anything else.
+
+@item -dumpversion
+@opindex dumpversion
+Print the compiler version (for example, @code{3.0}, @code{6.3.0} or @code{7})---and don't do
+anything else. This is the compiler version used in filesystem paths and
+specs. Depending on how the compiler has been configured it can be just
+a single number (major version), two numbers separated by a dot (major and
+minor version) or three numbers separated by dots (major, minor and patchlevel
+version).
+
+@item -dumpfullversion
+@opindex dumpfullversion
+Print the full compiler version---and don't do anything else. The output is
+always three numbers separated by dots, major, minor and patchlevel version.
+
+@item -dumpspecs
+@opindex dumpspecs
+Print the compiler's built-in specs---and don't do anything else. (This
+is used when GCC itself is being built.) @xref{Spec Files}.
+@end table
+
+@node Submodel Options
+@section Machine-Dependent Options
+@cindex submodel options
+@cindex specifying hardware config
+@cindex hardware models and configurations, specifying
+@cindex target-dependent options
+@cindex machine-dependent options
+
+Each target machine supported by GCC can have its own options---for
+example, to allow you to compile for a particular processor variant or
+ABI, or to control optimizations specific to that machine. By
+convention, the names of machine-specific options start with
+@samp{-m}.
+
+Some configurations of the compiler also support additional target-specific
+options, usually for compatibility with other compilers on the same
+platform.
+
+@c This list is ordered alphanumerically by subsection name.
+@c It should be the same order and spelling as these options are listed
+@c in Machine Dependent Options
+
+@menu
+* AArch64 Options::
+* Adapteva Epiphany Options::
+* AMD GCN Options::
+* ARC Options::
+* ARM Options::
+* AVR Options::
+* Blackfin Options::
+* C6X Options::
+* CRIS Options::
+* C-SKY Options::
+* Darwin Options::
+* DEC Alpha Options::
+* eBPF Options::
+* FR30 Options::
+* FT32 Options::
+* FRV Options::
+* GNU/Linux Options::
+* H8/300 Options::
+* HPPA Options::
+* IA-64 Options::
+* LM32 Options::
+* LoongArch Options::
+* M32C Options::
+* M32R/D Options::
+* M680x0 Options::
+* MCore Options::
+* MeP Options::
+* MicroBlaze Options::
+* MIPS Options::
+* MMIX Options::
+* MN10300 Options::
+* Moxie Options::
+* MSP430 Options::
+* NDS32 Options::
+* Nios II Options::
+* Nvidia PTX Options::
+* OpenRISC Options::
+* PDP-11 Options::
+* picoChip Options::
+* PowerPC Options::
+* PRU Options::
+* RISC-V Options::
+* RL78 Options::
+* RS/6000 and PowerPC Options::
+* RX Options::
+* S/390 and zSeries Options::
+* Score Options::
+* SH Options::
+* Solaris 2 Options::
+* SPARC Options::
+* System V Options::
+* V850 Options::
+* VAX Options::
+* Visium Options::
+* VMS Options::
+* VxWorks Options::
+* x86 Options::
+* x86 Windows Options::
+* Xstormy16 Options::
+* Xtensa Options::
+* zSeries Options::
+@end menu
+
+@node AArch64 Options
+@subsection AArch64 Options
+@cindex AArch64 Options
+
+These options are defined for AArch64 implementations:
+
+@table @gcctabopt
+
+@item -mabi=@var{name}
+@opindex mabi
+Generate code for the specified data model. Permissible values
+are @samp{ilp32} for SysV-like data model where int, long int and pointers
+are 32 bits, and @samp{lp64} for SysV-like data model where int is 32 bits,
+but long int and pointers are 64 bits.
+
+The default depends on the specific target configuration. Note that
+the LP64 and ILP32 ABIs are not link-compatible; you must compile your
+entire program with the same ABI, and link with a compatible set of libraries.
+
+@item -mbig-endian
+@opindex mbig-endian
+Generate big-endian code. This is the default when GCC is configured for an
+@samp{aarch64_be-*-*} target.
+
+@item -mgeneral-regs-only
+@opindex mgeneral-regs-only
+Generate code which uses only the general-purpose registers. This will prevent
+the compiler from using floating-point and Advanced SIMD registers but will not
+impose any restrictions on the assembler.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+Generate little-endian code. This is the default when GCC is configured for an
+@samp{aarch64-*-*} but not an @samp{aarch64_be-*-*} target.
+
+@item -mcmodel=tiny
+@opindex mcmodel=tiny
+Generate code for the tiny code model. The program and its statically defined
+symbols must be within 1MB of each other. Programs can be statically or
+dynamically linked.
+
+@item -mcmodel=small
+@opindex mcmodel=small
+Generate code for the small code model. The program and its statically defined
+symbols must be within 4GB of each other. Programs can be statically or
+dynamically linked. This is the default code model.
+
+@item -mcmodel=large
+@opindex mcmodel=large
+Generate code for the large code model. This makes no assumptions about
+addresses and sizes of sections. Programs can be statically linked only. The
+@option{-mcmodel=large} option is incompatible with @option{-mabi=ilp32},
+@option{-fpic} and @option{-fPIC}.
+
+@item -mstrict-align
+@itemx -mno-strict-align
+@opindex mstrict-align
+@opindex mno-strict-align
+Avoid or allow generating memory accesses that may not be aligned on a natural
+object boundary as described in the architecture specification.
+
+@item -momit-leaf-frame-pointer
+@itemx -mno-omit-leaf-frame-pointer
+@opindex momit-leaf-frame-pointer
+@opindex mno-omit-leaf-frame-pointer
+Omit or keep the frame pointer in leaf functions. The former behavior is the
+default.
+
+@item -mstack-protector-guard=@var{guard}
+@itemx -mstack-protector-guard-reg=@var{reg}
+@itemx -mstack-protector-guard-offset=@var{offset}
+@opindex mstack-protector-guard
+@opindex mstack-protector-guard-reg
+@opindex mstack-protector-guard-offset
+Generate stack protection code using canary at @var{guard}. Supported
+locations are @samp{global} for a global canary or @samp{sysreg} for a
+canary in an appropriate system register.
+
+With the latter choice the options
+@option{-mstack-protector-guard-reg=@var{reg}} and
+@option{-mstack-protector-guard-offset=@var{offset}} furthermore specify
+which system register to use as base register for reading the canary,
+and from what offset from that base register. There is no default
+register or offset as this is entirely for use within the Linux
+kernel.
+
+@item -mtls-dialect=desc
+@opindex mtls-dialect=desc
+Use TLS descriptors as the thread-local storage mechanism for dynamic accesses
+of TLS variables. This is the default.
+
+@item -mtls-dialect=traditional
+@opindex mtls-dialect=traditional
+Use traditional TLS as the thread-local storage mechanism for dynamic accesses
+of TLS variables.
+
+@item -mtls-size=@var{size}
+@opindex mtls-size
+Specify bit size of immediate TLS offsets. Valid values are 12, 24, 32, 48.
+This option requires binutils 2.26 or newer.
+
+@item -mfix-cortex-a53-835769
+@itemx -mno-fix-cortex-a53-835769
+@opindex mfix-cortex-a53-835769
+@opindex mno-fix-cortex-a53-835769
+Enable or disable the workaround for the ARM Cortex-A53 erratum number 835769.
+This involves inserting a NOP instruction between memory instructions and
+64-bit integer multiply-accumulate instructions.
+
+@item -mfix-cortex-a53-843419
+@itemx -mno-fix-cortex-a53-843419
+@opindex mfix-cortex-a53-843419
+@opindex mno-fix-cortex-a53-843419
+Enable or disable the workaround for the ARM Cortex-A53 erratum number 843419.
+This erratum workaround is made at link time and this will only pass the
+corresponding flag to the linker.
+
+@item -mlow-precision-recip-sqrt
+@itemx -mno-low-precision-recip-sqrt
+@opindex mlow-precision-recip-sqrt
+@opindex mno-low-precision-recip-sqrt
+Enable or disable the reciprocal square root approximation.
+This option only has an effect if @option{-ffast-math} or
+@option{-funsafe-math-optimizations} is used as well. Enabling this reduces
+precision of reciprocal square root results to about 16 bits for
+single precision and to 32 bits for double precision.
+
+@item -mlow-precision-sqrt
+@itemx -mno-low-precision-sqrt
+@opindex mlow-precision-sqrt
+@opindex mno-low-precision-sqrt
+Enable or disable the square root approximation.
+This option only has an effect if @option{-ffast-math} or
+@option{-funsafe-math-optimizations} is used as well. Enabling this reduces
+precision of square root results to about 16 bits for
+single precision and to 32 bits for double precision.
+If enabled, it implies @option{-mlow-precision-recip-sqrt}.
+
+@item -mlow-precision-div
+@itemx -mno-low-precision-div
+@opindex mlow-precision-div
+@opindex mno-low-precision-div
+Enable or disable the division approximation.
+This option only has an effect if @option{-ffast-math} or
+@option{-funsafe-math-optimizations} is used as well. Enabling this reduces
+precision of division results to about 16 bits for
+single precision and to 32 bits for double precision.
+
+@item -mtrack-speculation
+@itemx -mno-track-speculation
+Enable or disable generation of additional code to track speculative
+execution through conditional branches. The tracking state can then
+be used by the compiler when expanding calls to
+@code{__builtin_speculation_safe_copy} to permit a more efficient code
+sequence to be generated.
+
+@item -moutline-atomics
+@itemx -mno-outline-atomics
+Enable or disable calls to out-of-line helpers to implement atomic operations.
+These helpers will, at runtime, determine if the LSE instructions from
+ARMv8.1-A can be used; if not, they will use the load/store-exclusive
+instructions that are present in the base ARMv8.0 ISA.
+
+This option is only applicable when compiling for the base ARMv8.0
+instruction set. If using a later revision, e.g. @option{-march=armv8.1-a}
+or @option{-march=armv8-a+lse}, the ARMv8.1-Atomics instructions will be
+used directly. The same applies when using @option{-mcpu=} when the
+selected cpu supports the @samp{lse} feature.
+This option is on by default.
+
+@item -march=@var{name}
+@opindex march
+Specify the name of the target architecture and, optionally, one or
+more feature modifiers. This option has the form
+@option{-march=@var{arch}@r{@{}+@r{[}no@r{]}@var{feature}@r{@}*}}.
+
+The table below summarizes the permissible values for @var{arch}
+and the features that they enable by default:
+
+@multitable @columnfractions 0.20 0.20 0.60
+@headitem @var{arch} value @tab Architecture @tab Includes by default
+@item @samp{armv8-a} @tab Armv8-A @tab @samp{+fp}, @samp{+simd}
+@item @samp{armv8.1-a} @tab Armv8.1-A @tab @samp{armv8-a}, @samp{+crc}, @samp{+lse}, @samp{+rdma}
+@item @samp{armv8.2-a} @tab Armv8.2-A @tab @samp{armv8.1-a}
+@item @samp{armv8.3-a} @tab Armv8.3-A @tab @samp{armv8.2-a}, @samp{+pauth}
+@item @samp{armv8.4-a} @tab Armv8.4-A @tab @samp{armv8.3-a}, @samp{+flagm}, @samp{+fp16fml}, @samp{+dotprod}
+@item @samp{armv8.5-a} @tab Armv8.5-A @tab @samp{armv8.4-a}, @samp{+sb}, @samp{+ssbs}, @samp{+predres}
+@item @samp{armv8.6-a} @tab Armv8.6-A @tab @samp{armv8.5-a}, @samp{+bf16}, @samp{+i8mm}
+@item @samp{armv8.7-a} @tab Armv8.7-A @tab @samp{armv8.6-a}, @samp{+ls64}
+@item @samp{armv8.8-a} @tab Armv8.8-a @tab @samp{armv8.7-a}, @samp{+mops}
+@item @samp{armv9-a} @tab Armv9-A @tab @samp{armv8.5-a}, @samp{+sve}, @samp{+sve2}
+@item @samp{armv9.1-a} @tab Armv9.1-A @tab @samp{armv9-a}, @samp{+bf16}, @samp{+i8mm}
+@item @samp{armv9.2-a} @tab Armv9.2-A @tab @samp{armv9.1-a}, @samp{+ls64}
+@item @samp{armv9.3-a} @tab Armv9.3-A @tab @samp{armv9.2-a}, @samp{+mops}
+@item @samp{armv8-r} @tab Armv8-R @tab @samp{armv8-r}
+@end multitable
+
+The value @samp{native} is available on native AArch64 GNU/Linux and
+causes the compiler to pick the architecture of the host system. This
+option has no effect if the compiler is unable to recognize the
+architecture of the host system,
+
+The permissible values for @var{feature} are listed in the sub-section
+on @ref{aarch64-feature-modifiers,,@option{-march} and @option{-mcpu}
+Feature Modifiers}. Where conflicting feature modifiers are
+specified, the right-most feature is used.
+
+GCC uses @var{name} to determine what kind of instructions it can emit
+when generating assembly code. If @option{-march} is specified
+without either of @option{-mtune} or @option{-mcpu} also being
+specified, the code is tuned to perform well across a range of target
+processors implementing the target architecture.
+
+@item -mtune=@var{name}
+@opindex mtune
+Specify the name of the target processor for which GCC should tune the
+performance of the code. Permissible values for this option are:
+@samp{generic}, @samp{cortex-a35}, @samp{cortex-a53}, @samp{cortex-a55},
+@samp{cortex-a57}, @samp{cortex-a72}, @samp{cortex-a73}, @samp{cortex-a75},
+@samp{cortex-a76}, @samp{cortex-a76ae}, @samp{cortex-a77},
+@samp{cortex-a65}, @samp{cortex-a65ae}, @samp{cortex-a34},
+@samp{cortex-a78}, @samp{cortex-a78ae}, @samp{cortex-a78c},
+@samp{ares}, @samp{exynos-m1}, @samp{emag}, @samp{falkor},
+@samp{neoverse-512tvb}, @samp{neoverse-e1}, @samp{neoverse-n1},
+@samp{neoverse-n2}, @samp{neoverse-v1}, @samp{neoverse-v2}, @samp{qdf24xx},
+@samp{saphira}, @samp{phecda}, @samp{xgene1}, @samp{vulcan},
+@samp{octeontx}, @samp{octeontx81}, @samp{octeontx83},
+@samp{octeontx2}, @samp{octeontx2t98}, @samp{octeontx2t96}
+@samp{octeontx2t93}, @samp{octeontx2f95}, @samp{octeontx2f95n},
+@samp{octeontx2f95mm},
+@samp{a64fx},
+@samp{thunderx}, @samp{thunderxt88},
+@samp{thunderxt88p1}, @samp{thunderxt81}, @samp{tsv110},
+@samp{thunderxt83}, @samp{thunderx2t99}, @samp{thunderx3t110}, @samp{zeus},
+@samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
+@samp{cortex-a73.cortex-a35}, @samp{cortex-a73.cortex-a53},
+@samp{cortex-a75.cortex-a55}, @samp{cortex-a76.cortex-a55},
+@samp{cortex-r82}, @samp{cortex-x1}, @samp{cortex-x2},
+@samp{cortex-a510}, @samp{cortex-a710}, @samp{ampere1}, @samp{native}.
+
+The values @samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
+@samp{cortex-a73.cortex-a35}, @samp{cortex-a73.cortex-a53},
+@samp{cortex-a75.cortex-a55}, @samp{cortex-a76.cortex-a55} specify that GCC
+should tune for a big.LITTLE system.
+
+The value @samp{neoverse-512tvb} specifies that GCC should tune
+for Neoverse cores that (a) implement SVE and (b) have a total vector
+bandwidth of 512 bits per cycle. In other words, the option tells GCC to
+tune for Neoverse cores that can execute 4 128-bit Advanced SIMD arithmetic
+instructions a cycle and that can execute an equivalent number of SVE
+arithmetic instructions per cycle (2 for 256-bit SVE, 4 for 128-bit SVE).
+This is more general than tuning for a specific core like Neoverse V1
+but is more specific than the default tuning described below.
+
+Additionally on native AArch64 GNU/Linux systems the value
+@samp{native} tunes performance to the host system. This option has no effect
+if the compiler is unable to recognize the processor of the host system.
+
+Where none of @option{-mtune=}, @option{-mcpu=} or @option{-march=}
+are specified, the code is tuned to perform well across a range
+of target processors.
+
+This option cannot be suffixed by feature modifiers.
+
+@item -mcpu=@var{name}
+@opindex mcpu
+Specify the name of the target processor, optionally suffixed by one
+or more feature modifiers. This option has the form
+@option{-mcpu=@var{cpu}@r{@{}+@r{[}no@r{]}@var{feature}@r{@}*}}, where
+the permissible values for @var{cpu} are the same as those available
+for @option{-mtune}. The permissible values for @var{feature} are
+documented in the sub-section on
+@ref{aarch64-feature-modifiers,,@option{-march} and @option{-mcpu}
+Feature Modifiers}. Where conflicting feature modifiers are
+specified, the right-most feature is used.
+
+GCC uses @var{name} to determine what kind of instructions it can emit when
+generating assembly code (as if by @option{-march}) and to determine
+the target processor for which to tune for performance (as if
+by @option{-mtune}). Where this option is used in conjunction
+with @option{-march} or @option{-mtune}, those options take precedence
+over the appropriate part of this option.
+
+@option{-mcpu=neoverse-512tvb} is special in that it does not refer
+to a specific core, but instead refers to all Neoverse cores that
+(a) implement SVE and (b) have a total vector bandwidth of 512 bits
+a cycle. Unless overridden by @option{-march},
+@option{-mcpu=neoverse-512tvb} generates code that can run on a
+Neoverse V1 core, since Neoverse V1 is the first Neoverse core with
+these properties. Unless overridden by @option{-mtune},
+@option{-mcpu=neoverse-512tvb} tunes code in the same way as for
+@option{-mtune=neoverse-512tvb}.
+
+@item -moverride=@var{string}
+@opindex moverride
+Override tuning decisions made by the back-end in response to a
+@option{-mtune=} switch. The syntax, semantics, and accepted values
+for @var{string} in this option are not guaranteed to be consistent
+across releases.
+
+This option is only intended to be useful when developing GCC.
+
+@item -mverbose-cost-dump
+@opindex mverbose-cost-dump
+Enable verbose cost model dumping in the debug dump files. This option is
+provided for use in debugging the compiler.
+
+@item -mpc-relative-literal-loads
+@itemx -mno-pc-relative-literal-loads
+@opindex mpc-relative-literal-loads
+@opindex mno-pc-relative-literal-loads
+Enable or disable PC-relative literal loads. With this option literal pools are
+accessed using a single instruction and emitted after each function. This
+limits the maximum size of functions to 1MB. This is enabled by default for
+@option{-mcmodel=tiny}.
+
+@item -msign-return-address=@var{scope}
+@opindex msign-return-address
+Select the function scope on which return address signing will be applied.
+Permissible values are @samp{none}, which disables return address signing,
+@samp{non-leaf}, which enables pointer signing for functions which are not leaf
+functions, and @samp{all}, which enables pointer signing for all functions. The
+default value is @samp{none}. This option has been deprecated by
+-mbranch-protection.
+
+@item -mbranch-protection=@var{none}|@var{standard}|@var{pac-ret}[+@var{leaf}+@var{b-key}]|@var{bti}
+@opindex mbranch-protection
+Select the branch protection features to use.
+@samp{none} is the default and turns off all types of branch protection.
+@samp{standard} turns on all types of branch protection features. If a feature
+has additional tuning options, then @samp{standard} sets it to its standard
+level.
+@samp{pac-ret[+@var{leaf}]} turns on return address signing to its standard
+level: signing functions that save the return address to memory (non-leaf
+functions will practically always do this) using the a-key. The optional
+argument @samp{leaf} can be used to extend the signing to include leaf
+functions. The optional argument @samp{b-key} can be used to sign the functions
+with the B-key instead of the A-key.
+@samp{bti} turns on branch target identification mechanism.
+
+@item -mharden-sls=@var{opts}
+@opindex mharden-sls
+Enable compiler hardening against straight line speculation (SLS).
+@var{opts} is a comma-separated list of the following options:
+@table @samp
+@item retbr
+@item blr
+@end table
+In addition, @samp{-mharden-sls=all} enables all SLS hardening while
+@samp{-mharden-sls=none} disables all SLS hardening.
+
+@item -msve-vector-bits=@var{bits}
+@opindex msve-vector-bits
+Specify the number of bits in an SVE vector register. This option only has
+an effect when SVE is enabled.
+
+GCC supports two forms of SVE code generation: ``vector-length
+agnostic'' output that works with any size of vector register and
+``vector-length specific'' output that allows GCC to make assumptions
+about the vector length when it is useful for optimization reasons.
+The possible values of @samp{bits} are: @samp{scalable}, @samp{128},
+@samp{256}, @samp{512}, @samp{1024} and @samp{2048}.
+Specifying @samp{scalable} selects vector-length agnostic
+output. At present @samp{-msve-vector-bits=128} also generates vector-length
+agnostic output for big-endian targets. All other values generate
+vector-length specific code. The behavior of these values may change
+in future releases and no value except @samp{scalable} should be
+relied on for producing code that is portable across different
+hardware SVE vector lengths.
+
+The default is @samp{-msve-vector-bits=scalable}, which produces
+vector-length agnostic code.
+@end table
+
+@subsubsection @option{-march} and @option{-mcpu} Feature Modifiers
+@anchor{aarch64-feature-modifiers}
+@cindex @option{-march} feature modifiers
+@cindex @option{-mcpu} feature modifiers
+Feature modifiers used with @option{-march} and @option{-mcpu} can be any of
+the following and their inverses @option{no@var{feature}}:
+
+@table @samp
+@item crc
+Enable CRC extension. This is on by default for
+@option{-march=armv8.1-a}.
+@item crypto
+Enable Crypto extension. This also enables Advanced SIMD and floating-point
+instructions.
+@item fp
+Enable floating-point instructions. This is on by default for all possible
+values for options @option{-march} and @option{-mcpu}.
+@item simd
+Enable Advanced SIMD instructions. This also enables floating-point
+instructions. This is on by default for all possible values for options
+@option{-march} and @option{-mcpu}.
+@item sve
+Enable Scalable Vector Extension instructions. This also enables Advanced
+SIMD and floating-point instructions.
+@item lse
+Enable Large System Extension instructions. This is on by default for
+@option{-march=armv8.1-a}.
+@item rdma
+Enable Round Double Multiply Accumulate instructions. This is on by default
+for @option{-march=armv8.1-a}.
+@item fp16
+Enable FP16 extension. This also enables floating-point instructions.
+@item fp16fml
+Enable FP16 fmla extension. This also enables FP16 extensions and
+floating-point instructions. This option is enabled by default for @option{-march=armv8.4-a}. Use of this option with architectures prior to Armv8.2-A is not supported.
+
+@item rcpc
+Enable the RcPc extension. This does not change code generation from GCC,
+but is passed on to the assembler, enabling inline asm statements to use
+instructions from the RcPc extension.
+@item dotprod
+Enable the Dot Product extension. This also enables Advanced SIMD instructions.
+@item aes
+Enable the Armv8-a aes and pmull crypto extension. This also enables Advanced
+SIMD instructions.
+@item sha2
+Enable the Armv8-a sha2 crypto extension. This also enables Advanced SIMD instructions.
+@item sha3
+Enable the sha512 and sha3 crypto extension. This also enables Advanced SIMD
+instructions. Use of this option with architectures prior to Armv8.2-A is not supported.
+@item sm4
+Enable the sm3 and sm4 crypto extension. This also enables Advanced SIMD instructions.
+Use of this option with architectures prior to Armv8.2-A is not supported.
+@item profile
+Enable the Statistical Profiling extension. This option is only to enable the
+extension at the assembler level and does not affect code generation.
+@item rng
+Enable the Armv8.5-a Random Number instructions. This option is only to
+enable the extension at the assembler level and does not affect code
+generation.
+@item memtag
+Enable the Armv8.5-a Memory Tagging Extensions.
+Use of this option with architectures prior to Armv8.5-A is not supported.
+@item sb
+Enable the Armv8-a Speculation Barrier instruction. This option is only to
+enable the extension at the assembler level and does not affect code
+generation. This option is enabled by default for @option{-march=armv8.5-a}.
+@item ssbs
+Enable the Armv8-a Speculative Store Bypass Safe instruction. This option
+is only to enable the extension at the assembler level and does not affect code
+generation. This option is enabled by default for @option{-march=armv8.5-a}.
+@item predres
+Enable the Armv8-a Execution and Data Prediction Restriction instructions.
+This option is only to enable the extension at the assembler level and does
+not affect code generation. This option is enabled by default for
+@option{-march=armv8.5-a}.
+@item sve2
+Enable the Armv8-a Scalable Vector Extension 2. This also enables SVE
+instructions.
+@item sve2-bitperm
+Enable SVE2 bitperm instructions. This also enables SVE2 instructions.
+@item sve2-sm4
+Enable SVE2 sm4 instructions. This also enables SVE2 instructions.
+@item sve2-aes
+Enable SVE2 aes instructions. This also enables SVE2 instructions.
+@item sve2-sha3
+Enable SVE2 sha3 instructions. This also enables SVE2 instructions.
+@item tme
+Enable the Transactional Memory Extension.
+@item i8mm
+Enable 8-bit Integer Matrix Multiply instructions. This also enables
+Advanced SIMD and floating-point instructions. This option is enabled by
+default for @option{-march=armv8.6-a}. Use of this option with architectures
+prior to Armv8.2-A is not supported.
+@item f32mm
+Enable 32-bit Floating point Matrix Multiply instructions. This also enables
+SVE instructions. Use of this option with architectures prior to Armv8.2-A is
+not supported.
+@item f64mm
+Enable 64-bit Floating point Matrix Multiply instructions. This also enables
+SVE instructions. Use of this option with architectures prior to Armv8.2-A is
+not supported.
+@item bf16
+Enable brain half-precision floating-point instructions. This also enables
+Advanced SIMD and floating-point instructions. This option is enabled by
+default for @option{-march=armv8.6-a}. Use of this option with architectures
+prior to Armv8.2-A is not supported.
+@item ls64
+Enable the 64-byte atomic load and store instructions for accelerators.
+This option is enabled by default for @option{-march=armv8.7-a}.
+@item mops
+Enable the instructions to accelerate memory operations like @code{memcpy},
+@code{memmove}, @code{memset}. This option is enabled by default for
+@option{-march=armv8.8-a}
+@item flagm
+Enable the Flag Manipulation instructions Extension.
+@item pauth
+Enable the Pointer Authentication Extension.
+
+@end table
+
+Feature @option{crypto} implies @option{aes}, @option{sha2}, and @option{simd},
+which implies @option{fp}.
+Conversely, @option{nofp} implies @option{nosimd}, which implies
+@option{nocrypto}, @option{noaes} and @option{nosha2}.
+
+@node Adapteva Epiphany Options
+@subsection Adapteva Epiphany Options
+
+These @samp{-m} options are defined for Adapteva Epiphany:
+
+@table @gcctabopt
+@item -mhalf-reg-file
+@opindex mhalf-reg-file
+Don't allocate any register in the range @code{r32}@dots{}@code{r63}.
+That allows code to run on hardware variants that lack these registers.
+
+@item -mprefer-short-insn-regs
+@opindex mprefer-short-insn-regs
+Preferentially allocate registers that allow short instruction generation.
+This can result in increased instruction count, so this may either reduce or
+increase overall code size.
+
+@item -mbranch-cost=@var{num}
+@opindex mbranch-cost
+Set the cost of branches to roughly @var{num} ``simple'' instructions.
+This cost is only a heuristic and is not guaranteed to produce
+consistent results across releases.
+
+@item -mcmove
+@opindex mcmove
+Enable the generation of conditional moves.
+
+@item -mnops=@var{num}
+@opindex mnops
+Emit @var{num} NOPs before every other generated instruction.
+
+@item -mno-soft-cmpsf
+@opindex mno-soft-cmpsf
+@opindex msoft-cmpsf
+For single-precision floating-point comparisons, emit an @code{fsub} instruction
+and test the flags. This is faster than a software comparison, but can
+get incorrect results in the presence of NaNs, or when two different small
+numbers are compared such that their difference is calculated as zero.
+The default is @option{-msoft-cmpsf}, which uses slower, but IEEE-compliant,
+software comparisons.
+
+@item -mstack-offset=@var{num}
+@opindex mstack-offset
+Set the offset between the top of the stack and the stack pointer.
+E.g., a value of 8 means that the eight bytes in the range @code{sp+0@dots{}sp+7}
+can be used by leaf functions without stack allocation.
+Values other than @samp{8} or @samp{16} are untested and unlikely to work.
+Note also that this option changes the ABI; compiling a program with a
+different stack offset than the libraries have been compiled with
+generally does not work.
+This option can be useful if you want to evaluate if a different stack
+offset would give you better code, but to actually use a different stack
+offset to build working programs, it is recommended to configure the
+toolchain with the appropriate @option{--with-stack-offset=@var{num}} option.
+
+@item -mno-round-nearest
+@opindex mno-round-nearest
+@opindex mround-nearest
+Make the scheduler assume that the rounding mode has been set to
+truncating. The default is @option{-mround-nearest}.
+
+@item -mlong-calls
+@opindex mlong-calls
+If not otherwise specified by an attribute, assume all calls might be beyond
+the offset range of the @code{b} / @code{bl} instructions, and therefore load the
+function address into a register before performing a (otherwise direct) call.
+This is the default.
+
+@item -mshort-calls
+@opindex short-calls
+If not otherwise specified by an attribute, assume all direct calls are
+in the range of the @code{b} / @code{bl} instructions, so use these instructions
+for direct calls. The default is @option{-mlong-calls}.
+
+@item -msmall16
+@opindex msmall16
+Assume addresses can be loaded as 16-bit unsigned values. This does not
+apply to function addresses for which @option{-mlong-calls} semantics
+are in effect.
+
+@item -mfp-mode=@var{mode}
+@opindex mfp-mode
+Set the prevailing mode of the floating-point unit.
+This determines the floating-point mode that is provided and expected
+at function call and return time. Making this mode match the mode you
+predominantly need at function start can make your programs smaller and
+faster by avoiding unnecessary mode switches.
+
+@var{mode} can be set to one the following values:
+
+@table @samp
+@item caller
+Any mode at function entry is valid, and retained or restored when
+the function returns, and when it calls other functions.
+This mode is useful for compiling libraries or other compilation units
+you might want to incorporate into different programs with different
+prevailing FPU modes, and the convenience of being able to use a single
+object file outweighs the size and speed overhead for any extra
+mode switching that might be needed, compared with what would be needed
+with a more specific choice of prevailing FPU mode.
+
+@item truncate
+This is the mode used for floating-point calculations with
+truncating (i.e.@: round towards zero) rounding mode. That includes
+conversion from floating point to integer.
+
+@item round-nearest
+This is the mode used for floating-point calculations with
+round-to-nearest-or-even rounding mode.
+
+@item int
+This is the mode used to perform integer calculations in the FPU, e.g.@:
+integer multiply, or integer multiply-and-accumulate.
+@end table
+
+The default is @option{-mfp-mode=caller}
+
+@item -mno-split-lohi
+@itemx -mno-postinc
+@itemx -mno-postmodify
+@opindex mno-split-lohi
+@opindex msplit-lohi
+@opindex mno-postinc
+@opindex mpostinc
+@opindex mno-postmodify
+@opindex mpostmodify
+Code generation tweaks that disable, respectively, splitting of 32-bit
+loads, generation of post-increment addresses, and generation of
+post-modify addresses. The defaults are @option{msplit-lohi},
+@option{-mpost-inc}, and @option{-mpost-modify}.
+
+@item -mnovect-double
+@opindex mno-vect-double
+@opindex mvect-double
+Change the preferred SIMD mode to SImode. The default is
+@option{-mvect-double}, which uses DImode as preferred SIMD mode.
+
+@item -max-vect-align=@var{num}
+@opindex max-vect-align
+The maximum alignment for SIMD vector mode types.
+@var{num} may be 4 or 8. The default is 8.
+Note that this is an ABI change, even though many library function
+interfaces are unaffected if they don't use SIMD vector modes
+in places that affect size and/or alignment of relevant types.
+
+@item -msplit-vecmove-early
+@opindex msplit-vecmove-early
+Split vector moves into single word moves before reload. In theory this
+can give better register allocation, but so far the reverse seems to be
+generally the case.
+
+@item -m1reg-@var{reg}
+@opindex m1reg-
+Specify a register to hold the constant @minus{}1, which makes loading small negative
+constants and certain bitmasks faster.
+Allowable values for @var{reg} are @samp{r43} and @samp{r63},
+which specify use of that register as a fixed register,
+and @samp{none}, which means that no register is used for this
+purpose. The default is @option{-m1reg-none}.
+
+@end table
+
+@node AMD GCN Options
+@subsection AMD GCN Options
+@cindex AMD GCN Options
+
+These options are defined specifically for the AMD GCN port.
+
+@table @gcctabopt
+
+@item -march=@var{gpu}
+@opindex march
+@itemx -mtune=@var{gpu}
+@opindex mtune
+Set architecture type or tuning for @var{gpu}. Supported values for @var{gpu}
+are
+
+@table @samp
+@item fiji
+Compile for GCN3 Fiji devices (gfx803).
+
+@item gfx900
+Compile for GCN5 Vega 10 devices (gfx900).
+
+@item gfx906
+Compile for GCN5 Vega 20 devices (gfx906).
+
+@item gfx908
+Compile for CDNA1 Instinct MI100 series devices (gfx908).
+
+@item gfx90a
+Compile for CDNA2 Instinct MI200 series devices (gfx90a).
+
+@end table
+
+@item -msram-ecc=on
+@itemx -msram-ecc=off
+@itemx -msram-ecc=any
+@opindex msram-ecc
+Compile binaries suitable for devices with the SRAM-ECC feature enabled,
+disabled, or either mode. This feature can be enabled per-process on some
+devices. The compiled code must match the device mode. The default is
+@samp{any}, for devices that support it.
+
+@item -mstack-size=@var{bytes}
+@opindex mstack-size
+Specify how many @var{bytes} of stack space will be requested for each GPU
+thread (wave-front). Beware that there may be many threads and limited memory
+available. The size of the stack allocation may also have an impact on
+run-time performance. The default is 32KB when using OpenACC or OpenMP, and
+1MB otherwise.
+
+@item -mxnack
+@opindex mxnack
+Compile binaries suitable for devices with the XNACK feature enabled. Some
+devices always require XNACK and some allow the user to configure XNACK. The
+compiled code must match the device mode. The default is @samp{-mno-xnack}.
+At present this option is a placeholder for support that is not yet
+implemented.
+
+@end table
+
+@node ARC Options
+@subsection ARC Options
+@cindex ARC options
+
+The following options control the architecture variant for which code
+is being compiled:
+
+@c architecture variants
+@table @gcctabopt
+
+@item -mbarrel-shifter
+@opindex mbarrel-shifter
+Generate instructions supported by barrel shifter. This is the default
+unless @option{-mcpu=ARC601} or @samp{-mcpu=ARCEM} is in effect.
+
+@item -mjli-always
+@opindex mjli-always
+Force to call a function using jli_s instruction. This option is
+valid only for ARCv2 architecture.
+
+@item -mcpu=@var{cpu}
+@opindex mcpu
+Set architecture type, register usage, and instruction scheduling
+parameters for @var{cpu}. There are also shortcut alias options
+available for backward compatibility and convenience. Supported
+values for @var{cpu} are
+
+@table @samp
+@opindex mA6
+@opindex mARC600
+@item arc600
+Compile for ARC600. Aliases: @option{-mA6}, @option{-mARC600}.
+
+@item arc601
+@opindex mARC601
+Compile for ARC601. Alias: @option{-mARC601}.
+
+@item arc700
+@opindex mA7
+@opindex mARC700
+Compile for ARC700. Aliases: @option{-mA7}, @option{-mARC700}.
+This is the default when configured with @option{--with-cpu=arc700}@.
+
+@item arcem
+Compile for ARC EM.
+
+@item archs
+Compile for ARC HS.
+
+@item em
+Compile for ARC EM CPU with no hardware extensions.
+
+@item em4
+Compile for ARC EM4 CPU.
+
+@item em4_dmips
+Compile for ARC EM4 DMIPS CPU.
+
+@item em4_fpus
+Compile for ARC EM4 DMIPS CPU with the single-precision floating-point
+extension.
+
+@item em4_fpuda
+Compile for ARC EM4 DMIPS CPU with single-precision floating-point and
+double assist instructions.
+
+@item hs
+Compile for ARC HS CPU with no hardware extensions except the atomic
+instructions.
+
+@item hs34
+Compile for ARC HS34 CPU.
+
+@item hs38
+Compile for ARC HS38 CPU.
+
+@item hs38_linux
+Compile for ARC HS38 CPU with all hardware extensions on.
+
+@item hs4x
+Compile for ARC HS4x CPU.
+
+@item hs4xd
+Compile for ARC HS4xD CPU.
+
+@item hs4x_rel31
+Compile for ARC HS4x CPU release 3.10a.
+
+@item arc600_norm
+Compile for ARC 600 CPU with @code{norm} instructions enabled.
+
+@item arc600_mul32x16
+Compile for ARC 600 CPU with @code{norm} and 32x16-bit multiply
+instructions enabled.
+
+@item arc600_mul64
+Compile for ARC 600 CPU with @code{norm} and @code{mul64}-family
+instructions enabled.
+
+@item arc601_norm
+Compile for ARC 601 CPU with @code{norm} instructions enabled.
+
+@item arc601_mul32x16
+Compile for ARC 601 CPU with @code{norm} and 32x16-bit multiply
+instructions enabled.
+
+@item arc601_mul64
+Compile for ARC 601 CPU with @code{norm} and @code{mul64}-family
+instructions enabled.
+
+@item nps400
+Compile for ARC 700 on NPS400 chip.
+
+@item em_mini
+Compile for ARC EM minimalist configuration featuring reduced register
+set.
+
+@end table
+
+@item -mdpfp
+@opindex mdpfp
+@itemx -mdpfp-compact
+@opindex mdpfp-compact
+Generate double-precision FPX instructions, tuned for the compact
+implementation.
+
+@item -mdpfp-fast
+@opindex mdpfp-fast
+Generate double-precision FPX instructions, tuned for the fast
+implementation.
+
+@item -mno-dpfp-lrsr
+@opindex mno-dpfp-lrsr
+Disable @code{lr} and @code{sr} instructions from using FPX extension
+aux registers.
+
+@item -mea
+@opindex mea
+Generate extended arithmetic instructions. Currently only
+@code{divaw}, @code{adds}, @code{subs}, and @code{sat16} are
+supported. Only valid for @option{-mcpu=ARC700}.
+
+@item -mno-mpy
+@opindex mno-mpy
+@opindex mmpy
+Do not generate @code{mpy}-family instructions for ARC700. This option is
+deprecated.
+
+@item -mmul32x16
+@opindex mmul32x16
+Generate 32x16-bit multiply and multiply-accumulate instructions.
+
+@item -mmul64
+@opindex mmul64
+Generate @code{mul64} and @code{mulu64} instructions.
+Only valid for @option{-mcpu=ARC600}.
+
+@item -mnorm
+@opindex mnorm
+Generate @code{norm} instructions. This is the default if @option{-mcpu=ARC700}
+is in effect.
+
+@item -mspfp
+@opindex mspfp
+@itemx -mspfp-compact
+@opindex mspfp-compact
+Generate single-precision FPX instructions, tuned for the compact
+implementation.
+
+@item -mspfp-fast
+@opindex mspfp-fast
+Generate single-precision FPX instructions, tuned for the fast
+implementation.
+
+@item -msimd
+@opindex msimd
+Enable generation of ARC SIMD instructions via target-specific
+builtins. Only valid for @option{-mcpu=ARC700}.
+
+@item -msoft-float
+@opindex msoft-float
+This option ignored; it is provided for compatibility purposes only.
+Software floating-point code is emitted by default, and this default
+can overridden by FPX options; @option{-mspfp}, @option{-mspfp-compact}, or
+@option{-mspfp-fast} for single precision, and @option{-mdpfp},
+@option{-mdpfp-compact}, or @option{-mdpfp-fast} for double precision.
+
+@item -mswap
+@opindex mswap
+Generate @code{swap} instructions.
+
+@item -matomic
+@opindex matomic
+This enables use of the locked load/store conditional extension to implement
+atomic memory built-in functions. Not available for ARC 6xx or ARC
+EM cores.
+
+@item -mdiv-rem
+@opindex mdiv-rem
+Enable @code{div} and @code{rem} instructions for ARCv2 cores.
+
+@item -mcode-density
+@opindex mcode-density
+Enable code density instructions for ARC EM.
+This option is on by default for ARC HS.
+
+@item -mll64
+@opindex mll64
+Enable double load/store operations for ARC HS cores.
+
+@item -mtp-regno=@var{regno}
+@opindex mtp-regno
+Specify thread pointer register number.
+
+@item -mmpy-option=@var{multo}
+@opindex mmpy-option
+Compile ARCv2 code with a multiplier design option. You can specify
+the option using either a string or numeric value for @var{multo}.
+@samp{wlh1} is the default value. The recognized values are:
+
+@table @samp
+@item 0
+@itemx none
+No multiplier available.
+
+@item 1
+@itemx w
+16x16 multiplier, fully pipelined.
+The following instructions are enabled: @code{mpyw} and @code{mpyuw}.
+
+@item 2
+@itemx wlh1
+32x32 multiplier, fully
+pipelined (1 stage). The following instructions are additionally
+enabled: @code{mpy}, @code{mpyu}, @code{mpym}, @code{mpymu}, and @code{mpy_s}.
+
+@item 3
+@itemx wlh2
+32x32 multiplier, fully pipelined
+(2 stages). The following instructions are additionally enabled: @code{mpy},
+@code{mpyu}, @code{mpym}, @code{mpymu}, and @code{mpy_s}.
+
+@item 4
+@itemx wlh3
+Two 16x16 multipliers, blocking,
+sequential. The following instructions are additionally enabled: @code{mpy},
+@code{mpyu}, @code{mpym}, @code{mpymu}, and @code{mpy_s}.
+
+@item 5
+@itemx wlh4
+One 16x16 multiplier, blocking,
+sequential. The following instructions are additionally enabled: @code{mpy},
+@code{mpyu}, @code{mpym}, @code{mpymu}, and @code{mpy_s}.
+
+@item 6
+@itemx wlh5
+One 32x4 multiplier, blocking,
+sequential. The following instructions are additionally enabled: @code{mpy},
+@code{mpyu}, @code{mpym}, @code{mpymu}, and @code{mpy_s}.
+
+@item 7
+@itemx plus_dmpy
+ARC HS SIMD support.
+
+@item 8
+@itemx plus_macd
+ARC HS SIMD support.
+
+@item 9
+@itemx plus_qmacw
+ARC HS SIMD support.
+
+@end table
+
+This option is only available for ARCv2 cores@.
+
+@item -mfpu=@var{fpu}
+@opindex mfpu
+Enables support for specific floating-point hardware extensions for ARCv2
+cores. Supported values for @var{fpu} are:
+
+@table @samp
+
+@item fpus
+Enables support for single-precision floating-point hardware
+extensions@.
+
+@item fpud
+Enables support for double-precision floating-point hardware
+extensions. The single-precision floating-point extension is also
+enabled. Not available for ARC EM@.
+
+@item fpuda
+Enables support for double-precision floating-point hardware
+extensions using double-precision assist instructions. The single-precision
+floating-point extension is also enabled. This option is
+only available for ARC EM@.
+
+@item fpuda_div
+Enables support for double-precision floating-point hardware
+extensions using double-precision assist instructions.
+The single-precision floating-point, square-root, and divide
+extensions are also enabled. This option is
+only available for ARC EM@.
+
+@item fpuda_fma
+Enables support for double-precision floating-point hardware
+extensions using double-precision assist instructions.
+The single-precision floating-point and fused multiply and add
+hardware extensions are also enabled. This option is
+only available for ARC EM@.
+
+@item fpuda_all
+Enables support for double-precision floating-point hardware
+extensions using double-precision assist instructions.
+All single-precision floating-point hardware extensions are also
+enabled. This option is only available for ARC EM@.
+
+@item fpus_div
+Enables support for single-precision floating-point, square-root and divide
+hardware extensions@.
+
+@item fpud_div
+Enables support for double-precision floating-point, square-root and divide
+hardware extensions. This option
+includes option @samp{fpus_div}. Not available for ARC EM@.
+
+@item fpus_fma
+Enables support for single-precision floating-point and
+fused multiply and add hardware extensions@.
+
+@item fpud_fma
+Enables support for double-precision floating-point and
+fused multiply and add hardware extensions. This option
+includes option @samp{fpus_fma}. Not available for ARC EM@.
+
+@item fpus_all
+Enables support for all single-precision floating-point hardware
+extensions@.
+
+@item fpud_all
+Enables support for all single- and double-precision floating-point
+hardware extensions. Not available for ARC EM@.
+
+@end table
+
+@item -mirq-ctrl-saved=@var{register-range}, @var{blink}, @var{lp_count}
+@opindex mirq-ctrl-saved
+Specifies general-purposes registers that the processor automatically
+saves/restores on interrupt entry and exit. @var{register-range} is
+specified as two registers separated by a dash. The register range
+always starts with @code{r0}, the upper limit is @code{fp} register.
+@var{blink} and @var{lp_count} are optional. This option is only
+valid for ARC EM and ARC HS cores.
+
+@item -mrgf-banked-regs=@var{number}
+@opindex mrgf-banked-regs
+Specifies the number of registers replicated in second register bank
+on entry to fast interrupt. Fast interrupts are interrupts with the
+highest priority level P0. These interrupts save only PC and STATUS32
+registers to avoid memory transactions during interrupt entry and exit
+sequences. Use this option when you are using fast interrupts in an
+ARC V2 family processor. Permitted values are 4, 8, 16, and 32.
+
+@item -mlpc-width=@var{width}
+@opindex mlpc-width
+Specify the width of the @code{lp_count} register. Valid values for
+@var{width} are 8, 16, 20, 24, 28 and 32 bits. The default width is
+fixed to 32 bits. If the width is less than 32, the compiler does not
+attempt to transform loops in your program to use the zero-delay loop
+mechanism unless it is known that the @code{lp_count} register can
+hold the required loop-counter value. Depending on the width
+specified, the compiler and run-time library might continue to use the
+loop mechanism for various needs. This option defines macro
+@code{__ARC_LPC_WIDTH__} with the value of @var{width}.
+
+@item -mrf16
+@opindex mrf16
+This option instructs the compiler to generate code for a 16-entry
+register file. This option defines the @code{__ARC_RF16__}
+preprocessor macro.
+
+@item -mbranch-index
+@opindex mbranch-index
+Enable use of @code{bi} or @code{bih} instructions to implement jump
+tables.
+
+@end table
+
+The following options are passed through to the assembler, and also
+define preprocessor macro symbols.
+
+@c Flags used by the assembler, but for which we define preprocessor
+@c macro symbols as well.
+@table @gcctabopt
+@item -mdsp-packa
+@opindex mdsp-packa
+Passed down to the assembler to enable the DSP Pack A extensions.
+Also sets the preprocessor symbol @code{__Xdsp_packa}. This option is
+deprecated.
+
+@item -mdvbf
+@opindex mdvbf
+Passed down to the assembler to enable the dual Viterbi butterfly
+extension. Also sets the preprocessor symbol @code{__Xdvbf}. This
+option is deprecated.
+
+@c ARC700 4.10 extension instruction
+@item -mlock
+@opindex mlock
+Passed down to the assembler to enable the locked load/store
+conditional extension. Also sets the preprocessor symbol
+@code{__Xlock}.
+
+@item -mmac-d16
+@opindex mmac-d16
+Passed down to the assembler. Also sets the preprocessor symbol
+@code{__Xxmac_d16}. This option is deprecated.
+
+@item -mmac-24
+@opindex mmac-24
+Passed down to the assembler. Also sets the preprocessor symbol
+@code{__Xxmac_24}. This option is deprecated.
+
+@c ARC700 4.10 extension instruction
+@item -mrtsc
+@opindex mrtsc
+Passed down to the assembler to enable the 64-bit time-stamp counter
+extension instruction. Also sets the preprocessor symbol
+@code{__Xrtsc}. This option is deprecated.
+
+@c ARC700 4.10 extension instruction
+@item -mswape
+@opindex mswape
+Passed down to the assembler to enable the swap byte ordering
+extension instruction. Also sets the preprocessor symbol
+@code{__Xswape}.
+
+@item -mtelephony
+@opindex mtelephony
+Passed down to the assembler to enable dual- and single-operand
+instructions for telephony. Also sets the preprocessor symbol
+@code{__Xtelephony}. This option is deprecated.
+
+@item -mxy
+@opindex mxy
+Passed down to the assembler to enable the XY memory extension. Also
+sets the preprocessor symbol @code{__Xxy}.
+
+@end table
+
+The following options control how the assembly code is annotated:
+
+@c Assembly annotation options
+@table @gcctabopt
+@item -misize
+@opindex misize
+Annotate assembler instructions with estimated addresses.
+
+@item -mannotate-align
+@opindex mannotate-align
+Explain what alignment considerations lead to the decision to make an
+instruction short or long.
+
+@end table
+
+The following options are passed through to the linker:
+
+@c options passed through to the linker
+@table @gcctabopt
+@item -marclinux
+@opindex marclinux
+Passed through to the linker, to specify use of the @code{arclinux} emulation.
+This option is enabled by default in tool chains built for
+@w{@code{arc-linux-uclibc}} and @w{@code{arceb-linux-uclibc}} targets
+when profiling is not requested.
+
+@item -marclinux_prof
+@opindex marclinux_prof
+Passed through to the linker, to specify use of the
+@code{arclinux_prof} emulation. This option is enabled by default in
+tool chains built for @w{@code{arc-linux-uclibc}} and
+@w{@code{arceb-linux-uclibc}} targets when profiling is requested.
+
+@end table
+
+The following options control the semantics of generated code:
+
+@c semantically relevant code generation options
+@table @gcctabopt
+@item -mlong-calls
+@opindex mlong-calls
+Generate calls as register indirect calls, thus providing access
+to the full 32-bit address range.
+
+@item -mmedium-calls
+@opindex mmedium-calls
+Don't use less than 25-bit addressing range for calls, which is the
+offset available for an unconditional branch-and-link
+instruction. Conditional execution of function calls is suppressed, to
+allow use of the 25-bit range, rather than the 21-bit range with
+conditional branch-and-link. This is the default for tool chains built
+for @w{@code{arc-linux-uclibc}} and @w{@code{arceb-linux-uclibc}} targets.
+
+@item -G @var{num}
+@opindex G
+Put definitions of externally-visible data in a small data section if
+that data is no bigger than @var{num} bytes. The default value of
+@var{num} is 4 for any ARC configuration, or 8 when we have double
+load/store operations.
+
+@item -mno-sdata
+@opindex mno-sdata
+@opindex msdata
+Do not generate sdata references. This is the default for tool chains
+built for @w{@code{arc-linux-uclibc}} and @w{@code{arceb-linux-uclibc}}
+targets.
+
+@item -mvolatile-cache
+@opindex mvolatile-cache
+Use ordinarily cached memory accesses for volatile references. This is the
+default.
+
+@item -mno-volatile-cache
+@opindex mno-volatile-cache
+@opindex mvolatile-cache
+Enable cache bypass for volatile references.
+
+@end table
+
+The following options fine tune code generation:
+@c code generation tuning options
+@table @gcctabopt
+@item -malign-call
+@opindex malign-call
+Does nothing. Preserved for backward compatibility.
+
+@item -mauto-modify-reg
+@opindex mauto-modify-reg
+Enable the use of pre/post modify with register displacement.
+
+@item -mbbit-peephole
+@opindex mbbit-peephole
+Enable bbit peephole2.
+
+@item -mno-brcc
+@opindex mno-brcc
+This option disables a target-specific pass in @file{arc_reorg} to
+generate compare-and-branch (@code{br@var{cc}}) instructions.
+It has no effect on
+generation of these instructions driven by the combiner pass.
+
+@item -mcase-vector-pcrel
+@opindex mcase-vector-pcrel
+Use PC-relative switch case tables to enable case table shortening.
+This is the default for @option{-Os}.
+
+@item -mcompact-casesi
+@opindex mcompact-casesi
+Enable compact @code{casesi} pattern. This is the default for @option{-Os},
+and only available for ARCv1 cores. This option is deprecated.
+
+@item -mno-cond-exec
+@opindex mno-cond-exec
+Disable the ARCompact-specific pass to generate conditional
+execution instructions.
+
+Due to delay slot scheduling and interactions between operand numbers,
+literal sizes, instruction lengths, and the support for conditional execution,
+the target-independent pass to generate conditional execution is often lacking,
+so the ARC port has kept a special pass around that tries to find more
+conditional execution generation opportunities after register allocation,
+branch shortening, and delay slot scheduling have been done. This pass
+generally, but not always, improves performance and code size, at the cost of
+extra compilation time, which is why there is an option to switch it off.
+If you have a problem with call instructions exceeding their allowable
+offset range because they are conditionalized, you should consider using
+@option{-mmedium-calls} instead.
+
+@item -mearly-cbranchsi
+@opindex mearly-cbranchsi
+Enable pre-reload use of the @code{cbranchsi} pattern.
+
+@item -mexpand-adddi
+@opindex mexpand-adddi
+Expand @code{adddi3} and @code{subdi3} at RTL generation time into
+@code{add.f}, @code{adc} etc. This option is deprecated.
+
+@item -mindexed-loads
+@opindex mindexed-loads
+Enable the use of indexed loads. This can be problematic because some
+optimizers then assume that indexed stores exist, which is not
+the case.
+
+@item -mlra
+@opindex mlra
+Enable Local Register Allocation. This is still experimental for ARC,
+so by default the compiler uses standard reload
+(i.e.@: @option{-mno-lra}).
+
+@item -mlra-priority-none
+@opindex mlra-priority-none
+Don't indicate any priority for target registers.
+
+@item -mlra-priority-compact
+@opindex mlra-priority-compact
+Indicate target register priority for r0..r3 / r12..r15.
+
+@item -mlra-priority-noncompact
+@opindex mlra-priority-noncompact
+Reduce target register priority for r0..r3 / r12..r15.
+
+@item -mmillicode
+@opindex mmillicode
+When optimizing for size (using @option{-Os}), prologues and epilogues
+that have to save or restore a large number of registers are often
+shortened by using call to a special function in libgcc; this is
+referred to as a @emph{millicode} call. As these calls can pose
+performance issues, and/or cause linking issues when linking in a
+nonstandard way, this option is provided to turn on or off millicode
+call generation.
+
+@item -mcode-density-frame
+@opindex mcode-density-frame
+This option enable the compiler to emit @code{enter} and @code{leave}
+instructions. These instructions are only valid for CPUs with
+code-density feature.
+
+@item -mmixed-code
+@opindex mmixed-code
+Does nothing. Preserved for backward compatibility.
+
+@item -mq-class
+@opindex mq-class
+Ths option is deprecated. Enable @samp{q} instruction alternatives.
+This is the default for @option{-Os}.
+
+@item -mRcq
+@opindex mRcq
+Does nothing. Preserved for backward compatibility.
+
+@item -mRcw
+@opindex mRcw
+Does nothing. Preserved for backward compatibility.
+
+@item -msize-level=@var{level}
+@opindex msize-level
+Fine-tune size optimization with regards to instruction lengths and alignment.
+The recognized values for @var{level} are:
+@table @samp
+@item 0
+No size optimization. This level is deprecated and treated like @samp{1}.
+
+@item 1
+Short instructions are used opportunistically.
+
+@item 2
+In addition, alignment of loops and of code after barriers are dropped.
+
+@item 3
+In addition, optional data alignment is dropped, and the option @option{Os} is enabled.
+
+@end table
+
+This defaults to @samp{3} when @option{-Os} is in effect. Otherwise,
+the behavior when this is not set is equivalent to level @samp{1}.
+
+@item -mtune=@var{cpu}
+@opindex mtune
+Set instruction scheduling parameters for @var{cpu}, overriding any implied
+by @option{-mcpu=}.
+
+Supported values for @var{cpu} are
+
+@table @samp
+@item ARC600
+Tune for ARC600 CPU.
+
+@item ARC601
+Tune for ARC601 CPU.
+
+@item ARC700
+Tune for ARC700 CPU with standard multiplier block.
+
+@item ARC700-xmac
+Tune for ARC700 CPU with XMAC block.
+
+@item ARC725D
+Tune for ARC725D CPU.
+
+@item ARC750D
+Tune for ARC750D CPU.
+
+@item core3
+Tune for ARCv2 core3 type CPU. This option enable usage of
+@code{dbnz} instruction.
+
+@item release31a
+Tune for ARC4x release 3.10a.
+
+@end table
+
+@item -mmultcost=@var{num}
+@opindex mmultcost
+Cost to assume for a multiply instruction, with @samp{4} being equal to a
+normal instruction.
+
+@item -munalign-prob-threshold=@var{probability}
+@opindex munalign-prob-threshold
+Does nothing. Preserved for backward compatibility.
+
+@end table
+
+The following options are maintained for backward compatibility, but
+are now deprecated and will be removed in a future release:
+
+@c Deprecated options
+@table @gcctabopt
+
+@item -margonaut
+@opindex margonaut
+Obsolete FPX.
+
+@item -mbig-endian
+@opindex mbig-endian
+@itemx -EB
+@opindex EB
+Compile code for big-endian targets. Use of these options is now
+deprecated. Big-endian code is supported by configuring GCC to build
+@w{@code{arceb-elf32}} and @w{@code{arceb-linux-uclibc}} targets,
+for which big endian is the default.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+@itemx -EL
+@opindex EL
+Compile code for little-endian targets. Use of these options is now
+deprecated. Little-endian code is supported by configuring GCC to build
+@w{@code{arc-elf32}} and @w{@code{arc-linux-uclibc}} targets,
+for which little endian is the default.
+
+@item -mbarrel_shifter
+@opindex mbarrel_shifter
+Replaced by @option{-mbarrel-shifter}.
+
+@item -mdpfp_compact
+@opindex mdpfp_compact
+Replaced by @option{-mdpfp-compact}.
+
+@item -mdpfp_fast
+@opindex mdpfp_fast
+Replaced by @option{-mdpfp-fast}.
+
+@item -mdsp_packa
+@opindex mdsp_packa
+Replaced by @option{-mdsp-packa}.
+
+@item -mEA
+@opindex mEA
+Replaced by @option{-mea}.
+
+@item -mmac_24
+@opindex mmac_24
+Replaced by @option{-mmac-24}.
+
+@item -mmac_d16
+@opindex mmac_d16
+Replaced by @option{-mmac-d16}.
+
+@item -mspfp_compact
+@opindex mspfp_compact
+Replaced by @option{-mspfp-compact}.
+
+@item -mspfp_fast
+@opindex mspfp_fast
+Replaced by @option{-mspfp-fast}.
+
+@item -mtune=@var{cpu}
+@opindex mtune
+Values @samp{arc600}, @samp{arc601}, @samp{arc700} and
+@samp{arc700-xmac} for @var{cpu} are replaced by @samp{ARC600},
+@samp{ARC601}, @samp{ARC700} and @samp{ARC700-xmac} respectively.
+
+@item -multcost=@var{num}
+@opindex multcost
+Replaced by @option{-mmultcost}.
+
+@end table
+
+@node ARM Options
+@subsection ARM Options
+@cindex ARM options
+
+These @samp{-m} options are defined for the ARM port:
+
+@table @gcctabopt
+@item -mabi=@var{name}
+@opindex mabi
+Generate code for the specified ABI@. Permissible values are: @samp{apcs-gnu},
+@samp{atpcs}, @samp{aapcs}, @samp{aapcs-linux} and @samp{iwmmxt}.
+
+@item -mapcs-frame
+@opindex mapcs-frame
+Generate a stack frame that is compliant with the ARM Procedure Call
+Standard for all functions, even if this is not strictly necessary for
+correct execution of the code. Specifying @option{-fomit-frame-pointer}
+with this option causes the stack frames not to be generated for
+leaf functions. The default is @option{-mno-apcs-frame}.
+This option is deprecated.
+
+@item -mapcs
+@opindex mapcs
+This is a synonym for @option{-mapcs-frame} and is deprecated.
+
+@ignore
+@c not currently implemented
+@item -mapcs-stack-check
+@opindex mapcs-stack-check
+Generate code to check the amount of stack space available upon entry to
+every function (that actually uses some stack space). If there is
+insufficient space available then either the function
+@code{__rt_stkovf_split_small} or @code{__rt_stkovf_split_big} is
+called, depending upon the amount of stack space required. The runtime
+system is required to provide these functions. The default is
+@option{-mno-apcs-stack-check}, since this produces smaller code.
+
+@c not currently implemented
+@item -mapcs-reentrant
+@opindex mapcs-reentrant
+Generate reentrant, position-independent code. The default is
+@option{-mno-apcs-reentrant}.
+@end ignore
+
+@item -mthumb-interwork
+@opindex mthumb-interwork
+Generate code that supports calling between the ARM and Thumb
+instruction sets. Without this option, on pre-v5 architectures, the
+two instruction sets cannot be reliably used inside one program. The
+default is @option{-mno-thumb-interwork}, since slightly larger code
+is generated when @option{-mthumb-interwork} is specified. In AAPCS
+configurations this option is meaningless.
+
+@item -mno-sched-prolog
+@opindex mno-sched-prolog
+@opindex msched-prolog
+Prevent the reordering of instructions in the function prologue, or the
+merging of those instruction with the instructions in the function's
+body. This means that all functions start with a recognizable set
+of instructions (or in fact one of a choice from a small set of
+different function prologues), and this information can be used to
+locate the start of functions inside an executable piece of code. The
+default is @option{-msched-prolog}.
+
+@item -mfloat-abi=@var{name}
+@opindex mfloat-abi
+Specifies which floating-point ABI to use. Permissible values
+are: @samp{soft}, @samp{softfp} and @samp{hard}.
+
+Specifying @samp{soft} causes GCC to generate output containing
+library calls for floating-point operations.
+@samp{softfp} allows the generation of code using hardware floating-point
+instructions, but still uses the soft-float calling conventions.
+@samp{hard} allows generation of floating-point instructions
+and uses FPU-specific calling conventions.
+
+The default depends on the specific target configuration. Note that
+the hard-float and soft-float ABIs are not link-compatible; you must
+compile your entire program with the same ABI, and link with a
+compatible set of libraries.
+
+@item -mgeneral-regs-only
+@opindex mgeneral-regs-only
+Generate code which uses only the general-purpose registers. This will prevent
+the compiler from using floating-point and Advanced SIMD registers but will not
+impose any restrictions on the assembler.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+Generate code for a processor running in little-endian mode. This is
+the default for all standard configurations.
+
+@item -mbig-endian
+@opindex mbig-endian
+Generate code for a processor running in big-endian mode; the default is
+to compile code for a little-endian processor.
+
+@item -mbe8
+@itemx -mbe32
+@opindex mbe8
+When linking a big-endian image select between BE8 and BE32 formats.
+The option has no effect for little-endian images and is ignored. The
+default is dependent on the selected target architecture. For ARMv6
+and later architectures the default is BE8, for older architectures
+the default is BE32. BE32 format has been deprecated by ARM.
+
+@item -march=@var{name}@r{[}+extension@dots{}@r{]}
+@opindex march
+This specifies the name of the target ARM architecture. GCC uses this
+name to determine what kind of instructions it can emit when generating
+assembly code. This option can be used in conjunction with or instead
+of the @option{-mcpu=} option.
+
+Permissible names are:
+@samp{armv4t},
+@samp{armv5t}, @samp{armv5te},
+@samp{armv6}, @samp{armv6j}, @samp{armv6k}, @samp{armv6kz}, @samp{armv6t2},
+@samp{armv6z}, @samp{armv6zk},
+@samp{armv7}, @samp{armv7-a}, @samp{armv7ve},
+@samp{armv8-a}, @samp{armv8.1-a}, @samp{armv8.2-a}, @samp{armv8.3-a},
+@samp{armv8.4-a},
+@samp{armv8.5-a},
+@samp{armv8.6-a},
+@samp{armv9-a},
+@samp{armv7-r},
+@samp{armv8-r},
+@samp{armv6-m}, @samp{armv6s-m},
+@samp{armv7-m}, @samp{armv7e-m},
+@samp{armv8-m.base}, @samp{armv8-m.main},
+@samp{armv8.1-m.main},
+@samp{armv9-a},
+@samp{iwmmxt} and @samp{iwmmxt2}.
+
+Additionally, the following architectures, which lack support for the
+Thumb execution state, are recognized but support is deprecated: @samp{armv4}.
+
+Many of the architectures support extensions. These can be added by
+appending @samp{+@var{extension}} to the architecture name. Extension
+options are processed in order and capabilities accumulate. An extension
+will also enable any necessary base extensions
+upon which it depends. For example, the @samp{+crypto} extension
+will always enable the @samp{+simd} extension. The exception to the
+additive construction is for extensions that are prefixed with
+@samp{+no@dots{}}: these extensions disable the specified option and
+any other extensions that may depend on the presence of that
+extension.
+
+For example, @samp{-march=armv7-a+simd+nofp+vfpv4} is equivalent to
+writing @samp{-march=armv7-a+vfpv4} since the @samp{+simd} option is
+entirely disabled by the @samp{+nofp} option that follows it.
+
+Most extension names are generically named, but have an effect that is
+dependent upon the architecture to which it is applied. For example,
+the @samp{+simd} option can be applied to both @samp{armv7-a} and
+@samp{armv8-a} architectures, but will enable the original ARMv7-A
+Advanced SIMD (Neon) extensions for @samp{armv7-a} and the ARMv8-A
+variant for @samp{armv8-a}.
+
+The table below lists the supported extensions for each architecture.
+Architectures not mentioned do not support any extensions.
+
+@table @samp
+@item armv5te
+@itemx armv6
+@itemx armv6j
+@itemx armv6k
+@itemx armv6kz
+@itemx armv6t2
+@itemx armv6z
+@itemx armv6zk
+@table @samp
+@item +fp
+The VFPv2 floating-point instructions. The extension @samp{+vfpv2} can be
+used as an alias for this extension.
+
+@item +nofp
+Disable the floating-point instructions.
+@end table
+
+@item armv7
+The common subset of the ARMv7-A, ARMv7-R and ARMv7-M architectures.
+@table @samp
+@item +fp
+The VFPv3 floating-point instructions, with 16 double-precision
+registers. The extension @samp{+vfpv3-d16} can be used as an alias
+for this extension. Note that floating-point is not supported by the
+base ARMv7-M architecture, but is compatible with both the ARMv7-A and
+ARMv7-R architectures.
+
+@item +nofp
+Disable the floating-point instructions.
+@end table
+
+@item armv7-a
+@table @samp
+@item +mp
+The multiprocessing extension.
+
+@item +sec
+The security extension.
+
+@item +fp
+The VFPv3 floating-point instructions, with 16 double-precision
+registers. The extension @samp{+vfpv3-d16} can be used as an alias
+for this extension.
+
+@item +simd
+The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions.
+The extensions @samp{+neon} and @samp{+neon-vfpv3} can be used as aliases
+for this extension.
+
+@item +vfpv3
+The VFPv3 floating-point instructions, with 32 double-precision
+registers.
+
+@item +vfpv3-d16-fp16
+The VFPv3 floating-point instructions, with 16 double-precision
+registers and the half-precision floating-point conversion operations.
+
+@item +vfpv3-fp16
+The VFPv3 floating-point instructions, with 32 double-precision
+registers and the half-precision floating-point conversion operations.
+
+@item +vfpv4-d16
+The VFPv4 floating-point instructions, with 16 double-precision
+registers.
+
+@item +vfpv4
+The VFPv4 floating-point instructions, with 32 double-precision
+registers.
+
+@item +neon-fp16
+The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions, with
+the half-precision floating-point conversion operations.
+
+@item +neon-vfpv4
+The Advanced SIMD (Neon) v2 and the VFPv4 floating-point instructions.
+
+@item +nosimd
+Disable the Advanced SIMD instructions (does not disable floating point).
+
+@item +nofp
+Disable the floating-point and Advanced SIMD instructions.
+@end table
+
+@item armv7ve
+The extended version of the ARMv7-A architecture with support for
+virtualization.
+@table @samp
+@item +fp
+The VFPv4 floating-point instructions, with 16 double-precision registers.
+The extension @samp{+vfpv4-d16} can be used as an alias for this extension.
+
+@item +simd
+The Advanced SIMD (Neon) v2 and the VFPv4 floating-point instructions. The
+extension @samp{+neon-vfpv4} can be used as an alias for this extension.
+
+@item +vfpv3-d16
+The VFPv3 floating-point instructions, with 16 double-precision
+registers.
+
+@item +vfpv3
+The VFPv3 floating-point instructions, with 32 double-precision
+registers.
+
+@item +vfpv3-d16-fp16
+The VFPv3 floating-point instructions, with 16 double-precision
+registers and the half-precision floating-point conversion operations.
+
+@item +vfpv3-fp16
+The VFPv3 floating-point instructions, with 32 double-precision
+registers and the half-precision floating-point conversion operations.
+
+@item +vfpv4-d16
+The VFPv4 floating-point instructions, with 16 double-precision
+registers.
+
+@item +vfpv4
+The VFPv4 floating-point instructions, with 32 double-precision
+registers.
+
+@item +neon
+The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions.
+The extension @samp{+neon-vfpv3} can be used as an alias for this extension.
+
+@item +neon-fp16
+The Advanced SIMD (Neon) v1 and the VFPv3 floating-point instructions, with
+the half-precision floating-point conversion operations.
+
+@item +nosimd
+Disable the Advanced SIMD instructions (does not disable floating point).
+
+@item +nofp
+Disable the floating-point and Advanced SIMD instructions.
+@end table
+
+@item armv8-a
+@table @samp
+@item +crc
+The Cyclic Redundancy Check (CRC) instructions.
+@item +simd
+The ARMv8-A Advanced SIMD and floating-point instructions.
+@item +crypto
+The cryptographic instructions.
+@item +nocrypto
+Disable the cryptographic instructions.
+@item +nofp
+Disable the floating-point, Advanced SIMD and cryptographic instructions.
+@item +sb
+Speculation Barrier Instruction.
+@item +predres
+Execution and Data Prediction Restriction Instructions.
+@end table
+
+@item armv8.1-a
+@table @samp
+@item +simd
+The ARMv8.1-A Advanced SIMD and floating-point instructions.
+
+@item +crypto
+The cryptographic instructions. This also enables the Advanced SIMD and
+floating-point instructions.
+
+@item +nocrypto
+Disable the cryptographic instructions.
+
+@item +nofp
+Disable the floating-point, Advanced SIMD and cryptographic instructions.
+
+@item +sb
+Speculation Barrier Instruction.
+
+@item +predres
+Execution and Data Prediction Restriction Instructions.
+@end table
+
+@item armv8.2-a
+@itemx armv8.3-a
+@table @samp
+@item +fp16
+The half-precision floating-point data processing instructions.
+This also enables the Advanced SIMD and floating-point instructions.
+
+@item +fp16fml
+The half-precision floating-point fmla extension. This also enables
+the half-precision floating-point extension and Advanced SIMD and
+floating-point instructions.
+
+@item +simd
+The ARMv8.1-A Advanced SIMD and floating-point instructions.
+
+@item +crypto
+The cryptographic instructions. This also enables the Advanced SIMD and
+floating-point instructions.
+
+@item +dotprod
+Enable the Dot Product extension. This also enables Advanced SIMD instructions.
+
+@item +nocrypto
+Disable the cryptographic extension.
+
+@item +nofp
+Disable the floating-point, Advanced SIMD and cryptographic instructions.
+
+@item +sb
+Speculation Barrier Instruction.
+
+@item +predres
+Execution and Data Prediction Restriction Instructions.
+
+@item +i8mm
+8-bit Integer Matrix Multiply instructions.
+This also enables Advanced SIMD and floating-point instructions.
+
+@item +bf16
+Brain half-precision floating-point instructions.
+This also enables Advanced SIMD and floating-point instructions.
+@end table
+
+@item armv8.4-a
+@table @samp
+@item +fp16
+The half-precision floating-point data processing instructions.
+This also enables the Advanced SIMD and floating-point instructions as well
+as the Dot Product extension and the half-precision floating-point fmla
+extension.
+
+@item +simd
+The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the
+Dot Product extension.
+
+@item +crypto
+The cryptographic instructions. This also enables the Advanced SIMD and
+floating-point instructions as well as the Dot Product extension.
+
+@item +nocrypto
+Disable the cryptographic extension.
+
+@item +nofp
+Disable the floating-point, Advanced SIMD and cryptographic instructions.
+
+@item +sb
+Speculation Barrier Instruction.
+
+@item +predres
+Execution and Data Prediction Restriction Instructions.
+
+@item +i8mm
+8-bit Integer Matrix Multiply instructions.
+This also enables Advanced SIMD and floating-point instructions.
+
+@item +bf16
+Brain half-precision floating-point instructions.
+This also enables Advanced SIMD and floating-point instructions.
+@end table
+
+@item armv8.5-a
+@table @samp
+@item +fp16
+The half-precision floating-point data processing instructions.
+This also enables the Advanced SIMD and floating-point instructions as well
+as the Dot Product extension and the half-precision floating-point fmla
+extension.
+
+@item +simd
+The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the
+Dot Product extension.
+
+@item +crypto
+The cryptographic instructions. This also enables the Advanced SIMD and
+floating-point instructions as well as the Dot Product extension.
+
+@item +nocrypto
+Disable the cryptographic extension.
+
+@item +nofp
+Disable the floating-point, Advanced SIMD and cryptographic instructions.
+
+@item +i8mm
+8-bit Integer Matrix Multiply instructions.
+This also enables Advanced SIMD and floating-point instructions.
+
+@item +bf16
+Brain half-precision floating-point instructions.
+This also enables Advanced SIMD and floating-point instructions.
+@end table
+
+@item armv8.6-a
+@table @samp
+@item +fp16
+The half-precision floating-point data processing instructions.
+This also enables the Advanced SIMD and floating-point instructions as well
+as the Dot Product extension and the half-precision floating-point fmla
+extension.
+
+@item +simd
+The ARMv8.3-A Advanced SIMD and floating-point instructions as well as the
+Dot Product extension.
+
+@item +crypto
+The cryptographic instructions. This also enables the Advanced SIMD and
+floating-point instructions as well as the Dot Product extension.
+
+@item +nocrypto
+Disable the cryptographic extension.
+
+@item +nofp
+Disable the floating-point, Advanced SIMD and cryptographic instructions.
+
+@item +i8mm
+8-bit Integer Matrix Multiply instructions.
+This also enables Advanced SIMD and floating-point instructions.
+
+@item +bf16
+Brain half-precision floating-point instructions.
+This also enables Advanced SIMD and floating-point instructions.
+@end table
+
+@item armv7-r
+@table @samp
+@item +fp.sp
+The single-precision VFPv3 floating-point instructions. The extension
+@samp{+vfpv3xd} can be used as an alias for this extension.
+
+@item +fp
+The VFPv3 floating-point instructions with 16 double-precision registers.
+The extension +vfpv3-d16 can be used as an alias for this extension.
+
+@item +vfpv3xd-d16-fp16
+The single-precision VFPv3 floating-point instructions with 16 double-precision
+registers and the half-precision floating-point conversion operations.
+
+@item +vfpv3-d16-fp16
+The VFPv3 floating-point instructions with 16 double-precision
+registers and the half-precision floating-point conversion operations.
+
+@item +nofp
+Disable the floating-point extension.
+
+@item +idiv
+The ARM-state integer division instructions.
+
+@item +noidiv
+Disable the ARM-state integer division extension.
+@end table
+
+@item armv7e-m
+@table @samp
+@item +fp
+The single-precision VFPv4 floating-point instructions.
+
+@item +fpv5
+The single-precision FPv5 floating-point instructions.
+
+@item +fp.dp
+The single- and double-precision FPv5 floating-point instructions.
+
+@item +nofp
+Disable the floating-point extensions.
+@end table
+
+@item armv8.1-m.main
+@table @samp
+
+@item +dsp
+The DSP instructions.
+
+@item +mve
+The M-Profile Vector Extension (MVE) integer instructions.
+
+@item +mve.fp
+The M-Profile Vector Extension (MVE) integer and single precision
+floating-point instructions.
+
+@item +fp
+The single-precision floating-point instructions.
+
+@item +fp.dp
+The single- and double-precision floating-point instructions.
+
+@item +nofp
+Disable the floating-point extension.
+
+@item +cdecp0, +cdecp1, ... , +cdecp7
+Enable the Custom Datapath Extension (CDE) on selected coprocessors according
+to the numbers given in the options in the range 0 to 7.
+@end table
+
+@item armv8-m.main
+@table @samp
+@item +dsp
+The DSP instructions.
+
+@item +nodsp
+Disable the DSP extension.
+
+@item +fp
+The single-precision floating-point instructions.
+
+@item +fp.dp
+The single- and double-precision floating-point instructions.
+
+@item +nofp
+Disable the floating-point extension.
+
+@item +cdecp0, +cdecp1, ... , +cdecp7
+Enable the Custom Datapath Extension (CDE) on selected coprocessors according
+to the numbers given in the options in the range 0 to 7.
+@end table
+
+@item armv8-r
+@table @samp
+@item +crc
+The Cyclic Redundancy Check (CRC) instructions.
+@item +fp.sp
+The single-precision FPv5 floating-point instructions.
+@item +simd
+The ARMv8-A Advanced SIMD and floating-point instructions.
+@item +crypto
+The cryptographic instructions.
+@item +nocrypto
+Disable the cryptographic instructions.
+@item +nofp
+Disable the floating-point, Advanced SIMD and cryptographic instructions.
+@end table
+
+@end table
+
+@option{-march=native} causes the compiler to auto-detect the architecture
+of the build computer. At present, this feature is only supported on
+GNU/Linux, and not all architectures are recognized. If the auto-detect
+is unsuccessful the option has no effect.
+
+@item -mtune=@var{name}
+@opindex mtune
+This option specifies the name of the target ARM processor for
+which GCC should tune the performance of the code.
+For some ARM implementations better performance can be obtained by using
+this option.
+Permissible names are: @samp{arm7tdmi}, @samp{arm7tdmi-s}, @samp{arm710t},
+@samp{arm720t}, @samp{arm740t}, @samp{strongarm}, @samp{strongarm110},
+@samp{strongarm1100}, @samp{strongarm1110}, @samp{arm8}, @samp{arm810},
+@samp{arm9}, @samp{arm9e}, @samp{arm920}, @samp{arm920t}, @samp{arm922t},
+@samp{arm946e-s}, @samp{arm966e-s}, @samp{arm968e-s}, @samp{arm926ej-s},
+@samp{arm940t}, @samp{arm9tdmi}, @samp{arm10tdmi}, @samp{arm1020t},
+@samp{arm1026ej-s}, @samp{arm10e}, @samp{arm1020e}, @samp{arm1022e},
+@samp{arm1136j-s}, @samp{arm1136jf-s}, @samp{mpcore}, @samp{mpcorenovfp},
+@samp{arm1156t2-s}, @samp{arm1156t2f-s}, @samp{arm1176jz-s}, @samp{arm1176jzf-s},
+@samp{generic-armv7-a}, @samp{cortex-a5}, @samp{cortex-a7}, @samp{cortex-a8},
+@samp{cortex-a9}, @samp{cortex-a12}, @samp{cortex-a15}, @samp{cortex-a17},
+@samp{cortex-a32}, @samp{cortex-a35}, @samp{cortex-a53}, @samp{cortex-a55},
+@samp{cortex-a57}, @samp{cortex-a72}, @samp{cortex-a73}, @samp{cortex-a75},
+@samp{cortex-a76}, @samp{cortex-a76ae}, @samp{cortex-a77},
+@samp{cortex-a78}, @samp{cortex-a78ae}, @samp{cortex-a78c}, @samp{cortex-a710},
+@samp{ares}, @samp{cortex-r4}, @samp{cortex-r4f}, @samp{cortex-r5},
+@samp{cortex-r7}, @samp{cortex-r8}, @samp{cortex-r52}, @samp{cortex-r52plus},
+@samp{cortex-m0}, @samp{cortex-m0plus}, @samp{cortex-m1}, @samp{cortex-m3},
+@samp{cortex-m4}, @samp{cortex-m7}, @samp{cortex-m23}, @samp{cortex-m33},
+@samp{cortex-m35p}, @samp{cortex-m55}, @samp{cortex-x1},
+@samp{cortex-m1.small-multiply}, @samp{cortex-m0.small-multiply},
+@samp{cortex-m0plus.small-multiply}, @samp{exynos-m1}, @samp{marvell-pj4},
+@samp{neoverse-n1}, @samp{neoverse-n2}, @samp{neoverse-v1}, @samp{xscale},
+@samp{iwmmxt}, @samp{iwmmxt2}, @samp{ep9312}, @samp{fa526}, @samp{fa626},
+@samp{fa606te}, @samp{fa626te}, @samp{fmp626}, @samp{fa726te}, @samp{star-mc1},
+@samp{xgene1}.
+
+Additionally, this option can specify that GCC should tune the performance
+of the code for a big.LITTLE system. Permissible names are:
+@samp{cortex-a15.cortex-a7}, @samp{cortex-a17.cortex-a7},
+@samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
+@samp{cortex-a72.cortex-a35}, @samp{cortex-a73.cortex-a53},
+@samp{cortex-a75.cortex-a55}, @samp{cortex-a76.cortex-a55}.
+
+@option{-mtune=generic-@var{arch}} specifies that GCC should tune the
+performance for a blend of processors within architecture @var{arch}.
+The aim is to generate code that run well on the current most popular
+processors, balancing between optimizations that benefit some CPUs in the
+range, and avoiding performance pitfalls of other CPUs. The effects of
+this option may change in future GCC versions as CPU models come and go.
+
+@option{-mtune} permits the same extension options as @option{-mcpu}, but
+the extension options do not affect the tuning of the generated code.
+
+@option{-mtune=native} causes the compiler to auto-detect the CPU
+of the build computer. At present, this feature is only supported on
+GNU/Linux, and not all architectures are recognized. If the auto-detect is
+unsuccessful the option has no effect.
+
+@item -mcpu=@var{name}@r{[}+extension@dots{}@r{]}
+@opindex mcpu
+This specifies the name of the target ARM processor. GCC uses this name
+to derive the name of the target ARM architecture (as if specified
+by @option{-march}) and the ARM processor type for which to tune for
+performance (as if specified by @option{-mtune}). Where this option
+is used in conjunction with @option{-march} or @option{-mtune},
+those options take precedence over the appropriate part of this option.
+
+Many of the supported CPUs implement optional architectural
+extensions. Where this is so the architectural extensions are
+normally enabled by default. If implementations that lack the
+extension exist, then the extension syntax can be used to disable
+those extensions that have been omitted. For floating-point and
+Advanced SIMD (Neon) instructions, the settings of the options
+@option{-mfloat-abi} and @option{-mfpu} must also be considered:
+floating-point and Advanced SIMD instructions will only be used if
+@option{-mfloat-abi} is not set to @samp{soft}; and any setting of
+@option{-mfpu} other than @samp{auto} will override the available
+floating-point and SIMD extension instructions.
+
+For example, @samp{cortex-a9} can be found in three major
+configurations: integer only, with just a floating-point unit or with
+floating-point and Advanced SIMD. The default is to enable all the
+instructions, but the extensions @samp{+nosimd} and @samp{+nofp} can
+be used to disable just the SIMD or both the SIMD and floating-point
+instructions respectively.
+
+Permissible names for this option are the same as those for
+@option{-mtune}.
+
+The following extension options are common to the listed CPUs:
+
+@table @samp
+@item +nodsp
+Disable the DSP instructions on @samp{cortex-m33}, @samp{cortex-m35p}
+and @samp{cortex-m55}. Also disable the M-Profile Vector Extension (MVE)
+integer and single precision floating-point instructions on @samp{cortex-m55}.
+
+@item +nomve
+Disable the M-Profile Vector Extension (MVE) integer and single precision
+floating-point instructions on @samp{cortex-m55}.
+
+@item +nomve.fp
+Disable the M-Profile Vector Extension (MVE) single precision floating-point
+instructions on @samp{cortex-m55}.
+
+@item +nofp
+Disables the floating-point instructions on @samp{arm9e},
+@samp{arm946e-s}, @samp{arm966e-s}, @samp{arm968e-s}, @samp{arm10e},
+@samp{arm1020e}, @samp{arm1022e}, @samp{arm926ej-s},
+@samp{arm1026ej-s}, @samp{cortex-r5}, @samp{cortex-r7}, @samp{cortex-r8},
+@samp{cortex-m4}, @samp{cortex-m7}, @samp{cortex-m33}, @samp{cortex-m35p}
+and @samp{cortex-m55}.
+Disables the floating-point and SIMD instructions on
+@samp{generic-armv7-a}, @samp{cortex-a5}, @samp{cortex-a7},
+@samp{cortex-a8}, @samp{cortex-a9}, @samp{cortex-a12},
+@samp{cortex-a15}, @samp{cortex-a17}, @samp{cortex-a15.cortex-a7},
+@samp{cortex-a17.cortex-a7}, @samp{cortex-a32}, @samp{cortex-a35},
+@samp{cortex-a53} and @samp{cortex-a55}.
+
+@item +nofp.dp
+Disables the double-precision component of the floating-point instructions
+on @samp{cortex-r5}, @samp{cortex-r7}, @samp{cortex-r8}, @samp{cortex-r52},
+@samp{cortex-r52plus} and @samp{cortex-m7}.
+
+@item +nosimd
+Disables the SIMD (but not floating-point) instructions on
+@samp{generic-armv7-a}, @samp{cortex-a5}, @samp{cortex-a7}
+and @samp{cortex-a9}.
+
+@item +crypto
+Enables the cryptographic instructions on @samp{cortex-a32},
+@samp{cortex-a35}, @samp{cortex-a53}, @samp{cortex-a55}, @samp{cortex-a57},
+@samp{cortex-a72}, @samp{cortex-a73}, @samp{cortex-a75}, @samp{exynos-m1},
+@samp{xgene1}, @samp{cortex-a57.cortex-a53}, @samp{cortex-a72.cortex-a53},
+@samp{cortex-a73.cortex-a35}, @samp{cortex-a73.cortex-a53} and
+@samp{cortex-a75.cortex-a55}.
+@end table
+
+Additionally the @samp{generic-armv7-a} pseudo target defaults to
+VFPv3 with 16 double-precision registers. It supports the following
+extension options: @samp{mp}, @samp{sec}, @samp{vfpv3-d16},
+@samp{vfpv3}, @samp{vfpv3-d16-fp16}, @samp{vfpv3-fp16},
+@samp{vfpv4-d16}, @samp{vfpv4}, @samp{neon}, @samp{neon-vfpv3},
+@samp{neon-fp16}, @samp{neon-vfpv4}. The meanings are the same as for
+the extensions to @option{-march=armv7-a}.
+
+@option{-mcpu=generic-@var{arch}} is also permissible, and is
+equivalent to @option{-march=@var{arch} -mtune=generic-@var{arch}}.
+See @option{-mtune} for more information.
+
+@option{-mcpu=native} causes the compiler to auto-detect the CPU
+of the build computer. At present, this feature is only supported on
+GNU/Linux, and not all architectures are recognized. If the auto-detect
+is unsuccessful the option has no effect.
+
+@item -mfpu=@var{name}
+@opindex mfpu
+This specifies what floating-point hardware (or hardware emulation) is
+available on the target. Permissible names are: @samp{auto}, @samp{vfpv2},
+@samp{vfpv3},
+@samp{vfpv3-fp16}, @samp{vfpv3-d16}, @samp{vfpv3-d16-fp16}, @samp{vfpv3xd},
+@samp{vfpv3xd-fp16}, @samp{neon-vfpv3}, @samp{neon-fp16}, @samp{vfpv4},
+@samp{vfpv4-d16}, @samp{fpv4-sp-d16}, @samp{neon-vfpv4},
+@samp{fpv5-d16}, @samp{fpv5-sp-d16},
+@samp{fp-armv8}, @samp{neon-fp-armv8} and @samp{crypto-neon-fp-armv8}.
+Note that @samp{neon} is an alias for @samp{neon-vfpv3} and @samp{vfp}
+is an alias for @samp{vfpv2}.
+
+The setting @samp{auto} is the default and is special. It causes the
+compiler to select the floating-point and Advanced SIMD instructions
+based on the settings of @option{-mcpu} and @option{-march}.
+
+If the selected floating-point hardware includes the NEON extension
+(e.g.@: @option{-mfpu=neon}), note that floating-point
+operations are not generated by GCC's auto-vectorization pass unless
+@option{-funsafe-math-optimizations} is also specified. This is
+because NEON hardware does not fully implement the IEEE 754 standard for
+floating-point arithmetic (in particular denormal values are treated as
+zero), so the use of NEON instructions may lead to a loss of precision.
+
+You can also set the fpu name at function level by using the @code{target("fpu=")} function attributes (@pxref{ARM Function Attributes}) or pragmas (@pxref{Function Specific Option Pragmas}).
+
+@item -mfp16-format=@var{name}
+@opindex mfp16-format
+Specify the format of the @code{__fp16} half-precision floating-point type.
+Permissible names are @samp{none}, @samp{ieee}, and @samp{alternative};
+the default is @samp{none}, in which case the @code{__fp16} type is not
+defined. @xref{Half-Precision}, for more information.
+
+@item -mstructure-size-boundary=@var{n}
+@opindex mstructure-size-boundary
+The sizes of all structures and unions are rounded up to a multiple
+of the number of bits set by this option. Permissible values are 8, 32
+and 64. The default value varies for different toolchains. For the COFF
+targeted toolchain the default value is 8. A value of 64 is only allowed
+if the underlying ABI supports it.
+
+Specifying a larger number can produce faster, more efficient code, but
+can also increase the size of the program. Different values are potentially
+incompatible. Code compiled with one value cannot necessarily expect to
+work with code or libraries compiled with another value, if they exchange
+information using structures or unions.
+
+This option is deprecated.
+
+@item -mabort-on-noreturn
+@opindex mabort-on-noreturn
+Generate a call to the function @code{abort} at the end of a
+@code{noreturn} function. It is executed if the function tries to
+return.
+
+@item -mlong-calls
+@itemx -mno-long-calls
+@opindex mlong-calls
+@opindex mno-long-calls
+Tells the compiler to perform function calls by first loading the
+address of the function into a register and then performing a subroutine
+call on this register. This switch is needed if the target function
+lies outside of the 64-megabyte addressing range of the offset-based
+version of subroutine call instruction.
+
+Even if this switch is enabled, not all function calls are turned
+into long calls. The heuristic is that static functions, functions
+that have the @code{short_call} attribute, functions that are inside
+the scope of a @code{#pragma no_long_calls} directive, and functions whose
+definitions have already been compiled within the current compilation
+unit are not turned into long calls. The exceptions to this rule are
+that weak function definitions, functions with the @code{long_call}
+attribute or the @code{section} attribute, and functions that are within
+the scope of a @code{#pragma long_calls} directive are always
+turned into long calls.
+
+This feature is not enabled by default. Specifying
+@option{-mno-long-calls} restores the default behavior, as does
+placing the function calls within the scope of a @code{#pragma
+long_calls_off} directive. Note these switches have no effect on how
+the compiler generates code to handle function calls via function
+pointers.
+
+@item -msingle-pic-base
+@opindex msingle-pic-base
+Treat the register used for PIC addressing as read-only, rather than
+loading it in the prologue for each function. The runtime system is
+responsible for initializing this register with an appropriate value
+before execution begins.
+
+@item -mpic-register=@var{reg}
+@opindex mpic-register
+Specify the register to be used for PIC addressing.
+For standard PIC base case, the default is any suitable register
+determined by compiler. For single PIC base case, the default is
+@samp{R9} if target is EABI based or stack-checking is enabled,
+otherwise the default is @samp{R10}.
+
+@item -mpic-data-is-text-relative
+@opindex mpic-data-is-text-relative
+Assume that the displacement between the text and data segments is fixed
+at static link time. This permits using PC-relative addressing
+operations to access data known to be in the data segment. For
+non-VxWorks RTP targets, this option is enabled by default. When
+disabled on such targets, it will enable @option{-msingle-pic-base} by
+default.
+
+@item -mpoke-function-name
+@opindex mpoke-function-name
+Write the name of each function into the text section, directly
+preceding the function prologue. The generated code is similar to this:
+
+@smallexample
+ t0
+ .ascii "arm_poke_function_name", 0
+ .align
+ t1
+ .word 0xff000000 + (t1 - t0)
+ arm_poke_function_name
+ mov ip, sp
+ stmfd sp!, @{fp, ip, lr, pc@}
+ sub fp, ip, #4
+@end smallexample
+
+When performing a stack backtrace, code can inspect the value of
+@code{pc} stored at @code{fp + 0}. If the trace function then looks at
+location @code{pc - 12} and the top 8 bits are set, then we know that
+there is a function name embedded immediately preceding this location
+and has length @code{((pc[-3]) & 0xff000000)}.
+
+@item -mthumb
+@itemx -marm
+@opindex marm
+@opindex mthumb
+
+Select between generating code that executes in ARM and Thumb
+states. The default for most configurations is to generate code
+that executes in ARM state, but the default can be changed by
+configuring GCC with the @option{--with-mode=}@var{state}
+configure option.
+
+You can also override the ARM and Thumb mode for each function
+by using the @code{target("thumb")} and @code{target("arm")} function attributes
+(@pxref{ARM Function Attributes}) or pragmas (@pxref{Function Specific Option Pragmas}).
+
+@item -mflip-thumb
+@opindex mflip-thumb
+Switch ARM/Thumb modes on alternating functions.
+This option is provided for regression testing of mixed Thumb/ARM code
+generation, and is not intended for ordinary use in compiling code.
+
+@item -mtpcs-frame
+@opindex mtpcs-frame
+Generate a stack frame that is compliant with the Thumb Procedure Call
+Standard for all non-leaf functions. (A leaf function is one that does
+not call any other functions.) The default is @option{-mno-tpcs-frame}.
+
+@item -mtpcs-leaf-frame
+@opindex mtpcs-leaf-frame
+Generate a stack frame that is compliant with the Thumb Procedure Call
+Standard for all leaf functions. (A leaf function is one that does
+not call any other functions.) The default is @option{-mno-apcs-leaf-frame}.
+
+@item -mcallee-super-interworking
+@opindex mcallee-super-interworking
+Gives all externally visible functions in the file being compiled an ARM
+instruction set header which switches to Thumb mode before executing the
+rest of the function. This allows these functions to be called from
+non-interworking code. This option is not valid in AAPCS configurations
+because interworking is enabled by default.
+
+@item -mcaller-super-interworking
+@opindex mcaller-super-interworking
+Allows calls via function pointers (including virtual functions) to
+execute correctly regardless of whether the target code has been
+compiled for interworking or not. There is a small overhead in the cost
+of executing a function pointer if this option is enabled. This option
+is not valid in AAPCS configurations because interworking is enabled
+by default.
+
+@item -mtp=@var{name}
+@opindex mtp
+Specify the access model for the thread local storage pointer. The valid
+models are @samp{soft}, which generates calls to @code{__aeabi_read_tp},
+@samp{cp15}, which fetches the thread pointer from @code{cp15} directly
+(supported in the arm6k architecture), and @samp{auto}, which uses the
+best available method for the selected processor. The default setting is
+@samp{auto}.
+
+@item -mtls-dialect=@var{dialect}
+@opindex mtls-dialect
+Specify the dialect to use for accessing thread local storage. Two
+@var{dialect}s are supported---@samp{gnu} and @samp{gnu2}. The
+@samp{gnu} dialect selects the original GNU scheme for supporting
+local and global dynamic TLS models. The @samp{gnu2} dialect
+selects the GNU descriptor scheme, which provides better performance
+for shared libraries. The GNU descriptor scheme is compatible with
+the original scheme, but does require new assembler, linker and
+library support. Initial and local exec TLS models are unaffected by
+this option and always use the original scheme.
+
+@item -mword-relocations
+@opindex mword-relocations
+Only generate absolute relocations on word-sized values (i.e.@: R_ARM_ABS32).
+This is enabled by default on targets (uClinux, SymbianOS) where the runtime
+loader imposes this restriction, and when @option{-fpic} or @option{-fPIC}
+is specified. This option conflicts with @option{-mslow-flash-data}.
+
+@item -mfix-cortex-m3-ldrd
+@opindex mfix-cortex-m3-ldrd
+Some Cortex-M3 cores can cause data corruption when @code{ldrd} instructions
+with overlapping destination and base registers are used. This option avoids
+generating these instructions. This option is enabled by default when
+@option{-mcpu=cortex-m3} is specified.
+
+@item -mfix-cortex-a57-aes-1742098
+@itemx -mno-fix-cortex-a57-aes-1742098
+@itemx -mfix-cortex-a72-aes-1655431
+@itemx -mno-fix-cortex-a72-aes-1655431
+Enable (disable) mitigation for an erratum on Cortex-A57 and
+Cortex-A72 that affects the AES cryptographic instructions. This
+option is enabled by default when either @option{-mcpu=cortex-a57} or
+@option{-mcpu=cortex-a72} is specified.
+
+@item -munaligned-access
+@itemx -mno-unaligned-access
+@opindex munaligned-access
+@opindex mno-unaligned-access
+Enables (or disables) reading and writing of 16- and 32- bit values
+from addresses that are not 16- or 32- bit aligned. By default
+unaligned access is disabled for all pre-ARMv6, all ARMv6-M and for
+ARMv8-M Baseline architectures, and enabled for all other
+architectures. If unaligned access is not enabled then words in packed
+data structures are accessed a byte at a time.
+
+The ARM attribute @code{Tag_CPU_unaligned_access} is set in the
+generated object file to either true or false, depending upon the
+setting of this option. If unaligned access is enabled then the
+preprocessor symbol @code{__ARM_FEATURE_UNALIGNED} is also
+defined.
+
+@item -mneon-for-64bits
+@opindex mneon-for-64bits
+This option is deprecated and has no effect.
+
+@item -mslow-flash-data
+@opindex mslow-flash-data
+Assume loading data from flash is slower than fetching instruction.
+Therefore literal load is minimized for better performance.
+This option is only supported when compiling for ARMv7 M-profile and
+off by default. It conflicts with @option{-mword-relocations}.
+
+@item -masm-syntax-unified
+@opindex masm-syntax-unified
+Assume inline assembler is using unified asm syntax. The default is
+currently off which implies divided syntax. This option has no impact
+on Thumb2. However, this may change in future releases of GCC.
+Divided syntax should be considered deprecated.
+
+@item -mrestrict-it
+@opindex mrestrict-it
+Restricts generation of IT blocks to conform to the rules of ARMv8-A.
+IT blocks can only contain a single 16-bit instruction from a select
+set of instructions. This option is on by default for ARMv8-A Thumb mode.
+
+@item -mprint-tune-info
+@opindex mprint-tune-info
+Print CPU tuning information as comment in assembler file. This is
+an option used only for regression testing of the compiler and not
+intended for ordinary use in compiling code. This option is disabled
+by default.
+
+@item -mverbose-cost-dump
+@opindex mverbose-cost-dump
+Enable verbose cost model dumping in the debug dump files. This option is
+provided for use in debugging the compiler.
+
+@item -mpure-code
+@opindex mpure-code
+Do not allow constant data to be placed in code sections.
+Additionally, when compiling for ELF object format give all text sections the
+ELF processor-specific section attribute @code{SHF_ARM_PURECODE}. This option
+is only available when generating non-pic code for M-profile targets.
+
+@item -mcmse
+@opindex mcmse
+Generate secure code as per the "ARMv8-M Security Extensions: Requirements on
+Development Tools Engineering Specification", which can be found on
+@url{https://developer.arm.com/documentation/ecm0359818/latest/}.
+
+@item -mfix-cmse-cve-2021-35465
+@opindex mfix-cmse-cve-2021-35465
+Mitigate against a potential security issue with the @code{VLLDM} instruction
+in some M-profile devices when using CMSE (CVE-2021-365465). This option is
+enabled by default when the option @option{-mcpu=} is used with
+@code{cortex-m33}, @code{cortex-m35p}, @code{cortex-m55} or @code{star-mc1}.
+The option @option{-mno-fix-cmse-cve-2021-35465} can be used to disable
+the mitigation.
+
+@item -mstack-protector-guard=@var{guard}
+@itemx -mstack-protector-guard-offset=@var{offset}
+@opindex mstack-protector-guard
+@opindex mstack-protector-guard-offset
+Generate stack protection code using canary at @var{guard}. Supported
+locations are @samp{global} for a global canary or @samp{tls} for a
+canary accessible via the TLS register. The option
+@option{-mstack-protector-guard-offset=} is for use with
+@option{-fstack-protector-guard=tls} and not for use in user-land code.
+
+@item -mfdpic
+@itemx -mno-fdpic
+@opindex mfdpic
+@opindex mno-fdpic
+Select the FDPIC ABI, which uses 64-bit function descriptors to
+represent pointers to functions. When the compiler is configured for
+@code{arm-*-uclinuxfdpiceabi} targets, this option is on by default
+and implies @option{-fPIE} if none of the PIC/PIE-related options is
+provided. On other targets, it only enables the FDPIC-specific code
+generation features, and the user should explicitly provide the
+PIC/PIE-related options as needed.
+
+Note that static linking is not supported because it would still
+involve the dynamic linker when the program self-relocates. If such
+behavior is acceptable, use -static and -Wl,-dynamic-linker options.
+
+The opposite @option{-mno-fdpic} option is useful (and required) to
+build the Linux kernel using the same (@code{arm-*-uclinuxfdpiceabi})
+toolchain as the one used to build the userland programs.
+
+@end table
+
+@node AVR Options
+@subsection AVR Options
+@cindex AVR Options
+
+These options are defined for AVR implementations:
+
+@table @gcctabopt
+@item -mmcu=@var{mcu}
+@opindex mmcu
+Specify Atmel AVR instruction set architectures (ISA) or MCU type.
+
+The default for this option is@tie{}@samp{avr2}.
+
+GCC supports the following AVR devices and ISAs:
+
+@include avr-mmcu.texi
+
+@item -mabsdata
+@opindex mabsdata
+
+Assume that all data in static storage can be accessed by LDS / STS
+instructions. This option has only an effect on reduced Tiny devices like
+ATtiny40. See also the @code{absdata}
+@ref{AVR Variable Attributes,variable attribute}.
+
+@item -maccumulate-args
+@opindex maccumulate-args
+Accumulate outgoing function arguments and acquire/release the needed
+stack space for outgoing function arguments once in function
+prologue/epilogue. Without this option, outgoing arguments are pushed
+before calling a function and popped afterwards.
+
+Popping the arguments after the function call can be expensive on
+AVR so that accumulating the stack space might lead to smaller
+executables because arguments need not be removed from the
+stack after such a function call.
+
+This option can lead to reduced code size for functions that perform
+several calls to functions that get their arguments on the stack like
+calls to printf-like functions.
+
+@item -mbranch-cost=@var{cost}
+@opindex mbranch-cost
+Set the branch costs for conditional branch instructions to
+@var{cost}. Reasonable values for @var{cost} are small, non-negative
+integers. The default branch cost is 0.
+
+@item -mcall-prologues
+@opindex mcall-prologues
+Functions prologues/epilogues are expanded as calls to appropriate
+subroutines. Code size is smaller.
+
+@item -mdouble=@var{bits}
+@itemx -mlong-double=@var{bits}
+@opindex mdouble
+@opindex mlong-double
+Set the size (in bits) of the @code{double} or @code{long double} type,
+respectively. Possible values for @var{bits} are 32 and 64.
+Whether or not a specific value for @var{bits} is allowed depends on
+the @code{--with-double=} and @code{--with-long-double=}
+@w{@uref{https://gcc.gnu.org/install/configure.html#avr,configure options}},
+and the same applies for the default values of the options.
+
+@item -mgas-isr-prologues
+@opindex mgas-isr-prologues
+Interrupt service routines (ISRs) may use the @code{__gcc_isr} pseudo
+instruction supported by GNU Binutils.
+If this option is on, the feature can still be disabled for individual
+ISRs by means of the @ref{AVR Function Attributes,,@code{no_gccisr}}
+function attribute. This feature is activated per default
+if optimization is on (but not with @option{-Og}, @pxref{Optimize Options}),
+and if GNU Binutils support @w{@uref{https://sourceware.org/PR21683,PR21683}}.
+
+@item -mint8
+@opindex mint8
+Assume @code{int} to be 8-bit integer. This affects the sizes of all types: a
+@code{char} is 1 byte, an @code{int} is 1 byte, a @code{long} is 2 bytes,
+and @code{long long} is 4 bytes. Please note that this option does not
+conform to the C standards, but it results in smaller code
+size.
+
+@item -mmain-is-OS_task
+@opindex mmain-is-OS_task
+Do not save registers in @code{main}. The effect is the same like
+attaching attribute @ref{AVR Function Attributes,,@code{OS_task}}
+to @code{main}. It is activated per default if optimization is on.
+
+@item -mn-flash=@var{num}
+@opindex mn-flash
+Assume that the flash memory has a size of
+@var{num} times 64@tie{}KiB.
+
+@item -mno-interrupts
+@opindex mno-interrupts
+Generated code is not compatible with hardware interrupts.
+Code size is smaller.
+
+@item -mrelax
+@opindex mrelax
+Try to replace @code{CALL} resp.@: @code{JMP} instruction by the shorter
+@code{RCALL} resp.@: @code{RJMP} instruction if applicable.
+Setting @option{-mrelax} just adds the @option{--mlink-relax} option to
+the assembler's command line and the @option{--relax} option to the
+linker's command line.
+
+Jump relaxing is performed by the linker because jump offsets are not
+known before code is located. Therefore, the assembler code generated by the
+compiler is the same, but the instructions in the executable may
+differ from instructions in the assembler code.
+
+Relaxing must be turned on if linker stubs are needed, see the
+section on @code{EIND} and linker stubs below.
+
+@item -mrmw
+@opindex mrmw
+Assume that the device supports the Read-Modify-Write
+instructions @code{XCH}, @code{LAC}, @code{LAS} and @code{LAT}.
+
+@item -mshort-calls
+@opindex mshort-calls
+
+Assume that @code{RJMP} and @code{RCALL} can target the whole
+program memory.
+
+This option is used internally for multilib selection. It is
+not an optimization option, and you don't need to set it by hand.
+
+@item -msp8
+@opindex msp8
+Treat the stack pointer register as an 8-bit register,
+i.e.@: assume the high byte of the stack pointer is zero.
+In general, you don't need to set this option by hand.
+
+This option is used internally by the compiler to select and
+build multilibs for architectures @code{avr2} and @code{avr25}.
+These architectures mix devices with and without @code{SPH}.
+For any setting other than @option{-mmcu=avr2} or @option{-mmcu=avr25}
+the compiler driver adds or removes this option from the compiler
+proper's command line, because the compiler then knows if the device
+or architecture has an 8-bit stack pointer and thus no @code{SPH}
+register or not.
+
+@item -mstrict-X
+@opindex mstrict-X
+Use address register @code{X} in a way proposed by the hardware. This means
+that @code{X} is only used in indirect, post-increment or
+pre-decrement addressing.
+
+Without this option, the @code{X} register may be used in the same way
+as @code{Y} or @code{Z} which then is emulated by additional
+instructions.
+For example, loading a value with @code{X+const} addressing with a
+small non-negative @code{const < 64} to a register @var{Rn} is
+performed as
+
+@example
+adiw r26, const ; X += const
+ld @var{Rn}, X ; @var{Rn} = *X
+sbiw r26, const ; X -= const
+@end example
+
+@item -mtiny-stack
+@opindex mtiny-stack
+Only change the lower 8@tie{}bits of the stack pointer.
+
+@item -mfract-convert-truncate
+@opindex mfract-convert-truncate
+Allow to use truncation instead of rounding towards zero for fractional fixed-point types.
+
+@item -nodevicelib
+@opindex nodevicelib
+Don't link against AVR-LibC's device specific library @code{lib<mcu>.a}.
+
+@item -nodevicespecs
+@opindex nodevicespecs
+Don't add @option{-specs=device-specs/specs-@var{mcu}} to the compiler driver's
+command line. The user takes responsibility for supplying the sub-processes
+like compiler proper, assembler and linker with appropriate command line
+options. This means that the user has to supply her private device specs
+file by means of @option{-specs=@var{path-to-specs-file}}. There is no
+more need for option @option{-mmcu=@var{mcu}}.
+
+This option can also serve as a replacement for the older way of
+specifying custom device-specs files that needed @option{-B @var{some-path}} to point to a directory
+which contains a folder named @code{device-specs} which contains a specs file named
+@code{specs-@var{mcu}}, where @var{mcu} was specified by @option{-mmcu=@var{mcu}}.
+
+@item -Waddr-space-convert
+@opindex Waddr-space-convert
+@opindex Wno-addr-space-convert
+Warn about conversions between address spaces in the case where the
+resulting address space is not contained in the incoming address space.
+
+@item -Wmisspelled-isr
+@opindex Wmisspelled-isr
+@opindex Wno-misspelled-isr
+Warn if the ISR is misspelled, i.e.@: without __vector prefix.
+Enabled by default.
+@end table
+
+@subsubsection @code{EIND} and Devices with More Than 128 Ki Bytes of Flash
+@cindex @code{EIND}
+Pointers in the implementation are 16@tie{}bits wide.
+The address of a function or label is represented as word address so
+that indirect jumps and calls can target any code address in the
+range of 64@tie{}Ki words.
+
+In order to facilitate indirect jump on devices with more than 128@tie{}Ki
+bytes of program memory space, there is a special function register called
+@code{EIND} that serves as most significant part of the target address
+when @code{EICALL} or @code{EIJMP} instructions are used.
+
+Indirect jumps and calls on these devices are handled as follows by
+the compiler and are subject to some limitations:
+
+@itemize @bullet
+
+@item
+The compiler never sets @code{EIND}.
+
+@item
+The compiler uses @code{EIND} implicitly in @code{EICALL}/@code{EIJMP}
+instructions or might read @code{EIND} directly in order to emulate an
+indirect call/jump by means of a @code{RET} instruction.
+
+@item
+The compiler assumes that @code{EIND} never changes during the startup
+code or during the application. In particular, @code{EIND} is not
+saved/restored in function or interrupt service routine
+prologue/epilogue.
+
+@item
+For indirect calls to functions and computed goto, the linker
+generates @emph{stubs}. Stubs are jump pads sometimes also called
+@emph{trampolines}. Thus, the indirect call/jump jumps to such a stub.
+The stub contains a direct jump to the desired address.
+
+@item
+Linker relaxation must be turned on so that the linker generates
+the stubs correctly in all situations. See the compiler option
+@option{-mrelax} and the linker option @option{--relax}.
+There are corner cases where the linker is supposed to generate stubs
+but aborts without relaxation and without a helpful error message.
+
+@item
+The default linker script is arranged for code with @code{EIND = 0}.
+If code is supposed to work for a setup with @code{EIND != 0}, a custom
+linker script has to be used in order to place the sections whose
+name start with @code{.trampolines} into the segment where @code{EIND}
+points to.
+
+@item
+The startup code from libgcc never sets @code{EIND}.
+Notice that startup code is a blend of code from libgcc and AVR-LibC.
+For the impact of AVR-LibC on @code{EIND}, see the
+@w{@uref{http://nongnu.org/avr-libc/user-manual/,AVR-LibC user manual}}.
+
+@item
+It is legitimate for user-specific startup code to set up @code{EIND}
+early, for example by means of initialization code located in
+section @code{.init3}. Such code runs prior to general startup code
+that initializes RAM and calls constructors, but after the bit
+of startup code from AVR-LibC that sets @code{EIND} to the segment
+where the vector table is located.
+@example
+#include <avr/io.h>
+
+static void
+__attribute__((section(".init3"),naked,used,no_instrument_function))
+init3_set_eind (void)
+@{
+ __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
+ "out %i0,r24" :: "n" (&EIND) : "r24","memory");
+@}
+@end example
+
+@noindent
+The @code{__trampolines_start} symbol is defined in the linker script.
+
+@item
+Stubs are generated automatically by the linker if
+the following two conditions are met:
+@itemize @minus
+
+@item The address of a label is taken by means of the @code{gs} modifier
+(short for @emph{generate stubs}) like so:
+@example
+LDI r24, lo8(gs(@var{func}))
+LDI r25, hi8(gs(@var{func}))
+@end example
+@item The final location of that label is in a code segment
+@emph{outside} the segment where the stubs are located.
+@end itemize
+
+@item
+The compiler emits such @code{gs} modifiers for code labels in the
+following situations:
+@itemize @minus
+@item Taking address of a function or code label.
+@item Computed goto.
+@item If prologue-save function is used, see @option{-mcall-prologues}
+command-line option.
+@item Switch/case dispatch tables. If you do not want such dispatch
+tables you can specify the @option{-fno-jump-tables} command-line option.
+@item C and C++ constructors/destructors called during startup/shutdown.
+@item If the tools hit a @code{gs()} modifier explained above.
+@end itemize
+
+@item
+Jumping to non-symbolic addresses like so is @emph{not} supported:
+
+@example
+int main (void)
+@{
+ /* Call function at word address 0x2 */
+ return ((int(*)(void)) 0x2)();
+@}
+@end example
+
+Instead, a stub has to be set up, i.e.@: the function has to be called
+through a symbol (@code{func_4} in the example):
+
+@example
+int main (void)
+@{
+ extern int func_4 (void);
+
+ /* Call function at byte address 0x4 */
+ return func_4();
+@}
+@end example
+
+and the application be linked with @option{-Wl,--defsym,func_4=0x4}.
+Alternatively, @code{func_4} can be defined in the linker script.
+@end itemize
+
+@subsubsection Handling of the @code{RAMPD}, @code{RAMPX}, @code{RAMPY} and @code{RAMPZ} Special Function Registers
+@cindex @code{RAMPD}
+@cindex @code{RAMPX}
+@cindex @code{RAMPY}
+@cindex @code{RAMPZ}
+Some AVR devices support memories larger than the 64@tie{}KiB range
+that can be accessed with 16-bit pointers. To access memory locations
+outside this 64@tie{}KiB range, the content of a @code{RAMP}
+register is used as high part of the address:
+The @code{X}, @code{Y}, @code{Z} address register is concatenated
+with the @code{RAMPX}, @code{RAMPY}, @code{RAMPZ} special function
+register, respectively, to get a wide address. Similarly,
+@code{RAMPD} is used together with direct addressing.
+
+@itemize
+@item
+The startup code initializes the @code{RAMP} special function
+registers with zero.
+
+@item
+If a @ref{AVR Named Address Spaces,named address space} other than
+generic or @code{__flash} is used, then @code{RAMPZ} is set
+as needed before the operation.
+
+@item
+If the device supports RAM larger than 64@tie{}KiB and the compiler
+needs to change @code{RAMPZ} to accomplish an operation, @code{RAMPZ}
+is reset to zero after the operation.
+
+@item
+If the device comes with a specific @code{RAMP} register, the ISR
+prologue/epilogue saves/restores that SFR and initializes it with
+zero in case the ISR code might (implicitly) use it.
+
+@item
+RAM larger than 64@tie{}KiB is not supported by GCC for AVR targets.
+If you use inline assembler to read from locations outside the
+16-bit address range and change one of the @code{RAMP} registers,
+you must reset it to zero after the access.
+
+@end itemize
+
+@subsubsection AVR Built-in Macros
+
+GCC defines several built-in macros so that the user code can test
+for the presence or absence of features. Almost any of the following
+built-in macros are deduced from device capabilities and thus
+triggered by the @option{-mmcu=} command-line option.
+
+For even more AVR-specific built-in macros see
+@ref{AVR Named Address Spaces} and @ref{AVR Built-in Functions}.
+
+@table @code
+
+@item __AVR_ARCH__
+Build-in macro that resolves to a decimal number that identifies the
+architecture and depends on the @option{-mmcu=@var{mcu}} option.
+Possible values are:
+
+@code{2}, @code{25}, @code{3}, @code{31}, @code{35},
+@code{4}, @code{5}, @code{51}, @code{6}
+
+for @var{mcu}=@code{avr2}, @code{avr25}, @code{avr3}, @code{avr31},
+@code{avr35}, @code{avr4}, @code{avr5}, @code{avr51}, @code{avr6},
+
+respectively and
+
+@code{100},
+@code{102}, @code{103}, @code{104},
+@code{105}, @code{106}, @code{107}
+
+for @var{mcu}=@code{avrtiny},
+@code{avrxmega2}, @code{avrxmega3}, @code{avrxmega4},
+@code{avrxmega5}, @code{avrxmega6}, @code{avrxmega7}, respectively.
+If @var{mcu} specifies a device, this built-in macro is set
+accordingly. For example, with @option{-mmcu=atmega8} the macro is
+defined to @code{4}.
+
+@item __AVR_@var{Device}__
+Setting @option{-mmcu=@var{device}} defines this built-in macro which reflects
+the device's name. For example, @option{-mmcu=atmega8} defines the
+built-in macro @code{__AVR_ATmega8__}, @option{-mmcu=attiny261a} defines
+@code{__AVR_ATtiny261A__}, etc.
+
+The built-in macros' names follow
+the scheme @code{__AVR_@var{Device}__} where @var{Device} is
+the device name as from the AVR user manual. The difference between
+@var{Device} in the built-in macro and @var{device} in
+@option{-mmcu=@var{device}} is that the latter is always lowercase.
+
+If @var{device} is not a device but only a core architecture like
+@samp{avr51}, this macro is not defined.
+
+@item __AVR_DEVICE_NAME__
+Setting @option{-mmcu=@var{device}} defines this built-in macro to
+the device's name. For example, with @option{-mmcu=atmega8} the macro
+is defined to @code{atmega8}.
+
+If @var{device} is not a device but only a core architecture like
+@samp{avr51}, this macro is not defined.
+
+@item __AVR_XMEGA__
+The device / architecture belongs to the XMEGA family of devices.
+
+@item __AVR_HAVE_ELPM__
+The device has the @code{ELPM} instruction.
+
+@item __AVR_HAVE_ELPMX__
+The device has the @code{ELPM R@var{n},Z} and @code{ELPM
+R@var{n},Z+} instructions.
+
+@item __AVR_HAVE_MOVW__
+The device has the @code{MOVW} instruction to perform 16-bit
+register-register moves.
+
+@item __AVR_HAVE_LPMX__
+The device has the @code{LPM R@var{n},Z} and
+@code{LPM R@var{n},Z+} instructions.
+
+@item __AVR_HAVE_MUL__
+The device has a hardware multiplier.
+
+@item __AVR_HAVE_JMP_CALL__
+The device has the @code{JMP} and @code{CALL} instructions.
+This is the case for devices with more than 8@tie{}KiB of program
+memory.
+
+@item __AVR_HAVE_EIJMP_EICALL__
+@itemx __AVR_3_BYTE_PC__
+The device has the @code{EIJMP} and @code{EICALL} instructions.
+This is the case for devices with more than 128@tie{}KiB of program memory.
+This also means that the program counter
+(PC) is 3@tie{}bytes wide.
+
+@item __AVR_2_BYTE_PC__
+The program counter (PC) is 2@tie{}bytes wide. This is the case for devices
+with up to 128@tie{}KiB of program memory.
+
+@item __AVR_HAVE_8BIT_SP__
+@itemx __AVR_HAVE_16BIT_SP__
+The stack pointer (SP) register is treated as 8-bit respectively
+16-bit register by the compiler.
+The definition of these macros is affected by @option{-mtiny-stack}.
+
+@item __AVR_HAVE_SPH__
+@itemx __AVR_SP8__
+The device has the SPH (high part of stack pointer) special function
+register or has an 8-bit stack pointer, respectively.
+The definition of these macros is affected by @option{-mmcu=} and
+in the cases of @option{-mmcu=avr2} and @option{-mmcu=avr25} also
+by @option{-msp8}.
+
+@item __AVR_HAVE_RAMPD__
+@itemx __AVR_HAVE_RAMPX__
+@itemx __AVR_HAVE_RAMPY__
+@itemx __AVR_HAVE_RAMPZ__
+The device has the @code{RAMPD}, @code{RAMPX}, @code{RAMPY},
+@code{RAMPZ} special function register, respectively.
+
+@item __NO_INTERRUPTS__
+This macro reflects the @option{-mno-interrupts} command-line option.
+
+@item __AVR_ERRATA_SKIP__
+@itemx __AVR_ERRATA_SKIP_JMP_CALL__
+Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit
+instructions because of a hardware erratum. Skip instructions are
+@code{SBRS}, @code{SBRC}, @code{SBIS}, @code{SBIC} and @code{CPSE}.
+The second macro is only defined if @code{__AVR_HAVE_JMP_CALL__} is also
+set.
+
+@item __AVR_ISA_RMW__
+The device has Read-Modify-Write instructions (XCH, LAC, LAS and LAT).
+
+@item __AVR_SFR_OFFSET__=@var{offset}
+Instructions that can address I/O special function registers directly
+like @code{IN}, @code{OUT}, @code{SBI}, etc.@: may use a different
+address as if addressed by an instruction to access RAM like @code{LD}
+or @code{STS}. This offset depends on the device architecture and has
+to be subtracted from the RAM address in order to get the
+respective I/O@tie{}address.
+
+@item __AVR_SHORT_CALLS__
+The @option{-mshort-calls} command line option is set.
+
+@item __AVR_PM_BASE_ADDRESS__=@var{addr}
+Some devices support reading from flash memory by means of @code{LD*}
+instructions. The flash memory is seen in the data address space
+at an offset of @code{__AVR_PM_BASE_ADDRESS__}. If this macro
+is not defined, this feature is not available. If defined,
+the address space is linear and there is no need to put
+@code{.rodata} into RAM. This is handled by the default linker
+description file, and is currently available for
+@code{avrtiny} and @code{avrxmega3}. Even more convenient,
+there is no need to use address spaces like @code{__flash} or
+features like attribute @code{progmem} and @code{pgm_read_*}.
+
+@item __WITH_AVRLIBC__
+The compiler is configured to be used together with AVR-Libc.
+See the @option{--with-avrlibc} configure option.
+
+@item __HAVE_DOUBLE_MULTILIB__
+Defined if @option{-mdouble=} acts as a multilib option.
+
+@item __HAVE_DOUBLE32__
+@itemx __HAVE_DOUBLE64__
+Defined if the compiler supports 32-bit double resp. 64-bit double.
+The actual layout is specified by option @option{-mdouble=}.
+
+@item __DEFAULT_DOUBLE__
+The size in bits of @code{double} if @option{-mdouble=} is not set.
+To test the layout of @code{double} in a program, use the built-in
+macro @code{__SIZEOF_DOUBLE__}.
+
+@item __HAVE_LONG_DOUBLE32__
+@itemx __HAVE_LONG_DOUBLE64__
+@itemx __HAVE_LONG_DOUBLE_MULTILIB__
+@itemx __DEFAULT_LONG_DOUBLE__
+Same as above, but for @code{long double} instead of @code{double}.
+
+@item __WITH_DOUBLE_COMPARISON__
+Reflects the @code{--with-double-comparison=@{tristate|bool|libf7@}}
+@w{@uref{https://gcc.gnu.org/install/configure.html#avr,configure option}}
+and is defined to @code{2} or @code{3}.
+
+@item __WITH_LIBF7_LIBGCC__
+@itemx __WITH_LIBF7_MATH__
+@itemx __WITH_LIBF7_MATH_SYMBOLS__
+Reflects the @code{--with-libf7=@{libgcc|math|math-symbols@}}
+@w{@uref{https://gcc.gnu.org/install/configure.html#avr,configure option}}.
+
+@end table
+
+@node Blackfin Options
+@subsection Blackfin Options
+@cindex Blackfin Options
+
+@table @gcctabopt
+@item -mcpu=@var{cpu}@r{[}-@var{sirevision}@r{]}
+@opindex mcpu=
+Specifies the name of the target Blackfin processor. Currently, @var{cpu}
+can be one of @samp{bf512}, @samp{bf514}, @samp{bf516}, @samp{bf518},
+@samp{bf522}, @samp{bf523}, @samp{bf524}, @samp{bf525}, @samp{bf526},
+@samp{bf527}, @samp{bf531}, @samp{bf532}, @samp{bf533},
+@samp{bf534}, @samp{bf536}, @samp{bf537}, @samp{bf538}, @samp{bf539},
+@samp{bf542}, @samp{bf544}, @samp{bf547}, @samp{bf548}, @samp{bf549},
+@samp{bf542m}, @samp{bf544m}, @samp{bf547m}, @samp{bf548m}, @samp{bf549m},
+@samp{bf561}, @samp{bf592}.
+
+The optional @var{sirevision} specifies the silicon revision of the target
+Blackfin processor. Any workarounds available for the targeted silicon revision
+are enabled. If @var{sirevision} is @samp{none}, no workarounds are enabled.
+If @var{sirevision} is @samp{any}, all workarounds for the targeted processor
+are enabled. The @code{__SILICON_REVISION__} macro is defined to two
+hexadecimal digits representing the major and minor numbers in the silicon
+revision. If @var{sirevision} is @samp{none}, the @code{__SILICON_REVISION__}
+is not defined. If @var{sirevision} is @samp{any}, the
+@code{__SILICON_REVISION__} is defined to be @code{0xffff}.
+If this optional @var{sirevision} is not used, GCC assumes the latest known
+silicon revision of the targeted Blackfin processor.
+
+GCC defines a preprocessor macro for the specified @var{cpu}.
+For the @samp{bfin-elf} toolchain, this option causes the hardware BSP
+provided by libgloss to be linked in if @option{-msim} is not given.
+
+Without this option, @samp{bf532} is used as the processor by default.
+
+Note that support for @samp{bf561} is incomplete. For @samp{bf561},
+only the preprocessor macro is defined.
+
+@item -msim
+@opindex msim
+Specifies that the program will be run on the simulator. This causes
+the simulator BSP provided by libgloss to be linked in. This option
+has effect only for @samp{bfin-elf} toolchain.
+Certain other options, such as @option{-mid-shared-library} and
+@option{-mfdpic}, imply @option{-msim}.
+
+@item -momit-leaf-frame-pointer
+@opindex momit-leaf-frame-pointer
+Don't keep the frame pointer in a register for leaf functions. This
+avoids the instructions to save, set up and restore frame pointers and
+makes an extra register available in leaf functions.
+
+@item -mspecld-anomaly
+@opindex mspecld-anomaly
+When enabled, the compiler ensures that the generated code does not
+contain speculative loads after jump instructions. If this option is used,
+@code{__WORKAROUND_SPECULATIVE_LOADS} is defined.
+
+@item -mno-specld-anomaly
+@opindex mno-specld-anomaly
+@opindex mspecld-anomaly
+Don't generate extra code to prevent speculative loads from occurring.
+
+@item -mcsync-anomaly
+@opindex mcsync-anomaly
+When enabled, the compiler ensures that the generated code does not
+contain CSYNC or SSYNC instructions too soon after conditional branches.
+If this option is used, @code{__WORKAROUND_SPECULATIVE_SYNCS} is defined.
+
+@item -mno-csync-anomaly
+@opindex mno-csync-anomaly
+@opindex mcsync-anomaly
+Don't generate extra code to prevent CSYNC or SSYNC instructions from
+occurring too soon after a conditional branch.
+
+@item -mlow64k
+@opindex mlow64k
+When enabled, the compiler is free to take advantage of the knowledge that
+the entire program fits into the low 64k of memory.
+
+@item -mno-low64k
+@opindex mno-low64k
+Assume that the program is arbitrarily large. This is the default.
+
+@item -mstack-check-l1
+@opindex mstack-check-l1
+Do stack checking using information placed into L1 scratchpad memory by the
+uClinux kernel.
+
+@item -mid-shared-library
+@opindex mid-shared-library
+Generate code that supports shared libraries via the library ID method.
+This allows for execute in place and shared libraries in an environment
+without virtual memory management. This option implies @option{-fPIC}.
+With a @samp{bfin-elf} target, this option implies @option{-msim}.
+
+@item -mno-id-shared-library
+@opindex mno-id-shared-library
+@opindex mid-shared-library
+Generate code that doesn't assume ID-based shared libraries are being used.
+This is the default.
+
+@item -mleaf-id-shared-library
+@opindex mleaf-id-shared-library
+Generate code that supports shared libraries via the library ID method,
+but assumes that this library or executable won't link against any other
+ID shared libraries. That allows the compiler to use faster code for jumps
+and calls.
+
+@item -mno-leaf-id-shared-library
+@opindex mno-leaf-id-shared-library
+@opindex mleaf-id-shared-library
+Do not assume that the code being compiled won't link against any ID shared
+libraries. Slower code is generated for jump and call insns.
+
+@item -mshared-library-id=n
+@opindex mshared-library-id
+Specifies the identification number of the ID-based shared library being
+compiled. Specifying a value of 0 generates more compact code; specifying
+other values forces the allocation of that number to the current
+library but is no more space- or time-efficient than omitting this option.
+
+@item -msep-data
+@opindex msep-data
+Generate code that allows the data segment to be located in a different
+area of memory from the text segment. This allows for execute in place in
+an environment without virtual memory management by eliminating relocations
+against the text section.
+
+@item -mno-sep-data
+@opindex mno-sep-data
+@opindex msep-data
+Generate code that assumes that the data segment follows the text segment.
+This is the default.
+
+@item -mlong-calls
+@itemx -mno-long-calls
+@opindex mlong-calls
+@opindex mno-long-calls
+Tells the compiler to perform function calls by first loading the
+address of the function into a register and then performing a subroutine
+call on this register. This switch is needed if the target function
+lies outside of the 24-bit addressing range of the offset-based
+version of subroutine call instruction.
+
+This feature is not enabled by default. Specifying
+@option{-mno-long-calls} restores the default behavior. Note these
+switches have no effect on how the compiler generates code to handle
+function calls via function pointers.
+
+@item -mfast-fp
+@opindex mfast-fp
+Link with the fast floating-point library. This library relaxes some of
+the IEEE floating-point standard's rules for checking inputs against
+Not-a-Number (NAN), in the interest of performance.
+
+@item -minline-plt
+@opindex minline-plt
+Enable inlining of PLT entries in function calls to functions that are
+not known to bind locally. It has no effect without @option{-mfdpic}.
+
+@item -mmulticore
+@opindex mmulticore
+Build a standalone application for multicore Blackfin processors.
+This option causes proper start files and link scripts supporting
+multicore to be used, and defines the macro @code{__BFIN_MULTICORE}.
+It can only be used with @option{-mcpu=bf561@r{[}-@var{sirevision}@r{]}}.
+
+This option can be used with @option{-mcorea} or @option{-mcoreb}, which
+selects the one-application-per-core programming model. Without
+@option{-mcorea} or @option{-mcoreb}, the single-application/dual-core
+programming model is used. In this model, the main function of Core B
+should be named as @code{coreb_main}.
+
+If this option is not used, the single-core application programming
+model is used.
+
+@item -mcorea
+@opindex mcorea
+Build a standalone application for Core A of BF561 when using
+the one-application-per-core programming model. Proper start files
+and link scripts are used to support Core A, and the macro
+@code{__BFIN_COREA} is defined.
+This option can only be used in conjunction with @option{-mmulticore}.
+
+@item -mcoreb
+@opindex mcoreb
+Build a standalone application for Core B of BF561 when using
+the one-application-per-core programming model. Proper start files
+and link scripts are used to support Core B, and the macro
+@code{__BFIN_COREB} is defined. When this option is used, @code{coreb_main}
+should be used instead of @code{main}.
+This option can only be used in conjunction with @option{-mmulticore}.
+
+@item -msdram
+@opindex msdram
+Build a standalone application for SDRAM. Proper start files and
+link scripts are used to put the application into SDRAM, and the macro
+@code{__BFIN_SDRAM} is defined.
+The loader should initialize SDRAM before loading the application.
+
+@item -micplb
+@opindex micplb
+Assume that ICPLBs are enabled at run time. This has an effect on certain
+anomaly workarounds. For Linux targets, the default is to assume ICPLBs
+are enabled; for standalone applications the default is off.
+@end table
+
+@node C6X Options
+@subsection C6X Options
+@cindex C6X Options
+
+@table @gcctabopt
+@item -march=@var{name}
+@opindex march
+This specifies the name of the target architecture. GCC uses this
+name to determine what kind of instructions it can emit when generating
+assembly code. Permissible names are: @samp{c62x},
+@samp{c64x}, @samp{c64x+}, @samp{c67x}, @samp{c67x+}, @samp{c674x}.
+
+@item -mbig-endian
+@opindex mbig-endian
+Generate code for a big-endian target.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+Generate code for a little-endian target. This is the default.
+
+@item -msim
+@opindex msim
+Choose startup files and linker script suitable for the simulator.
+
+@item -msdata=default
+@opindex msdata=default
+Put small global and static data in the @code{.neardata} section,
+which is pointed to by register @code{B14}. Put small uninitialized
+global and static data in the @code{.bss} section, which is adjacent
+to the @code{.neardata} section. Put small read-only data into the
+@code{.rodata} section. The corresponding sections used for large
+pieces of data are @code{.fardata}, @code{.far} and @code{.const}.
+
+@item -msdata=all
+@opindex msdata=all
+Put all data, not just small objects, into the sections reserved for
+small data, and use addressing relative to the @code{B14} register to
+access them.
+
+@item -msdata=none
+@opindex msdata=none
+Make no use of the sections reserved for small data, and use absolute
+addresses to access all data. Put all initialized global and static
+data in the @code{.fardata} section, and all uninitialized data in the
+@code{.far} section. Put all constant data into the @code{.const}
+section.
+@end table
+
+@node CRIS Options
+@subsection CRIS Options
+@cindex CRIS Options
+
+These options are defined specifically for the CRIS ports.
+
+@table @gcctabopt
+@item -march=@var{architecture-type}
+@itemx -mcpu=@var{architecture-type}
+@opindex march
+@opindex mcpu
+Generate code for the specified architecture. The choices for
+@var{architecture-type} are @samp{v3}, @samp{v8} and @samp{v10} for
+respectively ETRAX@w{ }4, ETRAX@w{ }100, and ETRAX@w{ }100@w{ }LX@.
+Default is @samp{v0}.
+
+@item -mtune=@var{architecture-type}
+@opindex mtune
+Tune to @var{architecture-type} everything applicable about the generated
+code, except for the ABI and the set of available instructions. The
+choices for @var{architecture-type} are the same as for
+@option{-march=@var{architecture-type}}.
+
+@item -mmax-stack-frame=@var{n}
+@opindex mmax-stack-frame
+Warn when the stack frame of a function exceeds @var{n} bytes.
+
+@item -metrax4
+@itemx -metrax100
+@opindex metrax4
+@opindex metrax100
+The options @option{-metrax4} and @option{-metrax100} are synonyms for
+@option{-march=v3} and @option{-march=v8} respectively.
+
+@item -mmul-bug-workaround
+@itemx -mno-mul-bug-workaround
+@opindex mmul-bug-workaround
+@opindex mno-mul-bug-workaround
+Work around a bug in the @code{muls} and @code{mulu} instructions for CPU
+models where it applies. This option is disabled by default.
+
+@item -mpdebug
+@opindex mpdebug
+Enable CRIS-specific verbose debug-related information in the assembly
+code. This option also has the effect of turning off the @samp{#NO_APP}
+formatted-code indicator to the assembler at the beginning of the
+assembly file.
+
+@item -mcc-init
+@opindex mcc-init
+Do not use condition-code results from previous instruction; always emit
+compare and test instructions before use of condition codes.
+
+@item -mno-side-effects
+@opindex mno-side-effects
+@opindex mside-effects
+Do not emit instructions with side effects in addressing modes other than
+post-increment.
+
+@item -mstack-align
+@itemx -mno-stack-align
+@itemx -mdata-align
+@itemx -mno-data-align
+@itemx -mconst-align
+@itemx -mno-const-align
+@opindex mstack-align
+@opindex mno-stack-align
+@opindex mdata-align
+@opindex mno-data-align
+@opindex mconst-align
+@opindex mno-const-align
+These options (@samp{no-} options) arrange (eliminate arrangements) for the
+stack frame, individual data and constants to be aligned for the maximum
+single data access size for the chosen CPU model. The default is to
+arrange for 32-bit alignment. ABI details such as structure layout are
+not affected by these options.
+
+@item -m32-bit
+@itemx -m16-bit
+@itemx -m8-bit
+@opindex m32-bit
+@opindex m16-bit
+@opindex m8-bit
+Similar to the stack- data- and const-align options above, these options
+arrange for stack frame, writable data and constants to all be 32-bit,
+16-bit or 8-bit aligned. The default is 32-bit alignment.
+
+@item -mno-prologue-epilogue
+@itemx -mprologue-epilogue
+@opindex mno-prologue-epilogue
+@opindex mprologue-epilogue
+With @option{-mno-prologue-epilogue}, the normal function prologue and
+epilogue which set up the stack frame are omitted and no return
+instructions or return sequences are generated in the code. Use this
+option only together with visual inspection of the compiled code: no
+warnings or errors are generated when call-saved registers must be saved,
+or storage for local variables needs to be allocated.
+
+@item -melf
+@opindex melf
+Legacy no-op option.
+
+@item -sim
+@opindex sim
+This option arranges
+to link with input-output functions from a simulator library. Code,
+initialized data and zero-initialized data are allocated consecutively.
+
+@item -sim2
+@opindex sim2
+Like @option{-sim}, but pass linker options to locate initialized data at
+0x40000000 and zero-initialized data at 0x80000000.
+@end table
+
+@node C-SKY Options
+@subsection C-SKY Options
+@cindex C-SKY Options
+
+GCC supports these options when compiling for C-SKY V2 processors.
+
+@table @gcctabopt
+
+@item -march=@var{arch}
+@opindex march=
+Specify the C-SKY target architecture. Valid values for @var{arch} are:
+@samp{ck801}, @samp{ck802}, @samp{ck803}, @samp{ck807}, and @samp{ck810}.
+The default is @samp{ck810}.
+
+@item -mcpu=@var{cpu}
+@opindex mcpu=
+Specify the C-SKY target processor. Valid values for @var{cpu} are:
+@samp{ck801}, @samp{ck801t},
+@samp{ck802}, @samp{ck802t}, @samp{ck802j},
+@samp{ck803}, @samp{ck803h}, @samp{ck803t}, @samp{ck803ht},
+@samp{ck803f}, @samp{ck803fh}, @samp{ck803e}, @samp{ck803eh},
+@samp{ck803et}, @samp{ck803eht}, @samp{ck803ef}, @samp{ck803efh},
+@samp{ck803ft}, @samp{ck803eft}, @samp{ck803efht}, @samp{ck803r1},
+@samp{ck803hr1}, @samp{ck803tr1}, @samp{ck803htr1}, @samp{ck803fr1},
+@samp{ck803fhr1}, @samp{ck803er1}, @samp{ck803ehr1}, @samp{ck803etr1},
+@samp{ck803ehtr1}, @samp{ck803efr1}, @samp{ck803efhr1}, @samp{ck803ftr1},
+@samp{ck803eftr1}, @samp{ck803efhtr1},
+@samp{ck803s}, @samp{ck803st}, @samp{ck803se}, @samp{ck803sf},
+@samp{ck803sef}, @samp{ck803seft},
+@samp{ck807e}, @samp{ck807ef}, @samp{ck807}, @samp{ck807f},
+@samp{ck810e}, @samp{ck810et}, @samp{ck810ef}, @samp{ck810eft},
+@samp{ck810}, @samp{ck810v}, @samp{ck810f}, @samp{ck810t}, @samp{ck810fv},
+@samp{ck810tv}, @samp{ck810ft}, and @samp{ck810ftv}.
+
+@item -mbig-endian
+@opindex mbig-endian
+@itemx -EB
+@opindex EB
+@itemx -mlittle-endian
+@opindex mlittle-endian
+@itemx -EL
+@opindex EL
+
+Select big- or little-endian code. The default is little-endian.
+
+@item -mfloat-abi=@var{name}
+@opindex mfloat-abi
+Specifies which floating-point ABI to use. Permissible values
+are: @samp{soft}, @samp{softfp} and @samp{hard}.
+
+Specifying @samp{soft} causes GCC to generate output containing
+library calls for floating-point operations.
+@samp{softfp} allows the generation of code using hardware floating-point
+instructions, but still uses the soft-float calling conventions.
+@samp{hard} allows generation of floating-point instructions
+and uses FPU-specific calling conventions.
+
+The default depends on the specific target configuration. Note that
+the hard-float and soft-float ABIs are not link-compatible; you must
+compile your entire program with the same ABI, and link with a
+compatible set of libraries.
+
+@item -mhard-float
+@opindex mhard-float
+@itemx -msoft-float
+@opindex msoft-float
+
+Select hardware or software floating-point implementations.
+The default is soft float.
+
+@item -mdouble-float
+@itemx -mno-double-float
+@opindex mdouble-float
+When @option{-mhard-float} is in effect, enable generation of
+double-precision float instructions. This is the default except
+when compiling for CK803.
+
+@item -mfdivdu
+@itemx -mno-fdivdu
+@opindex mfdivdu
+When @option{-mhard-float} is in effect, enable generation of
+@code{frecipd}, @code{fsqrtd}, and @code{fdivd} instructions.
+This is the default except when compiling for CK803.
+
+@item -mfpu=@var{fpu}
+@opindex mfpu=
+Select the floating-point processor. This option can only be used with
+@option{-mhard-float}.
+Values for @var{fpu} are
+@samp{fpv2_sf} (equivalent to @samp{-mno-double-float -mno-fdivdu}),
+@samp{fpv2} (@samp{-mdouble-float -mno-divdu}), and
+@samp{fpv2_divd} (@samp{-mdouble-float -mdivdu}).
+
+@item -melrw
+@itemx -mno-elrw
+@opindex melrw
+Enable the extended @code{lrw} instruction. This option defaults to on
+for CK801 and off otherwise.
+
+@item -mistack
+@itemx -mno-istack
+@opindex mistack
+Enable interrupt stack instructions; the default is off.
+
+The @option{-mistack} option is required to handle the
+@code{interrupt} and @code{isr} function attributes
+(@pxref{C-SKY Function Attributes}).
+
+@item -mmp
+@opindex mmp
+Enable multiprocessor instructions; the default is off.
+
+@item -mcp
+@opindex mcp
+Enable coprocessor instructions; the default is off.
+
+@item -mcache
+@opindex mcache
+Enable coprocessor instructions; the default is off.
+
+@item -msecurity
+@opindex msecurity
+Enable C-SKY security instructions; the default is off.
+
+@item -mtrust
+@opindex mtrust
+Enable C-SKY trust instructions; the default is off.
+
+@item -mdsp
+@opindex mdsp
+@itemx -medsp
+@opindex medsp
+@itemx -mvdsp
+@opindex mvdsp
+Enable C-SKY DSP, Enhanced DSP, or Vector DSP instructions, respectively.
+All of these options default to off.
+
+@item -mdiv
+@itemx -mno-div
+@opindex mdiv
+Generate divide instructions. Default is off.
+
+@item -msmart
+@itemx -mno-smart
+@opindex msmart
+Generate code for Smart Mode, using only registers numbered 0-7 to allow
+use of 16-bit instructions. This option is ignored for CK801 where this
+is the required behavior, and it defaults to on for CK802.
+For other targets, the default is off.
+
+@item -mhigh-registers
+@itemx -mno-high-registers
+@opindex mhigh-registers
+Generate code using the high registers numbered 16-31. This option
+is not supported on CK801, CK802, or CK803, and is enabled by default
+for other processors.
+
+@item -manchor
+@itemx -mno-anchor
+@opindex manchor
+Generate code using global anchor symbol addresses.
+
+@item -mpushpop
+@itemx -mno-pushpop
+@opindex mpushpop
+Generate code using @code{push} and @code{pop} instructions. This option
+defaults to on.
+
+@item -mmultiple-stld
+@itemx -mstm
+@itemx -mno-multiple-stld
+@itemx -mno-stm
+@opindex mmultiple-stld
+Generate code using @code{stm} and @code{ldm} instructions. This option
+isn't supported on CK801 but is enabled by default on other processors.
+
+@item -mconstpool
+@itemx -mno-constpool
+@opindex mconstpool
+Create constant pools in the compiler instead of deferring it to the
+assembler. This option is the default and required for correct code
+generation on CK801 and CK802, and is optional on other processors.
+
+@item -mstack-size
+@item -mno-stack-size
+@opindex mstack-size
+Emit @code{.stack_size} directives for each function in the assembly
+output. This option defaults to off.
+
+@item -mccrt
+@itemx -mno-ccrt
+@opindex mccrt
+Generate code for the C-SKY compiler runtime instead of libgcc. This
+option defaults to off.
+
+@item -mbranch-cost=@var{n}
+@opindex mbranch-cost=
+Set the branch costs to roughly @code{n} instructions. The default is 1.
+
+@item -msched-prolog
+@itemx -mno-sched-prolog
+@opindex msched-prolog
+Permit scheduling of function prologue and epilogue sequences. Using
+this option can result in code that is not compliant with the C-SKY V2 ABI
+prologue requirements and that cannot be debugged or backtraced.
+It is disabled by default.
+
+@item -msim
+@opindex msim
+Links the library libsemi.a which is in compatible with simulator. Applicable
+to ELF compiler only.
+
+@end table
+
+@node Darwin Options
+@subsection Darwin Options
+@cindex Darwin options
+
+These options are defined for all architectures running the Darwin operating
+system.
+
+FSF GCC on Darwin does not create ``fat'' object files; it creates
+an object file for the single architecture that GCC was built to
+target. Apple's GCC on Darwin does create ``fat'' files if multiple
+@option{-arch} options are used; it does so by running the compiler or
+linker multiple times and joining the results together with
+@file{lipo}.
+
+The subtype of the file created (like @samp{ppc7400} or @samp{ppc970} or
+@samp{i686}) is determined by the flags that specify the ISA
+that GCC is targeting, like @option{-mcpu} or @option{-march}. The
+@option{-force_cpusubtype_ALL} option can be used to override this.
+
+The Darwin tools vary in their behavior when presented with an ISA
+mismatch. The assembler, @file{as}, only permits instructions to
+be used that are valid for the subtype of the file it is generating,
+so you cannot put 64-bit instructions in a @samp{ppc750} object file.
+The linker for shared libraries, @file{/usr/bin/libtool}, fails
+and prints an error if asked to create a shared library with a less
+restrictive subtype than its input files (for instance, trying to put
+a @samp{ppc970} object file in a @samp{ppc7400} library). The linker
+for executables, @command{ld}, quietly gives the executable the most
+restrictive subtype of any of its input files.
+
+@table @gcctabopt
+@item -F@var{dir}
+@opindex F
+Add the framework directory @var{dir} to the head of the list of
+directories to be searched for header files. These directories are
+interleaved with those specified by @option{-I} options and are
+scanned in a left-to-right order.
+
+A framework directory is a directory with frameworks in it. A
+framework is a directory with a @file{Headers} and/or
+@file{PrivateHeaders} directory contained directly in it that ends
+in @file{.framework}. The name of a framework is the name of this
+directory excluding the @file{.framework}. Headers associated with
+the framework are found in one of those two directories, with
+@file{Headers} being searched first. A subframework is a framework
+directory that is in a framework's @file{Frameworks} directory.
+Includes of subframework headers can only appear in a header of a
+framework that contains the subframework, or in a sibling subframework
+header. Two subframeworks are siblings if they occur in the same
+framework. A subframework should not have the same name as a
+framework; a warning is issued if this is violated. Currently a
+subframework cannot have subframeworks; in the future, the mechanism
+may be extended to support this. The standard frameworks can be found
+in @file{/System/Library/Frameworks} and
+@file{/Library/Frameworks}. An example include looks like
+@code{#include <Framework/header.h>}, where @file{Framework} denotes
+the name of the framework and @file{header.h} is found in the
+@file{PrivateHeaders} or @file{Headers} directory.
+
+@item -iframework@var{dir}
+@opindex iframework
+Like @option{-F} except the directory is a treated as a system
+directory. The main difference between this @option{-iframework} and
+@option{-F} is that with @option{-iframework} the compiler does not
+warn about constructs contained within header files found via
+@var{dir}. This option is valid only for the C family of languages.
+
+@item -gused
+@opindex gused
+Emit debugging information for symbols that are used. For stabs
+debugging format, this enables @option{-feliminate-unused-debug-symbols}.
+This is by default ON@.
+
+@item -gfull
+@opindex gfull
+Emit debugging information for all symbols and types.
+
+@item -mmacosx-version-min=@var{version}
+The earliest version of MacOS X that this executable will run on
+is @var{version}. Typical values of @var{version} include @code{10.1},
+@code{10.2}, and @code{10.3.9}.
+
+If the compiler was built to use the system's headers by default,
+then the default for this option is the system version on which the
+compiler is running, otherwise the default is to make choices that
+are compatible with as many systems and code bases as possible.
+
+@item -mkernel
+@opindex mkernel
+Enable kernel development mode. The @option{-mkernel} option sets
+@option{-static}, @option{-fno-common}, @option{-fno-use-cxa-atexit},
+@option{-fno-exceptions}, @option{-fno-non-call-exceptions},
+@option{-fapple-kext}, @option{-fno-weak} and @option{-fno-rtti} where
+applicable. This mode also sets @option{-mno-altivec},
+@option{-msoft-float}, @option{-fno-builtin} and
+@option{-mlong-branch} for PowerPC targets.
+
+@item -mone-byte-bool
+@opindex mone-byte-bool
+Override the defaults for @code{bool} so that @code{sizeof(bool)==1}.
+By default @code{sizeof(bool)} is @code{4} when compiling for
+Darwin/PowerPC and @code{1} when compiling for Darwin/x86, so this
+option has no effect on x86.
+
+@strong{Warning:} The @option{-mone-byte-bool} switch causes GCC
+to generate code that is not binary compatible with code generated
+without that switch. Using this switch may require recompiling all
+other modules in a program, including system libraries. Use this
+switch to conform to a non-default data model.
+
+@item -mfix-and-continue
+@itemx -ffix-and-continue
+@itemx -findirect-data
+@opindex mfix-and-continue
+@opindex ffix-and-continue
+@opindex findirect-data
+Generate code suitable for fast turnaround development, such as to
+allow GDB to dynamically load @file{.o} files into already-running
+programs. @option{-findirect-data} and @option{-ffix-and-continue}
+are provided for backwards compatibility.
+
+@item -all_load
+@opindex all_load
+Loads all members of static archive libraries.
+See man ld(1) for more information.
+
+@item -arch_errors_fatal
+@opindex arch_errors_fatal
+Cause the errors having to do with files that have the wrong architecture
+to be fatal.
+
+@item -bind_at_load
+@opindex bind_at_load
+Causes the output file to be marked such that the dynamic linker will
+bind all undefined references when the file is loaded or launched.
+
+@item -bundle
+@opindex bundle
+Produce a Mach-o bundle format file.
+See man ld(1) for more information.
+
+@item -bundle_loader @var{executable}
+@opindex bundle_loader
+This option specifies the @var{executable} that will load the build
+output file being linked. See man ld(1) for more information.
+
+@item -dynamiclib
+@opindex dynamiclib
+When passed this option, GCC produces a dynamic library instead of
+an executable when linking, using the Darwin @file{libtool} command.
+
+@item -force_cpusubtype_ALL
+@opindex force_cpusubtype_ALL
+This causes GCC's output file to have the @samp{ALL} subtype, instead of
+one controlled by the @option{-mcpu} or @option{-march} option.
+
+@item -allowable_client @var{client_name}
+@itemx -client_name
+@itemx -compatibility_version
+@itemx -current_version
+@itemx -dead_strip
+@itemx -dependency-file
+@itemx -dylib_file
+@itemx -dylinker_install_name
+@itemx -dynamic
+@itemx -exported_symbols_list
+@itemx -filelist
+@need 800
+@itemx -flat_namespace
+@itemx -force_flat_namespace
+@itemx -headerpad_max_install_names
+@itemx -image_base
+@itemx -init
+@itemx -install_name
+@itemx -keep_private_externs
+@itemx -multi_module
+@itemx -multiply_defined
+@itemx -multiply_defined_unused
+@need 800
+@itemx -noall_load
+@itemx -no_dead_strip_inits_and_terms
+@itemx -nofixprebinding
+@itemx -nomultidefs
+@itemx -noprebind
+@itemx -noseglinkedit
+@itemx -pagezero_size
+@itemx -prebind
+@itemx -prebind_all_twolevel_modules
+@itemx -private_bundle
+@need 800
+@itemx -read_only_relocs
+@itemx -sectalign
+@itemx -sectobjectsymbols
+@itemx -whyload
+@itemx -seg1addr
+@itemx -sectcreate
+@itemx -sectobjectsymbols
+@itemx -sectorder
+@itemx -segaddr
+@itemx -segs_read_only_addr
+@need 800
+@itemx -segs_read_write_addr
+@itemx -seg_addr_table
+@itemx -seg_addr_table_filename
+@itemx -seglinkedit
+@itemx -segprot
+@itemx -segs_read_only_addr
+@itemx -segs_read_write_addr
+@itemx -single_module
+@itemx -static
+@itemx -sub_library
+@need 800
+@itemx -sub_umbrella
+@itemx -twolevel_namespace
+@itemx -umbrella
+@itemx -undefined
+@itemx -unexported_symbols_list
+@itemx -weak_reference_mismatches
+@itemx -whatsloaded
+@opindex allowable_client
+@opindex client_name
+@opindex compatibility_version
+@opindex current_version
+@opindex dead_strip
+@opindex dependency-file
+@opindex dylib_file
+@opindex dylinker_install_name
+@opindex dynamic
+@opindex exported_symbols_list
+@opindex filelist
+@opindex flat_namespace
+@opindex force_flat_namespace
+@opindex headerpad_max_install_names
+@opindex image_base
+@opindex init
+@opindex install_name
+@opindex keep_private_externs
+@opindex multi_module
+@opindex multiply_defined
+@opindex multiply_defined_unused
+@opindex noall_load
+@opindex no_dead_strip_inits_and_terms
+@opindex nofixprebinding
+@opindex nomultidefs
+@opindex noprebind
+@opindex noseglinkedit
+@opindex pagezero_size
+@opindex prebind
+@opindex prebind_all_twolevel_modules
+@opindex private_bundle
+@opindex read_only_relocs
+@opindex sectalign
+@opindex sectobjectsymbols
+@opindex whyload
+@opindex seg1addr
+@opindex sectcreate
+@opindex sectobjectsymbols
+@opindex sectorder
+@opindex segaddr
+@opindex segs_read_only_addr
+@opindex segs_read_write_addr
+@opindex seg_addr_table
+@opindex seg_addr_table_filename
+@opindex seglinkedit
+@opindex segprot
+@opindex segs_read_only_addr
+@opindex segs_read_write_addr
+@opindex single_module
+@opindex static
+@opindex sub_library
+@opindex sub_umbrella
+@opindex twolevel_namespace
+@opindex umbrella
+@opindex undefined
+@opindex unexported_symbols_list
+@opindex weak_reference_mismatches
+@opindex whatsloaded
+These options are passed to the Darwin linker. The Darwin linker man page
+describes them in detail.
+@end table
+
+@node DEC Alpha Options
+@subsection DEC Alpha Options
+
+These @samp{-m} options are defined for the DEC Alpha implementations:
+
+@table @gcctabopt
+@item -mno-soft-float
+@itemx -msoft-float
+@opindex mno-soft-float
+@opindex msoft-float
+Use (do not use) the hardware floating-point instructions for
+floating-point operations. When @option{-msoft-float} is specified,
+functions in @file{libgcc.a} are used to perform floating-point
+operations. Unless they are replaced by routines that emulate the
+floating-point operations, or compiled in such a way as to call such
+emulations routines, these routines issue floating-point
+operations. If you are compiling for an Alpha without floating-point
+operations, you must ensure that the library is built so as not to call
+them.
+
+Note that Alpha implementations without floating-point operations are
+required to have floating-point registers.
+
+@item -mfp-reg
+@itemx -mno-fp-regs
+@opindex mfp-reg
+@opindex mno-fp-regs
+Generate code that uses (does not use) the floating-point register set.
+@option{-mno-fp-regs} implies @option{-msoft-float}. If the floating-point
+register set is not used, floating-point operands are passed in integer
+registers as if they were integers and floating-point results are passed
+in @code{$0} instead of @code{$f0}. This is a non-standard calling sequence,
+so any function with a floating-point argument or return value called by code
+compiled with @option{-mno-fp-regs} must also be compiled with that
+option.
+
+A typical use of this option is building a kernel that does not use,
+and hence need not save and restore, any floating-point registers.
+
+@item -mieee
+@opindex mieee
+The Alpha architecture implements floating-point hardware optimized for
+maximum performance. It is mostly compliant with the IEEE floating-point
+standard. However, for full compliance, software assistance is
+required. This option generates code fully IEEE-compliant code
+@emph{except} that the @var{inexact-flag} is not maintained (see below).
+If this option is turned on, the preprocessor macro @code{_IEEE_FP} is
+defined during compilation. The resulting code is less efficient but is
+able to correctly support denormalized numbers and exceptional IEEE
+values such as not-a-number and plus/minus infinity. Other Alpha
+compilers call this option @option{-ieee_with_no_inexact}.
+
+@item -mieee-with-inexact
+@opindex mieee-with-inexact
+This is like @option{-mieee} except the generated code also maintains
+the IEEE @var{inexact-flag}. Turning on this option causes the
+generated code to implement fully-compliant IEEE math. In addition to
+@code{_IEEE_FP}, @code{_IEEE_FP_EXACT} is defined as a preprocessor
+macro. On some Alpha implementations the resulting code may execute
+significantly slower than the code generated by default. Since there is
+very little code that depends on the @var{inexact-flag}, you should
+normally not specify this option. Other Alpha compilers call this
+option @option{-ieee_with_inexact}.
+
+@item -mfp-trap-mode=@var{trap-mode}
+@opindex mfp-trap-mode
+This option controls what floating-point related traps are enabled.
+Other Alpha compilers call this option @option{-fptm @var{trap-mode}}.
+The trap mode can be set to one of four values:
+
+@table @samp
+@item n
+This is the default (normal) setting. The only traps that are enabled
+are the ones that cannot be disabled in software (e.g., division by zero
+trap).
+
+@item u
+In addition to the traps enabled by @samp{n}, underflow traps are enabled
+as well.
+
+@item su
+Like @samp{u}, but the instructions are marked to be safe for software
+completion (see Alpha architecture manual for details).
+
+@item sui
+Like @samp{su}, but inexact traps are enabled as well.
+@end table
+
+@item -mfp-rounding-mode=@var{rounding-mode}
+@opindex mfp-rounding-mode
+Selects the IEEE rounding mode. Other Alpha compilers call this option
+@option{-fprm @var{rounding-mode}}. The @var{rounding-mode} can be one
+of:
+
+@table @samp
+@item n
+Normal IEEE rounding mode. Floating-point numbers are rounded towards
+the nearest machine number or towards the even machine number in case
+of a tie.
+
+@item m
+Round towards minus infinity.
+
+@item c
+Chopped rounding mode. Floating-point numbers are rounded towards zero.
+
+@item d
+Dynamic rounding mode. A field in the floating-point control register
+(@var{fpcr}, see Alpha architecture reference manual) controls the
+rounding mode in effect. The C library initializes this register for
+rounding towards plus infinity. Thus, unless your program modifies the
+@var{fpcr}, @samp{d} corresponds to round towards plus infinity.
+@end table
+
+@item -mtrap-precision=@var{trap-precision}
+@opindex mtrap-precision
+In the Alpha architecture, floating-point traps are imprecise. This
+means without software assistance it is impossible to recover from a
+floating trap and program execution normally needs to be terminated.
+GCC can generate code that can assist operating system trap handlers
+in determining the exact location that caused a floating-point trap.
+Depending on the requirements of an application, different levels of
+precisions can be selected:
+
+@table @samp
+@item p
+Program precision. This option is the default and means a trap handler
+can only identify which program caused a floating-point exception.
+
+@item f
+Function precision. The trap handler can determine the function that
+caused a floating-point exception.
+
+@item i
+Instruction precision. The trap handler can determine the exact
+instruction that caused a floating-point exception.
+@end table
+
+Other Alpha compilers provide the equivalent options called
+@option{-scope_safe} and @option{-resumption_safe}.
+
+@item -mieee-conformant
+@opindex mieee-conformant
+This option marks the generated code as IEEE conformant. You must not
+use this option unless you also specify @option{-mtrap-precision=i} and either
+@option{-mfp-trap-mode=su} or @option{-mfp-trap-mode=sui}. Its only effect
+is to emit the line @samp{.eflag 48} in the function prologue of the
+generated assembly file.
+
+@item -mbuild-constants
+@opindex mbuild-constants
+Normally GCC examines a 32- or 64-bit integer constant to
+see if it can construct it from smaller constants in two or three
+instructions. If it cannot, it outputs the constant as a literal and
+generates code to load it from the data segment at run time.
+
+Use this option to require GCC to construct @emph{all} integer constants
+using code, even if it takes more instructions (the maximum is six).
+
+You typically use this option to build a shared library dynamic
+loader. Itself a shared library, it must relocate itself in memory
+before it can find the variables and constants in its own data segment.
+
+@item -mbwx
+@itemx -mno-bwx
+@itemx -mcix
+@itemx -mno-cix
+@itemx -mfix
+@itemx -mno-fix
+@itemx -mmax
+@itemx -mno-max
+@opindex mbwx
+@opindex mno-bwx
+@opindex mcix
+@opindex mno-cix
+@opindex mfix
+@opindex mno-fix
+@opindex mmax
+@opindex mno-max
+Indicate whether GCC should generate code to use the optional BWX,
+CIX, FIX and MAX instruction sets. The default is to use the instruction
+sets supported by the CPU type specified via @option{-mcpu=} option or that
+of the CPU on which GCC was built if none is specified.
+
+@item -mfloat-vax
+@itemx -mfloat-ieee
+@opindex mfloat-vax
+@opindex mfloat-ieee
+Generate code that uses (does not use) VAX F and G floating-point
+arithmetic instead of IEEE single and double precision.
+
+@item -mexplicit-relocs
+@itemx -mno-explicit-relocs
+@opindex mexplicit-relocs
+@opindex mno-explicit-relocs
+Older Alpha assemblers provided no way to generate symbol relocations
+except via assembler macros. Use of these macros does not allow
+optimal instruction scheduling. GNU binutils as of version 2.12
+supports a new syntax that allows the compiler to explicitly mark
+which relocations should apply to which instructions. This option
+is mostly useful for debugging, as GCC detects the capabilities of
+the assembler when it is built and sets the default accordingly.
+
+@item -msmall-data
+@itemx -mlarge-data
+@opindex msmall-data
+@opindex mlarge-data
+When @option{-mexplicit-relocs} is in effect, static data is
+accessed via @dfn{gp-relative} relocations. When @option{-msmall-data}
+is used, objects 8 bytes long or smaller are placed in a @dfn{small data area}
+(the @code{.sdata} and @code{.sbss} sections) and are accessed via
+16-bit relocations off of the @code{$gp} register. This limits the
+size of the small data area to 64KB, but allows the variables to be
+directly accessed via a single instruction.
+
+The default is @option{-mlarge-data}. With this option the data area
+is limited to just below 2GB@. Programs that require more than 2GB of
+data must use @code{malloc} or @code{mmap} to allocate the data in the
+heap instead of in the program's data segment.
+
+When generating code for shared libraries, @option{-fpic} implies
+@option{-msmall-data} and @option{-fPIC} implies @option{-mlarge-data}.
+
+@item -msmall-text
+@itemx -mlarge-text
+@opindex msmall-text
+@opindex mlarge-text
+When @option{-msmall-text} is used, the compiler assumes that the
+code of the entire program (or shared library) fits in 4MB, and is
+thus reachable with a branch instruction. When @option{-msmall-data}
+is used, the compiler can assume that all local symbols share the
+same @code{$gp} value, and thus reduce the number of instructions
+required for a function call from 4 to 1.
+
+The default is @option{-mlarge-text}.
+
+@item -mcpu=@var{cpu_type}
+@opindex mcpu
+Set the instruction set and instruction scheduling parameters for
+machine type @var{cpu_type}. You can specify either the @samp{EV}
+style name or the corresponding chip number. GCC supports scheduling
+parameters for the EV4, EV5 and EV6 family of processors and
+chooses the default values for the instruction set from the processor
+you specify. If you do not specify a processor type, GCC defaults
+to the processor on which the compiler was built.
+
+Supported values for @var{cpu_type} are
+
+@table @samp
+@item ev4
+@itemx ev45
+@itemx 21064
+Schedules as an EV4 and has no instruction set extensions.
+
+@item ev5
+@itemx 21164
+Schedules as an EV5 and has no instruction set extensions.
+
+@item ev56
+@itemx 21164a
+Schedules as an EV5 and supports the BWX extension.
+
+@item pca56
+@itemx 21164pc
+@itemx 21164PC
+Schedules as an EV5 and supports the BWX and MAX extensions.
+
+@item ev6
+@itemx 21264
+Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.
+
+@item ev67
+@itemx 21264a
+Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.
+@end table
+
+Native toolchains also support the value @samp{native},
+which selects the best architecture option for the host processor.
+@option{-mcpu=native} has no effect if GCC does not recognize
+the processor.
+
+@item -mtune=@var{cpu_type}
+@opindex mtune
+Set only the instruction scheduling parameters for machine type
+@var{cpu_type}. The instruction set is not changed.
+
+Native toolchains also support the value @samp{native},
+which selects the best architecture option for the host processor.
+@option{-mtune=native} has no effect if GCC does not recognize
+the processor.
+
+@item -mmemory-latency=@var{time}
+@opindex mmemory-latency
+Sets the latency the scheduler should assume for typical memory
+references as seen by the application. This number is highly
+dependent on the memory access patterns used by the application
+and the size of the external cache on the machine.
+
+Valid options for @var{time} are
+
+@table @samp
+@item @var{number}
+A decimal number representing clock cycles.
+
+@item L1
+@itemx L2
+@itemx L3
+@itemx main
+The compiler contains estimates of the number of clock cycles for
+``typical'' EV4 & EV5 hardware for the Level 1, 2 & 3 caches
+(also called Dcache, Scache, and Bcache), as well as to main memory.
+Note that L3 is only valid for EV5.
+
+@end table
+@end table
+
+@node eBPF Options
+@subsection eBPF Options
+@cindex eBPF Options
+
+@table @gcctabopt
+@item -mframe-limit=@var{bytes}
+This specifies the hard limit for frame sizes, in bytes. Currently,
+the value that can be specified should be less than or equal to
+@samp{32767}. Defaults to whatever limit is imposed by the version of
+the Linux kernel targeted.
+
+@item -mkernel=@var{version}
+@opindex mkernel
+This specifies the minimum version of the kernel that will run the
+compiled program. GCC uses this version to determine which
+instructions to use, what kernel helpers to allow, etc. Currently,
+@var{version} can be one of @samp{4.0}, @samp{4.1}, @samp{4.2},
+@samp{4.3}, @samp{4.4}, @samp{4.5}, @samp{4.6}, @samp{4.7},
+@samp{4.8}, @samp{4.9}, @samp{4.10}, @samp{4.11}, @samp{4.12},
+@samp{4.13}, @samp{4.14}, @samp{4.15}, @samp{4.16}, @samp{4.17},
+@samp{4.18}, @samp{4.19}, @samp{4.20}, @samp{5.0}, @samp{5.1},
+@samp{5.2}, @samp{latest} and @samp{native}.
+
+@item -mbig-endian
+@opindex mbig-endian
+Generate code for a big-endian target.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+Generate code for a little-endian target. This is the default.
+
+@item -mjmpext
+@opindex mjmpext
+Enable generation of extra conditional-branch instructions.
+Enabled for CPU v2 and above.
+
+@item -mjmp32
+@opindex mjmp32
+Enable 32-bit jump instructions. Enabled for CPU v3 and above.
+
+@item -malu32
+@opindex malu32
+Enable 32-bit ALU instructions. Enabled for CPU v3 and above.
+
+@item -mcpu=@var{version}
+@opindex mcpu
+This specifies which version of the eBPF ISA to target. Newer versions
+may not be supported by all kernels. The default is @samp{v3}.
+
+Supported values for @var{version} are:
+
+@table @samp
+@item v1
+The first stable eBPF ISA with no special features or extensions.
+
+@item v2
+Supports the jump extensions, as in @option{-mjmpext}.
+
+@item v3
+All features of v2, plus:
+@itemize @minus
+@item 32-bit jump operations, as in @option{-mjmp32}
+@item 32-bit ALU operations, as in @option{-malu32}
+@end itemize
+
+@end table
+
+@item -mco-re
+@opindex mco-re
+Enable BPF Compile Once - Run Everywhere (CO-RE) support. Requires and
+is implied by @option{-gbtf}.
+
+@item -mno-co-re
+@opindex mno-co-re
+Disable BPF Compile Once - Run Everywhere (CO-RE) support. BPF CO-RE
+support is enabled by default when generating BTF debug information for
+the BPF target.
+
+@item -mxbpf
+Generate code for an expanded version of BPF, which relaxes some of
+the restrictions imposed by the BPF architecture:
+@itemize @minus
+@item Save and restore callee-saved registers at function entry and
+exit, respectively.
+@end itemize
+@end table
+
+@node FR30 Options
+@subsection FR30 Options
+@cindex FR30 Options
+
+These options are defined specifically for the FR30 port.
+
+@table @gcctabopt
+
+@item -msmall-model
+@opindex msmall-model
+Use the small address space model. This can produce smaller code, but
+it does assume that all symbolic values and addresses fit into a
+20-bit range.
+
+@item -mno-lsim
+@opindex mno-lsim
+Assume that runtime support has been provided and so there is no need
+to include the simulator library (@file{libsim.a}) on the linker
+command line.
+
+@end table
+
+@node FT32 Options
+@subsection FT32 Options
+@cindex FT32 Options
+
+These options are defined specifically for the FT32 port.
+
+@table @gcctabopt
+
+@item -msim
+@opindex msim
+Specifies that the program will be run on the simulator. This causes
+an alternate runtime startup and library to be linked.
+You must not use this option when generating programs that will run on
+real hardware; you must provide your own runtime library for whatever
+I/O functions are needed.
+
+@item -mlra
+@opindex mlra
+Enable Local Register Allocation. This is still experimental for FT32,
+so by default the compiler uses standard reload.
+
+@item -mnodiv
+@opindex mnodiv
+Do not use div and mod instructions.
+
+@item -mft32b
+@opindex mft32b
+Enable use of the extended instructions of the FT32B processor.
+
+@item -mcompress
+@opindex mcompress
+Compress all code using the Ft32B code compression scheme.
+
+@item -mnopm
+@opindex mnopm
+Do not generate code that reads program memory.
+
+@end table
+
+@node FRV Options
+@subsection FRV Options
+@cindex FRV Options
+
+@table @gcctabopt
+@item -mgpr-32
+@opindex mgpr-32
+
+Only use the first 32 general-purpose registers.
+
+@item -mgpr-64
+@opindex mgpr-64
+
+Use all 64 general-purpose registers.
+
+@item -mfpr-32
+@opindex mfpr-32
+
+Use only the first 32 floating-point registers.
+
+@item -mfpr-64
+@opindex mfpr-64
+
+Use all 64 floating-point registers.
+
+@item -mhard-float
+@opindex mhard-float
+
+Use hardware instructions for floating-point operations.
+
+@item -msoft-float
+@opindex msoft-float
+
+Use library routines for floating-point operations.
+
+@item -malloc-cc
+@opindex malloc-cc
+
+Dynamically allocate condition code registers.
+
+@item -mfixed-cc
+@opindex mfixed-cc
+
+Do not try to dynamically allocate condition code registers, only
+use @code{icc0} and @code{fcc0}.
+
+@item -mdword
+@opindex mdword
+
+Change ABI to use double word insns.
+
+@item -mno-dword
+@opindex mno-dword
+@opindex mdword
+
+Do not use double word instructions.
+
+@item -mdouble
+@opindex mdouble
+
+Use floating-point double instructions.
+
+@item -mno-double
+@opindex mno-double
+
+Do not use floating-point double instructions.
+
+@item -mmedia
+@opindex mmedia
+
+Use media instructions.
+
+@item -mno-media
+@opindex mno-media
+
+Do not use media instructions.
+
+@item -mmuladd
+@opindex mmuladd
+
+Use multiply and add/subtract instructions.
+
+@item -mno-muladd
+@opindex mno-muladd
+
+Do not use multiply and add/subtract instructions.
+
+@item -mfdpic
+@opindex mfdpic
+
+Select the FDPIC ABI, which uses function descriptors to represent
+pointers to functions. Without any PIC/PIE-related options, it
+implies @option{-fPIE}. With @option{-fpic} or @option{-fpie}, it
+assumes GOT entries and small data are within a 12-bit range from the
+GOT base address; with @option{-fPIC} or @option{-fPIE}, GOT offsets
+are computed with 32 bits.
+With a @samp{bfin-elf} target, this option implies @option{-msim}.
+
+@item -minline-plt
+@opindex minline-plt
+
+Enable inlining of PLT entries in function calls to functions that are
+not known to bind locally. It has no effect without @option{-mfdpic}.
+It's enabled by default if optimizing for speed and compiling for
+shared libraries (i.e., @option{-fPIC} or @option{-fpic}), or when an
+optimization option such as @option{-O3} or above is present in the
+command line.
+
+@item -mTLS
+@opindex mTLS
+
+Assume a large TLS segment when generating thread-local code.
+
+@item -mtls
+@opindex mtls
+
+Do not assume a large TLS segment when generating thread-local code.
+
+@item -mgprel-ro
+@opindex mgprel-ro
+
+Enable the use of @code{GPREL} relocations in the FDPIC ABI for data
+that is known to be in read-only sections. It's enabled by default,
+except for @option{-fpic} or @option{-fpie}: even though it may help
+make the global offset table smaller, it trades 1 instruction for 4.
+With @option{-fPIC} or @option{-fPIE}, it trades 3 instructions for 4,
+one of which may be shared by multiple symbols, and it avoids the need
+for a GOT entry for the referenced symbol, so it's more likely to be a
+win. If it is not, @option{-mno-gprel-ro} can be used to disable it.
+
+@item -multilib-library-pic
+@opindex multilib-library-pic
+
+Link with the (library, not FD) pic libraries. It's implied by
+@option{-mlibrary-pic}, as well as by @option{-fPIC} and
+@option{-fpic} without @option{-mfdpic}. You should never have to use
+it explicitly.
+
+@item -mlinked-fp
+@opindex mlinked-fp
+
+Follow the EABI requirement of always creating a frame pointer whenever
+a stack frame is allocated. This option is enabled by default and can
+be disabled with @option{-mno-linked-fp}.
+
+@item -mlong-calls
+@opindex mlong-calls
+
+Use indirect addressing to call functions outside the current
+compilation unit. This allows the functions to be placed anywhere
+within the 32-bit address space.
+
+@item -malign-labels
+@opindex malign-labels
+
+Try to align labels to an 8-byte boundary by inserting NOPs into the
+previous packet. This option only has an effect when VLIW packing
+is enabled. It doesn't create new packets; it merely adds NOPs to
+existing ones.
+
+@item -mlibrary-pic
+@opindex mlibrary-pic
+
+Generate position-independent EABI code.
+
+@item -macc-4
+@opindex macc-4
+
+Use only the first four media accumulator registers.
+
+@item -macc-8
+@opindex macc-8
+
+Use all eight media accumulator registers.
+
+@item -mpack
+@opindex mpack
+
+Pack VLIW instructions.
+
+@item -mno-pack
+@opindex mno-pack
+
+Do not pack VLIW instructions.
+
+@item -mno-eflags
+@opindex mno-eflags
+
+Do not mark ABI switches in e_flags.
+
+@item -mcond-move
+@opindex mcond-move
+
+Enable the use of conditional-move instructions (default).
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mno-cond-move
+@opindex mno-cond-move
+
+Disable the use of conditional-move instructions.
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mscc
+@opindex mscc
+
+Enable the use of conditional set instructions (default).
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mno-scc
+@opindex mno-scc
+
+Disable the use of conditional set instructions.
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mcond-exec
+@opindex mcond-exec
+
+Enable the use of conditional execution (default).
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mno-cond-exec
+@opindex mno-cond-exec
+
+Disable the use of conditional execution.
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mvliw-branch
+@opindex mvliw-branch
+
+Run a pass to pack branches into VLIW instructions (default).
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mno-vliw-branch
+@opindex mno-vliw-branch
+
+Do not run a pass to pack branches into VLIW instructions.
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mmulti-cond-exec
+@opindex mmulti-cond-exec
+
+Enable optimization of @code{&&} and @code{||} in conditional execution
+(default).
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mno-multi-cond-exec
+@opindex mno-multi-cond-exec
+
+Disable optimization of @code{&&} and @code{||} in conditional execution.
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mnested-cond-exec
+@opindex mnested-cond-exec
+
+Enable nested conditional execution optimizations (default).
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -mno-nested-cond-exec
+@opindex mno-nested-cond-exec
+
+Disable nested conditional execution optimizations.
+
+This switch is mainly for debugging the compiler and will likely be removed
+in a future version.
+
+@item -moptimize-membar
+@opindex moptimize-membar
+
+This switch removes redundant @code{membar} instructions from the
+compiler-generated code. It is enabled by default.
+
+@item -mno-optimize-membar
+@opindex mno-optimize-membar
+@opindex moptimize-membar
+
+This switch disables the automatic removal of redundant @code{membar}
+instructions from the generated code.
+
+@item -mtomcat-stats
+@opindex mtomcat-stats
+
+Cause gas to print out tomcat statistics.
+
+@item -mcpu=@var{cpu}
+@opindex mcpu
+
+Select the processor type for which to generate code. Possible values are
+@samp{frv}, @samp{fr550}, @samp{tomcat}, @samp{fr500}, @samp{fr450},
+@samp{fr405}, @samp{fr400}, @samp{fr300} and @samp{simple}.
+
+@end table
+
+@node GNU/Linux Options
+@subsection GNU/Linux Options
+
+These @samp{-m} options are defined for GNU/Linux targets:
+
+@table @gcctabopt
+@item -mglibc
+@opindex mglibc
+Use the GNU C library. This is the default except
+on @samp{*-*-linux-*uclibc*}, @samp{*-*-linux-*musl*} and
+@samp{*-*-linux-*android*} targets.
+
+@item -muclibc
+@opindex muclibc
+Use uClibc C library. This is the default on
+@samp{*-*-linux-*uclibc*} targets.
+
+@item -mmusl
+@opindex mmusl
+Use the musl C library. This is the default on
+@samp{*-*-linux-*musl*} targets.
+
+@item -mbionic
+@opindex mbionic
+Use Bionic C library. This is the default on
+@samp{*-*-linux-*android*} targets.
+
+@item -mandroid
+@opindex mandroid
+Compile code compatible with Android platform. This is the default on
+@samp{*-*-linux-*android*} targets.
+
+When compiling, this option enables @option{-mbionic}, @option{-fPIC},
+@option{-fno-exceptions} and @option{-fno-rtti} by default. When linking,
+this option makes the GCC driver pass Android-specific options to the linker.
+Finally, this option causes the preprocessor macro @code{__ANDROID__}
+to be defined.
+
+@item -tno-android-cc
+@opindex tno-android-cc
+Disable compilation effects of @option{-mandroid}, i.e., do not enable
+@option{-mbionic}, @option{-fPIC}, @option{-fno-exceptions} and
+@option{-fno-rtti} by default.
+
+@item -tno-android-ld
+@opindex tno-android-ld
+Disable linking effects of @option{-mandroid}, i.e., pass standard Linux
+linking options to the linker.
+
+@end table
+
+@node H8/300 Options
+@subsection H8/300 Options
+
+These @samp{-m} options are defined for the H8/300 implementations:
+
+@table @gcctabopt
+@item -mrelax
+@opindex mrelax
+Shorten some address references at link time, when possible; uses the
+linker option @option{-relax}. @xref{H8/300,, @code{ld} and the H8/300,
+ld, Using ld}, for a fuller description.
+
+@item -mh
+@opindex mh
+Generate code for the H8/300H@.
+
+@item -ms
+@opindex ms
+Generate code for the H8S@.
+
+@item -mn
+@opindex mn
+Generate code for the H8S and H8/300H in the normal mode. This switch
+must be used either with @option{-mh} or @option{-ms}.
+
+@item -ms2600
+@opindex ms2600
+Generate code for the H8S/2600. This switch must be used with @option{-ms}.
+
+@item -mexr
+@opindex mexr
+Extended registers are stored on stack before execution of function
+with monitor attribute. Default option is @option{-mexr}.
+This option is valid only for H8S targets.
+
+@item -mno-exr
+@opindex mno-exr
+@opindex mexr
+Extended registers are not stored on stack before execution of function
+with monitor attribute. Default option is @option{-mno-exr}.
+This option is valid only for H8S targets.
+
+@item -mint32
+@opindex mint32
+Make @code{int} data 32 bits by default.
+
+@item -malign-300
+@opindex malign-300
+On the H8/300H and H8S, use the same alignment rules as for the H8/300.
+The default for the H8/300H and H8S is to align longs and floats on
+4-byte boundaries.
+@option{-malign-300} causes them to be aligned on 2-byte boundaries.
+This option has no effect on the H8/300.
+@end table
+
+@node HPPA Options
+@subsection HPPA Options
+@cindex HPPA Options
+
+These @samp{-m} options are defined for the HPPA family of computers:
+
+@table @gcctabopt
+@item -march=@var{architecture-type}
+@opindex march
+Generate code for the specified architecture. The choices for
+@var{architecture-type} are @samp{1.0} for PA 1.0, @samp{1.1} for PA
+1.1, and @samp{2.0} for PA 2.0 processors. Refer to
+@file{/usr/lib/sched.models} on an HP-UX system to determine the proper
+architecture option for your machine. Code compiled for lower numbered
+architectures runs on higher numbered architectures, but not the
+other way around.
+
+@item -mpa-risc-1-0
+@itemx -mpa-risc-1-1
+@itemx -mpa-risc-2-0
+@opindex mpa-risc-1-0
+@opindex mpa-risc-1-1
+@opindex mpa-risc-2-0
+Synonyms for @option{-march=1.0}, @option{-march=1.1}, and @option{-march=2.0} respectively.
+
+@item -mcaller-copies
+@opindex mcaller-copies
+The caller copies function arguments passed by hidden reference. This
+option should be used with care as it is not compatible with the default
+32-bit runtime. However, only aggregates larger than eight bytes are
+passed by hidden reference and the option provides better compatibility
+with OpenMP.
+
+@item -mjump-in-delay
+@opindex mjump-in-delay
+This option is ignored and provided for compatibility purposes only.
+
+@item -mdisable-fpregs
+@opindex mdisable-fpregs
+Prevent floating-point registers from being used in any manner. This is
+necessary for compiling kernels that perform lazy context switching of
+floating-point registers. If you use this option and attempt to perform
+floating-point operations, the compiler aborts.
+
+@item -mdisable-indexing
+@opindex mdisable-indexing
+Prevent the compiler from using indexing address modes. This avoids some
+rather obscure problems when compiling MIG generated code under MACH@.
+
+@item -mno-space-regs
+@opindex mno-space-regs
+@opindex mspace-regs
+Generate code that assumes the target has no space registers. This allows
+GCC to generate faster indirect calls and use unscaled index address modes.
+
+Such code is suitable for level 0 PA systems and kernels.
+
+@item -mfast-indirect-calls
+@opindex mfast-indirect-calls
+Generate code that assumes calls never cross space boundaries. This
+allows GCC to emit code that performs faster indirect calls.
+
+This option does not work in the presence of shared libraries or nested
+functions.
+
+@item -mfixed-range=@var{register-range}
+@opindex mfixed-range
+Generate code treating the given register range as fixed registers.
+A fixed register is one that the register allocator cannot use. This is
+useful when compiling kernel code. A register range is specified as
+two registers separated by a dash. Multiple register ranges can be
+specified separated by a comma.
+
+@item -mlong-load-store
+@opindex mlong-load-store
+Generate 3-instruction load and store sequences as sometimes required by
+the HP-UX 10 linker. This is equivalent to the @samp{+k} option to
+the HP compilers.
+
+@item -mportable-runtime
+@opindex mportable-runtime
+Use the portable calling conventions proposed by HP for ELF systems.
+
+@item -mgas
+@opindex mgas
+Enable the use of assembler directives only GAS understands.
+
+@item -mschedule=@var{cpu-type}
+@opindex mschedule
+Schedule code according to the constraints for the machine type
+@var{cpu-type}. The choices for @var{cpu-type} are @samp{700}
+@samp{7100}, @samp{7100LC}, @samp{7200}, @samp{7300} and @samp{8000}. Refer
+to @file{/usr/lib/sched.models} on an HP-UX system to determine the
+proper scheduling option for your machine. The default scheduling is
+@samp{8000}.
+
+@item -mlinker-opt
+@opindex mlinker-opt
+Enable the optimization pass in the HP-UX linker. Note this makes symbolic
+debugging impossible. It also triggers a bug in the HP-UX 8 and HP-UX 9
+linkers in which they give bogus error messages when linking some programs.
+
+@item -msoft-float
+@opindex msoft-float
+Generate output containing library calls for floating point.
+@strong{Warning:} the requisite libraries are not available for all HPPA
+targets. Normally the facilities of the machine's usual C compiler are
+used, but this cannot be done directly in cross-compilation. You must make
+your own arrangements to provide suitable library functions for
+cross-compilation.
+
+@option{-msoft-float} changes the calling convention in the output file;
+therefore, it is only useful if you compile @emph{all} of a program with
+this option. In particular, you need to compile @file{libgcc.a}, the
+library that comes with GCC, with @option{-msoft-float} in order for
+this to work.
+
+@item -msio
+@opindex msio
+Generate the predefine, @code{_SIO}, for server IO@. The default is
+@option{-mwsio}. This generates the predefines, @code{__hp9000s700},
+@code{__hp9000s700__} and @code{_WSIO}, for workstation IO@. These
+options are available under HP-UX and HI-UX@.
+
+@item -mgnu-ld
+@opindex mgnu-ld
+Use options specific to GNU @command{ld}.
+This passes @option{-shared} to @command{ld} when
+building a shared library. It is the default when GCC is configured,
+explicitly or implicitly, with the GNU linker. This option does not
+affect which @command{ld} is called; it only changes what parameters
+are passed to that @command{ld}.
+The @command{ld} that is called is determined by the
+@option{--with-ld} configure option, GCC's program search path, and
+finally by the user's @env{PATH}. The linker used by GCC can be printed
+using @samp{which `gcc -print-prog-name=ld`}. This option is only available
+on the 64-bit HP-UX GCC, i.e.@: configured with @samp{hppa*64*-*-hpux*}.
+
+@item -mhp-ld
+@opindex mhp-ld
+Use options specific to HP @command{ld}.
+This passes @option{-b} to @command{ld} when building
+a shared library and passes @option{+Accept TypeMismatch} to @command{ld} on all
+links. It is the default when GCC is configured, explicitly or
+implicitly, with the HP linker. This option does not affect
+which @command{ld} is called; it only changes what parameters are passed to that
+@command{ld}.
+The @command{ld} that is called is determined by the @option{--with-ld}
+configure option, GCC's program search path, and finally by the user's
+@env{PATH}. The linker used by GCC can be printed using @samp{which
+`gcc -print-prog-name=ld`}. This option is only available on the 64-bit
+HP-UX GCC, i.e.@: configured with @samp{hppa*64*-*-hpux*}.
+
+@item -mlong-calls
+@opindex mno-long-calls
+@opindex mlong-calls
+Generate code that uses long call sequences. This ensures that a call
+is always able to reach linker generated stubs. The default is to generate
+long calls only when the distance from the call site to the beginning
+of the function or translation unit, as the case may be, exceeds a
+predefined limit set by the branch type being used. The limits for
+normal calls are 7,600,000 and 240,000 bytes, respectively for the
+PA 2.0 and PA 1.X architectures. Sibcalls are always limited at
+240,000 bytes.
+
+Distances are measured from the beginning of functions when using the
+@option{-ffunction-sections} option, or when using the @option{-mgas}
+and @option{-mno-portable-runtime} options together under HP-UX with
+the SOM linker.
+
+It is normally not desirable to use this option as it degrades
+performance. However, it may be useful in large applications,
+particularly when partial linking is used to build the application.
+
+The types of long calls used depends on the capabilities of the
+assembler and linker, and the type of code being generated. The
+impact on systems that support long absolute calls, and long pic
+symbol-difference or pc-relative calls should be relatively small.
+However, an indirect call is used on 32-bit ELF systems in pic code
+and it is quite long.
+
+@item -munix=@var{unix-std}
+@opindex march
+Generate compiler predefines and select a startfile for the specified
+UNIX standard. The choices for @var{unix-std} are @samp{93}, @samp{95}
+and @samp{98}. @samp{93} is supported on all HP-UX versions. @samp{95}
+is available on HP-UX 10.10 and later. @samp{98} is available on HP-UX
+11.11 and later. The default values are @samp{93} for HP-UX 10.00,
+@samp{95} for HP-UX 10.10 though to 11.00, and @samp{98} for HP-UX 11.11
+and later.
+
+@option{-munix=93} provides the same predefines as GCC 3.3 and 3.4.
+@option{-munix=95} provides additional predefines for @code{XOPEN_UNIX}
+and @code{_XOPEN_SOURCE_EXTENDED}, and the startfile @file{unix95.o}.
+@option{-munix=98} provides additional predefines for @code{_XOPEN_UNIX},
+@code{_XOPEN_SOURCE_EXTENDED}, @code{_INCLUDE__STDC_A1_SOURCE} and
+@code{_INCLUDE_XOPEN_SOURCE_500}, and the startfile @file{unix98.o}.
+
+It is @emph{important} to note that this option changes the interfaces
+for various library routines. It also affects the operational behavior
+of the C library. Thus, @emph{extreme} care is needed in using this
+option.
+
+Library code that is intended to operate with more than one UNIX
+standard must test, set and restore the variable @code{__xpg4_extended_mask}
+as appropriate. Most GNU software doesn't provide this capability.
+
+@item -nolibdld
+@opindex nolibdld
+Suppress the generation of link options to search libdld.sl when the
+@option{-static} option is specified on HP-UX 10 and later.
+
+@item -static
+@opindex static
+The HP-UX implementation of setlocale in libc has a dependency on
+libdld.sl. There isn't an archive version of libdld.sl. Thus,
+when the @option{-static} option is specified, special link options
+are needed to resolve this dependency.
+
+On HP-UX 10 and later, the GCC driver adds the necessary options to
+link with libdld.sl when the @option{-static} option is specified.
+This causes the resulting binary to be dynamic. On the 64-bit port,
+the linkers generate dynamic binaries by default in any case. The
+@option{-nolibdld} option can be used to prevent the GCC driver from
+adding these link options.
+
+@item -threads
+@opindex threads
+Add support for multithreading with the @dfn{dce thread} library
+under HP-UX@. This option sets flags for both the preprocessor and
+linker.
+@end table
+
+@node IA-64 Options
+@subsection IA-64 Options
+@cindex IA-64 Options
+
+These are the @samp{-m} options defined for the Intel IA-64 architecture.
+
+@table @gcctabopt
+@item -mbig-endian
+@opindex mbig-endian
+Generate code for a big-endian target. This is the default for HP-UX@.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+Generate code for a little-endian target. This is the default for AIX5
+and GNU/Linux.
+
+@item -mgnu-as
+@itemx -mno-gnu-as
+@opindex mgnu-as
+@opindex mno-gnu-as
+Generate (or don't) code for the GNU assembler. This is the default.
+@c Also, this is the default if the configure option @option{--with-gnu-as}
+@c is used.
+
+@item -mgnu-ld
+@itemx -mno-gnu-ld
+@opindex mgnu-ld
+@opindex mno-gnu-ld
+Generate (or don't) code for the GNU linker. This is the default.
+@c Also, this is the default if the configure option @option{--with-gnu-ld}
+@c is used.
+
+@item -mno-pic
+@opindex mno-pic
+Generate code that does not use a global pointer register. The result
+is not position independent code, and violates the IA-64 ABI@.
+
+@item -mvolatile-asm-stop
+@itemx -mno-volatile-asm-stop
+@opindex mvolatile-asm-stop
+@opindex mno-volatile-asm-stop
+Generate (or don't) a stop bit immediately before and after volatile asm
+statements.
+
+@item -mregister-names
+@itemx -mno-register-names
+@opindex mregister-names
+@opindex mno-register-names
+Generate (or don't) @samp{in}, @samp{loc}, and @samp{out} register names for
+the stacked registers. This may make assembler output more readable.
+
+@item -mno-sdata
+@itemx -msdata
+@opindex mno-sdata
+@opindex msdata
+Disable (or enable) optimizations that use the small data section. This may
+be useful for working around optimizer bugs.
+
+@item -mconstant-gp
+@opindex mconstant-gp
+Generate code that uses a single constant global pointer value. This is
+useful when compiling kernel code.
+
+@item -mauto-pic
+@opindex mauto-pic
+Generate code that is self-relocatable. This implies @option{-mconstant-gp}.
+This is useful when compiling firmware code.
+
+@item -minline-float-divide-min-latency
+@opindex minline-float-divide-min-latency
+Generate code for inline divides of floating-point values
+using the minimum latency algorithm.
+
+@item -minline-float-divide-max-throughput
+@opindex minline-float-divide-max-throughput
+Generate code for inline divides of floating-point values
+using the maximum throughput algorithm.
+
+@item -mno-inline-float-divide
+@opindex mno-inline-float-divide
+Do not generate inline code for divides of floating-point values.
+
+@item -minline-int-divide-min-latency
+@opindex minline-int-divide-min-latency
+Generate code for inline divides of integer values
+using the minimum latency algorithm.
+
+@item -minline-int-divide-max-throughput
+@opindex minline-int-divide-max-throughput
+Generate code for inline divides of integer values
+using the maximum throughput algorithm.
+
+@item -mno-inline-int-divide
+@opindex mno-inline-int-divide
+@opindex minline-int-divide
+Do not generate inline code for divides of integer values.
+
+@item -minline-sqrt-min-latency
+@opindex minline-sqrt-min-latency
+Generate code for inline square roots
+using the minimum latency algorithm.
+
+@item -minline-sqrt-max-throughput
+@opindex minline-sqrt-max-throughput
+Generate code for inline square roots
+using the maximum throughput algorithm.
+
+@item -mno-inline-sqrt
+@opindex mno-inline-sqrt
+Do not generate inline code for @code{sqrt}.
+
+@item -mfused-madd
+@itemx -mno-fused-madd
+@opindex mfused-madd
+@opindex mno-fused-madd
+Do (don't) generate code that uses the fused multiply/add or multiply/subtract
+instructions. The default is to use these instructions.
+
+@item -mno-dwarf2-asm
+@itemx -mdwarf2-asm
+@opindex mno-dwarf2-asm
+@opindex mdwarf2-asm
+Don't (or do) generate assembler code for the DWARF line number debugging
+info. This may be useful when not using the GNU assembler.
+
+@item -mearly-stop-bits
+@itemx -mno-early-stop-bits
+@opindex mearly-stop-bits
+@opindex mno-early-stop-bits
+Allow stop bits to be placed earlier than immediately preceding the
+instruction that triggered the stop bit. This can improve instruction
+scheduling, but does not always do so.
+
+@item -mfixed-range=@var{register-range}
+@opindex mfixed-range
+Generate code treating the given register range as fixed registers.
+A fixed register is one that the register allocator cannot use. This is
+useful when compiling kernel code. A register range is specified as
+two registers separated by a dash. Multiple register ranges can be
+specified separated by a comma.
+
+@item -mtls-size=@var{tls-size}
+@opindex mtls-size
+Specify bit size of immediate TLS offsets. Valid values are 14, 22, and
+64.
+
+@item -mtune=@var{cpu-type}
+@opindex mtune
+Tune the instruction scheduling for a particular CPU, Valid values are
+@samp{itanium}, @samp{itanium1}, @samp{merced}, @samp{itanium2},
+and @samp{mckinley}.
+
+@item -milp32
+@itemx -mlp64
+@opindex milp32
+@opindex mlp64
+Generate code for a 32-bit or 64-bit environment.
+The 32-bit environment sets int, long and pointer to 32 bits.
+The 64-bit environment sets int to 32 bits and long and pointer
+to 64 bits. These are HP-UX specific flags.
+
+@item -mno-sched-br-data-spec
+@itemx -msched-br-data-spec
+@opindex mno-sched-br-data-spec
+@opindex msched-br-data-spec
+(Dis/En)able data speculative scheduling before reload.
+This results in generation of @code{ld.a} instructions and
+the corresponding check instructions (@code{ld.c} / @code{chk.a}).
+The default setting is disabled.
+
+@item -msched-ar-data-spec
+@itemx -mno-sched-ar-data-spec
+@opindex msched-ar-data-spec
+@opindex mno-sched-ar-data-spec
+(En/Dis)able data speculative scheduling after reload.
+This results in generation of @code{ld.a} instructions and
+the corresponding check instructions (@code{ld.c} / @code{chk.a}).
+The default setting is enabled.
+
+@item -mno-sched-control-spec
+@itemx -msched-control-spec
+@opindex mno-sched-control-spec
+@opindex msched-control-spec
+(Dis/En)able control speculative scheduling. This feature is
+available only during region scheduling (i.e.@: before reload).
+This results in generation of the @code{ld.s} instructions and
+the corresponding check instructions @code{chk.s}.
+The default setting is disabled.
+
+@item -msched-br-in-data-spec
+@itemx -mno-sched-br-in-data-spec
+@opindex msched-br-in-data-spec
+@opindex mno-sched-br-in-data-spec
+(En/Dis)able speculative scheduling of the instructions that
+are dependent on the data speculative loads before reload.
+This is effective only with @option{-msched-br-data-spec} enabled.
+The default setting is enabled.
+
+@item -msched-ar-in-data-spec
+@itemx -mno-sched-ar-in-data-spec
+@opindex msched-ar-in-data-spec
+@opindex mno-sched-ar-in-data-spec
+(En/Dis)able speculative scheduling of the instructions that
+are dependent on the data speculative loads after reload.
+This is effective only with @option{-msched-ar-data-spec} enabled.
+The default setting is enabled.
+
+@item -msched-in-control-spec
+@itemx -mno-sched-in-control-spec
+@opindex msched-in-control-spec
+@opindex mno-sched-in-control-spec
+(En/Dis)able speculative scheduling of the instructions that
+are dependent on the control speculative loads.
+This is effective only with @option{-msched-control-spec} enabled.
+The default setting is enabled.
+
+@item -mno-sched-prefer-non-data-spec-insns
+@itemx -msched-prefer-non-data-spec-insns
+@opindex mno-sched-prefer-non-data-spec-insns
+@opindex msched-prefer-non-data-spec-insns
+If enabled, data-speculative instructions are chosen for schedule
+only if there are no other choices at the moment. This makes
+the use of the data speculation much more conservative.
+The default setting is disabled.
+
+@item -mno-sched-prefer-non-control-spec-insns
+@itemx -msched-prefer-non-control-spec-insns
+@opindex mno-sched-prefer-non-control-spec-insns
+@opindex msched-prefer-non-control-spec-insns
+If enabled, control-speculative instructions are chosen for schedule
+only if there are no other choices at the moment. This makes
+the use of the control speculation much more conservative.
+The default setting is disabled.
+
+@item -mno-sched-count-spec-in-critical-path
+@itemx -msched-count-spec-in-critical-path
+@opindex mno-sched-count-spec-in-critical-path
+@opindex msched-count-spec-in-critical-path
+If enabled, speculative dependencies are considered during
+computation of the instructions priorities. This makes the use of the
+speculation a bit more conservative.
+The default setting is disabled.
+
+@item -msched-spec-ldc
+@opindex msched-spec-ldc
+Use a simple data speculation check. This option is on by default.
+
+@item -msched-control-spec-ldc
+@opindex msched-spec-ldc
+Use a simple check for control speculation. This option is on by default.
+
+@item -msched-stop-bits-after-every-cycle
+@opindex msched-stop-bits-after-every-cycle
+Place a stop bit after every cycle when scheduling. This option is on
+by default.
+
+@item -msched-fp-mem-deps-zero-cost
+@opindex msched-fp-mem-deps-zero-cost
+Assume that floating-point stores and loads are not likely to cause a conflict
+when placed into the same instruction group. This option is disabled by
+default.
+
+@item -msel-sched-dont-check-control-spec
+@opindex msel-sched-dont-check-control-spec
+Generate checks for control speculation in selective scheduling.
+This flag is disabled by default.
+
+@item -msched-max-memory-insns=@var{max-insns}
+@opindex msched-max-memory-insns
+Limit on the number of memory insns per instruction group, giving lower
+priority to subsequent memory insns attempting to schedule in the same
+instruction group. Frequently useful to prevent cache bank conflicts.
+The default value is 1.
+
+@item -msched-max-memory-insns-hard-limit
+@opindex msched-max-memory-insns-hard-limit
+Makes the limit specified by @option{msched-max-memory-insns} a hard limit,
+disallowing more than that number in an instruction group.
+Otherwise, the limit is ``soft'', meaning that non-memory operations
+are preferred when the limit is reached, but memory operations may still
+be scheduled.
+
+@end table
+
+@node LM32 Options
+@subsection LM32 Options
+@cindex LM32 options
+
+These @option{-m} options are defined for the LatticeMico32 architecture:
+
+@table @gcctabopt
+@item -mbarrel-shift-enabled
+@opindex mbarrel-shift-enabled
+Enable barrel-shift instructions.
+
+@item -mdivide-enabled
+@opindex mdivide-enabled
+Enable divide and modulus instructions.
+
+@item -mmultiply-enabled
+@opindex multiply-enabled
+Enable multiply instructions.
+
+@item -msign-extend-enabled
+@opindex msign-extend-enabled
+Enable sign extend instructions.
+
+@item -muser-enabled
+@opindex muser-enabled
+Enable user-defined instructions.
+
+@end table
+
+@node LoongArch Options
+@subsection LoongArch Options
+@cindex LoongArch Options
+
+These command-line options are defined for LoongArch targets:
+
+@table @gcctabopt
+@item -march=@var{cpu-type}
+@opindex -march
+Generate instructions for the machine type @var{cpu-type}. In contrast to
+@option{-mtune=@var{cpu-type}}, which merely tunes the generated code
+for the specified @var{cpu-type}, @option{-march=@var{cpu-type}} allows GCC
+to generate code that may not run at all on processors other than the one
+indicated. Specifying @option{-march=@var{cpu-type}} implies
+@option{-mtune=@var{cpu-type}}, except where noted otherwise.
+
+The choices for @var{cpu-type} are:
+
+@table @samp
+@item native
+This selects the CPU to generate code for at compilation time by determining
+the processor type of the compiling machine. Using @option{-march=native}
+enables all instruction subsets supported by the local machine (hence
+the result might not run on different machines). Using @option{-mtune=native}
+produces code optimized for the local machine under the constraints
+of the selected instruction set.
+@item loongarch64
+A generic CPU with 64-bit extensions.
+@item la464
+LoongArch LA464 CPU with LBT, LSX, LASX, LVZ.
+@end table
+
+@item -mtune=@var{cpu-type}
+@opindex mtune
+Optimize the output for the given processor, specified by microarchitecture
+name.
+
+@item -mabi=@var{base-abi-type}
+@opindex mabi
+Generate code for the specified calling convention.
+@var{base-abi-type} can be one of:
+@table @samp
+@item lp64d
+Uses 64-bit general purpose registers and 32/64-bit floating-point
+registers for parameter passing. Data model is LP64, where @samp{int}
+is 32 bits, while @samp{long int} and pointers are 64 bits.
+@item lp64f
+Uses 64-bit general purpose registers and 32-bit floating-point
+registers for parameter passing. Data model is LP64, where @samp{int}
+is 32 bits, while @samp{long int} and pointers are 64 bits.
+@item lp64s
+Uses 64-bit general purpose registers and no floating-point
+registers for parameter passing. Data model is LP64, where @samp{int}
+is 32 bits, while @samp{long int} and pointers are 64 bits.
+@end table
+
+@item -mfpu=@var{fpu-type}
+@opindex mfpu
+Generate code for the specified FPU type, which can be one of:
+@table @samp
+@item 64
+Allow the use of hardware floating-point instructions for 32-bit
+and 64-bit operations.
+@item 32
+Allow the use of hardware floating-point instructions for 32-bit
+operations.
+@item none
+@item 0
+Prevent the use of hardware floating-point instructions.
+@end table
+
+@item -msoft-float
+@opindex msoft-float
+Force @option{-mfpu=none} and prevents the use of floating-point
+registers for parameter passing. This option may change the target
+ABI.
+
+@item -msingle-float
+@opindex -msingle-float
+Force @option{-mfpu=32} and allow the use of 32-bit floating-point
+registers for parameter passing. This option may change the target
+ABI.
+
+@item -mdouble-float
+@opindex -mdouble-float
+Force @option{-mfpu=64} and allow the use of 32/64-bit floating-point
+registers for parameter passing. This option may change the target
+ABI.
+
+@item -mbranch-cost=@var{n}
+@opindex -mbranch-cost
+Set the cost of branches to roughly @var{n} instructions.
+
+@item -mcheck-zero-division
+@itemx -mno-check-zero-divison
+@opindex -mcheck-zero-division
+Trap (do not trap) on integer division by zero. The default is
+@option{-mcheck-zero-division} for @option{-O0} or @option{-Og}, and
+@option{-mno-check-zero-division} for other optimization levels.
+
+@item -mcond-move-int
+@itemx -mno-cond-move-int
+@opindex -mcond-move-int
+Conditional moves for integral data in general-purpose registers
+are enabled (disabled). The default is @option{-mcond-move-int}.
+
+@item -mcond-move-float
+@itemx -mno-cond-move-float
+@opindex -mcond-move-float
+Conditional moves for floating-point registers are enabled (disabled).
+The default is @option{-mcond-move-float}.
+
+@item -mmemcpy
+@itemx -mno-memcpy
+@opindex -mmemcpy
+Force (do not force) the use of @code{memcpy} for non-trivial block moves.
+The default is @option{-mno-memcpy}, which allows GCC to inline most
+constant-sized copies. Setting optimization level to @option{-Os} also
+forces the use of @code{memcpy}, but @option{-mno-memcpy} may override this
+behavior if explicitly specified, regardless of the order these options on
+the command line.
+
+@item -mstrict-align
+@itemx -mno-strict-align
+@opindex -mstrict-align
+Avoid or allow generating memory accesses that may not be aligned on a natural
+object boundary as described in the architecture specification. The default is
+@option{-mno-strict-align}.
+
+@item -msmall-data-limit=@var{number}
+@opindex -msmall-data-limit
+Put global and static data smaller than @var{number} bytes into a special
+section (on some targets). The default value is 0.
+
+@item -mmax-inline-memcpy-size=@var{n}
+@opindex -mmax-inline-memcpy-size
+Inline all block moves (such as calls to @code{memcpy} or structure copies)
+less than or equal to @var{n} bytes. The default value of @var{n} is 1024.
+
+@item -mcmodel=@var{code-model}
+Set the code model to one of:
+@table @samp
+@item tiny-static (Not implemented yet)
+@item tiny (Not implemented yet)
+
+@item normal
+The text segment must be within 128MB addressing space. The data segment must
+be within 2GB addressing space.
+
+@item medium
+The text segment and data segment must be within 2GB addressing space.
+
+@item large (Not implemented yet)
+
+@item extreme
+This mode does not limit the size of the code segment and data segment.
+The @option{-mcmodel=extreme} option is incompatible with @option{-fplt} and
+@option{-mno-explicit-relocs}.
+@end table
+The default code model is @code{normal}.
+
+@item -mexplicit-relocs
+@itemx -mno-explicit-relocs
+@opindex mexplicit-relocs
+@opindex mno-explicit-relocs
+Use or do not use assembler relocation operators when dealing with symbolic
+addresses. The alternative is to use assembler macros instead, which may
+limit optimization. The default value for the option is determined during
+GCC build-time by detecting corresponding assembler support:
+@code{-mexplicit-relocs} if said support is present,
+@code{-mno-explicit-relocs} otherwise. This option is mostly useful for
+debugging, or interoperation with assemblers different from the build-time
+one.
+
+@item -mdirect-extern-access
+@itemx -mno-direct-extern-access
+@opindex mdirect-extern-access
+Do not use or use GOT to access external symbols. The default is
+@option{-mno-direct-extern-access}: GOT is used for external symbols with
+default visibility, but not used for other external symbols.
+
+With @option{-mdirect-extern-access}, GOT is not used and all external
+symbols are PC-relatively addressed. It is @strong{only} suitable for
+environments where no dynamic link is performed, like firmwares, OS
+kernels, executables linked with @option{-static} or @option{-static-pie}.
+@option{-mdirect-extern-access} is not compatible with @option{-fPIC} or
+@option{-fpic}.
+@end table
+
+@node M32C Options
+@subsection M32C Options
+@cindex M32C options
+
+@table @gcctabopt
+@item -mcpu=@var{name}
+@opindex mcpu=
+Select the CPU for which code is generated. @var{name} may be one of
+@samp{r8c} for the R8C/Tiny series, @samp{m16c} for the M16C (up to
+/60) series, @samp{m32cm} for the M16C/80 series, or @samp{m32c} for
+the M32C/80 series.
+
+@item -msim
+@opindex msim
+Specifies that the program will be run on the simulator. This causes
+an alternate runtime library to be linked in which supports, for
+example, file I/O@. You must not use this option when generating
+programs that will run on real hardware; you must provide your own
+runtime library for whatever I/O functions are needed.
+
+@item -memregs=@var{number}
+@opindex memregs=
+Specifies the number of memory-based pseudo-registers GCC uses
+during code generation. These pseudo-registers are used like real
+registers, so there is a tradeoff between GCC's ability to fit the
+code into available registers, and the performance penalty of using
+memory instead of registers. Note that all modules in a program must
+be compiled with the same value for this option. Because of that, you
+must not use this option with GCC's default runtime libraries.
+
+@end table
+
+@node M32R/D Options
+@subsection M32R/D Options
+@cindex M32R/D options
+
+These @option{-m} options are defined for Renesas M32R/D architectures:
+
+@table @gcctabopt
+@item -m32r2
+@opindex m32r2
+Generate code for the M32R/2@.
+
+@item -m32rx
+@opindex m32rx
+Generate code for the M32R/X@.
+
+@item -m32r
+@opindex m32r
+Generate code for the M32R@. This is the default.
+
+@item -mmodel=small
+@opindex mmodel=small
+Assume all objects live in the lower 16MB of memory (so that their addresses
+can be loaded with the @code{ld24} instruction), and assume all subroutines
+are reachable with the @code{bl} instruction.
+This is the default.
+
+The addressability of a particular object can be set with the
+@code{model} attribute.
+
+@item -mmodel=medium
+@opindex mmodel=medium
+Assume objects may be anywhere in the 32-bit address space (the compiler
+generates @code{seth/add3} instructions to load their addresses), and
+assume all subroutines are reachable with the @code{bl} instruction.
+
+@item -mmodel=large
+@opindex mmodel=large
+Assume objects may be anywhere in the 32-bit address space (the compiler
+generates @code{seth/add3} instructions to load their addresses), and
+assume subroutines may not be reachable with the @code{bl} instruction
+(the compiler generates the much slower @code{seth/add3/jl}
+instruction sequence).
+
+@item -msdata=none
+@opindex msdata=none
+Disable use of the small data area. Variables are put into
+one of @code{.data}, @code{.bss}, or @code{.rodata} (unless the
+@code{section} attribute has been specified).
+This is the default.
+
+The small data area consists of sections @code{.sdata} and @code{.sbss}.
+Objects may be explicitly put in the small data area with the
+@code{section} attribute using one of these sections.
+
+@item -msdata=sdata
+@opindex msdata=sdata
+Put small global and static data in the small data area, but do not
+generate special code to reference them.
+
+@item -msdata=use
+@opindex msdata=use
+Put small global and static data in the small data area, and generate
+special instructions to reference them.
+
+@item -G @var{num}
+@opindex G
+@cindex smaller data references
+Put global and static objects less than or equal to @var{num} bytes
+into the small data or BSS sections instead of the normal data or BSS
+sections. The default value of @var{num} is 8.
+The @option{-msdata} option must be set to one of @samp{sdata} or @samp{use}
+for this option to have any effect.
+
+All modules should be compiled with the same @option{-G @var{num}} value.
+Compiling with different values of @var{num} may or may not work; if it
+doesn't the linker gives an error message---incorrect code is not
+generated.
+
+@item -mdebug
+@opindex mdebug
+Makes the M32R-specific code in the compiler display some statistics
+that might help in debugging programs.
+
+@item -malign-loops
+@opindex malign-loops
+Align all loops to a 32-byte boundary.
+
+@item -mno-align-loops
+@opindex mno-align-loops
+Do not enforce a 32-byte alignment for loops. This is the default.
+
+@item -missue-rate=@var{number}
+@opindex missue-rate=@var{number}
+Issue @var{number} instructions per cycle. @var{number} can only be 1
+or 2.
+
+@item -mbranch-cost=@var{number}
+@opindex mbranch-cost=@var{number}
+@var{number} can only be 1 or 2. If it is 1 then branches are
+preferred over conditional code, if it is 2, then the opposite applies.
+
+@item -mflush-trap=@var{number}
+@opindex mflush-trap=@var{number}
+Specifies the trap number to use to flush the cache. The default is
+12. Valid numbers are between 0 and 15 inclusive.
+
+@item -mno-flush-trap
+@opindex mno-flush-trap
+Specifies that the cache cannot be flushed by using a trap.
+
+@item -mflush-func=@var{name}
+@opindex mflush-func=@var{name}
+Specifies the name of the operating system function to call to flush
+the cache. The default is @samp{_flush_cache}, but a function call
+is only used if a trap is not available.
+
+@item -mno-flush-func
+@opindex mno-flush-func
+Indicates that there is no OS function for flushing the cache.
+
+@end table
+
+@node M680x0 Options
+@subsection M680x0 Options
+@cindex M680x0 options
+
+These are the @samp{-m} options defined for M680x0 and ColdFire processors.
+The default settings depend on which architecture was selected when
+the compiler was configured; the defaults for the most common choices
+are given below.
+
+@table @gcctabopt
+@item -march=@var{arch}
+@opindex march
+Generate code for a specific M680x0 or ColdFire instruction set
+architecture. Permissible values of @var{arch} for M680x0
+architectures are: @samp{68000}, @samp{68010}, @samp{68020},
+@samp{68030}, @samp{68040}, @samp{68060} and @samp{cpu32}. ColdFire
+architectures are selected according to Freescale's ISA classification
+and the permissible values are: @samp{isaa}, @samp{isaaplus},
+@samp{isab} and @samp{isac}.
+
+GCC defines a macro @code{__mcf@var{arch}__} whenever it is generating
+code for a ColdFire target. The @var{arch} in this macro is one of the
+@option{-march} arguments given above.
+
+When used together, @option{-march} and @option{-mtune} select code
+that runs on a family of similar processors but that is optimized
+for a particular microarchitecture.
+
+@item -mcpu=@var{cpu}
+@opindex mcpu
+Generate code for a specific M680x0 or ColdFire processor.
+The M680x0 @var{cpu}s are: @samp{68000}, @samp{68010}, @samp{68020},
+@samp{68030}, @samp{68040}, @samp{68060}, @samp{68302}, @samp{68332}
+and @samp{cpu32}. The ColdFire @var{cpu}s are given by the table
+below, which also classifies the CPUs into families:
+
+@multitable @columnfractions 0.20 0.80
+@headitem @strong{Family} @tab @strong{@samp{-mcpu} arguments}
+@item @samp{51} @tab @samp{51} @samp{51ac} @samp{51ag} @samp{51cn} @samp{51em} @samp{51je} @samp{51jf} @samp{51jg} @samp{51jm} @samp{51mm} @samp{51qe} @samp{51qm}
+@item @samp{5206} @tab @samp{5202} @samp{5204} @samp{5206}
+@item @samp{5206e} @tab @samp{5206e}
+@item @samp{5208} @tab @samp{5207} @samp{5208}
+@item @samp{5211a} @tab @samp{5210a} @samp{5211a}
+@item @samp{5213} @tab @samp{5211} @samp{5212} @samp{5213}
+@item @samp{5216} @tab @samp{5214} @samp{5216}
+@item @samp{52235} @tab @samp{52230} @samp{52231} @samp{52232} @samp{52233} @samp{52234} @samp{52235}
+@item @samp{5225} @tab @samp{5224} @samp{5225}
+@item @samp{52259} @tab @samp{52252} @samp{52254} @samp{52255} @samp{52256} @samp{52258} @samp{52259}
+@item @samp{5235} @tab @samp{5232} @samp{5233} @samp{5234} @samp{5235} @samp{523x}
+@item @samp{5249} @tab @samp{5249}
+@item @samp{5250} @tab @samp{5250}
+@item @samp{5271} @tab @samp{5270} @samp{5271}
+@item @samp{5272} @tab @samp{5272}
+@item @samp{5275} @tab @samp{5274} @samp{5275}
+@item @samp{5282} @tab @samp{5280} @samp{5281} @samp{5282} @samp{528x}
+@item @samp{53017} @tab @samp{53011} @samp{53012} @samp{53013} @samp{53014} @samp{53015} @samp{53016} @samp{53017}
+@item @samp{5307} @tab @samp{5307}
+@item @samp{5329} @tab @samp{5327} @samp{5328} @samp{5329} @samp{532x}
+@item @samp{5373} @tab @samp{5372} @samp{5373} @samp{537x}
+@item @samp{5407} @tab @samp{5407}
+@item @samp{5475} @tab @samp{5470} @samp{5471} @samp{5472} @samp{5473} @samp{5474} @samp{5475} @samp{547x} @samp{5480} @samp{5481} @samp{5482} @samp{5483} @samp{5484} @samp{5485}
+@end multitable
+
+@option{-mcpu=@var{cpu}} overrides @option{-march=@var{arch}} if
+@var{arch} is compatible with @var{cpu}. Other combinations of
+@option{-mcpu} and @option{-march} are rejected.
+
+GCC defines the macro @code{__mcf_cpu_@var{cpu}} when ColdFire target
+@var{cpu} is selected. It also defines @code{__mcf_family_@var{family}},
+where the value of @var{family} is given by the table above.
+
+@item -mtune=@var{tune}
+@opindex mtune
+Tune the code for a particular microarchitecture within the
+constraints set by @option{-march} and @option{-mcpu}.
+The M680x0 microarchitectures are: @samp{68000}, @samp{68010},
+@samp{68020}, @samp{68030}, @samp{68040}, @samp{68060}
+and @samp{cpu32}. The ColdFire microarchitectures
+are: @samp{cfv1}, @samp{cfv2}, @samp{cfv3}, @samp{cfv4} and @samp{cfv4e}.
+
+You can also use @option{-mtune=68020-40} for code that needs
+to run relatively well on 68020, 68030 and 68040 targets.
+@option{-mtune=68020-60} is similar but includes 68060 targets
+as well. These two options select the same tuning decisions as
+@option{-m68020-40} and @option{-m68020-60} respectively.
+
+GCC defines the macros @code{__mc@var{arch}} and @code{__mc@var{arch}__}
+when tuning for 680x0 architecture @var{arch}. It also defines
+@code{mc@var{arch}} unless either @option{-ansi} or a non-GNU @option{-std}
+option is used. If GCC is tuning for a range of architectures,
+as selected by @option{-mtune=68020-40} or @option{-mtune=68020-60},
+it defines the macros for every architecture in the range.
+
+GCC also defines the macro @code{__m@var{uarch}__} when tuning for
+ColdFire microarchitecture @var{uarch}, where @var{uarch} is one
+of the arguments given above.
+
+@item -m68000
+@itemx -mc68000
+@opindex m68000
+@opindex mc68000
+Generate output for a 68000. This is the default
+when the compiler is configured for 68000-based systems.
+It is equivalent to @option{-march=68000}.
+
+Use this option for microcontrollers with a 68000 or EC000 core,
+including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.
+
+@item -m68010
+@opindex m68010
+Generate output for a 68010. This is the default
+when the compiler is configured for 68010-based systems.
+It is equivalent to @option{-march=68010}.
+
+@item -m68020
+@itemx -mc68020
+@opindex m68020
+@opindex mc68020
+Generate output for a 68020. This is the default
+when the compiler is configured for 68020-based systems.
+It is equivalent to @option{-march=68020}.
+
+@item -m68030
+@opindex m68030
+Generate output for a 68030. This is the default when the compiler is
+configured for 68030-based systems. It is equivalent to
+@option{-march=68030}.
+
+@item -m68040
+@opindex m68040
+Generate output for a 68040. This is the default when the compiler is
+configured for 68040-based systems. It is equivalent to
+@option{-march=68040}.
+
+This option inhibits the use of 68881/68882 instructions that have to be
+emulated by software on the 68040. Use this option if your 68040 does not
+have code to emulate those instructions.
+
+@item -m68060
+@opindex m68060
+Generate output for a 68060. This is the default when the compiler is
+configured for 68060-based systems. It is equivalent to
+@option{-march=68060}.
+
+This option inhibits the use of 68020 and 68881/68882 instructions that
+have to be emulated by software on the 68060. Use this option if your 68060
+does not have code to emulate those instructions.
+
+@item -mcpu32
+@opindex mcpu32
+Generate output for a CPU32. This is the default
+when the compiler is configured for CPU32-based systems.
+It is equivalent to @option{-march=cpu32}.
+
+Use this option for microcontrollers with a
+CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334,
+68336, 68340, 68341, 68349 and 68360.
+
+@item -m5200
+@opindex m5200
+Generate output for a 520X ColdFire CPU@. This is the default
+when the compiler is configured for 520X-based systems.
+It is equivalent to @option{-mcpu=5206}, and is now deprecated
+in favor of that option.
+
+Use this option for microcontroller with a 5200 core, including
+the MCF5202, MCF5203, MCF5204 and MCF5206.
+
+@item -m5206e
+@opindex m5206e
+Generate output for a 5206e ColdFire CPU@. The option is now
+deprecated in favor of the equivalent @option{-mcpu=5206e}.
+
+@item -m528x
+@opindex m528x
+Generate output for a member of the ColdFire 528X family.
+The option is now deprecated in favor of the equivalent
+@option{-mcpu=528x}.
+
+@item -m5307
+@opindex m5307
+Generate output for a ColdFire 5307 CPU@. The option is now deprecated
+in favor of the equivalent @option{-mcpu=5307}.
+
+@item -m5407
+@opindex m5407
+Generate output for a ColdFire 5407 CPU@. The option is now deprecated
+in favor of the equivalent @option{-mcpu=5407}.
+
+@item -mcfv4e
+@opindex mcfv4e
+Generate output for a ColdFire V4e family CPU (e.g.@: 547x/548x).
+This includes use of hardware floating-point instructions.
+The option is equivalent to @option{-mcpu=547x}, and is now
+deprecated in favor of that option.
+
+@item -m68020-40
+@opindex m68020-40
+Generate output for a 68040, without using any of the new instructions.
+This results in code that can run relatively efficiently on either a
+68020/68881 or a 68030 or a 68040. The generated code does use the
+68881 instructions that are emulated on the 68040.
+
+The option is equivalent to @option{-march=68020} @option{-mtune=68020-40}.
+
+@item -m68020-60
+@opindex m68020-60
+Generate output for a 68060, without using any of the new instructions.
+This results in code that can run relatively efficiently on either a
+68020/68881 or a 68030 or a 68040. The generated code does use the
+68881 instructions that are emulated on the 68060.
+
+The option is equivalent to @option{-march=68020} @option{-mtune=68020-60}.
+
+@item -mhard-float
+@itemx -m68881
+@opindex mhard-float
+@opindex m68881
+Generate floating-point instructions. This is the default for 68020
+and above, and for ColdFire devices that have an FPU@. It defines the
+macro @code{__HAVE_68881__} on M680x0 targets and @code{__mcffpu__}
+on ColdFire targets.
+
+@item -msoft-float
+@opindex msoft-float
+Do not generate floating-point instructions; use library calls instead.
+This is the default for 68000, 68010, and 68832 targets. It is also
+the default for ColdFire devices that have no FPU.
+
+@item -mdiv
+@itemx -mno-div
+@opindex mdiv
+@opindex mno-div
+Generate (do not generate) ColdFire hardware divide and remainder
+instructions. If @option{-march} is used without @option{-mcpu},
+the default is ``on'' for ColdFire architectures and ``off'' for M680x0
+architectures. Otherwise, the default is taken from the target CPU
+(either the default CPU, or the one specified by @option{-mcpu}). For
+example, the default is ``off'' for @option{-mcpu=5206} and ``on'' for
+@option{-mcpu=5206e}.
+
+GCC defines the macro @code{__mcfhwdiv__} when this option is enabled.
+
+@item -mshort
+@opindex mshort
+Consider type @code{int} to be 16 bits wide, like @code{short int}.
+Additionally, parameters passed on the stack are also aligned to a
+16-bit boundary even on targets whose API mandates promotion to 32-bit.
+
+@item -mno-short
+@opindex mno-short
+Do not consider type @code{int} to be 16 bits wide. This is the default.
+
+@item -mnobitfield
+@itemx -mno-bitfield
+@opindex mnobitfield
+@opindex mno-bitfield
+Do not use the bit-field instructions. The @option{-m68000}, @option{-mcpu32}
+and @option{-m5200} options imply @w{@option{-mnobitfield}}.
+
+@item -mbitfield
+@opindex mbitfield
+Do use the bit-field instructions. The @option{-m68020} option implies
+@option{-mbitfield}. This is the default if you use a configuration
+designed for a 68020.
+
+@item -mrtd
+@opindex mrtd
+Use a different function-calling convention, in which functions
+that take a fixed number of arguments return with the @code{rtd}
+instruction, which pops their arguments while returning. This
+saves one instruction in the caller since there is no need to pop
+the arguments there.
+
+This calling convention is incompatible with the one normally
+used on Unix, so you cannot use it if you need to call libraries
+compiled with the Unix compiler.
+
+Also, you must provide function prototypes for all functions that
+take variable numbers of arguments (including @code{printf});
+otherwise incorrect code is generated for calls to those
+functions.
+
+In addition, seriously incorrect code results if you call a
+function with too many arguments. (Normally, extra arguments are
+harmlessly ignored.)
+
+The @code{rtd} instruction is supported by the 68010, 68020, 68030,
+68040, 68060 and CPU32 processors, but not by the 68000 or 5200.
+
+The default is @option{-mno-rtd}.
+
+@item -malign-int
+@itemx -mno-align-int
+@opindex malign-int
+@opindex mno-align-int
+Control whether GCC aligns @code{int}, @code{long}, @code{long long},
+@code{float}, @code{double}, and @code{long double} variables on a 32-bit
+boundary (@option{-malign-int}) or a 16-bit boundary (@option{-mno-align-int}).
+Aligning variables on 32-bit boundaries produces code that runs somewhat
+faster on processors with 32-bit busses at the expense of more memory.
+
+@strong{Warning:} if you use the @option{-malign-int} switch, GCC
+aligns structures containing the above types differently than
+most published application binary interface specifications for the m68k.
+
+@opindex mpcrel
+Use the pc-relative addressing mode of the 68000 directly, instead of
+using a global offset table. At present, this option implies @option{-fpic},
+allowing at most a 16-bit offset for pc-relative addressing. @option{-fPIC} is
+not presently supported with @option{-mpcrel}, though this could be supported for
+68020 and higher processors.
+
+@item -mno-strict-align
+@itemx -mstrict-align
+@opindex mno-strict-align
+@opindex mstrict-align
+Do not (do) assume that unaligned memory references are handled by
+the system.
+
+@item -msep-data
+Generate code that allows the data segment to be located in a different
+area of memory from the text segment. This allows for execute-in-place in
+an environment without virtual memory management. This option implies
+@option{-fPIC}.
+
+@item -mno-sep-data
+Generate code that assumes that the data segment follows the text segment.
+This is the default.
+
+@item -mid-shared-library
+Generate code that supports shared libraries via the library ID method.
+This allows for execute-in-place and shared libraries in an environment
+without virtual memory management. This option implies @option{-fPIC}.
+
+@item -mno-id-shared-library
+Generate code that doesn't assume ID-based shared libraries are being used.
+This is the default.
+
+@item -mshared-library-id=n
+Specifies the identification number of the ID-based shared library being
+compiled. Specifying a value of 0 generates more compact code; specifying
+other values forces the allocation of that number to the current
+library, but is no more space- or time-efficient than omitting this option.
+
+@item -mxgot
+@itemx -mno-xgot
+@opindex mxgot
+@opindex mno-xgot
+When generating position-independent code for ColdFire, generate code
+that works if the GOT has more than 8192 entries. This code is
+larger and slower than code generated without this option. On M680x0
+processors, this option is not needed; @option{-fPIC} suffices.
+
+GCC normally uses a single instruction to load values from the GOT@.
+While this is relatively efficient, it only works if the GOT
+is smaller than about 64k. Anything larger causes the linker
+to report an error such as:
+
+@cindex relocation truncated to fit (ColdFire)
+@smallexample
+relocation truncated to fit: R_68K_GOT16O foobar
+@end smallexample
+
+If this happens, you should recompile your code with @option{-mxgot}.
+It should then work with very large GOTs. However, code generated with
+@option{-mxgot} is less efficient, since it takes 4 instructions to fetch
+the value of a global symbol.
+
+Note that some linkers, including newer versions of the GNU linker,
+can create multiple GOTs and sort GOT entries. If you have such a linker,
+you should only need to use @option{-mxgot} when compiling a single
+object file that accesses more than 8192 GOT entries. Very few do.
+
+These options have no effect unless GCC is generating
+position-independent code.
+
+@item -mlong-jump-table-offsets
+@opindex mlong-jump-table-offsets
+Use 32-bit offsets in @code{switch} tables. The default is to use
+16-bit offsets.
+
+@end table
+
+@node MCore Options
+@subsection MCore Options
+@cindex MCore options
+
+These are the @samp{-m} options defined for the Motorola M*Core
+processors.
+
+@table @gcctabopt
+
+@item -mhardlit
+@itemx -mno-hardlit
+@opindex mhardlit
+@opindex mno-hardlit
+Inline constants into the code stream if it can be done in two
+instructions or less.
+
+@item -mdiv
+@itemx -mno-div
+@opindex mdiv
+@opindex mno-div
+Use the divide instruction. (Enabled by default).
+
+@item -mrelax-immediate
+@itemx -mno-relax-immediate
+@opindex mrelax-immediate
+@opindex mno-relax-immediate
+Allow arbitrary-sized immediates in bit operations.
+
+@item -mwide-bitfields
+@itemx -mno-wide-bitfields
+@opindex mwide-bitfields
+@opindex mno-wide-bitfields
+Always treat bit-fields as @code{int}-sized.
+
+@item -m4byte-functions
+@itemx -mno-4byte-functions
+@opindex m4byte-functions
+@opindex mno-4byte-functions
+Force all functions to be aligned to a 4-byte boundary.
+
+@item -mcallgraph-data
+@itemx -mno-callgraph-data
+@opindex mcallgraph-data
+@opindex mno-callgraph-data
+Emit callgraph information.
+
+@item -mslow-bytes
+@itemx -mno-slow-bytes
+@opindex mslow-bytes
+@opindex mno-slow-bytes
+Prefer word access when reading byte quantities.
+
+@item -mlittle-endian
+@itemx -mbig-endian
+@opindex mlittle-endian
+@opindex mbig-endian
+Generate code for a little-endian target.
+
+@item -m210
+@itemx -m340
+@opindex m210
+@opindex m340
+Generate code for the 210 processor.
+
+@item -mno-lsim
+@opindex mno-lsim
+Assume that runtime support has been provided and so omit the
+simulator library (@file{libsim.a)} from the linker command line.
+
+@item -mstack-increment=@var{size}
+@opindex mstack-increment
+Set the maximum amount for a single stack increment operation. Large
+values can increase the speed of programs that contain functions
+that need a large amount of stack space, but they can also trigger a
+segmentation fault if the stack is extended too much. The default
+value is 0x1000.
+
+@end table
+
+@node MeP Options
+@subsection MeP Options
+@cindex MeP options
+
+@table @gcctabopt
+
+@item -mabsdiff
+@opindex mabsdiff
+Enables the @code{abs} instruction, which is the absolute difference
+between two registers.
+
+@item -mall-opts
+@opindex mall-opts
+Enables all the optional instructions---average, multiply, divide, bit
+operations, leading zero, absolute difference, min/max, clip, and
+saturation.
+
+
+@item -maverage
+@opindex maverage
+Enables the @code{ave} instruction, which computes the average of two
+registers.
+
+@item -mbased=@var{n}
+@opindex mbased=
+Variables of size @var{n} bytes or smaller are placed in the
+@code{.based} section by default. Based variables use the @code{$tp}
+register as a base register, and there is a 128-byte limit to the
+@code{.based} section.
+
+@item -mbitops
+@opindex mbitops
+Enables the bit operation instructions---bit test (@code{btstm}), set
+(@code{bsetm}), clear (@code{bclrm}), invert (@code{bnotm}), and
+test-and-set (@code{tas}).
+
+@item -mc=@var{name}
+@opindex mc=
+Selects which section constant data is placed in. @var{name} may
+be @samp{tiny}, @samp{near}, or @samp{far}.
+
+@item -mclip
+@opindex mclip
+Enables the @code{clip} instruction. Note that @option{-mclip} is not
+useful unless you also provide @option{-mminmax}.
+
+@item -mconfig=@var{name}
+@opindex mconfig=
+Selects one of the built-in core configurations. Each MeP chip has
+one or more modules in it; each module has a core CPU and a variety of
+coprocessors, optional instructions, and peripherals. The
+@code{MeP-Integrator} tool, not part of GCC, provides these
+configurations through this option; using this option is the same as
+using all the corresponding command-line options. The default
+configuration is @samp{default}.
+
+@item -mcop
+@opindex mcop
+Enables the coprocessor instructions. By default, this is a 32-bit
+coprocessor. Note that the coprocessor is normally enabled via the
+@option{-mconfig=} option.
+
+@item -mcop32
+@opindex mcop32
+Enables the 32-bit coprocessor's instructions.
+
+@item -mcop64
+@opindex mcop64
+Enables the 64-bit coprocessor's instructions.
+
+@item -mivc2
+@opindex mivc2
+Enables IVC2 scheduling. IVC2 is a 64-bit VLIW coprocessor.
+
+@item -mdc
+@opindex mdc
+Causes constant variables to be placed in the @code{.near} section.
+
+@item -mdiv
+@opindex mdiv
+Enables the @code{div} and @code{divu} instructions.
+
+@item -meb
+@opindex meb
+Generate big-endian code.
+
+@item -mel
+@opindex mel
+Generate little-endian code.
+
+@item -mio-volatile
+@opindex mio-volatile
+Tells the compiler that any variable marked with the @code{io}
+attribute is to be considered volatile.
+
+@item -ml
+@opindex ml
+Causes variables to be assigned to the @code{.far} section by default.
+
+@item -mleadz
+@opindex mleadz
+Enables the @code{leadz} (leading zero) instruction.
+
+@item -mm
+@opindex mm
+Causes variables to be assigned to the @code{.near} section by default.
+
+@item -mminmax
+@opindex mminmax
+Enables the @code{min} and @code{max} instructions.
+
+@item -mmult
+@opindex mmult
+Enables the multiplication and multiply-accumulate instructions.
+
+@item -mno-opts
+@opindex mno-opts
+Disables all the optional instructions enabled by @option{-mall-opts}.
+
+@item -mrepeat
+@opindex mrepeat
+Enables the @code{repeat} and @code{erepeat} instructions, used for
+low-overhead looping.
+
+@item -ms
+@opindex ms
+Causes all variables to default to the @code{.tiny} section. Note
+that there is a 65536-byte limit to this section. Accesses to these
+variables use the @code{%gp} base register.
+
+@item -msatur
+@opindex msatur
+Enables the saturation instructions. Note that the compiler does not
+currently generate these itself, but this option is included for
+compatibility with other tools, like @code{as}.
+
+@item -msdram
+@opindex msdram
+Link the SDRAM-based runtime instead of the default ROM-based runtime.
+
+@item -msim
+@opindex msim
+Link the simulator run-time libraries.
+
+@item -msimnovec
+@opindex msimnovec
+Link the simulator runtime libraries, excluding built-in support
+for reset and exception vectors and tables.
+
+@item -mtf
+@opindex mtf
+Causes all functions to default to the @code{.far} section. Without
+this option, functions default to the @code{.near} section.
+
+@item -mtiny=@var{n}
+@opindex mtiny=
+Variables that are @var{n} bytes or smaller are allocated to the
+@code{.tiny} section. These variables use the @code{$gp} base
+register. The default for this option is 4, but note that there's a
+65536-byte limit to the @code{.tiny} section.
+
+@end table
+
+@node MicroBlaze Options
+@subsection MicroBlaze Options
+@cindex MicroBlaze Options
+
+@table @gcctabopt
+
+@item -msoft-float
+@opindex msoft-float
+Use software emulation for floating point (default).
+
+@item -mhard-float
+@opindex mhard-float
+Use hardware floating-point instructions.
+
+@item -mmemcpy
+@opindex mmemcpy
+Do not optimize block moves, use @code{memcpy}.
+
+@item -mno-clearbss
+@opindex mno-clearbss
+This option is deprecated. Use @option{-fno-zero-initialized-in-bss} instead.
+
+@item -mcpu=@var{cpu-type}
+@opindex mcpu=
+Use features of, and schedule code for, the given CPU.
+Supported values are in the format @samp{v@var{X}.@var{YY}.@var{Z}},
+where @var{X} is a major version, @var{YY} is the minor version, and
+@var{Z} is compatibility code. Example values are @samp{v3.00.a},
+@samp{v4.00.b}, @samp{v5.00.a}, @samp{v5.00.b}, @samp{v6.00.a}.
+
+@item -mxl-soft-mul
+@opindex mxl-soft-mul
+Use software multiply emulation (default).
+
+@item -mxl-soft-div
+@opindex mxl-soft-div
+Use software emulation for divides (default).
+
+@item -mxl-barrel-shift
+@opindex mxl-barrel-shift
+Use the hardware barrel shifter.
+
+@item -mxl-pattern-compare
+@opindex mxl-pattern-compare
+Use pattern compare instructions.
+
+@item -msmall-divides
+@opindex msmall-divides
+Use table lookup optimization for small signed integer divisions.
+
+@item -mxl-stack-check
+@opindex mxl-stack-check
+This option is deprecated. Use @option{-fstack-check} instead.
+
+@item -mxl-gp-opt
+@opindex mxl-gp-opt
+Use GP-relative @code{.sdata}/@code{.sbss} sections.
+
+@item -mxl-multiply-high
+@opindex mxl-multiply-high
+Use multiply high instructions for high part of 32x32 multiply.
+
+@item -mxl-float-convert
+@opindex mxl-float-convert
+Use hardware floating-point conversion instructions.
+
+@item -mxl-float-sqrt
+@opindex mxl-float-sqrt
+Use hardware floating-point square root instruction.
+
+@item -mbig-endian
+@opindex mbig-endian
+Generate code for a big-endian target.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+Generate code for a little-endian target.
+
+@item -mxl-reorder
+@opindex mxl-reorder
+Use reorder instructions (swap and byte reversed load/store).
+
+@item -mxl-mode-@var{app-model}
+Select application model @var{app-model}. Valid models are
+@table @samp
+@item executable
+normal executable (default), uses startup code @file{crt0.o}.
+
+@item xmdstub
+for use with Xilinx Microprocessor Debugger (XMD) based
+software intrusive debug agent called xmdstub. This uses startup file
+@file{crt1.o} and sets the start address of the program to 0x800.
+
+@item bootstrap
+for applications that are loaded using a bootloader.
+This model uses startup file @file{crt2.o} which does not contain a processor
+reset vector handler. This is suitable for transferring control on a
+processor reset to the bootloader rather than the application.
+
+@item novectors
+for applications that do not require any of the
+MicroBlaze vectors. This option may be useful for applications running
+within a monitoring application. This model uses @file{crt3.o} as a startup file.
+@end table
+
+Option @option{-xl-mode-@var{app-model}} is a deprecated alias for
+@option{-mxl-mode-@var{app-model}}.
+
+@item -mpic-data-is-text-relative
+@opindex mpic-data-is-text-relative
+Assume that the displacement between the text and data segments is fixed
+at static link time. This allows data to be referenced by offset from start of
+text address instead of GOT since PC-relative addressing is not supported.
+
+@end table
+
+@node MIPS Options
+@subsection MIPS Options
+@cindex MIPS options
+
+@table @gcctabopt
+
+@item -EB
+@opindex EB
+Generate big-endian code.
+
+@item -EL
+@opindex EL
+Generate little-endian code. This is the default for @samp{mips*el-*-*}
+configurations.
+
+@item -march=@var{arch}
+@opindex march
+Generate code that runs on @var{arch}, which can be the name of a
+generic MIPS ISA, or the name of a particular processor.
+The ISA names are:
+@samp{mips1}, @samp{mips2}, @samp{mips3}, @samp{mips4},
+@samp{mips32}, @samp{mips32r2}, @samp{mips32r3}, @samp{mips32r5},
+@samp{mips32r6}, @samp{mips64}, @samp{mips64r2}, @samp{mips64r3},
+@samp{mips64r5} and @samp{mips64r6}.
+The processor names are:
+@samp{4kc}, @samp{4km}, @samp{4kp}, @samp{4ksc},
+@samp{4kec}, @samp{4kem}, @samp{4kep}, @samp{4ksd},
+@samp{5kc}, @samp{5kf},
+@samp{20kc},
+@samp{24kc}, @samp{24kf2_1}, @samp{24kf1_1},
+@samp{24kec}, @samp{24kef2_1}, @samp{24kef1_1},
+@samp{34kc}, @samp{34kf2_1}, @samp{34kf1_1}, @samp{34kn},
+@samp{74kc}, @samp{74kf2_1}, @samp{74kf1_1}, @samp{74kf3_2},
+@samp{1004kc}, @samp{1004kf2_1}, @samp{1004kf1_1},
+@samp{i6400}, @samp{i6500},
+@samp{interaptiv},
+@samp{loongson2e}, @samp{loongson2f}, @samp{loongson3a}, @samp{gs464},
+@samp{gs464e}, @samp{gs264e},
+@samp{m4k},
+@samp{m14k}, @samp{m14kc}, @samp{m14ke}, @samp{m14kec},
+@samp{m5100}, @samp{m5101},
+@samp{octeon}, @samp{octeon+}, @samp{octeon2}, @samp{octeon3},
+@samp{orion},
+@samp{p5600}, @samp{p6600},
+@samp{r2000}, @samp{r3000}, @samp{r3900}, @samp{r4000}, @samp{r4400},
+@samp{r4600}, @samp{r4650}, @samp{r4700}, @samp{r5900},
+@samp{r6000}, @samp{r8000},
+@samp{rm7000}, @samp{rm9000},
+@samp{r10000}, @samp{r12000}, @samp{r14000}, @samp{r16000},
+@samp{sb1},
+@samp{sr71000},
+@samp{vr4100}, @samp{vr4111}, @samp{vr4120}, @samp{vr4130}, @samp{vr4300},
+@samp{vr5000}, @samp{vr5400}, @samp{vr5500},
+@samp{xlr} and @samp{xlp}.
+The special value @samp{from-abi} selects the
+most compatible architecture for the selected ABI (that is,
+@samp{mips1} for 32-bit ABIs and @samp{mips3} for 64-bit ABIs)@.
+
+The native Linux/GNU toolchain also supports the value @samp{native},
+which selects the best architecture option for the host processor.
+@option{-march=native} has no effect if GCC does not recognize
+the processor.
+
+In processor names, a final @samp{000} can be abbreviated as @samp{k}
+(for example, @option{-march=r2k}). Prefixes are optional, and
+@samp{vr} may be written @samp{r}.
+
+Names of the form @samp{@var{n}f2_1} refer to processors with
+FPUs clocked at half the rate of the core, names of the form
+@samp{@var{n}f1_1} refer to processors with FPUs clocked at the same
+rate as the core, and names of the form @samp{@var{n}f3_2} refer to
+processors with FPUs clocked a ratio of 3:2 with respect to the core.
+For compatibility reasons, @samp{@var{n}f} is accepted as a synonym
+for @samp{@var{n}f2_1} while @samp{@var{n}x} and @samp{@var{b}fx} are
+accepted as synonyms for @samp{@var{n}f1_1}.
+
+GCC defines two macros based on the value of this option. The first
+is @code{_MIPS_ARCH}, which gives the name of target architecture, as
+a string. The second has the form @code{_MIPS_ARCH_@var{foo}},
+where @var{foo} is the capitalized value of @code{_MIPS_ARCH}@.
+For example, @option{-march=r2000} sets @code{_MIPS_ARCH}
+to @code{"r2000"} and defines the macro @code{_MIPS_ARCH_R2000}.
+
+Note that the @code{_MIPS_ARCH} macro uses the processor names given
+above. In other words, it has the full prefix and does not
+abbreviate @samp{000} as @samp{k}. In the case of @samp{from-abi},
+the macro names the resolved architecture (either @code{"mips1"} or
+@code{"mips3"}). It names the default architecture when no
+@option{-march} option is given.
+
+@item -mtune=@var{arch}
+@opindex mtune
+Optimize for @var{arch}. Among other things, this option controls
+the way instructions are scheduled, and the perceived cost of arithmetic
+operations. The list of @var{arch} values is the same as for
+@option{-march}.
+
+When this option is not used, GCC optimizes for the processor
+specified by @option{-march}. By using @option{-march} and
+@option{-mtune} together, it is possible to generate code that
+runs on a family of processors, but optimize the code for one
+particular member of that family.
+
+@option{-mtune} defines the macros @code{_MIPS_TUNE} and
+@code{_MIPS_TUNE_@var{foo}}, which work in the same way as the
+@option{-march} ones described above.
+
+@item -mips1
+@opindex mips1
+Equivalent to @option{-march=mips1}.
+
+@item -mips2
+@opindex mips2
+Equivalent to @option{-march=mips2}.
+
+@item -mips3
+@opindex mips3
+Equivalent to @option{-march=mips3}.
+
+@item -mips4
+@opindex mips4
+Equivalent to @option{-march=mips4}.
+
+@item -mips32
+@opindex mips32
+Equivalent to @option{-march=mips32}.
+
+@item -mips32r3
+@opindex mips32r3
+Equivalent to @option{-march=mips32r3}.
+
+@item -mips32r5
+@opindex mips32r5
+Equivalent to @option{-march=mips32r5}.
+
+@item -mips32r6
+@opindex mips32r6
+Equivalent to @option{-march=mips32r6}.
+
+@item -mips64
+@opindex mips64
+Equivalent to @option{-march=mips64}.
+
+@item -mips64r2
+@opindex mips64r2
+Equivalent to @option{-march=mips64r2}.
+
+@item -mips64r3
+@opindex mips64r3
+Equivalent to @option{-march=mips64r3}.
+
+@item -mips64r5
+@opindex mips64r5
+Equivalent to @option{-march=mips64r5}.
+
+@item -mips64r6
+@opindex mips64r6
+Equivalent to @option{-march=mips64r6}.
+
+@item -mips16
+@itemx -mno-mips16
+@opindex mips16
+@opindex mno-mips16
+Generate (do not generate) MIPS16 code. If GCC is targeting a
+MIPS32 or MIPS64 architecture, it makes use of the MIPS16e ASE@.
+
+MIPS16 code generation can also be controlled on a per-function basis
+by means of @code{mips16} and @code{nomips16} attributes.
+@xref{Function Attributes}, for more information.
+
+@item -mflip-mips16
+@opindex mflip-mips16
+Generate MIPS16 code on alternating functions. This option is provided
+for regression testing of mixed MIPS16/non-MIPS16 code generation, and is
+not intended for ordinary use in compiling user code.
+
+@item -minterlink-compressed
+@itemx -mno-interlink-compressed
+@opindex minterlink-compressed
+@opindex mno-interlink-compressed
+Require (do not require) that code using the standard (uncompressed) MIPS ISA
+be link-compatible with MIPS16 and microMIPS code, and vice versa.
+
+For example, code using the standard ISA encoding cannot jump directly
+to MIPS16 or microMIPS code; it must either use a call or an indirect jump.
+@option{-minterlink-compressed} therefore disables direct jumps unless GCC
+knows that the target of the jump is not compressed.
+
+@item -minterlink-mips16
+@itemx -mno-interlink-mips16
+@opindex minterlink-mips16
+@opindex mno-interlink-mips16
+Aliases of @option{-minterlink-compressed} and
+@option{-mno-interlink-compressed}. These options predate the microMIPS ASE
+and are retained for backwards compatibility.
+
+@item -mabi=32
+@itemx -mabi=o64
+@itemx -mabi=n32
+@itemx -mabi=64
+@itemx -mabi=eabi
+@opindex mabi=32
+@opindex mabi=o64
+@opindex mabi=n32
+@opindex mabi=64
+@opindex mabi=eabi
+Generate code for the given ABI@.
+
+Note that the EABI has a 32-bit and a 64-bit variant. GCC normally
+generates 64-bit code when you select a 64-bit architecture, but you
+can use @option{-mgp32} to get 32-bit code instead.
+
+For information about the O64 ABI, see
+@uref{https://gcc.gnu.org/@/projects/@/mipso64-abi.html}.
+
+GCC supports a variant of the o32 ABI in which floating-point registers
+are 64 rather than 32 bits wide. You can select this combination with
+@option{-mabi=32} @option{-mfp64}. This ABI relies on the @code{mthc1}
+and @code{mfhc1} instructions and is therefore only supported for
+MIPS32R2, MIPS32R3 and MIPS32R5 processors.
+
+The register assignments for arguments and return values remain the
+same, but each scalar value is passed in a single 64-bit register
+rather than a pair of 32-bit registers. For example, scalar
+floating-point values are returned in @samp{$f0} only, not a
+@samp{$f0}/@samp{$f1} pair. The set of call-saved registers also
+remains the same in that the even-numbered double-precision registers
+are saved.
+
+Two additional variants of the o32 ABI are supported to enable
+a transition from 32-bit to 64-bit registers. These are FPXX
+(@option{-mfpxx}) and FP64A (@option{-mfp64} @option{-mno-odd-spreg}).
+The FPXX extension mandates that all code must execute correctly
+when run using 32-bit or 64-bit registers. The code can be interlinked
+with either FP32 or FP64, but not both.
+The FP64A extension is similar to the FP64 extension but forbids the
+use of odd-numbered single-precision registers. This can be used
+in conjunction with the @code{FRE} mode of FPUs in MIPS32R5
+processors and allows both FP32 and FP64A code to interlink and
+run in the same process without changing FPU modes.
+
+@item -mabicalls
+@itemx -mno-abicalls
+@opindex mabicalls
+@opindex mno-abicalls
+Generate (do not generate) code that is suitable for SVR4-style
+dynamic objects. @option{-mabicalls} is the default for SVR4-based
+systems.
+
+@item -mshared
+@itemx -mno-shared
+Generate (do not generate) code that is fully position-independent,
+and that can therefore be linked into shared libraries. This option
+only affects @option{-mabicalls}.
+
+All @option{-mabicalls} code has traditionally been position-independent,
+regardless of options like @option{-fPIC} and @option{-fpic}. However,
+as an extension, the GNU toolchain allows executables to use absolute
+accesses for locally-binding symbols. It can also use shorter GP
+initialization sequences and generate direct calls to locally-defined
+functions. This mode is selected by @option{-mno-shared}.
+
+@option{-mno-shared} depends on binutils 2.16 or higher and generates
+objects that can only be linked by the GNU linker. However, the option
+does not affect the ABI of the final executable; it only affects the ABI
+of relocatable objects. Using @option{-mno-shared} generally makes
+executables both smaller and quicker.
+
+@option{-mshared} is the default.
+
+@item -mplt
+@itemx -mno-plt
+@opindex mplt
+@opindex mno-plt
+Assume (do not assume) that the static and dynamic linkers
+support PLTs and copy relocations. This option only affects
+@option{-mno-shared -mabicalls}. For the n64 ABI, this option
+has no effect without @option{-msym32}.
+
+You can make @option{-mplt} the default by configuring
+GCC with @option{--with-mips-plt}. The default is
+@option{-mno-plt} otherwise.
+
+@item -mxgot
+@itemx -mno-xgot
+@opindex mxgot
+@opindex mno-xgot
+Lift (do not lift) the usual restrictions on the size of the global
+offset table.
+
+GCC normally uses a single instruction to load values from the GOT@.
+While this is relatively efficient, it only works if the GOT
+is smaller than about 64k. Anything larger causes the linker
+to report an error such as:
+
+@cindex relocation truncated to fit (MIPS)
+@smallexample
+relocation truncated to fit: R_MIPS_GOT16 foobar
+@end smallexample
+
+If this happens, you should recompile your code with @option{-mxgot}.
+This works with very large GOTs, although the code is also
+less efficient, since it takes three instructions to fetch the
+value of a global symbol.
+
+Note that some linkers can create multiple GOTs. If you have such a
+linker, you should only need to use @option{-mxgot} when a single object
+file accesses more than 64k's worth of GOT entries. Very few do.
+
+These options have no effect unless GCC is generating position
+independent code.
+
+@item -mgp32
+@opindex mgp32
+Assume that general-purpose registers are 32 bits wide.
+
+@item -mgp64
+@opindex mgp64
+Assume that general-purpose registers are 64 bits wide.
+
+@item -mfp32
+@opindex mfp32
+Assume that floating-point registers are 32 bits wide.
+
+@item -mfp64
+@opindex mfp64
+Assume that floating-point registers are 64 bits wide.
+
+@item -mfpxx
+@opindex mfpxx
+Do not assume the width of floating-point registers.
+
+@item -mhard-float
+@opindex mhard-float
+Use floating-point coprocessor instructions.
+
+@item -msoft-float
+@opindex msoft-float
+Do not use floating-point coprocessor instructions. Implement
+floating-point calculations using library calls instead.
+
+@item -mno-float
+@opindex mno-float
+Equivalent to @option{-msoft-float}, but additionally asserts that the
+program being compiled does not perform any floating-point operations.
+This option is presently supported only by some bare-metal MIPS
+configurations, where it may select a special set of libraries
+that lack all floating-point support (including, for example, the
+floating-point @code{printf} formats).
+If code compiled with @option{-mno-float} accidentally contains
+floating-point operations, it is likely to suffer a link-time
+or run-time failure.
+
+@item -msingle-float
+@opindex msingle-float
+Assume that the floating-point coprocessor only supports single-precision
+operations.
+
+@item -mdouble-float
+@opindex mdouble-float
+Assume that the floating-point coprocessor supports double-precision
+operations. This is the default.
+
+@item -modd-spreg
+@itemx -mno-odd-spreg
+@opindex modd-spreg
+@opindex mno-odd-spreg
+Enable the use of odd-numbered single-precision floating-point registers
+for the o32 ABI. This is the default for processors that are known to
+support these registers. When using the o32 FPXX ABI, @option{-mno-odd-spreg}
+is set by default.
+
+@item -mabs=2008
+@itemx -mabs=legacy
+@opindex mabs=2008
+@opindex mabs=legacy
+These options control the treatment of the special not-a-number (NaN)
+IEEE 754 floating-point data with the @code{abs.@i{fmt}} and
+@code{neg.@i{fmt}} machine instructions.
+
+By default or when @option{-mabs=legacy} is used the legacy
+treatment is selected. In this case these instructions are considered
+arithmetic and avoided where correct operation is required and the
+input operand might be a NaN. A longer sequence of instructions that
+manipulate the sign bit of floating-point datum manually is used
+instead unless the @option{-ffinite-math-only} option has also been
+specified.
+
+The @option{-mabs=2008} option selects the IEEE 754-2008 treatment. In
+this case these instructions are considered non-arithmetic and therefore
+operating correctly in all cases, including in particular where the
+input operand is a NaN. These instructions are therefore always used
+for the respective operations.
+
+@item -mnan=2008
+@itemx -mnan=legacy
+@opindex mnan=2008
+@opindex mnan=legacy
+These options control the encoding of the special not-a-number (NaN)
+IEEE 754 floating-point data.
+
+The @option{-mnan=legacy} option selects the legacy encoding. In this
+case quiet NaNs (qNaNs) are denoted by the first bit of their trailing
+significand field being 0, whereas signaling NaNs (sNaNs) are denoted
+by the first bit of their trailing significand field being 1.
+
+The @option{-mnan=2008} option selects the IEEE 754-2008 encoding. In
+this case qNaNs are denoted by the first bit of their trailing
+significand field being 1, whereas sNaNs are denoted by the first bit of
+their trailing significand field being 0.
+
+The default is @option{-mnan=legacy} unless GCC has been configured with
+@option{--with-nan=2008}.
+
+@item -mllsc
+@itemx -mno-llsc
+@opindex mllsc
+@opindex mno-llsc
+Use (do not use) @samp{ll}, @samp{sc}, and @samp{sync} instructions to
+implement atomic memory built-in functions. When neither option is
+specified, GCC uses the instructions if the target architecture
+supports them.
+
+@option{-mllsc} is useful if the runtime environment can emulate the
+instructions and @option{-mno-llsc} can be useful when compiling for
+nonstandard ISAs. You can make either option the default by
+configuring GCC with @option{--with-llsc} and @option{--without-llsc}
+respectively. @option{--with-llsc} is the default for some
+configurations; see the installation documentation for details.
+
+@item -mdsp
+@itemx -mno-dsp
+@opindex mdsp
+@opindex mno-dsp
+Use (do not use) revision 1 of the MIPS DSP ASE@.
+@xref{MIPS DSP Built-in Functions}. This option defines the
+preprocessor macro @code{__mips_dsp}. It also defines
+@code{__mips_dsp_rev} to 1.
+
+@item -mdspr2
+@itemx -mno-dspr2
+@opindex mdspr2
+@opindex mno-dspr2
+Use (do not use) revision 2 of the MIPS DSP ASE@.
+@xref{MIPS DSP Built-in Functions}. This option defines the
+preprocessor macros @code{__mips_dsp} and @code{__mips_dspr2}.
+It also defines @code{__mips_dsp_rev} to 2.
+
+@item -msmartmips
+@itemx -mno-smartmips
+@opindex msmartmips
+@opindex mno-smartmips
+Use (do not use) the MIPS SmartMIPS ASE.
+
+@item -mpaired-single
+@itemx -mno-paired-single
+@opindex mpaired-single
+@opindex mno-paired-single
+Use (do not use) paired-single floating-point instructions.
+@xref{MIPS Paired-Single Support}. This option requires
+hardware floating-point support to be enabled.
+
+@item -mdmx
+@itemx -mno-mdmx
+@opindex mdmx
+@opindex mno-mdmx
+Use (do not use) MIPS Digital Media Extension instructions.
+This option can only be used when generating 64-bit code and requires
+hardware floating-point support to be enabled.
+
+@item -mips3d
+@itemx -mno-mips3d
+@opindex mips3d
+@opindex mno-mips3d
+Use (do not use) the MIPS-3D ASE@. @xref{MIPS-3D Built-in Functions}.
+The option @option{-mips3d} implies @option{-mpaired-single}.
+
+@item -mmicromips
+@itemx -mno-micromips
+@opindex mmicromips
+@opindex mno-mmicromips
+Generate (do not generate) microMIPS code.
+
+MicroMIPS code generation can also be controlled on a per-function basis
+by means of @code{micromips} and @code{nomicromips} attributes.
+@xref{Function Attributes}, for more information.
+
+@item -mmt
+@itemx -mno-mt
+@opindex mmt
+@opindex mno-mt
+Use (do not use) MT Multithreading instructions.
+
+@item -mmcu
+@itemx -mno-mcu
+@opindex mmcu
+@opindex mno-mcu
+Use (do not use) the MIPS MCU ASE instructions.
+
+@item -meva
+@itemx -mno-eva
+@opindex meva
+@opindex mno-eva
+Use (do not use) the MIPS Enhanced Virtual Addressing instructions.
+
+@item -mvirt
+@itemx -mno-virt
+@opindex mvirt
+@opindex mno-virt
+Use (do not use) the MIPS Virtualization (VZ) instructions.
+
+@item -mxpa
+@itemx -mno-xpa
+@opindex mxpa
+@opindex mno-xpa
+Use (do not use) the MIPS eXtended Physical Address (XPA) instructions.
+
+@item -mcrc
+@itemx -mno-crc
+@opindex mcrc
+@opindex mno-crc
+Use (do not use) the MIPS Cyclic Redundancy Check (CRC) instructions.
+
+@item -mginv
+@itemx -mno-ginv
+@opindex mginv
+@opindex mno-ginv
+Use (do not use) the MIPS Global INValidate (GINV) instructions.
+
+@item -mloongson-mmi
+@itemx -mno-loongson-mmi
+@opindex mloongson-mmi
+@opindex mno-loongson-mmi
+Use (do not use) the MIPS Loongson MultiMedia extensions Instructions (MMI).
+
+@item -mloongson-ext
+@itemx -mno-loongson-ext
+@opindex mloongson-ext
+@opindex mno-loongson-ext
+Use (do not use) the MIPS Loongson EXTensions (EXT) instructions.
+
+@item -mloongson-ext2
+@itemx -mno-loongson-ext2
+@opindex mloongson-ext2
+@opindex mno-loongson-ext2
+Use (do not use) the MIPS Loongson EXTensions r2 (EXT2) instructions.
+
+@item -mlong64
+@opindex mlong64
+Force @code{long} types to be 64 bits wide. See @option{-mlong32} for
+an explanation of the default and the way that the pointer size is
+determined.
+
+@item -mlong32
+@opindex mlong32
+Force @code{long}, @code{int}, and pointer types to be 32 bits wide.
+
+The default size of @code{int}s, @code{long}s and pointers depends on
+the ABI@. All the supported ABIs use 32-bit @code{int}s. The n64 ABI
+uses 64-bit @code{long}s, as does the 64-bit EABI; the others use
+32-bit @code{long}s. Pointers are the same size as @code{long}s,
+or the same size as integer registers, whichever is smaller.
+
+@item -msym32
+@itemx -mno-sym32
+@opindex msym32
+@opindex mno-sym32
+Assume (do not assume) that all symbols have 32-bit values, regardless
+of the selected ABI@. This option is useful in combination with
+@option{-mabi=64} and @option{-mno-abicalls} because it allows GCC
+to generate shorter and faster references to symbolic addresses.
+
+@item -G @var{num}
+@opindex G
+Put definitions of externally-visible data in a small data section
+if that data is no bigger than @var{num} bytes. GCC can then generate
+more efficient accesses to the data; see @option{-mgpopt} for details.
+
+The default @option{-G} option depends on the configuration.
+
+@item -mlocal-sdata
+@itemx -mno-local-sdata
+@opindex mlocal-sdata
+@opindex mno-local-sdata
+Extend (do not extend) the @option{-G} behavior to local data too,
+such as to static variables in C@. @option{-mlocal-sdata} is the
+default for all configurations.
+
+If the linker complains that an application is using too much small data,
+you might want to try rebuilding the less performance-critical parts with
+@option{-mno-local-sdata}. You might also want to build large
+libraries with @option{-mno-local-sdata}, so that the libraries leave
+more room for the main program.
+
+@item -mextern-sdata
+@itemx -mno-extern-sdata
+@opindex mextern-sdata
+@opindex mno-extern-sdata
+Assume (do not assume) that externally-defined data is in
+a small data section if the size of that data is within the @option{-G} limit.
+@option{-mextern-sdata} is the default for all configurations.
+
+If you compile a module @var{Mod} with @option{-mextern-sdata} @option{-G
+@var{num}} @option{-mgpopt}, and @var{Mod} references a variable @var{Var}
+that is no bigger than @var{num} bytes, you must make sure that @var{Var}
+is placed in a small data section. If @var{Var} is defined by another
+module, you must either compile that module with a high-enough
+@option{-G} setting or attach a @code{section} attribute to @var{Var}'s
+definition. If @var{Var} is common, you must link the application
+with a high-enough @option{-G} setting.
+
+The easiest way of satisfying these restrictions is to compile
+and link every module with the same @option{-G} option. However,
+you may wish to build a library that supports several different
+small data limits. You can do this by compiling the library with
+the highest supported @option{-G} setting and additionally using
+@option{-mno-extern-sdata} to stop the library from making assumptions
+about externally-defined data.
+
+@item -mgpopt
+@itemx -mno-gpopt
+@opindex mgpopt
+@opindex mno-gpopt
+Use (do not use) GP-relative accesses for symbols that are known to be
+in a small data section; see @option{-G}, @option{-mlocal-sdata} and
+@option{-mextern-sdata}. @option{-mgpopt} is the default for all
+configurations.
+
+@option{-mno-gpopt} is useful for cases where the @code{$gp} register
+might not hold the value of @code{_gp}. For example, if the code is
+part of a library that might be used in a boot monitor, programs that
+call boot monitor routines pass an unknown value in @code{$gp}.
+(In such situations, the boot monitor itself is usually compiled
+with @option{-G0}.)
+
+@option{-mno-gpopt} implies @option{-mno-local-sdata} and
+@option{-mno-extern-sdata}.
+
+@item -membedded-data
+@itemx -mno-embedded-data
+@opindex membedded-data
+@opindex mno-embedded-data
+Allocate variables to the read-only data section first if possible, then
+next in the small data section if possible, otherwise in data. This gives
+slightly slower code than the default, but reduces the amount of RAM required
+when executing, and thus may be preferred for some embedded systems.
+
+@item -muninit-const-in-rodata
+@itemx -mno-uninit-const-in-rodata
+@opindex muninit-const-in-rodata
+@opindex mno-uninit-const-in-rodata
+Put uninitialized @code{const} variables in the read-only data section.
+This option is only meaningful in conjunction with @option{-membedded-data}.
+
+@item -mcode-readable=@var{setting}
+@opindex mcode-readable
+Specify whether GCC may generate code that reads from executable sections.
+There are three possible settings:
+
+@table @gcctabopt
+@item -mcode-readable=yes
+Instructions may freely access executable sections. This is the
+default setting.
+
+@item -mcode-readable=pcrel
+MIPS16 PC-relative load instructions can access executable sections,
+but other instructions must not do so. This option is useful on 4KSc
+and 4KSd processors when the code TLBs have the Read Inhibit bit set.
+It is also useful on processors that can be configured to have a dual
+instruction/data SRAM interface and that, like the M4K, automatically
+redirect PC-relative loads to the instruction RAM.
+
+@item -mcode-readable=no
+Instructions must not access executable sections. This option can be
+useful on targets that are configured to have a dual instruction/data
+SRAM interface but that (unlike the M4K) do not automatically redirect
+PC-relative loads to the instruction RAM.
+@end table
+
+@item -msplit-addresses
+@itemx -mno-split-addresses
+@opindex msplit-addresses
+@opindex mno-split-addresses
+Enable (disable) use of the @code{%hi()} and @code{%lo()} assembler
+relocation operators. This option has been superseded by
+@option{-mexplicit-relocs} but is retained for backwards compatibility.
+
+@item -mexplicit-relocs
+@itemx -mno-explicit-relocs
+@opindex mexplicit-relocs
+@opindex mno-explicit-relocs
+Use (do not use) assembler relocation operators when dealing with symbolic
+addresses. The alternative, selected by @option{-mno-explicit-relocs},
+is to use assembler macros instead.
+
+@option{-mexplicit-relocs} is the default if GCC was configured
+to use an assembler that supports relocation operators.
+
+@item -mcheck-zero-division
+@itemx -mno-check-zero-division
+@opindex mcheck-zero-division
+@opindex mno-check-zero-division
+Trap (do not trap) on integer division by zero.
+
+The default is @option{-mcheck-zero-division}.
+
+@item -mdivide-traps
+@itemx -mdivide-breaks
+@opindex mdivide-traps
+@opindex mdivide-breaks
+MIPS systems check for division by zero by generating either a
+conditional trap or a break instruction. Using traps results in
+smaller code, but is only supported on MIPS II and later. Also, some
+versions of the Linux kernel have a bug that prevents trap from
+generating the proper signal (@code{SIGFPE}). Use @option{-mdivide-traps} to
+allow conditional traps on architectures that support them and
+@option{-mdivide-breaks} to force the use of breaks.
+
+The default is usually @option{-mdivide-traps}, but this can be
+overridden at configure time using @option{--with-divide=breaks}.
+Divide-by-zero checks can be completely disabled using
+@option{-mno-check-zero-division}.
+
+@item -mload-store-pairs
+@itemx -mno-load-store-pairs
+@opindex mload-store-pairs
+@opindex mno-load-store-pairs
+Enable (disable) an optimization that pairs consecutive load or store
+instructions to enable load/store bonding. This option is enabled by
+default but only takes effect when the selected architecture is known
+to support bonding.
+
+@item -munaligned-access
+@itemx -mno-unaligned-access
+@opindex munaligned-access
+@opindex mno-unaligned-access
+Enable (disable) direct unaligned access for MIPS Release 6.
+MIPSr6 requires load/store unaligned-access support,
+by hardware or trap&emulate.
+So @option{-mno-unaligned-access} may be needed by kernel.
+
+@item -mmemcpy
+@itemx -mno-memcpy
+@opindex mmemcpy
+@opindex mno-memcpy
+Force (do not force) the use of @code{memcpy} for non-trivial block
+moves. The default is @option{-mno-memcpy}, which allows GCC to inline
+most constant-sized copies.
+
+@item -mlong-calls
+@itemx -mno-long-calls
+@opindex mlong-calls
+@opindex mno-long-calls
+Disable (do not disable) use of the @code{jal} instruction. Calling
+functions using @code{jal} is more efficient but requires the caller
+and callee to be in the same 256 megabyte segment.
+
+This option has no effect on abicalls code. The default is
+@option{-mno-long-calls}.
+
+@item -mmad
+@itemx -mno-mad
+@opindex mmad
+@opindex mno-mad
+Enable (disable) use of the @code{mad}, @code{madu} and @code{mul}
+instructions, as provided by the R4650 ISA@.
+
+@item -mimadd
+@itemx -mno-imadd
+@opindex mimadd
+@opindex mno-imadd
+Enable (disable) use of the @code{madd} and @code{msub} integer
+instructions. The default is @option{-mimadd} on architectures
+that support @code{madd} and @code{msub} except for the 74k
+architecture where it was found to generate slower code.
+
+@item -mfused-madd
+@itemx -mno-fused-madd
+@opindex mfused-madd
+@opindex mno-fused-madd
+Enable (disable) use of the floating-point multiply-accumulate
+instructions, when they are available. The default is
+@option{-mfused-madd}.
+
+On the R8000 CPU when multiply-accumulate instructions are used,
+the intermediate product is calculated to infinite precision
+and is not subject to the FCSR Flush to Zero bit. This may be
+undesirable in some circumstances. On other processors the result
+is numerically identical to the equivalent computation using
+separate multiply, add, subtract and negate instructions.
+
+@item -nocpp
+@opindex nocpp
+Tell the MIPS assembler to not run its preprocessor over user
+assembler files (with a @samp{.s} suffix) when assembling them.
+
+@item -mfix-24k
+@itemx -mno-fix-24k
+@opindex mfix-24k
+@opindex mno-fix-24k
+Work around the 24K E48 (lost data on stores during refill) errata.
+The workarounds are implemented by the assembler rather than by GCC@.
+
+@item -mfix-r4000
+@itemx -mno-fix-r4000
+@opindex mfix-r4000
+@opindex mno-fix-r4000
+Work around certain R4000 CPU errata:
+@itemize @minus
+@item
+A double-word or a variable shift may give an incorrect result if executed
+immediately after starting an integer division.
+@item
+A double-word or a variable shift may give an incorrect result if executed
+while an integer multiplication is in progress.
+@item
+An integer division may give an incorrect result if started in a delay slot
+of a taken branch or a jump.
+@end itemize
+
+@item -mfix-r4400
+@itemx -mno-fix-r4400
+@opindex mfix-r4400
+@opindex mno-fix-r4400
+Work around certain R4400 CPU errata:
+@itemize @minus
+@item
+A double-word or a variable shift may give an incorrect result if executed
+immediately after starting an integer division.
+@end itemize
+
+@item -mfix-r10000
+@itemx -mno-fix-r10000
+@opindex mfix-r10000
+@opindex mno-fix-r10000
+Work around certain R10000 errata:
+@itemize @minus
+@item
+@code{ll}/@code{sc} sequences may not behave atomically on revisions
+prior to 3.0. They may deadlock on revisions 2.6 and earlier.
+@end itemize
+
+This option can only be used if the target architecture supports
+branch-likely instructions. @option{-mfix-r10000} is the default when
+@option{-march=r10000} is used; @option{-mno-fix-r10000} is the default
+otherwise.
+
+@item -mfix-r5900
+@itemx -mno-fix-r5900
+@opindex mfix-r5900
+Do not attempt to schedule the preceding instruction into the delay slot
+of a branch instruction placed at the end of a short loop of six
+instructions or fewer and always schedule a @code{nop} instruction there
+instead. The short loop bug under certain conditions causes loops to
+execute only once or twice, due to a hardware bug in the R5900 chip. The
+workaround is implemented by the assembler rather than by GCC@.
+
+@item -mfix-rm7000
+@itemx -mno-fix-rm7000
+@opindex mfix-rm7000
+Work around the RM7000 @code{dmult}/@code{dmultu} errata. The
+workarounds are implemented by the assembler rather than by GCC@.
+
+@item -mfix-vr4120
+@itemx -mno-fix-vr4120
+@opindex mfix-vr4120
+Work around certain VR4120 errata:
+@itemize @minus
+@item
+@code{dmultu} does not always produce the correct result.
+@item
+@code{div} and @code{ddiv} do not always produce the correct result if one
+of the operands is negative.
+@end itemize
+The workarounds for the division errata rely on special functions in
+@file{libgcc.a}. At present, these functions are only provided by
+the @code{mips64vr*-elf} configurations.
+
+Other VR4120 errata require a NOP to be inserted between certain pairs of
+instructions. These errata are handled by the assembler, not by GCC itself.
+
+@item -mfix-vr4130
+@opindex mfix-vr4130
+Work around the VR4130 @code{mflo}/@code{mfhi} errata. The
+workarounds are implemented by the assembler rather than by GCC,
+although GCC avoids using @code{mflo} and @code{mfhi} if the
+VR4130 @code{macc}, @code{macchi}, @code{dmacc} and @code{dmacchi}
+instructions are available instead.
+
+@item -mfix-sb1
+@itemx -mno-fix-sb1
+@opindex mfix-sb1
+Work around certain SB-1 CPU core errata.
+(This flag currently works around the SB-1 revision 2
+``F1'' and ``F2'' floating-point errata.)
+
+@item -mr10k-cache-barrier=@var{setting}
+@opindex mr10k-cache-barrier
+Specify whether GCC should insert cache barriers to avoid the
+side effects of speculation on R10K processors.
+
+In common with many processors, the R10K tries to predict the outcome
+of a conditional branch and speculatively executes instructions from
+the ``taken'' branch. It later aborts these instructions if the
+predicted outcome is wrong. However, on the R10K, even aborted
+instructions can have side effects.
+
+This problem only affects kernel stores and, depending on the system,
+kernel loads. As an example, a speculatively-executed store may load
+the target memory into cache and mark the cache line as dirty, even if
+the store itself is later aborted. If a DMA operation writes to the
+same area of memory before the ``dirty'' line is flushed, the cached
+data overwrites the DMA-ed data. See the R10K processor manual
+for a full description, including other potential problems.
+
+One workaround is to insert cache barrier instructions before every memory
+access that might be speculatively executed and that might have side
+effects even if aborted. @option{-mr10k-cache-barrier=@var{setting}}
+controls GCC's implementation of this workaround. It assumes that
+aborted accesses to any byte in the following regions does not have
+side effects:
+
+@enumerate
+@item
+the memory occupied by the current function's stack frame;
+
+@item
+the memory occupied by an incoming stack argument;
+
+@item
+the memory occupied by an object with a link-time-constant address.
+@end enumerate
+
+It is the kernel's responsibility to ensure that speculative
+accesses to these regions are indeed safe.
+
+If the input program contains a function declaration such as:
+
+@smallexample
+void foo (void);
+@end smallexample
+
+then the implementation of @code{foo} must allow @code{j foo} and
+@code{jal foo} to be executed speculatively. GCC honors this
+restriction for functions it compiles itself. It expects non-GCC
+functions (such as hand-written assembly code) to do the same.
+
+The option has three forms:
+
+@table @gcctabopt
+@item -mr10k-cache-barrier=load-store
+Insert a cache barrier before a load or store that might be
+speculatively executed and that might have side effects even
+if aborted.
+
+@item -mr10k-cache-barrier=store
+Insert a cache barrier before a store that might be speculatively
+executed and that might have side effects even if aborted.
+
+@item -mr10k-cache-barrier=none
+Disable the insertion of cache barriers. This is the default setting.
+@end table
+
+@item -mflush-func=@var{func}
+@itemx -mno-flush-func
+@opindex mflush-func
+Specifies the function to call to flush the I and D caches, or to not
+call any such function. If called, the function must take the same
+arguments as the common @code{_flush_func}, that is, the address of the
+memory range for which the cache is being flushed, the size of the
+memory range, and the number 3 (to flush both caches). The default
+depends on the target GCC was configured for, but commonly is either
+@code{_flush_func} or @code{__cpu_flush}.
+
+@item mbranch-cost=@var{num}
+@opindex mbranch-cost
+Set the cost of branches to roughly @var{num} ``simple'' instructions.
+This cost is only a heuristic and is not guaranteed to produce
+consistent results across releases. A zero cost redundantly selects
+the default, which is based on the @option{-mtune} setting.
+
+@item -mbranch-likely
+@itemx -mno-branch-likely
+@opindex mbranch-likely
+@opindex mno-branch-likely
+Enable or disable use of Branch Likely instructions, regardless of the
+default for the selected architecture. By default, Branch Likely
+instructions may be generated if they are supported by the selected
+architecture. An exception is for the MIPS32 and MIPS64 architectures
+and processors that implement those architectures; for those, Branch
+Likely instructions are not be generated by default because the MIPS32
+and MIPS64 architectures specifically deprecate their use.
+
+@item -mcompact-branches=never
+@itemx -mcompact-branches=optimal
+@itemx -mcompact-branches=always
+@opindex mcompact-branches=never
+@opindex mcompact-branches=optimal
+@opindex mcompact-branches=always
+These options control which form of branches will be generated. The
+default is @option{-mcompact-branches=optimal}.
+
+The @option{-mcompact-branches=never} option ensures that compact branch
+instructions will never be generated.
+
+The @option{-mcompact-branches=always} option ensures that a compact
+branch instruction will be generated if available for MIPS Release 6 onwards.
+If a compact branch instruction is not available (or pre-R6),
+a delay slot form of the branch will be used instead.
+
+If it is used for MIPS16/microMIPS targets, it will be just ignored now.
+The behaviour for MIPS16/microMIPS may change in future,
+since they do have some compact branch instructions.
+
+The @option{-mcompact-branches=optimal} option will cause a delay slot
+branch to be used if one is available in the current ISA and the delay
+slot is successfully filled. If the delay slot is not filled, a compact
+branch will be chosen if one is available.
+
+@item -mfp-exceptions
+@itemx -mno-fp-exceptions
+@opindex mfp-exceptions
+Specifies whether FP exceptions are enabled. This affects how
+FP instructions are scheduled for some processors.
+The default is that FP exceptions are
+enabled.
+
+For instance, on the SB-1, if FP exceptions are disabled, and we are emitting
+64-bit code, then we can use both FP pipes. Otherwise, we can only use one
+FP pipe.
+
+@item -mvr4130-align
+@itemx -mno-vr4130-align
+@opindex mvr4130-align
+The VR4130 pipeline is two-way superscalar, but can only issue two
+instructions together if the first one is 8-byte aligned. When this
+option is enabled, GCC aligns pairs of instructions that it
+thinks should execute in parallel.
+
+This option only has an effect when optimizing for the VR4130.
+It normally makes code faster, but at the expense of making it bigger.
+It is enabled by default at optimization level @option{-O3}.
+
+@item -msynci
+@itemx -mno-synci
+@opindex msynci
+Enable (disable) generation of @code{synci} instructions on
+architectures that support it. The @code{synci} instructions (if
+enabled) are generated when @code{__builtin___clear_cache} is
+compiled.
+
+This option defaults to @option{-mno-synci}, but the default can be
+overridden by configuring GCC with @option{--with-synci}.
+
+When compiling code for single processor systems, it is generally safe
+to use @code{synci}. However, on many multi-core (SMP) systems, it
+does not invalidate the instruction caches on all cores and may lead
+to undefined behavior.
+
+@item -mrelax-pic-calls
+@itemx -mno-relax-pic-calls
+@opindex mrelax-pic-calls
+Try to turn PIC calls that are normally dispatched via register
+@code{$25} into direct calls. This is only possible if the linker can
+resolve the destination at link time and if the destination is within
+range for a direct call.
+
+@option{-mrelax-pic-calls} is the default if GCC was configured to use
+an assembler and a linker that support the @code{.reloc} assembly
+directive and @option{-mexplicit-relocs} is in effect. With
+@option{-mno-explicit-relocs}, this optimization can be performed by the
+assembler and the linker alone without help from the compiler.
+
+@item -mmcount-ra-address
+@itemx -mno-mcount-ra-address
+@opindex mmcount-ra-address
+@opindex mno-mcount-ra-address
+Emit (do not emit) code that allows @code{_mcount} to modify the
+calling function's return address. When enabled, this option extends
+the usual @code{_mcount} interface with a new @var{ra-address}
+parameter, which has type @code{intptr_t *} and is passed in register
+@code{$12}. @code{_mcount} can then modify the return address by
+doing both of the following:
+@itemize
+@item
+Returning the new address in register @code{$31}.
+@item
+Storing the new address in @code{*@var{ra-address}},
+if @var{ra-address} is nonnull.
+@end itemize
+
+The default is @option{-mno-mcount-ra-address}.
+
+@item -mframe-header-opt
+@itemx -mno-frame-header-opt
+@opindex mframe-header-opt
+Enable (disable) frame header optimization in the o32 ABI. When using the
+o32 ABI, calling functions will allocate 16 bytes on the stack for the called
+function to write out register arguments. When enabled, this optimization
+will suppress the allocation of the frame header if it can be determined that
+it is unused.
+
+This optimization is off by default at all optimization levels.
+
+@item -mlxc1-sxc1
+@itemx -mno-lxc1-sxc1
+@opindex mlxc1-sxc1
+When applicable, enable (disable) the generation of @code{lwxc1},
+@code{swxc1}, @code{ldxc1}, @code{sdxc1} instructions. Enabled by default.
+
+@item -mmadd4
+@itemx -mno-madd4
+@opindex mmadd4
+When applicable, enable (disable) the generation of 4-operand @code{madd.s},
+@code{madd.d} and related instructions. Enabled by default.
+
+@end table
+
+@node MMIX Options
+@subsection MMIX Options
+@cindex MMIX Options
+
+These options are defined for the MMIX:
+
+@table @gcctabopt
+@item -mlibfuncs
+@itemx -mno-libfuncs
+@opindex mlibfuncs
+@opindex mno-libfuncs
+Specify that intrinsic library functions are being compiled, passing all
+values in registers, no matter the size.
+
+@item -mepsilon
+@itemx -mno-epsilon
+@opindex mepsilon
+@opindex mno-epsilon
+Generate floating-point comparison instructions that compare with respect
+to the @code{rE} epsilon register.
+
+@item -mabi=mmixware
+@itemx -mabi=gnu
+@opindex mabi=mmixware
+@opindex mabi=gnu
+Generate code that passes function parameters and return values that (in
+the called function) are seen as registers @code{$0} and up, as opposed to
+the GNU ABI which uses global registers @code{$231} and up.
+
+@item -mzero-extend
+@itemx -mno-zero-extend
+@opindex mzero-extend
+@opindex mno-zero-extend
+When reading data from memory in sizes shorter than 64 bits, use (do not
+use) zero-extending load instructions by default, rather than
+sign-extending ones.
+
+@item -mknuthdiv
+@itemx -mno-knuthdiv
+@opindex mknuthdiv
+@opindex mno-knuthdiv
+Make the result of a division yielding a remainder have the same sign as
+the divisor. With the default, @option{-mno-knuthdiv}, the sign of the
+remainder follows the sign of the dividend. Both methods are
+arithmetically valid, the latter being almost exclusively used.
+
+@item -mtoplevel-symbols
+@itemx -mno-toplevel-symbols
+@opindex mtoplevel-symbols
+@opindex mno-toplevel-symbols
+Prepend (do not prepend) a @samp{:} to all global symbols, so the assembly
+code can be used with the @code{PREFIX} assembly directive.
+
+@item -melf
+@opindex melf
+Generate an executable in the ELF format, rather than the default
+@samp{mmo} format used by the @command{mmix} simulator.
+
+@item -mbranch-predict
+@itemx -mno-branch-predict
+@opindex mbranch-predict
+@opindex mno-branch-predict
+Use (do not use) the probable-branch instructions, when static branch
+prediction indicates a probable branch.
+
+@item -mbase-addresses
+@itemx -mno-base-addresses
+@opindex mbase-addresses
+@opindex mno-base-addresses
+Generate (do not generate) code that uses @emph{base addresses}. Using a
+base address automatically generates a request (handled by the assembler
+and the linker) for a constant to be set up in a global register. The
+register is used for one or more base address requests within the range 0
+to 255 from the value held in the register. The generally leads to short
+and fast code, but the number of different data items that can be
+addressed is limited. This means that a program that uses lots of static
+data may require @option{-mno-base-addresses}.
+
+@item -msingle-exit
+@itemx -mno-single-exit
+@opindex msingle-exit
+@opindex mno-single-exit
+Force (do not force) generated code to have a single exit point in each
+function.
+@end table
+
+@node MN10300 Options
+@subsection MN10300 Options
+@cindex MN10300 options
+
+These @option{-m} options are defined for Matsushita MN10300 architectures:
+
+@table @gcctabopt
+@item -mmult-bug
+@opindex mmult-bug
+Generate code to avoid bugs in the multiply instructions for the MN10300
+processors. This is the default.
+
+@item -mno-mult-bug
+@opindex mno-mult-bug
+Do not generate code to avoid bugs in the multiply instructions for the
+MN10300 processors.
+
+@item -mam33
+@opindex mam33
+Generate code using features specific to the AM33 processor.
+
+@item -mno-am33
+@opindex mno-am33
+Do not generate code using features specific to the AM33 processor. This
+is the default.
+
+@item -mam33-2
+@opindex mam33-2
+Generate code using features specific to the AM33/2.0 processor.
+
+@item -mam34
+@opindex mam34
+Generate code using features specific to the AM34 processor.
+
+@item -mtune=@var{cpu-type}
+@opindex mtune
+Use the timing characteristics of the indicated CPU type when
+scheduling instructions. This does not change the targeted processor
+type. The CPU type must be one of @samp{mn10300}, @samp{am33},
+@samp{am33-2} or @samp{am34}.
+
+@item -mreturn-pointer-on-d0
+@opindex mreturn-pointer-on-d0
+When generating a function that returns a pointer, return the pointer
+in both @code{a0} and @code{d0}. Otherwise, the pointer is returned
+only in @code{a0}, and attempts to call such functions without a prototype
+result in errors. Note that this option is on by default; use
+@option{-mno-return-pointer-on-d0} to disable it.
+
+@item -mno-crt0
+@opindex mno-crt0
+Do not link in the C run-time initialization object file.
+
+@item -mrelax
+@opindex mrelax
+Indicate to the linker that it should perform a relaxation optimization pass
+to shorten branches, calls and absolute memory addresses. This option only
+has an effect when used on the command line for the final link step.
+
+This option makes symbolic debugging impossible.
+
+@item -mliw
+@opindex mliw
+Allow the compiler to generate @emph{Long Instruction Word}
+instructions if the target is the @samp{AM33} or later. This is the
+default. This option defines the preprocessor macro @code{__LIW__}.
+
+@item -mno-liw
+@opindex mno-liw
+Do not allow the compiler to generate @emph{Long Instruction Word}
+instructions. This option defines the preprocessor macro
+@code{__NO_LIW__}.
+
+@item -msetlb
+@opindex msetlb
+Allow the compiler to generate the @emph{SETLB} and @emph{Lcc}
+instructions if the target is the @samp{AM33} or later. This is the
+default. This option defines the preprocessor macro @code{__SETLB__}.
+
+@item -mno-setlb
+@opindex mno-setlb
+Do not allow the compiler to generate @emph{SETLB} or @emph{Lcc}
+instructions. This option defines the preprocessor macro
+@code{__NO_SETLB__}.
+
+@end table
+
+@node Moxie Options
+@subsection Moxie Options
+@cindex Moxie Options
+
+@table @gcctabopt
+
+@item -meb
+@opindex meb
+Generate big-endian code. This is the default for @samp{moxie-*-*}
+configurations.
+
+@item -mel
+@opindex mel
+Generate little-endian code.
+
+@item -mmul.x
+@opindex mmul.x
+Generate mul.x and umul.x instructions. This is the default for
+@samp{moxiebox-*-*} configurations.
+
+@item -mno-crt0
+@opindex mno-crt0
+Do not link in the C run-time initialization object file.
+
+@end table
+
+@node MSP430 Options
+@subsection MSP430 Options
+@cindex MSP430 Options
+
+These options are defined for the MSP430:
+
+@table @gcctabopt
+
+@item -masm-hex
+@opindex masm-hex
+Force assembly output to always use hex constants. Normally such
+constants are signed decimals, but this option is available for
+testsuite and/or aesthetic purposes.
+
+@item -mmcu=
+@opindex mmcu=
+Select the MCU to target. This is used to create a C preprocessor
+symbol based upon the MCU name, converted to upper case and pre- and
+post-fixed with @samp{__}. This in turn is used by the
+@file{msp430.h} header file to select an MCU-specific supplementary
+header file.
+
+The option also sets the ISA to use. If the MCU name is one that is
+known to only support the 430 ISA then that is selected, otherwise the
+430X ISA is selected. A generic MCU name of @samp{msp430} can also be
+used to select the 430 ISA. Similarly the generic @samp{msp430x} MCU
+name selects the 430X ISA.
+
+In addition an MCU-specific linker script is added to the linker
+command line. The script's name is the name of the MCU with
+@file{.ld} appended. Thus specifying @option{-mmcu=xxx} on the @command{gcc}
+command line defines the C preprocessor symbol @code{__XXX__} and
+cause the linker to search for a script called @file{xxx.ld}.
+
+The ISA and hardware multiply supported for the different MCUs is hard-coded
+into GCC. However, an external @samp{devices.csv} file can be used to
+extend device support beyond those that have been hard-coded.
+
+GCC searches for the @samp{devices.csv} file using the following methods in the
+given precedence order, where the first method takes precendence over the
+second which takes precedence over the third.
+
+@table @asis
+@item Include path specified with @code{-I} and @code{-L}
+@samp{devices.csv} will be searched for in each of the directories specified by
+include paths and linker library search paths.
+@item Path specified by the environment variable @samp{MSP430_GCC_INCLUDE_DIR}
+Define the value of the global environment variable
+@samp{MSP430_GCC_INCLUDE_DIR}
+to the full path to the directory containing devices.csv, and GCC will search
+this directory for devices.csv. If devices.csv is found, this directory will
+also be registered as an include path, and linker library path. Header files
+and linker scripts in this directory can therefore be used without manually
+specifying @code{-I} and @code{-L} on the command line.
+@item The @samp{msp430-elf@{,bare@}/include/devices} directory
+Finally, GCC will examine @samp{msp430-elf@{,bare@}/include/devices} from the
+toolchain root directory. This directory does not exist in a default
+installation, but if the user has created it and copied @samp{devices.csv}
+there, then the MCU data will be read. As above, this directory will
+also be registered as an include path, and linker library path.
+
+@end table
+If none of the above search methods find @samp{devices.csv}, then the
+hard-coded MCU data is used.
+
+
+@item -mwarn-mcu
+@itemx -mno-warn-mcu
+@opindex mwarn-mcu
+@opindex mno-warn-mcu
+This option enables or disables warnings about conflicts between the
+MCU name specified by the @option{-mmcu} option and the ISA set by the
+@option{-mcpu} option and/or the hardware multiply support set by the
+@option{-mhwmult} option. It also toggles warnings about unrecognized
+MCU names. This option is on by default.
+
+@item -mcpu=
+@opindex mcpu=
+Specifies the ISA to use. Accepted values are @samp{msp430},
+@samp{msp430x} and @samp{msp430xv2}. This option is deprecated. The
+@option{-mmcu=} option should be used to select the ISA.
+
+@item -msim
+@opindex msim
+Link to the simulator runtime libraries and linker script. Overrides
+any scripts that would be selected by the @option{-mmcu=} option.
+
+@item -mlarge
+@opindex mlarge
+Use large-model addressing (20-bit pointers, 20-bit @code{size_t}).
+
+@item -msmall
+@opindex msmall
+Use small-model addressing (16-bit pointers, 16-bit @code{size_t}).
+
+@item -mrelax
+@opindex mrelax
+This option is passed to the assembler and linker, and allows the
+linker to perform certain optimizations that cannot be done until
+the final link.
+
+@item mhwmult=
+@opindex mhwmult=
+Describes the type of hardware multiply supported by the target.
+Accepted values are @samp{none} for no hardware multiply, @samp{16bit}
+for the original 16-bit-only multiply supported by early MCUs.
+@samp{32bit} for the 16/32-bit multiply supported by later MCUs and
+@samp{f5series} for the 16/32-bit multiply supported by F5-series MCUs.
+A value of @samp{auto} can also be given. This tells GCC to deduce
+the hardware multiply support based upon the MCU name provided by the
+@option{-mmcu} option. If no @option{-mmcu} option is specified or if
+the MCU name is not recognized then no hardware multiply support is
+assumed. @code{auto} is the default setting.
+
+Hardware multiplies are normally performed by calling a library
+routine. This saves space in the generated code. When compiling at
+@option{-O3} or higher however the hardware multiplier is invoked
+inline. This makes for bigger, but faster code.
+
+The hardware multiply routines disable interrupts whilst running and
+restore the previous interrupt state when they finish. This makes
+them safe to use inside interrupt handlers as well as in normal code.
+
+@item -minrt
+@opindex minrt
+Enable the use of a minimum runtime environment - no static
+initializers or constructors. This is intended for memory-constrained
+devices. The compiler includes special symbols in some objects
+that tell the linker and runtime which code fragments are required.
+
+@item -mtiny-printf
+@opindex mtiny-printf
+Enable reduced code size @code{printf} and @code{puts} library functions.
+The @samp{tiny} implementations of these functions are not reentrant, so
+must be used with caution in multi-threaded applications.
+
+Support for streams has been removed and the string to be printed will
+always be sent to stdout via the @code{write} syscall. The string is not
+buffered before it is sent to write.
+
+This option requires Newlib Nano IO, so GCC must be configured with
+@samp{--enable-newlib-nano-formatted-io}.
+
+@item -mmax-inline-shift=
+@opindex mmax-inline-shift=
+This option takes an integer between 0 and 64 inclusive, and sets
+the maximum number of inline shift instructions which should be emitted to
+perform a shift operation by a constant amount. When this value needs to be
+exceeded, an mspabi helper function is used instead. The default value is 4.
+
+This only affects cases where a shift by multiple positions cannot be
+completed with a single instruction (e.g. all shifts >1 on the 430 ISA).
+
+Shifts of a 32-bit value are at least twice as costly, so the value passed for
+this option is divided by 2 and the resulting value used instead.
+
+@item -mcode-region=
+@itemx -mdata-region=
+@opindex mcode-region
+@opindex mdata-region
+These options tell the compiler where to place functions and data that
+do not have one of the @code{lower}, @code{upper}, @code{either} or
+@code{section} attributes. Possible values are @code{lower},
+@code{upper}, @code{either} or @code{any}. The first three behave
+like the corresponding attribute. The fourth possible value -
+@code{any} - is the default. It leaves placement entirely up to the
+linker script and how it assigns the standard sections
+(@code{.text}, @code{.data}, etc) to the memory regions.
+
+@item -msilicon-errata=
+@opindex msilicon-errata
+This option passes on a request to assembler to enable the fixes for
+the named silicon errata.
+
+@item -msilicon-errata-warn=
+@opindex msilicon-errata-warn
+This option passes on a request to the assembler to enable warning
+messages when a silicon errata might need to be applied.
+
+@item -mwarn-devices-csv
+@itemx -mno-warn-devices-csv
+@opindex mwarn-devices-csv
+@opindex mno-warn-devices-csv
+Warn if @samp{devices.csv} is not found or there are problem parsing it
+(default: on).
+
+@end table
+
+@node NDS32 Options
+@subsection NDS32 Options
+@cindex NDS32 Options
+
+These options are defined for NDS32 implementations:
+
+@table @gcctabopt
+
+@item -mbig-endian
+@opindex mbig-endian
+Generate code in big-endian mode.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+Generate code in little-endian mode.
+
+@item -mreduced-regs
+@opindex mreduced-regs
+Use reduced-set registers for register allocation.
+
+@item -mfull-regs
+@opindex mfull-regs
+Use full-set registers for register allocation.
+
+@item -mcmov
+@opindex mcmov
+Generate conditional move instructions.
+
+@item -mno-cmov
+@opindex mno-cmov
+Do not generate conditional move instructions.
+
+@item -mext-perf
+@opindex mext-perf
+Generate performance extension instructions.
+
+@item -mno-ext-perf
+@opindex mno-ext-perf
+Do not generate performance extension instructions.
+
+@item -mext-perf2
+@opindex mext-perf2
+Generate performance extension 2 instructions.
+
+@item -mno-ext-perf2
+@opindex mno-ext-perf2
+Do not generate performance extension 2 instructions.
+
+@item -mext-string
+@opindex mext-string
+Generate string extension instructions.
+
+@item -mno-ext-string
+@opindex mno-ext-string
+Do not generate string extension instructions.
+
+@item -mv3push
+@opindex mv3push
+Generate v3 push25/pop25 instructions.
+
+@item -mno-v3push
+@opindex mno-v3push
+Do not generate v3 push25/pop25 instructions.
+
+@item -m16-bit
+@opindex m16-bit
+Generate 16-bit instructions.
+
+@item -mno-16-bit
+@opindex mno-16-bit
+Do not generate 16-bit instructions.
+
+@item -misr-vector-size=@var{num}
+@opindex misr-vector-size
+Specify the size of each interrupt vector, which must be 4 or 16.
+
+@item -mcache-block-size=@var{num}
+@opindex mcache-block-size
+Specify the size of each cache block,
+which must be a power of 2 between 4 and 512.
+
+@item -march=@var{arch}
+@opindex march
+Specify the name of the target architecture.
+
+@item -mcmodel=@var{code-model}
+@opindex mcmodel
+Set the code model to one of
+@table @asis
+@item @samp{small}
+All the data and read-only data segments must be within 512KB addressing space.
+The text segment must be within 16MB addressing space.
+@item @samp{medium}
+The data segment must be within 512KB while the read-only data segment can be
+within 4GB addressing space. The text segment should be still within 16MB
+addressing space.
+@item @samp{large}
+All the text and data segments can be within 4GB addressing space.
+@end table
+
+@item -mctor-dtor
+@opindex mctor-dtor
+Enable constructor/destructor feature.
+
+@item -mrelax
+@opindex mrelax
+Guide linker to relax instructions.
+
+@end table
+
+@node Nios II Options
+@subsection Nios II Options
+@cindex Nios II options
+@cindex Altera Nios II options
+
+These are the options defined for the Altera Nios II processor.
+
+@table @gcctabopt
+
+@item -G @var{num}
+@opindex G
+@cindex smaller data references
+Put global and static objects less than or equal to @var{num} bytes
+into the small data or BSS sections instead of the normal data or BSS
+sections. The default value of @var{num} is 8.
+
+@item -mgpopt=@var{option}
+@itemx -mgpopt
+@itemx -mno-gpopt
+@opindex mgpopt
+@opindex mno-gpopt
+Generate (do not generate) GP-relative accesses. The following
+@var{option} names are recognized:
+
+@table @samp
+
+@item none
+Do not generate GP-relative accesses.
+
+@item local
+Generate GP-relative accesses for small data objects that are not
+external, weak, or uninitialized common symbols.
+Also use GP-relative addressing for objects that
+have been explicitly placed in a small data section via a @code{section}
+attribute.
+
+@item global
+As for @samp{local}, but also generate GP-relative accesses for
+small data objects that are external, weak, or common. If you use this option,
+you must ensure that all parts of your program (including libraries) are
+compiled with the same @option{-G} setting.
+
+@item data
+Generate GP-relative accesses for all data objects in the program. If you
+use this option, the entire data and BSS segments
+of your program must fit in 64K of memory and you must use an appropriate
+linker script to allocate them within the addressable range of the
+global pointer.
+
+@item all
+Generate GP-relative addresses for function pointers as well as data
+pointers. If you use this option, the entire text, data, and BSS segments
+of your program must fit in 64K of memory and you must use an appropriate
+linker script to allocate them within the addressable range of the
+global pointer.
+
+@end table
+
+@option{-mgpopt} is equivalent to @option{-mgpopt=local}, and
+@option{-mno-gpopt} is equivalent to @option{-mgpopt=none}.
+
+The default is @option{-mgpopt} except when @option{-fpic} or
+@option{-fPIC} is specified to generate position-independent code.
+Note that the Nios II ABI does not permit GP-relative accesses from
+shared libraries.
+
+You may need to specify @option{-mno-gpopt} explicitly when building
+programs that include large amounts of small data, including large
+GOT data sections. In this case, the 16-bit offset for GP-relative
+addressing may not be large enough to allow access to the entire
+small data section.
+
+@item -mgprel-sec=@var{regexp}
+@opindex mgprel-sec
+This option specifies additional section names that can be accessed via
+GP-relative addressing. It is most useful in conjunction with
+@code{section} attributes on variable declarations
+(@pxref{Common Variable Attributes}) and a custom linker script.
+The @var{regexp} is a POSIX Extended Regular Expression.
+
+This option does not affect the behavior of the @option{-G} option, and
+the specified sections are in addition to the standard @code{.sdata}
+and @code{.sbss} small-data sections that are recognized by @option{-mgpopt}.
+
+@item -mr0rel-sec=@var{regexp}
+@opindex mr0rel-sec
+This option specifies names of sections that can be accessed via a
+16-bit offset from @code{r0}; that is, in the low 32K or high 32K
+of the 32-bit address space. It is most useful in conjunction with
+@code{section} attributes on variable declarations
+(@pxref{Common Variable Attributes}) and a custom linker script.
+The @var{regexp} is a POSIX Extended Regular Expression.
+
+In contrast to the use of GP-relative addressing for small data,
+zero-based addressing is never generated by default and there are no
+conventional section names used in standard linker scripts for sections
+in the low or high areas of memory.
+
+@item -mel
+@itemx -meb
+@opindex mel
+@opindex meb
+Generate little-endian (default) or big-endian (experimental) code,
+respectively.
+
+@item -march=@var{arch}
+@opindex march
+This specifies the name of the target Nios II architecture. GCC uses this
+name to determine what kind of instructions it can emit when generating
+assembly code. Permissible names are: @samp{r1}, @samp{r2}.
+
+The preprocessor macro @code{__nios2_arch__} is available to programs,
+with value 1 or 2, indicating the targeted ISA level.
+
+@item -mbypass-cache
+@itemx -mno-bypass-cache
+@opindex mno-bypass-cache
+@opindex mbypass-cache
+Force all load and store instructions to always bypass cache by
+using I/O variants of the instructions. The default is not to
+bypass the cache.
+
+@item -mno-cache-volatile
+@itemx -mcache-volatile
+@opindex mcache-volatile
+@opindex mno-cache-volatile
+Volatile memory access bypass the cache using the I/O variants of
+the load and store instructions. The default is not to bypass the cache.
+
+@item -mno-fast-sw-div
+@itemx -mfast-sw-div
+@opindex mno-fast-sw-div
+@opindex mfast-sw-div
+Do not use table-based fast divide for small numbers. The default
+is to use the fast divide at @option{-O3} and above.
+
+@item -mno-hw-mul
+@itemx -mhw-mul
+@itemx -mno-hw-mulx
+@itemx -mhw-mulx
+@itemx -mno-hw-div
+@itemx -mhw-div
+@opindex mno-hw-mul
+@opindex mhw-mul
+@opindex mno-hw-mulx
+@opindex mhw-mulx
+@opindex mno-hw-div
+@opindex mhw-div
+Enable or disable emitting @code{mul}, @code{mulx} and @code{div} family of
+instructions by the compiler. The default is to emit @code{mul}
+and not emit @code{div} and @code{mulx}.
+
+@item -mbmx
+@itemx -mno-bmx
+@itemx -mcdx
+@itemx -mno-cdx
+Enable or disable generation of Nios II R2 BMX (bit manipulation) and
+CDX (code density) instructions. Enabling these instructions also
+requires @option{-march=r2}. Since these instructions are optional
+extensions to the R2 architecture, the default is not to emit them.
+
+@item -mcustom-@var{insn}=@var{N}
+@itemx -mno-custom-@var{insn}
+@opindex mcustom-@var{insn}
+@opindex mno-custom-@var{insn}
+Each @option{-mcustom-@var{insn}=@var{N}} option enables use of a
+custom instruction with encoding @var{N} when generating code that uses
+@var{insn}. For example, @option{-mcustom-fadds=253} generates custom
+instruction 253 for single-precision floating-point add operations instead
+of the default behavior of using a library call.
+
+The following values of @var{insn} are supported. Except as otherwise
+noted, floating-point operations are expected to be implemented with
+normal IEEE 754 semantics and correspond directly to the C operators or the
+equivalent GCC built-in functions (@pxref{Other Builtins}).
+
+Single-precision floating point:
+@table @asis
+
+@item @samp{fadds}, @samp{fsubs}, @samp{fdivs}, @samp{fmuls}
+Binary arithmetic operations.
+
+@item @samp{fnegs}
+Unary negation.
+
+@item @samp{fabss}
+Unary absolute value.
+
+@item @samp{fcmpeqs}, @samp{fcmpges}, @samp{fcmpgts}, @samp{fcmples}, @samp{fcmplts}, @samp{fcmpnes}
+Comparison operations.
+
+@item @samp{fmins}, @samp{fmaxs}
+Floating-point minimum and maximum. These instructions are only
+generated if @option{-ffinite-math-only} is specified.
+
+@item @samp{fsqrts}
+Unary square root operation.
+
+@item @samp{fcoss}, @samp{fsins}, @samp{ftans}, @samp{fatans}, @samp{fexps}, @samp{flogs}
+Floating-point trigonometric and exponential functions. These instructions
+are only generated if @option{-funsafe-math-optimizations} is also specified.
+
+@end table
+
+Double-precision floating point:
+@table @asis
+
+@item @samp{faddd}, @samp{fsubd}, @samp{fdivd}, @samp{fmuld}
+Binary arithmetic operations.
+
+@item @samp{fnegd}
+Unary negation.
+
+@item @samp{fabsd}
+Unary absolute value.
+
+@item @samp{fcmpeqd}, @samp{fcmpged}, @samp{fcmpgtd}, @samp{fcmpled}, @samp{fcmpltd}, @samp{fcmpned}
+Comparison operations.
+
+@item @samp{fmind}, @samp{fmaxd}
+Double-precision minimum and maximum. These instructions are only
+generated if @option{-ffinite-math-only} is specified.
+
+@item @samp{fsqrtd}
+Unary square root operation.
+
+@item @samp{fcosd}, @samp{fsind}, @samp{ftand}, @samp{fatand}, @samp{fexpd}, @samp{flogd}
+Double-precision trigonometric and exponential functions. These instructions
+are only generated if @option{-funsafe-math-optimizations} is also specified.
+
+@end table
+
+Conversions:
+@table @asis
+@item @samp{fextsd}
+Conversion from single precision to double precision.
+
+@item @samp{ftruncds}
+Conversion from double precision to single precision.
+
+@item @samp{fixsi}, @samp{fixsu}, @samp{fixdi}, @samp{fixdu}
+Conversion from floating point to signed or unsigned integer types, with
+truncation towards zero.
+
+@item @samp{round}
+Conversion from single-precision floating point to signed integer,
+rounding to the nearest integer and ties away from zero.
+This corresponds to the @code{__builtin_lroundf} function when
+@option{-fno-math-errno} is used.
+
+@item @samp{floatis}, @samp{floatus}, @samp{floatid}, @samp{floatud}
+Conversion from signed or unsigned integer types to floating-point types.
+
+@end table
+
+In addition, all of the following transfer instructions for internal
+registers X and Y must be provided to use any of the double-precision
+floating-point instructions. Custom instructions taking two
+double-precision source operands expect the first operand in the
+64-bit register X. The other operand (or only operand of a unary
+operation) is given to the custom arithmetic instruction with the
+least significant half in source register @var{src1} and the most
+significant half in @var{src2}. A custom instruction that returns a
+double-precision result returns the most significant 32 bits in the
+destination register and the other half in 32-bit register Y.
+GCC automatically generates the necessary code sequences to write
+register X and/or read register Y when double-precision floating-point
+instructions are used.
+
+@table @asis
+
+@item @samp{fwrx}
+Write @var{src1} into the least significant half of X and @var{src2} into
+the most significant half of X.
+
+@item @samp{fwry}
+Write @var{src1} into Y.
+
+@item @samp{frdxhi}, @samp{frdxlo}
+Read the most or least (respectively) significant half of X and store it in
+@var{dest}.
+
+@item @samp{frdy}
+Read the value of Y and store it into @var{dest}.
+@end table
+
+Note that you can gain more local control over generation of Nios II custom
+instructions by using the @code{target("custom-@var{insn}=@var{N}")}
+and @code{target("no-custom-@var{insn}")} function attributes
+(@pxref{Function Attributes})
+or pragmas (@pxref{Function Specific Option Pragmas}).
+
+@item -mcustom-fpu-cfg=@var{name}
+@opindex mcustom-fpu-cfg
+
+This option enables a predefined, named set of custom instruction encodings
+(see @option{-mcustom-@var{insn}} above).
+Currently, the following sets are defined:
+
+@option{-mcustom-fpu-cfg=60-1} is equivalent to:
+@gccoptlist{-mcustom-fmuls=252 @gol
+-mcustom-fadds=253 @gol
+-mcustom-fsubs=254 @gol
+-fsingle-precision-constant}
+
+@option{-mcustom-fpu-cfg=60-2} is equivalent to:
+@gccoptlist{-mcustom-fmuls=252 @gol
+-mcustom-fadds=253 @gol
+-mcustom-fsubs=254 @gol
+-mcustom-fdivs=255 @gol
+-fsingle-precision-constant}
+
+@option{-mcustom-fpu-cfg=72-3} is equivalent to:
+@gccoptlist{-mcustom-floatus=243 @gol
+-mcustom-fixsi=244 @gol
+-mcustom-floatis=245 @gol
+-mcustom-fcmpgts=246 @gol
+-mcustom-fcmples=249 @gol
+-mcustom-fcmpeqs=250 @gol
+-mcustom-fcmpnes=251 @gol
+-mcustom-fmuls=252 @gol
+-mcustom-fadds=253 @gol
+-mcustom-fsubs=254 @gol
+-mcustom-fdivs=255 @gol
+-fsingle-precision-constant}
+
+@option{-mcustom-fpu-cfg=fph2} is equivalent to:
+@gccoptlist{-mcustom-fabss=224 @gol
+-mcustom-fnegs=225 @gol
+-mcustom-fcmpnes=226 @gol
+-mcustom-fcmpeqs=227 @gol
+-mcustom-fcmpges=228 @gol
+-mcustom-fcmpgts=229 @gol
+-mcustom-fcmples=230 @gol
+-mcustom-fcmplts=231 @gol
+-mcustom-fmaxs=232 @gol
+-mcustom-fmins=233 @gol
+-mcustom-round=248 @gol
+-mcustom-fixsi=249 @gol
+-mcustom-floatis=250 @gol
+-mcustom-fsqrts=251 @gol
+-mcustom-fmuls=252 @gol
+-mcustom-fadds=253 @gol
+-mcustom-fsubs=254 @gol
+-mcustom-fdivs=255 @gol}
+
+Custom instruction assignments given by individual
+@option{-mcustom-@var{insn}=} options override those given by
+@option{-mcustom-fpu-cfg=}, regardless of the
+order of the options on the command line.
+
+Note that you can gain more local control over selection of a FPU
+configuration by using the @code{target("custom-fpu-cfg=@var{name}")}
+function attribute (@pxref{Function Attributes})
+or pragma (@pxref{Function Specific Option Pragmas}).
+
+The name @var{fph2} is an abbreviation for @emph{Nios II Floating Point
+Hardware 2 Component}. Please note that the custom instructions enabled by
+@option{-mcustom-fmins=233} and @option{-mcustom-fmaxs=234} are only generated
+if @option{-ffinite-math-only} is specified. The custom instruction enabled by
+@option{-mcustom-round=248} is only generated if @option{-fno-math-errno} is
+specified. In contrast to the other configurations,
+@option{-fsingle-precision-constant} is not set.
+
+@end table
+
+These additional @samp{-m} options are available for the Altera Nios II
+ELF (bare-metal) target:
+
+@table @gcctabopt
+
+@item -mhal
+@opindex mhal
+Link with HAL BSP. This suppresses linking with the GCC-provided C runtime
+startup and termination code, and is typically used in conjunction with
+@option{-msys-crt0=} to specify the location of the alternate startup code
+provided by the HAL BSP.
+
+@item -msmallc
+@opindex msmallc
+Link with a limited version of the C library, @option{-lsmallc}, rather than
+Newlib.
+
+@item -msys-crt0=@var{startfile}
+@opindex msys-crt0
+@var{startfile} is the file name of the startfile (crt0) to use
+when linking. This option is only useful in conjunction with @option{-mhal}.
+
+@item -msys-lib=@var{systemlib}
+@opindex msys-lib
+@var{systemlib} is the library name of the library that provides
+low-level system calls required by the C library,
+e.g.@: @code{read} and @code{write}.
+This option is typically used to link with a library provided by a HAL BSP.
+
+@end table
+
+@node Nvidia PTX Options
+@subsection Nvidia PTX Options
+@cindex Nvidia PTX options
+@cindex nvptx options
+
+These options are defined for Nvidia PTX:
+
+@table @gcctabopt
+
+@item -m64
+@opindex m64
+Ignored, but preserved for backward compatibility. Only 64-bit ABI is
+supported.
+
+@item -march=@var{architecture-string}
+@opindex march
+Generate code for the specified PTX ISA target architecture
+(e.g.@: @samp{sm_35}). Valid architecture strings are @samp{sm_30},
+@samp{sm_35}, @samp{sm_53}, @samp{sm_70}, @samp{sm_75} and
+@samp{sm_80}.
+The default depends on how the compiler has been configured, see
+@option{--with-arch}.
+
+This option sets the value of the preprocessor macro
+@code{__PTX_SM__}; for instance, for @samp{sm_35}, it has the value
+@samp{350}.
+
+@item -misa=@var{architecture-string}
+@opindex misa
+Alias of @option{-march=}.
+
+@item -march-map=@var{architecture-string}
+@opindex march
+Select the closest available @option{-march=} value that is not more
+capable. For instance, for @option{-march-map=sm_50} select
+@option{-march=sm_35}, and for @option{-march-map=sm_53} select
+@option{-march=sm_53}.
+
+@item -mptx=@var{version-string}
+@opindex mptx
+Generate code for the specified PTX ISA version (e.g.@: @samp{7.0}).
+Valid version strings include @samp{3.1}, @samp{6.0}, @samp{6.3}, and
+@samp{7.0}. The default PTX ISA version is 6.0, unless a higher
+version is required for specified PTX ISA target architecture via
+option @option{-march=}.
+
+This option sets the values of the preprocessor macros
+@code{__PTX_ISA_VERSION_MAJOR__} and @code{__PTX_ISA_VERSION_MINOR__};
+for instance, for @samp{3.1} the macros have the values @samp{3} and
+@samp{1}, respectively.
+
+@item -mmainkernel
+@opindex mmainkernel
+Link in code for a __main kernel. This is for stand-alone instead of
+offloading execution.
+
+@item -moptimize
+@opindex moptimize
+Apply partitioned execution optimizations. This is the default when any
+level of optimization is selected.
+
+@item -msoft-stack
+@opindex msoft-stack
+Generate code that does not use @code{.local} memory
+directly for stack storage. Instead, a per-warp stack pointer is
+maintained explicitly. This enables variable-length stack allocation (with
+variable-length arrays or @code{alloca}), and when global memory is used for
+underlying storage, makes it possible to access automatic variables from other
+threads, or with atomic instructions. This code generation variant is used
+for OpenMP offloading, but the option is exposed on its own for the purpose
+of testing the compiler; to generate code suitable for linking into programs
+using OpenMP offloading, use option @option{-mgomp}.
+
+@item -muniform-simt
+@opindex muniform-simt
+Switch to code generation variant that allows to execute all threads in each
+warp, while maintaining memory state and side effects as if only one thread
+in each warp was active outside of OpenMP SIMD regions. All atomic operations
+and calls to runtime (malloc, free, vprintf) are conditionally executed (iff
+current lane index equals the master lane index), and the register being
+assigned is copied via a shuffle instruction from the master lane. Outside of
+SIMD regions lane 0 is the master; inside, each thread sees itself as the
+master. Shared memory array @code{int __nvptx_uni[]} stores all-zeros or
+all-ones bitmasks for each warp, indicating current mode (0 outside of SIMD
+regions). Each thread can bitwise-and the bitmask at position @code{tid.y}
+with current lane index to compute the master lane index.
+
+@item -mgomp
+@opindex mgomp
+Generate code for use in OpenMP offloading: enables @option{-msoft-stack} and
+@option{-muniform-simt} options, and selects corresponding multilib variant.
+
+@end table
+
+@node OpenRISC Options
+@subsection OpenRISC Options
+@cindex OpenRISC Options
+
+These options are defined for OpenRISC:
+
+@table @gcctabopt
+
+@item -mboard=@var{name}
+@opindex mboard
+Configure a board specific runtime. This will be passed to the linker for
+newlib board library linking. The default is @code{or1ksim}.
+
+@item -mnewlib
+@opindex mnewlib
+This option is ignored; it is for compatibility purposes only. This used to
+select linker and preprocessor options for use with newlib.
+
+@item -msoft-div
+@itemx -mhard-div
+@opindex msoft-div
+@opindex mhard-div
+Select software or hardware divide (@code{l.div}, @code{l.divu}) instructions.
+This default is hardware divide.
+
+@item -msoft-mul
+@itemx -mhard-mul
+@opindex msoft-mul
+@opindex mhard-mul
+Select software or hardware multiply (@code{l.mul}, @code{l.muli}) instructions.
+This default is hardware multiply.
+
+@item -msoft-float
+@itemx -mhard-float
+@opindex msoft-float
+@opindex mhard-float
+Select software or hardware for floating point operations.
+The default is software.
+
+@item -mdouble-float
+@opindex mdouble-float
+When @option{-mhard-float} is selected, enables generation of double-precision
+floating point instructions. By default functions from @file{libgcc} are used
+to perform double-precision floating point operations.
+
+@item -munordered-float
+@opindex munordered-float
+When @option{-mhard-float} is selected, enables generation of unordered
+floating point compare and set flag (@code{lf.sfun*}) instructions. By default
+functions from @file{libgcc} are used to perform unordered floating point
+compare and set flag operations.
+
+@item -mcmov
+@opindex mcmov
+Enable generation of conditional move (@code{l.cmov}) instructions. By
+default the equivalent will be generated using set and branch.
+
+@item -mror
+@opindex mror
+Enable generation of rotate right (@code{l.ror}) instructions. By default
+functions from @file{libgcc} are used to perform rotate right operations.
+
+@item -mrori
+@opindex mrori
+Enable generation of rotate right with immediate (@code{l.rori}) instructions.
+By default functions from @file{libgcc} are used to perform rotate right with
+immediate operations.
+
+@item -msext
+@opindex msext
+Enable generation of sign extension (@code{l.ext*}) instructions. By default
+memory loads are used to perform sign extension.
+
+@item -msfimm
+@opindex msfimm
+Enable generation of compare and set flag with immediate (@code{l.sf*i})
+instructions. By default extra instructions will be generated to store the
+immediate to a register first.
+
+@item -mshftimm
+@opindex mshftimm
+Enable generation of shift with immediate (@code{l.srai}, @code{l.srli},
+@code{l.slli}) instructions. By default extra instructions will be generated
+to store the immediate to a register first.
+
+@item -mcmodel=small
+@opindex mcmodel=small
+Generate OpenRISC code for the small model: The GOT is limited to 64k. This is
+the default model.
+
+@item -mcmodel=large
+@opindex mcmodel=large
+Generate OpenRISC code for the large model: The GOT may grow up to 4G in size.
+
+
+@end table
+
+@node PDP-11 Options
+@subsection PDP-11 Options
+@cindex PDP-11 Options
+
+These options are defined for the PDP-11:
+
+@table @gcctabopt
+@item -mfpu
+@opindex mfpu
+Use hardware FPP floating point. This is the default. (FIS floating
+point on the PDP-11/40 is not supported.) Implies -m45.
+
+@item -msoft-float
+@opindex msoft-float
+Do not use hardware floating point.
+
+@item -mac0
+@opindex mac0
+Return floating-point results in ac0 (fr0 in Unix assembler syntax).
+
+@item -mno-ac0
+@opindex mno-ac0
+Return floating-point results in memory. This is the default.
+
+@item -m40
+@opindex m40
+Generate code for a PDP-11/40. Implies -msoft-float -mno-split.
+
+@item -m45
+@opindex m45
+Generate code for a PDP-11/45. This is the default.
+
+@item -m10
+@opindex m10
+Generate code for a PDP-11/10. Implies -msoft-float -mno-split.
+
+@item -mint16
+@itemx -mno-int32
+@opindex mint16
+@opindex mno-int32
+Use 16-bit @code{int}. This is the default.
+
+@item -mint32
+@itemx -mno-int16
+@opindex mint32
+@opindex mno-int16
+Use 32-bit @code{int}.
+
+@item -msplit
+@opindex msplit
+Target has split instruction and data space. Implies -m45.
+
+@item -munix-asm
+@opindex munix-asm
+Use Unix assembler syntax.
+
+@item -mdec-asm
+@opindex mdec-asm
+Use DEC assembler syntax.
+
+@item -mgnu-asm
+@opindex mgnu-asm
+Use GNU assembler syntax. This is the default.
+
+@item -mlra
+@opindex mlra
+Use the new LRA register allocator. By default, the old ``reload''
+allocator is used.
+@end table
+
+@node picoChip Options
+@subsection picoChip Options
+@cindex picoChip options
+
+These @samp{-m} options are defined for picoChip implementations:
+
+@table @gcctabopt
+
+@item -mae=@var{ae_type}
+@opindex mcpu
+Set the instruction set, register set, and instruction scheduling
+parameters for array element type @var{ae_type}. Supported values
+for @var{ae_type} are @samp{ANY}, @samp{MUL}, and @samp{MAC}.
+
+@option{-mae=ANY} selects a completely generic AE type. Code
+generated with this option runs on any of the other AE types. The
+code is not as efficient as it would be if compiled for a specific
+AE type, and some types of operation (e.g., multiplication) do not
+work properly on all types of AE.
+
+@option{-mae=MUL} selects a MUL AE type. This is the most useful AE type
+for compiled code, and is the default.
+
+@option{-mae=MAC} selects a DSP-style MAC AE. Code compiled with this
+option may suffer from poor performance of byte (char) manipulation,
+since the DSP AE does not provide hardware support for byte load/stores.
+
+@item -msymbol-as-address
+Enable the compiler to directly use a symbol name as an address in a
+load/store instruction, without first loading it into a
+register. Typically, the use of this option generates larger
+programs, which run faster than when the option isn't used. However, the
+results vary from program to program, so it is left as a user option,
+rather than being permanently enabled.
+
+@item -mno-inefficient-warnings
+Disables warnings about the generation of inefficient code. These
+warnings can be generated, for example, when compiling code that
+performs byte-level memory operations on the MAC AE type. The MAC AE has
+no hardware support for byte-level memory operations, so all byte
+load/stores must be synthesized from word load/store operations. This is
+inefficient and a warning is generated to indicate
+that you should rewrite the code to avoid byte operations, or to target
+an AE type that has the necessary hardware support. This option disables
+these warnings.
+
+@end table
+
+@node PowerPC Options
+@subsection PowerPC Options
+@cindex PowerPC options
+
+These are listed under @xref{RS/6000 and PowerPC Options}.
+
+@node PRU Options
+@subsection PRU Options
+@cindex PRU Options
+
+These command-line options are defined for PRU target:
+
+@table @gcctabopt
+@item -minrt
+@opindex minrt
+Link with a minimum runtime environment, with no support for static
+initializers and constructors. Using this option can significantly reduce
+the size of the final ELF binary. Beware that the compiler could still
+generate code with static initializers and constructors. It is up to the
+programmer to ensure that the source program will not use those features.
+
+@item -mmcu=@var{mcu}
+@opindex mmcu
+Specify the PRU MCU variant to use. Check Newlib for the exact list of
+supported MCUs.
+
+@item -mno-relax
+@opindex mno-relax
+Make GCC pass the @option{--no-relax} command-line option to the linker
+instead of the @option{--relax} option.
+
+@item -mloop
+@opindex mloop
+Allow (or do not allow) GCC to use the LOOP instruction.
+
+@item -mabi=@var{variant}
+@opindex mabi
+Specify the ABI variant to output code for. @option{-mabi=ti} selects the
+unmodified TI ABI while @option{-mabi=gnu} selects a GNU variant that copes
+more naturally with certain GCC assumptions. These are the differences:
+
+@table @samp
+@item Function Pointer Size
+TI ABI specifies that function (code) pointers are 16-bit, whereas GNU
+supports only 32-bit data and code pointers.
+
+@item Optional Return Value Pointer
+Function return values larger than 64 bits are passed by using a hidden
+pointer as the first argument of the function. TI ABI, though, mandates that
+the pointer can be NULL in case the caller is not using the returned value.
+GNU always passes and expects a valid return value pointer.
+
+@end table
+
+The current @option{-mabi=ti} implementation simply raises a compile error
+when any of the above code constructs is detected. As a consequence
+the standard C library cannot be built and it is omitted when linking with
+@option{-mabi=ti}.
+
+Relaxation is a GNU feature and for safety reasons is disabled when using
+@option{-mabi=ti}. The TI toolchain does not emit relocations for QBBx
+instructions, so the GNU linker cannot adjust them when shortening adjacent
+LDI32 pseudo instructions.
+
+@end table
+
+@node RISC-V Options
+@subsection RISC-V Options
+@cindex RISC-V Options
+
+These command-line options are defined for RISC-V targets:
+
+@table @gcctabopt
+@item -mbranch-cost=@var{n}
+@opindex mbranch-cost
+Set the cost of branches to roughly @var{n} instructions.
+
+@item -mplt
+@itemx -mno-plt
+@opindex plt
+When generating PIC code, do or don't allow the use of PLTs. Ignored for
+non-PIC. The default is @option{-mplt}.
+
+@item -mabi=@var{ABI-string}
+@opindex mabi
+Specify integer and floating-point calling convention. @var{ABI-string}
+contains two parts: the size of integer types and the registers used for
+floating-point types. For example @samp{-march=rv64ifd -mabi=lp64d} means that
+@samp{long} and pointers are 64-bit (implicitly defining @samp{int} to be
+32-bit), and that floating-point values up to 64 bits wide are passed in F
+registers. Contrast this with @samp{-march=rv64ifd -mabi=lp64f}, which still
+allows the compiler to generate code that uses the F and D extensions but only
+allows floating-point values up to 32 bits long to be passed in registers; or
+@samp{-march=rv64ifd -mabi=lp64}, in which no floating-point arguments will be
+passed in registers.
+
+The default for this argument is system dependent, users who want a specific
+calling convention should specify one explicitly. The valid calling
+conventions are: @samp{ilp32}, @samp{ilp32f}, @samp{ilp32d}, @samp{lp64},
+@samp{lp64f}, and @samp{lp64d}. Some calling conventions are impossible to
+implement on some ISAs: for example, @samp{-march=rv32if -mabi=ilp32d} is
+invalid because the ABI requires 64-bit values be passed in F registers, but F
+registers are only 32 bits wide. There is also the @samp{ilp32e} ABI that can
+only be used with the @samp{rv32e} architecture. This ABI is not well
+specified at present, and is subject to change.
+
+@item -mfdiv
+@itemx -mno-fdiv
+@opindex mfdiv
+Do or don't use hardware floating-point divide and square root instructions.
+This requires the F or D extensions for floating-point registers. The default
+is to use them if the specified architecture has these instructions.
+
+@item -mdiv
+@itemx -mno-div
+@opindex mdiv
+Do or don't use hardware instructions for integer division. This requires the
+M extension. The default is to use them if the specified architecture has
+these instructions.
+
+@item -misa-spec=@var{ISA-spec-string}
+@opindex misa-spec
+Specify the version of the RISC-V Unprivileged (formerly User-Level)
+ISA specification to produce code conforming to. The possibilities
+for @var{ISA-spec-string} are:
+@table @code
+@item 2.2
+Produce code conforming to version 2.2.
+@item 20190608
+Produce code conforming to version 20190608.
+@item 20191213
+Produce code conforming to version 20191213.
+@end table
+The default is @option{-misa-spec=20191213} unless GCC has been configured
+with @option{--with-isa-spec=} specifying a different default version.
+
+@item -march=@var{ISA-string}
+@opindex march
+Generate code for given RISC-V ISA (e.g.@: @samp{rv64im}). ISA strings must be
+lower-case. Examples include @samp{rv64i}, @samp{rv32g}, @samp{rv32e}, and
+@samp{rv32imaf}.
+
+When @option{-march=} is not specified, use the setting from @option{-mcpu}.
+
+If both @option{-march} and @option{-mcpu=} are not specified, the default for
+this argument is system dependent, users who want a specific architecture
+extensions should specify one explicitly.
+
+@item -mcpu=@var{processor-string}
+@opindex mcpu
+Use architecture of and optimize the output for the given processor, specified
+by particular CPU name.
+Permissible values for this option are: @samp{sifive-e20}, @samp{sifive-e21},
+@samp{sifive-e24}, @samp{sifive-e31}, @samp{sifive-e34}, @samp{sifive-e76},
+@samp{sifive-s21}, @samp{sifive-s51}, @samp{sifive-s54}, @samp{sifive-s76},
+@samp{sifive-u54}, and @samp{sifive-u74}.
+
+@item -mtune=@var{processor-string}
+@opindex mtune
+Optimize the output for the given processor, specified by microarchitecture or
+particular CPU name. Permissible values for this option are: @samp{rocket},
+@samp{sifive-3-series}, @samp{sifive-5-series}, @samp{sifive-7-series},
+@samp{thead-c906}, @samp{size}, and all valid options for @option{-mcpu=}.
+
+When @option{-mtune=} is not specified, use the setting from @option{-mcpu},
+the default is @samp{rocket} if both are not specified.
+
+The @samp{size} choice is not intended for use by end-users. This is used
+when @option{-Os} is specified. It overrides the instruction cost info
+provided by @option{-mtune=}, but does not override the pipeline info. This
+helps reduce code size while still giving good performance.
+
+@item -mpreferred-stack-boundary=@var{num}
+@opindex mpreferred-stack-boundary
+Attempt to keep the stack boundary aligned to a 2 raised to @var{num}
+byte boundary. If @option{-mpreferred-stack-boundary} is not specified,
+the default is 4 (16 bytes or 128-bits).
+
+@strong{Warning:} If you use this switch, then you must build all modules with
+the same value, including any libraries. This includes the system libraries
+and startup modules.
+
+@item -msmall-data-limit=@var{n}
+@opindex msmall-data-limit
+Put global and static data smaller than @var{n} bytes into a special section
+(on some targets).
+
+@item -msave-restore
+@itemx -mno-save-restore
+@opindex msave-restore
+Do or don't use smaller but slower prologue and epilogue code that uses
+library function calls. The default is to use fast inline prologues and
+epilogues.
+
+@item -mshorten-memrefs
+@itemx -mno-shorten-memrefs
+@opindex mshorten-memrefs
+Do or do not attempt to make more use of compressed load/store instructions by
+replacing a load/store of 'base register + large offset' with a new load/store
+of 'new base + small offset'. If the new base gets stored in a compressed
+register, then the new load/store can be compressed. Currently targets 32-bit
+integer load/stores only.
+
+@item -mstrict-align
+@itemx -mno-strict-align
+@opindex mstrict-align
+Do not or do generate unaligned memory accesses. The default is set depending
+on whether the processor we are optimizing for supports fast unaligned access
+or not.
+
+@item -mcmodel=medlow
+@opindex mcmodel=medlow
+Generate code for the medium-low code model. The program and its statically
+defined symbols must lie within a single 2 GiB address range and must lie
+between absolute addresses @minus{}2 GiB and +2 GiB. Programs can be
+statically or dynamically linked. This is the default code model.
+
+@item -mcmodel=medany
+@opindex mcmodel=medany
+Generate code for the medium-any code model. The program and its statically
+defined symbols must be within any single 2 GiB address range. Programs can be
+statically or dynamically linked.
+
+The code generated by the medium-any code model is position-independent, but is
+not guaranteed to function correctly when linked into position-independent
+executables or libraries.
+
+@item -mexplicit-relocs
+@itemx -mno-exlicit-relocs
+Use or do not use assembler relocation operators when dealing with symbolic
+addresses. The alternative is to use assembler macros instead, which may
+limit optimization.
+
+@item -mrelax
+@itemx -mno-relax
+@opindex mrelax
+Take advantage of linker relaxations to reduce the number of instructions
+required to materialize symbol addresses. The default is to take advantage of
+linker relaxations.
+
+@item -mriscv-attribute
+@itemx -mno-riscv-attribute
+@opindex mriscv-attribute
+Emit (do not emit) RISC-V attribute to record extra information into ELF
+objects. This feature requires at least binutils 2.32.
+
+@item -mcsr-check
+@itemx -mno-csr-check
+@opindex mcsr-check
+Enables or disables the CSR checking.
+
+@item -malign-data=@var{type}
+@opindex malign-data
+Control how GCC aligns variables and constants of array, structure, or union
+types. Supported values for @var{type} are @samp{xlen} which uses x register
+width as the alignment value, and @samp{natural} which uses natural alignment.
+@samp{xlen} is the default.
+
+@item -mbig-endian
+@opindex mbig-endian
+Generate big-endian code. This is the default when GCC is configured for a
+@samp{riscv64be-*-*} or @samp{riscv32be-*-*} target.
+
+@item -mlittle-endian
+@opindex mlittle-endian
+Generate little-endian code. This is the default when GCC is configured for a
+@samp{riscv64-*-*} or @samp{riscv32-*-*} but not a @samp{riscv64be-*-*} or
+@samp{riscv32be-*-*} target.
+
+@item -mstack-protector-guard=@var{guard}
+@itemx -mstack-protector-guard-reg=@var{reg}
+@itemx -mstack-protector-guard-offset=@var{offset}
+@opindex mstack-protector-guard
+@opindex mstack-protector-guard-reg
+@opindex mstack-protector-guard-offset
+Generate stack protection code using canary at @var{guard}. Supported
+locations are @samp{global} for a global canary or @samp{tls} for per-thread
+canary in the TLS block.
+
+With the latter choice the options
+@option{-mstack-protector-guard-reg=@var{reg}} and
+@option{-mstack-protector-guard-offset=@var{offset}} furthermore specify
+which register to use as base register for reading the canary,
+and from what offset from that base register. There is no default
+register or offset as this is entirely for use within the Linux
+kernel.
+@end table
+
+@node RL78 Options
+@subsection RL78 Options
+@cindex RL78 Options
+
+@table @gcctabopt
+
+@item -msim
+@opindex msim
+Links in additional target libraries to support operation within a
+simulator.
+
+@item -mmul=none
+@itemx -mmul=g10
+@itemx -mmul=g13
+@itemx -mmul=g14
+@itemx -mmul=rl78
+@opindex mmul
+Specifies the type of hardware multiplication and division support to
+be used. The simplest is @code{none}, which uses software for both
+multiplication and division. This is the default. The @code{g13}
+value is for the hardware multiply/divide peripheral found on the
+RL78/G13 (S2 core) targets. The @code{g14} value selects the use of
+the multiplication and division instructions supported by the RL78/G14
+(S3 core) parts. The value @code{rl78} is an alias for @code{g14} and
+the value @code{mg10} is an alias for @code{none}.
+
+In addition a C preprocessor macro is defined, based upon the setting
+of this option. Possible values are: @code{__RL78_MUL_NONE__},
+@code{__RL78_MUL_G13__} or @code{__RL78_MUL_G14__}.
+
+@item -mcpu=g10
+@itemx -mcpu=g13
+@itemx -mcpu=g14
+@itemx -mcpu=rl78
+@opindex mcpu
+Specifies the RL78 core to target. The default is the G14 core, also
+known as an S3 core or just RL78. The G13 or S2 core does not have
+multiply or divide instructions, instead it uses a hardware peripheral
+for these operations. The G10 or S1 core does not have register
+banks, so it uses a different calling convention.
+
+If this option is set it also selects the type of hardware multiply
+support to use, unless this is overridden by an explicit
+@option{-mmul=none} option on the command line. Thus specifying
+@option{-mcpu=g13} enables the use of the G13 hardware multiply
+peripheral and specifying @option{-mcpu=g10} disables the use of
+hardware multiplications altogether.
+
+Note, although the RL78/G14 core is the default target, specifying
+@option{-mcpu=g14} or @option{-mcpu=rl78} on the command line does
+change the behavior of the toolchain since it also enables G14
+hardware multiply support. If these options are not specified on the
+command line then software multiplication routines will be used even
+though the code targets the RL78 core. This is for backwards
+compatibility with older toolchains which did not have hardware
+multiply and divide support.
+
+In addition a C preprocessor macro is defined, based upon the setting
+of this option. Possible values are: @code{__RL78_G10__},
+@code{__RL78_G13__} or @code{__RL78_G14__}.
+
+@item -mg10
+@itemx -mg13
+@itemx -mg14
+@itemx -mrl78
+@opindex mg10
+@opindex mg13
+@opindex mg14
+@opindex mrl78
+These are aliases for the corresponding @option{-mcpu=} option. They
+are provided for backwards compatibility.
+
+@item -mallregs
+@opindex mallregs
+Allow the compiler to use all of the available registers. By default
+registers @code{r24..r31} are reserved for use in interrupt handlers.
+With this option enabled these registers can be used in ordinary
+functions as well.
+
+@item -m64bit-doubles
+@itemx -m32bit-doubles
+@opindex m64bit-doubles
+@opindex m32bit-doubles
+Make the @code{double} data type be 64 bits (@option{-m64bit-doubles})
+or 32 bits (@option{-m32bit-doubles}) in size. The default is
+@option{-m32bit-doubles}.
+
+@item -msave-mduc-in-interrupts
+@itemx -mno-save-mduc-in-interrupts
+@opindex msave-mduc-in-interrupts
+@opindex mno-save-mduc-in-interrupts
+Specifies that interrupt handler functions should preserve the
+MDUC registers. This is only necessary if normal code might use
+the MDUC registers, for example because it performs multiplication
+and division operations. The default is to ignore the MDUC registers
+as this makes the interrupt handlers faster. The target option -mg13
+needs to be passed for this to work as this feature is only available
+on the G13 target (S2 core). The MDUC registers will only be saved
+if the interrupt handler performs a multiplication or division
+operation or it calls another function.
+
+@end table
+
+@node RS/6000 and PowerPC Options
+@subsection IBM RS/6000 and PowerPC Options
+@cindex RS/6000 and PowerPC Options
+@cindex IBM RS/6000 and PowerPC Options
+
+These @samp{-m} options are defined for the IBM RS/6000 and PowerPC:
+@table @gcctabopt
+@item -mpowerpc-gpopt
+@itemx -mno-powerpc-gpopt
+@itemx -mpowerpc-gfxopt
+@itemx -mno-powerpc-gfxopt
+@need 800
+@itemx -mpowerpc64
+@itemx -mno-powerpc64
+@itemx -mmfcrf
+@itemx -mno-mfcrf
+@itemx -mpopcntb
+@itemx -mno-popcntb
+@itemx -mpopcntd
+@itemx -mno-popcntd
+@itemx -mfprnd
+@itemx -mno-fprnd
+@need 800
+@itemx -mcmpb
+@itemx -mno-cmpb
+@itemx -mhard-dfp
+@itemx -mno-hard-dfp
+@opindex mpowerpc-gpopt
+@opindex mno-powerpc-gpopt
+@opindex mpowerpc-gfxopt
+@opindex mno-powerpc-gfxopt
+@opindex mpowerpc64
+@opindex mno-powerpc64
+@opindex mmfcrf
+@opindex mno-mfcrf
+@opindex mpopcntb
+@opindex mno-popcntb
+@opindex mpopcntd
+@opindex mno-popcntd
+@opindex mfprnd
+@opindex mno-fprnd
+@opindex mcmpb
+@opindex mno-cmpb
+@opindex mhard-dfp
+@opindex mno-hard-dfp
+You use these options to specify which instructions are available on the
+processor you are using. The default value of these options is
+determined when configuring GCC@. Specifying the
+@option{-mcpu=@var{cpu_type}} overrides the specification of these
+options. We recommend you use the @option{-mcpu=@var{cpu_type}} option
+rather than the options listed above.
+
+Specifying @option{-mpowerpc-gpopt} allows
+GCC to use the optional PowerPC architecture instructions in the
+General Purpose group, including floating-point square root. Specifying
+@option{-mpowerpc-gfxopt} allows GCC to
+use the optional PowerPC architecture instructions in the Graphics
+group, including floating-point select.
+
+The @option{-mmfcrf} option allows GCC to generate the move from
+condition register field instruction implemented on the POWER4
+processor and other processors that support the PowerPC V2.01
+architecture.
+The @option{-mpopcntb} option allows GCC to generate the popcount and
+double-precision FP reciprocal estimate instruction implemented on the
+POWER5 processor and other processors that support the PowerPC V2.02
+architecture.
+The @option{-mpopcntd} option allows GCC to generate the popcount
+instruction implemented on the POWER7 processor and other processors
+that support the PowerPC V2.06 architecture.
+The @option{-mfprnd} option allows GCC to generate the FP round to
+integer instructions implemented on the POWER5+ processor and other
+processors that support the PowerPC V2.03 architecture.
+The @option{-mcmpb} option allows GCC to generate the compare bytes
+instruction implemented on the POWER6 processor and other processors
+that support the PowerPC V2.05 architecture.
+The @option{-mhard-dfp} option allows GCC to generate the decimal
+floating-point instructions implemented on some POWER processors.
+
+The @option{-mpowerpc64} option allows GCC to generate the additional
+64-bit instructions that are found in the full PowerPC64 architecture
+and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to
+@option{-mno-powerpc64}.
+
+@item -mcpu=@var{cpu_type}
+@opindex mcpu
+Set architecture type, register usage, and
+instruction scheduling parameters for machine type @var{cpu_type}.
+Supported values for @var{cpu_type} are @samp{401}, @samp{403},
+@samp{405}, @samp{405fp}, @samp{440}, @samp{440fp}, @samp{464}, @samp{464fp},
+@samp{476}, @samp{476fp}, @samp{505}, @samp{601}, @samp{602}, @samp{603},
+@samp{603e}, @samp{604}, @samp{604e}, @samp{620}, @samp{630}, @samp{740},
+@samp{7400}, @samp{7450}, @samp{750}, @samp{801}, @samp{821}, @samp{823},
+@samp{860}, @samp{970}, @samp{8540}, @samp{a2}, @samp{e300c2},
+@samp{e300c3}, @samp{e500mc}, @samp{e500mc64}, @samp{e5500},
+@samp{e6500}, @samp{ec603e}, @samp{G3}, @samp{G4}, @samp{G5},
+@samp{titan}, @samp{power3}, @samp{power4}, @samp{power5}, @samp{power5+},
+@samp{power6}, @samp{power6x}, @samp{power7}, @samp{power8},
+@samp{power9}, @samp{power10}, @samp{powerpc}, @samp{powerpc64},
+@samp{powerpc64le}, @samp{rs64}, and @samp{native}.
+
+@option{-mcpu=powerpc}, @option{-mcpu=powerpc64}, and
+@option{-mcpu=powerpc64le} specify pure 32-bit PowerPC (either
+endian), 64-bit big endian PowerPC and 64-bit little endian PowerPC
+architecture machine types, with an appropriate, generic processor
+model assumed for scheduling purposes.
+
+Specifying @samp{native} as cpu type detects and selects the
+architecture option that corresponds to the host processor of the
+system performing the compilation.
+@option{-mcpu=native} has no effect if GCC does not recognize the
+processor.
+
+The other options specify a specific processor. Code generated under
+those options runs best on that processor, and may not run at all on
+others.
+
+The @option{-mcpu} options automatically enable or disable the
+following options:
+
+@gccoptlist{-maltivec -mfprnd -mhard-float -mmfcrf -mmultiple @gol
+-mpopcntb -mpopcntd -mpowerpc64 @gol
+-mpowerpc-gpopt -mpowerpc-gfxopt @gol
+-mmulhw -mdlmzb -mmfpgpr -mvsx @gol
+-mcrypto -mhtm -mpower8-fusion -mpower8-vector @gol
+-mquad-memory -mquad-memory-atomic -mfloat128 @gol
+-mfloat128-hardware -mprefixed -mpcrel -mmma @gol
+-mrop-protect}
+
+The particular options set for any particular CPU varies between
+compiler versions, depending on what setting seems to produce optimal
+code for that CPU; it doesn't necessarily reflect the actual hardware's
+capabilities. If you wish to set an individual option to a particular
+value, you may specify it after the @option{-mcpu} option, like
+@option{-mcpu=970 -mno-altivec}.
+
+On AIX, the @option{-maltivec} and @option{-mpowerpc64} options are
+not enabled or disabled by the @option{-mcpu} option at present because
+AIX does not have full support for these options. You may still
+enable or disable them individually if you're sure it'll work in your
+environment.
+
+@item -mtune=@var{cpu_type}
+@opindex mtune
+Set the instruction scheduling parameters for machine type
+@var{cpu_type}, but do not set the architecture type or register usage,
+as @option{-mcpu=@var{cpu_type}} does. The same
+values for @var{cpu_type} are used for @option{-mtune} as for
+@option{-mcpu}. If both are specified, the code generated uses the
+architecture and registers set by @option{-mcpu}, but the
+scheduling parameters set by @option{-mtune}.
+
+@item -mcmodel=small
+@opindex mcmodel=small
+Generate PowerPC64 code for the small model: The TOC is limited to
+64k.
+
+@item -mcmodel=medium
+@opindex mcmodel=medium
+Generate PowerPC64 code for the medium model: The TOC and other static
+data may be up to a total of 4G in size. This is the default for 64-bit
+Linux.
+
+@item -mcmodel=large
+@opindex mcmodel=large
+Generate PowerPC64 code for the large model: The TOC may be up to 4G
+in size. Other data and code is only limited by the 64-bit address
+space.
+
+@item -maltivec
+@itemx -mno-altivec
+@opindex maltivec
+@opindex mno-altivec
+Generate code that uses (does not use) AltiVec instructions, and also
+enable the use of built-in functions that allow more direct access to
+the AltiVec instruction set. You may also need to set
+@option{-mabi=altivec} to adjust the current ABI with AltiVec ABI
+enhancements.
+
+When @option{-maltivec} is used, the element order for AltiVec intrinsics
+such as @code{vec_splat}, @code{vec_extract}, and @code{vec_insert}
+match array element order corresponding to the endianness of the
+target. That is, element zero identifies the leftmost element in a
+vector register when targeting a big-endian platform, and identifies
+the rightmost element in a vector register when targeting a
+little-endian platform.
+
+@item -mvrsave
+@itemx -mno-vrsave
+@opindex mvrsave
+@opindex mno-vrsave
+Generate VRSAVE instructions when generating AltiVec code.
+
+@item -msecure-plt
+@opindex msecure-plt
+Generate code that allows @command{ld} and @command{ld.so}
+to build executables and shared
+libraries with non-executable @code{.plt} and @code{.got} sections.
+This is a PowerPC
+32-bit SYSV ABI option.
+
+@item -mbss-plt
+@opindex mbss-plt
+Generate code that uses a BSS @code{.plt} section that @command{ld.so}
+fills in, and
+requires @code{.plt} and @code{.got}
+sections that are both writable and executable.
+This is a PowerPC 32-bit SYSV ABI option.
+
+@item -misel
+@itemx -mno-isel
+@opindex misel
+@opindex mno-isel
+This switch enables or disables the generation of ISEL instructions.
+
+@item -mvsx
+@itemx -mno-vsx
+@opindex mvsx
+@opindex mno-vsx
+Generate code that uses (does not use) vector/scalar (VSX)
+instructions, and also enable the use of built-in functions that allow
+more direct access to the VSX instruction set.
+
+@item -mcrypto
+@itemx -mno-crypto
+@opindex mcrypto
+@opindex mno-crypto
+Enable the use (disable) of the built-in functions that allow direct
+access to the cryptographic instructions that were added in version
+2.07 of the PowerPC ISA.
+
+@item -mhtm
+@itemx -mno-htm
+@opindex mhtm
+@opindex mno-htm
+Enable (disable) the use of the built-in functions that allow direct
+access to the Hardware Transactional Memory (HTM) instructions that
+were added in version 2.07 of the PowerPC ISA.
+
+@item -mpower8-fusion
+@itemx -mno-power8-fusion
+@opindex mpower8-fusion
+@opindex mno-power8-fusion
+Generate code that keeps (does not keeps) some integer operations
+adjacent so that the instructions can be fused together on power8 and
+later processors.
+
+@item -mpower8-vector
+@itemx -mno-power8-vector
+@opindex mpower8-vector
+@opindex mno-power8-vector
+Generate code that uses (does not use) the vector and scalar
+instructions that were added in version 2.07 of the PowerPC ISA. Also
+enable the use of built-in functions that allow more direct access to
+the vector instructions.
+
+@item -mquad-memory
+@itemx -mno-quad-memory
+@opindex mquad-memory
+@opindex mno-quad-memory
+Generate code that uses (does not use) the non-atomic quad word memory
+instructions. The @option{-mquad-memory} option requires use of
+64-bit mode.
+
+@item -mquad-memory-atomic
+@itemx -mno-quad-memory-atomic
+@opindex mquad-memory-atomic
+@opindex mno-quad-memory-atomic
+Generate code that uses (does not use) the atomic quad word memory
+instructions. The @option{-mquad-memory-atomic} option requires use of
+64-bit mode.
+
+@item -mfloat128
+@itemx -mno-float128
+@opindex mfloat128
+@opindex mno-float128
+Enable/disable the @var{__float128} keyword for IEEE 128-bit floating point
+and use either software emulation for IEEE 128-bit floating point or
+hardware instructions.
+
+The VSX instruction set (@option{-mvsx}) must be enabled to use the IEEE
+128-bit floating point support. The IEEE 128-bit floating point is only
+supported on Linux.
+
+The default for @option{-mfloat128} is enabled on PowerPC Linux
+systems using the VSX instruction set, and disabled on other systems.
+
+If you use the ISA 3.0 instruction set (@option{-mpower9-vector} or
+@option{-mcpu=power9}) on a 64-bit system, the IEEE 128-bit floating
+point support will also enable the generation of ISA 3.0 IEEE 128-bit
+floating point instructions. Otherwise, if you do not specify to
+generate ISA 3.0 instructions or you are targeting a 32-bit big endian
+system, IEEE 128-bit floating point will be done with software
+emulation.
+
+@item -mfloat128-hardware
+@itemx -mno-float128-hardware
+@opindex mfloat128-hardware
+@opindex mno-float128-hardware
+Enable/disable using ISA 3.0 hardware instructions to support the
+@var{__float128} data type.
+
+The default for @option{-mfloat128-hardware} is enabled on PowerPC
+Linux systems using the ISA 3.0 instruction set, and disabled on other
+systems.
+
+@item -m32
+@itemx -m64
+@opindex m32
+@opindex m64
+Generate code for 32-bit or 64-bit environments of Darwin and SVR4
+targets (including GNU/Linux). The 32-bit environment sets int, long
+and pointer to 32 bits and generates code that runs on any PowerPC
+variant. The 64-bit environment sets int to 32 bits and long and
+pointer to 64 bits, and generates code for PowerPC64, as for
+@option{-mpowerpc64}.
+
+@item -mfull-toc
+@itemx -mno-fp-in-toc
+@itemx -mno-sum-in-toc
+@itemx -mminimal-toc
+@opindex mfull-toc
+@opindex mno-fp-in-toc
+@opindex mno-sum-in-toc
+@opindex mminimal-toc
+Modify generation of the TOC (Table Of Contents), which is created for
+every executable file. The @option{-mfull-toc} option is selected by
+default. In that case, GCC allocates at least one TOC entry for
+each unique non-automatic variable reference in your program. GCC
+also places floating-point constants in the TOC@. However, only
+16,384 entries are available in the TOC@.
+
+If you receive a linker error message that saying you have overflowed
+the available TOC space, you can reduce the amount of TOC space used
+with the @option{-mno-fp-in-toc} and @option{-mno-sum-in-toc} options.
+@option{-mno-fp-in-toc} prevents GCC from putting floating-point
+constants in the TOC and @option{-mno-sum-in-toc} forces GCC to
+generate code to calculate the sum of an address and a constant at
+run time instead of putting that sum into the TOC@. You may specify one
+or both of these options. Each causes GCC to produce very slightly
+slower and larger code at the expense of conserving TOC space.
+
+If you still run out of space in the TOC even when you specify both of
+these options, specify @option{-mminimal-toc} instead. This option causes
+GCC to make only one TOC entry for every file. When you specify this
+option, GCC produces code that is slower and larger but which
+uses extremely little TOC space. You may wish to use this option
+only on files that contain less frequently-executed code.
+
+@item -maix64
+@itemx -maix32
+@opindex maix64
+@opindex maix32
+Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit
+@code{long} type, and the infrastructure needed to support them.
+Specifying @option{-maix64} implies @option{-mpowerpc64},
+while @option{-maix32} disables the 64-bit ABI and
+implies @option{-mno-powerpc64}. GCC defaults to @option{-maix32}.
+
+@item -mxl-compat
+@itemx -mno-xl-compat
+@opindex mxl-compat
+@opindex mno-xl-compat
+Produce code that conforms more closely to IBM XL compiler semantics
+when using AIX-compatible ABI@. Pass floating-point arguments to
+prototyped functions beyond the register save area (RSA) on the stack
+in addition to argument FPRs. Do not assume that most significant
+double in 128-bit long double value is properly rounded when comparing
+values and converting to double. Use XL symbol names for long double
+support routines.
+
+The AIX calling convention was extended but not initially documented to
+handle an obscure K&R C case of calling a function that takes the
+address of its arguments with fewer arguments than declared. IBM XL
+compilers access floating-point arguments that do not fit in the
+RSA from the stack when a subroutine is compiled without
+optimization. Because always storing floating-point arguments on the
+stack is inefficient and rarely needed, this option is not enabled by
+default and only is necessary when calling subroutines compiled by IBM
+XL compilers without optimization.
+
+@item -mpe
+@opindex mpe
+Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE)@. Link an
+application written to use message passing with special startup code to
+enable the application to run. The system must have PE installed in the
+standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file
+must be overridden with the @option{-specs=} option to specify the
+appropriate directory location. The Parallel Environment does not
+support threads, so the @option{-mpe} option and the @option{-pthread}
+option are incompatible.
+
+@item -malign-natural
+@itemx -malign-power
+@opindex malign-natural
+@opindex malign-power
+On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option
+@option{-malign-natural} overrides the ABI-defined alignment of larger
+types, such as floating-point doubles, on their natural size-based boundary.
+The option @option{-malign-power} instructs GCC to follow the ABI-specified
+alignment rules. GCC defaults to the standard alignment defined in the ABI@.
+
+On 64-bit Darwin, natural alignment is the default, and @option{-malign-power}
+is not supported.
+
+@item -msoft-float
+@itemx -mhard-float
+@opindex msoft-float
+@opindex mhard-float
+Generate code that does not use (uses) the floating-point register set.
+Software floating-point emulation is provided if you use the
+@option{-msoft-float} option, and pass the option to GCC when linking.
+
+@item -mmultiple
+@itemx -mno-multiple
+@opindex mmultiple
+@opindex mno-multiple
+Generate code that uses (does not use) the load multiple word
+instructions and the store multiple word instructions. These
+instructions are generated by default on POWER systems, and not
+generated on PowerPC systems. Do not use @option{-mmultiple} on little-endian
+PowerPC systems, since those instructions do not work when the
+processor is in little-endian mode. The exceptions are PPC740 and
+PPC750 which permit these instructions in little-endian mode.
+
+@item -mupdate
+@itemx -mno-update
+@opindex mupdate
+@opindex mno-update
+Generate code that uses (does not use) the load or store instructions
+that update the base register to the address of the calculated memory
+location. These instructions are generated by default. If you use
+@option{-mno-update}, there is a small window between the time that the
+stack pointer is updated and the address of the previous frame is
+stored, which means code that walks the stack frame across interrupts or
+signals may get corrupted data.
+
+@item -mavoid-indexed-addresses
+@itemx -mno-avoid-indexed-addresses
+@opindex mavoid-indexed-addresses
+@opindex mno-avoid-indexed-addresses
+Generate code that tries to avoid (not avoid) the use of indexed load
+or store instructions. These instructions can incur a performance
+penalty on Power6 processors in certain situations, such as when
+stepping through large arrays that cross a 16M boundary. This option
+is enabled by default when targeting Power6 and disabled otherwise.
+
+@item -mfused-madd
+@itemx -mno-fused-madd
+@opindex mfused-madd
+@opindex mno-fused-madd
+Generate code that uses (does not use) the floating-point multiply and
+accumulate instructions. These instructions are generated by default
+if hardware floating point is used. The machine-dependent
+@option{-mfused-madd} option is now mapped to the machine-independent
+@option{-ffp-contract=fast} option, and @option{-mno-fused-madd} is
+mapped to @option{-ffp-contract=off}.
+
+@item -mmulhw
+@itemx -mno-mulhw
+@opindex mmulhw
+@opindex mno-mulhw
+Generate code that uses (does not use) the half-word multiply and
+multiply-accumulate instructions on the IBM 405, 440, 464 and 476 processors.
+These instructions are generated by default when targeting those
+processors.
+
+@item -mdlmzb
+@itemx -mno-dlmzb
+@opindex mdlmzb
+@opindex mno-dlmzb
+Generate code that uses (does not use) the string-search @samp{dlmzb}
+instruction on the IBM 405, 440, 464 and 476 processors. This instruction is
+generated by default when targeting those processors.
+
+@item -mno-bit-align
+@itemx -mbit-align
+@opindex mno-bit-align
+@opindex mbit-align
+On System V.4 and embedded PowerPC systems do not (do) force structures
+and unions that contain bit-fields to be aligned to the base type of the
+bit-field.
+
+For example, by default a structure containing nothing but 8
+@code{unsigned} bit-fields of length 1 is aligned to a 4-byte
+boundary and has a size of 4 bytes. By using @option{-mno-bit-align},
+the structure is aligned to a 1-byte boundary and is 1 byte in
+size.
+
+@item -mno-strict-align
+@itemx -mstrict-align
+@opindex mno-strict-align
+@opindex mstrict-align
+On System V.4 and embedded PowerPC systems do not (do) assume that
+unaligned memory references are handled by the system.
+
+@item -mrelocatable
+@itemx -mno-relocatable
+@opindex mrelocatable
+@opindex mno-relocatable
+Generate code that allows (does not allow) a static executable to be
+relocated to a different address at run time. A simple embedded
+PowerPC system loader should relocate the entire contents of
+@code{.got2} and 4-byte locations listed in the @code{.fixup} section,
+a table of 32-bit addresses generated by this option. For this to
+work, all objects linked together must be compiled with
+@option{-mrelocatable} or @option{-mrelocatable-lib}.
+@option{-mrelocatable} code aligns the stack to an 8-byte boundary.
+
+@item -mrelocatable-lib
+@itemx -mno-relocatable-lib
+@opindex mrelocatable-lib
+@opindex mno-relocatable-lib
+Like @option{-mrelocatable}, @option{-mrelocatable-lib} generates a
+@code{.fixup} section to allow static executables to be relocated at
+run time, but @option{-mrelocatable-lib} does not use the smaller stack
+alignment of @option{-mrelocatable}. Objects compiled with
+@option{-mrelocatable-lib} may be linked with objects compiled with
+any combination of the @option{-mrelocatable} options.
+
+@item -mno-toc
+@itemx -mtoc
+@opindex mno-toc
+@opindex mtoc
+On System V.4 and embedded PowerPC systems do not (do) assume that
+register 2 contains a pointer to a global area pointing to the addresses
+used in the program.
+
+@item -mlittle
+@itemx -mlittle-endian
+@opindex mlittle
+@opindex mlittle-endian
+On System V.4 and embedded PowerPC systems compile code for the
+processor in little-endian mode. The @option{-mlittle-endian} option is
+the same as @option{-mlittle}.
+
+@item -mbig
+@itemx -mbig-endian
+@opindex mbig
+@opindex mbig-endian
+On System V.4 and embedded PowerPC systems compile code for the
+processor in big-endian mode. The @option{-mbig-endian} option is
+the same as @option{-mbig}.
+
+@item -mdynamic-no-pic
+@opindex mdynamic-no-pic
+On Darwin and Mac OS X systems, compile code so that it is not
+relocatable, but that its external references are relocatable. The
+resulting code is suitable for applications, but not shared
+libraries.
+
+@item -msingle-pic-base
+@opindex msingle-pic-base
+Treat the register used for PIC addressing as read-only, rather than
+loading it in the prologue for each function. The runtime system is
+responsible for initializing this register with an appropriate value
+before execution begins.
+
+@item -mprioritize-restricted-insns=@var{priority}
+@opindex mprioritize-restricted-insns
+This option controls the priority that is assigned to
+dispatch-slot restricted instructions during the second scheduling
+pass. The argument @var{priority} takes the value @samp{0}, @samp{1},
+or @samp{2} to assign no, highest, or second-highest (respectively)
+priority to dispatch-slot restricted
+instructions.
+
+@item -msched-costly-dep=@var{dependence_type}
+@opindex msched-costly-dep
+This option controls which dependences are considered costly
+by the target during instruction scheduling. The argument
+@var{dependence_type} takes one of the following values:
+
+@table @asis
+@item @samp{no}
+No dependence is costly.
+
+@item @samp{all}
+All dependences are costly.
+
+@item @samp{true_store_to_load}
+A true dependence from store to load is costly.
+
+@item @samp{store_to_load}
+Any dependence from store to load is costly.
+
+@item @var{number}
+Any dependence for which the latency is greater than or equal to
+@var{number} is costly.
+@end table
+
+@item -minsert-sched-nops=@var{scheme}
+@opindex minsert-sched-nops
+This option controls which NOP insertion scheme is used during
+the second scheduling pass. The argument @var{scheme} takes one of the
+following values:
+
+@table @asis
+@item @samp{no}
+Don't insert NOPs.
+
+@item @samp{pad}
+Pad with NOPs any dispatch group that has vacant issue slots,
+according to the scheduler's grouping.
+
+@item @samp{regroup_exact}
+Insert NOPs to force costly dependent insns into
+separate groups. Insert exactly as many NOPs as needed to force an insn
+to a new group, according to the estimated processor grouping.
+
+@item @var{number}
+Insert NOPs to force costly dependent insns into
+separate groups. Insert @var{number} NOPs to force an insn to a new group.
+@end table
+
+@item -mcall-sysv
+@opindex mcall-sysv
+On System V.4 and embedded PowerPC systems compile code using calling
+conventions that adhere to the March 1995 draft of the System V
+Application Binary Interface, PowerPC processor supplement. This is the
+default unless you configured GCC using @samp{powerpc-*-eabiaix}.
+
+@item -mcall-sysv-eabi
+@itemx -mcall-eabi
+@opindex mcall-sysv-eabi
+@opindex mcall-eabi
+Specify both @option{-mcall-sysv} and @option{-meabi} options.
+
+@item -mcall-sysv-noeabi
+@opindex mcall-sysv-noeabi
+Specify both @option{-mcall-sysv} and @option{-mno-eabi} options.
+
+@item -mcall-aixdesc
+@opindex m
+On System V.4 and embedded PowerPC systems compile code for the AIX
+operating system.
+
+@item -mcall-linux
+@opindex mcall-linux
+On System V.4 and embedded PowerPC systems compile code for the
+Linux-based GNU system.
+
+@item -mcall-freebsd
+@opindex mcall-freebsd
+On System V.4 and embedded PowerPC systems compile code for the
+FreeBSD operating system.
+
+@item -mcall-netbsd
+@opindex mcall-netbsd
+On System V.4 and embedded PowerPC systems compile code for the
+NetBSD operating system.
+
+@item -mcall-openbsd
+@opindex mcall-netbsd
+On System V.4 and embedded PowerPC systems compile code for the
+OpenBSD operating system.
+
+@item -mtraceback=@var{traceback_type}
+@opindex mtraceback
+Select the type of traceback table. Valid values for @var{traceback_type}
+are @samp{full}, @samp{part}, and @samp{no}.
+
+@item -maix-struct-return
+@opindex maix-struct-return
+Return all structures in memory (as specified by the AIX ABI)@.
+
+@item -msvr4-struct-return
+@opindex msvr4-struct-return
+Return structures smaller than 8 bytes in registers (as specified by the
+SVR4 ABI)@.
+
+@item -mabi=@var{abi-type}
+@opindex mabi
+Extend the current ABI with a particular extension, or remove such extension.
+Valid values are: @samp{altivec}, @samp{no-altivec},
+@samp{ibmlongdouble}, @samp{ieeelongdouble},
+@samp{elfv1}, @samp{elfv2},
+and for AIX: @samp{vec-extabi}, @samp{vec-default}@.
+
+@item -mabi=ibmlongdouble
+@opindex mabi=ibmlongdouble
+Change the current ABI to use IBM extended-precision long double.
+This is not likely to work if your system defaults to using IEEE
+extended-precision long double. If you change the long double type
+from IEEE extended-precision, the compiler will issue a warning unless
+you use the @option{-Wno-psabi} option. Requires @option{-mlong-double-128}
+to be enabled.
+
+@item -mabi=ieeelongdouble
+@opindex mabi=ieeelongdouble
+Change the current ABI to use IEEE extended-precision long double.
+This is not likely to work if your system defaults to using IBM
+extended-precision long double. If you change the long double type
+from IBM extended-precision, the compiler will issue a warning unless
+you use the @option{-Wno-psabi} option. Requires @option{-mlong-double-128}
+to be enabled.
+
+@item -mabi=elfv1
+@opindex mabi=elfv1
+Change the current ABI to use the ELFv1 ABI.
+This is the default ABI for big-endian PowerPC 64-bit Linux.
+Overriding the default ABI requires special system support and is
+likely to fail in spectacular ways.
+
+@item -mabi=elfv2
+@opindex mabi=elfv2
+Change the current ABI to use the ELFv2 ABI.
+This is the default ABI for little-endian PowerPC 64-bit Linux.
+Overriding the default ABI requires special system support and is
+likely to fail in spectacular ways.
+
+@item -mgnu-attribute
+@itemx -mno-gnu-attribute
+@opindex mgnu-attribute
+@opindex mno-gnu-attribute
+Emit .gnu_attribute assembly directives to set tag/value pairs in a
+.gnu.attributes section that specify ABI variations in function
+parameters or return values.
+
+@item -mprototype
+@itemx -mno-prototype
+@opindex mprototype
+@opindex mno-prototype
+On System V.4 and embedded PowerPC systems assume that all calls to
+variable argument functions are properly prototyped. Otherwise, the
+compiler must insert an instruction before every non-prototyped call to
+set or clear bit 6 of the condition code register (@code{CR}) to
+indicate whether floating-point values are passed in the floating-point
+registers in case the function takes variable arguments. With
+@option{-mprototype}, only calls to prototyped variable argument functions
+set or clear the bit.
+
+@item -msim
+@opindex msim
+On embedded PowerPC systems, assume that the startup module is called
+@file{sim-crt0.o} and that the standard C libraries are @file{libsim.a} and
+@file{libc.a}. This is the default for @samp{powerpc-*-eabisim}
+configurations.
+
+@item -mmvme
+@opindex mmvme
+On embedded PowerPC systems, assume that the startup module is called
+@file{crt0.o} and the standard C libraries are @file{libmvme.a} and
+@file{libc.a}.
+
+@item -mads
+@opindex mads
+On embedded PowerPC systems, assume that the startup module is called
+@file{crt0.o} and the standard C libraries are @file{libads.a} and
+@file{libc.a}.
+
+@item -myellowknife
+@opindex myellowknife
+On embedded PowerPC systems, assume that the startup module is called
+@file{crt0.o} and the standard C libraries are @file{libyk.a} and
+@file{libc.a}.
+
+@item -mvxworks
+@opindex mvxworks
+On System V.4 and embedded PowerPC systems, specify that you are
+compiling for a VxWorks system.
+
+@item -memb
+@opindex memb
+On embedded PowerPC systems, set the @code{PPC_EMB} bit in the ELF flags
+header to indicate that @samp{eabi} extended relocations are used.
+
+@item -meabi
+@itemx -mno-eabi
+@opindex meabi
+@opindex mno-eabi
+On System V.4 and embedded PowerPC systems do (do not) adhere to the
+Embedded Applications Binary Interface (EABI), which is a set of
+modifications to the System V.4 specifications. Selecting @option{-meabi}
+means that the stack is aligned to an 8-byte boundary, a function
+@code{__eabi} is called from @code{main} to set up the EABI
+environment, and the @option{-msdata} option can use both @code{r2} and
+@code{r13} to point to two separate small data areas. Selecting
+@option{-mno-eabi} means that the stack is aligned to a 16-byte boundary,
+no EABI initialization function is called from @code{main}, and the
+@option{-msdata} option only uses @code{r13} to point to a single
+small data area. The @option{-meabi} option is on by default if you
+configured GCC using one of the @samp{powerpc*-*-eabi*} options.
+
+@item -msdata=eabi
+@opindex msdata=eabi
+On System V.4 and embedded PowerPC systems, put small initialized
+@code{const} global and static data in the @code{.sdata2} section, which
+is pointed to by register @code{r2}. Put small initialized
+non-@code{const} global and static data in the @code{.sdata} section,
+which is pointed to by register @code{r13}. Put small uninitialized
+global and static data in the @code{.sbss} section, which is adjacent to
+the @code{.sdata} section. The @option{-msdata=eabi} option is
+incompatible with the @option{-mrelocatable} option. The
+@option{-msdata=eabi} option also sets the @option{-memb} option.
+
+@item -msdata=sysv
+@opindex msdata=sysv
+On System V.4 and embedded PowerPC systems, put small global and static
+data in the @code{.sdata} section, which is pointed to by register
+@code{r13}. Put small uninitialized global and static data in the
+@code{.sbss} section, which is adjacent to the @code{.sdata} section.
+The @option{-msdata=sysv} option is incompatible with the
+@option{-mrelocatable} option.
+
+@item -msdata=default
+@itemx -msdata
+@opindex msdata=default
+@opindex msdata
+On System V.4 and embedded PowerPC systems, if @option{-meabi} is used,
+compile code the same as @option{-msdata=eabi}, otherwise compile code the
+same as @option{-msdata=sysv}.
+
+@item -msdata=data
+@opindex msdata=data
+On System V.4 and embedded PowerPC systems, put small global
+data in the @code{.sdata} section. Put small uninitialized global
+data in the @code{.sbss} section. Do not use register @code{r13}
+to address small data however. This is the default behavior unless
+other @option{-msdata} options are used.
+
+@item -msdata=none
+@itemx -mno-sdata
+@opindex msdata=none
+@opindex mno-sdata
+On embedded PowerPC systems, put all initialized global and static data
+in the @code{.data} section, and all uninitialized data in the
+@code{.bss} section.
+
+@item -mreadonly-in-sdata
+@opindex mreadonly-in-sdata
+@opindex mno-readonly-in-sdata
+Put read-only objects in the @code{.sdata} section as well. This is the
+default.
+
+@item -mblock-move-inline-limit=@var{num}
+@opindex mblock-move-inline-limit
+Inline all block moves (such as calls to @code{memcpy} or structure
+copies) less than or equal to @var{num} bytes. The minimum value for
+@var{num} is 32 bytes on 32-bit targets and 64 bytes on 64-bit
+targets. The default value is target-specific.
+
+@item -mblock-compare-inline-limit=@var{num}
+@opindex mblock-compare-inline-limit
+Generate non-looping inline code for all block compares (such as calls
+to @code{memcmp} or structure compares) less than or equal to @var{num}
+bytes. If @var{num} is 0, all inline expansion (non-loop and loop) of
+block compare is disabled. The default value is target-specific.
+
+@item -mblock-compare-inline-loop-limit=@var{num}
+@opindex mblock-compare-inline-loop-limit
+Generate an inline expansion using loop code for all block compares that
+are less than or equal to @var{num} bytes, but greater than the limit
+for non-loop inline block compare expansion. If the block length is not
+constant, at most @var{num} bytes will be compared before @code{memcmp}
+is called to compare the remainder of the block. The default value is
+target-specific.
+
+@item -mstring-compare-inline-limit=@var{num}
+@opindex mstring-compare-inline-limit
+Compare at most @var{num} string bytes with inline code.
+If the difference or end of string is not found at the
+end of the inline compare a call to @code{strcmp} or @code{strncmp} will
+take care of the rest of the comparison. The default is 64 bytes.
+
+@item -G @var{num}
+@opindex G
+@cindex smaller data references (PowerPC)
+@cindex .sdata/.sdata2 references (PowerPC)
+On embedded PowerPC systems, put global and static items less than or
+equal to @var{num} bytes into the small data or BSS sections instead of
+the normal data or BSS section. By default, @var{num} is 8. The
+@option{-G @var{num}} switch is also passed to the linker.
+All modules should be compiled with the same @option{-G @var{num}} value.
+
+@item -mregnames
+@itemx -mno-regnames
+@opindex mregnames
+@opindex mno-regnames
+On System V.4 and embedded PowerPC systems do (do not) emit register
+names in the assembly language output using symbolic forms.
+
+@item -mlongcall
+@itemx -mno-longcall
+@opindex mlongcall
+@opindex mno-longcall
+By default assume that all calls are far away so that a longer and more
+expensive calling sequence is required. This is required for calls
+farther than 32 megabytes (33,554,432 bytes) from the current location.
+A short call is generated if the compiler knows
+the call cannot be that far away. This setting can be overridden by
+the @code{shortcall} function attribute, or by @code{#pragma
+longcall(0)}.
+
+Some linkers are capable of detecting out-of-range calls and generating
+glue code on the fly. On these systems, long calls are unnecessary and
+generate slower code. As of this writing, the AIX linker can do this,
+as can the GNU linker for PowerPC/64. It is planned to add this feature
+to the GNU linker for 32-bit PowerPC systems as well.
+
+On PowerPC64 ELFv2 and 32-bit PowerPC systems with newer GNU linkers,
+GCC can generate long calls using an inline PLT call sequence (see
+@option{-mpltseq}). PowerPC with @option{-mbss-plt} and PowerPC64
+ELFv1 (big-endian) do not support inline PLT calls.
+
+On Darwin/PPC systems, @code{#pragma longcall} generates @code{jbsr
+callee, L42}, plus a @dfn{branch island} (glue code). The two target
+addresses represent the callee and the branch island. The
+Darwin/PPC linker prefers the first address and generates a @code{bl
+callee} if the PPC @code{bl} instruction reaches the callee directly;
+otherwise, the linker generates @code{bl L42} to call the branch
+island. The branch island is appended to the body of the
+calling function; it computes the full 32-bit address of the callee
+and jumps to it.
+
+On Mach-O (Darwin) systems, this option directs the compiler emit to
+the glue for every direct call, and the Darwin linker decides whether
+to use or discard it.
+
+In the future, GCC may ignore all longcall specifications
+when the linker is known to generate glue.
+
+@item -mpltseq
+@itemx -mno-pltseq
+@opindex mpltseq
+@opindex mno-pltseq
+Implement (do not implement) -fno-plt and long calls using an inline
+PLT call sequence that supports lazy linking and long calls to
+functions in dlopen'd shared libraries. Inline PLT calls are only
+supported on PowerPC64 ELFv2 and 32-bit PowerPC systems with newer GNU
+linkers, and are enabled by default if the support is detected when
+configuring GCC, and, in the case of 32-bit PowerPC, if GCC is
+configured with @option{--enable-secureplt}. @option{-mpltseq} code
+and @option{-mbss-plt} 32-bit PowerPC relocatable objects may not be
+linked together.
+
+@item -mtls-markers
+@itemx -mno-tls-markers
+@opindex mtls-markers
+@opindex mno-tls-markers
+Mark (do not mark) calls to @code{__tls_get_addr} with a relocation
+specifying the function argument. The relocation allows the linker to
+reliably associate function call with argument setup instructions for
+TLS optimization, which in turn allows GCC to better schedule the
+sequence.
+
+@item -mrecip
+@itemx -mno-recip
+@opindex mrecip
+This option enables use of the reciprocal estimate and
+reciprocal square root estimate instructions with additional
+Newton-Raphson steps to increase precision instead of doing a divide or
+square root and divide for floating-point arguments. You should use
+the @option{-ffast-math} option when using @option{-mrecip} (or at
+least @option{-funsafe-math-optimizations},
+@option{-ffinite-math-only}, @option{-freciprocal-math} and
+@option{-fno-trapping-math}). Note that while the throughput of the
+sequence is generally higher than the throughput of the non-reciprocal
+instruction, the precision of the sequence can be decreased by up to 2
+ulp (i.e.@: the inverse of 1.0 equals 0.99999994) for reciprocal square
+roots.
+
+@item -mrecip=@var{opt}
+@opindex mrecip=opt
+This option controls which reciprocal estimate instructions
+may be used. @var{opt} is a comma-separated list of options, which may
+be preceded by a @code{!} to invert the option:
+
+@table @samp
+
+@item all
+Enable all estimate instructions.
+
+@item default
+Enable the default instructions, equivalent to @option{-mrecip}.
+
+@item none
+Disable all estimate instructions, equivalent to @option{-mno-recip}.
+
+@item div
+Enable the reciprocal approximation instructions for both
+single and double precision.
+
+@item divf
+Enable the single-precision reciprocal approximation instructions.
+
+@item divd
+Enable the double-precision reciprocal approximation instructions.
+
+@item rsqrt
+Enable the reciprocal square root approximation instructions for both
+single and double precision.
+
+@item rsqrtf
+Enable the single-precision reciprocal square root approximation instructions.
+
+@item rsqrtd
+Enable the double-precision reciprocal square root approximation instructions.
+
+@end table
+
+So, for example, @option{-mrecip=all,!rsqrtd} enables
+all of the reciprocal estimate instructions, except for the
+@code{FRSQRTE}, @code{XSRSQRTEDP}, and @code{XVRSQRTEDP} instructions
+which handle the double-precision reciprocal square root calculations.
+
+@item -mrecip-precision
+@itemx -mno-recip-precision
+@opindex mrecip-precision
+Assume (do not assume) that the reciprocal estimate instructions
+provide higher-precision estimates than is mandated by the PowerPC
+ABI. Selecting @option{-mcpu=power6}, @option{-mcpu=power7} or
+@option{-mcpu=power8} automatically selects @option{-mrecip-precision}.
+The double-precision square root estimate instructions are not generated by
+default on low-precision machines, since they do not provide an
+estimate that converges after three steps.
+
+@item -mveclibabi=@var{type}
+@opindex mveclibabi
+Specifies the ABI type to use for vectorizing intrinsics using an
+external library. The only type supported at present is @samp{mass},
+which specifies to use IBM's Mathematical Acceleration Subsystem
+(MASS) libraries for vectorizing intrinsics using external libraries.
+GCC currently emits calls to @code{acosd2}, @code{acosf4},
+@code{acoshd2}, @code{acoshf4}, @code{asind2}, @code{asinf4},
+@code{asinhd2}, @code{asinhf4}, @code{atan2d2}, @code{atan2f4},
+@code{atand2}, @code{atanf4}, @code{atanhd2}, @code{atanhf4},
+@code{cbrtd2}, @code{cbrtf4}, @code{cosd2}, @code{cosf4},
+@code{coshd2}, @code{coshf4}, @code{erfcd2}, @code{erfcf4},
+@code{erfd2}, @code{erff4}, @code{exp2d2}, @code{exp2f4},
+@code{expd2}, @code{expf4}, @code{expm1d2}, @code{expm1f4},
+@code{hypotd2}, @code{hypotf4}, @code{lgammad2}, @code{lgammaf4},
+@code{log10d2}, @code{log10f4}, @code{log1pd2}, @code{log1pf4},
+@code{log2d2}, @code{log2f4}, @code{logd2}, @code{logf4},
+@code{powd2}, @code{powf4}, @code{sind2}, @code{sinf4}, @code{sinhd2},
+@code{sinhf4}, @code{sqrtd2}, @code{sqrtf4}, @code{tand2},
+@code{tanf4}, @code{tanhd2}, and @code{tanhf4} when generating code
+for power7. Both @option{-ftree-vectorize} and
+@option{-funsafe-math-optimizations} must also be enabled. The MASS
+libraries must be specified at link time.
+
+@item -mfriz
+@itemx -mno-friz
+@opindex mfriz
+Generate (do not generate) the @code{friz} instruction when the
+@option{-funsafe-math-optimizations} option is used to optimize
+rounding of floating-point values to 64-bit integer and back to floating
+point. The @code{friz} instruction does not return the same value if
+the floating-point number is too large to fit in an integer.
+
+@item -mpointers-to-nested-functions
+@itemx -mno-pointers-to-nested-functions
+@opindex mpointers-to-nested-functions
+Generate (do not generate) code to load up the static chain register
+(@code{r11}) when calling through a pointer on AIX and 64-bit Linux
+systems where a function pointer points to a 3-word descriptor giving
+the function address, TOC value to be loaded in register @code{r2}, and
+static chain value to be loaded in register @code{r11}. The
+@option{-mpointers-to-nested-functions} is on by default. You cannot
+call through pointers to nested functions or pointers
+to functions compiled in other languages that use the static chain if
+you use @option{-mno-pointers-to-nested-functions}.
+
+@item -msave-toc-indirect
+@itemx -mno-save-toc-indirect
+@opindex msave-toc-indirect
+Generate (do not generate) code to save the TOC value in the reserved
+stack location in the function prologue if the function calls through
+a pointer on AIX and 64-bit Linux systems. If the TOC value is not
+saved in the prologue, it is saved just before the call through the
+pointer. The @option{-mno-save-toc-indirect} option is the default.
+
+@item -mcompat-align-parm
+@itemx -mno-compat-align-parm
+@opindex mcompat-align-parm
+Generate (do not generate) code to pass structure parameters with a
+maximum alignment of 64 bits, for compatibility with older versions
+of GCC.
+
+Older versions of GCC (prior to 4.9.0) incorrectly did not align a
+structure parameter on a 128-bit boundary when that structure contained
+a member requiring 128-bit alignment. This is corrected in more
+recent versions of GCC. This option may be used to generate code
+that is compatible with functions compiled with older versions of
+GCC.
+
+The @option{-mno-compat-align-parm} option is the default.
+
+@item -mstack-protector-guard=@var{guard}
+@itemx -mstack-protector-guard-reg=@var{reg}
+@itemx -mstack-protector-guard-offset=@var{offset}
+@itemx -mstack-protector-guard-symbol=@var{symbol}
+@opindex mstack-protector-guard
+@opindex mstack-protector-guard-reg
+@opindex mstack-protector-guard-offset
+@opindex mstack-protector-guard-symbol
+Generate stack protection code using canary at @var{guard}. Supported
+locations are @samp{global} for global canary or @samp{tls} for per-thread
+canary in the TLS block (the default with GNU libc version 2.4 or later).
+
+With the latter choice the options
+@option{-mstack-protector-guard-reg=@var{reg}} and
+@option{-mstack-protector-guard-offset=@var{offset}} furthermore specify
+which register to use as base register for reading the canary, and from what
+offset from that base register. The default for those is as specified in the
+relevant ABI. @option{-mstack-protector-guard-symbol=@var{symbol}} overrides
+the offset with a symbol reference to a canary in the TLS block.
+
+@item -mpcrel
+@itemx -mno-pcrel
+@opindex mpcrel
+@opindex mno-pcrel
+Generate (do not generate) pc-relative addressing. The @option{-mpcrel}
+option requires that the medium code model (@option{-mcmodel=medium})
+and prefixed addressing (@option{-mprefixed}) options are enabled.
+
+@item -mprefixed
+@itemx -mno-prefixed
+@opindex mprefixed
+@opindex mno-prefixed
+Generate (do not generate) addressing modes using prefixed load and
+store instructions. The @option{-mprefixed} option requires that
+the option @option{-mcpu=power10} (or later) is enabled.
+
+@item -mmma
+@itemx -mno-mma
+@opindex mmma
+@opindex mno-mma
+Generate (do not generate) the MMA instructions. The @option{-mma}
+option requires that the option @option{-mcpu=power10} (or later)
+is enabled.
+
+@item -mrop-protect
+@itemx -mno-rop-protect
+@opindex mrop-protect
+@opindex mno-rop-protect
+Generate (do not generate) ROP protection instructions when the target
+processor supports them. Currently this option disables the shrink-wrap
+optimization (@option{-fshrink-wrap}).
+
+@item -mprivileged
+@itemx -mno-privileged
+@opindex mprivileged
+@opindex mno-privileged
+Generate (do not generate) code that will run in privileged state.
+
+@item -mblock-ops-unaligned-vsx
+@itemx -mno-block-ops-unaligned-vsx
+@opindex block-ops-unaligned-vsx
+@opindex no-block-ops-unaligned-vsx
+Generate (do not generate) unaligned vsx loads and stores for
+inline expansion of @code{memcpy} and @code{memmove}.
+
+@item --param rs6000-vect-unroll-limit=
+The vectorizer will check with target information to determine whether it
+would be beneficial to unroll the main vectorized loop and by how much. This
+parameter sets the upper bound of how much the vectorizer will unroll the main
+loop. The default value is four.
+
+@end table
+
+@node RX Options
+@subsection RX Options
+@cindex RX Options
+
+These command-line options are defined for RX targets:
+
+@table @gcctabopt
+@item -m64bit-doubles
+@itemx -m32bit-doubles
+@opindex m64bit-doubles
+@opindex m32bit-doubles
+Make the @code{double} data type be 64 bits (@option{-m64bit-doubles})
+or 32 bits (@option{-m32bit-doubles}) in size. The default is
+@option{-m32bit-doubles}. @emph{Note} RX floating-point hardware only
+works on 32-bit values, which is why the default is
+@option{-m32bit-doubles}.
+
+@item -fpu
+@itemx -nofpu
+@opindex fpu
+@opindex nofpu
+Enables (@option{-fpu}) or disables (@option{-nofpu}) the use of RX
+floating-point hardware. The default is enabled for the RX600
+series and disabled for the RX200 series.
+
+Floating-point instructions are only generated for 32-bit floating-point
+values, however, so the FPU hardware is not used for doubles if the
+@option{-m64bit-doubles} option is used.
+
+@emph{Note} If the @option{-fpu} option is enabled then
+@option{-funsafe-math-optimizations} is also enabled automatically.
+This is because the RX FPU instructions are themselves unsafe.
+
+@item -mcpu=@var{name}
+@opindex mcpu
+Selects the type of RX CPU to be targeted. Currently three types are
+supported, the generic @samp{RX600} and @samp{RX200} series hardware and
+the specific @samp{RX610} CPU. The default is @samp{RX600}.
+
+The only difference between @samp{RX600} and @samp{RX610} is that the
+@samp{RX610} does not support the @code{MVTIPL} instruction.
+
+The @samp{RX200} series does not have a hardware floating-point unit
+and so @option{-nofpu} is enabled by default when this type is
+selected.
+
+@item -mbig-endian-data
+@itemx -mlittle-endian-data
+@opindex mbig-endian-data
+@opindex mlittle-endian-data
+Store data (but not code) in the big-endian format. The default is
+@option{-mlittle-endian-data}, i.e.@: to store data in the little-endian
+format.
+
+@item -msmall-data-limit=@var{N}
+@opindex msmall-data-limit
+Specifies the maximum size in bytes of global and static variables
+which can be placed into the small data area. Using the small data
+area can lead to smaller and faster code, but the size of area is
+limited and it is up to the programmer to ensure that the area does
+not overflow. Also when the small data area is used one of the RX's
+registers (usually @code{r13}) is reserved for use pointing to this
+area, so it is no longer available for use by the compiler. This
+could result in slower and/or larger code if variables are pushed onto
+the stack instead of being held in this register.
+
+Note, common variables (variables that have not been initialized) and
+constants are not placed into the small data area as they are assigned
+to other sections in the output executable.
+
+The default value is zero, which disables this feature. Note, this
+feature is not enabled by default with higher optimization levels
+(@option{-O2} etc) because of the potentially detrimental effects of
+reserving a register. It is up to the programmer to experiment and
+discover whether this feature is of benefit to their program. See the
+description of the @option{-mpid} option for a description of how the
+actual register to hold the small data area pointer is chosen.
+
+@item -msim
+@itemx -mno-sim
+@opindex msim
+@opindex mno-sim
+Use the simulator runtime. The default is to use the libgloss
+board-specific runtime.
+
+@item -mas100-syntax
+@itemx -mno-as100-syntax
+@opindex mas100-syntax
+@opindex mno-as100-syntax
+When generating assembler output use a syntax that is compatible with
+Renesas's AS100 assembler. This syntax can also be handled by the GAS
+assembler, but it has some restrictions so it is not generated by default.
+
+@item -mmax-constant-size=@var{N}
+@opindex mmax-constant-size
+Specifies the maximum size, in bytes, of a constant that can be used as
+an operand in a RX instruction. Although the RX instruction set does
+allow constants of up to 4 bytes in length to be used in instructions,
+a longer value equates to a longer instruction. Thus in some
+circumstances it can be beneficial to restrict the size of constants
+that are used in instructions. Constants that are too big are instead
+placed into a constant pool and referenced via register indirection.
+
+The value @var{N} can be between 0 and 4. A value of 0 (the default)
+or 4 means that constants of any size are allowed.
+
+@item -mrelax
+@opindex mrelax
+Enable linker relaxation. Linker relaxation is a process whereby the
+linker attempts to reduce the size of a program by finding shorter
+versions of various instructions. Disabled by default.
+
+@item -mint-register=@var{N}
+@opindex mint-register
+Specify the number of registers to reserve for fast interrupt handler
+functions. The value @var{N} can be between 0 and 4. A value of 1
+means that register @code{r13} is reserved for the exclusive use
+of fast interrupt handlers. A value of 2 reserves @code{r13} and
+@code{r12}. A value of 3 reserves @code{r13}, @code{r12} and
+@code{r11}, and a value of 4 reserves @code{r13} through @code{r10}.
+A value of 0, the default, does not reserve any registers.
+
+@item -msave-acc-in-interrupts
+@opindex msave-acc-in-interrupts
+Specifies that interrupt handler functions should preserve the
+accumulator register. This is only necessary if normal code might use
+the accumulator register, for example because it performs 64-bit
+multiplications. The default is to ignore the accumulator as this
+makes the interrupt handlers faster.
+
+@item -mpid
+@itemx -mno-pid
+@opindex mpid
+@opindex mno-pid
+Enables the generation of position independent data. When enabled any
+access to constant data is done via an offset from a base address
+held in a register. This allows the location of constant data to be
+determined at run time without requiring the executable to be
+relocated, which is a benefit to embedded applications with tight
+memory constraints. Data that can be modified is not affected by this
+option.
+
+Note, using this feature reserves a register, usually @code{r13}, for
+the constant data base address. This can result in slower and/or
+larger code, especially in complicated functions.
+
+The actual register chosen to hold the constant data base address
+depends upon whether the @option{-msmall-data-limit} and/or the
+@option{-mint-register} command-line options are enabled. Starting
+with register @code{r13} and proceeding downwards, registers are
+allocated first to satisfy the requirements of @option{-mint-register},
+then @option{-mpid} and finally @option{-msmall-data-limit}. Thus it
+is possible for the small data area register to be @code{r8} if both
+@option{-mint-register=4} and @option{-mpid} are specified on the
+command line.
+
+By default this feature is not enabled. The default can be restored
+via the @option{-mno-pid} command-line option.
+
+@item -mno-warn-multiple-fast-interrupts
+@itemx -mwarn-multiple-fast-interrupts
+@opindex mno-warn-multiple-fast-interrupts
+@opindex mwarn-multiple-fast-interrupts
+Prevents GCC from issuing a warning message if it finds more than one
+fast interrupt handler when it is compiling a file. The default is to
+issue a warning for each extra fast interrupt handler found, as the RX
+only supports one such interrupt.
+
+@item -mallow-string-insns
+@itemx -mno-allow-string-insns
+@opindex mallow-string-insns
+@opindex mno-allow-string-insns
+Enables or disables the use of the string manipulation instructions
+@code{SMOVF}, @code{SCMPU}, @code{SMOVB}, @code{SMOVU}, @code{SUNTIL}
+@code{SWHILE} and also the @code{RMPA} instruction. These
+instructions may prefetch data, which is not safe to do if accessing
+an I/O register. (See section 12.2.7 of the RX62N Group User's Manual
+for more information).
+
+The default is to allow these instructions, but it is not possible for
+GCC to reliably detect all circumstances where a string instruction
+might be used to access an I/O register, so their use cannot be
+disabled automatically. Instead it is reliant upon the programmer to
+use the @option{-mno-allow-string-insns} option if their program
+accesses I/O space.
+
+When the instructions are enabled GCC defines the C preprocessor
+symbol @code{__RX_ALLOW_STRING_INSNS__}, otherwise it defines the
+symbol @code{__RX_DISALLOW_STRING_INSNS__}.
+
+@item -mjsr
+@itemx -mno-jsr
+@opindex mjsr
+@opindex mno-jsr
+Use only (or not only) @code{JSR} instructions to access functions.
+This option can be used when code size exceeds the range of @code{BSR}
+instructions. Note that @option{-mno-jsr} does not mean to not use
+@code{JSR} but instead means that any type of branch may be used.
+@end table
+
+@emph{Note:} The generic GCC command-line option @option{-ffixed-@var{reg}}
+has special significance to the RX port when used with the
+@code{interrupt} function attribute. This attribute indicates a
+function intended to process fast interrupts. GCC ensures
+that it only uses the registers @code{r10}, @code{r11}, @code{r12}
+and/or @code{r13} and only provided that the normal use of the
+corresponding registers have been restricted via the
+@option{-ffixed-@var{reg}} or @option{-mint-register} command-line
+options.
+
+@node S/390 and zSeries Options
+@subsection S/390 and zSeries Options
+@cindex S/390 and zSeries Options
+
+These are the @samp{-m} options defined for the S/390 and zSeries architecture.
+
+@table @gcctabopt
+@item -mhard-float
+@itemx -msoft-float
+@opindex mhard-float
+@opindex msoft-float
+Use (do not use) the hardware floating-point instructions and registers
+for floating-point operations. When @option{-msoft-float} is specified,
+functions in @file{libgcc.a} are used to perform floating-point
+operations. When @option{-mhard-float} is specified, the compiler
+generates IEEE floating-point instructions. This is the default.
+
+@item -mhard-dfp
+@itemx -mno-hard-dfp
+@opindex mhard-dfp
+@opindex mno-hard-dfp
+Use (do not use) the hardware decimal-floating-point instructions for
+decimal-floating-point operations. When @option{-mno-hard-dfp} is
+specified, functions in @file{libgcc.a} are used to perform
+decimal-floating-point operations. When @option{-mhard-dfp} is
+specified, the compiler generates decimal-floating-point hardware
+instructions. This is the default for @option{-march=z9-ec} or higher.
+
+@item -mlong-double-64
+@itemx -mlong-double-128
+@opindex mlong-double-64
+@opindex mlong-double-128
+These switches control the size of @code{long double} type. A size
+of 64 bits makes the @code{long double} type equivalent to the @code{double}
+type. This is the default.
+
+@item -mbackchain
+@itemx -mno-backchain
+@opindex mbackchain
+@opindex mno-backchain
+Store (do not store) the address of the caller's frame as backchain pointer
+into the callee's stack frame.
+A backchain may be needed to allow debugging using tools that do not understand
+DWARF call frame information.
+When @option{-mno-packed-stack} is in effect, the backchain pointer is stored
+at the bottom of the stack frame; when @option{-mpacked-stack} is in effect,
+the backchain is placed into the topmost word of the 96/160 byte register
+save area.
+
+In general, code compiled with @option{-mbackchain} is call-compatible with
+code compiled with @option{-mno-backchain}; however, use of the backchain
+for debugging purposes usually requires that the whole binary is built with
+@option{-mbackchain}. Note that the combination of @option{-mbackchain},
+@option{-mpacked-stack} and @option{-mhard-float} is not supported. In order
+to build a linux kernel use @option{-msoft-float}.
+
+The default is to not maintain the backchain.
+
+@item -mpacked-stack
+@itemx -mno-packed-stack
+@opindex mpacked-stack
+@opindex mno-packed-stack
+Use (do not use) the packed stack layout. When @option{-mno-packed-stack} is
+specified, the compiler uses the all fields of the 96/160 byte register save
+area only for their default purpose; unused fields still take up stack space.
+When @option{-mpacked-stack} is specified, register save slots are densely
+packed at the top of the register save area; unused space is reused for other
+purposes, allowing for more efficient use of the available stack space.
+However, when @option{-mbackchain} is also in effect, the topmost word of
+the save area is always used to store the backchain, and the return address
+register is always saved two words below the backchain.
+
+As long as the stack frame backchain is not used, code generated with
+@option{-mpacked-stack} is call-compatible with code generated with
+@option{-mno-packed-stack}. Note that some non-FSF releases of GCC 2.95 for
+S/390 or zSeries generated code that uses the stack frame backchain at run
+time, not just for debugging purposes. Such code is not call-compatible
+with code compiled with @option{-mpacked-stack}. Also, note that the
+combination of @option{-mbackchain},
+@option{-mpacked-stack} and @option{-mhard-float} is not supported. In order
+to build a linux kernel use @option{-msoft-float}.
+
+The default is to not use the packed stack layout.
+
+@item -msmall-exec
+@itemx -mno-small-exec
+@opindex msmall-exec
+@opindex mno-small-exec
+Generate (or do not generate) code using the @code{bras} instruction
+to do subroutine calls.
+This only works reliably if the total executable size does not
+exceed 64k. The default is to use the @code{basr} instruction instead,
+which does not have this limitation.
+
+@item -m64
+@itemx -m31
+@opindex m64
+@opindex m31
+When @option{-m31} is specified, generate code compliant to the
+GNU/Linux for S/390 ABI@. When @option{-m64} is specified, generate
+code compliant to the GNU/Linux for zSeries ABI@. This allows GCC in
+particular to generate 64-bit instructions. For the @samp{s390}
+targets, the default is @option{-m31}, while the @samp{s390x}
+targets default to @option{-m64}.
+
+@item -mzarch
+@itemx -mesa
+@opindex mzarch
+@opindex mesa
+When @option{-mzarch} is specified, generate code using the
+instructions available on z/Architecture.
+When @option{-mesa} is specified, generate code using the
+instructions available on ESA/390. Note that @option{-mesa} is
+not possible with @option{-m64}.
+When generating code compliant to the GNU/Linux for S/390 ABI,
+the default is @option{-mesa}. When generating code compliant
+to the GNU/Linux for zSeries ABI, the default is @option{-mzarch}.
+
+@item -mhtm
+@itemx -mno-htm
+@opindex mhtm
+@opindex mno-htm
+The @option{-mhtm} option enables a set of builtins making use of
+instructions available with the transactional execution facility
+introduced with the IBM zEnterprise EC12 machine generation
+@ref{S/390 System z Built-in Functions}.
+@option{-mhtm} is enabled by default when using @option{-march=zEC12}.
+
+@item -mvx
+@itemx -mno-vx
+@opindex mvx
+@opindex mno-vx
+When @option{-mvx} is specified, generate code using the instructions
+available with the vector extension facility introduced with the IBM
+z13 machine generation.
+This option changes the ABI for some vector type values with regard to
+alignment and calling conventions. In case vector type values are
+being used in an ABI-relevant context a GAS @samp{.gnu_attribute}
+command will be added to mark the resulting binary with the ABI used.
+@option{-mvx} is enabled by default when using @option{-march=z13}.
+
+@item -mzvector
+@itemx -mno-zvector
+@opindex mzvector
+@opindex mno-zvector
+The @option{-mzvector} option enables vector language extensions and
+builtins using instructions available with the vector extension
+facility introduced with the IBM z13 machine generation.
+This option adds support for @samp{vector} to be used as a keyword to
+define vector type variables and arguments. @samp{vector} is only
+available when GNU extensions are enabled. It will not be expanded
+when requesting strict standard compliance e.g.@: with @option{-std=c99}.
+In addition to the GCC low-level builtins @option{-mzvector} enables
+a set of builtins added for compatibility with AltiVec-style
+implementations like Power and Cell. In order to make use of these
+builtins the header file @file{vecintrin.h} needs to be included.
+@option{-mzvector} is disabled by default.
+
+@item -mmvcle
+@itemx -mno-mvcle
+@opindex mmvcle
+@opindex mno-mvcle
+Generate (or do not generate) code using the @code{mvcle} instruction
+to perform block moves. When @option{-mno-mvcle} is specified,
+use a @code{mvc} loop instead. This is the default unless optimizing for
+size.
+
+@item -mdebug
+@itemx -mno-debug
+@opindex mdebug
+@opindex mno-debug
+Print (or do not print) additional debug information when compiling.
+The default is to not print debug information.
+
+@item -march=@var{cpu-type}
+@opindex march
+Generate code that runs on @var{cpu-type}, which is the name of a
+system representing a certain processor type. Possible values for
+@var{cpu-type} are @samp{z900}/@samp{arch5}, @samp{z990}/@samp{arch6},
+@samp{z9-109}, @samp{z9-ec}/@samp{arch7}, @samp{z10}/@samp{arch8},
+@samp{z196}/@samp{arch9}, @samp{zEC12}, @samp{z13}/@samp{arch11},
+@samp{z14}/@samp{arch12}, @samp{z15}/@samp{arch13},
+@samp{z16}/@samp{arch14}, and @samp{native}.
+
+The default is @option{-march=z900}.
+
+Specifying @samp{native} as cpu type can be used to select the best
+architecture option for the host processor.
+@option{-march=native} has no effect if GCC does not recognize the
+processor.
+
+@item -mtune=@var{cpu-type}
+@opindex mtune
+Tune to @var{cpu-type} everything applicable about the generated code,
+except for the ABI and the set of available instructions.
+The list of @var{cpu-type} values is the same as for @option{-march}.
+The default is the value used for @option{-march}.
+
+@item -mtpf-trace
+@itemx -mno-tpf-trace
+@opindex mtpf-trace
+@opindex mno-tpf-trace
+Generate code that adds (does not add) in TPF OS specific branches to trace
+routines in the operating system. This option is off by default, even
+when compiling for the TPF OS@.
+
+@item -mtpf-trace-skip
+@itemx -mno-tpf-trace-skip
+@opindex mtpf-trace-skip
+@opindex mno-tpf-trace-skip
+Generate code that changes (does not change) the default branch
+targets enabled by @option{-mtpf-trace} to point to specialized trace
+routines providing the ability of selectively skipping function trace
+entries for the TPF OS. This option is off by default, even when
+compiling for the TPF OS and specifying @option{-mtpf-trace}.
+
+@item -mfused-madd
+@itemx -mno-fused-madd
+@opindex mfused-madd
+@opindex mno-fused-madd
+Generate code that uses (does not use) the floating-point multiply and
+accumulate instructions. These instructions are generated by default if
+hardware floating point is used.
+
+@item -mwarn-framesize=@var{framesize}
+@opindex mwarn-framesize
+Emit a warning if the current function exceeds the given frame size. Because
+this is a compile-time check it doesn't need to be a real problem when the program
+runs. It is intended to identify functions that most probably cause
+a stack overflow. It is useful to be used in an environment with limited stack
+size e.g.@: the linux kernel.
+
+@item -mwarn-dynamicstack
+@opindex mwarn-dynamicstack
+Emit a warning if the function calls @code{alloca} or uses dynamically-sized
+arrays. This is generally a bad idea with a limited stack size.
+
+@item -mstack-guard=@var{stack-guard}
+@itemx -mstack-size=@var{stack-size}
+@opindex mstack-guard
+@opindex mstack-size
+If these options are provided the S/390 back end emits additional instructions in
+the function prologue that trigger a trap if the stack size is @var{stack-guard}
+bytes above the @var{stack-size} (remember that the stack on S/390 grows downward).
+If the @var{stack-guard} option is omitted the smallest power of 2 larger than
+the frame size of the compiled function is chosen.
+These options are intended to be used to help debugging stack overflow problems.
+The additionally emitted code causes only little overhead and hence can also be
+used in production-like systems without greater performance degradation. The given
+values have to be exact powers of 2 and @var{stack-size} has to be greater than
+@var{stack-guard} without exceeding 64k.
+In order to be efficient the extra code makes the assumption that the stack starts
+at an address aligned to the value given by @var{stack-size}.
+The @var{stack-guard} option can only be used in conjunction with @var{stack-size}.
+
+@item -mhotpatch=@var{pre-halfwords},@var{post-halfwords}
+@opindex mhotpatch
+If the hotpatch option is enabled, a ``hot-patching'' function
+prologue is generated for all functions in the compilation unit.
+The funtion label is prepended with the given number of two-byte
+NOP instructions (@var{pre-halfwords}, maximum 1000000). After
+the label, 2 * @var{post-halfwords} bytes are appended, using the
+largest NOP like instructions the architecture allows (maximum
+1000000).
+
+If both arguments are zero, hotpatching is disabled.
+
+This option can be overridden for individual functions with the
+@code{hotpatch} attribute.
+@end table
+
+@node Score Options
+@subsection Score Options
+@cindex Score Options
+
+These options are defined for Score implementations:
+
+@table @gcctabopt
+@item -meb
+@opindex meb
+Compile code for big-endian mode. This is the default.
+
+@item -mel
+@opindex mel
+Compile code for little-endian mode.
+
+@item -mnhwloop
+@opindex mnhwloop
+Disable generation of @code{bcnz} instructions.
+
+@item -muls
+@opindex muls
+Enable generation of unaligned load and store instructions.
+
+@item -mmac
+@opindex mmac
+Enable the use of multiply-accumulate instructions. Disabled by default.
+
+@item -mscore5
+@opindex mscore5
+Specify the SCORE5 as the target architecture.
+
+@item -mscore5u
+@opindex mscore5u
+Specify the SCORE5U of the target architecture.
+
+@item -mscore7
+@opindex mscore7
+Specify the SCORE7 as the target architecture. This is the default.
+
+@item -mscore7d
+@opindex mscore7d
+Specify the SCORE7D as the target architecture.
+@end table
+
+@node SH Options
+@subsection SH Options
+
+These @samp{-m} options are defined for the SH implementations:
+
+@table @gcctabopt
+@item -m1
+@opindex m1
+Generate code for the SH1.
+
+@item -m2
+@opindex m2
+Generate code for the SH2.
+
+@item -m2e
+Generate code for the SH2e.
+
+@item -m2a-nofpu
+@opindex m2a-nofpu
+Generate code for the SH2a without FPU, or for a SH2a-FPU in such a way
+that the floating-point unit is not used.
+
+@item -m2a-single-only
+@opindex m2a-single-only
+Generate code for the SH2a-FPU, in such a way that no double-precision
+floating-point operations are used.
+
+@item -m2a-single
+@opindex m2a-single
+Generate code for the SH2a-FPU assuming the floating-point unit is in
+single-precision mode by default.
+
+@item -m2a
+@opindex m2a
+Generate code for the SH2a-FPU assuming the floating-point unit is in
+double-precision mode by default.
+
+@item -m3
+@opindex m3
+Generate code for the SH3.
+
+@item -m3e
+@opindex m3e
+Generate code for the SH3e.
+
+@item -m4-nofpu
+@opindex m4-nofpu
+Generate code for the SH4 without a floating-point unit.
+
+@item -m4-single-only
+@opindex m4-single-only
+Generate code for the SH4 with a floating-point unit that only
+supports single-precision arithmetic.
+
+@item -m4-single
+@opindex m4-single
+Generate code for the SH4 assuming the floating-point unit is in
+single-precision mode by default.
+
+@item -m4
+@opindex m4
+Generate code for the SH4.
+
+@item -m4-100
+@opindex m4-100
+Generate code for SH4-100.
+
+@item -m4-100-nofpu
+@opindex m4-100-nofpu
+Generate code for SH4-100 in such a way that the
+floating-point unit is not used.
+
+@item -m4-100-single
+@opindex m4-100-single
+Generate code for SH4-100 assuming the floating-point unit is in
+single-precision mode by default.
+
+@item -m4-100-single-only
+@opindex m4-100-single-only
+Generate code for SH4-100 in such a way that no double-precision
+floating-point operations are used.
+
+@item -m4-200
+@opindex m4-200
+Generate code for SH4-200.
+
+@item -m4-200-nofpu
+@opindex m4-200-nofpu
+Generate code for SH4-200 without in such a way that the
+floating-point unit is not used.
+
+@item -m4-200-single
+@opindex m4-200-single
+Generate code for SH4-200 assuming the floating-point unit is in
+single-precision mode by default.
+
+@item -m4-200-single-only
+@opindex m4-200-single-only
+Generate code for SH4-200 in such a way that no double-precision
+floating-point operations are used.
+
+@item -m4-300
+@opindex m4-300
+Generate code for SH4-300.
+
+@item -m4-300-nofpu
+@opindex m4-300-nofpu
+Generate code for SH4-300 without in such a way that the
+floating-point unit is not used.
+
+@item -m4-300-single
+@opindex m4-300-single
+Generate code for SH4-300 in such a way that no double-precision
+floating-point operations are used.
+
+@item -m4-300-single-only
+@opindex m4-300-single-only
+Generate code for SH4-300 in such a way that no double-precision
+floating-point operations are used.
+
+@item -m4-340
+@opindex m4-340
+Generate code for SH4-340 (no MMU, no FPU).
+
+@item -m4-500
+@opindex m4-500
+Generate code for SH4-500 (no FPU). Passes @option{-isa=sh4-nofpu} to the
+assembler.
+
+@item -m4a-nofpu
+@opindex m4a-nofpu
+Generate code for the SH4al-dsp, or for a SH4a in such a way that the
+floating-point unit is not used.
+
+@item -m4a-single-only
+@opindex m4a-single-only
+Generate code for the SH4a, in such a way that no double-precision
+floating-point operations are used.
+
+@item -m4a-single
+@opindex m4a-single
+Generate code for the SH4a assuming the floating-point unit is in
+single-precision mode by default.
+
+@item -m4a
+@opindex m4a
+Generate code for the SH4a.
+
+@item -m4al
+@opindex m4al
+Same as @option{-m4a-nofpu}, except that it implicitly passes
+@option{-dsp} to the assembler. GCC doesn't generate any DSP
+instructions at the moment.
+
+@item -mb
+@opindex mb
+Compile code for the processor in big-endian mode.
+
+@item -ml
+@opindex ml
+Compile code for the processor in little-endian mode.
+
+@item -mdalign
+@opindex mdalign
+Align doubles at 64-bit boundaries. Note that this changes the calling
+conventions, and thus some functions from the standard C library do
+not work unless you recompile it first with @option{-mdalign}.
+
+@item -mrelax
+@opindex mrelax
+Shorten some address references at link time, when possible; uses the
+linker option @option{-relax}.
+
+@item -mbigtable
+@opindex mbigtable
+Use 32-bit offsets in @code{switch} tables. The default is to use
+16-bit offsets.
+
+@item -mbitops
+@opindex mbitops
+Enable the use of bit manipulation instructions on SH2A.
+
+@item -mfmovd
+@opindex mfmovd
+Enable the use of the instruction @code{fmovd}. Check @option{-mdalign} for
+alignment constraints.
+
+@item -mrenesas
+@opindex mrenesas
+Comply with the calling conventions defined by Renesas.
+
+@item -mno-renesas
+@opindex mno-renesas
+Comply with the calling conventions defined for GCC before the Renesas
+conventions were available. This option is the default for all
+targets of the SH toolchain.
+
+@item -mnomacsave
+@opindex mnomacsave
+Mark the @code{MAC} register as call-clobbered, even if
+@option{-mrenesas} is given.
+
+@item -mieee
+@itemx -mno-ieee
+@opindex mieee
+@opindex mno-ieee
+Control the IEEE compliance of floating-point comparisons, which affects the
+handling of cases where the result of a comparison is unordered. By default
+@option{-mieee} is implicitly enabled. If @option{-ffinite-math-only} is
+enabled @option{-mno-ieee} is implicitly set, which results in faster
+floating-point greater-equal and less-equal comparisons. The implicit settings
+can be overridden by specifying either @option{-mieee} or @option{-mno-ieee}.
+
+@item -minline-ic_invalidate
+@opindex minline-ic_invalidate
+Inline code to invalidate instruction cache entries after setting up
+nested function trampolines.
+This option has no effect if @option{-musermode} is in effect and the selected
+code generation option (e.g.@: @option{-m4}) does not allow the use of the @code{icbi}
+instruction.
+If the selected code generation option does not allow the use of the @code{icbi}
+instruction, and @option{-musermode} is not in effect, the inlined code
+manipulates the instruction cache address array directly with an associative
+write. This not only requires privileged mode at run time, but it also
+fails if the cache line had been mapped via the TLB and has become unmapped.
+
+@item -misize
+@opindex misize
+Dump instruction size and location in the assembly code.
+
+@item -mpadstruct
+@opindex mpadstruct
+This option is deprecated. It pads structures to multiple of 4 bytes,
+which is incompatible with the SH ABI@.
+
+@item -matomic-model=@var{model}
+@opindex matomic-model=@var{model}
+Sets the model of atomic operations and additional parameters as a comma
+separated list. For details on the atomic built-in functions see
+@ref{__atomic Builtins}. The following models and parameters are supported:
+
+@table @samp
+
+@item none
+Disable compiler generated atomic sequences and emit library calls for atomic
+operations. This is the default if the target is not @code{sh*-*-linux*}.
+
+@item soft-gusa
+Generate GNU/Linux compatible gUSA software atomic sequences for the atomic
+built-in functions. The generated atomic sequences require additional support
+from the interrupt/exception handling code of the system and are only suitable
+for SH3* and SH4* single-core systems. This option is enabled by default when
+the target is @code{sh*-*-linux*} and SH3* or SH4*. When the target is SH4A,
+this option also partially utilizes the hardware atomic instructions
+@code{movli.l} and @code{movco.l} to create more efficient code, unless
+@samp{strict} is specified.
+
+@item soft-tcb
+Generate software atomic sequences that use a variable in the thread control
+block. This is a variation of the gUSA sequences which can also be used on
+SH1* and SH2* targets. The generated atomic sequences require additional
+support from the interrupt/exception handling code of the system and are only
+suitable for single-core systems. When using this model, the @samp{gbr-offset=}
+parameter has to be specified as well.
+
+@item soft-imask
+Generate software atomic sequences that temporarily disable interrupts by
+setting @code{SR.IMASK = 1111}. This model works only when the program runs
+in privileged mode and is only suitable for single-core systems. Additional
+support from the interrupt/exception handling code of the system is not
+required. This model is enabled by default when the target is
+@code{sh*-*-linux*} and SH1* or SH2*.
+
+@item hard-llcs
+Generate hardware atomic sequences using the @code{movli.l} and @code{movco.l}
+instructions only. This is only available on SH4A and is suitable for
+multi-core systems. Since the hardware instructions support only 32 bit atomic
+variables access to 8 or 16 bit variables is emulated with 32 bit accesses.
+Code compiled with this option is also compatible with other software
+atomic model interrupt/exception handling systems if executed on an SH4A
+system. Additional support from the interrupt/exception handling code of the
+system is not required for this model.
+
+@item gbr-offset=
+This parameter specifies the offset in bytes of the variable in the thread
+control block structure that should be used by the generated atomic sequences
+when the @samp{soft-tcb} model has been selected. For other models this
+parameter is ignored. The specified value must be an integer multiple of four
+and in the range 0-1020.
+
+@item strict
+This parameter prevents mixed usage of multiple atomic models, even if they
+are compatible, and makes the compiler generate atomic sequences of the
+specified model only.
+
+@end table
+
+@item -mtas
+@opindex mtas
+Generate the @code{tas.b} opcode for @code{__atomic_test_and_set}.
+Notice that depending on the particular hardware and software configuration
+this can degrade overall performance due to the operand cache line flushes
+that are implied by the @code{tas.b} instruction. On multi-core SH4A
+processors the @code{tas.b} instruction must be used with caution since it
+can result in data corruption for certain cache configurations.
+
+@item -mprefergot
+@opindex mprefergot
+When generating position-independent code, emit function calls using
+the Global Offset Table instead of the Procedure Linkage Table.
+
+@item -musermode
+@itemx -mno-usermode
+@opindex musermode
+@opindex mno-usermode
+Don't allow (allow) the compiler generating privileged mode code. Specifying
+@option{-musermode} also implies @option{-mno-inline-ic_invalidate} if the
+inlined code would not work in user mode. @option{-musermode} is the default
+when the target is @code{sh*-*-linux*}. If the target is SH1* or SH2*
+@option{-musermode} has no effect, since there is no user mode.
+
+@item -multcost=@var{number}
+@opindex multcost=@var{number}
+Set the cost to assume for a multiply insn.
+
+@item -mdiv=@var{strategy}
+@opindex mdiv=@var{strategy}
+Set the division strategy to be used for integer division operations.
+@var{strategy} can be one of:
+
+@table @samp
+
+@item call-div1
+Calls a library function that uses the single-step division instruction
+@code{div1} to perform the operation. Division by zero calculates an
+unspecified result and does not trap. This is the default except for SH4,
+SH2A and SHcompact.
+
+@item call-fp
+Calls a library function that performs the operation in double precision
+floating point. Division by zero causes a floating-point exception. This is
+the default for SHcompact with FPU. Specifying this for targets that do not
+have a double precision FPU defaults to @code{call-div1}.
+
+@item call-table
+Calls a library function that uses a lookup table for small divisors and
+the @code{div1} instruction with case distinction for larger divisors. Division
+by zero calculates an unspecified result and does not trap. This is the default
+for SH4. Specifying this for targets that do not have dynamic shift
+instructions defaults to @code{call-div1}.
+
+@end table
+
+When a division strategy has not been specified the default strategy is
+selected based on the current target. For SH2A the default strategy is to
+use the @code{divs} and @code{divu} instructions instead of library function
+calls.
+
+@item -maccumulate-outgoing-args
+@opindex maccumulate-outgoing-args
+Reserve space once for outgoing arguments in the function prologue rather
+than around each call. Generally beneficial for performance and size. Also
+needed for unwinding to avoid changing the stack frame around conditional code.
+
+@item -mdivsi3_libfunc=@var{name}
+@opindex mdivsi3_libfunc=@var{name}
+Set the name of the library function used for 32-bit signed division to
+@var{name}.
+This only affects the name used in the @samp{call} division strategies, and
+the compiler still expects the same sets of input/output/clobbered registers as
+if this option were not present.
+
+@item -mfixed-range=@var{register-range}
+@opindex mfixed-range
+Generate code treating the given register range as fixed registers.
+A fixed register is one that the register allocator cannot use. This is
+useful when compiling kernel code. A register range is specified as
+two registers separated by a dash. Multiple register ranges can be
+specified separated by a comma.
+
+@item -mbranch-cost=@var{num}
+@opindex mbranch-cost=@var{num}
+Assume @var{num} to be the cost for a branch instruction. Higher numbers
+make the compiler try to generate more branch-free code if possible.
+If not specified the value is selected depending on the processor type that
+is being compiled for.
+
+@item -mzdcbranch
+@itemx -mno-zdcbranch
+@opindex mzdcbranch
+@opindex mno-zdcbranch
+Assume (do not assume) that zero displacement conditional branch instructions
+@code{bt} and @code{bf} are fast. If @option{-mzdcbranch} is specified, the
+compiler prefers zero displacement branch code sequences. This is
+enabled by default when generating code for SH4 and SH4A. It can be explicitly
+disabled by specifying @option{-mno-zdcbranch}.
+
+@item -mcbranch-force-delay-slot
+@opindex mcbranch-force-delay-slot
+Force the usage of delay slots for conditional branches, which stuffs the delay
+slot with a @code{nop} if a suitable instruction cannot be found. By default
+this option is disabled. It can be enabled to work around hardware bugs as
+found in the original SH7055.
+
+@item -mfused-madd
+@itemx -mno-fused-madd
+@opindex mfused-madd
+@opindex mno-fused-madd
+Generate code that uses (does not use) the floating-point multiply and
+accumulate instructions. These instructions are generated by default
+if hardware floating point is used. The machine-dependent
+@option{-mfused-madd} option is now mapped to the machine-independent
+@option{-ffp-contract=fast} option, and @option{-mno-fused-madd} is
+mapped to @option{-ffp-contract=off}.
+
+@item -mfsca
+@itemx -mno-fsca
+@opindex mfsca
+@opindex mno-fsca
+Allow or disallow the compiler to emit the @code{fsca} instruction for sine
+and cosine approximations. The option @option{-mfsca} must be used in
+combination with @option{-funsafe-math-optimizations}. It is enabled by default
+when generating code for SH4A. Using @option{-mno-fsca} disables sine and cosine
+approximations even if @option{-funsafe-math-optimizations} is in effect.
+
+@item -mfsrra
+@itemx -mno-fsrra
+@opindex mfsrra
+@opindex mno-fsrra
+Allow or disallow the compiler to emit the @code{fsrra} instruction for
+reciprocal square root approximations. The option @option{-mfsrra} must be used
+in combination with @option{-funsafe-math-optimizations} and
+@option{-ffinite-math-only}. It is enabled by default when generating code for
+SH4A. Using @option{-mno-fsrra} disables reciprocal square root approximations
+even if @option{-funsafe-math-optimizations} and @option{-ffinite-math-only} are
+in effect.
+
+@item -mpretend-cmove
+@opindex mpretend-cmove
+Prefer zero-displacement conditional branches for conditional move instruction
+patterns. This can result in faster code on the SH4 processor.
+
+@item -mfdpic
+@opindex fdpic
+Generate code using the FDPIC ABI.
+
+@end table
+
+@node Solaris 2 Options
+@subsection Solaris 2 Options
+@cindex Solaris 2 options
+
+These @samp{-m} options are supported on Solaris 2:
+
+@table @gcctabopt
+@item -mclear-hwcap
+@opindex mclear-hwcap
+@option{-mclear-hwcap} tells the compiler to remove the hardware
+capabilities generated by the Solaris assembler. This is only necessary
+when object files use ISA extensions not supported by the current
+machine, but check at runtime whether or not to use them.
+
+@item -mimpure-text
+@opindex mimpure-text
+@option{-mimpure-text}, used in addition to @option{-shared}, tells
+the compiler to not pass @option{-z text} to the linker when linking a
+shared object. Using this option, you can link position-dependent
+code into a shared object.
+
+@option{-mimpure-text} suppresses the ``relocations remain against
+allocatable but non-writable sections'' linker error message.
+However, the necessary relocations trigger copy-on-write, and the
+shared object is not actually shared across processes. Instead of
+using @option{-mimpure-text}, you should compile all source code with
+@option{-fpic} or @option{-fPIC}.
+
+@end table
+
+These switches are supported in addition to the above on Solaris 2:
+
+@table @gcctabopt
+@item -pthreads
+@opindex pthreads
+This is a synonym for @option{-pthread}.
+@end table
+
+@node SPARC Options
+@subsection SPARC Options
+@cindex SPARC options
+
+These @samp{-m} options are supported on the SPARC:
+
+@table @gcctabopt
+@item -mno-app-regs
+@itemx -mapp-regs
+@opindex mno-app-regs
+@opindex mapp-regs
+Specify @option{-mapp-regs} to generate output using the global registers
+2 through 4, which the SPARC SVR4 ABI reserves for applications. Like the
+global register 1, each global register 2 through 4 is then treated as an
+allocable register that is clobbered by function calls. This is the default.
+
+To be fully SVR4 ABI-compliant at the cost of some performance loss,
+specify @option{-mno-app-regs}. You should compile libraries and system
+software with this option.
+
+@item -mflat
+@itemx -mno-flat
+@opindex mflat
+@opindex mno-flat
+With @option{-mflat}, the compiler does not generate save/restore instructions
+and uses a ``flat'' or single register window model. This model is compatible
+with the regular register window model. The local registers and the input
+registers (0--5) are still treated as ``call-saved'' registers and are
+saved on the stack as needed.
+
+With @option{-mno-flat} (the default), the compiler generates save/restore
+instructions (except for leaf functions). This is the normal operating mode.
+
+@item -mfpu
+@itemx -mhard-float
+@opindex mfpu
+@opindex mhard-float
+Generate output containing floating-point instructions. This is the
+default.
+
+@item -mno-fpu
+@itemx -msoft-float
+@opindex mno-fpu
+@opindex msoft-float
+Generate output containing library calls for floating point.
+@strong{Warning:} the requisite libraries are not available for all SPARC
+targets. Normally the facilities of the machine's usual C compiler are
+used, but this cannot be done directly in cross-compilation. You must make
+your own arrangements to provide suitable library functions for
+cross-compilation. The embedded targets @samp{sparc-*-aout} and
+@samp{sparclite-*-*} do provide software floating-point support.
+
+@option{-msoft-float} changes the calling convention in the output file;
+therefore, it is only useful if you compile @emph{all} of a program with
+this option. In particular, you need to compile @file{libgcc.a}, the
+library that comes with GCC, with @option{-msoft-float} in order for
+this to work.
+
+@item -mhard-quad-float
+@opindex mhard-quad-float
+Generate output containing quad-word (long double) floating-point
+instructions.
+
+@item -msoft-quad-float
+@opindex msoft-quad-float
+Generate output containing library calls for quad-word (long double)
+floating-point instructions. The functions called are those specified
+in the SPARC ABI@. This is the default.
+
+As of this writing, there are no SPARC implementations that have hardware
+support for the quad-word floating-point instructions. They all invoke
+a trap handler for one of these instructions, and then the trap handler
+emulates the effect of the instruction. Because of the trap handler overhead,
+this is much slower than calling the ABI library routines. Thus the
+@option{-msoft-quad-float} option is the default.
+
+@item -mno-unaligned-doubles
+@itemx -munaligned-doubles
+@opindex mno-unaligned-doubles
+@opindex munaligned-doubles
+Assume that doubles have 8-byte alignment. This is the default.
+
+With @option{-munaligned-doubles}, GCC assumes that doubles have 8-byte
+alignment only if they are contained in another type, or if they have an
+absolute address. Otherwise, it assumes they have 4-byte alignment.
+Specifying this option avoids some rare compatibility problems with code
+generated by other compilers. It is not the default because it results
+in a performance loss, especially for floating-point code.
+
+@item -muser-mode
+@itemx -mno-user-mode
+@opindex muser-mode
+@opindex mno-user-mode
+Do not generate code that can only run in supervisor mode. This is relevant
+only for the @code{casa} instruction emitted for the LEON3 processor. This
+is the default.
+
+@item -mfaster-structs
+@itemx -mno-faster-structs
+@opindex mfaster-structs
+@opindex mno-faster-structs
+With @option{-mfaster-structs}, the compiler assumes that structures
+should have 8-byte alignment. This enables the use of pairs of
+@code{ldd} and @code{std} instructions for copies in structure
+assignment, in place of twice as many @code{ld} and @code{st} pairs.
+However, the use of this changed alignment directly violates the SPARC
+ABI@. Thus, it's intended only for use on targets where the developer
+acknowledges that their resulting code is not directly in line with
+the rules of the ABI@.
+
+@item -mstd-struct-return
+@itemx -mno-std-struct-return
+@opindex mstd-struct-return
+@opindex mno-std-struct-return
+With @option{-mstd-struct-return}, the compiler generates checking code
+in functions returning structures or unions to detect size mismatches
+between the two sides of function calls, as per the 32-bit ABI@.
+
+The default is @option{-mno-std-struct-return}. This option has no effect
+in 64-bit mode.
+
+@item -mlra
+@itemx -mno-lra
+@opindex mlra
+@opindex mno-lra
+Enable Local Register Allocation. This is the default for SPARC since GCC 7
+so @option{-mno-lra} needs to be passed to get old Reload.
+
+@item -mcpu=@var{cpu_type}
+@opindex mcpu
+Set the instruction set, register set, and instruction scheduling parameters
+for machine type @var{cpu_type}. Supported values for @var{cpu_type} are
+@samp{v7}, @samp{cypress}, @samp{v8}, @samp{supersparc}, @samp{hypersparc},
+@samp{leon}, @samp{leon3}, @samp{leon3v7}, @samp{leon5}, @samp{sparclite},
+@samp{f930}, @samp{f934}, @samp{sparclite86x}, @samp{sparclet}, @samp{tsc701},
+@samp{v9}, @samp{ultrasparc}, @samp{ultrasparc3}, @samp{niagara},
+@samp{niagara2}, @samp{niagara3}, @samp{niagara4}, @samp{niagara7} and
+@samp{m8}.
+
+Native Solaris and GNU/Linux toolchains also support the value @samp{native},
+which selects the best architecture option for the host processor.
+@option{-mcpu=native} has no effect if GCC does not recognize
+the processor.
+
+Default instruction scheduling parameters are used for values that select
+an architecture and not an implementation. These are @samp{v7}, @samp{v8},
+@samp{sparclite}, @samp{sparclet}, @samp{v9}.
+
+Here is a list of each supported architecture and their supported
+implementations.
+
+@table @asis
+@item v7
+cypress, leon3v7
+
+@item v8
+supersparc, hypersparc, leon, leon3, leon5
+
+@item sparclite
+f930, f934, sparclite86x
+
+@item sparclet
+tsc701
+
+@item v9
+ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4,
+niagara7, m8
+@end table
+
+By default (unless configured otherwise), GCC generates code for the V7
+variant of the SPARC architecture. With @option{-mcpu=cypress}, the compiler
+additionally optimizes it for the Cypress CY7C602 chip, as used in the
+SPARCStation/SPARCServer 3xx series. This is also appropriate for the older
+SPARCStation 1, 2, IPX etc.
+
+With @option{-mcpu=v8}, GCC generates code for the V8 variant of the SPARC
+architecture. The only difference from V7 code is that the compiler emits
+the integer multiply and integer divide instructions which exist in SPARC-V8
+but not in SPARC-V7. With @option{-mcpu=supersparc}, the compiler additionally
+optimizes it for the SuperSPARC chip, as used in the SPARCStation 10, 1000 and
+2000 series.
+
+With @option{-mcpu=sparclite}, GCC generates code for the SPARClite variant of
+the SPARC architecture. This adds the integer multiply, integer divide step
+and scan (@code{ffs}) instructions which exist in SPARClite but not in SPARC-V7.
+With @option{-mcpu=f930}, the compiler additionally optimizes it for the
+Fujitsu MB86930 chip, which is the original SPARClite, with no FPU@. With
+@option{-mcpu=f934}, the compiler additionally optimizes it for the Fujitsu
+MB86934 chip, which is the more recent SPARClite with FPU@.
+
+With @option{-mcpu=sparclet}, GCC generates code for the SPARClet variant of
+the SPARC architecture. This adds the integer multiply, multiply/accumulate,
+integer divide step and scan (@code{ffs}) instructions which exist in SPARClet
+but not in SPARC-V7. With @option{-mcpu=tsc701}, the compiler additionally
+optimizes it for the TEMIC SPARClet chip.
+
+With @option{-mcpu=v9}, GCC generates code for the V9 variant of the SPARC
+architecture. This adds 64-bit integer and floating-point move instructions,
+3 additional floating-point condition code registers and conditional move
+instructions. With @option{-mcpu=ultrasparc}, the compiler additionally
+optimizes it for the Sun UltraSPARC I/II/IIi chips. With
+@option{-mcpu=ultrasparc3}, the compiler additionally optimizes it for the
+Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips. With
+@option{-mcpu=niagara}, the compiler additionally optimizes it for
+Sun UltraSPARC T1 chips. With @option{-mcpu=niagara2}, the compiler
+additionally optimizes it for Sun UltraSPARC T2 chips. With
+@option{-mcpu=niagara3}, the compiler additionally optimizes it for Sun
+UltraSPARC T3 chips. With @option{-mcpu=niagara4}, the compiler
+additionally optimizes it for Sun UltraSPARC T4 chips. With
+@option{-mcpu=niagara7}, the compiler additionally optimizes it for
+Oracle SPARC M7 chips. With @option{-mcpu=m8}, the compiler
+additionally optimizes it for Oracle M8 chips.
+
+@item -mtune=@var{cpu_type}
+@opindex mtune
+Set the instruction scheduling parameters for machine type
+@var{cpu_type}, but do not set the instruction set or register set that the
+option @option{-mcpu=@var{cpu_type}} does.
+
+The same values for @option{-mcpu=@var{cpu_type}} can be used for
+@option{-mtune=@var{cpu_type}}, but the only useful values are those
+that select a particular CPU implementation. Those are
+@samp{cypress}, @samp{supersparc}, @samp{hypersparc}, @samp{leon},
+@samp{leon3}, @samp{leon3v7}, @samp{leon5}, @samp{f930}, @samp{f934},
+@samp{sparclite86x}, @samp{tsc701}, @samp{ultrasparc},
+@samp{ultrasparc3}, @samp{niagara}, @samp{niagara2}, @samp{niagara3},
+@samp{niagara4}, @samp{niagara7} and @samp{m8}. With native Solaris
+and GNU/Linux toolchains, @samp{native} can also be used.
+
+@item -mv8plus
+@itemx -mno-v8plus
+@opindex mv8plus
+@opindex mno-v8plus
+With @option{-mv8plus}, GCC generates code for the SPARC-V8+ ABI@. The
+difference from the V8 ABI is that the global and out registers are
+considered 64 bits wide. This is enabled by default on Solaris in 32-bit
+mode for all SPARC-V9 processors.
+
+@item -mvis
+@itemx -mno-vis
+@opindex mvis
+@opindex mno-vis
+With @option{-mvis}, GCC generates code that takes advantage of the UltraSPARC
+Visual Instruction Set extensions. The default is @option{-mno-vis}.
+
+@item -mvis2
+@itemx -mno-vis2
+@opindex mvis2
+@opindex mno-vis2
+With @option{-mvis2}, GCC generates code that takes advantage of
+version 2.0 of the UltraSPARC Visual Instruction Set extensions. The
+default is @option{-mvis2} when targeting a cpu that supports such
+instructions, such as UltraSPARC-III and later. Setting @option{-mvis2}
+also sets @option{-mvis}.
+
+@item -mvis3
+@itemx -mno-vis3
+@opindex mvis3
+@opindex mno-vis3
+With @option{-mvis3}, GCC generates code that takes advantage of
+version 3.0 of the UltraSPARC Visual Instruction Set extensions. The
+default is @option{-mvis3} when targeting a cpu that supports such
+instructions, such as niagara-3 and later. Setting @option{-mvis3}
+also sets @option{-mvis2} and @option{-mvis}.
+
+@item -mvis4
+@itemx -mno-vis4
+@opindex mvis4
+@opindex mno-vis4
+With @option{-mvis4}, GCC generates code that takes advantage of
+version 4.0 of the UltraSPARC Visual Instruction Set extensions. The
+default is @option{-mvis4} when targeting a cpu that supports such
+instructions, such as niagara-7 and later. Setting @option{-mvis4}
+also sets @option{-mvis3}, @option{-mvis2} and @option{-mvis}.
+
+@item -mvis4b
+@itemx -mno-vis4b
+@opindex mvis4b
+@opindex mno-vis4b
+With @option{-mvis4b}, GCC generates code that takes advantage of
+version 4.0 of the UltraSPARC Visual Instruction Set extensions, plus
+the additional VIS instructions introduced in the Oracle SPARC
+Architecture 2017. The default is @option{-mvis4b} when targeting a
+cpu that supports such instructions, such as m8 and later. Setting
+@option{-mvis4b} also sets @option{-mvis4}, @option{-mvis3},
+@option{-mvis2} and @option{-mvis}.
+
+@item -mcbcond
+@itemx -mno-cbcond
+@opindex mcbcond
+@opindex mno-cbcond
+With @option{-mcbcond}, GCC generates code that takes advantage of the UltraSPARC
+Compare-and-Branch-on-Condition instructions. The default is @option{-mcbcond}
+when targeting a CPU that supports such instructions, such as Niagara-4 and
+later.
+
+@item -mfmaf
+@itemx -mno-fmaf
+@opindex mfmaf
+@opindex mno-fmaf
+With @option{-mfmaf}, GCC generates code that takes advantage of the UltraSPARC
+Fused Multiply-Add Floating-point instructions. The default is @option{-mfmaf}
+when targeting a CPU that supports such instructions, such as Niagara-3 and
+later.
+
+@item -mfsmuld
+@itemx -mno-fsmuld
+@opindex mfsmuld
+@opindex mno-fsmuld
+With @option{-mfsmuld}, GCC generates code that takes advantage of the
+Floating-point Multiply Single to Double (FsMULd) instruction. The default is
+@option{-mfsmuld} when targeting a CPU supporting the architecture versions V8
+or V9 with FPU except @option{-mcpu=leon}.
+
+@item -mpopc
+@itemx -mno-popc
+@opindex mpopc
+@opindex mno-popc
+With @option{-mpopc}, GCC generates code that takes advantage of the UltraSPARC
+Population Count instruction. The default is @option{-mpopc}
+when targeting a CPU that supports such an instruction, such as Niagara-2 and
+later.
+
+@item -msubxc
+@itemx -mno-subxc
+@opindex msubxc
+@opindex mno-subxc
+With @option{-msubxc}, GCC generates code that takes advantage of the UltraSPARC
+Subtract-Extended-with-Carry instruction. The default is @option{-msubxc}
+when targeting a CPU that supports such an instruction, such as Niagara-7 and
+later.
+
+@item -mfix-at697f
+@opindex mfix-at697f
+Enable the documented workaround for the single erratum of the Atmel AT697F
+processor (which corresponds to erratum #13 of the AT697E processor).
+
+@item -mfix-ut699
+@opindex mfix-ut699
+Enable the documented workarounds for the floating-point errata and the data
+cache nullify errata of the UT699 processor.
+
+@item -mfix-ut700
+@opindex mfix-ut700
+Enable the documented workaround for the back-to-back store errata of
+the UT699E/UT700 processor.
+
+@item -mfix-gr712rc
+@opindex mfix-gr712rc
+Enable the documented workaround for the back-to-back store errata of
+the GR712RC processor.
+@end table
+
+These @samp{-m} options are supported in addition to the above
+on SPARC-V9 processors in 64-bit environments:
+
+@table @gcctabopt
+@item -m32
+@itemx -m64
+@opindex m32
+@opindex m64
+Generate code for a 32-bit or 64-bit environment.
+The 32-bit environment sets int, long and pointer to 32 bits.
+The 64-bit environment sets int to 32 bits and long and pointer
+to 64 bits.
+
+@item -mcmodel=@var{which}
+@opindex mcmodel
+Set the code model to one of
+
+@table @samp
+@item medlow
+The Medium/Low code model: 64-bit addresses, programs
+must be linked in the low 32 bits of memory. Programs can be statically
+or dynamically linked.
+
+@item medmid
+The Medium/Middle code model: 64-bit addresses, programs
+must be linked in the low 44 bits of memory, the text and data segments must
+be less than 2GB in size and the data segment must be located within 2GB of
+the text segment.
+
+@item medany
+The Medium/Anywhere code model: 64-bit addresses, programs
+may be linked anywhere in memory, the text and data segments must be less
+than 2GB in size and the data segment must be located within 2GB of the
+text segment.
+
+@item embmedany
+The Medium/Anywhere code model for embedded systems:
+64-bit addresses, the text and data segments must be less than 2GB in
+size, both starting anywhere in memory (determined at link time). The
+global register %g4 points to the base of the data segment. Programs
+are statically linked and PIC is not supported.
+@end table
+
+@item -mmemory-model=@var{mem-model}
+@opindex mmemory-model
+Set the memory model in force on the processor to one of
+
+@table @samp
+@item default
+The default memory model for the processor and operating system.
+
+@item rmo
+Relaxed Memory Order
+
+@item pso
+Partial Store Order
+
+@item tso
+Total Store Order
+
+@item sc
+Sequential Consistency
+@end table
+
+These memory models are formally defined in Appendix D of the SPARC-V9
+architecture manual, as set in the processor's @code{PSTATE.MM} field.
+
+@item -mstack-bias
+@itemx -mno-stack-bias
+@opindex mstack-bias
+@opindex mno-stack-bias
+With @option{-mstack-bias}, GCC assumes that the stack pointer, and
+frame pointer if present, are offset by @minus{}2047 which must be added back
+when making stack frame references. This is the default in 64-bit mode.
+Otherwise, assume no such offset is present.
+@end table
+
+@node System V Options
+@subsection Options for System V
+
+These additional options are available on System V Release 4 for
+compatibility with other compilers on those systems:
+
+@table @gcctabopt
+@item -G
+@opindex G
+Create a shared object.
+It is recommended that @option{-symbolic} or @option{-shared} be used instead.
+
+@item -Qy
+@opindex Qy
+Identify the versions of each tool used by the compiler, in a
+@code{.ident} assembler directive in the output.
+
+@item -Qn
+@opindex Qn
+Refrain from adding @code{.ident} directives to the output file (this is
+the default).
+
+@item -YP,@var{dirs}
+@opindex YP
+Search the directories @var{dirs}, and no others, for libraries
+specified with @option{-l}.
+
+@item -Ym,@var{dir}
+@opindex Ym
+Look in the directory @var{dir} to find the M4 preprocessor.
+The assembler uses this option.
+@c This is supposed to go with a -Yd for predefined M4 macro files, but
+@c the generic assembler that comes with Solaris takes just -Ym.
+@end table
+
+@node V850 Options
+@subsection V850 Options
+@cindex V850 Options
+
+These @samp{-m} options are defined for V850 implementations:
+
+@table @gcctabopt
+@item -mlong-calls
+@itemx -mno-long-calls
+@opindex mlong-calls
+@opindex mno-long-calls
+Treat all calls as being far away (near). If calls are assumed to be
+far away, the compiler always loads the function's address into a
+register, and calls indirect through the pointer.
+
+@item -mno-ep
+@itemx -mep
+@opindex mno-ep
+@opindex mep
+Do not optimize (do optimize) basic blocks that use the same index
+pointer 4 or more times to copy pointer into the @code{ep} register, and
+use the shorter @code{sld} and @code{sst} instructions. The @option{-mep}
+option is on by default if you optimize.
+
+@item -mno-prolog-function
+@itemx -mprolog-function
+@opindex mno-prolog-function
+@opindex mprolog-function
+Do not use (do use) external functions to save and restore registers
+at the prologue and epilogue of a function. The external functions
+are slower, but use less code space if more than one function saves
+the same number of registers. The @option{-mprolog-function} option
+is on by default if you optimize.
+
+@item -mspace
+@opindex mspace
+Try to make the code as small as possible. At present, this just turns
+on the @option{-mep} and @option{-mprolog-function} options.
+
+@item -mtda=@var{n}
+@opindex mtda
+Put static or global variables whose size is @var{n} bytes or less into
+the tiny data area that register @code{ep} points to. The tiny data
+area can hold up to 256 bytes in total (128 bytes for byte references).
+
+@item -msda=@var{n}
+@opindex msda
+Put static or global variables whose size is @var{n} bytes or less into
+the small data area that register @code{gp} points to. The small data
+area can hold up to 64 kilobytes.
+
+@item -mzda=@var{n}
+@opindex mzda
+Put static or global variables whose size is @var{n} bytes or less into
+the first 32 kilobytes of memory.
+
+@item -mv850
+@opindex mv850
+Specify that the target processor is the V850.
+
+@item -mv850e3v5
+@opindex mv850e3v5
+Specify that the target processor is the V850E3V5. The preprocessor
+constant @code{__v850e3v5__} is defined if this option is used.
+
+@item -mv850e2v4
+@opindex mv850e2v4
+Specify that the target processor is the V850E3V5. This is an alias for
+the @option{-mv850e3v5} option.
+
+@item -mv850e2v3
+@opindex mv850e2v3
+Specify that the target processor is the V850E2V3. The preprocessor
+constant @code{__v850e2v3__} is defined if this option is used.
+
+@item -mv850e2
+@opindex mv850e2
+Specify that the target processor is the V850E2. The preprocessor
+constant @code{__v850e2__} is defined if this option is used.
+
+@item -mv850e1
+@opindex mv850e1
+Specify that the target processor is the V850E1. The preprocessor
+constants @code{__v850e1__} and @code{__v850e__} are defined if
+this option is used.
+
+@item -mv850es
+@opindex mv850es
+Specify that the target processor is the V850ES. This is an alias for
+the @option{-mv850e1} option.
+
+@item -mv850e
+@opindex mv850e
+Specify that the target processor is the V850E@. The preprocessor
+constant @code{__v850e__} is defined if this option is used.
+
+If neither @option{-mv850} nor @option{-mv850e} nor @option{-mv850e1}
+nor @option{-mv850e2} nor @option{-mv850e2v3} nor @option{-mv850e3v5}
+are defined then a default target processor is chosen and the
+relevant @samp{__v850*__} preprocessor constant is defined.
+
+The preprocessor constants @code{__v850} and @code{__v851__} are always
+defined, regardless of which processor variant is the target.
+
+@item -mdisable-callt
+@itemx -mno-disable-callt
+@opindex mdisable-callt
+@opindex mno-disable-callt
+This option suppresses generation of the @code{CALLT} instruction for the
+v850e, v850e1, v850e2, v850e2v3 and v850e3v5 flavors of the v850
+architecture.
+
+This option is enabled by default when the RH850 ABI is
+in use (see @option{-mrh850-abi}), and disabled by default when the
+GCC ABI is in use. If @code{CALLT} instructions are being generated
+then the C preprocessor symbol @code{__V850_CALLT__} is defined.
+
+@item -mrelax
+@itemx -mno-relax
+@opindex mrelax
+@opindex mno-relax
+Pass on (or do not pass on) the @option{-mrelax} command-line option
+to the assembler.
+
+@item -mlong-jumps
+@itemx -mno-long-jumps
+@opindex mlong-jumps
+@opindex mno-long-jumps
+Disable (or re-enable) the generation of PC-relative jump instructions.
+
+@item -msoft-float
+@itemx -mhard-float
+@opindex msoft-float
+@opindex mhard-float
+Disable (or re-enable) the generation of hardware floating point
+instructions. This option is only significant when the target
+architecture is @samp{V850E2V3} or higher. If hardware floating point
+instructions are being generated then the C preprocessor symbol
+@code{__FPU_OK__} is defined, otherwise the symbol
+@code{__NO_FPU__} is defined.
+
+@item -mloop
+@opindex mloop
+Enables the use of the e3v5 LOOP instruction. The use of this
+instruction is not enabled by default when the e3v5 architecture is
+selected because its use is still experimental.
+
+@item -mrh850-abi
+@itemx -mghs
+@opindex mrh850-abi
+@opindex mghs
+Enables support for the RH850 version of the V850 ABI. This is the
+default. With this version of the ABI the following rules apply:
+
+@itemize
+@item
+Integer sized structures and unions are returned via a memory pointer
+rather than a register.
+
+@item
+Large structures and unions (more than 8 bytes in size) are passed by
+value.
+
+@item
+Functions are aligned to 16-bit boundaries.
+
+@item
+The @option{-m8byte-align} command-line option is supported.
+
+@item
+The @option{-mdisable-callt} command-line option is enabled by
+default. The @option{-mno-disable-callt} command-line option is not
+supported.
+@end itemize
+
+When this version of the ABI is enabled the C preprocessor symbol
+@code{__V850_RH850_ABI__} is defined.
+
+@item -mgcc-abi
+@opindex mgcc-abi
+Enables support for the old GCC version of the V850 ABI. With this
+version of the ABI the following rules apply:
+
+@itemize
+@item
+Integer sized structures and unions are returned in register @code{r10}.
+
+@item
+Large structures and unions (more than 8 bytes in size) are passed by
+reference.
+
+@item
+Functions are aligned to 32-bit boundaries, unless optimizing for
+size.
+
+@item
+The @option{-m8byte-align} command-line option is not supported.
+
+@item
+The @option{-mdisable-callt} command-line option is supported but not
+enabled by default.
+@end itemize
+
+When this version of the ABI is enabled the C preprocessor symbol
+@code{__V850_GCC_ABI__} is defined.
+
+@item -m8byte-align
+@itemx -mno-8byte-align
+@opindex m8byte-align
+@opindex mno-8byte-align
+Enables support for @code{double} and @code{long long} types to be
+aligned on 8-byte boundaries. The default is to restrict the
+alignment of all objects to at most 4-bytes. When
+@option{-m8byte-align} is in effect the C preprocessor symbol
+@code{__V850_8BYTE_ALIGN__} is defined.
+
+@item -mbig-switch
+@opindex mbig-switch
+Generate code suitable for big switch tables. Use this option only if
+the assembler/linker complain about out of range branches within a switch
+table.
+
+@item -mapp-regs
+@opindex mapp-regs
+This option causes r2 and r5 to be used in the code generated by
+the compiler. This setting is the default.
+
+@item -mno-app-regs
+@opindex mno-app-regs
+This option causes r2 and r5 to be treated as fixed registers.
+
+@end table
+
+@node VAX Options
+@subsection VAX Options
+@cindex VAX options
+
+These @samp{-m} options are defined for the VAX:
+
+@table @gcctabopt
+@item -munix
+@opindex munix
+Do not output certain jump instructions (@code{aobleq} and so on)
+that the Unix assembler for the VAX cannot handle across long
+ranges.
+
+@item -mgnu
+@opindex mgnu
+Do output those jump instructions, on the assumption that the
+GNU assembler is being used.
+
+@item -mg
+@opindex mg
+Output code for G-format floating-point numbers instead of D-format.
+
+@item -mlra
+@itemx -mno-lra
+@opindex mlra
+@opindex mno-lra
+Enable Local Register Allocation. This is still experimental for the VAX,
+so by default the compiler uses standard reload.
+@end table
+
+@node Visium Options
+@subsection Visium Options
+@cindex Visium options
+
+@table @gcctabopt
+
+@item -mdebug
+@opindex mdebug
+A program which performs file I/O and is destined to run on an MCM target
+should be linked with this option. It causes the libraries libc.a and
+libdebug.a to be linked. The program should be run on the target under
+the control of the GDB remote debugging stub.
+
+@item -msim
+@opindex msim
+A program which performs file I/O and is destined to run on the simulator
+should be linked with option. This causes libraries libc.a and libsim.a to
+be linked.
+
+@item -mfpu
+@itemx -mhard-float
+@opindex mfpu
+@opindex mhard-float
+Generate code containing floating-point instructions. This is the
+default.
+
+@item -mno-fpu
+@itemx -msoft-float
+@opindex mno-fpu
+@opindex msoft-float
+Generate code containing library calls for floating-point.
+
+@option{-msoft-float} changes the calling convention in the output file;
+therefore, it is only useful if you compile @emph{all} of a program with
+this option. In particular, you need to compile @file{libgcc.a}, the
+library that comes with GCC, with @option{-msoft-float} in order for
+this to work.
+
+@item -mcpu=@var{cpu_type}
+@opindex mcpu
+Set the instruction set, register set, and instruction scheduling parameters
+for machine type @var{cpu_type}. Supported values for @var{cpu_type} are
+@samp{mcm}, @samp{gr5} and @samp{gr6}.
+
+@samp{mcm} is a synonym of @samp{gr5} present for backward compatibility.
+
+By default (unless configured otherwise), GCC generates code for the GR5
+variant of the Visium architecture.
+
+With @option{-mcpu=gr6}, GCC generates code for the GR6 variant of the Visium
+architecture. The only difference from GR5 code is that the compiler will
+generate block move instructions.
+
+@item -mtune=@var{cpu_type}
+@opindex mtune
+Set the instruction scheduling parameters for machine type @var{cpu_type},
+but do not set the instruction set or register set that the option
+@option{-mcpu=@var{cpu_type}} would.
+
+@item -msv-mode
+@opindex msv-mode
+Generate code for the supervisor mode, where there are no restrictions on
+the access to general registers. This is the default.
+
+@item -muser-mode
+@opindex muser-mode
+Generate code for the user mode, where the access to some general registers
+is forbidden: on the GR5, registers r24 to r31 cannot be accessed in this
+mode; on the GR6, only registers r29 to r31 are affected.
+@end table
+
+@node VMS Options
+@subsection VMS Options
+
+These @samp{-m} options are defined for the VMS implementations:
+
+@table @gcctabopt
+@item -mvms-return-codes
+@opindex mvms-return-codes
+Return VMS condition codes from @code{main}. The default is to return POSIX-style
+condition (e.g.@: error) codes.
+
+@item -mdebug-main=@var{prefix}
+@opindex mdebug-main=@var{prefix}
+Flag the first routine whose name starts with @var{prefix} as the main
+routine for the debugger.
+
+@item -mmalloc64
+@opindex mmalloc64
+Default to 64-bit memory allocation routines.
+
+@item -mpointer-size=@var{size}
+@opindex mpointer-size=@var{size}
+Set the default size of pointers. Possible options for @var{size} are
+@samp{32} or @samp{short} for 32 bit pointers, @samp{64} or @samp{long}
+for 64 bit pointers, and @samp{no} for supporting only 32 bit pointers.
+The later option disables @code{pragma pointer_size}.
+@end table
+
+@node VxWorks Options
+@subsection VxWorks Options
+@cindex VxWorks Options
+
+The options in this section are defined for all VxWorks targets.
+Options specific to the target hardware are listed with the other
+options for that target.
+
+@table @gcctabopt
+@item -mrtp
+@opindex mrtp
+GCC can generate code for both VxWorks kernels and real time processes
+(RTPs). This option switches from the former to the latter. It also
+defines the preprocessor macro @code{__RTP__}.
+
+@item -non-static
+@opindex non-static
+Link an RTP executable against shared libraries rather than static
+libraries. The options @option{-static} and @option{-shared} can
+also be used for RTPs (@pxref{Link Options}); @option{-static}
+is the default.
+
+@item -Bstatic
+@itemx -Bdynamic
+@opindex Bstatic
+@opindex Bdynamic
+These options are passed down to the linker. They are defined for
+compatibility with Diab.
+
+@item -Xbind-lazy
+@opindex Xbind-lazy
+Enable lazy binding of function calls. This option is equivalent to
+@option{-Wl,-z,now} and is defined for compatibility with Diab.
+
+@item -Xbind-now
+@opindex Xbind-now
+Disable lazy binding of function calls. This option is the default and
+is defined for compatibility with Diab.
+@end table
+
+@node x86 Options
+@subsection x86 Options
+@cindex x86 Options
+
+These @samp{-m} options are defined for the x86 family of computers.
+
+@table @gcctabopt
+
+@item -march=@var{cpu-type}
+@opindex march
+Generate instructions for the machine type @var{cpu-type}. In contrast to
+@option{-mtune=@var{cpu-type}}, which merely tunes the generated code
+for the specified @var{cpu-type}, @option{-march=@var{cpu-type}} allows GCC
+to generate code that may not run at all on processors other than the one
+indicated. Specifying @option{-march=@var{cpu-type}} implies
+@option{-mtune=@var{cpu-type}}, except where noted otherwise.
+
+The choices for @var{cpu-type} are:
+
+@table @samp
+@item native
+This selects the CPU to generate code for at compilation time by determining
+the processor type of the compiling machine. Using @option{-march=native}
+enables all instruction subsets supported by the local machine (hence
+the result might not run on different machines). Using @option{-mtune=native}
+produces code optimized for the local machine under the constraints
+of the selected instruction set.
+
+@item x86-64
+A generic CPU with 64-bit extensions.
+
+@item x86-64-v2
+@itemx x86-64-v3
+@itemx x86-64-v4
+These choices for @var{cpu-type} select the corresponding
+micro-architecture level from the x86-64 psABI. On ABIs other than
+the x86-64 psABI they select the same CPU features as the x86-64 psABI
+documents for the particular micro-architecture level.
+
+Since these @var{cpu-type} values do not have a corresponding
+@option{-mtune} setting, using @option{-march} with these values enables
+generic tuning. Specific tuning can be enabled using the
+@option{-mtune=@var{other-cpu-type}} option with an appropriate
+@var{other-cpu-type} value.
+
+@item i386
+Original Intel i386 CPU@.
+
+@item i486
+Intel i486 CPU@. (No scheduling is implemented for this chip.)
+
+@item i586
+@itemx pentium
+Intel Pentium CPU with no MMX support.
+
+@item lakemont
+Intel Lakemont MCU, based on Intel Pentium CPU.
+
+@item pentium-mmx
+Intel Pentium MMX CPU, based on Pentium core with MMX instruction set support.
+
+@item pentiumpro
+Intel Pentium Pro CPU@.
+
+@item i686
+When used with @option{-march}, the Pentium Pro
+instruction set is used, so the code runs on all i686 family chips.
+When used with @option{-mtune}, it has the same meaning as @samp{generic}.
+
+@item pentium2
+Intel Pentium II CPU, based on Pentium Pro core with MMX and FXSR instruction
+set support.
+
+@item pentium3
+@itemx pentium3m
+Intel Pentium III CPU, based on Pentium Pro core with MMX, FXSR and SSE
+instruction set support.
+
+@item pentium-m
+Intel Pentium M; low-power version of Intel Pentium III CPU
+with MMX, SSE, SSE2 and FXSR instruction set support. Used by Centrino
+notebooks.
+
+@item pentium4
+@itemx pentium4m
+Intel Pentium 4 CPU with MMX, SSE, SSE2 and FXSR instruction set support.
+
+@item prescott
+Improved version of Intel Pentium 4 CPU with MMX, SSE, SSE2, SSE3 and FXSR
+instruction set support.
+
+@item nocona
+Improved version of Intel Pentium 4 CPU with 64-bit extensions, MMX, SSE,
+SSE2, SSE3 and FXSR instruction set support.
+
+@item core2
+Intel Core 2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, CX16,
+SAHF and FXSR instruction set support.
+
+@item nehalem
+Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF and FXSR instruction set support.
+
+@item westmere
+Intel Westmere CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR and PCLMUL instruction set support.
+
+@item sandybridge
+Intel Sandy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE and PCLMUL instruction set
+support.
+
+@item ivybridge
+Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND
+and F16C instruction set support.
+
+@item haswell
+Intel Haswell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND,
+F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE and HLE instruction set support.
+
+@item broadwell
+Intel Broadwell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND,
+F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX and PREFETCHW
+instruction set support.
+
+@item skylake
+Intel Skylake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND,
+F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES,
+CLFLUSHOPT, XSAVEC, XSAVES and SGX instruction set support.
+
+@item bonnell
+Intel Bonnell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3 and SSSE3
+instruction set support.
+
+@item silvermont
+Intel Silvermont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, PCLMUL, PREFETCHW and RDRND
+instruction set support.
+
+@item goldmont
+Intel Goldmont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, PCLMUL, PREFETCHW, RDRND, AES, SHA,
+RDSEED, XSAVE, XSAVEC, XSAVES, XSAVEOPT, CLFLUSHOPT and FSGSBASE instruction
+set support.
+
+@item goldmont-plus
+Intel Goldmont Plus CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, PCLMUL, PREFETCHW, RDRND, AES,
+SHA, RDSEED, XSAVE, XSAVEC, XSAVES, XSAVEOPT, CLFLUSHOPT, FSGSBASE, PTWRITE,
+RDPID and SGX instruction set support.
+
+@item tremont
+Intel Tremont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, PCLMUL, PREFETCHW, RDRND, AES, SHA,
+RDSEED, XSAVE, XSAVEC, XSAVES, XSAVEOPT, CLFLUSHOPT, FSGSBASE, PTWRITE, RDPID,
+SGX, CLWB, GFNI-SSE, MOVDIRI, MOVDIR64B, CLDEMOTE and WAITPKG instruction set
+support.
+
+@item sierraforest
+Intel Sierra Forest CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC,
+XSAVES, XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX, GFNI-SSE, CLWB, MOVDIRI,
+MOVDIR64B, CLDEMOTE, WAITPKG, ADCX, AVX, AVX2, BMI, BMI2, F16C, FMA, LZCNT,
+PCONFIG, PKU, VAES, VPCLMULQDQ, SERIALIZE, HRESET, KL, WIDEKL, AVX-VNNI,
+AVXIFMA, AVXVNNIINT8, AVXNECONVERT and CMPCCXADD instruction set support.
+
+@item grandridge
+Intel Grand Ridge CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC,
+XSAVES, XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX, GFNI-SSE, CLWB, MOVDIRI,
+MOVDIR64B, CLDEMOTE, WAITPKG, ADCX, AVX, AVX2, BMI, BMI2, F16C, FMA, LZCNT,
+PCONFIG, PKU, VAES, VPCLMULQDQ, SERIALIZE, HRESET, KL, WIDEKL, AVX-VNNI,
+AVXIFMA, AVXVNNIINT8, AVXNECONVERT, CMPCCXADD and RAOINT instruction set
+support.
+
+@item knl
+Intel Knight's Landing CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE,
+RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW,
+AVX512PF, AVX512ER, AVX512F, AVX512CD and PREFETCHWT1 instruction set support.
+
+@item knm
+Intel Knights Mill CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE,
+RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW,
+AVX512PF, AVX512ER, AVX512F, AVX512CD and PREFETCHWT1, AVX5124VNNIW,
+AVX5124FMAPS and AVX512VPOPCNTDQ instruction set support.
+
+@item skylake-avx512
+Intel Skylake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE,
+RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW,
+AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, CLWB, AVX512VL, AVX512BW,
+AVX512DQ and AVX512CD instruction set support.
+
+@item cannonlake
+Intel Cannonlake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2,
+SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL,
+FSGSBASE, RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX,
+PREFETCHW, AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW,
+AVX512DQ, AVX512CD, PKU, AVX512VBMI, AVX512IFMA and SHA instruction set
+support.
+
+@item icelake-client
+Intel Icelake Client CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE,
+RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW,
+AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ,
+AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2
+, VPCLMULQDQ, AVX512BITALG, RDPID and AVX512VPOPCNTDQ instruction set support.
+
+@item icelake-server
+Intel Icelake Server CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE,
+RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW,
+AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ,
+AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2
+, VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, PCONFIG, WBNOINVD and CLWB
+instruction set support.
+
+@item cascadelake
+Intel Cascadelake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND,
+F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES,
+CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, CLWB, AVX512VL, AVX512BW, AVX512DQ,
+AVX512CD and AVX512VNNI instruction set support.
+
+@item cooperlake
+Intel cooperlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND,
+F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES,
+CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, CLWB, AVX512VL, AVX512BW, AVX512DQ,
+AVX512CD, AVX512VNNI and AVX512BF16 instruction set support.
+
+@item tigerlake
+Intel Tigerlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND,
+F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES,
+CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD
+PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2,
+VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, MOVDIRI, MOVDIR64B, CLWB,
+AVX512VP2INTERSECT and KEYLOCKER instruction set support.
+
+@item sapphirerapids
+Intel sapphirerapids CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE,
+RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW,
+AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ,
+AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2,
+VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, PCONFIG, WBNOINVD, CLWB,
+MOVDIRI, MOVDIR64B, ENQCMD, CLDEMOTE, PTWRITE, WAITPKG, SERIALIZE, TSXLDTRK,
+UINTR, AMX-BF16, AMX-TILE, AMX-INT8, AVX-VNNI, AVX512FP16 and AVX512BF16
+instruction set support.
+
+@item alderlake
+Intel Alderlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
+SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW, PCLMUL, RDRND, XSAVE, XSAVEC, XSAVES,
+XSAVEOPT, FSGSBASE, PTWRITE, RDPID, SGX, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B,
+CLDEMOTE, WAITPKG, ADCX, AVX, AVX2, BMI, BMI2, F16C, FMA, LZCNT, PCONFIG, PKU,
+VAES, VPCLMULQDQ, SERIALIZE, HRESET, KL, WIDEKL and AVX-VNNI instruction set
+support.
+
+@item rocketlake
+Intel Rocketlake CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3
+, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE, RDRND,
+F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW, AES,
+CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL, AVX512BW, AVX512DQ, AVX512CD
+PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2,
+VPCLMULQDQ, AVX512BITALG, RDPID and AVX512VPOPCNTDQ instruction set support.
+
+@item graniterapids
+Intel graniterapids CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
+SSSE3, SSE4.1, SSE4.2, POPCNT, CX16, SAHF, FXSR, AVX, XSAVE, PCLMUL, FSGSBASE,
+RDRND, F16C, AVX2, BMI, BMI2, LZCNT, FMA, MOVBE, HLE, RDSEED, ADCX, PREFETCHW,
+AES, CLFLUSHOPT, XSAVEC, XSAVES, SGX, AVX512F, AVX512VL, AVX512BW, AVX512DQ,
+AVX512CD, PKU, AVX512VBMI, AVX512IFMA, SHA, AVX512VNNI, GFNI, VAES, AVX512VBMI2,
+VPCLMULQDQ, AVX512BITALG, RDPID, AVX512VPOPCNTDQ, PCONFIG, WBNOINVD, CLWB,
+MOVDIRI, MOVDIR64B, AVX512VP2INTERSECT, ENQCMD, CLDEMOTE, PTWRITE, WAITPKG,
+SERIALIZE, TSXLDTRK, UINTR, AMX-BF16, AMX-TILE, AMX-INT8, AVX-VNNI, AVX512FP16,
+AVX512BF16, AMX-FP16 and PREFETCHI instruction set support.
+
+@item k6
+AMD K6 CPU with MMX instruction set support.
+
+@item k6-2
+@itemx k6-3
+Improved versions of AMD K6 CPU with MMX and 3DNow!@: instruction set support.
+
+@item athlon
+@itemx athlon-tbird
+AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow!@: and SSE prefetch instructions
+support.
+
+@item athlon-4
+@itemx athlon-xp
+@itemx athlon-mp
+Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow!@: and full SSE
+instruction set support.
+
+@item k8
+@itemx opteron
+@itemx athlon64
+@itemx athlon-fx
+Processors based on the AMD K8 core with x86-64 instruction set support,
+including the AMD Opteron, Athlon 64, and Athlon 64 FX processors.
+(This supersets MMX, SSE, SSE2, 3DNow!, enhanced 3DNow!@: and 64-bit
+instruction set extensions.)
+
+@item k8-sse3
+@itemx opteron-sse3
+@itemx athlon64-sse3
+Improved versions of AMD K8 cores with SSE3 instruction set support.
+
+@item amdfam10
+@itemx barcelona
+CPUs based on AMD Family 10h cores with x86-64 instruction set support. (This
+supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!, enhanced 3DNow!, ABM and 64-bit
+instruction set extensions.)
+
+@item bdver1
+CPUs based on AMD Family 15h cores with x86-64 instruction set support. (This
+supersets FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A,
+SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)
+
+@item bdver2
+AMD Family 15h core based CPUs with x86-64 instruction set support. (This
+supersets BMI, TBM, F16C, FMA, FMA4, AVX, XOP, LWP, AES, PCLMUL, CX16, MMX,
+SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set
+extensions.)
+
+@item bdver3
+AMD Family 15h core based CPUs with x86-64 instruction set support. (This
+supersets BMI, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, XOP, LWP, AES,
+PCLMUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and
+64-bit instruction set extensions.)
+
+@item bdver4
+AMD Family 15h core based CPUs with x86-64 instruction set support. (This
+supersets BMI, BMI2, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, AVX2, XOP, LWP,
+AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1,
+SSE4.2, ABM and 64-bit instruction set extensions.)
+
+@item znver1
+AMD Family 17h core based CPUs with x86-64 instruction set support. (This
+supersets BMI, BMI2, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED, MWAITX,
+SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,
+SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, and 64-bit
+instruction set extensions.)
+
+@item znver2
+AMD Family 17h core based CPUs with x86-64 instruction set support. (This
+supersets BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED,
+MWAITX, SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A,
+SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID,
+WBNOINVD, and 64-bit instruction set extensions.)
+
+@item znver3
+AMD Family 19h core based CPUs with x86-64 instruction set support. (This
+supersets BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED,
+MWAITX, SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A,
+SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID,
+WBNOINVD, PKU, VPCLMULQDQ, VAES, and 64-bit instruction set extensions.)
+
+@item znver4
+AMD Family 19h core based CPUs with x86-64 instruction set support. (This
+supersets BMI, BMI2, CLWB, F16C, FMA, FSGSBASE, AVX, AVX2, ADCX, RDSEED,
+MWAITX, SHA, CLZERO, AES, PCLMUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A,
+SSSE3, SSE4.1, SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, RDPID,
+WBNOINVD, PKU, VPCLMULQDQ, VAES, AVX512F, AVX512DQ, AVX512IFMA, AVX512CD,
+AVX512BW, AVX512VL, AVX512BF16, AVX512VBMI, AVX512VBMI2, AVX512VNNI,
+AVX512BITALG, AVX512VPOPCNTDQ, GFNI and 64-bit instruction set extensions.)
+
+@item btver1
+CPUs based on AMD Family 14h cores with x86-64 instruction set support. (This
+supersets MMX, SSE, SSE2, SSE3, SSSE3, SSE4A, CX16, ABM and 64-bit
+instruction set extensions.)
+
+@item btver2
+CPUs based on AMD Family 16h cores with x86-64 instruction set support. This
+includes MOVBE, F16C, BMI, AVX, PCLMUL, AES, SSE4.2, SSE4.1, CX16, ABM,
+SSE4A, SSSE3, SSE3, SSE2, SSE, MMX and 64-bit instruction set extensions.
+
+@item winchip-c6
+IDT WinChip C6 CPU, dealt in same way as i486 with additional MMX instruction
+set support.
+
+@item winchip2
+IDT WinChip 2 CPU, dealt in same way as i486 with additional MMX and 3DNow!@:
+instruction set support.
+
+@item c3
+VIA C3 CPU with MMX and 3DNow!@: instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item c3-2
+VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item c7
+VIA C7 (Esther) CPU with MMX, SSE, SSE2 and SSE3 instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item samuel-2
+VIA Eden Samuel 2 CPU with MMX and 3DNow!@: instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item nehemiah
+VIA Eden Nehemiah CPU with MMX and SSE instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item esther
+VIA Eden Esther CPU with MMX, SSE, SSE2 and SSE3 instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item eden-x2
+VIA Eden X2 CPU with x86-64, MMX, SSE, SSE2 and SSE3 instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item eden-x4
+VIA Eden X4 CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2,
+AVX and AVX2 instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item nano
+Generic VIA Nano CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3
+instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item nano-1000
+VIA Nano 1xxx CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3
+instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item nano-2000
+VIA Nano 2xxx CPU with x86-64, MMX, SSE, SSE2, SSE3 and SSSE3
+instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item nano-3000
+VIA Nano 3xxx CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1
+instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item nano-x2
+VIA Nano Dual Core CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1
+instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item nano-x4
+VIA Nano Quad Core CPU with x86-64, MMX, SSE, SSE2, SSE3, SSSE3 and SSE4.1
+instruction set support.
+(No scheduling is implemented for this chip.)
+
+@item lujiazui
+ZHAOXIN lujiazui CPU with x86-64, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
+SSE4.2, AVX, POPCNT, AES, PCLMUL, RDRND, XSAVE, XSAVEOPT, FSGSBASE, CX16,
+ABM, BMI, BMI2, F16C, FXSR, RDSEED instruction set support.
+
+@item geode
+AMD Geode embedded processor with MMX and 3DNow!@: instruction set support.
+@end table
+
+@item -mtune=@var{cpu-type}
+@opindex mtune
+Tune to @var{cpu-type} everything applicable about the generated code, except
+for the ABI and the set of available instructions.
+While picking a specific @var{cpu-type} schedules things appropriately
+for that particular chip, the compiler does not generate any code that
+cannot run on the default machine type unless you use a
+@option{-march=@var{cpu-type}} option.
+For example, if GCC is configured for i686-pc-linux-gnu
+then @option{-mtune=pentium4} generates code that is tuned for Pentium 4
+but still runs on i686 machines.
+
+The choices for @var{cpu-type} are the same as for @option{-march}.
+In addition, @option{-mtune} supports 2 extra choices for @var{cpu-type}:
+
+@table @samp
+@item generic
+Produce code optimized for the most common IA32/@/AMD64/@/EM64T processors.
+If you know the CPU on which your code will run, then you should use
+the corresponding @option{-mtune} or @option{-march} option instead of
+@option{-mtune=generic}. But, if you do not know exactly what CPU users
+of your application will have, then you should use this option.
+
+As new processors are deployed in the marketplace, the behavior of this
+option will change. Therefore, if you upgrade to a newer version of
+GCC, code generation controlled by this option will change to reflect
+the processors
+that are most common at the time that version of GCC is released.
+
+There is no @option{-march=generic} option because @option{-march}
+indicates the instruction set the compiler can use, and there is no
+generic instruction set applicable to all processors. In contrast,
+@option{-mtune} indicates the processor (or, in this case, collection of
+processors) for which the code is optimized.
+
+@item intel
+Produce code optimized for the most current Intel processors, which are
+Haswell and Silvermont for this version of GCC. If you know the CPU
+on which your code will run, then you should use the corresponding
+@option{-mtune} or @option{-march} option instead of @option{-mtune=intel}.
+But, if you want your application performs better on both Haswell and
+Silvermont, then you should use this option.
+
+As new Intel processors are deployed in the marketplace, the behavior of
+this option will change. Therefore, if you upgrade to a newer version of
+GCC, code generation controlled by this option will change to reflect
+the most current Intel processors at the time that version of GCC is
+released.
+
+There is no @option{-march=intel} option because @option{-march} indicates
+the instruction set the compiler can use, and there is no common
+instruction set applicable to all processors. In contrast,
+@option{-mtune} indicates the processor (or, in this case, collection of
+processors) for which the code is optimized.
+@end table
+
+@item -mcpu=@var{cpu-type}
+@opindex mcpu
+A deprecated synonym for @option{-mtune}.
+
+@item -mfpmath=@var{unit}
+@opindex mfpmath
+Generate floating-point arithmetic for selected unit @var{unit}. The choices
+for @var{unit} are:
+
+@table @samp
+@item 387
+Use the standard 387 floating-point coprocessor present on the majority of chips and
+emulated otherwise. Code compiled with this option runs almost everywhere.
+The temporary results are computed in 80-bit precision instead of the precision
+specified by the type, resulting in slightly different results compared to most
+of other chips. See @option{-ffloat-store} for more detailed description.
+
+This is the default choice for non-Darwin x86-32 targets.
+
+@item sse
+Use scalar floating-point instructions present in the SSE instruction set.
+This instruction set is supported by Pentium III and newer chips,
+and in the AMD line
+by Athlon-4, Athlon XP and Athlon MP chips. The earlier version of the SSE
+instruction set supports only single-precision arithmetic, thus the double and
+extended-precision arithmetic are still done using 387. A later version, present
+only in Pentium 4 and AMD x86-64 chips, supports double-precision
+arithmetic too.
+
+For the x86-32 compiler, you must use @option{-march=@var{cpu-type}}, @option{-msse}
+or @option{-msse2} switches to enable SSE extensions and make this option
+effective. For the x86-64 compiler, these extensions are enabled by default.
+
+The resulting code should be considerably faster in the majority of cases and avoid
+the numerical instability problems of 387 code, but may break some existing
+code that expects temporaries to be 80 bits.
+
+This is the default choice for the x86-64 compiler, Darwin x86-32 targets,
+and the default choice for x86-32 targets with the SSE2 instruction set
+when @option{-ffast-math} is enabled.
+
+@item sse,387
+@itemx sse+387
+@itemx both
+Attempt to utilize both instruction sets at once. This effectively doubles the
+amount of available registers, and on chips with separate execution units for
+387 and SSE the execution resources too. Use this option with care, as it is
+still experimental, because the GCC register allocator does not model separate
+functional units well, resulting in unstable performance.
+@end table
+
+@item -masm=@var{dialect}
+@opindex masm=@var{dialect}
+Output assembly instructions using selected @var{dialect}. Also affects
+which dialect is used for basic @code{asm} (@pxref{Basic Asm}) and
+extended @code{asm} (@pxref{Extended Asm}). Supported choices (in dialect
+order) are @samp{att} or @samp{intel}. The default is @samp{att}. Darwin does
+not support @samp{intel}.
+
+@item -mieee-fp
+@itemx -mno-ieee-fp
+@opindex mieee-fp
+@opindex mno-ieee-fp
+Control whether or not the compiler uses IEEE floating-point
+comparisons. These correctly handle the case where the result of a
+comparison is unordered.
+
+@item -m80387
+@itemx -mhard-float
+@opindex 80387
+@opindex mhard-float
+Generate output containing 80387 instructions for floating point.
+
+@item -mno-80387
+@itemx -msoft-float
+@opindex no-80387
+@opindex msoft-float
+Generate output containing library calls for floating point.
+
+@strong{Warning:} the requisite libraries are not part of GCC@.
+Normally the facilities of the machine's usual C compiler are used, but
+this cannot be done directly in cross-compilation. You must make your
+own arrangements to provide suitable library functions for
+cross-compilation.
+
+On machines where a function returns floating-point results in the 80387
+register stack, some floating-point opcodes may be emitted even if
+@option{-msoft-float} is used.
+
+@item -mno-fp-ret-in-387
+@opindex mno-fp-ret-in-387
+@opindex mfp-ret-in-387
+Do not use the FPU registers for return values of functions.
+
+The usual calling convention has functions return values of types
+@code{float} and @code{double} in an FPU register, even if there
+is no FPU@. The idea is that the operating system should emulate
+an FPU@.
+
+The option @option{-mno-fp-ret-in-387} causes such values to be returned
+in ordinary CPU registers instead.
+
+@item -mno-fancy-math-387
+@opindex mno-fancy-math-387
+@opindex mfancy-math-387
+Some 387 emulators do not support the @code{sin}, @code{cos} and
+@code{sqrt} instructions for the 387. Specify this option to avoid
+generating those instructions.
+This option is overridden when @option{-march}
+indicates that the target CPU always has an FPU and so the
+instruction does not need emulation. These
+instructions are not generated unless you also use the
+@option{-funsafe-math-optimizations} switch.
+
+@item -malign-double
+@itemx -mno-align-double
+@opindex malign-double
+@opindex mno-align-double
+Control whether GCC aligns @code{double}, @code{long double}, and
+@code{long long} variables on a two-word boundary or a one-word
+boundary. Aligning @code{double} variables on a two-word boundary
+produces code that runs somewhat faster on a Pentium at the
+expense of more memory.
+
+On x86-64, @option{-malign-double} is enabled by default.
+
+@strong{Warning:} if you use the @option{-malign-double} switch,
+structures containing the above types are aligned differently than
+the published application binary interface specifications for the x86-32
+and are not binary compatible with structures in code compiled
+without that switch.
+
+@item -m96bit-long-double
+@itemx -m128bit-long-double
+@opindex m96bit-long-double
+@opindex m128bit-long-double
+These switches control the size of @code{long double} type. The x86-32
+application binary interface specifies the size to be 96 bits,
+so @option{-m96bit-long-double} is the default in 32-bit mode.
+
+Modern architectures (Pentium and newer) prefer @code{long double}
+to be aligned to an 8- or 16-byte boundary. In arrays or structures
+conforming to the ABI, this is not possible. So specifying
+@option{-m128bit-long-double} aligns @code{long double}
+to a 16-byte boundary by padding the @code{long double} with an additional
+32-bit zero.
+
+In the x86-64 compiler, @option{-m128bit-long-double} is the default choice as
+its ABI specifies that @code{long double} is aligned on 16-byte boundary.
+
+Notice that neither of these options enable any extra precision over the x87
+standard of 80 bits for a @code{long double}.
+
+@strong{Warning:} if you override the default value for your target ABI, this
+changes the size of
+structures and arrays containing @code{long double} variables,
+as well as modifying the function calling convention for functions taking
+@code{long double}. Hence they are not binary-compatible
+with code compiled without that switch.
+
+@item -mlong-double-64
+@itemx -mlong-double-80
+@itemx -mlong-double-128
+@opindex mlong-double-64
+@opindex mlong-double-80
+@opindex mlong-double-128
+These switches control the size of @code{long double} type. A size
+of 64 bits makes the @code{long double} type equivalent to the @code{double}
+type. This is the default for 32-bit Bionic C library. A size
+of 128 bits makes the @code{long double} type equivalent to the
+@code{__float128} type. This is the default for 64-bit Bionic C library.
+
+@strong{Warning:} if you override the default value for your target ABI, this
+changes the size of
+structures and arrays containing @code{long double} variables,
+as well as modifying the function calling convention for functions taking
+@code{long double}. Hence they are not binary-compatible
+with code compiled without that switch.
+
+@item -malign-data=@var{type}
+@opindex malign-data
+Control how GCC aligns variables. Supported values for @var{type} are
+@samp{compat} uses increased alignment value compatible uses GCC 4.8
+and earlier, @samp{abi} uses alignment value as specified by the
+psABI, and @samp{cacheline} uses increased alignment value to match
+the cache line size. @samp{compat} is the default.
+
+@item -mlarge-data-threshold=@var{threshold}
+@opindex mlarge-data-threshold
+When @option{-mcmodel=medium} is specified, data objects larger than
+@var{threshold} are placed in the large data section. This value must be the
+same across all objects linked into the binary, and defaults to 65535.
+
+@item -mrtd
+@opindex mrtd
+Use a different function-calling convention, in which functions that
+take a fixed number of arguments return with the @code{ret @var{num}}
+instruction, which pops their arguments while returning. This saves one
+instruction in the caller since there is no need to pop the arguments
+there.
+
+You can specify that an individual function is called with this calling
+sequence with the function attribute @code{stdcall}. You can also
+override the @option{-mrtd} option by using the function attribute
+@code{cdecl}. @xref{Function Attributes}.
+
+@strong{Warning:} this calling convention is incompatible with the one
+normally used on Unix, so you cannot use it if you need to call
+libraries compiled with the Unix compiler.
+
+Also, you must provide function prototypes for all functions that
+take variable numbers of arguments (including @code{printf});
+otherwise incorrect code is generated for calls to those
+functions.
+
+In addition, seriously incorrect code results if you call a
+function with too many arguments. (Normally, extra arguments are
+harmlessly ignored.)
+
+@item -mregparm=@var{num}
+@opindex mregparm
+Control how many registers are used to pass integer arguments. By
+default, no registers are used to pass arguments, and at most 3
+registers can be used. You can control this behavior for a specific
+function by using the function attribute @code{regparm}.
+@xref{Function Attributes}.
+
+@strong{Warning:} if you use this switch, and
+@var{num} is nonzero, then you must build all modules with the same
+value, including any libraries. This includes the system libraries and
+startup modules.
+
+@item -msseregparm
+@opindex msseregparm
+Use SSE register passing conventions for float and double arguments
+and return values. You can control this behavior for a specific
+function by using the function attribute @code{sseregparm}.
+@xref{Function Attributes}.
+
+@strong{Warning:} if you use this switch then you must build all
+modules with the same value, including any libraries. This includes
+the system libraries and startup modules.
+
+@item -mvect8-ret-in-mem
+@opindex mvect8-ret-in-mem
+Return 8-byte vectors in memory instead of MMX registers. This is the
+default on VxWorks to match the ABI of the Sun Studio compilers until
+version 12. @emph{Only} use this option if you need to remain
+compatible with existing code produced by those previous compiler
+versions or older versions of GCC@.
+
+@item -mpc32
+@itemx -mpc64
+@itemx -mpc80
+@opindex mpc32
+@opindex mpc64
+@opindex mpc80
+
+Set 80387 floating-point precision to 32, 64 or 80 bits. When @option{-mpc32}
+is specified, the significands of results of floating-point operations are
+rounded to 24 bits (single precision); @option{-mpc64} rounds the
+significands of results of floating-point operations to 53 bits (double
+precision) and @option{-mpc80} rounds the significands of results of
+floating-point operations to 64 bits (extended double precision), which is
+the default. When this option is used, floating-point operations in higher
+precisions are not available to the programmer without setting the FPU
+control word explicitly.
+
+Setting the rounding of floating-point operations to less than the default
+80 bits can speed some programs by 2% or more. Note that some mathematical
+libraries assume that extended-precision (80-bit) floating-point operations
+are enabled by default; routines in such libraries could suffer significant
+loss of accuracy, typically through so-called ``catastrophic cancellation'',
+when this option is used to set the precision to less than extended precision.
+
+@item -mstackrealign
+@opindex mstackrealign
+Realign the stack at entry. On the x86, the @option{-mstackrealign}
+option generates an alternate prologue and epilogue that realigns the
+run-time stack if necessary. This supports mixing legacy codes that keep
+4-byte stack alignment with modern codes that keep 16-byte stack alignment for
+SSE compatibility. See also the attribute @code{force_align_arg_pointer},
+applicable to individual functions.
+
+@item -mpreferred-stack-boundary=@var{num}
+@opindex mpreferred-stack-boundary
+Attempt to keep the stack boundary aligned to a 2 raised to @var{num}
+byte boundary. If @option{-mpreferred-stack-boundary} is not specified,
+the default is 4 (16 bytes or 128 bits).
+
+@strong{Warning:} When generating code for the x86-64 architecture with
+SSE extensions disabled, @option{-mpreferred-stack-boundary=3} can be
+used to keep the stack boundary aligned to 8 byte boundary. Since
+x86-64 ABI require 16 byte stack alignment, this is ABI incompatible and
+intended to be used in controlled environment where stack space is
+important limitation. This option leads to wrong code when functions
+compiled with 16 byte stack alignment (such as functions from a standard
+library) are called with misaligned stack. In this case, SSE
+instructions may lead to misaligned memory access traps. In addition,
+variable arguments are handled incorrectly for 16 byte aligned
+objects (including x87 long double and __int128), leading to wrong
+results. You must build all modules with
+@option{-mpreferred-stack-boundary=3}, including any libraries. This
+includes the system libraries and startup modules.
+
+@item -mincoming-stack-boundary=@var{num}
+@opindex mincoming-stack-boundary
+Assume the incoming stack is aligned to a 2 raised to @var{num} byte
+boundary. If @option{-mincoming-stack-boundary} is not specified,
+the one specified by @option{-mpreferred-stack-boundary} is used.
+
+On Pentium and Pentium Pro, @code{double} and @code{long double} values
+should be aligned to an 8-byte boundary (see @option{-malign-double}) or
+suffer significant run time performance penalties. On Pentium III, the
+Streaming SIMD Extension (SSE) data type @code{__m128} may not work
+properly if it is not 16-byte aligned.
+
+To ensure proper alignment of this values on the stack, the stack boundary
+must be as aligned as that required by any value stored on the stack.
+Further, every function must be generated such that it keeps the stack
+aligned. Thus calling a function compiled with a higher preferred
+stack boundary from a function compiled with a lower preferred stack
+boundary most likely misaligns the stack. It is recommended that
+libraries that use callbacks always use the default setting.
+
+This extra alignment does consume extra stack space, and generally
+increases code size. Code that is sensitive to stack space usage, such
+as embedded systems and operating system kernels, may want to reduce the
+preferred alignment to @option{-mpreferred-stack-boundary=2}.
+
+@need 200
+@item -mmmx
+@opindex mmmx
+@need 200
+@itemx -msse
+@opindex msse
+@need 200
+@itemx -msse2
+@opindex msse2
+@need 200
+@itemx -msse3
+@opindex msse3
+@need 200
+@itemx -mssse3
+@opindex mssse3
+@need 200
+@itemx -msse4
+@opindex msse4
+@need 200
+@itemx -msse4a
+@opindex msse4a
+@need 200
+@itemx -msse4.1
+@opindex msse4.1
+@need 200
+@itemx -msse4.2
+@opindex msse4.2
+@need 200
+@itemx -mavx
+@opindex mavx
+@need 200
+@itemx -mavx2
+@opindex mavx2
+@need 200
+@itemx -mavx512f
+@opindex mavx512f
+@need 200
+@itemx -mavx512pf
+@opindex mavx512pf
+@need 200
+@itemx -mavx512er
+@opindex mavx512er
+@need 200
+@itemx -mavx512cd
+@opindex mavx512cd
+@need 200
+@itemx -mavx512vl
+@opindex mavx512vl
+@need 200
+@itemx -mavx512bw
+@opindex mavx512bw
+@need 200
+@itemx -mavx512dq
+@opindex mavx512dq
+@need 200
+@itemx -mavx512ifma
+@opindex mavx512ifma
+@need 200
+@itemx -mavx512vbmi
+@opindex mavx512vbmi
+@need 200
+@itemx -msha
+@opindex msha
+@need 200
+@itemx -maes
+@opindex maes
+@need 200
+@itemx -mpclmul
+@opindex mpclmul
+@need 200
+@itemx -mclflushopt
+@opindex mclflushopt
+@need 200
+@itemx -mclwb
+@opindex mclwb
+@need 200
+@itemx -mfsgsbase
+@opindex mfsgsbase
+@need 200
+@itemx -mptwrite
+@opindex mptwrite
+@need 200
+@itemx -mrdrnd
+@opindex mrdrnd
+@need 200
+@itemx -mf16c
+@opindex mf16c
+@need 200
+@itemx -mfma
+@opindex mfma
+@need 200
+@itemx -mpconfig
+@opindex mpconfig
+@need 200
+@itemx -mwbnoinvd
+@opindex mwbnoinvd
+@need 200
+@itemx -mfma4
+@opindex mfma4
+@need 200
+@itemx -mprfchw
+@opindex mprfchw
+@need 200
+@itemx -mrdpid
+@opindex mrdpid
+@need 200
+@itemx -mprefetchwt1
+@opindex mprefetchwt1
+@need 200
+@itemx -mrdseed
+@opindex mrdseed
+@need 200
+@itemx -msgx
+@opindex msgx
+@need 200
+@itemx -mxop
+@opindex mxop
+@need 200
+@itemx -mlwp
+@opindex mlwp
+@need 200
+@itemx -m3dnow
+@opindex m3dnow
+@need 200
+@itemx -m3dnowa
+@opindex m3dnowa
+@need 200
+@itemx -mpopcnt
+@opindex mpopcnt
+@need 200
+@itemx -mabm
+@opindex mabm
+@need 200
+@itemx -madx
+@opindex madx
+@need 200
+@itemx -mbmi
+@opindex mbmi
+@need 200
+@itemx -mbmi2
+@opindex mbmi2
+@need 200
+@itemx -mlzcnt
+@opindex mlzcnt
+@need 200
+@itemx -mfxsr
+@opindex mfxsr
+@need 200
+@itemx -mxsave
+@opindex mxsave
+@need 200
+@itemx -mxsaveopt
+@opindex mxsaveopt
+@need 200
+@itemx -mxsavec
+@opindex mxsavec
+@need 200
+@itemx -mxsaves
+@opindex mxsaves
+@need 200
+@itemx -mrtm
+@opindex mrtm
+@need 200
+@itemx -mhle
+@opindex mhle
+@need 200
+@itemx -mtbm
+@opindex mtbm
+@need 200
+@itemx -mmwaitx
+@opindex mmwaitx
+@need 200
+@itemx -mclzero
+@opindex mclzero
+@need 200
+@itemx -mpku
+@opindex mpku
+@need 200
+@itemx -mavx512vbmi2
+@opindex mavx512vbmi2
+@need 200
+@itemx -mavx512bf16
+@opindex mavx512bf16
+@need 200
+@itemx -mavx512fp16
+@opindex mavx512fp16
+@need 200
+@itemx -mgfni
+@opindex mgfni
+@need 200
+@itemx -mvaes
+@opindex mvaes
+@need 200
+@itemx -mwaitpkg
+@opindex mwaitpkg
+@need 200
+@itemx -mvpclmulqdq
+@opindex mvpclmulqdq
+@need 200
+@itemx -mavx512bitalg
+@opindex mavx512bitalg
+@need 200
+@itemx -mmovdiri
+@opindex mmovdiri
+@need 200
+@itemx -mmovdir64b
+@opindex mmovdir64b
+@need 200
+@itemx -menqcmd
+@opindex menqcmd
+@itemx -muintr
+@opindex muintr
+@need 200
+@itemx -mtsxldtrk
+@opindex mtsxldtrk
+@need 200
+@itemx -mavx512vpopcntdq
+@opindex mavx512vpopcntdq
+@need 200
+@itemx -mavx512vp2intersect
+@opindex mavx512vp2intersect
+@need 200
+@itemx -mavx5124fmaps
+@opindex mavx5124fmaps
+@need 200
+@itemx -mavx512vnni
+@opindex mavx512vnni
+@need 200
+@itemx -mavxvnni
+@opindex mavxvnni
+@need 200
+@itemx -mavx5124vnniw
+@opindex mavx5124vnniw
+@need 200
+@itemx -mcldemote
+@opindex mcldemote
+@need 200
+@itemx -mserialize
+@opindex mserialize
+@need 200
+@itemx -mamx-tile
+@opindex mamx-tile
+@need 200
+@itemx -mamx-int8
+@opindex mamx-int8
+@need 200
+@itemx -mamx-bf16
+@opindex mamx-bf16
+@need 200
+@itemx -mhreset
+@opindex mhreset
+@itemx -mkl
+@opindex mkl
+@need 200
+@itemx -mwidekl
+@opindex mwidekl
+@need 200
+@itemx -mavxifma
+@opindex mavxifma
+@need 200
+@itemx -mavxvnniint8
+@opindex mavxvnniint8
+@need 200
+@itemx -mavxneconvert
+@opindex mavxneconvert
+@need 200
+@itemx -mcmpccxadd
+@opindex mcmpccxadd
+@need 200
+@itemx -mamx-fp16
+@opindex mamx-fp16
+@need 200
+@itemx -mprefetchi
+@opindex mprefetchi
+@need 200
+@itemx -mraoint
+@opindex mraoint
+These switches enable the use of instructions in the MMX, SSE,
+SSE2, SSE3, SSSE3, SSE4, SSE4A, SSE4.1, SSE4.2, AVX, AVX2, AVX512F, AVX512PF,
+AVX512ER, AVX512CD, AVX512VL, AVX512BW, AVX512DQ, AVX512IFMA, AVX512VBMI, SHA,
+AES, PCLMUL, CLFLUSHOPT, CLWB, FSGSBASE, PTWRITE, RDRND, F16C, FMA, PCONFIG,
+WBNOINVD, FMA4, PREFETCHW, RDPID, PREFETCHWT1, RDSEED, SGX, XOP, LWP,
+3DNow!@:, enhanced 3DNow!@:, POPCNT, ABM, ADX, BMI, BMI2, LZCNT, FXSR, XSAVE,
+XSAVEOPT, XSAVEC, XSAVES, RTM, HLE, TBM, MWAITX, CLZERO, PKU, AVX512VBMI2,
+GFNI, VAES, WAITPKG, VPCLMULQDQ, AVX512BITALG, MOVDIRI, MOVDIR64B, AVX512BF16,
+ENQCMD, AVX512VPOPCNTDQ, AVX5124FMAPS, AVX512VNNI, AVX5124VNNIW, SERIALIZE,
+UINTR, HRESET, AMXTILE, AMXINT8, AMXBF16, KL, WIDEKL, AVXVNNI, AVX512FP16,
+AVXIFMA, AVXVNNIINT8, AVXNECONVERT, CMPCCXADD, AMX-FP16, PREFETCHI, RAOINT or
+CLDEMOTE extended instruction sets. Each has a corresponding @option{-mno-}
+option to disable use of these instructions.
+
+These extensions are also available as built-in functions: see
+@ref{x86 Built-in Functions}, for details of the functions enabled and
+disabled by these switches.
+
+To generate SSE/SSE2 instructions automatically from floating-point
+code (as opposed to 387 instructions), see @option{-mfpmath=sse}.
+
+GCC depresses SSEx instructions when @option{-mavx} is used. Instead, it
+generates new AVX instructions or AVX equivalence for all SSEx instructions
+when needed.
+
+These options enable GCC to use these extended instructions in
+generated code, even without @option{-mfpmath=sse}. Applications that
+perform run-time CPU detection must compile separate files for each
+supported architecture, using the appropriate flags. In particular,
+the file containing the CPU detection code should be compiled without
+these options.
+
+@item -mdump-tune-features
+@opindex mdump-tune-features
+This option instructs GCC to dump the names of the x86 performance
+tuning features and default settings. The names can be used in
+@option{-mtune-ctrl=@var{feature-list}}.
+
+@item -mtune-ctrl=@var{feature-list}
+@opindex mtune-ctrl=@var{feature-list}
+This option is used to do fine grain control of x86 code generation features.
+@var{feature-list} is a comma separated list of @var{feature} names. See also
+@option{-mdump-tune-features}. When specified, the @var{feature} is turned
+on if it is not preceded with @samp{^}, otherwise, it is turned off.
+@option{-mtune-ctrl=@var{feature-list}} is intended to be used by GCC
+developers. Using it may lead to code paths not covered by testing and can
+potentially result in compiler ICEs or runtime errors.
+
+@item -mno-default
+@opindex mno-default
+This option instructs GCC to turn off all tunable features. See also
+@option{-mtune-ctrl=@var{feature-list}} and @option{-mdump-tune-features}.
+
+@item -mcld
+@opindex mcld
+This option instructs GCC to emit a @code{cld} instruction in the prologue
+of functions that use string instructions. String instructions depend on
+the DF flag to select between autoincrement or autodecrement mode. While the
+ABI specifies the DF flag to be cleared on function entry, some operating
+systems violate this specification by not clearing the DF flag in their
+exception dispatchers. The exception handler can be invoked with the DF flag
+set, which leads to wrong direction mode when string instructions are used.
+This option can be enabled by default on 32-bit x86 targets by configuring
+GCC with the @option{--enable-cld} configure option. Generation of @code{cld}
+instructions can be suppressed with the @option{-mno-cld} compiler option
+in this case.
+
+@item -mvzeroupper
+@opindex mvzeroupper
+This option instructs GCC to emit a @code{vzeroupper} instruction
+before a transfer of control flow out of the function to minimize
+the AVX to SSE transition penalty as well as remove unnecessary @code{zeroupper}
+intrinsics.
+
+@item -mprefer-avx128
+@opindex mprefer-avx128
+This option instructs GCC to use 128-bit AVX instructions instead of
+256-bit AVX instructions in the auto-vectorizer.
+
+@item -mprefer-vector-width=@var{opt}
+@opindex mprefer-vector-width
+This option instructs GCC to use @var{opt}-bit vector width in instructions
+instead of default on the selected platform.
+
+@item -mmove-max=@var{bits}
+@opindex mmove-max
+This option instructs GCC to set the maximum number of bits can be
+moved from memory to memory efficiently to @var{bits}. The valid
+@var{bits} are 128, 256 and 512.
+
+@item -mstore-max=@var{bits}
+@opindex mstore-max
+This option instructs GCC to set the maximum number of bits can be
+stored to memory efficiently to @var{bits}. The valid @var{bits} are
+128, 256 and 512.
+
+@table @samp
+@item none
+No extra limitations applied to GCC other than defined by the selected platform.
+
+@item 128
+Prefer 128-bit vector width for instructions.
+
+@item 256
+Prefer 256-bit vector width for instructions.
+
+@item 512
+Prefer 512-bit vector width for instructions.
+@end table
+
+@item -mcx16
+@opindex mcx16
+This option enables GCC to generate @code{CMPXCHG16B} instructions in 64-bit
+code to implement compare-and-exchange operations on 16-byte aligned 128-bit
+objects. This is useful for atomic updates of data structures exceeding one
+machine word in size. The compiler uses this instruction to implement
+@ref{__sync Builtins}. However, for @ref{__atomic Builtins} operating on
+128-bit integers, a library call is always used.
+
+@item -msahf
+@opindex msahf
+This option enables generation of @code{SAHF} instructions in 64-bit code.
+Early Intel Pentium 4 CPUs with Intel 64 support,
+prior to the introduction of Pentium 4 G1 step in December 2005,
+lacked the @code{LAHF} and @code{SAHF} instructions
+which are supported by AMD64.
+These are load and store instructions, respectively, for certain status flags.
+In 64-bit mode, the @code{SAHF} instruction is used to optimize @code{fmod},
+@code{drem}, and @code{remainder} built-in functions;
+see @ref{Other Builtins} for details.
+
+@item -mmovbe
+@opindex mmovbe
+This option enables use of the @code{movbe} instruction to implement
+@code{__builtin_bswap32} and @code{__builtin_bswap64}.
+
+@item -mshstk
+@opindex mshstk
+The @option{-mshstk} option enables shadow stack built-in functions
+from x86 Control-flow Enforcement Technology (CET).
+
+@item -mcrc32
+@opindex mcrc32
+This option enables built-in functions @code{__builtin_ia32_crc32qi},
+@code{__builtin_ia32_crc32hi}, @code{__builtin_ia32_crc32si} and
+@code{__builtin_ia32_crc32di} to generate the @code{crc32} machine instruction.
+
+@item -mmwait
+@opindex mmwait
+This option enables built-in functions @code{__builtin_ia32_monitor},
+and @code{__builtin_ia32_mwait} to generate the @code{monitor} and
+@code{mwait} machine instructions.
+
+@item -mrecip
+@opindex mrecip
+This option enables use of @code{RCPSS} and @code{RSQRTSS} instructions
+(and their vectorized variants @code{RCPPS} and @code{RSQRTPS})
+with an additional Newton-Raphson step
+to increase precision instead of @code{DIVSS} and @code{SQRTSS}
+(and their vectorized
+variants) for single-precision floating-point arguments. These instructions
+are generated only when @option{-funsafe-math-optimizations} is enabled
+together with @option{-ffinite-math-only} and @option{-fno-trapping-math}.
+Note that while the throughput of the sequence is higher than the throughput
+of the non-reciprocal instruction, the precision of the sequence can be
+decreased by up to 2 ulp (i.e.@: the inverse of 1.0 equals 0.99999994).
+
+Note that GCC implements @code{1.0f/sqrtf(@var{x})} in terms of @code{RSQRTSS}
+(or @code{RSQRTPS}) already with @option{-ffast-math} (or the above option
+combination), and doesn't need @option{-mrecip}.
+
+Also note that GCC emits the above sequence with additional Newton-Raphson step
+for vectorized single-float division and vectorized @code{sqrtf(@var{x})}
+already with @option{-ffast-math} (or the above option combination), and
+doesn't need @option{-mrecip}.
+
+@item -mrecip=@var{opt}
+@opindex mrecip=opt
+This option controls which reciprocal estimate instructions
+may be used. @var{opt} is a comma-separated list of options, which may
+be preceded by a @samp{!} to invert the option:
+
+@table @samp
+@item all
+Enable all estimate instructions.
+
+@item default
+Enable the default instructions, equivalent to @option{-mrecip}.
+
+@item none
+Disable all estimate instructions, equivalent to @option{-mno-recip}.
+
+@item div
+Enable the approximation for scalar division.
+
+@item vec-div
+Enable the approximation for vectorized division.
+
+@item sqrt
+Enable the approximation for scalar square root.
+
+@item vec-sqrt
+Enable the approximation for vectorized square root.
+@end table
+
+So, for example, @option{-mrecip=all,!sqrt} enables
+all of the reciprocal approximations, except for square root.
+
+@item -mveclibabi=@var{type}
+@opindex mveclibabi
+Specifies the ABI type to use for vectorizing intrinsics using an
+external library. Supported values for @var{type} are @samp{svml}
+for the Intel short
+vector math library and @samp{acml} for the AMD math core library.
+To use this option, both @option{-ftree-vectorize} and
+@option{-funsafe-math-optimizations} have to be enabled, and an SVML or ACML
+ABI-compatible library must be specified at link time.
+
+GCC currently emits calls to @code{vmldExp2},
+@code{vmldLn2}, @code{vmldLog102}, @code{vmldPow2},
+@code{vmldTanh2}, @code{vmldTan2}, @code{vmldAtan2}, @code{vmldAtanh2},
+@code{vmldCbrt2}, @code{vmldSinh2}, @code{vmldSin2}, @code{vmldAsinh2},
+@code{vmldAsin2}, @code{vmldCosh2}, @code{vmldCos2}, @code{vmldAcosh2},
+@code{vmldAcos2}, @code{vmlsExp4}, @code{vmlsLn4},
+@code{vmlsLog104}, @code{vmlsPow4}, @code{vmlsTanh4}, @code{vmlsTan4},
+@code{vmlsAtan4}, @code{vmlsAtanh4}, @code{vmlsCbrt4}, @code{vmlsSinh4},
+@code{vmlsSin4}, @code{vmlsAsinh4}, @code{vmlsAsin4}, @code{vmlsCosh4},
+@code{vmlsCos4}, @code{vmlsAcosh4} and @code{vmlsAcos4} for corresponding
+function type when @option{-mveclibabi=svml} is used, and @code{__vrd2_sin},
+@code{__vrd2_cos}, @code{__vrd2_exp}, @code{__vrd2_log}, @code{__vrd2_log2},
+@code{__vrd2_log10}, @code{__vrs4_sinf}, @code{__vrs4_cosf},
+@code{__vrs4_expf}, @code{__vrs4_logf}, @code{__vrs4_log2f},
+@code{__vrs4_log10f} and @code{__vrs4_powf} for the corresponding function type
+when @option{-mveclibabi=acml} is used.
+
+@item -mabi=@var{name}
+@opindex mabi
+Generate code for the specified calling convention. Permissible values
+are @samp{sysv} for the ABI used on GNU/Linux and other systems, and
+@samp{ms} for the Microsoft ABI. The default is to use the Microsoft
+ABI when targeting Microsoft Windows and the SysV ABI on all other systems.
+You can control this behavior for specific functions by
+using the function attributes @code{ms_abi} and @code{sysv_abi}.
+@xref{Function Attributes}.
+
+@item -mforce-indirect-call
+@opindex mforce-indirect-call
+Force all calls to functions to be indirect. This is useful
+when using Intel Processor Trace where it generates more precise timing
+information for function calls.
+
+@item -mmanual-endbr
+@opindex mmanual-endbr
+Insert ENDBR instruction at function entry only via the @code{cf_check}
+function attribute. This is useful when used with the option
+@option{-fcf-protection=branch} to control ENDBR insertion at the
+function entry.
+
+@item -mcet-switch
+@opindex mcet-switch
+By default, CET instrumentation is turned off on switch statements that
+use a jump table and indirect branch track is disabled. Since jump
+tables are stored in read-only memory, this does not result in a direct
+loss of hardening. But if the jump table index is attacker-controlled,
+the indirect jump may not be constrained by CET. This option turns on
+CET instrumentation to enable indirect branch track for switch statements
+with jump tables which leads to the jump targets reachable via any indirect
+jumps.
+
+@item -mcall-ms2sysv-xlogues
+@opindex mcall-ms2sysv-xlogues
+@opindex mno-call-ms2sysv-xlogues
+Due to differences in 64-bit ABIs, any Microsoft ABI function that calls a
+System V ABI function must consider RSI, RDI and XMM6-15 as clobbered. By
+default, the code for saving and restoring these registers is emitted inline,
+resulting in fairly lengthy prologues and epilogues. Using
+@option{-mcall-ms2sysv-xlogues} emits prologues and epilogues that
+use stubs in the static portion of libgcc to perform these saves and restores,
+thus reducing function size at the cost of a few extra instructions.
+
+@item -mtls-dialect=@var{type}
+@opindex mtls-dialect
+Generate code to access thread-local storage using the @samp{gnu} or
+@samp{gnu2} conventions. @samp{gnu} is the conservative default;
+@samp{gnu2} is more efficient, but it may add compile- and run-time
+requirements that cannot be satisfied on all systems.
+
+@item -mpush-args
+@itemx -mno-push-args
+@opindex mpush-args
+@opindex mno-push-args
+Use PUSH operations to store outgoing parameters. This method is shorter
+and usually equally fast as method using SUB/MOV operations and is enabled
+by default. In some cases disabling it may improve performance because of
+improved scheduling and reduced dependencies.
+
+@item -maccumulate-outgoing-args
+@opindex maccumulate-outgoing-args
+If enabled, the maximum amount of space required for outgoing arguments is
+computed in the function prologue. This is faster on most modern CPUs
+because of reduced dependencies, improved scheduling and reduced stack usage
+when the preferred stack boundary is not equal to 2. The drawback is a notable
+increase in code size. This switch implies @option{-mno-push-args}.
+
+@item -mthreads
+@opindex mthreads
+Support thread-safe exception handling on MinGW. Programs that rely
+on thread-safe exception handling must compile and link all code with the
+@option{-mthreads} option. When compiling, @option{-mthreads} defines
+@option{-D_MT}; when linking, it links in a special thread helper library
+@option{-lmingwthrd} which cleans up per-thread exception-handling data.
+
+@item -mms-bitfields
+@itemx -mno-ms-bitfields
+@opindex mms-bitfields
+@opindex mno-ms-bitfields
+
+Enable/disable bit-field layout compatible with the native Microsoft
+Windows compiler.
+
+If @code{packed} is used on a structure, or if bit-fields are used,
+it may be that the Microsoft ABI lays out the structure differently
+than the way GCC normally does. Particularly when moving packed
+data between functions compiled with GCC and the native Microsoft compiler
+(either via function call or as data in a file), it may be necessary to access
+either format.
+
+This option is enabled by default for Microsoft Windows
+targets. This behavior can also be controlled locally by use of variable
+or type attributes. For more information, see @ref{x86 Variable Attributes}
+and @ref{x86 Type Attributes}.
+
+The Microsoft structure layout algorithm is fairly simple with the exception
+of the bit-field packing.
+The padding and alignment of members of structures and whether a bit-field
+can straddle a storage-unit boundary are determine by these rules:
+
+@enumerate
+@item Structure members are stored sequentially in the order in which they are
+declared: the first member has the lowest memory address and the last member
+the highest.
+
+@item Every data object has an alignment requirement. The alignment requirement
+for all data except structures, unions, and arrays is either the size of the
+object or the current packing size (specified with either the
+@code{aligned} attribute or the @code{pack} pragma),
+whichever is less. For structures, unions, and arrays,
+the alignment requirement is the largest alignment requirement of its members.
+Every object is allocated an offset so that:
+
+@smallexample
+offset % alignment_requirement == 0
+@end smallexample
+
+@item Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte allocation
+unit if the integral types are the same size and if the next bit-field fits
+into the current allocation unit without crossing the boundary imposed by the
+common alignment requirements of the bit-fields.
+@end enumerate
+
+MSVC interprets zero-length bit-fields in the following ways:
+
+@enumerate
+@item If a zero-length bit-field is inserted between two bit-fields that
+are normally coalesced, the bit-fields are not coalesced.
+
+For example:
+
+@smallexample
+struct
+ @{
+ unsigned long bf_1 : 12;
+ unsigned long : 0;
+ unsigned long bf_2 : 12;
+ @} t1;
+@end smallexample
+
+@noindent
+The size of @code{t1} is 8 bytes with the zero-length bit-field. If the
+zero-length bit-field were removed, @code{t1}'s size would be 4 bytes.
+
+@item If a zero-length bit-field is inserted after a bit-field, @code{foo}, and the
+alignment of the zero-length bit-field is greater than the member that follows it,
+@code{bar}, @code{bar} is aligned as the type of the zero-length bit-field.
+
+For example:
+
+@smallexample
+struct
+ @{
+ char foo : 4;
+ short : 0;
+ char bar;
+ @} t2;
+
+struct
+ @{
+ char foo : 4;
+ short : 0;
+ double bar;
+ @} t3;
+@end smallexample
+
+@noindent
+For @code{t2}, @code{bar} is placed at offset 2, rather than offset 1.
+Accordingly, the size of @code{t2} is 4. For @code{t3}, the zero-length
+bit-field does not affect the alignment of @code{bar} or, as a result, the size
+of the structure.
+
+Taking this into account, it is important to note the following:
+
+@enumerate
+@item If a zero-length bit-field follows a normal bit-field, the type of the
+zero-length bit-field may affect the alignment of the structure as whole. For
+example, @code{t2} has a size of 4 bytes, since the zero-length bit-field follows a
+normal bit-field, and is of type short.
+
+@item Even if a zero-length bit-field is not followed by a normal bit-field, it may
+still affect the alignment of the structure:
+
+@smallexample
+struct
+ @{
+ char foo : 6;
+ long : 0;
+ @} t4;
+@end smallexample
+
+@noindent
+Here, @code{t4} takes up 4 bytes.
+@end enumerate
+
+@item Zero-length bit-fields following non-bit-field members are ignored:
+
+@smallexample
+struct
+ @{
+ char foo;
+ long : 0;
+ char bar;
+ @} t5;
+@end smallexample
+
+@noindent
+Here, @code{t5} takes up 2 bytes.
+@end enumerate
+
+
+@item -mno-align-stringops
+@opindex mno-align-stringops
+@opindex malign-stringops
+Do not align the destination of inlined string operations. This switch reduces
+code size and improves performance in case the destination is already aligned,
+but GCC doesn't know about it.
+
+@item -minline-all-stringops
+@opindex minline-all-stringops
+By default GCC inlines string operations only when the destination is
+known to be aligned to least a 4-byte boundary.
+This enables more inlining and increases code
+size, but may improve performance of code that depends on fast
+@code{memcpy} and @code{memset} for short lengths.
+The option enables inline expansion of @code{strlen} for all
+pointer alignments.
+
+@item -minline-stringops-dynamically
+@opindex minline-stringops-dynamically
+For string operations of unknown size, use run-time checks with
+inline code for small blocks and a library call for large blocks.
+
+@item -mstringop-strategy=@var{alg}
+@opindex mstringop-strategy=@var{alg}
+Override the internal decision heuristic for the particular algorithm to use
+for inlining string operations. The allowed values for @var{alg} are:
+
+@table @samp
+@item rep_byte
+@itemx rep_4byte
+@itemx rep_8byte
+Expand using i386 @code{rep} prefix of the specified size.
+
+@item byte_loop
+@itemx loop
+@itemx unrolled_loop
+Expand into an inline loop.
+
+@item libcall
+Always use a library call.
+@end table
+
+@item -mmemcpy-strategy=@var{strategy}
+@opindex mmemcpy-strategy=@var{strategy}
+Override the internal decision heuristic to decide if @code{__builtin_memcpy}
+should be inlined and what inline algorithm to use when the expected size
+of the copy operation is known. @var{strategy}
+is a comma-separated list of @var{alg}:@var{max_size}:@var{dest_align} triplets.
+@var{alg} is specified in @option{-mstringop-strategy}, @var{max_size} specifies
+the max byte size with which inline algorithm @var{alg} is allowed. For the last
+triplet, the @var{max_size} must be @code{-1}. The @var{max_size} of the triplets
+in the list must be specified in increasing order. The minimal byte size for
+@var{alg} is @code{0} for the first triplet and @code{@var{max_size} + 1} of the
+preceding range.
+
+@item -mmemset-strategy=@var{strategy}
+@opindex mmemset-strategy=@var{strategy}
+The option is similar to @option{-mmemcpy-strategy=} except that it is to control
+@code{__builtin_memset} expansion.
+
+@item -momit-leaf-frame-pointer
+@opindex momit-leaf-frame-pointer
+Don't keep the frame pointer in a register for leaf functions. This
+avoids the instructions to save, set up, and restore frame pointers and
+makes an extra register available in leaf functions. The option
+@option{-fomit-leaf-frame-pointer} removes the frame pointer for leaf functions,
+which might make debugging harder.
+
+@item -mtls-direct-seg-refs
+@itemx -mno-tls-direct-seg-refs
+@opindex mtls-direct-seg-refs
+Controls whether TLS variables may be accessed with offsets from the
+TLS segment register (@code{%gs} for 32-bit, @code{%fs} for 64-bit),
+or whether the thread base pointer must be added. Whether or not this
+is valid depends on the operating system, and whether it maps the
+segment to cover the entire TLS area.
+
+For systems that use the GNU C Library, the default is on.
+
+@item -msse2avx
+@itemx -mno-sse2avx
+@opindex msse2avx
+Specify that the assembler should encode SSE instructions with VEX
+prefix. The option @option{-mavx} turns this on by default.
+
+@item -mfentry
+@itemx -mno-fentry
+@opindex mfentry
+If profiling is active (@option{-pg}), put the profiling
+counter call before the prologue.
+Note: On x86 architectures the attribute @code{ms_hook_prologue}
+isn't possible at the moment for @option{-mfentry} and @option{-pg}.
+
+@item -mrecord-mcount
+@itemx -mno-record-mcount
+@opindex mrecord-mcount
+If profiling is active (@option{-pg}), generate a __mcount_loc section
+that contains pointers to each profiling call. This is useful for
+automatically patching and out calls.
+
+@item -mnop-mcount
+@itemx -mno-nop-mcount
+@opindex mnop-mcount
+If profiling is active (@option{-pg}), generate the calls to
+the profiling functions as NOPs. This is useful when they
+should be patched in later dynamically. This is likely only
+useful together with @option{-mrecord-mcount}.
+
+@item -minstrument-return=@var{type}
+@opindex minstrument-return
+Instrument function exit in -pg -mfentry instrumented functions with
+call to specified function. This only instruments true returns ending
+with ret, but not sibling calls ending with jump. Valid types
+are @var{none} to not instrument, @var{call} to generate a call to __return__,
+or @var{nop5} to generate a 5 byte nop.
+
+@item -mrecord-return
+@itemx -mno-record-return
+@opindex mrecord-return
+Generate a __return_loc section pointing to all return instrumentation code.
+
+@item -mfentry-name=@var{name}
+@opindex mfentry-name
+Set name of __fentry__ symbol called at function entry for -pg -mfentry functions.
+
+@item -mfentry-section=@var{name}
+@opindex mfentry-section
+Set name of section to record -mrecord-mcount calls (default __mcount_loc).
+
+@item -mskip-rax-setup
+@itemx -mno-skip-rax-setup
+@opindex mskip-rax-setup
+When generating code for the x86-64 architecture with SSE extensions
+disabled, @option{-mskip-rax-setup} can be used to skip setting up RAX
+register when there are no variable arguments passed in vector registers.
+
+@strong{Warning:} Since RAX register is used to avoid unnecessarily
+saving vector registers on stack when passing variable arguments, the
+impacts of this option are callees may waste some stack space,
+misbehave or jump to a random location. GCC 4.4 or newer don't have
+those issues, regardless the RAX register value.
+
+@item -m8bit-idiv
+@itemx -mno-8bit-idiv
+@opindex m8bit-idiv
+On some processors, like Intel Atom, 8-bit unsigned integer divide is
+much faster than 32-bit/64-bit integer divide. This option generates a
+run-time check. If both dividend and divisor are within range of 0
+to 255, 8-bit unsigned integer divide is used instead of
+32-bit/64-bit integer divide.
+
+@item -mavx256-split-unaligned-load
+@itemx -mavx256-split-unaligned-store
+@opindex mavx256-split-unaligned-load
+@opindex mavx256-split-unaligned-store
+Split 32-byte AVX unaligned load and store.
+
+@item -mstack-protector-guard=@var{guard}
+@itemx -mstack-protector-guard-reg=@var{reg}
+@itemx -mstack-protector-guard-offset=@var{offset}
+@opindex mstack-protector-guard
+@opindex mstack-protector-guard-reg
+@opindex mstack-protector-guard-offset
+Generate stack protection code using canary at @var{guard}. Supported
+locations are @samp{global} for global canary or @samp{tls} for per-thread
+canary in the TLS block (the default). This option has effect only when
+@option{-fstack-protector} or @option{-fstack-protector-all} is specified.
+
+With the latter choice the options
+@option{-mstack-protector-guard-reg=@var{reg}} and
+@option{-mstack-protector-guard-offset=@var{offset}} furthermore specify
+which segment register (@code{%fs} or @code{%gs}) to use as base register
+for reading the canary, and from what offset from that base register.
+The default for those is as specified in the relevant ABI.
+
+@item -mgeneral-regs-only
+@opindex mgeneral-regs-only
+Generate code that uses only the general-purpose registers. This
+prevents the compiler from using floating-point, vector, mask and bound
+registers.
+
+@item -mrelax-cmpxchg-loop
+@opindex mrelax-cmpxchg-loop
+Relax cmpxchg loop by emitting an early load and compare before cmpxchg,
+execute pause if load value is not expected. This reduces excessive
+cachline bouncing when and works for all atomic logic fetch builtins
+that generates compare and swap loop.
+
+@item -mindirect-branch=@var{choice}
+@opindex mindirect-branch
+Convert indirect call and jump with @var{choice}. The default is
+@samp{keep}, which keeps indirect call and jump unmodified.
+@samp{thunk} converts indirect call and jump to call and return thunk.
+@samp{thunk-inline} converts indirect call and jump to inlined call
+and return thunk. @samp{thunk-extern} converts indirect call and jump
+to external call and return thunk provided in a separate object file.
+You can control this behavior for a specific function by using the
+function attribute @code{indirect_branch}. @xref{Function Attributes}.
+
+Note that @option{-mcmodel=large} is incompatible with
+@option{-mindirect-branch=thunk} and
+@option{-mindirect-branch=thunk-extern} since the thunk function may
+not be reachable in the large code model.
+
+Note that @option{-mindirect-branch=thunk-extern} is compatible with
+@option{-fcf-protection=branch} since the external thunk can be made
+to enable control-flow check.
+
+@item -mfunction-return=@var{choice}
+@opindex mfunction-return
+Convert function return with @var{choice}. The default is @samp{keep},
+which keeps function return unmodified. @samp{thunk} converts function
+return to call and return thunk. @samp{thunk-inline} converts function
+return to inlined call and return thunk. @samp{thunk-extern} converts
+function return to external call and return thunk provided in a separate
+object file. You can control this behavior for a specific function by
+using the function attribute @code{function_return}.
+@xref{Function Attributes}.
+
+Note that @option{-mindirect-return=thunk-extern} is compatible with
+@option{-fcf-protection=branch} since the external thunk can be made
+to enable control-flow check.
+
+Note that @option{-mcmodel=large} is incompatible with
+@option{-mfunction-return=thunk} and
+@option{-mfunction-return=thunk-extern} since the thunk function may
+not be reachable in the large code model.
+
+
+@item -mindirect-branch-register
+@opindex mindirect-branch-register
+Force indirect call and jump via register.
+
+@item -mharden-sls=@var{choice}
+@opindex mharden-sls
+Generate code to mitigate against straight line speculation (SLS) with
+@var{choice}. The default is @samp{none} which disables all SLS
+hardening. @samp{return} enables SLS hardening for function returns.
+@samp{indirect-jmp} enables SLS hardening for indirect jumps.
+@samp{all} enables all SLS hardening.
+
+@item -mindirect-branch-cs-prefix
+@opindex mindirect-branch-cs-prefix
+Add CS prefix to call and jmp to indirect thunk with branch target in
+r8-r15 registers so that the call and jmp instruction length is 6 bytes
+to allow them to be replaced with @samp{lfence; call *%r8-r15} or
+@samp{lfence; jmp *%r8-r15} at run-time.
+
+@end table
+
+These @samp{-m} switches are supported in addition to the above
+on x86-64 processors in 64-bit environments.
+
+@table @gcctabopt
+@item -m32
+@itemx -m64
+@itemx -mx32
+@itemx -m16
+@itemx -miamcu
+@opindex m32
+@opindex m64
+@opindex mx32
+@opindex m16
+@opindex miamcu
+Generate code for a 16-bit, 32-bit or 64-bit environment.
+The @option{-m32} option sets @code{int}, @code{long}, and pointer types
+to 32 bits, and
+generates code that runs on any i386 system.
+
+The @option{-m64} option sets @code{int} to 32 bits and @code{long} and pointer
+types to 64 bits, and generates code for the x86-64 architecture.
+For Darwin only the @option{-m64} option also turns off the @option{-fno-pic}
+and @option{-mdynamic-no-pic} options.
+
+The @option{-mx32} option sets @code{int}, @code{long}, and pointer types
+to 32 bits, and
+generates code for the x86-64 architecture.
+
+The @option{-m16} option is the same as @option{-m32}, except for that
+it outputs the @code{.code16gcc} assembly directive at the beginning of
+the assembly output so that the binary can run in 16-bit mode.
+
+The @option{-miamcu} option generates code which conforms to Intel MCU
+psABI. It requires the @option{-m32} option to be turned on.
+
+@item -mno-red-zone
+@opindex mno-red-zone
+@opindex mred-zone
+Do not use a so-called ``red zone'' for x86-64 code. The red zone is mandated
+by the x86-64 ABI; it is a 128-byte area beyond the location of the
+stack pointer that is not modified by signal or interrupt handlers
+and therefore can be used for temporary data without adjusting the stack
+pointer. The flag @option{-mno-red-zone} disables this red zone.
+
+@item -mcmodel=small
+@opindex mcmodel=small
+Generate code for the small code model: the program and its symbols must
+be linked in the lower 2 GB of the address space. Pointers are 64 bits.
+Programs can be statically or dynamically linked. This is the default
+code model.
+
+@item -mcmodel=kernel
+@opindex mcmodel=kernel
+Generate code for the kernel code model. The kernel runs in the
+negative 2 GB of the address space.
+This model has to be used for Linux kernel code.
+
+@item -mcmodel=medium
+@opindex mcmodel=medium
+Generate code for the medium model: the program is linked in the lower 2
+GB of the address space. Small symbols are also placed there. Symbols
+with sizes larger than @option{-mlarge-data-threshold} are put into
+large data or BSS sections and can be located above 2GB. Programs can
+be statically or dynamically linked.
+
+@item -mcmodel=large
+@opindex mcmodel=large
+Generate code for the large model. This model makes no assumptions
+about addresses and sizes of sections.
+
+@item -maddress-mode=long
+@opindex maddress-mode=long
+Generate code for long address mode. This is only supported for 64-bit
+and x32 environments. It is the default address mode for 64-bit
+environments.
+
+@item -maddress-mode=short
+@opindex maddress-mode=short
+Generate code for short address mode. This is only supported for 32-bit
+and x32 environments. It is the default address mode for 32-bit and
+x32 environments.
+
+@item -mneeded
+@itemx -mno-needed
+@opindex mneeded
+Emit GNU_PROPERTY_X86_ISA_1_NEEDED GNU property for Linux target to
+indicate the micro-architecture ISA level required to execute the binary.
+
+@item -mno-direct-extern-access
+@opindex mno-direct-extern-access
+@opindex mdirect-extern-access
+Without @option{-fpic} nor @option{-fPIC}, always use the GOT pointer
+to access external symbols. With @option{-fpic} or @option{-fPIC},
+treat access to protected symbols as local symbols. The default is
+@option{-mdirect-extern-access}.
+
+@strong{Warning:} shared libraries compiled with
+@option{-mno-direct-extern-access} and executable compiled with
+@option{-mdirect-extern-access} may not be binary compatible if
+protected symbols are used in shared libraries and executable.
+@end table
+
+@node x86 Windows Options
+@subsection x86 Windows Options
+@cindex x86 Windows Options
+@cindex Windows Options for x86
+
+These additional options are available for Microsoft Windows targets:
+
+@table @gcctabopt
+@item -mconsole
+@opindex mconsole
+This option
+specifies that a console application is to be generated, by
+instructing the linker to set the PE header subsystem type
+required for console applications.
+This option is available for Cygwin and MinGW targets and is
+enabled by default on those targets.
+
+@item -mdll
+@opindex mdll
+This option is available for Cygwin and MinGW targets. It
+specifies that a DLL---a dynamic link library---is to be
+generated, enabling the selection of the required runtime
+startup object and entry point.
+
+@item -mnop-fun-dllimport
+@opindex mnop-fun-dllimport
+This option is available for Cygwin and MinGW targets. It
+specifies that the @code{dllimport} attribute should be ignored.
+
+@item -mthreads
+@opindex mthreads
+This option is available for MinGW targets. It specifies
+that MinGW-specific thread support is to be used.
+
+@item -municode
+@opindex municode
+This option is available for MinGW-w64 targets. It causes
+the @code{UNICODE} preprocessor macro to be predefined, and
+chooses Unicode-capable runtime startup code.
+
+@item -mwin32
+@opindex mwin32
+This option is available for Cygwin and MinGW targets. It
+specifies that the typical Microsoft Windows predefined macros are to
+be set in the pre-processor, but does not influence the choice
+of runtime library/startup code.
+
+@item -mwindows
+@opindex mwindows
+This option is available for Cygwin and MinGW targets. It
+specifies that a GUI application is to be generated by
+instructing the linker to set the PE header subsystem type
+appropriately.
+
+@item -fno-set-stack-executable
+@opindex fno-set-stack-executable
+@opindex fset-stack-executable
+This option is available for MinGW targets. It specifies that
+the executable flag for the stack used by nested functions isn't
+set. This is necessary for binaries running in kernel mode of
+Microsoft Windows, as there the User32 API, which is used to set executable
+privileges, isn't available.
+
+@item -fwritable-relocated-rdata
+@opindex fno-writable-relocated-rdata
+@opindex fwritable-relocated-rdata
+This option is available for MinGW and Cygwin targets. It specifies
+that relocated-data in read-only section is put into the @code{.data}
+section. This is a necessary for older runtimes not supporting
+modification of @code{.rdata} sections for pseudo-relocation.
+
+@item -mpe-aligned-commons
+@opindex mpe-aligned-commons
+This option is available for Cygwin and MinGW targets. It
+specifies that the GNU extension to the PE file format that
+permits the correct alignment of COMMON variables should be
+used when generating code. It is enabled by default if
+GCC detects that the target assembler found during configuration
+supports the feature.
+@end table
+
+See also under @ref{x86 Options} for standard options.
+
+@node Xstormy16 Options
+@subsection Xstormy16 Options
+@cindex Xstormy16 Options
+
+These options are defined for Xstormy16:
+
+@table @gcctabopt
+@item -msim
+@opindex msim
+Choose startup files and linker script suitable for the simulator.
+@end table
+
+@node Xtensa Options
+@subsection Xtensa Options
+@cindex Xtensa Options
+
+These options are supported for Xtensa targets:
+
+@table @gcctabopt
+@item -mconst16
+@itemx -mno-const16
+@opindex mconst16
+@opindex mno-const16
+Enable or disable use of @code{CONST16} instructions for loading
+constant values. The @code{CONST16} instruction is currently not a
+standard option from Tensilica. When enabled, @code{CONST16}
+instructions are always used in place of the standard @code{L32R}
+instructions. The use of @code{CONST16} is enabled by default only if
+the @code{L32R} instruction is not available.
+
+@item -mfused-madd
+@itemx -mno-fused-madd
+@opindex mfused-madd
+@opindex mno-fused-madd
+Enable or disable use of fused multiply/add and multiply/subtract
+instructions in the floating-point option. This has no effect if the
+floating-point option is not also enabled. Disabling fused multiply/add
+and multiply/subtract instructions forces the compiler to use separate
+instructions for the multiply and add/subtract operations. This may be
+desirable in some cases where strict IEEE 754-compliant results are
+required: the fused multiply add/subtract instructions do not round the
+intermediate result, thereby producing results with @emph{more} bits of
+precision than specified by the IEEE standard. Disabling fused multiply
+add/subtract instructions also ensures that the program output is not
+sensitive to the compiler's ability to combine multiply and add/subtract
+operations.
+
+@item -mserialize-volatile
+@itemx -mno-serialize-volatile
+@opindex mserialize-volatile
+@opindex mno-serialize-volatile
+When this option is enabled, GCC inserts @code{MEMW} instructions before
+@code{volatile} memory references to guarantee sequential consistency.
+The default is @option{-mserialize-volatile}. Use
+@option{-mno-serialize-volatile} to omit the @code{MEMW} instructions.
+
+@item -mforce-no-pic
+@opindex mforce-no-pic
+For targets, like GNU/Linux, where all user-mode Xtensa code must be
+position-independent code (PIC), this option disables PIC for compiling
+kernel code.
+
+@item -mtext-section-literals
+@itemx -mno-text-section-literals
+@opindex mtext-section-literals
+@opindex mno-text-section-literals
+These options control the treatment of literal pools. The default is
+@option{-mno-text-section-literals}, which places literals in a separate
+section in the output file. This allows the literal pool to be placed
+in a data RAM/ROM, and it also allows the linker to combine literal
+pools from separate object files to remove redundant literals and
+improve code size. With @option{-mtext-section-literals}, the literals
+are interspersed in the text section in order to keep them as close as
+possible to their references. This may be necessary for large assembly
+files. Literals for each function are placed right before that function.
+
+@item -mauto-litpools
+@itemx -mno-auto-litpools
+@opindex mauto-litpools
+@opindex mno-auto-litpools
+These options control the treatment of literal pools. The default is
+@option{-mno-auto-litpools}, which places literals in a separate
+section in the output file unless @option{-mtext-section-literals} is
+used. With @option{-mauto-litpools} the literals are interspersed in
+the text section by the assembler. Compiler does not produce explicit
+@code{.literal} directives and loads literals into registers with
+@code{MOVI} instructions instead of @code{L32R} to let the assembler
+do relaxation and place literals as necessary. This option allows
+assembler to create several literal pools per function and assemble
+very big functions, which may not be possible with
+@option{-mtext-section-literals}.
+
+@item -mtarget-align
+@itemx -mno-target-align
+@opindex mtarget-align
+@opindex mno-target-align
+When this option is enabled, GCC instructs the assembler to
+automatically align instructions to reduce branch penalties at the
+expense of some code density. The assembler attempts to widen density
+instructions to align branch targets and the instructions following call
+instructions. If there are not enough preceding safe density
+instructions to align a target, no widening is performed. The
+default is @option{-mtarget-align}. These options do not affect the
+treatment of auto-aligned instructions like @code{LOOP}, which the
+assembler always aligns, either by widening density instructions or
+by inserting NOP instructions.
+
+@item -mlongcalls
+@itemx -mno-longcalls
+@opindex mlongcalls
+@opindex mno-longcalls
+When this option is enabled, GCC instructs the assembler to translate
+direct calls to indirect calls unless it can determine that the target
+of a direct call is in the range allowed by the call instruction. This
+translation typically occurs for calls to functions in other source
+files. Specifically, the assembler translates a direct @code{CALL}
+instruction into an @code{L32R} followed by a @code{CALLX} instruction.
+The default is @option{-mno-longcalls}. This option should be used in
+programs where the call target can potentially be out of range. This
+option is implemented in the assembler, not the compiler, so the
+assembly code generated by GCC still shows direct call
+instructions---look at the disassembled object code to see the actual
+instructions. Note that the assembler uses an indirect call for
+every cross-file call, not just those that really are out of range.
+
+@item -mabi=@var{name}
+@opindex mabi
+Generate code for the specified ABI@. Permissible values are: @samp{call0},
+@samp{windowed}. Default ABI is chosen by the Xtensa core configuration.
+
+@item -mabi=call0
+@opindex mabi=call0
+When this option is enabled function parameters are passed in registers
+@code{a2} through @code{a7}, registers @code{a12} through @code{a15} are
+caller-saved, and register @code{a15} may be used as a frame pointer.
+When this version of the ABI is enabled the C preprocessor symbol
+@code{__XTENSA_CALL0_ABI__} is defined.
+
+@item -mabi=windowed
+@opindex mabi=windowed
+When this option is enabled function parameters are passed in registers
+@code{a10} through @code{a15}, and called function rotates register window
+by 8 registers on entry so that its arguments are found in registers
+@code{a2} through @code{a7}. Register @code{a7} may be used as a frame
+pointer. Register window is rotated 8 registers back upon return.
+When this version of the ABI is enabled the C preprocessor symbol
+@code{__XTENSA_WINDOWED_ABI__} is defined.
+
+@item -mextra-l32r-costs=@var{n}
+@opindex mextra-l32r-costs
+Specify an extra cost of instruction RAM/ROM access for @code{L32R}
+instructions, in clock cycles. This affects, when optimizing for speed,
+whether loading a constant from literal pool using @code{L32R} or
+synthesizing the constant from a small one with a couple of arithmetic
+instructions. The default value is 0.
+@end table
+
+@node zSeries Options
+@subsection zSeries Options
+@cindex zSeries options
+
+These are listed under @xref{S/390 and zSeries Options}.
+
+
+@c man end
+
+@node Spec Files
+@section Specifying Subprocesses and the Switches to Pass to Them
+@cindex Spec Files
+
+@command{gcc} is a driver program. It performs its job by invoking a
+sequence of other programs to do the work of compiling, assembling and
+linking. GCC interprets its command-line parameters and uses these to
+deduce which programs it should invoke, and which command-line options
+it ought to place on their command lines. This behavior is controlled
+by @dfn{spec strings}. In most cases there is one spec string for each
+program that GCC can invoke, but a few programs have multiple spec
+strings to control their behavior. The spec strings built into GCC can
+be overridden by using the @option{-specs=} command-line switch to specify
+a spec file.
+
+@dfn{Spec files} are plain-text files that are used to construct spec
+strings. They consist of a sequence of directives separated by blank
+lines. The type of directive is determined by the first non-whitespace
+character on the line, which can be one of the following:
+
+@table @code
+@item %@var{command}
+Issues a @var{command} to the spec file processor. The commands that can
+appear here are:
+
+@table @code
+@item %include <@var{file}>
+@cindex @code{%include}
+Search for @var{file} and insert its text at the current point in the
+specs file.
+
+@item %include_noerr <@var{file}>
+@cindex @code{%include_noerr}
+Just like @samp{%include}, but do not generate an error message if the include
+file cannot be found.
+
+@item %rename @var{old_name} @var{new_name}
+@cindex @code{%rename}
+Rename the spec string @var{old_name} to @var{new_name}.
+
+@end table
+
+@item *[@var{spec_name}]:
+This tells the compiler to create, override or delete the named spec
+string. All lines after this directive up to the next directive or
+blank line are considered to be the text for the spec string. If this
+results in an empty string then the spec is deleted. (Or, if the
+spec did not exist, then nothing happens.) Otherwise, if the spec
+does not currently exist a new spec is created. If the spec does
+exist then its contents are overridden by the text of this
+directive, unless the first character of that text is the @samp{+}
+character, in which case the text is appended to the spec.
+
+@item [@var{suffix}]:
+Creates a new @samp{[@var{suffix}] spec} pair. All lines after this directive
+and up to the next directive or blank line are considered to make up the
+spec string for the indicated suffix. When the compiler encounters an
+input file with the named suffix, it processes the spec string in
+order to work out how to compile that file. For example:
+
+@smallexample
+.ZZ:
+z-compile -input %i
+@end smallexample
+
+This says that any input file whose name ends in @samp{.ZZ} should be
+passed to the program @samp{z-compile}, which should be invoked with the
+command-line switch @option{-input} and with the result of performing the
+@samp{%i} substitution. (See below.)
+
+As an alternative to providing a spec string, the text following a
+suffix directive can be one of the following:
+
+@table @code
+@item @@@var{language}
+This says that the suffix is an alias for a known @var{language}. This is
+similar to using the @option{-x} command-line switch to GCC to specify a
+language explicitly. For example:
+
+@smallexample
+.ZZ:
+@@c++
+@end smallexample
+
+Says that .ZZ files are, in fact, C++ source files.
+
+@item #@var{name}
+This causes an error messages saying:
+
+@smallexample
+@var{name} compiler not installed on this system.
+@end smallexample
+@end table
+
+GCC already has an extensive list of suffixes built into it.
+This directive adds an entry to the end of the list of suffixes, but
+since the list is searched from the end backwards, it is effectively
+possible to override earlier entries using this technique.
+
+@end table
+
+GCC has the following spec strings built into it. Spec files can
+override these strings or create their own. Note that individual
+targets can also add their own spec strings to this list.
+
+@smallexample
+asm Options to pass to the assembler
+asm_final Options to pass to the assembler post-processor
+cpp Options to pass to the C preprocessor
+cc1 Options to pass to the C compiler
+cc1plus Options to pass to the C++ compiler
+endfile Object files to include at the end of the link
+link Options to pass to the linker
+lib Libraries to include on the command line to the linker
+libgcc Decides which GCC support library to pass to the linker
+linker Sets the name of the linker
+predefines Defines to be passed to the C preprocessor
+signed_char Defines to pass to CPP to say whether @code{char} is signed
+ by default
+startfile Object files to include at the start of the link
+@end smallexample
+
+Here is a small example of a spec file:
+
+@smallexample
+%rename lib old_lib
+
+*lib:
+--start-group -lgcc -lc -leval1 --end-group %(old_lib)
+@end smallexample
+
+This example renames the spec called @samp{lib} to @samp{old_lib} and
+then overrides the previous definition of @samp{lib} with a new one.
+The new definition adds in some extra command-line options before
+including the text of the old definition.
+
+@dfn{Spec strings} are a list of command-line options to be passed to their
+corresponding program. In addition, the spec strings can contain
+@samp{%}-prefixed sequences to substitute variable text or to
+conditionally insert text into the command line. Using these constructs
+it is possible to generate quite complex command lines.
+
+Here is a table of all defined @samp{%}-sequences for spec
+strings. Note that spaces are not generated automatically around the
+results of expanding these sequences. Therefore you can concatenate them
+together or combine them with constant text in a single argument.
+
+@table @code
+@item %%
+Substitute one @samp{%} into the program name or argument.
+
+@item %"
+Substitute an empty argument.
+
+@item %i
+Substitute the name of the input file being processed.
+
+@item %b
+Substitute the basename for outputs related with the input file being
+processed. This is often the substring up to (and not including) the
+last period and not including the directory but, unless %w is active, it
+expands to the basename for auxiliary outputs, which may be influenced
+by an explicit output name, and by various other options that control
+how auxiliary outputs are named.
+
+@item %B
+This is the same as @samp{%b}, but include the file suffix (text after
+the last period). Without %w, it expands to the basename for dump
+outputs.
+
+@item %d
+Marks the argument containing or following the @samp{%d} as a
+temporary file name, so that that file is deleted if GCC exits
+successfully. Unlike @samp{%g}, this contributes no text to the
+argument.
+
+@item %g@var{suffix}
+Substitute a file name that has suffix @var{suffix} and is chosen
+once per compilation, and mark the argument in the same way as
+@samp{%d}. To reduce exposure to denial-of-service attacks, the file
+name is now chosen in a way that is hard to predict even when previously
+chosen file names are known. For example, @samp{%g.s @dots{} %g.o @dots{} %g.s}
+might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}. @var{suffix} matches
+the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is
+treated exactly as if @samp{%O} had been preprocessed. Previously, @samp{%g}
+was simply substituted with a file name chosen once per compilation,
+without regard to any appended suffix (which was therefore treated
+just like ordinary text), making such attacks more likely to succeed.
+
+@item %u@var{suffix}
+Like @samp{%g}, but generates a new temporary file name
+each time it appears instead of once per compilation.
+
+@item %U@var{suffix}
+Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a
+new one if there is no such last file name. In the absence of any
+@samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share
+the same suffix @emph{space}, so @samp{%g.s @dots{} %U.s @dots{} %g.s @dots{} %U.s}
+involves the generation of two distinct file names, one
+for each @samp{%g.s} and another for each @samp{%U.s}. Previously, @samp{%U} was
+simply substituted with a file name chosen for the previous @samp{%u},
+without regard to any appended suffix.
+
+@item %j@var{suffix}
+Substitutes the name of the @code{HOST_BIT_BUCKET}, if any, and if it is
+writable, and if @option{-save-temps} is not used;
+otherwise, substitute the name
+of a temporary file, just like @samp{%u}. This temporary file is not
+meant for communication between processes, but rather as a junk
+disposal mechanism.
+
+@item %|@var{suffix}
+@itemx %m@var{suffix}
+Like @samp{%g}, except if @option{-pipe} is in effect. In that case
+@samp{%|} substitutes a single dash and @samp{%m} substitutes nothing at
+all. These are the two most common ways to instruct a program that it
+should read from standard input or write to standard output. If you
+need something more elaborate you can use an @samp{%@{pipe:@code{X}@}}
+construct: see for example @file{gcc/fortran/lang-specs.h}.
+
+@item %.@var{SUFFIX}
+Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args
+when it is subsequently output with @samp{%*}. @var{SUFFIX} is
+terminated by the next space or %.
+
+@item %w
+Marks the argument containing or following the @samp{%w} as the
+designated output file of this compilation. This puts the argument
+into the sequence of arguments that @samp{%o} substitutes.
+
+@item %V
+Indicates that this compilation produces no output file.
+
+@item %o
+Substitutes the names of all the output files, with spaces
+automatically placed around them. You should write spaces
+around the @samp{%o} as well or the results are undefined.
+@samp{%o} is for use in the specs for running the linker.
+Input files whose names have no recognized suffix are not compiled
+at all, but they are included among the output files, so they are
+linked.
+
+@item %O
+Substitutes the suffix for object files. Note that this is
+handled specially when it immediately follows @samp{%g, %u, or %U},
+because of the need for those to form complete file names. The
+handling is such that @samp{%O} is treated exactly as if it had already
+been substituted, except that @samp{%g, %u, and %U} do not currently
+support additional @var{suffix} characters following @samp{%O} as they do
+following, for example, @samp{.o}.
+
+@item %I
+Substitute any of @option{-iprefix} (made from @env{GCC_EXEC_PREFIX}),
+@option{-isysroot} (made from @env{TARGET_SYSTEM_ROOT}),
+@option{-isystem} (made from @env{COMPILER_PATH} and @option{-B} options)
+and @option{-imultilib} as necessary.
+
+@item %s
+Current argument is the name of a library or startup file of some sort.
+Search for that file in a standard list of directories and substitute
+the full name found. The current working directory is included in the
+list of directories scanned.
+
+@item %T
+Current argument is the name of a linker script. Search for that file
+in the current list of directories to scan for libraries. If the file
+is located insert a @option{--script} option into the command line
+followed by the full path name found. If the file is not found then
+generate an error message. Note: the current working directory is not
+searched.
+
+@item %e@var{str}
+Print @var{str} as an error message. @var{str} is terminated by a newline.
+Use this when inconsistent options are detected.
+
+@item %n@var{str}
+Print @var{str} as a notice. @var{str} is terminated by a newline.
+
+@item %(@var{name})
+Substitute the contents of spec string @var{name} at this point.
+
+@item %x@{@var{option}@}
+Accumulate an option for @samp{%X}.
+
+@item %X
+Output the accumulated linker options specified by a @samp{%x} spec string.
+
+@item %Y
+Output the accumulated assembler options specified by @option{-Wa}.
+
+@item %Z
+Output the accumulated preprocessor options specified by @option{-Wp}.
+
+@item %M
+Output @code{multilib_os_dir}.
+
+@item %R
+Output the concatenation of @code{target_system_root} and @code{target_sysroot_suffix}.
+
+@item %a
+Process the @code{asm} spec. This is used to compute the
+switches to be passed to the assembler.
+
+@item %A
+Process the @code{asm_final} spec. This is a spec string for
+passing switches to an assembler post-processor, if such a program is
+needed.
+
+@item %l
+Process the @code{link} spec. This is the spec for computing the
+command line passed to the linker. Typically it makes use of the
+@samp{%L %G %S %D and %E} sequences.
+
+@item %D
+Dump out a @option{-L} option for each directory that GCC believes might
+contain startup files. If the target supports multilibs then the
+current multilib directory is prepended to each of these paths.
+
+@item %L
+Process the @code{lib} spec. This is a spec string for deciding which
+libraries are included on the command line to the linker.
+
+@item %G
+Process the @code{libgcc} spec. This is a spec string for deciding
+which GCC support library is included on the command line to the linker.
+
+@item %S
+Process the @code{startfile} spec. This is a spec for deciding which
+object files are the first ones passed to the linker. Typically
+this might be a file named @file{crt0.o}.
+
+@item %E
+Process the @code{endfile} spec. This is a spec string that specifies
+the last object files that are passed to the linker.
+
+@item %C
+Process the @code{cpp} spec. This is used to construct the arguments
+to be passed to the C preprocessor.
+
+@item %1
+Process the @code{cc1} spec. This is used to construct the options to be
+passed to the actual C compiler (@command{cc1}).
+
+@item %2
+Process the @code{cc1plus} spec. This is used to construct the options to be
+passed to the actual C++ compiler (@command{cc1plus}).
+
+@item %*
+Substitute the variable part of a matched option. See below.
+Note that each comma in the substituted string is replaced by
+a single space.
+
+@item %<S
+Remove all occurrences of @code{-S} from the command line. Note---this
+command is position dependent. @samp{%} commands in the spec string
+before this one see @code{-S}, @samp{%} commands in the spec string
+after this one do not.
+
+@item %<S*
+Similar to @samp{%<S}, but match all switches beginning with @code{-S}.
+
+@item %>S
+Similar to @samp{%<S}, but keep @code{-S} in the GCC command line.
+
+@item %:@var{function}(@var{args})
+Call the named function @var{function}, passing it @var{args}.
+@var{args} is first processed as a nested spec string, then split
+into an argument vector in the usual fashion. The function returns
+a string which is processed as if it had appeared literally as part
+of the current spec.
+
+The following built-in spec functions are provided:
+
+@table @code
+@item @code{getenv}
+The @code{getenv} spec function takes two arguments: an environment
+variable name and a string. If the environment variable is not
+defined, a fatal error is issued. Otherwise, the return value is the
+value of the environment variable concatenated with the string. For
+example, if @env{TOPDIR} is defined as @file{/path/to/top}, then:
+
+@smallexample
+%:getenv(TOPDIR /include)
+@end smallexample
+
+expands to @file{/path/to/top/include}.
+
+@item @code{if-exists}
+The @code{if-exists} spec function takes one argument, an absolute
+pathname to a file. If the file exists, @code{if-exists} returns the
+pathname. Here is a small example of its usage:
+
+@smallexample
+*startfile:
+crt0%O%s %:if-exists(crti%O%s) crtbegin%O%s
+@end smallexample
+
+@item @code{if-exists-else}
+The @code{if-exists-else} spec function is similar to the @code{if-exists}
+spec function, except that it takes two arguments. The first argument is
+an absolute pathname to a file. If the file exists, @code{if-exists-else}
+returns the pathname. If it does not exist, it returns the second argument.
+This way, @code{if-exists-else} can be used to select one file or another,
+based on the existence of the first. Here is a small example of its usage:
+
+@smallexample
+*startfile:
+crt0%O%s %:if-exists(crti%O%s) \
+%:if-exists-else(crtbeginT%O%s crtbegin%O%s)
+@end smallexample
+
+@item @code{if-exists-then-else}
+The @code{if-exists-then-else} spec function takes at least two arguments
+and an optional third one. The first argument is an absolute pathname to a
+file. If the file exists, the function returns the second argument.
+If the file does not exist, the function returns the third argument if there
+is one, or NULL otherwise. This can be used to expand one text, or optionally
+another, based on the existence of a file. Here is a small example of its
+usage:
+
+@smallexample
+-l%:if-exists-then-else(%:getenv(VSB_DIR rtnet.h) rtnet net)
+@end smallexample
+
+@item @code{sanitize}
+The @code{sanitize} spec function takes no arguments. It returns non-NULL if
+any address, thread or undefined behavior sanitizers are active.
+
+@smallexample
+%@{%:sanitize(address):-funwind-tables@}
+@end smallexample
+
+@item @code{replace-outfile}
+The @code{replace-outfile} spec function takes two arguments. It looks for the
+first argument in the outfiles array and replaces it with the second argument. Here
+is a small example of its usage:
+
+@smallexample
+%@{fgnu-runtime:%:replace-outfile(-lobjc -lobjc-gnu)@}
+@end smallexample
+
+@item @code{remove-outfile}
+The @code{remove-outfile} spec function takes one argument. It looks for the
+first argument in the outfiles array and removes it. Here is a small example
+its usage:
+
+@smallexample
+%:remove-outfile(-lm)
+@end smallexample
+
+@item @code{version-compare}
+The @code{version-compare} spec function takes four or five arguments of the following
+form:
+
+@smallexample
+<comparison-op> <arg1> [<arg2>] <switch> <result>
+@end smallexample
+
+It returns @code{result} if the comparison evaluates to true, and NULL if it doesn't.
+The supported @code{comparison-op} values are:
+
+@table @code
+@item >=
+True if @code{switch} is a later (or same) version than @code{arg1}
+
+@item !>
+Opposite of @code{>=}
+
+@item <
+True if @code{switch} is an earlier version than @code{arg1}
+
+@item !<
+Opposite of @code{<}
+
+@item ><
+True if @code{switch} is @code{arg1} or later, and earlier than @code{arg2}
+
+@item <>
+True if @code{switch} is earlier than @code{arg1}, or is @code{arg2} or later
+@end table
+
+If the @code{switch} is not present at all, the condition is false unless the first character
+of the @code{comparison-op} is @code{!}.
+
+@smallexample
+%:version-compare(>= 10.3 mmacosx-version-min= -lmx)
+@end smallexample
+
+The above example would add @option{-lmx} if @option{-mmacosx-version-min=10.3.9} was
+passed.
+
+@item @code{include}
+The @code{include} spec function behaves much like @code{%include}, with the advantage
+that it can be nested inside a spec and thus be conditionalized. It takes one argument,
+the filename, and looks for it in the startfile path. It always returns NULL.
+
+@smallexample
+%@{static-libasan|static:%:include(libsanitizer.spec)%(link_libasan)@}
+@end smallexample
+
+@item @code{pass-through-libs}
+The @code{pass-through-libs} spec function takes any number of arguments. It
+finds any @option{-l} options and any non-options ending in @file{.a} (which it
+assumes are the names of linker input library archive files) and returns a
+result containing all the found arguments each prepended by
+@option{-plugin-opt=-pass-through=} and joined by spaces. This list is
+intended to be passed to the LTO linker plugin.
+
+@smallexample
+%:pass-through-libs(%G %L %G)
+@end smallexample
+
+@item @code{print-asm-header}
+The @code{print-asm-header} function takes no arguments and simply
+prints a banner like:
+
+@smallexample
+Assembler options
+=================
+
+Use "-Wa,OPTION" to pass "OPTION" to the assembler.
+@end smallexample
+
+It is used to separate compiler options from assembler options
+in the @option{--target-help} output.
+
+@item @code{gt}
+The @code{gt} spec function takes two or more arguments. It returns @code{""} (the
+empty string) if the second-to-last argument is greater than the last argument, and NULL
+otherwise. The following example inserts the @code{link_gomp} spec if the last
+@option{-ftree-parallelize-loops=} option given on the command line is greater than 1:
+
+@smallexample
+%@{%:gt(%@{ftree-parallelize-loops=*:%*@} 1):%:include(libgomp.spec)%(link_gomp)@}
+@end smallexample
+
+@item @code{debug-level-gt}
+The @code{debug-level-gt} spec function takes one argument and returns @code{""} (the
+empty string) if @code{debug_info_level} is greater than the specified number, and NULL
+otherwise.
+
+@smallexample
+%@{%:debug-level-gt(0):%@{gdwarf*:--gdwarf2@}@}
+@end smallexample
+@end table
+
+@item %@{S@}
+Substitutes the @code{-S} switch, if that switch is given to GCC@.
+If that switch is not specified, this substitutes nothing. Note that
+the leading dash is omitted when specifying this option, and it is
+automatically inserted if the substitution is performed. Thus the spec
+string @samp{%@{foo@}} matches the command-line option @option{-foo}
+and outputs the command-line option @option{-foo}.
+
+@item %W@{S@}
+Like %@{@code{S}@} but mark last argument supplied within as a file to be
+deleted on failure.
+
+@item %@@@{S@}
+Like %@{@code{S}@} but puts the result into a @code{FILE} and substitutes
+@code{@@FILE} if an @code{@@file} argument has been supplied.
+
+@item %@{S*@}
+Substitutes all the switches specified to GCC whose names start
+with @code{-S}, but which also take an argument. This is used for
+switches like @option{-o}, @option{-D}, @option{-I}, etc.
+GCC considers @option{-o foo} as being
+one switch whose name starts with @samp{o}. %@{o*@} substitutes this
+text, including the space. Thus two arguments are generated.
+
+@item %@{S*&T*@}
+Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options
+(the order of @code{S} and @code{T} in the spec is not significant).
+There can be any number of ampersand-separated variables; for each the
+wild card is optional. Useful for CPP as @samp{%@{D*&U*&A*@}}.
+
+@item %@{S:X@}
+Substitutes @code{X}, if the @option{-S} switch is given to GCC@.
+
+@item %@{!S:X@}
+Substitutes @code{X}, if the @option{-S} switch is @emph{not} given to GCC@.
+
+@item %@{S*:X@}
+Substitutes @code{X} if one or more switches whose names start with
+@code{-S} are specified to GCC@. Normally @code{X} is substituted only
+once, no matter how many such switches appeared. However, if @code{%*}
+appears somewhere in @code{X}, then @code{X} is substituted once
+for each matching switch, with the @code{%*} replaced by the part of
+that switch matching the @code{*}.
+
+If @code{%*} appears as the last part of a spec sequence then a space
+is added after the end of the last substitution. If there is more
+text in the sequence, however, then a space is not generated. This
+allows the @code{%*} substitution to be used as part of a larger
+string. For example, a spec string like this:
+
+@smallexample
+%@{mcu=*:--script=%*/memory.ld@}
+@end smallexample
+
+@noindent
+when matching an option like @option{-mcu=newchip} produces:
+
+@smallexample
+--script=newchip/memory.ld
+@end smallexample
+
+@item %@{.S:X@}
+Substitutes @code{X}, if processing a file with suffix @code{S}.
+
+@item %@{!.S:X@}
+Substitutes @code{X}, if @emph{not} processing a file with suffix @code{S}.
+
+@item %@{,S:X@}
+Substitutes @code{X}, if processing a file for language @code{S}.
+
+@item %@{!,S:X@}
+Substitutes @code{X}, if not processing a file for language @code{S}.
+
+@item %@{S|P:X@}
+Substitutes @code{X} if either @code{-S} or @code{-P} is given to
+GCC@. This may be combined with @samp{!}, @samp{.}, @samp{,}, and
+@code{*} sequences as well, although they have a stronger binding than
+the @samp{|}. If @code{%*} appears in @code{X}, all of the
+alternatives must be starred, and only the first matching alternative
+is substituted.
+
+For example, a spec string like this:
+
+@smallexample
+%@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@}
+@end smallexample
+
+@noindent
+outputs the following command-line options from the following input
+command-line options:
+
+@smallexample
+fred.c -foo -baz
+jim.d -bar -boggle
+-d fred.c -foo -baz -boggle
+-d jim.d -bar -baz -boggle
+@end smallexample
+
+@item %@{%:@var{function}(@var{args}):X@}
+
+Call function named @var{function} with args @var{args}. If the
+function returns non-NULL, then @code{X} is substituted, if it returns
+NULL, it isn't substituted.
+
+@item %@{S:X; T:Y; :D@}
+
+If @code{S} is given to GCC, substitutes @code{X}; else if @code{T} is
+given to GCC, substitutes @code{Y}; else substitutes @code{D}. There can
+be as many clauses as you need. This may be combined with @code{.},
+@code{,}, @code{!}, @code{|}, and @code{*} as needed.
+
+
+@end table
+
+The switch matching text @code{S} in a @samp{%@{S@}}, @samp{%@{S:X@}}
+or similar construct can use a backslash to ignore the special meaning
+of the character following it, thus allowing literal matching of a
+character that is otherwise specially treated. For example,
+@samp{%@{std=iso9899\:1999:X@}} substitutes @code{X} if the
+@option{-std=iso9899:1999} option is given.
+
+The conditional text @code{X} in a @samp{%@{S:X@}} or similar
+construct may contain other nested @samp{%} constructs or spaces, or
+even newlines. They are processed as usual, as described above.
+Trailing white space in @code{X} is ignored. White space may also
+appear anywhere on the left side of the colon in these constructs,
+except between @code{.} or @code{*} and the corresponding word.
+
+The @option{-O}, @option{-f}, @option{-m}, and @option{-W} switches are
+handled specifically in these constructs. If another value of
+@option{-O} or the negated form of a @option{-f}, @option{-m}, or
+@option{-W} switch is found later in the command line, the earlier
+switch value is ignored, except with @{@code{S}*@} where @code{S} is
+just one letter, which passes all matching options.
+
+The character @samp{|} at the beginning of the predicate text is used to
+indicate that a command should be piped to the following command, but
+only if @option{-pipe} is specified.
+
+It is built into GCC which switches take arguments and which do not.
+(You might think it would be useful to generalize this to allow each
+compiler's spec to say which switches take arguments. But this cannot
+be done in a consistent fashion. GCC cannot even decide which input
+files have been specified without knowing which switches take arguments,
+and it must know which input files to compile in order to tell which
+compilers to run).
+
+GCC also knows implicitly that arguments starting in @option{-l} are to be
+treated as compiler output files, and passed to the linker in their
+proper position among the other output files.
+
+@node Environment Variables
+@section Environment Variables Affecting GCC
+@cindex environment variables
+
+@c man begin ENVIRONMENT
+This section describes several environment variables that affect how GCC
+operates. Some of them work by specifying directories or prefixes to use
+when searching for various kinds of files. Some are used to specify other
+aspects of the compilation environment.
+
+Note that you can also specify places to search using options such as
+@option{-B}, @option{-I} and @option{-L} (@pxref{Directory Options}). These
+take precedence over places specified using environment variables, which
+in turn take precedence over those specified by the configuration of GCC@.
+@xref{Driver,, Controlling the Compilation Driver @file{gcc}, gccint,
+GNU Compiler Collection (GCC) Internals}.
+
+@table @env
+@item LANG
+@itemx LC_CTYPE
+@c @itemx LC_COLLATE
+@itemx LC_MESSAGES
+@c @itemx LC_MONETARY
+@c @itemx LC_NUMERIC
+@c @itemx LC_TIME
+@itemx LC_ALL
+@findex LANG
+@findex LC_CTYPE
+@c @findex LC_COLLATE
+@findex LC_MESSAGES
+@c @findex LC_MONETARY
+@c @findex LC_NUMERIC
+@c @findex LC_TIME
+@findex LC_ALL
+@cindex locale
+These environment variables control the way that GCC uses
+localization information which allows GCC to work with different
+national conventions. GCC inspects the locale categories
+@env{LC_CTYPE} and @env{LC_MESSAGES} if it has been configured to do
+so. These locale categories can be set to any value supported by your
+installation. A typical value is @samp{en_GB.UTF-8} for English in the United
+Kingdom encoded in UTF-8.
+
+The @env{LC_CTYPE} environment variable specifies character
+classification. GCC uses it to determine the character boundaries in
+a string; this is needed for some multibyte encodings that contain quote
+and escape characters that are otherwise interpreted as a string
+end or escape.
+
+The @env{LC_MESSAGES} environment variable specifies the language to
+use in diagnostic messages.
+
+If the @env{LC_ALL} environment variable is set, it overrides the value
+of @env{LC_CTYPE} and @env{LC_MESSAGES}; otherwise, @env{LC_CTYPE}
+and @env{LC_MESSAGES} default to the value of the @env{LANG}
+environment variable. If none of these variables are set, GCC
+defaults to traditional C English behavior.
+
+@item TMPDIR
+@findex TMPDIR
+If @env{TMPDIR} is set, it specifies the directory to use for temporary
+files. GCC uses temporary files to hold the output of one stage of
+compilation which is to be used as input to the next stage: for example,
+the output of the preprocessor, which is the input to the compiler
+proper.
+
+@item GCC_COMPARE_DEBUG
+@findex GCC_COMPARE_DEBUG
+Setting @env{GCC_COMPARE_DEBUG} is nearly equivalent to passing
+@option{-fcompare-debug} to the compiler driver. See the documentation
+of this option for more details.
+
+@item GCC_EXEC_PREFIX
+@findex GCC_EXEC_PREFIX
+If @env{GCC_EXEC_PREFIX} is set, it specifies a prefix to use in the
+names of the subprograms executed by the compiler. No slash is added
+when this prefix is combined with the name of a subprogram, but you can
+specify a prefix that ends with a slash if you wish.
+
+If @env{GCC_EXEC_PREFIX} is not set, GCC attempts to figure out
+an appropriate prefix to use based on the pathname it is invoked with.
+
+If GCC cannot find the subprogram using the specified prefix, it
+tries looking in the usual places for the subprogram.
+
+The default value of @env{GCC_EXEC_PREFIX} is
+@file{@var{prefix}/lib/gcc/} where @var{prefix} is the prefix to
+the installed compiler. In many cases @var{prefix} is the value
+of @code{prefix} when you ran the @file{configure} script.
+
+Other prefixes specified with @option{-B} take precedence over this prefix.
+
+This prefix is also used for finding files such as @file{crt0.o} that are
+used for linking.
+
+In addition, the prefix is used in an unusual way in finding the
+directories to search for header files. For each of the standard
+directories whose name normally begins with @samp{/usr/local/lib/gcc}
+(more precisely, with the value of @env{GCC_INCLUDE_DIR}), GCC tries
+replacing that beginning with the specified prefix to produce an
+alternate directory name. Thus, with @option{-Bfoo/}, GCC searches
+@file{foo/bar} just before it searches the standard directory
+@file{/usr/local/lib/bar}.
+If a standard directory begins with the configured
+@var{prefix} then the value of @var{prefix} is replaced by
+@env{GCC_EXEC_PREFIX} when looking for header files.
+
+@item COMPILER_PATH
+@findex COMPILER_PATH
+The value of @env{COMPILER_PATH} is a colon-separated list of
+directories, much like @env{PATH}. GCC tries the directories thus
+specified when searching for subprograms, if it cannot find the
+subprograms using @env{GCC_EXEC_PREFIX}.
+
+@item LIBRARY_PATH
+@findex LIBRARY_PATH
+The value of @env{LIBRARY_PATH} is a colon-separated list of
+directories, much like @env{PATH}. When configured as a native compiler,
+GCC tries the directories thus specified when searching for special
+linker files, if it cannot find them using @env{GCC_EXEC_PREFIX}. Linking
+using GCC also uses these directories when searching for ordinary
+libraries for the @option{-l} option (but directories specified with
+@option{-L} come first).
+
+@item LANG
+@findex LANG
+@cindex locale definition
+This variable is used to pass locale information to the compiler. One way in
+which this information is used is to determine the character set to be used
+when character literals, string literals and comments are parsed in C and C++.
+When the compiler is configured to allow multibyte characters,
+the following values for @env{LANG} are recognized:
+
+@table @samp
+@item C-JIS
+Recognize JIS characters.
+@item C-SJIS
+Recognize SJIS characters.
+@item C-EUCJP
+Recognize EUCJP characters.
+@end table
+
+If @env{LANG} is not defined, or if it has some other value, then the
+compiler uses @code{mblen} and @code{mbtowc} as defined by the default locale to
+recognize and translate multibyte characters.
+
+@item GCC_EXTRA_DIAGNOSTIC_OUTPUT
+@findex GCC_EXTRA_DIAGNOSTIC_OUTPUT
+If @env{GCC_EXTRA_DIAGNOSTIC_OUTPUT} is set to one of the following values,
+then additional text will be emitted to stderr when fix-it hints are
+emitted. @option{-fdiagnostics-parseable-fixits} and
+@option{-fno-diagnostics-parseable-fixits} take precedence over this
+environment variable.
+
+@table @samp
+@item fixits-v1
+Emit parseable fix-it hints, equivalent to
+@option{-fdiagnostics-parseable-fixits}. In particular, columns are
+expressed as a count of bytes, starting at byte 1 for the initial column.
+
+@item fixits-v2
+As @code{fixits-v1}, but columns are expressed as display columns,
+as per @option{-fdiagnostics-column-unit=display}.
+@end table
+
+@end table
+
+@noindent
+Some additional environment variables affect the behavior of the
+preprocessor.
+
+@include cppenv.texi
+
+@c man end
+
+@node Precompiled Headers
+@section Using Precompiled Headers
+@cindex precompiled headers
+@cindex speed of compilation
+
+Often large projects have many header files that are included in every
+source file. The time the compiler takes to process these header files
+over and over again can account for nearly all of the time required to
+build the project. To make builds faster, GCC allows you to
+@dfn{precompile} a header file.
+
+To create a precompiled header file, simply compile it as you would any
+other file, if necessary using the @option{-x} option to make the driver
+treat it as a C or C++ header file. You may want to use a
+tool like @command{make} to keep the precompiled header up-to-date when
+the headers it contains change.
+
+A precompiled header file is searched for when @code{#include} is
+seen in the compilation. As it searches for the included file
+(@pxref{Search Path,,Search Path,cpp,The C Preprocessor}) the
+compiler looks for a precompiled header in each directory just before it
+looks for the include file in that directory. The name searched for is
+the name specified in the @code{#include} with @samp{.gch} appended. If
+the precompiled header file cannot be used, it is ignored.
+
+For instance, if you have @code{#include "all.h"}, and you have
+@file{all.h.gch} in the same directory as @file{all.h}, then the
+precompiled header file is used if possible, and the original
+header is used otherwise.
+
+Alternatively, you might decide to put the precompiled header file in a
+directory and use @option{-I} to ensure that directory is searched
+before (or instead of) the directory containing the original header.
+Then, if you want to check that the precompiled header file is always
+used, you can put a file of the same name as the original header in this
+directory containing an @code{#error} command.
+
+This also works with @option{-include}. So yet another way to use
+precompiled headers, good for projects not designed with precompiled
+header files in mind, is to simply take most of the header files used by
+a project, include them from another header file, precompile that header
+file, and @option{-include} the precompiled header. If the header files
+have guards against multiple inclusion, they are skipped because
+they've already been included (in the precompiled header).
+
+If you need to precompile the same header file for different
+languages, targets, or compiler options, you can instead make a
+@emph{directory} named like @file{all.h.gch}, and put each precompiled
+header in the directory, perhaps using @option{-o}. It doesn't matter
+what you call the files in the directory; every precompiled header in
+the directory is considered. The first precompiled header
+encountered in the directory that is valid for this compilation is
+used; they're searched in no particular order.
+
+There are many other possibilities, limited only by your imagination,
+good sense, and the constraints of your build system.
+
+A precompiled header file can be used only when these conditions apply:
+
+@itemize
+@item
+Only one precompiled header can be used in a particular compilation.
+
+@item
+A precompiled header cannot be used once the first C token is seen. You
+can have preprocessor directives before a precompiled header; you cannot
+include a precompiled header from inside another header.
+
+@item
+The precompiled header file must be produced for the same language as
+the current compilation. You cannot use a C precompiled header for a C++
+compilation.
+
+@item
+The precompiled header file must have been produced by the same compiler
+binary as the current compilation is using.
+
+@item
+Any macros defined before the precompiled header is included must
+either be defined in the same way as when the precompiled header was
+generated, or must not affect the precompiled header, which usually
+means that they don't appear in the precompiled header at all.
+
+The @option{-D} option is one way to define a macro before a
+precompiled header is included; using a @code{#define} can also do it.
+There are also some options that define macros implicitly, like
+@option{-O} and @option{-Wdeprecated}; the same rule applies to macros
+defined this way.
+
+@item If debugging information is output when using the precompiled
+header, using @option{-g} or similar, the same kind of debugging information
+must have been output when building the precompiled header. However,
+a precompiled header built using @option{-g} can be used in a compilation
+when no debugging information is being output.
+
+@item The same @option{-m} options must generally be used when building
+and using the precompiled header. @xref{Submodel Options},
+for any cases where this rule is relaxed.
+
+@item Each of the following options must be the same when building and using
+the precompiled header:
+
+@gccoptlist{-fexceptions}
+
+@item
+Some other command-line options starting with @option{-f},
+@option{-p}, or @option{-O} must be defined in the same way as when
+the precompiled header was generated. At present, it's not clear
+which options are safe to change and which are not; the safest choice
+is to use exactly the same options when generating and using the
+precompiled header. The following are known to be safe:
+
+@gccoptlist{-fmessage-length= -fpreprocessed -fsched-interblock @gol
+-fsched-spec -fsched-spec-load -fsched-spec-load-dangerous @gol
+-fsched-verbose=@var{number} -fschedule-insns -fvisibility= @gol
+-pedantic-errors}
+
+@item Address space layout randomization (ASLR) can lead to not binary identical
+PCH files. If you rely on stable PCH file contents disable ASLR when generating
+PCH files.
+
+@end itemize
+
+For all of these except the last, the compiler automatically
+ignores the precompiled header if the conditions aren't met. If you
+find an option combination that doesn't work and doesn't cause the
+precompiled header to be ignored, please consider filing a bug report,
+see @ref{Bugs}.
+
+If you do use differing options when generating and using the
+precompiled header, the actual behavior is a mixture of the
+behavior for the options. For instance, if you use @option{-g} to
+generate the precompiled header but not when using it, you may or may
+not get debugging information for routines in the precompiled header.
+
+@node C++ Modules
+@section C++ Modules
+@cindex speed of compilation
+
+Modules are a C++20 language feature. As the name suggests, they
+provides a modular compilation system, intending to provide both
+faster builds and better library isolation. The ``Merging Modules''
+paper @uref{https://wg21.link/p1103}, provides the easiest to read set
+of changes to the standard, although it does not capture later
+changes.
+
+@emph{G++'s modules support is not complete.} Other than bugs, the
+known missing pieces are:
+
+@table @emph
+
+@item Private Module Fragment
+The Private Module Fragment is recognized, but an error is emitted.
+
+@item Partition definition visibility rules
+Entities may be defined in implementation partitions, and those
+definitions are not available outside of the module. This is not
+implemented, and the definitions are available to extra-module use.
+
+@item Textual merging of reachable GM entities
+Entities may be multiply defined across different header-units.
+These must be de-duplicated, and this is implemented across imports,
+or when an import redefines a textually-defined entity. However the
+reverse is not implemented---textually redefining an entity that has
+been defined in an imported header-unit. A redefinition error is
+emitted.
+
+@item Translation-Unit local referencing rules
+Papers p1815 (@uref{https://wg21.link/p1815}) and p2003
+(@uref{https://wg21.link/p2003}) add limitations on which entities an
+exported region may reference (for instance, the entities an exported
+template definition may reference). These are not fully implemented.
+
+@item Standard Library Header Units
+The Standard Library is not provided as importable header units. If
+you want to import such units, you must explicitly build them first.
+If you do not do this with care, you may have multiple declarations,
+which the module machinery must merge---compiler resource usage can be
+affected by how you partition header files into header units.
+
+@end table
+
+Modular compilation is @emph{not} enabled with just the
+@option{-std=c++20} option. You must explicitly enable it with the
+@option{-fmodules-ts} option. It is independent of the language
+version selected, although in pre-C++20 versions, it is of course an
+extension.
+
+No new source file suffixes are required or supported. If you wish to
+use a non-standard suffix (@pxref{Overall Options}), you also need
+to provide a @option{-x c++} option too.@footnote{Some users like to
+distinguish module interface files with a new suffix, such as naming
+the source @code{module.cppm}, which involves
+teaching all tools about the new suffix. A different scheme, such as
+naming @code{module-m.cpp} would be less invasive.}
+
+Compiling a module interface unit produces an additional output (to
+the assembly or object file), called a Compiled Module Interface
+(CMI). This encodes the exported declarations of the module.
+Importing a module reads in the CMI. The import graph is a Directed
+Acyclic Graph (DAG). You must build imports before the importer.
+
+Header files may themselves be compiled to header units, which are a
+transitional ability aiming at faster compilation. The
+@option{-fmodule-header} option is used to enable this, and implies
+the @option{-fmodules-ts} option. These CMIs are named by the fully
+resolved underlying header file, and thus may be a complete pathname
+containing subdirectories. If the header file is found at an absolute
+pathname, the CMI location is still relative to a CMI root directory.
+
+As header files often have no suffix, you commonly have to specify a
+@option{-x} option to tell the compiler the source is a header file.
+You may use @option{-x c++-header}, @option{-x c++-user-header} or
+@option{-x c++-system-header}. When used in conjunction with
+@option{-fmodules-ts}, these all imply an appropriate
+@option{-fmodule-header} option. The latter two variants use the
+user or system include path to search for the file specified. This
+allows you to, for instance, compile standard library header files as
+header units, without needing to know exactly where they are
+installed. Specifying the language as one of these variants also
+inhibits output of the object file, as header files have no associated
+object file.
+
+The @option{-fmodule-only} option disables generation of the
+associated object file for compiling a module interface. Only the CMI
+is generated. This option is implied when using the
+@option{-fmodule-header} option.
+
+The @option{-flang-info-include-translate} and
+@option{-flang-info-include-translate-not} options notes whether
+include translation occurs or not. With no argument, the first will
+note all include translation. The second will note all
+non-translations of include files not known to intentionally be
+textual. With an argument, queries about include translation of a
+header files with that particular trailing pathname are noted. You
+may repeat this form to cover several different header files. This
+option may be helpful in determining whether include translation is
+happening---if it is working correctly, it behaves as if it isn't
+there at all.
+
+The @option{-flang-info-module-cmi} option can be used to determine
+where the compiler is reading a CMI from. Without the option, the
+compiler is silent when such a read is successful. This option has an
+optional argument, which will restrict the notification to just the
+set of named modules or header units specified.
+
+The @option{-Winvalid-imported-macros} option causes all imported macros
+to be resolved at the end of compilation. Without this, imported
+macros are only resolved when expanded or (re)defined. This option
+detects conflicting import definitions for all macros.
+
+For details of the @option{-fmodule-mapper} family of options,
+@pxref{C++ Module Mapper}.
+
+@menu
+* C++ Module Mapper:: Module Mapper
+* C++ Module Preprocessing:: Module Preprocessing
+* C++ Compiled Module Interface:: Compiled Module Interface
+@end menu
+
+@node C++ Module Mapper
+@subsection Module Mapper
+@cindex C++ Module Mapper
+
+A module mapper provides a server or file that the compiler queries to
+determine the mapping between module names and CMI files. It is also
+used to build CMIs on demand. @emph{Mapper functionality is in its
+infancy and is intended for experimentation with build system
+interactions.}
+
+You can specify a mapper with the @option{-fmodule-mapper=@var{val}}
+option or @env{CXX_MODULE_MAPPER} environment variable. The value may
+have one of the following forms:
+
+@table @gcctabopt
+
+@item @r{[}@var{hostname}@r{]}:@var{port}@r{[}?@var{ident}@r{]}
+An optional hostname and a numeric port number to connect to. If the
+hostname is omitted, the loopback address is used. If the hostname
+corresponds to multiple IPV6 addresses, these are tried in turn, until
+one is successful. If your host lacks IPv6, this form is
+non-functional. If you must use IPv4 use
+@option{-fmodule-mapper='|ncat @var{ipv4host} @var{port}'}.
+
+@item =@var{socket}@r{[}?@var{ident}@r{]}
+A local domain socket. If your host lacks local domain sockets, this
+form is non-functional.
+
+@item |@var{program}@r{[}?@var{ident}@r{]} @r{[}@var{args...}@r{]}
+A program to spawn, and communicate with on its stdin/stdout streams.
+Your @var{PATH} environment variable is searched for the program.
+Arguments are separated by space characters, (it is not possible for
+one of the arguments delivered to the program to contain a space). An
+exception is if @var{program} begins with @@. In that case
+@var{program} (sans @@) is looked for in the compiler's internal
+binary directory. Thus the sample mapper-server can be specified
+with @code{@@g++-mapper-server}.
+
+@item <>@r{[}?@var{ident}@r{]}
+@item <>@var{inout}@r{[}?@var{ident}@r{]}
+@item <@var{in}>@var{out}@r{[}?@var{ident}@r{]}
+Named pipes or file descriptors to communicate over. The first form,
+@option{<>}, communicates over stdin and stdout. The other forms
+allow you to specify a file descriptor or name a pipe. A numeric value
+is interpreted as a file descriptor, otherwise named pipe is opened.
+The second form specifies a bidirectional pipe and the last form
+allows specifying two independent pipes. Using file descriptors
+directly in this manner is fragile in general, as it can require the
+cooperation of intermediate processes. In particular using stdin &
+stdout is fraught with danger as other compiler options might also
+cause the compiler to read stdin or write stdout, and it can have
+unfortunate interactions with signal delivery from the terminal.
+
+@item @var{file}@r{[}?@var{ident}@r{]}
+A mapping file consisting of space-separated module-name, filename
+pairs, one per line. Only the mappings for the direct imports and any
+module export name need be provided. If other mappings are provided,
+they override those stored in any imported CMI files. A repository
+root may be specified in the mapping file by using @samp{$root} as the
+module name in the first active line. Use of this option will disable
+any default module->CMI name mapping.
+
+@end table
+
+As shown, an optional @var{ident} may suffix the first word of the
+option, indicated by a @samp{?} prefix. The value is used in the
+initial handshake with the module server, or to specify a prefix on
+mapping file lines. In the server case, the main source file name is
+used if no @var{ident} is specified. In the file case, all non-blank
+lines are significant, unless a value is specified, in which case only
+lines beginning with @var{ident} are significant. The @var{ident}
+must be separated by whitespace from the module name. Be aware that
+@samp{<}, @samp{>}, @samp{?}, and @samp{|} characters are often
+significant to the shell, and therefore may need quoting.
+
+The mapper is connected to or loaded lazily, when the first module
+mapping is required. The networking protocols are only supported on
+hosts that provide networking. If no mapper is specified a default is
+provided.
+
+A project-specific mapper is expected to be provided by the build
+system that invokes the compiler. It is not expected that a
+general-purpose server is provided for all compilations. As such, the
+server will know the build configuration, the compiler it invoked, and
+the environment (such as working directory) in which that is
+operating. As it may parallelize builds, several compilations may
+connect to the same socket.
+
+The default mapper generates CMI files in a @samp{gcm.cache}
+directory. CMI files have a @samp{.gcm} suffix. The module unit name
+is used directly to provide the basename. Header units construct a
+relative path using the underlying header file name. If the path is
+already relative, a @samp{,} directory is prepended. Internal
+@samp{..} components are translated to @samp{,,}. No attempt is made
+to canonicalize these filenames beyond that done by the preprocessor's
+include search algorithm, as in general it is ambiguous when symbolic
+links are present.
+
+The mapper protocol was published as ``A Module Mapper''
+@uref{https://wg21.link/p1184}. The implementation is provided by
+@command{libcody}, @uref{https://github.com/urnathan/libcody},
+which specifies the canonical protocol definition. A proof of concept
+server implementation embedded in @command{make} was described in
+''Make Me A Module'', @uref{https://wg21.link/p1602}.
+
+@node C++ Module Preprocessing
+@subsection Module Preprocessing
+@cindex C++ Module Preprocessing
+
+Modules affect preprocessing because of header units and include
+translation. Some uses of the preprocessor as a separate step either
+do not produce a correct output, or require CMIs to be available.
+
+Header units import macros. These macros can affect later conditional
+inclusion, which therefore can cascade to differing import sets. When
+preprocessing, it is necessary to load the CMI. If a header unit is
+unavailable, the preprocessor issues a warning and continue (when
+not just preprocessing, an error is emitted). Detecting such imports
+requires preprocessor tokenization of the input stream to phase 4
+(macro expansion).
+
+Include translation converts @code{#include}, @code{#include_next} and
+@code{#import} directives to internal @code{import} declarations.
+Whether a particular directive is translated is controlled by the
+module mapper. Header unit names are canonicalized during
+preprocessing.
+
+Dependency information can be emitted for macro import, extending the
+functionality of @option{-MD} and @option{-MMD} options. Detection of
+import declarations also requires phase 4 preprocessing, and thus
+requires full preprocessing (or compilation).
+
+The @option{-M}, @option{-MM} and @option{-E -fdirectives-only} options halt
+preprocessing before phase 4.
+
+The @option{-save-temps} option uses @option{-fdirectives-only} for
+preprocessing, and preserve the macro definitions in the preprocessed
+output. Usually you also want to use this option when explicitly
+preprocessing a header-unit, or consuming such preprocessed output:
+
+@smallexample
+g++ -fmodules-ts -E -fdirectives-only my-header.hh -o my-header.ii
+g++ -x c++-header -fmodules-ts -fpreprocessed -fdirectives-only my-header.ii
+@end smallexample
+
+@node C++ Compiled Module Interface
+@subsection Compiled Module Interface
+@cindex C++ Compiled Module Interface
+
+CMIs are an additional artifact when compiling named module
+interfaces, partitions or header units. These are read when
+importing. CMI contents are implementation-specific, and in GCC's
+case tied to the compiler version. Consider them a rebuildable cache
+artifact, not a distributable object.
+
+When creating an output CMI, any missing directory components are
+created in a manner that is safe for concurrent builds creating
+multiple, different, CMIs within a common subdirectory tree.
+
+CMI contents are written to a temporary file, which is then atomically
+renamed. Observers either see old contents (if there is an
+existing file), or complete new contents. They do not observe the
+CMI during its creation. This is unlike object file writing, which
+may be observed by an external process.
+
+CMIs are read in lazily, if the host OS provides @code{mmap}
+functionality. Generally blocks are read when name lookup or template
+instantiation occurs. To inhibit this, the @option{-fno-module-lazy}
+option may be used.
+
+The @option{--param lazy-modules=@var{n}} parameter controls the limit
+on the number of concurrently open module files during lazy loading.
+Should more modules be imported, an LRU algorithm is used to determine
+which files to close---until that file is needed again. This limit
+may be exceeded with deep module dependency hierarchies. With large
+code bases there may be more imports than the process limit of file
+descriptors. By default, the limit is a few less than the per-process
+file descriptor hard limit, if that is determinable.@footnote{Where
+applicable the soft limit is incremented as needed towards the hard limit.}
+
+GCC CMIs use ELF32 as an architecture-neutral encapsulation mechanism.
+You may use @command{readelf} to inspect them, although section
+contents are largely undecipherable. There is a section named
+@code{.gnu.c++.README}, which contains human-readable text. Other
+than the first line, each line consists of @code{@var{tag}: @code{value}}
+tuples.
+
+@smallexample
+> @command{readelf -p.gnu.c++.README gcm.cache/foo.gcm}
+
+String dump of section '.gnu.c++.README':
+ [ 0] GNU C++ primary module interface
+ [ 21] compiler: 11.0.0 20201116 (experimental) [c++-modules revision 20201116-0454]
+ [ 6f] version: 2020/11/16-04:54
+ [ 89] module: foo
+ [ 95] source: c_b.ii
+ [ a4] dialect: C++20/coroutines
+ [ be] cwd: /data/users/nathans/modules/obj/x86_64/gcc
+ [ ee] repository: gcm.cache
+ [ 104] buildtime: 2020/11/16 15:03:21 UTC
+ [ 127] localtime: 2020/11/16 07:03:21 PST
+ [ 14a] export: foo:part1 foo-part1.gcm
+@end smallexample
+
+Amongst other things, this lists the source that was built, C++
+dialect used and imports of the module.@footnote{The precise contents
+of this output may change.} The timestamp is the same value as that
+provided by the @code{__DATE__} & @code{__TIME__} macros, and may be
+explicitly specified with the environment variable
+@code{SOURCE_DATE_EPOCH}. For further details
+@pxref{Environment Variables}.
+
+A set of related CMIs may be copied, provided the relative pathnames
+are preserved.
+
+The @code{.gnu.c++.README} contents do not affect CMI integrity, and
+it may be removed or altered. The section numbering of the sections
+whose names do not begin with @code{.gnu.c++.}, or are not the string
+section is significant and must not be altered.
--- /dev/null
+@c Copyright (C) 2002-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Languages
+@chapter Language Front Ends in GCC
+
+The interface to front ends for languages in GCC, and in particular
+the @code{tree} structure (@pxref{GENERIC}), was initially designed for
+C, and many aspects of it are still somewhat biased towards C and
+C-like languages. It is, however, reasonably well suited to other
+procedural languages, and front ends for many such languages have been
+written for GCC@.
+
+Writing a compiler as a front end for GCC, rather than compiling
+directly to assembler or generating C code which is then compiled by
+GCC, has several advantages:
+
+@itemize @bullet
+@item GCC front ends benefit from the support for many different
+target machines already present in GCC@.
+@item GCC front ends benefit from all the optimizations in GCC@. Some
+of these, such as alias analysis, may work better when GCC is
+compiling directly from source code than when it is compiling from
+generated C code.
+@item Better debugging information is generated when compiling
+directly from source code than when going via intermediate generated C
+code.
+@end itemize
+
+Because of the advantages of writing a compiler as a GCC front end,
+GCC front ends have also been created for languages very different
+from those for which GCC was designed, such as the declarative
+logic/functional language Mercury. For these reasons, it may also be
+useful to implement compilers created for specialized purposes (for
+example, as part of a research project) as GCC front ends.
--- /dev/null
+@c Copyright (C) 2003-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+@c Contributed by Aldy Hernandez <aldy@quesejoda.com>
+
+@node Libgcc
+@chapter The GCC low-level runtime library
+
+GCC provides a low-level runtime library, @file{libgcc.a} or
+@file{libgcc_s.so.1} on some platforms. GCC generates calls to
+routines in this library automatically, whenever it needs to perform
+some operation that is too complicated to emit inline code for.
+
+Most of the routines in @code{libgcc} handle arithmetic operations
+that the target processor cannot perform directly. This includes
+integer multiply and divide on some machines, and all floating-point
+and fixed-point operations on other machines. @code{libgcc} also includes
+routines for exception handling, and a handful of miscellaneous operations.
+
+Some of these routines can be defined in mostly machine-independent C@.
+Others must be hand-written in assembly language for each processor
+that needs them.
+
+GCC will also generate calls to C library routines, such as
+@code{memcpy} and @code{memset}, in some cases. The set of routines
+that GCC may possibly use is documented in @ref{Other
+Builtins,,,gcc, Using the GNU Compiler Collection (GCC)}.
+
+These routines take arguments and return values of a specific machine
+mode, not a specific C type. @xref{Machine Modes}, for an explanation
+of this concept. For illustrative purposes, in this chapter the
+floating point type @code{float} is assumed to correspond to @code{SFmode};
+@code{double} to @code{DFmode}; and @code{@w{long double}} to both
+@code{TFmode} and @code{XFmode}. Similarly, the integer types @code{int}
+and @code{@w{unsigned int}} correspond to @code{SImode}; @code{long} and
+@code{@w{unsigned long}} to @code{DImode}; and @code{@w{long long}} and
+@code{@w{unsigned long long}} to @code{TImode}.
+
+@menu
+* Integer library routines::
+* Soft float library routines::
+* Decimal float library routines::
+* Fixed-point fractional library routines::
+* Exception handling routines::
+* Miscellaneous routines::
+@end menu
+
+@node Integer library routines
+@section Routines for integer arithmetic
+
+The integer arithmetic routines are used on platforms that don't provide
+hardware support for arithmetic operations on some modes.
+
+@subsection Arithmetic functions
+
+@deftypefn {Runtime Function} int __ashlsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __ashldi3 (long @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long} __ashlti3 (long long @var{a}, int @var{b})
+These functions return the result of shifting @var{a} left by @var{b} bits.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __ashrsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __ashrdi3 (long @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long} __ashrti3 (long long @var{a}, int @var{b})
+These functions return the result of arithmetically shifting @var{a} right
+by @var{b} bits.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __divsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __divdi3 (long @var{a}, long @var{b})
+@deftypefnx {Runtime Function} {long long} __divti3 (long long @var{a}, long long @var{b})
+These functions return the quotient of the signed division of @var{a} and
+@var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __lshrsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __lshrdi3 (long @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long} __lshrti3 (long long @var{a}, int @var{b})
+These functions return the result of logically shifting @var{a} right by
+@var{b} bits.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __modsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __moddi3 (long @var{a}, long @var{b})
+@deftypefnx {Runtime Function} {long long} __modti3 (long long @var{a}, long long @var{b})
+These functions return the remainder of the signed division of @var{a}
+and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __mulsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __muldi3 (long @var{a}, long @var{b})
+@deftypefnx {Runtime Function} {long long} __multi3 (long long @var{a}, long long @var{b})
+These functions return the product of @var{a} and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} long __negdi2 (long @var{a})
+@deftypefnx {Runtime Function} {long long} __negti2 (long long @var{a})
+These functions return the negation of @var{a}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned int} __udivsi3 (unsigned int @var{a}, unsigned int @var{b})
+@deftypefnx {Runtime Function} {unsigned long} __udivdi3 (unsigned long @var{a}, unsigned long @var{b})
+@deftypefnx {Runtime Function} {unsigned long long} __udivti3 (unsigned long long @var{a}, unsigned long long @var{b})
+These functions return the quotient of the unsigned division of @var{a}
+and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned long} __udivmoddi4 (unsigned long @var{a}, unsigned long @var{b}, unsigned long *@var{c})
+@deftypefnx {Runtime Function} {unsigned long long} __udivmodti4 (unsigned long long @var{a}, unsigned long long @var{b}, unsigned long long *@var{c})
+These functions calculate both the quotient and remainder of the unsigned
+division of @var{a} and @var{b}. The return value is the quotient, and
+the remainder is placed in variable pointed to by @var{c}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned int} __umodsi3 (unsigned int @var{a}, unsigned int @var{b})
+@deftypefnx {Runtime Function} {unsigned long} __umoddi3 (unsigned long @var{a}, unsigned long @var{b})
+@deftypefnx {Runtime Function} {unsigned long long} __umodti3 (unsigned long long @var{a}, unsigned long long @var{b})
+These functions return the remainder of the unsigned division of @var{a}
+and @var{b}.
+@end deftypefn
+
+@subsection Comparison functions
+
+The following functions implement integral comparisons. These functions
+implement a low-level compare, upon which the higher level comparison
+operators (such as less than and greater than or equal to) can be
+constructed. The returned values lie in the range zero to two, to allow
+the high-level operators to be implemented by testing the returned
+result using either signed or unsigned comparison.
+
+@deftypefn {Runtime Function} int __cmpdi2 (long @var{a}, long @var{b})
+@deftypefnx {Runtime Function} int __cmpti2 (long long @var{a}, long long @var{b})
+These functions perform a signed comparison of @var{a} and @var{b}. If
+@var{a} is less than @var{b}, they return 0; if @var{a} is greater than
+@var{b}, they return 2; and if @var{a} and @var{b} are equal they return 1.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __ucmpdi2 (unsigned long @var{a}, unsigned long @var{b})
+@deftypefnx {Runtime Function} int __ucmpti2 (unsigned long long @var{a}, unsigned long long @var{b})
+These functions perform an unsigned comparison of @var{a} and @var{b}.
+If @var{a} is less than @var{b}, they return 0; if @var{a} is greater than
+@var{b}, they return 2; and if @var{a} and @var{b} are equal they return 1.
+@end deftypefn
+
+@subsection Trapping arithmetic functions
+
+The following functions implement trapping arithmetic. These functions
+call the libc function @code{abort} upon signed arithmetic overflow.
+
+@deftypefn {Runtime Function} int __absvsi2 (int @var{a})
+@deftypefnx {Runtime Function} long __absvdi2 (long @var{a})
+These functions return the absolute value of @var{a}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __addvsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __addvdi3 (long @var{a}, long @var{b})
+These functions return the sum of @var{a} and @var{b}; that is
+@code{@var{a} + @var{b}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __mulvsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __mulvdi3 (long @var{a}, long @var{b})
+The functions return the product of @var{a} and @var{b}; that is
+@code{@var{a} * @var{b}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __negvsi2 (int @var{a})
+@deftypefnx {Runtime Function} long __negvdi2 (long @var{a})
+These functions return the negation of @var{a}; that is @code{-@var{a}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __subvsi3 (int @var{a}, int @var{b})
+@deftypefnx {Runtime Function} long __subvdi3 (long @var{a}, long @var{b})
+These functions return the difference between @var{b} and @var{a};
+that is @code{@var{a} - @var{b}}.
+@end deftypefn
+
+@subsection Bit operations
+
+@deftypefn {Runtime Function} int __clzsi2 (unsigned int @var{a})
+@deftypefnx {Runtime Function} int __clzdi2 (unsigned long @var{a})
+@deftypefnx {Runtime Function} int __clzti2 (unsigned long long @var{a})
+These functions return the number of leading 0-bits in @var{a}, starting
+at the most significant bit position. If @var{a} is zero, the result is
+undefined.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __ctzsi2 (unsigned int @var{a})
+@deftypefnx {Runtime Function} int __ctzdi2 (unsigned long @var{a})
+@deftypefnx {Runtime Function} int __ctzti2 (unsigned long long @var{a})
+These functions return the number of trailing 0-bits in @var{a}, starting
+at the least significant bit position. If @var{a} is zero, the result is
+undefined.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __ffsdi2 (unsigned long @var{a})
+@deftypefnx {Runtime Function} int __ffsti2 (unsigned long long @var{a})
+These functions return the index of the least significant 1-bit in @var{a},
+or the value zero if @var{a} is zero. The least significant bit is index
+one.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __paritysi2 (unsigned int @var{a})
+@deftypefnx {Runtime Function} int __paritydi2 (unsigned long @var{a})
+@deftypefnx {Runtime Function} int __parityti2 (unsigned long long @var{a})
+These functions return the value zero if the number of bits set in
+@var{a} is even, and the value one otherwise.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __popcountsi2 (unsigned int @var{a})
+@deftypefnx {Runtime Function} int __popcountdi2 (unsigned long @var{a})
+@deftypefnx {Runtime Function} int __popcountti2 (unsigned long long @var{a})
+These functions return the number of bits set in @var{a}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int32_t __bswapsi2 (int32_t @var{a})
+@deftypefnx {Runtime Function} int64_t __bswapdi2 (int64_t @var{a})
+These functions return the @var{a} byteswapped.
+@end deftypefn
+
+@node Soft float library routines
+@section Routines for floating point emulation
+@cindex soft float library
+@cindex arithmetic library
+@cindex math library
+@opindex msoft-float
+
+The software floating point library is used on machines which do not
+have hardware support for floating point. It is also used whenever
+@option{-msoft-float} is used to disable generation of floating point
+instructions. (Not all targets support this switch.)
+
+For compatibility with other compilers, the floating point emulation
+routines can be renamed with the @code{DECLARE_LIBRARY_RENAMES} macro
+(@pxref{Library Calls}). In this section, the default names are used.
+
+Presently the library does not support @code{XFmode}, which is used
+for @code{long double} on some architectures.
+
+@subsection Arithmetic functions
+
+@deftypefn {Runtime Function} float __addsf3 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} double __adddf3 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} {long double} __addtf3 (long double @var{a}, long double @var{b})
+@deftypefnx {Runtime Function} {long double} __addxf3 (long double @var{a}, long double @var{b})
+These functions return the sum of @var{a} and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __subsf3 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} double __subdf3 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} {long double} __subtf3 (long double @var{a}, long double @var{b})
+@deftypefnx {Runtime Function} {long double} __subxf3 (long double @var{a}, long double @var{b})
+These functions return the difference between @var{b} and @var{a};
+that is, @w{@math{@var{a} - @var{b}}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __mulsf3 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} double __muldf3 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} {long double} __multf3 (long double @var{a}, long double @var{b})
+@deftypefnx {Runtime Function} {long double} __mulxf3 (long double @var{a}, long double @var{b})
+These functions return the product of @var{a} and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __divsf3 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} double __divdf3 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} {long double} __divtf3 (long double @var{a}, long double @var{b})
+@deftypefnx {Runtime Function} {long double} __divxf3 (long double @var{a}, long double @var{b})
+These functions return the quotient of @var{a} and @var{b}; that is,
+@w{@math{@var{a} / @var{b}}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __negsf2 (float @var{a})
+@deftypefnx {Runtime Function} double __negdf2 (double @var{a})
+@deftypefnx {Runtime Function} {long double} __negtf2 (long double @var{a})
+@deftypefnx {Runtime Function} {long double} __negxf2 (long double @var{a})
+These functions return the negation of @var{a}. They simply flip the
+sign bit, so they can produce negative zero and negative NaN@.
+@end deftypefn
+
+@subsection Conversion functions
+
+@deftypefn {Runtime Function} double __extendsfdf2 (float @var{a})
+@deftypefnx {Runtime Function} {long double} __extendsftf2 (float @var{a})
+@deftypefnx {Runtime Function} {long double} __extendsfxf2 (float @var{a})
+@deftypefnx {Runtime Function} {long double} __extenddftf2 (double @var{a})
+@deftypefnx {Runtime Function} {long double} __extenddfxf2 (double @var{a})
+These functions extend @var{a} to the wider mode of their return
+type.
+@end deftypefn
+
+@deftypefn {Runtime Function} double __truncxfdf2 (long double @var{a})
+@deftypefnx {Runtime Function} double __trunctfdf2 (long double @var{a})
+@deftypefnx {Runtime Function} float __truncxfsf2 (long double @var{a})
+@deftypefnx {Runtime Function} float __trunctfsf2 (long double @var{a})
+@deftypefnx {Runtime Function} float __truncdfsf2 (double @var{a})
+These functions truncate @var{a} to the narrower mode of their return
+type, rounding toward zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __fixsfsi (float @var{a})
+@deftypefnx {Runtime Function} int __fixdfsi (double @var{a})
+@deftypefnx {Runtime Function} int __fixtfsi (long double @var{a})
+@deftypefnx {Runtime Function} int __fixxfsi (long double @var{a})
+These functions convert @var{a} to a signed integer, rounding toward zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} long __fixsfdi (float @var{a})
+@deftypefnx {Runtime Function} long __fixdfdi (double @var{a})
+@deftypefnx {Runtime Function} long __fixtfdi (long double @var{a})
+@deftypefnx {Runtime Function} long __fixxfdi (long double @var{a})
+These functions convert @var{a} to a signed long, rounding toward zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} {long long} __fixsfti (float @var{a})
+@deftypefnx {Runtime Function} {long long} __fixdfti (double @var{a})
+@deftypefnx {Runtime Function} {long long} __fixtfti (long double @var{a})
+@deftypefnx {Runtime Function} {long long} __fixxfti (long double @var{a})
+These functions convert @var{a} to a signed long long, rounding toward zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned int} __fixunssfsi (float @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fixunsdfsi (double @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fixunstfsi (long double @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fixunsxfsi (long double @var{a})
+These functions convert @var{a} to an unsigned integer, rounding
+toward zero. Negative values all become zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned long} __fixunssfdi (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fixunsdfdi (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fixunstfdi (long double @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fixunsxfdi (long double @var{a})
+These functions convert @var{a} to an unsigned long, rounding
+toward zero. Negative values all become zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned long long} __fixunssfti (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fixunsdfti (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fixunstfti (long double @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fixunsxfti (long double @var{a})
+These functions convert @var{a} to an unsigned long long, rounding
+toward zero. Negative values all become zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __floatsisf (int @var{i})
+@deftypefnx {Runtime Function} double __floatsidf (int @var{i})
+@deftypefnx {Runtime Function} {long double} __floatsitf (int @var{i})
+@deftypefnx {Runtime Function} {long double} __floatsixf (int @var{i})
+These functions convert @var{i}, a signed integer, to floating point.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __floatdisf (long @var{i})
+@deftypefnx {Runtime Function} double __floatdidf (long @var{i})
+@deftypefnx {Runtime Function} {long double} __floatditf (long @var{i})
+@deftypefnx {Runtime Function} {long double} __floatdixf (long @var{i})
+These functions convert @var{i}, a signed long, to floating point.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __floattisf (long long @var{i})
+@deftypefnx {Runtime Function} double __floattidf (long long @var{i})
+@deftypefnx {Runtime Function} {long double} __floattitf (long long @var{i})
+@deftypefnx {Runtime Function} {long double} __floattixf (long long @var{i})
+These functions convert @var{i}, a signed long long, to floating point.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __floatunsisf (unsigned int @var{i})
+@deftypefnx {Runtime Function} double __floatunsidf (unsigned int @var{i})
+@deftypefnx {Runtime Function} {long double} __floatunsitf (unsigned int @var{i})
+@deftypefnx {Runtime Function} {long double} __floatunsixf (unsigned int @var{i})
+These functions convert @var{i}, an unsigned integer, to floating point.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __floatundisf (unsigned long @var{i})
+@deftypefnx {Runtime Function} double __floatundidf (unsigned long @var{i})
+@deftypefnx {Runtime Function} {long double} __floatunditf (unsigned long @var{i})
+@deftypefnx {Runtime Function} {long double} __floatundixf (unsigned long @var{i})
+These functions convert @var{i}, an unsigned long, to floating point.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __floatuntisf (unsigned long long @var{i})
+@deftypefnx {Runtime Function} double __floatuntidf (unsigned long long @var{i})
+@deftypefnx {Runtime Function} {long double} __floatuntitf (unsigned long long @var{i})
+@deftypefnx {Runtime Function} {long double} __floatuntixf (unsigned long long @var{i})
+These functions convert @var{i}, an unsigned long long, to floating point.
+@end deftypefn
+
+@subsection Comparison functions
+
+There are two sets of basic comparison functions.
+
+@deftypefn {Runtime Function} int __cmpsf2 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} int __cmpdf2 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} int __cmptf2 (long double @var{a}, long double @var{b})
+These functions calculate @math{a <=> b}. That is, if @var{a} is less
+than @var{b}, they return @minus{}1; if @var{a} is greater than @var{b}, they
+return 1; and if @var{a} and @var{b} are equal they return 0. If
+either argument is NaN they return 1, but you should not rely on this;
+if NaN is a possibility, use one of the higher-level comparison
+functions.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __unordsf2 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} int __unorddf2 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} int __unordtf2 (long double @var{a}, long double @var{b})
+These functions return a nonzero value if either argument is NaN, otherwise 0.
+@end deftypefn
+
+There is also a complete group of higher level functions which
+correspond directly to comparison operators. They implement the ISO C
+semantics for floating-point comparisons, taking NaN into account.
+Pay careful attention to the return values defined for each set.
+Under the hood, all of these routines are implemented as
+
+@smallexample
+ if (__unord@var{X}f2 (a, b))
+ return @var{E};
+ return __cmp@var{X}f2 (a, b);
+@end smallexample
+
+@noindent
+where @var{E} is a constant chosen to give the proper behavior for
+NaN@. Thus, the meaning of the return value is different for each set.
+Do not rely on this implementation; only the semantics documented
+below are guaranteed.
+
+@deftypefn {Runtime Function} int __eqsf2 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} int __eqdf2 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} int __eqtf2 (long double @var{a}, long double @var{b})
+These functions return zero if neither argument is NaN, and @var{a} and
+@var{b} are equal.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __nesf2 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} int __nedf2 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} int __netf2 (long double @var{a}, long double @var{b})
+These functions return a nonzero value if either argument is NaN, or
+if @var{a} and @var{b} are unequal.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __gesf2 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} int __gedf2 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} int __getf2 (long double @var{a}, long double @var{b})
+These functions return a value greater than or equal to zero if
+neither argument is NaN, and @var{a} is greater than or equal to
+@var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __ltsf2 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} int __ltdf2 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} int __lttf2 (long double @var{a}, long double @var{b})
+These functions return a value less than zero if neither argument is
+NaN, and @var{a} is strictly less than @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __lesf2 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} int __ledf2 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} int __letf2 (long double @var{a}, long double @var{b})
+These functions return a value less than or equal to zero if neither
+argument is NaN, and @var{a} is less than or equal to @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __gtsf2 (float @var{a}, float @var{b})
+@deftypefnx {Runtime Function} int __gtdf2 (double @var{a}, double @var{b})
+@deftypefnx {Runtime Function} int __gttf2 (long double @var{a}, long double @var{b})
+These functions return a value greater than zero if neither argument
+is NaN, and @var{a} is strictly greater than @var{b}.
+@end deftypefn
+
+@subsection Other floating-point functions
+
+@deftypefn {Runtime Function} float __powisf2 (float @var{a}, int @var{b})
+@deftypefnx {Runtime Function} double __powidf2 (double @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long double} __powitf2 (long double @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long double} __powixf2 (long double @var{a}, int @var{b})
+These functions convert raise @var{a} to the power @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {complex float} __mulsc3 (float @var{a}, float @var{b}, float @var{c}, float @var{d})
+@deftypefnx {Runtime Function} {complex double} __muldc3 (double @var{a}, double @var{b}, double @var{c}, double @var{d})
+@deftypefnx {Runtime Function} {complex long double} __multc3 (long double @var{a}, long double @var{b}, long double @var{c}, long double @var{d})
+@deftypefnx {Runtime Function} {complex long double} __mulxc3 (long double @var{a}, long double @var{b}, long double @var{c}, long double @var{d})
+These functions return the product of @math{@var{a} + i@var{b}} and
+@math{@var{c} + i@var{d}}, following the rules of C99 Annex G@.
+@end deftypefn
+
+@deftypefn {Runtime Function} {complex float} __divsc3 (float @var{a}, float @var{b}, float @var{c}, float @var{d})
+@deftypefnx {Runtime Function} {complex double} __divdc3 (double @var{a}, double @var{b}, double @var{c}, double @var{d})
+@deftypefnx {Runtime Function} {complex long double} __divtc3 (long double @var{a}, long double @var{b}, long double @var{c}, long double @var{d})
+@deftypefnx {Runtime Function} {complex long double} __divxc3 (long double @var{a}, long double @var{b}, long double @var{c}, long double @var{d})
+These functions return the quotient of @math{@var{a} + i@var{b}} and
+@math{@var{c} + i@var{d}} (i.e., @math{(@var{a} + i@var{b}) / (@var{c}
++ i@var{d})}), following the rules of C99 Annex G@.
+@end deftypefn
+
+@node Decimal float library routines
+@section Routines for decimal floating point emulation
+@cindex decimal float library
+@cindex IEEE 754-2008
+
+The software decimal floating point library implements IEEE 754-2008
+decimal floating point arithmetic and is only activated on selected
+targets.
+
+The software decimal floating point library supports either DPD
+(Densely Packed Decimal) or BID (Binary Integer Decimal) encoding
+as selected at configure time.
+
+
+@subsection Arithmetic functions
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_addsd3 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} _Decimal32 __bid_addsd3 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_adddd3 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} _Decimal64 __bid_adddd3 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_addtd3 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} _Decimal128 __bid_addtd3 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return the sum of @var{a} and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_subsd3 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} _Decimal32 __bid_subsd3 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_subdd3 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} _Decimal64 __bid_subdd3 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_subtd3 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} _Decimal128 __bid_subtd3 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return the difference between @var{b} and @var{a};
+that is, @w{@math{@var{a} - @var{b}}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_mulsd3 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} _Decimal32 __bid_mulsd3 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_muldd3 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} _Decimal64 __bid_muldd3 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_multd3 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} _Decimal128 __bid_multd3 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return the product of @var{a} and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_divsd3 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} _Decimal32 __bid_divsd3 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_divdd3 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} _Decimal64 __bid_divdd3 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_divtd3 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} _Decimal128 __bid_divtd3 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return the quotient of @var{a} and @var{b}; that is,
+@w{@math{@var{a} / @var{b}}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_negsd2 (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __bid_negsd2 (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_negdd2 (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __bid_negdd2 (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_negtd2 (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __bid_negtd2 (_Decimal128 @var{a})
+These functions return the negation of @var{a}. They simply flip the
+sign bit, so they can produce negative zero and negative NaN@.
+@end deftypefn
+
+@subsection Conversion functions
+
+@deftypefn {Runtime Function} _Decimal64 __dpd_extendsddd2 (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __bid_extendsddd2 (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_extendsdtd2 (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __bid_extendsdtd2 (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_extendddtd2 (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __bid_extendddtd2 (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __dpd_truncddsd2 (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __bid_truncddsd2 (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __dpd_trunctdsd2 (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __bid_trunctdsd2 (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_trunctddd2 (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __bid_trunctddd2 (_Decimal128 @var{a})
+These functions convert the value @var{a} from one decimal floating type
+to another.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal64 __dpd_extendsfdd (float @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __bid_extendsfdd (float @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_extendsftd (float @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __bid_extendsftd (float @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_extenddftd (double @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __bid_extenddftd (double @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_extendxftd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __bid_extendxftd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __dpd_truncdfsd (double @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __bid_truncdfsd (double @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __dpd_truncxfsd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __bid_truncxfsd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __dpd_trunctfsd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __bid_trunctfsd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_truncxfdd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __bid_truncxfdd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_trunctfdd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __bid_trunctfdd ({long double} @var{a})
+These functions convert the value of @var{a} from a binary floating type
+to a decimal floating type of a different size.
+@end deftypefn
+
+@deftypefn {Runtime Function} float __dpd_truncddsf (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} float __bid_truncddsf (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} float __dpd_trunctdsf (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} float __bid_trunctdsf (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} double __dpd_extendsddf (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} double __bid_extendsddf (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} double __dpd_trunctddf (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} double __bid_trunctddf (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} {long double} __dpd_extendsdxf (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} {long double} __bid_extendsdxf (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} {long double} __dpd_extendddxf (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} {long double} __bid_extendddxf (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} {long double} __dpd_trunctdxf (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} {long double} __bid_trunctdxf (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} {long double} __dpd_extendsdtf (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} {long double} __bid_extendsdtf (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} {long double} __dpd_extendddtf (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} {long double} __bid_extendddtf (_Decimal64 @var{a})
+These functions convert the value of @var{a} from a decimal floating type
+to a binary floating type of a different size.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_extendsfsd (float @var{a})
+@deftypefnx {Runtime Function} _Decimal32 __bid_extendsfsd (float @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_extenddfdd (double @var{a})
+@deftypefnx {Runtime Function} _Decimal64 __bid_extenddfdd (double @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_extendtftd ({long double} @var{a})
+@deftypefnx {Runtime Function} _Decimal128 __bid_extendtftd ({long double} @var{a})
+@deftypefnx {Runtime Function} float __dpd_truncsdsf (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} float __bid_truncsdsf (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} double __dpd_truncdddf (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} double __bid_truncdddf (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} {long double} __dpd_trunctdtf (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} {long double} __bid_trunctdtf (_Decimal128 @var{a})
+These functions convert the value of @var{a} between decimal and
+binary floating types of the same size.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __dpd_fixsdsi (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} int __bid_fixsdsi (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} int __dpd_fixddsi (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} int __bid_fixddsi (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} int __dpd_fixtdsi (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} int __bid_fixtdsi (_Decimal128 @var{a})
+These functions convert @var{a} to a signed integer.
+@end deftypefn
+
+@deftypefn {Runtime Function} long __dpd_fixsddi (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} long __bid_fixsddi (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} long __dpd_fixdddi (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} long __bid_fixdddi (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} long __dpd_fixtddi (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} long __bid_fixtddi (_Decimal128 @var{a})
+These functions convert @var{a} to a signed long.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned int} __dpd_fixunssdsi (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __bid_fixunssdsi (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __dpd_fixunsddsi (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __bid_fixunsddsi (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __dpd_fixunstdsi (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __bid_fixunstdsi (_Decimal128 @var{a})
+These functions convert @var{a} to an unsigned integer. Negative values all become zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned long} __dpd_fixunssddi (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __bid_fixunssddi (_Decimal32 @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __dpd_fixunsdddi (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __bid_fixunsdddi (_Decimal64 @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __dpd_fixunstddi (_Decimal128 @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __bid_fixunstddi (_Decimal128 @var{a})
+These functions convert @var{a} to an unsigned long. Negative values
+all become zero.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_floatsisd (int @var{i})
+@deftypefnx {Runtime Function} _Decimal32 __bid_floatsisd (int @var{i})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_floatsidd (int @var{i})
+@deftypefnx {Runtime Function} _Decimal64 __bid_floatsidd (int @var{i})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_floatsitd (int @var{i})
+@deftypefnx {Runtime Function} _Decimal128 __bid_floatsitd (int @var{i})
+These functions convert @var{i}, a signed integer, to decimal floating point.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_floatdisd (long @var{i})
+@deftypefnx {Runtime Function} _Decimal32 __bid_floatdisd (long @var{i})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_floatdidd (long @var{i})
+@deftypefnx {Runtime Function} _Decimal64 __bid_floatdidd (long @var{i})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_floatditd (long @var{i})
+@deftypefnx {Runtime Function} _Decimal128 __bid_floatditd (long @var{i})
+These functions convert @var{i}, a signed long, to decimal floating point.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_floatunssisd (unsigned int @var{i})
+@deftypefnx {Runtime Function} _Decimal32 __bid_floatunssisd (unsigned int @var{i})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_floatunssidd (unsigned int @var{i})
+@deftypefnx {Runtime Function} _Decimal64 __bid_floatunssidd (unsigned int @var{i})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_floatunssitd (unsigned int @var{i})
+@deftypefnx {Runtime Function} _Decimal128 __bid_floatunssitd (unsigned int @var{i})
+These functions convert @var{i}, an unsigned integer, to decimal floating point.
+@end deftypefn
+
+@deftypefn {Runtime Function} _Decimal32 __dpd_floatunsdisd (unsigned long @var{i})
+@deftypefnx {Runtime Function} _Decimal32 __bid_floatunsdisd (unsigned long @var{i})
+@deftypefnx {Runtime Function} _Decimal64 __dpd_floatunsdidd (unsigned long @var{i})
+@deftypefnx {Runtime Function} _Decimal64 __bid_floatunsdidd (unsigned long @var{i})
+@deftypefnx {Runtime Function} _Decimal128 __dpd_floatunsditd (unsigned long @var{i})
+@deftypefnx {Runtime Function} _Decimal128 __bid_floatunsditd (unsigned long @var{i})
+These functions convert @var{i}, an unsigned long, to decimal floating point.
+@end deftypefn
+
+@subsection Comparison functions
+
+@deftypefn {Runtime Function} int __dpd_unordsd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __bid_unordsd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __dpd_unorddd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __bid_unorddd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __dpd_unordtd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} int __bid_unordtd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return a nonzero value if either argument is NaN, otherwise 0.
+@end deftypefn
+
+There is also a complete group of higher level functions which
+correspond directly to comparison operators. They implement the ISO C
+semantics for floating-point comparisons, taking NaN into account.
+Pay careful attention to the return values defined for each set.
+Under the hood, all of these routines are implemented as
+
+@smallexample
+ if (__bid_unord@var{X}d2 (a, b))
+ return @var{E};
+ return __bid_cmp@var{X}d2 (a, b);
+@end smallexample
+
+@noindent
+where @var{E} is a constant chosen to give the proper behavior for
+NaN@. Thus, the meaning of the return value is different for each set.
+Do not rely on this implementation; only the semantics documented
+below are guaranteed.
+
+@deftypefn {Runtime Function} int __dpd_eqsd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __bid_eqsd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __dpd_eqdd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __bid_eqdd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __dpd_eqtd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} int __bid_eqtd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return zero if neither argument is NaN, and @var{a} and
+@var{b} are equal.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __dpd_nesd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __bid_nesd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __dpd_nedd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __bid_nedd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __dpd_netd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} int __bid_netd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return a nonzero value if either argument is NaN, or
+if @var{a} and @var{b} are unequal.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __dpd_gesd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __bid_gesd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __dpd_gedd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __bid_gedd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __dpd_getd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} int __bid_getd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return a value greater than or equal to zero if
+neither argument is NaN, and @var{a} is greater than or equal to
+@var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __dpd_ltsd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __bid_ltsd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __dpd_ltdd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __bid_ltdd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __dpd_lttd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} int __bid_lttd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return a value less than zero if neither argument is
+NaN, and @var{a} is strictly less than @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __dpd_lesd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __bid_lesd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __dpd_ledd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __bid_ledd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __dpd_letd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} int __bid_letd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return a value less than or equal to zero if neither
+argument is NaN, and @var{a} is less than or equal to @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} int __dpd_gtsd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __bid_gtsd2 (_Decimal32 @var{a}, _Decimal32 @var{b})
+@deftypefnx {Runtime Function} int __dpd_gtdd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __bid_gtdd2 (_Decimal64 @var{a}, _Decimal64 @var{b})
+@deftypefnx {Runtime Function} int __dpd_gttd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+@deftypefnx {Runtime Function} int __bid_gttd2 (_Decimal128 @var{a}, _Decimal128 @var{b})
+These functions return a value greater than zero if neither argument
+is NaN, and @var{a} is strictly greater than @var{b}.
+@end deftypefn
+
+@node Fixed-point fractional library routines
+@section Routines for fixed-point fractional emulation
+@cindex fixed-point fractional library
+@cindex fractional types
+@cindex Embedded C
+
+The software fixed-point library implements fixed-point fractional
+arithmetic, and is only activated on selected targets.
+
+For ease of comprehension @code{fract} is an alias for the
+@code{_Fract} type, @code{accum} an alias for @code{_Accum}, and
+@code{sat} an alias for @code{_Sat}.
+
+For illustrative purposes, in this section the fixed-point fractional type
+@code{@w{short fract}} is assumed to correspond to machine mode @code{QQmode};
+@code{@w{unsigned short fract}} to @code{UQQmode};
+@code{fract} to @code{HQmode};
+@code{@w{unsigned fract}} to @code{UHQmode};
+@code{@w{long fract}} to @code{SQmode};
+@code{@w{unsigned long fract}} to @code{USQmode};
+@code{@w{long long fract}} to @code{DQmode};
+and @code{@w{unsigned long long fract}} to @code{UDQmode}.
+Similarly the fixed-point accumulator type
+@code{@w{short accum}} corresponds to @code{HAmode};
+@code{@w{unsigned short accum}} to @code{UHAmode};
+@code{accum} to @code{SAmode};
+@code{@w{unsigned accum}} to @code{USAmode};
+@code{@w{long accum}} to @code{DAmode};
+@code{@w{unsigned long accum}} to @code{UDAmode};
+@code{@w{long long accum}} to @code{TAmode};
+and @code{@w{unsigned long long accum}} to @code{UTAmode}.
+
+@subsection Arithmetic functions
+
+@deftypefn {Runtime Function} {short fract} __addqq3 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {fract} __addhq3 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {long fract} __addsq3 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {long long fract} __adddq3 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned short fract} __adduqq3 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __adduhq3 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __addusq3 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __addudq3 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {short accum} __addha3 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {accum} __addsa3 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {long accum} __addda3 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {long long accum} __addta3 (long long accum @var{a}, long long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __adduha3 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __addusa3 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __adduda3 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __adduta3 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions return the sum of @var{a} and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __ssaddqq3 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {fract} __ssaddhq3 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {long fract} __ssaddsq3 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {long long fract} __ssadddq3 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {short accum} __ssaddha3 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {accum} __ssaddsa3 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {long accum} __ssaddda3 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {long long accum} __ssaddta3 (long long accum @var{a}, long long accum @var{b})
+These functions return the sum of @var{a} and @var{b} with signed saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned short fract} __usadduqq3 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __usadduhq3 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __usaddusq3 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __usaddudq3 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __usadduha3 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __usaddusa3 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __usadduda3 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __usadduta3 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions return the sum of @var{a} and @var{b} with unsigned saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __subqq3 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {fract} __subhq3 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {long fract} __subsq3 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {long long fract} __subdq3 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned short fract} __subuqq3 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __subuhq3 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __subusq3 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __subudq3 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {short accum} __subha3 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {accum} __subsa3 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {long accum} __subda3 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {long long accum} __subta3 (long long accum @var{a}, long long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __subuha3 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __subusa3 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __subuda3 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __subuta3 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions return the difference of @var{a} and @var{b};
+that is, @code{@var{a} - @var{b}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __sssubqq3 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {fract} __sssubhq3 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {long fract} __sssubsq3 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {long long fract} __sssubdq3 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {short accum} __sssubha3 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {accum} __sssubsa3 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {long accum} __sssubda3 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {long long accum} __sssubta3 (long long accum @var{a}, long long accum @var{b})
+These functions return the difference of @var{a} and @var{b} with signed
+saturation; that is, @code{@var{a} - @var{b}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned short fract} __ussubuqq3 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __ussubuhq3 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __ussubusq3 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __ussubudq3 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __ussubuha3 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __ussubusa3 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __ussubuda3 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __ussubuta3 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions return the difference of @var{a} and @var{b} with unsigned
+saturation; that is, @code{@var{a} - @var{b}}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __mulqq3 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {fract} __mulhq3 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {long fract} __mulsq3 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {long long fract} __muldq3 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned short fract} __muluqq3 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __muluhq3 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __mulusq3 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __muludq3 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {short accum} __mulha3 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {accum} __mulsa3 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {long accum} __mulda3 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {long long accum} __multa3 (long long accum @var{a}, long long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __muluha3 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __mulusa3 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __muluda3 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __muluta3 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions return the product of @var{a} and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __ssmulqq3 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {fract} __ssmulhq3 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {long fract} __ssmulsq3 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {long long fract} __ssmuldq3 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {short accum} __ssmulha3 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {accum} __ssmulsa3 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {long accum} __ssmulda3 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {long long accum} __ssmulta3 (long long accum @var{a}, long long accum @var{b})
+These functions return the product of @var{a} and @var{b} with signed
+saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned short fract} __usmuluqq3 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __usmuluhq3 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __usmulusq3 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __usmuludq3 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __usmuluha3 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __usmulusa3 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __usmuluda3 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __usmuluta3 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions return the product of @var{a} and @var{b} with unsigned
+saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __divqq3 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {fract} __divhq3 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {long fract} __divsq3 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {long long fract} __divdq3 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {short accum} __divha3 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {accum} __divsa3 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {long accum} __divda3 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {long long accum} __divta3 (long long accum @var{a}, long long accum @var{b})
+These functions return the quotient of the signed division of @var{a}
+and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned short fract} __udivuqq3 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __udivuhq3 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __udivusq3 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __udivudq3 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __udivuha3 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __udivusa3 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __udivuda3 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __udivuta3 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions return the quotient of the unsigned division of @var{a}
+and @var{b}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __ssdivqq3 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {fract} __ssdivhq3 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {long fract} __ssdivsq3 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {long long fract} __ssdivdq3 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {short accum} __ssdivha3 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {accum} __ssdivsa3 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {long accum} __ssdivda3 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {long long accum} __ssdivta3 (long long accum @var{a}, long long accum @var{b})
+These functions return the quotient of the signed division of @var{a}
+and @var{b} with signed saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned short fract} __usdivuqq3 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __usdivuhq3 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __usdivusq3 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __usdivudq3 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __usdivuha3 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __usdivusa3 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __usdivuda3 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __usdivuta3 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions return the quotient of the unsigned division of @var{a}
+and @var{b} with unsigned saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __negqq2 (short fract @var{a})
+@deftypefnx {Runtime Function} {fract} __neghq2 (fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __negsq2 (long fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __negdq2 (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __neguqq2 (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __neguhq2 (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __negusq2 (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __negudq2 (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __negha2 (short accum @var{a})
+@deftypefnx {Runtime Function} {accum} __negsa2 (accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __negda2 (long accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __negta2 (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __neguha2 (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __negusa2 (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __neguda2 (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __neguta2 (unsigned long long accum @var{a})
+These functions return the negation of @var{a}.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __ssnegqq2 (short fract @var{a})
+@deftypefnx {Runtime Function} {fract} __ssneghq2 (fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __ssnegsq2 (long fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __ssnegdq2 (long long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __ssnegha2 (short accum @var{a})
+@deftypefnx {Runtime Function} {accum} __ssnegsa2 (accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __ssnegda2 (long accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __ssnegta2 (long long accum @var{a})
+These functions return the negation of @var{a} with signed saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned short fract} __usneguqq2 (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __usneguhq2 (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __usnegusq2 (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __usnegudq2 (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __usneguha2 (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __usnegusa2 (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __usneguda2 (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __usneguta2 (unsigned long long accum @var{a})
+These functions return the negation of @var{a} with unsigned saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __ashlqq3 (short fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {fract} __ashlhq3 (fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long fract} __ashlsq3 (long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long fract} __ashldq3 (long long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned short fract} __ashluqq3 (unsigned short fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __ashluhq3 (unsigned fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __ashlusq3 (unsigned long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __ashludq3 (unsigned long long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {short accum} __ashlha3 (short accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {accum} __ashlsa3 (accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long accum} __ashlda3 (long accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long accum} __ashlta3 (long long accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __ashluha3 (unsigned short accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __ashlusa3 (unsigned accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __ashluda3 (unsigned long accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __ashluta3 (unsigned long long accum @var{a}, int @var{b})
+These functions return the result of shifting @var{a} left by @var{b} bits.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __ashrqq3 (short fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {fract} __ashrhq3 (fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long fract} __ashrsq3 (long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long fract} __ashrdq3 (long long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {short accum} __ashrha3 (short accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {accum} __ashrsa3 (accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long accum} __ashrda3 (long accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long accum} __ashrta3 (long long accum @var{a}, int @var{b})
+These functions return the result of arithmetically shifting @var{a} right
+by @var{b} bits.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned short fract} __lshruqq3 (unsigned short fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __lshruhq3 (unsigned fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __lshrusq3 (unsigned long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __lshrudq3 (unsigned long long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __lshruha3 (unsigned short accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __lshrusa3 (unsigned accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __lshruda3 (unsigned long accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __lshruta3 (unsigned long long accum @var{a}, int @var{b})
+These functions return the result of logically shifting @var{a} right
+by @var{b} bits.
+@end deftypefn
+
+@deftypefn {Runtime Function} {fract} __ssashlhq3 (fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long fract} __ssashlsq3 (long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long fract} __ssashldq3 (long long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {short accum} __ssashlha3 (short accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {accum} __ssashlsa3 (accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long accum} __ssashlda3 (long accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {long long accum} __ssashlta3 (long long accum @var{a}, int @var{b})
+These functions return the result of shifting @var{a} left by @var{b} bits
+with signed saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned short fract} __usashluqq3 (unsigned short fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned fract} __usashluhq3 (unsigned fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long fract} __usashlusq3 (unsigned long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long long fract} __usashludq3 (unsigned long long fract @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned short accum} __usashluha3 (unsigned short accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned accum} __usashlusa3 (unsigned accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long accum} __usashluda3 (unsigned long accum @var{a}, int @var{b})
+@deftypefnx {Runtime Function} {unsigned long long accum} __usashluta3 (unsigned long long accum @var{a}, int @var{b})
+These functions return the result of shifting @var{a} left by @var{b} bits
+with unsigned saturation.
+@end deftypefn
+
+@subsection Comparison functions
+
+The following functions implement fixed-point comparisons. These functions
+implement a low-level compare, upon which the higher level comparison
+operators (such as less than and greater than or equal to) can be
+constructed. The returned values lie in the range zero to two, to allow
+the high-level operators to be implemented by testing the returned
+result using either signed or unsigned comparison.
+
+@deftypefn {Runtime Function} {int} __cmpqq2 (short fract @var{a}, short fract @var{b})
+@deftypefnx {Runtime Function} {int} __cmphq2 (fract @var{a}, fract @var{b})
+@deftypefnx {Runtime Function} {int} __cmpsq2 (long fract @var{a}, long fract @var{b})
+@deftypefnx {Runtime Function} {int} __cmpdq2 (long long fract @var{a}, long long fract @var{b})
+@deftypefnx {Runtime Function} {int} __cmpuqq2 (unsigned short fract @var{a}, unsigned short fract @var{b})
+@deftypefnx {Runtime Function} {int} __cmpuhq2 (unsigned fract @var{a}, unsigned fract @var{b})
+@deftypefnx {Runtime Function} {int} __cmpusq2 (unsigned long fract @var{a}, unsigned long fract @var{b})
+@deftypefnx {Runtime Function} {int} __cmpudq2 (unsigned long long fract @var{a}, unsigned long long fract @var{b})
+@deftypefnx {Runtime Function} {int} __cmpha2 (short accum @var{a}, short accum @var{b})
+@deftypefnx {Runtime Function} {int} __cmpsa2 (accum @var{a}, accum @var{b})
+@deftypefnx {Runtime Function} {int} __cmpda2 (long accum @var{a}, long accum @var{b})
+@deftypefnx {Runtime Function} {int} __cmpta2 (long long accum @var{a}, long long accum @var{b})
+@deftypefnx {Runtime Function} {int} __cmpuha2 (unsigned short accum @var{a}, unsigned short accum @var{b})
+@deftypefnx {Runtime Function} {int} __cmpusa2 (unsigned accum @var{a}, unsigned accum @var{b})
+@deftypefnx {Runtime Function} {int} __cmpuda2 (unsigned long accum @var{a}, unsigned long accum @var{b})
+@deftypefnx {Runtime Function} {int} __cmputa2 (unsigned long long accum @var{a}, unsigned long long accum @var{b})
+These functions perform a signed or unsigned comparison of @var{a} and
+@var{b} (depending on the selected machine mode). If @var{a} is less
+than @var{b}, they return 0; if @var{a} is greater than @var{b}, they
+return 2; and if @var{a} and @var{b} are equal they return 1.
+@end deftypefn
+
+@subsection Conversion functions
+
+@deftypefn {Runtime Function} {fract} __fractqqhq2 (short fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractqqsq2 (short fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractqqdq2 (short fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractqqha (short fract @var{a})
+@deftypefnx {Runtime Function} {accum} __fractqqsa (short fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractqqda (short fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractqqta (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractqquqq (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractqquhq (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractqqusq (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractqqudq (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractqquha (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractqqusa (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractqquda (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractqquta (short fract @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractqqqi (short fract @var{a})
+@deftypefnx {Runtime Function} {short} __fractqqhi (short fract @var{a})
+@deftypefnx {Runtime Function} {int} __fractqqsi (short fract @var{a})
+@deftypefnx {Runtime Function} {long} __fractqqdi (short fract @var{a})
+@deftypefnx {Runtime Function} {long long} __fractqqti (short fract @var{a})
+@deftypefnx {Runtime Function} {float} __fractqqsf (short fract @var{a})
+@deftypefnx {Runtime Function} {double} __fractqqdf (short fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __fracthqqq2 (fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __fracthqsq2 (fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fracthqdq2 (fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __fracthqha (fract @var{a})
+@deftypefnx {Runtime Function} {accum} __fracthqsa (fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __fracthqda (fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fracthqta (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fracthquqq (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fracthquhq (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fracthqusq (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fracthqudq (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fracthquha (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fracthqusa (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fracthquda (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fracthquta (fract @var{a})
+@deftypefnx {Runtime Function} {signed char} __fracthqqi (fract @var{a})
+@deftypefnx {Runtime Function} {short} __fracthqhi (fract @var{a})
+@deftypefnx {Runtime Function} {int} __fracthqsi (fract @var{a})
+@deftypefnx {Runtime Function} {long} __fracthqdi (fract @var{a})
+@deftypefnx {Runtime Function} {long long} __fracthqti (fract @var{a})
+@deftypefnx {Runtime Function} {float} __fracthqsf (fract @var{a})
+@deftypefnx {Runtime Function} {double} __fracthqdf (fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractsqqq2 (long fract @var{a})
+@deftypefnx {Runtime Function} {fract} __fractsqhq2 (long fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractsqdq2 (long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractsqha (long fract @var{a})
+@deftypefnx {Runtime Function} {accum} __fractsqsa (long fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractsqda (long fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractsqta (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractsquqq (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractsquhq (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractsqusq (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractsqudq (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractsquha (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractsqusa (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractsquda (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractsquta (long fract @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractsqqi (long fract @var{a})
+@deftypefnx {Runtime Function} {short} __fractsqhi (long fract @var{a})
+@deftypefnx {Runtime Function} {int} __fractsqsi (long fract @var{a})
+@deftypefnx {Runtime Function} {long} __fractsqdi (long fract @var{a})
+@deftypefnx {Runtime Function} {long long} __fractsqti (long fract @var{a})
+@deftypefnx {Runtime Function} {float} __fractsqsf (long fract @var{a})
+@deftypefnx {Runtime Function} {double} __fractsqdf (long fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractdqqq2 (long long fract @var{a})
+@deftypefnx {Runtime Function} {fract} __fractdqhq2 (long long fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractdqsq2 (long long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractdqha (long long fract @var{a})
+@deftypefnx {Runtime Function} {accum} __fractdqsa (long long fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractdqda (long long fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractdqta (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractdquqq (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractdquhq (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractdqusq (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractdqudq (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractdquha (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractdqusa (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractdquda (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractdquta (long long fract @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractdqqi (long long fract @var{a})
+@deftypefnx {Runtime Function} {short} __fractdqhi (long long fract @var{a})
+@deftypefnx {Runtime Function} {int} __fractdqsi (long long fract @var{a})
+@deftypefnx {Runtime Function} {long} __fractdqdi (long long fract @var{a})
+@deftypefnx {Runtime Function} {long long} __fractdqti (long long fract @var{a})
+@deftypefnx {Runtime Function} {float} __fractdqsf (long long fract @var{a})
+@deftypefnx {Runtime Function} {double} __fractdqdf (long long fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __fracthaqq (short accum @var{a})
+@deftypefnx {Runtime Function} {fract} __fracthahq (short accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __fracthasq (short accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fracthadq (short accum @var{a})
+@deftypefnx {Runtime Function} {accum} __fracthasa2 (short accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __fracthada2 (short accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fracthata2 (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fracthauqq (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fracthauhq (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fracthausq (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fracthaudq (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fracthauha (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fracthausa (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fracthauda (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fracthauta (short accum @var{a})
+@deftypefnx {Runtime Function} {signed char} __fracthaqi (short accum @var{a})
+@deftypefnx {Runtime Function} {short} __fracthahi (short accum @var{a})
+@deftypefnx {Runtime Function} {int} __fracthasi (short accum @var{a})
+@deftypefnx {Runtime Function} {long} __fracthadi (short accum @var{a})
+@deftypefnx {Runtime Function} {long long} __fracthati (short accum @var{a})
+@deftypefnx {Runtime Function} {float} __fracthasf (short accum @var{a})
+@deftypefnx {Runtime Function} {double} __fracthadf (short accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractsaqq (accum @var{a})
+@deftypefnx {Runtime Function} {fract} __fractsahq (accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractsasq (accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractsadq (accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractsaha2 (accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractsada2 (accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractsata2 (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractsauqq (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractsauhq (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractsausq (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractsaudq (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractsauha (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractsausa (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractsauda (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractsauta (accum @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractsaqi (accum @var{a})
+@deftypefnx {Runtime Function} {short} __fractsahi (accum @var{a})
+@deftypefnx {Runtime Function} {int} __fractsasi (accum @var{a})
+@deftypefnx {Runtime Function} {long} __fractsadi (accum @var{a})
+@deftypefnx {Runtime Function} {long long} __fractsati (accum @var{a})
+@deftypefnx {Runtime Function} {float} __fractsasf (accum @var{a})
+@deftypefnx {Runtime Function} {double} __fractsadf (accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractdaqq (long accum @var{a})
+@deftypefnx {Runtime Function} {fract} __fractdahq (long accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractdasq (long accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractdadq (long accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractdaha2 (long accum @var{a})
+@deftypefnx {Runtime Function} {accum} __fractdasa2 (long accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractdata2 (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractdauqq (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractdauhq (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractdausq (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractdaudq (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractdauha (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractdausa (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractdauda (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractdauta (long accum @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractdaqi (long accum @var{a})
+@deftypefnx {Runtime Function} {short} __fractdahi (long accum @var{a})
+@deftypefnx {Runtime Function} {int} __fractdasi (long accum @var{a})
+@deftypefnx {Runtime Function} {long} __fractdadi (long accum @var{a})
+@deftypefnx {Runtime Function} {long long} __fractdati (long accum @var{a})
+@deftypefnx {Runtime Function} {float} __fractdasf (long accum @var{a})
+@deftypefnx {Runtime Function} {double} __fractdadf (long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fracttaqq (long long accum @var{a})
+@deftypefnx {Runtime Function} {fract} __fracttahq (long long accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __fracttasq (long long accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fracttadq (long long accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __fracttaha2 (long long accum @var{a})
+@deftypefnx {Runtime Function} {accum} __fracttasa2 (long long accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __fracttada2 (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fracttauqq (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fracttauhq (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fracttausq (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fracttaudq (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fracttauha (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fracttausa (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fracttauda (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fracttauta (long long accum @var{a})
+@deftypefnx {Runtime Function} {signed char} __fracttaqi (long long accum @var{a})
+@deftypefnx {Runtime Function} {short} __fracttahi (long long accum @var{a})
+@deftypefnx {Runtime Function} {int} __fracttasi (long long accum @var{a})
+@deftypefnx {Runtime Function} {long} __fracttadi (long long accum @var{a})
+@deftypefnx {Runtime Function} {long long} __fracttati (long long accum @var{a})
+@deftypefnx {Runtime Function} {float} __fracttasf (long long accum @var{a})
+@deftypefnx {Runtime Function} {double} __fracttadf (long long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractuqqqq (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {fract} __fractuqqhq (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractuqqsq (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractuqqdq (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractuqqha (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {accum} __fractuqqsa (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractuqqda (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractuqqta (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractuqquhq2 (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractuqqusq2 (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractuqqudq2 (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractuqquha (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractuqqusa (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractuqquda (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractuqquta (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractuqqqi (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {short} __fractuqqhi (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {int} __fractuqqsi (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long} __fractuqqdi (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long long} __fractuqqti (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {float} __fractuqqsf (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {double} __fractuqqdf (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractuhqqq (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {fract} __fractuhqhq (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractuhqsq (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractuhqdq (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractuhqha (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {accum} __fractuhqsa (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractuhqda (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractuhqta (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractuhquqq2 (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractuhqusq2 (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractuhqudq2 (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractuhquha (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractuhqusa (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractuhquda (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractuhquta (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractuhqqi (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {short} __fractuhqhi (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {int} __fractuhqsi (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long} __fractuhqdi (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long long} __fractuhqti (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {float} __fractuhqsf (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {double} __fractuhqdf (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractusqqq (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {fract} __fractusqhq (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractusqsq (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractusqdq (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractusqha (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {accum} __fractusqsa (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractusqda (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractusqta (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractusquqq2 (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractusquhq2 (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractusqudq2 (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractusquha (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractusqusa (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractusquda (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractusquta (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractusqqi (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {short} __fractusqhi (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {int} __fractusqsi (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long} __fractusqdi (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long long} __fractusqti (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {float} __fractusqsf (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {double} __fractusqdf (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractudqqq (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {fract} __fractudqhq (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractudqsq (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractudqdq (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractudqha (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {accum} __fractudqsa (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractudqda (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractudqta (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractudquqq2 (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractudquhq2 (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractudqusq2 (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractudquha (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractudqusa (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractudquda (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractudquta (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractudqqi (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {short} __fractudqhi (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {int} __fractudqsi (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long} __fractudqdi (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long long} __fractudqti (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {float} __fractudqsf (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {double} __fractudqdf (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractuhaqq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {fract} __fractuhahq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractuhasq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractuhadq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractuhaha (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {accum} __fractuhasa (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractuhada (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractuhata (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractuhauqq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractuhauhq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractuhausq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractuhaudq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractuhausa2 (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractuhauda2 (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractuhauta2 (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractuhaqi (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {short} __fractuhahi (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {int} __fractuhasi (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long} __fractuhadi (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long long} __fractuhati (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {float} __fractuhasf (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {double} __fractuhadf (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractusaqq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {fract} __fractusahq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractusasq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractusadq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractusaha (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {accum} __fractusasa (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractusada (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractusata (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractusauqq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractusauhq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractusausq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractusaudq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractusauha2 (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractusauda2 (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractusauta2 (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractusaqi (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {short} __fractusahi (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {int} __fractusasi (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long} __fractusadi (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long long} __fractusati (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {float} __fractusasf (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {double} __fractusadf (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractudaqq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {fract} __fractudahq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractudasq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractudadq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractudaha (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {accum} __fractudasa (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractudada (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractudata (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractudauqq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractudauhq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractudausq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractudaudq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractudauha2 (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractudausa2 (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractudauta2 (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractudaqi (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {short} __fractudahi (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {int} __fractudasi (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long} __fractudadi (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long long} __fractudati (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {float} __fractudasf (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {double} __fractudadf (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractutaqq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {fract} __fractutahq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractutasq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractutadq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractutaha (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {accum} __fractutasa (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractutada (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractutata (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractutauqq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractutauhq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractutausq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractutaudq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractutauha2 (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractutausa2 (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractutauda2 (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {signed char} __fractutaqi (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {short} __fractutahi (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {int} __fractutasi (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long} __fractutadi (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long long} __fractutati (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {float} __fractutasf (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {double} __fractutadf (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractqiqq (signed char @var{a})
+@deftypefnx {Runtime Function} {fract} __fractqihq (signed char @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractqisq (signed char @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractqidq (signed char @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractqiha (signed char @var{a})
+@deftypefnx {Runtime Function} {accum} __fractqisa (signed char @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractqida (signed char @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractqita (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractqiuqq (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractqiuhq (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractqiusq (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractqiudq (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractqiuha (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractqiusa (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractqiuda (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractqiuta (signed char @var{a})
+@deftypefnx {Runtime Function} {short fract} __fracthiqq (short @var{a})
+@deftypefnx {Runtime Function} {fract} __fracthihq (short @var{a})
+@deftypefnx {Runtime Function} {long fract} __fracthisq (short @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fracthidq (short @var{a})
+@deftypefnx {Runtime Function} {short accum} __fracthiha (short @var{a})
+@deftypefnx {Runtime Function} {accum} __fracthisa (short @var{a})
+@deftypefnx {Runtime Function} {long accum} __fracthida (short @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fracthita (short @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fracthiuqq (short @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fracthiuhq (short @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fracthiusq (short @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fracthiudq (short @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fracthiuha (short @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fracthiusa (short @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fracthiuda (short @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fracthiuta (short @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractsiqq (int @var{a})
+@deftypefnx {Runtime Function} {fract} __fractsihq (int @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractsisq (int @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractsidq (int @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractsiha (int @var{a})
+@deftypefnx {Runtime Function} {accum} __fractsisa (int @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractsida (int @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractsita (int @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractsiuqq (int @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractsiuhq (int @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractsiusq (int @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractsiudq (int @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractsiuha (int @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractsiusa (int @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractsiuda (int @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractsiuta (int @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractdiqq (long @var{a})
+@deftypefnx {Runtime Function} {fract} __fractdihq (long @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractdisq (long @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractdidq (long @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractdiha (long @var{a})
+@deftypefnx {Runtime Function} {accum} __fractdisa (long @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractdida (long @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractdita (long @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractdiuqq (long @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractdiuhq (long @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractdiusq (long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractdiudq (long @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractdiuha (long @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractdiusa (long @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractdiuda (long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractdiuta (long @var{a})
+@deftypefnx {Runtime Function} {short fract} __fracttiqq (long long @var{a})
+@deftypefnx {Runtime Function} {fract} __fracttihq (long long @var{a})
+@deftypefnx {Runtime Function} {long fract} __fracttisq (long long @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fracttidq (long long @var{a})
+@deftypefnx {Runtime Function} {short accum} __fracttiha (long long @var{a})
+@deftypefnx {Runtime Function} {accum} __fracttisa (long long @var{a})
+@deftypefnx {Runtime Function} {long accum} __fracttida (long long @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fracttita (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fracttiuqq (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fracttiuhq (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fracttiusq (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fracttiudq (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fracttiuha (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fracttiusa (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fracttiuda (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fracttiuta (long long @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractsfqq (float @var{a})
+@deftypefnx {Runtime Function} {fract} __fractsfhq (float @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractsfsq (float @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractsfdq (float @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractsfha (float @var{a})
+@deftypefnx {Runtime Function} {accum} __fractsfsa (float @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractsfda (float @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractsfta (float @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractsfuqq (float @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractsfuhq (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractsfusq (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractsfudq (float @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractsfuha (float @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractsfusa (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractsfuda (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractsfuta (float @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractdfqq (double @var{a})
+@deftypefnx {Runtime Function} {fract} __fractdfhq (double @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractdfsq (double @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractdfdq (double @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractdfha (double @var{a})
+@deftypefnx {Runtime Function} {accum} __fractdfsa (double @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractdfda (double @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractdfta (double @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractdfuqq (double @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractdfuhq (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractdfusq (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractdfudq (double @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractdfuha (double @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractdfusa (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractdfuda (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractdfuta (double @var{a})
+These functions convert from fractional and signed non-fractionals to
+fractionals and signed non-fractionals, without saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {fract} __satfractqqhq2 (short fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractqqsq2 (short fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractqqdq2 (short fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractqqha (short fract @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractqqsa (short fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractqqda (short fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractqqta (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractqquqq (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractqquhq (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractqqusq (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractqqudq (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractqquha (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractqqusa (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractqquda (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractqquta (short fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfracthqqq2 (fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfracthqsq2 (fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfracthqdq2 (fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfracthqha (fract @var{a})
+@deftypefnx {Runtime Function} {accum} __satfracthqsa (fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfracthqda (fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfracthqta (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfracthquqq (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfracthquhq (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfracthqusq (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfracthqudq (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfracthquha (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfracthqusa (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfracthquda (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfracthquta (fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractsqqq2 (long fract @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractsqhq2 (long fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractsqdq2 (long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractsqha (long fract @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractsqsa (long fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractsqda (long fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractsqta (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractsquqq (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractsquhq (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractsqusq (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractsqudq (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractsquha (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractsqusa (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractsquda (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractsquta (long fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractdqqq2 (long long fract @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractdqhq2 (long long fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractdqsq2 (long long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractdqha (long long fract @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractdqsa (long long fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractdqda (long long fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractdqta (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractdquqq (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractdquhq (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractdqusq (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractdqudq (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractdquha (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractdqusa (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractdquda (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractdquta (long long fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfracthaqq (short accum @var{a})
+@deftypefnx {Runtime Function} {fract} __satfracthahq (short accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfracthasq (short accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfracthadq (short accum @var{a})
+@deftypefnx {Runtime Function} {accum} __satfracthasa2 (short accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfracthada2 (short accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfracthata2 (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfracthauqq (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfracthauhq (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfracthausq (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfracthaudq (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfracthauha (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfracthausa (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfracthauda (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfracthauta (short accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractsaqq (accum @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractsahq (accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractsasq (accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractsadq (accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractsaha2 (accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractsada2 (accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractsata2 (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractsauqq (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractsauhq (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractsausq (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractsaudq (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractsauha (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractsausa (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractsauda (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractsauta (accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractdaqq (long accum @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractdahq (long accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractdasq (long accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractdadq (long accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractdaha2 (long accum @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractdasa2 (long accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractdata2 (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractdauqq (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractdauhq (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractdausq (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractdaudq (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractdauha (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractdausa (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractdauda (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractdauta (long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfracttaqq (long long accum @var{a})
+@deftypefnx {Runtime Function} {fract} __satfracttahq (long long accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfracttasq (long long accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfracttadq (long long accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfracttaha2 (long long accum @var{a})
+@deftypefnx {Runtime Function} {accum} __satfracttasa2 (long long accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfracttada2 (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfracttauqq (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfracttauhq (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfracttausq (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfracttaudq (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfracttauha (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfracttausa (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfracttauda (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfracttauta (long long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractuqqqq (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractuqqhq (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractuqqsq (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractuqqdq (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractuqqha (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractuqqsa (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractuqqda (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractuqqta (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractuqquhq2 (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractuqqusq2 (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractuqqudq2 (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractuqquha (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractuqqusa (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractuqquda (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractuqquta (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractuhqqq (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractuhqhq (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractuhqsq (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractuhqdq (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractuhqha (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractuhqsa (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractuhqda (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractuhqta (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractuhquqq2 (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractuhqusq2 (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractuhqudq2 (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractuhquha (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractuhqusa (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractuhquda (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractuhquta (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractusqqq (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractusqhq (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractusqsq (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractusqdq (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractusqha (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractusqsa (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractusqda (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractusqta (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractusquqq2 (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractusquhq2 (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractusqudq2 (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractusquha (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractusqusa (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractusquda (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractusquta (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractudqqq (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractudqhq (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractudqsq (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractudqdq (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractudqha (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractudqsa (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractudqda (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractudqta (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractudquqq2 (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractudquhq2 (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractudqusq2 (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractudquha (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractudqusa (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractudquda (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractudquta (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractuhaqq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractuhahq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractuhasq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractuhadq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractuhaha (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractuhasa (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractuhada (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractuhata (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractuhauqq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractuhauhq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractuhausq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractuhaudq (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractuhausa2 (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractuhauda2 (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractuhauta2 (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractusaqq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractusahq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractusasq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractusadq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractusaha (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractusasa (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractusada (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractusata (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractusauqq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractusauhq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractusausq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractusaudq (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractusauha2 (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractusauda2 (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractusauta2 (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractudaqq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractudahq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractudasq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractudadq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractudaha (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractudasa (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractudada (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractudata (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractudauqq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractudauhq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractudausq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractudaudq (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractudauha2 (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractudausa2 (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractudauta2 (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractutaqq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractutahq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractutasq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractutadq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractutaha (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractutasa (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractutada (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractutata (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractutauqq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractutauhq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractutausq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractutaudq (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractutauha2 (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractutausa2 (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractutauda2 (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractqiqq (signed char @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractqihq (signed char @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractqisq (signed char @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractqidq (signed char @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractqiha (signed char @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractqisa (signed char @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractqida (signed char @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractqita (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractqiuqq (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractqiuhq (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractqiusq (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractqiudq (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractqiuha (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractqiusa (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractqiuda (signed char @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractqiuta (signed char @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfracthiqq (short @var{a})
+@deftypefnx {Runtime Function} {fract} __satfracthihq (short @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfracthisq (short @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfracthidq (short @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfracthiha (short @var{a})
+@deftypefnx {Runtime Function} {accum} __satfracthisa (short @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfracthida (short @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfracthita (short @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfracthiuqq (short @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfracthiuhq (short @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfracthiusq (short @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfracthiudq (short @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfracthiuha (short @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfracthiusa (short @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfracthiuda (short @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfracthiuta (short @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractsiqq (int @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractsihq (int @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractsisq (int @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractsidq (int @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractsiha (int @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractsisa (int @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractsida (int @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractsita (int @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractsiuqq (int @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractsiuhq (int @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractsiusq (int @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractsiudq (int @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractsiuha (int @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractsiusa (int @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractsiuda (int @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractsiuta (int @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractdiqq (long @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractdihq (long @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractdisq (long @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractdidq (long @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractdiha (long @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractdisa (long @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractdida (long @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractdita (long @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractdiuqq (long @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractdiuhq (long @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractdiusq (long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractdiudq (long @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractdiuha (long @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractdiusa (long @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractdiuda (long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractdiuta (long @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfracttiqq (long long @var{a})
+@deftypefnx {Runtime Function} {fract} __satfracttihq (long long @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfracttisq (long long @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfracttidq (long long @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfracttiha (long long @var{a})
+@deftypefnx {Runtime Function} {accum} __satfracttisa (long long @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfracttida (long long @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfracttita (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfracttiuqq (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfracttiuhq (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfracttiusq (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfracttiudq (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfracttiuha (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfracttiusa (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfracttiuda (long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfracttiuta (long long @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractsfqq (float @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractsfhq (float @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractsfsq (float @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractsfdq (float @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractsfha (float @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractsfsa (float @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractsfda (float @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractsfta (float @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractsfuqq (float @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractsfuhq (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractsfusq (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractsfudq (float @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractsfuha (float @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractsfusa (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractsfuda (float @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractsfuta (float @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractdfqq (double @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractdfhq (double @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractdfsq (double @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractdfdq (double @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractdfha (double @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractdfsa (double @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractdfda (double @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractdfta (double @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractdfuqq (double @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractdfuhq (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractdfusq (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractdfudq (double @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractdfuha (double @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractdfusa (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractdfuda (double @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractdfuta (double @var{a})
+The functions convert from fractional and signed non-fractionals to
+fractionals, with saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {unsigned char} __fractunsqqqi (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsqqhi (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsqqsi (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsqqdi (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsqqti (short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunshqqi (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunshqhi (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunshqsi (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunshqdi (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunshqti (fract @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunssqqi (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunssqhi (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunssqsi (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunssqdi (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunssqti (long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsdqqi (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsdqhi (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsdqsi (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsdqdi (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsdqti (long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunshaqi (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunshahi (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunshasi (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunshadi (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunshati (short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunssaqi (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunssahi (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunssasi (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunssadi (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunssati (accum @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsdaqi (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsdahi (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsdasi (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsdadi (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsdati (long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunstaqi (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunstahi (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunstasi (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunstadi (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunstati (long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsuqqqi (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsuqqhi (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsuqqsi (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsuqqdi (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsuqqti (unsigned short fract @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsuhqqi (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsuhqhi (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsuhqsi (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsuhqdi (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsuhqti (unsigned fract @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsusqqi (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsusqhi (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsusqsi (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsusqdi (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsusqti (unsigned long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsudqqi (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsudqhi (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsudqsi (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsudqdi (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsudqti (unsigned long long fract @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsuhaqi (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsuhahi (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsuhasi (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsuhadi (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsuhati (unsigned short accum @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsusaqi (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsusahi (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsusasi (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsusadi (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsusati (unsigned accum @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsudaqi (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsudahi (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsudasi (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsudadi (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsudati (unsigned long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned char} __fractunsutaqi (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned short} __fractunsutahi (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned int} __fractunsutasi (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long} __fractunsutadi (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {unsigned long long} __fractunsutati (unsigned long long accum @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractunsqiqq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {fract} __fractunsqihq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractunsqisq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractunsqidq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractunsqiha (unsigned char @var{a})
+@deftypefnx {Runtime Function} {accum} __fractunsqisa (unsigned char @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractunsqida (unsigned char @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractunsqita (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractunsqiuqq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractunsqiuhq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractunsqiusq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractunsqiudq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractunsqiuha (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractunsqiusa (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractunsqiuda (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractunsqiuta (unsigned char @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractunshiqq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {fract} __fractunshihq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractunshisq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractunshidq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractunshiha (unsigned short @var{a})
+@deftypefnx {Runtime Function} {accum} __fractunshisa (unsigned short @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractunshida (unsigned short @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractunshita (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractunshiuqq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractunshiuhq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractunshiusq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractunshiudq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractunshiuha (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractunshiusa (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractunshiuda (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractunshiuta (unsigned short @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractunssiqq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {fract} __fractunssihq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractunssisq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractunssidq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractunssiha (unsigned int @var{a})
+@deftypefnx {Runtime Function} {accum} __fractunssisa (unsigned int @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractunssida (unsigned int @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractunssita (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractunssiuqq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractunssiuhq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractunssiusq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractunssiudq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractunssiuha (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractunssiusa (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractunssiuda (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractunssiuta (unsigned int @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractunsdiqq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {fract} __fractunsdihq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractunsdisq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractunsdidq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractunsdiha (unsigned long @var{a})
+@deftypefnx {Runtime Function} {accum} __fractunsdisa (unsigned long @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractunsdida (unsigned long @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractunsdita (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractunsdiuqq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractunsdiuhq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractunsdiusq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractunsdiudq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractunsdiuha (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractunsdiusa (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractunsdiuda (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractunsdiuta (unsigned long @var{a})
+@deftypefnx {Runtime Function} {short fract} __fractunstiqq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {fract} __fractunstihq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {long fract} __fractunstisq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {long long fract} __fractunstidq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {short accum} __fractunstiha (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {accum} __fractunstisa (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {long accum} __fractunstida (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {long long accum} __fractunstita (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __fractunstiuqq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __fractunstiuhq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __fractunstiusq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __fractunstiudq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __fractunstiuha (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __fractunstiusa (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __fractunstiuda (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __fractunstiuta (unsigned long long @var{a})
+These functions convert from fractionals to unsigned non-fractionals;
+and from unsigned non-fractionals to fractionals, without saturation.
+@end deftypefn
+
+@deftypefn {Runtime Function} {short fract} __satfractunsqiqq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractunsqihq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractunsqisq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractunsqidq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractunsqiha (unsigned char @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractunsqisa (unsigned char @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractunsqida (unsigned char @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractunsqita (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractunsqiuqq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractunsqiuhq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractunsqiusq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractunsqiudq (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractunsqiuha (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractunsqiusa (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractunsqiuda (unsigned char @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractunsqiuta (unsigned char @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractunshiqq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractunshihq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractunshisq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractunshidq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractunshiha (unsigned short @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractunshisa (unsigned short @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractunshida (unsigned short @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractunshita (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractunshiuqq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractunshiuhq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractunshiusq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractunshiudq (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractunshiuha (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractunshiusa (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractunshiuda (unsigned short @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractunshiuta (unsigned short @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractunssiqq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractunssihq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractunssisq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractunssidq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractunssiha (unsigned int @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractunssisa (unsigned int @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractunssida (unsigned int @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractunssita (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractunssiuqq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractunssiuhq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractunssiusq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractunssiudq (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractunssiuha (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractunssiusa (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractunssiuda (unsigned int @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractunssiuta (unsigned int @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractunsdiqq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractunsdihq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractunsdisq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractunsdidq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractunsdiha (unsigned long @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractunsdisa (unsigned long @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractunsdida (unsigned long @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractunsdita (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractunsdiuqq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractunsdiuhq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractunsdiusq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractunsdiudq (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractunsdiuha (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractunsdiusa (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractunsdiuda (unsigned long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractunsdiuta (unsigned long @var{a})
+@deftypefnx {Runtime Function} {short fract} __satfractunstiqq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {fract} __satfractunstihq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {long fract} __satfractunstisq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {long long fract} __satfractunstidq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {short accum} __satfractunstiha (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {accum} __satfractunstisa (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {long accum} __satfractunstida (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {long long accum} __satfractunstita (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned short fract} __satfractunstiuqq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned fract} __satfractunstiuhq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long fract} __satfractunstiusq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long fract} __satfractunstiudq (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned short accum} __satfractunstiuha (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned accum} __satfractunstiusa (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long accum} __satfractunstiuda (unsigned long long @var{a})
+@deftypefnx {Runtime Function} {unsigned long long accum} __satfractunstiuta (unsigned long long @var{a})
+These functions convert from unsigned non-fractionals to fractionals,
+with saturation.
+@end deftypefn
+
+@node Exception handling routines
+@section Language-independent routines for exception handling
+
+document me!
+
+@smallexample
+ _Unwind_DeleteException
+ _Unwind_Find_FDE
+ _Unwind_ForcedUnwind
+ _Unwind_GetGR
+ _Unwind_GetIP
+ _Unwind_GetLanguageSpecificData
+ _Unwind_GetRegionStart
+ _Unwind_GetTextRelBase
+ _Unwind_GetDataRelBase
+ _Unwind_RaiseException
+ _Unwind_Resume
+ _Unwind_SetGR
+ _Unwind_SetIP
+ _Unwind_FindEnclosingFunction
+ _Unwind_SjLj_Register
+ _Unwind_SjLj_Unregister
+ _Unwind_SjLj_RaiseException
+ _Unwind_SjLj_ForcedUnwind
+ _Unwind_SjLj_Resume
+ __deregister_frame
+ __deregister_frame_info
+ __deregister_frame_info_bases
+ __register_frame
+ __register_frame_info
+ __register_frame_info_bases
+ __register_frame_info_table
+ __register_frame_info_table_bases
+ __register_frame_table
+@end smallexample
+
+@node Miscellaneous routines
+@section Miscellaneous runtime library routines
+
+@subsection Cache control functions
+@deftypefn {Runtime Function} void __clear_cache (char *@var{beg}, char *@var{end})
+This function clears the instruction cache between @var{beg} and @var{end}.
+@end deftypefn
+
+@subsection Split stack functions and variables
+@deftypefn {Runtime Function} {void *} __splitstack_find (void *@var{segment_arg}, @
+void *@var{sp}, size_t @var{len}, void **@var{next_segment}, @
+void **@var{next_sp}, void **@var{initial_sp})
+When using @option{-fsplit-stack}, this call may be used to iterate
+over the stack segments. It may be called like this:
+@smallexample
+ void *next_segment = NULL;
+ void *next_sp = NULL;
+ void *initial_sp = NULL;
+ void *stack;
+ size_t stack_size;
+ while ((stack = __splitstack_find (next_segment, next_sp,
+ &stack_size, &next_segment,
+ &next_sp, &initial_sp))
+ != NULL)
+ @{
+ /* Stack segment starts at stack and is
+ stack_size bytes long. */
+ @}
+@end smallexample
+
+There is no way to iterate over the stack segments of a different
+thread. However, what is permitted is for one thread to call this
+with the @var{segment_arg} and @var{sp} arguments NULL, to pass
+@var{next_segment}, @var{next_sp}, and @var{initial_sp} to a different
+thread, and then to suspend one way or another. A different thread
+may run the subsequent @code{__splitstack_find} iterations. Of
+course, this will only work if the first thread is suspended while the
+second thread is calling @code{__splitstack_find}. If not, the second
+thread could be looking at the stack while it is changing, and
+anything could happen.
+@end deftypefn
+
+@defvar __morestack_segments
+@defvarx __morestack_current_segment
+@defvarx __morestack_initial_sp
+Internal variables used by the @option{-fsplit-stack} implementation.
+@end defvar
--- /dev/null
+@c Copyright (C) 2006-2022 Free Software Foundation, Inc.
+@c Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@c ---------------------------------------------------------------------
+@c Loop Representation
+@c ---------------------------------------------------------------------
+
+@node Loop Analysis and Representation
+@chapter Analysis and Representation of Loops
+
+GCC provides extensive infrastructure for work with natural loops, i.e.,
+strongly connected components of CFG with only one entry block. This
+chapter describes representation of loops in GCC, both on GIMPLE and in
+RTL, as well as the interfaces to loop-related analyses (induction
+variable analysis and number of iterations analysis).
+
+@menu
+* Loop representation:: Representation and analysis of loops.
+* Loop querying:: Getting information about loops.
+* Loop manipulation:: Loop manipulation functions.
+* LCSSA:: Loop-closed SSA form.
+* Scalar evolutions:: Induction variables on GIMPLE.
+* loop-iv:: Induction variables on RTL.
+* Number of iterations:: Number of iterations analysis.
+* Dependency analysis:: Data dependency analysis.
+@end menu
+
+@node Loop representation
+@section Loop representation
+@cindex Loop representation
+@cindex Loop analysis
+
+This chapter describes the representation of loops in GCC, and functions
+that can be used to build, modify and analyze this representation. Most
+of the interfaces and data structures are declared in @file{cfgloop.h}.
+Loop structures are analyzed and this information disposed or updated
+at the discretion of individual passes. Still most of the generic
+CFG manipulation routines are aware of loop structures and try to
+keep them up-to-date. By this means an increasing part of the
+compilation pipeline is setup to maintain loop structure across
+passes to allow attaching meta information to individual loops
+for consumption by later passes.
+
+In general, a natural loop has one entry block (header) and possibly
+several back edges (latches) leading to the header from the inside of
+the loop. Loops with several latches may appear if several loops share
+a single header, or if there is a branching in the middle of the loop.
+The representation of loops in GCC however allows only loops with a
+single latch. During loop analysis, headers of such loops are split and
+forwarder blocks are created in order to disambiguate their structures.
+Heuristic based on profile information and structure of the induction
+variables in the loops is used to determine whether the latches
+correspond to sub-loops or to control flow in a single loop. This means
+that the analysis sometimes changes the CFG, and if you run it in the
+middle of an optimization pass, you must be able to deal with the new
+blocks. You may avoid CFG changes by passing
+@code{LOOPS_MAY_HAVE_MULTIPLE_LATCHES} flag to the loop discovery,
+note however that most other loop manipulation functions will not work
+correctly for loops with multiple latch edges (the functions that only
+query membership of blocks to loops and subloop relationships, or
+enumerate and test loop exits, can be expected to work).
+
+Body of the loop is the set of blocks that are dominated by its header,
+and reachable from its latch against the direction of edges in CFG@. The
+loops are organized in a containment hierarchy (tree) such that all the
+loops immediately contained inside loop L are the children of L in the
+tree. This tree is represented by the @code{struct loops} structure.
+The root of this tree is a fake loop that contains all blocks in the
+function. Each of the loops is represented in a @code{struct loop}
+structure. Each loop is assigned an index (@code{num} field of the
+@code{struct loop} structure), and the pointer to the loop is stored in
+the corresponding field of the @code{larray} vector in the loops
+structure. The indices do not have to be continuous, there may be
+empty (@code{NULL}) entries in the @code{larray} created by deleting
+loops. Also, there is no guarantee on the relative order of a loop
+and its subloops in the numbering. The index of a loop never changes.
+
+The entries of the @code{larray} field should not be accessed directly.
+The function @code{get_loop} returns the loop description for a loop with
+the given index. @code{number_of_loops} function returns number of loops
+in the function. To traverse all loops, use a range-based for loop with
+class @code{loops_list} instance. The @code{flags} argument passed to the
+constructor function of class @code{loops_list} is used to determine the
+direction of traversal and the set of loops visited. Each loop is
+guaranteed to be visited exactly once, regardless of the changes to the
+loop tree, and the loops may be removed during the traversal. The newly
+created loops are never traversed, if they need to be visited, this must
+be done separately after their creation.
+
+Each basic block contains the reference to the innermost loop it belongs
+to (@code{loop_father}). For this reason, it is only possible to have
+one @code{struct loops} structure initialized at the same time for each
+CFG@. The global variable @code{current_loops} contains the
+@code{struct loops} structure. Many of the loop manipulation functions
+assume that dominance information is up-to-date.
+
+The loops are analyzed through @code{loop_optimizer_init} function. The
+argument of this function is a set of flags represented in an integer
+bitmask. These flags specify what other properties of the loop
+structures should be calculated/enforced and preserved later:
+
+@itemize
+@item @code{LOOPS_MAY_HAVE_MULTIPLE_LATCHES}: If this flag is set, no
+changes to CFG will be performed in the loop analysis, in particular,
+loops with multiple latch edges will not be disambiguated. If a loop
+has multiple latches, its latch block is set to NULL@. Most of
+the loop manipulation functions will not work for loops in this shape.
+No other flags that require CFG changes can be passed to
+loop_optimizer_init.
+@item @code{LOOPS_HAVE_PREHEADERS}: Forwarder blocks are created in such
+a way that each loop has only one entry edge, and additionally, the
+source block of this entry edge has only one successor. This creates a
+natural place where the code can be moved out of the loop, and ensures
+that the entry edge of the loop leads from its immediate super-loop.
+@item @code{LOOPS_HAVE_SIMPLE_LATCHES}: Forwarder blocks are created to
+force the latch block of each loop to have only one successor. This
+ensures that the latch of the loop does not belong to any of its
+sub-loops, and makes manipulation with the loops significantly easier.
+Most of the loop manipulation functions assume that the loops are in
+this shape. Note that with this flag, the ``normal'' loop without any
+control flow inside and with one exit consists of two basic blocks.
+@item @code{LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS}: Basic blocks and
+edges in the strongly connected components that are not natural loops
+(have more than one entry block) are marked with
+@code{BB_IRREDUCIBLE_LOOP} and @code{EDGE_IRREDUCIBLE_LOOP} flags. The
+flag is not set for blocks and edges that belong to natural loops that
+are in such an irreducible region (but it is set for the entry and exit
+edges of such a loop, if they lead to/from this region).
+@item @code{LOOPS_HAVE_RECORDED_EXITS}: The lists of exits are recorded
+and updated for each loop. This makes some functions (e.g.,
+@code{get_loop_exit_edges}) more efficient. Some functions (e.g.,
+@code{single_exit}) can be used only if the lists of exits are
+recorded.
+@end itemize
+
+These properties may also be computed/enforced later, using functions
+@code{create_preheaders}, @code{force_single_succ_latches},
+@code{mark_irreducible_loops} and @code{record_loop_exits}.
+The properties can be queried using @code{loops_state_satisfies_p}.
+
+The memory occupied by the loops structures should be freed with
+@code{loop_optimizer_finalize} function. When loop structures are
+setup to be preserved across passes this function reduces the
+information to be kept up-to-date to a minimum (only
+@code{LOOPS_MAY_HAVE_MULTIPLE_LATCHES} set).
+
+The CFG manipulation functions in general do not update loop structures.
+Specialized versions that additionally do so are provided for the most
+common tasks. On GIMPLE, @code{cleanup_tree_cfg_loop} function can be
+used to cleanup CFG while updating the loops structures if
+@code{current_loops} is set.
+
+At the moment loop structure is preserved from the start of GIMPLE
+loop optimizations until the end of RTL loop optimizations. During
+this time a loop can be tracked by its @code{struct loop} and number.
+
+@node Loop querying
+@section Loop querying
+@cindex Loop querying
+
+The functions to query the information about loops are declared in
+@file{cfgloop.h}. Some of the information can be taken directly from
+the structures. @code{loop_father} field of each basic block contains
+the innermost loop to that the block belongs. The most useful fields of
+loop structure (that are kept up-to-date at all times) are:
+
+@itemize
+@item @code{header}, @code{latch}: Header and latch basic blocks of the
+loop.
+@item @code{num_nodes}: Number of basic blocks in the loop (including
+the basic blocks of the sub-loops).
+@item @code{outer}, @code{inner}, @code{next}: The super-loop, the first
+sub-loop, and the sibling of the loop in the loops tree.
+@end itemize
+
+There are other fields in the loop structures, many of them used only by
+some of the passes, or not updated during CFG changes; in general, they
+should not be accessed directly.
+
+The most important functions to query loop structures are:
+
+@itemize
+@item @code{loop_depth}: The depth of the loop in the loops tree, i.e., the
+number of super-loops of the loop.
+@item @code{flow_loops_dump}: Dumps the information about loops to a
+file.
+@item @code{verify_loop_structure}: Checks consistency of the loop
+structures.
+@item @code{loop_latch_edge}: Returns the latch edge of a loop.
+@item @code{loop_preheader_edge}: If loops have preheaders, returns
+the preheader edge of a loop.
+@item @code{flow_loop_nested_p}: Tests whether loop is a sub-loop of
+another loop.
+@item @code{flow_bb_inside_loop_p}: Tests whether a basic block belongs
+to a loop (including its sub-loops).
+@item @code{find_common_loop}: Finds the common super-loop of two loops.
+@item @code{superloop_at_depth}: Returns the super-loop of a loop with
+the given depth.
+@item @code{tree_num_loop_insns}, @code{num_loop_insns}: Estimates the
+number of insns in the loop, on GIMPLE and on RTL.
+@item @code{loop_exit_edge_p}: Tests whether edge is an exit from a
+loop.
+@item @code{mark_loop_exit_edges}: Marks all exit edges of all loops
+with @code{EDGE_LOOP_EXIT} flag.
+@item @code{get_loop_body}, @code{get_loop_body_in_dom_order},
+@code{get_loop_body_in_bfs_order}: Enumerates the basic blocks in the
+loop in depth-first search order in reversed CFG, ordered by dominance
+relation, and breath-first search order, respectively.
+@item @code{single_exit}: Returns the single exit edge of the loop, or
+@code{NULL} if the loop has more than one exit. You can only use this
+function if @code{LOOPS_HAVE_RECORDED_EXITS} is used.
+@item @code{get_loop_exit_edges}: Enumerates the exit edges of a loop.
+@item @code{just_once_each_iteration_p}: Returns true if the basic block
+is executed exactly once during each iteration of a loop (that is, it
+does not belong to a sub-loop, and it dominates the latch of the loop).
+@end itemize
+
+@node Loop manipulation
+@section Loop manipulation
+@cindex Loop manipulation
+
+The loops tree can be manipulated using the following functions:
+
+@itemize
+@item @code{flow_loop_tree_node_add}: Adds a node to the tree.
+@item @code{flow_loop_tree_node_remove}: Removes a node from the tree.
+@item @code{add_bb_to_loop}: Adds a basic block to a loop.
+@item @code{remove_bb_from_loops}: Removes a basic block from loops.
+@end itemize
+
+Most low-level CFG functions update loops automatically. The following
+functions handle some more complicated cases of CFG manipulations:
+
+@itemize
+@item @code{remove_path}: Removes an edge and all blocks it dominates.
+@item @code{split_loop_exit_edge}: Splits exit edge of the loop,
+ensuring that PHI node arguments remain in the loop (this ensures that
+loop-closed SSA form is preserved). Only useful on GIMPLE.
+@end itemize
+
+Finally, there are some higher-level loop transformations implemented.
+While some of them are written so that they should work on non-innermost
+loops, they are mostly untested in that case, and at the moment, they
+are only reliable for the innermost loops:
+
+@itemize
+@item @code{create_iv}: Creates a new induction variable. Only works on
+GIMPLE@. @code{standard_iv_increment_position} can be used to find a
+suitable place for the iv increment.
+@item @code{duplicate_loop_body_to_header_edge},
+@code{tree_duplicate_loop_body_to_header_edge}: These functions (on RTL and
+on GIMPLE) duplicate the body of the loop prescribed number of times on
+one of the edges entering loop header, thus performing either loop
+unrolling or loop peeling. @code{can_duplicate_loop_p}
+(@code{can_unroll_loop_p} on GIMPLE) must be true for the duplicated
+loop.
+@item @code{loop_version}: This function creates a copy of a loop, and
+a branch before them that selects one of them depending on the
+prescribed condition. This is useful for optimizations that need to
+verify some assumptions in runtime (one of the copies of the loop is
+usually left unchanged, while the other one is transformed in some way).
+@item @code{tree_unroll_loop}: Unrolls the loop, including peeling the
+extra iterations to make the number of iterations divisible by unroll
+factor, updating the exit condition, and removing the exits that now
+cannot be taken. Works only on GIMPLE.
+@end itemize
+
+@node LCSSA
+@section Loop-closed SSA form
+@cindex LCSSA
+@cindex Loop-closed SSA form
+
+Throughout the loop optimizations on tree level, one extra condition is
+enforced on the SSA form: No SSA name is used outside of the loop in
+that it is defined. The SSA form satisfying this condition is called
+``loop-closed SSA form'' -- LCSSA@. To enforce LCSSA, PHI nodes must be
+created at the exits of the loops for the SSA names that are used
+outside of them. Only the real operands (not virtual SSA names) are
+held in LCSSA, in order to save memory.
+
+There are various benefits of LCSSA:
+
+@itemize
+@item Many optimizations (value range analysis, final value
+replacement) are interested in the values that are defined in the loop
+and used outside of it, i.e., exactly those for that we create new PHI
+nodes.
+@item In induction variable analysis, it is not necessary to specify the
+loop in that the analysis should be performed -- the scalar evolution
+analysis always returns the results with respect to the loop in that the
+SSA name is defined.
+@item It makes updating of SSA form during loop transformations simpler.
+Without LCSSA, operations like loop unrolling may force creation of PHI
+nodes arbitrarily far from the loop, while in LCSSA, the SSA form can be
+updated locally. However, since we only keep real operands in LCSSA, we
+cannot use this advantage (we could have local updating of real
+operands, but it is not much more efficient than to use generic SSA form
+updating for it as well; the amount of changes to SSA is the same).
+@end itemize
+
+However, it also means LCSSA must be updated. This is usually
+straightforward, unless you create a new value in loop and use it
+outside, or unless you manipulate loop exit edges (functions are
+provided to make these manipulations simple).
+@code{rewrite_into_loop_closed_ssa} is used to rewrite SSA form to
+LCSSA, and @code{verify_loop_closed_ssa} to check that the invariant of
+LCSSA is preserved.
+
+@node Scalar evolutions
+@section Scalar evolutions
+@cindex Scalar evolutions
+@cindex IV analysis on GIMPLE
+
+Scalar evolutions (SCEV) are used to represent results of induction
+variable analysis on GIMPLE@. They enable us to represent variables with
+complicated behavior in a simple and consistent way (we only use it to
+express values of polynomial induction variables, but it is possible to
+extend it). The interfaces to SCEV analysis are declared in
+@file{tree-scalar-evolution.h}. To use scalar evolutions analysis,
+@code{scev_initialize} must be used. To stop using SCEV,
+@code{scev_finalize} should be used. SCEV analysis caches results in
+order to save time and memory. This cache however is made invalid by
+most of the loop transformations, including removal of code. If such a
+transformation is performed, @code{scev_reset} must be called to clean
+the caches.
+
+Given an SSA name, its behavior in loops can be analyzed using the
+@code{analyze_scalar_evolution} function. The returned SCEV however
+does not have to be fully analyzed and it may contain references to
+other SSA names defined in the loop. To resolve these (potentially
+recursive) references, @code{instantiate_parameters} or
+@code{resolve_mixers} functions must be used.
+@code{instantiate_parameters} is useful when you use the results of SCEV
+only for some analysis, and when you work with whole nest of loops at
+once. It will try replacing all SSA names by their SCEV in all loops,
+including the super-loops of the current loop, thus providing a complete
+information about the behavior of the variable in the loop nest.
+@code{resolve_mixers} is useful if you work with only one loop at a
+time, and if you possibly need to create code based on the value of the
+induction variable. It will only resolve the SSA names defined in the
+current loop, leaving the SSA names defined outside unchanged, even if
+their evolution in the outer loops is known.
+
+The SCEV is a normal tree expression, except for the fact that it may
+contain several special tree nodes. One of them is
+@code{SCEV_NOT_KNOWN}, used for SSA names whose value cannot be
+expressed. The other one is @code{POLYNOMIAL_CHREC}. Polynomial chrec
+has three arguments -- base, step and loop (both base and step may
+contain further polynomial chrecs). Type of the expression and of base
+and step must be the same. A variable has evolution
+@code{POLYNOMIAL_CHREC(base, step, loop)} if it is (in the specified
+loop) equivalent to @code{x_1} in the following example
+
+@smallexample
+while (@dots{})
+ @{
+ x_1 = phi (base, x_2);
+ x_2 = x_1 + step;
+ @}
+@end smallexample
+
+Note that this includes the language restrictions on the operations.
+For example, if we compile C code and @code{x} has signed type, then the
+overflow in addition would cause undefined behavior, and we may assume
+that this does not happen. Hence, the value with this SCEV cannot
+overflow (which restricts the number of iterations of such a loop).
+
+In many cases, one wants to restrict the attention just to affine
+induction variables. In this case, the extra expressive power of SCEV
+is not useful, and may complicate the optimizations. In this case,
+@code{simple_iv} function may be used to analyze a value -- the result
+is a loop-invariant base and step.
+
+@node loop-iv
+@section IV analysis on RTL
+@cindex IV analysis on RTL
+
+The induction variable on RTL is simple and only allows analysis of
+affine induction variables, and only in one loop at once. The interface
+is declared in @file{cfgloop.h}. Before analyzing induction variables
+in a loop L, @code{iv_analysis_loop_init} function must be called on L.
+After the analysis (possibly calling @code{iv_analysis_loop_init} for
+several loops) is finished, @code{iv_analysis_done} should be called.
+The following functions can be used to access the results of the
+analysis:
+
+@itemize
+@item @code{iv_analyze}: Analyzes a single register used in the given
+insn. If no use of the register in this insn is found, the following
+insns are scanned, so that this function can be called on the insn
+returned by get_condition.
+@item @code{iv_analyze_result}: Analyzes result of the assignment in the
+given insn.
+@item @code{iv_analyze_expr}: Analyzes a more complicated expression.
+All its operands are analyzed by @code{iv_analyze}, and hence they must
+be used in the specified insn or one of the following insns.
+@end itemize
+
+The description of the induction variable is provided in @code{struct
+rtx_iv}. In order to handle subregs, the representation is a bit
+complicated; if the value of the @code{extend} field is not
+@code{UNKNOWN}, the value of the induction variable in the i-th
+iteration is
+
+@smallexample
+delta + mult * extend_@{extend_mode@} (subreg_@{mode@} (base + i * step)),
+@end smallexample
+
+with the following exception: if @code{first_special} is true, then the
+value in the first iteration (when @code{i} is zero) is @code{delta +
+mult * base}. However, if @code{extend} is equal to @code{UNKNOWN},
+then @code{first_special} must be false, @code{delta} 0, @code{mult} 1
+and the value in the i-th iteration is
+
+@smallexample
+subreg_@{mode@} (base + i * step)
+@end smallexample
+
+The function @code{get_iv_value} can be used to perform these
+calculations.
+
+@node Number of iterations
+@section Number of iterations analysis
+@cindex Number of iterations analysis
+
+Both on GIMPLE and on RTL, there are functions available to determine
+the number of iterations of a loop, with a similar interface. The
+number of iterations of a loop in GCC is defined as the number of
+executions of the loop latch. In many cases, it is not possible to
+determine the number of iterations unconditionally -- the determined
+number is correct only if some assumptions are satisfied. The analysis
+tries to verify these conditions using the information contained in the
+program; if it fails, the conditions are returned together with the
+result. The following information and conditions are provided by the
+analysis:
+
+@itemize
+@item @code{assumptions}: If this condition is false, the rest of
+the information is invalid.
+@item @code{noloop_assumptions} on RTL, @code{may_be_zero} on GIMPLE: If
+this condition is true, the loop exits in the first iteration.
+@item @code{infinite}: If this condition is true, the loop is infinite.
+This condition is only available on RTL@. On GIMPLE, conditions for
+finiteness of the loop are included in @code{assumptions}.
+@item @code{niter_expr} on RTL, @code{niter} on GIMPLE: The expression
+that gives number of iterations. The number of iterations is defined as
+the number of executions of the loop latch.
+@end itemize
+
+Both on GIMPLE and on RTL, it necessary for the induction variable
+analysis framework to be initialized (SCEV on GIMPLE, loop-iv on RTL).
+On GIMPLE, the results are stored to @code{struct tree_niter_desc}
+structure. Number of iterations before the loop is exited through a
+given exit can be determined using @code{number_of_iterations_exit}
+function. On RTL, the results are returned in @code{struct niter_desc}
+structure. The corresponding function is named
+@code{check_simple_exit}. There are also functions that pass through
+all the exits of a loop and try to find one with easy to determine
+number of iterations -- @code{find_loop_niter} on GIMPLE and
+@code{find_simple_exit} on RTL@. Finally, there are functions that
+provide the same information, but additionally cache it, so that
+repeated calls to number of iterations are not so costly --
+@code{number_of_latch_executions} on GIMPLE and @code{get_simple_loop_desc}
+on RTL.
+
+Note that some of these functions may behave slightly differently than
+others -- some of them return only the expression for the number of
+iterations, and fail if there are some assumptions. The function
+@code{number_of_latch_executions} works only for single-exit loops.
+The function @code{number_of_cond_exit_executions} can be used to
+determine number of executions of the exit condition of a single-exit
+loop (i.e., the @code{number_of_latch_executions} increased by one).
+
+On GIMPLE, below constraint flags affect semantics of some APIs of number
+of iterations analyzer:
+
+@itemize
+@item @code{LOOP_C_INFINITE}: If this constraint flag is set, the loop
+is known to be infinite. APIs like @code{number_of_iterations_exit} can
+return false directly without doing any analysis.
+@item @code{LOOP_C_FINITE}: If this constraint flag is set, the loop is
+known to be finite, in other words, loop's number of iterations can be
+computed with @code{assumptions} be true.
+@end itemize
+
+Generally, the constraint flags are set/cleared by consumers which are
+loop optimizers. It's also the consumers' responsibility to set/clear
+constraints correctly. Failing to do that might result in hard to track
+down bugs in scev/niter consumers. One typical use case is vectorizer:
+it drives number of iterations analyzer by setting @code{LOOP_C_FINITE}
+and vectorizes possibly infinite loop by versioning loop with analysis
+result. In return, constraints set by consumers can also help number of
+iterations analyzer in following optimizers. For example, @code{niter}
+of a loop versioned under @code{assumptions} is valid unconditionally.
+
+Other constraints may be added in the future, for example, a constraint
+indicating that loops' latch must roll thus @code{may_be_zero} would be
+false unconditionally.
+
+@node Dependency analysis
+@section Data Dependency Analysis
+@cindex Data Dependency Analysis
+
+The code for the data dependence analysis can be found in
+@file{tree-data-ref.cc} and its interface and data structures are
+described in @file{tree-data-ref.h}. The function that computes the
+data dependences for all the array and pointer references for a given
+loop is @code{compute_data_dependences_for_loop}. This function is
+currently used by the linear loop transform and the vectorization
+passes. Before calling this function, one has to allocate two vectors:
+a first vector will contain the set of data references that are
+contained in the analyzed loop body, and the second vector will contain
+the dependence relations between the data references. Thus if the
+vector of data references is of size @code{n}, the vector containing the
+dependence relations will contain @code{n*n} elements. However if the
+analyzed loop contains side effects, such as calls that potentially can
+interfere with the data references in the current analyzed loop, the
+analysis stops while scanning the loop body for data references, and
+inserts a single @code{chrec_dont_know} in the dependence relation
+array.
+
+The data references are discovered in a particular order during the
+scanning of the loop body: the loop body is analyzed in execution order,
+and the data references of each statement are pushed at the end of the
+data reference array. Two data references syntactically occur in the
+program in the same order as in the array of data references. This
+syntactic order is important in some classical data dependence tests,
+and mapping this order to the elements of this array avoids costly
+queries to the loop body representation.
+
+Three types of data references are currently handled: ARRAY_REF,
+INDIRECT_REF and COMPONENT_REF@. The data structure for the data reference
+is @code{data_reference}, where @code{data_reference_p} is a name of a
+pointer to the data reference structure. The structure contains the
+following elements:
+
+@itemize
+@item @code{base_object_info}: Provides information about the base object
+of the data reference and its access functions. These access functions
+represent the evolution of the data reference in the loop relative to
+its base, in keeping with the classical meaning of the data reference
+access function for the support of arrays. For example, for a reference
+@code{a.b[i][j]}, the base object is @code{a.b} and the access functions,
+one for each array subscript, are:
+@code{@{i_init, + i_step@}_1, @{j_init, +, j_step@}_2}.
+
+@item @code{first_location_in_loop}: Provides information about the first
+location accessed by the data reference in the loop and about the access
+function used to represent evolution relative to this location. This data
+is used to support pointers, and is not used for arrays (for which we
+have base objects). Pointer accesses are represented as a one-dimensional
+access that starts from the first location accessed in the loop. For
+example:
+
+@smallexample
+ for1 i
+ for2 j
+ *((int *)p + i + j) = a[i][j];
+@end smallexample
+
+The access function of the pointer access is @code{@{0, + 4B@}_for2}
+relative to @code{p + i}. The access functions of the array are
+@code{@{i_init, + i_step@}_for1} and @code{@{j_init, +, j_step@}_for2}
+relative to @code{a}.
+
+Usually, the object the pointer refers to is either unknown, or we cannot
+prove that the access is confined to the boundaries of a certain object.
+
+Two data references can be compared only if at least one of these two
+representations has all its fields filled for both data references.
+
+The current strategy for data dependence tests is as follows:
+If both @code{a} and @code{b} are represented as arrays, compare
+@code{a.base_object} and @code{b.base_object};
+if they are equal, apply dependence tests (use access functions based on
+base_objects).
+Else if both @code{a} and @code{b} are represented as pointers, compare
+@code{a.first_location} and @code{b.first_location};
+if they are equal, apply dependence tests (use access functions based on
+first location).
+However, if @code{a} and @code{b} are represented differently, only try
+to prove that the bases are definitely different.
+
+@item Aliasing information.
+@item Alignment information.
+@end itemize
+
+The structure describing the relation between two data references is
+@code{data_dependence_relation} and the shorter name for a pointer to
+such a structure is @code{ddr_p}. This structure contains:
+
+@itemize
+@item a pointer to each data reference,
+@item a tree node @code{are_dependent} that is set to @code{chrec_known}
+if the analysis has proved that there is no dependence between these two
+data references, @code{chrec_dont_know} if the analysis was not able to
+determine any useful result and potentially there could exist a
+dependence between these data references, and @code{are_dependent} is
+set to @code{NULL_TREE} if there exist a dependence relation between the
+data references, and the description of this dependence relation is
+given in the @code{subscripts}, @code{dir_vects}, and @code{dist_vects}
+arrays,
+@item a boolean that determines whether the dependence relation can be
+represented by a classical distance vector,
+@item an array @code{subscripts} that contains a description of each
+subscript of the data references. Given two array accesses a
+subscript is the tuple composed of the access functions for a given
+dimension. For example, given @code{A[f1][f2][f3]} and
+@code{B[g1][g2][g3]}, there are three subscripts: @code{(f1, g1), (f2,
+g2), (f3, g3)}.
+@item two arrays @code{dir_vects} and @code{dist_vects} that contain
+classical representations of the data dependences under the form of
+direction and distance dependence vectors,
+@item an array of loops @code{loop_nest} that contains the loops to
+which the distance and direction vectors refer to.
+@end itemize
+
+Several functions for pretty printing the information extracted by the
+data dependence analysis are available: @code{dump_ddrs} prints with a
+maximum verbosity the details of a data dependence relations array,
+@code{dump_dist_dir_vectors} prints only the classical distance and
+direction vectors for a data dependence relations array, and
+@code{dump_data_references} prints the details of the data references
+contained in a data reference array.
--- /dev/null
+@c Copyright (C) 2018-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@ignore
+@c man begin COPYRIGHT
+Copyright @copyright{} 2017-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``GNU General Public License'' and ``Funding
+Free Software'', the Front-Cover texts being (a) (see below), and with
+the Back-Cover Texts being (b) (see below). A copy of the license is
+included in the gfdl(7) man page.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@c Set file name and title for the man page.
+@setfilename lto-dump
+@settitle Tool for dumping LTO object files.
+@end ignore
+
+@node lto-dump
+@chapter @command{lto-dump}---Tool for dumping LTO object files.
+
+@menu
+* lto-dump Intro:: Introduction to lto-dump.
+* Invoking lto-dump:: How to use lto-dump.
+@end menu
+
+@node lto-dump Intro
+@section Introduction to @command{lto-dump}
+@c man begin DESCRIPTION
+
+@command{lto-dump} is a tool you can use in conjunction with GCC to
+dump link time optimization object files.
+
+@c man end
+
+@node Invoking lto-dump
+@section Invoking @command{lto-dump}
+
+@smallexample
+Usage: lto-dump @r{[}@var{OPTION}@r{]} ... @var{objfiles}
+@end smallexample
+
+@command{lto-dump} accepts the following options:
+
+@ignore
+@c man begin SYNOPSIS
+lto-dump [@option{-list}]
+ [@option{-demangle}]
+ [@option{-defined-only}]
+ [@option{-print-value}]
+ [@option{-name-sort}]
+ [@option{-size-sort}]
+ [@option{-reverse-sort}]
+ [@option{-no-sort}]
+ [@option{-symbol=}]
+ [@option{-objects}]
+ [@option{-type-stats}]
+ [@option{-tree-stats}]
+ [@option{-gimple-stats}]
+ [@option{-dump-level=}]
+ [@option{-dump-body=}]
+ [@option{-help}] @var{lto-dump}
+@c man end
+@end ignore
+
+@c man begin OPTIONS
+@table @gcctabopt
+@item -list
+Dumps list of details of functions and variables.
+
+@item -demangle
+Dump the demangled output.
+
+@item -defined-only
+Dump only the defined symbols.
+
+@item -print-value
+Dump initial values of the variables.
+
+@item -name-sort
+Sort the symbols alphabetically.
+
+@item -size-sort
+Sort the symbols according to size.
+
+@item -reverse-sort
+Dump the symbols in reverse order.
+
+@item -no-sort
+Dump the symbols in order of occurrence.
+
+@item -symbol=
+Dump the details of specific symbol.
+
+@item -objects
+Dump the details of LTO objects.
+
+@item -type-stats
+Dump the statistics of tree types.
+
+@item -tree-stats
+Dump the statistics of trees.
+
+@item -gimple-stats
+Dump the statistics of gimple statements.
+
+@item -dump-level=
+For deciding the optimization level of body.
+
+@item -dump-body=
+Dump the specific gimple body.
+
+@item -help
+Display the dump tool help.
+
+@end table
+
+@c man end
--- /dev/null
+@c Copyright (C) 2010-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+@c Contributed by Jan Hubicka <jh@suse.cz> and
+@c Diego Novillo <dnovillo@google.com>
+
+@node LTO
+@chapter Link Time Optimization
+@cindex lto
+@cindex whopr
+@cindex wpa
+@cindex ltrans
+
+Link Time Optimization (LTO) gives GCC the capability of
+dumping its internal representation (GIMPLE) to disk,
+so that all the different compilation units that make up
+a single executable can be optimized as a single module.
+This expands the scope of inter-procedural optimizations
+to encompass the whole program (or, rather, everything
+that is visible at link time).
+
+@menu
+* LTO Overview:: Overview of LTO.
+* LTO object file layout:: LTO file sections in ELF.
+* IPA:: Using summary information in IPA passes.
+* WHOPR:: Whole program assumptions,
+ linker plugin and symbol visibilities.
+* Internal flags:: Internal flags controlling @code{lto1}.
+@end menu
+
+@node LTO Overview
+@section Design Overview
+
+Link time optimization is implemented as a GCC front end for a
+bytecode representation of GIMPLE that is emitted in special sections
+of @code{.o} files. Currently, LTO support is enabled in most
+ELF-based systems, as well as darwin, cygwin and mingw systems.
+
+By default, object files generated with LTO support contain only GIMPLE
+bytecode. Such objects are called ``slim'', and they require that
+tools like @code{ar} and @code{nm} understand symbol tables of LTO
+sections. For most targets these tools have been extended to use the
+plugin infrastructure, so GCC can support ``slim'' objects consisting
+of the intermediate code alone.
+
+GIMPLE bytecode could also be saved alongside final object code if
+the @option{-ffat-lto-objects} option is passed, or if no plugin support
+is detected for @code{ar} and @code{nm} when GCC is configured. It makes
+the object files generated with LTO support larger than regular object
+files. This ``fat'' object format allows to ship one set of fat
+objects which could be used both for development and the production of
+optimized builds. A, perhaps surprising, side effect of this feature
+is that any mistake in the toolchain leads to LTO information not
+being used (e.g.@: an older @code{libtool} calling @code{ld} directly).
+This is both an advantage, as the system is more robust, and a
+disadvantage, as the user is not informed that the optimization has
+been disabled.
+
+At the highest level, LTO splits the compiler in two. The first half
+(the ``writer'') produces a streaming representation of all the
+internal data structures needed to optimize and generate code. This
+includes declarations, types, the callgraph and the GIMPLE representation
+of function bodies.
+
+When @option{-flto} is given during compilation of a source file, the
+pass manager executes all the passes in @code{all_lto_gen_passes}.
+Currently, this phase is composed of two IPA passes:
+
+@itemize @bullet
+@item @code{pass_ipa_lto_gimple_out}
+This pass executes the function @code{lto_output} in
+@file{lto-streamer-out.cc}, which traverses the call graph encoding
+every reachable declaration, type and function. This generates a
+memory representation of all the file sections described below.
+
+@item @code{pass_ipa_lto_finish_out}
+This pass executes the function @code{produce_asm_for_decls} in
+@file{lto-streamer-out.cc}, which takes the memory image built in the
+previous pass and encodes it in the corresponding ELF file sections.
+@end itemize
+
+The second half of LTO support is the ``reader''. This is implemented
+as the GCC front end @file{lto1} in @file{lto/lto.cc}. When
+@file{collect2} detects a link set of @code{.o}/@code{.a} files with
+LTO information and the @option{-flto} is enabled, it invokes
+@file{lto1} which reads the set of files and aggregates them into a
+single translation unit for optimization. The main entry point for
+the reader is @file{lto/lto.cc}:@code{lto_main}.
+
+@subsection LTO modes of operation
+
+One of the main goals of the GCC link-time infrastructure was to allow
+effective compilation of large programs. For this reason GCC implements two
+link-time compilation modes.
+
+@enumerate
+@item @emph{LTO mode}, in which the whole program is read into the
+compiler at link-time and optimized in a similar way as if it
+were a single source-level compilation unit.
+
+@item @emph{WHOPR or partitioned mode}, designed to utilize multiple
+CPUs and/or a distributed compilation environment to quickly link
+large applications. WHOPR stands for WHOle Program optimizeR (not to
+be confused with the semantics of @option{-fwhole-program}). It
+partitions the aggregated callgraph from many different @code{.o}
+files and distributes the compilation of the sub-graphs to different
+CPUs.
+
+Note that distributed compilation is not implemented yet, but since
+the parallelism is facilitated via generating a @code{Makefile}, it
+would be easy to implement.
+@end enumerate
+
+WHOPR splits LTO into three main stages:
+@enumerate
+@item Local generation (LGEN)
+This stage executes in parallel. Every file in the program is compiled
+into the intermediate language and packaged together with the local
+call-graph and summary information. This stage is the same for both
+the LTO and WHOPR compilation mode.
+
+@item Whole Program Analysis (WPA)
+WPA is performed sequentially. The global call-graph is generated, and
+a global analysis procedure makes transformation decisions. The global
+call-graph is partitioned to facilitate parallel optimization during
+phase 3. The results of the WPA stage are stored into new object files
+which contain the partitions of program expressed in the intermediate
+language and the optimization decisions.
+
+@item Local transformations (LTRANS)
+This stage executes in parallel. All the decisions made during phase 2
+are implemented locally in each partitioned object file, and the final
+object code is generated. Optimizations which cannot be decided
+efficiently during the phase 2 may be performed on the local
+call-graph partitions.
+@end enumerate
+
+WHOPR can be seen as an extension of the usual LTO mode of
+compilation. In LTO, WPA and LTRANS are executed within a single
+execution of the compiler, after the whole program has been read into
+memory.
+
+When compiling in WHOPR mode, the callgraph is partitioned during
+the WPA stage. The whole program is split into a given number of
+partitions of roughly the same size. The compiler tries to
+minimize the number of references which cross partition boundaries.
+The main advantage of WHOPR is to allow the parallel execution of
+LTRANS stages, which are the most time-consuming part of the
+compilation process. Additionally, it avoids the need to load the
+whole program into memory.
+
+
+@node LTO object file layout
+@section LTO file sections
+
+LTO information is stored in several ELF sections inside object files.
+Data structures and enum codes for sections are defined in
+@file{lto-streamer.h}.
+
+These sections are emitted from @file{lto-streamer-out.cc} and mapped
+in all at once from @file{lto/lto.cc}:@code{lto_file_read}. The
+individual functions dealing with the reading/writing of each section
+are described below.
+
+@itemize @bullet
+@item Command line options (@code{.gnu.lto_.opts})
+
+This section contains the command line options used to generate the
+object files. This is used at link time to determine the optimization
+level and other settings when they are not explicitly specified at the
+linker command line.
+
+Currently, GCC does not support combining LTO object files compiled
+with different set of the command line options into a single binary.
+At link time, the options given on the command line and the options
+saved on all the files in a link-time set are applied globally. No
+attempt is made at validating the combination of flags (other than the
+usual validation done by option processing). This is implemented in
+@file{lto/lto.cc}:@code{lto_read_all_file_options}.
+
+
+@item Symbol table (@code{.gnu.lto_.symtab})
+
+This table replaces the ELF symbol table for functions and variables
+represented in the LTO IL. Symbols used and exported by the optimized
+assembly code of ``fat'' objects might not match the ones used and
+exported by the intermediate code. This table is necessary because
+the intermediate code is less optimized and thus requires a separate
+symbol table.
+
+Additionally, the binary code in the ``fat'' object will lack a call
+to a function, since the call was optimized out at compilation time
+after the intermediate language was streamed out. In some special
+cases, the same optimization may not happen during link-time
+optimization. This would lead to an undefined symbol if only one
+symbol table was used.
+
+The symbol table is emitted in
+@file{lto-streamer-out.cc}:@code{produce_symtab}.
+
+
+@item Global declarations and types (@code{.gnu.lto_.decls})
+
+This section contains an intermediate language dump of all
+declarations and types required to represent the callgraph, static
+variables and top-level debug info.
+
+The contents of this section are emitted in
+@file{lto-streamer-out.cc}:@code{produce_asm_for_decls}. Types and
+symbols are emitted in a topological order that preserves the sharing
+of pointers when the file is read back in
+(@file{lto.cc}:@code{read_cgraph_and_symbols}).
+
+
+@item The callgraph (@code{.gnu.lto_.cgraph})
+
+This section contains the basic data structure used by the GCC
+inter-procedural optimization infrastructure. This section stores an
+annotated multi-graph which represents the functions and call sites as
+well as the variables, aliases and top-level @code{asm} statements.
+
+This section is emitted in
+@file{lto-streamer-out.cc}:@code{output_cgraph} and read in
+@file{lto-cgraph.cc}:@code{input_cgraph}.
+
+
+@item IPA references (@code{.gnu.lto_.refs})
+
+This section contains references between function and static
+variables. It is emitted by @file{lto-cgraph.cc}:@code{output_refs}
+and read by @file{lto-cgraph.cc}:@code{input_refs}.
+
+
+@item Function bodies (@code{.gnu.lto_.function_body.<name>})
+
+This section contains function bodies in the intermediate language
+representation. Every function body is in a separate section to allow
+copying of the section independently to different object files or
+reading the function on demand.
+
+Functions are emitted in
+@file{lto-streamer-out.cc}:@code{output_function} and read in
+@file{lto-streamer-in.cc}:@code{input_function}.
+
+
+@item Static variable initializers (@code{.gnu.lto_.vars})
+
+This section contains all the symbols in the global variable pool. It
+is emitted by @file{lto-cgraph.cc}:@code{output_varpool} and read in
+@file{lto-cgraph.cc}:@code{input_cgraph}.
+
+@item Summaries and optimization summaries used by IPA passes
+(@code{.gnu.lto_.<xxx>}, where @code{<xxx>} is one of @code{jmpfuncs},
+@code{pureconst} or @code{reference})
+
+These sections are used by IPA passes that need to emit summary
+information during LTO generation to be read and aggregated at
+link time. Each pass is responsible for implementing two pass manager
+hooks: one for writing the summary and another for reading it in. The
+format of these sections is entirely up to each individual pass. The
+only requirement is that the writer and reader hooks agree on the
+format.
+@end itemize
+
+
+@node IPA
+@section Using summary information in IPA passes
+
+Programs are represented internally as a @emph{callgraph} (a
+multi-graph where nodes are functions and edges are call sites)
+and a @emph{varpool} (a list of static and external variables in
+the program).
+
+The inter-procedural optimization is organized as a sequence of
+individual passes, which operate on the callgraph and the
+varpool. To make the implementation of WHOPR possible, every
+inter-procedural optimization pass is split into several stages
+that are executed at different times during WHOPR compilation:
+
+@itemize @bullet
+@item LGEN time
+@enumerate
+@item @emph{Generate summary} (@code{generate_summary} in
+@code{struct ipa_opt_pass_d}). This stage analyzes every function
+body and variable initializer is examined and stores relevant
+information into a pass-specific data structure.
+
+@item @emph{Write summary} (@code{write_summary} in
+@code{struct ipa_opt_pass_d}). This stage writes all the
+pass-specific information generated by @code{generate_summary}.
+Summaries go into their own @code{LTO_section_*} sections that
+have to be declared in @file{lto-streamer.h}:@code{enum
+lto_section_type}. A new section is created by calling
+@code{create_output_block} and data can be written using the
+@code{lto_output_*} routines.
+@end enumerate
+
+@item WPA time
+@enumerate
+@item @emph{Read summary} (@code{read_summary} in
+@code{struct ipa_opt_pass_d}). This stage reads all the
+pass-specific information in exactly the same order that it was
+written by @code{write_summary}.
+
+@item @emph{Execute} (@code{execute} in @code{struct
+opt_pass}). This performs inter-procedural propagation. This
+must be done without actual access to the individual function
+bodies or variable initializers. Typically, this results in a
+transitive closure operation over the summary information of all
+the nodes in the callgraph.
+
+@item @emph{Write optimization summary}
+(@code{write_optimization_summary} in @code{struct
+ipa_opt_pass_d}). This writes the result of the inter-procedural
+propagation into the object file. This can use the same data
+structures and helper routines used in @code{write_summary}.
+@end enumerate
+
+@item LTRANS time
+@enumerate
+@item @emph{Read optimization summary}
+(@code{read_optimization_summary} in @code{struct
+ipa_opt_pass_d}). The counterpart to
+@code{write_optimization_summary}. This reads the interprocedural
+optimization decisions in exactly the same format emitted by
+@code{write_optimization_summary}.
+
+@item @emph{Transform} (@code{function_transform} and
+@code{variable_transform} in @code{struct ipa_opt_pass_d}).
+The actual function bodies and variable initializers are updated
+based on the information passed down from the @emph{Execute} stage.
+@end enumerate
+@end itemize
+
+The implementation of the inter-procedural passes are shared
+between LTO, WHOPR and classic non-LTO compilation.
+
+@itemize
+@item During the traditional file-by-file mode every pass executes its
+own @emph{Generate summary}, @emph{Execute}, and @emph{Transform}
+stages within the single execution context of the compiler.
+
+@item In LTO compilation mode, every pass uses @emph{Generate
+summary} and @emph{Write summary} stages at compilation time,
+while the @emph{Read summary}, @emph{Execute}, and
+@emph{Transform} stages are executed at link time.
+
+@item In WHOPR mode all stages are used.
+@end itemize
+
+To simplify development, the GCC pass manager differentiates
+between normal inter-procedural passes (@pxref{Regular IPA passes}),
+small inter-procedural passes (@pxref{Small IPA passes})
+and late inter-procedural passes (@pxref{Late IPA passes}).
+A small or late IPA pass (@code{SIMPLE_IPA_PASS}) does
+everything at once and thus cannot be executed during WPA in
+WHOPR mode. It defines only the @emph{Execute} stage and during
+this stage it accesses and modifies the function bodies. Such
+passes are useful for optimization at LGEN or LTRANS time and are
+used, for example, to implement early optimization before writing
+object files. The simple inter-procedural passes can also be used
+for easier prototyping and development of a new inter-procedural
+pass.
+
+
+@subsection Virtual clones
+
+One of the main challenges of introducing the WHOPR compilation
+mode was addressing the interactions between optimization passes.
+In LTO compilation mode, the passes are executed in a sequence,
+each of which consists of analysis (or @emph{Generate summary}),
+propagation (or @emph{Execute}) and @emph{Transform} stages.
+Once the work of one pass is finished, the next pass sees the
+updated program representation and can execute. This makes the
+individual passes dependent on each other.
+
+In WHOPR mode all passes first execute their @emph{Generate
+summary} stage. Then summary writing marks the end of the LGEN
+stage. At WPA time,
+the summaries are read back into memory and all passes run the
+@emph{Execute} stage. Optimization summaries are streamed and
+sent to LTRANS, where all the passes execute the @emph{Transform}
+stage.
+
+Most optimization passes split naturally into analysis,
+propagation and transformation stages. But some do not. The
+main problem arises when one pass performs changes and the
+following pass gets confused by seeing different callgraphs
+between the @emph{Transform} stage and the @emph{Generate summary}
+or @emph{Execute} stage. This means that the passes are required
+to communicate their decisions with each other.
+
+To facilitate this communication, the GCC callgraph
+infrastructure implements @emph{virtual clones}, a method of
+representing the changes performed by the optimization passes in
+the callgraph without needing to update function bodies.
+
+A @emph{virtual clone} in the callgraph is a function that has no
+associated body, just a description of how to create its body based
+on a different function (which itself may be a virtual clone).
+
+The description of function modifications includes adjustments to
+the function's signature (which allows, for example, removing or
+adding function arguments), substitutions to perform on the
+function body, and, for inlined functions, a pointer to the
+function that it will be inlined into.
+
+It is also possible to redirect any edge of the callgraph from a
+function to its virtual clone. This implies updating of the call
+site to adjust for the new function signature.
+
+Most of the transformations performed by inter-procedural
+optimizations can be represented via virtual clones. For
+instance, a constant propagation pass can produce a virtual clone
+of the function which replaces one of its arguments by a
+constant. The inliner can represent its decisions by producing a
+clone of a function whose body will be later integrated into
+a given function.
+
+Using @emph{virtual clones}, the program can be easily updated
+during the @emph{Execute} stage, solving most of pass interactions
+problems that would otherwise occur during @emph{Transform}.
+
+Virtual clones are later materialized in the LTRANS stage and
+turned into real functions. Passes executed after the virtual
+clone were introduced also perform their @emph{Transform} stage
+on new functions, so for a pass there is no significant
+difference between operating on a real function or a virtual
+clone introduced before its @emph{Execute} stage.
+
+Optimization passes then work on virtual clones introduced before
+their @emph{Execute} stage as if they were real functions. The
+only difference is that clones are not visible during the
+@emph{Generate Summary} stage.
+
+To keep function summaries updated, the callgraph interface
+allows an optimizer to register a callback that is called every
+time a new clone is introduced as well as when the actual
+function or variable is generated or when a function or variable
+is removed. These hooks are registered in the @emph{Generate
+summary} stage and allow the pass to keep its information intact
+until the @emph{Execute} stage. The same hooks can also be
+registered during the @emph{Execute} stage to keep the
+optimization summaries updated for the @emph{Transform} stage.
+
+@subsection IPA references
+
+GCC represents IPA references in the callgraph. For a function
+or variable @code{A}, the @emph{IPA reference} is a list of all
+locations where the address of @code{A} is taken and, when
+@code{A} is a variable, a list of all direct stores and reads
+to/from @code{A}. References represent an oriented multi-graph on
+the union of nodes of the callgraph and the varpool. See
+@file{ipa-reference.cc}:@code{ipa_reference_write_optimization_summary}
+and
+@file{ipa-reference.cc}:@code{ipa_reference_read_optimization_summary}
+for details.
+
+@subsection Jump functions
+Suppose that an optimization pass sees a function @code{A} and it
+knows the values of (some of) its arguments. The @emph{jump
+function} describes the value of a parameter of a given function
+call in function @code{A} based on this knowledge.
+
+Jump functions are used by several optimizations, such as the
+inter-procedural constant propagation pass and the
+devirtualization pass. The inliner also uses jump functions to
+perform inlining of callbacks.
+
+@node WHOPR
+@section Whole program assumptions, linker plugin and symbol visibilities
+
+Link-time optimization gives relatively minor benefits when used
+alone. The problem is that propagation of inter-procedural
+information does not work well across functions and variables
+that are called or referenced by other compilation units (such as
+from a dynamically linked library). We say that such functions
+and variables are @emph{externally visible}.
+
+To make the situation even more difficult, many applications
+organize themselves as a set of shared libraries, and the default
+ELF visibility rules allow one to overwrite any externally
+visible symbol with a different symbol at runtime. This
+basically disables any optimizations across such functions and
+variables, because the compiler cannot be sure that the function
+body it is seeing is the same function body that will be used at
+runtime. Any function or variable not declared @code{static} in
+the sources degrades the quality of inter-procedural
+optimization.
+
+To avoid this problem the compiler must assume that it sees the
+whole program when doing link-time optimization. Strictly
+speaking, the whole program is rarely visible even at link-time.
+Standard system libraries are usually linked dynamically or not
+provided with the link-time information. In GCC, the whole
+program option (@option{-fwhole-program}) asserts that every
+function and variable defined in the current compilation
+unit is static, except for function @code{main} (note: at
+link time, the current unit is the union of all objects compiled
+with LTO). Since some functions and variables need to
+be referenced externally, for example by another DSO or from an
+assembler file, GCC also provides the function and variable
+attribute @code{externally_visible} which can be used to disable
+the effect of @option{-fwhole-program} on a specific symbol.
+
+The whole program mode assumptions are slightly more complex in
+C++, where inline functions in headers are put into @emph{COMDAT}
+sections. COMDAT function and variables can be defined by
+multiple object files and their bodies are unified at link-time
+and dynamic link-time. COMDAT functions are changed to local only
+when their address is not taken and thus un-sharing them with a
+library is not harmful. COMDAT variables always remain externally
+visible, however for readonly variables it is assumed that their
+initializers cannot be overwritten by a different value.
+
+GCC provides the function and variable attribute
+@code{visibility} that can be used to specify the visibility of
+externally visible symbols (or alternatively an
+@option{-fdefault-visibility} command line option). ELF defines
+the @code{default}, @code{protected}, @code{hidden} and
+@code{internal} visibilities.
+
+The most commonly used is visibility is @code{hidden}. It
+specifies that the symbol cannot be referenced from outside of
+the current shared library. Unfortunately, this information
+cannot be used directly by the link-time optimization in the
+compiler since the whole shared library also might contain
+non-LTO objects and those are not visible to the compiler.
+
+GCC solves this problem using linker plugins. A @emph{linker
+plugin} is an interface to the linker that allows an external
+program to claim the ownership of a given object file. The linker
+then performs the linking procedure by querying the plugin about
+the symbol table of the claimed objects and once the linking
+decisions are complete, the plugin is allowed to provide the
+final object file before the actual linking is made. The linker
+plugin obtains the symbol resolution information which specifies
+which symbols provided by the claimed objects are bound from the
+rest of a binary being linked.
+
+GCC is designed to be independent of the rest of the toolchain
+and aims to support linkers without plugin support. For this
+reason it does not use the linker plugin by default. Instead,
+the object files are examined by @command{collect2} before being
+passed to the linker and objects found to have LTO sections are
+passed to @command{lto1} first. This mode does not work for
+library archives. The decision on what object files from the
+archive are needed depends on the actual linking and thus GCC
+would have to implement the linker itself. The resolution
+information is missing too and thus GCC needs to make an educated
+guess based on @option{-fwhole-program}. Without the linker
+plugin GCC also assumes that symbols are declared @code{hidden}
+and not referred by non-LTO code by default.
+
+@node Internal flags
+@section Internal flags controlling @code{lto1}
+
+The following flags are passed into @command{lto1} and are not
+meant to be used directly from the command line.
+
+@itemize
+@item -fwpa
+@opindex fwpa
+This option runs the serial part of the link-time optimizer
+performing the inter-procedural propagation (WPA mode). The
+compiler reads in summary information from all inputs and
+performs an analysis based on summary information only. It
+generates object files for subsequent runs of the link-time
+optimizer where individual object files are optimized using both
+summary information from the WPA mode and the actual function
+bodies. It then drives the LTRANS phase.
+
+@item -fltrans
+@opindex fltrans
+This option runs the link-time optimizer in the
+local-transformation (LTRANS) mode, which reads in output from a
+previous run of the LTO in WPA mode. In the LTRANS mode, LTO
+optimizes an object and produces the final assembly.
+
+@item -fltrans-output-list=@var{file}
+@opindex fltrans-output-list
+This option specifies a file to which the names of LTRANS output
+files are written. This option is only meaningful in conjunction
+with @option{-fwpa}.
+
+@item -fresolution=@var{file}
+@opindex fresolution
+This option specifies the linker resolution file. This option is
+only meaningful in conjunction with @option{-fwpa} and as option
+to pass through to the LTO linker plugin.
+@end itemize
--- /dev/null
+@c Copyright (C) 2001-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Makefile
+@subsection Makefile Targets
+@cindex makefile targets
+@cindex targets, makefile
+
+These targets are available from the @samp{gcc} directory:
+
+@table @code
+@item all
+This is the default target. Depending on what your build/host/target
+configuration is, it coordinates all the things that need to be built.
+
+@item doc
+Produce info-formatted documentation and man pages. Essentially it
+calls @samp{make man} and @samp{make info}.
+
+@item dvi
+Produce DVI-formatted documentation.
+
+@item pdf
+Produce PDF-formatted documentation.
+
+@item html
+Produce HTML-formatted documentation.
+
+@item man
+Generate man pages.
+
+@item info
+Generate info-formatted pages.
+
+@item mostlyclean
+Delete the files made while building the compiler.
+
+@item clean
+That, and all the other files built by @samp{make all}.
+
+@item distclean
+That, and all the files created by @command{configure}.
+
+@item maintainer-clean
+Distclean plus any file that can be generated from other files. Note
+that additional tools may be required beyond what is normally needed to
+build GCC.
+
+@item srcextra
+Generates files in the source directory that are not version-controlled but
+should go into a release tarball.
+
+@item srcinfo
+@itemx srcman
+Copies the info-formatted and manpage documentation into the source
+directory usually for the purpose of generating a release tarball.
+
+@item install
+Installs GCC.
+
+@item uninstall
+Deletes installed files, though this is not supported.
+
+@item check
+Run the testsuite. This creates a @file{testsuite} subdirectory that
+has various @file{.sum} and @file{.log} files containing the results of
+the testing. You can run subsets with, for example, @samp{make check-gcc}.
+You can specify specific tests by setting @env{RUNTESTFLAGS} to be the name
+of the @file{.exp} file, optionally followed by (for some tests) an equals
+and a file wildcard, like:
+
+@smallexample
+make check-gcc RUNTESTFLAGS="execute.exp=19980413-*"
+@end smallexample
+
+Note that running the testsuite may require additional tools be
+installed, such as Tcl or DejaGnu.
+@end table
+
+The toplevel tree from which you start GCC compilation is not
+the GCC directory, but rather a complex Makefile that coordinates
+the various steps of the build, including bootstrapping the compiler
+and using the new compiler to build target libraries.
+
+When GCC is configured for a native configuration, the default action
+for @command{make} is to do a full three-stage bootstrap. This means
+that GCC is built three times---once with the native compiler, once with
+the native-built compiler it just built, and once with the compiler it
+built the second time. In theory, the last two should produce the same
+results, which @samp{make compare} can check. Each stage is configured
+separately and compiled into a separate directory, to minimize problems
+due to ABI incompatibilities between the native compiler and GCC.
+
+If you do a change, rebuilding will also start from the first stage
+and ``bubble'' up the change through the three stages. Each stage
+is taken from its build directory (if it had been built previously),
+rebuilt, and copied to its subdirectory. This will allow you to, for
+example, continue a bootstrap after fixing a bug which causes the
+stage2 build to crash. It does not provide as good coverage of the
+compiler as bootstrapping from scratch, but it ensures that the new
+code is syntactically correct (e.g., that you did not use GCC extensions
+by mistake), and avoids spurious bootstrap comparison
+failures@footnote{Except if the compiler was buggy and miscompiled
+some of the files that were not modified. In this case, it's best
+to use @command{make restrap}.}.
+
+Other targets available from the top level include:
+
+@table @code
+@item bootstrap-lean
+Like @code{bootstrap}, except that the various stages are removed once
+they're no longer needed. This saves disk space.
+
+@item bootstrap2
+@itemx bootstrap2-lean
+Performs only the first two stages of bootstrap. Unlike a three-stage
+bootstrap, this does not perform a comparison to test that the compiler
+is running properly. Note that the disk space required by a ``lean''
+bootstrap is approximately independent of the number of stages.
+
+@item stage@var{N}-bubble (@var{N} = 1@dots{}4, profile, feedback)
+Rebuild all the stages up to @var{N}, with the appropriate flags,
+``bubbling'' the changes as described above.
+
+@item all-stage@var{N} (@var{N} = 1@dots{}4, profile, feedback)
+Assuming that stage @var{N} has already been built, rebuild it with the
+appropriate flags. This is rarely needed.
+
+@item cleanstrap
+Remove everything (@samp{make clean}) and rebuilds (@samp{make bootstrap}).
+
+@item compare
+Compares the results of stages 2 and 3. This ensures that the compiler
+is running properly, since it should produce the same object files
+regardless of how it itself was compiled.
+
+@item distclean-stage@var{N} (@var{N} = 1@dots{}4, profile, feedback)
+Wipe stage @var{N} and all the following ones.
+
+For example,
+@samp{make distclean-stage3} wipes stage 3 and all the following ones,
+so that another @command{make} then rebuilds them from scratch.
+This can be useful if you're doing changes where
+``bubbling'' the changes as described above is not sufficient,
+but a full @command{make restrap} isn't necessary either.
+
+@item profiledbootstrap
+Builds a compiler with profiling feedback information. In this case,
+the second and third stages are named @samp{profile} and @samp{feedback},
+respectively. For more information, see the installation instructions.
+
+@item restrap
+Restart a bootstrap, so that everything that was not built with
+the system compiler is rebuilt.
+
+@item stage@var{N}-start (@var{N} = 1@dots{}4, profile, feedback)
+For each package that is bootstrapped, rename directories so that,
+for example, @file{gcc} points to the stage@var{N} GCC, compiled
+with the stage@var{N-1} GCC@footnote{Customarily, the system compiler
+is also termed the @file{stage0} GCC.}.
+
+You will invoke this target if you need to test or debug the
+stage@var{N} GCC@. If you only need to execute GCC (but you need
+not run @samp{make} either to rebuild it or to run test suites),
+you should be able to work directly in the @file{stage@var{N}-gcc}
+directory. This makes it easier to debug multiple stages in
+parallel.
+
+@item stage
+For each package that is bootstrapped, relocate its build directory
+to indicate its stage. For example, if the @file{gcc} directory
+points to the stage2 GCC, after invoking this target it will be
+renamed to @file{stage2-gcc}.
+
+@end table
+
+If you wish to use non-default GCC flags when compiling the stage2 and
+stage3 compilers, set @code{BOOT_CFLAGS} on the command line when doing
+@samp{make}.
+
+Usually, the first stage only builds the languages that the compiler
+is written in: typically, C and maybe Ada. If you are debugging a
+miscompilation of a different stage2 front-end (for example, of the
+Fortran front-end), you may want to have front-ends for other languages
+in the first stage as well. To do so, set @code{STAGE1_LANGUAGES}
+on the command line when doing @samp{make}.
+
+For example, in the aforementioned scenario of debugging a Fortran
+front-end miscompilation caused by the stage1 compiler, you may need a
+command like
+
+@example
+make stage2-bubble STAGE1_LANGUAGES=c,fortran
+@end example
+
+Alternatively, you can use per-language targets to build and test
+languages that are not enabled by default in stage1. For example,
+@command{make f951} will build a Fortran compiler even in the stage1
+build directory.
+
--- /dev/null
+@c Copyright (C) 2014-2022 Free Software Foundation, Inc.
+@c Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Match and Simplify
+@chapter Match and Simplify
+@cindex Match and Simplify
+
+The GIMPLE and GENERIC pattern matching project match-and-simplify
+tries to address several issues.
+
+@enumerate
+@item unify expression simplifications currently spread and duplicated
+ over separate files like fold-const.cc, gimple-fold.cc and builtins.cc
+@item allow for a cheap way to implement building and simplifying
+ non-trivial GIMPLE expressions, avoiding the need to go through
+ building and simplifying GENERIC via fold_buildN and then
+ gimplifying via force_gimple_operand
+@end enumerate
+
+To address these the project introduces a simple domain-specific language
+to write expression simplifications from which code targeting GIMPLE
+and GENERIC is auto-generated. The GENERIC variant follows the
+fold_buildN API while for the GIMPLE variant and to address 2) new
+APIs are introduced.
+
+@menu
+* GIMPLE API::
+* The Language::
+@end menu
+
+@node GIMPLE API
+@section GIMPLE API
+@cindex GIMPLE API
+
+@deftypefn {GIMPLE function} tree gimple_simplify (enum tree_code, tree, tree, gimple_seq *, tree (*)(tree))
+@deftypefnx {GIMPLE function} tree gimple_simplify (enum tree_code, tree, tree, tree, gimple_seq *, tree (*)(tree))
+@deftypefnx {GIMPLE function} tree gimple_simplify (enum tree_code, tree, tree, tree, tree, gimple_seq *, tree (*)(tree))
+@deftypefnx {GIMPLE function} tree gimple_simplify (enum built_in_function, tree, tree, gimple_seq *, tree (*)(tree))
+@deftypefnx {GIMPLE function} tree gimple_simplify (enum built_in_function, tree, tree, tree, gimple_seq *, tree (*)(tree))
+@deftypefnx {GIMPLE function} tree gimple_simplify (enum built_in_function, tree, tree, tree, tree, gimple_seq *, tree (*)(tree))
+The main GIMPLE API entry to the expression simplifications mimicking
+that of the GENERIC fold_@{unary,binary,ternary@} functions.
+@end deftypefn
+
+thus providing n-ary overloads for operation or function. The
+additional arguments are a gimple_seq where built statements are
+inserted on (if @code{NULL} then simplifications requiring new statements
+are not performed) and a valueization hook that can be used to
+tie simplifications to a SSA lattice.
+
+In addition to those APIs @code{fold_stmt} is overloaded with
+a valueization hook:
+
+@deftypefn bool fold_stmt (gimple_stmt_iterator *, tree (*)(tree));
+@end deftypefn
+
+
+On top of these a @code{fold_buildN}-like API for GIMPLE is introduced:
+
+@deftypefn {GIMPLE function} tree gimple_build (gimple_seq *, location_t, enum tree_code, tree, tree, tree (*valueize) (tree) = NULL);
+@deftypefnx {GIMPLE function} tree gimple_build (gimple_seq *, location_t, enum tree_code, tree, tree, tree, tree (*valueize) (tree) = NULL);
+@deftypefnx {GIMPLE function} tree gimple_build (gimple_seq *, location_t, enum tree_code, tree, tree, tree, tree, tree (*valueize) (tree) = NULL);
+@deftypefnx {GIMPLE function} tree gimple_build (gimple_seq *, location_t, enum built_in_function, tree, tree, tree (*valueize) (tree) = NULL);
+@deftypefnx {GIMPLE function} tree gimple_build (gimple_seq *, location_t, enum built_in_function, tree, tree, tree, tree (*valueize) (tree) = NULL);
+@deftypefnx {GIMPLE function} tree gimple_build (gimple_seq *, location_t, enum built_in_function, tree, tree, tree, tree, tree (*valueize) (tree) = NULL);
+@deftypefnx {GIMPLE function} tree gimple_convert (gimple_seq *, location_t, tree, tree);
+@end deftypefn
+
+which is supposed to replace @code{force_gimple_operand (fold_buildN (...), ...)}
+and calls to @code{fold_convert}. Overloads without the @code{location_t}
+argument exist. Built statements are inserted on the provided sequence
+and simplification is performed using the optional valueization hook.
+
+
+@node The Language
+@section The Language
+@cindex The Language
+
+The language in which to write expression simplifications resembles
+other domain-specific languages GCC uses. Thus it is lispy. Let's
+start with an example from the match.pd file:
+
+@smallexample
+(simplify
+ (bit_and @@0 integer_all_onesp)
+ @@0)
+@end smallexample
+
+This example contains all required parts of an expression simplification.
+A simplification is wrapped inside a @code{(simplify ...)} expression.
+That contains at least two operands - an expression that is matched
+with the GIMPLE or GENERIC IL and a replacement expression that is
+returned if the match was successful.
+
+Expressions have an operator ID, @code{bit_and} in this case. Expressions can
+be lower-case tree codes with @code{_expr} stripped off or builtin
+function code names in all-caps, like @code{BUILT_IN_SQRT}.
+
+@code{@@n} denotes a so-called capture. It captures the operand and lets
+you refer to it in other places of the match-and-simplify. In the
+above example it is referred to in the replacement expression. Captures
+are @code{@@} followed by a number or an identifier.
+
+@smallexample
+(simplify
+ (bit_xor @@0 @@0)
+ @{ build_zero_cst (type); @})
+@end smallexample
+
+In this example @code{@@0} is mentioned twice which constrains the matched
+expression to have two equal operands. Usually matches are constrained
+to equal types. If operands may be constants and conversions are involved,
+matching by value might be preferred in which case use @code{@@@@0} to
+denote a by-value match and the specific operand you want to refer to
+in the result part. This example also introduces
+operands written in C code. These can be used in the expression
+replacements and are supposed to evaluate to a tree node which has to
+be a valid GIMPLE operand (so you cannot generate expressions in C code).
+
+@smallexample
+(simplify
+ (trunc_mod integer_zerop@@0 @@1)
+ (if (!integer_zerop (@@1))
+ @@0))
+@end smallexample
+
+Here @code{@@0} captures the first operand of the trunc_mod expression
+which is also predicated with @code{integer_zerop}. Expression operands
+may be either expressions, predicates or captures. Captures
+can be unconstrained or capture expressions or predicates.
+
+This example introduces an optional operand of simplify,
+the if-expression. This condition is evaluated after the
+expression matched in the IL and is required to evaluate to true
+to enable the replacement expression in the second operand
+position. The expression operand of the @code{if} is a standard C
+expression which may contain references to captures. The @code{if}
+has an optional third operand which may contain the replacement
+expression that is enabled when the condition evaluates to false.
+
+A @code{if} expression can be used to specify a common condition
+for multiple simplify patterns, avoiding the need
+to repeat that multiple times:
+
+@smallexample
+(if (!TYPE_SATURATING (type)
+ && !FLOAT_TYPE_P (type) && !FIXED_POINT_TYPE_P (type))
+ (simplify
+ (minus (plus @@0 @@1) @@0)
+ @@1)
+ (simplify
+ (minus (minus @@0 @@1) @@0)
+ (negate @@1)))
+@end smallexample
+
+Note that @code{if}s in outer position do not have the optional
+else clause but instead have multiple then clauses.
+
+Ifs can be nested.
+
+There exists a @code{switch} expression which can be used to
+chain conditions avoiding nesting @code{if}s too much:
+
+@smallexample
+(simplify
+ (simple_comparison @@0 REAL_CST@@1)
+ (switch
+ /* a CMP (-0) -> a CMP 0 */
+ (if (REAL_VALUE_MINUS_ZERO (TREE_REAL_CST (@@1)))
+ (cmp @@0 @{ build_real (TREE_TYPE (@@1), dconst0); @}))
+ /* x != NaN is always true, other ops are always false. */
+ (if (REAL_VALUE_ISNAN (TREE_REAL_CST (@@1))
+ && ! HONOR_SNANS (@@1))
+ @{ constant_boolean_node (cmp == NE_EXPR, type); @})))
+@end smallexample
+
+Is equal to
+
+@smallexample
+(simplify
+ (simple_comparison @@0 REAL_CST@@1)
+ (switch
+ /* a CMP (-0) -> a CMP 0 */
+ (if (REAL_VALUE_MINUS_ZERO (TREE_REAL_CST (@@1)))
+ (cmp @@0 @{ build_real (TREE_TYPE (@@1), dconst0); @})
+ /* x != NaN is always true, other ops are always false. */
+ (if (REAL_VALUE_ISNAN (TREE_REAL_CST (@@1))
+ && ! HONOR_SNANS (@@1))
+ @{ constant_boolean_node (cmp == NE_EXPR, type); @}))))
+@end smallexample
+
+which has the second @code{if} in the else operand of the first.
+The @code{switch} expression takes @code{if} expressions as
+operands (which may not have else clauses) and as a last operand
+a replacement expression which should be enabled by default if
+no other condition evaluated to true.
+
+Captures can also be used for capturing results of sub-expressions.
+
+@smallexample
+#if GIMPLE
+(simplify
+ (pointer_plus (addr@@2 @@0) INTEGER_CST_P@@1)
+ (if (is_gimple_min_invariant (@@2)))
+ @{
+ poly_int64 off;
+ tree base = get_addr_base_and_unit_offset (@@0, &off);
+ off += tree_to_uhwi (@@1);
+ /* Now with that we should be able to simply write
+ (addr (mem_ref (addr @@base) (plus @@off @@1))) */
+ build1 (ADDR_EXPR, type,
+ build2 (MEM_REF, TREE_TYPE (TREE_TYPE (@@2)),
+ build_fold_addr_expr (base),
+ build_int_cst (ptr_type_node, off)));
+ @})
+#endif
+@end smallexample
+
+In the above example, @code{@@2} captures the result of the expression
+@code{(addr @@0)}. For the outermost expression only its type can be
+captured, and the keyword @code{type} is reserved for this purpose. The
+above example also gives a way to conditionalize patterns to only apply
+to @code{GIMPLE} or @code{GENERIC} by means of using the pre-defined
+preprocessor macros @code{GIMPLE} and @code{GENERIC} and using
+preprocessor directives.
+
+@smallexample
+(simplify
+ (bit_and:c integral_op_p@@0 (bit_ior:c (bit_not @@0) @@1))
+ (bit_and @@1 @@0))
+@end smallexample
+
+Here we introduce flags on match expressions. The flag used
+above, @code{c}, denotes that the expression should
+be also matched commutated. Thus the above match expression
+is really the following four match expressions:
+
+@smallexample
+ (bit_and integral_op_p@@0 (bit_ior (bit_not @@0) @@1))
+ (bit_and (bit_ior (bit_not @@0) @@1) integral_op_p@@0)
+ (bit_and integral_op_p@@0 (bit_ior @@1 (bit_not @@0)))
+ (bit_and (bit_ior @@1 (bit_not @@0)) integral_op_p@@0)
+@end smallexample
+
+Usual canonicalizations you know from GENERIC expressions are
+applied before matching, so for example constant operands always
+come second in commutative expressions.
+
+The second supported flag is @code{s} which tells the code
+generator to fail the pattern if the expression marked with
+@code{s} does have more than one use and the simplification
+results in an expression with more than one operator.
+For example in
+
+@smallexample
+(simplify
+ (pointer_plus (pointer_plus:s @@0 @@1) @@3)
+ (pointer_plus @@0 (plus @@1 @@3)))
+@end smallexample
+
+this avoids the association if @code{(pointer_plus @@0 @@1)} is
+used outside of the matched expression and thus it would stay
+live and not trivially removed by dead code elimination.
+Now consider @code{((x + 3) + -3)} with the temporary
+holding @code{(x + 3)} used elsewhere. This simplifies down
+to @code{x} which is desirable and thus flagging with @code{s}
+does not prevent the transform. Now consider @code{((x + 3) + 1)}
+which simplifies to @code{(x + 4)}. Despite being flagged with
+@code{s} the simplification will be performed. The
+simplification of @code{((x + a) + 1)} to @code{(x + (a + 1))} will
+not performed in this case though.
+
+More features exist to avoid too much repetition.
+
+@smallexample
+(for op (plus pointer_plus minus bit_ior bit_xor)
+ (simplify
+ (op @@0 integer_zerop)
+ @@0))
+@end smallexample
+
+A @code{for} expression can be used to repeat a pattern for each
+operator specified, substituting @code{op}. @code{for} can be
+nested and a @code{for} can have multiple operators to iterate.
+
+@smallexample
+(for opa (plus minus)
+ opb (minus plus)
+ (for opc (plus minus)
+ (simplify...
+@end smallexample
+
+In this example the pattern will be repeated four times with
+@code{opa, opb, opc} being @code{plus, minus, plus};
+@code{plus, minus, minus}; @code{minus, plus, plus};
+@code{minus, plus, minus}.
+
+To avoid repeating operator lists in @code{for} you can name
+them via
+
+@smallexample
+(define_operator_list pmm plus minus mult)
+@end smallexample
+
+and use them in @code{for} operator lists where they get expanded.
+
+@smallexample
+(for opa (pmm trunc_div)
+ (simplify...
+@end smallexample
+
+So this example iterates over @code{plus}, @code{minus}, @code{mult}
+and @code{trunc_div}.
+
+Using operator lists can also remove the need to explicitly write
+a @code{for}. All operator list uses that appear in a @code{simplify}
+or @code{match} pattern in operator positions will implicitly
+be added to a new @code{for}. For example
+
+@smallexample
+(define_operator_list SQRT BUILT_IN_SQRTF BUILT_IN_SQRT BUILT_IN_SQRTL)
+(define_operator_list POW BUILT_IN_POWF BUILT_IN_POW BUILT_IN_POWL)
+(simplify
+ (SQRT (POW @@0 @@1))
+ (POW (abs @@0) (mult @@1 @{ built_real (TREE_TYPE (@@1), dconsthalf); @})))
+@end smallexample
+
+is the same as
+
+@smallexample
+(for SQRT (BUILT_IN_SQRTF BUILT_IN_SQRT BUILT_IN_SQRTL)
+ POW (BUILT_IN_POWF BUILT_IN_POW BUILT_IN_POWL)
+ (simplify
+ (SQRT (POW @@0 @@1))
+ (POW (abs @@0) (mult @@1 @{ built_real (TREE_TYPE (@@1), dconsthalf); @}))))
+@end smallexample
+
+@code{for}s and operator lists can include the special identifier
+@code{null} that matches nothing and can never be generated. This can
+be used to pad an operator list so that it has a standard form,
+even if there isn't a suitable operator for every form.
+
+Another building block are @code{with} expressions in the
+result expression which nest the generated code in a new C block
+followed by its argument:
+
+@smallexample
+(simplify
+ (convert (mult @@0 @@1))
+ (with @{ tree utype = unsigned_type_for (type); @}
+ (convert (mult (convert:utype @@0) (convert:utype @@1)))))
+@end smallexample
+
+This allows code nested in the @code{with} to refer to the declared
+variables. In the above case we use the feature to specify the
+type of a generated expression with the @code{:type} syntax where
+@code{type} needs to be an identifier that refers to the desired type.
+Usually the types of the generated result expressions are
+determined from the context, but sometimes like in the above case
+it is required that you specify them explicitly.
+
+Another modifier for generated expressions is @code{!} which
+tells the machinery to only consider the simplification in case
+the marked expression simplified to a simple operand. Consider
+for example
+
+@smallexample
+(simplify
+ (plus (vec_cond:s @@0 @@1 @@2) @@3)
+ (vec_cond @@0 (plus! @@1 @@3) (plus! @@2 @@3)))
+@end smallexample
+
+which moves the outer @code{plus} operation to the inner arms
+of the @code{vec_cond} expression but only if the actual plus
+operations both simplify. Note that on @code{GENERIC} a simple
+operand means that the result satisfies @code{!EXPR_P} which
+can be limiting if the operation itself simplifies but the
+remaining operand is an (unrelated) expression.
+
+As intermediate conversions are often optional there is a way to
+avoid the need to repeat patterns both with and without such
+conversions. Namely you can mark a conversion as being optional
+with a @code{?}:
+
+@smallexample
+(simplify
+ (eq (convert@@0 @@1) (convert@? @@2))
+ (eq @@1 (convert @@2)))
+@end smallexample
+
+which will match both @code{(eq (convert @@1) (convert @@2))} and
+@code{(eq (convert @@1) @@2)}. The optional converts are supposed
+to be all either present or not, thus
+@code{(eq (convert@? @@1) (convert@? @@2))} will result in two
+patterns only. If you want to match all four combinations you
+have access to two additional conditional converts as in
+@code{(eq (convert1@? @@1) (convert2@? @@2))}.
+
+The support for @code{?} marking extends to all unary operations
+including predicates you declare yourself with @code{match}.
+
+Predicates available from the GCC middle-end need to be made
+available explicitly via @code{define_predicates}:
+
+@smallexample
+(define_predicates
+ integer_onep integer_zerop integer_all_onesp)
+@end smallexample
+
+You can also define predicates using the pattern matching language
+and the @code{match} form:
+
+@smallexample
+(match negate_expr_p
+ INTEGER_CST
+ (if (TYPE_OVERFLOW_WRAPS (type)
+ || may_negate_without_overflow_p (t))))
+(match negate_expr_p
+ (negate @@0))
+@end smallexample
+
+This shows that for @code{match} expressions there is @code{t}
+available which captures the outermost expression (something
+not possible in the @code{simplify} context). As you can see
+@code{match} has an identifier as first operand which is how
+you refer to the predicate in patterns. Multiple @code{match}
+for the same identifier add additional cases where the predicate
+matches.
+
+Predicates can also match an expression in which case you need
+to provide a template specifying the identifier and where to
+get its operands from:
+
+@smallexample
+(match (logical_inverted_value @@0)
+ (eq @@0 integer_zerop))
+(match (logical_inverted_value @@0)
+ (bit_not truth_valued_p@@0))
+@end smallexample
+
+You can use the above predicate like
+
+@smallexample
+(simplify
+ (bit_and @@0 (logical_inverted_value @@0))
+ @{ build_zero_cst (type); @})
+@end smallexample
+
+Which will match a bitwise and of an operand with its logical
+inverted value.
+
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@ifset INTERNALS
+@node Machine Desc
+@chapter Machine Descriptions
+@cindex machine descriptions
+
+A machine description has two parts: a file of instruction patterns
+(@file{.md} file) and a C header file of macro definitions.
+
+The @file{.md} file for a target machine contains a pattern for each
+instruction that the target machine supports (or at least each instruction
+that is worth telling the compiler about). It may also contain comments.
+A semicolon causes the rest of the line to be a comment, unless the semicolon
+is inside a quoted string.
+
+See the next chapter for information on the C header file.
+
+@menu
+* Overview:: How the machine description is used.
+* Patterns:: How to write instruction patterns.
+* Example:: An explained example of a @code{define_insn} pattern.
+* RTL Template:: The RTL template defines what insns match a pattern.
+* Output Template:: The output template says how to make assembler code
+ from such an insn.
+* Output Statement:: For more generality, write C code to output
+ the assembler code.
+* Predicates:: Controlling what kinds of operands can be used
+ for an insn.
+* Constraints:: Fine-tuning operand selection.
+* Standard Names:: Names mark patterns to use for code generation.
+* Pattern Ordering:: When the order of patterns makes a difference.
+* Dependent Patterns:: Having one pattern may make you need another.
+* Jump Patterns:: Special considerations for patterns for jump insns.
+* Looping Patterns:: How to define patterns for special looping insns.
+* Insn Canonicalizations::Canonicalization of Instructions
+* Expander Definitions::Generating a sequence of several RTL insns
+ for a standard operation.
+* Insn Splitting:: Splitting Instructions into Multiple Instructions.
+* Including Patterns:: Including Patterns in Machine Descriptions.
+* Peephole Definitions::Defining machine-specific peephole optimizations.
+* Insn Attributes:: Specifying the value of attributes for generated insns.
+* Conditional Execution::Generating @code{define_insn} patterns for
+ predication.
+* Define Subst:: Generating @code{define_insn} and @code{define_expand}
+ patterns from other patterns.
+* Constant Definitions::Defining symbolic constants that can be used in the
+ md file.
+* Iterators:: Using iterators to generate patterns from a template.
+@end menu
+
+@node Overview
+@section Overview of How the Machine Description is Used
+
+There are three main conversions that happen in the compiler:
+
+@enumerate
+
+@item
+The front end reads the source code and builds a parse tree.
+
+@item
+The parse tree is used to generate an RTL insn list based on named
+instruction patterns.
+
+@item
+The insn list is matched against the RTL templates to produce assembler
+code.
+
+@end enumerate
+
+For the generate pass, only the names of the insns matter, from either a
+named @code{define_insn} or a @code{define_expand}. The compiler will
+choose the pattern with the right name and apply the operands according
+to the documentation later in this chapter, without regard for the RTL
+template or operand constraints. Note that the names the compiler looks
+for are hard-coded in the compiler---it will ignore unnamed patterns and
+patterns with names it doesn't know about, but if you don't provide a
+named pattern it needs, it will abort.
+
+If a @code{define_insn} is used, the template given is inserted into the
+insn list. If a @code{define_expand} is used, one of three things
+happens, based on the condition logic. The condition logic may manually
+create new insns for the insn list, say via @code{emit_insn()}, and
+invoke @code{DONE}. For certain named patterns, it may invoke @code{FAIL} to tell the
+compiler to use an alternate way of performing that task. If it invokes
+neither @code{DONE} nor @code{FAIL}, the template given in the pattern
+is inserted, as if the @code{define_expand} were a @code{define_insn}.
+
+Once the insn list is generated, various optimization passes convert,
+replace, and rearrange the insns in the insn list. This is where the
+@code{define_split} and @code{define_peephole} patterns get used, for
+example.
+
+Finally, the insn list's RTL is matched up with the RTL templates in the
+@code{define_insn} patterns, and those patterns are used to emit the
+final assembly code. For this purpose, each named @code{define_insn}
+acts like it's unnamed, since the names are ignored.
+
+@node Patterns
+@section Everything about Instruction Patterns
+@cindex patterns
+@cindex instruction patterns
+
+@findex define_insn
+A @code{define_insn} expression is used to define instruction patterns
+to which insns may be matched. A @code{define_insn} expression contains
+an incomplete RTL expression, with pieces to be filled in later, operand
+constraints that restrict how the pieces can be filled in, and an output
+template or C code to generate the assembler output.
+
+A @code{define_insn} is an RTL expression containing four or five operands:
+
+@enumerate
+@item
+An optional name @var{n}. When a name is present, the compiler
+automically generates a C++ function @samp{gen_@var{n}} that takes
+the operands of the instruction as arguments and returns the instruction's
+rtx pattern. The compiler also assigns the instruction a unique code
+@samp{CODE_FOR_@var{n}}, with all such codes belonging to an enum
+called @code{insn_code}.
+
+These names serve one of two purposes. The first is to indicate that the
+instruction performs a certain standard job for the RTL-generation
+pass of the compiler, such as a move, an addition, or a conditional
+jump. The second is to help the target generate certain target-specific
+operations, such as when implementing target-specific intrinsic functions.
+
+It is better to prefix target-specific names with the name of the
+target, to avoid any clash with current or future standard names.
+
+The absence of a name is indicated by writing an empty string
+where the name should go. Nameless instruction patterns are never
+used for generating RTL code, but they may permit several simpler insns
+to be combined later on.
+
+For the purpose of debugging the compiler, you may also specify a
+name beginning with the @samp{*} character. Such a name is used only
+for identifying the instruction in RTL dumps; it is equivalent to having
+a nameless pattern for all other purposes. Names beginning with the
+@samp{*} character are not required to be unique.
+
+The name may also have the form @samp{@@@var{n}}. This has the same
+effect as a name @samp{@var{n}}, but in addition tells the compiler to
+generate further helper functions; see @ref{Parameterized Names} for details.
+
+@item
+The @dfn{RTL template}: This is a vector of incomplete RTL expressions
+which describe the semantics of the instruction (@pxref{RTL Template}).
+It is incomplete because it may contain @code{match_operand},
+@code{match_operator}, and @code{match_dup} expressions that stand for
+operands of the instruction.
+
+If the vector has multiple elements, the RTL template is treated as a
+@code{parallel} expression.
+
+@item
+@cindex pattern conditions
+@cindex conditions, in patterns
+The condition: This is a string which contains a C expression. When the
+compiler attempts to match RTL against a pattern, the condition is
+evaluated. If the condition evaluates to @code{true}, the match is
+permitted. The condition may be an empty string, which is treated
+as always @code{true}.
+
+@cindex named patterns and conditions
+For a named pattern, the condition may not depend on the data in the
+insn being matched, but only the target-machine-type flags. The compiler
+needs to test these conditions during initialization in order to learn
+exactly which named instructions are available in a particular run.
+
+@findex operands
+For nameless patterns, the condition is applied only when matching an
+individual insn, and only after the insn has matched the pattern's
+recognition template. The insn's operands may be found in the vector
+@code{operands}.
+
+An instruction condition cannot become more restrictive as compilation
+progresses. If the condition accepts a particular RTL instruction at
+one stage of compilation, it must continue to accept that instruction
+until the final pass. For example, @samp{!reload_completed} and
+@samp{can_create_pseudo_p ()} are both invalid instruction conditions,
+because they are true during the earlier RTL passes and false during
+the later ones. For the same reason, if a condition accepts an
+instruction before register allocation, it cannot later try to control
+register allocation by excluding certain register or value combinations.
+
+Although a condition cannot become more restrictive as compilation
+progresses, the condition for a nameless pattern @emph{can} become
+more permissive. For example, a nameless instruction can require
+@samp{reload_completed} to be true, in which case it only matches
+after register allocation.
+
+@item
+The @dfn{output template} or @dfn{output statement}: This is either
+a string, or a fragment of C code which returns a string.
+
+When simple substitution isn't general enough, you can specify a piece
+of C code to compute the output. @xref{Output Statement}.
+
+@item
+The @dfn{insn attributes}: This is an optional vector containing the values of
+attributes for insns matching this pattern (@pxref{Insn Attributes}).
+@end enumerate
+
+@node Example
+@section Example of @code{define_insn}
+@cindex @code{define_insn} example
+
+Here is an example of an instruction pattern, taken from the machine
+description for the 68000/68020.
+
+@smallexample
+(define_insn "tstsi"
+ [(set (cc0)
+ (match_operand:SI 0 "general_operand" "rm"))]
+ ""
+ "*
+@{
+ if (TARGET_68020 || ! ADDRESS_REG_P (operands[0]))
+ return \"tstl %0\";
+ return \"cmpl #0,%0\";
+@}")
+@end smallexample
+
+@noindent
+This can also be written using braced strings:
+
+@smallexample
+(define_insn "tstsi"
+ [(set (cc0)
+ (match_operand:SI 0 "general_operand" "rm"))]
+ ""
+@{
+ if (TARGET_68020 || ! ADDRESS_REG_P (operands[0]))
+ return "tstl %0";
+ return "cmpl #0,%0";
+@})
+@end smallexample
+
+This describes an instruction which sets the condition codes based on the
+value of a general operand. It has no condition, so any insn with an RTL
+description of the form shown may be matched to this pattern. The name
+@samp{tstsi} means ``test a @code{SImode} value'' and tells the RTL
+generation pass that, when it is necessary to test such a value, an insn
+to do so can be constructed using this pattern.
+
+The output control string is a piece of C code which chooses which
+output template to return based on the kind of operand and the specific
+type of CPU for which code is being generated.
+
+@samp{"rm"} is an operand constraint. Its meaning is explained below.
+
+@node RTL Template
+@section RTL Template
+@cindex RTL insn template
+@cindex generating insns
+@cindex insns, generating
+@cindex recognizing insns
+@cindex insns, recognizing
+
+The RTL template is used to define which insns match the particular pattern
+and how to find their operands. For named patterns, the RTL template also
+says how to construct an insn from specified operands.
+
+Construction involves substituting specified operands into a copy of the
+template. Matching involves determining the values that serve as the
+operands in the insn being matched. Both of these activities are
+controlled by special expression types that direct matching and
+substitution of the operands.
+
+@table @code
+@findex match_operand
+@item (match_operand:@var{m} @var{n} @var{predicate} @var{constraint})
+This expression is a placeholder for operand number @var{n} of
+the insn. When constructing an insn, operand number @var{n}
+will be substituted at this point. When matching an insn, whatever
+appears at this position in the insn will be taken as operand
+number @var{n}; but it must satisfy @var{predicate} or this instruction
+pattern will not match at all.
+
+Operand numbers must be chosen consecutively counting from zero in
+each instruction pattern. There may be only one @code{match_operand}
+expression in the pattern for each operand number. Usually operands
+are numbered in the order of appearance in @code{match_operand}
+expressions. In the case of a @code{define_expand}, any operand numbers
+used only in @code{match_dup} expressions have higher values than all
+other operand numbers.
+
+@var{predicate} is a string that is the name of a function that
+accepts two arguments, an expression and a machine mode.
+@xref{Predicates}. During matching, the function will be called with
+the putative operand as the expression and @var{m} as the mode
+argument (if @var{m} is not specified, @code{VOIDmode} will be used,
+which normally causes @var{predicate} to accept any mode). If it
+returns zero, this instruction pattern fails to match.
+@var{predicate} may be an empty string; then it means no test is to be
+done on the operand, so anything which occurs in this position is
+valid.
+
+Most of the time, @var{predicate} will reject modes other than @var{m}---but
+not always. For example, the predicate @code{address_operand} uses
+@var{m} as the mode of memory ref that the address should be valid for.
+Many predicates accept @code{const_int} nodes even though their mode is
+@code{VOIDmode}.
+
+@var{constraint} controls reloading and the choice of the best register
+class to use for a value, as explained later (@pxref{Constraints}).
+If the constraint would be an empty string, it can be omitted.
+
+People are often unclear on the difference between the constraint and the
+predicate. The predicate helps decide whether a given insn matches the
+pattern. The constraint plays no role in this decision; instead, it
+controls various decisions in the case of an insn which does match.
+
+@findex match_scratch
+@item (match_scratch:@var{m} @var{n} @var{constraint})
+This expression is also a placeholder for operand number @var{n}
+and indicates that operand must be a @code{scratch} or @code{reg}
+expression.
+
+When matching patterns, this is equivalent to
+
+@smallexample
+(match_operand:@var{m} @var{n} "scratch_operand" @var{constraint})
+@end smallexample
+
+but, when generating RTL, it produces a (@code{scratch}:@var{m})
+expression.
+
+If the last few expressions in a @code{parallel} are @code{clobber}
+expressions whose operands are either a hard register or
+@code{match_scratch}, the combiner can add or delete them when
+necessary. @xref{Side Effects}.
+
+@findex match_dup
+@item (match_dup @var{n})
+This expression is also a placeholder for operand number @var{n}.
+It is used when the operand needs to appear more than once in the
+insn.
+
+In construction, @code{match_dup} acts just like @code{match_operand}:
+the operand is substituted into the insn being constructed. But in
+matching, @code{match_dup} behaves differently. It assumes that operand
+number @var{n} has already been determined by a @code{match_operand}
+appearing earlier in the recognition template, and it matches only an
+identical-looking expression.
+
+Note that @code{match_dup} should not be used to tell the compiler that
+a particular register is being used for two operands (example:
+@code{add} that adds one register to another; the second register is
+both an input operand and the output operand). Use a matching
+constraint (@pxref{Simple Constraints}) for those. @code{match_dup} is for the cases where one
+operand is used in two places in the template, such as an instruction
+that computes both a quotient and a remainder, where the opcode takes
+two input operands but the RTL template has to refer to each of those
+twice; once for the quotient pattern and once for the remainder pattern.
+
+@findex match_operator
+@item (match_operator:@var{m} @var{n} @var{predicate} [@var{operands}@dots{}])
+This pattern is a kind of placeholder for a variable RTL expression
+code.
+
+When constructing an insn, it stands for an RTL expression whose
+expression code is taken from that of operand @var{n}, and whose
+operands are constructed from the patterns @var{operands}.
+
+When matching an expression, it matches an expression if the function
+@var{predicate} returns nonzero on that expression @emph{and} the
+patterns @var{operands} match the operands of the expression.
+
+Suppose that the function @code{commutative_operator} is defined as
+follows, to match any expression whose operator is one of the
+commutative arithmetic operators of RTL and whose mode is @var{mode}:
+
+@smallexample
+int
+commutative_integer_operator (x, mode)
+ rtx x;
+ machine_mode mode;
+@{
+ enum rtx_code code = GET_CODE (x);
+ if (GET_MODE (x) != mode)
+ return 0;
+ return (GET_RTX_CLASS (code) == RTX_COMM_ARITH
+ || code == EQ || code == NE);
+@}
+@end smallexample
+
+Then the following pattern will match any RTL expression consisting
+of a commutative operator applied to two general operands:
+
+@smallexample
+(match_operator:SI 3 "commutative_operator"
+ [(match_operand:SI 1 "general_operand" "g")
+ (match_operand:SI 2 "general_operand" "g")])
+@end smallexample
+
+Here the vector @code{[@var{operands}@dots{}]} contains two patterns
+because the expressions to be matched all contain two operands.
+
+When this pattern does match, the two operands of the commutative
+operator are recorded as operands 1 and 2 of the insn. (This is done
+by the two instances of @code{match_operand}.) Operand 3 of the insn
+will be the entire commutative expression: use @code{GET_CODE
+(operands[3])} to see which commutative operator was used.
+
+The machine mode @var{m} of @code{match_operator} works like that of
+@code{match_operand}: it is passed as the second argument to the
+predicate function, and that function is solely responsible for
+deciding whether the expression to be matched ``has'' that mode.
+
+When constructing an insn, argument 3 of the gen-function will specify
+the operation (i.e.@: the expression code) for the expression to be
+made. It should be an RTL expression, whose expression code is copied
+into a new expression whose operands are arguments 1 and 2 of the
+gen-function. The subexpressions of argument 3 are not used;
+only its expression code matters.
+
+When @code{match_operator} is used in a pattern for matching an insn,
+it usually best if the operand number of the @code{match_operator}
+is higher than that of the actual operands of the insn. This improves
+register allocation because the register allocator often looks at
+operands 1 and 2 of insns to see if it can do register tying.
+
+There is no way to specify constraints in @code{match_operator}. The
+operand of the insn which corresponds to the @code{match_operator}
+never has any constraints because it is never reloaded as a whole.
+However, if parts of its @var{operands} are matched by
+@code{match_operand} patterns, those parts may have constraints of
+their own.
+
+@findex match_op_dup
+@item (match_op_dup:@var{m} @var{n}[@var{operands}@dots{}])
+Like @code{match_dup}, except that it applies to operators instead of
+operands. When constructing an insn, operand number @var{n} will be
+substituted at this point. But in matching, @code{match_op_dup} behaves
+differently. It assumes that operand number @var{n} has already been
+determined by a @code{match_operator} appearing earlier in the
+recognition template, and it matches only an identical-looking
+expression.
+
+@findex match_parallel
+@item (match_parallel @var{n} @var{predicate} [@var{subpat}@dots{}])
+This pattern is a placeholder for an insn that consists of a
+@code{parallel} expression with a variable number of elements. This
+expression should only appear at the top level of an insn pattern.
+
+When constructing an insn, operand number @var{n} will be substituted at
+this point. When matching an insn, it matches if the body of the insn
+is a @code{parallel} expression with at least as many elements as the
+vector of @var{subpat} expressions in the @code{match_parallel}, if each
+@var{subpat} matches the corresponding element of the @code{parallel},
+@emph{and} the function @var{predicate} returns nonzero on the
+@code{parallel} that is the body of the insn. It is the responsibility
+of the predicate to validate elements of the @code{parallel} beyond
+those listed in the @code{match_parallel}.
+
+A typical use of @code{match_parallel} is to match load and store
+multiple expressions, which can contain a variable number of elements
+in a @code{parallel}. For example,
+
+@smallexample
+(define_insn ""
+ [(match_parallel 0 "load_multiple_operation"
+ [(set (match_operand:SI 1 "gpc_reg_operand" "=r")
+ (match_operand:SI 2 "memory_operand" "m"))
+ (use (reg:SI 179))
+ (clobber (reg:SI 179))])]
+ ""
+ "loadm 0,0,%1,%2")
+@end smallexample
+
+This example comes from @file{a29k.md}. The function
+@code{load_multiple_operation} is defined in @file{a29k.c} and checks
+that subsequent elements in the @code{parallel} are the same as the
+@code{set} in the pattern, except that they are referencing subsequent
+registers and memory locations.
+
+An insn that matches this pattern might look like:
+
+@smallexample
+(parallel
+ [(set (reg:SI 20) (mem:SI (reg:SI 100)))
+ (use (reg:SI 179))
+ (clobber (reg:SI 179))
+ (set (reg:SI 21)
+ (mem:SI (plus:SI (reg:SI 100)
+ (const_int 4))))
+ (set (reg:SI 22)
+ (mem:SI (plus:SI (reg:SI 100)
+ (const_int 8))))])
+@end smallexample
+
+@findex match_par_dup
+@item (match_par_dup @var{n} [@var{subpat}@dots{}])
+Like @code{match_op_dup}, but for @code{match_parallel} instead of
+@code{match_operator}.
+
+@end table
+
+@node Output Template
+@section Output Templates and Operand Substitution
+@cindex output templates
+@cindex operand substitution
+
+@cindex @samp{%} in template
+@cindex percent sign
+The @dfn{output template} is a string which specifies how to output the
+assembler code for an instruction pattern. Most of the template is a
+fixed string which is output literally. The character @samp{%} is used
+to specify where to substitute an operand; it can also be used to
+identify places where different variants of the assembler require
+different syntax.
+
+In the simplest case, a @samp{%} followed by a digit @var{n} says to output
+operand @var{n} at that point in the string.
+
+@samp{%} followed by a letter and a digit says to output an operand in an
+alternate fashion. Four letters have standard, built-in meanings described
+below. The machine description macro @code{PRINT_OPERAND} can define
+additional letters with nonstandard meanings.
+
+@samp{%c@var{digit}} can be used to substitute an operand that is a
+constant value without the syntax that normally indicates an immediate
+operand.
+
+@samp{%n@var{digit}} is like @samp{%c@var{digit}} except that the value of
+the constant is negated before printing.
+
+@samp{%a@var{digit}} can be used to substitute an operand as if it were a
+memory reference, with the actual operand treated as the address. This may
+be useful when outputting a ``load address'' instruction, because often the
+assembler syntax for such an instruction requires you to write the operand
+as if it were a memory reference.
+
+@samp{%l@var{digit}} is used to substitute a @code{label_ref} into a jump
+instruction.
+
+@samp{%=} outputs a number which is unique to each instruction in the
+entire compilation. This is useful for making local labels to be
+referred to more than once in a single template that generates multiple
+assembler instructions.
+
+@samp{%} followed by a punctuation character specifies a substitution that
+does not use an operand. Only one case is standard: @samp{%%} outputs a
+@samp{%} into the assembler code. Other nonstandard cases can be
+defined in the @code{PRINT_OPERAND} macro. You must also define
+which punctuation characters are valid with the
+@code{PRINT_OPERAND_PUNCT_VALID_P} macro.
+
+@cindex \
+@cindex backslash
+The template may generate multiple assembler instructions. Write the text
+for the instructions, with @samp{\;} between them.
+
+@cindex matching operands
+When the RTL contains two operands which are required by constraint to match
+each other, the output template must refer only to the lower-numbered operand.
+Matching operands are not always identical, and the rest of the compiler
+arranges to put the proper RTL expression for printing into the lower-numbered
+operand.
+
+One use of nonstandard letters or punctuation following @samp{%} is to
+distinguish between different assembler languages for the same machine; for
+example, Motorola syntax versus MIT syntax for the 68000. Motorola syntax
+requires periods in most opcode names, while MIT syntax does not. For
+example, the opcode @samp{movel} in MIT syntax is @samp{move.l} in Motorola
+syntax. The same file of patterns is used for both kinds of output syntax,
+but the character sequence @samp{%.} is used in each place where Motorola
+syntax wants a period. The @code{PRINT_OPERAND} macro for Motorola syntax
+defines the sequence to output a period; the macro for MIT syntax defines
+it to do nothing.
+
+@cindex @code{#} in template
+As a special case, a template consisting of the single character @code{#}
+instructs the compiler to first split the insn, and then output the
+resulting instructions separately. This helps eliminate redundancy in the
+output templates. If you have a @code{define_insn} that needs to emit
+multiple assembler instructions, and there is a matching @code{define_split}
+already defined, then you can simply use @code{#} as the output template
+instead of writing an output template that emits the multiple assembler
+instructions.
+
+Note that @code{#} only has an effect while generating assembly code;
+it does not affect whether a split occurs earlier. An associated
+@code{define_split} must exist and it must be suitable for use after
+register allocation.
+
+If the macro @code{ASSEMBLER_DIALECT} is defined, you can use construct
+of the form @samp{@{option0|option1|option2@}} in the templates. These
+describe multiple variants of assembler language syntax.
+@xref{Instruction Output}.
+
+@node Output Statement
+@section C Statements for Assembler Output
+@cindex output statements
+@cindex C statements for assembler output
+@cindex generating assembler output
+
+Often a single fixed template string cannot produce correct and efficient
+assembler code for all the cases that are recognized by a single
+instruction pattern. For example, the opcodes may depend on the kinds of
+operands; or some unfortunate combinations of operands may require extra
+machine instructions.
+
+If the output control string starts with a @samp{@@}, then it is actually
+a series of templates, each on a separate line. (Blank lines and
+leading spaces and tabs are ignored.) The templates correspond to the
+pattern's constraint alternatives (@pxref{Multi-Alternative}). For example,
+if a target machine has a two-address add instruction @samp{addr} to add
+into a register and another @samp{addm} to add a register to memory, you
+might write this pattern:
+
+@smallexample
+(define_insn "addsi3"
+ [(set (match_operand:SI 0 "general_operand" "=r,m")
+ (plus:SI (match_operand:SI 1 "general_operand" "0,0")
+ (match_operand:SI 2 "general_operand" "g,r")))]
+ ""
+ "@@
+ addr %2,%0
+ addm %2,%0")
+@end smallexample
+
+@cindex @code{*} in template
+@cindex asterisk in template
+If the output control string starts with a @samp{*}, then it is not an
+output template but rather a piece of C program that should compute a
+template. It should execute a @code{return} statement to return the
+template-string you want. Most such templates use C string literals, which
+require doublequote characters to delimit them. To include these
+doublequote characters in the string, prefix each one with @samp{\}.
+
+If the output control string is written as a brace block instead of a
+double-quoted string, it is automatically assumed to be C code. In that
+case, it is not necessary to put in a leading asterisk, or to escape the
+doublequotes surrounding C string literals.
+
+The operands may be found in the array @code{operands}, whose C data type
+is @code{rtx []}.
+
+It is very common to select different ways of generating assembler code
+based on whether an immediate operand is within a certain range. Be
+careful when doing this, because the result of @code{INTVAL} is an
+integer on the host machine. If the host machine has more bits in an
+@code{int} than the target machine has in the mode in which the constant
+will be used, then some of the bits you get from @code{INTVAL} will be
+superfluous. For proper results, you must carefully disregard the
+values of those bits.
+
+@findex output_asm_insn
+It is possible to output an assembler instruction and then go on to output
+or compute more of them, using the subroutine @code{output_asm_insn}. This
+receives two arguments: a template-string and a vector of operands. The
+vector may be @code{operands}, or it may be another array of @code{rtx}
+that you declare locally and initialize yourself.
+
+@findex which_alternative
+When an insn pattern has multiple alternatives in its constraints, often
+the appearance of the assembler code is determined mostly by which alternative
+was matched. When this is so, the C code can test the variable
+@code{which_alternative}, which is the ordinal number of the alternative
+that was actually satisfied (0 for the first, 1 for the second alternative,
+etc.).
+
+For example, suppose there are two opcodes for storing zero, @samp{clrreg}
+for registers and @samp{clrmem} for memory locations. Here is how
+a pattern could use @code{which_alternative} to choose between them:
+
+@smallexample
+(define_insn ""
+ [(set (match_operand:SI 0 "general_operand" "=r,m")
+ (const_int 0))]
+ ""
+ @{
+ return (which_alternative == 0
+ ? "clrreg %0" : "clrmem %0");
+ @})
+@end smallexample
+
+The example above, where the assembler code to generate was
+@emph{solely} determined by the alternative, could also have been specified
+as follows, having the output control string start with a @samp{@@}:
+
+@smallexample
+@group
+(define_insn ""
+ [(set (match_operand:SI 0 "general_operand" "=r,m")
+ (const_int 0))]
+ ""
+ "@@
+ clrreg %0
+ clrmem %0")
+@end group
+@end smallexample
+
+If you just need a little bit of C code in one (or a few) alternatives,
+you can use @samp{*} inside of a @samp{@@} multi-alternative template:
+
+@smallexample
+@group
+(define_insn ""
+ [(set (match_operand:SI 0 "general_operand" "=r,<,m")
+ (const_int 0))]
+ ""
+ "@@
+ clrreg %0
+ * return stack_mem_p (operands[0]) ? \"push 0\" : \"clrmem %0\";
+ clrmem %0")
+@end group
+@end smallexample
+
+@node Predicates
+@section Predicates
+@cindex predicates
+@cindex operand predicates
+@cindex operator predicates
+
+A predicate determines whether a @code{match_operand} or
+@code{match_operator} expression matches, and therefore whether the
+surrounding instruction pattern will be used for that combination of
+operands. GCC has a number of machine-independent predicates, and you
+can define machine-specific predicates as needed. By convention,
+predicates used with @code{match_operand} have names that end in
+@samp{_operand}, and those used with @code{match_operator} have names
+that end in @samp{_operator}.
+
+All predicates are boolean functions (in the mathematical sense) of
+two arguments: the RTL expression that is being considered at that
+position in the instruction pattern, and the machine mode that the
+@code{match_operand} or @code{match_operator} specifies. In this
+section, the first argument is called @var{op} and the second argument
+@var{mode}. Predicates can be called from C as ordinary two-argument
+functions; this can be useful in output templates or other
+machine-specific code.
+
+Operand predicates can allow operands that are not actually acceptable
+to the hardware, as long as the constraints give reload the ability to
+fix them up (@pxref{Constraints}). However, GCC will usually generate
+better code if the predicates specify the requirements of the machine
+instructions as closely as possible. Reload cannot fix up operands
+that must be constants (``immediate operands''); you must use a
+predicate that allows only constants, or else enforce the requirement
+in the extra condition.
+
+@cindex predicates and machine modes
+@cindex normal predicates
+@cindex special predicates
+Most predicates handle their @var{mode} argument in a uniform manner.
+If @var{mode} is @code{VOIDmode} (unspecified), then @var{op} can have
+any mode. If @var{mode} is anything else, then @var{op} must have the
+same mode, unless @var{op} is a @code{CONST_INT} or integer
+@code{CONST_DOUBLE}. These RTL expressions always have
+@code{VOIDmode}, so it would be counterproductive to check that their
+mode matches. Instead, predicates that accept @code{CONST_INT} and/or
+integer @code{CONST_DOUBLE} check that the value stored in the
+constant will fit in the requested mode.
+
+Predicates with this behavior are called @dfn{normal}.
+@command{genrecog} can optimize the instruction recognizer based on
+knowledge of how normal predicates treat modes. It can also diagnose
+certain kinds of common errors in the use of normal predicates; for
+instance, it is almost always an error to use a normal predicate
+without specifying a mode.
+
+Predicates that do something different with their @var{mode} argument
+are called @dfn{special}. The generic predicates
+@code{address_operand} and @code{pmode_register_operand} are special
+predicates. @command{genrecog} does not do any optimizations or
+diagnosis when special predicates are used.
+
+@menu
+* Machine-Independent Predicates:: Predicates available to all back ends.
+* Defining Predicates:: How to write machine-specific predicate
+ functions.
+@end menu
+
+@node Machine-Independent Predicates
+@subsection Machine-Independent Predicates
+@cindex machine-independent predicates
+@cindex generic predicates
+
+These are the generic predicates available to all back ends. They are
+defined in @file{recog.cc}. The first category of predicates allow
+only constant, or @dfn{immediate}, operands.
+
+@defun immediate_operand
+This predicate allows any sort of constant that fits in @var{mode}.
+It is an appropriate choice for instructions that take operands that
+must be constant.
+@end defun
+
+@defun const_int_operand
+This predicate allows any @code{CONST_INT} expression that fits in
+@var{mode}. It is an appropriate choice for an immediate operand that
+does not allow a symbol or label.
+@end defun
+
+@defun const_double_operand
+This predicate accepts any @code{CONST_DOUBLE} expression that has
+exactly @var{mode}. If @var{mode} is @code{VOIDmode}, it will also
+accept @code{CONST_INT}. It is intended for immediate floating point
+constants.
+@end defun
+
+@noindent
+The second category of predicates allow only some kind of machine
+register.
+
+@defun register_operand
+This predicate allows any @code{REG} or @code{SUBREG} expression that
+is valid for @var{mode}. It is often suitable for arithmetic
+instruction operands on a RISC machine.
+@end defun
+
+@defun pmode_register_operand
+This is a slight variant on @code{register_operand} which works around
+a limitation in the machine-description reader.
+
+@smallexample
+(match_operand @var{n} "pmode_register_operand" @var{constraint})
+@end smallexample
+
+@noindent
+means exactly what
+
+@smallexample
+(match_operand:P @var{n} "register_operand" @var{constraint})
+@end smallexample
+
+@noindent
+would mean, if the machine-description reader accepted @samp{:P}
+mode suffixes. Unfortunately, it cannot, because @code{Pmode} is an
+alias for some other mode, and might vary with machine-specific
+options. @xref{Misc}.
+@end defun
+
+@defun scratch_operand
+This predicate allows hard registers and @code{SCRATCH} expressions,
+but not pseudo-registers. It is used internally by @code{match_scratch};
+it should not be used directly.
+@end defun
+
+@noindent
+The third category of predicates allow only some kind of memory reference.
+
+@defun memory_operand
+This predicate allows any valid reference to a quantity of mode
+@var{mode} in memory, as determined by the weak form of
+@code{GO_IF_LEGITIMATE_ADDRESS} (@pxref{Addressing Modes}).
+@end defun
+
+@defun address_operand
+This predicate is a little unusual; it allows any operand that is a
+valid expression for the @emph{address} of a quantity of mode
+@var{mode}, again determined by the weak form of
+@code{GO_IF_LEGITIMATE_ADDRESS}. To first order, if
+@samp{@w{(mem:@var{mode} (@var{exp}))}} is acceptable to
+@code{memory_operand}, then @var{exp} is acceptable to
+@code{address_operand}. Note that @var{exp} does not necessarily have
+the mode @var{mode}.
+@end defun
+
+@defun indirect_operand
+This is a stricter form of @code{memory_operand} which allows only
+memory references with a @code{general_operand} as the address
+expression. New uses of this predicate are discouraged, because
+@code{general_operand} is very permissive, so it's hard to tell what
+an @code{indirect_operand} does or does not allow. If a target has
+different requirements for memory operands for different instructions,
+it is better to define target-specific predicates which enforce the
+hardware's requirements explicitly.
+@end defun
+
+@defun push_operand
+This predicate allows a memory reference suitable for pushing a value
+onto the stack. This will be a @code{MEM} which refers to
+@code{stack_pointer_rtx}, with a side effect in its address expression
+(@pxref{Incdec}); which one is determined by the
+@code{STACK_PUSH_CODE} macro (@pxref{Frame Layout}).
+@end defun
+
+@defun pop_operand
+This predicate allows a memory reference suitable for popping a value
+off the stack. Again, this will be a @code{MEM} referring to
+@code{stack_pointer_rtx}, with a side effect in its address
+expression. However, this time @code{STACK_POP_CODE} is expected.
+@end defun
+
+@noindent
+The fourth category of predicates allow some combination of the above
+operands.
+
+@defun nonmemory_operand
+This predicate allows any immediate or register operand valid for @var{mode}.
+@end defun
+
+@defun nonimmediate_operand
+This predicate allows any register or memory operand valid for @var{mode}.
+@end defun
+
+@defun general_operand
+This predicate allows any immediate, register, or memory operand
+valid for @var{mode}.
+@end defun
+
+@noindent
+Finally, there are two generic operator predicates.
+
+@defun comparison_operator
+This predicate matches any expression which performs an arithmetic
+comparison in @var{mode}; that is, @code{COMPARISON_P} is true for the
+expression code.
+@end defun
+
+@defun ordered_comparison_operator
+This predicate matches any expression which performs an arithmetic
+comparison in @var{mode} and whose expression code is valid for integer
+modes; that is, the expression code will be one of @code{eq}, @code{ne},
+@code{lt}, @code{ltu}, @code{le}, @code{leu}, @code{gt}, @code{gtu},
+@code{ge}, @code{geu}.
+@end defun
+
+@node Defining Predicates
+@subsection Defining Machine-Specific Predicates
+@cindex defining predicates
+@findex define_predicate
+@findex define_special_predicate
+
+Many machines have requirements for their operands that cannot be
+expressed precisely using the generic predicates. You can define
+additional predicates using @code{define_predicate} and
+@code{define_special_predicate} expressions. These expressions have
+three operands:
+
+@itemize @bullet
+@item
+The name of the predicate, as it will be referred to in
+@code{match_operand} or @code{match_operator} expressions.
+
+@item
+An RTL expression which evaluates to true if the predicate allows the
+operand @var{op}, false if it does not. This expression can only use
+the following RTL codes:
+
+@table @code
+@item MATCH_OPERAND
+When written inside a predicate expression, a @code{MATCH_OPERAND}
+expression evaluates to true if the predicate it names would allow
+@var{op}. The operand number and constraint are ignored. Due to
+limitations in @command{genrecog}, you can only refer to generic
+predicates and predicates that have already been defined.
+
+@item MATCH_CODE
+This expression evaluates to true if @var{op} or a specified
+subexpression of @var{op} has one of a given list of RTX codes.
+
+The first operand of this expression is a string constant containing a
+comma-separated list of RTX code names (in lower case). These are the
+codes for which the @code{MATCH_CODE} will be true.
+
+The second operand is a string constant which indicates what
+subexpression of @var{op} to examine. If it is absent or the empty
+string, @var{op} itself is examined. Otherwise, the string constant
+must be a sequence of digits and/or lowercase letters. Each character
+indicates a subexpression to extract from the current expression; for
+the first character this is @var{op}, for the second and subsequent
+characters it is the result of the previous character. A digit
+@var{n} extracts @samp{@w{XEXP (@var{e}, @var{n})}}; a letter @var{l}
+extracts @samp{@w{XVECEXP (@var{e}, 0, @var{n})}} where @var{n} is the
+alphabetic ordinal of @var{l} (0 for `a', 1 for 'b', and so on). The
+@code{MATCH_CODE} then examines the RTX code of the subexpression
+extracted by the complete string. It is not possible to extract
+components of an @code{rtvec} that is not at position 0 within its RTX
+object.
+
+@item MATCH_TEST
+This expression has one operand, a string constant containing a C
+expression. The predicate's arguments, @var{op} and @var{mode}, are
+available with those names in the C expression. The @code{MATCH_TEST}
+evaluates to true if the C expression evaluates to a nonzero value.
+@code{MATCH_TEST} expressions must not have side effects.
+
+@item AND
+@itemx IOR
+@itemx NOT
+@itemx IF_THEN_ELSE
+The basic @samp{MATCH_} expressions can be combined using these
+logical operators, which have the semantics of the C operators
+@samp{&&}, @samp{||}, @samp{!}, and @samp{@w{? :}} respectively. As
+in Common Lisp, you may give an @code{AND} or @code{IOR} expression an
+arbitrary number of arguments; this has exactly the same effect as
+writing a chain of two-argument @code{AND} or @code{IOR} expressions.
+@end table
+
+@item
+An optional block of C code, which should execute
+@samp{@w{return true}} if the predicate is found to match and
+@samp{@w{return false}} if it does not. It must not have any side
+effects. The predicate arguments, @var{op} and @var{mode}, are
+available with those names.
+
+If a code block is present in a predicate definition, then the RTL
+expression must evaluate to true @emph{and} the code block must
+execute @samp{@w{return true}} for the predicate to allow the operand.
+The RTL expression is evaluated first; do not re-check anything in the
+code block that was checked in the RTL expression.
+@end itemize
+
+The program @command{genrecog} scans @code{define_predicate} and
+@code{define_special_predicate} expressions to determine which RTX
+codes are possibly allowed. You should always make this explicit in
+the RTL predicate expression, using @code{MATCH_OPERAND} and
+@code{MATCH_CODE}.
+
+Here is an example of a simple predicate definition, from the IA64
+machine description:
+
+@smallexample
+@group
+;; @r{True if @var{op} is a @code{SYMBOL_REF} which refers to the sdata section.}
+(define_predicate "small_addr_symbolic_operand"
+ (and (match_code "symbol_ref")
+ (match_test "SYMBOL_REF_SMALL_ADDR_P (op)")))
+@end group
+@end smallexample
+
+@noindent
+And here is another, showing the use of the C block.
+
+@smallexample
+@group
+;; @r{True if @var{op} is a register operand that is (or could be) a GR reg.}
+(define_predicate "gr_register_operand"
+ (match_operand 0 "register_operand")
+@{
+ unsigned int regno;
+ if (GET_CODE (op) == SUBREG)
+ op = SUBREG_REG (op);
+
+ regno = REGNO (op);
+ return (regno >= FIRST_PSEUDO_REGISTER || GENERAL_REGNO_P (regno));
+@})
+@end group
+@end smallexample
+
+Predicates written with @code{define_predicate} automatically include
+a test that @var{mode} is @code{VOIDmode}, or @var{op} has the same
+mode as @var{mode}, or @var{op} is a @code{CONST_INT} or
+@code{CONST_DOUBLE}. They do @emph{not} check specifically for
+integer @code{CONST_DOUBLE}, nor do they test that the value of either
+kind of constant fits in the requested mode. This is because
+target-specific predicates that take constants usually have to do more
+stringent value checks anyway. If you need the exact same treatment
+of @code{CONST_INT} or @code{CONST_DOUBLE} that the generic predicates
+provide, use a @code{MATCH_OPERAND} subexpression to call
+@code{const_int_operand}, @code{const_double_operand}, or
+@code{immediate_operand}.
+
+Predicates written with @code{define_special_predicate} do not get any
+automatic mode checks, and are treated as having special mode handling
+by @command{genrecog}.
+
+The program @command{genpreds} is responsible for generating code to
+test predicates. It also writes a header file containing function
+declarations for all machine-specific predicates. It is not necessary
+to declare these predicates in @file{@var{cpu}-protos.h}.
+@end ifset
+
+@c Most of this node appears by itself (in a different place) even
+@c when the INTERNALS flag is clear. Passages that require the internals
+@c manual's context are conditionalized to appear only in the internals manual.
+@ifset INTERNALS
+@node Constraints
+@section Operand Constraints
+@cindex operand constraints
+@cindex constraints
+
+Each @code{match_operand} in an instruction pattern can specify
+constraints for the operands allowed. The constraints allow you to
+fine-tune matching within the set of operands allowed by the
+predicate.
+
+@end ifset
+@ifclear INTERNALS
+@node Constraints
+@section Constraints for @code{asm} Operands
+@cindex operand constraints, @code{asm}
+@cindex constraints, @code{asm}
+@cindex @code{asm} constraints
+
+Here are specific details on what constraint letters you can use with
+@code{asm} operands.
+@end ifclear
+Constraints can say whether
+an operand may be in a register, and which kinds of register; whether the
+operand can be a memory reference, and which kinds of address; whether the
+operand may be an immediate constant, and which possible values it may
+have. Constraints can also require two operands to match.
+Side-effects aren't allowed in operands of inline @code{asm}, unless
+@samp{<} or @samp{>} constraints are used, because there is no guarantee
+that the side effects will happen exactly once in an instruction that can update
+the addressing register.
+
+@ifset INTERNALS
+@menu
+* Simple Constraints:: Basic use of constraints.
+* Multi-Alternative:: When an insn has two alternative constraint-patterns.
+* Class Preferences:: Constraints guide which hard register to put things in.
+* Modifiers:: More precise control over effects of constraints.
+* Machine Constraints:: Existing constraints for some particular machines.
+* Disable Insn Alternatives:: Disable insn alternatives using attributes.
+* Define Constraints:: How to define machine-specific constraints.
+* C Constraint Interface:: How to test constraints from C code.
+@end menu
+@end ifset
+
+@ifclear INTERNALS
+@menu
+* Simple Constraints:: Basic use of constraints.
+* Multi-Alternative:: When an insn has two alternative constraint-patterns.
+* Modifiers:: More precise control over effects of constraints.
+* Machine Constraints:: Special constraints for some particular machines.
+@end menu
+@end ifclear
+
+@node Simple Constraints
+@subsection Simple Constraints
+@cindex simple constraints
+
+The simplest kind of constraint is a string full of letters, each of
+which describes one kind of operand that is permitted. Here are
+the letters that are allowed:
+
+@table @asis
+@item whitespace
+Whitespace characters are ignored and can be inserted at any position
+except the first. This enables each alternative for different operands to
+be visually aligned in the machine description even if they have different
+number of constraints and modifiers.
+
+@cindex @samp{m} in constraint
+@cindex memory references in constraints
+@item @samp{m}
+A memory operand is allowed, with any kind of address that the machine
+supports in general.
+Note that the letter used for the general memory constraint can be
+re-defined by a back end using the @code{TARGET_MEM_CONSTRAINT} macro.
+
+@cindex offsettable address
+@cindex @samp{o} in constraint
+@item @samp{o}
+A memory operand is allowed, but only if the address is
+@dfn{offsettable}. This means that adding a small integer (actually,
+the width in bytes of the operand, as determined by its machine mode)
+may be added to the address and the result is also a valid memory
+address.
+
+@cindex autoincrement/decrement addressing
+For example, an address which is constant is offsettable; so is an
+address that is the sum of a register and a constant (as long as a
+slightly larger constant is also within the range of address-offsets
+supported by the machine); but an autoincrement or autodecrement
+address is not offsettable. More complicated indirect/indexed
+addresses may or may not be offsettable depending on the other
+addressing modes that the machine supports.
+
+Note that in an output operand which can be matched by another
+operand, the constraint letter @samp{o} is valid only when accompanied
+by both @samp{<} (if the target machine has predecrement addressing)
+and @samp{>} (if the target machine has preincrement addressing).
+
+@cindex @samp{V} in constraint
+@item @samp{V}
+A memory operand that is not offsettable. In other words, anything that
+would fit the @samp{m} constraint but not the @samp{o} constraint.
+
+@cindex @samp{<} in constraint
+@item @samp{<}
+A memory operand with autodecrement addressing (either predecrement or
+postdecrement) is allowed. In inline @code{asm} this constraint is only
+allowed if the operand is used exactly once in an instruction that can
+handle the side effects. Not using an operand with @samp{<} in constraint
+string in the inline @code{asm} pattern at all or using it in multiple
+instructions isn't valid, because the side effects wouldn't be performed
+or would be performed more than once. Furthermore, on some targets
+the operand with @samp{<} in constraint string must be accompanied by
+special instruction suffixes like @code{%U0} instruction suffix on PowerPC
+or @code{%P0} on IA-64.
+
+@cindex @samp{>} in constraint
+@item @samp{>}
+A memory operand with autoincrement addressing (either preincrement or
+postincrement) is allowed. In inline @code{asm} the same restrictions
+as for @samp{<} apply.
+
+@cindex @samp{r} in constraint
+@cindex registers in constraints
+@item @samp{r}
+A register operand is allowed provided that it is in a general
+register.
+
+@cindex constants in constraints
+@cindex @samp{i} in constraint
+@item @samp{i}
+An immediate integer operand (one with constant value) is allowed.
+This includes symbolic constants whose values will be known only at
+assembly time or later.
+
+@cindex @samp{n} in constraint
+@item @samp{n}
+An immediate integer operand with a known numeric value is allowed.
+Many systems cannot support assembly-time constants for operands less
+than a word wide. Constraints for these operands should use @samp{n}
+rather than @samp{i}.
+
+@cindex @samp{I} in constraint
+@item @samp{I}, @samp{J}, @samp{K}, @dots{} @samp{P}
+Other letters in the range @samp{I} through @samp{P} may be defined in
+a machine-dependent fashion to permit immediate integer operands with
+explicit integer values in specified ranges. For example, on the
+68000, @samp{I} is defined to stand for the range of values 1 to 8.
+This is the range permitted as a shift count in the shift
+instructions.
+
+@cindex @samp{E} in constraint
+@item @samp{E}
+An immediate floating operand (expression code @code{const_double}) is
+allowed, but only if the target floating point format is the same as
+that of the host machine (on which the compiler is running).
+
+@cindex @samp{F} in constraint
+@item @samp{F}
+An immediate floating operand (expression code @code{const_double} or
+@code{const_vector}) is allowed.
+
+@cindex @samp{G} in constraint
+@cindex @samp{H} in constraint
+@item @samp{G}, @samp{H}
+@samp{G} and @samp{H} may be defined in a machine-dependent fashion to
+permit immediate floating operands in particular ranges of values.
+
+@cindex @samp{s} in constraint
+@item @samp{s}
+An immediate integer operand whose value is not an explicit integer is
+allowed.
+
+This might appear strange; if an insn allows a constant operand with a
+value not known at compile time, it certainly must allow any known
+value. So why use @samp{s} instead of @samp{i}? Sometimes it allows
+better code to be generated.
+
+For example, on the 68000 in a fullword instruction it is possible to
+use an immediate operand; but if the immediate value is between @minus{}128
+and 127, better code results from loading the value into a register and
+using the register. This is because the load into the register can be
+done with a @samp{moveq} instruction. We arrange for this to happen
+by defining the letter @samp{K} to mean ``any integer outside the
+range @minus{}128 to 127'', and then specifying @samp{Ks} in the operand
+constraints.
+
+@cindex @samp{g} in constraint
+@item @samp{g}
+Any register, memory or immediate integer operand is allowed, except for
+registers that are not general registers.
+
+@cindex @samp{X} in constraint
+@item @samp{X}
+@ifset INTERNALS
+Any operand whatsoever is allowed, even if it does not satisfy
+@code{general_operand}. This is normally used in the constraint of
+a @code{match_scratch} when certain alternatives will not actually
+require a scratch register.
+@end ifset
+@ifclear INTERNALS
+Any operand whatsoever is allowed.
+@end ifclear
+
+@cindex @samp{0} in constraint
+@cindex digits in constraint
+@item @samp{0}, @samp{1}, @samp{2}, @dots{} @samp{9}
+An operand that matches the specified operand number is allowed. If a
+digit is used together with letters within the same alternative, the
+digit should come last.
+
+This number is allowed to be more than a single digit. If multiple
+digits are encountered consecutively, they are interpreted as a single
+decimal integer. There is scant chance for ambiguity, since to-date
+it has never been desirable that @samp{10} be interpreted as matching
+either operand 1 @emph{or} operand 0. Should this be desired, one
+can use multiple alternatives instead.
+
+@cindex matching constraint
+@cindex constraint, matching
+This is called a @dfn{matching constraint} and what it really means is
+that the assembler has only a single operand that fills two roles
+@ifset INTERNALS
+considered separate in the RTL insn. For example, an add insn has two
+input operands and one output operand in the RTL, but on most CISC
+@end ifset
+@ifclear INTERNALS
+which @code{asm} distinguishes. For example, an add instruction uses
+two input operands and an output operand, but on most CISC
+@end ifclear
+machines an add instruction really has only two operands, one of them an
+input-output operand:
+
+@smallexample
+addl #35,r12
+@end smallexample
+
+Matching constraints are used in these circumstances.
+More precisely, the two operands that match must include one input-only
+operand and one output-only operand. Moreover, the digit must be a
+smaller number than the number of the operand that uses it in the
+constraint.
+
+@ifset INTERNALS
+For operands to match in a particular case usually means that they
+are identical-looking RTL expressions. But in a few special cases
+specific kinds of dissimilarity are allowed. For example, @code{*x}
+as an input operand will match @code{*x++} as an output operand.
+For proper results in such cases, the output template should always
+use the output-operand's number when printing the operand.
+@end ifset
+
+@cindex load address instruction
+@cindex push address instruction
+@cindex address constraints
+@cindex @samp{p} in constraint
+@item @samp{p}
+An operand that is a valid memory address is allowed. This is
+for ``load address'' and ``push address'' instructions.
+
+@findex address_operand
+@samp{p} in the constraint must be accompanied by @code{address_operand}
+as the predicate in the @code{match_operand}. This predicate interprets
+the mode specified in the @code{match_operand} as the mode of the memory
+reference for which the address would be valid.
+
+@cindex other register constraints
+@cindex extensible constraints
+@item @var{other-letters}
+Other letters can be defined in machine-dependent fashion to stand for
+particular classes of registers or other arbitrary operand types.
+@samp{d}, @samp{a} and @samp{f} are defined on the 68000/68020 to stand
+for data, address and floating point registers.
+@end table
+
+@ifset INTERNALS
+In order to have valid assembler code, each operand must satisfy
+its constraint. But a failure to do so does not prevent the pattern
+from applying to an insn. Instead, it directs the compiler to modify
+the code so that the constraint will be satisfied. Usually this is
+done by copying an operand into a register.
+
+Contrast, therefore, the two instruction patterns that follow:
+
+@smallexample
+(define_insn ""
+ [(set (match_operand:SI 0 "general_operand" "=r")
+ (plus:SI (match_dup 0)
+ (match_operand:SI 1 "general_operand" "r")))]
+ ""
+ "@dots{}")
+@end smallexample
+
+@noindent
+which has two operands, one of which must appear in two places, and
+
+@smallexample
+(define_insn ""
+ [(set (match_operand:SI 0 "general_operand" "=r")
+ (plus:SI (match_operand:SI 1 "general_operand" "0")
+ (match_operand:SI 2 "general_operand" "r")))]
+ ""
+ "@dots{}")
+@end smallexample
+
+@noindent
+which has three operands, two of which are required by a constraint to be
+identical. If we are considering an insn of the form
+
+@smallexample
+(insn @var{n} @var{prev} @var{next}
+ (set (reg:SI 3)
+ (plus:SI (reg:SI 6) (reg:SI 109)))
+ @dots{})
+@end smallexample
+
+@noindent
+the first pattern would not apply at all, because this insn does not
+contain two identical subexpressions in the right place. The pattern would
+say, ``That does not look like an add instruction; try other patterns''.
+The second pattern would say, ``Yes, that's an add instruction, but there
+is something wrong with it''. It would direct the reload pass of the
+compiler to generate additional insns to make the constraint true. The
+results might look like this:
+
+@smallexample
+(insn @var{n2} @var{prev} @var{n}
+ (set (reg:SI 3) (reg:SI 6))
+ @dots{})
+
+(insn @var{n} @var{n2} @var{next}
+ (set (reg:SI 3)
+ (plus:SI (reg:SI 3) (reg:SI 109)))
+ @dots{})
+@end smallexample
+
+It is up to you to make sure that each operand, in each pattern, has
+constraints that can handle any RTL expression that could be present for
+that operand. (When multiple alternatives are in use, each pattern must,
+for each possible combination of operand expressions, have at least one
+alternative which can handle that combination of operands.) The
+constraints don't need to @emph{allow} any possible operand---when this is
+the case, they do not constrain---but they must at least point the way to
+reloading any possible operand so that it will fit.
+
+@itemize @bullet
+@item
+If the constraint accepts whatever operands the predicate permits,
+there is no problem: reloading is never necessary for this operand.
+
+For example, an operand whose constraints permit everything except
+registers is safe provided its predicate rejects registers.
+
+An operand whose predicate accepts only constant values is safe
+provided its constraints include the letter @samp{i}. If any possible
+constant value is accepted, then nothing less than @samp{i} will do;
+if the predicate is more selective, then the constraints may also be
+more selective.
+
+@item
+Any operand expression can be reloaded by copying it into a register.
+So if an operand's constraints allow some kind of register, it is
+certain to be safe. It need not permit all classes of registers; the
+compiler knows how to copy a register into another register of the
+proper class in order to make an instruction valid.
+
+@cindex nonoffsettable memory reference
+@cindex memory reference, nonoffsettable
+@item
+A nonoffsettable memory reference can be reloaded by copying the
+address into a register. So if the constraint uses the letter
+@samp{o}, all memory references are taken care of.
+
+@item
+A constant operand can be reloaded by allocating space in memory to
+hold it as preinitialized data. Then the memory reference can be used
+in place of the constant. So if the constraint uses the letters
+@samp{o} or @samp{m}, constant operands are not a problem.
+
+@item
+If the constraint permits a constant and a pseudo register used in an insn
+was not allocated to a hard register and is equivalent to a constant,
+the register will be replaced with the constant. If the predicate does
+not permit a constant and the insn is re-recognized for some reason, the
+compiler will crash. Thus the predicate must always recognize any
+objects allowed by the constraint.
+@end itemize
+
+If the operand's predicate can recognize registers, but the constraint does
+not permit them, it can make the compiler crash. When this operand happens
+to be a register, the reload pass will be stymied, because it does not know
+how to copy a register temporarily into memory.
+
+If the predicate accepts a unary operator, the constraint applies to the
+operand. For example, the MIPS processor at ISA level 3 supports an
+instruction which adds two registers in @code{SImode} to produce a
+@code{DImode} result, but only if the registers are correctly sign
+extended. This predicate for the input operands accepts a
+@code{sign_extend} of an @code{SImode} register. Write the constraint
+to indicate the type of register that is required for the operand of the
+@code{sign_extend}.
+@end ifset
+
+@node Multi-Alternative
+@subsection Multiple Alternative Constraints
+@cindex multiple alternative constraints
+
+Sometimes a single instruction has multiple alternative sets of possible
+operands. For example, on the 68000, a logical-or instruction can combine
+register or an immediate value into memory, or it can combine any kind of
+operand into a register; but it cannot combine one memory location into
+another.
+
+These constraints are represented as multiple alternatives. An alternative
+can be described by a series of letters for each operand. The overall
+constraint for an operand is made from the letters for this operand
+from the first alternative, a comma, the letters for this operand from
+the second alternative, a comma, and so on until the last alternative.
+All operands for a single instruction must have the same number of
+alternatives.
+@ifset INTERNALS
+Here is how it is done for fullword logical-or on the 68000:
+
+@smallexample
+(define_insn "iorsi3"
+ [(set (match_operand:SI 0 "general_operand" "=m,d")
+ (ior:SI (match_operand:SI 1 "general_operand" "%0,0")
+ (match_operand:SI 2 "general_operand" "dKs,dmKs")))]
+ @dots{})
+@end smallexample
+
+The first alternative has @samp{m} (memory) for operand 0, @samp{0} for
+operand 1 (meaning it must match operand 0), and @samp{dKs} for operand
+2. The second alternative has @samp{d} (data register) for operand 0,
+@samp{0} for operand 1, and @samp{dmKs} for operand 2. The @samp{=} and
+@samp{%} in the constraints apply to all the alternatives; their
+meaning is explained in the next section (@pxref{Class Preferences}).
+
+If all the operands fit any one alternative, the instruction is valid.
+Otherwise, for each alternative, the compiler counts how many instructions
+must be added to copy the operands so that that alternative applies.
+The alternative requiring the least copying is chosen. If two alternatives
+need the same amount of copying, the one that comes first is chosen.
+These choices can be altered with the @samp{?} and @samp{!} characters:
+
+@table @code
+@cindex @samp{?} in constraint
+@cindex question mark
+@item ?
+Disparage slightly the alternative that the @samp{?} appears in,
+as a choice when no alternative applies exactly. The compiler regards
+this alternative as one unit more costly for each @samp{?} that appears
+in it.
+
+@cindex @samp{!} in constraint
+@cindex exclamation point
+@item !
+Disparage severely the alternative that the @samp{!} appears in.
+This alternative can still be used if it fits without reloading,
+but if reloading is needed, some other alternative will be used.
+
+@cindex @samp{^} in constraint
+@cindex caret
+@item ^
+This constraint is analogous to @samp{?} but it disparages slightly
+the alternative only if the operand with the @samp{^} needs a reload.
+
+@cindex @samp{$} in constraint
+@cindex dollar sign
+@item $
+This constraint is analogous to @samp{!} but it disparages severely
+the alternative only if the operand with the @samp{$} needs a reload.
+@end table
+
+When an insn pattern has multiple alternatives in its constraints, often
+the appearance of the assembler code is determined mostly by which
+alternative was matched. When this is so, the C code for writing the
+assembler code can use the variable @code{which_alternative}, which is
+the ordinal number of the alternative that was actually satisfied (0 for
+the first, 1 for the second alternative, etc.). @xref{Output Statement}.
+@end ifset
+@ifclear INTERNALS
+
+So the first alternative for the 68000's logical-or could be written as
+@code{"+m" (output) : "ir" (input)}. The second could be @code{"+r"
+(output): "irm" (input)}. However, the fact that two memory locations
+cannot be used in a single instruction prevents simply using @code{"+rm"
+(output) : "irm" (input)}. Using multi-alternatives, this might be
+written as @code{"+m,r" (output) : "ir,irm" (input)}. This describes
+all the available alternatives to the compiler, allowing it to choose
+the most efficient one for the current conditions.
+
+There is no way within the template to determine which alternative was
+chosen. However you may be able to wrap your @code{asm} statements with
+builtins such as @code{__builtin_constant_p} to achieve the desired results.
+@end ifclear
+
+@ifset INTERNALS
+@node Class Preferences
+@subsection Register Class Preferences
+@cindex class preference constraints
+@cindex register class preference constraints
+
+@cindex voting between constraint alternatives
+The operand constraints have another function: they enable the compiler
+to decide which kind of hardware register a pseudo register is best
+allocated to. The compiler examines the constraints that apply to the
+insns that use the pseudo register, looking for the machine-dependent
+letters such as @samp{d} and @samp{a} that specify classes of registers.
+The pseudo register is put in whichever class gets the most ``votes''.
+The constraint letters @samp{g} and @samp{r} also vote: they vote in
+favor of a general register. The machine description says which registers
+are considered general.
+
+Of course, on some machines all registers are equivalent, and no register
+classes are defined. Then none of this complexity is relevant.
+@end ifset
+
+@node Modifiers
+@subsection Constraint Modifier Characters
+@cindex modifiers in constraints
+@cindex constraint modifier characters
+
+@c prevent bad page break with this line
+Here are constraint modifier characters.
+
+@table @samp
+@cindex @samp{=} in constraint
+@item =
+Means that this operand is written to by this instruction:
+the previous value is discarded and replaced by new data.
+
+@cindex @samp{+} in constraint
+@item +
+Means that this operand is both read and written by the instruction.
+
+When the compiler fixes up the operands to satisfy the constraints,
+it needs to know which operands are read by the instruction and
+which are written by it. @samp{=} identifies an operand which is only
+written; @samp{+} identifies an operand that is both read and written; all
+other operands are assumed to only be read.
+
+If you specify @samp{=} or @samp{+} in a constraint, you put it in the
+first character of the constraint string.
+
+@cindex @samp{&} in constraint
+@cindex earlyclobber operand
+@item &
+Means (in a particular alternative) that this operand is an
+@dfn{earlyclobber} operand, which is written before the instruction is
+finished using the input operands. Therefore, this operand may not lie
+in a register that is read by the instruction or as part of any memory
+address.
+
+@samp{&} applies only to the alternative in which it is written. In
+constraints with multiple alternatives, sometimes one alternative
+requires @samp{&} while others do not. See, for example, the
+@samp{movdf} insn of the 68000.
+
+An operand which is read by the instruction can be tied to an earlyclobber
+operand if its only use as an input occurs before the early result is
+written. Adding alternatives of this form often allows GCC to produce
+better code when only some of the read operands can be affected by the
+earlyclobber. See, for example, the @samp{mulsi3} insn of the ARM@.
+
+Furthermore, if the @dfn{earlyclobber} operand is also a read/write
+operand, then that operand is written only after it's used.
+
+@samp{&} does not obviate the need to write @samp{=} or @samp{+}. As
+@dfn{earlyclobber} operands are always written, a read-only
+@dfn{earlyclobber} operand is ill-formed and will be rejected by the
+compiler.
+
+@cindex @samp{%} in constraint
+@item %
+Declares the instruction to be commutative for this operand and the
+following operand. This means that the compiler may interchange the
+two operands if that is the cheapest way to make all operands fit the
+constraints. @samp{%} applies to all alternatives and must appear as
+the first character in the constraint. Only read-only operands can use
+@samp{%}.
+
+@ifset INTERNALS
+This is often used in patterns for addition instructions
+that really have only two operands: the result must go in one of the
+arguments. Here for example, is how the 68000 halfword-add
+instruction is defined:
+
+@smallexample
+(define_insn "addhi3"
+ [(set (match_operand:HI 0 "general_operand" "=m,r")
+ (plus:HI (match_operand:HI 1 "general_operand" "%0,0")
+ (match_operand:HI 2 "general_operand" "di,g")))]
+ @dots{})
+@end smallexample
+@end ifset
+GCC can only handle one commutative pair in an asm; if you use more,
+the compiler may fail. Note that you need not use the modifier if
+the two alternatives are strictly identical; this would only waste
+time in the reload pass.
+@ifset INTERNALS
+The modifier is not operational after
+register allocation, so the result of @code{define_peephole2}
+and @code{define_split}s performed after reload cannot rely on
+@samp{%} to make the intended insn match.
+
+@cindex @samp{#} in constraint
+@item #
+Says that all following characters, up to the next comma, are to be
+ignored as a constraint. They are significant only for choosing
+register preferences.
+
+@cindex @samp{*} in constraint
+@item *
+Says that the following character should be ignored when choosing
+register preferences. @samp{*} has no effect on the meaning of the
+constraint as a constraint, and no effect on reloading. For LRA
+@samp{*} additionally disparages slightly the alternative if the
+following character matches the operand.
+
+Here is an example: the 68000 has an instruction to sign-extend a
+halfword in a data register, and can also sign-extend a value by
+copying it into an address register. While either kind of register is
+acceptable, the constraints on an address-register destination are
+less strict, so it is best if register allocation makes an address
+register its goal. Therefore, @samp{*} is used so that the @samp{d}
+constraint letter (for data register) is ignored when computing
+register preferences.
+
+@smallexample
+(define_insn "extendhisi2"
+ [(set (match_operand:SI 0 "general_operand" "=*d,a")
+ (sign_extend:SI
+ (match_operand:HI 1 "general_operand" "0,g")))]
+ @dots{})
+@end smallexample
+@end ifset
+@end table
+
+@node Machine Constraints
+@subsection Constraints for Particular Machines
+@cindex machine specific constraints
+@cindex constraints, machine specific
+
+Whenever possible, you should use the general-purpose constraint letters
+in @code{asm} arguments, since they will convey meaning more readily to
+people reading your code. Failing that, use the constraint letters
+that usually have very similar meanings across architectures. The most
+commonly used constraints are @samp{m} and @samp{r} (for memory and
+general-purpose registers respectively; @pxref{Simple Constraints}), and
+@samp{I}, usually the letter indicating the most common
+immediate-constant format.
+
+Each architecture defines additional constraints. These constraints
+are used by the compiler itself for instruction generation, as well as
+for @code{asm} statements; therefore, some of the constraints are not
+particularly useful for @code{asm}. Here is a summary of some of the
+machine-dependent constraints available on some particular machines;
+it includes both constraints that are useful for @code{asm} and
+constraints that aren't. The compiler source file mentioned in the
+table heading for each architecture is the definitive reference for
+the meanings of that architecture's constraints.
+
+@c Please keep this table alphabetized by target!
+@table @emph
+@item AArch64 family---@file{config/aarch64/constraints.md}
+@table @code
+@item k
+The stack pointer register (@code{SP})
+
+@item w
+Floating point register, Advanced SIMD vector register or SVE vector register
+
+@item x
+Like @code{w}, but restricted to registers 0 to 15 inclusive.
+
+@item y
+Like @code{w}, but restricted to registers 0 to 7 inclusive.
+
+@item Upl
+One of the low eight SVE predicate registers (@code{P0} to @code{P7})
+
+@item Upa
+Any of the SVE predicate registers (@code{P0} to @code{P15})
+
+@item I
+Integer constant that is valid as an immediate operand in an @code{ADD}
+instruction
+
+@item J
+Integer constant that is valid as an immediate operand in a @code{SUB}
+instruction (once negated)
+
+@item K
+Integer constant that can be used with a 32-bit logical instruction
+
+@item L
+Integer constant that can be used with a 64-bit logical instruction
+
+@item M
+Integer constant that is valid as an immediate operand in a 32-bit @code{MOV}
+pseudo instruction. The @code{MOV} may be assembled to one of several different
+machine instructions depending on the value
+
+@item N
+Integer constant that is valid as an immediate operand in a 64-bit @code{MOV}
+pseudo instruction
+
+@item S
+An absolute symbolic address or a label reference
+
+@item Y
+Floating point constant zero
+
+@item Z
+Integer constant zero
+
+@item Ush
+The high part (bits 12 and upwards) of the pc-relative address of a symbol
+within 4GB of the instruction
+
+@item Q
+A memory address which uses a single base register with no offset
+
+@item Ump
+A memory address suitable for a load/store pair instruction in SI, DI, SF and
+DF modes
+
+@end table
+
+
+@item AMD GCN ---@file{config/gcn/constraints.md}
+@table @code
+@item I
+Immediate integer in the range @minus{}16 to 64
+
+@item J
+Immediate 16-bit signed integer
+
+@item Kf
+Immediate constant @minus{}1
+
+@item L
+Immediate 15-bit unsigned integer
+
+@item A
+Immediate constant that can be inlined in an instruction encoding: integer
+@minus{}16..64, or float 0.0, +/@minus{}0.5, +/@minus{}1.0, +/@minus{}2.0,
++/@minus{}4.0, 1.0/(2.0*PI)
+
+@item B
+Immediate 32-bit signed integer that can be attached to an instruction encoding
+
+@item C
+Immediate 32-bit integer in range @minus{}16..4294967295 (i.e. 32-bit unsigned
+integer or @samp{A} constraint)
+
+@item DA
+Immediate 64-bit constant that can be split into two @samp{A} constants
+
+@item DB
+Immediate 64-bit constant that can be split into two @samp{B} constants
+
+@item U
+Any @code{unspec}
+
+@item Y
+Any @code{symbol_ref} or @code{label_ref}
+
+@item v
+VGPR register
+
+@item Sg
+SGPR register
+
+@item SD
+SGPR registers valid for instruction destinations, including VCC, M0 and EXEC
+
+@item SS
+SGPR registers valid for instruction sources, including VCC, M0, EXEC and SCC
+
+@item Sm
+SGPR registers valid as a source for scalar memory instructions (excludes M0
+and EXEC)
+
+@item Sv
+SGPR registers valid as a source or destination for vector instructions
+(excludes EXEC)
+
+@item ca
+All condition registers: SCC, VCCZ, EXECZ
+
+@item cs
+Scalar condition register: SCC
+
+@item cV
+Vector condition register: VCC, VCC_LO, VCC_HI
+
+@item e
+EXEC register (EXEC_LO and EXEC_HI)
+
+@item RB
+Memory operand with address space suitable for @code{buffer_*} instructions
+
+@item RF
+Memory operand with address space suitable for @code{flat_*} instructions
+
+@item RS
+Memory operand with address space suitable for @code{s_*} instructions
+
+@item RL
+Memory operand with address space suitable for @code{ds_*} LDS instructions
+
+@item RG
+Memory operand with address space suitable for @code{ds_*} GDS instructions
+
+@item RD
+Memory operand with address space suitable for any @code{ds_*} instructions
+
+@item RM
+Memory operand with address space suitable for @code{global_*} instructions
+
+@end table
+
+
+@item ARC ---@file{config/arc/constraints.md}
+@table @code
+@item q
+Registers usable in ARCompact 16-bit instructions: @code{r0}-@code{r3},
+@code{r12}-@code{r15}. This constraint can only match when the @option{-mq}
+option is in effect.
+
+@item e
+Registers usable as base-regs of memory addresses in ARCompact 16-bit memory
+instructions: @code{r0}-@code{r3}, @code{r12}-@code{r15}, @code{sp}.
+This constraint can only match when the @option{-mq}
+option is in effect.
+@item D
+ARC FPX (dpfp) 64-bit registers. @code{D0}, @code{D1}.
+
+@item I
+A signed 12-bit integer constant.
+
+@item Cal
+constant for arithmetic/logical operations. This might be any constant
+that can be put into a long immediate by the assmbler or linker without
+involving a PIC relocation.
+
+@item K
+A 3-bit unsigned integer constant.
+
+@item L
+A 6-bit unsigned integer constant.
+
+@item CnL
+One's complement of a 6-bit unsigned integer constant.
+
+@item CmL
+Two's complement of a 6-bit unsigned integer constant.
+
+@item M
+A 5-bit unsigned integer constant.
+
+@item O
+A 7-bit unsigned integer constant.
+
+@item P
+A 8-bit unsigned integer constant.
+
+@item H
+Any const_double value.
+@end table
+
+@item ARM family---@file{config/arm/constraints.md}
+@table @code
+
+@item h
+In Thumb state, the core registers @code{r8}-@code{r15}.
+
+@item k
+The stack pointer register.
+
+@item l
+In Thumb State the core registers @code{r0}-@code{r7}. In ARM state this
+is an alias for the @code{r} constraint.
+
+@item t
+VFP floating-point registers @code{s0}-@code{s31}. Used for 32 bit values.
+
+@item w
+VFP floating-point registers @code{d0}-@code{d31} and the appropriate
+subset @code{d0}-@code{d15} based on command line options.
+Used for 64 bit values only. Not valid for Thumb1.
+
+@item y
+The iWMMX co-processor registers.
+
+@item z
+The iWMMX GR registers.
+
+@item G
+The floating-point constant 0.0
+
+@item I
+Integer that is valid as an immediate operand in a data processing
+instruction. That is, an integer in the range 0 to 255 rotated by a
+multiple of 2
+
+@item J
+Integer in the range @minus{}4095 to 4095
+
+@item K
+Integer that satisfies constraint @samp{I} when inverted (ones complement)
+
+@item L
+Integer that satisfies constraint @samp{I} when negated (twos complement)
+
+@item M
+Integer in the range 0 to 32
+
+@item Q
+A memory reference where the exact address is in a single register
+(`@samp{m}' is preferable for @code{asm} statements)
+
+@item R
+An item in the constant pool
+
+@item S
+A symbol in the text segment of the current file
+
+@item Uv
+A memory reference suitable for VFP load/store insns (reg+constant offset)
+
+@item Uy
+A memory reference suitable for iWMMXt load/store instructions.
+
+@item Uq
+A memory reference suitable for the ARMv4 ldrsb instruction.
+@end table
+
+@item AVR family---@file{config/avr/constraints.md}
+@table @code
+@item l
+Registers from r0 to r15
+
+@item a
+Registers from r16 to r23
+
+@item d
+Registers from r16 to r31
+
+@item w
+Registers from r24 to r31. These registers can be used in @samp{adiw} command
+
+@item e
+Pointer register (r26--r31)
+
+@item b
+Base pointer register (r28--r31)
+
+@item q
+Stack pointer register (SPH:SPL)
+
+@item t
+Temporary register r0
+
+@item x
+Register pair X (r27:r26)
+
+@item y
+Register pair Y (r29:r28)
+
+@item z
+Register pair Z (r31:r30)
+
+@item I
+Constant greater than @minus{}1, less than 64
+
+@item J
+Constant greater than @minus{}64, less than 1
+
+@item K
+Constant integer 2
+
+@item L
+Constant integer 0
+
+@item M
+Constant that fits in 8 bits
+
+@item N
+Constant integer @minus{}1
+
+@item O
+Constant integer 8, 16, or 24
+
+@item P
+Constant integer 1
+
+@item G
+A floating point constant 0.0
+
+@item Q
+A memory address based on Y or Z pointer with displacement.
+@end table
+
+@item Blackfin family---@file{config/bfin/constraints.md}
+@table @code
+@item a
+P register
+
+@item d
+D register
+
+@item z
+A call clobbered P register.
+
+@item q@var{n}
+A single register. If @var{n} is in the range 0 to 7, the corresponding D
+register. If it is @code{A}, then the register P0.
+
+@item D
+Even-numbered D register
+
+@item W
+Odd-numbered D register
+
+@item e
+Accumulator register.
+
+@item A
+Even-numbered accumulator register.
+
+@item B
+Odd-numbered accumulator register.
+
+@item b
+I register
+
+@item v
+B register
+
+@item f
+M register
+
+@item c
+Registers used for circular buffering, i.e.@: I, B, or L registers.
+
+@item C
+The CC register.
+
+@item t
+LT0 or LT1.
+
+@item k
+LC0 or LC1.
+
+@item u
+LB0 or LB1.
+
+@item x
+Any D, P, B, M, I or L register.
+
+@item y
+Additional registers typically used only in prologues and epilogues: RETS,
+RETN, RETI, RETX, RETE, ASTAT, SEQSTAT and USP.
+
+@item w
+Any register except accumulators or CC.
+
+@item Ksh
+Signed 16 bit integer (in the range @minus{}32768 to 32767)
+
+@item Kuh
+Unsigned 16 bit integer (in the range 0 to 65535)
+
+@item Ks7
+Signed 7 bit integer (in the range @minus{}64 to 63)
+
+@item Ku7
+Unsigned 7 bit integer (in the range 0 to 127)
+
+@item Ku5
+Unsigned 5 bit integer (in the range 0 to 31)
+
+@item Ks4
+Signed 4 bit integer (in the range @minus{}8 to 7)
+
+@item Ks3
+Signed 3 bit integer (in the range @minus{}3 to 4)
+
+@item Ku3
+Unsigned 3 bit integer (in the range 0 to 7)
+
+@item P@var{n}
+Constant @var{n}, where @var{n} is a single-digit constant in the range 0 to 4.
+
+@item PA
+An integer equal to one of the MACFLAG_XXX constants that is suitable for
+use with either accumulator.
+
+@item PB
+An integer equal to one of the MACFLAG_XXX constants that is suitable for
+use only with accumulator A1.
+
+@item M1
+Constant 255.
+
+@item M2
+Constant 65535.
+
+@item J
+An integer constant with exactly a single bit set.
+
+@item L
+An integer constant with all bits set except exactly one.
+
+@item H
+
+@item Q
+Any SYMBOL_REF.
+@end table
+
+@item C-SKY---@file{config/csky/constraints.md}
+@table @code
+
+@item a
+The mini registers r0 - r7.
+
+@item b
+The low registers r0 - r15.
+
+@item c
+C register.
+
+@item y
+HI and LO registers.
+
+@item l
+LO register.
+
+@item h
+HI register.
+
+@item v
+Vector registers.
+
+@item z
+Stack pointer register (SP).
+
+@item Q
+A memory address which uses a base register with a short offset
+or with a index register with its scale.
+
+@item W
+A memory address which uses a base register with a index register
+with its scale.
+@end table
+
+@ifset INTERNALS
+The C-SKY back end supports a large set of additional constraints
+that are only useful for instruction selection or splitting rather
+than inline asm, such as constraints representing constant integer
+ranges accepted by particular instruction encodings.
+Refer to the source code for details.
+@end ifset
+
+@item Epiphany---@file{config/epiphany/constraints.md}
+@table @code
+@item U16
+An unsigned 16-bit constant.
+
+@item K
+An unsigned 5-bit constant.
+
+@item L
+A signed 11-bit constant.
+
+@item Cm1
+A signed 11-bit constant added to @minus{}1.
+Can only match when the @option{-m1reg-@var{reg}} option is active.
+
+@item Cl1
+Left-shift of @minus{}1, i.e., a bit mask with a block of leading ones, the rest
+being a block of trailing zeroes.
+Can only match when the @option{-m1reg-@var{reg}} option is active.
+
+@item Cr1
+Right-shift of @minus{}1, i.e., a bit mask with a trailing block of ones, the
+rest being zeroes. Or to put it another way, one less than a power of two.
+Can only match when the @option{-m1reg-@var{reg}} option is active.
+
+@item Cal
+Constant for arithmetic/logical operations.
+This is like @code{i}, except that for position independent code,
+no symbols / expressions needing relocations are allowed.
+
+@item Csy
+Symbolic constant for call/jump instruction.
+
+@item Rcs
+The register class usable in short insns. This is a register class
+constraint, and can thus drive register allocation.
+This constraint won't match unless @option{-mprefer-short-insn-regs} is
+in effect.
+
+@item Rsc
+The register class of registers that can be used to hold a
+sibcall call address. I.e., a caller-saved register.
+
+@item Rct
+Core control register class.
+
+@item Rgs
+The register group usable in short insns.
+This constraint does not use a register class, so that it only
+passively matches suitable registers, and doesn't drive register allocation.
+
+@ifset INTERNALS
+@item Car
+Constant suitable for the addsi3_r pattern. This is a valid offset
+For byte, halfword, or word addressing.
+@end ifset
+
+@item Rra
+Matches the return address if it can be replaced with the link register.
+
+@item Rcc
+Matches the integer condition code register.
+
+@item Sra
+Matches the return address if it is in a stack slot.
+
+@item Cfm
+Matches control register values to switch fp mode, which are encapsulated in
+@code{UNSPEC_FP_MODE}.
+@end table
+
+@item FRV---@file{config/frv/frv.h}
+@table @code
+@item a
+Register in the class @code{ACC_REGS} (@code{acc0} to @code{acc7}).
+
+@item b
+Register in the class @code{EVEN_ACC_REGS} (@code{acc0} to @code{acc7}).
+
+@item c
+Register in the class @code{CC_REGS} (@code{fcc0} to @code{fcc3} and
+@code{icc0} to @code{icc3}).
+
+@item d
+Register in the class @code{GPR_REGS} (@code{gr0} to @code{gr63}).
+
+@item e
+Register in the class @code{EVEN_REGS} (@code{gr0} to @code{gr63}).
+Odd registers are excluded not in the class but through the use of a machine
+mode larger than 4 bytes.
+
+@item f
+Register in the class @code{FPR_REGS} (@code{fr0} to @code{fr63}).
+
+@item h
+Register in the class @code{FEVEN_REGS} (@code{fr0} to @code{fr63}).
+Odd registers are excluded not in the class but through the use of a machine
+mode larger than 4 bytes.
+
+@item l
+Register in the class @code{LR_REG} (the @code{lr} register).
+
+@item q
+Register in the class @code{QUAD_REGS} (@code{gr2} to @code{gr63}).
+Register numbers not divisible by 4 are excluded not in the class but through
+the use of a machine mode larger than 8 bytes.
+
+@item t
+Register in the class @code{ICC_REGS} (@code{icc0} to @code{icc3}).
+
+@item u
+Register in the class @code{FCC_REGS} (@code{fcc0} to @code{fcc3}).
+
+@item v
+Register in the class @code{ICR_REGS} (@code{cc4} to @code{cc7}).
+
+@item w
+Register in the class @code{FCR_REGS} (@code{cc0} to @code{cc3}).
+
+@item x
+Register in the class @code{QUAD_FPR_REGS} (@code{fr0} to @code{fr63}).
+Register numbers not divisible by 4 are excluded not in the class but through
+the use of a machine mode larger than 8 bytes.
+
+@item z
+Register in the class @code{SPR_REGS} (@code{lcr} and @code{lr}).
+
+@item A
+Register in the class @code{QUAD_ACC_REGS} (@code{acc0} to @code{acc7}).
+
+@item B
+Register in the class @code{ACCG_REGS} (@code{accg0} to @code{accg7}).
+
+@item C
+Register in the class @code{CR_REGS} (@code{cc0} to @code{cc7}).
+
+@item G
+Floating point constant zero
+
+@item I
+6-bit signed integer constant
+
+@item J
+10-bit signed integer constant
+
+@item L
+16-bit signed integer constant
+
+@item M
+16-bit unsigned integer constant
+
+@item N
+12-bit signed integer constant that is negative---i.e.@: in the
+range of @minus{}2048 to @minus{}1
+
+@item O
+Constant zero
+
+@item P
+12-bit signed integer constant that is greater than zero---i.e.@: in the
+range of 1 to 2047.
+
+@end table
+
+@item FT32---@file{config/ft32/constraints.md}
+@table @code
+@item A
+An absolute address
+
+@item B
+An offset address
+
+@item W
+A register indirect memory operand
+
+@item e
+An offset address.
+
+@item f
+An offset address.
+
+@item O
+The constant zero or one
+
+@item I
+A 16-bit signed constant (@minus{}32768 @dots{} 32767)
+
+@item w
+A bitfield mask suitable for bext or bins
+
+@item x
+An inverted bitfield mask suitable for bext or bins
+
+@item L
+A 16-bit unsigned constant, multiple of 4 (0 @dots{} 65532)
+
+@item S
+A 20-bit signed constant (@minus{}524288 @dots{} 524287)
+
+@item b
+A constant for a bitfield width (1 @dots{} 16)
+
+@item KA
+A 10-bit signed constant (@minus{}512 @dots{} 511)
+
+@end table
+
+@item Hewlett-Packard PA-RISC---@file{config/pa/pa.h}
+@table @code
+@item a
+General register 1
+
+@item f
+Floating point register
+
+@item q
+Shift amount register
+
+@item x
+Floating point register (deprecated)
+
+@item y
+Upper floating point register (32-bit), floating point register (64-bit)
+
+@item Z
+Any register
+
+@item I
+Signed 11-bit integer constant
+
+@item J
+Signed 14-bit integer constant
+
+@item K
+Integer constant that can be deposited with a @code{zdepi} instruction
+
+@item L
+Signed 5-bit integer constant
+
+@item M
+Integer constant 0
+
+@item N
+Integer constant that can be loaded with a @code{ldil} instruction
+
+@item O
+Integer constant whose value plus one is a power of 2
+
+@item P
+Integer constant that can be used for @code{and} operations in @code{depi}
+and @code{extru} instructions
+
+@item S
+Integer constant 31
+
+@item U
+Integer constant 63
+
+@item G
+Floating-point constant 0.0
+
+@item A
+A @code{lo_sum} data-linkage-table memory operand
+
+@item Q
+A memory operand that can be used as the destination operand of an
+integer store instruction
+
+@item R
+A scaled or unscaled indexed memory operand
+
+@item T
+A memory operand for floating-point loads and stores
+
+@item W
+A register indirect memory operand
+@end table
+
+@item Intel IA-64---@file{config/ia64/ia64.h}
+@table @code
+@item a
+General register @code{r0} to @code{r3} for @code{addl} instruction
+
+@item b
+Branch register
+
+@item c
+Predicate register (@samp{c} as in ``conditional'')
+
+@item d
+Application register residing in M-unit
+
+@item e
+Application register residing in I-unit
+
+@item f
+Floating-point register
+
+@item m
+Memory operand. If used together with @samp{<} or @samp{>},
+the operand can have postincrement and postdecrement which
+require printing with @samp{%Pn} on IA-64.
+
+@item G
+Floating-point constant 0.0 or 1.0
+
+@item I
+14-bit signed integer constant
+
+@item J
+22-bit signed integer constant
+
+@item K
+8-bit signed integer constant for logical instructions
+
+@item L
+8-bit adjusted signed integer constant for compare pseudo-ops
+
+@item M
+6-bit unsigned integer constant for shift counts
+
+@item N
+9-bit signed integer constant for load and store postincrements
+
+@item O
+The constant zero
+
+@item P
+0 or @minus{}1 for @code{dep} instruction
+
+@item Q
+Non-volatile memory for floating-point loads and stores
+
+@item R
+Integer constant in the range 1 to 4 for @code{shladd} instruction
+
+@item S
+Memory operand except postincrement and postdecrement. This is
+now roughly the same as @samp{m} when not used together with @samp{<}
+or @samp{>}.
+@end table
+
+@item M32C---@file{config/m32c/m32c.cc}
+@table @code
+@item Rsp
+@itemx Rfb
+@itemx Rsb
+@samp{$sp}, @samp{$fb}, @samp{$sb}.
+
+@item Rcr
+Any control register, when they're 16 bits wide (nothing if control
+registers are 24 bits wide)
+
+@item Rcl
+Any control register, when they're 24 bits wide.
+
+@item R0w
+@itemx R1w
+@itemx R2w
+@itemx R3w
+$r0, $r1, $r2, $r3.
+
+@item R02
+$r0 or $r2, or $r2r0 for 32 bit values.
+
+@item R13
+$r1 or $r3, or $r3r1 for 32 bit values.
+
+@item Rdi
+A register that can hold a 64 bit value.
+
+@item Rhl
+$r0 or $r1 (registers with addressable high/low bytes)
+
+@item R23
+$r2 or $r3
+
+@item Raa
+Address registers
+
+@item Raw
+Address registers when they're 16 bits wide.
+
+@item Ral
+Address registers when they're 24 bits wide.
+
+@item Rqi
+Registers that can hold QI values.
+
+@item Rad
+Registers that can be used with displacements ($a0, $a1, $sb).
+
+@item Rsi
+Registers that can hold 32 bit values.
+
+@item Rhi
+Registers that can hold 16 bit values.
+
+@item Rhc
+Registers chat can hold 16 bit values, including all control
+registers.
+
+@item Rra
+$r0 through R1, plus $a0 and $a1.
+
+@item Rfl
+The flags register.
+
+@item Rmm
+The memory-based pseudo-registers $mem0 through $mem15.
+
+@item Rpi
+Registers that can hold pointers (16 bit registers for r8c, m16c; 24
+bit registers for m32cm, m32c).
+
+@item Rpa
+Matches multiple registers in a PARALLEL to form a larger register.
+Used to match function return values.
+
+@item Is3
+@minus{}8 @dots{} 7
+
+@item IS1
+@minus{}128 @dots{} 127
+
+@item IS2
+@minus{}32768 @dots{} 32767
+
+@item IU2
+0 @dots{} 65535
+
+@item In4
+@minus{}8 @dots{} @minus{}1 or 1 @dots{} 8
+
+@item In5
+@minus{}16 @dots{} @minus{}1 or 1 @dots{} 16
+
+@item In6
+@minus{}32 @dots{} @minus{}1 or 1 @dots{} 32
+
+@item IM2
+@minus{}65536 @dots{} @minus{}1
+
+@item Ilb
+An 8 bit value with exactly one bit set.
+
+@item Ilw
+A 16 bit value with exactly one bit set.
+
+@item Sd
+The common src/dest memory addressing modes.
+
+@item Sa
+Memory addressed using $a0 or $a1.
+
+@item Si
+Memory addressed with immediate addresses.
+
+@item Ss
+Memory addressed using the stack pointer ($sp).
+
+@item Sf
+Memory addressed using the frame base register ($fb).
+
+@item Ss
+Memory addressed using the small base register ($sb).
+
+@item S1
+$r1h
+@end table
+
+@item LoongArch---@file{config/loongarch/constraints.md}
+@table @code
+@item f
+A floating-point register (if available).
+@item k
+A memory operand whose address is formed by a base register and
+(optionally scaled) index register.
+@item l
+A signed 16-bit constant.
+@item m
+A memory operand whose address is formed by a base register and offset
+that is suitable for use in instructions with the same addressing mode
+as @code{st.w} and @code{ld.w}.
+@item I
+A signed 12-bit constant (for arithmetic instructions).
+@item K
+An unsigned 12-bit constant (for logic instructions).
+@item ZB
+An address that is held in a general-purpose register.
+The offset is zero.
+@item ZC
+A memory operand whose address is formed by a base register and offset
+that is suitable for use in instructions with the same addressing mode
+as @code{ll.w} and @code{sc.w}.
+@end table
+
+@item MicroBlaze---@file{config/microblaze/constraints.md}
+@table @code
+@item d
+A general register (@code{r0} to @code{r31}).
+
+@item z
+A status register (@code{rmsr}, @code{$fcc1} to @code{$fcc7}).
+
+@end table
+
+@item MIPS---@file{config/mips/constraints.md}
+@table @code
+@item d
+A general-purpose register. This is equivalent to @code{r} unless
+generating MIPS16 code, in which case the MIPS16 register set is used.
+
+@item f
+A floating-point register (if available).
+
+@item h
+Formerly the @code{hi} register. This constraint is no longer supported.
+
+@item l
+The @code{lo} register. Use this register to store values that are
+no bigger than a word.
+
+@item x
+The concatenated @code{hi} and @code{lo} registers. Use this register
+to store doubleword values.
+
+@item c
+A register suitable for use in an indirect jump. This will always be
+@code{$25} for @option{-mabicalls}.
+
+@item v
+Register @code{$3}. Do not use this constraint in new code;
+it is retained only for compatibility with glibc.
+
+@item y
+Equivalent to @code{r}; retained for backwards compatibility.
+
+@item z
+A floating-point condition code register.
+
+@item I
+A signed 16-bit constant (for arithmetic instructions).
+
+@item J
+Integer zero.
+
+@item K
+An unsigned 16-bit constant (for logic instructions).
+
+@item L
+A signed 32-bit constant in which the lower 16 bits are zero.
+Such constants can be loaded using @code{lui}.
+
+@item M
+A constant that cannot be loaded using @code{lui}, @code{addiu}
+or @code{ori}.
+
+@item N
+A constant in the range @minus{}65535 to @minus{}1 (inclusive).
+
+@item O
+A signed 15-bit constant.
+
+@item P
+A constant in the range 1 to 65535 (inclusive).
+
+@item G
+Floating-point zero.
+
+@item R
+An address that can be used in a non-macro load or store.
+
+@item ZC
+A memory operand whose address is formed by a base register and offset
+that is suitable for use in instructions with the same addressing mode
+as @code{ll} and @code{sc}.
+
+@item ZD
+An address suitable for a @code{prefetch} instruction, or for any other
+instruction with the same addressing mode as @code{prefetch}.
+@end table
+
+@item Motorola 680x0---@file{config/m68k/constraints.md}
+@table @code
+@item a
+Address register
+
+@item d
+Data register
+
+@item f
+68881 floating-point register, if available
+
+@item I
+Integer in the range 1 to 8
+
+@item J
+16-bit signed number
+
+@item K
+Signed number whose magnitude is greater than 0x80
+
+@item L
+Integer in the range @minus{}8 to @minus{}1
+
+@item M
+Signed number whose magnitude is greater than 0x100
+
+@item N
+Range 24 to 31, rotatert:SI 8 to 1 expressed as rotate
+
+@item O
+16 (for rotate using swap)
+
+@item P
+Range 8 to 15, rotatert:HI 8 to 1 expressed as rotate
+
+@item R
+Numbers that mov3q can handle
+
+@item G
+Floating point constant that is not a 68881 constant
+
+@item S
+Operands that satisfy 'm' when -mpcrel is in effect
+
+@item T
+Operands that satisfy 's' when -mpcrel is not in effect
+
+@item Q
+Address register indirect addressing mode
+
+@item U
+Register offset addressing
+
+@item W
+const_call_operand
+
+@item Cs
+symbol_ref or const
+
+@item Ci
+const_int
+
+@item C0
+const_int 0
+
+@item Cj
+Range of signed numbers that don't fit in 16 bits
+
+@item Cmvq
+Integers valid for mvq
+
+@item Capsw
+Integers valid for a moveq followed by a swap
+
+@item Cmvz
+Integers valid for mvz
+
+@item Cmvs
+Integers valid for mvs
+
+@item Ap
+push_operand
+
+@item Ac
+Non-register operands allowed in clr
+
+@end table
+
+@item Moxie---@file{config/moxie/constraints.md}
+@table @code
+@item A
+An absolute address
+
+@item B
+An offset address
+
+@item W
+A register indirect memory operand
+
+@item I
+A constant in the range of 0 to 255.
+
+@item N
+A constant in the range of 0 to @minus{}255.
+
+@end table
+
+@item MSP430--@file{config/msp430/constraints.md}
+@table @code
+
+@item R12
+Register R12.
+
+@item R13
+Register R13.
+
+@item K
+Integer constant 1.
+
+@item L
+Integer constant -1^20..1^19.
+
+@item M
+Integer constant 1-4.
+
+@item Ya
+Memory references which do not require an extended MOVX instruction.
+
+@item Yl
+Memory reference, labels only.
+
+@item Ys
+Memory reference, stack only.
+
+@end table
+
+@item NDS32---@file{config/nds32/constraints.md}
+@table @code
+@item w
+LOW register class $r0 to $r7 constraint for V3/V3M ISA.
+@item l
+LOW register class $r0 to $r7.
+@item d
+MIDDLE register class $r0 to $r11, $r16 to $r19.
+@item h
+HIGH register class $r12 to $r14, $r20 to $r31.
+@item t
+Temporary assist register $ta (i.e.@: $r15).
+@item k
+Stack register $sp.
+@item Iu03
+Unsigned immediate 3-bit value.
+@item In03
+Negative immediate 3-bit value in the range of @minus{}7--0.
+@item Iu04
+Unsigned immediate 4-bit value.
+@item Is05
+Signed immediate 5-bit value.
+@item Iu05
+Unsigned immediate 5-bit value.
+@item In05
+Negative immediate 5-bit value in the range of @minus{}31--0.
+@item Ip05
+Unsigned immediate 5-bit value for movpi45 instruction with range 16--47.
+@item Iu06
+Unsigned immediate 6-bit value constraint for addri36.sp instruction.
+@item Iu08
+Unsigned immediate 8-bit value.
+@item Iu09
+Unsigned immediate 9-bit value.
+@item Is10
+Signed immediate 10-bit value.
+@item Is11
+Signed immediate 11-bit value.
+@item Is15
+Signed immediate 15-bit value.
+@item Iu15
+Unsigned immediate 15-bit value.
+@item Ic15
+A constant which is not in the range of imm15u but ok for bclr instruction.
+@item Ie15
+A constant which is not in the range of imm15u but ok for bset instruction.
+@item It15
+A constant which is not in the range of imm15u but ok for btgl instruction.
+@item Ii15
+A constant whose compliment value is in the range of imm15u
+and ok for bitci instruction.
+@item Is16
+Signed immediate 16-bit value.
+@item Is17
+Signed immediate 17-bit value.
+@item Is19
+Signed immediate 19-bit value.
+@item Is20
+Signed immediate 20-bit value.
+@item Ihig
+The immediate value that can be simply set high 20-bit.
+@item Izeb
+The immediate value 0xff.
+@item Izeh
+The immediate value 0xffff.
+@item Ixls
+The immediate value 0x01.
+@item Ix11
+The immediate value 0x7ff.
+@item Ibms
+The immediate value with power of 2.
+@item Ifex
+The immediate value with power of 2 minus 1.
+@item U33
+Memory constraint for 333 format.
+@item U45
+Memory constraint for 45 format.
+@item U37
+Memory constraint for 37 format.
+@end table
+
+@item Nios II family---@file{config/nios2/constraints.md}
+@table @code
+
+@item I
+Integer that is valid as an immediate operand in an
+instruction taking a signed 16-bit number. Range
+@minus{}32768 to 32767.
+
+@item J
+Integer that is valid as an immediate operand in an
+instruction taking an unsigned 16-bit number. Range
+0 to 65535.
+
+@item K
+Integer that is valid as an immediate operand in an
+instruction taking only the upper 16-bits of a
+32-bit number. Range 32-bit numbers with the lower
+16-bits being 0.
+
+@item L
+Integer that is valid as an immediate operand for a
+shift instruction. Range 0 to 31.
+
+@item M
+Integer that is valid as an immediate operand for
+only the value 0. Can be used in conjunction with
+the format modifier @code{z} to use @code{r0}
+instead of @code{0} in the assembly output.
+
+@item N
+Integer that is valid as an immediate operand for
+a custom instruction opcode. Range 0 to 255.
+
+@item P
+An immediate operand for R2 andchi/andci instructions.
+
+@item S
+Matches immediates which are addresses in the small
+data section and therefore can be added to @code{gp}
+as a 16-bit immediate to re-create their 32-bit value.
+
+@item U
+Matches constants suitable as an operand for the rdprs and
+cache instructions.
+
+@item v
+A memory operand suitable for Nios II R2 load/store
+exclusive instructions.
+
+@item w
+A memory operand suitable for load/store IO and cache
+instructions.
+
+@ifset INTERNALS
+@item T
+A @code{const} wrapped @code{UNSPEC} expression,
+representing a supported PIC or TLS relocation.
+@end ifset
+
+@end table
+
+@item OpenRISC---@file{config/or1k/constraints.md}
+@table @code
+@item I
+Integer that is valid as an immediate operand in an
+instruction taking a signed 16-bit number. Range
+@minus{}32768 to 32767.
+
+@item K
+Integer that is valid as an immediate operand in an
+instruction taking an unsigned 16-bit number. Range
+0 to 65535.
+
+@item M
+Signed 16-bit constant shifted left 16 bits. (Used with @code{l.movhi})
+
+@item O
+Zero
+
+@ifset INTERNALS
+@item c
+Register usable for sibcalls.
+@end ifset
+
+@end table
+
+@item PDP-11---@file{config/pdp11/constraints.md}
+@table @code
+@item a
+Floating point registers AC0 through AC3. These can be loaded from/to
+memory with a single instruction.
+
+@item d
+Odd numbered general registers (R1, R3, R5). These are used for
+16-bit multiply operations.
+
+@item D
+A memory reference that is encoded within the opcode, but not
+auto-increment or auto-decrement.
+
+@item f
+Any of the floating point registers (AC0 through AC5).
+
+@item G
+Floating point constant 0.
+
+@item h
+Floating point registers AC4 and AC5. These cannot be loaded from/to
+memory with a single instruction.
+
+@item I
+An integer constant that fits in 16 bits.
+
+@item J
+An integer constant whose low order 16 bits are zero.
+
+@item K
+An integer constant that does not meet the constraints for codes
+@samp{I} or @samp{J}.
+
+@item L
+The integer constant 1.
+
+@item M
+The integer constant @minus{}1.
+
+@item N
+The integer constant 0.
+
+@item O
+Integer constants 0 through 3; shifts by these
+amounts are handled as multiple single-bit shifts rather than a single
+variable-length shift.
+
+@item Q
+A memory reference which requires an additional word (address or
+offset) after the opcode.
+
+@item R
+A memory reference that is encoded within the opcode.
+
+@end table
+
+@item PowerPC and IBM RS6000---@file{config/rs6000/constraints.md}
+@table @code
+@item r
+A general purpose register (GPR), @code{r0}@dots{}@code{r31}.
+
+@item b
+A base register. Like @code{r}, but @code{r0} is not allowed, so
+@code{r1}@dots{}@code{r31}.
+
+@item f
+A floating point register (FPR), @code{f0}@dots{}@code{f31}.
+
+@item d
+A floating point register. This is the same as @code{f} nowadays;
+historically @code{f} was for single-precision and @code{d} was for
+double-precision floating point.
+
+@item v
+An Altivec vector register (VR), @code{v0}@dots{}@code{v31}.
+
+@item wa
+A VSX register (VSR), @code{vs0}@dots{}@code{vs63}. This is either an
+FPR (@code{vs0}@dots{}@code{vs31} are @code{f0}@dots{}@code{f31}) or a VR
+(@code{vs32}@dots{}@code{vs63} are @code{v0}@dots{}@code{v31}).
+
+When using @code{wa}, you should use the @code{%x} output modifier, so that
+the correct register number is printed. For example:
+
+@smallexample
+asm ("xvadddp %x0,%x1,%x2"
+ : "=wa" (v1)
+ : "wa" (v2), "wa" (v3));
+@end smallexample
+
+You should not use @code{%x} for @code{v} operands:
+
+@smallexample
+asm ("xsaddqp %0,%1,%2"
+ : "=v" (v1)
+ : "v" (v2), "v" (v3));
+@end smallexample
+
+@ifset INTERNALS
+@item h
+A special register (@code{vrsave}, @code{ctr}, or @code{lr}).
+@end ifset
+
+@item c
+The count register, @code{ctr}.
+
+@item l
+The link register, @code{lr}.
+
+@item x
+Condition register field 0, @code{cr0}.
+
+@item y
+Any condition register field, @code{cr0}@dots{}@code{cr7}.
+
+@ifset INTERNALS
+@item z
+The carry bit, @code{XER[CA]}.
+
+@item we
+Like @code{wa}, if @option{-mpower9-vector} and @option{-m64} are used;
+otherwise, @code{NO_REGS}.
+
+@item wn
+No register (@code{NO_REGS}).
+
+@item wr
+Like @code{r}, if @option{-mpowerpc64} is used; otherwise, @code{NO_REGS}.
+
+@item wx
+Like @code{d}, if @option{-mpowerpc-gfxopt} is used; otherwise, @code{NO_REGS}.
+
+@item wA
+Like @code{b}, if @option{-mpowerpc64} is used; otherwise, @code{NO_REGS}.
+
+@item wB
+Signed 5-bit constant integer that can be loaded into an Altivec register.
+
+@item wE
+Vector constant that can be loaded with the XXSPLTIB instruction.
+
+@item wF
+Memory operand suitable for power8 GPR load fusion.
+
+@item wL
+Int constant that is the element number mfvsrld accesses in a vector.
+
+@item wM
+Match vector constant with all 1's if the XXLORC instruction is available.
+
+@item wO
+Memory operand suitable for the ISA 3.0 vector d-form instructions.
+
+@item wQ
+Memory operand suitable for the load/store quad instructions.
+
+@item wS
+Vector constant that can be loaded with XXSPLTIB & sign extension.
+
+@item wY
+A memory operand for a DS-form instruction.
+
+@item wZ
+An indexed or indirect memory operand, ignoring the bottom 4 bits.
+@end ifset
+
+@item I
+A signed 16-bit constant.
+
+@item J
+An unsigned 16-bit constant shifted left 16 bits (use @code{L} instead
+for @code{SImode} constants).
+
+@item K
+An unsigned 16-bit constant.
+
+@item L
+A signed 16-bit constant shifted left 16 bits.
+
+@ifset INTERNALS
+@item M
+An integer constant greater than 31.
+
+@item N
+An exact power of 2.
+
+@item O
+The integer constant zero.
+
+@item P
+A constant whose negation is a signed 16-bit constant.
+@end ifset
+
+@item eI
+A signed 34-bit integer constant if prefixed instructions are supported.
+
+@item eP
+A scalar floating point constant or a vector constant that can be
+loaded to a VSX register with one prefixed instruction.
+
+@item eQ
+An IEEE 128-bit constant that can be loaded into a VSX register with
+the @code{lxvkq} instruction.
+
+@ifset INTERNALS
+@item G
+A floating point constant that can be loaded into a register with one
+instruction per word.
+
+@item H
+A floating point constant that can be loaded into a register using
+three instructions.
+@end ifset
+
+@item m
+A memory operand.
+Normally, @code{m} does not allow addresses that update the base register.
+If the @code{<} or @code{>} constraint is also used, they are allowed and
+therefore on PowerPC targets in that case it is only safe
+to use @code{m<>} in an @code{asm} statement if that @code{asm} statement
+accesses the operand exactly once. The @code{asm} statement must also
+use @code{%U@var{<opno>}} as a placeholder for the ``update'' flag in the
+corresponding load or store instruction. For example:
+
+@smallexample
+asm ("st%U0 %1,%0" : "=m<>" (mem) : "r" (val));
+@end smallexample
+
+is correct but:
+
+@smallexample
+asm ("st %1,%0" : "=m<>" (mem) : "r" (val));
+@end smallexample
+
+is not.
+
+@ifset INTERNALS
+@item es
+A ``stable'' memory operand; that is, one which does not include any
+automodification of the base register. This used to be useful when
+@code{m} allowed automodification of the base register, but as those
+are now only allowed when @code{<} or @code{>} is used, @code{es} is
+basically the same as @code{m} without @code{<} and @code{>}.
+@end ifset
+
+@item Q
+A memory operand addressed by just a base register.
+
+@ifset INTERNALS
+@item Y
+A memory operand for a DQ-form instruction.
+@end ifset
+
+@item Z
+A memory operand accessed with indexed or indirect addressing.
+
+@ifset INTERNALS
+@item R
+An AIX TOC entry.
+@end ifset
+
+@item a
+An indexed or indirect address.
+
+@ifset INTERNALS
+@item U
+A V.4 small data reference.
+
+@item W
+A vector constant that does not require memory.
+
+@item j
+The zero vector constant.
+@end ifset
+
+@end table
+
+@item PRU---@file{config/pru/constraints.md}
+@table @code
+@item I
+An unsigned 8-bit integer constant.
+
+@item J
+An unsigned 16-bit integer constant.
+
+@item L
+An unsigned 5-bit integer constant (for shift counts).
+
+@item T
+A text segment (program memory) constant label.
+
+@item Z
+Integer constant zero.
+
+@end table
+
+@item RL78---@file{config/rl78/constraints.md}
+@table @code
+
+@item Int3
+An integer constant in the range 1 @dots{} 7.
+@item Int8
+An integer constant in the range 0 @dots{} 255.
+@item J
+An integer constant in the range @minus{}255 @dots{} 0
+@item K
+The integer constant 1.
+@item L
+The integer constant -1.
+@item M
+The integer constant 0.
+@item N
+The integer constant 2.
+@item O
+The integer constant -2.
+@item P
+An integer constant in the range 1 @dots{} 15.
+@item Qbi
+The built-in compare types--eq, ne, gtu, ltu, geu, and leu.
+@item Qsc
+The synthetic compare types--gt, lt, ge, and le.
+@item Wab
+A memory reference with an absolute address.
+@item Wbc
+A memory reference using @code{BC} as a base register, with an optional offset.
+@item Wca
+A memory reference using @code{AX}, @code{BC}, @code{DE}, or @code{HL} for the address, for calls.
+@item Wcv
+A memory reference using any 16-bit register pair for the address, for calls.
+@item Wd2
+A memory reference using @code{DE} as a base register, with an optional offset.
+@item Wde
+A memory reference using @code{DE} as a base register, without any offset.
+@item Wfr
+Any memory reference to an address in the far address space.
+@item Wh1
+A memory reference using @code{HL} as a base register, with an optional one-byte offset.
+@item Whb
+A memory reference using @code{HL} as a base register, with @code{B} or @code{C} as the index register.
+@item Whl
+A memory reference using @code{HL} as a base register, without any offset.
+@item Ws1
+A memory reference using @code{SP} as a base register, with an optional one-byte offset.
+@item Y
+Any memory reference to an address in the near address space.
+@item A
+The @code{AX} register.
+@item B
+The @code{BC} register.
+@item D
+The @code{DE} register.
+@item R
+@code{A} through @code{L} registers.
+@item S
+The @code{SP} register.
+@item T
+The @code{HL} register.
+@item Z08W
+The 16-bit @code{R8} register.
+@item Z10W
+The 16-bit @code{R10} register.
+@item Zint
+The registers reserved for interrupts (@code{R24} to @code{R31}).
+@item a
+The @code{A} register.
+@item b
+The @code{B} register.
+@item c
+The @code{C} register.
+@item d
+The @code{D} register.
+@item e
+The @code{E} register.
+@item h
+The @code{H} register.
+@item l
+The @code{L} register.
+@item v
+The virtual registers.
+@item w
+The @code{PSW} register.
+@item x
+The @code{X} register.
+
+@end table
+
+@item RISC-V---@file{config/riscv/constraints.md}
+@table @code
+
+@item f
+A floating-point register (if available).
+
+@item I
+An I-type 12-bit signed immediate.
+
+@item J
+Integer zero.
+
+@item K
+A 5-bit unsigned immediate for CSR access instructions.
+
+@item A
+An address that is held in a general-purpose register.
+
+@item S
+A constraint that matches an absolute symbolic address.
+
+@end table
+
+@item RX---@file{config/rx/constraints.md}
+@table @code
+@item Q
+An address which does not involve register indirect addressing or
+pre/post increment/decrement addressing.
+
+@item Symbol
+A symbol reference.
+
+@item Int08
+A constant in the range @minus{}256 to 255, inclusive.
+
+@item Sint08
+A constant in the range @minus{}128 to 127, inclusive.
+
+@item Sint16
+A constant in the range @minus{}32768 to 32767, inclusive.
+
+@item Sint24
+A constant in the range @minus{}8388608 to 8388607, inclusive.
+
+@item Uint04
+A constant in the range 0 to 15, inclusive.
+
+@end table
+
+@item S/390 and zSeries---@file{config/s390/s390.h}
+@table @code
+@item a
+Address register (general purpose register except r0)
+
+@item c
+Condition code register
+
+@item d
+Data register (arbitrary general purpose register)
+
+@item f
+Floating-point register
+
+@item I
+Unsigned 8-bit constant (0--255)
+
+@item J
+Unsigned 12-bit constant (0--4095)
+
+@item K
+Signed 16-bit constant (@minus{}32768--32767)
+
+@item L
+Value appropriate as displacement.
+@table @code
+@item (0..4095)
+for short displacement
+@item (@minus{}524288..524287)
+for long displacement
+@end table
+
+@item M
+Constant integer with a value of 0x7fffffff.
+
+@item N
+Multiple letter constraint followed by 4 parameter letters.
+@table @code
+@item 0..9:
+number of the part counting from most to least significant
+@item H,Q:
+mode of the part
+@item D,S,H:
+mode of the containing operand
+@item 0,F:
+value of the other parts (F---all bits set)
+@end table
+The constraint matches if the specified part of a constant
+has a value different from its other parts.
+
+@item Q
+Memory reference without index register and with short displacement.
+
+@item R
+Memory reference with index register and short displacement.
+
+@item S
+Memory reference without index register but with long displacement.
+
+@item T
+Memory reference with index register and long displacement.
+
+@item U
+Pointer with short displacement.
+
+@item W
+Pointer with long displacement.
+
+@item Y
+Shift count operand.
+
+@end table
+
+@need 1000
+@item SPARC---@file{config/sparc/sparc.h}
+@table @code
+@item f
+Floating-point register on the SPARC-V8 architecture and
+lower floating-point register on the SPARC-V9 architecture.
+
+@item e
+Floating-point register. It is equivalent to @samp{f} on the
+SPARC-V8 architecture and contains both lower and upper
+floating-point registers on the SPARC-V9 architecture.
+
+@item c
+Floating-point condition code register.
+
+@item d
+Lower floating-point register. It is only valid on the SPARC-V9
+architecture when the Visual Instruction Set is available.
+
+@item b
+Floating-point register. It is only valid on the SPARC-V9 architecture
+when the Visual Instruction Set is available.
+
+@item h
+64-bit global or out register for the SPARC-V8+ architecture.
+
+@item C
+The constant all-ones, for floating-point.
+
+@item A
+Signed 5-bit constant
+
+@item D
+A vector constant
+
+@item I
+Signed 13-bit constant
+
+@item J
+Zero
+
+@item K
+32-bit constant with the low 12 bits clear (a constant that can be
+loaded with the @code{sethi} instruction)
+
+@item L
+A constant in the range supported by @code{movcc} instructions (11-bit
+signed immediate)
+
+@item M
+A constant in the range supported by @code{movrcc} instructions (10-bit
+signed immediate)
+
+@item N
+Same as @samp{K}, except that it verifies that bits that are not in the
+lower 32-bit range are all zero. Must be used instead of @samp{K} for
+modes wider than @code{SImode}
+
+@item O
+The constant 4096
+
+@item G
+Floating-point zero
+
+@item H
+Signed 13-bit constant, sign-extended to 32 or 64 bits
+
+@item P
+The constant -1
+
+@item Q
+Floating-point constant whose integral representation can
+be moved into an integer register using a single sethi
+instruction
+
+@item R
+Floating-point constant whose integral representation can
+be moved into an integer register using a single mov
+instruction
+
+@item S
+Floating-point constant whose integral representation can
+be moved into an integer register using a high/lo_sum
+instruction sequence
+
+@item T
+Memory address aligned to an 8-byte boundary
+
+@item U
+Even register
+
+@item W
+Memory address for @samp{e} constraint registers
+
+@item w
+Memory address with only a base register
+
+@item Y
+Vector zero
+
+@end table
+
+@item TI C6X family---@file{config/c6x/constraints.md}
+@table @code
+@item a
+Register file A (A0--A31).
+
+@item b
+Register file B (B0--B31).
+
+@item A
+Predicate registers in register file A (A0--A2 on C64X and
+higher, A1 and A2 otherwise).
+
+@item B
+Predicate registers in register file B (B0--B2).
+
+@item C
+A call-used register in register file B (B0--B9, B16--B31).
+
+@item Da
+Register file A, excluding predicate registers (A3--A31,
+plus A0 if not C64X or higher).
+
+@item Db
+Register file B, excluding predicate registers (B3--B31).
+
+@item Iu4
+Integer constant in the range 0 @dots{} 15.
+
+@item Iu5
+Integer constant in the range 0 @dots{} 31.
+
+@item In5
+Integer constant in the range @minus{}31 @dots{} 0.
+
+@item Is5
+Integer constant in the range @minus{}16 @dots{} 15.
+
+@item I5x
+Integer constant that can be the operand of an ADDA or a SUBA insn.
+
+@item IuB
+Integer constant in the range 0 @dots{} 65535.
+
+@item IsB
+Integer constant in the range @minus{}32768 @dots{} 32767.
+
+@item IsC
+Integer constant in the range @math{-2^{20}} @dots{} @math{2^{20} - 1}.
+
+@item Jc
+Integer constant that is a valid mask for the clr instruction.
+
+@item Js
+Integer constant that is a valid mask for the set instruction.
+
+@item Q
+Memory location with A base register.
+
+@item R
+Memory location with B base register.
+
+@ifset INTERNALS
+@item S0
+On C64x+ targets, a GP-relative small data reference.
+
+@item S1
+Any kind of @code{SYMBOL_REF}, for use in a call address.
+
+@item Si
+Any kind of immediate operand, unless it matches the S0 constraint.
+
+@item T
+Memory location with B base register, but not using a long offset.
+
+@item W
+A memory operand with an address that cannot be used in an unaligned access.
+
+@end ifset
+@item Z
+Register B14 (aka DP).
+
+@end table
+
+@item Visium---@file{config/visium/constraints.md}
+@table @code
+@item b
+EAM register @code{mdb}
+
+@item c
+EAM register @code{mdc}
+
+@item f
+Floating point register
+
+@ifset INTERNALS
+@item k
+Register for sibcall optimization
+@end ifset
+
+@item l
+General register, but not @code{r29}, @code{r30} and @code{r31}
+
+@item t
+Register @code{r1}
+
+@item u
+Register @code{r2}
+
+@item v
+Register @code{r3}
+
+@item G
+Floating-point constant 0.0
+
+@item J
+Integer constant in the range 0 .. 65535 (16-bit immediate)
+
+@item K
+Integer constant in the range 1 .. 31 (5-bit immediate)
+
+@item L
+Integer constant in the range @minus{}65535 .. @minus{}1 (16-bit negative immediate)
+
+@item M
+Integer constant @minus{}1
+
+@item O
+Integer constant 0
+
+@item P
+Integer constant 32
+@end table
+
+@item x86 family---@file{config/i386/constraints.md}
+@table @code
+@item R
+Legacy register---the eight integer registers available on all
+i386 processors (@code{a}, @code{b}, @code{c}, @code{d},
+@code{si}, @code{di}, @code{bp}, @code{sp}).
+
+@item q
+Any register accessible as @code{@var{r}l}. In 32-bit mode, @code{a},
+@code{b}, @code{c}, and @code{d}; in 64-bit mode, any integer register.
+
+@item Q
+Any register accessible as @code{@var{r}h}: @code{a}, @code{b},
+@code{c}, and @code{d}.
+
+@ifset INTERNALS
+@item l
+Any register that can be used as the index in a base+index memory
+access: that is, any general register except the stack pointer.
+@end ifset
+
+@item a
+The @code{a} register.
+
+@item b
+The @code{b} register.
+
+@item c
+The @code{c} register.
+
+@item d
+The @code{d} register.
+
+@item S
+The @code{si} register.
+
+@item D
+The @code{di} register.
+
+@item A
+The @code{a} and @code{d} registers. This class is used for instructions
+that return double word results in the @code{ax:dx} register pair. Single
+word values will be allocated either in @code{ax} or @code{dx}.
+For example on i386 the following implements @code{rdtsc}:
+
+@smallexample
+unsigned long long rdtsc (void)
+@{
+ unsigned long long tick;
+ __asm__ __volatile__("rdtsc":"=A"(tick));
+ return tick;
+@}
+@end smallexample
+
+This is not correct on x86-64 as it would allocate tick in either @code{ax}
+or @code{dx}. You have to use the following variant instead:
+
+@smallexample
+unsigned long long rdtsc (void)
+@{
+ unsigned int tickl, tickh;
+ __asm__ __volatile__("rdtsc":"=a"(tickl),"=d"(tickh));
+ return ((unsigned long long)tickh << 32)|tickl;
+@}
+@end smallexample
+
+@item U
+The call-clobbered integer registers.
+
+@item f
+Any 80387 floating-point (stack) register.
+
+@item t
+Top of 80387 floating-point stack (@code{%st(0)}).
+
+@item u
+Second from top of 80387 floating-point stack (@code{%st(1)}).
+
+@ifset INTERNALS
+@item Yk
+Any mask register that can be used as a predicate, i.e.@: @code{k1-k7}.
+
+@item k
+Any mask register.
+@end ifset
+
+@item y
+Any MMX register.
+
+@item x
+Any SSE register.
+
+@item v
+Any EVEX encodable SSE register (@code{%xmm0-%xmm31}).
+
+@ifset INTERNALS
+@item w
+Any bound register.
+@end ifset
+
+@item Yz
+First SSE register (@code{%xmm0}).
+
+@ifset INTERNALS
+@item Yi
+Any SSE register, when SSE2 and inter-unit moves are enabled.
+
+@item Yj
+Any SSE register, when SSE2 and inter-unit moves from vector registers are enabled.
+
+@item Ym
+Any MMX register, when inter-unit moves are enabled.
+
+@item Yn
+Any MMX register, when inter-unit moves from vector registers are enabled.
+
+@item Yp
+Any integer register when @code{TARGET_PARTIAL_REG_STALL} is disabled.
+
+@item Ya
+Any integer register when zero extensions with @code{AND} are disabled.
+
+@item Yb
+Any register that can be used as the GOT base when calling@*
+@code{___tls_get_addr}: that is, any general register except @code{a}
+and @code{sp} registers, for @option{-fno-plt} if linker supports it.
+Otherwise, @code{b} register.
+
+@item Yf
+Any x87 register when 80387 floating-point arithmetic is enabled.
+
+@item Yr
+Lower SSE register when avoiding REX prefix and all SSE registers otherwise.
+
+@item Yv
+For AVX512VL, any EVEX-encodable SSE register (@code{%xmm0-%xmm31}),
+otherwise any SSE register.
+
+@item Yh
+Any EVEX-encodable SSE register, that has number factor of four.
+
+@item Bf
+Flags register operand.
+
+@item Bg
+GOT memory operand.
+
+@item Bm
+Vector memory operand.
+
+@item Bc
+Constant memory operand.
+
+@item Bn
+Memory operand without REX prefix.
+
+@item Bs
+Sibcall memory operand.
+
+@item Bw
+Call memory operand.
+
+@item Bz
+Constant call address operand.
+
+@item BC
+SSE constant -1 operand.
+@end ifset
+
+@item I
+Integer constant in the range 0 @dots{} 31, for 32-bit shifts.
+
+@item J
+Integer constant in the range 0 @dots{} 63, for 64-bit shifts.
+
+@item K
+Signed 8-bit integer constant.
+
+@item L
+@code{0xFF} or @code{0xFFFF}, for andsi as a zero-extending move.
+
+@item M
+0, 1, 2, or 3 (shifts for the @code{lea} instruction).
+
+@item N
+Unsigned 8-bit integer constant (for @code{in} and @code{out}
+instructions).
+
+@ifset INTERNALS
+@item O
+Integer constant in the range 0 @dots{} 127, for 128-bit shifts.
+@end ifset
+
+@item G
+Standard 80387 floating point constant.
+
+@item C
+SSE constant zero operand.
+
+@item e
+32-bit signed integer constant, or a symbolic reference known
+to fit that range (for immediate operands in sign-extending x86-64
+instructions).
+
+@item We
+32-bit signed integer constant, or a symbolic reference known
+to fit that range (for sign-extending conversion operations that
+require non-@code{VOIDmode} immediate operands).
+
+@item Wz
+32-bit unsigned integer constant, or a symbolic reference known
+to fit that range (for zero-extending conversion operations that
+require non-@code{VOIDmode} immediate operands).
+
+@item Wd
+128-bit integer constant where both the high and low 64-bit word
+satisfy the @code{e} constraint.
+
+@item Z
+32-bit unsigned integer constant, or a symbolic reference known
+to fit that range (for immediate operands in zero-extending x86-64
+instructions).
+
+@item Tv
+VSIB address operand.
+
+@item Ts
+Address operand without segment register.
+
+@end table
+
+@item Xstormy16---@file{config/stormy16/stormy16.h}
+@table @code
+@item a
+Register r0.
+
+@item b
+Register r1.
+
+@item c
+Register r2.
+
+@item d
+Register r8.
+
+@item e
+Registers r0 through r7.
+
+@item t
+Registers r0 and r1.
+
+@item y
+The carry register.
+
+@item z
+Registers r8 and r9.
+
+@item I
+A constant between 0 and 3 inclusive.
+
+@item J
+A constant that has exactly one bit set.
+
+@item K
+A constant that has exactly one bit clear.
+
+@item L
+A constant between 0 and 255 inclusive.
+
+@item M
+A constant between @minus{}255 and 0 inclusive.
+
+@item N
+A constant between @minus{}3 and 0 inclusive.
+
+@item O
+A constant between 1 and 4 inclusive.
+
+@item P
+A constant between @minus{}4 and @minus{}1 inclusive.
+
+@item Q
+A memory reference that is a stack push.
+
+@item R
+A memory reference that is a stack pop.
+
+@item S
+A memory reference that refers to a constant address of known value.
+
+@item T
+The register indicated by Rx (not implemented yet).
+
+@item U
+A constant that is not between 2 and 15 inclusive.
+
+@item Z
+The constant 0.
+
+@end table
+
+@item Xtensa---@file{config/xtensa/constraints.md}
+@table @code
+@item a
+General-purpose 32-bit register
+
+@item b
+One-bit boolean register
+
+@item A
+MAC16 40-bit accumulator register
+
+@item I
+Signed 12-bit integer constant, for use in MOVI instructions
+
+@item J
+Signed 8-bit integer constant, for use in ADDI instructions
+
+@item K
+Integer constant valid for BccI instructions
+
+@item L
+Unsigned constant valid for BccUI instructions
+
+@end table
+
+@end table
+
+@ifset INTERNALS
+@node Disable Insn Alternatives
+@subsection Disable insn alternatives using the @code{enabled} attribute
+@cindex enabled
+
+There are three insn attributes that may be used to selectively disable
+instruction alternatives:
+
+@table @code
+@item enabled
+Says whether an alternative is available on the current subtarget.
+
+@item preferred_for_size
+Says whether an enabled alternative should be used in code that is
+optimized for size.
+
+@item preferred_for_speed
+Says whether an enabled alternative should be used in code that is
+optimized for speed.
+@end table
+
+All these attributes should use @code{(const_int 1)} to allow an alternative
+or @code{(const_int 0)} to disallow it. The attributes must be a static
+property of the subtarget; they cannot for example depend on the
+current operands, on the current optimization level, on the location
+of the insn within the body of a loop, on whether register allocation
+has finished, or on the current compiler pass.
+
+The @code{enabled} attribute is a correctness property. It tells GCC to act
+as though the disabled alternatives were never defined in the first place.
+This is useful when adding new instructions to an existing pattern in
+cases where the new instructions are only available for certain cpu
+architecture levels (typically mapped to the @code{-march=} command-line
+option).
+
+In contrast, the @code{preferred_for_size} and @code{preferred_for_speed}
+attributes are strong optimization hints rather than correctness properties.
+@code{preferred_for_size} tells GCC which alternatives to consider when
+adding or modifying an instruction that GCC wants to optimize for size.
+@code{preferred_for_speed} does the same thing for speed. Note that things
+like code motion can lead to cases where code optimized for size uses
+alternatives that are not preferred for size, and similarly for speed.
+
+Although @code{define_insn}s can in principle specify the @code{enabled}
+attribute directly, it is often clearer to have subsiduary attributes
+for each architectural feature of interest. The @code{define_insn}s
+can then use these subsiduary attributes to say which alternatives
+require which features. The example below does this for @code{cpu_facility}.
+
+E.g. the following two patterns could easily be merged using the @code{enabled}
+attribute:
+
+@smallexample
+
+(define_insn "*movdi_old"
+ [(set (match_operand:DI 0 "register_operand" "=d")
+ (match_operand:DI 1 "register_operand" " d"))]
+ "!TARGET_NEW"
+ "lgr %0,%1")
+
+(define_insn "*movdi_new"
+ [(set (match_operand:DI 0 "register_operand" "=d,f,d")
+ (match_operand:DI 1 "register_operand" " d,d,f"))]
+ "TARGET_NEW"
+ "@@
+ lgr %0,%1
+ ldgr %0,%1
+ lgdr %0,%1")
+
+@end smallexample
+
+to:
+
+@smallexample
+
+(define_insn "*movdi_combined"
+ [(set (match_operand:DI 0 "register_operand" "=d,f,d")
+ (match_operand:DI 1 "register_operand" " d,d,f"))]
+ ""
+ "@@
+ lgr %0,%1
+ ldgr %0,%1
+ lgdr %0,%1"
+ [(set_attr "cpu_facility" "*,new,new")])
+
+@end smallexample
+
+with the @code{enabled} attribute defined like this:
+
+@smallexample
+
+(define_attr "cpu_facility" "standard,new" (const_string "standard"))
+
+(define_attr "enabled" ""
+ (cond [(eq_attr "cpu_facility" "standard") (const_int 1)
+ (and (eq_attr "cpu_facility" "new")
+ (ne (symbol_ref "TARGET_NEW") (const_int 0)))
+ (const_int 1)]
+ (const_int 0)))
+
+@end smallexample
+
+@end ifset
+
+@ifset INTERNALS
+@node Define Constraints
+@subsection Defining Machine-Specific Constraints
+@cindex defining constraints
+@cindex constraints, defining
+
+Machine-specific constraints fall into two categories: register and
+non-register constraints. Within the latter category, constraints
+which allow subsets of all possible memory or address operands should
+be specially marked, to give @code{reload} more information.
+
+Machine-specific constraints can be given names of arbitrary length,
+but they must be entirely composed of letters, digits, underscores
+(@samp{_}), and angle brackets (@samp{< >}). Like C identifiers, they
+must begin with a letter or underscore.
+
+In order to avoid ambiguity in operand constraint strings, no
+constraint can have a name that begins with any other constraint's
+name. For example, if @code{x} is defined as a constraint name,
+@code{xy} may not be, and vice versa. As a consequence of this rule,
+no constraint may begin with one of the generic constraint letters:
+@samp{E F V X g i m n o p r s}.
+
+Register constraints correspond directly to register classes.
+@xref{Register Classes}. There is thus not much flexibility in their
+definitions.
+
+@deffn {MD Expression} define_register_constraint name regclass docstring
+All three arguments are string constants.
+@var{name} is the name of the constraint, as it will appear in
+@code{match_operand} expressions. If @var{name} is a multi-letter
+constraint its length shall be the same for all constraints starting
+with the same letter. @var{regclass} can be either the
+name of the corresponding register class (@pxref{Register Classes}),
+or a C expression which evaluates to the appropriate register class.
+If it is an expression, it must have no side effects, and it cannot
+look at the operand. The usual use of expressions is to map some
+register constraints to @code{NO_REGS} when the register class
+is not available on a given subarchitecture.
+
+@var{docstring} is a sentence documenting the meaning of the
+constraint. Docstrings are explained further below.
+@end deffn
+
+Non-register constraints are more like predicates: the constraint
+definition gives a boolean expression which indicates whether the
+constraint matches.
+
+@deffn {MD Expression} define_constraint name docstring exp
+The @var{name} and @var{docstring} arguments are the same as for
+@code{define_register_constraint}, but note that the docstring comes
+immediately after the name for these expressions. @var{exp} is an RTL
+expression, obeying the same rules as the RTL expressions in predicate
+definitions. @xref{Defining Predicates}, for details. If it
+evaluates true, the constraint matches; if it evaluates false, it
+doesn't. Constraint expressions should indicate which RTL codes they
+might match, just like predicate expressions.
+
+@code{match_test} C expressions have access to the
+following variables:
+
+@table @var
+@item op
+The RTL object defining the operand.
+@item mode
+The machine mode of @var{op}.
+@item ival
+@samp{INTVAL (@var{op})}, if @var{op} is a @code{const_int}.
+@item hval
+@samp{CONST_DOUBLE_HIGH (@var{op})}, if @var{op} is an integer
+@code{const_double}.
+@item lval
+@samp{CONST_DOUBLE_LOW (@var{op})}, if @var{op} is an integer
+@code{const_double}.
+@item rval
+@samp{CONST_DOUBLE_REAL_VALUE (@var{op})}, if @var{op} is a floating-point
+@code{const_double}.
+@end table
+
+The @var{*val} variables should only be used once another piece of the
+expression has verified that @var{op} is the appropriate kind of RTL
+object.
+@end deffn
+
+Most non-register constraints should be defined with
+@code{define_constraint}. The remaining two definition expressions
+are only appropriate for constraints that should be handled specially
+by @code{reload} if they fail to match.
+
+@deffn {MD Expression} define_memory_constraint name docstring exp
+Use this expression for constraints that match a subset of all memory
+operands: that is, @code{reload} can make them match by converting the
+operand to the form @samp{@w{(mem (reg @var{X}))}}, where @var{X} is a
+base register (from the register class specified by
+@code{BASE_REG_CLASS}, @pxref{Register Classes}).
+
+For example, on the S/390, some instructions do not accept arbitrary
+memory references, but only those that do not make use of an index
+register. The constraint letter @samp{Q} is defined to represent a
+memory address of this type. If @samp{Q} is defined with
+@code{define_memory_constraint}, a @samp{Q} constraint can handle any
+memory operand, because @code{reload} knows it can simply copy the
+memory address into a base register if required. This is analogous to
+the way an @samp{o} constraint can handle any memory operand.
+
+The syntax and semantics are otherwise identical to
+@code{define_constraint}.
+@end deffn
+
+@deffn {MD Expression} define_special_memory_constraint name docstring exp
+Use this expression for constraints that match a subset of all memory
+operands: that is, @code{reload} cannot make them match by reloading
+the address as it is described for @code{define_memory_constraint} or
+such address reload is undesirable with the performance point of view.
+
+For example, @code{define_special_memory_constraint} can be useful if
+specifically aligned memory is necessary or desirable for some insn
+operand.
+
+The syntax and semantics are otherwise identical to
+@code{define_memory_constraint}.
+@end deffn
+
+@deffn {MD Expression} define_relaxed_memory_constraint name docstring exp
+The test expression in a @code{define_memory_constraint} can assume
+that @code{TARGET_LEGITIMATE_ADDRESS_P} holds for the address inside
+a @code{mem} rtx and so it does not need to test this condition itself.
+In other words, a @code{define_memory_constraint} test of the form:
+
+@smallexample
+(match_test "mem")
+@end smallexample
+
+is enough to test whether an rtx is a @code{mem} @emph{and} whether
+its address satisfies @code{TARGET_MEM_CONSTRAINT} (which is usually
+@samp{'m'}). Thus the conditions imposed by a @code{define_memory_constraint}
+always apply on top of the conditions imposed by @code{TARGET_MEM_CONSTRAINT}.
+
+However, it is sometimes useful to define memory constraints that allow
+addresses beyond those accepted by @code{TARGET_LEGITIMATE_ADDRESS_P}.
+@code{define_relaxed_memory_constraint} exists for this case.
+The test expression in a @code{define_relaxed_memory_constraint} is
+applied with no preconditions, so that the expression can determine
+``from scratch'' exactly which addresses are valid and which are not.
+
+The syntax and semantics are otherwise identical to
+@code{define_memory_constraint}.
+@end deffn
+
+@deffn {MD Expression} define_address_constraint name docstring exp
+Use this expression for constraints that match a subset of all address
+operands: that is, @code{reload} can make the constraint match by
+converting the operand to the form @samp{@w{(reg @var{X})}}, again
+with @var{X} a base register.
+
+Constraints defined with @code{define_address_constraint} can only be
+used with the @code{address_operand} predicate, or machine-specific
+predicates that work the same way. They are treated analogously to
+the generic @samp{p} constraint.
+
+The syntax and semantics are otherwise identical to
+@code{define_constraint}.
+@end deffn
+
+For historical reasons, names beginning with the letters @samp{G H}
+are reserved for constraints that match only @code{const_double}s, and
+names beginning with the letters @samp{I J K L M N O P} are reserved
+for constraints that match only @code{const_int}s. This may change in
+the future. For the time being, constraints with these names must be
+written in a stylized form, so that @code{genpreds} can tell you did
+it correctly:
+
+@smallexample
+@group
+(define_constraint "[@var{GHIJKLMNOP}]@dots{}"
+ "@var{doc}@dots{}"
+ (and (match_code "const_int") ; @r{@code{const_double} for G/H}
+ @var{condition}@dots{})) ; @r{usually a @code{match_test}}
+@end group
+@end smallexample
+@c the semicolons line up in the formatted manual
+
+It is fine to use names beginning with other letters for constraints
+that match @code{const_double}s or @code{const_int}s.
+
+Each docstring in a constraint definition should be one or more complete
+sentences, marked up in Texinfo format. @emph{They are currently unused.}
+In the future they will be copied into the GCC manual, in @ref{Machine
+Constraints}, replacing the hand-maintained tables currently found in
+that section. Also, in the future the compiler may use this to give
+more helpful diagnostics when poor choice of @code{asm} constraints
+causes a reload failure.
+
+If you put the pseudo-Texinfo directive @samp{@@internal} at the
+beginning of a docstring, then (in the future) it will appear only in
+the internals manual's version of the machine-specific constraint tables.
+Use this for constraints that should not appear in @code{asm} statements.
+
+@node C Constraint Interface
+@subsection Testing constraints from C
+@cindex testing constraints
+@cindex constraints, testing
+
+It is occasionally useful to test a constraint from C code rather than
+implicitly via the constraint string in a @code{match_operand}. The
+generated file @file{tm_p.h} declares a few interfaces for working
+with constraints. At present these are defined for all constraints
+except @code{g} (which is equivalent to @code{general_operand}).
+
+Some valid constraint names are not valid C identifiers, so there is a
+mangling scheme for referring to them from C@. Constraint names that
+do not contain angle brackets or underscores are left unchanged.
+Underscores are doubled, each @samp{<} is replaced with @samp{_l}, and
+each @samp{>} with @samp{_g}. Here are some examples:
+
+@c the @c's prevent double blank lines in the printed manual.
+@example
+@multitable {Original} {Mangled}
+@item @strong{Original} @tab @strong{Mangled} @c
+@item @code{x} @tab @code{x} @c
+@item @code{P42x} @tab @code{P42x} @c
+@item @code{P4_x} @tab @code{P4__x} @c
+@item @code{P4>x} @tab @code{P4_gx} @c
+@item @code{P4>>} @tab @code{P4_g_g} @c
+@item @code{P4_g>} @tab @code{P4__g_g} @c
+@end multitable
+@end example
+
+Throughout this section, the variable @var{c} is either a constraint
+in the abstract sense, or a constant from @code{enum constraint_num};
+the variable @var{m} is a mangled constraint name (usually as part of
+a larger identifier).
+
+@deftp Enum constraint_num
+For each constraint except @code{g}, there is a corresponding
+enumeration constant: @samp{CONSTRAINT_} plus the mangled name of the
+constraint. Functions that take an @code{enum constraint_num} as an
+argument expect one of these constants.
+@end deftp
+
+@deftypefun {inline bool} satisfies_constraint_@var{m} (rtx @var{exp})
+For each non-register constraint @var{m} except @code{g}, there is
+one of these functions; it returns @code{true} if @var{exp} satisfies the
+constraint. These functions are only visible if @file{rtl.h} was included
+before @file{tm_p.h}.
+@end deftypefun
+
+@deftypefun bool constraint_satisfied_p (rtx @var{exp}, enum constraint_num @var{c})
+Like the @code{satisfies_constraint_@var{m}} functions, but the
+constraint to test is given as an argument, @var{c}. If @var{c}
+specifies a register constraint, this function will always return
+@code{false}.
+@end deftypefun
+
+@deftypefun {enum reg_class} reg_class_for_constraint (enum constraint_num @var{c})
+Returns the register class associated with @var{c}. If @var{c} is not
+a register constraint, or those registers are not available for the
+currently selected subtarget, returns @code{NO_REGS}.
+@end deftypefun
+
+Here is an example use of @code{satisfies_constraint_@var{m}}. In
+peephole optimizations (@pxref{Peephole Definitions}), operand
+constraint strings are ignored, so if there are relevant constraints,
+they must be tested in the C condition. In the example, the
+optimization is applied if operand 2 does @emph{not} satisfy the
+@samp{K} constraint. (This is a simplified version of a peephole
+definition from the i386 machine description.)
+
+@smallexample
+(define_peephole2
+ [(match_scratch:SI 3 "r")
+ (set (match_operand:SI 0 "register_operand" "")
+ (mult:SI (match_operand:SI 1 "memory_operand" "")
+ (match_operand:SI 2 "immediate_operand" "")))]
+
+ "!satisfies_constraint_K (operands[2])"
+
+ [(set (match_dup 3) (match_dup 1))
+ (set (match_dup 0) (mult:SI (match_dup 3) (match_dup 2)))]
+
+ "")
+@end smallexample
+
+@node Standard Names
+@section Standard Pattern Names For Generation
+@cindex standard pattern names
+@cindex pattern names
+@cindex names, pattern
+
+Here is a table of the instruction names that are meaningful in the RTL
+generation pass of the compiler. Giving one of these names to an
+instruction pattern tells the RTL generation pass that it can use the
+pattern to accomplish a certain task.
+
+@table @asis
+@cindex @code{mov@var{m}} instruction pattern
+@item @samp{mov@var{m}}
+Here @var{m} stands for a two-letter machine mode name, in lowercase.
+This instruction pattern moves data with that machine mode from operand
+1 to operand 0. For example, @samp{movsi} moves full-word data.
+
+If operand 0 is a @code{subreg} with mode @var{m} of a register whose
+own mode is wider than @var{m}, the effect of this instruction is
+to store the specified value in the part of the register that corresponds
+to mode @var{m}. Bits outside of @var{m}, but which are within the
+same target word as the @code{subreg} are undefined. Bits which are
+outside the target word are left unchanged.
+
+This class of patterns is special in several ways. First of all, each
+of these names up to and including full word size @emph{must} be defined,
+because there is no other way to copy a datum from one place to another.
+If there are patterns accepting operands in larger modes,
+@samp{mov@var{m}} must be defined for integer modes of those sizes.
+
+Second, these patterns are not used solely in the RTL generation pass.
+Even the reload pass can generate move insns to copy values from stack
+slots into temporary registers. When it does so, one of the operands is
+a hard register and the other is an operand that can need to be reloaded
+into a register.
+
+@findex force_reg
+Therefore, when given such a pair of operands, the pattern must generate
+RTL which needs no reloading and needs no temporary registers---no
+registers other than the operands. For example, if you support the
+pattern with a @code{define_expand}, then in such a case the
+@code{define_expand} mustn't call @code{force_reg} or any other such
+function which might generate new pseudo registers.
+
+This requirement exists even for subword modes on a RISC machine where
+fetching those modes from memory normally requires several insns and
+some temporary registers.
+
+@findex change_address
+During reload a memory reference with an invalid address may be passed
+as an operand. Such an address will be replaced with a valid address
+later in the reload pass. In this case, nothing may be done with the
+address except to use it as it stands. If it is copied, it will not be
+replaced with a valid address. No attempt should be made to make such
+an address into a valid address and no routine (such as
+@code{change_address}) that will do so may be called. Note that
+@code{general_operand} will fail when applied to such an address.
+
+@findex reload_in_progress
+The global variable @code{reload_in_progress} (which must be explicitly
+declared if required) can be used to determine whether such special
+handling is required.
+
+The variety of operands that have reloads depends on the rest of the
+machine description, but typically on a RISC machine these can only be
+pseudo registers that did not get hard registers, while on other
+machines explicit memory references will get optional reloads.
+
+If a scratch register is required to move an object to or from memory,
+it can be allocated using @code{gen_reg_rtx} prior to life analysis.
+
+If there are cases which need scratch registers during or after reload,
+you must provide an appropriate secondary_reload target hook.
+
+@findex can_create_pseudo_p
+The macro @code{can_create_pseudo_p} can be used to determine if it
+is unsafe to create new pseudo registers. If this variable is nonzero, then
+it is unsafe to call @code{gen_reg_rtx} to allocate a new pseudo.
+
+The constraints on a @samp{mov@var{m}} must permit moving any hard
+register to any other hard register provided that
+@code{TARGET_HARD_REGNO_MODE_OK} permits mode @var{m} in both registers and
+@code{TARGET_REGISTER_MOVE_COST} applied to their classes returns a value
+of 2.
+
+It is obligatory to support floating point @samp{mov@var{m}}
+instructions into and out of any registers that can hold fixed point
+values, because unions and structures (which have modes @code{SImode} or
+@code{DImode}) can be in those registers and they may have floating
+point members.
+
+There may also be a need to support fixed point @samp{mov@var{m}}
+instructions in and out of floating point registers. Unfortunately, I
+have forgotten why this was so, and I don't know whether it is still
+true. If @code{TARGET_HARD_REGNO_MODE_OK} rejects fixed point values in
+floating point registers, then the constraints of the fixed point
+@samp{mov@var{m}} instructions must be designed to avoid ever trying to
+reload into a floating point register.
+
+@cindex @code{reload_in} instruction pattern
+@cindex @code{reload_out} instruction pattern
+@item @samp{reload_in@var{m}}
+@itemx @samp{reload_out@var{m}}
+These named patterns have been obsoleted by the target hook
+@code{secondary_reload}.
+
+Like @samp{mov@var{m}}, but used when a scratch register is required to
+move between operand 0 and operand 1. Operand 2 describes the scratch
+register. See the discussion of the @code{SECONDARY_RELOAD_CLASS}
+macro in @pxref{Register Classes}.
+
+There are special restrictions on the form of the @code{match_operand}s
+used in these patterns. First, only the predicate for the reload
+operand is examined, i.e., @code{reload_in} examines operand 1, but not
+the predicates for operand 0 or 2. Second, there may be only one
+alternative in the constraints. Third, only a single register class
+letter may be used for the constraint; subsequent constraint letters
+are ignored. As a special exception, an empty constraint string
+matches the @code{ALL_REGS} register class. This may relieve ports
+of the burden of defining an @code{ALL_REGS} constraint letter just
+for these patterns.
+
+@cindex @code{movstrict@var{m}} instruction pattern
+@item @samp{movstrict@var{m}}
+Like @samp{mov@var{m}} except that if operand 0 is a @code{subreg}
+with mode @var{m} of a register whose natural mode is wider,
+the @samp{movstrict@var{m}} instruction is guaranteed not to alter
+any of the register except the part which belongs to mode @var{m}.
+
+@cindex @code{movmisalign@var{m}} instruction pattern
+@item @samp{movmisalign@var{m}}
+This variant of a move pattern is designed to load or store a value
+from a memory address that is not naturally aligned for its mode.
+For a store, the memory will be in operand 0; for a load, the memory
+will be in operand 1. The other operand is guaranteed not to be a
+memory, so that it's easy to tell whether this is a load or store.
+
+This pattern is used by the autovectorizer, and when expanding a
+@code{MISALIGNED_INDIRECT_REF} expression.
+
+@cindex @code{load_multiple} instruction pattern
+@item @samp{load_multiple}
+Load several consecutive memory locations into consecutive registers.
+Operand 0 is the first of the consecutive registers, operand 1
+is the first memory location, and operand 2 is a constant: the
+number of consecutive registers.
+
+Define this only if the target machine really has such an instruction;
+do not define this if the most efficient way of loading consecutive
+registers from memory is to do them one at a time.
+
+On some machines, there are restrictions as to which consecutive
+registers can be stored into memory, such as particular starting or
+ending register numbers or only a range of valid counts. For those
+machines, use a @code{define_expand} (@pxref{Expander Definitions})
+and make the pattern fail if the restrictions are not met.
+
+Write the generated insn as a @code{parallel} with elements being a
+@code{set} of one register from the appropriate memory location (you may
+also need @code{use} or @code{clobber} elements). Use a
+@code{match_parallel} (@pxref{RTL Template}) to recognize the insn. See
+@file{rs6000.md} for examples of the use of this insn pattern.
+
+@cindex @samp{store_multiple} instruction pattern
+@item @samp{store_multiple}
+Similar to @samp{load_multiple}, but store several consecutive registers
+into consecutive memory locations. Operand 0 is the first of the
+consecutive memory locations, operand 1 is the first register, and
+operand 2 is a constant: the number of consecutive registers.
+
+@cindex @code{vec_load_lanes@var{m}@var{n}} instruction pattern
+@item @samp{vec_load_lanes@var{m}@var{n}}
+Perform an interleaved load of several vectors from memory operand 1
+into register operand 0. Both operands have mode @var{m}. The register
+operand is viewed as holding consecutive vectors of mode @var{n},
+while the memory operand is a flat array that contains the same number
+of elements. The operation is equivalent to:
+
+@smallexample
+int c = GET_MODE_SIZE (@var{m}) / GET_MODE_SIZE (@var{n});
+for (j = 0; j < GET_MODE_NUNITS (@var{n}); j++)
+ for (i = 0; i < c; i++)
+ operand0[i][j] = operand1[j * c + i];
+@end smallexample
+
+For example, @samp{vec_load_lanestiv4hi} loads 8 16-bit values
+from memory into a register of mode @samp{TI}@. The register
+contains two consecutive vectors of mode @samp{V4HI}@.
+
+This pattern can only be used if:
+@smallexample
+TARGET_ARRAY_MODE_SUPPORTED_P (@var{n}, @var{c})
+@end smallexample
+is true. GCC assumes that, if a target supports this kind of
+instruction for some mode @var{n}, it also supports unaligned
+loads for vectors of mode @var{n}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{vec_mask_load_lanes@var{m}@var{n}} instruction pattern
+@item @samp{vec_mask_load_lanes@var{m}@var{n}}
+Like @samp{vec_load_lanes@var{m}@var{n}}, but takes an additional
+mask operand (operand 2) that specifies which elements of the destination
+vectors should be loaded. Other elements of the destination
+vectors are set to zero. The operation is equivalent to:
+
+@smallexample
+int c = GET_MODE_SIZE (@var{m}) / GET_MODE_SIZE (@var{n});
+for (j = 0; j < GET_MODE_NUNITS (@var{n}); j++)
+ if (operand2[j])
+ for (i = 0; i < c; i++)
+ operand0[i][j] = operand1[j * c + i];
+ else
+ for (i = 0; i < c; i++)
+ operand0[i][j] = 0;
+@end smallexample
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{vec_store_lanes@var{m}@var{n}} instruction pattern
+@item @samp{vec_store_lanes@var{m}@var{n}}
+Equivalent to @samp{vec_load_lanes@var{m}@var{n}}, with the memory
+and register operands reversed. That is, the instruction is
+equivalent to:
+
+@smallexample
+int c = GET_MODE_SIZE (@var{m}) / GET_MODE_SIZE (@var{n});
+for (j = 0; j < GET_MODE_NUNITS (@var{n}); j++)
+ for (i = 0; i < c; i++)
+ operand0[j * c + i] = operand1[i][j];
+@end smallexample
+
+for a memory operand 0 and register operand 1.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{vec_mask_store_lanes@var{m}@var{n}} instruction pattern
+@item @samp{vec_mask_store_lanes@var{m}@var{n}}
+Like @samp{vec_store_lanes@var{m}@var{n}}, but takes an additional
+mask operand (operand 2) that specifies which elements of the source
+vectors should be stored. The operation is equivalent to:
+
+@smallexample
+int c = GET_MODE_SIZE (@var{m}) / GET_MODE_SIZE (@var{n});
+for (j = 0; j < GET_MODE_NUNITS (@var{n}); j++)
+ if (operand2[j])
+ for (i = 0; i < c; i++)
+ operand0[j * c + i] = operand1[i][j];
+@end smallexample
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{gather_load@var{m}@var{n}} instruction pattern
+@item @samp{gather_load@var{m}@var{n}}
+Load several separate memory locations into a vector of mode @var{m}.
+Operand 1 is a scalar base address and operand 2 is a vector of mode @var{n}
+containing offsets from that base. Operand 0 is a destination vector with
+the same number of elements as @var{n}. For each element index @var{i}:
+
+@itemize @bullet
+@item
+extend the offset element @var{i} to address width, using zero
+extension if operand 3 is 1 and sign extension if operand 3 is zero;
+@item
+multiply the extended offset by operand 4;
+@item
+add the result to the base; and
+@item
+load the value at that address into element @var{i} of operand 0.
+@end itemize
+
+The value of operand 3 does not matter if the offsets are already
+address width.
+
+@cindex @code{mask_gather_load@var{m}@var{n}} instruction pattern
+@item @samp{mask_gather_load@var{m}@var{n}}
+Like @samp{gather_load@var{m}@var{n}}, but takes an extra mask operand as
+operand 5. Bit @var{i} of the mask is set if element @var{i}
+of the result should be loaded from memory and clear if element @var{i}
+of the result should be set to zero.
+
+@cindex @code{scatter_store@var{m}@var{n}} instruction pattern
+@item @samp{scatter_store@var{m}@var{n}}
+Store a vector of mode @var{m} into several distinct memory locations.
+Operand 0 is a scalar base address and operand 1 is a vector of mode
+@var{n} containing offsets from that base. Operand 4 is the vector of
+values that should be stored, which has the same number of elements as
+@var{n}. For each element index @var{i}:
+
+@itemize @bullet
+@item
+extend the offset element @var{i} to address width, using zero
+extension if operand 2 is 1 and sign extension if operand 2 is zero;
+@item
+multiply the extended offset by operand 3;
+@item
+add the result to the base; and
+@item
+store element @var{i} of operand 4 to that address.
+@end itemize
+
+The value of operand 2 does not matter if the offsets are already
+address width.
+
+@cindex @code{mask_scatter_store@var{m}@var{n}} instruction pattern
+@item @samp{mask_scatter_store@var{m}@var{n}}
+Like @samp{scatter_store@var{m}@var{n}}, but takes an extra mask operand as
+operand 5. Bit @var{i} of the mask is set if element @var{i}
+of the result should be stored to memory.
+
+@cindex @code{vec_set@var{m}} instruction pattern
+@item @samp{vec_set@var{m}}
+Set given field in the vector value. Operand 0 is the vector to modify,
+operand 1 is new value of field and operand 2 specify the field index.
+
+@cindex @code{vec_extract@var{m}@var{n}} instruction pattern
+@item @samp{vec_extract@var{m}@var{n}}
+Extract given field from the vector value. Operand 1 is the vector, operand 2
+specify field index and operand 0 place to store value into. The
+@var{n} mode is the mode of the field or vector of fields that should be
+extracted, should be either element mode of the vector mode @var{m}, or
+a vector mode with the same element mode and smaller number of elements.
+If @var{n} is a vector mode, the index is counted in units of that mode.
+
+@cindex @code{vec_init@var{m}@var{n}} instruction pattern
+@item @samp{vec_init@var{m}@var{n}}
+Initialize the vector to given values. Operand 0 is the vector to initialize
+and operand 1 is parallel containing values for individual fields. The
+@var{n} mode is the mode of the elements, should be either element mode of
+the vector mode @var{m}, or a vector mode with the same element mode and
+smaller number of elements.
+
+@cindex @code{vec_duplicate@var{m}} instruction pattern
+@item @samp{vec_duplicate@var{m}}
+Initialize vector output operand 0 so that each element has the value given
+by scalar input operand 1. The vector has mode @var{m} and the scalar has
+the mode appropriate for one element of @var{m}.
+
+This pattern only handles duplicates of non-constant inputs. Constant
+vectors go through the @code{mov@var{m}} pattern instead.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{vec_series@var{m}} instruction pattern
+@item @samp{vec_series@var{m}}
+Initialize vector output operand 0 so that element @var{i} is equal to
+operand 1 plus @var{i} times operand 2. In other words, create a linear
+series whose base value is operand 1 and whose step is operand 2.
+
+The vector output has mode @var{m} and the scalar inputs have the mode
+appropriate for one element of @var{m}. This pattern is not used for
+floating-point vectors, in order to avoid having to specify the
+rounding behavior for @var{i} > 1.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{while_ult@var{m}@var{n}} instruction pattern
+@item @code{while_ult@var{m}@var{n}}
+Set operand 0 to a mask that is true while incrementing operand 1
+gives a value that is less than operand 2, for a vector length up to operand 3.
+Operand 0 has mode @var{n} and operands 1 and 2 are scalar integers of mode
+@var{m}. Operand 3 should be omitted when @var{n} is a vector mode, and
+a @code{CONST_INT} otherwise. The operation for vector modes is equivalent to:
+
+@smallexample
+operand0[0] = operand1 < operand2;
+for (i = 1; i < GET_MODE_NUNITS (@var{n}); i++)
+ operand0[i] = operand0[i - 1] && (operand1 + i < operand2);
+@end smallexample
+
+And for non-vector modes the operation is equivalent to:
+
+@smallexample
+operand0[0] = operand1 < operand2;
+for (i = 1; i < operand3; i++)
+ operand0[i] = operand0[i - 1] && (operand1 + i < operand2);
+@end smallexample
+
+@cindex @code{check_raw_ptrs@var{m}} instruction pattern
+@item @samp{check_raw_ptrs@var{m}}
+Check whether, given two pointers @var{a} and @var{b} and a length @var{len},
+a write of @var{len} bytes at @var{a} followed by a read of @var{len} bytes
+at @var{b} can be split into interleaved byte accesses
+@samp{@var{a}[0], @var{b}[0], @var{a}[1], @var{b}[1], @dots{}}
+without affecting the dependencies between the bytes. Set operand 0
+to true if the split is possible and false otherwise.
+
+Operands 1, 2 and 3 provide the values of @var{a}, @var{b} and @var{len}
+respectively. Operand 4 is a constant integer that provides the known
+common alignment of @var{a} and @var{b}. All inputs have mode @var{m}.
+
+This split is possible if:
+
+@smallexample
+@var{a} == @var{b} || @var{a} + @var{len} <= @var{b} || @var{b} + @var{len} <= @var{a}
+@end smallexample
+
+You should only define this pattern if the target has a way of accelerating
+the test without having to do the individual comparisons.
+
+@cindex @code{check_war_ptrs@var{m}} instruction pattern
+@item @samp{check_war_ptrs@var{m}}
+Like @samp{check_raw_ptrs@var{m}}, but with the read and write swapped round.
+The split is possible in this case if:
+
+@smallexample
+@var{b} <= @var{a} || @var{a} + @var{len} <= @var{b}
+@end smallexample
+
+@cindex @code{vec_cmp@var{m}@var{n}} instruction pattern
+@item @samp{vec_cmp@var{m}@var{n}}
+Output a vector comparison. Operand 0 of mode @var{n} is the destination for
+predicate in operand 1 which is a signed vector comparison with operands of
+mode @var{m} in operands 2 and 3. Predicate is computed by element-wise
+evaluation of the vector comparison with a truth value of all-ones and a false
+value of all-zeros.
+
+@cindex @code{vec_cmpu@var{m}@var{n}} instruction pattern
+@item @samp{vec_cmpu@var{m}@var{n}}
+Similar to @code{vec_cmp@var{m}@var{n}} but perform unsigned vector comparison.
+
+@cindex @code{vec_cmpeq@var{m}@var{n}} instruction pattern
+@item @samp{vec_cmpeq@var{m}@var{n}}
+Similar to @code{vec_cmp@var{m}@var{n}} but perform equality or non-equality
+vector comparison only. If @code{vec_cmp@var{m}@var{n}}
+or @code{vec_cmpu@var{m}@var{n}} instruction pattern is supported,
+it will be preferred over @code{vec_cmpeq@var{m}@var{n}}, so there is
+no need to define this instruction pattern if the others are supported.
+
+@cindex @code{vcond@var{m}@var{n}} instruction pattern
+@item @samp{vcond@var{m}@var{n}}
+Output a conditional vector move. Operand 0 is the destination to
+receive a combination of operand 1 and operand 2, which are of mode @var{m},
+dependent on the outcome of the predicate in operand 3 which is a signed
+vector comparison with operands of mode @var{n} in operands 4 and 5. The
+modes @var{m} and @var{n} should have the same size. Operand 0
+will be set to the value @var{op1} & @var{msk} | @var{op2} & ~@var{msk}
+where @var{msk} is computed by element-wise evaluation of the vector
+comparison with a truth value of all-ones and a false value of all-zeros.
+
+@cindex @code{vcondu@var{m}@var{n}} instruction pattern
+@item @samp{vcondu@var{m}@var{n}}
+Similar to @code{vcond@var{m}@var{n}} but performs unsigned vector
+comparison.
+
+@cindex @code{vcondeq@var{m}@var{n}} instruction pattern
+@item @samp{vcondeq@var{m}@var{n}}
+Similar to @code{vcond@var{m}@var{n}} but performs equality or
+non-equality vector comparison only. If @code{vcond@var{m}@var{n}}
+or @code{vcondu@var{m}@var{n}} instruction pattern is supported,
+it will be preferred over @code{vcondeq@var{m}@var{n}}, so there is
+no need to define this instruction pattern if the others are supported.
+
+@cindex @code{vcond_mask_@var{m}@var{n}} instruction pattern
+@item @samp{vcond_mask_@var{m}@var{n}}
+Similar to @code{vcond@var{m}@var{n}} but operand 3 holds a pre-computed
+result of vector comparison.
+
+@cindex @code{maskload@var{m}@var{n}} instruction pattern
+@item @samp{maskload@var{m}@var{n}}
+Perform a masked load of vector from memory operand 1 of mode @var{m}
+into register operand 0. Mask is provided in register operand 2 of
+mode @var{n}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{maskstore@var{m}@var{n}} instruction pattern
+@item @samp{maskstore@var{m}@var{n}}
+Perform a masked store of vector from register operand 1 of mode @var{m}
+into memory operand 0. Mask is provided in register operand 2 of
+mode @var{n}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{len_load_@var{m}} instruction pattern
+@item @samp{len_load_@var{m}}
+Load (operand 2 - operand 3) elements from vector memory operand 1
+into vector register operand 0, setting the other elements of
+operand 0 to undefined values. Operands 0 and 1 have mode @var{m},
+which must be a vector mode. Operand 2 has whichever integer mode the
+target prefers. Operand 3 conceptually has mode @code{QI}.
+
+Operand 2 can be a variable or a constant amount. Operand 3 specifies a
+constant bias: it is either a constant 0 or a constant -1. The predicate on
+operand 3 must only accept the bias values that the target actually supports.
+GCC handles a bias of 0 more efficiently than a bias of -1.
+
+If (operand 2 - operand 3) exceeds the number of elements in mode
+@var{m}, the behavior is undefined.
+
+If the target prefers the length to be measured in bytes rather than
+elements, it should only implement this pattern for vectors of @code{QI}
+elements.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{len_store_@var{m}} instruction pattern
+@item @samp{len_store_@var{m}}
+Store (operand 2 - operand 3) vector elements from vector register operand 1
+into memory operand 0, leaving the other elements of
+operand 0 unchanged. Operands 0 and 1 have mode @var{m}, which must be
+a vector mode. Operand 2 has whichever integer mode the target prefers.
+Operand 3 conceptually has mode @code{QI}.
+
+Operand 2 can be a variable or a constant amount. Operand 3 specifies a
+constant bias: it is either a constant 0 or a constant -1. The predicate on
+operand 3 must only accept the bias values that the target actually supports.
+GCC handles a bias of 0 more efficiently than a bias of -1.
+
+If (operand 2 - operand 3) exceeds the number of elements in mode
+@var{m}, the behavior is undefined.
+
+If the target prefers the length to be measured in bytes
+rather than elements, it should only implement this pattern for vectors
+of @code{QI} elements.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{vec_perm@var{m}} instruction pattern
+@item @samp{vec_perm@var{m}}
+Output a (variable) vector permutation. Operand 0 is the destination
+to receive elements from operand 1 and operand 2, which are of mode
+@var{m}. Operand 3 is the @dfn{selector}. It is an integral mode
+vector of the same width and number of elements as mode @var{m}.
+
+The input elements are numbered from 0 in operand 1 through
+@math{2*@var{N}-1} in operand 2. The elements of the selector must
+be computed modulo @math{2*@var{N}}. Note that if
+@code{rtx_equal_p(operand1, operand2)}, this can be implemented
+with just operand 1 and selector elements modulo @var{N}.
+
+In order to make things easy for a number of targets, if there is no
+@samp{vec_perm} pattern for mode @var{m}, but there is for mode @var{q}
+where @var{q} is a vector of @code{QImode} of the same width as @var{m},
+the middle-end will lower the mode @var{m} @code{VEC_PERM_EXPR} to
+mode @var{q}.
+
+See also @code{TARGET_VECTORIZER_VEC_PERM_CONST}, which performs
+the analogous operation for constant selectors.
+
+@cindex @code{push@var{m}1} instruction pattern
+@item @samp{push@var{m}1}
+Output a push instruction. Operand 0 is value to push. Used only when
+@code{PUSH_ROUNDING} is defined. For historical reason, this pattern may be
+missing and in such case an @code{mov} expander is used instead, with a
+@code{MEM} expression forming the push operation. The @code{mov} expander
+method is deprecated.
+
+@cindex @code{add@var{m}3} instruction pattern
+@item @samp{add@var{m}3}
+Add operand 2 and operand 1, storing the result in operand 0. All operands
+must have mode @var{m}. This can be used even on two-address machines, by
+means of constraints requiring operands 1 and 0 to be the same location.
+
+@cindex @code{ssadd@var{m}3} instruction pattern
+@cindex @code{usadd@var{m}3} instruction pattern
+@cindex @code{sub@var{m}3} instruction pattern
+@cindex @code{sssub@var{m}3} instruction pattern
+@cindex @code{ussub@var{m}3} instruction pattern
+@cindex @code{mul@var{m}3} instruction pattern
+@cindex @code{ssmul@var{m}3} instruction pattern
+@cindex @code{usmul@var{m}3} instruction pattern
+@cindex @code{div@var{m}3} instruction pattern
+@cindex @code{ssdiv@var{m}3} instruction pattern
+@cindex @code{udiv@var{m}3} instruction pattern
+@cindex @code{usdiv@var{m}3} instruction pattern
+@cindex @code{mod@var{m}3} instruction pattern
+@cindex @code{umod@var{m}3} instruction pattern
+@cindex @code{umin@var{m}3} instruction pattern
+@cindex @code{umax@var{m}3} instruction pattern
+@cindex @code{and@var{m}3} instruction pattern
+@cindex @code{ior@var{m}3} instruction pattern
+@cindex @code{xor@var{m}3} instruction pattern
+@item @samp{ssadd@var{m}3}, @samp{usadd@var{m}3}
+@itemx @samp{sub@var{m}3}, @samp{sssub@var{m}3}, @samp{ussub@var{m}3}
+@itemx @samp{mul@var{m}3}, @samp{ssmul@var{m}3}, @samp{usmul@var{m}3}
+@itemx @samp{div@var{m}3}, @samp{ssdiv@var{m}3}
+@itemx @samp{udiv@var{m}3}, @samp{usdiv@var{m}3}
+@itemx @samp{mod@var{m}3}, @samp{umod@var{m}3}
+@itemx @samp{umin@var{m}3}, @samp{umax@var{m}3}
+@itemx @samp{and@var{m}3}, @samp{ior@var{m}3}, @samp{xor@var{m}3}
+Similar, for other arithmetic operations.
+
+@cindex @code{addv@var{m}4} instruction pattern
+@item @samp{addv@var{m}4}
+Like @code{add@var{m}3} but takes a @code{code_label} as operand 3 and
+emits code to jump to it if signed overflow occurs during the addition.
+This pattern is used to implement the built-in functions performing
+signed integer addition with overflow checking.
+
+@cindex @code{subv@var{m}4} instruction pattern
+@cindex @code{mulv@var{m}4} instruction pattern
+@item @samp{subv@var{m}4}, @samp{mulv@var{m}4}
+Similar, for other signed arithmetic operations.
+
+@cindex @code{uaddv@var{m}4} instruction pattern
+@item @samp{uaddv@var{m}4}
+Like @code{addv@var{m}4} but for unsigned addition. That is to
+say, the operation is the same as signed addition but the jump
+is taken only on unsigned overflow.
+
+@cindex @code{usubv@var{m}4} instruction pattern
+@cindex @code{umulv@var{m}4} instruction pattern
+@item @samp{usubv@var{m}4}, @samp{umulv@var{m}4}
+Similar, for other unsigned arithmetic operations.
+
+@cindex @code{addptr@var{m}3} instruction pattern
+@item @samp{addptr@var{m}3}
+Like @code{add@var{m}3} but is guaranteed to only be used for address
+calculations. The expanded code is not allowed to clobber the
+condition code. It only needs to be defined if @code{add@var{m}3}
+sets the condition code. If adds used for address calculations and
+normal adds are not compatible it is required to expand a distinct
+pattern (e.g.@: using an unspec). The pattern is used by LRA to emit
+address calculations. @code{add@var{m}3} is used if
+@code{addptr@var{m}3} is not defined.
+
+@cindex @code{fma@var{m}4} instruction pattern
+@item @samp{fma@var{m}4}
+Multiply operand 2 and operand 1, then add operand 3, storing the
+result in operand 0 without doing an intermediate rounding step. All
+operands must have mode @var{m}. This pattern is used to implement
+the @code{fma}, @code{fmaf}, and @code{fmal} builtin functions from
+the ISO C99 standard.
+
+@cindex @code{fms@var{m}4} instruction pattern
+@item @samp{fms@var{m}4}
+Like @code{fma@var{m}4}, except operand 3 subtracted from the
+product instead of added to the product. This is represented
+in the rtl as
+
+@smallexample
+(fma:@var{m} @var{op1} @var{op2} (neg:@var{m} @var{op3}))
+@end smallexample
+
+@cindex @code{fnma@var{m}4} instruction pattern
+@item @samp{fnma@var{m}4}
+Like @code{fma@var{m}4} except that the intermediate product
+is negated before being added to operand 3. This is represented
+in the rtl as
+
+@smallexample
+(fma:@var{m} (neg:@var{m} @var{op1}) @var{op2} @var{op3})
+@end smallexample
+
+@cindex @code{fnms@var{m}4} instruction pattern
+@item @samp{fnms@var{m}4}
+Like @code{fms@var{m}4} except that the intermediate product
+is negated before subtracting operand 3. This is represented
+in the rtl as
+
+@smallexample
+(fma:@var{m} (neg:@var{m} @var{op1}) @var{op2} (neg:@var{m} @var{op3}))
+@end smallexample
+
+@cindex @code{min@var{m}3} instruction pattern
+@cindex @code{max@var{m}3} instruction pattern
+@item @samp{smin@var{m}3}, @samp{smax@var{m}3}
+Signed minimum and maximum operations. When used with floating point,
+if both operands are zeros, or if either operand is @code{NaN}, then
+it is unspecified which of the two operands is returned as the result.
+
+@cindex @code{fmin@var{m}3} instruction pattern
+@cindex @code{fmax@var{m}3} instruction pattern
+@item @samp{fmin@var{m}3}, @samp{fmax@var{m}3}
+IEEE-conformant minimum and maximum operations. If one operand is a quiet
+@code{NaN}, then the other operand is returned. If both operands are quiet
+@code{NaN}, then a quiet @code{NaN} is returned. In the case when gcc supports
+signaling @code{NaN} (-fsignaling-nans) an invalid floating point exception is
+raised and a quiet @code{NaN} is returned.
+
+All operands have mode @var{m}, which is a scalar or vector
+floating-point mode. These patterns are not allowed to @code{FAIL}.
+
+@cindex @code{reduc_smin_scal_@var{m}} instruction pattern
+@cindex @code{reduc_smax_scal_@var{m}} instruction pattern
+@item @samp{reduc_smin_scal_@var{m}}, @samp{reduc_smax_scal_@var{m}}
+Find the signed minimum/maximum of the elements of a vector. The vector is
+operand 1, and operand 0 is the scalar result, with mode equal to the mode of
+the elements of the input vector.
+
+@cindex @code{reduc_umin_scal_@var{m}} instruction pattern
+@cindex @code{reduc_umax_scal_@var{m}} instruction pattern
+@item @samp{reduc_umin_scal_@var{m}}, @samp{reduc_umax_scal_@var{m}}
+Find the unsigned minimum/maximum of the elements of a vector. The vector is
+operand 1, and operand 0 is the scalar result, with mode equal to the mode of
+the elements of the input vector.
+
+@cindex @code{reduc_fmin_scal_@var{m}} instruction pattern
+@cindex @code{reduc_fmax_scal_@var{m}} instruction pattern
+@item @samp{reduc_fmin_scal_@var{m}}, @samp{reduc_fmax_scal_@var{m}}
+Find the floating-point minimum/maximum of the elements of a vector,
+using the same rules as @code{fmin@var{m}3} and @code{fmax@var{m}3}.
+Operand 1 is a vector of mode @var{m} and operand 0 is the scalar
+result, which has mode @code{GET_MODE_INNER (@var{m})}.
+
+@cindex @code{reduc_plus_scal_@var{m}} instruction pattern
+@item @samp{reduc_plus_scal_@var{m}}
+Compute the sum of the elements of a vector. The vector is operand 1, and
+operand 0 is the scalar result, with mode equal to the mode of the elements of
+the input vector.
+
+@cindex @code{reduc_and_scal_@var{m}} instruction pattern
+@item @samp{reduc_and_scal_@var{m}}
+@cindex @code{reduc_ior_scal_@var{m}} instruction pattern
+@itemx @samp{reduc_ior_scal_@var{m}}
+@cindex @code{reduc_xor_scal_@var{m}} instruction pattern
+@itemx @samp{reduc_xor_scal_@var{m}}
+Compute the bitwise @code{AND}/@code{IOR}/@code{XOR} reduction of the elements
+of a vector of mode @var{m}. Operand 1 is the vector input and operand 0
+is the scalar result. The mode of the scalar result is the same as one
+element of @var{m}.
+
+@cindex @code{extract_last_@var{m}} instruction pattern
+@item @code{extract_last_@var{m}}
+Find the last set bit in mask operand 1 and extract the associated element
+of vector operand 2. Store the result in scalar operand 0. Operand 2
+has vector mode @var{m} while operand 0 has the mode appropriate for one
+element of @var{m}. Operand 1 has the usual mask mode for vectors of mode
+@var{m}; see @code{TARGET_VECTORIZE_GET_MASK_MODE}.
+
+@cindex @code{fold_extract_last_@var{m}} instruction pattern
+@item @code{fold_extract_last_@var{m}}
+If any bits of mask operand 2 are set, find the last set bit, extract
+the associated element from vector operand 3, and store the result
+in operand 0. Store operand 1 in operand 0 otherwise. Operand 3
+has mode @var{m} and operands 0 and 1 have the mode appropriate for
+one element of @var{m}. Operand 2 has the usual mask mode for vectors
+of mode @var{m}; see @code{TARGET_VECTORIZE_GET_MASK_MODE}.
+
+@cindex @code{fold_left_plus_@var{m}} instruction pattern
+@item @code{fold_left_plus_@var{m}}
+Take scalar operand 1 and successively add each element from vector
+operand 2. Store the result in scalar operand 0. The vector has
+mode @var{m} and the scalars have the mode appropriate for one
+element of @var{m}. The operation is strictly in-order: there is
+no reassociation.
+
+@cindex @code{mask_fold_left_plus_@var{m}} instruction pattern
+@item @code{mask_fold_left_plus_@var{m}}
+Like @samp{fold_left_plus_@var{m}}, but takes an additional mask operand
+(operand 3) that specifies which elements of the source vector should be added.
+
+@cindex @code{sdot_prod@var{m}} instruction pattern
+@item @samp{sdot_prod@var{m}}
+
+Compute the sum of the products of two signed elements.
+Operand 1 and operand 2 are of the same mode. Their
+product, which is of a wider mode, is computed and added to operand 3.
+Operand 3 is of a mode equal or wider than the mode of the product. The
+result is placed in operand 0, which is of the same mode as operand 3.
+
+Semantically the expressions perform the multiplication in the following signs
+
+@smallexample
+sdot<signed op0, signed op1, signed op2, signed op3> ==
+ op0 = sign-ext (op1) * sign-ext (op2) + op3
+@dots{}
+@end smallexample
+
+@cindex @code{udot_prod@var{m}} instruction pattern
+@item @samp{udot_prod@var{m}}
+
+Compute the sum of the products of two unsigned elements.
+Operand 1 and operand 2 are of the same mode. Their
+product, which is of a wider mode, is computed and added to operand 3.
+Operand 3 is of a mode equal or wider than the mode of the product. The
+result is placed in operand 0, which is of the same mode as operand 3.
+
+Semantically the expressions perform the multiplication in the following signs
+
+@smallexample
+udot<unsigned op0, unsigned op1, unsigned op2, unsigned op3> ==
+ op0 = zero-ext (op1) * zero-ext (op2) + op3
+@dots{}
+@end smallexample
+
+@cindex @code{usdot_prod@var{m}} instruction pattern
+@item @samp{usdot_prod@var{m}}
+Compute the sum of the products of elements of different signs.
+Operand 1 must be unsigned and operand 2 signed. Their
+product, which is of a wider mode, is computed and added to operand 3.
+Operand 3 is of a mode equal or wider than the mode of the product. The
+result is placed in operand 0, which is of the same mode as operand 3.
+
+Semantically the expressions perform the multiplication in the following signs
+
+@smallexample
+usdot<signed op0, unsigned op1, signed op2, signed op3> ==
+ op0 = ((signed-conv) zero-ext (op1)) * sign-ext (op2) + op3
+@dots{}
+@end smallexample
+
+@cindex @code{ssad@var{m}} instruction pattern
+@item @samp{ssad@var{m}}
+@cindex @code{usad@var{m}} instruction pattern
+@item @samp{usad@var{m}}
+Compute the sum of absolute differences of two signed/unsigned elements.
+Operand 1 and operand 2 are of the same mode. Their absolute difference, which
+is of a wider mode, is computed and added to operand 3. Operand 3 is of a mode
+equal or wider than the mode of the absolute difference. The result is placed
+in operand 0, which is of the same mode as operand 3.
+
+@cindex @code{widen_ssum@var{m3}} instruction pattern
+@item @samp{widen_ssum@var{m3}}
+@cindex @code{widen_usum@var{m3}} instruction pattern
+@itemx @samp{widen_usum@var{m3}}
+Operands 0 and 2 are of the same mode, which is wider than the mode of
+operand 1. Add operand 1 to operand 2 and place the widened result in
+operand 0. (This is used express accumulation of elements into an accumulator
+of a wider mode.)
+
+@cindex @code{smulhs@var{m3}} instruction pattern
+@item @samp{smulhs@var{m3}}
+@cindex @code{umulhs@var{m3}} instruction pattern
+@itemx @samp{umulhs@var{m3}}
+Signed/unsigned multiply high with scale. This is equivalent to the C code:
+@smallexample
+narrow op0, op1, op2;
+@dots{}
+op0 = (narrow) (((wide) op1 * (wide) op2) >> (N / 2 - 1));
+@end smallexample
+where the sign of @samp{narrow} determines whether this is a signed
+or unsigned operation, and @var{N} is the size of @samp{wide} in bits.
+
+@cindex @code{smulhrs@var{m3}} instruction pattern
+@item @samp{smulhrs@var{m3}}
+@cindex @code{umulhrs@var{m3}} instruction pattern
+@itemx @samp{umulhrs@var{m3}}
+Signed/unsigned multiply high with round and scale. This is
+equivalent to the C code:
+@smallexample
+narrow op0, op1, op2;
+@dots{}
+op0 = (narrow) (((((wide) op1 * (wide) op2) >> (N / 2 - 2)) + 1) >> 1);
+@end smallexample
+where the sign of @samp{narrow} determines whether this is a signed
+or unsigned operation, and @var{N} is the size of @samp{wide} in bits.
+
+@cindex @code{sdiv_pow2@var{m3}} instruction pattern
+@item @samp{sdiv_pow2@var{m3}}
+@cindex @code{sdiv_pow2@var{m3}} instruction pattern
+@itemx @samp{sdiv_pow2@var{m3}}
+Signed division by power-of-2 immediate. Equivalent to:
+@smallexample
+signed op0, op1;
+@dots{}
+op0 = op1 / (1 << imm);
+@end smallexample
+
+@cindex @code{vec_shl_insert_@var{m}} instruction pattern
+@item @samp{vec_shl_insert_@var{m}}
+Shift the elements in vector input operand 1 left one element (i.e.@:
+away from element 0) and fill the vacated element 0 with the scalar
+in operand 2. Store the result in vector output operand 0. Operands
+0 and 1 have mode @var{m} and operand 2 has the mode appropriate for
+one element of @var{m}.
+
+@cindex @code{vec_shl_@var{m}} instruction pattern
+@item @samp{vec_shl_@var{m}}
+Whole vector left shift in bits, i.e.@: away from element 0.
+Operand 1 is a vector to be shifted.
+Operand 2 is an integer shift amount in bits.
+Operand 0 is where the resulting shifted vector is stored.
+The output and input vectors should have the same modes.
+
+@cindex @code{vec_shr_@var{m}} instruction pattern
+@item @samp{vec_shr_@var{m}}
+Whole vector right shift in bits, i.e.@: towards element 0.
+Operand 1 is a vector to be shifted.
+Operand 2 is an integer shift amount in bits.
+Operand 0 is where the resulting shifted vector is stored.
+The output and input vectors should have the same modes.
+
+@cindex @code{vec_pack_trunc_@var{m}} instruction pattern
+@item @samp{vec_pack_trunc_@var{m}}
+Narrow (demote) and merge the elements of two vectors. Operands 1 and 2
+are vectors of the same mode having N integral or floating point elements
+of size S@. Operand 0 is the resulting vector in which 2*N elements of
+size S/2 are concatenated after narrowing them down using truncation.
+
+@cindex @code{vec_pack_sbool_trunc_@var{m}} instruction pattern
+@item @samp{vec_pack_sbool_trunc_@var{m}}
+Narrow and merge the elements of two vectors. Operands 1 and 2 are vectors
+of the same type having N boolean elements. Operand 0 is the resulting
+vector in which 2*N elements are concatenated. The last operand (operand 3)
+is the number of elements in the output vector 2*N as a @code{CONST_INT}.
+This instruction pattern is used when all the vector input and output
+operands have the same scalar mode @var{m} and thus using
+@code{vec_pack_trunc_@var{m}} would be ambiguous.
+
+@cindex @code{vec_pack_ssat_@var{m}} instruction pattern
+@cindex @code{vec_pack_usat_@var{m}} instruction pattern
+@item @samp{vec_pack_ssat_@var{m}}, @samp{vec_pack_usat_@var{m}}
+Narrow (demote) and merge the elements of two vectors. Operands 1 and 2
+are vectors of the same mode having N integral elements of size S.
+Operand 0 is the resulting vector in which the elements of the two input
+vectors are concatenated after narrowing them down using signed/unsigned
+saturating arithmetic.
+
+@cindex @code{vec_pack_sfix_trunc_@var{m}} instruction pattern
+@cindex @code{vec_pack_ufix_trunc_@var{m}} instruction pattern
+@item @samp{vec_pack_sfix_trunc_@var{m}}, @samp{vec_pack_ufix_trunc_@var{m}}
+Narrow, convert to signed/unsigned integral type and merge the elements
+of two vectors. Operands 1 and 2 are vectors of the same mode having N
+floating point elements of size S@. Operand 0 is the resulting vector
+in which 2*N elements of size S/2 are concatenated.
+
+@cindex @code{vec_packs_float_@var{m}} instruction pattern
+@cindex @code{vec_packu_float_@var{m}} instruction pattern
+@item @samp{vec_packs_float_@var{m}}, @samp{vec_packu_float_@var{m}}
+Narrow, convert to floating point type and merge the elements
+of two vectors. Operands 1 and 2 are vectors of the same mode having N
+signed/unsigned integral elements of size S@. Operand 0 is the resulting vector
+in which 2*N elements of size S/2 are concatenated.
+
+@cindex @code{vec_unpacks_hi_@var{m}} instruction pattern
+@cindex @code{vec_unpacks_lo_@var{m}} instruction pattern
+@item @samp{vec_unpacks_hi_@var{m}}, @samp{vec_unpacks_lo_@var{m}}
+Extract and widen (promote) the high/low part of a vector of signed
+integral or floating point elements. The input vector (operand 1) has N
+elements of size S@. Widen (promote) the high/low elements of the vector
+using signed or floating point extension and place the resulting N/2
+values of size 2*S in the output vector (operand 0).
+
+@cindex @code{vec_unpacku_hi_@var{m}} instruction pattern
+@cindex @code{vec_unpacku_lo_@var{m}} instruction pattern
+@item @samp{vec_unpacku_hi_@var{m}}, @samp{vec_unpacku_lo_@var{m}}
+Extract and widen (promote) the high/low part of a vector of unsigned
+integral elements. The input vector (operand 1) has N elements of size S.
+Widen (promote) the high/low elements of the vector using zero extension and
+place the resulting N/2 values of size 2*S in the output vector (operand 0).
+
+@cindex @code{vec_unpacks_sbool_hi_@var{m}} instruction pattern
+@cindex @code{vec_unpacks_sbool_lo_@var{m}} instruction pattern
+@item @samp{vec_unpacks_sbool_hi_@var{m}}, @samp{vec_unpacks_sbool_lo_@var{m}}
+Extract the high/low part of a vector of boolean elements that have scalar
+mode @var{m}. The input vector (operand 1) has N elements, the output
+vector (operand 0) has N/2 elements. The last operand (operand 2) is the
+number of elements of the input vector N as a @code{CONST_INT}. These
+patterns are used if both the input and output vectors have the same scalar
+mode @var{m} and thus using @code{vec_unpacks_hi_@var{m}} or
+@code{vec_unpacks_lo_@var{m}} would be ambiguous.
+
+@cindex @code{vec_unpacks_float_hi_@var{m}} instruction pattern
+@cindex @code{vec_unpacks_float_lo_@var{m}} instruction pattern
+@cindex @code{vec_unpacku_float_hi_@var{m}} instruction pattern
+@cindex @code{vec_unpacku_float_lo_@var{m}} instruction pattern
+@item @samp{vec_unpacks_float_hi_@var{m}}, @samp{vec_unpacks_float_lo_@var{m}}
+@itemx @samp{vec_unpacku_float_hi_@var{m}}, @samp{vec_unpacku_float_lo_@var{m}}
+Extract, convert to floating point type and widen the high/low part of a
+vector of signed/unsigned integral elements. The input vector (operand 1)
+has N elements of size S@. Convert the high/low elements of the vector using
+floating point conversion and place the resulting N/2 values of size 2*S in
+the output vector (operand 0).
+
+@cindex @code{vec_unpack_sfix_trunc_hi_@var{m}} instruction pattern
+@cindex @code{vec_unpack_sfix_trunc_lo_@var{m}} instruction pattern
+@cindex @code{vec_unpack_ufix_trunc_hi_@var{m}} instruction pattern
+@cindex @code{vec_unpack_ufix_trunc_lo_@var{m}} instruction pattern
+@item @samp{vec_unpack_sfix_trunc_hi_@var{m}},
+@itemx @samp{vec_unpack_sfix_trunc_lo_@var{m}}
+@itemx @samp{vec_unpack_ufix_trunc_hi_@var{m}}
+@itemx @samp{vec_unpack_ufix_trunc_lo_@var{m}}
+Extract, convert to signed/unsigned integer type and widen the high/low part of a
+vector of floating point elements. The input vector (operand 1)
+has N elements of size S@. Convert the high/low elements of the vector
+to integers and place the resulting N/2 values of size 2*S in
+the output vector (operand 0).
+
+@cindex @code{vec_widen_umult_hi_@var{m}} instruction pattern
+@cindex @code{vec_widen_umult_lo_@var{m}} instruction pattern
+@cindex @code{vec_widen_smult_hi_@var{m}} instruction pattern
+@cindex @code{vec_widen_smult_lo_@var{m}} instruction pattern
+@cindex @code{vec_widen_umult_even_@var{m}} instruction pattern
+@cindex @code{vec_widen_umult_odd_@var{m}} instruction pattern
+@cindex @code{vec_widen_smult_even_@var{m}} instruction pattern
+@cindex @code{vec_widen_smult_odd_@var{m}} instruction pattern
+@item @samp{vec_widen_umult_hi_@var{m}}, @samp{vec_widen_umult_lo_@var{m}}
+@itemx @samp{vec_widen_smult_hi_@var{m}}, @samp{vec_widen_smult_lo_@var{m}}
+@itemx @samp{vec_widen_umult_even_@var{m}}, @samp{vec_widen_umult_odd_@var{m}}
+@itemx @samp{vec_widen_smult_even_@var{m}}, @samp{vec_widen_smult_odd_@var{m}}
+Signed/Unsigned widening multiplication. The two inputs (operands 1 and 2)
+are vectors with N signed/unsigned elements of size S@. Multiply the high/low
+or even/odd elements of the two vectors, and put the N/2 products of size 2*S
+in the output vector (operand 0). A target shouldn't implement even/odd pattern
+pair if it is less efficient than lo/hi one.
+
+@cindex @code{vec_widen_ushiftl_hi_@var{m}} instruction pattern
+@cindex @code{vec_widen_ushiftl_lo_@var{m}} instruction pattern
+@cindex @code{vec_widen_sshiftl_hi_@var{m}} instruction pattern
+@cindex @code{vec_widen_sshiftl_lo_@var{m}} instruction pattern
+@item @samp{vec_widen_ushiftl_hi_@var{m}}, @samp{vec_widen_ushiftl_lo_@var{m}}
+@itemx @samp{vec_widen_sshiftl_hi_@var{m}}, @samp{vec_widen_sshiftl_lo_@var{m}}
+Signed/Unsigned widening shift left. The first input (operand 1) is a vector
+with N signed/unsigned elements of size S@. Operand 2 is a constant. Shift
+the high/low elements of operand 1, and put the N/2 results of size 2*S in the
+output vector (operand 0).
+
+@cindex @code{vec_widen_saddl_hi_@var{m}} instruction pattern
+@cindex @code{vec_widen_saddl_lo_@var{m}} instruction pattern
+@cindex @code{vec_widen_uaddl_hi_@var{m}} instruction pattern
+@cindex @code{vec_widen_uaddl_lo_@var{m}} instruction pattern
+@item @samp{vec_widen_uaddl_hi_@var{m}}, @samp{vec_widen_uaddl_lo_@var{m}}
+@itemx @samp{vec_widen_saddl_hi_@var{m}}, @samp{vec_widen_saddl_lo_@var{m}}
+Signed/Unsigned widening add long. Operands 1 and 2 are vectors with N
+signed/unsigned elements of size S@. Add the high/low elements of 1 and 2
+together, widen the resulting elements and put the N/2 results of size 2*S in
+the output vector (operand 0).
+
+@cindex @code{vec_widen_ssubl_hi_@var{m}} instruction pattern
+@cindex @code{vec_widen_ssubl_lo_@var{m}} instruction pattern
+@cindex @code{vec_widen_usubl_hi_@var{m}} instruction pattern
+@cindex @code{vec_widen_usubl_lo_@var{m}} instruction pattern
+@item @samp{vec_widen_usubl_hi_@var{m}}, @samp{vec_widen_usubl_lo_@var{m}}
+@itemx @samp{vec_widen_ssubl_hi_@var{m}}, @samp{vec_widen_ssubl_lo_@var{m}}
+Signed/Unsigned widening subtract long. Operands 1 and 2 are vectors with N
+signed/unsigned elements of size S@. Subtract the high/low elements of 2 from
+1 and widen the resulting elements. Put the N/2 results of size 2*S in the
+output vector (operand 0).
+
+@cindex @code{vec_addsub@var{m}3} instruction pattern
+@item @samp{vec_addsub@var{m}3}
+Alternating subtract, add with even lanes doing subtract and odd
+lanes doing addition. Operands 1 and 2 and the outout operand are vectors
+with mode @var{m}.
+
+@cindex @code{vec_fmaddsub@var{m}4} instruction pattern
+@item @samp{vec_fmaddsub@var{m}4}
+Alternating multiply subtract, add with even lanes doing subtract and odd
+lanes doing addition of the third operand to the multiplication result
+of the first two operands. Operands 1, 2 and 3 and the outout operand are vectors
+with mode @var{m}.
+
+@cindex @code{vec_fmsubadd@var{m}4} instruction pattern
+@item @samp{vec_fmsubadd@var{m}4}
+Alternating multiply add, subtract with even lanes doing addition and odd
+lanes doing subtraction of the third operand to the multiplication result
+of the first two operands. Operands 1, 2 and 3 and the outout operand are vectors
+with mode @var{m}.
+
+These instructions are not allowed to @code{FAIL}.
+
+@cindex @code{mulhisi3} instruction pattern
+@item @samp{mulhisi3}
+Multiply operands 1 and 2, which have mode @code{HImode}, and store
+a @code{SImode} product in operand 0.
+
+@cindex @code{mulqihi3} instruction pattern
+@cindex @code{mulsidi3} instruction pattern
+@item @samp{mulqihi3}, @samp{mulsidi3}
+Similar widening-multiplication instructions of other widths.
+
+@cindex @code{umulqihi3} instruction pattern
+@cindex @code{umulhisi3} instruction pattern
+@cindex @code{umulsidi3} instruction pattern
+@item @samp{umulqihi3}, @samp{umulhisi3}, @samp{umulsidi3}
+Similar widening-multiplication instructions that do unsigned
+multiplication.
+
+@cindex @code{usmulqihi3} instruction pattern
+@cindex @code{usmulhisi3} instruction pattern
+@cindex @code{usmulsidi3} instruction pattern
+@item @samp{usmulqihi3}, @samp{usmulhisi3}, @samp{usmulsidi3}
+Similar widening-multiplication instructions that interpret the first
+operand as unsigned and the second operand as signed, then do a signed
+multiplication.
+
+@cindex @code{smul@var{m}3_highpart} instruction pattern
+@item @samp{smul@var{m}3_highpart}
+Perform a signed multiplication of operands 1 and 2, which have mode
+@var{m}, and store the most significant half of the product in operand 0.
+The least significant half of the product is discarded. This may be
+represented in RTL using a @code{smul_highpart} RTX expression.
+
+@cindex @code{umul@var{m}3_highpart} instruction pattern
+@item @samp{umul@var{m}3_highpart}
+Similar, but the multiplication is unsigned. This may be represented
+in RTL using an @code{umul_highpart} RTX expression.
+
+@cindex @code{madd@var{m}@var{n}4} instruction pattern
+@item @samp{madd@var{m}@var{n}4}
+Multiply operands 1 and 2, sign-extend them to mode @var{n}, add
+operand 3, and store the result in operand 0. Operands 1 and 2
+have mode @var{m} and operands 0 and 3 have mode @var{n}.
+Both modes must be integer or fixed-point modes and @var{n} must be twice
+the size of @var{m}.
+
+In other words, @code{madd@var{m}@var{n}4} is like
+@code{mul@var{m}@var{n}3} except that it also adds operand 3.
+
+These instructions are not allowed to @code{FAIL}.
+
+@cindex @code{umadd@var{m}@var{n}4} instruction pattern
+@item @samp{umadd@var{m}@var{n}4}
+Like @code{madd@var{m}@var{n}4}, but zero-extend the multiplication
+operands instead of sign-extending them.
+
+@cindex @code{ssmadd@var{m}@var{n}4} instruction pattern
+@item @samp{ssmadd@var{m}@var{n}4}
+Like @code{madd@var{m}@var{n}4}, but all involved operations must be
+signed-saturating.
+
+@cindex @code{usmadd@var{m}@var{n}4} instruction pattern
+@item @samp{usmadd@var{m}@var{n}4}
+Like @code{umadd@var{m}@var{n}4}, but all involved operations must be
+unsigned-saturating.
+
+@cindex @code{msub@var{m}@var{n}4} instruction pattern
+@item @samp{msub@var{m}@var{n}4}
+Multiply operands 1 and 2, sign-extend them to mode @var{n}, subtract the
+result from operand 3, and store the result in operand 0. Operands 1 and 2
+have mode @var{m} and operands 0 and 3 have mode @var{n}.
+Both modes must be integer or fixed-point modes and @var{n} must be twice
+the size of @var{m}.
+
+In other words, @code{msub@var{m}@var{n}4} is like
+@code{mul@var{m}@var{n}3} except that it also subtracts the result
+from operand 3.
+
+These instructions are not allowed to @code{FAIL}.
+
+@cindex @code{umsub@var{m}@var{n}4} instruction pattern
+@item @samp{umsub@var{m}@var{n}4}
+Like @code{msub@var{m}@var{n}4}, but zero-extend the multiplication
+operands instead of sign-extending them.
+
+@cindex @code{ssmsub@var{m}@var{n}4} instruction pattern
+@item @samp{ssmsub@var{m}@var{n}4}
+Like @code{msub@var{m}@var{n}4}, but all involved operations must be
+signed-saturating.
+
+@cindex @code{usmsub@var{m}@var{n}4} instruction pattern
+@item @samp{usmsub@var{m}@var{n}4}
+Like @code{umsub@var{m}@var{n}4}, but all involved operations must be
+unsigned-saturating.
+
+@cindex @code{divmod@var{m}4} instruction pattern
+@item @samp{divmod@var{m}4}
+Signed division that produces both a quotient and a remainder.
+Operand 1 is divided by operand 2 to produce a quotient stored
+in operand 0 and a remainder stored in operand 3.
+
+For machines with an instruction that produces both a quotient and a
+remainder, provide a pattern for @samp{divmod@var{m}4} but do not
+provide patterns for @samp{div@var{m}3} and @samp{mod@var{m}3}. This
+allows optimization in the relatively common case when both the quotient
+and remainder are computed.
+
+If an instruction that just produces a quotient or just a remainder
+exists and is more efficient than the instruction that produces both,
+write the output routine of @samp{divmod@var{m}4} to call
+@code{find_reg_note} and look for a @code{REG_UNUSED} note on the
+quotient or remainder and generate the appropriate instruction.
+
+@cindex @code{udivmod@var{m}4} instruction pattern
+@item @samp{udivmod@var{m}4}
+Similar, but does unsigned division.
+
+@anchor{shift patterns}
+@cindex @code{ashl@var{m}3} instruction pattern
+@cindex @code{ssashl@var{m}3} instruction pattern
+@cindex @code{usashl@var{m}3} instruction pattern
+@item @samp{ashl@var{m}3}, @samp{ssashl@var{m}3}, @samp{usashl@var{m}3}
+Arithmetic-shift operand 1 left by a number of bits specified by operand
+2, and store the result in operand 0. Here @var{m} is the mode of
+operand 0 and operand 1; operand 2's mode is specified by the
+instruction pattern, and the compiler will convert the operand to that
+mode before generating the instruction. The shift or rotate expander
+or instruction pattern should explicitly specify the mode of the operand 2,
+it should never be @code{VOIDmode}. The meaning of out-of-range shift
+counts can optionally be specified by @code{TARGET_SHIFT_TRUNCATION_MASK}.
+@xref{TARGET_SHIFT_TRUNCATION_MASK}. Operand 2 is always a scalar type.
+
+@cindex @code{ashr@var{m}3} instruction pattern
+@cindex @code{lshr@var{m}3} instruction pattern
+@cindex @code{rotl@var{m}3} instruction pattern
+@cindex @code{rotr@var{m}3} instruction pattern
+@item @samp{ashr@var{m}3}, @samp{lshr@var{m}3}, @samp{rotl@var{m}3}, @samp{rotr@var{m}3}
+Other shift and rotate instructions, analogous to the
+@code{ashl@var{m}3} instructions. Operand 2 is always a scalar type.
+
+@cindex @code{vashl@var{m}3} instruction pattern
+@cindex @code{vashr@var{m}3} instruction pattern
+@cindex @code{vlshr@var{m}3} instruction pattern
+@cindex @code{vrotl@var{m}3} instruction pattern
+@cindex @code{vrotr@var{m}3} instruction pattern
+@item @samp{vashl@var{m}3}, @samp{vashr@var{m}3}, @samp{vlshr@var{m}3}, @samp{vrotl@var{m}3}, @samp{vrotr@var{m}3}
+Vector shift and rotate instructions that take vectors as operand 2
+instead of a scalar type.
+
+@cindex @code{avg@var{m}3_floor} instruction pattern
+@cindex @code{uavg@var{m}3_floor} instruction pattern
+@item @samp{avg@var{m}3_floor}
+@itemx @samp{uavg@var{m}3_floor}
+Signed and unsigned average instructions. These instructions add
+operands 1 and 2 without truncation, divide the result by 2,
+round towards -Inf, and store the result in operand 0. This is
+equivalent to the C code:
+@smallexample
+narrow op0, op1, op2;
+@dots{}
+op0 = (narrow) (((wide) op1 + (wide) op2) >> 1);
+@end smallexample
+where the sign of @samp{narrow} determines whether this is a signed
+or unsigned operation.
+
+@cindex @code{avg@var{m}3_ceil} instruction pattern
+@cindex @code{uavg@var{m}3_ceil} instruction pattern
+@item @samp{avg@var{m}3_ceil}
+@itemx @samp{uavg@var{m}3_ceil}
+Like @samp{avg@var{m}3_floor} and @samp{uavg@var{m}3_floor}, but round
+towards +Inf. This is equivalent to the C code:
+@smallexample
+narrow op0, op1, op2;
+@dots{}
+op0 = (narrow) (((wide) op1 + (wide) op2 + 1) >> 1);
+@end smallexample
+
+@cindex @code{bswap@var{m}2} instruction pattern
+@item @samp{bswap@var{m}2}
+Reverse the order of bytes of operand 1 and store the result in operand 0.
+
+@cindex @code{neg@var{m}2} instruction pattern
+@cindex @code{ssneg@var{m}2} instruction pattern
+@cindex @code{usneg@var{m}2} instruction pattern
+@item @samp{neg@var{m}2}, @samp{ssneg@var{m}2}, @samp{usneg@var{m}2}
+Negate operand 1 and store the result in operand 0.
+
+@cindex @code{negv@var{m}3} instruction pattern
+@item @samp{negv@var{m}3}
+Like @code{neg@var{m}2} but takes a @code{code_label} as operand 2 and
+emits code to jump to it if signed overflow occurs during the negation.
+
+@cindex @code{abs@var{m}2} instruction pattern
+@item @samp{abs@var{m}2}
+Store the absolute value of operand 1 into operand 0.
+
+@cindex @code{sqrt@var{m}2} instruction pattern
+@item @samp{sqrt@var{m}2}
+Store the square root of operand 1 into operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{rsqrt@var{m}2} instruction pattern
+@item @samp{rsqrt@var{m}2}
+Store the reciprocal of the square root of operand 1 into operand 0.
+Both operands have mode @var{m}, which is a scalar or vector
+floating-point mode.
+
+On most architectures this pattern is only approximate, so either
+its C condition or the @code{TARGET_OPTAB_SUPPORTED_P} hook should
+check for the appropriate math flags. (Using the C condition is
+more direct, but using @code{TARGET_OPTAB_SUPPORTED_P} can be useful
+if a target-specific built-in also uses the @samp{rsqrt@var{m}2}
+pattern.)
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{fmod@var{m}3} instruction pattern
+@item @samp{fmod@var{m}3}
+Store the remainder of dividing operand 1 by operand 2 into
+operand 0, rounded towards zero to an integer. All operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{remainder@var{m}3} instruction pattern
+@item @samp{remainder@var{m}3}
+Store the remainder of dividing operand 1 by operand 2 into
+operand 0, rounded to the nearest integer. All operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{scalb@var{m}3} instruction pattern
+@item @samp{scalb@var{m}3}
+Raise @code{FLT_RADIX} to the power of operand 2, multiply it by
+operand 1, and store the result in operand 0. All operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{ldexp@var{m}3} instruction pattern
+@item @samp{ldexp@var{m}3}
+Raise 2 to the power of operand 2, multiply it by operand 1, and store
+the result in operand 0. Operands 0 and 1 have mode @var{m}, which is
+a scalar or vector floating-point mode. Operand 2's mode has
+the same number of elements as @var{m} and each element is wide
+enough to store an @code{int}. The integers are signed.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{cos@var{m}2} instruction pattern
+@item @samp{cos@var{m}2}
+Store the cosine of operand 1 into operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{sin@var{m}2} instruction pattern
+@item @samp{sin@var{m}2}
+Store the sine of operand 1 into operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{sincos@var{m}3} instruction pattern
+@item @samp{sincos@var{m}3}
+Store the cosine of operand 2 into operand 0 and the sine of
+operand 2 into operand 1. All operands have mode @var{m},
+which is a scalar or vector floating-point mode.
+
+Targets that can calculate the sine and cosine simultaneously can
+implement this pattern as opposed to implementing individual
+@code{sin@var{m}2} and @code{cos@var{m}2} patterns. The @code{sin}
+and @code{cos} built-in functions will then be expanded to the
+@code{sincos@var{m}3} pattern, with one of the output values
+left unused.
+
+@cindex @code{tan@var{m}2} instruction pattern
+@item @samp{tan@var{m}2}
+Store the tangent of operand 1 into operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{asin@var{m}2} instruction pattern
+@item @samp{asin@var{m}2}
+Store the arc sine of operand 1 into operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{acos@var{m}2} instruction pattern
+@item @samp{acos@var{m}2}
+Store the arc cosine of operand 1 into operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{atan@var{m}2} instruction pattern
+@item @samp{atan@var{m}2}
+Store the arc tangent of operand 1 into operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{fegetround@var{m}} instruction pattern
+@item @samp{fegetround@var{m}}
+Store the current machine floating-point rounding mode into operand 0.
+Operand 0 has mode @var{m}, which is scalar. This pattern is used to
+implement the @code{fegetround} function from the ISO C99 standard.
+
+@cindex @code{feclearexcept@var{m}} instruction pattern
+@cindex @code{feraiseexcept@var{m}} instruction pattern
+@item @samp{feclearexcept@var{m}}
+@item @samp{feraiseexcept@var{m}}
+Clears or raises the supported machine floating-point exceptions
+represented by the bits in operand 1. Error status is stored as
+nonzero value in operand 0. Both operands have mode @var{m}, which is
+a scalar. These patterns are used to implement the
+@code{feclearexcept} and @code{feraiseexcept} functions from the ISO
+C99 standard.
+
+@cindex @code{exp@var{m}2} instruction pattern
+@item @samp{exp@var{m}2}
+Raise e (the base of natural logarithms) to the power of operand 1
+and store the result in operand 0. Both operands have mode @var{m},
+which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{expm1@var{m}2} instruction pattern
+@item @samp{expm1@var{m}2}
+Raise e (the base of natural logarithms) to the power of operand 1,
+subtract 1, and store the result in operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode.
+
+For inputs close to zero, the pattern is expected to be more
+accurate than a separate @code{exp@var{m}2} and @code{sub@var{m}3}
+would be.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{exp10@var{m}2} instruction pattern
+@item @samp{exp10@var{m}2}
+Raise 10 to the power of operand 1 and store the result in operand 0.
+Both operands have mode @var{m}, which is a scalar or vector
+floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{exp2@var{m}2} instruction pattern
+@item @samp{exp2@var{m}2}
+Raise 2 to the power of operand 1 and store the result in operand 0.
+Both operands have mode @var{m}, which is a scalar or vector
+floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{log@var{m}2} instruction pattern
+@item @samp{log@var{m}2}
+Store the natural logarithm of operand 1 into operand 0. Both operands
+have mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{log1p@var{m}2} instruction pattern
+@item @samp{log1p@var{m}2}
+Add 1 to operand 1, compute the natural logarithm, and store
+the result in operand 0. Both operands have mode @var{m}, which is
+a scalar or vector floating-point mode.
+
+For inputs close to zero, the pattern is expected to be more
+accurate than a separate @code{add@var{m}3} and @code{log@var{m}2}
+would be.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{log10@var{m}2} instruction pattern
+@item @samp{log10@var{m}2}
+Store the base-10 logarithm of operand 1 into operand 0. Both operands
+have mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{log2@var{m}2} instruction pattern
+@item @samp{log2@var{m}2}
+Store the base-2 logarithm of operand 1 into operand 0. Both operands
+have mode @var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{logb@var{m}2} instruction pattern
+@item @samp{logb@var{m}2}
+Store the base-@code{FLT_RADIX} logarithm of operand 1 into operand 0.
+Both operands have mode @var{m}, which is a scalar or vector
+floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{significand@var{m}2} instruction pattern
+@item @samp{significand@var{m}2}
+Store the significand of floating-point operand 1 in operand 0.
+Both operands have mode @var{m}, which is a scalar or vector
+floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{pow@var{m}3} instruction pattern
+@item @samp{pow@var{m}3}
+Store the value of operand 1 raised to the exponent operand 2
+into operand 0. All operands have mode @var{m}, which is a scalar
+or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{atan2@var{m}3} instruction pattern
+@item @samp{atan2@var{m}3}
+Store the arc tangent (inverse tangent) of operand 1 divided by
+operand 2 into operand 0, using the signs of both arguments to
+determine the quadrant of the result. All operands have mode
+@var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{floor@var{m}2} instruction pattern
+@item @samp{floor@var{m}2}
+Store the largest integral value not greater than operand 1 in operand 0.
+Both operands have mode @var{m}, which is a scalar or vector
+floating-point mode. If @option{-ffp-int-builtin-inexact} is in
+effect, the ``inexact'' exception may be raised for noninteger
+operands; otherwise, it may not.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{btrunc@var{m}2} instruction pattern
+@item @samp{btrunc@var{m}2}
+Round operand 1 to an integer, towards zero, and store the result in
+operand 0. Both operands have mode @var{m}, which is a scalar or
+vector floating-point mode. If @option{-ffp-int-builtin-inexact} is
+in effect, the ``inexact'' exception may be raised for noninteger
+operands; otherwise, it may not.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{round@var{m}2} instruction pattern
+@item @samp{round@var{m}2}
+Round operand 1 to the nearest integer, rounding away from zero in the
+event of a tie, and store the result in operand 0. Both operands have
+mode @var{m}, which is a scalar or vector floating-point mode. If
+@option{-ffp-int-builtin-inexact} is in effect, the ``inexact''
+exception may be raised for noninteger operands; otherwise, it may
+not.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{ceil@var{m}2} instruction pattern
+@item @samp{ceil@var{m}2}
+Store the smallest integral value not less than operand 1 in operand 0.
+Both operands have mode @var{m}, which is a scalar or vector
+floating-point mode. If @option{-ffp-int-builtin-inexact} is in
+effect, the ``inexact'' exception may be raised for noninteger
+operands; otherwise, it may not.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{nearbyint@var{m}2} instruction pattern
+@item @samp{nearbyint@var{m}2}
+Round operand 1 to an integer, using the current rounding mode, and
+store the result in operand 0. Do not raise an inexact condition when
+the result is different from the argument. Both operands have mode
+@var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{rint@var{m}2} instruction pattern
+@item @samp{rint@var{m}2}
+Round operand 1 to an integer, using the current rounding mode, and
+store the result in operand 0. Raise an inexact condition when
+the result is different from the argument. Both operands have mode
+@var{m}, which is a scalar or vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{lrint@var{m}@var{n}2}
+@item @samp{lrint@var{m}@var{n}2}
+Convert operand 1 (valid for floating point mode @var{m}) to fixed
+point mode @var{n} as a signed number according to the current
+rounding mode and store in operand 0 (which has mode @var{n}).
+
+@cindex @code{lround@var{m}@var{n}2}
+@item @samp{lround@var{m}@var{n}2}
+Convert operand 1 (valid for floating point mode @var{m}) to fixed
+point mode @var{n} as a signed number rounding to nearest and away
+from zero and store in operand 0 (which has mode @var{n}).
+
+@cindex @code{lfloor@var{m}@var{n}2}
+@item @samp{lfloor@var{m}@var{n}2}
+Convert operand 1 (valid for floating point mode @var{m}) to fixed
+point mode @var{n} as a signed number rounding down and store in
+operand 0 (which has mode @var{n}).
+
+@cindex @code{lceil@var{m}@var{n}2}
+@item @samp{lceil@var{m}@var{n}2}
+Convert operand 1 (valid for floating point mode @var{m}) to fixed
+point mode @var{n} as a signed number rounding up and store in
+operand 0 (which has mode @var{n}).
+
+@cindex @code{copysign@var{m}3} instruction pattern
+@item @samp{copysign@var{m}3}
+Store a value with the magnitude of operand 1 and the sign of operand
+2 into operand 0. All operands have mode @var{m}, which is a scalar or
+vector floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{xorsign@var{m}3} instruction pattern
+@item @samp{xorsign@var{m}3}
+Equivalent to @samp{op0 = op1 * copysign (1.0, op2)}: store a value with
+the magnitude of operand 1 and the sign of operand 2 into operand 0.
+All operands have mode @var{m}, which is a scalar or vector
+floating-point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{issignaling@var{m}2} instruction pattern
+@item @samp{issignaling@var{m}2}
+Set operand 0 to 1 if operand 1 is a signaling NaN and to 0 otherwise.
+
+@cindex @code{cadd90@var{m}3} instruction pattern
+@item @samp{cadd90@var{m}3}
+Perform vector add and subtract on even/odd number pairs. The operation being
+matched is semantically described as
+
+@smallexample
+ for (int i = 0; i < N; i += 2)
+ @{
+ c[i] = a[i] - b[i+1];
+ c[i+1] = a[i+1] + b[i];
+ @}
+@end smallexample
+
+This operation is semantically equivalent to performing a vector addition of
+complex numbers in operand 1 with operand 2 rotated by 90 degrees around
+the argand plane and storing the result in operand 0.
+
+In GCC lane ordering the real part of the number must be in the even lanes with
+the imaginary part in the odd lanes.
+
+The operation is only supported for vector modes @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{cadd270@var{m}3} instruction pattern
+@item @samp{cadd270@var{m}3}
+Perform vector add and subtract on even/odd number pairs. The operation being
+matched is semantically described as
+
+@smallexample
+ for (int i = 0; i < N; i += 2)
+ @{
+ c[i] = a[i] + b[i+1];
+ c[i+1] = a[i+1] - b[i];
+ @}
+@end smallexample
+
+This operation is semantically equivalent to performing a vector addition of
+complex numbers in operand 1 with operand 2 rotated by 270 degrees around
+the argand plane and storing the result in operand 0.
+
+In GCC lane ordering the real part of the number must be in the even lanes with
+the imaginary part in the odd lanes.
+
+The operation is only supported for vector modes @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{cmla@var{m}4} instruction pattern
+@item @samp{cmla@var{m}4}
+Perform a vector multiply and accumulate that is semantically the same as
+a multiply and accumulate of complex numbers.
+
+@smallexample
+ complex TYPE op0[N];
+ complex TYPE op1[N];
+ complex TYPE op2[N];
+ complex TYPE op3[N];
+ for (int i = 0; i < N; i += 1)
+ @{
+ op0[i] = op1[i] * op2[i] + op3[i];
+ @}
+@end smallexample
+
+In GCC lane ordering the real part of the number must be in the even lanes with
+the imaginary part in the odd lanes.
+
+The operation is only supported for vector modes @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{cmla_conj@var{m}4} instruction pattern
+@item @samp{cmla_conj@var{m}4}
+Perform a vector multiply by conjugate and accumulate that is semantically
+the same as a multiply and accumulate of complex numbers where the second
+multiply arguments is conjugated.
+
+@smallexample
+ complex TYPE op0[N];
+ complex TYPE op1[N];
+ complex TYPE op2[N];
+ complex TYPE op3[N];
+ for (int i = 0; i < N; i += 1)
+ @{
+ op0[i] = op1[i] * conj (op2[i]) + op3[i];
+ @}
+@end smallexample
+
+In GCC lane ordering the real part of the number must be in the even lanes with
+the imaginary part in the odd lanes.
+
+The operation is only supported for vector modes @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{cmls@var{m}4} instruction pattern
+@item @samp{cmls@var{m}4}
+Perform a vector multiply and subtract that is semantically the same as
+a multiply and subtract of complex numbers.
+
+@smallexample
+ complex TYPE op0[N];
+ complex TYPE op1[N];
+ complex TYPE op2[N];
+ complex TYPE op3[N];
+ for (int i = 0; i < N; i += 1)
+ @{
+ op0[i] = op1[i] * op2[i] - op3[i];
+ @}
+@end smallexample
+
+In GCC lane ordering the real part of the number must be in the even lanes with
+the imaginary part in the odd lanes.
+
+The operation is only supported for vector modes @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{cmls_conj@var{m}4} instruction pattern
+@item @samp{cmls_conj@var{m}4}
+Perform a vector multiply by conjugate and subtract that is semantically
+the same as a multiply and subtract of complex numbers where the second
+multiply arguments is conjugated.
+
+@smallexample
+ complex TYPE op0[N];
+ complex TYPE op1[N];
+ complex TYPE op2[N];
+ complex TYPE op3[N];
+ for (int i = 0; i < N; i += 1)
+ @{
+ op0[i] = op1[i] * conj (op2[i]) - op3[i];
+ @}
+@end smallexample
+
+In GCC lane ordering the real part of the number must be in the even lanes with
+the imaginary part in the odd lanes.
+
+The operation is only supported for vector modes @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{cmul@var{m}4} instruction pattern
+@item @samp{cmul@var{m}4}
+Perform a vector multiply that is semantically the same as multiply of
+complex numbers.
+
+@smallexample
+ complex TYPE op0[N];
+ complex TYPE op1[N];
+ complex TYPE op2[N];
+ for (int i = 0; i < N; i += 1)
+ @{
+ op0[i] = op1[i] * op2[i];
+ @}
+@end smallexample
+
+In GCC lane ordering the real part of the number must be in the even lanes with
+the imaginary part in the odd lanes.
+
+The operation is only supported for vector modes @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{cmul_conj@var{m}4} instruction pattern
+@item @samp{cmul_conj@var{m}4}
+Perform a vector multiply by conjugate that is semantically the same as a
+multiply of complex numbers where the second multiply arguments is conjugated.
+
+@smallexample
+ complex TYPE op0[N];
+ complex TYPE op1[N];
+ complex TYPE op2[N];
+ for (int i = 0; i < N; i += 1)
+ @{
+ op0[i] = op1[i] * conj (op2[i]);
+ @}
+@end smallexample
+
+In GCC lane ordering the real part of the number must be in the even lanes with
+the imaginary part in the odd lanes.
+
+The operation is only supported for vector modes @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{ffs@var{m}2} instruction pattern
+@item @samp{ffs@var{m}2}
+Store into operand 0 one plus the index of the least significant 1-bit
+of operand 1. If operand 1 is zero, store zero.
+
+@var{m} is either a scalar or vector integer mode. When it is a scalar,
+operand 1 has mode @var{m} but operand 0 can have whatever scalar
+integer mode is suitable for the target. The compiler will insert
+conversion instructions as necessary (typically to convert the result
+to the same width as @code{int}). When @var{m} is a vector, both
+operands must have mode @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{clrsb@var{m}2} instruction pattern
+@item @samp{clrsb@var{m}2}
+Count leading redundant sign bits.
+Store into operand 0 the number of redundant sign bits in operand 1, starting
+at the most significant bit position.
+A redundant sign bit is defined as any sign bit after the first. As such,
+this count will be one less than the count of leading sign bits.
+
+@var{m} is either a scalar or vector integer mode. When it is a scalar,
+operand 1 has mode @var{m} but operand 0 can have whatever scalar
+integer mode is suitable for the target. The compiler will insert
+conversion instructions as necessary (typically to convert the result
+to the same width as @code{int}). When @var{m} is a vector, both
+operands must have mode @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{clz@var{m}2} instruction pattern
+@item @samp{clz@var{m}2}
+Store into operand 0 the number of leading 0-bits in operand 1, starting
+at the most significant bit position. If operand 1 is 0, the
+@code{CLZ_DEFINED_VALUE_AT_ZERO} (@pxref{Misc}) macro defines if
+the result is undefined or has a useful value.
+
+@var{m} is either a scalar or vector integer mode. When it is a scalar,
+operand 1 has mode @var{m} but operand 0 can have whatever scalar
+integer mode is suitable for the target. The compiler will insert
+conversion instructions as necessary (typically to convert the result
+to the same width as @code{int}). When @var{m} is a vector, both
+operands must have mode @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{ctz@var{m}2} instruction pattern
+@item @samp{ctz@var{m}2}
+Store into operand 0 the number of trailing 0-bits in operand 1, starting
+at the least significant bit position. If operand 1 is 0, the
+@code{CTZ_DEFINED_VALUE_AT_ZERO} (@pxref{Misc}) macro defines if
+the result is undefined or has a useful value.
+
+@var{m} is either a scalar or vector integer mode. When it is a scalar,
+operand 1 has mode @var{m} but operand 0 can have whatever scalar
+integer mode is suitable for the target. The compiler will insert
+conversion instructions as necessary (typically to convert the result
+to the same width as @code{int}). When @var{m} is a vector, both
+operands must have mode @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{popcount@var{m}2} instruction pattern
+@item @samp{popcount@var{m}2}
+Store into operand 0 the number of 1-bits in operand 1.
+
+@var{m} is either a scalar or vector integer mode. When it is a scalar,
+operand 1 has mode @var{m} but operand 0 can have whatever scalar
+integer mode is suitable for the target. The compiler will insert
+conversion instructions as necessary (typically to convert the result
+to the same width as @code{int}). When @var{m} is a vector, both
+operands must have mode @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{parity@var{m}2} instruction pattern
+@item @samp{parity@var{m}2}
+Store into operand 0 the parity of operand 1, i.e.@: the number of 1-bits
+in operand 1 modulo 2.
+
+@var{m} is either a scalar or vector integer mode. When it is a scalar,
+operand 1 has mode @var{m} but operand 0 can have whatever scalar
+integer mode is suitable for the target. The compiler will insert
+conversion instructions as necessary (typically to convert the result
+to the same width as @code{int}). When @var{m} is a vector, both
+operands must have mode @var{m}.
+
+This pattern is not allowed to @code{FAIL}.
+
+@cindex @code{one_cmpl@var{m}2} instruction pattern
+@item @samp{one_cmpl@var{m}2}
+Store the bitwise-complement of operand 1 into operand 0.
+
+@cindex @code{cpymem@var{m}} instruction pattern
+@item @samp{cpymem@var{m}}
+Block copy instruction. The destination and source blocks of memory
+are the first two operands, and both are @code{mem:BLK}s with an
+address in mode @code{Pmode}.
+
+The number of bytes to copy is the third operand, in mode @var{m}.
+Usually, you specify @code{Pmode} for @var{m}. However, if you can
+generate better code knowing the range of valid lengths is smaller than
+those representable in a full Pmode pointer, you should provide
+a pattern with a
+mode corresponding to the range of values you can handle efficiently
+(e.g., @code{QImode} for values in the range 0--127; note we avoid numbers
+that appear negative) and also a pattern with @code{Pmode}.
+
+The fourth operand is the known shared alignment of the source and
+destination, in the form of a @code{const_int} rtx. Thus, if the
+compiler knows that both source and destination are word-aligned,
+it may provide the value 4 for this operand.
+
+Optional operands 5 and 6 specify expected alignment and size of block
+respectively. The expected alignment differs from alignment in operand 4
+in a way that the blocks are not required to be aligned according to it in
+all cases. This expected alignment is also in bytes, just like operand 4.
+Expected size, when unknown, is set to @code{(const_int -1)}.
+
+Descriptions of multiple @code{cpymem@var{m}} patterns can only be
+beneficial if the patterns for smaller modes have fewer restrictions
+on their first, second and fourth operands. Note that the mode @var{m}
+in @code{cpymem@var{m}} does not impose any restriction on the mode of
+individually copied data units in the block.
+
+The @code{cpymem@var{m}} patterns need not give special consideration
+to the possibility that the source and destination strings might
+overlap. These patterns are used to do inline expansion of
+@code{__builtin_memcpy}.
+
+@cindex @code{movmem@var{m}} instruction pattern
+@item @samp{movmem@var{m}}
+Block move instruction. The destination and source blocks of memory
+are the first two operands, and both are @code{mem:BLK}s with an
+address in mode @code{Pmode}.
+
+The number of bytes to copy is the third operand, in mode @var{m}.
+Usually, you specify @code{Pmode} for @var{m}. However, if you can
+generate better code knowing the range of valid lengths is smaller than
+those representable in a full Pmode pointer, you should provide
+a pattern with a
+mode corresponding to the range of values you can handle efficiently
+(e.g., @code{QImode} for values in the range 0--127; note we avoid numbers
+that appear negative) and also a pattern with @code{Pmode}.
+
+The fourth operand is the known shared alignment of the source and
+destination, in the form of a @code{const_int} rtx. Thus, if the
+compiler knows that both source and destination are word-aligned,
+it may provide the value 4 for this operand.
+
+Optional operands 5 and 6 specify expected alignment and size of block
+respectively. The expected alignment differs from alignment in operand 4
+in a way that the blocks are not required to be aligned according to it in
+all cases. This expected alignment is also in bytes, just like operand 4.
+Expected size, when unknown, is set to @code{(const_int -1)}.
+
+Descriptions of multiple @code{movmem@var{m}} patterns can only be
+beneficial if the patterns for smaller modes have fewer restrictions
+on their first, second and fourth operands. Note that the mode @var{m}
+in @code{movmem@var{m}} does not impose any restriction on the mode of
+individually copied data units in the block.
+
+The @code{movmem@var{m}} patterns must correctly handle the case where
+the source and destination strings overlap. These patterns are used to
+do inline expansion of @code{__builtin_memmove}.
+
+@cindex @code{movstr} instruction pattern
+@item @samp{movstr}
+String copy instruction, with @code{stpcpy} semantics. Operand 0 is
+an output operand in mode @code{Pmode}. The addresses of the
+destination and source strings are operands 1 and 2, and both are
+@code{mem:BLK}s with addresses in mode @code{Pmode}. The execution of
+the expansion of this pattern should store in operand 0 the address in
+which the @code{NUL} terminator was stored in the destination string.
+
+This pattern has also several optional operands that are same as in
+@code{setmem}.
+
+@cindex @code{setmem@var{m}} instruction pattern
+@item @samp{setmem@var{m}}
+Block set instruction. The destination string is the first operand,
+given as a @code{mem:BLK} whose address is in mode @code{Pmode}. The
+number of bytes to set is the second operand, in mode @var{m}. The value to
+initialize the memory with is the third operand. Targets that only support the
+clearing of memory should reject any value that is not the constant 0. See
+@samp{cpymem@var{m}} for a discussion of the choice of mode.
+
+The fourth operand is the known alignment of the destination, in the form
+of a @code{const_int} rtx. Thus, if the compiler knows that the
+destination is word-aligned, it may provide the value 4 for this
+operand.
+
+Optional operands 5 and 6 specify expected alignment and size of block
+respectively. The expected alignment differs from alignment in operand 4
+in a way that the blocks are not required to be aligned according to it in
+all cases. This expected alignment is also in bytes, just like operand 4.
+Expected size, when unknown, is set to @code{(const_int -1)}.
+Operand 7 is the minimal size of the block and operand 8 is the
+maximal size of the block (NULL if it cannot be represented as CONST_INT).
+Operand 9 is the probable maximal size (i.e.@: we cannot rely on it for
+correctness, but it can be used for choosing proper code sequence for a
+given size).
+
+The use for multiple @code{setmem@var{m}} is as for @code{cpymem@var{m}}.
+
+@cindex @code{cmpstrn@var{m}} instruction pattern
+@item @samp{cmpstrn@var{m}}
+String compare instruction, with five operands. Operand 0 is the output;
+it has mode @var{m}. The remaining four operands are like the operands
+of @samp{cpymem@var{m}}. The two memory blocks specified are compared
+byte by byte in lexicographic order starting at the beginning of each
+string. The instruction is not allowed to prefetch more than one byte
+at a time since either string may end in the first byte and reading past
+that may access an invalid page or segment and cause a fault. The
+comparison terminates early if the fetched bytes are different or if
+they are equal to zero. The effect of the instruction is to store a
+value in operand 0 whose sign indicates the result of the comparison.
+
+@cindex @code{cmpstr@var{m}} instruction pattern
+@item @samp{cmpstr@var{m}}
+String compare instruction, without known maximum length. Operand 0 is the
+output; it has mode @var{m}. The second and third operand are the blocks of
+memory to be compared; both are @code{mem:BLK} with an address in mode
+@code{Pmode}.
+
+The fourth operand is the known shared alignment of the source and
+destination, in the form of a @code{const_int} rtx. Thus, if the
+compiler knows that both source and destination are word-aligned,
+it may provide the value 4 for this operand.
+
+The two memory blocks specified are compared byte by byte in lexicographic
+order starting at the beginning of each string. The instruction is not allowed
+to prefetch more than one byte at a time since either string may end in the
+first byte and reading past that may access an invalid page or segment and
+cause a fault. The comparison will terminate when the fetched bytes
+are different or if they are equal to zero. The effect of the
+instruction is to store a value in operand 0 whose sign indicates the
+result of the comparison.
+
+@cindex @code{cmpmem@var{m}} instruction pattern
+@item @samp{cmpmem@var{m}}
+Block compare instruction, with five operands like the operands
+of @samp{cmpstr@var{m}}. The two memory blocks specified are compared
+byte by byte in lexicographic order starting at the beginning of each
+block. Unlike @samp{cmpstr@var{m}} the instruction can prefetch
+any bytes in the two memory blocks. Also unlike @samp{cmpstr@var{m}}
+the comparison will not stop if both bytes are zero. The effect of
+the instruction is to store a value in operand 0 whose sign indicates
+the result of the comparison.
+
+@cindex @code{strlen@var{m}} instruction pattern
+@item @samp{strlen@var{m}}
+Compute the length of a string, with three operands.
+Operand 0 is the result (of mode @var{m}), operand 1 is
+a @code{mem} referring to the first character of the string,
+operand 2 is the character to search for (normally zero),
+and operand 3 is a constant describing the known alignment
+of the beginning of the string.
+
+@cindex @code{rawmemchr@var{m}} instruction pattern
+@item @samp{rawmemchr@var{m}}
+Scan memory referred to by operand 1 for the first occurrence of operand 2.
+Operand 1 is a @code{mem} and operand 2 a @code{const_int} of mode @var{m}.
+Operand 0 is the result, i.e., a pointer to the first occurrence of operand 2
+in the memory block given by operand 1.
+
+@cindex @code{float@var{m}@var{n}2} instruction pattern
+@item @samp{float@var{m}@var{n}2}
+Convert signed integer operand 1 (valid for fixed point mode @var{m}) to
+floating point mode @var{n} and store in operand 0 (which has mode
+@var{n}).
+
+@cindex @code{floatuns@var{m}@var{n}2} instruction pattern
+@item @samp{floatuns@var{m}@var{n}2}
+Convert unsigned integer operand 1 (valid for fixed point mode @var{m})
+to floating point mode @var{n} and store in operand 0 (which has mode
+@var{n}).
+
+@cindex @code{fix@var{m}@var{n}2} instruction pattern
+@item @samp{fix@var{m}@var{n}2}
+Convert operand 1 (valid for floating point mode @var{m}) to fixed
+point mode @var{n} as a signed number and store in operand 0 (which
+has mode @var{n}). This instruction's result is defined only when
+the value of operand 1 is an integer.
+
+If the machine description defines this pattern, it also needs to
+define the @code{ftrunc} pattern.
+
+@cindex @code{fixuns@var{m}@var{n}2} instruction pattern
+@item @samp{fixuns@var{m}@var{n}2}
+Convert operand 1 (valid for floating point mode @var{m}) to fixed
+point mode @var{n} as an unsigned number and store in operand 0 (which
+has mode @var{n}). This instruction's result is defined only when the
+value of operand 1 is an integer.
+
+@cindex @code{ftrunc@var{m}2} instruction pattern
+@item @samp{ftrunc@var{m}2}
+Convert operand 1 (valid for floating point mode @var{m}) to an
+integer value, still represented in floating point mode @var{m}, and
+store it in operand 0 (valid for floating point mode @var{m}).
+
+@cindex @code{fix_trunc@var{m}@var{n}2} instruction pattern
+@item @samp{fix_trunc@var{m}@var{n}2}
+Like @samp{fix@var{m}@var{n}2} but works for any floating point value
+of mode @var{m} by converting the value to an integer.
+
+@cindex @code{fixuns_trunc@var{m}@var{n}2} instruction pattern
+@item @samp{fixuns_trunc@var{m}@var{n}2}
+Like @samp{fixuns@var{m}@var{n}2} but works for any floating point
+value of mode @var{m} by converting the value to an integer.
+
+@cindex @code{trunc@var{m}@var{n}2} instruction pattern
+@item @samp{trunc@var{m}@var{n}2}
+Truncate operand 1 (valid for mode @var{m}) to mode @var{n} and
+store in operand 0 (which has mode @var{n}). Both modes must be fixed
+point or both floating point.
+
+@cindex @code{extend@var{m}@var{n}2} instruction pattern
+@item @samp{extend@var{m}@var{n}2}
+Sign-extend operand 1 (valid for mode @var{m}) to mode @var{n} and
+store in operand 0 (which has mode @var{n}). Both modes must be fixed
+point or both floating point.
+
+@cindex @code{zero_extend@var{m}@var{n}2} instruction pattern
+@item @samp{zero_extend@var{m}@var{n}2}
+Zero-extend operand 1 (valid for mode @var{m}) to mode @var{n} and
+store in operand 0 (which has mode @var{n}). Both modes must be fixed
+point.
+
+@cindex @code{fract@var{m}@var{n}2} instruction pattern
+@item @samp{fract@var{m}@var{n}2}
+Convert operand 1 of mode @var{m} to mode @var{n} and store in
+operand 0 (which has mode @var{n}). Mode @var{m} and mode @var{n}
+could be fixed-point to fixed-point, signed integer to fixed-point,
+fixed-point to signed integer, floating-point to fixed-point,
+or fixed-point to floating-point.
+When overflows or underflows happen, the results are undefined.
+
+@cindex @code{satfract@var{m}@var{n}2} instruction pattern
+@item @samp{satfract@var{m}@var{n}2}
+Convert operand 1 of mode @var{m} to mode @var{n} and store in
+operand 0 (which has mode @var{n}). Mode @var{m} and mode @var{n}
+could be fixed-point to fixed-point, signed integer to fixed-point,
+or floating-point to fixed-point.
+When overflows or underflows happen, the instruction saturates the
+results to the maximum or the minimum.
+
+@cindex @code{fractuns@var{m}@var{n}2} instruction pattern
+@item @samp{fractuns@var{m}@var{n}2}
+Convert operand 1 of mode @var{m} to mode @var{n} and store in
+operand 0 (which has mode @var{n}). Mode @var{m} and mode @var{n}
+could be unsigned integer to fixed-point, or
+fixed-point to unsigned integer.
+When overflows or underflows happen, the results are undefined.
+
+@cindex @code{satfractuns@var{m}@var{n}2} instruction pattern
+@item @samp{satfractuns@var{m}@var{n}2}
+Convert unsigned integer operand 1 of mode @var{m} to fixed-point mode
+@var{n} and store in operand 0 (which has mode @var{n}).
+When overflows or underflows happen, the instruction saturates the
+results to the maximum or the minimum.
+
+@cindex @code{extv@var{m}} instruction pattern
+@item @samp{extv@var{m}}
+Extract a bit-field from register operand 1, sign-extend it, and store
+it in operand 0. Operand 2 specifies the width of the field in bits
+and operand 3 the starting bit, which counts from the most significant
+bit if @samp{BITS_BIG_ENDIAN} is true and from the least significant bit
+otherwise.
+
+Operands 0 and 1 both have mode @var{m}. Operands 2 and 3 have a
+target-specific mode.
+
+@cindex @code{extvmisalign@var{m}} instruction pattern
+@item @samp{extvmisalign@var{m}}
+Extract a bit-field from memory operand 1, sign extend it, and store
+it in operand 0. Operand 2 specifies the width in bits and operand 3
+the starting bit. The starting bit is always somewhere in the first byte of
+operand 1; it counts from the most significant bit if @samp{BITS_BIG_ENDIAN}
+is true and from the least significant bit otherwise.
+
+Operand 0 has mode @var{m} while operand 1 has @code{BLK} mode.
+Operands 2 and 3 have a target-specific mode.
+
+The instruction must not read beyond the last byte of the bit-field.
+
+@cindex @code{extzv@var{m}} instruction pattern
+@item @samp{extzv@var{m}}
+Like @samp{extv@var{m}} except that the bit-field value is zero-extended.
+
+@cindex @code{extzvmisalign@var{m}} instruction pattern
+@item @samp{extzvmisalign@var{m}}
+Like @samp{extvmisalign@var{m}} except that the bit-field value is
+zero-extended.
+
+@cindex @code{insv@var{m}} instruction pattern
+@item @samp{insv@var{m}}
+Insert operand 3 into a bit-field of register operand 0. Operand 1
+specifies the width of the field in bits and operand 2 the starting bit,
+which counts from the most significant bit if @samp{BITS_BIG_ENDIAN}
+is true and from the least significant bit otherwise.
+
+Operands 0 and 3 both have mode @var{m}. Operands 1 and 2 have a
+target-specific mode.
+
+@cindex @code{insvmisalign@var{m}} instruction pattern
+@item @samp{insvmisalign@var{m}}
+Insert operand 3 into a bit-field of memory operand 0. Operand 1
+specifies the width of the field in bits and operand 2 the starting bit.
+The starting bit is always somewhere in the first byte of operand 0;
+it counts from the most significant bit if @samp{BITS_BIG_ENDIAN}
+is true and from the least significant bit otherwise.
+
+Operand 3 has mode @var{m} while operand 0 has @code{BLK} mode.
+Operands 1 and 2 have a target-specific mode.
+
+The instruction must not read or write beyond the last byte of the bit-field.
+
+@cindex @code{extv} instruction pattern
+@item @samp{extv}
+Extract a bit-field from operand 1 (a register or memory operand), where
+operand 2 specifies the width in bits and operand 3 the starting bit,
+and store it in operand 0. Operand 0 must have mode @code{word_mode}.
+Operand 1 may have mode @code{byte_mode} or @code{word_mode}; often
+@code{word_mode} is allowed only for registers. Operands 2 and 3 must
+be valid for @code{word_mode}.
+
+The RTL generation pass generates this instruction only with constants
+for operands 2 and 3 and the constant is never zero for operand 2.
+
+The bit-field value is sign-extended to a full word integer
+before it is stored in operand 0.
+
+This pattern is deprecated; please use @samp{extv@var{m}} and
+@code{extvmisalign@var{m}} instead.
+
+@cindex @code{extzv} instruction pattern
+@item @samp{extzv}
+Like @samp{extv} except that the bit-field value is zero-extended.
+
+This pattern is deprecated; please use @samp{extzv@var{m}} and
+@code{extzvmisalign@var{m}} instead.
+
+@cindex @code{insv} instruction pattern
+@item @samp{insv}
+Store operand 3 (which must be valid for @code{word_mode}) into a
+bit-field in operand 0, where operand 1 specifies the width in bits and
+operand 2 the starting bit. Operand 0 may have mode @code{byte_mode} or
+@code{word_mode}; often @code{word_mode} is allowed only for registers.
+Operands 1 and 2 must be valid for @code{word_mode}.
+
+The RTL generation pass generates this instruction only with constants
+for operands 1 and 2 and the constant is never zero for operand 1.
+
+This pattern is deprecated; please use @samp{insv@var{m}} and
+@code{insvmisalign@var{m}} instead.
+
+@cindex @code{mov@var{mode}cc} instruction pattern
+@item @samp{mov@var{mode}cc}
+Conditionally move operand 2 or operand 3 into operand 0 according to the
+comparison in operand 1. If the comparison is true, operand 2 is moved
+into operand 0, otherwise operand 3 is moved.
+
+The mode of the operands being compared need not be the same as the operands
+being moved. Some machines, sparc64 for example, have instructions that
+conditionally move an integer value based on the floating point condition
+codes and vice versa.
+
+If the machine does not have conditional move instructions, do not
+define these patterns.
+
+@cindex @code{add@var{mode}cc} instruction pattern
+@item @samp{add@var{mode}cc}
+Similar to @samp{mov@var{mode}cc} but for conditional addition. Conditionally
+move operand 2 or (operands 2 + operand 3) into operand 0 according to the
+comparison in operand 1. If the comparison is false, operand 2 is moved into
+operand 0, otherwise (operand 2 + operand 3) is moved.
+
+@cindex @code{cond_add@var{mode}} instruction pattern
+@cindex @code{cond_sub@var{mode}} instruction pattern
+@cindex @code{cond_mul@var{mode}} instruction pattern
+@cindex @code{cond_div@var{mode}} instruction pattern
+@cindex @code{cond_udiv@var{mode}} instruction pattern
+@cindex @code{cond_mod@var{mode}} instruction pattern
+@cindex @code{cond_umod@var{mode}} instruction pattern
+@cindex @code{cond_and@var{mode}} instruction pattern
+@cindex @code{cond_ior@var{mode}} instruction pattern
+@cindex @code{cond_xor@var{mode}} instruction pattern
+@cindex @code{cond_smin@var{mode}} instruction pattern
+@cindex @code{cond_smax@var{mode}} instruction pattern
+@cindex @code{cond_umin@var{mode}} instruction pattern
+@cindex @code{cond_umax@var{mode}} instruction pattern
+@cindex @code{cond_fmin@var{mode}} instruction pattern
+@cindex @code{cond_fmax@var{mode}} instruction pattern
+@cindex @code{cond_ashl@var{mode}} instruction pattern
+@cindex @code{cond_ashr@var{mode}} instruction pattern
+@cindex @code{cond_lshr@var{mode}} instruction pattern
+@item @samp{cond_add@var{mode}}
+@itemx @samp{cond_sub@var{mode}}
+@itemx @samp{cond_mul@var{mode}}
+@itemx @samp{cond_div@var{mode}}
+@itemx @samp{cond_udiv@var{mode}}
+@itemx @samp{cond_mod@var{mode}}
+@itemx @samp{cond_umod@var{mode}}
+@itemx @samp{cond_and@var{mode}}
+@itemx @samp{cond_ior@var{mode}}
+@itemx @samp{cond_xor@var{mode}}
+@itemx @samp{cond_smin@var{mode}}
+@itemx @samp{cond_smax@var{mode}}
+@itemx @samp{cond_umin@var{mode}}
+@itemx @samp{cond_umax@var{mode}}
+@itemx @samp{cond_fmin@var{mode}}
+@itemx @samp{cond_fmax@var{mode}}
+@itemx @samp{cond_ashl@var{mode}}
+@itemx @samp{cond_ashr@var{mode}}
+@itemx @samp{cond_lshr@var{mode}}
+When operand 1 is true, perform an operation on operands 2 and 3 and
+store the result in operand 0, otherwise store operand 4 in operand 0.
+The operation works elementwise if the operands are vectors.
+
+The scalar case is equivalent to:
+
+@smallexample
+op0 = op1 ? op2 @var{op} op3 : op4;
+@end smallexample
+
+while the vector case is equivalent to:
+
+@smallexample
+for (i = 0; i < GET_MODE_NUNITS (@var{m}); i++)
+ op0[i] = op1[i] ? op2[i] @var{op} op3[i] : op4[i];
+@end smallexample
+
+where, for example, @var{op} is @code{+} for @samp{cond_add@var{mode}}.
+
+When defined for floating-point modes, the contents of @samp{op3[i]}
+are not interpreted if @samp{op1[i]} is false, just like they would not
+be in a normal C @samp{?:} condition.
+
+Operands 0, 2, 3 and 4 all have mode @var{m}. Operand 1 is a scalar
+integer if @var{m} is scalar, otherwise it has the mode returned by
+@code{TARGET_VECTORIZE_GET_MASK_MODE}.
+
+@samp{cond_@var{op}@var{mode}} generally corresponds to a conditional
+form of @samp{@var{op}@var{mode}3}. As an exception, the vector forms
+of shifts correspond to patterns like @code{vashl@var{mode}3} rather
+than patterns like @code{ashl@var{mode}3}.
+
+@cindex @code{cond_fma@var{mode}} instruction pattern
+@cindex @code{cond_fms@var{mode}} instruction pattern
+@cindex @code{cond_fnma@var{mode}} instruction pattern
+@cindex @code{cond_fnms@var{mode}} instruction pattern
+@item @samp{cond_fma@var{mode}}
+@itemx @samp{cond_fms@var{mode}}
+@itemx @samp{cond_fnma@var{mode}}
+@itemx @samp{cond_fnms@var{mode}}
+Like @samp{cond_add@var{m}}, except that the conditional operation
+takes 3 operands rather than two. For example, the vector form of
+@samp{cond_fma@var{mode}} is equivalent to:
+
+@smallexample
+for (i = 0; i < GET_MODE_NUNITS (@var{m}); i++)
+ op0[i] = op1[i] ? fma (op2[i], op3[i], op4[i]) : op5[i];
+@end smallexample
+
+@cindex @code{neg@var{mode}cc} instruction pattern
+@item @samp{neg@var{mode}cc}
+Similar to @samp{mov@var{mode}cc} but for conditional negation. Conditionally
+move the negation of operand 2 or the unchanged operand 3 into operand 0
+according to the comparison in operand 1. If the comparison is true, the negation
+of operand 2 is moved into operand 0, otherwise operand 3 is moved.
+
+@cindex @code{not@var{mode}cc} instruction pattern
+@item @samp{not@var{mode}cc}
+Similar to @samp{neg@var{mode}cc} but for conditional complement.
+Conditionally move the bitwise complement of operand 2 or the unchanged
+operand 3 into operand 0 according to the comparison in operand 1.
+If the comparison is true, the complement of operand 2 is moved into
+operand 0, otherwise operand 3 is moved.
+
+@cindex @code{cstore@var{mode}4} instruction pattern
+@item @samp{cstore@var{mode}4}
+Store zero or nonzero in operand 0 according to whether a comparison
+is true. Operand 1 is a comparison operator. Operand 2 and operand 3
+are the first and second operand of the comparison, respectively.
+You specify the mode that operand 0 must have when you write the
+@code{match_operand} expression. The compiler automatically sees which
+mode you have used and supplies an operand of that mode.
+
+The value stored for a true condition must have 1 as its low bit, or
+else must be negative. Otherwise the instruction is not suitable and
+you should omit it from the machine description. You describe to the
+compiler exactly which value is stored by defining the macro
+@code{STORE_FLAG_VALUE} (@pxref{Misc}). If a description cannot be
+found that can be used for all the possible comparison operators, you
+should pick one and use a @code{define_expand} to map all results
+onto the one you chose.
+
+These operations may @code{FAIL}, but should do so only in relatively
+uncommon cases; if they would @code{FAIL} for common cases involving
+integer comparisons, it is best to restrict the predicates to not
+allow these operands. Likewise if a given comparison operator will
+always fail, independent of the operands (for floating-point modes, the
+@code{ordered_comparison_operator} predicate is often useful in this case).
+
+If this pattern is omitted, the compiler will generate a conditional
+branch---for example, it may copy a constant one to the target and branching
+around an assignment of zero to the target---or a libcall. If the predicate
+for operand 1 only rejects some operators, it will also try reordering the
+operands and/or inverting the result value (e.g.@: by an exclusive OR).
+These possibilities could be cheaper or equivalent to the instructions
+used for the @samp{cstore@var{mode}4} pattern followed by those required
+to convert a positive result from @code{STORE_FLAG_VALUE} to 1; in this
+case, you can and should make operand 1's predicate reject some operators
+in the @samp{cstore@var{mode}4} pattern, or remove the pattern altogether
+from the machine description.
+
+@cindex @code{cbranch@var{mode}4} instruction pattern
+@item @samp{cbranch@var{mode}4}
+Conditional branch instruction combined with a compare instruction.
+Operand 0 is a comparison operator. Operand 1 and operand 2 are the
+first and second operands of the comparison, respectively. Operand 3
+is the @code{code_label} to jump to.
+
+@cindex @code{jump} instruction pattern
+@item @samp{jump}
+A jump inside a function; an unconditional branch. Operand 0 is the
+@code{code_label} to jump to. This pattern name is mandatory on all
+machines.
+
+@cindex @code{call} instruction pattern
+@item @samp{call}
+Subroutine call instruction returning no value. Operand 0 is the
+function to call; operand 1 is the number of bytes of arguments pushed
+as a @code{const_int}. Operand 2 is the result of calling the target
+hook @code{TARGET_FUNCTION_ARG} with the second argument @code{arg}
+yielding true for @code{arg.end_marker_p ()}, in a call after all
+parameters have been passed to that hook. By default this is the first
+register beyond those used for arguments in the call, or @code{NULL} if
+all the argument-registers are used in the call.
+
+On most machines, operand 2 is not actually stored into the RTL
+pattern. It is supplied for the sake of some RISC machines which need
+to put this information into the assembler code; they can put it in
+the RTL instead of operand 1.
+
+Operand 0 should be a @code{mem} RTX whose address is the address of the
+function. Note, however, that this address can be a @code{symbol_ref}
+expression even if it would not be a legitimate memory address on the
+target machine. If it is also not a valid argument for a call
+instruction, the pattern for this operation should be a
+@code{define_expand} (@pxref{Expander Definitions}) that places the
+address into a register and uses that register in the call instruction.
+
+@cindex @code{call_value} instruction pattern
+@item @samp{call_value}
+Subroutine call instruction returning a value. Operand 0 is the hard
+register in which the value is returned. There are three more
+operands, the same as the three operands of the @samp{call}
+instruction (but with numbers increased by one).
+
+Subroutines that return @code{BLKmode} objects use the @samp{call}
+insn.
+
+@cindex @code{call_pop} instruction pattern
+@cindex @code{call_value_pop} instruction pattern
+@item @samp{call_pop}, @samp{call_value_pop}
+Similar to @samp{call} and @samp{call_value}, except used if defined and
+if @code{RETURN_POPS_ARGS} is nonzero. They should emit a @code{parallel}
+that contains both the function call and a @code{set} to indicate the
+adjustment made to the frame pointer.
+
+For machines where @code{RETURN_POPS_ARGS} can be nonzero, the use of these
+patterns increases the number of functions for which the frame pointer
+can be eliminated, if desired.
+
+@cindex @code{untyped_call} instruction pattern
+@item @samp{untyped_call}
+Subroutine call instruction returning a value of any type. Operand 0 is
+the function to call; operand 1 is a memory location where the result of
+calling the function is to be stored; operand 2 is a @code{parallel}
+expression where each element is a @code{set} expression that indicates
+the saving of a function return value into the result block.
+
+This instruction pattern should be defined to support
+@code{__builtin_apply} on machines where special instructions are needed
+to call a subroutine with arbitrary arguments or to save the value
+returned. This instruction pattern is required on machines that have
+multiple registers that can hold a return value
+(i.e.@: @code{FUNCTION_VALUE_REGNO_P} is true for more than one register).
+
+@cindex @code{return} instruction pattern
+@item @samp{return}
+Subroutine return instruction. This instruction pattern name should be
+defined only if a single instruction can do all the work of returning
+from a function.
+
+Like the @samp{mov@var{m}} patterns, this pattern is also used after the
+RTL generation phase. In this case it is to support machines where
+multiple instructions are usually needed to return from a function, but
+some class of functions only requires one instruction to implement a
+return. Normally, the applicable functions are those which do not need
+to save any registers or allocate stack space.
+
+It is valid for this pattern to expand to an instruction using
+@code{simple_return} if no epilogue is required.
+
+@cindex @code{simple_return} instruction pattern
+@item @samp{simple_return}
+Subroutine return instruction. This instruction pattern name should be
+defined only if a single instruction can do all the work of returning
+from a function on a path where no epilogue is required. This pattern
+is very similar to the @code{return} instruction pattern, but it is emitted
+only by the shrink-wrapping optimization on paths where the function
+prologue has not been executed, and a function return should occur without
+any of the effects of the epilogue. Additional uses may be introduced on
+paths where both the prologue and the epilogue have executed.
+
+@findex reload_completed
+@findex leaf_function_p
+For such machines, the condition specified in this pattern should only
+be true when @code{reload_completed} is nonzero and the function's
+epilogue would only be a single instruction. For machines with register
+windows, the routine @code{leaf_function_p} may be used to determine if
+a register window push is required.
+
+Machines that have conditional return instructions should define patterns
+such as
+
+@smallexample
+(define_insn ""
+ [(set (pc)
+ (if_then_else (match_operator
+ 0 "comparison_operator"
+ [(reg:CC CC_REG) (const_int 0)])
+ (return)
+ (pc)))]
+ "@var{condition}"
+ "@dots{}")
+@end smallexample
+
+where @var{condition} would normally be the same condition specified on the
+named @samp{return} pattern.
+
+@cindex @code{untyped_return} instruction pattern
+@item @samp{untyped_return}
+Untyped subroutine return instruction. This instruction pattern should
+be defined to support @code{__builtin_return} on machines where special
+instructions are needed to return a value of any type.
+
+Operand 0 is a memory location where the result of calling a function
+with @code{__builtin_apply} is stored; operand 1 is a @code{parallel}
+expression where each element is a @code{set} expression that indicates
+the restoring of a function return value from the result block.
+
+@cindex @code{nop} instruction pattern
+@item @samp{nop}
+No-op instruction. This instruction pattern name should always be defined
+to output a no-op in assembler code. @code{(const_int 0)} will do as an
+RTL pattern.
+
+@cindex @code{indirect_jump} instruction pattern
+@item @samp{indirect_jump}
+An instruction to jump to an address which is operand zero.
+This pattern name is mandatory on all machines.
+
+@cindex @code{casesi} instruction pattern
+@item @samp{casesi}
+Instruction to jump through a dispatch table, including bounds checking.
+This instruction takes five operands:
+
+@enumerate
+@item
+The index to dispatch on, which has mode @code{SImode}.
+
+@item
+The lower bound for indices in the table, an integer constant.
+
+@item
+The total range of indices in the table---the largest index
+minus the smallest one (both inclusive).
+
+@item
+A label that precedes the table itself.
+
+@item
+A label to jump to if the index has a value outside the bounds.
+@end enumerate
+
+The table is an @code{addr_vec} or @code{addr_diff_vec} inside of a
+@code{jump_table_data}. The number of elements in the table is one plus the
+difference between the upper bound and the lower bound.
+
+@cindex @code{tablejump} instruction pattern
+@item @samp{tablejump}
+Instruction to jump to a variable address. This is a low-level
+capability which can be used to implement a dispatch table when there
+is no @samp{casesi} pattern.
+
+This pattern requires two operands: the address or offset, and a label
+which should immediately precede the jump table. If the macro
+@code{CASE_VECTOR_PC_RELATIVE} evaluates to a nonzero value then the first
+operand is an offset which counts from the address of the table; otherwise,
+it is an absolute address to jump to. In either case, the first operand has
+mode @code{Pmode}.
+
+The @samp{tablejump} insn is always the last insn before the jump
+table it uses. Its assembler code normally has no need to use the
+second operand, but you should incorporate it in the RTL pattern so
+that the jump optimizer will not delete the table as unreachable code.
+
+
+@cindex @code{doloop_end} instruction pattern
+@item @samp{doloop_end}
+Conditional branch instruction that decrements a register and
+jumps if the register is nonzero. Operand 0 is the register to
+decrement and test; operand 1 is the label to jump to if the
+register is nonzero.
+@xref{Looping Patterns}.
+
+This optional instruction pattern should be defined for machines with
+low-overhead looping instructions as the loop optimizer will try to
+modify suitable loops to utilize it. The target hook
+@code{TARGET_CAN_USE_DOLOOP_P} controls the conditions under which
+low-overhead loops can be used.
+
+@cindex @code{doloop_begin} instruction pattern
+@item @samp{doloop_begin}
+Companion instruction to @code{doloop_end} required for machines that
+need to perform some initialization, such as loading a special counter
+register. Operand 1 is the associated @code{doloop_end} pattern and
+operand 0 is the register that it decrements.
+
+If initialization insns do not always need to be emitted, use a
+@code{define_expand} (@pxref{Expander Definitions}) and make it fail.
+
+@cindex @code{canonicalize_funcptr_for_compare} instruction pattern
+@item @samp{canonicalize_funcptr_for_compare}
+Canonicalize the function pointer in operand 1 and store the result
+into operand 0.
+
+Operand 0 is always a @code{reg} and has mode @code{Pmode}; operand 1
+may be a @code{reg}, @code{mem}, @code{symbol_ref}, @code{const_int}, etc
+and also has mode @code{Pmode}.
+
+Canonicalization of a function pointer usually involves computing
+the address of the function which would be called if the function
+pointer were used in an indirect call.
+
+Only define this pattern if function pointers on the target machine
+can have different values but still call the same function when
+used in an indirect call.
+
+@cindex @code{save_stack_block} instruction pattern
+@cindex @code{save_stack_function} instruction pattern
+@cindex @code{save_stack_nonlocal} instruction pattern
+@cindex @code{restore_stack_block} instruction pattern
+@cindex @code{restore_stack_function} instruction pattern
+@cindex @code{restore_stack_nonlocal} instruction pattern
+@item @samp{save_stack_block}
+@itemx @samp{save_stack_function}
+@itemx @samp{save_stack_nonlocal}
+@itemx @samp{restore_stack_block}
+@itemx @samp{restore_stack_function}
+@itemx @samp{restore_stack_nonlocal}
+Most machines save and restore the stack pointer by copying it to or
+from an object of mode @code{Pmode}. Do not define these patterns on
+such machines.
+
+Some machines require special handling for stack pointer saves and
+restores. On those machines, define the patterns corresponding to the
+non-standard cases by using a @code{define_expand} (@pxref{Expander
+Definitions}) that produces the required insns. The three types of
+saves and restores are:
+
+@enumerate
+@item
+@samp{save_stack_block} saves the stack pointer at the start of a block
+that allocates a variable-sized object, and @samp{restore_stack_block}
+restores the stack pointer when the block is exited.
+
+@item
+@samp{save_stack_function} and @samp{restore_stack_function} do a
+similar job for the outermost block of a function and are used when the
+function allocates variable-sized objects or calls @code{alloca}. Only
+the epilogue uses the restored stack pointer, allowing a simpler save or
+restore sequence on some machines.
+
+@item
+@samp{save_stack_nonlocal} is used in functions that contain labels
+branched to by nested functions. It saves the stack pointer in such a
+way that the inner function can use @samp{restore_stack_nonlocal} to
+restore the stack pointer. The compiler generates code to restore the
+frame and argument pointer registers, but some machines require saving
+and restoring additional data such as register window information or
+stack backchains. Place insns in these patterns to save and restore any
+such required data.
+@end enumerate
+
+When saving the stack pointer, operand 0 is the save area and operand 1
+is the stack pointer. The mode used to allocate the save area defaults
+to @code{Pmode} but you can override that choice by defining the
+@code{STACK_SAVEAREA_MODE} macro (@pxref{Storage Layout}). You must
+specify an integral mode, or @code{VOIDmode} if no save area is needed
+for a particular type of save (either because no save is needed or
+because a machine-specific save area can be used). Operand 0 is the
+stack pointer and operand 1 is the save area for restore operations. If
+@samp{save_stack_block} is defined, operand 0 must not be
+@code{VOIDmode} since these saves can be arbitrarily nested.
+
+A save area is a @code{mem} that is at a constant offset from
+@code{virtual_stack_vars_rtx} when the stack pointer is saved for use by
+nonlocal gotos and a @code{reg} in the other two cases.
+
+@cindex @code{allocate_stack} instruction pattern
+@item @samp{allocate_stack}
+Subtract (or add if @code{STACK_GROWS_DOWNWARD} is undefined) operand 1 from
+the stack pointer to create space for dynamically allocated data.
+
+Store the resultant pointer to this space into operand 0. If you
+are allocating space from the main stack, do this by emitting a
+move insn to copy @code{virtual_stack_dynamic_rtx} to operand 0.
+If you are allocating the space elsewhere, generate code to copy the
+location of the space to operand 0. In the latter case, you must
+ensure this space gets freed when the corresponding space on the main
+stack is free.
+
+Do not define this pattern if all that must be done is the subtraction.
+Some machines require other operations such as stack probes or
+maintaining the back chain. Define this pattern to emit those
+operations in addition to updating the stack pointer.
+
+@cindex @code{check_stack} instruction pattern
+@item @samp{check_stack}
+If stack checking (@pxref{Stack Checking}) cannot be done on your system by
+probing the stack, define this pattern to perform the needed check and signal
+an error if the stack has overflowed. The single operand is the address in
+the stack farthest from the current stack pointer that you need to validate.
+Normally, on platforms where this pattern is needed, you would obtain the
+stack limit from a global or thread-specific variable or register.
+
+@cindex @code{probe_stack_address} instruction pattern
+@item @samp{probe_stack_address}
+If stack checking (@pxref{Stack Checking}) can be done on your system by
+probing the stack but without the need to actually access it, define this
+pattern and signal an error if the stack has overflowed. The single operand
+is the memory address in the stack that needs to be probed.
+
+@cindex @code{probe_stack} instruction pattern
+@item @samp{probe_stack}
+If stack checking (@pxref{Stack Checking}) can be done on your system by
+probing the stack but doing it with a ``store zero'' instruction is not valid
+or optimal, define this pattern to do the probing differently and signal an
+error if the stack has overflowed. The single operand is the memory reference
+in the stack that needs to be probed.
+
+@cindex @code{nonlocal_goto} instruction pattern
+@item @samp{nonlocal_goto}
+Emit code to generate a non-local goto, e.g., a jump from one function
+to a label in an outer function. This pattern has four arguments,
+each representing a value to be used in the jump. The first
+argument is to be loaded into the frame pointer, the second is
+the address to branch to (code to dispatch to the actual label),
+the third is the address of a location where the stack is saved,
+and the last is the address of the label, to be placed in the
+location for the incoming static chain.
+
+On most machines you need not define this pattern, since GCC will
+already generate the correct code, which is to load the frame pointer
+and static chain, restore the stack (using the
+@samp{restore_stack_nonlocal} pattern, if defined), and jump indirectly
+to the dispatcher. You need only define this pattern if this code will
+not work on your machine.
+
+@cindex @code{nonlocal_goto_receiver} instruction pattern
+@item @samp{nonlocal_goto_receiver}
+This pattern, if defined, contains code needed at the target of a
+nonlocal goto after the code already generated by GCC@. You will not
+normally need to define this pattern. A typical reason why you might
+need this pattern is if some value, such as a pointer to a global table,
+must be restored when the frame pointer is restored. Note that a nonlocal
+goto only occurs within a unit-of-translation, so a global table pointer
+that is shared by all functions of a given module need not be restored.
+There are no arguments.
+
+@cindex @code{exception_receiver} instruction pattern
+@item @samp{exception_receiver}
+This pattern, if defined, contains code needed at the site of an
+exception handler that isn't needed at the site of a nonlocal goto. You
+will not normally need to define this pattern. A typical reason why you
+might need this pattern is if some value, such as a pointer to a global
+table, must be restored after control flow is branched to the handler of
+an exception. There are no arguments.
+
+@cindex @code{builtin_setjmp_setup} instruction pattern
+@item @samp{builtin_setjmp_setup}
+This pattern, if defined, contains additional code needed to initialize
+the @code{jmp_buf}. You will not normally need to define this pattern.
+A typical reason why you might need this pattern is if some value, such
+as a pointer to a global table, must be restored. Though it is
+preferred that the pointer value be recalculated if possible (given the
+address of a label for instance). The single argument is a pointer to
+the @code{jmp_buf}. Note that the buffer is five words long and that
+the first three are normally used by the generic mechanism.
+
+@cindex @code{builtin_setjmp_receiver} instruction pattern
+@item @samp{builtin_setjmp_receiver}
+This pattern, if defined, contains code needed at the site of a
+built-in setjmp that isn't needed at the site of a nonlocal goto. You
+will not normally need to define this pattern. A typical reason why you
+might need this pattern is if some value, such as a pointer to a global
+table, must be restored. It takes one argument, which is the label
+to which builtin_longjmp transferred control; this pattern may be emitted
+at a small offset from that label.
+
+@cindex @code{builtin_longjmp} instruction pattern
+@item @samp{builtin_longjmp}
+This pattern, if defined, performs the entire action of the longjmp.
+You will not normally need to define this pattern unless you also define
+@code{builtin_setjmp_setup}. The single argument is a pointer to the
+@code{jmp_buf}.
+
+@cindex @code{eh_return} instruction pattern
+@item @samp{eh_return}
+This pattern, if defined, affects the way @code{__builtin_eh_return},
+and thence the call frame exception handling library routines, are
+built. It is intended to handle non-trivial actions needed along
+the abnormal return path.
+
+The address of the exception handler to which the function should return
+is passed as operand to this pattern. It will normally need to copied by
+the pattern to some special register or memory location.
+If the pattern needs to determine the location of the target call
+frame in order to do so, it may use @code{EH_RETURN_STACKADJ_RTX},
+if defined; it will have already been assigned.
+
+If this pattern is not defined, the default action will be to simply
+copy the return address to @code{EH_RETURN_HANDLER_RTX}. Either
+that macro or this pattern needs to be defined if call frame exception
+handling is to be used.
+
+@cindex @code{prologue} instruction pattern
+@anchor{prologue instruction pattern}
+@item @samp{prologue}
+This pattern, if defined, emits RTL for entry to a function. The function
+entry is responsible for setting up the stack frame, initializing the frame
+pointer register, saving callee saved registers, etc.
+
+Using a prologue pattern is generally preferred over defining
+@code{TARGET_ASM_FUNCTION_PROLOGUE} to emit assembly code for the prologue.
+
+The @code{prologue} pattern is particularly useful for targets which perform
+instruction scheduling.
+
+@cindex @code{window_save} instruction pattern
+@anchor{window_save instruction pattern}
+@item @samp{window_save}
+This pattern, if defined, emits RTL for a register window save. It should
+be defined if the target machine has register windows but the window events
+are decoupled from calls to subroutines. The canonical example is the SPARC
+architecture.
+
+@cindex @code{epilogue} instruction pattern
+@anchor{epilogue instruction pattern}
+@item @samp{epilogue}
+This pattern emits RTL for exit from a function. The function
+exit is responsible for deallocating the stack frame, restoring callee saved
+registers and emitting the return instruction.
+
+Using an epilogue pattern is generally preferred over defining
+@code{TARGET_ASM_FUNCTION_EPILOGUE} to emit assembly code for the epilogue.
+
+The @code{epilogue} pattern is particularly useful for targets which perform
+instruction scheduling or which have delay slots for their return instruction.
+
+@cindex @code{sibcall_epilogue} instruction pattern
+@item @samp{sibcall_epilogue}
+This pattern, if defined, emits RTL for exit from a function without the final
+branch back to the calling function. This pattern will be emitted before any
+sibling call (aka tail call) sites.
+
+The @code{sibcall_epilogue} pattern must not clobber any arguments used for
+parameter passing or any stack slots for arguments passed to the current
+function.
+
+@cindex @code{trap} instruction pattern
+@item @samp{trap}
+This pattern, if defined, signals an error, typically by causing some
+kind of signal to be raised.
+
+@cindex @code{ctrap@var{MM}4} instruction pattern
+@item @samp{ctrap@var{MM}4}
+Conditional trap instruction. Operand 0 is a piece of RTL which
+performs a comparison, and operands 1 and 2 are the arms of the
+comparison. Operand 3 is the trap code, an integer.
+
+A typical @code{ctrap} pattern looks like
+
+@smallexample
+(define_insn "ctrapsi4"
+ [(trap_if (match_operator 0 "trap_operator"
+ [(match_operand 1 "register_operand")
+ (match_operand 2 "immediate_operand")])
+ (match_operand 3 "const_int_operand" "i"))]
+ ""
+ "@dots{}")
+@end smallexample
+
+@cindex @code{prefetch} instruction pattern
+@item @samp{prefetch}
+This pattern, if defined, emits code for a non-faulting data prefetch
+instruction. Operand 0 is the address of the memory to prefetch. Operand 1
+is a constant 1 if the prefetch is preparing for a write to the memory
+address, or a constant 0 otherwise. Operand 2 is the expected degree of
+temporal locality of the data and is a value between 0 and 3, inclusive; 0
+means that the data has no temporal locality, so it need not be left in the
+cache after the access; 3 means that the data has a high degree of temporal
+locality and should be left in all levels of cache possible; 1 and 2 mean,
+respectively, a low or moderate degree of temporal locality.
+
+Targets that do not support write prefetches or locality hints can ignore
+the values of operands 1 and 2.
+
+@cindex @code{blockage} instruction pattern
+@item @samp{blockage}
+This pattern defines a pseudo insn that prevents the instruction
+scheduler and other passes from moving instructions and using register
+equivalences across the boundary defined by the blockage insn.
+This needs to be an UNSPEC_VOLATILE pattern or a volatile ASM.
+
+@cindex @code{memory_blockage} instruction pattern
+@item @samp{memory_blockage}
+This pattern, if defined, represents a compiler memory barrier, and will be
+placed at points across which RTL passes may not propagate memory accesses.
+This instruction needs to read and write volatile BLKmode memory. It does
+not need to generate any machine instruction. If this pattern is not defined,
+the compiler falls back to emitting an instruction corresponding
+to @code{asm volatile ("" ::: "memory")}.
+
+@cindex @code{memory_barrier} instruction pattern
+@item @samp{memory_barrier}
+If the target memory model is not fully synchronous, then this pattern
+should be defined to an instruction that orders both loads and stores
+before the instruction with respect to loads and stores after the instruction.
+This pattern has no operands.
+
+@cindex @code{speculation_barrier} instruction pattern
+@item @samp{speculation_barrier}
+If the target can support speculative execution, then this pattern should
+be defined to an instruction that will block subsequent execution until
+any prior speculation conditions has been resolved. The pattern must also
+ensure that the compiler cannot move memory operations past the barrier,
+so it needs to be an UNSPEC_VOLATILE pattern. The pattern has no
+operands.
+
+If this pattern is not defined then the default expansion of
+@code{__builtin_speculation_safe_value} will emit a warning. You can
+suppress this warning by defining this pattern with a final condition
+of @code{0} (zero), which tells the compiler that a speculation
+barrier is not needed for this target.
+
+@cindex @code{sync_compare_and_swap@var{mode}} instruction pattern
+@item @samp{sync_compare_and_swap@var{mode}}
+This pattern, if defined, emits code for an atomic compare-and-swap
+operation. Operand 1 is the memory on which the atomic operation is
+performed. Operand 2 is the ``old'' value to be compared against the
+current contents of the memory location. Operand 3 is the ``new'' value
+to store in the memory if the compare succeeds. Operand 0 is the result
+of the operation; it should contain the contents of the memory
+before the operation. If the compare succeeds, this should obviously be
+a copy of operand 2.
+
+This pattern must show that both operand 0 and operand 1 are modified.
+
+This pattern must issue any memory barrier instructions such that all
+memory operations before the atomic operation occur before the atomic
+operation and all memory operations after the atomic operation occur
+after the atomic operation.
+
+For targets where the success or failure of the compare-and-swap
+operation is available via the status flags, it is possible to
+avoid a separate compare operation and issue the subsequent
+branch or store-flag operation immediately after the compare-and-swap.
+To this end, GCC will look for a @code{MODE_CC} set in the
+output of @code{sync_compare_and_swap@var{mode}}; if the machine
+description includes such a set, the target should also define special
+@code{cbranchcc4} and/or @code{cstorecc4} instructions. GCC will then
+be able to take the destination of the @code{MODE_CC} set and pass it
+to the @code{cbranchcc4} or @code{cstorecc4} pattern as the first
+operand of the comparison (the second will be @code{(const_int 0)}).
+
+For targets where the operating system may provide support for this
+operation via library calls, the @code{sync_compare_and_swap_optab}
+may be initialized to a function with the same interface as the
+@code{__sync_val_compare_and_swap_@var{n}} built-in. If the entire
+set of @var{__sync} builtins are supported via library calls, the
+target can initialize all of the optabs at once with
+@code{init_sync_libfuncs}.
+For the purposes of C++11 @code{std::atomic::is_lock_free}, it is
+assumed that these library calls do @emph{not} use any kind of
+interruptable locking.
+
+@cindex @code{sync_add@var{mode}} instruction pattern
+@cindex @code{sync_sub@var{mode}} instruction pattern
+@cindex @code{sync_ior@var{mode}} instruction pattern
+@cindex @code{sync_and@var{mode}} instruction pattern
+@cindex @code{sync_xor@var{mode}} instruction pattern
+@cindex @code{sync_nand@var{mode}} instruction pattern
+@item @samp{sync_add@var{mode}}, @samp{sync_sub@var{mode}}
+@itemx @samp{sync_ior@var{mode}}, @samp{sync_and@var{mode}}
+@itemx @samp{sync_xor@var{mode}}, @samp{sync_nand@var{mode}}
+These patterns emit code for an atomic operation on memory.
+Operand 0 is the memory on which the atomic operation is performed.
+Operand 1 is the second operand to the binary operator.
+
+This pattern must issue any memory barrier instructions such that all
+memory operations before the atomic operation occur before the atomic
+operation and all memory operations after the atomic operation occur
+after the atomic operation.
+
+If these patterns are not defined, the operation will be constructed
+from a compare-and-swap operation, if defined.
+
+@cindex @code{sync_old_add@var{mode}} instruction pattern
+@cindex @code{sync_old_sub@var{mode}} instruction pattern
+@cindex @code{sync_old_ior@var{mode}} instruction pattern
+@cindex @code{sync_old_and@var{mode}} instruction pattern
+@cindex @code{sync_old_xor@var{mode}} instruction pattern
+@cindex @code{sync_old_nand@var{mode}} instruction pattern
+@item @samp{sync_old_add@var{mode}}, @samp{sync_old_sub@var{mode}}
+@itemx @samp{sync_old_ior@var{mode}}, @samp{sync_old_and@var{mode}}
+@itemx @samp{sync_old_xor@var{mode}}, @samp{sync_old_nand@var{mode}}
+These patterns emit code for an atomic operation on memory,
+and return the value that the memory contained before the operation.
+Operand 0 is the result value, operand 1 is the memory on which the
+atomic operation is performed, and operand 2 is the second operand
+to the binary operator.
+
+This pattern must issue any memory barrier instructions such that all
+memory operations before the atomic operation occur before the atomic
+operation and all memory operations after the atomic operation occur
+after the atomic operation.
+
+If these patterns are not defined, the operation will be constructed
+from a compare-and-swap operation, if defined.
+
+@cindex @code{sync_new_add@var{mode}} instruction pattern
+@cindex @code{sync_new_sub@var{mode}} instruction pattern
+@cindex @code{sync_new_ior@var{mode}} instruction pattern
+@cindex @code{sync_new_and@var{mode}} instruction pattern
+@cindex @code{sync_new_xor@var{mode}} instruction pattern
+@cindex @code{sync_new_nand@var{mode}} instruction pattern
+@item @samp{sync_new_add@var{mode}}, @samp{sync_new_sub@var{mode}}
+@itemx @samp{sync_new_ior@var{mode}}, @samp{sync_new_and@var{mode}}
+@itemx @samp{sync_new_xor@var{mode}}, @samp{sync_new_nand@var{mode}}
+These patterns are like their @code{sync_old_@var{op}} counterparts,
+except that they return the value that exists in the memory location
+after the operation, rather than before the operation.
+
+@cindex @code{sync_lock_test_and_set@var{mode}} instruction pattern
+@item @samp{sync_lock_test_and_set@var{mode}}
+This pattern takes two forms, based on the capabilities of the target.
+In either case, operand 0 is the result of the operand, operand 1 is
+the memory on which the atomic operation is performed, and operand 2
+is the value to set in the lock.
+
+In the ideal case, this operation is an atomic exchange operation, in
+which the previous value in memory operand is copied into the result
+operand, and the value operand is stored in the memory operand.
+
+For less capable targets, any value operand that is not the constant 1
+should be rejected with @code{FAIL}. In this case the target may use
+an atomic test-and-set bit operation. The result operand should contain
+1 if the bit was previously set and 0 if the bit was previously clear.
+The true contents of the memory operand are implementation defined.
+
+This pattern must issue any memory barrier instructions such that the
+pattern as a whole acts as an acquire barrier, that is all memory
+operations after the pattern do not occur until the lock is acquired.
+
+If this pattern is not defined, the operation will be constructed from
+a compare-and-swap operation, if defined.
+
+@cindex @code{sync_lock_release@var{mode}} instruction pattern
+@item @samp{sync_lock_release@var{mode}}
+This pattern, if defined, releases a lock set by
+@code{sync_lock_test_and_set@var{mode}}. Operand 0 is the memory
+that contains the lock; operand 1 is the value to store in the lock.
+
+If the target doesn't implement full semantics for
+@code{sync_lock_test_and_set@var{mode}}, any value operand which is not
+the constant 0 should be rejected with @code{FAIL}, and the true contents
+of the memory operand are implementation defined.
+
+This pattern must issue any memory barrier instructions such that the
+pattern as a whole acts as a release barrier, that is the lock is
+released only after all previous memory operations have completed.
+
+If this pattern is not defined, then a @code{memory_barrier} pattern
+will be emitted, followed by a store of the value to the memory operand.
+
+@cindex @code{atomic_compare_and_swap@var{mode}} instruction pattern
+@item @samp{atomic_compare_and_swap@var{mode}}
+This pattern, if defined, emits code for an atomic compare-and-swap
+operation with memory model semantics. Operand 2 is the memory on which
+the atomic operation is performed. Operand 0 is an output operand which
+is set to true or false based on whether the operation succeeded. Operand
+1 is an output operand which is set to the contents of the memory before
+the operation was attempted. Operand 3 is the value that is expected to
+be in memory. Operand 4 is the value to put in memory if the expected
+value is found there. Operand 5 is set to 1 if this compare and swap is to
+be treated as a weak operation. Operand 6 is the memory model to be used
+if the operation is a success. Operand 7 is the memory model to be used
+if the operation fails.
+
+If memory referred to in operand 2 contains the value in operand 3, then
+operand 4 is stored in memory pointed to by operand 2 and fencing based on
+the memory model in operand 6 is issued.
+
+If memory referred to in operand 2 does not contain the value in operand 3,
+then fencing based on the memory model in operand 7 is issued.
+
+If a target does not support weak compare-and-swap operations, or the port
+elects not to implement weak operations, the argument in operand 5 can be
+ignored. Note a strong implementation must be provided.
+
+If this pattern is not provided, the @code{__atomic_compare_exchange}
+built-in functions will utilize the legacy @code{sync_compare_and_swap}
+pattern with an @code{__ATOMIC_SEQ_CST} memory model.
+
+@cindex @code{atomic_load@var{mode}} instruction pattern
+@item @samp{atomic_load@var{mode}}
+This pattern implements an atomic load operation with memory model
+semantics. Operand 1 is the memory address being loaded from. Operand 0
+is the result of the load. Operand 2 is the memory model to be used for
+the load operation.
+
+If not present, the @code{__atomic_load} built-in function will either
+resort to a normal load with memory barriers, or a compare-and-swap
+operation if a normal load would not be atomic.
+
+@cindex @code{atomic_store@var{mode}} instruction pattern
+@item @samp{atomic_store@var{mode}}
+This pattern implements an atomic store operation with memory model
+semantics. Operand 0 is the memory address being stored to. Operand 1
+is the value to be written. Operand 2 is the memory model to be used for
+the operation.
+
+If not present, the @code{__atomic_store} built-in function will attempt to
+perform a normal store and surround it with any required memory fences. If
+the store would not be atomic, then an @code{__atomic_exchange} is
+attempted with the result being ignored.
+
+@cindex @code{atomic_exchange@var{mode}} instruction pattern
+@item @samp{atomic_exchange@var{mode}}
+This pattern implements an atomic exchange operation with memory model
+semantics. Operand 1 is the memory location the operation is performed on.
+Operand 0 is an output operand which is set to the original value contained
+in the memory pointed to by operand 1. Operand 2 is the value to be
+stored. Operand 3 is the memory model to be used.
+
+If this pattern is not present, the built-in function
+@code{__atomic_exchange} will attempt to preform the operation with a
+compare and swap loop.
+
+@cindex @code{atomic_add@var{mode}} instruction pattern
+@cindex @code{atomic_sub@var{mode}} instruction pattern
+@cindex @code{atomic_or@var{mode}} instruction pattern
+@cindex @code{atomic_and@var{mode}} instruction pattern
+@cindex @code{atomic_xor@var{mode}} instruction pattern
+@cindex @code{atomic_nand@var{mode}} instruction pattern
+@item @samp{atomic_add@var{mode}}, @samp{atomic_sub@var{mode}}
+@itemx @samp{atomic_or@var{mode}}, @samp{atomic_and@var{mode}}
+@itemx @samp{atomic_xor@var{mode}}, @samp{atomic_nand@var{mode}}
+These patterns emit code for an atomic operation on memory with memory
+model semantics. Operand 0 is the memory on which the atomic operation is
+performed. Operand 1 is the second operand to the binary operator.
+Operand 2 is the memory model to be used by the operation.
+
+If these patterns are not defined, attempts will be made to use legacy
+@code{sync} patterns, or equivalent patterns which return a result. If
+none of these are available a compare-and-swap loop will be used.
+
+@cindex @code{atomic_fetch_add@var{mode}} instruction pattern
+@cindex @code{atomic_fetch_sub@var{mode}} instruction pattern
+@cindex @code{atomic_fetch_or@var{mode}} instruction pattern
+@cindex @code{atomic_fetch_and@var{mode}} instruction pattern
+@cindex @code{atomic_fetch_xor@var{mode}} instruction pattern
+@cindex @code{atomic_fetch_nand@var{mode}} instruction pattern
+@item @samp{atomic_fetch_add@var{mode}}, @samp{atomic_fetch_sub@var{mode}}
+@itemx @samp{atomic_fetch_or@var{mode}}, @samp{atomic_fetch_and@var{mode}}
+@itemx @samp{atomic_fetch_xor@var{mode}}, @samp{atomic_fetch_nand@var{mode}}
+These patterns emit code for an atomic operation on memory with memory
+model semantics, and return the original value. Operand 0 is an output
+operand which contains the value of the memory location before the
+operation was performed. Operand 1 is the memory on which the atomic
+operation is performed. Operand 2 is the second operand to the binary
+operator. Operand 3 is the memory model to be used by the operation.
+
+If these patterns are not defined, attempts will be made to use legacy
+@code{sync} patterns. If none of these are available a compare-and-swap
+loop will be used.
+
+@cindex @code{atomic_add_fetch@var{mode}} instruction pattern
+@cindex @code{atomic_sub_fetch@var{mode}} instruction pattern
+@cindex @code{atomic_or_fetch@var{mode}} instruction pattern
+@cindex @code{atomic_and_fetch@var{mode}} instruction pattern
+@cindex @code{atomic_xor_fetch@var{mode}} instruction pattern
+@cindex @code{atomic_nand_fetch@var{mode}} instruction pattern
+@item @samp{atomic_add_fetch@var{mode}}, @samp{atomic_sub_fetch@var{mode}}
+@itemx @samp{atomic_or_fetch@var{mode}}, @samp{atomic_and_fetch@var{mode}}
+@itemx @samp{atomic_xor_fetch@var{mode}}, @samp{atomic_nand_fetch@var{mode}}
+These patterns emit code for an atomic operation on memory with memory
+model semantics and return the result after the operation is performed.
+Operand 0 is an output operand which contains the value after the
+operation. Operand 1 is the memory on which the atomic operation is
+performed. Operand 2 is the second operand to the binary operator.
+Operand 3 is the memory model to be used by the operation.
+
+If these patterns are not defined, attempts will be made to use legacy
+@code{sync} patterns, or equivalent patterns which return the result before
+the operation followed by the arithmetic operation required to produce the
+result. If none of these are available a compare-and-swap loop will be
+used.
+
+@cindex @code{atomic_test_and_set} instruction pattern
+@item @samp{atomic_test_and_set}
+This pattern emits code for @code{__builtin_atomic_test_and_set}.
+Operand 0 is an output operand which is set to true if the previous
+previous contents of the byte was "set", and false otherwise. Operand 1
+is the @code{QImode} memory to be modified. Operand 2 is the memory
+model to be used.
+
+The specific value that defines "set" is implementation defined, and
+is normally based on what is performed by the native atomic test and set
+instruction.
+
+@cindex @code{atomic_bit_test_and_set@var{mode}} instruction pattern
+@cindex @code{atomic_bit_test_and_complement@var{mode}} instruction pattern
+@cindex @code{atomic_bit_test_and_reset@var{mode}} instruction pattern
+@item @samp{atomic_bit_test_and_set@var{mode}}
+@itemx @samp{atomic_bit_test_and_complement@var{mode}}
+@itemx @samp{atomic_bit_test_and_reset@var{mode}}
+These patterns emit code for an atomic bitwise operation on memory with memory
+model semantics, and return the original value of the specified bit.
+Operand 0 is an output operand which contains the value of the specified bit
+from the memory location before the operation was performed. Operand 1 is the
+memory on which the atomic operation is performed. Operand 2 is the bit within
+the operand, starting with least significant bit. Operand 3 is the memory model
+to be used by the operation. Operand 4 is a flag - it is @code{const1_rtx}
+if operand 0 should contain the original value of the specified bit in the
+least significant bit of the operand, and @code{const0_rtx} if the bit should
+be in its original position in the operand.
+@code{atomic_bit_test_and_set@var{mode}} atomically sets the specified bit after
+remembering its original value, @code{atomic_bit_test_and_complement@var{mode}}
+inverts the specified bit and @code{atomic_bit_test_and_reset@var{mode}} clears
+the specified bit.
+
+If these patterns are not defined, attempts will be made to use
+@code{atomic_fetch_or@var{mode}}, @code{atomic_fetch_xor@var{mode}} or
+@code{atomic_fetch_and@var{mode}} instruction patterns, or their @code{sync}
+counterparts. If none of these are available a compare-and-swap
+loop will be used.
+
+@cindex @code{atomic_add_fetch_cmp_0@var{mode}} instruction pattern
+@cindex @code{atomic_sub_fetch_cmp_0@var{mode}} instruction pattern
+@cindex @code{atomic_and_fetch_cmp_0@var{mode}} instruction pattern
+@cindex @code{atomic_or_fetch_cmp_0@var{mode}} instruction pattern
+@cindex @code{atomic_xor_fetch_cmp_0@var{mode}} instruction pattern
+@item @samp{atomic_add_fetch_cmp_0@var{mode}}
+@itemx @samp{atomic_sub_fetch_cmp_0@var{mode}}
+@itemx @samp{atomic_and_fetch_cmp_0@var{mode}}
+@itemx @samp{atomic_or_fetch_cmp_0@var{mode}}
+@itemx @samp{atomic_xor_fetch_cmp_0@var{mode}}
+These patterns emit code for an atomic operation on memory with memory
+model semantics if the fetch result is used only in a comparison against
+zero.
+Operand 0 is an output operand which contains a boolean result of comparison
+of the value after the operation against zero. Operand 1 is the memory on
+which the atomic operation is performed. Operand 2 is the second operand
+to the binary operator. Operand 3 is the memory model to be used by the
+operation. Operand 4 is an integer holding the comparison code, one of
+@code{EQ}, @code{NE}, @code{LT}, @code{GT}, @code{LE} or @code{GE}.
+
+If these patterns are not defined, attempts will be made to use separate
+atomic operation and fetch pattern followed by comparison of the result
+against zero.
+
+@cindex @code{mem_thread_fence} instruction pattern
+@item @samp{mem_thread_fence}
+This pattern emits code required to implement a thread fence with
+memory model semantics. Operand 0 is the memory model to be used.
+
+For the @code{__ATOMIC_RELAXED} model no instructions need to be issued
+and this expansion is not invoked.
+
+The compiler always emits a compiler memory barrier regardless of what
+expanding this pattern produced.
+
+If this pattern is not defined, the compiler falls back to expanding the
+@code{memory_barrier} pattern, then to emitting @code{__sync_synchronize}
+library call, and finally to just placing a compiler memory barrier.
+
+@cindex @code{get_thread_pointer@var{mode}} instruction pattern
+@cindex @code{set_thread_pointer@var{mode}} instruction pattern
+@item @samp{get_thread_pointer@var{mode}}
+@itemx @samp{set_thread_pointer@var{mode}}
+These patterns emit code that reads/sets the TLS thread pointer. Currently,
+these are only needed if the target needs to support the
+@code{__builtin_thread_pointer} and @code{__builtin_set_thread_pointer}
+builtins.
+
+The get/set patterns have a single output/input operand respectively,
+with @var{mode} intended to be @code{Pmode}.
+
+@cindex @code{stack_protect_combined_set} instruction pattern
+@item @samp{stack_protect_combined_set}
+This pattern, if defined, moves a @code{ptr_mode} value from an address
+whose declaration RTX is given in operand 1 to the memory in operand 0
+without leaving the value in a register afterward. If several
+instructions are needed by the target to perform the operation (eg. to
+load the address from a GOT entry then load the @code{ptr_mode} value
+and finally store it), it is the backend's responsibility to ensure no
+intermediate result gets spilled. This is to avoid leaking the value
+some place that an attacker might use to rewrite the stack guard slot
+after having clobbered it.
+
+If this pattern is not defined, then the address declaration is
+expanded first in the standard way and a @code{stack_protect_set}
+pattern is then generated to move the value from that address to the
+address in operand 0.
+
+@cindex @code{stack_protect_set} instruction pattern
+@item @samp{stack_protect_set}
+This pattern, if defined, moves a @code{ptr_mode} value from the valid
+memory location in operand 1 to the memory in operand 0 without leaving
+the value in a register afterward. This is to avoid leaking the value
+some place that an attacker might use to rewrite the stack guard slot
+after having clobbered it.
+
+Note: on targets where the addressing modes do not allow to load
+directly from stack guard address, the address is expanded in a standard
+way first which could cause some spills.
+
+If this pattern is not defined, then a plain move pattern is generated.
+
+@cindex @code{stack_protect_combined_test} instruction pattern
+@item @samp{stack_protect_combined_test}
+This pattern, if defined, compares a @code{ptr_mode} value from an
+address whose declaration RTX is given in operand 1 with the memory in
+operand 0 without leaving the value in a register afterward and
+branches to operand 2 if the values were equal. If several
+instructions are needed by the target to perform the operation (eg. to
+load the address from a GOT entry then load the @code{ptr_mode} value
+and finally store it), it is the backend's responsibility to ensure no
+intermediate result gets spilled. This is to avoid leaking the value
+some place that an attacker might use to rewrite the stack guard slot
+after having clobbered it.
+
+If this pattern is not defined, then the address declaration is
+expanded first in the standard way and a @code{stack_protect_test}
+pattern is then generated to compare the value from that address to the
+value at the memory in operand 0.
+
+@cindex @code{stack_protect_test} instruction pattern
+@item @samp{stack_protect_test}
+This pattern, if defined, compares a @code{ptr_mode} value from the
+valid memory location in operand 1 with the memory in operand 0 without
+leaving the value in a register afterward and branches to operand 2 if
+the values were equal.
+
+If this pattern is not defined, then a plain compare pattern and
+conditional branch pattern is used.
+
+@cindex @code{clear_cache} instruction pattern
+@item @samp{clear_cache}
+This pattern, if defined, flushes the instruction cache for a region of
+memory. The region is bounded to by the Pmode pointers in operand 0
+inclusive and operand 1 exclusive.
+
+If this pattern is not defined, a call to the library function
+@code{__clear_cache} is used.
+
+@cindex @code{spaceship@var{m}3} instruction pattern
+@item @samp{spaceship@var{m}3}
+Initialize output operand 0 with mode of integer type to -1, 0, 1 or 2
+if operand 1 with mode @var{m} compares less than operand 2, equal to
+operand 2, greater than operand 2 or is unordered with operand 2.
+@var{m} should be a scalar floating point mode.
+
+This pattern is not allowed to @code{FAIL}.
+
+@end table
+
+@end ifset
+@c Each of the following nodes are wrapped in separate
+@c "@ifset INTERNALS" to work around memory limits for the default
+@c configuration in older tetex distributions. Known to not work:
+@c tetex-1.0.7, known to work: tetex-2.0.2.
+@ifset INTERNALS
+@node Pattern Ordering
+@section When the Order of Patterns Matters
+@cindex Pattern Ordering
+@cindex Ordering of Patterns
+
+Sometimes an insn can match more than one instruction pattern. Then the
+pattern that appears first in the machine description is the one used.
+Therefore, more specific patterns (patterns that will match fewer things)
+and faster instructions (those that will produce better code when they
+do match) should usually go first in the description.
+
+In some cases the effect of ordering the patterns can be used to hide
+a pattern when it is not valid. For example, the 68000 has an
+instruction for converting a fullword to floating point and another
+for converting a byte to floating point. An instruction converting
+an integer to floating point could match either one. We put the
+pattern to convert the fullword first to make sure that one will
+be used rather than the other. (Otherwise a large integer might
+be generated as a single-byte immediate quantity, which would not work.)
+Instead of using this pattern ordering it would be possible to make the
+pattern for convert-a-byte smart enough to deal properly with any
+constant value.
+
+@end ifset
+@ifset INTERNALS
+@node Dependent Patterns
+@section Interdependence of Patterns
+@cindex Dependent Patterns
+@cindex Interdependence of Patterns
+
+In some cases machines support instructions identical except for the
+machine mode of one or more operands. For example, there may be
+``sign-extend halfword'' and ``sign-extend byte'' instructions whose
+patterns are
+
+@smallexample
+(set (match_operand:SI 0 @dots{})
+ (extend:SI (match_operand:HI 1 @dots{})))
+
+(set (match_operand:SI 0 @dots{})
+ (extend:SI (match_operand:QI 1 @dots{})))
+@end smallexample
+
+@noindent
+Constant integers do not specify a machine mode, so an instruction to
+extend a constant value could match either pattern. The pattern it
+actually will match is the one that appears first in the file. For correct
+results, this must be the one for the widest possible mode (@code{HImode},
+here). If the pattern matches the @code{QImode} instruction, the results
+will be incorrect if the constant value does not actually fit that mode.
+
+Such instructions to extend constants are rarely generated because they are
+optimized away, but they do occasionally happen in nonoptimized
+compilations.
+
+If a constraint in a pattern allows a constant, the reload pass may
+replace a register with a constant permitted by the constraint in some
+cases. Similarly for memory references. Because of this substitution,
+you should not provide separate patterns for increment and decrement
+instructions. Instead, they should be generated from the same pattern
+that supports register-register add insns by examining the operands and
+generating the appropriate machine instruction.
+
+@end ifset
+@ifset INTERNALS
+@node Jump Patterns
+@section Defining Jump Instruction Patterns
+@cindex jump instruction patterns
+@cindex defining jump instruction patterns
+
+GCC does not assume anything about how the machine realizes jumps.
+The machine description should define a single pattern, usually
+a @code{define_expand}, which expands to all the required insns.
+
+Usually, this would be a comparison insn to set the condition code
+and a separate branch insn testing the condition code and branching
+or not according to its value. For many machines, however,
+separating compares and branches is limiting, which is why the
+more flexible approach with one @code{define_expand} is used in GCC.
+The machine description becomes clearer for architectures that
+have compare-and-branch instructions but no condition code. It also
+works better when different sets of comparison operators are supported
+by different kinds of conditional branches (e.g.@: integer vs.@:
+floating-point), or by conditional branches with respect to conditional stores.
+
+Two separate insns are always used on most machines that use a separate
+condition code register (@pxref{Condition Code}).
+
+Even in this case having a single entry point for conditional branches
+is advantageous, because it handles equally well the case where a single
+comparison instruction records the results of both signed and unsigned
+comparison of the given operands (with the branch insns coming in distinct
+signed and unsigned flavors) as in the x86 or SPARC, and the case where
+there are distinct signed and unsigned compare instructions and only
+one set of conditional branch instructions as in the PowerPC.
+
+@end ifset
+@ifset INTERNALS
+@node Looping Patterns
+@section Defining Looping Instruction Patterns
+@cindex looping instruction patterns
+@cindex defining looping instruction patterns
+
+Some machines have special jump instructions that can be utilized to
+make loops more efficient. A common example is the 68000 @samp{dbra}
+instruction which performs a decrement of a register and a branch if the
+result was greater than zero. Other machines, in particular digital
+signal processors (DSPs), have special block repeat instructions to
+provide low-overhead loop support. For example, the TI TMS320C3x/C4x
+DSPs have a block repeat instruction that loads special registers to
+mark the top and end of a loop and to count the number of loop
+iterations. This avoids the need for fetching and executing a
+@samp{dbra}-like instruction and avoids pipeline stalls associated with
+the jump.
+
+GCC has two special named patterns to support low overhead looping.
+They are @samp{doloop_begin} and @samp{doloop_end}. These are emitted
+by the loop optimizer for certain well-behaved loops with a finite
+number of loop iterations using information collected during strength
+reduction.
+
+The @samp{doloop_end} pattern describes the actual looping instruction
+(or the implicit looping operation) and the @samp{doloop_begin} pattern
+is an optional companion pattern that can be used for initialization
+needed for some low-overhead looping instructions.
+
+Note that some machines require the actual looping instruction to be
+emitted at the top of the loop (e.g., the TMS320C3x/C4x DSPs). Emitting
+the true RTL for a looping instruction at the top of the loop can cause
+problems with flow analysis. So instead, a dummy @code{doloop} insn is
+emitted at the end of the loop. The machine dependent reorg pass checks
+for the presence of this @code{doloop} insn and then searches back to
+the top of the loop, where it inserts the true looping insn (provided
+there are no instructions in the loop which would cause problems). Any
+additional labels can be emitted at this point. In addition, if the
+desired special iteration counter register was not allocated, this
+machine dependent reorg pass could emit a traditional compare and jump
+instruction pair.
+
+For the @samp{doloop_end} pattern, the loop optimizer allocates an
+additional pseudo register as an iteration counter. This pseudo
+register cannot be used within the loop (i.e., general induction
+variables cannot be derived from it), however, in many cases the loop
+induction variable may become redundant and removed by the flow pass.
+
+The @samp{doloop_end} pattern must have a specific structure to be
+handled correctly by GCC. The example below is taken (slightly
+simplified) from the PDP-11 target:
+
+@smallexample
+@group
+(define_expand "doloop_end"
+ [(parallel [(set (pc)
+ (if_then_else
+ (ne (match_operand:HI 0 "nonimmediate_operand" "+r,!m")
+ (const_int 1))
+ (label_ref (match_operand 1 "" ""))
+ (pc)))
+ (set (match_dup 0)
+ (plus:HI (match_dup 0)
+ (const_int -1)))])]
+ ""
+ "@{
+ if (GET_MODE (operands[0]) != HImode)
+ FAIL;
+ @}")
+
+(define_insn "doloop_end_insn"
+ [(set (pc)
+ (if_then_else
+ (ne (match_operand:HI 0 "nonimmediate_operand" "+r,!m")
+ (const_int 1))
+ (label_ref (match_operand 1 "" ""))
+ (pc)))
+ (set (match_dup 0)
+ (plus:HI (match_dup 0)
+ (const_int -1)))]
+ ""
+
+ @{
+ if (which_alternative == 0)
+ return "sob %0,%l1";
+
+ /* emulate sob */
+ output_asm_insn ("dec %0", operands);
+ return "bne %l1";
+ @})
+@end group
+@end smallexample
+
+The first part of the pattern describes the branch condition. GCC
+supports three cases for the way the target machine handles the loop
+counter:
+@itemize @bullet
+@item Loop terminates when the loop register decrements to zero. This
+is represented by a @code{ne} comparison of the register (its old value)
+with constant 1 (as in the example above).
+@item Loop terminates when the loop register decrements to @minus{}1.
+This is represented by a @code{ne} comparison of the register with
+constant zero.
+@item Loop terminates when the loop register decrements to a negative
+value. This is represented by a @code{ge} comparison of the register
+with constant zero. For this case, GCC will attach a @code{REG_NONNEG}
+note to the @code{doloop_end} insn if it can determine that the register
+will be non-negative.
+@end itemize
+
+Since the @code{doloop_end} insn is a jump insn that also has an output,
+the reload pass does not handle the output operand. Therefore, the
+constraint must allow for that operand to be in memory rather than a
+register. In the example shown above, that is handled (in the
+@code{doloop_end_insn} pattern) by using a loop instruction sequence
+that can handle memory operands when the memory alternative appears.
+
+GCC does not check the mode of the loop register operand when generating
+the @code{doloop_end} pattern. If the pattern is only valid for some
+modes but not others, the pattern should be a @code{define_expand}
+pattern that checks the operand mode in the preparation code, and issues
+@code{FAIL} if an unsupported mode is found. The example above does
+this, since the machine instruction to be used only exists for
+@code{HImode}.
+
+If the @code{doloop_end} pattern is a @code{define_expand}, there must
+also be a @code{define_insn} or @code{define_insn_and_split} matching
+the generated pattern. Otherwise, the compiler will fail during loop
+optimization.
+
+@end ifset
+@ifset INTERNALS
+@node Insn Canonicalizations
+@section Canonicalization of Instructions
+@cindex canonicalization of instructions
+@cindex insn canonicalization
+
+There are often cases where multiple RTL expressions could represent an
+operation performed by a single machine instruction. This situation is
+most commonly encountered with logical, branch, and multiply-accumulate
+instructions. In such cases, the compiler attempts to convert these
+multiple RTL expressions into a single canonical form to reduce the
+number of insn patterns required.
+
+In addition to algebraic simplifications, following canonicalizations
+are performed:
+
+@itemize @bullet
+@item
+For commutative and comparison operators, a constant is always made the
+second operand. If a machine only supports a constant as the second
+operand, only patterns that match a constant in the second operand need
+be supplied.
+
+@item
+For associative operators, a sequence of operators will always chain
+to the left; for instance, only the left operand of an integer @code{plus}
+can itself be a @code{plus}. @code{and}, @code{ior}, @code{xor},
+@code{plus}, @code{mult}, @code{smin}, @code{smax}, @code{umin}, and
+@code{umax} are associative when applied to integers, and sometimes to
+floating-point.
+
+@item
+@cindex @code{neg}, canonicalization of
+@cindex @code{not}, canonicalization of
+@cindex @code{mult}, canonicalization of
+@cindex @code{plus}, canonicalization of
+@cindex @code{minus}, canonicalization of
+For these operators, if only one operand is a @code{neg}, @code{not},
+@code{mult}, @code{plus}, or @code{minus} expression, it will be the
+first operand.
+
+@item
+In combinations of @code{neg}, @code{mult}, @code{plus}, and
+@code{minus}, the @code{neg} operations (if any) will be moved inside
+the operations as far as possible. For instance,
+@code{(neg (mult A B))} is canonicalized as @code{(mult (neg A) B)}, but
+@code{(plus (mult (neg B) C) A)} is canonicalized as
+@code{(minus A (mult B C))}.
+
+@cindex @code{compare}, canonicalization of
+@item
+For the @code{compare} operator, a constant is always the second operand
+if the first argument is a condition code register.
+
+@item
+For instructions that inherently set a condition code register, the
+@code{compare} operator is always written as the first RTL expression of
+the @code{parallel} instruction pattern. For example,
+
+@smallexample
+(define_insn ""
+ [(set (reg:CCZ FLAGS_REG)
+ (compare:CCZ
+ (plus:SI
+ (match_operand:SI 1 "register_operand" "%r")
+ (match_operand:SI 2 "register_operand" "r"))
+ (const_int 0)))
+ (set (match_operand:SI 0 "register_operand" "=r")
+ (plus:SI (match_dup 1) (match_dup 2)))]
+ ""
+ "addl %0, %1, %2")
+@end smallexample
+
+@item
+An operand of @code{neg}, @code{not}, @code{mult}, @code{plus}, or
+@code{minus} is made the first operand under the same conditions as
+above.
+
+@item
+@code{(ltu (plus @var{a} @var{b}) @var{b})} is converted to
+@code{(ltu (plus @var{a} @var{b}) @var{a})}. Likewise with @code{geu} instead
+of @code{ltu}.
+
+@item
+@code{(minus @var{x} (const_int @var{n}))} is converted to
+@code{(plus @var{x} (const_int @var{-n}))}.
+
+@item
+Within address computations (i.e., inside @code{mem}), a left shift is
+converted into the appropriate multiplication by a power of two.
+
+@cindex @code{ior}, canonicalization of
+@cindex @code{and}, canonicalization of
+@cindex De Morgan's law
+@item
+De Morgan's Law is used to move bitwise negation inside a bitwise
+logical-and or logical-or operation. If this results in only one
+operand being a @code{not} expression, it will be the first one.
+
+A machine that has an instruction that performs a bitwise logical-and of one
+operand with the bitwise negation of the other should specify the pattern
+for that instruction as
+
+@smallexample
+(define_insn ""
+ [(set (match_operand:@var{m} 0 @dots{})
+ (and:@var{m} (not:@var{m} (match_operand:@var{m} 1 @dots{}))
+ (match_operand:@var{m} 2 @dots{})))]
+ "@dots{}"
+ "@dots{}")
+@end smallexample
+
+@noindent
+Similarly, a pattern for a ``NAND'' instruction should be written
+
+@smallexample
+(define_insn ""
+ [(set (match_operand:@var{m} 0 @dots{})
+ (ior:@var{m} (not:@var{m} (match_operand:@var{m} 1 @dots{}))
+ (not:@var{m} (match_operand:@var{m} 2 @dots{}))))]
+ "@dots{}"
+ "@dots{}")
+@end smallexample
+
+In both cases, it is not necessary to include patterns for the many
+logically equivalent RTL expressions.
+
+@cindex @code{xor}, canonicalization of
+@item
+The only possible RTL expressions involving both bitwise exclusive-or
+and bitwise negation are @code{(xor:@var{m} @var{x} @var{y})}
+and @code{(not:@var{m} (xor:@var{m} @var{x} @var{y}))}.
+
+@item
+The sum of three items, one of which is a constant, will only appear in
+the form
+
+@smallexample
+(plus:@var{m} (plus:@var{m} @var{x} @var{y}) @var{constant})
+@end smallexample
+
+@cindex @code{zero_extract}, canonicalization of
+@cindex @code{sign_extract}, canonicalization of
+@item
+Equality comparisons of a group of bits (usually a single bit) with zero
+will be written using @code{zero_extract} rather than the equivalent
+@code{and} or @code{sign_extract} operations.
+
+@cindex @code{mult}, canonicalization of
+@item
+@code{(sign_extend:@var{m1} (mult:@var{m2} (sign_extend:@var{m2} @var{x})
+(sign_extend:@var{m2} @var{y})))} is converted to @code{(mult:@var{m1}
+(sign_extend:@var{m1} @var{x}) (sign_extend:@var{m1} @var{y}))}, and likewise
+for @code{zero_extend}.
+
+@item
+@code{(sign_extend:@var{m1} (mult:@var{m2} (ashiftrt:@var{m2}
+@var{x} @var{s}) (sign_extend:@var{m2} @var{y})))} is converted
+to @code{(mult:@var{m1} (sign_extend:@var{m1} (ashiftrt:@var{m2}
+@var{x} @var{s})) (sign_extend:@var{m1} @var{y}))}, and likewise for
+patterns using @code{zero_extend} and @code{lshiftrt}. If the second
+operand of @code{mult} is also a shift, then that is extended also.
+This transformation is only applied when it can be proven that the
+original operation had sufficient precision to prevent overflow.
+
+@end itemize
+
+Further canonicalization rules are defined in the function
+@code{commutative_operand_precedence} in @file{gcc/rtlanal.cc}.
+
+@end ifset
+@ifset INTERNALS
+@node Expander Definitions
+@section Defining RTL Sequences for Code Generation
+@cindex expander definitions
+@cindex code generation RTL sequences
+@cindex defining RTL sequences for code generation
+
+On some target machines, some standard pattern names for RTL generation
+cannot be handled with single insn, but a sequence of RTL insns can
+represent them. For these target machines, you can write a
+@code{define_expand} to specify how to generate the sequence of RTL@.
+
+@findex define_expand
+A @code{define_expand} is an RTL expression that looks almost like a
+@code{define_insn}; but, unlike the latter, a @code{define_expand} is used
+only for RTL generation and it can produce more than one RTL insn.
+
+A @code{define_expand} RTX has four operands:
+
+@itemize @bullet
+@item
+The name. Each @code{define_expand} must have a name, since the only
+use for it is to refer to it by name.
+
+@item
+The RTL template. This is a vector of RTL expressions representing
+a sequence of separate instructions. Unlike @code{define_insn}, there
+is no implicit surrounding @code{PARALLEL}.
+
+@item
+The condition, a string containing a C expression. This expression is
+used to express how the availability of this pattern depends on
+subclasses of target machine, selected by command-line options when GCC
+is run. This is just like the condition of a @code{define_insn} that
+has a standard name. Therefore, the condition (if present) may not
+depend on the data in the insn being matched, but only the
+target-machine-type flags. The compiler needs to test these conditions
+during initialization in order to learn exactly which named instructions
+are available in a particular run.
+
+@item
+The preparation statements, a string containing zero or more C
+statements which are to be executed before RTL code is generated from
+the RTL template.
+
+Usually these statements prepare temporary registers for use as
+internal operands in the RTL template, but they can also generate RTL
+insns directly by calling routines such as @code{emit_insn}, etc.
+Any such insns precede the ones that come from the RTL template.
+
+@item
+Optionally, a vector containing the values of attributes. @xref{Insn
+Attributes}.
+@end itemize
+
+Every RTL insn emitted by a @code{define_expand} must match some
+@code{define_insn} in the machine description. Otherwise, the compiler
+will crash when trying to generate code for the insn or trying to optimize
+it.
+
+The RTL template, in addition to controlling generation of RTL insns,
+also describes the operands that need to be specified when this pattern
+is used. In particular, it gives a predicate for each operand.
+
+A true operand, which needs to be specified in order to generate RTL from
+the pattern, should be described with a @code{match_operand} in its first
+occurrence in the RTL template. This enters information on the operand's
+predicate into the tables that record such things. GCC uses the
+information to preload the operand into a register if that is required for
+valid RTL code. If the operand is referred to more than once, subsequent
+references should use @code{match_dup}.
+
+The RTL template may also refer to internal ``operands'' which are
+temporary registers or labels used only within the sequence made by the
+@code{define_expand}. Internal operands are substituted into the RTL
+template with @code{match_dup}, never with @code{match_operand}. The
+values of the internal operands are not passed in as arguments by the
+compiler when it requests use of this pattern. Instead, they are computed
+within the pattern, in the preparation statements. These statements
+compute the values and store them into the appropriate elements of
+@code{operands} so that @code{match_dup} can find them.
+
+There are two special macros defined for use in the preparation statements:
+@code{DONE} and @code{FAIL}. Use them with a following semicolon,
+as a statement.
+
+@table @code
+
+@findex DONE
+@item DONE
+Use the @code{DONE} macro to end RTL generation for the pattern. The
+only RTL insns resulting from the pattern on this occasion will be
+those already emitted by explicit calls to @code{emit_insn} within the
+preparation statements; the RTL template will not be generated.
+
+@findex FAIL
+@item FAIL
+Make the pattern fail on this occasion. When a pattern fails, it means
+that the pattern was not truly available. The calling routines in the
+compiler will try other strategies for code generation using other patterns.
+
+Failure is currently supported only for binary (addition, multiplication,
+shifting, etc.) and bit-field (@code{extv}, @code{extzv}, and @code{insv})
+operations.
+@end table
+
+If the preparation falls through (invokes neither @code{DONE} nor
+@code{FAIL}), then the @code{define_expand} acts like a
+@code{define_insn} in that the RTL template is used to generate the
+insn.
+
+The RTL template is not used for matching, only for generating the
+initial insn list. If the preparation statement always invokes
+@code{DONE} or @code{FAIL}, the RTL template may be reduced to a simple
+list of operands, such as this example:
+
+@smallexample
+@group
+(define_expand "addsi3"
+ [(match_operand:SI 0 "register_operand" "")
+ (match_operand:SI 1 "register_operand" "")
+ (match_operand:SI 2 "register_operand" "")]
+ ""
+ "
+@{
+ handle_add (operands[0], operands[1], operands[2]);
+ DONE;
+@}")
+@end group
+@end smallexample
+
+Here is an example, the definition of left-shift for the SPUR chip:
+
+@smallexample
+@group
+(define_expand "ashlsi3"
+ [(set (match_operand:SI 0 "register_operand" "")
+ (ashift:SI
+ (match_operand:SI 1 "register_operand" "")
+ (match_operand:SI 2 "nonmemory_operand" "")))]
+ ""
+ "
+@{
+ if (GET_CODE (operands[2]) != CONST_INT
+ || (unsigned) INTVAL (operands[2]) > 3)
+ FAIL;
+@}")
+@end group
+@end smallexample
+
+@noindent
+This example uses @code{define_expand} so that it can generate an RTL insn
+for shifting when the shift-count is in the supported range of 0 to 3 but
+fail in other cases where machine insns aren't available. When it fails,
+the compiler tries another strategy using different patterns (such as, a
+library call).
+
+If the compiler were able to handle nontrivial condition-strings in
+patterns with names, then it would be possible to use a
+@code{define_insn} in that case. Here is another case (zero-extension
+on the 68000) which makes more use of the power of @code{define_expand}:
+
+@smallexample
+(define_expand "zero_extendhisi2"
+ [(set (match_operand:SI 0 "general_operand" "")
+ (const_int 0))
+ (set (strict_low_part
+ (subreg:HI
+ (match_dup 0)
+ 0))
+ (match_operand:HI 1 "general_operand" ""))]
+ ""
+ "operands[1] = make_safe_from (operands[1], operands[0]);")
+@end smallexample
+
+@noindent
+@findex make_safe_from
+Here two RTL insns are generated, one to clear the entire output operand
+and the other to copy the input operand into its low half. This sequence
+is incorrect if the input operand refers to [the old value of] the output
+operand, so the preparation statement makes sure this isn't so. The
+function @code{make_safe_from} copies the @code{operands[1]} into a
+temporary register if it refers to @code{operands[0]}. It does this
+by emitting another RTL insn.
+
+Finally, a third example shows the use of an internal operand.
+Zero-extension on the SPUR chip is done by @code{and}-ing the result
+against a halfword mask. But this mask cannot be represented by a
+@code{const_int} because the constant value is too large to be legitimate
+on this machine. So it must be copied into a register with
+@code{force_reg} and then the register used in the @code{and}.
+
+@smallexample
+(define_expand "zero_extendhisi2"
+ [(set (match_operand:SI 0 "register_operand" "")
+ (and:SI (subreg:SI
+ (match_operand:HI 1 "register_operand" "")
+ 0)
+ (match_dup 2)))]
+ ""
+ "operands[2]
+ = force_reg (SImode, GEN_INT (65535)); ")
+@end smallexample
+
+@emph{Note:} If the @code{define_expand} is used to serve a
+standard binary or unary arithmetic operation or a bit-field operation,
+then the last insn it generates must not be a @code{code_label},
+@code{barrier} or @code{note}. It must be an @code{insn},
+@code{jump_insn} or @code{call_insn}. If you don't need a real insn
+at the end, emit an insn to copy the result of the operation into
+itself. Such an insn will generate no code, but it can avoid problems
+in the compiler.
+
+@end ifset
+@ifset INTERNALS
+@node Insn Splitting
+@section Defining How to Split Instructions
+@cindex insn splitting
+@cindex instruction splitting
+@cindex splitting instructions
+
+There are two cases where you should specify how to split a pattern
+into multiple insns. On machines that have instructions requiring
+delay slots (@pxref{Delay Slots}) or that have instructions whose
+output is not available for multiple cycles (@pxref{Processor pipeline
+description}), the compiler phases that optimize these cases need to
+be able to move insns into one-instruction delay slots. However, some
+insns may generate more than one machine instruction. These insns
+cannot be placed into a delay slot.
+
+Often you can rewrite the single insn as a list of individual insns,
+each corresponding to one machine instruction. The disadvantage of
+doing so is that it will cause the compilation to be slower and require
+more space. If the resulting insns are too complex, it may also
+suppress some optimizations. The compiler splits the insn if there is a
+reason to believe that it might improve instruction or delay slot
+scheduling.
+
+The insn combiner phase also splits putative insns. If three insns are
+merged into one insn with a complex expression that cannot be matched by
+some @code{define_insn} pattern, the combiner phase attempts to split
+the complex pattern into two insns that are recognized. Usually it can
+break the complex pattern into two patterns by splitting out some
+subexpression. However, in some other cases, such as performing an
+addition of a large constant in two insns on a RISC machine, the way to
+split the addition into two insns is machine-dependent.
+
+@findex define_split
+The @code{define_split} definition tells the compiler how to split a
+complex insn into several simpler insns. It looks like this:
+
+@smallexample
+(define_split
+ [@var{insn-pattern}]
+ "@var{condition}"
+ [@var{new-insn-pattern-1}
+ @var{new-insn-pattern-2}
+ @dots{}]
+ "@var{preparation-statements}")
+@end smallexample
+
+@var{insn-pattern} is a pattern that needs to be split and
+@var{condition} is the final condition to be tested, as in a
+@code{define_insn}. When an insn matching @var{insn-pattern} and
+satisfying @var{condition} is found, it is replaced in the insn list
+with the insns given by @var{new-insn-pattern-1},
+@var{new-insn-pattern-2}, etc.
+
+The @var{preparation-statements} are similar to those statements that
+are specified for @code{define_expand} (@pxref{Expander Definitions})
+and are executed before the new RTL is generated to prepare for the
+generated code or emit some insns whose pattern is not fixed. Unlike
+those in @code{define_expand}, however, these statements must not
+generate any new pseudo-registers. Once reload has completed, they also
+must not allocate any space in the stack frame.
+
+There are two special macros defined for use in the preparation statements:
+@code{DONE} and @code{FAIL}. Use them with a following semicolon,
+as a statement.
+
+@table @code
+
+@findex DONE
+@item DONE
+Use the @code{DONE} macro to end RTL generation for the splitter. The
+only RTL insns generated as replacement for the matched input insn will
+be those already emitted by explicit calls to @code{emit_insn} within
+the preparation statements; the replacement pattern is not used.
+
+@findex FAIL
+@item FAIL
+Make the @code{define_split} fail on this occasion. When a @code{define_split}
+fails, it means that the splitter was not truly available for the inputs
+it was given, and the input insn will not be split.
+@end table
+
+If the preparation falls through (invokes neither @code{DONE} nor
+@code{FAIL}), then the @code{define_split} uses the replacement
+template.
+
+Patterns are matched against @var{insn-pattern} in two different
+circumstances. If an insn needs to be split for delay slot scheduling
+or insn scheduling, the insn is already known to be valid, which means
+that it must have been matched by some @code{define_insn} and, if
+@code{reload_completed} is nonzero, is known to satisfy the constraints
+of that @code{define_insn}. In that case, the new insn patterns must
+also be insns that are matched by some @code{define_insn} and, if
+@code{reload_completed} is nonzero, must also satisfy the constraints
+of those definitions.
+
+As an example of this usage of @code{define_split}, consider the following
+example from @file{a29k.md}, which splits a @code{sign_extend} from
+@code{HImode} to @code{SImode} into a pair of shift insns:
+
+@smallexample
+(define_split
+ [(set (match_operand:SI 0 "gen_reg_operand" "")
+ (sign_extend:SI (match_operand:HI 1 "gen_reg_operand" "")))]
+ ""
+ [(set (match_dup 0)
+ (ashift:SI (match_dup 1)
+ (const_int 16)))
+ (set (match_dup 0)
+ (ashiftrt:SI (match_dup 0)
+ (const_int 16)))]
+ "
+@{ operands[1] = gen_lowpart (SImode, operands[1]); @}")
+@end smallexample
+
+When the combiner phase tries to split an insn pattern, it is always the
+case that the pattern is @emph{not} matched by any @code{define_insn}.
+The combiner pass first tries to split a single @code{set} expression
+and then the same @code{set} expression inside a @code{parallel}, but
+followed by a @code{clobber} of a pseudo-reg to use as a scratch
+register. In these cases, the combiner expects exactly one or two new insn
+patterns to be generated. It will verify that these patterns match some
+@code{define_insn} definitions, so you need not do this test in the
+@code{define_split} (of course, there is no point in writing a
+@code{define_split} that will never produce insns that match).
+
+Here is an example of this use of @code{define_split}, taken from
+@file{rs6000.md}:
+
+@smallexample
+(define_split
+ [(set (match_operand:SI 0 "gen_reg_operand" "")
+ (plus:SI (match_operand:SI 1 "gen_reg_operand" "")
+ (match_operand:SI 2 "non_add_cint_operand" "")))]
+ ""
+ [(set (match_dup 0) (plus:SI (match_dup 1) (match_dup 3)))
+ (set (match_dup 0) (plus:SI (match_dup 0) (match_dup 4)))]
+"
+@{
+ int low = INTVAL (operands[2]) & 0xffff;
+ int high = (unsigned) INTVAL (operands[2]) >> 16;
+
+ if (low & 0x8000)
+ high++, low |= 0xffff0000;
+
+ operands[3] = GEN_INT (high << 16);
+ operands[4] = GEN_INT (low);
+@}")
+@end smallexample
+
+Here the predicate @code{non_add_cint_operand} matches any
+@code{const_int} that is @emph{not} a valid operand of a single add
+insn. The add with the smaller displacement is written so that it
+can be substituted into the address of a subsequent operation.
+
+An example that uses a scratch register, from the same file, generates
+an equality comparison of a register and a large constant:
+
+@smallexample
+(define_split
+ [(set (match_operand:CC 0 "cc_reg_operand" "")
+ (compare:CC (match_operand:SI 1 "gen_reg_operand" "")
+ (match_operand:SI 2 "non_short_cint_operand" "")))
+ (clobber (match_operand:SI 3 "gen_reg_operand" ""))]
+ "find_single_use (operands[0], insn, 0)
+ && (GET_CODE (*find_single_use (operands[0], insn, 0)) == EQ
+ || GET_CODE (*find_single_use (operands[0], insn, 0)) == NE)"
+ [(set (match_dup 3) (xor:SI (match_dup 1) (match_dup 4)))
+ (set (match_dup 0) (compare:CC (match_dup 3) (match_dup 5)))]
+ "
+@{
+ /* @r{Get the constant we are comparing against, C, and see what it
+ looks like sign-extended to 16 bits. Then see what constant
+ could be XOR'ed with C to get the sign-extended value.} */
+
+ int c = INTVAL (operands[2]);
+ int sextc = (c << 16) >> 16;
+ int xorv = c ^ sextc;
+
+ operands[4] = GEN_INT (xorv);
+ operands[5] = GEN_INT (sextc);
+@}")
+@end smallexample
+
+To avoid confusion, don't write a single @code{define_split} that
+accepts some insns that match some @code{define_insn} as well as some
+insns that don't. Instead, write two separate @code{define_split}
+definitions, one for the insns that are valid and one for the insns that
+are not valid.
+
+The splitter is allowed to split jump instructions into sequence of
+jumps or create new jumps in while splitting non-jump instructions. As
+the control flow graph and branch prediction information needs to be updated,
+several restriction apply.
+
+Splitting of jump instruction into sequence that over by another jump
+instruction is always valid, as compiler expect identical behavior of new
+jump. When new sequence contains multiple jump instructions or new labels,
+more assistance is needed. Splitter is required to create only unconditional
+jumps, or simple conditional jump instructions. Additionally it must attach a
+@code{REG_BR_PROB} note to each conditional jump. A global variable
+@code{split_branch_probability} holds the probability of the original branch in case
+it was a simple conditional jump, @minus{}1 otherwise. To simplify
+recomputing of edge frequencies, the new sequence is required to have only
+forward jumps to the newly created labels.
+
+@findex define_insn_and_split
+For the common case where the pattern of a define_split exactly matches the
+pattern of a define_insn, use @code{define_insn_and_split}. It looks like
+this:
+
+@smallexample
+(define_insn_and_split
+ [@var{insn-pattern}]
+ "@var{condition}"
+ "@var{output-template}"
+ "@var{split-condition}"
+ [@var{new-insn-pattern-1}
+ @var{new-insn-pattern-2}
+ @dots{}]
+ "@var{preparation-statements}"
+ [@var{insn-attributes}])
+
+@end smallexample
+
+@var{insn-pattern}, @var{condition}, @var{output-template}, and
+@var{insn-attributes} are used as in @code{define_insn}. The
+@var{new-insn-pattern} vector and the @var{preparation-statements} are used as
+in a @code{define_split}. The @var{split-condition} is also used as in
+@code{define_split}, with the additional behavior that if the condition starts
+with @samp{&&}, the condition used for the split will be the constructed as a
+logical ``and'' of the split condition with the insn condition. For example,
+from i386.md:
+
+@smallexample
+(define_insn_and_split "zero_extendhisi2_and"
+ [(set (match_operand:SI 0 "register_operand" "=r")
+ (zero_extend:SI (match_operand:HI 1 "register_operand" "0")))
+ (clobber (reg:CC 17))]
+ "TARGET_ZERO_EXTEND_WITH_AND && !optimize_size"
+ "#"
+ "&& reload_completed"
+ [(parallel [(set (match_dup 0)
+ (and:SI (match_dup 0) (const_int 65535)))
+ (clobber (reg:CC 17))])]
+ ""
+ [(set_attr "type" "alu1")])
+
+@end smallexample
+
+In this case, the actual split condition will be
+@samp{TARGET_ZERO_EXTEND_WITH_AND && !optimize_size && reload_completed}.
+
+The @code{define_insn_and_split} construction provides exactly the same
+functionality as two separate @code{define_insn} and @code{define_split}
+patterns. It exists for compactness, and as a maintenance tool to prevent
+having to ensure the two patterns' templates match.
+
+@findex define_insn_and_rewrite
+It is sometimes useful to have a @code{define_insn_and_split}
+that replaces specific operands of an instruction but leaves the
+rest of the instruction pattern unchanged. You can do this directly
+with a @code{define_insn_and_split}, but it requires a
+@var{new-insn-pattern-1} that repeats most of the original @var{insn-pattern}.
+There is also the complication that an implicit @code{parallel} in
+@var{insn-pattern} must become an explicit @code{parallel} in
+@var{new-insn-pattern-1}, which is easy to overlook.
+A simpler alternative is to use @code{define_insn_and_rewrite}, which
+is a form of @code{define_insn_and_split} that automatically generates
+@var{new-insn-pattern-1} by replacing each @code{match_operand}
+in @var{insn-pattern} with a corresponding @code{match_dup}, and each
+@code{match_operator} in the pattern with a corresponding @code{match_op_dup}.
+The arguments are otherwise identical to @code{define_insn_and_split}:
+
+@smallexample
+(define_insn_and_rewrite
+ [@var{insn-pattern}]
+ "@var{condition}"
+ "@var{output-template}"
+ "@var{split-condition}"
+ "@var{preparation-statements}"
+ [@var{insn-attributes}])
+@end smallexample
+
+The @code{match_dup}s and @code{match_op_dup}s in the new
+instruction pattern use any new operand values that the
+@var{preparation-statements} store in the @code{operands} array,
+as for a normal @code{define_insn_and_split}. @var{preparation-statements}
+can also emit additional instructions before the new instruction.
+They can even emit an entirely different sequence of instructions and
+use @code{DONE} to avoid emitting a new form of the original
+instruction.
+
+The split in a @code{define_insn_and_rewrite} is only intended
+to apply to existing instructions that match @var{insn-pattern}.
+@var{split-condition} must therefore start with @code{&&},
+so that the split condition applies on top of @var{condition}.
+
+Here is an example from the AArch64 SVE port, in which operand 1 is
+known to be equivalent to an all-true constant and isn't used by the
+output template:
+
+@smallexample
+(define_insn_and_rewrite "*while_ult<GPI:mode><PRED_ALL:mode>_cc"
+ [(set (reg:CC CC_REGNUM)
+ (compare:CC
+ (unspec:SI [(match_operand:PRED_ALL 1)
+ (unspec:PRED_ALL
+ [(match_operand:GPI 2 "aarch64_reg_or_zero" "rZ")
+ (match_operand:GPI 3 "aarch64_reg_or_zero" "rZ")]
+ UNSPEC_WHILE_LO)]
+ UNSPEC_PTEST_PTRUE)
+ (const_int 0)))
+ (set (match_operand:PRED_ALL 0 "register_operand" "=Upa")
+ (unspec:PRED_ALL [(match_dup 2)
+ (match_dup 3)]
+ UNSPEC_WHILE_LO))]
+ "TARGET_SVE"
+ "whilelo\t%0.<PRED_ALL:Vetype>, %<w>2, %<w>3"
+ ;; Force the compiler to drop the unused predicate operand, so that we
+ ;; don't have an unnecessary PTRUE.
+ "&& !CONSTANT_P (operands[1])"
+ @{
+ operands[1] = CONSTM1_RTX (<MODE>mode);
+ @}
+)
+@end smallexample
+
+The splitter in this case simply replaces operand 1 with the constant
+value that it is known to have. The equivalent @code{define_insn_and_split}
+would be:
+
+@smallexample
+(define_insn_and_split "*while_ult<GPI:mode><PRED_ALL:mode>_cc"
+ [(set (reg:CC CC_REGNUM)
+ (compare:CC
+ (unspec:SI [(match_operand:PRED_ALL 1)
+ (unspec:PRED_ALL
+ [(match_operand:GPI 2 "aarch64_reg_or_zero" "rZ")
+ (match_operand:GPI 3 "aarch64_reg_or_zero" "rZ")]
+ UNSPEC_WHILE_LO)]
+ UNSPEC_PTEST_PTRUE)
+ (const_int 0)))
+ (set (match_operand:PRED_ALL 0 "register_operand" "=Upa")
+ (unspec:PRED_ALL [(match_dup 2)
+ (match_dup 3)]
+ UNSPEC_WHILE_LO))]
+ "TARGET_SVE"
+ "whilelo\t%0.<PRED_ALL:Vetype>, %<w>2, %<w>3"
+ ;; Force the compiler to drop the unused predicate operand, so that we
+ ;; don't have an unnecessary PTRUE.
+ "&& !CONSTANT_P (operands[1])"
+ [(parallel
+ [(set (reg:CC CC_REGNUM)
+ (compare:CC
+ (unspec:SI [(match_dup 1)
+ (unspec:PRED_ALL [(match_dup 2)
+ (match_dup 3)]
+ UNSPEC_WHILE_LO)]
+ UNSPEC_PTEST_PTRUE)
+ (const_int 0)))
+ (set (match_dup 0)
+ (unspec:PRED_ALL [(match_dup 2)
+ (match_dup 3)]
+ UNSPEC_WHILE_LO))])]
+ @{
+ operands[1] = CONSTM1_RTX (<MODE>mode);
+ @}
+)
+@end smallexample
+
+@end ifset
+@ifset INTERNALS
+@node Including Patterns
+@section Including Patterns in Machine Descriptions.
+@cindex insn includes
+
+@findex include
+The @code{include} pattern tells the compiler tools where to
+look for patterns that are in files other than in the file
+@file{.md}. This is used only at build time and there is no preprocessing allowed.
+
+It looks like:
+
+@smallexample
+
+(include
+ @var{pathname})
+@end smallexample
+
+For example:
+
+@smallexample
+
+(include "filestuff")
+
+@end smallexample
+
+Where @var{pathname} is a string that specifies the location of the file,
+specifies the include file to be in @file{gcc/config/target/filestuff}. The
+directory @file{gcc/config/target} is regarded as the default directory.
+
+
+Machine descriptions may be split up into smaller more manageable subsections
+and placed into subdirectories.
+
+By specifying:
+
+@smallexample
+
+(include "BOGUS/filestuff")
+
+@end smallexample
+
+the include file is specified to be in @file{gcc/config/@var{target}/BOGUS/filestuff}.
+
+Specifying an absolute path for the include file such as;
+@smallexample
+
+(include "/u2/BOGUS/filestuff")
+
+@end smallexample
+is permitted but is not encouraged.
+
+@subsection RTL Generation Tool Options for Directory Search
+@cindex directory options .md
+@cindex options, directory search
+@cindex search options
+
+The @option{-I@var{dir}} option specifies directories to search for machine descriptions.
+For example:
+
+@smallexample
+
+genrecog -I/p1/abc/proc1 -I/p2/abcd/pro2 target.md
+
+@end smallexample
+
+
+Add the directory @var{dir} to the head of the list of directories to be
+searched for header files. This can be used to override a system machine definition
+file, substituting your own version, since these directories are
+searched before the default machine description file directories. If you use more than
+one @option{-I} option, the directories are scanned in left-to-right
+order; the standard default directory come after.
+
+
+@end ifset
+@ifset INTERNALS
+@node Peephole Definitions
+@section Machine-Specific Peephole Optimizers
+@cindex peephole optimizer definitions
+@cindex defining peephole optimizers
+
+In addition to instruction patterns the @file{md} file may contain
+definitions of machine-specific peephole optimizations.
+
+The combiner does not notice certain peephole optimizations when the data
+flow in the program does not suggest that it should try them. For example,
+sometimes two consecutive insns related in purpose can be combined even
+though the second one does not appear to use a register computed in the
+first one. A machine-specific peephole optimizer can detect such
+opportunities.
+
+There are two forms of peephole definitions that may be used. The
+original @code{define_peephole} is run at assembly output time to
+match insns and substitute assembly text. Use of @code{define_peephole}
+is deprecated.
+
+A newer @code{define_peephole2} matches insns and substitutes new
+insns. The @code{peephole2} pass is run after register allocation
+but before scheduling, which may result in much better code for
+targets that do scheduling.
+
+@menu
+* define_peephole:: RTL to Text Peephole Optimizers
+* define_peephole2:: RTL to RTL Peephole Optimizers
+@end menu
+
+@end ifset
+@ifset INTERNALS
+@node define_peephole
+@subsection RTL to Text Peephole Optimizers
+@findex define_peephole
+
+@need 1000
+A definition looks like this:
+
+@smallexample
+(define_peephole
+ [@var{insn-pattern-1}
+ @var{insn-pattern-2}
+ @dots{}]
+ "@var{condition}"
+ "@var{template}"
+ "@var{optional-insn-attributes}")
+@end smallexample
+
+@noindent
+The last string operand may be omitted if you are not using any
+machine-specific information in this machine description. If present,
+it must obey the same rules as in a @code{define_insn}.
+
+In this skeleton, @var{insn-pattern-1} and so on are patterns to match
+consecutive insns. The optimization applies to a sequence of insns when
+@var{insn-pattern-1} matches the first one, @var{insn-pattern-2} matches
+the next, and so on.
+
+Each of the insns matched by a peephole must also match a
+@code{define_insn}. Peepholes are checked only at the last stage just
+before code generation, and only optionally. Therefore, any insn which
+would match a peephole but no @code{define_insn} will cause a crash in code
+generation in an unoptimized compilation, or at various optimization
+stages.
+
+The operands of the insns are matched with @code{match_operands},
+@code{match_operator}, and @code{match_dup}, as usual. What is not
+usual is that the operand numbers apply to all the insn patterns in the
+definition. So, you can check for identical operands in two insns by
+using @code{match_operand} in one insn and @code{match_dup} in the
+other.
+
+The operand constraints used in @code{match_operand} patterns do not have
+any direct effect on the applicability of the peephole, but they will
+be validated afterward, so make sure your constraints are general enough
+to apply whenever the peephole matches. If the peephole matches
+but the constraints are not satisfied, the compiler will crash.
+
+It is safe to omit constraints in all the operands of the peephole; or
+you can write constraints which serve as a double-check on the criteria
+previously tested.
+
+Once a sequence of insns matches the patterns, the @var{condition} is
+checked. This is a C expression which makes the final decision whether to
+perform the optimization (we do so if the expression is nonzero). If
+@var{condition} is omitted (in other words, the string is empty) then the
+optimization is applied to every sequence of insns that matches the
+patterns.
+
+The defined peephole optimizations are applied after register allocation
+is complete. Therefore, the peephole definition can check which
+operands have ended up in which kinds of registers, just by looking at
+the operands.
+
+@findex prev_active_insn
+The way to refer to the operands in @var{condition} is to write
+@code{operands[@var{i}]} for operand number @var{i} (as matched by
+@code{(match_operand @var{i} @dots{})}). Use the variable @code{insn}
+to refer to the last of the insns being matched; use
+@code{prev_active_insn} to find the preceding insns.
+
+@findex dead_or_set_p
+When optimizing computations with intermediate results, you can use
+@var{condition} to match only when the intermediate results are not used
+elsewhere. Use the C expression @code{dead_or_set_p (@var{insn},
+@var{op})}, where @var{insn} is the insn in which you expect the value
+to be used for the last time (from the value of @code{insn}, together
+with use of @code{prev_nonnote_insn}), and @var{op} is the intermediate
+value (from @code{operands[@var{i}]}).
+
+Applying the optimization means replacing the sequence of insns with one
+new insn. The @var{template} controls ultimate output of assembler code
+for this combined insn. It works exactly like the template of a
+@code{define_insn}. Operand numbers in this template are the same ones
+used in matching the original sequence of insns.
+
+The result of a defined peephole optimizer does not need to match any of
+the insn patterns in the machine description; it does not even have an
+opportunity to match them. The peephole optimizer definition itself serves
+as the insn pattern to control how the insn is output.
+
+Defined peephole optimizers are run as assembler code is being output,
+so the insns they produce are never combined or rearranged in any way.
+
+Here is an example, taken from the 68000 machine description:
+
+@smallexample
+(define_peephole
+ [(set (reg:SI 15) (plus:SI (reg:SI 15) (const_int 4)))
+ (set (match_operand:DF 0 "register_operand" "=f")
+ (match_operand:DF 1 "register_operand" "ad"))]
+ "FP_REG_P (operands[0]) && ! FP_REG_P (operands[1])"
+@{
+ rtx xoperands[2];
+ xoperands[1] = gen_rtx_REG (SImode, REGNO (operands[1]) + 1);
+#ifdef MOTOROLA
+ output_asm_insn ("move.l %1,(sp)", xoperands);
+ output_asm_insn ("move.l %1,-(sp)", operands);
+ return "fmove.d (sp)+,%0";
+#else
+ output_asm_insn ("movel %1,sp@@", xoperands);
+ output_asm_insn ("movel %1,sp@@-", operands);
+ return "fmoved sp@@+,%0";
+#endif
+@})
+@end smallexample
+
+@need 1000
+The effect of this optimization is to change
+
+@smallexample
+@group
+jbsr _foobar
+addql #4,sp
+movel d1,sp@@-
+movel d0,sp@@-
+fmoved sp@@+,fp0
+@end group
+@end smallexample
+
+@noindent
+into
+
+@smallexample
+@group
+jbsr _foobar
+movel d1,sp@@
+movel d0,sp@@-
+fmoved sp@@+,fp0
+@end group
+@end smallexample
+
+@ignore
+@findex CC_REVERSED
+If a peephole matches a sequence including one or more jump insns, you must
+take account of the flags such as @code{CC_REVERSED} which specify that the
+condition codes are represented in an unusual manner. The compiler
+automatically alters any ordinary conditional jumps which occur in such
+situations, but the compiler cannot alter jumps which have been replaced by
+peephole optimizations. So it is up to you to alter the assembler code
+that the peephole produces. Supply C code to write the assembler output,
+and in this C code check the condition code status flags and change the
+assembler code as appropriate.
+@end ignore
+
+@var{insn-pattern-1} and so on look @emph{almost} like the second
+operand of @code{define_insn}. There is one important difference: the
+second operand of @code{define_insn} consists of one or more RTX's
+enclosed in square brackets. Usually, there is only one: then the same
+action can be written as an element of a @code{define_peephole}. But
+when there are multiple actions in a @code{define_insn}, they are
+implicitly enclosed in a @code{parallel}. Then you must explicitly
+write the @code{parallel}, and the square brackets within it, in the
+@code{define_peephole}. Thus, if an insn pattern looks like this,
+
+@smallexample
+(define_insn "divmodsi4"
+ [(set (match_operand:SI 0 "general_operand" "=d")
+ (div:SI (match_operand:SI 1 "general_operand" "0")
+ (match_operand:SI 2 "general_operand" "dmsK")))
+ (set (match_operand:SI 3 "general_operand" "=d")
+ (mod:SI (match_dup 1) (match_dup 2)))]
+ "TARGET_68020"
+ "divsl%.l %2,%3:%0")
+@end smallexample
+
+@noindent
+then the way to mention this insn in a peephole is as follows:
+
+@smallexample
+(define_peephole
+ [@dots{}
+ (parallel
+ [(set (match_operand:SI 0 "general_operand" "=d")
+ (div:SI (match_operand:SI 1 "general_operand" "0")
+ (match_operand:SI 2 "general_operand" "dmsK")))
+ (set (match_operand:SI 3 "general_operand" "=d")
+ (mod:SI (match_dup 1) (match_dup 2)))])
+ @dots{}]
+ @dots{})
+@end smallexample
+
+@end ifset
+@ifset INTERNALS
+@node define_peephole2
+@subsection RTL to RTL Peephole Optimizers
+@findex define_peephole2
+
+The @code{define_peephole2} definition tells the compiler how to
+substitute one sequence of instructions for another sequence,
+what additional scratch registers may be needed and what their
+lifetimes must be.
+
+@smallexample
+(define_peephole2
+ [@var{insn-pattern-1}
+ @var{insn-pattern-2}
+ @dots{}]
+ "@var{condition}"
+ [@var{new-insn-pattern-1}
+ @var{new-insn-pattern-2}
+ @dots{}]
+ "@var{preparation-statements}")
+@end smallexample
+
+The definition is almost identical to @code{define_split}
+(@pxref{Insn Splitting}) except that the pattern to match is not a
+single instruction, but a sequence of instructions.
+
+It is possible to request additional scratch registers for use in the
+output template. If appropriate registers are not free, the pattern
+will simply not match.
+
+@findex match_scratch
+@findex match_dup
+Scratch registers are requested with a @code{match_scratch} pattern at
+the top level of the input pattern. The allocated register (initially) will
+be dead at the point requested within the original sequence. If the scratch
+is used at more than a single point, a @code{match_dup} pattern at the
+top level of the input pattern marks the last position in the input sequence
+at which the register must be available.
+
+Here is an example from the IA-32 machine description:
+
+@smallexample
+(define_peephole2
+ [(match_scratch:SI 2 "r")
+ (parallel [(set (match_operand:SI 0 "register_operand" "")
+ (match_operator:SI 3 "arith_or_logical_operator"
+ [(match_dup 0)
+ (match_operand:SI 1 "memory_operand" "")]))
+ (clobber (reg:CC 17))])]
+ "! optimize_size && ! TARGET_READ_MODIFY"
+ [(set (match_dup 2) (match_dup 1))
+ (parallel [(set (match_dup 0)
+ (match_op_dup 3 [(match_dup 0) (match_dup 2)]))
+ (clobber (reg:CC 17))])]
+ "")
+@end smallexample
+
+@noindent
+This pattern tries to split a load from its use in the hopes that we'll be
+able to schedule around the memory load latency. It allocates a single
+@code{SImode} register of class @code{GENERAL_REGS} (@code{"r"}) that needs
+to be live only at the point just before the arithmetic.
+
+A real example requiring extended scratch lifetimes is harder to come by,
+so here's a silly made-up example:
+
+@smallexample
+(define_peephole2
+ [(match_scratch:SI 4 "r")
+ (set (match_operand:SI 0 "" "") (match_operand:SI 1 "" ""))
+ (set (match_operand:SI 2 "" "") (match_dup 1))
+ (match_dup 4)
+ (set (match_operand:SI 3 "" "") (match_dup 1))]
+ "/* @r{determine 1 does not overlap 0 and 2} */"
+ [(set (match_dup 4) (match_dup 1))
+ (set (match_dup 0) (match_dup 4))
+ (set (match_dup 2) (match_dup 4))
+ (set (match_dup 3) (match_dup 4))]
+ "")
+@end smallexample
+
+There are two special macros defined for use in the preparation statements:
+@code{DONE} and @code{FAIL}. Use them with a following semicolon,
+as a statement.
+
+@table @code
+
+@findex DONE
+@item DONE
+Use the @code{DONE} macro to end RTL generation for the peephole. The
+only RTL insns generated as replacement for the matched input insn will
+be those already emitted by explicit calls to @code{emit_insn} within
+the preparation statements; the replacement pattern is not used.
+
+@findex FAIL
+@item FAIL
+Make the @code{define_peephole2} fail on this occasion. When a @code{define_peephole2}
+fails, it means that the replacement was not truly available for the
+particular inputs it was given. In that case, GCC may still apply a
+later @code{define_peephole2} that also matches the given insn pattern.
+(Note that this is different from @code{define_split}, where @code{FAIL}
+prevents the input insn from being split at all.)
+@end table
+
+If the preparation falls through (invokes neither @code{DONE} nor
+@code{FAIL}), then the @code{define_peephole2} uses the replacement
+template.
+
+@noindent
+If we had not added the @code{(match_dup 4)} in the middle of the input
+sequence, it might have been the case that the register we chose at the
+beginning of the sequence is killed by the first or second @code{set}.
+
+@end ifset
+@ifset INTERNALS
+@node Insn Attributes
+@section Instruction Attributes
+@cindex insn attributes
+@cindex instruction attributes
+
+In addition to describing the instruction supported by the target machine,
+the @file{md} file also defines a group of @dfn{attributes} and a set of
+values for each. Every generated insn is assigned a value for each attribute.
+One possible attribute would be the effect that the insn has on the machine's
+condition code.
+
+@menu
+* Defining Attributes:: Specifying attributes and their values.
+* Expressions:: Valid expressions for attribute values.
+* Tagging Insns:: Assigning attribute values to insns.
+* Attr Example:: An example of assigning attributes.
+* Insn Lengths:: Computing the length of insns.
+* Constant Attributes:: Defining attributes that are constant.
+* Mnemonic Attribute:: Obtain the instruction mnemonic as attribute value.
+* Delay Slots:: Defining delay slots required for a machine.
+* Processor pipeline description:: Specifying information for insn scheduling.
+@end menu
+
+@end ifset
+@ifset INTERNALS
+@node Defining Attributes
+@subsection Defining Attributes and their Values
+@cindex defining attributes and their values
+@cindex attributes, defining
+
+@findex define_attr
+The @code{define_attr} expression is used to define each attribute required
+by the target machine. It looks like:
+
+@smallexample
+(define_attr @var{name} @var{list-of-values} @var{default})
+@end smallexample
+
+@var{name} is a string specifying the name of the attribute being
+defined. Some attributes are used in a special way by the rest of the
+compiler. The @code{enabled} attribute can be used to conditionally
+enable or disable insn alternatives (@pxref{Disable Insn
+Alternatives}). The @code{predicable} attribute, together with a
+suitable @code{define_cond_exec} (@pxref{Conditional Execution}), can
+be used to automatically generate conditional variants of instruction
+patterns. The @code{mnemonic} attribute can be used to check for the
+instruction mnemonic (@pxref{Mnemonic Attribute}). The compiler
+internally uses the names @code{ce_enabled} and @code{nonce_enabled},
+so they should not be used elsewhere as alternative names.
+
+@var{list-of-values} is either a string that specifies a comma-separated
+list of values that can be assigned to the attribute, or a null string to
+indicate that the attribute takes numeric values.
+
+@var{default} is an attribute expression that gives the value of this
+attribute for insns that match patterns whose definition does not include
+an explicit value for this attribute. @xref{Attr Example}, for more
+information on the handling of defaults. @xref{Constant Attributes},
+for information on attributes that do not depend on any particular insn.
+
+@findex insn-attr.h
+For each defined attribute, a number of definitions are written to the
+@file{insn-attr.h} file. For cases where an explicit set of values is
+specified for an attribute, the following are defined:
+
+@itemize @bullet
+@item
+A @samp{#define} is written for the symbol @samp{HAVE_ATTR_@var{name}}.
+
+@item
+An enumerated class is defined for @samp{attr_@var{name}} with
+elements of the form @samp{@var{upper-name}_@var{upper-value}} where
+the attribute name and value are first converted to uppercase.
+
+@item
+A function @samp{get_attr_@var{name}} is defined that is passed an insn and
+returns the attribute value for that insn.
+@end itemize
+
+For example, if the following is present in the @file{md} file:
+
+@smallexample
+(define_attr "type" "branch,fp,load,store,arith" @dots{})
+@end smallexample
+
+@noindent
+the following lines will be written to the file @file{insn-attr.h}.
+
+@smallexample
+#define HAVE_ATTR_type 1
+enum attr_type @{TYPE_BRANCH, TYPE_FP, TYPE_LOAD,
+ TYPE_STORE, TYPE_ARITH@};
+extern enum attr_type get_attr_type ();
+@end smallexample
+
+If the attribute takes numeric values, no @code{enum} type will be
+defined and the function to obtain the attribute's value will return
+@code{int}.
+
+There are attributes which are tied to a specific meaning. These
+attributes are not free to use for other purposes:
+
+@table @code
+@item length
+The @code{length} attribute is used to calculate the length of emitted
+code chunks. This is especially important when verifying branch
+distances. @xref{Insn Lengths}.
+
+@item enabled
+The @code{enabled} attribute can be defined to prevent certain
+alternatives of an insn definition from being used during code
+generation. @xref{Disable Insn Alternatives}.
+
+@item mnemonic
+The @code{mnemonic} attribute can be defined to implement instruction
+specific checks in e.g.@: the pipeline description.
+@xref{Mnemonic Attribute}.
+@end table
+
+For each of these special attributes, the corresponding
+@samp{HAVE_ATTR_@var{name}} @samp{#define} is also written when the
+attribute is not defined; in that case, it is defined as @samp{0}.
+
+@findex define_enum_attr
+@anchor{define_enum_attr}
+Another way of defining an attribute is to use:
+
+@smallexample
+(define_enum_attr "@var{attr}" "@var{enum}" @var{default})
+@end smallexample
+
+This works in just the same way as @code{define_attr}, except that
+the list of values is taken from a separate enumeration called
+@var{enum} (@pxref{define_enum}). This form allows you to use
+the same list of values for several attributes without having to
+repeat the list each time. For example:
+
+@smallexample
+(define_enum "processor" [
+ model_a
+ model_b
+ @dots{}
+])
+(define_enum_attr "arch" "processor"
+ (const (symbol_ref "target_arch")))
+(define_enum_attr "tune" "processor"
+ (const (symbol_ref "target_tune")))
+@end smallexample
+
+defines the same attributes as:
+
+@smallexample
+(define_attr "arch" "model_a,model_b,@dots{}"
+ (const (symbol_ref "target_arch")))
+(define_attr "tune" "model_a,model_b,@dots{}"
+ (const (symbol_ref "target_tune")))
+@end smallexample
+
+but without duplicating the processor list. The second example defines two
+separate C enums (@code{attr_arch} and @code{attr_tune}) whereas the first
+defines a single C enum (@code{processor}).
+@end ifset
+@ifset INTERNALS
+@node Expressions
+@subsection Attribute Expressions
+@cindex attribute expressions
+
+RTL expressions used to define attributes use the codes described above
+plus a few specific to attribute definitions, to be discussed below.
+Attribute value expressions must have one of the following forms:
+
+@table @code
+@cindex @code{const_int} and attributes
+@item (const_int @var{i})
+The integer @var{i} specifies the value of a numeric attribute. @var{i}
+must be non-negative.
+
+The value of a numeric attribute can be specified either with a
+@code{const_int}, or as an integer represented as a string in
+@code{const_string}, @code{eq_attr} (see below), @code{attr},
+@code{symbol_ref}, simple arithmetic expressions, and @code{set_attr}
+overrides on specific instructions (@pxref{Tagging Insns}).
+
+@cindex @code{const_string} and attributes
+@item (const_string @var{value})
+The string @var{value} specifies a constant attribute value.
+If @var{value} is specified as @samp{"*"}, it means that the default value of
+the attribute is to be used for the insn containing this expression.
+@samp{"*"} obviously cannot be used in the @var{default} expression
+of a @code{define_attr}.
+
+If the attribute whose value is being specified is numeric, @var{value}
+must be a string containing a non-negative integer (normally
+@code{const_int} would be used in this case). Otherwise, it must
+contain one of the valid values for the attribute.
+
+@cindex @code{if_then_else} and attributes
+@item (if_then_else @var{test} @var{true-value} @var{false-value})
+@var{test} specifies an attribute test, whose format is defined below.
+The value of this expression is @var{true-value} if @var{test} is true,
+otherwise it is @var{false-value}.
+
+@cindex @code{cond} and attributes
+@item (cond [@var{test1} @var{value1} @dots{}] @var{default})
+The first operand of this expression is a vector containing an even
+number of expressions and consisting of pairs of @var{test} and @var{value}
+expressions. The value of the @code{cond} expression is that of the
+@var{value} corresponding to the first true @var{test} expression. If
+none of the @var{test} expressions are true, the value of the @code{cond}
+expression is that of the @var{default} expression.
+@end table
+
+@var{test} expressions can have one of the following forms:
+
+@table @code
+@cindex @code{const_int} and attribute tests
+@item (const_int @var{i})
+This test is true if @var{i} is nonzero and false otherwise.
+
+@cindex @code{not} and attributes
+@cindex @code{ior} and attributes
+@cindex @code{and} and attributes
+@item (not @var{test})
+@itemx (ior @var{test1} @var{test2})
+@itemx (and @var{test1} @var{test2})
+These tests are true if the indicated logical function is true.
+
+@cindex @code{match_operand} and attributes
+@item (match_operand:@var{m} @var{n} @var{pred} @var{constraints})
+This test is true if operand @var{n} of the insn whose attribute value
+is being determined has mode @var{m} (this part of the test is ignored
+if @var{m} is @code{VOIDmode}) and the function specified by the string
+@var{pred} returns a nonzero value when passed operand @var{n} and mode
+@var{m} (this part of the test is ignored if @var{pred} is the null
+string).
+
+The @var{constraints} operand is ignored and should be the null string.
+
+@cindex @code{match_test} and attributes
+@item (match_test @var{c-expr})
+The test is true if C expression @var{c-expr} is true. In non-constant
+attributes, @var{c-expr} has access to the following variables:
+
+@table @var
+@item insn
+The rtl instruction under test.
+@item which_alternative
+The @code{define_insn} alternative that @var{insn} matches.
+@xref{Output Statement}.
+@item operands
+An array of @var{insn}'s rtl operands.
+@end table
+
+@var{c-expr} behaves like the condition in a C @code{if} statement,
+so there is no need to explicitly convert the expression into a boolean
+0 or 1 value. For example, the following two tests are equivalent:
+
+@smallexample
+(match_test "x & 2")
+(match_test "(x & 2) != 0")
+@end smallexample
+
+@cindex @code{le} and attributes
+@cindex @code{leu} and attributes
+@cindex @code{lt} and attributes
+@cindex @code{gt} and attributes
+@cindex @code{gtu} and attributes
+@cindex @code{ge} and attributes
+@cindex @code{geu} and attributes
+@cindex @code{ne} and attributes
+@cindex @code{eq} and attributes
+@cindex @code{plus} and attributes
+@cindex @code{minus} and attributes
+@cindex @code{mult} and attributes
+@cindex @code{div} and attributes
+@cindex @code{mod} and attributes
+@cindex @code{abs} and attributes
+@cindex @code{neg} and attributes
+@cindex @code{ashift} and attributes
+@cindex @code{lshiftrt} and attributes
+@cindex @code{ashiftrt} and attributes
+@item (le @var{arith1} @var{arith2})
+@itemx (leu @var{arith1} @var{arith2})
+@itemx (lt @var{arith1} @var{arith2})
+@itemx (ltu @var{arith1} @var{arith2})
+@itemx (gt @var{arith1} @var{arith2})
+@itemx (gtu @var{arith1} @var{arith2})
+@itemx (ge @var{arith1} @var{arith2})
+@itemx (geu @var{arith1} @var{arith2})
+@itemx (ne @var{arith1} @var{arith2})
+@itemx (eq @var{arith1} @var{arith2})
+These tests are true if the indicated comparison of the two arithmetic
+expressions is true. Arithmetic expressions are formed with
+@code{plus}, @code{minus}, @code{mult}, @code{div}, @code{mod},
+@code{abs}, @code{neg}, @code{and}, @code{ior}, @code{xor}, @code{not},
+@code{ashift}, @code{lshiftrt}, and @code{ashiftrt} expressions.
+
+@findex get_attr
+@code{const_int} and @code{symbol_ref} are always valid terms (@pxref{Insn
+Lengths},for additional forms). @code{symbol_ref} is a string
+denoting a C expression that yields an @code{int} when evaluated by the
+@samp{get_attr_@dots{}} routine. It should normally be a global
+variable.
+
+@findex eq_attr
+@item (eq_attr @var{name} @var{value})
+@var{name} is a string specifying the name of an attribute.
+
+@var{value} is a string that is either a valid value for attribute
+@var{name}, a comma-separated list of values, or @samp{!} followed by a
+value or list. If @var{value} does not begin with a @samp{!}, this
+test is true if the value of the @var{name} attribute of the current
+insn is in the list specified by @var{value}. If @var{value} begins
+with a @samp{!}, this test is true if the attribute's value is
+@emph{not} in the specified list.
+
+For example,
+
+@smallexample
+(eq_attr "type" "load,store")
+@end smallexample
+
+@noindent
+is equivalent to
+
+@smallexample
+(ior (eq_attr "type" "load") (eq_attr "type" "store"))
+@end smallexample
+
+If @var{name} specifies an attribute of @samp{alternative}, it refers to the
+value of the compiler variable @code{which_alternative}
+(@pxref{Output Statement}) and the values must be small integers. For
+example,
+
+@smallexample
+(eq_attr "alternative" "2,3")
+@end smallexample
+
+@noindent
+is equivalent to
+
+@smallexample
+(ior (eq (symbol_ref "which_alternative") (const_int 2))
+ (eq (symbol_ref "which_alternative") (const_int 3)))
+@end smallexample
+
+Note that, for most attributes, an @code{eq_attr} test is simplified in cases
+where the value of the attribute being tested is known for all insns matching
+a particular pattern. This is by far the most common case.
+
+@findex attr_flag
+@item (attr_flag @var{name})
+The value of an @code{attr_flag} expression is true if the flag
+specified by @var{name} is true for the @code{insn} currently being
+scheduled.
+
+@var{name} is a string specifying one of a fixed set of flags to test.
+Test the flags @code{forward} and @code{backward} to determine the
+direction of a conditional branch.
+
+This example describes a conditional branch delay slot which
+can be nullified for forward branches that are taken (annul-true) or
+for backward branches which are not taken (annul-false).
+
+@smallexample
+(define_delay (eq_attr "type" "cbranch")
+ [(eq_attr "in_branch_delay" "true")
+ (and (eq_attr "in_branch_delay" "true")
+ (attr_flag "forward"))
+ (and (eq_attr "in_branch_delay" "true")
+ (attr_flag "backward"))])
+@end smallexample
+
+The @code{forward} and @code{backward} flags are false if the current
+@code{insn} being scheduled is not a conditional branch.
+
+@code{attr_flag} is only used during delay slot scheduling and has no
+meaning to other passes of the compiler.
+
+@findex attr
+@item (attr @var{name})
+The value of another attribute is returned. This is most useful
+for numeric attributes, as @code{eq_attr} and @code{attr_flag}
+produce more efficient code for non-numeric attributes.
+@end table
+
+@end ifset
+@ifset INTERNALS
+@node Tagging Insns
+@subsection Assigning Attribute Values to Insns
+@cindex tagging insns
+@cindex assigning attribute values to insns
+
+The value assigned to an attribute of an insn is primarily determined by
+which pattern is matched by that insn (or which @code{define_peephole}
+generated it). Every @code{define_insn} and @code{define_peephole} can
+have an optional last argument to specify the values of attributes for
+matching insns. The value of any attribute not specified in a particular
+insn is set to the default value for that attribute, as specified in its
+@code{define_attr}. Extensive use of default values for attributes
+permits the specification of the values for only one or two attributes
+in the definition of most insn patterns, as seen in the example in the
+next section.
+
+The optional last argument of @code{define_insn} and
+@code{define_peephole} is a vector of expressions, each of which defines
+the value for a single attribute. The most general way of assigning an
+attribute's value is to use a @code{set} expression whose first operand is an
+@code{attr} expression giving the name of the attribute being set. The
+second operand of the @code{set} is an attribute expression
+(@pxref{Expressions}) giving the value of the attribute.
+
+When the attribute value depends on the @samp{alternative} attribute
+(i.e., which is the applicable alternative in the constraint of the
+insn), the @code{set_attr_alternative} expression can be used. It
+allows the specification of a vector of attribute expressions, one for
+each alternative.
+
+@findex set_attr
+When the generality of arbitrary attribute expressions is not required,
+the simpler @code{set_attr} expression can be used, which allows
+specifying a string giving either a single attribute value or a list
+of attribute values, one for each alternative.
+
+The form of each of the above specifications is shown below. In each case,
+@var{name} is a string specifying the attribute to be set.
+
+@table @code
+@item (set_attr @var{name} @var{value-string})
+@var{value-string} is either a string giving the desired attribute value,
+or a string containing a comma-separated list giving the values for
+succeeding alternatives. The number of elements must match the number
+of alternatives in the constraint of the insn pattern.
+
+Note that it may be useful to specify @samp{*} for some alternative, in
+which case the attribute will assume its default value for insns matching
+that alternative.
+
+@findex set_attr_alternative
+@item (set_attr_alternative @var{name} [@var{value1} @var{value2} @dots{}])
+Depending on the alternative of the insn, the value will be one of the
+specified values. This is a shorthand for using a @code{cond} with
+tests on the @samp{alternative} attribute.
+
+@findex attr
+@item (set (attr @var{name}) @var{value})
+The first operand of this @code{set} must be the special RTL expression
+@code{attr}, whose sole operand is a string giving the name of the
+attribute being set. @var{value} is the value of the attribute.
+@end table
+
+The following shows three different ways of representing the same
+attribute value specification:
+
+@smallexample
+(set_attr "type" "load,store,arith")
+
+(set_attr_alternative "type"
+ [(const_string "load") (const_string "store")
+ (const_string "arith")])
+
+(set (attr "type")
+ (cond [(eq_attr "alternative" "1") (const_string "load")
+ (eq_attr "alternative" "2") (const_string "store")]
+ (const_string "arith")))
+@end smallexample
+
+@need 1000
+@findex define_asm_attributes
+The @code{define_asm_attributes} expression provides a mechanism to
+specify the attributes assigned to insns produced from an @code{asm}
+statement. It has the form:
+
+@smallexample
+(define_asm_attributes [@var{attr-sets}])
+@end smallexample
+
+@noindent
+where @var{attr-sets} is specified the same as for both the
+@code{define_insn} and the @code{define_peephole} expressions.
+
+These values will typically be the ``worst case'' attribute values. For
+example, they might indicate that the condition code will be clobbered.
+
+A specification for a @code{length} attribute is handled specially. The
+way to compute the length of an @code{asm} insn is to multiply the
+length specified in the expression @code{define_asm_attributes} by the
+number of machine instructions specified in the @code{asm} statement,
+determined by counting the number of semicolons and newlines in the
+string. Therefore, the value of the @code{length} attribute specified
+in a @code{define_asm_attributes} should be the maximum possible length
+of a single machine instruction.
+
+@end ifset
+@ifset INTERNALS
+@node Attr Example
+@subsection Example of Attribute Specifications
+@cindex attribute specifications example
+@cindex attribute specifications
+
+The judicious use of defaulting is important in the efficient use of
+insn attributes. Typically, insns are divided into @dfn{types} and an
+attribute, customarily called @code{type}, is used to represent this
+value. This attribute is normally used only to define the default value
+for other attributes. An example will clarify this usage.
+
+Assume we have a RISC machine with a condition code and in which only
+full-word operations are performed in registers. Let us assume that we
+can divide all insns into loads, stores, (integer) arithmetic
+operations, floating point operations, and branches.
+
+Here we will concern ourselves with determining the effect of an insn on
+the condition code and will limit ourselves to the following possible
+effects: The condition code can be set unpredictably (clobbered), not
+be changed, be set to agree with the results of the operation, or only
+changed if the item previously set into the condition code has been
+modified.
+
+Here is part of a sample @file{md} file for such a machine:
+
+@smallexample
+(define_attr "type" "load,store,arith,fp,branch" (const_string "arith"))
+
+(define_attr "cc" "clobber,unchanged,set,change0"
+ (cond [(eq_attr "type" "load")
+ (const_string "change0")
+ (eq_attr "type" "store,branch")
+ (const_string "unchanged")
+ (eq_attr "type" "arith")
+ (if_then_else (match_operand:SI 0 "" "")
+ (const_string "set")
+ (const_string "clobber"))]
+ (const_string "clobber")))
+
+(define_insn ""
+ [(set (match_operand:SI 0 "general_operand" "=r,r,m")
+ (match_operand:SI 1 "general_operand" "r,m,r"))]
+ ""
+ "@@
+ move %0,%1
+ load %0,%1
+ store %0,%1"
+ [(set_attr "type" "arith,load,store")])
+@end smallexample
+
+Note that we assume in the above example that arithmetic operations
+performed on quantities smaller than a machine word clobber the condition
+code since they will set the condition code to a value corresponding to the
+full-word result.
+
+@end ifset
+@ifset INTERNALS
+@node Insn Lengths
+@subsection Computing the Length of an Insn
+@cindex insn lengths, computing
+@cindex computing the length of an insn
+
+For many machines, multiple types of branch instructions are provided, each
+for different length branch displacements. In most cases, the assembler
+will choose the correct instruction to use. However, when the assembler
+cannot do so, GCC can when a special attribute, the @code{length}
+attribute, is defined. This attribute must be defined to have numeric
+values by specifying a null string in its @code{define_attr}.
+
+In the case of the @code{length} attribute, two additional forms of
+arithmetic terms are allowed in test expressions:
+
+@table @code
+@cindex @code{match_dup} and attributes
+@item (match_dup @var{n})
+This refers to the address of operand @var{n} of the current insn, which
+must be a @code{label_ref}.
+
+@cindex @code{pc} and attributes
+@item (pc)
+For non-branch instructions and backward branch instructions, this refers
+to the address of the current insn. But for forward branch instructions,
+this refers to the address of the next insn, because the length of the
+current insn is to be computed.
+@end table
+
+@cindex @code{addr_vec}, length of
+@cindex @code{addr_diff_vec}, length of
+For normal insns, the length will be determined by value of the
+@code{length} attribute. In the case of @code{addr_vec} and
+@code{addr_diff_vec} insn patterns, the length is computed as
+the number of vectors multiplied by the size of each vector.
+
+Lengths are measured in addressable storage units (bytes).
+
+Note that it is possible to call functions via the @code{symbol_ref}
+mechanism to compute the length of an insn. However, if you use this
+mechanism you must provide dummy clauses to express the maximum length
+without using the function call. You can see an example of this in the
+@code{pa} machine description for the @code{call_symref} pattern.
+
+The following macros can be used to refine the length computation:
+
+@table @code
+@findex ADJUST_INSN_LENGTH
+@item ADJUST_INSN_LENGTH (@var{insn}, @var{length})
+If defined, modifies the length assigned to instruction @var{insn} as a
+function of the context in which it is used. @var{length} is an lvalue
+that contains the initially computed length of the insn and should be
+updated with the correct length of the insn.
+
+This macro will normally not be required. A case in which it is
+required is the ROMP@. On this machine, the size of an @code{addr_vec}
+insn must be increased by two to compensate for the fact that alignment
+may be required.
+@end table
+
+@findex get_attr_length
+The routine that returns @code{get_attr_length} (the value of the
+@code{length} attribute) can be used by the output routine to
+determine the form of the branch instruction to be written, as the
+example below illustrates.
+
+As an example of the specification of variable-length branches, consider
+the IBM 360. If we adopt the convention that a register will be set to
+the starting address of a function, we can jump to labels within 4k of
+the start using a four-byte instruction. Otherwise, we need a six-byte
+sequence to load the address from memory and then branch to it.
+
+On such a machine, a pattern for a branch instruction might be specified
+as follows:
+
+@smallexample
+(define_insn "jump"
+ [(set (pc)
+ (label_ref (match_operand 0 "" "")))]
+ ""
+@{
+ return (get_attr_length (insn) == 4
+ ? "b %l0" : "l r15,=a(%l0); br r15");
+@}
+ [(set (attr "length")
+ (if_then_else (lt (match_dup 0) (const_int 4096))
+ (const_int 4)
+ (const_int 6)))])
+@end smallexample
+
+@end ifset
+@ifset INTERNALS
+@node Constant Attributes
+@subsection Constant Attributes
+@cindex constant attributes
+
+A special form of @code{define_attr}, where the expression for the
+default value is a @code{const} expression, indicates an attribute that
+is constant for a given run of the compiler. Constant attributes may be
+used to specify which variety of processor is used. For example,
+
+@smallexample
+(define_attr "cpu" "m88100,m88110,m88000"
+ (const
+ (cond [(symbol_ref "TARGET_88100") (const_string "m88100")
+ (symbol_ref "TARGET_88110") (const_string "m88110")]
+ (const_string "m88000"))))
+
+(define_attr "memory" "fast,slow"
+ (const
+ (if_then_else (symbol_ref "TARGET_FAST_MEM")
+ (const_string "fast")
+ (const_string "slow"))))
+@end smallexample
+
+The routine generated for constant attributes has no parameters as it
+does not depend on any particular insn. RTL expressions used to define
+the value of a constant attribute may use the @code{symbol_ref} form,
+but may not use either the @code{match_operand} form or @code{eq_attr}
+forms involving insn attributes.
+
+@end ifset
+@ifset INTERNALS
+@node Mnemonic Attribute
+@subsection Mnemonic Attribute
+@cindex mnemonic attribute
+
+The @code{mnemonic} attribute is a string type attribute holding the
+instruction mnemonic for an insn alternative. The attribute values
+will automatically be generated by the machine description parser if
+there is an attribute definition in the md file:
+
+@smallexample
+(define_attr "mnemonic" "unknown" (const_string "unknown"))
+@end smallexample
+
+The default value can be freely chosen as long as it does not collide
+with any of the instruction mnemonics. This value will be used
+whenever the machine description parser is not able to determine the
+mnemonic string. This might be the case for output templates
+containing more than a single instruction as in
+@code{"mvcle\t%0,%1,0\;jo\t.-4"}.
+
+The @code{mnemonic} attribute set is not generated automatically if the
+instruction string is generated via C code.
+
+An existing @code{mnemonic} attribute set in an insn definition will not
+be overriden by the md file parser. That way it is possible to
+manually set the instruction mnemonics for the cases where the md file
+parser fails to determine it automatically.
+
+The @code{mnemonic} attribute is useful for dealing with instruction
+specific properties in the pipeline description without defining
+additional insn attributes.
+
+@smallexample
+(define_attr "ooo_expanded" ""
+ (cond [(eq_attr "mnemonic" "dlr,dsgr,d,dsgf,stam,dsgfr,dlgr")
+ (const_int 1)]
+ (const_int 0)))
+@end smallexample
+
+@end ifset
+@ifset INTERNALS
+@node Delay Slots
+@subsection Delay Slot Scheduling
+@cindex delay slots, defining
+
+The insn attribute mechanism can be used to specify the requirements for
+delay slots, if any, on a target machine. An instruction is said to
+require a @dfn{delay slot} if some instructions that are physically
+after the instruction are executed as if they were located before it.
+Classic examples are branch and call instructions, which often execute
+the following instruction before the branch or call is performed.
+
+On some machines, conditional branch instructions can optionally
+@dfn{annul} instructions in the delay slot. This means that the
+instruction will not be executed for certain branch outcomes. Both
+instructions that annul if the branch is true and instructions that
+annul if the branch is false are supported.
+
+Delay slot scheduling differs from instruction scheduling in that
+determining whether an instruction needs a delay slot is dependent only
+on the type of instruction being generated, not on data flow between the
+instructions. See the next section for a discussion of data-dependent
+instruction scheduling.
+
+@findex define_delay
+The requirement of an insn needing one or more delay slots is indicated
+via the @code{define_delay} expression. It has the following form:
+
+@smallexample
+(define_delay @var{test}
+ [@var{delay-1} @var{annul-true-1} @var{annul-false-1}
+ @var{delay-2} @var{annul-true-2} @var{annul-false-2}
+ @dots{}])
+@end smallexample
+
+@var{test} is an attribute test that indicates whether this
+@code{define_delay} applies to a particular insn. If so, the number of
+required delay slots is determined by the length of the vector specified
+as the second argument. An insn placed in delay slot @var{n} must
+satisfy attribute test @var{delay-n}. @var{annul-true-n} is an
+attribute test that specifies which insns may be annulled if the branch
+is true. Similarly, @var{annul-false-n} specifies which insns in the
+delay slot may be annulled if the branch is false. If annulling is not
+supported for that delay slot, @code{(nil)} should be coded.
+
+For example, in the common case where branch and call insns require
+a single delay slot, which may contain any insn other than a branch or
+call, the following would be placed in the @file{md} file:
+
+@smallexample
+(define_delay (eq_attr "type" "branch,call")
+ [(eq_attr "type" "!branch,call") (nil) (nil)])
+@end smallexample
+
+Multiple @code{define_delay} expressions may be specified. In this
+case, each such expression specifies different delay slot requirements
+and there must be no insn for which tests in two @code{define_delay}
+expressions are both true.
+
+For example, if we have a machine that requires one delay slot for branches
+but two for calls, no delay slot can contain a branch or call insn,
+and any valid insn in the delay slot for the branch can be annulled if the
+branch is true, we might represent this as follows:
+
+@smallexample
+(define_delay (eq_attr "type" "branch")
+ [(eq_attr "type" "!branch,call")
+ (eq_attr "type" "!branch,call")
+ (nil)])
+
+(define_delay (eq_attr "type" "call")
+ [(eq_attr "type" "!branch,call") (nil) (nil)
+ (eq_attr "type" "!branch,call") (nil) (nil)])
+@end smallexample
+@c the above is *still* too long. --mew 4feb93
+
+@end ifset
+@ifset INTERNALS
+@node Processor pipeline description
+@subsection Specifying processor pipeline description
+@cindex processor pipeline description
+@cindex processor functional units
+@cindex instruction latency time
+@cindex interlock delays
+@cindex data dependence delays
+@cindex reservation delays
+@cindex pipeline hazard recognizer
+@cindex automaton based pipeline description
+@cindex regular expressions
+@cindex deterministic finite state automaton
+@cindex automaton based scheduler
+@cindex RISC
+@cindex VLIW
+
+To achieve better performance, most modern processors
+(super-pipelined, superscalar @acronym{RISC}, and @acronym{VLIW}
+processors) have many @dfn{functional units} on which several
+instructions can be executed simultaneously. An instruction starts
+execution if its issue conditions are satisfied. If not, the
+instruction is stalled until its conditions are satisfied. Such
+@dfn{interlock (pipeline) delay} causes interruption of the fetching
+of successor instructions (or demands nop instructions, e.g.@: for some
+MIPS processors).
+
+There are two major kinds of interlock delays in modern processors.
+The first one is a data dependence delay determining @dfn{instruction
+latency time}. The instruction execution is not started until all
+source data have been evaluated by prior instructions (there are more
+complex cases when the instruction execution starts even when the data
+are not available but will be ready in given time after the
+instruction execution start). Taking the data dependence delays into
+account is simple. The data dependence (true, output, and
+anti-dependence) delay between two instructions is given by a
+constant. In most cases this approach is adequate. The second kind
+of interlock delays is a reservation delay. The reservation delay
+means that two instructions under execution will be in need of shared
+processors resources, i.e.@: buses, internal registers, and/or
+functional units, which are reserved for some time. Taking this kind
+of delay into account is complex especially for modern @acronym{RISC}
+processors.
+
+The task of exploiting more processor parallelism is solved by an
+instruction scheduler. For a better solution to this problem, the
+instruction scheduler has to have an adequate description of the
+processor parallelism (or @dfn{pipeline description}). GCC
+machine descriptions describe processor parallelism and functional
+unit reservations for groups of instructions with the aid of
+@dfn{regular expressions}.
+
+The GCC instruction scheduler uses a @dfn{pipeline hazard recognizer} to
+figure out the possibility of the instruction issue by the processor
+on a given simulated processor cycle. The pipeline hazard recognizer is
+automatically generated from the processor pipeline description. The
+pipeline hazard recognizer generated from the machine description
+is based on a deterministic finite state automaton (@acronym{DFA}):
+the instruction issue is possible if there is a transition from one
+automaton state to another one. This algorithm is very fast, and
+furthermore, its speed is not dependent on processor
+complexity@footnote{However, the size of the automaton depends on
+processor complexity. To limit this effect, machine descriptions
+can split orthogonal parts of the machine description among several
+automata: but then, since each of these must be stepped independently,
+this does cause a small decrease in the algorithm's performance.}.
+
+@cindex automaton based pipeline description
+The rest of this section describes the directives that constitute
+an automaton-based processor pipeline description. The order of
+these constructions within the machine description file is not
+important.
+
+@findex define_automaton
+@cindex pipeline hazard recognizer
+The following optional construction describes names of automata
+generated and used for the pipeline hazards recognition. Sometimes
+the generated finite state automaton used by the pipeline hazard
+recognizer is large. If we use more than one automaton and bind functional
+units to the automata, the total size of the automata is usually
+less than the size of the single automaton. If there is no one such
+construction, only one finite state automaton is generated.
+
+@smallexample
+(define_automaton @var{automata-names})
+@end smallexample
+
+@var{automata-names} is a string giving names of the automata. The
+names are separated by commas. All the automata should have unique names.
+The automaton name is used in the constructions @code{define_cpu_unit} and
+@code{define_query_cpu_unit}.
+
+@findex define_cpu_unit
+@cindex processor functional units
+Each processor functional unit used in the description of instruction
+reservations should be described by the following construction.
+
+@smallexample
+(define_cpu_unit @var{unit-names} [@var{automaton-name}])
+@end smallexample
+
+@var{unit-names} is a string giving the names of the functional units
+separated by commas. Don't use name @samp{nothing}, it is reserved
+for other goals.
+
+@var{automaton-name} is a string giving the name of the automaton with
+which the unit is bound. The automaton should be described in
+construction @code{define_automaton}. You should give
+@dfn{automaton-name}, if there is a defined automaton.
+
+The assignment of units to automata are constrained by the uses of the
+units in insn reservations. The most important constraint is: if a
+unit reservation is present on a particular cycle of an alternative
+for an insn reservation, then some unit from the same automaton must
+be present on the same cycle for the other alternatives of the insn
+reservation. The rest of the constraints are mentioned in the
+description of the subsequent constructions.
+
+@findex define_query_cpu_unit
+@cindex querying function unit reservations
+The following construction describes CPU functional units analogously
+to @code{define_cpu_unit}. The reservation of such units can be
+queried for an automaton state. The instruction scheduler never
+queries reservation of functional units for given automaton state. So
+as a rule, you don't need this construction. This construction could
+be used for future code generation goals (e.g.@: to generate
+@acronym{VLIW} insn templates).
+
+@smallexample
+(define_query_cpu_unit @var{unit-names} [@var{automaton-name}])
+@end smallexample
+
+@var{unit-names} is a string giving names of the functional units
+separated by commas.
+
+@var{automaton-name} is a string giving the name of the automaton with
+which the unit is bound.
+
+@findex define_insn_reservation
+@cindex instruction latency time
+@cindex regular expressions
+@cindex data bypass
+The following construction is the major one to describe pipeline
+characteristics of an instruction.
+
+@smallexample
+(define_insn_reservation @var{insn-name} @var{default_latency}
+ @var{condition} @var{regexp})
+@end smallexample
+
+@var{default_latency} is a number giving latency time of the
+instruction. There is an important difference between the old
+description and the automaton based pipeline description. The latency
+time is used for all dependencies when we use the old description. In
+the automaton based pipeline description, the given latency time is only
+used for true dependencies. The cost of anti-dependencies is always
+zero and the cost of output dependencies is the difference between
+latency times of the producing and consuming insns (if the difference
+is negative, the cost is considered to be zero). You can always
+change the default costs for any description by using the target hook
+@code{TARGET_SCHED_ADJUST_COST} (@pxref{Scheduling}).
+
+@var{insn-name} is a string giving the internal name of the insn. The
+internal names are used in constructions @code{define_bypass} and in
+the automaton description file generated for debugging. The internal
+name has nothing in common with the names in @code{define_insn}. It is a
+good practice to use insn classes described in the processor manual.
+
+@var{condition} defines what RTL insns are described by this
+construction. You should remember that you will be in trouble if
+@var{condition} for two or more different
+@code{define_insn_reservation} constructions is TRUE for an insn. In
+this case what reservation will be used for the insn is not defined.
+Such cases are not checked during generation of the pipeline hazards
+recognizer because in general recognizing that two conditions may have
+the same value is quite difficult (especially if the conditions
+contain @code{symbol_ref}). It is also not checked during the
+pipeline hazard recognizer work because it would slow down the
+recognizer considerably.
+
+@var{regexp} is a string describing the reservation of the cpu's functional
+units by the instruction. The reservations are described by a regular
+expression according to the following syntax:
+
+@smallexample
+ regexp = regexp "," oneof
+ | oneof
+
+ oneof = oneof "|" allof
+ | allof
+
+ allof = allof "+" repeat
+ | repeat
+
+ repeat = element "*" number
+ | element
+
+ element = cpu_function_unit_name
+ | reservation_name
+ | result_name
+ | "nothing"
+ | "(" regexp ")"
+@end smallexample
+
+@itemize @bullet
+@item
+@samp{,} is used for describing the start of the next cycle in
+the reservation.
+
+@item
+@samp{|} is used for describing a reservation described by the first
+regular expression @strong{or} a reservation described by the second
+regular expression @strong{or} etc.
+
+@item
+@samp{+} is used for describing a reservation described by the first
+regular expression @strong{and} a reservation described by the
+second regular expression @strong{and} etc.
+
+@item
+@samp{*} is used for convenience and simply means a sequence in which
+the regular expression are repeated @var{number} times with cycle
+advancing (see @samp{,}).
+
+@item
+@samp{cpu_function_unit_name} denotes reservation of the named
+functional unit.
+
+@item
+@samp{reservation_name} --- see description of construction
+@samp{define_reservation}.
+
+@item
+@samp{nothing} denotes no unit reservations.
+@end itemize
+
+@findex define_reservation
+Sometimes unit reservations for different insns contain common parts.
+In such case, you can simplify the pipeline description by describing
+the common part by the following construction
+
+@smallexample
+(define_reservation @var{reservation-name} @var{regexp})
+@end smallexample
+
+@var{reservation-name} is a string giving name of @var{regexp}.
+Functional unit names and reservation names are in the same name
+space. So the reservation names should be different from the
+functional unit names and cannot be the reserved name @samp{nothing}.
+
+@findex define_bypass
+@cindex instruction latency time
+@cindex data bypass
+The following construction is used to describe exceptions in the
+latency time for given instruction pair. This is so called bypasses.
+
+@smallexample
+(define_bypass @var{number} @var{out_insn_names} @var{in_insn_names}
+ [@var{guard}])
+@end smallexample
+
+@var{number} defines when the result generated by the instructions
+given in string @var{out_insn_names} will be ready for the
+instructions given in string @var{in_insn_names}. Each of these
+strings is a comma-separated list of filename-style globs and
+they refer to the names of @code{define_insn_reservation}s.
+For example:
+@smallexample
+(define_bypass 1 "cpu1_load_*, cpu1_store_*" "cpu1_load_*")
+@end smallexample
+defines a bypass between instructions that start with
+@samp{cpu1_load_} or @samp{cpu1_store_} and those that start with
+@samp{cpu1_load_}.
+
+@var{guard} is an optional string giving the name of a C function which
+defines an additional guard for the bypass. The function will get the
+two insns as parameters. If the function returns zero the bypass will
+be ignored for this case. The additional guard is necessary to
+recognize complicated bypasses, e.g.@: when the consumer is only an address
+of insn @samp{store} (not a stored value).
+
+If there are more one bypass with the same output and input insns, the
+chosen bypass is the first bypass with a guard in description whose
+guard function returns nonzero. If there is no such bypass, then
+bypass without the guard function is chosen.
+
+@findex exclusion_set
+@findex presence_set
+@findex final_presence_set
+@findex absence_set
+@findex final_absence_set
+@cindex VLIW
+@cindex RISC
+The following five constructions are usually used to describe
+@acronym{VLIW} processors, or more precisely, to describe a placement
+of small instructions into @acronym{VLIW} instruction slots. They
+can be used for @acronym{RISC} processors, too.
+
+@smallexample
+(exclusion_set @var{unit-names} @var{unit-names})
+(presence_set @var{unit-names} @var{patterns})
+(final_presence_set @var{unit-names} @var{patterns})
+(absence_set @var{unit-names} @var{patterns})
+(final_absence_set @var{unit-names} @var{patterns})
+@end smallexample
+
+@var{unit-names} is a string giving names of functional units
+separated by commas.
+
+@var{patterns} is a string giving patterns of functional units
+separated by comma. Currently pattern is one unit or units
+separated by white-spaces.
+
+The first construction (@samp{exclusion_set}) means that each
+functional unit in the first string cannot be reserved simultaneously
+with a unit whose name is in the second string and vice versa. For
+example, the construction is useful for describing processors
+(e.g.@: some SPARC processors) with a fully pipelined floating point
+functional unit which can execute simultaneously only single floating
+point insns or only double floating point insns.
+
+The second construction (@samp{presence_set}) means that each
+functional unit in the first string cannot be reserved unless at
+least one of pattern of units whose names are in the second string is
+reserved. This is an asymmetric relation. For example, it is useful
+for description that @acronym{VLIW} @samp{slot1} is reserved after
+@samp{slot0} reservation. We could describe it by the following
+construction
+
+@smallexample
+(presence_set "slot1" "slot0")
+@end smallexample
+
+Or @samp{slot1} is reserved only after @samp{slot0} and unit @samp{b0}
+reservation. In this case we could write
+
+@smallexample
+(presence_set "slot1" "slot0 b0")
+@end smallexample
+
+The third construction (@samp{final_presence_set}) is analogous to
+@samp{presence_set}. The difference between them is when checking is
+done. When an instruction is issued in given automaton state
+reflecting all current and planned unit reservations, the automaton
+state is changed. The first state is a source state, the second one
+is a result state. Checking for @samp{presence_set} is done on the
+source state reservation, checking for @samp{final_presence_set} is
+done on the result reservation. This construction is useful to
+describe a reservation which is actually two subsequent reservations.
+For example, if we use
+
+@smallexample
+(presence_set "slot1" "slot0")
+@end smallexample
+
+the following insn will be never issued (because @samp{slot1} requires
+@samp{slot0} which is absent in the source state).
+
+@smallexample
+(define_reservation "insn_and_nop" "slot0 + slot1")
+@end smallexample
+
+but it can be issued if we use analogous @samp{final_presence_set}.
+
+The forth construction (@samp{absence_set}) means that each functional
+unit in the first string can be reserved only if each pattern of units
+whose names are in the second string is not reserved. This is an
+asymmetric relation (actually @samp{exclusion_set} is analogous to
+this one but it is symmetric). For example it might be useful in a
+@acronym{VLIW} description to say that @samp{slot0} cannot be reserved
+after either @samp{slot1} or @samp{slot2} have been reserved. This
+can be described as:
+
+@smallexample
+(absence_set "slot0" "slot1, slot2")
+@end smallexample
+
+Or @samp{slot2} cannot be reserved if @samp{slot0} and unit @samp{b0}
+are reserved or @samp{slot1} and unit @samp{b1} are reserved. In
+this case we could write
+
+@smallexample
+(absence_set "slot2" "slot0 b0, slot1 b1")
+@end smallexample
+
+All functional units mentioned in a set should belong to the same
+automaton.
+
+The last construction (@samp{final_absence_set}) is analogous to
+@samp{absence_set} but checking is done on the result (state)
+reservation. See comments for @samp{final_presence_set}.
+
+@findex automata_option
+@cindex deterministic finite state automaton
+@cindex nondeterministic finite state automaton
+@cindex finite state automaton minimization
+You can control the generator of the pipeline hazard recognizer with
+the following construction.
+
+@smallexample
+(automata_option @var{options})
+@end smallexample
+
+@var{options} is a string giving options which affect the generated
+code. Currently there are the following options:
+
+@itemize @bullet
+@item
+@dfn{no-minimization} makes no minimization of the automaton. This is
+only worth to do when we are debugging the description and need to
+look more accurately at reservations of states.
+
+@item
+@dfn{time} means printing time statistics about the generation of
+automata.
+
+@item
+@dfn{stats} means printing statistics about the generated automata
+such as the number of DFA states, NDFA states and arcs.
+
+@item
+@dfn{v} means a generation of the file describing the result automata.
+The file has suffix @samp{.dfa} and can be used for the description
+verification and debugging.
+
+@item
+@dfn{w} means a generation of warning instead of error for
+non-critical errors.
+
+@item
+@dfn{no-comb-vect} prevents the automaton generator from generating
+two data structures and comparing them for space efficiency. Using
+a comb vector to represent transitions may be better, but it can be
+very expensive to construct. This option is useful if the build
+process spends an unacceptably long time in genautomata.
+
+@item
+@dfn{ndfa} makes nondeterministic finite state automata. This affects
+the treatment of operator @samp{|} in the regular expressions. The
+usual treatment of the operator is to try the first alternative and,
+if the reservation is not possible, the second alternative. The
+nondeterministic treatment means trying all alternatives, some of them
+may be rejected by reservations in the subsequent insns.
+
+@item
+@dfn{collapse-ndfa} modifies the behavior of the generator when
+producing an automaton. An additional state transition to collapse a
+nondeterministic @acronym{NDFA} state to a deterministic @acronym{DFA}
+state is generated. It can be triggered by passing @code{const0_rtx} to
+state_transition. In such an automaton, cycle advance transitions are
+available only for these collapsed states. This option is useful for
+ports that want to use the @code{ndfa} option, but also want to use
+@code{define_query_cpu_unit} to assign units to insns issued in a cycle.
+
+@item
+@dfn{progress} means output of a progress bar showing how many states
+were generated so far for automaton being processed. This is useful
+during debugging a @acronym{DFA} description. If you see too many
+generated states, you could interrupt the generator of the pipeline
+hazard recognizer and try to figure out a reason for generation of the
+huge automaton.
+@end itemize
+
+As an example, consider a superscalar @acronym{RISC} machine which can
+issue three insns (two integer insns and one floating point insn) on
+the cycle but can finish only two insns. To describe this, we define
+the following functional units.
+
+@smallexample
+(define_cpu_unit "i0_pipeline, i1_pipeline, f_pipeline")
+(define_cpu_unit "port0, port1")
+@end smallexample
+
+All simple integer insns can be executed in any integer pipeline and
+their result is ready in two cycles. The simple integer insns are
+issued into the first pipeline unless it is reserved, otherwise they
+are issued into the second pipeline. Integer division and
+multiplication insns can be executed only in the second integer
+pipeline and their results are ready correspondingly in 9 and 4
+cycles. The integer division is not pipelined, i.e.@: the subsequent
+integer division insn cannot be issued until the current division
+insn finished. Floating point insns are fully pipelined and their
+results are ready in 3 cycles. Where the result of a floating point
+insn is used by an integer insn, an additional delay of one cycle is
+incurred. To describe all of this we could specify
+
+@smallexample
+(define_cpu_unit "div")
+
+(define_insn_reservation "simple" 2 (eq_attr "type" "int")
+ "(i0_pipeline | i1_pipeline), (port0 | port1)")
+
+(define_insn_reservation "mult" 4 (eq_attr "type" "mult")
+ "i1_pipeline, nothing*2, (port0 | port1)")
+
+(define_insn_reservation "div" 9 (eq_attr "type" "div")
+ "i1_pipeline, div*7, div + (port0 | port1)")
+
+(define_insn_reservation "float" 3 (eq_attr "type" "float")
+ "f_pipeline, nothing, (port0 | port1))
+
+(define_bypass 4 "float" "simple,mult,div")
+@end smallexample
+
+To simplify the description we could describe the following reservation
+
+@smallexample
+(define_reservation "finish" "port0|port1")
+@end smallexample
+
+and use it in all @code{define_insn_reservation} as in the following
+construction
+
+@smallexample
+(define_insn_reservation "simple" 2 (eq_attr "type" "int")
+ "(i0_pipeline | i1_pipeline), finish")
+@end smallexample
+
+
+@end ifset
+@ifset INTERNALS
+@node Conditional Execution
+@section Conditional Execution
+@cindex conditional execution
+@cindex predication
+
+A number of architectures provide for some form of conditional
+execution, or predication. The hallmark of this feature is the
+ability to nullify most of the instructions in the instruction set.
+When the instruction set is large and not entirely symmetric, it
+can be quite tedious to describe these forms directly in the
+@file{.md} file. An alternative is the @code{define_cond_exec} template.
+
+@findex define_cond_exec
+@smallexample
+(define_cond_exec
+ [@var{predicate-pattern}]
+ "@var{condition}"
+ "@var{output-template}"
+ "@var{optional-insn-attribues}")
+@end smallexample
+
+@var{predicate-pattern} is the condition that must be true for the
+insn to be executed at runtime and should match a relational operator.
+One can use @code{match_operator} to match several relational operators
+at once. Any @code{match_operand} operands must have no more than one
+alternative.
+
+@var{condition} is a C expression that must be true for the generated
+pattern to match.
+
+@findex current_insn_predicate
+@var{output-template} is a string similar to the @code{define_insn}
+output template (@pxref{Output Template}), except that the @samp{*}
+and @samp{@@} special cases do not apply. This is only useful if the
+assembly text for the predicate is a simple prefix to the main insn.
+In order to handle the general case, there is a global variable
+@code{current_insn_predicate} that will contain the entire predicate
+if the current insn is predicated, and will otherwise be @code{NULL}.
+
+@var{optional-insn-attributes} is an optional vector of attributes that gets
+appended to the insn attributes of the produced cond_exec rtx. It can
+be used to add some distinguishing attribute to cond_exec rtxs produced
+that way. An example usage would be to use this attribute in conjunction
+with attributes on the main pattern to disable particular alternatives under
+certain conditions.
+
+When @code{define_cond_exec} is used, an implicit reference to
+the @code{predicable} instruction attribute is made.
+@xref{Insn Attributes}. This attribute must be a boolean (i.e.@: have
+exactly two elements in its @var{list-of-values}), with the possible
+values being @code{no} and @code{yes}. The default and all uses in
+the insns must be a simple constant, not a complex expressions. It
+may, however, depend on the alternative, by using a comma-separated
+list of values. If that is the case, the port should also define an
+@code{enabled} attribute (@pxref{Disable Insn Alternatives}), which
+should also allow only @code{no} and @code{yes} as its values.
+
+For each @code{define_insn} for which the @code{predicable}
+attribute is true, a new @code{define_insn} pattern will be
+generated that matches a predicated version of the instruction.
+For example,
+
+@smallexample
+(define_insn "addsi"
+ [(set (match_operand:SI 0 "register_operand" "r")
+ (plus:SI (match_operand:SI 1 "register_operand" "r")
+ (match_operand:SI 2 "register_operand" "r")))]
+ "@var{test1}"
+ "add %2,%1,%0")
+
+(define_cond_exec
+ [(ne (match_operand:CC 0 "register_operand" "c")
+ (const_int 0))]
+ "@var{test2}"
+ "(%0)")
+@end smallexample
+
+@noindent
+generates a new pattern
+
+@smallexample
+(define_insn ""
+ [(cond_exec
+ (ne (match_operand:CC 3 "register_operand" "c") (const_int 0))
+ (set (match_operand:SI 0 "register_operand" "r")
+ (plus:SI (match_operand:SI 1 "register_operand" "r")
+ (match_operand:SI 2 "register_operand" "r"))))]
+ "(@var{test2}) && (@var{test1})"
+ "(%3) add %2,%1,%0")
+@end smallexample
+
+@end ifset
+@ifset INTERNALS
+@node Define Subst
+@section RTL Templates Transformations
+@cindex define_subst
+
+For some hardware architectures there are common cases when the RTL
+templates for the instructions can be derived from the other RTL
+templates using simple transformations. E.g., @file{i386.md} contains
+an RTL template for the ordinary @code{sub} instruction---
+@code{*subsi_1}, and for the @code{sub} instruction with subsequent
+zero-extension---@code{*subsi_1_zext}. Such cases can be easily
+implemented by a single meta-template capable of generating a modified
+case based on the initial one:
+
+@findex define_subst
+@smallexample
+(define_subst "@var{name}"
+ [@var{input-template}]
+ "@var{condition}"
+ [@var{output-template}])
+@end smallexample
+@var{input-template} is a pattern describing the source RTL template,
+which will be transformed.
+
+@var{condition} is a C expression that is conjunct with the condition
+from the input-template to generate a condition to be used in the
+output-template.
+
+@var{output-template} is a pattern that will be used in the resulting
+template.
+
+@code{define_subst} mechanism is tightly coupled with the notion of the
+subst attribute (@pxref{Subst Iterators}). The use of
+@code{define_subst} is triggered by a reference to a subst attribute in
+the transforming RTL template. This reference initiates duplication of
+the source RTL template and substitution of the attributes with their
+values. The source RTL template is left unchanged, while the copy is
+transformed by @code{define_subst}. This transformation can fail in the
+case when the source RTL template is not matched against the
+input-template of the @code{define_subst}. In such case the copy is
+deleted.
+
+@code{define_subst} can be used only in @code{define_insn} and
+@code{define_expand}, it cannot be used in other expressions (e.g.@: in
+@code{define_insn_and_split}).
+
+@menu
+* Define Subst Example:: Example of @code{define_subst} work.
+* Define Subst Pattern Matching:: Process of template comparison.
+* Define Subst Output Template:: Generation of output template.
+@end menu
+
+@node Define Subst Example
+@subsection @code{define_subst} Example
+@cindex define_subst
+
+To illustrate how @code{define_subst} works, let us examine a simple
+template transformation.
+
+Suppose there are two kinds of instructions: one that touches flags and
+the other that does not. The instructions of the second type could be
+generated with the following @code{define_subst}:
+
+@smallexample
+(define_subst "add_clobber_subst"
+ [(set (match_operand:SI 0 "" "")
+ (match_operand:SI 1 "" ""))]
+ ""
+ [(set (match_dup 0)
+ (match_dup 1))
+ (clobber (reg:CC FLAGS_REG))])
+@end smallexample
+
+This @code{define_subst} can be applied to any RTL pattern containing
+@code{set} of mode SI and generates a copy with clobber when it is
+applied.
+
+Assume there is an RTL template for a @code{max} instruction to be used
+in @code{define_subst} mentioned above:
+
+@smallexample
+(define_insn "maxsi"
+ [(set (match_operand:SI 0 "register_operand" "=r")
+ (max:SI
+ (match_operand:SI 1 "register_operand" "r")
+ (match_operand:SI 2 "register_operand" "r")))]
+ ""
+ "max\t@{%2, %1, %0|%0, %1, %2@}"
+ [@dots{}])
+@end smallexample
+
+To mark the RTL template for @code{define_subst} application,
+subst-attributes are used. They should be declared in advance:
+
+@smallexample
+(define_subst_attr "add_clobber_name" "add_clobber_subst" "_noclobber" "_clobber")
+@end smallexample
+
+Here @samp{add_clobber_name} is the attribute name,
+@samp{add_clobber_subst} is the name of the corresponding
+@code{define_subst}, the third argument (@samp{_noclobber}) is the
+attribute value that would be substituted into the unchanged version of
+the source RTL template, and the last argument (@samp{_clobber}) is the
+value that would be substituted into the second, transformed,
+version of the RTL template.
+
+Once the subst-attribute has been defined, it should be used in RTL
+templates which need to be processed by the @code{define_subst}. So,
+the original RTL template should be changed:
+
+@smallexample
+(define_insn "maxsi<add_clobber_name>"
+ [(set (match_operand:SI 0 "register_operand" "=r")
+ (max:SI
+ (match_operand:SI 1 "register_operand" "r")
+ (match_operand:SI 2 "register_operand" "r")))]
+ ""
+ "max\t@{%2, %1, %0|%0, %1, %2@}"
+ [@dots{}])
+@end smallexample
+
+The result of the @code{define_subst} usage would look like the following:
+
+@smallexample
+(define_insn "maxsi_noclobber"
+ [(set (match_operand:SI 0 "register_operand" "=r")
+ (max:SI
+ (match_operand:SI 1 "register_operand" "r")
+ (match_operand:SI 2 "register_operand" "r")))]
+ ""
+ "max\t@{%2, %1, %0|%0, %1, %2@}"
+ [@dots{}])
+(define_insn "maxsi_clobber"
+ [(set (match_operand:SI 0 "register_operand" "=r")
+ (max:SI
+ (match_operand:SI 1 "register_operand" "r")
+ (match_operand:SI 2 "register_operand" "r")))
+ (clobber (reg:CC FLAGS_REG))]
+ ""
+ "max\t@{%2, %1, %0|%0, %1, %2@}"
+ [@dots{}])
+@end smallexample
+
+@node Define Subst Pattern Matching
+@subsection Pattern Matching in @code{define_subst}
+@cindex define_subst
+
+All expressions, allowed in @code{define_insn} or @code{define_expand},
+are allowed in the input-template of @code{define_subst}, except
+@code{match_par_dup}, @code{match_scratch}, @code{match_parallel}. The
+meanings of expressions in the input-template were changed:
+
+@code{match_operand} matches any expression (possibly, a subtree in
+RTL-template), if modes of the @code{match_operand} and this expression
+are the same, or mode of the @code{match_operand} is @code{VOIDmode}, or
+this expression is @code{match_dup}, @code{match_op_dup}. If the
+expression is @code{match_operand} too, and predicate of
+@code{match_operand} from the input pattern is not empty, then the
+predicates are compared. That can be used for more accurate filtering
+of accepted RTL-templates.
+
+@code{match_operator} matches common operators (like @code{plus},
+@code{minus}), @code{unspec}, @code{unspec_volatile} operators and
+@code{match_operator}s from the original pattern if the modes match and
+@code{match_operator} from the input pattern has the same number of
+operands as the operator from the original pattern.
+
+@node Define Subst Output Template
+@subsection Generation of output template in @code{define_subst}
+@cindex define_subst
+
+If all necessary checks for @code{define_subst} application pass, a new
+RTL-pattern, based on the output-template, is created to replace the old
+template. Like in input-patterns, meanings of some RTL expressions are
+changed when they are used in output-patterns of a @code{define_subst}.
+Thus, @code{match_dup} is used for copying the whole expression from the
+original pattern, which matched corresponding @code{match_operand} from
+the input pattern.
+
+@code{match_dup N} is used in the output template to be replaced with
+the expression from the original pattern, which matched
+@code{match_operand N} from the input pattern. As a consequence,
+@code{match_dup} cannot be used to point to @code{match_operand}s from
+the output pattern, it should always refer to a @code{match_operand}
+from the input pattern. If a @code{match_dup N} occurs more than once
+in the output template, its first occurrence is replaced with the
+expression from the original pattern, and the subsequent expressions
+are replaced with @code{match_dup N}, i.e., a reference to the first
+expression.
+
+In the output template one can refer to the expressions from the
+original pattern and create new ones. For instance, some operands could
+be added by means of standard @code{match_operand}.
+
+After replacing @code{match_dup} with some RTL-subtree from the original
+pattern, it could happen that several @code{match_operand}s in the
+output pattern have the same indexes. It is unknown, how many and what
+indexes would be used in the expression which would replace
+@code{match_dup}, so such conflicts in indexes are inevitable. To
+overcome this issue, @code{match_operands} and @code{match_operators},
+which were introduced into the output pattern, are renumerated when all
+@code{match_dup}s are replaced.
+
+Number of alternatives in @code{match_operand}s introduced into the
+output template @code{M} could differ from the number of alternatives in
+the original pattern @code{N}, so in the resultant pattern there would
+be @code{N*M} alternatives. Thus, constraints from the original pattern
+would be duplicated @code{N} times, constraints from the output pattern
+would be duplicated @code{M} times, producing all possible combinations.
+@end ifset
+
+@ifset INTERNALS
+@node Constant Definitions
+@section Constant Definitions
+@cindex constant definitions
+@findex define_constants
+
+Using literal constants inside instruction patterns reduces legibility and
+can be a maintenance problem.
+
+To overcome this problem, you may use the @code{define_constants}
+expression. It contains a vector of name-value pairs. From that
+point on, wherever any of the names appears in the MD file, it is as
+if the corresponding value had been written instead. You may use
+@code{define_constants} multiple times; each appearance adds more
+constants to the table. It is an error to redefine a constant with
+a different value.
+
+To come back to the a29k load multiple example, instead of
+
+@smallexample
+(define_insn ""
+ [(match_parallel 0 "load_multiple_operation"
+ [(set (match_operand:SI 1 "gpc_reg_operand" "=r")
+ (match_operand:SI 2 "memory_operand" "m"))
+ (use (reg:SI 179))
+ (clobber (reg:SI 179))])]
+ ""
+ "loadm 0,0,%1,%2")
+@end smallexample
+
+You could write:
+
+@smallexample
+(define_constants [
+ (R_BP 177)
+ (R_FC 178)
+ (R_CR 179)
+ (R_Q 180)
+])
+
+(define_insn ""
+ [(match_parallel 0 "load_multiple_operation"
+ [(set (match_operand:SI 1 "gpc_reg_operand" "=r")
+ (match_operand:SI 2 "memory_operand" "m"))
+ (use (reg:SI R_CR))
+ (clobber (reg:SI R_CR))])]
+ ""
+ "loadm 0,0,%1,%2")
+@end smallexample
+
+The constants that are defined with a define_constant are also output
+in the insn-codes.h header file as #defines.
+
+@cindex enumerations
+@findex define_c_enum
+You can also use the machine description file to define enumerations.
+Like the constants defined by @code{define_constant}, these enumerations
+are visible to both the machine description file and the main C code.
+
+The syntax is as follows:
+
+@smallexample
+(define_c_enum "@var{name}" [
+ @var{value0}
+ @var{value1}
+ (@var{value32} 32)
+ @var{value33}
+ @dots{}
+ @var{valuen}
+])
+@end smallexample
+
+This definition causes the equivalent of the following C code to appear
+in @file{insn-constants.h}:
+
+@smallexample
+enum @var{name} @{
+ @var{value0} = 0,
+ @var{value1} = 1,
+ @var{value32} = 32,
+ @var{value33} = 33,
+ @dots{}
+ @var{valuen} = @var{n}
+@};
+#define NUM_@var{cname}_VALUES (@var{n} + 1)
+@end smallexample
+
+where @var{cname} is the capitalized form of @var{name}.
+It also makes each @var{valuei} available in the machine description
+file, just as if it had been declared with:
+
+@smallexample
+(define_constants [(@var{valuei} @var{i})])
+@end smallexample
+
+Each @var{valuei} is usually an upper-case identifier and usually
+begins with @var{cname}.
+
+You can split the enumeration definition into as many statements as
+you like. The above example is directly equivalent to:
+
+@smallexample
+(define_c_enum "@var{name}" [@var{value0}])
+(define_c_enum "@var{name}" [@var{value1}])
+@dots{}
+(define_c_enum "@var{name}" [@var{valuen}])
+@end smallexample
+
+Splitting the enumeration helps to improve the modularity of each
+individual @code{.md} file. For example, if a port defines its
+synchronization instructions in a separate @file{sync.md} file,
+it is convenient to define all synchronization-specific enumeration
+values in @file{sync.md} rather than in the main @file{.md} file.
+
+Some enumeration names have special significance to GCC:
+
+@table @code
+@item unspecv
+@findex unspec_volatile
+If an enumeration called @code{unspecv} is defined, GCC will use it
+when printing out @code{unspec_volatile} expressions. For example:
+
+@smallexample
+(define_c_enum "unspecv" [
+ UNSPECV_BLOCKAGE
+])
+@end smallexample
+
+causes GCC to print @samp{(unspec_volatile @dots{} 0)} as:
+
+@smallexample
+(unspec_volatile ... UNSPECV_BLOCKAGE)
+@end smallexample
+
+@item unspec
+@findex unspec
+If an enumeration called @code{unspec} is defined, GCC will use
+it when printing out @code{unspec} expressions. GCC will also use
+it when printing out @code{unspec_volatile} expressions unless an
+@code{unspecv} enumeration is also defined. You can therefore
+decide whether to keep separate enumerations for volatile and
+non-volatile expressions or whether to use the same enumeration
+for both.
+@end table
+
+@findex define_enum
+@anchor{define_enum}
+Another way of defining an enumeration is to use @code{define_enum}:
+
+@smallexample
+(define_enum "@var{name}" [
+ @var{value0}
+ @var{value1}
+ @dots{}
+ @var{valuen}
+])
+@end smallexample
+
+This directive implies:
+
+@smallexample
+(define_c_enum "@var{name}" [
+ @var{cname}_@var{cvalue0}
+ @var{cname}_@var{cvalue1}
+ @dots{}
+ @var{cname}_@var{cvaluen}
+])
+@end smallexample
+
+@findex define_enum_attr
+where @var{cvaluei} is the capitalized form of @var{valuei}.
+However, unlike @code{define_c_enum}, the enumerations defined
+by @code{define_enum} can be used in attribute specifications
+(@pxref{define_enum_attr}).
+@end ifset
+@ifset INTERNALS
+@node Iterators
+@section Iterators
+@cindex iterators in @file{.md} files
+
+Ports often need to define similar patterns for more than one machine
+mode or for more than one rtx code. GCC provides some simple iterator
+facilities to make this process easier.
+
+@menu
+* Mode Iterators:: Generating variations of patterns for different modes.
+* Code Iterators:: Doing the same for codes.
+* Int Iterators:: Doing the same for integers.
+* Subst Iterators:: Generating variations of patterns for define_subst.
+* Parameterized Names:: Specifying iterator values in C++ code.
+@end menu
+
+@node Mode Iterators
+@subsection Mode Iterators
+@cindex mode iterators in @file{.md} files
+
+Ports often need to define similar patterns for two or more different modes.
+For example:
+
+@itemize @bullet
+@item
+If a processor has hardware support for both single and double
+floating-point arithmetic, the @code{SFmode} patterns tend to be
+very similar to the @code{DFmode} ones.
+
+@item
+If a port uses @code{SImode} pointers in one configuration and
+@code{DImode} pointers in another, it will usually have very similar
+@code{SImode} and @code{DImode} patterns for manipulating pointers.
+@end itemize
+
+Mode iterators allow several patterns to be instantiated from one
+@file{.md} file template. They can be used with any type of
+rtx-based construct, such as a @code{define_insn},
+@code{define_split}, or @code{define_peephole2}.
+
+@menu
+* Defining Mode Iterators:: Defining a new mode iterator.
+* Substitutions:: Combining mode iterators with substitutions
+* Examples:: Examples
+@end menu
+
+@node Defining Mode Iterators
+@subsubsection Defining Mode Iterators
+@findex define_mode_iterator
+
+The syntax for defining a mode iterator is:
+
+@smallexample
+(define_mode_iterator @var{name} [(@var{mode1} "@var{cond1}") @dots{} (@var{moden} "@var{condn}")])
+@end smallexample
+
+This allows subsequent @file{.md} file constructs to use the mode suffix
+@code{:@var{name}}. Every construct that does so will be expanded
+@var{n} times, once with every use of @code{:@var{name}} replaced by
+@code{:@var{mode1}}, once with every use replaced by @code{:@var{mode2}},
+and so on. In the expansion for a particular @var{modei}, every
+C condition will also require that @var{condi} be true.
+
+For example:
+
+@smallexample
+(define_mode_iterator P [(SI "Pmode == SImode") (DI "Pmode == DImode")])
+@end smallexample
+
+defines a new mode suffix @code{:P}. Every construct that uses
+@code{:P} will be expanded twice, once with every @code{:P} replaced
+by @code{:SI} and once with every @code{:P} replaced by @code{:DI}.
+The @code{:SI} version will only apply if @code{Pmode == SImode} and
+the @code{:DI} version will only apply if @code{Pmode == DImode}.
+
+As with other @file{.md} conditions, an empty string is treated
+as ``always true''. @code{(@var{mode} "")} can also be abbreviated
+to @code{@var{mode}}. For example:
+
+@smallexample
+(define_mode_iterator GPR [SI (DI "TARGET_64BIT")])
+@end smallexample
+
+means that the @code{:DI} expansion only applies if @code{TARGET_64BIT}
+but that the @code{:SI} expansion has no such constraint.
+
+Iterators are applied in the order they are defined. This can be
+significant if two iterators are used in a construct that requires
+substitutions. @xref{Substitutions}.
+
+@node Substitutions
+@subsubsection Substitution in Mode Iterators
+@findex define_mode_attr
+
+If an @file{.md} file construct uses mode iterators, each version of the
+construct will often need slightly different strings or modes. For
+example:
+
+@itemize @bullet
+@item
+When a @code{define_expand} defines several @code{add@var{m}3} patterns
+(@pxref{Standard Names}), each expander will need to use the
+appropriate mode name for @var{m}.
+
+@item
+When a @code{define_insn} defines several instruction patterns,
+each instruction will often use a different assembler mnemonic.
+
+@item
+When a @code{define_insn} requires operands with different modes,
+using an iterator for one of the operand modes usually requires a specific
+mode for the other operand(s).
+@end itemize
+
+GCC supports such variations through a system of ``mode attributes''.
+There are two standard attributes: @code{mode}, which is the name of
+the mode in lower case, and @code{MODE}, which is the same thing in
+upper case. You can define other attributes using:
+
+@smallexample
+(define_mode_attr @var{name} [(@var{mode1} "@var{value1}") @dots{} (@var{moden} "@var{valuen}")])
+@end smallexample
+
+where @var{name} is the name of the attribute and @var{valuei}
+is the value associated with @var{modei}.
+
+When GCC replaces some @var{:iterator} with @var{:mode}, it will scan
+each string and mode in the pattern for sequences of the form
+@code{<@var{iterator}:@var{attr}>}, where @var{attr} is the name of a
+mode attribute. If the attribute is defined for @var{mode}, the whole
+@code{<@dots{}>} sequence will be replaced by the appropriate attribute
+value.
+
+For example, suppose an @file{.md} file has:
+
+@smallexample
+(define_mode_iterator P [(SI "Pmode == SImode") (DI "Pmode == DImode")])
+(define_mode_attr load [(SI "lw") (DI "ld")])
+@end smallexample
+
+If one of the patterns that uses @code{:P} contains the string
+@code{"<P:load>\t%0,%1"}, the @code{SI} version of that pattern
+will use @code{"lw\t%0,%1"} and the @code{DI} version will use
+@code{"ld\t%0,%1"}.
+
+Here is an example of using an attribute for a mode:
+
+@smallexample
+(define_mode_iterator LONG [SI DI])
+(define_mode_attr SHORT [(SI "HI") (DI "SI")])
+(define_insn @dots{}
+ (sign_extend:LONG (match_operand:<LONG:SHORT> @dots{})) @dots{})
+@end smallexample
+
+The @code{@var{iterator}:} prefix may be omitted, in which case the
+substitution will be attempted for every iterator expansion.
+
+@node Examples
+@subsubsection Mode Iterator Examples
+
+Here is an example from the MIPS port. It defines the following
+modes and attributes (among others):
+
+@smallexample
+(define_mode_iterator GPR [SI (DI "TARGET_64BIT")])
+(define_mode_attr d [(SI "") (DI "d")])
+@end smallexample
+
+and uses the following template to define both @code{subsi3}
+and @code{subdi3}:
+
+@smallexample
+(define_insn "sub<mode>3"
+ [(set (match_operand:GPR 0 "register_operand" "=d")
+ (minus:GPR (match_operand:GPR 1 "register_operand" "d")
+ (match_operand:GPR 2 "register_operand" "d")))]
+ ""
+ "<d>subu\t%0,%1,%2"
+ [(set_attr "type" "arith")
+ (set_attr "mode" "<MODE>")])
+@end smallexample
+
+This is exactly equivalent to:
+
+@smallexample
+(define_insn "subsi3"
+ [(set (match_operand:SI 0 "register_operand" "=d")
+ (minus:SI (match_operand:SI 1 "register_operand" "d")
+ (match_operand:SI 2 "register_operand" "d")))]
+ ""
+ "subu\t%0,%1,%2"
+ [(set_attr "type" "arith")
+ (set_attr "mode" "SI")])
+
+(define_insn "subdi3"
+ [(set (match_operand:DI 0 "register_operand" "=d")
+ (minus:DI (match_operand:DI 1 "register_operand" "d")
+ (match_operand:DI 2 "register_operand" "d")))]
+ "TARGET_64BIT"
+ "dsubu\t%0,%1,%2"
+ [(set_attr "type" "arith")
+ (set_attr "mode" "DI")])
+@end smallexample
+
+@node Code Iterators
+@subsection Code Iterators
+@cindex code iterators in @file{.md} files
+@findex define_code_iterator
+@findex define_code_attr
+
+Code iterators operate in a similar way to mode iterators. @xref{Mode Iterators}.
+
+The construct:
+
+@smallexample
+(define_code_iterator @var{name} [(@var{code1} "@var{cond1}") @dots{} (@var{coden} "@var{condn}")])
+@end smallexample
+
+defines a pseudo rtx code @var{name} that can be instantiated as
+@var{codei} if condition @var{condi} is true. Each @var{codei}
+must have the same rtx format. @xref{RTL Classes}.
+
+As with mode iterators, each pattern that uses @var{name} will be
+expanded @var{n} times, once with all uses of @var{name} replaced by
+@var{code1}, once with all uses replaced by @var{code2}, and so on.
+@xref{Defining Mode Iterators}.
+
+It is possible to define attributes for codes as well as for modes.
+There are two standard code attributes: @code{code}, the name of the
+code in lower case, and @code{CODE}, the name of the code in upper case.
+Other attributes are defined using:
+
+@smallexample
+(define_code_attr @var{name} [(@var{code1} "@var{value1}") @dots{} (@var{coden} "@var{valuen}")])
+@end smallexample
+
+Instruction patterns can use code attributes as rtx codes, which can be
+useful if two sets of codes act in tandem. For example, the following
+@code{define_insn} defines two patterns, one calculating a signed absolute
+difference and another calculating an unsigned absolute difference:
+
+@smallexample
+(define_code_iterator any_max [smax umax])
+(define_code_attr paired_min [(smax "smin") (umax "umin")])
+(define_insn @dots{}
+ [(set (match_operand:SI 0 @dots{})
+ (minus:SI (any_max:SI (match_operand:SI 1 @dots{})
+ (match_operand:SI 2 @dots{}))
+ (<paired_min>:SI (match_dup 1) (match_dup 2))))]
+ @dots{})
+@end smallexample
+
+The signed version of the instruction uses @code{smax} and @code{smin}
+while the unsigned version uses @code{umax} and @code{umin}. There
+are no versions that pair @code{smax} with @code{umin} or @code{umax}
+with @code{smin}.
+
+Here's an example of code iterators in action, taken from the MIPS port:
+
+@smallexample
+(define_code_iterator any_cond [unordered ordered unlt unge uneq ltgt unle ungt
+ eq ne gt ge lt le gtu geu ltu leu])
+
+(define_expand "b<code>"
+ [(set (pc)
+ (if_then_else (any_cond:CC (cc0)
+ (const_int 0))
+ (label_ref (match_operand 0 ""))
+ (pc)))]
+ ""
+@{
+ gen_conditional_branch (operands, <CODE>);
+ DONE;
+@})
+@end smallexample
+
+This is equivalent to:
+
+@smallexample
+(define_expand "bunordered"
+ [(set (pc)
+ (if_then_else (unordered:CC (cc0)
+ (const_int 0))
+ (label_ref (match_operand 0 ""))
+ (pc)))]
+ ""
+@{
+ gen_conditional_branch (operands, UNORDERED);
+ DONE;
+@})
+
+(define_expand "bordered"
+ [(set (pc)
+ (if_then_else (ordered:CC (cc0)
+ (const_int 0))
+ (label_ref (match_operand 0 ""))
+ (pc)))]
+ ""
+@{
+ gen_conditional_branch (operands, ORDERED);
+ DONE;
+@})
+
+@dots{}
+@end smallexample
+
+@node Int Iterators
+@subsection Int Iterators
+@cindex int iterators in @file{.md} files
+@findex define_int_iterator
+@findex define_int_attr
+
+Int iterators operate in a similar way to code iterators. @xref{Code Iterators}.
+
+The construct:
+
+@smallexample
+(define_int_iterator @var{name} [(@var{int1} "@var{cond1}") @dots{} (@var{intn} "@var{condn}")])
+@end smallexample
+
+defines a pseudo integer constant @var{name} that can be instantiated as
+@var{inti} if condition @var{condi} is true. Each @var{int} must have the
+same rtx format. @xref{RTL Classes}. Int iterators can appear in only
+those rtx fields that have 'i', 'n', 'w', or 'p' as the specifier. This
+means that each @var{int} has to be a constant defined using define_constant
+or define_c_enum.
+
+As with mode and code iterators, each pattern that uses @var{name} will be
+expanded @var{n} times, once with all uses of @var{name} replaced by
+@var{int1}, once with all uses replaced by @var{int2}, and so on.
+@xref{Defining Mode Iterators}.
+
+It is possible to define attributes for ints as well as for codes and modes.
+Attributes are defined using:
+
+@smallexample
+(define_int_attr @var{name} [(@var{int1} "@var{value1}") @dots{} (@var{intn} "@var{valuen}")])
+@end smallexample
+
+Here's an example of int iterators in action, taken from the ARM port:
+
+@smallexample
+(define_int_iterator QABSNEG [UNSPEC_VQABS UNSPEC_VQNEG])
+
+(define_int_attr absneg [(UNSPEC_VQABS "abs") (UNSPEC_VQNEG "neg")])
+
+(define_insn "neon_vq<absneg><mode>"
+ [(set (match_operand:VDQIW 0 "s_register_operand" "=w")
+ (unspec:VDQIW [(match_operand:VDQIW 1 "s_register_operand" "w")
+ (match_operand:SI 2 "immediate_operand" "i")]
+ QABSNEG))]
+ "TARGET_NEON"
+ "vq<absneg>.<V_s_elem>\t%<V_reg>0, %<V_reg>1"
+ [(set_attr "type" "neon_vqneg_vqabs")]
+)
+
+@end smallexample
+
+This is equivalent to:
+
+@smallexample
+(define_insn "neon_vqabs<mode>"
+ [(set (match_operand:VDQIW 0 "s_register_operand" "=w")
+ (unspec:VDQIW [(match_operand:VDQIW 1 "s_register_operand" "w")
+ (match_operand:SI 2 "immediate_operand" "i")]
+ UNSPEC_VQABS))]
+ "TARGET_NEON"
+ "vqabs.<V_s_elem>\t%<V_reg>0, %<V_reg>1"
+ [(set_attr "type" "neon_vqneg_vqabs")]
+)
+
+(define_insn "neon_vqneg<mode>"
+ [(set (match_operand:VDQIW 0 "s_register_operand" "=w")
+ (unspec:VDQIW [(match_operand:VDQIW 1 "s_register_operand" "w")
+ (match_operand:SI 2 "immediate_operand" "i")]
+ UNSPEC_VQNEG))]
+ "TARGET_NEON"
+ "vqneg.<V_s_elem>\t%<V_reg>0, %<V_reg>1"
+ [(set_attr "type" "neon_vqneg_vqabs")]
+)
+
+@end smallexample
+
+@node Subst Iterators
+@subsection Subst Iterators
+@cindex subst iterators in @file{.md} files
+@findex define_subst
+@findex define_subst_attr
+
+Subst iterators are special type of iterators with the following
+restrictions: they could not be declared explicitly, they always have
+only two values, and they do not have explicit dedicated name.
+Subst-iterators are triggered only when corresponding subst-attribute is
+used in RTL-pattern.
+
+Subst iterators transform templates in the following way: the templates
+are duplicated, the subst-attributes in these templates are replaced
+with the corresponding values, and a new attribute is implicitly added
+to the given @code{define_insn}/@code{define_expand}. The name of the
+added attribute matches the name of @code{define_subst}. Such
+attributes are declared implicitly, and it is not allowed to have a
+@code{define_attr} named as a @code{define_subst}.
+
+Each subst iterator is linked to a @code{define_subst}. It is declared
+implicitly by the first appearance of the corresponding
+@code{define_subst_attr}, and it is not allowed to define it explicitly.
+
+Declarations of subst-attributes have the following syntax:
+
+@findex define_subst_attr
+@smallexample
+(define_subst_attr "@var{name}"
+ "@var{subst-name}"
+ "@var{no-subst-value}"
+ "@var{subst-applied-value}")
+@end smallexample
+
+@var{name} is a string with which the given subst-attribute could be
+referred to.
+
+@var{subst-name} shows which @code{define_subst} should be applied to an
+RTL-template if the given subst-attribute is present in the
+RTL-template.
+
+@var{no-subst-value} is a value with which subst-attribute would be
+replaced in the first copy of the original RTL-template.
+
+@var{subst-applied-value} is a value with which subst-attribute would be
+replaced in the second copy of the original RTL-template.
+
+@node Parameterized Names
+@subsection Parameterized Names
+@cindex @samp{@@} in instruction pattern names
+Ports sometimes need to apply iterators using C++ code, in order to
+get the code or RTL pattern for a specific instruction. For example,
+suppose we have the @samp{neon_vq<absneg><mode>} pattern given above:
+
+@smallexample
+(define_int_iterator QABSNEG [UNSPEC_VQABS UNSPEC_VQNEG])
+
+(define_int_attr absneg [(UNSPEC_VQABS "abs") (UNSPEC_VQNEG "neg")])
+
+(define_insn "neon_vq<absneg><mode>"
+ [(set (match_operand:VDQIW 0 "s_register_operand" "=w")
+ (unspec:VDQIW [(match_operand:VDQIW 1 "s_register_operand" "w")
+ (match_operand:SI 2 "immediate_operand" "i")]
+ QABSNEG))]
+ @dots{}
+)
+@end smallexample
+
+A port might need to generate this pattern for a variable
+@samp{QABSNEG} value and a variable @samp{VDQIW} mode. There are two
+ways of doing this. The first is to build the rtx for the pattern
+directly from C++ code; this is a valid technique and avoids any risk
+of combinatorial explosion. The second is to prefix the instruction
+name with the special character @samp{@@}, which tells GCC to generate
+the four additional functions below. In each case, @var{name} is the
+name of the instruction without the leading @samp{@@} character,
+without the @samp{<@dots{}>} placeholders, and with any underscore
+before a @samp{<@dots{}>} placeholder removed if keeping it would
+lead to a double or trailing underscore.
+
+@table @samp
+@item insn_code maybe_code_for_@var{name} (@var{i1}, @var{i2}, @dots{})
+See whether replacing the first @samp{<@dots{}>} placeholder with
+iterator value @var{i1}, the second with iterator value @var{i2}, and
+so on, gives a valid instruction. Return its code if so, otherwise
+return @code{CODE_FOR_nothing}.
+
+@item insn_code code_for_@var{name} (@var{i1}, @var{i2}, @dots{})
+Same, but abort the compiler if the requested instruction does not exist.
+
+@item rtx maybe_gen_@var{name} (@var{i1}, @var{i2}, @dots{}, @var{op0}, @var{op1}, @dots{})
+Check for a valid instruction in the same way as
+@code{maybe_code_for_@var{name}}. If the instruction exists,
+generate an instance of it using the operand values given by @var{op0},
+@var{op1}, and so on, otherwise return null.
+
+@item rtx gen_@var{name} (@var{i1}, @var{i2}, @dots{}, @var{op0}, @var{op1}, @dots{})
+Same, but abort the compiler if the requested instruction does not exist,
+or if the instruction generator invoked the @code{FAIL} macro.
+@end table
+
+For example, changing the pattern above to:
+
+@smallexample
+(define_insn "@@neon_vq<absneg><mode>"
+ [(set (match_operand:VDQIW 0 "s_register_operand" "=w")
+ (unspec:VDQIW [(match_operand:VDQIW 1 "s_register_operand" "w")
+ (match_operand:SI 2 "immediate_operand" "i")]
+ QABSNEG))]
+ @dots{}
+)
+@end smallexample
+
+would define the same patterns as before, but in addition would generate
+the four functions below:
+
+@smallexample
+insn_code maybe_code_for_neon_vq (int, machine_mode);
+insn_code code_for_neon_vq (int, machine_mode);
+rtx maybe_gen_neon_vq (int, machine_mode, rtx, rtx, rtx);
+rtx gen_neon_vq (int, machine_mode, rtx, rtx, rtx);
+@end smallexample
+
+Calling @samp{code_for_neon_vq (UNSPEC_VQABS, V8QImode)}
+would then give @code{CODE_FOR_neon_vqabsv8qi}.
+
+It is possible to have multiple @samp{@@} patterns with the same
+name and same types of iterator. For example:
+
+@smallexample
+(define_insn "@@some_arithmetic_op<mode>"
+ [(set (match_operand:INTEGER_MODES 0 "register_operand") @dots{})]
+ @dots{}
+)
+
+(define_insn "@@some_arithmetic_op<mode>"
+ [(set (match_operand:FLOAT_MODES 0 "register_operand") @dots{})]
+ @dots{}
+)
+@end smallexample
+
+would produce a single set of functions that handles both
+@code{INTEGER_MODES} and @code{FLOAT_MODES}.
+
+It is also possible for these @samp{@@} patterns to have different
+numbers of operands from each other. For example, patterns with
+a binary rtl code might take three operands (one output and two inputs)
+while patterns with a ternary rtl code might take four operands (one
+output and three inputs). This combination would produce separate
+@samp{maybe_gen_@var{name}} and @samp{gen_@var{name}} functions for
+each operand count, but it would still produce a single
+@samp{maybe_code_for_@var{name}} and a single @samp{code_for_@var{name}}.
+
+@end ifset
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Objective-C
+@comment node-name, next, previous, up
+
+@chapter GNU Objective-C Features
+
+This document is meant to describe some of the GNU Objective-C
+features. It is not intended to teach you Objective-C. There are
+several resources on the Internet that present the language.
+
+@menu
+* GNU Objective-C runtime API::
+* Executing code before main::
+* Type encoding::
+* Garbage Collection::
+* Constant string objects::
+* compatibility_alias::
+* Exceptions::
+* Synchronization::
+* Fast enumeration::
+* Messaging with the GNU Objective-C runtime::
+@end menu
+
+@c =========================================================================
+@node GNU Objective-C runtime API
+@section GNU Objective-C Runtime API
+
+This section is specific for the GNU Objective-C runtime. If you are
+using a different runtime, you can skip it.
+
+The GNU Objective-C runtime provides an API that allows you to
+interact with the Objective-C runtime system, querying the live
+runtime structures and even manipulating them. This allows you for
+example to inspect and navigate classes, methods and protocols; to
+define new classes or new methods, and even to modify existing classes
+or protocols.
+
+If you are using a ``Foundation'' library such as GNUstep-Base, this
+library will provide you with a rich set of functionality to do most
+of the inspection tasks, and you probably will only need direct access
+to the GNU Objective-C runtime API to define new classes or methods.
+
+@menu
+* Modern GNU Objective-C runtime API::
+* Traditional GNU Objective-C runtime API::
+@end menu
+
+@c =========================================================================
+@node Modern GNU Objective-C runtime API
+@subsection Modern GNU Objective-C Runtime API
+
+The GNU Objective-C runtime provides an API which is similar to the
+one provided by the ``Objective-C 2.0'' Apple/NeXT Objective-C
+runtime. The API is documented in the public header files of the GNU
+Objective-C runtime:
+
+@itemize @bullet
+
+@item
+@file{objc/objc.h}: this is the basic Objective-C header file,
+defining the basic Objective-C types such as @code{id}, @code{Class}
+and @code{BOOL}. You have to include this header to do almost
+anything with Objective-C.
+
+@item
+@file{objc/runtime.h}: this header declares most of the public runtime
+API functions allowing you to inspect and manipulate the Objective-C
+runtime data structures. These functions are fairly standardized
+across Objective-C runtimes and are almost identical to the Apple/NeXT
+Objective-C runtime ones. It does not declare functions in some
+specialized areas (constructing and forwarding message invocations,
+threading) which are in the other headers below. You have to include
+@file{objc/objc.h} and @file{objc/runtime.h} to use any of the
+functions, such as @code{class_getName()}, declared in
+@file{objc/runtime.h}.
+
+@item
+@file{objc/message.h}: this header declares public functions used to
+construct, deconstruct and forward message invocations. Because
+messaging is done in quite a different way on different runtimes,
+functions in this header are specific to the GNU Objective-C runtime
+implementation.
+
+@item
+@file{objc/objc-exception.h}: this header declares some public
+functions related to Objective-C exceptions. For example functions in
+this header allow you to throw an Objective-C exception from plain
+C/C++ code.
+
+@item
+@file{objc/objc-sync.h}: this header declares some public functions
+related to the Objective-C @code{@@synchronized()} syntax, allowing
+you to emulate an Objective-C @code{@@synchronized()} block in plain
+C/C++ code.
+
+@item
+@file{objc/thr.h}: this header declares a public runtime API threading
+layer that is only provided by the GNU Objective-C runtime. It
+declares functions such as @code{objc_mutex_lock()}, which provide a
+platform-independent set of threading functions.
+
+@end itemize
+
+The header files contain detailed documentation for each function in
+the GNU Objective-C runtime API.
+
+@c =========================================================================
+@node Traditional GNU Objective-C runtime API
+@subsection Traditional GNU Objective-C Runtime API
+
+The GNU Objective-C runtime used to provide a different API, which we
+call the ``traditional'' GNU Objective-C runtime API. Functions
+belonging to this API are easy to recognize because they use a
+different naming convention, such as @code{class_get_super_class()}
+(traditional API) instead of @code{class_getSuperclass()} (modern
+API). Software using this API includes the file
+@file{objc/objc-api.h} where it is declared.
+
+Starting with GCC 4.7.0, the traditional GNU runtime API is no longer
+available.
+
+@c =========================================================================
+@node Executing code before main
+@section @code{+load}: Executing Code before @code{main}
+
+This section is specific for the GNU Objective-C runtime. If you are
+using a different runtime, you can skip it.
+
+The GNU Objective-C runtime provides a way that allows you to execute
+code before the execution of the program enters the @code{main}
+function. The code is executed on a per-class and a per-category basis,
+through a special class method @code{+load}.
+
+This facility is very useful if you want to initialize global variables
+which can be accessed by the program directly, without sending a message
+to the class first. The usual way to initialize global variables, in the
+@code{+initialize} method, might not be useful because
+@code{+initialize} is only called when the first message is sent to a
+class object, which in some cases could be too late.
+
+Suppose for example you have a @code{FileStream} class that declares
+@code{Stdin}, @code{Stdout} and @code{Stderr} as global variables, like
+below:
+
+@smallexample
+
+FileStream *Stdin = nil;
+FileStream *Stdout = nil;
+FileStream *Stderr = nil;
+
+@@implementation FileStream
+
++ (void)initialize
+@{
+ Stdin = [[FileStream new] initWithFd:0];
+ Stdout = [[FileStream new] initWithFd:1];
+ Stderr = [[FileStream new] initWithFd:2];
+@}
+
+/* @r{Other methods here} */
+@@end
+
+@end smallexample
+
+In this example, the initialization of @code{Stdin}, @code{Stdout} and
+@code{Stderr} in @code{+initialize} occurs too late. The programmer can
+send a message to one of these objects before the variables are actually
+initialized, thus sending messages to the @code{nil} object. The
+@code{+initialize} method which actually initializes the global
+variables is not invoked until the first message is sent to the class
+object. The solution would require these variables to be initialized
+just before entering @code{main}.
+
+The correct solution of the above problem is to use the @code{+load}
+method instead of @code{+initialize}:
+
+@smallexample
+
+@@implementation FileStream
+
++ (void)load
+@{
+ Stdin = [[FileStream new] initWithFd:0];
+ Stdout = [[FileStream new] initWithFd:1];
+ Stderr = [[FileStream new] initWithFd:2];
+@}
+
+/* @r{Other methods here} */
+@@end
+
+@end smallexample
+
+The @code{+load} is a method that is not overridden by categories. If a
+class and a category of it both implement @code{+load}, both methods are
+invoked. This allows some additional initializations to be performed in
+a category.
+
+This mechanism is not intended to be a replacement for @code{+initialize}.
+You should be aware of its limitations when you decide to use it
+instead of @code{+initialize}.
+
+@menu
+* What you can and what you cannot do in +load::
+@end menu
+
+
+@node What you can and what you cannot do in +load
+@subsection What You Can and Cannot Do in @code{+load}
+
+@code{+load} is to be used only as a last resort. Because it is
+executed very early, most of the Objective-C runtime machinery will
+not be ready when @code{+load} is executed; hence @code{+load} works
+best for executing C code that is independent on the Objective-C
+runtime.
+
+The @code{+load} implementation in the GNU runtime guarantees you the
+following things:
+
+@itemize @bullet
+
+@item
+you can write whatever C code you like;
+
+@item
+you can allocate and send messages to objects whose class is implemented
+in the same file;
+
+@item
+the @code{+load} implementation of all super classes of a class are
+executed before the @code{+load} of that class is executed;
+
+@item
+the @code{+load} implementation of a class is executed before the
+@code{+load} implementation of any category.
+
+@end itemize
+
+In particular, the following things, even if they can work in a
+particular case, are not guaranteed:
+
+@itemize @bullet
+
+@item
+allocation of or sending messages to arbitrary objects;
+
+@item
+allocation of or sending messages to objects whose classes have a
+category implemented in the same file;
+
+@item
+sending messages to Objective-C constant strings (@code{@@"this is a
+constant string"});
+
+@end itemize
+
+You should make no assumptions about receiving @code{+load} in sibling
+classes when you write @code{+load} of a class. The order in which
+sibling classes receive @code{+load} is not guaranteed.
+
+The order in which @code{+load} and @code{+initialize} are called could
+be problematic if this matters. If you don't allocate objects inside
+@code{+load}, it is guaranteed that @code{+load} is called before
+@code{+initialize}. If you create an object inside @code{+load} the
+@code{+initialize} method of object's class is invoked even if
+@code{+load} was not invoked. Note if you explicitly call @code{+load}
+on a class, @code{+initialize} will be called first. To avoid possible
+problems try to implement only one of these methods.
+
+The @code{+load} method is also invoked when a bundle is dynamically
+loaded into your running program. This happens automatically without any
+intervening operation from you. When you write bundles and you need to
+write @code{+load} you can safely create and send messages to objects whose
+classes already exist in the running program. The same restrictions as
+above apply to classes defined in bundle.
+
+
+
+@node Type encoding
+@section Type Encoding
+
+This is an advanced section. Type encodings are used extensively by
+the compiler and by the runtime, but you generally do not need to know
+about them to use Objective-C.
+
+The Objective-C compiler generates type encodings for all the types.
+These type encodings are used at runtime to find out information about
+selectors and methods and about objects and classes.
+
+The types are encoded in the following way:
+
+@c @sp 1
+
+@multitable @columnfractions .25 .75
+@item @code{_Bool}
+@tab @code{B}
+@item @code{char}
+@tab @code{c}
+@item @code{unsigned char}
+@tab @code{C}
+@item @code{short}
+@tab @code{s}
+@item @code{unsigned short}
+@tab @code{S}
+@item @code{int}
+@tab @code{i}
+@item @code{unsigned int}
+@tab @code{I}
+@item @code{long}
+@tab @code{l}
+@item @code{unsigned long}
+@tab @code{L}
+@item @code{long long}
+@tab @code{q}
+@item @code{unsigned long long}
+@tab @code{Q}
+@item @code{float}
+@tab @code{f}
+@item @code{double}
+@tab @code{d}
+@item @code{long double}
+@tab @code{D}
+@item @code{void}
+@tab @code{v}
+@item @code{id}
+@tab @code{@@}
+@item @code{Class}
+@tab @code{#}
+@item @code{SEL}
+@tab @code{:}
+@item @code{char*}
+@tab @code{*}
+@item @code{enum}
+@tab an @code{enum} is encoded exactly as the integer type that the compiler uses for it, which depends on the enumeration
+values. Often the compiler users @code{unsigned int}, which is then encoded as @code{I}.
+@item unknown type
+@tab @code{?}
+@item Complex types
+@tab @code{j} followed by the inner type. For example @code{_Complex double} is encoded as "jd".
+@item bit-fields
+@tab @code{b} followed by the starting position of the bit-field, the type of the bit-field and the size of the bit-field (the bit-fields encoding was changed from the NeXT's compiler encoding, see below)
+@end multitable
+
+@c @sp 1
+
+The encoding of bit-fields has changed to allow bit-fields to be
+properly handled by the runtime functions that compute sizes and
+alignments of types that contain bit-fields. The previous encoding
+contained only the size of the bit-field. Using only this information
+it is not possible to reliably compute the size occupied by the
+bit-field. This is very important in the presence of the Boehm's
+garbage collector because the objects are allocated using the typed
+memory facility available in this collector. The typed memory
+allocation requires information about where the pointers are located
+inside the object.
+
+The position in the bit-field is the position, counting in bits, of the
+bit closest to the beginning of the structure.
+
+The non-atomic types are encoded as follows:
+
+@c @sp 1
+
+@multitable @columnfractions .2 .8
+@item pointers
+@tab @samp{^} followed by the pointed type.
+@item arrays
+@tab @samp{[} followed by the number of elements in the array followed by the type of the elements followed by @samp{]}
+@item structures
+@tab @samp{@{} followed by the name of the structure (or @samp{?} if the structure is unnamed), the @samp{=} sign, the type of the members and by @samp{@}}
+@item unions
+@tab @samp{(} followed by the name of the structure (or @samp{?} if the union is unnamed), the @samp{=} sign, the type of the members followed by @samp{)}
+@item vectors
+@tab @samp{![} followed by the vector_size (the number of bytes composing the vector) followed by a comma, followed by the alignment (in bytes) of the vector, followed by the type of the elements followed by @samp{]}
+@end multitable
+
+Here are some types and their encodings, as they are generated by the
+compiler on an i386 machine:
+
+@sp 1
+
+@multitable @columnfractions .60 .40
+@headitem Objective-C type
+@tab Compiler encoding
+@item
+@smallexample
+int a[10];
+@end smallexample
+@tab @code{[10i]}
+@item
+@smallexample
+struct @{
+ int i;
+ float f[3];
+ int a:3;
+ int b:2;
+ char c;
+@}
+@end smallexample
+@tab @code{@{?=i[3f]b128i3b131i2c@}}
+@item
+@smallexample
+int a __attribute__ ((vector_size (16)));
+@end smallexample
+@tab @code{![16,16i]} (alignment depends on the machine)
+@end multitable
+
+@sp 1
+
+In addition to the types the compiler also encodes the type
+specifiers. The table below describes the encoding of the current
+Objective-C type specifiers:
+
+@sp 1
+
+@multitable @columnfractions .25 .75
+@headitem Specifier
+@tab Encoding
+@item @code{const}
+@tab @code{r}
+@item @code{in}
+@tab @code{n}
+@item @code{inout}
+@tab @code{N}
+@item @code{out}
+@tab @code{o}
+@item @code{bycopy}
+@tab @code{O}
+@item @code{byref}
+@tab @code{R}
+@item @code{oneway}
+@tab @code{V}
+@end multitable
+
+@sp 1
+
+The type specifiers are encoded just before the type. Unlike types
+however, the type specifiers are only encoded when they appear in method
+argument types.
+
+Note how @code{const} interacts with pointers:
+
+@sp 1
+
+@multitable @columnfractions .25 .75
+@headitem Objective-C type
+@tab Compiler encoding
+@item
+@smallexample
+const int
+@end smallexample
+@tab @code{ri}
+@item
+@smallexample
+const int*
+@end smallexample
+@tab @code{^ri}
+@item
+@smallexample
+int *const
+@end smallexample
+@tab @code{r^i}
+@end multitable
+
+@sp 1
+
+@code{const int*} is a pointer to a @code{const int}, and so is
+encoded as @code{^ri}. @code{int* const}, instead, is a @code{const}
+pointer to an @code{int}, and so is encoded as @code{r^i}.
+
+Finally, there is a complication when encoding @code{const char *}
+versus @code{char * const}. Because @code{char *} is encoded as
+@code{*} and not as @code{^c}, there is no way to express the fact
+that @code{r} applies to the pointer or to the pointee.
+
+Hence, it is assumed as a convention that @code{r*} means @code{const
+char *} (since it is what is most often meant), and there is no way to
+encode @code{char *const}. @code{char *const} would simply be encoded
+as @code{*}, and the @code{const} is lost.
+
+@menu
+* Legacy type encoding::
+* @@encode::
+* Method signatures::
+@end menu
+
+@node Legacy type encoding
+@subsection Legacy Type Encoding
+
+Unfortunately, historically GCC used to have a number of bugs in its
+encoding code. The NeXT runtime expects GCC to emit type encodings in
+this historical format (compatible with GCC-3.3), so when using the
+NeXT runtime, GCC will introduce on purpose a number of incorrect
+encodings:
+
+@itemize @bullet
+
+@item
+the read-only qualifier of the pointee gets emitted before the '^'.
+The read-only qualifier of the pointer itself gets ignored, unless it
+is a typedef. Also, the 'r' is only emitted for the outermost type.
+
+@item
+32-bit longs are encoded as 'l' or 'L', but not always. For typedefs,
+the compiler uses 'i' or 'I' instead if encoding a struct field or a
+pointer.
+
+@item
+@code{enum}s are always encoded as 'i' (int) even if they are actually
+unsigned or long.
+
+@end itemize
+
+In addition to that, the NeXT runtime uses a different encoding for
+bitfields. It encodes them as @code{b} followed by the size, without
+a bit offset or the underlying field type.
+
+@node @@encode
+@subsection @code{@@encode}
+
+GNU Objective-C supports the @code{@@encode} syntax that allows you to
+create a type encoding from a C/Objective-C type. For example,
+@code{@@encode(int)} is compiled by the compiler into @code{"i"}.
+
+@code{@@encode} does not support type qualifiers other than
+@code{const}. For example, @code{@@encode(const char*)} is valid and
+is compiled into @code{"r*"}, while @code{@@encode(bycopy char *)} is
+invalid and will cause a compilation error.
+
+@node Method signatures
+@subsection Method Signatures
+
+This section documents the encoding of method types, which is rarely
+needed to use Objective-C. You should skip it at a first reading; the
+runtime provides functions that will work on methods and can walk
+through the list of parameters and interpret them for you. These
+functions are part of the public ``API'' and are the preferred way to
+interact with method signatures from user code.
+
+But if you need to debug a problem with method signatures and need to
+know how they are implemented (i.e., the ``ABI''), read on.
+
+Methods have their ``signature'' encoded and made available to the
+runtime. The ``signature'' encodes all the information required to
+dynamically build invocations of the method at runtime: return type
+and arguments.
+
+The ``signature'' is a null-terminated string, composed of the following:
+
+@itemize @bullet
+
+@item
+The return type, including type qualifiers. For example, a method
+returning @code{int} would have @code{i} here.
+
+@item
+The total size (in bytes) required to pass all the parameters. This
+includes the two hidden parameters (the object @code{self} and the
+method selector @code{_cmd}).
+
+@item
+Each argument, with the type encoding, followed by the offset (in
+bytes) of the argument in the list of parameters.
+
+@end itemize
+
+For example, a method with no arguments and returning @code{int} would
+have the signature @code{i8@@0:4} if the size of a pointer is 4. The
+signature is interpreted as follows: the @code{i} is the return type
+(an @code{int}), the @code{8} is the total size of the parameters in
+bytes (two pointers each of size 4), the @code{@@0} is the first
+parameter (an object at byte offset @code{0}) and @code{:4} is the
+second parameter (a @code{SEL} at byte offset @code{4}).
+
+You can easily find more examples by running the ``strings'' program
+on an Objective-C object file compiled by GCC. You'll see a lot of
+strings that look very much like @code{i8@@0:4}. They are signatures
+of Objective-C methods.
+
+
+@node Garbage Collection
+@section Garbage Collection
+
+This section is specific for the GNU Objective-C runtime. If you are
+using a different runtime, you can skip it.
+
+Support for garbage collection with the GNU runtime has been added by
+using a powerful conservative garbage collector, known as the
+Boehm-Demers-Weiser conservative garbage collector.
+
+To enable the support for it you have to configure the compiler using
+an additional argument, @w{@option{--enable-objc-gc}}. This will
+build the boehm-gc library, and build an additional runtime library
+which has several enhancements to support the garbage collector. The
+new library has a new name, @file{libobjc_gc.a} to not conflict with
+the non-garbage-collected library.
+
+When the garbage collector is used, the objects are allocated using the
+so-called typed memory allocation mechanism available in the
+Boehm-Demers-Weiser collector. This mode requires precise information on
+where pointers are located inside objects. This information is computed
+once per class, immediately after the class has been initialized.
+
+There is a new runtime function @code{class_ivar_set_gcinvisible()}
+which can be used to declare a so-called @dfn{weak pointer}
+reference. Such a pointer is basically hidden for the garbage collector;
+this can be useful in certain situations, especially when you want to
+keep track of the allocated objects, yet allow them to be
+collected. This kind of pointers can only be members of objects, you
+cannot declare a global pointer as a weak reference. Every type which is
+a pointer type can be declared a weak pointer, including @code{id},
+@code{Class} and @code{SEL}.
+
+Here is an example of how to use this feature. Suppose you want to
+implement a class whose instances hold a weak pointer reference; the
+following class does this:
+
+@smallexample
+
+@@interface WeakPointer : Object
+@{
+ const void* weakPointer;
+@}
+
+- initWithPointer:(const void*)p;
+- (const void*)weakPointer;
+@@end
+
+
+@@implementation WeakPointer
+
++ (void)initialize
+@{
+ if (self == objc_lookUpClass ("WeakPointer"))
+ class_ivar_set_gcinvisible (self, "weakPointer", YES);
+@}
+
+- initWithPointer:(const void*)p
+@{
+ weakPointer = p;
+ return self;
+@}
+
+- (const void*)weakPointer
+@{
+ return weakPointer;
+@}
+
+@@end
+
+@end smallexample
+
+Weak pointers are supported through a new type character specifier
+represented by the @samp{!} character. The
+@code{class_ivar_set_gcinvisible()} function adds or removes this
+specifier to the string type description of the instance variable named
+as argument.
+
+@c =========================================================================
+@node Constant string objects
+@section Constant String Objects
+
+GNU Objective-C provides constant string objects that are generated
+directly by the compiler. You declare a constant string object by
+prefixing a C constant string with the character @samp{@@}:
+
+@smallexample
+ id myString = @@"this is a constant string object";
+@end smallexample
+
+The constant string objects are by default instances of the
+@code{NXConstantString} class which is provided by the GNU Objective-C
+runtime. To get the definition of this class you must include the
+@file{objc/NXConstStr.h} header file.
+
+User defined libraries may want to implement their own constant string
+class. To be able to support them, the GNU Objective-C compiler provides
+a new command line options @option{-fconstant-string-class=@var{class-name}}.
+The provided class should adhere to a strict structure, the same
+as @code{NXConstantString}'s structure:
+
+@smallexample
+
+@@interface MyConstantStringClass
+@{
+ Class isa;
+ char *c_string;
+ unsigned int len;
+@}
+@@end
+
+@end smallexample
+
+@code{NXConstantString} inherits from @code{Object}; user class
+libraries may choose to inherit the customized constant string class
+from a different class than @code{Object}. There is no requirement in
+the methods the constant string class has to implement, but the final
+ivar layout of the class must be the compatible with the given
+structure.
+
+When the compiler creates the statically allocated constant string
+object, the @code{c_string} field will be filled by the compiler with
+the string; the @code{length} field will be filled by the compiler with
+the string length; the @code{isa} pointer will be filled with
+@code{NULL} by the compiler, and it will later be fixed up automatically
+at runtime by the GNU Objective-C runtime library to point to the class
+which was set by the @option{-fconstant-string-class} option when the
+object file is loaded (if you wonder how it works behind the scenes, the
+name of the class to use, and the list of static objects to fixup, are
+stored by the compiler in the object file in a place where the GNU
+runtime library will find them at runtime).
+
+As a result, when a file is compiled with the
+@option{-fconstant-string-class} option, all the constant string objects
+will be instances of the class specified as argument to this option. It
+is possible to have multiple compilation units referring to different
+constant string classes, neither the compiler nor the linker impose any
+restrictions in doing this.
+
+@c =========================================================================
+@node compatibility_alias
+@section @code{compatibility_alias}
+
+The keyword @code{@@compatibility_alias} allows you to define a class name
+as equivalent to another class name. For example:
+
+@smallexample
+@@compatibility_alias WOApplication GSWApplication;
+@end smallexample
+
+tells the compiler that each time it encounters @code{WOApplication} as
+a class name, it should replace it with @code{GSWApplication} (that is,
+@code{WOApplication} is just an alias for @code{GSWApplication}).
+
+There are some constraints on how this can be used---
+
+@itemize @bullet
+
+@item @code{WOApplication} (the alias) must not be an existing class;
+
+@item @code{GSWApplication} (the real class) must be an existing class.
+
+@end itemize
+
+@c =========================================================================
+@node Exceptions
+@section Exceptions
+
+GNU Objective-C provides exception support built into the language, as
+in the following example:
+
+@smallexample
+ @@try @{
+ @dots{}
+ @@throw expr;
+ @dots{}
+ @}
+ @@catch (AnObjCClass *exc) @{
+ @dots{}
+ @@throw expr;
+ @dots{}
+ @@throw;
+ @dots{}
+ @}
+ @@catch (AnotherClass *exc) @{
+ @dots{}
+ @}
+ @@catch (id allOthers) @{
+ @dots{}
+ @}
+ @@finally @{
+ @dots{}
+ @@throw expr;
+ @dots{}
+ @}
+@end smallexample
+
+The @code{@@throw} statement may appear anywhere in an Objective-C or
+Objective-C++ program; when used inside of a @code{@@catch} block, the
+@code{@@throw} may appear without an argument (as shown above), in
+which case the object caught by the @code{@@catch} will be rethrown.
+
+Note that only (pointers to) Objective-C objects may be thrown and
+caught using this scheme. When an object is thrown, it will be caught
+by the nearest @code{@@catch} clause capable of handling objects of
+that type, analogously to how @code{catch} blocks work in C++ and
+Java. A @code{@@catch(id @dots{})} clause (as shown above) may also
+be provided to catch any and all Objective-C exceptions not caught by
+previous @code{@@catch} clauses (if any).
+
+The @code{@@finally} clause, if present, will be executed upon exit
+from the immediately preceding @code{@@try @dots{} @@catch} section.
+This will happen regardless of whether any exceptions are thrown,
+caught or rethrown inside the @code{@@try @dots{} @@catch} section,
+analogously to the behavior of the @code{finally} clause in Java.
+
+There are several caveats to using the new exception mechanism:
+
+@itemize @bullet
+@item
+The @option{-fobjc-exceptions} command line option must be used when
+compiling Objective-C files that use exceptions.
+
+@item
+With the GNU runtime, exceptions are always implemented as ``native''
+exceptions and it is recommended that the @option{-fexceptions} and
+@option{-shared-libgcc} options are used when linking.
+
+@item
+With the NeXT runtime, although currently designed to be binary
+compatible with @code{NS_HANDLER}-style idioms provided by the
+@code{NSException} class, the new exceptions can only be used on Mac
+OS X 10.3 (Panther) and later systems, due to additional functionality
+needed in the NeXT Objective-C runtime.
+
+@item
+As mentioned above, the new exceptions do not support handling
+types other than Objective-C objects. Furthermore, when used from
+Objective-C++, the Objective-C exception model does not interoperate with C++
+exceptions at this time. This means you cannot @code{@@throw} an exception
+from Objective-C and @code{catch} it in C++, or vice versa
+(i.e., @code{throw @dots{} @@catch}).
+@end itemize
+
+@c =========================================================================
+@node Synchronization
+@section Synchronization
+
+GNU Objective-C provides support for synchronized blocks:
+
+@smallexample
+ @@synchronized (ObjCClass *guard) @{
+ @dots{}
+ @}
+@end smallexample
+
+Upon entering the @code{@@synchronized} block, a thread of execution
+shall first check whether a lock has been placed on the corresponding
+@code{guard} object by another thread. If it has, the current thread
+shall wait until the other thread relinquishes its lock. Once
+@code{guard} becomes available, the current thread will place its own
+lock on it, execute the code contained in the @code{@@synchronized}
+block, and finally relinquish the lock (thereby making @code{guard}
+available to other threads).
+
+Unlike Java, Objective-C does not allow for entire methods to be
+marked @code{@@synchronized}. Note that throwing exceptions out of
+@code{@@synchronized} blocks is allowed, and will cause the guarding
+object to be unlocked properly.
+
+Because of the interactions between synchronization and exception
+handling, you can only use @code{@@synchronized} when compiling with
+exceptions enabled, that is with the command line option
+@option{-fobjc-exceptions}.
+
+
+@c =========================================================================
+@node Fast enumeration
+@section Fast Enumeration
+
+@menu
+* Using fast enumeration::
+* c99-like fast enumeration syntax::
+* Fast enumeration details::
+* Fast enumeration protocol::
+@end menu
+
+@c ================================
+@node Using fast enumeration
+@subsection Using Fast Enumeration
+
+GNU Objective-C provides support for the fast enumeration syntax:
+
+@smallexample
+ id array = @dots{};
+ id object;
+
+ for (object in array)
+ @{
+ /* Do something with 'object' */
+ @}
+@end smallexample
+
+@code{array} needs to be an Objective-C object (usually a collection
+object, for example an array, a dictionary or a set) which implements
+the ``Fast Enumeration Protocol'' (see below). If you are using a
+Foundation library such as GNUstep Base or Apple Cocoa Foundation, all
+collection objects in the library implement this protocol and can be
+used in this way.
+
+The code above would iterate over all objects in @code{array}. For
+each of them, it assigns it to @code{object}, then executes the
+@code{Do something with 'object'} statements.
+
+Here is a fully worked-out example using a Foundation library (which
+provides the implementation of @code{NSArray}, @code{NSString} and
+@code{NSLog}):
+
+@smallexample
+ NSArray *array = [NSArray arrayWithObjects: @@"1", @@"2", @@"3", nil];
+ NSString *object;
+
+ for (object in array)
+ NSLog (@@"Iterating over %@@", object);
+@end smallexample
+
+
+@c ================================
+@node c99-like fast enumeration syntax
+@subsection C99-Like Fast Enumeration Syntax
+
+A c99-like declaration syntax is also allowed:
+
+@smallexample
+ id array = @dots{};
+
+ for (id object in array)
+ @{
+ /* Do something with 'object' */
+ @}
+@end smallexample
+
+this is completely equivalent to:
+
+@smallexample
+ id array = @dots{};
+
+ @{
+ id object;
+ for (object in array)
+ @{
+ /* Do something with 'object' */
+ @}
+ @}
+@end smallexample
+
+but can save some typing.
+
+Note that the option @option{-std=c99} is not required to allow this
+syntax in Objective-C.
+
+@c ================================
+@node Fast enumeration details
+@subsection Fast Enumeration Details
+
+Here is a more technical description with the gory details. Consider the code
+
+@smallexample
+ for (@var{object expression} in @var{collection expression})
+ @{
+ @var{statements}
+ @}
+@end smallexample
+
+here is what happens when you run it:
+
+@itemize @bullet
+@item
+@code{@var{collection expression}} is evaluated exactly once and the
+result is used as the collection object to iterate over. This means
+it is safe to write code such as @code{for (object in [NSDictionary
+keyEnumerator]) @dots{}}.
+
+@item
+the iteration is implemented by the compiler by repeatedly getting
+batches of objects from the collection object using the fast
+enumeration protocol (see below), then iterating over all objects in
+the batch. This is faster than a normal enumeration where objects are
+retrieved one by one (hence the name ``fast enumeration'').
+
+@item
+if there are no objects in the collection, then
+@code{@var{object expression}} is set to @code{nil} and the loop
+immediately terminates.
+
+@item
+if there are objects in the collection, then for each object in the
+collection (in the order they are returned) @code{@var{object expression}}
+is set to the object, then @code{@var{statements}} are executed.
+
+@item
+@code{@var{statements}} can contain @code{break} and @code{continue}
+commands, which will abort the iteration or skip to the next loop
+iteration as expected.
+
+@item
+when the iteration ends because there are no more objects to iterate
+over, @code{@var{object expression}} is set to @code{nil}. This allows
+you to determine whether the iteration finished because a @code{break}
+command was used (in which case @code{@var{object expression}} will remain
+set to the last object that was iterated over) or because it iterated
+over all the objects (in which case @code{@var{object expression}} will be
+set to @code{nil}).
+
+@item
+@code{@var{statements}} must not make any changes to the collection
+object; if they do, it is a hard error and the fast enumeration
+terminates by invoking @code{objc_enumerationMutation}, a runtime
+function that normally aborts the program but which can be customized
+by Foundation libraries via @code{objc_set_mutation_handler} to do
+something different, such as raising an exception.
+
+@end itemize
+
+@c ================================
+@node Fast enumeration protocol
+@subsection Fast Enumeration Protocol
+
+If you want your own collection object to be usable with fast
+enumeration, you need to have it implement the method
+
+@smallexample
+- (unsigned long) countByEnumeratingWithState: (NSFastEnumerationState *)state
+ objects: (id *)objects
+ count: (unsigned long)len;
+@end smallexample
+
+where @code{NSFastEnumerationState} must be defined in your code as follows:
+
+@smallexample
+typedef struct
+@{
+ unsigned long state;
+ id *itemsPtr;
+ unsigned long *mutationsPtr;
+ unsigned long extra[5];
+@} NSFastEnumerationState;
+@end smallexample
+
+If no @code{NSFastEnumerationState} is defined in your code, the
+compiler will automatically replace @code{NSFastEnumerationState *}
+with @code{struct __objcFastEnumerationState *}, where that type is
+silently defined by the compiler in an identical way. This can be
+confusing and we recommend that you define
+@code{NSFastEnumerationState} (as shown above) instead.
+
+The method is called repeatedly during a fast enumeration to retrieve
+batches of objects. Each invocation of the method should retrieve the
+next batch of objects.
+
+The return value of the method is the number of objects in the current
+batch; this should not exceed @code{len}, which is the maximum size of
+a batch as requested by the caller. The batch itself is returned in
+the @code{itemsPtr} field of the @code{NSFastEnumerationState} struct.
+
+To help with returning the objects, the @code{objects} array is a C
+array preallocated by the caller (on the stack) of size @code{len}.
+In many cases you can put the objects you want to return in that
+@code{objects} array, then do @code{itemsPtr = objects}. But you
+don't have to; if your collection already has the objects to return in
+some form of C array, it could return them from there instead.
+
+The @code{state} and @code{extra} fields of the
+@code{NSFastEnumerationState} structure allows your collection object
+to keep track of the state of the enumeration. In a simple array
+implementation, @code{state} may keep track of the index of the last
+object that was returned, and @code{extra} may be unused.
+
+The @code{mutationsPtr} field of the @code{NSFastEnumerationState} is
+used to keep track of mutations. It should point to a number; before
+working on each object, the fast enumeration loop will check that this
+number has not changed. If it has, a mutation has happened and the
+fast enumeration will abort. So, @code{mutationsPtr} could be set to
+point to some sort of version number of your collection, which is
+increased by one every time there is a change (for example when an
+object is added or removed). Or, if you are content with less strict
+mutation checks, it could point to the number of objects in your
+collection or some other value that can be checked to perform an
+approximate check that the collection has not been mutated.
+
+Finally, note how we declared the @code{len} argument and the return
+value to be of type @code{unsigned long}. They could also be declared
+to be of type @code{unsigned int} and everything would still work.
+
+@c =========================================================================
+@node Messaging with the GNU Objective-C runtime
+@section Messaging with the GNU Objective-C Runtime
+
+This section is specific for the GNU Objective-C runtime. If you are
+using a different runtime, you can skip it.
+
+The implementation of messaging in the GNU Objective-C runtime is
+designed to be portable, and so is based on standard C.
+
+Sending a message in the GNU Objective-C runtime is composed of two
+separate steps. First, there is a call to the lookup function,
+@code{objc_msg_lookup ()} (or, in the case of messages to super,
+@code{objc_msg_lookup_super ()}). This runtime function takes as
+argument the receiver and the selector of the method to be called; it
+returns the @code{IMP}, that is a pointer to the function implementing
+the method. The second step of method invocation consists of casting
+this pointer function to the appropriate function pointer type, and
+calling the function pointed to it with the right arguments.
+
+For example, when the compiler encounters a method invocation such as
+@code{[object init]}, it compiles it into a call to
+@code{objc_msg_lookup (object, @@selector(init))} followed by a cast
+of the returned value to the appropriate function pointer type, and
+then it calls it.
+
+@menu
+* Dynamically registering methods::
+* Forwarding hook::
+@end menu
+
+@c =========================================================================
+@node Dynamically registering methods
+@subsection Dynamically Registering Methods
+
+If @code{objc_msg_lookup()} does not find a suitable method
+implementation, because the receiver does not implement the required
+method, it tries to see if the class can dynamically register the
+method.
+
+To do so, the runtime checks if the class of the receiver implements
+the method
+
+@smallexample
++ (BOOL) resolveInstanceMethod: (SEL)selector;
+@end smallexample
+
+in the case of an instance method, or
+
+@smallexample
++ (BOOL) resolveClassMethod: (SEL)selector;
+@end smallexample
+
+in the case of a class method. If the class implements it, the
+runtime invokes it, passing as argument the selector of the original
+method, and if it returns @code{YES}, the runtime tries the lookup
+again, which could now succeed if a matching method was added
+dynamically by @code{+resolveInstanceMethod:} or
+@code{+resolveClassMethod:}.
+
+This allows classes to dynamically register methods (by adding them to
+the class using @code{class_addMethod}) when they are first called.
+To do so, a class should implement @code{+resolveInstanceMethod:} (or,
+depending on the case, @code{+resolveClassMethod:}) and have it
+recognize the selectors of methods that can be registered dynamically
+at runtime, register them, and return @code{YES}. It should return
+@code{NO} for methods that it does not dynamically registered at
+runtime.
+
+If @code{+resolveInstanceMethod:} (or @code{+resolveClassMethod:}) is
+not implemented or returns @code{NO}, the runtime then tries the
+forwarding hook.
+
+Support for @code{+resolveInstanceMethod:} and
+@code{resolveClassMethod:} was added to the GNU Objective-C runtime in
+GCC version 4.6.
+
+@c =========================================================================
+@node Forwarding hook
+@subsection Forwarding Hook
+
+The GNU Objective-C runtime provides a hook, called
+@code{__objc_msg_forward2}, which is called by
+@code{objc_msg_lookup()} when it cannot find a method implementation in
+the runtime tables and after calling @code{+resolveInstanceMethod:}
+and @code{+resolveClassMethod:} has been attempted and did not succeed
+in dynamically registering the method.
+
+To configure the hook, you set the global variable
+@code{__objc_msg_forward2} to a function with the same argument and
+return types of @code{objc_msg_lookup()}. When
+@code{objc_msg_lookup()} cannot find a method implementation, it
+invokes the hook function you provided to get a method implementation
+to return. So, in practice @code{__objc_msg_forward2} allows you to
+extend @code{objc_msg_lookup()} by adding some custom code that is
+called to do a further lookup when no standard method implementation
+can be found using the normal lookup.
+
+This hook is generally reserved for ``Foundation'' libraries such as
+GNUstep Base, which use it to implement their high-level method
+forwarding API, typically based around the @code{forwardInvocation:}
+method. So, unless you are implementing your own ``Foundation''
+library, you should not set this hook.
+
+In a typical forwarding implementation, the @code{__objc_msg_forward2}
+hook function determines the argument and return type of the method
+that is being looked up, and then creates a function that takes these
+arguments and has that return type, and returns it to the caller.
+Creating this function is non-trivial and is typically performed using
+a dedicated library such as @code{libffi}.
+
+The forwarding method implementation thus created is returned by
+@code{objc_msg_lookup()} and is executed as if it was a normal method
+implementation. When the forwarding method implementation is called,
+it is usually expected to pack all arguments into some sort of object
+(typically, an @code{NSInvocation} in a ``Foundation'' library), and
+hand it over to the programmer (@code{forwardInvocation:}) who is then
+allowed to manipulate the method invocation using a high-level API
+provided by the ``Foundation'' library. For example, the programmer
+may want to examine the method invocation arguments and name and
+potentially change them before forwarding the method invocation to one
+or more local objects (@code{performInvocation:}) or even to remote
+objects (by using Distributed Objects or some other mechanism). When
+all this completes, the return value is passed back and must be
+returned correctly to the original caller.
+
+Note that the GNU Objective-C runtime currently provides no support
+for method forwarding or method invocations other than the
+@code{__objc_msg_forward2} hook.
+
+If the forwarding hook does not exist or returns @code{NULL}, the
+runtime currently attempts forwarding using an older, deprecated API,
+and if that fails, it aborts the program. In future versions of the
+GNU Objective-C runtime, the runtime will immediately abort.
--- /dev/null
+@c Copyright (C) 2013-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@cindex optimization dumps
+
+This section is describes dump infrastructure which is common to both
+pass dumps as well as optimization dumps. The goal for this
+infrastructure is to provide both gcc developers and users detailed
+information about various compiler transformations and optimizations.
+
+@menu
+* Dump setup:: Setup of optimization dumps.
+* Optimization groups:: Groups made up of optimization passes.
+* Dump files and streams:: Dump output file names and streams.
+* Dump output verbosity:: How much information to dump.
+* Dump types:: Various types of dump functions.
+* Dump examples:: Sample usage.
+@end menu
+
+@node Dump setup
+@subsection Dump setup
+@cindex dump setup
+
+A dump_manager class is defined in @file{dumpfile.h}. Various passes
+register dumping pass-specific information via @code{dump_register} in
+@file{passes.cc}. During the registration, an optimization pass can
+select its optimization group (@pxref{Optimization groups}). After
+that optimization information corresponding to the entire group
+(presumably from multiple passes) can be output via command-line
+switches. Note that if a pass does not fit into any of the pre-defined
+groups, it can select @code{OPTGROUP_NONE}.
+
+Note that in general, a pass need not know its dump output file name,
+whether certain flags are enabled, etc. However, for legacy reasons,
+passes could also call @code{dump_begin} which returns a stream in
+case the particular pass has optimization dumps enabled. A pass could
+call @code{dump_end} when the dump has ended. These methods should go
+away once all the passes are converted to use the new dump
+infrastructure.
+
+The recommended way to setup the dump output is via @code{dump_start}
+and @code{dump_end}.
+
+@node Optimization groups
+@subsection Optimization groups
+@cindex optimization groups
+The optimization passes are grouped into several categories. Currently
+defined categories in @file{dumpfile.h} are
+
+@ftable @code
+
+@item OPTGROUP_IPA
+IPA optimization passes. Enabled by @option{-ipa}
+
+@item OPTGROUP_LOOP
+Loop optimization passes. Enabled by @option{-loop}.
+
+@item OPTGROUP_INLINE
+Inlining passes. Enabled by @option{-inline}.
+
+@item OPTGROUP_OMP
+OMP (Offloading and Multi Processing) passes. Enabled by
+@option{-omp}.
+
+@item OPTGROUP_VEC
+Vectorization passes. Enabled by @option{-vec}.
+
+@item OPTGROUP_OTHER
+All other optimization passes which do not fall into one of the above.
+
+@item OPTGROUP_ALL
+All optimization passes. Enabled by @option{-optall}.
+
+@end ftable
+
+By using groups a user could selectively enable optimization
+information only for a group of passes. By default, the optimization
+information for all the passes is dumped.
+
+@node Dump files and streams
+@subsection Dump files and streams
+@cindex optimization info file names
+
+There are two separate output streams available for outputting
+optimization information from passes. Note that both these streams
+accept @code{stderr} and @code{stdout} as valid streams and thus it is
+possible to dump output to standard output or error. This is specially
+handy for outputting all available information in a single file by
+redirecting @code{stderr}.
+
+@table @code
+@item @code{pstream}
+This stream is for pass-specific dump output. For example,
+@option{-fdump-tree-vect=foo.v} dumps tree vectorization pass output
+into the given file name @file{foo.v}. If the file name is not provided,
+the default file name is based on the source file and pass number. Note
+that one could also use special file names @code{stdout} and
+@code{stderr} for dumping to standard output and standard error
+respectively.
+
+@item @code{alt_stream}
+This steam is used for printing optimization specific output in
+response to the @option{-fopt-info}. Again a file name can be given. If
+the file name is not given, it defaults to @code{stderr}.
+@end table
+
+@node Dump output verbosity
+@subsection Dump output verbosity
+@cindex dump verbosity
+
+The dump verbosity has the following options
+
+@table @samp
+@item optimized
+Print information when an optimization is successfully applied. It is
+up to a pass to decide which information is relevant. For example, the
+vectorizer passes print the source location of loops which got
+successfully vectorized.
+
+@item missed
+Print information about missed optimizations. Individual passes
+control which information to include in the output. For example,
+
+@smallexample
+gcc -O2 -ftree-vectorize -fopt-info-vec-missed
+@end smallexample
+
+will print information about missed optimization opportunities from
+vectorization passes on stderr.
+
+@item note
+Print verbose information about optimizations, such as certain
+transformations, more detailed messages about decisions etc.
+
+@item all
+Print detailed optimization information. This includes
+@var{optimized}, @var{missed}, and @var{note}.
+@end table
+
+@node Dump types
+@subsection Dump types
+@cindex dump types
+
+@ftable @code
+
+@item dump_printf
+
+This is a generic method for doing formatted output. It takes an
+additional argument @code{dump_kind} which signifies the type of
+dump. This method outputs information only when the dumps are enabled
+for this particular @code{dump_kind}. Note that the caller doesn't
+need to know if the particular dump is enabled or not, or even the
+file name. The caller only needs to decide which dump output
+information is relevant, and under what conditions. This determines
+the associated flags.
+
+Consider the following example from @file{loop-unroll.cc} where an
+informative message about a loop (along with its location) is printed
+when any of the following flags is enabled
+@itemize @minus
+
+@item optimization messages
+@item RTL dumps
+@item detailed dumps
+
+@end itemize
+
+@example
+int report_flags = MSG_OPTIMIZED_LOCATIONS | TDF_RTL | TDF_DETAILS;
+dump_printf_loc (report_flags, insn,
+ "loop turned into non-loop; it never loops.\n");
+@end example
+
+@item dump_basic_block
+Output basic block.
+@item dump_generic_expr
+Output generic expression.
+@item dump_gimple_stmt
+Output gimple statement.
+
+Note that the above methods also have variants prefixed with
+@code{_loc}, such as @code{dump_printf_loc}, which are similar except
+they also output the source location information. The @code{_loc} variants
+take a @code{const dump_location_t &}. This class can be constructed from
+a @code{gimple *} or from a @code{rtx_insn *}, and so callers can pass
+a @code{gimple *} or a @code{rtx_insn *} as the @code{_loc} argument.
+The @code{dump_location_t} constructor will extract the source location
+from the statement or instruction, along with the profile count, and
+the location in GCC's own source code (or the plugin) from which the dump
+call was emitted. Only the source location is currently used.
+There is also a @code{dump_user_location_t} class, capturing the
+source location and profile count, but not the dump emission location,
+so that locations in the user's code can be passed around. This
+can also be constructed from a @code{gimple *} and from a @code{rtx_insn *},
+and it too can be passed as the @code{_loc} argument.
+
+@end ftable
+
+@node Dump examples
+@subsection Dump examples
+@cindex dump examples
+
+@smallexample
+gcc -O3 -fopt-info-missed=missed.all
+@end smallexample
+
+outputs missed optimization report from all the passes into
+@file{missed.all}.
+
+As another example,
+@smallexample
+gcc -O3 -fopt-info-inline-optimized-missed=inline.txt
+@end smallexample
+
+will output information about missed optimizations as well as
+optimized locations from all the inlining passes into
+@file{inline.txt}.
+
+If the @var{filename} is provided, then the dumps from all the
+applicable optimizations are concatenated into the @file{filename}.
+Otherwise the dump is output onto @file{stderr}. If @var{options} is
+omitted, it defaults to @option{optimized-optall}, which means dump
+all information about successful optimizations from all the passes.
+In the following example, the optimization information is output on
+to @file{stderr}.
+
+@smallexample
+gcc -O3 -fopt-info
+@end smallexample
+
+Note that @option{-fopt-info-vec-missed} behaves the same as
+@option{-fopt-info-missed-vec}. The order of the optimization group
+names and message types listed after @option{-fopt-info} does not matter.
+
+As another example, consider
+
+@smallexample
+gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt
+@end smallexample
+
+Here the two output file names @file{vec.miss} and @file{loop.opt} are
+in conflict since only one output file is allowed. In this case, only
+the first option takes effect and the subsequent options are
+ignored. Thus only the @file{vec.miss} is produced which containts
+dumps from the vectorizer about missed opportunities.
--- /dev/null
+@c Copyright (C) 2003-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Options
+@chapter Option specification files
+@cindex option specification files
+@cindex @samp{optc-gen.awk}
+
+Most GCC command-line options are described by special option
+definition files, the names of which conventionally end in
+@code{.opt}. This chapter describes the format of these files.
+
+@menu
+* Option file format:: The general layout of the files
+* Option properties:: Supported option properties
+@end menu
+
+@node Option file format
+@section Option file format
+
+Option files are a simple list of records in which each field occupies
+its own line and in which the records themselves are separated by
+blank lines. Comments may appear on their own line anywhere within
+the file and are preceded by semicolons. Whitespace is allowed before
+the semicolon.
+
+The files can contain the following types of record:
+
+@itemize @bullet
+@item
+A language definition record. These records have two fields: the
+string @samp{Language} and the name of the language. Once a language
+has been declared in this way, it can be used as an option property.
+@xref{Option properties}.
+
+@item
+A target specific save record to save additional information. These
+records have two fields: the string @samp{TargetSave}, and a
+declaration type to go in the @code{cl_target_option} structure.
+
+@item
+A variable record to define a variable used to store option
+information. These records have two fields: the string
+@samp{Variable}, and a declaration of the type and name of the
+variable, optionally with an initializer (but without any trailing
+@samp{;}). These records may be used for variables used for many
+options where declaring the initializer in a single option definition
+record, or duplicating it in many records, would be inappropriate, or
+for variables set in option handlers rather than referenced by
+@code{Var} properties.
+
+@item
+A variable record to define a variable used to store option
+information. These records have two fields: the string
+@samp{TargetVariable}, and a declaration of the type and name of the
+variable, optionally with an initializer (but without any trailing
+@samp{;}). @samp{TargetVariable} is a combination of @samp{Variable}
+and @samp{TargetSave} records in that the variable is defined in the
+@code{gcc_options} structure, but these variables are also stored in
+the @code{cl_target_option} structure. The variables are saved in the
+target save code and restored in the target restore code.
+
+@item
+A variable record to record any additional files that the
+@file{options.h} file should include. This is useful to provide
+enumeration or structure definitions needed for target variables.
+These records have two fields: the string @samp{HeaderInclude} and the
+name of the include file.
+
+@item
+A variable record to record any additional files that the
+@file{options.cc} or @file{options-save.cc} file should include. This
+is useful to provide
+inline functions needed for target variables and/or @code{#ifdef}
+sequences to properly set up the initialization. These records have
+two fields: the string @samp{SourceInclude} and the name of the
+include file.
+
+@item
+An enumeration record to define a set of strings that may be used as
+arguments to an option or options. These records have three fields:
+the string @samp{Enum}, a space-separated list of properties and help
+text used to describe the set of strings in @option{--help} output.
+Properties use the same format as option properties; the following are
+valid:
+@table @code
+@item Name(@var{name})
+This property is required; @var{name} must be a name (suitable for use
+in C identifiers) used to identify the set of strings in @code{Enum}
+option properties.
+
+@item Type(@var{type})
+This property is required; @var{type} is the C type for variables set
+by options using this enumeration together with @code{Var}.
+
+@item UnknownError(@var{message})
+The message @var{message} will be used as an error message if the
+argument is invalid; for enumerations without @code{UnknownError}, a
+generic error message is used. @var{message} should contain a single
+@samp{%qs} format, which will be used to format the invalid argument.
+@end table
+
+@item
+An enumeration value record to define one of the strings in a set
+given in an @samp{Enum} record. These records have two fields: the
+string @samp{EnumValue} and a space-separated list of properties.
+Properties use the same format as option properties; the following are
+valid:
+@table @code
+@item Enum(@var{name})
+This property is required; @var{name} says which @samp{Enum} record
+this @samp{EnumValue} record corresponds to.
+
+@item String(@var{string})
+This property is required; @var{string} is the string option argument
+being described by this record.
+
+@item Value(@var{value})
+This property is required; it says what value (representable as
+@code{int}) should be used for the given string.
+
+@item Canonical
+This property is optional. If present, it says the present string is
+the canonical one among all those with the given value. Other strings
+yielding that value will be mapped to this one so specs do not need to
+handle them.
+
+@item DriverOnly
+This property is optional. If present, the present string will only
+be accepted by the driver. This is used for cases such as
+@option{-march=native} that are processed by the driver so that
+@samp{gcc -v} shows how the options chosen depended on the system on
+which the compiler was run.
+
+@item Set(@var{number})
+This property is optional, required for enumerations used in
+@code{EnumSet} options. @var{number} should be decimal number between
+1 and 64 inclusive and divides the enumeration into a set of
+sets of mutually exclusive arguments. Arguments with the same
+@var{number} can't be specified together in the same option, but
+arguments with different @var{number} can. @var{value} needs to be
+chosen such that a mask of all @var{value} values from the same set
+@var{number} bitwise ored doesn't overlap with masks for other sets.
+When @code{-foption=arg_from_set1,arg_from_set4} and
+@code{-fno-option=arg_from_set3} are used, the effect is that previous
+value of the @code{Var} will get bits from set 1 and 4 masks cleared,
+ored @code{Value} of @code{arg_from_set1} and @code{arg_from_set4}
+and then will get bits from set 3 mask cleared.
+@end table
+
+@item
+An option definition record. These records have the following fields:
+@enumerate
+@item
+the name of the option, with the leading ``-'' removed
+@item
+a space-separated list of option properties (@pxref{Option properties})
+@item
+the help text to use for @option{--help} (omitted if the second field
+contains the @code{Undocumented} property).
+@end enumerate
+
+By default, all options beginning with ``f'', ``W'' or ``m'' are
+implicitly assumed to take a ``no-'' form. This form should not be
+listed separately. If an option beginning with one of these letters
+does not have a ``no-'' form, you can use the @code{RejectNegative}
+property to reject it.
+
+The help text is automatically line-wrapped before being displayed.
+Normally the name of the option is printed on the left-hand side of
+the output and the help text is printed on the right. However, if the
+help text contains a tab character, the text to the left of the tab is
+used instead of the option's name and the text to the right of the
+tab forms the help text. This allows you to elaborate on what type
+of argument the option takes.
+
+There is no support for different help texts for different languages.
+If an option is supported for multiple languages, use a generic
+description that is correct for all of them.
+
+If an option has multiple option definition records (in different
+front ends' @file{*.opt} files, and/or @file{gcc/common.opt}, for
+example), convention is to not duplicate the help text for each of
+them, but instead put a comment like @code{; documented in common.opt}
+in place of the help text for all but one of the multiple option
+definition records.
+
+@item
+A target mask record. These records have one field of the form
+@samp{Mask(@var{x})}. The options-processing script will automatically
+allocate a bit in @code{target_flags} (@pxref{Run-time Target}) for
+each mask name @var{x} and set the macro @code{MASK_@var{x}} to the
+appropriate bitmask. It will also declare a @code{TARGET_@var{x}}
+macro that has the value 1 when bit @code{MASK_@var{x}} is set and
+0 otherwise.
+
+They are primarily intended to declare target masks that are not
+associated with user options, either because these masks represent
+internal switches or because the options are not available on all
+configurations and yet the masks always need to be defined.
+@end itemize
+
+@node Option properties
+@section Option properties
+
+The second field of an option record can specify any of the following
+properties. When an option takes an argument, it is enclosed in parentheses
+following the option property name. The parser that handles option files
+is quite simplistic, and will be tricked by any nested parentheses within
+the argument text itself; in this case, the entire option argument can
+be wrapped in curly braces within the parentheses to demarcate it, e.g.:
+
+@smallexample
+Condition(@{defined (USE_CYGWIN_LIBSTDCXX_WRAPPERS)@})
+@end smallexample
+
+@table @code
+@item Common
+The option is available for all languages and targets.
+
+@item Target
+The option is available for all languages but is target-specific.
+
+@item Driver
+The option is handled by the compiler driver using code not shared
+with the compilers proper (@file{cc1} etc.).
+
+@item @var{language}
+The option is available when compiling for the given language.
+
+It is possible to specify several different languages for the same
+option. Each @var{language} must have been declared by an earlier
+@code{Language} record. @xref{Option file format}.
+
+@item RejectDriver
+The option is only handled by the compilers proper (@file{cc1} etc.)@:
+and should not be accepted by the driver.
+
+@item RejectNegative
+The option does not have a ``no-'' form. All options beginning with
+``f'', ``W'' or ``m'' are assumed to have a ``no-'' form unless this
+property is used.
+
+@item Negative(@var{othername})
+The option will turn off another option @var{othername}, which is
+the option name with the leading ``-'' removed. This chain action will
+propagate through the @code{Negative} property of the option to be
+turned off. The driver will prune options, removing those that are
+turned off by some later option. This pruning is not done for options
+with @code{Joined} or @code{JoinedOrMissing} properties, unless the
+options have both the @code{RejectNegative} property and the @code{Negative}
+property mentions itself.
+
+As a consequence, if you have a group of mutually-exclusive
+options, their @code{Negative} properties should form a circular chain.
+For example, if options @option{-@var{a}}, @option{-@var{b}} and
+@option{-@var{c}} are mutually exclusive, their respective @code{Negative}
+properties should be @samp{Negative(@var{b})}, @samp{Negative(@var{c})}
+and @samp{Negative(@var{a})}.
+
+@item Joined
+@itemx Separate
+The option takes a mandatory argument. @code{Joined} indicates
+that the option and argument can be included in the same @code{argv}
+entry (as with @code{-mflush-func=@var{name}}, for example).
+@code{Separate} indicates that the option and argument can be
+separate @code{argv} entries (as with @code{-o}). An option is
+allowed to have both of these properties.
+
+@item JoinedOrMissing
+The option takes an optional argument. If the argument is given,
+it will be part of the same @code{argv} entry as the option itself.
+
+This property cannot be used alongside @code{Joined} or @code{Separate}.
+
+@item MissingArgError(@var{message})
+For an option marked @code{Joined} or @code{Separate}, the message
+@var{message} will be used as an error message if the mandatory
+argument is missing; for options without @code{MissingArgError}, a
+generic error message is used. @var{message} should contain a single
+@samp{%qs} format, which will be used to format the name of the option
+passed.
+
+@item Args(@var{n})
+For an option marked @code{Separate}, indicate that it takes @var{n}
+arguments. The default is 1.
+
+@item UInteger
+The option's argument is a non-negative integer consisting of either
+decimal or hexadecimal digits interpreted as @code{int}. Hexadecimal
+integers may optionally start with the @code{0x} or @code{0X} prefix.
+The option parser validates and converts the argument before passing
+it to the relevant option handler. @code{UInteger} should also be used
+with options like @code{-falign-loops} where both @code{-falign-loops}
+and @code{-falign-loops}=@var{n} are supported to make sure the saved
+options are given a full integer. Positive values of the argument in
+excess of @code{INT_MAX} wrap around zero.
+
+@item Host_Wide_Int
+The option's argument is a non-negative integer consisting of either
+decimal or hexadecimal digits interpreted as the widest integer type
+on the host. As with an @code{UInteger} argument, hexadecimal integers
+may optionally start with the @code{0x} or @code{0X} prefix. The option
+parser validates and converts the argument before passing it to
+the relevant option handler. @code{Host_Wide_Int} should be used with
+options that need to accept very large values. Positive values of
+the argument in excess of @code{HOST_WIDE_INT_M1U} are assigned
+@code{HOST_WIDE_INT_M1U}.
+
+@item IntegerRange(@var{n}, @var{m})
+The options's arguments are integers of type @code{int}. The option's
+parser validates that the value of an option integer argument is within
+the closed range [@var{n}, @var{m}].
+
+@item ByteSize
+A property applicable only to @code{UInteger} or @code{Host_Wide_Int}
+arguments. The option's integer argument is interpreted as if in infinite
+precision using saturation arithmetic in the corresponding type. The argument
+may be followed by a @samp{byte-size} suffix designating a multiple of bytes
+such as @code{kB} and @code{KiB} for kilobyte and kibibyte, respectively,
+@code{MB} and @code{MiB} for megabyte and mebibyte, @code{GB} and @code{GiB}
+for gigabyte and gigibyte, and so on. @code{ByteSize} should be used for
+with options that take a very large argument representing a size in bytes,
+such as @option{-Wlarger-than=}.
+
+@item ToLower
+The option's argument should be converted to lowercase as part of
+putting it in canonical form, and before comparing with the strings
+indicated by any @code{Enum} property.
+
+@item NoDriverArg
+For an option marked @code{Separate}, the option only takes an
+argument in the compiler proper, not in the driver. This is for
+compatibility with existing options that are used both directly and
+via @option{-Wp,}; new options should not have this property.
+
+@item Var(@var{var})
+The state of this option should be stored in variable @var{var}
+(actually a macro for @code{global_options.x_@var{var}}).
+The way that the state is stored depends on the type of option:
+
+@item WarnRemoved
+The option is removed and every usage of such option will
+result in a warning. We use it option backward compatibility.
+
+@item Var(@var{var}, @var{set})
+The option controls an integer variable @var{var} and is active when
+@var{var} equals @var{set}. The option parser will set @var{var} to
+@var{set} when the positive form of the option is used and @code{!@var{set}}
+when the ``no-'' form is used.
+
+@var{var} is declared in the same way as for the single-argument form
+described above.
+
+@itemize @bullet
+@item
+If the option uses the @code{Mask} or @code{InverseMask} properties,
+@var{var} is the integer variable that contains the mask.
+
+@item
+If the option is a normal on/off switch, @var{var} is an integer
+variable that is nonzero when the option is enabled. The options
+parser will set the variable to 1 when the positive form of the
+option is used and 0 when the ``no-'' form is used.
+
+@item
+If the option takes an argument and has the @code{UInteger} property,
+@var{var} is an integer variable that stores the value of the argument.
+
+@item
+If the option takes an argument and has the @code{Enum} property,
+@var{var} is a variable (type given in the @code{Type} property of the
+@samp{Enum} record whose @code{Name} property has the same argument as
+the @code{Enum} property of this option) that stores the value of the
+argument.
+
+@item
+If the option has the @code{Defer} property, @var{var} is a pointer to
+a @code{VEC(cl_deferred_option,heap)} that stores the option for later
+processing. (@var{var} is declared with type @code{void *} and needs
+to be cast to @code{VEC(cl_deferred_option,heap)} before use.)
+
+@item
+Otherwise, if the option takes an argument, @var{var} is a pointer to
+the argument string. The pointer will be null if the argument is optional
+and wasn't given.
+@end itemize
+
+The option-processing script will usually zero-initialize @var{var}.
+You can modify this behavior using @code{Init}.
+
+@item Init(@var{value})
+The variable specified by the @code{Var} property should be statically
+initialized to @var{value}. If more than one option using the same
+variable specifies @code{Init}, all must specify the same initializer.
+
+@item Mask(@var{name})
+The option is associated with a bit in the @code{target_flags}
+variable (@pxref{Run-time Target}) and is active when that bit is set.
+You may also specify @code{Var} to select a variable other than
+@code{target_flags}.
+
+The options-processing script will automatically allocate a unique bit
+for the option. If the option is attached to @samp{target_flags},
+the script will set the macro @code{MASK_@var{name}} to the appropriate
+bitmask. It will also declare a @code{TARGET_@var{name}} macro that has
+the value 1 when the option is active and 0 otherwise. If you use @code{Var}
+to attach the option to a different variable, the bitmask macro with be
+called @code{OPTION_MASK_@var{name}}.
+
+@item InverseMask(@var{othername})
+@itemx InverseMask(@var{othername}, @var{thisname})
+The option is the inverse of another option that has the
+@code{Mask(@var{othername})} property. If @var{thisname} is given,
+the options-processing script will declare a @code{TARGET_@var{thisname}}
+macro that is 1 when the option is active and 0 otherwise.
+
+@item Enum(@var{name})
+The option's argument is a string from the set of strings associated
+with the corresponding @samp{Enum} record. The string is checked and
+converted to the integer specified in the corresponding
+@samp{EnumValue} record before being passed to option handlers.
+
+@item EnumSet
+Must be used together with the @code{Enum(@var{name})} property.
+Corresponding @samp{Enum} record must use @code{Set} properties.
+The option's argument is either a string from the set like for
+@code{Enum(@var{name})}, but with a slightly different behavior that
+the whole @code{Var} isn't overwritten, but only the bits in all the
+enumeration values with the same set bitwise ored together.
+Or option's argument can be a comma separated list of strings where
+each string is from a different @code{Set(@var{number})}.
+
+@item EnumBitSet
+Must be used together with the @code{Enum(@var{name})} property.
+Similar to @samp{EnumSet}, but corresponding @samp{Enum} record must
+not use @code{Set} properties, each @code{EnumValue} should have
+@code{Value} that is a power of 2, each value is treated as its own
+set and its value as the set's mask, so there are no mutually
+exclusive arguments.
+
+@item Defer
+The option should be stored in a vector, specified with @code{Var},
+for later processing.
+
+@item Alias(@var{opt})
+@itemx Alias(@var{opt}, @var{arg})
+@itemx Alias(@var{opt}, @var{posarg}, @var{negarg})
+The option is an alias for @option{-@var{opt}} (or the negative form
+of that option, depending on @code{NegativeAlias}). In the first form,
+any argument passed to the alias is considered to be passed to
+@option{-@var{opt}}, and @option{-@var{opt}} is considered to be
+negated if the alias is used in negated form. In the second form, the
+alias may not be negated or have an argument, and @var{posarg} is
+considered to be passed as an argument to @option{-@var{opt}}. In the
+third form, the alias may not have an argument, if the alias is used
+in the positive form then @var{posarg} is considered to be passed to
+@option{-@var{opt}}, and if the alias is used in the negative form
+then @var{negarg} is considered to be passed to @option{-@var{opt}}.
+
+Aliases should not specify @code{Var} or @code{Mask} or
+@code{UInteger}. Aliases should normally specify the same languages
+as the target of the alias; the flags on the target will be used to
+determine any diagnostic for use of an option for the wrong language,
+while those on the alias will be used to identify what command-line
+text is the option and what text is any argument to that option.
+
+When an @code{Alias} definition is used for an option, driver specs do
+not need to handle it and no @samp{OPT_} enumeration value is defined
+for it; only the canonical form of the option will be seen in those
+places.
+
+@item NegativeAlias
+For an option marked with @code{Alias(@var{opt})}, the option is
+considered to be an alias for the positive form of @option{-@var{opt}}
+if negated and for the negative form of @option{-@var{opt}} if not
+negated. @code{NegativeAlias} may not be used with the forms of
+@code{Alias} taking more than one argument.
+
+@item Ignore
+This option is ignored apart from printing any warning specified using
+@code{Warn}. The option will not be seen by specs and no @samp{OPT_}
+enumeration value is defined for it.
+
+@item SeparateAlias
+For an option marked with @code{Joined}, @code{Separate} and
+@code{Alias}, the option only acts as an alias when passed a separate
+argument; with a joined argument it acts as a normal option, with an
+@samp{OPT_} enumeration value. This is for compatibility with the
+Java @option{-d} option and should not be used for new options.
+
+@item Warn(@var{message})
+If this option is used, output the warning @var{message}.
+@var{message} is a format string, either taking a single operand with
+a @samp{%qs} format which is the option name, or not taking any
+operands, which is passed to the @samp{warning} function. If an alias
+is marked @code{Warn}, the target of the alias must not also be marked
+@code{Warn}.
+
+@item Warning
+This is a warning option and should be shown as such in
+@option{--help} output. This flag does not currently affect anything
+other than @option{--help}.
+
+@item Optimization
+This is an optimization option. It should be shown as such in
+@option{--help} output, and any associated variable named using
+@code{Var} should be saved and restored when the optimization level is
+changed with @code{optimize} attributes.
+
+@item PerFunction
+This is an option that can be overridden on a per-function basis.
+@code{Optimization} implies @code{PerFunction}, but options that do not
+affect executable code generation may use this flag instead, so that the
+option is not taken into account in ways that might affect executable
+code generation.
+
+@item Param
+This is an option that is a parameter.
+
+@item Undocumented
+The option is deliberately missing documentation and should not
+be included in the @option{--help} output.
+
+@item Condition(@var{cond})
+The option should only be accepted if preprocessor condition
+@var{cond} is true. Note that any C declarations associated with the
+option will be present even if @var{cond} is false; @var{cond} simply
+controls whether the option is accepted and whether it is printed in
+the @option{--help} output.
+
+@item Save
+Build the @code{cl_target_option} structure to hold a copy of the
+option, add the functions @code{cl_target_option_save} and
+@code{cl_target_option_restore} to save and restore the options.
+
+@item SetByCombined
+The option may also be set by a combined option such as
+@option{-ffast-math}. This causes the @code{gcc_options} struct to
+have a field @code{frontend_set_@var{name}}, where @code{@var{name}}
+is the name of the field holding the value of this option (without the
+leading @code{x_}). This gives the front end a way to indicate that
+the value has been set explicitly and should not be changed by the
+combined option. For example, some front ends use this to prevent
+@option{-ffast-math} and @option{-fno-fast-math} from changing the
+value of @option{-fmath-errno} for languages that do not use
+@code{errno}.
+
+@item EnabledBy(@var{opt})
+@itemx EnabledBy(@var{opt} || @var{opt2})
+@itemx EnabledBy(@var{opt} && @var{opt2})
+If not explicitly set, the option is set to the value of
+@option{-@var{opt}}; multiple options can be given, separated by
+@code{||}. The third form using @code{&&} specifies that the option is
+only set if both @var{opt} and @var{opt2} are set. The options @var{opt}
+and @var{opt2} must have the @code{Common} property; otherwise, use
+@code{LangEnabledBy}.
+
+@item LangEnabledBy(@var{language}, @var{opt})
+@itemx LangEnabledBy(@var{language}, @var{opt}, @var{posarg}, @var{negarg})
+When compiling for the given language, the option is set to the value
+of @option{-@var{opt}}, if not explicitly set. @var{opt} can be also a list
+of @code{||} separated options. In the second form, if
+@var{opt} is used in the positive form then @var{posarg} is considered
+to be passed to the option, and if @var{opt} is used in the negative
+form then @var{negarg} is considered to be passed to the option. It
+is possible to specify several different languages. Each
+@var{language} must have been declared by an earlier @code{Language}
+record. @xref{Option file format}.
+
+@item NoDWARFRecord
+The option is omitted from the producer string written by
+@option{-grecord-gcc-switches}.
+
+@item PchIgnore
+Even if this is a target option, this option will not be recorded / compared
+to determine if a precompiled header file matches.
+
+@item CPP(@var{var})
+The state of this option should be kept in sync with the preprocessor
+option @var{var}. If this property is set, then properties @code{Var}
+and @code{Init} must be set as well.
+
+@item CppReason(@var{CPP_W_Enum})
+This warning option corresponds to @code{cpplib.h} warning reason code
+@var{CPP_W_Enum}. This should only be used for warning options of the
+C-family front-ends.
+
+@end table
--- /dev/null
+@c markers: BUG TODO
+
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Passes
+@chapter Passes and Files of the Compiler
+@cindex passes and files of the compiler
+@cindex files and passes of the compiler
+@cindex compiler passes and files
+@cindex pass dumps
+
+This chapter is dedicated to giving an overview of the optimization and
+code generation passes of the compiler. In the process, it describes
+some of the language front end interface, though this description is no
+where near complete.
+
+@menu
+* Parsing pass:: The language front end turns text into bits.
+* Gimplification pass:: The bits are turned into something we can optimize.
+* Pass manager:: Sequencing the optimization passes.
+* IPA passes:: Inter-procedural optimizations.
+* Tree SSA passes:: Optimizations on a high-level representation.
+* RTL passes:: Optimizations on a low-level representation.
+* Optimization info:: Dumping optimization information from passes.
+@end menu
+
+@node Parsing pass
+@section Parsing pass
+@cindex GENERIC
+@findex lang_hooks.parse_file
+The language front end is invoked only once, via
+@code{lang_hooks.parse_file}, to parse the entire input. The language
+front end may use any intermediate language representation deemed
+appropriate. The C front end uses GENERIC trees (@pxref{GENERIC}), plus
+a double handful of language specific tree codes defined in
+@file{c-common.def}. The Fortran front end uses a completely different
+private representation.
+
+@cindex GIMPLE
+@cindex gimplification
+@cindex gimplifier
+@cindex language-independent intermediate representation
+@cindex intermediate representation lowering
+@cindex lowering, language-dependent intermediate representation
+At some point the front end must translate the representation used in the
+front end to a representation understood by the language-independent
+portions of the compiler. Current practice takes one of two forms.
+The C front end manually invokes the gimplifier (@pxref{GIMPLE}) on each function,
+and uses the gimplifier callbacks to convert the language-specific tree
+nodes directly to GIMPLE before passing the function off to be compiled.
+The Fortran front end converts from a private representation to GENERIC,
+which is later lowered to GIMPLE when the function is compiled. Which
+route to choose probably depends on how well GENERIC (plus extensions)
+can be made to match up with the source language and necessary parsing
+data structures.
+
+BUG: Gimplification must occur before nested function lowering,
+and nested function lowering must be done by the front end before
+passing the data off to cgraph.
+
+TODO: Cgraph should control nested function lowering. It would
+only be invoked when it is certain that the outer-most function
+is used.
+
+TODO: Cgraph needs a gimplify_function callback. It should be
+invoked when (1) it is certain that the function is used, (2)
+warning flags specified by the user require some amount of
+compilation in order to honor, (3) the language indicates that
+semantic analysis is not complete until gimplification occurs.
+Hum@dots{} this sounds overly complicated. Perhaps we should just
+have the front end gimplify always; in most cases it's only one
+function call.
+
+The front end needs to pass all function definitions and top level
+declarations off to the middle-end so that they can be compiled and
+emitted to the object file. For a simple procedural language, it is
+usually most convenient to do this as each top level declaration or
+definition is seen. There is also a distinction to be made between
+generating functional code and generating complete debug information.
+The only thing that is absolutely required for functional code is that
+function and data @emph{definitions} be passed to the middle-end. For
+complete debug information, function, data and type declarations
+should all be passed as well.
+
+@findex rest_of_decl_compilation
+@findex rest_of_type_compilation
+@findex cgraph_finalize_function
+In any case, the front end needs each complete top-level function or
+data declaration, and each data definition should be passed to
+@code{rest_of_decl_compilation}. Each complete type definition should
+be passed to @code{rest_of_type_compilation}. Each function definition
+should be passed to @code{cgraph_finalize_function}.
+
+TODO: I know rest_of_compilation currently has all sorts of
+RTL generation semantics. I plan to move all code generation
+bits (both Tree and RTL) to compile_function. Should we hide
+cgraph from the front ends and move back to rest_of_compilation
+as the official interface? Possibly we should rename all three
+interfaces such that the names match in some meaningful way and
+that is more descriptive than "rest_of".
+
+The middle-end will, at its option, emit the function and data
+definitions immediately or queue them for later processing.
+
+@node Gimplification pass
+@section Gimplification pass
+
+@cindex gimplification
+@cindex GIMPLE
+@dfn{Gimplification} is a whimsical term for the process of converting
+the intermediate representation of a function into the GIMPLE language
+(@pxref{GIMPLE}). The term stuck, and so words like ``gimplification'',
+``gimplify'', ``gimplifier'' and the like are sprinkled throughout this
+section of code.
+
+While a front end may certainly choose to generate GIMPLE directly if
+it chooses, this can be a moderately complex process unless the
+intermediate language used by the front end is already fairly simple.
+Usually it is easier to generate GENERIC trees plus extensions
+and let the language-independent gimplifier do most of the work.
+
+@findex gimplify_function_tree
+@findex gimplify_expr
+@findex lang_hooks.gimplify_expr
+The main entry point to this pass is @code{gimplify_function_tree}
+located in @file{gimplify.cc}. From here we process the entire
+function gimplifying each statement in turn. The main workhorse
+for this pass is @code{gimplify_expr}. Approximately everything
+passes through here at least once, and it is from here that we
+invoke the @code{lang_hooks.gimplify_expr} callback.
+
+The callback should examine the expression in question and return
+@code{GS_UNHANDLED} if the expression is not a language specific
+construct that requires attention. Otherwise it should alter the
+expression in some way to such that forward progress is made toward
+producing valid GIMPLE@. If the callback is certain that the
+transformation is complete and the expression is valid GIMPLE, it
+should return @code{GS_ALL_DONE}. Otherwise it should return
+@code{GS_OK}, which will cause the expression to be processed again.
+If the callback encounters an error during the transformation (because
+the front end is relying on the gimplification process to finish
+semantic checks), it should return @code{GS_ERROR}.
+
+@node Pass manager
+@section Pass manager
+
+The pass manager is located in @file{passes.cc}, @file{tree-optimize.c}
+and @file{tree-pass.h}.
+It processes passes as described in @file{passes.def}.
+Its job is to run all of the individual passes in the correct order,
+and take care of standard bookkeeping that applies to every pass.
+
+The theory of operation is that each pass defines a structure that
+represents everything we need to know about that pass---when it
+should be run, how it should be run, what intermediate language
+form or on-the-side data structures it needs. We register the pass
+to be run in some particular order, and the pass manager arranges
+for everything to happen in the correct order.
+
+The actuality doesn't completely live up to the theory at present.
+Command-line switches and @code{timevar_id_t} enumerations must still
+be defined elsewhere. The pass manager validates constraints but does
+not attempt to (re-)generate data structures or lower intermediate
+language form based on the requirements of the next pass. Nevertheless,
+what is present is useful, and a far sight better than nothing at all.
+
+Each pass should have a unique name.
+Each pass may have its own dump file (for GCC debugging purposes).
+Passes with a name starting with a star do not dump anything.
+Sometimes passes are supposed to share a dump file / option name.
+To still give these unique names, you can use a prefix that is delimited
+by a space from the part that is used for the dump file / option name.
+E.g. When the pass name is "ud dce", the name used for dump file/options
+is "dce".
+
+TODO: describe the global variables set up by the pass manager,
+and a brief description of how a new pass should use it.
+I need to look at what info RTL passes use first@enddots{}
+
+@node IPA passes
+@section Inter-procedural optimization passes
+@cindex IPA passes
+@cindex inter-procedural optimization passes
+
+The inter-procedural optimization (IPA) passes use call graph
+information to perform transformations across function boundaries.
+IPA is a critical part of link-time optimization (LTO) and
+whole-program (WHOPR) optimization, and these passes are structured
+with the needs of LTO and WHOPR in mind by dividing their operations
+into stages. For detailed discussion of the LTO/WHOPR IPA pass stages
+and interfaces, see @ref{IPA}.
+
+The following briefly describes the inter-procedural optimization (IPA)
+passes, which are split into small IPA passes, regular IPA passes,
+and late IPA passes, according to the LTO/WHOPR processing model.
+
+@menu
+* Small IPA passes::
+* Regular IPA passes::
+* Late IPA passes::
+@end menu
+
+@node Small IPA passes
+@subsection Small IPA passes
+@cindex small IPA passes
+A small IPA pass is a pass derived from @code{simple_ipa_opt_pass}.
+As described in @ref{IPA}, it does everything at once and
+defines only the @emph{Execute} stage. During this
+stage it accesses and modifies the function bodies.
+No @code{generate_summary}, @code{read_summary}, or @code{write_summary}
+hooks are defined.
+
+@itemize @bullet
+@item IPA free lang data
+
+This pass frees resources that are used by the front end but are
+not needed once it is done. It is located in @file{tree.cc} and is described by
+@code{pass_ipa_free_lang_data}.
+
+@item IPA function and variable visibility
+
+This is a local function pass handling visibilities of all symbols. This
+happens before LTO streaming, so @option{-fwhole-program} should be ignored
+at this level. It is located in @file{ipa-visibility.cc} and is described by
+@code{pass_ipa_function_and_variable_visibility}.
+
+@item IPA remove symbols
+
+This pass performs reachability analysis and reclaims all unreachable nodes.
+It is located in @file{passes.cc} and is described by
+@code{pass_ipa_remove_symbols}.
+
+@item IPA OpenACC
+
+This is a pass group for OpenACC processing. It is located in
+@file{tree-ssa-loop.cc} and is described by @code{pass_ipa_oacc}.
+
+@item IPA points-to analysis
+
+This is a tree-based points-to analysis pass. The idea behind this analyzer
+is to generate set constraints from the program, then solve the resulting
+constraints in order to generate the points-to sets. It is located in
+@file{tree-ssa-structalias.cc} and is described by @code{pass_ipa_pta}.
+
+@item IPA OpenACC kernels
+
+This is a pass group for processing OpenACC kernels regions. It is a
+subpass of the IPA OpenACC pass group that runs on offloaded functions
+containing OpenACC kernels loops. It is located in
+@file{tree-ssa-loop.cc} and is described by
+@code{pass_ipa_oacc_kernels}.
+
+@item Target clone
+
+This is a pass for parsing functions with multiple target attributes.
+It is located in @file{multiple_target.cc} and is described by
+@code{pass_target_clone}.
+
+@item IPA auto profile
+
+This pass uses AutoFDO profiling data to annotate the control flow graph.
+It is located in @file{auto-profile.cc} and is described by
+@code{pass_ipa_auto_profile}.
+
+@item IPA tree profile
+
+This pass does profiling for all functions in the call graph.
+It calculates branch
+probabilities and basic block execution counts. It is located
+in @file{tree-profile.cc} and is described by @code{pass_ipa_tree_profile}.
+
+@item IPA free function summary
+
+This pass is a small IPA pass when argument @code{small_p} is true.
+It releases inline function summaries and call summaries.
+It is located in @file{ipa-fnsummary.cc} and is described by
+@code{pass_ipa_free_free_fn_summary}.
+
+@item IPA increase alignment
+
+This pass increases the alignment of global arrays to improve
+vectorization. It is located in @file{tree-vectorizer.cc}
+and is described by @code{pass_ipa_increase_alignment}.
+
+@item IPA transactional memory
+
+This pass is for transactional memory support.
+It is located in @file{trans-mem.cc} and is described by
+@code{pass_ipa_tm}.
+
+@item IPA lower emulated TLS
+
+This pass lowers thread-local storage (TLS) operations
+to emulation functions provided by libgcc.
+It is located in @file{tree-emutls.cc} and is described by
+@code{pass_ipa_lower_emutls}.
+
+@end itemize
+
+@node Regular IPA passes
+@subsection Regular IPA passes
+@cindex regular IPA passes
+
+A regular IPA pass is a pass derived from @code{ipa_opt_pass_d} that
+is executed in WHOPR compilation. Regular IPA passes may have summary
+hooks implemented in any of the LGEN, WPA or LTRANS stages (@pxref{IPA}).
+
+@itemize @bullet
+@item IPA whole program visibility
+
+This pass performs various optimizations involving symbol visibility
+with @option{-fwhole-program}, including symbol privatization,
+discovering local functions, and dismantling comdat groups. It is
+located in @file{ipa-visibility.cc} and is described by
+@code{pass_ipa_whole_program_visibility}.
+
+@item IPA profile
+
+The IPA profile pass propagates profiling frequencies across the call
+graph. It is located in @file{ipa-profile.cc} and is described by
+@code{pass_ipa_profile}.
+
+@item IPA identical code folding
+
+This is the inter-procedural identical code folding pass.
+The goal of this transformation is to discover functions
+and read-only variables that have exactly the same semantics. It is
+located in @file{ipa-icf.cc} and is described by @code{pass_ipa_icf}.
+
+@item IPA devirtualization
+
+This pass performs speculative devirtualization based on the type
+inheritance graph. When a polymorphic call has only one likely target
+in the unit, it is turned into a speculative call. It is located in
+@file{ipa-devirt.cc} and is described by @code{pass_ipa_devirt}.
+
+@item IPA constant propagation
+
+The goal of this pass is to discover functions that are always invoked
+with some arguments with the same known constant values and to modify
+the functions accordingly. It can also do partial specialization and
+type-based devirtualization. It is located in @file{ipa-cp.cc} and is
+described by @code{pass_ipa_cp}.
+
+@item IPA scalar replacement of aggregates
+
+This pass can replace an aggregate parameter with a set of other parameters
+representing part of the original, turning those passed by reference
+into new ones which pass the value directly. It also removes unused
+function return values and unused function parameters. This pass is
+located in @file{ipa-sra.cc} and is described by @code{pass_ipa_sra}.
+
+@item IPA constructor/destructor merge
+
+This pass merges multiple constructors and destructors for static
+objects into single functions. It's only run at LTO time unless the
+target doesn't support constructors and destructors natively. The
+pass is located in @file{ipa.cc} and is described by
+@code{pass_ipa_cdtor_merge}.
+
+@item IPA function summary
+
+This pass provides function analysis for inter-procedural passes.
+It collects estimates of function body size, execution time, and frame
+size for each function. It also estimates information about function
+calls: call statement size, time and how often the parameters change
+for each call. It is located in @file{ipa-fnsummary.cc} and is
+described by @code{pass_ipa_fn_summary}.
+
+@item IPA inline
+
+The IPA inline pass handles function inlining with whole-program
+knowledge. Small functions that are candidates for inlining are
+ordered in increasing badness, bounded by unit growth parameters.
+Unreachable functions are removed from the call graph. Functions called
+once and not exported from the unit are inlined. This pass is located in
+@file{ipa-inline.cc} and is described by @code{pass_ipa_inline}.
+
+@item IPA pure/const analysis
+
+This pass marks functions as being either const (@code{TREE_READONLY}) or
+pure (@code{DECL_PURE_P}). The per-function information is produced
+by @code{pure_const_generate_summary}, then the global information is computed
+by performing a transitive closure over the call graph. It is located in
+@file{ipa-pure-const.cc} and is described by @code{pass_ipa_pure_const}.
+
+@item IPA free function summary
+
+This pass is a regular IPA pass when argument @code{small_p} is false.
+It releases inline function summaries and call summaries.
+It is located in @file{ipa-fnsummary.cc} and is described by
+@code{pass_ipa_free_fn_summary}.
+
+@item IPA reference
+
+This pass gathers information about how variables whose scope is
+confined to the compilation unit are used. It is located in
+@file{ipa-reference.cc} and is described by @code{pass_ipa_reference}.
+
+@item IPA single use
+
+This pass checks whether variables are used by a single function.
+It is located in @file{ipa.cc} and is described by
+@code{pass_ipa_single_use}.
+
+@item IPA comdats
+
+This pass looks for static symbols that are used exclusively
+within one comdat group, and moves them into that comdat group. It is
+located in @file{ipa-comdats.cc} and is described by
+@code{pass_ipa_comdats}.
+
+@end itemize
+
+@node Late IPA passes
+@subsection Late IPA passes
+@cindex late IPA passes
+
+Late IPA passes are simple IPA passes executed after
+the regular passes. In WHOPR mode the passes are executed after
+partitioning and thus see just parts of the compiled unit.
+
+@itemize @bullet
+@item Materialize all clones
+
+Once all functions from compilation unit are in memory, produce all clones
+and update all calls. It is located in @file{ipa.cc} and is described by
+@code{pass_materialize_all_clones}.
+
+@item IPA points-to analysis
+
+Points-to analysis; this is the same as the points-to-analysis pass
+run with the small IPA passes (@pxref{Small IPA passes}).
+
+@item OpenMP simd clone
+
+This is the OpenMP constructs' SIMD clone pass. It creates the appropriate
+SIMD clones for functions tagged as elemental SIMD functions.
+It is located in @file{omp-simd-clone.cc} and is described by
+@code{pass_omp_simd_clone}.
+
+@end itemize
+
+@node Tree SSA passes
+@section Tree SSA passes
+
+The following briefly describes the Tree optimization passes that are
+run after gimplification and what source files they are located in.
+
+@itemize @bullet
+@item Remove useless statements
+
+This pass is an extremely simple sweep across the gimple code in which
+we identify obviously dead code and remove it. Here we do things like
+simplify @code{if} statements with constant conditions, remove
+exception handling constructs surrounding code that obviously cannot
+throw, remove lexical bindings that contain no variables, and other
+assorted simplistic cleanups. The idea is to get rid of the obvious
+stuff quickly rather than wait until later when it's more work to get
+rid of it. This pass is located in @file{tree-cfg.cc} and described by
+@code{pass_remove_useless_stmts}.
+
+@item OpenMP lowering
+
+If OpenMP generation (@option{-fopenmp}) is enabled, this pass lowers
+OpenMP constructs into GIMPLE.
+
+Lowering of OpenMP constructs involves creating replacement
+expressions for local variables that have been mapped using data
+sharing clauses, exposing the control flow of most synchronization
+directives and adding region markers to facilitate the creation of the
+control flow graph. The pass is located in @file{omp-low.cc} and is
+described by @code{pass_lower_omp}.
+
+@item OpenMP expansion
+
+If OpenMP generation (@option{-fopenmp}) is enabled, this pass expands
+parallel regions into their own functions to be invoked by the thread
+library. The pass is located in @file{omp-low.cc} and is described by
+@code{pass_expand_omp}.
+
+@item Lower control flow
+
+This pass flattens @code{if} statements (@code{COND_EXPR})
+and moves lexical bindings (@code{BIND_EXPR}) out of line. After
+this pass, all @code{if} statements will have exactly two @code{goto}
+statements in its @code{then} and @code{else} arms. Lexical binding
+information for each statement will be found in @code{TREE_BLOCK} rather
+than being inferred from its position under a @code{BIND_EXPR}. This
+pass is found in @file{gimple-low.cc} and is described by
+@code{pass_lower_cf}.
+
+@item Lower exception handling control flow
+
+This pass decomposes high-level exception handling constructs
+(@code{TRY_FINALLY_EXPR} and @code{TRY_CATCH_EXPR}) into a form
+that explicitly represents the control flow involved. After this
+pass, @code{lookup_stmt_eh_region} will return a non-negative
+number for any statement that may have EH control flow semantics;
+examine @code{tree_can_throw_internal} or @code{tree_can_throw_external}
+for exact semantics. Exact control flow may be extracted from
+@code{foreach_reachable_handler}. The EH region nesting tree is defined
+in @file{except.h} and built in @file{except.cc}. The lowering pass
+itself is in @file{tree-eh.cc} and is described by @code{pass_lower_eh}.
+
+@item Build the control flow graph
+
+This pass decomposes a function into basic blocks and creates all of
+the edges that connect them. It is located in @file{tree-cfg.cc} and
+is described by @code{pass_build_cfg}.
+
+@item Find all referenced variables
+
+This pass walks the entire function and collects an array of all
+variables referenced in the function, @code{referenced_vars}. The
+index at which a variable is found in the array is used as a UID
+for the variable within this function. This data is needed by the
+SSA rewriting routines. The pass is located in @file{tree-dfa.cc}
+and is described by @code{pass_referenced_vars}.
+
+@item Enter static single assignment form
+
+This pass rewrites the function such that it is in SSA form. After
+this pass, all @code{is_gimple_reg} variables will be referenced by
+@code{SSA_NAME}, and all occurrences of other variables will be
+annotated with @code{VDEFS} and @code{VUSES}; PHI nodes will have
+been inserted as necessary for each basic block. This pass is
+located in @file{tree-ssa.cc} and is described by @code{pass_build_ssa}.
+
+@item Warn for uninitialized variables
+
+This pass scans the function for uses of @code{SSA_NAME}s that
+are fed by default definition. For non-parameter variables, such
+uses are uninitialized. The pass is run twice, before and after
+optimization (if turned on). In the first pass we only warn for uses that are
+positively uninitialized; in the second pass we warn for uses that
+are possibly uninitialized. The pass is located in @file{tree-ssa.cc}
+and is defined by @code{pass_early_warn_uninitialized} and
+@code{pass_late_warn_uninitialized}.
+
+@item Dead code elimination
+
+This pass scans the function for statements without side effects whose
+result is unused. It does not do memory life analysis, so any value
+that is stored in memory is considered used. The pass is run multiple
+times throughout the optimization process. It is located in
+@file{tree-ssa-dce.cc} and is described by @code{pass_dce}.
+
+@item Dominator optimizations
+
+This pass performs trivial dominator-based copy and constant propagation,
+expression simplification, and jump threading. It is run multiple times
+throughout the optimization process. It is located in @file{tree-ssa-dom.cc}
+and is described by @code{pass_dominator}.
+
+@item Forward propagation of single-use variables
+
+This pass attempts to remove redundant computation by substituting
+variables that are used once into the expression that uses them and
+seeing if the result can be simplified. It is located in
+@file{tree-ssa-forwprop.cc} and is described by @code{pass_forwprop}.
+
+@item Copy Renaming
+
+This pass attempts to change the name of compiler temporaries involved in
+copy operations such that SSA->normal can coalesce the copy away. When compiler
+temporaries are copies of user variables, it also renames the compiler
+temporary to the user variable resulting in better use of user symbols. It is
+located in @file{tree-ssa-copyrename.c} and is described by
+@code{pass_copyrename}.
+
+@item PHI node optimizations
+
+This pass recognizes forms of PHI inputs that can be represented as
+conditional expressions and rewrites them into straight line code.
+It is located in @file{tree-ssa-phiopt.cc} and is described by
+@code{pass_phiopt}.
+
+@item May-alias optimization
+
+This pass performs a flow sensitive SSA-based points-to analysis.
+The resulting may-alias, must-alias, and escape analysis information
+is used to promote variables from in-memory addressable objects to
+non-aliased variables that can be renamed into SSA form. We also
+update the @code{VDEF}/@code{VUSE} memory tags for non-renameable
+aggregates so that we get fewer false kills. The pass is located
+in @file{tree-ssa-alias.cc} and is described by @code{pass_may_alias}.
+
+Interprocedural points-to information is located in
+@file{tree-ssa-structalias.cc} and described by @code{pass_ipa_pta}.
+
+@item Profiling
+
+This pass instruments the function in order to collect runtime block
+and value profiling data. Such data may be fed back into the compiler
+on a subsequent run so as to allow optimization based on expected
+execution frequencies. The pass is located in @file{tree-profile.cc} and
+is described by @code{pass_ipa_tree_profile}.
+
+@item Static profile estimation
+
+This pass implements series of heuristics to guess propababilities
+of branches. The resulting predictions are turned into edge profile
+by propagating branches across the control flow graphs.
+The pass is located in @file{tree-profile.cc} and is described by
+@code{pass_profile}.
+
+@item Lower complex arithmetic
+
+This pass rewrites complex arithmetic operations into their component
+scalar arithmetic operations. The pass is located in @file{tree-complex.cc}
+and is described by @code{pass_lower_complex}.
+
+@item Scalar replacement of aggregates
+
+This pass rewrites suitable non-aliased local aggregate variables into
+a set of scalar variables. The resulting scalar variables are
+rewritten into SSA form, which allows subsequent optimization passes
+to do a significantly better job with them. The pass is located in
+@file{tree-sra.cc} and is described by @code{pass_sra}.
+
+@item Dead store elimination
+
+This pass eliminates stores to memory that are subsequently overwritten
+by another store, without any intervening loads. The pass is located
+in @file{tree-ssa-dse.cc} and is described by @code{pass_dse}.
+
+@item Tail recursion elimination
+
+This pass transforms tail recursion into a loop. It is located in
+@file{tree-tailcall.cc} and is described by @code{pass_tail_recursion}.
+
+@item Forward store motion
+
+This pass sinks stores and assignments down the flowgraph closer to their
+use point. The pass is located in @file{tree-ssa-sink.cc} and is
+described by @code{pass_sink_code}.
+
+@item Partial redundancy elimination
+
+This pass eliminates partially redundant computations, as well as
+performing load motion. The pass is located in @file{tree-ssa-pre.cc}
+and is described by @code{pass_pre}.
+
+Just before partial redundancy elimination, if
+@option{-funsafe-math-optimizations} is on, GCC tries to convert
+divisions to multiplications by the reciprocal. The pass is located
+in @file{tree-ssa-math-opts.cc} and is described by
+@code{pass_cse_reciprocal}.
+
+@item Full redundancy elimination
+
+This is a simpler form of PRE that only eliminates redundancies that
+occur on all paths. It is located in @file{tree-ssa-pre.cc} and
+described by @code{pass_fre}.
+
+@item Loop optimization
+
+The main driver of the pass is placed in @file{tree-ssa-loop.cc}
+and described by @code{pass_loop}.
+
+The optimizations performed by this pass are:
+
+Loop invariant motion. This pass moves only invariants that
+would be hard to handle on RTL level (function calls, operations that expand to
+nontrivial sequences of insns). With @option{-funswitch-loops} it also moves
+operands of conditions that are invariant out of the loop, so that we can use
+just trivial invariantness analysis in loop unswitching. The pass also includes
+store motion. The pass is implemented in @file{tree-ssa-loop-im.cc}.
+
+Canonical induction variable creation. This pass creates a simple counter
+for number of iterations of the loop and replaces the exit condition of the
+loop using it, in case when a complicated analysis is necessary to determine
+the number of iterations. Later optimizations then may determine the number
+easily. The pass is implemented in @file{tree-ssa-loop-ivcanon.cc}.
+
+Induction variable optimizations. This pass performs standard induction
+variable optimizations, including strength reduction, induction variable
+merging and induction variable elimination. The pass is implemented in
+@file{tree-ssa-loop-ivopts.cc}.
+
+Loop unswitching. This pass moves the conditional jumps that are invariant
+out of the loops. To achieve this, a duplicate of the loop is created for
+each possible outcome of conditional jump(s). The pass is implemented in
+@file{tree-ssa-loop-unswitch.cc}.
+
+Loop splitting. If a loop contains a conditional statement that is
+always true for one part of the iteration space and false for the other
+this pass splits the loop into two, one dealing with one side the other
+only with the other, thereby removing one inner-loop conditional. The
+pass is implemented in @file{tree-ssa-loop-split.cc}.
+
+The optimizations also use various utility functions contained in
+@file{tree-ssa-loop-manip.cc}, @file{cfgloop.cc}, @file{cfgloopanal.cc} and
+@file{cfgloopmanip.cc}.
+
+Vectorization. This pass transforms loops to operate on vector types
+instead of scalar types. Data parallelism across loop iterations is exploited
+to group data elements from consecutive iterations into a vector and operate
+on them in parallel. Depending on available target support the loop is
+conceptually unrolled by a factor @code{VF} (vectorization factor), which is
+the number of elements operated upon in parallel in each iteration, and the
+@code{VF} copies of each scalar operation are fused to form a vector operation.
+Additional loop transformations such as peeling and versioning may take place
+to align the number of iterations, and to align the memory accesses in the
+loop.
+The pass is implemented in @file{tree-vectorizer.cc} (the main driver),
+@file{tree-vect-loop.cc} and @file{tree-vect-loop-manip.cc} (loop specific parts
+and general loop utilities), @file{tree-vect-slp} (loop-aware SLP
+functionality), @file{tree-vect-stmts.cc}, @file{tree-vect-data-refs.cc} and
+@file{tree-vect-slp-patterns.cc} containing the SLP pattern matcher.
+Analysis of data references is in @file{tree-data-ref.cc}.
+
+SLP Vectorization. This pass performs vectorization of straight-line code. The
+pass is implemented in @file{tree-vectorizer.cc} (the main driver),
+@file{tree-vect-slp.cc}, @file{tree-vect-stmts.cc} and
+@file{tree-vect-data-refs.cc}.
+
+Autoparallelization. This pass splits the loop iteration space to run
+into several threads. The pass is implemented in @file{tree-parloops.cc}.
+
+Graphite is a loop transformation framework based on the polyhedral
+model. Graphite stands for Gimple Represented as Polyhedra. The
+internals of this infrastructure are documented in
+@w{@uref{https://gcc.gnu.org/wiki/Graphite}}. The passes working on
+this representation are implemented in the various @file{graphite-*}
+files.
+
+@item Tree level if-conversion for vectorizer
+
+This pass applies if-conversion to simple loops to help vectorizer.
+We identify if convertible loops, if-convert statements and merge
+basic blocks in one big block. The idea is to present loop in such
+form so that vectorizer can have one to one mapping between statements
+and available vector operations. This pass is located in
+@file{tree-if-conv.cc} and is described by @code{pass_if_conversion}.
+
+@item Conditional constant propagation
+
+This pass relaxes a lattice of values in order to identify those
+that must be constant even in the presence of conditional branches.
+The pass is located in @file{tree-ssa-ccp.cc} and is described
+by @code{pass_ccp}.
+
+A related pass that works on memory loads and stores, and not just
+register values, is located in @file{tree-ssa-ccp.cc} and described by
+@code{pass_store_ccp}.
+
+@item Conditional copy propagation
+
+This is similar to constant propagation but the lattice of values is
+the ``copy-of'' relation. It eliminates redundant copies from the
+code. The pass is located in @file{tree-ssa-copy.cc} and described by
+@code{pass_copy_prop}.
+
+A related pass that works on memory copies, and not just register
+copies, is located in @file{tree-ssa-copy.cc} and described by
+@code{pass_store_copy_prop}.
+
+@item Value range propagation
+
+This transformation is similar to constant propagation but
+instead of propagating single constant values, it propagates
+known value ranges. The implementation is based on Patterson's
+range propagation algorithm (Accurate Static Branch Prediction by
+Value Range Propagation, J. R. C. Patterson, PLDI '95). In
+contrast to Patterson's algorithm, this implementation does not
+propagate branch probabilities nor it uses more than a single
+range per SSA name. This means that the current implementation
+cannot be used for branch prediction (though adapting it would
+not be difficult). The pass is located in @file{tree-vrp.cc} and is
+described by @code{pass_vrp}.
+
+@item Folding built-in functions
+
+This pass simplifies built-in functions, as applicable, with constant
+arguments or with inferable string lengths. It is located in
+@file{tree-ssa-ccp.cc} and is described by @code{pass_fold_builtins}.
+
+@item Split critical edges
+
+This pass identifies critical edges and inserts empty basic blocks
+such that the edge is no longer critical. The pass is located in
+@file{tree-cfg.cc} and is described by @code{pass_split_crit_edges}.
+
+@item Control dependence dead code elimination
+
+This pass is a stronger form of dead code elimination that can
+eliminate unnecessary control flow statements. It is located
+in @file{tree-ssa-dce.cc} and is described by @code{pass_cd_dce}.
+
+@item Tail call elimination
+
+This pass identifies function calls that may be rewritten into
+jumps. No code transformation is actually applied here, but the
+data and control flow problem is solved. The code transformation
+requires target support, and so is delayed until RTL@. In the
+meantime @code{CALL_EXPR_TAILCALL} is set indicating the possibility.
+The pass is located in @file{tree-tailcall.cc} and is described by
+@code{pass_tail_calls}. The RTL transformation is handled by
+@code{fixup_tail_calls} in @file{calls.cc}.
+
+@item Warn for function return without value
+
+For non-void functions, this pass locates return statements that do
+not specify a value and issues a warning. Such a statement may have
+been injected by falling off the end of the function. This pass is
+run last so that we have as much time as possible to prove that the
+statement is not reachable. It is located in @file{tree-cfg.cc} and
+is described by @code{pass_warn_function_return}.
+
+@item Leave static single assignment form
+
+This pass rewrites the function such that it is in normal form. At
+the same time, we eliminate as many single-use temporaries as possible,
+so the intermediate language is no longer GIMPLE, but GENERIC@. The
+pass is located in @file{tree-outof-ssa.cc} and is described by
+@code{pass_del_ssa}.
+
+@item Merge PHI nodes that feed into one another
+
+This is part of the CFG cleanup passes. It attempts to join PHI nodes
+from a forwarder CFG block into another block with PHI nodes. The
+pass is located in @file{tree-cfgcleanup.cc} and is described by
+@code{pass_merge_phi}.
+
+@item Return value optimization
+
+If a function always returns the same local variable, and that local
+variable is an aggregate type, then the variable is replaced with the
+return value for the function (i.e., the function's DECL_RESULT). This
+is equivalent to the C++ named return value optimization applied to
+GIMPLE@. The pass is located in @file{tree-nrv.cc} and is described by
+@code{pass_nrv}.
+
+@item Return slot optimization
+
+If a function returns a memory object and is called as @code{var =
+foo()}, this pass tries to change the call so that the address of
+@code{var} is sent to the caller to avoid an extra memory copy. This
+pass is located in @code{tree-nrv.cc} and is described by
+@code{pass_return_slot}.
+
+@item Optimize calls to @code{__builtin_object_size}
+
+This is a propagation pass similar to CCP that tries to remove calls
+to @code{__builtin_object_size} when the size of the object can be
+computed at compile-time. This pass is located in
+@file{tree-object-size.cc} and is described by
+@code{pass_object_sizes}.
+
+@item Loop invariant motion
+
+This pass removes expensive loop-invariant computations out of loops.
+The pass is located in @file{tree-ssa-loop.cc} and described by
+@code{pass_lim}.
+
+@item Loop nest optimizations
+
+This is a family of loop transformations that works on loop nests. It
+includes loop interchange, scaling, skewing and reversal and they are
+all geared to the optimization of data locality in array traversals
+and the removal of dependencies that hamper optimizations such as loop
+parallelization and vectorization. The pass is located in
+@file{tree-loop-linear.c} and described by
+@code{pass_linear_transform}.
+
+@item Removal of empty loops
+
+This pass removes loops with no code in them. The pass is located in
+@file{tree-ssa-loop-ivcanon.cc} and described by
+@code{pass_empty_loop}.
+
+@item Unrolling of small loops
+
+This pass completely unrolls loops with few iterations. The pass
+is located in @file{tree-ssa-loop-ivcanon.cc} and described by
+@code{pass_complete_unroll}.
+
+@item Predictive commoning
+
+This pass makes the code reuse the computations from the previous
+iterations of the loops, especially loads and stores to memory.
+It does so by storing the values of these computations to a bank
+of temporary variables that are rotated at the end of loop. To avoid
+the need for this rotation, the loop is then unrolled and the copies
+of the loop body are rewritten to use the appropriate version of
+the temporary variable. This pass is located in @file{tree-predcom.cc}
+and described by @code{pass_predcom}.
+
+@item Array prefetching
+
+This pass issues prefetch instructions for array references inside
+loops. The pass is located in @file{tree-ssa-loop-prefetch.cc} and
+described by @code{pass_loop_prefetch}.
+
+@item Reassociation
+
+This pass rewrites arithmetic expressions to enable optimizations that
+operate on them, like redundancy elimination and vectorization. The
+pass is located in @file{tree-ssa-reassoc.cc} and described by
+@code{pass_reassoc}.
+
+@item Optimization of @code{stdarg} functions
+
+This pass tries to avoid the saving of register arguments into the
+stack on entry to @code{stdarg} functions. If the function doesn't
+use any @code{va_start} macros, no registers need to be saved. If
+@code{va_start} macros are used, the @code{va_list} variables don't
+escape the function, it is only necessary to save registers that will
+be used in @code{va_arg} macros. For instance, if @code{va_arg} is
+only used with integral types in the function, floating point
+registers don't need to be saved. This pass is located in
+@code{tree-stdarg.cc} and described by @code{pass_stdarg}.
+
+@end itemize
+
+@node RTL passes
+@section RTL passes
+
+The following briefly describes the RTL generation and optimization
+passes that are run after the Tree optimization passes.
+
+@itemize @bullet
+@item RTL generation
+
+@c Avoiding overfull is tricky here.
+The source files for RTL generation include
+@file{stmt.cc},
+@file{calls.cc},
+@file{expr.cc},
+@file{explow.cc},
+@file{expmed.cc},
+@file{function.cc},
+@file{optabs.cc}
+and @file{emit-rtl.cc}.
+Also, the file
+@file{insn-emit.cc}, generated from the machine description by the
+program @code{genemit}, is used in this pass. The header file
+@file{expr.h} is used for communication within this pass.
+
+@findex genflags
+@findex gencodes
+The header files @file{insn-flags.h} and @file{insn-codes.h},
+generated from the machine description by the programs @code{genflags}
+and @code{gencodes}, tell this pass which standard names are available
+for use and which patterns correspond to them.
+
+@item Generation of exception landing pads
+
+This pass generates the glue that handles communication between the
+exception handling library routines and the exception handlers within
+the function. Entry points in the function that are invoked by the
+exception handling library are called @dfn{landing pads}. The code
+for this pass is located in @file{except.cc}.
+
+@item Control flow graph cleanup
+
+This pass removes unreachable code, simplifies jumps to next, jumps to
+jump, jumps across jumps, etc. The pass is run multiple times.
+For historical reasons, it is occasionally referred to as the ``jump
+optimization pass''. The bulk of the code for this pass is in
+@file{cfgcleanup.cc}, and there are support routines in @file{cfgrtl.cc}
+and @file{jump.cc}.
+
+@item Forward propagation of single-def values
+
+This pass attempts to remove redundant computation by substituting
+variables that come from a single definition, and
+seeing if the result can be simplified. It performs copy propagation
+and addressing mode selection. The pass is run twice, with values
+being propagated into loops only on the second run. The code is
+located in @file{fwprop.cc}.
+
+@item Common subexpression elimination
+
+This pass removes redundant computation within basic blocks, and
+optimizes addressing modes based on cost. The pass is run twice.
+The code for this pass is located in @file{cse.cc}.
+
+@item Global common subexpression elimination
+
+This pass performs two
+different types of GCSE depending on whether you are optimizing for
+size or not (LCM based GCSE tends to increase code size for a gain in
+speed, while Morel-Renvoise based GCSE does not).
+When optimizing for size, GCSE is done using Morel-Renvoise Partial
+Redundancy Elimination, with the exception that it does not try to move
+invariants out of loops---that is left to the loop optimization pass.
+If MR PRE GCSE is done, code hoisting (aka unification) is also done, as
+well as load motion.
+If you are optimizing for speed, LCM (lazy code motion) based GCSE is
+done. LCM is based on the work of Knoop, Ruthing, and Steffen. LCM
+based GCSE also does loop invariant code motion. We also perform load
+and store motion when optimizing for speed.
+Regardless of which type of GCSE is used, the GCSE pass also performs
+global constant and copy propagation.
+The source file for this pass is @file{gcse.cc}, and the LCM routines
+are in @file{lcm.cc}.
+
+@item Loop optimization
+
+This pass performs several loop related optimizations.
+The source files @file{cfgloopanal.cc} and @file{cfgloopmanip.cc} contain
+generic loop analysis and manipulation code. Initialization and finalization
+of loop structures is handled by @file{loop-init.cc}.
+A loop invariant motion pass is implemented in @file{loop-invariant.cc}.
+Basic block level optimizations---unrolling, and peeling loops---
+are implemented in @file{loop-unroll.cc}.
+Replacing of the exit condition of loops by special machine-dependent
+instructions is handled by @file{loop-doloop.cc}.
+
+@item Jump bypassing
+
+This pass is an aggressive form of GCSE that transforms the control
+flow graph of a function by propagating constants into conditional
+branch instructions. The source file for this pass is @file{gcse.cc}.
+
+@item If conversion
+
+This pass attempts to replace conditional branches and surrounding
+assignments with arithmetic, boolean value producing comparison
+instructions, and conditional move instructions. In the very last
+invocation after reload/LRA, it will generate predicated instructions
+when supported by the target. The code is located in @file{ifcvt.cc}.
+
+@item Web construction
+
+This pass splits independent uses of each pseudo-register. This can
+improve effect of the other transformation, such as CSE or register
+allocation. The code for this pass is located in @file{web.cc}.
+
+@item Instruction combination
+
+This pass attempts to combine groups of two or three instructions that
+are related by data flow into single instructions. It combines the
+RTL expressions for the instructions by substitution, simplifies the
+result using algebra, and then attempts to match the result against
+the machine description. The code is located in @file{combine.cc}.
+
+@item Mode switching optimization
+
+This pass looks for instructions that require the processor to be in a
+specific ``mode'' and minimizes the number of mode changes required to
+satisfy all users. What these modes are, and what they apply to are
+completely target-specific. The code for this pass is located in
+@file{mode-switching.cc}.
+
+@cindex modulo scheduling
+@cindex sms, swing, software pipelining
+@item Modulo scheduling
+
+This pass looks at innermost loops and reorders their instructions
+by overlapping different iterations. Modulo scheduling is performed
+immediately before instruction scheduling. The code for this pass is
+located in @file{modulo-sched.cc}.
+
+@item Instruction scheduling
+
+This pass looks for instructions whose output will not be available by
+the time that it is used in subsequent instructions. Memory loads and
+floating point instructions often have this behavior on RISC machines.
+It re-orders instructions within a basic block to try to separate the
+definition and use of items that otherwise would cause pipeline
+stalls. This pass is performed twice, before and after register
+allocation. The code for this pass is located in @file{haifa-sched.cc},
+@file{sched-deps.cc}, @file{sched-ebb.cc}, @file{sched-rgn.cc} and
+@file{sched-vis.c}.
+
+@item Register allocation
+
+These passes make sure that all occurrences of pseudo registers are
+eliminated, either by allocating them to a hard register, replacing
+them by an equivalent expression (e.g.@: a constant) or by placing
+them on the stack. This is done in several subpasses:
+
+@itemize @bullet
+@item
+The integrated register allocator (@acronym{IRA}). It is called
+integrated because coalescing, register live range splitting, and hard
+register preferencing are done on-the-fly during coloring. It also
+has better integration with the reload/LRA pass. Pseudo-registers spilled
+by the allocator or the reload/LRA have still a chance to get
+hard-registers if the reload/LRA evicts some pseudo-registers from
+hard-registers. The allocator helps to choose better pseudos for
+spilling based on their live ranges and to coalesce stack slots
+allocated for the spilled pseudo-registers. IRA is a regional
+register allocator which is transformed into Chaitin-Briggs allocator
+if there is one region. By default, IRA chooses regions using
+register pressure but the user can force it to use one region or
+regions corresponding to all loops.
+
+Source files of the allocator are @file{ira.cc}, @file{ira-build.cc},
+@file{ira-costs.cc}, @file{ira-conflicts.cc}, @file{ira-color.cc},
+@file{ira-emit.cc}, @file{ira-lives}, plus header files @file{ira.h}
+and @file{ira-int.h} used for the communication between the allocator
+and the rest of the compiler and between the IRA files.
+
+@cindex reloading
+@item
+Reloading. This pass renumbers pseudo registers with the hardware
+registers numbers they were allocated. Pseudo registers that did not
+get hard registers are replaced with stack slots. Then it finds
+instructions that are invalid because a value has failed to end up in
+a register, or has ended up in a register of the wrong kind. It fixes
+up these instructions by reloading the problematical values
+temporarily into registers. Additional instructions are generated to
+do the copying.
+
+The reload pass also optionally eliminates the frame pointer and inserts
+instructions to save and restore call-clobbered registers around calls.
+
+Source files are @file{reload.cc} and @file{reload1.cc}, plus the header
+@file{reload.h} used for communication between them.
+
+@cindex Local Register Allocator (LRA)
+@item
+This pass is a modern replacement of the reload pass. Source files
+are @file{lra.cc}, @file{lra-assign.c}, @file{lra-coalesce.cc},
+@file{lra-constraints.cc}, @file{lra-eliminations.cc},
+@file{lra-lives.cc}, @file{lra-remat.cc}, @file{lra-spills.cc}, the
+header @file{lra-int.h} used for communication between them, and the
+header @file{lra.h} used for communication between LRA and the rest of
+compiler.
+
+Unlike the reload pass, intermediate LRA decisions are reflected in
+RTL as much as possible. This reduces the number of target-dependent
+macros and hooks, leaving instruction constraints as the primary
+source of control.
+
+LRA is run on targets for which TARGET_LRA_P returns true.
+@end itemize
+
+@item Basic block reordering
+
+This pass implements profile guided code positioning. If profile
+information is not available, various types of static analysis are
+performed to make the predictions normally coming from the profile
+feedback (IE execution frequency, branch probability, etc). It is
+implemented in the file @file{bb-reorder.cc}, and the various
+prediction routines are in @file{predict.cc}.
+
+@item Variable tracking
+
+This pass computes where the variables are stored at each
+position in code and generates notes describing the variable locations
+to RTL code. The location lists are then generated according to these
+notes to debug information if the debugging information format supports
+location lists. The code is located in @file{var-tracking.cc}.
+
+@item Delayed branch scheduling
+
+This optional pass attempts to find instructions that can go into the
+delay slots of other instructions, usually jumps and calls. The code
+for this pass is located in @file{reorg.cc}.
+
+@item Branch shortening
+
+On many RISC machines, branch instructions have a limited range.
+Thus, longer sequences of instructions must be used for long branches.
+In this pass, the compiler figures out what how far each instruction
+will be from each other instruction, and therefore whether the usual
+instructions, or the longer sequences, must be used for each branch.
+The code for this pass is located in @file{final.cc}.
+
+@item Register-to-stack conversion
+
+Conversion from usage of some hard registers to usage of a register
+stack may be done at this point. Currently, this is supported only
+for the floating-point registers of the Intel 80387 coprocessor. The
+code for this pass is located in @file{reg-stack.cc}.
+
+@item Final
+
+This pass outputs the assembler code for the function. The source files
+are @file{final.cc} plus @file{insn-output.cc}; the latter is generated
+automatically from the machine description by the tool @file{genoutput}.
+The header file @file{conditions.h} is used for communication between
+these files.
+
+@item Debugging information output
+
+This is run after final because it must output the stack slot offsets
+for pseudo registers that did not get hard registers. Source files
+are @file{dwarfout.c} for
+DWARF symbol table format, files @file{dwarf2out.cc} and @file{dwarf2asm.cc}
+for DWARF2 symbol table format, and @file{vmsdbgout.cc} for VMS debug
+symbol table format.
+
+@end itemize
+
+@node Optimization info
+@section Optimization info
+@include optinfo.texi
--- /dev/null
+@c Copyright (C) 2009-2022 Free Software Foundation, Inc.
+@c Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Plugins
+@chapter Plugins
+@cindex Plugins
+
+GCC plugins are loadable modules that provide extra features to the
+compiler. Like GCC itself they can be distributed in source and
+binary forms.
+
+GCC plugins provide developers with a rich subset of
+the GCC API to allow them to extend GCC as they see fit.
+Whether it is writing an additional optimization pass,
+transforming code, or analyzing information, plugins
+can be quite useful.
+
+@menu
+* Plugins loading:: How can we load plugins.
+* Plugin API:: The APIs for plugins.
+* Plugins pass:: How a plugin interact with the pass manager.
+* Plugins GC:: How a plugin Interact with GCC Garbage Collector.
+* Plugins description:: Giving information about a plugin itself.
+* Plugins attr:: Registering custom attributes or pragmas.
+* Plugins recording:: Recording information about pass execution.
+* Plugins gate:: Controlling which passes are being run.
+* Plugins tracking:: Keeping track of available passes.
+* Plugins building:: How can we build a plugin.
+@end menu
+
+@node Plugins loading
+@section Loading Plugins
+
+Plugins are supported on platforms that support @option{-ldl
+-rdynamic} as well as Windows/MinGW. They are loaded by the compiler
+using @code{dlopen} or equivalent and invoked at pre-determined
+locations in the compilation process.
+
+Plugins are loaded with
+
+@option{-fplugin=/path/to/@var{name}.@var{ext}} @option{-fplugin-arg-@var{name}-@var{key1}[=@var{value1}]}
+
+Where @var{name} is the plugin name and @var{ext} is the platform-specific
+dynamic library extension. It should be @code{dll} on Windows/MinGW,
+@code{dylib} on Darwin/Mac OS X, and @code{so} on all other platforms.
+The plugin arguments are parsed by GCC and passed to respective
+plugins as key-value pairs. Multiple plugins can be invoked by
+specifying multiple @option{-fplugin} arguments.
+
+A plugin can be simply given by its short name (no dots or
+slashes). When simply passing @option{-fplugin=@var{name}}, the plugin is
+loaded from the @file{plugin} directory, so @option{-fplugin=@var{name}} is
+the same as @option{-fplugin=`gcc -print-file-name=plugin`/@var{name}.@var{ext}},
+using backquote shell syntax to query the @file{plugin} directory.
+
+@node Plugin API
+@section Plugin API
+
+Plugins are activated by the compiler at specific events as defined in
+@file{gcc-plugin.h}. For each event of interest, the plugin should
+call @code{register_callback} specifying the name of the event and
+address of the callback function that will handle that event.
+
+The header @file{gcc-plugin.h} must be the first gcc header to be included.
+
+@subsection Plugin license check
+
+Every plugin should define the global symbol @code{plugin_is_GPL_compatible}
+to assert that it has been licensed under a GPL-compatible license.
+If this symbol does not exist, the compiler will emit a fatal error
+and exit with the error message:
+
+@smallexample
+fatal error: plugin @var{name} is not licensed under a GPL-compatible license
+@var{name}: undefined symbol: plugin_is_GPL_compatible
+compilation terminated
+@end smallexample
+
+The declared type of the symbol should be int, to match a forward declaration
+in @file{gcc-plugin.h} that suppresses C++ mangling. It does not need to be in
+any allocated section, though. The compiler merely asserts that
+the symbol exists in the global scope. Something like this is enough:
+
+@smallexample
+int plugin_is_GPL_compatible;
+@end smallexample
+
+@subsection Plugin initialization
+
+Every plugin should export a function called @code{plugin_init} that
+is called right after the plugin is loaded. This function is
+responsible for registering all the callbacks required by the plugin
+and do any other required initialization.
+
+This function is called from @code{compile_file} right before invoking
+the parser. The arguments to @code{plugin_init} are:
+
+@itemize @bullet
+@item @code{plugin_info}: Plugin invocation information.
+@item @code{version}: GCC version.
+@end itemize
+
+The @code{plugin_info} struct is defined as follows:
+
+@smallexample
+struct plugin_name_args
+@{
+ char *base_name; /* Short name of the plugin
+ (filename without .so suffix). */
+ const char *full_name; /* Path to the plugin as specified with
+ -fplugin=. */
+ int argc; /* Number of arguments specified with
+ -fplugin-arg-.... */
+ struct plugin_argument *argv; /* Array of ARGC key-value pairs. */
+ const char *version; /* Version string provided by plugin. */
+ const char *help; /* Help string provided by plugin. */
+@}
+@end smallexample
+
+If initialization fails, @code{plugin_init} must return a non-zero
+value. Otherwise, it should return 0.
+
+The version of the GCC compiler loading the plugin is described by the
+following structure:
+
+@smallexample
+struct plugin_gcc_version
+@{
+ const char *basever;
+ const char *datestamp;
+ const char *devphase;
+ const char *revision;
+ const char *configuration_arguments;
+@};
+@end smallexample
+
+The function @code{plugin_default_version_check} takes two pointers to
+such structure and compare them field by field. It can be used by the
+plugin's @code{plugin_init} function.
+
+The version of GCC used to compile the plugin can be found in the symbol
+@code{gcc_version} defined in the header @file{plugin-version.h}. The
+recommended version check to perform looks like
+
+@smallexample
+#include "plugin-version.h"
+...
+
+int
+plugin_init (struct plugin_name_args *plugin_info,
+ struct plugin_gcc_version *version)
+@{
+ if (!plugin_default_version_check (version, &gcc_version))
+ return 1;
+
+@}
+@end smallexample
+
+but you can also check the individual fields if you want a less strict check.
+
+@subsection Plugin callbacks
+
+Callback functions have the following prototype:
+
+@smallexample
+/* The prototype for a plugin callback function.
+ gcc_data - event-specific data provided by GCC
+ user_data - plugin-specific data provided by the plug-in. */
+typedef void (*plugin_callback_func)(void *gcc_data, void *user_data);
+@end smallexample
+
+Callbacks can be invoked at the following pre-determined events:
+
+
+@smallexample
+enum plugin_event
+@{
+ PLUGIN_START_PARSE_FUNCTION, /* Called before parsing the body of a function. */
+ PLUGIN_FINISH_PARSE_FUNCTION, /* After finishing parsing a function. */
+ PLUGIN_PASS_MANAGER_SETUP, /* To hook into pass manager. */
+ PLUGIN_FINISH_TYPE, /* After finishing parsing a type. */
+ PLUGIN_FINISH_DECL, /* After finishing parsing a declaration. */
+ PLUGIN_FINISH_UNIT, /* Useful for summary processing. */
+ PLUGIN_PRE_GENERICIZE, /* Allows to see low level AST in C and C++ frontends. */
+ PLUGIN_FINISH, /* Called before GCC exits. */
+ PLUGIN_INFO, /* Information about the plugin. */
+ PLUGIN_GGC_START, /* Called at start of GCC Garbage Collection. */
+ PLUGIN_GGC_MARKING, /* Extend the GGC marking. */
+ PLUGIN_GGC_END, /* Called at end of GGC. */
+ PLUGIN_REGISTER_GGC_ROOTS, /* Register an extra GGC root table. */
+ PLUGIN_ATTRIBUTES, /* Called during attribute registration */
+ PLUGIN_START_UNIT, /* Called before processing a translation unit. */
+ PLUGIN_PRAGMAS, /* Called during pragma registration. */
+ /* Called before first pass from all_passes. */
+ PLUGIN_ALL_PASSES_START,
+ /* Called after last pass from all_passes. */
+ PLUGIN_ALL_PASSES_END,
+ /* Called before first ipa pass. */
+ PLUGIN_ALL_IPA_PASSES_START,
+ /* Called after last ipa pass. */
+ PLUGIN_ALL_IPA_PASSES_END,
+ /* Allows to override pass gate decision for current_pass. */
+ PLUGIN_OVERRIDE_GATE,
+ /* Called before executing a pass. */
+ PLUGIN_PASS_EXECUTION,
+ /* Called before executing subpasses of a GIMPLE_PASS in
+ execute_ipa_pass_list. */
+ PLUGIN_EARLY_GIMPLE_PASSES_START,
+ /* Called after executing subpasses of a GIMPLE_PASS in
+ execute_ipa_pass_list. */
+ PLUGIN_EARLY_GIMPLE_PASSES_END,
+ /* Called when a pass is first instantiated. */
+ PLUGIN_NEW_PASS,
+/* Called when a file is #include-d or given via the #line directive.
+ This could happen many times. The event data is the included file path,
+ as a const char* pointer. */
+ PLUGIN_INCLUDE_FILE,
+
+ /* Called when -fanalyzer starts. The event data is an
+ ana::plugin_analyzer_init_iface *. */
+ PLUGIN_ANALYZER_INIT,
+
+ PLUGIN_EVENT_FIRST_DYNAMIC /* Dummy event used for indexing callback
+ array. */
+@};
+@end smallexample
+
+In addition, plugins can also look up the enumerator of a named event,
+and / or generate new events dynamically, by calling the function
+@code{get_named_event_id}.
+
+To register a callback, the plugin calls @code{register_callback} with
+the arguments:
+
+@itemize
+@item @code{char *name}: Plugin name.
+@item @code{int event}: The event code.
+@item @code{plugin_callback_func callback}: The function that handles @code{event}.
+@item @code{void *user_data}: Pointer to plugin-specific data.
+@end itemize
+
+For the @i{PLUGIN_PASS_MANAGER_SETUP}, @i{PLUGIN_INFO}, and
+@i{PLUGIN_REGISTER_GGC_ROOTS} pseudo-events the @code{callback} should be null,
+and the @code{user_data} is specific.
+
+When the @i{PLUGIN_PRAGMAS} event is triggered (with a null pointer as
+data from GCC), plugins may register their own pragmas. Notice that
+pragmas are not available from @file{lto1}, so plugins used with
+@code{-flto} option to GCC during link-time optimization cannot use
+pragmas and do not even see functions like @code{c_register_pragma} or
+@code{pragma_lex}.
+
+The @i{PLUGIN_INCLUDE_FILE} event, with a @code{const char*} file path as
+GCC data, is triggered for processing of @code{#include} or
+@code{#line} directives.
+
+The @i{PLUGIN_FINISH} event is the last time that plugins can call GCC
+functions, notably emit diagnostics with @code{warning}, @code{error}
+etc.
+
+
+@node Plugins pass
+@section Interacting with the pass manager
+
+There needs to be a way to add/reorder/remove passes dynamically. This
+is useful for both analysis plugins (plugging in after a certain pass
+such as CFG or an IPA pass) and optimization plugins.
+
+Basic support for inserting new passes or replacing existing passes is
+provided. A plugin registers a new pass with GCC by calling
+@code{register_callback} with the @code{PLUGIN_PASS_MANAGER_SETUP}
+event and a pointer to a @code{struct register_pass_info} object defined as follows
+
+@smallexample
+enum pass_positioning_ops
+@{
+ PASS_POS_INSERT_AFTER, // Insert after the reference pass.
+ PASS_POS_INSERT_BEFORE, // Insert before the reference pass.
+ PASS_POS_REPLACE // Replace the reference pass.
+@};
+
+struct register_pass_info
+@{
+ struct opt_pass *pass; /* New pass provided by the plugin. */
+ const char *reference_pass_name; /* Name of the reference pass for hooking
+ up the new pass. */
+ int ref_pass_instance_number; /* Insert the pass at the specified
+ instance number of the reference pass. */
+ /* Do it for every instance if it is 0. */
+ enum pass_positioning_ops pos_op; /* how to insert the new pass. */
+@};
+
+
+/* Sample plugin code that registers a new pass. */
+int
+plugin_init (struct plugin_name_args *plugin_info,
+ struct plugin_gcc_version *version)
+@{
+ struct register_pass_info pass_info;
+
+ ...
+
+ /* Code to fill in the pass_info object with new pass information. */
+
+ ...
+
+ /* Register the new pass. */
+ register_callback (plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &pass_info);
+
+ ...
+@}
+@end smallexample
+
+
+@node Plugins GC
+@section Interacting with the GCC Garbage Collector
+
+Some plugins may want to be informed when GGC (the GCC Garbage
+Collector) is running. They can register callbacks for the
+@code{PLUGIN_GGC_START} and @code{PLUGIN_GGC_END} events (for which
+the callback is called with a null @code{gcc_data}) to be notified of
+the start or end of the GCC garbage collection.
+
+Some plugins may need to have GGC mark additional data. This can be
+done by registering a callback (called with a null @code{gcc_data})
+for the @code{PLUGIN_GGC_MARKING} event. Such callbacks can call the
+@code{ggc_set_mark} routine, preferably through the @code{ggc_mark} macro
+(and conversely, these routines should usually not be used in plugins
+outside of the @code{PLUGIN_GGC_MARKING} event). Plugins that wish to hold
+weak references to gc data may also use this event to drop weak references when
+the object is about to be collected. The @code{ggc_marked_p} function can be
+used to tell if an object is marked, or is about to be collected. The
+@code{gt_clear_cache} overloads which some types define may also be of use in
+managing weak references.
+
+Some plugins may need to add extra GGC root tables, e.g.@: to handle their own
+@code{GTY}-ed data. This can be done with the @code{PLUGIN_REGISTER_GGC_ROOTS}
+pseudo-event with a null callback and the extra root table (of type @code{struct
+ggc_root_tab*}) as @code{user_data}. Running the
+ @code{gengtype -p @var{source-dir} @var{file-list} @var{plugin*.c} ...}
+utility generates these extra root tables.
+
+You should understand the details of memory management inside GCC
+before using @code{PLUGIN_GGC_MARKING} or @code{PLUGIN_REGISTER_GGC_ROOTS}.
+
+
+@node Plugins description
+@section Giving information about a plugin
+
+A plugin should give some information to the user about itself. This
+uses the following structure:
+
+@smallexample
+struct plugin_info
+@{
+ const char *version;
+ const char *help;
+@};
+@end smallexample
+
+Such a structure is passed as the @code{user_data} by the plugin's
+init routine using @code{register_callback} with the
+@code{PLUGIN_INFO} pseudo-event and a null callback.
+
+@node Plugins attr
+@section Registering custom attributes or pragmas
+
+For analysis (or other) purposes it is useful to be able to add custom
+attributes or pragmas.
+
+The @code{PLUGIN_ATTRIBUTES} callback is called during attribute
+registration. Use the @code{register_attribute} function to register
+custom attributes.
+
+@smallexample
+/* Attribute handler callback */
+static tree
+handle_user_attribute (tree *node, tree name, tree args,
+ int flags, bool *no_add_attrs)
+@{
+ return NULL_TREE;
+@}
+
+/* Attribute definition */
+static struct attribute_spec user_attr =
+ @{ "user", 1, 1, false, false, false, false, handle_user_attribute, NULL @};
+
+/* Plugin callback called during attribute registration.
+Registered with register_callback (plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL)
+*/
+static void
+register_attributes (void *event_data, void *data)
+@{
+ warning (0, G_("Callback to register attributes"));
+ register_attribute (&user_attr);
+@}
+
+@end smallexample
+
+
+The @i{PLUGIN_PRAGMAS} callback is called once during pragmas
+registration. Use the @code{c_register_pragma},
+@code{c_register_pragma_with_data},
+@code{c_register_pragma_with_expansion},
+@code{c_register_pragma_with_expansion_and_data} functions to register
+custom pragmas and their handlers (which often want to call
+@code{pragma_lex}) from @file{c-family/c-pragma.h}.
+
+@smallexample
+/* Plugin callback called during pragmas registration. Registered with
+ register_callback (plugin_name, PLUGIN_PRAGMAS,
+ register_my_pragma, NULL);
+*/
+static void
+register_my_pragma (void *event_data, void *data)
+@{
+ warning (0, G_("Callback to register pragmas"));
+ c_register_pragma ("GCCPLUGIN", "sayhello", handle_pragma_sayhello);
+@}
+@end smallexample
+
+It is suggested to pass @code{"GCCPLUGIN"} (or a short name identifying
+your plugin) as the ``space'' argument of your pragma.
+
+Pragmas registered with @code{c_register_pragma_with_expansion} or
+@code{c_register_pragma_with_expansion_and_data} support
+preprocessor expansions. For example:
+
+@smallexample
+#define NUMBER 10
+#pragma GCCPLUGIN foothreshold (NUMBER)
+@end smallexample
+
+@node Plugins recording
+@section Recording information about pass execution
+
+The event PLUGIN_PASS_EXECUTION passes the pointer to the executed pass
+(the same as current_pass) as @code{gcc_data} to the callback. You can also
+inspect cfun to find out about which function this pass is executed for.
+Note that this event will only be invoked if the gate check (if
+applicable, modified by PLUGIN_OVERRIDE_GATE) succeeds.
+You can use other hooks, like @code{PLUGIN_ALL_PASSES_START},
+@code{PLUGIN_ALL_PASSES_END}, @code{PLUGIN_ALL_IPA_PASSES_START},
+@code{PLUGIN_ALL_IPA_PASSES_END}, @code{PLUGIN_EARLY_GIMPLE_PASSES_START},
+and/or @code{PLUGIN_EARLY_GIMPLE_PASSES_END} to manipulate global state
+in your plugin(s) in order to get context for the pass execution.
+
+
+@node Plugins gate
+@section Controlling which passes are being run
+
+After the original gate function for a pass is called, its result
+- the gate status - is stored as an integer.
+Then the event @code{PLUGIN_OVERRIDE_GATE} is invoked, with a pointer
+to the gate status in the @code{gcc_data} parameter to the callback function.
+A nonzero value of the gate status means that the pass is to be executed.
+You can both read and write the gate status via the passed pointer.
+
+
+@node Plugins tracking
+@section Keeping track of available passes
+
+When your plugin is loaded, you can inspect the various
+pass lists to determine what passes are available. However, other
+plugins might add new passes. Also, future changes to GCC might cause
+generic passes to be added after plugin loading.
+When a pass is first added to one of the pass lists, the event
+@code{PLUGIN_NEW_PASS} is invoked, with the callback parameter
+@code{gcc_data} pointing to the new pass.
+
+
+@node Plugins building
+@section Building GCC plugins
+
+If plugins are enabled, GCC installs the headers needed to build a
+plugin (somewhere in the installation tree, e.g.@: under
+@file{/usr/local}). In particular a @file{plugin/include} directory
+is installed, containing all the header files needed to build plugins.
+
+On most systems, you can query this @code{plugin} directory by
+invoking @command{gcc -print-file-name=plugin} (replace if needed
+@command{gcc} with the appropriate program path).
+
+Inside plugins, this @code{plugin} directory name can be queried by
+calling @code{default_plugin_dir_name ()}.
+
+Plugins may know, when they are compiled, the GCC version for which
+@file{plugin-version.h} is provided. The constant macros
+@code{GCCPLUGIN_VERSION_MAJOR}, @code{GCCPLUGIN_VERSION_MINOR},
+@code{GCCPLUGIN_VERSION_PATCHLEVEL}, @code{GCCPLUGIN_VERSION} are
+integer numbers, so a plugin could ensure it is built for GCC 4.7 with
+@smallexample
+#if GCCPLUGIN_VERSION != 4007
+#error this GCC plugin is for GCC 4.7
+#endif
+@end smallexample
+
+The following GNU Makefile excerpt shows how to build a simple plugin:
+
+@smallexample
+HOST_GCC=g++
+TARGET_GCC=gcc
+PLUGIN_SOURCE_FILES= plugin1.c plugin2.cc
+GCCPLUGINS_DIR:= $(shell $(TARGET_GCC) -print-file-name=plugin)
+CXXFLAGS+= -I$(GCCPLUGINS_DIR)/include -fPIC -fno-rtti -O2
+
+plugin.so: $(PLUGIN_SOURCE_FILES)
+ $(HOST_GCC) -shared $(CXXFLAGS) $^ -o $@@
+@end smallexample
+
+A single source file plugin may be built with @code{g++ -I`gcc
+-print-file-name=plugin`/include -fPIC -shared -fno-rtti -O2 plugin.cc -o
+plugin.so}, using backquote shell syntax to query the @file{plugin}
+directory.
+
+Plugin support on Windows/MinGW has a number of limitations and
+additional requirements. When building a plugin on Windows we have to
+link an import library for the corresponding backend executable, for
+example, @file{cc1.exe}, @file{cc1plus.exe}, etc., in order to gain
+access to the symbols provided by GCC. This means that on Windows a
+plugin is language-specific, for example, for C, C++, etc. If you wish
+to use your plugin with multiple languages, then you will need to
+build multiple plugin libraries and either instruct your users on how
+to load the correct version or provide a compiler wrapper that does
+this automatically.
+
+Additionally, on Windows the plugin library has to export the
+@code{plugin_is_GPL_compatible} and @code{plugin_init} symbols. If you
+do not wish to modify the source code of your plugin, then you can use
+the @option{-Wl,--export-all-symbols} option or provide a suitable DEF
+file. Alternatively, you can export just these two symbols by decorating
+them with @code{__declspec(dllexport)}, for example:
+
+@smallexample
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int plugin_is_GPL_compatible;
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int plugin_init (plugin_name_args *, plugin_gcc_version *)
+@end smallexample
+
+The import libraries are installed into the @code{plugin} directory
+and their names are derived by appending the @code{.a} extension to
+the backend executable names, for example, @file{cc1.exe.a},
+@file{cc1plus.exe.a}, etc. The following command line shows how to
+build the single source file plugin on Windows to be used with the C++
+compiler:
+
+@smallexample
+g++ -I`gcc -print-file-name=plugin`/include -shared -Wl,--export-all-symbols \
+-o plugin.dll plugin.cc `gcc -print-file-name=plugin`/cc1plus.exe.a
+@end smallexample
+
+When a plugin needs to use @command{gengtype}, be sure that both
+@file{gengtype} and @file{gtype.state} have the same version as the
+GCC for which the plugin is built.
--- /dev/null
+@node poly_int
+@chapter Sizes and offsets as runtime invariants
+@cindex polynomial integers
+@findex poly_int
+
+GCC allows the size of a hardware register to be a runtime invariant
+rather than a compile-time constant. This in turn means that various
+sizes and offsets must also be runtime invariants rather than
+compile-time constants, such as:
+
+@itemize @bullet
+@item
+the size of a general @code{machine_mode} (@pxref{Machine Modes});
+
+@item
+the size of a spill slot;
+
+@item
+the offset of something within a stack frame;
+
+@item
+the number of elements in a vector;
+
+@item
+the size and offset of a @code{mem} rtx (@pxref{Regs and Memory}); and
+
+@item
+the byte offset in a @code{subreg} rtx (@pxref{Regs and Memory}).
+@end itemize
+
+The motivating example is the Arm SVE ISA, whose vector registers can be
+any multiple of 128 bits between 128 and 2048 inclusive. The compiler
+normally produces code that works for all SVE register sizes, with the
+actual size only being known at runtime.
+
+GCC's main representation of such runtime invariants is the
+@code{poly_int} class. This chapter describes what @code{poly_int}
+does, lists the available operations, and gives some general
+usage guidelines.
+
+@menu
+* Overview of @code{poly_int}::
+* Consequences of using @code{poly_int}::
+* Comparisons involving @code{poly_int}::
+* Arithmetic on @code{poly_int}s::
+* Alignment of @code{poly_int}s::
+* Computing bounds on @code{poly_int}s::
+* Converting @code{poly_int}s::
+* Miscellaneous @code{poly_int} routines::
+* Guidelines for using @code{poly_int}::
+@end menu
+
+@node Overview of @code{poly_int}
+@section Overview of @code{poly_int}
+
+@cindex @code{poly_int}, runtime value
+We define indeterminates @var{x1}, @dots{}, @var{xn} whose values are
+only known at runtime and use polynomials of the form:
+
+@smallexample
+@var{c0} + @var{c1} * @var{x1} + @dots{} + @var{cn} * @var{xn}
+@end smallexample
+
+to represent a size or offset whose value might depend on some
+of these indeterminates. The coefficients @var{c0}, @dots{}, @var{cn}
+are always known at compile time, with the @var{c0} term being the
+``constant'' part that does not depend on any runtime value.
+
+GCC uses the @code{poly_int} class to represent these coefficients.
+The class has two template parameters: the first specifies the number of
+coefficients (@var{n} + 1) and the second specifies the type of the
+coefficients. For example, @samp{poly_int<2, unsigned short>} represents
+a polynomial with two coefficients (and thus one indeterminate), with each
+coefficient having type @code{unsigned short}. When @var{n} is 0,
+the class degenerates to a single compile-time constant @var{c0}.
+
+@cindex @code{poly_int}, template parameters
+@findex NUM_POLY_INT_COEFFS
+The number of coefficients needed for compilation is a fixed
+property of each target and is specified by the configuration macro
+@code{NUM_POLY_INT_COEFFS}. The default value is 1, since most targets
+do not have such runtime invariants. Targets that need a different
+value should @code{#define} the macro in their @file{@var{cpu}-modes.def}
+file. @xref{Back End}.
+
+@cindex @code{poly_int}, invariant range
+@code{poly_int} makes the simplifying requirement that each indeterminate
+must be a nonnegative integer. An indeterminate value of 0 should usually
+represent the minimum possible runtime value, with @var{c0} specifying
+the value in that case.
+
+For example, when targetting the Arm SVE ISA, the single indeterminate
+represents the number of 128-bit blocks in a vector @emph{beyond the minimum
+length of 128 bits}. Thus the number of 64-bit doublewords in a vector
+is 2 + 2 * @var{x1}. If an aggregate has a single SVE vector and 16
+additional bytes, its total size is 32 + 16 * @var{x1} bytes.
+
+The header file @file{poly-int-types.h} provides typedefs for the
+most common forms of @code{poly_int}, all having
+@code{NUM_POLY_INT_COEFFS} coefficients:
+
+@cindex @code{poly_int}, main typedefs
+@table @code
+@item poly_uint16
+a @samp{poly_int} with @code{unsigned short} coefficients.
+
+@item poly_int64
+a @samp{poly_int} with @code{HOST_WIDE_INT} coefficients.
+
+@item poly_uint64
+a @samp{poly_int} with @code{unsigned HOST_WIDE_INT} coefficients.
+
+@item poly_offset_int
+a @samp{poly_int} with @code{offset_int} coefficients.
+
+@item poly_wide_int
+a @samp{poly_int} with @code{wide_int} coefficients.
+
+@item poly_widest_int
+a @samp{poly_int} with @code{widest_int} coefficients.
+@end table
+
+Since the main purpose of @code{poly_int} is to represent sizes and
+offsets, the last two typedefs are only rarely used.
+
+@node Consequences of using @code{poly_int}
+@section Consequences of using @code{poly_int}
+
+The two main consequences of using polynomial sizes and offsets are that:
+
+@itemize
+@item
+there is no total ordering between the values at compile time, and
+
+@item
+some operations might yield results that cannot be expressed as a
+@code{poly_int}.
+@end itemize
+
+For example, if @var{x} is a runtime invariant, we cannot tell at
+compile time whether:
+
+@smallexample
+3 + 4@var{x} <= 1 + 5@var{x}
+@end smallexample
+
+since the condition is false when @var{x} <= 1 and true when @var{x} >= 2.
+
+Similarly, @code{poly_int} cannot represent the result of:
+
+@smallexample
+(3 + 4@var{x}) * (1 + 5@var{x})
+@end smallexample
+
+since it cannot (and in practice does not need to) store powers greater
+than one. It also cannot represent the result of:
+
+@smallexample
+(3 + 4@var{x}) / (1 + 5@var{x})
+@end smallexample
+
+The following sections describe how we deal with these restrictions.
+
+@cindex @code{poly_int}, use in target-independent code
+As described earlier, a @code{poly_int<1, @var{T}>} has no indeterminates
+and so degenerates to a compile-time constant of type @var{T}. It would
+be possible in that case to do all normal arithmetic on the @var{T},
+and to compare the @var{T} using the normal C++ operators. We deliberately
+prevent target-independent code from doing this, since the compiler needs
+to support other @code{poly_int<@var{n}, @var{T}>} as well, regardless of
+the current target's @code{NUM_POLY_INT_COEFFS}.
+
+@cindex @code{poly_int}, use in target-specific code
+However, it would be very artificial to force target-specific code
+to follow these restrictions if the target has no runtime indeterminates.
+There is therefore an implicit conversion from @code{poly_int<1, @var{T}>}
+to @var{T} when compiling target-specific translation units.
+
+@node Comparisons involving @code{poly_int}
+@section Comparisons involving @code{poly_int}
+
+In general we need to compare sizes and offsets in two situations:
+those in which the values need to be ordered, and those in which
+the values can be unordered. More loosely, the distinction is often
+between values that have a definite link (usually because they refer to the
+same underlying register or memory location) and values that have
+no definite link. An example of the former is the relationship between
+the inner and outer sizes of a subreg, where we must know at compile time
+whether the subreg is paradoxical, partial, or complete. An example of
+the latter is alias analysis: we might want to check whether two
+arbitrary memory references overlap.
+
+Referring back to the examples in the previous section, it makes sense
+to ask whether a memory reference of size @samp{3 + 4@var{x}} overlaps
+one of size @samp{1 + 5@var{x}}, but it does not make sense to have a
+subreg in which the outer mode has @samp{3 + 4@var{x}} bytes and the
+inner mode has @samp{1 + 5@var{x}} bytes (or vice versa). Such subregs
+are always invalid and should trigger an internal compiler error
+if formed.
+
+The underlying operators are the same in both cases, but the distinction
+affects how they are used.
+
+@menu
+* Comparison functions for @code{poly_int}::
+* Properties of the @code{poly_int} comparisons::
+* Comparing potentially-unordered @code{poly_int}s::
+* Comparing ordered @code{poly_int}s::
+* Checking for a @code{poly_int} marker value::
+* Range checks on @code{poly_int}s::
+* Sorting @code{poly_int}s::
+@end menu
+
+@node Comparison functions for @code{poly_int}
+@subsection Comparison functions for @code{poly_int}
+
+@code{poly_int} provides the following routines for checking whether
+a particular condition ``may be'' (might be) true:
+
+@example
+maybe_lt maybe_le maybe_eq maybe_ge maybe_gt
+ maybe_ne
+@end example
+
+The functions have their natural meaning:
+
+@table @samp
+@item maybe_lt(@var{a}, @var{b})
+Return true if @var{a} might be less than @var{b}.
+
+@item maybe_le(@var{a}, @var{b})
+Return true if @var{a} might be less than or equal to @var{b}.
+
+@item maybe_eq(@var{a}, @var{b})
+Return true if @var{a} might be equal to @var{b}.
+
+@item maybe_ne(@var{a}, @var{b})
+Return true if @var{a} might not be equal to @var{b}.
+
+@item maybe_ge(@var{a}, @var{b})
+Return true if @var{a} might be greater than or equal to @var{b}.
+
+@item maybe_gt(@var{a}, @var{b})
+Return true if @var{a} might be greater than @var{b}.
+@end table
+
+For readability, @code{poly_int} also provides ``known'' inverses of these
+functions:
+
+@example
+known_lt (@var{a}, @var{b}) == !maybe_ge (@var{a}, @var{b})
+known_le (@var{a}, @var{b}) == !maybe_gt (@var{a}, @var{b})
+known_eq (@var{a}, @var{b}) == !maybe_ne (@var{a}, @var{b})
+known_ge (@var{a}, @var{b}) == !maybe_lt (@var{a}, @var{b})
+known_gt (@var{a}, @var{b}) == !maybe_le (@var{a}, @var{b})
+known_ne (@var{a}, @var{b}) == !maybe_eq (@var{a}, @var{b})
+@end example
+
+@node Properties of the @code{poly_int} comparisons
+@subsection Properties of the @code{poly_int} comparisons
+
+All ``maybe'' relations except @code{maybe_ne} are transitive, so for example:
+
+@smallexample
+maybe_lt (@var{a}, @var{b}) && maybe_lt (@var{b}, @var{c}) implies maybe_lt (@var{a}, @var{c})
+@end smallexample
+
+for all @var{a}, @var{b} and @var{c}. @code{maybe_lt}, @code{maybe_gt}
+and @code{maybe_ne} are irreflexive, so for example:
+
+@smallexample
+!maybe_lt (@var{a}, @var{a})
+@end smallexample
+
+is true for all @var{a}. @code{maybe_le}, @code{maybe_eq} and @code{maybe_ge}
+are reflexive, so for example:
+
+@smallexample
+maybe_le (@var{a}, @var{a})
+@end smallexample
+
+is true for all @var{a}. @code{maybe_eq} and @code{maybe_ne} are symmetric, so:
+
+@smallexample
+maybe_eq (@var{a}, @var{b}) == maybe_eq (@var{b}, @var{a})
+maybe_ne (@var{a}, @var{b}) == maybe_ne (@var{b}, @var{a})
+@end smallexample
+
+for all @var{a} and @var{b}. In addition:
+
+@smallexample
+maybe_le (@var{a}, @var{b}) == maybe_lt (@var{a}, @var{b}) || maybe_eq (@var{a}, @var{b})
+maybe_ge (@var{a}, @var{b}) == maybe_gt (@var{a}, @var{b}) || maybe_eq (@var{a}, @var{b})
+maybe_lt (@var{a}, @var{b}) == maybe_gt (@var{b}, @var{a})
+maybe_le (@var{a}, @var{b}) == maybe_ge (@var{b}, @var{a})
+@end smallexample
+
+However:
+
+@smallexample
+maybe_le (@var{a}, @var{b}) && maybe_le (@var{b}, @var{a}) does not imply !maybe_ne (@var{a}, @var{b}) [== known_eq (@var{a}, @var{b})]
+maybe_ge (@var{a}, @var{b}) && maybe_ge (@var{b}, @var{a}) does not imply !maybe_ne (@var{a}, @var{b}) [== known_eq (@var{a}, @var{b})]
+@end smallexample
+
+One example is again @samp{@var{a} == 3 + 4@var{x}}
+and @samp{@var{b} == 1 + 5@var{x}}, where @samp{maybe_le (@var{a}, @var{b})},
+@samp{maybe_ge (@var{a}, @var{b})} and @samp{maybe_ne (@var{a}, @var{b})}
+all hold. @code{maybe_le} and @code{maybe_ge} are therefore not antisymetric
+and do not form a partial order.
+
+From the above, it follows that:
+
+@itemize @bullet
+@item
+All ``known'' relations except @code{known_ne} are transitive.
+
+@item
+@code{known_lt}, @code{known_ne} and @code{known_gt} are irreflexive.
+
+@item
+@code{known_le}, @code{known_eq} and @code{known_ge} are reflexive.
+@end itemize
+
+Also:
+
+@smallexample
+known_lt (@var{a}, @var{b}) == known_gt (@var{b}, @var{a})
+known_le (@var{a}, @var{b}) == known_ge (@var{b}, @var{a})
+known_lt (@var{a}, @var{b}) implies !known_lt (@var{b}, @var{a}) [asymmetry]
+known_gt (@var{a}, @var{b}) implies !known_gt (@var{b}, @var{a})
+known_le (@var{a}, @var{b}) && known_le (@var{b}, @var{a}) == known_eq (@var{a}, @var{b}) [== !maybe_ne (@var{a}, @var{b})]
+known_ge (@var{a}, @var{b}) && known_ge (@var{b}, @var{a}) == known_eq (@var{a}, @var{b}) [== !maybe_ne (@var{a}, @var{b})]
+@end smallexample
+
+@code{known_le} and @code{known_ge} are therefore antisymmetric and are
+partial orders. However:
+
+@smallexample
+known_le (@var{a}, @var{b}) does not imply known_lt (@var{a}, @var{b}) || known_eq (@var{a}, @var{b})
+known_ge (@var{a}, @var{b}) does not imply known_gt (@var{a}, @var{b}) || known_eq (@var{a}, @var{b})
+@end smallexample
+
+For example, @samp{known_le (4, 4 + 4@var{x})} holds because the runtime
+indeterminate @var{x} is a nonnegative integer, but neither
+@code{known_lt (4, 4 + 4@var{x})} nor @code{known_eq (4, 4 + 4@var{x})} hold.
+
+@node Comparing potentially-unordered @code{poly_int}s
+@subsection Comparing potentially-unordered @code{poly_int}s
+
+In cases where there is no definite link between two @code{poly_int}s,
+we can usually make a conservatively-correct assumption. For example,
+the conservative assumption for alias analysis is that two references
+@emph{might} alias.
+
+One way of checking whether [@var{begin1}, @var{end1}) might overlap
+[@var{begin2}, @var{end2}) using the @code{poly_int} comparisons is:
+
+@smallexample
+maybe_gt (@var{end1}, @var{begin2}) && maybe_gt (@var{end2}, @var{begin1})
+@end smallexample
+
+and another (equivalent) way is:
+
+@smallexample
+!(known_le (@var{end1}, @var{begin2}) || known_le (@var{end2}, @var{begin1}))
+@end smallexample
+
+However, in this particular example, it is better to use the range helper
+functions instead. @xref{Range checks on @code{poly_int}s}.
+
+@node Comparing ordered @code{poly_int}s
+@subsection Comparing ordered @code{poly_int}s
+
+In cases where there is a definite link between two @code{poly_int}s,
+such as the outer and inner sizes of subregs, we usually require the sizes
+to be ordered by the @code{known_le} partial order. @code{poly_int} provides
+the following utility functions for ordered values:
+
+@table @samp
+@item ordered_p (@var{a}, @var{b})
+Return true if @var{a} and @var{b} are ordered by the @code{known_le}
+partial order.
+
+@item ordered_min (@var{a}, @var{b})
+Assert that @var{a} and @var{b} are ordered by @code{known_le} and return the
+minimum of the two. When using this function, please add a comment explaining
+why the values are known to be ordered.
+
+@item ordered_max (@var{a}, @var{b})
+Assert that @var{a} and @var{b} are ordered by @code{known_le} and return the
+maximum of the two. When using this function, please add a comment explaining
+why the values are known to be ordered.
+@end table
+
+For example, if a subreg has an outer mode of size @var{outer} and an
+inner mode of size @var{inner}:
+
+@itemize @bullet
+@item
+the subreg is complete if known_eq (@var{inner}, @var{outer})
+
+@item
+otherwise, the subreg is paradoxical if known_le (@var{inner}, @var{outer})
+
+@item
+otherwise, the subreg is partial if known_le (@var{outer}, @var{inner})
+
+@item
+otherwise, the subreg is ill-formed
+@end itemize
+
+Thus the subreg is only valid if
+@samp{ordered_p (@var{outer}, @var{inner})} is true. If this condition
+is already known to be true then:
+
+@itemize @bullet
+@item
+the subreg is complete if known_eq (@var{inner}, @var{outer})
+
+@item
+the subreg is paradoxical if maybe_lt (@var{inner}, @var{outer})
+
+@item
+the subreg is partial if maybe_lt (@var{outer}, @var{inner})
+@end itemize
+
+with the three conditions being mutually exclusive.
+
+Code that checks whether a subreg is valid would therefore generally
+check whether @code{ordered_p} holds (in addition to whatever other
+checks are required for subreg validity). Code that is dealing
+with existing subregs can assert that @code{ordered_p} holds
+and use either of the classifications above.
+
+@node Checking for a @code{poly_int} marker value
+@subsection Checking for a @code{poly_int} marker value
+
+It is sometimes useful to have a special ``marker value'' that is not
+meant to be taken literally. For example, some code uses a size
+of -1 to represent an unknown size, rather than having to carry around
+a separate boolean to say whether the size is known.
+
+The best way of checking whether something is a marker value is
+@code{known_eq}. Conversely the best way of checking whether something
+is @emph{not} a marker value is @code{maybe_ne}.
+
+Thus in the size example just mentioned, @samp{known_eq (size, -1)} would
+check for an unknown size and @samp{maybe_ne (size, -1)} would check for a
+known size.
+
+@node Range checks on @code{poly_int}s
+@subsection Range checks on @code{poly_int}s
+
+As well as the core comparisons
+(@pxref{Comparison functions for @code{poly_int}}), @code{poly_int} provides
+utilities for various kinds of range check. In each case the range
+is represented by a start position and a size rather than a start
+position and an end position; this is because the former is used
+much more often than the latter in GCC@. Also, the sizes can be
+-1 (or all ones for unsigned sizes) to indicate a range with a known
+start position but an unknown size. All other sizes must be nonnegative.
+A range of size 0 does not contain anything or overlap anything.
+
+@table @samp
+@item known_size_p (@var{size})
+Return true if @var{size} represents a known range size, false if it
+is -1 or all ones (for signed and unsigned types respectively).
+
+@item ranges_maybe_overlap_p (@var{pos1}, @var{size1}, @var{pos2}, @var{size2})
+Return true if the range described by @var{pos1} and @var{size1} @emph{might}
+overlap the range described by @var{pos2} and @var{size2} (in other words,
+return true if we cannot prove that the ranges are disjoint).
+
+@item ranges_known_overlap_p (@var{pos1}, @var{size1}, @var{pos2}, @var{size2})
+Return true if the range described by @var{pos1} and @var{size1} is known to
+overlap the range described by @var{pos2} and @var{size2}.
+
+@item known_subrange_p (@var{pos1}, @var{size1}, @var{pos2}, @var{size2})
+Return true if the range described by @var{pos1} and @var{size1} is known to
+be contained in the range described by @var{pos2} and @var{size2}.
+
+@item maybe_in_range_p (@var{value}, @var{pos}, @var{size})
+Return true if @var{value} @emph{might} be in the range described by
+@var{pos} and @var{size} (in other words, return true if we cannot
+prove that @var{value} is outside that range).
+
+@item known_in_range_p (@var{value}, @var{pos}, @var{size})
+Return true if @var{value} is known to be in the range described
+by @var{pos} and @var{size}.
+
+@item endpoint_representable_p (@var{pos}, @var{size})
+Return true if the range described by @var{pos} and @var{size} is
+open-ended or if the endpoint (@var{pos} + @var{size}) is representable
+in the same type as @var{pos} and @var{size}. The function returns false
+if adding @var{size} to @var{pos} makes conceptual sense but could overflow.
+@end table
+
+There is also a @code{poly_int} version of the @code{IN_RANGE_P} macro:
+
+@table @samp
+@item coeffs_in_range_p (@var{x}, @var{lower}, @var{upper})
+Return true if every coefficient of @var{x} is in the inclusive range
+[@var{lower}, @var{upper}]. This function can be useful when testing
+whether an operation would cause the values of coefficients to
+overflow.
+
+Note that the function does not indicate whether @var{x} itself is in the
+given range. @var{x} can be either a constant or a @code{poly_int}.
+@end table
+
+@node Sorting @code{poly_int}s
+@subsection Sorting @code{poly_int}s
+
+@code{poly_int} provides the following routine for sorting:
+
+@table @samp
+@item compare_sizes_for_sort (@var{a}, @var{b})
+Compare @var{a} and @var{b} in reverse lexicographical order (that is,
+compare the highest-indexed coefficients first). This can be useful when
+sorting data structures, since it has the effect of separating constant
+and non-constant values. If all values are nonnegative, the constant
+values come first.
+
+Note that the values do not necessarily end up in numerical order.
+For example, @samp{1 + 1@var{x}} would come after @samp{100} in the sort order,
+but may well be less than @samp{100} at run time.
+@end table
+
+@node Arithmetic on @code{poly_int}s
+@section Arithmetic on @code{poly_int}s
+
+Addition, subtraction, negation and bit inversion all work normally for
+@code{poly_int}s. Multiplication by a constant multiplier and left
+shifting by a constant shift amount also work normally. General
+multiplication of two @code{poly_int}s is not supported and is not
+useful in practice.
+
+Other operations are only conditionally supported: the operation
+might succeed or might fail, depending on the inputs.
+
+This section describes both types of operation.
+
+@menu
+* Using @code{poly_int} with C++ arithmetic operators::
+* @code{wi} arithmetic on @code{poly_int}s::
+* Division of @code{poly_int}s::
+* Other @code{poly_int} arithmetic::
+@end menu
+
+@node Using @code{poly_int} with C++ arithmetic operators
+@subsection Using @code{poly_int} with C++ arithmetic operators
+
+The following C++ expressions are supported, where @var{p1} and @var{p2}
+are @code{poly_int}s and where @var{c1} and @var{c2} are scalars:
+
+@smallexample
+-@var{p1}
+~@var{p1}
+
+@var{p1} + @var{p2}
+@var{p1} + @var{c2}
+@var{c1} + @var{p2}
+
+@var{p1} - @var{p2}
+@var{p1} - @var{c2}
+@var{c1} - @var{p2}
+
+@var{c1} * @var{p2}
+@var{p1} * @var{c2}
+
+@var{p1} << @var{c2}
+
+@var{p1} += @var{p2}
+@var{p1} += @var{c2}
+
+@var{p1} -= @var{p2}
+@var{p1} -= @var{c2}
+
+@var{p1} *= @var{c2}
+@var{p1} <<= @var{c2}
+@end smallexample
+
+These arithmetic operations handle integer ranks in a similar way
+to C++. The main difference is that every coefficient narrower than
+@code{HOST_WIDE_INT} promotes to @code{HOST_WIDE_INT}, whereas in
+C++ everything narrower than @code{int} promotes to @code{int}.
+For example:
+
+@smallexample
+poly_uint16 + int -> poly_int64
+unsigned int + poly_uint16 -> poly_int64
+poly_int64 + int -> poly_int64
+poly_int32 + poly_uint64 -> poly_uint64
+uint64 + poly_int64 -> poly_uint64
+poly_offset_int + int32 -> poly_offset_int
+offset_int + poly_uint16 -> poly_offset_int
+@end smallexample
+
+In the first two examples, both coefficients are narrower than
+@code{HOST_WIDE_INT}, so the result has coefficients of type
+@code{HOST_WIDE_INT}. In the other examples, the coefficient
+with the highest rank ``wins''.
+
+If one of the operands is @code{wide_int} or @code{poly_wide_int},
+the rules are the same as for @code{wide_int} arithmetic.
+
+@node @code{wi} arithmetic on @code{poly_int}s
+@subsection @code{wi} arithmetic on @code{poly_int}s
+
+As well as the C++ operators, @code{poly_int} supports the following
+@code{wi} routines:
+
+@smallexample
+wi::neg (@var{p1}, &@var{overflow})
+
+wi::add (@var{p1}, @var{p2})
+wi::add (@var{p1}, @var{c2})
+wi::add (@var{c1}, @var{p1})
+wi::add (@var{p1}, @var{p2}, @var{sign}, &@var{overflow})
+
+wi::sub (@var{p1}, @var{p2})
+wi::sub (@var{p1}, @var{c2})
+wi::sub (@var{c1}, @var{p1})
+wi::sub (@var{p1}, @var{p2}, @var{sign}, &@var{overflow})
+
+wi::mul (@var{p1}, @var{c2})
+wi::mul (@var{c1}, @var{p1})
+wi::mul (@var{p1}, @var{c2}, @var{sign}, &@var{overflow})
+
+wi::lshift (@var{p1}, @var{c2})
+@end smallexample
+
+These routines just check whether overflow occurs on any individual
+coefficient; it is not possible to know at compile time whether the
+final runtime value would overflow.
+
+@node Division of @code{poly_int}s
+@subsection Division of @code{poly_int}s
+
+Division of @code{poly_int}s is possible for certain inputs. The functions
+for division return true if the operation is possible and in most cases
+return the results by pointer. The routines are:
+
+@table @samp
+@item multiple_p (@var{a}, @var{b})
+@itemx multiple_p (@var{a}, @var{b}, &@var{quotient})
+Return true if @var{a} is an exact multiple of @var{b}, storing the result
+in @var{quotient} if so. There are overloads for various combinations
+of polynomial and constant @var{a}, @var{b} and @var{quotient}.
+
+@item constant_multiple_p (@var{a}, @var{b})
+@itemx constant_multiple_p (@var{a}, @var{b}, &@var{quotient})
+Like @code{multiple_p}, but also test whether the multiple is a
+compile-time constant.
+
+@item can_div_trunc_p (@var{a}, @var{b}, &@var{quotient})
+@itemx can_div_trunc_p (@var{a}, @var{b}, &@var{quotient}, &@var{remainder})
+Return true if we can calculate @samp{trunc (@var{a} / @var{b})} at compile
+time, storing the result in @var{quotient} and @var{remainder} if so.
+
+@item can_div_away_from_zero_p (@var{a}, @var{b}, &@var{quotient})
+Return true if we can calculate @samp{@var{a} / @var{b}} at compile time,
+rounding away from zero. Store the result in @var{quotient} if so.
+
+Note that this is true if and only if @code{can_div_trunc_p} is true.
+The only difference is in the rounding of the result.
+@end table
+
+There is also an asserting form of division:
+
+@table @samp
+@item exact_div (@var{a}, @var{b})
+Assert that @var{a} is a multiple of @var{b} and return
+@samp{@var{a} / @var{b}}. The result is a @code{poly_int} if @var{a}
+is a @code{poly_int}.
+@end table
+
+@node Other @code{poly_int} arithmetic
+@subsection Other @code{poly_int} arithmetic
+
+There are tentative routines for other operations besides division:
+
+@table @samp
+@item can_ior_p (@var{a}, @var{b}, &@var{result})
+Return true if we can calculate @samp{@var{a} | @var{b}} at compile time,
+storing the result in @var{result} if so.
+@end table
+
+Also, ANDs with a value @samp{(1 << @var{y}) - 1} or its inverse can be
+treated as alignment operations. @xref{Alignment of @code{poly_int}s}.
+
+In addition, the following miscellaneous routines are available:
+
+@table @samp
+@item coeff_gcd (@var{a})
+Return the greatest common divisor of all nonzero coefficients in
+@var{a}, or zero if @var{a} is known to be zero.
+
+@item common_multiple (@var{a}, @var{b})
+Return a value that is a multiple of both @var{a} and @var{b}, where
+one value is a @code{poly_int} and the other is a scalar. The result
+will be the least common multiple for some indeterminate values but
+not necessarily for all.
+
+@item force_common_multiple (@var{a}, @var{b})
+Return a value that is a multiple of both @code{poly_int} @var{a} and
+@code{poly_int} @var{b}, asserting that such a value exists. The
+result will be the least common multiple for some indeterminate values
+but not necessarily for all.
+
+When using this routine, please add a comment explaining why the
+assertion is known to hold.
+@end table
+
+Please add any other operations that you find to be useful.
+
+@node Alignment of @code{poly_int}s
+@section Alignment of @code{poly_int}s
+
+@code{poly_int} provides various routines for aligning values and for querying
+misalignments. In each case the alignment must be a power of 2.
+
+@table @samp
+@item can_align_p (@var{value}, @var{align})
+Return true if we can align @var{value} up or down to the nearest multiple
+of @var{align} at compile time. The answer is the same for both directions.
+
+@item can_align_down (@var{value}, @var{align}, &@var{aligned})
+Return true if @code{can_align_p}; if so, set @var{aligned} to the greatest
+aligned value that is less than or equal to @var{value}.
+
+@item can_align_up (@var{value}, @var{align}, &@var{aligned})
+Return true if @code{can_align_p}; if so, set @var{aligned} to the lowest
+aligned value that is greater than or equal to @var{value}.
+
+@item known_equal_after_align_down (@var{a}, @var{b}, @var{align})
+Return true if we can align @var{a} and @var{b} down to the nearest
+@var{align} boundary at compile time and if the two results are equal.
+
+@item known_equal_after_align_up (@var{a}, @var{b}, @var{align})
+Return true if we can align @var{a} and @var{b} up to the nearest
+@var{align} boundary at compile time and if the two results are equal.
+
+@item aligned_lower_bound (@var{value}, @var{align})
+Return a result that is no greater than @var{value} and that is aligned
+to @var{align}. The result will the closest aligned value for some
+indeterminate values but not necessarily for all.
+
+For example, suppose we are allocating an object of @var{size} bytes
+in a downward-growing stack whose current limit is given by @var{limit}.
+If the object requires @var{align} bytes of alignment, the new stack
+limit is given by:
+
+@smallexample
+aligned_lower_bound (@var{limit} - @var{size}, @var{align})
+@end smallexample
+
+@item aligned_upper_bound (@var{value}, @var{align})
+Likewise return a result that is no less than @var{value} and that is
+aligned to @var{align}. This is the routine that would be used for
+upward-growing stacks in the scenario just described.
+
+@item known_misalignment (@var{value}, @var{align}, &@var{misalign})
+Return true if we can calculate the misalignment of @var{value}
+with respect to @var{align} at compile time, storing the result in
+@var{misalign} if so.
+
+@item known_alignment (@var{value})
+Return the minimum alignment that @var{value} is known to have
+(in other words, the largest alignment that can be guaranteed
+whatever the values of the indeterminates turn out to be).
+Return 0 if @var{value} is known to be 0.
+
+@item force_align_down (@var{value}, @var{align})
+Assert that @var{value} can be aligned down to @var{align} at compile
+time and return the result. When using this routine, please add a
+comment explaining why the assertion is known to hold.
+
+@item force_align_up (@var{value}, @var{align})
+Likewise, but aligning up.
+
+@item force_align_down_and_div (@var{value}, @var{align})
+Divide the result of @code{force_align_down} by @var{align}. Again,
+please add a comment explaining why the assertion in @code{force_align_down}
+is known to hold.
+
+@item force_align_up_and_div (@var{value}, @var{align})
+Likewise for @code{force_align_up}.
+
+@item force_get_misalignment (@var{value}, @var{align})
+Assert that we can calculate the misalignment of @var{value} with
+respect to @var{align} at compile time and return the misalignment.
+When using this function, please add a comment explaining why
+the assertion is known to hold.
+@end table
+
+@node Computing bounds on @code{poly_int}s
+@section Computing bounds on @code{poly_int}s
+
+@code{poly_int} also provides routines for calculating lower and upper bounds:
+
+@table @samp
+@item constant_lower_bound (@var{a})
+Assert that @var{a} is nonnegative and return the smallest value it can have.
+
+@item constant_lower_bound_with_limit (@var{a}, @var{b})
+Return the least value @var{a} can have, given that the context in
+which @var{a} appears guarantees that the answer is no less than @var{b}.
+In other words, the caller is asserting that @var{a} is greater than or
+equal to @var{b} even if @samp{known_ge (@var{a}, @var{b})} doesn't hold.
+
+@item constant_upper_bound_with_limit (@var{a}, @var{b})
+Return the greatest value @var{a} can have, given that the context in
+which @var{a} appears guarantees that the answer is no greater than @var{b}.
+In other words, the caller is asserting that @var{a} is less than or equal
+to @var{b} even if @samp{known_le (@var{a}, @var{b})} doesn't hold.
+
+@item lower_bound (@var{a}, @var{b})
+Return a value that is always less than or equal to both @var{a} and @var{b}.
+It will be the greatest such value for some indeterminate values
+but necessarily for all.
+
+@item upper_bound (@var{a}, @var{b})
+Return a value that is always greater than or equal to both @var{a} and
+@var{b}. It will be the least such value for some indeterminate values
+but necessarily for all.
+@end table
+
+@node Converting @code{poly_int}s
+@section Converting @code{poly_int}s
+
+A @code{poly_int<@var{n}, @var{T}>} can be constructed from up to
+@var{n} individual @var{T} coefficients, with the remaining coefficients
+being implicitly zero. In particular, this means that every
+@code{poly_int<@var{n}, @var{T}>} can be constructed from a single
+scalar @var{T}, or something compatible with @var{T}.
+
+Also, a @code{poly_int<@var{n}, @var{T}>} can be constructed from
+a @code{poly_int<@var{n}, @var{U}>} if @var{T} can be constructed
+from @var{U}.
+
+The following functions provide other forms of conversion,
+or test whether such a conversion would succeed.
+
+@table @samp
+@item @var{value}.is_constant ()
+Return true if @code{poly_int} @var{value} is a compile-time constant.
+
+@item @var{value}.is_constant (&@var{c1})
+Return true if @code{poly_int} @var{value} is a compile-time constant,
+storing it in @var{c1} if so. @var{c1} must be able to hold all
+constant values of @var{value} without loss of precision.
+
+@item @var{value}.to_constant ()
+Assert that @var{value} is a compile-time constant and return its value.
+When using this function, please add a comment explaining why the
+condition is known to hold (for example, because an earlier phase
+of analysis rejected non-constants).
+
+@item @var{value}.to_shwi (&@var{p2})
+Return true if @samp{poly_int<@var{N}, @var{T}>} @var{value} can be
+represented without loss of precision as a
+@samp{poly_int<@var{N}, @code{HOST_WIDE_INT}>}, storing it in that
+form in @var{p2} if so.
+
+@item @var{value}.to_uhwi (&@var{p2})
+Return true if @samp{poly_int<@var{N}, @var{T}>} @var{value} can be
+represented without loss of precision as a
+@samp{poly_int<@var{N}, @code{unsigned HOST_WIDE_INT}>}, storing it in that
+form in @var{p2} if so.
+
+@item @var{value}.force_shwi ()
+Forcibly convert each coefficient of @samp{poly_int<@var{N}, @var{T}>}
+@var{value} to @code{HOST_WIDE_INT}, truncating any that are out of range.
+Return the result as a @samp{poly_int<@var{N}, @code{HOST_WIDE_INT}>}.
+
+@item @var{value}.force_uhwi ()
+Forcibly convert each coefficient of @samp{poly_int<@var{N}, @var{T}>}
+@var{value} to @code{unsigned HOST_WIDE_INT}, truncating any that are
+out of range. Return the result as a
+@samp{poly_int<@var{N}, @code{unsigned HOST_WIDE_INT}>}.
+
+@item wi::shwi (@var{value}, @var{precision})
+Return a @code{poly_int} with the same value as @var{value}, but with
+the coefficients converted from @code{HOST_WIDE_INT} to @code{wide_int}.
+@var{precision} specifies the precision of the @code{wide_int} cofficients;
+if this is wider than a @code{HOST_WIDE_INT}, the coefficients of
+@var{value} will be sign-extended to fit.
+
+@item wi::uhwi (@var{value}, @var{precision})
+Like @code{wi::shwi}, except that @var{value} has coefficients of
+type @code{unsigned HOST_WIDE_INT}. If @var{precision} is wider than
+a @code{HOST_WIDE_INT}, the coefficients of @var{value} will be
+zero-extended to fit.
+
+@item wi::sext (@var{value}, @var{precision})
+Return a @code{poly_int} of the same type as @var{value}, sign-extending
+every coefficient from the low @var{precision} bits. This in effect
+applies @code{wi::sext} to each coefficient individually.
+
+@item wi::zext (@var{value}, @var{precision})
+Like @code{wi::sext}, but for zero extension.
+
+@item poly_wide_int::from (@var{value}, @var{precision}, @var{sign})
+Convert @var{value} to a @code{poly_wide_int} in which each coefficient
+has @var{precision} bits. Extend the coefficients according to
+@var{sign} if the coefficients have fewer bits.
+
+@item poly_offset_int::from (@var{value}, @var{sign})
+Convert @var{value} to a @code{poly_offset_int}, extending its coefficients
+according to @var{sign} if they have fewer bits than @code{offset_int}.
+
+@item poly_widest_int::from (@var{value}, @var{sign})
+Convert @var{value} to a @code{poly_widest_int}, extending its coefficients
+according to @var{sign} if they have fewer bits than @code{widest_int}.
+@end table
+
+@node Miscellaneous @code{poly_int} routines
+@section Miscellaneous @code{poly_int} routines
+
+@table @samp
+@item print_dec (@var{value}, @var{file}, @var{sign})
+@itemx print_dec (@var{value}, @var{file})
+Print @var{value} to @var{file} as a decimal value, interpreting
+the coefficients according to @var{sign}. The final argument is
+optional if @var{value} has an inherent sign; for example,
+@code{poly_int64} values print as signed by default and
+@code{poly_uint64} values print as unsigned by default.
+
+This is a simply a @code{poly_int} version of a wide-int routine.
+@end table
+
+@node Guidelines for using @code{poly_int}
+@section Guidelines for using @code{poly_int}
+
+One of the main design goals of @code{poly_int} was to make it easy
+to write target-independent code that handles variable-sized registers
+even when the current target has fixed-sized registers. There are two
+aspects to this:
+
+@itemize
+@item
+The set of @code{poly_int} operations should be complete enough that
+the question in most cases becomes ``Can we do this operation on these
+particular @code{poly_int} values? If not, bail out'' rather than
+``Are these @code{poly_int} values constant? If so, do the operation,
+otherwise bail out''.
+
+@item
+If target-independent code compiles and runs correctly on a target
+with one value of @code{NUM_POLY_INT_COEFFS}, and if the code does not
+use asserting functions like @code{to_constant}, it is reasonable to
+assume that the code also works on targets with other values of
+@code{NUM_POLY_INT_COEFFS}. There is no need to check this during
+everyday development.
+@end itemize
+
+So the general principle is: if target-independent code is dealing
+with a @code{poly_int} value, it is better to operate on it as a
+@code{poly_int} if at all possible, choosing conservatively-correct
+behavior if a particular operation fails. For example, the following
+code handles an index @code{pos} into a sequence of vectors that each
+have @code{nunits} elements:
+
+@smallexample
+/* Calculate which vector contains the result, and which lane of
+ that vector we need. */
+if (!can_div_trunc_p (pos, nunits, &vec_entry, &vec_index))
+ @{
+ if (dump_enabled_p ())
+ dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+ "Cannot determine which vector holds the"
+ " final result.\n");
+ return false;
+ @}
+@end smallexample
+
+However, there are some contexts in which operating on a
+@code{poly_int} is not possible or does not make sense. One example
+is when handling static initializers, since no current target supports
+the concept of a variable-length static initializer. In these
+situations, a reasonable fallback is:
+
+@smallexample
+if (@var{poly_value}.is_constant (&@var{const_value}))
+ @{
+ @dots{}
+ /* Operate on @var{const_value}. */
+ @dots{}
+ @}
+else
+ @{
+ @dots{}
+ /* Conservatively correct fallback. */
+ @dots{}
+ @}
+@end smallexample
+
+@code{poly_int} also provides some asserting functions like
+@code{to_constant}. Please only use these functions if there is a
+good theoretical reason to believe that the assertion cannot fire.
+For example, if some work is divided into an analysis phase and an
+implementation phase, the analysis phase might reject inputs that are
+not @code{is_constant}, in which case the implementation phase can
+reasonably use @code{to_constant} on the remaining inputs. The assertions
+should not be used to discover whether a condition ever occurs ``in the
+field''; in other words, they should not be used to restrict code to
+constants at first, with the intention of only implementing a
+@code{poly_int} version if a user hits the assertion.
+
+If a particular asserting function like @code{to_constant} is needed
+more than once for the same reason, it is probably worth adding a
+helper function or macro for that situation, so that the justification
+only needs to be given once. For example:
+
+@smallexample
+/* Return the size of an element in a vector of size SIZE, given that
+ the vector has NELTS elements. The return value is in the same units
+ as SIZE (either bits or bytes).
+
+ to_constant () is safe in this situation because vector elements are
+ always constant-sized scalars. */
+#define vector_element_size(SIZE, NELTS) \
+ (exact_div (SIZE, NELTS).to_constant ())
+@end smallexample
+
+Target-specific code in @file{config/@var{cpu}} only needs to handle
+non-constant @code{poly_int}s if @code{NUM_POLY_INT_COEFFS} is greater
+than one. For other targets, @code{poly_int} degenerates to a compile-time
+constant and is often interchangable with a normal scalar integer.
+There are two main exceptions:
+
+@itemize
+@item
+Sometimes an explicit cast to an integer type might be needed, such as to
+resolve ambiguities in a @code{?:} expression, or when passing values
+through @code{...} to things like print functions.
+
+@item
+Target macros are included in target-independent code and so do not
+have access to the implicit conversion to a scalar integer.
+If this becomes a problem for a particular target macro, the
+possible solutions, in order of preference, are:
+
+@itemize
+@item
+Convert the target macro to a target hook (for all targets).
+
+@item
+Put the target's implementation of the target macro in its
+@file{@var{cpu}.c} file and call it from the target macro in the
+@file{@var{cpu}.h} file.
+
+@item
+Add @code{to_constant ()} calls where necessary. The previous option
+is preferable because it will help with any future conversion of the
+macro to a hook.
+@end itemize
+@end itemize
+
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Portability
+@chapter GCC and Portability
+@cindex portability
+@cindex GCC and portability
+
+GCC itself aims to be portable to any machine where @code{int} is at least
+a 32-bit type. It aims to target machines with a flat (non-segmented) byte
+addressed data address space (the code address space can be separate).
+Target ABIs may have 8, 16, 32 or 64-bit @code{int} type. @code{char}
+can be wider than 8 bits.
+
+GCC gets most of the information about the target machine from a machine
+description which gives an algebraic formula for each of the machine's
+instructions. This is a very clean way to describe the target. But when
+the compiler needs information that is difficult to express in this
+fashion, ad-hoc parameters have been defined for machine descriptions.
+The purpose of portability is to reduce the total work needed on the
+compiler; it was not of interest for its own sake.
+
+@cindex endianness
+@cindex autoincrement addressing, availability
+@findex abort
+GCC does not contain machine dependent code, but it does contain code
+that depends on machine parameters such as endianness (whether the most
+significant byte has the highest or lowest address of the bytes in a word)
+and the availability of autoincrement addressing. In the RTL-generation
+pass, it is often necessary to have multiple strategies for generating code
+for a particular kind of syntax tree, strategies that are usable for different
+combinations of parameters. Often, not all possible cases have been
+addressed, but only the common ones or only the ones that have been
+encountered. As a result, a new target may require additional
+strategies. You will know
+if this happens because the compiler will call @code{abort}. Fortunately,
+the new strategies can be added in a machine-independent fashion, and will
+affect only the target machines that need them.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node RTL
+@chapter RTL Representation
+@cindex RTL representation
+@cindex representation of RTL
+@cindex Register Transfer Language (RTL)
+
+The last part of the compiler work is done on a low-level intermediate
+representation called Register Transfer Language. In this language, the
+instructions to be output are described, pretty much one by one, in an
+algebraic form that describes what the instruction does.
+
+RTL is inspired by Lisp lists. It has both an internal form, made up of
+structures that point at other structures, and a textual form that is used
+in the machine description and in printed debugging dumps. The textual
+form uses nested parentheses to indicate the pointers in the internal form.
+
+@menu
+* RTL Objects:: Expressions vs vectors vs strings vs integers.
+* RTL Classes:: Categories of RTL expression objects, and their structure.
+* Accessors:: Macros to access expression operands or vector elts.
+* Special Accessors:: Macros to access specific annotations on RTL.
+* Flags:: Other flags in an RTL expression.
+* Machine Modes:: Describing the size and format of a datum.
+* Constants:: Expressions with constant values.
+* Regs and Memory:: Expressions representing register contents or memory.
+* Arithmetic:: Expressions representing arithmetic on other expressions.
+* Comparisons:: Expressions representing comparison of expressions.
+* Bit-Fields:: Expressions representing bit-fields in memory or reg.
+* Vector Operations:: Expressions involving vector datatypes.
+* Conversions:: Extending, truncating, floating or fixing.
+* RTL Declarations:: Declaring volatility, constancy, etc.
+* Side Effects:: Expressions for storing in registers, etc.
+* Incdec:: Embedded side-effects for autoincrement addressing.
+* Assembler:: Representing @code{asm} with operands.
+* Debug Information:: Expressions representing debugging information.
+* Insns:: Expression types for entire insns.
+* Calls:: RTL representation of function call insns.
+* RTL SSA:: An on-the-side SSA form for RTL
+* Sharing:: Some expressions are unique; others *must* be copied.
+* Reading RTL:: Reading textual RTL from a file.
+@end menu
+
+@node RTL Objects
+@section RTL Object Types
+@cindex RTL object types
+
+@cindex RTL integers
+@cindex RTL strings
+@cindex RTL vectors
+@cindex RTL expression
+@cindex RTX (See RTL)
+RTL uses five kinds of objects: expressions, integers, wide integers,
+strings and vectors. Expressions are the most important ones. An RTL
+expression (``RTX'', for short) is a C structure, but it is usually
+referred to with a pointer; a type that is given the typedef name
+@code{rtx}.
+
+An integer is simply an @code{int}; their written form uses decimal
+digits. A wide integer is an integral object whose type is
+@code{HOST_WIDE_INT}; their written form uses decimal digits.
+
+A string is a sequence of characters. In core it is represented as a
+@code{char *} in usual C fashion, and it is written in C syntax as well.
+However, strings in RTL may never be null. If you write an empty string in
+a machine description, it is represented in core as a null pointer rather
+than as a pointer to a null character. In certain contexts, these null
+pointers instead of strings are valid. Within RTL code, strings are most
+commonly found inside @code{symbol_ref} expressions, but they appear in
+other contexts in the RTL expressions that make up machine descriptions.
+
+In a machine description, strings are normally written with double
+quotes, as you would in C@. However, strings in machine descriptions may
+extend over many lines, which is invalid C, and adjacent string
+constants are not concatenated as they are in C@. Any string constant
+may be surrounded with a single set of parentheses. Sometimes this
+makes the machine description easier to read.
+
+There is also a special syntax for strings, which can be useful when C
+code is embedded in a machine description. Wherever a string can
+appear, it is also valid to write a C-style brace block. The entire
+brace block, including the outermost pair of braces, is considered to be
+the string constant. Double quote characters inside the braces are not
+special. Therefore, if you write string constants in the C code, you
+need not escape each quote character with a backslash.
+
+A vector contains an arbitrary number of pointers to expressions. The
+number of elements in the vector is explicitly present in the vector.
+The written form of a vector consists of square brackets
+(@samp{[@dots{}]}) surrounding the elements, in sequence and with
+whitespace separating them. Vectors of length zero are not created;
+null pointers are used instead.
+
+@cindex expression codes
+@cindex codes, RTL expression
+@findex GET_CODE
+@findex PUT_CODE
+Expressions are classified by @dfn{expression codes} (also called RTX
+codes). The expression code is a name defined in @file{rtl.def}, which is
+also (in uppercase) a C enumeration constant. The possible expression
+codes and their meanings are machine-independent. The code of an RTX can
+be extracted with the macro @code{GET_CODE (@var{x})} and altered with
+@code{PUT_CODE (@var{x}, @var{newcode})}.
+
+The expression code determines how many operands the expression contains,
+and what kinds of objects they are. In RTL, unlike Lisp, you cannot tell
+by looking at an operand what kind of object it is. Instead, you must know
+from its context---from the expression code of the containing expression.
+For example, in an expression of code @code{subreg}, the first operand is
+to be regarded as an expression and the second operand as a polynomial
+integer. In an expression of code @code{plus}, there are two operands,
+both of which are to be regarded as expressions. In a @code{symbol_ref}
+expression, there is one operand, which is to be regarded as a string.
+
+Expressions are written as parentheses containing the name of the
+expression type, its flags and machine mode if any, and then the operands
+of the expression (separated by spaces).
+
+Expression code names in the @samp{md} file are written in lowercase,
+but when they appear in C code they are written in uppercase. In this
+manual, they are shown as follows: @code{const_int}.
+
+@cindex (nil)
+@cindex nil
+In a few contexts a null pointer is valid where an expression is normally
+wanted. The written form of this is @code{(nil)}.
+
+@node RTL Classes
+@section RTL Classes and Formats
+@cindex RTL classes
+@cindex classes of RTX codes
+@cindex RTX codes, classes of
+@findex GET_RTX_CLASS
+
+The various expression codes are divided into several @dfn{classes},
+which are represented by single characters. You can determine the class
+of an RTX code with the macro @code{GET_RTX_CLASS (@var{code})}.
+Currently, @file{rtl.def} defines these classes:
+
+@table @code
+@item RTX_OBJ
+An RTX code that represents an actual object, such as a register
+(@code{REG}) or a memory location (@code{MEM}, @code{SYMBOL_REF}).
+@code{LO_SUM} is also included; instead, @code{SUBREG} and
+@code{STRICT_LOW_PART} are not in this class, but in class
+@code{RTX_EXTRA}.
+
+@item RTX_CONST_OBJ
+An RTX code that represents a constant object. @code{HIGH} is also
+included in this class.
+
+@item RTX_COMPARE
+An RTX code for a non-symmetric comparison, such as @code{GEU} or
+@code{LT}.
+
+@item RTX_COMM_COMPARE
+An RTX code for a symmetric (commutative) comparison, such as @code{EQ}
+or @code{ORDERED}.
+
+@item RTX_UNARY
+An RTX code for a unary arithmetic operation, such as @code{NEG},
+@code{NOT}, or @code{ABS}. This category also includes value extension
+(sign or zero) and conversions between integer and floating point.
+
+@item RTX_COMM_ARITH
+An RTX code for a commutative binary operation, such as @code{PLUS} or
+@code{AND}. @code{NE} and @code{EQ} are comparisons, so they have class
+@code{RTX_COMM_COMPARE}.
+
+@item RTX_BIN_ARITH
+An RTX code for a non-commutative binary operation, such as @code{MINUS},
+@code{DIV}, or @code{ASHIFTRT}.
+
+@item RTX_BITFIELD_OPS
+An RTX code for a bit-field operation. Currently only
+@code{ZERO_EXTRACT} and @code{SIGN_EXTRACT}. These have three inputs
+and are lvalues (so they can be used for insertion as well).
+@xref{Bit-Fields}.
+
+@item RTX_TERNARY
+An RTX code for other three input operations. Currently only
+@code{IF_THEN_ELSE}, @code{VEC_MERGE}, @code{SIGN_EXTRACT},
+@code{ZERO_EXTRACT}, and @code{FMA}.
+
+@item RTX_INSN
+An RTX code for an entire instruction: @code{INSN}, @code{JUMP_INSN}, and
+@code{CALL_INSN}. @xref{Insns}.
+
+@item RTX_MATCH
+An RTX code for something that matches in insns, such as
+@code{MATCH_DUP}. These only occur in machine descriptions.
+
+@item RTX_AUTOINC
+An RTX code for an auto-increment addressing mode, such as
+@code{POST_INC}. @samp{XEXP (@var{x}, 0)} gives the auto-modified
+register.
+
+@item RTX_EXTRA
+All other RTX codes. This category includes the remaining codes used
+only in machine descriptions (@code{DEFINE_*}, etc.). It also includes
+all the codes describing side effects (@code{SET}, @code{USE},
+@code{CLOBBER}, etc.) and the non-insns that may appear on an insn
+chain, such as @code{NOTE}, @code{BARRIER}, and @code{CODE_LABEL}.
+@code{SUBREG} is also part of this class.
+@end table
+
+@cindex RTL format
+For each expression code, @file{rtl.def} specifies the number of
+contained objects and their kinds using a sequence of characters
+called the @dfn{format} of the expression code. For example,
+the format of @code{subreg} is @samp{ep}.
+
+@cindex RTL format characters
+These are the most commonly used format characters:
+
+@table @code
+@item e
+An expression (actually a pointer to an expression).
+
+@item i
+An integer.
+
+@item w
+A wide integer.
+
+@item s
+A string.
+
+@item E
+A vector of expressions.
+@end table
+
+A few other format characters are used occasionally:
+
+@table @code
+@item u
+@samp{u} is equivalent to @samp{e} except that it is printed differently
+in debugging dumps. It is used for pointers to insns.
+
+@item n
+@samp{n} is equivalent to @samp{i} except that it is printed differently
+in debugging dumps. It is used for the line number or code number of a
+@code{note} insn.
+
+@item S
+@samp{S} indicates a string which is optional. In the RTL objects in
+core, @samp{S} is equivalent to @samp{s}, but when the object is read,
+from an @samp{md} file, the string value of this operand may be omitted.
+An omitted string is taken to be the null string.
+
+@item V
+@samp{V} indicates a vector which is optional. In the RTL objects in
+core, @samp{V} is equivalent to @samp{E}, but when the object is read
+from an @samp{md} file, the vector value of this operand may be omitted.
+An omitted vector is effectively the same as a vector of no elements.
+
+@item B
+@samp{B} indicates a pointer to basic block structure.
+
+@item p
+A polynomial integer. At present this is used only for @code{SUBREG_BYTE}.
+
+@item 0
+@samp{0} means a slot whose contents do not fit any normal category.
+@samp{0} slots are not printed at all in dumps, and are often used in
+special ways by small parts of the compiler.
+@end table
+
+There are macros to get the number of operands and the format
+of an expression code:
+
+@table @code
+@findex GET_RTX_LENGTH
+@item GET_RTX_LENGTH (@var{code})
+Number of operands of an RTX of code @var{code}.
+
+@findex GET_RTX_FORMAT
+@item GET_RTX_FORMAT (@var{code})
+The format of an RTX of code @var{code}, as a C string.
+@end table
+
+Some classes of RTX codes always have the same format. For example, it
+is safe to assume that all comparison operations have format @code{ee}.
+
+@table @code
+@item RTX_UNARY
+All codes of this class have format @code{e}.
+
+@item RTX_BIN_ARITH
+@itemx RTX_COMM_ARITH
+@itemx RTX_COMM_COMPARE
+@itemx RTX_COMPARE
+All codes of these classes have format @code{ee}.
+
+@item RTX_BITFIELD_OPS
+@itemx RTX_TERNARY
+All codes of these classes have format @code{eee}.
+
+@item RTX_INSN
+All codes of this class have formats that begin with @code{iuueiee}.
+@xref{Insns}. Note that not all RTL objects linked onto an insn chain
+are of class @code{RTX_INSN}.
+
+@item RTX_CONST_OBJ
+@itemx RTX_OBJ
+@itemx RTX_MATCH
+@itemx RTX_EXTRA
+You can make no assumptions about the format of these codes.
+@end table
+
+@node Accessors
+@section Access to Operands
+@cindex accessors
+@cindex access to operands
+@cindex operand access
+
+@findex XEXP
+@findex XINT
+@findex XWINT
+@findex XSTR
+Operands of expressions are accessed using the macros @code{XEXP},
+@code{XINT}, @code{XWINT} and @code{XSTR}. Each of these macros takes
+two arguments: an expression-pointer (RTX) and an operand number
+(counting from zero). Thus,
+
+@smallexample
+XEXP (@var{x}, 2)
+@end smallexample
+
+@noindent
+accesses operand 2 of expression @var{x}, as an expression.
+
+@smallexample
+XINT (@var{x}, 2)
+@end smallexample
+
+@noindent
+accesses the same operand as an integer. @code{XSTR}, used in the same
+fashion, would access it as a string.
+
+Any operand can be accessed as an integer, as an expression or as a string.
+You must choose the correct method of access for the kind of value actually
+stored in the operand. You would do this based on the expression code of
+the containing expression. That is also how you would know how many
+operands there are.
+
+For example, if @var{x} is an @code{int_list} expression, you know that it has
+two operands which can be correctly accessed as @code{XINT (@var{x}, 0)}
+and @code{XEXP (@var{x}, 1)}. Incorrect accesses like
+@code{XEXP (@var{x}, 0)} and @code{XINT (@var{x}, 1)} would compile,
+but would trigger an internal compiler error when rtl checking is enabled.
+Nothing stops you from writing @code{XEXP (@var{x}, 28)} either, but
+this will access memory past the end of the expression with
+unpredictable results.
+
+Access to operands which are vectors is more complicated. You can use the
+macro @code{XVEC} to get the vector-pointer itself, or the macros
+@code{XVECEXP} and @code{XVECLEN} to access the elements and length of a
+vector.
+
+@table @code
+@findex XVEC
+@item XVEC (@var{exp}, @var{idx})
+Access the vector-pointer which is operand number @var{idx} in @var{exp}.
+
+@findex XVECLEN
+@item XVECLEN (@var{exp}, @var{idx})
+Access the length (number of elements) in the vector which is
+in operand number @var{idx} in @var{exp}. This value is an @code{int}.
+
+@findex XVECEXP
+@item XVECEXP (@var{exp}, @var{idx}, @var{eltnum})
+Access element number @var{eltnum} in the vector which is
+in operand number @var{idx} in @var{exp}. This value is an RTX@.
+
+It is up to you to make sure that @var{eltnum} is not negative
+and is less than @code{XVECLEN (@var{exp}, @var{idx})}.
+@end table
+
+All the macros defined in this section expand into lvalues and therefore
+can be used to assign the operands, lengths and vector elements as well as
+to access them.
+
+@node Special Accessors
+@section Access to Special Operands
+@cindex access to special operands
+
+Some RTL nodes have special annotations associated with them.
+
+@table @code
+@item MEM
+@table @code
+@findex MEM_ALIAS_SET
+@item MEM_ALIAS_SET (@var{x})
+If 0, @var{x} is not in any alias set, and may alias anything. Otherwise,
+@var{x} can only alias @code{MEM}s in a conflicting alias set. This value
+is set in a language-dependent manner in the front-end, and should not be
+altered in the back-end. In some front-ends, these numbers may correspond
+in some way to types, or other language-level entities, but they need not,
+and the back-end makes no such assumptions.
+These set numbers are tested with @code{alias_sets_conflict_p}.
+
+@findex MEM_EXPR
+@item MEM_EXPR (@var{x})
+If this register is known to hold the value of some user-level
+declaration, this is that tree node. It may also be a
+@code{COMPONENT_REF}, in which case this is some field reference,
+and @code{TREE_OPERAND (@var{x}, 0)} contains the declaration,
+or another @code{COMPONENT_REF}, or null if there is no compile-time
+object associated with the reference.
+
+@findex MEM_OFFSET_KNOWN_P
+@item MEM_OFFSET_KNOWN_P (@var{x})
+True if the offset of the memory reference from @code{MEM_EXPR} is known.
+@samp{MEM_OFFSET (@var{x})} provides the offset if so.
+
+@findex MEM_OFFSET
+@item MEM_OFFSET (@var{x})
+The offset from the start of @code{MEM_EXPR}. The value is only valid if
+@samp{MEM_OFFSET_KNOWN_P (@var{x})} is true.
+
+@findex MEM_SIZE_KNOWN_P
+@item MEM_SIZE_KNOWN_P (@var{x})
+True if the size of the memory reference is known.
+@samp{MEM_SIZE (@var{x})} provides its size if so.
+
+@findex MEM_SIZE
+@item MEM_SIZE (@var{x})
+The size in bytes of the memory reference.
+This is mostly relevant for @code{BLKmode} references as otherwise
+the size is implied by the mode. The value is only valid if
+@samp{MEM_SIZE_KNOWN_P (@var{x})} is true.
+
+@findex MEM_ALIGN
+@item MEM_ALIGN (@var{x})
+The known alignment in bits of the memory reference.
+
+@findex MEM_ADDR_SPACE
+@item MEM_ADDR_SPACE (@var{x})
+The address space of the memory reference. This will commonly be zero
+for the generic address space.
+@end table
+
+@item REG
+@table @code
+@findex ORIGINAL_REGNO
+@item ORIGINAL_REGNO (@var{x})
+This field holds the number the register ``originally'' had; for a
+pseudo register turned into a hard reg this will hold the old pseudo
+register number.
+
+@findex REG_EXPR
+@item REG_EXPR (@var{x})
+If this register is known to hold the value of some user-level
+declaration, this is that tree node.
+
+@findex REG_OFFSET
+@item REG_OFFSET (@var{x})
+If this register is known to hold the value of some user-level
+declaration, this is the offset into that logical storage.
+@end table
+
+@item SYMBOL_REF
+@table @code
+@findex SYMBOL_REF_DECL
+@item SYMBOL_REF_DECL (@var{x})
+If the @code{symbol_ref} @var{x} was created for a @code{VAR_DECL} or
+a @code{FUNCTION_DECL}, that tree is recorded here. If this value is
+null, then @var{x} was created by back end code generation routines,
+and there is no associated front end symbol table entry.
+
+@code{SYMBOL_REF_DECL} may also point to a tree of class @code{'c'},
+that is, some sort of constant. In this case, the @code{symbol_ref}
+is an entry in the per-file constant pool; again, there is no associated
+front end symbol table entry.
+
+@findex SYMBOL_REF_CONSTANT
+@item SYMBOL_REF_CONSTANT (@var{x})
+If @samp{CONSTANT_POOL_ADDRESS_P (@var{x})} is true, this is the constant
+pool entry for @var{x}. It is null otherwise.
+
+@findex SYMBOL_REF_DATA
+@item SYMBOL_REF_DATA (@var{x})
+A field of opaque type used to store @code{SYMBOL_REF_DECL} or
+@code{SYMBOL_REF_CONSTANT}.
+
+@findex SYMBOL_REF_FLAGS
+@item SYMBOL_REF_FLAGS (@var{x})
+In a @code{symbol_ref}, this is used to communicate various predicates
+about the symbol. Some of these are common enough to be computed by
+common code, some are specific to the target. The common bits are:
+
+@table @code
+@findex SYMBOL_REF_FUNCTION_P
+@findex SYMBOL_FLAG_FUNCTION
+@item SYMBOL_FLAG_FUNCTION
+Set if the symbol refers to a function.
+
+@findex SYMBOL_REF_LOCAL_P
+@findex SYMBOL_FLAG_LOCAL
+@item SYMBOL_FLAG_LOCAL
+Set if the symbol is local to this ``module''.
+See @code{TARGET_BINDS_LOCAL_P}.
+
+@findex SYMBOL_REF_EXTERNAL_P
+@findex SYMBOL_FLAG_EXTERNAL
+@item SYMBOL_FLAG_EXTERNAL
+Set if this symbol is not defined in this translation unit.
+Note that this is not the inverse of @code{SYMBOL_FLAG_LOCAL}.
+
+@findex SYMBOL_REF_SMALL_P
+@findex SYMBOL_FLAG_SMALL
+@item SYMBOL_FLAG_SMALL
+Set if the symbol is located in the small data section.
+See @code{TARGET_IN_SMALL_DATA_P}.
+
+@findex SYMBOL_FLAG_TLS_SHIFT
+@findex SYMBOL_REF_TLS_MODEL
+@item SYMBOL_REF_TLS_MODEL (@var{x})
+This is a multi-bit field accessor that returns the @code{tls_model}
+to be used for a thread-local storage symbol. It returns zero for
+non-thread-local symbols.
+
+@findex SYMBOL_REF_HAS_BLOCK_INFO_P
+@findex SYMBOL_FLAG_HAS_BLOCK_INFO
+@item SYMBOL_FLAG_HAS_BLOCK_INFO
+Set if the symbol has @code{SYMBOL_REF_BLOCK} and
+@code{SYMBOL_REF_BLOCK_OFFSET} fields.
+
+@findex SYMBOL_REF_ANCHOR_P
+@findex SYMBOL_FLAG_ANCHOR
+@cindex @option{-fsection-anchors}
+@item SYMBOL_FLAG_ANCHOR
+Set if the symbol is used as a section anchor. ``Section anchors''
+are symbols that have a known position within an @code{object_block}
+and that can be used to access nearby members of that block.
+They are used to implement @option{-fsection-anchors}.
+
+If this flag is set, then @code{SYMBOL_FLAG_HAS_BLOCK_INFO} will be too.
+@end table
+
+Bits beginning with @code{SYMBOL_FLAG_MACH_DEP} are available for
+the target's use.
+@end table
+
+@findex SYMBOL_REF_BLOCK
+@item SYMBOL_REF_BLOCK (@var{x})
+If @samp{SYMBOL_REF_HAS_BLOCK_INFO_P (@var{x})}, this is the
+@samp{object_block} structure to which the symbol belongs,
+or @code{NULL} if it has not been assigned a block.
+
+@findex SYMBOL_REF_BLOCK_OFFSET
+@item SYMBOL_REF_BLOCK_OFFSET (@var{x})
+If @samp{SYMBOL_REF_HAS_BLOCK_INFO_P (@var{x})}, this is the offset of @var{x}
+from the first object in @samp{SYMBOL_REF_BLOCK (@var{x})}. The value is
+negative if @var{x} has not yet been assigned to a block, or it has not
+been given an offset within that block.
+@end table
+
+@node Flags
+@section Flags in an RTL Expression
+@cindex flags in RTL expression
+
+RTL expressions contain several flags (one-bit bit-fields)
+that are used in certain types of expression. Most often they
+are accessed with the following macros, which expand into lvalues.
+
+@table @code
+@findex CROSSING_JUMP_P
+@cindex @code{jump_insn} and @samp{/j}
+@item CROSSING_JUMP_P (@var{x})
+Nonzero in a @code{jump_insn} if it crosses between hot and cold sections,
+which could potentially be very far apart in the executable. The presence
+of this flag indicates to other optimizations that this branching instruction
+should not be ``collapsed'' into a simpler branching construct. It is used
+when the optimization to partition basic blocks into hot and cold sections
+is turned on.
+
+@findex CONSTANT_POOL_ADDRESS_P
+@cindex @code{symbol_ref} and @samp{/u}
+@cindex @code{unchanging}, in @code{symbol_ref}
+@item CONSTANT_POOL_ADDRESS_P (@var{x})
+Nonzero in a @code{symbol_ref} if it refers to part of the current
+function's constant pool. For most targets these addresses are in a
+@code{.rodata} section entirely separate from the function, but for
+some targets the addresses are close to the beginning of the function.
+In either case GCC assumes these addresses can be addressed directly,
+perhaps with the help of base registers.
+Stored in the @code{unchanging} field and printed as @samp{/u}.
+
+@findex INSN_ANNULLED_BRANCH_P
+@cindex @code{jump_insn} and @samp{/u}
+@cindex @code{call_insn} and @samp{/u}
+@cindex @code{insn} and @samp{/u}
+@cindex @code{unchanging}, in @code{jump_insn}, @code{call_insn} and @code{insn}
+@item INSN_ANNULLED_BRANCH_P (@var{x})
+In a @code{jump_insn}, @code{call_insn}, or @code{insn} indicates
+that the branch is an annulling one. See the discussion under
+@code{sequence} below. Stored in the @code{unchanging} field and
+printed as @samp{/u}.
+
+@findex INSN_DELETED_P
+@cindex @code{insn} and @samp{/v}
+@cindex @code{call_insn} and @samp{/v}
+@cindex @code{jump_insn} and @samp{/v}
+@cindex @code{code_label} and @samp{/v}
+@cindex @code{jump_table_data} and @samp{/v}
+@cindex @code{barrier} and @samp{/v}
+@cindex @code{note} and @samp{/v}
+@cindex @code{volatil}, in @code{insn}, @code{call_insn}, @code{jump_insn}, @code{code_label}, @code{jump_table_data}, @code{barrier}, and @code{note}
+@item INSN_DELETED_P (@var{x})
+In an @code{insn}, @code{call_insn}, @code{jump_insn}, @code{code_label},
+@code{jump_table_data}, @code{barrier}, or @code{note},
+nonzero if the insn has been deleted. Stored in the
+@code{volatil} field and printed as @samp{/v}.
+
+@findex INSN_FROM_TARGET_P
+@cindex @code{insn} and @samp{/s}
+@cindex @code{jump_insn} and @samp{/s}
+@cindex @code{call_insn} and @samp{/s}
+@cindex @code{in_struct}, in @code{insn} and @code{jump_insn} and @code{call_insn}
+@item INSN_FROM_TARGET_P (@var{x})
+In an @code{insn} or @code{jump_insn} or @code{call_insn} in a delay
+slot of a branch, indicates that the insn
+is from the target of the branch. If the branch insn has
+@code{INSN_ANNULLED_BRANCH_P} set, this insn will only be executed if
+the branch is taken. For annulled branches with
+@code{INSN_FROM_TARGET_P} clear, the insn will be executed only if the
+branch is not taken. When @code{INSN_ANNULLED_BRANCH_P} is not set,
+this insn will always be executed. Stored in the @code{in_struct}
+field and printed as @samp{/s}.
+
+@findex LABEL_PRESERVE_P
+@cindex @code{code_label} and @samp{/i}
+@cindex @code{note} and @samp{/i}
+@cindex @code{in_struct}, in @code{code_label} and @code{note}
+@item LABEL_PRESERVE_P (@var{x})
+In a @code{code_label} or @code{note}, indicates that the label is referenced by
+code or data not visible to the RTL of a given function.
+Labels referenced by a non-local goto will have this bit set. Stored
+in the @code{in_struct} field and printed as @samp{/s}.
+
+@findex LABEL_REF_NONLOCAL_P
+@cindex @code{label_ref} and @samp{/v}
+@cindex @code{reg_label} and @samp{/v}
+@cindex @code{volatil}, in @code{label_ref} and @code{reg_label}
+@item LABEL_REF_NONLOCAL_P (@var{x})
+In @code{label_ref} and @code{reg_label} expressions, nonzero if this is
+a reference to a non-local label.
+Stored in the @code{volatil} field and printed as @samp{/v}.
+
+@findex MEM_KEEP_ALIAS_SET_P
+@cindex @code{mem} and @samp{/j}
+@cindex @code{jump}, in @code{mem}
+@item MEM_KEEP_ALIAS_SET_P (@var{x})
+In @code{mem} expressions, 1 if we should keep the alias set for this
+mem unchanged when we access a component. Set to 1, for example, when we
+are already in a non-addressable component of an aggregate.
+Stored in the @code{jump} field and printed as @samp{/j}.
+
+@findex MEM_VOLATILE_P
+@cindex @code{mem} and @samp{/v}
+@cindex @code{asm_input} and @samp{/v}
+@cindex @code{asm_operands} and @samp{/v}
+@cindex @code{volatil}, in @code{mem}, @code{asm_operands}, and @code{asm_input}
+@item MEM_VOLATILE_P (@var{x})
+In @code{mem}, @code{asm_operands}, and @code{asm_input} expressions,
+nonzero for volatile memory references.
+Stored in the @code{volatil} field and printed as @samp{/v}.
+
+@findex MEM_NOTRAP_P
+@cindex @code{mem} and @samp{/c}
+@cindex @code{call}, in @code{mem}
+@item MEM_NOTRAP_P (@var{x})
+In @code{mem}, nonzero for memory references that will not trap.
+Stored in the @code{call} field and printed as @samp{/c}.
+
+@findex MEM_POINTER
+@cindex @code{mem} and @samp{/f}
+@cindex @code{frame_related}, in @code{mem}
+@item MEM_POINTER (@var{x})
+Nonzero in a @code{mem} if the memory reference holds a pointer.
+Stored in the @code{frame_related} field and printed as @samp{/f}.
+
+@findex MEM_READONLY_P
+@cindex @code{mem} and @samp{/u}
+@cindex @code{unchanging}, in @code{mem}
+@item MEM_READONLY_P (@var{x})
+Nonzero in a @code{mem}, if the memory is statically allocated and read-only.
+
+Read-only in this context means never modified during the lifetime of the
+program, not necessarily in ROM or in write-disabled pages. A common
+example of the later is a shared library's global offset table. This
+table is initialized by the runtime loader, so the memory is technically
+writable, but after control is transferred from the runtime loader to the
+application, this memory will never be subsequently modified.
+
+Stored in the @code{unchanging} field and printed as @samp{/u}.
+
+@findex PREFETCH_SCHEDULE_BARRIER_P
+@cindex @code{prefetch} and @samp{/v}
+@cindex @code{volatile}, in @code{prefetch}
+@item PREFETCH_SCHEDULE_BARRIER_P (@var{x})
+In a @code{prefetch}, indicates that the prefetch is a scheduling barrier.
+No other INSNs will be moved over it.
+Stored in the @code{volatil} field and printed as @samp{/v}.
+
+@findex REG_FUNCTION_VALUE_P
+@cindex @code{reg} and @samp{/i}
+@cindex @code{return_val}, in @code{reg}
+@item REG_FUNCTION_VALUE_P (@var{x})
+Nonzero in a @code{reg} if it is the place in which this function's
+value is going to be returned. (This happens only in a hard
+register.) Stored in the @code{return_val} field and printed as
+@samp{/i}.
+
+@findex REG_POINTER
+@cindex @code{reg} and @samp{/f}
+@cindex @code{frame_related}, in @code{reg}
+@item REG_POINTER (@var{x})
+Nonzero in a @code{reg} if the register holds a pointer. Stored in the
+@code{frame_related} field and printed as @samp{/f}.
+
+@findex REG_USERVAR_P
+@cindex @code{reg} and @samp{/v}
+@cindex @code{volatil}, in @code{reg}
+@item REG_USERVAR_P (@var{x})
+In a @code{reg}, nonzero if it corresponds to a variable present in
+the user's source code. Zero for temporaries generated internally by
+the compiler. Stored in the @code{volatil} field and printed as
+@samp{/v}.
+
+The same hard register may be used also for collecting the values of
+functions called by this one, but @code{REG_FUNCTION_VALUE_P} is zero
+in this kind of use.
+
+@findex RTL_CONST_CALL_P
+@cindex @code{call_insn} and @samp{/u}
+@cindex @code{unchanging}, in @code{call_insn}
+@item RTL_CONST_CALL_P (@var{x})
+In a @code{call_insn} indicates that the insn represents a call to a
+const function. Stored in the @code{unchanging} field and printed as
+@samp{/u}.
+
+@findex RTL_PURE_CALL_P
+@cindex @code{call_insn} and @samp{/i}
+@cindex @code{return_val}, in @code{call_insn}
+@item RTL_PURE_CALL_P (@var{x})
+In a @code{call_insn} indicates that the insn represents a call to a
+pure function. Stored in the @code{return_val} field and printed as
+@samp{/i}.
+
+@findex RTL_CONST_OR_PURE_CALL_P
+@cindex @code{call_insn} and @samp{/u} or @samp{/i}
+@item RTL_CONST_OR_PURE_CALL_P (@var{x})
+In a @code{call_insn}, true if @code{RTL_CONST_CALL_P} or
+@code{RTL_PURE_CALL_P} is true.
+
+@findex RTL_LOOPING_CONST_OR_PURE_CALL_P
+@cindex @code{call_insn} and @samp{/c}
+@cindex @code{call}, in @code{call_insn}
+@item RTL_LOOPING_CONST_OR_PURE_CALL_P (@var{x})
+In a @code{call_insn} indicates that the insn represents a possibly
+infinite looping call to a const or pure function. Stored in the
+@code{call} field and printed as @samp{/c}. Only true if one of
+@code{RTL_CONST_CALL_P} or @code{RTL_PURE_CALL_P} is true.
+
+@findex RTX_FRAME_RELATED_P
+@cindex @code{insn} and @samp{/f}
+@cindex @code{call_insn} and @samp{/f}
+@cindex @code{jump_insn} and @samp{/f}
+@cindex @code{barrier} and @samp{/f}
+@cindex @code{set} and @samp{/f}
+@cindex @code{frame_related}, in @code{insn}, @code{call_insn}, @code{jump_insn}, @code{barrier}, and @code{set}
+@item RTX_FRAME_RELATED_P (@var{x})
+Nonzero in an @code{insn}, @code{call_insn}, @code{jump_insn},
+@code{barrier}, or @code{set} which is part of a function prologue
+and sets the stack pointer, sets the frame pointer, or saves a register.
+This flag should also be set on an instruction that sets up a temporary
+register to use in place of the frame pointer.
+Stored in the @code{frame_related} field and printed as @samp{/f}.
+
+In particular, on RISC targets where there are limits on the sizes of
+immediate constants, it is sometimes impossible to reach the register
+save area directly from the stack pointer. In that case, a temporary
+register is used that is near enough to the register save area, and the
+Canonical Frame Address, i.e., DWARF2's logical frame pointer, register
+must (temporarily) be changed to be this temporary register. So, the
+instruction that sets this temporary register must be marked as
+@code{RTX_FRAME_RELATED_P}.
+
+If the marked instruction is overly complex (defined in terms of what
+@code{dwarf2out_frame_debug_expr} can handle), you will also have to
+create a @code{REG_FRAME_RELATED_EXPR} note and attach it to the
+instruction. This note should contain a simple expression of the
+computation performed by this instruction, i.e., one that
+@code{dwarf2out_frame_debug_expr} can handle.
+
+This flag is required for exception handling support on targets with RTL
+prologues.
+
+@findex SCHED_GROUP_P
+@cindex @code{insn} and @samp{/s}
+@cindex @code{call_insn} and @samp{/s}
+@cindex @code{jump_insn} and @samp{/s}
+@cindex @code{jump_table_data} and @samp{/s}
+@cindex @code{in_struct}, in @code{insn}, @code{call_insn}, @code{jump_insn} and @code{jump_table_data}
+@item SCHED_GROUP_P (@var{x})
+During instruction scheduling, in an @code{insn}, @code{call_insn},
+@code{jump_insn} or @code{jump_table_data}, indicates that the
+previous insn must be scheduled together with this insn. This is used to
+ensure that certain groups of instructions will not be split up by the
+instruction scheduling pass, for example, @code{use} insns before
+a @code{call_insn} may not be separated from the @code{call_insn}.
+Stored in the @code{in_struct} field and printed as @samp{/s}.
+
+@findex SET_IS_RETURN_P
+@cindex @code{insn} and @samp{/j}
+@cindex @code{jump}, in @code{insn}
+@item SET_IS_RETURN_P (@var{x})
+For a @code{set}, nonzero if it is for a return.
+Stored in the @code{jump} field and printed as @samp{/j}.
+
+@findex SIBLING_CALL_P
+@cindex @code{call_insn} and @samp{/j}
+@cindex @code{jump}, in @code{call_insn}
+@item SIBLING_CALL_P (@var{x})
+For a @code{call_insn}, nonzero if the insn is a sibling call.
+Stored in the @code{jump} field and printed as @samp{/j}.
+
+@findex STRING_POOL_ADDRESS_P
+@cindex @code{symbol_ref} and @samp{/f}
+@cindex @code{frame_related}, in @code{symbol_ref}
+@item STRING_POOL_ADDRESS_P (@var{x})
+For a @code{symbol_ref} expression, nonzero if it addresses this function's
+string constant pool.
+Stored in the @code{frame_related} field and printed as @samp{/f}.
+
+@findex SUBREG_PROMOTED_UNSIGNED_P
+@cindex @code{subreg} and @samp{/u} and @samp{/v}
+@cindex @code{unchanging}, in @code{subreg}
+@cindex @code{volatil}, in @code{subreg}
+@item SUBREG_PROMOTED_UNSIGNED_P (@var{x})
+Returns a value greater then zero for a @code{subreg} that has
+@code{SUBREG_PROMOTED_VAR_P} nonzero if the object being referenced is kept
+zero-extended, zero if it is kept sign-extended, and less then zero if it is
+extended some other way via the @code{ptr_extend} instruction.
+Stored in the @code{unchanging}
+field and @code{volatil} field, printed as @samp{/u} and @samp{/v}.
+This macro may only be used to get the value it may not be used to change
+the value. Use @code{SUBREG_PROMOTED_UNSIGNED_SET} to change the value.
+
+@findex SUBREG_PROMOTED_UNSIGNED_SET
+@cindex @code{subreg} and @samp{/u}
+@cindex @code{unchanging}, in @code{subreg}
+@cindex @code{volatil}, in @code{subreg}
+@item SUBREG_PROMOTED_UNSIGNED_SET (@var{x})
+Set the @code{unchanging} and @code{volatil} fields in a @code{subreg}
+to reflect zero, sign, or other extension. If @code{volatil} is
+zero, then @code{unchanging} as nonzero means zero extension and as
+zero means sign extension. If @code{volatil} is nonzero then some
+other type of extension was done via the @code{ptr_extend} instruction.
+
+@findex SUBREG_PROMOTED_VAR_P
+@cindex @code{subreg} and @samp{/s}
+@cindex @code{in_struct}, in @code{subreg}
+@item SUBREG_PROMOTED_VAR_P (@var{x})
+Nonzero in a @code{subreg} if it was made when accessing an object that
+was promoted to a wider mode in accord with the @code{PROMOTED_MODE} machine
+description macro (@pxref{Storage Layout}). In this case, the mode of
+the @code{subreg} is the declared mode of the object and the mode of
+@code{SUBREG_REG} is the mode of the register that holds the object.
+Promoted variables are always either sign- or zero-extended to the wider
+mode on every assignment. Stored in the @code{in_struct} field and
+printed as @samp{/s}.
+
+@findex SYMBOL_REF_USED
+@cindex @code{used}, in @code{symbol_ref}
+@item SYMBOL_REF_USED (@var{x})
+In a @code{symbol_ref}, indicates that @var{x} has been used. This is
+normally only used to ensure that @var{x} is only declared external
+once. Stored in the @code{used} field.
+
+@findex SYMBOL_REF_WEAK
+@cindex @code{symbol_ref} and @samp{/i}
+@cindex @code{return_val}, in @code{symbol_ref}
+@item SYMBOL_REF_WEAK (@var{x})
+In a @code{symbol_ref}, indicates that @var{x} has been declared weak.
+Stored in the @code{return_val} field and printed as @samp{/i}.
+
+@findex SYMBOL_REF_FLAG
+@cindex @code{symbol_ref} and @samp{/v}
+@cindex @code{volatil}, in @code{symbol_ref}
+@item SYMBOL_REF_FLAG (@var{x})
+In a @code{symbol_ref}, this is used as a flag for machine-specific purposes.
+Stored in the @code{volatil} field and printed as @samp{/v}.
+
+Most uses of @code{SYMBOL_REF_FLAG} are historic and may be subsumed
+by @code{SYMBOL_REF_FLAGS}. Certainly use of @code{SYMBOL_REF_FLAGS}
+is mandatory if the target requires more than one bit of storage.
+@end table
+
+These are the fields to which the above macros refer:
+
+@table @code
+@findex call
+@cindex @samp{/c} in RTL dump
+@item call
+In a @code{mem}, 1 means that the memory reference will not trap.
+
+In a @code{call}, 1 means that this pure or const call may possibly
+infinite loop.
+
+In an RTL dump, this flag is represented as @samp{/c}.
+
+@findex frame_related
+@cindex @samp{/f} in RTL dump
+@item frame_related
+In an @code{insn} or @code{set} expression, 1 means that it is part of
+a function prologue and sets the stack pointer, sets the frame pointer,
+saves a register, or sets up a temporary register to use in place of the
+frame pointer.
+
+In @code{reg} expressions, 1 means that the register holds a pointer.
+
+In @code{mem} expressions, 1 means that the memory reference holds a pointer.
+
+In @code{symbol_ref} expressions, 1 means that the reference addresses
+this function's string constant pool.
+
+In an RTL dump, this flag is represented as @samp{/f}.
+
+@findex in_struct
+@cindex @samp{/s} in RTL dump
+@item in_struct
+In @code{reg} expressions, it is 1 if the register has its entire life
+contained within the test expression of some loop.
+
+In @code{subreg} expressions, 1 means that the @code{subreg} is accessing
+an object that has had its mode promoted from a wider mode.
+
+In @code{label_ref} expressions, 1 means that the referenced label is
+outside the innermost loop containing the insn in which the @code{label_ref}
+was found.
+
+In @code{code_label} expressions, it is 1 if the label may never be deleted.
+This is used for labels which are the target of non-local gotos. Such a
+label that would have been deleted is replaced with a @code{note} of type
+@code{NOTE_INSN_DELETED_LABEL}.
+
+In an @code{insn} during dead-code elimination, 1 means that the insn is
+dead code.
+
+In an @code{insn} or @code{jump_insn} during reorg for an insn in the
+delay slot of a branch,
+1 means that this insn is from the target of the branch.
+
+In an @code{insn} during instruction scheduling, 1 means that this insn
+must be scheduled as part of a group together with the previous insn.
+
+In an RTL dump, this flag is represented as @samp{/s}.
+
+@findex return_val
+@cindex @samp{/i} in RTL dump
+@item return_val
+In @code{reg} expressions, 1 means the register contains
+the value to be returned by the current function. On
+machines that pass parameters in registers, the same register number
+may be used for parameters as well, but this flag is not set on such
+uses.
+
+In @code{symbol_ref} expressions, 1 means the referenced symbol is weak.
+
+In @code{call} expressions, 1 means the call is pure.
+
+In an RTL dump, this flag is represented as @samp{/i}.
+
+@findex jump
+@cindex @samp{/j} in RTL dump
+@item jump
+In a @code{mem} expression, 1 means we should keep the alias set for this
+mem unchanged when we access a component.
+
+In a @code{set}, 1 means it is for a return.
+
+In a @code{call_insn}, 1 means it is a sibling call.
+
+In a @code{jump_insn}, 1 means it is a crossing jump.
+
+In an RTL dump, this flag is represented as @samp{/j}.
+
+@findex unchanging
+@cindex @samp{/u} in RTL dump
+@item unchanging
+In @code{reg} and @code{mem} expressions, 1 means
+that the value of the expression never changes.
+
+In @code{subreg} expressions, it is 1 if the @code{subreg} references an
+unsigned object whose mode has been promoted to a wider mode.
+
+In an @code{insn} or @code{jump_insn} in the delay slot of a branch
+instruction, 1 means an annulling branch should be used.
+
+In a @code{symbol_ref} expression, 1 means that this symbol addresses
+something in the per-function constant pool.
+
+In a @code{call_insn} 1 means that this instruction is a call to a const
+function.
+
+In an RTL dump, this flag is represented as @samp{/u}.
+
+@findex used
+@item used
+This flag is used directly (without an access macro) at the end of RTL
+generation for a function, to count the number of times an expression
+appears in insns. Expressions that appear more than once are copied,
+according to the rules for shared structure (@pxref{Sharing}).
+
+For a @code{reg}, it is used directly (without an access macro) by the
+leaf register renumbering code to ensure that each register is only
+renumbered once.
+
+In a @code{symbol_ref}, it indicates that an external declaration for
+the symbol has already been written.
+
+@findex volatil
+@cindex @samp{/v} in RTL dump
+@item volatil
+@cindex volatile memory references
+In a @code{mem}, @code{asm_operands}, or @code{asm_input}
+expression, it is 1 if the memory
+reference is volatile. Volatile memory references may not be deleted,
+reordered or combined.
+
+In a @code{symbol_ref} expression, it is used for machine-specific
+purposes.
+
+In a @code{reg} expression, it is 1 if the value is a user-level variable.
+0 indicates an internal compiler temporary.
+
+In an @code{insn}, 1 means the insn has been deleted.
+
+In @code{label_ref} and @code{reg_label} expressions, 1 means a reference
+to a non-local label.
+
+In @code{prefetch} expressions, 1 means that the containing insn is a
+scheduling barrier.
+
+In an RTL dump, this flag is represented as @samp{/v}.
+@end table
+
+@node Machine Modes
+@section Machine Modes
+@cindex machine modes
+
+@findex machine_mode
+A machine mode describes a size of data object and the representation used
+for it. In the C code, machine modes are represented by an enumeration
+type, @code{machine_mode}, defined in @file{machmode.def}. Each RTL
+expression has room for a machine mode and so do certain kinds of tree
+expressions (declarations and types, to be precise).
+
+In debugging dumps and machine descriptions, the machine mode of an RTL
+expression is written after the expression code with a colon to separate
+them. The letters @samp{mode} which appear at the end of each machine mode
+name are omitted. For example, @code{(reg:SI 38)} is a @code{reg}
+expression with machine mode @code{SImode}. If the mode is
+@code{VOIDmode}, it is not written at all.
+
+Here is a table of machine modes. The term ``byte'' below refers to an
+object of @code{BITS_PER_UNIT} bits (@pxref{Storage Layout}).
+
+@table @code
+@findex BImode
+@item BImode
+``Bit'' mode represents a single bit, for predicate registers.
+
+@findex QImode
+@item QImode
+``Quarter-Integer'' mode represents a single byte treated as an integer.
+
+@findex HImode
+@item HImode
+``Half-Integer'' mode represents a two-byte integer.
+
+@findex PSImode
+@item PSImode
+``Partial Single Integer'' mode represents an integer which occupies
+four bytes but which doesn't really use all four. On some machines,
+this is the right mode to use for pointers.
+
+@findex SImode
+@item SImode
+``Single Integer'' mode represents a four-byte integer.
+
+@findex PDImode
+@item PDImode
+``Partial Double Integer'' mode represents an integer which occupies
+eight bytes but which doesn't really use all eight. On some machines,
+this is the right mode to use for certain pointers.
+
+@findex DImode
+@item DImode
+``Double Integer'' mode represents an eight-byte integer.
+
+@findex TImode
+@item TImode
+``Tetra Integer'' (?) mode represents a sixteen-byte integer.
+
+@findex OImode
+@item OImode
+``Octa Integer'' (?) mode represents a thirty-two-byte integer.
+
+@findex XImode
+@item XImode
+``Hexadeca Integer'' (?) mode represents a sixty-four-byte integer.
+
+@findex QFmode
+@item QFmode
+``Quarter-Floating'' mode represents a quarter-precision (single byte)
+floating point number.
+
+@findex HFmode
+@item HFmode
+``Half-Floating'' mode represents a half-precision (two byte) floating
+point number.
+
+@findex TQFmode
+@item TQFmode
+``Three-Quarter-Floating'' (?) mode represents a three-quarter-precision
+(three byte) floating point number.
+
+@findex SFmode
+@item SFmode
+``Single Floating'' mode represents a four byte floating point number.
+In the common case, of a processor with IEEE arithmetic and 8-bit bytes,
+this is a single-precision IEEE floating point number; it can also be
+used for double-precision (on processors with 16-bit bytes) and
+single-precision VAX and IBM types.
+
+@findex DFmode
+@item DFmode
+``Double Floating'' mode represents an eight byte floating point number.
+In the common case, of a processor with IEEE arithmetic and 8-bit bytes,
+this is a double-precision IEEE floating point number.
+
+@findex XFmode
+@item XFmode
+``Extended Floating'' mode represents an IEEE extended floating point
+number. This mode only has 80 meaningful bits (ten bytes). Some
+processors require such numbers to be padded to twelve bytes, others
+to sixteen; this mode is used for either.
+
+@findex SDmode
+@item SDmode
+``Single Decimal Floating'' mode represents a four byte decimal
+floating point number (as distinct from conventional binary floating
+point).
+
+@findex DDmode
+@item DDmode
+``Double Decimal Floating'' mode represents an eight byte decimal
+floating point number.
+
+@findex TDmode
+@item TDmode
+``Tetra Decimal Floating'' mode represents a sixteen byte decimal
+floating point number all 128 of whose bits are meaningful.
+
+@findex TFmode
+@item TFmode
+``Tetra Floating'' mode represents a sixteen byte floating point number
+all 128 of whose bits are meaningful. One common use is the
+IEEE quad-precision format.
+
+@findex QQmode
+@item QQmode
+``Quarter-Fractional'' mode represents a single byte treated as a signed
+fractional number. The default format is ``s.7''.
+
+@findex HQmode
+@item HQmode
+``Half-Fractional'' mode represents a two-byte signed fractional number.
+The default format is ``s.15''.
+
+@findex SQmode
+@item SQmode
+``Single Fractional'' mode represents a four-byte signed fractional number.
+The default format is ``s.31''.
+
+@findex DQmode
+@item DQmode
+``Double Fractional'' mode represents an eight-byte signed fractional number.
+The default format is ``s.63''.
+
+@findex TQmode
+@item TQmode
+``Tetra Fractional'' mode represents a sixteen-byte signed fractional number.
+The default format is ``s.127''.
+
+@findex UQQmode
+@item UQQmode
+``Unsigned Quarter-Fractional'' mode represents a single byte treated as an
+unsigned fractional number. The default format is ``.8''.
+
+@findex UHQmode
+@item UHQmode
+``Unsigned Half-Fractional'' mode represents a two-byte unsigned fractional
+number. The default format is ``.16''.
+
+@findex USQmode
+@item USQmode
+``Unsigned Single Fractional'' mode represents a four-byte unsigned fractional
+number. The default format is ``.32''.
+
+@findex UDQmode
+@item UDQmode
+``Unsigned Double Fractional'' mode represents an eight-byte unsigned
+fractional number. The default format is ``.64''.
+
+@findex UTQmode
+@item UTQmode
+``Unsigned Tetra Fractional'' mode represents a sixteen-byte unsigned
+fractional number. The default format is ``.128''.
+
+@findex HAmode
+@item HAmode
+``Half-Accumulator'' mode represents a two-byte signed accumulator.
+The default format is ``s8.7''.
+
+@findex SAmode
+@item SAmode
+``Single Accumulator'' mode represents a four-byte signed accumulator.
+The default format is ``s16.15''.
+
+@findex DAmode
+@item DAmode
+``Double Accumulator'' mode represents an eight-byte signed accumulator.
+The default format is ``s32.31''.
+
+@findex TAmode
+@item TAmode
+``Tetra Accumulator'' mode represents a sixteen-byte signed accumulator.
+The default format is ``s64.63''.
+
+@findex UHAmode
+@item UHAmode
+``Unsigned Half-Accumulator'' mode represents a two-byte unsigned accumulator.
+The default format is ``8.8''.
+
+@findex USAmode
+@item USAmode
+``Unsigned Single Accumulator'' mode represents a four-byte unsigned
+accumulator. The default format is ``16.16''.
+
+@findex UDAmode
+@item UDAmode
+``Unsigned Double Accumulator'' mode represents an eight-byte unsigned
+accumulator. The default format is ``32.32''.
+
+@findex UTAmode
+@item UTAmode
+``Unsigned Tetra Accumulator'' mode represents a sixteen-byte unsigned
+accumulator. The default format is ``64.64''.
+
+@findex CCmode
+@item CCmode
+``Condition Code'' mode represents the value of a condition code, which
+is a machine-specific set of bits used to represent the result of a
+comparison operation. Other machine-specific modes may also be used for
+the condition code. (@pxref{Condition Code}).
+
+@findex BLKmode
+@item BLKmode
+``Block'' mode represents values that are aggregates to which none of
+the other modes apply. In RTL, only memory references can have this mode,
+and only if they appear in string-move or vector instructions. On machines
+which have no such instructions, @code{BLKmode} will not appear in RTL@.
+
+@findex VOIDmode
+@item VOIDmode
+Void mode means the absence of a mode or an unspecified mode.
+For example, RTL expressions of code @code{const_int} have mode
+@code{VOIDmode} because they can be taken to have whatever mode the context
+requires. In debugging dumps of RTL, @code{VOIDmode} is expressed by
+the absence of any mode.
+
+@findex QCmode
+@findex HCmode
+@findex SCmode
+@findex DCmode
+@findex XCmode
+@findex TCmode
+@item QCmode, HCmode, SCmode, DCmode, XCmode, TCmode
+These modes stand for a complex number represented as a pair of floating
+point values. The floating point values are in @code{QFmode},
+@code{HFmode}, @code{SFmode}, @code{DFmode}, @code{XFmode}, and
+@code{TFmode}, respectively.
+
+@findex CQImode
+@findex CHImode
+@findex CSImode
+@findex CDImode
+@findex CTImode
+@findex COImode
+@findex CPSImode
+@item CQImode, CHImode, CSImode, CDImode, CTImode, COImode, CPSImode
+These modes stand for a complex number represented as a pair of integer
+values. The integer values are in @code{QImode}, @code{HImode},
+@code{SImode}, @code{DImode}, @code{TImode}, @code{OImode}, and @code{PSImode},
+respectively.
+
+@findex BND32mode
+@findex BND64mode
+@item BND32mode BND64mode
+These modes stand for bounds for pointer of 32 and 64 bit size respectively.
+Mode size is double pointer mode size.
+@end table
+
+The machine description defines @code{Pmode} as a C macro which expands
+into the machine mode used for addresses. Normally this is the mode
+whose size is @code{BITS_PER_WORD}, @code{SImode} on 32-bit machines.
+
+The only modes which a machine description @i{must} support are
+@code{QImode}, and the modes corresponding to @code{BITS_PER_WORD},
+@code{FLOAT_TYPE_SIZE} and @code{DOUBLE_TYPE_SIZE}.
+The compiler will attempt to use @code{DImode} for 8-byte structures and
+unions, but this can be prevented by overriding the definition of
+@code{MAX_FIXED_MODE_SIZE}. Alternatively, you can have the compiler
+use @code{TImode} for 16-byte structures and unions. Likewise, you can
+arrange for the C type @code{short int} to avoid using @code{HImode}.
+
+@cindex mode classes
+Very few explicit references to machine modes remain in the compiler and
+these few references will soon be removed. Instead, the machine modes
+are divided into mode classes. These are represented by the enumeration
+type @code{enum mode_class} defined in @file{machmode.h}. The possible
+mode classes are:
+
+@table @code
+@findex MODE_INT
+@item MODE_INT
+Integer modes. By default these are @code{BImode}, @code{QImode},
+@code{HImode}, @code{SImode}, @code{DImode}, @code{TImode}, and
+@code{OImode}.
+
+@findex MODE_PARTIAL_INT
+@item MODE_PARTIAL_INT
+The ``partial integer'' modes, @code{PQImode}, @code{PHImode},
+@code{PSImode} and @code{PDImode}.
+
+@findex MODE_FLOAT
+@item MODE_FLOAT
+Floating point modes. By default these are @code{QFmode},
+@code{HFmode}, @code{TQFmode}, @code{SFmode}, @code{DFmode},
+@code{XFmode} and @code{TFmode}.
+
+@findex MODE_DECIMAL_FLOAT
+@item MODE_DECIMAL_FLOAT
+Decimal floating point modes. By default these are @code{SDmode},
+@code{DDmode} and @code{TDmode}.
+
+@findex MODE_FRACT
+@item MODE_FRACT
+Signed fractional modes. By default these are @code{QQmode}, @code{HQmode},
+@code{SQmode}, @code{DQmode} and @code{TQmode}.
+
+@findex MODE_UFRACT
+@item MODE_UFRACT
+Unsigned fractional modes. By default these are @code{UQQmode}, @code{UHQmode},
+@code{USQmode}, @code{UDQmode} and @code{UTQmode}.
+
+@findex MODE_ACCUM
+@item MODE_ACCUM
+Signed accumulator modes. By default these are @code{HAmode},
+@code{SAmode}, @code{DAmode} and @code{TAmode}.
+
+@findex MODE_UACCUM
+@item MODE_UACCUM
+Unsigned accumulator modes. By default these are @code{UHAmode},
+@code{USAmode}, @code{UDAmode} and @code{UTAmode}.
+
+@findex MODE_COMPLEX_INT
+@item MODE_COMPLEX_INT
+Complex integer modes. (These are not currently implemented).
+
+@findex MODE_COMPLEX_FLOAT
+@item MODE_COMPLEX_FLOAT
+Complex floating point modes. By default these are @code{QCmode},
+@code{HCmode}, @code{SCmode}, @code{DCmode}, @code{XCmode}, and
+@code{TCmode}.
+
+@findex MODE_CC
+@item MODE_CC
+Modes representing condition code values. These are @code{CCmode} plus
+any @code{CC_MODE} modes listed in the @file{@var{machine}-modes.def}.
+@xref{Jump Patterns},
+also see @ref{Condition Code}.
+
+@findex MODE_POINTER_BOUNDS
+@item MODE_POINTER_BOUNDS
+Pointer bounds modes. Used to represent values of pointer bounds type.
+Operations in these modes may be executed as NOPs depending on hardware
+features and environment setup.
+
+@findex MODE_OPAQUE
+@item MODE_OPAQUE
+This is a mode class for modes that don't want to provide operations
+other than register moves, memory moves, loads, stores, and
+@code{unspec}s. They have a size and precision and that's all.
+
+@findex MODE_RANDOM
+@item MODE_RANDOM
+This is a catchall mode class for modes which don't fit into the above
+classes. Currently @code{VOIDmode} and @code{BLKmode} are in
+@code{MODE_RANDOM}.
+@end table
+
+@cindex machine mode wrapper classes
+@code{machmode.h} also defines various wrapper classes that combine a
+@code{machine_mode} with a static assertion that a particular
+condition holds. The classes are:
+
+@table @code
+@findex scalar_int_mode
+@item scalar_int_mode
+A mode that has class @code{MODE_INT} or @code{MODE_PARTIAL_INT}.
+
+@findex scalar_float_mode
+@item scalar_float_mode
+A mode that has class @code{MODE_FLOAT} or @code{MODE_DECIMAL_FLOAT}.
+
+@findex scalar_mode
+@item scalar_mode
+A mode that holds a single numerical value. In practice this means
+that the mode is a @code{scalar_int_mode}, is a @code{scalar_float_mode},
+or has class @code{MODE_FRACT}, @code{MODE_UFRACT}, @code{MODE_ACCUM},
+@code{MODE_UACCUM} or @code{MODE_POINTER_BOUNDS}.
+
+@findex complex_mode
+@item complex_mode
+A mode that has class @code{MODE_COMPLEX_INT} or @code{MODE_COMPLEX_FLOAT}.
+
+@findex fixed_size_mode
+@item fixed_size_mode
+A mode whose size is known at compile time.
+@end table
+
+Named modes use the most constrained of the available wrapper classes,
+if one exists, otherwise they use @code{machine_mode}. For example,
+@code{QImode} is a @code{scalar_int_mode}, @code{SFmode} is a
+@code{scalar_float_mode} and @code{BLKmode} is a plain
+@code{machine_mode}. It is possible to refer to any mode as a raw
+@code{machine_mode} by adding the @code{E_} prefix, where @code{E}
+stands for ``enumeration''. For example, the raw @code{machine_mode}
+names of the modes just mentioned are @code{E_QImode}, @code{E_SFmode}
+and @code{E_BLKmode} respectively.
+
+The wrapper classes implicitly convert to @code{machine_mode} and to any
+wrapper class that represents a more general condition; for example
+@code{scalar_int_mode} and @code{scalar_float_mode} both convert
+to @code{scalar_mode} and all three convert to @code{fixed_size_mode}.
+The classes act like @code{machine_mode}s that accept only certain
+named modes.
+
+@findex opt_mode
+@file{machmode.h} also defines a template class @code{opt_mode<@var{T}>}
+that holds a @code{T} or nothing, where @code{T} can be either
+@code{machine_mode} or one of the wrapper classes above. The main
+operations on an @code{opt_mode<@var{T}>} @var{x} are as follows:
+
+@table @samp
+@item @var{x}.exists ()
+Return true if @var{x} holds a mode rather than nothing.
+
+@item @var{x}.exists (&@var{y})
+Return true if @var{x} holds a mode rather than nothing, storing the
+mode in @var{y} if so. @var{y} must be assignment-compatible with @var{T}.
+
+@item @var{x}.require ()
+Assert that @var{x} holds a mode rather than nothing and return that mode.
+
+@item @var{x} = @var{y}
+Set @var{x} to @var{y}, where @var{y} is a @var{T} or implicitly converts
+to a @var{T}.
+@end table
+
+The default constructor sets an @code{opt_mode<@var{T}>} to nothing.
+There is also a constructor that takes an initial value of type @var{T}.
+
+It is possible to use the @file{is-a.h} accessors on a @code{machine_mode}
+or machine mode wrapper @var{x}:
+
+@table @samp
+@findex is_a
+@item is_a <@var{T}> (@var{x})
+Return true if @var{x} meets the conditions for wrapper class @var{T}.
+
+@item is_a <@var{T}> (@var{x}, &@var{y})
+Return true if @var{x} meets the conditions for wrapper class @var{T},
+storing it in @var{y} if so. @var{y} must be assignment-compatible with
+@var{T}.
+
+@item as_a <@var{T}> (@var{x})
+Assert that @var{x} meets the conditions for wrapper class @var{T}
+and return it as a @var{T}.
+
+@item dyn_cast <@var{T}> (@var{x})
+Return an @code{opt_mode<@var{T}>} that holds @var{x} if @var{x} meets
+the conditions for wrapper class @var{T} and that holds nothing otherwise.
+@end table
+
+The purpose of these wrapper classes is to give stronger static type
+checking. For example, if a function takes a @code{scalar_int_mode},
+a caller that has a general @code{machine_mode} must either check or
+assert that the code is indeed a scalar integer first, using one of
+the functions above.
+
+The wrapper classes are normal C++ classes, with user-defined
+constructors. Sometimes it is useful to have a POD version of
+the same type, particularly if the type appears in a @code{union}.
+The template class @code{pod_mode<@var{T}>} provides a POD version
+of wrapper class @var{T}. It is assignment-compatible with @var{T}
+and implicitly converts to both @code{machine_mode} and @var{T}.
+
+Here are some C macros that relate to machine modes:
+
+@table @code
+@findex GET_MODE
+@item GET_MODE (@var{x})
+Returns the machine mode of the RTX @var{x}.
+
+@findex PUT_MODE
+@item PUT_MODE (@var{x}, @var{newmode})
+Alters the machine mode of the RTX @var{x} to be @var{newmode}.
+
+@findex NUM_MACHINE_MODES
+@item NUM_MACHINE_MODES
+Stands for the number of machine modes available on the target
+machine. This is one greater than the largest numeric value of any
+machine mode.
+
+@findex GET_MODE_NAME
+@item GET_MODE_NAME (@var{m})
+Returns the name of mode @var{m} as a string.
+
+@findex GET_MODE_CLASS
+@item GET_MODE_CLASS (@var{m})
+Returns the mode class of mode @var{m}.
+
+@findex GET_MODE_WIDER_MODE
+@item GET_MODE_WIDER_MODE (@var{m})
+Returns the next wider natural mode. For example, the expression
+@code{GET_MODE_WIDER_MODE (QImode)} returns @code{HImode}.
+
+@findex GET_MODE_SIZE
+@item GET_MODE_SIZE (@var{m})
+Returns the size in bytes of a datum of mode @var{m}.
+
+@findex GET_MODE_BITSIZE
+@item GET_MODE_BITSIZE (@var{m})
+Returns the size in bits of a datum of mode @var{m}.
+
+@findex GET_MODE_IBIT
+@item GET_MODE_IBIT (@var{m})
+Returns the number of integral bits of a datum of fixed-point mode @var{m}.
+
+@findex GET_MODE_FBIT
+@item GET_MODE_FBIT (@var{m})
+Returns the number of fractional bits of a datum of fixed-point mode @var{m}.
+
+@findex GET_MODE_MASK
+@item GET_MODE_MASK (@var{m})
+Returns a bitmask containing 1 for all bits in a word that fit within
+mode @var{m}. This macro can only be used for modes whose bitsize is
+less than or equal to @code{HOST_BITS_PER_INT}.
+
+@findex GET_MODE_ALIGNMENT
+@item GET_MODE_ALIGNMENT (@var{m})
+Return the required alignment, in bits, for an object of mode @var{m}.
+
+@findex GET_MODE_UNIT_SIZE
+@item GET_MODE_UNIT_SIZE (@var{m})
+Returns the size in bytes of the subunits of a datum of mode @var{m}.
+This is the same as @code{GET_MODE_SIZE} except in the case of complex
+modes. For them, the unit size is the size of the real or imaginary
+part.
+
+@findex GET_MODE_NUNITS
+@item GET_MODE_NUNITS (@var{m})
+Returns the number of units contained in a mode, i.e.,
+@code{GET_MODE_SIZE} divided by @code{GET_MODE_UNIT_SIZE}.
+
+@findex GET_CLASS_NARROWEST_MODE
+@item GET_CLASS_NARROWEST_MODE (@var{c})
+Returns the narrowest mode in mode class @var{c}.
+@end table
+
+The following 3 variables are defined on every target. They can be
+used to allocate buffers that are guaranteed to be large enough to
+hold any value that can be represented on the target. The first two
+can be overridden by defining them in the target's mode.def file,
+however, the value must be a constant that can determined very early
+in the compilation process. The third symbol cannot be overridden.
+
+@table @code
+@findex BITS_PER_UNIT
+@item BITS_PER_UNIT
+The number of bits in an addressable storage unit (byte). If you do
+not define this, the default is 8.
+
+@findex MAX_BITSIZE_MODE_ANY_INT
+@item MAX_BITSIZE_MODE_ANY_INT
+The maximum bitsize of any mode that is used in integer math. This
+should be overridden by the target if it uses large integers as
+containers for larger vectors but otherwise never uses the contents to
+compute integer values.
+
+@findex MAX_BITSIZE_MODE_ANY_MODE
+@item MAX_BITSIZE_MODE_ANY_MODE
+The bitsize of the largest mode on the target. The default value is
+the largest mode size given in the mode definition file, which is
+always correct for targets whose modes have a fixed size. Targets
+that might increase the size of a mode beyond this default should define
+@code{MAX_BITSIZE_MODE_ANY_MODE} to the actual upper limit in
+@file{@var{machine}-modes.def}.
+@end table
+
+@findex byte_mode
+@findex word_mode
+The global variables @code{byte_mode} and @code{word_mode} contain modes
+whose classes are @code{MODE_INT} and whose bitsizes are either
+@code{BITS_PER_UNIT} or @code{BITS_PER_WORD}, respectively. On 32-bit
+machines, these are @code{QImode} and @code{SImode}, respectively.
+
+@node Constants
+@section Constant Expression Types
+@cindex RTL constants
+@cindex RTL constant expression types
+
+The simplest RTL expressions are those that represent constant values.
+
+@table @code
+@findex const_int
+@item (const_int @var{i})
+This type of expression represents the integer value @var{i}. @var{i}
+is customarily accessed with the macro @code{INTVAL} as in
+@code{INTVAL (@var{exp})}, which is equivalent to @code{XWINT (@var{exp}, 0)}.
+
+Constants generated for modes with fewer bits than in
+@code{HOST_WIDE_INT} must be sign extended to full width (e.g., with
+@code{gen_int_mode}). For constants for modes with more bits than in
+@code{HOST_WIDE_INT} the implied high order bits of that constant are
+copies of the top bit. Note however that values are neither
+inherently signed nor inherently unsigned; where necessary, signedness
+is determined by the rtl operation instead.
+
+@findex const0_rtx
+@findex const1_rtx
+@findex const2_rtx
+@findex constm1_rtx
+There is only one expression object for the integer value zero; it is
+the value of the variable @code{const0_rtx}. Likewise, the only
+expression for integer value one is found in @code{const1_rtx}, the only
+expression for integer value two is found in @code{const2_rtx}, and the
+only expression for integer value negative one is found in
+@code{constm1_rtx}. Any attempt to create an expression of code
+@code{const_int} and value zero, one, two or negative one will return
+@code{const0_rtx}, @code{const1_rtx}, @code{const2_rtx} or
+@code{constm1_rtx} as appropriate.
+
+@findex const_true_rtx
+Similarly, there is only one object for the integer whose value is
+@code{STORE_FLAG_VALUE}. It is found in @code{const_true_rtx}. If
+@code{STORE_FLAG_VALUE} is one, @code{const_true_rtx} and
+@code{const1_rtx} will point to the same object. If
+@code{STORE_FLAG_VALUE} is @minus{}1, @code{const_true_rtx} and
+@code{constm1_rtx} will point to the same object.
+
+@findex const_double
+@item (const_double:@var{m} @var{i0} @var{i1} @dots{})
+This represents either a floating-point constant of mode @var{m} or
+(on older ports that do not define
+@code{TARGET_SUPPORTS_WIDE_INT}) an integer constant too large to fit
+into @code{HOST_BITS_PER_WIDE_INT} bits but small enough to fit within
+twice that number of bits. In the latter case, @var{m} will be
+@code{VOIDmode}. For integral values constants for modes with more
+bits than twice the number in @code{HOST_WIDE_INT} the implied high
+order bits of that constant are copies of the top bit of
+@code{CONST_DOUBLE_HIGH}. Note however that integral values are
+neither inherently signed nor inherently unsigned; where necessary,
+signedness is determined by the rtl operation instead.
+
+On more modern ports, @code{CONST_DOUBLE} only represents floating
+point values. New ports define @code{TARGET_SUPPORTS_WIDE_INT} to
+make this designation.
+
+@findex CONST_DOUBLE_LOW
+If @var{m} is @code{VOIDmode}, the bits of the value are stored in
+@var{i0} and @var{i1}. @var{i0} is customarily accessed with the macro
+@code{CONST_DOUBLE_LOW} and @var{i1} with @code{CONST_DOUBLE_HIGH}.
+
+If the constant is floating point (regardless of its precision), then
+the number of integers used to store the value depends on the size of
+@code{REAL_VALUE_TYPE} (@pxref{Floating Point}). The integers
+represent a floating point number, but not precisely in the target
+machine's or host machine's floating point format. To convert them to
+the precise bit pattern used by the target machine, use the macro
+@code{REAL_VALUE_TO_TARGET_DOUBLE} and friends (@pxref{Data Output}).
+
+@findex const_double_zero
+The host dependency for the number of integers used to store a double
+value makes it problematic for machine descriptions to use expressions
+of code @code{const_double} and therefore a syntactic alias has been
+provided:
+
+@smallexample
+(const_double_zero:@var{m})
+@end smallexample
+
+standing for:
+
+@smallexample
+(const_double:@var{m} 0 0 @dots{})
+@end smallexample
+
+for matching the floating-point value zero, possibly the only useful one.
+
+@findex CONST_WIDE_INT
+@item (const_wide_int:@var{m} @var{nunits} @var{elt0} @dots{})
+This contains an array of @code{HOST_WIDE_INT}s that is large enough
+to hold any constant that can be represented on the target. This form
+of rtl is only used on targets that define
+@code{TARGET_SUPPORTS_WIDE_INT} to be nonzero and then
+@code{CONST_DOUBLE}s are only used to hold floating-point values. If
+the target leaves @code{TARGET_SUPPORTS_WIDE_INT} defined as 0,
+@code{CONST_WIDE_INT}s are not used and @code{CONST_DOUBLE}s are as
+they were before.
+
+The values are stored in a compressed format. The higher-order
+0s or -1s are not represented if they are just the logical sign
+extension of the number that is represented.
+
+@findex CONST_WIDE_INT_VEC
+@item CONST_WIDE_INT_VEC (@var{code})
+Returns the entire array of @code{HOST_WIDE_INT}s that are used to
+store the value. This macro should be rarely used.
+
+@findex CONST_WIDE_INT_NUNITS
+@item CONST_WIDE_INT_NUNITS (@var{code})
+The number of @code{HOST_WIDE_INT}s used to represent the number.
+Note that this generally is smaller than the number of
+@code{HOST_WIDE_INT}s implied by the mode size.
+
+@findex CONST_WIDE_INT_ELT
+@item CONST_WIDE_INT_ELT (@var{code},@var{i})
+Returns the @code{i}th element of the array. Element 0 is contains
+the low order bits of the constant.
+
+@findex const_fixed
+@item (const_fixed:@var{m} @dots{})
+Represents a fixed-point constant of mode @var{m}.
+The operand is a data structure of type @code{struct fixed_value} and
+is accessed with the macro @code{CONST_FIXED_VALUE}. The high part of
+data is accessed with @code{CONST_FIXED_VALUE_HIGH}; the low part is
+accessed with @code{CONST_FIXED_VALUE_LOW}.
+
+@findex const_poly_int
+@item (const_poly_int:@var{m} [@var{c0} @var{c1} @dots{}])
+Represents a @code{poly_int}-style polynomial integer with coefficients
+@var{c0}, @var{c1}, @dots{}. The coefficients are @code{wide_int}-based
+integers rather than rtxes. @code{CONST_POLY_INT_COEFFS} gives the
+values of individual coefficients (which is mostly only useful in
+low-level routines) and @code{const_poly_int_value} gives the full
+@code{poly_int} value.
+
+@findex const_vector
+@item (const_vector:@var{m} [@var{x0} @var{x1} @dots{}])
+Represents a vector constant. The values in square brackets are
+elements of the vector, which are always @code{const_int},
+@code{const_wide_int}, @code{const_double} or @code{const_fixed}
+expressions.
+
+Each vector constant @var{v} is treated as a specific instance of an
+arbitrary-length sequence that itself contains
+@samp{CONST_VECTOR_NPATTERNS (@var{v})} interleaved patterns. Each
+pattern has the form:
+
+@smallexample
+@{ @var{base0}, @var{base1}, @var{base1} + @var{step}, @var{base1} + @var{step} * 2, @dots{} @}
+@end smallexample
+
+The first three elements in each pattern are enough to determine the
+values of the other elements. However, if all @var{step}s are zero,
+only the first two elements are needed. If in addition each @var{base1}
+is equal to the corresponding @var{base0}, only the first element in
+each pattern is needed. The number of determining elements per pattern
+is given by @samp{CONST_VECTOR_NELTS_PER_PATTERN (@var{v})}.
+
+For example, the constant:
+
+@smallexample
+@{ 0, 1, 2, 6, 3, 8, 4, 10, 5, 12, 6, 14, 7, 16, 8, 18 @}
+@end smallexample
+
+is interpreted as an interleaving of the sequences:
+
+@smallexample
+@{ 0, 2, 3, 4, 5, 6, 7, 8 @}
+@{ 1, 6, 8, 10, 12, 14, 16, 18 @}
+@end smallexample
+
+where the sequences are represented by the following patterns:
+
+@smallexample
+@var{base0} == 0, @var{base1} == 2, @var{step} == 1
+@var{base0} == 1, @var{base1} == 6, @var{step} == 2
+@end smallexample
+
+In this case:
+
+@smallexample
+CONST_VECTOR_NPATTERNS (@var{v}) == 2
+CONST_VECTOR_NELTS_PER_PATTERN (@var{v}) == 3
+@end smallexample
+
+Thus the first 6 elements (@samp{@{ 0, 1, 2, 6, 3, 8 @}}) are enough
+to determine the whole sequence; we refer to them as the ``encoded''
+elements. They are the only elements present in the square brackets
+for variable-length @code{const_vector}s (i.e.@: for
+@code{const_vector}s whose mode @var{m} has a variable number of
+elements). However, as a convenience to code that needs to handle
+both @code{const_vector}s and @code{parallel}s, all elements are
+present in the square brackets for fixed-length @code{const_vector}s;
+the encoding scheme simply reduces the amount of work involved in
+processing constants that follow a regular pattern.
+
+Sometimes this scheme can create two possible encodings of the same
+vector. For example @{ 0, 1 @} could be seen as two patterns with
+one element each or one pattern with two elements (@var{base0} and
+@var{base1}). The canonical encoding is always the one with the
+fewest patterns or (if both encodings have the same number of
+petterns) the one with the fewest encoded elements.
+
+@samp{const_vector_encoding_nelts (@var{v})} gives the total number of
+encoded elements in @var{v}, which is 6 in the example above.
+@code{CONST_VECTOR_ENCODED_ELT (@var{v}, @var{i})} accesses the value
+of encoded element @var{i}.
+
+@samp{CONST_VECTOR_DUPLICATE_P (@var{v})} is true if @var{v} simply contains
+repeated instances of @samp{CONST_VECTOR_NPATTERNS (@var{v})} values. This is
+a shorthand for testing @samp{CONST_VECTOR_NELTS_PER_PATTERN (@var{v}) == 1}.
+
+@samp{CONST_VECTOR_STEPPED_P (@var{v})} is true if at least one
+pattern in @var{v} has a nonzero step. This is a shorthand for
+testing @samp{CONST_VECTOR_NELTS_PER_PATTERN (@var{v}) == 3}.
+
+@code{CONST_VECTOR_NUNITS (@var{v})} gives the total number of elements
+in @var{v}; it is a shorthand for getting the number of units in
+@samp{GET_MODE (@var{v})}.
+
+The utility function @code{const_vector_elt} gives the value of an
+arbitrary element as an @code{rtx}. @code{const_vector_int_elt} gives
+the same value as a @code{wide_int}.
+
+@findex const_string
+@item (const_string @var{str})
+Represents a constant string with value @var{str}. Currently this is
+used only for insn attributes (@pxref{Insn Attributes}) since constant
+strings in C are placed in memory.
+
+@findex symbol_ref
+@item (symbol_ref:@var{mode} @var{symbol})
+Represents the value of an assembler label for data. @var{symbol} is
+a string that describes the name of the assembler label. If it starts
+with a @samp{*}, the label is the rest of @var{symbol} not including
+the @samp{*}. Otherwise, the label is @var{symbol}, usually prefixed
+with @samp{_}.
+
+The @code{symbol_ref} contains a mode, which is usually @code{Pmode}.
+Usually that is the only mode for which a symbol is directly valid.
+
+@findex label_ref
+@item (label_ref:@var{mode} @var{label})
+Represents the value of an assembler label for code. It contains one
+operand, an expression, which must be a @code{code_label} or a @code{note}
+of type @code{NOTE_INSN_DELETED_LABEL} that appears in the instruction
+sequence to identify the place where the label should go.
+
+The reason for using a distinct expression type for code label
+references is so that jump optimization can distinguish them.
+
+The @code{label_ref} contains a mode, which is usually @code{Pmode}.
+Usually that is the only mode for which a label is directly valid.
+
+@findex const
+@item (const:@var{m} @var{exp})
+Represents a constant that is the result of an assembly-time
+arithmetic computation. The operand, @var{exp}, contains only
+@code{const_int}, @code{symbol_ref}, @code{label_ref} or @code{unspec}
+expressions, combined with @code{plus} and @code{minus}. Any such
+@code{unspec}s are target-specific and typically represent some form
+of relocation operator. @var{m} should be a valid address mode.
+
+@findex high
+@item (high:@var{m} @var{exp})
+Represents the high-order bits of @var{exp}.
+The number of bits is machine-dependent and is
+normally the number of bits specified in an instruction that initializes
+the high order bits of a register. It is used with @code{lo_sum} to
+represent the typical two-instruction sequence used in RISC machines to
+reference large immediate values and/or link-time constants such
+as global memory addresses. In the latter case, @var{m} is @code{Pmode}
+and @var{exp} is usually a constant expression involving @code{symbol_ref}.
+@end table
+
+@findex CONST0_RTX
+@findex CONST1_RTX
+@findex CONST2_RTX
+The macro @code{CONST0_RTX (@var{mode})} refers to an expression with
+value 0 in mode @var{mode}. If mode @var{mode} is of mode class
+@code{MODE_INT}, it returns @code{const0_rtx}. If mode @var{mode} is of
+mode class @code{MODE_FLOAT}, it returns a @code{CONST_DOUBLE}
+expression in mode @var{mode}. Otherwise, it returns a
+@code{CONST_VECTOR} expression in mode @var{mode}. Similarly, the macro
+@code{CONST1_RTX (@var{mode})} refers to an expression with value 1 in
+mode @var{mode} and similarly for @code{CONST2_RTX}. The
+@code{CONST1_RTX} and @code{CONST2_RTX} macros are undefined
+for vector modes.
+
+@node Regs and Memory
+@section Registers and Memory
+@cindex RTL register expressions
+@cindex RTL memory expressions
+
+Here are the RTL expression types for describing access to machine
+registers and to main memory.
+
+@table @code
+@findex reg
+@cindex hard registers
+@cindex pseudo registers
+@item (reg:@var{m} @var{n})
+For small values of the integer @var{n} (those that are less than
+@code{FIRST_PSEUDO_REGISTER}), this stands for a reference to machine
+register number @var{n}: a @dfn{hard register}. For larger values of
+@var{n}, it stands for a temporary value or @dfn{pseudo register}.
+The compiler's strategy is to generate code assuming an unlimited
+number of such pseudo registers, and later convert them into hard
+registers or into memory references.
+
+@var{m} is the machine mode of the reference. It is necessary because
+machines can generally refer to each register in more than one mode.
+For example, a register may contain a full word but there may be
+instructions to refer to it as a half word or as a single byte, as
+well as instructions to refer to it as a floating point number of
+various precisions.
+
+Even for a register that the machine can access in only one mode,
+the mode must always be specified.
+
+The symbol @code{FIRST_PSEUDO_REGISTER} is defined by the machine
+description, since the number of hard registers on the machine is an
+invariant characteristic of the machine. Note, however, that not
+all of the machine registers must be general registers. All the
+machine registers that can be used for storage of data are given
+hard register numbers, even those that can be used only in certain
+instructions or can hold only certain types of data.
+
+A hard register may be accessed in various modes throughout one
+function, but each pseudo register is given a natural mode
+and is accessed only in that mode. When it is necessary to describe
+an access to a pseudo register using a nonnatural mode, a @code{subreg}
+expression is used.
+
+A @code{reg} expression with a machine mode that specifies more than
+one word of data may actually stand for several consecutive registers.
+If in addition the register number specifies a hardware register, then
+it actually represents several consecutive hardware registers starting
+with the specified one.
+
+Each pseudo register number used in a function's RTL code is
+represented by a unique @code{reg} expression.
+
+@findex FIRST_VIRTUAL_REGISTER
+@findex LAST_VIRTUAL_REGISTER
+Some pseudo register numbers, those within the range of
+@code{FIRST_VIRTUAL_REGISTER} to @code{LAST_VIRTUAL_REGISTER} only
+appear during the RTL generation phase and are eliminated before the
+optimization phases. These represent locations in the stack frame that
+cannot be determined until RTL generation for the function has been
+completed. The following virtual register numbers are defined:
+
+@table @code
+@findex VIRTUAL_INCOMING_ARGS_REGNUM
+@item VIRTUAL_INCOMING_ARGS_REGNUM
+This points to the first word of the incoming arguments passed on the
+stack. Normally these arguments are placed there by the caller, but the
+callee may have pushed some arguments that were previously passed in
+registers.
+
+@cindex @code{FIRST_PARM_OFFSET} and virtual registers
+@cindex @code{ARG_POINTER_REGNUM} and virtual registers
+When RTL generation is complete, this virtual register is replaced
+by the sum of the register given by @code{ARG_POINTER_REGNUM} and the
+value of @code{FIRST_PARM_OFFSET}.
+
+@findex VIRTUAL_STACK_VARS_REGNUM
+@cindex @code{FRAME_GROWS_DOWNWARD} and virtual registers
+@item VIRTUAL_STACK_VARS_REGNUM
+If @code{FRAME_GROWS_DOWNWARD} is defined to a nonzero value, this points
+to immediately above the first variable on the stack. Otherwise, it points
+to the first variable on the stack.
+
+@cindex @code{TARGET_STARTING_FRAME_OFFSET} and virtual registers
+@cindex @code{FRAME_POINTER_REGNUM} and virtual registers
+@code{VIRTUAL_STACK_VARS_REGNUM} is replaced with the sum of the
+register given by @code{FRAME_POINTER_REGNUM} and the value
+@code{TARGET_STARTING_FRAME_OFFSET}.
+
+@findex VIRTUAL_STACK_DYNAMIC_REGNUM
+@item VIRTUAL_STACK_DYNAMIC_REGNUM
+This points to the location of dynamically allocated memory on the stack
+immediately after the stack pointer has been adjusted by the amount of
+memory desired.
+
+@cindex @code{STACK_DYNAMIC_OFFSET} and virtual registers
+@cindex @code{STACK_POINTER_REGNUM} and virtual registers
+This virtual register is replaced by the sum of the register given by
+@code{STACK_POINTER_REGNUM} and the value @code{STACK_DYNAMIC_OFFSET}.
+
+@findex VIRTUAL_OUTGOING_ARGS_REGNUM
+@item VIRTUAL_OUTGOING_ARGS_REGNUM
+This points to the location in the stack at which outgoing arguments
+should be written when the stack is pre-pushed (arguments pushed using
+push insns should always use @code{STACK_POINTER_REGNUM}).
+
+@cindex @code{STACK_POINTER_OFFSET} and virtual registers
+This virtual register is replaced by the sum of the register given by
+@code{STACK_POINTER_REGNUM} and the value @code{STACK_POINTER_OFFSET}.
+@end table
+
+@findex subreg
+@item (subreg:@var{m1} @var{reg:m2} @var{bytenum})
+
+@code{subreg} expressions are used to refer to a register in a machine
+mode other than its natural one, or to refer to one register of
+a multi-part @code{reg} that actually refers to several registers.
+
+Each pseudo register has a natural mode. If it is necessary to
+operate on it in a different mode, the register must be
+enclosed in a @code{subreg}.
+
+There are currently three supported types for the first operand of a
+@code{subreg}:
+@itemize
+@item pseudo registers
+This is the most common case. Most @code{subreg}s have pseudo
+@code{reg}s as their first operand.
+
+@item mem
+@code{subreg}s of @code{mem} were common in earlier versions of GCC and
+are still supported. During the reload pass these are replaced by plain
+@code{mem}s. On machines that do not do instruction scheduling, use of
+@code{subreg}s of @code{mem} are still used, but this is no longer
+recommended. Such @code{subreg}s are considered to be
+@code{register_operand}s rather than @code{memory_operand}s before and
+during reload. Because of this, the scheduling passes cannot properly
+schedule instructions with @code{subreg}s of @code{mem}, so for machines
+that do scheduling, @code{subreg}s of @code{mem} should never be used.
+To support this, the combine and recog passes have explicit code to
+inhibit the creation of @code{subreg}s of @code{mem} when
+@code{INSN_SCHEDULING} is defined.
+
+The use of @code{subreg}s of @code{mem} after the reload pass is an area
+that is not well understood and should be avoided. There is still some
+code in the compiler to support this, but this code has possibly rotted.
+This use of @code{subreg}s is discouraged and will most likely not be
+supported in the future.
+
+@item hard registers
+It is seldom necessary to wrap hard registers in @code{subreg}s; such
+registers would normally reduce to a single @code{reg} rtx. This use of
+@code{subreg}s is discouraged and may not be supported in the future.
+
+@end itemize
+
+@code{subreg}s of @code{subreg}s are not supported. Using
+@code{simplify_gen_subreg} is the recommended way to avoid this problem.
+
+@code{subreg}s come in two distinct flavors, each having its own
+usage and rules:
+
+@table @asis
+@item Paradoxical subregs
+When @var{m1} is strictly wider than @var{m2}, the @code{subreg}
+expression is called @dfn{paradoxical}. The canonical test for this
+class of @code{subreg} is:
+
+@smallexample
+paradoxical_subreg_p (@var{m1}, @var{m2})
+@end smallexample
+
+Paradoxical @code{subreg}s can be used as both lvalues and rvalues.
+When used as an lvalue, the low-order bits of the source value
+are stored in @var{reg} and the high-order bits are discarded.
+When used as an rvalue, the low-order bits of the @code{subreg} are
+taken from @var{reg} while the high-order bits may or may not be
+defined.
+
+The high-order bits of rvalues are defined in the following circumstances:
+
+@itemize
+@item @code{subreg}s of @code{mem}
+When @var{m2} is smaller than a word, the macro @code{LOAD_EXTEND_OP},
+can control how the high-order bits are defined.
+
+@item @code{subreg} of @code{reg}s
+The upper bits are defined when @code{SUBREG_PROMOTED_VAR_P} is true.
+@code{SUBREG_PROMOTED_UNSIGNED_P} describes what the upper bits hold.
+Such subregs usually represent local variables, register variables
+and parameter pseudo variables that have been promoted to a wider mode.
+
+@end itemize
+
+@var{bytenum} is always zero for a paradoxical @code{subreg}, even on
+big-endian targets.
+
+For example, the paradoxical @code{subreg}:
+
+@smallexample
+(set (subreg:SI (reg:HI @var{x}) 0) @var{y})
+@end smallexample
+
+stores the lower 2 bytes of @var{y} in @var{x} and discards the upper
+2 bytes. A subsequent:
+
+@smallexample
+(set @var{z} (subreg:SI (reg:HI @var{x}) 0))
+@end smallexample
+
+would set the lower two bytes of @var{z} to @var{y} and set the upper
+two bytes to an unknown value assuming @code{SUBREG_PROMOTED_VAR_P} is
+false.
+
+@item Normal subregs
+When @var{m1} is at least as narrow as @var{m2} the @code{subreg}
+expression is called @dfn{normal}.
+
+@findex REGMODE_NATURAL_SIZE
+Normal @code{subreg}s restrict consideration to certain bits of
+@var{reg}. For this purpose, @var{reg} is divided into
+individually-addressable blocks in which each block has:
+
+@smallexample
+REGMODE_NATURAL_SIZE (@var{m2})
+@end smallexample
+
+bytes. Usually the value is @code{UNITS_PER_WORD}; that is,
+most targets usually treat each word of a register as being
+independently addressable.
+
+There are two types of normal @code{subreg}. If @var{m1} is known
+to be no bigger than a block, the @code{subreg} refers to the
+least-significant part (or @dfn{lowpart}) of one block of @var{reg}.
+If @var{m1} is known to be larger than a block, the @code{subreg} refers
+to two or more complete blocks.
+
+When used as an lvalue, @code{subreg} is a block-based accessor.
+Storing to a @code{subreg} modifies all the blocks of @var{reg} that
+overlap the @code{subreg}, but it leaves the other blocks of @var{reg}
+alone.
+
+When storing to a normal @code{subreg} that is smaller than a block,
+the other bits of the referenced block are usually left in an undefined
+state. This laxity makes it easier to generate efficient code for
+such instructions. To represent an instruction that preserves all the
+bits outside of those in the @code{subreg}, use @code{strict_low_part}
+or @code{zero_extract} around the @code{subreg}.
+
+@var{bytenum} must identify the offset of the first byte of the
+@code{subreg} from the start of @var{reg}, assuming that @var{reg} is
+laid out in memory order. The memory order of bytes is defined by
+two target macros, @code{WORDS_BIG_ENDIAN} and @code{BYTES_BIG_ENDIAN}:
+
+@itemize
+@item
+@cindex @code{WORDS_BIG_ENDIAN}, effect on @code{subreg}
+@code{WORDS_BIG_ENDIAN}, if set to 1, says that byte number zero is
+part of the most significant word; otherwise, it is part of the least
+significant word.
+
+@item
+@cindex @code{BYTES_BIG_ENDIAN}, effect on @code{subreg}
+@code{BYTES_BIG_ENDIAN}, if set to 1, says that byte number zero is
+the most significant byte within a word; otherwise, it is the least
+significant byte within a word.
+@end itemize
+
+@cindex @code{FLOAT_WORDS_BIG_ENDIAN}, (lack of) effect on @code{subreg}
+On a few targets, @code{FLOAT_WORDS_BIG_ENDIAN} disagrees with
+@code{WORDS_BIG_ENDIAN}. However, most parts of the compiler treat
+floating point values as if they had the same endianness as integer
+values. This works because they handle them solely as a collection of
+integer values, with no particular numerical value. Only real.cc and
+the runtime libraries care about @code{FLOAT_WORDS_BIG_ENDIAN}.
+
+Thus,
+
+@smallexample
+(subreg:HI (reg:SI @var{x}) 2)
+@end smallexample
+
+on a @code{BYTES_BIG_ENDIAN}, @samp{UNITS_PER_WORD == 4} target is the same as
+
+@smallexample
+(subreg:HI (reg:SI @var{x}) 0)
+@end smallexample
+
+on a little-endian, @samp{UNITS_PER_WORD == 4} target. Both
+@code{subreg}s access the lower two bytes of register @var{x}.
+
+Note that the byte offset is a polynomial integer; it may not be a
+compile-time constant on targets with variable-sized modes. However,
+the restrictions above mean that there are only a certain set of
+acceptable offsets for a given combination of @var{m1} and @var{m2}.
+The compiler can always tell which blocks a valid subreg occupies, and
+whether the subreg is a lowpart of a block.
+
+@end table
+
+A @code{MODE_PARTIAL_INT} mode behaves as if it were as wide as the
+corresponding @code{MODE_INT} mode, except that it has a number of
+undefined bits, which are determined by the precision of the
+mode.
+
+For example, on a little-endian target which defines @code{PSImode}
+to have a precision of 20 bits:
+
+@smallexample
+(subreg:PSI (reg:SI 0) 0)
+@end smallexample
+
+accesses the low 20 bits of @samp{(reg:SI 0)}.
+
+@findex REGMODE_NATURAL_SIZE
+Continuing with a @code{PSImode} precision of 20 bits, if we assume
+@samp{REGMODE_NATURAL_SIZE (DImode) <= 4},
+then the following two @code{subreg}s:
+
+@smallexample
+(subreg:PSI (reg:DI 0) 0)
+(subreg:PSI (reg:DI 0) 4)
+@end smallexample
+
+represent accesses to the low 20 bits of the two halves of
+@samp{(reg:DI 0)}.
+
+If @samp{REGMODE_NATURAL_SIZE (PSImode) <= 2} then these two @code{subreg}s:
+
+@smallexample
+(subreg:HI (reg:PSI 0) 0)
+(subreg:HI (reg:PSI 0) 2)
+@end smallexample
+
+represent independent 2-byte accesses that together span the whole
+of @samp{(reg:PSI 0)}. Storing to the first @code{subreg} does not
+affect the value of the second, and vice versa, so the assignment:
+
+@smallexample
+(set (subreg:HI (reg:PSI 0) 0) (reg:HI 4))
+@end smallexample
+
+sets the low 16 bits of @samp{(reg:PSI 0)} to @samp{(reg:HI 4)}, and
+the high 4 defined bits of @samp{(reg:PSI 0)} retain their
+original value. The behavior here is the same as for
+normal @code{subreg}s, when there are no
+@code{MODE_PARTIAL_INT} modes involved.
+
+@cindex @code{TARGET_CAN_CHANGE_MODE_CLASS} and subreg semantics
+The rules above apply to both pseudo @var{reg}s and hard @var{reg}s.
+If the semantics are not correct for particular combinations of
+@var{m1}, @var{m2} and hard @var{reg}, the target-specific code
+must ensure that those combinations are never used. For example:
+
+@smallexample
+TARGET_CAN_CHANGE_MODE_CLASS (@var{m2}, @var{m1}, @var{class})
+@end smallexample
+
+must be false for every class @var{class} that includes @var{reg}.
+
+GCC must be able to determine at compile time whether a subreg is
+paradoxical, whether it occupies a whole number of blocks, or whether
+it is a lowpart of a block. This means that certain combinations of
+variable-sized mode are not permitted. For example, if @var{m2}
+holds @var{n} @code{SI} values, where @var{n} is greater than zero,
+it is not possible to form a @code{DI} @code{subreg} of it; such a
+@code{subreg} would be paradoxical when @var{n} is 1 but not when
+@var{n} is greater than 1.
+
+@findex SUBREG_REG
+@findex SUBREG_BYTE
+The first operand of a @code{subreg} expression is customarily accessed
+with the @code{SUBREG_REG} macro and the second operand is customarily
+accessed with the @code{SUBREG_BYTE} macro.
+
+It has been several years since a platform in which
+@code{BYTES_BIG_ENDIAN} not equal to @code{WORDS_BIG_ENDIAN} has
+been tested. Anyone wishing to support such a platform in the future
+may be confronted with code rot.
+
+@findex scratch
+@cindex scratch operands
+@item (scratch:@var{m})
+This represents a scratch register that will be required for the
+execution of a single instruction and not used subsequently. It is
+converted into a @code{reg} by either the local register allocator or
+the reload pass.
+
+@code{scratch} is usually present inside a @code{clobber} operation
+(@pxref{Side Effects}).
+
+On some machines, the condition code register is given a register number
+and a @code{reg} is used.
+Other machines store condition codes in general
+registers; in such cases a pseudo register should be used.
+
+Some machines, such as the SPARC and RS/6000, have two sets of
+arithmetic instructions, one that sets and one that does not set the
+condition code. This is best handled by normally generating the
+instruction that does not set the condition code, and making a pattern
+that both performs the arithmetic and sets the condition code register.
+For examples, search for @samp{addcc} and @samp{andcc} in @file{sparc.md}.
+
+@findex pc
+@item (pc)
+@cindex program counter
+This represents the machine's program counter. It has no operands and
+may not have a machine mode. @code{(pc)} may be validly used only in
+certain specific contexts in jump instructions.
+
+@findex pc_rtx
+There is only one expression object of code @code{pc}; it is the value
+of the variable @code{pc_rtx}. Any attempt to create an expression of
+code @code{pc} will return @code{pc_rtx}.
+
+All instructions that do not jump alter the program counter implicitly
+by incrementing it, but there is no need to mention this in the RTL@.
+
+@findex mem
+@item (mem:@var{m} @var{addr} @var{alias})
+This RTX represents a reference to main memory at an address
+represented by the expression @var{addr}. @var{m} specifies how large
+a unit of memory is accessed. @var{alias} specifies an alias set for the
+reference. In general two items are in different alias sets if they cannot
+reference the same memory address.
+
+The construct @code{(mem:BLK (scratch))} is considered to alias all
+other memories. Thus it may be used as a memory barrier in epilogue
+stack deallocation patterns.
+
+@findex concat
+@item (concat@var{m} @var{rtx} @var{rtx})
+This RTX represents the concatenation of two other RTXs. This is used
+for complex values. It should only appear in the RTL attached to
+declarations and during RTL generation. It should not appear in the
+ordinary insn chain.
+
+@findex concatn
+@item (concatn@var{m} [@var{rtx} @dots{}])
+This RTX represents the concatenation of all the @var{rtx} to make a
+single value. Like @code{concat}, this should only appear in
+declarations, and not in the insn chain.
+@end table
+
+@node Arithmetic
+@section RTL Expressions for Arithmetic
+@cindex arithmetic, in RTL
+@cindex math, in RTL
+@cindex RTL expressions for arithmetic
+
+Unless otherwise specified, all the operands of arithmetic expressions
+must be valid for mode @var{m}. An operand is valid for mode @var{m}
+if it has mode @var{m}, or if it is a @code{const_int} or
+@code{const_double} and @var{m} is a mode of class @code{MODE_INT}.
+
+For commutative binary operations, constants should be placed in the
+second operand.
+
+@table @code
+@findex plus
+@findex ss_plus
+@findex us_plus
+@cindex RTL sum
+@cindex RTL addition
+@cindex RTL addition with signed saturation
+@cindex RTL addition with unsigned saturation
+@item (plus:@var{m} @var{x} @var{y})
+@itemx (ss_plus:@var{m} @var{x} @var{y})
+@itemx (us_plus:@var{m} @var{x} @var{y})
+
+These three expressions all represent the sum of the values
+represented by @var{x} and @var{y} carried out in machine mode
+@var{m}. They differ in their behavior on overflow of integer modes.
+@code{plus} wraps round modulo the width of @var{m}; @code{ss_plus}
+saturates at the maximum signed value representable in @var{m};
+@code{us_plus} saturates at the maximum unsigned value.
+
+@c ??? What happens on overflow of floating point modes?
+
+@findex lo_sum
+@item (lo_sum:@var{m} @var{x} @var{y})
+
+This expression represents the sum of @var{x} and the low-order bits
+of @var{y}. It is used with @code{high} (@pxref{Constants}) to
+represent the typical two-instruction sequence used in RISC machines to
+reference large immediate values and/or link-time constants such
+as global memory addresses. In the latter case, @var{m} is @code{Pmode}
+and @var{y} is usually a constant expression involving @code{symbol_ref}.
+
+The number of low order bits is machine-dependent but is
+normally the number of bits in mode @var{m} minus the number of
+bits set by @code{high}.
+
+@findex minus
+@findex ss_minus
+@findex us_minus
+@cindex RTL difference
+@cindex RTL subtraction
+@cindex RTL subtraction with signed saturation
+@cindex RTL subtraction with unsigned saturation
+@item (minus:@var{m} @var{x} @var{y})
+@itemx (ss_minus:@var{m} @var{x} @var{y})
+@itemx (us_minus:@var{m} @var{x} @var{y})
+
+These three expressions represent the result of subtracting @var{y}
+from @var{x}, carried out in mode @var{M}. Behavior on overflow is
+the same as for the three variants of @code{plus} (see above).
+
+@findex compare
+@cindex RTL comparison
+@item (compare:@var{m} @var{x} @var{y})
+Represents the result of subtracting @var{y} from @var{x} for purposes
+of comparison. The result is computed without overflow, as if with
+infinite precision.
+
+Of course, machines cannot really subtract with infinite precision.
+However, they can pretend to do so when only the sign of the result will
+be used, which is the case when the result is stored in the condition
+code. And that is the @emph{only} way this kind of expression may
+validly be used: as a value to be stored in the condition codes, in a
+register. @xref{Comparisons}.
+
+The mode @var{m} is not related to the modes of @var{x} and @var{y}, but
+instead is the mode of the condition code value. It is some mode in class
+@code{MODE_CC}, often @code{CCmode}. @xref{Condition Code}. If @var{m}
+is @code{CCmode}, the operation returns sufficient
+information (in an unspecified format) so that any comparison operator
+can be applied to the result of the @code{COMPARE} operation. For other
+modes in class @code{MODE_CC}, the operation only returns a subset of
+this information.
+
+Normally, @var{x} and @var{y} must have the same mode. Otherwise,
+@code{compare} is valid only if the mode of @var{x} is in class
+@code{MODE_INT} and @var{y} is a @code{const_int} or
+@code{const_double} with mode @code{VOIDmode}. The mode of @var{x}
+determines what mode the comparison is to be done in; thus it must not
+be @code{VOIDmode}.
+
+If one of the operands is a constant, it should be placed in the
+second operand and the comparison code adjusted as appropriate.
+
+A @code{compare} specifying two @code{VOIDmode} constants is not valid
+since there is no way to know in what mode the comparison is to be
+performed; the comparison must either be folded during the compilation
+or the first operand must be loaded into a register while its mode is
+still known.
+
+@findex neg
+@findex ss_neg
+@findex us_neg
+@cindex negation
+@cindex negation with signed saturation
+@cindex negation with unsigned saturation
+@item (neg:@var{m} @var{x})
+@itemx (ss_neg:@var{m} @var{x})
+@itemx (us_neg:@var{m} @var{x})
+These two expressions represent the negation (subtraction from zero) of
+the value represented by @var{x}, carried out in mode @var{m}. They
+differ in the behavior on overflow of integer modes. In the case of
+@code{neg}, the negation of the operand may be a number not representable
+in mode @var{m}, in which case it is truncated to @var{m}. @code{ss_neg}
+and @code{us_neg} ensure that an out-of-bounds result saturates to the
+maximum or minimum signed or unsigned value.
+
+@findex mult
+@findex ss_mult
+@findex us_mult
+@cindex multiplication
+@cindex product
+@cindex multiplication with signed saturation
+@cindex multiplication with unsigned saturation
+@item (mult:@var{m} @var{x} @var{y})
+@itemx (ss_mult:@var{m} @var{x} @var{y})
+@itemx (us_mult:@var{m} @var{x} @var{y})
+Represents the signed product of the values represented by @var{x} and
+@var{y} carried out in machine mode @var{m}.
+@code{ss_mult} and @code{us_mult} ensure that an out-of-bounds result
+saturates to the maximum or minimum signed or unsigned value.
+
+Some machines support a multiplication that generates a product wider
+than the operands. Write the pattern for this as
+
+@smallexample
+(mult:@var{m} (sign_extend:@var{m} @var{x}) (sign_extend:@var{m} @var{y}))
+@end smallexample
+
+where @var{m} is wider than the modes of @var{x} and @var{y}, which need
+not be the same.
+
+For unsigned widening multiplication, use the same idiom, but with
+@code{zero_extend} instead of @code{sign_extend}.
+
+@findex smul_highpart
+@findex umul_highpart
+@cindex high-part multiplication
+@cindex multiplication high part
+@item (smul_highpart:@var{m} @var{x} @var{y})
+@itemx (umul_highpart:@var{m} @var{x} @var{y})
+Represents the high-part multiplication of @var{x} and @var{y} carried
+out in machine mode @var{m}. @code{smul_highpart} returns the high part
+of a signed multiplication, @code{umul_highpart} returns the high part
+of an unsigned multiplication.
+
+@findex fma
+@cindex fused multiply-add
+@item (fma:@var{m} @var{x} @var{y} @var{z})
+Represents the @code{fma}, @code{fmaf}, and @code{fmal} builtin
+functions, which compute @samp{@var{x} * @var{y} + @var{z}}
+without doing an intermediate rounding step.
+
+@findex div
+@findex ss_div
+@cindex division
+@cindex signed division
+@cindex signed division with signed saturation
+@cindex quotient
+@item (div:@var{m} @var{x} @var{y})
+@itemx (ss_div:@var{m} @var{x} @var{y})
+Represents the quotient in signed division of @var{x} by @var{y},
+carried out in machine mode @var{m}. If @var{m} is a floating point
+mode, it represents the exact quotient; otherwise, the integerized
+quotient.
+@code{ss_div} ensures that an out-of-bounds result saturates to the maximum
+or minimum signed value.
+
+Some machines have division instructions in which the operands and
+quotient widths are not all the same; you should represent
+such instructions using @code{truncate} and @code{sign_extend} as in,
+
+@smallexample
+(truncate:@var{m1} (div:@var{m2} @var{x} (sign_extend:@var{m2} @var{y})))
+@end smallexample
+
+@findex udiv
+@cindex unsigned division
+@cindex unsigned division with unsigned saturation
+@cindex division
+@item (udiv:@var{m} @var{x} @var{y})
+@itemx (us_div:@var{m} @var{x} @var{y})
+Like @code{div} but represents unsigned division.
+@code{us_div} ensures that an out-of-bounds result saturates to the maximum
+or minimum unsigned value.
+
+@findex mod
+@findex umod
+@cindex remainder
+@cindex division
+@item (mod:@var{m} @var{x} @var{y})
+@itemx (umod:@var{m} @var{x} @var{y})
+Like @code{div} and @code{udiv} but represent the remainder instead of
+the quotient.
+
+@findex smin
+@findex smax
+@cindex signed minimum
+@cindex signed maximum
+@item (smin:@var{m} @var{x} @var{y})
+@itemx (smax:@var{m} @var{x} @var{y})
+Represents the smaller (for @code{smin}) or larger (for @code{smax}) of
+@var{x} and @var{y}, interpreted as signed values in mode @var{m}.
+When used with floating point, if both operands are zeros, or if either
+operand is @code{NaN}, then it is unspecified which of the two operands
+is returned as the result.
+
+@findex umin
+@findex umax
+@cindex unsigned minimum and maximum
+@item (umin:@var{m} @var{x} @var{y})
+@itemx (umax:@var{m} @var{x} @var{y})
+Like @code{smin} and @code{smax}, but the values are interpreted as unsigned
+integers.
+
+@findex not
+@cindex complement, bitwise
+@cindex bitwise complement
+@item (not:@var{m} @var{x})
+Represents the bitwise complement of the value represented by @var{x},
+carried out in mode @var{m}, which must be a fixed-point machine mode.
+
+@findex and
+@cindex logical-and, bitwise
+@cindex bitwise logical-and
+@item (and:@var{m} @var{x} @var{y})
+Represents the bitwise logical-and of the values represented by
+@var{x} and @var{y}, carried out in machine mode @var{m}, which must be
+a fixed-point machine mode.
+
+@findex ior
+@cindex inclusive-or, bitwise
+@cindex bitwise inclusive-or
+@item (ior:@var{m} @var{x} @var{y})
+Represents the bitwise inclusive-or of the values represented by @var{x}
+and @var{y}, carried out in machine mode @var{m}, which must be a
+fixed-point mode.
+
+@findex xor
+@cindex exclusive-or, bitwise
+@cindex bitwise exclusive-or
+@item (xor:@var{m} @var{x} @var{y})
+Represents the bitwise exclusive-or of the values represented by @var{x}
+and @var{y}, carried out in machine mode @var{m}, which must be a
+fixed-point mode.
+
+@findex ashift
+@findex ss_ashift
+@findex us_ashift
+@cindex left shift
+@cindex shift
+@cindex arithmetic shift
+@cindex arithmetic shift with signed saturation
+@cindex arithmetic shift with unsigned saturation
+@item (ashift:@var{m} @var{x} @var{c})
+@itemx (ss_ashift:@var{m} @var{x} @var{c})
+@itemx (us_ashift:@var{m} @var{x} @var{c})
+These three expressions represent the result of arithmetically shifting @var{x}
+left by @var{c} places. They differ in their behavior on overflow of integer
+modes. An @code{ashift} operation is a plain shift with no special behavior
+in case of a change in the sign bit; @code{ss_ashift} and @code{us_ashift}
+saturates to the minimum or maximum representable value if any of the bits
+shifted out differs from the final sign bit.
+
+@var{x} have mode @var{m}, a fixed-point machine mode. @var{c}
+be a fixed-point mode or be a constant with mode @code{VOIDmode}; which
+mode is determined by the mode called for in the machine description
+entry for the left-shift instruction. For example, on the VAX, the mode
+of @var{c} is @code{QImode} regardless of @var{m}.
+
+@findex lshiftrt
+@cindex right shift
+@findex ashiftrt
+@item (lshiftrt:@var{m} @var{x} @var{c})
+@itemx (ashiftrt:@var{m} @var{x} @var{c})
+Like @code{ashift} but for right shift. Unlike the case for left shift,
+these two operations are distinct.
+
+@findex rotate
+@cindex rotate
+@cindex left rotate
+@findex rotatert
+@cindex right rotate
+@item (rotate:@var{m} @var{x} @var{c})
+@itemx (rotatert:@var{m} @var{x} @var{c})
+Similar but represent left and right rotate. If @var{c} is a constant,
+use @code{rotate}.
+
+@findex abs
+@findex ss_abs
+@cindex absolute value
+@item (abs:@var{m} @var{x})
+@item (ss_abs:@var{m} @var{x})
+Represents the absolute value of @var{x}, computed in mode @var{m}.
+@code{ss_abs} ensures that an out-of-bounds result saturates to the
+maximum signed value.
+
+
+@findex sqrt
+@cindex square root
+@item (sqrt:@var{m} @var{x})
+Represents the square root of @var{x}, computed in mode @var{m}.
+Most often @var{m} will be a floating point mode.
+
+@findex ffs
+@item (ffs:@var{m} @var{x})
+Represents one plus the index of the least significant 1-bit in
+@var{x}, represented as an integer of mode @var{m}. (The value is
+zero if @var{x} is zero.) The mode of @var{x} must be @var{m}
+or @code{VOIDmode}.
+
+@findex clrsb
+@item (clrsb:@var{m} @var{x})
+Represents the number of redundant leading sign bits in @var{x},
+represented as an integer of mode @var{m}, starting at the most
+significant bit position. This is one less than the number of leading
+sign bits (either 0 or 1), with no special cases. The mode of @var{x}
+must be @var{m} or @code{VOIDmode}.
+
+@findex clz
+@item (clz:@var{m} @var{x})
+Represents the number of leading 0-bits in @var{x}, represented as an
+integer of mode @var{m}, starting at the most significant bit position.
+If @var{x} is zero, the value is determined by
+@code{CLZ_DEFINED_VALUE_AT_ZERO} (@pxref{Misc}). Note that this is one of
+the few expressions that is not invariant under widening. The mode of
+@var{x} must be @var{m} or @code{VOIDmode}.
+
+@findex ctz
+@item (ctz:@var{m} @var{x})
+Represents the number of trailing 0-bits in @var{x}, represented as an
+integer of mode @var{m}, starting at the least significant bit position.
+If @var{x} is zero, the value is determined by
+@code{CTZ_DEFINED_VALUE_AT_ZERO} (@pxref{Misc}). Except for this case,
+@code{ctz(x)} is equivalent to @code{ffs(@var{x}) - 1}. The mode of
+@var{x} must be @var{m} or @code{VOIDmode}.
+
+@findex popcount
+@item (popcount:@var{m} @var{x})
+Represents the number of 1-bits in @var{x}, represented as an integer of
+mode @var{m}. The mode of @var{x} must be @var{m} or @code{VOIDmode}.
+
+@findex parity
+@item (parity:@var{m} @var{x})
+Represents the number of 1-bits modulo 2 in @var{x}, represented as an
+integer of mode @var{m}. The mode of @var{x} must be @var{m} or
+@code{VOIDmode}.
+
+@findex bswap
+@item (bswap:@var{m} @var{x})
+Represents the value @var{x} with the order of bytes reversed, carried out
+in mode @var{m}, which must be a fixed-point machine mode.
+The mode of @var{x} must be @var{m} or @code{VOIDmode}.
+@end table
+
+@node Comparisons
+@section Comparison Operations
+@cindex RTL comparison operations
+
+Comparison operators test a relation on two operands and are considered
+to represent a machine-dependent nonzero value described by, but not
+necessarily equal to, @code{STORE_FLAG_VALUE} (@pxref{Misc})
+if the relation holds, or zero if it does not, for comparison operators
+whose results have a `MODE_INT' mode,
+@code{FLOAT_STORE_FLAG_VALUE} (@pxref{Misc}) if the relation holds, or
+zero if it does not, for comparison operators that return floating-point
+values, and a vector of either @code{VECTOR_STORE_FLAG_VALUE} (@pxref{Misc})
+if the relation holds, or of zeros if it does not, for comparison operators
+that return vector results.
+The mode of the comparison operation is independent of the mode
+of the data being compared. If the comparison operation is being tested
+(e.g., the first operand of an @code{if_then_else}), the mode must be
+@code{VOIDmode}.
+
+@cindex condition codes
+A comparison operation compares two data
+objects. The mode of the comparison is determined by the operands; they
+must both be valid for a common machine mode. A comparison with both
+operands constant would be invalid as the machine mode could not be
+deduced from it, but such a comparison should never exist in RTL due to
+constant folding.
+
+Usually only one style
+of comparisons is supported on a particular machine, but the combine
+pass will try to merge operations to produce code like
+@code{(eq @var{x} @var{y})},
+in case it exists in the context of the particular insn involved.
+
+Inequality comparisons come in two flavors, signed and unsigned. Thus,
+there are distinct expression codes @code{gt} and @code{gtu} for signed and
+unsigned greater-than. These can produce different results for the same
+pair of integer values: for example, 1 is signed greater-than @minus{}1 but not
+unsigned greater-than, because @minus{}1 when regarded as unsigned is actually
+@code{0xffffffff} which is greater than 1.
+
+The signed comparisons are also used for floating point values. Floating
+point comparisons are distinguished by the machine modes of the operands.
+
+@table @code
+@findex eq
+@cindex equal
+@item (eq:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the values represented by @var{x} and @var{y}
+are equal, otherwise 0.
+
+@findex ne
+@cindex not equal
+@item (ne:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the values represented by @var{x} and @var{y}
+are not equal, otherwise 0.
+
+@findex gt
+@cindex greater than
+@item (gt:@var{m} @var{x} @var{y})
+@code{STORE_FLAG_VALUE} if the @var{x} is greater than @var{y}. If they
+are fixed-point, the comparison is done in a signed sense.
+
+@findex gtu
+@cindex greater than
+@cindex unsigned greater than
+@item (gtu:@var{m} @var{x} @var{y})
+Like @code{gt} but does unsigned comparison, on fixed-point numbers only.
+
+@findex lt
+@cindex less than
+@findex ltu
+@cindex unsigned less than
+@item (lt:@var{m} @var{x} @var{y})
+@itemx (ltu:@var{m} @var{x} @var{y})
+Like @code{gt} and @code{gtu} but test for ``less than''.
+
+@findex ge
+@cindex greater than
+@findex geu
+@cindex unsigned greater than
+@item (ge:@var{m} @var{x} @var{y})
+@itemx (geu:@var{m} @var{x} @var{y})
+Like @code{gt} and @code{gtu} but test for ``greater than or equal''.
+
+@findex le
+@cindex less than or equal
+@findex leu
+@cindex unsigned less than
+@item (le:@var{m} @var{x} @var{y})
+@itemx (leu:@var{m} @var{x} @var{y})
+Like @code{gt} and @code{gtu} but test for ``less than or equal''.
+
+@findex if_then_else
+@item (if_then_else @var{cond} @var{then} @var{else})
+This is not a comparison operation but is listed here because it is
+always used in conjunction with a comparison operation. To be
+precise, @var{cond} is a comparison expression. This expression
+represents a choice, according to @var{cond}, between the value
+represented by @var{then} and the one represented by @var{else}.
+
+On most machines, @code{if_then_else} expressions are valid only
+to express conditional jumps.
+
+@findex cond
+@item (cond [@var{test1} @var{value1} @var{test2} @var{value2} @dots{}] @var{default})
+Similar to @code{if_then_else}, but more general. Each of @var{test1},
+@var{test2}, @dots{} is performed in turn. The result of this expression is
+the @var{value} corresponding to the first nonzero test, or @var{default} if
+none of the tests are nonzero expressions.
+
+This is currently not valid for instruction patterns and is supported only
+for insn attributes. @xref{Insn Attributes}.
+@end table
+
+@node Bit-Fields
+@section Bit-Fields
+@cindex bit-fields
+
+Special expression codes exist to represent bit-field instructions.
+
+@table @code
+@findex sign_extract
+@cindex @code{BITS_BIG_ENDIAN}, effect on @code{sign_extract}
+@item (sign_extract:@var{m} @var{loc} @var{size} @var{pos})
+This represents a reference to a sign-extended bit-field contained or
+starting in @var{loc} (a memory or register reference). The bit-field
+is @var{size} bits wide and starts at bit @var{pos}. The compilation
+option @code{BITS_BIG_ENDIAN} says which end of the memory unit
+@var{pos} counts from.
+
+If @var{loc} is in memory, its mode must be a single-byte integer mode.
+If @var{loc} is in a register, the mode to use is specified by the
+operand of the @code{insv} or @code{extv} pattern
+(@pxref{Standard Names}) and is usually a full-word integer mode,
+which is the default if none is specified.
+
+The mode of @var{pos} is machine-specific and is also specified
+in the @code{insv} or @code{extv} pattern.
+
+The mode @var{m} is the same as the mode that would be used for
+@var{loc} if it were a register.
+
+A @code{sign_extract} cannot appear as an lvalue, or part thereof,
+in RTL.
+
+@findex zero_extract
+@item (zero_extract:@var{m} @var{loc} @var{size} @var{pos})
+Like @code{sign_extract} but refers to an unsigned or zero-extended
+bit-field. The same sequence of bits are extracted, but they
+are filled to an entire word with zeros instead of by sign-extension.
+
+Unlike @code{sign_extract}, this type of expressions can be lvalues
+in RTL; they may appear on the left side of an assignment, indicating
+insertion of a value into the specified bit-field.
+@end table
+
+@node Vector Operations
+@section Vector Operations
+@cindex vector operations
+
+All normal RTL expressions can be used with vector modes; they are
+interpreted as operating on each part of the vector independently.
+Additionally, there are a few new expressions to describe specific vector
+operations.
+
+@table @code
+@findex vec_merge
+@item (vec_merge:@var{m} @var{vec1} @var{vec2} @var{items})
+This describes a merge operation between two vectors. The result is a vector
+of mode @var{m}; its elements are selected from either @var{vec1} or
+@var{vec2}. Which elements are selected is described by @var{items}, which
+is a bit mask represented by a @code{const_int}; a zero bit indicates the
+corresponding element in the result vector is taken from @var{vec2} while
+a set bit indicates it is taken from @var{vec1}.
+
+@findex vec_select
+@item (vec_select:@var{m} @var{vec1} @var{selection})
+This describes an operation that selects parts of a vector. @var{vec1} is
+the source vector, and @var{selection} is a @code{parallel} that contains a
+@code{const_int} (or another expression, if the selection can be made at
+runtime) for each of the subparts of the result vector, giving the number of
+the source subpart that should be stored into it. The result mode @var{m} is
+either the submode for a single element of @var{vec1} (if only one subpart is
+selected), or another vector mode with that element submode (if multiple
+subparts are selected).
+
+@findex vec_concat
+@item (vec_concat:@var{m} @var{x1} @var{x2})
+Describes a vector concat operation. The result is a concatenation of the
+vectors or scalars @var{x1} and @var{x2}; its length is the sum of the
+lengths of the two inputs.
+
+@findex vec_duplicate
+@item (vec_duplicate:@var{m} @var{x})
+This operation converts a scalar into a vector or a small vector into a
+larger one by duplicating the input values. The output vector mode must have
+the same submodes as the input vector mode or the scalar modes, and the
+number of output parts must be an integer multiple of the number of input
+parts.
+
+@findex vec_series
+@item (vec_series:@var{m} @var{base} @var{step})
+This operation creates a vector in which element @var{i} is equal to
+@samp{@var{base} + @var{i}*@var{step}}. @var{m} must be a vector integer mode.
+@end table
+
+@node Conversions
+@section Conversions
+@cindex conversions
+@cindex machine mode conversions
+
+All conversions between machine modes must be represented by
+explicit conversion operations. For example, an expression
+which is the sum of a byte and a full word cannot be written as
+@code{(plus:SI (reg:QI 34) (reg:SI 80))} because the @code{plus}
+operation requires two operands of the same machine mode.
+Therefore, the byte-sized operand is enclosed in a conversion
+operation, as in
+
+@smallexample
+(plus:SI (sign_extend:SI (reg:QI 34)) (reg:SI 80))
+@end smallexample
+
+The conversion operation is not a mere placeholder, because there
+may be more than one way of converting from a given starting mode
+to the desired final mode. The conversion operation code says how
+to do it.
+
+For all conversion operations, @var{x} must not be @code{VOIDmode}
+because the mode in which to do the conversion would not be known.
+The conversion must either be done at compile-time or @var{x}
+must be placed into a register.
+
+@table @code
+@findex sign_extend
+@item (sign_extend:@var{m} @var{x})
+Represents the result of sign-extending the value @var{x}
+to machine mode @var{m}. @var{m} must be a fixed-point mode
+and @var{x} a fixed-point value of a mode narrower than @var{m}.
+
+@findex zero_extend
+@item (zero_extend:@var{m} @var{x})
+Represents the result of zero-extending the value @var{x}
+to machine mode @var{m}. @var{m} must be a fixed-point mode
+and @var{x} a fixed-point value of a mode narrower than @var{m}.
+
+@findex float_extend
+@item (float_extend:@var{m} @var{x})
+Represents the result of extending the value @var{x}
+to machine mode @var{m}. @var{m} must be a floating point mode
+and @var{x} a floating point value of a mode narrower than @var{m}.
+
+@findex truncate
+@item (truncate:@var{m} @var{x})
+Represents the result of truncating the value @var{x}
+to machine mode @var{m}. @var{m} must be a fixed-point mode
+and @var{x} a fixed-point value of a mode wider than @var{m}.
+
+@findex ss_truncate
+@item (ss_truncate:@var{m} @var{x})
+Represents the result of truncating the value @var{x}
+to machine mode @var{m}, using signed saturation in the case of
+overflow. Both @var{m} and the mode of @var{x} must be fixed-point
+modes.
+
+@findex us_truncate
+@item (us_truncate:@var{m} @var{x})
+Represents the result of truncating the value @var{x}
+to machine mode @var{m}, using unsigned saturation in the case of
+overflow. Both @var{m} and the mode of @var{x} must be fixed-point
+modes.
+
+@findex float_truncate
+@item (float_truncate:@var{m} @var{x})
+Represents the result of truncating the value @var{x}
+to machine mode @var{m}. @var{m} must be a floating point mode
+and @var{x} a floating point value of a mode wider than @var{m}.
+
+@findex float
+@item (float:@var{m} @var{x})
+Represents the result of converting fixed point value @var{x},
+regarded as signed, to floating point mode @var{m}.
+
+@findex unsigned_float
+@item (unsigned_float:@var{m} @var{x})
+Represents the result of converting fixed point value @var{x},
+regarded as unsigned, to floating point mode @var{m}.
+
+@findex fix
+@item (fix:@var{m} @var{x})
+When @var{m} is a floating-point mode, represents the result of
+converting floating point value @var{x} (valid for mode @var{m}) to an
+integer, still represented in floating point mode @var{m}, by rounding
+towards zero.
+
+When @var{m} is a fixed-point mode, represents the result of
+converting floating point value @var{x} to mode @var{m}, regarded as
+signed. How rounding is done is not specified, so this operation may
+be used validly in compiling C code only for integer-valued operands.
+
+@findex unsigned_fix
+@item (unsigned_fix:@var{m} @var{x})
+Represents the result of converting floating point value @var{x} to
+fixed point mode @var{m}, regarded as unsigned. How rounding is done
+is not specified.
+
+@findex fract_convert
+@item (fract_convert:@var{m} @var{x})
+Represents the result of converting fixed-point value @var{x} to
+fixed-point mode @var{m}, signed integer value @var{x} to
+fixed-point mode @var{m}, floating-point value @var{x} to
+fixed-point mode @var{m}, fixed-point value @var{x} to integer mode @var{m}
+regarded as signed, or fixed-point value @var{x} to floating-point mode @var{m}.
+When overflows or underflows happen, the results are undefined.
+
+@findex sat_fract
+@item (sat_fract:@var{m} @var{x})
+Represents the result of converting fixed-point value @var{x} to
+fixed-point mode @var{m}, signed integer value @var{x} to
+fixed-point mode @var{m}, or floating-point value @var{x} to
+fixed-point mode @var{m}.
+When overflows or underflows happen, the results are saturated to the
+maximum or the minimum.
+
+@findex unsigned_fract_convert
+@item (unsigned_fract_convert:@var{m} @var{x})
+Represents the result of converting fixed-point value @var{x} to
+integer mode @var{m} regarded as unsigned, or unsigned integer value @var{x} to
+fixed-point mode @var{m}.
+When overflows or underflows happen, the results are undefined.
+
+@findex unsigned_sat_fract
+@item (unsigned_sat_fract:@var{m} @var{x})
+Represents the result of converting unsigned integer value @var{x} to
+fixed-point mode @var{m}.
+When overflows or underflows happen, the results are saturated to the
+maximum or the minimum.
+@end table
+
+@node RTL Declarations
+@section Declarations
+@cindex RTL declarations
+@cindex declarations, RTL
+
+Declaration expression codes do not represent arithmetic operations
+but rather state assertions about their operands.
+
+@table @code
+@findex strict_low_part
+@cindex @code{subreg}, in @code{strict_low_part}
+@item (strict_low_part (subreg:@var{m} (reg:@var{n} @var{r}) 0))
+This expression code is used in only one context: as the destination operand of a
+@code{set} expression. In addition, the operand of this expression
+must be a non-paradoxical @code{subreg} expression.
+
+The presence of @code{strict_low_part} says that the part of the
+register which is meaningful in mode @var{n}, but is not part of
+mode @var{m}, is not to be altered. Normally, an assignment to such
+a subreg is allowed to have undefined effects on the rest of the
+register when @var{m} is smaller than @samp{REGMODE_NATURAL_SIZE (@var{n})}.
+@end table
+
+@node Side Effects
+@section Side Effect Expressions
+@cindex RTL side effect expressions
+
+The expression codes described so far represent values, not actions.
+But machine instructions never produce values; they are meaningful
+only for their side effects on the state of the machine. Special
+expression codes are used to represent side effects.
+
+The body of an instruction is always one of these side effect codes;
+the codes described above, which represent values, appear only as
+the operands of these.
+
+@table @code
+@findex set
+@item (set @var{lval} @var{x})
+Represents the action of storing the value of @var{x} into the place
+represented by @var{lval}. @var{lval} must be an expression
+representing a place that can be stored in: @code{reg} (or @code{subreg},
+@code{strict_low_part} or @code{zero_extract}), @code{mem}, @code{pc},
+or @code{parallel}.
+
+If @var{lval} is a @code{reg}, @code{subreg} or @code{mem}, it has a
+machine mode; then @var{x} must be valid for that mode.
+
+If @var{lval} is a @code{reg} whose machine mode is less than the full
+width of the register, then it means that the part of the register
+specified by the machine mode is given the specified value and the
+rest of the register receives an undefined value. Likewise, if
+@var{lval} is a @code{subreg} whose machine mode is narrower than
+the mode of the register, the rest of the register can be changed in
+an undefined way.
+
+If @var{lval} is a @code{strict_low_part} of a subreg, then the part
+of the register specified by the machine mode of the @code{subreg} is
+given the value @var{x} and the rest of the register is not changed.
+
+If @var{lval} is a @code{zero_extract}, then the referenced part of
+the bit-field (a memory or register reference) specified by the
+@code{zero_extract} is given the value @var{x} and the rest of the
+bit-field is not changed. Note that @code{sign_extract} cannot
+appear in @var{lval}.
+
+If @var{lval} is a @code{parallel}, it is used to represent the case of
+a function returning a structure in multiple registers. Each element
+of the @code{parallel} is an @code{expr_list} whose first operand is a
+@code{reg} and whose second operand is a @code{const_int} representing the
+offset (in bytes) into the structure at which the data in that register
+corresponds. The first element may be null to indicate that the structure
+is also passed partly in memory.
+
+@cindex jump instructions and @code{set}
+@cindex @code{if_then_else} usage
+If @var{lval} is @code{(pc)}, we have a jump instruction, and the
+possibilities for @var{x} are very limited. It may be a
+@code{label_ref} expression (unconditional jump). It may be an
+@code{if_then_else} (conditional jump), in which case either the
+second or the third operand must be @code{(pc)} (for the case which
+does not jump) and the other of the two must be a @code{label_ref}
+(for the case which does jump). @var{x} may also be a @code{mem} or
+@code{(plus:SI (pc) @var{y})}, where @var{y} may be a @code{reg} or a
+@code{mem}; these unusual patterns are used to represent jumps through
+branch tables.
+
+If @var{lval} is not @code{(pc)}, the mode of
+@var{lval} must not be @code{VOIDmode} and the mode of @var{x} must be
+valid for the mode of @var{lval}.
+
+@findex SET_DEST
+@findex SET_SRC
+@var{lval} is customarily accessed with the @code{SET_DEST} macro and
+@var{x} with the @code{SET_SRC} macro.
+
+@findex return
+@item (return)
+As the sole expression in a pattern, represents a return from the
+current function, on machines where this can be done with one
+instruction, such as VAXen. On machines where a multi-instruction
+``epilogue'' must be executed in order to return from the function,
+returning is done by jumping to a label which precedes the epilogue, and
+the @code{return} expression code is never used.
+
+Inside an @code{if_then_else} expression, represents the value to be
+placed in @code{pc} to return to the caller.
+
+Note that an insn pattern of @code{(return)} is logically equivalent to
+@code{(set (pc) (return))}, but the latter form is never used.
+
+@findex simple_return
+@item (simple_return)
+Like @code{(return)}, but truly represents only a function return, while
+@code{(return)} may represent an insn that also performs other functions
+of the function epilogue. Like @code{(return)}, this may also occur in
+conditional jumps.
+
+@findex call
+@item (call @var{function} @var{nargs})
+Represents a function call. @var{function} is a @code{mem} expression
+whose address is the address of the function to be called.
+@var{nargs} is an expression which can be used for two purposes: on
+some machines it represents the number of bytes of stack argument; on
+others, it represents the number of argument registers.
+
+Each machine has a standard machine mode which @var{function} must
+have. The machine description defines macro @code{FUNCTION_MODE} to
+expand into the requisite mode name. The purpose of this mode is to
+specify what kind of addressing is allowed, on machines where the
+allowed kinds of addressing depend on the machine mode being
+addressed.
+
+@findex clobber
+@item (clobber @var{x})
+Represents the storing or possible storing of an unpredictable,
+undescribed value into @var{x}, which must be a @code{reg},
+@code{scratch}, @code{parallel} or @code{mem} expression.
+
+One place this is used is in string instructions that store standard
+values into particular hard registers. It may not be worth the
+trouble to describe the values that are stored, but it is essential to
+inform the compiler that the registers will be altered, lest it
+attempt to keep data in them across the string instruction.
+
+If @var{x} is @code{(mem:BLK (const_int 0))} or
+@code{(mem:BLK (scratch))}, it means that all memory
+locations must be presumed clobbered. If @var{x} is a @code{parallel},
+it has the same meaning as a @code{parallel} in a @code{set} expression.
+
+Note that the machine description classifies certain hard registers as
+``call-clobbered''. All function call instructions are assumed by
+default to clobber these registers, so there is no need to use
+@code{clobber} expressions to indicate this fact. Also, each function
+call is assumed to have the potential to alter any memory location,
+unless the function is declared @code{const}.
+
+If the last group of expressions in a @code{parallel} are each a
+@code{clobber} expression whose arguments are @code{reg} or
+@code{match_scratch} (@pxref{RTL Template}) expressions, the combiner
+phase can add the appropriate @code{clobber} expressions to an insn it
+has constructed when doing so will cause a pattern to be matched.
+
+This feature can be used, for example, on a machine that whose multiply
+and add instructions don't use an MQ register but which has an
+add-accumulate instruction that does clobber the MQ register. Similarly,
+a combined instruction might require a temporary register while the
+constituent instructions might not.
+
+When a @code{clobber} expression for a register appears inside a
+@code{parallel} with other side effects, the register allocator
+guarantees that the register is unoccupied both before and after that
+insn if it is a hard register clobber. For pseudo-register clobber,
+the register allocator and the reload pass do not assign the same hard
+register to the clobber and the input operands if there is an insn
+alternative containing the @samp{&} constraint (@pxref{Modifiers}) for
+the clobber and the hard register is in register classes of the
+clobber in the alternative. You can clobber either a specific hard
+register, a pseudo register, or a @code{scratch} expression; in the
+latter two cases, GCC will allocate a hard register that is available
+there for use as a temporary.
+
+For instructions that require a temporary register, you should use
+@code{scratch} instead of a pseudo-register because this will allow the
+combiner phase to add the @code{clobber} when required. You do this by
+coding (@code{clobber} (@code{match_scratch} @dots{})). If you do
+clobber a pseudo register, use one which appears nowhere else---generate
+a new one each time. Otherwise, you may confuse CSE@.
+
+There is one other known use for clobbering a pseudo register in a
+@code{parallel}: when one of the input operands of the insn is also
+clobbered by the insn. In this case, using the same pseudo register in
+the clobber and elsewhere in the insn produces the expected results.
+
+@findex use
+@item (use @var{x})
+Represents the use of the value of @var{x}. It indicates that the
+value in @var{x} at this point in the program is needed, even though
+it may not be apparent why this is so. Therefore, the compiler will
+not attempt to delete previous instructions whose only effect is to
+store a value in @var{x}. @var{x} must be a @code{reg} expression.
+
+In some situations, it may be tempting to add a @code{use} of a
+register in a @code{parallel} to describe a situation where the value
+of a special register will modify the behavior of the instruction.
+A hypothetical example might be a pattern for an addition that can
+either wrap around or use saturating addition depending on the value
+of a special control register:
+
+@smallexample
+(parallel [(set (reg:SI 2) (unspec:SI [(reg:SI 3)
+ (reg:SI 4)] 0))
+ (use (reg:SI 1))])
+@end smallexample
+
+@noindent
+
+This will not work, several of the optimizers only look at expressions
+locally; it is very likely that if you have multiple insns with
+identical inputs to the @code{unspec}, they will be optimized away even
+if register 1 changes in between.
+
+This means that @code{use} can @emph{only} be used to describe
+that the register is live. You should think twice before adding
+@code{use} statements, more often you will want to use @code{unspec}
+instead. The @code{use} RTX is most commonly useful to describe that
+a fixed register is implicitly used in an insn. It is also safe to use
+in patterns where the compiler knows for other reasons that the result
+of the whole pattern is variable, such as @samp{cpymem@var{m}} or
+@samp{call} patterns.
+
+During the reload phase, an insn that has a @code{use} as pattern
+can carry a reg_equal note. These @code{use} insns will be deleted
+before the reload phase exits.
+
+During the delayed branch scheduling phase, @var{x} may be an insn.
+This indicates that @var{x} previously was located at this place in the
+code and its data dependencies need to be taken into account. These
+@code{use} insns will be deleted before the delayed branch scheduling
+phase exits.
+
+@findex parallel
+@item (parallel [@var{x0} @var{x1} @dots{}])
+Represents several side effects performed in parallel. The square
+brackets stand for a vector; the operand of @code{parallel} is a
+vector of expressions. @var{x0}, @var{x1} and so on are individual
+side effect expressions---expressions of code @code{set}, @code{call},
+@code{return}, @code{simple_return}, @code{clobber} or @code{use}.
+
+``In parallel'' means that first all the values used in the individual
+side-effects are computed, and second all the actual side-effects are
+performed. For example,
+
+@smallexample
+(parallel [(set (reg:SI 1) (mem:SI (reg:SI 1)))
+ (set (mem:SI (reg:SI 1)) (reg:SI 1))])
+@end smallexample
+
+@noindent
+says unambiguously that the values of hard register 1 and the memory
+location addressed by it are interchanged. In both places where
+@code{(reg:SI 1)} appears as a memory address it refers to the value
+in register 1 @emph{before} the execution of the insn.
+
+It follows that it is @emph{incorrect} to use @code{parallel} and
+expect the result of one @code{set} to be available for the next one.
+For example, people sometimes attempt to represent a jump-if-zero
+instruction this way:
+
+@smallexample
+(parallel [(set (reg:CC CC_REG) (reg:SI 34))
+ (set (pc) (if_then_else
+ (eq (reg:CC CC_REG) (const_int 0))
+ (label_ref @dots{})
+ (pc)))])
+@end smallexample
+
+@noindent
+But this is incorrect, because it says that the jump condition depends
+on the condition code value @emph{before} this instruction, not on the
+new value that is set by this instruction.
+
+@cindex peephole optimization, RTL representation
+Peephole optimization, which takes place together with final assembly
+code output, can produce insns whose patterns consist of a @code{parallel}
+whose elements are the operands needed to output the resulting
+assembler code---often @code{reg}, @code{mem} or constant expressions.
+This would not be well-formed RTL at any other stage in compilation,
+but it is OK then because no further optimization remains to be done.
+
+@findex cond_exec
+@item (cond_exec [@var{cond} @var{expr}])
+Represents a conditionally executed expression. The @var{expr} is
+executed only if the @var{cond} is nonzero. The @var{cond} expression
+must not have side-effects, but the @var{expr} may very well have
+side-effects.
+
+@findex sequence
+@item (sequence [@var{insns} @dots{}])
+Represents a sequence of insns. If a @code{sequence} appears in the
+chain of insns, then each of the @var{insns} that appears in the sequence
+must be suitable for appearing in the chain of insns, i.e.@: must satisfy
+the @code{INSN_P} predicate.
+
+After delay-slot scheduling is completed, an insn and all the insns that
+reside in its delay slots are grouped together into a @code{sequence}.
+The insn requiring the delay slot is the first insn in the vector;
+subsequent insns are to be placed in the delay slot.
+
+@code{INSN_ANNULLED_BRANCH_P} is set on an insn in a delay slot to
+indicate that a branch insn should be used that will conditionally annul
+the effect of the insns in the delay slots. In such a case,
+@code{INSN_FROM_TARGET_P} indicates that the insn is from the target of
+the branch and should be executed only if the branch is taken; otherwise
+the insn should be executed only if the branch is not taken.
+@xref{Delay Slots}.
+
+Some back ends also use @code{sequence} objects for purposes other than
+delay-slot groups. This is not supported in the common parts of the
+compiler, which treat such sequences as delay-slot groups.
+
+DWARF2 Call Frame Address (CFA) adjustments are sometimes also expressed
+using @code{sequence} objects as the value of a @code{RTX_FRAME_RELATED_P}
+note. This only happens if the CFA adjustments cannot be easily derived
+from the pattern of the instruction to which the note is attached. In
+such cases, the value of the note is used instead of best-guesing the
+semantics of the instruction. The back end can attach notes containing
+a @code{sequence} of @code{set} patterns that express the effect of the
+parent instruction.
+@end table
+
+These expression codes appear in place of a side effect, as the body of
+an insn, though strictly speaking they do not always describe side
+effects as such:
+
+@table @code
+@findex asm_input
+@item (asm_input @var{s})
+Represents literal assembler code as described by the string @var{s}.
+
+@findex unspec
+@findex unspec_volatile
+@item (unspec [@var{operands} @dots{}] @var{index})
+@itemx (unspec_volatile [@var{operands} @dots{}] @var{index})
+Represents a machine-specific operation on @var{operands}. @var{index}
+selects between multiple machine-specific operations.
+@code{unspec_volatile} is used for volatile operations and operations
+that may trap; @code{unspec} is used for other operations.
+
+These codes may appear inside a @code{pattern} of an
+insn, inside a @code{parallel}, or inside an expression.
+
+@findex addr_vec
+@item (addr_vec:@var{m} [@var{lr0} @var{lr1} @dots{}])
+Represents a table of jump addresses. The vector elements @var{lr0},
+etc., are @code{label_ref} expressions. The mode @var{m} specifies
+how much space is given to each address; normally @var{m} would be
+@code{Pmode}.
+
+@findex addr_diff_vec
+@item (addr_diff_vec:@var{m} @var{base} [@var{lr0} @var{lr1} @dots{}] @var{min} @var{max} @var{flags})
+Represents a table of jump addresses expressed as offsets from
+@var{base}. The vector elements @var{lr0}, etc., are @code{label_ref}
+expressions and so is @var{base}. The mode @var{m} specifies how much
+space is given to each address-difference. @var{min} and @var{max}
+are set up by branch shortening and hold a label with a minimum and a
+maximum address, respectively. @var{flags} indicates the relative
+position of @var{base}, @var{min} and @var{max} to the containing insn
+and of @var{min} and @var{max} to @var{base}. See rtl.def for details.
+
+@findex prefetch
+@item (prefetch:@var{m} @var{addr} @var{rw} @var{locality})
+Represents prefetch of memory at address @var{addr}.
+Operand @var{rw} is 1 if the prefetch is for data to be written, 0 otherwise;
+targets that do not support write prefetches should treat this as a normal
+prefetch.
+Operand @var{locality} specifies the amount of temporal locality; 0 if there
+is none or 1, 2, or 3 for increasing levels of temporal locality;
+targets that do not support locality hints should ignore this.
+
+This insn is used to minimize cache-miss latency by moving data into a
+cache before it is accessed. It should use only non-faulting data prefetch
+instructions.
+@end table
+
+@node Incdec
+@section Embedded Side-Effects on Addresses
+@cindex RTL preincrement
+@cindex RTL postincrement
+@cindex RTL predecrement
+@cindex RTL postdecrement
+
+Six special side-effect expression codes appear as memory addresses.
+
+@table @code
+@findex pre_dec
+@item (pre_dec:@var{m} @var{x})
+Represents the side effect of decrementing @var{x} by a standard
+amount and represents also the value that @var{x} has after being
+decremented. @var{x} must be a @code{reg} or @code{mem}, but most
+machines allow only a @code{reg}. @var{m} must be the machine mode
+for pointers on the machine in use. The amount @var{x} is decremented
+by is the length in bytes of the machine mode of the containing memory
+reference of which this expression serves as the address. Here is an
+example of its use:
+
+@smallexample
+(mem:DF (pre_dec:SI (reg:SI 39)))
+@end smallexample
+
+@noindent
+This says to decrement pseudo register 39 by the length of a @code{DFmode}
+value and use the result to address a @code{DFmode} value.
+
+@findex pre_inc
+@item (pre_inc:@var{m} @var{x})
+Similar, but specifies incrementing @var{x} instead of decrementing it.
+
+@findex post_dec
+@item (post_dec:@var{m} @var{x})
+Represents the same side effect as @code{pre_dec} but a different
+value. The value represented here is the value @var{x} has @i{before}
+being decremented.
+
+@findex post_inc
+@item (post_inc:@var{m} @var{x})
+Similar, but specifies incrementing @var{x} instead of decrementing it.
+
+@findex post_modify
+@item (post_modify:@var{m} @var{x} @var{y})
+
+Represents the side effect of setting @var{x} to @var{y} and
+represents @var{x} before @var{x} is modified. @var{x} must be a
+@code{reg} or @code{mem}, but most machines allow only a @code{reg}.
+@var{m} must be the machine mode for pointers on the machine in use.
+
+The expression @var{y} must be one of three forms:
+@code{(plus:@var{m} @var{x} @var{z})},
+@code{(minus:@var{m} @var{x} @var{z})}, or
+@code{(plus:@var{m} @var{x} @var{i})},
+where @var{z} is an index register and @var{i} is a constant.
+
+Here is an example of its use:
+
+@smallexample
+(mem:SF (post_modify:SI (reg:SI 42) (plus (reg:SI 42)
+ (reg:SI 48))))
+@end smallexample
+
+This says to modify pseudo register 42 by adding the contents of pseudo
+register 48 to it, after the use of what ever 42 points to.
+
+@findex pre_modify
+@item (pre_modify:@var{m} @var{x} @var{expr})
+Similar except side effects happen before the use.
+@end table
+
+These embedded side effect expressions must be used with care. Instruction
+patterns may not use them. Until the @samp{flow} pass of the compiler,
+they may occur only to represent pushes onto the stack. The @samp{flow}
+pass finds cases where registers are incremented or decremented in one
+instruction and used as an address shortly before or after; these cases are
+then transformed to use pre- or post-increment or -decrement.
+
+If a register used as the operand of these expressions is used in
+another address in an insn, the original value of the register is used.
+Uses of the register outside of an address are not permitted within the
+same insn as a use in an embedded side effect expression because such
+insns behave differently on different machines and hence must be treated
+as ambiguous and disallowed.
+
+An instruction that can be represented with an embedded side effect
+could also be represented using @code{parallel} containing an additional
+@code{set} to describe how the address register is altered. This is not
+done because machines that allow these operations at all typically
+allow them wherever a memory address is called for. Describing them as
+additional parallel stores would require doubling the number of entries
+in the machine description.
+
+@node Assembler
+@section Assembler Instructions as Expressions
+@cindex assembler instructions in RTL
+
+@cindex @code{asm_operands}, usage
+The RTX code @code{asm_operands} represents a value produced by a
+user-specified assembler instruction. It is used to represent
+an @code{asm} statement with arguments. An @code{asm} statement with
+a single output operand, like this:
+
+@smallexample
+asm ("foo %1,%2,%0" : "=a" (outputvar) : "g" (x + y), "di" (*z));
+@end smallexample
+
+@noindent
+is represented using a single @code{asm_operands} RTX which represents
+the value that is stored in @code{outputvar}:
+
+@smallexample
+(set @var{rtx-for-outputvar}
+ (asm_operands "foo %1,%2,%0" "a" 0
+ [@var{rtx-for-addition-result} @var{rtx-for-*z}]
+ [(asm_input:@var{m1} "g")
+ (asm_input:@var{m2} "di")]))
+@end smallexample
+
+@noindent
+Here the operands of the @code{asm_operands} RTX are the assembler
+template string, the output-operand's constraint, the index-number of the
+output operand among the output operands specified, a vector of input
+operand RTX's, and a vector of input-operand modes and constraints. The
+mode @var{m1} is the mode of the sum @code{x+y}; @var{m2} is that of
+@code{*z}.
+
+When an @code{asm} statement has multiple output values, its insn has
+several such @code{set} RTX's inside of a @code{parallel}. Each @code{set}
+contains an @code{asm_operands}; all of these share the same assembler
+template and vectors, but each contains the constraint for the respective
+output operand. They are also distinguished by the output-operand index
+number, which is 0, 1, @dots{} for successive output operands.
+
+@node Debug Information
+@section Variable Location Debug Information in RTL
+@cindex Variable Location Debug Information in RTL
+
+Variable tracking relies on @code{MEM_EXPR} and @code{REG_EXPR}
+annotations to determine what user variables memory and register
+references refer to.
+
+Variable tracking at assignments uses these notes only when they refer
+to variables that live at fixed locations (e.g., addressable
+variables, global non-automatic variables). For variables whose
+location may vary, it relies on the following types of notes.
+
+@table @code
+@findex var_location
+@item (var_location:@var{mode} @var{var} @var{exp} @var{stat})
+Binds variable @code{var}, a tree, to value @var{exp}, an RTL
+expression. It appears only in @code{NOTE_INSN_VAR_LOCATION} and
+@code{DEBUG_INSN}s, with slightly different meanings. @var{mode}, if
+present, represents the mode of @var{exp}, which is useful if it is a
+modeless expression. @var{stat} is only meaningful in notes,
+indicating whether the variable is known to be initialized or
+uninitialized.
+
+@findex debug_expr
+@item (debug_expr:@var{mode} @var{decl})
+Stands for the value bound to the @code{DEBUG_EXPR_DECL} @var{decl},
+that points back to it, within value expressions in
+@code{VAR_LOCATION} nodes.
+
+@findex debug_implicit_ptr
+@item (debug_implicit_ptr:@var{mode} @var{decl})
+Stands for the location of a @var{decl} that is no longer addressable.
+
+@findex entry_value
+@item (entry_value:@var{mode} @var{decl})
+Stands for the value a @var{decl} had at the entry point of the
+containing function.
+
+@findex debug_parameter_ref
+@item (debug_parameter_ref:@var{mode} @var{decl})
+Refers to a parameter that was completely optimized out.
+
+@findex debug_marker
+@item (debug_marker:@var{mode})
+Marks a program location. With @code{VOIDmode}, it stands for the
+beginning of a statement, a recommended inspection point logically after
+all prior side effects, and before any subsequent side effects. With
+@code{BLKmode}, it indicates an inline entry point: the lexical block
+encoded in the @code{INSN_LOCATION} is the enclosing block that encloses
+the inlined function.
+
+@end table
+
+@node Insns
+@section Insns
+@cindex insns
+
+The RTL representation of the code for a function is a doubly-linked
+chain of objects called @dfn{insns}. Insns are expressions with
+special codes that are used for no other purpose. Some insns are
+actual instructions; others represent dispatch tables for @code{switch}
+statements; others represent labels to jump to or various sorts of
+declarative information.
+
+In addition to its own specific data, each insn must have a unique
+id-number that distinguishes it from all other insns in the current
+function (after delayed branch scheduling, copies of an insn with the
+same id-number may be present in multiple places in a function, but
+these copies will always be identical and will only appear inside a
+@code{sequence}), and chain pointers to the preceding and following
+insns. These three fields occupy the same position in every insn,
+independent of the expression code of the insn. They could be accessed
+with @code{XEXP} and @code{XINT}, but instead three special macros are
+always used:
+
+@table @code
+@findex INSN_UID
+@item INSN_UID (@var{i})
+Accesses the unique id of insn @var{i}.
+
+@findex PREV_INSN
+@item PREV_INSN (@var{i})
+Accesses the chain pointer to the insn preceding @var{i}.
+If @var{i} is the first insn, this is a null pointer.
+
+@findex NEXT_INSN
+@item NEXT_INSN (@var{i})
+Accesses the chain pointer to the insn following @var{i}.
+If @var{i} is the last insn, this is a null pointer.
+@end table
+
+@findex get_insns
+@findex get_last_insn
+The first insn in the chain is obtained by calling @code{get_insns}; the
+last insn is the result of calling @code{get_last_insn}. Within the
+chain delimited by these insns, the @code{NEXT_INSN} and
+@code{PREV_INSN} pointers must always correspond: if @var{insn} is not
+the first insn,
+
+@smallexample
+NEXT_INSN (PREV_INSN (@var{insn})) == @var{insn}
+@end smallexample
+
+@noindent
+is always true and if @var{insn} is not the last insn,
+
+@smallexample
+PREV_INSN (NEXT_INSN (@var{insn})) == @var{insn}
+@end smallexample
+
+@noindent
+is always true.
+
+After delay slot scheduling, some of the insns in the chain might be
+@code{sequence} expressions, which contain a vector of insns. The value
+of @code{NEXT_INSN} in all but the last of these insns is the next insn
+in the vector; the value of @code{NEXT_INSN} of the last insn in the vector
+is the same as the value of @code{NEXT_INSN} for the @code{sequence} in
+which it is contained. Similar rules apply for @code{PREV_INSN}.
+
+This means that the above invariants are not necessarily true for insns
+inside @code{sequence} expressions. Specifically, if @var{insn} is the
+first insn in a @code{sequence}, @code{NEXT_INSN (PREV_INSN (@var{insn}))}
+is the insn containing the @code{sequence} expression, as is the value
+of @code{PREV_INSN (NEXT_INSN (@var{insn}))} if @var{insn} is the last
+insn in the @code{sequence} expression. You can use these expressions
+to find the containing @code{sequence} expression.
+
+Every insn has one of the following expression codes:
+
+@table @code
+@findex insn
+@item insn
+The expression code @code{insn} is used for instructions that do not jump
+and do not do function calls. @code{sequence} expressions are always
+contained in insns with code @code{insn} even if one of those insns
+should jump or do function calls.
+
+Insns with code @code{insn} have four additional fields beyond the three
+mandatory ones listed above. These four are described in a table below.
+
+@findex jump_insn
+@item jump_insn
+The expression code @code{jump_insn} is used for instructions that may
+jump (or, more generally, may contain @code{label_ref} expressions to
+which @code{pc} can be set in that instruction). If there is an
+instruction to return from the current function, it is recorded as a
+@code{jump_insn}.
+
+@findex JUMP_LABEL
+@code{jump_insn} insns have the same extra fields as @code{insn} insns,
+accessed in the same way and in addition contain a field
+@code{JUMP_LABEL} which is defined once jump optimization has completed.
+
+For simple conditional and unconditional jumps, this field contains
+the @code{code_label} to which this insn will (possibly conditionally)
+branch. In a more complex jump, @code{JUMP_LABEL} records one of the
+labels that the insn refers to; other jump target labels are recorded
+as @code{REG_LABEL_TARGET} notes. The exception is @code{addr_vec}
+and @code{addr_diff_vec}, where @code{JUMP_LABEL} is @code{NULL_RTX}
+and the only way to find the labels is to scan the entire body of the
+insn.
+
+Return insns count as jumps, but their @code{JUMP_LABEL} is @code{RETURN}
+or @code{SIMPLE_RETURN}.
+
+@findex call_insn
+@item call_insn
+The expression code @code{call_insn} is used for instructions that may do
+function calls. It is important to distinguish these instructions because
+they imply that certain registers and memory locations may be altered
+unpredictably.
+
+@findex CALL_INSN_FUNCTION_USAGE
+@code{call_insn} insns have the same extra fields as @code{insn} insns,
+accessed in the same way and in addition contain a field
+@code{CALL_INSN_FUNCTION_USAGE}, which contains a list (chain of
+@code{expr_list} expressions) containing @code{use}, @code{clobber} and
+sometimes @code{set} expressions that denote hard registers and
+@code{mem}s used or clobbered by the called function.
+
+A @code{mem} generally points to a stack slot in which arguments passed
+to the libcall by reference (@pxref{Register Arguments,
+TARGET_PASS_BY_REFERENCE}) are stored. If the argument is
+caller-copied (@pxref{Register Arguments, TARGET_CALLEE_COPIES}),
+the stack slot will be mentioned in @code{clobber} and @code{use}
+entries; if it's callee-copied, only a @code{use} will appear, and the
+@code{mem} may point to addresses that are not stack slots.
+
+Registers occurring inside a @code{clobber} in this list augment
+registers specified in @code{CALL_USED_REGISTERS} (@pxref{Register
+Basics}).
+
+If the list contains a @code{set} involving two registers, it indicates
+that the function returns one of its arguments. Such a @code{set} may
+look like a no-op if the same register holds the argument and the return
+value.
+
+@findex code_label
+@findex CODE_LABEL_NUMBER
+@item code_label
+A @code{code_label} insn represents a label that a jump insn can jump
+to. It contains two special fields of data in addition to the three
+standard ones. @code{CODE_LABEL_NUMBER} is used to hold the @dfn{label
+number}, a number that identifies this label uniquely among all the
+labels in the compilation (not just in the current function).
+Ultimately, the label is represented in the assembler output as an
+assembler label, usually of the form @samp{L@var{n}} where @var{n} is
+the label number.
+
+When a @code{code_label} appears in an RTL expression, it normally
+appears within a @code{label_ref} which represents the address of
+the label, as a number.
+
+Besides as a @code{code_label}, a label can also be represented as a
+@code{note} of type @code{NOTE_INSN_DELETED_LABEL}.
+
+@findex LABEL_NUSES
+The field @code{LABEL_NUSES} is only defined once the jump optimization
+phase is completed. It contains the number of times this label is
+referenced in the current function.
+
+@findex LABEL_KIND
+@findex SET_LABEL_KIND
+@findex LABEL_ALT_ENTRY_P
+@cindex alternate entry points
+The field @code{LABEL_KIND} differentiates four different types of
+labels: @code{LABEL_NORMAL}, @code{LABEL_STATIC_ENTRY},
+@code{LABEL_GLOBAL_ENTRY}, and @code{LABEL_WEAK_ENTRY}. The only labels
+that do not have type @code{LABEL_NORMAL} are @dfn{alternate entry
+points} to the current function. These may be static (visible only in
+the containing translation unit), global (exposed to all translation
+units), or weak (global, but can be overridden by another symbol with the
+same name).
+
+Much of the compiler treats all four kinds of label identically. Some
+of it needs to know whether or not a label is an alternate entry point;
+for this purpose, the macro @code{LABEL_ALT_ENTRY_P} is provided. It is
+equivalent to testing whether @samp{LABEL_KIND (label) == LABEL_NORMAL}.
+The only place that cares about the distinction between static, global,
+and weak alternate entry points, besides the front-end code that creates
+them, is the function @code{output_alternate_entry_point}, in
+@file{final.cc}.
+
+To set the kind of a label, use the @code{SET_LABEL_KIND} macro.
+
+@findex jump_table_data
+@item jump_table_data
+A @code{jump_table_data} insn is a placeholder for the jump-table data
+of a @code{casesi} or @code{tablejump} insn. They are placed after
+a @code{tablejump_p} insn. A @code{jump_table_data} insn is not part o
+a basic blockm but it is associated with the basic block that ends with
+the @code{tablejump_p} insn. The @code{PATTERN} of a @code{jump_table_data}
+is always either an @code{addr_vec} or an @code{addr_diff_vec}, and a
+@code{jump_table_data} insn is always preceded by a @code{code_label}.
+The @code{tablejump_p} insn refers to that @code{code_label} via its
+@code{JUMP_LABEL}.
+
+@findex barrier
+@item barrier
+Barriers are placed in the instruction stream when control cannot flow
+past them. They are placed after unconditional jump instructions to
+indicate that the jumps are unconditional and after calls to
+@code{volatile} functions, which do not return (e.g., @code{exit}).
+They contain no information beyond the three standard fields.
+
+@findex note
+@findex NOTE_LINE_NUMBER
+@findex NOTE_SOURCE_FILE
+@item note
+@code{note} insns are used to represent additional debugging and
+declarative information. They contain two nonstandard fields, an
+integer which is accessed with the macro @code{NOTE_LINE_NUMBER} and a
+string accessed with @code{NOTE_SOURCE_FILE}.
+
+If @code{NOTE_LINE_NUMBER} is positive, the note represents the
+position of a source line and @code{NOTE_SOURCE_FILE} is the source file name
+that the line came from. These notes control generation of line
+number data in the assembler output.
+
+Otherwise, @code{NOTE_LINE_NUMBER} is not really a line number but a
+code with one of the following values (and @code{NOTE_SOURCE_FILE}
+must contain a null pointer):
+
+@table @code
+@findex NOTE_INSN_DELETED
+@item NOTE_INSN_DELETED
+Such a note is completely ignorable. Some passes of the compiler
+delete insns by altering them into notes of this kind.
+
+@findex NOTE_INSN_DELETED_LABEL
+@item NOTE_INSN_DELETED_LABEL
+This marks what used to be a @code{code_label}, but was not used for other
+purposes than taking its address and was transformed to mark that no
+code jumps to it.
+
+@findex NOTE_INSN_BLOCK_BEG
+@findex NOTE_INSN_BLOCK_END
+@item NOTE_INSN_BLOCK_BEG
+@itemx NOTE_INSN_BLOCK_END
+These types of notes indicate the position of the beginning and end
+of a level of scoping of variable names. They control the output
+of debugging information.
+
+@findex NOTE_INSN_EH_REGION_BEG
+@findex NOTE_INSN_EH_REGION_END
+@item NOTE_INSN_EH_REGION_BEG
+@itemx NOTE_INSN_EH_REGION_END
+These types of notes indicate the position of the beginning and end of a
+level of scoping for exception handling. @code{NOTE_EH_HANDLER}
+identifies which region is associated with these notes.
+
+@findex NOTE_INSN_FUNCTION_BEG
+@item NOTE_INSN_FUNCTION_BEG
+Appears at the start of the function body, after the function
+prologue.
+
+@findex NOTE_INSN_VAR_LOCATION
+@findex NOTE_VAR_LOCATION
+@item NOTE_INSN_VAR_LOCATION
+This note is used to generate variable location debugging information.
+It indicates that the user variable in its @code{VAR_LOCATION} operand
+is at the location given in the RTL expression, or holds a value that
+can be computed by evaluating the RTL expression from that static
+point in the program up to the next such note for the same user
+variable.
+
+@findex NOTE_INSN_BEGIN_STMT
+@item NOTE_INSN_BEGIN_STMT
+This note is used to generate @code{is_stmt} markers in line number
+debugging information. It indicates the beginning of a user
+statement.
+
+@findex NOTE_INSN_INLINE_ENTRY
+@item NOTE_INSN_INLINE_ENTRY
+This note is used to generate @code{entry_pc} for inlined subroutines in
+debugging information. It indicates an inspection point at which all
+arguments for the inlined function have been bound, and before its first
+statement.
+
+@end table
+
+These codes are printed symbolically when they appear in debugging dumps.
+
+@findex debug_insn
+@findex INSN_VAR_LOCATION
+@item debug_insn
+The expression code @code{debug_insn} is used for pseudo-instructions
+that hold debugging information for variable tracking at assignments
+(see @option{-fvar-tracking-assignments} option). They are the RTL
+representation of @code{GIMPLE_DEBUG} statements
+(@ref{@code{GIMPLE_DEBUG}}), with a @code{VAR_LOCATION} operand that
+binds a user variable tree to an RTL representation of the
+@code{value} in the corresponding statement. A @code{DEBUG_EXPR} in
+it stands for the value bound to the corresponding
+@code{DEBUG_EXPR_DECL}.
+
+@code{GIMPLE_DEBUG_BEGIN_STMT} and @code{GIMPLE_DEBUG_INLINE_ENTRY} are
+expanded to RTL as a @code{DEBUG_INSN} with a @code{DEBUG_MARKER}
+@code{PATTERN}; the difference is the RTL mode: the former's
+@code{DEBUG_MARKER} is @code{VOIDmode}, whereas the latter is
+@code{BLKmode}; information about the inlined function can be taken from
+the lexical block encoded in the @code{INSN_LOCATION}. These
+@code{DEBUG_INSN}s, that do not carry @code{VAR_LOCATION} information,
+just @code{DEBUG_MARKER}s, can be detected by testing
+@code{DEBUG_MARKER_INSN_P}, whereas those that do can be recognized as
+@code{DEBUG_BIND_INSN_P}.
+
+Throughout optimization passes, @code{DEBUG_INSN}s are not reordered
+with respect to each other, particularly during scheduling. Binding
+information is kept in pseudo-instruction form, so that, unlike notes,
+it gets the same treatment and adjustments that regular instructions
+would. It is the variable tracking pass that turns these
+pseudo-instructions into @code{NOTE_INSN_VAR_LOCATION},
+@code{NOTE_INSN_BEGIN_STMT} and @code{NOTE_INSN_INLINE_ENTRY} notes,
+analyzing control flow, value equivalences and changes to registers and
+memory referenced in value expressions, propagating the values of debug
+temporaries and determining expressions that can be used to compute the
+value of each user variable at as many points (ranges, actually) in the
+program as possible.
+
+Unlike @code{NOTE_INSN_VAR_LOCATION}, the value expression in an
+@code{INSN_VAR_LOCATION} denotes a value at that specific point in the
+program, rather than an expression that can be evaluated at any later
+point before an overriding @code{VAR_LOCATION} is encountered. E.g.,
+if a user variable is bound to a @code{REG} and then a subsequent insn
+modifies the @code{REG}, the note location would keep mapping the user
+variable to the register across the insn, whereas the insn location
+would keep the variable bound to the value, so that the variable
+tracking pass would emit another location note for the variable at the
+point in which the register is modified.
+
+@end table
+
+@cindex @code{TImode}, in @code{insn}
+@cindex @code{HImode}, in @code{insn}
+@cindex @code{QImode}, in @code{insn}
+The machine mode of an insn is normally @code{VOIDmode}, but some
+phases use the mode for various purposes.
+
+The common subexpression elimination pass sets the mode of an insn to
+@code{QImode} when it is the first insn in a block that has already
+been processed.
+
+The second Haifa scheduling pass, for targets that can multiple issue,
+sets the mode of an insn to @code{TImode} when it is believed that the
+instruction begins an issue group. That is, when the instruction
+cannot issue simultaneously with the previous. This may be relied on
+by later passes, in particular machine-dependent reorg.
+
+Here is a table of the extra fields of @code{insn}, @code{jump_insn}
+and @code{call_insn} insns:
+
+@table @code
+@findex PATTERN
+@item PATTERN (@var{i})
+An expression for the side effect performed by this insn. This must
+be one of the following codes: @code{set}, @code{call}, @code{use},
+@code{clobber}, @code{return}, @code{simple_return}, @code{asm_input},
+@code{asm_output}, @code{addr_vec}, @code{addr_diff_vec},
+@code{trap_if}, @code{unspec}, @code{unspec_volatile},
+@code{parallel}, @code{cond_exec}, or @code{sequence}. If it is a
+@code{parallel}, each element of the @code{parallel} must be one these
+codes, except that @code{parallel} expressions cannot be nested and
+@code{addr_vec} and @code{addr_diff_vec} are not permitted inside a
+@code{parallel} expression.
+
+@findex INSN_CODE
+@item INSN_CODE (@var{i})
+An integer that says which pattern in the machine description matches
+this insn, or @minus{}1 if the matching has not yet been attempted.
+
+Such matching is never attempted and this field remains @minus{}1 on an insn
+whose pattern consists of a single @code{use}, @code{clobber},
+@code{asm_input}, @code{addr_vec} or @code{addr_diff_vec} expression.
+
+@findex asm_noperands
+Matching is also never attempted on insns that result from an @code{asm}
+statement. These contain at least one @code{asm_operands} expression.
+The function @code{asm_noperands} returns a non-negative value for
+such insns.
+
+In the debugging output, this field is printed as a number followed by
+a symbolic representation that locates the pattern in the @file{md}
+file as some small positive or negative offset from a named pattern.
+
+@findex REG_NOTES
+@item REG_NOTES (@var{i})
+A list (chain of @code{expr_list}, @code{insn_list} and @code{int_list}
+expressions) giving miscellaneous information about the insn. It is often
+information pertaining to the registers used in this insn.
+@end table
+
+The @code{REG_NOTES} field of an insn is a chain that includes
+@code{expr_list} and @code{int_list} expressions as well as @code{insn_list}
+expressions. There are several
+kinds of register notes, which are distinguished by the machine mode, which
+in a register note is really understood as being an @code{enum reg_note}.
+The first operand @var{op} of the note is data whose meaning depends on
+the kind of note.
+
+@findex REG_NOTE_KIND
+@findex PUT_REG_NOTE_KIND
+The macro @code{REG_NOTE_KIND (@var{x})} returns the kind of
+register note. Its counterpart, the macro @code{PUT_REG_NOTE_KIND
+(@var{x}, @var{newkind})} sets the register note type of @var{x} to be
+@var{newkind}.
+
+Register notes are of three classes: They may say something about an
+input to an insn, they may say something about an output of an insn, or
+they may create a linkage between two insns.
+
+These register notes annotate inputs to an insn:
+
+@table @code
+@findex REG_DEAD
+@item REG_DEAD
+The value in @var{op} dies in this insn; that is to say, altering the
+value immediately after this insn would not affect the future behavior
+of the program.
+
+It does not follow that the register @var{op} has no useful value after
+this insn since @var{op} is not necessarily modified by this insn.
+Rather, no subsequent instruction uses the contents of @var{op}.
+
+@findex REG_UNUSED
+@item REG_UNUSED
+The register @var{op} being set by this insn will not be used in a
+subsequent insn. This differs from a @code{REG_DEAD} note, which
+indicates that the value in an input will not be used subsequently.
+These two notes are independent; both may be present for the same
+register.
+
+@findex REG_INC
+@item REG_INC
+The register @var{op} is incremented (or decremented; at this level
+there is no distinction) by an embedded side effect inside this insn.
+This means it appears in a @code{post_inc}, @code{pre_inc},
+@code{post_dec} or @code{pre_dec} expression.
+
+@findex REG_NONNEG
+@item REG_NONNEG
+The register @var{op} is known to have a nonnegative value when this
+insn is reached. This is used by special looping instructions
+that terminate when the register goes negative.
+
+The @code{REG_NONNEG} note is added only to @samp{doloop_end}
+insns, if its pattern uses a @code{ge} condition.
+
+@findex REG_LABEL_OPERAND
+@item REG_LABEL_OPERAND
+This insn uses @var{op}, a @code{code_label} or a @code{note} of type
+@code{NOTE_INSN_DELETED_LABEL}, but is not a @code{jump_insn}, or it
+is a @code{jump_insn} that refers to the operand as an ordinary
+operand. The label may still eventually be a jump target, but if so
+in an indirect jump in a subsequent insn. The presence of this note
+allows jump optimization to be aware that @var{op} is, in fact, being
+used, and flow optimization to build an accurate flow graph.
+
+@findex REG_LABEL_TARGET
+@item REG_LABEL_TARGET
+This insn is a @code{jump_insn} but not an @code{addr_vec} or
+@code{addr_diff_vec}. It uses @var{op}, a @code{code_label} as a
+direct or indirect jump target. Its purpose is similar to that of
+@code{REG_LABEL_OPERAND}. This note is only present if the insn has
+multiple targets; the last label in the insn (in the highest numbered
+insn-field) goes into the @code{JUMP_LABEL} field and does not have a
+@code{REG_LABEL_TARGET} note. @xref{Insns, JUMP_LABEL}.
+
+@findex REG_SETJMP
+@item REG_SETJMP
+Appears attached to each @code{CALL_INSN} to @code{setjmp} or a
+related function.
+@end table
+
+The following notes describe attributes of outputs of an insn:
+
+@table @code
+@findex REG_EQUIV
+@findex REG_EQUAL
+@item REG_EQUIV
+@itemx REG_EQUAL
+This note is only valid on an insn that sets only one register and
+indicates that that register will be equal to @var{op} at run time; the
+scope of this equivalence differs between the two types of notes. The
+value which the insn explicitly copies into the register may look
+different from @var{op}, but they will be equal at run time. If the
+output of the single @code{set} is a @code{strict_low_part} or
+@code{zero_extract} expression, the note refers to the register that
+is contained in its first operand.
+
+For @code{REG_EQUIV}, the register is equivalent to @var{op} throughout
+the entire function, and could validly be replaced in all its
+occurrences by @var{op}. (``Validly'' here refers to the data flow of
+the program; simple replacement may make some insns invalid.) For
+example, when a constant is loaded into a register that is never
+assigned any other value, this kind of note is used.
+
+When a parameter is copied into a pseudo-register at entry to a function,
+a note of this kind records that the register is equivalent to the stack
+slot where the parameter was passed. Although in this case the register
+may be set by other insns, it is still valid to replace the register
+by the stack slot throughout the function.
+
+A @code{REG_EQUIV} note is also used on an instruction which copies a
+register parameter into a pseudo-register at entry to a function, if
+there is a stack slot where that parameter could be stored. Although
+other insns may set the pseudo-register, it is valid for the compiler to
+replace the pseudo-register by stack slot throughout the function,
+provided the compiler ensures that the stack slot is properly
+initialized by making the replacement in the initial copy instruction as
+well. This is used on machines for which the calling convention
+allocates stack space for register parameters. See
+@code{REG_PARM_STACK_SPACE} in @ref{Stack Arguments}.
+
+In the case of @code{REG_EQUAL}, the register that is set by this insn
+will be equal to @var{op} at run time at the end of this insn but not
+necessarily elsewhere in the function. In this case, @var{op}
+is typically an arithmetic expression. For example, when a sequence of
+insns such as a library call is used to perform an arithmetic operation,
+this kind of note is attached to the insn that produces or copies the
+final value.
+
+These two notes are used in different ways by the compiler passes.
+@code{REG_EQUAL} is used by passes prior to register allocation (such as
+common subexpression elimination and loop optimization) to tell them how
+to think of that value. @code{REG_EQUIV} notes are used by register
+allocation to indicate that there is an available substitute expression
+(either a constant or a @code{mem} expression for the location of a
+parameter on the stack) that may be used in place of a register if
+insufficient registers are available.
+
+Except for stack homes for parameters, which are indicated by a
+@code{REG_EQUIV} note and are not useful to the early optimization
+passes and pseudo registers that are equivalent to a memory location
+throughout their entire life, which is not detected until later in
+the compilation, all equivalences are initially indicated by an attached
+@code{REG_EQUAL} note. In the early stages of register allocation, a
+@code{REG_EQUAL} note is changed into a @code{REG_EQUIV} note if
+@var{op} is a constant and the insn represents the only set of its
+destination register.
+
+Thus, compiler passes prior to register allocation need only check for
+@code{REG_EQUAL} notes and passes subsequent to register allocation
+need only check for @code{REG_EQUIV} notes.
+@end table
+
+These notes describe linkages between insns. They occur in pairs: one
+insn has one of a pair of notes that points to a second insn, which has
+the inverse note pointing back to the first insn.
+
+@table @code
+@findex REG_DEP_TRUE
+@item REG_DEP_TRUE
+This indicates a true dependence (a read after write dependence).
+
+@findex REG_DEP_OUTPUT
+@item REG_DEP_OUTPUT
+This indicates an output dependence (a write after write dependence).
+
+@findex REG_DEP_ANTI
+@item REG_DEP_ANTI
+This indicates an anti dependence (a write after read dependence).
+
+@end table
+
+These notes describe information gathered from gcov profile data. They
+are stored in the @code{REG_NOTES} field of an insn.
+
+@table @code
+@findex REG_BR_PROB
+@item REG_BR_PROB
+This is used to specify the ratio of branches to non-branches of a
+branch insn according to the profile data. The note is represented
+as an @code{int_list} expression whose integer value is an encoding
+of @code{profile_probability} type. @code{profile_probability} provide
+member function @code{from_reg_br_prob_note} and @code{to_reg_br_prob_note}
+to extract and store the probability into the RTL encoding.
+
+@findex REG_BR_PRED
+@item REG_BR_PRED
+These notes are found in JUMP insns after delayed branch scheduling
+has taken place. They indicate both the direction and the likelihood
+of the JUMP@. The format is a bitmask of ATTR_FLAG_* values.
+
+@findex REG_FRAME_RELATED_EXPR
+@item REG_FRAME_RELATED_EXPR
+This is used on an RTX_FRAME_RELATED_P insn wherein the attached expression
+is used in place of the actual insn pattern. This is done in cases where
+the pattern is either complex or misleading.
+@end table
+
+The note @code{REG_CALL_NOCF_CHECK} is used in conjunction with the
+@option{-fcf-protection=branch} option. The note is set if a
+@code{nocf_check} attribute is specified for a function type or a
+pointer to function type. The note is stored in the @code{REG_NOTES}
+field of an insn.
+
+@table @code
+@findex REG_CALL_NOCF_CHECK
+@item REG_CALL_NOCF_CHECK
+Users have control through the @code{nocf_check} attribute to identify
+which calls to a function should be skipped from control-flow instrumentation
+when the option @option{-fcf-protection=branch} is specified. The compiler
+puts a @code{REG_CALL_NOCF_CHECK} note on each @code{CALL_INSN} instruction
+that has a function type marked with a @code{nocf_check} attribute.
+@end table
+
+For convenience, the machine mode in an @code{insn_list} or
+@code{expr_list} is printed using these symbolic codes in debugging dumps.
+
+@findex insn_list
+@findex expr_list
+The only difference between the expression codes @code{insn_list} and
+@code{expr_list} is that the first operand of an @code{insn_list} is
+assumed to be an insn and is printed in debugging dumps as the insn's
+unique id; the first operand of an @code{expr_list} is printed in the
+ordinary way as an expression.
+
+@node Calls
+@section RTL Representation of Function-Call Insns
+@cindex calling functions in RTL
+@cindex RTL function-call insns
+@cindex function-call insns
+
+Insns that call subroutines have the RTL expression code @code{call_insn}.
+These insns must satisfy special rules, and their bodies must use a special
+RTL expression code, @code{call}.
+
+@cindex @code{call} usage
+A @code{call} expression has two operands, as follows:
+
+@smallexample
+(call (mem:@var{fm} @var{addr}) @var{nbytes})
+@end smallexample
+
+@noindent
+Here @var{nbytes} is an operand that represents the number of bytes of
+argument data being passed to the subroutine, @var{fm} is a machine mode
+(which must equal as the definition of the @code{FUNCTION_MODE} macro in
+the machine description) and @var{addr} represents the address of the
+subroutine.
+
+For a subroutine that returns no value, the @code{call} expression as
+shown above is the entire body of the insn, except that the insn might
+also contain @code{use} or @code{clobber} expressions.
+
+@cindex @code{BLKmode}, and function return values
+For a subroutine that returns a value whose mode is not @code{BLKmode},
+the value is returned in a hard register. If this register's number is
+@var{r}, then the body of the call insn looks like this:
+
+@smallexample
+(set (reg:@var{m} @var{r})
+ (call (mem:@var{fm} @var{addr}) @var{nbytes}))
+@end smallexample
+
+@noindent
+This RTL expression makes it clear (to the optimizer passes) that the
+appropriate register receives a useful value in this insn.
+
+When a subroutine returns a @code{BLKmode} value, it is handled by
+passing to the subroutine the address of a place to store the value.
+So the call insn itself does not ``return'' any value, and it has the
+same RTL form as a call that returns nothing.
+
+On some machines, the call instruction itself clobbers some register,
+for example to contain the return address. @code{call_insn} insns
+on these machines should have a body which is a @code{parallel}
+that contains both the @code{call} expression and @code{clobber}
+expressions that indicate which registers are destroyed. Similarly,
+if the call instruction requires some register other than the stack
+pointer that is not explicitly mentioned in its RTL, a @code{use}
+subexpression should mention that register.
+
+Functions that are called are assumed to modify all registers listed in
+the configuration macro @code{CALL_USED_REGISTERS} (@pxref{Register
+Basics}) and, with the exception of @code{const} functions and library
+calls, to modify all of memory.
+
+Insns containing just @code{use} expressions directly precede the
+@code{call_insn} insn to indicate which registers contain inputs to the
+function. Similarly, if registers other than those in
+@code{CALL_USED_REGISTERS} are clobbered by the called function, insns
+containing a single @code{clobber} follow immediately after the call to
+indicate which registers.
+
+@node RTL SSA
+@section On-the-Side SSA Form for RTL
+@cindex SSA, RTL form
+@cindex RTL SSA
+
+The patterns of an individual RTL instruction describe which registers
+are inputs to that instruction and which registers are outputs from
+that instruction. However, it is often useful to know where the
+definition of a register input comes from and where the result of
+a register output is used. One way of obtaining this information
+is to use the RTL SSA form, which provides a Static Single Assignment
+representation of the RTL instructions.
+
+The RTL SSA code is located in the @file{rtl-ssa} subdirectory of the GCC
+source tree. This section only gives a brief overview of it; please
+see the comments in the source code for more details.
+
+@menu
+* Using RTL SSA:: What a pass needs to do to use the RTL SSA form
+* RTL SSA Instructions:: How instructions are represented and organized
+* RTL SSA Basic Blocks:: How instructions are grouped into blocks
+* RTL SSA Resources:: How registers and memory are represented
+* RTL SSA Accesses:: How register and memory accesses are represented
+* RTL SSA Phi Nodes:: How multiple sources are combined into one
+* RTL SSA Access Lists:: How accesses are chained together
+* Changing RTL Instructions:: How to use the RTL SSA framework to change insns
+@end menu
+
+@node Using RTL SSA
+@subsection Using RTL SSA in a pass
+
+A pass that wants to use the RTL SSA form should start with the following:
+
+@smallexample
+#define INCLUDE_ALGORITHM
+#define INCLUDE_FUNCTIONAL
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "backend.h"
+#include "rtl.h"
+#include "df.h"
+#include "rtl-ssa.h"
+@end smallexample
+
+All the RTL SSA code is contained in the @code{rtl_ssa} namespace,
+so most passes will then want to do:
+
+@smallexample
+using namespace rtl_ssa;
+@end smallexample
+
+However, this is purely a matter of taste, and the examples in the rest of
+this section do not require it.
+
+The RTL SSA represention is an optional on-the-side feature that applies
+on top of the normal RTL instructions. It is currently local to individual
+RTL passes and is not maintained across passes.
+
+However, in order to allow the RTL SSA information to be preserved across
+passes in future, @samp{crtl->ssa} points to the current function's
+SSA form (if any). Passes that want to use the RTL SSA form should
+first do:
+
+@smallexample
+crtl->ssa = new rtl_ssa::function_info (@var{fn});
+@end smallexample
+
+where @var{fn} is the function that the pass is processing.
+(Passes that are @code{using namespace rtl_ssa} do not need
+the @samp{rtl_ssa::}.)
+
+Once the pass has finished with the SSA form, it should do the following:
+
+@smallexample
+free_dominance_info (CDI_DOMINATORS);
+if (crtl->ssa->perform_pending_updates ())
+ cleanup_cfg (0);
+
+delete crtl->ssa;
+crtl->ssa = nullptr;
+@end smallexample
+
+The @code{free_dominance_info} call is necessary because
+dominance information is not currently maintained between RTL passes.
+The next two lines commit any changes to the RTL instructions that
+were queued for later; see the comment above the declaration of
+@code{perform_pending_updates} for details. The final two lines
+discard the RTL SSA form and free the associated memory.
+
+@node RTL SSA Instructions
+@subsection RTL SSA Instructions
+
+@cindex RPO
+@cindex reverse postorder
+@cindex instructions, RTL SSA
+@findex rtl_ssa::insn_info
+RTL SSA instructions are represented by an @code{rtl_ssa::insn_info}.
+These instructions are chained together in a single list that follows
+a reverse postorder (RPO) traversal of the function. This means that
+if any path through the function can execute an instruction @var{I1}
+and then later execute an instruction @var{I2} for the first time,
+@var{I1} appears before @var{I2} in the list@footnote{Note that this
+order is different from the order of the underlying RTL instructions,
+which follow machine code order instead.}.
+
+Two RTL SSA instructions can be compared to find which instruction
+occurs earlier than the other in the RPO@. One way to do this is
+to use the C++ comparison operators, such as:
+
+@example
+*@var{insn1} < *@var{insn2}
+@end example
+
+Another way is to use the @code{compare_with} function:
+
+@example
+@var{insn1}->compare_with (@var{insn2})
+@end example
+
+This expression is greater than zero if @var{insn1} comes after @var{insn2}
+in the RPO, less than zero if @var{insn1} comes before @var{insn2} in the
+RPO, or zero if @var{insn1} and @var{insn2} are the same. This order is
+maintained even if instructions are added to the function or moved around.
+
+The main purpose of @code{rtl_ssa::insn_info} is to hold
+SSA information about an instruction. However, it also caches
+certain properties of the instruction, such as whether it is an
+inline assembly instruction, whether it has volatile accesses, and so on.
+
+@node RTL SSA Basic Blocks
+@subsection RTL SSA Basic Blocks
+
+@cindex basic blocks, RTL SSA
+@findex basic_block
+@findex rtl_ssa::bb_info
+RTL SSA instructions (@pxref{RTL SSA Instructions}) are organized into
+basic blocks, with each block being represented by an @code{rtl_ssa:bb_info}.
+There is a one-to-one mapping between these @code{rtl_ssa:bb_info}
+structures and the underlying CFG @code{basic_block} structures
+(@pxref{Basic Blocks}).
+
+@cindex ``real'' instructions, RTL SSA
+@anchor{real RTL SSA insns}
+If a CFG basic block @var{bb} contains an RTL instruction @var{insn},
+the RTL SSA represenation of @var{bb} also contains an RTL SSA representation
+of @var{insn}@footnote{Note that this excludes non-instruction things like
+@code{note}s and @code{barrier}s that also appear in the chain of RTL
+instructions.}. Within RTL SSA, these instructions are referred to as
+``real'' instructions. These real instructions fall into two groups:
+debug instructions and nondebug instructions. Only nondebug instructions
+should affect code generation decisions.
+
+In addition, each RTL SSA basic block has two ``artificial''
+instructions: a ``head'' instruction that comes before all the real
+instructions and an ``end'' instruction that comes after all real
+instructions. These instructions exist to represent things that
+are conceptually defined or used at the start and end of a basic block.
+The instructions always exist, even if they do not currently do anything.
+
+Like instructions, these blocks are chained together in a reverse
+postorder. This list includes the entry block (which always comes
+first) and the exit block (which always comes last).
+
+@cindex extended basic blocks, RTL SSA
+@findex rtl_ssa::ebb_info
+RTL SSA basic blocks are chained together into ``extended basic blocks''
+(EBBs), represented by an @code{rtl_ssa::ebb_info}. Extended basic
+blocks contain one or more basic blocks. They have the property
+that if a block @var{bby} comes immediately after a block @var{bbx}
+in an EBB, then @var{bby} can only be reached by @var{bbx}; in other words,
+@var{bbx} is the sole predecessor of @var{bby}.
+
+Each extended basic block starts with an artificial ``phi node''
+instruction. This instruction defines all phi nodes for the EBB
+(@pxref{RTL SSA Phi Nodes}). (Individual blocks in an EBB do not
+need phi nodes because their live values can only come from one source.)
+
+The contents of a function are therefore represented using a
+four-level hierarchy:
+
+@itemize @bullet
+@item
+functions (@code{rtl_ssa::function_info}), which contain @dots{}
+
+@item
+extended basic blocks (@code{rtl_ssa::ebb_info}), which contain @dots{}
+
+@item
+basic blocks (@code{rtl_ssa::bb_info}), which contain @dots{}
+
+@item
+instructions (@code{rtl_ssa::insn_info})
+@end itemize
+
+In dumps, a basic block is identified as @code{bb@var{n}}, where @var{n}
+is the index of the associated CFG @code{basic_block} structure.
+An EBB is in turn identified by the index of its first block.
+For example, an EBB that contains @samp{bb10}, @code{bb5}, @code{bb6}
+and @code{bb9} is identified as @var{ebb10}.
+
+@node RTL SSA Resources
+@subsection RTL SSA Resources
+
+The RTL SSA form tracks two types of ``resource'': registers and memory.
+Each hard and pseudo register is a separate resource. Memory is a
+single unified resource, like it is in GIMPLE (@pxref{GIMPLE}).
+
+Each resource has a unique identifier. The unique identifier for a
+register is simply its register number. The unique identifier for
+memory is a special register number called @code{MEM_REGNO}.
+
+Since resource numbers so closely match register numbers, it is sometimes
+convenient to refer to them simply as register numbers, or ``regnos''
+for short. However, the RTL SSA form also provides an abstraction
+of resources in the form of @code{rtl_ssa::resource_info}.
+This is a lightweight class that records both the regno of a resource
+and the @code{machine_mode} that the resource has (@pxref{Machine Modes}).
+It has functions for testing whether a resource is a register or memory.
+In principle it could be extended to other kinds of resource in future.
+
+@node RTL SSA Accesses
+@subsection RTL SSA Register and Memory Accesses
+
+In the RTL SSA form, most reads or writes of a resource are
+represented as a @code{rtl_ssa::access_info}@footnote{The exceptions
+are call clobbers, which are generally represented separately.
+See the comment above @code{rtl_ssa::insn_info} for details.}.
+These @code{rtl_ssa::access_info}s are organized into the following
+class hierarchy:
+
+@findex rtl_ssa::access_info
+@findex rtl_ssa::use_info
+@findex rtl_ssa::def_info
+@findex rtl_ssa::clobber_info
+@findex rtl_ssa::set_info
+@findex rtl_ssa::phi_info
+@smallexample
+rtl_ssa::access_info
+ |
+ +-- rtl_ssa::use_info
+ |
+ +-- rtl_ssa::def_info
+ |
+ +-- rtl_ssa::clobber_info
+ |
+ +-- rtl_ssa::set_info
+ |
+ +-- rtl_ssa::phi_info
+@end smallexample
+
+A @code{rtl_ssa::use_info} represents a read or use of a resource and
+a @code{rtl_ssa::def_info} represents a write or definition of a resource.
+As in the main RTL representation, there are two basic types of
+definition: clobbers and sets. The difference is that a clobber
+leaves the register with an unspecified value that cannot be used
+or relied on by later instructions, while a set leaves the register
+with a known value that later instructions could use if they wanted to.
+A @code{rtl_ssa::clobber_info} represents a clobber and
+a @code{rtl_ssa::set_info} represent a set.
+
+Each @code{rtl_ssa::use_info} records which single @code{rtl_ssa::set_info}
+provides the value of the resource; this is null if the resource is
+completely undefined at the point of use. Each @code{rtl_ssa::set_info}
+in turn records all the @code{rtl_ssa::use_info}s that use its value.
+
+If a value of a resource can come from multiple sources,
+a @code{rtl_ssa::phi_info} brings those multiple sources together
+into a single definition (@pxref{RTL SSA Phi Nodes}).
+
+@node RTL SSA Phi Nodes
+@subsection RTL SSA Phi Nodes
+
+@cindex phi nodes, RTL SSA
+@findex rtl_ssa::phi_info
+If a resource is live on entry to an extended basic block and if the
+resource's value can come from multiple sources, the extended basic block
+has a ``phi node'' that collects together these multiple sources.
+The phi node conceptually has one input for each incoming edge of
+the extended basic block, with the input specifying the value of
+the resource on that edge. For example, suppose a function contains
+the following RTL:
+
+@smallexample
+;; Basic block bb3
+@dots{}
+(set (reg:SI R1) (const_int 0)) ;; A
+(set (pc) (label_ref bb5))
+
+;; Basic block bb4
+@dots{}
+(set (reg:SI R1) (const_int 1)) ;; B
+;; Fall through
+
+;; Basic block bb5
+;; preds: bb3, bb4
+;; live in: R1 @dots{}
+(code_label bb5)
+@dots{}
+(set (reg:SI @var{R2})
+ (plus:SI (reg:SI R1) @dots{})) ;; C
+@end smallexample
+
+The value of R1 on entry to block 5 can come from either A or B@.
+The extended basic block that contains block 5 would therefore have a
+phi node with two inputs: the first input would have the value of
+R1 defined by A and the second input would have the value of
+R1 defined by B@. This phi node would then provide the value of
+R1 for C (assuming that R1 does not change again between
+the start of block 5 and C).
+
+Since RTL is not a ``native'' SSA representation, these phi nodes
+simply collect together definitions that already exist. Each input
+to a phi node for a resource @var{R} is itself a definition of
+resource @var{R} (or is null if the resource is completely
+undefined for a particular incoming edge). This is in contrast
+to a native SSA representation like GIMPLE, where the phi inputs
+can be arbitrary expressions. As a result, RTL SSA phi nodes
+never involve ``hidden'' moves: all moves are instead explicit.
+
+Phi nodes are represented as a @code{rtl_ssa::phi_node}.
+Each input to a phi node is represented as an @code{rtl_ssa::use_info}.
+
+@node RTL SSA Access Lists
+@subsection RTL SSA Access Lists
+
+All the definitions of a resource are chained together in reverse postorder.
+In general, this list can contain an arbitrary mix of both sets
+(@code{rtl_ssa::set_info}) and clobbers (@code{rtl_ssa::clobber_info}).
+However, it is often useful to skip over all intervening clobbers
+of a resource in order to find the next set. The list is constructed
+in such a way that this can be done in amortized constant time.
+
+All uses (@code{rtl_ssa::use_info}) of a given set are also chained
+together into a list. This list of uses is divided into three parts:
+
+@enumerate
+@item
+uses by ``real'' nondebug instructions (@pxref{real RTL SSA insns})
+
+@item
+uses by real debug instructions
+
+@item
+uses by phi nodes (@pxref{RTL SSA Phi Nodes})
+@end enumerate
+
+The first and second parts individually follow reverse postorder.
+The third part has no particular order.
+
+@cindex degenerate phi node, RTL SSA
+The last use by a real nondebug instruction always comes earlier in
+the reverse postorder than the next definition of the resource (if any).
+This means that the accesses follow a linear sequence of the form:
+
+@itemize @bullet
+@item
+first definition of resource R
+
+@itemize @bullet
+@item
+first use by a real nondebug instruction of the first definition of resource R
+
+@item
+@dots{}
+
+@item
+last use by a real nondebug instruction of the first definition of resource R
+@end itemize
+
+@item
+second definition of resource R
+
+@itemize @bullet
+@item
+first use by a real nondebug instruction of the second definition of resource R
+
+@item
+@dots{}
+
+@item
+last use by a real nondebug instruction of the second definition of resource R
+@end itemize
+
+@item
+@dots{}
+
+@item
+last definition of resource R
+
+@itemize @bullet
+@item
+first use by a real nondebug instruction of the last definition of resource R
+
+@item
+@dots{}
+
+@item
+last use by a real nondebug instruction of the last definition of resource R
+@end itemize
+@end itemize
+
+(Note that clobbers never have uses; only sets do.)
+
+This linear view is easy to achieve when there is only a single definition
+of a resource, which is commonly true for pseudo registers. However,
+things are more complex if code has a structure like the following:
+
+@smallexample
+// ebb2, bb2
+R = @var{va}; // A
+if (@dots{})
+ @{
+ // ebb2, bb3
+ use1 (R); // B
+ @dots{}
+ R = @var{vc}; // C
+ @}
+else
+ @{
+ // ebb4, bb4
+ use2 (R); // D
+ @}
+@end smallexample
+
+The list of accesses would begin as follows:
+
+@itemize @bullet
+@item
+definition of R by A
+
+@itemize @bullet
+@item
+use of A's definition of R by B
+@end itemize
+
+@item
+definition of R by C
+@end itemize
+
+The next access to R is in D, but the value of R that D uses comes from
+A rather than C@.
+
+This is resolved by adding a phi node for @code{ebb4}. All inputs to this
+phi node have the same value, which in the example above is A's definition
+of R@. In other circumstances, it would not be necessary to create a phi
+node when all inputs are equal, so these phi nodes are referred to as
+``degenerate'' phi nodes.
+
+The full list of accesses to R is therefore:
+
+@itemize @bullet
+@item
+definition of R by A
+
+@itemize @bullet
+@item
+use of A's definition of R by B
+@end itemize
+
+@item
+definition of R by C
+
+@item
+definition of R by ebb4's phi instruction, with the input coming from A
+
+@itemize @bullet
+@item
+use of the ebb4's R phi definition of R by B
+@end itemize
+@end itemize
+
+Note that A's definition is also used by ebb4's phi node, but this
+use belongs to the third part of the use list described above and
+so does not form part of the linear sequence.
+
+It is possible to ``look through'' any degenerate phi to the ultimate
+definition using the function @code{look_through_degenerate_phi}.
+Note that the input to a degenerate phi is never itself provided
+by a degenerate phi.
+
+At present, the SSA form takes this principle one step further
+and guarantees that, for any given resource @var{res}, one of the
+following is true:
+
+@itemize
+@item
+The resource has a single definition @var{def}, which is not a phi node.
+Excluding uses of undefined registers, all uses of @var{res} by real
+nondebug instructions use the value provided by @var{def}.
+
+@item
+Excluding uses of undefined registers, all uses of @var{res} use
+values provided by definitions that occur earlier in the same
+extended basic block. These definitions might come from phi nodes
+or from real instructions.
+@end itemize
+
+@node Changing RTL Instructions
+@subsection Using the RTL SSA framework to change instructions
+
+@findex rtl_ssa::insn_change
+There are various routines that help to change a single RTL instruction
+or a group of RTL instructions while keeping the RTL SSA form up-to-date.
+This section first describes the process for changing a single instruction,
+then goes on to describe the differences when changing multiple instructions.
+
+@menu
+* Changing One RTL SSA Instruction::
+* Changing Multiple RTL SSA Instructions::
+@end menu
+
+@node Changing One RTL SSA Instruction
+@subsubsection Changing One RTL SSA Instruction
+
+Before making a change, passes should first use a statement like the
+following:
+
+@smallexample
+auto attempt = crtl->ssa->new_change_attempt ();
+@end smallexample
+
+Here, @code{attempt} is an RAII object that should remain in scope
+for the entire change attempt. It automatically frees temporary
+memory related to the changes when it goes out of scope.
+
+Next, the pass should create an @code{rtl_ssa::insn_change} object
+for the instruction that it wants to change. This object specifies
+several things:
+
+@itemize @bullet
+@item
+what the instruction's new list of uses should be (@code{new_uses}).
+By default this is the same as the instruction's current list of uses.
+
+@item
+what the instruction's new list of definitions should be (@code{new_defs}).
+By default this is the same as the instruction's current list of
+definitions.
+
+@item
+where the instruction should be located (@code{move_range}).
+This is a range of instructions after which the instruction could
+be placed, represented as an @code{rtl_ssa::insn_range}.
+By default the instruction must remain at its current position.
+@end itemize
+
+If a pass was attempting to change all these properties of an instruction
+@code{insn}, it might do something like this:
+
+@smallexample
+rtl_ssa::insn_change change (insn);
+change.new_defs = @dots{};
+change.new_uses = @dots{};
+change.move_range = @dots{};
+@end smallexample
+
+This @code{rtl_ssa::insn_change} only describes something that the
+pass @emph{might} do; at this stage, nothing has actually changed.
+
+As noted above, the default @code{move_range} requires the instruction
+to remain where it is. At the other extreme, it is possible to allow
+the instruction to move anywhere within its extended basic block,
+provided that all the new uses and definitions can be performed
+at the new location. The way to do this is:
+
+@smallexample
+change.move_range = insn->ebb ()->insn_range ();
+@end smallexample
+
+In either case, the next step is to make sure that move range is
+consistent with the new uses and definitions. The way to do this is:
+
+@smallexample
+if (!rtl_ssa::restrict_movement (change))
+ return false;
+@end smallexample
+
+This function tries to limit @code{move_range} to a range of instructions
+at which @code{new_uses} and @code{new_defs} can be correctly performed.
+It returns true on success or false if no suitable location exists.
+
+The pass should also tentatively change the pattern of the instruction
+to whatever form the pass wants the instruction to have. This should use
+the facilities provided by @file{recog.cc}. For example:
+
+@smallexample
+rtl_insn *rtl = insn->rtl ();
+insn_change_watermark watermark;
+validate_change (rtl, &PATTERN (rtl), new_pat, 1);
+@end smallexample
+
+will tentatively replace @code{insn}'s pattern with @code{new_pat}.
+
+These changes and the construction of the @code{rtl_ssa::insn_change}
+can happen in either order or be interleaved.
+
+After the tentative changes to the instruction are complete,
+the pass should check whether the new pattern matches a target
+instruction or satisfies the requirements of an inline asm:
+
+@smallexample
+if (!rtl_ssa::recog (change))
+ return false;
+@end smallexample
+
+This step might change the instruction pattern further in order to
+make it match. It might also add new definitions or restrict the range
+of the move. For example, if the new pattern did not match in its original
+form, but could be made to match by adding a clobber of the flags
+register, @code{rtl_ssa::recog} will check whether the flags register
+is free at an appropriate point. If so, it will add a clobber of the
+flags register to @code{new_defs} and restrict @code{move_range} to
+the locations at which the flags register can be safely clobbered.
+
+Even if the proposed new instruction is valid according to
+@code{rtl_ssa::recog}, the change might not be worthwhile.
+For example, when optimizing for speed, the new instruction might
+turn out to be slower than the original one. When optimizing for
+size, the new instruction might turn out to be bigger than the
+original one.
+
+Passes should check for this case using @code{change_is_worthwhile}.
+For example:
+
+@smallexample
+if (!rtl_ssa::change_is_worthwhile (change))
+ return false;
+@end smallexample
+
+If the change passes this test too then the pass can perform the change using:
+
+@smallexample
+confirm_change_group ();
+crtl->ssa->change_insn (change);
+@end smallexample
+
+Putting all this together, the change has the following form:
+
+@smallexample
+auto attempt = crtl->ssa->new_change_attempt ();
+
+rtl_ssa::insn_change change (insn);
+change.new_defs = @dots{};
+change.new_uses = @dots{};
+change.move_range = @dots{};
+
+if (!rtl_ssa::restrict_movement (change))
+ return false;
+
+insn_change_watermark watermark;
+// Use validate_change etc. to change INSN's pattern.
+@dots{}
+if (!rtl_ssa::recog (change)
+ || !rtl_ssa::change_is_worthwhile (change))
+ return false;
+
+confirm_change_group ();
+crtl->ssa->change_insn (change);
+@end smallexample
+
+@node Changing Multiple RTL SSA Instructions
+@subsubsection Changing Multiple RTL SSA Instructions
+
+The process for changing multiple instructions is similar
+to the process for changing single instructions
+(@pxref{Changing One RTL SSA Instruction}). The pass should
+again start the change attempt with:
+
+@smallexample
+auto attempt = crtl->ssa->new_change_attempt ();
+@end smallexample
+
+and keep @code{attempt} in scope for the duration of the change
+attempt. It should then construct an @code{rtl_ssa::insn_change}
+for each change that it wants to make.
+
+After this, it should combine the changes into a sequence of
+@code{rtl_ssa::insn_change} pointers. This sequence must be in
+reverse postorder; the instructions will remain strictly in the
+order that the sequence specifies.
+
+For example, if a pass is changing exactly two instructions,
+it might do:
+
+@smallexample
+rtl_ssa::insn_change *changes[] = @{ &change1, change2 @};
+@end smallexample
+
+where @code{change1}'s instruction must come before @code{change2}'s.
+Alternatively, if the pass is changing a variable number of
+instructions, it might build up the sequence in a
+@code{vec<rtl_ssa::insn_change *>}.
+
+By default, @code{rtl_ssa::restrict_movement} assumes that all
+instructions other than the one passed to it will remain in their
+current positions and will retain their current uses and definitions.
+When changing multiple instructions, it is usually more effective
+to ignore the other instructions that are changing. The sequencing
+described above ensures that the changing instructions remain
+in the correct order with respect to each other.
+The way to do this is:
+
+@smallexample
+if (!rtl_ssa::restrict_movement (change, insn_is_changing (changes)))
+ return false;
+@end smallexample
+
+Similarly, when @code{rtl_ssa::restrict_movement} is detecting
+whether a register can be clobbered, it by default assumes that
+all other instructions will remain in their current positions and
+retain their current form. It is again more effective to ignore
+changing instructions (which might, for example, no longer need
+to clobber the flags register). The way to do this is:
+
+@smallexample
+if (!rtl_ssa::recog (change, insn_is_changing (changes)))
+ return false;
+@end smallexample
+
+When changing multiple instructions, the important question is usually
+not whether each individual change is worthwhile, but whether the changes
+as a whole are worthwhile. The way to test this is:
+
+@smallexample
+if (!rtl_ssa::changes_are_worthwhile (changes))
+ return false;
+@end smallexample
+
+The process for changing single instructions makes sure that one
+@code{rtl_ssa::insn_change} in isolation is valid. But when changing
+multiple instructions, it is also necessary to test whether the
+sequence as a whole is valid. For example, it might be impossible
+to satisfy all of the @code{move_range}s at once.
+
+Therefore, once the pass has a sequence of changes that are
+individually correct, it should use:
+
+@smallexample
+if (!crtl->ssa->verify_insn_changes (changes))
+ return false;
+@end smallexample
+
+to check whether the sequence as a whole is valid. If all checks pass,
+the final step is:
+
+@smallexample
+confirm_change_group ();
+crtl->ssa->change_insns (changes);
+@end smallexample
+
+Putting all this together, the process for a two-instruction change is:
+
+@smallexample
+auto attempt = crtl->ssa->new_change_attempt ();
+
+rtl_ssa::insn_change change (insn1);
+change1.new_defs = @dots{};
+change1.new_uses = @dots{};
+change1.move_range = @dots{};
+
+rtl_ssa::insn_change change (insn2);
+change2.new_defs = @dots{};
+change2.new_uses = @dots{};
+change2.move_range = @dots{};
+
+rtl_ssa::insn_change *changes[] = @{ &change1, change2 @};
+
+auto is_changing = insn_is_changing (changes);
+if (!rtl_ssa::restrict_movement (change1, is_changing)
+ || !rtl_ssa::restrict_movement (change2, is_changing))
+ return false;
+
+insn_change_watermark watermark;
+// Use validate_change etc. to change INSN1's and INSN2's patterns.
+@dots{}
+if (!rtl_ssa::recog (change1, is_changing)
+ || !rtl_ssa::recog (change2, is_changing)
+ || !rtl_ssa::changes_are_worthwhile (changes)
+ || !crtl->ssa->verify_insn_changes (changes))
+ return false;
+
+confirm_change_group ();
+crtl->ssa->change_insns (changes);
+@end smallexample
+
+@node Sharing
+@section Structure Sharing Assumptions
+@cindex sharing of RTL components
+@cindex RTL structure sharing assumptions
+
+The compiler assumes that certain kinds of RTL expressions are unique;
+there do not exist two distinct objects representing the same value.
+In other cases, it makes an opposite assumption: that no RTL expression
+object of a certain kind appears in more than one place in the
+containing structure.
+
+These assumptions refer to a single function; except for the RTL
+objects that describe global variables and external functions,
+and a few standard objects such as small integer constants,
+no RTL objects are common to two functions.
+
+@itemize @bullet
+@cindex @code{reg}, RTL sharing
+@item
+Each pseudo-register has only a single @code{reg} object to represent it,
+and therefore only a single machine mode.
+
+@cindex symbolic label
+@cindex @code{symbol_ref}, RTL sharing
+@item
+For any symbolic label, there is only one @code{symbol_ref} object
+referring to it.
+
+@cindex @code{const_int}, RTL sharing
+@item
+All @code{const_int} expressions with equal values are shared.
+
+@cindex @code{const_poly_int}, RTL sharing
+@item
+All @code{const_poly_int} expressions with equal modes and values
+are shared.
+
+@cindex @code{pc}, RTL sharing
+@item
+There is only one @code{pc} expression.
+
+@cindex @code{const_double}, RTL sharing
+@item
+There is only one @code{const_double} expression with value 0 for
+each floating point mode. Likewise for values 1 and 2.
+
+@cindex @code{const_vector}, RTL sharing
+@item
+There is only one @code{const_vector} expression with value 0 for
+each vector mode, be it an integer or a double constant vector.
+
+@cindex @code{label_ref}, RTL sharing
+@cindex @code{scratch}, RTL sharing
+@item
+No @code{label_ref} or @code{scratch} appears in more than one place in
+the RTL structure; in other words, it is safe to do a tree-walk of all
+the insns in the function and assume that each time a @code{label_ref}
+or @code{scratch} is seen it is distinct from all others that are seen.
+
+@cindex @code{mem}, RTL sharing
+@item
+Only one @code{mem} object is normally created for each static
+variable or stack slot, so these objects are frequently shared in all
+the places they appear. However, separate but equal objects for these
+variables are occasionally made.
+
+@cindex @code{asm_operands}, RTL sharing
+@item
+When a single @code{asm} statement has multiple output operands, a
+distinct @code{asm_operands} expression is made for each output operand.
+However, these all share the vector which contains the sequence of input
+operands. This sharing is used later on to test whether two
+@code{asm_operands} expressions come from the same statement, so all
+optimizations must carefully preserve the sharing if they copy the
+vector at all.
+
+@item
+No RTL object appears in more than one place in the RTL structure
+except as described above. Many passes of the compiler rely on this
+by assuming that they can modify RTL objects in place without unwanted
+side-effects on other insns.
+
+@findex unshare_all_rtl
+@item
+During initial RTL generation, shared structure is freely introduced.
+After all the RTL for a function has been generated, all shared
+structure is copied by @code{unshare_all_rtl} in @file{emit-rtl.cc},
+after which the above rules are guaranteed to be followed.
+
+@findex copy_rtx_if_shared
+@item
+During the combiner pass, shared structure within an insn can exist
+temporarily. However, the shared structure is copied before the
+combiner is finished with the insn. This is done by calling
+@code{copy_rtx_if_shared}, which is a subroutine of
+@code{unshare_all_rtl}.
+@end itemize
+
+@node Reading RTL
+@section Reading RTL
+
+To read an RTL object from a file, call @code{read_rtx}. It takes one
+argument, a stdio stream, and returns a single RTL object. This routine
+is defined in @file{read-rtl.cc}. It is not available in the compiler
+itself, only the various programs that generate the compiler back end
+from the machine description.
+
+People frequently have the idea of using RTL stored as text in a file as
+an interface between a language front end and the bulk of GCC@. This
+idea is not feasible.
+
+GCC was designed to use RTL internally only. Correct RTL for a given
+program is very dependent on the particular target machine. And the RTL
+does not contain all the information about the program.
+
+The proper way to interface GCC to a new language front end is with
+the ``tree'' data structure, described in the files @file{tree.h} and
+@file{tree.def}. The documentation for this structure (@pxref{GENERIC})
+is incomplete.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Service
+@chapter How To Get Help with GCC
+
+If you need help installing, using or changing GCC, there are two
+ways to find it:
+
+@itemize @bullet
+@item
+Send a message to a suitable network mailing list. First try
+@email{gcc-help@@gcc.gnu.org} (for help installing or using GCC), and if
+that brings no response, try @email{gcc@@gcc.gnu.org}. For help
+changing GCC, ask @email{gcc@@gcc.gnu.org}. If you think you have found
+a bug in GCC, please report it following the instructions at
+@pxref{Bug Reporting}.
+
+@item
+Look in the service directory for someone who might help you for a fee.
+The service directory is found at
+@uref{https://www.fsf.org/resources/service}.
+@end itemize
+
+For further information, see
+@uref{https://gcc.gnu.org/faq.html#support}.
--- /dev/null
+@c Copyright (C) 2002-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Source Tree
+@chapter Source Tree Structure and Build System
+
+This chapter describes the structure of the GCC source tree, and how
+GCC is built. The user documentation for building and installing GCC
+is in a separate manual (@uref{https://gcc.gnu.org/install/}), with
+which it is presumed that you are familiar.
+
+@menu
+* Configure Terms:: Configuration terminology and history.
+* Top Level:: The top level source directory.
+* gcc Directory:: The @file{gcc} subdirectory.
+@end menu
+
+@include configterms.texi
+
+@node Top Level
+@section Top Level Source Directory
+
+The top level source directory in a GCC distribution contains several
+files and directories that are shared with other software
+distributions such as that of GNU Binutils. It also contains several
+subdirectories that contain parts of GCC and its runtime libraries:
+
+@table @file
+@item c++tools
+Contains the sources for the g++-mapper-server, a tool used with
+C++ modules.
+
+@item config
+Autoconf macros and Makefile fragments used throughout the tree.
+
+@item contrib
+Contributed scripts that may be found useful in conjunction with GCC@.
+One of these, @file{contrib/texi2pod.pl}, is used to generate man
+pages from Texinfo manuals as part of the GCC build process.
+
+@item fixincludes
+The support for fixing system headers to work with GCC@. See
+@file{fixincludes/README} for more information. The headers fixed by
+this mechanism are installed in @file{@var{libsubdir}/include-fixed}.
+Along with those headers, @file{README-fixinc} is also installed, as
+@file{@var{libsubdir}/include-fixed/README}.
+
+@item gcc
+The main sources of GCC itself (except for runtime libraries),
+including optimizers, support for different target architectures,
+language front ends, and testsuites. @xref{gcc Directory, , The
+@file{gcc} Subdirectory}, for details.
+
+@item gnattools
+Support tools for GNAT.
+
+@item gotools
+Support tools for Go.
+
+@item include
+Headers for the @code{libiberty} library.
+
+@item intl
+GNU @code{libintl}, from GNU @code{gettext}, for systems which do not
+include it in @code{libc}.
+
+@item libada
+The Ada runtime library.
+
+@item libatomic
+The runtime support library for atomic operations (e.g.@: for @code{__sync}
+and @code{__atomic}).
+
+@item libbacktrace
+A library that allows gcc to produce backtraces when it crashes.
+
+@item libcc1
+A library that allows gdb to make use of the compiler.
+
+@item libcody
+A compiler dynamism library to allow communication between compilers and
+build systems, for purposes such as C++ modules.
+
+@item libcpp
+The C preprocessor library.
+
+@item libdecnumber
+The Decimal Float support library.
+
+@item libffi
+The @code{libffi} library, used as part of the Go runtime library.
+
+@item libgcc
+The GCC runtime library.
+
+@item libgfortran
+The Fortran runtime library.
+
+@item libgo
+The Go runtime library. The bulk of this library is mirrored from the
+@uref{https://github.com/@/golang/go, master Go repository}.
+
+@item libgomp
+The GNU Offloading and Multi Processing Runtime Library.
+
+@item libiberty
+The @code{libiberty} library, used for portability and for some
+generally useful data structures and algorithms. @xref{Top, ,
+Introduction, libiberty, @sc{gnu} libiberty}, for more information
+about this library.
+
+@item libitm
+The runtime support library for transactional memory.
+
+@item libobjc
+The Objective-C and Objective-C++ runtime library.
+
+@item libphobos
+The D standard and runtime library. The bulk of this library is mirrored
+from the @uref{https://github.com/@/dlang, master D repositories}.
+
+@item libquadmath
+The runtime support library for quad-precision math operations.
+
+@item libsanitizer
+Libraries for various sanitizers. The bulk of this directory is mirrored
+from the @uref{https://github.com/google/sanitizers, Google sanitizers
+repositories}.
+
+@item libssp
+The Stack protector runtime library.
+
+@item libstdc++-v3
+The C++ runtime library.
+
+@item libvtv
+The vtable verification library.
+
+@item lto-plugin
+Plugin used by the linker if link-time optimizations are enabled.
+
+@item maintainer-scripts
+Scripts used by the @code{gccadmin} account on @code{gcc.gnu.org}.
+
+@item zlib
+The @code{zlib} compression library, used for compressing and
+uncompressing GCC's intermediate language in LTO object files.
+@end table
+
+The build system in the top level directory, including how recursion
+into subdirectories works and how building runtime libraries for
+multilibs is handled, is documented in a separate manual, included
+with GNU Binutils. @xref{Top, , GNU configure and build system,
+configure, The GNU configure and build system}, for details.
+
+@node gcc Directory
+@section The @file{gcc} Subdirectory
+
+The @file{gcc} directory contains many files that are part of the C
+sources of GCC, other files used as part of the configuration and
+build process, and subdirectories including documentation and a
+testsuite. The files that are sources of GCC are documented in a
+separate chapter. @xref{Passes, , Passes and Files of the Compiler}.
+
+@menu
+* Subdirectories:: Subdirectories of @file{gcc}.
+* Configuration:: The configuration process, and the files it uses.
+* Build:: The build system in the @file{gcc} directory.
+* Makefile:: Targets in @file{gcc/Makefile}.
+* Library Files:: Library source files and headers under @file{gcc/}.
+* Headers:: Headers installed by GCC.
+* Documentation:: Building documentation in GCC.
+* Front End:: Anatomy of a language front end.
+* Back End:: Anatomy of a target back end.
+@end menu
+
+@node Subdirectories
+@subsection Subdirectories of @file{gcc}
+
+The @file{gcc} directory contains the following subdirectories:
+
+@table @file
+@item @var{language}
+Subdirectories for various languages. Directories containing a file
+@file{config-lang.in} are language subdirectories. The contents of
+the subdirectories @file{c} (for C), @file{cp} (for C++),
+@file{objc} (for Objective-C), @file{objcp} (for Objective-C++),
+and @file{lto} (for LTO) are documented in this
+manual (@pxref{Passes, , Passes and Files of the Compiler});
+those for other languages are not. @xref{Front End, ,
+Anatomy of a Language Front End}, for details of the files in these
+directories.
+
+@item common
+Source files shared between the compiler drivers (such as
+@command{gcc}) and the compilers proper (such as @file{cc1}). If an
+architecture defines target hooks shared between those places, it also
+has a subdirectory in @file{common/config}. @xref{Target Structure}.
+
+@item config
+Configuration files for supported architectures and operating
+systems. @xref{Back End, , Anatomy of a Target Back End}, for
+details of the files in this directory.
+
+@item doc
+Texinfo documentation for GCC, together with automatically generated
+man pages and support for converting the installation manual to
+HTML@. @xref{Documentation}.
+
+@item ginclude
+System headers installed by GCC, mainly those required by the C
+standard of freestanding implementations. @xref{Headers, , Headers
+Installed by GCC}, for details of when these and other headers are
+installed.
+
+@item po
+Message catalogs with translations of messages produced by GCC into
+various languages, @file{@var{language}.po}. This directory also
+contains @file{gcc.pot}, the template for these message catalogues,
+@file{exgettext}, a wrapper around @command{gettext} to extract the
+messages from the GCC sources and create @file{gcc.pot}, which is run
+by @samp{make gcc.pot}, and @file{EXCLUDES}, a list of files from
+which messages should not be extracted.
+
+@item testsuite
+The GCC testsuites (except for those for runtime libraries).
+@xref{Testsuites}.
+@end table
+
+@node Configuration
+@subsection Configuration in the @file{gcc} Directory
+
+The @file{gcc} directory is configured with an Autoconf-generated
+script @file{configure}. The @file{configure} script is generated
+from @file{configure.ac} and @file{aclocal.m4}. From the files
+@file{configure.ac} and @file{acconfig.h}, Autoheader generates the
+file @file{config.in}. The file @file{cstamp-h.in} is used as a
+timestamp.
+
+@menu
+* Config Fragments:: Scripts used by @file{configure}.
+* System Config:: The @file{config.build}, @file{config.host}, and
+ @file{config.gcc} files.
+* Configuration Files:: Files created by running @file{configure}.
+@end menu
+
+@node Config Fragments
+@subsubsection Scripts Used by @file{configure}
+
+@file{configure} uses some other scripts to help in its work:
+
+@itemize @bullet
+@item The standard GNU @file{config.sub} and @file{config.guess}
+files, kept in the top level directory, are used.
+
+@item The file @file{config.gcc} is used to handle configuration
+specific to the particular target machine. The file
+@file{config.build} is used to handle configuration specific to the
+particular build machine. The file @file{config.host} is used to handle
+configuration specific to the particular host machine. (In general,
+these should only be used for features that cannot reasonably be tested in
+Autoconf feature tests.)
+@xref{System Config, , The @file{config.build}; @file{config.host};
+and @file{config.gcc} Files}, for details of the contents of these files.
+
+@item Each language subdirectory has a file
+@file{@var{language}/config-lang.in} that is used for
+front-end-specific configuration. @xref{Front End Config, , The Front
+End @file{config-lang.in} File}, for details of this file.
+
+@item A helper script @file{configure.frag} is used as part of
+creating the output of @file{configure}.
+@end itemize
+
+@node System Config
+@subsubsection The @file{config.build}; @file{config.host}; and @file{config.gcc} Files
+
+The @file{config.build} file contains specific rules for particular systems
+which GCC is built on. This should be used as rarely as possible, as the
+behavior of the build system can always be detected by autoconf.
+
+The @file{config.host} file contains specific rules for particular systems
+which GCC will run on. This is rarely needed.
+
+The @file{config.gcc} file contains specific rules for particular systems
+which GCC will generate code for. This is usually needed.
+
+Each file has a list of the shell variables it sets, with descriptions, at the
+top of the file.
+
+FIXME: document the contents of these files, and what variables should
+be set to control build, host and target configuration.
+
+@include configfiles.texi
+
+@node Build
+@subsection Build System in the @file{gcc} Directory
+
+FIXME: describe the build system, including what is built in what
+stages. Also list the various source files that are used in the build
+process but aren't source files of GCC itself and so aren't documented
+below (@pxref{Passes}).
+
+@include makefile.texi
+
+@node Library Files
+@subsection Library Source Files and Headers under the @file{gcc} Directory
+
+FIXME: list here, with explanation, all the C source files and headers
+under the @file{gcc} directory that aren't built into the GCC
+executable but rather are part of runtime libraries and object files,
+such as @file{crtstuff.c} and @file{unwind-dw2.c}. @xref{Headers, ,
+Headers Installed by GCC}, for more information about the
+@file{ginclude} directory.
+
+@node Headers
+@subsection Headers Installed by GCC
+
+In general, GCC expects the system C library to provide most of the
+headers to be used with it. However, GCC will fix those headers if
+necessary to make them work with GCC, and will install some headers
+required of freestanding implementations. These headers are installed
+in @file{@var{libsubdir}/include}. Headers for non-C runtime
+libraries are also installed by GCC; these are not documented here.
+(FIXME: document them somewhere.)
+
+Several of the headers GCC installs are in the @file{ginclude}
+directory. These headers, @file{iso646.h},
+@file{stdarg.h}, @file{stdbool.h}, and @file{stddef.h},
+are installed in @file{@var{libsubdir}/include},
+unless the target Makefile fragment (@pxref{Target Fragment})
+overrides this by setting @code{USER_H}.
+
+In addition to these headers and those generated by fixing system
+headers to work with GCC, some other headers may also be installed in
+@file{@var{libsubdir}/include}. @file{config.gcc} may set
+@code{extra_headers}; this specifies additional headers under
+@file{config} to be installed on some systems.
+
+GCC installs its own version of @code{<float.h>}, from @file{ginclude/float.h}.
+This is done to cope with command-line options that change the
+representation of floating point numbers.
+
+GCC also installs its own version of @code{<limits.h>}; this is generated
+from @file{glimits.h}, together with @file{limitx.h} and
+@file{limity.h} if the system also has its own version of
+@code{<limits.h>}. (GCC provides its own header because it is
+required of ISO C freestanding implementations, but needs to include
+the system header from its own header as well because other standards
+such as POSIX specify additional values to be defined in
+@code{<limits.h>}.) The system's @code{<limits.h>} header is used via
+@file{@var{libsubdir}/include/syslimits.h}, which is copied from
+@file{gsyslimits.h} if it does not need fixing to work with GCC; if it
+needs fixing, @file{syslimits.h} is the fixed copy.
+
+GCC can also install @code{<tgmath.h>}. It will do this when
+@file{config.gcc} sets @code{use_gcc_tgmath} to @code{yes}.
+
+@node Documentation
+@subsection Building Documentation
+
+The main GCC documentation is in the form of manuals in Texinfo
+format. These are installed in Info format; DVI versions may be
+generated by @samp{make dvi}, PDF versions by @samp{make pdf}, and
+HTML versions by @samp{make html}. In addition, some man pages are
+generated from the Texinfo manuals, there are some other text files
+with miscellaneous documentation, and runtime libraries have their own
+documentation outside the @file{gcc} directory. FIXME: document the
+documentation for runtime libraries somewhere.
+
+@menu
+* Texinfo Manuals:: GCC manuals in Texinfo format.
+* Man Page Generation:: Generating man pages from Texinfo manuals.
+* Miscellaneous Docs:: Miscellaneous text files with documentation.
+@end menu
+
+@node Texinfo Manuals
+@subsubsection Texinfo Manuals
+
+The manuals for GCC as a whole, and the C and C++ front ends, are in
+files @file{doc/*.texi}. Other front ends have their own manuals in
+files @file{@var{language}/*.texi}. Common files
+@file{doc/include/*.texi} are provided which may be included in
+multiple manuals; the following files are in @file{doc/include}:
+
+@table @file
+@item fdl.texi
+The GNU Free Documentation License.
+@item funding.texi
+The section ``Funding Free Software''.
+@item gcc-common.texi
+Common definitions for manuals.
+@item gpl_v3.texi
+The GNU General Public License.
+@item texinfo.tex
+A copy of @file{texinfo.tex} known to work with the GCC manuals.
+@end table
+
+DVI-formatted manuals are generated by @samp{make dvi}, which uses
+@command{texi2dvi} (via the Makefile macro @code{$(TEXI2DVI)}).
+PDF-formatted manuals are generated by @samp{make pdf}, which uses
+@command{texi2pdf} (via the Makefile macro @code{$(TEXI2PDF)}). HTML
+formatted manuals are generated by @samp{make html}. Info
+manuals are generated by @samp{make info} (which is run as part of
+a bootstrap); this generates the manuals in the source directory,
+using @command{makeinfo} via the Makefile macro @code{$(MAKEINFO)},
+and they are included in release distributions.
+
+Manuals are also provided on the GCC web site, in both HTML and
+PostScript forms. This is done via the script
+@file{maintainer-scripts/update_web_docs_git}. Each manual to be
+provided online must be listed in the definition of @code{MANUALS} in
+that file; a file @file{@var{name}.texi} must only appear once in the
+source tree, and the output manual must have the same name as the
+source file. (However, other Texinfo files, included in manuals but
+not themselves the root files of manuals, may have names that appear
+more than once in the source tree.) The manual file
+@file{@var{name}.texi} should only include other files in its own
+directory or in @file{doc/include}. HTML manuals will be generated by
+@samp{makeinfo --html}, PostScript manuals by @command{texi2dvi}
+and @command{dvips}, and PDF manuals by @command{texi2pdf}.
+All Texinfo files that are parts of manuals must
+be version-controlled, even if they are generated files, for the
+generation of online manuals to work.
+
+The installation manual, @file{doc/install.texi}, is also provided on
+the GCC web site. The HTML version is generated by the script
+@file{doc/install.texi2html}.
+
+@node Man Page Generation
+@subsubsection Man Page Generation
+
+Because of user demand, in addition to full Texinfo manuals, man pages
+are provided which contain extracts from those manuals. These man
+pages are generated from the Texinfo manuals using
+@file{contrib/texi2pod.pl} and @command{pod2man}. (The man page for
+@command{g++}, @file{cp/g++.1}, just contains a @samp{.so} reference
+to @file{gcc.1}, but all the other man pages are generated from
+Texinfo manuals.)
+
+Because many systems may not have the necessary tools installed to
+generate the man pages, they are only generated if the
+@file{configure} script detects that recent enough tools are
+installed, and the Makefiles allow generating man pages to fail
+without aborting the build. Man pages are also included in release
+distributions. They are generated in the source directory.
+
+Magic comments in Texinfo files starting @samp{@@c man} control what
+parts of a Texinfo file go into a man page. Only a subset of Texinfo
+is supported by @file{texi2pod.pl}, and it may be necessary to add
+support for more Texinfo features to this script when generating new
+man pages. To improve the man page output, some special Texinfo
+macros are provided in @file{doc/include/gcc-common.texi} which
+@file{texi2pod.pl} understands:
+
+@table @code
+@item @@gcctabopt
+Use in the form @samp{@@table @@gcctabopt} for tables of options,
+where for printed output the effect of @samp{@@code} is better than
+that of @samp{@@option} but for man page output a different effect is
+wanted.
+@item @@gccoptlist
+Use for summary lists of options in manuals.
+@item @@gol
+Use at the end of each line inside @samp{@@gccoptlist}. This is
+necessary to avoid problems with differences in how the
+@samp{@@gccoptlist} macro is handled by different Texinfo formatters.
+@end table
+
+FIXME: describe the @file{texi2pod.pl} input language and magic
+comments in more detail.
+
+@node Miscellaneous Docs
+@subsubsection Miscellaneous Documentation
+
+In addition to the formal documentation that is installed by GCC,
+there are several other text files in the @file{gcc} subdirectory
+with miscellaneous documentation:
+
+@table @file
+@item ABOUT-GCC-NLS
+Notes on GCC's Native Language Support. FIXME: this should be part of
+this manual rather than a separate file.
+@item ABOUT-NLS
+Notes on the Free Translation Project.
+@item COPYING
+@itemx COPYING3
+The GNU General Public License, Versions 2 and 3.
+@item COPYING.LIB
+@itemx COPYING3.LIB
+The GNU Lesser General Public License, Versions 2.1 and 3.
+@item *ChangeLog*
+@itemx */ChangeLog*
+Change log files for various parts of GCC@.
+@item LANGUAGES
+Details of a few changes to the GCC front-end interface. FIXME: the
+information in this file should be part of general documentation of
+the front-end interface in this manual.
+@item ONEWS
+Information about new features in old versions of GCC@. (For recent
+versions, the information is on the GCC web site.)
+@item README.Portability
+Information about portability issues when writing code in GCC@. FIXME:
+why isn't this part of this manual or of the GCC Coding Conventions?
+@end table
+
+FIXME: document such files in subdirectories, at least @file{config},
+@file{c}, @file{cp}, @file{objc}, @file{testsuite}.
+
+@node Front End
+@subsection Anatomy of a Language Front End
+
+A front end for a language in GCC has the following parts:
+
+@itemize @bullet
+@item
+A directory @file{@var{language}} under @file{gcc} containing source
+files for that front end. @xref{Front End Directory, , The Front End
+@file{@var{language}} Directory}, for details.
+@item
+A mention of the language in the list of supported languages in
+@file{gcc/doc/install.texi}.
+@item
+A mention of the name under which the language's runtime library is
+recognized by @option{--enable-shared=@var{package}} in the
+documentation of that option in @file{gcc/doc/install.texi}.
+@item
+A mention of any special prerequisites for building the front end in
+the documentation of prerequisites in @file{gcc/doc/install.texi}.
+@item
+Details of contributors to that front end in
+@file{gcc/doc/contrib.texi}. If the details are in that front end's
+own manual then there should be a link to that manual's list in
+@file{contrib.texi}.
+@item
+Information about support for that language in
+@file{gcc/doc/frontends.texi}.
+@item
+Information about standards for that language, and the front end's
+support for them, in @file{gcc/doc/standards.texi}. This may be a
+link to such information in the front end's own manual.
+@item
+Details of source file suffixes for that language and @option{-x
+@var{lang}} options supported, in @file{gcc/doc/invoke.texi}.
+@item
+Entries in @code{default_compilers} in @file{gcc.cc} for source file
+suffixes for that language.
+@item
+Preferably testsuites, which may be under @file{gcc/testsuite} or
+runtime library directories. FIXME: document somewhere how to write
+testsuite harnesses.
+@item
+Probably a runtime library for the language, outside the @file{gcc}
+directory. FIXME: document this further.
+@item
+Details of the directories of any runtime libraries in
+@file{gcc/doc/sourcebuild.texi}.
+@item
+Check targets in @file{Makefile.def} for the top-level @file{Makefile}
+to check just the compiler or the compiler and runtime library for the
+language.
+@end itemize
+
+If the front end is added to the official GCC source repository, the
+following are also necessary:
+
+@itemize @bullet
+@item
+At least one Bugzilla component for bugs in that front end and runtime
+libraries. This category needs to be added to the Bugzilla database.
+@item
+Normally, one or more maintainers of that front end listed in
+@file{MAINTAINERS}.
+@item
+Mentions on the GCC web site in @file{index.html} and
+@file{frontends.html}, with any relevant links on
+@file{readings.html}. (Front ends that are not an official part of
+GCC may also be listed on @file{frontends.html}, with relevant links.)
+@item
+A news item on @file{index.html}, and possibly an announcement on the
+@email{gcc-announce@@gcc.gnu.org} mailing list.
+@item
+The front end's manuals should be mentioned in
+@file{maintainer-scripts/update_web_docs_git} (@pxref{Texinfo Manuals})
+and the online manuals should be linked to from
+@file{onlinedocs/index.html}.
+@item
+Any old releases or CVS repositories of the front end, before its
+inclusion in GCC, should be made available on the GCC web site at
+@uref{https://gcc.gnu.org/pub/gcc/old-releases/}.
+@item
+The release and snapshot script @file{maintainer-scripts/gcc_release}
+should be updated to generate appropriate tarballs for this front end.
+@item
+If this front end includes its own version files that include the
+current date, @file{maintainer-scripts/update_version} should be
+updated accordingly.
+@end itemize
+
+@menu
+* Front End Directory:: The front end @file{@var{language}} directory.
+* Front End Config:: The front end @file{config-lang.in} file.
+* Front End Makefile:: The front end @file{Make-lang.in} file.
+@end menu
+
+@node Front End Directory
+@subsubsection The Front End @file{@var{language}} Directory
+
+A front end @file{@var{language}} directory contains the source files
+of that front end (but not of any runtime libraries, which should be
+outside the @file{gcc} directory). This includes documentation, and
+possibly some subsidiary programs built alongside the front end.
+Certain files are special and other parts of the compiler depend on
+their names:
+
+@table @file
+@item config-lang.in
+This file is required in all language subdirectories. @xref{Front End
+Config, , The Front End @file{config-lang.in} File}, for details of
+its contents
+@item Make-lang.in
+This file is required in all language subdirectories. @xref{Front End
+Makefile, , The Front End @file{Make-lang.in} File}, for details of its
+contents.
+@item lang.opt
+This file registers the set of switches that the front end accepts on
+the command line, and their @option{--help} text. @xref{Options}.
+@item lang-specs.h
+This file provides entries for @code{default_compilers} in
+@file{gcc.cc} which override the default of giving an error that a
+compiler for that language is not installed.
+@item @var{language}-tree.def
+This file, which need not exist, defines any language-specific tree
+codes.
+@end table
+
+@node Front End Config
+@subsubsection The Front End @file{config-lang.in} File
+
+Each language subdirectory contains a @file{config-lang.in} file.
+This file is a shell script that may define some variables describing
+the language:
+
+@table @code
+@item language
+This definition must be present, and gives the name of the language
+for some purposes such as arguments to @option{--enable-languages}.
+@item lang_requires
+If defined, this variable lists (space-separated) language front ends
+other than C that this front end requires to be enabled (with the
+names given being their @code{language} settings). For example, the
+Obj-C++ front end depends on the C++ and ObjC front ends, so sets
+@samp{lang_requires="objc c++"}.
+@item subdir_requires
+If defined, this variable lists (space-separated) front end directories
+other than C that this front end requires to be present. For example,
+the Objective-C++ front end uses source files from the C++ and
+Objective-C front ends, so sets @samp{subdir_requires="cp objc"}.
+@item target_libs
+If defined, this variable lists (space-separated) targets in the top
+level @file{Makefile} to build the runtime libraries for this
+language, such as @code{target-libobjc}.
+@item lang_dirs
+If defined, this variable lists (space-separated) top level
+directories (parallel to @file{gcc}), apart from the runtime libraries,
+that should not be configured if this front end is not built.
+@item build_by_default
+If defined to @samp{no}, this language front end is not built unless
+enabled in a @option{--enable-languages} argument. Otherwise, front
+ends are built by default, subject to any special logic in
+@file{configure.ac} (as is present to disable the Ada front end if the
+Ada compiler is not already installed).
+@item boot_language
+If defined to @samp{yes}, this front end is built in stage1 of the
+bootstrap. This is only relevant to front ends written in their own
+languages.
+@item compilers
+If defined, a space-separated list of compiler executables that will
+be run by the driver. The names here will each end
+with @samp{\$(exeext)}.
+@item outputs
+If defined, a space-separated list of files that should be generated
+by @file{configure} substituting values in them. This mechanism can
+be used to create a file @file{@var{language}/Makefile} from
+@file{@var{language}/Makefile.in}, but this is deprecated, building
+everything from the single @file{gcc/Makefile} is preferred.
+@item gtfiles
+If defined, a space-separated list of files that should be scanned by
+@file{gengtype.cc} to generate the garbage collection tables and routines for
+this language. This excludes the files that are common to all front
+ends. @xref{Type Information}.
+
+@end table
+
+@node Front End Makefile
+@subsubsection The Front End @file{Make-lang.in} File
+
+Each language subdirectory contains a @file{Make-lang.in} file. It contains
+targets @code{@var{lang}.@var{hook}} (where @code{@var{lang}} is the
+setting of @code{language} in @file{config-lang.in}) for the following
+values of @code{@var{hook}}, and any other Makefile rules required to
+build those targets (which may if necessary use other Makefiles
+specified in @code{outputs} in @file{config-lang.in}, although this is
+deprecated). It also adds any testsuite targets that can use the
+standard rule in @file{gcc/Makefile.in} to the variable
+@code{lang_checks}.
+
+@table @code
+@item all.cross
+@itemx start.encap
+@itemx rest.encap
+FIXME: exactly what goes in each of these targets?
+@item tags
+Build an @command{etags} @file{TAGS} file in the language subdirectory
+in the source tree.
+@item info
+Build info documentation for the front end, in the build directory.
+This target is only called by @samp{make bootstrap} if a suitable
+version of @command{makeinfo} is available, so does not need to check
+for this, and should fail if an error occurs.
+@item dvi
+Build DVI documentation for the front end, in the build directory.
+This should be done using @code{$(TEXI2DVI)}, with appropriate
+@option{-I} arguments pointing to directories of included files.
+@item pdf
+Build PDF documentation for the front end, in the build directory.
+This should be done using @code{$(TEXI2PDF)}, with appropriate
+@option{-I} arguments pointing to directories of included files.
+@item html
+Build HTML documentation for the front end, in the build directory.
+@item man
+Build generated man pages for the front end from Texinfo manuals
+(@pxref{Man Page Generation}), in the build directory. This target
+is only called if the necessary tools are available, but should ignore
+errors so as not to stop the build if errors occur; man pages are
+optional and the tools involved may be installed in a broken way.
+@item install-common
+Install everything that is part of the front end, apart from the
+compiler executables listed in @code{compilers} in
+@file{config-lang.in}.
+@item install-info
+Install info documentation for the front end, if it is present in the
+source directory. This target should have dependencies on info files
+that should be installed.
+@item install-man
+Install man pages for the front end. This target should ignore
+errors.
+@item install-plugin
+Install headers needed for plugins.
+@item srcextra
+Copies its dependencies into the source directory. This generally should
+be used for generated files such as Bison output files which are not
+version-controlled, but should be included in any release tarballs. This
+target will be executed during a bootstrap if
+@samp{--enable-generated-files-in-srcdir} was specified as a
+@file{configure} option.
+@item srcinfo
+@itemx srcman
+Copies its dependencies into the source directory. These targets will be
+executed during a bootstrap if @samp{--enable-generated-files-in-srcdir}
+was specified as a @file{configure} option.
+@item uninstall
+Uninstall files installed by installing the compiler. This is
+currently documented not to be supported, so the hook need not do
+anything.
+@item mostlyclean
+@itemx clean
+@itemx distclean
+@itemx maintainer-clean
+The language parts of the standard GNU
+@samp{*clean} targets. @xref{Standard Targets, , Standard Targets for
+Users, standards, GNU Coding Standards}, for details of the standard
+targets. For GCC, @code{maintainer-clean} should delete
+all generated files in the source directory that are not version-controlled,
+but should not delete anything that is.
+@end table
+
+@file{Make-lang.in} must also define a variable @code{@var{lang}_OBJS}
+to a list of host object files that are used by that language.
+
+@node Back End
+@subsection Anatomy of a Target Back End
+
+A back end for a target architecture in GCC has the following parts:
+
+@itemize @bullet
+@item
+A directory @file{@var{machine}} under @file{gcc/config}, containing a
+machine description @file{@var{machine}.md} file (@pxref{Machine Desc,
+, Machine Descriptions}), header files @file{@var{machine}.h} and
+@file{@var{machine}-protos.h} and a source file @file{@var{machine}.c}
+(@pxref{Target Macros, , Target Description Macros and Functions}),
+possibly a target Makefile fragment @file{t-@var{machine}}
+(@pxref{Target Fragment, , The Target Makefile Fragment}), and maybe
+some other files. The names of these files may be changed from the
+defaults given by explicit specifications in @file{config.gcc}.
+@item
+If necessary, a file @file{@var{machine}-modes.def} in the
+@file{@var{machine}} directory, containing additional machine modes to
+represent condition codes. @xref{Condition Code}, for further details.
+@item
+An optional @file{@var{machine}.opt} file in the @file{@var{machine}}
+directory, containing a list of target-specific options. You can also
+add other option files using the @code{extra_options} variable in
+@file{config.gcc}. @xref{Options}.
+@item
+Entries in @file{config.gcc} (@pxref{System Config, , The
+@file{config.gcc} File}) for the systems with this target
+architecture.
+@item
+Documentation in @file{gcc/doc/invoke.texi} for any command-line
+options supported by this target (@pxref{Run-time Target, , Run-time
+Target Specification}). This means both entries in the summary table
+of options and details of the individual options.
+@item
+Documentation in @file{gcc/doc/extend.texi} for any target-specific
+attributes supported (@pxref{Target Attributes, , Defining
+target-specific uses of @code{__attribute__}}), including where the
+same attribute is already supported on some targets, which are
+enumerated in the manual.
+@item
+Documentation in @file{gcc/doc/extend.texi} for any target-specific
+pragmas supported.
+@item
+Documentation in @file{gcc/doc/extend.texi} of any target-specific
+built-in functions supported.
+@item
+Documentation in @file{gcc/doc/extend.texi} of any target-specific
+format checking styles supported.
+@item
+Documentation in @file{gcc/doc/md.texi} of any target-specific
+constraint letters (@pxref{Machine Constraints, , Constraints for
+Particular Machines}).
+@item
+A note in @file{gcc/doc/contrib.texi} under the person or people who
+contributed the target support.
+@item
+Entries in @file{gcc/doc/install.texi} for all target triplets
+supported with this target architecture, giving details of any special
+notes about installation for this target, or saying that there are no
+special notes if there are none.
+@item
+Possibly other support outside the @file{gcc} directory for runtime
+libraries. FIXME: reference docs for this. The @code{libstdc++} porting
+manual needs to be installed as info for this to work, or to be a
+chapter of this manual.
+@end itemize
+
+The @file{@var{machine}.h} header is included very early in GCC's
+standard sequence of header files, while @file{@var{machine}-protos.h}
+is included late in the sequence. Thus @file{@var{machine}-protos.h}
+can include declarations referencing types that are not defined when
+@file{@var{machine}.h} is included, specifically including those from
+@file{rtl.h} and @file{tree.h}. Since both RTL and tree types may not
+be available in every context where @file{@var{machine}-protos.h} is
+included, in this file you should guard declarations using these types
+inside appropriate @code{#ifdef RTX_CODE} or @code{#ifdef TREE_CODE}
+conditional code segments.
+
+If the backend uses shared data structures that require @code{GTY} markers
+for garbage collection (@pxref{Type Information}), you must declare those
+in @file{@var{machine}.h} rather than @file{@var{machine}-protos.h}.
+Any definitions required for building libgcc must also go in
+@file{@var{machine}.h}.
+
+GCC uses the macro @code{IN_TARGET_CODE} to distinguish between
+machine-specific @file{.c} and @file{.cc} files and
+machine-independent @file{.c} and @file{.cc} files. Machine-specific
+files should use the directive:
+
+@example
+#define IN_TARGET_CODE 1
+@end example
+
+before including @code{config.h}.
+
+If the back end is added to the official GCC source repository, the
+following are also necessary:
+
+@itemize @bullet
+@item
+An entry for the target architecture in @file{readings.html} on the
+GCC web site, with any relevant links.
+@item
+Details of the properties of the back end and target architecture in
+@file{backends.html} on the GCC web site.
+@item
+A news item about the contribution of support for that target
+architecture, in @file{index.html} on the GCC web site.
+@item
+Normally, one or more maintainers of that target listed in
+@file{MAINTAINERS}. Some existing architectures may be unmaintained,
+but it would be unusual to add support for a target that does not have
+a maintainer when support is added.
+@item
+Target triplets covering all @file{config.gcc} stanzas for the target,
+in the list in @file{contrib/config-list.mk}.
+@end itemize
+
+@node Testsuites
+@chapter Testsuites
+
+GCC contains several testsuites to help maintain compiler quality.
+Most of the runtime libraries and language front ends in GCC have
+testsuites. Currently only the C language testsuites are documented
+here; FIXME: document the others.
+
+@menu
+* Test Idioms:: Idioms used in testsuite code.
+* Test Directives:: Directives used within DejaGnu tests.
+* Ada Tests:: The Ada language testsuites.
+* C Tests:: The C language testsuites.
+* LTO Testing:: Support for testing link-time optimizations.
+* gcov Testing:: Support for testing gcov.
+* profopt Testing:: Support for testing profile-directed optimizations.
+* compat Testing:: Support for testing binary compatibility.
+* Torture Tests:: Support for torture testing using multiple options.
+* GIMPLE Tests:: Support for testing GIMPLE passes.
+* RTL Tests:: Support for testing RTL passes.
+@end menu
+
+@node Test Idioms
+@section Idioms Used in Testsuite Code
+
+In general, C testcases have a trailing @file{-@var{n}.c}, starting
+with @file{-1.c}, in case other testcases with similar names are added
+later. If the test is a test of some well-defined feature, it should
+have a name referring to that feature such as
+@file{@var{feature}-1.c}. If it does not test a well-defined feature
+but just happens to exercise a bug somewhere in the compiler, and a
+bug report has been filed for this bug in the GCC bug database,
+@file{pr@var{bug-number}-1.c} is the appropriate form of name.
+Otherwise (for miscellaneous bugs not filed in the GCC bug database),
+and previously more generally, test cases are named after the date on
+which they were added. This allows people to tell at a glance whether
+a test failure is because of a recently found bug that has not yet
+been fixed, or whether it may be a regression, but does not give any
+other information about the bug or where discussion of it may be
+found. Some other language testsuites follow similar conventions.
+
+In the @file{gcc.dg} testsuite, it is often necessary to test that an
+error is indeed a hard error and not just a warning---for example,
+where it is a constraint violation in the C standard, which must
+become an error with @option{-pedantic-errors}. The following idiom,
+where the first line shown is line @var{line} of the file and the line
+that generates the error, is used for this:
+
+@smallexample
+/* @{ dg-bogus "warning" "warning in place of error" @} */
+/* @{ dg-error "@var{regexp}" "@var{message}" @{ target *-*-* @} @var{line} @} */
+@end smallexample
+
+It may be necessary to check that an expression is an integer constant
+expression and has a certain value. To check that @code{@var{E}} has
+value @code{@var{V}}, an idiom similar to the following is used:
+
+@smallexample
+char x[((E) == (V) ? 1 : -1)];
+@end smallexample
+
+In @file{gcc.dg} tests, @code{__typeof__} is sometimes used to make
+assertions about the types of expressions. See, for example,
+@file{gcc.dg/c99-condexpr-1.c}. The more subtle uses depend on the
+exact rules for the types of conditional expressions in the C
+standard; see, for example, @file{gcc.dg/c99-intconst-1.c}.
+
+It is useful to be able to test that optimizations are being made
+properly. This cannot be done in all cases, but it can be done where
+the optimization will lead to code being optimized away (for example,
+where flow analysis or alias analysis should show that certain code
+cannot be called) or to functions not being called because they have
+been expanded as built-in functions. Such tests go in
+@file{gcc.c-torture/execute}. Where code should be optimized away, a
+call to a nonexistent function such as @code{link_failure ()} may be
+inserted; a definition
+
+@smallexample
+#ifndef __OPTIMIZE__
+void
+link_failure (void)
+@{
+ abort ();
+@}
+#endif
+@end smallexample
+
+@noindent
+will also be needed so that linking still succeeds when the test is
+run without optimization. When all calls to a built-in function
+should have been optimized and no calls to the non-built-in version of
+the function should remain, that function may be defined as
+@code{static} to call @code{abort ()} (although redeclaring a function
+as static may not work on all targets).
+
+All testcases must be portable. Target-specific testcases must have
+appropriate code to avoid causing failures on unsupported systems;
+unfortunately, the mechanisms for this differ by directory.
+
+FIXME: discuss non-C testsuites here.
+
+@node Test Directives
+@section Directives used within DejaGnu tests
+
+@menu
+* Directives:: Syntax and descriptions of test directives.
+* Selectors:: Selecting targets to which a test applies.
+* Effective-Target Keywords:: Keywords describing target attributes.
+* Add Options:: Features for @code{dg-add-options}
+* Require Support:: Variants of @code{dg-require-@var{support}}
+* Final Actions:: Commands for use in @code{dg-final}
+@end menu
+
+@node Directives
+@subsection Syntax and Descriptions of test directives
+
+Test directives appear within comments in a test source file and begin
+with @code{dg-}. Some of these are defined within DejaGnu and others
+are local to the GCC testsuite.
+
+The order in which test directives appear in a test can be important:
+directives local to GCC sometimes override information used by the
+DejaGnu directives, which know nothing about the GCC directives, so the
+DejaGnu directives must precede GCC directives.
+
+Several test directives include selectors (@pxref{Selectors, , })
+which are usually preceded by the keyword @code{target} or @code{xfail}.
+
+@subsubsection Specify how to build the test
+
+@table @code
+@item @{ dg-do @var{do-what-keyword} [@{ target/xfail @var{selector} @}] @}
+@var{do-what-keyword} specifies how the test is compiled and whether
+it is executed. It is one of:
+
+@table @code
+@item preprocess
+Compile with @option{-E} to run only the preprocessor.
+@item compile
+Compile with @option{-S} to produce an assembly code file.
+@item assemble
+Compile with @option{-c} to produce a relocatable object file.
+@item link
+Compile, assemble, and link to produce an executable file.
+@item run
+Produce and run an executable file, which is expected to return
+an exit code of 0.
+@end table
+
+The default is @code{compile}. That can be overridden for a set of
+tests by redefining @code{dg-do-what-default} within the @code{.exp}
+file for those tests.
+
+If the directive includes the optional @samp{@{ target @var{selector} @}}
+then the test is skipped unless the target system matches the
+@var{selector}.
+
+If @var{do-what-keyword} is @code{run} and the directive includes
+the optional @samp{@{ xfail @var{selector} @}} and the selector is met
+then the test is expected to fail. The @code{xfail} clause is ignored
+for other values of @var{do-what-keyword}; those tests can use
+directive @code{dg-xfail-if}.
+@end table
+
+@subsubsection Specify additional compiler options
+
+@table @code
+@item @{ dg-options @var{options} [@{ target @var{selector} @}] @}
+This DejaGnu directive provides a list of compiler options, to be used
+if the target system matches @var{selector}, that replace the default
+options used for this set of tests.
+
+@item @{ dg-add-options @var{feature} @dots{} @}
+Add any compiler options that are needed to access certain features.
+This directive does nothing on targets that enable the features by
+default, or that don't provide them at all. It must come after
+all @code{dg-options} directives.
+For supported values of @var{feature} see @ref{Add Options, ,}.
+
+@item @{ dg-additional-options @var{options} [@{ target @var{selector} @}] @}
+This directive provides a list of compiler options, to be used
+if the target system matches @var{selector}, that are added to the default
+options used for this set of tests.
+@end table
+
+@subsubsection Modify the test timeout value
+
+The normal timeout limit, in seconds, is found by searching the
+following in order:
+
+@itemize @bullet
+@item the value defined by an earlier @code{dg-timeout} directive in
+the test
+
+@item variable @var{tool_timeout} defined by the set of tests
+
+@item @var{gcc},@var{timeout} set in the target board
+
+@item 300
+@end itemize
+
+@table @code
+@item @{ dg-timeout @var{n} [@{target @var{selector} @}] @}
+Set the time limit for the compilation and for the execution of the test
+to the specified number of seconds.
+
+@item @{ dg-timeout-factor @var{x} [@{ target @var{selector} @}] @}
+Multiply the normal time limit for compilation and execution of the test
+by the specified floating-point factor.
+@end table
+
+@subsubsection Skip a test for some targets
+
+@table @code
+@item @{ dg-skip-if @var{comment} @{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]] @}
+Arguments @var{include-opts} and @var{exclude-opts} are lists in which
+each element is a string of zero or more GCC options.
+Skip the test if all of the following conditions are met:
+@itemize @bullet
+@item the test system is included in @var{selector}
+
+@item for at least one of the option strings in @var{include-opts},
+every option from that string is in the set of options with which
+the test would be compiled; use @samp{"*"} for an @var{include-opts} list
+that matches any options; that is the default if @var{include-opts} is
+not specified
+
+@item for each of the option strings in @var{exclude-opts}, at least one
+option from that string is not in the set of options with which the test
+would be compiled; use @samp{""} for an empty @var{exclude-opts} list;
+that is the default if @var{exclude-opts} is not specified
+@end itemize
+
+For example, to skip a test if option @code{-Os} is present:
+
+@smallexample
+/* @{ dg-skip-if "" @{ *-*-* @} @{ "-Os" @} @{ "" @} @} */
+@end smallexample
+
+To skip a test if both options @code{-O2} and @code{-g} are present:
+
+@smallexample
+/* @{ dg-skip-if "" @{ *-*-* @} @{ "-O2 -g" @} @{ "" @} @} */
+@end smallexample
+
+To skip a test if either @code{-O2} or @code{-O3} is present:
+
+@smallexample
+/* @{ dg-skip-if "" @{ *-*-* @} @{ "-O2" "-O3" @} @{ "" @} @} */
+@end smallexample
+
+To skip a test unless option @code{-Os} is present:
+
+@smallexample
+/* @{ dg-skip-if "" @{ *-*-* @} @{ "*" @} @{ "-Os" @} @} */
+@end smallexample
+
+To skip a test if either @code{-O2} or @code{-O3} is used with @code{-g}
+but not if @code{-fpic} is also present:
+
+@smallexample
+/* @{ dg-skip-if "" @{ *-*-* @} @{ "-O2 -g" "-O3 -g" @} @{ "-fpic" @} @} */
+@end smallexample
+
+@item @{ dg-require-effective-target @var{keyword} [@{ target @var{selector} @}] @}
+Skip the test if the test target, including current multilib flags,
+is not covered by the effective-target keyword.
+If the directive includes the optional @samp{@{ @var{selector} @}}
+then the effective-target test is only performed if the target system
+matches the @var{selector}.
+This directive must appear after any @code{dg-do} directive in the test
+and before any @code{dg-additional-sources} directive.
+@xref{Effective-Target Keywords, , }.
+
+@item @{ dg-require-@var{support} args @}
+Skip the test if the target does not provide the required support.
+These directives must appear after any @code{dg-do} directive in the test
+and before any @code{dg-additional-sources} directive.
+They require at least one argument, which can be an empty string if the
+specific procedure does not examine the argument.
+@xref{Require Support, , }, for a complete list of these directives.
+@end table
+
+@subsubsection Expect a test to fail for some targets
+
+@table @code
+@item @{ dg-xfail-if @var{comment} @{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]] @}
+Expect the test to fail if the conditions (which are the same as for
+@code{dg-skip-if}) are met. This does not affect the execute step.
+
+@item @{ dg-xfail-run-if @var{comment} @{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]] @}
+Expect the execute step of a test to fail if the conditions (which are
+the same as for @code{dg-skip-if}) are met.
+@end table
+
+@subsubsection Expect the compiler to crash
+
+@table @code
+@item @{ dg-ice @var{comment} [@{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]]] @}
+Expect the compiler to crash with an internal compiler error and return
+a nonzero exit status if the conditions (which are the same as for
+@code{dg-skip-if}) are met. Used for tests that test bugs that have not been
+fixed yet.
+@end table
+
+@subsubsection Expect the test executable to fail
+
+@table @code
+@item @{ dg-shouldfail @var{comment} [@{ @var{selector} @} [@{ @var{include-opts} @} [@{ @var{exclude-opts} @}]]] @}
+Expect the test executable to return a nonzero exit status if the
+conditions (which are the same as for @code{dg-skip-if}) are met.
+@end table
+
+@subsubsection Verify compiler messages
+Where @var{line} is an accepted argument for these commands, a value of @samp{0}
+can be used if there is no line associated with the message.
+
+@table @code
+@item @{ dg-error @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
+This DejaGnu directive appears on a source line that is expected to get
+an error message, or else specifies the source line associated with the
+message. If there is no message for that line or if the text of that
+message is not matched by @var{regexp} then the check fails and
+@var{comment} is included in the @code{FAIL} message. The check does
+not look for the string @samp{error} unless it is part of @var{regexp}.
+
+@item @{ dg-warning @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
+This DejaGnu directive appears on a source line that is expected to get
+a warning message, or else specifies the source line associated with the
+message. If there is no message for that line or if the text of that
+message is not matched by @var{regexp} then the check fails and
+@var{comment} is included in the @code{FAIL} message. The check does
+not look for the string @samp{warning} unless it is part of @var{regexp}.
+
+@item @{ dg-message @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
+The line is expected to get a message other than an error or warning.
+If there is no message for that line or if the text of that message is
+not matched by @var{regexp} then the check fails and @var{comment} is
+included in the @code{FAIL} message.
+
+@item @{ dg-note @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
+The line is expected to get a @samp{note} message.
+If there is no message for that line or if the text of that message is
+not matched by @var{regexp} then the check fails and @var{comment} is
+included in the @code{FAIL} message.
+
+By default, any @emph{excess} @samp{note} messages are pruned, meaning
+their appearance doesn't trigger @emph{excess errors}.
+However, if @samp{dg-note} is used at least once in a testcase,
+they're not pruned and instead must @emph{all} be handled explicitly.
+Thus, if looking for just single instances of messages with
+@samp{note: } prefixes without caring for all of them, use
+@samp{dg-message "note: [@dots{}]"} instead of @samp{dg-note}, or use
+@samp{dg-note} together with @samp{dg-prune-output "note: "}.
+
+@item @{ dg-bogus @var{regexp} [@var{comment} [@{ target/xfail @var{selector} @} [@var{line}] ]] @}
+This DejaGnu directive appears on a source line that should not get a
+message matching @var{regexp}, or else specifies the source line
+associated with the bogus message. It is usually used with @samp{xfail}
+to indicate that the message is a known problem for a particular set of
+targets.
+
+@item @{ dg-line @var{linenumvar} @}
+This DejaGnu directive sets the variable @var{linenumvar} to the line number of
+the source line. The variable @var{linenumvar} can then be used in subsequent
+@code{dg-error}, @code{dg-warning}, @code{dg-message}, @code{dg-note}
+and @code{dg-bogus}
+directives. For example:
+
+@smallexample
+int a; /* @{ dg-line first_def_a @} */
+float a; /* @{ dg-error "conflicting types of" @} */
+/* @{ dg-message "previous declaration of" "" @{ target *-*-* @} first_def_a @} */
+@end smallexample
+
+@item @{ dg-excess-errors @var{comment} [@{ target/xfail @var{selector} @}] @}
+This DejaGnu directive indicates that the test is expected to fail due
+to compiler messages that are not handled by @samp{dg-error},
+@samp{dg-warning}, @code{dg-message}, @samp{dg-note} or
+@samp{dg-bogus}.
+For this directive @samp{xfail}
+has the same effect as @samp{target}.
+
+@item @{ dg-prune-output @var{regexp} @}
+Prune messages matching @var{regexp} from the test output.
+@end table
+
+@subsubsection Verify output of the test executable
+
+@table @code
+@item @{ dg-output @var{regexp} [@{ target/xfail @var{selector} @}] @}
+This DejaGnu directive compares @var{regexp} to the combined output
+that the test executable writes to @file{stdout} and @file{stderr}.
+@end table
+
+@subsubsection Specify environment variables for a test
+
+@table @code
+@item @{ dg-set-compiler-env-var @var{var_name} "@var{var_value}" @}
+Specify that the environment variable @var{var_name} needs to be set
+to @var{var_value} before invoking the compiler on the test file.
+
+@item @{ dg-set-target-env-var @var{var_name} "@var{var_value}" @}
+Specify that the environment variable @var{var_name} needs to be set
+to @var{var_value} before execution of the program created by the test.
+@end table
+
+@subsubsection Specify additional files for a test
+
+@table @code
+@item @{ dg-additional-files "@var{filelist}" @}
+Specify additional files, other than source files, that must be copied
+to the system where the compiler runs.
+
+@item @{ dg-additional-sources "@var{filelist}" @}
+Specify additional source files to appear in the compile line
+following the main test file.
+@end table
+
+@subsubsection Add checks at the end of a test
+
+@table @code
+@item @{ dg-final @{ @var{local-directive} @} @}
+This DejaGnu directive is placed within a comment anywhere in the
+source file and is processed after the test has been compiled and run.
+Multiple @samp{dg-final} commands are processed in the order in which
+they appear in the source file. @xref{Final Actions, , }, for a list
+of directives that can be used within @code{dg-final}.
+@end table
+
+@node Selectors
+@subsection Selecting targets to which a test applies
+
+Several test directives include @var{selector}s to limit the targets
+for which a test is run or to declare that a test is expected to fail
+on particular targets.
+
+A selector is:
+@itemize @bullet
+@item one or more target triplets, possibly including wildcard characters;
+use @samp{*-*-*} to match any target
+@item a single effective-target keyword (@pxref{Effective-Target Keywords})
+@item a list of compiler options that should be included or excluded
+(as described in more detail below)
+@item a logical expression
+@end itemize
+
+Depending on the context, the selector specifies whether a test is
+skipped and reported as unsupported or is expected to fail. A context
+that allows either @samp{target} or @samp{xfail} also allows
+@samp{@{ target @var{selector1} xfail @var{selector2} @}}
+to skip the test for targets that don't match @var{selector1} and the
+test to fail for targets that match @var{selector2}.
+
+A selector expression appears within curly braces and uses a single
+logical operator: one of @samp{!}, @samp{&&}, or @samp{||}. An
+operand is one of the following:
+
+@itemize @bullet
+@item
+another selector expression, in curly braces
+
+@item
+an effective-target keyword, such as @code{lp64}
+
+@item
+a single target triplet
+
+@item
+a list of target triplets within quotes or curly braces
+
+@item
+one of the following:
+
+@table @samp
+@item @{ any-opts @var{opt1} @dots{} @var{optn} @}
+Each of @var{opt1} to @var{optn} is a space-separated list of option globs.
+The selector expression evaluates to true if, for one of these strings,
+every glob in the string matches an option that was passed to the compiler.
+For example:
+
+@smallexample
+@{ any-opts "-O3 -flto" "-O[2g]" @}
+@end smallexample
+
+is true if any of the following are true:
+
+@itemize @bullet
+@item
+@option{-O2} was passed to the compiler
+
+@item
+@option{-Og} was passed to the compiler
+
+@item
+both @option{-O3} and @option{-flto} were passed to the compiler
+@end itemize
+
+This kind of selector can only be used within @code{dg-final} directives.
+Use @code{dg-skip-if}, @code{dg-xfail-if} or @code{dg-xfail-run-if} to
+skip whole tests based on options, or to mark them as expected to fail
+with certain options.
+
+@item @{ no-opts @var{opt1} @dots{} @var{optn} @}
+As for @code{any-opts} above, each of @var{opt1} to @var{optn} is a
+space-separated list of option globs. The selector expression
+evaluates to true if, for all of these strings, there is at least
+one glob that does not match an option that was passed to the compiler.
+It is shorthand for:
+
+@smallexample
+@{ ! @{ any-opts @var{opt1} @dots{} @var{optn} @} @}
+@end smallexample
+
+For example:
+
+@smallexample
+@{ no-opts "-O3 -flto" "-O[2g]" @}
+@end smallexample
+
+is true if all of the following are true:
+
+@itemize @bullet
+@item
+@option{-O2} was not passed to the compiler
+
+@item
+@option{-Og} was not passed to the compiler
+
+@item
+at least one of @option{-O3} or @option{-flto} was not passed to the compiler
+@end itemize
+
+Like @code{any-opts}, this kind of selector can only be used within
+@code{dg-final} directives.
+
+@end table
+@end itemize
+
+Here are some examples of full target selectors:
+
+@smallexample
+@{ target @{ ! "hppa*-*-* ia64*-*-*" @} @}
+@{ target @{ powerpc*-*-* && lp64 @} @}
+@{ xfail @{ lp64 || vect_no_align @} @}
+@{ xfail @{ aarch64*-*-* && @{ any-opts "-O2" @} @} @}
+@end smallexample
+
+@node Effective-Target Keywords
+@subsection Keywords describing target attributes
+
+Effective-target keywords identify sets of targets that support
+particular functionality. They are used to limit tests to be run only
+for particular targets, or to specify that particular sets of targets
+are expected to fail some tests.
+
+Effective-target keywords are defined in @file{lib/target-supports.exp} in
+the GCC testsuite, with the exception of those that are documented as
+being local to a particular test directory.
+
+The @samp{effective target} takes into account all of the compiler options
+with which the test will be compiled, including the multilib options.
+By convention, keywords ending in @code{_nocache} can also include options
+specified for the particular test in an earlier @code{dg-options} or
+@code{dg-add-options} directive.
+
+@subsubsection Endianness
+
+@table @code
+@item be
+Target uses big-endian memory order for multi-byte and multi-word data.
+
+@item le
+Target uses little-endian memory order for multi-byte and multi-word data.
+@end table
+
+@subsubsection Data type sizes
+
+@table @code
+@item ilp32
+Target has 32-bit @code{int}, @code{long}, and pointers.
+
+@item lp64
+Target has 32-bit @code{int}, 64-bit @code{long} and pointers.
+
+@item llp64
+Target has 32-bit @code{int} and @code{long}, 64-bit @code{long long}
+and pointers.
+
+@item double64
+Target has 64-bit @code{double}.
+
+@item double64plus
+Target has @code{double} that is 64 bits or longer.
+
+@item longdouble128
+Target has 128-bit @code{long double}.
+
+@item int32plus
+Target has @code{int} that is at 32 bits or longer.
+
+@item int16
+Target has @code{int} that is 16 bits or shorter.
+
+@item longlong64
+Target has 64-bit @code{long long}.
+
+@item long_neq_int
+Target has @code{int} and @code{long} with different sizes.
+
+@item short_eq_int
+Target has @code{short} and @code{int} with the same size.
+
+@item ptr_eq_short
+Target has pointers (@code{void *}) and @code{short} with the same size.
+
+@item int_eq_float
+Target has @code{int} and @code{float} with the same size.
+
+@item ptr_eq_long
+Target has pointers (@code{void *}) and @code{long} with the same size.
+
+@item large_double
+Target supports @code{double} that is longer than @code{float}.
+
+@item large_long_double
+Target supports @code{long double} that is longer than @code{double}.
+
+@item ptr32plus
+Target has pointers that are 32 bits or longer.
+
+@item size20plus
+Target has a 20-bit or larger address space, so supports at least
+16-bit array and structure sizes.
+
+@item size24plus
+Target has a 24-bit or larger address space, so supports at least
+20-bit array and structure sizes.
+
+@item size32plus
+Target has a 32-bit or larger address space, so supports at least
+24-bit array and structure sizes.
+
+@item 4byte_wchar_t
+Target has @code{wchar_t} that is at least 4 bytes.
+
+@item float@var{n}
+Target has the @code{_Float@var{n}} type.
+
+@item float@var{n}x
+Target has the @code{_Float@var{n}x} type.
+
+@item float@var{n}_runtime
+Target has the @code{_Float@var{n}} type, including runtime support
+for any options added with @code{dg-add-options}.
+
+@item float@var{n}x_runtime
+Target has the @code{_Float@var{n}x} type, including runtime support
+for any options added with @code{dg-add-options}.
+
+@item floatn_nx_runtime
+Target has runtime support for any options added with
+@code{dg-add-options} for any @code{_Float@var{n}} or
+@code{_Float@var{n}x} type.
+
+@item inf
+Target supports floating point infinite (@code{inf}) for type
+@code{double}.
+
+@item inff
+Target supports floating point infinite (@code{inf}) for type
+@code{float}.
+@end table
+@subsubsection Fortran-specific attributes
+
+@table @code
+@item fortran_integer_16
+Target supports Fortran @code{integer} that is 16 bytes or longer.
+
+@item fortran_real_10
+Target supports Fortran @code{real} that is 10 bytes or longer.
+
+@item fortran_real_16
+Target supports Fortran @code{real} that is 16 bytes or longer.
+
+@item fortran_large_int
+Target supports Fortran @code{integer} kinds larger than @code{integer(8)}.
+
+@item fortran_large_real
+Target supports Fortran @code{real} kinds larger than @code{real(8)}.
+@end table
+
+@subsubsection Vector-specific attributes
+
+@table @code
+@item vect_align_stack_vars
+The target's ABI allows stack variables to be aligned to the preferred
+vector alignment.
+
+@item vect_avg_qi
+Target supports both signed and unsigned averaging operations on vectors
+of bytes.
+
+@item vect_mulhrs_hi
+Target supports both signed and unsigned multiply-high-with-round-and-scale
+operations on vectors of half-words.
+
+@item vect_sdiv_pow2_si
+Target supports signed division by constant power-of-2 operations
+on vectors of 4-byte integers.
+
+@item vect_condition
+Target supports vector conditional operations.
+
+@item vect_cond_mixed
+Target supports vector conditional operations where comparison operands
+have different type from the value operands.
+
+@item vect_double
+Target supports hardware vectors of @code{double}.
+
+@item vect_double_cond_arith
+Target supports conditional addition, subtraction, multiplication,
+division, minimum and maximum on vectors of @code{double}, via the
+@code{cond_} optabs.
+
+@item vect_element_align_preferred
+The target's preferred vector alignment is the same as the element
+alignment.
+
+@item vect_float
+Target supports hardware vectors of @code{float} when
+@option{-funsafe-math-optimizations} is in effect.
+
+@item vect_float_strict
+Target supports hardware vectors of @code{float} when
+@option{-funsafe-math-optimizations} is not in effect.
+This implies @code{vect_float}.
+
+@item vect_int
+Target supports hardware vectors of @code{int}.
+
+@item vect_long
+Target supports hardware vectors of @code{long}.
+
+@item vect_long_long
+Target supports hardware vectors of @code{long long}.
+
+@item vect_check_ptrs
+Target supports the @code{check_raw_ptrs} and @code{check_war_ptrs}
+optabs on vectors.
+
+@item vect_fully_masked
+Target supports fully-masked (also known as fully-predicated) loops,
+so that vector loops can handle partial as well as full vectors.
+
+@item vect_masked_load
+Target supports vector masked loads.
+
+@item vect_masked_store
+Target supports vector masked stores.
+
+@item vect_gather_load_ifn
+Target supports vector gather loads using internal functions
+(rather than via built-in functions or emulation).
+
+@item vect_scatter_store
+Target supports vector scatter stores.
+
+@item vect_aligned_arrays
+Target aligns arrays to vector alignment boundary.
+
+@item vect_hw_misalign
+Target supports a vector misalign access.
+
+@item vect_no_align
+Target does not support a vector alignment mechanism.
+
+@item vect_peeling_profitable
+Target might require to peel loops for alignment purposes.
+
+@item vect_no_int_min_max
+Target does not support a vector min and max instruction on @code{int}.
+
+@item vect_no_int_add
+Target does not support a vector add instruction on @code{int}.
+
+@item vect_no_bitwise
+Target does not support vector bitwise instructions.
+
+@item vect_bool_cmp
+Target supports comparison of @code{bool} vectors for at least one
+vector length.
+
+@item vect_char_add
+Target supports addition of @code{char} vectors for at least one
+vector length.
+
+@item vect_char_mult
+Target supports @code{vector char} multiplication.
+
+@item vect_short_mult
+Target supports @code{vector short} multiplication.
+
+@item vect_int_mult
+Target supports @code{vector int} multiplication.
+
+@item vect_long_mult
+Target supports 64 bit @code{vector long} multiplication.
+
+@item vect_extract_even_odd
+Target supports vector even/odd element extraction.
+
+@item vect_extract_even_odd_wide
+Target supports vector even/odd element extraction of vectors with elements
+@code{SImode} or larger.
+
+@item vect_interleave
+Target supports vector interleaving.
+
+@item vect_strided
+Target supports vector interleaving and extract even/odd.
+
+@item vect_strided_wide
+Target supports vector interleaving and extract even/odd for wide
+element types.
+
+@item vect_perm
+Target supports vector permutation.
+
+@item vect_perm_byte
+Target supports permutation of vectors with 8-bit elements.
+
+@item vect_perm_short
+Target supports permutation of vectors with 16-bit elements.
+
+@item vect_perm3_byte
+Target supports permutation of vectors with 8-bit elements, and for the
+default vector length it is possible to permute:
+@example
+@{ a0, a1, a2, b0, b1, b2, @dots{} @}
+@end example
+to:
+@example
+@{ a0, a0, a0, b0, b0, b0, @dots{} @}
+@{ a1, a1, a1, b1, b1, b1, @dots{} @}
+@{ a2, a2, a2, b2, b2, b2, @dots{} @}
+@end example
+using only two-vector permutes, regardless of how long the sequence is.
+
+@item vect_perm3_int
+Like @code{vect_perm3_byte}, but for 32-bit elements.
+
+@item vect_perm3_short
+Like @code{vect_perm3_byte}, but for 16-bit elements.
+
+@item vect_shift
+Target supports a hardware vector shift operation.
+
+@item vect_unaligned_possible
+Target prefers vectors to have an alignment greater than element
+alignment, but also allows unaligned vector accesses in some
+circumstances.
+
+@item vect_variable_length
+Target has variable-length vectors.
+
+@item vect64
+Target supports vectors of 64 bits.
+
+@item vect32
+Target supports vectors of 32 bits.
+
+@item vect_widen_sum_hi_to_si
+Target supports a vector widening summation of @code{short} operands
+into @code{int} results, or can promote (unpack) from @code{short}
+to @code{int}.
+
+@item vect_widen_sum_qi_to_hi
+Target supports a vector widening summation of @code{char} operands
+into @code{short} results, or can promote (unpack) from @code{char}
+to @code{short}.
+
+@item vect_widen_sum_qi_to_si
+Target supports a vector widening summation of @code{char} operands
+into @code{int} results.
+
+@item vect_widen_mult_qi_to_hi
+Target supports a vector widening multiplication of @code{char} operands
+into @code{short} results, or can promote (unpack) from @code{char} to
+@code{short} and perform non-widening multiplication of @code{short}.
+
+@item vect_widen_mult_hi_to_si
+Target supports a vector widening multiplication of @code{short} operands
+into @code{int} results, or can promote (unpack) from @code{short} to
+@code{int} and perform non-widening multiplication of @code{int}.
+
+@item vect_widen_mult_si_to_di_pattern
+Target supports a vector widening multiplication of @code{int} operands
+into @code{long} results.
+
+@item vect_sdot_qi
+Target supports a vector dot-product of @code{signed char}.
+
+@item vect_udot_qi
+Target supports a vector dot-product of @code{unsigned char}.
+
+@item vect_usdot_qi
+Target supports a vector dot-product where one operand of the multiply is
+@code{signed char} and the other of @code{unsigned char}.
+
+@item vect_sdot_hi
+Target supports a vector dot-product of @code{signed short}.
+
+@item vect_udot_hi
+Target supports a vector dot-product of @code{unsigned short}.
+
+@item vect_pack_trunc
+Target supports a vector demotion (packing) of @code{short} to @code{char}
+and from @code{int} to @code{short} using modulo arithmetic.
+
+@item vect_unpack
+Target supports a vector promotion (unpacking) of @code{char} to @code{short}
+and from @code{char} to @code{int}.
+
+@item vect_intfloat_cvt
+Target supports conversion from @code{signed int} to @code{float}.
+
+@item vect_uintfloat_cvt
+Target supports conversion from @code{unsigned int} to @code{float}.
+
+@item vect_floatint_cvt
+Target supports conversion from @code{float} to @code{signed int}.
+
+@item vect_floatuint_cvt
+Target supports conversion from @code{float} to @code{unsigned int}.
+
+@item vect_intdouble_cvt
+Target supports conversion from @code{signed int} to @code{double}.
+
+@item vect_doubleint_cvt
+Target supports conversion from @code{double} to @code{signed int}.
+
+@item vect_max_reduc
+Target supports max reduction for vectors.
+
+@item vect_sizes_16B_8B
+Target supports 16- and 8-bytes vectors.
+
+@item vect_sizes_32B_16B
+Target supports 32- and 16-bytes vectors.
+
+@item vect_logical_reduc
+Target supports AND, IOR and XOR reduction on vectors.
+
+@item vect_fold_extract_last
+Target supports the @code{fold_extract_last} optab.
+
+@item vect_len_load_store
+Target supports the @code{len_load} and @code{len_store} optabs.
+
+@item vect_partial_vectors_usage_1
+Target supports loop vectorization with partial vectors and
+@code{vect-partial-vector-usage} is set to 1.
+
+@item vect_partial_vectors_usage_2
+Target supports loop vectorization with partial vectors and
+@code{vect-partial-vector-usage} is set to 2.
+
+@item vect_partial_vectors
+Target supports loop vectorization with partial vectors and
+@code{vect-partial-vector-usage} is nonzero.
+
+@item vect_slp_v2qi_store_align
+Target supports vectorization of 2-byte char stores with 2-byte aligned
+address at plain @option{-O2}.
+
+@item vect_slp_v4qi_store_align
+Target supports vectorization of 4-byte char stores with 4-byte aligned
+address at plain @option{-O2}.
+
+@item vect_slp_v4qi_store_unalign
+Target supports vectorization of 4-byte char stores with unaligned address
+at plain @option{-O2}.
+
+@item struct_4char_block_move
+Target supports block move for 8-byte aligned 4-byte size struct initialization.
+
+@item vect_slp_v4qi_store_unalign_1
+Target supports vectorization of 4-byte char stores with unaligned address
+or store them with constant pool at plain @option{-O2}.
+
+@item struct_8char_block_move
+Target supports block move for 8-byte aligned 8-byte size struct initialization.
+
+@item vect_slp_v8qi_store_unalign_1
+Target supports vectorization of 8-byte char stores with unaligned address
+or store them with constant pool at plain @option{-O2}.
+
+@item struct_16char_block_move
+Target supports block move for 8-byte aligned 16-byte size struct
+initialization.
+
+@item vect_slp_v16qi_store_unalign_1
+Target supports vectorization of 16-byte char stores with unaligned address
+or store them with constant pool at plain @option{-O2}.
+
+@item vect_slp_v2hi_store_align
+Target supports vectorization of 4-byte short stores with 4-byte aligned
+addressat plain @option{-O2}.
+
+@item vect_slp_v2hi_store_unalign
+Target supports vectorization of 4-byte short stores with unaligned address
+at plain @option{-O2}.
+
+@item vect_slp_v4hi_store_unalign
+Target supports vectorization of 8-byte short stores with unaligned address
+at plain @option{-O2}.
+
+@item vect_slp_v2si_store_align
+Target supports vectorization of 8-byte int stores with 8-byte aligned address
+at plain @option{-O2}.
+
+@item vect_slp_v4si_store_unalign
+Target supports vectorization of 16-byte int stores with unaligned address
+at plain @option{-O2}.
+@end table
+
+@subsubsection Thread Local Storage attributes
+
+@table @code
+@item tls
+Target supports thread-local storage.
+
+@item tls_native
+Target supports native (rather than emulated) thread-local storage.
+
+@item tls_runtime
+Test system supports executing TLS executables.
+@end table
+
+@subsubsection Decimal floating point attributes
+
+@table @code
+@item dfp
+Targets supports compiling decimal floating point extension to C.
+
+@item dfp_nocache
+Including the options used to compile this particular test, the
+target supports compiling decimal floating point extension to C.
+
+@item dfprt
+Test system can execute decimal floating point tests.
+
+@item dfprt_nocache
+Including the options used to compile this particular test, the
+test system can execute decimal floating point tests.
+
+@item hard_dfp
+Target generates decimal floating point instructions with current options.
+
+@item dfp_bid
+Target uses the BID format for decimal floating point.
+@end table
+
+@subsubsection ARM-specific attributes
+
+@table @code
+@item arm32
+ARM target generates 32-bit code.
+
+@item arm_little_endian
+ARM target that generates little-endian code.
+
+@item arm_eabi
+ARM target adheres to the ABI for the ARM Architecture.
+
+@item arm_fp_ok
+@anchor{arm_fp_ok}
+ARM target defines @code{__ARM_FP} using @code{-mfloat-abi=softfp} or
+equivalent options. Some multilibs may be incompatible with these
+options.
+
+@item arm_fp_dp_ok
+@anchor{arm_fp_dp_ok}
+ARM target defines @code{__ARM_FP} with double-precision support using
+@code{-mfloat-abi=softfp} or equivalent options. Some multilibs may
+be incompatible with these options.
+
+@item arm_hf_eabi
+ARM target adheres to the VFP and Advanced SIMD Register Arguments
+variant of the ABI for the ARM Architecture (as selected with
+@code{-mfloat-abi=hard}).
+
+@item arm_softfloat
+ARM target uses emulated floating point operations.
+
+@item arm_hard_vfp_ok
+ARM target supports @code{-mfpu=vfp -mfloat-abi=hard}.
+Some multilibs may be incompatible with these options.
+
+@item arm_iwmmxt_ok
+ARM target supports @code{-mcpu=iwmmxt}.
+Some multilibs may be incompatible with this option.
+
+@item arm_neon
+ARM target supports generating NEON instructions.
+
+@item arm_tune_string_ops_prefer_neon
+Test CPU tune supports inlining string operations with NEON instructions.
+
+@item arm_neon_hw
+Test system supports executing NEON instructions.
+
+@item arm_neonv2_hw
+Test system supports executing NEON v2 instructions.
+
+@item arm_neon_ok
+@anchor{arm_neon_ok}
+ARM Target supports @code{-mfpu=neon -mfloat-abi=softfp} or compatible
+options. Some multilibs may be incompatible with these options.
+
+@item arm_neon_ok_no_float_abi
+@anchor{arm_neon_ok_no_float_abi}
+ARM Target supports NEON with @code{-mfpu=neon}, but without any
+-mfloat-abi= option. Some multilibs may be incompatible with this
+option.
+
+@item arm_neonv2_ok
+@anchor{arm_neonv2_ok}
+ARM Target supports @code{-mfpu=neon-vfpv4 -mfloat-abi=softfp} or compatible
+options. Some multilibs may be incompatible with these options.
+
+@item arm_fp16_ok
+@anchor{arm_fp16_ok}
+Target supports options to generate VFP half-precision floating-point
+instructions. Some multilibs may be incompatible with these
+options. This test is valid for ARM only.
+
+@item arm_fp16_hw
+Target supports executing VFP half-precision floating-point
+instructions. This test is valid for ARM only.
+
+@item arm_neon_fp16_ok
+@anchor{arm_neon_fp16_ok}
+ARM Target supports @code{-mfpu=neon-fp16 -mfloat-abi=softfp} or compatible
+options, including @code{-mfp16-format=ieee} if necessary to obtain the
+@code{__fp16} type. Some multilibs may be incompatible with these options.
+
+@item arm_neon_fp16_hw
+Test system supports executing Neon half-precision float instructions.
+(Implies previous.)
+
+@item arm_fp16_alternative_ok
+ARM target supports the ARM FP16 alternative format. Some multilibs
+may be incompatible with the options needed.
+
+@item arm_fp16_none_ok
+ARM target supports specifying none as the ARM FP16 format.
+
+@item arm_thumb1_ok
+ARM target generates Thumb-1 code for @code{-mthumb}.
+
+@item arm_thumb2_ok
+ARM target generates Thumb-2 code for @code{-mthumb}.
+
+@item arm_nothumb
+ARM target that is not using Thumb.
+
+@item arm_vfp_ok
+ARM target supports @code{-mfpu=vfp -mfloat-abi=softfp}.
+Some multilibs may be incompatible with these options.
+
+@item arm_vfp3_ok
+@anchor{arm_vfp3_ok}
+ARM target supports @code{-mfpu=vfp3 -mfloat-abi=softfp}.
+Some multilibs may be incompatible with these options.
+
+@item arm_arch_v8a_hard_ok
+@anchor{arm_arch_v8a_hard_ok}
+The compiler is targeting @code{arm*-*-*} and can compile and assemble code
+using the options @code{-march=armv8-a -mfpu=neon-fp-armv8 -mfloat-abi=hard}.
+This is not enough to guarantee that linking works.
+
+@item arm_arch_v8a_hard_multilib
+The compiler is targeting @code{arm*-*-*} and can build programs using
+the options @code{-march=armv8-a -mfpu=neon-fp-armv8 -mfloat-abi=hard}.
+The target can also run the resulting binaries.
+
+@item arm_v8_vfp_ok
+ARM target supports @code{-mfpu=fp-armv8 -mfloat-abi=softfp}.
+Some multilibs may be incompatible with these options.
+
+@item arm_v8_neon_ok
+ARM target supports @code{-mfpu=neon-fp-armv8 -mfloat-abi=softfp}.
+Some multilibs may be incompatible with these options.
+
+@item arm_v8_1a_neon_ok
+@anchor{arm_v8_1a_neon_ok}
+ARM target supports options to generate ARMv8.1-A Adv.SIMD instructions.
+Some multilibs may be incompatible with these options.
+
+@item arm_v8_1a_neon_hw
+ARM target supports executing ARMv8.1-A Adv.SIMD instructions. Some
+multilibs may be incompatible with the options needed. Implies
+arm_v8_1a_neon_ok.
+
+@item arm_acq_rel
+ARM target supports acquire-release instructions.
+
+@item arm_v8_2a_fp16_scalar_ok
+@anchor{arm_v8_2a_fp16_scalar_ok}
+ARM target supports options to generate instructions for ARMv8.2-A and
+scalar instructions from the FP16 extension. Some multilibs may be
+incompatible with these options.
+
+@item arm_v8_2a_fp16_scalar_hw
+ARM target supports executing instructions for ARMv8.2-A and scalar
+instructions from the FP16 extension. Some multilibs may be
+incompatible with these options. Implies arm_v8_2a_fp16_neon_ok.
+
+@item arm_v8_2a_fp16_neon_ok
+@anchor{arm_v8_2a_fp16_neon_ok}
+ARM target supports options to generate instructions from ARMv8.2-A with
+the FP16 extension. Some multilibs may be incompatible with these
+options. Implies arm_v8_2a_fp16_scalar_ok.
+
+@item arm_v8_2a_fp16_neon_hw
+ARM target supports executing instructions from ARMv8.2-A with the FP16
+extension. Some multilibs may be incompatible with these options.
+Implies arm_v8_2a_fp16_neon_ok and arm_v8_2a_fp16_scalar_hw.
+
+@item arm_v8_2a_dotprod_neon_ok
+@anchor{arm_v8_2a_dotprod_neon_ok}
+ARM target supports options to generate instructions from ARMv8.2-A with
+the Dot Product extension. Some multilibs may be incompatible with these
+options.
+
+@item arm_v8_2a_dotprod_neon_hw
+ARM target supports executing instructions from ARMv8.2-A with the Dot
+Product extension. Some multilibs may be incompatible with these options.
+Implies arm_v8_2a_dotprod_neon_ok.
+
+@item arm_v8_2a_i8mm_neon_hw
+ARM target supports executing instructions from ARMv8.2-A with the 8-bit
+Matrix Multiply extension. Some multilibs may be incompatible with these
+options. Implies arm_v8_2a_i8mm_ok.
+
+@item arm_fp16fml_neon_ok
+@anchor{arm_fp16fml_neon_ok}
+ARM target supports extensions to generate the @code{VFMAL} and @code{VFMLS}
+half-precision floating-point instructions available from ARMv8.2-A and
+onwards. Some multilibs may be incompatible with these options.
+
+@item arm_v8_2a_bf16_neon_ok
+ARM target supports options to generate instructions from ARMv8.2-A with
+the BFloat16 extension (bf16). Some multilibs may be incompatible with these
+options.
+
+@item arm_v8_2a_i8mm_ok
+ARM target supports options to generate instructions from ARMv8.2-A with
+the 8-Bit Integer Matrix Multiply extension (i8mm). Some multilibs may be
+incompatible with these options.
+
+@item arm_v8_1m_mve_ok
+ARM target supports options to generate instructions from ARMv8.1-M with
+the M-Profile Vector Extension (MVE). Some multilibs may be incompatible
+with these options.
+
+@item arm_v8_1m_mve_fp_ok
+ARM target supports options to generate instructions from ARMv8.1-M with
+the Half-precision floating-point instructions (HP), Floating-point Extension
+(FP) along with M-Profile Vector Extension (MVE). Some multilibs may be
+incompatible with these options.
+
+@item arm_mve_hw
+Test system supports executing MVE instructions.
+
+@item arm_v8m_main_cde
+ARM target supports options to generate instructions from ARMv8-M with
+the Custom Datapath Extension (CDE). Some multilibs may be incompatible
+with these options.
+
+@item arm_v8m_main_cde_fp
+ARM target supports options to generate instructions from ARMv8-M with
+the Custom Datapath Extension (CDE) and floating-point (VFP).
+Some multilibs may be incompatible with these options.
+
+@item arm_v8_1m_main_cde_mve
+ARM target supports options to generate instructions from ARMv8.1-M with
+the Custom Datapath Extension (CDE) and M-Profile Vector Extension (MVE).
+Some multilibs may be incompatible with these options.
+
+@item arm_prefer_ldrd_strd
+ARM target prefers @code{LDRD} and @code{STRD} instructions over
+@code{LDM} and @code{STM} instructions.
+
+@item arm_thumb1_movt_ok
+ARM target generates Thumb-1 code for @code{-mthumb} with @code{MOVW}
+and @code{MOVT} instructions available.
+
+@item arm_thumb1_cbz_ok
+ARM target generates Thumb-1 code for @code{-mthumb} with
+@code{CBZ} and @code{CBNZ} instructions available.
+
+@item arm_divmod_simode
+ARM target for which divmod transform is disabled, if it supports hardware
+div instruction.
+
+@item arm_cmse_ok
+ARM target supports ARMv8-M Security Extensions, enabled by the @code{-mcmse}
+option.
+
+@item arm_cmse_hw
+Test system supports executing CMSE instructions.
+
+@item arm_coproc1_ok
+@anchor{arm_coproc1_ok}
+ARM target supports the following coprocessor instructions: @code{CDP},
+@code{LDC}, @code{STC}, @code{MCR} and @code{MRC}.
+
+@item arm_coproc2_ok
+@anchor{arm_coproc2_ok}
+ARM target supports all the coprocessor instructions also listed as supported
+in @ref{arm_coproc1_ok} in addition to the following: @code{CDP2}, @code{LDC2},
+@code{LDC2l}, @code{STC2}, @code{STC2l}, @code{MCR2} and @code{MRC2}.
+
+@item arm_coproc3_ok
+@anchor{arm_coproc3_ok}
+ARM target supports all the coprocessor instructions also listed as supported
+in @ref{arm_coproc2_ok} in addition the following: @code{MCRR} and @code{MRRC}.
+
+@item arm_coproc4_ok
+ARM target supports all the coprocessor instructions also listed as supported
+in @ref{arm_coproc3_ok} in addition the following: @code{MCRR2} and @code{MRRC2}.
+
+@item arm_simd32_ok
+@anchor{arm_simd32_ok}
+ARM Target supports options suitable for accessing the SIMD32 intrinsics from
+@code{arm_acle.h}.
+Some multilibs may be incompatible with these options.
+
+@item arm_sat_ok
+@anchor{arm_sat_ok}
+ARM Target supports options suitable for accessing the saturation
+intrinsics from @code{arm_acle.h}.
+Some multilibs may be incompatible with these options.
+
+@item arm_dsp_ok
+@anchor{arm_dsp_ok}
+ARM Target supports options suitable for accessing the DSP intrinsics
+from @code{arm_acle.h}.
+Some multilibs may be incompatible with these options.
+
+@item arm_softfp_ok
+@anchor{arm_softfp_ok}
+ARM target supports the @code{-mfloat-abi=softfp} option.
+
+@item arm_hard_ok
+@anchor{arm_hard_ok}
+ARM target supports the @code{-mfloat-abi=hard} option.
+
+@item arm_mve
+@anchor{arm_mve}
+ARM target supports generating MVE instructions.
+
+@item arm_v8_1_lob_ok
+@anchor{arm_v8_1_lob_ok}
+ARM Target supports executing the Armv8.1-M Mainline Low Overhead Loop
+instructions @code{DLS} and @code{LE}.
+Some multilibs may be incompatible with these options.
+
+@item arm_thumb2_no_arm_v8_1_lob
+ARM target where Thumb-2 is used without options but does not support
+executing the Armv8.1-M Mainline Low Overhead Loop instructions
+@code{DLS} and @code{LE}.
+
+@item arm_thumb2_ok_no_arm_v8_1_lob
+ARM target generates Thumb-2 code for @code{-mthumb} but does not
+support executing the Armv8.1-M Mainline Low Overhead Loop
+instructions @code{DLS} and @code{LE}.
+
+@end table
+
+@subsubsection AArch64-specific attributes
+
+@table @code
+@item aarch64_asm_<ext>_ok
+AArch64 assembler supports the architecture extension @code{ext} via the
+@code{.arch_extension} pseudo-op.
+@item aarch64_tiny
+AArch64 target which generates instruction sequences for tiny memory model.
+@item aarch64_small
+AArch64 target which generates instruction sequences for small memory model.
+@item aarch64_large
+AArch64 target which generates instruction sequences for large memory model.
+@item aarch64_little_endian
+AArch64 target which generates instruction sequences for little endian.
+@item aarch64_big_endian
+AArch64 target which generates instruction sequences for big endian.
+@item aarch64_small_fpic
+Binutils installed on test system supports relocation types required by -fpic
+for AArch64 small memory model.
+@item aarch64_sve_hw
+AArch64 target that is able to generate and execute SVE code (regardless of
+whether it does so by default).
+@item aarch64_sve128_hw
+@itemx aarch64_sve256_hw
+@itemx aarch64_sve512_hw
+@itemx aarch64_sve1024_hw
+@itemx aarch64_sve2048_hw
+Like @code{aarch64_sve_hw}, but also test for an exact hardware vector length.
+
+@item aarch64_fjcvtzs_hw
+AArch64 target that is able to generate and execute armv8.3-a FJCVTZS
+instruction.
+@end table
+
+@subsubsection MIPS-specific attributes
+
+@table @code
+@item mips64
+MIPS target supports 64-bit instructions.
+
+@item nomips16
+MIPS target does not produce MIPS16 code.
+
+@item mips16_attribute
+MIPS target can generate MIPS16 code.
+
+@item mips_loongson
+MIPS target is a Loongson-2E or -2F target using an ABI that supports
+the Loongson vector modes.
+
+@item mips_msa
+MIPS target supports @code{-mmsa}, MIPS SIMD Architecture (MSA).
+
+@item mips_newabi_large_long_double
+MIPS target supports @code{long double} larger than @code{double}
+when using the new ABI.
+
+@item mpaired_single
+MIPS target supports @code{-mpaired-single}.
+@end table
+
+@subsubsection MSP430-specific attributes
+
+@table @code
+@item msp430_small
+MSP430 target has the small memory model enabled (@code{-msmall}).
+
+@item msp430_large
+MSP430 target has the large memory model enabled (@code{-mlarge}).
+@end table
+
+@subsubsection PowerPC-specific attributes
+
+@table @code
+
+@item dfp_hw
+PowerPC target supports executing hardware DFP instructions.
+
+@item p8vector_hw
+PowerPC target supports executing VSX instructions (ISA 2.07).
+
+@item powerpc64
+Test system supports executing 64-bit instructions.
+
+@item powerpc_altivec
+PowerPC target supports AltiVec.
+
+@item powerpc_altivec_ok
+PowerPC target supports @code{-maltivec}.
+
+@item powerpc_eabi_ok
+PowerPC target supports @code{-meabi}.
+
+@item powerpc_elfv2
+PowerPC target supports @code{-mabi=elfv2}.
+
+@item powerpc_fprs
+PowerPC target supports floating-point registers.
+
+@item powerpc_hard_double
+PowerPC target supports hardware double-precision floating-point.
+
+@item powerpc_htm_ok
+PowerPC target supports @code{-mhtm}
+
+@item powerpc_p8vector_ok
+PowerPC target supports @code{-mpower8-vector}
+
+@item powerpc_popcntb_ok
+PowerPC target supports the @code{popcntb} instruction, indicating
+that this target supports @code{-mcpu=power5}.
+
+@item powerpc_ppu_ok
+PowerPC target supports @code{-mcpu=cell}.
+
+@item powerpc_spe
+PowerPC target supports PowerPC SPE.
+
+@item powerpc_spe_nocache
+Including the options used to compile this particular test, the
+PowerPC target supports PowerPC SPE.
+
+@item powerpc_spu
+PowerPC target supports PowerPC SPU.
+
+@item powerpc_vsx_ok
+PowerPC target supports @code{-mvsx}.
+
+@item powerpc_405_nocache
+Including the options used to compile this particular test, the
+PowerPC target supports PowerPC 405.
+
+@item ppc_recip_hw
+PowerPC target supports executing reciprocal estimate instructions.
+
+@item vmx_hw
+PowerPC target supports executing AltiVec instructions.
+
+@item vsx_hw
+PowerPC target supports executing VSX instructions (ISA 2.06).
+
+@item has_arch_pwr5
+PowerPC target pre-defines macro _ARCH_PWR5 which means the @code{-mcpu}
+setting is Power5 or later.
+
+@item has_arch_pwr6
+PowerPC target pre-defines macro _ARCH_PWR6 which means the @code{-mcpu}
+setting is Power6 or later.
+
+@item has_arch_pwr7
+PowerPC target pre-defines macro _ARCH_PWR7 which means the @code{-mcpu}
+setting is Power7 or later.
+
+@item has_arch_pwr8
+PowerPC target pre-defines macro _ARCH_PWR8 which means the @code{-mcpu}
+setting is Power8 or later.
+
+@item has_arch_pwr9
+PowerPC target pre-defines macro _ARCH_PWR9 which means the @code{-mcpu}
+setting is Power9 or later.
+@end table
+
+@subsubsection RISC-V specific attributes
+
+@table @code
+
+@item rv32
+Test system has an integer register width of 32 bits.
+
+@item rv64
+Test system has an integer register width of 64 bits.
+
+@end table
+
+@subsubsection Other hardware attributes
+
+@c Please keep this table sorted alphabetically.
+@table @code
+@item autoincdec
+Target supports autoincrement/decrement addressing.
+
+@item avx
+Target supports compiling @code{avx} instructions.
+
+@item avx_runtime
+Target supports the execution of @code{avx} instructions.
+
+@item avx2
+Target supports compiling @code{avx2} instructions.
+
+@item avx2_runtime
+Target supports the execution of @code{avx2} instructions.
+
+@item avxvnni
+Target supports the execution of @code{avxvnni} instructions.
+
+@item avx512f
+Target supports compiling @code{avx512f} instructions.
+
+@item avx512f_runtime
+Target supports the execution of @code{avx512f} instructions.
+
+@item avx512vp2intersect
+Target supports the execution of @code{avx512vp2intersect} instructions.
+
+@item avxifma
+Target supports the execution of @code{avxifma} instructions.
+
+@item avxneconvert
+Target supports the execution of @code{avxneconvert} instructions.
+
+@item avxvnniint8
+Target supports the execution of @code{avxvnniint8} instructions.
+
+@item amx_tile
+Target supports the execution of @code{amx-tile} instructions.
+
+@item amx_int8
+Target supports the execution of @code{amx-int8} instructions.
+
+@item amx_bf16
+Target supports the execution of @code{amx-bf16} instructions.
+
+@item amx_fp16
+Target supports the execution of @code{amx-fp16} instructions.
+
+@item cell_hw
+Test system can execute AltiVec and Cell PPU instructions.
+
+@item cmpccxadd
+Target supports the execution of @code{cmpccxadd} instructions.
+
+@item coldfire_fpu
+Target uses a ColdFire FPU.
+
+@item divmod
+Target supporting hardware divmod insn or divmod libcall.
+
+@item divmod_simode
+Target supporting hardware divmod insn or divmod libcall for SImode.
+
+@item hard_float
+Target supports FPU instructions.
+
+@item non_strict_align
+Target does not require strict alignment.
+
+@item pie_copyreloc
+The x86-64 target linker supports PIE with copy reloc.
+
+@item prefetchi
+Target supports the execution of @code{prefetchi} instructions.
+
+@item raoint
+Target supports the execution of @code{raoint} instructions.
+
+@item rdrand
+Target supports x86 @code{rdrand} instruction.
+
+@item sqrt_insn
+Target has a square root instruction that the compiler can generate.
+
+@item sse
+Target supports compiling @code{sse} instructions.
+
+@item sse_runtime
+Target supports the execution of @code{sse} instructions.
+
+@item sse2
+Target supports compiling @code{sse2} instructions.
+
+@item sse2_runtime
+Target supports the execution of @code{sse2} instructions.
+
+@item sync_char_short
+Target supports atomic operations on @code{char} and @code{short}.
+
+@item sync_int_long
+Target supports atomic operations on @code{int} and @code{long}.
+
+@item ultrasparc_hw
+Test environment appears to run executables on a simulator that
+accepts only @code{EM_SPARC} executables and chokes on @code{EM_SPARC32PLUS}
+or @code{EM_SPARCV9} executables.
+
+@item vect_cmdline_needed
+Target requires a command line argument to enable a SIMD instruction set.
+
+@item xorsign
+Target supports the xorsign optab expansion.
+
+@end table
+
+@subsubsection Environment attributes
+
+@table @code
+@item c
+The language for the compiler under test is C.
+
+@item c++
+The language for the compiler under test is C++.
+
+@item c99_runtime
+Target provides a full C99 runtime.
+
+@item correct_iso_cpp_string_wchar_protos
+Target @code{string.h} and @code{wchar.h} headers provide C++ required
+overloads for @code{strchr} etc. functions.
+
+@item d_runtime
+Target provides the D runtime.
+
+@item d_runtime_has_std_library
+Target provides the D standard library (Phobos).
+
+@item dummy_wcsftime
+Target uses a dummy @code{wcsftime} function that always returns zero.
+
+@item fd_truncate
+Target can truncate a file from a file descriptor, as used by
+@file{libgfortran/io/unix.c:fd_truncate}; i.e.@: @code{ftruncate} or
+@code{chsize}.
+
+@item fenv
+Target provides @file{fenv.h} include file.
+
+@item fenv_exceptions
+Target supports @file{fenv.h} with all the standard IEEE exceptions
+and floating-point exceptions are raised by arithmetic operations.
+
+@item fenv_exceptions_dfp
+Target supports @file{fenv.h} with all the standard IEEE exceptions
+and floating-point exceptions are raised by arithmetic operations for
+decimal floating point.
+
+@item fileio
+Target offers such file I/O library functions as @code{fopen},
+@code{fclose}, @code{tmpnam}, and @code{remove}. This is a link-time
+requirement for the presence of the functions in the library; even if
+they fail at runtime, the requirement is still regarded as satisfied.
+
+@item freestanding
+Target is @samp{freestanding} as defined in section 4 of the C99 standard.
+Effectively, it is a target which supports no extra headers or libraries
+other than what is considered essential.
+
+@item gettimeofday
+Target supports @code{gettimeofday}.
+
+@item init_priority
+Target supports constructors with initialization priority arguments.
+
+@item inttypes_types
+Target has the basic signed and unsigned types in @code{inttypes.h}.
+This is for tests that GCC's notions of these types agree with those
+in the header, as some systems have only @code{inttypes.h}.
+
+@item lax_strtofp
+Target might have errors of a few ULP in string to floating-point
+conversion functions and overflow is not always detected correctly by
+those functions.
+
+@item mempcpy
+Target provides @code{mempcpy} function.
+
+@item mmap
+Target supports @code{mmap}.
+
+@item newlib
+Target supports Newlib.
+
+@item newlib_nano_io
+GCC was configured with @code{--enable-newlib-nano-formatted-io}, which reduces
+the code size of Newlib formatted I/O functions.
+
+@item pow10
+Target provides @code{pow10} function.
+
+@item pthread
+Target can compile using @code{pthread.h} with no errors or warnings.
+
+@item pthread_h
+Target has @code{pthread.h}.
+
+@item run_expensive_tests
+Expensive testcases (usually those that consume excessive amounts of CPU
+time) should be run on this target. This can be enabled by setting the
+@env{GCC_TEST_RUN_EXPENSIVE} environment variable to a non-empty string.
+
+@item simulator
+Test system runs executables on a simulator (i.e.@: slowly) rather than
+hardware (i.e.@: fast).
+
+@item signal
+Target has @code{signal.h}.
+
+@item stabs
+Target supports the stabs debugging format.
+
+@item stdint_types
+Target has the basic signed and unsigned C types in @code{stdint.h}.
+This will be obsolete when GCC ensures a working @code{stdint.h} for
+all targets.
+
+@item stdint_types_mbig_endian
+Target accepts the option @option{-mbig-endian} and @code{stdint.h}
+can be included without error when @option{-mbig-endian} is passed.
+
+@item stpcpy
+Target provides @code{stpcpy} function.
+
+@item sysconf
+Target supports @code{sysconf}.
+
+@item trampolines
+Target supports trampolines.
+
+@item two_plus_gigs
+Target supports linking programs with 2+GiB of data.
+
+@item uclibc
+Target supports uClibc.
+
+@item unwrapped
+Target does not use a status wrapper.
+
+@item vxworks_kernel
+Target is a VxWorks kernel.
+
+@item vxworks_rtp
+Target is a VxWorks RTP.
+
+@item wchar
+Target supports wide characters.
+@end table
+
+@subsubsection Other attributes
+
+@table @code
+@item R_flag_in_section
+Target supports the 'R' flag in .section directive in assembly inputs.
+
+@item automatic_stack_alignment
+Target supports automatic stack alignment.
+
+@item branch_cost
+Target supports @option{-branch-cost=N}.
+
+@item cxa_atexit
+Target uses @code{__cxa_atexit}.
+
+@item default_packed
+@anchor{default_packed}
+Target has packed layout of structure members by default.
+
+@item exceptions
+Target supports exceptions.
+
+@item exceptions_enabled
+Target supports exceptions and they are enabled in the current
+testing configuration.
+
+@item fgraphite
+Target supports Graphite optimizations.
+
+@item fixed_point
+Target supports fixed-point extension to C.
+
+@item fopenacc
+Target supports OpenACC via @option{-fopenacc}.
+
+@item fopenmp
+Target supports OpenMP via @option{-fopenmp}.
+
+@item fpic
+Target supports @option{-fpic} and @option{-fPIC}.
+
+@item freorder
+Target supports @option{-freorder-blocks-and-partition}.
+
+@item fstack_protector
+Target supports @option{-fstack-protector}.
+
+@item gas
+Target uses GNU @command{as}.
+
+@item gc_sections
+Target supports @option{--gc-sections}.
+
+@item gld
+Target uses GNU @command{ld}.
+
+@item keeps_null_pointer_checks
+Target keeps null pointer checks, either due to the use of
+@option{-fno-delete-null-pointer-checks} or hardwired into the target.
+
+@item llvm_binutils
+Target is using an LLVM assembler and/or linker, instead of GNU Binutils.
+
+@item lra
+Target supports local register allocator (LRA).
+
+@item lto
+Compiler has been configured to support link-time optimization (LTO).
+
+@item lto_incremental
+Compiler and linker support link-time optimization relocatable linking
+with @option{-r} and @option{-flto} options.
+
+@item naked_functions
+Target supports the @code{naked} function attribute.
+
+@item named_sections
+Target supports named sections.
+
+@item natural_alignment_32
+Target uses natural alignment (aligned to type size) for types of
+32 bits or less.
+
+@item target_natural_alignment_64
+Target uses natural alignment (aligned to type size) for types of
+64 bits or less.
+
+@item no_alignment_constraints
+Target defines __BIGGEST_ALIGNMENT__=1. Hence target imposes
+no alignment constraints. This is similar, but not necessarily
+the same as @ref{default_packed}. Although @code{BIGGEST_FIELD_ALIGNMENT}
+defaults to @code{BIGGEST_ALIGNMENT} for most targets, it is possible
+for a target to set those two with different values and have different
+alignment constraints for aggregate and non-aggregate types.
+
+@item noinit
+Target supports the @code{noinit} variable attribute.
+
+@item nonpic
+Target does not generate PIC by default.
+
+@item o_flag_in_section
+Target supports the 'o' flag in .section directive in assembly inputs.
+
+@item offload_gcn
+Target has been configured for OpenACC/OpenMP offloading on AMD GCN.
+
+@item persistent
+Target supports the @code{persistent} variable attribute.
+
+@item pie_enabled
+Target generates PIE by default.
+
+@item pcc_bitfield_type_matters
+Target defines @code{PCC_BITFIELD_TYPE_MATTERS}.
+
+@item pe_aligned_commons
+Target supports @option{-mpe-aligned-commons}.
+
+@item pie
+Target supports @option{-pie}, @option{-fpie} and @option{-fPIE}.
+
+@item rdynamic
+Target supports @option{-rdynamic}.
+
+@item scalar_all_fma
+Target supports all four fused multiply-add optabs for both @code{float}
+and @code{double}. These optabs are: @code{fma_optab}, @code{fms_optab},
+@code{fnma_optab} and @code{fnms_optab}.
+
+@item section_anchors
+Target supports section anchors.
+
+@item short_enums
+Target defaults to short enums.
+
+@item stack_size
+@anchor{stack_size_et}
+Target has limited stack size. The stack size limit can be obtained using the
+STACK_SIZE macro defined by @ref{stack_size_ao,,@code{dg-add-options} feature
+@code{stack_size}}.
+
+@item static
+Target supports @option{-static}.
+
+@item static_libgfortran
+Target supports statically linking @samp{libgfortran}.
+
+@item string_merging
+Target supports merging string constants at link time.
+
+@item ucn
+Target supports compiling and assembling UCN.
+
+@item ucn_nocache
+Including the options used to compile this particular test, the
+target supports compiling and assembling UCN.
+
+@item unaligned_stack
+Target does not guarantee that its @code{STACK_BOUNDARY} is greater than
+or equal to the required vector alignment.
+
+@item vector_alignment_reachable
+Vector alignment is reachable for types of 32 bits or less.
+
+@item vector_alignment_reachable_for_64bit
+Vector alignment is reachable for types of 64 bits or less.
+
+@item vma_equals_lma
+Target generates executable with VMA equal to LMA for .data section.
+
+@item wchar_t_char16_t_compatible
+Target supports @code{wchar_t} that is compatible with @code{char16_t}.
+
+@item wchar_t_char32_t_compatible
+Target supports @code{wchar_t} that is compatible with @code{char32_t}.
+
+@item comdat_group
+Target uses comdat groups.
+
+@item indirect_calls
+Target supports indirect calls, i.e. calls where the target is not
+constant.
+
+@item lgccjit
+Target supports -lgccjit, i.e. libgccjit.so can be linked into jit tests.
+
+@item __OPTIMIZE__
+Optimizations are enabled (@code{__OPTIMIZE__}) per the current
+compiler flags.
+@end table
+
+@subsubsection Local to tests in @code{gcc.target/i386}
+
+@table @code
+@item 3dnow
+Target supports compiling @code{3dnow} instructions.
+
+@item aes
+Target supports compiling @code{aes} instructions.
+
+@item fma4
+Target supports compiling @code{fma4} instructions.
+
+@item mfentry
+Target supports the @code{-mfentry} option that alters the
+position of profiling calls such that they precede the prologue.
+
+@item ms_hook_prologue
+Target supports attribute @code{ms_hook_prologue}.
+
+@item pclmul
+Target supports compiling @code{pclmul} instructions.
+
+@item sse3
+Target supports compiling @code{sse3} instructions.
+
+@item sse4
+Target supports compiling @code{sse4} instructions.
+
+@item sse4a
+Target supports compiling @code{sse4a} instructions.
+
+@item ssse3
+Target supports compiling @code{ssse3} instructions.
+
+@item vaes
+Target supports compiling @code{vaes} instructions.
+
+@item vpclmul
+Target supports compiling @code{vpclmul} instructions.
+
+@item xop
+Target supports compiling @code{xop} instructions.
+@end table
+
+@subsubsection Local to tests in @code{gcc.test-framework}
+
+@table @code
+@item no
+Always returns 0.
+
+@item yes
+Always returns 1.
+@end table
+
+@node Add Options
+@subsection Features for @code{dg-add-options}
+
+The supported values of @var{feature} for directive @code{dg-add-options}
+are:
+
+@table @code
+@item arm_fp
+@code{__ARM_FP} definition. Only ARM targets support this feature, and only then
+in certain modes; see the @ref{arm_fp_ok,,arm_fp_ok effective target
+keyword}.
+
+@item arm_fp_dp
+@code{__ARM_FP} definition with double-precision support. Only ARM
+targets support this feature, and only then in certain modes; see the
+@ref{arm_fp_dp_ok,,arm_fp_dp_ok effective target keyword}.
+
+@item arm_neon
+NEON support. Only ARM targets support this feature, and only then
+in certain modes; see the @ref{arm_neon_ok,,arm_neon_ok effective target
+keyword}.
+
+@item arm_fp16
+VFP half-precision floating point support. This does not select the
+FP16 format; for that, use @ref{arm_fp16_ieee,,arm_fp16_ieee} or
+@ref{arm_fp16_alternative,,arm_fp16_alternative} instead. This
+feature is only supported by ARM targets and then only in certain
+modes; see the @ref{arm_fp16_ok,,arm_fp16_ok effective target
+keyword}.
+
+@item arm_fp16_ieee
+@anchor{arm_fp16_ieee}
+ARM IEEE 754-2008 format VFP half-precision floating point support.
+This feature is only supported by ARM targets and then only in certain
+modes; see the @ref{arm_fp16_ok,,arm_fp16_ok effective target
+keyword}.
+
+@item arm_fp16_alternative
+@anchor{arm_fp16_alternative}
+ARM Alternative format VFP half-precision floating point support.
+This feature is only supported by ARM targets and then only in certain
+modes; see the @ref{arm_fp16_ok,,arm_fp16_ok effective target
+keyword}.
+
+@item arm_neon_fp16
+NEON and half-precision floating point support. Only ARM targets
+support this feature, and only then in certain modes; see
+the @ref{arm_neon_fp16_ok,,arm_neon_fp16_ok effective target keyword}.
+
+@item arm_vfp3
+arm vfp3 floating point support; see
+the @ref{arm_vfp3_ok,,arm_vfp3_ok effective target keyword}.
+
+@item arm_arch_v8a_hard
+Add options for ARMv8-A and the hard-float variant of the AAPCS,
+if this is supported by the compiler; see the
+@ref{arm_arch_v8a_hard_ok,,arm_arch_v8a_hard_ok} effective target keyword.
+
+@item arm_v8_1a_neon
+Add options for ARMv8.1-A with Adv.SIMD support, if this is supported
+by the target; see the @ref{arm_v8_1a_neon_ok,,arm_v8_1a_neon_ok}
+effective target keyword.
+
+@item arm_v8_2a_fp16_scalar
+Add options for ARMv8.2-A with scalar FP16 support, if this is
+supported by the target; see the
+@ref{arm_v8_2a_fp16_scalar_ok,,arm_v8_2a_fp16_scalar_ok} effective
+target keyword.
+
+@item arm_v8_2a_fp16_neon
+Add options for ARMv8.2-A with Adv.SIMD FP16 support, if this is
+supported by the target; see the
+@ref{arm_v8_2a_fp16_neon_ok,,arm_v8_2a_fp16_neon_ok} effective target
+keyword.
+
+@item arm_v8_2a_dotprod_neon
+Add options for ARMv8.2-A with Adv.SIMD Dot Product support, if this is
+supported by the target; see the
+@ref{arm_v8_2a_dotprod_neon_ok} effective target keyword.
+
+@item arm_fp16fml_neon
+Add options to enable generation of the @code{VFMAL} and @code{VFMSL}
+instructions, if this is supported by the target; see the
+@ref{arm_fp16fml_neon_ok} effective target keyword.
+
+@item arm_dsp
+Add options for ARM DSP intrinsics support, if this is supported by
+the target; see the @ref{arm_dsp_ok,,arm_dsp_ok effective target
+keyword}.
+
+@item bind_pic_locally
+Add the target-specific flags needed to enable functions to bind
+locally when using pic/PIC passes in the testsuite.
+
+@item float@var{n}
+Add the target-specific flags needed to use the @code{_Float@var{n}} type.
+
+@item float@var{n}x
+Add the target-specific flags needed to use the @code{_Float@var{n}x} type.
+
+@item ieee
+Add the target-specific flags needed to enable full IEEE
+compliance mode.
+
+@item mips16_attribute
+@code{mips16} function attributes.
+Only MIPS targets support this feature, and only then in certain modes.
+
+@item stack_size
+@anchor{stack_size_ao}
+Add the flags needed to define macro STACK_SIZE and set it to the stack size
+limit associated with the @ref{stack_size_et,,@code{stack_size} effective
+target}.
+
+@item sqrt_insn
+Add the target-specific flags needed to enable hardware square root
+instructions, if any.
+
+@item tls
+Add the target-specific flags needed to use thread-local storage.
+@end table
+
+@node Require Support
+@subsection Variants of @code{dg-require-@var{support}}
+
+A few of the @code{dg-require} directives take arguments.
+
+@table @code
+@item dg-require-iconv @var{codeset}
+Skip the test if the target does not support iconv. @var{codeset} is
+the codeset to convert to.
+
+@item dg-require-profiling @var{profopt}
+Skip the test if the target does not support profiling with option
+@var{profopt}.
+
+@item dg-require-stack-check @var{check}
+Skip the test if the target does not support the @code{-fstack-check}
+option. If @var{check} is @code{""}, support for @code{-fstack-check}
+is checked, for @code{-fstack-check=("@var{check}")} otherwise.
+
+@item dg-require-stack-size @var{size}
+Skip the test if the target does not support a stack size of @var{size}.
+
+@item dg-require-visibility @var{vis}
+Skip the test if the target does not support the @code{visibility} attribute.
+If @var{vis} is @code{""}, support for @code{visibility("hidden")} is
+checked, for @code{visibility("@var{vis}")} otherwise.
+@end table
+
+The original @code{dg-require} directives were defined before there
+was support for effective-target keywords. The directives that do not
+take arguments could be replaced with effective-target keywords.
+
+@table @code
+@item dg-require-alias ""
+Skip the test if the target does not support the @samp{alias} attribute.
+
+@item dg-require-ascii-locale ""
+Skip the test if the host does not support an ASCII locale.
+
+@item dg-require-compat-dfp ""
+Skip this test unless both compilers in a @file{compat} testsuite
+support decimal floating point.
+
+@item dg-require-cxa-atexit ""
+Skip the test if the target does not support @code{__cxa_atexit}.
+This is equivalent to @code{dg-require-effective-target cxa_atexit}.
+
+@item dg-require-dll ""
+Skip the test if the target does not support DLL attributes.
+
+@item dg-require-dot ""
+Skip the test if the host does not have @command{dot}.
+
+@item dg-require-fork ""
+Skip the test if the target does not support @code{fork}.
+
+@item dg-require-gc-sections ""
+Skip the test if the target's linker does not support the
+@code{--gc-sections} flags.
+This is equivalent to @code{dg-require-effective-target gc-sections}.
+
+@item dg-require-host-local ""
+Skip the test if the host is remote, rather than the same as the build
+system. Some tests are incompatible with DejaGnu's handling of remote
+hosts, which involves copying the source file to the host and compiling
+it with a relative path and "@code{-o a.out}".
+
+@item dg-require-mkfifo ""
+Skip the test if the target does not support @code{mkfifo}.
+
+@item dg-require-named-sections ""
+Skip the test is the target does not support named sections.
+This is equivalent to @code{dg-require-effective-target named_sections}.
+
+@item dg-require-weak ""
+Skip the test if the target does not support weak symbols.
+
+@item dg-require-weak-override ""
+Skip the test if the target does not support overriding weak symbols.
+@end table
+
+@node Final Actions
+@subsection Commands for use in @code{dg-final}
+
+The GCC testsuite defines the following directives to be used within
+@code{dg-final}.
+
+@subsubsection Scan a particular file
+
+@table @code
+@item scan-file @var{filename} @var{regexp} [@{ target/xfail @var{selector} @}]
+Passes if @var{regexp} matches text in @var{filename}.
+@item scan-file-not @var{filename} @var{regexp} [@{ target/xfail @var{selector} @}]
+Passes if @var{regexp} does not match text in @var{filename}.
+@item scan-module @var{module} @var{regexp} [@{ target/xfail @var{selector} @}]
+Passes if @var{regexp} matches in Fortran module @var{module}.
+@item dg-check-dot @var{filename}
+Passes if @var{filename} is a valid @file{.dot} file (by running
+@code{dot -Tpng} on it, and verifying the exit code is 0).
+@item scan-sarif-file @var{regexp} [@{ target/xfail @var{selector} @}]
+Passes if @var{regexp} matches text in the file generated by
+@option{-fdiagnostics-format=sarif-file}.
+@item scan-sarif-file-not @var{regexp} [@{ target/xfail @var{selector} @}]
+Passes if @var{regexp} does not match text in the file generated by
+@option{-fdiagnostics-format=sarif-file}.
+@end table
+
+@subsubsection Scan the assembly output
+
+@table @code
+@item scan-assembler @var{regex} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} matches text in the test's assembler output.
+
+@item scan-assembler-not @var{regex} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} does not match text in the test's assembler output.
+
+@item scan-assembler-times @var{regex} @var{num} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} is matched exactly @var{num} times in the test's
+assembler output.
+
+@item scan-assembler-dem @var{regex} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} matches text in the test's demangled assembler output.
+
+@item scan-assembler-dem-not @var{regex} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} does not match text in the test's demangled assembler
+output.
+
+@item scan-assembler-symbol-section @var{functions} @var{section} [@{ target/xfail @var{selector} @}]
+Passes if @var{functions} are all in @var{section}. The caller needs to
+allow for @code{USER_LABEL_PREFIX} and different section name conventions.
+
+@item scan-symbol-section @var{filename} @var{functions} @var{section} [@{ target/xfail @var{selector} @}]
+Passes if @var{functions} are all in @var{section}in @var{filename}.
+The same caveats as for @code{scan-assembler-symbol-section} apply.
+
+@item scan-hidden @var{symbol} [@{ target/xfail @var{selector} @}]
+Passes if @var{symbol} is defined as a hidden symbol in the test's
+assembly output.
+
+@item scan-not-hidden @var{symbol} [@{ target/xfail @var{selector} @}]
+Passes if @var{symbol} is not defined as a hidden symbol in the test's
+assembly output.
+
+@item check-function-bodies @var{prefix} @var{terminator} [@var{options} [@{ target/xfail @var{selector} @}]]
+Looks through the source file for comments that give the expected assembly
+output for selected functions. Each line of expected output starts with the
+prefix string @var{prefix} and the expected output for a function as a whole
+is followed by a line that starts with the string @var{terminator}.
+Specifying an empty terminator is equivalent to specifying @samp{"*/"}.
+
+@var{options}, if specified, is a list of regular expressions, each of
+which matches a full command-line option. A non-empty list prevents
+the test from running unless all of the given options are present on the
+command line. This can help if a source file is compiled both with
+and without optimization, since it is rarely useful to check the full
+function body for unoptimized code.
+
+The first line of the expected output for a function @var{fn} has the form:
+
+@smallexample
+@var{prefix} @var{fn}: [@{ target/xfail @var{selector} @}]
+@end smallexample
+
+Subsequent lines of the expected output also start with @var{prefix}.
+In both cases, whitespace after @var{prefix} is not significant.
+
+The test discards assembly directives such as @code{.cfi_startproc}
+and local label definitions such as @code{.LFB0} from the compiler's
+assembly output. It then matches the result against the expected
+output for a function as a single regular expression. This means that
+later lines can use backslashes to refer back to @samp{(@dots{})}
+captures on earlier lines. For example:
+
+@smallexample
+/* @{ dg-final @{ check-function-bodies "**" "" "-DCHECK_ASM" @} @} */
+@dots{}
+/*
+** add_w0_s8_m:
+** mov (z[0-9]+\.b), w0
+** add z0\.b, p0/m, z0\.b, \1
+** ret
+*/
+svint8_t add_w0_s8_m (@dots{}) @{ @dots{} @}
+@dots{}
+/*
+** add_b0_s8_m:
+** mov (z[0-9]+\.b), b0
+** add z1\.b, p0/m, z1\.b, \1
+** ret
+*/
+svint8_t add_b0_s8_m (@dots{}) @{ @dots{} @}
+@end smallexample
+
+checks whether the implementations of @code{add_w0_s8_m} and
+@code{add_b0_s8_m} match the regular expressions given. The test only
+runs when @samp{-DCHECK_ASM} is passed on the command line.
+
+It is possible to create non-capturing multi-line regular expression
+groups of the form @samp{(@var{a}|@var{b}|@dots{})} by putting the
+@samp{(}, @samp{|} and @samp{)} on separate lines (each still using
+@var{prefix}). For example:
+
+@smallexample
+/*
+** cmple_f16_tied:
+** (
+** fcmge p0\.h, p0/z, z1\.h, z0\.h
+** |
+** fcmle p0\.h, p0/z, z0\.h, z1\.h
+** )
+** ret
+*/
+svbool_t cmple_f16_tied (@dots{}) @{ @dots{} @}
+@end smallexample
+
+checks whether @code{cmple_f16_tied} is implemented by the
+@code{fcmge} instruction followed by @code{ret} or by the
+@code{fcmle} instruction followed by @code{ret}. The test is
+still a single regular rexpression.
+
+A line containing just:
+
+@smallexample
+@var{prefix} ...
+@end smallexample
+
+stands for zero or more unmatched lines; the whitespace after
+@var{prefix} is again not significant.
+
+@end table
+
+@subsubsection Scan optimization dump files
+
+These commands are available for @var{kind} of @code{tree}, @code{ltrans-tree},
+@code{offload-tree}, @code{rtl}, @code{offload-rtl}, @code{ipa}, and
+@code{wpa-ipa}.
+
+@table @code
+@item scan-@var{kind}-dump @var{regex} @var{suffix} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} matches text in the dump file with suffix @var{suffix}.
+
+@item scan-@var{kind}-dump-not @var{regex} @var{suffix} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} does not match text in the dump file with suffix
+@var{suffix}.
+
+@item scan-@var{kind}-dump-times @var{regex} @var{num} @var{suffix} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} is found exactly @var{num} times in the dump file
+with suffix @var{suffix}.
+
+@item scan-@var{kind}-dump-dem @var{regex} @var{suffix} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} matches demangled text in the dump file with
+suffix @var{suffix}.
+
+@item scan-@var{kind}-dump-dem-not @var{regex} @var{suffix} [@{ target/xfail @var{selector} @}]
+Passes if @var{regex} does not match demangled text in the dump file with
+suffix @var{suffix}.
+@end table
+
+The @var{suffix} argument which describes the dump file to be scanned
+may contain a glob pattern that must expand to exactly one file
+name. This is useful if, e.g., different pass instances are executed
+depending on torture testing command-line flags, producing dump files
+whose names differ only in their pass instance number suffix. For
+example, to scan instances 1, 2, 3 of a tree pass ``mypass'' for
+occurrences of the string ``code has been optimized'', use:
+@smallexample
+/* @{ dg-options "-fdump-tree-mypass" @} */
+/* @{ dg-final @{ scan-tree-dump "code has been optimized" "mypass\[1-3\]" @} @} */
+@end smallexample
+
+
+@subsubsection Check for output files
+
+@table @code
+@item output-exists [@{ target/xfail @var{selector} @}]
+Passes if compiler output file exists.
+
+@item output-exists-not [@{ target/xfail @var{selector} @}]
+Passes if compiler output file does not exist.
+
+@item scan-symbol @var{regexp} [@{ target/xfail @var{selector} @}]
+Passes if the pattern is present in the final executable.
+
+@item scan-symbol-not @var{regexp} [@{ target/xfail @var{selector} @}]
+Passes if the pattern is absent from the final executable.
+@end table
+
+@subsubsection Checks for @command{gcov} tests
+
+@table @code
+@item run-gcov @var{sourcefile}
+Check line counts in @command{gcov} tests.
+
+@item run-gcov [branches] [calls] @{ @var{opts} @var{sourcefile} @}
+Check branch and/or call counts, in addition to line counts, in
+@command{gcov} tests.
+
+@item run-gcov-pytest @{ @var{sourcefile} @var{pytest_file} @}
+Check output of @command{gcov} intermediate format with a pytest
+script.
+@end table
+
+@subsubsection Clean up generated test files
+
+Usually the test-framework removes files that were generated during
+testing. If a testcase, for example, uses any dumping mechanism to
+inspect a passes dump file, the testsuite recognized the dump option
+passed to the tool and schedules a final cleanup to remove these files.
+
+There are, however, following additional cleanup directives that can be
+used to annotate a testcase "manually".
+@table @code
+@item cleanup-coverage-files
+Removes coverage data files generated for this test.
+
+@item cleanup-modules "@var{list-of-extra-modules}"
+Removes Fortran module files generated for this test, excluding the
+module names listed in keep-modules.
+Cleaning up module files is usually done automatically by the testsuite
+by looking at the source files and removing the modules after the test
+has been executed.
+@smallexample
+module MoD1
+end module MoD1
+module Mod2
+end module Mod2
+module moD3
+end module moD3
+module mod4
+end module mod4
+! @{ dg-final @{ cleanup-modules "mod1 mod2" @} @} ! redundant
+! @{ dg-final @{ keep-modules "mod3 mod4" @} @}
+@end smallexample
+
+@item keep-modules "@var{list-of-modules-not-to-delete}"
+Whitespace separated list of module names that should not be deleted by
+cleanup-modules.
+If the list of modules is empty, all modules defined in this file are kept.
+@smallexample
+module maybe_unneeded
+end module maybe_unneeded
+module keep1
+end module keep1
+module keep2
+end module keep2
+! @{ dg-final @{ keep-modules "keep1 keep2" @} @} ! just keep these two
+! @{ dg-final @{ keep-modules "" @} @} ! keep all
+@end smallexample
+
+@item dg-keep-saved-temps "@var{list-of-suffixes-not-to-delete}"
+Whitespace separated list of suffixes that should not be deleted
+automatically in a testcase that uses @option{-save-temps}.
+@smallexample
+// @{ dg-options "-save-temps -fpch-preprocess -I." @}
+int main() @{ return 0; @}
+// @{ dg-keep-saved-temps ".s" @} ! just keep assembler file
+// @{ dg-keep-saved-temps ".s" ".i" @} ! ... and .i
+// @{ dg-keep-saved-temps ".ii" ".o" @} ! or just .ii and .o
+@end smallexample
+
+@item cleanup-profile-file
+Removes profiling files generated for this test.
+
+@end table
+
+@node Ada Tests
+@section Ada Language Testsuites
+
+The Ada testsuite includes executable tests from the ACATS
+testsuite, publicly available at
+@uref{http://www.ada-auth.org/acats.html}.
+
+These tests are integrated in the GCC testsuite in the
+@file{ada/acats} directory, and
+enabled automatically when running @code{make check}, assuming
+the Ada language has been enabled when configuring GCC@.
+
+You can also run the Ada testsuite independently, using
+@code{make check-ada}, or run a subset of the tests by specifying which
+chapter to run, e.g.:
+
+@smallexample
+$ make check-ada CHAPTERS="c3 c9"
+@end smallexample
+
+The tests are organized by directory, each directory corresponding to
+a chapter of the Ada Reference Manual. So for example, @file{c9} corresponds
+to chapter 9, which deals with tasking features of the language.
+
+The tests are run using two @command{sh} scripts: @file{run_acats} and
+@file{run_all.sh}. To run the tests using a simulator or a cross
+target, see the small
+customization section at the top of @file{run_all.sh}.
+
+These tests are run using the build tree: they can be run without doing
+a @code{make install}.
+
+@node C Tests
+@section C Language Testsuites
+
+GCC contains the following C language testsuites, in the
+@file{gcc/testsuite} directory:
+
+@table @file
+@item gcc.dg
+This contains tests of particular features of the C compiler, using the
+more modern @samp{dg} harness. Correctness tests for various compiler
+features should go here if possible.
+
+Magic comments determine whether the file
+is preprocessed, compiled, linked or run. In these tests, error and warning
+message texts are compared against expected texts or regular expressions
+given in comments. These tests are run with the options @samp{-ansi -pedantic}
+unless other options are given in the test. Except as noted below they
+are not run with multiple optimization options.
+@item gcc.dg/compat
+This subdirectory contains tests for binary compatibility using
+@file{lib/compat.exp}, which in turn uses the language-independent support
+(@pxref{compat Testing, , Support for testing binary compatibility}).
+@item gcc.dg/cpp
+This subdirectory contains tests of the preprocessor.
+@item gcc.dg/debug
+This subdirectory contains tests for debug formats. Tests in this
+subdirectory are run for each debug format that the compiler supports.
+@item gcc.dg/format
+This subdirectory contains tests of the @option{-Wformat} format
+checking. Tests in this directory are run with and without
+@option{-DWIDE}.
+@item gcc.dg/noncompile
+This subdirectory contains tests of code that should not compile and
+does not need any special compilation options. They are run with
+multiple optimization options, since sometimes invalid code crashes
+the compiler with optimization.
+@item gcc.dg/special
+FIXME: describe this.
+
+@item gcc.c-torture
+This contains particular code fragments which have historically broken easily.
+These tests are run with multiple optimization options, so tests for features
+which only break at some optimization levels belong here. This also contains
+tests to check that certain optimizations occur. It might be worthwhile to
+separate the correctness tests cleanly from the code quality tests, but
+it hasn't been done yet.
+
+@item gcc.c-torture/compat
+FIXME: describe this.
+
+This directory should probably not be used for new tests.
+@item gcc.c-torture/compile
+This testsuite contains test cases that should compile, but do not
+need to link or run. These test cases are compiled with several
+different combinations of optimization options. All warnings are
+disabled for these test cases, so this directory is not suitable if
+you wish to test for the presence or absence of compiler warnings.
+While special options can be set, and tests disabled on specific
+platforms, by the use of @file{.x} files, mostly these test cases
+should not contain platform dependencies. FIXME: discuss how defines
+such as @code{STACK_SIZE} are used.
+@item gcc.c-torture/execute
+This testsuite contains test cases that should compile, link and run;
+otherwise the same comments as for @file{gcc.c-torture/compile} apply.
+@item gcc.c-torture/execute/ieee
+This contains tests which are specific to IEEE floating point.
+@item gcc.c-torture/unsorted
+FIXME: describe this.
+
+This directory should probably not be used for new tests.
+@item gcc.misc-tests
+This directory contains C tests that require special handling. Some
+of these tests have individual expect files, and others share
+special-purpose expect files:
+
+@table @file
+@item @code{bprob*.c}
+Test @option{-fbranch-probabilities} using
+@file{gcc.misc-tests/bprob.exp}, which
+in turn uses the generic, language-independent framework
+(@pxref{profopt Testing, , Support for testing profile-directed
+optimizations}).
+
+@item @code{gcov*.c}
+Test @command{gcov} output using @file{gcov.exp}, which in turn uses the
+language-independent support (@pxref{gcov Testing, , Support for testing gcov}).
+
+@item @code{i386-pf-*.c}
+Test i386-specific support for data prefetch using @file{i386-prefetch.exp}.
+@end table
+
+@item gcc.test-framework
+@table @file
+@item @code{dg-*.c}
+Test the testsuite itself using @file{gcc.test-framework/test-framework.exp}.
+@end table
+
+@end table
+
+FIXME: merge in @file{testsuite/README.gcc} and discuss the format of
+test cases and magic comments more.
+
+@node LTO Testing
+@section Support for testing link-time optimizations
+
+Tests for link-time optimizations usually require multiple source files
+that are compiled separately, perhaps with different sets of options.
+There are several special-purpose test directives used for these tests.
+
+@table @code
+@item @{ dg-lto-do @var{do-what-keyword} @}
+@var{do-what-keyword} specifies how the test is compiled and whether
+it is executed. It is one of:
+
+@table @code
+@item assemble
+Compile with @option{-c} to produce a relocatable object file.
+@item link
+Compile, assemble, and link to produce an executable file.
+@item run
+Produce and run an executable file, which is expected to return
+an exit code of 0.
+@end table
+
+The default is @code{assemble}. That can be overridden for a set of
+tests by redefining @code{dg-do-what-default} within the @code{.exp}
+file for those tests.
+
+Unlike @code{dg-do}, @code{dg-lto-do} does not support an optional
+@samp{target} or @samp{xfail} list. Use @code{dg-skip-if},
+@code{dg-xfail-if}, or @code{dg-xfail-run-if}.
+
+@item @{ dg-lto-options @{ @{ @var{options} @} [@{ @var{options} @}] @} [@{ target @var{selector} @}]@}
+This directive provides a list of one or more sets of compiler options
+to override @var{LTO_OPTIONS}. Each test will be compiled and run with
+each of these sets of options.
+
+@item @{ dg-extra-ld-options @var{options} [@{ target @var{selector} @}]@}
+This directive adds @var{options} to the linker options used.
+
+@item @{ dg-suppress-ld-options @var{options} [@{ target @var{selector} @}]@}
+This directive removes @var{options} from the set of linker options used.
+@end table
+
+@node gcov Testing
+@section Support for testing @command{gcov}
+
+Language-independent support for testing @command{gcov}, and for checking
+that branch profiling produces expected values, is provided by the
+expect file @file{lib/gcov.exp}. @command{gcov} tests also rely on procedures
+in @file{lib/gcc-dg.exp} to compile and run the test program. A typical
+@command{gcov} test contains the following DejaGnu commands within comments:
+
+@smallexample
+@{ dg-options "--coverage" @}
+@{ dg-do run @{ target native @} @}
+@{ dg-final @{ run-gcov sourcefile @} @}
+@end smallexample
+
+Checks of @command{gcov} output can include line counts, branch percentages,
+and call return percentages. All of these checks are requested via
+commands that appear in comments in the test's source file.
+Commands to check line counts are processed by default.
+Commands to check branch percentages and call return percentages are
+processed if the @command{run-gcov} command has arguments @code{branches}
+or @code{calls}, respectively. For example, the following specifies
+checking both, as well as passing @option{-b} to @command{gcov}:
+
+@smallexample
+@{ dg-final @{ run-gcov branches calls @{ -b sourcefile @} @} @}
+@end smallexample
+
+A line count command appears within a comment on the source line
+that is expected to get the specified count and has the form
+@code{count(@var{cnt})}. A test should only check line counts for
+lines that will get the same count for any architecture.
+
+Commands to check branch percentages (@code{branch}) and call
+return percentages (@code{returns}) are very similar to each other.
+A beginning command appears on or before the first of a range of
+lines that will report the percentage, and the ending command
+follows that range of lines. The beginning command can include a
+list of percentages, all of which are expected to be found within
+the range. A range is terminated by the next command of the same
+kind. A command @code{branch(end)} or @code{returns(end)} marks
+the end of a range without starting a new one. For example:
+
+@smallexample
+if (i > 10 && j > i && j < 20) /* @r{branch(27 50 75)} */
+ /* @r{branch(end)} */
+ foo (i, j);
+@end smallexample
+
+For a call return percentage, the value specified is the
+percentage of calls reported to return. For a branch percentage,
+the value is either the expected percentage or 100 minus that
+value, since the direction of a branch can differ depending on the
+target or the optimization level.
+
+Not all branches and calls need to be checked. A test should not
+check for branches that might be optimized away or replaced with
+predicated instructions. Don't check for calls inserted by the
+compiler or ones that might be inlined or optimized away.
+
+A single test can check for combinations of line counts, branch
+percentages, and call return percentages. The command to check a
+line count must appear on the line that will report that count, but
+commands to check branch percentages and call return percentages can
+bracket the lines that report them.
+
+@node profopt Testing
+@section Support for testing profile-directed optimizations
+
+The file @file{profopt.exp} provides language-independent support for
+checking correct execution of a test built with profile-directed
+optimization. This testing requires that a test program be built and
+executed twice. The first time it is compiled to generate profile
+data, and the second time it is compiled to use the data that was
+generated during the first execution. The second execution is to
+verify that the test produces the expected results.
+
+To check that the optimization actually generated better code, a
+test can be built and run a third time with normal optimizations to
+verify that the performance is better with the profile-directed
+optimizations. @file{profopt.exp} has the beginnings of this kind
+of support.
+
+@file{profopt.exp} provides generic support for profile-directed
+optimizations. Each set of tests that uses it provides information
+about a specific optimization:
+
+@table @code
+@item tool
+tool being tested, e.g., @command{gcc}
+
+@item profile_option
+options used to generate profile data
+
+@item feedback_option
+options used to optimize using that profile data
+
+@item prof_ext
+suffix of profile data files
+
+@item PROFOPT_OPTIONS
+list of options with which to run each test, similar to the lists for
+torture tests
+
+@item @{ dg-final-generate @{ @var{local-directive} @} @}
+This directive is similar to @code{dg-final}, but the
+@var{local-directive} is run after the generation of profile data.
+
+@item @{ dg-final-use @{ @var{local-directive} @} @}
+The @var{local-directive} is run after the profile data have been
+used.
+@end table
+
+@node compat Testing
+@section Support for testing binary compatibility
+
+The file @file{compat.exp} provides language-independent support for
+binary compatibility testing. It supports testing interoperability of
+two compilers that follow the same ABI, or of multiple sets of
+compiler options that should not affect binary compatibility. It is
+intended to be used for testsuites that complement ABI testsuites.
+
+A test supported by this framework has three parts, each in a
+separate source file: a main program and two pieces that interact
+with each other to split up the functionality being tested.
+
+@table @file
+@item @var{testname}_main.@var{suffix}
+Contains the main program, which calls a function in file
+@file{@var{testname}_x.@var{suffix}}.
+
+@item @var{testname}_x.@var{suffix}
+Contains at least one call to a function in
+@file{@var{testname}_y.@var{suffix}}.
+
+@item @var{testname}_y.@var{suffix}
+Shares data with, or gets arguments from,
+@file{@var{testname}_x.@var{suffix}}.
+@end table
+
+Within each test, the main program and one functional piece are
+compiled by the GCC under test. The other piece can be compiled by
+an alternate compiler. If no alternate compiler is specified,
+then all three source files are all compiled by the GCC under test.
+You can specify pairs of sets of compiler options. The first element
+of such a pair specifies options used with the GCC under test, and the
+second element of the pair specifies options used with the alternate
+compiler. Each test is compiled with each pair of options.
+
+@file{compat.exp} defines default pairs of compiler options.
+These can be overridden by defining the environment variable
+@env{COMPAT_OPTIONS} as:
+
+@smallexample
+COMPAT_OPTIONS="[list [list @{@var{tst1}@} @{@var{alt1}@}]
+ @dots{}[list @{@var{tstn}@} @{@var{altn}@}]]"
+@end smallexample
+
+where @var{tsti} and @var{alti} are lists of options, with @var{tsti}
+used by the compiler under test and @var{alti} used by the alternate
+compiler. For example, with
+@code{[list [list @{-g -O0@} @{-O3@}] [list @{-fpic@} @{-fPIC -O2@}]]},
+the test is first built with @option{-g -O0} by the compiler under
+test and with @option{-O3} by the alternate compiler. The test is
+built a second time using @option{-fpic} by the compiler under test
+and @option{-fPIC -O2} by the alternate compiler.
+
+An alternate compiler is specified by defining an environment
+variable to be the full pathname of an installed compiler; for C
+define @env{ALT_CC_UNDER_TEST}, and for C++ define
+@env{ALT_CXX_UNDER_TEST}. These will be written to the
+@file{site.exp} file used by DejaGnu. The default is to build each
+test with the compiler under test using the first of each pair of
+compiler options from @env{COMPAT_OPTIONS}. When
+@env{ALT_CC_UNDER_TEST} or
+@env{ALT_CXX_UNDER_TEST} is @code{same}, each test is built using
+the compiler under test but with combinations of the options from
+@env{COMPAT_OPTIONS}.
+
+To run only the C++ compatibility suite using the compiler under test
+and another version of GCC using specific compiler options, do the
+following from @file{@var{objdir}/gcc}:
+
+@smallexample
+rm site.exp
+make -k \
+ ALT_CXX_UNDER_TEST=$@{alt_prefix@}/bin/g++ \
+ COMPAT_OPTIONS="@var{lists as shown above}" \
+ check-c++ \
+ RUNTESTFLAGS="compat.exp"
+@end smallexample
+
+A test that fails when the source files are compiled with different
+compilers, but passes when the files are compiled with the same
+compiler, demonstrates incompatibility of the generated code or
+runtime support. A test that fails for the alternate compiler but
+passes for the compiler under test probably tests for a bug that was
+fixed in the compiler under test but is present in the alternate
+compiler.
+
+The binary compatibility tests support a small number of test framework
+commands that appear within comments in a test file.
+
+@table @code
+@item dg-require-*
+These commands can be used in @file{@var{testname}_main.@var{suffix}}
+to skip the test if specific support is not available on the target.
+
+@item dg-options
+The specified options are used for compiling this particular source
+file, appended to the options from @env{COMPAT_OPTIONS}. When this
+command appears in @file{@var{testname}_main.@var{suffix}} the options
+are also used to link the test program.
+
+@item dg-xfail-if
+This command can be used in a secondary source file to specify that
+compilation is expected to fail for particular options on particular
+targets.
+@end table
+
+@node Torture Tests
+@section Support for torture testing using multiple options
+
+Throughout the compiler testsuite there are several directories whose
+tests are run multiple times, each with a different set of options.
+These are known as torture tests.
+@file{lib/torture-options.exp} defines procedures to
+set up these lists:
+
+@table @code
+@item torture-init
+Initialize use of torture lists.
+@item set-torture-options
+Set lists of torture options to use for tests with and without loops.
+Optionally combine a set of torture options with a set of other
+options, as is done with Objective-C runtime options.
+@item torture-finish
+Finalize use of torture lists.
+@end table
+
+The @file{.exp} file for a set of tests that use torture options must
+include calls to these three procedures if:
+
+@itemize @bullet
+@item It calls @code{gcc-dg-runtest} and overrides @var{DG_TORTURE_OPTIONS}.
+
+@item It calls @var{$@{tool@}}@code{-torture} or
+@var{$@{tool@}}@code{-torture-execute}, where @var{tool} is @code{c},
+@code{fortran}, or @code{objc}.
+
+@item It calls @code{dg-pch}.
+@end itemize
+
+It is not necessary for a @file{.exp} file that calls @code{gcc-dg-runtest}
+to call the torture procedures if the tests should use the list in
+@var{DG_TORTURE_OPTIONS} defined in @file{gcc-dg.exp}.
+
+Most uses of torture options can override the default lists by defining
+@var{TORTURE_OPTIONS} or add to the default list by defining
+@var{ADDITIONAL_TORTURE_OPTIONS}. Define these in a @file{.dejagnurc}
+file or add them to the @file{site.exp} file; for example
+
+@smallexample
+set ADDITIONAL_TORTURE_OPTIONS [list \
+ @{ -O2 -ftree-loop-linear @} \
+ @{ -O2 -fpeel-loops @} ]
+@end smallexample
+
+@node GIMPLE Tests
+@section Support for testing GIMPLE passes
+
+As of gcc 7, C functions can be tagged with @code{__GIMPLE} to indicate
+that the function body will be GIMPLE, rather than C. The compiler requires
+the option @option{-fgimple} to enable this functionality. For example:
+
+@smallexample
+/* @{ dg-do compile @} */
+/* @{ dg-options "-O -fgimple" @} */
+
+void __GIMPLE (startwith ("dse2")) foo ()
+@{
+ int a;
+
+bb_2:
+ if (a > 4)
+ goto bb_3;
+ else
+ goto bb_4;
+
+bb_3:
+ a_2 = 10;
+ goto bb_5;
+
+bb_4:
+ a_3 = 20;
+
+bb_5:
+ a_1 = __PHI (bb_3: a_2, bb_4: a_3);
+ a_4 = a_1 + 4;
+
+ return;
+@}
+@end smallexample
+
+The @code{startwith} argument indicates at which pass to begin.
+
+Use the dump modifier @code{-gimple} (e.g.@: @option{-fdump-tree-all-gimple})
+to make tree dumps more closely follow the format accepted by the GIMPLE
+parser.
+
+Example DejaGnu tests of GIMPLE can be seen in the source tree at
+@file{gcc/testsuite/gcc.dg/gimplefe-*.c}.
+
+The @code{__GIMPLE} parser is integrated with the C tokenizer and
+preprocessor, so it should be possible to use macros to build out
+test coverage.
+
+@node RTL Tests
+@section Support for testing RTL passes
+
+As of gcc 7, C functions can be tagged with @code{__RTL} to indicate that the
+function body will be RTL, rather than C. For example:
+
+@smallexample
+double __RTL (startwith ("ira")) test (struct foo *f, const struct bar *b)
+@{
+ (function "test"
+ [...snip; various directives go in here...]
+ ) ;; function "test"
+@}
+@end smallexample
+
+The @code{startwith} argument indicates at which pass to begin.
+
+The parser expects the RTL body to be in the format emitted by this
+dumping function:
+
+@smallexample
+DEBUG_FUNCTION void
+print_rtx_function (FILE *outfile, function *fn, bool compact);
+@end smallexample
+
+when "compact" is true. So you can capture RTL in the correct format
+from the debugger using:
+
+@smallexample
+(gdb) print_rtx_function (stderr, cfun, true);
+@end smallexample
+
+and copy and paste the output into the body of the C function.
+
+Example DejaGnu tests of RTL can be seen in the source tree under
+@file{gcc/testsuite/gcc.dg/rtl}.
+
+The @code{__RTL} parser is not integrated with the C tokenizer or
+preprocessor, and works simply by reading the relevant lines within
+the braces. In particular, the RTL body must be on separate lines from
+the enclosing braces, and the preprocessor is not usable within it.
--- /dev/null
+@c Copyright (C) 2000-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Standards
+@chapter Language Standards Supported by GCC
+
+For each language compiled by GCC for which there is a standard, GCC
+attempts to follow one or more versions of that standard, possibly
+with some exceptions, and possibly with some extensions.
+
+@section C Language
+@cindex C standard
+@cindex C standards
+@cindex ANSI C standard
+@cindex ANSI C
+@cindex ANSI C89
+@cindex C89
+@cindex ANSI X3.159-1989
+@cindex X3.159-1989
+@cindex ISO C standard
+@cindex ISO C
+@cindex ISO C90
+@cindex ISO/IEC 9899
+@cindex ISO 9899
+@cindex C90
+@cindex ISO C94
+@cindex C94
+@cindex ISO C95
+@cindex C95
+@cindex ISO C99
+@cindex C99
+@cindex ISO C9X
+@cindex C9X
+@cindex ISO C11
+@cindex C11
+@cindex ISO C1X
+@cindex C1X
+@cindex ISO C17
+@cindex C17
+@cindex ISO C2X
+@cindex C2X
+@cindex Technical Corrigenda
+@cindex TC1
+@cindex Technical Corrigendum 1
+@cindex TC2
+@cindex Technical Corrigendum 2
+@cindex TC3
+@cindex Technical Corrigendum 3
+@cindex AMD1
+@cindex freestanding implementation
+@cindex freestanding environment
+@cindex hosted implementation
+@cindex hosted environment
+@findex __STDC_HOSTED__
+
+@opindex std
+@opindex ansi
+@opindex pedantic
+@opindex pedantic-errors
+The original ANSI C standard (X3.159-1989) was ratified in 1989 and
+published in 1990. This standard was ratified as an ISO standard
+(ISO/IEC 9899:1990) later in 1990. There were no technical
+differences between these publications, although the sections of the
+ANSI standard were renumbered and became clauses in the ISO standard.
+The ANSI
+standard, but not the ISO standard, also came with a Rationale
+document.
+This standard, in both its forms, is commonly known as @dfn{C89}, or
+occasionally as @dfn{C90}, from the dates of ratification.
+To select this standard in GCC, use one of the options
+@option{-ansi}, @option{-std=c90} or @option{-std=iso9899:1990}; to obtain
+all the diagnostics required by the standard, you should also specify
+@option{-pedantic} (or @option{-pedantic-errors} if you want them to be
+errors rather than warnings). @xref{C Dialect Options,,Options
+Controlling C Dialect}.
+
+Errors in the 1990 ISO C standard were corrected in two Technical
+Corrigenda published in 1994 and 1996. GCC does not support the
+uncorrected version.
+
+An amendment to the 1990 standard was published in 1995. This
+amendment added digraphs and @code{__STDC_VERSION__} to the language,
+but otherwise concerned the library. This amendment is commonly known
+as @dfn{AMD1}; the amended standard is sometimes known as @dfn{C94} or
+@dfn{C95}. To select this standard in GCC, use the option
+@option{-std=iso9899:199409} (with, as for other standard versions,
+@option{-pedantic} to receive all required diagnostics).
+
+A new edition of the ISO C standard was published in 1999 as ISO/IEC
+9899:1999, and is commonly known as @dfn{C99}. (While in
+development, drafts of this standard version were referred to as
+@dfn{C9X}.) GCC has substantially
+complete support for this standard version; see
+@uref{https://gcc.gnu.org/c99status.html} for details. To select this
+standard, use @option{-std=c99} or @option{-std=iso9899:1999}.
+
+Errors in the 1999 ISO C standard were corrected in three Technical
+Corrigenda published in 2001, 2004 and 2007. GCC does not support the
+uncorrected version.
+
+A fourth version of the C standard, known as @dfn{C11}, was published
+in 2011 as ISO/IEC 9899:2011. (While in development, drafts of this
+standard version were referred to as @dfn{C1X}.)
+GCC has substantially complete support
+for this standard, enabled with @option{-std=c11} or
+@option{-std=iso9899:2011}. A version with corrections integrated was
+prepared in 2017 and published in 2018 as ISO/IEC 9899:2018; it is
+known as @dfn{C17} and is supported with @option{-std=c17} or
+@option{-std=iso9899:2017}; the corrections are also applied with
+@option{-std=c11}, and the only difference between the options is the
+value of @code{__STDC_VERSION__}.
+
+A further version of the C standard, known as @dfn{C2X}, is under
+development; experimental and incomplete support for this is enabled
+with @option{-std=c2x}.
+
+By default, GCC provides some extensions to the C language that, on
+rare occasions conflict with the C standard. @xref{C
+Extensions,,Extensions to the C Language Family}.
+Some features that are part of the C99 standard
+are accepted as extensions in C90 mode, and some features that are part
+of the C11 standard are accepted as extensions in C90 and C99 modes.
+Use of the
+@option{-std} options listed above disables these extensions where
+they conflict with the C standard version selected. You may also
+select an extended version of the C language explicitly with
+@option{-std=gnu90} (for C90 with GNU extensions), @option{-std=gnu99}
+(for C99 with GNU extensions) or @option{-std=gnu11} (for C11 with GNU
+extensions).
+
+The default, if no C language dialect options are given,
+is @option{-std=gnu17}.
+
+The ISO C standard defines (in clause 4) two classes of conforming
+implementation. A @dfn{conforming hosted implementation} supports the
+whole standard including all the library facilities; a @dfn{conforming
+freestanding implementation} is only required to provide certain
+library facilities: those in @code{<float.h>}, @code{<limits.h>},
+@code{<stdarg.h>}, and @code{<stddef.h>}; since AMD1, also those in
+@code{<iso646.h>}; since C99, also those in @code{<stdbool.h>} and
+@code{<stdint.h>}; and since C11, also those in @code{<stdalign.h>}
+and @code{<stdnoreturn.h>}. In addition, complex types, added in C99, are not
+required for freestanding implementations.
+
+The standard also defines two environments for programs, a
+@dfn{freestanding environment}, required of all implementations and
+which may not have library facilities beyond those required of
+freestanding implementations, where the handling of program startup
+and termination are implementation-defined; and a @dfn{hosted
+environment}, which is not required, in which all the library
+facilities are provided and startup is through a function @code{int
+main (void)} or @code{int main (int, char *[])}. An OS kernel is an example
+of a program running in a freestanding environment;
+a program using the facilities of an
+operating system is an example of a program running in a hosted environment.
+
+@opindex ffreestanding
+GCC aims towards being usable as a conforming freestanding
+implementation, or as the compiler for a conforming hosted
+implementation. By default, it acts as the compiler for a hosted
+implementation, defining @code{__STDC_HOSTED__} as @code{1} and
+presuming that when the names of ISO C functions are used, they have
+the semantics defined in the standard. To make it act as a conforming
+freestanding implementation for a freestanding environment, use the
+option @option{-ffreestanding}; it then defines
+@code{__STDC_HOSTED__} to @code{0} and does not make assumptions about the
+meanings of function names from the standard library, with exceptions
+noted below. To build an OS kernel, you may well still need to make
+your own arrangements for linking and startup.
+@xref{C Dialect Options,,Options Controlling C Dialect}.
+
+GCC does not provide the library facilities required only of hosted
+implementations, nor yet all the facilities required by C99 of
+freestanding implementations on all platforms.
+To use the facilities of a hosted
+environment, you need to find them elsewhere (for example, in the
+GNU C library). @xref{Standard Libraries,,Standard Libraries}.
+
+Most of the compiler support routines used by GCC are present in
+@file{libgcc}, but there are a few exceptions. GCC requires the
+freestanding environment provide @code{memcpy}, @code{memmove},
+@code{memset} and @code{memcmp}.
+Finally, if @code{__builtin_trap} is used, and the target does
+not implement the @code{trap} pattern, then GCC emits a call
+to @code{abort}.
+
+For references to Technical Corrigenda, Rationale documents and
+information concerning the history of C that is available online, see
+@uref{https://gcc.gnu.org/readings.html}
+
+@section C++ Language
+
+GCC supports the original ISO C++ standard published in 1998,
+and the 2011, 2014, 2017 and mostly 2020 revisions.
+
+The original ISO C++ standard was published as the ISO standard (ISO/IEC
+14882:1998) and amended by a Technical Corrigenda published in 2003
+(ISO/IEC 14882:2003). These standards are referred to as C++98 and
+C++03, respectively. GCC implements the majority of C++98 (@code{export}
+is a notable exception) and most of the changes in C++03. To select
+this standard in GCC, use one of the options @option{-ansi},
+@option{-std=c++98}, or @option{-std=c++03}; to obtain all the diagnostics
+required by the standard, you should also specify @option{-pedantic} (or
+@option{-pedantic-errors} if you want them to be errors rather than
+warnings).
+
+A revised ISO C++ standard was published in 2011 as ISO/IEC
+14882:2011, and is referred to as C++11; before its publication it was
+commonly referred to as C++0x. C++11 contains several changes to the
+C++ language, all of which have been implemented in GCC@. For details
+see @uref{https://gcc.gnu.org/projects/@/cxx-status.html#cxx11}.
+To select this standard in GCC, use the option @option{-std=c++11}.
+
+Another revised ISO C++ standard was published in 2014 as ISO/IEC
+14882:2014, and is referred to as C++14; before its publication it was
+sometimes referred to as C++1y. C++14 contains several further
+changes to the C++ language, all of which have been implemented in GCC@.
+For details see @uref{https://gcc.gnu.org/projects/@/cxx-status.html#cxx14}.
+To select this standard in GCC, use the option @option{-std=c++14}.
+
+The C++ language was further revised in 2017 and ISO/IEC 14882:2017 was
+published. This is referred to as C++17, and before publication was
+often referred to as C++1z. GCC supports all the changes in that
+specification. For further details see
+@uref{https://gcc.gnu.org/projects/@/cxx-status.html#cxx17}. Use the option
+@option{-std=c++17} to select this variant of C++.
+
+Another revised ISO C++ standard was published in 2020 as ISO/IEC
+14882:2020, and is referred to as C++20; before its publication it was
+sometimes referred to as C++2a. GCC supports most of the changes in the
+new specification. For further details see
+@uref{https://gcc.gnu.org/projects/@/cxx-status.html#cxx20}.
+To select this standard in GCC, use the option @option{-std=c++20}.
+
+More information about the C++ standards is available on the ISO C++
+committee's web site at @uref{http://www.open-std.org/@/jtc1/@/sc22/@/wg21/}.
+
+To obtain all the diagnostics required by any of the standard versions
+described above you should specify @option{-pedantic}
+or @option{-pedantic-errors}, otherwise GCC will allow some non-ISO C++
+features as extensions. @xref{Warning Options}.
+
+By default, GCC also provides some additional extensions to the C++ language
+that on rare occasions conflict with the C++ standard. @xref{C++
+Dialect Options,Options Controlling C++ Dialect}. Use of the
+@option{-std} options listed above disables these extensions where they
+they conflict with the C++ standard version selected. You may also
+select an extended version of the C++ language explicitly with
+@option{-std=gnu++98} (for C++98 with GNU extensions), or
+@option{-std=gnu++11} (for C++11 with GNU extensions), or
+@option{-std=gnu++14} (for C++14 with GNU extensions), or
+@option{-std=gnu++17} (for C++17 with GNU extensions), or
+@option{-std=gnu++20} (for C++20 with GNU extensions).
+
+The default, if
+no C++ language dialect options are given, is @option{-std=gnu++17}.
+
+@section Objective-C and Objective-C++ Languages
+@cindex Objective-C
+@cindex Objective-C++
+
+GCC supports ``traditional'' Objective-C (also known as ``Objective-C
+1.0'') and contains support for the Objective-C exception and
+synchronization syntax. It has also support for a number of
+``Objective-C 2.0'' language extensions, including properties, fast
+enumeration (only for Objective-C), method attributes and the
+@@optional and @@required keywords in protocols. GCC supports
+Objective-C++ and features available in Objective-C are also available
+in Objective-C++@.
+
+GCC by default uses the GNU Objective-C runtime library, which is part
+of GCC and is not the same as the Apple/NeXT Objective-C runtime
+library used on Apple systems. There are a number of differences
+documented in this manual. The options @option{-fgnu-runtime} and
+@option{-fnext-runtime} allow you to switch between producing output
+that works with the GNU Objective-C runtime library and output that
+works with the Apple/NeXT Objective-C runtime library.
+
+There is no formal written standard for Objective-C or Objective-C++@.
+The authoritative manual on traditional Objective-C (1.0) is
+``Object-Oriented Programming and the Objective-C Language'':
+@uref{http://www.gnustep.org/@/resources/@/documentation/@/ObjectivCBook.pdf}
+is the original NeXTstep document.
+
+The Objective-C exception and synchronization syntax (that is, the
+keywords @code{@@try}, @code{@@throw}, @code{@@catch},
+@code{@@finally} and @code{@@synchronized}) is
+supported by GCC and is enabled with the option
+@option{-fobjc-exceptions}. The syntax is briefly documented in this
+manual and in the Objective-C 2.0 manuals from Apple.
+
+The Objective-C 2.0 language extensions and features are automatically
+enabled; they include properties (via the @code{@@property},
+@code{@@synthesize} and
+@code{@@dynamic keywords}), fast enumeration (not available in
+Objective-C++), attributes for methods (such as @code{deprecated},
+@code{noreturn}, @code{sentinel}, @code{format}),
+the @code{unused} attribute for method arguments, the
+@code{@@package} keyword for instance variables and the @code{@@optional} and
+@code{@@required} keywords in protocols. You can disable all these
+Objective-C 2.0 language extensions with the option
+@option{-fobjc-std=objc1}, which causes the compiler to recognize the
+same Objective-C language syntax recognized by GCC 4.0, and to produce
+an error if one of the new features is used.
+
+GCC has currently no support for non-fragile instance variables.
+
+The authoritative manual on Objective-C 2.0 is available from Apple:
+@itemize
+@item
+@uref{https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/Introduction/Introduction.html}
+@end itemize
+
+For more information concerning the history of Objective-C that is
+available online, see @uref{https://gcc.gnu.org/readings.html}
+
+@section Go Language
+
+As of the GCC 4.7.1 release, GCC supports the Go 1 language standard,
+described at @uref{https://golang.org/doc/go1}.
+
+@section D language
+
+GCC supports the D 2.0 programming language. The D language itself is
+currently defined by its reference implementation and supporting language
+specification, described at @uref{https://dlang.org/spec/spec.html}.
+
+@section References for Other Languages
+
+@xref{Top, GNAT Reference Manual, About This Guide, gnat_rm,
+GNAT Reference Manual}, for information on standard
+conformance and compatibility of the Ada compiler.
+
+@xref{Standards,,Standards, gfortran, The GNU Fortran Compiler}, for details
+of standards supported by GNU Fortran.
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Target Macros
+@chapter Target Description Macros and Functions
+@cindex machine description macros
+@cindex target description macros
+@cindex macros, target description
+@cindex @file{tm.h} macros
+
+In addition to the file @file{@var{machine}.md}, a machine description
+includes a C header file conventionally given the name
+@file{@var{machine}.h} and a C source file named @file{@var{machine}.c}.
+The header file defines numerous macros that convey the information
+about the target machine that does not fit into the scheme of the
+@file{.md} file. The file @file{tm.h} should be a link to
+@file{@var{machine}.h}. The header file @file{config.h} includes
+@file{tm.h} and most compiler source files include @file{config.h}. The
+source file defines a variable @code{targetm}, which is a structure
+containing pointers to functions and data relating to the target
+machine. @file{@var{machine}.c} should also contain their definitions,
+if they are not defined elsewhere in GCC, and other functions called
+through the macros defined in the @file{.h} file.
+
+@menu
+* Target Structure:: The @code{targetm} variable.
+* Driver:: Controlling how the driver runs the compilation passes.
+* Run-time Target:: Defining @samp{-m} options like @option{-m68000} and @option{-m68020}.
+* Per-Function Data:: Defining data structures for per-function information.
+* Storage Layout:: Defining sizes and alignments of data.
+* Type Layout:: Defining sizes and properties of basic user data types.
+* Registers:: Naming and describing the hardware registers.
+* Register Classes:: Defining the classes of hardware registers.
+* Stack and Calling:: Defining which way the stack grows and by how much.
+* Varargs:: Defining the varargs macros.
+* Trampolines:: Code set up at run time to enter a nested function.
+* Library Calls:: Controlling how library routines are implicitly called.
+* Addressing Modes:: Defining addressing modes valid for memory operands.
+* Anchored Addresses:: Defining how @option{-fsection-anchors} should work.
+* Condition Code:: Defining how insns update the condition code.
+* Costs:: Defining relative costs of different operations.
+* Scheduling:: Adjusting the behavior of the instruction scheduler.
+* Sections:: Dividing storage into text, data, and other sections.
+* PIC:: Macros for position independent code.
+* Assembler Format:: Defining how to write insns and pseudo-ops to output.
+* Debugging Info:: Defining the format of debugging output.
+* Floating Point:: Handling floating point for cross-compilers.
+* Mode Switching:: Insertion of mode-switching instructions.
+* Target Attributes:: Defining target-specific uses of @code{__attribute__}.
+* Emulated TLS:: Emulated TLS support.
+* MIPS Coprocessors:: MIPS coprocessor support and how to customize it.
+* PCH Target:: Validity checking for precompiled headers.
+* C++ ABI:: Controlling C++ ABI changes.
+* D Language and ABI:: Controlling D ABI changes.
+* Named Address Spaces:: Adding support for named address spaces
+* Misc:: Everything else.
+@end menu
+
+@node Target Structure
+@section The Global @code{targetm} Variable
+@cindex target hooks
+@cindex target functions
+
+@deftypevar {struct gcc_target} targetm
+The target @file{.c} file must define the global @code{targetm} variable
+which contains pointers to functions and data relating to the target
+machine. The variable is declared in @file{target.h};
+@file{target-def.h} defines the macro @code{TARGET_INITIALIZER} which is
+used to initialize the variable, and macros for the default initializers
+for elements of the structure. The @file{.c} file should override those
+macros for which the default definition is inappropriate. For example:
+@smallexample
+#include "target.h"
+#include "target-def.h"
+
+/* @r{Initialize the GCC target structure.} */
+
+#undef TARGET_COMP_TYPE_ATTRIBUTES
+#define TARGET_COMP_TYPE_ATTRIBUTES @var{machine}_comp_type_attributes
+
+struct gcc_target targetm = TARGET_INITIALIZER;
+@end smallexample
+@end deftypevar
+
+Where a macro should be defined in the @file{.c} file in this manner to
+form part of the @code{targetm} structure, it is documented below as a
+``Target Hook'' with a prototype. Many macros will change in future
+from being defined in the @file{.h} file to being part of the
+@code{targetm} structure.
+
+Similarly, there is a @code{targetcm} variable for hooks that are
+specific to front ends for C-family languages, documented as ``C
+Target Hook''. This is declared in @file{c-family/c-target.h}, the
+initializer @code{TARGETCM_INITIALIZER} in
+@file{c-family/c-target-def.h}. If targets initialize @code{targetcm}
+themselves, they should set @code{target_has_targetcm=yes} in
+@file{config.gcc}; otherwise a default definition is used.
+
+Similarly, there is a @code{targetm_common} variable for hooks that
+are shared between the compiler driver and the compilers proper,
+documented as ``Common Target Hook''. This is declared in
+@file{common/common-target.h}, the initializer
+@code{TARGETM_COMMON_INITIALIZER} in
+@file{common/common-target-def.h}. If targets initialize
+@code{targetm_common} themselves, they should set
+@code{target_has_targetm_common=yes} in @file{config.gcc}; otherwise a
+default definition is used.
+
+Similarly, there is a @code{targetdm} variable for hooks that are
+specific to the D language front end, documented as ``D Target Hook''.
+This is declared in @file{d/d-target.h}, the initializer
+@code{TARGETDM_INITIALIZER} in @file{d/d-target-def.h}. If targets
+initialize @code{targetdm} themselves, they should set
+@code{target_has_targetdm=yes} in @file{config.gcc}; otherwise a default
+definition is used.
+
+@node Driver
+@section Controlling the Compilation Driver, @file{gcc}
+@cindex driver
+@cindex controlling the compilation driver
+
+@c prevent bad page break with this line
+You can control the compilation driver.
+
+@defmac DRIVER_SELF_SPECS
+A list of specs for the driver itself. It should be a suitable
+initializer for an array of strings, with no surrounding braces.
+
+The driver applies these specs to its own command line between loading
+default @file{specs} files (but not command-line specified ones) and
+choosing the multilib directory or running any subcommands. It
+applies them in the order given, so each spec can depend on the
+options added by earlier ones. It is also possible to remove options
+using @samp{%<@var{option}} in the usual way.
+
+This macro can be useful when a port has several interdependent target
+options. It provides a way of standardizing the command line so
+that the other specs are easier to write.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac OPTION_DEFAULT_SPECS
+A list of specs used to support configure-time default options (i.e.@:
+@option{--with} options) in the driver. It should be a suitable initializer
+for an array of structures, each containing two strings, without the
+outermost pair of surrounding braces.
+
+The first item in the pair is the name of the default. This must match
+the code in @file{config.gcc} for the target. The second item is a spec
+to apply if a default with this name was specified. The string
+@samp{%(VALUE)} in the spec will be replaced by the value of the default
+everywhere it occurs.
+
+The driver will apply these specs to its own command line between loading
+default @file{specs} files and processing @code{DRIVER_SELF_SPECS}, using
+the same mechanism as @code{DRIVER_SELF_SPECS}.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac CPP_SPEC
+A C string constant that tells the GCC driver program options to
+pass to CPP@. It can also specify how to translate options you
+give to GCC into options for GCC to pass to the CPP@.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac CPLUSPLUS_CPP_SPEC
+This macro is just like @code{CPP_SPEC}, but is used for C++, rather
+than C@. If you do not define this macro, then the value of
+@code{CPP_SPEC} (if any) will be used instead.
+@end defmac
+
+@defmac CC1_SPEC
+A C string constant that tells the GCC driver program options to
+pass to @code{cc1}, @code{cc1plus}, @code{f771}, and the other language
+front ends.
+It can also specify how to translate options you give to GCC into options
+for GCC to pass to front ends.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac CC1PLUS_SPEC
+A C string constant that tells the GCC driver program options to
+pass to @code{cc1plus}. It can also specify how to translate options you
+give to GCC into options for GCC to pass to the @code{cc1plus}.
+
+Do not define this macro if it does not need to do anything.
+Note that everything defined in CC1_SPEC is already passed to
+@code{cc1plus} so there is no need to duplicate the contents of
+CC1_SPEC in CC1PLUS_SPEC@.
+@end defmac
+
+@defmac ASM_SPEC
+A C string constant that tells the GCC driver program options to
+pass to the assembler. It can also specify how to translate options
+you give to GCC into options for GCC to pass to the assembler.
+See the file @file{sun3.h} for an example of this.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac ASM_FINAL_SPEC
+A C string constant that tells the GCC driver program how to
+run any programs which cleanup after the normal assembler.
+Normally, this is not needed. See the file @file{mips.h} for
+an example of this.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac AS_NEEDS_DASH_FOR_PIPED_INPUT
+Define this macro, with no value, if the driver should give the assembler
+an argument consisting of a single dash, @option{-}, to instruct it to
+read from its standard input (which will be a pipe connected to the
+output of the compiler proper). This argument is given after any
+@option{-o} option specifying the name of the output file.
+
+If you do not define this macro, the assembler is assumed to read its
+standard input if given no non-option arguments. If your assembler
+cannot read standard input at all, use a @samp{%@{pipe:%e@}} construct;
+see @file{mips.h} for instance.
+@end defmac
+
+@defmac LINK_SPEC
+A C string constant that tells the GCC driver program options to
+pass to the linker. It can also specify how to translate options you
+give to GCC into options for GCC to pass to the linker.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac LIB_SPEC
+Another C string constant used much like @code{LINK_SPEC}. The difference
+between the two is that @code{LIB_SPEC} is used at the end of the
+command given to the linker.
+
+If this macro is not defined, a default is provided that
+loads the standard C library from the usual place. See @file{gcc.cc}.
+@end defmac
+
+@defmac LIBGCC_SPEC
+Another C string constant that tells the GCC driver program
+how and when to place a reference to @file{libgcc.a} into the
+linker command line. This constant is placed both before and after
+the value of @code{LIB_SPEC}.
+
+If this macro is not defined, the GCC driver provides a default that
+passes the string @option{-lgcc} to the linker.
+@end defmac
+
+@defmac REAL_LIBGCC_SPEC
+By default, if @code{ENABLE_SHARED_LIBGCC} is defined, the
+@code{LIBGCC_SPEC} is not directly used by the driver program but is
+instead modified to refer to different versions of @file{libgcc.a}
+depending on the values of the command line flags @option{-static},
+@option{-shared}, @option{-static-libgcc}, and @option{-shared-libgcc}. On
+targets where these modifications are inappropriate, define
+@code{REAL_LIBGCC_SPEC} instead. @code{REAL_LIBGCC_SPEC} tells the
+driver how to place a reference to @file{libgcc} on the link command
+line, but, unlike @code{LIBGCC_SPEC}, it is used unmodified.
+@end defmac
+
+@defmac USE_LD_AS_NEEDED
+A macro that controls the modifications to @code{LIBGCC_SPEC}
+mentioned in @code{REAL_LIBGCC_SPEC}. If nonzero, a spec will be
+generated that uses @option{--as-needed} or equivalent options and the
+shared @file{libgcc} in place of the
+static exception handler library, when linking without any of
+@code{-static}, @code{-static-libgcc}, or @code{-shared-libgcc}.
+@end defmac
+
+@defmac LINK_EH_SPEC
+If defined, this C string constant is added to @code{LINK_SPEC}.
+When @code{USE_LD_AS_NEEDED} is zero or undefined, it also affects
+the modifications to @code{LIBGCC_SPEC} mentioned in
+@code{REAL_LIBGCC_SPEC}.
+@end defmac
+
+@defmac STARTFILE_SPEC
+Another C string constant used much like @code{LINK_SPEC}. The
+difference between the two is that @code{STARTFILE_SPEC} is used at
+the very beginning of the command given to the linker.
+
+If this macro is not defined, a default is provided that loads the
+standard C startup file from the usual place. See @file{gcc.cc}.
+@end defmac
+
+@defmac ENDFILE_SPEC
+Another C string constant used much like @code{LINK_SPEC}. The
+difference between the two is that @code{ENDFILE_SPEC} is used at
+the very end of the command given to the linker.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac THREAD_MODEL_SPEC
+GCC @code{-v} will print the thread model GCC was configured to use.
+However, this doesn't work on platforms that are multilibbed on thread
+models, such as AIX 4.3. On such platforms, define
+@code{THREAD_MODEL_SPEC} such that it evaluates to a string without
+blanks that names one of the recognized thread models. @code{%*}, the
+default value of this macro, will expand to the value of
+@code{thread_file} set in @file{config.gcc}.
+@end defmac
+
+@defmac SYSROOT_SUFFIX_SPEC
+Define this macro to add a suffix to the target sysroot when GCC is
+configured with a sysroot. This will cause GCC to search for usr/lib,
+et al, within sysroot+suffix.
+@end defmac
+
+@defmac SYSROOT_HEADERS_SUFFIX_SPEC
+Define this macro to add a headers_suffix to the target sysroot when
+GCC is configured with a sysroot. This will cause GCC to pass the
+updated sysroot+headers_suffix to CPP, causing it to search for
+usr/include, et al, within sysroot+headers_suffix.
+@end defmac
+
+@defmac EXTRA_SPECS
+Define this macro to provide additional specifications to put in the
+@file{specs} file that can be used in various specifications like
+@code{CC1_SPEC}.
+
+The definition should be an initializer for an array of structures,
+containing a string constant, that defines the specification name, and a
+string constant that provides the specification.
+
+Do not define this macro if it does not need to do anything.
+
+@code{EXTRA_SPECS} is useful when an architecture contains several
+related targets, which have various @code{@dots{}_SPECS} which are similar
+to each other, and the maintainer would like one central place to keep
+these definitions.
+
+For example, the PowerPC System V.4 targets use @code{EXTRA_SPECS} to
+define either @code{_CALL_SYSV} when the System V calling sequence is
+used or @code{_CALL_AIX} when the older AIX-based calling sequence is
+used.
+
+The @file{config/rs6000/rs6000.h} target file defines:
+
+@smallexample
+#define EXTRA_SPECS \
+ @{ "cpp_sysv_default", CPP_SYSV_DEFAULT @},
+
+#define CPP_SYS_DEFAULT ""
+@end smallexample
+
+The @file{config/rs6000/sysv.h} target file defines:
+@smallexample
+#undef CPP_SPEC
+#define CPP_SPEC \
+"%@{posix: -D_POSIX_SOURCE @} \
+%@{mcall-sysv: -D_CALL_SYSV @} \
+%@{!mcall-sysv: %(cpp_sysv_default) @} \
+%@{msoft-float: -D_SOFT_FLOAT@} %@{mcpu=403: -D_SOFT_FLOAT@}"
+
+#undef CPP_SYSV_DEFAULT
+#define CPP_SYSV_DEFAULT "-D_CALL_SYSV"
+@end smallexample
+
+while the @file{config/rs6000/eabiaix.h} target file defines
+@code{CPP_SYSV_DEFAULT} as:
+
+@smallexample
+#undef CPP_SYSV_DEFAULT
+#define CPP_SYSV_DEFAULT "-D_CALL_AIX"
+@end smallexample
+@end defmac
+
+@defmac LINK_LIBGCC_SPECIAL_1
+Define this macro if the driver program should find the library
+@file{libgcc.a}. If you do not define this macro, the driver program will pass
+the argument @option{-lgcc} to tell the linker to do the search.
+@end defmac
+
+@defmac LINK_GCC_C_SEQUENCE_SPEC
+The sequence in which libgcc and libc are specified to the linker.
+By default this is @code{%G %L %G}.
+@end defmac
+
+@defmac POST_LINK_SPEC
+Define this macro to add additional steps to be executed after linker.
+The default value of this macro is empty string.
+@end defmac
+
+@defmac LINK_COMMAND_SPEC
+A C string constant giving the complete command line need to execute the
+linker. When you do this, you will need to update your port each time a
+change is made to the link command line within @file{gcc.cc}. Therefore,
+define this macro only if you need to completely redefine the command
+line for invoking the linker and there is no other way to accomplish
+the effect you need. Overriding this macro may be avoidable by overriding
+@code{LINK_GCC_C_SEQUENCE_SPEC} instead.
+@end defmac
+
+@deftypevr {Common Target Hook} bool TARGET_ALWAYS_STRIP_DOTDOT
+True if @file{..} components should always be removed from directory names
+computed relative to GCC's internal directories, false (default) if such
+components should be preserved and directory names containing them passed
+to other tools such as the linker.
+@end deftypevr
+
+@defmac MULTILIB_DEFAULTS
+Define this macro as a C expression for the initializer of an array of
+string to tell the driver program which options are defaults for this
+target and thus do not need to be handled specially when using
+@code{MULTILIB_OPTIONS}.
+
+Do not define this macro if @code{MULTILIB_OPTIONS} is not defined in
+the target makefile fragment or if none of the options listed in
+@code{MULTILIB_OPTIONS} are set by default.
+@xref{Target Fragment}.
+@end defmac
+
+@defmac RELATIVE_PREFIX_NOT_LINKDIR
+Define this macro to tell @command{gcc} that it should only translate
+a @option{-B} prefix into a @option{-L} linker option if the prefix
+indicates an absolute file name.
+@end defmac
+
+@defmac MD_EXEC_PREFIX
+If defined, this macro is an additional prefix to try after
+@code{STANDARD_EXEC_PREFIX}. @code{MD_EXEC_PREFIX} is not searched
+when the compiler is built as a cross
+compiler. If you define @code{MD_EXEC_PREFIX}, then be sure to add it
+to the list of directories used to find the assembler in @file{configure.ac}.
+@end defmac
+
+@defmac STANDARD_STARTFILE_PREFIX
+Define this macro as a C string constant if you wish to override the
+standard choice of @code{libdir} as the default prefix to
+try when searching for startup files such as @file{crt0.o}.
+@code{STANDARD_STARTFILE_PREFIX} is not searched when the compiler
+is built as a cross compiler.
+@end defmac
+
+@defmac STANDARD_STARTFILE_PREFIX_1
+Define this macro as a C string constant if you wish to override the
+standard choice of @code{/lib} as a prefix to try after the default prefix
+when searching for startup files such as @file{crt0.o}.
+@code{STANDARD_STARTFILE_PREFIX_1} is not searched when the compiler
+is built as a cross compiler.
+@end defmac
+
+@defmac STANDARD_STARTFILE_PREFIX_2
+Define this macro as a C string constant if you wish to override the
+standard choice of @code{/lib} as yet another prefix to try after the
+default prefix when searching for startup files such as @file{crt0.o}.
+@code{STANDARD_STARTFILE_PREFIX_2} is not searched when the compiler
+is built as a cross compiler.
+@end defmac
+
+@defmac MD_STARTFILE_PREFIX
+If defined, this macro supplies an additional prefix to try after the
+standard prefixes. @code{MD_EXEC_PREFIX} is not searched when the
+compiler is built as a cross compiler.
+@end defmac
+
+@defmac MD_STARTFILE_PREFIX_1
+If defined, this macro supplies yet another prefix to try after the
+standard prefixes. It is not searched when the compiler is built as a
+cross compiler.
+@end defmac
+
+@defmac INIT_ENVIRONMENT
+Define this macro as a C string constant if you wish to set environment
+variables for programs called by the driver, such as the assembler and
+loader. The driver passes the value of this macro to @code{putenv} to
+initialize the necessary environment variables.
+@end defmac
+
+@defmac LOCAL_INCLUDE_DIR
+Define this macro as a C string constant if you wish to override the
+standard choice of @file{/usr/local/include} as the default prefix to
+try when searching for local header files. @code{LOCAL_INCLUDE_DIR}
+comes before @code{NATIVE_SYSTEM_HEADER_DIR} (set in
+@file{config.gcc}, normally @file{/usr/include}) in the search order.
+
+Cross compilers do not search either @file{/usr/local/include} or its
+replacement.
+@end defmac
+
+@defmac NATIVE_SYSTEM_HEADER_COMPONENT
+The ``component'' corresponding to @code{NATIVE_SYSTEM_HEADER_DIR}.
+See @code{INCLUDE_DEFAULTS}, below, for the description of components.
+If you do not define this macro, no component is used.
+@end defmac
+
+@defmac INCLUDE_DEFAULTS
+Define this macro if you wish to override the entire default search path
+for include files. For a native compiler, the default search path
+usually consists of @code{GCC_INCLUDE_DIR}, @code{LOCAL_INCLUDE_DIR},
+@code{GPLUSPLUS_INCLUDE_DIR}, and
+@code{NATIVE_SYSTEM_HEADER_DIR}. In addition, @code{GPLUSPLUS_INCLUDE_DIR}
+and @code{GCC_INCLUDE_DIR} are defined automatically by @file{Makefile},
+and specify private search areas for GCC@. The directory
+@code{GPLUSPLUS_INCLUDE_DIR} is used only for C++ programs.
+
+The definition should be an initializer for an array of structures.
+Each array element should have four elements: the directory name (a
+string constant), the component name (also a string constant), a flag
+for C++-only directories,
+and a flag showing that the includes in the directory don't need to be
+wrapped in @code{extern @samp{C}} when compiling C++. Mark the end of
+the array with a null element.
+
+The component name denotes what GNU package the include file is part of,
+if any, in all uppercase letters. For example, it might be @samp{GCC}
+or @samp{BINUTILS}. If the package is part of a vendor-supplied
+operating system, code the component name as @samp{0}.
+
+For example, here is the definition used for VAX/VMS:
+
+@smallexample
+#define INCLUDE_DEFAULTS \
+@{ \
+ @{ "GNU_GXX_INCLUDE:", "G++", 1, 1@}, \
+ @{ "GNU_CC_INCLUDE:", "GCC", 0, 0@}, \
+ @{ "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0@}, \
+ @{ ".", 0, 0, 0@}, \
+ @{ 0, 0, 0, 0@} \
+@}
+@end smallexample
+@end defmac
+
+Here is the order of prefixes tried for exec files:
+
+@enumerate
+@item
+Any prefixes specified by the user with @option{-B}.
+
+@item
+The environment variable @code{GCC_EXEC_PREFIX} or, if @code{GCC_EXEC_PREFIX}
+is not set and the compiler has not been installed in the configure-time
+@var{prefix}, the location in which the compiler has actually been installed.
+
+@item
+The directories specified by the environment variable @code{COMPILER_PATH}.
+
+@item
+The macro @code{STANDARD_EXEC_PREFIX}, if the compiler has been installed
+in the configured-time @var{prefix}.
+
+@item
+The location @file{/usr/libexec/gcc/}, but only if this is a native compiler.
+
+@item
+The location @file{/usr/lib/gcc/}, but only if this is a native compiler.
+
+@item
+The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native
+compiler.
+@end enumerate
+
+Here is the order of prefixes tried for startfiles:
+
+@enumerate
+@item
+Any prefixes specified by the user with @option{-B}.
+
+@item
+The environment variable @code{GCC_EXEC_PREFIX} or its automatically determined
+value based on the installed toolchain location.
+
+@item
+The directories specified by the environment variable @code{LIBRARY_PATH}
+(or port-specific name; native only, cross compilers do not use this).
+
+@item
+The macro @code{STANDARD_EXEC_PREFIX}, but only if the toolchain is installed
+in the configured @var{prefix} or this is a native compiler.
+
+@item
+The location @file{/usr/lib/gcc/}, but only if this is a native compiler.
+
+@item
+The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native
+compiler.
+
+@item
+The macro @code{MD_STARTFILE_PREFIX}, if defined, but only if this is a
+native compiler, or we have a target system root.
+
+@item
+The macro @code{MD_STARTFILE_PREFIX_1}, if defined, but only if this is a
+native compiler, or we have a target system root.
+
+@item
+The macro @code{STANDARD_STARTFILE_PREFIX}, with any sysroot modifications.
+If this path is relative it will be prefixed by @code{GCC_EXEC_PREFIX} and
+the machine suffix or @code{STANDARD_EXEC_PREFIX} and the machine suffix.
+
+@item
+The macro @code{STANDARD_STARTFILE_PREFIX_1}, but only if this is a native
+compiler, or we have a target system root. The default for this macro is
+@file{/lib/}.
+
+@item
+The macro @code{STANDARD_STARTFILE_PREFIX_2}, but only if this is a native
+compiler, or we have a target system root. The default for this macro is
+@file{/usr/lib/}.
+@end enumerate
+
+@node Run-time Target
+@section Run-time Target Specification
+@cindex run-time target specification
+@cindex predefined macros
+@cindex target specifications
+
+@c prevent bad page break with this line
+Here are run-time target specifications.
+
+@defmac TARGET_CPU_CPP_BUILTINS ()
+This function-like macro expands to a block of code that defines
+built-in preprocessor macros and assertions for the target CPU, using
+the functions @code{builtin_define}, @code{builtin_define_std} and
+@code{builtin_assert}. When the front end
+calls this macro it provides a trailing semicolon, and since it has
+finished command line option processing your code can use those
+results freely.
+
+@code{builtin_assert} takes a string in the form you pass to the
+command-line option @option{-A}, such as @code{cpu=mips}, and creates
+the assertion. @code{builtin_define} takes a string in the form
+accepted by option @option{-D} and unconditionally defines the macro.
+
+@code{builtin_define_std} takes a string representing the name of an
+object-like macro. If it doesn't lie in the user's namespace,
+@code{builtin_define_std} defines it unconditionally. Otherwise, it
+defines a version with two leading underscores, and another version
+with two leading and trailing underscores, and defines the original
+only if an ISO standard was not requested on the command line. For
+example, passing @code{unix} defines @code{__unix}, @code{__unix__}
+and possibly @code{unix}; passing @code{_mips} defines @code{__mips},
+@code{__mips__} and possibly @code{_mips}, and passing @code{_ABI64}
+defines only @code{_ABI64}.
+
+You can also test for the C dialect being compiled. The variable
+@code{c_language} is set to one of @code{clk_c}, @code{clk_cplusplus}
+or @code{clk_objective_c}. Note that if we are preprocessing
+assembler, this variable will be @code{clk_c} but the function-like
+macro @code{preprocessing_asm_p()} will return true, so you might want
+to check for that first. If you need to check for strict ANSI, the
+variable @code{flag_iso} can be used. The function-like macro
+@code{preprocessing_trad_p()} can be used to check for traditional
+preprocessing.
+@end defmac
+
+@defmac TARGET_OS_CPP_BUILTINS ()
+Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional
+and is used for the target operating system instead.
+@end defmac
+
+@defmac TARGET_OBJFMT_CPP_BUILTINS ()
+Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional
+and is used for the target object format. @file{elfos.h} uses this
+macro to define @code{__ELF__}, so you probably do not need to define
+it yourself.
+@end defmac
+
+@deftypevar {extern int} target_flags
+This variable is declared in @file{options.h}, which is included before
+any target-specific headers.
+@end deftypevar
+
+@deftypevr {Common Target Hook} int TARGET_DEFAULT_TARGET_FLAGS
+This variable specifies the initial value of @code{target_flags}.
+Its default setting is 0.
+@end deftypevr
+
+@cindex optional hardware or system features
+@cindex features, optional, in system conventions
+
+@deftypefn {Common Target Hook} bool TARGET_HANDLE_OPTION (struct gcc_options *@var{opts}, struct gcc_options *@var{opts_set}, const struct cl_decoded_option *@var{decoded}, location_t @var{loc})
+This hook is called whenever the user specifies one of the
+target-specific options described by the @file{.opt} definition files
+(@pxref{Options}). It has the opportunity to do some option-specific
+processing and should return true if the option is valid. The default
+definition does nothing but return true.
+
+@var{decoded} specifies the option and its arguments. @var{opts} and
+@var{opts_set} are the @code{gcc_options} structures to be used for
+storing option state, and @var{loc} is the location at which the
+option was passed (@code{UNKNOWN_LOCATION} except for options passed
+via attributes).
+@end deftypefn
+
+@deftypefn {C Target Hook} bool TARGET_HANDLE_C_OPTION (size_t @var{code}, const char *@var{arg}, int @var{value})
+This target hook is called whenever the user specifies one of the
+target-specific C language family options described by the @file{.opt}
+definition files(@pxref{Options}). It has the opportunity to do some
+option-specific processing and should return true if the option is
+valid. The arguments are like for @code{TARGET_HANDLE_OPTION}. The
+default definition does nothing but return false.
+
+In general, you should use @code{TARGET_HANDLE_OPTION} to handle
+options. However, if processing an option requires routines that are
+only available in the C (and related language) front ends, then you
+should use @code{TARGET_HANDLE_C_OPTION} instead.
+@end deftypefn
+
+@deftypefn {C Target Hook} tree TARGET_OBJC_CONSTRUCT_STRING_OBJECT (tree @var{string})
+Targets may provide a string object type that can be used within
+and between C, C++ and their respective Objective-C dialects.
+A string object might, for example, embed encoding and length information.
+These objects are considered opaque to the compiler and handled as references.
+An ideal implementation makes the composition of the string object
+match that of the Objective-C @code{NSString} (@code{NXString} for GNUStep),
+allowing efficient interworking between C-only and Objective-C code.
+If a target implements string objects then this hook should return a
+reference to such an object constructed from the normal `C' string
+representation provided in @var{string}.
+At present, the hook is used by Objective-C only, to obtain a
+ common-format string object when the target provides one.
+@end deftypefn
+
+@deftypefn {C Target Hook} void TARGET_OBJC_DECLARE_UNRESOLVED_CLASS_REFERENCE (const char *@var{classname})
+Declare that Objective C class @var{classname} is referenced
+by the current TU.
+@end deftypefn
+
+@deftypefn {C Target Hook} void TARGET_OBJC_DECLARE_CLASS_DEFINITION (const char *@var{classname})
+Declare that Objective C class @var{classname} is defined
+by the current TU.
+@end deftypefn
+
+@deftypefn {C Target Hook} bool TARGET_STRING_OBJECT_REF_TYPE_P (const_tree @var{stringref})
+If a target implements string objects then this hook should return
+@code{true} if @var{stringref} is a valid reference to such an object.
+@end deftypefn
+
+@deftypefn {C Target Hook} void TARGET_CHECK_STRING_OBJECT_FORMAT_ARG (tree @var{format_arg}, tree @var{args_list})
+If a target implements string objects then this hook should
+provide a facility to check the function arguments in @var{args_list}
+against the format specifiers in @var{format_arg} where the type of
+@var{format_arg} is one recognized as a valid string reference type.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE (void)
+This target function is similar to the hook @code{TARGET_OPTION_OVERRIDE}
+but is called when the optimize level is changed via an attribute or
+pragma or when it is reset at the end of the code affected by the
+attribute or pragma. It is not called at the beginning of compilation
+when @code{TARGET_OPTION_OVERRIDE} is called so if you want to perform these
+actions then, you should have @code{TARGET_OPTION_OVERRIDE} call
+@code{TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE}.
+@end deftypefn
+
+@defmac C_COMMON_OVERRIDE_OPTIONS
+This is similar to the @code{TARGET_OPTION_OVERRIDE} hook
+but is only used in the C
+language frontends (C, Objective-C, C++, Objective-C++) and so can be
+used to alter option flag variables which only exist in those
+frontends.
+@end defmac
+
+@deftypevr {Common Target Hook} {const struct default_options *} TARGET_OPTION_OPTIMIZATION_TABLE
+Some machines may desire to change what optimizations are performed for
+various optimization levels. This variable, if defined, describes
+options to enable at particular sets of optimization levels. These
+options are processed once
+just after the optimization level is determined and before the remainder
+of the command options have been parsed, so may be overridden by other
+options passed explicitly.
+
+This processing is run once at program startup and when the optimization
+options are changed via @code{#pragma GCC optimize} or by using the
+@code{optimize} attribute.
+@end deftypevr
+
+@deftypefn {Common Target Hook} void TARGET_OPTION_INIT_STRUCT (struct gcc_options *@var{opts})
+Set target-dependent initial values of fields in @var{opts}.
+@end deftypefn
+
+@deftypefn {Common Target Hook} {const char *} TARGET_COMPUTE_MULTILIB (const struct switchstr *@var{switches}, int @var{n_switches}, const char *@var{multilib_dir}, const char *@var{multilib_defaults}, const char *@var{multilib_select}, const char *@var{multilib_matches}, const char *@var{multilib_exclusions}, const char *@var{multilib_reuse})
+Some targets like RISC-V might have complicated multilib reuse rules which
+are hard to implement with the current multilib scheme. This hook allows
+targets to override the result from the built-in multilib mechanism.
+@var{switches} is the raw option list with @var{n_switches} items;
+@var{multilib_dir} is the multi-lib result which is computed by the built-in
+multi-lib mechanism;
+@var{multilib_defaults} is the default options list for multi-lib;
+@var{multilib_select} is the string containing the list of supported
+multi-libs, and the option checking list.
+@var{multilib_matches}, @var{multilib_exclusions}, and @var{multilib_reuse}
+are corresponding to @var{MULTILIB_MATCHES}, @var{MULTILIB_EXCLUSIONS},
+and @var{MULTILIB_REUSE}.
+The default definition does nothing but return @var{multilib_dir} directly.
+@end deftypefn
+
+
+@defmac SWITCHABLE_TARGET
+Some targets need to switch between substantially different subtargets
+during compilation. For example, the MIPS target has one subtarget for
+the traditional MIPS architecture and another for MIPS16. Source code
+can switch between these two subarchitectures using the @code{mips16}
+and @code{nomips16} attributes.
+
+Such subtargets can differ in things like the set of available
+registers, the set of available instructions, the costs of various
+operations, and so on. GCC caches a lot of this type of information
+in global variables, and recomputing them for each subtarget takes a
+significant amount of time. The compiler therefore provides a facility
+for maintaining several versions of the global variables and quickly
+switching between them; see @file{target-globals.h} for details.
+
+Define this macro to 1 if your target needs this facility. The default
+is 0.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_FLOAT_EXCEPTIONS_ROUNDING_SUPPORTED_P (void)
+Returns true if the target supports IEEE 754 floating-point exceptions
+and rounding modes, false otherwise. This is intended to relate to the
+@code{float} and @code{double} types, but not necessarily @code{long double}.
+By default, returns true if the @code{adddf3} instruction pattern is
+available and false otherwise, on the assumption that hardware floating
+point supports exceptions and rounding modes but software floating point
+does not.
+@end deftypefn
+
+@node Per-Function Data
+@section Defining data structures for per-function information.
+@cindex per-function data
+@cindex data structures
+
+If the target needs to store information on a per-function basis, GCC
+provides a macro and a couple of variables to allow this. Note, just
+using statics to store the information is a bad idea, since GCC supports
+nested functions, so you can be halfway through encoding one function
+when another one comes along.
+
+GCC defines a data structure called @code{struct function} which
+contains all of the data specific to an individual function. This
+structure contains a field called @code{machine} whose type is
+@code{struct machine_function *}, which can be used by targets to point
+to their own specific data.
+
+If a target needs per-function specific data it should define the type
+@code{struct machine_function} and also the macro @code{INIT_EXPANDERS}.
+This macro should be used to initialize the function pointer
+@code{init_machine_status}. This pointer is explained below.
+
+One typical use of per-function, target specific data is to create an
+RTX to hold the register containing the function's return address. This
+RTX can then be used to implement the @code{__builtin_return_address}
+function, for level 0.
+
+Note---earlier implementations of GCC used a single data area to hold
+all of the per-function information. Thus when processing of a nested
+function began the old per-function data had to be pushed onto a
+stack, and when the processing was finished, it had to be popped off the
+stack. GCC used to provide function pointers called
+@code{save_machine_status} and @code{restore_machine_status} to handle
+the saving and restoring of the target specific information. Since the
+single data area approach is no longer used, these pointers are no
+longer supported.
+
+@defmac INIT_EXPANDERS
+Macro called to initialize any target specific information. This macro
+is called once per function, before generation of any RTL has begun.
+The intention of this macro is to allow the initialization of the
+function pointer @code{init_machine_status}.
+@end defmac
+
+@deftypevar {void (*)(struct function *)} init_machine_status
+If this function pointer is non-@code{NULL} it will be called once per
+function, before function compilation starts, in order to allow the
+target to perform any target specific initialization of the
+@code{struct function} structure. It is intended that this would be
+used to initialize the @code{machine} of that structure.
+
+@code{struct machine_function} structures are expected to be freed by GC@.
+Generally, any memory that they reference must be allocated by using
+GC allocation, including the structure itself.
+@end deftypevar
+
+@node Storage Layout
+@section Storage Layout
+@cindex storage layout
+
+Note that the definitions of the macros in this table which are sizes or
+alignments measured in bits do not need to be constant. They can be C
+expressions that refer to static variables, such as the @code{target_flags}.
+@xref{Run-time Target}.
+
+@defmac BITS_BIG_ENDIAN
+Define this macro to have the value 1 if the most significant bit in a
+byte has the lowest number; otherwise define it to have the value zero.
+This means that bit-field instructions count from the most significant
+bit. If the machine has no bit-field instructions, then this must still
+be defined, but it doesn't matter which value it is defined to. This
+macro need not be a constant.
+
+This macro does not affect the way structure fields are packed into
+bytes or words; that is controlled by @code{BYTES_BIG_ENDIAN}.
+@end defmac
+
+@defmac BYTES_BIG_ENDIAN
+Define this macro to have the value 1 if the most significant byte in a
+word has the lowest number. This macro need not be a constant.
+@end defmac
+
+@defmac WORDS_BIG_ENDIAN
+Define this macro to have the value 1 if, in a multiword object, the
+most significant word has the lowest number. This applies to both
+memory locations and registers; see @code{REG_WORDS_BIG_ENDIAN} if the
+order of words in memory is not the same as the order in registers. This
+macro need not be a constant.
+@end defmac
+
+@defmac REG_WORDS_BIG_ENDIAN
+On some machines, the order of words in a multiword object differs between
+registers in memory. In such a situation, define this macro to describe
+the order of words in a register. The macro @code{WORDS_BIG_ENDIAN} controls
+the order of words in memory.
+@end defmac
+
+@defmac FLOAT_WORDS_BIG_ENDIAN
+Define this macro to have the value 1 if @code{DFmode}, @code{XFmode} or
+@code{TFmode} floating point numbers are stored in memory with the word
+containing the sign bit at the lowest address; otherwise define it to
+have the value 0. This macro need not be a constant.
+
+You need not define this macro if the ordering is the same as for
+multi-word integers.
+@end defmac
+
+@defmac BITS_PER_WORD
+Number of bits in a word. If you do not define this macro, the default
+is @code{BITS_PER_UNIT * UNITS_PER_WORD}.
+@end defmac
+
+@defmac MAX_BITS_PER_WORD
+Maximum number of bits in a word. If this is undefined, the default is
+@code{BITS_PER_WORD}. Otherwise, it is the constant value that is the
+largest value that @code{BITS_PER_WORD} can have at run-time.
+@end defmac
+
+@defmac UNITS_PER_WORD
+Number of storage units in a word; normally the size of a general-purpose
+register, a power of two from 1 or 8.
+@end defmac
+
+@defmac MIN_UNITS_PER_WORD
+Minimum number of units in a word. If this is undefined, the default is
+@code{UNITS_PER_WORD}. Otherwise, it is the constant value that is the
+smallest value that @code{UNITS_PER_WORD} can have at run-time.
+@end defmac
+
+@defmac POINTER_SIZE
+Width of a pointer, in bits. You must specify a value no wider than the
+width of @code{Pmode}. If it is not equal to the width of @code{Pmode},
+you must define @code{POINTERS_EXTEND_UNSIGNED}. If you do not specify
+a value the default is @code{BITS_PER_WORD}.
+@end defmac
+
+@defmac POINTERS_EXTEND_UNSIGNED
+A C expression that determines how pointers should be extended from
+@code{ptr_mode} to either @code{Pmode} or @code{word_mode}. It is
+greater than zero if pointers should be zero-extended, zero if they
+should be sign-extended, and negative if some other sort of conversion
+is needed. In the last case, the extension is done by the target's
+@code{ptr_extend} instruction.
+
+You need not define this macro if the @code{ptr_mode}, @code{Pmode}
+and @code{word_mode} are all the same width.
+@end defmac
+
+@defmac PROMOTE_MODE (@var{m}, @var{unsignedp}, @var{type})
+A macro to update @var{m} and @var{unsignedp} when an object whose type
+is @var{type} and which has the specified mode and signedness is to be
+stored in a register. This macro is only called when @var{type} is a
+scalar type.
+
+On most RISC machines, which only have operations that operate on a full
+register, define this macro to set @var{m} to @code{word_mode} if
+@var{m} is an integer mode narrower than @code{BITS_PER_WORD}. In most
+cases, only integer modes should be widened because wider-precision
+floating-point operations are usually more expensive than their narrower
+counterparts.
+
+For most machines, the macro definition does not change @var{unsignedp}.
+However, some machines, have instructions that preferentially handle
+either signed or unsigned quantities of certain modes. For example, on
+the DEC Alpha, 32-bit loads from memory and 32-bit add instructions
+sign-extend the result to 64 bits. On such machines, set
+@var{unsignedp} according to which kind of extension is more efficient.
+
+Do not define this macro if it would never modify @var{m}.
+@end defmac
+
+@deftypefn {Target Hook} {enum flt_eval_method} TARGET_C_EXCESS_PRECISION (enum excess_precision_type @var{type})
+Return a value, with the same meaning as the C99 macro
+@code{FLT_EVAL_METHOD} that describes which excess precision should be
+applied. @var{type} is either @code{EXCESS_PRECISION_TYPE_IMPLICIT},
+@code{EXCESS_PRECISION_TYPE_FAST},
+@code{EXCESS_PRECISION_TYPE_STANDARD}, or
+@code{EXCESS_PRECISION_TYPE_FLOAT16}. For
+@code{EXCESS_PRECISION_TYPE_IMPLICIT}, the target should return which
+precision and range operations will be implictly evaluated in regardless
+of the excess precision explicitly added. For
+@code{EXCESS_PRECISION_TYPE_STANDARD},
+@code{EXCESS_PRECISION_TYPE_FLOAT16}, and
+@code{EXCESS_PRECISION_TYPE_FAST}, the target should return the
+explicit excess precision that should be added depending on the
+value set for @option{-fexcess-precision=@r{[}standard@r{|}fast@r{|}16@r{]}}.
+Note that unpredictable explicit excess precision does not make sense,
+so a target should never return @code{FLT_EVAL_METHOD_UNPREDICTABLE}
+when @var{type} is @code{EXCESS_PRECISION_TYPE_STANDARD},
+@code{EXCESS_PRECISION_TYPE_FLOAT16} or
+@code{EXCESS_PRECISION_TYPE_FAST}.
+@end deftypefn
+Return a value, with the same meaning as the C99 macro
+@code{FLT_EVAL_METHOD} that describes which excess precision should be
+applied.
+
+@deftypefn {Target Hook} machine_mode TARGET_PROMOTE_FUNCTION_MODE (const_tree @var{type}, machine_mode @var{mode}, int *@var{punsignedp}, const_tree @var{funtype}, int @var{for_return})
+Like @code{PROMOTE_MODE}, but it is applied to outgoing function arguments or
+function return values. The target hook should return the new mode
+and possibly change @code{*@var{punsignedp}} if the promotion should
+change signedness. This function is called only for scalar @emph{or
+pointer} types.
+
+@var{for_return} allows to distinguish the promotion of arguments and
+return values. If it is @code{1}, a return value is being promoted and
+@code{TARGET_FUNCTION_VALUE} must perform the same promotions done here.
+If it is @code{2}, the returned mode should be that of the register in
+which an incoming parameter is copied, or the outgoing result is computed;
+then the hook should return the same mode as @code{promote_mode}, though
+the signedness may be different.
+
+@var{type} can be NULL when promoting function arguments of libcalls.
+
+The default is to not promote arguments and return values. You can
+also define the hook to @code{default_promote_function_mode_always_promote}
+if you would like to apply the same rules given by @code{PROMOTE_MODE}.
+@end deftypefn
+
+@defmac PARM_BOUNDARY
+Normal alignment required for function parameters on the stack, in
+bits. All stack parameters receive at least this much alignment
+regardless of data type. On most machines, this is the same as the
+size of an integer.
+@end defmac
+
+@defmac STACK_BOUNDARY
+Define this macro to the minimum alignment enforced by hardware for the
+stack pointer on this machine. The definition is a C expression for the
+desired alignment (measured in bits). This value is used as a default
+if @code{PREFERRED_STACK_BOUNDARY} is not defined. On most machines,
+this should be the same as @code{PARM_BOUNDARY}.
+@end defmac
+
+@defmac PREFERRED_STACK_BOUNDARY
+Define this macro if you wish to preserve a certain alignment for the
+stack pointer, greater than what the hardware enforces. The definition
+is a C expression for the desired alignment (measured in bits). This
+macro must evaluate to a value equal to or larger than
+@code{STACK_BOUNDARY}.
+@end defmac
+
+@defmac INCOMING_STACK_BOUNDARY
+Define this macro if the incoming stack boundary may be different
+from @code{PREFERRED_STACK_BOUNDARY}. This macro must evaluate
+to a value equal to or larger than @code{STACK_BOUNDARY}.
+@end defmac
+
+@defmac FUNCTION_BOUNDARY
+Alignment required for a function entry point, in bits.
+@end defmac
+
+@defmac BIGGEST_ALIGNMENT
+Biggest alignment that any data type can require on this machine, in
+bits. Note that this is not the biggest alignment that is supported,
+just the biggest alignment that, when violated, may cause a fault.
+@end defmac
+
+@deftypevr {Target Hook} HOST_WIDE_INT TARGET_ABSOLUTE_BIGGEST_ALIGNMENT
+If defined, this target hook specifies the absolute biggest alignment
+that a type or variable can have on this machine, otherwise,
+@code{BIGGEST_ALIGNMENT} is used.
+@end deftypevr
+
+@defmac MALLOC_ABI_ALIGNMENT
+Alignment, in bits, a C conformant malloc implementation has to
+provide. If not defined, the default value is @code{BITS_PER_WORD}.
+@end defmac
+
+@defmac ATTRIBUTE_ALIGNED_VALUE
+Alignment used by the @code{__attribute__ ((aligned))} construct. If
+not defined, the default value is @code{BIGGEST_ALIGNMENT}.
+@end defmac
+
+@defmac MINIMUM_ATOMIC_ALIGNMENT
+If defined, the smallest alignment, in bits, that can be given to an
+object that can be referenced in one operation, without disturbing any
+nearby object. Normally, this is @code{BITS_PER_UNIT}, but may be larger
+on machines that don't have byte or half-word store operations.
+@end defmac
+
+@defmac BIGGEST_FIELD_ALIGNMENT
+Biggest alignment that any structure or union field can require on this
+machine, in bits. If defined, this overrides @code{BIGGEST_ALIGNMENT} for
+structure and union fields only, unless the field alignment has been set
+by the @code{__attribute__ ((aligned (@var{n})))} construct.
+@end defmac
+
+@defmac ADJUST_FIELD_ALIGN (@var{field}, @var{type}, @var{computed})
+An expression for the alignment of a structure field @var{field} of
+type @var{type} if the alignment computed in the usual way (including
+applying of @code{BIGGEST_ALIGNMENT} and @code{BIGGEST_FIELD_ALIGNMENT} to the
+alignment) is @var{computed}. It overrides alignment only if the
+field alignment has not been set by the
+@code{__attribute__ ((aligned (@var{n})))} construct. Note that @var{field}
+may be @code{NULL_TREE} in case we just query for the minimum alignment
+of a field of type @var{type} in structure context.
+@end defmac
+
+@defmac MAX_STACK_ALIGNMENT
+Biggest stack alignment guaranteed by the backend. Use this macro
+to specify the maximum alignment of a variable on stack.
+
+If not defined, the default value is @code{STACK_BOUNDARY}.
+
+@c FIXME: The default should be @code{PREFERRED_STACK_BOUNDARY}.
+@c But the fix for PR 32893 indicates that we can only guarantee
+@c maximum stack alignment on stack up to @code{STACK_BOUNDARY}, not
+@c @code{PREFERRED_STACK_BOUNDARY}, if stack alignment isn't supported.
+@end defmac
+
+@defmac MAX_OFILE_ALIGNMENT
+Biggest alignment supported by the object file format of this machine.
+Use this macro to limit the alignment which can be specified using the
+@code{__attribute__ ((aligned (@var{n})))} construct for functions and
+objects with static storage duration. The alignment of automatic
+objects may exceed the object file format maximum up to the maximum
+supported by GCC. If not defined, the default value is
+@code{BIGGEST_ALIGNMENT}.
+
+On systems that use ELF, the default (in @file{config/elfos.h}) is
+the largest supported 32-bit ELF section alignment representable on
+a 32-bit host e.g.@: @samp{(((uint64_t) 1 << 28) * 8)}.
+On 32-bit ELF the largest supported section alignment in bits is
+@samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_LOWER_LOCAL_DECL_ALIGNMENT (tree @var{decl})
+Define this hook to lower alignment of local, parm or result
+decl @samp{(@var{decl})}.
+@end deftypefn
+
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_STATIC_RTX_ALIGNMENT (machine_mode @var{mode})
+This hook returns the preferred alignment in bits for a
+statically-allocated rtx, such as a constant pool entry. @var{mode}
+is the mode of the rtx. The default implementation returns
+@samp{GET_MODE_ALIGNMENT (@var{mode})}.
+@end deftypefn
+
+@defmac DATA_ALIGNMENT (@var{type}, @var{basic-align})
+If defined, a C expression to compute the alignment for a variable in
+the static store. @var{type} is the data type, and @var{basic-align} is
+the alignment that the object would ordinarily have. The value of this
+macro is used instead of that alignment to align the object.
+
+If this macro is not defined, then @var{basic-align} is used.
+
+@findex strcpy
+One use of this macro is to increase alignment of medium-size data to
+make it all fit in fewer cache lines. Another is to cause character
+arrays to be word-aligned so that @code{strcpy} calls that copy
+constants to character arrays can be done inline.
+@end defmac
+
+@defmac DATA_ABI_ALIGNMENT (@var{type}, @var{basic-align})
+Similar to @code{DATA_ALIGNMENT}, but for the cases where the ABI mandates
+some alignment increase, instead of optimization only purposes. E.g.@
+AMD x86-64 psABI says that variables with array type larger than 15 bytes
+must be aligned to 16 byte boundaries.
+
+If this macro is not defined, then @var{basic-align} is used.
+@end defmac
+
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_CONSTANT_ALIGNMENT (const_tree @var{constant}, HOST_WIDE_INT @var{basic_align})
+This hook returns the alignment in bits of a constant that is being
+placed in memory. @var{constant} is the constant and @var{basic_align}
+is the alignment that the object would ordinarily have.
+
+The default definition just returns @var{basic_align}.
+
+The typical use of this hook is to increase alignment for string
+constants to be word aligned so that @code{strcpy} calls that copy
+constants can be done inline. The function
+@code{constant_alignment_word_strings} provides such a definition.
+@end deftypefn
+
+@defmac LOCAL_ALIGNMENT (@var{type}, @var{basic-align})
+If defined, a C expression to compute the alignment for a variable in
+the local store. @var{type} is the data type, and @var{basic-align} is
+the alignment that the object would ordinarily have. The value of this
+macro is used instead of that alignment to align the object.
+
+If this macro is not defined, then @var{basic-align} is used.
+
+One use of this macro is to increase alignment of medium-size data to
+make it all fit in fewer cache lines.
+
+If the value of this macro has a type, it should be an unsigned type.
+@end defmac
+
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_VECTOR_ALIGNMENT (const_tree @var{type})
+This hook can be used to define the alignment for a vector of type
+@var{type}, in order to comply with a platform ABI. The default is to
+require natural alignment for vector types. The alignment returned by
+this hook must be a power-of-two multiple of the default alignment of
+the vector element type.
+@end deftypefn
+
+@defmac STACK_SLOT_ALIGNMENT (@var{type}, @var{mode}, @var{basic-align})
+If defined, a C expression to compute the alignment for stack slot.
+@var{type} is the data type, @var{mode} is the widest mode available,
+and @var{basic-align} is the alignment that the slot would ordinarily
+have. The value of this macro is used instead of that alignment to
+align the slot.
+
+If this macro is not defined, then @var{basic-align} is used when
+@var{type} is @code{NULL}. Otherwise, @code{LOCAL_ALIGNMENT} will
+be used.
+
+This macro is to set alignment of stack slot to the maximum alignment
+of all possible modes which the slot may have.
+
+If the value of this macro has a type, it should be an unsigned type.
+@end defmac
+
+@defmac LOCAL_DECL_ALIGNMENT (@var{decl})
+If defined, a C expression to compute the alignment for a local
+variable @var{decl}.
+
+If this macro is not defined, then
+@code{LOCAL_ALIGNMENT (TREE_TYPE (@var{decl}), DECL_ALIGN (@var{decl}))}
+is used.
+
+One use of this macro is to increase alignment of medium-size data to
+make it all fit in fewer cache lines.
+
+If the value of this macro has a type, it should be an unsigned type.
+@end defmac
+
+@defmac MINIMUM_ALIGNMENT (@var{exp}, @var{mode}, @var{align})
+If defined, a C expression to compute the minimum required alignment
+for dynamic stack realignment purposes for @var{exp} (a type or decl),
+@var{mode}, assuming normal alignment @var{align}.
+
+If this macro is not defined, then @var{align} will be used.
+@end defmac
+
+@defmac EMPTY_FIELD_BOUNDARY
+Alignment in bits to be given to a structure bit-field that follows an
+empty field such as @code{int : 0;}.
+
+If @code{PCC_BITFIELD_TYPE_MATTERS} is true, it overrides this macro.
+@end defmac
+
+@defmac STRUCTURE_SIZE_BOUNDARY
+Number of bits which any structure or union's size must be a multiple of.
+Each structure or union's size is rounded up to a multiple of this.
+
+If you do not define this macro, the default is the same as
+@code{BITS_PER_UNIT}.
+@end defmac
+
+@defmac STRICT_ALIGNMENT
+Define this macro to be the value 1 if instructions will fail to work
+if given data not on the nominal alignment. If instructions will merely
+go slower in that case, define this macro as 0.
+@end defmac
+
+@defmac PCC_BITFIELD_TYPE_MATTERS
+Define this if you wish to imitate the way many other C compilers handle
+alignment of bit-fields and the structures that contain them.
+
+The behavior is that the type written for a named bit-field (@code{int},
+@code{short}, or other integer type) imposes an alignment for the entire
+structure, as if the structure really did contain an ordinary field of
+that type. In addition, the bit-field is placed within the structure so
+that it would fit within such a field, not crossing a boundary for it.
+
+Thus, on most machines, a named bit-field whose type is written as
+@code{int} would not cross a four-byte boundary, and would force
+four-byte alignment for the whole structure. (The alignment used may
+not be four bytes; it is controlled by the other alignment parameters.)
+
+An unnamed bit-field will not affect the alignment of the containing
+structure.
+
+If the macro is defined, its definition should be a C expression;
+a nonzero value for the expression enables this behavior.
+
+Note that if this macro is not defined, or its value is zero, some
+bit-fields may cross more than one alignment boundary. The compiler can
+support such references if there are @samp{insv}, @samp{extv}, and
+@samp{extzv} insns that can directly reference memory.
+
+The other known way of making bit-fields work is to define
+@code{STRUCTURE_SIZE_BOUNDARY} as large as @code{BIGGEST_ALIGNMENT}.
+Then every structure can be accessed with fullwords.
+
+Unless the machine has bit-field instructions or you define
+@code{STRUCTURE_SIZE_BOUNDARY} that way, you must define
+@code{PCC_BITFIELD_TYPE_MATTERS} to have a nonzero value.
+
+If your aim is to make GCC use the same conventions for laying out
+bit-fields as are used by another compiler, here is how to investigate
+what the other compiler does. Compile and run this program:
+
+@smallexample
+struct foo1
+@{
+ char x;
+ char :0;
+ char y;
+@};
+
+struct foo2
+@{
+ char x;
+ int :0;
+ char y;
+@};
+
+main ()
+@{
+ printf ("Size of foo1 is %d\n",
+ sizeof (struct foo1));
+ printf ("Size of foo2 is %d\n",
+ sizeof (struct foo2));
+ exit (0);
+@}
+@end smallexample
+
+If this prints 2 and 5, then the compiler's behavior is what you would
+get from @code{PCC_BITFIELD_TYPE_MATTERS}.
+@end defmac
+
+@defmac BITFIELD_NBYTES_LIMITED
+Like @code{PCC_BITFIELD_TYPE_MATTERS} except that its effect is limited
+to aligning a bit-field within the structure.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_ALIGN_ANON_BITFIELD (void)
+When @code{PCC_BITFIELD_TYPE_MATTERS} is true this hook will determine
+whether unnamed bitfields affect the alignment of the containing
+structure. The hook should return true if the structure should inherit
+the alignment requirements of an unnamed bitfield's type.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_NARROW_VOLATILE_BITFIELD (void)
+This target hook should return @code{true} if accesses to volatile bitfields
+should use the narrowest mode possible. It should return @code{false} if
+these accesses should use the bitfield container type.
+
+The default is @code{false}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_MEMBER_TYPE_FORCES_BLK (const_tree @var{field}, machine_mode @var{mode})
+Return true if a structure, union or array containing @var{field} should
+be accessed using @code{BLKMODE}.
+
+If @var{field} is the only field in the structure, @var{mode} is its
+mode, otherwise @var{mode} is VOIDmode. @var{mode} is provided in the
+case where structures of one field would require the structure's mode to
+retain the field's mode.
+
+Normally, this is not needed.
+@end deftypefn
+
+@defmac ROUND_TYPE_ALIGN (@var{type}, @var{computed}, @var{specified})
+Define this macro as an expression for the alignment of a type (given
+by @var{type} as a tree node) if the alignment computed in the usual
+way is @var{computed} and the alignment explicitly specified was
+@var{specified}.
+
+The default is to use @var{specified} if it is larger; otherwise, use
+the smaller of @var{computed} and @code{BIGGEST_ALIGNMENT}
+@end defmac
+
+@defmac MAX_FIXED_MODE_SIZE
+An integer expression for the size in bits of the largest integer
+machine mode that should actually be used. All integer machine modes of
+this size or smaller can be used for structures and unions with the
+appropriate sizes. If this macro is undefined, @code{GET_MODE_BITSIZE
+(DImode)} is assumed.
+@end defmac
+
+@defmac STACK_SAVEAREA_MODE (@var{save_level})
+If defined, an expression of type @code{machine_mode} that
+specifies the mode of the save area operand of a
+@code{save_stack_@var{level}} named pattern (@pxref{Standard Names}).
+@var{save_level} is one of @code{SAVE_BLOCK}, @code{SAVE_FUNCTION}, or
+@code{SAVE_NONLOCAL} and selects which of the three named patterns is
+having its mode specified.
+
+You need not define this macro if it always returns @code{Pmode}. You
+would most commonly define this macro if the
+@code{save_stack_@var{level}} patterns need to support both a 32- and a
+64-bit mode.
+@end defmac
+
+@defmac STACK_SIZE_MODE
+If defined, an expression of type @code{machine_mode} that
+specifies the mode of the size increment operand of an
+@code{allocate_stack} named pattern (@pxref{Standard Names}).
+
+You need not define this macro if it always returns @code{word_mode}.
+You would most commonly define this macro if the @code{allocate_stack}
+pattern needs to support both a 32- and a 64-bit mode.
+@end defmac
+
+@deftypefn {Target Hook} scalar_int_mode TARGET_LIBGCC_CMP_RETURN_MODE (void)
+This target hook should return the mode to be used for the return value
+of compare instructions expanded to libgcc calls. If not defined
+@code{word_mode} is returned which is the right choice for a majority of
+targets.
+@end deftypefn
+
+@deftypefn {Target Hook} scalar_int_mode TARGET_LIBGCC_SHIFT_COUNT_MODE (void)
+This target hook should return the mode to be used for the shift count operand
+of shift instructions expanded to libgcc calls. If not defined
+@code{word_mode} is returned which is the right choice for a majority of
+targets.
+@end deftypefn
+
+@deftypefn {Target Hook} scalar_int_mode TARGET_UNWIND_WORD_MODE (void)
+Return machine mode to be used for @code{_Unwind_Word} type.
+The default is to use @code{word_mode}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_MS_BITFIELD_LAYOUT_P (const_tree @var{record_type})
+This target hook returns @code{true} if bit-fields in the given
+@var{record_type} are to be laid out following the rules of Microsoft
+Visual C/C++, namely: (i) a bit-field won't share the same storage
+unit with the previous bit-field if their underlying types have
+different sizes, and the bit-field will be aligned to the highest
+alignment of the underlying types of itself and of the previous
+bit-field; (ii) a zero-sized bit-field will affect the alignment of
+the whole enclosing structure, even if it is unnamed; except that
+(iii) a zero-sized bit-field will be disregarded unless it follows
+another bit-field of nonzero size. If this hook returns @code{true},
+other macros that control bit-field layout are ignored.
+
+When a bit-field is inserted into a packed record, the whole size
+of the underlying type is used by one or more same-size adjacent
+bit-fields (that is, if its long:3, 32 bits is used in the record,
+and any additional adjacent long bit-fields are packed into the same
+chunk of 32 bits. However, if the size changes, a new field of that
+size is allocated). In an unpacked record, this is the same as using
+alignment, but not equivalent when packing.
+
+If both MS bit-fields and @samp{__attribute__((packed))} are used,
+the latter will take precedence. If @samp{__attribute__((packed))} is
+used on a single field when MS bit-fields are in use, it will take
+precedence for that field, but the alignment of the rest of the structure
+may affect its placement.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_DECIMAL_FLOAT_SUPPORTED_P (void)
+Returns true if the target supports decimal floating point.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_FIXED_POINT_SUPPORTED_P (void)
+Returns true if the target supports fixed-point arithmetic.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_EXPAND_TO_RTL_HOOK (void)
+This hook is called just before expansion into rtl, allowing the target
+to perform additional initializations or analysis before the expansion.
+For example, the rs6000 port uses it to allocate a scratch stack slot
+for use in copying SDmode values between memory and floating point
+registers whenever the function being expanded has any SDmode
+usage.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_INSTANTIATE_DECLS (void)
+This hook allows the backend to perform additional instantiations on rtl
+that are not actually in any insns yet, but will be later.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_MANGLE_TYPE (const_tree @var{type})
+If your target defines any fundamental types, or any types your target
+uses should be mangled differently from the default, define this hook
+to return the appropriate encoding for these types as part of a C++
+mangled name. The @var{type} argument is the tree structure representing
+the type to be mangled. The hook may be applied to trees which are
+not target-specific fundamental types; it should return @code{NULL}
+for all such types, as well as arguments it does not recognize. If the
+return value is not @code{NULL}, it must point to a statically-allocated
+string constant.
+
+Target-specific fundamental types might be new fundamental types or
+qualified versions of ordinary fundamental types. Encode new
+fundamental types as @samp{@w{u @var{n} @var{name}}}, where @var{name}
+is the name used for the type in source code, and @var{n} is the
+length of @var{name} in decimal. Encode qualified versions of
+ordinary types as @samp{@w{U @var{n} @var{name} @var{code}}}, where
+@var{name} is the name used for the type qualifier in source code,
+@var{n} is the length of @var{name} as above, and @var{code} is the
+code used to represent the unqualified version of this type. (See
+@code{write_builtin_type} in @file{cp/mangle.cc} for the list of
+codes.) In both cases the spaces are for clarity; do not include any
+spaces in your string.
+
+This hook is applied to types prior to typedef resolution. If the mangled
+name for a particular type depends only on that type's main variant, you
+can perform typedef resolution yourself using @code{TYPE_MAIN_VARIANT}
+before mangling.
+
+The default version of this hook always returns @code{NULL}, which is
+appropriate for a target that does not define any new fundamental
+types.
+@end deftypefn
+
+@node Type Layout
+@section Layout of Source Language Data Types
+
+These macros define the sizes and other characteristics of the standard
+basic data types used in programs being compiled. Unlike the macros in
+the previous section, these apply to specific features of C and related
+languages, rather than to fundamental aspects of storage layout.
+
+@defmac INT_TYPE_SIZE
+A C expression for the size in bits of the type @code{int} on the
+target machine. If you don't define this, the default is one word.
+@end defmac
+
+@defmac SHORT_TYPE_SIZE
+A C expression for the size in bits of the type @code{short} on the
+target machine. If you don't define this, the default is half a word.
+(If this would be less than one storage unit, it is rounded up to one
+unit.)
+@end defmac
+
+@defmac LONG_TYPE_SIZE
+A C expression for the size in bits of the type @code{long} on the
+target machine. If you don't define this, the default is one word.
+@end defmac
+
+@defmac ADA_LONG_TYPE_SIZE
+On some machines, the size used for the Ada equivalent of the type
+@code{long} by a native Ada compiler differs from that used by C@. In
+that situation, define this macro to be a C expression to be used for
+the size of that type. If you don't define this, the default is the
+value of @code{LONG_TYPE_SIZE}.
+@end defmac
+
+@defmac LONG_LONG_TYPE_SIZE
+A C expression for the size in bits of the type @code{long long} on the
+target machine. If you don't define this, the default is two
+words. If you want to support GNU Ada on your machine, the value of this
+macro must be at least 64.
+@end defmac
+
+@defmac CHAR_TYPE_SIZE
+A C expression for the size in bits of the type @code{char} on the
+target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT}.
+@end defmac
+
+@defmac BOOL_TYPE_SIZE
+A C expression for the size in bits of the C++ type @code{bool} and
+C99 type @code{_Bool} on the target machine. If you don't define
+this, and you probably shouldn't, the default is @code{CHAR_TYPE_SIZE}.
+@end defmac
+
+@defmac FLOAT_TYPE_SIZE
+A C expression for the size in bits of the type @code{float} on the
+target machine. If you don't define this, the default is one word.
+@end defmac
+
+@defmac DOUBLE_TYPE_SIZE
+A C expression for the size in bits of the type @code{double} on the
+target machine. If you don't define this, the default is two
+words.
+@end defmac
+
+@defmac LONG_DOUBLE_TYPE_SIZE
+A C expression for the size in bits of the type @code{long double} on
+the target machine. If you don't define this, the default is two
+words.
+@end defmac
+
+@defmac SHORT_FRACT_TYPE_SIZE
+A C expression for the size in bits of the type @code{short _Fract} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT}.
+@end defmac
+
+@defmac FRACT_TYPE_SIZE
+A C expression for the size in bits of the type @code{_Fract} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 2}.
+@end defmac
+
+@defmac LONG_FRACT_TYPE_SIZE
+A C expression for the size in bits of the type @code{long _Fract} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 4}.
+@end defmac
+
+@defmac LONG_LONG_FRACT_TYPE_SIZE
+A C expression for the size in bits of the type @code{long long _Fract} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 8}.
+@end defmac
+
+@defmac SHORT_ACCUM_TYPE_SIZE
+A C expression for the size in bits of the type @code{short _Accum} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 2}.
+@end defmac
+
+@defmac ACCUM_TYPE_SIZE
+A C expression for the size in bits of the type @code{_Accum} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 4}.
+@end defmac
+
+@defmac LONG_ACCUM_TYPE_SIZE
+A C expression for the size in bits of the type @code{long _Accum} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 8}.
+@end defmac
+
+@defmac LONG_LONG_ACCUM_TYPE_SIZE
+A C expression for the size in bits of the type @code{long long _Accum} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 16}.
+@end defmac
+
+@defmac LIBGCC2_GNU_PREFIX
+This macro corresponds to the @code{TARGET_LIBFUNC_GNU_PREFIX} target
+hook and should be defined if that hook is overriden to be true. It
+causes function names in libgcc to be changed to use a @code{__gnu_}
+prefix for their name rather than the default @code{__}. A port which
+uses this macro should also arrange to use @file{t-gnu-prefix} in
+the libgcc @file{config.host}.
+@end defmac
+
+@defmac WIDEST_HARDWARE_FP_SIZE
+A C expression for the size in bits of the widest floating-point format
+supported by the hardware. If you define this macro, you must specify a
+value less than or equal to the value of @code{LONG_DOUBLE_TYPE_SIZE}.
+If you do not define this macro, the value of @code{LONG_DOUBLE_TYPE_SIZE}
+is the default.
+@end defmac
+
+@defmac DEFAULT_SIGNED_CHAR
+An expression whose value is 1 or 0, according to whether the type
+@code{char} should be signed or unsigned by default. The user can
+always override this default with the options @option{-fsigned-char}
+and @option{-funsigned-char}.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_DEFAULT_SHORT_ENUMS (void)
+This target hook should return true if the compiler should give an
+@code{enum} type only as many bytes as it takes to represent the range
+of possible values of that type. It should return false if all
+@code{enum} types should be allocated like @code{int}.
+
+The default is to return false.
+@end deftypefn
+
+@defmac SIZE_TYPE
+A C expression for a string describing the name of the data type to use
+for size values. The typedef name @code{size_t} is defined using the
+contents of the string.
+
+The string can contain more than one keyword. If so, separate them with
+spaces, and write first any length keyword, then @code{unsigned} if
+appropriate, and finally @code{int}. The string must exactly match one
+of the data type names defined in the function
+@code{c_common_nodes_and_builtins} in the file @file{c-family/c-common.cc}.
+You may not omit @code{int} or change the order---that would cause the
+compiler to crash on startup.
+
+If you don't define this macro, the default is @code{"long unsigned
+int"}.
+@end defmac
+
+@defmac SIZETYPE
+GCC defines internal types (@code{sizetype}, @code{ssizetype},
+@code{bitsizetype} and @code{sbitsizetype}) for expressions
+dealing with size. This macro is a C expression for a string describing
+the name of the data type from which the precision of @code{sizetype}
+is extracted.
+
+The string has the same restrictions as @code{SIZE_TYPE} string.
+
+If you don't define this macro, the default is @code{SIZE_TYPE}.
+@end defmac
+
+@defmac PTRDIFF_TYPE
+A C expression for a string describing the name of the data type to use
+for the result of subtracting two pointers. The typedef name
+@code{ptrdiff_t} is defined using the contents of the string. See
+@code{SIZE_TYPE} above for more information.
+
+If you don't define this macro, the default is @code{"long int"}.
+@end defmac
+
+@defmac WCHAR_TYPE
+A C expression for a string describing the name of the data type to use
+for wide characters. The typedef name @code{wchar_t} is defined using
+the contents of the string. See @code{SIZE_TYPE} above for more
+information.
+
+If you don't define this macro, the default is @code{"int"}.
+@end defmac
+
+@defmac WCHAR_TYPE_SIZE
+A C expression for the size in bits of the data type for wide
+characters. This is used in @code{cpp}, which cannot make use of
+@code{WCHAR_TYPE}.
+@end defmac
+
+@defmac WINT_TYPE
+A C expression for a string describing the name of the data type to
+use for wide characters passed to @code{printf} and returned from
+@code{getwc}. The typedef name @code{wint_t} is defined using the
+contents of the string. See @code{SIZE_TYPE} above for more
+information.
+
+If you don't define this macro, the default is @code{"unsigned int"}.
+@end defmac
+
+@defmac INTMAX_TYPE
+A C expression for a string describing the name of the data type that
+can represent any value of any standard or extended signed integer type.
+The typedef name @code{intmax_t} is defined using the contents of the
+string. See @code{SIZE_TYPE} above for more information.
+
+If you don't define this macro, the default is the first of
+@code{"int"}, @code{"long int"}, or @code{"long long int"} that has as
+much precision as @code{long long int}.
+@end defmac
+
+@defmac UINTMAX_TYPE
+A C expression for a string describing the name of the data type that
+can represent any value of any standard or extended unsigned integer
+type. The typedef name @code{uintmax_t} is defined using the contents
+of the string. See @code{SIZE_TYPE} above for more information.
+
+If you don't define this macro, the default is the first of
+@code{"unsigned int"}, @code{"long unsigned int"}, or @code{"long long
+unsigned int"} that has as much precision as @code{long long unsigned
+int}.
+@end defmac
+
+@defmac SIG_ATOMIC_TYPE
+@defmacx INT8_TYPE
+@defmacx INT16_TYPE
+@defmacx INT32_TYPE
+@defmacx INT64_TYPE
+@defmacx UINT8_TYPE
+@defmacx UINT16_TYPE
+@defmacx UINT32_TYPE
+@defmacx UINT64_TYPE
+@defmacx INT_LEAST8_TYPE
+@defmacx INT_LEAST16_TYPE
+@defmacx INT_LEAST32_TYPE
+@defmacx INT_LEAST64_TYPE
+@defmacx UINT_LEAST8_TYPE
+@defmacx UINT_LEAST16_TYPE
+@defmacx UINT_LEAST32_TYPE
+@defmacx UINT_LEAST64_TYPE
+@defmacx INT_FAST8_TYPE
+@defmacx INT_FAST16_TYPE
+@defmacx INT_FAST32_TYPE
+@defmacx INT_FAST64_TYPE
+@defmacx UINT_FAST8_TYPE
+@defmacx UINT_FAST16_TYPE
+@defmacx UINT_FAST32_TYPE
+@defmacx UINT_FAST64_TYPE
+@defmacx INTPTR_TYPE
+@defmacx UINTPTR_TYPE
+C expressions for the standard types @code{sig_atomic_t},
+@code{int8_t}, @code{int16_t}, @code{int32_t}, @code{int64_t},
+@code{uint8_t}, @code{uint16_t}, @code{uint32_t}, @code{uint64_t},
+@code{int_least8_t}, @code{int_least16_t}, @code{int_least32_t},
+@code{int_least64_t}, @code{uint_least8_t}, @code{uint_least16_t},
+@code{uint_least32_t}, @code{uint_least64_t}, @code{int_fast8_t},
+@code{int_fast16_t}, @code{int_fast32_t}, @code{int_fast64_t},
+@code{uint_fast8_t}, @code{uint_fast16_t}, @code{uint_fast32_t},
+@code{uint_fast64_t}, @code{intptr_t}, and @code{uintptr_t}. See
+@code{SIZE_TYPE} above for more information.
+
+If any of these macros evaluates to a null pointer, the corresponding
+type is not supported; if GCC is configured to provide
+@code{<stdint.h>} in such a case, the header provided may not conform
+to C99, depending on the type in question. The defaults for all of
+these macros are null pointers.
+@end defmac
+
+@defmac TARGET_PTRMEMFUNC_VBIT_LOCATION
+The C++ compiler represents a pointer-to-member-function with a struct
+that looks like:
+
+@smallexample
+ struct @{
+ union @{
+ void (*fn)();
+ ptrdiff_t vtable_index;
+ @};
+ ptrdiff_t delta;
+ @};
+@end smallexample
+
+@noindent
+The C++ compiler must use one bit to indicate whether the function that
+will be called through a pointer-to-member-function is virtual.
+Normally, we assume that the low-order bit of a function pointer must
+always be zero. Then, by ensuring that the vtable_index is odd, we can
+distinguish which variant of the union is in use. But, on some
+platforms function pointers can be odd, and so this doesn't work. In
+that case, we use the low-order bit of the @code{delta} field, and shift
+the remainder of the @code{delta} field to the left.
+
+GCC will automatically make the right selection about where to store
+this bit using the @code{FUNCTION_BOUNDARY} setting for your platform.
+However, some platforms such as ARM/Thumb have @code{FUNCTION_BOUNDARY}
+set such that functions always start at even addresses, but the lowest
+bit of pointers to functions indicate whether the function at that
+address is in ARM or Thumb mode. If this is the case of your
+architecture, you should define this macro to
+@code{ptrmemfunc_vbit_in_delta}.
+
+In general, you should not have to define this macro. On architectures
+in which function addresses are always even, according to
+@code{FUNCTION_BOUNDARY}, GCC will automatically define this macro to
+@code{ptrmemfunc_vbit_in_pfn}.
+@end defmac
+
+@defmac TARGET_VTABLE_USES_DESCRIPTORS
+Normally, the C++ compiler uses function pointers in vtables. This
+macro allows the target to change to use ``function descriptors''
+instead. Function descriptors are found on targets for whom a
+function pointer is actually a small data structure. Normally the
+data structure consists of the actual code address plus a data
+pointer to which the function's data is relative.
+
+If vtables are used, the value of this macro should be the number
+of words that the function descriptor occupies.
+@end defmac
+
+@defmac TARGET_VTABLE_ENTRY_ALIGN
+By default, the vtable entries are void pointers, the so the alignment
+is the same as pointer alignment. The value of this macro specifies
+the alignment of the vtable entry in bits. It should be defined only
+when special alignment is necessary. */
+@end defmac
+
+@defmac TARGET_VTABLE_DATA_ENTRY_DISTANCE
+There are a few non-descriptor entries in the vtable at offsets below
+zero. If these entries must be padded (say, to preserve the alignment
+specified by @code{TARGET_VTABLE_ENTRY_ALIGN}), set this to the number
+of words in each data entry.
+@end defmac
+
+@node Registers
+@section Register Usage
+@cindex register usage
+
+This section explains how to describe what registers the target machine
+has, and how (in general) they can be used.
+
+The description of which registers a specific instruction can use is
+done with register classes; see @ref{Register Classes}. For information
+on using registers to access a stack frame, see @ref{Frame Registers}.
+For passing values in registers, see @ref{Register Arguments}.
+For returning values in registers, see @ref{Scalar Return}.
+
+@menu
+* Register Basics:: Number and kinds of registers.
+* Allocation Order:: Order in which registers are allocated.
+* Values in Registers:: What kinds of values each reg can hold.
+* Leaf Functions:: Renumbering registers for leaf functions.
+* Stack Registers:: Handling a register stack such as 80387.
+@end menu
+
+@node Register Basics
+@subsection Basic Characteristics of Registers
+
+@c prevent bad page break with this line
+Registers have various characteristics.
+
+@defmac FIRST_PSEUDO_REGISTER
+Number of hardware registers known to the compiler. They receive
+numbers 0 through @code{FIRST_PSEUDO_REGISTER-1}; thus, the first
+pseudo register's number really is assigned the number
+@code{FIRST_PSEUDO_REGISTER}.
+@end defmac
+
+@defmac FIXED_REGISTERS
+@cindex fixed register
+An initializer that says which registers are used for fixed purposes
+all throughout the compiled code and are therefore not available for
+general allocation. These would include the stack pointer, the frame
+pointer (except on machines where that can be used as a general
+register when no frame pointer is needed), the program counter on
+machines where that is considered one of the addressable registers,
+and any other numbered register with a standard use.
+
+This information is expressed as a sequence of numbers, separated by
+commas and surrounded by braces. The @var{n}th number is 1 if
+register @var{n} is fixed, 0 otherwise.
+
+The table initialized from this macro, and the table initialized by
+the following one, may be overridden at run time either automatically,
+by the actions of the macro @code{CONDITIONAL_REGISTER_USAGE}, or by
+the user with the command options @option{-ffixed-@var{reg}},
+@option{-fcall-used-@var{reg}} and @option{-fcall-saved-@var{reg}}.
+@end defmac
+
+@defmac CALL_USED_REGISTERS
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+Like @code{FIXED_REGISTERS} but has 1 for each register that is
+clobbered (in general) by function calls as well as for fixed
+registers. This macro therefore identifies the registers that are not
+available for general allocation of values that must live across
+function calls.
+
+If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler
+automatically saves it on function entry and restores it on function
+exit, if the register is used within the function.
+
+Exactly one of @code{CALL_USED_REGISTERS} and @code{CALL_REALLY_USED_REGISTERS}
+must be defined. Modern ports should define @code{CALL_REALLY_USED_REGISTERS}.
+@end defmac
+
+@defmac CALL_REALLY_USED_REGISTERS
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+Like @code{CALL_USED_REGISTERS} except this macro doesn't require
+that the entire set of @code{FIXED_REGISTERS} be included.
+(@code{CALL_USED_REGISTERS} must be a superset of @code{FIXED_REGISTERS}).
+
+Exactly one of @code{CALL_USED_REGISTERS} and @code{CALL_REALLY_USED_REGISTERS}
+must be defined. Modern ports should define @code{CALL_REALLY_USED_REGISTERS}.
+@end defmac
+
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+@deftypefn {Target Hook} {const predefined_function_abi &} TARGET_FNTYPE_ABI (const_tree @var{type})
+Return the ABI used by a function with type @var{type}; see the
+definition of @code{predefined_function_abi} for details of the ABI
+descriptor. Targets only need to define this hook if they support
+interoperability between several ABIs in the same translation unit.
+@end deftypefn
+
+@deftypefn {Target Hook} {const predefined_function_abi &} TARGET_INSN_CALLEE_ABI (const rtx_insn *@var{insn})
+This hook returns a description of the ABI used by the target of
+call instruction @var{insn}; see the definition of
+@code{predefined_function_abi} for details of the ABI descriptor.
+Only the global function @code{insn_callee_abi} should call this hook
+directly.
+
+Targets only need to define this hook if they support
+interoperability between several ABIs in the same translation unit.
+@end deftypefn
+
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+@deftypefn {Target Hook} bool TARGET_HARD_REGNO_CALL_PART_CLOBBERED (unsigned int @var{abi_id}, unsigned int @var{regno}, machine_mode @var{mode})
+ABIs usually specify that calls must preserve the full contents
+of a particular register, or that calls can alter any part of a
+particular register. This information is captured by the target macro
+@code{CALL_REALLY_USED_REGISTERS}. However, some ABIs specify that calls
+must preserve certain bits of a particular register but can alter others.
+This hook should return true if this applies to at least one of the
+registers in @samp{(reg:@var{mode} @var{regno})}, and if as a result the
+call would alter part of the @var{mode} value. For example, if a call
+preserves the low 32 bits of a 64-bit hard register @var{regno} but can
+clobber the upper 32 bits, this hook should return true for a 64-bit mode
+but false for a 32-bit mode.
+
+The value of @var{abi_id} comes from the @code{predefined_function_abi}
+structure that describes the ABI of the call; see the definition of the
+structure for more details. If (as is usual) the target uses the same ABI
+for all functions in a translation unit, @var{abi_id} is always 0.
+
+The default implementation returns false, which is correct
+for targets that don't have partly call-clobbered registers.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_GET_MULTILIB_ABI_NAME (void)
+This hook returns name of multilib ABI name.
+@end deftypefn
+
+@findex fixed_regs
+@findex call_used_regs
+@findex global_regs
+@findex reg_names
+@findex reg_class_contents
+@deftypefn {Target Hook} void TARGET_CONDITIONAL_REGISTER_USAGE (void)
+This hook may conditionally modify five variables
+@code{fixed_regs}, @code{call_used_regs}, @code{global_regs},
+@code{reg_names}, and @code{reg_class_contents}, to take into account
+any dependence of these register sets on target flags. The first three
+of these are of type @code{char []} (interpreted as boolean vectors).
+@code{global_regs} is a @code{const char *[]}, and
+@code{reg_class_contents} is a @code{HARD_REG_SET}. Before the macro is
+called, @code{fixed_regs}, @code{call_used_regs},
+@code{reg_class_contents}, and @code{reg_names} have been initialized
+from @code{FIXED_REGISTERS}, @code{CALL_USED_REGISTERS},
+@code{REG_CLASS_CONTENTS}, and @code{REGISTER_NAMES}, respectively.
+@code{global_regs} has been cleared, and any @option{-ffixed-@var{reg}},
+@option{-fcall-used-@var{reg}} and @option{-fcall-saved-@var{reg}}
+command options have been applied.
+
+@cindex disabling certain registers
+@cindex controlling register usage
+If the usage of an entire class of registers depends on the target
+flags, you may indicate this to GCC by using this macro to modify
+@code{fixed_regs} and @code{call_used_regs} to 1 for each of the
+registers in the classes which should not be used by GCC@. Also make
+@code{define_register_constraint}s return @code{NO_REGS} for constraints
+that shouldn't be used.
+
+(However, if this class is not included in @code{GENERAL_REGS} and all
+of the insn patterns whose constraints permit this class are
+controlled by target switches, then GCC will automatically avoid using
+these registers when the target switches are opposed to them.)
+@end deftypefn
+
+@defmac INCOMING_REGNO (@var{out})
+Define this macro if the target machine has register windows. This C
+expression returns the register number as seen by the called function
+corresponding to the register number @var{out} as seen by the calling
+function. Return @var{out} if register number @var{out} is not an
+outbound register.
+@end defmac
+
+@defmac OUTGOING_REGNO (@var{in})
+Define this macro if the target machine has register windows. This C
+expression returns the register number as seen by the calling function
+corresponding to the register number @var{in} as seen by the called
+function. Return @var{in} if register number @var{in} is not an inbound
+register.
+@end defmac
+
+@defmac LOCAL_REGNO (@var{regno})
+Define this macro if the target machine has register windows. This C
+expression returns true if the register is call-saved but is in the
+register window. Unlike most call-saved registers, such registers
+need not be explicitly restored on function exit or during non-local
+gotos.
+@end defmac
+
+@defmac PC_REGNUM
+If the program counter has a register number, define this as that
+register number. Otherwise, do not define it.
+@end defmac
+
+@node Allocation Order
+@subsection Order of Allocation of Registers
+@cindex order of register allocation
+@cindex register allocation order
+
+@c prevent bad page break with this line
+Registers are allocated in order.
+
+@defmac REG_ALLOC_ORDER
+If defined, an initializer for a vector of integers, containing the
+numbers of hard registers in the order in which GCC should prefer
+to use them (from most preferred to least).
+
+If this macro is not defined, registers are used lowest numbered first
+(all else being equal).
+
+One use of this macro is on machines where the highest numbered
+registers must always be saved and the save-multiple-registers
+instruction supports only sequences of consecutive registers. On such
+machines, define @code{REG_ALLOC_ORDER} to be an initializer that lists
+the highest numbered allocable register first.
+@end defmac
+
+@defmac ADJUST_REG_ALLOC_ORDER
+A C statement (sans semicolon) to choose the order in which to allocate
+hard registers for pseudo-registers local to a basic block.
+
+Store the desired register order in the array @code{reg_alloc_order}.
+Element 0 should be the register to allocate first; element 1, the next
+register; and so on.
+
+The macro body should not assume anything about the contents of
+@code{reg_alloc_order} before execution of the macro.
+
+On most machines, it is not necessary to define this macro.
+@end defmac
+
+@defmac HONOR_REG_ALLOC_ORDER
+Normally, IRA tries to estimate the costs for saving a register in the
+prologue and restoring it in the epilogue. This discourages it from
+using call-saved registers. If a machine wants to ensure that IRA
+allocates registers in the order given by REG_ALLOC_ORDER even if some
+call-saved registers appear earlier than call-used ones, then define this
+macro as a C expression to nonzero. Default is 0.
+@end defmac
+
+@defmac IRA_HARD_REGNO_ADD_COST_MULTIPLIER (@var{regno})
+In some case register allocation order is not enough for the
+Integrated Register Allocator (@acronym{IRA}) to generate a good code.
+If this macro is defined, it should return a floating point value
+based on @var{regno}. The cost of using @var{regno} for a pseudo will
+be increased by approximately the pseudo's usage frequency times the
+value returned by this macro. Not defining this macro is equivalent
+to having it always return @code{0.0}.
+
+On most machines, it is not necessary to define this macro.
+@end defmac
+
+@node Values in Registers
+@subsection How Values Fit in Registers
+
+This section discusses the macros that describe which kinds of values
+(specifically, which machine modes) each register can hold, and how many
+consecutive registers are needed for a given mode.
+
+@deftypefn {Target Hook} {unsigned int} TARGET_HARD_REGNO_NREGS (unsigned int @var{regno}, machine_mode @var{mode})
+This hook returns the number of consecutive hard registers, starting
+at register number @var{regno}, required to hold a value of mode
+@var{mode}. This hook must never return zero, even if a register
+cannot hold the requested mode - indicate that with
+@code{TARGET_HARD_REGNO_MODE_OK} and/or
+@code{TARGET_CAN_CHANGE_MODE_CLASS} instead.
+
+The default definition returns the number of words in @var{mode}.
+@end deftypefn
+
+@defmac HARD_REGNO_NREGS_HAS_PADDING (@var{regno}, @var{mode})
+A C expression that is nonzero if a value of mode @var{mode}, stored
+in memory, ends with padding that causes it to take up more space than
+in registers starting at register number @var{regno} (as determined by
+multiplying GCC's notion of the size of the register when containing
+this mode by the number of registers returned by
+@code{TARGET_HARD_REGNO_NREGS}). By default this is zero.
+
+For example, if a floating-point value is stored in three 32-bit
+registers but takes up 128 bits in memory, then this would be
+nonzero.
+
+This macros only needs to be defined if there are cases where
+@code{subreg_get_info}
+would otherwise wrongly determine that a @code{subreg} can be
+represented by an offset to the register number, when in fact such a
+@code{subreg} would contain some of the padding not stored in
+registers and so not be representable.
+@end defmac
+
+@defmac HARD_REGNO_NREGS_WITH_PADDING (@var{regno}, @var{mode})
+For values of @var{regno} and @var{mode} for which
+@code{HARD_REGNO_NREGS_HAS_PADDING} returns nonzero, a C expression
+returning the greater number of registers required to hold the value
+including any padding. In the example above, the value would be four.
+@end defmac
+
+@defmac REGMODE_NATURAL_SIZE (@var{mode})
+Define this macro if the natural size of registers that hold values
+of mode @var{mode} is not the word size. It is a C expression that
+should give the natural size in bytes for the specified mode. It is
+used by the register allocator to try to optimize its results. This
+happens for example on SPARC 64-bit where the natural size of
+floating-point registers is still 32-bit.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_HARD_REGNO_MODE_OK (unsigned int @var{regno}, machine_mode @var{mode})
+This hook returns true if it is permissible to store a value
+of mode @var{mode} in hard register number @var{regno} (or in several
+registers starting with that one). The default definition returns true
+unconditionally.
+
+You need not include code to check for the numbers of fixed registers,
+because the allocation mechanism considers them to be always occupied.
+
+@cindex register pairs
+On some machines, double-precision values must be kept in even/odd
+register pairs. You can implement that by defining this hook to reject
+odd register numbers for such modes.
+
+The minimum requirement for a mode to be OK in a register is that the
+@samp{mov@var{mode}} instruction pattern support moves between the
+register and other hard register in the same class and that moving a
+value into the register and back out not alter it.
+
+Since the same instruction used to move @code{word_mode} will work for
+all narrower integer modes, it is not necessary on any machine for
+this hook to distinguish between these modes, provided you define
+patterns @samp{movhi}, etc., to take advantage of this. This is
+useful because of the interaction between @code{TARGET_HARD_REGNO_MODE_OK}
+and @code{TARGET_MODES_TIEABLE_P}; it is very desirable for all integer
+modes to be tieable.
+
+Many machines have special registers for floating point arithmetic.
+Often people assume that floating point machine modes are allowed only
+in floating point registers. This is not true. Any registers that
+can hold integers can safely @emph{hold} a floating point machine
+mode, whether or not floating arithmetic can be done on it in those
+registers. Integer move instructions can be used to move the values.
+
+On some machines, though, the converse is true: fixed-point machine
+modes may not go in floating registers. This is true if the floating
+registers normalize any value stored in them, because storing a
+non-floating value there would garble it. In this case,
+@code{TARGET_HARD_REGNO_MODE_OK} should reject fixed-point machine modes in
+floating registers. But if the floating registers do not automatically
+normalize, if you can store any bit pattern in one and retrieve it
+unchanged without a trap, then any machine mode may go in a floating
+register, so you can define this hook to say so.
+
+The primary significance of special floating registers is rather that
+they are the registers acceptable in floating point arithmetic
+instructions. However, this is of no concern to
+@code{TARGET_HARD_REGNO_MODE_OK}. You handle it by writing the proper
+constraints for those instructions.
+
+On some machines, the floating registers are especially slow to access,
+so that it is better to store a value in a stack frame than in such a
+register if floating point arithmetic is not being done. As long as the
+floating registers are not in class @code{GENERAL_REGS}, they will not
+be used unless some pattern's constraint asks for one.
+@end deftypefn
+
+@defmac HARD_REGNO_RENAME_OK (@var{from}, @var{to})
+A C expression that is nonzero if it is OK to rename a hard register
+@var{from} to another hard register @var{to}.
+
+One common use of this macro is to prevent renaming of a register to
+another register that is not saved by a prologue in an interrupt
+handler.
+
+The default is always nonzero.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_MODES_TIEABLE_P (machine_mode @var{mode1}, machine_mode @var{mode2})
+This hook returns true if a value of mode @var{mode1} is accessible
+in mode @var{mode2} without copying.
+
+If @code{TARGET_HARD_REGNO_MODE_OK (@var{r}, @var{mode1})} and
+@code{TARGET_HARD_REGNO_MODE_OK (@var{r}, @var{mode2})} are always
+the same for any @var{r}, then
+@code{TARGET_MODES_TIEABLE_P (@var{mode1}, @var{mode2})}
+should be true. If they differ for any @var{r}, you should define
+this hook to return false unless some other mechanism ensures the
+accessibility of the value in a narrower mode.
+
+You should define this hook to return true in as many cases as
+possible since doing so will allow GCC to perform better register
+allocation. The default definition returns true unconditionally.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_HARD_REGNO_SCRATCH_OK (unsigned int @var{regno})
+This target hook should return @code{true} if it is OK to use a hard register
+@var{regno} as scratch reg in peephole2.
+
+One common use of this macro is to prevent using of a register that
+is not saved by a prologue in an interrupt handler.
+
+The default version of this hook always returns @code{true}.
+@end deftypefn
+
+@defmac AVOID_CCMODE_COPIES
+Define this macro if the compiler should avoid copies to/from @code{CCmode}
+registers. You should only define this macro if support for copying to/from
+@code{CCmode} is incomplete.
+@end defmac
+
+@node Leaf Functions
+@subsection Handling Leaf Functions
+
+@cindex leaf functions
+@cindex functions, leaf
+On some machines, a leaf function (i.e., one which makes no calls) can run
+more efficiently if it does not make its own register window. Often this
+means it is required to receive its arguments in the registers where they
+are passed by the caller, instead of the registers where they would
+normally arrive.
+
+The special treatment for leaf functions generally applies only when
+other conditions are met; for example, often they may use only those
+registers for its own variables and temporaries. We use the term ``leaf
+function'' to mean a function that is suitable for this special
+handling, so that functions with no calls are not necessarily ``leaf
+functions''.
+
+GCC assigns register numbers before it knows whether the function is
+suitable for leaf function treatment. So it needs to renumber the
+registers in order to output a leaf function. The following macros
+accomplish this.
+
+@defmac LEAF_REGISTERS
+Name of a char vector, indexed by hard register number, which
+contains 1 for a register that is allowable in a candidate for leaf
+function treatment.
+
+If leaf function treatment involves renumbering the registers, then the
+registers marked here should be the ones before renumbering---those that
+GCC would ordinarily allocate. The registers which will actually be
+used in the assembler code, after renumbering, should not be marked with 1
+in this vector.
+
+Define this macro only if the target machine offers a way to optimize
+the treatment of leaf functions.
+@end defmac
+
+@defmac LEAF_REG_REMAP (@var{regno})
+A C expression whose value is the register number to which @var{regno}
+should be renumbered, when a function is treated as a leaf function.
+
+If @var{regno} is a register number which should not appear in a leaf
+function before renumbering, then the expression should yield @minus{}1, which
+will cause the compiler to abort.
+
+Define this macro only if the target machine offers a way to optimize the
+treatment of leaf functions, and registers need to be renumbered to do
+this.
+@end defmac
+
+@findex current_function_is_leaf
+@findex current_function_uses_only_leaf_regs
+@code{TARGET_ASM_FUNCTION_PROLOGUE} and
+@code{TARGET_ASM_FUNCTION_EPILOGUE} must usually treat leaf functions
+specially. They can test the C variable @code{current_function_is_leaf}
+which is nonzero for leaf functions. @code{current_function_is_leaf} is
+set prior to local register allocation and is valid for the remaining
+compiler passes. They can also test the C variable
+@code{current_function_uses_only_leaf_regs} which is nonzero for leaf
+functions which only use leaf registers.
+@code{current_function_uses_only_leaf_regs} is valid after all passes
+that modify the instructions have been run and is only useful if
+@code{LEAF_REGISTERS} is defined.
+@c changed this to fix overfull. ALSO: why the "it" at the beginning
+@c of the next paragraph?! --mew 2feb93
+
+@node Stack Registers
+@subsection Registers That Form a Stack
+
+There are special features to handle computers where some of the
+``registers'' form a stack. Stack registers are normally written by
+pushing onto the stack, and are numbered relative to the top of the
+stack.
+
+Currently, GCC can only handle one group of stack-like registers, and
+they must be consecutively numbered. Furthermore, the existing
+support for stack-like registers is specific to the 80387 floating
+point coprocessor. If you have a new architecture that uses
+stack-like registers, you will need to do substantial work on
+@file{reg-stack.cc} and write your machine description to cooperate
+with it, as well as defining these macros.
+
+@defmac STACK_REGS
+Define this if the machine has any stack-like registers.
+@end defmac
+
+@defmac STACK_REG_COVER_CLASS
+This is a cover class containing the stack registers. Define this if
+the machine has any stack-like registers.
+@end defmac
+
+@defmac FIRST_STACK_REG
+The number of the first stack-like register. This one is the top
+of the stack.
+@end defmac
+
+@defmac LAST_STACK_REG
+The number of the last stack-like register. This one is the bottom of
+the stack.
+@end defmac
+
+@node Register Classes
+@section Register Classes
+@cindex register class definitions
+@cindex class definitions, register
+
+On many machines, the numbered registers are not all equivalent.
+For example, certain registers may not be allowed for indexed addressing;
+certain registers may not be allowed in some instructions. These machine
+restrictions are described to the compiler using @dfn{register classes}.
+
+You define a number of register classes, giving each one a name and saying
+which of the registers belong to it. Then you can specify register classes
+that are allowed as operands to particular instruction patterns.
+
+@findex ALL_REGS
+@findex NO_REGS
+In general, each register will belong to several classes. In fact, one
+class must be named @code{ALL_REGS} and contain all the registers. Another
+class must be named @code{NO_REGS} and contain no registers. Often the
+union of two classes will be another class; however, this is not required.
+
+@findex GENERAL_REGS
+One of the classes must be named @code{GENERAL_REGS}. There is nothing
+terribly special about the name, but the operand constraint letters
+@samp{r} and @samp{g} specify this class. If @code{GENERAL_REGS} is
+the same as @code{ALL_REGS}, just define it as a macro which expands
+to @code{ALL_REGS}.
+
+Order the classes so that if class @var{x} is contained in class @var{y}
+then @var{x} has a lower class number than @var{y}.
+
+The way classes other than @code{GENERAL_REGS} are specified in operand
+constraints is through machine-dependent operand constraint letters.
+You can define such letters to correspond to various classes, then use
+them in operand constraints.
+
+You must define the narrowest register classes for allocatable
+registers, so that each class either has no subclasses, or that for
+some mode, the move cost between registers within the class is
+cheaper than moving a register in the class to or from memory
+(@pxref{Costs}).
+
+You should define a class for the union of two classes whenever some
+instruction allows both classes. For example, if an instruction allows
+either a floating point (coprocessor) register or a general register for a
+certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS}
+which includes both of them. Otherwise you will get suboptimal code,
+or even internal compiler errors when reload cannot find a register in the
+class computed via @code{reg_class_subunion}.
+
+You must also specify certain redundant information about the register
+classes: for each class, which classes contain it and which ones are
+contained in it; for each pair of classes, the largest class contained
+in their union.
+
+When a value occupying several consecutive registers is expected in a
+certain class, all the registers used must belong to that class.
+Therefore, register classes cannot be used to enforce a requirement for
+a register pair to start with an even-numbered register. The way to
+specify this requirement is with @code{TARGET_HARD_REGNO_MODE_OK}.
+
+Register classes used for input-operands of bitwise-and or shift
+instructions have a special requirement: each such class must have, for
+each fixed-point machine mode, a subclass whose registers can transfer that
+mode to or from memory. For example, on some machines, the operations for
+single-byte values (@code{QImode}) are limited to certain registers. When
+this is so, each register class that is used in a bitwise-and or shift
+instruction must have a subclass consisting of registers from which
+single-byte values can be loaded or stored. This is so that
+@code{PREFERRED_RELOAD_CLASS} can always have a possible value to return.
+
+@deftp {Data type} {enum reg_class}
+An enumerated type that must be defined with all the register class names
+as enumerated values. @code{NO_REGS} must be first. @code{ALL_REGS}
+must be the last register class, followed by one more enumerated value,
+@code{LIM_REG_CLASSES}, which is not a register class but rather
+tells how many classes there are.
+
+Each register class has a number, which is the value of casting
+the class name to type @code{int}. The number serves as an index
+in many of the tables described below.
+@end deftp
+
+@defmac N_REG_CLASSES
+The number of distinct register classes, defined as follows:
+
+@smallexample
+#define N_REG_CLASSES (int) LIM_REG_CLASSES
+@end smallexample
+@end defmac
+
+@defmac REG_CLASS_NAMES
+An initializer containing the names of the register classes as C string
+constants. These names are used in writing some of the debugging dumps.
+@end defmac
+
+@defmac REG_CLASS_CONTENTS
+An initializer containing the contents of the register classes, as integers
+which are bit masks. The @var{n}th integer specifies the contents of class
+@var{n}. The way the integer @var{mask} is interpreted is that
+register @var{r} is in the class if @code{@var{mask} & (1 << @var{r})} is 1.
+
+When the machine has more than 32 registers, an integer does not suffice.
+Then the integers are replaced by sub-initializers, braced groupings containing
+several integers. Each sub-initializer must be suitable as an initializer
+for the type @code{HARD_REG_SET} which is defined in @file{hard-reg-set.h}.
+In this situation, the first integer in each sub-initializer corresponds to
+registers 0 through 31, the second integer to registers 32 through 63, and
+so on.
+@end defmac
+
+@defmac REGNO_REG_CLASS (@var{regno})
+A C expression whose value is a register class containing hard register
+@var{regno}. In general there is more than one such class; choose a class
+which is @dfn{minimal}, meaning that no smaller class also contains the
+register.
+@end defmac
+
+@defmac BASE_REG_CLASS
+A macro whose definition is the name of the class to which a valid
+base register must belong. A base register is one used in an address
+which is the register value plus a displacement.
+@end defmac
+
+@defmac MODE_BASE_REG_CLASS (@var{mode})
+This is a variation of the @code{BASE_REG_CLASS} macro which allows
+the selection of a base register in a mode dependent manner. If
+@var{mode} is VOIDmode then it should return the same value as
+@code{BASE_REG_CLASS}.
+@end defmac
+
+@defmac MODE_BASE_REG_REG_CLASS (@var{mode})
+A C expression whose value is the register class to which a valid
+base register must belong in order to be used in a base plus index
+register address. You should define this macro if base plus index
+addresses have different requirements than other base register uses.
+@end defmac
+
+@defmac MODE_CODE_BASE_REG_CLASS (@var{mode}, @var{address_space}, @var{outer_code}, @var{index_code})
+A C expression whose value is the register class to which a valid
+base register for a memory reference in mode @var{mode} to address
+space @var{address_space} must belong. @var{outer_code} and @var{index_code}
+define the context in which the base register occurs. @var{outer_code} is
+the code of the immediately enclosing expression (@code{MEM} for the top level
+of an address, @code{ADDRESS} for something that occurs in an
+@code{address_operand}). @var{index_code} is the code of the corresponding
+index expression if @var{outer_code} is @code{PLUS}; @code{SCRATCH} otherwise.
+@end defmac
+
+@defmac INDEX_REG_CLASS
+A macro whose definition is the name of the class to which a valid
+index register must belong. An index register is one used in an
+address where its value is either multiplied by a scale factor or
+added to another register (as well as added to a displacement).
+@end defmac
+
+@defmac REGNO_OK_FOR_BASE_P (@var{num})
+A C expression which is nonzero if register number @var{num} is
+suitable for use as a base register in operand addresses.
+@end defmac
+
+@defmac REGNO_MODE_OK_FOR_BASE_P (@var{num}, @var{mode})
+A C expression that is just like @code{REGNO_OK_FOR_BASE_P}, except that
+that expression may examine the mode of the memory reference in
+@var{mode}. You should define this macro if the mode of the memory
+reference affects whether a register may be used as a base register. If
+you define this macro, the compiler will use it instead of
+@code{REGNO_OK_FOR_BASE_P}. The mode may be @code{VOIDmode} for
+addresses that appear outside a @code{MEM}, i.e., as an
+@code{address_operand}.
+@end defmac
+
+@defmac REGNO_MODE_OK_FOR_REG_BASE_P (@var{num}, @var{mode})
+A C expression which is nonzero if register number @var{num} is suitable for
+use as a base register in base plus index operand addresses, accessing
+memory in mode @var{mode}. It may be either a suitable hard register or a
+pseudo register that has been allocated such a hard register. You should
+define this macro if base plus index addresses have different requirements
+than other base register uses.
+
+Use of this macro is deprecated; please use the more general
+@code{REGNO_MODE_CODE_OK_FOR_BASE_P}.
+@end defmac
+
+@defmac REGNO_MODE_CODE_OK_FOR_BASE_P (@var{num}, @var{mode}, @var{address_space}, @var{outer_code}, @var{index_code})
+A C expression which is nonzero if register number @var{num} is
+suitable for use as a base register in operand addresses, accessing
+memory in mode @var{mode} in address space @var{address_space}.
+This is similar to @code{REGNO_MODE_OK_FOR_BASE_P}, except
+that that expression may examine the context in which the register
+appears in the memory reference. @var{outer_code} is the code of the
+immediately enclosing expression (@code{MEM} if at the top level of the
+address, @code{ADDRESS} for something that occurs in an
+@code{address_operand}). @var{index_code} is the code of the
+corresponding index expression if @var{outer_code} is @code{PLUS};
+@code{SCRATCH} otherwise. The mode may be @code{VOIDmode} for addresses
+that appear outside a @code{MEM}, i.e., as an @code{address_operand}.
+@end defmac
+
+@defmac REGNO_OK_FOR_INDEX_P (@var{num})
+A C expression which is nonzero if register number @var{num} is
+suitable for use as an index register in operand addresses. It may be
+either a suitable hard register or a pseudo register that has been
+allocated such a hard register.
+
+The difference between an index register and a base register is that
+the index register may be scaled. If an address involves the sum of
+two registers, neither one of them scaled, then either one may be
+labeled the ``base'' and the other the ``index''; but whichever
+labeling is used must fit the machine's constraints of which registers
+may serve in each capacity. The compiler will try both labelings,
+looking for one that is valid, and will reload one or both registers
+only if neither labeling works.
+@end defmac
+
+@deftypefn {Target Hook} reg_class_t TARGET_PREFERRED_RENAME_CLASS (reg_class_t @var{rclass})
+A target hook that places additional preference on the register
+class to use when it is necessary to rename a register in class
+@var{rclass} to another class, or perhaps @var{NO_REGS}, if no
+preferred register class is found or hook @code{preferred_rename_class}
+is not implemented.
+Sometimes returning a more restrictive class makes better code. For
+example, on ARM, thumb-2 instructions using @code{LO_REGS} may be
+smaller than instructions using @code{GENERIC_REGS}. By returning
+@code{LO_REGS} from @code{preferred_rename_class}, code size can
+be reduced.
+@end deftypefn
+
+@deftypefn {Target Hook} reg_class_t TARGET_PREFERRED_RELOAD_CLASS (rtx @var{x}, reg_class_t @var{rclass})
+A target hook that places additional restrictions on the register class
+to use when it is necessary to copy value @var{x} into a register in class
+@var{rclass}. The value is a register class; perhaps @var{rclass}, or perhaps
+another, smaller class.
+
+The default version of this hook always returns value of @code{rclass} argument.
+
+Sometimes returning a more restrictive class makes better code. For
+example, on the 68000, when @var{x} is an integer constant that is in range
+for a @samp{moveq} instruction, the value of this macro is always
+@code{DATA_REGS} as long as @var{rclass} includes the data registers.
+Requiring a data register guarantees that a @samp{moveq} will be used.
+
+One case where @code{TARGET_PREFERRED_RELOAD_CLASS} must not return
+@var{rclass} is if @var{x} is a legitimate constant which cannot be
+loaded into some register class. By returning @code{NO_REGS} you can
+force @var{x} into a memory location. For example, rs6000 can load
+immediate values into general-purpose registers, but does not have an
+instruction for loading an immediate value into a floating-point
+register, so @code{TARGET_PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when
+@var{x} is a floating-point constant. If the constant can't be loaded
+into any kind of register, code generation will be better if
+@code{TARGET_LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead
+of using @code{TARGET_PREFERRED_RELOAD_CLASS}.
+
+If an insn has pseudos in it after register allocation, reload will go
+through the alternatives and call repeatedly @code{TARGET_PREFERRED_RELOAD_CLASS}
+to find the best one. Returning @code{NO_REGS}, in this case, makes
+reload add a @code{!} in front of the constraint: the x86 back-end uses
+this feature to discourage usage of 387 registers when math is done in
+the SSE registers (and vice versa).
+@end deftypefn
+
+@defmac PREFERRED_RELOAD_CLASS (@var{x}, @var{class})
+A C expression that places additional restrictions on the register class
+to use when it is necessary to copy value @var{x} into a register in class
+@var{class}. The value is a register class; perhaps @var{class}, or perhaps
+another, smaller class. On many machines, the following definition is
+safe:
+
+@smallexample
+#define PREFERRED_RELOAD_CLASS(X,CLASS) CLASS
+@end smallexample
+
+Sometimes returning a more restrictive class makes better code. For
+example, on the 68000, when @var{x} is an integer constant that is in range
+for a @samp{moveq} instruction, the value of this macro is always
+@code{DATA_REGS} as long as @var{class} includes the data registers.
+Requiring a data register guarantees that a @samp{moveq} will be used.
+
+One case where @code{PREFERRED_RELOAD_CLASS} must not return
+@var{class} is if @var{x} is a legitimate constant which cannot be
+loaded into some register class. By returning @code{NO_REGS} you can
+force @var{x} into a memory location. For example, rs6000 can load
+immediate values into general-purpose registers, but does not have an
+instruction for loading an immediate value into a floating-point
+register, so @code{PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when
+@var{x} is a floating-point constant. If the constant cannot be loaded
+into any kind of register, code generation will be better if
+@code{TARGET_LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead
+of using @code{TARGET_PREFERRED_RELOAD_CLASS}.
+
+If an insn has pseudos in it after register allocation, reload will go
+through the alternatives and call repeatedly @code{PREFERRED_RELOAD_CLASS}
+to find the best one. Returning @code{NO_REGS}, in this case, makes
+reload add a @code{!} in front of the constraint: the x86 back-end uses
+this feature to discourage usage of 387 registers when math is done in
+the SSE registers (and vice versa).
+@end defmac
+
+@deftypefn {Target Hook} reg_class_t TARGET_PREFERRED_OUTPUT_RELOAD_CLASS (rtx @var{x}, reg_class_t @var{rclass})
+Like @code{TARGET_PREFERRED_RELOAD_CLASS}, but for output reloads instead of
+input reloads.
+
+The default version of this hook always returns value of @code{rclass}
+argument.
+
+You can also use @code{TARGET_PREFERRED_OUTPUT_RELOAD_CLASS} to discourage
+reload from using some alternatives, like @code{TARGET_PREFERRED_RELOAD_CLASS}.
+@end deftypefn
+
+@defmac LIMIT_RELOAD_CLASS (@var{mode}, @var{class})
+A C expression that places additional restrictions on the register class
+to use when it is necessary to be able to hold a value of mode
+@var{mode} in a reload register for which class @var{class} would
+ordinarily be used.
+
+Unlike @code{PREFERRED_RELOAD_CLASS}, this macro should be used when
+there are certain modes that simply cannot go in certain reload classes.
+
+The value is a register class; perhaps @var{class}, or perhaps another,
+smaller class.
+
+Don't define this macro unless the target machine has limitations which
+require the macro to do something nontrivial.
+@end defmac
+
+@deftypefn {Target Hook} reg_class_t TARGET_SECONDARY_RELOAD (bool @var{in_p}, rtx @var{x}, reg_class_t @var{reload_class}, machine_mode @var{reload_mode}, secondary_reload_info *@var{sri})
+Many machines have some registers that cannot be copied directly to or
+from memory or even from other types of registers. An example is the
+@samp{MQ} register, which on most machines, can only be copied to or
+from general registers, but not memory. Below, we shall be using the
+term 'intermediate register' when a move operation cannot be performed
+directly, but has to be done by copying the source into the intermediate
+register first, and then copying the intermediate register to the
+destination. An intermediate register always has the same mode as
+source and destination. Since it holds the actual value being copied,
+reload might apply optimizations to re-use an intermediate register
+and eliding the copy from the source when it can determine that the
+intermediate register still holds the required value.
+
+Another kind of secondary reload is required on some machines which
+allow copying all registers to and from memory, but require a scratch
+register for stores to some memory locations (e.g., those with symbolic
+address on the RT, and those with certain symbolic address on the SPARC
+when compiling PIC)@. Scratch registers need not have the same mode
+as the value being copied, and usually hold a different value than
+that being copied. Special patterns in the md file are needed to
+describe how the copy is performed with the help of the scratch register;
+these patterns also describe the number, register class(es) and mode(s)
+of the scratch register(s).
+
+In some cases, both an intermediate and a scratch register are required.
+
+For input reloads, this target hook is called with nonzero @var{in_p},
+and @var{x} is an rtx that needs to be copied to a register of class
+@var{reload_class} in @var{reload_mode}. For output reloads, this target
+hook is called with zero @var{in_p}, and a register of class @var{reload_class}
+needs to be copied to rtx @var{x} in @var{reload_mode}.
+
+If copying a register of @var{reload_class} from/to @var{x} requires
+an intermediate register, the hook @code{secondary_reload} should
+return the register class required for this intermediate register.
+If no intermediate register is required, it should return NO_REGS.
+If more than one intermediate register is required, describe the one
+that is closest in the copy chain to the reload register.
+
+If scratch registers are needed, you also have to describe how to
+perform the copy from/to the reload register to/from this
+closest intermediate register. Or if no intermediate register is
+required, but still a scratch register is needed, describe the
+copy from/to the reload register to/from the reload operand @var{x}.
+
+You do this by setting @code{sri->icode} to the instruction code of a pattern
+in the md file which performs the move. Operands 0 and 1 are the output
+and input of this copy, respectively. Operands from operand 2 onward are
+for scratch operands. These scratch operands must have a mode, and a
+single-register-class
+@c [later: or memory]
+output constraint.
+
+When an intermediate register is used, the @code{secondary_reload}
+hook will be called again to determine how to copy the intermediate
+register to/from the reload operand @var{x}, so your hook must also
+have code to handle the register class of the intermediate operand.
+
+@c [For later: maybe we'll allow multi-alternative reload patterns -
+@c the port maintainer could name a mov<mode> pattern that has clobbers -
+@c and match the constraints of input and output to determine the required
+@c alternative. A restriction would be that constraints used to match
+@c against reloads registers would have to be written as register class
+@c constraints, or we need a new target macro / hook that tells us if an
+@c arbitrary constraint can match an unknown register of a given class.
+@c Such a macro / hook would also be useful in other places.]
+
+
+@var{x} might be a pseudo-register or a @code{subreg} of a
+pseudo-register, which could either be in a hard register or in memory.
+Use @code{true_regnum} to find out; it will return @minus{}1 if the pseudo is
+in memory and the hard register number if it is in a register.
+
+Scratch operands in memory (constraint @code{"=m"} / @code{"=&m"}) are
+currently not supported. For the time being, you will have to continue
+to use @code{TARGET_SECONDARY_MEMORY_NEEDED} for that purpose.
+
+@code{copy_cost} also uses this target hook to find out how values are
+copied. If you want it to include some extra cost for the need to allocate
+(a) scratch register(s), set @code{sri->extra_cost} to the additional cost.
+Or if two dependent moves are supposed to have a lower cost than the sum
+of the individual moves due to expected fortuitous scheduling and/or special
+forwarding logic, you can set @code{sri->extra_cost} to a negative amount.
+@end deftypefn
+
+@defmac SECONDARY_RELOAD_CLASS (@var{class}, @var{mode}, @var{x})
+@defmacx SECONDARY_INPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x})
+@defmacx SECONDARY_OUTPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x})
+These macros are obsolete, new ports should use the target hook
+@code{TARGET_SECONDARY_RELOAD} instead.
+
+These are obsolete macros, replaced by the @code{TARGET_SECONDARY_RELOAD}
+target hook. Older ports still define these macros to indicate to the
+reload phase that it may
+need to allocate at least one register for a reload in addition to the
+register to contain the data. Specifically, if copying @var{x} to a
+register @var{class} in @var{mode} requires an intermediate register,
+you were supposed to define @code{SECONDARY_INPUT_RELOAD_CLASS} to return the
+largest register class all of whose registers can be used as
+intermediate registers or scratch registers.
+
+If copying a register @var{class} in @var{mode} to @var{x} requires an
+intermediate or scratch register, @code{SECONDARY_OUTPUT_RELOAD_CLASS}
+was supposed to be defined to return the largest register
+class required. If the
+requirements for input and output reloads were the same, the macro
+@code{SECONDARY_RELOAD_CLASS} should have been used instead of defining both
+macros identically.
+
+The values returned by these macros are often @code{GENERAL_REGS}.
+Return @code{NO_REGS} if no spare register is needed; i.e., if @var{x}
+can be directly copied to or from a register of @var{class} in
+@var{mode} without requiring a scratch register. Do not define this
+macro if it would always return @code{NO_REGS}.
+
+If a scratch register is required (either with or without an
+intermediate register), you were supposed to define patterns for
+@samp{reload_in@var{m}} or @samp{reload_out@var{m}}, as required
+(@pxref{Standard Names}. These patterns, which were normally
+implemented with a @code{define_expand}, should be similar to the
+@samp{mov@var{m}} patterns, except that operand 2 is the scratch
+register.
+
+These patterns need constraints for the reload register and scratch
+register that
+contain a single register class. If the original reload register (whose
+class is @var{class}) can meet the constraint given in the pattern, the
+value returned by these macros is used for the class of the scratch
+register. Otherwise, two additional reload registers are required.
+Their classes are obtained from the constraints in the insn pattern.
+
+@var{x} might be a pseudo-register or a @code{subreg} of a
+pseudo-register, which could either be in a hard register or in memory.
+Use @code{true_regnum} to find out; it will return @minus{}1 if the pseudo is
+in memory and the hard register number if it is in a register.
+
+These macros should not be used in the case where a particular class of
+registers can only be copied to memory and not to another class of
+registers. In that case, secondary reload registers are not needed and
+would not be helpful. Instead, a stack location must be used to perform
+the copy and the @code{mov@var{m}} pattern should use memory as an
+intermediate storage. This case often occurs between floating-point and
+general registers.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_SECONDARY_MEMORY_NEEDED (machine_mode @var{mode}, reg_class_t @var{class1}, reg_class_t @var{class2})
+Certain machines have the property that some registers cannot be copied
+to some other registers without using memory. Define this hook on
+those machines to return true if objects of mode @var{m} in registers
+of @var{class1} can only be copied to registers of class @var{class2} by
+ storing a register of @var{class1} into memory and loading that memory
+location into a register of @var{class2}. The default definition returns
+false for all inputs.
+@end deftypefn
+
+@defmac SECONDARY_MEMORY_NEEDED_RTX (@var{mode})
+Normally when @code{TARGET_SECONDARY_MEMORY_NEEDED} is defined, the compiler
+allocates a stack slot for a memory location needed for register copies.
+If this macro is defined, the compiler instead uses the memory location
+defined by this macro.
+
+Do not define this macro if you do not define
+@code{TARGET_SECONDARY_MEMORY_NEEDED}.
+@end defmac
+
+@deftypefn {Target Hook} machine_mode TARGET_SECONDARY_MEMORY_NEEDED_MODE (machine_mode @var{mode})
+If @code{TARGET_SECONDARY_MEMORY_NEEDED} tells the compiler to use memory
+when moving between two particular registers of mode @var{mode},
+this hook specifies the mode that the memory should have.
+
+The default depends on @code{TARGET_LRA_P}. Without LRA, the default
+is to use a word-sized mode for integral modes that are smaller than a
+a word. This is right thing to do on most machines because it ensures
+that all bits of the register are copied and prevents accesses to the
+registers in a narrower mode, which some machines prohibit for
+floating-point registers.
+
+However, this default behavior is not correct on some machines, such as
+the DEC Alpha, that store short integers in floating-point registers
+differently than in integer registers. On those machines, the default
+widening will not work correctly and you must define this hook to
+suppress that widening in some cases. See the file @file{alpha.cc} for
+details.
+
+With LRA, the default is to use @var{mode} unmodified.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SELECT_EARLY_REMAT_MODES (sbitmap @var{modes})
+On some targets, certain modes cannot be held in registers around a
+standard ABI call and are relatively expensive to spill to the stack.
+The early rematerialization pass can help in such cases by aggressively
+recomputing values after calls, so that they don't need to be spilled.
+
+This hook returns the set of such modes by setting the associated bits
+in @var{modes}. The default implementation selects no modes, which has
+the effect of disabling the early rematerialization pass.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CLASS_LIKELY_SPILLED_P (reg_class_t @var{rclass})
+A target hook which returns @code{true} if pseudos that have been assigned
+to registers of class @var{rclass} would likely be spilled because
+registers of @var{rclass} are needed for spill registers.
+
+The default version of this target hook returns @code{true} if @var{rclass}
+has exactly one register and @code{false} otherwise. On most machines, this
+default should be used. For generally register-starved machines, such as
+i386, or machines with right register constraints, such as SH, this hook
+can be used to avoid excessive spilling.
+
+This hook is also used by some of the global intra-procedural code
+transformations to throtle code motion, to avoid increasing register
+pressure.
+@end deftypefn
+
+@deftypefn {Target Hook} {unsigned char} TARGET_CLASS_MAX_NREGS (reg_class_t @var{rclass}, machine_mode @var{mode})
+A target hook returns the maximum number of consecutive registers
+of class @var{rclass} needed to hold a value of mode @var{mode}.
+
+This is closely related to the macro @code{TARGET_HARD_REGNO_NREGS}.
+In fact, the value returned by @code{TARGET_CLASS_MAX_NREGS (@var{rclass},
+@var{mode})} target hook should be the maximum value of
+@code{TARGET_HARD_REGNO_NREGS (@var{regno}, @var{mode})} for all @var{regno}
+values in the class @var{rclass}.
+
+This target hook helps control the handling of multiple-word values
+in the reload pass.
+
+The default version of this target hook returns the size of @var{mode}
+in words.
+@end deftypefn
+
+@defmac CLASS_MAX_NREGS (@var{class}, @var{mode})
+A C expression for the maximum number of consecutive registers
+of class @var{class} needed to hold a value of mode @var{mode}.
+
+This is closely related to the macro @code{TARGET_HARD_REGNO_NREGS}. In fact,
+the value of the macro @code{CLASS_MAX_NREGS (@var{class}, @var{mode})}
+should be the maximum value of @code{TARGET_HARD_REGNO_NREGS (@var{regno},
+@var{mode})} for all @var{regno} values in the class @var{class}.
+
+This macro helps control the handling of multiple-word values
+in the reload pass.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_CAN_CHANGE_MODE_CLASS (machine_mode @var{from}, machine_mode @var{to}, reg_class_t @var{rclass})
+This hook returns true if it is possible to bitcast values held in
+registers of class @var{rclass} from mode @var{from} to mode @var{to}
+and if doing so preserves the low-order bits that are common to both modes.
+The result is only meaningful if @var{rclass} has registers that can hold
+both @code{from} and @code{to}. The default implementation returns true.
+
+As an example of when such bitcasting is invalid, loading 32-bit integer or
+floating-point objects into floating-point registers on Alpha extends them
+to 64 bits. Therefore loading a 64-bit object and then storing it as a
+32-bit object does not store the low-order 32 bits, as would be the case
+for a normal register. Therefore, @file{alpha.h} defines
+@code{TARGET_CAN_CHANGE_MODE_CLASS} to return:
+
+@smallexample
+(GET_MODE_SIZE (from) == GET_MODE_SIZE (to)
+ || !reg_classes_intersect_p (FLOAT_REGS, rclass))
+@end smallexample
+
+Even if storing from a register in mode @var{to} would be valid,
+if both @var{from} and @code{raw_reg_mode} for @var{rclass} are wider
+than @code{word_mode}, then we must prevent @var{to} narrowing the
+mode. This happens when the middle-end assumes that it can load
+or store pieces of an @var{N}-word pseudo, and that the pseudo will
+eventually be allocated to @var{N} @code{word_mode} hard registers.
+Failure to prevent this kind of mode change will result in the
+entire @code{raw_reg_mode} being modified instead of the partial
+value that the middle-end intended.
+@end deftypefn
+
+@deftypefn {Target Hook} reg_class_t TARGET_IRA_CHANGE_PSEUDO_ALLOCNO_CLASS (int, @var{reg_class_t}, @var{reg_class_t})
+A target hook which can change allocno class for given pseudo from
+ allocno and best class calculated by IRA.
+
+ The default version of this target hook always returns given class.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_LRA_P (void)
+A target hook which returns true if we use LRA instead of reload pass.
+
+The default version of this target hook returns true. New ports
+should use LRA, and existing ports are encouraged to convert.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_REGISTER_PRIORITY (int)
+A target hook which returns the register priority number to which the
+register @var{hard_regno} belongs to. The bigger the number, the
+more preferable the hard register usage (when all other conditions are
+the same). This hook can be used to prefer some hard register over
+others in LRA. For example, some x86-64 register usage needs
+additional prefix which makes instructions longer. The hook can
+return lower priority number for such registers make them less favorable
+and as result making the generated code smaller.
+
+The default version of this target hook returns always zero.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_REGISTER_USAGE_LEVELING_P (void)
+A target hook which returns true if we need register usage leveling.
+That means if a few hard registers are equally good for the
+assignment, we choose the least used hard register. The register
+usage leveling may be profitable for some targets. Don't use the
+usage leveling for targets with conditional execution or targets
+with big register files as it hurts if-conversion and cross-jumping
+optimizations.
+
+The default version of this target hook returns always false.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_DIFFERENT_ADDR_DISPLACEMENT_P (void)
+A target hook which returns true if an address with the same structure
+can have different maximal legitimate displacement. For example, the
+displacement can depend on memory mode or on operand combinations in
+the insn.
+
+The default version of this target hook returns always false.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CANNOT_SUBSTITUTE_MEM_EQUIV_P (rtx @var{subst})
+A target hook which returns @code{true} if @var{subst} can't
+substitute safely pseudos with equivalent memory values during
+register allocation.
+The default version of this target hook returns @code{false}.
+On most machines, this default should be used. For generally
+machines with non orthogonal register usage for addressing, such
+as SH, this hook can be used to avoid excessive spilling.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_LEGITIMIZE_ADDRESS_DISPLACEMENT (rtx *@var{offset1}, rtx *@var{offset2}, poly_int64 @var{orig_offset}, machine_mode @var{mode})
+This hook tries to split address offset @var{orig_offset} into
+two parts: one that should be added to the base address to create
+a local anchor point, and an additional offset that can be applied
+to the anchor to address a value of mode @var{mode}. The idea is that
+the local anchor could be shared by other accesses to nearby locations.
+
+The hook returns true if it succeeds, storing the offset of the
+anchor from the base in @var{offset1} and the offset of the final address
+from the anchor in @var{offset2}. The default implementation returns false.
+@end deftypefn
+
+@deftypefn {Target Hook} reg_class_t TARGET_SPILL_CLASS (reg_class_t, @var{machine_mode})
+This hook defines a class of registers which could be used for spilling
+pseudos of the given mode and class, or @code{NO_REGS} if only memory
+should be used. Not defining this hook is equivalent to returning
+@code{NO_REGS} for all inputs.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ADDITIONAL_ALLOCNO_CLASS_P (reg_class_t)
+This hook should return @code{true} if given class of registers should
+be an allocno class in any way. Usually RA uses only one register
+class from all classes containing the same register set. In some
+complicated cases, you need to have two or more such classes as
+allocno ones for RA correct work. Not defining this hook is
+equivalent to returning @code{false} for all inputs.
+@end deftypefn
+
+@deftypefn {Target Hook} scalar_int_mode TARGET_CSTORE_MODE (enum insn_code @var{icode})
+This hook defines the machine mode to use for the boolean result of
+conditional store patterns. The ICODE argument is the instruction code
+for the cstore being performed. Not definiting this hook is the same
+as accepting the mode encoded into operand 0 of the cstore expander
+patterns.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_COMPUTE_PRESSURE_CLASSES (enum reg_class *@var{pressure_classes})
+A target hook which lets a backend compute the set of pressure classes to
+be used by those optimization passes which take register pressure into
+account, as opposed to letting IRA compute them. It returns the number of
+register classes stored in the array @var{pressure_classes}.
+@end deftypefn
+
+@node Stack and Calling
+@section Stack Layout and Calling Conventions
+@cindex calling conventions
+
+@c prevent bad page break with this line
+This describes the stack layout and calling conventions.
+
+@menu
+* Frame Layout::
+* Exception Handling::
+* Stack Checking::
+* Frame Registers::
+* Elimination::
+* Stack Arguments::
+* Register Arguments::
+* Scalar Return::
+* Aggregate Return::
+* Caller Saves::
+* Function Entry::
+* Profiling::
+* Tail Calls::
+* Shrink-wrapping separate components::
+* Stack Smashing Protection::
+* Miscellaneous Register Hooks::
+@end menu
+
+@node Frame Layout
+@subsection Basic Stack Layout
+@cindex stack frame layout
+@cindex frame layout
+
+@c prevent bad page break with this line
+Here is the basic stack layout.
+
+@defmac STACK_GROWS_DOWNWARD
+Define this macro to be true if pushing a word onto the stack moves the stack
+pointer to a smaller address, and false otherwise.
+@end defmac
+
+@defmac STACK_PUSH_CODE
+This macro defines the operation used when something is pushed
+on the stack. In RTL, a push operation will be
+@code{(set (mem (STACK_PUSH_CODE (reg sp))) @dots{})}
+
+The choices are @code{PRE_DEC}, @code{POST_DEC}, @code{PRE_INC},
+and @code{POST_INC}. Which of these is correct depends on
+the stack direction and on whether the stack pointer points
+to the last item on the stack or whether it points to the
+space for the next item on the stack.
+
+The default is @code{PRE_DEC} when @code{STACK_GROWS_DOWNWARD} is
+true, which is almost always right, and @code{PRE_INC} otherwise,
+which is often wrong.
+@end defmac
+
+@defmac FRAME_GROWS_DOWNWARD
+Define this macro to nonzero value if the addresses of local variable slots
+are at negative offsets from the frame pointer.
+@end defmac
+
+@defmac ARGS_GROW_DOWNWARD
+Define this macro if successive arguments to a function occupy decreasing
+addresses on the stack.
+@end defmac
+
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_STARTING_FRAME_OFFSET (void)
+This hook returns the offset from the frame pointer to the first local
+variable slot to be allocated. If @code{FRAME_GROWS_DOWNWARD}, it is the
+offset to @emph{end} of the first slot allocated, otherwise it is the
+offset to @emph{beginning} of the first slot allocated. The default
+implementation returns 0.
+@end deftypefn
+
+@defmac STACK_ALIGNMENT_NEEDED
+Define to zero to disable final alignment of the stack during reload.
+The nonzero default for this macro is suitable for most ports.
+
+On ports where @code{TARGET_STARTING_FRAME_OFFSET} is nonzero or where there
+is a register save block following the local block that doesn't require
+alignment to @code{STACK_BOUNDARY}, it may be beneficial to disable
+stack alignment and do it in the backend.
+@end defmac
+
+@defmac STACK_POINTER_OFFSET
+Offset from the stack pointer register to the first location at which
+outgoing arguments are placed. If not specified, the default value of
+zero is used. This is the proper value for most machines.
+
+If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above
+the first location at which outgoing arguments are placed.
+@end defmac
+
+@defmac FIRST_PARM_OFFSET (@var{fundecl})
+Offset from the argument pointer register to the first argument's
+address. On some machines it may depend on the data type of the
+function.
+
+If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above
+the first argument's address.
+@end defmac
+
+@defmac STACK_DYNAMIC_OFFSET (@var{fundecl})
+Offset from the stack pointer register to an item dynamically allocated
+on the stack, e.g., by @code{alloca}.
+
+The default value for this macro is @code{STACK_POINTER_OFFSET} plus the
+length of the outgoing arguments. The default is correct for most
+machines. See @file{function.cc} for details.
+@end defmac
+
+@defmac INITIAL_FRAME_ADDRESS_RTX
+A C expression whose value is RTL representing the address of the initial
+stack frame. This address is passed to @code{RETURN_ADDR_RTX} and
+@code{DYNAMIC_CHAIN_ADDRESS}. If you don't define this macro, a reasonable
+default value will be used. Define this macro in order to make frame pointer
+elimination work in the presence of @code{__builtin_frame_address (count)} and
+@code{__builtin_return_address (count)} for @code{count} not equal to zero.
+@end defmac
+
+@defmac DYNAMIC_CHAIN_ADDRESS (@var{frameaddr})
+A C expression whose value is RTL representing the address in a stack
+frame where the pointer to the caller's frame is stored. Assume that
+@var{frameaddr} is an RTL expression for the address of the stack frame
+itself.
+
+If you don't define this macro, the default is to return the value
+of @var{frameaddr}---that is, the stack frame address is also the
+address of the stack word that points to the previous frame.
+@end defmac
+
+@defmac SETUP_FRAME_ADDRESSES
+A C expression that produces the machine-specific code to
+setup the stack so that arbitrary frames can be accessed. For example,
+on the SPARC, we must flush all of the register windows to the stack
+before we can access arbitrary stack frames. You will seldom need to
+define this macro. The default is to do nothing.
+@end defmac
+
+@deftypefn {Target Hook} rtx TARGET_BUILTIN_SETJMP_FRAME_VALUE (void)
+This target hook should return an rtx that is used to store
+the address of the current frame into the built in @code{setjmp} buffer.
+The default value, @code{virtual_stack_vars_rtx}, is correct for most
+machines. One reason you may need to define this target hook is if
+@code{hard_frame_pointer_rtx} is the appropriate value on your machine.
+@end deftypefn
+
+@defmac FRAME_ADDR_RTX (@var{frameaddr})
+A C expression whose value is RTL representing the value of the frame
+address for the current frame. @var{frameaddr} is the frame pointer
+of the current frame. This is used for __builtin_frame_address.
+You need only define this macro if the frame address is not the same
+as the frame pointer. Most machines do not need to define it.
+@end defmac
+
+@defmac RETURN_ADDR_RTX (@var{count}, @var{frameaddr})
+A C expression whose value is RTL representing the value of the return
+address for the frame @var{count} steps up from the current frame, after
+the prologue. @var{frameaddr} is the frame pointer of the @var{count}
+frame, or the frame pointer of the @var{count} @minus{} 1 frame if
+@code{RETURN_ADDR_IN_PREVIOUS_FRAME} is nonzero.
+
+The value of the expression must always be the correct address when
+@var{count} is zero, but may be @code{NULL_RTX} if there is no way to
+determine the return address of other frames.
+@end defmac
+
+@defmac RETURN_ADDR_IN_PREVIOUS_FRAME
+Define this macro to nonzero value if the return address of a particular
+stack frame is accessed from the frame pointer of the previous stack
+frame. The zero default for this macro is suitable for most ports.
+@end defmac
+
+@defmac INCOMING_RETURN_ADDR_RTX
+A C expression whose value is RTL representing the location of the
+incoming return address at the beginning of any function, before the
+prologue. This RTL is either a @code{REG}, indicating that the return
+value is saved in @samp{REG}, or a @code{MEM} representing a location in
+the stack.
+
+You only need to define this macro if you want to support call frame
+debugging information like that provided by DWARF 2.
+
+If this RTL is a @code{REG}, you should also define
+@code{DWARF_FRAME_RETURN_COLUMN} to @code{DWARF_FRAME_REGNUM (REGNO)}.
+@end defmac
+
+@defmac DWARF_ALT_FRAME_RETURN_COLUMN
+A C expression whose value is an integer giving a DWARF 2 column
+number that may be used as an alternative return column. The column
+must not correspond to any gcc hard register (that is, it must not
+be in the range of @code{DWARF_FRAME_REGNUM}).
+
+This macro can be useful if @code{DWARF_FRAME_RETURN_COLUMN} is set to a
+general register, but an alternative column needs to be used for signal
+frames. Some targets have also used different frame return columns
+over time.
+@end defmac
+
+@defmac DWARF_ZERO_REG
+A C expression whose value is an integer giving a DWARF 2 register
+number that is considered to always have the value zero. This should
+only be defined if the target has an architected zero register, and
+someone decided it was a good idea to use that register number to
+terminate the stack backtrace. New ports should avoid this.
+@end defmac
+
+@defmac DWARF_VERSION_DEFAULT
+A C expression whose value is the default dwarf standard version we'll honor
+and advertise when generating dwarf debug information, in absence of
+an explicit @option{-gdwarf-@var{version}} option on the command line.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_DWARF_HANDLE_FRAME_UNSPEC (const char *@var{label}, rtx @var{pattern}, int @var{index})
+This target hook allows the backend to emit frame-related insns that
+contain UNSPECs or UNSPEC_VOLATILEs. The DWARF 2 call frame debugging
+info engine will invoke it on insns of the form
+@smallexample
+(set (reg) (unspec [@dots{}] UNSPEC_INDEX))
+@end smallexample
+and
+@smallexample
+(set (reg) (unspec_volatile [@dots{}] UNSPECV_INDEX)).
+@end smallexample
+to let the backend emit the call frame instructions. @var{label} is
+the CFI label attached to the insn, @var{pattern} is the pattern of
+the insn and @var{index} is @code{UNSPEC_INDEX} or @code{UNSPECV_INDEX}.
+@end deftypefn
+
+@deftypefn {Target Hook} {unsigned int} TARGET_DWARF_POLY_INDETERMINATE_VALUE (unsigned int @var{i}, unsigned int *@var{factor}, int *@var{offset})
+Express the value of @code{poly_int} indeterminate @var{i} as a DWARF
+expression, with @var{i} counting from 1. Return the number of a DWARF
+register @var{R} and set @samp{*@var{factor}} and @samp{*@var{offset}} such
+that the value of the indeterminate is:
+@smallexample
+value_of(@var{R}) / @var{factor} - @var{offset}
+@end smallexample
+
+A target only needs to define this hook if it sets
+@samp{NUM_POLY_INT_COEFFS} to a value greater than 1.
+@end deftypefn
+
+@defmac INCOMING_FRAME_SP_OFFSET
+A C expression whose value is an integer giving the offset, in bytes,
+from the value of the stack pointer register to the top of the stack
+frame at the beginning of any function, before the prologue. The top of
+the frame is defined to be the value of the stack pointer in the
+previous frame, just before the call instruction.
+
+You only need to define this macro if you want to support call frame
+debugging information like that provided by DWARF 2.
+@end defmac
+
+@defmac DEFAULT_INCOMING_FRAME_SP_OFFSET
+Like @code{INCOMING_FRAME_SP_OFFSET}, but must be the same for all
+functions of the same ABI, and when using GAS @code{.cfi_*} directives
+must also agree with the default CFI GAS emits. Define this macro
+only if @code{INCOMING_FRAME_SP_OFFSET} can have different values
+between different functions of the same ABI or when
+@code{INCOMING_FRAME_SP_OFFSET} does not agree with GAS default CFI.
+@end defmac
+
+@defmac ARG_POINTER_CFA_OFFSET (@var{fundecl})
+A C expression whose value is an integer giving the offset, in bytes,
+from the argument pointer to the canonical frame address (cfa). The
+final value should coincide with that calculated by
+@code{INCOMING_FRAME_SP_OFFSET}. Which is unfortunately not usable
+during virtual register instantiation.
+
+The default value for this macro is
+@code{FIRST_PARM_OFFSET (fundecl) + crtl->args.pretend_args_size},
+which is correct for most machines; in general, the arguments are found
+immediately before the stack frame. Note that this is not the case on
+some targets that save registers into the caller's frame, such as SPARC
+and rs6000, and so such targets need to define this macro.
+
+You only need to define this macro if the default is incorrect, and you
+want to support call frame debugging information like that provided by
+DWARF 2.
+@end defmac
+
+@defmac FRAME_POINTER_CFA_OFFSET (@var{fundecl})
+If defined, a C expression whose value is an integer giving the offset
+in bytes from the frame pointer to the canonical frame address (cfa).
+The final value should coincide with that calculated by
+@code{INCOMING_FRAME_SP_OFFSET}.
+
+Normally the CFA is calculated as an offset from the argument pointer,
+via @code{ARG_POINTER_CFA_OFFSET}, but if the argument pointer is
+variable due to the ABI, this may not be possible. If this macro is
+defined, it implies that the virtual register instantiation should be
+based on the frame pointer instead of the argument pointer. Only one
+of @code{FRAME_POINTER_CFA_OFFSET} and @code{ARG_POINTER_CFA_OFFSET}
+should be defined.
+@end defmac
+
+@defmac CFA_FRAME_BASE_OFFSET (@var{fundecl})
+If defined, a C expression whose value is an integer giving the offset
+in bytes from the canonical frame address (cfa) to the frame base used
+in DWARF 2 debug information. The default is zero. A different value
+may reduce the size of debug information on some ports.
+@end defmac
+
+@node Exception Handling
+@subsection Exception Handling Support
+@cindex exception handling
+
+@defmac EH_RETURN_DATA_REGNO (@var{N})
+A C expression whose value is the @var{N}th register number used for
+data by exception handlers, or @code{INVALID_REGNUM} if fewer than
+@var{N} registers are usable.
+
+The exception handling library routines communicate with the exception
+handlers via a set of agreed upon registers. Ideally these registers
+should be call-clobbered; it is possible to use call-saved registers,
+but may negatively impact code size. The target must support at least
+2 data registers, but should define 4 if there are enough free registers.
+
+You must define this macro if you want to support call frame exception
+handling like that provided by DWARF 2.
+@end defmac
+
+@defmac EH_RETURN_STACKADJ_RTX
+A C expression whose value is RTL representing a location in which
+to store a stack adjustment to be applied before function return.
+This is used to unwind the stack to an exception handler's call frame.
+It will be assigned zero on code paths that return normally.
+
+Typically this is a call-clobbered hard register that is otherwise
+untouched by the epilogue, but could also be a stack slot.
+
+Do not define this macro if the stack pointer is saved and restored
+by the regular prolog and epilog code in the call frame itself; in
+this case, the exception handling library routines will update the
+stack location to be restored in place. Otherwise, you must define
+this macro if you want to support call frame exception handling like
+that provided by DWARF 2.
+@end defmac
+
+@defmac EH_RETURN_HANDLER_RTX
+A C expression whose value is RTL representing a location in which
+to store the address of an exception handler to which we should
+return. It will not be assigned on code paths that return normally.
+
+Typically this is the location in the call frame at which the normal
+return address is stored. For targets that return by popping an
+address off the stack, this might be a memory address just below
+the @emph{target} call frame rather than inside the current call
+frame. If defined, @code{EH_RETURN_STACKADJ_RTX} will have already
+been assigned, so it may be used to calculate the location of the
+target call frame.
+
+Some targets have more complex requirements than storing to an
+address calculable during initial code generation. In that case
+the @code{eh_return} instruction pattern should be used instead.
+
+If you want to support call frame exception handling, you must
+define either this macro or the @code{eh_return} instruction pattern.
+@end defmac
+
+@defmac RETURN_ADDR_OFFSET
+If defined, an integer-valued C expression for which rtl will be generated
+to add it to the exception handler address before it is searched in the
+exception handling tables, and to subtract it again from the address before
+using it to return to the exception handler.
+@end defmac
+
+@defmac ASM_PREFERRED_EH_DATA_FORMAT (@var{code}, @var{global})
+This macro chooses the encoding of pointers embedded in the exception
+handling sections. If at all possible, this should be defined such
+that the exception handling section will not require dynamic relocations,
+and so may be read-only.
+
+@var{code} is 0 for data, 1 for code labels, 2 for function pointers.
+@var{global} is true if the symbol may be affected by dynamic relocations.
+The macro should return a combination of the @code{DW_EH_PE_*} defines
+as found in @file{dwarf2.h}.
+
+If this macro is not defined, pointers will not be encoded but
+represented directly.
+@end defmac
+
+@defmac ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX (@var{file}, @var{encoding}, @var{size}, @var{addr}, @var{done})
+This macro allows the target to emit whatever special magic is required
+to represent the encoding chosen by @code{ASM_PREFERRED_EH_DATA_FORMAT}.
+Generic code takes care of pc-relative and indirect encodings; this must
+be defined if the target uses text-relative or data-relative encodings.
+
+This is a C statement that branches to @var{done} if the format was
+handled. @var{encoding} is the format chosen, @var{size} is the number
+of bytes that the format occupies, @var{addr} is the @code{SYMBOL_REF}
+to be emitted.
+@end defmac
+
+@defmac MD_FALLBACK_FRAME_STATE_FOR (@var{context}, @var{fs})
+This macro allows the target to add CPU and operating system specific
+code to the call-frame unwinder for use when there is no unwind data
+available. The most common reason to implement this macro is to unwind
+through signal frames.
+
+This macro is called from @code{uw_frame_state_for} in
+@file{unwind-dw2.c}, @file{unwind-dw2-xtensa.c} and
+@file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context};
+@var{fs} is an @code{_Unwind_FrameState}. Examine @code{context->ra}
+for the address of the code being executed and @code{context->cfa} for
+the stack pointer value. If the frame can be decoded, the register
+save addresses should be updated in @var{fs} and the macro should
+evaluate to @code{_URC_NO_REASON}. If the frame cannot be decoded,
+the macro should evaluate to @code{_URC_END_OF_STACK}.
+
+For proper signal handling in Java this macro is accompanied by
+@code{MAKE_THROW_FRAME}, defined in @file{libjava/include/*-signal.h} headers.
+@end defmac
+
+@defmac MD_HANDLE_UNWABI (@var{context}, @var{fs})
+This macro allows the target to add operating system specific code to the
+call-frame unwinder to handle the IA-64 @code{.unwabi} unwinding directive,
+usually used for signal or interrupt frames.
+
+This macro is called from @code{uw_update_context} in libgcc's
+@file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context};
+@var{fs} is an @code{_Unwind_FrameState}. Examine @code{fs->unwabi}
+for the abi and context in the @code{.unwabi} directive. If the
+@code{.unwabi} directive can be handled, the register save addresses should
+be updated in @var{fs}.
+@end defmac
+
+@defmac TARGET_USES_WEAK_UNWIND_INFO
+A C expression that evaluates to true if the target requires unwind
+info to be given comdat linkage. Define it to be @code{1} if comdat
+linkage is necessary. The default is @code{0}.
+@end defmac
+
+@node Stack Checking
+@subsection Specifying How Stack Checking is Done
+
+GCC will check that stack references are within the boundaries of the
+stack, if the option @option{-fstack-check} is specified, in one of
+three ways:
+
+@enumerate
+@item
+If the value of the @code{STACK_CHECK_BUILTIN} macro is nonzero, GCC
+will assume that you have arranged for full stack checking to be done
+at appropriate places in the configuration files. GCC will not do
+other special processing.
+
+@item
+If @code{STACK_CHECK_BUILTIN} is zero and the value of the
+@code{STACK_CHECK_STATIC_BUILTIN} macro is nonzero, GCC will assume
+that you have arranged for static stack checking (checking of the
+static stack frame of functions) to be done at appropriate places
+in the configuration files. GCC will only emit code to do dynamic
+stack checking (checking on dynamic stack allocations) using the third
+approach below.
+
+@item
+If neither of the above are true, GCC will generate code to periodically
+``probe'' the stack pointer using the values of the macros defined below.
+@end enumerate
+
+If neither STACK_CHECK_BUILTIN nor STACK_CHECK_STATIC_BUILTIN is defined,
+GCC will change its allocation strategy for large objects if the option
+@option{-fstack-check} is specified: they will always be allocated
+dynamically if their size exceeds @code{STACK_CHECK_MAX_VAR_SIZE} bytes.
+
+@defmac STACK_CHECK_BUILTIN
+A nonzero value if stack checking is done by the configuration files in a
+machine-dependent manner. You should define this macro if stack checking
+is required by the ABI of your machine or if you would like to do stack
+checking in some more efficient way than the generic approach. The default
+value of this macro is zero.
+@end defmac
+
+@defmac STACK_CHECK_STATIC_BUILTIN
+A nonzero value if static stack checking is done by the configuration files
+in a machine-dependent manner. You should define this macro if you would
+like to do static stack checking in some more efficient way than the generic
+approach. The default value of this macro is zero.
+@end defmac
+
+@defmac STACK_CHECK_PROBE_INTERVAL_EXP
+An integer specifying the interval at which GCC must generate stack probe
+instructions, defined as 2 raised to this integer. You will normally
+define this macro so that the interval be no larger than the size of
+the ``guard pages'' at the end of a stack area. The default value
+of 12 (4096-byte interval) is suitable for most systems.
+@end defmac
+
+@defmac STACK_CHECK_MOVING_SP
+An integer which is nonzero if GCC should move the stack pointer page by page
+when doing probes. This can be necessary on systems where the stack pointer
+contains the bottom address of the memory area accessible to the executing
+thread at any point in time. In this situation an alternate signal stack
+is required in order to be able to recover from a stack overflow. The
+default value of this macro is zero.
+@end defmac
+
+@defmac STACK_CHECK_PROTECT
+The number of bytes of stack needed to recover from a stack overflow, for
+languages where such a recovery is supported. The default value of 4KB/8KB
+with the @code{setjmp}/@code{longjmp}-based exception handling mechanism and
+8KB/12KB with other exception handling mechanisms should be adequate for most
+architectures and operating systems.
+@end defmac
+
+The following macros are relevant only if neither STACK_CHECK_BUILTIN
+nor STACK_CHECK_STATIC_BUILTIN is defined; you can omit them altogether
+in the opposite case.
+
+@defmac STACK_CHECK_MAX_FRAME_SIZE
+The maximum size of a stack frame, in bytes. GCC will generate probe
+instructions in non-leaf functions to ensure at least this many bytes of
+stack are available. If a stack frame is larger than this size, stack
+checking will not be reliable and GCC will issue a warning. The
+default is chosen so that GCC only generates one instruction on most
+systems. You should normally not change the default value of this macro.
+@end defmac
+
+@defmac STACK_CHECK_FIXED_FRAME_SIZE
+GCC uses this value to generate the above warning message. It
+represents the amount of fixed frame used by a function, not including
+space for any callee-saved registers, temporaries and user variables.
+You need only specify an upper bound for this amount and will normally
+use the default of four words.
+@end defmac
+
+@defmac STACK_CHECK_MAX_VAR_SIZE
+The maximum size, in bytes, of an object that GCC will place in the
+fixed area of the stack frame when the user specifies
+@option{-fstack-check}.
+GCC computed the default from the values of the above macros and you will
+normally not need to override that default.
+@end defmac
+
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE (void)
+Some targets have an ABI defined interval for which no probing needs to be done.
+When a probe does need to be done this same interval is used as the probe distance
+up when doing stack clash protection for alloca.
+On such targets this value can be set to override the default probing up interval.
+Define this variable to return nonzero if such a probe range is required or zero otherwise.
+Defining this hook also requires your functions which make use of alloca to have at least 8 byes
+of outgoing arguments. If this is not the case the stack will be corrupted.
+You need not define this macro if it would always have the value zero.
+@end deftypefn
+
+@need 2000
+@node Frame Registers
+@subsection Registers That Address the Stack Frame
+
+@c prevent bad page break with this line
+This discusses registers that address the stack frame.
+
+@defmac STACK_POINTER_REGNUM
+The register number of the stack pointer register, which must also be a
+fixed register according to @code{FIXED_REGISTERS}. On most machines,
+the hardware determines which register this is.
+@end defmac
+
+@defmac FRAME_POINTER_REGNUM
+The register number of the frame pointer register, which is used to
+access automatic variables in the stack frame. On some machines, the
+hardware determines which register this is. On other machines, you can
+choose any register you wish for this purpose.
+@end defmac
+
+@defmac HARD_FRAME_POINTER_REGNUM
+On some machines the offset between the frame pointer and starting
+offset of the automatic variables is not known until after register
+allocation has been done (for example, because the saved registers are
+between these two locations). On those machines, define
+@code{FRAME_POINTER_REGNUM} the number of a special, fixed register to
+be used internally until the offset is known, and define
+@code{HARD_FRAME_POINTER_REGNUM} to be the actual hard register number
+used for the frame pointer.
+
+You should define this macro only in the very rare circumstances when it
+is not possible to calculate the offset between the frame pointer and
+the automatic variables until after register allocation has been
+completed. When this macro is defined, you must also indicate in your
+definition of @code{ELIMINABLE_REGS} how to eliminate
+@code{FRAME_POINTER_REGNUM} into either @code{HARD_FRAME_POINTER_REGNUM}
+or @code{STACK_POINTER_REGNUM}.
+
+Do not define this macro if it would be the same as
+@code{FRAME_POINTER_REGNUM}.
+@end defmac
+
+@defmac ARG_POINTER_REGNUM
+The register number of the arg pointer register, which is used to access
+the function's argument list. On some machines, this is the same as the
+frame pointer register. On some machines, the hardware determines which
+register this is. On other machines, you can choose any register you
+wish for this purpose. If this is not the same register as the frame
+pointer register, then you must mark it as a fixed register according to
+@code{FIXED_REGISTERS}, or arrange to be able to eliminate it
+(@pxref{Elimination}).
+@end defmac
+
+@defmac HARD_FRAME_POINTER_IS_FRAME_POINTER
+Define this to a preprocessor constant that is nonzero if
+@code{hard_frame_pointer_rtx} and @code{frame_pointer_rtx} should be
+the same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM
+== FRAME_POINTER_REGNUM)}; you only need to define this macro if that
+definition is not suitable for use in preprocessor conditionals.
+@end defmac
+
+@defmac HARD_FRAME_POINTER_IS_ARG_POINTER
+Define this to a preprocessor constant that is nonzero if
+@code{hard_frame_pointer_rtx} and @code{arg_pointer_rtx} should be the
+same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM ==
+ARG_POINTER_REGNUM)}; you only need to define this macro if that
+definition is not suitable for use in preprocessor conditionals.
+@end defmac
+
+@defmac RETURN_ADDRESS_POINTER_REGNUM
+The register number of the return address pointer register, which is used to
+access the current function's return address from the stack. On some
+machines, the return address is not at a fixed offset from the frame
+pointer or stack pointer or argument pointer. This register can be defined
+to point to the return address on the stack, and then be converted by
+@code{ELIMINABLE_REGS} into either the frame pointer or stack pointer.
+
+Do not define this macro unless there is no other way to get the return
+address from the stack.
+@end defmac
+
+@defmac STATIC_CHAIN_REGNUM
+@defmacx STATIC_CHAIN_INCOMING_REGNUM
+Register numbers used for passing a function's static chain pointer. If
+register windows are used, the register number as seen by the called
+function is @code{STATIC_CHAIN_INCOMING_REGNUM}, while the register
+number as seen by the calling function is @code{STATIC_CHAIN_REGNUM}. If
+these registers are the same, @code{STATIC_CHAIN_INCOMING_REGNUM} need
+not be defined.
+
+The static chain register need not be a fixed register.
+
+If the static chain is passed in memory, these macros should not be
+defined; instead, the @code{TARGET_STATIC_CHAIN} hook should be used.
+@end defmac
+
+@deftypefn {Target Hook} rtx TARGET_STATIC_CHAIN (const_tree @var{fndecl_or_type}, bool @var{incoming_p})
+This hook replaces the use of @code{STATIC_CHAIN_REGNUM} et al for
+targets that may use different static chain locations for different
+nested functions. This may be required if the target has function
+attributes that affect the calling conventions of the function and
+those calling conventions use different static chain locations.
+
+The default version of this hook uses @code{STATIC_CHAIN_REGNUM} et al.
+
+If the static chain is passed in memory, this hook should be used to
+provide rtx giving @code{mem} expressions that denote where they are stored.
+Often the @code{mem} expression as seen by the caller will be at an offset
+from the stack pointer and the @code{mem} expression as seen by the callee
+will be at an offset from the frame pointer.
+@findex stack_pointer_rtx
+@findex frame_pointer_rtx
+@findex arg_pointer_rtx
+The variables @code{stack_pointer_rtx}, @code{frame_pointer_rtx}, and
+@code{arg_pointer_rtx} will have been initialized and should be used
+to refer to those items.
+@end deftypefn
+
+@defmac DWARF_FRAME_REGISTERS
+This macro specifies the maximum number of hard registers that can be
+saved in a call frame. This is used to size data structures used in
+DWARF2 exception handling.
+
+Prior to GCC 3.0, this macro was needed in order to establish a stable
+exception handling ABI in the face of adding new hard registers for ISA
+extensions. In GCC 3.0 and later, the EH ABI is insulated from changes
+in the number of hard registers. Nevertheless, this macro can still be
+used to reduce the runtime memory requirements of the exception handling
+routines, which can be substantial if the ISA contains a lot of
+registers that are not call-saved.
+
+If this macro is not defined, it defaults to
+@code{FIRST_PSEUDO_REGISTER}.
+@end defmac
+
+@defmac PRE_GCC3_DWARF_FRAME_REGISTERS
+
+This macro is similar to @code{DWARF_FRAME_REGISTERS}, but is provided
+for backward compatibility in pre GCC 3.0 compiled code.
+
+If this macro is not defined, it defaults to
+@code{DWARF_FRAME_REGISTERS}.
+@end defmac
+
+@defmac DWARF_REG_TO_UNWIND_COLUMN (@var{regno})
+
+Define this macro if the target's representation for dwarf registers
+is different than the internal representation for unwind column.
+Given a dwarf register, this macro should return the internal unwind
+column number to use instead.
+@end defmac
+
+@defmac DWARF_FRAME_REGNUM (@var{regno})
+
+Define this macro if the target's representation for dwarf registers
+used in .eh_frame or .debug_frame is different from that used in other
+debug info sections. Given a GCC hard register number, this macro
+should return the .eh_frame register number. The default is
+@code{DEBUGGER_REGNO (@var{regno})}.
+
+@end defmac
+
+@defmac DWARF2_FRAME_REG_OUT (@var{regno}, @var{for_eh})
+
+Define this macro to map register numbers held in the call frame info
+that GCC has collected using @code{DWARF_FRAME_REGNUM} to those that
+should be output in .debug_frame (@code{@var{for_eh}} is zero) and
+.eh_frame (@code{@var{for_eh}} is nonzero). The default is to
+return @code{@var{regno}}.
+
+@end defmac
+
+@defmac REG_VALUE_IN_UNWIND_CONTEXT
+
+Define this macro if the target stores register values as
+@code{_Unwind_Word} type in unwind context. It should be defined if
+target register size is larger than the size of @code{void *}. The
+default is to store register values as @code{void *} type.
+
+@end defmac
+
+@defmac ASSUME_EXTENDED_UNWIND_CONTEXT
+
+Define this macro to be 1 if the target always uses extended unwind
+context with version, args_size and by_value fields. If it is undefined,
+it will be defined to 1 when @code{REG_VALUE_IN_UNWIND_CONTEXT} is
+defined and 0 otherwise.
+
+@end defmac
+
+@defmac DWARF_LAZY_REGISTER_VALUE (@var{regno}, @var{value})
+Define this macro if the target has pseudo DWARF registers whose
+values need to be computed lazily on demand by the unwinder (such as when
+referenced in a CFA expression). The macro returns true if @var{regno}
+is such a register and stores its value in @samp{*@var{value}} if so.
+@end defmac
+
+@node Elimination
+@subsection Eliminating Frame Pointer and Arg Pointer
+
+@c prevent bad page break with this line
+This is about eliminating the frame pointer and arg pointer.
+
+@deftypefn {Target Hook} bool TARGET_FRAME_POINTER_REQUIRED (void)
+This target hook should return @code{true} if a function must have and use
+a frame pointer. This target hook is called in the reload pass. If its return
+value is @code{true} the function will have a frame pointer.
+
+This target hook can in principle examine the current function and decide
+according to the facts, but on most machines the constant @code{false} or the
+constant @code{true} suffices. Use @code{false} when the machine allows code
+to be generated with no frame pointer, and doing so saves some time or space.
+Use @code{true} when there is no possible advantage to avoiding a frame
+pointer.
+
+In certain cases, the compiler does not know how to produce valid code
+without a frame pointer. The compiler recognizes those cases and
+automatically gives the function a frame pointer regardless of what
+@code{targetm.frame_pointer_required} returns. You don't need to worry about
+them.
+
+In a function that does not require a frame pointer, the frame pointer
+register can be allocated for ordinary usage, unless you mark it as a
+fixed register. See @code{FIXED_REGISTERS} for more information.
+
+Default return value is @code{false}.
+@end deftypefn
+
+@defmac ELIMINABLE_REGS
+This macro specifies a table of register pairs used to eliminate
+unneeded registers that point into the stack frame.
+
+The definition of this macro is a list of structure initializations, each
+of which specifies an original and replacement register.
+
+On some machines, the position of the argument pointer is not known until
+the compilation is completed. In such a case, a separate hard register
+must be used for the argument pointer. This register can be eliminated by
+replacing it with either the frame pointer or the argument pointer,
+depending on whether or not the frame pointer has been eliminated.
+
+In this case, you might specify:
+@smallexample
+#define ELIMINABLE_REGS \
+@{@{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM@}, \
+ @{ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM@}, \
+ @{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM@}@}
+@end smallexample
+
+Note that the elimination of the argument pointer with the stack pointer is
+specified first since that is the preferred elimination.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_CAN_ELIMINATE (const int @var{from_reg}, const int @var{to_reg})
+This target hook should return @code{true} if the compiler is allowed to
+try to replace register number @var{from_reg} with register number
+@var{to_reg}. This target hook will usually be @code{true}, since most of the
+cases preventing register elimination are things that the compiler already
+knows about.
+
+Default return value is @code{true}.
+@end deftypefn
+
+@defmac INITIAL_ELIMINATION_OFFSET (@var{from-reg}, @var{to-reg}, @var{offset-var})
+This macro returns the initial difference between the specified pair
+of registers. The value would be computed from information
+such as the result of @code{get_frame_size ()} and the tables of
+registers @code{df_regs_ever_live_p} and @code{call_used_regs}.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_COMPUTE_FRAME_LAYOUT (void)
+This target hook is called once each time the frame layout needs to be
+recalculated. The calculations can be cached by the target and can then
+be used by @code{INITIAL_ELIMINATION_OFFSET} instead of re-computing the
+layout on every invocation of that hook. This is particularly useful
+for targets that have an expensive frame layout function. Implementing
+this callback is optional.
+@end deftypefn
+
+@node Stack Arguments
+@subsection Passing Function Arguments on the Stack
+@cindex arguments on stack
+@cindex stack arguments
+
+The macros in this section control how arguments are passed
+on the stack. See the following section for other macros that
+control passing certain arguments in registers.
+
+@deftypefn {Target Hook} bool TARGET_PROMOTE_PROTOTYPES (const_tree @var{fntype})
+This target hook returns @code{true} if an argument declared in a
+prototype as an integral type smaller than @code{int} should actually be
+passed as an @code{int}. In addition to avoiding errors in certain
+cases of mismatch, it also makes for better code on certain machines.
+The default is to not promote prototypes.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_PUSH_ARGUMENT (unsigned int @var{npush})
+This target hook returns @code{true} if push instructions will be
+used to pass outgoing arguments. When the push instruction usage is
+optional, @var{npush} is nonzero to indicate the number of bytes to
+push. Otherwise, @var{npush} is zero. If the target machine does not
+have a push instruction or push instruction should be avoided,
+@code{false} should be returned. That directs GCC to use an alternate
+strategy: to allocate the entire argument block and then store the
+arguments into it. If this target hook may return @code{true},
+@code{PUSH_ROUNDING} must be defined.
+@end deftypefn
+
+@defmac PUSH_ARGS_REVERSED
+A C expression. If nonzero, function arguments will be evaluated from
+last to first, rather than from first to last. If this macro is not
+defined, it defaults to @code{PUSH_ARGS} on targets where the stack
+and args grow in opposite directions, and 0 otherwise.
+@end defmac
+
+@defmac PUSH_ROUNDING (@var{npushed})
+A C expression that is the number of bytes actually pushed onto the
+stack when an instruction attempts to push @var{npushed} bytes.
+
+On some machines, the definition
+
+@smallexample
+#define PUSH_ROUNDING(BYTES) (BYTES)
+@end smallexample
+
+@noindent
+will suffice. But on other machines, instructions that appear
+to push one byte actually push two bytes in an attempt to maintain
+alignment. Then the definition should be
+
+@smallexample
+#define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1)
+@end smallexample
+
+If the value of this macro has a type, it should be an unsigned type.
+@end defmac
+
+@findex outgoing_args_size
+@findex crtl->outgoing_args_size
+@defmac ACCUMULATE_OUTGOING_ARGS
+A C expression. If nonzero, the maximum amount of space required for outgoing arguments
+will be computed and placed into
+@code{crtl->outgoing_args_size}. No space will be pushed
+onto the stack for each call; instead, the function prologue should
+increase the stack frame size by this amount.
+
+Setting both @code{PUSH_ARGS} and @code{ACCUMULATE_OUTGOING_ARGS}
+is not proper.
+@end defmac
+
+@defmac REG_PARM_STACK_SPACE (@var{fndecl})
+Define this macro if functions should assume that stack space has been
+allocated for arguments even when their values are passed in
+registers.
+
+The value of this macro is the size, in bytes, of the area reserved for
+arguments passed in registers for the function represented by @var{fndecl},
+which can be zero if GCC is calling a library function.
+The argument @var{fndecl} can be the FUNCTION_DECL, or the type itself
+of the function.
+
+This space can be allocated by the caller, or be a part of the
+machine-dependent stack frame: @code{OUTGOING_REG_PARM_STACK_SPACE} says
+which.
+@end defmac
+@c above is overfull. not sure what to do. --mew 5feb93 did
+@c something, not sure if it looks good. --mew 10feb93
+
+@defmac INCOMING_REG_PARM_STACK_SPACE (@var{fndecl})
+Like @code{REG_PARM_STACK_SPACE}, but for incoming register arguments.
+Define this macro if space guaranteed when compiling a function body
+is different to space required when making a call, a situation that
+can arise with K&R style function definitions.
+@end defmac
+
+@defmac OUTGOING_REG_PARM_STACK_SPACE (@var{fntype})
+Define this to a nonzero value if it is the responsibility of the
+caller to allocate the area reserved for arguments passed in registers
+when calling a function of @var{fntype}. @var{fntype} may be NULL
+if the function called is a library function.
+
+If @code{ACCUMULATE_OUTGOING_ARGS} is defined, this macro controls
+whether the space for these arguments counts in the value of
+@code{crtl->outgoing_args_size}.
+@end defmac
+
+@defmac STACK_PARMS_IN_REG_PARM_AREA
+Define this macro if @code{REG_PARM_STACK_SPACE} is defined, but the
+stack parameters don't skip the area specified by it.
+@c i changed this, makes more sens and it should have taken care of the
+@c overfull.. not as specific, tho. --mew 5feb93
+
+Normally, when a parameter is not passed in registers, it is placed on the
+stack beyond the @code{REG_PARM_STACK_SPACE} area. Defining this macro
+suppresses this behavior and causes the parameter to be passed on the
+stack in its natural location.
+@end defmac
+
+@deftypefn {Target Hook} poly_int64 TARGET_RETURN_POPS_ARGS (tree @var{fundecl}, tree @var{funtype}, poly_int64 @var{size})
+This target hook returns the number of bytes of its own arguments that
+a function pops on returning, or 0 if the function pops no arguments
+and the caller must therefore pop them all after the function returns.
+
+@var{fundecl} is a C variable whose value is a tree node that describes
+the function in question. Normally it is a node of type
+@code{FUNCTION_DECL} that describes the declaration of the function.
+From this you can obtain the @code{DECL_ATTRIBUTES} of the function.
+
+@var{funtype} is a C variable whose value is a tree node that
+describes the function in question. Normally it is a node of type
+@code{FUNCTION_TYPE} that describes the data type of the function.
+From this it is possible to obtain the data types of the value and
+arguments (if known).
+
+When a call to a library function is being considered, @var{fundecl}
+will contain an identifier node for the library function. Thus, if
+you need to distinguish among various library functions, you can do so
+by their names. Note that ``library function'' in this context means
+a function used to perform arithmetic, whose name is known specially
+in the compiler and was not mentioned in the C code being compiled.
+
+@var{size} is the number of bytes of arguments passed on the
+stack. If a variable number of bytes is passed, it is zero, and
+argument popping will always be the responsibility of the calling function.
+
+On the VAX, all functions always pop their arguments, so the definition
+of this macro is @var{size}. On the 68000, using the standard
+calling convention, no functions pop their arguments, so the value of
+the macro is always 0 in this case. But an alternative calling
+convention is available in which functions that take a fixed number of
+arguments pop them but other functions (such as @code{printf}) pop
+nothing (the caller pops all). When this convention is in use,
+@var{funtype} is examined to determine whether a function takes a fixed
+number of arguments.
+@end deftypefn
+
+@defmac CALL_POPS_ARGS (@var{cum})
+A C expression that should indicate the number of bytes a call sequence
+pops off the stack. It is added to the value of @code{RETURN_POPS_ARGS}
+when compiling a function call.
+
+@var{cum} is the variable in which all arguments to the called function
+have been accumulated.
+
+On certain architectures, such as the SH5, a call trampoline is used
+that pops certain registers off the stack, depending on the arguments
+that have been passed to the function. Since this is a property of the
+call site, not of the called function, @code{RETURN_POPS_ARGS} is not
+appropriate.
+@end defmac
+
+@node Register Arguments
+@subsection Passing Arguments in Registers
+@cindex arguments in registers
+@cindex registers arguments
+
+This section describes the macros which let you control how various
+types of arguments are passed in registers or how they are arranged in
+the stack.
+
+@deftypefn {Target Hook} rtx TARGET_FUNCTION_ARG (cumulative_args_t @var{ca}, const function_arg_info @var{&arg})
+Return an RTX indicating whether function argument @var{arg} is passed
+in a register and if so, which register. Argument @var{ca} summarizes all
+the previous arguments.
+
+The return value is usually either a @code{reg} RTX for the hard
+register in which to pass the argument, or zero to pass the argument
+on the stack.
+
+The value of the expression can also be a @code{parallel} RTX@. This is
+used when an argument is passed in multiple locations. The mode of the
+@code{parallel} should be the mode of the entire argument. The
+@code{parallel} holds any number of @code{expr_list} pairs; each one
+describes where part of the argument is passed. In each
+@code{expr_list} the first operand must be a @code{reg} RTX for the hard
+register in which to pass this part of the argument, and the mode of the
+register RTX indicates how large this part of the argument is. The
+second operand of the @code{expr_list} is a @code{const_int} which gives
+the offset in bytes into the entire argument of where this part starts.
+As a special exception the first @code{expr_list} in the @code{parallel}
+RTX may have a first operand of zero. This indicates that the entire
+argument is also stored on the stack.
+
+The last time this hook is called, it is called with @code{MODE ==
+VOIDmode}, and its result is passed to the @code{call} or @code{call_value}
+pattern as operands 2 and 3 respectively.
+
+@cindex @file{stdarg.h} and register arguments
+The usual way to make the ISO library @file{stdarg.h} work on a
+machine where some arguments are usually passed in registers, is to
+cause nameless arguments to be passed on the stack instead. This is
+done by making @code{TARGET_FUNCTION_ARG} return 0 whenever
+@var{named} is @code{false}.
+
+@cindex @code{TARGET_MUST_PASS_IN_STACK}, and @code{TARGET_FUNCTION_ARG}
+@cindex @code{REG_PARM_STACK_SPACE}, and @code{TARGET_FUNCTION_ARG}
+You may use the hook @code{targetm.calls.must_pass_in_stack}
+in the definition of this macro to determine if this argument is of a
+type that must be passed in the stack. If @code{REG_PARM_STACK_SPACE}
+is not defined and @code{TARGET_FUNCTION_ARG} returns nonzero for such an
+argument, the compiler will abort. If @code{REG_PARM_STACK_SPACE} is
+defined, the argument will be computed in the stack and then loaded into
+a register.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_MUST_PASS_IN_STACK (const function_arg_info @var{&arg})
+This target hook should return @code{true} if we should not pass @var{arg}
+solely in registers. The file @file{expr.h} defines a
+definition that is usually appropriate, refer to @file{expr.h} for additional
+documentation.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_FUNCTION_INCOMING_ARG (cumulative_args_t @var{ca}, const function_arg_info @var{&arg})
+Define this hook if the caller and callee on the target have different
+views of where arguments are passed. Also define this hook if there are
+functions that are never directly called, but are invoked by the hardware
+and which have nonstandard calling conventions.
+
+In this case @code{TARGET_FUNCTION_ARG} computes the register in
+which the caller passes the value, and
+@code{TARGET_FUNCTION_INCOMING_ARG} should be defined in a similar
+fashion to tell the function being called where the arguments will
+arrive.
+
+@code{TARGET_FUNCTION_INCOMING_ARG} can also return arbitrary address
+computation using hard register, which can be forced into a register,
+so that it can be used to pass special arguments.
+
+If @code{TARGET_FUNCTION_INCOMING_ARG} is not defined,
+@code{TARGET_FUNCTION_ARG} serves both purposes.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_USE_PSEUDO_PIC_REG (void)
+This hook should return 1 in case pseudo register should be created
+for pic_offset_table_rtx during function expand.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_INIT_PIC_REG (void)
+Perform a target dependent initialization of pic_offset_table_rtx.
+This hook is called at the start of register allocation.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_ARG_PARTIAL_BYTES (cumulative_args_t @var{cum}, const function_arg_info @var{&arg})
+This target hook returns the number of bytes at the beginning of an
+argument that must be put in registers. The value must be zero for
+arguments that are passed entirely in registers or that are entirely
+pushed on the stack.
+
+On some machines, certain arguments must be passed partially in
+registers and partially in memory. On these machines, typically the
+first few words of arguments are passed in registers, and the rest
+on the stack. If a multi-word argument (a @code{double} or a
+structure) crosses that boundary, its first few words must be passed
+in registers and the rest must be pushed. This macro tells the
+compiler when this occurs, and how many bytes should go in registers.
+
+@code{TARGET_FUNCTION_ARG} for these arguments should return the first
+register to be used by the caller for this argument; likewise
+@code{TARGET_FUNCTION_INCOMING_ARG}, for the called function.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_PASS_BY_REFERENCE (cumulative_args_t @var{cum}, const function_arg_info @var{&arg})
+This target hook should return @code{true} if argument @var{arg} at the
+position indicated by @var{cum} should be passed by reference. This
+predicate is queried after target independent reasons for being
+passed by reference, such as @code{TREE_ADDRESSABLE (@var{arg}.type)}.
+
+If the hook returns true, a copy of that argument is made in memory and a
+pointer to the argument is passed instead of the argument itself.
+The pointer is passed in whatever way is appropriate for passing a pointer
+to that type.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CALLEE_COPIES (cumulative_args_t @var{cum}, const function_arg_info @var{&arg})
+The function argument described by the parameters to this hook is
+known to be passed by reference. The hook should return true if the
+function argument should be copied by the callee instead of copied
+by the caller.
+
+For any argument for which the hook returns true, if it can be
+determined that the argument is not modified, then a copy need
+not be generated.
+
+The default version of this hook always returns false.
+@end deftypefn
+
+@defmac CUMULATIVE_ARGS
+A C type for declaring a variable that is used as the first argument
+of @code{TARGET_FUNCTION_ARG} and other related values. For some
+target machines, the type @code{int} suffices and can hold the number
+of bytes of argument so far.
+
+There is no need to record in @code{CUMULATIVE_ARGS} anything about the
+arguments that have been passed on the stack. The compiler has other
+variables to keep track of that. For target machines on which all
+arguments are passed on the stack, there is no need to store anything in
+@code{CUMULATIVE_ARGS}; however, the data structure must exist and
+should not be empty, so use @code{int}.
+@end defmac
+
+@defmac OVERRIDE_ABI_FORMAT (@var{fndecl})
+If defined, this macro is called before generating any code for a
+function, but after the @var{cfun} descriptor for the function has been
+created. The back end may use this macro to update @var{cfun} to
+reflect an ABI other than that which would normally be used by default.
+If the compiler is generating code for a compiler-generated function,
+@var{fndecl} may be @code{NULL}.
+@end defmac
+
+@defmac INIT_CUMULATIVE_ARGS (@var{cum}, @var{fntype}, @var{libname}, @var{fndecl}, @var{n_named_args})
+A C statement (sans semicolon) for initializing the variable
+@var{cum} for the state at the beginning of the argument list. The
+variable has type @code{CUMULATIVE_ARGS}. The value of @var{fntype}
+is the tree node for the data type of the function which will receive
+the args, or 0 if the args are to a compiler support library function.
+For direct calls that are not libcalls, @var{fndecl} contain the
+declaration node of the function. @var{fndecl} is also set when
+@code{INIT_CUMULATIVE_ARGS} is used to find arguments for the function
+being compiled. @var{n_named_args} is set to the number of named
+arguments, including a structure return address if it is passed as a
+parameter, when making a call. When processing incoming arguments,
+@var{n_named_args} is set to @minus{}1.
+
+When processing a call to a compiler support library function,
+@var{libname} identifies which one. It is a @code{symbol_ref} rtx which
+contains the name of the function, as a string. @var{libname} is 0 when
+an ordinary C function call is being processed. Thus, each time this
+macro is called, either @var{libname} or @var{fntype} is nonzero, but
+never both of them at once.
+@end defmac
+
+@defmac INIT_CUMULATIVE_LIBCALL_ARGS (@var{cum}, @var{mode}, @var{libname})
+Like @code{INIT_CUMULATIVE_ARGS} but only used for outgoing libcalls,
+it gets a @code{MODE} argument instead of @var{fntype}, that would be
+@code{NULL}. @var{indirect} would always be zero, too. If this macro
+is not defined, @code{INIT_CUMULATIVE_ARGS (cum, NULL_RTX, libname,
+0)} is used instead.
+@end defmac
+
+@defmac INIT_CUMULATIVE_INCOMING_ARGS (@var{cum}, @var{fntype}, @var{libname})
+Like @code{INIT_CUMULATIVE_ARGS} but overrides it for the purposes of
+finding the arguments for the function being compiled. If this macro is
+undefined, @code{INIT_CUMULATIVE_ARGS} is used instead.
+
+The value passed for @var{libname} is always 0, since library routines
+with special calling conventions are never compiled with GCC@. The
+argument @var{libname} exists for symmetry with
+@code{INIT_CUMULATIVE_ARGS}.
+@c could use "this macro" in place of @code{INIT_CUMULATIVE_ARGS}, maybe.
+@c --mew 5feb93 i switched the order of the sentences. --mew 10feb93
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_FUNCTION_ARG_ADVANCE (cumulative_args_t @var{ca}, const function_arg_info @var{&arg})
+This hook updates the summarizer variable pointed to by @var{ca} to
+advance past argument @var{arg} in the argument list. Once this is done,
+the variable @var{cum} is suitable for analyzing the @emph{following}
+argument with @code{TARGET_FUNCTION_ARG}, etc.
+
+This hook need not do anything if the argument in question was passed
+on the stack. The compiler knows how to track the amount of stack space
+used for arguments without any special help.
+@end deftypefn
+
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_FUNCTION_ARG_OFFSET (machine_mode @var{mode}, const_tree @var{type})
+This hook returns the number of bytes to add to the offset of an
+argument of type @var{type} and mode @var{mode} when passed in memory.
+This is needed for the SPU, which passes @code{char} and @code{short}
+arguments in the preferred slot that is in the middle of the quad word
+instead of starting at the top. The default implementation returns 0.
+@end deftypefn
+
+@deftypefn {Target Hook} pad_direction TARGET_FUNCTION_ARG_PADDING (machine_mode @var{mode}, const_tree @var{type})
+This hook determines whether, and in which direction, to pad out
+an argument of mode @var{mode} and type @var{type}. It returns
+@code{PAD_UPWARD} to insert padding above the argument, @code{PAD_DOWNWARD}
+to insert padding below the argument, or @code{PAD_NONE} to inhibit padding.
+
+The @emph{amount} of padding is not controlled by this hook, but by
+@code{TARGET_FUNCTION_ARG_ROUND_BOUNDARY}. It is always just enough
+to reach the next multiple of that boundary.
+
+This hook has a default definition that is right for most systems.
+For little-endian machines, the default is to pad upward. For
+big-endian machines, the default is to pad downward for an argument of
+constant size shorter than an @code{int}, and upward otherwise.
+@end deftypefn
+
+@defmac PAD_VARARGS_DOWN
+If defined, a C expression which determines whether the default
+implementation of va_arg will attempt to pad down before reading the
+next argument, if that argument is smaller than its aligned space as
+controlled by @code{PARM_BOUNDARY}. If this macro is not defined, all such
+arguments are padded down if @code{BYTES_BIG_ENDIAN} is true.
+@end defmac
+
+@defmac BLOCK_REG_PADDING (@var{mode}, @var{type}, @var{first})
+Specify padding for the last element of a block move between registers and
+memory. @var{first} is nonzero if this is the only element. Defining this
+macro allows better control of register function parameters on big-endian
+machines, without using @code{PARALLEL} rtl. In particular,
+@code{MUST_PASS_IN_STACK} need not test padding and mode of types in
+registers, as there is no longer a "wrong" part of a register; For example,
+a three byte aggregate may be passed in the high part of a register if so
+required.
+@end defmac
+
+@deftypefn {Target Hook} {unsigned int} TARGET_FUNCTION_ARG_BOUNDARY (machine_mode @var{mode}, const_tree @var{type})
+This hook returns the alignment boundary, in bits, of an argument
+with the specified mode and type. The default hook returns
+@code{PARM_BOUNDARY} for all arguments.
+@end deftypefn
+
+@deftypefn {Target Hook} {unsigned int} TARGET_FUNCTION_ARG_ROUND_BOUNDARY (machine_mode @var{mode}, const_tree @var{type})
+Normally, the size of an argument is rounded up to @code{PARM_BOUNDARY},
+which is the default value for this hook. You can define this hook to
+return a different value if an argument size must be rounded to a larger
+value.
+@end deftypefn
+
+@defmac FUNCTION_ARG_REGNO_P (@var{regno})
+A C expression that is nonzero if @var{regno} is the number of a hard
+register in which function arguments are sometimes passed. This does
+@emph{not} include implicit arguments such as the static chain and
+the structure-value address. On many machines, no registers can be
+used for this purpose since all function arguments are pushed on the
+stack.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_SPLIT_COMPLEX_ARG (const_tree @var{type})
+This hook should return true if parameter of type @var{type} are passed
+as two scalar parameters. By default, GCC will attempt to pack complex
+arguments into the target's word size. Some ABIs require complex arguments
+to be split and treated as their individual components. For example, on
+AIX64, complex floats should be passed in a pair of floating point
+registers, even though a complex float would fit in one 64-bit floating
+point register.
+
+The default value of this hook is @code{NULL}, which is treated as always
+false.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_BUILD_BUILTIN_VA_LIST (void)
+This hook returns a type node for @code{va_list} for the target.
+The default version of the hook returns @code{void*}.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_ENUM_VA_LIST_P (int @var{idx}, const char **@var{pname}, tree *@var{ptree})
+This target hook is used in function @code{c_common_nodes_and_builtins}
+to iterate through the target specific builtin types for va_list. The
+variable @var{idx} is used as iterator. @var{pname} has to be a pointer
+to a @code{const char *} and @var{ptree} a pointer to a @code{tree} typed
+variable.
+The arguments @var{pname} and @var{ptree} are used to store the result of
+this macro and are set to the name of the va_list builtin type and its
+internal type.
+If the return value of this macro is zero, then there is no more element.
+Otherwise the @var{IDX} should be increased for the next call of this
+macro to iterate through all types.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_FN_ABI_VA_LIST (tree @var{fndecl})
+This hook returns the va_list type of the calling convention specified by
+@var{fndecl}.
+The default version of this hook returns @code{va_list_type_node}.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_CANONICAL_VA_LIST_TYPE (tree @var{type})
+This hook returns the va_list type of the calling convention specified by the
+type of @var{type}. If @var{type} is not a valid va_list type, it returns
+@code{NULL_TREE}.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_GIMPLIFY_VA_ARG_EXPR (tree @var{valist}, tree @var{type}, gimple_seq *@var{pre_p}, gimple_seq *@var{post_p})
+This hook performs target-specific gimplification of
+@code{VA_ARG_EXPR}. The first two parameters correspond to the
+arguments to @code{va_arg}; the latter two are as in
+@code{gimplify.cc:gimplify_expr}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_VALID_POINTER_MODE (scalar_int_mode @var{mode})
+Define this to return nonzero if the port can handle pointers
+with machine mode @var{mode}. The default version of this
+hook returns true for both @code{ptr_mode} and @code{Pmode}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_REF_MAY_ALIAS_ERRNO (ao_ref *@var{ref})
+Define this to return nonzero if the memory reference @var{ref}
+may alias with the system C library errno location. The default
+version of this hook assumes the system C library errno location
+is either a declaration of type int or accessed by dereferencing
+a pointer to int.
+@end deftypefn
+
+@deftypefn {Target Hook} machine_mode TARGET_TRANSLATE_MODE_ATTRIBUTE (machine_mode @var{mode})
+Define this hook if during mode attribute processing, the port should
+translate machine_mode @var{mode} to another mode. For example, rs6000's
+@code{KFmode}, when it is the same as @code{TFmode}.
+
+The default version of the hook returns that mode that was passed in.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SCALAR_MODE_SUPPORTED_P (scalar_mode @var{mode})
+Define this to return nonzero if the port is prepared to handle
+insns involving scalar mode @var{mode}. For a scalar mode to be
+considered supported, all the basic arithmetic and comparisons
+must work.
+
+The default version of this hook returns true for any mode
+required to handle the basic C types (as defined by the port).
+Included here are the double-word arithmetic supported by the
+code in @file{optabs.cc}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_VECTOR_MODE_SUPPORTED_P (machine_mode @var{mode})
+Define this to return nonzero if the port is prepared to handle
+insns involving vector mode @var{mode}. At the very least, it
+must have move patterns for this mode.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_COMPATIBLE_VECTOR_TYPES_P (const_tree @var{type1}, const_tree @var{type2})
+Return true if there is no target-specific reason for treating
+vector types @var{type1} and @var{type2} as distinct types. The caller
+has already checked for target-independent reasons, meaning that the
+types are known to have the same mode, to have the same number of elements,
+and to have what the caller considers to be compatible element types.
+
+The main reason for defining this hook is to reject pairs of types
+that are handled differently by the target's calling convention.
+For example, when a new @var{N}-bit vector architecture is added
+to a target, the target may want to handle normal @var{N}-bit
+@code{VECTOR_TYPE} arguments and return values in the same way as
+before, to maintain backwards compatibility. However, it may also
+provide new, architecture-specific @code{VECTOR_TYPE}s that are passed
+and returned in a more efficient way. It is then important to maintain
+a distinction between the ``normal'' @code{VECTOR_TYPE}s and the new
+architecture-specific ones.
+
+The default implementation returns true, which is correct for most targets.
+@end deftypefn
+
+@deftypefn {Target Hook} opt_machine_mode TARGET_ARRAY_MODE (machine_mode @var{mode}, unsigned HOST_WIDE_INT @var{nelems})
+Return the mode that GCC should use for an array that has
+@var{nelems} elements, with each element having mode @var{mode}.
+Return no mode if the target has no special requirements. In the
+latter case, GCC looks for an integer mode of the appropriate size
+if available and uses BLKmode otherwise. Usually the search for the
+integer mode is limited to @code{MAX_FIXED_MODE_SIZE}, but the
+@code{TARGET_ARRAY_MODE_SUPPORTED_P} hook allows a larger mode to be
+used in specific cases.
+
+The main use of this hook is to specify that an array of vectors should
+also have a vector mode. The default implementation returns no mode.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ARRAY_MODE_SUPPORTED_P (machine_mode @var{mode}, unsigned HOST_WIDE_INT @var{nelems})
+Return true if GCC should try to use a scalar mode to store an array
+of @var{nelems} elements, given that each element has mode @var{mode}.
+Returning true here overrides the usual @code{MAX_FIXED_MODE} limit
+and allows GCC to use any defined integer mode.
+
+One use of this hook is to support vector load and store operations
+that operate on several homogeneous vectors. For example, ARM NEON
+has operations like:
+
+@smallexample
+int8x8x3_t vld3_s8 (const int8_t *)
+@end smallexample
+
+where the return type is defined as:
+
+@smallexample
+typedef struct int8x8x3_t
+@{
+ int8x8_t val[3];
+@} int8x8x3_t;
+@end smallexample
+
+If this hook allows @code{val} to have a scalar mode, then
+@code{int8x8x3_t} can have the same mode. GCC can then store
+@code{int8x8x3_t}s in registers rather than forcing them onto the stack.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P (scalar_float_mode @var{mode})
+Define this to return nonzero if libgcc provides support for the
+floating-point mode @var{mode}, which is known to pass
+@code{TARGET_SCALAR_MODE_SUPPORTED_P}. The default version of this
+hook returns true for all of @code{SFmode}, @code{DFmode},
+@code{XFmode} and @code{TFmode}, if such modes exist.
+@end deftypefn
+
+@deftypefn {Target Hook} opt_scalar_float_mode TARGET_FLOATN_MODE (int @var{n}, bool @var{extended})
+Define this to return the machine mode to use for the type
+@code{_Float@var{n}}, if @var{extended} is false, or the type
+@code{_Float@var{n}x}, if @var{extended} is true. If such a type is not
+supported, return @code{opt_scalar_float_mode ()}. The default version of
+this hook returns @code{SFmode} for @code{_Float32}, @code{DFmode} for
+@code{_Float64} and @code{_Float32x} and @code{TFmode} for
+@code{_Float128}, if those modes exist and satisfy the requirements for
+those types and pass @code{TARGET_SCALAR_MODE_SUPPORTED_P} and
+@code{TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P}; for @code{_Float64x}, it
+returns the first of @code{XFmode} and @code{TFmode} that exists and
+satisfies the same requirements; for other types, it returns
+@code{opt_scalar_float_mode ()}. The hook is only called for values
+of @var{n} and @var{extended} that are valid according to
+ISO/IEC TS 18661-3:2015; that is, @var{n} is one of 32, 64, 128, or,
+if @var{extended} is false, 16 or greater than 128 and a multiple of 32.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_FLOATN_BUILTIN_P (int @var{func})
+Define this to return true if the @code{_Float@var{n}} and
+@code{_Float@var{n}x} built-in functions should implicitly enable the
+built-in function without the @code{__builtin_} prefix in addition to the
+normal built-in function with the @code{__builtin_} prefix. The default is
+to only enable built-in functions without the @code{__builtin_} prefix for
+the GNU C langauge. In strict ANSI/ISO mode, the built-in function without
+the @code{__builtin_} prefix is not enabled. The argument @code{FUNC} is the
+@code{enum built_in_function} id of the function to be enabled.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P (machine_mode @var{mode})
+Define this to return nonzero for machine modes for which the port has
+small register classes. If this target hook returns nonzero for a given
+@var{mode}, the compiler will try to minimize the lifetime of registers
+in @var{mode}. The hook may be called with @code{VOIDmode} as argument.
+In this case, the hook is expected to return nonzero if it returns nonzero
+for any mode.
+
+On some machines, it is risky to let hard registers live across arbitrary
+insns. Typically, these machines have instructions that require values
+to be in specific registers (like an accumulator), and reload will fail
+if the required hard register is used for another purpose across such an
+insn.
+
+Passes before reload do not know which hard registers will be used
+in an instruction, but the machine modes of the registers set or used in
+the instruction are already known. And for some machines, register
+classes are small for, say, integer registers but not for floating point
+registers. For example, the AMD x86-64 architecture requires specific
+registers for the legacy x86 integer instructions, but there are many
+SSE registers for floating point operations. On such targets, a good
+strategy may be to return nonzero from this hook for @code{INTEGRAL_MODE_P}
+machine modes but zero for the SSE register classes.
+
+The default version of this hook returns false for any mode. It is always
+safe to redefine this hook to return with a nonzero value. But if you
+unnecessarily define it, you will reduce the amount of optimizations
+that can be performed in some cases. If you do not define this hook
+to return a nonzero value when it is required, the compiler will run out
+of spill registers and print a fatal error message.
+@end deftypefn
+
+@node Scalar Return
+@subsection How Scalar Function Values Are Returned
+@cindex return values in registers
+@cindex values, returned by functions
+@cindex scalars, returned as values
+
+This section discusses the macros that control returning scalars as
+values---values that can fit in registers.
+
+@deftypefn {Target Hook} rtx TARGET_FUNCTION_VALUE (const_tree @var{ret_type}, const_tree @var{fn_decl_or_type}, bool @var{outgoing})
+
+Define this to return an RTX representing the place where a function
+returns or receives a value of data type @var{ret_type}, a tree node
+representing a data type. @var{fn_decl_or_type} is a tree node
+representing @code{FUNCTION_DECL} or @code{FUNCTION_TYPE} of a
+function being called. If @var{outgoing} is false, the hook should
+compute the register in which the caller will see the return value.
+Otherwise, the hook should return an RTX representing the place where
+a function returns a value.
+
+On many machines, only @code{TYPE_MODE (@var{ret_type})} is relevant.
+(Actually, on most machines, scalar values are returned in the same
+place regardless of mode.) The value of the expression is usually a
+@code{reg} RTX for the hard register where the return value is stored.
+The value can also be a @code{parallel} RTX, if the return value is in
+multiple places. See @code{TARGET_FUNCTION_ARG} for an explanation of the
+@code{parallel} form. Note that the callee will populate every
+location specified in the @code{parallel}, but if the first element of
+the @code{parallel} contains the whole return value, callers will use
+that element as the canonical location and ignore the others. The m68k
+port uses this type of @code{parallel} to return pointers in both
+@samp{%a0} (the canonical location) and @samp{%d0}.
+
+If @code{TARGET_PROMOTE_FUNCTION_RETURN} returns true, you must apply
+the same promotion rules specified in @code{PROMOTE_MODE} if
+@var{valtype} is a scalar type.
+
+If the precise function being called is known, @var{func} is a tree
+node (@code{FUNCTION_DECL}) for it; otherwise, @var{func} is a null
+pointer. This makes it possible to use a different value-returning
+convention for specific functions when all their calls are
+known.
+
+Some target machines have ``register windows'' so that the register in
+which a function returns its value is not the same as the one in which
+the caller sees the value. For such machines, you should return
+different RTX depending on @var{outgoing}.
+
+@code{TARGET_FUNCTION_VALUE} is not used for return values with
+aggregate data types, because these are returned in another way. See
+@code{TARGET_STRUCT_VALUE_RTX} and related macros, below.
+@end deftypefn
+
+@defmac FUNCTION_VALUE (@var{valtype}, @var{func})
+This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE} for
+a new target instead.
+@end defmac
+
+@defmac LIBCALL_VALUE (@var{mode})
+A C expression to create an RTX representing the place where a library
+function returns a value of mode @var{mode}.
+
+Note that ``library function'' in this context means a compiler
+support routine, used to perform arithmetic, whose name is known
+specially by the compiler and was not mentioned in the C code being
+compiled.
+@end defmac
+
+@deftypefn {Target Hook} rtx TARGET_LIBCALL_VALUE (machine_mode @var{mode}, const_rtx @var{fun})
+Define this hook if the back-end needs to know the name of the libcall
+function in order to determine where the result should be returned.
+
+The mode of the result is given by @var{mode} and the name of the called
+library function is given by @var{fun}. The hook should return an RTX
+representing the place where the library function result will be returned.
+
+If this hook is not defined, then LIBCALL_VALUE will be used.
+@end deftypefn
+
+@defmac FUNCTION_VALUE_REGNO_P (@var{regno})
+A C expression that is nonzero if @var{regno} is the number of a hard
+register in which the values of called function may come back.
+
+A register whose use for returning values is limited to serving as the
+second of a pair (for a value of type @code{double}, say) need not be
+recognized by this macro. So for most machines, this definition
+suffices:
+
+@smallexample
+#define FUNCTION_VALUE_REGNO_P(N) ((N) == 0)
+@end smallexample
+
+If the machine has register windows, so that the caller and the called
+function use different registers for the return value, this macro
+should recognize only the caller's register numbers.
+
+This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE_REGNO_P}
+for a new target instead.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_FUNCTION_VALUE_REGNO_P (const unsigned int @var{regno})
+A target hook that return @code{true} if @var{regno} is the number of a hard
+register in which the values of called function may come back.
+
+A register whose use for returning values is limited to serving as the
+second of a pair (for a value of type @code{double}, say) need not be
+recognized by this target hook.
+
+If the machine has register windows, so that the caller and the called
+function use different registers for the return value, this target hook
+should recognize only the caller's register numbers.
+
+If this hook is not defined, then FUNCTION_VALUE_REGNO_P will be used.
+@end deftypefn
+
+@defmac APPLY_RESULT_SIZE
+Define this macro if @samp{untyped_call} and @samp{untyped_return}
+need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for
+saving and restoring an arbitrary return value.
+@end defmac
+
+@deftypevr {Target Hook} bool TARGET_OMIT_STRUCT_RETURN_REG
+Normally, when a function returns a structure by memory, the address
+is passed as an invisible pointer argument, but the compiler also
+arranges to return the address from the function like it would a normal
+pointer return value. Define this to true if that behavior is
+undesirable on your target.
+@end deftypevr
+
+@deftypefn {Target Hook} bool TARGET_RETURN_IN_MSB (const_tree @var{type})
+This hook should return true if values of type @var{type} are returned
+at the most significant end of a register (in other words, if they are
+padded at the least significant end). You can assume that @var{type}
+is returned in a register; the caller is required to check this.
+
+Note that the register provided by @code{TARGET_FUNCTION_VALUE} must
+be able to hold the complete return value. For example, if a 1-, 2-
+or 3-byte structure is returned at the most significant end of a
+4-byte register, @code{TARGET_FUNCTION_VALUE} should provide an
+@code{SImode} rtx.
+@end deftypefn
+
+@node Aggregate Return
+@subsection How Large Values Are Returned
+@cindex aggregates as return values
+@cindex large return values
+@cindex returning aggregate values
+@cindex structure value address
+
+When a function value's mode is @code{BLKmode} (and in some other
+cases), the value is not returned according to
+@code{TARGET_FUNCTION_VALUE} (@pxref{Scalar Return}). Instead, the
+caller passes the address of a block of memory in which the value
+should be stored. This address is called the @dfn{structure value
+address}.
+
+This section describes how to control returning structure values in
+memory.
+
+@deftypefn {Target Hook} bool TARGET_RETURN_IN_MEMORY (const_tree @var{type}, const_tree @var{fntype})
+This target hook should return a nonzero value to say to return the
+function value in memory, just as large structures are always returned.
+Here @var{type} will be the data type of the value, and @var{fntype}
+will be the type of the function doing the returning, or @code{NULL} for
+libcalls.
+
+Note that values of mode @code{BLKmode} must be explicitly handled
+by this function. Also, the option @option{-fpcc-struct-return}
+takes effect regardless of this macro. On most systems, it is
+possible to leave the hook undefined; this causes a default
+definition to be used, whose value is the constant 1 for @code{BLKmode}
+values, and 0 otherwise.
+
+Do not use this hook to indicate that structures and unions should always
+be returned in memory. You should instead use @code{DEFAULT_PCC_STRUCT_RETURN}
+to indicate this.
+@end deftypefn
+
+@defmac DEFAULT_PCC_STRUCT_RETURN
+Define this macro to be 1 if all structure and union return values must be
+in memory. Since this results in slower code, this should be defined
+only if needed for compatibility with other compilers or with an ABI@.
+If you define this macro to be 0, then the conventions used for structure
+and union return values are decided by the @code{TARGET_RETURN_IN_MEMORY}
+target hook.
+
+If not defined, this defaults to the value 1.
+@end defmac
+
+@deftypefn {Target Hook} rtx TARGET_STRUCT_VALUE_RTX (tree @var{fndecl}, int @var{incoming})
+This target hook should return the location of the structure value
+address (normally a @code{mem} or @code{reg}), or 0 if the address is
+passed as an ``invisible'' first argument. Note that @var{fndecl} may
+be @code{NULL}, for libcalls. You do not need to define this target
+hook if the address is always passed as an ``invisible'' first
+argument.
+
+On some architectures the place where the structure value address
+is found by the called function is not the same place that the
+caller put it. This can be due to register windows, or it could
+be because the function prologue moves it to a different place.
+@var{incoming} is @code{1} or @code{2} when the location is needed in
+the context of the called function, and @code{0} in the context of
+the caller.
+
+If @var{incoming} is nonzero and the address is to be found on the
+stack, return a @code{mem} which refers to the frame pointer. If
+@var{incoming} is @code{2}, the result is being used to fetch the
+structure value address at the beginning of a function. If you need
+to emit adjusting code, you should do it at this point.
+@end deftypefn
+
+@defmac PCC_STATIC_STRUCT_RETURN
+Define this macro if the usual system convention on the target machine
+for returning structures and unions is for the called function to return
+the address of a static variable containing the value.
+
+Do not define this if the usual system convention is for the caller to
+pass an address to the subroutine.
+
+This macro has effect in @option{-fpcc-struct-return} mode, but it does
+nothing when you use @option{-freg-struct-return} mode.
+@end defmac
+
+@deftypefn {Target Hook} fixed_size_mode TARGET_GET_RAW_RESULT_MODE (int @var{regno})
+This target hook returns the mode to be used when accessing raw return
+registers in @code{__builtin_return}. Define this macro if the value
+in @var{reg_raw_mode} is not correct.
+@end deftypefn
+
+@deftypefn {Target Hook} fixed_size_mode TARGET_GET_RAW_ARG_MODE (int @var{regno})
+This target hook returns the mode to be used when accessing raw argument
+registers in @code{__builtin_apply_args}. Define this macro if the value
+in @var{reg_raw_mode} is not correct.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_EMPTY_RECORD_P (const_tree @var{type})
+This target hook returns true if the type is an empty record. The default
+is to return @code{false}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_WARN_PARAMETER_PASSING_ABI (cumulative_args_t @var{ca}, tree @var{type})
+This target hook warns about the change in empty class parameter passing
+ABI.
+@end deftypefn
+
+@node Caller Saves
+@subsection Caller-Saves Register Allocation
+
+If you enable it, GCC can save registers around function calls. This
+makes it possible to use call-clobbered registers to hold variables that
+must live across calls.
+
+@defmac HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs})
+A C expression specifying which mode is required for saving @var{nregs}
+of a pseudo-register in call-clobbered hard register @var{regno}. If
+@var{regno} is unsuitable for caller save, @code{VOIDmode} should be
+returned. For most machines this macro need not be defined since GCC
+will select the smallest suitable mode.
+@end defmac
+
+@node Function Entry
+@subsection Function Entry and Exit
+@cindex function entry and exit
+@cindex prologue
+@cindex epilogue
+
+This section describes the macros that output function entry
+(@dfn{prologue}) and exit (@dfn{epilogue}) code.
+
+@deftypefn {Target Hook} void TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY (FILE *@var{file}, unsigned HOST_WIDE_INT @var{patch_area_size}, bool @var{record_p})
+Generate a patchable area at the function start, consisting of
+@var{patch_area_size} NOP instructions. If the target supports named
+sections and if @var{record_p} is true, insert a pointer to the current
+location in the table of patchable functions. The default implementation
+of the hook places the table of pointers in the special section named
+@code{__patchable_function_entries}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_PROLOGUE (FILE *@var{file})
+If defined, a function that outputs the assembler code for entry to a
+function. The prologue is responsible for setting up the stack frame,
+initializing the frame pointer register, saving registers that must be
+saved, and allocating @var{size} additional bytes of storage for the
+local variables. @var{file} is a stdio stream to which the assembler
+code should be output.
+
+The label for the beginning of the function need not be output by this
+macro. That has already been done when the macro is run.
+
+@findex regs_ever_live
+To determine which registers to save, the macro can refer to the array
+@code{regs_ever_live}: element @var{r} is nonzero if hard register
+@var{r} is used anywhere within the function. This implies the function
+prologue should save register @var{r}, provided it is not one of the
+call-used registers. (@code{TARGET_ASM_FUNCTION_EPILOGUE} must likewise use
+@code{regs_ever_live}.)
+
+On machines that have ``register windows'', the function entry code does
+not save on the stack the registers that are in the windows, even if
+they are supposed to be preserved by function calls; instead it takes
+appropriate steps to ``push'' the register stack, if any non-call-used
+registers are used in the function.
+
+@findex frame_pointer_needed
+On machines where functions may or may not have frame-pointers, the
+function entry code must vary accordingly; it must set up the frame
+pointer if one is wanted, and not otherwise. To determine whether a
+frame pointer is in wanted, the macro can refer to the variable
+@code{frame_pointer_needed}. The variable's value will be 1 at run
+time in a function that needs a frame pointer. @xref{Elimination}.
+
+The function entry code is responsible for allocating any stack space
+required for the function. This stack space consists of the regions
+listed below. In most cases, these regions are allocated in the
+order listed, with the last listed region closest to the top of the
+stack (the lowest address if @code{STACK_GROWS_DOWNWARD} is defined, and
+the highest address if it is not defined). You can use a different order
+for a machine if doing so is more convenient or required for
+compatibility reasons. Except in cases where required by standard
+or by a debugger, there is no reason why the stack layout used by GCC
+need agree with that used by other compilers for a machine.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_END_PROLOGUE (FILE *@var{file})
+If defined, a function that outputs assembler code at the end of a
+prologue. This should be used when the function prologue is being
+emitted as RTL, and you have some extra assembler that needs to be
+emitted. @xref{prologue instruction pattern}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_BEGIN_EPILOGUE (FILE *@var{file})
+If defined, a function that outputs assembler code at the start of an
+epilogue. This should be used when the function epilogue is being
+emitted as RTL, and you have some extra assembler that needs to be
+emitted. @xref{epilogue instruction pattern}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_EPILOGUE (FILE *@var{file})
+If defined, a function that outputs the assembler code for exit from a
+function. The epilogue is responsible for restoring the saved
+registers and stack pointer to their values when the function was
+called, and returning control to the caller. This macro takes the
+same argument as the macro @code{TARGET_ASM_FUNCTION_PROLOGUE}, and the
+registers to restore are determined from @code{regs_ever_live} and
+@code{CALL_USED_REGISTERS} in the same way.
+
+On some machines, there is a single instruction that does all the work
+of returning from the function. On these machines, give that
+instruction the name @samp{return} and do not define the macro
+@code{TARGET_ASM_FUNCTION_EPILOGUE} at all.
+
+Do not define a pattern named @samp{return} if you want the
+@code{TARGET_ASM_FUNCTION_EPILOGUE} to be used. If you want the target
+switches to control whether return instructions or epilogues are used,
+define a @samp{return} pattern with a validity condition that tests the
+target switches appropriately. If the @samp{return} pattern's validity
+condition is false, epilogues will be used.
+
+On machines where functions may or may not have frame-pointers, the
+function exit code must vary accordingly. Sometimes the code for these
+two cases is completely different. To determine whether a frame pointer
+is wanted, the macro can refer to the variable
+@code{frame_pointer_needed}. The variable's value will be 1 when compiling
+a function that needs a frame pointer.
+
+Normally, @code{TARGET_ASM_FUNCTION_PROLOGUE} and
+@code{TARGET_ASM_FUNCTION_EPILOGUE} must treat leaf functions specially.
+The C variable @code{current_function_is_leaf} is nonzero for such a
+function. @xref{Leaf Functions}.
+
+On some machines, some functions pop their arguments on exit while
+others leave that for the caller to do. For example, the 68020 when
+given @option{-mrtd} pops arguments in functions that take a fixed
+number of arguments.
+
+@findex pops_args
+@findex crtl->args.pops_args
+Your definition of the macro @code{RETURN_POPS_ARGS} decides which
+functions pop their own arguments. @code{TARGET_ASM_FUNCTION_EPILOGUE}
+needs to know what was decided. The number of bytes of the current
+function's arguments that this function should pop is available in
+@code{crtl->args.pops_args}. @xref{Scalar Return}.
+@end deftypefn
+
+@itemize @bullet
+@item
+@findex pretend_args_size
+@findex crtl->args.pretend_args_size
+A region of @code{crtl->args.pretend_args_size} bytes of
+uninitialized space just underneath the first argument arriving on the
+stack. (This may not be at the very start of the allocated stack region
+if the calling sequence has pushed anything else since pushing the stack
+arguments. But usually, on such machines, nothing else has been pushed
+yet, because the function prologue itself does all the pushing.) This
+region is used on machines where an argument may be passed partly in
+registers and partly in memory, and, in some cases to support the
+features in @code{<stdarg.h>}.
+
+@item
+An area of memory used to save certain registers used by the function.
+The size of this area, which may also include space for such things as
+the return address and pointers to previous stack frames, is
+machine-specific and usually depends on which registers have been used
+in the function. Machines with register windows often do not require
+a save area.
+
+@item
+A region of at least @var{size} bytes, possibly rounded up to an allocation
+boundary, to contain the local variables of the function. On some machines,
+this region and the save area may occur in the opposite order, with the
+save area closer to the top of the stack.
+
+@item
+@cindex @code{ACCUMULATE_OUTGOING_ARGS} and stack frames
+Optionally, when @code{ACCUMULATE_OUTGOING_ARGS} is defined, a region of
+@code{crtl->outgoing_args_size} bytes to be used for outgoing
+argument lists of the function. @xref{Stack Arguments}.
+@end itemize
+
+@defmac EXIT_IGNORE_STACK
+Define this macro as a C expression that is nonzero if the return
+instruction or the function epilogue ignores the value of the stack
+pointer; in other words, if it is safe to delete an instruction to
+adjust the stack pointer before a return from the function. The
+default is 0.
+
+Note that this macro's value is relevant only for functions for which
+frame pointers are maintained. It is never safe to delete a final
+stack adjustment in a function that has no frame pointer, and the
+compiler knows this regardless of @code{EXIT_IGNORE_STACK}.
+@end defmac
+
+@defmac EPILOGUE_USES (@var{regno})
+Define this macro as a C expression that is nonzero for registers that are
+used by the epilogue or the @samp{return} pattern. The stack and frame
+pointer registers are already assumed to be used as needed.
+@end defmac
+
+@defmac EH_USES (@var{regno})
+Define this macro as a C expression that is nonzero for registers that are
+used by the exception handling mechanism, and so should be considered live
+on entry to an exception edge.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_MI_THUNK (FILE *@var{file}, tree @var{thunk_fndecl}, HOST_WIDE_INT @var{delta}, HOST_WIDE_INT @var{vcall_offset}, tree @var{function})
+A function that outputs the assembler code for a thunk
+function, used to implement C++ virtual function calls with multiple
+inheritance. The thunk acts as a wrapper around a virtual function,
+adjusting the implicit object parameter before handing control off to
+the real function.
+
+First, emit code to add the integer @var{delta} to the location that
+contains the incoming first argument. Assume that this argument
+contains a pointer, and is the one used to pass the @code{this} pointer
+in C++. This is the incoming argument @emph{before} the function prologue,
+e.g.@: @samp{%o0} on a sparc. The addition must preserve the values of
+all other incoming arguments.
+
+Then, if @var{vcall_offset} is nonzero, an additional adjustment should be
+made after adding @code{delta}. In particular, if @var{p} is the
+adjusted pointer, the following adjustment should be made:
+
+@smallexample
+p += (*((ptrdiff_t **)p))[vcall_offset/sizeof(ptrdiff_t)]
+@end smallexample
+
+After the additions, emit code to jump to @var{function}, which is a
+@code{FUNCTION_DECL}. This is a direct pure jump, not a call, and does
+not touch the return address. Hence returning from @var{FUNCTION} will
+return to whoever called the current @samp{thunk}.
+
+The effect must be as if @var{function} had been called directly with
+the adjusted first argument. This macro is responsible for emitting all
+of the code for a thunk function; @code{TARGET_ASM_FUNCTION_PROLOGUE}
+and @code{TARGET_ASM_FUNCTION_EPILOGUE} are not invoked.
+
+The @var{thunk_fndecl} is redundant. (@var{delta} and @var{function}
+have already been extracted from it.) It might possibly be useful on
+some targets, but probably not.
+
+If you do not define this macro, the target-independent code in the C++
+front end will generate a less efficient heavyweight thunk that calls
+@var{function} instead of jumping to it. The generic approach does
+not support varargs.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ASM_CAN_OUTPUT_MI_THUNK (const_tree @var{thunk_fndecl}, HOST_WIDE_INT @var{delta}, HOST_WIDE_INT @var{vcall_offset}, const_tree @var{function})
+A function that returns true if TARGET_ASM_OUTPUT_MI_THUNK would be able
+to output the assembler code for the thunk function specified by the
+arguments it is passed, and false otherwise. In the latter case, the
+generic approach will be used by the C++ front end, with the limitations
+previously exposed.
+@end deftypefn
+
+@node Profiling
+@subsection Generating Code for Profiling
+@cindex profiling, code generation
+
+These macros will help you generate code for profiling.
+
+@defmac FUNCTION_PROFILER (@var{file}, @var{labelno})
+A C statement or compound statement to output to @var{file} some
+assembler code to call the profiling subroutine @code{mcount}.
+
+@findex mcount
+The details of how @code{mcount} expects to be called are determined by
+your operating system environment, not by GCC@. To figure them out,
+compile a small program for profiling using the system's installed C
+compiler and look at the assembler code that results.
+
+Older implementations of @code{mcount} expect the address of a counter
+variable to be loaded into some register. The name of this variable is
+@samp{LP} followed by the number @var{labelno}, so you would generate
+the name using @samp{LP%d} in a @code{fprintf}.
+@end defmac
+
+@defmac PROFILE_HOOK
+A C statement or compound statement to output to @var{file} some assembly
+code to call the profiling subroutine @code{mcount} even the target does
+not support profiling.
+@end defmac
+
+@defmac NO_PROFILE_COUNTERS
+Define this macro to be an expression with a nonzero value if the
+@code{mcount} subroutine on your system does not need a counter variable
+allocated for each function. This is true for almost all modern
+implementations. If you define this macro, you must not use the
+@var{labelno} argument to @code{FUNCTION_PROFILER}.
+@end defmac
+
+@defmac PROFILE_BEFORE_PROLOGUE
+Define this macro if the code for function profiling should come before
+the function prologue. Normally, the profiling code comes after.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_KEEP_LEAF_WHEN_PROFILED (void)
+This target hook returns true if the target wants the leaf flag for
+the current function to stay true even if it calls mcount. This might
+make sense for targets using the leaf flag only to determine whether a
+stack frame needs to be generated or not and for which the call to
+mcount is generated before the function prologue.
+@end deftypefn
+
+@node Tail Calls
+@subsection Permitting tail calls
+@cindex tail calls
+
+@deftypefn {Target Hook} bool TARGET_FUNCTION_OK_FOR_SIBCALL (tree @var{decl}, tree @var{exp})
+True if it is OK to do sibling call optimization for the specified
+call expression @var{exp}. @var{decl} will be the called function,
+or @code{NULL} if this is an indirect call.
+
+It is not uncommon for limitations of calling conventions to prevent
+tail calls to functions outside the current unit of translation, or
+during PIC compilation. The hook is used to enforce these restrictions,
+as the @code{sibcall} md pattern cannot fail, or fall over to a
+``normal'' call. The criteria for successful sibling call optimization
+may vary greatly between different architectures.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_EXTRA_LIVE_ON_ENTRY (bitmap @var{regs})
+Add any hard registers to @var{regs} that are live on entry to the
+function. This hook only needs to be defined to provide registers that
+cannot be found by examination of FUNCTION_ARG_REGNO_P, the callee saved
+registers, STATIC_CHAIN_INCOMING_REGNUM, STATIC_CHAIN_REGNUM,
+TARGET_STRUCT_VALUE_RTX, FRAME_POINTER_REGNUM, EH_USES,
+FRAME_POINTER_REGNUM, ARG_POINTER_REGNUM, and the PIC_OFFSET_TABLE_REGNUM.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SET_UP_BY_PROLOGUE (struct hard_reg_set_container *@var{})
+This hook should add additional registers that are computed by the prologue
+to the hard regset for shrink-wrapping optimization purposes.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_WARN_FUNC_RETURN (tree)
+True if a function's return statements should be checked for matching
+the function's return type. This includes checking for falling off the end
+of a non-void function. Return false if no such check should be made.
+@end deftypefn
+
+@node Shrink-wrapping separate components
+@subsection Shrink-wrapping separate components
+@cindex shrink-wrapping separate components
+
+The prologue may perform a variety of target dependent tasks such as
+saving callee-saved registers, saving the return address, aligning the
+stack, creating a stack frame, initializing the PIC register, setting
+up the static chain, etc.
+
+On some targets some of these tasks may be independent of others and
+thus may be shrink-wrapped separately. These independent tasks are
+referred to as components and are handled generically by the target
+independent parts of GCC.
+
+Using the following hooks those prologue or epilogue components can be
+shrink-wrapped separately, so that the initialization (and possibly
+teardown) those components do is not done as frequently on execution
+paths where this would unnecessary.
+
+What exactly those components are is up to the target code; the generic
+code treats them abstractly, as a bit in an @code{sbitmap}. These
+@code{sbitmap}s are allocated by the @code{shrink_wrap.get_separate_components}
+and @code{shrink_wrap.components_for_bb} hooks, and deallocated by the
+generic code.
+
+@deftypefn {Target Hook} sbitmap TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS (void)
+This hook should return an @code{sbitmap} with the bits set for those
+components that can be separately shrink-wrapped in the current function.
+Return @code{NULL} if the current function should not get any separate
+shrink-wrapping.
+Don't define this hook if it would always return @code{NULL}.
+If it is defined, the other hooks in this group have to be defined as well.
+@end deftypefn
+
+@deftypefn {Target Hook} sbitmap TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB (basic_block)
+This hook should return an @code{sbitmap} with the bits set for those
+components where either the prologue component has to be executed before
+the @code{basic_block}, or the epilogue component after it, or both.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS (sbitmap @var{components}, edge @var{e}, sbitmap @var{edge_components}, bool @var{is_prologue})
+This hook should clear the bits in the @var{components} bitmap for those
+components in @var{edge_components} that the target cannot handle on edge
+@var{e}, where @var{is_prologue} says if this is for a prologue or an
+epilogue instead.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS (sbitmap)
+Emit prologue insns for the components indicated by the parameter.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS (sbitmap)
+Emit epilogue insns for the components indicated by the parameter.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SHRINK_WRAP_SET_HANDLED_COMPONENTS (sbitmap)
+Mark the components in the parameter as handled, so that the
+@code{prologue} and @code{epilogue} named patterns know to ignore those
+components. The target code should not hang on to the @code{sbitmap}, it
+will be deleted after this call.
+@end deftypefn
+
+@node Stack Smashing Protection
+@subsection Stack smashing protection
+@cindex stack smashing protection
+
+@deftypefn {Target Hook} tree TARGET_STACK_PROTECT_GUARD (void)
+This hook returns a @code{DECL} node for the external variable to use
+for the stack protection guard. This variable is initialized by the
+runtime to some random value and is used to initialize the guard value
+that is placed at the top of the local stack frame. The type of this
+variable must be @code{ptr_type_node}.
+
+The default version of this hook creates a variable called
+@samp{__stack_chk_guard}, which is normally defined in @file{libgcc2.c}.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_STACK_PROTECT_FAIL (void)
+This hook returns a @code{CALL_EXPR} that alerts the runtime that the
+stack protect guard variable has been modified. This expression should
+involve a call to a @code{noreturn} function.
+
+The default version of this hook invokes a function called
+@samp{__stack_chk_fail}, taking no arguments. This function is
+normally defined in @file{libgcc2.c}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_STACK_PROTECT_RUNTIME_ENABLED_P (void)
+Returns true if the target wants GCC's default stack protect runtime support,
+otherwise return false. The default implementation always returns true.
+@end deftypefn
+
+@deftypefn {Common Target Hook} bool TARGET_SUPPORTS_SPLIT_STACK (bool @var{report}, struct gcc_options *@var{opts})
+Whether this target supports splitting the stack when the options
+described in @var{opts} have been passed. This is called
+after options have been parsed, so the target may reject splitting
+the stack in some configurations. The default version of this hook
+returns false. If @var{report} is true, this function may issue a warning
+or error; if @var{report} is false, it must simply return a value
+@end deftypefn
+
+@deftypefn {Common Target Hook} {vec<const char *>} TARGET_GET_VALID_OPTION_VALUES (int @var{option_code}, const char *@var{prefix})
+The hook is used for options that have a non-trivial list of
+possible option values. OPTION_CODE is option code of opt_code
+enum type. PREFIX is used for bash completion and allows an implementation
+to return more specific completion based on the prefix. All string values
+should be allocated from heap memory and consumers should release them.
+The result will be pruned to cases with PREFIX if not NULL.
+@end deftypefn
+
+@node Miscellaneous Register Hooks
+@subsection Miscellaneous register hooks
+@cindex miscellaneous register hooks
+
+@deftypevr {Target Hook} bool TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS
+Set to true if each call that binds to a local definition explicitly
+clobbers or sets all non-fixed registers modified by performing the call.
+That is, by the call pattern itself, or by code that might be inserted by the
+linker (e.g.@: stubs, veneers, branch islands), but not including those
+modifiable by the callee. The affected registers may be mentioned explicitly
+in the call pattern, or included as clobbers in CALL_INSN_FUNCTION_USAGE.
+The default version of this hook is set to false. The purpose of this hook
+is to enable the fipa-ra optimization.
+@end deftypevr
+
+@node Varargs
+@section Implementing the Varargs Macros
+@cindex varargs implementation
+
+GCC comes with an implementation of @code{<varargs.h>} and
+@code{<stdarg.h>} that work without change on machines that pass arguments
+on the stack. Other machines require their own implementations of
+varargs, and the two machine independent header files must have
+conditionals to include it.
+
+ISO @code{<stdarg.h>} differs from traditional @code{<varargs.h>} mainly in
+the calling convention for @code{va_start}. The traditional
+implementation takes just one argument, which is the variable in which
+to store the argument pointer. The ISO implementation of
+@code{va_start} takes an additional second argument. The user is
+supposed to write the last named argument of the function here.
+
+However, @code{va_start} should not use this argument. The way to find
+the end of the named arguments is with the built-in functions described
+below.
+
+@defmac __builtin_saveregs ()
+Use this built-in function to save the argument registers in memory so
+that the varargs mechanism can access them. Both ISO and traditional
+versions of @code{va_start} must use @code{__builtin_saveregs}, unless
+you use @code{TARGET_SETUP_INCOMING_VARARGS} (see below) instead.
+
+On some machines, @code{__builtin_saveregs} is open-coded under the
+control of the target hook @code{TARGET_EXPAND_BUILTIN_SAVEREGS}. On
+other machines, it calls a routine written in assembler language,
+found in @file{libgcc2.c}.
+
+Code generated for the call to @code{__builtin_saveregs} appears at the
+beginning of the function, as opposed to where the call to
+@code{__builtin_saveregs} is written, regardless of what the code is.
+This is because the registers must be saved before the function starts
+to use them for its own purposes.
+@c i rewrote the first sentence above to fix an overfull hbox. --mew
+@c 10feb93
+@end defmac
+
+@defmac __builtin_next_arg (@var{lastarg})
+This builtin returns the address of the first anonymous stack
+argument, as type @code{void *}. If @code{ARGS_GROW_DOWNWARD}, it
+returns the address of the location above the first anonymous stack
+argument. Use it in @code{va_start} to initialize the pointer for
+fetching arguments from the stack. Also use it in @code{va_start} to
+verify that the second parameter @var{lastarg} is the last named argument
+of the current function.
+@end defmac
+
+@defmac __builtin_classify_type (@var{object})
+Since each machine has its own conventions for which data types are
+passed in which kind of register, your implementation of @code{va_arg}
+has to embody these conventions. The easiest way to categorize the
+specified data type is to use @code{__builtin_classify_type} together
+with @code{sizeof} and @code{__alignof__}.
+
+@code{__builtin_classify_type} ignores the value of @var{object},
+considering only its data type. It returns an integer describing what
+kind of type that is---integer, floating, pointer, structure, and so on.
+
+The file @file{typeclass.h} defines an enumeration that you can use to
+interpret the values of @code{__builtin_classify_type}.
+@end defmac
+
+These machine description macros help implement varargs:
+
+@deftypefn {Target Hook} rtx TARGET_EXPAND_BUILTIN_SAVEREGS (void)
+If defined, this hook produces the machine-specific code for a call to
+@code{__builtin_saveregs}. This code will be moved to the very
+beginning of the function, before any parameter access are made. The
+return value of this function should be an RTX that contains the value
+to use as the return of @code{__builtin_saveregs}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SETUP_INCOMING_VARARGS (cumulative_args_t @var{args_so_far}, const function_arg_info @var{&arg}, int *@var{pretend_args_size}, int @var{second_time})
+This target hook offers an alternative to using
+@code{__builtin_saveregs} and defining the hook
+@code{TARGET_EXPAND_BUILTIN_SAVEREGS}. Use it to store the anonymous
+register arguments into the stack so that all the arguments appear to
+have been passed consecutively on the stack. Once this is done, you can
+use the standard implementation of varargs that works for machines that
+pass all their arguments on the stack.
+
+The argument @var{args_so_far} points to the @code{CUMULATIVE_ARGS} data
+structure, containing the values that are obtained after processing the
+named arguments. The argument @var{arg} describes the last of these named
+arguments. The argument @var{arg} should not be used if the function type
+satisfies @code{TYPE_NO_NAMED_ARGS_STDARG_P}, since in that case there are
+no named arguments and all arguments are accessed with @code{va_arg}.
+
+The target hook should do two things: first, push onto the stack all the
+argument registers @emph{not} used for the named arguments, and second,
+store the size of the data thus pushed into the @code{int}-valued
+variable pointed to by @var{pretend_args_size}. The value that you
+store here will serve as additional offset for setting up the stack
+frame.
+
+Because you must generate code to push the anonymous arguments at
+compile time without knowing their data types,
+@code{TARGET_SETUP_INCOMING_VARARGS} is only useful on machines that
+have just a single category of argument register and use it uniformly
+for all data types.
+
+If the argument @var{second_time} is nonzero, it means that the
+arguments of the function are being analyzed for the second time. This
+happens for an inline function, which is not actually compiled until the
+end of the source file. The hook @code{TARGET_SETUP_INCOMING_VARARGS} should
+not generate any instructions in this case.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_STRICT_ARGUMENT_NAMING (cumulative_args_t @var{ca})
+Define this hook to return @code{true} if the location where a function
+argument is passed depends on whether or not it is a named argument.
+
+This hook controls how the @var{named} argument to @code{TARGET_FUNCTION_ARG}
+is set for varargs and stdarg functions. If this hook returns
+@code{true}, the @var{named} argument is always true for named
+arguments, and false for unnamed arguments. If it returns @code{false},
+but @code{TARGET_PRETEND_OUTGOING_VARARGS_NAMED} returns @code{true},
+then all arguments are treated as named. Otherwise, all named arguments
+except the last are treated as named.
+
+You need not define this hook if it always returns @code{false}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_CALL_ARGS (rtx, @var{tree})
+While generating RTL for a function call, this target hook is invoked once
+for each argument passed to the function, either a register returned by
+@code{TARGET_FUNCTION_ARG} or a memory location. It is called just
+before the point where argument registers are stored. The type of the
+function to be called is also passed as the second argument; it is
+@code{NULL_TREE} for libcalls. The @code{TARGET_END_CALL_ARGS} hook is
+invoked just after the code to copy the return reg has been emitted.
+This functionality can be used to perform special setup of call argument
+registers if a target needs it.
+For functions without arguments, the hook is called once with @code{pc_rtx}
+passed instead of an argument register.
+Most ports do not need to implement anything for this hook.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_END_CALL_ARGS (void)
+This target hook is invoked while generating RTL for a function call,
+just after the point where the return reg is copied into a pseudo. It
+signals that all the call argument and return registers for the just
+emitted call are now no longer in use.
+Most ports do not need to implement anything for this hook.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_PRETEND_OUTGOING_VARARGS_NAMED (cumulative_args_t @var{ca})
+If you need to conditionally change ABIs so that one works with
+@code{TARGET_SETUP_INCOMING_VARARGS}, but the other works like neither
+@code{TARGET_SETUP_INCOMING_VARARGS} nor @code{TARGET_STRICT_ARGUMENT_NAMING} was
+defined, then define this hook to return @code{true} if
+@code{TARGET_SETUP_INCOMING_VARARGS} is used, @code{false} otherwise.
+Otherwise, you should not define this hook.
+@end deftypefn
+
+@node Trampolines
+@section Support for Nested Functions
+@cindex support for nested functions
+@cindex trampolines for nested functions
+@cindex descriptors for nested functions
+@cindex nested functions, support for
+
+Taking the address of a nested function requires special compiler
+handling to ensure that the static chain register is loaded when
+the function is invoked via an indirect call.
+
+GCC has traditionally supported nested functions by creating an
+executable @dfn{trampoline} at run time when the address of a nested
+function is taken. This is a small piece of code which normally
+resides on the stack, in the stack frame of the containing function.
+The trampoline loads the static chain register and then jumps to the
+real address of the nested function.
+
+The use of trampolines requires an executable stack, which is a
+security risk. To avoid this problem, GCC also supports another
+strategy: using descriptors for nested functions. Under this model,
+taking the address of a nested function results in a pointer to a
+non-executable function descriptor object. Initializing the static chain
+from the descriptor is handled at indirect call sites.
+
+On some targets, including HPPA and IA-64, function descriptors may be
+mandated by the ABI or be otherwise handled in a target-specific way
+by the back end in its code generation strategy for indirect calls.
+GCC also provides its own generic descriptor implementation to support the
+@option{-fno-trampolines} option. In this case runtime detection of
+function descriptors at indirect call sites relies on descriptor
+pointers being tagged with a bit that is never set in bare function
+addresses. Since GCC's generic function descriptors are
+not ABI-compliant, this option is typically used only on a
+per-language basis (notably by Ada) or when it can otherwise be
+applied to the whole program.
+
+For languages other than Ada, the @code{-ftrampolines} and
+@code{-fno-trampolines} options currently have no effect, and
+trampolines are always generated on platforms that need them
+for nested functions.
+
+Define the following hook if your backend either implements ABI-specified
+descriptor support, or can use GCC's generic descriptor implementation
+for nested functions.
+
+@deftypevr {Target Hook} int TARGET_CUSTOM_FUNCTION_DESCRIPTORS
+If the target can use GCC's generic descriptor mechanism for nested
+functions, define this hook to a power of 2 representing an unused bit
+in function pointers which can be used to differentiate descriptors at
+run time. This value gives the number of bytes by which descriptor
+pointers are misaligned compared to function pointers. For example, on
+targets that require functions to be aligned to a 4-byte boundary, a
+value of either 1 or 2 is appropriate unless the architecture already
+reserves the bit for another purpose, such as on ARM.
+
+Define this hook to 0 if the target implements ABI support for
+function descriptors in its standard calling sequence, like for example
+HPPA or IA-64.
+
+Using descriptors for nested functions
+eliminates the need for trampolines that reside on the stack and require
+it to be made executable.
+@end deftypevr
+
+The following macros tell GCC how to generate code to allocate and
+initialize an executable trampoline. You can also use this interface
+if your back end needs to create ABI-specified non-executable descriptors; in
+this case the "trampoline" created is the descriptor containing data only.
+
+The instructions in an executable trampoline must do two things: load
+a constant address into the static chain register, and jump to the real
+address of the nested function. On CISC machines such as the m68k,
+this requires two instructions, a move immediate and a jump. Then the
+two addresses exist in the trampoline as word-long immediate operands.
+On RISC machines, it is often necessary to load each address into a
+register in two parts. Then pieces of each address form separate
+immediate operands.
+
+The code generated to initialize the trampoline must store the variable
+parts---the static chain value and the function address---into the
+immediate operands of the instructions. On a CISC machine, this is
+simply a matter of copying each address to a memory reference at the
+proper offset from the start of the trampoline. On a RISC machine, it
+may be necessary to take out pieces of the address and store them
+separately.
+
+@deftypefn {Target Hook} void TARGET_ASM_TRAMPOLINE_TEMPLATE (FILE *@var{f})
+This hook is called by @code{assemble_trampoline_template} to output,
+on the stream @var{f}, assembler code for a block of data that contains
+the constant parts of a trampoline. This code should not include a
+label---the label is taken care of automatically.
+
+If you do not define this hook, it means no template is needed
+for the target. Do not define this hook on systems where the block move
+code to copy the trampoline into place would be larger than the code
+to generate it on the spot.
+@end deftypefn
+
+@defmac TRAMPOLINE_SECTION
+Return the section into which the trampoline template is to be placed
+(@pxref{Sections}). The default value is @code{readonly_data_section}.
+@end defmac
+
+@defmac TRAMPOLINE_SIZE
+A C expression for the size in bytes of the trampoline, as an integer.
+@end defmac
+
+@defmac TRAMPOLINE_ALIGNMENT
+Alignment required for trampolines, in bits.
+
+If you don't define this macro, the value of @code{FUNCTION_ALIGNMENT}
+is used for aligning trampolines.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_TRAMPOLINE_INIT (rtx @var{m_tramp}, tree @var{fndecl}, rtx @var{static_chain})
+This hook is called to initialize a trampoline.
+@var{m_tramp} is an RTX for the memory block for the trampoline; @var{fndecl}
+is the @code{FUNCTION_DECL} for the nested function; @var{static_chain} is an
+RTX for the static chain value that should be passed to the function
+when it is called.
+
+If the target defines @code{TARGET_ASM_TRAMPOLINE_TEMPLATE}, then the
+first thing this hook should do is emit a block move into @var{m_tramp}
+from the memory block returned by @code{assemble_trampoline_template}.
+Note that the block move need only cover the constant parts of the
+trampoline. If the target isolates the variable parts of the trampoline
+to the end, not all @code{TRAMPOLINE_SIZE} bytes need be copied.
+
+If the target requires any other actions, such as flushing caches
+(possibly calling function maybe_emit_call_builtin___clear_cache) or
+enabling stack execution, these actions should be performed after
+initializing the trampoline proper.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_EMIT_CALL_BUILTIN___CLEAR_CACHE (rtx @var{begin}, rtx @var{end})
+On targets that do not define a @code{clear_cache} insn expander,
+but that define the @code{CLEAR_CACHE_INSN} macro,
+maybe_emit_call_builtin___clear_cache relies on this target hook
+to clear an address range in the instruction cache.
+
+The default implementation calls the @code{__clear_cache} builtin,
+taking the assembler name from the builtin declaration. Overriding
+definitions may call alternate functions, with alternate calling
+conventions, or emit alternate RTX to perform the job.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_TRAMPOLINE_ADJUST_ADDRESS (rtx @var{addr})
+This hook should perform any machine-specific adjustment in
+the address of the trampoline. Its argument contains the address of the
+memory block that was passed to @code{TARGET_TRAMPOLINE_INIT}. In case
+the address to be used for a function call should be different from the
+address at which the template was stored, the different address should
+be returned; otherwise @var{addr} should be returned unchanged.
+If this hook is not defined, @var{addr} will be used for function calls.
+@end deftypefn
+
+Implementing trampolines is difficult on many machines because they have
+separate instruction and data caches. Writing into a stack location
+fails to clear the memory in the instruction cache, so when the program
+jumps to that location, it executes the old contents.
+
+Here are two possible solutions. One is to clear the relevant parts of
+the instruction cache whenever a trampoline is set up. The other is to
+make all trampolines identical, by having them jump to a standard
+subroutine. The former technique makes trampoline execution faster; the
+latter makes initialization faster.
+
+To clear the instruction cache when a trampoline is initialized, define
+the following macro.
+
+@defmac CLEAR_INSN_CACHE (@var{beg}, @var{end})
+If defined, expands to a C expression clearing the @emph{instruction
+cache} in the specified interval. The definition of this macro would
+typically be a series of @code{asm} statements. Both @var{beg} and
+@var{end} are pointer expressions.
+@end defmac
+
+To use a standard subroutine, define the following macro. In addition,
+you must make sure that the instructions in a trampoline fill an entire
+cache line with identical instructions, or else ensure that the
+beginning of the trampoline code is always aligned at the same point in
+its cache line. Look in @file{m68k.h} as a guide.
+
+@defmac TRANSFER_FROM_TRAMPOLINE
+Define this macro if trampolines need a special subroutine to do their
+work. The macro should expand to a series of @code{asm} statements
+which will be compiled with GCC@. They go in a library function named
+@code{__transfer_from_trampoline}.
+
+If you need to avoid executing the ordinary prologue code of a compiled
+C function when you jump to the subroutine, you can do so by placing a
+special label of your own in the assembler code. Use one @code{asm}
+statement to generate an assembler label, and another to make the label
+global. Then trampolines can use that label to jump directly to your
+special assembler code.
+@end defmac
+
+@node Library Calls
+@section Implicit Calls to Library Routines
+@cindex library subroutine names
+@cindex @file{libgcc.a}
+
+@c prevent bad page break with this line
+Here is an explanation of implicit calls to library routines.
+
+@defmac DECLARE_LIBRARY_RENAMES
+This macro, if defined, should expand to a piece of C code that will get
+expanded when compiling functions for libgcc.a. It can be used to
+provide alternate names for GCC's internal library functions if there
+are ABI-mandated names that the compiler should provide.
+@end defmac
+
+@findex set_optab_libfunc
+@findex init_one_libfunc
+@deftypefn {Target Hook} void TARGET_INIT_LIBFUNCS (void)
+This hook should declare additional library routines or rename
+existing ones, using the functions @code{set_optab_libfunc} and
+@code{init_one_libfunc} defined in @file{optabs.cc}.
+@code{init_optabs} calls this macro after initializing all the normal
+library routines.
+
+The default is to do nothing. Most ports don't need to define this hook.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_LIBFUNC_GNU_PREFIX
+If false (the default), internal library routines start with two
+underscores. If set to true, these routines start with @code{__gnu_}
+instead. E.g., @code{__muldi3} changes to @code{__gnu_muldi3}. This
+currently only affects functions defined in @file{libgcc2.c}. If this
+is set to true, the @file{tm.h} file must also
+@code{#define LIBGCC2_GNU_PREFIX}.
+@end deftypevr
+
+@defmac FLOAT_LIB_COMPARE_RETURNS_BOOL (@var{mode}, @var{comparison})
+This macro should return @code{true} if the library routine that
+implements the floating point comparison operator @var{comparison} in
+mode @var{mode} will return a boolean, and @var{false} if it will
+return a tristate.
+
+GCC's own floating point libraries return tristates from the
+comparison operators, so the default returns false always. Most ports
+don't need to define this macro.
+@end defmac
+
+@defmac TARGET_LIB_INT_CMP_BIASED
+This macro should evaluate to @code{true} if the integer comparison
+functions (like @code{__cmpdi2}) return 0 to indicate that the first
+operand is smaller than the second, 1 to indicate that they are equal,
+and 2 to indicate that the first operand is greater than the second.
+If this macro evaluates to @code{false} the comparison functions return
+@minus{}1, 0, and 1 instead of 0, 1, and 2. If the target uses the routines
+in @file{libgcc.a}, you do not need to define this macro.
+@end defmac
+
+@defmac TARGET_HAS_NO_HW_DIVIDE
+This macro should be defined if the target has no hardware divide
+instructions. If this macro is defined, GCC will use an algorithm which
+make use of simple logical and arithmetic operations for 64-bit
+division. If the macro is not defined, GCC will use an algorithm which
+make use of a 64-bit by 32-bit divide primitive.
+@end defmac
+
+@cindex @code{EDOM}, implicit usage
+@findex matherr
+@defmac TARGET_EDOM
+The value of @code{EDOM} on the target machine, as a C integer constant
+expression. If you don't define this macro, GCC does not attempt to
+deposit the value of @code{EDOM} into @code{errno} directly. Look in
+@file{/usr/include/errno.h} to find the value of @code{EDOM} on your
+system.
+
+If you do not define @code{TARGET_EDOM}, then compiled code reports
+domain errors by calling the library function and letting it report the
+error. If mathematical functions on your system use @code{matherr} when
+there is an error, then you should leave @code{TARGET_EDOM} undefined so
+that @code{matherr} is used normally.
+@end defmac
+
+@cindex @code{errno}, implicit usage
+@defmac GEN_ERRNO_RTX
+Define this macro as a C expression to create an rtl expression that
+refers to the global ``variable'' @code{errno}. (On certain systems,
+@code{errno} may not actually be a variable.) If you don't define this
+macro, a reasonable default is used.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_LIBC_HAS_FUNCTION (enum function_class @var{fn_class}, tree @var{type})
+This hook determines whether a function from a class of functions
+@var{fn_class} is present in the target C library. If @var{type} is NULL,
+the caller asks for support for all standard (float, double, long double)
+types. If @var{type} is non-NULL, the caller asks for support for a
+specific type.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_LIBC_HAS_FAST_FUNCTION (int @var{fcode})
+This hook determines whether a function from a class of functions
+@code{(enum function_class)}@var{fcode} has a fast implementation.
+@end deftypefn
+
+@defmac NEXT_OBJC_RUNTIME
+Set this macro to 1 to use the "NeXT" Objective-C message sending conventions
+by default. This calling convention involves passing the object, the selector
+and the method arguments all at once to the method-lookup library function.
+This is the usual setting when targeting Darwin/Mac OS X systems, which have
+the NeXT runtime installed.
+
+If the macro is set to 0, the "GNU" Objective-C message sending convention
+will be used by default. This convention passes just the object and the
+selector to the method-lookup function, which returns a pointer to the method.
+
+In either case, it remains possible to select code-generation for the alternate
+scheme, by means of compiler command line switches.
+@end defmac
+
+@node Addressing Modes
+@section Addressing Modes
+@cindex addressing modes
+
+@c prevent bad page break with this line
+This is about addressing modes.
+
+@defmac HAVE_PRE_INCREMENT
+@defmacx HAVE_PRE_DECREMENT
+@defmacx HAVE_POST_INCREMENT
+@defmacx HAVE_POST_DECREMENT
+A C expression that is nonzero if the machine supports pre-increment,
+pre-decrement, post-increment, or post-decrement addressing respectively.
+@end defmac
+
+@defmac HAVE_PRE_MODIFY_DISP
+@defmacx HAVE_POST_MODIFY_DISP
+A C expression that is nonzero if the machine supports pre- or
+post-address side-effect generation involving constants other than
+the size of the memory operand.
+@end defmac
+
+@defmac HAVE_PRE_MODIFY_REG
+@defmacx HAVE_POST_MODIFY_REG
+A C expression that is nonzero if the machine supports pre- or
+post-address side-effect generation involving a register displacement.
+@end defmac
+
+@defmac CONSTANT_ADDRESS_P (@var{x})
+A C expression that is 1 if the RTX @var{x} is a constant which
+is a valid address. On most machines the default definition of
+@code{(CONSTANT_P (@var{x}) && GET_CODE (@var{x}) != CONST_DOUBLE)}
+is acceptable, but a few machines are more restrictive as to which
+constant addresses are supported.
+@end defmac
+
+@defmac CONSTANT_P (@var{x})
+@code{CONSTANT_P}, which is defined by target-independent code,
+accepts integer-values expressions whose values are not explicitly
+known, such as @code{symbol_ref}, @code{label_ref}, and @code{high}
+expressions and @code{const} arithmetic expressions, in addition to
+@code{const_int} and @code{const_double} expressions.
+@end defmac
+
+@defmac MAX_REGS_PER_ADDRESS
+A number, the maximum number of registers that can appear in a valid
+memory address. Note that it is up to you to specify a value equal to
+the maximum number that @code{TARGET_LEGITIMATE_ADDRESS_P} would ever
+accept.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_LEGITIMATE_ADDRESS_P (machine_mode @var{mode}, rtx @var{x}, bool @var{strict})
+A function that returns whether @var{x} (an RTX) is a legitimate memory
+address on the target machine for a memory operand of mode @var{mode}.
+
+Legitimate addresses are defined in two variants: a strict variant and a
+non-strict one. The @var{strict} parameter chooses which variant is
+desired by the caller.
+
+The strict variant is used in the reload pass. It must be defined so
+that any pseudo-register that has not been allocated a hard register is
+considered a memory reference. This is because in contexts where some
+kind of register is required, a pseudo-register with no hard register
+must be rejected. For non-hard registers, the strict variant should look
+up the @code{reg_renumber} array; it should then proceed using the hard
+register number in the array, or treat the pseudo as a memory reference
+if the array holds @code{-1}.
+
+The non-strict variant is used in other passes. It must be defined to
+accept all pseudo-registers in every context where some kind of
+register is required.
+
+Normally, constant addresses which are the sum of a @code{symbol_ref}
+and an integer are stored inside a @code{const} RTX to mark them as
+constant. Therefore, there is no need to recognize such sums
+specifically as legitimate addresses. Normally you would simply
+recognize any @code{const} as legitimate.
+
+Usually @code{PRINT_OPERAND_ADDRESS} is not prepared to handle constant
+sums that are not marked with @code{const}. It assumes that a naked
+@code{plus} indicates indexing. If so, then you @emph{must} reject such
+naked constant sums as illegitimate addresses, so that none of them will
+be given to @code{PRINT_OPERAND_ADDRESS}.
+
+@cindex @code{TARGET_ENCODE_SECTION_INFO} and address validation
+On some machines, whether a symbolic address is legitimate depends on
+the section that the address refers to. On these machines, define the
+target hook @code{TARGET_ENCODE_SECTION_INFO} to store the information
+into the @code{symbol_ref}, and then check for it here. When you see a
+@code{const}, you will have to look inside it to find the
+@code{symbol_ref} in order to determine the section. @xref{Assembler
+Format}.
+
+@cindex @code{GO_IF_LEGITIMATE_ADDRESS}
+Some ports are still using a deprecated legacy substitute for
+this hook, the @code{GO_IF_LEGITIMATE_ADDRESS} macro. This macro
+has this syntax:
+
+@example
+#define GO_IF_LEGITIMATE_ADDRESS (@var{mode}, @var{x}, @var{label})
+@end example
+
+@noindent
+and should @code{goto @var{label}} if the address @var{x} is a valid
+address on the target machine for a memory operand of mode @var{mode}.
+
+@findex REG_OK_STRICT
+Compiler source files that want to use the strict variant of this
+macro define the macro @code{REG_OK_STRICT}. You should use an
+@code{#ifdef REG_OK_STRICT} conditional to define the strict variant in
+that case and the non-strict variant otherwise.
+
+Using the hook is usually simpler because it limits the number of
+files that are recompiled when changes are made.
+@end deftypefn
+
+@defmac TARGET_MEM_CONSTRAINT
+A single character to be used instead of the default @code{'m'}
+character for general memory addresses. This defines the constraint
+letter which matches the memory addresses accepted by
+@code{TARGET_LEGITIMATE_ADDRESS_P}. Define this macro if you want to
+support new address formats in your back end without changing the
+semantics of the @code{'m'} constraint. This is necessary in order to
+preserve functionality of inline assembly constructs using the
+@code{'m'} constraint.
+@end defmac
+
+@defmac FIND_BASE_TERM (@var{x})
+A C expression to determine the base term of address @var{x},
+or to provide a simplified version of @var{x} from which @file{alias.cc}
+can easily find the base term. This macro is used in only two places:
+@code{find_base_value} and @code{find_base_term} in @file{alias.cc}.
+
+It is always safe for this macro to not be defined. It exists so
+that alias analysis can understand machine-dependent addresses.
+
+The typical use of this macro is to handle addresses containing
+a label_ref or symbol_ref within an UNSPEC@.
+@end defmac
+
+@deftypefn {Target Hook} rtx TARGET_LEGITIMIZE_ADDRESS (rtx @var{x}, rtx @var{oldx}, machine_mode @var{mode})
+This hook is given an invalid memory address @var{x} for an
+operand of mode @var{mode} and should try to return a valid memory
+address.
+
+@findex break_out_memory_refs
+@var{x} will always be the result of a call to @code{break_out_memory_refs},
+and @var{oldx} will be the operand that was given to that function to produce
+@var{x}.
+
+The code of the hook should not alter the substructure of
+@var{x}. If it transforms @var{x} into a more legitimate form, it
+should return the new @var{x}.
+
+It is not necessary for this hook to come up with a legitimate address,
+with the exception of native TLS addresses (@pxref{Emulated TLS}).
+The compiler has standard ways of doing so in all cases. In fact, if
+the target supports only emulated TLS, it
+is safe to omit this hook or make it return @var{x} if it cannot find
+a valid way to legitimize the address. But often a machine-dependent
+strategy can generate better code.
+@end deftypefn
+
+@defmac LEGITIMIZE_RELOAD_ADDRESS (@var{x}, @var{mode}, @var{opnum}, @var{type}, @var{ind_levels}, @var{win})
+A C compound statement that attempts to replace @var{x}, which is an address
+that needs reloading, with a valid memory address for an operand of mode
+@var{mode}. @var{win} will be a C statement label elsewhere in the code.
+It is not necessary to define this macro, but it might be useful for
+performance reasons.
+
+For example, on the i386, it is sometimes possible to use a single
+reload register instead of two by reloading a sum of two pseudo
+registers into a register. On the other hand, for number of RISC
+processors offsets are limited so that often an intermediate address
+needs to be generated in order to address a stack slot. By defining
+@code{LEGITIMIZE_RELOAD_ADDRESS} appropriately, the intermediate addresses
+generated for adjacent some stack slots can be made identical, and thus
+be shared.
+
+@emph{Note}: This macro should be used with caution. It is necessary
+to know something of how reload works in order to effectively use this,
+and it is quite easy to produce macros that build in too much knowledge
+of reload internals.
+
+@emph{Note}: This macro must be able to reload an address created by a
+previous invocation of this macro. If it fails to handle such addresses
+then the compiler may generate incorrect code or abort.
+
+@findex push_reload
+The macro definition should use @code{push_reload} to indicate parts that
+need reloading; @var{opnum}, @var{type} and @var{ind_levels} are usually
+suitable to be passed unaltered to @code{push_reload}.
+
+The code generated by this macro must not alter the substructure of
+@var{x}. If it transforms @var{x} into a more legitimate form, it
+should assign @var{x} (which will always be a C variable) a new value.
+This also applies to parts that you change indirectly by calling
+@code{push_reload}.
+
+@findex strict_memory_address_p
+The macro definition may use @code{strict_memory_address_p} to test if
+the address has become legitimate.
+
+@findex copy_rtx
+If you want to change only a part of @var{x}, one standard way of doing
+this is to use @code{copy_rtx}. Note, however, that it unshares only a
+single level of rtl. Thus, if the part to be changed is not at the
+top level, you'll need to replace first the top level.
+It is not necessary for this macro to come up with a legitimate
+address; but often a machine-dependent strategy can generate better code.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_MODE_DEPENDENT_ADDRESS_P (const_rtx @var{addr}, addr_space_t @var{addrspace})
+This hook returns @code{true} if memory address @var{addr} in address
+space @var{addrspace} can have
+different meanings depending on the machine mode of the memory
+reference it is used for or if the address is valid for some modes
+but not others.
+
+Autoincrement and autodecrement addresses typically have mode-dependent
+effects because the amount of the increment or decrement is the size
+of the operand being addressed. Some machines have other mode-dependent
+addresses. Many RISC machines have no mode-dependent addresses.
+
+You may assume that @var{addr} is a valid address for the machine.
+
+The default version of this hook returns @code{false}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_LEGITIMATE_CONSTANT_P (machine_mode @var{mode}, rtx @var{x})
+This hook returns true if @var{x} is a legitimate constant for a
+@var{mode}-mode immediate operand on the target machine. You can assume that
+@var{x} satisfies @code{CONSTANT_P}, so you need not check this.
+
+The default definition returns true.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_PRECOMPUTE_TLS_P (machine_mode @var{mode}, rtx @var{x})
+This hook returns true if @var{x} is a TLS operand on the target
+machine that should be pre-computed when used as the argument in a call.
+You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not
+check this.
+
+The default definition returns false.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_DELEGITIMIZE_ADDRESS (rtx @var{x})
+This hook is used to undo the possibly obfuscating effects of the
+@code{LEGITIMIZE_ADDRESS} and @code{LEGITIMIZE_RELOAD_ADDRESS} target
+macros. Some backend implementations of these macros wrap symbol
+references inside an @code{UNSPEC} rtx to represent PIC or similar
+addressing modes. This target hook allows GCC's optimizers to understand
+the semantics of these opaque @code{UNSPEC}s by converting them back
+into their original form.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CONST_NOT_OK_FOR_DEBUG_P (rtx @var{x})
+This hook should return true if @var{x} should not be emitted into
+debug sections.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CANNOT_FORCE_CONST_MEM (machine_mode @var{mode}, rtx @var{x})
+This hook should return true if @var{x} is of a form that cannot (or
+should not) be spilled to the constant pool. @var{mode} is the mode
+of @var{x}.
+
+The default version of this hook returns false.
+
+The primary reason to define this hook is to prevent reload from
+deciding that a non-legitimate constant would be better reloaded
+from the constant pool instead of spilling and reloading a register
+holding the constant. This restriction is often true of addresses
+of TLS symbols for various targets.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_USE_BLOCKS_FOR_CONSTANT_P (machine_mode @var{mode}, const_rtx @var{x})
+This hook should return true if pool entries for constant @var{x} can
+be placed in an @code{object_block} structure. @var{mode} is the mode
+of @var{x}.
+
+The default version returns false for all constants.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_USE_BLOCKS_FOR_DECL_P (const_tree @var{decl})
+This hook should return true if pool entries for @var{decl} should
+be placed in an @code{object_block} structure.
+
+The default version returns true for all decls.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_BUILTIN_RECIPROCAL (tree @var{fndecl})
+This hook should return the DECL of a function that implements the
+reciprocal of the machine-specific builtin function @var{fndecl}, or
+@code{NULL_TREE} if such a function is not available.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_MASK_FOR_LOAD (void)
+This hook should return the DECL of a function @var{f} that given an
+address @var{addr} as an argument returns a mask @var{m} that can be
+used to extract from two vectors the relevant data that resides in
+@var{addr} in case @var{addr} is not properly aligned.
+
+The autovectorizer, when vectorizing a load operation from an address
+@var{addr} that may be unaligned, will generate two vector loads from
+the two aligned addresses around @var{addr}. It then generates a
+@code{REALIGN_LOAD} operation to extract the relevant data from the
+two loaded vectors. The first two arguments to @code{REALIGN_LOAD},
+@var{v1} and @var{v2}, are the two vectors, each of size @var{VS}, and
+the third argument, @var{OFF}, defines how the data will be extracted
+from these two vectors: if @var{OFF} is 0, then the returned vector is
+@var{v2}; otherwise, the returned vector is composed from the last
+@var{VS}-@var{OFF} elements of @var{v1} concatenated to the first
+@var{OFF} elements of @var{v2}.
+
+If this hook is defined, the autovectorizer will generate a call
+to @var{f} (using the DECL tree that this hook returns) and will
+use the return value of @var{f} as the argument @var{OFF} to
+@code{REALIGN_LOAD}. Therefore, the mask @var{m} returned by @var{f}
+should comply with the semantics expected by @code{REALIGN_LOAD}
+described above.
+If this hook is not defined, then @var{addr} will be used as
+the argument @var{OFF} to @code{REALIGN_LOAD}, in which case the low
+log2(@var{VS}) @minus{} 1 bits of @var{addr} will be considered.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST (enum vect_cost_for_stmt @var{type_of_cost}, tree @var{vectype}, int @var{misalign})
+Returns cost of different scalar or vector statements for vectorization cost model.
+For vector memory operations the cost may depend on type (@var{vectype}) and
+misalignment value (@var{misalign}).
+@end deftypefn
+
+@deftypefn {Target Hook} poly_uint64 TARGET_VECTORIZE_PREFERRED_VECTOR_ALIGNMENT (const_tree @var{type})
+This hook returns the preferred alignment in bits for accesses to
+vectors of type @var{type} in vectorized code. This might be less than
+or greater than the ABI-defined value returned by
+@code{TARGET_VECTOR_ALIGNMENT}. It can be equal to the alignment of
+a single element, in which case the vectorizer will not try to optimize
+for alignment.
+
+The default hook returns @code{TYPE_ALIGN (@var{type})}, which is
+correct for most targets.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_VECTORIZE_VECTOR_ALIGNMENT_REACHABLE (const_tree @var{type}, bool @var{is_packed})
+Return true if vector alignment is reachable (by peeling N iterations)
+for the given scalar type @var{type}. @var{is_packed} is false if the scalar
+access using @var{type} is known to be naturally aligned.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_VECTORIZE_VEC_PERM_CONST (machine_mode @var{mode}, machine_mode @var{op_mode}, rtx @var{output}, rtx @var{in0}, rtx @var{in1}, const vec_perm_indices @var{&sel})
+This hook is used to test whether the target can permute up to two
+vectors of mode @var{op_mode} using the permutation vector @code{sel},
+producing a vector of mode @var{mode}. The hook is also used to emit such
+a permutation.
+
+When the hook is being used to test whether the target supports a permutation,
+@var{in0}, @var{in1}, and @var{out} are all null. When the hook is being used
+to emit a permutation, @var{in0} and @var{in1} are the source vectors of mode
+@var{op_mode} and @var{out} is the destination vector of mode @var{mode}.
+@var{in1} is the same as @var{in0} if @var{sel} describes a permutation on one
+vector instead of two.
+
+Return true if the operation is possible, emitting instructions for it
+if rtxes are provided.
+
+@cindex @code{vec_perm@var{m}} instruction pattern
+If the hook returns false for a mode with multibyte elements, GCC will
+try the equivalent byte operation. If that also fails, it will try forcing
+the selector into a register and using the @var{vec_perm@var{mode}}
+instruction pattern. There is no need for the hook to handle these two
+implementation approaches itself.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_VECTORIZED_FUNCTION (unsigned @var{code}, tree @var{vec_type_out}, tree @var{vec_type_in})
+This hook should return the decl of a function that implements the
+vectorized variant of the function with the @code{combined_fn} code
+@var{code} or @code{NULL_TREE} if such a function is not available.
+The return type of the vectorized function shall be of vector type
+@var{vec_type_out} and the argument types should be @var{vec_type_in}.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_MD_VECTORIZED_FUNCTION (tree @var{fndecl}, tree @var{vec_type_out}, tree @var{vec_type_in})
+This hook should return the decl of a function that implements the
+vectorized variant of target built-in function @code{fndecl}. The
+return type of the vectorized function shall be of vector type
+@var{vec_type_out} and the argument types should be @var{vec_type_in}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_VECTORIZE_SUPPORT_VECTOR_MISALIGNMENT (machine_mode @var{mode}, const_tree @var{type}, int @var{misalignment}, bool @var{is_packed})
+This hook should return true if the target supports misaligned vector
+store/load of a specific factor denoted in the @var{misalignment}
+parameter. The vector store/load should be of machine mode @var{mode} and
+the elements in the vectors should be of type @var{type}. @var{is_packed}
+parameter is true if the memory access is defined in a packed struct.
+@end deftypefn
+
+@deftypefn {Target Hook} machine_mode TARGET_VECTORIZE_PREFERRED_SIMD_MODE (scalar_mode @var{mode})
+This hook should return the preferred mode for vectorizing scalar
+mode @var{mode}. The default is
+equal to @code{word_mode}, because the vectorizer can do some
+transformations even in absence of specialized @acronym{SIMD} hardware.
+@end deftypefn
+
+@deftypefn {Target Hook} machine_mode TARGET_VECTORIZE_SPLIT_REDUCTION (machine_mode)
+This hook should return the preferred mode to split the final reduction
+step on @var{mode} to. The reduction is then carried out reducing upper
+against lower halves of vectors recursively until the specified mode is
+reached. The default is @var{mode} which means no splitting.
+@end deftypefn
+
+@deftypefn {Target Hook} {unsigned int} TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES (vector_modes *@var{modes}, bool @var{all})
+If using the mode returned by @code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE}
+is not the only approach worth considering, this hook should add one mode to
+@var{modes} for each useful alternative approach. These modes are then
+passed to @code{TARGET_VECTORIZE_RELATED_MODE} to obtain the vector mode
+for a given element mode.
+
+The modes returned in @var{modes} should use the smallest element mode
+possible for the vectorization approach that they represent, preferring
+integer modes over floating-poing modes in the event of a tie. The first
+mode should be the @code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE} for its
+element mode.
+
+If @var{all} is true, add suitable vector modes even when they are generally
+not expected to be worthwhile.
+
+The hook returns a bitmask of flags that control how the modes in
+@var{modes} are used. The flags are:
+@table @code
+@item VECT_COMPARE_COSTS
+Tells the loop vectorizer to try all the provided modes and pick the one
+with the lowest cost. By default the vectorizer will choose the first
+mode that works.
+@end table
+
+The hook does not need to do anything if the vector returned by
+@code{TARGET_VECTORIZE_PREFERRED_SIMD_MODE} is the only one relevant
+for autovectorization. The default implementation adds no modes and
+returns 0.
+@end deftypefn
+
+@deftypefn {Target Hook} opt_machine_mode TARGET_VECTORIZE_RELATED_MODE (machine_mode @var{vector_mode}, scalar_mode @var{element_mode}, poly_uint64 @var{nunits})
+If a piece of code is using vector mode @var{vector_mode} and also wants
+to operate on elements of mode @var{element_mode}, return the vector mode
+it should use for those elements. If @var{nunits} is nonzero, ensure that
+the mode has exactly @var{nunits} elements, otherwise pick whichever vector
+size pairs the most naturally with @var{vector_mode}. Return an empty
+@code{opt_machine_mode} if there is no supported vector mode with the
+required properties.
+
+There is no prescribed way of handling the case in which @var{nunits}
+is zero. One common choice is to pick a vector mode with the same size
+as @var{vector_mode}; this is the natural choice if the target has a
+fixed vector size. Another option is to choose a vector mode with the
+same number of elements as @var{vector_mode}; this is the natural choice
+if the target has a fixed number of elements. Alternatively, the hook
+might choose a middle ground, such as trying to keep the number of
+elements as similar as possible while applying maximum and minimum
+vector sizes.
+
+The default implementation uses @code{mode_for_vector} to find the
+requested mode, returning a mode with the same size as @var{vector_mode}
+when @var{nunits} is zero. This is the correct behavior for most targets.
+@end deftypefn
+
+@deftypefn {Target Hook} opt_machine_mode TARGET_VECTORIZE_GET_MASK_MODE (machine_mode @var{mode})
+Return the mode to use for a vector mask that holds one boolean
+result for each element of vector mode @var{mode}. The returned mask mode
+can be a vector of integers (class @code{MODE_VECTOR_INT}), a vector of
+booleans (class @code{MODE_VECTOR_BOOL}) or a scalar integer (class
+@code{MODE_INT}). Return an empty @code{opt_machine_mode} if no such
+mask mode exists.
+
+The default implementation returns a @code{MODE_VECTOR_INT} with the
+same size and number of elements as @var{mode}, if such a mode exists.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_VECTORIZE_EMPTY_MASK_IS_EXPENSIVE (unsigned @var{ifn})
+This hook returns true if masked internal function @var{ifn} (really of
+type @code{internal_fn}) should be considered expensive when the mask is
+all zeros. GCC can then try to branch around the instruction instead.
+@end deftypefn
+
+@deftypefn {Target Hook} {class vector_costs *} TARGET_VECTORIZE_CREATE_COSTS (vec_info *@var{vinfo}, bool @var{costing_for_scalar})
+This hook should initialize target-specific data structures in preparation
+for modeling the costs of vectorizing a loop or basic block. The default
+allocates three unsigned integers for accumulating costs for the prologue,
+body, and epilogue of the loop or basic block. If @var{loop_info} is
+non-NULL, it identifies the loop being vectorized; otherwise a single block
+is being vectorized. If @var{costing_for_scalar} is true, it indicates the
+current cost model is for the scalar version of a loop or block; otherwise
+it is for the vector version.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_GATHER (const_tree @var{mem_vectype}, const_tree @var{index_type}, int @var{scale})
+Target builtin that implements vector gather operation. @var{mem_vectype}
+is the vector type of the load and @var{index_type} is scalar type of
+the index, scaled by @var{scale}.
+The default is @code{NULL_TREE} which means to not vectorize gather
+loads.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_VECTORIZE_BUILTIN_SCATTER (const_tree @var{vectype}, const_tree @var{index_type}, int @var{scale})
+Target builtin that implements vector scatter operation. @var{vectype}
+is the vector type of the store and @var{index_type} is scalar type of
+the index, scaled by @var{scale}.
+The default is @code{NULL_TREE} which means to not vectorize scatter
+stores.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SIMD_CLONE_COMPUTE_VECSIZE_AND_SIMDLEN (struct cgraph_node *@var{}, struct cgraph_simd_clone *@var{}, @var{tree}, @var{int})
+This hook should set @var{vecsize_mangle}, @var{vecsize_int}, @var{vecsize_float}
+fields in @var{simd_clone} structure pointed by @var{clone_info} argument and also
+@var{simdlen} field if it was previously 0.
+@var{vecsize_mangle} is a marker for the backend only. @var{vecsize_int} and
+@var{vecsize_float} should be left zero on targets where the number of lanes is
+not determined by the bitsize (in which case @var{simdlen} is always used).
+The hook should return 0 if SIMD clones shouldn't be emitted,
+or number of @var{vecsize_mangle} variants that should be emitted.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SIMD_CLONE_ADJUST (struct cgraph_node *@var{})
+This hook should add implicit @code{attribute(target("..."))} attribute
+to SIMD clone @var{node} if needed.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SIMD_CLONE_USABLE (struct cgraph_node *@var{})
+This hook should return -1 if SIMD clone @var{node} shouldn't be used
+in vectorized loops in current function, or non-negative number if it is
+usable. In that case, the smaller the number is, the more desirable it is
+to use it.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SIMT_VF (void)
+Return number of threads in SIMT thread group on the target.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_OMP_DEVICE_KIND_ARCH_ISA (enum omp_device_kind_arch_isa @var{trait}, const char *@var{name})
+Return 1 if @var{trait} @var{name} is present in the OpenMP context's
+device trait set, return 0 if not present in any OpenMP context in the
+whole translation unit, or -1 if not present in the current OpenMP context
+but might be present in another OpenMP context in the same TU.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_GOACC_VALIDATE_DIMS (tree @var{decl}, int *@var{dims}, int @var{fn_level}, unsigned @var{used})
+This hook should check the launch dimensions provided for an OpenACC
+compute region, or routine. Defaulted values are represented as -1
+and non-constant values as 0. The @var{fn_level} is negative for the
+function corresponding to the compute region. For a routine it is the
+outermost level at which partitioned execution may be spawned. The hook
+should verify non-default values. If DECL is NULL, global defaults
+are being validated and unspecified defaults should be filled in.
+Diagnostics should be issued as appropriate. Return
+true, if changes have been made. You must override this hook to
+provide dimensions larger than 1.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_GOACC_DIM_LIMIT (int @var{axis})
+This hook should return the maximum size of a particular dimension,
+or zero if unbounded.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_GOACC_FORK_JOIN (gcall *@var{call}, const int *@var{dims}, bool @var{is_fork})
+This hook can be used to convert IFN_GOACC_FORK and IFN_GOACC_JOIN
+function calls to target-specific gimple, or indicate whether they
+should be retained. It is executed during the oacc_device_lower pass.
+It should return true, if the call should be retained. It should
+return false, if it is to be deleted (either because target-specific
+gimple has been inserted before it, or there is no need for it).
+The default hook returns false, if there are no RTL expanders for them.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_GOACC_REDUCTION (gcall *@var{call})
+This hook is used by the oacc_transform pass to expand calls to the
+@var{GOACC_REDUCTION} internal function, into a sequence of gimple
+instructions. @var{call} is gimple statement containing the call to
+the function. This hook removes statement @var{call} after the
+expanded sequence has been inserted. This hook is also responsible
+for allocating any storage for reductions when necessary.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_PREFERRED_ELSE_VALUE (unsigned @var{ifn}, tree @var{type}, unsigned @var{nops}, tree *@var{ops})
+This hook returns the target's preferred final argument for a call
+to conditional internal function @var{ifn} (really of type
+@code{internal_fn}). @var{type} specifies the return type of the
+function and @var{ops} are the operands to the conditional operation,
+of which there are @var{nops}.
+
+For example, if @var{ifn} is @code{IFN_COND_ADD}, the hook returns
+a value of type @var{type} that should be used when @samp{@var{ops}[0]}
+and @samp{@var{ops}[1]} are conditionally added together.
+
+This hook is only relevant if the target supports conditional patterns
+like @code{cond_add@var{m}}. The default implementation returns a zero
+constant of type @var{type}.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_GOACC_ADJUST_PRIVATE_DECL (location_t @var{loc}, tree @var{var}, int @var{level})
+This hook, if defined, is used by accelerator target back-ends to adjust
+OpenACC variable declarations that should be made private to the given
+parallelism level (i.e. @code{GOMP_DIM_GANG}, @code{GOMP_DIM_WORKER} or
+@code{GOMP_DIM_VECTOR}). A typical use for this hook is to force variable
+declarations at the @code{gang} level to reside in GPU shared memory.
+@var{loc} may be used for diagnostic purposes.
+
+You may also use the @code{TARGET_GOACC_EXPAND_VAR_DECL} hook if the
+adjusted variable declaration needs to be expanded to RTL in a non-standard
+way.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_GOACC_EXPAND_VAR_DECL (tree @var{var})
+This hook, if defined, is used by accelerator target back-ends to expand
+specially handled kinds of @code{VAR_DECL} expressions. A particular use is
+to place variables with specific attributes inside special accelarator
+memories. A return value of @code{NULL} indicates that the target does not
+handle this @code{VAR_DECL}, and normal RTL expanding is resumed.
+
+Only define this hook if your accelerator target needs to expand certain
+@code{VAR_DECL} nodes in a way that differs from the default. You can also adjust
+private variables at OpenACC device-lowering time using the
+@code{TARGET_GOACC_ADJUST_PRIVATE_DECL} target hook.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_GOACC_CREATE_WORKER_BROADCAST_RECORD (tree @var{rec}, bool @var{sender}, const char *@var{name}, unsigned HOST_WIDE_INT @var{offset})
+Create a record used to propagate local-variable state from an active
+worker to other workers. A possible implementation might adjust the type
+of REC to place the new variable in shared GPU memory.
+
+Presence of this target hook indicates that middle end neutering/broadcasting
+be used.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_GOACC_SHARED_MEM_LAYOUT (unsigned HOST_WIDE_INT *@var{}, unsigned HOST_WIDE_INT *@var{}, @var{int[]}, unsigned @var{HOST_WIDE_INT[]}, unsigned @var{HOST_WIDE_INT[]})
+Lay out a fixed shared-memory region on the target. The LO and HI
+arguments should be set to a range of addresses that can be used for worker
+broadcasting. The dimensions, reduction size and gang-private size
+arguments are for the current offload region.
+@end deftypefn
+
+@node Anchored Addresses
+@section Anchored Addresses
+@cindex anchored addresses
+@cindex @option{-fsection-anchors}
+
+GCC usually addresses every static object as a separate entity.
+For example, if we have:
+
+@smallexample
+static int a, b, c;
+int foo (void) @{ return a + b + c; @}
+@end smallexample
+
+the code for @code{foo} will usually calculate three separate symbolic
+addresses: those of @code{a}, @code{b} and @code{c}. On some targets,
+it would be better to calculate just one symbolic address and access
+the three variables relative to it. The equivalent pseudocode would
+be something like:
+
+@smallexample
+int foo (void)
+@{
+ register int *xr = &x;
+ return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
+@}
+@end smallexample
+
+(which isn't valid C). We refer to shared addresses like @code{x} as
+``section anchors''. Their use is controlled by @option{-fsection-anchors}.
+
+The hooks below describe the target properties that GCC needs to know
+in order to make effective use of section anchors. It won't use
+section anchors at all unless either @code{TARGET_MIN_ANCHOR_OFFSET}
+or @code{TARGET_MAX_ANCHOR_OFFSET} is set to a nonzero value.
+
+@deftypevr {Target Hook} HOST_WIDE_INT TARGET_MIN_ANCHOR_OFFSET
+The minimum offset that should be applied to a section anchor.
+On most targets, it should be the smallest offset that can be
+applied to a base register while still giving a legitimate address
+for every mode. The default value is 0.
+@end deftypevr
+
+@deftypevr {Target Hook} HOST_WIDE_INT TARGET_MAX_ANCHOR_OFFSET
+Like @code{TARGET_MIN_ANCHOR_OFFSET}, but the maximum (inclusive)
+offset that should be applied to section anchors. The default
+value is 0.
+@end deftypevr
+
+@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_ANCHOR (rtx @var{x})
+Write the assembly code to define section anchor @var{x}, which is a
+@code{SYMBOL_REF} for which @samp{SYMBOL_REF_ANCHOR_P (@var{x})} is true.
+The hook is called with the assembly output position set to the beginning
+of @code{SYMBOL_REF_BLOCK (@var{x})}.
+
+If @code{ASM_OUTPUT_DEF} is available, the hook's default definition uses
+it to define the symbol as @samp{. + SYMBOL_REF_BLOCK_OFFSET (@var{x})}.
+If @code{ASM_OUTPUT_DEF} is not available, the hook's default definition
+is @code{NULL}, which disables the use of section anchors altogether.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_USE_ANCHORS_FOR_SYMBOL_P (const_rtx @var{x})
+Return true if GCC should attempt to use anchors to access @code{SYMBOL_REF}
+@var{x}. You can assume @samp{SYMBOL_REF_HAS_BLOCK_INFO_P (@var{x})} and
+@samp{!SYMBOL_REF_ANCHOR_P (@var{x})}.
+
+The default version is correct for most targets, but you might need to
+intercept this hook to handle things like target-specific attributes
+or target-specific sections.
+@end deftypefn
+
+@node Condition Code
+@section Condition Code Status
+@cindex condition code status
+
+Condition codes in GCC are represented as registers,
+which provides better schedulability for
+architectures that do have a condition code register, but on which
+most instructions do not affect it. The latter category includes
+most RISC machines.
+
+Implicit clobbering would pose a strong restriction on the placement of
+the definition and use of the condition code. In the past the definition
+and use were always adjacent. However, recent changes to support trapping
+arithmetic may result in the definition and user being in different blocks.
+Thus, there may be a @code{NOTE_INSN_BASIC_BLOCK} between them. Additionally,
+the definition may be the source of exception handling edges.
+
+These restrictions can prevent important
+optimizations on some machines. For example, on the IBM RS/6000, there
+is a delay for taken branches unless the condition code register is set
+three instructions earlier than the conditional branch. The instruction
+scheduler cannot perform this optimization if it is not permitted to
+separate the definition and use of the condition code register.
+
+If there is a specific
+condition code register in the machine, use a hard register. If the
+condition code or comparison result can be placed in any general register,
+or if there are multiple condition registers, use a pseudo register.
+Registers used to store the condition code value will usually have a mode
+that is in class @code{MODE_CC}.
+
+Alternatively, you can use @code{BImode} if the comparison operator is
+specified already in the compare instruction. In this case, you are not
+interested in most macros in this section.
+
+@menu
+* MODE_CC Condition Codes:: Modern representation of condition codes.
+@end menu
+
+@node MODE_CC Condition Codes
+@subsection Representation of condition codes using registers
+@findex CCmode
+@findex MODE_CC
+
+@defmac SELECT_CC_MODE (@var{op}, @var{x}, @var{y})
+On many machines, the condition code may be produced by other instructions
+than compares, for example the branch can use directly the condition
+code set by a subtract instruction. However, on some machines
+when the condition code is set this way some bits (such as the overflow
+bit) are not set in the same way as a test instruction, so that a different
+branch instruction must be used for some conditional branches. When
+this happens, use the machine mode of the condition code register to
+record different formats of the condition code register. Modes can
+also be used to record which compare instruction (e.g.@: a signed or an
+unsigned comparison) produced the condition codes.
+
+If other modes than @code{CCmode} are required, add them to
+@file{@var{machine}-modes.def} and define @code{SELECT_CC_MODE} to choose
+a mode given an operand of a compare. This is needed because the modes
+have to be chosen not only during RTL generation but also, for example,
+by instruction combination. The result of @code{SELECT_CC_MODE} should
+be consistent with the mode used in the patterns; for example to support
+the case of the add on the SPARC discussed above, we have the pattern
+
+@smallexample
+(define_insn ""
+ [(set (reg:CCNZ 0)
+ (compare:CCNZ
+ (plus:SI (match_operand:SI 0 "register_operand" "%r")
+ (match_operand:SI 1 "arith_operand" "rI"))
+ (const_int 0)))]
+ ""
+ "@dots{}")
+@end smallexample
+
+@noindent
+together with a @code{SELECT_CC_MODE} that returns @code{CCNZmode}
+for comparisons whose argument is a @code{plus}:
+
+@smallexample
+#define SELECT_CC_MODE(OP,X,Y) \
+ (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \
+ ? ((OP == LT || OP == LE || OP == GT || OP == GE) \
+ ? CCFPEmode : CCFPmode) \
+ : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS \
+ || GET_CODE (X) == NEG || GET_CODE (x) == ASHIFT) \
+ ? CCNZmode : CCmode))
+@end smallexample
+
+Another reason to use modes is to retain information on which operands
+were used by the comparison; see @code{REVERSIBLE_CC_MODE} later in
+this section.
+
+You should define this macro if and only if you define extra CC modes
+in @file{@var{machine}-modes.def}.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_CANONICALIZE_COMPARISON (int *@var{code}, rtx *@var{op0}, rtx *@var{op1}, bool @var{op0_preserve_value})
+On some machines not all possible comparisons are defined, but you can
+convert an invalid comparison into a valid one. For example, the Alpha
+does not have a @code{GT} comparison, but you can use an @code{LT}
+comparison instead and swap the order of the operands.
+
+On such machines, implement this hook to do any required conversions.
+@var{code} is the initial comparison code and @var{op0} and @var{op1}
+are the left and right operands of the comparison, respectively. If
+@var{op0_preserve_value} is @code{true} the implementation is not
+allowed to change the value of @var{op0} since the value might be used
+in RTXs which aren't comparisons. E.g. the implementation is not
+allowed to swap operands in that case.
+
+GCC will not assume that the comparison resulting from this macro is
+valid but will see if the resulting insn matches a pattern in the
+@file{md} file.
+
+You need not to implement this hook if it would never change the
+comparison code or operands.
+@end deftypefn
+
+@defmac REVERSIBLE_CC_MODE (@var{mode})
+A C expression whose value is one if it is always safe to reverse a
+comparison whose mode is @var{mode}. If @code{SELECT_CC_MODE}
+can ever return @var{mode} for a floating-point inequality comparison,
+then @code{REVERSIBLE_CC_MODE (@var{mode})} must be zero.
+
+You need not define this macro if it would always returns zero or if the
+floating-point format is anything other than @code{IEEE_FLOAT_FORMAT}.
+For example, here is the definition used on the SPARC, where floating-point
+inequality comparisons are given either @code{CCFPEmode} or @code{CCFPmode}:
+
+@smallexample
+#define REVERSIBLE_CC_MODE(MODE) \
+ ((MODE) != CCFPEmode && (MODE) != CCFPmode)
+@end smallexample
+@end defmac
+
+@defmac REVERSE_CONDITION (@var{code}, @var{mode})
+A C expression whose value is reversed condition code of the @var{code} for
+comparison done in CC_MODE @var{mode}. The macro is used only in case
+@code{REVERSIBLE_CC_MODE (@var{mode})} is nonzero. Define this macro in case
+machine has some non-standard way how to reverse certain conditionals. For
+instance in case all floating point conditions are non-trapping, compiler may
+freely convert unordered compares to ordered ones. Then definition may look
+like:
+
+@smallexample
+#define REVERSE_CONDITION(CODE, MODE) \
+ ((MODE) != CCFPmode ? reverse_condition (CODE) \
+ : reverse_condition_maybe_unordered (CODE))
+@end smallexample
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_FIXED_CONDITION_CODE_REGS (unsigned int *@var{p1}, unsigned int *@var{p2})
+On targets which use a hard
+register rather than a pseudo-register to hold condition codes, the
+regular CSE passes are often not able to identify cases in which the
+hard register is set to a common value. Use this hook to enable a
+small pass which optimizes such cases. This hook should return true
+to enable this pass, and it should set the integers to which its
+arguments point to the hard register numbers used for condition codes.
+When there is only one such register, as is true on most systems, the
+integer pointed to by @var{p2} should be set to
+@code{INVALID_REGNUM}.
+
+The default version of this hook returns false.
+@end deftypefn
+
+@deftypefn {Target Hook} machine_mode TARGET_CC_MODES_COMPATIBLE (machine_mode @var{m1}, machine_mode @var{m2})
+On targets which use multiple condition code modes in class
+@code{MODE_CC}, it is sometimes the case that a comparison can be
+validly done in more than one mode. On such a system, define this
+target hook to take two mode arguments and to return a mode in which
+both comparisons may be validly done. If there is no such mode,
+return @code{VOIDmode}.
+
+The default version of this hook checks whether the modes are the
+same. If they are, it returns that mode. If they are different, it
+returns @code{VOIDmode}.
+@end deftypefn
+
+@deftypevr {Target Hook} {unsigned int} TARGET_FLAGS_REGNUM
+If the target has a dedicated flags register, and it needs to use the
+post-reload comparison elimination pass, or the delay slot filler pass,
+then this value should be set appropriately.
+@end deftypevr
+
+@node Costs
+@section Describing Relative Costs of Operations
+@cindex costs of instructions
+@cindex relative costs
+@cindex speed of instructions
+
+These macros let you describe the relative speed of various operations
+on the target machine.
+
+@defmac REGISTER_MOVE_COST (@var{mode}, @var{from}, @var{to})
+A C expression for the cost of moving data of mode @var{mode} from a
+register in class @var{from} to one in class @var{to}. The classes are
+expressed using the enumeration values such as @code{GENERAL_REGS}. A
+value of 2 is the default; other values are interpreted relative to
+that.
+
+It is not required that the cost always equal 2 when @var{from} is the
+same as @var{to}; on some machines it is expensive to move between
+registers if they are not general registers.
+
+If reload sees an insn consisting of a single @code{set} between two
+hard registers, and if @code{REGISTER_MOVE_COST} applied to their
+classes returns a value of 2, reload does not check to ensure that the
+constraints of the insn are met. Setting a cost of other than 2 will
+allow reload to verify that the constraints are met. You should do this
+if the @samp{mov@var{m}} pattern's constraints do not allow such copying.
+
+These macros are obsolete, new ports should use the target hook
+@code{TARGET_REGISTER_MOVE_COST} instead.
+@end defmac
+
+@deftypefn {Target Hook} int TARGET_REGISTER_MOVE_COST (machine_mode @var{mode}, reg_class_t @var{from}, reg_class_t @var{to})
+This target hook should return the cost of moving data of mode @var{mode}
+from a register in class @var{from} to one in class @var{to}. The classes
+are expressed using the enumeration values such as @code{GENERAL_REGS}.
+A value of 2 is the default; other values are interpreted relative to
+that.
+
+It is not required that the cost always equal 2 when @var{from} is the
+same as @var{to}; on some machines it is expensive to move between
+registers if they are not general registers.
+
+If reload sees an insn consisting of a single @code{set} between two
+hard registers, and if @code{TARGET_REGISTER_MOVE_COST} applied to their
+classes returns a value of 2, reload does not check to ensure that the
+constraints of the insn are met. Setting a cost of other than 2 will
+allow reload to verify that the constraints are met. You should do this
+if the @samp{mov@var{m}} pattern's constraints do not allow such copying.
+
+The default version of this function returns 2.
+@end deftypefn
+
+@defmac MEMORY_MOVE_COST (@var{mode}, @var{class}, @var{in})
+A C expression for the cost of moving data of mode @var{mode} between a
+register of class @var{class} and memory; @var{in} is zero if the value
+is to be written to memory, nonzero if it is to be read in. This cost
+is relative to those in @code{REGISTER_MOVE_COST}. If moving between
+registers and memory is more expensive than between two registers, you
+should define this macro to express the relative cost.
+
+If you do not define this macro, GCC uses a default cost of 4 plus
+the cost of copying via a secondary reload register, if one is
+needed. If your machine requires a secondary reload register to copy
+between memory and a register of @var{class} but the reload mechanism is
+more complex than copying via an intermediate, define this macro to
+reflect the actual cost of the move.
+
+GCC defines the function @code{memory_move_secondary_cost} if
+secondary reloads are needed. It computes the costs due to copying via
+a secondary register. If your machine copies from memory using a
+secondary register in the conventional way but the default base value of
+4 is not correct for your machine, define this macro to add some other
+value to the result of that function. The arguments to that function
+are the same as to this macro.
+
+These macros are obsolete, new ports should use the target hook
+@code{TARGET_MEMORY_MOVE_COST} instead.
+@end defmac
+
+@deftypefn {Target Hook} int TARGET_MEMORY_MOVE_COST (machine_mode @var{mode}, reg_class_t @var{rclass}, bool @var{in})
+This target hook should return the cost of moving data of mode @var{mode}
+between a register of class @var{rclass} and memory; @var{in} is @code{false}
+if the value is to be written to memory, @code{true} if it is to be read in.
+This cost is relative to those in @code{TARGET_REGISTER_MOVE_COST}.
+If moving between registers and memory is more expensive than between two
+registers, you should add this target hook to express the relative cost.
+
+If you do not add this target hook, GCC uses a default cost of 4 plus
+the cost of copying via a secondary reload register, if one is
+needed. If your machine requires a secondary reload register to copy
+between memory and a register of @var{rclass} but the reload mechanism is
+more complex than copying via an intermediate, use this target hook to
+reflect the actual cost of the move.
+
+GCC defines the function @code{memory_move_secondary_cost} if
+secondary reloads are needed. It computes the costs due to copying via
+a secondary register. If your machine copies from memory using a
+secondary register in the conventional way but the default base value of
+4 is not correct for your machine, use this target hook to add some other
+value to the result of that function. The arguments to that function
+are the same as to this target hook.
+@end deftypefn
+
+@defmac BRANCH_COST (@var{speed_p}, @var{predictable_p})
+A C expression for the cost of a branch instruction. A value of 1 is
+the default; other values are interpreted relative to that. Parameter
+@var{speed_p} is true when the branch in question should be optimized
+for speed. When it is false, @code{BRANCH_COST} should return a value
+optimal for code size rather than performance. @var{predictable_p} is
+true for well-predicted branches. On many architectures the
+@code{BRANCH_COST} can be reduced then.
+@end defmac
+
+Here are additional macros which do not specify precise relative costs,
+but only that certain actions are more expensive than GCC would
+ordinarily expect.
+
+@defmac SLOW_BYTE_ACCESS
+Define this macro as a C expression which is nonzero if accessing less
+than a word of memory (i.e.@: a @code{char} or a @code{short}) is no
+faster than accessing a word of memory, i.e., if such access
+require more than one instruction or if there is no difference in cost
+between byte and (aligned) word loads.
+
+When this macro is not defined, the compiler will access a field by
+finding the smallest containing object; when it is defined, a fullword
+load will be used if alignment permits. Unless bytes accesses are
+faster than word accesses, using word accesses is preferable since it
+may eliminate subsequent memory access if subsequent accesses occur to
+other fields in the same word of the structure, but to different bytes.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_SLOW_UNALIGNED_ACCESS (machine_mode @var{mode}, unsigned int @var{align})
+This hook returns true if memory accesses described by the
+@var{mode} and @var{alignment} parameters have a cost many times greater
+than aligned accesses, for example if they are emulated in a trap handler.
+This hook is invoked only for unaligned accesses, i.e.@: when
+@code{@var{alignment} < GET_MODE_ALIGNMENT (@var{mode})}.
+
+When this hook returns true, the compiler will act as if
+@code{STRICT_ALIGNMENT} were true when generating code for block
+moves. This can cause significantly more instructions to be produced.
+Therefore, do not make this hook return true if unaligned accesses only
+add a cycle or two to the time for a memory access.
+
+The hook must return true whenever @code{STRICT_ALIGNMENT} is true.
+The default implementation returns @code{STRICT_ALIGNMENT}.
+@end deftypefn
+
+@defmac MOVE_RATIO (@var{speed})
+The threshold of number of scalar memory-to-memory move insns, @emph{below}
+which a sequence of insns should be generated instead of a
+string move insn or a library call. Increasing the value will always
+make code faster, but eventually incurs high cost in increased code size.
+
+Note that on machines where the corresponding move insn is a
+@code{define_expand} that emits a sequence of insns, this macro counts
+the number of such sequences.
+
+The parameter @var{speed} is true if the code is currently being
+optimized for speed rather than size.
+
+If you don't define this, a reasonable default is used.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_USE_BY_PIECES_INFRASTRUCTURE_P (unsigned HOST_WIDE_INT @var{size}, unsigned int @var{alignment}, enum by_pieces_operation @var{op}, bool @var{speed_p})
+GCC will attempt several strategies when asked to copy between
+two areas of memory, or to set, clear or store to memory, for example
+when copying a @code{struct}. The @code{by_pieces} infrastructure
+implements such memory operations as a sequence of load, store or move
+insns. Alternate strategies are to expand the
+@code{cpymem} or @code{setmem} optabs, to emit a library call, or to emit
+unit-by-unit, loop-based operations.
+
+This target hook should return true if, for a memory operation with a
+given @var{size} and @var{alignment}, using the @code{by_pieces}
+infrastructure is expected to result in better code generation.
+Both @var{size} and @var{alignment} are measured in terms of storage
+units.
+
+The parameter @var{op} is one of: @code{CLEAR_BY_PIECES},
+@code{MOVE_BY_PIECES}, @code{SET_BY_PIECES}, @code{STORE_BY_PIECES} or
+@code{COMPARE_BY_PIECES}. These describe the type of memory operation
+under consideration.
+
+The parameter @var{speed_p} is true if the code is currently being
+optimized for speed rather than size.
+
+Returning true for higher values of @var{size} can improve code generation
+for speed if the target does not provide an implementation of the
+@code{cpymem} or @code{setmem} standard names, if the @code{cpymem} or
+@code{setmem} implementation would be more expensive than a sequence of
+insns, or if the overhead of a library call would dominate that of
+the body of the memory operation.
+
+Returning true for higher values of @code{size} may also cause an increase
+in code size, for example where the number of insns emitted to perform a
+move would be greater than that of a library call.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_OVERLAP_OP_BY_PIECES_P (void)
+This target hook should return true if when the @code{by_pieces}
+infrastructure is used, an offset adjusted unaligned memory operation
+in the smallest integer mode for the last piece operation of a memory
+region can be generated to avoid doing more than one smaller operations.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_COMPARE_BY_PIECES_BRANCH_RATIO (machine_mode @var{mode})
+When expanding a block comparison in MODE, gcc can try to reduce the
+number of branches at the expense of more memory operations. This hook
+allows the target to override the default choice. It should return the
+factor by which branches should be reduced over the plain expansion with
+one comparison per @var{mode}-sized piece. A port can also prevent a
+particular mode from being used for block comparisons by returning a
+negative number from this hook.
+@end deftypefn
+
+@defmac MOVE_MAX_PIECES
+A C expression used by @code{move_by_pieces} to determine the largest unit
+a load or store used to copy memory is. Defaults to @code{MOVE_MAX}.
+@end defmac
+
+@defmac STORE_MAX_PIECES
+A C expression used by @code{store_by_pieces} to determine the largest unit
+a store used to memory is. Defaults to @code{MOVE_MAX_PIECES}, or two times
+the size of @code{HOST_WIDE_INT}, whichever is smaller.
+@end defmac
+
+@defmac COMPARE_MAX_PIECES
+A C expression used by @code{compare_by_pieces} to determine the largest unit
+a load or store used to compare memory is. Defaults to
+@code{MOVE_MAX_PIECES}.
+@end defmac
+
+@defmac CLEAR_RATIO (@var{speed})
+The threshold of number of scalar move insns, @emph{below} which a sequence
+of insns should be generated to clear memory instead of a string clear insn
+or a library call. Increasing the value will always make code faster, but
+eventually incurs high cost in increased code size.
+
+The parameter @var{speed} is true if the code is currently being
+optimized for speed rather than size.
+
+If you don't define this, a reasonable default is used.
+@end defmac
+
+@defmac SET_RATIO (@var{speed})
+The threshold of number of scalar move insns, @emph{below} which a sequence
+of insns should be generated to set memory to a constant value, instead of
+a block set insn or a library call.
+Increasing the value will always make code faster, but
+eventually incurs high cost in increased code size.
+
+The parameter @var{speed} is true if the code is currently being
+optimized for speed rather than size.
+
+If you don't define this, it defaults to the value of @code{MOVE_RATIO}.
+@end defmac
+
+@defmac USE_LOAD_POST_INCREMENT (@var{mode})
+A C expression used to determine whether a load postincrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_POST_INCREMENT}.
+@end defmac
+
+@defmac USE_LOAD_POST_DECREMENT (@var{mode})
+A C expression used to determine whether a load postdecrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_POST_DECREMENT}.
+@end defmac
+
+@defmac USE_LOAD_PRE_INCREMENT (@var{mode})
+A C expression used to determine whether a load preincrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_PRE_INCREMENT}.
+@end defmac
+
+@defmac USE_LOAD_PRE_DECREMENT (@var{mode})
+A C expression used to determine whether a load predecrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_PRE_DECREMENT}.
+@end defmac
+
+@defmac USE_STORE_POST_INCREMENT (@var{mode})
+A C expression used to determine whether a store postincrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_POST_INCREMENT}.
+@end defmac
+
+@defmac USE_STORE_POST_DECREMENT (@var{mode})
+A C expression used to determine whether a store postdecrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_POST_DECREMENT}.
+@end defmac
+
+@defmac USE_STORE_PRE_INCREMENT (@var{mode})
+This macro is used to determine whether a store preincrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_PRE_INCREMENT}.
+@end defmac
+
+@defmac USE_STORE_PRE_DECREMENT (@var{mode})
+This macro is used to determine whether a store predecrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_PRE_DECREMENT}.
+@end defmac
+
+@defmac NO_FUNCTION_CSE
+Define this macro to be true if it is as good or better to call a constant
+function address than to call an address kept in a register.
+@end defmac
+
+@defmac LOGICAL_OP_NON_SHORT_CIRCUIT
+Define this macro if a non-short-circuit operation produced by
+@samp{fold_range_test ()} is optimal. This macro defaults to true if
+@code{BRANCH_COST} is greater than or equal to the value 2.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_OPTAB_SUPPORTED_P (int @var{op}, machine_mode @var{mode1}, machine_mode @var{mode2}, optimization_type @var{opt_type})
+Return true if the optimizers should use optab @var{op} with
+modes @var{mode1} and @var{mode2} for optimization type @var{opt_type}.
+The optab is known to have an associated @file{.md} instruction
+whose C condition is true. @var{mode2} is only meaningful for conversion
+optabs; for direct optabs it is a copy of @var{mode1}.
+
+For example, when called with @var{op} equal to @code{rint_optab} and
+@var{mode1} equal to @code{DFmode}, the hook should say whether the
+optimizers should use optab @code{rintdf2}.
+
+The default hook returns true for all inputs.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_RTX_COSTS (rtx @var{x}, machine_mode @var{mode}, int @var{outer_code}, int @var{opno}, int *@var{total}, bool @var{speed})
+This target hook describes the relative costs of RTL expressions.
+
+The cost may depend on the precise form of the expression, which is
+available for examination in @var{x}, and the fact that @var{x} appears
+as operand @var{opno} of an expression with rtx code @var{outer_code}.
+That is, the hook can assume that there is some rtx @var{y} such
+that @samp{GET_CODE (@var{y}) == @var{outer_code}} and such that
+either (a) @samp{XEXP (@var{y}, @var{opno}) == @var{x}} or
+(b) @samp{XVEC (@var{y}, @var{opno})} contains @var{x}.
+
+@var{mode} is @var{x}'s machine mode, or for cases like @code{const_int} that
+do not have a mode, the mode in which @var{x} is used.
+
+In implementing this hook, you can use the construct
+@code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast
+instructions.
+
+On entry to the hook, @code{*@var{total}} contains a default estimate
+for the cost of the expression. The hook should modify this value as
+necessary. Traditionally, the default costs are @code{COSTS_N_INSNS (5)}
+for multiplications, @code{COSTS_N_INSNS (7)} for division and modulus
+operations, and @code{COSTS_N_INSNS (1)} for all other operations.
+
+When optimizing for code size, i.e.@: when @code{speed} is
+false, this target hook should be used to estimate the relative
+size cost of an expression, again relative to @code{COSTS_N_INSNS}.
+
+The hook returns true when all subexpressions of @var{x} have been
+processed, and false when @code{rtx_cost} should recurse.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_ADDRESS_COST (rtx @var{address}, machine_mode @var{mode}, addr_space_t @var{as}, bool @var{speed})
+This hook computes the cost of an addressing mode that contains
+@var{address}. If not defined, the cost is computed from
+the @var{address} expression and the @code{TARGET_RTX_COST} hook.
+
+For most CISC machines, the default cost is a good approximation of the
+true cost of the addressing mode. However, on RISC machines, all
+instructions normally have the same length and execution time. Hence
+all addresses will have equal costs.
+
+In cases where more than one form of an address is known, the form with
+the lowest cost will be used. If multiple forms have the same, lowest,
+cost, the one that is the most complex will be used.
+
+For example, suppose an address that is equal to the sum of a register
+and a constant is used twice in the same basic block. When this macro
+is not defined, the address will be computed in a register and memory
+references will be indirect through that register. On machines where
+the cost of the addressing mode containing the sum is no higher than
+that of a simple indirect reference, this will produce an additional
+instruction and possibly require an additional register. Proper
+specification of this macro eliminates this overhead for such machines.
+
+This hook is never called with an invalid address.
+
+On machines where an address involving more than one register is as
+cheap as an address computation involving only one register, defining
+@code{TARGET_ADDRESS_COST} to reflect this can cause two registers to
+be live over a region of code where only one would have been if
+@code{TARGET_ADDRESS_COST} were not defined in that manner. This effect
+should be considered in the definition of this macro. Equivalent costs
+should probably only be given to addresses with different numbers of
+registers on machines with lots of registers.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_INSN_COST (rtx_insn *@var{insn}, bool @var{speed})
+This target hook describes the relative costs of RTL instructions.
+
+In implementing this hook, you can use the construct
+@code{COSTS_N_INSNS (@var{n})} to specify a cost equal to @var{n} fast
+instructions.
+
+When optimizing for code size, i.e.@: when @code{speed} is
+false, this target hook should be used to estimate the relative
+size cost of an expression, again relative to @code{COSTS_N_INSNS}.
+@end deftypefn
+
+@deftypefn {Target Hook} {unsigned int} TARGET_MAX_NOCE_IFCVT_SEQ_COST (edge @var{e})
+This hook returns a value in the same units as @code{TARGET_RTX_COSTS},
+giving the maximum acceptable cost for a sequence generated by the RTL
+if-conversion pass when conditional execution is not available.
+The RTL if-conversion pass attempts to convert conditional operations
+that would require a branch to a series of unconditional operations and
+@code{mov@var{mode}cc} insns. This hook returns the maximum cost of the
+unconditional instructions and the @code{mov@var{mode}cc} insns.
+RTL if-conversion is cancelled if the cost of the converted sequence
+is greater than the value returned by this hook.
+
+@code{e} is the edge between the basic block containing the conditional
+branch to the basic block which would be executed if the condition
+were true.
+
+The default implementation of this hook uses the
+@code{max-rtl-if-conversion-[un]predictable} parameters if they are set,
+and uses a multiple of @code{BRANCH_COST} otherwise.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_NOCE_CONVERSION_PROFITABLE_P (rtx_insn *@var{seq}, struct noce_if_info *@var{if_info})
+This hook returns true if the instruction sequence @code{seq} is a good
+candidate as a replacement for the if-convertible sequence described in
+@code{if_info}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_NEW_ADDRESS_PROFITABLE_P (rtx @var{memref}, rtx_insn * @var{insn}, rtx @var{new_addr})
+Return @code{true} if it is profitable to replace the address in
+@var{memref} with @var{new_addr}. This allows targets to prevent the
+scheduler from undoing address optimizations. The instruction containing the
+memref is @var{insn}. The default implementation returns @code{true}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_NO_SPECULATION_IN_DELAY_SLOTS_P (void)
+This predicate controls the use of the eager delay slot filler to disallow
+speculatively executed instructions being placed in delay slots. Targets
+such as certain MIPS architectures possess both branches with and without
+delay slots. As the eager delay slot filler can decrease performance,
+disabling it is beneficial when ordinary branches are available. Use of
+delay slot branches filled using the basic filler is often still desirable
+as the delay slot can hide a pipeline bubble.
+@end deftypefn
+
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_ESTIMATED_POLY_VALUE (poly_int64 @var{val}, poly_value_estimate_kind @var{kind})
+Return an estimate of the runtime value of @var{val}, for use in
+things like cost calculations or profiling frequencies. @var{kind} is used
+to ask for the minimum, maximum, and likely estimates of the value through
+the @code{POLY_VALUE_MIN}, @code{POLY_VALUE_MAX} and
+@code{POLY_VALUE_LIKELY} values. The default
+implementation returns the lowest possible value of @var{val}.
+@end deftypefn
+
+@node Scheduling
+@section Adjusting the Instruction Scheduler
+
+The instruction scheduler may need a fair amount of machine-specific
+adjustment in order to produce good code. GCC provides several target
+hooks for this purpose. It is usually enough to define just a few of
+them: try the first ones in this list first.
+
+@deftypefn {Target Hook} int TARGET_SCHED_ISSUE_RATE (void)
+This hook returns the maximum number of instructions that can ever
+issue at the same time on the target machine. The default is one.
+Although the insn scheduler can define itself the possibility of issue
+an insn on the same cycle, the value can serve as an additional
+constraint to issue insns on the same simulated processor cycle (see
+hooks @samp{TARGET_SCHED_REORDER} and @samp{TARGET_SCHED_REORDER2}).
+This value must be constant over the entire compilation. If you need
+it to vary depending on what the instructions are, you must use
+@samp{TARGET_SCHED_VARIABLE_ISSUE}.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_VARIABLE_ISSUE (FILE *@var{file}, int @var{verbose}, rtx_insn *@var{insn}, int @var{more})
+This hook is executed by the scheduler after it has scheduled an insn
+from the ready list. It should return the number of insns which can
+still be issued in the current cycle. The default is
+@samp{@w{@var{more} - 1}} for insns other than @code{CLOBBER} and
+@code{USE}, which normally are not counted against the issue rate.
+You should define this hook if some insns take more machine resources
+than others, so that fewer insns can follow them in the same cycle.
+@var{file} is either a null pointer, or a stdio stream to write any
+debug output to. @var{verbose} is the verbose level provided by
+@option{-fsched-verbose-@var{n}}. @var{insn} is the instruction that
+was scheduled.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_ADJUST_COST (rtx_insn *@var{insn}, int @var{dep_type1}, rtx_insn *@var{dep_insn}, int @var{cost}, unsigned int @var{dw})
+This function corrects the value of @var{cost} based on the
+relationship between @var{insn} and @var{dep_insn} through a
+dependence of type dep_type, and strength @var{dw}. It should return the new
+value. The default is to make no adjustment to @var{cost}. This can be
+used for example to specify to the scheduler using the traditional pipeline
+description that an output- or anti-dependence does not incur the same cost
+as a data-dependence. If the scheduler using the automaton based pipeline
+description, the cost of anti-dependence is zero and the cost of
+output-dependence is maximum of one and the difference of latency
+times of the first and the second insns. If these values are not
+acceptable, you could use the hook to modify them too. See also
+@pxref{Processor pipeline description}.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_ADJUST_PRIORITY (rtx_insn *@var{insn}, int @var{priority})
+This hook adjusts the integer scheduling priority @var{priority} of
+@var{insn}. It should return the new priority. Increase the priority to
+execute @var{insn} earlier, reduce the priority to execute @var{insn}
+later. Do not define this hook if you do not need to adjust the
+scheduling priorities of insns.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_REORDER (FILE *@var{file}, int @var{verbose}, rtx_insn **@var{ready}, int *@var{n_readyp}, int @var{clock})
+This hook is executed by the scheduler after it has scheduled the ready
+list, to allow the machine description to reorder it (for example to
+combine two small instructions together on @samp{VLIW} machines).
+@var{file} is either a null pointer, or a stdio stream to write any
+debug output to. @var{verbose} is the verbose level provided by
+@option{-fsched-verbose-@var{n}}. @var{ready} is a pointer to the ready
+list of instructions that are ready to be scheduled. @var{n_readyp} is
+a pointer to the number of elements in the ready list. The scheduler
+reads the ready list in reverse order, starting with
+@var{ready}[@var{*n_readyp} @minus{} 1] and going to @var{ready}[0]. @var{clock}
+is the timer tick of the scheduler. You may modify the ready list and
+the number of ready insns. The return value is the number of insns that
+can issue this cycle; normally this is just @code{issue_rate}. See also
+@samp{TARGET_SCHED_REORDER2}.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_REORDER2 (FILE *@var{file}, int @var{verbose}, rtx_insn **@var{ready}, int *@var{n_readyp}, int @var{clock})
+Like @samp{TARGET_SCHED_REORDER}, but called at a different time. That
+function is called whenever the scheduler starts a new cycle. This one
+is called once per iteration over a cycle, immediately after
+@samp{TARGET_SCHED_VARIABLE_ISSUE}; it can reorder the ready list and
+return the number of insns to be scheduled in the same cycle. Defining
+this hook can be useful if there are frequent situations where
+scheduling one insn causes other insns to become ready in the same
+cycle. These other insns can then be taken into account properly.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SCHED_MACRO_FUSION_P (void)
+This hook is used to check whether target platform supports macro fusion.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SCHED_MACRO_FUSION_PAIR_P (rtx_insn *@var{prev}, rtx_insn *@var{curr})
+This hook is used to check whether two insns should be macro fused for
+a target microarchitecture. If this hook returns true for the given insn pair
+(@var{prev} and @var{curr}), the scheduler will put them into a sched
+group, and they will not be scheduled apart. The two insns will be either
+two SET insns or a compare and a conditional jump and this hook should
+validate any dependencies needed to fuse the two insns together.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_DEPENDENCIES_EVALUATION_HOOK (rtx_insn *@var{head}, rtx_insn *@var{tail})
+This hook is called after evaluation forward dependencies of insns in
+chain given by two parameter values (@var{head} and @var{tail}
+correspondingly) but before insns scheduling of the insn chain. For
+example, it can be used for better insn classification if it requires
+analysis of dependencies. This hook can use backward and forward
+dependencies of the insn scheduler because they are already
+calculated.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_INIT (FILE *@var{file}, int @var{verbose}, int @var{max_ready})
+This hook is executed by the scheduler at the beginning of each block of
+instructions that are to be scheduled. @var{file} is either a null
+pointer, or a stdio stream to write any debug output to. @var{verbose}
+is the verbose level provided by @option{-fsched-verbose-@var{n}}.
+@var{max_ready} is the maximum number of insns in the current scheduling
+region that can be live at the same time. This can be used to allocate
+scratch space if it is needed, e.g.@: by @samp{TARGET_SCHED_REORDER}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FINISH (FILE *@var{file}, int @var{verbose})
+This hook is executed by the scheduler at the end of each block of
+instructions that are to be scheduled. It can be used to perform
+cleanup of any actions done by the other scheduling hooks. @var{file}
+is either a null pointer, or a stdio stream to write any debug output
+to. @var{verbose} is the verbose level provided by
+@option{-fsched-verbose-@var{n}}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_INIT_GLOBAL (FILE *@var{file}, int @var{verbose}, int @var{old_max_uid})
+This hook is executed by the scheduler after function level initializations.
+@var{file} is either a null pointer, or a stdio stream to write any debug output to.
+@var{verbose} is the verbose level provided by @option{-fsched-verbose-@var{n}}.
+@var{old_max_uid} is the maximum insn uid when scheduling begins.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FINISH_GLOBAL (FILE *@var{file}, int @var{verbose})
+This is the cleanup hook corresponding to @code{TARGET_SCHED_INIT_GLOBAL}.
+@var{file} is either a null pointer, or a stdio stream to write any debug output to.
+@var{verbose} is the verbose level provided by @option{-fsched-verbose-@var{n}}.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_SCHED_DFA_PRE_CYCLE_INSN (void)
+The hook returns an RTL insn. The automaton state used in the
+pipeline hazard recognizer is changed as if the insn were scheduled
+when the new simulated processor cycle starts. Usage of the hook may
+simplify the automaton pipeline description for some @acronym{VLIW}
+processors. If the hook is defined, it is used only for the automaton
+based pipeline description. The default is not to change the state
+when the new simulated processor cycle starts.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_INIT_DFA_PRE_CYCLE_INSN (void)
+The hook can be used to initialize data used by the previous hook.
+@end deftypefn
+
+@deftypefn {Target Hook} {rtx_insn *} TARGET_SCHED_DFA_POST_CYCLE_INSN (void)
+The hook is analogous to @samp{TARGET_SCHED_DFA_PRE_CYCLE_INSN} but used
+to changed the state as if the insn were scheduled when the new
+simulated processor cycle finishes.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_INIT_DFA_POST_CYCLE_INSN (void)
+The hook is analogous to @samp{TARGET_SCHED_INIT_DFA_PRE_CYCLE_INSN} but
+used to initialize data used by the previous hook.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_DFA_PRE_ADVANCE_CYCLE (void)
+The hook to notify target that the current simulated cycle is about to finish.
+The hook is analogous to @samp{TARGET_SCHED_DFA_PRE_CYCLE_INSN} but used
+to change the state in more complicated situations - e.g., when advancing
+state on a single insn is not enough.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_DFA_POST_ADVANCE_CYCLE (void)
+The hook to notify target that new simulated cycle has just started.
+The hook is analogous to @samp{TARGET_SCHED_DFA_POST_CYCLE_INSN} but used
+to change the state in more complicated situations - e.g., when advancing
+state on a single insn is not enough.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD (void)
+This hook controls better choosing an insn from the ready insn queue
+for the @acronym{DFA}-based insn scheduler. Usually the scheduler
+chooses the first insn from the queue. If the hook returns a positive
+value, an additional scheduler code tries all permutations of
+@samp{TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD ()}
+subsequent ready insns to choose an insn whose issue will result in
+maximal number of issued insns on the same cycle. For the
+@acronym{VLIW} processor, the code could actually solve the problem of
+packing simple insns into the @acronym{VLIW} insn. Of course, if the
+rules of @acronym{VLIW} packing are described in the automaton.
+
+This code also could be used for superscalar @acronym{RISC}
+processors. Let us consider a superscalar @acronym{RISC} processor
+with 3 pipelines. Some insns can be executed in pipelines @var{A} or
+@var{B}, some insns can be executed only in pipelines @var{B} or
+@var{C}, and one insn can be executed in pipeline @var{B}. The
+processor may issue the 1st insn into @var{A} and the 2nd one into
+@var{B}. In this case, the 3rd insn will wait for freeing @var{B}
+until the next cycle. If the scheduler issues the 3rd insn the first,
+the processor could issue all 3 insns per cycle.
+
+Actually this code demonstrates advantages of the automaton based
+pipeline hazard recognizer. We try quickly and easy many insn
+schedules to choose the best one.
+
+The default is no multipass scheduling.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD_GUARD (rtx_insn *@var{insn}, int @var{ready_index})
+
+This hook controls what insns from the ready insn queue will be
+considered for the multipass insn scheduling. If the hook returns
+zero for @var{insn}, the insn will be considered in multipass scheduling.
+Positive return values will remove @var{insn} from consideration on
+the current round of multipass scheduling.
+Negative return values will remove @var{insn} from consideration for given
+number of cycles.
+Backends should be careful about returning non-zero for highest priority
+instruction at position 0 in the ready list. @var{ready_index} is passed
+to allow backends make correct judgements.
+
+The default is that any ready insns can be chosen to be issued.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BEGIN (void *@var{data}, signed char *@var{ready_try}, int @var{n_ready}, bool @var{first_cycle_insn_p})
+This hook prepares the target backend for a new round of multipass
+scheduling.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_ISSUE (void *@var{data}, signed char *@var{ready_try}, int @var{n_ready}, rtx_insn *@var{insn}, const void *@var{prev_data})
+This hook is called when multipass scheduling evaluates instruction INSN.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BACKTRACK (const void *@var{data}, signed char *@var{ready_try}, int @var{n_ready})
+This is called when multipass scheduling backtracks from evaluation of
+an instruction.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_END (const void *@var{data})
+This hook notifies the target about the result of the concluded current
+round of multipass scheduling.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_INIT (void *@var{data})
+This hook initializes target-specific data used in multipass scheduling.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FIRST_CYCLE_MULTIPASS_FINI (void *@var{data})
+This hook finalizes target-specific data used in multipass scheduling.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_DFA_NEW_CYCLE (FILE *@var{dump}, int @var{verbose}, rtx_insn *@var{insn}, int @var{last_clock}, int @var{clock}, int *@var{sort_p})
+This hook is called by the insn scheduler before issuing @var{insn}
+on cycle @var{clock}. If the hook returns nonzero,
+@var{insn} is not issued on this processor cycle. Instead,
+the processor cycle is advanced. If *@var{sort_p}
+is zero, the insn ready queue is not sorted on the new cycle
+start as usually. @var{dump} and @var{verbose} specify the file and
+verbosity level to use for debugging output.
+@var{last_clock} and @var{clock} are, respectively, the
+processor cycle on which the previous insn has been issued,
+and the current processor cycle.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SCHED_IS_COSTLY_DEPENDENCE (struct _dep *@var{_dep}, int @var{cost}, int @var{distance})
+This hook is used to define which dependences are considered costly by
+the target, so costly that it is not advisable to schedule the insns that
+are involved in the dependence too close to one another. The parameters
+to this hook are as follows: The first parameter @var{_dep} is the dependence
+being evaluated. The second parameter @var{cost} is the cost of the
+dependence as estimated by the scheduler, and the third
+parameter @var{distance} is the distance in cycles between the two insns.
+The hook returns @code{true} if considering the distance between the two
+insns the dependence between them is considered costly by the target,
+and @code{false} otherwise.
+
+Defining this hook can be useful in multiple-issue out-of-order machines,
+where (a) it's practically hopeless to predict the actual data/resource
+delays, however: (b) there's a better chance to predict the actual grouping
+that will be formed, and (c) correctly emulating the grouping can be very
+important. In such targets one may want to allow issuing dependent insns
+closer to one another---i.e., closer than the dependence distance; however,
+not in cases of ``costly dependences'', which this hooks allows to define.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_H_I_D_EXTENDED (void)
+This hook is called by the insn scheduler after emitting a new instruction to
+the instruction stream. The hook notifies a target backend to extend its
+per instruction data structures.
+@end deftypefn
+
+@deftypefn {Target Hook} {void *} TARGET_SCHED_ALLOC_SCHED_CONTEXT (void)
+Return a pointer to a store large enough to hold target scheduling context.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_INIT_SCHED_CONTEXT (void *@var{tc}, bool @var{clean_p})
+Initialize store pointed to by @var{tc} to hold target scheduling context.
+It @var{clean_p} is true then initialize @var{tc} as if scheduler is at the
+beginning of the block. Otherwise, copy the current context into @var{tc}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_SET_SCHED_CONTEXT (void *@var{tc})
+Copy target scheduling context pointed to by @var{tc} to the current context.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_CLEAR_SCHED_CONTEXT (void *@var{tc})
+Deallocate internal data in target scheduling context pointed to by @var{tc}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FREE_SCHED_CONTEXT (void *@var{tc})
+Deallocate a store for target scheduling context pointed to by @var{tc}.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_SPECULATE_INSN (rtx_insn *@var{insn}, unsigned int @var{dep_status}, rtx *@var{new_pat})
+This hook is called by the insn scheduler when @var{insn} has only
+speculative dependencies and therefore can be scheduled speculatively.
+The hook is used to check if the pattern of @var{insn} has a speculative
+version and, in case of successful check, to generate that speculative
+pattern. The hook should return 1, if the instruction has a speculative form,
+or @minus{}1, if it doesn't. @var{request} describes the type of requested
+speculation. If the return value equals 1 then @var{new_pat} is assigned
+the generated speculative pattern.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SCHED_NEEDS_BLOCK_P (unsigned int @var{dep_status})
+This hook is called by the insn scheduler during generation of recovery code
+for @var{insn}. It should return @code{true}, if the corresponding check
+instruction should branch to recovery code, or @code{false} otherwise.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_SCHED_GEN_SPEC_CHECK (rtx_insn *@var{insn}, rtx_insn *@var{label}, unsigned int @var{ds})
+This hook is called by the insn scheduler to generate a pattern for recovery
+check instruction. If @var{mutate_p} is zero, then @var{insn} is a
+speculative instruction for which the check should be generated.
+@var{label} is either a label of a basic block, where recovery code should
+be emitted, or a null pointer, when requested check doesn't branch to
+recovery code (a simple check). If @var{mutate_p} is nonzero, then
+a pattern for a branchy check corresponding to a simple check denoted by
+@var{insn} should be generated. In this case @var{label} can't be null.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_SET_SCHED_FLAGS (struct spec_info_def *@var{spec_info})
+This hook is used by the insn scheduler to find out what features should be
+enabled/used.
+The structure *@var{spec_info} should be filled in by the target.
+The structure describes speculation types that can be used in the scheduler.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SCHED_CAN_SPECULATE_INSN (rtx_insn *@var{insn})
+Some instructions should never be speculated by the schedulers, usually
+ because the instruction is too expensive to get this wrong. Often such
+ instructions have long latency, and often they are not fully modeled in the
+ pipeline descriptions. This hook should return @code{false} if @var{insn}
+ should not be speculated.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_SCHED_SMS_RES_MII (struct ddg *@var{g})
+This hook is called by the swing modulo scheduler to calculate a
+resource-based lower bound which is based on the resources available in
+the machine and the resources required by each instruction. The target
+backend can use @var{g} to calculate such bound. A very simple lower
+bound will be used in case this hook is not implemented: the total number
+of instructions divided by the issue rate.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SCHED_DISPATCH (rtx_insn *@var{insn}, int @var{x})
+This hook is called by Haifa Scheduler. It returns true if dispatch scheduling
+is supported in hardware and the condition specified in the parameter is true.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_DISPATCH_DO (rtx_insn *@var{insn}, int @var{x})
+This hook is called by Haifa Scheduler. It performs the operation specified
+in its second parameter.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_SCHED_EXPOSED_PIPELINE
+True if the processor has an exposed pipeline, which means that not just
+the order of instructions is important for correctness when scheduling, but
+also the latencies of operations.
+@end deftypevr
+
+@deftypefn {Target Hook} int TARGET_SCHED_REASSOCIATION_WIDTH (unsigned int @var{opc}, machine_mode @var{mode})
+This hook is called by tree reassociator to determine a level of
+parallelism required in output calculations chain.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SCHED_FUSION_PRIORITY (rtx_insn *@var{insn}, int @var{max_pri}, int *@var{fusion_pri}, int *@var{pri})
+This hook is called by scheduling fusion pass. It calculates fusion
+priorities for each instruction passed in by parameter. The priorities
+are returned via pointer parameters.
+
+@var{insn} is the instruction whose priorities need to be calculated.
+@var{max_pri} is the maximum priority can be returned in any cases.
+@var{fusion_pri} is the pointer parameter through which @var{insn}'s
+fusion priority should be calculated and returned.
+@var{pri} is the pointer parameter through which @var{insn}'s priority
+should be calculated and returned.
+
+Same @var{fusion_pri} should be returned for instructions which should
+be scheduled together. Different @var{pri} should be returned for
+instructions with same @var{fusion_pri}. @var{fusion_pri} is the major
+sort key, @var{pri} is the minor sort key. All instructions will be
+scheduled according to the two priorities. All priorities calculated
+should be between 0 (exclusive) and @var{max_pri} (inclusive). To avoid
+false dependencies, @var{fusion_pri} of instructions which need to be
+scheduled together should be smaller than @var{fusion_pri} of irrelevant
+instructions.
+
+Given below example:
+
+@smallexample
+ ldr r10, [r1, 4]
+ add r4, r4, r10
+ ldr r15, [r2, 8]
+ sub r5, r5, r15
+ ldr r11, [r1, 0]
+ add r4, r4, r11
+ ldr r16, [r2, 12]
+ sub r5, r5, r16
+@end smallexample
+
+On targets like ARM/AArch64, the two pairs of consecutive loads should be
+merged. Since peephole2 pass can't help in this case unless consecutive
+loads are actually next to each other in instruction flow. That's where
+this scheduling fusion pass works. This hook calculates priority for each
+instruction based on its fustion type, like:
+
+@smallexample
+ ldr r10, [r1, 4] ; fusion_pri=99, pri=96
+ add r4, r4, r10 ; fusion_pri=100, pri=100
+ ldr r15, [r2, 8] ; fusion_pri=98, pri=92
+ sub r5, r5, r15 ; fusion_pri=100, pri=100
+ ldr r11, [r1, 0] ; fusion_pri=99, pri=100
+ add r4, r4, r11 ; fusion_pri=100, pri=100
+ ldr r16, [r2, 12] ; fusion_pri=98, pri=88
+ sub r5, r5, r16 ; fusion_pri=100, pri=100
+@end smallexample
+
+Scheduling fusion pass then sorts all ready to issue instructions according
+to the priorities. As a result, instructions of same fusion type will be
+pushed together in instruction flow, like:
+
+@smallexample
+ ldr r11, [r1, 0]
+ ldr r10, [r1, 4]
+ ldr r15, [r2, 8]
+ ldr r16, [r2, 12]
+ add r4, r4, r10
+ sub r5, r5, r15
+ add r4, r4, r11
+ sub r5, r5, r16
+@end smallexample
+
+Now peephole2 pass can simply merge the two pairs of loads.
+
+Since scheduling fusion pass relies on peephole2 to do real fusion
+work, it is only enabled by default when peephole2 is in effect.
+
+This is firstly introduced on ARM/AArch64 targets, please refer to
+the hook implementation for how different fusion types are supported.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_EXPAND_DIVMOD_LIBFUNC (rtx @var{libfunc}, machine_mode @var{mode}, rtx @var{op0}, rtx @var{op1}, rtx *@var{quot}, rtx *@var{rem})
+Define this hook for enabling divmod transform if the port does not have
+hardware divmod insn but defines target-specific divmod libfuncs.
+@end deftypefn
+
+@node Sections
+@section Dividing the Output into Sections (Texts, Data, @dots{})
+@c the above section title is WAY too long. maybe cut the part between
+@c the (...)? --mew 10feb93
+
+An object file is divided into sections containing different types of
+data. In the most common case, there are three sections: the @dfn{text
+section}, which holds instructions and read-only data; the @dfn{data
+section}, which holds initialized writable data; and the @dfn{bss
+section}, which holds uninitialized data. Some systems have other kinds
+of sections.
+
+@file{varasm.cc} provides several well-known sections, such as
+@code{text_section}, @code{data_section} and @code{bss_section}.
+The normal way of controlling a @code{@var{foo}_section} variable
+is to define the associated @code{@var{FOO}_SECTION_ASM_OP} macro,
+as described below. The macros are only read once, when @file{varasm.cc}
+initializes itself, so their values must be run-time constants.
+They may however depend on command-line flags.
+
+@emph{Note:} Some run-time files, such @file{crtstuff.c}, also make
+use of the @code{@var{FOO}_SECTION_ASM_OP} macros, and expect them
+to be string literals.
+
+Some assemblers require a different string to be written every time a
+section is selected. If your assembler falls into this category, you
+should define the @code{TARGET_ASM_INIT_SECTIONS} hook and use
+@code{get_unnamed_section} to set up the sections.
+
+You must always create a @code{text_section}, either by defining
+@code{TEXT_SECTION_ASM_OP} or by initializing @code{text_section}
+in @code{TARGET_ASM_INIT_SECTIONS}. The same is true of
+@code{data_section} and @code{DATA_SECTION_ASM_OP}. If you do not
+create a distinct @code{readonly_data_section}, the default is to
+reuse @code{text_section}.
+
+All the other @file{varasm.cc} sections are optional, and are null
+if the target does not provide them.
+
+@defmac TEXT_SECTION_ASM_OP
+A C expression whose value is a string, including spacing, containing the
+assembler operation that should precede instructions and read-only data.
+Normally @code{"\t.text"} is right.
+@end defmac
+
+@defmac HOT_TEXT_SECTION_NAME
+If defined, a C string constant for the name of the section containing most
+frequently executed functions of the program. If not defined, GCC will provide
+a default definition if the target supports named sections.
+@end defmac
+
+@defmac UNLIKELY_EXECUTED_TEXT_SECTION_NAME
+If defined, a C string constant for the name of the section containing unlikely
+executed functions in the program.
+@end defmac
+
+@defmac DATA_SECTION_ASM_OP
+A C expression whose value is a string, including spacing, containing the
+assembler operation to identify the following data as writable initialized
+data. Normally @code{"\t.data"} is right.
+@end defmac
+
+@defmac SDATA_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+initialized, writable small data.
+@end defmac
+
+@defmac READONLY_DATA_SECTION_ASM_OP
+A C expression whose value is a string, including spacing, containing the
+assembler operation to identify the following data as read-only initialized
+data.
+@end defmac
+
+@defmac BSS_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+uninitialized global data. If not defined, and
+@code{ASM_OUTPUT_ALIGNED_BSS} not defined,
+uninitialized global data will be output in the data section if
+@option{-fno-common} is passed, otherwise @code{ASM_OUTPUT_COMMON} will be
+used.
+@end defmac
+
+@defmac SBSS_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+uninitialized, writable small data.
+@end defmac
+
+@defmac TLS_COMMON_ASM_OP
+If defined, a C expression whose value is a string containing the
+assembler operation to identify the following data as thread-local
+common data. The default is @code{".tls_common"}.
+@end defmac
+
+@defmac TLS_SECTION_ASM_FLAG
+If defined, a C expression whose value is a character constant
+containing the flag used to mark a section as a TLS section. The
+default is @code{'T'}.
+@end defmac
+
+@defmac INIT_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+initialization code. If not defined, GCC will assume such a section does
+not exist. This section has no corresponding @code{init_section}
+variable; it is used entirely in runtime code.
+@end defmac
+
+@defmac FINI_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+finalization code. If not defined, GCC will assume such a section does
+not exist. This section has no corresponding @code{fini_section}
+variable; it is used entirely in runtime code.
+@end defmac
+
+@defmac INIT_ARRAY_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+part of the @code{.init_array} (or equivalent) section. If not
+defined, GCC will assume such a section does not exist. Do not define
+both this macro and @code{INIT_SECTION_ASM_OP}.
+@end defmac
+
+@defmac FINI_ARRAY_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+part of the @code{.fini_array} (or equivalent) section. If not
+defined, GCC will assume such a section does not exist. Do not define
+both this macro and @code{FINI_SECTION_ASM_OP}.
+@end defmac
+
+@defmac MACH_DEP_SECTION_ASM_FLAG
+If defined, a C expression whose value is a character constant
+containing the flag used to mark a machine-dependent section. This
+corresponds to the @code{SECTION_MACH_DEP} section flag.
+@end defmac
+
+@defmac CRT_CALL_STATIC_FUNCTION (@var{section_op}, @var{function})
+If defined, an ASM statement that switches to a different section
+via @var{section_op}, calls @var{function}, and switches back to
+the text section. This is used in @file{crtstuff.c} if
+@code{INIT_SECTION_ASM_OP} or @code{FINI_SECTION_ASM_OP} to calls
+to initialization and finalization functions from the init and fini
+sections. By default, this macro uses a simple function call. Some
+ports need hand-crafted assembly code to avoid dependencies on
+registers initialized in the function prologue or to ensure that
+constant pools don't end up too far way in the text section.
+@end defmac
+
+@defmac TARGET_LIBGCC_SDATA_SECTION
+If defined, a string which names the section into which small
+variables defined in crtstuff and libgcc should go. This is useful
+when the target has options for optimizing access to small data, and
+you want the crtstuff and libgcc routines to be conservative in what
+they expect of your application yet liberal in what your application
+expects. For example, for targets with a @code{.sdata} section (like
+MIPS), you could compile crtstuff with @code{-G 0} so that it doesn't
+require small data support from your application, but use this macro
+to put small data into @code{.sdata} so that your application can
+access these variables whether it uses small data or not.
+@end defmac
+
+@defmac FORCE_CODE_SECTION_ALIGN
+If defined, an ASM statement that aligns a code section to some
+arbitrary boundary. This is used to force all fragments of the
+@code{.init} and @code{.fini} sections to have to same alignment
+and thus prevent the linker from having to add any padding.
+@end defmac
+
+@defmac JUMP_TABLES_IN_TEXT_SECTION
+Define this macro to be an expression with a nonzero value if jump
+tables (for @code{tablejump} insns) should be output in the text
+section, along with the assembler instructions. Otherwise, the
+readonly data section is used.
+
+This macro is irrelevant if there is no separate readonly data section.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_INIT_SECTIONS (void)
+Define this hook if you need to do something special to set up the
+@file{varasm.cc} sections, or if your target has some special sections
+of its own that you need to create.
+
+GCC calls this hook after processing the command line, but before writing
+any assembly code, and before calling any of the section-returning hooks
+described below.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_ASM_RELOC_RW_MASK (void)
+Return a mask describing how relocations should be treated when
+selecting sections. Bit 1 should be set if global relocations
+should be placed in a read-write section; bit 0 should be set if
+local relocations should be placed in a read-write section.
+
+The default version of this function returns 3 when @option{-fpic}
+is in effect, and 0 otherwise. The hook is typically redefined
+when the target cannot support (some kinds of) dynamic relocations
+in read-only sections even in executables.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ASM_GENERATE_PIC_ADDR_DIFF_VEC (void)
+Return true to generate ADDR_DIF_VEC table
+or false to generate ADDR_VEC table for jumps in case of -fPIC.
+
+The default version of this function returns true if flag_pic
+equals true and false otherwise
+@end deftypefn
+
+@deftypefn {Target Hook} {section *} TARGET_ASM_SELECT_SECTION (tree @var{exp}, int @var{reloc}, unsigned HOST_WIDE_INT @var{align})
+Return the section into which @var{exp} should be placed. You can
+assume that @var{exp} is either a @code{VAR_DECL} node or a constant of
+some sort. @var{reloc} indicates whether the initial value of @var{exp}
+requires link-time relocations. Bit 0 is set when variable contains
+local relocations only, while bit 1 is set for global relocations.
+@var{align} is the constant alignment in bits.
+
+The default version of this function takes care of putting read-only
+variables in @code{readonly_data_section}.
+
+See also @var{USE_SELECT_SECTION_FOR_FUNCTIONS}.
+@end deftypefn
+
+@defmac USE_SELECT_SECTION_FOR_FUNCTIONS
+Define this macro if you wish TARGET_ASM_SELECT_SECTION to be called
+for @code{FUNCTION_DECL}s as well as for variables and constants.
+
+In the case of a @code{FUNCTION_DECL}, @var{reloc} will be zero if the
+function has been determined to be likely to be called, and nonzero if
+it is unlikely to be called.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_UNIQUE_SECTION (tree @var{decl}, int @var{reloc})
+Build up a unique section name, expressed as a @code{STRING_CST} node,
+and assign it to @samp{DECL_SECTION_NAME (@var{decl})}.
+As with @code{TARGET_ASM_SELECT_SECTION}, @var{reloc} indicates whether
+the initial value of @var{exp} requires link-time relocations.
+
+The default version of this function appends the symbol name to the
+ELF section name that would normally be used for the symbol. For
+example, the function @code{foo} would be placed in @code{.text.foo}.
+Whatever the actual target object format, this is often good enough.
+@end deftypefn
+
+@deftypefn {Target Hook} {section *} TARGET_ASM_FUNCTION_RODATA_SECTION (tree @var{decl}, bool @var{relocatable})
+Return the readonly data or reloc readonly data section associated with
+@samp{DECL_SECTION_NAME (@var{decl})}. @var{relocatable} selects the latter
+over the former.
+The default version of this function selects @code{.gnu.linkonce.r.name} if
+the function's section is @code{.gnu.linkonce.t.name}, @code{.rodata.name}
+or @code{.data.rel.ro.name} if function is in @code{.text.name}, and
+the normal readonly-data or reloc readonly data section otherwise.
+@end deftypefn
+
+@deftypevr {Target Hook} {const char *} TARGET_ASM_MERGEABLE_RODATA_PREFIX
+Usually, the compiler uses the prefix @code{".rodata"} to construct
+section names for mergeable constant data. Define this macro to override
+the string if a different section name should be used.
+@end deftypevr
+
+@deftypefn {Target Hook} {section *} TARGET_ASM_TM_CLONE_TABLE_SECTION (void)
+Return the section that should be used for transactional memory clone
+tables.
+@end deftypefn
+
+@deftypefn {Target Hook} {section *} TARGET_ASM_SELECT_RTX_SECTION (machine_mode @var{mode}, rtx @var{x}, unsigned HOST_WIDE_INT @var{align})
+Return the section into which a constant @var{x}, of mode @var{mode},
+should be placed. You can assume that @var{x} is some kind of
+constant in RTL@. The argument @var{mode} is redundant except in the
+case of a @code{const_int} rtx. @var{align} is the constant alignment
+in bits.
+
+The default version of this function takes care of putting symbolic
+constants in @code{flag_pic} mode in @code{data_section} and everything
+else in @code{readonly_data_section}.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_MANGLE_DECL_ASSEMBLER_NAME (tree @var{decl}, tree @var{id})
+Define this hook if you need to postprocess the assembler name generated
+by target-independent code. The @var{id} provided to this hook will be
+the computed name (e.g., the macro @code{DECL_NAME} of the @var{decl} in C,
+or the mangled name of the @var{decl} in C++). The return value of the
+hook is an @code{IDENTIFIER_NODE} for the appropriate mangled name on
+your target system. The default implementation of this hook just
+returns the @var{id} provided.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ENCODE_SECTION_INFO (tree @var{decl}, rtx @var{rtl}, int @var{new_decl_p})
+Define this hook if references to a symbol or a constant must be
+treated differently depending on something about the variable or
+function named by the symbol (such as what section it is in).
+
+The hook is executed immediately after rtl has been created for
+@var{decl}, which may be a variable or function declaration or
+an entry in the constant pool. In either case, @var{rtl} is the
+rtl in question. Do @emph{not} use @code{DECL_RTL (@var{decl})}
+in this hook; that field may not have been initialized yet.
+
+In the case of a constant, it is safe to assume that the rtl is
+a @code{mem} whose address is a @code{symbol_ref}. Most decls
+will also have this form, but that is not guaranteed. Global
+register variables, for instance, will have a @code{reg} for their
+rtl. (Normally the right thing to do with such unusual rtl is
+leave it alone.)
+
+The @var{new_decl_p} argument will be true if this is the first time
+that @code{TARGET_ENCODE_SECTION_INFO} has been invoked on this decl. It will
+be false for subsequent invocations, which will happen for duplicate
+declarations. Whether or not anything must be done for the duplicate
+declaration depends on whether the hook examines @code{DECL_ATTRIBUTES}.
+@var{new_decl_p} is always true when the hook is called for a constant.
+
+@cindex @code{SYMBOL_REF_FLAG}, in @code{TARGET_ENCODE_SECTION_INFO}
+The usual thing for this hook to do is to record flags in the
+@code{symbol_ref}, using @code{SYMBOL_REF_FLAG} or @code{SYMBOL_REF_FLAGS}.
+Historically, the name string was modified if it was necessary to
+encode more than one bit of information, but this practice is now
+discouraged; use @code{SYMBOL_REF_FLAGS}.
+
+The default definition of this hook, @code{default_encode_section_info}
+in @file{varasm.cc}, sets a number of commonly-useful bits in
+@code{SYMBOL_REF_FLAGS}. Check whether the default does what you need
+before overriding it.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_STRIP_NAME_ENCODING (const char *@var{name})
+Decode @var{name} and return the real name part, sans
+the characters that @code{TARGET_ENCODE_SECTION_INFO}
+may have added.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_IN_SMALL_DATA_P (const_tree @var{exp})
+Returns true if @var{exp} should be placed into a ``small data'' section.
+The default version of this hook always returns false.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_HAVE_SRODATA_SECTION
+Contains the value true if the target places read-only
+``small data'' into a separate section. The default value is false.
+@end deftypevr
+
+@deftypefn {Target Hook} bool TARGET_PROFILE_BEFORE_PROLOGUE (void)
+It returns true if target wants profile code emitted before prologue.
+
+The default version of this hook use the target macro
+@code{PROFILE_BEFORE_PROLOGUE}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_BINDS_LOCAL_P (const_tree @var{exp})
+Returns true if @var{exp} names an object for which name resolution
+rules must resolve to the current ``module'' (dynamic shared library
+or executable image).
+
+The default version of this hook implements the name resolution rules
+for ELF, which has a looser model of global name binding than other
+currently supported object file formats.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_HAVE_TLS
+Contains the value true if the target supports thread-local storage.
+The default value is false.
+@end deftypevr
+
+
+@node PIC
+@section Position Independent Code
+@cindex position independent code
+@cindex PIC
+
+This section describes macros that help implement generation of position
+independent code. Simply defining these macros is not enough to
+generate valid PIC; you must also add support to the hook
+@code{TARGET_LEGITIMATE_ADDRESS_P} and to the macro
+@code{PRINT_OPERAND_ADDRESS}, as well as @code{LEGITIMIZE_ADDRESS}. You
+must modify the definition of @samp{movsi} to do something appropriate
+when the source operand contains a symbolic address. You may also
+need to alter the handling of switch statements so that they use
+relative addresses.
+@c i rearranged the order of the macros above to try to force one of
+@c them to the next line, to eliminate an overfull hbox. --mew 10feb93
+
+@defmac PIC_OFFSET_TABLE_REGNUM
+The register number of the register used to address a table of static
+data addresses in memory. In some cases this register is defined by a
+processor's ``application binary interface'' (ABI)@. When this macro
+is defined, RTL is generated for this register once, as with the stack
+pointer and frame pointer registers. If this macro is not defined, it
+is up to the machine-dependent files to allocate such a register (if
+necessary). Note that this register must be fixed when in use (e.g.@:
+when @code{flag_pic} is true).
+@end defmac
+
+@defmac PIC_OFFSET_TABLE_REG_CALL_CLOBBERED
+A C expression that is nonzero if the register defined by
+@code{PIC_OFFSET_TABLE_REGNUM} is clobbered by calls. If not defined,
+the default is zero. Do not define
+this macro if @code{PIC_OFFSET_TABLE_REGNUM} is not defined.
+@end defmac
+
+@defmac LEGITIMATE_PIC_OPERAND_P (@var{x})
+A C expression that is nonzero if @var{x} is a legitimate immediate
+operand on the target machine when generating position independent code.
+You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not
+check this. You can also assume @var{flag_pic} is true, so you need not
+check it either. You need not define this macro if all constants
+(including @code{SYMBOL_REF}) can be immediate operands when generating
+position independent code.
+@end defmac
+
+@node Assembler Format
+@section Defining the Output Assembler Language
+
+This section describes macros whose principal purpose is to describe how
+to write instructions in assembler language---rather than what the
+instructions do.
+
+@menu
+* File Framework:: Structural information for the assembler file.
+* Data Output:: Output of constants (numbers, strings, addresses).
+* Uninitialized Data:: Output of uninitialized variables.
+* Label Output:: Output and generation of labels.
+* Initialization:: General principles of initialization
+ and termination routines.
+* Macros for Initialization::
+ Specific macros that control the handling of
+ initialization and termination routines.
+* Instruction Output:: Output of actual instructions.
+* Dispatch Tables:: Output of jump tables.
+* Exception Region Output:: Output of exception region code.
+* Alignment Output:: Pseudo ops for alignment and skipping data.
+@end menu
+
+@node File Framework
+@subsection The Overall Framework of an Assembler File
+@cindex assembler format
+@cindex output of assembler code
+
+@c prevent bad page break with this line
+This describes the overall framework of an assembly file.
+
+@findex default_file_start
+@deftypefn {Target Hook} void TARGET_ASM_FILE_START (void)
+Output to @code{asm_out_file} any text which the assembler expects to
+find at the beginning of a file. The default behavior is controlled
+by two flags, documented below. Unless your target's assembler is
+quite unusual, if you override the default, you should call
+@code{default_file_start} at some point in your target hook. This
+lets other target files rely on these variables.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_ASM_FILE_START_APP_OFF
+If this flag is true, the text of the macro @code{ASM_APP_OFF} will be
+printed as the very first line in the assembly file, unless
+@option{-fverbose-asm} is in effect. (If that macro has been defined
+to the empty string, this variable has no effect.) With the normal
+definition of @code{ASM_APP_OFF}, the effect is to notify the GNU
+assembler that it need not bother stripping comments or extra
+whitespace from its input. This allows it to work a bit faster.
+
+The default is false. You should not set it to true unless you have
+verified that your port does not generate any extra whitespace or
+comments that will cause GAS to issue errors in NO_APP mode.
+@end deftypevr
+
+@deftypevr {Target Hook} bool TARGET_ASM_FILE_START_FILE_DIRECTIVE
+If this flag is true, @code{output_file_directive} will be called
+for the primary source file, immediately after printing
+@code{ASM_APP_OFF} (if that is enabled). Most ELF assemblers expect
+this to be done. The default is false.
+@end deftypevr
+
+@deftypefn {Target Hook} void TARGET_ASM_FILE_END (void)
+Output to @code{asm_out_file} any text which the assembler expects
+to find at the end of a file. The default is to output nothing.
+@end deftypefn
+
+@deftypefun void file_end_indicate_exec_stack ()
+Some systems use a common convention, the @samp{.note.GNU-stack}
+special section, to indicate whether or not an object file relies on
+the stack being executable. If your system uses this convention, you
+should define @code{TARGET_ASM_FILE_END} to this function. If you
+need to do other things in that hook, have your hook function call
+this function.
+@end deftypefun
+
+@deftypefn {Target Hook} void TARGET_ASM_LTO_START (void)
+Output to @code{asm_out_file} any text which the assembler expects
+to find at the start of an LTO section. The default is to output
+nothing.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_LTO_END (void)
+Output to @code{asm_out_file} any text which the assembler expects
+to find at the end of an LTO section. The default is to output
+nothing.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_CODE_END (void)
+Output to @code{asm_out_file} any text which is needed before emitting
+unwind info and debug info at the end of a file. Some targets emit
+here PIC setup thunks that cannot be emitted at the end of file,
+because they couldn't have unwind info then. The default is to output
+nothing.
+@end deftypefn
+
+@defmac ASM_COMMENT_START
+A C string constant describing how to begin a comment in the target
+assembler language. The compiler assumes that the comment will end at
+the end of the line.
+@end defmac
+
+@defmac ASM_APP_ON
+A C string constant for text to be output before each @code{asm}
+statement or group of consecutive ones. Normally this is
+@code{"#APP"}, which is a comment that has no effect on most
+assemblers but tells the GNU assembler that it must check the lines
+that follow for all valid assembler constructs.
+@end defmac
+
+@defmac ASM_APP_OFF
+A C string constant for text to be output after each @code{asm}
+statement or group of consecutive ones. Normally this is
+@code{"#NO_APP"}, which tells the GNU assembler to resume making the
+time-saving assumptions that are valid for ordinary compiler output.
+@end defmac
+
+@defmac ASM_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name})
+A C statement to output COFF information or DWARF debugging information
+which indicates that filename @var{name} is the current source file to
+the stdio stream @var{stream}.
+
+This macro need not be defined if the standard form of output
+for the file format in use is appropriate.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_SOURCE_FILENAME (FILE *@var{file}, const char *@var{name})
+Output DWARF debugging information which indicates that filename
+@var{name} is the current source file to the stdio stream @var{file}.
+
+This target hook need not be defined if the standard form of output
+for the file format in use is appropriate.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_IDENT (const char *@var{name})
+Output a string based on @var{name}, suitable for the @samp{#ident}
+directive, or the equivalent directive or pragma in non-C-family languages.
+If this hook is not defined, nothing is output for the @samp{#ident}
+directive.
+@end deftypefn
+
+@defmac OUTPUT_QUOTED_STRING (@var{stream}, @var{string})
+A C statement to output the string @var{string} to the stdio stream
+@var{stream}. If you do not call the function @code{output_quoted_string}
+in your config files, GCC will only call it to output filenames to
+the assembler source. So you can use it to canonicalize the format
+of the filename using this macro.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_NAMED_SECTION (const char *@var{name}, unsigned int @var{flags}, tree @var{decl})
+Output assembly directives to switch to section @var{name}. The section
+should have attributes as specified by @var{flags}, which is a bit mask
+of the @code{SECTION_*} flags defined in @file{output.h}. If @var{decl}
+is non-NULL, it is the @code{VAR_DECL} or @code{FUNCTION_DECL} with which
+this section is associated.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ASM_ELF_FLAGS_NUMERIC (unsigned int @var{flags}, unsigned int *@var{num})
+This hook can be used to encode ELF section flags for which no letter
+code has been defined in the assembler. It is called by
+@code{default_asm_named_section} whenever the section flags need to be
+emitted in the assembler output. If the hook returns true, then the
+numerical value for ELF section flags should be calculated from
+@var{flags} and saved in @var{*num}; the value is printed out instead of the
+normal sequence of letter codes. If the hook is not defined, or if it
+returns false, then @var{num} is ignored and the traditional letter sequence
+is emitted.
+@end deftypefn
+
+@deftypefn {Target Hook} {section *} TARGET_ASM_FUNCTION_SECTION (tree @var{decl}, enum node_frequency @var{freq}, bool @var{startup}, bool @var{exit})
+Return preferred text (sub)section for function @var{decl}.
+Main purpose of this function is to separate cold, normal and hot
+functions. @var{startup} is true when function is known to be used only
+at startup (from static constructors or it is @code{main()}).
+@var{exit} is true when function is known to be used only at exit
+(from static destructors).
+Return NULL if function should go to default text section.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_SWITCHED_TEXT_SECTIONS (FILE *@var{file}, tree @var{decl}, bool @var{new_is_cold})
+Used by the target to emit any assembler directives or additional
+labels needed when a function is partitioned between different
+sections. Output should be written to @var{file}. The function
+decl is available as @var{decl} and the new section is `cold' if
+@var{new_is_cold} is @code{true}.
+@end deftypefn
+
+@deftypevr {Common Target Hook} bool TARGET_HAVE_NAMED_SECTIONS
+This flag is true if the target supports @code{TARGET_ASM_NAMED_SECTION}.
+It must not be modified by command-line option processing.
+@end deftypevr
+
+@anchor{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS}
+@deftypevr {Target Hook} bool TARGET_HAVE_SWITCHABLE_BSS_SECTIONS
+This flag is true if we can create zeroed data by switching to a BSS
+section and then using @code{ASM_OUTPUT_SKIP} to allocate the space.
+This is true on most ELF targets.
+@end deftypevr
+
+@deftypefn {Target Hook} {unsigned int} TARGET_SECTION_TYPE_FLAGS (tree @var{decl}, const char *@var{name}, int @var{reloc})
+Choose a set of section attributes for use by @code{TARGET_ASM_NAMED_SECTION}
+based on a variable or function decl, a section name, and whether or not the
+declaration's initializer may contain runtime relocations. @var{decl} may be
+null, in which case read-write data should be assumed.
+
+The default version of this function handles choosing code vs data,
+read-only vs read-write data, and @code{flag_pic}. You should only
+need to override this if your target has special flags that might be
+set via @code{__attribute__}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_RECORD_GCC_SWITCHES (const char *@var{})
+Provides the target with the ability to record the gcc command line
+switches provided as argument.
+
+By default this hook is set to NULL, but an example implementation is
+provided for ELF based targets. Called @var{elf_record_gcc_switches},
+it records the switches as ASCII text inside a new, string mergeable
+section in the assembler output file. The name of the new section is
+provided by the @code{TARGET_ASM_RECORD_GCC_SWITCHES_SECTION} target
+hook.
+@end deftypefn
+
+@deftypevr {Target Hook} {const char *} TARGET_ASM_RECORD_GCC_SWITCHES_SECTION
+This is the name of the section that will be created by the example
+ELF implementation of the @code{TARGET_ASM_RECORD_GCC_SWITCHES} target
+hook.
+@end deftypevr
+
+@need 2000
+@node Data Output
+@subsection Output of Data
+
+
+@deftypevr {Target Hook} {const char *} TARGET_ASM_BYTE_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_HI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_PSI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_SI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_PDI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_DI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_PTI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_ALIGNED_TI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_HI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_PSI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_SI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_PDI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_DI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_PTI_OP
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_UNALIGNED_TI_OP
+These hooks specify assembly directives for creating certain kinds
+of integer object. The @code{TARGET_ASM_BYTE_OP} directive creates a
+byte-sized object, the @code{TARGET_ASM_ALIGNED_HI_OP} one creates an
+aligned two-byte object, and so on. Any of the hooks may be
+@code{NULL}, indicating that no suitable directive is available.
+
+The compiler will print these strings at the start of a new line,
+followed immediately by the object's initial value. In most cases,
+the string should contain a tab, a pseudo-op, and then another tab.
+@end deftypevr
+
+@deftypefn {Target Hook} bool TARGET_ASM_INTEGER (rtx @var{x}, unsigned int @var{size}, int @var{aligned_p})
+The @code{assemble_integer} function uses this hook to output an
+integer object. @var{x} is the object's value, @var{size} is its size
+in bytes and @var{aligned_p} indicates whether it is aligned. The
+function should return @code{true} if it was able to output the
+object. If it returns false, @code{assemble_integer} will try to
+split the object into smaller parts.
+
+The default implementation of this hook will use the
+@code{TARGET_ASM_BYTE_OP} family of strings, returning @code{false}
+when the relevant string is @code{NULL}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_DECL_END (void)
+Define this hook if the target assembler requires a special marker to
+terminate an initialized variable declaration.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ASM_OUTPUT_ADDR_CONST_EXTRA (FILE *@var{file}, rtx @var{x})
+A target hook to recognize @var{rtx} patterns that @code{output_addr_const}
+can't deal with, and output assembly code to @var{file} corresponding to
+the pattern @var{x}. This may be used to allow machine-dependent
+@code{UNSPEC}s to appear within constants.
+
+If target hook fails to recognize a pattern, it must return @code{false},
+so that a standard error message is printed. If it prints an error message
+itself, by calling, for example, @code{output_operand_lossage}, it may just
+return @code{true}.
+@end deftypefn
+
+@defmac ASM_OUTPUT_ASCII (@var{stream}, @var{ptr}, @var{len})
+A C statement to output to the stdio stream @var{stream} an assembler
+instruction to assemble a string constant containing the @var{len}
+bytes at @var{ptr}. @var{ptr} will be a C expression of type
+@code{char *} and @var{len} a C expression of type @code{int}.
+
+If the assembler has a @code{.ascii} pseudo-op as found in the
+Berkeley Unix assembler, do not define the macro
+@code{ASM_OUTPUT_ASCII}.
+@end defmac
+
+@defmac ASM_OUTPUT_FDESC (@var{stream}, @var{decl}, @var{n})
+A C statement to output word @var{n} of a function descriptor for
+@var{decl}. This must be defined if @code{TARGET_VTABLE_USES_DESCRIPTORS}
+is defined, and is otherwise unused.
+@end defmac
+
+@defmac CONSTANT_POOL_BEFORE_FUNCTION
+You may define this macro as a C expression. You should define the
+expression to have a nonzero value if GCC should output the constant
+pool for a function before the code for the function, or a zero value if
+GCC should output the constant pool after the function. If you do
+not define this macro, the usual case, GCC will output the constant
+pool before the function.
+@end defmac
+
+@defmac ASM_OUTPUT_POOL_PROLOGUE (@var{file}, @var{funname}, @var{fundecl}, @var{size})
+A C statement to output assembler commands to define the start of the
+constant pool for a function. @var{funname} is a string giving
+the name of the function. Should the return type of the function
+be required, it can be obtained via @var{fundecl}. @var{size}
+is the size, in bytes, of the constant pool that will be written
+immediately after this call.
+
+If no constant-pool prefix is required, the usual case, this macro need
+not be defined.
+@end defmac
+
+@defmac ASM_OUTPUT_SPECIAL_POOL_ENTRY (@var{file}, @var{x}, @var{mode}, @var{align}, @var{labelno}, @var{jumpto})
+A C statement (with or without semicolon) to output a constant in the
+constant pool, if it needs special treatment. (This macro need not do
+anything for RTL expressions that can be output normally.)
+
+The argument @var{file} is the standard I/O stream to output the
+assembler code on. @var{x} is the RTL expression for the constant to
+output, and @var{mode} is the machine mode (in case @var{x} is a
+@samp{const_int}). @var{align} is the required alignment for the value
+@var{x}; you should output an assembler directive to force this much
+alignment.
+
+The argument @var{labelno} is a number to use in an internal label for
+the address of this pool entry. The definition of this macro is
+responsible for outputting the label definition at the proper place.
+Here is how to do this:
+
+@smallexample
+@code{(*targetm.asm_out.internal_label)} (@var{file}, "LC", @var{labelno});
+@end smallexample
+
+When you output a pool entry specially, you should end with a
+@code{goto} to the label @var{jumpto}. This will prevent the same pool
+entry from being output a second time in the usual manner.
+
+You need not define this macro if it would do nothing.
+@end defmac
+
+@defmac ASM_OUTPUT_POOL_EPILOGUE (@var{file} @var{funname} @var{fundecl} @var{size})
+A C statement to output assembler commands to at the end of the constant
+pool for a function. @var{funname} is a string giving the name of the
+function. Should the return type of the function be required, you can
+obtain it via @var{fundecl}. @var{size} is the size, in bytes, of the
+constant pool that GCC wrote immediately before this call.
+
+If no constant-pool epilogue is required, the usual case, you need not
+define this macro.
+@end defmac
+
+@defmac IS_ASM_LOGICAL_LINE_SEPARATOR (@var{C}, @var{STR})
+Define this macro as a C expression which is nonzero if @var{C} is
+used as a logical line separator by the assembler. @var{STR} points
+to the position in the string where @var{C} was found; this can be used if
+a line separator uses multiple characters.
+
+If you do not define this macro, the default is that only
+the character @samp{;} is treated as a logical line separator.
+@end defmac
+
+@deftypevr {Target Hook} {const char *} TARGET_ASM_OPEN_PAREN
+@deftypevrx {Target Hook} {const char *} TARGET_ASM_CLOSE_PAREN
+These target hooks are C string constants, describing the syntax in the
+assembler for grouping arithmetic expressions. If not overridden, they
+default to normal parentheses, which is correct for most assemblers.
+@end deftypevr
+
+These macros are provided by @file{real.h} for writing the definitions
+of @code{ASM_OUTPUT_DOUBLE} and the like:
+
+@defmac REAL_VALUE_TO_TARGET_SINGLE (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_DOUBLE (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_LONG_DOUBLE (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_DECIMAL32 (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_DECIMAL64 (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_DECIMAL128 (@var{x}, @var{l})
+These translate @var{x}, of type @code{REAL_VALUE_TYPE}, to the
+target's floating point representation, and store its bit pattern in
+the variable @var{l}. For @code{REAL_VALUE_TO_TARGET_SINGLE} and
+@code{REAL_VALUE_TO_TARGET_DECIMAL32}, this variable should be a
+simple @code{long int}. For the others, it should be an array of
+@code{long int}. The number of elements in this array is determined
+by the size of the desired target floating point data type: 32 bits of
+it go in each @code{long int} array element. Each array element holds
+32 bits of the result, even if @code{long int} is wider than 32 bits
+on the host machine.
+
+The array element values are designed so that you can print them out
+using @code{fprintf} in the order they should appear in the target
+machine's memory.
+@end defmac
+
+@node Uninitialized Data
+@subsection Output of Uninitialized Variables
+
+Each of the macros in this section is used to do the whole job of
+outputting a single uninitialized variable.
+
+@defmac ASM_OUTPUT_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of a common-label named
+@var{name} whose size is @var{size} bytes. The variable @var{rounded}
+is the size rounded up to whatever alignment the caller wants. It is
+possible that @var{size} may be zero, for instance if a struct with no
+other member than a zero-length array is defined. In this case, the
+backend must output a symbol definition that allocates at least one
+byte, both so that the address of the resulting object does not compare
+equal to any other, and because some object formats cannot even express
+the concept of a zero-sized common symbol, as that is how they represent
+an ordinary undefined external.
+
+Use the expression @code{assemble_name (@var{stream}, @var{name})} to
+output the name itself; before and after that, output the additional
+assembler syntax for defining the name, and a newline.
+
+This macro controls how the assembler definitions of uninitialized
+common global variables are output.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_COMMON (@var{stream}, @var{name}, @var{size}, @var{alignment})
+Like @code{ASM_OUTPUT_COMMON} except takes the required alignment as a
+separate, explicit argument. If you define this macro, it is used in
+place of @code{ASM_OUTPUT_COMMON}, and gives you more flexibility in
+handling the required alignment of the variable. The alignment is specified
+as the number of bits.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_DECL_COMMON (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment})
+Like @code{ASM_OUTPUT_ALIGNED_COMMON} except that @var{decl} of the
+variable to be output, if there is one, or @code{NULL_TREE} if there
+is no corresponding variable. If you define this macro, GCC will use it
+in place of both @code{ASM_OUTPUT_COMMON} and
+@code{ASM_OUTPUT_ALIGNED_COMMON}. Define this macro when you need to see
+the variable's decl in order to chose what to output.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of uninitialized global @var{decl} named
+@var{name} whose size is @var{size} bytes. The variable @var{alignment}
+is the alignment specified as the number of bits.
+
+Try to use function @code{asm_output_aligned_bss} defined in file
+@file{varasm.cc} when defining this macro. If unable, use the expression
+@code{assemble_name (@var{stream}, @var{name})} to output the name itself;
+before and after that, output the additional assembler syntax for defining
+the name, and a newline.
+
+There are two ways of handling global BSS@. One is to define this macro.
+The other is to have @code{TARGET_ASM_SELECT_SECTION} return a
+switchable BSS section (@pxref{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS}).
+You do not need to do both.
+
+Some languages do not have @code{common} data, and require a
+non-common form of global BSS in order to handle uninitialized globals
+efficiently. C++ is one example of this. However, if the target does
+not support global BSS, the front end may choose to make globals
+common in order to save space in the object file.
+@end defmac
+
+@defmac ASM_OUTPUT_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of a local-common-label named
+@var{name} whose size is @var{size} bytes. The variable @var{rounded}
+is the size rounded up to whatever alignment the caller wants.
+
+Use the expression @code{assemble_name (@var{stream}, @var{name})} to
+output the name itself; before and after that, output the additional
+assembler syntax for defining the name, and a newline.
+
+This macro controls how the assembler definitions of uninitialized
+static variables are output.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{alignment})
+Like @code{ASM_OUTPUT_LOCAL} except takes the required alignment as a
+separate, explicit argument. If you define this macro, it is used in
+place of @code{ASM_OUTPUT_LOCAL}, and gives you more flexibility in
+handling the required alignment of the variable. The alignment is specified
+as the number of bits.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_DECL_LOCAL (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment})
+Like @code{ASM_OUTPUT_ALIGNED_LOCAL} except that @var{decl} of the
+variable to be output, if there is one, or @code{NULL_TREE} if there
+is no corresponding variable. If you define this macro, GCC will use it
+in place of both @code{ASM_OUTPUT_LOCAL} and
+@code{ASM_OUTPUT_ALIGNED_LOCAL}. Define this macro when you need to see
+the variable's decl in order to chose what to output.
+@end defmac
+
+@node Label Output
+@subsection Output and Generation of Labels
+
+@c prevent bad page break with this line
+This is about outputting labels.
+
+@findex assemble_name
+@defmac ASM_OUTPUT_LABEL (@var{stream}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of a label named @var{name}.
+Use the expression @code{assemble_name (@var{stream}, @var{name})} to
+output the name itself; before and after that, output the additional
+assembler syntax for defining the name, and a newline. A default
+definition of this macro is provided which is correct for most systems.
+@end defmac
+
+@defmac ASM_OUTPUT_FUNCTION_LABEL (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of a label named @var{name} of
+a function.
+Use the expression @code{assemble_name (@var{stream}, @var{name})} to
+output the name itself; before and after that, output the additional
+assembler syntax for defining the name, and a newline. A default
+definition of this macro is provided which is correct for most systems.
+
+If this macro is not defined, then the function name is defined in the
+usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}).
+@end defmac
+
+@findex assemble_name_raw
+@defmac ASM_OUTPUT_INTERNAL_LABEL (@var{stream}, @var{name})
+Identical to @code{ASM_OUTPUT_LABEL}, except that @var{name} is known
+to refer to a compiler-generated label. The default definition uses
+@code{assemble_name_raw}, which is like @code{assemble_name} except
+that it is more efficient.
+@end defmac
+
+@defmac SIZE_ASM_OP
+A C string containing the appropriate assembler directive to specify the
+size of a symbol, without any arguments. On systems that use ELF, the
+default (in @file{config/elfos.h}) is @samp{"\t.size\t"}; on other
+systems, the default is not to define this macro.
+
+Define this macro only if it is correct to use the default definitions
+of @code{ASM_OUTPUT_SIZE_DIRECTIVE} and @code{ASM_OUTPUT_MEASURED_SIZE}
+for your system. If you need your own custom definitions of those
+macros, or if you do not need explicit symbol sizes at all, do not
+define this macro.
+@end defmac
+
+@defmac ASM_OUTPUT_SIZE_DIRECTIVE (@var{stream}, @var{name}, @var{size})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} a directive telling the assembler that the size of the
+symbol @var{name} is @var{size}. @var{size} is a @code{HOST_WIDE_INT}.
+If you define @code{SIZE_ASM_OP}, a default definition of this macro is
+provided.
+@end defmac
+
+@defmac ASM_OUTPUT_MEASURED_SIZE (@var{stream}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} a directive telling the assembler to calculate the size of
+the symbol @var{name} by subtracting its address from the current
+address.
+
+If you define @code{SIZE_ASM_OP}, a default definition of this macro is
+provided. The default assumes that the assembler recognizes a special
+@samp{.} symbol as referring to the current address, and can calculate
+the difference between this and another symbol. If your assembler does
+not recognize @samp{.} or cannot do calculations with it, you will need
+to redefine @code{ASM_OUTPUT_MEASURED_SIZE} to use some other technique.
+@end defmac
+
+@defmac NO_DOLLAR_IN_LABEL
+Define this macro if the assembler does not accept the character
+@samp{$} in label names. By default constructors and destructors in
+G++ have @samp{$} in the identifiers. If this macro is defined,
+@samp{.} is used instead.
+@end defmac
+
+@defmac NO_DOT_IN_LABEL
+Define this macro if the assembler does not accept the character
+@samp{.} in label names. By default constructors and destructors in G++
+have names that use @samp{.}. If this macro is defined, these names
+are rewritten to avoid @samp{.}.
+@end defmac
+
+@defmac TYPE_ASM_OP
+A C string containing the appropriate assembler directive to specify the
+type of a symbol, without any arguments. On systems that use ELF, the
+default (in @file{config/elfos.h}) is @samp{"\t.type\t"}; on other
+systems, the default is not to define this macro.
+
+Define this macro only if it is correct to use the default definition of
+@code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own
+custom definition of this macro, or if you do not need explicit symbol
+types at all, do not define this macro.
+@end defmac
+
+@defmac TYPE_OPERAND_FMT
+A C string which specifies (using @code{printf} syntax) the format of
+the second operand to @code{TYPE_ASM_OP}. On systems that use ELF, the
+default (in @file{config/elfos.h}) is @samp{"@@%s"}; on other systems,
+the default is not to define this macro.
+
+Define this macro only if it is correct to use the default definition of
+@code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own
+custom definition of this macro, or if you do not need explicit symbol
+types at all, do not define this macro.
+@end defmac
+
+@defmac ASM_OUTPUT_TYPE_DIRECTIVE (@var{stream}, @var{type})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} a directive telling the assembler that the type of the
+symbol @var{name} is @var{type}. @var{type} is a C string; currently,
+that string is always either @samp{"function"} or @samp{"object"}, but
+you should not count on this.
+
+If you define @code{TYPE_ASM_OP} and @code{TYPE_OPERAND_FMT}, a default
+definition of this macro is provided.
+@end defmac
+
+@defmac ASM_DECLARE_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the name @var{name} of a
+function which is being defined. This macro is responsible for
+outputting the label definition (perhaps using
+@code{ASM_OUTPUT_FUNCTION_LABEL}). The argument @var{decl} is the
+@code{FUNCTION_DECL} tree node representing the function.
+
+If this macro is not defined, then the function name is defined in the
+usual manner as a label (by means of @code{ASM_OUTPUT_FUNCTION_LABEL}).
+
+You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in the definition
+of this macro.
+@end defmac
+
+@defmac ASM_DECLARE_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the size of a function
+which is being defined. The argument @var{name} is the name of the
+function. The argument @var{decl} is the @code{FUNCTION_DECL} tree node
+representing the function.
+
+If this macro is not defined, then the function size is not defined.
+
+You may wish to use @code{ASM_OUTPUT_MEASURED_SIZE} in the definition
+of this macro.
+@end defmac
+
+@defmac ASM_DECLARE_COLD_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the name @var{name} of a
+cold function partition which is being defined. This macro is responsible
+for outputting the label definition (perhaps using
+@code{ASM_OUTPUT_FUNCTION_LABEL}). The argument @var{decl} is the
+@code{FUNCTION_DECL} tree node representing the function.
+
+If this macro is not defined, then the cold partition name is defined in the
+usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}).
+
+You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in the definition
+of this macro.
+@end defmac
+
+@defmac ASM_DECLARE_COLD_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the size of a cold function
+partition which is being defined. The argument @var{name} is the name of the
+cold partition of the function. The argument @var{decl} is the
+@code{FUNCTION_DECL} tree node representing the function.
+
+If this macro is not defined, then the partition size is not defined.
+
+You may wish to use @code{ASM_OUTPUT_MEASURED_SIZE} in the definition
+of this macro.
+@end defmac
+
+@defmac ASM_DECLARE_OBJECT_NAME (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the name @var{name} of an
+initialized variable which is being defined. This macro must output the
+label definition (perhaps using @code{ASM_OUTPUT_LABEL}). The argument
+@var{decl} is the @code{VAR_DECL} tree node representing the variable.
+
+If this macro is not defined, then the variable name is defined in the
+usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}).
+
+You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} and/or
+@code{ASM_OUTPUT_SIZE_DIRECTIVE} in the definition of this macro.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_DECLARE_CONSTANT_NAME (FILE *@var{file}, const char *@var{name}, const_tree @var{expr}, HOST_WIDE_INT @var{size})
+A target hook to output to the stdio stream @var{file} any text necessary
+for declaring the name @var{name} of a constant which is being defined. This
+target hook is responsible for outputting the label definition (perhaps using
+@code{assemble_label}). The argument @var{exp} is the value of the constant,
+and @var{size} is the size of the constant in bytes. The @var{name}
+will be an internal label.
+
+The default version of this target hook, define the @var{name} in the
+usual manner as a label (by means of @code{assemble_label}).
+
+You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in this target hook.
+@end deftypefn
+
+@defmac ASM_DECLARE_REGISTER_GLOBAL (@var{stream}, @var{decl}, @var{regno}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for claiming a register @var{regno}
+for a global variable @var{decl} with name @var{name}.
+
+If you don't define this macro, that is equivalent to defining it to do
+nothing.
+@end defmac
+
+@defmac ASM_FINISH_DECLARE_OBJECT (@var{stream}, @var{decl}, @var{toplevel}, @var{atend})
+A C statement (sans semicolon) to finish up declaring a variable name
+once the compiler has processed its initializer fully and thus has had a
+chance to determine the size of an array when controlled by an
+initializer. This is used on systems where it's necessary to declare
+something about the size of the object.
+
+If you don't define this macro, that is equivalent to defining it to do
+nothing.
+
+You may wish to use @code{ASM_OUTPUT_SIZE_DIRECTIVE} and/or
+@code{ASM_OUTPUT_MEASURED_SIZE} in the definition of this macro.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_GLOBALIZE_LABEL (FILE *@var{stream}, const char *@var{name})
+This target hook is a function to output to the stdio stream
+@var{stream} some commands that will make the label @var{name} global;
+that is, available for reference from other files.
+
+The default implementation relies on a proper definition of
+@code{GLOBAL_ASM_OP}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_GLOBALIZE_DECL_NAME (FILE *@var{stream}, tree @var{decl})
+This target hook is a function to output to the stdio stream
+@var{stream} some commands that will make the name associated with @var{decl}
+global; that is, available for reference from other files.
+
+The default implementation uses the TARGET_ASM_GLOBALIZE_LABEL target hook.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_ASSEMBLE_UNDEFINED_DECL (FILE *@var{stream}, const char *@var{name}, const_tree @var{decl})
+This target hook is a function to output to the stdio stream
+@var{stream} some commands that will declare the name associated with
+@var{decl} which is not defined in the current translation unit. Most
+assemblers do not require anything to be output in this case.
+@end deftypefn
+
+@defmac ASM_WEAKEN_LABEL (@var{stream}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} some commands that will make the label @var{name} weak;
+that is, available for reference from other files but only used if
+no other definition is available. Use the expression
+@code{assemble_name (@var{stream}, @var{name})} to output the name
+itself; before and after that, output the additional assembler syntax
+for making that name weak, and a newline.
+
+If you don't define this macro or @code{ASM_WEAKEN_DECL}, GCC will not
+support weak symbols and you should not define the @code{SUPPORTS_WEAK}
+macro.
+@end defmac
+
+@defmac ASM_WEAKEN_DECL (@var{stream}, @var{decl}, @var{name}, @var{value})
+Combines (and replaces) the function of @code{ASM_WEAKEN_LABEL} and
+@code{ASM_OUTPUT_WEAK_ALIAS}, allowing access to the associated function
+or variable decl. If @var{value} is not @code{NULL}, this C statement
+should output to the stdio stream @var{stream} assembler code which
+defines (equates) the weak symbol @var{name} to have the value
+@var{value}. If @var{value} is @code{NULL}, it should output commands
+to make @var{name} weak.
+@end defmac
+
+@defmac ASM_OUTPUT_WEAKREF (@var{stream}, @var{decl}, @var{name}, @var{value})
+Outputs a directive that enables @var{name} to be used to refer to
+symbol @var{value} with weak-symbol semantics. @code{decl} is the
+declaration of @code{name}.
+@end defmac
+
+@defmac SUPPORTS_WEAK
+A preprocessor constant expression which evaluates to true if the target
+supports weak symbols.
+
+If you don't define this macro, @file{defaults.h} provides a default
+definition. If either @code{ASM_WEAKEN_LABEL} or @code{ASM_WEAKEN_DECL}
+is defined, the default definition is @samp{1}; otherwise, it is @samp{0}.
+@end defmac
+
+@defmac TARGET_SUPPORTS_WEAK
+A C expression which evaluates to true if the target supports weak symbols.
+
+If you don't define this macro, @file{defaults.h} provides a default
+definition. The default definition is @samp{(SUPPORTS_WEAK)}. Define
+this macro if you want to control weak symbol support with a compiler
+flag such as @option{-melf}.
+@end defmac
+
+@defmac MAKE_DECL_ONE_ONLY (@var{decl})
+A C statement (sans semicolon) to mark @var{decl} to be emitted as a
+public symbol such that extra copies in multiple translation units will
+be discarded by the linker. Define this macro if your object file
+format provides support for this concept, such as the @samp{COMDAT}
+section flags in the Microsoft Windows PE/COFF format, and this support
+requires changes to @var{decl}, such as putting it in a separate section.
+@end defmac
+
+@defmac SUPPORTS_ONE_ONLY
+A C expression which evaluates to true if the target supports one-only
+semantics.
+
+If you don't define this macro, @file{varasm.cc} provides a default
+definition. If @code{MAKE_DECL_ONE_ONLY} is defined, the default
+definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if
+you want to control one-only symbol support with a compiler flag, or if
+setting the @code{DECL_ONE_ONLY} flag is enough to mark a declaration to
+be emitted as one-only.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_ASSEMBLE_VISIBILITY (tree @var{decl}, int @var{visibility})
+This target hook is a function to output to @var{asm_out_file} some
+commands that will make the symbol(s) associated with @var{decl} have
+hidden, protected or internal visibility as specified by @var{visibility}.
+@end deftypefn
+
+@defmac TARGET_WEAK_NOT_IN_ARCHIVE_TOC
+A C expression that evaluates to true if the target's linker expects
+that weak symbols do not appear in a static archive's table of contents.
+The default is @code{0}.
+
+Leaving weak symbols out of an archive's table of contents means that,
+if a symbol will only have a definition in one translation unit and
+will have undefined references from other translation units, that
+symbol should not be weak. Defining this macro to be nonzero will
+thus have the effect that certain symbols that would normally be weak
+(explicit template instantiations, and vtables for polymorphic classes
+with noninline key methods) will instead be nonweak.
+
+The C++ ABI requires this macro to be zero. Define this macro for
+targets where full C++ ABI compliance is impossible and where linker
+restrictions require weak symbols to be left out of a static archive's
+table of contents.
+@end defmac
+
+@defmac ASM_OUTPUT_EXTERNAL (@var{stream}, @var{decl}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the name of an external
+symbol named @var{name} which is referenced in this compilation but
+not defined. The value of @var{decl} is the tree node for the
+declaration.
+
+This macro need not be defined if it does not need to output anything.
+The GNU assembler and most Unix assemblers don't require anything.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_EXTERNAL_LIBCALL (rtx @var{symref})
+This target hook is a function to output to @var{asm_out_file} an assembler
+pseudo-op to declare a library function name external. The name of the
+library function is given by @var{symref}, which is a @code{symbol_ref}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_MARK_DECL_PRESERVED (const char *@var{symbol})
+This target hook is a function to output to @var{asm_out_file} an assembler
+directive to annotate @var{symbol} as used. The Darwin target uses the
+.no_dead_code_strip directive.
+@end deftypefn
+
+@defmac ASM_OUTPUT_LABELREF (@var{stream}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} a reference in assembler syntax to a label named
+@var{name}. This should add @samp{_} to the front of the name, if that
+is customary on your operating system, as it is in most Berkeley Unix
+systems. This macro is used in @code{assemble_name}.
+@end defmac
+
+@deftypefn {Target Hook} tree TARGET_MANGLE_ASSEMBLER_NAME (const char *@var{name})
+Given a symbol @var{name}, perform same mangling as @code{varasm.cc}'s
+@code{assemble_name}, but in memory rather than to a file stream, returning
+result as an @code{IDENTIFIER_NODE}. Required for correct LTO symtabs. The
+default implementation calls the @code{TARGET_STRIP_NAME_ENCODING} hook and
+then prepends the @code{USER_LABEL_PREFIX}, if any.
+@end deftypefn
+
+@defmac ASM_OUTPUT_SYMBOL_REF (@var{stream}, @var{sym})
+A C statement (sans semicolon) to output a reference to
+@code{SYMBOL_REF} @var{sym}. If not defined, @code{assemble_name}
+will be used to output the name of the symbol. This macro may be used
+to modify the way a symbol is referenced depending on information
+encoded by @code{TARGET_ENCODE_SECTION_INFO}.
+@end defmac
+
+@defmac ASM_OUTPUT_LABEL_REF (@var{stream}, @var{buf})
+A C statement (sans semicolon) to output a reference to @var{buf}, the
+result of @code{ASM_GENERATE_INTERNAL_LABEL}. If not defined,
+@code{assemble_name} will be used to output the name of the symbol.
+This macro is not used by @code{output_asm_label}, or the @code{%l}
+specifier that calls it; the intention is that this macro should be set
+when it is necessary to output a label differently when its address is
+being taken.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_INTERNAL_LABEL (FILE *@var{stream}, const char *@var{prefix}, unsigned long @var{labelno})
+A function to output to the stdio stream @var{stream} a label whose
+name is made from the string @var{prefix} and the number @var{labelno}.
+
+It is absolutely essential that these labels be distinct from the labels
+used for user-level functions and variables. Otherwise, certain programs
+will have name conflicts with internal labels.
+
+It is desirable to exclude internal labels from the symbol table of the
+object file. Most assemblers have a naming convention for labels that
+should be excluded; on many systems, the letter @samp{L} at the
+beginning of a label has this effect. You should find out what
+convention your system uses, and follow it.
+
+The default version of this function utilizes @code{ASM_GENERATE_INTERNAL_LABEL}.
+@end deftypefn
+
+@defmac ASM_OUTPUT_DEBUG_LABEL (@var{stream}, @var{prefix}, @var{num})
+A C statement to output to the stdio stream @var{stream} a debug info
+label whose name is made from the string @var{prefix} and the number
+@var{num}. This is useful for VLIW targets, where debug info labels
+may need to be treated differently than branch target labels. On some
+systems, branch target labels must be at the beginning of instruction
+bundles, but debug info labels can occur in the middle of instruction
+bundles.
+
+If this macro is not defined, then @code{(*targetm.asm_out.internal_label)} will be
+used.
+@end defmac
+
+@defmac ASM_GENERATE_INTERNAL_LABEL (@var{string}, @var{prefix}, @var{num})
+A C statement to store into the string @var{string} a label whose name
+is made from the string @var{prefix} and the number @var{num}.
+
+This string, when output subsequently by @code{assemble_name}, should
+produce the output that @code{(*targetm.asm_out.internal_label)} would produce
+with the same @var{prefix} and @var{num}.
+
+If the string begins with @samp{*}, then @code{assemble_name} will
+output the rest of the string unchanged. It is often convenient for
+@code{ASM_GENERATE_INTERNAL_LABEL} to use @samp{*} in this way. If the
+string doesn't start with @samp{*}, then @code{ASM_OUTPUT_LABELREF} gets
+to output the string, and may change it. (Of course,
+@code{ASM_OUTPUT_LABELREF} is also part of your machine description, so
+you should know what it does on your machine.)
+@end defmac
+
+@defmac ASM_FORMAT_PRIVATE_NAME (@var{outvar}, @var{name}, @var{number})
+A C expression to assign to @var{outvar} (which is a variable of type
+@code{char *}) a newly allocated string made from the string
+@var{name} and the number @var{number}, with some suitable punctuation
+added. Use @code{alloca} to get space for the string.
+
+The string will be used as an argument to @code{ASM_OUTPUT_LABELREF} to
+produce an assembler label for an internal static variable whose name is
+@var{name}. Therefore, the string must be such as to result in valid
+assembler code. The argument @var{number} is different each time this
+macro is executed; it prevents conflicts between similarly-named
+internal static variables in different scopes.
+
+Ideally this string should not be a valid C identifier, to prevent any
+conflict with the user's own symbols. Most assemblers allow periods
+or percent signs in assembler symbols; putting at least one of these
+between the name and the number will suffice.
+
+If this macro is not defined, a default definition will be provided
+which is correct for most systems.
+@end defmac
+
+@defmac ASM_OUTPUT_DEF (@var{stream}, @var{name}, @var{value})
+A C statement to output to the stdio stream @var{stream} assembler code
+which defines (equates) the symbol @var{name} to have the value @var{value}.
+
+@findex SET_ASM_OP
+If @code{SET_ASM_OP} is defined, a default definition is provided which is
+correct for most systems.
+@end defmac
+
+@defmac ASM_OUTPUT_DEF_FROM_DECLS (@var{stream}, @var{decl_of_name}, @var{decl_of_value})
+A C statement to output to the stdio stream @var{stream} assembler code
+which defines (equates) the symbol whose tree node is @var{decl_of_name}
+to have the value of the tree node @var{decl_of_value}. This macro will
+be used in preference to @samp{ASM_OUTPUT_DEF} if it is defined and if
+the tree nodes are available.
+
+@findex SET_ASM_OP
+If @code{SET_ASM_OP} is defined, a default definition is provided which is
+correct for most systems.
+@end defmac
+
+@defmac TARGET_DEFERRED_OUTPUT_DEFS (@var{decl_of_name}, @var{decl_of_value})
+A C statement that evaluates to true if the assembler code which defines
+(equates) the symbol whose tree node is @var{decl_of_name} to have the value
+of the tree node @var{decl_of_value} should be emitted near the end of the
+current compilation unit. The default is to not defer output of defines.
+This macro affects defines output by @samp{ASM_OUTPUT_DEF} and
+@samp{ASM_OUTPUT_DEF_FROM_DECLS}.
+@end defmac
+
+@defmac ASM_OUTPUT_WEAK_ALIAS (@var{stream}, @var{name}, @var{value})
+A C statement to output to the stdio stream @var{stream} assembler code
+which defines (equates) the weak symbol @var{name} to have the value
+@var{value}. If @var{value} is @code{NULL}, it defines @var{name} as
+an undefined weak symbol.
+
+Define this macro if the target only supports weak aliases; define
+@code{ASM_OUTPUT_DEF} instead if possible.
+@end defmac
+
+@defmac OBJC_GEN_METHOD_LABEL (@var{buf}, @var{is_inst}, @var{class_name}, @var{cat_name}, @var{sel_name})
+Define this macro to override the default assembler names used for
+Objective-C methods.
+
+The default name is a unique method number followed by the name of the
+class (e.g.@: @samp{_1_Foo}). For methods in categories, the name of
+the category is also included in the assembler name (e.g.@:
+@samp{_1_Foo_Bar}).
+
+These names are safe on most systems, but make debugging difficult since
+the method's selector is not present in the name. Therefore, particular
+systems define other ways of computing names.
+
+@var{buf} is an expression of type @code{char *} which gives you a
+buffer in which to store the name; its length is as long as
+@var{class_name}, @var{cat_name} and @var{sel_name} put together, plus
+50 characters extra.
+
+The argument @var{is_inst} specifies whether the method is an instance
+method or a class method; @var{class_name} is the name of the class;
+@var{cat_name} is the name of the category (or @code{NULL} if the method is not
+in a category); and @var{sel_name} is the name of the selector.
+
+On systems where the assembler can handle quoted names, you can use this
+macro to provide more human-readable names.
+@end defmac
+
+@node Initialization
+@subsection How Initialization Functions Are Handled
+@cindex initialization routines
+@cindex termination routines
+@cindex constructors, output of
+@cindex destructors, output of
+
+The compiled code for certain languages includes @dfn{constructors}
+(also called @dfn{initialization routines})---functions to initialize
+data in the program when the program is started. These functions need
+to be called before the program is ``started''---that is to say, before
+@code{main} is called.
+
+Compiling some languages generates @dfn{destructors} (also called
+@dfn{termination routines}) that should be called when the program
+terminates.
+
+To make the initialization and termination functions work, the compiler
+must output something in the assembler code to cause those functions to
+be called at the appropriate time. When you port the compiler to a new
+system, you need to specify how to do this.
+
+There are two major ways that GCC currently supports the execution of
+initialization and termination functions. Each way has two variants.
+Much of the structure is common to all four variations.
+
+@findex __CTOR_LIST__
+@findex __DTOR_LIST__
+The linker must build two lists of these functions---a list of
+initialization functions, called @code{__CTOR_LIST__}, and a list of
+termination functions, called @code{__DTOR_LIST__}.
+
+Each list always begins with an ignored function pointer (which may hold
+0, @minus{}1, or a count of the function pointers after it, depending on
+the environment). This is followed by a series of zero or more function
+pointers to constructors (or destructors), followed by a function
+pointer containing zero.
+
+Depending on the operating system and its executable file format, either
+@file{crtstuff.c} or @file{libgcc2.c} traverses these lists at startup
+time and exit time. Constructors are called in reverse order of the
+list; destructors in forward order.
+
+The best way to handle static constructors works only for object file
+formats which provide arbitrarily-named sections. A section is set
+aside for a list of constructors, and another for a list of destructors.
+Traditionally these are called @samp{.ctors} and @samp{.dtors}. Each
+object file that defines an initialization function also puts a word in
+the constructor section to point to that function. The linker
+accumulates all these words into one contiguous @samp{.ctors} section.
+Termination functions are handled similarly.
+
+This method will be chosen as the default by @file{target-def.h} if
+@code{TARGET_ASM_NAMED_SECTION} is defined. A target that does not
+support arbitrary sections, but does support special designated
+constructor and destructor sections may define @code{CTORS_SECTION_ASM_OP}
+and @code{DTORS_SECTION_ASM_OP} to achieve the same effect.
+
+When arbitrary sections are available, there are two variants, depending
+upon how the code in @file{crtstuff.c} is called. On systems that
+support a @dfn{.init} section which is executed at program startup,
+parts of @file{crtstuff.c} are compiled into that section. The
+program is linked by the @command{gcc} driver like this:
+
+@smallexample
+ld -o @var{output_file} crti.o crtbegin.o @dots{} -lgcc crtend.o crtn.o
+@end smallexample
+
+The prologue of a function (@code{__init}) appears in the @code{.init}
+section of @file{crti.o}; the epilogue appears in @file{crtn.o}. Likewise
+for the function @code{__fini} in the @dfn{.fini} section. Normally these
+files are provided by the operating system or by the GNU C library, but
+are provided by GCC for a few targets.
+
+The objects @file{crtbegin.o} and @file{crtend.o} are (for most targets)
+compiled from @file{crtstuff.c}. They contain, among other things, code
+fragments within the @code{.init} and @code{.fini} sections that branch
+to routines in the @code{.text} section. The linker will pull all parts
+of a section together, which results in a complete @code{__init} function
+that invokes the routines we need at startup.
+
+To use this variant, you must define the @code{INIT_SECTION_ASM_OP}
+macro properly.
+
+If no init section is available, when GCC compiles any function called
+@code{main} (or more accurately, any function designated as a program
+entry point by the language front end calling @code{expand_main_function}),
+it inserts a procedure call to @code{__main} as the first executable code
+after the function prologue. The @code{__main} function is defined
+in @file{libgcc2.c} and runs the global constructors.
+
+In file formats that don't support arbitrary sections, there are again
+two variants. In the simplest variant, the GNU linker (GNU @code{ld})
+and an `a.out' format must be used. In this case,
+@code{TARGET_ASM_CONSTRUCTOR} is defined to produce a @code{.stabs}
+entry of type @samp{N_SETT}, referencing the name @code{__CTOR_LIST__},
+and with the address of the void function containing the initialization
+code as its value. The GNU linker recognizes this as a request to add
+the value to a @dfn{set}; the values are accumulated, and are eventually
+placed in the executable as a vector in the format described above, with
+a leading (ignored) count and a trailing zero element.
+@code{TARGET_ASM_DESTRUCTOR} is handled similarly. Since no init
+section is available, the absence of @code{INIT_SECTION_ASM_OP} causes
+the compilation of @code{main} to call @code{__main} as above, starting
+the initialization process.
+
+The last variant uses neither arbitrary sections nor the GNU linker.
+This is preferable when you want to do dynamic linking and when using
+file formats which the GNU linker does not support, such as `ECOFF'@. In
+this case, @code{TARGET_HAVE_CTORS_DTORS} is false, initialization and
+termination functions are recognized simply by their names. This requires
+an extra program in the linkage step, called @command{collect2}. This program
+pretends to be the linker, for use with GCC; it does its job by running
+the ordinary linker, but also arranges to include the vectors of
+initialization and termination functions. These functions are called
+via @code{__main} as described above. In order to use this method,
+@code{use_collect2} must be defined in the target in @file{config.gcc}.
+
+@ifinfo
+The following section describes the specific macros that control and
+customize the handling of initialization and termination functions.
+@end ifinfo
+
+@node Macros for Initialization
+@subsection Macros Controlling Initialization Routines
+
+Here are the macros that control how the compiler handles initialization
+and termination functions:
+
+@defmac INIT_SECTION_ASM_OP
+If defined, a C string constant, including spacing, for the assembler
+operation to identify the following data as initialization code. If not
+defined, GCC will assume such a section does not exist. When you are
+using special sections for initialization and termination functions, this
+macro also controls how @file{crtstuff.c} and @file{libgcc2.c} arrange to
+run the initialization functions.
+@end defmac
+
+@defmac HAS_INIT_SECTION
+If defined, @code{main} will not call @code{__main} as described above.
+This macro should be defined for systems that control start-up code
+on a symbol-by-symbol basis, such as OSF/1, and should not
+be defined explicitly for systems that support @code{INIT_SECTION_ASM_OP}.
+@end defmac
+
+@defmac LD_INIT_SWITCH
+If defined, a C string constant for a switch that tells the linker that
+the following symbol is an initialization routine.
+@end defmac
+
+@defmac LD_FINI_SWITCH
+If defined, a C string constant for a switch that tells the linker that
+the following symbol is a finalization routine.
+@end defmac
+
+@defmac COLLECT_SHARED_INIT_FUNC (@var{stream}, @var{func})
+If defined, a C statement that will write a function that can be
+automatically called when a shared library is loaded. The function
+should call @var{func}, which takes no arguments. If not defined, and
+the object format requires an explicit initialization function, then a
+function called @code{_GLOBAL__DI} will be generated.
+
+This function and the following one are used by collect2 when linking a
+shared library that needs constructors or destructors, or has DWARF2
+exception tables embedded in the code.
+@end defmac
+
+@defmac COLLECT_SHARED_FINI_FUNC (@var{stream}, @var{func})
+If defined, a C statement that will write a function that can be
+automatically called when a shared library is unloaded. The function
+should call @var{func}, which takes no arguments. If not defined, and
+the object format requires an explicit finalization function, then a
+function called @code{_GLOBAL__DD} will be generated.
+@end defmac
+
+@defmac INVOKE__main
+If defined, @code{main} will call @code{__main} despite the presence of
+@code{INIT_SECTION_ASM_OP}. This macro should be defined for systems
+where the init section is not actually run automatically, but is still
+useful for collecting the lists of constructors and destructors.
+@end defmac
+
+@defmac SUPPORTS_INIT_PRIORITY
+If nonzero, the C++ @code{init_priority} attribute is supported and the
+compiler should emit instructions to control the order of initialization
+of objects. If zero, the compiler will issue an error message upon
+encountering an @code{init_priority} attribute.
+@end defmac
+
+@deftypevr {Target Hook} bool TARGET_HAVE_CTORS_DTORS
+This value is true if the target supports some ``native'' method of
+collecting constructors and destructors to be run at startup and exit.
+It is false if we must use @command{collect2}.
+@end deftypevr
+
+@deftypevr {Target Hook} bool TARGET_DTORS_FROM_CXA_ATEXIT
+This value is true if the target wants destructors to be queued to be
+run from __cxa_atexit. If this is the case then, for each priority level,
+a new constructor will be entered that registers the destructors for that
+level with __cxa_atexit (and there will be no destructors emitted).
+It is false the method implied by @code{have_ctors_dtors} is used.
+@end deftypevr
+
+@deftypefn {Target Hook} void TARGET_ASM_CONSTRUCTOR (rtx @var{symbol}, int @var{priority})
+If defined, a function that outputs assembler code to arrange to call
+the function referenced by @var{symbol} at initialization time.
+
+Assume that @var{symbol} is a @code{SYMBOL_REF} for a function taking
+no arguments and with no return value. If the target supports initialization
+priorities, @var{priority} is a value between 0 and @code{MAX_INIT_PRIORITY};
+otherwise it must be @code{DEFAULT_INIT_PRIORITY}.
+
+If this macro is not defined by the target, a suitable default will
+be chosen if (1) the target supports arbitrary section names, (2) the
+target defines @code{CTORS_SECTION_ASM_OP}, or (3) @code{USE_COLLECT2}
+is not defined.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_DESTRUCTOR (rtx @var{symbol}, int @var{priority})
+This is like @code{TARGET_ASM_CONSTRUCTOR} but used for termination
+functions rather than initialization functions.
+@end deftypefn
+
+If @code{TARGET_HAVE_CTORS_DTORS} is true, the initialization routine
+generated for the generated object file will have static linkage.
+
+If your system uses @command{collect2} as the means of processing
+constructors, then that program normally uses @command{nm} to scan
+an object file for constructor functions to be called.
+
+On certain kinds of systems, you can define this macro to make
+@command{collect2} work faster (and, in some cases, make it work at all):
+
+@defmac OBJECT_FORMAT_COFF
+Define this macro if the system uses COFF (Common Object File Format)
+object files, so that @command{collect2} can assume this format and scan
+object files directly for dynamic constructor/destructor functions.
+
+This macro is effective only in a native compiler; @command{collect2} as
+part of a cross compiler always uses @command{nm} for the target machine.
+@end defmac
+
+@defmac REAL_NM_FILE_NAME
+Define this macro as a C string constant containing the file name to use
+to execute @command{nm}. The default is to search the path normally for
+@command{nm}.
+@end defmac
+
+@defmac NM_FLAGS
+@command{collect2} calls @command{nm} to scan object files for static
+constructors and destructors and LTO info. By default, @option{-n} is
+passed. Define @code{NM_FLAGS} to a C string constant if other options
+are needed to get the same output format as GNU @command{nm -n}
+produces.
+@end defmac
+
+If your system supports shared libraries and has a program to list the
+dynamic dependencies of a given library or executable, you can define
+these macros to enable support for running initialization and
+termination functions in shared libraries:
+
+@defmac LDD_SUFFIX
+Define this macro to a C string constant containing the name of the program
+which lists dynamic dependencies, like @command{ldd} under SunOS 4.
+@end defmac
+
+@defmac PARSE_LDD_OUTPUT (@var{ptr})
+Define this macro to be C code that extracts filenames from the output
+of the program denoted by @code{LDD_SUFFIX}. @var{ptr} is a variable
+of type @code{char *} that points to the beginning of a line of output
+from @code{LDD_SUFFIX}. If the line lists a dynamic dependency, the
+code must advance @var{ptr} to the beginning of the filename on that
+line. Otherwise, it must set @var{ptr} to @code{NULL}.
+@end defmac
+
+@defmac SHLIB_SUFFIX
+Define this macro to a C string constant containing the default shared
+library extension of the target (e.g., @samp{".so"}). @command{collect2}
+strips version information after this suffix when generating global
+constructor and destructor names. This define is only needed on targets
+that use @command{collect2} to process constructors and destructors.
+@end defmac
+
+@node Instruction Output
+@subsection Output of Assembler Instructions
+
+@c prevent bad page break with this line
+This describes assembler instruction output.
+
+@defmac REGISTER_NAMES
+A C initializer containing the assembler's names for the machine
+registers, each one as a C string constant. This is what translates
+register numbers in the compiler into assembler language.
+@end defmac
+
+@defmac ADDITIONAL_REGISTER_NAMES
+If defined, a C initializer for an array of structures containing a name
+and a register number. This macro defines additional names for hard
+registers, thus allowing the @code{asm} option in declarations to refer
+to registers using alternate names.
+@end defmac
+
+@defmac OVERLAPPING_REGISTER_NAMES
+If defined, a C initializer for an array of structures containing a
+name, a register number and a count of the number of consecutive
+machine registers the name overlaps. This macro defines additional
+names for hard registers, thus allowing the @code{asm} option in
+declarations to refer to registers using alternate names. Unlike
+@code{ADDITIONAL_REGISTER_NAMES}, this macro should be used when the
+register name implies multiple underlying registers.
+
+This macro should be used when it is important that a clobber in an
+@code{asm} statement clobbers all the underlying values implied by the
+register name. For example, on ARM, clobbering the double-precision
+VFP register ``d0'' implies clobbering both single-precision registers
+``s0'' and ``s1''.
+@end defmac
+
+@defmac ASM_OUTPUT_OPCODE (@var{stream}, @var{ptr})
+Define this macro if you are using an unusual assembler that
+requires different names for the machine instructions.
+
+The definition is a C statement or statements which output an
+assembler instruction opcode to the stdio stream @var{stream}. The
+macro-operand @var{ptr} is a variable of type @code{char *} which
+points to the opcode name in its ``internal'' form---the form that is
+written in the machine description. The definition should output the
+opcode name to @var{stream}, performing any translation you desire, and
+increment the variable @var{ptr} to point at the end of the opcode
+so that it will not be output twice.
+
+In fact, your macro definition may process less than the entire opcode
+name, or more than the opcode name; but if you want to process text
+that includes @samp{%}-sequences to substitute operands, you must take
+care of the substitution yourself. Just be sure to increment
+@var{ptr} over whatever text should not be output normally.
+
+@findex recog_data.operand
+If you need to look at the operand values, they can be found as the
+elements of @code{recog_data.operand}.
+
+If the macro definition does nothing, the instruction is output
+in the usual way.
+@end defmac
+
+@defmac FINAL_PRESCAN_INSN (@var{insn}, @var{opvec}, @var{noperands})
+If defined, a C statement to be executed just prior to the output of
+assembler code for @var{insn}, to modify the extracted operands so
+they will be output differently.
+
+Here the argument @var{opvec} is the vector containing the operands
+extracted from @var{insn}, and @var{noperands} is the number of
+elements of the vector which contain meaningful data for this insn.
+The contents of this vector are what will be used to convert the insn
+template into assembler code, so you can change the assembler output
+by changing the contents of the vector.
+
+This macro is useful when various assembler syntaxes share a single
+file of instruction patterns; by defining this macro differently, you
+can cause a large class of instructions to be output differently (such
+as with rearranged operands). Naturally, variations in assembler
+syntax affecting individual insn patterns ought to be handled by
+writing conditional output routines in those patterns.
+
+If this macro is not defined, it is equivalent to a null statement.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_FINAL_POSTSCAN_INSN (FILE *@var{file}, rtx_insn *@var{insn}, rtx *@var{opvec}, int @var{noperands})
+If defined, this target hook is a function which is executed just after the
+output of assembler code for @var{insn}, to change the mode of the assembler
+if necessary.
+
+Here the argument @var{opvec} is the vector containing the operands
+extracted from @var{insn}, and @var{noperands} is the number of
+elements of the vector which contain meaningful data for this insn.
+The contents of this vector are what was used to convert the insn
+template into assembler code, so you can change the assembler mode
+by checking the contents of the vector.
+@end deftypefn
+
+@defmac PRINT_OPERAND (@var{stream}, @var{x}, @var{code})
+A C compound statement to output to stdio stream @var{stream} the
+assembler syntax for an instruction operand @var{x}. @var{x} is an
+RTL expression.
+
+@var{code} is a value that can be used to specify one of several ways
+of printing the operand. It is used when identical operands must be
+printed differently depending on the context. @var{code} comes from
+the @samp{%} specification that was used to request printing of the
+operand. If the specification was just @samp{%@var{digit}} then
+@var{code} is 0; if the specification was @samp{%@var{ltr}
+@var{digit}} then @var{code} is the ASCII code for @var{ltr}.
+
+@findex reg_names
+If @var{x} is a register, this macro should print the register's name.
+The names can be found in an array @code{reg_names} whose type is
+@code{char *[]}. @code{reg_names} is initialized from
+@code{REGISTER_NAMES}.
+
+When the machine description has a specification @samp{%@var{punct}}
+(a @samp{%} followed by a punctuation character), this macro is called
+with a null pointer for @var{x} and the punctuation character for
+@var{code}.
+@end defmac
+
+@defmac PRINT_OPERAND_PUNCT_VALID_P (@var{code})
+A C expression which evaluates to true if @var{code} is a valid
+punctuation character for use in the @code{PRINT_OPERAND} macro. If
+@code{PRINT_OPERAND_PUNCT_VALID_P} is not defined, it means that no
+punctuation characters (except for the standard one, @samp{%}) are used
+in this way.
+@end defmac
+
+@defmac PRINT_OPERAND_ADDRESS (@var{stream}, @var{x})
+A C compound statement to output to stdio stream @var{stream} the
+assembler syntax for an instruction operand that is a memory reference
+whose address is @var{x}. @var{x} is an RTL expression.
+
+@cindex @code{TARGET_ENCODE_SECTION_INFO} usage
+On some machines, the syntax for a symbolic address depends on the
+section that the address refers to. On these machines, define the hook
+@code{TARGET_ENCODE_SECTION_INFO} to store the information into the
+@code{symbol_ref}, and then check for it here. @xref{Assembler
+Format}.
+@end defmac
+
+@findex dbr_sequence_length
+@defmac DBR_OUTPUT_SEQEND (@var{file})
+A C statement, to be executed after all slot-filler instructions have
+been output. If necessary, call @code{dbr_sequence_length} to
+determine the number of slots filled in a sequence (zero if not
+currently outputting a sequence), to decide how many no-ops to output,
+or whatever.
+
+Don't define this macro if it has nothing to do, but it is helpful in
+reading assembly output if the extent of the delay sequence is made
+explicit (e.g.@: with white space).
+@end defmac
+
+@findex final_sequence
+Note that output routines for instructions with delay slots must be
+prepared to deal with not being output as part of a sequence
+(i.e.@: when the scheduling pass is not run, or when no slot fillers could be
+found.) The variable @code{final_sequence} is null when not
+processing a sequence, otherwise it contains the @code{sequence} rtx
+being output.
+
+@findex asm_fprintf
+@defmac REGISTER_PREFIX
+@defmacx LOCAL_LABEL_PREFIX
+@defmacx USER_LABEL_PREFIX
+@defmacx IMMEDIATE_PREFIX
+If defined, C string expressions to be used for the @samp{%R}, @samp{%L},
+@samp{%U}, and @samp{%I} options of @code{asm_fprintf} (see
+@file{final.cc}). These are useful when a single @file{md} file must
+support multiple assembler formats. In that case, the various @file{tm.h}
+files can define these macros differently.
+@end defmac
+
+@defmac ASM_FPRINTF_EXTENSIONS (@var{file}, @var{argptr}, @var{format})
+If defined this macro should expand to a series of @code{case}
+statements which will be parsed inside the @code{switch} statement of
+the @code{asm_fprintf} function. This allows targets to define extra
+printf formats which may useful when generating their assembler
+statements. Note that uppercase letters are reserved for future
+generic extensions to asm_fprintf, and so are not available to target
+specific code. The output file is given by the parameter @var{file}.
+The varargs input pointer is @var{argptr} and the rest of the format
+string, starting the character after the one that is being switched
+upon, is pointed to by @var{format}.
+@end defmac
+
+@defmac ASSEMBLER_DIALECT
+If your target supports multiple dialects of assembler language (such as
+different opcodes), define this macro as a C expression that gives the
+numeric index of the assembler language dialect to use, with zero as the
+first variant.
+
+If this macro is defined, you may use constructs of the form
+@smallexample
+@samp{@{option0|option1|option2@dots{}@}}
+@end smallexample
+@noindent
+in the output templates of patterns (@pxref{Output Template}) or in the
+first argument of @code{asm_fprintf}. This construct outputs
+@samp{option0}, @samp{option1}, @samp{option2}, etc., if the value of
+@code{ASSEMBLER_DIALECT} is zero, one, two, etc. Any special characters
+within these strings retain their usual meaning. If there are fewer
+alternatives within the braces than the value of
+@code{ASSEMBLER_DIALECT}, the construct outputs nothing. If it's needed
+to print curly braces or @samp{|} character in assembler output directly,
+@samp{%@{}, @samp{%@}} and @samp{%|} can be used.
+
+If you do not define this macro, the characters @samp{@{}, @samp{|} and
+@samp{@}} do not have any special meaning when used in templates or
+operands to @code{asm_fprintf}.
+
+Define the macros @code{REGISTER_PREFIX}, @code{LOCAL_LABEL_PREFIX},
+@code{USER_LABEL_PREFIX} and @code{IMMEDIATE_PREFIX} if you can express
+the variations in assembler language syntax with that mechanism. Define
+@code{ASSEMBLER_DIALECT} and use the @samp{@{option0|option1@}} syntax
+if the syntax variant are larger and involve such things as different
+opcodes or operand order.
+@end defmac
+
+@defmac ASM_OUTPUT_REG_PUSH (@var{stream}, @var{regno})
+A C expression to output to @var{stream} some assembler code
+which will push hard register number @var{regno} onto the stack.
+The code need not be optimal, since this macro is used only when
+profiling.
+@end defmac
+
+@defmac ASM_OUTPUT_REG_POP (@var{stream}, @var{regno})
+A C expression to output to @var{stream} some assembler code
+which will pop hard register number @var{regno} off of the stack.
+The code need not be optimal, since this macro is used only when
+profiling.
+@end defmac
+
+@node Dispatch Tables
+@subsection Output of Dispatch Tables
+
+@c prevent bad page break with this line
+This concerns dispatch tables.
+
+@cindex dispatch table
+@defmac ASM_OUTPUT_ADDR_DIFF_ELT (@var{stream}, @var{body}, @var{value}, @var{rel})
+A C statement to output to the stdio stream @var{stream} an assembler
+pseudo-instruction to generate a difference between two labels.
+@var{value} and @var{rel} are the numbers of two internal labels. The
+definitions of these labels are output using
+@code{(*targetm.asm_out.internal_label)}, and they must be printed in the same
+way here. For example,
+
+@smallexample
+fprintf (@var{stream}, "\t.word L%d-L%d\n",
+ @var{value}, @var{rel})
+@end smallexample
+
+You must provide this macro on machines where the addresses in a
+dispatch table are relative to the table's own address. If defined, GCC
+will also use this macro on all machines when producing PIC@.
+@var{body} is the body of the @code{ADDR_DIFF_VEC}; it is provided so that the
+mode and flags can be read.
+@end defmac
+
+@defmac ASM_OUTPUT_ADDR_VEC_ELT (@var{stream}, @var{value})
+This macro should be provided on machines where the addresses
+in a dispatch table are absolute.
+
+The definition should be a C statement to output to the stdio stream
+@var{stream} an assembler pseudo-instruction to generate a reference to
+a label. @var{value} is the number of an internal label whose
+definition is output using @code{(*targetm.asm_out.internal_label)}.
+For example,
+
+@smallexample
+fprintf (@var{stream}, "\t.word L%d\n", @var{value})
+@end smallexample
+@end defmac
+
+@defmac ASM_OUTPUT_CASE_LABEL (@var{stream}, @var{prefix}, @var{num}, @var{table})
+Define this if the label before a jump-table needs to be output
+specially. The first three arguments are the same as for
+@code{(*targetm.asm_out.internal_label)}; the fourth argument is the
+jump-table which follows (a @code{jump_table_data} containing an
+@code{addr_vec} or @code{addr_diff_vec}).
+
+This feature is used on system V to output a @code{swbeg} statement
+for the table.
+
+If this macro is not defined, these labels are output with
+@code{(*targetm.asm_out.internal_label)}.
+@end defmac
+
+@defmac ASM_OUTPUT_CASE_END (@var{stream}, @var{num}, @var{table})
+Define this if something special must be output at the end of a
+jump-table. The definition should be a C statement to be executed
+after the assembler code for the table is written. It should write
+the appropriate code to stdio stream @var{stream}. The argument
+@var{table} is the jump-table insn, and @var{num} is the label-number
+of the preceding label.
+
+If this macro is not defined, nothing special is output at the end of
+the jump-table.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_POST_CFI_STARTPROC (FILE *@var{}, @var{tree})
+This target hook is used to emit assembly strings required by the target
+after the .cfi_startproc directive. The first argument is the file stream to
+write the strings to and the second argument is the function's declaration. The
+expected use is to add more .cfi_* directives.
+
+The default is to not output any assembly strings.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_EMIT_UNWIND_LABEL (FILE *@var{stream}, tree @var{decl}, int @var{for_eh}, int @var{empty})
+This target hook emits a label at the beginning of each FDE@. It
+should be defined on targets where FDEs need special labels, and it
+should write the appropriate label, for the FDE associated with the
+function declaration @var{decl}, to the stdio stream @var{stream}.
+The third argument, @var{for_eh}, is a boolean: true if this is for an
+exception table. The fourth argument, @var{empty}, is a boolean:
+true if this is a placeholder label for an omitted FDE@.
+
+The default is that FDEs are not given nonlocal labels.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_EMIT_EXCEPT_TABLE_LABEL (FILE *@var{stream})
+This target hook emits a label at the beginning of the exception table.
+It should be defined on targets where it is desirable for the table
+to be broken up according to function.
+
+The default is that no label is emitted.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_EMIT_EXCEPT_PERSONALITY (rtx @var{personality})
+If the target implements @code{TARGET_ASM_UNWIND_EMIT}, this hook may be
+used to emit a directive to install a personality hook into the unwind
+info. This hook should not be used if dwarf2 unwind info is used.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ASM_UNWIND_EMIT (FILE *@var{stream}, rtx_insn *@var{insn})
+This target hook emits assembly directives required to unwind the
+given instruction. This is only used when @code{TARGET_EXCEPT_UNWIND_INFO}
+returns @code{UI_TARGET}.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_ASM_MAKE_EH_SYMBOL_INDIRECT (rtx @var{origsymbol}, bool @var{pubvis})
+If necessary, modify personality and LSDA references to handle indirection.
+The original symbol is in @code{origsymbol} and if @code{pubvis} is true
+the symbol is visible outside the TU.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_ASM_UNWIND_EMIT_BEFORE_INSN
+True if the @code{TARGET_ASM_UNWIND_EMIT} hook should be called before
+the assembly for @var{insn} has been emitted, false if the hook should
+be called afterward.
+@end deftypevr
+
+@deftypefn {Target Hook} bool TARGET_ASM_SHOULD_RESTORE_CFA_STATE (void)
+For DWARF-based unwind frames, two CFI instructions provide for save and
+restore of register state. GCC maintains the current frame address (CFA)
+separately from the register bank but the unwinder in libgcc preserves this
+state along with the registers (and this is expected by the code that writes
+the unwind frames). This hook allows the target to specify that the CFA data
+is not saved/restored along with the registers by the target unwinder so that
+suitable additional instructions should be emitted to restore it.
+@end deftypefn
+
+@node Exception Region Output
+@subsection Assembler Commands for Exception Regions
+
+@c prevent bad page break with this line
+
+This describes commands marking the start and the end of an exception
+region.
+
+@defmac EH_FRAME_SECTION_NAME
+If defined, a C string constant for the name of the section containing
+exception handling frame unwind information. If not defined, GCC will
+provide a default definition if the target supports named sections.
+@file{crtstuff.c} uses this macro to switch to the appropriate section.
+
+You should define this symbol if your target supports DWARF 2 frame
+unwind information and the default definition does not work.
+@end defmac
+
+@defmac EH_FRAME_THROUGH_COLLECT2
+If defined, DWARF 2 frame unwind information will identified by
+specially named labels. The collect2 process will locate these
+labels and generate code to register the frames.
+
+This might be necessary, for instance, if the system linker will not
+place the eh_frames in-between the sentinals from @file{crtstuff.c},
+or if the system linker does garbage collection and sections cannot
+be marked as not to be collected.
+@end defmac
+
+@defmac EH_TABLES_CAN_BE_READ_ONLY
+Define this macro to 1 if your target is such that no frame unwind
+information encoding used with non-PIC code will ever require a
+runtime relocation, but the linker may not support merging read-only
+and read-write sections into a single read-write section.
+@end defmac
+
+@defmac MASK_RETURN_ADDR
+An rtx used to mask the return address found via @code{RETURN_ADDR_RTX}, so
+that it does not contain any extraneous set bits in it.
+@end defmac
+
+@defmac DWARF2_UNWIND_INFO
+Define this macro to 0 if your target supports DWARF 2 frame unwind
+information, but it does not yet work with exception handling.
+Otherwise, if your target supports this information (if it defines
+@code{INCOMING_RETURN_ADDR_RTX} and @code{OBJECT_FORMAT_ELF}),
+GCC will provide a default definition of 1.
+@end defmac
+
+@deftypefn {Common Target Hook} {enum unwind_info_type} TARGET_EXCEPT_UNWIND_INFO (struct gcc_options *@var{opts})
+This hook defines the mechanism that will be used for exception handling
+by the target. If the target has ABI specified unwind tables, the hook
+should return @code{UI_TARGET}. If the target is to use the
+@code{setjmp}/@code{longjmp}-based exception handling scheme, the hook
+should return @code{UI_SJLJ}. If the target supports DWARF 2 frame unwind
+information, the hook should return @code{UI_DWARF2}.
+
+A target may, if exceptions are disabled, choose to return @code{UI_NONE}.
+This may end up simplifying other parts of target-specific code. The
+default implementation of this hook never returns @code{UI_NONE}.
+
+Note that the value returned by this hook should be constant. It should
+not depend on anything except the command-line switches described by
+@var{opts}. In particular, the
+setting @code{UI_SJLJ} must be fixed at compiler start-up as C pre-processor
+macros and builtin functions related to exception handling are set up
+depending on this setting.
+
+The default implementation of the hook first honors the
+@option{--enable-sjlj-exceptions} configure option, then
+@code{DWARF2_UNWIND_INFO}, and finally defaults to @code{UI_SJLJ}. If
+@code{DWARF2_UNWIND_INFO} depends on command-line options, the target
+must define this hook so that @var{opts} is used correctly.
+@end deftypefn
+
+@deftypevr {Common Target Hook} bool TARGET_UNWIND_TABLES_DEFAULT
+This variable should be set to @code{true} if the target ABI requires unwinding
+tables even when exceptions are not used. It must not be modified by
+command-line option processing.
+@end deftypevr
+
+@defmac DONT_USE_BUILTIN_SETJMP
+Define this macro to 1 if the @code{setjmp}/@code{longjmp}-based scheme
+should use the @code{setjmp}/@code{longjmp} functions from the C library
+instead of the @code{__builtin_setjmp}/@code{__builtin_longjmp} machinery.
+@end defmac
+
+@defmac JMP_BUF_SIZE
+This macro has no effect unless @code{DONT_USE_BUILTIN_SETJMP} is also
+defined. Define this macro if the default size of @code{jmp_buf} buffer
+for the @code{setjmp}/@code{longjmp}-based exception handling mechanism
+is not large enough, or if it is much too large.
+The default size is @code{FIRST_PSEUDO_REGISTER * sizeof(void *)}.
+@end defmac
+
+@defmac DWARF_CIE_DATA_ALIGNMENT
+This macro need only be defined if the target might save registers in the
+function prologue at an offset to the stack pointer that is not aligned to
+@code{UNITS_PER_WORD}. The definition should be the negative minimum
+alignment if @code{STACK_GROWS_DOWNWARD} is true, and the positive
+minimum alignment otherwise. @xref{DWARF}. Only applicable if
+the target supports DWARF 2 frame unwind information.
+@end defmac
+
+@deftypevr {Target Hook} bool TARGET_TERMINATE_DW2_EH_FRAME_INFO
+Contains the value true if the target should add a zero word onto the
+end of a Dwarf-2 frame info section when used for exception handling.
+Default value is false if @code{EH_FRAME_SECTION_NAME} is defined, and
+true otherwise.
+@end deftypevr
+
+@deftypefn {Target Hook} rtx TARGET_DWARF_REGISTER_SPAN (rtx @var{reg})
+Given a register, this hook should return a parallel of registers to
+represent where to find the register pieces. Define this hook if the
+register and its mode are represented in Dwarf in non-contiguous
+locations, or if the register should be represented in more than one
+register in Dwarf. Otherwise, this hook should return @code{NULL_RTX}.
+If not defined, the default is to return @code{NULL_RTX}.
+@end deftypefn
+
+@deftypefn {Target Hook} machine_mode TARGET_DWARF_FRAME_REG_MODE (int @var{regno})
+Given a register, this hook should return the mode which the
+corresponding Dwarf frame register should have. This is normally
+used to return a smaller mode than the raw mode to prevent call
+clobbered parts of a register altering the frame register size
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_INIT_DWARF_REG_SIZES_EXTRA (tree @var{address})
+If some registers are represented in Dwarf-2 unwind information in
+multiple pieces, define this hook to fill in information about the
+sizes of those pieces in the table used by the unwinder at runtime.
+It will be called by @code{expand_builtin_init_dwarf_reg_sizes} after
+filling in a single size corresponding to each hard register;
+@var{address} is the address of the table.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ASM_TTYPE (rtx @var{sym})
+This hook is used to output a reference from a frame unwinding table to
+the type_info object identified by @var{sym}. It should return @code{true}
+if the reference was output. Returning @code{false} will cause the
+reference to be output using the normal Dwarf2 routines.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_ARM_EABI_UNWINDER
+This flag should be set to @code{true} on targets that use an ARM EABI
+based unwinding library, and @code{false} on other targets. This effects
+the format of unwinding tables, and how the unwinder in entered after
+running a cleanup. The default is @code{false}.
+@end deftypevr
+
+@node Alignment Output
+@subsection Assembler Commands for Alignment
+
+@c prevent bad page break with this line
+This describes commands for alignment.
+
+@defmac JUMP_ALIGN (@var{label})
+The alignment (log base 2) to put in front of @var{label}, which is
+a common destination of jumps and has no fallthru incoming edge.
+
+This macro need not be defined if you don't want any special alignment
+to be done at such a time. Most machine descriptions do not currently
+define the macro.
+
+Unless it's necessary to inspect the @var{label} parameter, it is better
+to set the variable @var{align_jumps} in the target's
+@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's
+selection in @var{align_jumps} in a @code{JUMP_ALIGN} implementation.
+@end defmac
+
+@defmac LABEL_ALIGN_AFTER_BARRIER (@var{label})
+The alignment (log base 2) to put in front of @var{label}, which follows
+a @code{BARRIER}.
+
+This macro need not be defined if you don't want any special alignment
+to be done at such a time. Most machine descriptions do not currently
+define the macro.
+@end defmac
+
+@defmac LOOP_ALIGN (@var{label})
+The alignment (log base 2) to put in front of @var{label} that heads
+a frequently executed basic block (usually the header of a loop).
+
+This macro need not be defined if you don't want any special alignment
+to be done at such a time. Most machine descriptions do not currently
+define the macro.
+
+Unless it's necessary to inspect the @var{label} parameter, it is better
+to set the variable @code{align_loops} in the target's
+@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's
+selection in @code{align_loops} in a @code{LOOP_ALIGN} implementation.
+@end defmac
+
+@defmac LABEL_ALIGN (@var{label})
+The alignment (log base 2) to put in front of @var{label}.
+If @code{LABEL_ALIGN_AFTER_BARRIER} / @code{LOOP_ALIGN} specify a different alignment,
+the maximum of the specified values is used.
+
+Unless it's necessary to inspect the @var{label} parameter, it is better
+to set the variable @code{align_labels} in the target's
+@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's
+selection in @code{align_labels} in a @code{LABEL_ALIGN} implementation.
+@end defmac
+
+@defmac ASM_OUTPUT_SKIP (@var{stream}, @var{nbytes})
+A C statement to output to the stdio stream @var{stream} an assembler
+instruction to advance the location counter by @var{nbytes} bytes.
+Those bytes should be zero when loaded. @var{nbytes} will be a C
+expression of type @code{unsigned HOST_WIDE_INT}.
+@end defmac
+
+@defmac ASM_NO_SKIP_IN_TEXT
+Define this macro if @code{ASM_OUTPUT_SKIP} should not be used in the
+text section because it fails to put zeros in the bytes that are skipped.
+This is true on many Unix systems, where the pseudo--op to skip bytes
+produces no-op instructions rather than zeros when used in the text
+section.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGN (@var{stream}, @var{power})
+A C statement to output to the stdio stream @var{stream} an assembler
+command to advance the location counter to a multiple of 2 to the
+@var{power} bytes. @var{power} will be a C expression of type @code{int}.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGN_WITH_NOP (@var{stream}, @var{power})
+Like @code{ASM_OUTPUT_ALIGN}, except that the ``nop'' instruction is used
+for padding, if necessary.
+@end defmac
+
+@defmac ASM_OUTPUT_MAX_SKIP_ALIGN (@var{stream}, @var{power}, @var{max_skip})
+A C statement to output to the stdio stream @var{stream} an assembler
+command to advance the location counter to a multiple of 2 to the
+@var{power} bytes, but only if @var{max_skip} or fewer bytes are needed to
+satisfy the alignment request. @var{power} and @var{max_skip} will be
+a C expression of type @code{int}.
+@end defmac
+
+@need 3000
+@node Debugging Info
+@section Controlling Debugging Information Format
+
+@c prevent bad page break with this line
+This describes how to specify debugging information.
+
+@menu
+* All Debuggers:: Macros that affect all debugging formats uniformly.
+* DWARF:: Macros for DWARF format.
+* VMS Debug:: Macros for VMS debug format.
+* CTF Debug:: Macros for CTF debug format.
+* BTF Debug:: Macros for BTF debug format.
+@end menu
+
+@node All Debuggers
+@subsection Macros Affecting All Debugging Formats
+
+@c prevent bad page break with this line
+These macros affect all debugging formats.
+
+@defmac DEBUGGER_REGNO (@var{regno})
+A C expression that returns the debugger register number for the compiler
+register number @var{regno}. In the default macro provided, the value
+of this expression will be @var{regno} itself. But sometimes there are
+some registers that the compiler knows about and debugger does not, or vice
+versa. In such cases, some register may need to have one number in the
+compiler and another for debugger@.
+
+If two registers have consecutive numbers inside GCC, and they can be
+used as a pair to hold a multiword value, then they @emph{must} have
+consecutive numbers after renumbering with @code{DEBUGGER_REGNO}.
+Otherwise, debuggers will be unable to access such a pair, because they
+expect register pairs to be consecutive in their own numbering scheme.
+
+If you find yourself defining @code{DEBUGGER_REGNO} in way that
+does not preserve register pairs, then what you must do instead is
+redefine the actual register numbering scheme.
+@end defmac
+
+@defmac DEBUGGER_AUTO_OFFSET (@var{x})
+A C expression that returns the integer offset value for an automatic
+variable having address @var{x} (an RTL expression). The default
+computation assumes that @var{x} is based on the frame-pointer and
+gives the offset from the frame-pointer. This is required for targets
+that produce debugging output for debugger and allow the frame-pointer to be
+eliminated when the @option{-g} option is used.
+@end defmac
+
+@defmac DEBUGGER_ARG_OFFSET (@var{offset}, @var{x})
+A C expression that returns the integer offset value for an argument
+having address @var{x} (an RTL expression). The nominal offset is
+@var{offset}.
+@end defmac
+
+@defmac PREFERRED_DEBUGGING_TYPE
+A C expression that returns the type of debugging output GCC should
+produce when the user specifies just @option{-g}. Define
+this if you have arranged for GCC to support more than one format of
+debugging output. Currently, the allowable values are
+@code{DWARF2_DEBUG}, @code{VMS_DEBUG},
+and @code{VMS_AND_DWARF2_DEBUG}.
+
+When the user specifies @option{-ggdb}, GCC normally also uses the
+value of this macro to select the debugging output format, but with two
+exceptions. If @code{DWARF2_DEBUGGING_INFO} is defined, GCC uses the
+value @code{DWARF2_DEBUG}.
+
+The value of this macro only affects the default debugging output; the
+user can always get a specific type of output by using @option{-gdwarf-2},
+or @option{-gvms}.
+@end defmac
+
+@defmac DEFAULT_GDB_EXTENSIONS
+Define this macro to control whether GCC should by default generate
+GDB's extended version of debugging information. If you don't define the
+macro, the default is 1: always generate the extended information
+if there is any occasion to.
+@end defmac
+
+@need 2000
+@node DWARF
+@subsection Macros for DWARF Output
+
+@c prevent bad page break with this line
+Here are macros for DWARF output.
+
+@defmac DWARF2_DEBUGGING_INFO
+Define this macro if GCC should produce dwarf version 2 format
+debugging output in response to the @option{-g} option.
+
+To support optional call frame debugging information, you must also
+define @code{INCOMING_RETURN_ADDR_RTX} and either set
+@code{RTX_FRAME_RELATED_P} on the prologue insns if you use RTL for the
+prologue, or call @code{dwarf2out_def_cfa} and @code{dwarf2out_reg_save}
+as appropriate from @code{TARGET_ASM_FUNCTION_PROLOGUE} if you don't.
+@end defmac
+
+@deftypefn {Target Hook} int TARGET_DWARF_CALLING_CONVENTION (const_tree @var{function})
+Define this to enable the dwarf attribute @code{DW_AT_calling_convention} to
+be emitted for each function. Instead of an integer return the enum
+value for the @code{DW_CC_} tag.
+@end deftypefn
+
+@defmac DWARF2_FRAME_INFO
+Define this macro to a nonzero value if GCC should always output
+Dwarf 2 frame information. If @code{TARGET_EXCEPT_UNWIND_INFO}
+(@pxref{Exception Region Output}) returns @code{UI_DWARF2}, and
+exceptions are enabled, GCC will output this information not matter
+how you define @code{DWARF2_FRAME_INFO}.
+@end defmac
+
+@deftypefn {Target Hook} {enum unwind_info_type} TARGET_DEBUG_UNWIND_INFO (void)
+This hook defines the mechanism that will be used for describing frame
+unwind information to the debugger. Normally the hook will return
+@code{UI_DWARF2} if DWARF 2 debug information is enabled, and
+return @code{UI_NONE} otherwise.
+
+A target may return @code{UI_DWARF2} even when DWARF 2 debug information
+is disabled in order to always output DWARF 2 frame information.
+
+A target may return @code{UI_TARGET} if it has ABI specified unwind tables.
+This will suppress generation of the normal debug frame unwind information.
+@end deftypefn
+
+@defmac DWARF2_ASM_LINE_DEBUG_INFO
+Define this macro to be a nonzero value if the assembler can generate Dwarf 2
+line debug info sections. This will result in much more compact line number
+tables, and hence is desirable if it works.
+@end defmac
+
+@defmac DWARF2_ASM_VIEW_DEBUG_INFO
+Define this macro to be a nonzero value if the assembler supports view
+assignment and verification in @code{.loc}. If it does not, but the
+user enables location views, the compiler may have to fallback to
+internal line number tables.
+@end defmac
+
+@deftypefn {Target Hook} int TARGET_RESET_LOCATION_VIEW (rtx_insn *@var{})
+This hook, if defined, enables -ginternal-reset-location-views, and
+uses its result to override cases in which the estimated min insn
+length might be nonzero even when a PC advance (i.e., a view reset)
+cannot be taken for granted.
+
+If the hook is defined, it must return a positive value to indicate
+the insn definitely advances the PC, and so the view number can be
+safely assumed to be reset; a negative value to mean the insn
+definitely does not advance the PC, and os the view number must not
+be reset; or zero to decide based on the estimated insn length.
+
+If insn length is to be regarded as reliable, set the hook to
+@code{hook_int_rtx_insn_0}.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_WANT_DEBUG_PUB_SECTIONS
+True if the @code{.debug_pubtypes} and @code{.debug_pubnames} sections
+should be emitted. These sections are not used on most platforms, and
+in particular GDB does not use them.
+@end deftypevr
+
+@deftypevr {Target Hook} bool TARGET_DELAY_SCHED2
+True if sched2 is not to be run at its normal place.
+This usually means it will be run as part of machine-specific reorg.
+@end deftypevr
+
+@deftypevr {Target Hook} bool TARGET_DELAY_VARTRACK
+True if vartrack is not to be run at its normal place.
+This usually means it will be run as part of machine-specific reorg.
+@end deftypevr
+
+@deftypevr {Target Hook} bool TARGET_NO_REGISTER_ALLOCATION
+True if register allocation and the passes
+following it should not be run. Usually true only for virtual assembler
+targets.
+@end deftypevr
+
+@defmac ASM_OUTPUT_DWARF_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2})
+A C statement to issue assembly directives that create a difference
+@var{lab1} minus @var{lab2}, using an integer of the given @var{size}.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_VMS_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2})
+A C statement to issue assembly directives that create a difference
+between the two given labels in system defined units, e.g.@: instruction
+slots on IA64 VMS, using an integer of the given size.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_OFFSET (@var{stream}, @var{size}, @var{label}, @var{offset}, @var{section})
+A C statement to issue assembly directives that create a
+section-relative reference to the given @var{label} plus @var{offset}, using
+an integer of the given @var{size}. The label is known to be defined in the
+given @var{section}.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_PCREL (@var{stream}, @var{size}, @var{label})
+A C statement to issue assembly directives that create a self-relative
+reference to the given @var{label}, using an integer of the given @var{size}.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_DATAREL (@var{stream}, @var{size}, @var{label})
+A C statement to issue assembly directives that create a reference to the
+given @var{label} relative to the dbase, using an integer of the given @var{size}.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_TABLE_REF (@var{label})
+A C statement to issue assembly directives that create a reference to
+the DWARF table identifier @var{label} from the current section. This
+is used on some systems to avoid garbage collecting a DWARF table which
+is referenced by a function.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_ASM_OUTPUT_DWARF_DTPREL (FILE *@var{file}, int @var{size}, rtx @var{x})
+If defined, this target hook is a function which outputs a DTP-relative
+reference to the given TLS symbol of the specified size.
+@end deftypefn
+
+@need 2000
+@node VMS Debug
+@subsection Macros for VMS Debug Format
+
+@c prevent bad page break with this line
+Here are macros for VMS debug format.
+
+@defmac VMS_DEBUGGING_INFO
+Define this macro if GCC should produce debugging output for VMS
+in response to the @option{-g} option. The default behavior for VMS
+is to generate minimal debug info for a traceback in the absence of
+@option{-g} unless explicitly overridden with @option{-g0}. This
+behavior is controlled by @code{TARGET_OPTION_OPTIMIZATION} and
+@code{TARGET_OPTION_OVERRIDE}.
+@end defmac
+
+@need 2000
+@node CTF Debug
+@subsection Macros for CTF Debug Format
+
+@c prevent bad page break with this line
+Here are macros for CTF debug format.
+
+@defmac CTF_DEBUGGING_INFO
+Define this macro if GCC should produce debugging output in CTF debug
+format in response to the @option{-gctf} option.
+@end defmac
+
+@need 2000
+@node BTF Debug
+@subsection Macros for BTF Debug Format
+
+@c prevent bad page break with this line
+Here are macros for BTF debug format.
+
+@defmac BTF_DEBUGGING_INFO
+Define this macro if GCC should produce debugging output in BTF debug
+format in response to the @option{-gbtf} option.
+@end defmac
+
+@node Floating Point
+@section Cross Compilation and Floating Point
+@cindex cross compilation and floating point
+@cindex floating point and cross compilation
+
+While all modern machines use twos-complement representation for integers,
+there are a variety of representations for floating point numbers. This
+means that in a cross-compiler the representation of floating point numbers
+in the compiled program may be different from that used in the machine
+doing the compilation.
+
+Because different representation systems may offer different amounts of
+range and precision, all floating point constants must be represented in
+the target machine's format. Therefore, the cross compiler cannot
+safely use the host machine's floating point arithmetic; it must emulate
+the target's arithmetic. To ensure consistency, GCC always uses
+emulation to work with floating point values, even when the host and
+target floating point formats are identical.
+
+The following macros are provided by @file{real.h} for the compiler to
+use. All parts of the compiler which generate or optimize
+floating-point calculations must use these macros. They may evaluate
+their operands more than once, so operands must not have side effects.
+
+@defmac REAL_VALUE_TYPE
+The C data type to be used to hold a floating point value in the target
+machine's format. Typically this is a @code{struct} containing an
+array of @code{HOST_WIDE_INT}, but all code should treat it as an opaque
+quantity.
+@end defmac
+
+@deftypefn Macro HOST_WIDE_INT REAL_VALUE_FIX (REAL_VALUE_TYPE @var{x})
+Truncates @var{x} to a signed integer, rounding toward zero.
+@end deftypefn
+
+@deftypefn Macro {unsigned HOST_WIDE_INT} REAL_VALUE_UNSIGNED_FIX (REAL_VALUE_TYPE @var{x})
+Truncates @var{x} to an unsigned integer, rounding toward zero. If
+@var{x} is negative, returns zero.
+@end deftypefn
+
+@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ATOF (const char *@var{string}, machine_mode @var{mode})
+Converts @var{string} into a floating point number in the target machine's
+representation for mode @var{mode}. This routine can handle both
+decimal and hexadecimal floating point constants, using the syntax
+defined by the C language for both.
+@end deftypefn
+
+@deftypefn Macro int REAL_VALUE_NEGATIVE (REAL_VALUE_TYPE @var{x})
+Returns 1 if @var{x} is negative (including negative zero), 0 otherwise.
+@end deftypefn
+
+@deftypefn Macro int REAL_VALUE_ISINF (REAL_VALUE_TYPE @var{x})
+Determines whether @var{x} represents infinity (positive or negative).
+@end deftypefn
+
+@deftypefn Macro int REAL_VALUE_ISNAN (REAL_VALUE_TYPE @var{x})
+Determines whether @var{x} represents a ``NaN'' (not-a-number).
+@end deftypefn
+
+@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_NEGATE (REAL_VALUE_TYPE @var{x})
+Returns the negative of the floating point value @var{x}.
+@end deftypefn
+
+@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ABS (REAL_VALUE_TYPE @var{x})
+Returns the absolute value of @var{x}.
+@end deftypefn
+
+@node Mode Switching
+@section Mode Switching Instructions
+@cindex mode switching
+The following macros control mode switching optimizations:
+
+@defmac OPTIMIZE_MODE_SWITCHING (@var{entity})
+Define this macro if the port needs extra instructions inserted for mode
+switching in an optimizing compilation.
+
+For an example, the SH4 can perform both single and double precision
+floating point operations, but to perform a single precision operation,
+the FPSCR PR bit has to be cleared, while for a double precision
+operation, this bit has to be set. Changing the PR bit requires a general
+purpose register as a scratch register, hence these FPSCR sets have to
+be inserted before reload, i.e.@: you cannot put this into instruction emitting
+or @code{TARGET_MACHINE_DEPENDENT_REORG}.
+
+You can have multiple entities that are mode-switched, and select at run time
+which entities actually need it. @code{OPTIMIZE_MODE_SWITCHING} should
+return nonzero for any @var{entity} that needs mode-switching.
+If you define this macro, you also have to define
+@code{NUM_MODES_FOR_MODE_SWITCHING}, @code{TARGET_MODE_NEEDED},
+@code{TARGET_MODE_PRIORITY} and @code{TARGET_MODE_EMIT}.
+@code{TARGET_MODE_AFTER}, @code{TARGET_MODE_ENTRY}, and @code{TARGET_MODE_EXIT}
+are optional.
+@end defmac
+
+@defmac NUM_MODES_FOR_MODE_SWITCHING
+If you define @code{OPTIMIZE_MODE_SWITCHING}, you have to define this as
+initializer for an array of integers. Each initializer element
+N refers to an entity that needs mode switching, and specifies the number
+of different modes that might need to be set for this entity.
+The position of the initializer in the initializer---starting counting at
+zero---determines the integer that is used to refer to the mode-switched
+entity in question.
+In macros that take mode arguments / yield a mode result, modes are
+represented as numbers 0 @dots{} N @minus{} 1. N is used to specify that no mode
+switch is needed / supplied.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_MODE_EMIT (int @var{entity}, int @var{mode}, int @var{prev_mode}, HARD_REG_SET @var{regs_live})
+Generate one or more insns to set @var{entity} to @var{mode}.
+@var{hard_reg_live} is the set of hard registers live at the point where
+the insn(s) are to be inserted. @var{prev_moxde} indicates the mode
+to switch from. Sets of a lower numbered entity will be emitted before
+sets of a higher numbered entity to a mode of the same or lower priority.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_MODE_NEEDED (int @var{entity}, rtx_insn *@var{insn})
+@var{entity} is an integer specifying a mode-switched entity.
+If @code{OPTIMIZE_MODE_SWITCHING} is defined, you must define this macro
+to return an integer value not larger than the corresponding element
+in @code{NUM_MODES_FOR_MODE_SWITCHING}, to denote the mode that @var{entity}
+must be switched into prior to the execution of @var{insn}.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_MODE_AFTER (int @var{entity}, int @var{mode}, rtx_insn *@var{insn})
+@var{entity} is an integer specifying a mode-switched entity.
+If this macro is defined, it is evaluated for every @var{insn} during mode
+switching. It determines the mode that an insn results
+in (if different from the incoming mode).
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_MODE_ENTRY (int @var{entity})
+If this macro is defined, it is evaluated for every @var{entity} that
+needs mode switching. It should evaluate to an integer, which is a mode
+that @var{entity} is assumed to be switched to at function entry.
+If @code{TARGET_MODE_ENTRY} is defined then @code{TARGET_MODE_EXIT}
+must be defined.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_MODE_EXIT (int @var{entity})
+If this macro is defined, it is evaluated for every @var{entity} that
+needs mode switching. It should evaluate to an integer, which is a mode
+that @var{entity} is assumed to be switched to at function exit.
+If @code{TARGET_MODE_EXIT} is defined then @code{TARGET_MODE_ENTRY}
+must be defined.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_MODE_PRIORITY (int @var{entity}, int @var{n})
+This macro specifies the order in which modes for @var{entity}
+are processed. 0 is the highest priority,
+@code{NUM_MODES_FOR_MODE_SWITCHING[@var{entity}] - 1} the lowest.
+The value of the macro should be an integer designating a mode
+for @var{entity}. For any fixed @var{entity}, @code{mode_priority}
+(@var{entity}, @var{n}) shall be a bijection in 0 @dots{}
+@code{num_modes_for_mode_switching[@var{entity}] - 1}.
+@end deftypefn
+
+@node Target Attributes
+@section Defining target-specific uses of @code{__attribute__}
+@cindex target attributes
+@cindex machine attributes
+@cindex attributes, target-specific
+
+Target-specific attributes may be defined for functions, data and types.
+These are described using the following target hooks; they also need to
+be documented in @file{extend.texi}.
+
+@deftypevr {Target Hook} {const struct attribute_spec *} TARGET_ATTRIBUTE_TABLE
+If defined, this target hook points to an array of @samp{struct
+attribute_spec} (defined in @file{tree-core.h}) specifying the machine
+specific attributes for this target and some of the restrictions on the
+entities to which these attributes are applied and the arguments they
+take.
+@end deftypevr
+
+@deftypefn {Target Hook} bool TARGET_ATTRIBUTE_TAKES_IDENTIFIER_P (const_tree @var{name})
+If defined, this target hook is a function which returns true if the
+machine-specific attribute named @var{name} expects an identifier
+given as its first argument to be passed on as a plain identifier, not
+subjected to name lookup. If this is not defined, the default is
+false for all machine-specific attributes.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_COMP_TYPE_ATTRIBUTES (const_tree @var{type1}, const_tree @var{type2})
+If defined, this target hook is a function which returns zero if the attributes on
+@var{type1} and @var{type2} are incompatible, one if they are compatible,
+and two if they are nearly compatible (which causes a warning to be
+generated). If this is not defined, machine-specific attributes are
+supposed always to be compatible.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SET_DEFAULT_TYPE_ATTRIBUTES (tree @var{type})
+If defined, this target hook is a function which assigns default attributes to
+the newly defined @var{type}.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_MERGE_TYPE_ATTRIBUTES (tree @var{type1}, tree @var{type2})
+Define this target hook if the merging of type attributes needs special
+handling. If defined, the result is a list of the combined
+@code{TYPE_ATTRIBUTES} of @var{type1} and @var{type2}. It is assumed
+that @code{comptypes} has already been called and returned 1. This
+function may call @code{merge_attributes} to handle machine-independent
+merging.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_MERGE_DECL_ATTRIBUTES (tree @var{olddecl}, tree @var{newdecl})
+Define this target hook if the merging of decl attributes needs special
+handling. If defined, the result is a list of the combined
+@code{DECL_ATTRIBUTES} of @var{olddecl} and @var{newdecl}.
+@var{newdecl} is a duplicate declaration of @var{olddecl}. Examples of
+when this is needed are when one attribute overrides another, or when an
+attribute is nullified by a subsequent definition. This function may
+call @code{merge_attributes} to handle machine-independent merging.
+
+@findex TARGET_DLLIMPORT_DECL_ATTRIBUTES
+If the only target-specific handling you require is @samp{dllimport}
+for Microsoft Windows targets, you should define the macro
+@code{TARGET_DLLIMPORT_DECL_ATTRIBUTES} to @code{1}. The compiler
+will then define a function called
+@code{merge_dllimport_decl_attributes} which can then be defined as
+the expansion of @code{TARGET_MERGE_DECL_ATTRIBUTES}. You can also
+add @code{handle_dll_attribute} in the attribute table for your port
+to perform initial processing of the @samp{dllimport} and
+@samp{dllexport} attributes. This is done in @file{i386/cygwin.h} and
+@file{i386/i386.cc}, for example.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_VALID_DLLIMPORT_ATTRIBUTE_P (const_tree @var{decl})
+@var{decl} is a variable or function with @code{__attribute__((dllimport))}
+specified. Use this hook if the target needs to add extra validation
+checks to @code{handle_dll_attribute}.
+@end deftypefn
+
+@defmac TARGET_DECLSPEC
+Define this macro to a nonzero value if you want to treat
+@code{__declspec(X)} as equivalent to @code{__attribute((X))}. By
+default, this behavior is enabled only for targets that define
+@code{TARGET_DLLIMPORT_DECL_ATTRIBUTES}. The current implementation
+of @code{__declspec} is via a built-in macro, but you should not rely
+on this implementation detail.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_INSERT_ATTRIBUTES (tree @var{node}, tree *@var{attr_ptr})
+Define this target hook if you want to be able to add attributes to a decl
+when it is being created. This is normally useful for back ends which
+wish to implement a pragma by using the attributes which correspond to
+the pragma's effect. The @var{node} argument is the decl which is being
+created. The @var{attr_ptr} argument is a pointer to the attribute list
+for this decl. The list itself should not be modified, since it may be
+shared with other decls, but attributes may be chained on the head of
+the list and @code{*@var{attr_ptr}} modified to point to the new
+attributes, or a copy of the list may be made if further changes are
+needed.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_HANDLE_GENERIC_ATTRIBUTE (tree *@var{node}, tree @var{name}, tree @var{args}, int @var{flags}, bool *@var{no_add_attrs})
+Define this target hook if you want to be able to perform additional
+target-specific processing of an attribute which is handled generically
+by a front end. The arguments are the same as those which are passed to
+attribute handlers. So far this only affects the @var{noinit} and
+@var{section} attribute.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_FUNCTION_ATTRIBUTE_INLINABLE_P (const_tree @var{fndecl})
+@cindex inlining
+This target hook returns @code{true} if it is OK to inline @var{fndecl}
+into the current function, despite its having target-specific
+attributes, @code{false} otherwise. By default, if a function has a
+target specific attribute attached to it, it will not be inlined.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_OPTION_VALID_ATTRIBUTE_P (tree @var{fndecl}, tree @var{name}, tree @var{args}, int @var{flags})
+This hook is called to parse @code{attribute(target("..."))}, which
+allows setting target-specific options on individual functions.
+These function-specific options may differ
+from the options specified on the command line. The hook should return
+@code{true} if the options are valid.
+
+The hook should set the @code{DECL_FUNCTION_SPECIFIC_TARGET} field in
+the function declaration to hold a pointer to a target-specific
+@code{struct cl_target_option} structure.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_OPTION_SAVE (struct cl_target_option *@var{ptr}, struct gcc_options *@var{opts}, struct gcc_options *@var{opts_set})
+This hook is called to save any additional target-specific information
+in the @code{struct cl_target_option} structure for function-specific
+options from the @code{struct gcc_options} structure.
+@xref{Option file format}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_OPTION_RESTORE (struct gcc_options *@var{opts}, struct gcc_options *@var{opts_set}, struct cl_target_option *@var{ptr})
+This hook is called to restore any additional target-specific
+information in the @code{struct cl_target_option} structure for
+function-specific options to the @code{struct gcc_options} structure.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_OPTION_POST_STREAM_IN (struct cl_target_option *@var{ptr})
+This hook is called to update target-specific information in the
+@code{struct cl_target_option} structure after it is streamed in from
+LTO bytecode.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_OPTION_PRINT (FILE *@var{file}, int @var{indent}, struct cl_target_option *@var{ptr})
+This hook is called to print any additional target-specific
+information in the @code{struct cl_target_option} structure for
+function-specific options.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_OPTION_PRAGMA_PARSE (tree @var{args}, tree @var{pop_target})
+This target hook parses the options for @code{#pragma GCC target}, which
+sets the target-specific options for functions that occur later in the
+input stream. The options accepted should be the same as those handled by the
+@code{TARGET_OPTION_VALID_ATTRIBUTE_P} hook.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_OPTION_OVERRIDE (void)
+Sometimes certain combinations of command options do not make sense on
+a particular target machine. You can override the hook
+@code{TARGET_OPTION_OVERRIDE} to take account of this. This hooks is called
+once just after all the command options have been parsed.
+
+Don't use this hook to turn on various extra optimizations for
+@option{-O}. That is what @code{TARGET_OPTION_OPTIMIZATION} is for.
+
+If you need to do something whenever the optimization level is
+changed via the optimize attribute or pragma, see
+@code{TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE}
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_OPTION_FUNCTION_VERSIONS (tree @var{decl1}, tree @var{decl2})
+This target hook returns @code{true} if @var{DECL1} and @var{DECL2} are
+versions of the same function. @var{DECL1} and @var{DECL2} are function
+versions if and only if they have the same function signature and
+different target specific attributes, that is, they are compiled for
+different target machines.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CAN_INLINE_P (tree @var{caller}, tree @var{callee})
+This target hook returns @code{false} if the @var{caller} function
+cannot inline @var{callee}, based on target specific information. By
+default, inlining is not allowed if the callee function has function
+specific target options and the caller does not use the same options.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_UPDATE_IPA_FN_TARGET_INFO (unsigned int& @var{info}, const gimple* @var{stmt})
+Allow target to analyze all gimple statements for the given function to
+record and update some target specific information for inlining. A typical
+example is that a caller with one isa feature disabled is normally not
+allowed to inline a callee with that same isa feature enabled even which is
+attributed by always_inline, but with the conservative analysis on all
+statements of the callee if we are able to guarantee the callee does not
+exploit any instructions from the mismatch isa feature, it would be safe to
+allow the caller to inline the callee.
+@var{info} is one @code{unsigned int} value to record information in which
+one set bit indicates one corresponding feature is detected in the analysis,
+@var{stmt} is the statement being analyzed. Return true if target still
+need to analyze the subsequent statements, otherwise return false to stop
+subsequent analysis.
+The default version of this hook returns false.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_NEED_IPA_FN_TARGET_INFO (const_tree @var{decl}, unsigned int& @var{info})
+Allow target to check early whether it is necessary to analyze all gimple
+statements in the given function to update target specific information for
+inlining. See hook @code{update_ipa_fn_target_info} for usage example of
+target specific information. This hook is expected to be invoked ahead of
+the iterating with hook @code{update_ipa_fn_target_info}.
+@var{decl} is the function being analyzed, @var{info} is the same as what
+in hook @code{update_ipa_fn_target_info}, target can do one time update
+into @var{info} without iterating for some case. Return true if target
+decides to analyze all gimple statements to collect information, otherwise
+return false.
+The default version of this hook returns false.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_RELAYOUT_FUNCTION (tree @var{fndecl})
+This target hook fixes function @var{fndecl} after attributes are processed.
+Default does nothing. On ARM, the default function's alignment is updated
+with the attribute target.
+@end deftypefn
+
+@node Emulated TLS
+@section Emulating TLS
+@cindex Emulated TLS
+
+For targets whose psABI does not provide Thread Local Storage via
+specific relocations and instruction sequences, an emulation layer is
+used. A set of target hooks allows this emulation layer to be
+configured for the requirements of a particular target. For instance
+the psABI may in fact specify TLS support in terms of an emulation
+layer.
+
+The emulation layer works by creating a control object for every TLS
+object. To access the TLS object, a lookup function is provided
+which, when given the address of the control object, will return the
+address of the current thread's instance of the TLS object.
+
+@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_GET_ADDRESS
+Contains the name of the helper function that uses a TLS control
+object to locate a TLS instance. The default causes libgcc's
+emulated TLS helper function to be used.
+@end deftypevr
+
+@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_REGISTER_COMMON
+Contains the name of the helper function that should be used at
+program startup to register TLS objects that are implicitly
+initialized to zero. If this is @code{NULL}, all TLS objects will
+have explicit initializers. The default causes libgcc's emulated TLS
+registration function to be used.
+@end deftypevr
+
+@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_VAR_SECTION
+Contains the name of the section in which TLS control variables should
+be placed. The default of @code{NULL} allows these to be placed in
+any section.
+@end deftypevr
+
+@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_TMPL_SECTION
+Contains the name of the section in which TLS initializers should be
+placed. The default of @code{NULL} allows these to be placed in any
+section.
+@end deftypevr
+
+@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_VAR_PREFIX
+Contains the prefix to be prepended to TLS control variable names.
+The default of @code{NULL} uses a target-specific prefix.
+@end deftypevr
+
+@deftypevr {Target Hook} {const char *} TARGET_EMUTLS_TMPL_PREFIX
+Contains the prefix to be prepended to TLS initializer objects. The
+default of @code{NULL} uses a target-specific prefix.
+@end deftypevr
+
+@deftypefn {Target Hook} tree TARGET_EMUTLS_VAR_FIELDS (tree @var{type}, tree *@var{name})
+Specifies a function that generates the FIELD_DECLs for a TLS control
+object type. @var{type} is the RECORD_TYPE the fields are for and
+@var{name} should be filled with the structure tag, if the default of
+@code{__emutls_object} is unsuitable. The default creates a type suitable
+for libgcc's emulated TLS function.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_EMUTLS_VAR_INIT (tree @var{var}, tree @var{decl}, tree @var{tmpl_addr})
+Specifies a function that generates the CONSTRUCTOR to initialize a
+TLS control object. @var{var} is the TLS control object, @var{decl}
+is the TLS object and @var{tmpl_addr} is the address of the
+initializer. The default initializes libgcc's emulated TLS control object.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_EMUTLS_VAR_ALIGN_FIXED
+Specifies whether the alignment of TLS control variable objects is
+fixed and should not be increased as some backends may do to optimize
+single objects. The default is false.
+@end deftypevr
+
+@deftypevr {Target Hook} bool TARGET_EMUTLS_DEBUG_FORM_TLS_ADDRESS
+Specifies whether a DWARF @code{DW_OP_form_tls_address} location descriptor
+may be used to describe emulated TLS control objects.
+@end deftypevr
+
+@node MIPS Coprocessors
+@section Defining coprocessor specifics for MIPS targets.
+@cindex MIPS coprocessor-definition macros
+
+The MIPS specification allows MIPS implementations to have as many as 4
+coprocessors, each with as many as 32 private registers. GCC supports
+accessing these registers and transferring values between the registers
+and memory using asm-ized variables. For example:
+
+@smallexample
+ register unsigned int cp0count asm ("c0r1");
+ unsigned int d;
+
+ d = cp0count + 3;
+@end smallexample
+
+(``c0r1'' is the default name of register 1 in coprocessor 0; alternate
+names may be added as described below, or the default names may be
+overridden entirely in @code{SUBTARGET_CONDITIONAL_REGISTER_USAGE}.)
+
+Coprocessor registers are assumed to be epilogue-used; sets to them will
+be preserved even if it does not appear that the register is used again
+later in the function.
+
+Another note: according to the MIPS spec, coprocessor 1 (if present) is
+the FPU@. One accesses COP1 registers through standard mips
+floating-point support; they are not included in this mechanism.
+
+@node PCH Target
+@section Parameters for Precompiled Header Validity Checking
+@cindex parameters, precompiled headers
+
+@deftypefn {Target Hook} {void *} TARGET_GET_PCH_VALIDITY (size_t *@var{sz})
+This hook returns a pointer to the data needed by
+@code{TARGET_PCH_VALID_P} and sets
+@samp{*@var{sz}} to the size of the data in bytes.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_PCH_VALID_P (const void *@var{data}, size_t @var{sz})
+This hook checks whether the options used to create a PCH file are
+compatible with the current settings. It returns @code{NULL}
+if so and a suitable error message if not. Error messages will
+be presented to the user and must be localized using @samp{_(@var{msg})}.
+
+@var{data} is the data that was returned by @code{TARGET_GET_PCH_VALIDITY}
+when the PCH file was created and @var{sz} is the size of that data in bytes.
+It's safe to assume that the data was created by the same version of the
+compiler, so no format checking is needed.
+
+The default definition of @code{default_pch_valid_p} should be
+suitable for most targets.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_CHECK_PCH_TARGET_FLAGS (int @var{pch_flags})
+If this hook is nonnull, the default implementation of
+@code{TARGET_PCH_VALID_P} will use it to check for compatible values
+of @code{target_flags}. @var{pch_flags} specifies the value that
+@code{target_flags} had when the PCH file was created. The return
+value is the same as for @code{TARGET_PCH_VALID_P}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_PREPARE_PCH_SAVE (void)
+Called before writing out a PCH file. If the target has some
+garbage-collected data that needs to be in a particular state on PCH loads,
+it can use this hook to enforce that state. Very few targets need
+to do anything here.
+@end deftypefn
+
+@node C++ ABI
+@section C++ ABI parameters
+@cindex parameters, c++ abi
+
+@deftypefn {Target Hook} tree TARGET_CXX_GUARD_TYPE (void)
+Define this hook to override the integer type used for guard variables.
+These are used to implement one-time construction of static objects. The
+default is long_long_integer_type_node.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CXX_GUARD_MASK_BIT (void)
+This hook determines how guard variables are used. It should return
+@code{false} (the default) if the first byte should be used. A return value of
+@code{true} indicates that only the least significant bit should be used.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_CXX_GET_COOKIE_SIZE (tree @var{type})
+This hook returns the size of the cookie to use when allocating an array
+whose elements have the indicated @var{type}. Assumes that it is already
+known that a cookie is needed. The default is
+@code{max(sizeof (size_t), alignof(type))}, as defined in section 2.7 of the
+IA64/Generic C++ ABI@.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CXX_COOKIE_HAS_SIZE (void)
+This hook should return @code{true} if the element size should be stored in
+array cookies. The default is to return @code{false}.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_CXX_IMPORT_EXPORT_CLASS (tree @var{type}, int @var{import_export})
+If defined by a backend this hook allows the decision made to export
+class @var{type} to be overruled. Upon entry @var{import_export}
+will contain 1 if the class is going to be exported, @minus{}1 if it is going
+to be imported and 0 otherwise. This function should return the
+modified value and perform any other actions necessary to support the
+backend's targeted operating system.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CXX_CDTOR_RETURNS_THIS (void)
+This hook should return @code{true} if constructors and destructors return
+the address of the object created/destroyed. The default is to return
+@code{false}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CXX_KEY_METHOD_MAY_BE_INLINE (void)
+This hook returns true if the key method for a class (i.e., the method
+which, if defined in the current translation unit, causes the virtual
+table to be emitted) may be an inline function. Under the standard
+Itanium C++ ABI the key method may be an inline function so long as
+the function is not declared inline in the class definition. Under
+some variants of the ABI, an inline function can never be the key
+method. The default is to return @code{true}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_CXX_DETERMINE_CLASS_DATA_VISIBILITY (tree @var{decl})
+@var{decl} is a virtual table, virtual table table, typeinfo object,
+or other similar implicit class data object that will be emitted with
+external linkage in this translation unit. No ELF visibility has been
+explicitly specified. If the target needs to specify a visibility
+other than that of the containing class, use this hook to set
+@code{DECL_VISIBILITY} and @code{DECL_VISIBILITY_SPECIFIED}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CXX_CLASS_DATA_ALWAYS_COMDAT (void)
+This hook returns true (the default) if virtual tables and other
+similar implicit class data objects are always COMDAT if they have
+external linkage. If this hook returns false, then class data for
+classes whose virtual table will be emitted in only one translation
+unit will not be COMDAT.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CXX_LIBRARY_RTTI_COMDAT (void)
+This hook returns true (the default) if the RTTI information for
+the basic types which is defined in the C++ runtime should always
+be COMDAT, false if it should not be COMDAT.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CXX_USE_AEABI_ATEXIT (void)
+This hook returns true if @code{__aeabi_atexit} (as defined by the ARM EABI)
+should be used to register static destructors when @option{-fuse-cxa-atexit}
+is in effect. The default is to return false to use @code{__cxa_atexit}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT (void)
+This hook returns true if the target @code{atexit} function can be used
+in the same manner as @code{__cxa_atexit} to register C++ static
+destructors. This requires that @code{atexit}-registered functions in
+shared libraries are run in the correct order when the libraries are
+unloaded. The default is to return false.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_CXX_ADJUST_CLASS_AT_DEFINITION (tree @var{type})
+@var{type} is a C++ class (i.e., RECORD_TYPE or UNION_TYPE) that has just
+been defined. Use this hook to make adjustments to the class (eg, tweak
+visibility or perform any other required target modifications).
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_CXX_DECL_MANGLING_CONTEXT (const_tree @var{decl})
+Return target-specific mangling context of @var{decl} or @code{NULL_TREE}.
+@end deftypefn
+
+@node D Language and ABI
+@section D ABI parameters
+@cindex parameters, d abi
+
+@deftypefn {D Target Hook} void TARGET_D_CPU_VERSIONS (void)
+Declare all environmental version identifiers relating to the target CPU
+using the function @code{builtin_version}, which takes a string representing
+the name of the version. Version identifiers predefined by this hook apply
+to all modules that are being compiled and imported.
+@end deftypefn
+
+@deftypefn {D Target Hook} void TARGET_D_OS_VERSIONS (void)
+Similarly to @code{TARGET_D_CPU_VERSIONS}, but is used for versions
+relating to the target operating system.
+@end deftypefn
+
+@deftypefn {D Target Hook} void TARGET_D_REGISTER_CPU_TARGET_INFO (void)
+Register all target information keys relating to the target CPU using the
+function @code{d_add_target_info_handlers}, which takes a
+@samp{struct d_target_info_spec} (defined in @file{d/d-target.h}). The keys
+added by this hook are made available at compile time by the
+@code{__traits(getTargetInfo)} extension, the result is an expression
+describing the requested target information.
+@end deftypefn
+
+@deftypefn {D Target Hook} void TARGET_D_REGISTER_OS_TARGET_INFO (void)
+Same as @code{TARGET_D_CPU_TARGET_INFO}, but is used for keys relating to
+the target operating system.
+@end deftypefn
+
+@deftypevr {D Target Hook} {const char *} TARGET_D_MINFO_SECTION
+Contains the name of the section in which module info references should be
+placed. By default, the compiler puts all module info symbols in the
+@code{"minfo"} section. Define this macro to override the string if a
+different section name should be used. This section is expected to be
+bracketed by two symbols @code{TARGET_D_MINFO_SECTION_START} and
+@code{TARGET_D_MINFO_SECTION_END} to indicate the start and end address of
+the section, so that the runtime library can collect all modules for each
+loaded shared library and executable. Setting the value to @code{NULL}
+disables the use of sections for storing module info altogether.
+@end deftypevr
+
+@deftypevr {D Target Hook} {const char *} TARGET_D_MINFO_SECTION_START
+If @code{TARGET_D_MINFO_SECTION} is defined, then this must also be defined
+as the name of the symbol indicating the start address of the module info
+section
+@end deftypevr
+
+@deftypevr {D Target Hook} {const char *} TARGET_D_MINFO_SECTION_END
+If @code{TARGET_D_MINFO_SECTION} is defined, then this must also be defined
+as the name of the symbol indicating the end address of the module info
+section
+@end deftypevr
+
+@deftypefn {D Target Hook} bool TARGET_D_HAS_STDCALL_CONVENTION (unsigned int *@var{link_system}, unsigned int *@var{link_windows})
+Returns @code{true} if the target supports the stdcall calling convention.
+The hook should also set @var{link_system} to @code{1} if the @code{stdcall}
+attribute should be applied to functions with @code{extern(System)} linkage,
+and @var{link_windows} to @code{1} to apply @code{stdcall} to functions with
+@code{extern(Windows)} linkage.
+@end deftypefn
+
+@deftypevr {D Target Hook} bool TARGET_D_TEMPLATES_ALWAYS_COMDAT
+This flag is true if instantiated functions and variables are always COMDAT
+if they have external linkage. If this flag is false, then instantiated
+decls will be emitted as weak symbols. The default is @code{false}.
+@end deftypevr
+
+@node Named Address Spaces
+@section Adding support for named address spaces
+@cindex named address spaces
+
+The draft technical report of the ISO/IEC JTC1 S22 WG14 N1275
+standards committee, @cite{Programming Languages - C - Extensions to
+support embedded processors}, specifies a syntax for embedded
+processors to specify alternate address spaces. You can configure a
+GCC port to support section 5.1 of the draft report to add support for
+address spaces other than the default address space. These address
+spaces are new keywords that are similar to the @code{volatile} and
+@code{const} type attributes.
+
+Pointers to named address spaces can have a different size than
+pointers to the generic address space.
+
+For example, the SPU port uses the @code{__ea} address space to refer
+to memory in the host processor, rather than memory local to the SPU
+processor. Access to memory in the @code{__ea} address space involves
+issuing DMA operations to move data between the host processor and the
+local processor memory address space. Pointers in the @code{__ea}
+address space are either 32 bits or 64 bits based on the
+@option{-mea32} or @option{-mea64} switches (native SPU pointers are
+always 32 bits).
+
+Internally, address spaces are represented as a small integer in the
+range 0 to 15 with address space 0 being reserved for the generic
+address space.
+
+To register a named address space qualifier keyword with the C front end,
+the target may call the @code{c_register_addr_space} routine. For example,
+the SPU port uses the following to declare @code{__ea} as the keyword for
+named address space #1:
+@smallexample
+#define ADDR_SPACE_EA 1
+c_register_addr_space ("__ea", ADDR_SPACE_EA);
+@end smallexample
+
+@deftypefn {Target Hook} scalar_int_mode TARGET_ADDR_SPACE_POINTER_MODE (addr_space_t @var{address_space})
+Define this to return the machine mode to use for pointers to
+@var{address_space} if the target supports named address spaces.
+The default version of this hook returns @code{ptr_mode}.
+@end deftypefn
+
+@deftypefn {Target Hook} scalar_int_mode TARGET_ADDR_SPACE_ADDRESS_MODE (addr_space_t @var{address_space})
+Define this to return the machine mode to use for addresses in
+@var{address_space} if the target supports named address spaces.
+The default version of this hook returns @code{Pmode}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ADDR_SPACE_VALID_POINTER_MODE (scalar_int_mode @var{mode}, addr_space_t @var{as})
+Define this to return nonzero if the port can handle pointers
+with machine mode @var{mode} to address space @var{as}. This target
+hook is the same as the @code{TARGET_VALID_POINTER_MODE} target hook,
+except that it includes explicit named address space support. The default
+version of this hook returns true for the modes returned by either the
+@code{TARGET_ADDR_SPACE_POINTER_MODE} or @code{TARGET_ADDR_SPACE_ADDRESS_MODE}
+target hooks for the given address space.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ADDR_SPACE_LEGITIMATE_ADDRESS_P (machine_mode @var{mode}, rtx @var{exp}, bool @var{strict}, addr_space_t @var{as})
+Define this to return true if @var{exp} is a valid address for mode
+@var{mode} in the named address space @var{as}. The @var{strict}
+parameter says whether strict addressing is in effect after reload has
+finished. This target hook is the same as the
+@code{TARGET_LEGITIMATE_ADDRESS_P} target hook, except that it includes
+explicit named address space support.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_ADDR_SPACE_LEGITIMIZE_ADDRESS (rtx @var{x}, rtx @var{oldx}, machine_mode @var{mode}, addr_space_t @var{as})
+Define this to modify an invalid address @var{x} to be a valid address
+with mode @var{mode} in the named address space @var{as}. This target
+hook is the same as the @code{TARGET_LEGITIMIZE_ADDRESS} target hook,
+except that it includes explicit named address space support.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ADDR_SPACE_SUBSET_P (addr_space_t @var{subset}, addr_space_t @var{superset})
+Define this to return whether the @var{subset} named address space is
+contained within the @var{superset} named address space. Pointers to
+a named address space that is a subset of another named address space
+will be converted automatically without a cast if used together in
+arithmetic operations. Pointers to a superset address space can be
+converted to pointers to a subset address space via explicit casts.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID (addr_space_t @var{as})
+Define this to modify the default handling of address 0 for the
+address space. Return true if 0 should be considered a valid address.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_ADDR_SPACE_CONVERT (rtx @var{op}, tree @var{from_type}, tree @var{to_type})
+Define this to convert the pointer expression represented by the RTL
+@var{op} with type @var{from_type} that points to a named address
+space to a new pointer expression with type @var{to_type} that points
+to a different named address space. When this hook it called, it is
+guaranteed that one of the two address spaces is a subset of the other,
+as determined by the @code{TARGET_ADDR_SPACE_SUBSET_P} target hook.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_ADDR_SPACE_DEBUG (addr_space_t @var{as})
+Define this to define how the address space is encoded in dwarf.
+The result is the value to be used with @code{DW_AT_address_class}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ADDR_SPACE_DIAGNOSE_USAGE (addr_space_t @var{as}, location_t @var{loc})
+Define this hook if the availability of an address space depends on
+command line options and some diagnostics should be printed when the
+address space is used. This hook is called during parsing and allows
+to emit a better diagnostic compared to the case where the address space
+was not registered with @code{c_register_addr_space}. @var{as} is
+the address space as registered with @code{c_register_addr_space}.
+@var{loc} is the location of the address space qualifier token.
+The default implementation does nothing.
+@end deftypefn
+
+@node Misc
+@section Miscellaneous Parameters
+@cindex parameters, miscellaneous
+
+@c prevent bad page break with this line
+Here are several miscellaneous parameters.
+
+@defmac HAS_LONG_COND_BRANCH
+Define this boolean macro to indicate whether or not your architecture
+has conditional branches that can span all of memory. It is used in
+conjunction with an optimization that partitions hot and cold basic
+blocks into separate sections of the executable. If this macro is
+set to false, gcc will convert any conditional branches that attempt
+to cross between sections into unconditional branches or indirect jumps.
+@end defmac
+
+@defmac HAS_LONG_UNCOND_BRANCH
+Define this boolean macro to indicate whether or not your architecture
+has unconditional branches that can span all of memory. It is used in
+conjunction with an optimization that partitions hot and cold basic
+blocks into separate sections of the executable. If this macro is
+set to false, gcc will convert any unconditional branches that attempt
+to cross between sections into indirect jumps.
+@end defmac
+
+@defmac CASE_VECTOR_MODE
+An alias for a machine mode name. This is the machine mode that
+elements of a jump-table should have.
+@end defmac
+
+@defmac CASE_VECTOR_SHORTEN_MODE (@var{min_offset}, @var{max_offset}, @var{body})
+Optional: return the preferred mode for an @code{addr_diff_vec}
+when the minimum and maximum offset are known. If you define this,
+it enables extra code in branch shortening to deal with @code{addr_diff_vec}.
+To make this work, you also have to define @code{INSN_ALIGN} and
+make the alignment for @code{addr_diff_vec} explicit.
+The @var{body} argument is provided so that the offset_unsigned and scale
+flags can be updated.
+@end defmac
+
+@defmac CASE_VECTOR_PC_RELATIVE
+Define this macro to be a C expression to indicate when jump-tables
+should contain relative addresses. You need not define this macro if
+jump-tables never contain relative addresses, or jump-tables should
+contain relative addresses only when @option{-fPIC} or @option{-fPIC}
+is in effect.
+@end defmac
+
+@deftypefn {Target Hook} {unsigned int} TARGET_CASE_VALUES_THRESHOLD (void)
+This function return the smallest number of different values for which it
+is best to use a jump-table instead of a tree of conditional branches.
+The default is four for machines with a @code{casesi} instruction and
+five otherwise. This is best for most machines.
+@end deftypefn
+
+@defmac WORD_REGISTER_OPERATIONS
+Define this macro to 1 if operations between registers with integral mode
+smaller than a word are always performed on the entire register. To be
+more explicit, if you start with a pair of @code{word_mode} registers with
+known values and you do a subword, for example @code{QImode}, addition on
+the low part of the registers, then the compiler may consider that the
+result has a known value in @code{word_mode} too if the macro is defined
+to 1. Most RISC machines have this property and most CISC machines do not.
+@end defmac
+
+@deftypefn {Target Hook} {unsigned int} TARGET_MIN_ARITHMETIC_PRECISION (void)
+On some RISC architectures with 64-bit registers, the processor also
+maintains 32-bit condition codes that make it possible to do real 32-bit
+arithmetic, although the operations are performed on the full registers.
+
+On such architectures, defining this hook to 32 tells the compiler to try
+using 32-bit arithmetical operations setting the condition codes instead
+of doing full 64-bit arithmetic.
+
+More generally, define this hook on RISC architectures if you want the
+compiler to try using arithmetical operations setting the condition codes
+with a precision lower than the word precision.
+
+You need not define this hook if @code{WORD_REGISTER_OPERATIONS} is not
+defined to 1.
+@end deftypefn
+
+@defmac LOAD_EXTEND_OP (@var{mem_mode})
+Define this macro to be a C expression indicating when insns that read
+memory in @var{mem_mode}, an integral mode narrower than a word, set the
+bits outside of @var{mem_mode} to be either the sign-extension or the
+zero-extension of the data read. Return @code{SIGN_EXTEND} for values
+of @var{mem_mode} for which the
+insn sign-extends, @code{ZERO_EXTEND} for which it zero-extends, and
+@code{UNKNOWN} for other modes.
+
+This macro is not called with @var{mem_mode} non-integral or with a width
+greater than or equal to @code{BITS_PER_WORD}, so you may return any
+value in this case. Do not define this macro if it would always return
+@code{UNKNOWN}. On machines where this macro is defined, you will normally
+define it as the constant @code{SIGN_EXTEND} or @code{ZERO_EXTEND}.
+
+You may return a non-@code{UNKNOWN} value even if for some hard registers
+the sign extension is not performed, if for the @code{REGNO_REG_CLASS}
+of these hard registers @code{TARGET_CAN_CHANGE_MODE_CLASS} returns false
+when the @var{from} mode is @var{mem_mode} and the @var{to} mode is any
+integral mode larger than this but not larger than @code{word_mode}.
+
+You must return @code{UNKNOWN} if for some hard registers that allow this
+mode, @code{TARGET_CAN_CHANGE_MODE_CLASS} says that they cannot change to
+@code{word_mode}, but that they can change to another integral mode that
+is larger then @var{mem_mode} but still smaller than @code{word_mode}.
+@end defmac
+
+@defmac SHORT_IMMEDIATES_SIGN_EXTEND
+Define this macro to 1 if loading short immediate values into registers sign
+extends.
+@end defmac
+
+@deftypefn {Target Hook} {unsigned int} TARGET_MIN_DIVISIONS_FOR_RECIP_MUL (machine_mode @var{mode})
+When @option{-ffast-math} is in effect, GCC tries to optimize
+divisions by the same divisor, by turning them into multiplications by
+the reciprocal. This target hook specifies the minimum number of divisions
+that should be there for GCC to perform the optimization for a variable
+of mode @var{mode}. The default implementation returns 3 if the machine
+has an instruction for the division, and 2 if it does not.
+@end deftypefn
+
+@defmac MOVE_MAX
+The maximum number of bytes that a single instruction can move quickly
+between memory and registers or between two memory locations.
+@end defmac
+
+@defmac MAX_MOVE_MAX
+The maximum number of bytes that a single instruction can move quickly
+between memory and registers or between two memory locations. If this
+is undefined, the default is @code{MOVE_MAX}. Otherwise, it is the
+constant value that is the largest value that @code{MOVE_MAX} can have
+at run-time.
+@end defmac
+
+@defmac SHIFT_COUNT_TRUNCATED
+A C expression that is nonzero if on this machine the number of bits
+actually used for the count of a shift operation is equal to the number
+of bits needed to represent the size of the object being shifted. When
+this macro is nonzero, the compiler will assume that it is safe to omit
+a sign-extend, zero-extend, and certain bitwise `and' instructions that
+truncates the count of a shift operation. On machines that have
+instructions that act on bit-fields at variable positions, which may
+include `bit test' instructions, a nonzero @code{SHIFT_COUNT_TRUNCATED}
+also enables deletion of truncations of the values that serve as
+arguments to bit-field instructions.
+
+If both types of instructions truncate the count (for shifts) and
+position (for bit-field operations), or if no variable-position bit-field
+instructions exist, you should define this macro.
+
+However, on some machines, such as the 80386 and the 680x0, truncation
+only applies to shift operations and not the (real or pretended)
+bit-field operations. Define @code{SHIFT_COUNT_TRUNCATED} to be zero on
+such machines. Instead, add patterns to the @file{md} file that include
+the implied truncation of the shift instructions.
+
+You need not define this macro if it would always have the value of zero.
+@end defmac
+
+@anchor{TARGET_SHIFT_TRUNCATION_MASK}
+@deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_SHIFT_TRUNCATION_MASK (machine_mode @var{mode})
+This function describes how the standard shift patterns for @var{mode}
+deal with shifts by negative amounts or by more than the width of the mode.
+@xref{shift patterns}.
+
+On many machines, the shift patterns will apply a mask @var{m} to the
+shift count, meaning that a fixed-width shift of @var{x} by @var{y} is
+equivalent to an arbitrary-width shift of @var{x} by @var{y & m}. If
+this is true for mode @var{mode}, the function should return @var{m},
+otherwise it should return 0. A return value of 0 indicates that no
+particular behavior is guaranteed.
+
+Note that, unlike @code{SHIFT_COUNT_TRUNCATED}, this function does
+@emph{not} apply to general shift rtxes; it applies only to instructions
+that are generated by the named shift patterns.
+
+The default implementation of this function returns
+@code{GET_MODE_BITSIZE (@var{mode}) - 1} if @code{SHIFT_COUNT_TRUNCATED}
+and 0 otherwise. This definition is always safe, but if
+@code{SHIFT_COUNT_TRUNCATED} is false, and some shift patterns
+nevertheless truncate the shift count, you may get better code
+by overriding it.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_TRULY_NOOP_TRUNCATION (poly_uint64 @var{outprec}, poly_uint64 @var{inprec})
+This hook returns true if it is safe to ``convert'' a value of
+@var{inprec} bits to one of @var{outprec} bits (where @var{outprec} is
+smaller than @var{inprec}) by merely operating on it as if it had only
+@var{outprec} bits. The default returns true unconditionally, which
+is correct for most machines. When @code{TARGET_TRULY_NOOP_TRUNCATION}
+returns false, the machine description should provide a @code{trunc}
+optab to specify the RTL that performs the required truncation.
+
+If @code{TARGET_MODES_TIEABLE_P} returns false for a pair of modes,
+suboptimal code can result if this hook returns true for the corresponding
+mode sizes. Making this hook return false in such cases may improve things.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_MODE_REP_EXTENDED (scalar_int_mode @var{mode}, scalar_int_mode @var{rep_mode})
+The representation of an integral mode can be such that the values
+are always extended to a wider integral mode. Return
+@code{SIGN_EXTEND} if values of @var{mode} are represented in
+sign-extended form to @var{rep_mode}. Return @code{UNKNOWN}
+otherwise. (Currently, none of the targets use zero-extended
+representation this way so unlike @code{LOAD_EXTEND_OP},
+@code{TARGET_MODE_REP_EXTENDED} is expected to return either
+@code{SIGN_EXTEND} or @code{UNKNOWN}. Also no target extends
+@var{mode} to @var{rep_mode} so that @var{rep_mode} is not the next
+widest integral mode and currently we take advantage of this fact.)
+
+Similarly to @code{LOAD_EXTEND_OP} you may return a non-@code{UNKNOWN}
+value even if the extension is not performed on certain hard registers
+as long as for the @code{REGNO_REG_CLASS} of these hard registers
+@code{TARGET_CAN_CHANGE_MODE_CLASS} returns false.
+
+Note that @code{TARGET_MODE_REP_EXTENDED} and @code{LOAD_EXTEND_OP}
+describe two related properties. If you define
+@code{TARGET_MODE_REP_EXTENDED (mode, word_mode)} you probably also want
+to define @code{LOAD_EXTEND_OP (mode)} to return the same type of
+extension.
+
+In order to enforce the representation of @code{mode},
+@code{TARGET_TRULY_NOOP_TRUNCATION} should return false when truncating to
+@code{mode}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_SETJMP_PRESERVES_NONVOLATILE_REGS_P (void)
+On some targets, it is assumed that the compiler will spill all pseudos
+ that are live across a call to @code{setjmp}, while other targets treat
+ @code{setjmp} calls as normal function calls.
+
+ This hook returns false if @code{setjmp} calls do not preserve all
+ non-volatile registers so that gcc that must spill all pseudos that are
+ live across @code{setjmp} calls. Define this to return true if the
+ target does not need to spill all pseudos live across @code{setjmp} calls.
+ The default implementation conservatively assumes all pseudos must be
+ spilled across @code{setjmp} calls.
+@end deftypefn
+
+@defmac STORE_FLAG_VALUE
+A C expression describing the value returned by a comparison operator
+with an integral mode and stored by a store-flag instruction
+(@samp{cstore@var{mode}4}) when the condition is true. This description must
+apply to @emph{all} the @samp{cstore@var{mode}4} patterns and all the
+comparison operators whose results have a @code{MODE_INT} mode.
+
+A value of 1 or @minus{}1 means that the instruction implementing the
+comparison operator returns exactly 1 or @minus{}1 when the comparison is true
+and 0 when the comparison is false. Otherwise, the value indicates
+which bits of the result are guaranteed to be 1 when the comparison is
+true. This value is interpreted in the mode of the comparison
+operation, which is given by the mode of the first operand in the
+@samp{cstore@var{mode}4} pattern. Either the low bit or the sign bit of
+@code{STORE_FLAG_VALUE} be on. Presently, only those bits are used by
+the compiler.
+
+If @code{STORE_FLAG_VALUE} is neither 1 or @minus{}1, the compiler will
+generate code that depends only on the specified bits. It can also
+replace comparison operators with equivalent operations if they cause
+the required bits to be set, even if the remaining bits are undefined.
+For example, on a machine whose comparison operators return an
+@code{SImode} value and where @code{STORE_FLAG_VALUE} is defined as
+@samp{0x80000000}, saying that just the sign bit is relevant, the
+expression
+
+@smallexample
+(ne:SI (and:SI @var{x} (const_int @var{power-of-2})) (const_int 0))
+@end smallexample
+
+@noindent
+can be converted to
+
+@smallexample
+(ashift:SI @var{x} (const_int @var{n}))
+@end smallexample
+
+@noindent
+where @var{n} is the appropriate shift count to move the bit being
+tested into the sign bit.
+
+There is no way to describe a machine that always sets the low-order bit
+for a true value, but does not guarantee the value of any other bits,
+but we do not know of any machine that has such an instruction. If you
+are trying to port GCC to such a machine, include an instruction to
+perform a logical-and of the result with 1 in the pattern for the
+comparison operators and let us know at @email{gcc@@gcc.gnu.org}.
+
+Often, a machine will have multiple instructions that obtain a value
+from a comparison (or the condition codes). Here are rules to guide the
+choice of value for @code{STORE_FLAG_VALUE}, and hence the instructions
+to be used:
+
+@itemize @bullet
+@item
+Use the shortest sequence that yields a valid definition for
+@code{STORE_FLAG_VALUE}. It is more efficient for the compiler to
+``normalize'' the value (convert it to, e.g., 1 or 0) than for the
+comparison operators to do so because there may be opportunities to
+combine the normalization with other operations.
+
+@item
+For equal-length sequences, use a value of 1 or @minus{}1, with @minus{}1 being
+slightly preferred on machines with expensive jumps and 1 preferred on
+other machines.
+
+@item
+As a second choice, choose a value of @samp{0x80000001} if instructions
+exist that set both the sign and low-order bits but do not define the
+others.
+
+@item
+Otherwise, use a value of @samp{0x80000000}.
+@end itemize
+
+Many machines can produce both the value chosen for
+@code{STORE_FLAG_VALUE} and its negation in the same number of
+instructions. On those machines, you should also define a pattern for
+those cases, e.g., one matching
+
+@smallexample
+(set @var{A} (neg:@var{m} (ne:@var{m} @var{B} @var{C})))
+@end smallexample
+
+Some machines can also perform @code{and} or @code{plus} operations on
+condition code values with less instructions than the corresponding
+@samp{cstore@var{mode}4} insn followed by @code{and} or @code{plus}. On those
+machines, define the appropriate patterns. Use the names @code{incscc}
+and @code{decscc}, respectively, for the patterns which perform
+@code{plus} or @code{minus} operations on condition code values. See
+@file{rs6000.md} for some examples. The GNU Superoptimizer can be used to
+find such instruction sequences on other machines.
+
+If this macro is not defined, the default value, 1, is used. You need
+not define @code{STORE_FLAG_VALUE} if the machine has no store-flag
+instructions, or if the value generated by these instructions is 1.
+@end defmac
+
+@defmac FLOAT_STORE_FLAG_VALUE (@var{mode})
+A C expression that gives a nonzero @code{REAL_VALUE_TYPE} value that is
+returned when comparison operators with floating-point results are true.
+Define this macro on machines that have comparison operations that return
+floating-point values. If there are no such operations, do not define
+this macro.
+@end defmac
+
+@defmac VECTOR_STORE_FLAG_VALUE (@var{mode})
+A C expression that gives an rtx representing the nonzero true element
+for vector comparisons. The returned rtx should be valid for the inner
+mode of @var{mode} which is guaranteed to be a vector mode. Define
+this macro on machines that have vector comparison operations that
+return a vector result. If there are no such operations, do not define
+this macro. Typically, this macro is defined as @code{const1_rtx} or
+@code{constm1_rtx}. This macro may return @code{NULL_RTX} to prevent
+the compiler optimizing such vector comparison operations for the
+given mode.
+@end defmac
+
+@defmac CLZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value})
+@defmacx CTZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value})
+A C expression that indicates whether the architecture defines a value
+for @code{clz} or @code{ctz} with a zero operand.
+A result of @code{0} indicates the value is undefined.
+If the value is defined for only the RTL expression, the macro should
+evaluate to @code{1}; if the value applies also to the corresponding optab
+entry (which is normally the case if it expands directly into
+the corresponding RTL), then the macro should evaluate to @code{2}.
+In the cases where the value is defined, @var{value} should be set to
+this value.
+
+If this macro is not defined, the value of @code{clz} or
+@code{ctz} at zero is assumed to be undefined.
+
+This macro must be defined if the target's expansion for @code{ffs}
+relies on a particular value to get correct results. Otherwise it
+is not necessary, though it may be used to optimize some corner cases, and
+to provide a default expansion for the @code{ffs} optab.
+
+Note that regardless of this macro the ``definedness'' of @code{clz}
+and @code{ctz} at zero do @emph{not} extend to the builtin functions
+visible to the user. Thus one may be free to adjust the value at will
+to match the target expansion of these operations without fear of
+breaking the API@.
+@end defmac
+
+@defmac Pmode
+An alias for the machine mode for pointers. On most machines, define
+this to be the integer mode corresponding to the width of a hardware
+pointer; @code{SImode} on 32-bit machine or @code{DImode} on 64-bit machines.
+On some machines you must define this to be one of the partial integer
+modes, such as @code{PSImode}.
+
+The width of @code{Pmode} must be at least as large as the value of
+@code{POINTER_SIZE}. If it is not equal, you must define the macro
+@code{POINTERS_EXTEND_UNSIGNED} to specify how pointers are extended
+to @code{Pmode}.
+@end defmac
+
+@defmac FUNCTION_MODE
+An alias for the machine mode used for memory references to functions
+being called, in @code{call} RTL expressions. On most CISC machines,
+where an instruction can begin at any byte address, this should be
+@code{QImode}. On most RISC machines, where all instructions have fixed
+size and alignment, this should be a mode with the same size and alignment
+as the machine instruction words - typically @code{SImode} or @code{HImode}.
+@end defmac
+
+@defmac STDC_0_IN_SYSTEM_HEADERS
+In normal operation, the preprocessor expands @code{__STDC__} to the
+constant 1, to signify that GCC conforms to ISO Standard C@. On some
+hosts, like Solaris, the system compiler uses a different convention,
+where @code{__STDC__} is normally 0, but is 1 if the user specifies
+strict conformance to the C Standard.
+
+Defining @code{STDC_0_IN_SYSTEM_HEADERS} makes GNU CPP follows the host
+convention when processing system header files, but when processing user
+files @code{__STDC__} will always expand to 1.
+@end defmac
+
+@deftypefn {C Target Hook} {const char *} TARGET_C_PREINCLUDE (void)
+Define this hook to return the name of a header file to be included at
+the start of all compilations, as if it had been included with
+@code{#include <@var{file}>}. If this hook returns @code{NULL}, or is
+not defined, or the header is not found, or if the user specifies
+@option{-ffreestanding} or @option{-nostdinc}, no header is included.
+
+This hook can be used together with a header provided by the system C
+library to implement ISO C requirements for certain macros to be
+predefined that describe properties of the whole implementation rather
+than just the compiler.
+@end deftypefn
+
+@deftypefn {C Target Hook} bool TARGET_CXX_IMPLICIT_EXTERN_C (const char*@var{})
+Define this hook to add target-specific C++ implicit extern C functions.
+If this function returns true for the name of a file-scope function, that
+function implicitly gets extern "C" linkage rather than whatever language
+linkage the declaration would normally have. An example of such function
+is WinMain on Win32 targets.
+@end deftypefn
+
+@defmac SYSTEM_IMPLICIT_EXTERN_C
+Define this macro if the system header files do not support C++@.
+This macro handles system header files by pretending that system
+header files are enclosed in @samp{extern "C" @{@dots{}@}}.
+@end defmac
+
+@findex #pragma
+@findex pragma
+@defmac REGISTER_TARGET_PRAGMAS ()
+Define this macro if you want to implement any target-specific pragmas.
+If defined, it is a C expression which makes a series of calls to
+@code{c_register_pragma} or @code{c_register_pragma_with_expansion}
+for each pragma. The macro may also do any
+setup required for the pragmas.
+
+The primary reason to define this macro is to provide compatibility with
+other compilers for the same target. In general, we discourage
+definition of target-specific pragmas for GCC@.
+
+If the pragma can be implemented by attributes then you should consider
+defining the target hook @samp{TARGET_INSERT_ATTRIBUTES} as well.
+
+Preprocessor macros that appear on pragma lines are not expanded. All
+@samp{#pragma} directives that do not match any registered pragma are
+silently ignored, unless the user specifies @option{-Wunknown-pragmas}.
+@end defmac
+
+@deftypefun void c_register_pragma (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *))
+@deftypefunx void c_register_pragma_with_expansion (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *))
+
+Each call to @code{c_register_pragma} or
+@code{c_register_pragma_with_expansion} establishes one pragma. The
+@var{callback} routine will be called when the preprocessor encounters a
+pragma of the form
+
+@smallexample
+#pragma [@var{space}] @var{name} @dots{}
+@end smallexample
+
+@var{space} is the case-sensitive namespace of the pragma, or
+@code{NULL} to put the pragma in the global namespace. The callback
+routine receives @var{pfile} as its first argument, which can be passed
+on to cpplib's functions if necessary. You can lex tokens after the
+@var{name} by calling @code{pragma_lex}. Tokens that are not read by the
+callback will be silently ignored. The end of the line is indicated by
+a token of type @code{CPP_EOF}. Macro expansion occurs on the
+arguments of pragmas registered with
+@code{c_register_pragma_with_expansion} but not on the arguments of
+pragmas registered with @code{c_register_pragma}.
+
+Note that the use of @code{pragma_lex} is specific to the C and C++
+compilers. It will not work in the Java or Fortran compilers, or any
+other language compilers for that matter. Thus if @code{pragma_lex} is going
+to be called from target-specific code, it must only be done so when
+building the C and C++ compilers. This can be done by defining the
+variables @code{c_target_objs} and @code{cxx_target_objs} in the
+target entry in the @file{config.gcc} file. These variables should name
+the target-specific, language-specific object file which contains the
+code that uses @code{pragma_lex}. Note it will also be necessary to add a
+rule to the makefile fragment pointed to by @code{tmake_file} that shows
+how to build this object file.
+@end deftypefun
+
+@defmac HANDLE_PRAGMA_PACK_WITH_EXPANSION
+Define this macro if macros should be expanded in the
+arguments of @samp{#pragma pack}.
+@end defmac
+
+@defmac TARGET_DEFAULT_PACK_STRUCT
+If your target requires a structure packing default other than 0 (meaning
+the machine default), define this macro to the necessary value (in bytes).
+This must be a value that would also be valid to use with
+@samp{#pragma pack()} (that is, a small power of two).
+@end defmac
+
+@defmac DOLLARS_IN_IDENTIFIERS
+Define this macro to control use of the character @samp{$} in
+identifier names for the C family of languages. 0 means @samp{$} is
+not allowed by default; 1 means it is allowed. 1 is the default;
+there is no need to define this macro in that case.
+@end defmac
+
+@defmac INSN_SETS_ARE_DELAYED (@var{insn})
+Define this macro as a C expression that is nonzero if it is safe for the
+delay slot scheduler to place instructions in the delay slot of @var{insn},
+even if they appear to use a resource set or clobbered in @var{insn}.
+@var{insn} is always a @code{jump_insn} or an @code{insn}; GCC knows that
+every @code{call_insn} has this behavior. On machines where some @code{insn}
+or @code{jump_insn} is really a function call and hence has this behavior,
+you should define this macro.
+
+You need not define this macro if it would always return zero.
+@end defmac
+
+@defmac INSN_REFERENCES_ARE_DELAYED (@var{insn})
+Define this macro as a C expression that is nonzero if it is safe for the
+delay slot scheduler to place instructions in the delay slot of @var{insn},
+even if they appear to set or clobber a resource referenced in @var{insn}.
+@var{insn} is always a @code{jump_insn} or an @code{insn}. On machines where
+some @code{insn} or @code{jump_insn} is really a function call and its operands
+are registers whose use is actually in the subroutine it calls, you should
+define this macro. Doing so allows the delay slot scheduler to move
+instructions which copy arguments into the argument registers into the delay
+slot of @var{insn}.
+
+You need not define this macro if it would always return zero.
+@end defmac
+
+@defmac MULTIPLE_SYMBOL_SPACES
+Define this macro as a C expression that is nonzero if, in some cases,
+global symbols from one translation unit may not be bound to undefined
+symbols in another translation unit without user intervention. For
+instance, under Microsoft Windows symbols must be explicitly imported
+from shared libraries (DLLs).
+
+You need not define this macro if it would always evaluate to zero.
+@end defmac
+
+@deftypefn {Target Hook} {rtx_insn *} TARGET_MD_ASM_ADJUST (vec<rtx>& @var{outputs}, vec<rtx>& @var{inputs}, vec<machine_mode>& @var{input_modes}, vec<const char *>& @var{constraints}, vec<rtx>& @var{clobbers}, HARD_REG_SET& @var{clobbered_regs}, location_t @var{loc})
+This target hook may add @dfn{clobbers} to @var{clobbers} and
+@var{clobbered_regs} for any hard regs the port wishes to automatically
+clobber for an asm. The @var{outputs} and @var{inputs} may be inspected
+to avoid clobbering a register that is already used by the asm. @var{loc}
+is the source location of the asm.
+
+It may modify the @var{outputs}, @var{inputs}, @var{input_modes}, and
+@var{constraints} as necessary for other pre-processing. In this case the
+return value is a sequence of insns to emit after the asm. Note that
+changes to @var{inputs} must be accompanied by the corresponding changes
+to @var{input_modes}.
+@end deftypefn
+
+@defmac MATH_LIBRARY
+Define this macro as a C string constant for the linker argument to link
+in the system math library, minus the initial @samp{"-l"}, or
+@samp{""} if the target does not have a
+separate math library.
+
+You need only define this macro if the default of @samp{"m"} is wrong.
+@end defmac
+
+@defmac LIBRARY_PATH_ENV
+Define this macro as a C string constant for the environment variable that
+specifies where the linker should look for libraries.
+
+You need only define this macro if the default of @samp{"LIBRARY_PATH"}
+is wrong.
+@end defmac
+
+@defmac TARGET_POSIX_IO
+Define this macro if the target supports the following POSIX@ file
+functions, access, mkdir and file locking with fcntl / F_SETLKW@.
+Defining @code{TARGET_POSIX_IO} will enable the test coverage code
+to use file locking when exiting a program, which avoids race conditions
+if the program has forked. It will also create directories at run-time
+for cross-profiling.
+@end defmac
+
+@defmac MAX_CONDITIONAL_EXECUTE
+
+A C expression for the maximum number of instructions to execute via
+conditional execution instructions instead of a branch. A value of
+@code{BRANCH_COST}+1 is the default.
+@end defmac
+
+@defmac IFCVT_MODIFY_TESTS (@var{ce_info}, @var{true_expr}, @var{false_expr})
+Used if the target needs to perform machine-dependent modifications on the
+conditionals used for turning basic blocks into conditionally executed code.
+@var{ce_info} points to a data structure, @code{struct ce_if_block}, which
+contains information about the currently processed blocks. @var{true_expr}
+and @var{false_expr} are the tests that are used for converting the
+then-block and the else-block, respectively. Set either @var{true_expr} or
+@var{false_expr} to a null pointer if the tests cannot be converted.
+@end defmac
+
+@defmac IFCVT_MODIFY_MULTIPLE_TESTS (@var{ce_info}, @var{bb}, @var{true_expr}, @var{false_expr})
+Like @code{IFCVT_MODIFY_TESTS}, but used when converting more complicated
+if-statements into conditions combined by @code{and} and @code{or} operations.
+@var{bb} contains the basic block that contains the test that is currently
+being processed and about to be turned into a condition.
+@end defmac
+
+@defmac IFCVT_MODIFY_INSN (@var{ce_info}, @var{pattern}, @var{insn})
+A C expression to modify the @var{PATTERN} of an @var{INSN} that is to
+be converted to conditional execution format. @var{ce_info} points to
+a data structure, @code{struct ce_if_block}, which contains information
+about the currently processed blocks.
+@end defmac
+
+@defmac IFCVT_MODIFY_FINAL (@var{ce_info})
+A C expression to perform any final machine dependent modifications in
+converting code to conditional execution. The involved basic blocks
+can be found in the @code{struct ce_if_block} structure that is pointed
+to by @var{ce_info}.
+@end defmac
+
+@defmac IFCVT_MODIFY_CANCEL (@var{ce_info})
+A C expression to cancel any machine dependent modifications in
+converting code to conditional execution. The involved basic blocks
+can be found in the @code{struct ce_if_block} structure that is pointed
+to by @var{ce_info}.
+@end defmac
+
+@defmac IFCVT_MACHDEP_INIT (@var{ce_info})
+A C expression to initialize any machine specific data for if-conversion
+of the if-block in the @code{struct ce_if_block} structure that is pointed
+to by @var{ce_info}.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_MACHINE_DEPENDENT_REORG (void)
+If non-null, this hook performs a target-specific pass over the
+instruction stream. The compiler will run it at all optimization levels,
+just before the point at which it normally does delayed-branch scheduling.
+
+The exact purpose of the hook varies from target to target. Some use
+it to do transformations that are necessary for correctness, such as
+laying out in-function constant pools or avoiding hardware hazards.
+Others use it as an opportunity to do some machine-dependent optimizations.
+
+You need not implement the hook if it has nothing to do. The default
+definition is null.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_INIT_BUILTINS (void)
+Define this hook if you have any machine-specific built-in functions
+that need to be defined. It should be a function that performs the
+necessary setup.
+
+Machine specific built-in functions can be useful to expand special machine
+instructions that would otherwise not normally be generated because
+they have no equivalent in the source language (for example, SIMD vector
+instructions or prefetch instructions).
+
+To create a built-in function, call the function
+@code{lang_hooks.builtin_function}
+which is defined by the language front end. You can use any type nodes set
+up by @code{build_common_tree_nodes};
+only language front ends that use those two functions will call
+@samp{TARGET_INIT_BUILTINS}.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_BUILTIN_DECL (unsigned @var{code}, bool @var{initialize_p})
+Define this hook if you have any machine-specific built-in functions
+that need to be defined. It should be a function that returns the
+builtin function declaration for the builtin function code @var{code}.
+If there is no such builtin and it cannot be initialized at this time
+if @var{initialize_p} is true the function should return @code{NULL_TREE}.
+If @var{code} is out of range the function should return
+@code{error_mark_node}.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_EXPAND_BUILTIN (tree @var{exp}, rtx @var{target}, rtx @var{subtarget}, machine_mode @var{mode}, int @var{ignore})
+
+Expand a call to a machine specific built-in function that was set up by
+@samp{TARGET_INIT_BUILTINS}. @var{exp} is the expression for the
+function call; the result should go to @var{target} if that is
+convenient, and have mode @var{mode} if that is convenient.
+@var{subtarget} may be used as the target for computing one of
+@var{exp}'s operands. @var{ignore} is nonzero if the value is to be
+ignored. This function should return the result of the call to the
+built-in function.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_RESOLVE_OVERLOADED_BUILTIN (unsigned int @var{loc}, tree @var{fndecl}, void *@var{arglist})
+Select a replacement for a machine specific built-in function that
+was set up by @samp{TARGET_INIT_BUILTINS}. This is done
+@emph{before} regular type checking, and so allows the target to
+implement a crude form of function overloading. @var{fndecl} is the
+declaration of the built-in function. @var{arglist} is the list of
+arguments passed to the built-in function. The result is a
+complete expression that implements the operation, usually
+another @code{CALL_EXPR}.
+@var{arglist} really has type @samp{VEC(tree,gc)*}
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CHECK_BUILTIN_CALL (location_t @var{loc}, vec<location_t> @var{arg_loc}, tree @var{fndecl}, tree @var{orig_fndecl}, unsigned int @var{nargs}, tree *@var{args})
+Perform semantic checking on a call to a machine-specific built-in
+function after its arguments have been constrained to the function
+signature. Return true if the call is valid, otherwise report an error
+and return false.
+
+This hook is called after @code{TARGET_RESOLVE_OVERLOADED_BUILTIN}.
+The call was originally to built-in function @var{orig_fndecl},
+but after the optional @code{TARGET_RESOLVE_OVERLOADED_BUILTIN}
+step is now to built-in function @var{fndecl}. @var{loc} is the
+location of the call and @var{args} is an array of function arguments,
+of which there are @var{nargs}. @var{arg_loc} specifies the location
+of each argument.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_FOLD_BUILTIN (tree @var{fndecl}, int @var{n_args}, tree *@var{argp}, bool @var{ignore})
+Fold a call to a machine specific built-in function that was set up by
+@samp{TARGET_INIT_BUILTINS}. @var{fndecl} is the declaration of the
+built-in function. @var{n_args} is the number of arguments passed to
+the function; the arguments themselves are pointed to by @var{argp}.
+The result is another tree, valid for both GIMPLE and GENERIC,
+containing a simplified expression for the call's result. If
+@var{ignore} is true the value will be ignored.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_GIMPLE_FOLD_BUILTIN (gimple_stmt_iterator *@var{gsi})
+Fold a call to a machine specific built-in function that was set up
+by @samp{TARGET_INIT_BUILTINS}. @var{gsi} points to the gimple
+statement holding the function call. Returns true if any change
+was made to the GIMPLE stream.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_COMPARE_VERSION_PRIORITY (tree @var{decl1}, tree @var{decl2})
+This hook is used to compare the target attributes in two functions to
+determine which function's features get higher priority. This is used
+during function multi-versioning to figure out the order in which two
+versions must be dispatched. A function version with a higher priority
+is checked for dispatching earlier. @var{decl1} and @var{decl2} are
+ the two function decls that will be compared.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_GET_FUNCTION_VERSIONS_DISPATCHER (void *@var{decl})
+This hook is used to get the dispatcher function for a set of function
+versions. The dispatcher function is called to invoke the right function
+version at run-time. @var{decl} is one version from a set of semantically
+identical versions.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_GENERATE_VERSION_DISPATCHER_BODY (void *@var{arg})
+This hook is used to generate the dispatcher logic to invoke the right
+function version at run-time for a given set of function versions.
+@var{arg} points to the callgraph node of the dispatcher function whose
+body must be generated.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_PREDICT_DOLOOP_P (class loop *@var{loop})
+Return true if we can predict it is possible to use a low-overhead loop
+for a particular loop. The parameter @var{loop} is a pointer to the loop.
+This target hook is required only when the target supports low-overhead
+loops, and will help ivopts to make some decisions.
+The default version of this hook returns false.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_HAVE_COUNT_REG_DECR_P
+Return true if the target supports hardware count register for decrement
+and branch.
+The default value is false.
+@end deftypevr
+
+@deftypevr {Target Hook} int64_t TARGET_DOLOOP_COST_FOR_GENERIC
+One IV candidate dedicated for doloop is introduced in IVOPTs, we can
+calculate the computation cost of adopting it to any generic IV use by
+function get_computation_cost as before. But for targets which have
+hardware count register support for decrement and branch, it may have to
+move IV value from hardware count register to general purpose register
+while doloop IV candidate is used for generic IV uses. It probably takes
+expensive penalty. This hook allows target owners to define the cost for
+this especially for generic IV uses.
+The default value is zero.
+@end deftypevr
+
+@deftypevr {Target Hook} int64_t TARGET_DOLOOP_COST_FOR_ADDRESS
+One IV candidate dedicated for doloop is introduced in IVOPTs, we can
+calculate the computation cost of adopting it to any address IV use by
+function get_computation_cost as before. But for targets which have
+hardware count register support for decrement and branch, it may have to
+move IV value from hardware count register to general purpose register
+while doloop IV candidate is used for address IV uses. It probably takes
+expensive penalty. This hook allows target owners to define the cost for
+this escpecially for address IV uses.
+The default value is zero.
+@end deftypevr
+
+@deftypefn {Target Hook} bool TARGET_CAN_USE_DOLOOP_P (const widest_int @var{&iterations}, const widest_int @var{&iterations_max}, unsigned int @var{loop_depth}, bool @var{entered_at_top})
+Return true if it is possible to use low-overhead loops (@code{doloop_end}
+and @code{doloop_begin}) for a particular loop. @var{iterations} gives the
+exact number of iterations, or 0 if not known. @var{iterations_max} gives
+the maximum number of iterations, or 0 if not known. @var{loop_depth} is
+the nesting depth of the loop, with 1 for innermost loops, 2 for loops that
+contain innermost loops, and so on. @var{entered_at_top} is true if the
+loop is only entered from the top.
+
+This hook is only used if @code{doloop_end} is available. The default
+implementation returns true. You can use @code{can_use_doloop_if_innermost}
+if the loop must be the innermost, and if there are no other restrictions.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_INVALID_WITHIN_DOLOOP (const rtx_insn *@var{insn})
+
+Take an instruction in @var{insn} and return NULL if it is valid within a
+low-overhead loop, otherwise return a string explaining why doloop
+could not be applied.
+
+Many targets use special registers for low-overhead looping. For any
+instruction that clobbers these this function should return a string indicating
+the reason why the doloop could not be applied.
+By default, the RTL loop optimizer does not use a present doloop pattern for
+loops containing function calls or branch on table instructions.
+@end deftypefn
+
+@deftypefn {Target Hook} machine_mode TARGET_PREFERRED_DOLOOP_MODE (machine_mode @var{mode})
+This hook takes a @var{mode} for a doloop IV, where @code{mode} is the
+original mode for the operation. If the target prefers an alternate
+@code{mode} for the operation, then this hook should return that mode;
+otherwise the original @code{mode} should be returned. For example, on a
+64-bit target, @code{DImode} might be preferred over @code{SImode}. Both the
+original and the returned modes should be @code{MODE_INT}.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_LEGITIMATE_COMBINED_INSN (rtx_insn *@var{insn})
+Take an instruction in @var{insn} and return @code{false} if the instruction
+is not appropriate as a combination of two or more instructions. The
+default is to accept all instructions.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_CAN_FOLLOW_JUMP (const rtx_insn *@var{follower}, const rtx_insn *@var{followee})
+FOLLOWER and FOLLOWEE are JUMP_INSN instructions;
+return true if FOLLOWER may be modified to follow FOLLOWEE;
+false, if it can't.
+For example, on some targets, certain kinds of branches can't be made to
+follow through a hot/cold partitioning.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_COMMUTATIVE_P (const_rtx @var{x}, int @var{outer_code})
+This target hook returns @code{true} if @var{x} is considered to be commutative.
+Usually, this is just COMMUTATIVE_P (@var{x}), but the HP PA doesn't consider
+PLUS to be commutative inside a MEM@. @var{outer_code} is the rtx code
+of the enclosing rtl, if known, otherwise it is UNKNOWN.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_ALLOCATE_INITIAL_VALUE (rtx @var{hard_reg})
+
+When the initial value of a hard register has been copied in a pseudo
+register, it is often not necessary to actually allocate another register
+to this pseudo register, because the original hard register or a stack slot
+it has been saved into can be used. @code{TARGET_ALLOCATE_INITIAL_VALUE}
+is called at the start of register allocation once for each hard register
+that had its initial value copied by using
+@code{get_func_hard_reg_initial_val} or @code{get_hard_reg_initial_val}.
+Possible values are @code{NULL_RTX}, if you don't want
+to do any special allocation, a @code{REG} rtx---that would typically be
+the hard register itself, if it is known not to be clobbered---or a
+@code{MEM}.
+If you are returning a @code{MEM}, this is only a hint for the allocator;
+it might decide to use another register anyways.
+You may use @code{current_function_is_leaf} or
+@code{REG_N_SETS} in the hook to determine if the hard
+register in question will not be clobbered.
+The default value of this hook is @code{NULL}, which disables any special
+allocation.
+@end deftypefn
+
+@deftypefn {Target Hook} int TARGET_UNSPEC_MAY_TRAP_P (const_rtx @var{x}, unsigned @var{flags})
+This target hook returns nonzero if @var{x}, an @code{unspec} or
+@code{unspec_volatile} operation, might cause a trap. Targets can use
+this hook to enhance precision of analysis for @code{unspec} and
+@code{unspec_volatile} operations. You may call @code{may_trap_p_1}
+to analyze inner elements of @var{x} in which case @var{flags} should be
+passed along.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_SET_CURRENT_FUNCTION (tree @var{decl})
+The compiler invokes this hook whenever it changes its current function
+context (@code{cfun}). You can define this function if
+the back end needs to perform any initialization or reset actions on a
+per-function basis. For example, it may be used to implement function
+attributes that affect register usage or code generation patterns.
+The argument @var{decl} is the declaration for the new function context,
+and may be null to indicate that the compiler has left a function context
+and is returning to processing at the top level.
+The default hook function does nothing.
+
+GCC sets @code{cfun} to a dummy function context during initialization of
+some parts of the back end. The hook function is not invoked in this
+situation; you need not worry about the hook being invoked recursively,
+or when the back end is in a partially-initialized state.
+@code{cfun} might be @code{NULL} to indicate processing at top level,
+outside of any function scope.
+@end deftypefn
+
+@defmac TARGET_OBJECT_SUFFIX
+Define this macro to be a C string representing the suffix for object
+files on your target machine. If you do not define this macro, GCC will
+use @samp{.o} as the suffix for object files.
+@end defmac
+
+@defmac TARGET_EXECUTABLE_SUFFIX
+Define this macro to be a C string representing the suffix to be
+automatically added to executable files on your target machine. If you
+do not define this macro, GCC will use the null string as the suffix for
+executable files.
+@end defmac
+
+@defmac COLLECT_EXPORT_LIST
+If defined, @code{collect2} will scan the individual object files
+specified on its command line and create an export list for the linker.
+Define this macro for systems like AIX, where the linker discards
+object files that are not referenced from @code{main} and uses export
+lists.
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_CANNOT_MODIFY_JUMPS_P (void)
+This target hook returns @code{true} past the point in which new jump
+instructions could be created. On machines that require a register for
+every jump such as the SHmedia ISA of SH5, this point would typically be
+reload, so this target hook should be defined to a function such as:
+
+@smallexample
+static bool
+cannot_modify_jumps_past_reload_p ()
+@{
+ return (reload_completed || reload_in_progress);
+@}
+@end smallexample
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_HAVE_CONDITIONAL_EXECUTION (void)
+This target hook returns true if the target supports conditional execution.
+This target hook is required only when the target has several different
+modes and they have different conditional execution capability, such as ARM.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_GEN_CCMP_FIRST (rtx_insn **@var{prep_seq}, rtx_insn **@var{gen_seq}, int @var{code}, tree @var{op0}, tree @var{op1})
+This function prepares to emit a comparison insn for the first compare in a
+ sequence of conditional comparisions. It returns an appropriate comparison
+ with @code{CC} for passing to @code{gen_ccmp_next} or @code{cbranch_optab}.
+ The insns to prepare the compare are saved in @var{prep_seq} and the compare
+ insns are saved in @var{gen_seq}. They will be emitted when all the
+ compares in the conditional comparision are generated without error.
+ @var{code} is the @code{rtx_code} of the compare for @var{op0} and @var{op1}.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_GEN_CCMP_NEXT (rtx_insn **@var{prep_seq}, rtx_insn **@var{gen_seq}, rtx @var{prev}, int @var{cmp_code}, tree @var{op0}, tree @var{op1}, int @var{bit_code})
+This function prepares to emit a conditional comparison within a sequence
+ of conditional comparisons. It returns an appropriate comparison with
+ @code{CC} for passing to @code{gen_ccmp_next} or @code{cbranch_optab}.
+ The insns to prepare the compare are saved in @var{prep_seq} and the compare
+ insns are saved in @var{gen_seq}. They will be emitted when all the
+ compares in the conditional comparision are generated without error. The
+ @var{prev} expression is the result of a prior call to @code{gen_ccmp_first}
+ or @code{gen_ccmp_next}. It may return @code{NULL} if the combination of
+ @var{prev} and this comparison is not supported, otherwise the result must
+ be appropriate for passing to @code{gen_ccmp_next} or @code{cbranch_optab}.
+ @var{code} is the @code{rtx_code} of the compare for @var{op0} and @var{op1}.
+ @var{bit_code} is @code{AND} or @code{IOR}, which is the op on the compares.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_GEN_MEMSET_SCRATCH_RTX (machine_mode @var{mode})
+This hook should return an rtx for a scratch register in @var{mode} to
+be used when expanding memset calls. The backend can use a hard scratch
+register to avoid stack realignment when expanding memset. The default
+is @code{gen_reg_rtx}.
+@end deftypefn
+
+@deftypefn {Target Hook} unsigned TARGET_LOOP_UNROLL_ADJUST (unsigned @var{nunroll}, class loop *@var{loop})
+This target hook returns a new value for the number of times @var{loop}
+should be unrolled. The parameter @var{nunroll} is the number of times
+the loop is to be unrolled. The parameter @var{loop} is a pointer to
+the loop, which is going to be checked for unrolling. This target hook
+is required only when the target has special constraints like maximum
+number of memory accesses.
+@end deftypefn
+
+@defmac POWI_MAX_MULTS
+If defined, this macro is interpreted as a signed integer C expression
+that specifies the maximum number of floating point multiplications
+that should be emitted when expanding exponentiation by an integer
+constant inline. When this value is defined, exponentiation requiring
+more than this number of multiplications is implemented by calling the
+system library's @code{pow}, @code{powf} or @code{powl} routines.
+The default value places no upper bound on the multiplication count.
+@end defmac
+
+@deftypefn Macro void TARGET_EXTRA_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc})
+This target hook should register any extra include files for the
+target. The parameter @var{stdinc} indicates if normal include files
+are present. The parameter @var{sysroot} is the system root directory.
+The parameter @var{iprefix} is the prefix for the gcc directory.
+@end deftypefn
+
+@deftypefn Macro void TARGET_EXTRA_PRE_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc})
+This target hook should register any extra include files for the
+target before any standard headers. The parameter @var{stdinc}
+indicates if normal include files are present. The parameter
+@var{sysroot} is the system root directory. The parameter
+@var{iprefix} is the prefix for the gcc directory.
+@end deftypefn
+
+@deftypefn Macro void TARGET_OPTF (char *@var{path})
+This target hook should register special include paths for the target.
+The parameter @var{path} is the include to register. On Darwin
+systems, this is used for Framework includes, which have semantics
+that are different from @option{-I}.
+@end deftypefn
+
+@defmac bool TARGET_USE_LOCAL_THUNK_ALIAS_P (tree @var{fndecl})
+This target macro returns @code{true} if it is safe to use a local alias
+for a virtual function @var{fndecl} when constructing thunks,
+@code{false} otherwise. By default, the macro returns @code{true} for all
+functions, if a target supports aliases (i.e.@: defines
+@code{ASM_OUTPUT_DEF}), @code{false} otherwise,
+@end defmac
+
+@defmac TARGET_FORMAT_TYPES
+If defined, this macro is the name of a global variable containing
+target-specific format checking information for the @option{-Wformat}
+option. The default is to have no target-specific format checks.
+@end defmac
+
+@defmac TARGET_N_FORMAT_TYPES
+If defined, this macro is the number of entries in
+@code{TARGET_FORMAT_TYPES}.
+@end defmac
+
+@defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES
+If defined, this macro is the name of a global variable containing
+target-specific format overrides for the @option{-Wformat} option. The
+default is to have no target-specific format overrides. If defined,
+@code{TARGET_FORMAT_TYPES} and @code{TARGET_OVERRIDES_FORMAT_ATTRIBUTES_COUNT}
+must be defined, too.
+@end defmac
+
+@defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES_COUNT
+If defined, this macro specifies the number of entries in
+@code{TARGET_OVERRIDES_FORMAT_ATTRIBUTES}.
+@end defmac
+
+@defmac TARGET_OVERRIDES_FORMAT_INIT
+If defined, this macro specifies the optional initialization
+routine for target specific customizations of the system printf
+and scanf formatter settings.
+@end defmac
+
+@deftypefn {Target Hook} {const char *} TARGET_INVALID_ARG_FOR_UNPROTOTYPED_FN (const_tree @var{typelist}, const_tree @var{funcdecl}, const_tree @var{val})
+If defined, this macro returns the diagnostic message when it is
+illegal to pass argument @var{val} to function @var{funcdecl}
+with prototype @var{typelist}.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_INVALID_CONVERSION (const_tree @var{fromtype}, const_tree @var{totype})
+If defined, this macro returns the diagnostic message when it is
+invalid to convert from @var{fromtype} to @var{totype}, or @code{NULL}
+if validity should be determined by the front end.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_INVALID_UNARY_OP (int @var{op}, const_tree @var{type})
+If defined, this macro returns the diagnostic message when it is
+invalid to apply operation @var{op} (where unary plus is denoted by
+@code{CONVERT_EXPR}) to an operand of type @var{type}, or @code{NULL}
+if validity should be determined by the front end.
+@end deftypefn
+
+@deftypefn {Target Hook} {const char *} TARGET_INVALID_BINARY_OP (int @var{op}, const_tree @var{type1}, const_tree @var{type2})
+If defined, this macro returns the diagnostic message when it is
+invalid to apply operation @var{op} to operands of types @var{type1}
+and @var{type2}, or @code{NULL} if validity should be determined by
+the front end.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_PROMOTED_TYPE (const_tree @var{type})
+If defined, this target hook returns the type to which values of
+@var{type} should be promoted when they appear in expressions,
+analogous to the integer promotions, or @code{NULL_TREE} to use the
+front end's normal promotion rules. This hook is useful when there are
+target-specific types with special promotion rules.
+This is currently used only by the C and C++ front ends.
+@end deftypefn
+
+@deftypefn {Target Hook} tree TARGET_CONVERT_TO_TYPE (tree @var{type}, tree @var{expr})
+If defined, this hook returns the result of converting @var{expr} to
+@var{type}. It should return the converted expression,
+or @code{NULL_TREE} to apply the front end's normal conversion rules.
+This hook is useful when there are target-specific types with special
+conversion rules.
+This is currently used only by the C and C++ front ends.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_VERIFY_TYPE_CONTEXT (location_t @var{loc}, type_context_kind @var{context}, const_tree @var{type}, bool @var{silent_p})
+If defined, this hook returns false if there is a target-specific reason
+why type @var{type} cannot be used in the source language context described
+by @var{context}. When @var{silent_p} is false, the hook also reports an
+error against @var{loc} for invalid uses of @var{type}.
+
+Calls to this hook should be made through the global function
+@code{verify_type_context}, which makes the @var{silent_p} parameter
+default to false and also handles @code{error_mark_node}.
+
+The default implementation always returns true.
+@end deftypefn
+
+@defmac OBJC_JBLEN
+This macro determines the size of the objective C jump buffer for the
+NeXT runtime. By default, OBJC_JBLEN is defined to an innocuous value.
+@end defmac
+
+@defmac LIBGCC2_UNWIND_ATTRIBUTE
+Define this macro if any target-specific attributes need to be attached
+to the functions in @file{libgcc} that provide low-level support for
+call stack unwinding. It is used in declarations in @file{unwind-generic.h}
+and the associated definitions of those functions.
+@end defmac
+
+@deftypefn {Target Hook} void TARGET_UPDATE_STACK_BOUNDARY (void)
+Define this macro to update the current function stack boundary if
+necessary.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_GET_DRAP_RTX (void)
+This hook should return an rtx for Dynamic Realign Argument Pointer (DRAP) if a
+different argument pointer register is needed to access the function's
+argument list due to stack realignment. Return @code{NULL} if no DRAP
+is needed.
+@end deftypefn
+
+@deftypefn {Target Hook} HARD_REG_SET TARGET_ZERO_CALL_USED_REGS (HARD_REG_SET @var{selected_regs})
+This target hook emits instructions to zero the subset of @var{selected_regs}
+that could conceivably contain values that are useful to an attacker.
+Return the set of registers that were actually cleared.
+
+For most targets, the returned set of registers is a subset of
+@var{selected_regs}, however, for some of the targets (for example MIPS),
+clearing some registers that are in the @var{selected_regs} requires
+clearing other call used registers that are not in the @var{selected_regs},
+under such situation, the returned set of registers must be a subset of all
+call used registers.
+
+The default implementation uses normal move instructions to zero
+all the registers in @var{selected_regs}. Define this hook if the
+target has more efficient ways of zeroing certain registers,
+or if you believe that certain registers would never contain
+values that are useful to an attacker.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS (void)
+When optimization is disabled, this hook indicates whether or not
+arguments should be allocated to stack slots. Normally, GCC allocates
+stacks slots for arguments when not optimizing in order to make
+debugging easier. However, when a function is declared with
+@code{__attribute__((naked))}, there is no stack frame, and the compiler
+cannot safely move arguments from the registers in which they are passed
+to the stack. Therefore, this hook should return true in general, but
+false for naked functions. The default implementation always returns true.
+@end deftypefn
+
+@deftypevr {Target Hook} {unsigned HOST_WIDE_INT} TARGET_CONST_ANCHOR
+On some architectures it can take multiple instructions to synthesize
+a constant. If there is another constant already in a register that
+is close enough in value then it is preferable that the new constant
+is computed from this register using immediate addition or
+subtraction. We accomplish this through CSE. Besides the value of
+the constant we also add a lower and an upper constant anchor to the
+available expressions. These are then queried when encountering new
+constants. The anchors are computed by rounding the constant up and
+down to a multiple of the value of @code{TARGET_CONST_ANCHOR}.
+@code{TARGET_CONST_ANCHOR} should be the maximum positive value
+accepted by immediate-add plus one. We currently assume that the
+value of @code{TARGET_CONST_ANCHOR} is a power of 2. For example, on
+MIPS, where add-immediate takes a 16-bit signed value,
+@code{TARGET_CONST_ANCHOR} is set to @samp{0x8000}. The default value
+is zero, which disables this optimization.
+@end deftypevr
+
+@deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_ASAN_SHADOW_OFFSET (void)
+Return the offset bitwise ored into shifted address to get corresponding
+Address Sanitizer shadow memory address. NULL if Address Sanitizer is not
+supported by the target. May return 0 if Address Sanitizer is not supported
+by a subtarget.
+@end deftypefn
+
+@deftypefn {Target Hook} {unsigned HOST_WIDE_INT} TARGET_MEMMODEL_CHECK (unsigned HOST_WIDE_INT @var{val})
+Validate target specific memory model mask bits. When NULL no target specific
+memory model bits are allowed.
+@end deftypefn
+
+@deftypevr {Target Hook} {unsigned char} TARGET_ATOMIC_TEST_AND_SET_TRUEVAL
+This value should be set if the result written by
+@code{atomic_test_and_set} is not exactly 1, i.e.@: the
+@code{bool} @code{true}.
+@end deftypevr
+
+@deftypefn {Target Hook} bool TARGET_HAS_IFUNC_P (void)
+It returns true if the target supports GNU indirect functions.
+The support includes the assembler, linker and dynamic linker.
+The default value of this hook is based on target's libc.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_IFUNC_REF_LOCAL_OK (void)
+Return true if it is OK to reference indirect function resolvers
+locally. The default is to return false.
+@end deftypefn
+
+@deftypefn {Target Hook} {unsigned int} TARGET_ATOMIC_ALIGN_FOR_MODE (machine_mode @var{mode})
+If defined, this function returns an appropriate alignment in bits for an
+atomic object of machine_mode @var{mode}. If 0 is returned then the
+default alignment for the specified mode is used.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_ATOMIC_ASSIGN_EXPAND_FENV (tree *@var{hold}, tree *@var{clear}, tree *@var{update})
+ISO C11 requires atomic compound assignments that may raise floating-point
+exceptions to raise exceptions corresponding to the arithmetic operation
+whose result was successfully stored in a compare-and-exchange sequence.
+This requires code equivalent to calls to @code{feholdexcept},
+@code{feclearexcept} and @code{feupdateenv} to be generated at
+appropriate points in the compare-and-exchange sequence. This hook should
+set @code{*@var{hold}} to an expression equivalent to the call to
+@code{feholdexcept}, @code{*@var{clear}} to an expression equivalent to
+the call to @code{feclearexcept} and @code{*@var{update}} to an expression
+equivalent to the call to @code{feupdateenv}. The three expressions are
+@code{NULL_TREE} on entry to the hook and may be left as @code{NULL_TREE}
+if no code is required in a particular place. The default implementation
+leaves all three expressions as @code{NULL_TREE}. The
+@code{__atomic_feraiseexcept} function from @code{libatomic} may be of use
+as part of the code generated in @code{*@var{update}}.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_RECORD_OFFLOAD_SYMBOL (tree)
+Used when offloaded functions are seen in the compilation unit and no named
+sections are available. It is called once for each symbol that must be
+recorded in the offload function and variable table.
+@end deftypefn
+
+@deftypefn {Target Hook} {char *} TARGET_OFFLOAD_OPTIONS (void)
+Used when writing out the list of options into an LTO file. It should
+translate any relevant target-specific options (such as the ABI in use)
+into one of the @option{-foffload} options that exist as a common interface
+to express such options. It should return a string containing these options,
+separated by spaces, which the caller will free.
+
+@end deftypefn
+
+@defmac TARGET_SUPPORTS_WIDE_INT
+
+On older ports, large integers are stored in @code{CONST_DOUBLE} rtl
+objects. Newer ports define @code{TARGET_SUPPORTS_WIDE_INT} to be nonzero
+to indicate that large integers are stored in
+@code{CONST_WIDE_INT} rtl objects. The @code{CONST_WIDE_INT} allows
+very large integer constants to be represented. @code{CONST_DOUBLE}
+is limited to twice the size of the host's @code{HOST_WIDE_INT}
+representation.
+
+Converting a port mostly requires looking for the places where
+@code{CONST_DOUBLE}s are used with @code{VOIDmode} and replacing that
+code with code that accesses @code{CONST_WIDE_INT}s. @samp{"grep -i
+const_double"} at the port level gets you to 95% of the changes that
+need to be made. There are a few places that require a deeper look.
+
+@itemize @bullet
+@item
+There is no equivalent to @code{hval} and @code{lval} for
+@code{CONST_WIDE_INT}s. This would be difficult to express in the md
+language since there are a variable number of elements.
+
+Most ports only check that @code{hval} is either 0 or -1 to see if the
+value is small. As mentioned above, this will no longer be necessary
+since small constants are always @code{CONST_INT}. Of course there
+are still a few exceptions, the alpha's constraint used by the zap
+instruction certainly requires careful examination by C code.
+However, all the current code does is pass the hval and lval to C
+code, so evolving the c code to look at the @code{CONST_WIDE_INT} is
+not really a large change.
+
+@item
+Because there is no standard template that ports use to materialize
+constants, there is likely to be some futzing that is unique to each
+port in this code.
+
+@item
+The rtx costs may have to be adjusted to properly account for larger
+constants that are represented as @code{CONST_WIDE_INT}.
+@end itemize
+
+All and all it does not take long to convert ports that the
+maintainer is familiar with.
+
+@end defmac
+
+@deftypefn {Target Hook} bool TARGET_HAVE_SPECULATION_SAFE_VALUE (bool @var{active})
+This hook is used to determine the level of target support for
+ @code{__builtin_speculation_safe_value}. If called with an argument
+ of false, it returns true if the target has been modified to support
+ this builtin. If called with an argument of true, it returns true
+ if the target requires active mitigation execution might be speculative.
+
+ The default implementation returns false if the target does not define
+ a pattern named @code{speculation_barrier}. Else it returns true
+ for the first case and whether the pattern is enabled for the current
+ compilation for the second case.
+
+ For targets that have no processors that can execute instructions
+ speculatively an alternative implemenation of this hook is available:
+ simply redefine this hook to @code{speculation_safe_value_not_needed}
+ along with your other target hooks.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_SPECULATION_SAFE_VALUE (machine_mode @var{mode}, rtx @var{result}, rtx @var{val}, rtx @var{failval})
+This target hook can be used to generate a target-specific code
+ sequence that implements the @code{__builtin_speculation_safe_value}
+ built-in function. The function must always return @var{val} in
+ @var{result} in mode @var{mode} when the cpu is not executing
+ speculatively, but must never return that when speculating until it
+ is known that the speculation will not be unwound. The hook supports
+ two primary mechanisms for implementing the requirements. The first
+ is to emit a speculation barrier which forces the processor to wait
+ until all prior speculative operations have been resolved; the second
+ is to use a target-specific mechanism that can track the speculation
+ state and to return @var{failval} if it can determine that
+ speculation must be unwound at a later time.
+
+ The default implementation simply copies @var{val} to @var{result} and
+ emits a @code{speculation_barrier} instruction if that is defined.
+@end deftypefn
+
+@deftypefn {Target Hook} void TARGET_RUN_TARGET_SELFTESTS (void)
+If selftests are enabled, run any selftests for this target.
+@end deftypefn
+
+@deftypefn {Target Hook} bool TARGET_MEMTAG_CAN_TAG_ADDRESSES ()
+True if the backend architecture naturally supports ignoring some region
+of pointers. This feature means that @option{-fsanitize=hwaddress} can
+work.
+
+At preset, this feature does not support address spaces. It also requires
+@code{Pmode} to be the same as @code{ptr_mode}.
+@end deftypefn
+
+@deftypefn {Target Hook} uint8_t TARGET_MEMTAG_TAG_SIZE ()
+Return the size of a tag (in bits) for this platform.
+
+The default returns 8.
+@end deftypefn
+
+@deftypefn {Target Hook} uint8_t TARGET_MEMTAG_GRANULE_SIZE ()
+Return the size in real memory that each byte in shadow memory refers to.
+I.e. if a variable is @var{X} bytes long in memory, then this hook should
+return the value @var{Y} such that the tag in shadow memory spans
+@var{X}/@var{Y} bytes.
+
+Most variables will need to be aligned to this amount since two variables
+that are neighbors in memory and share a tag granule would need to share
+the same tag.
+
+The default returns 16.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_MEMTAG_INSERT_RANDOM_TAG (rtx @var{untagged}, rtx @var{target})
+Return an RTX representing the value of @var{untagged} but with a
+(possibly) random tag in it.
+Put that value into @var{target} if it is convenient to do so.
+This function is used to generate a tagged base for the current stack frame.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_MEMTAG_ADD_TAG (rtx @var{base}, poly_int64 @var{addr_offset}, uint8_t @var{tag_offset})
+Return an RTX that represents the result of adding @var{addr_offset} to
+the address in pointer @var{base} and @var{tag_offset} to the tag in pointer
+@var{base}.
+The resulting RTX must either be a valid memory address or be able to get
+put into an operand with @code{force_operand}.
+
+Unlike other memtag hooks, this must return an expression and not emit any
+RTL.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_MEMTAG_SET_TAG (rtx @var{untagged_base}, rtx @var{tag}, rtx @var{target})
+Return an RTX representing @var{untagged_base} but with the tag @var{tag}.
+Try and store this in @var{target} if convenient.
+@var{untagged_base} is required to have a zero tag when this hook is called.
+The default of this hook is to set the top byte of @var{untagged_base} to
+@var{tag}.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_MEMTAG_EXTRACT_TAG (rtx @var{tagged_pointer}, rtx @var{target})
+Return an RTX representing the tag stored in @var{tagged_pointer}.
+Store the result in @var{target} if it is convenient.
+The default represents the top byte of the original pointer.
+@end deftypefn
+
+@deftypefn {Target Hook} rtx TARGET_MEMTAG_UNTAGGED_POINTER (rtx @var{tagged_pointer}, rtx @var{target})
+Return an RTX representing @var{tagged_pointer} with its tag set to zero.
+Store the result in @var{target} if convenient.
+The default clears the top byte of the original pointer.
+@end deftypefn
+
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_GCOV_TYPE_SIZE (void)
+Returns the gcov type size in bits. This type is used for example for
+counters incremented by profiling and code-coverage events. The default
+value is 64, if the type size of long long is greater than 32, otherwise the
+default value is 32. A 64-bit type is recommended to avoid overflows of the
+counters. If the @option{-fprofile-update=atomic} is used, then the
+counters are incremented using atomic operations. Targets not supporting
+64-bit atomic operations may override the default value and request a 32-bit
+type.
+@end deftypefn
+
+@deftypevr {Target Hook} bool TARGET_HAVE_SHADOW_CALL_STACK
+This value is true if the target platform supports
+@option{-fsanitize=shadow-call-stack}. The default value is false.
+@end deftypevr
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Target Macros
+@chapter Target Description Macros and Functions
+@cindex machine description macros
+@cindex target description macros
+@cindex macros, target description
+@cindex @file{tm.h} macros
+
+In addition to the file @file{@var{machine}.md}, a machine description
+includes a C header file conventionally given the name
+@file{@var{machine}.h} and a C source file named @file{@var{machine}.c}.
+The header file defines numerous macros that convey the information
+about the target machine that does not fit into the scheme of the
+@file{.md} file. The file @file{tm.h} should be a link to
+@file{@var{machine}.h}. The header file @file{config.h} includes
+@file{tm.h} and most compiler source files include @file{config.h}. The
+source file defines a variable @code{targetm}, which is a structure
+containing pointers to functions and data relating to the target
+machine. @file{@var{machine}.c} should also contain their definitions,
+if they are not defined elsewhere in GCC, and other functions called
+through the macros defined in the @file{.h} file.
+
+@menu
+* Target Structure:: The @code{targetm} variable.
+* Driver:: Controlling how the driver runs the compilation passes.
+* Run-time Target:: Defining @samp{-m} options like @option{-m68000} and @option{-m68020}.
+* Per-Function Data:: Defining data structures for per-function information.
+* Storage Layout:: Defining sizes and alignments of data.
+* Type Layout:: Defining sizes and properties of basic user data types.
+* Registers:: Naming and describing the hardware registers.
+* Register Classes:: Defining the classes of hardware registers.
+* Stack and Calling:: Defining which way the stack grows and by how much.
+* Varargs:: Defining the varargs macros.
+* Trampolines:: Code set up at run time to enter a nested function.
+* Library Calls:: Controlling how library routines are implicitly called.
+* Addressing Modes:: Defining addressing modes valid for memory operands.
+* Anchored Addresses:: Defining how @option{-fsection-anchors} should work.
+* Condition Code:: Defining how insns update the condition code.
+* Costs:: Defining relative costs of different operations.
+* Scheduling:: Adjusting the behavior of the instruction scheduler.
+* Sections:: Dividing storage into text, data, and other sections.
+* PIC:: Macros for position independent code.
+* Assembler Format:: Defining how to write insns and pseudo-ops to output.
+* Debugging Info:: Defining the format of debugging output.
+* Floating Point:: Handling floating point for cross-compilers.
+* Mode Switching:: Insertion of mode-switching instructions.
+* Target Attributes:: Defining target-specific uses of @code{__attribute__}.
+* Emulated TLS:: Emulated TLS support.
+* MIPS Coprocessors:: MIPS coprocessor support and how to customize it.
+* PCH Target:: Validity checking for precompiled headers.
+* C++ ABI:: Controlling C++ ABI changes.
+* D Language and ABI:: Controlling D ABI changes.
+* Named Address Spaces:: Adding support for named address spaces
+* Misc:: Everything else.
+@end menu
+
+@node Target Structure
+@section The Global @code{targetm} Variable
+@cindex target hooks
+@cindex target functions
+
+@deftypevar {struct gcc_target} targetm
+The target @file{.c} file must define the global @code{targetm} variable
+which contains pointers to functions and data relating to the target
+machine. The variable is declared in @file{target.h};
+@file{target-def.h} defines the macro @code{TARGET_INITIALIZER} which is
+used to initialize the variable, and macros for the default initializers
+for elements of the structure. The @file{.c} file should override those
+macros for which the default definition is inappropriate. For example:
+@smallexample
+#include "target.h"
+#include "target-def.h"
+
+/* @r{Initialize the GCC target structure.} */
+
+#undef TARGET_COMP_TYPE_ATTRIBUTES
+#define TARGET_COMP_TYPE_ATTRIBUTES @var{machine}_comp_type_attributes
+
+struct gcc_target targetm = TARGET_INITIALIZER;
+@end smallexample
+@end deftypevar
+
+Where a macro should be defined in the @file{.c} file in this manner to
+form part of the @code{targetm} structure, it is documented below as a
+``Target Hook'' with a prototype. Many macros will change in future
+from being defined in the @file{.h} file to being part of the
+@code{targetm} structure.
+
+Similarly, there is a @code{targetcm} variable for hooks that are
+specific to front ends for C-family languages, documented as ``C
+Target Hook''. This is declared in @file{c-family/c-target.h}, the
+initializer @code{TARGETCM_INITIALIZER} in
+@file{c-family/c-target-def.h}. If targets initialize @code{targetcm}
+themselves, they should set @code{target_has_targetcm=yes} in
+@file{config.gcc}; otherwise a default definition is used.
+
+Similarly, there is a @code{targetm_common} variable for hooks that
+are shared between the compiler driver and the compilers proper,
+documented as ``Common Target Hook''. This is declared in
+@file{common/common-target.h}, the initializer
+@code{TARGETM_COMMON_INITIALIZER} in
+@file{common/common-target-def.h}. If targets initialize
+@code{targetm_common} themselves, they should set
+@code{target_has_targetm_common=yes} in @file{config.gcc}; otherwise a
+default definition is used.
+
+Similarly, there is a @code{targetdm} variable for hooks that are
+specific to the D language front end, documented as ``D Target Hook''.
+This is declared in @file{d/d-target.h}, the initializer
+@code{TARGETDM_INITIALIZER} in @file{d/d-target-def.h}. If targets
+initialize @code{targetdm} themselves, they should set
+@code{target_has_targetdm=yes} in @file{config.gcc}; otherwise a default
+definition is used.
+
+@node Driver
+@section Controlling the Compilation Driver, @file{gcc}
+@cindex driver
+@cindex controlling the compilation driver
+
+@c prevent bad page break with this line
+You can control the compilation driver.
+
+@defmac DRIVER_SELF_SPECS
+A list of specs for the driver itself. It should be a suitable
+initializer for an array of strings, with no surrounding braces.
+
+The driver applies these specs to its own command line between loading
+default @file{specs} files (but not command-line specified ones) and
+choosing the multilib directory or running any subcommands. It
+applies them in the order given, so each spec can depend on the
+options added by earlier ones. It is also possible to remove options
+using @samp{%<@var{option}} in the usual way.
+
+This macro can be useful when a port has several interdependent target
+options. It provides a way of standardizing the command line so
+that the other specs are easier to write.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac OPTION_DEFAULT_SPECS
+A list of specs used to support configure-time default options (i.e.@:
+@option{--with} options) in the driver. It should be a suitable initializer
+for an array of structures, each containing two strings, without the
+outermost pair of surrounding braces.
+
+The first item in the pair is the name of the default. This must match
+the code in @file{config.gcc} for the target. The second item is a spec
+to apply if a default with this name was specified. The string
+@samp{%(VALUE)} in the spec will be replaced by the value of the default
+everywhere it occurs.
+
+The driver will apply these specs to its own command line between loading
+default @file{specs} files and processing @code{DRIVER_SELF_SPECS}, using
+the same mechanism as @code{DRIVER_SELF_SPECS}.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac CPP_SPEC
+A C string constant that tells the GCC driver program options to
+pass to CPP@. It can also specify how to translate options you
+give to GCC into options for GCC to pass to the CPP@.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac CPLUSPLUS_CPP_SPEC
+This macro is just like @code{CPP_SPEC}, but is used for C++, rather
+than C@. If you do not define this macro, then the value of
+@code{CPP_SPEC} (if any) will be used instead.
+@end defmac
+
+@defmac CC1_SPEC
+A C string constant that tells the GCC driver program options to
+pass to @code{cc1}, @code{cc1plus}, @code{f771}, and the other language
+front ends.
+It can also specify how to translate options you give to GCC into options
+for GCC to pass to front ends.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac CC1PLUS_SPEC
+A C string constant that tells the GCC driver program options to
+pass to @code{cc1plus}. It can also specify how to translate options you
+give to GCC into options for GCC to pass to the @code{cc1plus}.
+
+Do not define this macro if it does not need to do anything.
+Note that everything defined in CC1_SPEC is already passed to
+@code{cc1plus} so there is no need to duplicate the contents of
+CC1_SPEC in CC1PLUS_SPEC@.
+@end defmac
+
+@defmac ASM_SPEC
+A C string constant that tells the GCC driver program options to
+pass to the assembler. It can also specify how to translate options
+you give to GCC into options for GCC to pass to the assembler.
+See the file @file{sun3.h} for an example of this.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac ASM_FINAL_SPEC
+A C string constant that tells the GCC driver program how to
+run any programs which cleanup after the normal assembler.
+Normally, this is not needed. See the file @file{mips.h} for
+an example of this.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac AS_NEEDS_DASH_FOR_PIPED_INPUT
+Define this macro, with no value, if the driver should give the assembler
+an argument consisting of a single dash, @option{-}, to instruct it to
+read from its standard input (which will be a pipe connected to the
+output of the compiler proper). This argument is given after any
+@option{-o} option specifying the name of the output file.
+
+If you do not define this macro, the assembler is assumed to read its
+standard input if given no non-option arguments. If your assembler
+cannot read standard input at all, use a @samp{%@{pipe:%e@}} construct;
+see @file{mips.h} for instance.
+@end defmac
+
+@defmac LINK_SPEC
+A C string constant that tells the GCC driver program options to
+pass to the linker. It can also specify how to translate options you
+give to GCC into options for GCC to pass to the linker.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac LIB_SPEC
+Another C string constant used much like @code{LINK_SPEC}. The difference
+between the two is that @code{LIB_SPEC} is used at the end of the
+command given to the linker.
+
+If this macro is not defined, a default is provided that
+loads the standard C library from the usual place. See @file{gcc.cc}.
+@end defmac
+
+@defmac LIBGCC_SPEC
+Another C string constant that tells the GCC driver program
+how and when to place a reference to @file{libgcc.a} into the
+linker command line. This constant is placed both before and after
+the value of @code{LIB_SPEC}.
+
+If this macro is not defined, the GCC driver provides a default that
+passes the string @option{-lgcc} to the linker.
+@end defmac
+
+@defmac REAL_LIBGCC_SPEC
+By default, if @code{ENABLE_SHARED_LIBGCC} is defined, the
+@code{LIBGCC_SPEC} is not directly used by the driver program but is
+instead modified to refer to different versions of @file{libgcc.a}
+depending on the values of the command line flags @option{-static},
+@option{-shared}, @option{-static-libgcc}, and @option{-shared-libgcc}. On
+targets where these modifications are inappropriate, define
+@code{REAL_LIBGCC_SPEC} instead. @code{REAL_LIBGCC_SPEC} tells the
+driver how to place a reference to @file{libgcc} on the link command
+line, but, unlike @code{LIBGCC_SPEC}, it is used unmodified.
+@end defmac
+
+@defmac USE_LD_AS_NEEDED
+A macro that controls the modifications to @code{LIBGCC_SPEC}
+mentioned in @code{REAL_LIBGCC_SPEC}. If nonzero, a spec will be
+generated that uses @option{--as-needed} or equivalent options and the
+shared @file{libgcc} in place of the
+static exception handler library, when linking without any of
+@code{-static}, @code{-static-libgcc}, or @code{-shared-libgcc}.
+@end defmac
+
+@defmac LINK_EH_SPEC
+If defined, this C string constant is added to @code{LINK_SPEC}.
+When @code{USE_LD_AS_NEEDED} is zero or undefined, it also affects
+the modifications to @code{LIBGCC_SPEC} mentioned in
+@code{REAL_LIBGCC_SPEC}.
+@end defmac
+
+@defmac STARTFILE_SPEC
+Another C string constant used much like @code{LINK_SPEC}. The
+difference between the two is that @code{STARTFILE_SPEC} is used at
+the very beginning of the command given to the linker.
+
+If this macro is not defined, a default is provided that loads the
+standard C startup file from the usual place. See @file{gcc.cc}.
+@end defmac
+
+@defmac ENDFILE_SPEC
+Another C string constant used much like @code{LINK_SPEC}. The
+difference between the two is that @code{ENDFILE_SPEC} is used at
+the very end of the command given to the linker.
+
+Do not define this macro if it does not need to do anything.
+@end defmac
+
+@defmac THREAD_MODEL_SPEC
+GCC @code{-v} will print the thread model GCC was configured to use.
+However, this doesn't work on platforms that are multilibbed on thread
+models, such as AIX 4.3. On such platforms, define
+@code{THREAD_MODEL_SPEC} such that it evaluates to a string without
+blanks that names one of the recognized thread models. @code{%*}, the
+default value of this macro, will expand to the value of
+@code{thread_file} set in @file{config.gcc}.
+@end defmac
+
+@defmac SYSROOT_SUFFIX_SPEC
+Define this macro to add a suffix to the target sysroot when GCC is
+configured with a sysroot. This will cause GCC to search for usr/lib,
+et al, within sysroot+suffix.
+@end defmac
+
+@defmac SYSROOT_HEADERS_SUFFIX_SPEC
+Define this macro to add a headers_suffix to the target sysroot when
+GCC is configured with a sysroot. This will cause GCC to pass the
+updated sysroot+headers_suffix to CPP, causing it to search for
+usr/include, et al, within sysroot+headers_suffix.
+@end defmac
+
+@defmac EXTRA_SPECS
+Define this macro to provide additional specifications to put in the
+@file{specs} file that can be used in various specifications like
+@code{CC1_SPEC}.
+
+The definition should be an initializer for an array of structures,
+containing a string constant, that defines the specification name, and a
+string constant that provides the specification.
+
+Do not define this macro if it does not need to do anything.
+
+@code{EXTRA_SPECS} is useful when an architecture contains several
+related targets, which have various @code{@dots{}_SPECS} which are similar
+to each other, and the maintainer would like one central place to keep
+these definitions.
+
+For example, the PowerPC System V.4 targets use @code{EXTRA_SPECS} to
+define either @code{_CALL_SYSV} when the System V calling sequence is
+used or @code{_CALL_AIX} when the older AIX-based calling sequence is
+used.
+
+The @file{config/rs6000/rs6000.h} target file defines:
+
+@smallexample
+#define EXTRA_SPECS \
+ @{ "cpp_sysv_default", CPP_SYSV_DEFAULT @},
+
+#define CPP_SYS_DEFAULT ""
+@end smallexample
+
+The @file{config/rs6000/sysv.h} target file defines:
+@smallexample
+#undef CPP_SPEC
+#define CPP_SPEC \
+"%@{posix: -D_POSIX_SOURCE @} \
+%@{mcall-sysv: -D_CALL_SYSV @} \
+%@{!mcall-sysv: %(cpp_sysv_default) @} \
+%@{msoft-float: -D_SOFT_FLOAT@} %@{mcpu=403: -D_SOFT_FLOAT@}"
+
+#undef CPP_SYSV_DEFAULT
+#define CPP_SYSV_DEFAULT "-D_CALL_SYSV"
+@end smallexample
+
+while the @file{config/rs6000/eabiaix.h} target file defines
+@code{CPP_SYSV_DEFAULT} as:
+
+@smallexample
+#undef CPP_SYSV_DEFAULT
+#define CPP_SYSV_DEFAULT "-D_CALL_AIX"
+@end smallexample
+@end defmac
+
+@defmac LINK_LIBGCC_SPECIAL_1
+Define this macro if the driver program should find the library
+@file{libgcc.a}. If you do not define this macro, the driver program will pass
+the argument @option{-lgcc} to tell the linker to do the search.
+@end defmac
+
+@defmac LINK_GCC_C_SEQUENCE_SPEC
+The sequence in which libgcc and libc are specified to the linker.
+By default this is @code{%G %L %G}.
+@end defmac
+
+@defmac POST_LINK_SPEC
+Define this macro to add additional steps to be executed after linker.
+The default value of this macro is empty string.
+@end defmac
+
+@defmac LINK_COMMAND_SPEC
+A C string constant giving the complete command line need to execute the
+linker. When you do this, you will need to update your port each time a
+change is made to the link command line within @file{gcc.cc}. Therefore,
+define this macro only if you need to completely redefine the command
+line for invoking the linker and there is no other way to accomplish
+the effect you need. Overriding this macro may be avoidable by overriding
+@code{LINK_GCC_C_SEQUENCE_SPEC} instead.
+@end defmac
+
+@hook TARGET_ALWAYS_STRIP_DOTDOT
+
+@defmac MULTILIB_DEFAULTS
+Define this macro as a C expression for the initializer of an array of
+string to tell the driver program which options are defaults for this
+target and thus do not need to be handled specially when using
+@code{MULTILIB_OPTIONS}.
+
+Do not define this macro if @code{MULTILIB_OPTIONS} is not defined in
+the target makefile fragment or if none of the options listed in
+@code{MULTILIB_OPTIONS} are set by default.
+@xref{Target Fragment}.
+@end defmac
+
+@defmac RELATIVE_PREFIX_NOT_LINKDIR
+Define this macro to tell @command{gcc} that it should only translate
+a @option{-B} prefix into a @option{-L} linker option if the prefix
+indicates an absolute file name.
+@end defmac
+
+@defmac MD_EXEC_PREFIX
+If defined, this macro is an additional prefix to try after
+@code{STANDARD_EXEC_PREFIX}. @code{MD_EXEC_PREFIX} is not searched
+when the compiler is built as a cross
+compiler. If you define @code{MD_EXEC_PREFIX}, then be sure to add it
+to the list of directories used to find the assembler in @file{configure.ac}.
+@end defmac
+
+@defmac STANDARD_STARTFILE_PREFIX
+Define this macro as a C string constant if you wish to override the
+standard choice of @code{libdir} as the default prefix to
+try when searching for startup files such as @file{crt0.o}.
+@code{STANDARD_STARTFILE_PREFIX} is not searched when the compiler
+is built as a cross compiler.
+@end defmac
+
+@defmac STANDARD_STARTFILE_PREFIX_1
+Define this macro as a C string constant if you wish to override the
+standard choice of @code{/lib} as a prefix to try after the default prefix
+when searching for startup files such as @file{crt0.o}.
+@code{STANDARD_STARTFILE_PREFIX_1} is not searched when the compiler
+is built as a cross compiler.
+@end defmac
+
+@defmac STANDARD_STARTFILE_PREFIX_2
+Define this macro as a C string constant if you wish to override the
+standard choice of @code{/lib} as yet another prefix to try after the
+default prefix when searching for startup files such as @file{crt0.o}.
+@code{STANDARD_STARTFILE_PREFIX_2} is not searched when the compiler
+is built as a cross compiler.
+@end defmac
+
+@defmac MD_STARTFILE_PREFIX
+If defined, this macro supplies an additional prefix to try after the
+standard prefixes. @code{MD_EXEC_PREFIX} is not searched when the
+compiler is built as a cross compiler.
+@end defmac
+
+@defmac MD_STARTFILE_PREFIX_1
+If defined, this macro supplies yet another prefix to try after the
+standard prefixes. It is not searched when the compiler is built as a
+cross compiler.
+@end defmac
+
+@defmac INIT_ENVIRONMENT
+Define this macro as a C string constant if you wish to set environment
+variables for programs called by the driver, such as the assembler and
+loader. The driver passes the value of this macro to @code{putenv} to
+initialize the necessary environment variables.
+@end defmac
+
+@defmac LOCAL_INCLUDE_DIR
+Define this macro as a C string constant if you wish to override the
+standard choice of @file{/usr/local/include} as the default prefix to
+try when searching for local header files. @code{LOCAL_INCLUDE_DIR}
+comes before @code{NATIVE_SYSTEM_HEADER_DIR} (set in
+@file{config.gcc}, normally @file{/usr/include}) in the search order.
+
+Cross compilers do not search either @file{/usr/local/include} or its
+replacement.
+@end defmac
+
+@defmac NATIVE_SYSTEM_HEADER_COMPONENT
+The ``component'' corresponding to @code{NATIVE_SYSTEM_HEADER_DIR}.
+See @code{INCLUDE_DEFAULTS}, below, for the description of components.
+If you do not define this macro, no component is used.
+@end defmac
+
+@defmac INCLUDE_DEFAULTS
+Define this macro if you wish to override the entire default search path
+for include files. For a native compiler, the default search path
+usually consists of @code{GCC_INCLUDE_DIR}, @code{LOCAL_INCLUDE_DIR},
+@code{GPLUSPLUS_INCLUDE_DIR}, and
+@code{NATIVE_SYSTEM_HEADER_DIR}. In addition, @code{GPLUSPLUS_INCLUDE_DIR}
+and @code{GCC_INCLUDE_DIR} are defined automatically by @file{Makefile},
+and specify private search areas for GCC@. The directory
+@code{GPLUSPLUS_INCLUDE_DIR} is used only for C++ programs.
+
+The definition should be an initializer for an array of structures.
+Each array element should have four elements: the directory name (a
+string constant), the component name (also a string constant), a flag
+for C++-only directories,
+and a flag showing that the includes in the directory don't need to be
+wrapped in @code{extern @samp{C}} when compiling C++. Mark the end of
+the array with a null element.
+
+The component name denotes what GNU package the include file is part of,
+if any, in all uppercase letters. For example, it might be @samp{GCC}
+or @samp{BINUTILS}. If the package is part of a vendor-supplied
+operating system, code the component name as @samp{0}.
+
+For example, here is the definition used for VAX/VMS:
+
+@smallexample
+#define INCLUDE_DEFAULTS \
+@{ \
+ @{ "GNU_GXX_INCLUDE:", "G++", 1, 1@}, \
+ @{ "GNU_CC_INCLUDE:", "GCC", 0, 0@}, \
+ @{ "SYS$SYSROOT:[SYSLIB.]", 0, 0, 0@}, \
+ @{ ".", 0, 0, 0@}, \
+ @{ 0, 0, 0, 0@} \
+@}
+@end smallexample
+@end defmac
+
+Here is the order of prefixes tried for exec files:
+
+@enumerate
+@item
+Any prefixes specified by the user with @option{-B}.
+
+@item
+The environment variable @code{GCC_EXEC_PREFIX} or, if @code{GCC_EXEC_PREFIX}
+is not set and the compiler has not been installed in the configure-time
+@var{prefix}, the location in which the compiler has actually been installed.
+
+@item
+The directories specified by the environment variable @code{COMPILER_PATH}.
+
+@item
+The macro @code{STANDARD_EXEC_PREFIX}, if the compiler has been installed
+in the configured-time @var{prefix}.
+
+@item
+The location @file{/usr/libexec/gcc/}, but only if this is a native compiler.
+
+@item
+The location @file{/usr/lib/gcc/}, but only if this is a native compiler.
+
+@item
+The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native
+compiler.
+@end enumerate
+
+Here is the order of prefixes tried for startfiles:
+
+@enumerate
+@item
+Any prefixes specified by the user with @option{-B}.
+
+@item
+The environment variable @code{GCC_EXEC_PREFIX} or its automatically determined
+value based on the installed toolchain location.
+
+@item
+The directories specified by the environment variable @code{LIBRARY_PATH}
+(or port-specific name; native only, cross compilers do not use this).
+
+@item
+The macro @code{STANDARD_EXEC_PREFIX}, but only if the toolchain is installed
+in the configured @var{prefix} or this is a native compiler.
+
+@item
+The location @file{/usr/lib/gcc/}, but only if this is a native compiler.
+
+@item
+The macro @code{MD_EXEC_PREFIX}, if defined, but only if this is a native
+compiler.
+
+@item
+The macro @code{MD_STARTFILE_PREFIX}, if defined, but only if this is a
+native compiler, or we have a target system root.
+
+@item
+The macro @code{MD_STARTFILE_PREFIX_1}, if defined, but only if this is a
+native compiler, or we have a target system root.
+
+@item
+The macro @code{STANDARD_STARTFILE_PREFIX}, with any sysroot modifications.
+If this path is relative it will be prefixed by @code{GCC_EXEC_PREFIX} and
+the machine suffix or @code{STANDARD_EXEC_PREFIX} and the machine suffix.
+
+@item
+The macro @code{STANDARD_STARTFILE_PREFIX_1}, but only if this is a native
+compiler, or we have a target system root. The default for this macro is
+@file{/lib/}.
+
+@item
+The macro @code{STANDARD_STARTFILE_PREFIX_2}, but only if this is a native
+compiler, or we have a target system root. The default for this macro is
+@file{/usr/lib/}.
+@end enumerate
+
+@node Run-time Target
+@section Run-time Target Specification
+@cindex run-time target specification
+@cindex predefined macros
+@cindex target specifications
+
+@c prevent bad page break with this line
+Here are run-time target specifications.
+
+@defmac TARGET_CPU_CPP_BUILTINS ()
+This function-like macro expands to a block of code that defines
+built-in preprocessor macros and assertions for the target CPU, using
+the functions @code{builtin_define}, @code{builtin_define_std} and
+@code{builtin_assert}. When the front end
+calls this macro it provides a trailing semicolon, and since it has
+finished command line option processing your code can use those
+results freely.
+
+@code{builtin_assert} takes a string in the form you pass to the
+command-line option @option{-A}, such as @code{cpu=mips}, and creates
+the assertion. @code{builtin_define} takes a string in the form
+accepted by option @option{-D} and unconditionally defines the macro.
+
+@code{builtin_define_std} takes a string representing the name of an
+object-like macro. If it doesn't lie in the user's namespace,
+@code{builtin_define_std} defines it unconditionally. Otherwise, it
+defines a version with two leading underscores, and another version
+with two leading and trailing underscores, and defines the original
+only if an ISO standard was not requested on the command line. For
+example, passing @code{unix} defines @code{__unix}, @code{__unix__}
+and possibly @code{unix}; passing @code{_mips} defines @code{__mips},
+@code{__mips__} and possibly @code{_mips}, and passing @code{_ABI64}
+defines only @code{_ABI64}.
+
+You can also test for the C dialect being compiled. The variable
+@code{c_language} is set to one of @code{clk_c}, @code{clk_cplusplus}
+or @code{clk_objective_c}. Note that if we are preprocessing
+assembler, this variable will be @code{clk_c} but the function-like
+macro @code{preprocessing_asm_p()} will return true, so you might want
+to check for that first. If you need to check for strict ANSI, the
+variable @code{flag_iso} can be used. The function-like macro
+@code{preprocessing_trad_p()} can be used to check for traditional
+preprocessing.
+@end defmac
+
+@defmac TARGET_OS_CPP_BUILTINS ()
+Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional
+and is used for the target operating system instead.
+@end defmac
+
+@defmac TARGET_OBJFMT_CPP_BUILTINS ()
+Similarly to @code{TARGET_CPU_CPP_BUILTINS} but this macro is optional
+and is used for the target object format. @file{elfos.h} uses this
+macro to define @code{__ELF__}, so you probably do not need to define
+it yourself.
+@end defmac
+
+@deftypevar {extern int} target_flags
+This variable is declared in @file{options.h}, which is included before
+any target-specific headers.
+@end deftypevar
+
+@hook TARGET_DEFAULT_TARGET_FLAGS
+This variable specifies the initial value of @code{target_flags}.
+Its default setting is 0.
+@end deftypevr
+
+@cindex optional hardware or system features
+@cindex features, optional, in system conventions
+
+@hook TARGET_HANDLE_OPTION
+This hook is called whenever the user specifies one of the
+target-specific options described by the @file{.opt} definition files
+(@pxref{Options}). It has the opportunity to do some option-specific
+processing and should return true if the option is valid. The default
+definition does nothing but return true.
+
+@var{decoded} specifies the option and its arguments. @var{opts} and
+@var{opts_set} are the @code{gcc_options} structures to be used for
+storing option state, and @var{loc} is the location at which the
+option was passed (@code{UNKNOWN_LOCATION} except for options passed
+via attributes).
+@end deftypefn
+
+@hook TARGET_HANDLE_C_OPTION
+This target hook is called whenever the user specifies one of the
+target-specific C language family options described by the @file{.opt}
+definition files(@pxref{Options}). It has the opportunity to do some
+option-specific processing and should return true if the option is
+valid. The arguments are like for @code{TARGET_HANDLE_OPTION}. The
+default definition does nothing but return false.
+
+In general, you should use @code{TARGET_HANDLE_OPTION} to handle
+options. However, if processing an option requires routines that are
+only available in the C (and related language) front ends, then you
+should use @code{TARGET_HANDLE_C_OPTION} instead.
+@end deftypefn
+
+@hook TARGET_OBJC_CONSTRUCT_STRING_OBJECT
+
+@hook TARGET_OBJC_DECLARE_UNRESOLVED_CLASS_REFERENCE
+
+@hook TARGET_OBJC_DECLARE_CLASS_DEFINITION
+
+@hook TARGET_STRING_OBJECT_REF_TYPE_P
+
+@hook TARGET_CHECK_STRING_OBJECT_FORMAT_ARG
+
+@hook TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE
+
+@defmac C_COMMON_OVERRIDE_OPTIONS
+This is similar to the @code{TARGET_OPTION_OVERRIDE} hook
+but is only used in the C
+language frontends (C, Objective-C, C++, Objective-C++) and so can be
+used to alter option flag variables which only exist in those
+frontends.
+@end defmac
+
+@hook TARGET_OPTION_OPTIMIZATION_TABLE
+Some machines may desire to change what optimizations are performed for
+various optimization levels. This variable, if defined, describes
+options to enable at particular sets of optimization levels. These
+options are processed once
+just after the optimization level is determined and before the remainder
+of the command options have been parsed, so may be overridden by other
+options passed explicitly.
+
+This processing is run once at program startup and when the optimization
+options are changed via @code{#pragma GCC optimize} or by using the
+@code{optimize} attribute.
+@end deftypevr
+
+@hook TARGET_OPTION_INIT_STRUCT
+
+@hook TARGET_COMPUTE_MULTILIB
+
+
+@defmac SWITCHABLE_TARGET
+Some targets need to switch between substantially different subtargets
+during compilation. For example, the MIPS target has one subtarget for
+the traditional MIPS architecture and another for MIPS16. Source code
+can switch between these two subarchitectures using the @code{mips16}
+and @code{nomips16} attributes.
+
+Such subtargets can differ in things like the set of available
+registers, the set of available instructions, the costs of various
+operations, and so on. GCC caches a lot of this type of information
+in global variables, and recomputing them for each subtarget takes a
+significant amount of time. The compiler therefore provides a facility
+for maintaining several versions of the global variables and quickly
+switching between them; see @file{target-globals.h} for details.
+
+Define this macro to 1 if your target needs this facility. The default
+is 0.
+@end defmac
+
+@hook TARGET_FLOAT_EXCEPTIONS_ROUNDING_SUPPORTED_P
+
+@node Per-Function Data
+@section Defining data structures for per-function information.
+@cindex per-function data
+@cindex data structures
+
+If the target needs to store information on a per-function basis, GCC
+provides a macro and a couple of variables to allow this. Note, just
+using statics to store the information is a bad idea, since GCC supports
+nested functions, so you can be halfway through encoding one function
+when another one comes along.
+
+GCC defines a data structure called @code{struct function} which
+contains all of the data specific to an individual function. This
+structure contains a field called @code{machine} whose type is
+@code{struct machine_function *}, which can be used by targets to point
+to their own specific data.
+
+If a target needs per-function specific data it should define the type
+@code{struct machine_function} and also the macro @code{INIT_EXPANDERS}.
+This macro should be used to initialize the function pointer
+@code{init_machine_status}. This pointer is explained below.
+
+One typical use of per-function, target specific data is to create an
+RTX to hold the register containing the function's return address. This
+RTX can then be used to implement the @code{__builtin_return_address}
+function, for level 0.
+
+Note---earlier implementations of GCC used a single data area to hold
+all of the per-function information. Thus when processing of a nested
+function began the old per-function data had to be pushed onto a
+stack, and when the processing was finished, it had to be popped off the
+stack. GCC used to provide function pointers called
+@code{save_machine_status} and @code{restore_machine_status} to handle
+the saving and restoring of the target specific information. Since the
+single data area approach is no longer used, these pointers are no
+longer supported.
+
+@defmac INIT_EXPANDERS
+Macro called to initialize any target specific information. This macro
+is called once per function, before generation of any RTL has begun.
+The intention of this macro is to allow the initialization of the
+function pointer @code{init_machine_status}.
+@end defmac
+
+@deftypevar {void (*)(struct function *)} init_machine_status
+If this function pointer is non-@code{NULL} it will be called once per
+function, before function compilation starts, in order to allow the
+target to perform any target specific initialization of the
+@code{struct function} structure. It is intended that this would be
+used to initialize the @code{machine} of that structure.
+
+@code{struct machine_function} structures are expected to be freed by GC@.
+Generally, any memory that they reference must be allocated by using
+GC allocation, including the structure itself.
+@end deftypevar
+
+@node Storage Layout
+@section Storage Layout
+@cindex storage layout
+
+Note that the definitions of the macros in this table which are sizes or
+alignments measured in bits do not need to be constant. They can be C
+expressions that refer to static variables, such as the @code{target_flags}.
+@xref{Run-time Target}.
+
+@defmac BITS_BIG_ENDIAN
+Define this macro to have the value 1 if the most significant bit in a
+byte has the lowest number; otherwise define it to have the value zero.
+This means that bit-field instructions count from the most significant
+bit. If the machine has no bit-field instructions, then this must still
+be defined, but it doesn't matter which value it is defined to. This
+macro need not be a constant.
+
+This macro does not affect the way structure fields are packed into
+bytes or words; that is controlled by @code{BYTES_BIG_ENDIAN}.
+@end defmac
+
+@defmac BYTES_BIG_ENDIAN
+Define this macro to have the value 1 if the most significant byte in a
+word has the lowest number. This macro need not be a constant.
+@end defmac
+
+@defmac WORDS_BIG_ENDIAN
+Define this macro to have the value 1 if, in a multiword object, the
+most significant word has the lowest number. This applies to both
+memory locations and registers; see @code{REG_WORDS_BIG_ENDIAN} if the
+order of words in memory is not the same as the order in registers. This
+macro need not be a constant.
+@end defmac
+
+@defmac REG_WORDS_BIG_ENDIAN
+On some machines, the order of words in a multiword object differs between
+registers in memory. In such a situation, define this macro to describe
+the order of words in a register. The macro @code{WORDS_BIG_ENDIAN} controls
+the order of words in memory.
+@end defmac
+
+@defmac FLOAT_WORDS_BIG_ENDIAN
+Define this macro to have the value 1 if @code{DFmode}, @code{XFmode} or
+@code{TFmode} floating point numbers are stored in memory with the word
+containing the sign bit at the lowest address; otherwise define it to
+have the value 0. This macro need not be a constant.
+
+You need not define this macro if the ordering is the same as for
+multi-word integers.
+@end defmac
+
+@defmac BITS_PER_WORD
+Number of bits in a word. If you do not define this macro, the default
+is @code{BITS_PER_UNIT * UNITS_PER_WORD}.
+@end defmac
+
+@defmac MAX_BITS_PER_WORD
+Maximum number of bits in a word. If this is undefined, the default is
+@code{BITS_PER_WORD}. Otherwise, it is the constant value that is the
+largest value that @code{BITS_PER_WORD} can have at run-time.
+@end defmac
+
+@defmac UNITS_PER_WORD
+Number of storage units in a word; normally the size of a general-purpose
+register, a power of two from 1 or 8.
+@end defmac
+
+@defmac MIN_UNITS_PER_WORD
+Minimum number of units in a word. If this is undefined, the default is
+@code{UNITS_PER_WORD}. Otherwise, it is the constant value that is the
+smallest value that @code{UNITS_PER_WORD} can have at run-time.
+@end defmac
+
+@defmac POINTER_SIZE
+Width of a pointer, in bits. You must specify a value no wider than the
+width of @code{Pmode}. If it is not equal to the width of @code{Pmode},
+you must define @code{POINTERS_EXTEND_UNSIGNED}. If you do not specify
+a value the default is @code{BITS_PER_WORD}.
+@end defmac
+
+@defmac POINTERS_EXTEND_UNSIGNED
+A C expression that determines how pointers should be extended from
+@code{ptr_mode} to either @code{Pmode} or @code{word_mode}. It is
+greater than zero if pointers should be zero-extended, zero if they
+should be sign-extended, and negative if some other sort of conversion
+is needed. In the last case, the extension is done by the target's
+@code{ptr_extend} instruction.
+
+You need not define this macro if the @code{ptr_mode}, @code{Pmode}
+and @code{word_mode} are all the same width.
+@end defmac
+
+@defmac PROMOTE_MODE (@var{m}, @var{unsignedp}, @var{type})
+A macro to update @var{m} and @var{unsignedp} when an object whose type
+is @var{type} and which has the specified mode and signedness is to be
+stored in a register. This macro is only called when @var{type} is a
+scalar type.
+
+On most RISC machines, which only have operations that operate on a full
+register, define this macro to set @var{m} to @code{word_mode} if
+@var{m} is an integer mode narrower than @code{BITS_PER_WORD}. In most
+cases, only integer modes should be widened because wider-precision
+floating-point operations are usually more expensive than their narrower
+counterparts.
+
+For most machines, the macro definition does not change @var{unsignedp}.
+However, some machines, have instructions that preferentially handle
+either signed or unsigned quantities of certain modes. For example, on
+the DEC Alpha, 32-bit loads from memory and 32-bit add instructions
+sign-extend the result to 64 bits. On such machines, set
+@var{unsignedp} according to which kind of extension is more efficient.
+
+Do not define this macro if it would never modify @var{m}.
+@end defmac
+
+@hook TARGET_C_EXCESS_PRECISION
+Return a value, with the same meaning as the C99 macro
+@code{FLT_EVAL_METHOD} that describes which excess precision should be
+applied.
+
+@hook TARGET_PROMOTE_FUNCTION_MODE
+
+@defmac PARM_BOUNDARY
+Normal alignment required for function parameters on the stack, in
+bits. All stack parameters receive at least this much alignment
+regardless of data type. On most machines, this is the same as the
+size of an integer.
+@end defmac
+
+@defmac STACK_BOUNDARY
+Define this macro to the minimum alignment enforced by hardware for the
+stack pointer on this machine. The definition is a C expression for the
+desired alignment (measured in bits). This value is used as a default
+if @code{PREFERRED_STACK_BOUNDARY} is not defined. On most machines,
+this should be the same as @code{PARM_BOUNDARY}.
+@end defmac
+
+@defmac PREFERRED_STACK_BOUNDARY
+Define this macro if you wish to preserve a certain alignment for the
+stack pointer, greater than what the hardware enforces. The definition
+is a C expression for the desired alignment (measured in bits). This
+macro must evaluate to a value equal to or larger than
+@code{STACK_BOUNDARY}.
+@end defmac
+
+@defmac INCOMING_STACK_BOUNDARY
+Define this macro if the incoming stack boundary may be different
+from @code{PREFERRED_STACK_BOUNDARY}. This macro must evaluate
+to a value equal to or larger than @code{STACK_BOUNDARY}.
+@end defmac
+
+@defmac FUNCTION_BOUNDARY
+Alignment required for a function entry point, in bits.
+@end defmac
+
+@defmac BIGGEST_ALIGNMENT
+Biggest alignment that any data type can require on this machine, in
+bits. Note that this is not the biggest alignment that is supported,
+just the biggest alignment that, when violated, may cause a fault.
+@end defmac
+
+@hook TARGET_ABSOLUTE_BIGGEST_ALIGNMENT
+
+@defmac MALLOC_ABI_ALIGNMENT
+Alignment, in bits, a C conformant malloc implementation has to
+provide. If not defined, the default value is @code{BITS_PER_WORD}.
+@end defmac
+
+@defmac ATTRIBUTE_ALIGNED_VALUE
+Alignment used by the @code{__attribute__ ((aligned))} construct. If
+not defined, the default value is @code{BIGGEST_ALIGNMENT}.
+@end defmac
+
+@defmac MINIMUM_ATOMIC_ALIGNMENT
+If defined, the smallest alignment, in bits, that can be given to an
+object that can be referenced in one operation, without disturbing any
+nearby object. Normally, this is @code{BITS_PER_UNIT}, but may be larger
+on machines that don't have byte or half-word store operations.
+@end defmac
+
+@defmac BIGGEST_FIELD_ALIGNMENT
+Biggest alignment that any structure or union field can require on this
+machine, in bits. If defined, this overrides @code{BIGGEST_ALIGNMENT} for
+structure and union fields only, unless the field alignment has been set
+by the @code{__attribute__ ((aligned (@var{n})))} construct.
+@end defmac
+
+@defmac ADJUST_FIELD_ALIGN (@var{field}, @var{type}, @var{computed})
+An expression for the alignment of a structure field @var{field} of
+type @var{type} if the alignment computed in the usual way (including
+applying of @code{BIGGEST_ALIGNMENT} and @code{BIGGEST_FIELD_ALIGNMENT} to the
+alignment) is @var{computed}. It overrides alignment only if the
+field alignment has not been set by the
+@code{__attribute__ ((aligned (@var{n})))} construct. Note that @var{field}
+may be @code{NULL_TREE} in case we just query for the minimum alignment
+of a field of type @var{type} in structure context.
+@end defmac
+
+@defmac MAX_STACK_ALIGNMENT
+Biggest stack alignment guaranteed by the backend. Use this macro
+to specify the maximum alignment of a variable on stack.
+
+If not defined, the default value is @code{STACK_BOUNDARY}.
+
+@c FIXME: The default should be @code{PREFERRED_STACK_BOUNDARY}.
+@c But the fix for PR 32893 indicates that we can only guarantee
+@c maximum stack alignment on stack up to @code{STACK_BOUNDARY}, not
+@c @code{PREFERRED_STACK_BOUNDARY}, if stack alignment isn't supported.
+@end defmac
+
+@defmac MAX_OFILE_ALIGNMENT
+Biggest alignment supported by the object file format of this machine.
+Use this macro to limit the alignment which can be specified using the
+@code{__attribute__ ((aligned (@var{n})))} construct for functions and
+objects with static storage duration. The alignment of automatic
+objects may exceed the object file format maximum up to the maximum
+supported by GCC. If not defined, the default value is
+@code{BIGGEST_ALIGNMENT}.
+
+On systems that use ELF, the default (in @file{config/elfos.h}) is
+the largest supported 32-bit ELF section alignment representable on
+a 32-bit host e.g.@: @samp{(((uint64_t) 1 << 28) * 8)}.
+On 32-bit ELF the largest supported section alignment in bits is
+@samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts.
+@end defmac
+
+@hook TARGET_LOWER_LOCAL_DECL_ALIGNMENT
+
+@hook TARGET_STATIC_RTX_ALIGNMENT
+
+@defmac DATA_ALIGNMENT (@var{type}, @var{basic-align})
+If defined, a C expression to compute the alignment for a variable in
+the static store. @var{type} is the data type, and @var{basic-align} is
+the alignment that the object would ordinarily have. The value of this
+macro is used instead of that alignment to align the object.
+
+If this macro is not defined, then @var{basic-align} is used.
+
+@findex strcpy
+One use of this macro is to increase alignment of medium-size data to
+make it all fit in fewer cache lines. Another is to cause character
+arrays to be word-aligned so that @code{strcpy} calls that copy
+constants to character arrays can be done inline.
+@end defmac
+
+@defmac DATA_ABI_ALIGNMENT (@var{type}, @var{basic-align})
+Similar to @code{DATA_ALIGNMENT}, but for the cases where the ABI mandates
+some alignment increase, instead of optimization only purposes. E.g.@
+AMD x86-64 psABI says that variables with array type larger than 15 bytes
+must be aligned to 16 byte boundaries.
+
+If this macro is not defined, then @var{basic-align} is used.
+@end defmac
+
+@hook TARGET_CONSTANT_ALIGNMENT
+
+@defmac LOCAL_ALIGNMENT (@var{type}, @var{basic-align})
+If defined, a C expression to compute the alignment for a variable in
+the local store. @var{type} is the data type, and @var{basic-align} is
+the alignment that the object would ordinarily have. The value of this
+macro is used instead of that alignment to align the object.
+
+If this macro is not defined, then @var{basic-align} is used.
+
+One use of this macro is to increase alignment of medium-size data to
+make it all fit in fewer cache lines.
+
+If the value of this macro has a type, it should be an unsigned type.
+@end defmac
+
+@hook TARGET_VECTOR_ALIGNMENT
+
+@defmac STACK_SLOT_ALIGNMENT (@var{type}, @var{mode}, @var{basic-align})
+If defined, a C expression to compute the alignment for stack slot.
+@var{type} is the data type, @var{mode} is the widest mode available,
+and @var{basic-align} is the alignment that the slot would ordinarily
+have. The value of this macro is used instead of that alignment to
+align the slot.
+
+If this macro is not defined, then @var{basic-align} is used when
+@var{type} is @code{NULL}. Otherwise, @code{LOCAL_ALIGNMENT} will
+be used.
+
+This macro is to set alignment of stack slot to the maximum alignment
+of all possible modes which the slot may have.
+
+If the value of this macro has a type, it should be an unsigned type.
+@end defmac
+
+@defmac LOCAL_DECL_ALIGNMENT (@var{decl})
+If defined, a C expression to compute the alignment for a local
+variable @var{decl}.
+
+If this macro is not defined, then
+@code{LOCAL_ALIGNMENT (TREE_TYPE (@var{decl}), DECL_ALIGN (@var{decl}))}
+is used.
+
+One use of this macro is to increase alignment of medium-size data to
+make it all fit in fewer cache lines.
+
+If the value of this macro has a type, it should be an unsigned type.
+@end defmac
+
+@defmac MINIMUM_ALIGNMENT (@var{exp}, @var{mode}, @var{align})
+If defined, a C expression to compute the minimum required alignment
+for dynamic stack realignment purposes for @var{exp} (a type or decl),
+@var{mode}, assuming normal alignment @var{align}.
+
+If this macro is not defined, then @var{align} will be used.
+@end defmac
+
+@defmac EMPTY_FIELD_BOUNDARY
+Alignment in bits to be given to a structure bit-field that follows an
+empty field such as @code{int : 0;}.
+
+If @code{PCC_BITFIELD_TYPE_MATTERS} is true, it overrides this macro.
+@end defmac
+
+@defmac STRUCTURE_SIZE_BOUNDARY
+Number of bits which any structure or union's size must be a multiple of.
+Each structure or union's size is rounded up to a multiple of this.
+
+If you do not define this macro, the default is the same as
+@code{BITS_PER_UNIT}.
+@end defmac
+
+@defmac STRICT_ALIGNMENT
+Define this macro to be the value 1 if instructions will fail to work
+if given data not on the nominal alignment. If instructions will merely
+go slower in that case, define this macro as 0.
+@end defmac
+
+@defmac PCC_BITFIELD_TYPE_MATTERS
+Define this if you wish to imitate the way many other C compilers handle
+alignment of bit-fields and the structures that contain them.
+
+The behavior is that the type written for a named bit-field (@code{int},
+@code{short}, or other integer type) imposes an alignment for the entire
+structure, as if the structure really did contain an ordinary field of
+that type. In addition, the bit-field is placed within the structure so
+that it would fit within such a field, not crossing a boundary for it.
+
+Thus, on most machines, a named bit-field whose type is written as
+@code{int} would not cross a four-byte boundary, and would force
+four-byte alignment for the whole structure. (The alignment used may
+not be four bytes; it is controlled by the other alignment parameters.)
+
+An unnamed bit-field will not affect the alignment of the containing
+structure.
+
+If the macro is defined, its definition should be a C expression;
+a nonzero value for the expression enables this behavior.
+
+Note that if this macro is not defined, or its value is zero, some
+bit-fields may cross more than one alignment boundary. The compiler can
+support such references if there are @samp{insv}, @samp{extv}, and
+@samp{extzv} insns that can directly reference memory.
+
+The other known way of making bit-fields work is to define
+@code{STRUCTURE_SIZE_BOUNDARY} as large as @code{BIGGEST_ALIGNMENT}.
+Then every structure can be accessed with fullwords.
+
+Unless the machine has bit-field instructions or you define
+@code{STRUCTURE_SIZE_BOUNDARY} that way, you must define
+@code{PCC_BITFIELD_TYPE_MATTERS} to have a nonzero value.
+
+If your aim is to make GCC use the same conventions for laying out
+bit-fields as are used by another compiler, here is how to investigate
+what the other compiler does. Compile and run this program:
+
+@smallexample
+struct foo1
+@{
+ char x;
+ char :0;
+ char y;
+@};
+
+struct foo2
+@{
+ char x;
+ int :0;
+ char y;
+@};
+
+main ()
+@{
+ printf ("Size of foo1 is %d\n",
+ sizeof (struct foo1));
+ printf ("Size of foo2 is %d\n",
+ sizeof (struct foo2));
+ exit (0);
+@}
+@end smallexample
+
+If this prints 2 and 5, then the compiler's behavior is what you would
+get from @code{PCC_BITFIELD_TYPE_MATTERS}.
+@end defmac
+
+@defmac BITFIELD_NBYTES_LIMITED
+Like @code{PCC_BITFIELD_TYPE_MATTERS} except that its effect is limited
+to aligning a bit-field within the structure.
+@end defmac
+
+@hook TARGET_ALIGN_ANON_BITFIELD
+
+@hook TARGET_NARROW_VOLATILE_BITFIELD
+
+@hook TARGET_MEMBER_TYPE_FORCES_BLK
+
+@defmac ROUND_TYPE_ALIGN (@var{type}, @var{computed}, @var{specified})
+Define this macro as an expression for the alignment of a type (given
+by @var{type} as a tree node) if the alignment computed in the usual
+way is @var{computed} and the alignment explicitly specified was
+@var{specified}.
+
+The default is to use @var{specified} if it is larger; otherwise, use
+the smaller of @var{computed} and @code{BIGGEST_ALIGNMENT}
+@end defmac
+
+@defmac MAX_FIXED_MODE_SIZE
+An integer expression for the size in bits of the largest integer
+machine mode that should actually be used. All integer machine modes of
+this size or smaller can be used for structures and unions with the
+appropriate sizes. If this macro is undefined, @code{GET_MODE_BITSIZE
+(DImode)} is assumed.
+@end defmac
+
+@defmac STACK_SAVEAREA_MODE (@var{save_level})
+If defined, an expression of type @code{machine_mode} that
+specifies the mode of the save area operand of a
+@code{save_stack_@var{level}} named pattern (@pxref{Standard Names}).
+@var{save_level} is one of @code{SAVE_BLOCK}, @code{SAVE_FUNCTION}, or
+@code{SAVE_NONLOCAL} and selects which of the three named patterns is
+having its mode specified.
+
+You need not define this macro if it always returns @code{Pmode}. You
+would most commonly define this macro if the
+@code{save_stack_@var{level}} patterns need to support both a 32- and a
+64-bit mode.
+@end defmac
+
+@defmac STACK_SIZE_MODE
+If defined, an expression of type @code{machine_mode} that
+specifies the mode of the size increment operand of an
+@code{allocate_stack} named pattern (@pxref{Standard Names}).
+
+You need not define this macro if it always returns @code{word_mode}.
+You would most commonly define this macro if the @code{allocate_stack}
+pattern needs to support both a 32- and a 64-bit mode.
+@end defmac
+
+@hook TARGET_LIBGCC_CMP_RETURN_MODE
+
+@hook TARGET_LIBGCC_SHIFT_COUNT_MODE
+
+@hook TARGET_UNWIND_WORD_MODE
+
+@hook TARGET_MS_BITFIELD_LAYOUT_P
+
+@hook TARGET_DECIMAL_FLOAT_SUPPORTED_P
+
+@hook TARGET_FIXED_POINT_SUPPORTED_P
+
+@hook TARGET_EXPAND_TO_RTL_HOOK
+
+@hook TARGET_INSTANTIATE_DECLS
+
+@hook TARGET_MANGLE_TYPE
+
+@node Type Layout
+@section Layout of Source Language Data Types
+
+These macros define the sizes and other characteristics of the standard
+basic data types used in programs being compiled. Unlike the macros in
+the previous section, these apply to specific features of C and related
+languages, rather than to fundamental aspects of storage layout.
+
+@defmac INT_TYPE_SIZE
+A C expression for the size in bits of the type @code{int} on the
+target machine. If you don't define this, the default is one word.
+@end defmac
+
+@defmac SHORT_TYPE_SIZE
+A C expression for the size in bits of the type @code{short} on the
+target machine. If you don't define this, the default is half a word.
+(If this would be less than one storage unit, it is rounded up to one
+unit.)
+@end defmac
+
+@defmac LONG_TYPE_SIZE
+A C expression for the size in bits of the type @code{long} on the
+target machine. If you don't define this, the default is one word.
+@end defmac
+
+@defmac ADA_LONG_TYPE_SIZE
+On some machines, the size used for the Ada equivalent of the type
+@code{long} by a native Ada compiler differs from that used by C@. In
+that situation, define this macro to be a C expression to be used for
+the size of that type. If you don't define this, the default is the
+value of @code{LONG_TYPE_SIZE}.
+@end defmac
+
+@defmac LONG_LONG_TYPE_SIZE
+A C expression for the size in bits of the type @code{long long} on the
+target machine. If you don't define this, the default is two
+words. If you want to support GNU Ada on your machine, the value of this
+macro must be at least 64.
+@end defmac
+
+@defmac CHAR_TYPE_SIZE
+A C expression for the size in bits of the type @code{char} on the
+target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT}.
+@end defmac
+
+@defmac BOOL_TYPE_SIZE
+A C expression for the size in bits of the C++ type @code{bool} and
+C99 type @code{_Bool} on the target machine. If you don't define
+this, and you probably shouldn't, the default is @code{CHAR_TYPE_SIZE}.
+@end defmac
+
+@defmac FLOAT_TYPE_SIZE
+A C expression for the size in bits of the type @code{float} on the
+target machine. If you don't define this, the default is one word.
+@end defmac
+
+@defmac DOUBLE_TYPE_SIZE
+A C expression for the size in bits of the type @code{double} on the
+target machine. If you don't define this, the default is two
+words.
+@end defmac
+
+@defmac LONG_DOUBLE_TYPE_SIZE
+A C expression for the size in bits of the type @code{long double} on
+the target machine. If you don't define this, the default is two
+words.
+@end defmac
+
+@defmac SHORT_FRACT_TYPE_SIZE
+A C expression for the size in bits of the type @code{short _Fract} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT}.
+@end defmac
+
+@defmac FRACT_TYPE_SIZE
+A C expression for the size in bits of the type @code{_Fract} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 2}.
+@end defmac
+
+@defmac LONG_FRACT_TYPE_SIZE
+A C expression for the size in bits of the type @code{long _Fract} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 4}.
+@end defmac
+
+@defmac LONG_LONG_FRACT_TYPE_SIZE
+A C expression for the size in bits of the type @code{long long _Fract} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 8}.
+@end defmac
+
+@defmac SHORT_ACCUM_TYPE_SIZE
+A C expression for the size in bits of the type @code{short _Accum} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 2}.
+@end defmac
+
+@defmac ACCUM_TYPE_SIZE
+A C expression for the size in bits of the type @code{_Accum} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 4}.
+@end defmac
+
+@defmac LONG_ACCUM_TYPE_SIZE
+A C expression for the size in bits of the type @code{long _Accum} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 8}.
+@end defmac
+
+@defmac LONG_LONG_ACCUM_TYPE_SIZE
+A C expression for the size in bits of the type @code{long long _Accum} on
+the target machine. If you don't define this, the default is
+@code{BITS_PER_UNIT * 16}.
+@end defmac
+
+@defmac LIBGCC2_GNU_PREFIX
+This macro corresponds to the @code{TARGET_LIBFUNC_GNU_PREFIX} target
+hook and should be defined if that hook is overriden to be true. It
+causes function names in libgcc to be changed to use a @code{__gnu_}
+prefix for their name rather than the default @code{__}. A port which
+uses this macro should also arrange to use @file{t-gnu-prefix} in
+the libgcc @file{config.host}.
+@end defmac
+
+@defmac WIDEST_HARDWARE_FP_SIZE
+A C expression for the size in bits of the widest floating-point format
+supported by the hardware. If you define this macro, you must specify a
+value less than or equal to the value of @code{LONG_DOUBLE_TYPE_SIZE}.
+If you do not define this macro, the value of @code{LONG_DOUBLE_TYPE_SIZE}
+is the default.
+@end defmac
+
+@defmac DEFAULT_SIGNED_CHAR
+An expression whose value is 1 or 0, according to whether the type
+@code{char} should be signed or unsigned by default. The user can
+always override this default with the options @option{-fsigned-char}
+and @option{-funsigned-char}.
+@end defmac
+
+@hook TARGET_DEFAULT_SHORT_ENUMS
+
+@defmac SIZE_TYPE
+A C expression for a string describing the name of the data type to use
+for size values. The typedef name @code{size_t} is defined using the
+contents of the string.
+
+The string can contain more than one keyword. If so, separate them with
+spaces, and write first any length keyword, then @code{unsigned} if
+appropriate, and finally @code{int}. The string must exactly match one
+of the data type names defined in the function
+@code{c_common_nodes_and_builtins} in the file @file{c-family/c-common.cc}.
+You may not omit @code{int} or change the order---that would cause the
+compiler to crash on startup.
+
+If you don't define this macro, the default is @code{"long unsigned
+int"}.
+@end defmac
+
+@defmac SIZETYPE
+GCC defines internal types (@code{sizetype}, @code{ssizetype},
+@code{bitsizetype} and @code{sbitsizetype}) for expressions
+dealing with size. This macro is a C expression for a string describing
+the name of the data type from which the precision of @code{sizetype}
+is extracted.
+
+The string has the same restrictions as @code{SIZE_TYPE} string.
+
+If you don't define this macro, the default is @code{SIZE_TYPE}.
+@end defmac
+
+@defmac PTRDIFF_TYPE
+A C expression for a string describing the name of the data type to use
+for the result of subtracting two pointers. The typedef name
+@code{ptrdiff_t} is defined using the contents of the string. See
+@code{SIZE_TYPE} above for more information.
+
+If you don't define this macro, the default is @code{"long int"}.
+@end defmac
+
+@defmac WCHAR_TYPE
+A C expression for a string describing the name of the data type to use
+for wide characters. The typedef name @code{wchar_t} is defined using
+the contents of the string. See @code{SIZE_TYPE} above for more
+information.
+
+If you don't define this macro, the default is @code{"int"}.
+@end defmac
+
+@defmac WCHAR_TYPE_SIZE
+A C expression for the size in bits of the data type for wide
+characters. This is used in @code{cpp}, which cannot make use of
+@code{WCHAR_TYPE}.
+@end defmac
+
+@defmac WINT_TYPE
+A C expression for a string describing the name of the data type to
+use for wide characters passed to @code{printf} and returned from
+@code{getwc}. The typedef name @code{wint_t} is defined using the
+contents of the string. See @code{SIZE_TYPE} above for more
+information.
+
+If you don't define this macro, the default is @code{"unsigned int"}.
+@end defmac
+
+@defmac INTMAX_TYPE
+A C expression for a string describing the name of the data type that
+can represent any value of any standard or extended signed integer type.
+The typedef name @code{intmax_t} is defined using the contents of the
+string. See @code{SIZE_TYPE} above for more information.
+
+If you don't define this macro, the default is the first of
+@code{"int"}, @code{"long int"}, or @code{"long long int"} that has as
+much precision as @code{long long int}.
+@end defmac
+
+@defmac UINTMAX_TYPE
+A C expression for a string describing the name of the data type that
+can represent any value of any standard or extended unsigned integer
+type. The typedef name @code{uintmax_t} is defined using the contents
+of the string. See @code{SIZE_TYPE} above for more information.
+
+If you don't define this macro, the default is the first of
+@code{"unsigned int"}, @code{"long unsigned int"}, or @code{"long long
+unsigned int"} that has as much precision as @code{long long unsigned
+int}.
+@end defmac
+
+@defmac SIG_ATOMIC_TYPE
+@defmacx INT8_TYPE
+@defmacx INT16_TYPE
+@defmacx INT32_TYPE
+@defmacx INT64_TYPE
+@defmacx UINT8_TYPE
+@defmacx UINT16_TYPE
+@defmacx UINT32_TYPE
+@defmacx UINT64_TYPE
+@defmacx INT_LEAST8_TYPE
+@defmacx INT_LEAST16_TYPE
+@defmacx INT_LEAST32_TYPE
+@defmacx INT_LEAST64_TYPE
+@defmacx UINT_LEAST8_TYPE
+@defmacx UINT_LEAST16_TYPE
+@defmacx UINT_LEAST32_TYPE
+@defmacx UINT_LEAST64_TYPE
+@defmacx INT_FAST8_TYPE
+@defmacx INT_FAST16_TYPE
+@defmacx INT_FAST32_TYPE
+@defmacx INT_FAST64_TYPE
+@defmacx UINT_FAST8_TYPE
+@defmacx UINT_FAST16_TYPE
+@defmacx UINT_FAST32_TYPE
+@defmacx UINT_FAST64_TYPE
+@defmacx INTPTR_TYPE
+@defmacx UINTPTR_TYPE
+C expressions for the standard types @code{sig_atomic_t},
+@code{int8_t}, @code{int16_t}, @code{int32_t}, @code{int64_t},
+@code{uint8_t}, @code{uint16_t}, @code{uint32_t}, @code{uint64_t},
+@code{int_least8_t}, @code{int_least16_t}, @code{int_least32_t},
+@code{int_least64_t}, @code{uint_least8_t}, @code{uint_least16_t},
+@code{uint_least32_t}, @code{uint_least64_t}, @code{int_fast8_t},
+@code{int_fast16_t}, @code{int_fast32_t}, @code{int_fast64_t},
+@code{uint_fast8_t}, @code{uint_fast16_t}, @code{uint_fast32_t},
+@code{uint_fast64_t}, @code{intptr_t}, and @code{uintptr_t}. See
+@code{SIZE_TYPE} above for more information.
+
+If any of these macros evaluates to a null pointer, the corresponding
+type is not supported; if GCC is configured to provide
+@code{<stdint.h>} in such a case, the header provided may not conform
+to C99, depending on the type in question. The defaults for all of
+these macros are null pointers.
+@end defmac
+
+@defmac TARGET_PTRMEMFUNC_VBIT_LOCATION
+The C++ compiler represents a pointer-to-member-function with a struct
+that looks like:
+
+@smallexample
+ struct @{
+ union @{
+ void (*fn)();
+ ptrdiff_t vtable_index;
+ @};
+ ptrdiff_t delta;
+ @};
+@end smallexample
+
+@noindent
+The C++ compiler must use one bit to indicate whether the function that
+will be called through a pointer-to-member-function is virtual.
+Normally, we assume that the low-order bit of a function pointer must
+always be zero. Then, by ensuring that the vtable_index is odd, we can
+distinguish which variant of the union is in use. But, on some
+platforms function pointers can be odd, and so this doesn't work. In
+that case, we use the low-order bit of the @code{delta} field, and shift
+the remainder of the @code{delta} field to the left.
+
+GCC will automatically make the right selection about where to store
+this bit using the @code{FUNCTION_BOUNDARY} setting for your platform.
+However, some platforms such as ARM/Thumb have @code{FUNCTION_BOUNDARY}
+set such that functions always start at even addresses, but the lowest
+bit of pointers to functions indicate whether the function at that
+address is in ARM or Thumb mode. If this is the case of your
+architecture, you should define this macro to
+@code{ptrmemfunc_vbit_in_delta}.
+
+In general, you should not have to define this macro. On architectures
+in which function addresses are always even, according to
+@code{FUNCTION_BOUNDARY}, GCC will automatically define this macro to
+@code{ptrmemfunc_vbit_in_pfn}.
+@end defmac
+
+@defmac TARGET_VTABLE_USES_DESCRIPTORS
+Normally, the C++ compiler uses function pointers in vtables. This
+macro allows the target to change to use ``function descriptors''
+instead. Function descriptors are found on targets for whom a
+function pointer is actually a small data structure. Normally the
+data structure consists of the actual code address plus a data
+pointer to which the function's data is relative.
+
+If vtables are used, the value of this macro should be the number
+of words that the function descriptor occupies.
+@end defmac
+
+@defmac TARGET_VTABLE_ENTRY_ALIGN
+By default, the vtable entries are void pointers, the so the alignment
+is the same as pointer alignment. The value of this macro specifies
+the alignment of the vtable entry in bits. It should be defined only
+when special alignment is necessary. */
+@end defmac
+
+@defmac TARGET_VTABLE_DATA_ENTRY_DISTANCE
+There are a few non-descriptor entries in the vtable at offsets below
+zero. If these entries must be padded (say, to preserve the alignment
+specified by @code{TARGET_VTABLE_ENTRY_ALIGN}), set this to the number
+of words in each data entry.
+@end defmac
+
+@node Registers
+@section Register Usage
+@cindex register usage
+
+This section explains how to describe what registers the target machine
+has, and how (in general) they can be used.
+
+The description of which registers a specific instruction can use is
+done with register classes; see @ref{Register Classes}. For information
+on using registers to access a stack frame, see @ref{Frame Registers}.
+For passing values in registers, see @ref{Register Arguments}.
+For returning values in registers, see @ref{Scalar Return}.
+
+@menu
+* Register Basics:: Number and kinds of registers.
+* Allocation Order:: Order in which registers are allocated.
+* Values in Registers:: What kinds of values each reg can hold.
+* Leaf Functions:: Renumbering registers for leaf functions.
+* Stack Registers:: Handling a register stack such as 80387.
+@end menu
+
+@node Register Basics
+@subsection Basic Characteristics of Registers
+
+@c prevent bad page break with this line
+Registers have various characteristics.
+
+@defmac FIRST_PSEUDO_REGISTER
+Number of hardware registers known to the compiler. They receive
+numbers 0 through @code{FIRST_PSEUDO_REGISTER-1}; thus, the first
+pseudo register's number really is assigned the number
+@code{FIRST_PSEUDO_REGISTER}.
+@end defmac
+
+@defmac FIXED_REGISTERS
+@cindex fixed register
+An initializer that says which registers are used for fixed purposes
+all throughout the compiled code and are therefore not available for
+general allocation. These would include the stack pointer, the frame
+pointer (except on machines where that can be used as a general
+register when no frame pointer is needed), the program counter on
+machines where that is considered one of the addressable registers,
+and any other numbered register with a standard use.
+
+This information is expressed as a sequence of numbers, separated by
+commas and surrounded by braces. The @var{n}th number is 1 if
+register @var{n} is fixed, 0 otherwise.
+
+The table initialized from this macro, and the table initialized by
+the following one, may be overridden at run time either automatically,
+by the actions of the macro @code{CONDITIONAL_REGISTER_USAGE}, or by
+the user with the command options @option{-ffixed-@var{reg}},
+@option{-fcall-used-@var{reg}} and @option{-fcall-saved-@var{reg}}.
+@end defmac
+
+@defmac CALL_USED_REGISTERS
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+Like @code{FIXED_REGISTERS} but has 1 for each register that is
+clobbered (in general) by function calls as well as for fixed
+registers. This macro therefore identifies the registers that are not
+available for general allocation of values that must live across
+function calls.
+
+If a register has 0 in @code{CALL_USED_REGISTERS}, the compiler
+automatically saves it on function entry and restores it on function
+exit, if the register is used within the function.
+
+Exactly one of @code{CALL_USED_REGISTERS} and @code{CALL_REALLY_USED_REGISTERS}
+must be defined. Modern ports should define @code{CALL_REALLY_USED_REGISTERS}.
+@end defmac
+
+@defmac CALL_REALLY_USED_REGISTERS
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+Like @code{CALL_USED_REGISTERS} except this macro doesn't require
+that the entire set of @code{FIXED_REGISTERS} be included.
+(@code{CALL_USED_REGISTERS} must be a superset of @code{FIXED_REGISTERS}).
+
+Exactly one of @code{CALL_USED_REGISTERS} and @code{CALL_REALLY_USED_REGISTERS}
+must be defined. Modern ports should define @code{CALL_REALLY_USED_REGISTERS}.
+@end defmac
+
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+@hook TARGET_FNTYPE_ABI
+
+@hook TARGET_INSN_CALLEE_ABI
+
+@cindex call-used register
+@cindex call-clobbered register
+@cindex call-saved register
+@hook TARGET_HARD_REGNO_CALL_PART_CLOBBERED
+
+@hook TARGET_GET_MULTILIB_ABI_NAME
+
+@findex fixed_regs
+@findex call_used_regs
+@findex global_regs
+@findex reg_names
+@findex reg_class_contents
+@hook TARGET_CONDITIONAL_REGISTER_USAGE
+
+@defmac INCOMING_REGNO (@var{out})
+Define this macro if the target machine has register windows. This C
+expression returns the register number as seen by the called function
+corresponding to the register number @var{out} as seen by the calling
+function. Return @var{out} if register number @var{out} is not an
+outbound register.
+@end defmac
+
+@defmac OUTGOING_REGNO (@var{in})
+Define this macro if the target machine has register windows. This C
+expression returns the register number as seen by the calling function
+corresponding to the register number @var{in} as seen by the called
+function. Return @var{in} if register number @var{in} is not an inbound
+register.
+@end defmac
+
+@defmac LOCAL_REGNO (@var{regno})
+Define this macro if the target machine has register windows. This C
+expression returns true if the register is call-saved but is in the
+register window. Unlike most call-saved registers, such registers
+need not be explicitly restored on function exit or during non-local
+gotos.
+@end defmac
+
+@defmac PC_REGNUM
+If the program counter has a register number, define this as that
+register number. Otherwise, do not define it.
+@end defmac
+
+@node Allocation Order
+@subsection Order of Allocation of Registers
+@cindex order of register allocation
+@cindex register allocation order
+
+@c prevent bad page break with this line
+Registers are allocated in order.
+
+@defmac REG_ALLOC_ORDER
+If defined, an initializer for a vector of integers, containing the
+numbers of hard registers in the order in which GCC should prefer
+to use them (from most preferred to least).
+
+If this macro is not defined, registers are used lowest numbered first
+(all else being equal).
+
+One use of this macro is on machines where the highest numbered
+registers must always be saved and the save-multiple-registers
+instruction supports only sequences of consecutive registers. On such
+machines, define @code{REG_ALLOC_ORDER} to be an initializer that lists
+the highest numbered allocable register first.
+@end defmac
+
+@defmac ADJUST_REG_ALLOC_ORDER
+A C statement (sans semicolon) to choose the order in which to allocate
+hard registers for pseudo-registers local to a basic block.
+
+Store the desired register order in the array @code{reg_alloc_order}.
+Element 0 should be the register to allocate first; element 1, the next
+register; and so on.
+
+The macro body should not assume anything about the contents of
+@code{reg_alloc_order} before execution of the macro.
+
+On most machines, it is not necessary to define this macro.
+@end defmac
+
+@defmac HONOR_REG_ALLOC_ORDER
+Normally, IRA tries to estimate the costs for saving a register in the
+prologue and restoring it in the epilogue. This discourages it from
+using call-saved registers. If a machine wants to ensure that IRA
+allocates registers in the order given by REG_ALLOC_ORDER even if some
+call-saved registers appear earlier than call-used ones, then define this
+macro as a C expression to nonzero. Default is 0.
+@end defmac
+
+@defmac IRA_HARD_REGNO_ADD_COST_MULTIPLIER (@var{regno})
+In some case register allocation order is not enough for the
+Integrated Register Allocator (@acronym{IRA}) to generate a good code.
+If this macro is defined, it should return a floating point value
+based on @var{regno}. The cost of using @var{regno} for a pseudo will
+be increased by approximately the pseudo's usage frequency times the
+value returned by this macro. Not defining this macro is equivalent
+to having it always return @code{0.0}.
+
+On most machines, it is not necessary to define this macro.
+@end defmac
+
+@node Values in Registers
+@subsection How Values Fit in Registers
+
+This section discusses the macros that describe which kinds of values
+(specifically, which machine modes) each register can hold, and how many
+consecutive registers are needed for a given mode.
+
+@hook TARGET_HARD_REGNO_NREGS
+
+@defmac HARD_REGNO_NREGS_HAS_PADDING (@var{regno}, @var{mode})
+A C expression that is nonzero if a value of mode @var{mode}, stored
+in memory, ends with padding that causes it to take up more space than
+in registers starting at register number @var{regno} (as determined by
+multiplying GCC's notion of the size of the register when containing
+this mode by the number of registers returned by
+@code{TARGET_HARD_REGNO_NREGS}). By default this is zero.
+
+For example, if a floating-point value is stored in three 32-bit
+registers but takes up 128 bits in memory, then this would be
+nonzero.
+
+This macros only needs to be defined if there are cases where
+@code{subreg_get_info}
+would otherwise wrongly determine that a @code{subreg} can be
+represented by an offset to the register number, when in fact such a
+@code{subreg} would contain some of the padding not stored in
+registers and so not be representable.
+@end defmac
+
+@defmac HARD_REGNO_NREGS_WITH_PADDING (@var{regno}, @var{mode})
+For values of @var{regno} and @var{mode} for which
+@code{HARD_REGNO_NREGS_HAS_PADDING} returns nonzero, a C expression
+returning the greater number of registers required to hold the value
+including any padding. In the example above, the value would be four.
+@end defmac
+
+@defmac REGMODE_NATURAL_SIZE (@var{mode})
+Define this macro if the natural size of registers that hold values
+of mode @var{mode} is not the word size. It is a C expression that
+should give the natural size in bytes for the specified mode. It is
+used by the register allocator to try to optimize its results. This
+happens for example on SPARC 64-bit where the natural size of
+floating-point registers is still 32-bit.
+@end defmac
+
+@hook TARGET_HARD_REGNO_MODE_OK
+
+@defmac HARD_REGNO_RENAME_OK (@var{from}, @var{to})
+A C expression that is nonzero if it is OK to rename a hard register
+@var{from} to another hard register @var{to}.
+
+One common use of this macro is to prevent renaming of a register to
+another register that is not saved by a prologue in an interrupt
+handler.
+
+The default is always nonzero.
+@end defmac
+
+@hook TARGET_MODES_TIEABLE_P
+
+@hook TARGET_HARD_REGNO_SCRATCH_OK
+
+@defmac AVOID_CCMODE_COPIES
+Define this macro if the compiler should avoid copies to/from @code{CCmode}
+registers. You should only define this macro if support for copying to/from
+@code{CCmode} is incomplete.
+@end defmac
+
+@node Leaf Functions
+@subsection Handling Leaf Functions
+
+@cindex leaf functions
+@cindex functions, leaf
+On some machines, a leaf function (i.e., one which makes no calls) can run
+more efficiently if it does not make its own register window. Often this
+means it is required to receive its arguments in the registers where they
+are passed by the caller, instead of the registers where they would
+normally arrive.
+
+The special treatment for leaf functions generally applies only when
+other conditions are met; for example, often they may use only those
+registers for its own variables and temporaries. We use the term ``leaf
+function'' to mean a function that is suitable for this special
+handling, so that functions with no calls are not necessarily ``leaf
+functions''.
+
+GCC assigns register numbers before it knows whether the function is
+suitable for leaf function treatment. So it needs to renumber the
+registers in order to output a leaf function. The following macros
+accomplish this.
+
+@defmac LEAF_REGISTERS
+Name of a char vector, indexed by hard register number, which
+contains 1 for a register that is allowable in a candidate for leaf
+function treatment.
+
+If leaf function treatment involves renumbering the registers, then the
+registers marked here should be the ones before renumbering---those that
+GCC would ordinarily allocate. The registers which will actually be
+used in the assembler code, after renumbering, should not be marked with 1
+in this vector.
+
+Define this macro only if the target machine offers a way to optimize
+the treatment of leaf functions.
+@end defmac
+
+@defmac LEAF_REG_REMAP (@var{regno})
+A C expression whose value is the register number to which @var{regno}
+should be renumbered, when a function is treated as a leaf function.
+
+If @var{regno} is a register number which should not appear in a leaf
+function before renumbering, then the expression should yield @minus{}1, which
+will cause the compiler to abort.
+
+Define this macro only if the target machine offers a way to optimize the
+treatment of leaf functions, and registers need to be renumbered to do
+this.
+@end defmac
+
+@findex current_function_is_leaf
+@findex current_function_uses_only_leaf_regs
+@code{TARGET_ASM_FUNCTION_PROLOGUE} and
+@code{TARGET_ASM_FUNCTION_EPILOGUE} must usually treat leaf functions
+specially. They can test the C variable @code{current_function_is_leaf}
+which is nonzero for leaf functions. @code{current_function_is_leaf} is
+set prior to local register allocation and is valid for the remaining
+compiler passes. They can also test the C variable
+@code{current_function_uses_only_leaf_regs} which is nonzero for leaf
+functions which only use leaf registers.
+@code{current_function_uses_only_leaf_regs} is valid after all passes
+that modify the instructions have been run and is only useful if
+@code{LEAF_REGISTERS} is defined.
+@c changed this to fix overfull. ALSO: why the "it" at the beginning
+@c of the next paragraph?! --mew 2feb93
+
+@node Stack Registers
+@subsection Registers That Form a Stack
+
+There are special features to handle computers where some of the
+``registers'' form a stack. Stack registers are normally written by
+pushing onto the stack, and are numbered relative to the top of the
+stack.
+
+Currently, GCC can only handle one group of stack-like registers, and
+they must be consecutively numbered. Furthermore, the existing
+support for stack-like registers is specific to the 80387 floating
+point coprocessor. If you have a new architecture that uses
+stack-like registers, you will need to do substantial work on
+@file{reg-stack.cc} and write your machine description to cooperate
+with it, as well as defining these macros.
+
+@defmac STACK_REGS
+Define this if the machine has any stack-like registers.
+@end defmac
+
+@defmac STACK_REG_COVER_CLASS
+This is a cover class containing the stack registers. Define this if
+the machine has any stack-like registers.
+@end defmac
+
+@defmac FIRST_STACK_REG
+The number of the first stack-like register. This one is the top
+of the stack.
+@end defmac
+
+@defmac LAST_STACK_REG
+The number of the last stack-like register. This one is the bottom of
+the stack.
+@end defmac
+
+@node Register Classes
+@section Register Classes
+@cindex register class definitions
+@cindex class definitions, register
+
+On many machines, the numbered registers are not all equivalent.
+For example, certain registers may not be allowed for indexed addressing;
+certain registers may not be allowed in some instructions. These machine
+restrictions are described to the compiler using @dfn{register classes}.
+
+You define a number of register classes, giving each one a name and saying
+which of the registers belong to it. Then you can specify register classes
+that are allowed as operands to particular instruction patterns.
+
+@findex ALL_REGS
+@findex NO_REGS
+In general, each register will belong to several classes. In fact, one
+class must be named @code{ALL_REGS} and contain all the registers. Another
+class must be named @code{NO_REGS} and contain no registers. Often the
+union of two classes will be another class; however, this is not required.
+
+@findex GENERAL_REGS
+One of the classes must be named @code{GENERAL_REGS}. There is nothing
+terribly special about the name, but the operand constraint letters
+@samp{r} and @samp{g} specify this class. If @code{GENERAL_REGS} is
+the same as @code{ALL_REGS}, just define it as a macro which expands
+to @code{ALL_REGS}.
+
+Order the classes so that if class @var{x} is contained in class @var{y}
+then @var{x} has a lower class number than @var{y}.
+
+The way classes other than @code{GENERAL_REGS} are specified in operand
+constraints is through machine-dependent operand constraint letters.
+You can define such letters to correspond to various classes, then use
+them in operand constraints.
+
+You must define the narrowest register classes for allocatable
+registers, so that each class either has no subclasses, or that for
+some mode, the move cost between registers within the class is
+cheaper than moving a register in the class to or from memory
+(@pxref{Costs}).
+
+You should define a class for the union of two classes whenever some
+instruction allows both classes. For example, if an instruction allows
+either a floating point (coprocessor) register or a general register for a
+certain operand, you should define a class @code{FLOAT_OR_GENERAL_REGS}
+which includes both of them. Otherwise you will get suboptimal code,
+or even internal compiler errors when reload cannot find a register in the
+class computed via @code{reg_class_subunion}.
+
+You must also specify certain redundant information about the register
+classes: for each class, which classes contain it and which ones are
+contained in it; for each pair of classes, the largest class contained
+in their union.
+
+When a value occupying several consecutive registers is expected in a
+certain class, all the registers used must belong to that class.
+Therefore, register classes cannot be used to enforce a requirement for
+a register pair to start with an even-numbered register. The way to
+specify this requirement is with @code{TARGET_HARD_REGNO_MODE_OK}.
+
+Register classes used for input-operands of bitwise-and or shift
+instructions have a special requirement: each such class must have, for
+each fixed-point machine mode, a subclass whose registers can transfer that
+mode to or from memory. For example, on some machines, the operations for
+single-byte values (@code{QImode}) are limited to certain registers. When
+this is so, each register class that is used in a bitwise-and or shift
+instruction must have a subclass consisting of registers from which
+single-byte values can be loaded or stored. This is so that
+@code{PREFERRED_RELOAD_CLASS} can always have a possible value to return.
+
+@deftp {Data type} {enum reg_class}
+An enumerated type that must be defined with all the register class names
+as enumerated values. @code{NO_REGS} must be first. @code{ALL_REGS}
+must be the last register class, followed by one more enumerated value,
+@code{LIM_REG_CLASSES}, which is not a register class but rather
+tells how many classes there are.
+
+Each register class has a number, which is the value of casting
+the class name to type @code{int}. The number serves as an index
+in many of the tables described below.
+@end deftp
+
+@defmac N_REG_CLASSES
+The number of distinct register classes, defined as follows:
+
+@smallexample
+#define N_REG_CLASSES (int) LIM_REG_CLASSES
+@end smallexample
+@end defmac
+
+@defmac REG_CLASS_NAMES
+An initializer containing the names of the register classes as C string
+constants. These names are used in writing some of the debugging dumps.
+@end defmac
+
+@defmac REG_CLASS_CONTENTS
+An initializer containing the contents of the register classes, as integers
+which are bit masks. The @var{n}th integer specifies the contents of class
+@var{n}. The way the integer @var{mask} is interpreted is that
+register @var{r} is in the class if @code{@var{mask} & (1 << @var{r})} is 1.
+
+When the machine has more than 32 registers, an integer does not suffice.
+Then the integers are replaced by sub-initializers, braced groupings containing
+several integers. Each sub-initializer must be suitable as an initializer
+for the type @code{HARD_REG_SET} which is defined in @file{hard-reg-set.h}.
+In this situation, the first integer in each sub-initializer corresponds to
+registers 0 through 31, the second integer to registers 32 through 63, and
+so on.
+@end defmac
+
+@defmac REGNO_REG_CLASS (@var{regno})
+A C expression whose value is a register class containing hard register
+@var{regno}. In general there is more than one such class; choose a class
+which is @dfn{minimal}, meaning that no smaller class also contains the
+register.
+@end defmac
+
+@defmac BASE_REG_CLASS
+A macro whose definition is the name of the class to which a valid
+base register must belong. A base register is one used in an address
+which is the register value plus a displacement.
+@end defmac
+
+@defmac MODE_BASE_REG_CLASS (@var{mode})
+This is a variation of the @code{BASE_REG_CLASS} macro which allows
+the selection of a base register in a mode dependent manner. If
+@var{mode} is VOIDmode then it should return the same value as
+@code{BASE_REG_CLASS}.
+@end defmac
+
+@defmac MODE_BASE_REG_REG_CLASS (@var{mode})
+A C expression whose value is the register class to which a valid
+base register must belong in order to be used in a base plus index
+register address. You should define this macro if base plus index
+addresses have different requirements than other base register uses.
+@end defmac
+
+@defmac MODE_CODE_BASE_REG_CLASS (@var{mode}, @var{address_space}, @var{outer_code}, @var{index_code})
+A C expression whose value is the register class to which a valid
+base register for a memory reference in mode @var{mode} to address
+space @var{address_space} must belong. @var{outer_code} and @var{index_code}
+define the context in which the base register occurs. @var{outer_code} is
+the code of the immediately enclosing expression (@code{MEM} for the top level
+of an address, @code{ADDRESS} for something that occurs in an
+@code{address_operand}). @var{index_code} is the code of the corresponding
+index expression if @var{outer_code} is @code{PLUS}; @code{SCRATCH} otherwise.
+@end defmac
+
+@defmac INDEX_REG_CLASS
+A macro whose definition is the name of the class to which a valid
+index register must belong. An index register is one used in an
+address where its value is either multiplied by a scale factor or
+added to another register (as well as added to a displacement).
+@end defmac
+
+@defmac REGNO_OK_FOR_BASE_P (@var{num})
+A C expression which is nonzero if register number @var{num} is
+suitable for use as a base register in operand addresses.
+@end defmac
+
+@defmac REGNO_MODE_OK_FOR_BASE_P (@var{num}, @var{mode})
+A C expression that is just like @code{REGNO_OK_FOR_BASE_P}, except that
+that expression may examine the mode of the memory reference in
+@var{mode}. You should define this macro if the mode of the memory
+reference affects whether a register may be used as a base register. If
+you define this macro, the compiler will use it instead of
+@code{REGNO_OK_FOR_BASE_P}. The mode may be @code{VOIDmode} for
+addresses that appear outside a @code{MEM}, i.e., as an
+@code{address_operand}.
+@end defmac
+
+@defmac REGNO_MODE_OK_FOR_REG_BASE_P (@var{num}, @var{mode})
+A C expression which is nonzero if register number @var{num} is suitable for
+use as a base register in base plus index operand addresses, accessing
+memory in mode @var{mode}. It may be either a suitable hard register or a
+pseudo register that has been allocated such a hard register. You should
+define this macro if base plus index addresses have different requirements
+than other base register uses.
+
+Use of this macro is deprecated; please use the more general
+@code{REGNO_MODE_CODE_OK_FOR_BASE_P}.
+@end defmac
+
+@defmac REGNO_MODE_CODE_OK_FOR_BASE_P (@var{num}, @var{mode}, @var{address_space}, @var{outer_code}, @var{index_code})
+A C expression which is nonzero if register number @var{num} is
+suitable for use as a base register in operand addresses, accessing
+memory in mode @var{mode} in address space @var{address_space}.
+This is similar to @code{REGNO_MODE_OK_FOR_BASE_P}, except
+that that expression may examine the context in which the register
+appears in the memory reference. @var{outer_code} is the code of the
+immediately enclosing expression (@code{MEM} if at the top level of the
+address, @code{ADDRESS} for something that occurs in an
+@code{address_operand}). @var{index_code} is the code of the
+corresponding index expression if @var{outer_code} is @code{PLUS};
+@code{SCRATCH} otherwise. The mode may be @code{VOIDmode} for addresses
+that appear outside a @code{MEM}, i.e., as an @code{address_operand}.
+@end defmac
+
+@defmac REGNO_OK_FOR_INDEX_P (@var{num})
+A C expression which is nonzero if register number @var{num} is
+suitable for use as an index register in operand addresses. It may be
+either a suitable hard register or a pseudo register that has been
+allocated such a hard register.
+
+The difference between an index register and a base register is that
+the index register may be scaled. If an address involves the sum of
+two registers, neither one of them scaled, then either one may be
+labeled the ``base'' and the other the ``index''; but whichever
+labeling is used must fit the machine's constraints of which registers
+may serve in each capacity. The compiler will try both labelings,
+looking for one that is valid, and will reload one or both registers
+only if neither labeling works.
+@end defmac
+
+@hook TARGET_PREFERRED_RENAME_CLASS
+
+@hook TARGET_PREFERRED_RELOAD_CLASS
+
+@defmac PREFERRED_RELOAD_CLASS (@var{x}, @var{class})
+A C expression that places additional restrictions on the register class
+to use when it is necessary to copy value @var{x} into a register in class
+@var{class}. The value is a register class; perhaps @var{class}, or perhaps
+another, smaller class. On many machines, the following definition is
+safe:
+
+@smallexample
+#define PREFERRED_RELOAD_CLASS(X,CLASS) CLASS
+@end smallexample
+
+Sometimes returning a more restrictive class makes better code. For
+example, on the 68000, when @var{x} is an integer constant that is in range
+for a @samp{moveq} instruction, the value of this macro is always
+@code{DATA_REGS} as long as @var{class} includes the data registers.
+Requiring a data register guarantees that a @samp{moveq} will be used.
+
+One case where @code{PREFERRED_RELOAD_CLASS} must not return
+@var{class} is if @var{x} is a legitimate constant which cannot be
+loaded into some register class. By returning @code{NO_REGS} you can
+force @var{x} into a memory location. For example, rs6000 can load
+immediate values into general-purpose registers, but does not have an
+instruction for loading an immediate value into a floating-point
+register, so @code{PREFERRED_RELOAD_CLASS} returns @code{NO_REGS} when
+@var{x} is a floating-point constant. If the constant cannot be loaded
+into any kind of register, code generation will be better if
+@code{TARGET_LEGITIMATE_CONSTANT_P} makes the constant illegitimate instead
+of using @code{TARGET_PREFERRED_RELOAD_CLASS}.
+
+If an insn has pseudos in it after register allocation, reload will go
+through the alternatives and call repeatedly @code{PREFERRED_RELOAD_CLASS}
+to find the best one. Returning @code{NO_REGS}, in this case, makes
+reload add a @code{!} in front of the constraint: the x86 back-end uses
+this feature to discourage usage of 387 registers when math is done in
+the SSE registers (and vice versa).
+@end defmac
+
+@hook TARGET_PREFERRED_OUTPUT_RELOAD_CLASS
+
+@defmac LIMIT_RELOAD_CLASS (@var{mode}, @var{class})
+A C expression that places additional restrictions on the register class
+to use when it is necessary to be able to hold a value of mode
+@var{mode} in a reload register for which class @var{class} would
+ordinarily be used.
+
+Unlike @code{PREFERRED_RELOAD_CLASS}, this macro should be used when
+there are certain modes that simply cannot go in certain reload classes.
+
+The value is a register class; perhaps @var{class}, or perhaps another,
+smaller class.
+
+Don't define this macro unless the target machine has limitations which
+require the macro to do something nontrivial.
+@end defmac
+
+@hook TARGET_SECONDARY_RELOAD
+
+@defmac SECONDARY_RELOAD_CLASS (@var{class}, @var{mode}, @var{x})
+@defmacx SECONDARY_INPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x})
+@defmacx SECONDARY_OUTPUT_RELOAD_CLASS (@var{class}, @var{mode}, @var{x})
+These macros are obsolete, new ports should use the target hook
+@code{TARGET_SECONDARY_RELOAD} instead.
+
+These are obsolete macros, replaced by the @code{TARGET_SECONDARY_RELOAD}
+target hook. Older ports still define these macros to indicate to the
+reload phase that it may
+need to allocate at least one register for a reload in addition to the
+register to contain the data. Specifically, if copying @var{x} to a
+register @var{class} in @var{mode} requires an intermediate register,
+you were supposed to define @code{SECONDARY_INPUT_RELOAD_CLASS} to return the
+largest register class all of whose registers can be used as
+intermediate registers or scratch registers.
+
+If copying a register @var{class} in @var{mode} to @var{x} requires an
+intermediate or scratch register, @code{SECONDARY_OUTPUT_RELOAD_CLASS}
+was supposed to be defined to return the largest register
+class required. If the
+requirements for input and output reloads were the same, the macro
+@code{SECONDARY_RELOAD_CLASS} should have been used instead of defining both
+macros identically.
+
+The values returned by these macros are often @code{GENERAL_REGS}.
+Return @code{NO_REGS} if no spare register is needed; i.e., if @var{x}
+can be directly copied to or from a register of @var{class} in
+@var{mode} without requiring a scratch register. Do not define this
+macro if it would always return @code{NO_REGS}.
+
+If a scratch register is required (either with or without an
+intermediate register), you were supposed to define patterns for
+@samp{reload_in@var{m}} or @samp{reload_out@var{m}}, as required
+(@pxref{Standard Names}. These patterns, which were normally
+implemented with a @code{define_expand}, should be similar to the
+@samp{mov@var{m}} patterns, except that operand 2 is the scratch
+register.
+
+These patterns need constraints for the reload register and scratch
+register that
+contain a single register class. If the original reload register (whose
+class is @var{class}) can meet the constraint given in the pattern, the
+value returned by these macros is used for the class of the scratch
+register. Otherwise, two additional reload registers are required.
+Their classes are obtained from the constraints in the insn pattern.
+
+@var{x} might be a pseudo-register or a @code{subreg} of a
+pseudo-register, which could either be in a hard register or in memory.
+Use @code{true_regnum} to find out; it will return @minus{}1 if the pseudo is
+in memory and the hard register number if it is in a register.
+
+These macros should not be used in the case where a particular class of
+registers can only be copied to memory and not to another class of
+registers. In that case, secondary reload registers are not needed and
+would not be helpful. Instead, a stack location must be used to perform
+the copy and the @code{mov@var{m}} pattern should use memory as an
+intermediate storage. This case often occurs between floating-point and
+general registers.
+@end defmac
+
+@hook TARGET_SECONDARY_MEMORY_NEEDED
+
+@defmac SECONDARY_MEMORY_NEEDED_RTX (@var{mode})
+Normally when @code{TARGET_SECONDARY_MEMORY_NEEDED} is defined, the compiler
+allocates a stack slot for a memory location needed for register copies.
+If this macro is defined, the compiler instead uses the memory location
+defined by this macro.
+
+Do not define this macro if you do not define
+@code{TARGET_SECONDARY_MEMORY_NEEDED}.
+@end defmac
+
+@hook TARGET_SECONDARY_MEMORY_NEEDED_MODE
+
+@hook TARGET_SELECT_EARLY_REMAT_MODES
+
+@hook TARGET_CLASS_LIKELY_SPILLED_P
+
+@hook TARGET_CLASS_MAX_NREGS
+
+@defmac CLASS_MAX_NREGS (@var{class}, @var{mode})
+A C expression for the maximum number of consecutive registers
+of class @var{class} needed to hold a value of mode @var{mode}.
+
+This is closely related to the macro @code{TARGET_HARD_REGNO_NREGS}. In fact,
+the value of the macro @code{CLASS_MAX_NREGS (@var{class}, @var{mode})}
+should be the maximum value of @code{TARGET_HARD_REGNO_NREGS (@var{regno},
+@var{mode})} for all @var{regno} values in the class @var{class}.
+
+This macro helps control the handling of multiple-word values
+in the reload pass.
+@end defmac
+
+@hook TARGET_CAN_CHANGE_MODE_CLASS
+
+@hook TARGET_IRA_CHANGE_PSEUDO_ALLOCNO_CLASS
+
+@hook TARGET_LRA_P
+
+@hook TARGET_REGISTER_PRIORITY
+
+@hook TARGET_REGISTER_USAGE_LEVELING_P
+
+@hook TARGET_DIFFERENT_ADDR_DISPLACEMENT_P
+
+@hook TARGET_CANNOT_SUBSTITUTE_MEM_EQUIV_P
+
+@hook TARGET_LEGITIMIZE_ADDRESS_DISPLACEMENT
+
+@hook TARGET_SPILL_CLASS
+
+@hook TARGET_ADDITIONAL_ALLOCNO_CLASS_P
+
+@hook TARGET_CSTORE_MODE
+
+@hook TARGET_COMPUTE_PRESSURE_CLASSES
+
+@node Stack and Calling
+@section Stack Layout and Calling Conventions
+@cindex calling conventions
+
+@c prevent bad page break with this line
+This describes the stack layout and calling conventions.
+
+@menu
+* Frame Layout::
+* Exception Handling::
+* Stack Checking::
+* Frame Registers::
+* Elimination::
+* Stack Arguments::
+* Register Arguments::
+* Scalar Return::
+* Aggregate Return::
+* Caller Saves::
+* Function Entry::
+* Profiling::
+* Tail Calls::
+* Shrink-wrapping separate components::
+* Stack Smashing Protection::
+* Miscellaneous Register Hooks::
+@end menu
+
+@node Frame Layout
+@subsection Basic Stack Layout
+@cindex stack frame layout
+@cindex frame layout
+
+@c prevent bad page break with this line
+Here is the basic stack layout.
+
+@defmac STACK_GROWS_DOWNWARD
+Define this macro to be true if pushing a word onto the stack moves the stack
+pointer to a smaller address, and false otherwise.
+@end defmac
+
+@defmac STACK_PUSH_CODE
+This macro defines the operation used when something is pushed
+on the stack. In RTL, a push operation will be
+@code{(set (mem (STACK_PUSH_CODE (reg sp))) @dots{})}
+
+The choices are @code{PRE_DEC}, @code{POST_DEC}, @code{PRE_INC},
+and @code{POST_INC}. Which of these is correct depends on
+the stack direction and on whether the stack pointer points
+to the last item on the stack or whether it points to the
+space for the next item on the stack.
+
+The default is @code{PRE_DEC} when @code{STACK_GROWS_DOWNWARD} is
+true, which is almost always right, and @code{PRE_INC} otherwise,
+which is often wrong.
+@end defmac
+
+@defmac FRAME_GROWS_DOWNWARD
+Define this macro to nonzero value if the addresses of local variable slots
+are at negative offsets from the frame pointer.
+@end defmac
+
+@defmac ARGS_GROW_DOWNWARD
+Define this macro if successive arguments to a function occupy decreasing
+addresses on the stack.
+@end defmac
+
+@hook TARGET_STARTING_FRAME_OFFSET
+
+@defmac STACK_ALIGNMENT_NEEDED
+Define to zero to disable final alignment of the stack during reload.
+The nonzero default for this macro is suitable for most ports.
+
+On ports where @code{TARGET_STARTING_FRAME_OFFSET} is nonzero or where there
+is a register save block following the local block that doesn't require
+alignment to @code{STACK_BOUNDARY}, it may be beneficial to disable
+stack alignment and do it in the backend.
+@end defmac
+
+@defmac STACK_POINTER_OFFSET
+Offset from the stack pointer register to the first location at which
+outgoing arguments are placed. If not specified, the default value of
+zero is used. This is the proper value for most machines.
+
+If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above
+the first location at which outgoing arguments are placed.
+@end defmac
+
+@defmac FIRST_PARM_OFFSET (@var{fundecl})
+Offset from the argument pointer register to the first argument's
+address. On some machines it may depend on the data type of the
+function.
+
+If @code{ARGS_GROW_DOWNWARD}, this is the offset to the location above
+the first argument's address.
+@end defmac
+
+@defmac STACK_DYNAMIC_OFFSET (@var{fundecl})
+Offset from the stack pointer register to an item dynamically allocated
+on the stack, e.g., by @code{alloca}.
+
+The default value for this macro is @code{STACK_POINTER_OFFSET} plus the
+length of the outgoing arguments. The default is correct for most
+machines. See @file{function.cc} for details.
+@end defmac
+
+@defmac INITIAL_FRAME_ADDRESS_RTX
+A C expression whose value is RTL representing the address of the initial
+stack frame. This address is passed to @code{RETURN_ADDR_RTX} and
+@code{DYNAMIC_CHAIN_ADDRESS}. If you don't define this macro, a reasonable
+default value will be used. Define this macro in order to make frame pointer
+elimination work in the presence of @code{__builtin_frame_address (count)} and
+@code{__builtin_return_address (count)} for @code{count} not equal to zero.
+@end defmac
+
+@defmac DYNAMIC_CHAIN_ADDRESS (@var{frameaddr})
+A C expression whose value is RTL representing the address in a stack
+frame where the pointer to the caller's frame is stored. Assume that
+@var{frameaddr} is an RTL expression for the address of the stack frame
+itself.
+
+If you don't define this macro, the default is to return the value
+of @var{frameaddr}---that is, the stack frame address is also the
+address of the stack word that points to the previous frame.
+@end defmac
+
+@defmac SETUP_FRAME_ADDRESSES
+A C expression that produces the machine-specific code to
+setup the stack so that arbitrary frames can be accessed. For example,
+on the SPARC, we must flush all of the register windows to the stack
+before we can access arbitrary stack frames. You will seldom need to
+define this macro. The default is to do nothing.
+@end defmac
+
+@hook TARGET_BUILTIN_SETJMP_FRAME_VALUE
+
+@defmac FRAME_ADDR_RTX (@var{frameaddr})
+A C expression whose value is RTL representing the value of the frame
+address for the current frame. @var{frameaddr} is the frame pointer
+of the current frame. This is used for __builtin_frame_address.
+You need only define this macro if the frame address is not the same
+as the frame pointer. Most machines do not need to define it.
+@end defmac
+
+@defmac RETURN_ADDR_RTX (@var{count}, @var{frameaddr})
+A C expression whose value is RTL representing the value of the return
+address for the frame @var{count} steps up from the current frame, after
+the prologue. @var{frameaddr} is the frame pointer of the @var{count}
+frame, or the frame pointer of the @var{count} @minus{} 1 frame if
+@code{RETURN_ADDR_IN_PREVIOUS_FRAME} is nonzero.
+
+The value of the expression must always be the correct address when
+@var{count} is zero, but may be @code{NULL_RTX} if there is no way to
+determine the return address of other frames.
+@end defmac
+
+@defmac RETURN_ADDR_IN_PREVIOUS_FRAME
+Define this macro to nonzero value if the return address of a particular
+stack frame is accessed from the frame pointer of the previous stack
+frame. The zero default for this macro is suitable for most ports.
+@end defmac
+
+@defmac INCOMING_RETURN_ADDR_RTX
+A C expression whose value is RTL representing the location of the
+incoming return address at the beginning of any function, before the
+prologue. This RTL is either a @code{REG}, indicating that the return
+value is saved in @samp{REG}, or a @code{MEM} representing a location in
+the stack.
+
+You only need to define this macro if you want to support call frame
+debugging information like that provided by DWARF 2.
+
+If this RTL is a @code{REG}, you should also define
+@code{DWARF_FRAME_RETURN_COLUMN} to @code{DWARF_FRAME_REGNUM (REGNO)}.
+@end defmac
+
+@defmac DWARF_ALT_FRAME_RETURN_COLUMN
+A C expression whose value is an integer giving a DWARF 2 column
+number that may be used as an alternative return column. The column
+must not correspond to any gcc hard register (that is, it must not
+be in the range of @code{DWARF_FRAME_REGNUM}).
+
+This macro can be useful if @code{DWARF_FRAME_RETURN_COLUMN} is set to a
+general register, but an alternative column needs to be used for signal
+frames. Some targets have also used different frame return columns
+over time.
+@end defmac
+
+@defmac DWARF_ZERO_REG
+A C expression whose value is an integer giving a DWARF 2 register
+number that is considered to always have the value zero. This should
+only be defined if the target has an architected zero register, and
+someone decided it was a good idea to use that register number to
+terminate the stack backtrace. New ports should avoid this.
+@end defmac
+
+@defmac DWARF_VERSION_DEFAULT
+A C expression whose value is the default dwarf standard version we'll honor
+and advertise when generating dwarf debug information, in absence of
+an explicit @option{-gdwarf-@var{version}} option on the command line.
+@end defmac
+
+@hook TARGET_DWARF_HANDLE_FRAME_UNSPEC
+
+@hook TARGET_DWARF_POLY_INDETERMINATE_VALUE
+
+@defmac INCOMING_FRAME_SP_OFFSET
+A C expression whose value is an integer giving the offset, in bytes,
+from the value of the stack pointer register to the top of the stack
+frame at the beginning of any function, before the prologue. The top of
+the frame is defined to be the value of the stack pointer in the
+previous frame, just before the call instruction.
+
+You only need to define this macro if you want to support call frame
+debugging information like that provided by DWARF 2.
+@end defmac
+
+@defmac DEFAULT_INCOMING_FRAME_SP_OFFSET
+Like @code{INCOMING_FRAME_SP_OFFSET}, but must be the same for all
+functions of the same ABI, and when using GAS @code{.cfi_*} directives
+must also agree with the default CFI GAS emits. Define this macro
+only if @code{INCOMING_FRAME_SP_OFFSET} can have different values
+between different functions of the same ABI or when
+@code{INCOMING_FRAME_SP_OFFSET} does not agree with GAS default CFI.
+@end defmac
+
+@defmac ARG_POINTER_CFA_OFFSET (@var{fundecl})
+A C expression whose value is an integer giving the offset, in bytes,
+from the argument pointer to the canonical frame address (cfa). The
+final value should coincide with that calculated by
+@code{INCOMING_FRAME_SP_OFFSET}. Which is unfortunately not usable
+during virtual register instantiation.
+
+The default value for this macro is
+@code{FIRST_PARM_OFFSET (fundecl) + crtl->args.pretend_args_size},
+which is correct for most machines; in general, the arguments are found
+immediately before the stack frame. Note that this is not the case on
+some targets that save registers into the caller's frame, such as SPARC
+and rs6000, and so such targets need to define this macro.
+
+You only need to define this macro if the default is incorrect, and you
+want to support call frame debugging information like that provided by
+DWARF 2.
+@end defmac
+
+@defmac FRAME_POINTER_CFA_OFFSET (@var{fundecl})
+If defined, a C expression whose value is an integer giving the offset
+in bytes from the frame pointer to the canonical frame address (cfa).
+The final value should coincide with that calculated by
+@code{INCOMING_FRAME_SP_OFFSET}.
+
+Normally the CFA is calculated as an offset from the argument pointer,
+via @code{ARG_POINTER_CFA_OFFSET}, but if the argument pointer is
+variable due to the ABI, this may not be possible. If this macro is
+defined, it implies that the virtual register instantiation should be
+based on the frame pointer instead of the argument pointer. Only one
+of @code{FRAME_POINTER_CFA_OFFSET} and @code{ARG_POINTER_CFA_OFFSET}
+should be defined.
+@end defmac
+
+@defmac CFA_FRAME_BASE_OFFSET (@var{fundecl})
+If defined, a C expression whose value is an integer giving the offset
+in bytes from the canonical frame address (cfa) to the frame base used
+in DWARF 2 debug information. The default is zero. A different value
+may reduce the size of debug information on some ports.
+@end defmac
+
+@node Exception Handling
+@subsection Exception Handling Support
+@cindex exception handling
+
+@defmac EH_RETURN_DATA_REGNO (@var{N})
+A C expression whose value is the @var{N}th register number used for
+data by exception handlers, or @code{INVALID_REGNUM} if fewer than
+@var{N} registers are usable.
+
+The exception handling library routines communicate with the exception
+handlers via a set of agreed upon registers. Ideally these registers
+should be call-clobbered; it is possible to use call-saved registers,
+but may negatively impact code size. The target must support at least
+2 data registers, but should define 4 if there are enough free registers.
+
+You must define this macro if you want to support call frame exception
+handling like that provided by DWARF 2.
+@end defmac
+
+@defmac EH_RETURN_STACKADJ_RTX
+A C expression whose value is RTL representing a location in which
+to store a stack adjustment to be applied before function return.
+This is used to unwind the stack to an exception handler's call frame.
+It will be assigned zero on code paths that return normally.
+
+Typically this is a call-clobbered hard register that is otherwise
+untouched by the epilogue, but could also be a stack slot.
+
+Do not define this macro if the stack pointer is saved and restored
+by the regular prolog and epilog code in the call frame itself; in
+this case, the exception handling library routines will update the
+stack location to be restored in place. Otherwise, you must define
+this macro if you want to support call frame exception handling like
+that provided by DWARF 2.
+@end defmac
+
+@defmac EH_RETURN_HANDLER_RTX
+A C expression whose value is RTL representing a location in which
+to store the address of an exception handler to which we should
+return. It will not be assigned on code paths that return normally.
+
+Typically this is the location in the call frame at which the normal
+return address is stored. For targets that return by popping an
+address off the stack, this might be a memory address just below
+the @emph{target} call frame rather than inside the current call
+frame. If defined, @code{EH_RETURN_STACKADJ_RTX} will have already
+been assigned, so it may be used to calculate the location of the
+target call frame.
+
+Some targets have more complex requirements than storing to an
+address calculable during initial code generation. In that case
+the @code{eh_return} instruction pattern should be used instead.
+
+If you want to support call frame exception handling, you must
+define either this macro or the @code{eh_return} instruction pattern.
+@end defmac
+
+@defmac RETURN_ADDR_OFFSET
+If defined, an integer-valued C expression for which rtl will be generated
+to add it to the exception handler address before it is searched in the
+exception handling tables, and to subtract it again from the address before
+using it to return to the exception handler.
+@end defmac
+
+@defmac ASM_PREFERRED_EH_DATA_FORMAT (@var{code}, @var{global})
+This macro chooses the encoding of pointers embedded in the exception
+handling sections. If at all possible, this should be defined such
+that the exception handling section will not require dynamic relocations,
+and so may be read-only.
+
+@var{code} is 0 for data, 1 for code labels, 2 for function pointers.
+@var{global} is true if the symbol may be affected by dynamic relocations.
+The macro should return a combination of the @code{DW_EH_PE_*} defines
+as found in @file{dwarf2.h}.
+
+If this macro is not defined, pointers will not be encoded but
+represented directly.
+@end defmac
+
+@defmac ASM_MAYBE_OUTPUT_ENCODED_ADDR_RTX (@var{file}, @var{encoding}, @var{size}, @var{addr}, @var{done})
+This macro allows the target to emit whatever special magic is required
+to represent the encoding chosen by @code{ASM_PREFERRED_EH_DATA_FORMAT}.
+Generic code takes care of pc-relative and indirect encodings; this must
+be defined if the target uses text-relative or data-relative encodings.
+
+This is a C statement that branches to @var{done} if the format was
+handled. @var{encoding} is the format chosen, @var{size} is the number
+of bytes that the format occupies, @var{addr} is the @code{SYMBOL_REF}
+to be emitted.
+@end defmac
+
+@defmac MD_FALLBACK_FRAME_STATE_FOR (@var{context}, @var{fs})
+This macro allows the target to add CPU and operating system specific
+code to the call-frame unwinder for use when there is no unwind data
+available. The most common reason to implement this macro is to unwind
+through signal frames.
+
+This macro is called from @code{uw_frame_state_for} in
+@file{unwind-dw2.c}, @file{unwind-dw2-xtensa.c} and
+@file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context};
+@var{fs} is an @code{_Unwind_FrameState}. Examine @code{context->ra}
+for the address of the code being executed and @code{context->cfa} for
+the stack pointer value. If the frame can be decoded, the register
+save addresses should be updated in @var{fs} and the macro should
+evaluate to @code{_URC_NO_REASON}. If the frame cannot be decoded,
+the macro should evaluate to @code{_URC_END_OF_STACK}.
+
+For proper signal handling in Java this macro is accompanied by
+@code{MAKE_THROW_FRAME}, defined in @file{libjava/include/*-signal.h} headers.
+@end defmac
+
+@defmac MD_HANDLE_UNWABI (@var{context}, @var{fs})
+This macro allows the target to add operating system specific code to the
+call-frame unwinder to handle the IA-64 @code{.unwabi} unwinding directive,
+usually used for signal or interrupt frames.
+
+This macro is called from @code{uw_update_context} in libgcc's
+@file{unwind-ia64.c}. @var{context} is an @code{_Unwind_Context};
+@var{fs} is an @code{_Unwind_FrameState}. Examine @code{fs->unwabi}
+for the abi and context in the @code{.unwabi} directive. If the
+@code{.unwabi} directive can be handled, the register save addresses should
+be updated in @var{fs}.
+@end defmac
+
+@defmac TARGET_USES_WEAK_UNWIND_INFO
+A C expression that evaluates to true if the target requires unwind
+info to be given comdat linkage. Define it to be @code{1} if comdat
+linkage is necessary. The default is @code{0}.
+@end defmac
+
+@node Stack Checking
+@subsection Specifying How Stack Checking is Done
+
+GCC will check that stack references are within the boundaries of the
+stack, if the option @option{-fstack-check} is specified, in one of
+three ways:
+
+@enumerate
+@item
+If the value of the @code{STACK_CHECK_BUILTIN} macro is nonzero, GCC
+will assume that you have arranged for full stack checking to be done
+at appropriate places in the configuration files. GCC will not do
+other special processing.
+
+@item
+If @code{STACK_CHECK_BUILTIN} is zero and the value of the
+@code{STACK_CHECK_STATIC_BUILTIN} macro is nonzero, GCC will assume
+that you have arranged for static stack checking (checking of the
+static stack frame of functions) to be done at appropriate places
+in the configuration files. GCC will only emit code to do dynamic
+stack checking (checking on dynamic stack allocations) using the third
+approach below.
+
+@item
+If neither of the above are true, GCC will generate code to periodically
+``probe'' the stack pointer using the values of the macros defined below.
+@end enumerate
+
+If neither STACK_CHECK_BUILTIN nor STACK_CHECK_STATIC_BUILTIN is defined,
+GCC will change its allocation strategy for large objects if the option
+@option{-fstack-check} is specified: they will always be allocated
+dynamically if their size exceeds @code{STACK_CHECK_MAX_VAR_SIZE} bytes.
+
+@defmac STACK_CHECK_BUILTIN
+A nonzero value if stack checking is done by the configuration files in a
+machine-dependent manner. You should define this macro if stack checking
+is required by the ABI of your machine or if you would like to do stack
+checking in some more efficient way than the generic approach. The default
+value of this macro is zero.
+@end defmac
+
+@defmac STACK_CHECK_STATIC_BUILTIN
+A nonzero value if static stack checking is done by the configuration files
+in a machine-dependent manner. You should define this macro if you would
+like to do static stack checking in some more efficient way than the generic
+approach. The default value of this macro is zero.
+@end defmac
+
+@defmac STACK_CHECK_PROBE_INTERVAL_EXP
+An integer specifying the interval at which GCC must generate stack probe
+instructions, defined as 2 raised to this integer. You will normally
+define this macro so that the interval be no larger than the size of
+the ``guard pages'' at the end of a stack area. The default value
+of 12 (4096-byte interval) is suitable for most systems.
+@end defmac
+
+@defmac STACK_CHECK_MOVING_SP
+An integer which is nonzero if GCC should move the stack pointer page by page
+when doing probes. This can be necessary on systems where the stack pointer
+contains the bottom address of the memory area accessible to the executing
+thread at any point in time. In this situation an alternate signal stack
+is required in order to be able to recover from a stack overflow. The
+default value of this macro is zero.
+@end defmac
+
+@defmac STACK_CHECK_PROTECT
+The number of bytes of stack needed to recover from a stack overflow, for
+languages where such a recovery is supported. The default value of 4KB/8KB
+with the @code{setjmp}/@code{longjmp}-based exception handling mechanism and
+8KB/12KB with other exception handling mechanisms should be adequate for most
+architectures and operating systems.
+@end defmac
+
+The following macros are relevant only if neither STACK_CHECK_BUILTIN
+nor STACK_CHECK_STATIC_BUILTIN is defined; you can omit them altogether
+in the opposite case.
+
+@defmac STACK_CHECK_MAX_FRAME_SIZE
+The maximum size of a stack frame, in bytes. GCC will generate probe
+instructions in non-leaf functions to ensure at least this many bytes of
+stack are available. If a stack frame is larger than this size, stack
+checking will not be reliable and GCC will issue a warning. The
+default is chosen so that GCC only generates one instruction on most
+systems. You should normally not change the default value of this macro.
+@end defmac
+
+@defmac STACK_CHECK_FIXED_FRAME_SIZE
+GCC uses this value to generate the above warning message. It
+represents the amount of fixed frame used by a function, not including
+space for any callee-saved registers, temporaries and user variables.
+You need only specify an upper bound for this amount and will normally
+use the default of four words.
+@end defmac
+
+@defmac STACK_CHECK_MAX_VAR_SIZE
+The maximum size, in bytes, of an object that GCC will place in the
+fixed area of the stack frame when the user specifies
+@option{-fstack-check}.
+GCC computed the default from the values of the above macros and you will
+normally not need to override that default.
+@end defmac
+
+@hook TARGET_STACK_CLASH_PROTECTION_ALLOCA_PROBE_RANGE
+
+@need 2000
+@node Frame Registers
+@subsection Registers That Address the Stack Frame
+
+@c prevent bad page break with this line
+This discusses registers that address the stack frame.
+
+@defmac STACK_POINTER_REGNUM
+The register number of the stack pointer register, which must also be a
+fixed register according to @code{FIXED_REGISTERS}. On most machines,
+the hardware determines which register this is.
+@end defmac
+
+@defmac FRAME_POINTER_REGNUM
+The register number of the frame pointer register, which is used to
+access automatic variables in the stack frame. On some machines, the
+hardware determines which register this is. On other machines, you can
+choose any register you wish for this purpose.
+@end defmac
+
+@defmac HARD_FRAME_POINTER_REGNUM
+On some machines the offset between the frame pointer and starting
+offset of the automatic variables is not known until after register
+allocation has been done (for example, because the saved registers are
+between these two locations). On those machines, define
+@code{FRAME_POINTER_REGNUM} the number of a special, fixed register to
+be used internally until the offset is known, and define
+@code{HARD_FRAME_POINTER_REGNUM} to be the actual hard register number
+used for the frame pointer.
+
+You should define this macro only in the very rare circumstances when it
+is not possible to calculate the offset between the frame pointer and
+the automatic variables until after register allocation has been
+completed. When this macro is defined, you must also indicate in your
+definition of @code{ELIMINABLE_REGS} how to eliminate
+@code{FRAME_POINTER_REGNUM} into either @code{HARD_FRAME_POINTER_REGNUM}
+or @code{STACK_POINTER_REGNUM}.
+
+Do not define this macro if it would be the same as
+@code{FRAME_POINTER_REGNUM}.
+@end defmac
+
+@defmac ARG_POINTER_REGNUM
+The register number of the arg pointer register, which is used to access
+the function's argument list. On some machines, this is the same as the
+frame pointer register. On some machines, the hardware determines which
+register this is. On other machines, you can choose any register you
+wish for this purpose. If this is not the same register as the frame
+pointer register, then you must mark it as a fixed register according to
+@code{FIXED_REGISTERS}, or arrange to be able to eliminate it
+(@pxref{Elimination}).
+@end defmac
+
+@defmac HARD_FRAME_POINTER_IS_FRAME_POINTER
+Define this to a preprocessor constant that is nonzero if
+@code{hard_frame_pointer_rtx} and @code{frame_pointer_rtx} should be
+the same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM
+== FRAME_POINTER_REGNUM)}; you only need to define this macro if that
+definition is not suitable for use in preprocessor conditionals.
+@end defmac
+
+@defmac HARD_FRAME_POINTER_IS_ARG_POINTER
+Define this to a preprocessor constant that is nonzero if
+@code{hard_frame_pointer_rtx} and @code{arg_pointer_rtx} should be the
+same. The default definition is @samp{(HARD_FRAME_POINTER_REGNUM ==
+ARG_POINTER_REGNUM)}; you only need to define this macro if that
+definition is not suitable for use in preprocessor conditionals.
+@end defmac
+
+@defmac RETURN_ADDRESS_POINTER_REGNUM
+The register number of the return address pointer register, which is used to
+access the current function's return address from the stack. On some
+machines, the return address is not at a fixed offset from the frame
+pointer or stack pointer or argument pointer. This register can be defined
+to point to the return address on the stack, and then be converted by
+@code{ELIMINABLE_REGS} into either the frame pointer or stack pointer.
+
+Do not define this macro unless there is no other way to get the return
+address from the stack.
+@end defmac
+
+@defmac STATIC_CHAIN_REGNUM
+@defmacx STATIC_CHAIN_INCOMING_REGNUM
+Register numbers used for passing a function's static chain pointer. If
+register windows are used, the register number as seen by the called
+function is @code{STATIC_CHAIN_INCOMING_REGNUM}, while the register
+number as seen by the calling function is @code{STATIC_CHAIN_REGNUM}. If
+these registers are the same, @code{STATIC_CHAIN_INCOMING_REGNUM} need
+not be defined.
+
+The static chain register need not be a fixed register.
+
+If the static chain is passed in memory, these macros should not be
+defined; instead, the @code{TARGET_STATIC_CHAIN} hook should be used.
+@end defmac
+
+@hook TARGET_STATIC_CHAIN
+
+@defmac DWARF_FRAME_REGISTERS
+This macro specifies the maximum number of hard registers that can be
+saved in a call frame. This is used to size data structures used in
+DWARF2 exception handling.
+
+Prior to GCC 3.0, this macro was needed in order to establish a stable
+exception handling ABI in the face of adding new hard registers for ISA
+extensions. In GCC 3.0 and later, the EH ABI is insulated from changes
+in the number of hard registers. Nevertheless, this macro can still be
+used to reduce the runtime memory requirements of the exception handling
+routines, which can be substantial if the ISA contains a lot of
+registers that are not call-saved.
+
+If this macro is not defined, it defaults to
+@code{FIRST_PSEUDO_REGISTER}.
+@end defmac
+
+@defmac PRE_GCC3_DWARF_FRAME_REGISTERS
+
+This macro is similar to @code{DWARF_FRAME_REGISTERS}, but is provided
+for backward compatibility in pre GCC 3.0 compiled code.
+
+If this macro is not defined, it defaults to
+@code{DWARF_FRAME_REGISTERS}.
+@end defmac
+
+@defmac DWARF_REG_TO_UNWIND_COLUMN (@var{regno})
+
+Define this macro if the target's representation for dwarf registers
+is different than the internal representation for unwind column.
+Given a dwarf register, this macro should return the internal unwind
+column number to use instead.
+@end defmac
+
+@defmac DWARF_FRAME_REGNUM (@var{regno})
+
+Define this macro if the target's representation for dwarf registers
+used in .eh_frame or .debug_frame is different from that used in other
+debug info sections. Given a GCC hard register number, this macro
+should return the .eh_frame register number. The default is
+@code{DEBUGGER_REGNO (@var{regno})}.
+
+@end defmac
+
+@defmac DWARF2_FRAME_REG_OUT (@var{regno}, @var{for_eh})
+
+Define this macro to map register numbers held in the call frame info
+that GCC has collected using @code{DWARF_FRAME_REGNUM} to those that
+should be output in .debug_frame (@code{@var{for_eh}} is zero) and
+.eh_frame (@code{@var{for_eh}} is nonzero). The default is to
+return @code{@var{regno}}.
+
+@end defmac
+
+@defmac REG_VALUE_IN_UNWIND_CONTEXT
+
+Define this macro if the target stores register values as
+@code{_Unwind_Word} type in unwind context. It should be defined if
+target register size is larger than the size of @code{void *}. The
+default is to store register values as @code{void *} type.
+
+@end defmac
+
+@defmac ASSUME_EXTENDED_UNWIND_CONTEXT
+
+Define this macro to be 1 if the target always uses extended unwind
+context with version, args_size and by_value fields. If it is undefined,
+it will be defined to 1 when @code{REG_VALUE_IN_UNWIND_CONTEXT} is
+defined and 0 otherwise.
+
+@end defmac
+
+@defmac DWARF_LAZY_REGISTER_VALUE (@var{regno}, @var{value})
+Define this macro if the target has pseudo DWARF registers whose
+values need to be computed lazily on demand by the unwinder (such as when
+referenced in a CFA expression). The macro returns true if @var{regno}
+is such a register and stores its value in @samp{*@var{value}} if so.
+@end defmac
+
+@node Elimination
+@subsection Eliminating Frame Pointer and Arg Pointer
+
+@c prevent bad page break with this line
+This is about eliminating the frame pointer and arg pointer.
+
+@hook TARGET_FRAME_POINTER_REQUIRED
+
+@defmac ELIMINABLE_REGS
+This macro specifies a table of register pairs used to eliminate
+unneeded registers that point into the stack frame.
+
+The definition of this macro is a list of structure initializations, each
+of which specifies an original and replacement register.
+
+On some machines, the position of the argument pointer is not known until
+the compilation is completed. In such a case, a separate hard register
+must be used for the argument pointer. This register can be eliminated by
+replacing it with either the frame pointer or the argument pointer,
+depending on whether or not the frame pointer has been eliminated.
+
+In this case, you might specify:
+@smallexample
+#define ELIMINABLE_REGS \
+@{@{ARG_POINTER_REGNUM, STACK_POINTER_REGNUM@}, \
+ @{ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM@}, \
+ @{FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM@}@}
+@end smallexample
+
+Note that the elimination of the argument pointer with the stack pointer is
+specified first since that is the preferred elimination.
+@end defmac
+
+@hook TARGET_CAN_ELIMINATE
+
+@defmac INITIAL_ELIMINATION_OFFSET (@var{from-reg}, @var{to-reg}, @var{offset-var})
+This macro returns the initial difference between the specified pair
+of registers. The value would be computed from information
+such as the result of @code{get_frame_size ()} and the tables of
+registers @code{df_regs_ever_live_p} and @code{call_used_regs}.
+@end defmac
+
+@hook TARGET_COMPUTE_FRAME_LAYOUT
+
+@node Stack Arguments
+@subsection Passing Function Arguments on the Stack
+@cindex arguments on stack
+@cindex stack arguments
+
+The macros in this section control how arguments are passed
+on the stack. See the following section for other macros that
+control passing certain arguments in registers.
+
+@hook TARGET_PROMOTE_PROTOTYPES
+
+@hook TARGET_PUSH_ARGUMENT
+
+@defmac PUSH_ARGS_REVERSED
+A C expression. If nonzero, function arguments will be evaluated from
+last to first, rather than from first to last. If this macro is not
+defined, it defaults to @code{PUSH_ARGS} on targets where the stack
+and args grow in opposite directions, and 0 otherwise.
+@end defmac
+
+@defmac PUSH_ROUNDING (@var{npushed})
+A C expression that is the number of bytes actually pushed onto the
+stack when an instruction attempts to push @var{npushed} bytes.
+
+On some machines, the definition
+
+@smallexample
+#define PUSH_ROUNDING(BYTES) (BYTES)
+@end smallexample
+
+@noindent
+will suffice. But on other machines, instructions that appear
+to push one byte actually push two bytes in an attempt to maintain
+alignment. Then the definition should be
+
+@smallexample
+#define PUSH_ROUNDING(BYTES) (((BYTES) + 1) & ~1)
+@end smallexample
+
+If the value of this macro has a type, it should be an unsigned type.
+@end defmac
+
+@findex outgoing_args_size
+@findex crtl->outgoing_args_size
+@defmac ACCUMULATE_OUTGOING_ARGS
+A C expression. If nonzero, the maximum amount of space required for outgoing arguments
+will be computed and placed into
+@code{crtl->outgoing_args_size}. No space will be pushed
+onto the stack for each call; instead, the function prologue should
+increase the stack frame size by this amount.
+
+Setting both @code{PUSH_ARGS} and @code{ACCUMULATE_OUTGOING_ARGS}
+is not proper.
+@end defmac
+
+@defmac REG_PARM_STACK_SPACE (@var{fndecl})
+Define this macro if functions should assume that stack space has been
+allocated for arguments even when their values are passed in
+registers.
+
+The value of this macro is the size, in bytes, of the area reserved for
+arguments passed in registers for the function represented by @var{fndecl},
+which can be zero if GCC is calling a library function.
+The argument @var{fndecl} can be the FUNCTION_DECL, or the type itself
+of the function.
+
+This space can be allocated by the caller, or be a part of the
+machine-dependent stack frame: @code{OUTGOING_REG_PARM_STACK_SPACE} says
+which.
+@end defmac
+@c above is overfull. not sure what to do. --mew 5feb93 did
+@c something, not sure if it looks good. --mew 10feb93
+
+@defmac INCOMING_REG_PARM_STACK_SPACE (@var{fndecl})
+Like @code{REG_PARM_STACK_SPACE}, but for incoming register arguments.
+Define this macro if space guaranteed when compiling a function body
+is different to space required when making a call, a situation that
+can arise with K&R style function definitions.
+@end defmac
+
+@defmac OUTGOING_REG_PARM_STACK_SPACE (@var{fntype})
+Define this to a nonzero value if it is the responsibility of the
+caller to allocate the area reserved for arguments passed in registers
+when calling a function of @var{fntype}. @var{fntype} may be NULL
+if the function called is a library function.
+
+If @code{ACCUMULATE_OUTGOING_ARGS} is defined, this macro controls
+whether the space for these arguments counts in the value of
+@code{crtl->outgoing_args_size}.
+@end defmac
+
+@defmac STACK_PARMS_IN_REG_PARM_AREA
+Define this macro if @code{REG_PARM_STACK_SPACE} is defined, but the
+stack parameters don't skip the area specified by it.
+@c i changed this, makes more sens and it should have taken care of the
+@c overfull.. not as specific, tho. --mew 5feb93
+
+Normally, when a parameter is not passed in registers, it is placed on the
+stack beyond the @code{REG_PARM_STACK_SPACE} area. Defining this macro
+suppresses this behavior and causes the parameter to be passed on the
+stack in its natural location.
+@end defmac
+
+@hook TARGET_RETURN_POPS_ARGS
+
+@defmac CALL_POPS_ARGS (@var{cum})
+A C expression that should indicate the number of bytes a call sequence
+pops off the stack. It is added to the value of @code{RETURN_POPS_ARGS}
+when compiling a function call.
+
+@var{cum} is the variable in which all arguments to the called function
+have been accumulated.
+
+On certain architectures, such as the SH5, a call trampoline is used
+that pops certain registers off the stack, depending on the arguments
+that have been passed to the function. Since this is a property of the
+call site, not of the called function, @code{RETURN_POPS_ARGS} is not
+appropriate.
+@end defmac
+
+@node Register Arguments
+@subsection Passing Arguments in Registers
+@cindex arguments in registers
+@cindex registers arguments
+
+This section describes the macros which let you control how various
+types of arguments are passed in registers or how they are arranged in
+the stack.
+
+@hook TARGET_FUNCTION_ARG
+
+@hook TARGET_MUST_PASS_IN_STACK
+
+@hook TARGET_FUNCTION_INCOMING_ARG
+
+@hook TARGET_USE_PSEUDO_PIC_REG
+
+@hook TARGET_INIT_PIC_REG
+
+@hook TARGET_ARG_PARTIAL_BYTES
+
+@hook TARGET_PASS_BY_REFERENCE
+
+@hook TARGET_CALLEE_COPIES
+
+@defmac CUMULATIVE_ARGS
+A C type for declaring a variable that is used as the first argument
+of @code{TARGET_FUNCTION_ARG} and other related values. For some
+target machines, the type @code{int} suffices and can hold the number
+of bytes of argument so far.
+
+There is no need to record in @code{CUMULATIVE_ARGS} anything about the
+arguments that have been passed on the stack. The compiler has other
+variables to keep track of that. For target machines on which all
+arguments are passed on the stack, there is no need to store anything in
+@code{CUMULATIVE_ARGS}; however, the data structure must exist and
+should not be empty, so use @code{int}.
+@end defmac
+
+@defmac OVERRIDE_ABI_FORMAT (@var{fndecl})
+If defined, this macro is called before generating any code for a
+function, but after the @var{cfun} descriptor for the function has been
+created. The back end may use this macro to update @var{cfun} to
+reflect an ABI other than that which would normally be used by default.
+If the compiler is generating code for a compiler-generated function,
+@var{fndecl} may be @code{NULL}.
+@end defmac
+
+@defmac INIT_CUMULATIVE_ARGS (@var{cum}, @var{fntype}, @var{libname}, @var{fndecl}, @var{n_named_args})
+A C statement (sans semicolon) for initializing the variable
+@var{cum} for the state at the beginning of the argument list. The
+variable has type @code{CUMULATIVE_ARGS}. The value of @var{fntype}
+is the tree node for the data type of the function which will receive
+the args, or 0 if the args are to a compiler support library function.
+For direct calls that are not libcalls, @var{fndecl} contain the
+declaration node of the function. @var{fndecl} is also set when
+@code{INIT_CUMULATIVE_ARGS} is used to find arguments for the function
+being compiled. @var{n_named_args} is set to the number of named
+arguments, including a structure return address if it is passed as a
+parameter, when making a call. When processing incoming arguments,
+@var{n_named_args} is set to @minus{}1.
+
+When processing a call to a compiler support library function,
+@var{libname} identifies which one. It is a @code{symbol_ref} rtx which
+contains the name of the function, as a string. @var{libname} is 0 when
+an ordinary C function call is being processed. Thus, each time this
+macro is called, either @var{libname} or @var{fntype} is nonzero, but
+never both of them at once.
+@end defmac
+
+@defmac INIT_CUMULATIVE_LIBCALL_ARGS (@var{cum}, @var{mode}, @var{libname})
+Like @code{INIT_CUMULATIVE_ARGS} but only used for outgoing libcalls,
+it gets a @code{MODE} argument instead of @var{fntype}, that would be
+@code{NULL}. @var{indirect} would always be zero, too. If this macro
+is not defined, @code{INIT_CUMULATIVE_ARGS (cum, NULL_RTX, libname,
+0)} is used instead.
+@end defmac
+
+@defmac INIT_CUMULATIVE_INCOMING_ARGS (@var{cum}, @var{fntype}, @var{libname})
+Like @code{INIT_CUMULATIVE_ARGS} but overrides it for the purposes of
+finding the arguments for the function being compiled. If this macro is
+undefined, @code{INIT_CUMULATIVE_ARGS} is used instead.
+
+The value passed for @var{libname} is always 0, since library routines
+with special calling conventions are never compiled with GCC@. The
+argument @var{libname} exists for symmetry with
+@code{INIT_CUMULATIVE_ARGS}.
+@c could use "this macro" in place of @code{INIT_CUMULATIVE_ARGS}, maybe.
+@c --mew 5feb93 i switched the order of the sentences. --mew 10feb93
+@end defmac
+
+@hook TARGET_FUNCTION_ARG_ADVANCE
+
+@hook TARGET_FUNCTION_ARG_OFFSET
+
+@hook TARGET_FUNCTION_ARG_PADDING
+
+@defmac PAD_VARARGS_DOWN
+If defined, a C expression which determines whether the default
+implementation of va_arg will attempt to pad down before reading the
+next argument, if that argument is smaller than its aligned space as
+controlled by @code{PARM_BOUNDARY}. If this macro is not defined, all such
+arguments are padded down if @code{BYTES_BIG_ENDIAN} is true.
+@end defmac
+
+@defmac BLOCK_REG_PADDING (@var{mode}, @var{type}, @var{first})
+Specify padding for the last element of a block move between registers and
+memory. @var{first} is nonzero if this is the only element. Defining this
+macro allows better control of register function parameters on big-endian
+machines, without using @code{PARALLEL} rtl. In particular,
+@code{MUST_PASS_IN_STACK} need not test padding and mode of types in
+registers, as there is no longer a "wrong" part of a register; For example,
+a three byte aggregate may be passed in the high part of a register if so
+required.
+@end defmac
+
+@hook TARGET_FUNCTION_ARG_BOUNDARY
+
+@hook TARGET_FUNCTION_ARG_ROUND_BOUNDARY
+
+@defmac FUNCTION_ARG_REGNO_P (@var{regno})
+A C expression that is nonzero if @var{regno} is the number of a hard
+register in which function arguments are sometimes passed. This does
+@emph{not} include implicit arguments such as the static chain and
+the structure-value address. On many machines, no registers can be
+used for this purpose since all function arguments are pushed on the
+stack.
+@end defmac
+
+@hook TARGET_SPLIT_COMPLEX_ARG
+
+@hook TARGET_BUILD_BUILTIN_VA_LIST
+
+@hook TARGET_ENUM_VA_LIST_P
+
+@hook TARGET_FN_ABI_VA_LIST
+
+@hook TARGET_CANONICAL_VA_LIST_TYPE
+
+@hook TARGET_GIMPLIFY_VA_ARG_EXPR
+
+@hook TARGET_VALID_POINTER_MODE
+
+@hook TARGET_REF_MAY_ALIAS_ERRNO
+
+@hook TARGET_TRANSLATE_MODE_ATTRIBUTE
+
+@hook TARGET_SCALAR_MODE_SUPPORTED_P
+
+@hook TARGET_VECTOR_MODE_SUPPORTED_P
+
+@hook TARGET_COMPATIBLE_VECTOR_TYPES_P
+
+@hook TARGET_ARRAY_MODE
+
+@hook TARGET_ARRAY_MODE_SUPPORTED_P
+
+@hook TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P
+
+@hook TARGET_FLOATN_MODE
+
+@hook TARGET_FLOATN_BUILTIN_P
+
+@hook TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P
+
+@node Scalar Return
+@subsection How Scalar Function Values Are Returned
+@cindex return values in registers
+@cindex values, returned by functions
+@cindex scalars, returned as values
+
+This section discusses the macros that control returning scalars as
+values---values that can fit in registers.
+
+@hook TARGET_FUNCTION_VALUE
+
+@defmac FUNCTION_VALUE (@var{valtype}, @var{func})
+This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE} for
+a new target instead.
+@end defmac
+
+@defmac LIBCALL_VALUE (@var{mode})
+A C expression to create an RTX representing the place where a library
+function returns a value of mode @var{mode}.
+
+Note that ``library function'' in this context means a compiler
+support routine, used to perform arithmetic, whose name is known
+specially by the compiler and was not mentioned in the C code being
+compiled.
+@end defmac
+
+@hook TARGET_LIBCALL_VALUE
+
+@defmac FUNCTION_VALUE_REGNO_P (@var{regno})
+A C expression that is nonzero if @var{regno} is the number of a hard
+register in which the values of called function may come back.
+
+A register whose use for returning values is limited to serving as the
+second of a pair (for a value of type @code{double}, say) need not be
+recognized by this macro. So for most machines, this definition
+suffices:
+
+@smallexample
+#define FUNCTION_VALUE_REGNO_P(N) ((N) == 0)
+@end smallexample
+
+If the machine has register windows, so that the caller and the called
+function use different registers for the return value, this macro
+should recognize only the caller's register numbers.
+
+This macro has been deprecated. Use @code{TARGET_FUNCTION_VALUE_REGNO_P}
+for a new target instead.
+@end defmac
+
+@hook TARGET_FUNCTION_VALUE_REGNO_P
+
+@defmac APPLY_RESULT_SIZE
+Define this macro if @samp{untyped_call} and @samp{untyped_return}
+need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for
+saving and restoring an arbitrary return value.
+@end defmac
+
+@hook TARGET_OMIT_STRUCT_RETURN_REG
+
+@hook TARGET_RETURN_IN_MSB
+
+@node Aggregate Return
+@subsection How Large Values Are Returned
+@cindex aggregates as return values
+@cindex large return values
+@cindex returning aggregate values
+@cindex structure value address
+
+When a function value's mode is @code{BLKmode} (and in some other
+cases), the value is not returned according to
+@code{TARGET_FUNCTION_VALUE} (@pxref{Scalar Return}). Instead, the
+caller passes the address of a block of memory in which the value
+should be stored. This address is called the @dfn{structure value
+address}.
+
+This section describes how to control returning structure values in
+memory.
+
+@hook TARGET_RETURN_IN_MEMORY
+
+@defmac DEFAULT_PCC_STRUCT_RETURN
+Define this macro to be 1 if all structure and union return values must be
+in memory. Since this results in slower code, this should be defined
+only if needed for compatibility with other compilers or with an ABI@.
+If you define this macro to be 0, then the conventions used for structure
+and union return values are decided by the @code{TARGET_RETURN_IN_MEMORY}
+target hook.
+
+If not defined, this defaults to the value 1.
+@end defmac
+
+@hook TARGET_STRUCT_VALUE_RTX
+
+@defmac PCC_STATIC_STRUCT_RETURN
+Define this macro if the usual system convention on the target machine
+for returning structures and unions is for the called function to return
+the address of a static variable containing the value.
+
+Do not define this if the usual system convention is for the caller to
+pass an address to the subroutine.
+
+This macro has effect in @option{-fpcc-struct-return} mode, but it does
+nothing when you use @option{-freg-struct-return} mode.
+@end defmac
+
+@hook TARGET_GET_RAW_RESULT_MODE
+
+@hook TARGET_GET_RAW_ARG_MODE
+
+@hook TARGET_EMPTY_RECORD_P
+
+@hook TARGET_WARN_PARAMETER_PASSING_ABI
+
+@node Caller Saves
+@subsection Caller-Saves Register Allocation
+
+If you enable it, GCC can save registers around function calls. This
+makes it possible to use call-clobbered registers to hold variables that
+must live across calls.
+
+@defmac HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs})
+A C expression specifying which mode is required for saving @var{nregs}
+of a pseudo-register in call-clobbered hard register @var{regno}. If
+@var{regno} is unsuitable for caller save, @code{VOIDmode} should be
+returned. For most machines this macro need not be defined since GCC
+will select the smallest suitable mode.
+@end defmac
+
+@node Function Entry
+@subsection Function Entry and Exit
+@cindex function entry and exit
+@cindex prologue
+@cindex epilogue
+
+This section describes the macros that output function entry
+(@dfn{prologue}) and exit (@dfn{epilogue}) code.
+
+@hook TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY
+
+@hook TARGET_ASM_FUNCTION_PROLOGUE
+
+@hook TARGET_ASM_FUNCTION_END_PROLOGUE
+
+@hook TARGET_ASM_FUNCTION_BEGIN_EPILOGUE
+
+@hook TARGET_ASM_FUNCTION_EPILOGUE
+
+@itemize @bullet
+@item
+@findex pretend_args_size
+@findex crtl->args.pretend_args_size
+A region of @code{crtl->args.pretend_args_size} bytes of
+uninitialized space just underneath the first argument arriving on the
+stack. (This may not be at the very start of the allocated stack region
+if the calling sequence has pushed anything else since pushing the stack
+arguments. But usually, on such machines, nothing else has been pushed
+yet, because the function prologue itself does all the pushing.) This
+region is used on machines where an argument may be passed partly in
+registers and partly in memory, and, in some cases to support the
+features in @code{<stdarg.h>}.
+
+@item
+An area of memory used to save certain registers used by the function.
+The size of this area, which may also include space for such things as
+the return address and pointers to previous stack frames, is
+machine-specific and usually depends on which registers have been used
+in the function. Machines with register windows often do not require
+a save area.
+
+@item
+A region of at least @var{size} bytes, possibly rounded up to an allocation
+boundary, to contain the local variables of the function. On some machines,
+this region and the save area may occur in the opposite order, with the
+save area closer to the top of the stack.
+
+@item
+@cindex @code{ACCUMULATE_OUTGOING_ARGS} and stack frames
+Optionally, when @code{ACCUMULATE_OUTGOING_ARGS} is defined, a region of
+@code{crtl->outgoing_args_size} bytes to be used for outgoing
+argument lists of the function. @xref{Stack Arguments}.
+@end itemize
+
+@defmac EXIT_IGNORE_STACK
+Define this macro as a C expression that is nonzero if the return
+instruction or the function epilogue ignores the value of the stack
+pointer; in other words, if it is safe to delete an instruction to
+adjust the stack pointer before a return from the function. The
+default is 0.
+
+Note that this macro's value is relevant only for functions for which
+frame pointers are maintained. It is never safe to delete a final
+stack adjustment in a function that has no frame pointer, and the
+compiler knows this regardless of @code{EXIT_IGNORE_STACK}.
+@end defmac
+
+@defmac EPILOGUE_USES (@var{regno})
+Define this macro as a C expression that is nonzero for registers that are
+used by the epilogue or the @samp{return} pattern. The stack and frame
+pointer registers are already assumed to be used as needed.
+@end defmac
+
+@defmac EH_USES (@var{regno})
+Define this macro as a C expression that is nonzero for registers that are
+used by the exception handling mechanism, and so should be considered live
+on entry to an exception edge.
+@end defmac
+
+@hook TARGET_ASM_OUTPUT_MI_THUNK
+
+@hook TARGET_ASM_CAN_OUTPUT_MI_THUNK
+
+@node Profiling
+@subsection Generating Code for Profiling
+@cindex profiling, code generation
+
+These macros will help you generate code for profiling.
+
+@defmac FUNCTION_PROFILER (@var{file}, @var{labelno})
+A C statement or compound statement to output to @var{file} some
+assembler code to call the profiling subroutine @code{mcount}.
+
+@findex mcount
+The details of how @code{mcount} expects to be called are determined by
+your operating system environment, not by GCC@. To figure them out,
+compile a small program for profiling using the system's installed C
+compiler and look at the assembler code that results.
+
+Older implementations of @code{mcount} expect the address of a counter
+variable to be loaded into some register. The name of this variable is
+@samp{LP} followed by the number @var{labelno}, so you would generate
+the name using @samp{LP%d} in a @code{fprintf}.
+@end defmac
+
+@defmac PROFILE_HOOK
+A C statement or compound statement to output to @var{file} some assembly
+code to call the profiling subroutine @code{mcount} even the target does
+not support profiling.
+@end defmac
+
+@defmac NO_PROFILE_COUNTERS
+Define this macro to be an expression with a nonzero value if the
+@code{mcount} subroutine on your system does not need a counter variable
+allocated for each function. This is true for almost all modern
+implementations. If you define this macro, you must not use the
+@var{labelno} argument to @code{FUNCTION_PROFILER}.
+@end defmac
+
+@defmac PROFILE_BEFORE_PROLOGUE
+Define this macro if the code for function profiling should come before
+the function prologue. Normally, the profiling code comes after.
+@end defmac
+
+@hook TARGET_KEEP_LEAF_WHEN_PROFILED
+
+@node Tail Calls
+@subsection Permitting tail calls
+@cindex tail calls
+
+@hook TARGET_FUNCTION_OK_FOR_SIBCALL
+
+@hook TARGET_EXTRA_LIVE_ON_ENTRY
+
+@hook TARGET_SET_UP_BY_PROLOGUE
+
+@hook TARGET_WARN_FUNC_RETURN
+
+@node Shrink-wrapping separate components
+@subsection Shrink-wrapping separate components
+@cindex shrink-wrapping separate components
+
+The prologue may perform a variety of target dependent tasks such as
+saving callee-saved registers, saving the return address, aligning the
+stack, creating a stack frame, initializing the PIC register, setting
+up the static chain, etc.
+
+On some targets some of these tasks may be independent of others and
+thus may be shrink-wrapped separately. These independent tasks are
+referred to as components and are handled generically by the target
+independent parts of GCC.
+
+Using the following hooks those prologue or epilogue components can be
+shrink-wrapped separately, so that the initialization (and possibly
+teardown) those components do is not done as frequently on execution
+paths where this would unnecessary.
+
+What exactly those components are is up to the target code; the generic
+code treats them abstractly, as a bit in an @code{sbitmap}. These
+@code{sbitmap}s are allocated by the @code{shrink_wrap.get_separate_components}
+and @code{shrink_wrap.components_for_bb} hooks, and deallocated by the
+generic code.
+
+@hook TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS
+
+@hook TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB
+
+@hook TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS
+
+@hook TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS
+
+@hook TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS
+
+@hook TARGET_SHRINK_WRAP_SET_HANDLED_COMPONENTS
+
+@node Stack Smashing Protection
+@subsection Stack smashing protection
+@cindex stack smashing protection
+
+@hook TARGET_STACK_PROTECT_GUARD
+
+@hook TARGET_STACK_PROTECT_FAIL
+
+@hook TARGET_STACK_PROTECT_RUNTIME_ENABLED_P
+
+@hook TARGET_SUPPORTS_SPLIT_STACK
+
+@hook TARGET_GET_VALID_OPTION_VALUES
+
+@node Miscellaneous Register Hooks
+@subsection Miscellaneous register hooks
+@cindex miscellaneous register hooks
+
+@hook TARGET_CALL_FUSAGE_CONTAINS_NON_CALLEE_CLOBBERS
+
+@node Varargs
+@section Implementing the Varargs Macros
+@cindex varargs implementation
+
+GCC comes with an implementation of @code{<varargs.h>} and
+@code{<stdarg.h>} that work without change on machines that pass arguments
+on the stack. Other machines require their own implementations of
+varargs, and the two machine independent header files must have
+conditionals to include it.
+
+ISO @code{<stdarg.h>} differs from traditional @code{<varargs.h>} mainly in
+the calling convention for @code{va_start}. The traditional
+implementation takes just one argument, which is the variable in which
+to store the argument pointer. The ISO implementation of
+@code{va_start} takes an additional second argument. The user is
+supposed to write the last named argument of the function here.
+
+However, @code{va_start} should not use this argument. The way to find
+the end of the named arguments is with the built-in functions described
+below.
+
+@defmac __builtin_saveregs ()
+Use this built-in function to save the argument registers in memory so
+that the varargs mechanism can access them. Both ISO and traditional
+versions of @code{va_start} must use @code{__builtin_saveregs}, unless
+you use @code{TARGET_SETUP_INCOMING_VARARGS} (see below) instead.
+
+On some machines, @code{__builtin_saveregs} is open-coded under the
+control of the target hook @code{TARGET_EXPAND_BUILTIN_SAVEREGS}. On
+other machines, it calls a routine written in assembler language,
+found in @file{libgcc2.c}.
+
+Code generated for the call to @code{__builtin_saveregs} appears at the
+beginning of the function, as opposed to where the call to
+@code{__builtin_saveregs} is written, regardless of what the code is.
+This is because the registers must be saved before the function starts
+to use them for its own purposes.
+@c i rewrote the first sentence above to fix an overfull hbox. --mew
+@c 10feb93
+@end defmac
+
+@defmac __builtin_next_arg (@var{lastarg})
+This builtin returns the address of the first anonymous stack
+argument, as type @code{void *}. If @code{ARGS_GROW_DOWNWARD}, it
+returns the address of the location above the first anonymous stack
+argument. Use it in @code{va_start} to initialize the pointer for
+fetching arguments from the stack. Also use it in @code{va_start} to
+verify that the second parameter @var{lastarg} is the last named argument
+of the current function.
+@end defmac
+
+@defmac __builtin_classify_type (@var{object})
+Since each machine has its own conventions for which data types are
+passed in which kind of register, your implementation of @code{va_arg}
+has to embody these conventions. The easiest way to categorize the
+specified data type is to use @code{__builtin_classify_type} together
+with @code{sizeof} and @code{__alignof__}.
+
+@code{__builtin_classify_type} ignores the value of @var{object},
+considering only its data type. It returns an integer describing what
+kind of type that is---integer, floating, pointer, structure, and so on.
+
+The file @file{typeclass.h} defines an enumeration that you can use to
+interpret the values of @code{__builtin_classify_type}.
+@end defmac
+
+These machine description macros help implement varargs:
+
+@hook TARGET_EXPAND_BUILTIN_SAVEREGS
+
+@hook TARGET_SETUP_INCOMING_VARARGS
+
+@hook TARGET_STRICT_ARGUMENT_NAMING
+
+@hook TARGET_CALL_ARGS
+
+@hook TARGET_END_CALL_ARGS
+
+@hook TARGET_PRETEND_OUTGOING_VARARGS_NAMED
+
+@node Trampolines
+@section Support for Nested Functions
+@cindex support for nested functions
+@cindex trampolines for nested functions
+@cindex descriptors for nested functions
+@cindex nested functions, support for
+
+Taking the address of a nested function requires special compiler
+handling to ensure that the static chain register is loaded when
+the function is invoked via an indirect call.
+
+GCC has traditionally supported nested functions by creating an
+executable @dfn{trampoline} at run time when the address of a nested
+function is taken. This is a small piece of code which normally
+resides on the stack, in the stack frame of the containing function.
+The trampoline loads the static chain register and then jumps to the
+real address of the nested function.
+
+The use of trampolines requires an executable stack, which is a
+security risk. To avoid this problem, GCC also supports another
+strategy: using descriptors for nested functions. Under this model,
+taking the address of a nested function results in a pointer to a
+non-executable function descriptor object. Initializing the static chain
+from the descriptor is handled at indirect call sites.
+
+On some targets, including HPPA and IA-64, function descriptors may be
+mandated by the ABI or be otherwise handled in a target-specific way
+by the back end in its code generation strategy for indirect calls.
+GCC also provides its own generic descriptor implementation to support the
+@option{-fno-trampolines} option. In this case runtime detection of
+function descriptors at indirect call sites relies on descriptor
+pointers being tagged with a bit that is never set in bare function
+addresses. Since GCC's generic function descriptors are
+not ABI-compliant, this option is typically used only on a
+per-language basis (notably by Ada) or when it can otherwise be
+applied to the whole program.
+
+For languages other than Ada, the @code{-ftrampolines} and
+@code{-fno-trampolines} options currently have no effect, and
+trampolines are always generated on platforms that need them
+for nested functions.
+
+Define the following hook if your backend either implements ABI-specified
+descriptor support, or can use GCC's generic descriptor implementation
+for nested functions.
+
+@hook TARGET_CUSTOM_FUNCTION_DESCRIPTORS
+
+The following macros tell GCC how to generate code to allocate and
+initialize an executable trampoline. You can also use this interface
+if your back end needs to create ABI-specified non-executable descriptors; in
+this case the "trampoline" created is the descriptor containing data only.
+
+The instructions in an executable trampoline must do two things: load
+a constant address into the static chain register, and jump to the real
+address of the nested function. On CISC machines such as the m68k,
+this requires two instructions, a move immediate and a jump. Then the
+two addresses exist in the trampoline as word-long immediate operands.
+On RISC machines, it is often necessary to load each address into a
+register in two parts. Then pieces of each address form separate
+immediate operands.
+
+The code generated to initialize the trampoline must store the variable
+parts---the static chain value and the function address---into the
+immediate operands of the instructions. On a CISC machine, this is
+simply a matter of copying each address to a memory reference at the
+proper offset from the start of the trampoline. On a RISC machine, it
+may be necessary to take out pieces of the address and store them
+separately.
+
+@hook TARGET_ASM_TRAMPOLINE_TEMPLATE
+
+@defmac TRAMPOLINE_SECTION
+Return the section into which the trampoline template is to be placed
+(@pxref{Sections}). The default value is @code{readonly_data_section}.
+@end defmac
+
+@defmac TRAMPOLINE_SIZE
+A C expression for the size in bytes of the trampoline, as an integer.
+@end defmac
+
+@defmac TRAMPOLINE_ALIGNMENT
+Alignment required for trampolines, in bits.
+
+If you don't define this macro, the value of @code{FUNCTION_ALIGNMENT}
+is used for aligning trampolines.
+@end defmac
+
+@hook TARGET_TRAMPOLINE_INIT
+
+@hook TARGET_EMIT_CALL_BUILTIN___CLEAR_CACHE
+
+@hook TARGET_TRAMPOLINE_ADJUST_ADDRESS
+
+Implementing trampolines is difficult on many machines because they have
+separate instruction and data caches. Writing into a stack location
+fails to clear the memory in the instruction cache, so when the program
+jumps to that location, it executes the old contents.
+
+Here are two possible solutions. One is to clear the relevant parts of
+the instruction cache whenever a trampoline is set up. The other is to
+make all trampolines identical, by having them jump to a standard
+subroutine. The former technique makes trampoline execution faster; the
+latter makes initialization faster.
+
+To clear the instruction cache when a trampoline is initialized, define
+the following macro.
+
+@defmac CLEAR_INSN_CACHE (@var{beg}, @var{end})
+If defined, expands to a C expression clearing the @emph{instruction
+cache} in the specified interval. The definition of this macro would
+typically be a series of @code{asm} statements. Both @var{beg} and
+@var{end} are pointer expressions.
+@end defmac
+
+To use a standard subroutine, define the following macro. In addition,
+you must make sure that the instructions in a trampoline fill an entire
+cache line with identical instructions, or else ensure that the
+beginning of the trampoline code is always aligned at the same point in
+its cache line. Look in @file{m68k.h} as a guide.
+
+@defmac TRANSFER_FROM_TRAMPOLINE
+Define this macro if trampolines need a special subroutine to do their
+work. The macro should expand to a series of @code{asm} statements
+which will be compiled with GCC@. They go in a library function named
+@code{__transfer_from_trampoline}.
+
+If you need to avoid executing the ordinary prologue code of a compiled
+C function when you jump to the subroutine, you can do so by placing a
+special label of your own in the assembler code. Use one @code{asm}
+statement to generate an assembler label, and another to make the label
+global. Then trampolines can use that label to jump directly to your
+special assembler code.
+@end defmac
+
+@node Library Calls
+@section Implicit Calls to Library Routines
+@cindex library subroutine names
+@cindex @file{libgcc.a}
+
+@c prevent bad page break with this line
+Here is an explanation of implicit calls to library routines.
+
+@defmac DECLARE_LIBRARY_RENAMES
+This macro, if defined, should expand to a piece of C code that will get
+expanded when compiling functions for libgcc.a. It can be used to
+provide alternate names for GCC's internal library functions if there
+are ABI-mandated names that the compiler should provide.
+@end defmac
+
+@findex set_optab_libfunc
+@findex init_one_libfunc
+@hook TARGET_INIT_LIBFUNCS
+
+@hook TARGET_LIBFUNC_GNU_PREFIX
+
+@defmac FLOAT_LIB_COMPARE_RETURNS_BOOL (@var{mode}, @var{comparison})
+This macro should return @code{true} if the library routine that
+implements the floating point comparison operator @var{comparison} in
+mode @var{mode} will return a boolean, and @var{false} if it will
+return a tristate.
+
+GCC's own floating point libraries return tristates from the
+comparison operators, so the default returns false always. Most ports
+don't need to define this macro.
+@end defmac
+
+@defmac TARGET_LIB_INT_CMP_BIASED
+This macro should evaluate to @code{true} if the integer comparison
+functions (like @code{__cmpdi2}) return 0 to indicate that the first
+operand is smaller than the second, 1 to indicate that they are equal,
+and 2 to indicate that the first operand is greater than the second.
+If this macro evaluates to @code{false} the comparison functions return
+@minus{}1, 0, and 1 instead of 0, 1, and 2. If the target uses the routines
+in @file{libgcc.a}, you do not need to define this macro.
+@end defmac
+
+@defmac TARGET_HAS_NO_HW_DIVIDE
+This macro should be defined if the target has no hardware divide
+instructions. If this macro is defined, GCC will use an algorithm which
+make use of simple logical and arithmetic operations for 64-bit
+division. If the macro is not defined, GCC will use an algorithm which
+make use of a 64-bit by 32-bit divide primitive.
+@end defmac
+
+@cindex @code{EDOM}, implicit usage
+@findex matherr
+@defmac TARGET_EDOM
+The value of @code{EDOM} on the target machine, as a C integer constant
+expression. If you don't define this macro, GCC does not attempt to
+deposit the value of @code{EDOM} into @code{errno} directly. Look in
+@file{/usr/include/errno.h} to find the value of @code{EDOM} on your
+system.
+
+If you do not define @code{TARGET_EDOM}, then compiled code reports
+domain errors by calling the library function and letting it report the
+error. If mathematical functions on your system use @code{matherr} when
+there is an error, then you should leave @code{TARGET_EDOM} undefined so
+that @code{matherr} is used normally.
+@end defmac
+
+@cindex @code{errno}, implicit usage
+@defmac GEN_ERRNO_RTX
+Define this macro as a C expression to create an rtl expression that
+refers to the global ``variable'' @code{errno}. (On certain systems,
+@code{errno} may not actually be a variable.) If you don't define this
+macro, a reasonable default is used.
+@end defmac
+
+@hook TARGET_LIBC_HAS_FUNCTION
+
+@hook TARGET_LIBC_HAS_FAST_FUNCTION
+
+@defmac NEXT_OBJC_RUNTIME
+Set this macro to 1 to use the "NeXT" Objective-C message sending conventions
+by default. This calling convention involves passing the object, the selector
+and the method arguments all at once to the method-lookup library function.
+This is the usual setting when targeting Darwin/Mac OS X systems, which have
+the NeXT runtime installed.
+
+If the macro is set to 0, the "GNU" Objective-C message sending convention
+will be used by default. This convention passes just the object and the
+selector to the method-lookup function, which returns a pointer to the method.
+
+In either case, it remains possible to select code-generation for the alternate
+scheme, by means of compiler command line switches.
+@end defmac
+
+@node Addressing Modes
+@section Addressing Modes
+@cindex addressing modes
+
+@c prevent bad page break with this line
+This is about addressing modes.
+
+@defmac HAVE_PRE_INCREMENT
+@defmacx HAVE_PRE_DECREMENT
+@defmacx HAVE_POST_INCREMENT
+@defmacx HAVE_POST_DECREMENT
+A C expression that is nonzero if the machine supports pre-increment,
+pre-decrement, post-increment, or post-decrement addressing respectively.
+@end defmac
+
+@defmac HAVE_PRE_MODIFY_DISP
+@defmacx HAVE_POST_MODIFY_DISP
+A C expression that is nonzero if the machine supports pre- or
+post-address side-effect generation involving constants other than
+the size of the memory operand.
+@end defmac
+
+@defmac HAVE_PRE_MODIFY_REG
+@defmacx HAVE_POST_MODIFY_REG
+A C expression that is nonzero if the machine supports pre- or
+post-address side-effect generation involving a register displacement.
+@end defmac
+
+@defmac CONSTANT_ADDRESS_P (@var{x})
+A C expression that is 1 if the RTX @var{x} is a constant which
+is a valid address. On most machines the default definition of
+@code{(CONSTANT_P (@var{x}) && GET_CODE (@var{x}) != CONST_DOUBLE)}
+is acceptable, but a few machines are more restrictive as to which
+constant addresses are supported.
+@end defmac
+
+@defmac CONSTANT_P (@var{x})
+@code{CONSTANT_P}, which is defined by target-independent code,
+accepts integer-values expressions whose values are not explicitly
+known, such as @code{symbol_ref}, @code{label_ref}, and @code{high}
+expressions and @code{const} arithmetic expressions, in addition to
+@code{const_int} and @code{const_double} expressions.
+@end defmac
+
+@defmac MAX_REGS_PER_ADDRESS
+A number, the maximum number of registers that can appear in a valid
+memory address. Note that it is up to you to specify a value equal to
+the maximum number that @code{TARGET_LEGITIMATE_ADDRESS_P} would ever
+accept.
+@end defmac
+
+@hook TARGET_LEGITIMATE_ADDRESS_P
+
+@defmac TARGET_MEM_CONSTRAINT
+A single character to be used instead of the default @code{'m'}
+character for general memory addresses. This defines the constraint
+letter which matches the memory addresses accepted by
+@code{TARGET_LEGITIMATE_ADDRESS_P}. Define this macro if you want to
+support new address formats in your back end without changing the
+semantics of the @code{'m'} constraint. This is necessary in order to
+preserve functionality of inline assembly constructs using the
+@code{'m'} constraint.
+@end defmac
+
+@defmac FIND_BASE_TERM (@var{x})
+A C expression to determine the base term of address @var{x},
+or to provide a simplified version of @var{x} from which @file{alias.cc}
+can easily find the base term. This macro is used in only two places:
+@code{find_base_value} and @code{find_base_term} in @file{alias.cc}.
+
+It is always safe for this macro to not be defined. It exists so
+that alias analysis can understand machine-dependent addresses.
+
+The typical use of this macro is to handle addresses containing
+a label_ref or symbol_ref within an UNSPEC@.
+@end defmac
+
+@hook TARGET_LEGITIMIZE_ADDRESS
+
+@defmac LEGITIMIZE_RELOAD_ADDRESS (@var{x}, @var{mode}, @var{opnum}, @var{type}, @var{ind_levels}, @var{win})
+A C compound statement that attempts to replace @var{x}, which is an address
+that needs reloading, with a valid memory address for an operand of mode
+@var{mode}. @var{win} will be a C statement label elsewhere in the code.
+It is not necessary to define this macro, but it might be useful for
+performance reasons.
+
+For example, on the i386, it is sometimes possible to use a single
+reload register instead of two by reloading a sum of two pseudo
+registers into a register. On the other hand, for number of RISC
+processors offsets are limited so that often an intermediate address
+needs to be generated in order to address a stack slot. By defining
+@code{LEGITIMIZE_RELOAD_ADDRESS} appropriately, the intermediate addresses
+generated for adjacent some stack slots can be made identical, and thus
+be shared.
+
+@emph{Note}: This macro should be used with caution. It is necessary
+to know something of how reload works in order to effectively use this,
+and it is quite easy to produce macros that build in too much knowledge
+of reload internals.
+
+@emph{Note}: This macro must be able to reload an address created by a
+previous invocation of this macro. If it fails to handle such addresses
+then the compiler may generate incorrect code or abort.
+
+@findex push_reload
+The macro definition should use @code{push_reload} to indicate parts that
+need reloading; @var{opnum}, @var{type} and @var{ind_levels} are usually
+suitable to be passed unaltered to @code{push_reload}.
+
+The code generated by this macro must not alter the substructure of
+@var{x}. If it transforms @var{x} into a more legitimate form, it
+should assign @var{x} (which will always be a C variable) a new value.
+This also applies to parts that you change indirectly by calling
+@code{push_reload}.
+
+@findex strict_memory_address_p
+The macro definition may use @code{strict_memory_address_p} to test if
+the address has become legitimate.
+
+@findex copy_rtx
+If you want to change only a part of @var{x}, one standard way of doing
+this is to use @code{copy_rtx}. Note, however, that it unshares only a
+single level of rtl. Thus, if the part to be changed is not at the
+top level, you'll need to replace first the top level.
+It is not necessary for this macro to come up with a legitimate
+address; but often a machine-dependent strategy can generate better code.
+@end defmac
+
+@hook TARGET_MODE_DEPENDENT_ADDRESS_P
+
+@hook TARGET_LEGITIMATE_CONSTANT_P
+
+@hook TARGET_PRECOMPUTE_TLS_P
+
+@hook TARGET_DELEGITIMIZE_ADDRESS
+
+@hook TARGET_CONST_NOT_OK_FOR_DEBUG_P
+
+@hook TARGET_CANNOT_FORCE_CONST_MEM
+
+@hook TARGET_USE_BLOCKS_FOR_CONSTANT_P
+
+@hook TARGET_USE_BLOCKS_FOR_DECL_P
+
+@hook TARGET_BUILTIN_RECIPROCAL
+
+@hook TARGET_VECTORIZE_BUILTIN_MASK_FOR_LOAD
+
+@hook TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST
+
+@hook TARGET_VECTORIZE_PREFERRED_VECTOR_ALIGNMENT
+
+@hook TARGET_VECTORIZE_VECTOR_ALIGNMENT_REACHABLE
+
+@hook TARGET_VECTORIZE_VEC_PERM_CONST
+
+@hook TARGET_VECTORIZE_BUILTIN_VECTORIZED_FUNCTION
+
+@hook TARGET_VECTORIZE_BUILTIN_MD_VECTORIZED_FUNCTION
+
+@hook TARGET_VECTORIZE_SUPPORT_VECTOR_MISALIGNMENT
+
+@hook TARGET_VECTORIZE_PREFERRED_SIMD_MODE
+
+@hook TARGET_VECTORIZE_SPLIT_REDUCTION
+
+@hook TARGET_VECTORIZE_AUTOVECTORIZE_VECTOR_MODES
+
+@hook TARGET_VECTORIZE_RELATED_MODE
+
+@hook TARGET_VECTORIZE_GET_MASK_MODE
+
+@hook TARGET_VECTORIZE_EMPTY_MASK_IS_EXPENSIVE
+
+@hook TARGET_VECTORIZE_CREATE_COSTS
+
+@hook TARGET_VECTORIZE_BUILTIN_GATHER
+
+@hook TARGET_VECTORIZE_BUILTIN_SCATTER
+
+@hook TARGET_SIMD_CLONE_COMPUTE_VECSIZE_AND_SIMDLEN
+
+@hook TARGET_SIMD_CLONE_ADJUST
+
+@hook TARGET_SIMD_CLONE_USABLE
+
+@hook TARGET_SIMT_VF
+
+@hook TARGET_OMP_DEVICE_KIND_ARCH_ISA
+
+@hook TARGET_GOACC_VALIDATE_DIMS
+
+@hook TARGET_GOACC_DIM_LIMIT
+
+@hook TARGET_GOACC_FORK_JOIN
+
+@hook TARGET_GOACC_REDUCTION
+
+@hook TARGET_PREFERRED_ELSE_VALUE
+
+@hook TARGET_GOACC_ADJUST_PRIVATE_DECL
+
+@hook TARGET_GOACC_EXPAND_VAR_DECL
+
+@hook TARGET_GOACC_CREATE_WORKER_BROADCAST_RECORD
+
+@hook TARGET_GOACC_SHARED_MEM_LAYOUT
+
+@node Anchored Addresses
+@section Anchored Addresses
+@cindex anchored addresses
+@cindex @option{-fsection-anchors}
+
+GCC usually addresses every static object as a separate entity.
+For example, if we have:
+
+@smallexample
+static int a, b, c;
+int foo (void) @{ return a + b + c; @}
+@end smallexample
+
+the code for @code{foo} will usually calculate three separate symbolic
+addresses: those of @code{a}, @code{b} and @code{c}. On some targets,
+it would be better to calculate just one symbolic address and access
+the three variables relative to it. The equivalent pseudocode would
+be something like:
+
+@smallexample
+int foo (void)
+@{
+ register int *xr = &x;
+ return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
+@}
+@end smallexample
+
+(which isn't valid C). We refer to shared addresses like @code{x} as
+``section anchors''. Their use is controlled by @option{-fsection-anchors}.
+
+The hooks below describe the target properties that GCC needs to know
+in order to make effective use of section anchors. It won't use
+section anchors at all unless either @code{TARGET_MIN_ANCHOR_OFFSET}
+or @code{TARGET_MAX_ANCHOR_OFFSET} is set to a nonzero value.
+
+@hook TARGET_MIN_ANCHOR_OFFSET
+
+@hook TARGET_MAX_ANCHOR_OFFSET
+
+@hook TARGET_ASM_OUTPUT_ANCHOR
+
+@hook TARGET_USE_ANCHORS_FOR_SYMBOL_P
+
+@node Condition Code
+@section Condition Code Status
+@cindex condition code status
+
+Condition codes in GCC are represented as registers,
+which provides better schedulability for
+architectures that do have a condition code register, but on which
+most instructions do not affect it. The latter category includes
+most RISC machines.
+
+Implicit clobbering would pose a strong restriction on the placement of
+the definition and use of the condition code. In the past the definition
+and use were always adjacent. However, recent changes to support trapping
+arithmetic may result in the definition and user being in different blocks.
+Thus, there may be a @code{NOTE_INSN_BASIC_BLOCK} between them. Additionally,
+the definition may be the source of exception handling edges.
+
+These restrictions can prevent important
+optimizations on some machines. For example, on the IBM RS/6000, there
+is a delay for taken branches unless the condition code register is set
+three instructions earlier than the conditional branch. The instruction
+scheduler cannot perform this optimization if it is not permitted to
+separate the definition and use of the condition code register.
+
+If there is a specific
+condition code register in the machine, use a hard register. If the
+condition code or comparison result can be placed in any general register,
+or if there are multiple condition registers, use a pseudo register.
+Registers used to store the condition code value will usually have a mode
+that is in class @code{MODE_CC}.
+
+Alternatively, you can use @code{BImode} if the comparison operator is
+specified already in the compare instruction. In this case, you are not
+interested in most macros in this section.
+
+@menu
+* MODE_CC Condition Codes:: Modern representation of condition codes.
+@end menu
+
+@node MODE_CC Condition Codes
+@subsection Representation of condition codes using registers
+@findex CCmode
+@findex MODE_CC
+
+@defmac SELECT_CC_MODE (@var{op}, @var{x}, @var{y})
+On many machines, the condition code may be produced by other instructions
+than compares, for example the branch can use directly the condition
+code set by a subtract instruction. However, on some machines
+when the condition code is set this way some bits (such as the overflow
+bit) are not set in the same way as a test instruction, so that a different
+branch instruction must be used for some conditional branches. When
+this happens, use the machine mode of the condition code register to
+record different formats of the condition code register. Modes can
+also be used to record which compare instruction (e.g.@: a signed or an
+unsigned comparison) produced the condition codes.
+
+If other modes than @code{CCmode} are required, add them to
+@file{@var{machine}-modes.def} and define @code{SELECT_CC_MODE} to choose
+a mode given an operand of a compare. This is needed because the modes
+have to be chosen not only during RTL generation but also, for example,
+by instruction combination. The result of @code{SELECT_CC_MODE} should
+be consistent with the mode used in the patterns; for example to support
+the case of the add on the SPARC discussed above, we have the pattern
+
+@smallexample
+(define_insn ""
+ [(set (reg:CCNZ 0)
+ (compare:CCNZ
+ (plus:SI (match_operand:SI 0 "register_operand" "%r")
+ (match_operand:SI 1 "arith_operand" "rI"))
+ (const_int 0)))]
+ ""
+ "@dots{}")
+@end smallexample
+
+@noindent
+together with a @code{SELECT_CC_MODE} that returns @code{CCNZmode}
+for comparisons whose argument is a @code{plus}:
+
+@smallexample
+#define SELECT_CC_MODE(OP,X,Y) \
+ (GET_MODE_CLASS (GET_MODE (X)) == MODE_FLOAT \
+ ? ((OP == LT || OP == LE || OP == GT || OP == GE) \
+ ? CCFPEmode : CCFPmode) \
+ : ((GET_CODE (X) == PLUS || GET_CODE (X) == MINUS \
+ || GET_CODE (X) == NEG || GET_CODE (x) == ASHIFT) \
+ ? CCNZmode : CCmode))
+@end smallexample
+
+Another reason to use modes is to retain information on which operands
+were used by the comparison; see @code{REVERSIBLE_CC_MODE} later in
+this section.
+
+You should define this macro if and only if you define extra CC modes
+in @file{@var{machine}-modes.def}.
+@end defmac
+
+@hook TARGET_CANONICALIZE_COMPARISON
+
+@defmac REVERSIBLE_CC_MODE (@var{mode})
+A C expression whose value is one if it is always safe to reverse a
+comparison whose mode is @var{mode}. If @code{SELECT_CC_MODE}
+can ever return @var{mode} for a floating-point inequality comparison,
+then @code{REVERSIBLE_CC_MODE (@var{mode})} must be zero.
+
+You need not define this macro if it would always returns zero or if the
+floating-point format is anything other than @code{IEEE_FLOAT_FORMAT}.
+For example, here is the definition used on the SPARC, where floating-point
+inequality comparisons are given either @code{CCFPEmode} or @code{CCFPmode}:
+
+@smallexample
+#define REVERSIBLE_CC_MODE(MODE) \
+ ((MODE) != CCFPEmode && (MODE) != CCFPmode)
+@end smallexample
+@end defmac
+
+@defmac REVERSE_CONDITION (@var{code}, @var{mode})
+A C expression whose value is reversed condition code of the @var{code} for
+comparison done in CC_MODE @var{mode}. The macro is used only in case
+@code{REVERSIBLE_CC_MODE (@var{mode})} is nonzero. Define this macro in case
+machine has some non-standard way how to reverse certain conditionals. For
+instance in case all floating point conditions are non-trapping, compiler may
+freely convert unordered compares to ordered ones. Then definition may look
+like:
+
+@smallexample
+#define REVERSE_CONDITION(CODE, MODE) \
+ ((MODE) != CCFPmode ? reverse_condition (CODE) \
+ : reverse_condition_maybe_unordered (CODE))
+@end smallexample
+@end defmac
+
+@hook TARGET_FIXED_CONDITION_CODE_REGS
+
+@hook TARGET_CC_MODES_COMPATIBLE
+
+@hook TARGET_FLAGS_REGNUM
+
+@node Costs
+@section Describing Relative Costs of Operations
+@cindex costs of instructions
+@cindex relative costs
+@cindex speed of instructions
+
+These macros let you describe the relative speed of various operations
+on the target machine.
+
+@defmac REGISTER_MOVE_COST (@var{mode}, @var{from}, @var{to})
+A C expression for the cost of moving data of mode @var{mode} from a
+register in class @var{from} to one in class @var{to}. The classes are
+expressed using the enumeration values such as @code{GENERAL_REGS}. A
+value of 2 is the default; other values are interpreted relative to
+that.
+
+It is not required that the cost always equal 2 when @var{from} is the
+same as @var{to}; on some machines it is expensive to move between
+registers if they are not general registers.
+
+If reload sees an insn consisting of a single @code{set} between two
+hard registers, and if @code{REGISTER_MOVE_COST} applied to their
+classes returns a value of 2, reload does not check to ensure that the
+constraints of the insn are met. Setting a cost of other than 2 will
+allow reload to verify that the constraints are met. You should do this
+if the @samp{mov@var{m}} pattern's constraints do not allow such copying.
+
+These macros are obsolete, new ports should use the target hook
+@code{TARGET_REGISTER_MOVE_COST} instead.
+@end defmac
+
+@hook TARGET_REGISTER_MOVE_COST
+
+@defmac MEMORY_MOVE_COST (@var{mode}, @var{class}, @var{in})
+A C expression for the cost of moving data of mode @var{mode} between a
+register of class @var{class} and memory; @var{in} is zero if the value
+is to be written to memory, nonzero if it is to be read in. This cost
+is relative to those in @code{REGISTER_MOVE_COST}. If moving between
+registers and memory is more expensive than between two registers, you
+should define this macro to express the relative cost.
+
+If you do not define this macro, GCC uses a default cost of 4 plus
+the cost of copying via a secondary reload register, if one is
+needed. If your machine requires a secondary reload register to copy
+between memory and a register of @var{class} but the reload mechanism is
+more complex than copying via an intermediate, define this macro to
+reflect the actual cost of the move.
+
+GCC defines the function @code{memory_move_secondary_cost} if
+secondary reloads are needed. It computes the costs due to copying via
+a secondary register. If your machine copies from memory using a
+secondary register in the conventional way but the default base value of
+4 is not correct for your machine, define this macro to add some other
+value to the result of that function. The arguments to that function
+are the same as to this macro.
+
+These macros are obsolete, new ports should use the target hook
+@code{TARGET_MEMORY_MOVE_COST} instead.
+@end defmac
+
+@hook TARGET_MEMORY_MOVE_COST
+
+@defmac BRANCH_COST (@var{speed_p}, @var{predictable_p})
+A C expression for the cost of a branch instruction. A value of 1 is
+the default; other values are interpreted relative to that. Parameter
+@var{speed_p} is true when the branch in question should be optimized
+for speed. When it is false, @code{BRANCH_COST} should return a value
+optimal for code size rather than performance. @var{predictable_p} is
+true for well-predicted branches. On many architectures the
+@code{BRANCH_COST} can be reduced then.
+@end defmac
+
+Here are additional macros which do not specify precise relative costs,
+but only that certain actions are more expensive than GCC would
+ordinarily expect.
+
+@defmac SLOW_BYTE_ACCESS
+Define this macro as a C expression which is nonzero if accessing less
+than a word of memory (i.e.@: a @code{char} or a @code{short}) is no
+faster than accessing a word of memory, i.e., if such access
+require more than one instruction or if there is no difference in cost
+between byte and (aligned) word loads.
+
+When this macro is not defined, the compiler will access a field by
+finding the smallest containing object; when it is defined, a fullword
+load will be used if alignment permits. Unless bytes accesses are
+faster than word accesses, using word accesses is preferable since it
+may eliminate subsequent memory access if subsequent accesses occur to
+other fields in the same word of the structure, but to different bytes.
+@end defmac
+
+@hook TARGET_SLOW_UNALIGNED_ACCESS
+
+@defmac MOVE_RATIO (@var{speed})
+The threshold of number of scalar memory-to-memory move insns, @emph{below}
+which a sequence of insns should be generated instead of a
+string move insn or a library call. Increasing the value will always
+make code faster, but eventually incurs high cost in increased code size.
+
+Note that on machines where the corresponding move insn is a
+@code{define_expand} that emits a sequence of insns, this macro counts
+the number of such sequences.
+
+The parameter @var{speed} is true if the code is currently being
+optimized for speed rather than size.
+
+If you don't define this, a reasonable default is used.
+@end defmac
+
+@hook TARGET_USE_BY_PIECES_INFRASTRUCTURE_P
+
+@hook TARGET_OVERLAP_OP_BY_PIECES_P
+
+@hook TARGET_COMPARE_BY_PIECES_BRANCH_RATIO
+
+@defmac MOVE_MAX_PIECES
+A C expression used by @code{move_by_pieces} to determine the largest unit
+a load or store used to copy memory is. Defaults to @code{MOVE_MAX}.
+@end defmac
+
+@defmac STORE_MAX_PIECES
+A C expression used by @code{store_by_pieces} to determine the largest unit
+a store used to memory is. Defaults to @code{MOVE_MAX_PIECES}, or two times
+the size of @code{HOST_WIDE_INT}, whichever is smaller.
+@end defmac
+
+@defmac COMPARE_MAX_PIECES
+A C expression used by @code{compare_by_pieces} to determine the largest unit
+a load or store used to compare memory is. Defaults to
+@code{MOVE_MAX_PIECES}.
+@end defmac
+
+@defmac CLEAR_RATIO (@var{speed})
+The threshold of number of scalar move insns, @emph{below} which a sequence
+of insns should be generated to clear memory instead of a string clear insn
+or a library call. Increasing the value will always make code faster, but
+eventually incurs high cost in increased code size.
+
+The parameter @var{speed} is true if the code is currently being
+optimized for speed rather than size.
+
+If you don't define this, a reasonable default is used.
+@end defmac
+
+@defmac SET_RATIO (@var{speed})
+The threshold of number of scalar move insns, @emph{below} which a sequence
+of insns should be generated to set memory to a constant value, instead of
+a block set insn or a library call.
+Increasing the value will always make code faster, but
+eventually incurs high cost in increased code size.
+
+The parameter @var{speed} is true if the code is currently being
+optimized for speed rather than size.
+
+If you don't define this, it defaults to the value of @code{MOVE_RATIO}.
+@end defmac
+
+@defmac USE_LOAD_POST_INCREMENT (@var{mode})
+A C expression used to determine whether a load postincrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_POST_INCREMENT}.
+@end defmac
+
+@defmac USE_LOAD_POST_DECREMENT (@var{mode})
+A C expression used to determine whether a load postdecrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_POST_DECREMENT}.
+@end defmac
+
+@defmac USE_LOAD_PRE_INCREMENT (@var{mode})
+A C expression used to determine whether a load preincrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_PRE_INCREMENT}.
+@end defmac
+
+@defmac USE_LOAD_PRE_DECREMENT (@var{mode})
+A C expression used to determine whether a load predecrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_PRE_DECREMENT}.
+@end defmac
+
+@defmac USE_STORE_POST_INCREMENT (@var{mode})
+A C expression used to determine whether a store postincrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_POST_INCREMENT}.
+@end defmac
+
+@defmac USE_STORE_POST_DECREMENT (@var{mode})
+A C expression used to determine whether a store postdecrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_POST_DECREMENT}.
+@end defmac
+
+@defmac USE_STORE_PRE_INCREMENT (@var{mode})
+This macro is used to determine whether a store preincrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_PRE_INCREMENT}.
+@end defmac
+
+@defmac USE_STORE_PRE_DECREMENT (@var{mode})
+This macro is used to determine whether a store predecrement is a good
+thing to use for a given mode. Defaults to the value of
+@code{HAVE_PRE_DECREMENT}.
+@end defmac
+
+@defmac NO_FUNCTION_CSE
+Define this macro to be true if it is as good or better to call a constant
+function address than to call an address kept in a register.
+@end defmac
+
+@defmac LOGICAL_OP_NON_SHORT_CIRCUIT
+Define this macro if a non-short-circuit operation produced by
+@samp{fold_range_test ()} is optimal. This macro defaults to true if
+@code{BRANCH_COST} is greater than or equal to the value 2.
+@end defmac
+
+@hook TARGET_OPTAB_SUPPORTED_P
+
+@hook TARGET_RTX_COSTS
+
+@hook TARGET_ADDRESS_COST
+
+@hook TARGET_INSN_COST
+
+@hook TARGET_MAX_NOCE_IFCVT_SEQ_COST
+
+@hook TARGET_NOCE_CONVERSION_PROFITABLE_P
+
+@hook TARGET_NEW_ADDRESS_PROFITABLE_P
+
+@hook TARGET_NO_SPECULATION_IN_DELAY_SLOTS_P
+
+@hook TARGET_ESTIMATED_POLY_VALUE
+
+@node Scheduling
+@section Adjusting the Instruction Scheduler
+
+The instruction scheduler may need a fair amount of machine-specific
+adjustment in order to produce good code. GCC provides several target
+hooks for this purpose. It is usually enough to define just a few of
+them: try the first ones in this list first.
+
+@hook TARGET_SCHED_ISSUE_RATE
+
+@hook TARGET_SCHED_VARIABLE_ISSUE
+
+@hook TARGET_SCHED_ADJUST_COST
+
+@hook TARGET_SCHED_ADJUST_PRIORITY
+
+@hook TARGET_SCHED_REORDER
+
+@hook TARGET_SCHED_REORDER2
+
+@hook TARGET_SCHED_MACRO_FUSION_P
+
+@hook TARGET_SCHED_MACRO_FUSION_PAIR_P
+
+@hook TARGET_SCHED_DEPENDENCIES_EVALUATION_HOOK
+
+@hook TARGET_SCHED_INIT
+
+@hook TARGET_SCHED_FINISH
+
+@hook TARGET_SCHED_INIT_GLOBAL
+
+@hook TARGET_SCHED_FINISH_GLOBAL
+
+@hook TARGET_SCHED_DFA_PRE_CYCLE_INSN
+
+@hook TARGET_SCHED_INIT_DFA_PRE_CYCLE_INSN
+
+@hook TARGET_SCHED_DFA_POST_CYCLE_INSN
+
+@hook TARGET_SCHED_INIT_DFA_POST_CYCLE_INSN
+
+@hook TARGET_SCHED_DFA_PRE_ADVANCE_CYCLE
+
+@hook TARGET_SCHED_DFA_POST_ADVANCE_CYCLE
+
+@hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD
+
+@hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_DFA_LOOKAHEAD_GUARD
+
+@hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BEGIN
+
+@hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_ISSUE
+
+@hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_BACKTRACK
+
+@hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_END
+
+@hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_INIT
+
+@hook TARGET_SCHED_FIRST_CYCLE_MULTIPASS_FINI
+
+@hook TARGET_SCHED_DFA_NEW_CYCLE
+
+@hook TARGET_SCHED_IS_COSTLY_DEPENDENCE
+
+@hook TARGET_SCHED_H_I_D_EXTENDED
+
+@hook TARGET_SCHED_ALLOC_SCHED_CONTEXT
+
+@hook TARGET_SCHED_INIT_SCHED_CONTEXT
+
+@hook TARGET_SCHED_SET_SCHED_CONTEXT
+
+@hook TARGET_SCHED_CLEAR_SCHED_CONTEXT
+
+@hook TARGET_SCHED_FREE_SCHED_CONTEXT
+
+@hook TARGET_SCHED_SPECULATE_INSN
+
+@hook TARGET_SCHED_NEEDS_BLOCK_P
+
+@hook TARGET_SCHED_GEN_SPEC_CHECK
+
+@hook TARGET_SCHED_SET_SCHED_FLAGS
+
+@hook TARGET_SCHED_CAN_SPECULATE_INSN
+
+@hook TARGET_SCHED_SMS_RES_MII
+
+@hook TARGET_SCHED_DISPATCH
+
+@hook TARGET_SCHED_DISPATCH_DO
+
+@hook TARGET_SCHED_EXPOSED_PIPELINE
+
+@hook TARGET_SCHED_REASSOCIATION_WIDTH
+
+@hook TARGET_SCHED_FUSION_PRIORITY
+
+@hook TARGET_EXPAND_DIVMOD_LIBFUNC
+
+@node Sections
+@section Dividing the Output into Sections (Texts, Data, @dots{})
+@c the above section title is WAY too long. maybe cut the part between
+@c the (...)? --mew 10feb93
+
+An object file is divided into sections containing different types of
+data. In the most common case, there are three sections: the @dfn{text
+section}, which holds instructions and read-only data; the @dfn{data
+section}, which holds initialized writable data; and the @dfn{bss
+section}, which holds uninitialized data. Some systems have other kinds
+of sections.
+
+@file{varasm.cc} provides several well-known sections, such as
+@code{text_section}, @code{data_section} and @code{bss_section}.
+The normal way of controlling a @code{@var{foo}_section} variable
+is to define the associated @code{@var{FOO}_SECTION_ASM_OP} macro,
+as described below. The macros are only read once, when @file{varasm.cc}
+initializes itself, so their values must be run-time constants.
+They may however depend on command-line flags.
+
+@emph{Note:} Some run-time files, such @file{crtstuff.c}, also make
+use of the @code{@var{FOO}_SECTION_ASM_OP} macros, and expect them
+to be string literals.
+
+Some assemblers require a different string to be written every time a
+section is selected. If your assembler falls into this category, you
+should define the @code{TARGET_ASM_INIT_SECTIONS} hook and use
+@code{get_unnamed_section} to set up the sections.
+
+You must always create a @code{text_section}, either by defining
+@code{TEXT_SECTION_ASM_OP} or by initializing @code{text_section}
+in @code{TARGET_ASM_INIT_SECTIONS}. The same is true of
+@code{data_section} and @code{DATA_SECTION_ASM_OP}. If you do not
+create a distinct @code{readonly_data_section}, the default is to
+reuse @code{text_section}.
+
+All the other @file{varasm.cc} sections are optional, and are null
+if the target does not provide them.
+
+@defmac TEXT_SECTION_ASM_OP
+A C expression whose value is a string, including spacing, containing the
+assembler operation that should precede instructions and read-only data.
+Normally @code{"\t.text"} is right.
+@end defmac
+
+@defmac HOT_TEXT_SECTION_NAME
+If defined, a C string constant for the name of the section containing most
+frequently executed functions of the program. If not defined, GCC will provide
+a default definition if the target supports named sections.
+@end defmac
+
+@defmac UNLIKELY_EXECUTED_TEXT_SECTION_NAME
+If defined, a C string constant for the name of the section containing unlikely
+executed functions in the program.
+@end defmac
+
+@defmac DATA_SECTION_ASM_OP
+A C expression whose value is a string, including spacing, containing the
+assembler operation to identify the following data as writable initialized
+data. Normally @code{"\t.data"} is right.
+@end defmac
+
+@defmac SDATA_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+initialized, writable small data.
+@end defmac
+
+@defmac READONLY_DATA_SECTION_ASM_OP
+A C expression whose value is a string, including spacing, containing the
+assembler operation to identify the following data as read-only initialized
+data.
+@end defmac
+
+@defmac BSS_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+uninitialized global data. If not defined, and
+@code{ASM_OUTPUT_ALIGNED_BSS} not defined,
+uninitialized global data will be output in the data section if
+@option{-fno-common} is passed, otherwise @code{ASM_OUTPUT_COMMON} will be
+used.
+@end defmac
+
+@defmac SBSS_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+uninitialized, writable small data.
+@end defmac
+
+@defmac TLS_COMMON_ASM_OP
+If defined, a C expression whose value is a string containing the
+assembler operation to identify the following data as thread-local
+common data. The default is @code{".tls_common"}.
+@end defmac
+
+@defmac TLS_SECTION_ASM_FLAG
+If defined, a C expression whose value is a character constant
+containing the flag used to mark a section as a TLS section. The
+default is @code{'T'}.
+@end defmac
+
+@defmac INIT_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+initialization code. If not defined, GCC will assume such a section does
+not exist. This section has no corresponding @code{init_section}
+variable; it is used entirely in runtime code.
+@end defmac
+
+@defmac FINI_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+finalization code. If not defined, GCC will assume such a section does
+not exist. This section has no corresponding @code{fini_section}
+variable; it is used entirely in runtime code.
+@end defmac
+
+@defmac INIT_ARRAY_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+part of the @code{.init_array} (or equivalent) section. If not
+defined, GCC will assume such a section does not exist. Do not define
+both this macro and @code{INIT_SECTION_ASM_OP}.
+@end defmac
+
+@defmac FINI_ARRAY_SECTION_ASM_OP
+If defined, a C expression whose value is a string, including spacing,
+containing the assembler operation to identify the following data as
+part of the @code{.fini_array} (or equivalent) section. If not
+defined, GCC will assume such a section does not exist. Do not define
+both this macro and @code{FINI_SECTION_ASM_OP}.
+@end defmac
+
+@defmac MACH_DEP_SECTION_ASM_FLAG
+If defined, a C expression whose value is a character constant
+containing the flag used to mark a machine-dependent section. This
+corresponds to the @code{SECTION_MACH_DEP} section flag.
+@end defmac
+
+@defmac CRT_CALL_STATIC_FUNCTION (@var{section_op}, @var{function})
+If defined, an ASM statement that switches to a different section
+via @var{section_op}, calls @var{function}, and switches back to
+the text section. This is used in @file{crtstuff.c} if
+@code{INIT_SECTION_ASM_OP} or @code{FINI_SECTION_ASM_OP} to calls
+to initialization and finalization functions from the init and fini
+sections. By default, this macro uses a simple function call. Some
+ports need hand-crafted assembly code to avoid dependencies on
+registers initialized in the function prologue or to ensure that
+constant pools don't end up too far way in the text section.
+@end defmac
+
+@defmac TARGET_LIBGCC_SDATA_SECTION
+If defined, a string which names the section into which small
+variables defined in crtstuff and libgcc should go. This is useful
+when the target has options for optimizing access to small data, and
+you want the crtstuff and libgcc routines to be conservative in what
+they expect of your application yet liberal in what your application
+expects. For example, for targets with a @code{.sdata} section (like
+MIPS), you could compile crtstuff with @code{-G 0} so that it doesn't
+require small data support from your application, but use this macro
+to put small data into @code{.sdata} so that your application can
+access these variables whether it uses small data or not.
+@end defmac
+
+@defmac FORCE_CODE_SECTION_ALIGN
+If defined, an ASM statement that aligns a code section to some
+arbitrary boundary. This is used to force all fragments of the
+@code{.init} and @code{.fini} sections to have to same alignment
+and thus prevent the linker from having to add any padding.
+@end defmac
+
+@defmac JUMP_TABLES_IN_TEXT_SECTION
+Define this macro to be an expression with a nonzero value if jump
+tables (for @code{tablejump} insns) should be output in the text
+section, along with the assembler instructions. Otherwise, the
+readonly data section is used.
+
+This macro is irrelevant if there is no separate readonly data section.
+@end defmac
+
+@hook TARGET_ASM_INIT_SECTIONS
+
+@hook TARGET_ASM_RELOC_RW_MASK
+
+@hook TARGET_ASM_GENERATE_PIC_ADDR_DIFF_VEC
+
+@hook TARGET_ASM_SELECT_SECTION
+
+@defmac USE_SELECT_SECTION_FOR_FUNCTIONS
+Define this macro if you wish TARGET_ASM_SELECT_SECTION to be called
+for @code{FUNCTION_DECL}s as well as for variables and constants.
+
+In the case of a @code{FUNCTION_DECL}, @var{reloc} will be zero if the
+function has been determined to be likely to be called, and nonzero if
+it is unlikely to be called.
+@end defmac
+
+@hook TARGET_ASM_UNIQUE_SECTION
+
+@hook TARGET_ASM_FUNCTION_RODATA_SECTION
+
+@hook TARGET_ASM_MERGEABLE_RODATA_PREFIX
+
+@hook TARGET_ASM_TM_CLONE_TABLE_SECTION
+
+@hook TARGET_ASM_SELECT_RTX_SECTION
+
+@hook TARGET_MANGLE_DECL_ASSEMBLER_NAME
+
+@hook TARGET_ENCODE_SECTION_INFO
+
+@hook TARGET_STRIP_NAME_ENCODING
+
+@hook TARGET_IN_SMALL_DATA_P
+
+@hook TARGET_HAVE_SRODATA_SECTION
+
+@hook TARGET_PROFILE_BEFORE_PROLOGUE
+
+@hook TARGET_BINDS_LOCAL_P
+
+@hook TARGET_HAVE_TLS
+
+
+@node PIC
+@section Position Independent Code
+@cindex position independent code
+@cindex PIC
+
+This section describes macros that help implement generation of position
+independent code. Simply defining these macros is not enough to
+generate valid PIC; you must also add support to the hook
+@code{TARGET_LEGITIMATE_ADDRESS_P} and to the macro
+@code{PRINT_OPERAND_ADDRESS}, as well as @code{LEGITIMIZE_ADDRESS}. You
+must modify the definition of @samp{movsi} to do something appropriate
+when the source operand contains a symbolic address. You may also
+need to alter the handling of switch statements so that they use
+relative addresses.
+@c i rearranged the order of the macros above to try to force one of
+@c them to the next line, to eliminate an overfull hbox. --mew 10feb93
+
+@defmac PIC_OFFSET_TABLE_REGNUM
+The register number of the register used to address a table of static
+data addresses in memory. In some cases this register is defined by a
+processor's ``application binary interface'' (ABI)@. When this macro
+is defined, RTL is generated for this register once, as with the stack
+pointer and frame pointer registers. If this macro is not defined, it
+is up to the machine-dependent files to allocate such a register (if
+necessary). Note that this register must be fixed when in use (e.g.@:
+when @code{flag_pic} is true).
+@end defmac
+
+@defmac PIC_OFFSET_TABLE_REG_CALL_CLOBBERED
+A C expression that is nonzero if the register defined by
+@code{PIC_OFFSET_TABLE_REGNUM} is clobbered by calls. If not defined,
+the default is zero. Do not define
+this macro if @code{PIC_OFFSET_TABLE_REGNUM} is not defined.
+@end defmac
+
+@defmac LEGITIMATE_PIC_OPERAND_P (@var{x})
+A C expression that is nonzero if @var{x} is a legitimate immediate
+operand on the target machine when generating position independent code.
+You can assume that @var{x} satisfies @code{CONSTANT_P}, so you need not
+check this. You can also assume @var{flag_pic} is true, so you need not
+check it either. You need not define this macro if all constants
+(including @code{SYMBOL_REF}) can be immediate operands when generating
+position independent code.
+@end defmac
+
+@node Assembler Format
+@section Defining the Output Assembler Language
+
+This section describes macros whose principal purpose is to describe how
+to write instructions in assembler language---rather than what the
+instructions do.
+
+@menu
+* File Framework:: Structural information for the assembler file.
+* Data Output:: Output of constants (numbers, strings, addresses).
+* Uninitialized Data:: Output of uninitialized variables.
+* Label Output:: Output and generation of labels.
+* Initialization:: General principles of initialization
+ and termination routines.
+* Macros for Initialization::
+ Specific macros that control the handling of
+ initialization and termination routines.
+* Instruction Output:: Output of actual instructions.
+* Dispatch Tables:: Output of jump tables.
+* Exception Region Output:: Output of exception region code.
+* Alignment Output:: Pseudo ops for alignment and skipping data.
+@end menu
+
+@node File Framework
+@subsection The Overall Framework of an Assembler File
+@cindex assembler format
+@cindex output of assembler code
+
+@c prevent bad page break with this line
+This describes the overall framework of an assembly file.
+
+@findex default_file_start
+@hook TARGET_ASM_FILE_START
+
+@hook TARGET_ASM_FILE_START_APP_OFF
+
+@hook TARGET_ASM_FILE_START_FILE_DIRECTIVE
+
+@hook TARGET_ASM_FILE_END
+
+@deftypefun void file_end_indicate_exec_stack ()
+Some systems use a common convention, the @samp{.note.GNU-stack}
+special section, to indicate whether or not an object file relies on
+the stack being executable. If your system uses this convention, you
+should define @code{TARGET_ASM_FILE_END} to this function. If you
+need to do other things in that hook, have your hook function call
+this function.
+@end deftypefun
+
+@hook TARGET_ASM_LTO_START
+
+@hook TARGET_ASM_LTO_END
+
+@hook TARGET_ASM_CODE_END
+
+@defmac ASM_COMMENT_START
+A C string constant describing how to begin a comment in the target
+assembler language. The compiler assumes that the comment will end at
+the end of the line.
+@end defmac
+
+@defmac ASM_APP_ON
+A C string constant for text to be output before each @code{asm}
+statement or group of consecutive ones. Normally this is
+@code{"#APP"}, which is a comment that has no effect on most
+assemblers but tells the GNU assembler that it must check the lines
+that follow for all valid assembler constructs.
+@end defmac
+
+@defmac ASM_APP_OFF
+A C string constant for text to be output after each @code{asm}
+statement or group of consecutive ones. Normally this is
+@code{"#NO_APP"}, which tells the GNU assembler to resume making the
+time-saving assumptions that are valid for ordinary compiler output.
+@end defmac
+
+@defmac ASM_OUTPUT_SOURCE_FILENAME (@var{stream}, @var{name})
+A C statement to output COFF information or DWARF debugging information
+which indicates that filename @var{name} is the current source file to
+the stdio stream @var{stream}.
+
+This macro need not be defined if the standard form of output
+for the file format in use is appropriate.
+@end defmac
+
+@hook TARGET_ASM_OUTPUT_SOURCE_FILENAME
+
+@hook TARGET_ASM_OUTPUT_IDENT
+
+@defmac OUTPUT_QUOTED_STRING (@var{stream}, @var{string})
+A C statement to output the string @var{string} to the stdio stream
+@var{stream}. If you do not call the function @code{output_quoted_string}
+in your config files, GCC will only call it to output filenames to
+the assembler source. So you can use it to canonicalize the format
+of the filename using this macro.
+@end defmac
+
+@hook TARGET_ASM_NAMED_SECTION
+
+@hook TARGET_ASM_ELF_FLAGS_NUMERIC
+
+@hook TARGET_ASM_FUNCTION_SECTION
+
+@hook TARGET_ASM_FUNCTION_SWITCHED_TEXT_SECTIONS
+
+@hook TARGET_HAVE_NAMED_SECTIONS
+This flag is true if the target supports @code{TARGET_ASM_NAMED_SECTION}.
+It must not be modified by command-line option processing.
+@end deftypevr
+
+@anchor{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS}
+@hook TARGET_HAVE_SWITCHABLE_BSS_SECTIONS
+
+@hook TARGET_SECTION_TYPE_FLAGS
+
+@hook TARGET_ASM_RECORD_GCC_SWITCHES
+
+@hook TARGET_ASM_RECORD_GCC_SWITCHES_SECTION
+
+@need 2000
+@node Data Output
+@subsection Output of Data
+
+
+@hook TARGET_ASM_BYTE_OP
+
+@hook TARGET_ASM_INTEGER
+
+@hook TARGET_ASM_DECL_END
+
+@hook TARGET_ASM_OUTPUT_ADDR_CONST_EXTRA
+
+@defmac ASM_OUTPUT_ASCII (@var{stream}, @var{ptr}, @var{len})
+A C statement to output to the stdio stream @var{stream} an assembler
+instruction to assemble a string constant containing the @var{len}
+bytes at @var{ptr}. @var{ptr} will be a C expression of type
+@code{char *} and @var{len} a C expression of type @code{int}.
+
+If the assembler has a @code{.ascii} pseudo-op as found in the
+Berkeley Unix assembler, do not define the macro
+@code{ASM_OUTPUT_ASCII}.
+@end defmac
+
+@defmac ASM_OUTPUT_FDESC (@var{stream}, @var{decl}, @var{n})
+A C statement to output word @var{n} of a function descriptor for
+@var{decl}. This must be defined if @code{TARGET_VTABLE_USES_DESCRIPTORS}
+is defined, and is otherwise unused.
+@end defmac
+
+@defmac CONSTANT_POOL_BEFORE_FUNCTION
+You may define this macro as a C expression. You should define the
+expression to have a nonzero value if GCC should output the constant
+pool for a function before the code for the function, or a zero value if
+GCC should output the constant pool after the function. If you do
+not define this macro, the usual case, GCC will output the constant
+pool before the function.
+@end defmac
+
+@defmac ASM_OUTPUT_POOL_PROLOGUE (@var{file}, @var{funname}, @var{fundecl}, @var{size})
+A C statement to output assembler commands to define the start of the
+constant pool for a function. @var{funname} is a string giving
+the name of the function. Should the return type of the function
+be required, it can be obtained via @var{fundecl}. @var{size}
+is the size, in bytes, of the constant pool that will be written
+immediately after this call.
+
+If no constant-pool prefix is required, the usual case, this macro need
+not be defined.
+@end defmac
+
+@defmac ASM_OUTPUT_SPECIAL_POOL_ENTRY (@var{file}, @var{x}, @var{mode}, @var{align}, @var{labelno}, @var{jumpto})
+A C statement (with or without semicolon) to output a constant in the
+constant pool, if it needs special treatment. (This macro need not do
+anything for RTL expressions that can be output normally.)
+
+The argument @var{file} is the standard I/O stream to output the
+assembler code on. @var{x} is the RTL expression for the constant to
+output, and @var{mode} is the machine mode (in case @var{x} is a
+@samp{const_int}). @var{align} is the required alignment for the value
+@var{x}; you should output an assembler directive to force this much
+alignment.
+
+The argument @var{labelno} is a number to use in an internal label for
+the address of this pool entry. The definition of this macro is
+responsible for outputting the label definition at the proper place.
+Here is how to do this:
+
+@smallexample
+@code{(*targetm.asm_out.internal_label)} (@var{file}, "LC", @var{labelno});
+@end smallexample
+
+When you output a pool entry specially, you should end with a
+@code{goto} to the label @var{jumpto}. This will prevent the same pool
+entry from being output a second time in the usual manner.
+
+You need not define this macro if it would do nothing.
+@end defmac
+
+@defmac ASM_OUTPUT_POOL_EPILOGUE (@var{file} @var{funname} @var{fundecl} @var{size})
+A C statement to output assembler commands to at the end of the constant
+pool for a function. @var{funname} is a string giving the name of the
+function. Should the return type of the function be required, you can
+obtain it via @var{fundecl}. @var{size} is the size, in bytes, of the
+constant pool that GCC wrote immediately before this call.
+
+If no constant-pool epilogue is required, the usual case, you need not
+define this macro.
+@end defmac
+
+@defmac IS_ASM_LOGICAL_LINE_SEPARATOR (@var{C}, @var{STR})
+Define this macro as a C expression which is nonzero if @var{C} is
+used as a logical line separator by the assembler. @var{STR} points
+to the position in the string where @var{C} was found; this can be used if
+a line separator uses multiple characters.
+
+If you do not define this macro, the default is that only
+the character @samp{;} is treated as a logical line separator.
+@end defmac
+
+@hook TARGET_ASM_OPEN_PAREN
+
+These macros are provided by @file{real.h} for writing the definitions
+of @code{ASM_OUTPUT_DOUBLE} and the like:
+
+@defmac REAL_VALUE_TO_TARGET_SINGLE (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_DOUBLE (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_LONG_DOUBLE (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_DECIMAL32 (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_DECIMAL64 (@var{x}, @var{l})
+@defmacx REAL_VALUE_TO_TARGET_DECIMAL128 (@var{x}, @var{l})
+These translate @var{x}, of type @code{REAL_VALUE_TYPE}, to the
+target's floating point representation, and store its bit pattern in
+the variable @var{l}. For @code{REAL_VALUE_TO_TARGET_SINGLE} and
+@code{REAL_VALUE_TO_TARGET_DECIMAL32}, this variable should be a
+simple @code{long int}. For the others, it should be an array of
+@code{long int}. The number of elements in this array is determined
+by the size of the desired target floating point data type: 32 bits of
+it go in each @code{long int} array element. Each array element holds
+32 bits of the result, even if @code{long int} is wider than 32 bits
+on the host machine.
+
+The array element values are designed so that you can print them out
+using @code{fprintf} in the order they should appear in the target
+machine's memory.
+@end defmac
+
+@node Uninitialized Data
+@subsection Output of Uninitialized Variables
+
+Each of the macros in this section is used to do the whole job of
+outputting a single uninitialized variable.
+
+@defmac ASM_OUTPUT_COMMON (@var{stream}, @var{name}, @var{size}, @var{rounded})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of a common-label named
+@var{name} whose size is @var{size} bytes. The variable @var{rounded}
+is the size rounded up to whatever alignment the caller wants. It is
+possible that @var{size} may be zero, for instance if a struct with no
+other member than a zero-length array is defined. In this case, the
+backend must output a symbol definition that allocates at least one
+byte, both so that the address of the resulting object does not compare
+equal to any other, and because some object formats cannot even express
+the concept of a zero-sized common symbol, as that is how they represent
+an ordinary undefined external.
+
+Use the expression @code{assemble_name (@var{stream}, @var{name})} to
+output the name itself; before and after that, output the additional
+assembler syntax for defining the name, and a newline.
+
+This macro controls how the assembler definitions of uninitialized
+common global variables are output.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_COMMON (@var{stream}, @var{name}, @var{size}, @var{alignment})
+Like @code{ASM_OUTPUT_COMMON} except takes the required alignment as a
+separate, explicit argument. If you define this macro, it is used in
+place of @code{ASM_OUTPUT_COMMON}, and gives you more flexibility in
+handling the required alignment of the variable. The alignment is specified
+as the number of bits.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_DECL_COMMON (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment})
+Like @code{ASM_OUTPUT_ALIGNED_COMMON} except that @var{decl} of the
+variable to be output, if there is one, or @code{NULL_TREE} if there
+is no corresponding variable. If you define this macro, GCC will use it
+in place of both @code{ASM_OUTPUT_COMMON} and
+@code{ASM_OUTPUT_ALIGNED_COMMON}. Define this macro when you need to see
+the variable's decl in order to chose what to output.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_BSS (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of uninitialized global @var{decl} named
+@var{name} whose size is @var{size} bytes. The variable @var{alignment}
+is the alignment specified as the number of bits.
+
+Try to use function @code{asm_output_aligned_bss} defined in file
+@file{varasm.cc} when defining this macro. If unable, use the expression
+@code{assemble_name (@var{stream}, @var{name})} to output the name itself;
+before and after that, output the additional assembler syntax for defining
+the name, and a newline.
+
+There are two ways of handling global BSS@. One is to define this macro.
+The other is to have @code{TARGET_ASM_SELECT_SECTION} return a
+switchable BSS section (@pxref{TARGET_HAVE_SWITCHABLE_BSS_SECTIONS}).
+You do not need to do both.
+
+Some languages do not have @code{common} data, and require a
+non-common form of global BSS in order to handle uninitialized globals
+efficiently. C++ is one example of this. However, if the target does
+not support global BSS, the front end may choose to make globals
+common in order to save space in the object file.
+@end defmac
+
+@defmac ASM_OUTPUT_LOCAL (@var{stream}, @var{name}, @var{size}, @var{rounded})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of a local-common-label named
+@var{name} whose size is @var{size} bytes. The variable @var{rounded}
+is the size rounded up to whatever alignment the caller wants.
+
+Use the expression @code{assemble_name (@var{stream}, @var{name})} to
+output the name itself; before and after that, output the additional
+assembler syntax for defining the name, and a newline.
+
+This macro controls how the assembler definitions of uninitialized
+static variables are output.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_LOCAL (@var{stream}, @var{name}, @var{size}, @var{alignment})
+Like @code{ASM_OUTPUT_LOCAL} except takes the required alignment as a
+separate, explicit argument. If you define this macro, it is used in
+place of @code{ASM_OUTPUT_LOCAL}, and gives you more flexibility in
+handling the required alignment of the variable. The alignment is specified
+as the number of bits.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGNED_DECL_LOCAL (@var{stream}, @var{decl}, @var{name}, @var{size}, @var{alignment})
+Like @code{ASM_OUTPUT_ALIGNED_LOCAL} except that @var{decl} of the
+variable to be output, if there is one, or @code{NULL_TREE} if there
+is no corresponding variable. If you define this macro, GCC will use it
+in place of both @code{ASM_OUTPUT_LOCAL} and
+@code{ASM_OUTPUT_ALIGNED_LOCAL}. Define this macro when you need to see
+the variable's decl in order to chose what to output.
+@end defmac
+
+@node Label Output
+@subsection Output and Generation of Labels
+
+@c prevent bad page break with this line
+This is about outputting labels.
+
+@findex assemble_name
+@defmac ASM_OUTPUT_LABEL (@var{stream}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of a label named @var{name}.
+Use the expression @code{assemble_name (@var{stream}, @var{name})} to
+output the name itself; before and after that, output the additional
+assembler syntax for defining the name, and a newline. A default
+definition of this macro is provided which is correct for most systems.
+@end defmac
+
+@defmac ASM_OUTPUT_FUNCTION_LABEL (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} the assembler definition of a label named @var{name} of
+a function.
+Use the expression @code{assemble_name (@var{stream}, @var{name})} to
+output the name itself; before and after that, output the additional
+assembler syntax for defining the name, and a newline. A default
+definition of this macro is provided which is correct for most systems.
+
+If this macro is not defined, then the function name is defined in the
+usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}).
+@end defmac
+
+@findex assemble_name_raw
+@defmac ASM_OUTPUT_INTERNAL_LABEL (@var{stream}, @var{name})
+Identical to @code{ASM_OUTPUT_LABEL}, except that @var{name} is known
+to refer to a compiler-generated label. The default definition uses
+@code{assemble_name_raw}, which is like @code{assemble_name} except
+that it is more efficient.
+@end defmac
+
+@defmac SIZE_ASM_OP
+A C string containing the appropriate assembler directive to specify the
+size of a symbol, without any arguments. On systems that use ELF, the
+default (in @file{config/elfos.h}) is @samp{"\t.size\t"}; on other
+systems, the default is not to define this macro.
+
+Define this macro only if it is correct to use the default definitions
+of @code{ASM_OUTPUT_SIZE_DIRECTIVE} and @code{ASM_OUTPUT_MEASURED_SIZE}
+for your system. If you need your own custom definitions of those
+macros, or if you do not need explicit symbol sizes at all, do not
+define this macro.
+@end defmac
+
+@defmac ASM_OUTPUT_SIZE_DIRECTIVE (@var{stream}, @var{name}, @var{size})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} a directive telling the assembler that the size of the
+symbol @var{name} is @var{size}. @var{size} is a @code{HOST_WIDE_INT}.
+If you define @code{SIZE_ASM_OP}, a default definition of this macro is
+provided.
+@end defmac
+
+@defmac ASM_OUTPUT_MEASURED_SIZE (@var{stream}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} a directive telling the assembler to calculate the size of
+the symbol @var{name} by subtracting its address from the current
+address.
+
+If you define @code{SIZE_ASM_OP}, a default definition of this macro is
+provided. The default assumes that the assembler recognizes a special
+@samp{.} symbol as referring to the current address, and can calculate
+the difference between this and another symbol. If your assembler does
+not recognize @samp{.} or cannot do calculations with it, you will need
+to redefine @code{ASM_OUTPUT_MEASURED_SIZE} to use some other technique.
+@end defmac
+
+@defmac NO_DOLLAR_IN_LABEL
+Define this macro if the assembler does not accept the character
+@samp{$} in label names. By default constructors and destructors in
+G++ have @samp{$} in the identifiers. If this macro is defined,
+@samp{.} is used instead.
+@end defmac
+
+@defmac NO_DOT_IN_LABEL
+Define this macro if the assembler does not accept the character
+@samp{.} in label names. By default constructors and destructors in G++
+have names that use @samp{.}. If this macro is defined, these names
+are rewritten to avoid @samp{.}.
+@end defmac
+
+@defmac TYPE_ASM_OP
+A C string containing the appropriate assembler directive to specify the
+type of a symbol, without any arguments. On systems that use ELF, the
+default (in @file{config/elfos.h}) is @samp{"\t.type\t"}; on other
+systems, the default is not to define this macro.
+
+Define this macro only if it is correct to use the default definition of
+@code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own
+custom definition of this macro, or if you do not need explicit symbol
+types at all, do not define this macro.
+@end defmac
+
+@defmac TYPE_OPERAND_FMT
+A C string which specifies (using @code{printf} syntax) the format of
+the second operand to @code{TYPE_ASM_OP}. On systems that use ELF, the
+default (in @file{config/elfos.h}) is @samp{"@@%s"}; on other systems,
+the default is not to define this macro.
+
+Define this macro only if it is correct to use the default definition of
+@code{ASM_OUTPUT_TYPE_DIRECTIVE} for your system. If you need your own
+custom definition of this macro, or if you do not need explicit symbol
+types at all, do not define this macro.
+@end defmac
+
+@defmac ASM_OUTPUT_TYPE_DIRECTIVE (@var{stream}, @var{type})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} a directive telling the assembler that the type of the
+symbol @var{name} is @var{type}. @var{type} is a C string; currently,
+that string is always either @samp{"function"} or @samp{"object"}, but
+you should not count on this.
+
+If you define @code{TYPE_ASM_OP} and @code{TYPE_OPERAND_FMT}, a default
+definition of this macro is provided.
+@end defmac
+
+@defmac ASM_DECLARE_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the name @var{name} of a
+function which is being defined. This macro is responsible for
+outputting the label definition (perhaps using
+@code{ASM_OUTPUT_FUNCTION_LABEL}). The argument @var{decl} is the
+@code{FUNCTION_DECL} tree node representing the function.
+
+If this macro is not defined, then the function name is defined in the
+usual manner as a label (by means of @code{ASM_OUTPUT_FUNCTION_LABEL}).
+
+You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in the definition
+of this macro.
+@end defmac
+
+@defmac ASM_DECLARE_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the size of a function
+which is being defined. The argument @var{name} is the name of the
+function. The argument @var{decl} is the @code{FUNCTION_DECL} tree node
+representing the function.
+
+If this macro is not defined, then the function size is not defined.
+
+You may wish to use @code{ASM_OUTPUT_MEASURED_SIZE} in the definition
+of this macro.
+@end defmac
+
+@defmac ASM_DECLARE_COLD_FUNCTION_NAME (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the name @var{name} of a
+cold function partition which is being defined. This macro is responsible
+for outputting the label definition (perhaps using
+@code{ASM_OUTPUT_FUNCTION_LABEL}). The argument @var{decl} is the
+@code{FUNCTION_DECL} tree node representing the function.
+
+If this macro is not defined, then the cold partition name is defined in the
+usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}).
+
+You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} in the definition
+of this macro.
+@end defmac
+
+@defmac ASM_DECLARE_COLD_FUNCTION_SIZE (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the size of a cold function
+partition which is being defined. The argument @var{name} is the name of the
+cold partition of the function. The argument @var{decl} is the
+@code{FUNCTION_DECL} tree node representing the function.
+
+If this macro is not defined, then the partition size is not defined.
+
+You may wish to use @code{ASM_OUTPUT_MEASURED_SIZE} in the definition
+of this macro.
+@end defmac
+
+@defmac ASM_DECLARE_OBJECT_NAME (@var{stream}, @var{name}, @var{decl})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the name @var{name} of an
+initialized variable which is being defined. This macro must output the
+label definition (perhaps using @code{ASM_OUTPUT_LABEL}). The argument
+@var{decl} is the @code{VAR_DECL} tree node representing the variable.
+
+If this macro is not defined, then the variable name is defined in the
+usual manner as a label (by means of @code{ASM_OUTPUT_LABEL}).
+
+You may wish to use @code{ASM_OUTPUT_TYPE_DIRECTIVE} and/or
+@code{ASM_OUTPUT_SIZE_DIRECTIVE} in the definition of this macro.
+@end defmac
+
+@hook TARGET_ASM_DECLARE_CONSTANT_NAME
+
+@defmac ASM_DECLARE_REGISTER_GLOBAL (@var{stream}, @var{decl}, @var{regno}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for claiming a register @var{regno}
+for a global variable @var{decl} with name @var{name}.
+
+If you don't define this macro, that is equivalent to defining it to do
+nothing.
+@end defmac
+
+@defmac ASM_FINISH_DECLARE_OBJECT (@var{stream}, @var{decl}, @var{toplevel}, @var{atend})
+A C statement (sans semicolon) to finish up declaring a variable name
+once the compiler has processed its initializer fully and thus has had a
+chance to determine the size of an array when controlled by an
+initializer. This is used on systems where it's necessary to declare
+something about the size of the object.
+
+If you don't define this macro, that is equivalent to defining it to do
+nothing.
+
+You may wish to use @code{ASM_OUTPUT_SIZE_DIRECTIVE} and/or
+@code{ASM_OUTPUT_MEASURED_SIZE} in the definition of this macro.
+@end defmac
+
+@hook TARGET_ASM_GLOBALIZE_LABEL
+
+@hook TARGET_ASM_GLOBALIZE_DECL_NAME
+
+@hook TARGET_ASM_ASSEMBLE_UNDEFINED_DECL
+
+@defmac ASM_WEAKEN_LABEL (@var{stream}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} some commands that will make the label @var{name} weak;
+that is, available for reference from other files but only used if
+no other definition is available. Use the expression
+@code{assemble_name (@var{stream}, @var{name})} to output the name
+itself; before and after that, output the additional assembler syntax
+for making that name weak, and a newline.
+
+If you don't define this macro or @code{ASM_WEAKEN_DECL}, GCC will not
+support weak symbols and you should not define the @code{SUPPORTS_WEAK}
+macro.
+@end defmac
+
+@defmac ASM_WEAKEN_DECL (@var{stream}, @var{decl}, @var{name}, @var{value})
+Combines (and replaces) the function of @code{ASM_WEAKEN_LABEL} and
+@code{ASM_OUTPUT_WEAK_ALIAS}, allowing access to the associated function
+or variable decl. If @var{value} is not @code{NULL}, this C statement
+should output to the stdio stream @var{stream} assembler code which
+defines (equates) the weak symbol @var{name} to have the value
+@var{value}. If @var{value} is @code{NULL}, it should output commands
+to make @var{name} weak.
+@end defmac
+
+@defmac ASM_OUTPUT_WEAKREF (@var{stream}, @var{decl}, @var{name}, @var{value})
+Outputs a directive that enables @var{name} to be used to refer to
+symbol @var{value} with weak-symbol semantics. @code{decl} is the
+declaration of @code{name}.
+@end defmac
+
+@defmac SUPPORTS_WEAK
+A preprocessor constant expression which evaluates to true if the target
+supports weak symbols.
+
+If you don't define this macro, @file{defaults.h} provides a default
+definition. If either @code{ASM_WEAKEN_LABEL} or @code{ASM_WEAKEN_DECL}
+is defined, the default definition is @samp{1}; otherwise, it is @samp{0}.
+@end defmac
+
+@defmac TARGET_SUPPORTS_WEAK
+A C expression which evaluates to true if the target supports weak symbols.
+
+If you don't define this macro, @file{defaults.h} provides a default
+definition. The default definition is @samp{(SUPPORTS_WEAK)}. Define
+this macro if you want to control weak symbol support with a compiler
+flag such as @option{-melf}.
+@end defmac
+
+@defmac MAKE_DECL_ONE_ONLY (@var{decl})
+A C statement (sans semicolon) to mark @var{decl} to be emitted as a
+public symbol such that extra copies in multiple translation units will
+be discarded by the linker. Define this macro if your object file
+format provides support for this concept, such as the @samp{COMDAT}
+section flags in the Microsoft Windows PE/COFF format, and this support
+requires changes to @var{decl}, such as putting it in a separate section.
+@end defmac
+
+@defmac SUPPORTS_ONE_ONLY
+A C expression which evaluates to true if the target supports one-only
+semantics.
+
+If you don't define this macro, @file{varasm.cc} provides a default
+definition. If @code{MAKE_DECL_ONE_ONLY} is defined, the default
+definition is @samp{1}; otherwise, it is @samp{0}. Define this macro if
+you want to control one-only symbol support with a compiler flag, or if
+setting the @code{DECL_ONE_ONLY} flag is enough to mark a declaration to
+be emitted as one-only.
+@end defmac
+
+@hook TARGET_ASM_ASSEMBLE_VISIBILITY
+
+@defmac TARGET_WEAK_NOT_IN_ARCHIVE_TOC
+A C expression that evaluates to true if the target's linker expects
+that weak symbols do not appear in a static archive's table of contents.
+The default is @code{0}.
+
+Leaving weak symbols out of an archive's table of contents means that,
+if a symbol will only have a definition in one translation unit and
+will have undefined references from other translation units, that
+symbol should not be weak. Defining this macro to be nonzero will
+thus have the effect that certain symbols that would normally be weak
+(explicit template instantiations, and vtables for polymorphic classes
+with noninline key methods) will instead be nonweak.
+
+The C++ ABI requires this macro to be zero. Define this macro for
+targets where full C++ ABI compliance is impossible and where linker
+restrictions require weak symbols to be left out of a static archive's
+table of contents.
+@end defmac
+
+@defmac ASM_OUTPUT_EXTERNAL (@var{stream}, @var{decl}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} any text necessary for declaring the name of an external
+symbol named @var{name} which is referenced in this compilation but
+not defined. The value of @var{decl} is the tree node for the
+declaration.
+
+This macro need not be defined if it does not need to output anything.
+The GNU assembler and most Unix assemblers don't require anything.
+@end defmac
+
+@hook TARGET_ASM_EXTERNAL_LIBCALL
+
+@hook TARGET_ASM_MARK_DECL_PRESERVED
+
+@defmac ASM_OUTPUT_LABELREF (@var{stream}, @var{name})
+A C statement (sans semicolon) to output to the stdio stream
+@var{stream} a reference in assembler syntax to a label named
+@var{name}. This should add @samp{_} to the front of the name, if that
+is customary on your operating system, as it is in most Berkeley Unix
+systems. This macro is used in @code{assemble_name}.
+@end defmac
+
+@hook TARGET_MANGLE_ASSEMBLER_NAME
+
+@defmac ASM_OUTPUT_SYMBOL_REF (@var{stream}, @var{sym})
+A C statement (sans semicolon) to output a reference to
+@code{SYMBOL_REF} @var{sym}. If not defined, @code{assemble_name}
+will be used to output the name of the symbol. This macro may be used
+to modify the way a symbol is referenced depending on information
+encoded by @code{TARGET_ENCODE_SECTION_INFO}.
+@end defmac
+
+@defmac ASM_OUTPUT_LABEL_REF (@var{stream}, @var{buf})
+A C statement (sans semicolon) to output a reference to @var{buf}, the
+result of @code{ASM_GENERATE_INTERNAL_LABEL}. If not defined,
+@code{assemble_name} will be used to output the name of the symbol.
+This macro is not used by @code{output_asm_label}, or the @code{%l}
+specifier that calls it; the intention is that this macro should be set
+when it is necessary to output a label differently when its address is
+being taken.
+@end defmac
+
+@hook TARGET_ASM_INTERNAL_LABEL
+
+@defmac ASM_OUTPUT_DEBUG_LABEL (@var{stream}, @var{prefix}, @var{num})
+A C statement to output to the stdio stream @var{stream} a debug info
+label whose name is made from the string @var{prefix} and the number
+@var{num}. This is useful for VLIW targets, where debug info labels
+may need to be treated differently than branch target labels. On some
+systems, branch target labels must be at the beginning of instruction
+bundles, but debug info labels can occur in the middle of instruction
+bundles.
+
+If this macro is not defined, then @code{(*targetm.asm_out.internal_label)} will be
+used.
+@end defmac
+
+@defmac ASM_GENERATE_INTERNAL_LABEL (@var{string}, @var{prefix}, @var{num})
+A C statement to store into the string @var{string} a label whose name
+is made from the string @var{prefix} and the number @var{num}.
+
+This string, when output subsequently by @code{assemble_name}, should
+produce the output that @code{(*targetm.asm_out.internal_label)} would produce
+with the same @var{prefix} and @var{num}.
+
+If the string begins with @samp{*}, then @code{assemble_name} will
+output the rest of the string unchanged. It is often convenient for
+@code{ASM_GENERATE_INTERNAL_LABEL} to use @samp{*} in this way. If the
+string doesn't start with @samp{*}, then @code{ASM_OUTPUT_LABELREF} gets
+to output the string, and may change it. (Of course,
+@code{ASM_OUTPUT_LABELREF} is also part of your machine description, so
+you should know what it does on your machine.)
+@end defmac
+
+@defmac ASM_FORMAT_PRIVATE_NAME (@var{outvar}, @var{name}, @var{number})
+A C expression to assign to @var{outvar} (which is a variable of type
+@code{char *}) a newly allocated string made from the string
+@var{name} and the number @var{number}, with some suitable punctuation
+added. Use @code{alloca} to get space for the string.
+
+The string will be used as an argument to @code{ASM_OUTPUT_LABELREF} to
+produce an assembler label for an internal static variable whose name is
+@var{name}. Therefore, the string must be such as to result in valid
+assembler code. The argument @var{number} is different each time this
+macro is executed; it prevents conflicts between similarly-named
+internal static variables in different scopes.
+
+Ideally this string should not be a valid C identifier, to prevent any
+conflict with the user's own symbols. Most assemblers allow periods
+or percent signs in assembler symbols; putting at least one of these
+between the name and the number will suffice.
+
+If this macro is not defined, a default definition will be provided
+which is correct for most systems.
+@end defmac
+
+@defmac ASM_OUTPUT_DEF (@var{stream}, @var{name}, @var{value})
+A C statement to output to the stdio stream @var{stream} assembler code
+which defines (equates) the symbol @var{name} to have the value @var{value}.
+
+@findex SET_ASM_OP
+If @code{SET_ASM_OP} is defined, a default definition is provided which is
+correct for most systems.
+@end defmac
+
+@defmac ASM_OUTPUT_DEF_FROM_DECLS (@var{stream}, @var{decl_of_name}, @var{decl_of_value})
+A C statement to output to the stdio stream @var{stream} assembler code
+which defines (equates) the symbol whose tree node is @var{decl_of_name}
+to have the value of the tree node @var{decl_of_value}. This macro will
+be used in preference to @samp{ASM_OUTPUT_DEF} if it is defined and if
+the tree nodes are available.
+
+@findex SET_ASM_OP
+If @code{SET_ASM_OP} is defined, a default definition is provided which is
+correct for most systems.
+@end defmac
+
+@defmac TARGET_DEFERRED_OUTPUT_DEFS (@var{decl_of_name}, @var{decl_of_value})
+A C statement that evaluates to true if the assembler code which defines
+(equates) the symbol whose tree node is @var{decl_of_name} to have the value
+of the tree node @var{decl_of_value} should be emitted near the end of the
+current compilation unit. The default is to not defer output of defines.
+This macro affects defines output by @samp{ASM_OUTPUT_DEF} and
+@samp{ASM_OUTPUT_DEF_FROM_DECLS}.
+@end defmac
+
+@defmac ASM_OUTPUT_WEAK_ALIAS (@var{stream}, @var{name}, @var{value})
+A C statement to output to the stdio stream @var{stream} assembler code
+which defines (equates) the weak symbol @var{name} to have the value
+@var{value}. If @var{value} is @code{NULL}, it defines @var{name} as
+an undefined weak symbol.
+
+Define this macro if the target only supports weak aliases; define
+@code{ASM_OUTPUT_DEF} instead if possible.
+@end defmac
+
+@defmac OBJC_GEN_METHOD_LABEL (@var{buf}, @var{is_inst}, @var{class_name}, @var{cat_name}, @var{sel_name})
+Define this macro to override the default assembler names used for
+Objective-C methods.
+
+The default name is a unique method number followed by the name of the
+class (e.g.@: @samp{_1_Foo}). For methods in categories, the name of
+the category is also included in the assembler name (e.g.@:
+@samp{_1_Foo_Bar}).
+
+These names are safe on most systems, but make debugging difficult since
+the method's selector is not present in the name. Therefore, particular
+systems define other ways of computing names.
+
+@var{buf} is an expression of type @code{char *} which gives you a
+buffer in which to store the name; its length is as long as
+@var{class_name}, @var{cat_name} and @var{sel_name} put together, plus
+50 characters extra.
+
+The argument @var{is_inst} specifies whether the method is an instance
+method or a class method; @var{class_name} is the name of the class;
+@var{cat_name} is the name of the category (or @code{NULL} if the method is not
+in a category); and @var{sel_name} is the name of the selector.
+
+On systems where the assembler can handle quoted names, you can use this
+macro to provide more human-readable names.
+@end defmac
+
+@node Initialization
+@subsection How Initialization Functions Are Handled
+@cindex initialization routines
+@cindex termination routines
+@cindex constructors, output of
+@cindex destructors, output of
+
+The compiled code for certain languages includes @dfn{constructors}
+(also called @dfn{initialization routines})---functions to initialize
+data in the program when the program is started. These functions need
+to be called before the program is ``started''---that is to say, before
+@code{main} is called.
+
+Compiling some languages generates @dfn{destructors} (also called
+@dfn{termination routines}) that should be called when the program
+terminates.
+
+To make the initialization and termination functions work, the compiler
+must output something in the assembler code to cause those functions to
+be called at the appropriate time. When you port the compiler to a new
+system, you need to specify how to do this.
+
+There are two major ways that GCC currently supports the execution of
+initialization and termination functions. Each way has two variants.
+Much of the structure is common to all four variations.
+
+@findex __CTOR_LIST__
+@findex __DTOR_LIST__
+The linker must build two lists of these functions---a list of
+initialization functions, called @code{__CTOR_LIST__}, and a list of
+termination functions, called @code{__DTOR_LIST__}.
+
+Each list always begins with an ignored function pointer (which may hold
+0, @minus{}1, or a count of the function pointers after it, depending on
+the environment). This is followed by a series of zero or more function
+pointers to constructors (or destructors), followed by a function
+pointer containing zero.
+
+Depending on the operating system and its executable file format, either
+@file{crtstuff.c} or @file{libgcc2.c} traverses these lists at startup
+time and exit time. Constructors are called in reverse order of the
+list; destructors in forward order.
+
+The best way to handle static constructors works only for object file
+formats which provide arbitrarily-named sections. A section is set
+aside for a list of constructors, and another for a list of destructors.
+Traditionally these are called @samp{.ctors} and @samp{.dtors}. Each
+object file that defines an initialization function also puts a word in
+the constructor section to point to that function. The linker
+accumulates all these words into one contiguous @samp{.ctors} section.
+Termination functions are handled similarly.
+
+This method will be chosen as the default by @file{target-def.h} if
+@code{TARGET_ASM_NAMED_SECTION} is defined. A target that does not
+support arbitrary sections, but does support special designated
+constructor and destructor sections may define @code{CTORS_SECTION_ASM_OP}
+and @code{DTORS_SECTION_ASM_OP} to achieve the same effect.
+
+When arbitrary sections are available, there are two variants, depending
+upon how the code in @file{crtstuff.c} is called. On systems that
+support a @dfn{.init} section which is executed at program startup,
+parts of @file{crtstuff.c} are compiled into that section. The
+program is linked by the @command{gcc} driver like this:
+
+@smallexample
+ld -o @var{output_file} crti.o crtbegin.o @dots{} -lgcc crtend.o crtn.o
+@end smallexample
+
+The prologue of a function (@code{__init}) appears in the @code{.init}
+section of @file{crti.o}; the epilogue appears in @file{crtn.o}. Likewise
+for the function @code{__fini} in the @dfn{.fini} section. Normally these
+files are provided by the operating system or by the GNU C library, but
+are provided by GCC for a few targets.
+
+The objects @file{crtbegin.o} and @file{crtend.o} are (for most targets)
+compiled from @file{crtstuff.c}. They contain, among other things, code
+fragments within the @code{.init} and @code{.fini} sections that branch
+to routines in the @code{.text} section. The linker will pull all parts
+of a section together, which results in a complete @code{__init} function
+that invokes the routines we need at startup.
+
+To use this variant, you must define the @code{INIT_SECTION_ASM_OP}
+macro properly.
+
+If no init section is available, when GCC compiles any function called
+@code{main} (or more accurately, any function designated as a program
+entry point by the language front end calling @code{expand_main_function}),
+it inserts a procedure call to @code{__main} as the first executable code
+after the function prologue. The @code{__main} function is defined
+in @file{libgcc2.c} and runs the global constructors.
+
+In file formats that don't support arbitrary sections, there are again
+two variants. In the simplest variant, the GNU linker (GNU @code{ld})
+and an `a.out' format must be used. In this case,
+@code{TARGET_ASM_CONSTRUCTOR} is defined to produce a @code{.stabs}
+entry of type @samp{N_SETT}, referencing the name @code{__CTOR_LIST__},
+and with the address of the void function containing the initialization
+code as its value. The GNU linker recognizes this as a request to add
+the value to a @dfn{set}; the values are accumulated, and are eventually
+placed in the executable as a vector in the format described above, with
+a leading (ignored) count and a trailing zero element.
+@code{TARGET_ASM_DESTRUCTOR} is handled similarly. Since no init
+section is available, the absence of @code{INIT_SECTION_ASM_OP} causes
+the compilation of @code{main} to call @code{__main} as above, starting
+the initialization process.
+
+The last variant uses neither arbitrary sections nor the GNU linker.
+This is preferable when you want to do dynamic linking and when using
+file formats which the GNU linker does not support, such as `ECOFF'@. In
+this case, @code{TARGET_HAVE_CTORS_DTORS} is false, initialization and
+termination functions are recognized simply by their names. This requires
+an extra program in the linkage step, called @command{collect2}. This program
+pretends to be the linker, for use with GCC; it does its job by running
+the ordinary linker, but also arranges to include the vectors of
+initialization and termination functions. These functions are called
+via @code{__main} as described above. In order to use this method,
+@code{use_collect2} must be defined in the target in @file{config.gcc}.
+
+@ifinfo
+The following section describes the specific macros that control and
+customize the handling of initialization and termination functions.
+@end ifinfo
+
+@node Macros for Initialization
+@subsection Macros Controlling Initialization Routines
+
+Here are the macros that control how the compiler handles initialization
+and termination functions:
+
+@defmac INIT_SECTION_ASM_OP
+If defined, a C string constant, including spacing, for the assembler
+operation to identify the following data as initialization code. If not
+defined, GCC will assume such a section does not exist. When you are
+using special sections for initialization and termination functions, this
+macro also controls how @file{crtstuff.c} and @file{libgcc2.c} arrange to
+run the initialization functions.
+@end defmac
+
+@defmac HAS_INIT_SECTION
+If defined, @code{main} will not call @code{__main} as described above.
+This macro should be defined for systems that control start-up code
+on a symbol-by-symbol basis, such as OSF/1, and should not
+be defined explicitly for systems that support @code{INIT_SECTION_ASM_OP}.
+@end defmac
+
+@defmac LD_INIT_SWITCH
+If defined, a C string constant for a switch that tells the linker that
+the following symbol is an initialization routine.
+@end defmac
+
+@defmac LD_FINI_SWITCH
+If defined, a C string constant for a switch that tells the linker that
+the following symbol is a finalization routine.
+@end defmac
+
+@defmac COLLECT_SHARED_INIT_FUNC (@var{stream}, @var{func})
+If defined, a C statement that will write a function that can be
+automatically called when a shared library is loaded. The function
+should call @var{func}, which takes no arguments. If not defined, and
+the object format requires an explicit initialization function, then a
+function called @code{_GLOBAL__DI} will be generated.
+
+This function and the following one are used by collect2 when linking a
+shared library that needs constructors or destructors, or has DWARF2
+exception tables embedded in the code.
+@end defmac
+
+@defmac COLLECT_SHARED_FINI_FUNC (@var{stream}, @var{func})
+If defined, a C statement that will write a function that can be
+automatically called when a shared library is unloaded. The function
+should call @var{func}, which takes no arguments. If not defined, and
+the object format requires an explicit finalization function, then a
+function called @code{_GLOBAL__DD} will be generated.
+@end defmac
+
+@defmac INVOKE__main
+If defined, @code{main} will call @code{__main} despite the presence of
+@code{INIT_SECTION_ASM_OP}. This macro should be defined for systems
+where the init section is not actually run automatically, but is still
+useful for collecting the lists of constructors and destructors.
+@end defmac
+
+@defmac SUPPORTS_INIT_PRIORITY
+If nonzero, the C++ @code{init_priority} attribute is supported and the
+compiler should emit instructions to control the order of initialization
+of objects. If zero, the compiler will issue an error message upon
+encountering an @code{init_priority} attribute.
+@end defmac
+
+@hook TARGET_HAVE_CTORS_DTORS
+
+@hook TARGET_DTORS_FROM_CXA_ATEXIT
+
+@hook TARGET_ASM_CONSTRUCTOR
+
+@hook TARGET_ASM_DESTRUCTOR
+
+If @code{TARGET_HAVE_CTORS_DTORS} is true, the initialization routine
+generated for the generated object file will have static linkage.
+
+If your system uses @command{collect2} as the means of processing
+constructors, then that program normally uses @command{nm} to scan
+an object file for constructor functions to be called.
+
+On certain kinds of systems, you can define this macro to make
+@command{collect2} work faster (and, in some cases, make it work at all):
+
+@defmac OBJECT_FORMAT_COFF
+Define this macro if the system uses COFF (Common Object File Format)
+object files, so that @command{collect2} can assume this format and scan
+object files directly for dynamic constructor/destructor functions.
+
+This macro is effective only in a native compiler; @command{collect2} as
+part of a cross compiler always uses @command{nm} for the target machine.
+@end defmac
+
+@defmac REAL_NM_FILE_NAME
+Define this macro as a C string constant containing the file name to use
+to execute @command{nm}. The default is to search the path normally for
+@command{nm}.
+@end defmac
+
+@defmac NM_FLAGS
+@command{collect2} calls @command{nm} to scan object files for static
+constructors and destructors and LTO info. By default, @option{-n} is
+passed. Define @code{NM_FLAGS} to a C string constant if other options
+are needed to get the same output format as GNU @command{nm -n}
+produces.
+@end defmac
+
+If your system supports shared libraries and has a program to list the
+dynamic dependencies of a given library or executable, you can define
+these macros to enable support for running initialization and
+termination functions in shared libraries:
+
+@defmac LDD_SUFFIX
+Define this macro to a C string constant containing the name of the program
+which lists dynamic dependencies, like @command{ldd} under SunOS 4.
+@end defmac
+
+@defmac PARSE_LDD_OUTPUT (@var{ptr})
+Define this macro to be C code that extracts filenames from the output
+of the program denoted by @code{LDD_SUFFIX}. @var{ptr} is a variable
+of type @code{char *} that points to the beginning of a line of output
+from @code{LDD_SUFFIX}. If the line lists a dynamic dependency, the
+code must advance @var{ptr} to the beginning of the filename on that
+line. Otherwise, it must set @var{ptr} to @code{NULL}.
+@end defmac
+
+@defmac SHLIB_SUFFIX
+Define this macro to a C string constant containing the default shared
+library extension of the target (e.g., @samp{".so"}). @command{collect2}
+strips version information after this suffix when generating global
+constructor and destructor names. This define is only needed on targets
+that use @command{collect2} to process constructors and destructors.
+@end defmac
+
+@node Instruction Output
+@subsection Output of Assembler Instructions
+
+@c prevent bad page break with this line
+This describes assembler instruction output.
+
+@defmac REGISTER_NAMES
+A C initializer containing the assembler's names for the machine
+registers, each one as a C string constant. This is what translates
+register numbers in the compiler into assembler language.
+@end defmac
+
+@defmac ADDITIONAL_REGISTER_NAMES
+If defined, a C initializer for an array of structures containing a name
+and a register number. This macro defines additional names for hard
+registers, thus allowing the @code{asm} option in declarations to refer
+to registers using alternate names.
+@end defmac
+
+@defmac OVERLAPPING_REGISTER_NAMES
+If defined, a C initializer for an array of structures containing a
+name, a register number and a count of the number of consecutive
+machine registers the name overlaps. This macro defines additional
+names for hard registers, thus allowing the @code{asm} option in
+declarations to refer to registers using alternate names. Unlike
+@code{ADDITIONAL_REGISTER_NAMES}, this macro should be used when the
+register name implies multiple underlying registers.
+
+This macro should be used when it is important that a clobber in an
+@code{asm} statement clobbers all the underlying values implied by the
+register name. For example, on ARM, clobbering the double-precision
+VFP register ``d0'' implies clobbering both single-precision registers
+``s0'' and ``s1''.
+@end defmac
+
+@defmac ASM_OUTPUT_OPCODE (@var{stream}, @var{ptr})
+Define this macro if you are using an unusual assembler that
+requires different names for the machine instructions.
+
+The definition is a C statement or statements which output an
+assembler instruction opcode to the stdio stream @var{stream}. The
+macro-operand @var{ptr} is a variable of type @code{char *} which
+points to the opcode name in its ``internal'' form---the form that is
+written in the machine description. The definition should output the
+opcode name to @var{stream}, performing any translation you desire, and
+increment the variable @var{ptr} to point at the end of the opcode
+so that it will not be output twice.
+
+In fact, your macro definition may process less than the entire opcode
+name, or more than the opcode name; but if you want to process text
+that includes @samp{%}-sequences to substitute operands, you must take
+care of the substitution yourself. Just be sure to increment
+@var{ptr} over whatever text should not be output normally.
+
+@findex recog_data.operand
+If you need to look at the operand values, they can be found as the
+elements of @code{recog_data.operand}.
+
+If the macro definition does nothing, the instruction is output
+in the usual way.
+@end defmac
+
+@defmac FINAL_PRESCAN_INSN (@var{insn}, @var{opvec}, @var{noperands})
+If defined, a C statement to be executed just prior to the output of
+assembler code for @var{insn}, to modify the extracted operands so
+they will be output differently.
+
+Here the argument @var{opvec} is the vector containing the operands
+extracted from @var{insn}, and @var{noperands} is the number of
+elements of the vector which contain meaningful data for this insn.
+The contents of this vector are what will be used to convert the insn
+template into assembler code, so you can change the assembler output
+by changing the contents of the vector.
+
+This macro is useful when various assembler syntaxes share a single
+file of instruction patterns; by defining this macro differently, you
+can cause a large class of instructions to be output differently (such
+as with rearranged operands). Naturally, variations in assembler
+syntax affecting individual insn patterns ought to be handled by
+writing conditional output routines in those patterns.
+
+If this macro is not defined, it is equivalent to a null statement.
+@end defmac
+
+@hook TARGET_ASM_FINAL_POSTSCAN_INSN
+
+@defmac PRINT_OPERAND (@var{stream}, @var{x}, @var{code})
+A C compound statement to output to stdio stream @var{stream} the
+assembler syntax for an instruction operand @var{x}. @var{x} is an
+RTL expression.
+
+@var{code} is a value that can be used to specify one of several ways
+of printing the operand. It is used when identical operands must be
+printed differently depending on the context. @var{code} comes from
+the @samp{%} specification that was used to request printing of the
+operand. If the specification was just @samp{%@var{digit}} then
+@var{code} is 0; if the specification was @samp{%@var{ltr}
+@var{digit}} then @var{code} is the ASCII code for @var{ltr}.
+
+@findex reg_names
+If @var{x} is a register, this macro should print the register's name.
+The names can be found in an array @code{reg_names} whose type is
+@code{char *[]}. @code{reg_names} is initialized from
+@code{REGISTER_NAMES}.
+
+When the machine description has a specification @samp{%@var{punct}}
+(a @samp{%} followed by a punctuation character), this macro is called
+with a null pointer for @var{x} and the punctuation character for
+@var{code}.
+@end defmac
+
+@defmac PRINT_OPERAND_PUNCT_VALID_P (@var{code})
+A C expression which evaluates to true if @var{code} is a valid
+punctuation character for use in the @code{PRINT_OPERAND} macro. If
+@code{PRINT_OPERAND_PUNCT_VALID_P} is not defined, it means that no
+punctuation characters (except for the standard one, @samp{%}) are used
+in this way.
+@end defmac
+
+@defmac PRINT_OPERAND_ADDRESS (@var{stream}, @var{x})
+A C compound statement to output to stdio stream @var{stream} the
+assembler syntax for an instruction operand that is a memory reference
+whose address is @var{x}. @var{x} is an RTL expression.
+
+@cindex @code{TARGET_ENCODE_SECTION_INFO} usage
+On some machines, the syntax for a symbolic address depends on the
+section that the address refers to. On these machines, define the hook
+@code{TARGET_ENCODE_SECTION_INFO} to store the information into the
+@code{symbol_ref}, and then check for it here. @xref{Assembler
+Format}.
+@end defmac
+
+@findex dbr_sequence_length
+@defmac DBR_OUTPUT_SEQEND (@var{file})
+A C statement, to be executed after all slot-filler instructions have
+been output. If necessary, call @code{dbr_sequence_length} to
+determine the number of slots filled in a sequence (zero if not
+currently outputting a sequence), to decide how many no-ops to output,
+or whatever.
+
+Don't define this macro if it has nothing to do, but it is helpful in
+reading assembly output if the extent of the delay sequence is made
+explicit (e.g.@: with white space).
+@end defmac
+
+@findex final_sequence
+Note that output routines for instructions with delay slots must be
+prepared to deal with not being output as part of a sequence
+(i.e.@: when the scheduling pass is not run, or when no slot fillers could be
+found.) The variable @code{final_sequence} is null when not
+processing a sequence, otherwise it contains the @code{sequence} rtx
+being output.
+
+@findex asm_fprintf
+@defmac REGISTER_PREFIX
+@defmacx LOCAL_LABEL_PREFIX
+@defmacx USER_LABEL_PREFIX
+@defmacx IMMEDIATE_PREFIX
+If defined, C string expressions to be used for the @samp{%R}, @samp{%L},
+@samp{%U}, and @samp{%I} options of @code{asm_fprintf} (see
+@file{final.cc}). These are useful when a single @file{md} file must
+support multiple assembler formats. In that case, the various @file{tm.h}
+files can define these macros differently.
+@end defmac
+
+@defmac ASM_FPRINTF_EXTENSIONS (@var{file}, @var{argptr}, @var{format})
+If defined this macro should expand to a series of @code{case}
+statements which will be parsed inside the @code{switch} statement of
+the @code{asm_fprintf} function. This allows targets to define extra
+printf formats which may useful when generating their assembler
+statements. Note that uppercase letters are reserved for future
+generic extensions to asm_fprintf, and so are not available to target
+specific code. The output file is given by the parameter @var{file}.
+The varargs input pointer is @var{argptr} and the rest of the format
+string, starting the character after the one that is being switched
+upon, is pointed to by @var{format}.
+@end defmac
+
+@defmac ASSEMBLER_DIALECT
+If your target supports multiple dialects of assembler language (such as
+different opcodes), define this macro as a C expression that gives the
+numeric index of the assembler language dialect to use, with zero as the
+first variant.
+
+If this macro is defined, you may use constructs of the form
+@smallexample
+@samp{@{option0|option1|option2@dots{}@}}
+@end smallexample
+@noindent
+in the output templates of patterns (@pxref{Output Template}) or in the
+first argument of @code{asm_fprintf}. This construct outputs
+@samp{option0}, @samp{option1}, @samp{option2}, etc., if the value of
+@code{ASSEMBLER_DIALECT} is zero, one, two, etc. Any special characters
+within these strings retain their usual meaning. If there are fewer
+alternatives within the braces than the value of
+@code{ASSEMBLER_DIALECT}, the construct outputs nothing. If it's needed
+to print curly braces or @samp{|} character in assembler output directly,
+@samp{%@{}, @samp{%@}} and @samp{%|} can be used.
+
+If you do not define this macro, the characters @samp{@{}, @samp{|} and
+@samp{@}} do not have any special meaning when used in templates or
+operands to @code{asm_fprintf}.
+
+Define the macros @code{REGISTER_PREFIX}, @code{LOCAL_LABEL_PREFIX},
+@code{USER_LABEL_PREFIX} and @code{IMMEDIATE_PREFIX} if you can express
+the variations in assembler language syntax with that mechanism. Define
+@code{ASSEMBLER_DIALECT} and use the @samp{@{option0|option1@}} syntax
+if the syntax variant are larger and involve such things as different
+opcodes or operand order.
+@end defmac
+
+@defmac ASM_OUTPUT_REG_PUSH (@var{stream}, @var{regno})
+A C expression to output to @var{stream} some assembler code
+which will push hard register number @var{regno} onto the stack.
+The code need not be optimal, since this macro is used only when
+profiling.
+@end defmac
+
+@defmac ASM_OUTPUT_REG_POP (@var{stream}, @var{regno})
+A C expression to output to @var{stream} some assembler code
+which will pop hard register number @var{regno} off of the stack.
+The code need not be optimal, since this macro is used only when
+profiling.
+@end defmac
+
+@node Dispatch Tables
+@subsection Output of Dispatch Tables
+
+@c prevent bad page break with this line
+This concerns dispatch tables.
+
+@cindex dispatch table
+@defmac ASM_OUTPUT_ADDR_DIFF_ELT (@var{stream}, @var{body}, @var{value}, @var{rel})
+A C statement to output to the stdio stream @var{stream} an assembler
+pseudo-instruction to generate a difference between two labels.
+@var{value} and @var{rel} are the numbers of two internal labels. The
+definitions of these labels are output using
+@code{(*targetm.asm_out.internal_label)}, and they must be printed in the same
+way here. For example,
+
+@smallexample
+fprintf (@var{stream}, "\t.word L%d-L%d\n",
+ @var{value}, @var{rel})
+@end smallexample
+
+You must provide this macro on machines where the addresses in a
+dispatch table are relative to the table's own address. If defined, GCC
+will also use this macro on all machines when producing PIC@.
+@var{body} is the body of the @code{ADDR_DIFF_VEC}; it is provided so that the
+mode and flags can be read.
+@end defmac
+
+@defmac ASM_OUTPUT_ADDR_VEC_ELT (@var{stream}, @var{value})
+This macro should be provided on machines where the addresses
+in a dispatch table are absolute.
+
+The definition should be a C statement to output to the stdio stream
+@var{stream} an assembler pseudo-instruction to generate a reference to
+a label. @var{value} is the number of an internal label whose
+definition is output using @code{(*targetm.asm_out.internal_label)}.
+For example,
+
+@smallexample
+fprintf (@var{stream}, "\t.word L%d\n", @var{value})
+@end smallexample
+@end defmac
+
+@defmac ASM_OUTPUT_CASE_LABEL (@var{stream}, @var{prefix}, @var{num}, @var{table})
+Define this if the label before a jump-table needs to be output
+specially. The first three arguments are the same as for
+@code{(*targetm.asm_out.internal_label)}; the fourth argument is the
+jump-table which follows (a @code{jump_table_data} containing an
+@code{addr_vec} or @code{addr_diff_vec}).
+
+This feature is used on system V to output a @code{swbeg} statement
+for the table.
+
+If this macro is not defined, these labels are output with
+@code{(*targetm.asm_out.internal_label)}.
+@end defmac
+
+@defmac ASM_OUTPUT_CASE_END (@var{stream}, @var{num}, @var{table})
+Define this if something special must be output at the end of a
+jump-table. The definition should be a C statement to be executed
+after the assembler code for the table is written. It should write
+the appropriate code to stdio stream @var{stream}. The argument
+@var{table} is the jump-table insn, and @var{num} is the label-number
+of the preceding label.
+
+If this macro is not defined, nothing special is output at the end of
+the jump-table.
+@end defmac
+
+@hook TARGET_ASM_POST_CFI_STARTPROC
+
+@hook TARGET_ASM_EMIT_UNWIND_LABEL
+
+@hook TARGET_ASM_EMIT_EXCEPT_TABLE_LABEL
+
+@hook TARGET_ASM_EMIT_EXCEPT_PERSONALITY
+
+@hook TARGET_ASM_UNWIND_EMIT
+
+@hook TARGET_ASM_MAKE_EH_SYMBOL_INDIRECT
+
+@hook TARGET_ASM_UNWIND_EMIT_BEFORE_INSN
+
+@hook TARGET_ASM_SHOULD_RESTORE_CFA_STATE
+
+@node Exception Region Output
+@subsection Assembler Commands for Exception Regions
+
+@c prevent bad page break with this line
+
+This describes commands marking the start and the end of an exception
+region.
+
+@defmac EH_FRAME_SECTION_NAME
+If defined, a C string constant for the name of the section containing
+exception handling frame unwind information. If not defined, GCC will
+provide a default definition if the target supports named sections.
+@file{crtstuff.c} uses this macro to switch to the appropriate section.
+
+You should define this symbol if your target supports DWARF 2 frame
+unwind information and the default definition does not work.
+@end defmac
+
+@defmac EH_FRAME_THROUGH_COLLECT2
+If defined, DWARF 2 frame unwind information will identified by
+specially named labels. The collect2 process will locate these
+labels and generate code to register the frames.
+
+This might be necessary, for instance, if the system linker will not
+place the eh_frames in-between the sentinals from @file{crtstuff.c},
+or if the system linker does garbage collection and sections cannot
+be marked as not to be collected.
+@end defmac
+
+@defmac EH_TABLES_CAN_BE_READ_ONLY
+Define this macro to 1 if your target is such that no frame unwind
+information encoding used with non-PIC code will ever require a
+runtime relocation, but the linker may not support merging read-only
+and read-write sections into a single read-write section.
+@end defmac
+
+@defmac MASK_RETURN_ADDR
+An rtx used to mask the return address found via @code{RETURN_ADDR_RTX}, so
+that it does not contain any extraneous set bits in it.
+@end defmac
+
+@defmac DWARF2_UNWIND_INFO
+Define this macro to 0 if your target supports DWARF 2 frame unwind
+information, but it does not yet work with exception handling.
+Otherwise, if your target supports this information (if it defines
+@code{INCOMING_RETURN_ADDR_RTX} and @code{OBJECT_FORMAT_ELF}),
+GCC will provide a default definition of 1.
+@end defmac
+
+@hook TARGET_EXCEPT_UNWIND_INFO
+This hook defines the mechanism that will be used for exception handling
+by the target. If the target has ABI specified unwind tables, the hook
+should return @code{UI_TARGET}. If the target is to use the
+@code{setjmp}/@code{longjmp}-based exception handling scheme, the hook
+should return @code{UI_SJLJ}. If the target supports DWARF 2 frame unwind
+information, the hook should return @code{UI_DWARF2}.
+
+A target may, if exceptions are disabled, choose to return @code{UI_NONE}.
+This may end up simplifying other parts of target-specific code. The
+default implementation of this hook never returns @code{UI_NONE}.
+
+Note that the value returned by this hook should be constant. It should
+not depend on anything except the command-line switches described by
+@var{opts}. In particular, the
+setting @code{UI_SJLJ} must be fixed at compiler start-up as C pre-processor
+macros and builtin functions related to exception handling are set up
+depending on this setting.
+
+The default implementation of the hook first honors the
+@option{--enable-sjlj-exceptions} configure option, then
+@code{DWARF2_UNWIND_INFO}, and finally defaults to @code{UI_SJLJ}. If
+@code{DWARF2_UNWIND_INFO} depends on command-line options, the target
+must define this hook so that @var{opts} is used correctly.
+@end deftypefn
+
+@hook TARGET_UNWIND_TABLES_DEFAULT
+This variable should be set to @code{true} if the target ABI requires unwinding
+tables even when exceptions are not used. It must not be modified by
+command-line option processing.
+@end deftypevr
+
+@defmac DONT_USE_BUILTIN_SETJMP
+Define this macro to 1 if the @code{setjmp}/@code{longjmp}-based scheme
+should use the @code{setjmp}/@code{longjmp} functions from the C library
+instead of the @code{__builtin_setjmp}/@code{__builtin_longjmp} machinery.
+@end defmac
+
+@defmac JMP_BUF_SIZE
+This macro has no effect unless @code{DONT_USE_BUILTIN_SETJMP} is also
+defined. Define this macro if the default size of @code{jmp_buf} buffer
+for the @code{setjmp}/@code{longjmp}-based exception handling mechanism
+is not large enough, or if it is much too large.
+The default size is @code{FIRST_PSEUDO_REGISTER * sizeof(void *)}.
+@end defmac
+
+@defmac DWARF_CIE_DATA_ALIGNMENT
+This macro need only be defined if the target might save registers in the
+function prologue at an offset to the stack pointer that is not aligned to
+@code{UNITS_PER_WORD}. The definition should be the negative minimum
+alignment if @code{STACK_GROWS_DOWNWARD} is true, and the positive
+minimum alignment otherwise. @xref{DWARF}. Only applicable if
+the target supports DWARF 2 frame unwind information.
+@end defmac
+
+@hook TARGET_TERMINATE_DW2_EH_FRAME_INFO
+
+@hook TARGET_DWARF_REGISTER_SPAN
+
+@hook TARGET_DWARF_FRAME_REG_MODE
+
+@hook TARGET_INIT_DWARF_REG_SIZES_EXTRA
+
+@hook TARGET_ASM_TTYPE
+
+@hook TARGET_ARM_EABI_UNWINDER
+
+@node Alignment Output
+@subsection Assembler Commands for Alignment
+
+@c prevent bad page break with this line
+This describes commands for alignment.
+
+@defmac JUMP_ALIGN (@var{label})
+The alignment (log base 2) to put in front of @var{label}, which is
+a common destination of jumps and has no fallthru incoming edge.
+
+This macro need not be defined if you don't want any special alignment
+to be done at such a time. Most machine descriptions do not currently
+define the macro.
+
+Unless it's necessary to inspect the @var{label} parameter, it is better
+to set the variable @var{align_jumps} in the target's
+@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's
+selection in @var{align_jumps} in a @code{JUMP_ALIGN} implementation.
+@end defmac
+
+@defmac LABEL_ALIGN_AFTER_BARRIER (@var{label})
+The alignment (log base 2) to put in front of @var{label}, which follows
+a @code{BARRIER}.
+
+This macro need not be defined if you don't want any special alignment
+to be done at such a time. Most machine descriptions do not currently
+define the macro.
+@end defmac
+
+@defmac LOOP_ALIGN (@var{label})
+The alignment (log base 2) to put in front of @var{label} that heads
+a frequently executed basic block (usually the header of a loop).
+
+This macro need not be defined if you don't want any special alignment
+to be done at such a time. Most machine descriptions do not currently
+define the macro.
+
+Unless it's necessary to inspect the @var{label} parameter, it is better
+to set the variable @code{align_loops} in the target's
+@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's
+selection in @code{align_loops} in a @code{LOOP_ALIGN} implementation.
+@end defmac
+
+@defmac LABEL_ALIGN (@var{label})
+The alignment (log base 2) to put in front of @var{label}.
+If @code{LABEL_ALIGN_AFTER_BARRIER} / @code{LOOP_ALIGN} specify a different alignment,
+the maximum of the specified values is used.
+
+Unless it's necessary to inspect the @var{label} parameter, it is better
+to set the variable @code{align_labels} in the target's
+@code{TARGET_OPTION_OVERRIDE}. Otherwise, you should try to honor the user's
+selection in @code{align_labels} in a @code{LABEL_ALIGN} implementation.
+@end defmac
+
+@defmac ASM_OUTPUT_SKIP (@var{stream}, @var{nbytes})
+A C statement to output to the stdio stream @var{stream} an assembler
+instruction to advance the location counter by @var{nbytes} bytes.
+Those bytes should be zero when loaded. @var{nbytes} will be a C
+expression of type @code{unsigned HOST_WIDE_INT}.
+@end defmac
+
+@defmac ASM_NO_SKIP_IN_TEXT
+Define this macro if @code{ASM_OUTPUT_SKIP} should not be used in the
+text section because it fails to put zeros in the bytes that are skipped.
+This is true on many Unix systems, where the pseudo--op to skip bytes
+produces no-op instructions rather than zeros when used in the text
+section.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGN (@var{stream}, @var{power})
+A C statement to output to the stdio stream @var{stream} an assembler
+command to advance the location counter to a multiple of 2 to the
+@var{power} bytes. @var{power} will be a C expression of type @code{int}.
+@end defmac
+
+@defmac ASM_OUTPUT_ALIGN_WITH_NOP (@var{stream}, @var{power})
+Like @code{ASM_OUTPUT_ALIGN}, except that the ``nop'' instruction is used
+for padding, if necessary.
+@end defmac
+
+@defmac ASM_OUTPUT_MAX_SKIP_ALIGN (@var{stream}, @var{power}, @var{max_skip})
+A C statement to output to the stdio stream @var{stream} an assembler
+command to advance the location counter to a multiple of 2 to the
+@var{power} bytes, but only if @var{max_skip} or fewer bytes are needed to
+satisfy the alignment request. @var{power} and @var{max_skip} will be
+a C expression of type @code{int}.
+@end defmac
+
+@need 3000
+@node Debugging Info
+@section Controlling Debugging Information Format
+
+@c prevent bad page break with this line
+This describes how to specify debugging information.
+
+@menu
+* All Debuggers:: Macros that affect all debugging formats uniformly.
+* DWARF:: Macros for DWARF format.
+* VMS Debug:: Macros for VMS debug format.
+* CTF Debug:: Macros for CTF debug format.
+* BTF Debug:: Macros for BTF debug format.
+@end menu
+
+@node All Debuggers
+@subsection Macros Affecting All Debugging Formats
+
+@c prevent bad page break with this line
+These macros affect all debugging formats.
+
+@defmac DEBUGGER_REGNO (@var{regno})
+A C expression that returns the debugger register number for the compiler
+register number @var{regno}. In the default macro provided, the value
+of this expression will be @var{regno} itself. But sometimes there are
+some registers that the compiler knows about and debugger does not, or vice
+versa. In such cases, some register may need to have one number in the
+compiler and another for debugger@.
+
+If two registers have consecutive numbers inside GCC, and they can be
+used as a pair to hold a multiword value, then they @emph{must} have
+consecutive numbers after renumbering with @code{DEBUGGER_REGNO}.
+Otherwise, debuggers will be unable to access such a pair, because they
+expect register pairs to be consecutive in their own numbering scheme.
+
+If you find yourself defining @code{DEBUGGER_REGNO} in way that
+does not preserve register pairs, then what you must do instead is
+redefine the actual register numbering scheme.
+@end defmac
+
+@defmac DEBUGGER_AUTO_OFFSET (@var{x})
+A C expression that returns the integer offset value for an automatic
+variable having address @var{x} (an RTL expression). The default
+computation assumes that @var{x} is based on the frame-pointer and
+gives the offset from the frame-pointer. This is required for targets
+that produce debugging output for debugger and allow the frame-pointer to be
+eliminated when the @option{-g} option is used.
+@end defmac
+
+@defmac DEBUGGER_ARG_OFFSET (@var{offset}, @var{x})
+A C expression that returns the integer offset value for an argument
+having address @var{x} (an RTL expression). The nominal offset is
+@var{offset}.
+@end defmac
+
+@defmac PREFERRED_DEBUGGING_TYPE
+A C expression that returns the type of debugging output GCC should
+produce when the user specifies just @option{-g}. Define
+this if you have arranged for GCC to support more than one format of
+debugging output. Currently, the allowable values are
+@code{DWARF2_DEBUG}, @code{VMS_DEBUG},
+and @code{VMS_AND_DWARF2_DEBUG}.
+
+When the user specifies @option{-ggdb}, GCC normally also uses the
+value of this macro to select the debugging output format, but with two
+exceptions. If @code{DWARF2_DEBUGGING_INFO} is defined, GCC uses the
+value @code{DWARF2_DEBUG}.
+
+The value of this macro only affects the default debugging output; the
+user can always get a specific type of output by using @option{-gdwarf-2},
+or @option{-gvms}.
+@end defmac
+
+@defmac DEFAULT_GDB_EXTENSIONS
+Define this macro to control whether GCC should by default generate
+GDB's extended version of debugging information. If you don't define the
+macro, the default is 1: always generate the extended information
+if there is any occasion to.
+@end defmac
+
+@need 2000
+@node DWARF
+@subsection Macros for DWARF Output
+
+@c prevent bad page break with this line
+Here are macros for DWARF output.
+
+@defmac DWARF2_DEBUGGING_INFO
+Define this macro if GCC should produce dwarf version 2 format
+debugging output in response to the @option{-g} option.
+
+To support optional call frame debugging information, you must also
+define @code{INCOMING_RETURN_ADDR_RTX} and either set
+@code{RTX_FRAME_RELATED_P} on the prologue insns if you use RTL for the
+prologue, or call @code{dwarf2out_def_cfa} and @code{dwarf2out_reg_save}
+as appropriate from @code{TARGET_ASM_FUNCTION_PROLOGUE} if you don't.
+@end defmac
+
+@hook TARGET_DWARF_CALLING_CONVENTION
+
+@defmac DWARF2_FRAME_INFO
+Define this macro to a nonzero value if GCC should always output
+Dwarf 2 frame information. If @code{TARGET_EXCEPT_UNWIND_INFO}
+(@pxref{Exception Region Output}) returns @code{UI_DWARF2}, and
+exceptions are enabled, GCC will output this information not matter
+how you define @code{DWARF2_FRAME_INFO}.
+@end defmac
+
+@hook TARGET_DEBUG_UNWIND_INFO
+
+@defmac DWARF2_ASM_LINE_DEBUG_INFO
+Define this macro to be a nonzero value if the assembler can generate Dwarf 2
+line debug info sections. This will result in much more compact line number
+tables, and hence is desirable if it works.
+@end defmac
+
+@defmac DWARF2_ASM_VIEW_DEBUG_INFO
+Define this macro to be a nonzero value if the assembler supports view
+assignment and verification in @code{.loc}. If it does not, but the
+user enables location views, the compiler may have to fallback to
+internal line number tables.
+@end defmac
+
+@hook TARGET_RESET_LOCATION_VIEW
+
+@hook TARGET_WANT_DEBUG_PUB_SECTIONS
+
+@hook TARGET_DELAY_SCHED2
+
+@hook TARGET_DELAY_VARTRACK
+
+@hook TARGET_NO_REGISTER_ALLOCATION
+
+@defmac ASM_OUTPUT_DWARF_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2})
+A C statement to issue assembly directives that create a difference
+@var{lab1} minus @var{lab2}, using an integer of the given @var{size}.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_VMS_DELTA (@var{stream}, @var{size}, @var{label1}, @var{label2})
+A C statement to issue assembly directives that create a difference
+between the two given labels in system defined units, e.g.@: instruction
+slots on IA64 VMS, using an integer of the given size.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_OFFSET (@var{stream}, @var{size}, @var{label}, @var{offset}, @var{section})
+A C statement to issue assembly directives that create a
+section-relative reference to the given @var{label} plus @var{offset}, using
+an integer of the given @var{size}. The label is known to be defined in the
+given @var{section}.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_PCREL (@var{stream}, @var{size}, @var{label})
+A C statement to issue assembly directives that create a self-relative
+reference to the given @var{label}, using an integer of the given @var{size}.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_DATAREL (@var{stream}, @var{size}, @var{label})
+A C statement to issue assembly directives that create a reference to the
+given @var{label} relative to the dbase, using an integer of the given @var{size}.
+@end defmac
+
+@defmac ASM_OUTPUT_DWARF_TABLE_REF (@var{label})
+A C statement to issue assembly directives that create a reference to
+the DWARF table identifier @var{label} from the current section. This
+is used on some systems to avoid garbage collecting a DWARF table which
+is referenced by a function.
+@end defmac
+
+@hook TARGET_ASM_OUTPUT_DWARF_DTPREL
+
+@need 2000
+@node VMS Debug
+@subsection Macros for VMS Debug Format
+
+@c prevent bad page break with this line
+Here are macros for VMS debug format.
+
+@defmac VMS_DEBUGGING_INFO
+Define this macro if GCC should produce debugging output for VMS
+in response to the @option{-g} option. The default behavior for VMS
+is to generate minimal debug info for a traceback in the absence of
+@option{-g} unless explicitly overridden with @option{-g0}. This
+behavior is controlled by @code{TARGET_OPTION_OPTIMIZATION} and
+@code{TARGET_OPTION_OVERRIDE}.
+@end defmac
+
+@need 2000
+@node CTF Debug
+@subsection Macros for CTF Debug Format
+
+@c prevent bad page break with this line
+Here are macros for CTF debug format.
+
+@defmac CTF_DEBUGGING_INFO
+Define this macro if GCC should produce debugging output in CTF debug
+format in response to the @option{-gctf} option.
+@end defmac
+
+@need 2000
+@node BTF Debug
+@subsection Macros for BTF Debug Format
+
+@c prevent bad page break with this line
+Here are macros for BTF debug format.
+
+@defmac BTF_DEBUGGING_INFO
+Define this macro if GCC should produce debugging output in BTF debug
+format in response to the @option{-gbtf} option.
+@end defmac
+
+@node Floating Point
+@section Cross Compilation and Floating Point
+@cindex cross compilation and floating point
+@cindex floating point and cross compilation
+
+While all modern machines use twos-complement representation for integers,
+there are a variety of representations for floating point numbers. This
+means that in a cross-compiler the representation of floating point numbers
+in the compiled program may be different from that used in the machine
+doing the compilation.
+
+Because different representation systems may offer different amounts of
+range and precision, all floating point constants must be represented in
+the target machine's format. Therefore, the cross compiler cannot
+safely use the host machine's floating point arithmetic; it must emulate
+the target's arithmetic. To ensure consistency, GCC always uses
+emulation to work with floating point values, even when the host and
+target floating point formats are identical.
+
+The following macros are provided by @file{real.h} for the compiler to
+use. All parts of the compiler which generate or optimize
+floating-point calculations must use these macros. They may evaluate
+their operands more than once, so operands must not have side effects.
+
+@defmac REAL_VALUE_TYPE
+The C data type to be used to hold a floating point value in the target
+machine's format. Typically this is a @code{struct} containing an
+array of @code{HOST_WIDE_INT}, but all code should treat it as an opaque
+quantity.
+@end defmac
+
+@deftypefn Macro HOST_WIDE_INT REAL_VALUE_FIX (REAL_VALUE_TYPE @var{x})
+Truncates @var{x} to a signed integer, rounding toward zero.
+@end deftypefn
+
+@deftypefn Macro {unsigned HOST_WIDE_INT} REAL_VALUE_UNSIGNED_FIX (REAL_VALUE_TYPE @var{x})
+Truncates @var{x} to an unsigned integer, rounding toward zero. If
+@var{x} is negative, returns zero.
+@end deftypefn
+
+@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ATOF (const char *@var{string}, machine_mode @var{mode})
+Converts @var{string} into a floating point number in the target machine's
+representation for mode @var{mode}. This routine can handle both
+decimal and hexadecimal floating point constants, using the syntax
+defined by the C language for both.
+@end deftypefn
+
+@deftypefn Macro int REAL_VALUE_NEGATIVE (REAL_VALUE_TYPE @var{x})
+Returns 1 if @var{x} is negative (including negative zero), 0 otherwise.
+@end deftypefn
+
+@deftypefn Macro int REAL_VALUE_ISINF (REAL_VALUE_TYPE @var{x})
+Determines whether @var{x} represents infinity (positive or negative).
+@end deftypefn
+
+@deftypefn Macro int REAL_VALUE_ISNAN (REAL_VALUE_TYPE @var{x})
+Determines whether @var{x} represents a ``NaN'' (not-a-number).
+@end deftypefn
+
+@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_NEGATE (REAL_VALUE_TYPE @var{x})
+Returns the negative of the floating point value @var{x}.
+@end deftypefn
+
+@deftypefn Macro REAL_VALUE_TYPE REAL_VALUE_ABS (REAL_VALUE_TYPE @var{x})
+Returns the absolute value of @var{x}.
+@end deftypefn
+
+@node Mode Switching
+@section Mode Switching Instructions
+@cindex mode switching
+The following macros control mode switching optimizations:
+
+@defmac OPTIMIZE_MODE_SWITCHING (@var{entity})
+Define this macro if the port needs extra instructions inserted for mode
+switching in an optimizing compilation.
+
+For an example, the SH4 can perform both single and double precision
+floating point operations, but to perform a single precision operation,
+the FPSCR PR bit has to be cleared, while for a double precision
+operation, this bit has to be set. Changing the PR bit requires a general
+purpose register as a scratch register, hence these FPSCR sets have to
+be inserted before reload, i.e.@: you cannot put this into instruction emitting
+or @code{TARGET_MACHINE_DEPENDENT_REORG}.
+
+You can have multiple entities that are mode-switched, and select at run time
+which entities actually need it. @code{OPTIMIZE_MODE_SWITCHING} should
+return nonzero for any @var{entity} that needs mode-switching.
+If you define this macro, you also have to define
+@code{NUM_MODES_FOR_MODE_SWITCHING}, @code{TARGET_MODE_NEEDED},
+@code{TARGET_MODE_PRIORITY} and @code{TARGET_MODE_EMIT}.
+@code{TARGET_MODE_AFTER}, @code{TARGET_MODE_ENTRY}, and @code{TARGET_MODE_EXIT}
+are optional.
+@end defmac
+
+@defmac NUM_MODES_FOR_MODE_SWITCHING
+If you define @code{OPTIMIZE_MODE_SWITCHING}, you have to define this as
+initializer for an array of integers. Each initializer element
+N refers to an entity that needs mode switching, and specifies the number
+of different modes that might need to be set for this entity.
+The position of the initializer in the initializer---starting counting at
+zero---determines the integer that is used to refer to the mode-switched
+entity in question.
+In macros that take mode arguments / yield a mode result, modes are
+represented as numbers 0 @dots{} N @minus{} 1. N is used to specify that no mode
+switch is needed / supplied.
+@end defmac
+
+@hook TARGET_MODE_EMIT
+
+@hook TARGET_MODE_NEEDED
+
+@hook TARGET_MODE_AFTER
+
+@hook TARGET_MODE_ENTRY
+
+@hook TARGET_MODE_EXIT
+
+@hook TARGET_MODE_PRIORITY
+
+@node Target Attributes
+@section Defining target-specific uses of @code{__attribute__}
+@cindex target attributes
+@cindex machine attributes
+@cindex attributes, target-specific
+
+Target-specific attributes may be defined for functions, data and types.
+These are described using the following target hooks; they also need to
+be documented in @file{extend.texi}.
+
+@hook TARGET_ATTRIBUTE_TABLE
+
+@hook TARGET_ATTRIBUTE_TAKES_IDENTIFIER_P
+
+@hook TARGET_COMP_TYPE_ATTRIBUTES
+
+@hook TARGET_SET_DEFAULT_TYPE_ATTRIBUTES
+
+@hook TARGET_MERGE_TYPE_ATTRIBUTES
+
+@hook TARGET_MERGE_DECL_ATTRIBUTES
+
+@hook TARGET_VALID_DLLIMPORT_ATTRIBUTE_P
+
+@defmac TARGET_DECLSPEC
+Define this macro to a nonzero value if you want to treat
+@code{__declspec(X)} as equivalent to @code{__attribute((X))}. By
+default, this behavior is enabled only for targets that define
+@code{TARGET_DLLIMPORT_DECL_ATTRIBUTES}. The current implementation
+of @code{__declspec} is via a built-in macro, but you should not rely
+on this implementation detail.
+@end defmac
+
+@hook TARGET_INSERT_ATTRIBUTES
+
+@hook TARGET_HANDLE_GENERIC_ATTRIBUTE
+
+@hook TARGET_FUNCTION_ATTRIBUTE_INLINABLE_P
+
+@hook TARGET_OPTION_VALID_ATTRIBUTE_P
+
+@hook TARGET_OPTION_SAVE
+
+@hook TARGET_OPTION_RESTORE
+
+@hook TARGET_OPTION_POST_STREAM_IN
+
+@hook TARGET_OPTION_PRINT
+
+@hook TARGET_OPTION_PRAGMA_PARSE
+
+@hook TARGET_OPTION_OVERRIDE
+
+@hook TARGET_OPTION_FUNCTION_VERSIONS
+
+@hook TARGET_CAN_INLINE_P
+
+@hook TARGET_UPDATE_IPA_FN_TARGET_INFO
+
+@hook TARGET_NEED_IPA_FN_TARGET_INFO
+
+@hook TARGET_RELAYOUT_FUNCTION
+
+@node Emulated TLS
+@section Emulating TLS
+@cindex Emulated TLS
+
+For targets whose psABI does not provide Thread Local Storage via
+specific relocations and instruction sequences, an emulation layer is
+used. A set of target hooks allows this emulation layer to be
+configured for the requirements of a particular target. For instance
+the psABI may in fact specify TLS support in terms of an emulation
+layer.
+
+The emulation layer works by creating a control object for every TLS
+object. To access the TLS object, a lookup function is provided
+which, when given the address of the control object, will return the
+address of the current thread's instance of the TLS object.
+
+@hook TARGET_EMUTLS_GET_ADDRESS
+
+@hook TARGET_EMUTLS_REGISTER_COMMON
+
+@hook TARGET_EMUTLS_VAR_SECTION
+
+@hook TARGET_EMUTLS_TMPL_SECTION
+
+@hook TARGET_EMUTLS_VAR_PREFIX
+
+@hook TARGET_EMUTLS_TMPL_PREFIX
+
+@hook TARGET_EMUTLS_VAR_FIELDS
+
+@hook TARGET_EMUTLS_VAR_INIT
+
+@hook TARGET_EMUTLS_VAR_ALIGN_FIXED
+
+@hook TARGET_EMUTLS_DEBUG_FORM_TLS_ADDRESS
+
+@node MIPS Coprocessors
+@section Defining coprocessor specifics for MIPS targets.
+@cindex MIPS coprocessor-definition macros
+
+The MIPS specification allows MIPS implementations to have as many as 4
+coprocessors, each with as many as 32 private registers. GCC supports
+accessing these registers and transferring values between the registers
+and memory using asm-ized variables. For example:
+
+@smallexample
+ register unsigned int cp0count asm ("c0r1");
+ unsigned int d;
+
+ d = cp0count + 3;
+@end smallexample
+
+(``c0r1'' is the default name of register 1 in coprocessor 0; alternate
+names may be added as described below, or the default names may be
+overridden entirely in @code{SUBTARGET_CONDITIONAL_REGISTER_USAGE}.)
+
+Coprocessor registers are assumed to be epilogue-used; sets to them will
+be preserved even if it does not appear that the register is used again
+later in the function.
+
+Another note: according to the MIPS spec, coprocessor 1 (if present) is
+the FPU@. One accesses COP1 registers through standard mips
+floating-point support; they are not included in this mechanism.
+
+@node PCH Target
+@section Parameters for Precompiled Header Validity Checking
+@cindex parameters, precompiled headers
+
+@hook TARGET_GET_PCH_VALIDITY
+
+@hook TARGET_PCH_VALID_P
+
+@hook TARGET_CHECK_PCH_TARGET_FLAGS
+
+@hook TARGET_PREPARE_PCH_SAVE
+
+@node C++ ABI
+@section C++ ABI parameters
+@cindex parameters, c++ abi
+
+@hook TARGET_CXX_GUARD_TYPE
+
+@hook TARGET_CXX_GUARD_MASK_BIT
+
+@hook TARGET_CXX_GET_COOKIE_SIZE
+
+@hook TARGET_CXX_COOKIE_HAS_SIZE
+
+@hook TARGET_CXX_IMPORT_EXPORT_CLASS
+
+@hook TARGET_CXX_CDTOR_RETURNS_THIS
+
+@hook TARGET_CXX_KEY_METHOD_MAY_BE_INLINE
+
+@hook TARGET_CXX_DETERMINE_CLASS_DATA_VISIBILITY
+
+@hook TARGET_CXX_CLASS_DATA_ALWAYS_COMDAT
+
+@hook TARGET_CXX_LIBRARY_RTTI_COMDAT
+
+@hook TARGET_CXX_USE_AEABI_ATEXIT
+
+@hook TARGET_CXX_USE_ATEXIT_FOR_CXA_ATEXIT
+
+@hook TARGET_CXX_ADJUST_CLASS_AT_DEFINITION
+
+@hook TARGET_CXX_DECL_MANGLING_CONTEXT
+
+@node D Language and ABI
+@section D ABI parameters
+@cindex parameters, d abi
+
+@hook TARGET_D_CPU_VERSIONS
+
+@hook TARGET_D_OS_VERSIONS
+
+@hook TARGET_D_REGISTER_CPU_TARGET_INFO
+
+@hook TARGET_D_REGISTER_OS_TARGET_INFO
+
+@hook TARGET_D_MINFO_SECTION
+
+@hook TARGET_D_MINFO_SECTION_START
+
+@hook TARGET_D_MINFO_SECTION_END
+
+@hook TARGET_D_HAS_STDCALL_CONVENTION
+
+@hook TARGET_D_TEMPLATES_ALWAYS_COMDAT
+
+@node Named Address Spaces
+@section Adding support for named address spaces
+@cindex named address spaces
+
+The draft technical report of the ISO/IEC JTC1 S22 WG14 N1275
+standards committee, @cite{Programming Languages - C - Extensions to
+support embedded processors}, specifies a syntax for embedded
+processors to specify alternate address spaces. You can configure a
+GCC port to support section 5.1 of the draft report to add support for
+address spaces other than the default address space. These address
+spaces are new keywords that are similar to the @code{volatile} and
+@code{const} type attributes.
+
+Pointers to named address spaces can have a different size than
+pointers to the generic address space.
+
+For example, the SPU port uses the @code{__ea} address space to refer
+to memory in the host processor, rather than memory local to the SPU
+processor. Access to memory in the @code{__ea} address space involves
+issuing DMA operations to move data between the host processor and the
+local processor memory address space. Pointers in the @code{__ea}
+address space are either 32 bits or 64 bits based on the
+@option{-mea32} or @option{-mea64} switches (native SPU pointers are
+always 32 bits).
+
+Internally, address spaces are represented as a small integer in the
+range 0 to 15 with address space 0 being reserved for the generic
+address space.
+
+To register a named address space qualifier keyword with the C front end,
+the target may call the @code{c_register_addr_space} routine. For example,
+the SPU port uses the following to declare @code{__ea} as the keyword for
+named address space #1:
+@smallexample
+#define ADDR_SPACE_EA 1
+c_register_addr_space ("__ea", ADDR_SPACE_EA);
+@end smallexample
+
+@hook TARGET_ADDR_SPACE_POINTER_MODE
+
+@hook TARGET_ADDR_SPACE_ADDRESS_MODE
+
+@hook TARGET_ADDR_SPACE_VALID_POINTER_MODE
+
+@hook TARGET_ADDR_SPACE_LEGITIMATE_ADDRESS_P
+
+@hook TARGET_ADDR_SPACE_LEGITIMIZE_ADDRESS
+
+@hook TARGET_ADDR_SPACE_SUBSET_P
+
+@hook TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID
+
+@hook TARGET_ADDR_SPACE_CONVERT
+
+@hook TARGET_ADDR_SPACE_DEBUG
+
+@hook TARGET_ADDR_SPACE_DIAGNOSE_USAGE
+
+@node Misc
+@section Miscellaneous Parameters
+@cindex parameters, miscellaneous
+
+@c prevent bad page break with this line
+Here are several miscellaneous parameters.
+
+@defmac HAS_LONG_COND_BRANCH
+Define this boolean macro to indicate whether or not your architecture
+has conditional branches that can span all of memory. It is used in
+conjunction with an optimization that partitions hot and cold basic
+blocks into separate sections of the executable. If this macro is
+set to false, gcc will convert any conditional branches that attempt
+to cross between sections into unconditional branches or indirect jumps.
+@end defmac
+
+@defmac HAS_LONG_UNCOND_BRANCH
+Define this boolean macro to indicate whether or not your architecture
+has unconditional branches that can span all of memory. It is used in
+conjunction with an optimization that partitions hot and cold basic
+blocks into separate sections of the executable. If this macro is
+set to false, gcc will convert any unconditional branches that attempt
+to cross between sections into indirect jumps.
+@end defmac
+
+@defmac CASE_VECTOR_MODE
+An alias for a machine mode name. This is the machine mode that
+elements of a jump-table should have.
+@end defmac
+
+@defmac CASE_VECTOR_SHORTEN_MODE (@var{min_offset}, @var{max_offset}, @var{body})
+Optional: return the preferred mode for an @code{addr_diff_vec}
+when the minimum and maximum offset are known. If you define this,
+it enables extra code in branch shortening to deal with @code{addr_diff_vec}.
+To make this work, you also have to define @code{INSN_ALIGN} and
+make the alignment for @code{addr_diff_vec} explicit.
+The @var{body} argument is provided so that the offset_unsigned and scale
+flags can be updated.
+@end defmac
+
+@defmac CASE_VECTOR_PC_RELATIVE
+Define this macro to be a C expression to indicate when jump-tables
+should contain relative addresses. You need not define this macro if
+jump-tables never contain relative addresses, or jump-tables should
+contain relative addresses only when @option{-fPIC} or @option{-fPIC}
+is in effect.
+@end defmac
+
+@hook TARGET_CASE_VALUES_THRESHOLD
+
+@defmac WORD_REGISTER_OPERATIONS
+Define this macro to 1 if operations between registers with integral mode
+smaller than a word are always performed on the entire register. To be
+more explicit, if you start with a pair of @code{word_mode} registers with
+known values and you do a subword, for example @code{QImode}, addition on
+the low part of the registers, then the compiler may consider that the
+result has a known value in @code{word_mode} too if the macro is defined
+to 1. Most RISC machines have this property and most CISC machines do not.
+@end defmac
+
+@hook TARGET_MIN_ARITHMETIC_PRECISION
+
+@defmac LOAD_EXTEND_OP (@var{mem_mode})
+Define this macro to be a C expression indicating when insns that read
+memory in @var{mem_mode}, an integral mode narrower than a word, set the
+bits outside of @var{mem_mode} to be either the sign-extension or the
+zero-extension of the data read. Return @code{SIGN_EXTEND} for values
+of @var{mem_mode} for which the
+insn sign-extends, @code{ZERO_EXTEND} for which it zero-extends, and
+@code{UNKNOWN} for other modes.
+
+This macro is not called with @var{mem_mode} non-integral or with a width
+greater than or equal to @code{BITS_PER_WORD}, so you may return any
+value in this case. Do not define this macro if it would always return
+@code{UNKNOWN}. On machines where this macro is defined, you will normally
+define it as the constant @code{SIGN_EXTEND} or @code{ZERO_EXTEND}.
+
+You may return a non-@code{UNKNOWN} value even if for some hard registers
+the sign extension is not performed, if for the @code{REGNO_REG_CLASS}
+of these hard registers @code{TARGET_CAN_CHANGE_MODE_CLASS} returns false
+when the @var{from} mode is @var{mem_mode} and the @var{to} mode is any
+integral mode larger than this but not larger than @code{word_mode}.
+
+You must return @code{UNKNOWN} if for some hard registers that allow this
+mode, @code{TARGET_CAN_CHANGE_MODE_CLASS} says that they cannot change to
+@code{word_mode}, but that they can change to another integral mode that
+is larger then @var{mem_mode} but still smaller than @code{word_mode}.
+@end defmac
+
+@defmac SHORT_IMMEDIATES_SIGN_EXTEND
+Define this macro to 1 if loading short immediate values into registers sign
+extends.
+@end defmac
+
+@hook TARGET_MIN_DIVISIONS_FOR_RECIP_MUL
+
+@defmac MOVE_MAX
+The maximum number of bytes that a single instruction can move quickly
+between memory and registers or between two memory locations.
+@end defmac
+
+@defmac MAX_MOVE_MAX
+The maximum number of bytes that a single instruction can move quickly
+between memory and registers or between two memory locations. If this
+is undefined, the default is @code{MOVE_MAX}. Otherwise, it is the
+constant value that is the largest value that @code{MOVE_MAX} can have
+at run-time.
+@end defmac
+
+@defmac SHIFT_COUNT_TRUNCATED
+A C expression that is nonzero if on this machine the number of bits
+actually used for the count of a shift operation is equal to the number
+of bits needed to represent the size of the object being shifted. When
+this macro is nonzero, the compiler will assume that it is safe to omit
+a sign-extend, zero-extend, and certain bitwise `and' instructions that
+truncates the count of a shift operation. On machines that have
+instructions that act on bit-fields at variable positions, which may
+include `bit test' instructions, a nonzero @code{SHIFT_COUNT_TRUNCATED}
+also enables deletion of truncations of the values that serve as
+arguments to bit-field instructions.
+
+If both types of instructions truncate the count (for shifts) and
+position (for bit-field operations), or if no variable-position bit-field
+instructions exist, you should define this macro.
+
+However, on some machines, such as the 80386 and the 680x0, truncation
+only applies to shift operations and not the (real or pretended)
+bit-field operations. Define @code{SHIFT_COUNT_TRUNCATED} to be zero on
+such machines. Instead, add patterns to the @file{md} file that include
+the implied truncation of the shift instructions.
+
+You need not define this macro if it would always have the value of zero.
+@end defmac
+
+@anchor{TARGET_SHIFT_TRUNCATION_MASK}
+@hook TARGET_SHIFT_TRUNCATION_MASK
+
+@hook TARGET_TRULY_NOOP_TRUNCATION
+
+@hook TARGET_MODE_REP_EXTENDED
+
+@hook TARGET_SETJMP_PRESERVES_NONVOLATILE_REGS_P
+
+@defmac STORE_FLAG_VALUE
+A C expression describing the value returned by a comparison operator
+with an integral mode and stored by a store-flag instruction
+(@samp{cstore@var{mode}4}) when the condition is true. This description must
+apply to @emph{all} the @samp{cstore@var{mode}4} patterns and all the
+comparison operators whose results have a @code{MODE_INT} mode.
+
+A value of 1 or @minus{}1 means that the instruction implementing the
+comparison operator returns exactly 1 or @minus{}1 when the comparison is true
+and 0 when the comparison is false. Otherwise, the value indicates
+which bits of the result are guaranteed to be 1 when the comparison is
+true. This value is interpreted in the mode of the comparison
+operation, which is given by the mode of the first operand in the
+@samp{cstore@var{mode}4} pattern. Either the low bit or the sign bit of
+@code{STORE_FLAG_VALUE} be on. Presently, only those bits are used by
+the compiler.
+
+If @code{STORE_FLAG_VALUE} is neither 1 or @minus{}1, the compiler will
+generate code that depends only on the specified bits. It can also
+replace comparison operators with equivalent operations if they cause
+the required bits to be set, even if the remaining bits are undefined.
+For example, on a machine whose comparison operators return an
+@code{SImode} value and where @code{STORE_FLAG_VALUE} is defined as
+@samp{0x80000000}, saying that just the sign bit is relevant, the
+expression
+
+@smallexample
+(ne:SI (and:SI @var{x} (const_int @var{power-of-2})) (const_int 0))
+@end smallexample
+
+@noindent
+can be converted to
+
+@smallexample
+(ashift:SI @var{x} (const_int @var{n}))
+@end smallexample
+
+@noindent
+where @var{n} is the appropriate shift count to move the bit being
+tested into the sign bit.
+
+There is no way to describe a machine that always sets the low-order bit
+for a true value, but does not guarantee the value of any other bits,
+but we do not know of any machine that has such an instruction. If you
+are trying to port GCC to such a machine, include an instruction to
+perform a logical-and of the result with 1 in the pattern for the
+comparison operators and let us know at @email{gcc@@gcc.gnu.org}.
+
+Often, a machine will have multiple instructions that obtain a value
+from a comparison (or the condition codes). Here are rules to guide the
+choice of value for @code{STORE_FLAG_VALUE}, and hence the instructions
+to be used:
+
+@itemize @bullet
+@item
+Use the shortest sequence that yields a valid definition for
+@code{STORE_FLAG_VALUE}. It is more efficient for the compiler to
+``normalize'' the value (convert it to, e.g., 1 or 0) than for the
+comparison operators to do so because there may be opportunities to
+combine the normalization with other operations.
+
+@item
+For equal-length sequences, use a value of 1 or @minus{}1, with @minus{}1 being
+slightly preferred on machines with expensive jumps and 1 preferred on
+other machines.
+
+@item
+As a second choice, choose a value of @samp{0x80000001} if instructions
+exist that set both the sign and low-order bits but do not define the
+others.
+
+@item
+Otherwise, use a value of @samp{0x80000000}.
+@end itemize
+
+Many machines can produce both the value chosen for
+@code{STORE_FLAG_VALUE} and its negation in the same number of
+instructions. On those machines, you should also define a pattern for
+those cases, e.g., one matching
+
+@smallexample
+(set @var{A} (neg:@var{m} (ne:@var{m} @var{B} @var{C})))
+@end smallexample
+
+Some machines can also perform @code{and} or @code{plus} operations on
+condition code values with less instructions than the corresponding
+@samp{cstore@var{mode}4} insn followed by @code{and} or @code{plus}. On those
+machines, define the appropriate patterns. Use the names @code{incscc}
+and @code{decscc}, respectively, for the patterns which perform
+@code{plus} or @code{minus} operations on condition code values. See
+@file{rs6000.md} for some examples. The GNU Superoptimizer can be used to
+find such instruction sequences on other machines.
+
+If this macro is not defined, the default value, 1, is used. You need
+not define @code{STORE_FLAG_VALUE} if the machine has no store-flag
+instructions, or if the value generated by these instructions is 1.
+@end defmac
+
+@defmac FLOAT_STORE_FLAG_VALUE (@var{mode})
+A C expression that gives a nonzero @code{REAL_VALUE_TYPE} value that is
+returned when comparison operators with floating-point results are true.
+Define this macro on machines that have comparison operations that return
+floating-point values. If there are no such operations, do not define
+this macro.
+@end defmac
+
+@defmac VECTOR_STORE_FLAG_VALUE (@var{mode})
+A C expression that gives an rtx representing the nonzero true element
+for vector comparisons. The returned rtx should be valid for the inner
+mode of @var{mode} which is guaranteed to be a vector mode. Define
+this macro on machines that have vector comparison operations that
+return a vector result. If there are no such operations, do not define
+this macro. Typically, this macro is defined as @code{const1_rtx} or
+@code{constm1_rtx}. This macro may return @code{NULL_RTX} to prevent
+the compiler optimizing such vector comparison operations for the
+given mode.
+@end defmac
+
+@defmac CLZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value})
+@defmacx CTZ_DEFINED_VALUE_AT_ZERO (@var{mode}, @var{value})
+A C expression that indicates whether the architecture defines a value
+for @code{clz} or @code{ctz} with a zero operand.
+A result of @code{0} indicates the value is undefined.
+If the value is defined for only the RTL expression, the macro should
+evaluate to @code{1}; if the value applies also to the corresponding optab
+entry (which is normally the case if it expands directly into
+the corresponding RTL), then the macro should evaluate to @code{2}.
+In the cases where the value is defined, @var{value} should be set to
+this value.
+
+If this macro is not defined, the value of @code{clz} or
+@code{ctz} at zero is assumed to be undefined.
+
+This macro must be defined if the target's expansion for @code{ffs}
+relies on a particular value to get correct results. Otherwise it
+is not necessary, though it may be used to optimize some corner cases, and
+to provide a default expansion for the @code{ffs} optab.
+
+Note that regardless of this macro the ``definedness'' of @code{clz}
+and @code{ctz} at zero do @emph{not} extend to the builtin functions
+visible to the user. Thus one may be free to adjust the value at will
+to match the target expansion of these operations without fear of
+breaking the API@.
+@end defmac
+
+@defmac Pmode
+An alias for the machine mode for pointers. On most machines, define
+this to be the integer mode corresponding to the width of a hardware
+pointer; @code{SImode} on 32-bit machine or @code{DImode} on 64-bit machines.
+On some machines you must define this to be one of the partial integer
+modes, such as @code{PSImode}.
+
+The width of @code{Pmode} must be at least as large as the value of
+@code{POINTER_SIZE}. If it is not equal, you must define the macro
+@code{POINTERS_EXTEND_UNSIGNED} to specify how pointers are extended
+to @code{Pmode}.
+@end defmac
+
+@defmac FUNCTION_MODE
+An alias for the machine mode used for memory references to functions
+being called, in @code{call} RTL expressions. On most CISC machines,
+where an instruction can begin at any byte address, this should be
+@code{QImode}. On most RISC machines, where all instructions have fixed
+size and alignment, this should be a mode with the same size and alignment
+as the machine instruction words - typically @code{SImode} or @code{HImode}.
+@end defmac
+
+@defmac STDC_0_IN_SYSTEM_HEADERS
+In normal operation, the preprocessor expands @code{__STDC__} to the
+constant 1, to signify that GCC conforms to ISO Standard C@. On some
+hosts, like Solaris, the system compiler uses a different convention,
+where @code{__STDC__} is normally 0, but is 1 if the user specifies
+strict conformance to the C Standard.
+
+Defining @code{STDC_0_IN_SYSTEM_HEADERS} makes GNU CPP follows the host
+convention when processing system header files, but when processing user
+files @code{__STDC__} will always expand to 1.
+@end defmac
+
+@hook TARGET_C_PREINCLUDE
+
+@hook TARGET_CXX_IMPLICIT_EXTERN_C
+
+@defmac SYSTEM_IMPLICIT_EXTERN_C
+Define this macro if the system header files do not support C++@.
+This macro handles system header files by pretending that system
+header files are enclosed in @samp{extern "C" @{@dots{}@}}.
+@end defmac
+
+@findex #pragma
+@findex pragma
+@defmac REGISTER_TARGET_PRAGMAS ()
+Define this macro if you want to implement any target-specific pragmas.
+If defined, it is a C expression which makes a series of calls to
+@code{c_register_pragma} or @code{c_register_pragma_with_expansion}
+for each pragma. The macro may also do any
+setup required for the pragmas.
+
+The primary reason to define this macro is to provide compatibility with
+other compilers for the same target. In general, we discourage
+definition of target-specific pragmas for GCC@.
+
+If the pragma can be implemented by attributes then you should consider
+defining the target hook @samp{TARGET_INSERT_ATTRIBUTES} as well.
+
+Preprocessor macros that appear on pragma lines are not expanded. All
+@samp{#pragma} directives that do not match any registered pragma are
+silently ignored, unless the user specifies @option{-Wunknown-pragmas}.
+@end defmac
+
+@deftypefun void c_register_pragma (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *))
+@deftypefunx void c_register_pragma_with_expansion (const char *@var{space}, const char *@var{name}, void (*@var{callback}) (struct cpp_reader *))
+
+Each call to @code{c_register_pragma} or
+@code{c_register_pragma_with_expansion} establishes one pragma. The
+@var{callback} routine will be called when the preprocessor encounters a
+pragma of the form
+
+@smallexample
+#pragma [@var{space}] @var{name} @dots{}
+@end smallexample
+
+@var{space} is the case-sensitive namespace of the pragma, or
+@code{NULL} to put the pragma in the global namespace. The callback
+routine receives @var{pfile} as its first argument, which can be passed
+on to cpplib's functions if necessary. You can lex tokens after the
+@var{name} by calling @code{pragma_lex}. Tokens that are not read by the
+callback will be silently ignored. The end of the line is indicated by
+a token of type @code{CPP_EOF}. Macro expansion occurs on the
+arguments of pragmas registered with
+@code{c_register_pragma_with_expansion} but not on the arguments of
+pragmas registered with @code{c_register_pragma}.
+
+Note that the use of @code{pragma_lex} is specific to the C and C++
+compilers. It will not work in the Java or Fortran compilers, or any
+other language compilers for that matter. Thus if @code{pragma_lex} is going
+to be called from target-specific code, it must only be done so when
+building the C and C++ compilers. This can be done by defining the
+variables @code{c_target_objs} and @code{cxx_target_objs} in the
+target entry in the @file{config.gcc} file. These variables should name
+the target-specific, language-specific object file which contains the
+code that uses @code{pragma_lex}. Note it will also be necessary to add a
+rule to the makefile fragment pointed to by @code{tmake_file} that shows
+how to build this object file.
+@end deftypefun
+
+@defmac HANDLE_PRAGMA_PACK_WITH_EXPANSION
+Define this macro if macros should be expanded in the
+arguments of @samp{#pragma pack}.
+@end defmac
+
+@defmac TARGET_DEFAULT_PACK_STRUCT
+If your target requires a structure packing default other than 0 (meaning
+the machine default), define this macro to the necessary value (in bytes).
+This must be a value that would also be valid to use with
+@samp{#pragma pack()} (that is, a small power of two).
+@end defmac
+
+@defmac DOLLARS_IN_IDENTIFIERS
+Define this macro to control use of the character @samp{$} in
+identifier names for the C family of languages. 0 means @samp{$} is
+not allowed by default; 1 means it is allowed. 1 is the default;
+there is no need to define this macro in that case.
+@end defmac
+
+@defmac INSN_SETS_ARE_DELAYED (@var{insn})
+Define this macro as a C expression that is nonzero if it is safe for the
+delay slot scheduler to place instructions in the delay slot of @var{insn},
+even if they appear to use a resource set or clobbered in @var{insn}.
+@var{insn} is always a @code{jump_insn} or an @code{insn}; GCC knows that
+every @code{call_insn} has this behavior. On machines where some @code{insn}
+or @code{jump_insn} is really a function call and hence has this behavior,
+you should define this macro.
+
+You need not define this macro if it would always return zero.
+@end defmac
+
+@defmac INSN_REFERENCES_ARE_DELAYED (@var{insn})
+Define this macro as a C expression that is nonzero if it is safe for the
+delay slot scheduler to place instructions in the delay slot of @var{insn},
+even if they appear to set or clobber a resource referenced in @var{insn}.
+@var{insn} is always a @code{jump_insn} or an @code{insn}. On machines where
+some @code{insn} or @code{jump_insn} is really a function call and its operands
+are registers whose use is actually in the subroutine it calls, you should
+define this macro. Doing so allows the delay slot scheduler to move
+instructions which copy arguments into the argument registers into the delay
+slot of @var{insn}.
+
+You need not define this macro if it would always return zero.
+@end defmac
+
+@defmac MULTIPLE_SYMBOL_SPACES
+Define this macro as a C expression that is nonzero if, in some cases,
+global symbols from one translation unit may not be bound to undefined
+symbols in another translation unit without user intervention. For
+instance, under Microsoft Windows symbols must be explicitly imported
+from shared libraries (DLLs).
+
+You need not define this macro if it would always evaluate to zero.
+@end defmac
+
+@hook TARGET_MD_ASM_ADJUST
+
+@defmac MATH_LIBRARY
+Define this macro as a C string constant for the linker argument to link
+in the system math library, minus the initial @samp{"-l"}, or
+@samp{""} if the target does not have a
+separate math library.
+
+You need only define this macro if the default of @samp{"m"} is wrong.
+@end defmac
+
+@defmac LIBRARY_PATH_ENV
+Define this macro as a C string constant for the environment variable that
+specifies where the linker should look for libraries.
+
+You need only define this macro if the default of @samp{"LIBRARY_PATH"}
+is wrong.
+@end defmac
+
+@defmac TARGET_POSIX_IO
+Define this macro if the target supports the following POSIX@ file
+functions, access, mkdir and file locking with fcntl / F_SETLKW@.
+Defining @code{TARGET_POSIX_IO} will enable the test coverage code
+to use file locking when exiting a program, which avoids race conditions
+if the program has forked. It will also create directories at run-time
+for cross-profiling.
+@end defmac
+
+@defmac MAX_CONDITIONAL_EXECUTE
+
+A C expression for the maximum number of instructions to execute via
+conditional execution instructions instead of a branch. A value of
+@code{BRANCH_COST}+1 is the default.
+@end defmac
+
+@defmac IFCVT_MODIFY_TESTS (@var{ce_info}, @var{true_expr}, @var{false_expr})
+Used if the target needs to perform machine-dependent modifications on the
+conditionals used for turning basic blocks into conditionally executed code.
+@var{ce_info} points to a data structure, @code{struct ce_if_block}, which
+contains information about the currently processed blocks. @var{true_expr}
+and @var{false_expr} are the tests that are used for converting the
+then-block and the else-block, respectively. Set either @var{true_expr} or
+@var{false_expr} to a null pointer if the tests cannot be converted.
+@end defmac
+
+@defmac IFCVT_MODIFY_MULTIPLE_TESTS (@var{ce_info}, @var{bb}, @var{true_expr}, @var{false_expr})
+Like @code{IFCVT_MODIFY_TESTS}, but used when converting more complicated
+if-statements into conditions combined by @code{and} and @code{or} operations.
+@var{bb} contains the basic block that contains the test that is currently
+being processed and about to be turned into a condition.
+@end defmac
+
+@defmac IFCVT_MODIFY_INSN (@var{ce_info}, @var{pattern}, @var{insn})
+A C expression to modify the @var{PATTERN} of an @var{INSN} that is to
+be converted to conditional execution format. @var{ce_info} points to
+a data structure, @code{struct ce_if_block}, which contains information
+about the currently processed blocks.
+@end defmac
+
+@defmac IFCVT_MODIFY_FINAL (@var{ce_info})
+A C expression to perform any final machine dependent modifications in
+converting code to conditional execution. The involved basic blocks
+can be found in the @code{struct ce_if_block} structure that is pointed
+to by @var{ce_info}.
+@end defmac
+
+@defmac IFCVT_MODIFY_CANCEL (@var{ce_info})
+A C expression to cancel any machine dependent modifications in
+converting code to conditional execution. The involved basic blocks
+can be found in the @code{struct ce_if_block} structure that is pointed
+to by @var{ce_info}.
+@end defmac
+
+@defmac IFCVT_MACHDEP_INIT (@var{ce_info})
+A C expression to initialize any machine specific data for if-conversion
+of the if-block in the @code{struct ce_if_block} structure that is pointed
+to by @var{ce_info}.
+@end defmac
+
+@hook TARGET_MACHINE_DEPENDENT_REORG
+
+@hook TARGET_INIT_BUILTINS
+
+@hook TARGET_BUILTIN_DECL
+
+@hook TARGET_EXPAND_BUILTIN
+
+@hook TARGET_RESOLVE_OVERLOADED_BUILTIN
+
+@hook TARGET_CHECK_BUILTIN_CALL
+
+@hook TARGET_FOLD_BUILTIN
+
+@hook TARGET_GIMPLE_FOLD_BUILTIN
+
+@hook TARGET_COMPARE_VERSION_PRIORITY
+
+@hook TARGET_GET_FUNCTION_VERSIONS_DISPATCHER
+
+@hook TARGET_GENERATE_VERSION_DISPATCHER_BODY
+
+@hook TARGET_PREDICT_DOLOOP_P
+
+@hook TARGET_HAVE_COUNT_REG_DECR_P
+
+@hook TARGET_DOLOOP_COST_FOR_GENERIC
+
+@hook TARGET_DOLOOP_COST_FOR_ADDRESS
+
+@hook TARGET_CAN_USE_DOLOOP_P
+
+@hook TARGET_INVALID_WITHIN_DOLOOP
+
+@hook TARGET_PREFERRED_DOLOOP_MODE
+
+@hook TARGET_LEGITIMATE_COMBINED_INSN
+
+@hook TARGET_CAN_FOLLOW_JUMP
+
+@hook TARGET_COMMUTATIVE_P
+
+@hook TARGET_ALLOCATE_INITIAL_VALUE
+
+@hook TARGET_UNSPEC_MAY_TRAP_P
+
+@hook TARGET_SET_CURRENT_FUNCTION
+
+@defmac TARGET_OBJECT_SUFFIX
+Define this macro to be a C string representing the suffix for object
+files on your target machine. If you do not define this macro, GCC will
+use @samp{.o} as the suffix for object files.
+@end defmac
+
+@defmac TARGET_EXECUTABLE_SUFFIX
+Define this macro to be a C string representing the suffix to be
+automatically added to executable files on your target machine. If you
+do not define this macro, GCC will use the null string as the suffix for
+executable files.
+@end defmac
+
+@defmac COLLECT_EXPORT_LIST
+If defined, @code{collect2} will scan the individual object files
+specified on its command line and create an export list for the linker.
+Define this macro for systems like AIX, where the linker discards
+object files that are not referenced from @code{main} and uses export
+lists.
+@end defmac
+
+@hook TARGET_CANNOT_MODIFY_JUMPS_P
+
+@hook TARGET_HAVE_CONDITIONAL_EXECUTION
+
+@hook TARGET_GEN_CCMP_FIRST
+
+@hook TARGET_GEN_CCMP_NEXT
+
+@hook TARGET_GEN_MEMSET_SCRATCH_RTX
+
+@hook TARGET_LOOP_UNROLL_ADJUST
+
+@defmac POWI_MAX_MULTS
+If defined, this macro is interpreted as a signed integer C expression
+that specifies the maximum number of floating point multiplications
+that should be emitted when expanding exponentiation by an integer
+constant inline. When this value is defined, exponentiation requiring
+more than this number of multiplications is implemented by calling the
+system library's @code{pow}, @code{powf} or @code{powl} routines.
+The default value places no upper bound on the multiplication count.
+@end defmac
+
+@deftypefn Macro void TARGET_EXTRA_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc})
+This target hook should register any extra include files for the
+target. The parameter @var{stdinc} indicates if normal include files
+are present. The parameter @var{sysroot} is the system root directory.
+The parameter @var{iprefix} is the prefix for the gcc directory.
+@end deftypefn
+
+@deftypefn Macro void TARGET_EXTRA_PRE_INCLUDES (const char *@var{sysroot}, const char *@var{iprefix}, int @var{stdinc})
+This target hook should register any extra include files for the
+target before any standard headers. The parameter @var{stdinc}
+indicates if normal include files are present. The parameter
+@var{sysroot} is the system root directory. The parameter
+@var{iprefix} is the prefix for the gcc directory.
+@end deftypefn
+
+@deftypefn Macro void TARGET_OPTF (char *@var{path})
+This target hook should register special include paths for the target.
+The parameter @var{path} is the include to register. On Darwin
+systems, this is used for Framework includes, which have semantics
+that are different from @option{-I}.
+@end deftypefn
+
+@defmac bool TARGET_USE_LOCAL_THUNK_ALIAS_P (tree @var{fndecl})
+This target macro returns @code{true} if it is safe to use a local alias
+for a virtual function @var{fndecl} when constructing thunks,
+@code{false} otherwise. By default, the macro returns @code{true} for all
+functions, if a target supports aliases (i.e.@: defines
+@code{ASM_OUTPUT_DEF}), @code{false} otherwise,
+@end defmac
+
+@defmac TARGET_FORMAT_TYPES
+If defined, this macro is the name of a global variable containing
+target-specific format checking information for the @option{-Wformat}
+option. The default is to have no target-specific format checks.
+@end defmac
+
+@defmac TARGET_N_FORMAT_TYPES
+If defined, this macro is the number of entries in
+@code{TARGET_FORMAT_TYPES}.
+@end defmac
+
+@defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES
+If defined, this macro is the name of a global variable containing
+target-specific format overrides for the @option{-Wformat} option. The
+default is to have no target-specific format overrides. If defined,
+@code{TARGET_FORMAT_TYPES} and @code{TARGET_OVERRIDES_FORMAT_ATTRIBUTES_COUNT}
+must be defined, too.
+@end defmac
+
+@defmac TARGET_OVERRIDES_FORMAT_ATTRIBUTES_COUNT
+If defined, this macro specifies the number of entries in
+@code{TARGET_OVERRIDES_FORMAT_ATTRIBUTES}.
+@end defmac
+
+@defmac TARGET_OVERRIDES_FORMAT_INIT
+If defined, this macro specifies the optional initialization
+routine for target specific customizations of the system printf
+and scanf formatter settings.
+@end defmac
+
+@hook TARGET_INVALID_ARG_FOR_UNPROTOTYPED_FN
+
+@hook TARGET_INVALID_CONVERSION
+
+@hook TARGET_INVALID_UNARY_OP
+
+@hook TARGET_INVALID_BINARY_OP
+
+@hook TARGET_PROMOTED_TYPE
+
+@hook TARGET_CONVERT_TO_TYPE
+
+@hook TARGET_VERIFY_TYPE_CONTEXT
+
+@defmac OBJC_JBLEN
+This macro determines the size of the objective C jump buffer for the
+NeXT runtime. By default, OBJC_JBLEN is defined to an innocuous value.
+@end defmac
+
+@defmac LIBGCC2_UNWIND_ATTRIBUTE
+Define this macro if any target-specific attributes need to be attached
+to the functions in @file{libgcc} that provide low-level support for
+call stack unwinding. It is used in declarations in @file{unwind-generic.h}
+and the associated definitions of those functions.
+@end defmac
+
+@hook TARGET_UPDATE_STACK_BOUNDARY
+
+@hook TARGET_GET_DRAP_RTX
+
+@hook TARGET_ZERO_CALL_USED_REGS
+
+@hook TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS
+
+@hook TARGET_CONST_ANCHOR
+
+@hook TARGET_ASAN_SHADOW_OFFSET
+
+@hook TARGET_MEMMODEL_CHECK
+
+@hook TARGET_ATOMIC_TEST_AND_SET_TRUEVAL
+
+@hook TARGET_HAS_IFUNC_P
+
+@hook TARGET_IFUNC_REF_LOCAL_OK
+
+@hook TARGET_ATOMIC_ALIGN_FOR_MODE
+
+@hook TARGET_ATOMIC_ASSIGN_EXPAND_FENV
+
+@hook TARGET_RECORD_OFFLOAD_SYMBOL
+
+@hook TARGET_OFFLOAD_OPTIONS
+
+@defmac TARGET_SUPPORTS_WIDE_INT
+
+On older ports, large integers are stored in @code{CONST_DOUBLE} rtl
+objects. Newer ports define @code{TARGET_SUPPORTS_WIDE_INT} to be nonzero
+to indicate that large integers are stored in
+@code{CONST_WIDE_INT} rtl objects. The @code{CONST_WIDE_INT} allows
+very large integer constants to be represented. @code{CONST_DOUBLE}
+is limited to twice the size of the host's @code{HOST_WIDE_INT}
+representation.
+
+Converting a port mostly requires looking for the places where
+@code{CONST_DOUBLE}s are used with @code{VOIDmode} and replacing that
+code with code that accesses @code{CONST_WIDE_INT}s. @samp{"grep -i
+const_double"} at the port level gets you to 95% of the changes that
+need to be made. There are a few places that require a deeper look.
+
+@itemize @bullet
+@item
+There is no equivalent to @code{hval} and @code{lval} for
+@code{CONST_WIDE_INT}s. This would be difficult to express in the md
+language since there are a variable number of elements.
+
+Most ports only check that @code{hval} is either 0 or -1 to see if the
+value is small. As mentioned above, this will no longer be necessary
+since small constants are always @code{CONST_INT}. Of course there
+are still a few exceptions, the alpha's constraint used by the zap
+instruction certainly requires careful examination by C code.
+However, all the current code does is pass the hval and lval to C
+code, so evolving the c code to look at the @code{CONST_WIDE_INT} is
+not really a large change.
+
+@item
+Because there is no standard template that ports use to materialize
+constants, there is likely to be some futzing that is unique to each
+port in this code.
+
+@item
+The rtx costs may have to be adjusted to properly account for larger
+constants that are represented as @code{CONST_WIDE_INT}.
+@end itemize
+
+All and all it does not take long to convert ports that the
+maintainer is familiar with.
+
+@end defmac
+
+@hook TARGET_HAVE_SPECULATION_SAFE_VALUE
+
+@hook TARGET_SPECULATION_SAFE_VALUE
+
+@hook TARGET_RUN_TARGET_SELFTESTS
+
+@hook TARGET_MEMTAG_CAN_TAG_ADDRESSES
+
+@hook TARGET_MEMTAG_TAG_SIZE
+
+@hook TARGET_MEMTAG_GRANULE_SIZE
+
+@hook TARGET_MEMTAG_INSERT_RANDOM_TAG
+
+@hook TARGET_MEMTAG_ADD_TAG
+
+@hook TARGET_MEMTAG_SET_TAG
+
+@hook TARGET_MEMTAG_EXTRACT_TAG
+
+@hook TARGET_MEMTAG_UNTAGGED_POINTER
+
+@hook TARGET_GCOV_TYPE_SIZE
+
+@hook TARGET_HAVE_SHADOW_CALL_STACK
--- /dev/null
+@c Copyright (C) 2004-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@c ---------------------------------------------------------------------
+@c Tree SSA
+@c ---------------------------------------------------------------------
+
+@node Tree SSA
+@chapter Analysis and Optimization of GIMPLE tuples
+@cindex Tree SSA
+@cindex Optimization infrastructure for GIMPLE
+
+GCC uses three main intermediate languages to represent the program
+during compilation: GENERIC, GIMPLE and RTL@. GENERIC is a
+language-independent representation generated by each front end. It
+is used to serve as an interface between the parser and optimizer.
+GENERIC is a common representation that is able to represent programs
+written in all the languages supported by GCC@.
+
+GIMPLE and RTL are used to optimize the program. GIMPLE is used for
+target and language independent optimizations (e.g., inlining,
+constant propagation, tail call elimination, redundancy elimination,
+etc). Much like GENERIC, GIMPLE is a language independent, tree based
+representation. However, it differs from GENERIC in that the GIMPLE
+grammar is more restrictive: expressions contain no more than 3
+operands (except function calls), it has no control flow structures
+and expressions with side effects are only allowed on the right hand
+side of assignments. See the chapter describing GENERIC and GIMPLE
+for more details.
+
+This chapter describes the data structures and functions used in the
+GIMPLE optimizers (also known as ``tree optimizers'' or ``middle
+end''). In particular, it focuses on all the macros, data structures,
+functions and programming constructs needed to implement optimization
+passes for GIMPLE@.
+
+@menu
+* Annotations:: Attributes for variables.
+* SSA Operands:: SSA names referenced by GIMPLE statements.
+* SSA:: Static Single Assignment representation.
+* Alias analysis:: Representing aliased loads and stores.
+* Memory model:: Memory model used by the middle-end.
+@end menu
+
+@node Annotations
+@section Annotations
+@cindex annotations
+
+The optimizers need to associate attributes with variables during the
+optimization process. For instance, we need to know whether a
+variable has aliases. All these attributes are stored in data
+structures called annotations which are then linked to the field
+@code{ann} in @code{struct tree_common}.
+
+
+@node SSA Operands
+@section SSA Operands
+@cindex operands
+@cindex virtual operands
+@cindex real operands
+@findex update_stmt
+
+Almost every GIMPLE statement will contain a reference to a variable
+or memory location. Since statements come in different shapes and
+sizes, their operands are going to be located at various spots inside
+the statement's tree. To facilitate access to the statement's
+operands, they are organized into lists associated inside each
+statement's annotation. Each element in an operand list is a pointer
+to a @code{VAR_DECL}, @code{PARM_DECL} or @code{SSA_NAME} tree node.
+This provides a very convenient way of examining and replacing
+operands.
+
+Data flow analysis and optimization is done on all tree nodes
+representing variables. Any node for which @code{SSA_VAR_P} returns
+nonzero is considered when scanning statement operands. However, not
+all @code{SSA_VAR_P} variables are processed in the same way. For the
+purposes of optimization, we need to distinguish between references to
+local scalar variables and references to globals, statics, structures,
+arrays, aliased variables, etc. The reason is simple, the compiler
+can gather complete data flow information for a local scalar. On the
+other hand, a global variable may be modified by a function call, it
+may not be possible to keep track of all the elements of an array or
+the fields of a structure, etc.
+
+The operand scanner gathers two kinds of operands: @dfn{real} and
+@dfn{virtual}. An operand for which @code{is_gimple_reg} returns true
+is considered real, otherwise it is a virtual operand. We also
+distinguish between uses and definitions. An operand is used if its
+value is loaded by the statement (e.g., the operand at the RHS of an
+assignment). If the statement assigns a new value to the operand, the
+operand is considered a definition (e.g., the operand at the LHS of
+an assignment).
+
+Virtual and real operands also have very different data flow
+properties. Real operands are unambiguous references to the
+full object that they represent. For instance, given
+
+@smallexample
+@{
+ int a, b;
+ a = b
+@}
+@end smallexample
+
+Since @code{a} and @code{b} are non-aliased locals, the statement
+@code{a = b} will have one real definition and one real use because
+variable @code{a} is completely modified with the contents of
+variable @code{b}. Real definition are also known as @dfn{killing
+definitions}. Similarly, the use of @code{b} reads all its bits.
+
+In contrast, virtual operands are used with variables that can have
+a partial or ambiguous reference. This includes structures, arrays,
+globals, and aliased variables. In these cases, we have two types of
+definitions. For globals, structures, and arrays, we can determine from
+a statement whether a variable of these types has a killing definition.
+If the variable does, then the statement is marked as having a
+@dfn{must definition} of that variable. However, if a statement is only
+defining a part of the variable (i.e.@: a field in a structure), or if we
+know that a statement might define the variable but we cannot say for sure,
+then we mark that statement as having a @dfn{may definition}. For
+instance, given
+
+@smallexample
+@{
+ int a, b, *p;
+
+ if (@dots{})
+ p = &a;
+ else
+ p = &b;
+ *p = 5;
+ return *p;
+@}
+@end smallexample
+
+The assignment @code{*p = 5} may be a definition of @code{a} or
+@code{b}. If we cannot determine statically where @code{p} is
+pointing to at the time of the store operation, we create virtual
+definitions to mark that statement as a potential definition site for
+@code{a} and @code{b}. Memory loads are similarly marked with virtual
+use operands. Virtual operands are shown in tree dumps right before
+the statement that contains them. To request a tree dump with virtual
+operands, use the @option{-vops} option to @option{-fdump-tree}:
+
+@smallexample
+@{
+ int a, b, *p;
+
+ if (@dots{})
+ p = &a;
+ else
+ p = &b;
+ # a = VDEF <a>
+ # b = VDEF <b>
+ *p = 5;
+
+ # VUSE <a>
+ # VUSE <b>
+ return *p;
+@}
+@end smallexample
+
+Notice that @code{VDEF} operands have two copies of the referenced
+variable. This indicates that this is not a killing definition of
+that variable. In this case we refer to it as a @dfn{may definition}
+or @dfn{aliased store}. The presence of the second copy of the
+variable in the @code{VDEF} operand will become important when the
+function is converted into SSA form. This will be used to link all
+the non-killing definitions to prevent optimizations from making
+incorrect assumptions about them.
+
+Operands are updated as soon as the statement is finished via a call
+to @code{update_stmt}. If statement elements are changed via
+@code{SET_USE} or @code{SET_DEF}, then no further action is required
+(i.e., those macros take care of updating the statement). If changes
+are made by manipulating the statement's tree directly, then a call
+must be made to @code{update_stmt} when complete. Calling one of the
+@code{bsi_insert} routines or @code{bsi_replace} performs an implicit
+call to @code{update_stmt}.
+
+@subsection Operand Iterators And Access Routines
+@cindex Operand Iterators
+@cindex Operand Access Routines
+
+Operands are collected by @file{tree-ssa-operands.cc}. They are stored
+inside each statement's annotation and can be accessed through either the
+operand iterators or an access routine.
+
+The following access routines are available for examining operands:
+
+@enumerate
+@item @code{SINGLE_SSA_@{USE,DEF,TREE@}_OPERAND}: These accessors will return
+NULL unless there is exactly one operand matching the specified flags. If
+there is exactly one operand, the operand is returned as either a @code{tree},
+@code{def_operand_p}, or @code{use_operand_p}.
+
+@smallexample
+tree t = SINGLE_SSA_TREE_OPERAND (stmt, flags);
+use_operand_p u = SINGLE_SSA_USE_OPERAND (stmt, SSA_ALL_VIRTUAL_USES);
+def_operand_p d = SINGLE_SSA_DEF_OPERAND (stmt, SSA_OP_ALL_DEFS);
+@end smallexample
+
+@item @code{ZERO_SSA_OPERANDS}: This macro returns true if there are no
+operands matching the specified flags.
+
+@smallexample
+if (ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS))
+ return;
+@end smallexample
+
+@item @code{NUM_SSA_OPERANDS}: This macro Returns the number of operands
+matching 'flags'. This actually executes a loop to perform the count, so
+only use this if it is really needed.
+
+@smallexample
+int count = NUM_SSA_OPERANDS (stmt, flags)
+@end smallexample
+@end enumerate
+
+
+If you wish to iterate over some or all operands, use the
+@code{FOR_EACH_SSA_@{USE,DEF,TREE@}_OPERAND} iterator. For example, to print
+all the operands for a statement:
+
+@smallexample
+void
+print_ops (tree stmt)
+@{
+ ssa_op_iter;
+ tree var;
+
+ FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_ALL_OPERANDS)
+ print_generic_expr (stderr, var, TDF_SLIM);
+@}
+@end smallexample
+
+
+How to choose the appropriate iterator:
+
+@enumerate
+@item Determine whether you are need to see the operand pointers, or just the
+trees, and choose the appropriate macro:
+
+@smallexample
+Need Macro:
+---- -------
+use_operand_p FOR_EACH_SSA_USE_OPERAND
+def_operand_p FOR_EACH_SSA_DEF_OPERAND
+tree FOR_EACH_SSA_TREE_OPERAND
+@end smallexample
+
+@item You need to declare a variable of the type you are interested
+in, and an ssa_op_iter structure which serves as the loop controlling
+variable.
+
+@item Determine which operands you wish to use, and specify the flags of
+those you are interested in. They are documented in
+@file{tree-ssa-operands.h}:
+
+@smallexample
+#define SSA_OP_USE 0x01 /* @r{Real USE operands.} */
+#define SSA_OP_DEF 0x02 /* @r{Real DEF operands.} */
+#define SSA_OP_VUSE 0x04 /* @r{VUSE operands.} */
+#define SSA_OP_VDEF 0x08 /* @r{VDEF operands.} */
+
+/* @r{These are commonly grouped operand flags.} */
+#define SSA_OP_VIRTUAL_USES (SSA_OP_VUSE)
+#define SSA_OP_VIRTUAL_DEFS (SSA_OP_VDEF)
+#define SSA_OP_ALL_VIRTUALS (SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_DEFS)
+#define SSA_OP_ALL_USES (SSA_OP_VIRTUAL_USES | SSA_OP_USE)
+#define SSA_OP_ALL_DEFS (SSA_OP_VIRTUAL_DEFS | SSA_OP_DEF)
+#define SSA_OP_ALL_OPERANDS (SSA_OP_ALL_USES | SSA_OP_ALL_DEFS)
+@end smallexample
+@end enumerate
+
+So if you want to look at the use pointers for all the @code{USE} and
+@code{VUSE} operands, you would do something like:
+
+@smallexample
+ use_operand_p use_p;
+ ssa_op_iter iter;
+
+ FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, (SSA_OP_USE | SSA_OP_VUSE))
+ @{
+ process_use_ptr (use_p);
+ @}
+@end smallexample
+
+The @code{TREE} macro is basically the same as the @code{USE} and
+@code{DEF} macros, only with the use or def dereferenced via
+@code{USE_FROM_PTR (use_p)} and @code{DEF_FROM_PTR (def_p)}. Since we
+aren't using operand pointers, use and defs flags can be mixed.
+
+@smallexample
+ tree var;
+ ssa_op_iter iter;
+
+ FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_VUSE)
+ @{
+ print_generic_expr (stderr, var, TDF_SLIM);
+ @}
+@end smallexample
+
+@code{VDEF}s are broken into two flags, one for the
+@code{DEF} portion (@code{SSA_OP_VDEF}) and one for the USE portion
+(@code{SSA_OP_VUSE}).
+
+There are many examples in the code, in addition to the documentation
+in @file{tree-ssa-operands.h} and @file{ssa-iterators.h}.
+
+There are also a couple of variants on the stmt iterators regarding PHI
+nodes.
+
+@code{FOR_EACH_PHI_ARG} Works exactly like
+@code{FOR_EACH_SSA_USE_OPERAND}, except it works over @code{PHI} arguments
+instead of statement operands.
+
+@smallexample
+/* Look at every virtual PHI use. */
+FOR_EACH_PHI_ARG (use_p, phi_stmt, iter, SSA_OP_VIRTUAL_USES)
+@{
+ my_code;
+@}
+
+/* Look at every real PHI use. */
+FOR_EACH_PHI_ARG (use_p, phi_stmt, iter, SSA_OP_USES)
+ my_code;
+
+/* Look at every PHI use. */
+FOR_EACH_PHI_ARG (use_p, phi_stmt, iter, SSA_OP_ALL_USES)
+ my_code;
+@end smallexample
+
+@code{FOR_EACH_PHI_OR_STMT_@{USE,DEF@}} works exactly like
+@code{FOR_EACH_SSA_@{USE,DEF@}_OPERAND}, except it will function on
+either a statement or a @code{PHI} node. These should be used when it is
+appropriate but they are not quite as efficient as the individual
+@code{FOR_EACH_PHI} and @code{FOR_EACH_SSA} routines.
+
+@smallexample
+FOR_EACH_PHI_OR_STMT_USE (use_operand_p, stmt, iter, flags)
+ @{
+ my_code;
+ @}
+
+FOR_EACH_PHI_OR_STMT_DEF (def_operand_p, phi, iter, flags)
+ @{
+ my_code;
+ @}
+@end smallexample
+
+@subsection Immediate Uses
+@cindex Immediate Uses
+
+Immediate use information is now always available. Using the immediate use
+iterators, you may examine every use of any @code{SSA_NAME}. For instance,
+to change each use of @code{ssa_var} to @code{ssa_var2} and call fold_stmt on
+each stmt after that is done:
+
+@smallexample
+ use_operand_p imm_use_p;
+ imm_use_iterator iterator;
+ tree ssa_var, stmt;
+
+
+ FOR_EACH_IMM_USE_STMT (stmt, iterator, ssa_var)
+ @{
+ FOR_EACH_IMM_USE_ON_STMT (imm_use_p, iterator)
+ SET_USE (imm_use_p, ssa_var_2);
+ fold_stmt (stmt);
+ @}
+@end smallexample
+
+There are 2 iterators which can be used. @code{FOR_EACH_IMM_USE_FAST} is
+used when the immediate uses are not changed, i.e., you are looking at the
+uses, but not setting them.
+
+If they do get changed, then care must be taken that things are not changed
+under the iterators, so use the @code{FOR_EACH_IMM_USE_STMT} and
+@code{FOR_EACH_IMM_USE_ON_STMT} iterators. They attempt to preserve the
+sanity of the use list by moving all the uses for a statement into
+a controlled position, and then iterating over those uses. Then the
+optimization can manipulate the stmt when all the uses have been
+processed. This is a little slower than the FAST version since it adds a
+placeholder element and must sort through the list a bit for each statement.
+This placeholder element must be also be removed if the loop is
+terminated early; a destructor takes care of that when leaving the
+@code{FOR_EACH_IMM_USE_STMT} scope.
+
+There are checks in @code{verify_ssa} which verify that the immediate use list
+is up to date, as well as checking that an optimization didn't break from the
+loop without using this macro. It is safe to simply 'break'; from a
+@code{FOR_EACH_IMM_USE_FAST} traverse.
+
+Some useful functions and macros:
+@enumerate
+@item @code{has_zero_uses (ssa_var)} : Returns true if there are no uses of
+@code{ssa_var}.
+@item @code{has_single_use (ssa_var)} : Returns true if there is only a
+single use of @code{ssa_var}.
+@item @code{single_imm_use (ssa_var, use_operand_p *ptr, tree *stmt)} :
+Returns true if there is only a single use of @code{ssa_var}, and also returns
+the use pointer and statement it occurs in, in the second and third parameters.
+@item @code{num_imm_uses (ssa_var)} : Returns the number of immediate uses of
+@code{ssa_var}. It is better not to use this if possible since it simply
+utilizes a loop to count the uses.
+@item @code{PHI_ARG_INDEX_FROM_USE (use_p)} : Given a use within a @code{PHI}
+node, return the index number for the use. An assert is triggered if the use
+isn't located in a @code{PHI} node.
+@item @code{USE_STMT (use_p)} : Return the statement a use occurs in.
+@end enumerate
+
+Note that uses are not put into an immediate use list until their statement is
+actually inserted into the instruction stream via a @code{bsi_*} routine.
+
+It is also still possible to utilize lazy updating of statements, but this
+should be used only when absolutely required. Both alias analysis and the
+dominator optimizations currently do this.
+
+When lazy updating is being used, the immediate use information is out of date
+and cannot be used reliably. Lazy updating is achieved by simply marking
+statements modified via calls to @code{gimple_set_modified} instead of
+@code{update_stmt}. When lazy updating is no longer required, all the
+modified statements must have @code{update_stmt} called in order to bring them
+up to date. This must be done before the optimization is finished, or
+@code{verify_ssa} will trigger an abort.
+
+This is done with a simple loop over the instruction stream:
+@smallexample
+ block_stmt_iterator bsi;
+ basic_block bb;
+ FOR_EACH_BB (bb)
+ @{
+ for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
+ update_stmt_if_modified (bsi_stmt (bsi));
+ @}
+@end smallexample
+
+@node SSA
+@section Static Single Assignment
+@cindex SSA
+@cindex static single assignment
+
+Most of the tree optimizers rely on the data flow information provided
+by the Static Single Assignment (SSA) form. We implement the SSA form
+as described in @cite{R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and
+K. Zadeck. Efficiently Computing Static Single Assignment Form and the
+Control Dependence Graph. ACM Transactions on Programming Languages
+and Systems, 13(4):451-490, October 1991}.
+
+The SSA form is based on the premise that program variables are
+assigned in exactly one location in the program. Multiple assignments
+to the same variable create new versions of that variable. Naturally,
+actual programs are seldom in SSA form initially because variables
+tend to be assigned multiple times. The compiler modifies the program
+representation so that every time a variable is assigned in the code,
+a new version of the variable is created. Different versions of the
+same variable are distinguished by subscripting the variable name with
+its version number. Variables used in the right-hand side of
+expressions are renamed so that their version number matches that of
+the most recent assignment.
+
+We represent variable versions using @code{SSA_NAME} nodes. The
+renaming process in @file{tree-ssa.cc} wraps every real and
+virtual operand with an @code{SSA_NAME} node which contains
+the version number and the statement that created the
+@code{SSA_NAME}. Only definitions and virtual definitions may
+create new @code{SSA_NAME} nodes.
+
+@cindex PHI nodes
+Sometimes, flow of control makes it impossible to determine the
+most recent version of a variable. In these cases, the compiler
+inserts an artificial definition for that variable called
+@dfn{PHI function} or @dfn{PHI node}. This new definition merges
+all the incoming versions of the variable to create a new name
+for it. For instance,
+
+@smallexample
+if (@dots{})
+ a_1 = 5;
+else if (@dots{})
+ a_2 = 2;
+else
+ a_3 = 13;
+
+# a_4 = PHI <a_1, a_2, a_3>
+return a_4;
+@end smallexample
+
+Since it is not possible to determine which of the three branches
+will be taken at runtime, we don't know which of @code{a_1},
+@code{a_2} or @code{a_3} to use at the return statement. So, the
+SSA renamer creates a new version @code{a_4} which is assigned
+the result of ``merging'' @code{a_1}, @code{a_2} and @code{a_3}.
+Hence, PHI nodes mean ``one of these operands. I don't know
+which''.
+
+The following functions can be used to examine PHI nodes
+
+@defun gimple_phi_result (@var{phi})
+Returns the @code{SSA_NAME} created by PHI node @var{phi} (i.e.,
+@var{phi}'s LHS)@.
+@end defun
+
+@defun gimple_phi_num_args (@var{phi})
+Returns the number of arguments in @var{phi}. This number is exactly
+the number of incoming edges to the basic block holding @var{phi}@.
+@end defun
+
+@defun gimple_phi_arg (@var{phi}, @var{i})
+Returns @var{i}th argument of @var{phi}@.
+@end defun
+
+@defun gimple_phi_arg_edge (@var{phi}, @var{i})
+Returns the incoming edge for the @var{i}th argument of @var{phi}.
+@end defun
+
+@defun gimple_phi_arg_def (@var{phi}, @var{i})
+Returns the @code{SSA_NAME} for the @var{i}th argument of @var{phi}.
+@end defun
+
+
+@subsection Preserving the SSA form
+@findex update_ssa
+@cindex preserving SSA form
+Some optimization passes make changes to the function that
+invalidate the SSA property. This can happen when a pass has
+added new symbols or changed the program so that variables that
+were previously aliased aren't anymore. Whenever something like this
+happens, the affected symbols must be renamed into SSA form again.
+Transformations that emit new code or replicate existing statements
+will also need to update the SSA form@.
+
+Since GCC implements two different SSA forms for register and virtual
+variables, keeping the SSA form up to date depends on whether you are
+updating register or virtual names. In both cases, the general idea
+behind incremental SSA updates is similar: when new SSA names are
+created, they typically are meant to replace other existing names in
+the program@.
+
+For instance, given the following code:
+
+@smallexample
+ 1 L0:
+ 2 x_1 = PHI (0, x_5)
+ 3 if (x_1 < 10)
+ 4 if (x_1 > 7)
+ 5 y_2 = 0
+ 6 else
+ 7 y_3 = x_1 + x_7
+ 8 endif
+ 9 x_5 = x_1 + 1
+ 10 goto L0;
+ 11 endif
+@end smallexample
+
+Suppose that we insert new names @code{x_10} and @code{x_11} (lines
+@code{4} and @code{8})@.
+
+@smallexample
+ 1 L0:
+ 2 x_1 = PHI (0, x_5)
+ 3 if (x_1 < 10)
+ 4 x_10 = @dots{}
+ 5 if (x_1 > 7)
+ 6 y_2 = 0
+ 7 else
+ 8 x_11 = @dots{}
+ 9 y_3 = x_1 + x_7
+ 10 endif
+ 11 x_5 = x_1 + 1
+ 12 goto L0;
+ 13 endif
+@end smallexample
+
+We want to replace all the uses of @code{x_1} with the new definitions
+of @code{x_10} and @code{x_11}. Note that the only uses that should
+be replaced are those at lines @code{5}, @code{9} and @code{11}.
+Also, the use of @code{x_7} at line @code{9} should @emph{not} be
+replaced (this is why we cannot just mark symbol @code{x} for
+renaming)@.
+
+Additionally, we may need to insert a PHI node at line @code{11}
+because that is a merge point for @code{x_10} and @code{x_11}. So the
+use of @code{x_1} at line @code{11} will be replaced with the new PHI
+node. The insertion of PHI nodes is optional. They are not strictly
+necessary to preserve the SSA form, and depending on what the caller
+inserted, they may not even be useful for the optimizers@.
+
+Updating the SSA form is a two step process. First, the pass has to
+identify which names need to be updated and/or which symbols need to
+be renamed into SSA form for the first time. When new names are
+introduced to replace existing names in the program, the mapping
+between the old and the new names are registered by calling
+@code{register_new_name_mapping} (note that if your pass creates new
+code by duplicating basic blocks, the call to @code{tree_duplicate_bb}
+will set up the necessary mappings automatically).
+
+After the replacement mappings have been registered and new symbols
+marked for renaming, a call to @code{update_ssa} makes the registered
+changes. This can be done with an explicit call or by creating
+@code{TODO} flags in the @code{tree_opt_pass} structure for your pass.
+There are several @code{TODO} flags that control the behavior of
+@code{update_ssa}:
+
+@itemize @bullet
+@item @code{TODO_update_ssa}. Update the SSA form inserting PHI nodes
+for newly exposed symbols and virtual names marked for updating.
+When updating real names, only insert PHI nodes for a real name
+@code{O_j} in blocks reached by all the new and old definitions for
+@code{O_j}. If the iterated dominance frontier for @code{O_j}
+is not pruned, we may end up inserting PHI nodes in blocks that
+have one or more edges with no incoming definition for
+@code{O_j}. This would lead to uninitialized warnings for
+@code{O_j}'s symbol@.
+
+@item @code{TODO_update_ssa_no_phi}. Update the SSA form without
+inserting any new PHI nodes at all. This is used by passes that
+have either inserted all the PHI nodes themselves or passes that
+need only to patch use-def and def-def chains for virtuals
+(e.g., DCE)@.
+
+
+@item @code{TODO_update_ssa_full_phi}. Insert PHI nodes everywhere
+they are needed. No pruning of the IDF is done. This is used
+by passes that need the PHI nodes for @code{O_j} even if it
+means that some arguments will come from the default definition
+of @code{O_j}'s symbol (e.g., @code{pass_linear_transform})@.
+
+WARNING: If you need to use this flag, chances are that your
+pass may be doing something wrong. Inserting PHI nodes for an
+old name where not all edges carry a new replacement may lead to
+silent codegen errors or spurious uninitialized warnings@.
+
+@item @code{TODO_update_ssa_only_virtuals}. Passes that update the
+SSA form on their own may want to delegate the updating of
+virtual names to the generic updater. Since FUD chains are
+easier to maintain, this simplifies the work they need to do.
+NOTE: If this flag is used, any OLD->NEW mappings for real names
+are explicitly destroyed and only the symbols marked for
+renaming are processed@.
+@end itemize
+
+@subsection Examining @code{SSA_NAME} nodes
+@cindex examining SSA_NAMEs
+
+The following macros can be used to examine @code{SSA_NAME} nodes
+
+@defmac SSA_NAME_DEF_STMT (@var{var})
+Returns the statement @var{s} that creates the @code{SSA_NAME}
+@var{var}. If @var{s} is an empty statement (i.e., @code{IS_EMPTY_STMT
+(@var{s})} returns @code{true}), it means that the first reference to
+this variable is a USE or a VUSE@.
+@end defmac
+
+@defmac SSA_NAME_VERSION (@var{var})
+Returns the version number of the @code{SSA_NAME} object @var{var}.
+@end defmac
+
+
+@subsection Walking the dominator tree
+
+@deftypefn {Tree SSA function} void walk_dominator_tree (@var{walk_data}, @var{bb})
+
+This function walks the dominator tree for the current CFG calling a
+set of callback functions defined in @var{struct dom_walk_data} in
+@file{domwalk.h}. The call back functions you need to define give you
+hooks to execute custom code at various points during traversal:
+
+@enumerate
+@item Once to initialize any local data needed while processing
+@var{bb} and its children. This local data is pushed into an
+internal stack which is automatically pushed and popped as the
+walker traverses the dominator tree.
+
+@item Once before traversing all the statements in the @var{bb}.
+
+@item Once for every statement inside @var{bb}.
+
+@item Once after traversing all the statements and before recursing
+into @var{bb}'s dominator children.
+
+@item It then recurses into all the dominator children of @var{bb}.
+
+@item After recursing into all the dominator children of @var{bb} it
+can, optionally, traverse every statement in @var{bb} again
+(i.e., repeating steps 2 and 3).
+
+@item Once after walking the statements in @var{bb} and @var{bb}'s
+dominator children. At this stage, the block local data stack
+is popped.
+@end enumerate
+@end deftypefn
+
+@node Alias analysis
+@section Alias analysis
+@cindex alias
+@cindex flow-sensitive alias analysis
+@cindex flow-insensitive alias analysis
+
+Alias analysis in GIMPLE SSA form consists of two pieces. First
+the virtual SSA web ties conflicting memory accesses and provides
+a SSA use-def chain and SSA immediate-use chains for walking
+possibly dependent memory accesses. Second an alias-oracle can
+be queried to disambiguate explicit and implicit memory references.
+
+@enumerate
+@item Memory SSA form.
+
+All statements that may use memory have exactly one accompanied use of
+a virtual SSA name that represents the state of memory at the
+given point in the IL.
+
+All statements that may define memory have exactly one accompanied
+definition of a virtual SSA name using the previous state of memory
+and defining the new state of memory after the given point in the IL.
+
+@smallexample
+int i;
+int foo (void)
+@{
+ # .MEM_3 = VDEF <.MEM_2(D)>
+ i = 1;
+ # VUSE <.MEM_3>
+ return i;
+@}
+@end smallexample
+
+The virtual SSA names in this case are @code{.MEM_2(D)} and
+@code{.MEM_3}. The store to the global variable @code{i}
+defines @code{.MEM_3} invalidating @code{.MEM_2(D)}. The
+load from @code{i} uses that new state @code{.MEM_3}.
+
+The virtual SSA web serves as constraints to SSA optimizers
+preventing illegitimate code-motion and optimization. It
+also provides a way to walk related memory statements.
+
+@item Points-to and escape analysis.
+
+Points-to analysis builds a set of constraints from the GIMPLE
+SSA IL representing all pointer operations and facts we do
+or do not know about pointers. Solving this set of constraints
+yields a conservatively correct solution for each pointer
+variable in the program (though we are only interested in
+SSA name pointers) as to what it may possibly point to.
+
+This points-to solution for a given SSA name pointer is stored
+in the @code{pt_solution} sub-structure of the
+@code{SSA_NAME_PTR_INFO} record. The following accessor
+functions are available:
+
+@itemize @bullet
+@item @code{pt_solution_includes}
+@item @code{pt_solutions_intersect}
+@end itemize
+
+Points-to analysis also computes the solution for two special
+set of pointers, @code{ESCAPED} and @code{CALLUSED}. Those
+represent all memory that has escaped the scope of analysis
+or that is used by pure or nested const calls.
+
+@item Type-based alias analysis
+
+Type-based alias analysis is frontend dependent though generic
+support is provided by the middle-end in @code{alias.cc}. TBAA
+code is used by both tree optimizers and RTL optimizers.
+
+Every language that wishes to perform language-specific alias analysis
+should define a function that computes, given a @code{tree}
+node, an alias set for the node. Nodes in different alias sets are not
+allowed to alias. For an example, see the C front-end function
+@code{c_get_alias_set}.
+
+@item Tree alias-oracle
+
+The tree alias-oracle provides means to disambiguate two memory
+references and memory references against statements. The following
+queries are available:
+
+@itemize @bullet
+@item @code{refs_may_alias_p}
+@item @code{ref_maybe_used_by_stmt_p}
+@item @code{stmt_may_clobber_ref_p}
+@end itemize
+
+In addition to those two kind of statement walkers are available
+walking statements related to a reference ref.
+@code{walk_non_aliased_vuses} walks over dominating memory defining
+statements and calls back if the statement does not clobber ref
+providing the non-aliased VUSE. The walk stops at
+the first clobbering statement or if asked to.
+@code{walk_aliased_vdefs} walks over dominating memory defining
+statements and calls back on each statement clobbering ref
+providing its aliasing VDEF. The walk stops if asked to.
+
+@end enumerate
+
+
+@node Memory model
+@section Memory model
+@cindex memory model
+
+The memory model used by the middle-end models that of the C/C++
+languages. The middle-end has the notion of an effective type
+of a memory region which is used for type-based alias analysis.
+
+The following is a refinement of ISO C99 6.5/6, clarifying the block copy case
+to follow common sense and extending the concept of a dynamic effective
+type to objects with a declared type as required for C++.
+
+@smallexample
+The effective type of an object for an access to its stored value is
+the declared type of the object or the effective type determined by
+a previous store to it. If a value is stored into an object through
+an lvalue having a type that is not a character type, then the
+type of the lvalue becomes the effective type of the object for that
+access and for subsequent accesses that do not modify the stored value.
+If a value is copied into an object using @code{memcpy} or @code{memmove},
+or is copied as an array of character type, then the effective type
+of the modified object for that access and for subsequent accesses that
+do not modify the value is undetermined. For all other accesses to an
+object, the effective type of the object is simply the type of the
+lvalue used for the access.
+@end smallexample
+
--- /dev/null
+@c Copyright (C) 1988-2022 Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node Trouble
+@chapter Known Causes of Trouble with GCC
+@cindex bugs, known
+@cindex installation trouble
+@cindex known causes of trouble
+
+This section describes known problems that affect users of GCC@. Most
+of these are not GCC bugs per se---if they were, we would fix them.
+But the result for a user may be like the result of a bug.
+
+Some of these problems are due to bugs in other software, some are
+missing features that are too much work to add, and some are places
+where people's opinions differ as to what is best.
+
+@menu
+* Actual Bugs:: Bugs we will fix later.
+* Interoperation:: Problems using GCC with other compilers,
+ and with certain linkers, assemblers and debuggers.
+* Incompatibilities:: GCC is incompatible with traditional C.
+* Fixed Headers:: GCC uses corrected versions of system header files.
+ This is necessary, but doesn't always work smoothly.
+* Standard Libraries:: GCC uses the system C library, which might not be
+ compliant with the ISO C standard.
+* Disappointments:: Regrettable things we cannot change, but not quite bugs.
+* C++ Misunderstandings:: Common misunderstandings with GNU C++.
+* Non-bugs:: Things we think are right, but some others disagree.
+* Warnings and Errors:: Which problems in your code get warnings,
+ and which get errors.
+@end menu
+
+@node Actual Bugs
+@section Actual Bugs We Haven't Fixed Yet
+
+@itemize @bullet
+@item
+The @code{fixincludes} script interacts badly with automounters; if the
+directory of system header files is automounted, it tends to be
+unmounted while @code{fixincludes} is running. This would seem to be a
+bug in the automounter. We don't know any good way to work around it.
+@end itemize
+
+@node Interoperation
+@section Interoperation
+
+This section lists various difficulties encountered in using GCC
+together with other compilers or with the assemblers, linkers,
+libraries and debuggers on certain systems.
+
+@itemize @bullet
+@item
+On many platforms, GCC supports a different ABI for C++ than do other
+compilers, so the object files compiled by GCC cannot be used with object
+files generated by another C++ compiler.
+
+An area where the difference is most apparent is name mangling. The use
+of different name mangling is intentional, to protect you from more subtle
+problems.
+Compilers differ as to many internal details of C++ implementation,
+including: how class instances are laid out, how multiple inheritance is
+implemented, and how virtual function calls are handled. If the name
+encoding were made the same, your programs would link against libraries
+provided from other compilers---but the programs would then crash when
+run. Incompatible libraries are then detected at link time, rather than
+at run time.
+
+@item
+On some BSD systems, including some versions of Ultrix, use of profiling
+causes static variable destructors (currently used only in C++) not to
+be run.
+
+@item
+On a SPARC, GCC aligns all values of type @code{double} on an 8-byte
+boundary, and it expects every @code{double} to be so aligned. The Sun
+compiler usually gives @code{double} values 8-byte alignment, with one
+exception: function arguments of type @code{double} may not be aligned.
+
+As a result, if a function compiled with Sun CC takes the address of an
+argument of type @code{double} and passes this pointer of type
+@code{double *} to a function compiled with GCC, dereferencing the
+pointer may cause a fatal signal.
+
+One way to solve this problem is to compile your entire program with GCC@.
+Another solution is to modify the function that is compiled with
+Sun CC to copy the argument into a local variable; local variables
+are always properly aligned. A third solution is to modify the function
+that uses the pointer to dereference it via the following function
+@code{access_double} instead of directly with @samp{*}:
+
+@smallexample
+inline double
+access_double (double *unaligned_ptr)
+@{
+ union d2i @{ double d; int i[2]; @};
+
+ union d2i *p = (union d2i *) unaligned_ptr;
+ union d2i u;
+
+ u.i[0] = p->i[0];
+ u.i[1] = p->i[1];
+
+ return u.d;
+@}
+@end smallexample
+
+@noindent
+Storing into the pointer can be done likewise with the same union.
+
+@item
+On Solaris, the @code{malloc} function in the @file{libmalloc.a} library
+may allocate memory that is only 4 byte aligned. Since GCC on the
+SPARC assumes that doubles are 8 byte aligned, this may result in a
+fatal signal if doubles are stored in memory allocated by the
+@file{libmalloc.a} library.
+
+The solution is to not use the @file{libmalloc.a} library. Use instead
+@code{malloc} and related functions from @file{libc.a}; they do not have
+this problem.
+
+@item
+On the HP PA machine, ADB sometimes fails to work on functions compiled
+with GCC@. Specifically, it fails to work on functions that use
+@code{alloca} or variable-size arrays. This is because GCC doesn't
+generate HP-UX unwind descriptors for such functions. It may even be
+impossible to generate them.
+
+@item
+Debugging (@option{-g}) is not supported on the HP PA machine, unless you use
+the preliminary GNU tools.
+
+@item
+Taking the address of a label may generate errors from the HP-UX
+PA assembler. GAS for the PA does not have this problem.
+
+@item
+Using floating point parameters for indirect calls to static functions
+will not work when using the HP assembler. There simply is no way for GCC
+to specify what registers hold arguments for static functions when using
+the HP assembler. GAS for the PA does not have this problem.
+
+@item
+In extremely rare cases involving some very large functions you may
+receive errors from the HP linker complaining about an out of bounds
+unconditional branch offset. This used to occur more often in previous
+versions of GCC, but is now exceptionally rare. If you should run
+into it, you can work around by making your function smaller.
+
+@item
+GCC compiled code sometimes emits warnings from the HP-UX assembler of
+the form:
+
+@smallexample
+(warning) Use of GR3 when
+ frame >= 8192 may cause conflict.
+@end smallexample
+
+These warnings are harmless and can be safely ignored.
+
+@item
+In extremely rare cases involving some very large functions you may
+receive errors from the AIX Assembler complaining about a displacement
+that is too large. If you should run into it, you can work around by
+making your function smaller.
+
+@item
+The @file{libstdc++.a} library in GCC relies on the SVR4 dynamic
+linker semantics which merges global symbols between libraries and
+applications, especially necessary for C++ streams functionality.
+This is not the default behavior of AIX shared libraries and dynamic
+linking. @file{libstdc++.a} is built on AIX with ``runtime-linking''
+enabled so that symbol merging can occur. To utilize this feature,
+the application linked with @file{libstdc++.a} must include the
+@option{-Wl,-brtl} flag on the link line. G++ cannot impose this
+because this option may interfere with the semantics of the user
+program and users may not always use @samp{g++} to link his or her
+application. Applications are not required to use the
+@option{-Wl,-brtl} flag on the link line---the rest of the
+@file{libstdc++.a} library which is not dependent on the symbol
+merging semantics will continue to function correctly.
+
+@item
+An application can interpose its own definition of functions for
+functions invoked by @file{libstdc++.a} with ``runtime-linking''
+enabled on AIX@. To accomplish this the application must be linked
+with ``runtime-linking'' option and the functions explicitly must be
+exported by the application (@option{-Wl,-brtl,-bE:exportfile}).
+
+@item
+AIX on the RS/6000 provides support (NLS) for environments outside of
+the United States. Compilers and assemblers use NLS to support
+locale-specific representations of various objects including
+floating-point numbers (@samp{.} vs @samp{,} for separating decimal
+fractions). There have been problems reported where the library linked
+with GCC does not produce the same floating-point formats that the
+assembler accepts. If you have this problem, set the @env{LANG}
+environment variable to @samp{C} or @samp{En_US}.
+
+@item
+@opindex fdollars-in-identifiers
+Even if you specify @option{-fdollars-in-identifiers},
+you cannot successfully use @samp{$} in identifiers on the RS/6000 due
+to a restriction in the IBM assembler. GAS supports these
+identifiers.
+
+@end itemize
+
+@node Incompatibilities
+@section Incompatibilities of GCC
+@cindex incompatibilities of GCC
+@opindex traditional
+
+There are several noteworthy incompatibilities between GNU C and K&R
+(non-ISO) versions of C@.
+
+@itemize @bullet
+@cindex string constants
+@cindex read-only strings
+@cindex shared strings
+@item
+GCC normally makes string constants read-only. If several
+identical-looking string constants are used, GCC stores only one
+copy of the string.
+
+@cindex @code{mktemp}, and constant strings
+One consequence is that you cannot call @code{mktemp} with a string
+constant argument. The function @code{mktemp} always alters the
+string its argument points to.
+
+@cindex @code{sscanf}, and constant strings
+@cindex @code{fscanf}, and constant strings
+@cindex @code{scanf}, and constant strings
+Another consequence is that @code{sscanf} does not work on some very
+old systems when passed a string constant as its format control string
+or input. This is because @code{sscanf} incorrectly tries to write
+into the string constant. Likewise @code{fscanf} and @code{scanf}.
+
+The solution to these problems is to change the program to use
+@code{char}-array variables with initialization strings for these
+purposes instead of string constants.
+
+@item
+@code{-2147483648} is positive.
+
+This is because 2147483648 cannot fit in the type @code{int}, so
+(following the ISO C rules) its data type is @code{unsigned long int}.
+Negating this value yields 2147483648 again.
+
+@item
+GCC does not substitute macro arguments when they appear inside of
+string constants. For example, the following macro in GCC
+
+@smallexample
+#define foo(a) "a"
+@end smallexample
+
+@noindent
+will produce output @code{"a"} regardless of what the argument @var{a} is.
+
+@cindex @code{setjmp} incompatibilities
+@cindex @code{longjmp} incompatibilities
+@item
+When you use @code{setjmp} and @code{longjmp}, the only automatic
+variables guaranteed to remain valid are those declared
+@code{volatile}. This is a consequence of automatic register
+allocation. Consider this function:
+
+@smallexample
+jmp_buf j;
+
+foo ()
+@{
+ int a, b;
+
+ a = fun1 ();
+ if (setjmp (j))
+ return a;
+
+ a = fun2 ();
+ /* @r{@code{longjmp (j)} may occur in @code{fun3}.} */
+ return a + fun3 ();
+@}
+@end smallexample
+
+Here @code{a} may or may not be restored to its first value when the
+@code{longjmp} occurs. If @code{a} is allocated in a register, then
+its first value is restored; otherwise, it keeps the last value stored
+in it.
+
+@opindex W
+If you use the @option{-W} option with the @option{-O} option, you will
+get a warning when GCC thinks such a problem might be possible.
+
+@item
+Programs that use preprocessing directives in the middle of macro
+arguments do not work with GCC@. For example, a program like this
+will not work:
+
+@smallexample
+@group
+foobar (
+#define luser
+ hack)
+@end group
+@end smallexample
+
+ISO C does not permit such a construct.
+
+@item
+K&R compilers allow comments to cross over an inclusion boundary
+(i.e.@: started in an include file and ended in the including file).
+
+@cindex external declaration scope
+@cindex scope of external declarations
+@cindex declaration scope
+@item
+Declarations of external variables and functions within a block apply
+only to the block containing the declaration. In other words, they
+have the same scope as any other declaration in the same place.
+
+In some other C compilers, an @code{extern} declaration affects all the
+rest of the file even if it happens within a block.
+
+@item
+In traditional C, you can combine @code{long}, etc., with a typedef name,
+as shown here:
+
+@smallexample
+typedef int foo;
+typedef long foo bar;
+@end smallexample
+
+In ISO C, this is not allowed: @code{long} and other type modifiers
+require an explicit @code{int}.
+
+@cindex typedef names as function parameters
+@item
+PCC allows typedef names to be used as function parameters.
+
+@item
+Traditional C allows the following erroneous pair of declarations to
+appear together in a given scope:
+
+@smallexample
+typedef int foo;
+typedef foo foo;
+@end smallexample
+
+@item
+GCC treats all characters of identifiers as significant. According to
+K&R-1 (2.2), ``No more than the first eight characters are significant,
+although more may be used.''. Also according to K&R-1 (2.2), ``An
+identifier is a sequence of letters and digits; the first character must
+be a letter. The underscore _ counts as a letter.'', but GCC also
+allows dollar signs in identifiers.
+
+@cindex whitespace
+@item
+PCC allows whitespace in the middle of compound assignment operators
+such as @samp{+=}. GCC, following the ISO standard, does not
+allow this.
+
+@cindex apostrophes
+@cindex @code{'}
+@item
+GCC complains about unterminated character constants inside of
+preprocessing conditionals that fail. Some programs have English
+comments enclosed in conditionals that are guaranteed to fail; if these
+comments contain apostrophes, GCC will probably report an error. For
+example, this code would produce an error:
+
+@smallexample
+#if 0
+You can't expect this to work.
+#endif
+@end smallexample
+
+The best solution to such a problem is to put the text into an actual
+C comment delimited by @samp{/*@dots{}*/}.
+
+@item
+Many user programs contain the declaration @samp{long time ();}. In the
+past, the system header files on many systems did not actually declare
+@code{time}, so it did not matter what type your program declared it to
+return. But in systems with ISO C headers, @code{time} is declared to
+return @code{time_t}, and if that is not the same as @code{long}, then
+@samp{long time ();} is erroneous.
+
+The solution is to change your program to use appropriate system headers
+(@code{<time.h>} on systems with ISO C headers) and not to declare
+@code{time} if the system header files declare it, or failing that to
+use @code{time_t} as the return type of @code{time}.
+
+@cindex @code{float} as function value type
+@item
+When compiling functions that return @code{float}, PCC converts it to
+a double. GCC actually returns a @code{float}. If you are concerned
+with PCC compatibility, you should declare your functions to return
+@code{double}; you might as well say what you mean.
+
+@cindex structures
+@cindex unions
+@item
+When compiling functions that return structures or unions, GCC
+output code normally uses a method different from that used on most
+versions of Unix. As a result, code compiled with GCC cannot call
+a structure-returning function compiled with PCC, and vice versa.
+
+The method used by GCC is as follows: a structure or union which is
+1, 2, 4 or 8 bytes long is returned like a scalar. A structure or union
+with any other size is stored into an address supplied by the caller
+(usually in a special, fixed register, but on some machines it is passed
+on the stack). The target hook @code{TARGET_STRUCT_VALUE_RTX}
+tells GCC where to pass this address.
+
+By contrast, PCC on most target machines returns structures and unions
+of any size by copying the data into an area of static storage, and then
+returning the address of that storage as if it were a pointer value.
+The caller must copy the data from that memory area to the place where
+the value is wanted. GCC does not use this method because it is
+slower and nonreentrant.
+
+On some newer machines, PCC uses a reentrant convention for all
+structure and union returning. GCC on most of these machines uses a
+compatible convention when returning structures and unions in memory,
+but still returns small structures and unions in registers.
+
+@opindex fpcc-struct-return
+You can tell GCC to use a compatible convention for all structure and
+union returning with the option @option{-fpcc-struct-return}.
+
+@cindex preprocessing tokens
+@cindex preprocessing numbers
+@item
+GCC complains about program fragments such as @samp{0x74ae-0x4000}
+which appear to be two hexadecimal constants separated by the minus
+operator. Actually, this string is a single @dfn{preprocessing token}.
+Each such token must correspond to one token in C@. Since this does not,
+GCC prints an error message. Although it may appear obvious that what
+is meant is an operator and two values, the ISO C standard specifically
+requires that this be treated as erroneous.
+
+A @dfn{preprocessing token} is a @dfn{preprocessing number} if it
+begins with a digit and is followed by letters, underscores, digits,
+periods and @samp{e+}, @samp{e-}, @samp{E+}, @samp{E-}, @samp{p+},
+@samp{p-}, @samp{P+}, or @samp{P-} character sequences. (In strict C90
+mode, the sequences @samp{p+}, @samp{p-}, @samp{P+} and @samp{P-} cannot
+appear in preprocessing numbers.)
+
+To make the above program fragment valid, place whitespace in front of
+the minus sign. This whitespace will end the preprocessing number.
+@end itemize
+
+@node Fixed Headers
+@section Fixed Header Files
+
+GCC needs to install corrected versions of some system header files.
+This is because most target systems have some header files that won't
+work with GCC unless they are changed. Some have bugs, some are
+incompatible with ISO C, and some depend on special features of other
+compilers.
+
+Installing GCC automatically creates and installs the fixed header
+files, by running a program called @code{fixincludes}. Normally, you
+don't need to pay attention to this. But there are cases where it
+doesn't do the right thing automatically.
+
+@itemize @bullet
+@item
+If you update the system's header files, such as by installing a new
+system version, the fixed header files of GCC are not automatically
+updated. They can be updated using the @command{mkheaders} script
+installed in
+@file{@var{libexecdir}/gcc/@var{target}/@var{version}/install-tools/}.
+
+@item
+On some systems, header file directories contain
+machine-specific symbolic links in certain places. This makes it
+possible to share most of the header files among hosts running the
+same version of the system on different machine models.
+
+The programs that fix the header files do not understand this special
+way of using symbolic links; therefore, the directory of fixed header
+files is good only for the machine model used to build it.
+
+It is possible to make separate sets of fixed header files for the
+different machine models, and arrange a structure of symbolic links so
+as to use the proper set, but you'll have to do this by hand.
+@end itemize
+
+@node Standard Libraries
+@section Standard Libraries
+
+@opindex Wall
+GCC by itself attempts to be a conforming freestanding implementation.
+@xref{Standards,,Language Standards Supported by GCC}, for details of
+what this means. Beyond the library facilities required of such an
+implementation, the rest of the C library is supplied by the vendor of
+the operating system. If that C library doesn't conform to the C
+standards, then your programs might get warnings (especially when using
+@option{-Wall}) that you don't expect.
+
+For example, the @code{sprintf} function on SunOS 4.1.3 returns
+@code{char *} while the C standard says that @code{sprintf} returns an
+@code{int}. The @code{fixincludes} program could make the prototype for
+this function match the Standard, but that would be wrong, since the
+function will still return @code{char *}.
+
+If you need a Standard compliant library, then you need to find one, as
+GCC does not provide one. The GNU C library (called @code{glibc})
+provides ISO C, POSIX, BSD, SystemV and X/Open compatibility for
+GNU/Linux and HURD-based GNU systems; no recent version of it supports
+other systems, though some very old versions did. Version 2.2 of the
+GNU C library includes nearly complete C99 support. You could also ask
+your operating system vendor if newer libraries are available.
+
+@node Disappointments
+@section Disappointments and Misunderstandings
+
+These problems are perhaps regrettable, but we don't know any practical
+way around them.
+
+@itemize @bullet
+@item
+Certain local variables aren't recognized by debuggers when you compile
+with optimization.
+
+This occurs because sometimes GCC optimizes the variable out of
+existence. There is no way to tell the debugger how to compute the
+value such a variable ``would have had'', and it is not clear that would
+be desirable anyway. So GCC simply does not mention the eliminated
+variable when it writes debugging information.
+
+You have to expect a certain amount of disagreement between the
+executable and your source code, when you use optimization.
+
+@cindex conflicting types
+@cindex scope of declaration
+@item
+Users often think it is a bug when GCC reports an error for code
+like this:
+
+@smallexample
+int foo (struct mumble *);
+
+struct mumble @{ @dots{} @};
+
+int foo (struct mumble *x)
+@{ @dots{} @}
+@end smallexample
+
+This code really is erroneous, because the scope of @code{struct
+mumble} in the prototype is limited to the argument list containing it.
+It does not refer to the @code{struct mumble} defined with file scope
+immediately below---they are two unrelated types with similar names in
+different scopes.
+
+But in the definition of @code{foo}, the file-scope type is used
+because that is available to be inherited. Thus, the definition and
+the prototype do not match, and you get an error.
+
+This behavior may seem silly, but it's what the ISO standard specifies.
+It is easy enough for you to make your code work by moving the
+definition of @code{struct mumble} above the prototype. It's not worth
+being incompatible with ISO C just to avoid an error for the example
+shown above.
+
+@item
+Accesses to bit-fields even in volatile objects works by accessing larger
+objects, such as a byte or a word. You cannot rely on what size of
+object is accessed in order to read or write the bit-field; it may even
+vary for a given bit-field according to the precise usage.
+
+If you care about controlling the amount of memory that is accessed, use
+volatile but do not use bit-fields.
+
+@item
+GCC comes with shell scripts to fix certain known problems in system
+header files. They install corrected copies of various header files in
+a special directory where only GCC will normally look for them. The
+scripts adapt to various systems by searching all the system header
+files for the problem cases that we know about.
+
+If new system header files are installed, nothing automatically arranges
+to update the corrected header files. They can be updated using the
+@command{mkheaders} script installed in
+@file{@var{libexecdir}/gcc/@var{target}/@var{version}/install-tools/}.
+
+@item
+@cindex floating point precision
+On 68000 and x86 systems, for instance, you can get paradoxical results
+if you test the precise values of floating point numbers. For example,
+you can find that a floating point value which is not a NaN is not equal
+to itself. This results from the fact that the floating point registers
+hold a few more bits of precision than fit in a @code{double} in memory.
+Compiled code moves values between memory and floating point registers
+at its convenience, and moving them into memory truncates them.
+
+@opindex ffloat-store
+You can partially avoid this problem by using the @option{-ffloat-store}
+option (@pxref{Optimize Options}).
+
+@item
+On AIX and other platforms without weak symbol support, templates
+need to be instantiated explicitly and symbols for static members
+of templates will not be generated.
+
+@item
+On AIX, GCC scans object files and library archives for static
+constructors and destructors when linking an application before the
+linker prunes unreferenced symbols. This is necessary to prevent the
+AIX linker from mistakenly assuming that static constructor or
+destructor are unused and removing them before the scanning can occur.
+All static constructors and destructors found will be referenced even
+though the modules in which they occur may not be used by the program.
+This may lead to both increased executable size and unexpected symbol
+references.
+@end itemize
+
+@node C++ Misunderstandings
+@section Common Misunderstandings with GNU C++
+
+@cindex misunderstandings in C++
+@cindex surprises in C++
+@cindex C++ misunderstandings
+C++ is a complex language and an evolving one, and its standard
+definition (the ISO C++ standard) was only recently completed. As a
+result, your C++ compiler may occasionally surprise you, even when its
+behavior is correct. This section discusses some areas that frequently
+give rise to questions of this sort.
+
+@menu
+* Static Definitions:: Static member declarations are not definitions
+* Name lookup:: Name lookup, templates, and accessing members of base classes
+* Temporaries:: Temporaries may vanish before you expect
+* Copy Assignment:: Copy Assignment operators copy virtual bases twice
+@end menu
+
+@node Static Definitions
+@subsection Declare @emph{and} Define Static Members
+
+@cindex C++ static data, declaring and defining
+@cindex static data in C++, declaring and defining
+@cindex declaring static data in C++
+@cindex defining static data in C++
+When a class has static data members, it is not enough to @emph{declare}
+the static member; you must also @emph{define} it. For example:
+
+@smallexample
+class Foo
+@{
+ @dots{}
+ void method();
+ static int bar;
+@};
+@end smallexample
+
+This declaration only establishes that the class @code{Foo} has an
+@code{int} named @code{Foo::bar}, and a member function named
+@code{Foo::method}. But you still need to define @emph{both}
+@code{method} and @code{bar} elsewhere. According to the ISO
+standard, you must supply an initializer in one (and only one) source
+file, such as:
+
+@smallexample
+int Foo::bar = 0;
+@end smallexample
+
+Other C++ compilers may not correctly implement the standard behavior.
+As a result, when you switch to @command{g++} from one of these compilers,
+you may discover that a program that appeared to work correctly in fact
+does not conform to the standard: @command{g++} reports as undefined
+symbols any static data members that lack definitions.
+
+
+@node Name lookup
+@subsection Name Lookup, Templates, and Accessing Members of Base Classes
+
+@cindex base class members
+@cindex two-stage name lookup
+@cindex dependent name lookup
+
+The C++ standard prescribes that all names that are not dependent on
+template parameters are bound to their present definitions when parsing
+a template function or class.@footnote{The C++ standard just uses the
+term ``dependent'' for names that depend on the type or value of
+template parameters. This shorter term will also be used in the rest of
+this section.} Only names that are dependent are looked up at the point
+of instantiation. For example, consider
+
+@smallexample
+ void foo(double);
+
+ struct A @{
+ template <typename T>
+ void f () @{
+ foo (1); // @r{1}
+ int i = N; // @r{2}
+ T t;
+ t.bar(); // @r{3}
+ foo (t); // @r{4}
+ @}
+
+ static const int N;
+ @};
+@end smallexample
+
+Here, the names @code{foo} and @code{N} appear in a context that does
+not depend on the type of @code{T}. The compiler will thus require that
+they are defined in the context of use in the template, not only before
+the point of instantiation, and will here use @code{::foo(double)} and
+@code{A::N}, respectively. In particular, it will convert the integer
+value to a @code{double} when passing it to @code{::foo(double)}.
+
+Conversely, @code{bar} and the call to @code{foo} in the fourth marked
+line are used in contexts that do depend on the type of @code{T}, so
+they are only looked up at the point of instantiation, and you can
+provide declarations for them after declaring the template, but before
+instantiating it. In particular, if you instantiate @code{A::f<int>},
+the last line will call an overloaded @code{::foo(int)} if one was
+provided, even if after the declaration of @code{struct A}.
+
+This distinction between lookup of dependent and non-dependent names is
+called two-stage (or dependent) name lookup. G++ implements it
+since version 3.4.
+
+Two-stage name lookup sometimes leads to situations with behavior
+different from non-template codes. The most common is probably this:
+
+@smallexample
+ template <typename T> struct Base @{
+ int i;
+ @};
+
+ template <typename T> struct Derived : public Base<T> @{
+ int get_i() @{ return i; @}
+ @};
+@end smallexample
+
+In @code{get_i()}, @code{i} is not used in a dependent context, so the
+compiler will look for a name declared at the enclosing namespace scope
+(which is the global scope here). It will not look into the base class,
+since that is dependent and you may declare specializations of
+@code{Base} even after declaring @code{Derived}, so the compiler cannot
+really know what @code{i} would refer to. If there is no global
+variable @code{i}, then you will get an error message.
+
+In order to make it clear that you want the member of the base class,
+you need to defer lookup until instantiation time, at which the base
+class is known. For this, you need to access @code{i} in a dependent
+context, by either using @code{this->i} (remember that @code{this} is of
+type @code{Derived<T>*}, so is obviously dependent), or using
+@code{Base<T>::i}. Alternatively, @code{Base<T>::i} might be brought
+into scope by a @code{using}-declaration.
+
+Another, similar example involves calling member functions of a base
+class:
+
+@smallexample
+ template <typename T> struct Base @{
+ int f();
+ @};
+
+ template <typename T> struct Derived : Base<T> @{
+ int g() @{ return f(); @};
+ @};
+@end smallexample
+
+Again, the call to @code{f()} is not dependent on template arguments
+(there are no arguments that depend on the type @code{T}, and it is also
+not otherwise specified that the call should be in a dependent context).
+Thus a global declaration of such a function must be available, since
+the one in the base class is not visible until instantiation time. The
+compiler will consequently produce the following error message:
+
+@smallexample
+ x.cc: In member function `int Derived<T>::g()':
+ x.cc:6: error: there are no arguments to `f' that depend on a template
+ parameter, so a declaration of `f' must be available
+ x.cc:6: error: (if you use `-fpermissive', G++ will accept your code, but
+ allowing the use of an undeclared name is deprecated)
+@end smallexample
+
+To make the code valid either use @code{this->f()}, or
+@code{Base<T>::f()}. Using the @option{-fpermissive} flag will also let
+the compiler accept the code, by marking all function calls for which no
+declaration is visible at the time of definition of the template for
+later lookup at instantiation time, as if it were a dependent call.
+We do not recommend using @option{-fpermissive} to work around invalid
+code, and it will also only catch cases where functions in base classes
+are called, not where variables in base classes are used (as in the
+example above).
+
+Note that some compilers (including G++ versions prior to 3.4) get these
+examples wrong and accept above code without an error. Those compilers
+do not implement two-stage name lookup correctly.
+
+
+@node Temporaries
+@subsection Temporaries May Vanish Before You Expect
+
+@cindex temporaries, lifetime of
+@cindex portions of temporary objects, pointers to
+It is dangerous to use pointers or references to @emph{portions} of a
+temporary object. The compiler may very well delete the object before
+you expect it to, leaving a pointer to garbage. The most common place
+where this problem crops up is in classes like string classes,
+especially ones that define a conversion function to type @code{char *}
+or @code{const char *}---which is one reason why the standard
+@code{string} class requires you to call the @code{c_str} member
+function. However, any class that returns a pointer to some internal
+structure is potentially subject to this problem.
+
+For example, a program may use a function @code{strfunc} that returns
+@code{string} objects, and another function @code{charfunc} that
+operates on pointers to @code{char}:
+
+@smallexample
+string strfunc ();
+void charfunc (const char *);
+
+void
+f ()
+@{
+ const char *p = strfunc().c_str();
+ @dots{}
+ charfunc (p);
+ @dots{}
+ charfunc (p);
+@}
+@end smallexample
+
+@noindent
+In this situation, it may seem reasonable to save a pointer to the C
+string returned by the @code{c_str} member function and use that rather
+than call @code{c_str} repeatedly. However, the temporary string
+created by the call to @code{strfunc} is destroyed after @code{p} is
+initialized, at which point @code{p} is left pointing to freed memory.
+
+Code like this may run successfully under some other compilers,
+particularly obsolete cfront-based compilers that delete temporaries
+along with normal local variables. However, the GNU C++ behavior is
+standard-conforming, so if your program depends on late destruction of
+temporaries it is not portable.
+
+The safe way to write such code is to give the temporary a name, which
+forces it to remain until the end of the scope of the name. For
+example:
+
+@smallexample
+const string& tmp = strfunc ();
+charfunc (tmp.c_str ());
+@end smallexample
+
+@node Copy Assignment
+@subsection Implicit Copy-Assignment for Virtual Bases
+
+When a base class is virtual, only one subobject of the base class
+belongs to each full object. Also, the constructors and destructors are
+invoked only once, and called from the most-derived class. However, such
+objects behave unspecified when being assigned. For example:
+
+@smallexample
+struct Base@{
+ char *name;
+ Base(const char *n) : name(strdup(n))@{@}
+ Base& operator= (const Base& other)@{
+ free (name);
+ name = strdup (other.name);
+ return *this;
+ @}
+@};
+
+struct A:virtual Base@{
+ int val;
+ A():Base("A")@{@}
+@};
+
+struct B:virtual Base@{
+ int bval;
+ B():Base("B")@{@}
+@};
+
+struct Derived:public A, public B@{
+ Derived():Base("Derived")@{@}
+@};
+
+void func(Derived &d1, Derived &d2)
+@{
+ d1 = d2;
+@}
+@end smallexample
+
+The C++ standard specifies that @samp{Base::Base} is only called once
+when constructing or copy-constructing a Derived object. It is
+unspecified whether @samp{Base::operator=} is called more than once when
+the implicit copy-assignment for Derived objects is invoked (as it is
+inside @samp{func} in the example).
+
+G++ implements the ``intuitive'' algorithm for copy-assignment: assign all
+direct bases, then assign all members. In that algorithm, the virtual
+base subobject can be encountered more than once. In the example, copying
+proceeds in the following order: @samp{name} (via @code{strdup}),
+@samp{val}, @samp{name} again, and @samp{bval}.
+
+If application code relies on copy-assignment, a user-defined
+copy-assignment operator removes any uncertainties. With such an
+operator, the application can define whether and how the virtual base
+subobject is assigned.
+
+@node Non-bugs
+@section Certain Changes We Don't Want to Make
+
+This section lists changes that people frequently request, but which
+we do not make because we think GCC is better without them.
+
+@itemize @bullet
+@item
+Checking the number and type of arguments to a function which has an
+old-fashioned definition and no prototype.
+
+Such a feature would work only occasionally---only for calls that appear
+in the same file as the called function, following the definition. The
+only way to check all calls reliably is to add a prototype for the
+function. But adding a prototype eliminates the motivation for this
+feature. So the feature is not worthwhile.
+
+@item
+Warning about using an expression whose type is signed as a shift count.
+
+Shift count operands are probably signed more often than unsigned.
+Warning about this would cause far more annoyance than good.
+
+@item
+Warning about assigning a signed value to an unsigned variable.
+
+Such assignments must be very common; warning about them would cause
+more annoyance than good.
+
+@item
+Warning when a non-void function value is ignored.
+
+C contains many standard functions that return a value that most
+programs choose to ignore. One obvious example is @code{printf}.
+Warning about this practice only leads the defensive programmer to
+clutter programs with dozens of casts to @code{void}. Such casts are
+required so frequently that they become visual noise. Writing those
+casts becomes so automatic that they no longer convey useful
+information about the intentions of the programmer. For functions
+where the return value should never be ignored, use the
+@code{warn_unused_result} function attribute (@pxref{Function
+Attributes}).
+
+@item
+@opindex fshort-enums
+Making @option{-fshort-enums} the default.
+
+This would cause storage layout to be incompatible with most other C
+compilers. And it doesn't seem very important, given that you can get
+the same result in other ways. The case where it matters most is when
+the enumeration-valued object is inside a structure, and in that case
+you can specify a field width explicitly.
+
+@item
+Making bit-fields unsigned by default on particular machines where ``the
+ABI standard'' says to do so.
+
+The ISO C standard leaves it up to the implementation whether a bit-field
+declared plain @code{int} is signed or not. This in effect creates two
+alternative dialects of C@.
+
+@opindex fsigned-bitfields
+@opindex funsigned-bitfields
+The GNU C compiler supports both dialects; you can specify the signed
+dialect with @option{-fsigned-bitfields} and the unsigned dialect with
+@option{-funsigned-bitfields}. However, this leaves open the question of
+which dialect to use by default.
+
+Currently, the preferred dialect makes plain bit-fields signed, because
+this is simplest. Since @code{int} is the same as @code{signed int} in
+every other context, it is cleanest for them to be the same in bit-fields
+as well.
+
+Some computer manufacturers have published Application Binary Interface
+standards which specify that plain bit-fields should be unsigned. It is
+a mistake, however, to say anything about this issue in an ABI@. This is
+because the handling of plain bit-fields distinguishes two dialects of C@.
+Both dialects are meaningful on every type of machine. Whether a
+particular object file was compiled using signed bit-fields or unsigned
+is of no concern to other object files, even if they access the same
+bit-fields in the same data structures.
+
+A given program is written in one or the other of these two dialects.
+The program stands a chance to work on most any machine if it is
+compiled with the proper dialect. It is unlikely to work at all if
+compiled with the wrong dialect.
+
+Many users appreciate the GNU C compiler because it provides an
+environment that is uniform across machines. These users would be
+inconvenienced if the compiler treated plain bit-fields differently on
+certain machines.
+
+Occasionally users write programs intended only for a particular machine
+type. On these occasions, the users would benefit if the GNU C compiler
+were to support by default the same dialect as the other compilers on
+that machine. But such applications are rare. And users writing a
+program to run on more than one type of machine cannot possibly benefit
+from this kind of compatibility.
+
+This is why GCC does and will treat plain bit-fields in the same
+fashion on all types of machines (by default).
+
+There are some arguments for making bit-fields unsigned by default on all
+machines. If, for example, this becomes a universal de facto standard,
+it would make sense for GCC to go along with it. This is something
+to be considered in the future.
+
+(Of course, users strongly concerned about portability should indicate
+explicitly in each bit-field whether it is signed or not. In this way,
+they write programs which have the same meaning in both C dialects.)
+
+@item
+@opindex ansi
+@opindex std
+Undefining @code{__STDC__} when @option{-ansi} is not used.
+
+Currently, GCC defines @code{__STDC__} unconditionally. This provides
+good results in practice.
+
+Programmers normally use conditionals on @code{__STDC__} to ask whether
+it is safe to use certain features of ISO C, such as function
+prototypes or ISO token concatenation. Since plain @command{gcc} supports
+all the features of ISO C, the correct answer to these questions is
+``yes''.
+
+Some users try to use @code{__STDC__} to check for the availability of
+certain library facilities. This is actually incorrect usage in an ISO
+C program, because the ISO C standard says that a conforming
+freestanding implementation should define @code{__STDC__} even though it
+does not have the library facilities. @samp{gcc -ansi -pedantic} is a
+conforming freestanding implementation, and it is therefore required to
+define @code{__STDC__}, even though it does not come with an ISO C
+library.
+
+Sometimes people say that defining @code{__STDC__} in a compiler that
+does not completely conform to the ISO C standard somehow violates the
+standard. This is illogical. The standard is a standard for compilers
+that claim to support ISO C, such as @samp{gcc -ansi}---not for other
+compilers such as plain @command{gcc}. Whatever the ISO C standard says
+is relevant to the design of plain @command{gcc} without @option{-ansi} only
+for pragmatic reasons, not as a requirement.
+
+GCC normally defines @code{__STDC__} to be 1, and in addition
+defines @code{__STRICT_ANSI__} if you specify the @option{-ansi} option,
+or a @option{-std} option for strict conformance to some version of ISO C@.
+On some hosts, system include files use a different convention, where
+@code{__STDC__} is normally 0, but is 1 if the user specifies strict
+conformance to the C Standard. GCC follows the host convention when
+processing system include files, but when processing user files it follows
+the usual GNU C convention.
+
+@item
+Undefining @code{__STDC__} in C++.
+
+Programs written to compile with C++-to-C translators get the
+value of @code{__STDC__} that goes with the C compiler that is
+subsequently used. These programs must test @code{__STDC__}
+to determine what kind of C preprocessor that compiler uses:
+whether they should concatenate tokens in the ISO C fashion
+or in the traditional fashion.
+
+These programs work properly with GNU C++ if @code{__STDC__} is defined.
+They would not work otherwise.
+
+In addition, many header files are written to provide prototypes in ISO
+C but not in traditional C@. Many of these header files can work without
+change in C++ provided @code{__STDC__} is defined. If @code{__STDC__}
+is not defined, they will all fail, and will all need to be changed to
+test explicitly for C++ as well.
+
+@item
+Deleting ``empty'' loops.
+
+Historically, GCC has not deleted ``empty'' loops under the
+assumption that the most likely reason you would put one in a program is
+to have a delay, so deleting them will not make real programs run any
+faster.
+
+However, the rationale here is that optimization of a nonempty loop
+cannot produce an empty one. This held for carefully written C compiled
+with less powerful optimizers but is not always the case for carefully
+written C++ or with more powerful optimizers.
+Thus GCC will remove operations from loops whenever it can determine
+those operations are not externally visible (apart from the time taken
+to execute them, of course). In case the loop can be proved to be finite,
+GCC will also remove the loop itself.
+
+Be aware of this when performing timing tests, for instance the
+following loop can be completely removed, provided
+@code{some_expression} can provably not change any global state.
+
+@smallexample
+@{
+ int sum = 0;
+ int ix;
+
+ for (ix = 0; ix != 10000; ix++)
+ sum += some_expression;
+@}
+@end smallexample
+
+Even though @code{sum} is accumulated in the loop, no use is made of
+that summation, so the accumulation can be removed.
+
+@item
+Making side effects happen in the same order as in some other compiler.
+
+@cindex side effects, order of evaluation
+@cindex order of evaluation, side effects
+It is never safe to depend on the order of evaluation of side effects.
+For example, a function call like this may very well behave differently
+from one compiler to another:
+
+@smallexample
+void func (int, int);
+
+int i = 2;
+func (i++, i++);
+@end smallexample
+
+There is no guarantee (in either the C or the C++ standard language
+definitions) that the increments will be evaluated in any particular
+order. Either increment might happen first. @code{func} might get the
+arguments @samp{2, 3}, or it might get @samp{3, 2}, or even @samp{2, 2}.
+
+@item
+Making certain warnings into errors by default.
+
+Some ISO C testsuites report failure when the compiler does not produce
+an error message for a certain program.
+
+@opindex pedantic-errors
+ISO C requires a ``diagnostic'' message for certain kinds of invalid
+programs, but a warning is defined by GCC to count as a diagnostic. If
+GCC produces a warning but not an error, that is correct ISO C support.
+If testsuites call this ``failure'', they should be run with the GCC
+option @option{-pedantic-errors}, which will turn these warnings into
+errors.
+
+@end itemize
+
+@node Warnings and Errors
+@section Warning Messages and Error Messages
+
+@cindex error messages
+@cindex warnings vs errors
+@cindex messages, warning and error
+The GNU compiler can produce two kinds of diagnostics: errors and
+warnings. Each kind has a different purpose:
+
+@itemize @w{}
+@item
+@dfn{Errors} report problems that make it impossible to compile your
+program. GCC reports errors with the source file name and line
+number where the problem is apparent.
+
+@item
+@dfn{Warnings} report other unusual conditions in your code that
+@emph{may} indicate a problem, although compilation can (and does)
+proceed. Warning messages also report the source file name and line
+number, but include the text @samp{warning:} to distinguish them
+from error messages.
+@end itemize
+
+Warnings may indicate danger points where you should check to make sure
+that your program really does what you intend; or the use of obsolete
+features; or the use of nonstandard features of GNU C or C++. Many
+warnings are issued only if you ask for them, with one of the @option{-W}
+options (for instance, @option{-Wall} requests a variety of useful
+warnings).
+
+@opindex pedantic
+@opindex pedantic-errors
+GCC always tries to compile your program if possible; it never
+gratuitously rejects a program whose meaning is clear merely because
+(for instance) it fails to conform to a standard. In some cases,
+however, the C and C++ standards specify that certain extensions are
+forbidden, and a diagnostic @emph{must} be issued by a conforming
+compiler. The @option{-pedantic} option tells GCC to issue warnings in
+such cases; @option{-pedantic-errors} says to make them errors instead.
+This does not mean that @emph{all} non-ISO constructs get warnings
+or errors.
+
+@xref{Warning Options,,Options to Request or Suppress Warnings}, for
+more detail on these and related command-line options.
--- /dev/null
+@c Copyright (C) 2018-2022 Free Software Foundation, Inc.
+@c Free Software Foundation, Inc.
+@c This is part of the GCC manual.
+@c For copying conditions, see the file gcc.texi.
+
+@node User Experience Guidelines
+@chapter User Experience Guidelines
+@cindex user experience guidelines
+@cindex guidelines, user experience
+
+To borrow a slogan from
+@uref{https://elm-lang.org/news/compilers-as-assistants, Elm},
+
+@quotation
+@strong{Compilers should be assistants, not adversaries.} A compiler should
+not just detect bugs, it should then help you understand why there is a bug.
+It should not berate you in a robot voice, it should give you specific hints
+that help you write better code. Ultimately, a compiler should make
+programming faster and more fun!
+@author Evan Czaplicki
+@end quotation
+
+This chapter provides guidelines on how to implement diagnostics and
+command-line options in ways that we hope achieve the above ideal.
+
+@menu
+* Guidelines for Diagnostics:: How to implement diagnostics.
+* Guidelines for Options:: Guidelines for command-line options.
+@end menu
+
+
+@node Guidelines for Diagnostics
+@section Guidelines for Diagnostics
+@cindex guidelines for diagnostics
+@cindex diagnostics, guidelines for
+
+@subsection Talk in terms of the user's code
+
+Diagnostics should be worded in terms of the user's source code, and the
+source language, rather than GCC's own implementation details.
+
+@subsection Diagnostics are actionable
+@cindex diagnostics, actionable
+
+A good diagnostic is @dfn{actionable}: it should assist the user in
+taking action.
+
+Consider what an end user will want to do when encountering a diagnostic.
+
+Given an error, an end user will think: ``How do I fix this?''
+
+Given a warning, an end user will think:
+
+@itemize @bullet
+@item
+``Is this a real problem?''
+@item
+``Do I care?''
+@item
+if they decide it's genuine: ``How do I fix this?''
+@end itemize
+
+A good diagnostic provides pertinent information to allow the user to
+easily answer the above questions.
+
+@subsection The user's attention is important
+
+A perfect compiler would issue a warning on every aspect of the user's
+source code that ought to be fixed, and issue no other warnings.
+Naturally, this ideal is impossible to achieve.
+
+@cindex signal-to-noise ratio (metaphorical usage for diagnostics)
+@cindex diagnostics, false positive
+@cindex diagnostics, true positive
+@cindex false positive
+@cindex true positive
+
+Warnings should have a good @dfn{signal-to-noise ratio}: we should have few
+@dfn{false positives} (falsely issuing a warning when no warning is
+warranted) and few @dfn{false negatives} (failing to issue a warning when
+one @emph{is} justified).
+
+Note that a false positive can mean, in practice, a warning that the
+user doesn't agree with. Ideally a diagnostic should contain enough
+information to allow the user to make an informed choice about whether
+they should care (and how to fix it), but a balance must be drawn against
+overloading the user with irrelevant data.
+
+@subsection Sometimes the user didn't write the code
+
+GCC is typically used in two different ways:
+
+@itemize @bullet
+@item
+Semi-interactive usage: GCC is used as a development tool when the user
+is writing code, as the ``compile'' part of the ``edit-compile-debug''
+cycle. The user is actively hacking on the code themself (perhaps a
+project they wrote, or someone else's), where they just made a change
+to the code and want to see what happens, and to be warned about
+mistakes.
+
+@item
+Batch rebuilds: where the user is recompiling one or more existing
+packages, and GCC is a detail that's being invoked by various build
+scripts. Examples include a user trying to bring up an operating system
+consisting of hundreds of packages on a new CPU architecture, where the
+packages were written by many different people, or simply rebuilding
+packages after a dependency changed, where the user is hoping
+``nothing breaks'', since they are unfamiliar with the code.
+@end itemize
+
+Keep both of these styles of usage in mind when implementing diagnostics.
+
+@subsection Precision of Wording
+
+Provide the user with details that allow them to identify what the
+problem is. For example, the vaguely-worded message:
+
+@smallexample
+demo.c:1:1: warning: 'noinline' attribute ignored [-Wattributes]
+ 1 | int foo __attribute__((noinline));
+ | ^~~
+@end smallexample
+
+@noindent
+doesn't tell the user why the attribute was ignored, or what kind of
+entity the compiler thought the attribute was being applied to (the
+source location for the diagnostic is also poor;
+@pxref{input_location_example,,discussion of @code{input_location}}).
+A better message would be:
+
+@smallexample
+demo.c:1:24: warning: attribute 'noinline' on variable 'foo' was
+ ignored [-Wattributes]
+ 1 | int foo __attribute__((noinline));
+ | ~~~ ~~~~~~~~~~~~~~~^~~~~~~~~
+demo.c:1:24: note: attribute 'noinline' is only applicable to functions
+@end smallexample
+
+@noindent
+which spells out the missing information (and fixes the location
+information, as discussed below).
+
+The above example uses a note to avoid a combinatorial explosion of possible
+messages.
+
+@subsection Try the diagnostic on real-world code
+
+It's worth testing a new warning on many instances of real-world code,
+written by different people, and seeing what it complains about, and
+what it doesn't complain about.
+
+This may suggest heuristics that silence common false positives.
+
+It may also suggest ways to improve the precision of the message.
+
+@subsection Make mismatches clear
+
+Many diagnostics relate to a mismatch between two different places in the
+user's source code. Examples include:
+@itemize @bullet
+ @item
+ a type mismatch, where the type at a usage site does not match the type
+ at a declaration
+
+ @item
+ the argument count at a call site does not match the parameter count
+ at the declaration
+
+ @item
+ something is erroneously duplicated (e.g.@: an error, due to breaking a
+ uniqueness requirement, or a warning, if it's suggestive of a bug)
+
+ @item
+ an ``opened'' syntactic construct (such as an open-parenthesis) is not
+ closed
+
+ @c TODO: more examples?
+@end itemize
+
+In each case, the diagnostic should indicate @strong{both} pertinent
+locations (so that the user can easily see the problem and how to fix it).
+
+The standard way to do this is with a note (via @code{inform}). For
+example:
+
+@smallexample
+ auto_diagnostic_group d;
+ if (warning_at (loc, OPT_Wduplicated_cond,
+ "duplicated %<if%> condition"))
+ inform (EXPR_LOCATION (t), "previously used here");
+@end smallexample
+
+@noindent
+which leads to:
+
+@smallexample
+demo.c: In function 'test':
+demo.c:5:17: warning: duplicated 'if' condition [-Wduplicated-cond]
+ 5 | else if (flag > 3)
+ | ~~~~~^~~
+demo.c:3:12: note: previously used here
+ 3 | if (flag > 3)
+ | ~~~~~^~~
+@end smallexample
+
+@noindent
+The @code{inform} call should be guarded by the return value from the
+@code{warning_at} call so that the note isn't emitted when the warning
+is suppressed.
+
+For cases involving punctuation where the locations might be near
+each other, they can be conditionally consolidated via
+@code{gcc_rich_location::add_location_if_nearby}:
+
+@smallexample
+ auto_diagnostic_group d;
+ gcc_rich_location richloc (primary_loc);
+ bool added secondary = richloc.add_location_if_nearby (secondary_loc);
+ error_at (&richloc, "main message");
+ if (!added secondary)
+ inform (secondary_loc, "message for secondary");
+@end smallexample
+
+@noindent
+This will emit either one diagnostic with two locations:
+@smallexample
+ demo.c:42:10: error: main message
+ (foo)
+ ~ ^
+@end smallexample
+
+@noindent
+or two diagnostics:
+
+@smallexample
+ demo.c:42:4: error: main message
+ foo)
+ ^
+ demo.c:40:2: note: message for secondary
+ (
+ ^
+@end smallexample
+
+@subsection Location Information
+@cindex diagnostics, locations
+@cindex location information
+@cindex source code, location information
+@cindex caret
+
+GCC's @code{location_t} type can support both ordinary locations,
+and locations relating to a macro expansion.
+
+As of GCC 6, ordinary locations changed from supporting just a
+point in the user's source code to supporting three points: the
+@dfn{caret} location, plus a start and a finish:
+
+@smallexample
+ a = foo && bar;
+ ~~~~^~~~~~
+ | | |
+ | | finish
+ | caret
+ start
+@end smallexample
+
+Tokens coming out of libcpp have locations of the form @code{caret == start},
+such as for @code{foo} here:
+
+@smallexample
+ a = foo && bar;
+ ^~~
+ | |
+ | finish
+ caret == start
+@end smallexample
+
+Compound expressions should be reported using the location of the
+expression as a whole, rather than just of one token within it.
+
+For example, in @code{-Wformat}, rather than underlining just the first
+token of a bad argument:
+
+@smallexample
+ printf("hello %i %s", (long)0, "world");
+ ~^ ~
+ %li
+@end smallexample
+
+@noindent
+the whole of the expression should be underlined, so that the user can
+easily identify what is being referred to:
+
+@smallexample
+ printf("hello %i %s", (long)0, "world");
+ ~^ ~~~~~~~
+ %li
+@end smallexample
+
+@c this was r251239
+
+Avoid using the @code{input_location} global, and the diagnostic functions
+that implicitly use it---use @code{error_at} and @code{warning_at} rather
+than @code{error} and @code{warning}, and provide the most appropriate
+@code{location_t} value available at that phase of the compilation. It's
+possible to supply secondary @code{location_t} values via
+@code{rich_location}.
+
+@noindent
+@anchor{input_location_example}
+For example, in the example of imprecise wording above, generating the
+diagnostic using @code{warning}:
+
+@smallexample
+ // BAD: implicitly uses @code{input_location}
+ warning (OPT_Wattributes, "%qE attribute ignored", name);
+@end smallexample
+
+@noindent
+leads to:
+
+@smallexample
+// BAD: uses @code{input_location}
+demo.c:1:1: warning: 'noinline' attribute ignored [-Wattributes]
+ 1 | int foo __attribute__((noinline));
+ | ^~~
+@end smallexample
+
+@noindent
+which thus happened to use the location of the @code{int} token, rather
+than that of the attribute. Using @code{warning_at} with the location of
+the attribute, providing the location of the declaration in question
+as a secondary location, and adding a note:
+
+@smallexample
+ auto_diagnostic_group d;
+ gcc_rich_location richloc (attrib_loc);
+ richloc.add_range (decl_loc);
+ if (warning_at (OPT_Wattributes, &richloc,
+ "attribute %qE on variable %qE was ignored", name))
+ inform (attrib_loc, "attribute %qE is only applicable to functions");
+@end smallexample
+
+@noindent
+would lead to:
+
+@smallexample
+// OK: use location of attribute, with a secondary location
+demo.c:1:24: warning: attribute 'noinline' on variable 'foo' was
+ ignored [-Wattributes]
+ 1 | int foo __attribute__((noinline));
+ | ~~~ ~~~~~~~~~~~~~~~^~~~~~~~~
+demo.c:1:24: note: attribute 'noinline' is only applicable to functions
+@end smallexample
+
+@c TODO labelling of ranges
+
+@subsection Coding Conventions
+
+See the @uref{https://gcc.gnu.org/codingconventions.html#Diagnostics,
+diagnostics section} of the GCC coding conventions.
+
+In the C++ front end, when comparing two types in a message, use @samp{%H}
+and @samp{%I} rather than @samp{%T}, as this allows the diagnostics
+subsystem to highlight differences between template-based types.
+For example, rather than using @samp{%qT}:
+
+@smallexample
+ // BAD: a pair of %qT used in C++ front end for type comparison
+ error_at (loc, "could not convert %qE from %qT to %qT", expr,
+ TREE_TYPE (expr), type);
+@end smallexample
+
+@noindent
+which could lead to:
+
+@smallexample
+error: could not convert 'map<int, double>()' from 'map<int,double>'
+ to 'map<int,int>'
+@end smallexample
+
+@noindent
+using @samp{%H} and @samp{%I} (via @samp{%qH} and @samp{%qI}):
+
+@smallexample
+ // OK: compare types in C++ front end via %qH and %qI
+ error_at (loc, "could not convert %qE from %qH to %qI", expr,
+ TREE_TYPE (expr), type);
+@end smallexample
+
+@noindent
+allows the above output to be simplified to:
+
+@smallexample
+error: could not convert 'map<int, double>()' from 'map<[...],double>'
+ to 'map<[...],int>'
+@end smallexample
+
+@noindent
+where the @code{double} and @code{int} are colorized to highlight them.
+
+@c %H and %I were added in r248698.
+
+@subsection Group logically-related diagnostics
+
+Use @code{auto_diagnostic_group} when issuing multiple related
+diagnostics (seen in various examples on this page). This informs the
+diagnostic subsystem that all diagnostics issued within the lifetime
+of the @code{auto_diagnostic_group} are related. For example,
+@option{-fdiagnostics-format=json} will treat the first diagnostic
+emitted within the group as a top-level diagnostic, and all subsequent
+diagnostics within the group as its children.
+
+@subsection Quoting
+Text should be quoted by either using the @samp{q} modifier in a directive
+such as @samp{%qE}, or by enclosing the quoted text in a pair of @samp{%<}
+and @samp{%>} directives, and never by using explicit quote characters.
+The directives handle the appropriate quote characters for each language
+and apply the correct color or highlighting.
+
+The following elements should be quoted in GCC diagnostics:
+
+@itemize @bullet
+@item
+Language keywords.
+@item
+Tokens.
+@item
+Boolean, numerical, character, and string constants that appear in the
+source code.
+@item
+Identifiers, including function, macro, type, and variable names.
+@end itemize
+
+Other elements such as numbers that do not refer to numeric constants that
+appear in the source code should not be quoted. For example, in the message:
+
+@smallexample
+argument %d of %qE must be a pointer type
+@end smallexample
+
+@noindent
+since the argument number does not refer to a numerical constant in the
+source code it should not be quoted.
+
+@subsection Spelling and Terminology
+
+See the @uref{https://gcc.gnu.org/codingconventions.html#Spelling
+Spelling, terminology and markup} section of the GCC coding conventions.
+
+@subsection Fix-it hints
+@cindex fix-it hints
+@cindex diagnostics guidelines, fix-it hints
+
+GCC's diagnostic subsystem can emit @dfn{fix-it hints}: small suggested
+edits to the user's source code.
+
+They are printed by default underneath the code in question. They
+can also be viewed via @option{-fdiagnostics-generate-patch} and
+@option{-fdiagnostics-parseable-fixits}. With the latter, an IDE
+ought to be able to offer to automatically apply the suggested fix.
+
+Fix-it hints contain code fragments, and thus they should not be marked
+for translation.
+
+Fix-it hints can be added to a diagnostic by using a @code{rich_location}
+rather than a @code{location_t} - the fix-it hints are added to the
+@code{rich_location} using one of the various @code{add_fixit} member
+functions of @code{rich_location}. They are documented with
+@code{rich_location} in @file{libcpp/line-map.h}.
+It's easiest to use the @code{gcc_rich_location} subclass of
+@code{rich_location} found in @file{gcc-rich-location.h}, as this
+implicitly supplies the @code{line_table} variable.
+
+For example:
+
+@smallexample
+ if (const char *suggestion = hint.suggestion ())
+ @{
+ gcc_rich_location richloc (location);
+ richloc.add_fixit_replace (suggestion);
+ error_at (&richloc,
+ "%qE does not name a type; did you mean %qs?",
+ id, suggestion);
+ @}
+@end smallexample
+
+@noindent
+which can lead to:
+
+@smallexample
+spellcheck-typenames.C:73:1: error: 'singed' does not name a type; did
+ you mean 'signed'?
+ 73 | singed char ch;
+ | ^~~~~~
+ | signed
+@end smallexample
+
+Non-trivial edits can be built up by adding multiple fix-it hints to one
+@code{rich_location}. It's best to express the edits in terms of the
+locations of individual tokens. Various handy functions for adding
+fix-it hints for idiomatic C and C++ can be seen in
+@file{gcc-rich-location.h}.
+
+@subsubsection Fix-it hints should work
+
+When implementing a fix-it hint, please verify that the suggested edit
+leads to fixed, compilable code. (Unfortunately, this currently must be
+done by hand using @option{-fdiagnostics-generate-patch}. It would be
+good to have an automated way of verifying that fix-it hints actually fix
+the code).
+
+For example, a ``gotcha'' here is to forget to add a space when adding a
+missing reserved word. Consider a C++ fix-it hint that adds
+@code{typename} in front of a template declaration. A naive way to
+implement this might be:
+
+@smallexample
+gcc_rich_location richloc (loc);
+// BAD: insertion is missing a trailing space
+richloc.add_fixit_insert_before ("typename");
+error_at (&richloc, "need %<typename%> before %<%T::%E%> because "
+ "%qT is a dependent scope",
+ parser->scope, id, parser->scope);
+@end smallexample
+
+@noindent
+When applied to the code, this might lead to:
+
+@smallexample
+T::type x;
+@end smallexample
+
+@noindent
+being ``corrected'' to:
+
+@smallexample
+typenameT::type x;
+@end smallexample
+
+@noindent
+In this case, the correct thing to do is to add a trailing space after
+@code{typename}:
+
+@smallexample
+gcc_rich_location richloc (loc);
+// OK: note that here we have a trailing space
+richloc.add_fixit_insert_before ("typename ");
+error_at (&richloc, "need %<typename%> before %<%T::%E%> because "
+ "%qT is a dependent scope",
+ parser->scope, id, parser->scope);
+@end smallexample
+
+@noindent
+leading to this corrected code:
+
+@smallexample
+typename T::type x;
+@end smallexample
+
+@subsubsection Express deletion in terms of deletion, not replacement
+
+It's best to express deletion suggestions in terms of deletion fix-it
+hints, rather than replacement fix-it hints. For example, consider this:
+
+@smallexample
+ auto_diagnostic_group d;
+ gcc_rich_location richloc (location_of (retval));
+ tree name = DECL_NAME (arg);
+ richloc.add_fixit_replace (IDENTIFIER_POINTER (name));
+ warning_at (&richloc, OPT_Wredundant_move,
+ "redundant move in return statement");
+@end smallexample
+
+@noindent
+which is intended to e.g.@: replace a @code{std::move} with the underlying
+value:
+
+@smallexample
+ return std::move (retval);
+ ~~~~~~~~~~^~~~~~~~
+ retval
+@end smallexample
+
+@noindent
+where the change has been expressed as replacement, replacing
+with the name of the declaration.
+This works for simple cases, but consider this case:
+
+@smallexample
+#ifdef SOME_CONFIG_FLAG
+# define CONFIGURY_GLOBAL global_a
+#else
+# define CONFIGURY_GLOBAL global_b
+#endif
+
+int fn ()
+@{
+ return std::move (CONFIGURY_GLOBAL /* some comment */);
+@}
+@end smallexample
+
+@noindent
+The above implementation erroneously strips out the macro and the
+comment in the fix-it hint:
+
+@smallexample
+ return std::move (CONFIGURY_GLOBAL /* some comment */);
+ ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ global_a
+@end smallexample
+
+@noindent
+and thus this resulting code:
+
+@smallexample
+ return global_a;
+@end smallexample
+
+@noindent
+It's better to do deletions in terms of deletions; deleting the
+@code{std::move (} and the trailing close-paren, leading to
+this:
+
+@smallexample
+ return std::move (CONFIGURY_GLOBAL /* some comment */);
+ ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CONFIGURY_GLOBAL /* some comment */
+@end smallexample
+
+@noindent
+and thus this result:
+
+@smallexample
+ return CONFIGURY_GLOBAL /* some comment */;
+@end smallexample
+
+@noindent
+Unfortunately, the pertinent @code{location_t} values are not always
+available.
+
+@c the above was https://gcc.gnu.org/ml/gcc-patches/2018-08/msg01474.html
+
+@subsubsection Multiple suggestions
+
+In the rare cases where you need to suggest more than one mutually
+exclusive solution to a problem, this can be done by emitting
+multiple notes and calling
+@code{rich_location::fixits_cannot_be_auto_applied} on each note's
+@code{rich_location}. If this is called, then the fix-it hints in
+the @code{rich_location} will be printed, but will not be added to
+generated patches.
+
+
+@node Guidelines for Options
+@section Guidelines for Options
+@cindex command-line options, guidelines for
+@cindex options, guidelines for
+@cindex guidelines for options
+
+@c TODO
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@c %**start of header
+@setfilename gfc-internals.info
+@set copyrights-gfortran 2007-2022
+
+@include gcc-common.texi
+
+@synindex tp cp
+
+@settitle GNU Fortran Compiler Internals
+
+@c %**end of header
+
+@c Use with @@smallbook.
+
+@c %** start of document
+
+@c Cause even numbered pages to be printed on the left hand side of
+@c the page and odd numbered pages to be printed on the right hand
+@c side of the page. Using this, you can print on both sides of a
+@c sheet of paper and have the text on the same part of the sheet.
+
+@c The text on right hand pages is pushed towards the right hand
+@c margin and the text on left hand pages is pushed toward the left
+@c hand margin.
+@c (To provide the reverse effect, set bindingoffset to -0.75in.)
+
+@c @tex
+@c \global\bindingoffset=0.75in
+@c \global\normaloffset =0.75in
+@c @end tex
+
+@copying
+Copyright @copyright{} @value{copyrights-gfortran} Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``Funding Free Software'', the Front-Cover
+Texts being (a) (see below), and with the Back-Cover Texts being (b)
+(see below). A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@end copying
+
+@ifinfo
+@dircategory Software development
+@direntry
+* gfortran: (gfortran). The GNU Fortran Compiler.
+@end direntry
+This file documents the internals of the GNU Fortran
+compiler, (@command{gfortran}).
+
+Published by the Free Software Foundation
+51 Franklin Street, Fifth Floor
+Boston, MA 02110-1301 USA
+
+@insertcopying
+@end ifinfo
+
+
+@setchapternewpage odd
+@titlepage
+@title GNU Fortran Internals
+@versionsubtitle
+@author The @t{gfortran} team
+@page
+@vskip 0pt plus 1filll
+Published by the Free Software Foundation@*
+51 Franklin Street, Fifth Floor@*
+Boston, MA 02110-1301, USA@*
+@c Last printed ??ber, 19??.@*
+@c Printed copies are available for $? each.@*
+@c ISBN ???
+@sp 1
+@insertcopying
+@end titlepage
+
+@summarycontents
+@contents
+
+@page
+
+@c ---------------------------------------------------------------------
+@c TexInfo table of contents.
+@c ---------------------------------------------------------------------
+
+@ifnottex
+@node Top
+@top Introduction
+@cindex Introduction
+
+This manual documents the internals of @command{gfortran},
+the GNU Fortran compiler.
+
+@ifset DEVELOPMENT
+@emph{Warning:} This document, and the compiler it describes, are still
+under development. While efforts are made to keep it up-to-date, it might
+not accurately reflect the status of the most recent GNU Fortran compiler.
+@end ifset
+
+@comment
+@comment When you add a new menu item, please keep the right hand
+@comment aligned to the same column. Do not use tabs. This provides
+@comment better formatting.
+@comment
+@menu
+* Introduction:: About this manual.
+* User Interface:: Code that Interacts with the User.
+* Frontend Data Structures::
+ Data structures used by the frontend
+* Object Orientation:: Internals of Fortran 2003 OOP features.
+* Translating to GENERIC::
+ Generating the intermediate language for later stages.
+* LibGFortran:: The LibGFortran Runtime Library.
+* GNU Free Documentation License::
+ How you can copy and share this manual.
+* Index:: Index of this documentation.
+@end menu
+@end ifnottex
+
+@c ---------------------------------------------------------------------
+@c Introduction
+@c ---------------------------------------------------------------------
+
+@node Introduction
+@chapter Introduction
+
+@c The following duplicates the text on the TexInfo table of contents.
+@iftex
+This manual documents the internals of @command{gfortran}, the GNU Fortran
+compiler.
+
+@ifset DEVELOPMENT
+@emph{Warning:} This document, and the compiler it describes, are still
+under development. While efforts are made to keep it up-to-date, it
+might not accurately reflect the status of the most recent GNU Fortran
+compiler.
+@end ifset
+@end iftex
+
+At present, this manual is very much a work in progress, containing
+miscellaneous notes about the internals of the compiler. It is hoped
+that at some point in the future it will become a reasonably complete
+guide; in the interim, GNU Fortran developers are strongly encouraged to
+contribute to it as a way of keeping notes while working on the
+compiler.
+
+
+@c ---------------------------------------------------------------------
+@c Code that Interacts with the User
+@c ---------------------------------------------------------------------
+
+@node User Interface
+@chapter Code that Interacts with the User
+
+@menu
+* Command-Line Options:: Command-Line Options.
+* Error Handling:: Error Handling.
+@end menu
+
+
+@c ---------------------------------------------------------------------
+@c Command-Line Options
+@c ---------------------------------------------------------------------
+
+@node Command-Line Options
+@section Command-Line Options
+
+Command-line options for @command{gfortran} involve four interrelated
+pieces within the Fortran compiler code.
+
+The relevant command-line flag is defined in @file{lang.opt}, according
+to the documentation in @ref{Options,, Options, gccint, GNU Compiler
+Collection Internals}. This is then processed by the overall GCC
+machinery to create the code that enables @command{gfortran} and
+@command{gcc} to recognize the option in the command-line arguments and
+call the relevant handler function.
+
+This generated code calls the @code{gfc_handle_option} code in
+@file{options.cc} with an enumerator variable indicating which option is
+to be processed, and the relevant integer or string values associated
+with that option flag. Typically, @code{gfc_handle_option} uses these
+arguments to set global flags which record the option states.
+
+The global flags that record the option states are stored in the
+@code{gfc_option_t} struct, which is defined in @file{gfortran.h}.
+Before the options are processed, initial values for these flags are set
+in @code{gfc_init_option} in @file{options.cc}; these become the default
+values for the options.
+
+
+
+@c ---------------------------------------------------------------------
+@c Error Handling
+@c ---------------------------------------------------------------------
+
+@node Error Handling
+@section Error Handling
+
+The GNU Fortran compiler's parser operates by testing each piece of
+source code against a variety of matchers. In some cases, if these
+matchers do not match the source code, they will store an error message
+in a buffer. If the parser later finds a matcher that does correctly
+match the source code, then the buffered error is discarded. However,
+if the parser cannot find a match, then the buffered error message is
+reported to the user. This enables the compiler to provide more
+meaningful error messages even in the many cases where (erroneous)
+Fortran syntax is ambiguous due to things like the absence of reserved
+keywords.
+
+As an example of how this works, consider the following line:
+@smallexample
+IF = 3
+@end smallexample
+Hypothetically, this may get passed to the matcher for an @code{IF}
+statement. Since this could plausibly be an erroneous @code{IF}
+statement, the matcher will buffer an error message reporting the
+absence of an expected @samp{(} following an @code{IF}. Since no
+matchers reported an error-free match, however, the parser will also try
+matching this against a variable assignment. When @code{IF} is a valid
+variable, this will be parsed as an assignment statement, and the error
+discarded. However, when @code{IF} is not a valid variable, this
+buffered error message will be reported to the user.
+
+The error handling code is implemented in @file{error.cc}. Errors are
+normally entered into the buffer with the @code{gfc_error} function.
+Warnings go through a similar buffering process, and are entered into
+the buffer with @code{gfc_warning}. There is also a special-purpose
+function, @code{gfc_notify_std}, for things which have an error/warning
+status that depends on the currently-selected language standard.
+
+The @code{gfc_error_check} function checks the buffer for errors,
+reports the error message to the user if one exists, clears the buffer,
+and returns a flag to the user indicating whether or not an error
+existed. To check the state of the buffer without changing its state or
+reporting the errors, the @code{gfc_error_flag_test} function can be
+used. The @code{gfc_clear_error} function will clear out any errors in
+the buffer, without reporting them. The @code{gfc_warning_check} and
+@code{gfc_clear_warning} functions provide equivalent functionality for
+the warning buffer.
+
+Only one error and one warning can be in the buffers at a time, and
+buffering another will overwrite the existing one. In cases where one
+may wish to work on a smaller piece of source code without disturbing an
+existing error state, the @code{gfc_push_error}, @code{gfc_pop_error},
+and @code{gfc_free_error} mechanism exists to implement a stack for the
+error buffer.
+
+For cases where an error or warning should be reported immediately
+rather than buffered, the @code{gfc_error_now} and
+@code{gfc_warning_now} functions can be used. Normally, the compiler
+will continue attempting to parse the program after an error has
+occurred, but if this is not appropriate, the @code{gfc_fatal_error}
+function should be used instead. For errors that are always the result
+of a bug somewhere in the compiler, the @code{gfc_internal_error}
+function should be used.
+
+The syntax for the strings used to produce the error/warning message in
+the various error and warning functions is similar to the @code{printf}
+syntax, with @samp{%}-escapes to insert variable values. The details,
+and the allowable codes, are documented in the @code{error_print}
+function in @file{error.cc}.
+
+@c ---------------------------------------------------------------------
+@c Frontend Data Structures
+@c ---------------------------------------------------------------------
+
+@node Frontend Data Structures
+@chapter Frontend Data Structures
+@cindex data structures
+
+This chapter should describe the details necessary to understand how
+the various @code{gfc_*} data are used and interact. In general it is
+advisable to read the code in @file{dump-parse-tree.cc} as its routines
+should exhaust all possible valid combinations of content for these
+structures.
+
+@menu
+* gfc_code:: Representation of Executable Statements.
+* gfc_expr:: Representation of Values and Expressions.
+@end menu
+
+
+@c gfc_code
+@c --------
+
+@node gfc_code
+@section @code{gfc_code}
+@cindex statement chaining
+@tindex @code{gfc_code}
+@tindex @code{struct gfc_code}
+
+The executable statements in a program unit are represented by a
+nested chain of @code{gfc_code} structures. The type of statement is
+identified by the @code{op} member of the structure, the different
+possible values are enumerated in @code{gfc_exec_op}. A special
+member of this @code{enum} is @code{EXEC_NOP} which is used to
+represent the various @code{END} statements if they carry a label.
+Depending on the type of statement some of the other fields will be
+filled in. Fields that are generally applicable are the @code{next}
+and @code{here} fields. The former points to the next statement in
+the current block or is @code{NULL} if the current statement is the
+last in a block, @code{here} points to the statement label of the
+current statement.
+
+If the current statement is one of @code{IF}, @code{DO}, @code{SELECT}
+it starts a block, i.e.@: a nested level in the program. In order to
+represent this, the @code{block} member is set to point to a
+@code{gfc_code} structure whose @code{next} member starts the chain of
+statements inside the block; this structure's @code{op} member should be set to
+the same value as the parent structure's @code{op} member. The @code{SELECT}
+and @code{IF} statements may contain various blocks (the chain of @code{ELSE IF}
+and @code{ELSE} blocks or the various @code{CASE}s, respectively). These chains
+are linked-lists formed by the @code{block} members.
+
+Consider the following example code:
+
+@example
+IF (foo < 20) THEN
+ PRINT *, "Too small"
+ foo = 20
+ELSEIF (foo > 50) THEN
+ PRINT *, "Too large"
+ foo = 50
+ELSE
+ PRINT *, "Good"
+END IF
+@end example
+
+This statement-block will be represented in the internal gfortran tree as
+follows, were the horizontal link-chains are those induced by the @code{next}
+members and vertical links down are those of @code{block}. @samp{==|} and
+@samp{--|} mean @code{NULL} pointers to mark the end of a chain:
+
+@example
+... ==> IF ==> ...
+ |
+ +--> IF foo < 20 ==> PRINT *, "Too small" ==> foo = 20 ==|
+ |
+ +--> IF foo > 50 ==> PRINT *, "Too large" ==> foo = 50 ==|
+ |
+ +--> ELSE ==> PRINT *, "Good" ==|
+ |
+ +--|
+@end example
+
+
+@subsection IF Blocks
+
+Conditionals are represented by @code{gfc_code} structures with their
+@code{op} member set to @code{EXEC_IF}. This structure's @code{block}
+member must point to another @code{gfc_code} node that is the header of the
+if-block. This header's @code{op} member must be set to @code{EXEC_IF}, too,
+its @code{expr} member holds the condition to check for, and its @code{next}
+should point to the code-chain of the statements to execute if the condition is
+true.
+
+If in addition an @code{ELSEIF} or @code{ELSE} block is present, the
+@code{block} member of the if-block-header node points to yet another
+@code{gfc_code} structure that is the header of the elseif- or else-block. Its
+structure is identical to that of the if-block-header, except that in case of an
+@code{ELSE} block without a new condition the @code{expr} member should be
+@code{NULL}. This block can itself have its @code{block} member point to the
+next @code{ELSEIF} or @code{ELSE} block if there's a chain of them.
+
+
+@subsection Loops
+
+@code{DO} loops are stored in the tree as @code{gfc_code} nodes with their
+@code{op} set to @code{EXEC_DO} for a @code{DO} loop with iterator variable and
+to @code{EXEC_DO_WHILE} for infinite @code{DO}s and @code{DO WHILE} blocks.
+Their @code{block} member should point to a @code{gfc_code} structure heading
+the code-chain of the loop body; its @code{op} member should be set to
+@code{EXEC_DO} or @code{EXEC_DO_WHILE}, too, respectively.
+
+For @code{DO WHILE} loops, the loop condition is stored on the top
+@code{gfc_code} structure's @code{expr} member; @code{DO} forever loops are
+simply @code{DO WHILE} loops with a constant @code{.TRUE.} loop condition in
+the internal representation.
+
+Similarly, @code{DO} loops with an iterator have instead of the condition their
+@code{ext.iterator} member set to the correct values for the loop iterator
+variable and its range.
+
+
+@subsection @code{SELECT} Statements
+
+A @code{SELECT} block is introduced by a @code{gfc_code} structure with an
+@code{op} member of @code{EXEC_SELECT} and @code{expr} containing the expression
+to evaluate and test. Its @code{block} member starts a list of @code{gfc_code}
+structures linked together by their @code{block} members that stores the various
+@code{CASE} parts.
+
+Each @code{CASE} node has its @code{op} member set to @code{EXEC_SELECT}, too,
+its @code{next} member points to the code-chain to be executed in the current
+case-block, and @code{extx.case_list} contains the case-values this block
+corresponds to. The @code{block} member links to the next case in the list.
+
+
+@subsection @code{BLOCK} and @code{ASSOCIATE}
+
+The code related to a @code{BLOCK} statement is stored inside an
+@code{gfc_code} structure (say @var{c})
+with @code{c.op} set to @code{EXEC_BLOCK}. The
+@code{gfc_namespace} holding the locally defined variables of the
+@code{BLOCK} is stored in @code{c.ext.block.ns}. The code inside the
+construct is in @code{c.code}.
+
+@code{ASSOCIATE} constructs are based on @code{BLOCK} and thus also have
+the internal storage structure described above (including @code{EXEC_BLOCK}).
+However, for them @code{c.ext.block.assoc} is set additionally and points
+to a linked list of @code{gfc_association_list} structures. Those
+structures basically store a link of associate-names to target expressions.
+The associate-names themselves are still also added to the @code{BLOCK}'s
+namespace as ordinary symbols, but they have their @code{gfc_symbol}'s
+member @code{assoc} set also pointing to the association-list structure.
+This way associate-names can be distinguished from ordinary variables
+and their target expressions identified.
+
+For association to expressions (as opposed to variables), at the very beginning
+of the @code{BLOCK} construct assignments are automatically generated to
+set the corresponding variables to their target expressions' values, and
+later on the compiler simply disallows using such associate-names in contexts
+that may change the value.
+
+
+@c gfc_expr
+@c --------
+
+@node gfc_expr
+@section @code{gfc_expr}
+@tindex @code{gfc_expr}
+@tindex @code{struct gfc_expr}
+
+Expressions and ``values'', including constants, variable-, array- and
+component-references as well as complex expressions consisting of operators and
+function calls are internally represented as one or a whole tree of
+@code{gfc_expr} objects. The member @code{expr_type} specifies the overall
+type of an expression (for instance, @code{EXPR_CONSTANT} for constants or
+@code{EXPR_VARIABLE} for variable references). The members @code{ts} and
+@code{rank} as well as @code{shape}, which can be @code{NULL}, specify
+the type, rank and, if applicable, shape of the whole expression or expression
+tree of which the current structure is the root. @code{where} is the locus of
+this expression in the source code.
+
+Depending on the flavor of the expression being described by the object
+(that is, the value of its @code{expr_type} member), the corresponding structure
+in the @code{value} union will usually contain additional data describing the
+expression's value in a type-specific manner. The @code{ref} member is used to
+build chains of (array-, component- and substring-) references if the expression
+in question contains such references, see below for details.
+
+
+@subsection Constants
+
+Scalar constants are represented by @code{gfc_expr} nodes with their
+@code{expr_type} set to @code{EXPR_CONSTANT}. The constant's value shall
+already be known at compile-time and is stored in the @code{logical},
+@code{integer}, @code{real}, @code{complex} or @code{character} struct inside
+@code{value}, depending on the constant's type specification.
+
+
+@subsection Operators
+
+Operator-expressions are expressions that are the result of the execution of
+some operator on one or two operands. The expressions have an @code{expr_type}
+of @code{EXPR_OP}. Their @code{value.op} structure contains additional data.
+
+@code{op1} and optionally @code{op2} if the operator is binary point to the
+two operands, and @code{operator} or @code{uop} describe the operator that
+should be evaluated on these operands, where @code{uop} describes a user-defined
+operator.
+
+
+@subsection Function Calls
+
+If the expression is the return value of a function-call, its @code{expr_type}
+is set to @code{EXPR_FUNCTION}, and @code{symtree} must point to the symtree
+identifying the function to be called. @code{value.function.actual} holds the
+actual arguments given to the function as a linked list of
+@code{gfc_actual_arglist} nodes.
+
+The other members of @code{value.function} describe the function being called
+in more detail, containing a link to the intrinsic symbol or user-defined
+function symbol if the call is to an intrinsic or external function,
+respectively. These values are determined during resolution-phase from the
+structure's @code{symtree} member.
+
+A special case of function calls are ``component calls'' to type-bound
+procedures; those have the @code{expr_type} @code{EXPR_COMPCALL} with
+@code{value.compcall} containing the argument list and the procedure called,
+while @code{symtree} and @code{ref} describe the object on which the procedure
+was called in the same way as a @code{EXPR_VARIABLE} expression would.
+@xref{Type-bound Procedures}.
+
+
+@subsection Array- and Structure-Constructors
+
+Array- and structure-constructors (one could probably call them ``array-'' and
+``derived-type constants'') are @code{gfc_expr} structures with their
+@code{expr_type} member set to @code{EXPR_ARRAY} or @code{EXPR_STRUCTURE},
+respectively. For structure constructors, @code{symtree} points to the
+derived-type symbol for the type being constructed.
+
+The values for initializing each array element or structure component are
+stored as linked-list of @code{gfc_constructor} nodes in the
+@code{value.constructor} member.
+
+
+@subsection Null
+
+@code{NULL} is a special value for pointers; it can be of different base types.
+Such a @code{NULL} value is represented in the internal tree by a
+@code{gfc_expr} node with @code{expr_type} @code{EXPR_NULL}. If the base type
+of the @code{NULL} expression is known, it is stored in @code{ts} (that's for
+instance the case for default-initializers of @code{ALLOCATABLE} components),
+but this member can also be set to @code{BT_UNKNOWN} if the information is not
+available (for instance, when the expression is a pointer-initializer
+@code{NULL()}).
+
+
+@subsection Variables and Reference Expressions
+
+Variable references are @code{gfc_expr} structures with their @code{expr_type}
+set to @code{EXPR_VARIABLE}; their @code{symtree} should point to the variable
+that is referenced.
+
+For this type of expression, it's also possible to chain array-, component-
+or substring-references to the original expression to get something like
+@samp{struct%component(2:5)}, where @code{component} is either an array or
+a @code{CHARACTER} member of @code{struct} that is of some derived-type. Such a
+chain of references is achieved by a linked list headed by @code{ref} of the
+@code{gfc_expr} node. For the example above it would be (@samp{==|} is the
+last @code{NULL} pointer):
+
+@smallexample
+EXPR_VARIABLE(struct) ==> REF_COMPONENT(component) ==> REF_ARRAY(2:5) ==|
+@end smallexample
+
+If @code{component} is a string rather than an array, the last element would be
+a @code{REF_SUBSTRING} reference, of course. If the variable itself or some
+component referenced is an array and the expression should reference the whole
+array rather than being followed by an array-element or -section reference, a
+@code{REF_ARRAY} reference must be built as the last element in the chain with
+an array-reference type of @code{AR_FULL}. Consider this example code:
+
+@smallexample
+TYPE :: mytype
+ INTEGER :: array(42)
+END TYPE mytype
+
+TYPE(mytype) :: variable
+INTEGER :: local_array(5)
+
+CALL do_something (variable%array, local_array)
+@end smallexample
+
+The @code{gfc_expr} nodes representing the arguments to the @samp{do_something}
+call will have a reference-chain like this:
+
+@smallexample
+EXPR_VARIABLE(variable) ==> REF_COMPONENT(array) ==> REF_ARRAY(FULL) ==|
+EXPR_VARIABLE(local_array) ==> REF_ARRAY(FULL) ==|
+@end smallexample
+
+
+@subsection Constant Substring References
+
+@code{EXPR_SUBSTRING} is a special type of expression that encodes a substring
+reference of a constant string, as in the following code snippet:
+
+@smallexample
+x = "abcde"(1:2)
+@end smallexample
+
+In this case, @code{value.character} contains the full string's data as if it
+was a string constant, but the @code{ref} member is also set and points to a
+substring reference as described in the subsection above.
+
+
+@c ---------------------------------------------------------------------
+@c F2003 OOP
+@c ---------------------------------------------------------------------
+
+@node Object Orientation
+@chapter Internals of Fortran 2003 OOP Features
+
+@menu
+* Type-bound Procedures:: Type-bound procedures.
+* Type-bound Operators:: Type-bound operators.
+@end menu
+
+
+@c Type-bound procedures
+@c ---------------------
+
+@node Type-bound Procedures
+@section Type-bound Procedures
+
+Type-bound procedures are stored in the @code{tb_sym_root} of the namespace
+@code{f2k_derived} associated with the derived-type symbol as @code{gfc_symtree}
+nodes. The name and symbol of these symtrees corresponds to the binding-name
+of the procedure, i.e. the name that is used to call it from the context of an
+object of the derived-type.
+
+In addition, this type of symtrees stores in @code{n.tb} a struct of type
+@code{gfc_typebound_proc} containing the additional data needed: The
+binding attributes (like @code{PASS} and @code{NOPASS}, @code{NON_OVERRIDABLE}
+or the access-specifier), the binding's target(s) and, if the current binding
+overrides or extends an inherited binding of the same name, @code{overridden}
+points to this binding's @code{gfc_typebound_proc} structure.
+
+
+@subsection Specific Bindings
+@c --------------------------
+
+For specific bindings (declared with @code{PROCEDURE}), if they have a
+passed-object argument, the passed-object dummy argument is first saved by its
+name, and later during resolution phase the corresponding argument is looked for
+and its position remembered as @code{pass_arg_num} in @code{gfc_typebound_proc}.
+The binding's target procedure is pointed-to by @code{u.specific}.
+
+@code{DEFERRED} bindings are just like ordinary specific bindings, except
+that their @code{deferred} flag is set of course and that @code{u.specific}
+points to their ``interface'' defining symbol (might be an abstract interface)
+instead of the target procedure.
+
+At the moment, all type-bound procedure calls are statically dispatched and
+transformed into ordinary procedure calls at resolution time; their actual
+argument list is updated to include at the right position the passed-object
+argument, if applicable, and then a simple procedure call to the binding's
+target procedure is built. To handle dynamic dispatch in the future, this will
+be extended to allow special code generation during the trans-phase to dispatch
+based on the object's dynamic type.
+
+
+@subsection Generic Bindings
+@c -------------------------
+
+Bindings declared as @code{GENERIC} store the specific bindings they target as
+a linked list using nodes of type @code{gfc_tbp_generic} in @code{u.generic}.
+For each specific target, the parser records its symtree and during resolution
+this symtree is bound to the corresponding @code{gfc_typebound_proc} structure
+of the specific target.
+
+Calls to generic bindings are handled entirely in the resolution-phase, where
+for the actual argument list present the matching specific binding is found
+and the call's target procedure (@code{value.compcall.tbp}) is re-pointed to
+the found specific binding and this call is subsequently handled by the logic
+for specific binding calls.
+
+
+@subsection Calls to Type-bound Procedures
+@c ---------------------------------------
+
+Calls to type-bound procedures are stored in the parse-tree as @code{gfc_expr}
+nodes of type @code{EXPR_COMPCALL}. Their @code{value.compcall.actual} saves
+the actual argument list of the call and @code{value.compcall.tbp} points to the
+@code{gfc_typebound_proc} structure of the binding to be called. The object
+in whose context the procedure was called is saved by combination of
+@code{symtree} and @code{ref}, as if the expression was of type
+@code{EXPR_VARIABLE}.
+
+For code like this:
+@smallexample
+CALL myobj%procedure (arg1, arg2)
+@end smallexample
+@noindent
+the @code{CALL} is represented in the parse-tree as a @code{gfc_code} node of
+type @code{EXEC_COMPCALL}. The @code{expr} member of this node holds an
+expression of type @code{EXPR_COMPCALL} of the same structure as mentioned above
+except that its target procedure is of course a @code{SUBROUTINE} and not a
+@code{FUNCTION}.
+
+Expressions that are generated internally (as expansion of a type-bound
+operator call) may also use additional flags and members.
+@code{value.compcall.ignore_pass} signals that even though a @code{PASS}
+attribute may be present the actual argument list should not be updated because
+it already contains the passed-object.
+@code{value.compcall.base_object} overrides, if it is set, the base-object
+(that is normally stored in @code{symtree} and @code{ref} as mentioned above);
+this is needed because type-bound operators can be called on a base-object that
+need not be of type @code{EXPR_VARIABLE} and thus representable in this way.
+Finally, if @code{value.compcall.assign} is set, the call was produced in
+expansion of a type-bound assignment; this means that proper dependency-checking
+needs to be done when relevant.
+
+
+@c Type-bound operators
+@c --------------------
+
+@node Type-bound Operators
+@section Type-bound Operators
+
+Type-bound operators are in fact basically just @code{GENERIC} procedure
+bindings and are represented much in the same way as those (see
+@ref{Type-bound Procedures}).
+
+They come in two flavours:
+User-defined operators (like @code{.MYOPERATOR.})
+are stored in the @code{f2k_derived} namespace's @code{tb_uop_root}
+symtree exactly like ordinary type-bound procedures are stored in
+@code{tb_sym_root}; their symtrees' names are the operator-names (e.g.
+@samp{myoperator} in the example).
+Intrinsic operators on the other hand are stored in the namespace's
+array member @code{tb_op} indexed by the intrinsic operator's enum
+value. Those need not be packed into @code{gfc_symtree} structures and are
+only @code{gfc_typebound_proc} instances.
+
+When an operator call or assignment is found that cannot be handled in
+another way (i.e. neither matches an intrinsic nor interface operator
+definition) but that contains a derived-type expression, all type-bound
+operators defined on that derived-type are checked for a match with
+the operator call. If there's indeed a relevant definition, the
+operator call is replaced with an internally generated @code{GENERIC}
+type-bound procedure call to the respective definition and that call is
+further processed.
+
+@c ---------------------------------------------------------------------
+@c - Translating to GENERIC
+@c ---------------------------------------------------------------------
+
+@node Translating to GENERIC
+@chapter Generating the intermediate language for later stages.
+
+This chapter deals with the transformation of gfortran's frontend data
+structures to the intermediate language used by the later stages of
+the compiler, the so-called middle end.
+
+Data structures relating to this are found in the source files
+@file{trans*.h} and @file{trans-*.c}.
+
+@menu
+* Basic Data Structures:: Basic data structures.
+* Converting Expressions:: Converting expressions to tree.
+* Translating Statements:: Translating statements.
+* Accessing Declarations:: Accessing declarations.
+@end menu
+
+@node Basic Data Structures
+@section Basic data structures
+
+Gfortran creates GENERIC as an intermediate language for the
+middle-end. Details about GENERIC can be found in the GCC manual.
+
+The basic data structure of GENERIC is a @code{tree}. Everything in
+GENERIC is a @code{tree}, including types and statements. Fortunately
+for the gfortran programmer, @code{tree} variables are
+garbage-collected, so doing memory management for them is not
+necessary.
+
+@code{tree} expressions are built using functions such as, for
+example, @code{fold_build2_loc}. For two tree variables @code{a} and
+@code{b}, both of which have the type @code{gfc_arry_index_type},
+calculation @code{c = a * b} would be done by
+
+@smallexample
+c = fold_build2_loc (input_location, MULT_EXPR,
+ gfc_array_index_type, a, b);
+@end smallexample
+
+The types have to agree, otherwise internal compiler errors will occur
+at a later stage. Expressions can be converted to a different type
+using @code{fold_convert}.
+
+Accessing individual members in the @code{tree} structures should not
+be done. Rather, access should be done via macros.
+
+One basic data structure is the @code{stmtblock_t} struct. This is
+used for holding a list of statements, expressed as @code{tree}
+expressions. If a block is created using @code{gfc_start_block}, it
+has its own scope for variables; if it is created using
+@code{gfc_init_block}, it does not have its own scope.
+
+It is possible to
+@itemize @bullet
+@item Add an expression to the end of a block using
+ @code{gfc_add_expr_to_block}
+@item Add an expression to the beginning of a block using
+ @code{void gfc_prepend_expr_to_block}
+@item Make a block into a single @code{tree} using
+ @code{gfc_finish_block}. For example, this is needed to put the
+ contents of a block into the @code{if} or @code{else} branch of
+ a @code{COND_EXPR}.
+@end itemize
+
+Variables are also @code{tree} expressions, they can be created using
+@code{gfc_create_var}. Assigning to a variable can be done with
+@code{gfc_add_modify}.
+
+An example: Creating a default integer type variable in the current
+scope with the prefix ``everything'' in the @code{stmt_block}
+@code{block} and assigning the value 42 would be
+
+@smallexample
+tree var, *block;
+/* Initialize block somewhere here. */
+var = gfc_create_var (integer_type_node, "everything");
+gfc_add_modify (block, var, build_int_cst (integer_type_node, 42));
+@end smallexample
+
+@node Converting Expressions
+@section Converting Expressions to tree
+
+Converting expressions to @code{tree} is done by functions called
+@code{gfc_conv_*}.
+
+The central data structure for a GENERIC expression is the
+@code{gfc_se} structure. Its @code{expr} member is a @code{tree} that
+holds the value of the expression. A @code{gfc_se} structure is
+initialized using @code{gfc_init_se}; it needs to be embedded in an
+outer @code{gfc_se}.
+
+Evaluating Fortran expressions often require things to be done before
+and after evaluation of the expression, for example code for the
+allocation of a temporary variable and its subsequent deallocation.
+Therefore, @code{gfc_se} contains the members @code{pre} and
+@code{post}, which point to @code{stmt_block} blocks for code that
+needs to be executed before and after evaluation of the expression.
+
+When using a local @code{gfc_se} to convert some expression, it is
+often necessary to add the generated @code{pre} and @code{post} blocks
+to the @code{pre} or @code{post} blocks of the outer @code{gfc_se}.
+Code like this (lifted from @file{trans-expr.cc}) is fairly common:
+
+@smallexample
+gfc_se cont_se;
+tree cont_var;
+
+/* cont_var = is_contiguous (expr); . */
+gfc_init_se (&cont_se, parmse);
+gfc_conv_is_contiguous_expr (&cont_se, expr);
+gfc_add_block_to_block (&se->pre, &(&cont_se)->pre);
+gfc_add_modify (&se->pre, cont_var, cont_se.expr);
+gfc_add_block_to_block (&se->pre, &(&cont_se)->post);
+@end smallexample
+
+Conversion functions which need a @code{gfc_se} structure will have a
+corresponding argument.
+
+@code{gfc_se} also contains pointers to a @code{gfc_ss} and a
+@code{gfc_loopinfo} structure. These are needed by the scalarizer.
+
+@node Translating Statements
+@section Translating statements
+Translating statements to @code{tree} is done by functions called
+@code{gfc_trans_*}. These functions usually get passed a
+@code{gfc_code} structure, evaluate any expressions and then
+return a @code{tree} structure.
+
+@node Accessing Declarations
+@section Accessing declarations
+
+@code{gfc_symbol}, @code{gfc_charlen} and other front-end structures
+contain a @code{backend_decl} variable, which contains the @code{tree}
+used for accessing that entity in the middle-end.
+
+Accessing declarations is usually done by functions called
+@code{gfc_get*}.
+
+@c ---------------------------------------------------------------------
+@c LibGFortran
+@c ---------------------------------------------------------------------
+
+@node LibGFortran
+@chapter The LibGFortran Runtime Library
+
+@menu
+* Symbol Versioning:: Symbol Versioning.
+@end menu
+
+
+@c ---------------------------------------------------------------------
+@c Symbol Versioning
+@c ---------------------------------------------------------------------
+
+@node Symbol Versioning
+@section Symbol Versioning
+@comment Based on https://gcc.gnu.org/wiki/SymbolVersioning,
+@comment as of 2006-11-05, written by Janne Blomqvist.
+
+In general, this capability exists only on a few platforms, thus there
+is a need for configure magic so that it is used only on those targets
+where it is supported.
+
+The central concept in symbol versioning is the so-called map file,
+which specifies the version node(s) exported symbols are labeled with.
+Also, the map file is used to hide local symbols.
+
+Some relevant references:
+@itemize @bullet
+@item
+@uref{https://sourceware.org/binutils/docs/ld/VERSION.html,
+GNU @command{ld} manual}
+
+@item
+@uref{https://www.akkadia.org/drepper/symbol-versioning, ELF Symbol
+Versioning - Ulrich Depper}
+
+@item
+@uref{https://www.akkadia.org/drepper/dsohowto.pdf, How to Write Shared
+Libraries - Ulrich Drepper (see Chapter 3)}
+
+@end itemize
+
+If one adds a new symbol to a library that should be exported, the new
+symbol should be mentioned in the map file and a new version node
+defined, e.g., if one adds a new symbols @code{foo} and @code{bar} to
+libgfortran for the next GCC release, the following should be added to
+the map file:
+@smallexample
+GFORTRAN_1.1 @{
+ global:
+ foo;
+ bar;
+@} GFORTRAN_1.0;
+@end smallexample
+@noindent
+where @code{GFORTRAN_1.0} is the version node of the current release,
+and @code{GFORTRAN_1.1} is the version node of the next release where
+foo and bar are made available.
+
+If one wants to change an existing interface, it is possible by using
+some asm trickery (from the @command{ld} manual referenced above):
+
+@smallexample
+__asm__(".symver original_foo,foo@@");
+__asm__(".symver old_foo,foo@@VERS_1.1");
+__asm__(".symver old_foo1,foo@@VERS_1.2");
+__asm__(".symver new_foo,foo@@VERS_2.0");
+@end smallexample
+
+In this example, @code{foo@@} represents the symbol @code{foo} bound to
+the unspecified base version of the symbol. The source file that
+contains this example would define 4 C functions: @code{original_foo},
+@code{old_foo}, @code{old_foo1}, and @code{new_foo}.
+
+In this case the map file must contain @code{foo} in @code{VERS_1.1}
+and @code{VERS_1.2} as well as in @code{VERS_2.0}.
+
+
+@c ---------------------------------------------------------------------
+@c GNU Free Documentation License
+@c ---------------------------------------------------------------------
+
+@include fdl.texi
+
+
+@c ---------------------------------------------------------------------
+@c Index
+@c ---------------------------------------------------------------------
+
+@node Index
+@unnumbered Index
+
+@printindex cp
+
+@bye
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@c %**start of header
+@setfilename gfortran.info
+@set copyrights-gfortran 1999-2022
+
+@include gcc-common.texi
+
+@settitle The GNU Fortran Compiler
+
+@c Create a separate index for command line options
+@defcodeindex op
+@c Merge the standard indexes into a single one.
+@syncodeindex fn cp
+@syncodeindex vr cp
+@syncodeindex ky cp
+@syncodeindex pg cp
+@syncodeindex tp cp
+
+@c TODO: The following "Part" definitions are included here temporarily
+@c until they are incorporated into the official Texinfo distribution.
+@c They borrow heavily from Texinfo's \unnchapentry definitions.
+
+@tex
+\gdef\part#1#2{%
+ \pchapsepmacro
+ \gdef\thischapter{}
+ \begingroup
+ \vglue\titlepagetopglue
+ \titlefonts \rm
+ \leftline{Part #1:@* #2}
+ \vskip4pt \hrule height 4pt width \hsize \vskip4pt
+ \endgroup
+ \writetocentry{part}{#2}{#1}
+}
+\gdef\blankpart{%
+ \writetocentry{blankpart}{}{}
+}
+% Part TOC-entry definition for summary contents.
+\gdef\dosmallpartentry#1#2#3#4{%
+ \vskip .5\baselineskip plus.2\baselineskip
+ \begingroup
+ \let\rm=\bf \rm
+ \tocentry{Part #2: #1}{\doshortpageno\bgroup#4\egroup}
+ \endgroup
+}
+\gdef\dosmallblankpartentry#1#2#3#4{%
+ \vskip .5\baselineskip plus.2\baselineskip
+}
+% Part TOC-entry definition for regular contents. This has to be
+% equated to an existing entry to not cause problems when the PDF
+% outline is created.
+\gdef\dopartentry#1#2#3#4{%
+ \unnchapentry{Part #2: #1}{}{#3}{#4}
+}
+\gdef\doblankpartentry#1#2#3#4{}
+@end tex
+
+@c %**end of header
+
+@c Use with @@smallbook.
+
+@c %** start of document
+
+@c Cause even numbered pages to be printed on the left hand side of
+@c the page and odd numbered pages to be printed on the right hand
+@c side of the page. Using this, you can print on both sides of a
+@c sheet of paper and have the text on the same part of the sheet.
+
+@c The text on right hand pages is pushed towards the right hand
+@c margin and the text on left hand pages is pushed toward the left
+@c hand margin.
+@c (To provide the reverse effect, set bindingoffset to -0.75in.)
+
+@c @tex
+@c \global\bindingoffset=0.75in
+@c \global\normaloffset =0.75in
+@c @end tex
+
+@copying
+Copyright @copyright{} @value{copyrights-gfortran} Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``Funding Free Software'', the Front-Cover
+Texts being (a) (see below), and with the Back-Cover Texts being (b)
+(see below). A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@end copying
+
+@ifinfo
+@dircategory Software development
+@direntry
+* gfortran: (gfortran). The GNU Fortran Compiler.
+@end direntry
+This file documents the use and the internals of
+the GNU Fortran compiler, (@command{gfortran}).
+
+Published by the Free Software Foundation
+51 Franklin Street, Fifth Floor
+Boston, MA 02110-1301 USA
+
+@insertcopying
+@end ifinfo
+
+
+@setchapternewpage odd
+@titlepage
+@title Using GNU Fortran
+@versionsubtitle
+@author The @t{gfortran} team
+@page
+@vskip 0pt plus 1filll
+Published by the Free Software Foundation@*
+51 Franklin Street, Fifth Floor@*
+Boston, MA 02110-1301, USA@*
+@c Last printed ??ber, 19??.@*
+@c Printed copies are available for $? each.@*
+@c ISBN ???
+@sp 1
+@insertcopying
+@end titlepage
+
+@c TODO: The following "Part" definitions are included here temporarily
+@c until they are incorporated into the official Texinfo distribution.
+
+@tex
+\global\let\partentry=\dosmallpartentry
+\global\let\blankpartentry=\dosmallblankpartentry
+@end tex
+@summarycontents
+
+@tex
+\global\let\partentry=\dopartentry
+\global\let\blankpartentry=\doblankpartentry
+@end tex
+@contents
+
+@page
+
+@c ---------------------------------------------------------------------
+@c TexInfo table of contents.
+@c ---------------------------------------------------------------------
+
+@ifnottex
+@node Top
+@top Introduction
+@cindex Introduction
+
+This manual documents the use of @command{gfortran},
+the GNU Fortran compiler. You can find in this manual how to invoke
+@command{gfortran}, as well as its features and incompatibilities.
+
+@ifset DEVELOPMENT
+@emph{Warning:} This document, and the compiler it describes, are still
+under development. While efforts are made to keep it up-to-date, it might
+not accurately reflect the status of the most recent GNU Fortran compiler.
+@end ifset
+
+@comment
+@comment When you add a new menu item, please keep the right hand
+@comment aligned to the same column. Do not use tabs. This provides
+@comment better formatting.
+@comment
+@menu
+* Introduction::
+
+Part I: Invoking GNU Fortran
+* Invoking GNU Fortran:: Command options supported by @command{gfortran}.
+* Runtime:: Influencing runtime behavior with environment variables.
+
+Part II: Language Reference
+* Compiler Characteristics:: User-visible implementation details.
+* Extensions:: Language extensions implemented by GNU Fortran.
+* Mixed-Language Programming:: Interoperability with C
+* Coarray Programming::
+* Intrinsic Procedures:: Intrinsic procedures supported by GNU Fortran.
+* Intrinsic Modules:: Intrinsic modules supported by GNU Fortran.
+
+* Contributing:: How you can help.
+* Copying:: GNU General Public License says
+ how you can copy and share GNU Fortran.
+* GNU Free Documentation License::
+ How you can copy and share this manual.
+* Funding:: How to help assure continued work for free software.
+* Option Index:: Index of command line options
+* Keyword Index:: Index of concepts
+@end menu
+@end ifnottex
+
+@c ---------------------------------------------------------------------
+@c Introduction
+@c ---------------------------------------------------------------------
+
+@node Introduction
+@chapter Introduction
+
+@c The following duplicates the text on the TexInfo table of contents.
+@iftex
+This manual documents the use of @command{gfortran}, the GNU Fortran
+compiler. You can find in this manual how to invoke @command{gfortran},
+as well as its features and incompatibilities.
+
+@ifset DEVELOPMENT
+@emph{Warning:} This document, and the compiler it describes, are still
+under development. While efforts are made to keep it up-to-date, it
+might not accurately reflect the status of the most recent GNU Fortran
+compiler.
+@end ifset
+@end iftex
+
+@menu
+* About GNU Fortran:: What you should know about the GNU Fortran compiler.
+* GNU Fortran and GCC:: You can compile Fortran, C, or other programs.
+* Standards:: Standards supported by GNU Fortran.
+@end menu
+
+
+@c ---------------------------------------------------------------------
+@c About GNU Fortran
+@c ---------------------------------------------------------------------
+
+@node About GNU Fortran
+@section About GNU Fortran
+
+The GNU Fortran compiler is the successor to @command{g77}, the
+Fortran 77 front end included in GCC prior to version 4 (released in
+2005). While it is backward-compatible with most @command{g77}
+extensions and command-line options, @command{gfortran} is a completely new
+implemention designed to support more modern dialects of Fortran.
+GNU Fortran implements the Fortran 77, 90 and 95 standards
+completely, most of the Fortran 2003 and 2008 standards, and some
+features from the 2018 standard. It also implements several extensions
+including OpenMP and OpenACC support for parallel programming.
+
+The GNU Fortran compiler passes the
+@uref{http://www.fortran-2000.com/ArnaudRecipes/fcvs21_f95.html,
+NIST Fortran 77 Test Suite}, and produces acceptable results on the
+@uref{https://www.netlib.org/lapack/faq.html, LAPACK Test Suite}.
+It also provides respectable performance on
+the @uref{https://polyhedron.com/?page_id=175,
+Polyhedron Fortran compiler benchmarks} and the
+@uref{https://www.netlib.org/benchmark/livermore,
+Livermore Fortran Kernels test}. It has been used to compile a number of
+large real-world programs, including
+@uref{http://hirlam.org/, the HARMONIE and HIRLAM weather forecasting code} and
+@uref{https://github.com/dylan-jayatilaka/tonto,
+the Tonto quantum chemistry package}; see
+@url{https://gcc.gnu.org/@/wiki/@/GfortranApps} for an extended list.
+
+GNU Fortran provides the following functionality:
+
+@itemize @bullet
+@item
+Read a program, stored in a file and containing @dfn{source code}
+instructions written in Fortran 77.
+
+@item
+Translate the program into instructions a computer
+can carry out more quickly than it takes to translate the
+original Fortran instructions.
+The result after compilation of a program is
+@dfn{machine code},
+which is efficiently translated and processed
+by a machine such as your computer.
+Humans usually are not as good writing machine code
+as they are at writing Fortran (or C++, Ada, or Java),
+because it is easy to make tiny mistakes writing machine code.
+
+@item
+Provide information about the reasons why
+the compiler may be unable to create a binary from the source code,
+for example if the source code is flawed.
+The Fortran language standards require that the compiler can point out
+mistakes in your code.
+An incorrect usage of the language causes an @dfn{error message}.
+
+The compiler also attempts to diagnose cases where your
+program contains a correct usage of the language,
+but instructs the computer to do something questionable.
+This kind of diagnostic message is called a @dfn{warning message}.
+
+@item
+Provide optional information about the translation passes
+from the source code to machine code.
+This can help you to find the cause of
+certain bugs which may not be obvious in the source code,
+but may be more easily found at a lower level compiler output.
+It also helps developers to find bugs in the compiler itself.
+
+@item
+Provide information in the generated machine code that can
+make it easier to find bugs in the program (using a debugging tool,
+called a @dfn{debugger}, such as the GNU Debugger @command{gdb}).
+
+@item
+Locate and gather machine code already generated to
+perform actions requested by statements in the program.
+This machine code is organized into @dfn{modules} and is located
+and @dfn{linked} to the user program.
+@end itemize
+
+The GNU Fortran compiler consists of several components:
+
+@itemize @bullet
+@item
+A version of the @command{gcc} command
+(which also might be installed as the system's @command{cc} command)
+that also understands and accepts Fortran source code.
+The @command{gcc} command is the @dfn{driver} program for
+all the languages in the GNU Compiler Collection (GCC);
+With @command{gcc},
+you can compile the source code of any language for
+which a front end is available in GCC.
+
+@item
+The @command{gfortran} command itself,
+which also might be installed as the
+system's @command{f95} command.
+@command{gfortran} is just another driver program,
+but specifically for the Fortran compiler only.
+The primary difference between the @command{gcc} and @command{gfortran}
+commands is that the latter automatically links the correct libraries
+to your program.
+
+@item
+A collection of run-time libraries.
+These libraries contain the machine code needed to support
+capabilities of the Fortran language that are not directly
+provided by the machine code generated by the
+@command{gfortran} compilation phase,
+such as intrinsic functions and subroutines,
+and routines for interaction with files and the operating system.
+@c and mechanisms to spawn,
+@c unleash and pause threads in parallelized code.
+
+@item
+The Fortran compiler itself, (@command{f951}).
+This is the GNU Fortran parser and code generator,
+linked to and interfaced with the GCC backend library.
+@command{f951} ``translates'' the source code to
+assembler code. You would typically not use this
+program directly;
+instead, the @command{gcc} or @command{gfortran} driver
+programs call it for you.
+@end itemize
+
+
+@c ---------------------------------------------------------------------
+@c GNU Fortran and GCC
+@c ---------------------------------------------------------------------
+
+@node GNU Fortran and GCC
+@section GNU Fortran and GCC
+@cindex GNU Compiler Collection
+@cindex GCC
+
+GNU Fortran is a part of GCC, the @dfn{GNU Compiler Collection}. GCC
+consists of a collection of front ends for various languages, which
+translate the source code into a language-independent form called
+@dfn{GENERIC}. This is then processed by a common middle end which
+provides optimization, and then passed to one of a collection of back
+ends which generate code for different computer architectures and
+operating systems.
+
+Functionally, this is implemented with a driver program (@command{gcc})
+which provides the command-line interface for the compiler. It calls
+the relevant compiler front-end program (e.g., @command{f951} for
+Fortran) for each file in the source code, and then calls the assembler
+and linker as appropriate to produce the compiled output. In a copy of
+GCC that has been compiled with Fortran language support enabled,
+@command{gcc} recognizes files with @file{.f}, @file{.for}, @file{.ftn},
+@file{.f90}, @file{.f95}, @file{.f03} and @file{.f08} extensions as
+Fortran source code, and compiles it accordingly. A @command{gfortran}
+driver program is also provided, which is identical to @command{gcc}
+except that it automatically links the Fortran runtime libraries into the
+compiled program.
+
+Source files with @file{.f}, @file{.for}, @file{.fpp}, @file{.ftn}, @file{.F},
+@file{.FOR}, @file{.FPP}, and @file{.FTN} extensions are treated as fixed form.
+Source files with @file{.f90}, @file{.f95}, @file{.f03}, @file{.f08},
+@file{.F90}, @file{.F95}, @file{.F03} and @file{.F08} extensions are
+treated as free form. The capitalized versions of either form are run
+through preprocessing. Source files with the lower case @file{.fpp}
+extension are also run through preprocessing.
+
+This manual specifically documents the Fortran front end, which handles
+the programming language's syntax and semantics. The aspects of GCC
+that relate to the optimization passes and the back-end code generation
+are documented in the GCC manual; see
+@ref{Top,,Introduction,gcc,Using the GNU Compiler Collection (GCC)}.
+The two manuals together provide a complete reference for the GNU
+Fortran compiler.
+
+@c ---------------------------------------------------------------------
+@c Standards
+@c ---------------------------------------------------------------------
+
+@node Standards
+@section Standards
+@cindex Standards
+
+@menu
+* Fortran 95 status::
+* Fortran 2003 status::
+* Fortran 2008 status::
+* Fortran 2018 status::
+@end menu
+
+Fortran is developed by the Working Group 5 of Sub-Committee 22 of the
+Joint Technical Committee 1 of the International Organization for
+Standardization and the International Electrotechnical Commission (IEC).
+This group is known as @uref{http://www.nag.co.uk/sc22wg5/, WG5}.
+Official Fortran standard documents are available for purchase
+from ISO; a collection of free documents (typically final drafts) are
+also available on the @uref{https://gcc.gnu.org/wiki/GFortranStandards, wiki}.
+
+The GNU Fortran compiler implements ISO/IEC 1539:1997 (Fortran 95).
+As such, it can also compile essentially all standard-compliant
+Fortran 90 and Fortran 77 programs. It also supports the ISO/IEC
+TR-15581 enhancements to allocatable arrays.
+
+GNU Fortran also supports almost all of ISO/IEC 1539-1:2004
+(Fortran 2003) and ISO/IEC 1539-1:2010 (Fortran 2008).
+It has partial support for features introduced in ISO/IEC
+1539:2018 (Fortran 2018), the most recent version of the Fortran
+language standard, including full support for the Technical Specification
+@code{Further Interoperability of Fortran with C} (ISO/IEC TS 29113:2012).
+More details on support for these standards can be
+found in the following sections of the documentation.
+
+Additionally, the GNU Fortran compilers supports the OpenMP specification
+(version 4.5 and partial support of the features of the 5.0 version,
+@url{https://openmp.org/@/specifications/}).
+There also is support for the OpenACC specification (targeting
+version 2.6, @uref{https://www.openacc.org/}). See
+@uref{https://gcc.gnu.org/wiki/OpenACC} for more information.
+
+@node Fortran 95 status
+@subsection Fortran 95 status
+@cindex Varying length strings
+@cindex strings, varying length
+@cindex conditional compilation
+
+The Fortran 95 standard specifies in Part 2 (ISO/IEC 1539-2:2000)
+varying length character strings. While GNU Fortran currently does not
+support such strings directly, there exist two Fortran implementations
+for them, which work with GNU Fortran. One can be found at
+@uref{http://user.astro.wisc.edu/~townsend/static.php?ref=iso-varying-string}.
+
+Deferred-length character strings of Fortran 2003 supports part of
+the features of @code{ISO_VARYING_STRING} and should be considered as
+replacement. (Namely, allocatable or pointers of the type
+@code{character(len=:)}.)
+
+Part 3 of the Fortran 95 standard (ISO/IEC 1539-3:1998) defines
+Conditional Compilation, which is not widely used and not directly
+supported by the GNU Fortran compiler. You can use the program coco
+to preprocess such files (@uref{http://www.daniellnagle.com/coco.html}).
+
+@node Fortran 2003 status
+@subsection Fortran 2003 status
+
+GNU Fortran implements the Fortran 2003 (ISO/IEC 1539-1:2004) standard
+except for finalization support, which is incomplete.
+See the
+@uref{https://gcc.gnu.org/wiki/Fortran2003, wiki page} for a full list
+of new features introduced by Fortran 2003 and their implementation status.
+
+@node Fortran 2008 status
+@subsection Fortran 2008 status
+
+The GNU Fortran compiler supports almost all features of Fortran 2008;
+the @uref{https://gcc.gnu.org/wiki/Fortran2008Status, wiki}
+has some information about the current implementation status.
+In particular, the following are not yet supported:
+
+@itemize @bullet
+@item
+@code{DO CONCURRENT} and @code{FORALL} do not recognize a
+type-spec in the loop header.
+
+@item
+The change to permit any constant expression in subscripts and
+nested implied-do limits in a @code{DATA} statement has not been implemented.
+@end itemize
+
+
+@node Fortran 2018 status
+@subsection Fortran 2018 status
+
+Fortran 2018 (ISO/IEC 1539:2018) is the most recent version
+of the Fortran language standard. GNU Fortran implements some of the
+new features of this standard:
+
+@itemize @bullet
+@item
+All Fortran 2018 features derived from ISO/IEC TS 29113:2012,
+``Further Interoperability of Fortran with C'', are supported by GNU Fortran.
+This includes assumed-type and assumed-rank objects and
+the @code{SELECT RANK} construct as well as the parts relating to
+@code{BIND(C)} functions.
+See also @ref{Further Interoperability of Fortran with C}.
+
+@item
+GNU Fortran supports a subset of features derived from ISO/IEC TS 18508:2015,
+``Additional Parallel Features in Fortran'':
+
+@itemize @bullet
+@item
+The new atomic ADD, CAS, FETCH and ADD/OR/XOR, OR and XOR intrinsics.
+
+@item
+The @code{CO_MIN} and @code{CO_MAX} and @code{SUM} reduction intrinsics,
+and the @code{CO_BROADCAST} and @code{CO_REDUCE} intrinsic, except that those
+do not support polymorphic types or types with allocatable, pointer or
+polymorphic components.
+
+@item
+Events (@code{EVENT POST}, @code{EVENT WAIT}, @code{EVENT_QUERY}).
+
+@item
+Failed images (@code{FAIL IMAGE}, @code{IMAGE_STATUS},
+@code{FAILED_IMAGES}, @code{STOPPED_IMAGES}).
+
+@end itemize
+
+@item
+An @code{ERROR STOP} statement is permitted in a @code{PURE}
+procedure.
+
+@item
+GNU Fortran supports the @code{IMPLICIT NONE} statement with an
+@code{implicit-none-spec-list}.
+
+@item
+The behavior of the @code{INQUIRE} statement with the @code{RECL=}
+specifier now conforms to Fortran 2018.
+
+@end itemize
+
+
+@c =====================================================================
+@c PART I: INVOCATION REFERENCE
+@c =====================================================================
+
+@tex
+\part{I}{Invoking GNU Fortran}
+@end tex
+
+@c ---------------------------------------------------------------------
+@c Compiler Options
+@c ---------------------------------------------------------------------
+
+@include invoke.texi
+
+
+@c ---------------------------------------------------------------------
+@c Runtime
+@c ---------------------------------------------------------------------
+
+@node Runtime
+@chapter Runtime: Influencing runtime behavior with environment variables
+@cindex environment variable
+
+The behavior of the @command{gfortran} can be influenced by
+environment variables.
+
+Malformed environment variables are silently ignored.
+
+@menu
+* TMPDIR:: Directory for scratch files
+* GFORTRAN_STDIN_UNIT:: Unit number for standard input
+* GFORTRAN_STDOUT_UNIT:: Unit number for standard output
+* GFORTRAN_STDERR_UNIT:: Unit number for standard error
+* GFORTRAN_UNBUFFERED_ALL:: Do not buffer I/O for all units
+* GFORTRAN_UNBUFFERED_PRECONNECTED:: Do not buffer I/O for preconnected units.
+* GFORTRAN_SHOW_LOCUS:: Show location for runtime errors
+* GFORTRAN_OPTIONAL_PLUS:: Print leading + where permitted
+* GFORTRAN_LIST_SEPARATOR:: Separator for list output
+* GFORTRAN_CONVERT_UNIT:: Set conversion for unformatted I/O
+* GFORTRAN_ERROR_BACKTRACE:: Show backtrace on run-time errors
+* GFORTRAN_FORMATTED_BUFFER_SIZE:: Buffer size for formatted files
+* GFORTRAN_UNFORMATTED_BUFFER_SIZE:: Buffer size for unformatted files
+@end menu
+
+@node TMPDIR
+@section @env{TMPDIR}---Directory for scratch files
+
+When opening a file with @code{STATUS='SCRATCH'}, GNU Fortran tries to
+create the file in one of the potential directories by testing each
+directory in the order below.
+
+@enumerate
+@item
+The environment variable @env{TMPDIR}, if it exists.
+
+@item
+On the MinGW target, the directory returned by the @code{GetTempPath}
+function. Alternatively, on the Cygwin target, the @env{TMP} and
+@env{TEMP} environment variables, if they exist, in that order.
+
+@item
+The @code{P_tmpdir} macro if it is defined, otherwise the directory
+@file{/tmp}.
+@end enumerate
+
+@node GFORTRAN_STDIN_UNIT
+@section @env{GFORTRAN_STDIN_UNIT}---Unit number for standard input
+
+This environment variable can be used to select the unit number
+preconnected to standard input. This must be a positive integer.
+The default value is 5.
+
+@node GFORTRAN_STDOUT_UNIT
+@section @env{GFORTRAN_STDOUT_UNIT}---Unit number for standard output
+
+This environment variable can be used to select the unit number
+preconnected to standard output. This must be a positive integer.
+The default value is 6.
+
+@node GFORTRAN_STDERR_UNIT
+@section @env{GFORTRAN_STDERR_UNIT}---Unit number for standard error
+
+This environment variable can be used to select the unit number
+preconnected to standard error. This must be a positive integer.
+The default value is 0.
+
+@node GFORTRAN_UNBUFFERED_ALL
+@section @env{GFORTRAN_UNBUFFERED_ALL}---Do not buffer I/O on all units
+
+This environment variable controls whether all I/O is unbuffered. If
+the first letter is @samp{y}, @samp{Y} or @samp{1}, all I/O is
+unbuffered. This will slow down small sequential reads and writes. If
+the first letter is @samp{n}, @samp{N} or @samp{0}, I/O is buffered.
+This is the default.
+
+@node GFORTRAN_UNBUFFERED_PRECONNECTED
+@section @env{GFORTRAN_UNBUFFERED_PRECONNECTED}---Do not buffer I/O on preconnected units
+
+The environment variable named @env{GFORTRAN_UNBUFFERED_PRECONNECTED} controls
+whether I/O on a preconnected unit (i.e.@: STDOUT or STDERR) is unbuffered. If
+the first letter is @samp{y}, @samp{Y} or @samp{1}, I/O is unbuffered. This
+will slow down small sequential reads and writes. If the first letter
+is @samp{n}, @samp{N} or @samp{0}, I/O is buffered. This is the default.
+
+@node GFORTRAN_SHOW_LOCUS
+@section @env{GFORTRAN_SHOW_LOCUS}---Show location for runtime errors
+
+If the first letter is @samp{y}, @samp{Y} or @samp{1}, filename and
+line numbers for runtime errors are printed. If the first letter is
+@samp{n}, @samp{N} or @samp{0}, do not print filename and line numbers
+for runtime errors. The default is to print the location.
+
+@node GFORTRAN_OPTIONAL_PLUS
+@section @env{GFORTRAN_OPTIONAL_PLUS}---Print leading + where permitted
+
+If the first letter is @samp{y}, @samp{Y} or @samp{1},
+a plus sign is printed
+where permitted by the Fortran standard. If the first letter
+is @samp{n}, @samp{N} or @samp{0}, a plus sign is not printed
+in most cases. Default is not to print plus signs.
+
+@node GFORTRAN_LIST_SEPARATOR
+@section @env{GFORTRAN_LIST_SEPARATOR}---Separator for list output
+
+This environment variable specifies the separator when writing
+list-directed output. It may contain any number of spaces and
+at most one comma. If you specify this on the command line,
+be sure to quote spaces, as in
+@smallexample
+$ GFORTRAN_LIST_SEPARATOR=' , ' ./a.out
+@end smallexample
+when @command{a.out} is the compiled Fortran program that you want to run.
+Default is a single space.
+
+@node GFORTRAN_CONVERT_UNIT
+@section @env{GFORTRAN_CONVERT_UNIT}---Set conversion for unformatted I/O
+
+By setting the @env{GFORTRAN_CONVERT_UNIT} variable, it is possible
+to change the representation of data for unformatted files.
+The syntax for the @env{GFORTRAN_CONVERT_UNIT} variable for
+most systems is:
+@smallexample
+GFORTRAN_CONVERT_UNIT: mode | mode ';' exception | exception ;
+mode: 'native' | 'swap' | 'big_endian' | 'little_endian' ;
+exception: mode ':' unit_list | unit_list ;
+unit_list: unit_spec | unit_list unit_spec ;
+unit_spec: INTEGER | INTEGER '-' INTEGER ;
+@end smallexample
+The variable consists of an optional default mode, followed by
+a list of optional exceptions, which are separated by semicolons
+from the preceding default and each other. Each exception consists
+of a format and a comma-separated list of units. Valid values for
+the modes are the same as for the @code{CONVERT} specifier:
+
+@itemize @w{}
+@item @code{NATIVE} Use the native format. This is the default.
+@item @code{SWAP} Swap between little- and big-endian.
+@item @code{LITTLE_ENDIAN} Use the little-endian format
+for unformatted files.
+@item @code{BIG_ENDIAN} Use the big-endian format for unformatted files.
+@end itemize
+For POWER systems which support @option{-mabi=ieeelongdouble},
+there are additional options, which can be combined with the
+others with commas. Those are
+@itemize @w{}
+@item @code{R16_IEEE} Use IEEE 128-bit format for @code{REAL(KIND=16)}.
+@item @code{R16_IBM} Use IBM @code{long double} format for
+@code{REAL(KIND=16)}.
+@end itemize
+A missing mode for an exception is taken to mean @code{BIG_ENDIAN}.
+Examples of values for @env{GFORTRAN_CONVERT_UNIT} are:
+@itemize @w{}
+@item @code{'big_endian'} Do all unformatted I/O in big_endian mode.
+@item @code{'little_endian;native:10-20,25'} Do all unformatted I/O
+in little_endian mode, except for units 10 to 20 and 25, which are in
+native format.
+@item @code{'10-20'} Units 10 to 20 are big-endian, the rest is native.
+@item @code{'big_endian,r16_ibm'} Do all unformatted I/O in big-endian
+mode and use IBM long double for output of @code{REAL(KIND=16)} values.
+@end itemize
+
+Setting the environment variables should be done on the command
+line or via the @command{export}
+command for @command{sh}-compatible shells and via @command{setenv}
+for @command{csh}-compatible shells.
+
+Example for @command{sh}:
+@smallexample
+$ gfortran foo.f90
+$ GFORTRAN_CONVERT_UNIT='big_endian;native:10-20' ./a.out
+@end smallexample
+
+Example code for @command{csh}:
+@smallexample
+% gfortran foo.f90
+% setenv GFORTRAN_CONVERT_UNIT 'big_endian;native:10-20'
+% ./a.out
+@end smallexample
+
+Using anything but the native representation for unformatted data
+carries a significant speed overhead. If speed in this area matters
+to you, it is best if you use this only for data that needs to be
+portable.
+
+@xref{CONVERT specifier}, for an alternative way to specify the
+data representation for unformatted files. @xref{Runtime Options}, for
+setting a default data representation for the whole program. The
+@code{CONVERT} specifier overrides the @option{-fconvert} compile options.
+
+@emph{Note that the values specified via the GFORTRAN_CONVERT_UNIT
+environment variable will override the CONVERT specifier in the
+open statement}. This is to give control over data formats to
+users who do not have the source code of their program available.
+
+@node GFORTRAN_ERROR_BACKTRACE
+@section @env{GFORTRAN_ERROR_BACKTRACE}---Show backtrace on run-time errors
+
+If the @env{GFORTRAN_ERROR_BACKTRACE} variable is set to @samp{y},
+@samp{Y} or @samp{1} (only the first letter is relevant) then a
+backtrace is printed when a serious run-time error occurs. To disable
+the backtracing, set the variable to @samp{n}, @samp{N}, @samp{0}.
+Default is to print a backtrace unless the @option{-fno-backtrace}
+compile option was used.
+
+@node GFORTRAN_FORMATTED_BUFFER_SIZE
+@section @env{GFORTRAN_FORMATTED_BUFFER_SIZE}---Set buffer size for formatted I/O
+
+The @env{GFORTRAN_FORMATTED_BUFFER_SIZE} environment variable
+specifies buffer size in bytes to be used for formatted output.
+The default value is 8192.
+
+@node GFORTRAN_UNFORMATTED_BUFFER_SIZE
+@section @env{GFORTRAN_UNFORMATTED_BUFFER_SIZE}---Set buffer size for unformatted I/O
+
+The @env{GFORTRAN_UNFORMATTED_BUFFER_SIZE} environment variable
+specifies buffer size in bytes to be used for unformatted output.
+The default value is 131072.
+
+@c =====================================================================
+@c PART II: LANGUAGE REFERENCE
+@c =====================================================================
+
+@tex
+\part{II}{Language Reference}
+@end tex
+
+
+
+@c ---------------------------------------------------------------------
+@c Compiler Characteristics
+@c ---------------------------------------------------------------------
+
+@node Compiler Characteristics
+@chapter Compiler Characteristics
+
+This chapter describes certain characteristics of the GNU Fortran
+compiler, that are not specified by the Fortran standard, but which
+might in some way or another become visible to the programmer.
+
+@menu
+* KIND Type Parameters::
+* Internal representation of LOGICAL variables::
+* Evaluation of logical expressions::
+* MAX and MIN intrinsics with REAL NaN arguments::
+* Thread-safety of the runtime library::
+* Data consistency and durability::
+* Files opened without an explicit ACTION= specifier::
+* File operations on symbolic links::
+* File format of unformatted sequential files::
+* Asynchronous I/O::
+@end menu
+
+
+@node KIND Type Parameters
+@section KIND Type Parameters
+@cindex kind
+
+The @code{KIND} type parameters supported by GNU Fortran for the primitive
+data types are:
+
+@table @code
+
+@item INTEGER
+1, 2, 4, 8*, 16*, default: 4**
+
+@item LOGICAL
+1, 2, 4, 8*, 16*, default: 4**
+
+@item REAL
+4, 8, 10*, 16*, default: 4***
+
+@item COMPLEX
+4, 8, 10*, 16*, default: 4***
+
+@item DOUBLE PRECISION
+4, 8, 10*, 16*, default: 8***
+
+@item CHARACTER
+1, 4, default: 1
+
+@end table
+
+@noindent
+* not available on all systems @*
+** unless @option{-fdefault-integer-8} is used @*
+*** unless @option{-fdefault-real-8} is used (see @ref{Fortran Dialect Options})
+
+@noindent
+The @code{KIND} value matches the storage size in bytes, except for
+@code{COMPLEX} where the storage size is twice as much (or both real and
+imaginary part are a real value of the given size). It is recommended to use
+the @ref{SELECTED_CHAR_KIND}, @ref{SELECTED_INT_KIND} and
+@ref{SELECTED_REAL_KIND} intrinsics or the @code{INT8}, @code{INT16},
+@code{INT32}, @code{INT64}, @code{REAL32}, @code{REAL64}, and @code{REAL128}
+parameters of the @code{ISO_FORTRAN_ENV} module instead of the concrete values.
+The available kind parameters can be found in the constant arrays
+@code{CHARACTER_KINDS}, @code{INTEGER_KINDS}, @code{LOGICAL_KINDS} and
+@code{REAL_KINDS} in the @ref{ISO_FORTRAN_ENV} module. For C interoperability,
+the kind parameters of the @ref{ISO_C_BINDING} module should be used.
+
+
+@node Internal representation of LOGICAL variables
+@section Internal representation of LOGICAL variables
+@cindex logical, variable representation
+
+The Fortran standard does not specify how variables of @code{LOGICAL}
+type are represented, beyond requiring that @code{LOGICAL} variables
+of default kind have the same storage size as default @code{INTEGER}
+and @code{REAL} variables. The GNU Fortran internal representation is
+as follows.
+
+A @code{LOGICAL(KIND=N)} variable is represented as an
+@code{INTEGER(KIND=N)} variable, however, with only two permissible
+values: @code{1} for @code{.TRUE.} and @code{0} for
+@code{.FALSE.}. Any other integer value results in undefined behavior.
+
+See also @ref{Argument passing conventions} and @ref{Interoperability with C}.
+
+
+@node Evaluation of logical expressions
+@section Evaluation of logical expressions
+
+The Fortran standard does not require the compiler to evaluate all parts of an
+expression, if they do not contribute to the final result. For logical
+expressions with @code{.AND.} or @code{.OR.} operators, in particular, GNU
+Fortran will optimize out function calls (even to impure functions) if the
+result of the expression can be established without them. However, since not
+all compilers do that, and such an optimization can potentially modify the
+program flow and subsequent results, GNU Fortran throws warnings for such
+situations with the @option{-Wfunction-elimination} flag.
+
+
+@node MAX and MIN intrinsics with REAL NaN arguments
+@section MAX and MIN intrinsics with REAL NaN arguments
+@cindex MAX, MIN, NaN
+
+The Fortran standard does not specify what the result of the
+@code{MAX} and @code{MIN} intrinsics are if one of the arguments is a
+@code{NaN}. Accordingly, the GNU Fortran compiler does not specify
+that either, as this allows for faster and more compact code to be
+generated. If the programmer wishes to take some specific action in
+case one of the arguments is a @code{NaN}, it is necessary to
+explicitly test the arguments before calling @code{MAX} or @code{MIN},
+e.g. with the @code{IEEE_IS_NAN} function from the intrinsic module
+@code{IEEE_ARITHMETIC}.
+
+
+@node Thread-safety of the runtime library
+@section Thread-safety of the runtime library
+@cindex thread-safety, threads
+
+GNU Fortran can be used in programs with multiple threads, e.g.@: by
+using OpenMP, by calling OS thread handling functions via the
+@code{ISO_C_BINDING} facility, or by GNU Fortran compiled library code
+being called from a multi-threaded program.
+
+The GNU Fortran runtime library, (@code{libgfortran}), supports being
+called concurrently from multiple threads with the following
+exceptions.
+
+During library initialization, the C @code{getenv} function is used,
+which need not be thread-safe. Similarly, the @code{getenv}
+function is used to implement the @code{GET_ENVIRONMENT_VARIABLE} and
+@code{GETENV} intrinsics. It is the responsibility of the user to
+ensure that the environment is not being updated concurrently when any
+of these actions are taking place.
+
+The @code{EXECUTE_COMMAND_LINE} and @code{SYSTEM} intrinsics are
+implemented with the @code{system} function, which need not be
+thread-safe. It is the responsibility of the user to ensure that
+@code{system} is not called concurrently.
+
+For platforms not supporting thread-safe POSIX functions, further
+functionality might not be thread-safe. For details, please consult
+the documentation for your operating system.
+
+The GNU Fortran runtime library uses various C library functions that
+depend on the locale, such as @code{strtod} and @code{snprintf}. In
+order to work correctly in locale-aware programs that set the locale
+using @code{setlocale}, the locale is reset to the default ``C''
+locale while executing a formatted @code{READ} or @code{WRITE}
+statement. On targets supporting the POSIX 2008 per-thread locale
+functions (e.g. @code{newlocale}, @code{uselocale},
+@code{freelocale}), these are used and thus the global locale set
+using @code{setlocale} or the per-thread locales in other threads are
+not affected. However, on targets lacking this functionality, the
+global LC_NUMERIC locale is set to ``C'' during the formatted I/O.
+Thus, on such targets it's not safe to call @code{setlocale}
+concurrently from another thread while a Fortran formatted I/O
+operation is in progress. Also, other threads doing something
+dependent on the LC_NUMERIC locale might not work correctly if a
+formatted I/O operation is in progress in another thread.
+
+@node Data consistency and durability
+@section Data consistency and durability
+@cindex consistency, durability
+
+This section contains a brief overview of data and metadata
+consistency and durability issues when doing I/O.
+
+With respect to durability, GNU Fortran makes no effort to ensure that
+data is committed to stable storage. If this is required, the GNU
+Fortran programmer can use the intrinsic @code{FNUM} to retrieve the
+low level file descriptor corresponding to an open Fortran unit. Then,
+using e.g. the @code{ISO_C_BINDING} feature, one can call the
+underlying system call to flush dirty data to stable storage, such as
+@code{fsync} on POSIX, @code{_commit} on MingW, or @code{fcntl(fd,
+F_FULLSYNC, 0)} on Mac OS X. The following example shows how to call
+fsync:
+
+@smallexample
+ ! Declare the interface for POSIX fsync function
+ interface
+ function fsync (fd) bind(c,name="fsync")
+ use iso_c_binding, only: c_int
+ integer(c_int), value :: fd
+ integer(c_int) :: fsync
+ end function fsync
+ end interface
+
+ ! Variable declaration
+ integer :: ret
+
+ ! Opening unit 10
+ open (10,file="foo")
+
+ ! ...
+ ! Perform I/O on unit 10
+ ! ...
+
+ ! Flush and sync
+ flush(10)
+ ret = fsync(fnum(10))
+
+ ! Handle possible error
+ if (ret /= 0) stop "Error calling FSYNC"
+@end smallexample
+
+With respect to consistency, for regular files GNU Fortran uses
+buffered I/O in order to improve performance. This buffer is flushed
+automatically when full and in some other situations, e.g. when
+closing a unit. It can also be explicitly flushed with the
+@code{FLUSH} statement. Also, the buffering can be turned off with the
+@code{GFORTRAN_UNBUFFERED_ALL} and
+@code{GFORTRAN_UNBUFFERED_PRECONNECTED} environment variables. Special
+files, such as terminals and pipes, are always unbuffered. Sometimes,
+however, further things may need to be done in order to allow other
+processes to see data that GNU Fortran has written, as follows.
+
+The Windows platform supports a relaxed metadata consistency model,
+where file metadata is written to the directory lazily. This means
+that, for instance, the @code{dir} command can show a stale size for a
+file. One can force a directory metadata update by closing the unit,
+or by calling @code{_commit} on the file descriptor. Note, though,
+that @code{_commit} will force all dirty data to stable storage, which
+is often a very slow operation.
+
+The Network File System (NFS) implements a relaxed consistency model
+called open-to-close consistency. Closing a file forces dirty data and
+metadata to be flushed to the server, and opening a file forces the
+client to contact the server in order to revalidate cached
+data. @code{fsync} will also force a flush of dirty data and metadata
+to the server. Similar to @code{open} and @code{close}, acquiring and
+releasing @code{fcntl} file locks, if the server supports them, will
+also force cache validation and flushing dirty data and metadata.
+
+
+@node Files opened without an explicit ACTION= specifier
+@section Files opened without an explicit ACTION= specifier
+@cindex open, action
+
+The Fortran standard says that if an @code{OPEN} statement is executed
+without an explicit @code{ACTION=} specifier, the default value is
+processor dependent. GNU Fortran behaves as follows:
+
+@enumerate
+@item Attempt to open the file with @code{ACTION='READWRITE'}
+@item If that fails, try to open with @code{ACTION='READ'}
+@item If that fails, try to open with @code{ACTION='WRITE'}
+@item If that fails, generate an error
+@end enumerate
+
+
+@node File operations on symbolic links
+@section File operations on symbolic links
+@cindex file, symbolic link
+
+This section documents the behavior of GNU Fortran for file operations on
+symbolic links, on systems that support them.
+
+@itemize
+
+@item Results of INQUIRE statements of the ``inquire by file'' form will
+relate to the target of the symbolic link. For example,
+@code{INQUIRE(FILE="foo",EXIST=ex)} will set @var{ex} to @var{.true.} if
+@var{foo} is a symbolic link pointing to an existing file, and @var{.false.}
+if @var{foo} points to an non-existing file (``dangling'' symbolic link).
+
+@item Using the @code{OPEN} statement with a @code{STATUS="NEW"} specifier
+on a symbolic link will result in an error condition, whether the symbolic
+link points to an existing target or is dangling.
+
+@item If a symbolic link was connected, using the @code{CLOSE} statement
+with a @code{STATUS="DELETE"} specifier will cause the symbolic link itself
+to be deleted, not its target.
+
+@end itemize
+
+@node File format of unformatted sequential files
+@section File format of unformatted sequential files
+@cindex file, unformatted sequential
+@cindex unformatted sequential
+@cindex sequential, unformatted
+@cindex record marker
+@cindex subrecord
+
+Unformatted sequential files are stored as logical records using
+record markers. Each logical record consists of one of more
+subrecords.
+
+Each subrecord consists of a leading record marker, the data written
+by the user program, and a trailing record marker. The record markers
+are four-byte integers by default, and eight-byte integers if the
+@option{-fmax-subrecord-length=8} option (which exists for backwards
+compability only) is in effect.
+
+The representation of the record markers is that of unformatted files
+given with the @option{-fconvert} option, the @ref{CONVERT specifier}
+in an open statement or the @ref{GFORTRAN_CONVERT_UNIT} environment
+variable.
+
+The maximum number of bytes of user data in a subrecord is 2147483639
+(2 GiB - 9) for a four-byte record marker. This limit can be lowered
+with the @option{-fmax-subrecord-length} option, although this is
+rarely useful. If the length of a logical record exceeds this limit,
+the data is distributed among several subrecords.
+
+The absolute of the number stored in the record markers is the number
+of bytes of user data in the corresponding subrecord. If the leading
+record marker of a subrecord contains a negative number, another
+subrecord follows the current one. If the trailing record marker
+contains a negative number, then there is a preceding subrecord.
+
+In the most simple case, with only one subrecord per logical record,
+both record markers contain the number of bytes of user data in the
+record.
+
+The format for unformatted sequential data can be duplicated using
+unformatted stream, as shown in the example program for an unformatted
+record containing a single subrecord:
+
+@smallexample
+program main
+ use iso_fortran_env, only: int32
+ implicit none
+ integer(int32) :: i
+ real, dimension(10) :: a, b
+ call random_number(a)
+ open (10,file='test.dat',form='unformatted',access='stream')
+ inquire (iolength=i) a
+ write (10) i, a, i
+ close (10)
+ open (10,file='test.dat',form='unformatted')
+ read (10) b
+ if (all (a == b)) print *,'success!'
+end program main
+@end smallexample
+
+@node Asynchronous I/O
+@section Asynchronous I/O
+@cindex input/output, asynchronous
+@cindex asynchronous I/O
+
+Asynchronous I/O is supported if the program is linked against the
+POSIX thread library. If that is not the case, all I/O is performed
+as synchronous. On systems which do not support pthread condition
+variables, such as AIX, I/O is also performed as synchronous.
+
+On some systems, such as Darwin or Solaris, the POSIX thread library
+is always linked in, so asynchronous I/O is always performed. On other
+sytems, such as Linux, it is necessary to specify @option{-pthread},
+@option{-lpthread} or @option{-fopenmp} during the linking step.
+
+@c ---------------------------------------------------------------------
+@c Extensions
+@c ---------------------------------------------------------------------
+
+@c Maybe this chapter should be merged with the 'Standards' section,
+@c whenever that is written :-)
+
+@node Extensions
+@chapter Extensions
+@cindex extensions
+
+The two sections below detail the extensions to standard Fortran that are
+implemented in GNU Fortran, as well as some of the popular or
+historically important extensions that are not (or not yet) implemented.
+For the latter case, we explain the alternatives available to GNU Fortran
+users, including replacement by standard-conforming code or GNU
+extensions.
+
+@menu
+* Extensions implemented in GNU Fortran::
+* Extensions not implemented in GNU Fortran::
+@end menu
+
+
+@node Extensions implemented in GNU Fortran
+@section Extensions implemented in GNU Fortran
+@cindex extensions, implemented
+
+GNU Fortran implements a number of extensions over standard Fortran.
+This chapter contains information on their syntax and meaning. There
+are currently two categories of GNU Fortran extensions, those that
+provide functionality beyond that provided by any standard, and those
+that are supported by GNU Fortran purely for backward compatibility
+with legacy compilers. By default, @option{-std=gnu} allows the
+compiler to accept both types of extensions, but to warn about the use
+of the latter. Specifying either @option{-std=f95},
+@option{-std=f2003}, @option{-std=f2008}, or @option{-std=f2018}
+disables both types of extensions, and @option{-std=legacy} allows
+both without warning. The special compile flag @option{-fdec} enables
+additional compatibility extensions along with those enabled by
+@option{-std=legacy}.
+
+@menu
+* Old-style kind specifications::
+* Old-style variable initialization::
+* Extensions to namelist::
+* X format descriptor without count field::
+* Commas in FORMAT specifications::
+* Missing period in FORMAT specifications::
+* Default widths for F@comma{} G and I format descriptors::
+* I/O item lists::
+* @code{Q} exponent-letter::
+* BOZ literal constants::
+* Real array indices::
+* Unary operators::
+* Implicitly convert LOGICAL and INTEGER values::
+* Hollerith constants support::
+* Character conversion::
+* Cray pointers::
+* CONVERT specifier::
+* OpenMP::
+* OpenACC::
+* Argument list functions::
+* Read/Write after EOF marker::
+* STRUCTURE and RECORD::
+* UNION and MAP::
+* Type variants for integer intrinsics::
+* AUTOMATIC and STATIC attributes::
+* Extended math intrinsics::
+* Form feed as whitespace::
+* TYPE as an alias for PRINT::
+* %LOC as an rvalue::
+* .XOR. operator::
+* Bitwise logical operators::
+* Extended I/O specifiers::
+* Legacy PARAMETER statements::
+* Default exponents::
+@end menu
+
+@node Old-style kind specifications
+@subsection Old-style kind specifications
+@cindex kind, old-style
+
+GNU Fortran allows old-style kind specifications in declarations. These
+look like:
+@smallexample
+ TYPESPEC*size x,y,z
+@end smallexample
+@noindent
+where @code{TYPESPEC} is a basic type (@code{INTEGER}, @code{REAL},
+etc.), and where @code{size} is a byte count corresponding to the
+storage size of a valid kind for that type. (For @code{COMPLEX}
+variables, @code{size} is the total size of the real and imaginary
+parts.) The statement then declares @code{x}, @code{y} and @code{z} to
+be of type @code{TYPESPEC} with the appropriate kind. This is
+equivalent to the standard-conforming declaration
+@smallexample
+ TYPESPEC(k) x,y,z
+@end smallexample
+@noindent
+where @code{k} is the kind parameter suitable for the intended precision. As
+kind parameters are implementation-dependent, use the @code{KIND},
+@code{SELECTED_INT_KIND} and @code{SELECTED_REAL_KIND} intrinsics to retrieve
+the correct value, for instance @code{REAL*8 x} can be replaced by:
+@smallexample
+INTEGER, PARAMETER :: dbl = KIND(1.0d0)
+REAL(KIND=dbl) :: x
+@end smallexample
+
+@node Old-style variable initialization
+@subsection Old-style variable initialization
+
+GNU Fortran allows old-style initialization of variables of the
+form:
+@smallexample
+ INTEGER i/1/,j/2/
+ REAL x(2,2) /3*0.,1./
+@end smallexample
+The syntax for the initializers is as for the @code{DATA} statement, but
+unlike in a @code{DATA} statement, an initializer only applies to the
+variable immediately preceding the initialization. In other words,
+something like @code{INTEGER I,J/2,3/} is not valid. This style of
+initialization is only allowed in declarations without double colons
+(@code{::}); the double colons were introduced in Fortran 90, which also
+introduced a standard syntax for initializing variables in type
+declarations.
+
+Examples of standard-conforming code equivalent to the above example
+are:
+@smallexample
+! Fortran 90
+ INTEGER :: i = 1, j = 2
+ REAL :: x(2,2) = RESHAPE((/0.,0.,0.,1./),SHAPE(x))
+! Fortran 77
+ INTEGER i, j
+ REAL x(2,2)
+ DATA i/1/, j/2/, x/3*0.,1./
+@end smallexample
+
+Note that variables which are explicitly initialized in declarations
+or in @code{DATA} statements automatically acquire the @code{SAVE}
+attribute.
+
+@node Extensions to namelist
+@subsection Extensions to namelist
+@cindex Namelist
+
+GNU Fortran fully supports the Fortran 95 standard for namelist I/O
+including array qualifiers, substrings and fully qualified derived types.
+The output from a namelist write is compatible with namelist read. The
+output has all names in upper case and indentation to column 1 after the
+namelist name. Two extensions are permitted:
+
+Old-style use of @samp{$} instead of @samp{&}
+@smallexample
+$MYNML
+ X(:)%Y(2) = 1.0 2.0 3.0
+ CH(1:4) = "abcd"
+$END
+@end smallexample
+
+It should be noted that the default terminator is @samp{/} rather than
+@samp{&END}.
+
+Querying of the namelist when inputting from stdin. After at least
+one space, entering @samp{?} sends to stdout the namelist name and the names of
+the variables in the namelist:
+@smallexample
+ ?
+
+&mynml
+ x
+ x%y
+ ch
+&end
+@end smallexample
+
+Entering @samp{=?} outputs the namelist to stdout, as if
+@code{WRITE(*,NML = mynml)} had been called:
+@smallexample
+=?
+
+&MYNML
+ X(1)%Y= 0.000000 , 1.000000 , 0.000000 ,
+ X(2)%Y= 0.000000 , 2.000000 , 0.000000 ,
+ X(3)%Y= 0.000000 , 3.000000 , 0.000000 ,
+ CH=abcd, /
+@end smallexample
+
+To aid this dialog, when input is from stdin, errors send their
+messages to stderr and execution continues, even if @code{IOSTAT} is set.
+
+@code{PRINT} namelist is permitted. This causes an error if
+@option{-std=f95} is used.
+@smallexample
+PROGRAM test_print
+ REAL, dimension (4) :: x = (/1.0, 2.0, 3.0, 4.0/)
+ NAMELIST /mynml/ x
+ PRINT mynml
+END PROGRAM test_print
+@end smallexample
+
+Expanded namelist reads are permitted. This causes an error if
+@option{-std=f95} is used. In the following example, the first element
+of the array will be given the value 0.00 and the two succeeding
+elements will be given the values 1.00 and 2.00.
+@smallexample
+&MYNML
+ X(1,1) = 0.00 , 1.00 , 2.00
+/
+@end smallexample
+
+When writing a namelist, if no @code{DELIM=} is specified, by default a
+double quote is used to delimit character strings. If -std=F95, F2003,
+or F2008, etc, the delim status is set to 'none'. Defaulting to
+quotes ensures that namelists with character strings can be subsequently
+read back in accurately.
+
+@node X format descriptor without count field
+@subsection @code{X} format descriptor without count field
+
+To support legacy codes, GNU Fortran permits the count field of the
+@code{X} edit descriptor in @code{FORMAT} statements to be omitted.
+When omitted, the count is implicitly assumed to be one.
+
+@smallexample
+ PRINT 10, 2, 3
+10 FORMAT (I1, X, I1)
+@end smallexample
+
+@node Commas in FORMAT specifications
+@subsection Commas in @code{FORMAT} specifications
+
+To support legacy codes, GNU Fortran allows the comma separator
+to be omitted immediately before and after character string edit
+descriptors in @code{FORMAT} statements. A comma with no following format
+decriptor is permited if the @option{-fdec-blank-format-item} is given on
+the command line. This is considered non-conforming code and is
+discouraged.
+
+@smallexample
+ PRINT 10, 2, 3
+10 FORMAT ('FOO='I1' BAR='I2)
+ print 20, 5, 6
+20 FORMAT (I3, I3,)
+@end smallexample
+
+
+@node Missing period in FORMAT specifications
+@subsection Missing period in @code{FORMAT} specifications
+
+To support legacy codes, GNU Fortran allows missing periods in format
+specifications if and only if @option{-std=legacy} is given on the
+command line. This is considered non-conforming code and is
+discouraged.
+
+@smallexample
+ REAL :: value
+ READ(*,10) value
+10 FORMAT ('F4')
+@end smallexample
+
+@node Default widths for F@comma{} G and I format descriptors
+@subsection Default widths for @code{F}, @code{G} and @code{I} format descriptors
+
+To support legacy codes, GNU Fortran allows width to be omitted from format
+specifications if and only if @option{-fdec-format-defaults} is given on the
+command line. Default widths will be used. This is considered non-conforming
+code and is discouraged.
+
+@smallexample
+ REAL :: value1
+ INTEGER :: value2
+ WRITE(*,10) value1, value1, value2
+10 FORMAT ('F, G, I')
+@end smallexample
+
+
+@node I/O item lists
+@subsection I/O item lists
+@cindex I/O item lists
+
+To support legacy codes, GNU Fortran allows the input item list
+of the @code{READ} statement, and the output item lists of the
+@code{WRITE} and @code{PRINT} statements, to start with a comma.
+
+@node @code{Q} exponent-letter
+@subsection @code{Q} exponent-letter
+@cindex @code{Q} exponent-letter
+
+GNU Fortran accepts real literal constants with an exponent-letter
+of @code{Q}, for example, @code{1.23Q45}. The constant is interpreted
+as a @code{REAL(16)} entity on targets that support this type. If
+the target does not support @code{REAL(16)} but has a @code{REAL(10)}
+type, then the real-literal-constant will be interpreted as a
+@code{REAL(10)} entity. In the absence of @code{REAL(16)} and
+@code{REAL(10)}, an error will occur.
+
+@node BOZ literal constants
+@subsection BOZ literal constants
+@cindex BOZ literal constants
+
+Besides decimal constants, Fortran also supports binary (@code{b}),
+octal (@code{o}) and hexadecimal (@code{z}) integer constants. The
+syntax is: @samp{prefix quote digits quote}, where the prefix is
+either @code{b}, @code{o} or @code{z}, quote is either @code{'} or
+@code{"} and the digits are @code{0} or @code{1} for binary,
+between @code{0} and @code{7} for octal, and between @code{0} and
+@code{F} for hexadecimal. (Example: @code{b'01011101'}.)
+
+Up to Fortran 95, BOZ literal constants were only allowed to initialize
+integer variables in DATA statements. Since Fortran 2003 BOZ literal
+constants are also allowed as actual arguments to the @code{REAL},
+@code{DBLE}, @code{INT} and @code{CMPLX} intrinsic functions.
+The BOZ literal constant is simply a string of bits, which is padded
+or truncated as needed, during conversion to a numeric type. The
+Fortran standard states that the treatment of the sign bit is processor
+dependent. Gfortran interprets the sign bit as a user would expect.
+
+As a deprecated extension, GNU Fortran allows hexadecimal BOZ literal
+constants to be specified using the @code{X} prefix. That the BOZ literal
+constant can also be specified by adding a suffix to the string, for
+example, @code{Z'ABC'} and @code{'ABC'X} are equivalent. Additionally,
+as extension, BOZ literals are permitted in some contexts outside of
+@code{DATA} and the intrinsic functions listed in the Fortran standard.
+Use @option{-fallow-invalid-boz} to enable the extension.
+
+@node Real array indices
+@subsection Real array indices
+@cindex array, indices of type real
+
+As an extension, GNU Fortran allows the use of @code{REAL} expressions
+or variables as array indices.
+
+@node Unary operators
+@subsection Unary operators
+@cindex operators, unary
+
+As an extension, GNU Fortran allows unary plus and unary minus operators
+to appear as the second operand of binary arithmetic operators without
+the need for parenthesis.
+
+@smallexample
+ X = Y * -Z
+@end smallexample
+
+@node Implicitly convert LOGICAL and INTEGER values
+@subsection Implicitly convert @code{LOGICAL} and @code{INTEGER} values
+@cindex conversion, to integer
+@cindex conversion, to logical
+
+As an extension for backwards compatibility with other compilers, GNU
+Fortran allows the implicit conversion of @code{LOGICAL} values to
+@code{INTEGER} values and vice versa. When converting from a
+@code{LOGICAL} to an @code{INTEGER}, @code{.FALSE.} is interpreted as
+zero, and @code{.TRUE.} is interpreted as one. When converting from
+@code{INTEGER} to @code{LOGICAL}, the value zero is interpreted as
+@code{.FALSE.} and any nonzero value is interpreted as @code{.TRUE.}.
+
+@smallexample
+ LOGICAL :: l
+ l = 1
+@end smallexample
+@smallexample
+ INTEGER :: i
+ i = .TRUE.
+@end smallexample
+
+However, there is no implicit conversion of @code{INTEGER} values in
+@code{if}-statements, nor of @code{LOGICAL} or @code{INTEGER} values
+in I/O operations.
+
+@node Hollerith constants support
+@subsection Hollerith constants support
+@cindex Hollerith constants
+
+GNU Fortran supports Hollerith constants in assignments, @code{DATA}
+statements, function and subroutine arguments. A Hollerith constant is
+written as a string of characters preceded by an integer constant
+indicating the character count, and the letter @code{H} or
+@code{h}, and stored in bytewise fashion in a numeric (@code{INTEGER},
+@code{REAL}, or @code{COMPLEX}), @code{LOGICAL} or @code{CHARACTER} variable.
+The constant will be padded with spaces or truncated to fit the size of
+the variable in which it is stored.
+
+Examples of valid uses of Hollerith constants:
+@smallexample
+ complex*16 x(2)
+ data x /16Habcdefghijklmnop, 16Hqrstuvwxyz012345/
+ x(1) = 16HABCDEFGHIJKLMNOP
+ call foo (4h abc)
+@end smallexample
+
+Examples of Hollerith constants:
+@smallexample
+ integer*4 a
+ a = 0H ! Invalid, at least one character is needed.
+ a = 4HAB12 ! Valid
+ a = 8H12345678 ! Valid, but the Hollerith constant will be truncated.
+ a = 3Hxyz ! Valid, but the Hollerith constant will be padded.
+@end smallexample
+
+In general, Hollerith constants were used to provide a rudimentary
+facility for handling character strings in early Fortran compilers,
+prior to the introduction of @code{CHARACTER} variables in Fortran 77;
+in those cases, the standard-compliant equivalent is to convert the
+program to use proper character strings. On occasion, there may be a
+case where the intent is specifically to initialize a numeric variable
+with a given byte sequence. In these cases, the same result can be
+obtained by using the @code{TRANSFER} statement, as in this example.
+@smallexample
+ integer(kind=4) :: a
+ a = transfer ("abcd", a) ! equivalent to: a = 4Habcd
+@end smallexample
+
+The use of the @option{-fdec} option extends support of Hollerith constants
+to comparisons:
+@smallexample
+ integer*4 a
+ a = 4hABCD
+ if (a .ne. 4habcd) then
+ write(*,*) "no match"
+ end if
+@end smallexample
+
+Supported types are numeric (@code{INTEGER}, @code{REAL}, or @code{COMPLEX}),
+and @code{CHARACTER}.
+
+@node Character conversion
+@subsection Character conversion
+@cindex conversion, to character
+
+Allowing character literals to be used in a similar way to Hollerith constants
+is a non-standard extension. This feature is enabled using
+-fdec-char-conversions and only applies to character literals of @code{kind=1}.
+
+Character literals can be used in @code{DATA} statements and assignments with
+numeric (@code{INTEGER}, @code{REAL}, or @code{COMPLEX}) or @code{LOGICAL}
+variables. Like Hollerith constants they are copied byte-wise fashion. The
+constant will be padded with spaces or truncated to fit the size of the
+variable in which it is stored.
+
+Examples:
+@smallexample
+ integer*4 x
+ data x / 'abcd' /
+
+ x = 'A' ! Will be padded.
+ x = 'ab1234' ! Will be truncated.
+@end smallexample
+
+
+@node Cray pointers
+@subsection Cray pointers
+@cindex pointer, Cray
+
+Cray pointers are part of a non-standard extension that provides a
+C-like pointer in Fortran. This is accomplished through a pair of
+variables: an integer "pointer" that holds a memory address, and a
+"pointee" that is used to dereference the pointer.
+
+Pointer/pointee pairs are declared in statements of the form:
+@smallexample
+ pointer ( <pointer> , <pointee> )
+@end smallexample
+or,
+@smallexample
+ pointer ( <pointer1> , <pointee1> ), ( <pointer2> , <pointee2> ), ...
+@end smallexample
+The pointer is an integer that is intended to hold a memory address.
+The pointee may be an array or scalar.
+If an assumed-size array is permitted within the scoping unit, a
+pointee can be an assumed-size array.
+That is, the last dimension may be left unspecified by using a @code{*}
+in place of a value. A pointee cannot be an assumed shape array.
+No space is allocated for the pointee.
+
+The pointee may have its type declared before or after the pointer
+statement, and its array specification (if any) may be declared
+before, during, or after the pointer statement. The pointer may be
+declared as an integer prior to the pointer statement. However, some
+machines have default integer sizes that are different than the size
+of a pointer, and so the following code is not portable:
+@smallexample
+ integer ipt
+ pointer (ipt, iarr)
+@end smallexample
+If a pointer is declared with a kind that is too small, the compiler
+will issue a warning; the resulting binary will probably not work
+correctly, because the memory addresses stored in the pointers may be
+truncated. It is safer to omit the first line of the above example;
+if explicit declaration of ipt's type is omitted, then the compiler
+will ensure that ipt is an integer variable large enough to hold a
+pointer.
+
+Pointer arithmetic is valid with Cray pointers, but it is not the same
+as C pointer arithmetic. Cray pointers are just ordinary integers, so
+the user is responsible for determining how many bytes to add to a
+pointer in order to increment it. Consider the following example:
+@smallexample
+ real target(10)
+ real pointee(10)
+ pointer (ipt, pointee)
+ ipt = loc (target)
+ ipt = ipt + 1
+@end smallexample
+The last statement does not set @code{ipt} to the address of
+@code{target(1)}, as it would in C pointer arithmetic. Adding @code{1}
+to @code{ipt} just adds one byte to the address stored in @code{ipt}.
+
+Any expression involving the pointee will be translated to use the
+value stored in the pointer as the base address.
+
+To get the address of elements, this extension provides an intrinsic
+function @code{LOC()}. The @code{LOC()} function is equivalent to the
+@code{&} operator in C, except the address is cast to an integer type:
+@smallexample
+ real ar(10)
+ pointer(ipt, arpte(10))
+ real arpte
+ ipt = loc(ar) ! Makes arpte is an alias for ar
+ arpte(1) = 1.0 ! Sets ar(1) to 1.0
+@end smallexample
+The pointer can also be set by a call to the @code{MALLOC} intrinsic
+(see @ref{MALLOC}).
+
+Cray pointees often are used to alias an existing variable. For
+example:
+@smallexample
+ integer target(10)
+ integer iarr(10)
+ pointer (ipt, iarr)
+ ipt = loc(target)
+@end smallexample
+As long as @code{ipt} remains unchanged, @code{iarr} is now an alias for
+@code{target}. The optimizer, however, will not detect this aliasing, so
+it is unsafe to use @code{iarr} and @code{target} simultaneously. Using
+a pointee in any way that violates the Fortran aliasing rules or
+assumptions is illegal. It is the user's responsibility to avoid doing
+this; the compiler works under the assumption that no such aliasing
+occurs.
+
+Cray pointers will work correctly when there is no aliasing (i.e., when
+they are used to access a dynamically allocated block of memory), and
+also in any routine where a pointee is used, but any variable with which
+it shares storage is not used. Code that violates these rules may not
+run as the user intends. This is not a bug in the optimizer; any code
+that violates the aliasing rules is illegal. (Note that this is not
+unique to GNU Fortran; any Fortran compiler that supports Cray pointers
+will ``incorrectly'' optimize code with illegal aliasing.)
+
+There are a number of restrictions on the attributes that can be applied
+to Cray pointers and pointees. Pointees may not have the
+@code{ALLOCATABLE}, @code{INTENT}, @code{OPTIONAL}, @code{DUMMY},
+@code{TARGET}, @code{INTRINSIC}, or @code{POINTER} attributes. Pointers
+may not have the @code{DIMENSION}, @code{POINTER}, @code{TARGET},
+@code{ALLOCATABLE}, @code{EXTERNAL}, or @code{INTRINSIC} attributes, nor
+may they be function results. Pointees may not occur in more than one
+pointer statement. A pointee cannot be a pointer. Pointees cannot occur
+in equivalence, common, or data statements.
+
+A Cray pointer may also point to a function or a subroutine. For
+example, the following excerpt is valid:
+@smallexample
+ implicit none
+ external sub
+ pointer (subptr,subpte)
+ external subpte
+ subptr = loc(sub)
+ call subpte()
+ [...]
+ subroutine sub
+ [...]
+ end subroutine sub
+@end smallexample
+
+A pointer may be modified during the course of a program, and this
+will change the location to which the pointee refers. However, when
+pointees are passed as arguments, they are treated as ordinary
+variables in the invoked function. Subsequent changes to the pointer
+will not change the base address of the array that was passed.
+
+@node CONVERT specifier
+@subsection @code{CONVERT} specifier
+@cindex @code{CONVERT} specifier
+
+GNU Fortran allows the conversion of unformatted data between little-
+and big-endian representation to facilitate moving of data
+between different systems. The conversion can be indicated with
+the @code{CONVERT} specifier on the @code{OPEN} statement.
+@xref{GFORTRAN_CONVERT_UNIT}, for an alternative way of specifying
+the data format via an environment variable.
+
+Valid values for @code{CONVERT} on most systems are:
+@itemize @w{}
+@item @code{CONVERT='NATIVE'} Use the native format. This is the default.
+@item @code{CONVERT='SWAP'} Swap between little- and big-endian.
+@item @code{CONVERT='LITTLE_ENDIAN'} Use the little-endian representation
+for unformatted files.
+@item @code{CONVERT='BIG_ENDIAN'} Use the big-endian representation for
+unformatted files.
+@end itemize
+On POWER systems which support @option{-mabi=ieeelongdouble},
+there are additional options, which can be combined with the others
+with commas. Those are
+@itemize @w{}
+@item @code{CONVERT='R16_IEEE'} Use IEEE 128-bit format for
+@code{REAL(KIND=16)}.
+@item @code{CONVERT='R16_IBM'} Use IBM @code{long double} format for
+real@code{REAL(KIND=16)}.
+@end itemize
+
+Using the option could look like this:
+@smallexample
+ open(file='big.dat',form='unformatted',access='sequential', &
+ convert='big_endian')
+@end smallexample
+
+The value of the conversion can be queried by using
+@code{INQUIRE(CONVERT=ch)}. The values returned are
+@code{'BIG_ENDIAN'} and @code{'LITTLE_ENDIAN'}.
+
+@code{CONVERT} works between big- and little-endian for
+@code{INTEGER} values of all supported kinds and for @code{REAL}
+on IEEE systems of kinds 4 and 8. Conversion between different
+``extended double'' types on different architectures such as
+m68k and x86_64, which GNU Fortran
+supports as @code{REAL(KIND=10)} and @code{REAL(KIND=16)}, will
+probably not work.
+
+@emph{Note that the values specified via the GFORTRAN_CONVERT_UNIT
+environment variable will override the CONVERT specifier in the
+open statement}. This is to give control over data formats to
+users who do not have the source code of their program available.
+
+Using anything but the native representation for unformatted data
+carries a significant speed overhead. If speed in this area matters
+to you, it is best if you use this only for data that needs to be
+portable.
+
+@node OpenMP
+@subsection OpenMP
+@cindex OpenMP
+
+OpenMP (Open Multi-Processing) is an application programming
+interface (API) that supports multi-platform shared memory
+multiprocessing programming in C/C++ and Fortran on many
+architectures, including Unix and Microsoft Windows platforms.
+It consists of a set of compiler directives, library routines,
+and environment variables that influence run-time behavior.
+
+GNU Fortran strives to be compatible to the
+@uref{https://openmp.org/specifications/,
+OpenMP Application Program Interface v4.5}.
+
+To enable the processing of the OpenMP directive @code{!$omp} in
+free-form source code; the @code{c$omp}, @code{*$omp} and @code{!$omp}
+directives in fixed form; the @code{!$} conditional compilation sentinels
+in free form; and the @code{c$}, @code{*$} and @code{!$} sentinels
+in fixed form, @command{gfortran} needs to be invoked with the
+@option{-fopenmp}. This also arranges for automatic linking of the
+GNU Offloading and Multi Processing Runtime Library
+@ref{Top,,libgomp,libgomp,GNU Offloading and Multi Processing Runtime
+Library}.
+
+The OpenMP Fortran runtime library routines are provided both in a
+form of a Fortran 90 module named @code{omp_lib} and in a form of
+a Fortran @code{include} file named @file{omp_lib.h}.
+
+An example of a parallelized loop taken from Appendix A.1 of
+the OpenMP Application Program Interface v2.5:
+@smallexample
+SUBROUTINE A1(N, A, B)
+ INTEGER I, N
+ REAL B(N), A(N)
+!$OMP PARALLEL DO !I is private by default
+ DO I=2,N
+ B(I) = (A(I) + A(I-1)) / 2.0
+ ENDDO
+!$OMP END PARALLEL DO
+END SUBROUTINE A1
+@end smallexample
+
+Please note:
+@itemize
+@item
+@option{-fopenmp} implies @option{-frecursive}, i.e., all local arrays
+will be allocated on the stack. When porting existing code to OpenMP,
+this may lead to surprising results, especially to segmentation faults
+if the stacksize is limited.
+
+@item
+On glibc-based systems, OpenMP enabled applications cannot be statically
+linked due to limitations of the underlying pthreads-implementation. It
+might be possible to get a working solution if
+@command{-Wl,--whole-archive -lpthread -Wl,--no-whole-archive} is added
+to the command line. However, this is not supported by @command{gcc} and
+thus not recommended.
+@end itemize
+
+@node OpenACC
+@subsection OpenACC
+@cindex OpenACC
+
+OpenACC is an application programming interface (API) that supports
+offloading of code to accelerator devices. It consists of a set of
+compiler directives, library routines, and environment variables that
+influence run-time behavior.
+
+GNU Fortran strives to be compatible to the
+@uref{https://www.openacc.org/, OpenACC Application Programming
+Interface v2.6}.
+
+To enable the processing of the OpenACC directive @code{!$acc} in
+free-form source code; the @code{c$acc}, @code{*$acc} and @code{!$acc}
+directives in fixed form; the @code{!$} conditional compilation
+sentinels in free form; and the @code{c$}, @code{*$} and @code{!$}
+sentinels in fixed form, @command{gfortran} needs to be invoked with
+the @option{-fopenacc}. This also arranges for automatic linking of
+the GNU Offloading and Multi Processing Runtime Library
+@ref{Top,,libgomp,libgomp,GNU Offloading and Multi Processing Runtime
+Library}.
+
+The OpenACC Fortran runtime library routines are provided both in a
+form of a Fortran 90 module named @code{openacc} and in a form of a
+Fortran @code{include} file named @file{openacc_lib.h}.
+
+@node Argument list functions
+@subsection Argument list functions @code{%VAL}, @code{%REF} and @code{%LOC}
+@cindex argument list functions
+@cindex @code{%VAL}
+@cindex @code{%REF}
+@cindex @code{%LOC}
+
+GNU Fortran supports argument list functions @code{%VAL}, @code{%REF}
+and @code{%LOC} statements, for backward compatibility with g77.
+It is recommended that these should be used only for code that is
+accessing facilities outside of GNU Fortran, such as operating system
+or windowing facilities. It is best to constrain such uses to isolated
+portions of a program--portions that deal specifically and exclusively
+with low-level, system-dependent facilities. Such portions might well
+provide a portable interface for use by the program as a whole, but are
+themselves not portable, and should be thoroughly tested each time they
+are rebuilt using a new compiler or version of a compiler.
+
+@code{%VAL} passes a scalar argument by value, @code{%REF} passes it by
+reference and @code{%LOC} passes its memory location. Since gfortran
+already passes scalar arguments by reference, @code{%REF} is in effect
+a do-nothing. @code{%LOC} has the same effect as a Fortran pointer.
+
+An example of passing an argument by value to a C subroutine foo.:
+@smallexample
+C
+C prototype void foo_ (float x);
+C
+ external foo
+ real*4 x
+ x = 3.14159
+ call foo (%VAL (x))
+ end
+@end smallexample
+
+For details refer to the g77 manual
+@uref{https://gcc.gnu.org/@/onlinedocs/@/gcc-3.4.6/@/g77/@/index.html#Top}.
+
+Also, @code{c_by_val.f} and its partner @code{c_by_val.c} of the
+GNU Fortran testsuite are worth a look.
+
+@node Read/Write after EOF marker
+@subsection Read/Write after EOF marker
+@cindex @code{EOF}
+@cindex @code{BACKSPACE}
+@cindex @code{REWIND}
+
+Some legacy codes rely on allowing @code{READ} or @code{WRITE} after the
+EOF file marker in order to find the end of a file. GNU Fortran normally
+rejects these codes with a run-time error message and suggests the user
+consider @code{BACKSPACE} or @code{REWIND} to properly position
+the file before the EOF marker. As an extension, the run-time error may
+be disabled using -std=legacy.
+
+
+@node STRUCTURE and RECORD
+@subsection @code{STRUCTURE} and @code{RECORD}
+@cindex @code{STRUCTURE}
+@cindex @code{RECORD}
+
+Record structures are a pre-Fortran-90 vendor extension to create
+user-defined aggregate data types. Support for record structures in GNU
+Fortran can be enabled with the @option{-fdec-structure} compile flag.
+If you have a choice, you should instead use Fortran 90's ``derived types'',
+which have a different syntax.
+
+In many cases, record structures can easily be converted to derived types.
+To convert, replace @code{STRUCTURE /}@var{structure-name}@code{/}
+by @code{TYPE} @var{type-name}. Additionally, replace
+@code{RECORD /}@var{structure-name}@code{/} by
+@code{TYPE(}@var{type-name}@code{)}. Finally, in the component access,
+replace the period (@code{.}) by the percent sign (@code{%}).
+
+Here is an example of code using the non portable record structure syntax:
+
+@example
+! Declaring a structure named ``item'' and containing three fields:
+! an integer ID, an description string and a floating-point price.
+STRUCTURE /item/
+ INTEGER id
+ CHARACTER(LEN=200) description
+ REAL price
+END STRUCTURE
+
+! Define two variables, an single record of type ``item''
+! named ``pear'', and an array of items named ``store_catalog''
+RECORD /item/ pear, store_catalog(100)
+
+! We can directly access the fields of both variables
+pear.id = 92316
+pear.description = "juicy D'Anjou pear"
+pear.price = 0.15
+store_catalog(7).id = 7831
+store_catalog(7).description = "milk bottle"
+store_catalog(7).price = 1.2
+
+! We can also manipulate the whole structure
+store_catalog(12) = pear
+print *, store_catalog(12)
+@end example
+
+@noindent
+This code can easily be rewritten in the Fortran 90 syntax as following:
+
+@example
+! ``STRUCTURE /name/ ... END STRUCTURE'' becomes
+! ``TYPE name ... END TYPE''
+TYPE item
+ INTEGER id
+ CHARACTER(LEN=200) description
+ REAL price
+END TYPE
+
+! ``RECORD /name/ variable'' becomes ``TYPE(name) variable''
+TYPE(item) pear, store_catalog(100)
+
+! Instead of using a dot (.) to access fields of a record, the
+! standard syntax uses a percent sign (%)
+pear%id = 92316
+pear%description = "juicy D'Anjou pear"
+pear%price = 0.15
+store_catalog(7)%id = 7831
+store_catalog(7)%description = "milk bottle"
+store_catalog(7)%price = 1.2
+
+! Assignments of a whole variable do not change
+store_catalog(12) = pear
+print *, store_catalog(12)
+@end example
+
+@noindent
+GNU Fortran implements STRUCTURES like derived types with the following
+rules and exceptions:
+
+@itemize @bullet
+@item Structures act like derived types with the @code{SEQUENCE} attribute.
+Otherwise they may contain no specifiers.
+
+@item Structures may contain a special field with the name @code{%FILL}.
+This will create an anonymous component which cannot be accessed but occupies
+space just as if a component of the same type was declared in its place, useful
+for alignment purposes. As an example, the following structure will consist
+of at least sixteen bytes:
+
+@smallexample
+structure /padded/
+ character(4) start
+ character(8) %FILL
+ character(4) end
+end structure
+@end smallexample
+
+@item Structures may share names with other symbols. For example, the following
+is invalid for derived types, but valid for structures:
+
+@smallexample
+structure /header/
+ ! ...
+end structure
+record /header/ header
+@end smallexample
+
+@item Structure types may be declared nested within another parent structure.
+The syntax is:
+@smallexample
+structure /type-name/
+ ...
+ structure [/<type-name>/] <field-list>
+...
+@end smallexample
+
+The type name may be ommitted, in which case the structure type itself is
+anonymous, and other structures of the same type cannot be instantiated. The
+following shows some examples:
+
+@example
+structure /appointment/
+ ! nested structure definition: app_time is an array of two 'time'
+ structure /time/ app_time (2)
+ integer(1) hour, minute
+ end structure
+ character(10) memo
+end structure
+
+! The 'time' structure is still usable
+record /time/ now
+now = time(5, 30)
+
+...
+
+structure /appointment/
+ ! anonymous nested structure definition
+ structure start, end
+ integer(1) hour, minute
+ end structure
+ character(10) memo
+end structure
+@end example
+
+@item Structures may contain @code{UNION} blocks. For more detail see the
+section on @ref{UNION and MAP}.
+
+@item Structures support old-style initialization of components, like
+those described in @ref{Old-style variable initialization}. For array
+initializers, an initializer may contain a repeat specification of the form
+@code{<literal-integer> * <constant-initializer>}. The value of the integer
+indicates the number of times to repeat the constant initializer when expanding
+the initializer list.
+@end itemize
+
+@node UNION and MAP
+@subsection @code{UNION} and @code{MAP}
+@cindex @code{UNION}
+@cindex @code{MAP}
+
+Unions are an old vendor extension which were commonly used with the
+non-standard @ref{STRUCTURE and RECORD} extensions. Use of @code{UNION} and
+@code{MAP} is automatically enabled with @option{-fdec-structure}.
+
+A @code{UNION} declaration occurs within a structure; within the definition of
+each union is a number of @code{MAP} blocks. Each @code{MAP} shares storage
+with its sibling maps (in the same union), and the size of the union is the
+size of the largest map within it, just as with unions in C. The major
+difference is that component references do not indicate which union or map the
+component is in (the compiler gets to figure that out).
+
+Here is a small example:
+@smallexample
+structure /myunion/
+union
+ map
+ character(2) w0, w1, w2
+ end map
+ map
+ character(6) long
+ end map
+end union
+end structure
+
+record /myunion/ rec
+! After this assignment...
+rec.long = 'hello!'
+
+! The following is true:
+! rec.w0 === 'he'
+! rec.w1 === 'll'
+! rec.w2 === 'o!'
+@end smallexample
+
+The two maps share memory, and the size of the union is ultimately six bytes:
+
+@example
+0 1 2 3 4 5 6 Byte offset
+-------------------------------
+| | | | | | |
+-------------------------------
+
+^ W0 ^ W1 ^ W2 ^
+ \-------/ \-------/ \-------/
+
+^ LONG ^
+ \---------------------------/
+@end example
+
+Following is an example mirroring the layout of an Intel x86_64 register:
+
+@example
+structure /reg/
+ union ! U0 ! rax
+ map
+ character(16) rx
+ end map
+ map
+ character(8) rh ! rah
+ union ! U1
+ map
+ character(8) rl ! ral
+ end map
+ map
+ character(8) ex ! eax
+ end map
+ map
+ character(4) eh ! eah
+ union ! U2
+ map
+ character(4) el ! eal
+ end map
+ map
+ character(4) x ! ax
+ end map
+ map
+ character(2) h ! ah
+ character(2) l ! al
+ end map
+ end union
+ end map
+ end union
+ end map
+ end union
+end structure
+record /reg/ a
+
+! After this assignment...
+a.rx = 'AAAAAAAA.BBB.C.D'
+
+! The following is true:
+a.rx === 'AAAAAAAA.BBB.C.D'
+a.rh === 'AAAAAAAA'
+a.rl === '.BBB.C.D'
+a.ex === '.BBB.C.D'
+a.eh === '.BBB'
+a.el === '.C.D'
+a.x === '.C.D'
+a.h === '.C'
+a.l === '.D'
+@end example
+
+@node Type variants for integer intrinsics
+@subsection Type variants for integer intrinsics
+@cindex intrinsics, integer
+
+Similar to the D/C prefixes to real functions to specify the input/output
+types, GNU Fortran offers B/I/J/K prefixes to integer functions for
+compatibility with DEC programs. The types implied by each are:
+
+@example
+@code{B} - @code{INTEGER(kind=1)}
+@code{I} - @code{INTEGER(kind=2)}
+@code{J} - @code{INTEGER(kind=4)}
+@code{K} - @code{INTEGER(kind=8)}
+@end example
+
+GNU Fortran supports these with the flag @option{-fdec-intrinsic-ints}.
+Intrinsics for which prefixed versions are available and in what form are noted
+in @ref{Intrinsic Procedures}. The complete list of supported intrinsics is
+here:
+
+@multitable @columnfractions .2 .2 .2 .2 .2
+
+@headitem Intrinsic @tab B @tab I @tab J @tab K
+
+@item @code{@ref{ABS}}
+ @tab @code{BABS} @tab @code{IIABS} @tab @code{JIABS} @tab @code{KIABS}
+@item @code{@ref{BTEST}}
+ @tab @code{BBTEST} @tab @code{BITEST} @tab @code{BJTEST} @tab @code{BKTEST}
+@item @code{@ref{IAND}}
+ @tab @code{BIAND} @tab @code{IIAND} @tab @code{JIAND} @tab @code{KIAND}
+@item @code{@ref{IBCLR}}
+ @tab @code{BBCLR} @tab @code{IIBCLR} @tab @code{JIBCLR} @tab @code{KIBCLR}
+@item @code{@ref{IBITS}}
+ @tab @code{BBITS} @tab @code{IIBITS} @tab @code{JIBITS} @tab @code{KIBITS}
+@item @code{@ref{IBSET}}
+ @tab @code{BBSET} @tab @code{IIBSET} @tab @code{JIBSET} @tab @code{KIBSET}
+@item @code{@ref{IEOR}}
+ @tab @code{BIEOR} @tab @code{IIEOR} @tab @code{JIEOR} @tab @code{KIEOR}
+@item @code{@ref{IOR}}
+ @tab @code{BIOR} @tab @code{IIOR} @tab @code{JIOR} @tab @code{KIOR}
+@item @code{@ref{ISHFT}}
+ @tab @code{BSHFT} @tab @code{IISHFT} @tab @code{JISHFT} @tab @code{KISHFT}
+@item @code{@ref{ISHFTC}}
+ @tab @code{BSHFTC} @tab @code{IISHFTC} @tab @code{JISHFTC} @tab @code{KISHFTC}
+@item @code{@ref{MOD}}
+ @tab @code{BMOD} @tab @code{IMOD} @tab @code{JMOD} @tab @code{KMOD}
+@item @code{@ref{NOT}}
+ @tab @code{BNOT} @tab @code{INOT} @tab @code{JNOT} @tab @code{KNOT}
+@item @code{@ref{REAL}}
+ @tab @code{--} @tab @code{FLOATI} @tab @code{FLOATJ} @tab @code{FLOATK}
+@end multitable
+
+@node AUTOMATIC and STATIC attributes
+@subsection @code{AUTOMATIC} and @code{STATIC} attributes
+@cindex variable attributes
+@cindex @code{AUTOMATIC}
+@cindex @code{STATIC}
+
+With @option{-fdec-static} GNU Fortran supports the DEC extended attributes
+@code{STATIC} and @code{AUTOMATIC} to provide explicit specification of entity
+storage. These follow the syntax of the Fortran standard @code{SAVE} attribute.
+
+@code{STATIC} is exactly equivalent to @code{SAVE}, and specifies that
+an entity should be allocated in static memory. As an example, @code{STATIC}
+local variables will retain their values across multiple calls to a function.
+
+Entities marked @code{AUTOMATIC} will be stack automatic whenever possible.
+@code{AUTOMATIC} is the default for local variables smaller than
+@option{-fmax-stack-var-size}, unless @option{-fno-automatic} is given. This
+attribute overrides @option{-fno-automatic}, @option{-fmax-stack-var-size}, and
+blanket @code{SAVE} statements.
+
+
+Examples:
+
+@example
+subroutine f
+ integer, automatic :: i ! automatic variable
+ integer x, y ! static variables
+ save
+ ...
+endsubroutine
+@end example
+@example
+subroutine f
+ integer a, b, c, x, y, z
+ static :: x
+ save y
+ automatic z, c
+ ! a, b, c, and z are automatic
+ ! x and y are static
+endsubroutine
+@end example
+@example
+! Compiled with -fno-automatic
+subroutine f
+ integer a, b, c, d
+ automatic :: a
+ ! a is automatic; b, c, and d are static
+endsubroutine
+@end example
+
+@node Extended math intrinsics
+@subsection Extended math intrinsics
+@cindex intrinsics, math
+@cindex intrinsics, trigonometric functions
+
+GNU Fortran supports an extended list of mathematical intrinsics with the
+compile flag @option{-fdec-math} for compatability with legacy code.
+These intrinsics are described fully in @ref{Intrinsic Procedures} where it is
+noted that they are extensions and should be avoided whenever possible.
+
+Specifically, @option{-fdec-math} enables the @ref{COTAN} intrinsic, and
+trigonometric intrinsics which accept or produce values in degrees instead of
+radians. Here is a summary of the new intrinsics:
+
+@multitable @columnfractions .5 .5
+@headitem Radians @tab Degrees
+@item @code{@ref{ACOS}} @tab @code{@ref{ACOSD}}*
+@item @code{@ref{ASIN}} @tab @code{@ref{ASIND}}*
+@item @code{@ref{ATAN}} @tab @code{@ref{ATAND}}*
+@item @code{@ref{ATAN2}} @tab @code{@ref{ATAN2D}}*
+@item @code{@ref{COS}} @tab @code{@ref{COSD}}*
+@item @code{@ref{COTAN}}* @tab @code{@ref{COTAND}}*
+@item @code{@ref{SIN}} @tab @code{@ref{SIND}}*
+@item @code{@ref{TAN}} @tab @code{@ref{TAND}}*
+@end multitable
+
+* Enabled with @option{-fdec-math}.
+
+For advanced users, it may be important to know the implementation of these
+functions. They are simply wrappers around the standard radian functions, which
+have more accurate builtin versions. These functions convert their arguments
+(or results) to degrees (or radians) by taking the value modulus 360 (or 2*pi)
+and then multiplying it by a constant radian-to-degree (or degree-to-radian)
+factor, as appropriate. The factor is computed at compile-time as 180/pi (or
+pi/180).
+
+@node Form feed as whitespace
+@subsection Form feed as whitespace
+@cindex form feed whitespace
+
+Historically, legacy compilers allowed insertion of form feed characters ('\f',
+ASCII 0xC) at the beginning of lines for formatted output to line printers,
+though the Fortran standard does not mention this. GNU Fortran supports the
+interpretation of form feed characters in source as whitespace for
+compatibility.
+
+@node TYPE as an alias for PRINT
+@subsection TYPE as an alias for PRINT
+@cindex type alias print
+For compatibility, GNU Fortran will interpret @code{TYPE} statements as
+@code{PRINT} statements with the flag @option{-fdec}. With this flag asserted,
+the following two examples are equivalent:
+
+@smallexample
+TYPE *, 'hello world'
+@end smallexample
+
+@smallexample
+PRINT *, 'hello world'
+@end smallexample
+
+@node %LOC as an rvalue
+@subsection %LOC as an rvalue
+@cindex LOC
+Normally @code{%LOC} is allowed only in parameter lists. However the intrinsic
+function @code{LOC} does the same thing, and is usable as the right-hand-side of
+assignments. For compatibility, GNU Fortran supports the use of @code{%LOC} as
+an alias for the builtin @code{LOC} with @option{-std=legacy}. With this
+feature enabled the following two examples are equivalent:
+
+@smallexample
+integer :: i, l
+l = %loc(i)
+call sub(l)
+@end smallexample
+
+@smallexample
+integer :: i
+call sub(%loc(i))
+@end smallexample
+
+@node .XOR. operator
+@subsection .XOR. operator
+@cindex operators, xor
+
+GNU Fortran supports @code{.XOR.} as a logical operator with @code{-std=legacy}
+for compatibility with legacy code. @code{.XOR.} is equivalent to
+@code{.NEQV.}. That is, the output is true if and only if the inputs differ.
+
+@node Bitwise logical operators
+@subsection Bitwise logical operators
+@cindex logical, bitwise
+
+With @option{-fdec}, GNU Fortran relaxes the type constraints on
+logical operators to allow integer operands, and performs the corresponding
+bitwise operation instead. This flag is for compatibility only, and should be
+avoided in new code. Consider:
+
+@smallexample
+ INTEGER :: i, j
+ i = z'33'
+ j = z'cc'
+ print *, i .AND. j
+@end smallexample
+
+In this example, compiled with @option{-fdec}, GNU Fortran will
+replace the @code{.AND.} operation with a call to the intrinsic
+@code{@ref{IAND}} function, yielding the bitwise-and of @code{i} and @code{j}.
+
+Note that this conversion will occur if at least one operand is of integral
+type. As a result, a logical operand will be converted to an integer when the
+other operand is an integer in a logical operation. In this case,
+@code{.TRUE.} is converted to @code{1} and @code{.FALSE.} to @code{0}.
+
+Here is the mapping of logical operator to bitwise intrinsic used with
+@option{-fdec}:
+
+@multitable @columnfractions .25 .25 .5
+@headitem Operator @tab Intrinsic @tab Bitwise operation
+@item @code{.NOT.} @tab @code{@ref{NOT}} @tab complement
+@item @code{.AND.} @tab @code{@ref{IAND}} @tab intersection
+@item @code{.OR.} @tab @code{@ref{IOR}} @tab union
+@item @code{.NEQV.} @tab @code{@ref{IEOR}} @tab exclusive or
+@item @code{.EQV.} @tab @code{@ref{NOT}(@ref{IEOR})} @tab complement of exclusive or
+@end multitable
+
+@node Extended I/O specifiers
+@subsection Extended I/O specifiers
+@cindex @code{CARRIAGECONTROL}
+@cindex @code{READONLY}
+@cindex @code{SHARE}
+@cindex @code{SHARED}
+@cindex @code{NOSHARED}
+@cindex I/O specifiers
+
+GNU Fortran supports the additional legacy I/O specifiers
+@code{CARRIAGECONTROL}, @code{READONLY}, and @code{SHARE} with the
+compile flag @option{-fdec}, for compatibility.
+
+@table @code
+@item CARRIAGECONTROL
+The @code{CARRIAGECONTROL} specifier allows a user to control line
+termination settings between output records for an I/O unit. The specifier has
+no meaning for readonly files. When @code{CARRAIGECONTROL} is specified upon
+opening a unit for formatted writing, the exact @code{CARRIAGECONTROL} setting
+determines what characters to write between output records. The syntax is:
+
+@smallexample
+OPEN(..., CARRIAGECONTROL=cc)
+@end smallexample
+
+Where @emph{cc} is a character expression that evaluates to one of the
+following values:
+
+@multitable @columnfractions .2 .8
+@item @code{'LIST'} @tab One line feed between records (default)
+@item @code{'FORTRAN'} @tab Legacy interpretation of the first character (see below)
+@item @code{'NONE'} @tab No separator between records
+@end multitable
+
+With @code{CARRIAGECONTROL='FORTRAN'}, when a record is written, the first
+character of the input record is not written, and instead determines the output
+record separator as follows:
+
+@multitable @columnfractions .3 .3 .4
+@headitem Leading character @tab Meaning @tab Output separating character(s)
+@item @code{'+'} @tab Overprinting @tab Carriage return only
+@item @code{'-'} @tab New line @tab Line feed and carriage return
+@item @code{'0'} @tab Skip line @tab Two line feeds and carriage return
+@item @code{'1'} @tab New page @tab Form feed and carriage return
+@item @code{'$'} @tab Prompting @tab Line feed (no carriage return)
+@item @code{CHAR(0)} @tab Overprinting (no advance) @tab None
+@end multitable
+
+@item READONLY
+The @code{READONLY} specifier may be given upon opening a unit, and is
+equivalent to specifying @code{ACTION='READ'}, except that the file may not be
+deleted on close (i.e. @code{CLOSE} with @code{STATUS="DELETE"}). The syntax
+is:
+
+@smallexample
+@code{OPEN(..., READONLY)}
+@end smallexample
+
+@item SHARE
+The @code{SHARE} specifier allows system-level locking on a unit upon opening
+it for controlled access from multiple processes/threads. The @code{SHARE}
+specifier has several forms:
+
+@smallexample
+OPEN(..., SHARE=sh)
+OPEN(..., SHARED)
+OPEN(..., NOSHARED)
+@end smallexample
+
+Where @emph{sh} in the first form is a character expression that evaluates to
+a value as seen in the table below. The latter two forms are aliases
+for particular values of @emph{sh}:
+
+@multitable @columnfractions .3 .3 .4
+@headitem Explicit form @tab Short form @tab Meaning
+@item @code{SHARE='DENYRW'} @tab @code{NOSHARED} @tab Exclusive (write) lock
+@item @code{SHARE='DENYNONE'} @tab @code{SHARED} @tab Shared (read) lock
+@end multitable
+
+In general only one process may hold an exclusive (write) lock for a given file
+at a time, whereas many processes may hold shared (read) locks for the same
+file.
+
+The behavior of locking may vary with your operating system. On POSIX systems,
+locking is implemented with @code{fcntl}. Consult your corresponding operating
+system's manual pages for further details. Locking via @code{SHARE=} is not
+supported on other systems.
+
+@end table
+
+@node Legacy PARAMETER statements
+@subsection Legacy PARAMETER statements
+@cindex PARAMETER
+
+For compatibility, GNU Fortran supports legacy PARAMETER statements without
+parentheses with @option{-std=legacy}. A warning is emitted if used with
+@option{-std=gnu}, and an error is acknowledged with a real Fortran standard
+flag (@option{-std=f95}, etc...). These statements take the following form:
+
+@smallexample
+implicit real (E)
+parameter e = 2.718282
+real c
+parameter c = 3.0e8
+@end smallexample
+
+@node Default exponents
+@subsection Default exponents
+@cindex exponent
+
+For compatibility, GNU Fortran supports a default exponent of zero in real
+constants with @option{-fdec}. For example, @code{9e} would be
+interpreted as @code{9e0}, rather than an error.
+
+
+@node Extensions not implemented in GNU Fortran
+@section Extensions not implemented in GNU Fortran
+@cindex extensions, not implemented
+
+The long history of the Fortran language, its wide use and broad
+userbase, the large number of different compiler vendors and the lack of
+some features crucial to users in the first standards have lead to the
+existence of a number of important extensions to the language. While
+some of the most useful or popular extensions are supported by the GNU
+Fortran compiler, not all existing extensions are supported. This section
+aims at listing these extensions and offering advice on how best make
+code that uses them running with the GNU Fortran compiler.
+
+@c More can be found here:
+@c -- https://gcc.gnu.org/onlinedocs/gcc-3.4.6/g77/Missing-Features.html
+@c -- the list of Fortran and libgfortran bugs closed as WONTFIX:
+@c http://tinyurl.com/2u4h5y
+
+@menu
+* ENCODE and DECODE statements::
+* Variable FORMAT expressions::
+@c * TYPE and ACCEPT I/O Statements::
+@c * DEFAULTFILE, DISPOSE and RECORDTYPE I/O specifiers::
+@c * Omitted arguments in procedure call::
+* Alternate complex function syntax::
+* Volatile COMMON blocks::
+* OPEN( ... NAME=)::
+* Q edit descriptor::
+@end menu
+
+@node ENCODE and DECODE statements
+@subsection @code{ENCODE} and @code{DECODE} statements
+@cindex @code{ENCODE}
+@cindex @code{DECODE}
+
+GNU Fortran does not support the @code{ENCODE} and @code{DECODE}
+statements. These statements are best replaced by @code{READ} and
+@code{WRITE} statements involving internal files (@code{CHARACTER}
+variables and arrays), which have been part of the Fortran standard since
+Fortran 77. For example, replace a code fragment like
+
+@smallexample
+ INTEGER*1 LINE(80)
+ REAL A, B, C
+c ... Code that sets LINE
+ DECODE (80, 9000, LINE) A, B, C
+ 9000 FORMAT (1X, 3(F10.5))
+@end smallexample
+
+@noindent
+with the following:
+
+@smallexample
+ CHARACTER(LEN=80) LINE
+ REAL A, B, C
+c ... Code that sets LINE
+ READ (UNIT=LINE, FMT=9000) A, B, C
+ 9000 FORMAT (1X, 3(F10.5))
+@end smallexample
+
+Similarly, replace a code fragment like
+
+@smallexample
+ INTEGER*1 LINE(80)
+ REAL A, B, C
+c ... Code that sets A, B and C
+ ENCODE (80, 9000, LINE) A, B, C
+ 9000 FORMAT (1X, 'OUTPUT IS ', 3(F10.5))
+@end smallexample
+
+@noindent
+with the following:
+
+@smallexample
+ CHARACTER(LEN=80) LINE
+ REAL A, B, C
+c ... Code that sets A, B and C
+ WRITE (UNIT=LINE, FMT=9000) A, B, C
+ 9000 FORMAT (1X, 'OUTPUT IS ', 3(F10.5))
+@end smallexample
+
+
+@node Variable FORMAT expressions
+@subsection Variable @code{FORMAT} expressions
+@cindex @code{FORMAT}
+
+A variable @code{FORMAT} expression is format statement which includes
+angle brackets enclosing a Fortran expression: @code{FORMAT(I<N>)}. GNU
+Fortran does not support this legacy extension. The effect of variable
+format expressions can be reproduced by using the more powerful (and
+standard) combination of internal output and string formats. For example,
+replace a code fragment like this:
+
+@smallexample
+ WRITE(6,20) INT1
+ 20 FORMAT(I<N+1>)
+@end smallexample
+
+@noindent
+with the following:
+
+@smallexample
+c Variable declaration
+ CHARACTER(LEN=20) FMT
+c
+c Other code here...
+c
+ WRITE(FMT,'("(I", I0, ")")') N+1
+ WRITE(6,FMT) INT1
+@end smallexample
+
+@noindent
+or with:
+
+@smallexample
+c Variable declaration
+ CHARACTER(LEN=20) FMT
+c
+c Other code here...
+c
+ WRITE(FMT,*) N+1
+ WRITE(6,"(I" // ADJUSTL(FMT) // ")") INT1
+@end smallexample
+
+
+@node Alternate complex function syntax
+@subsection Alternate complex function syntax
+@cindex Complex function
+
+Some Fortran compilers, including @command{g77}, let the user declare
+complex functions with the syntax @code{COMPLEX FUNCTION name*16()}, as
+well as @code{COMPLEX*16 FUNCTION name()}. Both are non-standard, legacy
+extensions. @command{gfortran} accepts the latter form, which is more
+common, but not the former.
+
+
+@node Volatile COMMON blocks
+@subsection Volatile @code{COMMON} blocks
+@cindex @code{VOLATILE}
+@cindex @code{COMMON}
+
+Some Fortran compilers, including @command{g77}, let the user declare
+@code{COMMON} with the @code{VOLATILE} attribute. This is
+invalid standard Fortran syntax and is not supported by
+@command{gfortran}. Note that @command{gfortran} accepts
+@code{VOLATILE} variables in @code{COMMON} blocks since revision 4.3.
+
+
+@node OPEN( ... NAME=)
+@subsection @code{OPEN( ... NAME=)}
+@cindex @code{NAME}
+
+Some Fortran compilers, including @command{g77}, let the user declare
+@code{OPEN( ... NAME=)}. This is
+invalid standard Fortran syntax and is not supported by
+@command{gfortran}. @code{OPEN( ... NAME=)} should be replaced
+with @code{OPEN( ... FILE=)}.
+
+@node Q edit descriptor
+@subsection @code{Q} edit descriptor
+@cindex @code{Q} edit descriptor
+
+Some Fortran compilers provide the @code{Q} edit descriptor, which
+transfers the number of characters left within an input record into an
+integer variable.
+
+A direct replacement of the @code{Q} edit descriptor is not available
+in @command{gfortran}. How to replicate its functionality using
+standard-conforming code depends on what the intent of the original
+code is.
+
+Options to replace @code{Q} may be to read the whole line into a
+character variable and then counting the number of non-blank
+characters left using @code{LEN_TRIM}. Another method may be to use
+formatted stream, read the data up to the position where the @code{Q}
+descriptor occurred, use @code{INQUIRE} to get the file position,
+count the characters up to the next @code{NEW_LINE} and then start
+reading from the position marked previously.
+
+
+@c ---------------------------------------------------------------------
+@c ---------------------------------------------------------------------
+@c Mixed-Language Programming
+@c ---------------------------------------------------------------------
+
+@node Mixed-Language Programming
+@chapter Mixed-Language Programming
+@cindex Interoperability
+@cindex Mixed-language programming
+
+@menu
+* Interoperability with C::
+* GNU Fortran Compiler Directives::
+* Non-Fortran Main Program::
+* Naming and argument-passing conventions::
+@end menu
+
+This chapter is about mixed-language interoperability, but also
+applies if you link Fortran code compiled by different compilers. In
+most cases, use of the C Binding features of the Fortran 2003 and
+later standards is sufficient.
+
+For example, it is possible to mix Fortran code with C++ code as well
+as C, if you declare the interface functions as @code{extern "C"} on
+the C++ side and @code{BIND(C)} on the Fortran side, and follow the
+rules for interoperability with C. Note that you cannot manipulate
+C++ class objects in Fortran or vice versa except as opaque pointers.
+
+You can use the @command{gfortran} command to link both Fortran and
+non-Fortran code into the same program, or you can use @command{gcc}
+or @command{g++} if you also add an explicit @option{-lgfortran} option
+to link with the Fortran library. If your main program is written in
+C or some other language instead of Fortran, see
+@ref{Non-Fortran Main Program}, below.
+
+@node Interoperability with C
+@section Interoperability with C
+@cindex interoperability with C
+@cindex C interoperability
+
+@menu
+* Intrinsic Types::
+* Derived Types and struct::
+* Interoperable Global Variables::
+* Interoperable Subroutines and Functions::
+* Working with C Pointers::
+* Further Interoperability of Fortran with C::
+@end menu
+
+Since Fortran 2003 (ISO/IEC 1539-1:2004(E)) there is a
+standardized way to generate procedure and derived-type
+declarations and global variables that are interoperable with C
+(ISO/IEC 9899:1999). The @code{BIND(C)} attribute has been added
+to inform the compiler that a symbol shall be interoperable with C;
+also, some constraints are added. Note, however, that not
+all C features have a Fortran equivalent or vice versa. For instance,
+neither C's unsigned integers nor C's functions with variable number
+of arguments have an equivalent in Fortran.
+
+Note that array dimensions are reversely ordered in C and that arrays in
+C always start with index 0 while in Fortran they start by default with
+1. Thus, an array declaration @code{A(n,m)} in Fortran matches
+@code{A[m][n]} in C and accessing the element @code{A(i,j)} matches
+@code{A[j-1][i-1]}. The element following @code{A(i,j)} (C: @code{A[j-1][i-1]};
+assuming @math{i < n}) in memory is @code{A(i+1,j)} (C: @code{A[j-1][i]}).
+
+@node Intrinsic Types
+@subsection Intrinsic Types
+@cindex C intrinsic type interoperability
+@cindex intrinsic type interoperability with C
+@cindex interoperability, intrinsic type
+
+In order to ensure that exactly the same variable type and kind is used
+in C and Fortran, you should use the named constants for kind parameters
+that are defined in the @code{ISO_C_BINDING} intrinsic module.
+That module contains named constants of character type representing
+the escaped special characters in C, such as newline.
+For a list of the constants, see @ref{ISO_C_BINDING}.
+
+For logical types, please note that the Fortran standard only guarantees
+interoperability between C99's @code{_Bool} and Fortran's @code{C_Bool}-kind
+logicals and C99 defines that @code{true} has the value 1 and @code{false}
+the value 0. Using any other integer value with GNU Fortran's @code{LOGICAL}
+(with any kind parameter) gives an undefined result. (Passing other integer
+values than 0 and 1 to GCC's @code{_Bool} is also undefined, unless the
+integer is explicitly or implicitly casted to @code{_Bool}.)
+
+@node Derived Types and struct
+@subsection Derived Types and struct
+@cindex C derived type and struct interoperability
+@cindex derived type interoperability with C
+@cindex interoperability, derived type and struct
+
+For compatibility of derived types with @code{struct}, use
+the @code{BIND(C)} attribute in the type declaration. For instance, the
+following type declaration
+
+@smallexample
+ USE ISO_C_BINDING
+ TYPE, BIND(C) :: myType
+ INTEGER(C_INT) :: i1, i2
+ INTEGER(C_SIGNED_CHAR) :: i3
+ REAL(C_DOUBLE) :: d1
+ COMPLEX(C_FLOAT_COMPLEX) :: c1
+ CHARACTER(KIND=C_CHAR) :: str(5)
+ END TYPE
+@end smallexample
+
+@noindent
+matches the following @code{struct} declaration in C
+
+@smallexample
+ struct @{
+ int i1, i2;
+ /* Note: "char" might be signed or unsigned. */
+ signed char i3;
+ double d1;
+ float _Complex c1;
+ char str[5];
+ @} myType;
+@end smallexample
+
+Derived types with the C binding attribute shall not have the @code{sequence}
+attribute, type parameters, the @code{extends} attribute, nor type-bound
+procedures. Every component must be of interoperable type and kind and may not
+have the @code{pointer} or @code{allocatable} attribute. The names of the
+components are irrelevant for interoperability.
+
+As there exist no direct Fortran equivalents, neither unions nor structs
+with bit field or variable-length array members are interoperable.
+
+@node Interoperable Global Variables
+@subsection Interoperable Global Variables
+@cindex C variable interoperability
+@cindex variable interoperability with C
+@cindex interoperability, variable
+
+Variables can be made accessible from C using the C binding attribute,
+optionally together with specifying a binding name. Those variables
+have to be declared in the declaration part of a @code{MODULE},
+be of interoperable type, and have neither the @code{pointer} nor
+the @code{allocatable} attribute.
+
+@smallexample
+ MODULE m
+ USE myType_module
+ USE ISO_C_BINDING
+ integer(C_INT), bind(C, name="_MyProject_flags") :: global_flag
+ type(myType), bind(C) :: tp
+ END MODULE
+@end smallexample
+
+Here, @code{_MyProject_flags} is the case-sensitive name of the variable
+as seen from C programs while @code{global_flag} is the case-insensitive
+name as seen from Fortran. If no binding name is specified, as for
+@var{tp}, the C binding name is the (lowercase) Fortran binding name.
+If a binding name is specified, only a single variable may be after the
+double colon. Note of warning: You cannot use a global variable to
+access @var{errno} of the C library as the C standard allows it to be
+a macro. Use the @code{IERRNO} intrinsic (GNU extension) instead.
+
+@node Interoperable Subroutines and Functions
+@subsection Interoperable Subroutines and Functions
+@cindex C procedure interoperability
+@cindex procedure interoperability with C
+@cindex function interoperability with C
+@cindex subroutine interoperability with C
+@cindex interoperability, subroutine and function
+
+Subroutines and functions have to have the @code{BIND(C)} attribute to
+be compatible with C. The dummy argument declaration is relatively
+straightforward. However, one needs to be careful because C uses
+call-by-value by default while Fortran behaves usually similar to
+call-by-reference. Furthermore, strings and pointers are handled
+differently.
+
+To pass a variable by value, use the @code{VALUE} attribute.
+Thus, the following C prototype
+
+@smallexample
+@code{int func(int i, int *j)}
+@end smallexample
+
+@noindent
+matches the Fortran declaration
+
+@smallexample
+ integer(c_int) function func(i,j)
+ use iso_c_binding, only: c_int
+ integer(c_int), VALUE :: i
+ integer(c_int) :: j
+@end smallexample
+
+Note that pointer arguments also frequently need the @code{VALUE} attribute,
+see @ref{Working with C Pointers}.
+
+Strings are handled quite differently in C and Fortran. In C a string
+is a @code{NUL}-terminated array of characters while in Fortran each string
+has a length associated with it and is thus not terminated (by e.g.
+@code{NUL}). For example, if you want to use the following C function,
+
+@smallexample
+ #include <stdio.h>
+ void print_C(char *string) /* equivalent: char string[] */
+ @{
+ printf("%s\n", string);
+ @}
+@end smallexample
+
+@noindent
+to print ``Hello World'' from Fortran, you can call it using
+
+@smallexample
+ use iso_c_binding, only: C_CHAR, C_NULL_CHAR
+ interface
+ subroutine print_c(string) bind(C, name="print_C")
+ use iso_c_binding, only: c_char
+ character(kind=c_char) :: string(*)
+ end subroutine print_c
+ end interface
+ call print_c(C_CHAR_"Hello World"//C_NULL_CHAR)
+@end smallexample
+
+As the example shows, you need to ensure that the
+string is @code{NUL} terminated. Additionally, the dummy argument
+@var{string} of @code{print_C} is a length-one assumed-size
+array; using @code{character(len=*)} is not allowed. The example
+above uses @code{c_char_"Hello World"} to ensure the string
+literal has the right type; typically the default character
+kind and @code{c_char} are the same and thus @code{"Hello World"}
+is equivalent. However, the standard does not guarantee this.
+
+The use of strings is now further illustrated using the C library
+function @code{strncpy}, whose prototype is
+
+@smallexample
+ char *strncpy(char *restrict s1, const char *restrict s2, size_t n);
+@end smallexample
+
+@noindent
+The function @code{strncpy} copies at most @var{n} characters from
+string @var{s2} to @var{s1} and returns @var{s1}. In the following
+example, we ignore the return value:
+
+@smallexample
+ use iso_c_binding
+ implicit none
+ character(len=30) :: str,str2
+ interface
+ ! Ignore the return value of strncpy -> subroutine
+ ! "restrict" is always assumed if we do not pass a pointer
+ subroutine strncpy(dest, src, n) bind(C)
+ import
+ character(kind=c_char), intent(out) :: dest(*)
+ character(kind=c_char), intent(in) :: src(*)
+ integer(c_size_t), value, intent(in) :: n
+ end subroutine strncpy
+ end interface
+ str = repeat('X',30) ! Initialize whole string with 'X'
+ call strncpy(str, c_char_"Hello World"//C_NULL_CHAR, &
+ len(c_char_"Hello World",kind=c_size_t))
+ print '(a)', str ! prints: "Hello WorldXXXXXXXXXXXXXXXXXXX"
+ end
+@end smallexample
+
+The intrinsic procedures are described in @ref{Intrinsic Procedures}.
+
+@node Working with C Pointers
+@subsection Working with C Pointers
+@cindex C pointers
+@cindex pointers, C
+
+C pointers are represented in Fortran via the special opaque derived
+type @code{type(c_ptr)} (with private components). C pointers are distinct
+from Fortran objects with the @code{POINTER} attribute. Thus one needs to
+use intrinsic conversion procedures to convert from or to C pointers.
+For some applications, using an assumed type (@code{TYPE(*)}) can be
+an alternative to a C pointer, and you can also use library routines
+to access Fortran pointers from C. See @ref{Further Interoperability
+of Fortran with C}.
+
+Here is an example of using C pointers in Fortran:
+
+@smallexample
+ use iso_c_binding
+ type(c_ptr) :: cptr1, cptr2
+ integer, target :: array(7), scalar
+ integer, pointer :: pa(:), ps
+ cptr1 = c_loc(array(1)) ! The programmer needs to ensure that the
+ ! array is contiguous if required by the C
+ ! procedure
+ cptr2 = c_loc(scalar)
+ call c_f_pointer(cptr2, ps)
+ call c_f_pointer(cptr2, pa, shape=[7])
+@end smallexample
+
+When converting C to Fortran arrays, the one-dimensional @code{SHAPE} argument
+has to be passed.
+
+If a pointer is a dummy argument of an interoperable procedure, it usually
+has to be declared using the @code{VALUE} attribute. @code{void*}
+matches @code{TYPE(C_PTR), VALUE}, while @code{TYPE(C_PTR)} alone
+matches @code{void**}.
+
+Procedure pointers are handled analogously to pointers; the C type is
+@code{TYPE(C_FUNPTR)} and the intrinsic conversion procedures are
+@code{C_F_PROCPOINTER} and @code{C_FUNLOC}.
+
+Let us consider two examples of actually passing a procedure pointer from
+C to Fortran and vice versa. Note that these examples are also very
+similar to passing ordinary pointers between both languages. First,
+consider this code in C:
+
+@smallexample
+/* Procedure implemented in Fortran. */
+void get_values (void (*)(double));
+
+/* Call-back routine we want called from Fortran. */
+void
+print_it (double x)
+@{
+ printf ("Number is %f.\n", x);
+@}
+
+/* Call Fortran routine and pass call-back to it. */
+void
+foobar ()
+@{
+ get_values (&print_it);
+@}
+@end smallexample
+
+A matching implementation for @code{get_values} in Fortran, that correctly
+receives the procedure pointer from C and is able to call it, is given
+in the following @code{MODULE}:
+
+@smallexample
+MODULE m
+ IMPLICIT NONE
+
+ ! Define interface of call-back routine.
+ ABSTRACT INTERFACE
+ SUBROUTINE callback (x)
+ USE, INTRINSIC :: ISO_C_BINDING
+ REAL(KIND=C_DOUBLE), INTENT(IN), VALUE :: x
+ END SUBROUTINE callback
+ END INTERFACE
+
+CONTAINS
+
+ ! Define C-bound procedure.
+ SUBROUTINE get_values (cproc) BIND(C)
+ USE, INTRINSIC :: ISO_C_BINDING
+ TYPE(C_FUNPTR), INTENT(IN), VALUE :: cproc
+
+ PROCEDURE(callback), POINTER :: proc
+
+ ! Convert C to Fortran procedure pointer.
+ CALL C_F_PROCPOINTER (cproc, proc)
+
+ ! Call it.
+ CALL proc (1.0_C_DOUBLE)
+ CALL proc (-42.0_C_DOUBLE)
+ CALL proc (18.12_C_DOUBLE)
+ END SUBROUTINE get_values
+
+END MODULE m
+@end smallexample
+
+Next, we want to call a C routine that expects a procedure pointer argument
+and pass it a Fortran procedure (which clearly must be interoperable!).
+Again, the C function may be:
+
+@smallexample
+int
+call_it (int (*func)(int), int arg)
+@{
+ return func (arg);
+@}
+@end smallexample
+
+It can be used as in the following Fortran code:
+
+@smallexample
+MODULE m
+ USE, INTRINSIC :: ISO_C_BINDING
+ IMPLICIT NONE
+
+ ! Define interface of C function.
+ INTERFACE
+ INTEGER(KIND=C_INT) FUNCTION call_it (func, arg) BIND(C)
+ USE, INTRINSIC :: ISO_C_BINDING
+ TYPE(C_FUNPTR), INTENT(IN), VALUE :: func
+ INTEGER(KIND=C_INT), INTENT(IN), VALUE :: arg
+ END FUNCTION call_it
+ END INTERFACE
+
+CONTAINS
+
+ ! Define procedure passed to C function.
+ ! It must be interoperable!
+ INTEGER(KIND=C_INT) FUNCTION double_it (arg) BIND(C)
+ INTEGER(KIND=C_INT), INTENT(IN), VALUE :: arg
+ double_it = arg + arg
+ END FUNCTION double_it
+
+ ! Call C function.
+ SUBROUTINE foobar ()
+ TYPE(C_FUNPTR) :: cproc
+ INTEGER(KIND=C_INT) :: i
+
+ ! Get C procedure pointer.
+ cproc = C_FUNLOC (double_it)
+
+ ! Use it.
+ DO i = 1_C_INT, 10_C_INT
+ PRINT *, call_it (cproc, i)
+ END DO
+ END SUBROUTINE foobar
+
+END MODULE m
+@end smallexample
+
+@node Further Interoperability of Fortran with C
+@subsection Further Interoperability of Fortran with C
+@cindex Further Interoperability of Fortran with C
+@cindex TS 29113
+@cindex array descriptor
+@cindex dope vector
+@cindex assumed-type
+@cindex assumed-rank
+
+GNU Fortran implements the Technical Specification ISO/IEC TS
+29113:2012, which extends the interoperability support of Fortran 2003
+and Fortran 2008 and is now part of the 2018 Fortran standard.
+Besides removing some restrictions and constraints, the Technical
+Specification adds assumed-type (@code{TYPE(*)}) and assumed-rank
+(@code{DIMENSION(..)}) variables and allows for interoperability of
+assumed-shape, assumed-rank, and deferred-shape arrays, as well as
+allocatables and pointers. Objects of these types are passed to
+@code{BIND(C)} functions as descriptors with a standard interface,
+declared in the header file @code{<ISO_Fortran_binding.h>}.
+
+Note: Currently, GNU Fortran does not use internally the array descriptor
+(dope vector) as specified in the Technical Specification, but uses
+an array descriptor with different fields in functions without the
+@code{BIND(C)} attribute. Arguments to functions marked @code{BIND(C)}
+are converted to the specified form. If you need to access GNU Fortran's
+internal array descriptor, you can use the Chasm Language Interoperability
+Tools, @url{http://chasm-interop.sourceforge.net/}.
+
+@node GNU Fortran Compiler Directives
+@section GNU Fortran Compiler Directives
+
+@menu
+* ATTRIBUTES directive::
+* UNROLL directive::
+* BUILTIN directive::
+* IVDEP directive::
+* VECTOR directive::
+* NOVECTOR directive::
+@end menu
+
+@node ATTRIBUTES directive
+@subsection ATTRIBUTES directive
+
+The Fortran standard describes how a conforming program shall
+behave; however, the exact implementation is not standardized. In order
+to allow the user to choose specific implementation details, compiler
+directives can be used to set attributes of variables and procedures
+which are not part of the standard. Whether a given attribute is
+supported and its exact effects depend on both the operating system and
+on the processor; see
+@ref{Top,,C Extensions,gcc,Using the GNU Compiler Collection (GCC)}
+for details.
+
+For procedures and procedure pointers, the following attributes can
+be used to change the calling convention:
+
+@itemize
+@item @code{CDECL} -- standard C calling convention
+@item @code{STDCALL} -- convention where the called procedure pops the stack
+@item @code{FASTCALL} -- part of the arguments are passed via registers
+instead using the stack
+@end itemize
+
+Besides changing the calling convention, the attributes also influence
+the decoration of the symbol name, e.g., by a leading underscore or by
+a trailing at-sign followed by the number of bytes on the stack. When
+assigning a procedure to a procedure pointer, both should use the same
+calling convention.
+
+On some systems, procedures and global variables (module variables and
+@code{COMMON} blocks) need special handling to be accessible when they
+are in a shared library. The following attributes are available:
+
+@itemize
+@item @code{DLLEXPORT} -- provide a global pointer to a pointer in the DLL
+@item @code{DLLIMPORT} -- reference the function or variable using a
+global pointer
+@end itemize
+
+For dummy arguments, the @code{NO_ARG_CHECK} attribute can be used; in
+other compilers, it is also known as @code{IGNORE_TKR}. For dummy arguments
+with this attribute actual arguments of any type and kind (similar to
+@code{TYPE(*)}), scalars and arrays of any rank (no equivalent
+in Fortran standard) are accepted. As with @code{TYPE(*)}, the argument
+is unlimited polymorphic and no type information is available.
+Additionally, the argument may only be passed to dummy arguments
+with the @code{NO_ARG_CHECK} attribute and as argument to the
+@code{PRESENT} intrinsic function and to @code{C_LOC} of the
+@code{ISO_C_BINDING} module.
+
+Variables with @code{NO_ARG_CHECK} attribute shall be of assumed-type
+(@code{TYPE(*)}; recommended) or of type @code{INTEGER}, @code{LOGICAL},
+@code{REAL} or @code{COMPLEX}. They shall not have the @code{ALLOCATE},
+@code{CODIMENSION}, @code{INTENT(OUT)}, @code{POINTER} or @code{VALUE}
+attribute; furthermore, they shall be either scalar or of assumed-size
+(@code{dimension(*)}). As @code{TYPE(*)}, the @code{NO_ARG_CHECK} attribute
+requires an explicit interface.
+
+@itemize
+@item @code{NO_ARG_CHECK} -- disable the type, kind and rank checking
+@item @code{DEPRECATED} -- print a warning when using a such-tagged
+deprecated procedure, variable or parameter; the warning can be suppressed
+with @option{-Wno-deprecated-declarations}.
+@end itemize
+
+
+The attributes are specified using the syntax
+
+@code{!GCC$ ATTRIBUTES} @var{attribute-list} @code{::} @var{variable-list}
+
+where in free-form source code only whitespace is allowed before @code{!GCC$}
+and in fixed-form source code @code{!GCC$}, @code{cGCC$} or @code{*GCC$} shall
+start in the first column.
+
+For procedures, the compiler directives shall be placed into the body
+of the procedure; for variables and procedure pointers, they shall be in
+the same declaration part as the variable or procedure pointer.
+
+
+@node UNROLL directive
+@subsection UNROLL directive
+
+The syntax of the directive is
+
+@code{!GCC$ unroll N}
+
+You can use this directive to control how many times a loop should be unrolled.
+It must be placed immediately before a @code{DO} loop and applies only to the
+loop that follows. N is an integer constant specifying the unrolling factor.
+The values of 0 and 1 block any unrolling of the loop.
+
+
+@node BUILTIN directive
+@subsection BUILTIN directive
+
+The syntax of the directive is
+
+@code{!GCC$ BUILTIN (B) attributes simd FLAGS IF('target')}
+
+You can use this directive to define which middle-end built-ins provide vector
+implementations. @code{B} is name of the middle-end built-in. @code{FLAGS}
+are optional and must be either "(inbranch)" or "(notinbranch)".
+@code{IF} statement is optional and is used to filter multilib ABIs
+for the built-in that should be vectorized. Example usage:
+
+@smallexample
+!GCC$ builtin (sinf) attributes simd (notinbranch) if('x86_64')
+@end smallexample
+
+The purpose of the directive is to provide an API among the GCC compiler and
+the GNU C Library which would define vector implementations of math routines.
+
+
+@node IVDEP directive
+@subsection IVDEP directive
+
+The syntax of the directive is
+
+@code{!GCC$ ivdep}
+
+This directive tells the compiler to ignore vector dependencies in the
+following loop. It must be placed immediately before a @code{DO} loop
+and applies only to the loop that follows.
+
+Sometimes the compiler may not have sufficient information to decide
+whether a particular loop is vectorizable due to potential
+dependencies between iterations. The purpose of the directive is to
+tell the compiler that vectorization is safe.
+
+This directive is intended for annotation of existing code. For new
+code it is recommended to consider OpenMP SIMD directives as potential
+alternative.
+
+
+@node VECTOR directive
+@subsection VECTOR directive
+
+The syntax of the directive is
+
+@code{!GCC$ vector}
+
+This directive tells the compiler to vectorize the following loop. It
+must be placed immediately before a @code{DO} loop and applies only to
+the loop that follows.
+
+
+@node NOVECTOR directive
+@subsection NOVECTOR directive
+
+The syntax of the directive is
+
+@code{!GCC$ novector}
+
+This directive tells the compiler to not vectorize the following loop.
+It must be placed immediately before a @code{DO} loop and applies only
+to the loop that follows.
+
+
+@node Non-Fortran Main Program
+@section Non-Fortran Main Program
+
+@menu
+* _gfortran_set_args:: Save command-line arguments
+* _gfortran_set_options:: Set library option flags
+* _gfortran_set_convert:: Set endian conversion
+* _gfortran_set_record_marker:: Set length of record markers
+* _gfortran_set_fpe:: Set when a Floating Point Exception should be raised
+* _gfortran_set_max_subrecord_length:: Set subrecord length
+@end menu
+
+Even if you are doing mixed-language programming, it is very
+likely that you do not need to know or use the information in this
+section. Since it is about the internal structure of GNU Fortran,
+it may also change in GCC minor releases.
+
+When you compile a @code{PROGRAM} with GNU Fortran, a function
+with the name @code{main} (in the symbol table of the object file)
+is generated, which initializes the libgfortran library and then
+calls the actual program which uses the name @code{MAIN__}, for
+historic reasons. If you link GNU Fortran compiled procedures
+to, e.g., a C or C++ program or to a Fortran program compiled by
+a different compiler, the libgfortran library is not initialized
+and thus a few intrinsic procedures do not work properly, e.g.
+those for obtaining the command-line arguments.
+
+Therefore, if your @code{PROGRAM} is not compiled with
+GNU Fortran and the GNU Fortran compiled procedures require
+intrinsics relying on the library initialization, you need to
+initialize the library yourself. Using the default options,
+gfortran calls @code{_gfortran_set_args} and
+@code{_gfortran_set_options}. The initialization of the former
+is needed if the called procedures access the command line
+(and for backtracing); the latter sets some flags based on the
+standard chosen or to enable backtracing. In typical programs,
+it is not necessary to call any initialization function.
+
+If your @code{PROGRAM} is compiled with GNU Fortran, you shall
+not call any of the following functions. The libgfortran
+initialization functions are shown in C syntax but using C
+bindings they are also accessible from Fortran.
+
+
+@node _gfortran_set_args
+@subsection @code{_gfortran_set_args} --- Save command-line arguments
+@fnindex _gfortran_set_args
+@cindex libgfortran initialization, set_args
+
+@table @asis
+@item @emph{Description}:
+@code{_gfortran_set_args} saves the command-line arguments; this
+initialization is required if any of the command-line intrinsics
+is called. Additionally, it shall be called if backtracing is
+enabled (see @code{_gfortran_set_options}).
+
+@item @emph{Syntax}:
+@code{void _gfortran_set_args (int argc, char *argv[])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{argc} @tab number of command line argument strings
+@item @var{argv} @tab the command-line argument strings; argv[0]
+is the pathname of the executable itself.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+int main (int argc, char *argv[])
+@{
+ /* Initialize libgfortran. */
+ _gfortran_set_args (argc, argv);
+ return 0;
+@}
+@end smallexample
+@end table
+
+
+@node _gfortran_set_options
+@subsection @code{_gfortran_set_options} --- Set library option flags
+@fnindex _gfortran_set_options
+@cindex libgfortran initialization, set_options
+
+@table @asis
+@item @emph{Description}:
+@code{_gfortran_set_options} sets several flags related to the Fortran
+standard to be used, whether backtracing should be enabled
+and whether range checks should be performed. The syntax allows for
+upward compatibility since the number of passed flags is specified; for
+non-passed flags, the default value is used. See also
+@pxref{Code Gen Options}. Please note that not all flags are actually
+used.
+
+@item @emph{Syntax}:
+@code{void _gfortran_set_options (int num, int options[])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{num} @tab number of options passed
+@item @var{argv} @tab The list of flag values
+@end multitable
+
+@item @emph{option flag list}:
+@multitable @columnfractions .15 .70
+@item @var{option}[0] @tab Allowed standard; can give run-time errors
+if e.g. an input-output edit descriptor is invalid in a given
+standard. Possible values are (bitwise or-ed) @code{GFC_STD_F77} (1),
+@code{GFC_STD_F95_OBS} (2), @code{GFC_STD_F95_DEL} (4),
+@code{GFC_STD_F95} (8), @code{GFC_STD_F2003} (16), @code{GFC_STD_GNU}
+(32), @code{GFC_STD_LEGACY} (64), @code{GFC_STD_F2008} (128),
+@code{GFC_STD_F2008_OBS} (256), @code{GFC_STD_F2008_TS} (512),
+@code{GFC_STD_F2018} (1024), @code{GFC_STD_F2018_OBS} (2048), and
+@code{GFC_STD=F2018_DEL} (4096). Default: @code{GFC_STD_F95_OBS |
+GFC_STD_F95_DEL | GFC_STD_F95 | GFC_STD_F2003 | GFC_STD_F2008 |
+GFC_STD_F2008_TS | GFC_STD_F2008_OBS | GFC_STD_F77 | GFC_STD_F2018 |
+GFC_STD_F2018_OBS | GFC_STD_F2018_DEL | GFC_STD_GNU | GFC_STD_LEGACY}.
+@item @var{option}[1] @tab Standard-warning flag; prints a warning to
+standard error. Default: @code{GFC_STD_F95_DEL | GFC_STD_LEGACY}.
+@item @var{option}[2] @tab If non zero, enable pedantic checking.
+Default: off.
+@item @var{option}[3] @tab Unused.
+@item @var{option}[4] @tab If non zero, enable backtracing on run-time
+errors. Default: off. (Default in the compiler: on.)
+Note: Installs a signal handler and requires command-line
+initialization using @code{_gfortran_set_args}.
+@item @var{option}[5] @tab If non zero, supports signed zeros.
+Default: enabled.
+@item @var{option}[6] @tab Enables run-time checking. Possible values
+are (bitwise or-ed): GFC_RTCHECK_BOUNDS (1), GFC_RTCHECK_ARRAY_TEMPS (2),
+GFC_RTCHECK_RECURSION (4), GFC_RTCHECK_DO (8), GFC_RTCHECK_POINTER (16),
+GFC_RTCHECK_MEM (32), GFC_RTCHECK_BITS (64).
+Default: disabled.
+@item @var{option}[7] @tab Unused.
+@item @var{option}[8] @tab Show a warning when invoking @code{STOP} and
+@code{ERROR STOP} if a floating-point exception occurred. Possible values
+are (bitwise or-ed) @code{GFC_FPE_INVALID} (1), @code{GFC_FPE_DENORMAL} (2),
+@code{GFC_FPE_ZERO} (4), @code{GFC_FPE_OVERFLOW} (8),
+@code{GFC_FPE_UNDERFLOW} (16), @code{GFC_FPE_INEXACT} (32). Default: None (0).
+(Default in the compiler: @code{GFC_FPE_INVALID | GFC_FPE_DENORMAL |
+GFC_FPE_ZERO | GFC_FPE_OVERFLOW | GFC_FPE_UNDERFLOW}.)
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+ /* Use gfortran 4.9 default options. */
+ static int options[] = @{68, 511, 0, 0, 1, 1, 0, 0, 31@};
+ _gfortran_set_options (9, &options);
+@end smallexample
+@end table
+
+
+@node _gfortran_set_convert
+@subsection @code{_gfortran_set_convert} --- Set endian conversion
+@fnindex _gfortran_set_convert
+@cindex libgfortran initialization, set_convert
+
+@table @asis
+@item @emph{Description}:
+@code{_gfortran_set_convert} set the representation of data for
+unformatted files.
+
+@item @emph{Syntax}:
+@code{void _gfortran_set_convert (int conv)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{conv} @tab Endian conversion, possible values:
+GFC_CONVERT_NATIVE (0, default), GFC_CONVERT_SWAP (1),
+GFC_CONVERT_BIG (2), GFC_CONVERT_LITTLE (3).
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+int main (int argc, char *argv[])
+@{
+ /* Initialize libgfortran. */
+ _gfortran_set_args (argc, argv);
+ _gfortran_set_convert (1);
+ return 0;
+@}
+@end smallexample
+@end table
+
+
+@node _gfortran_set_record_marker
+@subsection @code{_gfortran_set_record_marker} --- Set length of record markers
+@fnindex _gfortran_set_record_marker
+@cindex libgfortran initialization, set_record_marker
+
+@table @asis
+@item @emph{Description}:
+@code{_gfortran_set_record_marker} sets the length of record markers
+for unformatted files.
+
+@item @emph{Syntax}:
+@code{void _gfortran_set_record_marker (int val)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{val} @tab Length of the record marker; valid values
+are 4 and 8. Default is 4.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+int main (int argc, char *argv[])
+@{
+ /* Initialize libgfortran. */
+ _gfortran_set_args (argc, argv);
+ _gfortran_set_record_marker (8);
+ return 0;
+@}
+@end smallexample
+@end table
+
+
+@node _gfortran_set_fpe
+@subsection @code{_gfortran_set_fpe} --- Enable floating point exception traps
+@fnindex _gfortran_set_fpe
+@cindex libgfortran initialization, set_fpe
+
+@table @asis
+@item @emph{Description}:
+@code{_gfortran_set_fpe} enables floating point exception traps for
+the specified exceptions. On most systems, this will result in a
+SIGFPE signal being sent and the program being aborted.
+
+@item @emph{Syntax}:
+@code{void _gfortran_set_fpe (int val)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{option}[0] @tab IEEE exceptions. Possible values are
+(bitwise or-ed) zero (0, default) no trapping,
+@code{GFC_FPE_INVALID} (1), @code{GFC_FPE_DENORMAL} (2),
+@code{GFC_FPE_ZERO} (4), @code{GFC_FPE_OVERFLOW} (8),
+@code{GFC_FPE_UNDERFLOW} (16), and @code{GFC_FPE_INEXACT} (32).
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+int main (int argc, char *argv[])
+@{
+ /* Initialize libgfortran. */
+ _gfortran_set_args (argc, argv);
+ /* FPE for invalid operations such as SQRT(-1.0). */
+ _gfortran_set_fpe (1);
+ return 0;
+@}
+@end smallexample
+@end table
+
+
+@node _gfortran_set_max_subrecord_length
+@subsection @code{_gfortran_set_max_subrecord_length} --- Set subrecord length
+@fnindex _gfortran_set_max_subrecord_length
+@cindex libgfortran initialization, set_max_subrecord_length
+
+@table @asis
+@item @emph{Description}:
+@code{_gfortran_set_max_subrecord_length} set the maximum length
+for a subrecord. This option only makes sense for testing and
+debugging of unformatted I/O.
+
+@item @emph{Syntax}:
+@code{void _gfortran_set_max_subrecord_length (int val)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{val} @tab the maximum length for a subrecord;
+the maximum permitted value is 2147483639, which is also
+the default.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+int main (int argc, char *argv[])
+@{
+ /* Initialize libgfortran. */
+ _gfortran_set_args (argc, argv);
+ _gfortran_set_max_subrecord_length (8);
+ return 0;
+@}
+@end smallexample
+@end table
+
+
+@node Naming and argument-passing conventions
+@section Naming and argument-passing conventions
+
+This section gives an overview about the naming convention of procedures
+and global variables and about the argument passing conventions used by
+GNU Fortran. If a C binding has been specified, the naming convention
+and some of the argument-passing conventions change. If possible,
+mixed-language and mixed-compiler projects should use the better defined
+C binding for interoperability. See @pxref{Interoperability with C}.
+
+@menu
+* Naming conventions::
+* Argument passing conventions::
+@end menu
+
+
+@node Naming conventions
+@subsection Naming conventions
+
+According the Fortran standard, valid Fortran names consist of a letter
+between @code{A} to @code{Z}, @code{a} to @code{z}, digits @code{0},
+@code{1} to @code{9} and underscores (@code{_}) with the restriction
+that names may only start with a letter. As vendor extension, the
+dollar sign (@code{$}) is additionally permitted with the option
+@option{-fdollar-ok}, but not as first character and only if the
+target system supports it.
+
+By default, the procedure name is the lower-cased Fortran name with an
+appended underscore (@code{_}); using @option{-fno-underscoring} no
+underscore is appended while @code{-fsecond-underscore} appends two
+underscores. Depending on the target system and the calling convention,
+the procedure might be additionally dressed; for instance, on 32bit
+Windows with @code{stdcall}, an at-sign @code{@@} followed by an integer
+number is appended. For the changing the calling convention, see
+@pxref{GNU Fortran Compiler Directives}.
+
+For common blocks, the same convention is used, i.e. by default an
+underscore is appended to the lower-cased Fortran name. Blank commons
+have the name @code{__BLNK__}.
+
+For procedures and variables declared in the specification space of a
+module, the name is formed by @code{__}, followed by the lower-cased
+module name, @code{_MOD_}, and the lower-cased Fortran name. Note that
+no underscore is appended.
+
+
+@node Argument passing conventions
+@subsection Argument passing conventions
+
+Subroutines do not return a value (matching C99's @code{void}) while
+functions either return a value as specified in the platform ABI or
+the result variable is passed as hidden argument to the function and
+no result is returned. A hidden result variable is used when the
+result variable is an array or of type @code{CHARACTER}.
+
+Arguments are passed according to the platform ABI. In particular,
+complex arguments might not be compatible to a struct with two real
+components for the real and imaginary part. The argument passing
+matches the one of C99's @code{_Complex}. Functions with scalar
+complex result variables return their value and do not use a
+by-reference argument. Note that with the @option{-ff2c} option,
+the argument passing is modified and no longer completely matches
+the platform ABI. Some other Fortran compilers use @code{f2c}
+semantic by default; this might cause problems with
+interoperablility.
+
+GNU Fortran passes most arguments by reference, i.e. by passing a
+pointer to the data. Note that the compiler might use a temporary
+variable into which the actual argument has been copied, if required
+semantically (copy-in/copy-out).
+
+For arguments with @code{ALLOCATABLE} and @code{POINTER}
+attribute (including procedure pointers), a pointer to the pointer
+is passed such that the pointer address can be modified in the
+procedure.
+
+For dummy arguments with the @code{VALUE} attribute: Scalar arguments
+of the type @code{INTEGER}, @code{LOGICAL}, @code{REAL} and
+@code{COMPLEX} are passed by value according to the platform ABI.
+(As vendor extension and not recommended, using @code{%VAL()} in the
+call to a procedure has the same effect.) For @code{TYPE(C_PTR)} and
+procedure pointers, the pointer itself is passed such that it can be
+modified without affecting the caller.
+@c FIXME: Document how VALUE is handled for CHARACTER, TYPE,
+@c CLASS and arrays, i.e. whether the copy-in is done in the caller
+@c or in the callee.
+
+For Boolean (@code{LOGICAL}) arguments, please note that GCC expects
+only the integer value 0 and 1. If a GNU Fortran @code{LOGICAL}
+variable contains another integer value, the result is undefined.
+As some other Fortran compilers use @math{-1} for @code{.TRUE.},
+extra care has to be taken -- such as passing the value as
+@code{INTEGER}. (The same value restriction also applies to other
+front ends of GCC, e.g. to GCC's C99 compiler for @code{_Bool}
+or GCC's Ada compiler for @code{Boolean}.)
+
+For arguments of @code{CHARACTER} type, the character length is passed
+as a hidden argument at the end of the argument list. For
+deferred-length strings, the value is passed by reference, otherwise
+by value. The character length has the C type @code{size_t} (or
+@code{INTEGER(kind=C_SIZE_T)} in Fortran). Note that this is
+different to older versions of the GNU Fortran compiler, where the
+type of the hidden character length argument was a C @code{int}. In
+order to retain compatibility with older versions, one can e.g. for
+the following Fortran procedure
+
+@smallexample
+subroutine fstrlen (s, a)
+ character(len=*) :: s
+ integer :: a
+ print*, len(s)
+end subroutine fstrlen
+@end smallexample
+
+define the corresponding C prototype as follows:
+
+@smallexample
+#if __GNUC__ > 7
+typedef size_t fortran_charlen_t;
+#else
+typedef int fortran_charlen_t;
+#endif
+
+void fstrlen_ (char*, int*, fortran_charlen_t);
+@end smallexample
+
+In order to avoid such compiler-specific details, for new code it is
+instead recommended to use the ISO_C_BINDING feature.
+
+Note with C binding, @code{CHARACTER(len=1)} result variables are
+returned according to the platform ABI and no hidden length argument
+is used for dummy arguments; with @code{VALUE}, those variables are
+passed by value.
+
+For @code{OPTIONAL} dummy arguments, an absent argument is denoted
+by a NULL pointer, except for scalar dummy arguments of type
+@code{INTEGER}, @code{LOGICAL}, @code{REAL} and @code{COMPLEX}
+which have the @code{VALUE} attribute. For those, a hidden Boolean
+argument (@code{logical(kind=C_bool),value}) is used to indicate
+whether the argument is present.
+
+Arguments which are assumed-shape, assumed-rank or deferred-rank
+arrays or, with @option{-fcoarray=lib}, allocatable scalar coarrays use
+an array descriptor. All other arrays pass the address of the
+first element of the array. With @option{-fcoarray=lib}, the token
+and the offset belonging to nonallocatable coarrays dummy arguments
+are passed as hidden argument along the character length hidden
+arguments. The token is an opaque pointer identifying the coarray
+and the offset is a passed-by-value integer of kind @code{C_PTRDIFF_T},
+denoting the byte offset between the base address of the coarray and
+the passed scalar or first element of the passed array.
+
+The arguments are passed in the following order
+@itemize @bullet
+@item Result variable, when the function result is passed by reference
+@item Character length of the function result, if it is a of type
+@code{CHARACTER} and no C binding is used
+@item The arguments in the order in which they appear in the Fortran
+declaration
+@item The present status for optional arguments with value attribute,
+which are internally passed by value
+@item The character length and/or coarray token and offset for the first
+argument which is a @code{CHARACTER} or a nonallocatable coarray dummy
+argument, followed by the hidden arguments of the next dummy argument
+of such a type
+@end itemize
+
+
+@c ---------------------------------------------------------------------
+@c Coarray Programming
+@c ---------------------------------------------------------------------
+
+@node Coarray Programming
+@chapter Coarray Programming
+@cindex Coarrays
+
+@menu
+* Type and enum ABI Documentation::
+* Function ABI Documentation::
+@end menu
+
+
+@node Type and enum ABI Documentation
+@section Type and enum ABI Documentation
+
+@menu
+* caf_token_t::
+* caf_register_t::
+* caf_deregister_t::
+* caf_reference_t::
+* caf_team_t::
+@end menu
+
+@node caf_token_t
+@subsection @code{caf_token_t}
+
+Typedef of type @code{void *} on the compiler side. Can be any data
+type on the library side.
+
+@node caf_register_t
+@subsection @code{caf_register_t}
+
+Indicates which kind of coarray variable should be registered.
+
+@verbatim
+typedef enum caf_register_t {
+ CAF_REGTYPE_COARRAY_STATIC,
+ CAF_REGTYPE_COARRAY_ALLOC,
+ CAF_REGTYPE_LOCK_STATIC,
+ CAF_REGTYPE_LOCK_ALLOC,
+ CAF_REGTYPE_CRITICAL,
+ CAF_REGTYPE_EVENT_STATIC,
+ CAF_REGTYPE_EVENT_ALLOC,
+ CAF_REGTYPE_COARRAY_ALLOC_REGISTER_ONLY,
+ CAF_REGTYPE_COARRAY_ALLOC_ALLOCATE_ONLY
+}
+caf_register_t;
+@end verbatim
+
+The values @code{CAF_REGTYPE_COARRAY_ALLOC_REGISTER_ONLY} and
+@code{CAF_REGTYPE_COARRAY_ALLOC_ALLOCATE_ONLY} are for allocatable components
+in derived type coarrays only. The first one sets up the token without
+allocating memory for allocatable component. The latter one only allocates the
+memory for an allocatable component in a derived type coarray. The token
+needs to be setup previously by the REGISTER_ONLY. This allows to have
+allocatable components un-allocated on some images. The status whether an
+allocatable component is allocated on a remote image can be queried by
+@code{_caf_is_present} which used internally by the @code{ALLOCATED}
+intrinsic.
+
+@node caf_deregister_t
+@subsection @code{caf_deregister_t}
+
+@verbatim
+typedef enum caf_deregister_t {
+ CAF_DEREGTYPE_COARRAY_DEREGISTER,
+ CAF_DEREGTYPE_COARRAY_DEALLOCATE_ONLY
+}
+caf_deregister_t;
+@end verbatim
+
+Allows to specifiy the type of deregistration of a coarray object. The
+@code{CAF_DEREGTYPE_COARRAY_DEALLOCATE_ONLY} flag is only allowed for
+allocatable components in derived type coarrays.
+
+@node caf_reference_t
+@subsection @code{caf_reference_t}
+
+The structure used for implementing arbitrary reference chains.
+A @code{CAF_REFERENCE_T} allows to specify a component reference or any kind
+of array reference of any rank supported by gfortran. For array references all
+kinds as known by the compiler/Fortran standard are supported indicated by
+a @code{MODE}.
+
+@verbatim
+typedef enum caf_ref_type_t {
+ /* Reference a component of a derived type, either regular one or an
+ allocatable or pointer type. For regular ones idx in caf_reference_t is
+ set to -1. */
+ CAF_REF_COMPONENT,
+ /* Reference an allocatable array. */
+ CAF_REF_ARRAY,
+ /* Reference a non-allocatable/non-pointer array. I.e., the coarray object
+ has no array descriptor associated and the addressing is done
+ completely using the ref. */
+ CAF_REF_STATIC_ARRAY
+} caf_ref_type_t;
+@end verbatim
+
+@verbatim
+typedef enum caf_array_ref_t {
+ /* No array ref. This terminates the array ref. */
+ CAF_ARR_REF_NONE = 0,
+ /* Reference array elements given by a vector. Only for this mode
+ caf_reference_t.u.a.dim[i].v is valid. */
+ CAF_ARR_REF_VECTOR,
+ /* A full array ref (:). */
+ CAF_ARR_REF_FULL,
+ /* Reference a range on elements given by start, end and stride. */
+ CAF_ARR_REF_RANGE,
+ /* Only a single item is referenced given in the start member. */
+ CAF_ARR_REF_SINGLE,
+ /* An array ref of the kind (i:), where i is an arbitrary valid index in the
+ array. The index i is given in the start member. */
+ CAF_ARR_REF_OPEN_END,
+ /* An array ref of the kind (:i), where the lower bound of the array ref
+ is given by the remote side. The index i is given in the end member. */
+ CAF_ARR_REF_OPEN_START
+} caf_array_ref_t;
+@end verbatim
+
+@verbatim
+/* References to remote components of a derived type. */
+typedef struct caf_reference_t {
+ /* A pointer to the next ref or NULL. */
+ struct caf_reference_t *next;
+ /* The type of the reference. */
+ /* caf_ref_type_t, replaced by int to allow specification in fortran FE. */
+ int type;
+ /* The size of an item referenced in bytes. I.e. in an array ref this is
+ the factor to advance the array pointer with to get to the next item.
+ For component refs this gives just the size of the element referenced. */
+ size_t item_size;
+ union {
+ struct {
+ /* The offset (in bytes) of the component in the derived type.
+ Unused for allocatable or pointer components. */
+ ptrdiff_t offset;
+ /* The offset (in bytes) to the caf_token associated with this
+ component. NULL, when not allocatable/pointer ref. */
+ ptrdiff_t caf_token_offset;
+ } c;
+ struct {
+ /* The mode of the array ref. See CAF_ARR_REF_*. */
+ /* caf_array_ref_t, replaced by unsigend char to allow specification in
+ fortran FE. */
+ unsigned char mode[GFC_MAX_DIMENSIONS];
+ /* The type of a static array. Unset for array's with descriptors. */
+ int static_array_type;
+ /* Subscript refs (s) or vector refs (v). */
+ union {
+ struct {
+ /* The start and end boundary of the ref and the stride. */
+ index_type start, end, stride;
+ } s;
+ struct {
+ /* nvec entries of kind giving the elements to reference. */
+ void *vector;
+ /* The number of entries in vector. */
+ size_t nvec;
+ /* The integer kind used for the elements in vector. */
+ int kind;
+ } v;
+ } dim[GFC_MAX_DIMENSIONS];
+ } a;
+ } u;
+} caf_reference_t;
+@end verbatim
+
+The references make up a single linked list of reference operations. The
+@code{NEXT} member links to the next reference or NULL to indicate the end of
+the chain. Component and array refs can be arbitrarily mixed as long as they
+comply to the Fortran standard.
+
+@emph{NOTES}
+The member @code{STATIC_ARRAY_TYPE} is used only when the @code{TYPE} is
+@code{CAF_REF_STATIC_ARRAY}. The member gives the type of the data referenced.
+Because no array descriptor is available for a descriptor-less array and
+type conversion still needs to take place the type is transported here.
+
+At the moment @code{CAF_ARR_REF_VECTOR} is not implemented in the front end for
+descriptor-less arrays. The library caf_single has untested support for it.
+
+@node caf_team_t
+@subsection @code{caf_team_t}
+
+Opaque pointer to represent a team-handle. This type is a stand-in for the
+future implementation of teams. It is about to change without further notice.
+
+@node Function ABI Documentation
+@section Function ABI Documentation
+
+@menu
+* _gfortran_caf_init:: Initialiation function
+* _gfortran_caf_finish:: Finalization function
+* _gfortran_caf_this_image:: Querying the image number
+* _gfortran_caf_num_images:: Querying the maximal number of images
+* _gfortran_caf_image_status :: Query the status of an image
+* _gfortran_caf_failed_images :: Get an array of the indexes of the failed images
+* _gfortran_caf_stopped_images :: Get an array of the indexes of the stopped images
+* _gfortran_caf_register:: Registering coarrays
+* _gfortran_caf_deregister:: Deregistering coarrays
+* _gfortran_caf_is_present:: Query whether an allocatable or pointer component in a derived type coarray is allocated
+* _gfortran_caf_send:: Sending data from a local image to a remote image
+* _gfortran_caf_get:: Getting data from a remote image
+* _gfortran_caf_sendget:: Sending data between remote images
+* _gfortran_caf_send_by_ref:: Sending data from a local image to a remote image using enhanced references
+* _gfortran_caf_get_by_ref:: Getting data from a remote image using enhanced references
+* _gfortran_caf_sendget_by_ref:: Sending data between remote images using enhanced references
+* _gfortran_caf_lock:: Locking a lock variable
+* _gfortran_caf_unlock:: Unlocking a lock variable
+* _gfortran_caf_event_post:: Post an event
+* _gfortran_caf_event_wait:: Wait that an event occurred
+* _gfortran_caf_event_query:: Query event count
+* _gfortran_caf_sync_all:: All-image barrier
+* _gfortran_caf_sync_images:: Barrier for selected images
+* _gfortran_caf_sync_memory:: Wait for completion of segment-memory operations
+* _gfortran_caf_error_stop:: Error termination with exit code
+* _gfortran_caf_error_stop_str:: Error termination with string
+* _gfortran_caf_fail_image :: Mark the image failed and end its execution
+* _gfortran_caf_atomic_define:: Atomic variable assignment
+* _gfortran_caf_atomic_ref:: Atomic variable reference
+* _gfortran_caf_atomic_cas:: Atomic compare and swap
+* _gfortran_caf_atomic_op:: Atomic operation
+* _gfortran_caf_co_broadcast:: Sending data to all images
+* _gfortran_caf_co_max:: Collective maximum reduction
+* _gfortran_caf_co_min:: Collective minimum reduction
+* _gfortran_caf_co_sum:: Collective summing reduction
+* _gfortran_caf_co_reduce:: Generic collective reduction
+@end menu
+
+
+@node _gfortran_caf_init
+@subsection @code{_gfortran_caf_init} --- Initialiation function
+@cindex Coarray, _gfortran_caf_init
+
+@table @asis
+@item @emph{Description}:
+This function is called at startup of the program before the Fortran main
+program, if the latter has been compiled with @option{-fcoarray=lib}.
+It takes as arguments the command-line arguments of the program. It is
+permitted to pass two @code{NULL} pointers as argument; if non-@code{NULL},
+the library is permitted to modify the arguments.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_init (int *argc, char ***argv)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{argc} @tab intent(inout) An integer pointer with the number of
+arguments passed to the program or @code{NULL}.
+@item @var{argv} @tab intent(inout) A pointer to an array of strings with the
+command-line arguments or @code{NULL}.
+@end multitable
+
+@item @emph{NOTES}
+The function is modelled after the initialization function of the Message
+Passing Interface (MPI) specification. Due to the way coarray registration
+works, it might not be the first call to the library. If the main program is
+not written in Fortran and only a library uses coarrays, it can happen that
+this function is never called. Therefore, it is recommended that the library
+does not rely on the passed arguments and whether the call has been done.
+@end table
+
+
+@node _gfortran_caf_finish
+@subsection @code{_gfortran_caf_finish} --- Finalization function
+@cindex Coarray, _gfortran_caf_finish
+
+@table @asis
+@item @emph{Description}:
+This function is called at the end of the Fortran main program, if it has
+been compiled with the @option{-fcoarray=lib} option.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_finish (void)}
+
+@item @emph{NOTES}
+For non-Fortran programs, it is recommended to call the function at the end
+of the main program. To ensure that the shutdown is also performed for
+programs where this function is not explicitly invoked, for instance
+non-Fortran programs or calls to the system's exit() function, the library
+can use a destructor function. Note that programs can also be terminated
+using the STOP and ERROR STOP statements; those use different library calls.
+@end table
+
+
+@node _gfortran_caf_this_image
+@subsection @code{_gfortran_caf_this_image} --- Querying the image number
+@cindex Coarray, _gfortran_caf_this_image
+
+@table @asis
+@item @emph{Description}:
+This function returns the current image number, which is a positive number.
+
+@item @emph{Syntax}:
+@code{int _gfortran_caf_this_image (int distance)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{distance} @tab As specified for the @code{this_image} intrinsic
+in TS18508. Shall be a non-negative number.
+@end multitable
+
+@item @emph{NOTES}
+If the Fortran intrinsic @code{this_image} is invoked without an argument, which
+is the only permitted form in Fortran 2008, GCC passes @code{0} as
+first argument.
+@end table
+
+
+@node _gfortran_caf_num_images
+@subsection @code{_gfortran_caf_num_images} --- Querying the maximal number of images
+@cindex Coarray, _gfortran_caf_num_images
+
+@table @asis
+@item @emph{Description}:
+This function returns the number of images in the current team, if
+@var{distance} is 0 or the number of images in the parent team at the specified
+distance. If failed is -1, the function returns the number of all images at
+the specified distance; if it is 0, the function returns the number of
+nonfailed images, and if it is 1, it returns the number of failed images.
+
+@item @emph{Syntax}:
+@code{int _gfortran_caf_num_images(int distance, int failed)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{distance} @tab the distance from this image to the ancestor.
+Shall be positive.
+@item @var{failed} @tab shall be -1, 0, or 1
+@end multitable
+
+@item @emph{NOTES}
+This function follows TS18508. If the num_image intrinsic has no arguments,
+then the compiler passes @code{distance=0} and @code{failed=-1} to the function.
+@end table
+
+
+@node _gfortran_caf_image_status
+@subsection @code{_gfortran_caf_image_status} --- Query the status of an image
+@cindex Coarray, _gfortran_caf_image_status
+
+@table @asis
+@item @emph{Description}:
+Get the status of the image given by the id @var{image} of the team given by
+@var{team}. Valid results are zero, for image is ok, @code{STAT_STOPPED_IMAGE}
+from the ISO_FORTRAN_ENV module to indicate that the image has been stopped and
+@code{STAT_FAILED_IMAGE} also from ISO_FORTRAN_ENV to indicate that the image
+has executed a @code{FAIL IMAGE} statement.
+
+@item @emph{Syntax}:
+@code{int _gfortran_caf_image_status (int image, caf_team_t * team)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{image} @tab the positive scalar id of the image in the current TEAM.
+@item @var{team} @tab optional; team on the which the inquiry is to be
+performed.
+@end multitable
+
+@item @emph{NOTES}
+This function follows TS18508. Because team-functionality is not yet
+implemented a null-pointer is passed for the @var{team} argument at the moment.
+@end table
+
+
+@node _gfortran_caf_failed_images
+@subsection @code{_gfortran_caf_failed_images} --- Get an array of the indexes of the failed images
+@cindex Coarray, _gfortran_caf_failed_images
+
+@table @asis
+@item @emph{Description}:
+Get an array of image indexes in the current @var{team} that have failed. The
+array is sorted ascendingly. When @var{team} is not provided the current team
+is to be used. When @var{kind} is provided then the resulting array is of that
+integer kind else it is of default integer kind. The returns an unallocated
+size zero array when no images have failed.
+
+@item @emph{Syntax}:
+@code{int _gfortran_caf_failed_images (caf_team_t * team, int * kind)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{team} @tab optional; team on the which the inquiry is to be
+performed.
+@item @var{image} @tab optional; the kind of the resulting integer array.
+@end multitable
+
+@item @emph{NOTES}
+This function follows TS18508. Because team-functionality is not yet
+implemented a null-pointer is passed for the @var{team} argument at the moment.
+@end table
+
+
+@node _gfortran_caf_stopped_images
+@subsection @code{_gfortran_caf_stopped_images} --- Get an array of the indexes of the stopped images
+@cindex Coarray, _gfortran_caf_stopped_images
+
+@table @asis
+@item @emph{Description}:
+Get an array of image indexes in the current @var{team} that have stopped. The
+array is sorted ascendingly. When @var{team} is not provided the current team
+is to be used. When @var{kind} is provided then the resulting array is of that
+integer kind else it is of default integer kind. The returns an unallocated
+size zero array when no images have failed.
+
+@item @emph{Syntax}:
+@code{int _gfortran_caf_stopped_images (caf_team_t * team, int * kind)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{team} @tab optional; team on the which the inquiry is to be
+performed.
+@item @var{image} @tab optional; the kind of the resulting integer array.
+@end multitable
+
+@item @emph{NOTES}
+This function follows TS18508. Because team-functionality is not yet
+implemented a null-pointer is passed for the @var{team} argument at the moment.
+@end table
+
+
+@node _gfortran_caf_register
+@subsection @code{_gfortran_caf_register} --- Registering coarrays
+@cindex Coarray, _gfortran_caf_register
+
+@table @asis
+@item @emph{Description}:
+Registers memory for a coarray and creates a token to identify the coarray. The
+routine is called for both coarrays with @code{SAVE} attribute and using an
+explicit @code{ALLOCATE} statement. If an error occurs and @var{STAT} is a
+@code{NULL} pointer, the function shall abort with printing an error message
+and starting the error termination. If no error occurs and @var{STAT} is
+present, it shall be set to zero. Otherwise, it shall be set to a positive
+value and, if not-@code{NULL}, @var{ERRMSG} shall be set to a string describing
+the failure. The routine shall register the memory provided in the
+@code{DATA}-component of the array descriptor @var{DESC}, when that component
+is non-@code{NULL}, else it shall allocate sufficient memory and provide a
+pointer to it in the @code{DATA}-component of @var{DESC}. The array descriptor
+has rank zero, when a scalar object is to be registered and the array
+descriptor may be invalid after the call to @code{_gfortran_caf_register}.
+When an array is to be allocated the descriptor persists.
+
+For @code{CAF_REGTYPE_COARRAY_STATIC} and @code{CAF_REGTYPE_COARRAY_ALLOC},
+the passed size is the byte size requested. For @code{CAF_REGTYPE_LOCK_STATIC},
+@code{CAF_REGTYPE_LOCK_ALLOC} and @code{CAF_REGTYPE_CRITICAL} it is the array
+size or one for a scalar.
+
+When @code{CAF_REGTYPE_COARRAY_ALLOC_REGISTER_ONLY} is used, then only a token
+for an allocatable or pointer component is created. The @code{SIZE} parameter
+is not used then. On the contrary when
+@code{CAF_REGTYPE_COARRAY_ALLOC_ALLOCATE_ONLY} is specified, then the
+@var{token} needs to be registered by a previous call with regtype
+@code{CAF_REGTYPE_COARRAY_ALLOC_REGISTER_ONLY} and either the memory specified
+in the @var{DESC}'s data-ptr is registered or allocate when the data-ptr is
+@code{NULL}.
+
+@item @emph{Syntax}:
+@code{void caf_register (size_t size, caf_register_t type, caf_token_t *token,
+gfc_descriptor_t *desc, int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{size} @tab For normal coarrays, the byte size of the coarray to be
+allocated; for lock types and event types, the number of elements.
+@item @var{type} @tab one of the caf_register_t types.
+@item @var{token} @tab intent(out) An opaque pointer identifying the coarray.
+@item @var{desc} @tab intent(inout) The (pseudo) array descriptor.
+@item @var{stat} @tab intent(out) For allocatable coarrays, stores the STAT=;
+may be @code{NULL}
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be @code{NULL}
+@item @var{errmsg_len} @tab the buffer size of errmsg.
+@end multitable
+
+@item @emph{NOTES}
+Nonallocatable coarrays have to be registered prior use from remote images.
+In order to guarantee this, they have to be registered before the main
+program. This can be achieved by creating constructor functions. That is what
+GCC does such that also for nonallocatable coarrays the memory is allocated and
+no static memory is used. The token permits to identify the coarray; to the
+processor, the token is a nonaliasing pointer. The library can, for instance,
+store the base address of the coarray in the token, some handle or a more
+complicated struct. The library may also store the array descriptor
+@var{DESC} when its rank is non-zero.
+
+For lock types, the value shall only be used for checking the allocation
+status. Note that for critical blocks, the locking is only required on one
+image; in the locking statement, the processor shall always pass an
+image index of one for critical-block lock variables
+(@code{CAF_REGTYPE_CRITICAL}). For lock types and critical-block variables,
+the initial value shall be unlocked (or, respectively, not in critical
+section) such as the value false; for event types, the initial state should
+be no event, e.g. zero.
+@end table
+
+
+@node _gfortran_caf_deregister
+@subsection @code{_gfortran_caf_deregister} --- Deregistering coarrays
+@cindex Coarray, _gfortran_caf_deregister
+
+@table @asis
+@item @emph{Description}:
+Called to free or deregister the memory of a coarray; the processor calls this
+function for automatic and explicit deallocation. In case of an error, this
+function shall fail with an error message, unless the @var{STAT} variable is
+not null. The library is only expected to free memory it allocated itself
+during a call to @code{_gfortran_caf_register}.
+
+@item @emph{Syntax}:
+@code{void caf_deregister (caf_token_t *token, caf_deregister_t type,
+int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab the token to free.
+@item @var{type} @tab the type of action to take for the coarray. A
+@code{CAF_DEREGTYPE_COARRAY_DEALLOCATE_ONLY} is allowed only for allocatable or
+pointer components of derived type coarrays. The action only deallocates the
+local memory without deleting the token.
+@item @var{stat} @tab intent(out) Stores the STAT=; may be NULL
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set
+to an error message; may be NULL
+@item @var{errmsg_len} @tab the buffer size of errmsg.
+@end multitable
+
+@item @emph{NOTES}
+For nonalloatable coarrays this function is never called. If a cleanup is
+required, it has to be handled via the finish, stop and error stop functions,
+and via destructors.
+@end table
+
+
+@node _gfortran_caf_is_present
+@subsection @code{_gfortran_caf_is_present} --- Query whether an allocatable or pointer component in a derived type coarray is allocated
+@cindex Coarray, _gfortran_caf_is_present
+
+@table @asis
+@item @emph{Description}:
+Used to query the coarray library whether an allocatable component in a derived
+type coarray is allocated on a remote image.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_is_present (caf_token_t token, int image_index,
+gfc_reference_t *ref)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab An opaque pointer identifying the coarray.
+@item @var{image_index} @tab The ID of the remote image; must be a positive
+number.
+@item @var{ref} @tab A chain of references to address the allocatable or
+pointer component in the derived type coarray. The object reference needs to be
+a scalar or a full array reference, respectively.
+@end multitable
+
+@end table
+
+@node _gfortran_caf_send
+@subsection @code{_gfortran_caf_send} --- Sending data from a local image to a remote image
+@cindex Coarray, _gfortran_caf_send
+
+@table @asis
+@item @emph{Description}:
+Called to send a scalar, an array section or a whole array from a local
+to a remote image identified by the image_index.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_send (caf_token_t token, size_t offset,
+int image_index, gfc_descriptor_t *dest, caf_vector_t *dst_vector,
+gfc_descriptor_t *src, int dst_kind, int src_kind, bool may_require_tmp,
+int *stat)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{offset} @tab intent(in) By which amount of bytes the actual data is
+shifted compared to the base address of the coarray.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number.
+@item @var{dest} @tab intent(in) Array descriptor for the remote image for the
+bounds and the size. The @code{base_addr} shall not be accessed.
+@item @var{dst_vector} @tab intent(in) If not NULL, it contains the vector
+subscript of the destination array; the values are relative to the dimension
+triplet of the dest argument.
+@item @var{src} @tab intent(in) Array descriptor of the local array to be
+transferred to the remote image
+@item @var{dst_kind} @tab intent(in) Kind of the destination argument
+@item @var{src_kind} @tab intent(in) Kind of the source argument
+@item @var{may_require_tmp} @tab intent(in) The variable is @code{false} when
+it is known at compile time that the @var{dest} and @var{src} either cannot
+overlap or overlap (fully or partially) such that walking @var{src} and
+@var{dest} in element wise element order (honoring the stride value) will not
+lead to wrong results. Otherwise, the value is @code{true}.
+@item @var{stat} @tab intent(out) when non-NULL give the result of the
+operation, i.e., zero on success and non-zero on error. When NULL and an error
+occurs, then an error message is printed and the program is terminated.
+@end multitable
+
+@item @emph{NOTES}
+It is permitted to have @var{image_index} equal the current image; the memory
+of the send-to and the send-from might (partially) overlap in that case. The
+implementation has to take care that it handles this case, e.g. using
+@code{memmove} which handles (partially) overlapping memory. If
+@var{may_require_tmp} is true, the library might additionally create a
+temporary variable, unless additional checks show that this is not required
+(e.g. because walking backward is possible or because both arrays are
+contiguous and @code{memmove} takes care of overlap issues).
+
+Note that the assignment of a scalar to an array is permitted. In addition,
+the library has to handle numeric-type conversion and for strings, padding
+and different character kinds.
+@end table
+
+
+@node _gfortran_caf_get
+@subsection @code{_gfortran_caf_get} --- Getting data from a remote image
+@cindex Coarray, _gfortran_caf_get
+
+@table @asis
+@item @emph{Description}:
+Called to get an array section or a whole array from a remote,
+image identified by the image_index.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_get (caf_token_t token, size_t offset,
+int image_index, gfc_descriptor_t *src, caf_vector_t *src_vector,
+gfc_descriptor_t *dest, int src_kind, int dst_kind, bool may_require_tmp,
+int *stat)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{offset} @tab intent(in) By which amount of bytes the actual data is
+shifted compared to the base address of the coarray.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number.
+@item @var{dest} @tab intent(out) Array descriptor of the local array to store
+the data retrieved from the remote image
+@item @var{src} @tab intent(in) Array descriptor for the remote image for the
+bounds and the size. The @code{base_addr} shall not be accessed.
+@item @var{src_vector} @tab intent(in) If not NULL, it contains the vector
+subscript of the source array; the values are relative to the dimension
+triplet of the @var{src} argument.
+@item @var{dst_kind} @tab intent(in) Kind of the destination argument
+@item @var{src_kind} @tab intent(in) Kind of the source argument
+@item @var{may_require_tmp} @tab intent(in) The variable is @code{false} when
+it is known at compile time that the @var{dest} and @var{src} either cannot
+overlap or overlap (fully or partially) such that walking @var{src} and
+@var{dest} in element wise element order (honoring the stride value) will not
+lead to wrong results. Otherwise, the value is @code{true}.
+@item @var{stat} @tab intent(out) When non-NULL give the result of the
+operation, i.e., zero on success and non-zero on error. When NULL and an error
+occurs, then an error message is printed and the program is terminated.
+@end multitable
+
+@item @emph{NOTES}
+It is permitted to have @var{image_index} equal the current image; the memory of
+the send-to and the send-from might (partially) overlap in that case. The
+implementation has to take care that it handles this case, e.g. using
+@code{memmove} which handles (partially) overlapping memory. If
+@var{may_require_tmp} is true, the library might additionally create a
+temporary variable, unless additional checks show that this is not required
+(e.g. because walking backward is possible or because both arrays are
+contiguous and @code{memmove} takes care of overlap issues).
+
+Note that the library has to handle numeric-type conversion and for strings,
+padding and different character kinds.
+@end table
+
+
+@node _gfortran_caf_sendget
+@subsection @code{_gfortran_caf_sendget} --- Sending data between remote images
+@cindex Coarray, _gfortran_caf_sendget
+
+@table @asis
+@item @emph{Description}:
+Called to send a scalar, an array section or a whole array from a remote image
+identified by the @var{src_image_index} to a remote image identified by the
+@var{dst_image_index}.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_sendget (caf_token_t dst_token, size_t dst_offset,
+int dst_image_index, gfc_descriptor_t *dest, caf_vector_t *dst_vector,
+caf_token_t src_token, size_t src_offset, int src_image_index,
+gfc_descriptor_t *src, caf_vector_t *src_vector, int dst_kind, int src_kind,
+bool may_require_tmp, int *stat)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{dst_token} @tab intent(in) An opaque pointer identifying the
+destination coarray.
+@item @var{dst_offset} @tab intent(in) By which amount of bytes the actual data
+is shifted compared to the base address of the destination coarray.
+@item @var{dst_image_index} @tab intent(in) The ID of the destination remote
+image; must be a positive number.
+@item @var{dest} @tab intent(in) Array descriptor for the destination
+remote image for the bounds and the size. The @code{base_addr} shall not be
+accessed.
+@item @var{dst_vector} @tab intent(int) If not NULL, it contains the vector
+subscript of the destination array; the values are relative to the dimension
+triplet of the @var{dest} argument.
+@item @var{src_token} @tab intent(in) An opaque pointer identifying the source
+coarray.
+@item @var{src_offset} @tab intent(in) By which amount of bytes the actual data
+is shifted compared to the base address of the source coarray.
+@item @var{src_image_index} @tab intent(in) The ID of the source remote image;
+must be a positive number.
+@item @var{src} @tab intent(in) Array descriptor of the local array to be
+transferred to the remote image.
+@item @var{src_vector} @tab intent(in) Array descriptor of the local array to
+be transferred to the remote image
+@item @var{dst_kind} @tab intent(in) Kind of the destination argument
+@item @var{src_kind} @tab intent(in) Kind of the source argument
+@item @var{may_require_tmp} @tab intent(in) The variable is @code{false} when
+it is known at compile time that the @var{dest} and @var{src} either cannot
+overlap or overlap (fully or partially) such that walking @var{src} and
+@var{dest} in element wise element order (honoring the stride value) will not
+lead to wrong results. Otherwise, the value is @code{true}.
+@item @var{stat} @tab intent(out) when non-NULL give the result of the
+operation, i.e., zero on success and non-zero on error. When NULL and an error
+occurs, then an error message is printed and the program is terminated.
+@end multitable
+
+@item @emph{NOTES}
+It is permitted to have the same image index for both @var{src_image_index} and
+@var{dst_image_index}; the memory of the send-to and the send-from might
+(partially) overlap in that case. The implementation has to take care that it
+handles this case, e.g. using @code{memmove} which handles (partially)
+overlapping memory. If @var{may_require_tmp} is true, the library
+might additionally create a temporary variable, unless additional checks show
+that this is not required (e.g. because walking backward is possible or because
+both arrays are contiguous and @code{memmove} takes care of overlap issues).
+
+Note that the assignment of a scalar to an array is permitted. In addition,
+the library has to handle numeric-type conversion and for strings, padding and
+different character kinds.
+@end table
+
+@node _gfortran_caf_send_by_ref
+@subsection @code{_gfortran_caf_send_by_ref} --- Sending data from a local image to a remote image with enhanced referencing options
+@cindex Coarray, _gfortran_caf_send_by_ref
+
+@table @asis
+@item @emph{Description}:
+Called to send a scalar, an array section or a whole array from a local to a
+remote image identified by the @var{image_index}.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_send_by_ref (caf_token_t token, int image_index,
+gfc_descriptor_t *src, caf_reference_t *refs, int dst_kind, int src_kind,
+bool may_require_tmp, bool dst_reallocatable, int *stat, int dst_type)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number.
+@item @var{src} @tab intent(in) Array descriptor of the local array to be
+transferred to the remote image
+@item @var{refs} @tab intent(in) The references on the remote array to store
+the data given by src. Guaranteed to have at least one entry.
+@item @var{dst_kind} @tab intent(in) Kind of the destination argument
+@item @var{src_kind} @tab intent(in) Kind of the source argument
+@item @var{may_require_tmp} @tab intent(in) The variable is @code{false} when
+it is known at compile time that the @var{dest} and @var{src} either cannot
+overlap or overlap (fully or partially) such that walking @var{src} and
+@var{dest} in element wise element order (honoring the stride value) will not
+lead to wrong results. Otherwise, the value is @code{true}.
+@item @var{dst_reallocatable} @tab intent(in) Set when the destination is of
+allocatable or pointer type and the refs will allow reallocation, i.e., the ref
+is a full array or component ref.
+@item @var{stat} @tab intent(out) When non-@code{NULL} give the result of the
+operation, i.e., zero on success and non-zero on error. When @code{NULL} and
+an error occurs, then an error message is printed and the program is terminated.
+@item @var{dst_type} @tab intent(in) Give the type of the destination. When
+the destination is not an array, than the precise type, e.g. of a component in
+a derived type, is not known, but provided here.
+@end multitable
+
+@item @emph{NOTES}
+It is permitted to have @var{image_index} equal the current image; the memory of
+the send-to and the send-from might (partially) overlap in that case. The
+implementation has to take care that it handles this case, e.g. using
+@code{memmove} which handles (partially) overlapping memory. If
+@var{may_require_tmp} is true, the library might additionally create a
+temporary variable, unless additional checks show that this is not required
+(e.g. because walking backward is possible or because both arrays are
+contiguous and @code{memmove} takes care of overlap issues).
+
+Note that the assignment of a scalar to an array is permitted. In addition,
+the library has to handle numeric-type conversion and for strings, padding
+and different character kinds.
+
+Because of the more complicated references possible some operations may be
+unsupported by certain libraries. The library is expected to issue a precise
+error message why the operation is not permitted.
+@end table
+
+
+@node _gfortran_caf_get_by_ref
+@subsection @code{_gfortran_caf_get_by_ref} --- Getting data from a remote image using enhanced references
+@cindex Coarray, _gfortran_caf_get_by_ref
+
+@table @asis
+@item @emph{Description}:
+Called to get a scalar, an array section or a whole array from a remote image
+identified by the @var{image_index}.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_get_by_ref (caf_token_t token, int image_index,
+caf_reference_t *refs, gfc_descriptor_t *dst, int dst_kind, int src_kind,
+bool may_require_tmp, bool dst_reallocatable, int *stat, int src_type)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number.
+@item @var{refs} @tab intent(in) The references to apply to the remote structure
+to get the data.
+@item @var{dst} @tab intent(in) Array descriptor of the local array to store
+the data transferred from the remote image. May be reallocated where needed
+and when @var{DST_REALLOCATABLE} allows it.
+@item @var{dst_kind} @tab intent(in) Kind of the destination argument
+@item @var{src_kind} @tab intent(in) Kind of the source argument
+@item @var{may_require_tmp} @tab intent(in) The variable is @code{false} when
+it is known at compile time that the @var{dest} and @var{src} either cannot
+overlap or overlap (fully or partially) such that walking @var{src} and
+@var{dest} in element wise element order (honoring the stride value) will not
+lead to wrong results. Otherwise, the value is @code{true}.
+@item @var{dst_reallocatable} @tab intent(in) Set when @var{DST} is of
+allocatable or pointer type and its refs allow reallocation, i.e., the full
+array or a component is referenced.
+@item @var{stat} @tab intent(out) When non-@code{NULL} give the result of the
+operation, i.e., zero on success and non-zero on error. When @code{NULL} and an
+error occurs, then an error message is printed and the program is terminated.
+@item @var{src_type} @tab intent(in) Give the type of the source. When the
+source is not an array, than the precise type, e.g. of a component in a
+derived type, is not known, but provided here.
+@end multitable
+
+@item @emph{NOTES}
+It is permitted to have @code{image_index} equal the current image; the memory
+of the send-to and the send-from might (partially) overlap in that case. The
+implementation has to take care that it handles this case, e.g. using
+@code{memmove} which handles (partially) overlapping memory. If
+@var{may_require_tmp} is true, the library might additionally create a
+temporary variable, unless additional checks show that this is not required
+(e.g. because walking backward is possible or because both arrays are
+contiguous and @code{memmove} takes care of overlap issues).
+
+Note that the library has to handle numeric-type conversion and for strings,
+padding and different character kinds.
+
+Because of the more complicated references possible some operations may be
+unsupported by certain libraries. The library is expected to issue a precise
+error message why the operation is not permitted.
+@end table
+
+
+@node _gfortran_caf_sendget_by_ref
+@subsection @code{_gfortran_caf_sendget_by_ref} --- Sending data between remote images using enhanced references on both sides
+@cindex Coarray, _gfortran_caf_sendget_by_ref
+
+@table @asis
+@item @emph{Description}:
+Called to send a scalar, an array section or a whole array from a remote image
+identified by the @var{src_image_index} to a remote image identified by the
+@var{dst_image_index}.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_sendget_by_ref (caf_token_t dst_token,
+int dst_image_index, caf_reference_t *dst_refs,
+caf_token_t src_token, int src_image_index, caf_reference_t *src_refs,
+int dst_kind, int src_kind, bool may_require_tmp, int *dst_stat,
+int *src_stat, int dst_type, int src_type)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{dst_token} @tab intent(in) An opaque pointer identifying the
+destination coarray.
+@item @var{dst_image_index} @tab intent(in) The ID of the destination remote
+image; must be a positive number.
+@item @var{dst_refs} @tab intent(in) The references on the remote array to store
+the data given by the source. Guaranteed to have at least one entry.
+@item @var{src_token} @tab intent(in) An opaque pointer identifying the source
+coarray.
+@item @var{src_image_index} @tab intent(in) The ID of the source remote image;
+must be a positive number.
+@item @var{src_refs} @tab intent(in) The references to apply to the remote
+structure to get the data.
+@item @var{dst_kind} @tab intent(in) Kind of the destination argument
+@item @var{src_kind} @tab intent(in) Kind of the source argument
+@item @var{may_require_tmp} @tab intent(in) The variable is @code{false} when
+it is known at compile time that the @var{dest} and @var{src} either cannot
+overlap or overlap (fully or partially) such that walking @var{src} and
+@var{dest} in element wise element order (honoring the stride value) will not
+lead to wrong results. Otherwise, the value is @code{true}.
+@item @var{dst_stat} @tab intent(out) when non-@code{NULL} give the result of
+the send-operation, i.e., zero on success and non-zero on error. When
+@code{NULL} and an error occurs, then an error message is printed and the
+program is terminated.
+@item @var{src_stat} @tab intent(out) When non-@code{NULL} give the result of
+the get-operation, i.e., zero on success and non-zero on error. When
+@code{NULL} and an error occurs, then an error message is printed and the
+program is terminated.
+@item @var{dst_type} @tab intent(in) Give the type of the destination. When
+the destination is not an array, than the precise type, e.g. of a component in
+a derived type, is not known, but provided here.
+@item @var{src_type} @tab intent(in) Give the type of the source. When the
+source is not an array, than the precise type, e.g. of a component in a
+derived type, is not known, but provided here.
+@end multitable
+
+@item @emph{NOTES}
+It is permitted to have the same image index for both @var{src_image_index} and
+@var{dst_image_index}; the memory of the send-to and the send-from might
+(partially) overlap in that case. The implementation has to take care that it
+handles this case, e.g. using @code{memmove} which handles (partially)
+overlapping memory. If @var{may_require_tmp} is true, the library
+might additionally create a temporary variable, unless additional checks show
+that this is not required (e.g. because walking backward is possible or because
+both arrays are contiguous and @code{memmove} takes care of overlap issues).
+
+Note that the assignment of a scalar to an array is permitted. In addition,
+the library has to handle numeric-type conversion and for strings, padding and
+different character kinds.
+
+Because of the more complicated references possible some operations may be
+unsupported by certain libraries. The library is expected to issue a precise
+error message why the operation is not permitted.
+@end table
+
+
+@node _gfortran_caf_lock
+@subsection @code{_gfortran_caf_lock} --- Locking a lock variable
+@cindex Coarray, _gfortran_caf_lock
+
+@table @asis
+@item @emph{Description}:
+Acquire a lock on the given image on a scalar locking variable or for the
+given array element for an array-valued variable. If the @var{acquired_lock}
+is @code{NULL}, the function returns after having obtained the lock. If it is
+non-@code{NULL}, then @var{acquired_lock} is assigned the value true (one) when
+the lock could be obtained and false (zero) otherwise. Locking a lock variable
+which has already been locked by the same image is an error.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_lock (caf_token_t token, size_t index, int image_index,
+int *acquired_lock, int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{index} @tab intent(in) Array index; first array index is 0. For
+scalars, it is always 0.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number.
+@item @var{acquired_lock} @tab intent(out) If not NULL, it returns whether lock
+could be obtained.
+@item @var{stat} @tab intent(out) Stores the STAT=; may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTES}
+This function is also called for critical blocks; for those, the array index
+is always zero and the image index is one. Libraries are permitted to use other
+images for critical-block locking variables.
+@end table
+
+@node _gfortran_caf_unlock
+@subsection @code{_gfortran_caf_lock} --- Unlocking a lock variable
+@cindex Coarray, _gfortran_caf_unlock
+
+@table @asis
+@item @emph{Description}:
+Release a lock on the given image on a scalar locking variable or for the
+given array element for an array-valued variable. Unlocking a lock variable
+which is unlocked or has been locked by a different image is an error.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_unlock (caf_token_t token, size_t index, int image_index,
+int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{index} @tab intent(in) Array index; first array index is 0. For
+scalars, it is always 0.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number.
+@item @var{stat} @tab intent(out) For allocatable coarrays, stores the STAT=;
+may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTES}
+This function is also called for critical block; for those, the array index
+is always zero and the image index is one. Libraries are permitted to use other
+images for critical-block locking variables.
+@end table
+
+@node _gfortran_caf_event_post
+@subsection @code{_gfortran_caf_event_post} --- Post an event
+@cindex Coarray, _gfortran_caf_event_post
+
+@table @asis
+@item @emph{Description}:
+Increment the event count of the specified event variable.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_event_post (caf_token_t token, size_t index,
+int image_index, int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{index} @tab intent(in) Array index; first array index is 0. For
+scalars, it is always 0.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number; zero indicates the current image, when accessed noncoindexed.
+@item @var{stat} @tab intent(out) Stores the STAT=; may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTES}
+This acts like an atomic add of one to the remote image's event variable.
+The statement is an image-control statement but does not imply sync memory.
+Still, all preceeding push communications of this image to the specified
+remote image have to be completed before @code{event_wait} on the remote
+image returns.
+@end table
+
+
+
+@node _gfortran_caf_event_wait
+@subsection @code{_gfortran_caf_event_wait} --- Wait that an event occurred
+@cindex Coarray, _gfortran_caf_event_wait
+
+@table @asis
+@item @emph{Description}:
+Wait until the event count has reached at least the specified
+@var{until_count}; if so, atomically decrement the event variable by this
+amount and return.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_event_wait (caf_token_t token, size_t index,
+int until_count, int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{index} @tab intent(in) Array index; first array index is 0. For
+scalars, it is always 0.
+@item @var{until_count} @tab intent(in) The number of events which have to be
+available before the function returns.
+@item @var{stat} @tab intent(out) Stores the STAT=; may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTES}
+This function only operates on a local coarray. It acts like a loop checking
+atomically the value of the event variable, breaking if the value is greater
+or equal the requested number of counts. Before the function returns, the
+event variable has to be decremented by the requested @var{until_count} value.
+A possible implementation would be a busy loop for a certain number of spins
+(possibly depending on the number of threads relative to the number of available
+cores) followed by another waiting strategy such as a sleeping wait (possibly
+with an increasing number of sleep time) or, if possible, a futex wait.
+
+The statement is an image-control statement but does not imply sync memory.
+Still, all preceeding push communications of this image to the specified
+remote image have to be completed before @code{event_wait} on the remote
+image returns.
+@end table
+
+
+
+@node _gfortran_caf_event_query
+@subsection @code{_gfortran_caf_event_query} --- Query event count
+@cindex Coarray, _gfortran_caf_event_query
+
+@table @asis
+@item @emph{Description}:
+Return the event count of the specified event variable.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_event_query (caf_token_t token, size_t index,
+int image_index, int *count, int *stat)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{index} @tab intent(in) Array index; first array index is 0. For
+scalars, it is always 0.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number; zero indicates the current image when accessed noncoindexed.
+@item @var{count} @tab intent(out) The number of events currently posted to
+the event variable.
+@item @var{stat} @tab intent(out) Stores the STAT=; may be NULL.
+@end multitable
+
+@item @emph{NOTES}
+The typical use is to check the local event variable to only call
+@code{event_wait} when the data is available. However, a coindexed variable
+is permitted; there is no ordering or synchronization implied. It acts like
+an atomic fetch of the value of the event variable.
+@end table
+
+
+
+@node _gfortran_caf_sync_all
+@subsection @code{_gfortran_caf_sync_all} --- All-image barrier
+@cindex Coarray, _gfortran_caf_sync_all
+
+@table @asis
+@item @emph{Description}:
+Synchronization of all images in the current team; the program only continues
+on a given image after this function has been called on all images of the
+current team. Additionally, it ensures that all pending data transfers of
+previous segment have completed.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_sync_all (int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+@end table
+
+
+
+@node _gfortran_caf_sync_images
+@subsection @code{_gfortran_caf_sync_images} --- Barrier for selected images
+@cindex Coarray, _gfortran_caf_sync_images
+
+@table @asis
+@item @emph{Description}:
+Synchronization between the specified images; the program only continues on a
+given image after this function has been called on all images specified for
+that image. Note that one image can wait for all other images in the current
+team (e.g. via @code{sync images(*)}) while those only wait for that specific
+image. Additionally, @code{sync images} ensures that all pending data
+transfers of previous segments have completed.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_sync_images (int count, int images[], int *stat,
+char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{count} @tab intent(in) The number of images which are provided in
+the next argument. For a zero-sized array, the value is zero. For
+@code{sync images (*)}, the value is @math{-1}.
+@item @var{images} @tab intent(in) An array with the images provided by the
+user. If @var{count} is zero, a NULL pointer is passed.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+@end table
+
+
+
+@node _gfortran_caf_sync_memory
+@subsection @code{_gfortran_caf_sync_memory} --- Wait for completion of segment-memory operations
+@cindex Coarray, _gfortran_caf_sync_memory
+
+@table @asis
+@item @emph{Description}:
+Acts as optimization barrier between different segments. It also ensures that
+all pending memory operations of this image have been completed.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_sync_memory (int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTE} A simple implementation could be
+@code{__asm__ __volatile__ ("":::"memory")} to prevent code movements.
+@end table
+
+
+
+@node _gfortran_caf_error_stop
+@subsection @code{_gfortran_caf_error_stop} --- Error termination with exit code
+@cindex Coarray, _gfortran_caf_error_stop
+
+@table @asis
+@item @emph{Description}:
+Invoked for an @code{ERROR STOP} statement which has an integer argument. The
+function should terminate the program with the specified exit code.
+
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_error_stop (int error)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{error} @tab intent(in) The exit status to be used.
+@end multitable
+@end table
+
+
+
+@node _gfortran_caf_error_stop_str
+@subsection @code{_gfortran_caf_error_stop_str} --- Error termination with string
+@cindex Coarray, _gfortran_caf_error_stop_str
+
+@table @asis
+@item @emph{Description}:
+Invoked for an @code{ERROR STOP} statement which has a string as argument. The
+function should terminate the program with a nonzero-exit code.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_error_stop (const char *string, size_t len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{string} @tab intent(in) the error message (not zero terminated)
+@item @var{len} @tab intent(in) the length of the string
+@end multitable
+@end table
+
+
+
+@node _gfortran_caf_fail_image
+@subsection @code{_gfortran_caf_fail_image} --- Mark the image failed and end its execution
+@cindex Coarray, _gfortran_caf_fail_image
+
+@table @asis
+@item @emph{Description}:
+Invoked for an @code{FAIL IMAGE} statement. The function should terminate the
+current image.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_fail_image ()}
+
+@item @emph{NOTES}
+This function follows TS18508.
+@end table
+
+
+
+@node _gfortran_caf_atomic_define
+@subsection @code{_gfortran_caf_atomic_define} --- Atomic variable assignment
+@cindex Coarray, _gfortran_caf_atomic_define
+
+@table @asis
+@item @emph{Description}:
+Assign atomically a value to an integer or logical variable.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_atomic_define (caf_token_t token, size_t offset,
+int image_index, void *value, int *stat, int type, int kind)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{offset} @tab intent(in) By which amount of bytes the actual data is
+shifted compared to the base address of the coarray.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number; zero indicates the current image when used noncoindexed.
+@item @var{value} @tab intent(in) the value to be assigned, passed by reference
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{type} @tab intent(in) The data type, i.e. @code{BT_INTEGER} (1) or
+@code{BT_LOGICAL} (2).
+@item @var{kind} @tab intent(in) The kind value (only 4; always @code{int})
+@end multitable
+@end table
+
+
+
+@node _gfortran_caf_atomic_ref
+@subsection @code{_gfortran_caf_atomic_ref} --- Atomic variable reference
+@cindex Coarray, _gfortran_caf_atomic_ref
+
+@table @asis
+@item @emph{Description}:
+Reference atomically a value of a kind-4 integer or logical variable.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_atomic_ref (caf_token_t token, size_t offset,
+int image_index, void *value, int *stat, int type, int kind)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{offset} @tab intent(in) By which amount of bytes the actual data is
+shifted compared to the base address of the coarray.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number; zero indicates the current image when used noncoindexed.
+@item @var{value} @tab intent(out) The variable assigned the atomically
+referenced variable.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{type} @tab the data type, i.e. @code{BT_INTEGER} (1) or
+@code{BT_LOGICAL} (2).
+@item @var{kind} @tab The kind value (only 4; always @code{int})
+@end multitable
+@end table
+
+
+
+@node _gfortran_caf_atomic_cas
+@subsection @code{_gfortran_caf_atomic_cas} --- Atomic compare and swap
+@cindex Coarray, _gfortran_caf_atomic_cas
+
+@table @asis
+@item @emph{Description}:
+Atomic compare and swap of a kind-4 integer or logical variable. Assigns
+atomically the specified value to the atomic variable, if the latter has
+the value specified by the passed condition value.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_atomic_cas (caf_token_t token, size_t offset,
+int image_index, void *old, void *compare, void *new_val, int *stat,
+int type, int kind)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{offset} @tab intent(in) By which amount of bytes the actual data is
+shifted compared to the base address of the coarray.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number; zero indicates the current image when used noncoindexed.
+@item @var{old} @tab intent(out) The value which the atomic variable had
+just before the cas operation.
+@item @var{compare} @tab intent(in) The value used for comparision.
+@item @var{new_val} @tab intent(in) The new value for the atomic variable,
+assigned to the atomic variable, if @code{compare} equals the value of the
+atomic variable.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{type} @tab intent(in) the data type, i.e. @code{BT_INTEGER} (1) or
+@code{BT_LOGICAL} (2).
+@item @var{kind} @tab intent(in) The kind value (only 4; always @code{int})
+@end multitable
+@end table
+
+
+
+@node _gfortran_caf_atomic_op
+@subsection @code{_gfortran_caf_atomic_op} --- Atomic operation
+@cindex Coarray, _gfortran_caf_atomic_op
+
+@table @asis
+@item @emph{Description}:
+Apply an operation atomically to an atomic integer or logical variable.
+After the operation, @var{old} contains the value just before the operation,
+which, respectively, adds (GFC_CAF_ATOMIC_ADD) atomically the @code{value} to
+the atomic integer variable or does a bitwise AND, OR or exclusive OR
+between the atomic variable and @var{value}; the result is then stored in the
+atomic variable.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_atomic_op (int op, caf_token_t token, size_t offset,
+int image_index, void *value, void *old, int *stat, int type, int kind)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{op} @tab intent(in) the operation to be performed; possible values
+@code{GFC_CAF_ATOMIC_ADD} (1), @code{GFC_CAF_ATOMIC_AND} (2),
+@code{GFC_CAF_ATOMIC_OR} (3), @code{GFC_CAF_ATOMIC_XOR} (4).
+@item @var{token} @tab intent(in) An opaque pointer identifying the coarray.
+@item @var{offset} @tab intent(in) By which amount of bytes the actual data is
+shifted compared to the base address of the coarray.
+@item @var{image_index} @tab intent(in) The ID of the remote image; must be a
+positive number; zero indicates the current image when used noncoindexed.
+@item @var{old} @tab intent(out) The value which the atomic variable had
+just before the atomic operation.
+@item @var{val} @tab intent(in) The new value for the atomic variable,
+assigned to the atomic variable, if @code{compare} equals the value of the
+atomic variable.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{type} @tab intent(in) the data type, i.e. @code{BT_INTEGER} (1) or
+@code{BT_LOGICAL} (2)
+@item @var{kind} @tab intent(in) the kind value (only 4; always @code{int})
+@end multitable
+@end table
+
+
+
+
+@node _gfortran_caf_co_broadcast
+@subsection @code{_gfortran_caf_co_broadcast} --- Sending data to all images
+@cindex Coarray, _gfortran_caf_co_broadcast
+
+@table @asis
+@item @emph{Description}:
+Distribute a value from a given image to all other images in the team. Has to
+be called collectively.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_co_broadcast (gfc_descriptor_t *a,
+int source_image, int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{a} @tab intent(inout) An array descriptor with the data to be
+broadcasted (on @var{source_image}) or to be received (other images).
+@item @var{source_image} @tab intent(in) The ID of the image from which the
+data should be broadcasted.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg.
+@end multitable
+@end table
+
+
+
+@node _gfortran_caf_co_max
+@subsection @code{_gfortran_caf_co_max} --- Collective maximum reduction
+@cindex Coarray, _gfortran_caf_co_max
+
+@table @asis
+@item @emph{Description}:
+Calculates for each array element of the variable @var{a} the maximum
+value for that element in the current team; if @var{result_image} has the
+value 0, the result shall be stored on all images, otherwise, only on the
+specified image. This function operates on numeric values and character
+strings.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_co_max (gfc_descriptor_t *a, int result_image,
+int *stat, char *errmsg, int a_len, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{a} @tab intent(inout) An array descriptor for the data to be
+processed. On the destination image(s) the result overwrites the old content.
+@item @var{result_image} @tab intent(in) The ID of the image to which the
+reduced value should be copied to; if zero, it has to be copied to all images.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{a_len} @tab intent(in) the string length of argument @var{a}
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTES}
+If @var{result_image} is nonzero, the data in the array descriptor @var{a} on
+all images except of the specified one become undefined; hence, the library may
+make use of this.
+@end table
+
+
+
+@node _gfortran_caf_co_min
+@subsection @code{_gfortran_caf_co_min} --- Collective minimum reduction
+@cindex Coarray, _gfortran_caf_co_min
+
+@table @asis
+@item @emph{Description}:
+Calculates for each array element of the variable @var{a} the minimum
+value for that element in the current team; if @var{result_image} has the
+value 0, the result shall be stored on all images, otherwise, only on the
+specified image. This function operates on numeric values and character
+strings.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_co_min (gfc_descriptor_t *a, int result_image,
+int *stat, char *errmsg, int a_len, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{a} @tab intent(inout) An array descriptor for the data to be
+processed. On the destination image(s) the result overwrites the old content.
+@item @var{result_image} @tab intent(in) The ID of the image to which the
+reduced value should be copied to; if zero, it has to be copied to all images.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{a_len} @tab intent(in) the string length of argument @var{a}
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTES}
+If @var{result_image} is nonzero, the data in the array descriptor @var{a} on
+all images except of the specified one become undefined; hence, the library may
+make use of this.
+@end table
+
+
+
+@node _gfortran_caf_co_sum
+@subsection @code{_gfortran_caf_co_sum} --- Collective summing reduction
+@cindex Coarray, _gfortran_caf_co_sum
+
+@table @asis
+@item @emph{Description}:
+Calculates for each array element of the variable @var{a} the sum of all
+values for that element in the current team; if @var{result_image} has the
+value 0, the result shall be stored on all images, otherwise, only on the
+specified image. This function operates on numeric values only.
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_co_sum (gfc_descriptor_t *a, int result_image,
+int *stat, char *errmsg, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{a} @tab intent(inout) An array descriptor with the data to be
+processed. On the destination image(s) the result overwrites the old content.
+@item @var{result_image} @tab intent(in) The ID of the image to which the
+reduced value should be copied to; if zero, it has to be copied to all images.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTES}
+If @var{result_image} is nonzero, the data in the array descriptor @var{a} on
+all images except of the specified one become undefined; hence, the library may
+make use of this.
+@end table
+
+
+
+@node _gfortran_caf_co_reduce
+@subsection @code{_gfortran_caf_co_reduce} --- Generic collective reduction
+@cindex Coarray, _gfortran_caf_co_reduce
+
+@table @asis
+@item @emph{Description}:
+Calculates for each array element of the variable @var{a} the reduction
+value for that element in the current team; if @var{result_image} has the
+value 0, the result shall be stored on all images, otherwise, only on the
+specified image. The @var{opr} is a pure function doing a mathematically
+commutative and associative operation.
+
+The @var{opr_flags} denote the following; the values are bitwise ored.
+@code{GFC_CAF_BYREF} (1) if the result should be returned
+by reference; @code{GFC_CAF_HIDDENLEN} (2) whether the result and argument
+string lengths shall be specified as hidden arguments;
+@code{GFC_CAF_ARG_VALUE} (4) whether the arguments shall be passed by value,
+@code{GFC_CAF_ARG_DESC} (8) whether the arguments shall be passed by descriptor.
+
+
+@item @emph{Syntax}:
+@code{void _gfortran_caf_co_reduce (gfc_descriptor_t *a,
+void * (*opr) (void *, void *), int opr_flags, int result_image,
+int *stat, char *errmsg, int a_len, size_t errmsg_len)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{a} @tab intent(inout) An array descriptor with the data to be
+processed. On the destination image(s) the result overwrites the old content.
+@item @var{opr} @tab intent(in) Function pointer to the reduction function
+@item @var{opr_flags} @tab intent(in) Flags regarding the reduction function
+@item @var{result_image} @tab intent(in) The ID of the image to which the
+reduced value should be copied to; if zero, it has to be copied to all images.
+@item @var{stat} @tab intent(out) Stores the status STAT= and may be NULL.
+@item @var{errmsg} @tab intent(out) When an error occurs, this will be set to
+an error message; may be NULL.
+@item @var{a_len} @tab intent(in) the string length of argument @var{a}
+@item @var{errmsg_len} @tab intent(in) the buffer size of errmsg
+@end multitable
+
+@item @emph{NOTES}
+If @var{result_image} is nonzero, the data in the array descriptor @var{a} on
+all images except of the specified one become undefined; hence, the library may
+make use of this.
+
+For character arguments, the result is passed as first argument, followed
+by the result string length, next come the two string arguments, followed
+by the two hidden string length arguments. With C binding, there are no hidden
+arguments and by-reference passing and either only a single character is passed
+or an array descriptor.
+@end table
+
+
+@c Intrinsic Procedures
+@c ---------------------------------------------------------------------
+
+@include intrinsic.texi
+
+
+@tex
+\blankpart
+@end tex
+
+@c ---------------------------------------------------------------------
+@c Contributing
+@c ---------------------------------------------------------------------
+
+@node Contributing
+@unnumbered Contributing
+@cindex Contributing
+
+Free software is only possible if people contribute to efforts
+to create it.
+We're always in need of more people helping out with ideas
+and comments, writing documentation and contributing code.
+
+If you want to contribute to GNU Fortran,
+have a look at the long lists of projects you can take on.
+Some of these projects are small,
+some of them are large;
+some are completely orthogonal to the rest of what is
+happening on GNU Fortran,
+but others are ``mainstream'' projects in need of enthusiastic hackers.
+All of these projects are important!
+We will eventually get around to the things here,
+but they are also things doable by someone who is willing and able.
+
+@menu
+* Contributors::
+* Projects::
+@end menu
+
+
+@node Contributors
+@section Contributors to GNU Fortran
+@cindex Contributors
+@cindex Credits
+@cindex Authors
+
+Most of the parser was hand-crafted by @emph{Andy Vaught}, who is
+also the initiator of the whole project. Thanks Andy!
+Most of the interface with GCC was written by @emph{Paul Brook}.
+
+The following individuals have contributed code and/or
+ideas and significant help to the GNU Fortran project
+(in alphabetical order):
+
+@itemize @minus
+@item Janne Blomqvist
+@item Steven Bosscher
+@item Paul Brook
+@item Tobias Burnus
+@item Fran@,{c}ois-Xavier Coudert
+@item Bud Davis
+@item Jerry DeLisle
+@item Erik Edelmann
+@item Bernhard Fischer
+@item Daniel Franke
+@item Richard Guenther
+@item Richard Henderson
+@item Katherine Holcomb
+@item Jakub Jelinek
+@item Niels Kristian Bech Jensen
+@item Steven Johnson
+@item Steven G. Kargl
+@item Thomas Koenig
+@item Asher Langton
+@item H. J. Lu
+@item Toon Moene
+@item Brooks Moses
+@item Andrew Pinski
+@item Tim Prince
+@item Christopher D. Rickett
+@item Richard Sandiford
+@item Tobias Schl@"uter
+@item Roger Sayle
+@item Paul Thomas
+@item Andy Vaught
+@item Feng Wang
+@item Janus Weil
+@item Daniel Kraft
+@end itemize
+
+The following people have contributed bug reports,
+smaller or larger patches,
+and much needed feedback and encouragement for the
+GNU Fortran project:
+
+@itemize @minus
+@item Bill Clodius
+@item Dominique d'Humi@`eres
+@item Kate Hedstrom
+@item Erik Schnetter
+@item Gerhard Steinmetz
+@item Joost VandeVondele
+@end itemize
+
+Many other individuals have helped debug,
+test and improve the GNU Fortran compiler over the past few years,
+and we welcome you to do the same!
+If you already have done so,
+and you would like to see your name listed in the
+list above, please contact us.
+
+
+@node Projects
+@section Projects
+
+@table @emph
+
+@item Help build the test suite
+Solicit more code for donation to the test suite: the more extensive the
+testsuite, the smaller the risk of breaking things in the future! We can
+keep code private on request.
+
+@item Bug hunting/squishing
+Find bugs and write more test cases! Test cases are especially very
+welcome, because it allows us to concentrate on fixing bugs instead of
+isolating them. Going through the bugzilla database at
+@url{https://gcc.gnu.org/@/bugzilla/} to reduce testcases posted there and
+add more information (for example, for which version does the testcase
+work, for which versions does it fail?) is also very helpful.
+
+@item Missing features
+For a larger project, consider working on the missing features required for
+Fortran language standards compliance (@pxref{Standards}), or contributing
+to the implementation of extensions such as OpenMP (@pxref{OpenMP}) or
+OpenACC (@pxref{OpenACC}) that are under active development. Again,
+contributing test cases for these features is useful too!
+
+@end table
+
+
+@c ---------------------------------------------------------------------
+@c GNU General Public License
+@c ---------------------------------------------------------------------
+
+@include gpl_v3.texi
+
+
+
+@c ---------------------------------------------------------------------
+@c GNU Free Documentation License
+@c ---------------------------------------------------------------------
+
+@include fdl.texi
+
+
+
+@c ---------------------------------------------------------------------
+@c Funding Free Software
+@c ---------------------------------------------------------------------
+
+@include funding.texi
+
+@c ---------------------------------------------------------------------
+@c Indices
+@c ---------------------------------------------------------------------
+
+@node Option Index
+@unnumbered Option Index
+@command{gfortran}'s command line options are indexed here without any
+initial @samp{-} or @samp{--}. Where an option has both positive and
+negative forms (such as -foption and -fno-option), relevant entries in
+the manual are indexed under the most appropriate form; it may sometimes
+be useful to look up both forms.
+@printindex op
+
+@node Keyword Index
+@unnumbered Keyword Index
+@printindex cp
+
+@bye
--- /dev/null
+@ignore
+Copyright (C) 2005-2022 Free Software Foundation, Inc.
+This is part of the GNU Fortran manual.
+For copying conditions, see the file gfortran.texi.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``Funding Free Software'', the Front-Cover
+Texts being (a) (see below), and with the Back-Cover Texts being (b)
+(see below). A copy of the license is included in the gfdl(7) man page.
+
+
+Some basic guidelines for editing this document:
+
+ (1) The intrinsic procedures are to be listed in alphabetical order.
+ (2) The generic name is to be used.
+ (3) The specific names are included in the function index and in a
+ table at the end of the node (See ABS entry).
+ (4) Try to maintain the same style for each entry.
+
+
+@end ignore
+
+@tex
+\gdef\acosd{\mathop{\rm acosd}\nolimits}
+\gdef\asind{\mathop{\rm asind}\nolimits}
+\gdef\atand{\mathop{\rm atand}\nolimits}
+\gdef\acos{\mathop{\rm acos}\nolimits}
+\gdef\asin{\mathop{\rm asin}\nolimits}
+\gdef\atan{\mathop{\rm atan}\nolimits}
+\gdef\acosh{\mathop{\rm acosh}\nolimits}
+\gdef\asinh{\mathop{\rm asinh}\nolimits}
+\gdef\atanh{\mathop{\rm atanh}\nolimits}
+\gdef\cosd{\mathop{\rm cosd}\nolimits}
+@end tex
+
+
+@node Intrinsic Procedures
+@chapter Intrinsic Procedures
+@cindex intrinsic procedures
+
+@menu
+* Introduction: Introduction to Intrinsics
+* @code{ABORT}: ABORT, Abort the program
+* @code{ABS}: ABS, Absolute value
+* @code{ACCESS}: ACCESS, Checks file access modes
+* @code{ACHAR}: ACHAR, Character in @acronym{ASCII} collating sequence
+* @code{ACOS}: ACOS, Arccosine function
+* @code{ACOSD}: ACOSD, Arccosine function, degrees
+* @code{ACOSH}: ACOSH, Inverse hyperbolic cosine function
+* @code{ADJUSTL}: ADJUSTL, Left adjust a string
+* @code{ADJUSTR}: ADJUSTR, Right adjust a string
+* @code{AIMAG}: AIMAG, Imaginary part of complex number
+* @code{AINT}: AINT, Truncate to a whole number
+* @code{ALARM}: ALARM, Set an alarm clock
+* @code{ALL}: ALL, Determine if all values are true
+* @code{ALLOCATED}: ALLOCATED, Status of allocatable entity
+* @code{AND}: AND, Bitwise logical AND
+* @code{ANINT}: ANINT, Nearest whole number
+* @code{ANY}: ANY, Determine if any values are true
+* @code{ASIN}: ASIN, Arcsine function
+* @code{ASIND}: ASIND, Arcsine function, degrees
+* @code{ASINH}: ASINH, Inverse hyperbolic sine function
+* @code{ASSOCIATED}: ASSOCIATED, Status of a pointer or pointer/target pair
+* @code{ATAN}: ATAN, Arctangent function
+* @code{ATAND}: ATAND, Arctangent function, degrees
+* @code{ATAN2}: ATAN2, Arctangent function
+* @code{ATAN2D}: ATAN2D, Arctangent function, degrees
+* @code{ATANH}: ATANH, Inverse hyperbolic tangent function
+* @code{ATOMIC_ADD}: ATOMIC_ADD, Atomic ADD operation
+* @code{ATOMIC_AND}: ATOMIC_AND, Atomic bitwise AND operation
+* @code{ATOMIC_CAS}: ATOMIC_CAS, Atomic compare and swap
+* @code{ATOMIC_DEFINE}: ATOMIC_DEFINE, Setting a variable atomically
+* @code{ATOMIC_FETCH_ADD}: ATOMIC_FETCH_ADD, Atomic ADD operation with prior fetch
+* @code{ATOMIC_FETCH_AND}: ATOMIC_FETCH_AND, Atomic bitwise AND operation with prior fetch
+* @code{ATOMIC_FETCH_OR}: ATOMIC_FETCH_OR, Atomic bitwise OR operation with prior fetch
+* @code{ATOMIC_FETCH_XOR}: ATOMIC_FETCH_XOR, Atomic bitwise XOR operation with prior fetch
+* @code{ATOMIC_OR}: ATOMIC_OR, Atomic bitwise OR operation
+* @code{ATOMIC_REF}: ATOMIC_REF, Obtaining the value of a variable atomically
+* @code{ATOMIC_XOR}: ATOMIC_XOR, Atomic bitwise OR operation
+* @code{BACKTRACE}: BACKTRACE, Show a backtrace
+* @code{BESSEL_J0}: BESSEL_J0, Bessel function of the first kind of order 0
+* @code{BESSEL_J1}: BESSEL_J1, Bessel function of the first kind of order 1
+* @code{BESSEL_JN}: BESSEL_JN, Bessel function of the first kind
+* @code{BESSEL_Y0}: BESSEL_Y0, Bessel function of the second kind of order 0
+* @code{BESSEL_Y1}: BESSEL_Y1, Bessel function of the second kind of order 1
+* @code{BESSEL_YN}: BESSEL_YN, Bessel function of the second kind
+* @code{BGE}: BGE, Bitwise greater than or equal to
+* @code{BGT}: BGT, Bitwise greater than
+* @code{BIT_SIZE}: BIT_SIZE, Bit size inquiry function
+* @code{BLE}: BLE, Bitwise less than or equal to
+* @code{BLT}: BLT, Bitwise less than
+* @code{BTEST}: BTEST, Bit test function
+* @code{C_ASSOCIATED}: C_ASSOCIATED, Status of a C pointer
+* @code{C_F_POINTER}: C_F_POINTER, Convert C into Fortran pointer
+* @code{C_F_PROCPOINTER}: C_F_PROCPOINTER, Convert C into Fortran procedure pointer
+* @code{C_FUNLOC}: C_FUNLOC, Obtain the C address of a procedure
+* @code{C_LOC}: C_LOC, Obtain the C address of an object
+* @code{C_SIZEOF}: C_SIZEOF, Size in bytes of an expression
+* @code{CEILING}: CEILING, Integer ceiling function
+* @code{CHAR}: CHAR, Integer-to-character conversion function
+* @code{CHDIR}: CHDIR, Change working directory
+* @code{CHMOD}: CHMOD, Change access permissions of files
+* @code{CMPLX}: CMPLX, Complex conversion function
+* @code{CO_BROADCAST}: CO_BROADCAST, Copy a value to all images the current set of images
+* @code{CO_MAX}: CO_MAX, Maximal value on the current set of images
+* @code{CO_MIN}: CO_MIN, Minimal value on the current set of images
+* @code{CO_REDUCE}: CO_REDUCE, Reduction of values on the current set of images
+* @code{CO_SUM}: CO_SUM, Sum of values on the current set of images
+* @code{COMMAND_ARGUMENT_COUNT}: COMMAND_ARGUMENT_COUNT, Get number of command line arguments
+* @code{COMPILER_OPTIONS}: COMPILER_OPTIONS, Options passed to the compiler
+* @code{COMPILER_VERSION}: COMPILER_VERSION, Compiler version string
+* @code{COMPLEX}: COMPLEX, Complex conversion function
+* @code{CONJG}: CONJG, Complex conjugate function
+* @code{COS}: COS, Cosine function
+* @code{COSD}: COSD, Cosine function, degrees
+* @code{COSH}: COSH, Hyperbolic cosine function
+* @code{COTAN}: COTAN, Cotangent function
+* @code{COTAND}: COTAND, Cotangent function, degrees
+* @code{COUNT}: COUNT, Count occurrences of TRUE in an array
+* @code{CPU_TIME}: CPU_TIME, CPU time subroutine
+* @code{CSHIFT}: CSHIFT, Circular shift elements of an array
+* @code{CTIME}: CTIME, Subroutine (or function) to convert a time into a string
+* @code{DATE_AND_TIME}: DATE_AND_TIME, Date and time subroutine
+* @code{DBLE}: DBLE, Double precision conversion function
+* @code{DCMPLX}: DCMPLX, Double complex conversion function
+* @code{DIGITS}: DIGITS, Significant digits function
+* @code{DIM}: DIM, Positive difference
+* @code{DOT_PRODUCT}: DOT_PRODUCT, Dot product function
+* @code{DPROD}: DPROD, Double product function
+* @code{DREAL}: DREAL, Double real part function
+* @code{DSHIFTL}: DSHIFTL, Combined left shift
+* @code{DSHIFTR}: DSHIFTR, Combined right shift
+* @code{DTIME}: DTIME, Execution time subroutine (or function)
+* @code{EOSHIFT}: EOSHIFT, End-off shift elements of an array
+* @code{EPSILON}: EPSILON, Epsilon function
+* @code{ERF}: ERF, Error function
+* @code{ERFC}: ERFC, Complementary error function
+* @code{ERFC_SCALED}: ERFC_SCALED, Exponentially-scaled complementary error function
+* @code{ETIME}: ETIME, Execution time subroutine (or function)
+* @code{EVENT_QUERY}: EVENT_QUERY, Query whether a coarray event has occurred
+* @code{EXECUTE_COMMAND_LINE}: EXECUTE_COMMAND_LINE, Execute a shell command
+* @code{EXIT}: EXIT, Exit the program with status.
+* @code{EXP}: EXP, Exponential function
+* @code{EXPONENT}: EXPONENT, Exponent function
+* @code{EXTENDS_TYPE_OF}: EXTENDS_TYPE_OF, Query dynamic type for extension
+* @code{FDATE}: FDATE, Subroutine (or function) to get the current time as a string
+* @code{FGET}: FGET, Read a single character in stream mode from stdin
+* @code{FGETC}: FGETC, Read a single character in stream mode
+* @code{FINDLOC}: FINDLOC, Search an array for a value
+* @code{FLOOR}: FLOOR, Integer floor function
+* @code{FLUSH}: FLUSH, Flush I/O unit(s)
+* @code{FNUM}: FNUM, File number function
+* @code{FPUT}: FPUT, Write a single character in stream mode to stdout
+* @code{FPUTC}: FPUTC, Write a single character in stream mode
+* @code{FRACTION}: FRACTION, Fractional part of the model representation
+* @code{FREE}: FREE, Memory de-allocation subroutine
+* @code{FSEEK}: FSEEK, Low level file positioning subroutine
+* @code{FSTAT}: FSTAT, Get file status
+* @code{FTELL}: FTELL, Current stream position
+* @code{GAMMA}: GAMMA, Gamma function
+* @code{GERROR}: GERROR, Get last system error message
+* @code{GETARG}: GETARG, Get command line arguments
+* @code{GET_COMMAND}: GET_COMMAND, Get the entire command line
+* @code{GET_COMMAND_ARGUMENT}: GET_COMMAND_ARGUMENT, Get command line arguments
+* @code{GETCWD}: GETCWD, Get current working directory
+* @code{GETENV}: GETENV, Get an environmental variable
+* @code{GET_ENVIRONMENT_VARIABLE}: GET_ENVIRONMENT_VARIABLE, Get an environmental variable
+* @code{GETGID}: GETGID, Group ID function
+* @code{GETLOG}: GETLOG, Get login name
+* @code{GETPID}: GETPID, Process ID function
+* @code{GETUID}: GETUID, User ID function
+* @code{GMTIME}: GMTIME, Convert time to GMT info
+* @code{HOSTNM}: HOSTNM, Get system host name
+* @code{HUGE}: HUGE, Largest number of a kind
+* @code{HYPOT}: HYPOT, Euclidean distance function
+* @code{IACHAR}: IACHAR, Code in @acronym{ASCII} collating sequence
+* @code{IALL}: IALL, Bitwise AND of array elements
+* @code{IAND}: IAND, Bitwise logical and
+* @code{IANY}: IANY, Bitwise OR of array elements
+* @code{IARGC}: IARGC, Get the number of command line arguments
+* @code{IBCLR}: IBCLR, Clear bit
+* @code{IBITS}: IBITS, Bit extraction
+* @code{IBSET}: IBSET, Set bit
+* @code{ICHAR}: ICHAR, Character-to-integer conversion function
+* @code{IDATE}: IDATE, Current local time (day/month/year)
+* @code{IEOR}: IEOR, Bitwise logical exclusive or
+* @code{IERRNO}: IERRNO, Function to get the last system error number
+* @code{IMAGE_INDEX}: IMAGE_INDEX, Cosubscript to image index conversion
+* @code{INDEX}: INDEX intrinsic, Position of a substring within a string
+* @code{INT}: INT, Convert to integer type
+* @code{INT2}: INT2, Convert to 16-bit integer type
+* @code{INT8}: INT8, Convert to 64-bit integer type
+* @code{IOR}: IOR, Bitwise logical or
+* @code{IPARITY}: IPARITY, Bitwise XOR of array elements
+* @code{IRAND}: IRAND, Integer pseudo-random number
+* @code{IS_CONTIGUOUS}: IS_CONTIGUOUS, Test whether an array is contiguous
+* @code{IS_IOSTAT_END}: IS_IOSTAT_END, Test for end-of-file value
+* @code{IS_IOSTAT_EOR}: IS_IOSTAT_EOR, Test for end-of-record value
+* @code{ISATTY}: ISATTY, Whether a unit is a terminal device
+* @code{ISHFT}: ISHFT, Shift bits
+* @code{ISHFTC}: ISHFTC, Shift bits circularly
+* @code{ISNAN}: ISNAN, Tests for a NaN
+* @code{ITIME}: ITIME, Current local time (hour/minutes/seconds)
+* @code{KILL}: KILL, Send a signal to a process
+* @code{KIND}: KIND, Kind of an entity
+* @code{LBOUND}: LBOUND, Lower dimension bounds of an array
+* @code{LCOBOUND}: LCOBOUND, Lower codimension bounds of an array
+* @code{LEADZ}: LEADZ, Number of leading zero bits of an integer
+* @code{LEN}: LEN, Length of a character entity
+* @code{LEN_TRIM}: LEN_TRIM, Length of a character entity without trailing blank characters
+* @code{LGE}: LGE, Lexical greater than or equal
+* @code{LGT}: LGT, Lexical greater than
+* @code{LINK}: LINK, Create a hard link
+* @code{LLE}: LLE, Lexical less than or equal
+* @code{LLT}: LLT, Lexical less than
+* @code{LNBLNK}: LNBLNK, Index of the last non-blank character in a string
+* @code{LOC}: LOC, Returns the address of a variable
+* @code{LOG}: LOG, Logarithm function
+* @code{LOG10}: LOG10, Base 10 logarithm function
+* @code{LOG_GAMMA}: LOG_GAMMA, Logarithm of the Gamma function
+* @code{LOGICAL}: LOGICAL, Convert to logical type
+* @code{LSHIFT}: LSHIFT, Left shift bits
+* @code{LSTAT}: LSTAT, Get file status
+* @code{LTIME}: LTIME, Convert time to local time info
+* @code{MALLOC}: MALLOC, Dynamic memory allocation function
+* @code{MASKL}: MASKL, Left justified mask
+* @code{MASKR}: MASKR, Right justified mask
+* @code{MATMUL}: MATMUL, matrix multiplication
+* @code{MAX}: MAX, Maximum value of an argument list
+* @code{MAXEXPONENT}: MAXEXPONENT, Maximum exponent of a real kind
+* @code{MAXLOC}: MAXLOC, Location of the maximum value within an array
+* @code{MAXVAL}: MAXVAL, Maximum value of an array
+* @code{MCLOCK}: MCLOCK, Time function
+* @code{MCLOCK8}: MCLOCK8, Time function (64-bit)
+* @code{MERGE}: MERGE, Merge arrays
+* @code{MERGE_BITS}: MERGE_BITS, Merge of bits under mask
+* @code{MIN}: MIN, Minimum value of an argument list
+* @code{MINEXPONENT}: MINEXPONENT, Minimum exponent of a real kind
+* @code{MINLOC}: MINLOC, Location of the minimum value within an array
+* @code{MINVAL}: MINVAL, Minimum value of an array
+* @code{MOD}: MOD, Remainder function
+* @code{MODULO}: MODULO, Modulo function
+* @code{MOVE_ALLOC}: MOVE_ALLOC, Move allocation from one object to another
+* @code{MVBITS}: MVBITS, Move bits from one integer to another
+* @code{NEAREST}: NEAREST, Nearest representable number
+* @code{NEW_LINE}: NEW_LINE, New line character
+* @code{NINT}: NINT, Nearest whole number
+* @code{NORM2}: NORM2, Euclidean vector norm
+* @code{NOT}: NOT, Logical negation
+* @code{NULL}: NULL, Function that returns an disassociated pointer
+* @code{NUM_IMAGES}: NUM_IMAGES, Number of images
+* @code{OR}: OR, Bitwise logical OR
+* @code{PACK}: PACK, Pack an array into an array of rank one
+* @code{PARITY}: PARITY, Reduction with exclusive OR
+* @code{PERROR}: PERROR, Print system error message
+* @code{POPCNT}: POPCNT, Number of bits set
+* @code{POPPAR}: POPPAR, Parity of the number of bits set
+* @code{PRECISION}: PRECISION, Decimal precision of a real kind
+* @code{PRESENT}: PRESENT, Determine whether an optional dummy argument is specified
+* @code{PRODUCT}: PRODUCT, Product of array elements
+* @code{RADIX}: RADIX, Base of a data model
+* @code{RAN}: RAN, Real pseudo-random number
+* @code{RAND}: RAND, Real pseudo-random number
+* @code{RANDOM_INIT}: RANDOM_INIT, Initialize pseudo-random number generator
+* @code{RANDOM_NUMBER}: RANDOM_NUMBER, Pseudo-random number
+* @code{RANDOM_SEED}: RANDOM_SEED, Initialize a pseudo-random number sequence
+* @code{RANGE}: RANGE, Decimal exponent range
+* @code{RANK} : RANK, Rank of a data object
+* @code{REAL}: REAL, Convert to real type
+* @code{RENAME}: RENAME, Rename a file
+* @code{REPEAT}: REPEAT, Repeated string concatenation
+* @code{RESHAPE}: RESHAPE, Function to reshape an array
+* @code{RRSPACING}: RRSPACING, Reciprocal of the relative spacing
+* @code{RSHIFT}: RSHIFT, Right shift bits
+* @code{SAME_TYPE_AS}: SAME_TYPE_AS, Query dynamic types for equality
+* @code{SCALE}: SCALE, Scale a real value
+* @code{SCAN}: SCAN, Scan a string for the presence of a set of characters
+* @code{SECNDS}: SECNDS, Time function
+* @code{SECOND}: SECOND, CPU time function
+* @code{SELECTED_CHAR_KIND}: SELECTED_CHAR_KIND, Choose character kind
+* @code{SELECTED_INT_KIND}: SELECTED_INT_KIND, Choose integer kind
+* @code{SELECTED_REAL_KIND}: SELECTED_REAL_KIND, Choose real kind
+* @code{SET_EXPONENT}: SET_EXPONENT, Set the exponent of the model
+* @code{SHAPE}: SHAPE, Determine the shape of an array
+* @code{SHIFTA}: SHIFTA, Right shift with fill
+* @code{SHIFTL}: SHIFTL, Left shift
+* @code{SHIFTR}: SHIFTR, Right shift
+* @code{SIGN}: SIGN, Sign copying function
+* @code{SIGNAL}: SIGNAL, Signal handling subroutine (or function)
+* @code{SIN}: SIN, Sine function
+* @code{SIND}: SIND, Sine function, degrees
+* @code{SINH}: SINH, Hyperbolic sine function
+* @code{SIZE}: SIZE, Function to determine the size of an array
+* @code{SIZEOF}: SIZEOF, Determine the size in bytes of an expression
+* @code{SLEEP}: SLEEP, Sleep for the specified number of seconds
+* @code{SPACING}: SPACING, Smallest distance between two numbers of a given type
+* @code{SPREAD}: SPREAD, Add a dimension to an array
+* @code{SQRT}: SQRT, Square-root function
+* @code{SRAND}: SRAND, Reinitialize the random number generator
+* @code{STAT}: STAT, Get file status
+* @code{STORAGE_SIZE}: STORAGE_SIZE, Storage size in bits
+* @code{SUM}: SUM, Sum of array elements
+* @code{SYMLNK}: SYMLNK, Create a symbolic link
+* @code{SYSTEM}: SYSTEM, Execute a shell command
+* @code{SYSTEM_CLOCK}: SYSTEM_CLOCK, Time function
+* @code{TAN}: TAN, Tangent function
+* @code{TAND}: TAND, Tangent function, degrees
+* @code{TANH}: TANH, Hyperbolic tangent function
+* @code{THIS_IMAGE}: THIS_IMAGE, Cosubscript index of this image
+* @code{TIME}: TIME, Time function
+* @code{TIME8}: TIME8, Time function (64-bit)
+* @code{TINY}: TINY, Smallest positive number of a real kind
+* @code{TRAILZ}: TRAILZ, Number of trailing zero bits of an integer
+* @code{TRANSFER}: TRANSFER, Transfer bit patterns
+* @code{TRANSPOSE}: TRANSPOSE, Transpose an array of rank two
+* @code{TRIM}: TRIM, Remove trailing blank characters of a string
+* @code{TTYNAM}: TTYNAM, Get the name of a terminal device
+* @code{UBOUND}: UBOUND, Upper dimension bounds of an array
+* @code{UCOBOUND}: UCOBOUND, Upper codimension bounds of an array
+* @code{UMASK}: UMASK, Set the file creation mask
+* @code{UNLINK}: UNLINK, Remove a file from the file system
+* @code{UNPACK}: UNPACK, Unpack an array of rank one into an array
+* @code{VERIFY}: VERIFY, Scan a string for the absence of a set of characters
+* @code{XOR}: XOR, Bitwise logical exclusive or
+@end menu
+
+@node Introduction to Intrinsics
+@section Introduction to intrinsic procedures
+
+The intrinsic procedures provided by GNU Fortran include procedures required
+by the Fortran 95 and later supported standards, and a set of intrinsic
+procedures for backwards compatibility with G77. Any conflict between
+a description here and a description in the Fortran standards is
+unintentional, and the standard(s) should be considered authoritative.
+
+The enumeration of the @code{KIND} type parameter is processor defined in
+the Fortran 95 standard. GNU Fortran defines the default integer type and
+default real type by @code{INTEGER(KIND=4)} and @code{REAL(KIND=4)},
+respectively. The standard mandates that both data types shall have
+another kind, which have more precision. On typical target architectures
+supported by @command{gfortran}, this kind type parameter is @code{KIND=8}.
+Hence, @code{REAL(KIND=8)} and @code{DOUBLE PRECISION} are equivalent.
+In the description of generic intrinsic procedures, the kind type parameter
+will be specified by @code{KIND=*}, and in the description of specific
+names for an intrinsic procedure the kind type parameter will be explicitly
+given (e.g., @code{REAL(KIND=4)} or @code{REAL(KIND=8)}). Finally, for
+brevity the optional @code{KIND=} syntax will be omitted.
+
+Many of the intrinsic procedures take one or more optional arguments.
+This document follows the convention used in the Fortran 95 standard,
+and denotes such arguments by square brackets.
+
+GNU Fortran offers the @option{-std=} command-line option,
+which can be used to restrict the set of intrinsic procedures to a
+given standard. By default, @command{gfortran} sets the @option{-std=gnu}
+option, and so all intrinsic procedures described here are accepted. There
+is one caveat. For a select group of intrinsic procedures, @command{g77}
+implemented both a function and a subroutine. Both classes
+have been implemented in @command{gfortran} for backwards compatibility
+with @command{g77}. It is noted here that these functions and subroutines
+cannot be intermixed in a given subprogram. In the descriptions that follow,
+the applicable standard for each intrinsic procedure is noted.
+
+
+
+@node ABORT
+@section @code{ABORT} --- Abort the program
+@fnindex ABORT
+@cindex program termination, with core dump
+@cindex terminate program, with core dump
+@cindex core, dump
+
+@table @asis
+@item @emph{Description}:
+@code{ABORT} causes immediate termination of the program. On operating
+systems that support a core dump, @code{ABORT} will produce a core dump.
+It will also print a backtrace, unless @code{-fno-backtrace} is given.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL ABORT}
+
+@item @emph{Return value}:
+Does not return.
+
+@item @emph{Example}:
+@smallexample
+program test_abort
+ integer :: i = 1, j = 2
+ if (i /= j) call abort
+end program test_abort
+@end smallexample
+
+@item @emph{See also}:
+@ref{EXIT}, @gol
+@ref{KILL}, @gol
+@ref{BACKTRACE}
+@end table
+
+
+
+@node ABS
+@section @code{ABS} --- Absolute value
+@fnindex ABS
+@fnindex CABS
+@fnindex DABS
+@fnindex IABS
+@fnindex ZABS
+@fnindex CDABS
+@fnindex BABS
+@fnindex IIABS
+@fnindex JIABS
+@fnindex KIABS
+@cindex absolute value
+
+@table @asis
+@item @emph{Description}:
+@code{ABS(A)} computes the absolute value of @code{A}.
+
+@item @emph{Standard}:
+Fortran 77 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ABS(A)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab The type of the argument shall be an @code{INTEGER},
+@code{REAL}, or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and
+kind as the argument except the return value is @code{REAL} for a
+@code{COMPLEX} argument.
+
+@item @emph{Example}:
+@smallexample
+program test_abs
+ integer :: i = -1
+ real :: x = -1.e0
+ complex :: z = (-1.e0,0.e0)
+ i = abs(i)
+ x = abs(x)
+ x = abs(z)
+end program test_abs
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ABS(A)} @tab @code{REAL(4) A} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{CABS(A)} @tab @code{COMPLEX(4) A} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DABS(A)} @tab @code{REAL(8) A} @tab @code{REAL(8)} @tab Fortran 77 and later
+@item @code{IABS(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab Fortran 77 and later
+@item @code{BABS(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IIABS(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JIABS(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KIABS(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@item @code{ZABS(A)} @tab @code{COMPLEX(8) A} @tab @code{REAL(8)} @tab GNU extension
+@item @code{CDABS(A)} @tab @code{COMPLEX(8) A} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node ACCESS
+@section @code{ACCESS} --- Checks file access modes
+@fnindex ACCESS
+@cindex file system, access mode
+
+@table @asis
+@item @emph{Description}:
+@code{ACCESS(NAME, MODE)} checks whether the file @var{NAME}
+exists, is readable, writable or executable. Except for the
+executable check, @code{ACCESS} can be replaced by
+Fortran 95's @code{INQUIRE}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = ACCESS(NAME, MODE)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NAME} @tab Scalar @code{CHARACTER} of default kind with the
+file name. Trailing blank are ignored unless the character @code{achar(0)}
+is present, then all characters up to and excluding @code{achar(0)} are
+used as file name.
+@item @var{MODE} @tab Scalar @code{CHARACTER} of default kind with the
+file access mode, may be any concatenation of @code{"r"} (readable),
+@code{"w"} (writable) and @code{"x"} (executable), or @code{" "} to check
+for existence.
+@end multitable
+
+@item @emph{Return value}:
+Returns a scalar @code{INTEGER}, which is @code{0} if the file is
+accessible in the given mode; otherwise or if an invalid argument
+has been given for @code{MODE} the value @code{1} is returned.
+
+@item @emph{Example}:
+@smallexample
+program access_test
+ implicit none
+ character(len=*), parameter :: file = 'test.dat'
+ character(len=*), parameter :: file2 = 'test.dat '//achar(0)
+ if(access(file,' ') == 0) print *, trim(file),' is exists'
+ if(access(file,'r') == 0) print *, trim(file),' is readable'
+ if(access(file,'w') == 0) print *, trim(file),' is writable'
+ if(access(file,'x') == 0) print *, trim(file),' is executable'
+ if(access(file2,'rwx') == 0) &
+ print *, trim(file2),' is readable, writable and executable'
+end program access_test
+@end smallexample
+@end table
+
+
+
+@node ACHAR
+@section @code{ACHAR} --- Character in @acronym{ASCII} collating sequence
+@fnindex ACHAR
+@cindex @acronym{ASCII} collating sequence
+@cindex collating sequence, @acronym{ASCII}
+
+@table @asis
+@item @emph{Description}:
+@code{ACHAR(I)} returns the character located at position @code{I}
+in the @acronym{ASCII} collating sequence.
+
+@item @emph{Standard}:
+Fortran 77 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ACHAR(I [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{CHARACTER} with a length of one.
+If the @var{KIND} argument is present, the return value is of the
+specified kind and of the default kind otherwise.
+
+@item @emph{Example}:
+@smallexample
+program test_achar
+ character c
+ c = achar(32)
+end program test_achar
+@end smallexample
+
+@item @emph{Note}:
+See @ref{ICHAR} for a discussion of converting between numerical values
+and formatted string representations.
+
+@item @emph{See also}:
+@ref{CHAR}, @gol
+@ref{IACHAR}, @gol
+@ref{ICHAR}
+@end table
+
+
+
+@node ACOS
+@section @code{ACOS} --- Arccosine function
+@fnindex ACOS
+@fnindex DACOS
+@cindex trigonometric function, cosine, inverse
+@cindex cosine, inverse
+
+@table @asis
+@item @emph{Description}:
+@code{ACOS(X)} computes the arccosine of @var{X} (inverse of @code{COS(X)}).
+
+@item @emph{Standard}:
+Fortran 77 and later, for a complex argument Fortran 2008 or later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ACOS(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall either be @code{REAL} with a magnitude that is
+less than or equal to one - or the type shall be @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+The real part of the result is in radians and lies in the range
+@math{0 \leq \Re \acos(x) \leq \pi}.
+
+@item @emph{Example}:
+@smallexample
+program test_acos
+ real(8) :: x = 0.866_8
+ x = acos(x)
+end program test_acos
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ACOS(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DACOS(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{COS} @gol
+Degrees function: @gol
+@ref{ACOSD}
+@end table
+
+
+
+@node ACOSD
+@section @code{ACOSD} --- Arccosine function, degrees
+@fnindex ACOSD
+@fnindex DACOSD
+@cindex trigonometric function, cosine, inverse, degrees
+@cindex cosine, inverse, degrees
+
+@table @asis
+@item @emph{Description}:
+@code{ACOSD(X)} computes the arccosine of @var{X} in degrees (inverse of
+@code{COSD(X)}).
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ACOSD(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall either be @code{REAL} with a magnitude that is
+less than or equal to one - or the type shall be @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+The real part of the result is in degrees and lies in the range
+@math{0 \leq \Re \acos(x) \leq 180}.
+
+@item @emph{Example}:
+@smallexample
+program test_acosd
+ real(8) :: x = 0.866_8
+ x = acosd(x)
+end program test_acosd
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ACOSD(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DACOSD(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{COSD} @gol
+Radians function: @gol
+@ref{ACOS} @gol
+@end table
+
+
+
+@node ACOSH
+@section @code{ACOSH} --- Inverse hyperbolic cosine function
+@fnindex ACOSH
+@fnindex DACOSH
+@cindex area hyperbolic cosine
+@cindex inverse hyperbolic cosine
+@cindex hyperbolic function, cosine, inverse
+@cindex cosine, hyperbolic, inverse
+
+@table @asis
+@item @emph{Description}:
+@code{ACOSH(X)} computes the inverse hyperbolic cosine of @var{X}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ACOSH(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has the same type and kind as @var{X}. If @var{X} is
+complex, the imaginary part of the result is in radians and lies between
+@math{ 0 \leq \Im \acosh(x) \leq \pi}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_acosh
+ REAL(8), DIMENSION(3) :: x = (/ 1.0, 2.0, 3.0 /)
+ WRITE (*,*) ACOSH(x)
+END PROGRAM
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DACOSH(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{COSH}
+@end table
+
+
+
+@node ADJUSTL
+@section @code{ADJUSTL} --- Left adjust a string
+@fnindex ADJUSTL
+@cindex string, adjust left
+@cindex adjust string
+
+@table @asis
+@item @emph{Description}:
+@code{ADJUSTL(STRING)} will left adjust a string by removing leading spaces.
+Spaces are inserted at the end of the string as needed.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ADJUSTL(STRING)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab The type shall be @code{CHARACTER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{CHARACTER} and of the same kind as
+@var{STRING} where leading spaces are removed and the same number of
+spaces are inserted on the end of @var{STRING}.
+
+@item @emph{Example}:
+@smallexample
+program test_adjustl
+ character(len=20) :: str = ' gfortran'
+ str = adjustl(str)
+ print *, str
+end program test_adjustl
+@end smallexample
+
+@item @emph{See also}:
+@ref{ADJUSTR}, @gol
+@ref{TRIM}
+@end table
+
+
+
+@node ADJUSTR
+@section @code{ADJUSTR} --- Right adjust a string
+@fnindex ADJUSTR
+@cindex string, adjust right
+@cindex adjust string
+
+@table @asis
+@item @emph{Description}:
+@code{ADJUSTR(STRING)} will right adjust a string by removing trailing spaces.
+Spaces are inserted at the start of the string as needed.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ADJUSTR(STRING)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STR} @tab The type shall be @code{CHARACTER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{CHARACTER} and of the same kind as
+@var{STRING} where trailing spaces are removed and the same number of
+spaces are inserted at the start of @var{STRING}.
+
+@item @emph{Example}:
+@smallexample
+program test_adjustr
+ character(len=20) :: str = 'gfortran'
+ str = adjustr(str)
+ print *, str
+end program test_adjustr
+@end smallexample
+
+@item @emph{See also}:
+@ref{ADJUSTL}, @gol
+@ref{TRIM}
+@end table
+
+
+
+@node AIMAG
+@section @code{AIMAG} --- Imaginary part of complex number
+@fnindex AIMAG
+@fnindex DIMAG
+@fnindex IMAG
+@fnindex IMAGPART
+@cindex complex numbers, imaginary part
+
+@table @asis
+@item @emph{Description}:
+@code{AIMAG(Z)} yields the imaginary part of complex argument @code{Z}.
+The @code{IMAG(Z)} and @code{IMAGPART(Z)} intrinsic functions are provided
+for compatibility with @command{g77}, and their use in new code is
+strongly discouraged.
+
+@item @emph{Standard}:
+Fortran 77 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = AIMAG(Z)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{Z} @tab The type of the argument shall be @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} with the
+kind type parameter of the argument.
+
+@item @emph{Example}:
+@smallexample
+program test_aimag
+ complex(4) z4
+ complex(8) z8
+ z4 = cmplx(1.e0_4, 0.e0_4)
+ z8 = cmplx(0.e0_8, 1.e0_8)
+ print *, aimag(z4), dimag(z8)
+end program test_aimag
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{AIMAG(Z)} @tab @code{COMPLEX Z} @tab @code{REAL} @tab Fortran 77 and later
+@item @code{DIMAG(Z)} @tab @code{COMPLEX(8) Z} @tab @code{REAL(8)} @tab GNU extension
+@item @code{IMAG(Z)} @tab @code{COMPLEX Z} @tab @code{REAL} @tab GNU extension
+@item @code{IMAGPART(Z)} @tab @code{COMPLEX Z} @tab @code{REAL} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node AINT
+@section @code{AINT} --- Truncate to a whole number
+@fnindex AINT
+@fnindex DINT
+@cindex floor
+@cindex rounding, floor
+
+@table @asis
+@item @emph{Description}:
+@code{AINT(A [, KIND])} truncates its argument to a whole number.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = AINT(A [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab The type of the argument shall be @code{REAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} with the kind type parameter of the
+argument if the optional @var{KIND} is absent; otherwise, the kind
+type parameter will be given by @var{KIND}. If the magnitude of
+@var{X} is less than one, @code{AINT(X)} returns zero. If the
+magnitude is equal to or greater than one then it returns the largest
+whole number that does not exceed its magnitude. The sign is the same
+as the sign of @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_aint
+ real(4) x4
+ real(8) x8
+ x4 = 1.234E0_4
+ x8 = 4.321_8
+ print *, aint(x4), dint(x8)
+ x8 = aint(x4,8)
+end program test_aint
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{AINT(A)} @tab @code{REAL(4) A} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DINT(A)} @tab @code{REAL(8) A} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+@end table
+
+
+
+@node ALARM
+@section @code{ALARM} --- Execute a routine after a given delay
+@fnindex ALARM
+@cindex delayed execution
+
+@table @asis
+@item @emph{Description}:
+@code{ALARM(SECONDS, HANDLER [, STATUS])} causes external subroutine @var{HANDLER}
+to be executed after a delay of @var{SECONDS} by using @code{alarm(2)} to
+set up a signal and @code{signal(2)} to catch it. If @var{STATUS} is
+supplied, it will be returned with the number of seconds remaining until
+any previously scheduled alarm was due to be delivered, or zero if there
+was no previously scheduled alarm.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL ALARM(SECONDS, HANDLER [, STATUS])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SECONDS} @tab The type of the argument shall be a scalar
+@code{INTEGER}. It is @code{INTENT(IN)}.
+@item @var{HANDLER} @tab Signal handler (@code{INTEGER FUNCTION} or
+@code{SUBROUTINE}) or dummy/global @code{INTEGER} scalar. The scalar
+values may be either @code{SIG_IGN=1} to ignore the alarm generated
+or @code{SIG_DFL=0} to set the default action. It is @code{INTENT(IN)}.
+@item @var{STATUS} @tab (Optional) @var{STATUS} shall be a scalar
+variable of the default @code{INTEGER} kind. It is @code{INTENT(OUT)}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test_alarm
+ external handler_print
+ integer i
+ call alarm (3, handler_print, i)
+ print *, i
+ call sleep(10)
+end program test_alarm
+@end smallexample
+This will cause the external routine @var{handler_print} to be called
+after 3 seconds.
+@end table
+
+
+
+@node ALL
+@section @code{ALL} --- All values in @var{MASK} along @var{DIM} are true
+@fnindex ALL
+@cindex array, apply condition
+@cindex array, condition testing
+
+@table @asis
+@item @emph{Description}:
+@code{ALL(MASK [, DIM])} determines if all the values are true in @var{MASK}
+in the array along dimension @var{DIM}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = ALL(MASK [, DIM])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{MASK} @tab The type of the argument shall be @code{LOGICAL} and
+it shall not be scalar.
+@item @var{DIM} @tab (Optional) @var{DIM} shall be a scalar integer
+with a value that lies between one and the rank of @var{MASK}.
+@end multitable
+
+@item @emph{Return value}:
+@code{ALL(MASK)} returns a scalar value of type @code{LOGICAL} where
+the kind type parameter is the same as the kind type parameter of
+@var{MASK}. If @var{DIM} is present, then @code{ALL(MASK, DIM)} returns
+an array with the rank of @var{MASK} minus 1. The shape is determined from
+the shape of @var{MASK} where the @var{DIM} dimension is elided.
+
+@table @asis
+@item (A)
+@code{ALL(MASK)} is true if all elements of @var{MASK} are true.
+It also is true if @var{MASK} has zero size; otherwise, it is false.
+@item (B)
+If the rank of @var{MASK} is one, then @code{ALL(MASK,DIM)} is equivalent
+to @code{ALL(MASK)}. If the rank is greater than one, then @code{ALL(MASK,DIM)}
+is determined by applying @code{ALL} to the array sections.
+@end table
+
+@item @emph{Example}:
+@smallexample
+program test_all
+ logical l
+ l = all((/.true., .true., .true./))
+ print *, l
+ call section
+ contains
+ subroutine section
+ integer a(2,3), b(2,3)
+ a = 1
+ b = 1
+ b(2,2) = 2
+ print *, all(a .eq. b, 1)
+ print *, all(a .eq. b, 2)
+ end subroutine section
+end program test_all
+@end smallexample
+@end table
+
+
+
+@node ALLOCATED
+@section @code{ALLOCATED} --- Status of an allocatable entity
+@fnindex ALLOCATED
+@cindex allocation, status
+
+@table @asis
+@item @emph{Description}:
+@code{ALLOCATED(ARRAY)} and @code{ALLOCATED(SCALAR)} check the allocation
+status of @var{ARRAY} and @var{SCALAR}, respectively.
+
+@item @emph{Standard}:
+Fortran 90 and later. Note, the @code{SCALAR=} keyword and allocatable
+scalar entities are available in Fortran 2003 and later.
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = ALLOCATED(ARRAY)}
+@item @code{RESULT = ALLOCATED(SCALAR)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab The argument shall be an @code{ALLOCATABLE} array.
+@item @var{SCALAR} @tab The argument shall be an @code{ALLOCATABLE} scalar.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a scalar @code{LOGICAL} with the default logical
+kind type parameter. If the argument is allocated, then the result is
+@code{.TRUE.}; otherwise, it returns @code{.FALSE.}
+
+@item @emph{Example}:
+@smallexample
+program test_allocated
+ integer :: i = 4
+ real(4), allocatable :: x(:)
+ if (.not. allocated(x)) allocate(x(i))
+end program test_allocated
+@end smallexample
+@end table
+
+
+
+@node AND
+@section @code{AND} --- Bitwise logical AND
+@fnindex AND
+@cindex bitwise logical and
+@cindex logical and, bitwise
+
+@table @asis
+@item @emph{Description}:
+Bitwise logical @code{AND}.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. For integer arguments, programmers should consider
+the use of the @ref{IAND} intrinsic defined by the Fortran standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = AND(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be either a scalar @code{INTEGER}
+type or a scalar @code{LOGICAL} type or a boz-literal-constant.
+@item @var{J} @tab The type shall be the same as the type of @var{I} or
+a boz-literal-constant. @var{I} and @var{J} shall not both be
+boz-literal-constants. If either @var{I} or @var{J} is a
+boz-literal-constant, then the other argument must be a scalar @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return type is either a scalar @code{INTEGER} or a scalar
+@code{LOGICAL}. If the kind type parameters differ, then the
+smaller kind type is implicitly converted to larger kind, and the
+return has the larger kind. A boz-literal-constant is
+converted to an @code{INTEGER} with the kind type parameter of
+the other argument as-if a call to @ref{INT} occurred.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_and
+ LOGICAL :: T = .TRUE., F = .FALSE.
+ INTEGER :: a, b
+ DATA a / Z'F' /, b / Z'3' /
+
+ WRITE (*,*) AND(T, T), AND(T, F), AND(F, T), AND(F, F)
+ WRITE (*,*) AND(a, b)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+Fortran 95 elemental function: @gol
+@ref{IAND}
+@end table
+
+
+
+@node ANINT
+@section @code{ANINT} --- Nearest whole number
+@fnindex ANINT
+@fnindex DNINT
+@cindex ceiling
+@cindex rounding, ceiling
+
+@table @asis
+@item @emph{Description}:
+@code{ANINT(A [, KIND])} rounds its argument to the nearest whole number.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ANINT(A [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab The type of the argument shall be @code{REAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type real with the kind type parameter of the
+argument if the optional @var{KIND} is absent; otherwise, the kind
+type parameter will be given by @var{KIND}. If @var{A} is greater than
+zero, @code{ANINT(A)} returns @code{AINT(X+0.5)}. If @var{A} is
+less than or equal to zero then it returns @code{AINT(X-0.5)}.
+
+@item @emph{Example}:
+@smallexample
+program test_anint
+ real(4) x4
+ real(8) x8
+ x4 = 1.234E0_4
+ x8 = 4.321_8
+ print *, anint(x4), dnint(x8)
+ x8 = anint(x4,8)
+end program test_anint
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ANINT(A)} @tab @code{REAL(4) A} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DNINT(A)} @tab @code{REAL(8) A} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+@end table
+
+
+
+@node ANY
+@section @code{ANY} --- Any value in @var{MASK} along @var{DIM} is true
+@fnindex ANY
+@cindex array, apply condition
+@cindex array, condition testing
+
+@table @asis
+@item @emph{Description}:
+@code{ANY(MASK [, DIM])} determines if any of the values in the logical array
+@var{MASK} along dimension @var{DIM} are @code{.TRUE.}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = ANY(MASK [, DIM])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{MASK} @tab The type of the argument shall be @code{LOGICAL} and
+it shall not be scalar.
+@item @var{DIM} @tab (Optional) @var{DIM} shall be a scalar integer
+with a value that lies between one and the rank of @var{MASK}.
+@end multitable
+
+@item @emph{Return value}:
+@code{ANY(MASK)} returns a scalar value of type @code{LOGICAL} where
+the kind type parameter is the same as the kind type parameter of
+@var{MASK}. If @var{DIM} is present, then @code{ANY(MASK, DIM)} returns
+an array with the rank of @var{MASK} minus 1. The shape is determined from
+the shape of @var{MASK} where the @var{DIM} dimension is elided.
+
+@table @asis
+@item (A)
+@code{ANY(MASK)} is true if any element of @var{MASK} is true;
+otherwise, it is false. It also is false if @var{MASK} has zero size.
+@item (B)
+If the rank of @var{MASK} is one, then @code{ANY(MASK,DIM)} is equivalent
+to @code{ANY(MASK)}. If the rank is greater than one, then @code{ANY(MASK,DIM)}
+is determined by applying @code{ANY} to the array sections.
+@end table
+
+@item @emph{Example}:
+@smallexample
+program test_any
+ logical l
+ l = any((/.true., .true., .true./))
+ print *, l
+ call section
+ contains
+ subroutine section
+ integer a(2,3), b(2,3)
+ a = 1
+ b = 1
+ b(2,2) = 2
+ print *, any(a .eq. b, 1)
+ print *, any(a .eq. b, 2)
+ end subroutine section
+end program test_any
+@end smallexample
+@end table
+
+
+
+@node ASIN
+@section @code{ASIN} --- Arcsine function
+@fnindex ASIN
+@fnindex DASIN
+@cindex trigonometric function, sine, inverse
+@cindex sine, inverse
+
+@table @asis
+@item @emph{Description}:
+@code{ASIN(X)} computes the arcsine of its @var{X} (inverse of @code{SIN(X)}).
+
+@item @emph{Standard}:
+Fortran 77 and later, for a complex argument Fortran 2008 or later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ASIN(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be either @code{REAL} and a magnitude that is
+less than or equal to one - or be @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+The real part of the result is in radians and lies in the range
+@math{-\pi/2 \leq \Re \asin(x) \leq \pi/2}.
+
+@item @emph{Example}:
+@smallexample
+program test_asin
+ real(8) :: x = 0.866_8
+ x = asin(x)
+end program test_asin
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ASIN(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DASIN(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{SIN} @gol
+Degrees function: @gol
+@ref{ASIND}
+@end table
+
+
+
+@node ASIND
+@section @code{ASIND} --- Arcsine function, degrees
+@fnindex ASIND
+@fnindex DASIND
+@cindex trigonometric function, sine, inverse, degrees
+@cindex sine, inverse, degrees
+
+@table @asis
+@item @emph{Description}:
+@code{ASIND(X)} computes the arcsine of its @var{X} in degrees (inverse of
+@code{SIND(X)}).
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ASIND(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be either @code{REAL} and a magnitude that is
+less than or equal to one - or be @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+The real part of the result is in degrees and lies in the range
+@math{-90 \leq \Re \asin(x) \leq 90}.
+
+@item @emph{Example}:
+@smallexample
+program test_asind
+ real(8) :: x = 0.866_8
+ x = asind(x)
+end program test_asind
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ASIND(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DASIND(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{SIND} @gol
+Radians function: @gol
+@ref{ASIN}
+@end table
+
+
+
+@node ASINH
+@section @code{ASINH} --- Inverse hyperbolic sine function
+@fnindex ASINH
+@fnindex DASINH
+@cindex area hyperbolic sine
+@cindex inverse hyperbolic sine
+@cindex hyperbolic function, sine, inverse
+@cindex sine, hyperbolic, inverse
+
+@table @asis
+@item @emph{Description}:
+@code{ASINH(X)} computes the inverse hyperbolic sine of @var{X}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ASINH(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}. If @var{X} is
+complex, the imaginary part of the result is in radians and lies between
+@math{-\pi/2 \leq \Im \asinh(x) \leq \pi/2}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_asinh
+ REAL(8), DIMENSION(3) :: x = (/ -1.0, 0.0, 1.0 /)
+ WRITE (*,*) ASINH(x)
+END PROGRAM
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DASINH(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension.
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{SINH}
+@end table
+
+
+
+@node ASSOCIATED
+@section @code{ASSOCIATED} --- Status of a pointer or pointer/target pair
+@fnindex ASSOCIATED
+@cindex pointer, status
+@cindex association status
+
+@table @asis
+@item @emph{Description}:
+@code{ASSOCIATED(POINTER [, TARGET])} determines the status of the pointer
+@var{POINTER} or if @var{POINTER} is associated with the target @var{TARGET}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = ASSOCIATED(POINTER [, TARGET])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{POINTER} @tab @var{POINTER} shall have the @code{POINTER} attribute
+and it can be of any type.
+@item @var{TARGET} @tab (Optional) @var{TARGET} shall be a pointer or
+a target. It must have the same type, kind type parameter, and
+array rank as @var{POINTER}.
+@end multitable
+The association status of neither @var{POINTER} nor @var{TARGET} shall be
+undefined.
+
+@item @emph{Return value}:
+@code{ASSOCIATED(POINTER)} returns a scalar value of type @code{LOGICAL(4)}.
+There are several cases:
+@table @asis
+@item (A) When the optional @var{TARGET} is not present then
+@code{ASSOCIATED(POINTER)} is true if @var{POINTER} is associated with a target; otherwise, it returns false.
+@item (B) If @var{TARGET} is present and a scalar target, the result is true if
+@var{TARGET} is not a zero-sized storage sequence and the target associated with @var{POINTER} occupies the same storage units. If @var{POINTER} is
+disassociated, the result is false.
+@item (C) If @var{TARGET} is present and an array target, the result is true if
+@var{TARGET} and @var{POINTER} have the same shape, are not zero-sized arrays,
+are arrays whose elements are not zero-sized storage sequences, and
+@var{TARGET} and @var{POINTER} occupy the same storage units in array element
+order.
+As in case(B), the result is false, if @var{POINTER} is disassociated.
+@item (D) If @var{TARGET} is present and an scalar pointer, the result is true
+if @var{TARGET} is associated with @var{POINTER}, the target associated with
+@var{TARGET} are not zero-sized storage sequences and occupy the same storage
+units.
+The result is false, if either @var{TARGET} or @var{POINTER} is disassociated.
+@item (E) If @var{TARGET} is present and an array pointer, the result is true if
+target associated with @var{POINTER} and the target associated with @var{TARGET}
+have the same shape, are not zero-sized arrays, are arrays whose elements are
+not zero-sized storage sequences, and @var{TARGET} and @var{POINTER} occupy
+the same storage units in array element order.
+The result is false, if either @var{TARGET} or @var{POINTER} is disassociated.
+@end table
+
+@item @emph{Example}:
+@smallexample
+program test_associated
+ implicit none
+ real, target :: tgt(2) = (/1., 2./)
+ real, pointer :: ptr(:)
+ ptr => tgt
+ if (associated(ptr) .eqv. .false.) call abort
+ if (associated(ptr,tgt) .eqv. .false.) call abort
+end program test_associated
+@end smallexample
+
+@item @emph{See also}:
+@ref{NULL}
+@end table
+
+
+
+@node ATAN
+@section @code{ATAN} --- Arctangent function
+@fnindex ATAN
+@fnindex DATAN
+@cindex trigonometric function, tangent, inverse
+@cindex tangent, inverse
+
+@table @asis
+@item @emph{Description}:
+@code{ATAN(X)} computes the arctangent of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later, for a complex argument and for two arguments
+Fortran 2008 or later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = ATAN(X)}
+@item @code{RESULT = ATAN(Y, X)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX};
+if @var{Y} is present, @var{X} shall be REAL.
+@item @var{Y} @tab The type and kind type parameter shall be the same as @var{X}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+If @var{Y} is present, the result is identical to @code{ATAN2(Y,X)}.
+Otherwise, it the arcus tangent of @var{X}, where the real part of
+the result is in radians and lies in the range
+@math{-\pi/2 \leq \Re \atan(x) \leq \pi/2}.
+
+@item @emph{Example}:
+@smallexample
+program test_atan
+ real(8) :: x = 2.866_8
+ x = atan(x)
+end program test_atan
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ATAN(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DATAN(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{TAN} @gol
+Degrees function: @gol
+@ref{ATAND}
+@end table
+
+
+
+@node ATAND
+@section @code{ATAND} --- Arctangent function, degrees
+@fnindex ATAND
+@fnindex DATAND
+@cindex trigonometric function, tangent, inverse, degrees
+@cindex tangent, inverse, degrees
+
+@table @asis
+@item @emph{Description}:
+@code{ATAND(X)} computes the arctangent of @var{X} in degrees (inverse of
+@ref{TAND}).
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = ATAND(X)}
+@item @code{RESULT = ATAND(Y, X)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX};
+if @var{Y} is present, @var{X} shall be REAL.
+@item @var{Y} @tab The type and kind type parameter shall be the same as @var{X}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+If @var{Y} is present, the result is identical to @code{ATAND2(Y,X)}.
+Otherwise, it is the arcus tangent of @var{X}, where the real part of
+the result is in degrees and lies in the range
+@math{-90 \leq \Re \atand(x) \leq 90}.
+
+@item @emph{Example}:
+@smallexample
+program test_atand
+ real(8) :: x = 2.866_8
+ x = atand(x)
+end program test_atand
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .23 .23 .20 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ATAND(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DATAND(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{TAND} @gol
+Radians function: @gol
+@ref{ATAN}
+@end table
+
+
+
+@node ATAN2
+@section @code{ATAN2} --- Arctangent function
+@fnindex ATAN2
+@fnindex DATAN2
+@cindex trigonometric function, tangent, inverse
+@cindex tangent, inverse
+
+@table @asis
+@item @emph{Description}:
+@code{ATAN2(Y, X)} computes the principal value of the argument
+function of the complex number @math{X + i Y}. This function can
+be used to transform from Cartesian into polar coordinates and
+allows to determine the angle in the correct quadrant.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ATAN2(Y, X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{Y} @tab The type shall be @code{REAL}.
+@item @var{X} @tab The type and kind type parameter shall be the same as @var{Y}.
+If @var{Y} is zero, then @var{X} must be nonzero.
+@end multitable
+
+@item @emph{Return value}:
+The return value has the same type and kind type parameter as @var{Y}. It
+is the principal value of the complex number @math{X + i Y}. If @var{X}
+is nonzero, then it lies in the range @math{-\pi \le \atan (x) \leq \pi}.
+The sign is positive if @var{Y} is positive. If @var{Y} is zero, then
+the return value is zero if @var{X} is strictly positive, @math{\pi} if
+@var{X} is negative and @var{Y} is positive zero (or the processor does
+not handle signed zeros), and @math{-\pi} if @var{X} is negative and
+@var{Y} is negative zero. Finally, if @var{X} is zero, then the
+magnitude of the result is @math{\pi/2}.
+
+@item @emph{Example}:
+@smallexample
+program test_atan2
+ real(4) :: x = 1.e0_4, y = 0.5e0_4
+ x = atan2(y,x)
+end program test_atan2
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .22 .22 .20 .32
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ATAN2(X, Y)} @tab @code{REAL(4) X, Y} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DATAN2(X, Y)} @tab @code{REAL(8) X, Y} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+Alias: @gol
+@ref{ATAN} @gol
+Degrees function: @gol
+@ref{ATAN2D}
+@end table
+
+
+
+@node ATAN2D
+@section @code{ATAN2D} --- Arctangent function, degrees
+@fnindex ATAN2D
+@fnindex DATAN2D
+@cindex trigonometric function, tangent, inverse, degrees
+@cindex tangent, inverse, degrees
+
+@table @asis
+@item @emph{Description}:
+@code{ATAN2D(Y, X)} computes the principal value of the argument
+function of the complex number @math{X + i Y} in degrees. This function can
+be used to transform from Cartesian into polar coordinates and
+allows to determine the angle in the correct quadrant.
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ATAN2D(Y, X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{Y} @tab The type shall be @code{REAL}.
+@item @var{X} @tab The type and kind type parameter shall be the same as @var{Y}.
+If @var{Y} is zero, then @var{X} must be nonzero.
+@end multitable
+
+@item @emph{Return value}:
+The return value has the same type and kind type parameter as @var{Y}. It
+is the principal value of the complex number @math{X + i Y}. If @var{X}
+is nonzero, then it lies in the range @math{-180 \le \atan (x) \leq 180}.
+The sign is positive if @var{Y} is positive. If @var{Y} is zero, then
+the return value is zero if @var{X} is strictly positive, @math{180} if
+@var{X} is negative and @var{Y} is positive zero (or the processor does
+not handle signed zeros), and @math{-180} if @var{X} is negative and
+@var{Y} is negative zero. Finally, if @var{X} is zero, then the
+magnitude of the result is @math{90}.
+
+@item @emph{Example}:
+@smallexample
+program test_atan2d
+ real(4) :: x = 1.e0_4, y = 0.5e0_4
+ x = atan2d(y,x)
+end program test_atan2d
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .23 .23 .20 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ATAN2D(X, Y)} @tab @code{REAL(4) X, Y} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DATAN2D(X, Y)} @tab @code{REAL(8) X, Y} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Alias: @gol
+@ref{ATAND} @gol
+Radians function: @gol
+@ref{ATAN2}
+@end table
+
+
+
+@node ATANH
+@section @code{ATANH} --- Inverse hyperbolic tangent function
+@fnindex ATANH
+@fnindex DATANH
+@cindex area hyperbolic tangent
+@cindex inverse hyperbolic tangent
+@cindex hyperbolic function, tangent, inverse
+@cindex tangent, hyperbolic, inverse
+
+@table @asis
+@item @emph{Description}:
+@code{ATANH(X)} computes the inverse hyperbolic tangent of @var{X}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ATANH(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}. If @var{X} is
+complex, the imaginary part of the result is in radians and lies between
+@math{-\pi/2 \leq \Im \atanh(x) \leq \pi/2}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_atanh
+ REAL, DIMENSION(3) :: x = (/ -1.0, 0.0, 1.0 /)
+ WRITE (*,*) ATANH(x)
+END PROGRAM
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DATANH(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{TANH}
+@end table
+
+
+
+@node ATOMIC_ADD
+@section @code{ATOMIC_ADD} --- Atomic ADD operation
+@fnindex ATOMIC_ADD
+@cindex Atomic subroutine, add
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_ADD(ATOM, VALUE)} atomically adds the value of @var{VALUE} to the
+variable @var{ATOM}. When @var{STAT} is present and the invocation was
+successful, it is assigned the value 0. If it is present and the invocation
+has failed, it is assigned a positive value; in particular, for a coindexed
+@var{ATOM}, if the remote image has stopped, it is assigned the value of
+@code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote image has
+failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_ADD (ATOM, VALUE [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of integer
+type with @code{ATOMIC_INT_KIND} kind.
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*]
+ call atomic_add (atom[1], this_image())
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_FETCH_ADD}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_AND}, @gol
+@ref{ATOMIC_OR}, @gol
+@ref{ATOMIC_XOR}
+@end table
+
+
+
+
+@node ATOMIC_AND
+@section @code{ATOMIC_AND} --- Atomic bitwise AND operation
+@fnindex ATOMIC_AND
+@cindex Atomic subroutine, AND
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_AND(ATOM, VALUE)} atomically defines @var{ATOM} with the bitwise
+AND between the values of @var{ATOM} and @var{VALUE}. When @var{STAT} is present
+and the invocation was successful, it is assigned the value 0. If it is present
+and the invocation has failed, it is assigned a positive value; in particular,
+for a coindexed @var{ATOM}, if the remote image has stopped, it is assigned the
+value of @code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote
+image has failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_AND (ATOM, VALUE [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of integer
+type with @code{ATOMIC_INT_KIND} kind.
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*]
+ call atomic_and (atom[1], int(b'10100011101'))
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_FETCH_AND}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_ADD}, @gol
+@ref{ATOMIC_OR}, @gol
+@ref{ATOMIC_XOR}
+@end table
+
+
+
+@node ATOMIC_CAS
+@section @code{ATOMIC_CAS} --- Atomic compare and swap
+@fnindex ATOMIC_DEFINE
+@cindex Atomic subroutine, compare and swap
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_CAS} compares the variable @var{ATOM} with the value of
+@var{COMPARE}; if the value is the same, @var{ATOM} is set to the value
+of @var{NEW}. Additionally, @var{OLD} is set to the value of @var{ATOM}
+that was used for the comparison. When @var{STAT} is present and the invocation
+was successful, it is assigned the value 0. If it is present and the invocation
+has failed, it is assigned a positive value; in particular, for a coindexed
+@var{ATOM}, if the remote image has stopped, it is assigned the value of
+@code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote image has
+failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_CAS (ATOM, OLD, COMPARE, NEW [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of either integer
+type with @code{ATOMIC_INT_KIND} kind or logical type with
+@code{ATOMIC_LOGICAL_KIND} kind.
+@item @var{OLD} @tab Scalar of the same type and kind as @var{ATOM}.
+@item @var{COMPARE} @tab Scalar variable of the same type and kind as
+@var{ATOM}.
+@item @var{NEW} @tab Scalar variable of the same type as @var{ATOM}. If kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ logical(atomic_logical_kind) :: atom[*], prev
+ call atomic_cas (atom[1], prev, .false., .true.))
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_REF}, @gol
+@ref{ISO_FORTRAN_ENV}
+@end table
+
+
+
+@node ATOMIC_DEFINE
+@section @code{ATOMIC_DEFINE} --- Setting a variable atomically
+@fnindex ATOMIC_DEFINE
+@cindex Atomic subroutine, define
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_DEFINE(ATOM, VALUE)} defines the variable @var{ATOM} with the value
+@var{VALUE} atomically. When @var{STAT} is present and the invocation was
+successful, it is assigned the value 0. If it is present and the invocation
+has failed, it is assigned a positive value; in particular, for a coindexed
+@var{ATOM}, if the remote image has stopped, it is assigned the value of
+@code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote image has
+failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+Fortran 2008 and later; with @var{STAT}, TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_DEFINE (ATOM, VALUE [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of either integer
+type with @code{ATOMIC_INT_KIND} kind or logical type with
+@code{ATOMIC_LOGICAL_KIND} kind.
+
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*]
+ call atomic_define (atom[1], this_image())
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_REF}, @gol
+@ref{ATOMIC_CAS}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_ADD}, @gol
+@ref{ATOMIC_AND}, @gol
+@ref{ATOMIC_OR}, @gol
+@ref{ATOMIC_XOR}
+@end table
+
+
+
+@node ATOMIC_FETCH_ADD
+@section @code{ATOMIC_FETCH_ADD} --- Atomic ADD operation with prior fetch
+@fnindex ATOMIC_FETCH_ADD
+@cindex Atomic subroutine, ADD with fetch
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_FETCH_ADD(ATOM, VALUE, OLD)} atomically stores the value of
+@var{ATOM} in @var{OLD} and adds the value of @var{VALUE} to the
+variable @var{ATOM}. When @var{STAT} is present and the invocation was
+successful, it is assigned the value 0. If it is present and the invocation
+has failed, it is assigned a positive value; in particular, for a coindexed
+@var{ATOM}, if the remote image has stopped, it is assigned the value of
+@code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote image has
+failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_FETCH_ADD (ATOM, VALUE, old [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of integer
+type with @code{ATOMIC_INT_KIND} kind.
+@code{ATOMIC_LOGICAL_KIND} kind.
+
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{OLD} @tab Scalar of the same type and kind as @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*], old
+ call atomic_add (atom[1], this_image(), old)
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_ADD}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_FETCH_AND}, @gol
+@ref{ATOMIC_FETCH_OR}, @gol
+@ref{ATOMIC_FETCH_XOR}
+@end table
+
+
+
+@node ATOMIC_FETCH_AND
+@section @code{ATOMIC_FETCH_AND} --- Atomic bitwise AND operation with prior fetch
+@fnindex ATOMIC_FETCH_AND
+@cindex Atomic subroutine, AND with fetch
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_AND(ATOM, VALUE)} atomically stores the value of @var{ATOM} in
+@var{OLD} and defines @var{ATOM} with the bitwise AND between the values of
+@var{ATOM} and @var{VALUE}. When @var{STAT} is present and the invocation was
+successful, it is assigned the value 0. If it is present and the invocation has
+failed, it is assigned a positive value; in particular, for a coindexed
+@var{ATOM}, if the remote image has stopped, it is assigned the value of
+@code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote image has
+failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_FETCH_AND (ATOM, VALUE, OLD [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of integer
+type with @code{ATOMIC_INT_KIND} kind.
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{OLD} @tab Scalar of the same type and kind as @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*], old
+ call atomic_fetch_and (atom[1], int(b'10100011101'), old)
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_AND}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_FETCH_ADD}, @gol
+@ref{ATOMIC_FETCH_OR}, @gol
+@ref{ATOMIC_FETCH_XOR}
+@end table
+
+
+
+@node ATOMIC_FETCH_OR
+@section @code{ATOMIC_FETCH_OR} --- Atomic bitwise OR operation with prior fetch
+@fnindex ATOMIC_FETCH_OR
+@cindex Atomic subroutine, OR with fetch
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_OR(ATOM, VALUE)} atomically stores the value of @var{ATOM} in
+@var{OLD} and defines @var{ATOM} with the bitwise OR between the values of
+@var{ATOM} and @var{VALUE}. When @var{STAT} is present and the invocation was
+successful, it is assigned the value 0. If it is present and the invocation has
+failed, it is assigned a positive value; in particular, for a coindexed
+@var{ATOM}, if the remote image has stopped, it is assigned the value of
+@code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote image has
+failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_FETCH_OR (ATOM, VALUE, OLD [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of integer
+type with @code{ATOMIC_INT_KIND} kind.
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{OLD} @tab Scalar of the same type and kind as @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*], old
+ call atomic_fetch_or (atom[1], int(b'10100011101'), old)
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_OR}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_FETCH_ADD}, @gol
+@ref{ATOMIC_FETCH_AND}, @gol
+@ref{ATOMIC_FETCH_XOR}
+@end table
+
+
+
+@node ATOMIC_FETCH_XOR
+@section @code{ATOMIC_FETCH_XOR} --- Atomic bitwise XOR operation with prior fetch
+@fnindex ATOMIC_FETCH_XOR
+@cindex Atomic subroutine, XOR with fetch
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_XOR(ATOM, VALUE)} atomically stores the value of @var{ATOM} in
+@var{OLD} and defines @var{ATOM} with the bitwise XOR between the values of
+@var{ATOM} and @var{VALUE}. When @var{STAT} is present and the invocation was
+successful, it is assigned the value 0. If it is present and the invocation has
+failed, it is assigned a positive value; in particular, for a coindexed
+@var{ATOM}, if the remote image has stopped, it is assigned the value of
+@code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote image has
+failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_FETCH_XOR (ATOM, VALUE, OLD [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of integer
+type with @code{ATOMIC_INT_KIND} kind.
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{OLD} @tab Scalar of the same type and kind as @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*], old
+ call atomic_fetch_xor (atom[1], int(b'10100011101'), old)
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_XOR}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_FETCH_ADD}, @gol
+@ref{ATOMIC_FETCH_AND}, @gol
+@ref{ATOMIC_FETCH_OR}
+@end table
+
+
+
+@node ATOMIC_OR
+@section @code{ATOMIC_OR} --- Atomic bitwise OR operation
+@fnindex ATOMIC_OR
+@cindex Atomic subroutine, OR
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_OR(ATOM, VALUE)} atomically defines @var{ATOM} with the bitwise
+AND between the values of @var{ATOM} and @var{VALUE}. When @var{STAT} is present
+and the invocation was successful, it is assigned the value 0. If it is present
+and the invocation has failed, it is assigned a positive value; in particular,
+for a coindexed @var{ATOM}, if the remote image has stopped, it is assigned the
+value of @code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote
+image has failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_OR (ATOM, VALUE [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of integer
+type with @code{ATOMIC_INT_KIND} kind.
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*]
+ call atomic_or (atom[1], int(b'10100011101'))
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_FETCH_OR}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_ADD}, @gol
+@ref{ATOMIC_OR}, @gol
+@ref{ATOMIC_XOR}
+@end table
+
+
+
+@node ATOMIC_REF
+@section @code{ATOMIC_REF} --- Obtaining the value of a variable atomically
+@fnindex ATOMIC_REF
+@cindex Atomic subroutine, reference
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_DEFINE(ATOM, VALUE)} atomically assigns the value of the
+variable @var{ATOM} to @var{VALUE}. When @var{STAT} is present and the
+invocation was successful, it is assigned the value 0. If it is present and the
+invocation has failed, it is assigned a positive value; in particular, for a
+coindexed @var{ATOM}, if the remote image has stopped, it is assigned the value
+of @code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote image
+has failed, the value @code{STAT_FAILED_IMAGE}.
+
+
+@item @emph{Standard}:
+Fortran 2008 and later; with @var{STAT}, TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_REF(VALUE, ATOM [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of either integer
+type with @code{ATOMIC_INT_KIND} kind or logical type with
+@code{ATOMIC_LOGICAL_KIND} kind.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ logical(atomic_logical_kind) :: atom[*]
+ logical :: val
+ call atomic_ref (atom, .false.)
+ ! ...
+ call atomic_ref (atom, val)
+ if (val) then
+ print *, "Obtained"
+ end if
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_CAS}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_FETCH_ADD}, @gol
+@ref{ATOMIC_FETCH_AND}, @gol
+@ref{ATOMIC_FETCH_OR}, @gol
+@ref{ATOMIC_FETCH_XOR}
+@end table
+
+
+@node ATOMIC_XOR
+@section @code{ATOMIC_XOR} --- Atomic bitwise OR operation
+@fnindex ATOMIC_XOR
+@cindex Atomic subroutine, XOR
+
+@table @asis
+@item @emph{Description}:
+@code{ATOMIC_AND(ATOM, VALUE)} atomically defines @var{ATOM} with the bitwise
+XOR between the values of @var{ATOM} and @var{VALUE}. When @var{STAT} is present
+and the invocation was successful, it is assigned the value 0. If it is present
+and the invocation has failed, it is assigned a positive value; in particular,
+for a coindexed @var{ATOM}, if the remote image has stopped, it is assigned the
+value of @code{ISO_FORTRAN_ENV}'s @code{STAT_STOPPED_IMAGE} and if the remote
+image has failed, the value @code{STAT_FAILED_IMAGE}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+Atomic subroutine
+
+@item @emph{Syntax}:
+@code{CALL ATOMIC_XOR (ATOM, VALUE [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ATOM} @tab Scalar coarray or coindexed variable of integer
+type with @code{ATOMIC_INT_KIND} kind.
+@item @var{VALUE} @tab Scalar of the same type as @var{ATOM}. If the kind
+is different, the value is converted to the kind of @var{ATOM}.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ integer(atomic_int_kind) :: atom[*]
+ call atomic_xor (atom[1], int(b'10100011101'))
+end program atomic
+@end smallexample
+
+@item @emph{See also}:
+@ref{ATOMIC_DEFINE}, @gol
+@ref{ATOMIC_FETCH_XOR}, @gol
+@ref{ISO_FORTRAN_ENV}, @gol
+@ref{ATOMIC_ADD}, @gol
+@ref{ATOMIC_OR}, @gol
+@ref{ATOMIC_XOR}
+@end table
+
+
+@node BACKTRACE
+@section @code{BACKTRACE} --- Show a backtrace
+@fnindex BACKTRACE
+@cindex backtrace
+
+@table @asis
+@item @emph{Description}:
+@code{BACKTRACE} shows a backtrace at an arbitrary place in user code. Program
+execution continues normally afterwards. The backtrace information is printed
+to the unit corresponding to @code{ERROR_UNIT} in @code{ISO_FORTRAN_ENV}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL BACKTRACE}
+
+@item @emph{Arguments}:
+None
+
+@item @emph{See also}:
+@ref{ABORT}
+@end table
+
+
+
+@node BESSEL_J0
+@section @code{BESSEL_J0} --- Bessel function of the first kind of order 0
+@fnindex BESSEL_J0
+@fnindex BESJ0
+@fnindex DBESJ0
+@cindex Bessel function, first kind
+
+@table @asis
+@item @emph{Description}:
+@code{BESSEL_J0(X)} computes the Bessel function of the first kind of
+order 0 of @var{X}. This function is available under the name
+@code{BESJ0} as a GNU extension.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BESSEL_J0(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} and lies in the
+range @math{ - 0.4027... \leq Bessel (0,x) \leq 1}. It has the same
+kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_besj0
+ real(8) :: x = 0.0_8
+ x = bessel_j0(x)
+end program test_besj0
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .21 .22 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DBESJ0(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node BESSEL_J1
+@section @code{BESSEL_J1} --- Bessel function of the first kind of order 1
+@fnindex BESSEL_J1
+@fnindex BESJ1
+@fnindex DBESJ1
+@cindex Bessel function, first kind
+
+@table @asis
+@item @emph{Description}:
+@code{BESSEL_J1(X)} computes the Bessel function of the first kind of
+order 1 of @var{X}. This function is available under the name
+@code{BESJ1} as a GNU extension.
+
+@item @emph{Standard}:
+Fortran 2008
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BESSEL_J1(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} and lies in the
+range @math{ - 0.5818... \leq Bessel (0,x) \leq 0.5818 }. It has the same
+kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_besj1
+ real(8) :: x = 1.0_8
+ x = bessel_j1(x)
+end program test_besj1
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DBESJ1(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node BESSEL_JN
+@section @code{BESSEL_JN} --- Bessel function of the first kind
+@fnindex BESSEL_JN
+@fnindex BESJN
+@fnindex DBESJN
+@cindex Bessel function, first kind
+
+@table @asis
+@item @emph{Description}:
+@code{BESSEL_JN(N, X)} computes the Bessel function of the first kind of
+order @var{N} of @var{X}. This function is available under the name
+@code{BESJN} as a GNU extension. If @var{N} and @var{X} are arrays,
+their ranks and shapes shall conform.
+
+@code{BESSEL_JN(N1, N2, X)} returns an array with the Bessel functions
+of the first kind of the orders @var{N1} to @var{N2}.
+
+@item @emph{Standard}:
+Fortran 2008 and later, negative @var{N} is allowed as GNU extension
+
+@item @emph{Class}:
+Elemental function, except for the transformational function
+@code{BESSEL_JN(N1, N2, X)}
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = BESSEL_JN(N, X)}
+@item @code{RESULT = BESSEL_JN(N1, N2, X)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{N} @tab Shall be a scalar or an array of type @code{INTEGER}.
+@item @var{N1} @tab Shall be a non-negative scalar of type @code{INTEGER}.
+@item @var{N2} @tab Shall be a non-negative scalar of type @code{INTEGER}.
+@item @var{X} @tab Shall be a scalar or an array of type @code{REAL};
+for @code{BESSEL_JN(N1, N2, X)} it shall be scalar.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a scalar of type @code{REAL}. It has the same
+kind as @var{X}.
+
+@item @emph{Note}:
+The transformational function uses a recurrence algorithm which might,
+for some values of @var{X}, lead to different results than calls to
+the elemental function.
+
+@item @emph{Example}:
+@smallexample
+program test_besjn
+ real(8) :: x = 1.0_8
+ x = bessel_jn(5,x)
+end program test_besjn
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .22 .22 .20 .32
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DBESJN(N, X)} @tab @code{INTEGER N} @tab @code{REAL(8)} @tab GNU extension
+@item @tab @code{REAL(8) X} @tab @tab
+@end multitable
+@end table
+
+
+
+@node BESSEL_Y0
+@section @code{BESSEL_Y0} --- Bessel function of the second kind of order 0
+@fnindex BESSEL_Y0
+@fnindex BESY0
+@fnindex DBESY0
+@cindex Bessel function, second kind
+
+@table @asis
+@item @emph{Description}:
+@code{BESSEL_Y0(X)} computes the Bessel function of the second kind of
+order 0 of @var{X}. This function is available under the name
+@code{BESY0} as a GNU extension.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BESSEL_Y0(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL}. It has the same kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_besy0
+ real(8) :: x = 0.0_8
+ x = bessel_y0(x)
+end program test_besy0
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DBESY0(X)}@tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node BESSEL_Y1
+@section @code{BESSEL_Y1} --- Bessel function of the second kind of order 1
+@fnindex BESSEL_Y1
+@fnindex BESY1
+@fnindex DBESY1
+@cindex Bessel function, second kind
+
+@table @asis
+@item @emph{Description}:
+@code{BESSEL_Y1(X)} computes the Bessel function of the second kind of
+order 1 of @var{X}. This function is available under the name
+@code{BESY1} as a GNU extension.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BESSEL_Y1(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL}. It has the same kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_besy1
+ real(8) :: x = 1.0_8
+ x = bessel_y1(x)
+end program test_besy1
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DBESY1(X)}@tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node BESSEL_YN
+@section @code{BESSEL_YN} --- Bessel function of the second kind
+@fnindex BESSEL_YN
+@fnindex BESYN
+@fnindex DBESYN
+@cindex Bessel function, second kind
+
+@table @asis
+@item @emph{Description}:
+@code{BESSEL_YN(N, X)} computes the Bessel function of the second kind of
+order @var{N} of @var{X}. This function is available under the name
+@code{BESYN} as a GNU extension. If @var{N} and @var{X} are arrays,
+their ranks and shapes shall conform.
+
+@code{BESSEL_YN(N1, N2, X)} returns an array with the Bessel functions
+of the first kind of the orders @var{N1} to @var{N2}.
+
+@item @emph{Standard}:
+Fortran 2008 and later, negative @var{N} is allowed as GNU extension
+
+@item @emph{Class}:
+Elemental function, except for the transformational function
+@code{BESSEL_YN(N1, N2, X)}
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = BESSEL_YN(N, X)}
+@item @code{RESULT = BESSEL_YN(N1, N2, X)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{N} @tab Shall be a scalar or an array of type @code{INTEGER} .
+@item @var{N1} @tab Shall be a non-negative scalar of type @code{INTEGER}.
+@item @var{N2} @tab Shall be a non-negative scalar of type @code{INTEGER}.
+@item @var{X} @tab Shall be a scalar or an array of type @code{REAL};
+for @code{BESSEL_YN(N1, N2, X)} it shall be scalar.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a scalar of type @code{REAL}. It has the same
+kind as @var{X}.
+
+@item @emph{Note}:
+The transformational function uses a recurrence algorithm which might,
+for some values of @var{X}, lead to different results than calls to
+the elemental function.
+
+@item @emph{Example}:
+@smallexample
+program test_besyn
+ real(8) :: x = 1.0_8
+ x = bessel_yn(5,x)
+end program test_besyn
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DBESYN(N,X)} @tab @code{INTEGER N} @tab @code{REAL(8)} @tab GNU extension
+@item @tab @code{REAL(8) X} @tab @tab
+@end multitable
+@end table
+
+
+
+@node BGE
+@section @code{BGE} --- Bitwise greater than or equal to
+@fnindex BGE
+@cindex bitwise comparison
+
+@table @asis
+@item @emph{Description}:
+Determines whether an integral is a bitwise greater than or equal to
+another.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BGE(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of @code{INTEGER} type.
+@item @var{J} @tab Shall be of @code{INTEGER} type, and of the same kind
+as @var{I}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{LOGICAL} and of the default kind.
+
+@item @emph{See also}:
+@ref{BGT}, @gol
+@ref{BLE}, @gol
+@ref{BLT}
+@end table
+
+
+
+@node BGT
+@section @code{BGT} --- Bitwise greater than
+@fnindex BGT
+@cindex bitwise comparison
+
+@table @asis
+@item @emph{Description}:
+Determines whether an integral is a bitwise greater than another.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BGT(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of @code{INTEGER} type.
+@item @var{J} @tab Shall be of @code{INTEGER} type, and of the same kind
+as @var{I}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{LOGICAL} and of the default kind.
+
+@item @emph{See also}:
+@ref{BGE}, @gol
+@ref{BLE}, @gol
+@ref{BLT}
+@end table
+
+
+
+@node BIT_SIZE
+@section @code{BIT_SIZE} --- Bit size inquiry function
+@fnindex BIT_SIZE
+@cindex bits, number of
+@cindex size of a variable, in bits
+
+@table @asis
+@item @emph{Description}:
+@code{BIT_SIZE(I)} returns the number of bits (integer precision plus sign bit)
+represented by the type of @var{I}. The result of @code{BIT_SIZE(I)} is
+independent of the actual value of @var{I}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = BIT_SIZE(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER}
+
+@item @emph{Example}:
+@smallexample
+program test_bit_size
+ integer :: i = 123
+ integer :: size
+ size = bit_size(i)
+ print *, size
+end program test_bit_size
+@end smallexample
+@end table
+
+
+
+@node BLE
+@section @code{BLE} --- Bitwise less than or equal to
+@fnindex BLE
+@cindex bitwise comparison
+
+@table @asis
+@item @emph{Description}:
+Determines whether an integral is a bitwise less than or equal to
+another.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BLE(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of @code{INTEGER} type.
+@item @var{J} @tab Shall be of @code{INTEGER} type, and of the same kind
+as @var{I}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{LOGICAL} and of the default kind.
+
+@item @emph{See also}:
+@ref{BGT}, @gol
+@ref{BGE}, @gol
+@ref{BLT}
+@end table
+
+
+
+@node BLT
+@section @code{BLT} --- Bitwise less than
+@fnindex BLT
+@cindex bitwise comparison
+
+@table @asis
+@item @emph{Description}:
+Determines whether an integral is a bitwise less than another.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BLT(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of @code{INTEGER} type.
+@item @var{J} @tab Shall be of @code{INTEGER} type, and of the same kind
+as @var{I}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{LOGICAL} and of the default kind.
+
+@item @emph{See also}:
+@ref{BGE}, @gol
+@ref{BGT}, @gol
+@ref{BLE}
+@end table
+
+
+
+@node BTEST
+@section @code{BTEST} --- Bit test function
+@fnindex BTEST
+@fnindex BBTEST
+@fnindex BITEST
+@fnindex BJTEST
+@fnindex BKTEST
+@cindex bits, testing
+
+@table @asis
+@item @emph{Description}:
+@code{BTEST(I,POS)} returns logical @code{.TRUE.} if the bit at @var{POS}
+in @var{I} is set. The counting of the bits starts at 0.
+
+@item @emph{Standard}:
+Fortran 90 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = BTEST(I, POS)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{POS} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{LOGICAL}
+
+@item @emph{Example}:
+@smallexample
+program test_btest
+ integer :: i = 32768 + 1024 + 64
+ integer :: pos
+ logical :: bool
+ do pos=0,16
+ bool = btest(i, pos)
+ print *, pos, bool
+ end do
+end program test_btest
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .21 .28 .18 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{BTEST(I,POS)} @tab @code{INTEGER I,POS} @tab @code{LOGICAL} @tab Fortran 95 and later
+@item @code{BBTEST(I,POS)} @tab @code{INTEGER(1) I,POS} @tab @code{LOGICAL(1)} @tab GNU extension
+@item @code{BITEST(I,POS)} @tab @code{INTEGER(2) I,POS} @tab @code{LOGICAL(2)} @tab GNU extension
+@item @code{BJTEST(I,POS)} @tab @code{INTEGER(4) I,POS} @tab @code{LOGICAL(4)} @tab GNU extension
+@item @code{BKTEST(I,POS)} @tab @code{INTEGER(8) I,POS} @tab @code{LOGICAL(8)} @tab GNU extension
+@end multitable
+@end table
+
+@node C_ASSOCIATED
+@section @code{C_ASSOCIATED} --- Status of a C pointer
+@fnindex C_ASSOCIATED
+@cindex association status, C pointer
+@cindex pointer, C association status
+
+@table @asis
+@item @emph{Description}:
+@code{C_ASSOCIATED(c_ptr_1[, c_ptr_2])} determines the status of the C pointer
+@var{c_ptr_1} or if @var{c_ptr_1} is associated with the target @var{c_ptr_2}.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = C_ASSOCIATED(c_ptr_1[, c_ptr_2])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{c_ptr_1} @tab Scalar of the type @code{C_PTR} or @code{C_FUNPTR}.
+@item @var{c_ptr_2} @tab (Optional) Scalar of the same type as @var{c_ptr_1}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{LOGICAL}; it is @code{.false.} if either
+@var{c_ptr_1} is a C NULL pointer or if @var{c_ptr1} and @var{c_ptr_2}
+point to different addresses.
+
+@item @emph{Example}:
+@smallexample
+subroutine association_test(a,b)
+ use iso_c_binding, only: c_associated, c_loc, c_ptr
+ implicit none
+ real, pointer :: a
+ type(c_ptr) :: b
+ if(c_associated(b, c_loc(a))) &
+ stop 'b and a do not point to same target'
+end subroutine association_test
+@end smallexample
+
+@item @emph{See also}:
+@ref{C_LOC}, @gol
+@ref{C_FUNLOC}
+@end table
+
+
+@node C_F_POINTER
+@section @code{C_F_POINTER} --- Convert C into Fortran pointer
+@fnindex C_F_POINTER
+@cindex pointer, convert C to Fortran
+
+@table @asis
+@item @emph{Description}:
+@code{C_F_POINTER(CPTR, FPTR[, SHAPE])} assigns the target of the C pointer
+@var{CPTR} to the Fortran pointer @var{FPTR} and specifies its shape.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL C_F_POINTER(CPTR, FPTR[, SHAPE])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{CPTR} @tab scalar of the type @code{C_PTR}. It is
+@code{INTENT(IN)}.
+@item @var{FPTR} @tab pointer interoperable with @var{cptr}. It is
+@code{INTENT(OUT)}.
+@item @var{SHAPE} @tab (Optional) Rank-one array of type @code{INTEGER}
+with @code{INTENT(IN)}. It shall be present
+if and only if @var{fptr} is an array. The size
+must be equal to the rank of @var{fptr}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program main
+ use iso_c_binding
+ implicit none
+ interface
+ subroutine my_routine(p) bind(c,name='myC_func')
+ import :: c_ptr
+ type(c_ptr), intent(out) :: p
+ end subroutine
+ end interface
+ type(c_ptr) :: cptr
+ real,pointer :: a(:)
+ call my_routine(cptr)
+ call c_f_pointer(cptr, a, [12])
+end program main
+@end smallexample
+
+@item @emph{See also}:
+@ref{C_LOC}, @gol
+@ref{C_F_PROCPOINTER}
+@end table
+
+
+@node C_F_PROCPOINTER
+@section @code{C_F_PROCPOINTER} --- Convert C into Fortran procedure pointer
+@fnindex C_F_PROCPOINTER
+@cindex pointer, C address of pointers
+
+@table @asis
+@item @emph{Description}:
+@code{C_F_PROCPOINTER(CPTR, FPTR)} Assign the target of the C function pointer
+@var{CPTR} to the Fortran procedure pointer @var{FPTR}.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL C_F_PROCPOINTER(cptr, fptr)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{CPTR} @tab scalar of the type @code{C_FUNPTR}. It is
+@code{INTENT(IN)}.
+@item @var{FPTR} @tab procedure pointer interoperable with @var{cptr}. It is
+@code{INTENT(OUT)}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program main
+ use iso_c_binding
+ implicit none
+ abstract interface
+ function func(a)
+ import :: c_float
+ real(c_float), intent(in) :: a
+ real(c_float) :: func
+ end function
+ end interface
+ interface
+ function getIterFunc() bind(c,name="getIterFunc")
+ import :: c_funptr
+ type(c_funptr) :: getIterFunc
+ end function
+ end interface
+ type(c_funptr) :: cfunptr
+ procedure(func), pointer :: myFunc
+ cfunptr = getIterFunc()
+ call c_f_procpointer(cfunptr, myFunc)
+end program main
+@end smallexample
+
+@item @emph{See also}:
+@ref{C_LOC}, @gol
+@ref{C_F_POINTER}
+@end table
+
+
+@node C_FUNLOC
+@section @code{C_FUNLOC} --- Obtain the C address of a procedure
+@fnindex C_FUNLOC
+@cindex pointer, C address of procedures
+
+@table @asis
+@item @emph{Description}:
+@code{C_FUNLOC(x)} determines the C address of the argument.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = C_FUNLOC(x)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{x} @tab Interoperable function or pointer to such function.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{C_FUNPTR} and contains the C address
+of the argument.
+
+@item @emph{Example}:
+@smallexample
+module x
+ use iso_c_binding
+ implicit none
+contains
+ subroutine sub(a) bind(c)
+ real(c_float) :: a
+ a = sqrt(a)+5.0
+ end subroutine sub
+end module x
+program main
+ use iso_c_binding
+ use x
+ implicit none
+ interface
+ subroutine my_routine(p) bind(c,name='myC_func')
+ import :: c_funptr
+ type(c_funptr), intent(in) :: p
+ end subroutine
+ end interface
+ call my_routine(c_funloc(sub))
+end program main
+@end smallexample
+
+@item @emph{See also}:
+@ref{C_ASSOCIATED}, @gol
+@ref{C_LOC}, @gol
+@ref{C_F_POINTER}, @gol
+@ref{C_F_PROCPOINTER}
+@end table
+
+
+@node C_LOC
+@section @code{C_LOC} --- Obtain the C address of an object
+@fnindex C_LOC
+@cindex procedure pointer, convert C to Fortran
+
+@table @asis
+@item @emph{Description}:
+@code{C_LOC(X)} determines the C address of the argument.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = C_LOC(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .10 .75
+@item @var{X} @tab Shall have either the POINTER or TARGET attribute. It shall not be a coindexed object. It shall either be a variable with interoperable type and kind type parameters, or be a scalar, nonpolymorphic variable with no length type parameters.
+
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{C_PTR} and contains the C address
+of the argument.
+
+@item @emph{Example}:
+@smallexample
+subroutine association_test(a,b)
+ use iso_c_binding, only: c_associated, c_loc, c_ptr
+ implicit none
+ real, pointer :: a
+ type(c_ptr) :: b
+ if(c_associated(b, c_loc(a))) &
+ stop 'b and a do not point to same target'
+end subroutine association_test
+@end smallexample
+
+@item @emph{See also}:
+@ref{C_ASSOCIATED}, @gol
+@ref{C_FUNLOC}, @gol
+@ref{C_F_POINTER}, @gol
+@ref{C_F_PROCPOINTER}
+@end table
+
+
+@node C_SIZEOF
+@section @code{C_SIZEOF} --- Size in bytes of an expression
+@fnindex C_SIZEOF
+@cindex expression size
+@cindex size of an expression
+
+@table @asis
+@item @emph{Description}:
+@code{C_SIZEOF(X)} calculates the number of bytes of storage the
+expression @code{X} occupies.
+
+@item @emph{Standard}:
+Fortran 2008
+
+@item @emph{Class}:
+Inquiry function of the module @code{ISO_C_BINDING}
+
+@item @emph{Syntax}:
+@code{N = C_SIZEOF(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The argument shall be an interoperable data entity.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type integer and of the system-dependent kind
+@code{C_SIZE_T} (from the @code{ISO_C_BINDING} module). Its value is the
+number of bytes occupied by the argument. If the argument has the
+@code{POINTER} attribute, the number of bytes of the storage area pointed
+to is returned. If the argument is of a derived type with @code{POINTER}
+or @code{ALLOCATABLE} components, the return value does not account for
+the sizes of the data pointed to by these components.
+
+@item @emph{Example}:
+@smallexample
+ use iso_c_binding
+ integer(c_int) :: i
+ real(c_float) :: r, s(5)
+ print *, (c_sizeof(s)/c_sizeof(r) == 5)
+ end
+@end smallexample
+The example will print @code{T} unless you are using a platform
+where default @code{REAL} variables are unusually padded.
+
+@item @emph{See also}:
+@ref{SIZEOF}, @gol
+@ref{STORAGE_SIZE}
+@end table
+
+
+@node CEILING
+@section @code{CEILING} --- Integer ceiling function
+@fnindex CEILING
+@cindex ceiling
+@cindex rounding, ceiling
+
+@table @asis
+@item @emph{Description}:
+@code{CEILING(A)} returns the least integer greater than or equal to @var{A}.
+
+@item @emph{Standard}:
+Fortran 95 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = CEILING(A [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab The type shall be @code{REAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER(KIND)} if @var{KIND} is present
+and a default-kind @code{INTEGER} otherwise.
+
+@item @emph{Example}:
+@smallexample
+program test_ceiling
+ real :: x = 63.29
+ real :: y = -63.59
+ print *, ceiling(x) ! returns 64
+ print *, ceiling(y) ! returns -63
+end program test_ceiling
+@end smallexample
+
+@item @emph{See also}:
+@ref{FLOOR}, @gol
+@ref{NINT}
+@end table
+
+
+
+@node CHAR
+@section @code{CHAR} --- Character conversion function
+@fnindex CHAR
+@cindex conversion, to character
+
+@table @asis
+@item @emph{Description}:
+@code{CHAR(I [, KIND])} returns the character represented by the integer @var{I}.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = CHAR(I [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{CHARACTER(1)}
+
+@item @emph{Example}:
+@smallexample
+program test_char
+ integer :: i = 74
+ character(1) :: c
+ c = char(i)
+ print *, i, c ! returns 'J'
+end program test_char
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .19 .19 .25 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{CHAR(I)} @tab @code{INTEGER I} @tab @code{CHARACTER(LEN=1)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{Note}:
+See @ref{ICHAR} for a discussion of converting between numerical values
+and formatted string representations.
+
+@item @emph{See also}:
+@ref{ACHAR}, @gol
+@ref{IACHAR}, @gol
+@ref{ICHAR}
+
+@end table
+
+
+
+@node CHDIR
+@section @code{CHDIR} --- Change working directory
+@fnindex CHDIR
+@cindex system, working directory
+
+@table @asis
+@item @emph{Description}:
+Change current working directory to a specified path.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL CHDIR(NAME [, STATUS])}
+@item @code{STATUS = CHDIR(NAME)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NAME} @tab The type shall be @code{CHARACTER} of default
+kind and shall specify a valid path within the file system.
+@item @var{STATUS} @tab (Optional) @code{INTEGER} status flag of the default
+kind. Returns 0 on success, and a system specific and nonzero error code
+otherwise.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_chdir
+ CHARACTER(len=255) :: path
+ CALL getcwd(path)
+ WRITE(*,*) TRIM(path)
+ CALL chdir("/tmp")
+ CALL getcwd(path)
+ WRITE(*,*) TRIM(path)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{GETCWD}
+@end table
+
+
+
+@node CHMOD
+@section @code{CHMOD} --- Change access permissions of files
+@fnindex CHMOD
+@cindex file system, change access mode
+
+@table @asis
+@item @emph{Description}:
+@code{CHMOD} changes the permissions of a file.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL CHMOD(NAME, MODE[, STATUS])}
+@item @code{STATUS = CHMOD(NAME, MODE)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+
+@item @var{NAME} @tab Scalar @code{CHARACTER} of default kind with the
+file name. Trailing blanks are ignored unless the character
+@code{achar(0)} is present, then all characters up to and excluding
+@code{achar(0)} are used as the file name.
+
+@item @var{MODE} @tab Scalar @code{CHARACTER} of default kind giving the
+file permission. @var{MODE} uses the same syntax as the @code{chmod} utility
+as defined by the POSIX standard. The argument shall either be a string of
+a nonnegative octal number or a symbolic mode.
+
+@item @var{STATUS} @tab (optional) scalar @code{INTEGER}, which is
+@code{0} on success and nonzero otherwise.
+@end multitable
+
+@item @emph{Return value}:
+In either syntax, @var{STATUS} is set to @code{0} on success and nonzero
+otherwise.
+
+@item @emph{Example}:
+@code{CHMOD} as subroutine
+@smallexample
+program chmod_test
+ implicit none
+ integer :: status
+ call chmod('test.dat','u+x',status)
+ print *, 'Status: ', status
+end program chmod_test
+@end smallexample
+@code{CHMOD} as function:
+@smallexample
+program chmod_test
+ implicit none
+ integer :: status
+ status = chmod('test.dat','u+x')
+ print *, 'Status: ', status
+end program chmod_test
+@end smallexample
+
+@end table
+
+
+
+@node CMPLX
+@section @code{CMPLX} --- Complex conversion function
+@fnindex CMPLX
+@cindex complex numbers, conversion to
+@cindex conversion, to complex
+
+@table @asis
+@item @emph{Description}:
+@code{CMPLX(X [, Y [, KIND]])} returns a complex number where @var{X} is converted to
+the real component. If @var{Y} is present it is converted to the imaginary
+component. If @var{Y} is not present then the imaginary component is set to
+0.0. If @var{X} is complex then @var{Y} must not be present.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = CMPLX(X [, Y [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type may be @code{INTEGER}, @code{REAL},
+or @code{COMPLEX}.
+@item @var{Y} @tab (Optional; only allowed if @var{X} is not
+@code{COMPLEX}.) May be @code{INTEGER} or @code{REAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of @code{COMPLEX} type, with a kind equal to
+@var{KIND} if it is specified. If @var{KIND} is not specified, the
+result is of the default @code{COMPLEX} kind, regardless of the kinds of
+@var{X} and @var{Y}.
+
+@item @emph{Example}:
+@smallexample
+program test_cmplx
+ integer :: i = 42
+ real :: x = 3.14
+ complex :: z
+ z = cmplx(i, x)
+ print *, z, cmplx(x)
+end program test_cmplx
+@end smallexample
+
+@item @emph{See also}:
+@ref{COMPLEX}
+@end table
+
+
+
+@node CO_BROADCAST
+@section @code{CO_BROADCAST} --- Copy a value to all images the current set of images
+@fnindex CO_BROADCAST
+@cindex Collectives, value broadcasting
+
+@table @asis
+@item @emph{Description}:
+@code{CO_BROADCAST} copies the value of argument @var{A} on the image with
+image index @code{SOURCE_IMAGE} to all images in the current team. @var{A}
+becomes defined as if by intrinsic assignment. If the execution was
+successful and @var{STAT} is present, it is assigned the value zero. If the
+execution failed, @var{STAT} gets assigned a nonzero value and, if present,
+@var{ERRMSG} gets assigned a value describing the occurred error.
+
+@item @emph{Standard}:
+Technical Specification (TS) 18508 or later
+
+@item @emph{Class}:
+Collective subroutine
+
+@item @emph{Syntax}:
+@code{CALL CO_BROADCAST(A, SOURCE_IMAGE [, STAT, ERRMSG])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .20 .65
+@item @var{A} @tab INTENT(INOUT) argument; shall have the same
+dynamic type and type parameters on all images of the current team. If it
+is an array, it shall have the same shape on all images.
+@item @var{SOURCE_IMAGE} @tab a scalar integer expression.
+It shall have the same value on all images and refer to an
+image of the current team.
+@item @var{STAT} @tab (optional) a scalar integer variable
+@item @var{ERRMSG} @tab (optional) a scalar character variable
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test
+ integer :: val(3)
+ if (this_image() == 1) then
+ val = [1, 5, 3]
+ end if
+ call co_broadcast (val, source_image=1)
+ print *, this_image, ":", val
+end program test
+@end smallexample
+
+@item @emph{See also}:
+@ref{CO_MAX}, @gol
+@ref{CO_MIN}, @gol
+@ref{CO_SUM}, @gol
+@ref{CO_REDUCE}
+@end table
+
+
+
+@node CO_MAX
+@section @code{CO_MAX} --- Maximal value on the current set of images
+@fnindex CO_MAX
+@cindex Collectives, maximal value
+
+@table @asis
+@item @emph{Description}:
+@code{CO_MAX} determines element-wise the maximal value of @var{A} on all
+images of the current team. If @var{RESULT_IMAGE} is present, the maximum
+values are returned in @var{A} on the specified image only and the value
+of @var{A} on the other images become undefined. If @var{RESULT_IMAGE} is
+not present, the value is returned on all images. If the execution was
+successful and @var{STAT} is present, it is assigned the value zero. If the
+execution failed, @var{STAT} gets assigned a nonzero value and, if present,
+@var{ERRMSG} gets assigned a value describing the occurred error.
+
+@item @emph{Standard}:
+Technical Specification (TS) 18508 or later
+
+@item @emph{Class}:
+Collective subroutine
+
+@item @emph{Syntax}:
+@code{CALL CO_MAX(A [, RESULT_IMAGE, STAT, ERRMSG])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .20 .65
+@item @var{A} @tab shall be an integer, real or character variable,
+which has the same type and type parameters on all images of the team.
+@item @var{RESULT_IMAGE} @tab (optional) a scalar integer expression; if
+present, it shall have the same value on all images and refer to an
+image of the current team.
+@item @var{STAT} @tab (optional) a scalar integer variable
+@item @var{ERRMSG} @tab (optional) a scalar character variable
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test
+ integer :: val
+ val = this_image ()
+ call co_max (val, result_image=1)
+ if (this_image() == 1) then
+ write(*,*) "Maximal value", val ! prints num_images()
+ end if
+end program test
+@end smallexample
+
+@item @emph{See also}:
+@ref{CO_MIN}, @gol
+@ref{CO_SUM}, @gol
+@ref{CO_REDUCE}, @gol
+@ref{CO_BROADCAST}
+@end table
+
+
+
+@node CO_MIN
+@section @code{CO_MIN} --- Minimal value on the current set of images
+@fnindex CO_MIN
+@cindex Collectives, minimal value
+
+@table @asis
+@item @emph{Description}:
+@code{CO_MIN} determines element-wise the minimal value of @var{A} on all
+images of the current team. If @var{RESULT_IMAGE} is present, the minimal
+values are returned in @var{A} on the specified image only and the value
+of @var{A} on the other images become undefined. If @var{RESULT_IMAGE} is
+not present, the value is returned on all images. If the execution was
+successful and @var{STAT} is present, it is assigned the value zero. If the
+execution failed, @var{STAT} gets assigned a nonzero value and, if present,
+@var{ERRMSG} gets assigned a value describing the occurred error.
+
+@item @emph{Standard}:
+Technical Specification (TS) 18508 or later
+
+@item @emph{Class}:
+Collective subroutine
+
+@item @emph{Syntax}:
+@code{CALL CO_MIN(A [, RESULT_IMAGE, STAT, ERRMSG])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .20 .65
+@item @var{A} @tab shall be an integer, real or character variable,
+which has the same type and type parameters on all images of the team.
+@item @var{RESULT_IMAGE} @tab (optional) a scalar integer expression; if
+present, it shall have the same value on all images and refer to an
+image of the current team.
+@item @var{STAT} @tab (optional) a scalar integer variable
+@item @var{ERRMSG} @tab (optional) a scalar character variable
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test
+ integer :: val
+ val = this_image ()
+ call co_min (val, result_image=1)
+ if (this_image() == 1) then
+ write(*,*) "Minimal value", val ! prints 1
+ end if
+end program test
+@end smallexample
+
+@item @emph{See also}:
+@ref{CO_MAX}, @gol
+@ref{CO_SUM}, @gol
+@ref{CO_REDUCE}, @gol
+@ref{CO_BROADCAST}
+@end table
+
+
+
+@node CO_REDUCE
+@section @code{CO_REDUCE} --- Reduction of values on the current set of images
+@fnindex CO_REDUCE
+@cindex Collectives, generic reduction
+
+@table @asis
+@item @emph{Description}:
+@code{CO_REDUCE} determines element-wise the reduction of the value of @var{A}
+on all images of the current team. The pure function passed as @var{OPERATION}
+is used to pairwise reduce the values of @var{A} by passing either the value
+of @var{A} of different images or the result values of such a reduction as
+argument. If @var{A} is an array, the deduction is done element wise. If
+@var{RESULT_IMAGE} is present, the result values are returned in @var{A} on
+the specified image only and the value of @var{A} on the other images become
+undefined. If @var{RESULT_IMAGE} is not present, the value is returned on all
+images. If the execution was successful and @var{STAT} is present, it is
+assigned the value zero. If the execution failed, @var{STAT} gets assigned
+a nonzero value and, if present, @var{ERRMSG} gets assigned a value describing
+the occurred error.
+
+@item @emph{Standard}:
+Technical Specification (TS) 18508 or later
+
+@item @emph{Class}:
+Collective subroutine
+
+@item @emph{Syntax}:
+@code{CALL CO_REDUCE(A, OPERATION, [, RESULT_IMAGE, STAT, ERRMSG])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .20 .65
+@item @var{A} @tab is an @code{INTENT(INOUT)} argument and shall be
+nonpolymorphic. If it is allocatable, it shall be allocated; if it is a pointer,
+it shall be associated. @var{A} shall have the same type and type parameters on
+all images of the team; if it is an array, it shall have the same shape on all
+images.
+@item @var{OPERATION} @tab pure function with two scalar nonallocatable
+arguments, which shall be nonpolymorphic and have the same type and type
+parameters as @var{A}. The function shall return a nonallocatable scalar of
+the same type and type parameters as @var{A}. The function shall be the same on
+all images and with regards to the arguments mathematically commutative and
+associative. Note that @var{OPERATION} may not be an elemental function, unless
+it is an intrisic function.
+@item @var{RESULT_IMAGE} @tab (optional) a scalar integer expression; if
+present, it shall have the same value on all images and refer to an
+image of the current team.
+@item @var{STAT} @tab (optional) a scalar integer variable
+@item @var{ERRMSG} @tab (optional) a scalar character variable
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test
+ integer :: val
+ val = this_image ()
+ call co_reduce (val, result_image=1, operation=myprod)
+ if (this_image() == 1) then
+ write(*,*) "Product value", val ! prints num_images() factorial
+ end if
+contains
+ pure function myprod(a, b)
+ integer, value :: a, b
+ integer :: myprod
+ myprod = a * b
+ end function myprod
+end program test
+@end smallexample
+
+@item @emph{Note}:
+While the rules permit in principle an intrinsic function, none of the
+intrinsics in the standard fulfill the criteria of having a specific
+function, which takes two arguments of the same type and returning that
+type as result.
+
+@item @emph{See also}:
+@ref{CO_MIN}, @gol
+@ref{CO_MAX}, @gol
+@ref{CO_SUM}, @gol
+@ref{CO_BROADCAST}
+@end table
+
+
+
+@node CO_SUM
+@section @code{CO_SUM} --- Sum of values on the current set of images
+@fnindex CO_SUM
+@cindex Collectives, sum of values
+
+@table @asis
+@item @emph{Description}:
+@code{CO_SUM} sums up the values of each element of @var{A} on all
+images of the current team. If @var{RESULT_IMAGE} is present, the summed-up
+values are returned in @var{A} on the specified image only and the value
+of @var{A} on the other images become undefined. If @var{RESULT_IMAGE} is
+not present, the value is returned on all images. If the execution was
+successful and @var{STAT} is present, it is assigned the value zero. If the
+execution failed, @var{STAT} gets assigned a nonzero value and, if present,
+@var{ERRMSG} gets assigned a value describing the occurred error.
+
+@item @emph{Standard}:
+Technical Specification (TS) 18508 or later
+
+@item @emph{Class}:
+Collective subroutine
+
+@item @emph{Syntax}:
+@code{CALL CO_SUM(A [, RESULT_IMAGE, STAT, ERRMSG])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .20 .65
+@item @var{A} @tab shall be an integer, real or complex variable,
+which has the same type and type parameters on all images of the team.
+@item @var{RESULT_IMAGE} @tab (optional) a scalar integer expression; if
+present, it shall have the same value on all images and refer to an
+image of the current team.
+@item @var{STAT} @tab (optional) a scalar integer variable
+@item @var{ERRMSG} @tab (optional) a scalar character variable
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test
+ integer :: val
+ val = this_image ()
+ call co_sum (val, result_image=1)
+ if (this_image() == 1) then
+ write(*,*) "The sum is ", val ! prints (n**2 + n)/2,
+ ! with n = num_images()
+ end if
+end program test
+@end smallexample
+
+@item @emph{See also}:
+@ref{CO_MAX}, @gol
+@ref{CO_MIN}, @gol
+@ref{CO_REDUCE}, @gol
+@ref{CO_BROADCAST}
+@end table
+
+
+
+@node COMMAND_ARGUMENT_COUNT
+@section @code{COMMAND_ARGUMENT_COUNT} --- Get number of command line arguments
+@fnindex COMMAND_ARGUMENT_COUNT
+@cindex command-line arguments
+@cindex command-line arguments, number of
+@cindex arguments, to program
+
+@table @asis
+@item @emph{Description}:
+@code{COMMAND_ARGUMENT_COUNT} returns the number of arguments passed on the
+command line when the containing program was invoked.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = COMMAND_ARGUMENT_COUNT()}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item None
+@end multitable
+
+@item @emph{Return value}:
+The return value is an @code{INTEGER} of default kind.
+
+@item @emph{Example}:
+@smallexample
+program test_command_argument_count
+ integer :: count
+ count = command_argument_count()
+ print *, count
+end program test_command_argument_count
+@end smallexample
+
+@item @emph{See also}:
+@ref{GET_COMMAND}, @gol
+@ref{GET_COMMAND_ARGUMENT}
+@end table
+
+
+
+@node COMPILER_OPTIONS
+@section @code{COMPILER_OPTIONS} --- Options passed to the compiler
+@fnindex COMPILER_OPTIONS
+@cindex flags inquiry function
+@cindex options inquiry function
+@cindex compiler flags inquiry function
+
+@table @asis
+@item @emph{Description}:
+@code{COMPILER_OPTIONS} returns a string with the options used for
+compiling.
+
+@item @emph{Standard}:
+Fortran 2008
+
+@item @emph{Class}:
+Inquiry function of the module @code{ISO_FORTRAN_ENV}
+
+@item @emph{Syntax}:
+@code{STR = COMPILER_OPTIONS()}
+
+@item @emph{Arguments}:
+None
+
+@item @emph{Return value}:
+The return value is a default-kind string with system-dependent length.
+It contains the compiler flags used to compile the file, which called
+the @code{COMPILER_OPTIONS} intrinsic.
+
+@item @emph{Example}:
+@smallexample
+ use iso_fortran_env
+ print '(4a)', 'This file was compiled by ', &
+ compiler_version(), ' using the options ', &
+ compiler_options()
+ end
+@end smallexample
+
+@item @emph{See also}:
+@ref{COMPILER_VERSION}, @gol
+@ref{ISO_FORTRAN_ENV}
+@end table
+
+
+
+@node COMPILER_VERSION
+@section @code{COMPILER_VERSION} --- Compiler version string
+@fnindex COMPILER_VERSION
+@cindex compiler, name and version
+@cindex version of the compiler
+
+@table @asis
+@item @emph{Description}:
+@code{COMPILER_VERSION} returns a string with the name and the
+version of the compiler.
+
+@item @emph{Standard}:
+Fortran 2008
+
+@item @emph{Class}:
+Inquiry function of the module @code{ISO_FORTRAN_ENV}
+
+@item @emph{Syntax}:
+@code{STR = COMPILER_VERSION()}
+
+@item @emph{Arguments}:
+None
+
+@item @emph{Return value}:
+The return value is a default-kind string with system-dependent length.
+It contains the name of the compiler and its version number.
+
+@item @emph{Example}:
+@smallexample
+ use iso_fortran_env
+ print '(4a)', 'This file was compiled by ', &
+ compiler_version(), ' using the options ', &
+ compiler_options()
+ end
+@end smallexample
+
+@item @emph{See also}:
+@ref{COMPILER_OPTIONS}, @gol
+@ref{ISO_FORTRAN_ENV}
+@end table
+
+
+
+@node COMPLEX
+@section @code{COMPLEX} --- Complex conversion function
+@fnindex COMPLEX
+@cindex complex numbers, conversion to
+@cindex conversion, to complex
+
+@table @asis
+@item @emph{Description}:
+@code{COMPLEX(X, Y)} returns a complex number where @var{X} is converted
+to the real component and @var{Y} is converted to the imaginary
+component.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = COMPLEX(X, Y)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type may be @code{INTEGER} or @code{REAL}.
+@item @var{Y} @tab The type may be @code{INTEGER} or @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+If @var{X} and @var{Y} are both of @code{INTEGER} type, then the return
+value is of default @code{COMPLEX} type.
+
+If @var{X} and @var{Y} are of @code{REAL} type, or one is of @code{REAL}
+type and one is of @code{INTEGER} type, then the return value is of
+@code{COMPLEX} type with a kind equal to that of the @code{REAL}
+argument with the highest precision.
+
+@item @emph{Example}:
+@smallexample
+program test_complex
+ integer :: i = 42
+ real :: x = 3.14
+ print *, complex(i, x)
+end program test_complex
+@end smallexample
+
+@item @emph{See also}:
+@ref{CMPLX}
+@end table
+
+
+
+@node CONJG
+@section @code{CONJG} --- Complex conjugate function
+@fnindex CONJG
+@fnindex DCONJG
+@cindex complex conjugate
+
+@table @asis
+@item @emph{Description}:
+@code{CONJG(Z)} returns the conjugate of @var{Z}. If @var{Z} is @code{(x, y)}
+then the result is @code{(x, -y)}
+
+@item @emph{Standard}:
+Fortran 77 and later, has an overload that is a GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{Z = CONJG(Z)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{Z} @tab The type shall be @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{COMPLEX}.
+
+@item @emph{Example}:
+@smallexample
+program test_conjg
+ complex :: z = (2.0, 3.0)
+ complex(8) :: dz = (2.71_8, -3.14_8)
+ z= conjg(z)
+ print *, z
+ dz = dconjg(dz)
+ print *, dz
+end program test_conjg
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DCONJG(Z)} @tab @code{COMPLEX(8) Z} @tab @code{COMPLEX(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node COS
+@section @code{COS} --- Cosine function
+@fnindex COS
+@fnindex DCOS
+@fnindex CCOS
+@fnindex ZCOS
+@fnindex CDCOS
+@cindex trigonometric function, cosine
+@cindex cosine
+
+@table @asis
+@item @emph{Description}:
+@code{COS(X)} computes the cosine of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = COS(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or
+@code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}. The real part
+of the result is in radians. If @var{X} is of the type @code{REAL},
+the return value lies in the range @math{ -1 \leq \cos (x) \leq 1}.
+
+@item @emph{Example}:
+@smallexample
+program test_cos
+ real :: x = 0.0
+ x = cos(x)
+end program test_cos
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{COS(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DCOS(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@item @code{CCOS(X)} @tab @code{COMPLEX(4) X} @tab @code{COMPLEX(4)} @tab Fortran 77 and later
+@item @code{ZCOS(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@item @code{CDCOS(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{ACOS} @gol
+Degrees function: @gol
+@ref{COSD}
+@end table
+
+
+
+@node COSD
+@section @code{COSD} --- Cosine function, degrees
+@fnindex COSD
+@fnindex DCOSD
+@fnindex CCOSD
+@fnindex ZCOSD
+@fnindex CDCOSD
+@cindex trigonometric function, cosine, degrees
+@cindex cosine, degrees
+
+@table @asis
+@item @emph{Description}:
+@code{COSD(X)} computes the cosine of @var{X} in degrees.
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = COSD(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or
+@code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}. The real part
+of the result is in degrees. If @var{X} is of the type @code{REAL},
+the return value lies in the range @math{ -1 \leq \cosd (x) \leq 1}.
+
+@item @emph{Example}:
+@smallexample
+program test_cosd
+ real :: x = 0.0
+ x = cosd(x)
+end program test_cosd
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{COSD(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DCOSD(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@item @code{CCOSD(X)} @tab @code{COMPLEX(4) X} @tab @code{COMPLEX(4)} @tab GNU extension
+@item @code{ZCOSD(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@item @code{CDCOSD(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{ACOSD} @gol
+Radians function: @gol
+@ref{COS}
+@end table
+
+
+
+@node COSH
+@section @code{COSH} --- Hyperbolic cosine function
+@fnindex COSH
+@fnindex DCOSH
+@cindex hyperbolic cosine
+@cindex hyperbolic function, cosine
+@cindex cosine, hyperbolic
+
+@table @asis
+@item @emph{Description}:
+@code{COSH(X)} computes the hyperbolic cosine of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later, for a complex argument Fortran 2008 or later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{X = COSH(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}. If @var{X} is
+complex, the imaginary part of the result is in radians. If @var{X}
+is @code{REAL}, the return value has a lower bound of one,
+@math{\cosh (x) \geq 1}.
+
+@item @emph{Example}:
+@smallexample
+program test_cosh
+ real(8) :: x = 1.0_8
+ x = cosh(x)
+end program test_cosh
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{COSH(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DCOSH(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{ACOSH}
+@end table
+
+
+
+@node COTAN
+@section @code{COTAN} --- Cotangent function
+@fnindex COTAN
+@fnindex DCOTAN
+@cindex trigonometric function, cotangent
+@cindex cotangent
+
+@table @asis
+@item @emph{Description}:
+@code{COTAN(X)} computes the cotangent of @var{X}. Equivalent to @code{COS(x)}
+divided by @code{SIN(x)}, or @code{1 / TAN(x)}.
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = COTAN(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}, and its value is in radians.
+
+@item @emph{Example}:
+@smallexample
+program test_cotan
+ real(8) :: x = 0.165_8
+ x = cotan(x)
+end program test_cotan
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{COTAN(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DCOTAN(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Converse function: @gol
+@ref{TAN} @gol
+Degrees function: @gol
+@ref{COTAND}
+@end table
+
+
+
+@node COTAND
+@section @code{COTAND} --- Cotangent function, degrees
+@fnindex COTAND
+@fnindex DCOTAND
+@cindex trigonometric function, cotangent, degrees
+@cindex cotangent, degrees
+
+@table @asis
+@item @emph{Description}:
+@code{COTAND(X)} computes the cotangent of @var{X} in degrees. Equivalent to
+@code{COSD(x)} divided by @code{SIND(x)}, or @code{1 / TAND(x)}.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}.
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = COTAND(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}, and its value is in degrees.
+
+@item @emph{Example}:
+@smallexample
+program test_cotand
+ real(8) :: x = 0.165_8
+ x = cotand(x)
+end program test_cotand
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{COTAND(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DCOTAND(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Converse function: @gol
+@ref{TAND} @gol
+Radians function: @gol
+@ref{COTAN}
+@end table
+
+
+
+@node COUNT
+@section @code{COUNT} --- Count function
+@fnindex COUNT
+@cindex array, conditionally count elements
+@cindex array, element counting
+@cindex array, number of elements
+
+@table @asis
+@item @emph{Description}:
+
+Counts the number of @code{.TRUE.} elements in a logical @var{MASK},
+or, if the @var{DIM} argument is supplied, counts the number of
+elements along each row of the array in the @var{DIM} direction.
+If the array has zero size, or all of the elements of @var{MASK} are
+@code{.FALSE.}, then the result is @code{0}.
+
+@item @emph{Standard}:
+Fortran 90 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = COUNT(MASK [, DIM, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{MASK} @tab The type shall be @code{LOGICAL}.
+@item @var{DIM} @tab (Optional) The type shall be @code{INTEGER}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+If @var{DIM} is present, the result is an array with a rank one less
+than the rank of @var{ARRAY}, and a size corresponding to the shape
+of @var{ARRAY} with the @var{DIM} dimension removed.
+
+@item @emph{Example}:
+@smallexample
+program test_count
+ integer, dimension(2,3) :: a, b
+ logical, dimension(2,3) :: mask
+ a = reshape( (/ 1, 2, 3, 4, 5, 6 /), (/ 2, 3 /))
+ b = reshape( (/ 0, 7, 3, 4, 5, 8 /), (/ 2, 3 /))
+ print '(3i3)', a(1,:)
+ print '(3i3)', a(2,:)
+ print *
+ print '(3i3)', b(1,:)
+ print '(3i3)', b(2,:)
+ print *
+ mask = a.ne.b
+ print '(3l3)', mask(1,:)
+ print '(3l3)', mask(2,:)
+ print *
+ print '(3i3)', count(mask)
+ print *
+ print '(3i3)', count(mask, 1)
+ print *
+ print '(3i3)', count(mask, 2)
+end program test_count
+@end smallexample
+@end table
+
+
+
+@node CPU_TIME
+@section @code{CPU_TIME} --- CPU elapsed time in seconds
+@fnindex CPU_TIME
+@cindex time, elapsed
+
+@table @asis
+@item @emph{Description}:
+Returns a @code{REAL} value representing the elapsed CPU time in
+seconds. This is useful for testing segments of code to determine
+execution time.
+
+If a time source is available, time will be reported with microsecond
+resolution. If no time source is available, @var{TIME} is set to
+@code{-1.0}.
+
+Note that @var{TIME} may contain a, system dependent, arbitrary offset
+and may not start with @code{0.0}. For @code{CPU_TIME}, the absolute
+value is meaningless, only differences between subsequent calls to
+this subroutine, as shown in the example below, should be used.
+
+
+@item @emph{Standard}:
+Fortran 95 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL CPU_TIME(TIME)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{TIME} @tab The type shall be @code{REAL} with @code{INTENT(OUT)}.
+@end multitable
+
+@item @emph{Return value}:
+None
+
+@item @emph{Example}:
+@smallexample
+program test_cpu_time
+ real :: start, finish
+ call cpu_time(start)
+ ! put code to test here
+ call cpu_time(finish)
+ print '("Time = ",f6.3," seconds.")',finish-start
+end program test_cpu_time
+@end smallexample
+
+@item @emph{See also}:
+@ref{SYSTEM_CLOCK}, @gol
+@ref{DATE_AND_TIME}
+@end table
+
+
+
+@node CSHIFT
+@section @code{CSHIFT} --- Circular shift elements of an array
+@fnindex CSHIFT
+@cindex array, shift circularly
+@cindex array, permutation
+@cindex array, rotate
+
+@table @asis
+@item @emph{Description}:
+@code{CSHIFT(ARRAY, SHIFT [, DIM])} performs a circular shift on elements of
+@var{ARRAY} along the dimension of @var{DIM}. If @var{DIM} is omitted it is
+taken to be @code{1}. @var{DIM} is a scalar of type @code{INTEGER} in the
+range of @math{1 \leq DIM \leq n)} where @math{n} is the rank of @var{ARRAY}.
+If the rank of @var{ARRAY} is one, then all elements of @var{ARRAY} are shifted
+by @var{SHIFT} places. If rank is greater than one, then all complete rank one
+sections of @var{ARRAY} along the given dimension are shifted. Elements
+shifted out one end of each rank one section are shifted back in the other end.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = CSHIFT(ARRAY, SHIFT [, DIM])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of any type.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@item @var{DIM} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+Returns an array of same type and rank as the @var{ARRAY} argument.
+
+@item @emph{Example}:
+@smallexample
+program test_cshift
+ integer, dimension(3,3) :: a
+ a = reshape( (/ 1, 2, 3, 4, 5, 6, 7, 8, 9 /), (/ 3, 3 /))
+ print '(3i3)', a(1,:)
+ print '(3i3)', a(2,:)
+ print '(3i3)', a(3,:)
+ a = cshift(a, SHIFT=(/1, 2, -1/), DIM=2)
+ print *
+ print '(3i3)', a(1,:)
+ print '(3i3)', a(2,:)
+ print '(3i3)', a(3,:)
+end program test_cshift
+@end smallexample
+@end table
+
+
+
+@node CTIME
+@section @code{CTIME} --- Convert a time into a string
+@fnindex CTIME
+@cindex time, conversion to string
+@cindex conversion, to string
+
+@table @asis
+@item @emph{Description}:
+@code{CTIME} converts a system time value, such as returned by
+@ref{TIME8}, to a string. The output will be of the form @samp{Sat
+Aug 19 18:13:14 1995}.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL CTIME(TIME, RESULT)}.
+@item @code{RESULT = CTIME(TIME)}.
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{TIME} @tab The type shall be of type @code{INTEGER}.
+@item @var{RESULT} @tab The type shall be of type @code{CHARACTER} and
+of default kind. It is an @code{INTENT(OUT)} argument. If the length
+of this variable is too short for the time and date string to fit
+completely, it will be blank on procedure return.
+@end multitable
+
+@item @emph{Return value}:
+The converted date and time as a string.
+
+@item @emph{Example}:
+@smallexample
+program test_ctime
+ integer(8) :: i
+ character(len=30) :: date
+ i = time8()
+
+ ! Do something, main part of the program
+
+ call ctime(i,date)
+ print *, 'Program was started on ', date
+end program test_ctime
+@end smallexample
+
+@item @emph{See Also}:
+@ref{DATE_AND_TIME}, @gol
+@ref{GMTIME}, @gol
+@ref{LTIME}, @gol
+@ref{TIME}, @gol
+@ref{TIME8}
+@end table
+
+
+
+@node DATE_AND_TIME
+@section @code{DATE_AND_TIME} --- Date and time subroutine
+@fnindex DATE_AND_TIME
+@cindex date, current
+@cindex current date
+@cindex time, current
+@cindex current time
+
+@table @asis
+@item @emph{Description}:
+@code{DATE_AND_TIME(DATE, TIME, ZONE, VALUES)} gets the corresponding date and
+time information from the real-time system clock. @var{DATE} is
+@code{INTENT(OUT)} and has form ccyymmdd. @var{TIME} is @code{INTENT(OUT)} and
+has form hhmmss.sss. @var{ZONE} is @code{INTENT(OUT)} and has form (+-)hhmm,
+representing the difference with respect to Coordinated Universal Time (UTC).
+Unavailable time and date parameters return blanks.
+
+@var{VALUES} is @code{INTENT(OUT)} and provides the following:
+
+@multitable @columnfractions .15 .70
+@item @code{VALUE(1)}: @tab The year
+@item @code{VALUE(2)}: @tab The month
+@item @code{VALUE(3)}: @tab The day of the month
+@item @code{VALUE(4)}: @tab Time difference with UTC in minutes
+@item @code{VALUE(5)}: @tab The hour of the day
+@item @code{VALUE(6)}: @tab The minutes of the hour
+@item @code{VALUE(7)}: @tab The seconds of the minute
+@item @code{VALUE(8)}: @tab The milliseconds of the second
+@end multitable
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL DATE_AND_TIME([DATE, TIME, ZONE, VALUES])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{DATE} @tab (Optional) The type shall be @code{CHARACTER(LEN=8)}
+or larger, and of default kind.
+@item @var{TIME} @tab (Optional) The type shall be @code{CHARACTER(LEN=10)}
+or larger, and of default kind.
+@item @var{ZONE} @tab (Optional) The type shall be @code{CHARACTER(LEN=5)}
+or larger, and of default kind.
+@item @var{VALUES}@tab (Optional) The type shall be @code{INTEGER(8)}.
+@end multitable
+
+@item @emph{Return value}:
+None
+
+@item @emph{Example}:
+@smallexample
+program test_time_and_date
+ character(8) :: date
+ character(10) :: time
+ character(5) :: zone
+ integer,dimension(8) :: values
+ ! using keyword arguments
+ call date_and_time(date,time,zone,values)
+ call date_and_time(DATE=date,ZONE=zone)
+ call date_and_time(TIME=time)
+ call date_and_time(VALUES=values)
+ print '(a,2x,a,2x,a)', date, time, zone
+ print '(8i5)', values
+end program test_time_and_date
+@end smallexample
+
+@item @emph{See also}:
+@ref{CPU_TIME}, @gol
+@ref{SYSTEM_CLOCK}
+@end table
+
+
+
+@node DBLE
+@section @code{DBLE} --- Double conversion function
+@fnindex DBLE
+@cindex conversion, to real
+
+@table @asis
+@item @emph{Description}:
+@code{DBLE(A)} Converts @var{A} to double precision real type.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = DBLE(A)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab The type shall be @code{INTEGER}, @code{REAL},
+or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type double precision real.
+
+@item @emph{Example}:
+@smallexample
+program test_dble
+ real :: x = 2.18
+ integer :: i = 5
+ complex :: z = (2.3,1.14)
+ print *, dble(x), dble(i), dble(z)
+end program test_dble
+@end smallexample
+
+@item @emph{See also}:
+@ref{REAL}
+@end table
+
+
+
+@node DCMPLX
+@section @code{DCMPLX} --- Double complex conversion function
+@fnindex DCMPLX
+@cindex complex numbers, conversion to
+@cindex conversion, to complex
+
+@table @asis
+@item @emph{Description}:
+@code{DCMPLX(X [,Y])} returns a double complex number where @var{X} is
+converted to the real component. If @var{Y} is present it is converted to the
+imaginary component. If @var{Y} is not present then the imaginary component is
+set to 0.0. If @var{X} is complex then @var{Y} must not be present.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = DCMPLX(X [, Y])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type may be @code{INTEGER}, @code{REAL},
+or @code{COMPLEX}.
+@item @var{Y} @tab (Optional if @var{X} is not @code{COMPLEX}.) May be
+@code{INTEGER} or @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{COMPLEX(8)}
+
+@item @emph{Example}:
+@smallexample
+program test_dcmplx
+ integer :: i = 42
+ real :: x = 3.14
+ complex :: z
+ z = cmplx(i, x)
+ print *, dcmplx(i)
+ print *, dcmplx(x)
+ print *, dcmplx(z)
+ print *, dcmplx(x,i)
+end program test_dcmplx
+@end smallexample
+@end table
+
+
+@node DIGITS
+@section @code{DIGITS} --- Significant binary digits function
+@fnindex DIGITS
+@cindex model representation, significant digits
+
+@table @asis
+@item @emph{Description}:
+@code{DIGITS(X)} returns the number of significant binary digits of the internal
+model representation of @var{X}. For example, on a system using a 32-bit
+floating point representation, a default real number would likely return 24.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = DIGITS(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type may be @code{INTEGER} or @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER}.
+
+@item @emph{Example}:
+@smallexample
+program test_digits
+ integer :: i = 12345
+ real :: x = 3.143
+ real(8) :: y = 2.33
+ print *, digits(i)
+ print *, digits(x)
+ print *, digits(y)
+end program test_digits
+@end smallexample
+@end table
+
+
+
+@node DIM
+@section @code{DIM} --- Positive difference
+@fnindex DIM
+@fnindex IDIM
+@fnindex DDIM
+@cindex positive difference
+
+@table @asis
+@item @emph{Description}:
+@code{DIM(X,Y)} returns the difference @code{X-Y} if the result is positive;
+otherwise returns zero.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = DIM(X, Y)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{INTEGER} or @code{REAL}
+@item @var{Y} @tab The type shall be the same type and kind as @var{X}. (As
+a GNU extension, arguments of different kinds are permitted.)
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} or @code{REAL}. (As a GNU
+extension, kind is the largest kind of the actual arguments.)
+
+@item @emph{Example}:
+@smallexample
+program test_dim
+ integer :: i
+ real(8) :: x
+ i = dim(4, 15)
+ x = dim(4.345_8, 2.111_8)
+ print *, i
+ print *, x
+end program test_dim
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .26 .20 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DIM(X,Y)} @tab @code{REAL(4) X, Y} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{IDIM(X,Y)} @tab @code{INTEGER(4) X, Y} @tab @code{INTEGER(4)} @tab Fortran 77 and later
+@item @code{DDIM(X,Y)} @tab @code{REAL(8) X, Y} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+@end table
+
+
+
+@node DOT_PRODUCT
+@section @code{DOT_PRODUCT} --- Dot product function
+@fnindex DOT_PRODUCT
+@cindex dot product
+@cindex vector product
+@cindex product, vector
+
+@table @asis
+@item @emph{Description}:
+@code{DOT_PRODUCT(VECTOR_A, VECTOR_B)} computes the dot product multiplication
+of two vectors @var{VECTOR_A} and @var{VECTOR_B}. The two vectors may be
+either numeric or logical and must be arrays of rank one and of equal size. If
+the vectors are @code{INTEGER} or @code{REAL}, the result is
+@code{SUM(VECTOR_A*VECTOR_B)}. If the vectors are @code{COMPLEX}, the result
+is @code{SUM(CONJG(VECTOR_A)*VECTOR_B)}. If the vectors are @code{LOGICAL},
+the result is @code{ANY(VECTOR_A .AND. VECTOR_B)}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = DOT_PRODUCT(VECTOR_A, VECTOR_B)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{VECTOR_A} @tab The type shall be numeric or @code{LOGICAL}, rank 1.
+@item @var{VECTOR_B} @tab The type shall be numeric if @var{VECTOR_A} is of numeric type or @code{LOGICAL} if @var{VECTOR_A} is of type @code{LOGICAL}. @var{VECTOR_B} shall be a rank-one array.
+@end multitable
+
+@item @emph{Return value}:
+If the arguments are numeric, the return value is a scalar of numeric type,
+@code{INTEGER}, @code{REAL}, or @code{COMPLEX}. If the arguments are
+@code{LOGICAL}, the return value is @code{.TRUE.} or @code{.FALSE.}.
+
+@item @emph{Example}:
+@smallexample
+program test_dot_prod
+ integer, dimension(3) :: a, b
+ a = (/ 1, 2, 3 /)
+ b = (/ 4, 5, 6 /)
+ print '(3i3)', a
+ print *
+ print '(3i3)', b
+ print *
+ print *, dot_product(a,b)
+end program test_dot_prod
+@end smallexample
+@end table
+
+
+
+@node DPROD
+@section @code{DPROD} --- Double product function
+@fnindex DPROD
+@cindex product, double-precision
+
+@table @asis
+@item @emph{Description}:
+@code{DPROD(X,Y)} returns the product @code{X*Y}.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = DPROD(X, Y)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@item @var{Y} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL(8)}.
+
+@item @emph{Example}:
+@smallexample
+program test_dprod
+ real :: x = 5.2
+ real :: y = 2.3
+ real(8) :: d
+ d = dprod(x,y)
+ print *, d
+end program test_dprod
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DPROD(X,Y)} @tab @code{REAL(4) X, Y} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@end table
+
+
+@node DREAL
+@section @code{DREAL} --- Double real part function
+@fnindex DREAL
+@cindex complex numbers, real part
+
+@table @asis
+@item @emph{Description}:
+@code{DREAL(Z)} returns the real part of complex variable @var{Z}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = DREAL(A)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab The type shall be @code{COMPLEX(8)}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL(8)}.
+
+@item @emph{Example}:
+@smallexample
+program test_dreal
+ complex(8) :: z = (1.3_8,7.2_8)
+ print *, dreal(z)
+end program test_dreal
+@end smallexample
+
+@item @emph{See also}:
+@ref{AIMAG}
+
+@end table
+
+
+
+@node DSHIFTL
+@section @code{DSHIFTL} --- Combined left shift
+@fnindex DSHIFTL
+@cindex left shift, combined
+@cindex shift, left
+
+@table @asis
+@item @emph{Description}:
+@code{DSHIFTL(I, J, SHIFT)} combines bits of @var{I} and @var{J}. The
+rightmost @var{SHIFT} bits of the result are the leftmost @var{SHIFT}
+bits of @var{J}, and the remaining bits are the rightmost bits of
+@var{I}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = DSHIFTL(I, J, SHIFT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER} or a BOZ constant.
+@item @var{J} @tab Shall be of type @code{INTEGER} or a BOZ constant.
+If both @var{I} and @var{J} have integer type, then they shall have
+the same kind type parameter. @var{I} and @var{J} shall not both be
+BOZ constants.
+@item @var{SHIFT} @tab Shall be of type @code{INTEGER}. It shall
+be nonnegative. If @var{I} is not a BOZ constant, then @var{SHIFT}
+shall be less than or equal to @code{BIT_SIZE(I)}; otherwise,
+@var{SHIFT} shall be less than or equal to @code{BIT_SIZE(J)}.
+@end multitable
+
+@item @emph{Return value}:
+If either @var{I} or @var{J} is a BOZ constant, it is first converted
+as if by the intrinsic function @code{INT} to an integer type with the
+kind type parameter of the other.
+
+@item @emph{See also}:
+@ref{DSHIFTR}
+@end table
+
+
+@node DSHIFTR
+@section @code{DSHIFTR} --- Combined right shift
+@fnindex DSHIFTR
+@cindex right shift, combined
+@cindex shift, right
+
+@table @asis
+@item @emph{Description}:
+@code{DSHIFTR(I, J, SHIFT)} combines bits of @var{I} and @var{J}. The
+leftmost @var{SHIFT} bits of the result are the rightmost @var{SHIFT}
+bits of @var{I}, and the remaining bits are the leftmost bits of
+@var{J}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = DSHIFTR(I, J, SHIFT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER} or a BOZ constant.
+@item @var{J} @tab Shall be of type @code{INTEGER} or a BOZ constant.
+If both @var{I} and @var{J} have integer type, then they shall have
+the same kind type parameter. @var{I} and @var{J} shall not both be
+BOZ constants.
+@item @var{SHIFT} @tab Shall be of type @code{INTEGER}. It shall
+be nonnegative. If @var{I} is not a BOZ constant, then @var{SHIFT}
+shall be less than or equal to @code{BIT_SIZE(I)}; otherwise,
+@var{SHIFT} shall be less than or equal to @code{BIT_SIZE(J)}.
+@end multitable
+
+@item @emph{Return value}:
+If either @var{I} or @var{J} is a BOZ constant, it is first converted
+as if by the intrinsic function @code{INT} to an integer type with the
+kind type parameter of the other.
+
+@item @emph{See also}:
+@ref{DSHIFTL}
+@end table
+
+
+@node DTIME
+@section @code{DTIME} --- Execution time subroutine (or function)
+@fnindex DTIME
+@cindex time, elapsed
+@cindex elapsed time
+
+@table @asis
+@item @emph{Description}:
+@code{DTIME(VALUES, TIME)} initially returns the number of seconds of runtime
+since the start of the process's execution in @var{TIME}. @var{VALUES}
+returns the user and system components of this time in @code{VALUES(1)} and
+@code{VALUES(2)} respectively. @var{TIME} is equal to @code{VALUES(1) +
+VALUES(2)}.
+
+Subsequent invocations of @code{DTIME} return values accumulated since the
+previous invocation.
+
+On some systems, the underlying timings are represented using types with
+sufficiently small limits that overflows (wrap around) are possible, such as
+32-bit types. Therefore, the values returned by this intrinsic might be, or
+become, negative, or numerically less than previous values, during a single
+run of the compiled program.
+
+Please note, that this implementation is thread safe if used within OpenMP
+directives, i.e., its state will be consistent while called from multiple
+threads. However, if @code{DTIME} is called from multiple threads, the result
+is still the time since the last invocation. This may not give the intended
+results. If possible, use @code{CPU_TIME} instead.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@var{VALUES} and @var{TIME} are @code{INTENT(OUT)} and provide the following:
+
+@multitable @columnfractions .15 .70
+@item @code{VALUES(1)}: @tab User time in seconds.
+@item @code{VALUES(2)}: @tab System time in seconds.
+@item @code{TIME}: @tab Run time since start in seconds.
+@end multitable
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL DTIME(VALUES, TIME)}.
+@item @code{TIME = DTIME(VALUES)}, (not recommended).
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{VALUES}@tab The type shall be @code{REAL(4), DIMENSION(2)}.
+@item @var{TIME}@tab The type shall be @code{REAL(4)}.
+@end multitable
+
+@item @emph{Return value}:
+Elapsed time in seconds since the last invocation or since the start of program
+execution if not called before.
+
+@item @emph{Example}:
+@smallexample
+program test_dtime
+ integer(8) :: i, j
+ real, dimension(2) :: tarray
+ real :: result
+ call dtime(tarray, result)
+ print *, result
+ print *, tarray(1)
+ print *, tarray(2)
+ do i=1,100000000 ! Just a delay
+ j = i * i - i
+ end do
+ call dtime(tarray, result)
+ print *, result
+ print *, tarray(1)
+ print *, tarray(2)
+end program test_dtime
+@end smallexample
+
+@item @emph{See also}:
+@ref{CPU_TIME}
+
+@end table
+
+
+
+@node EOSHIFT
+@section @code{EOSHIFT} --- End-off shift elements of an array
+@fnindex EOSHIFT
+@cindex array, shift
+
+@table @asis
+@item @emph{Description}:
+@code{EOSHIFT(ARRAY, SHIFT[, BOUNDARY, DIM])} performs an end-off shift on
+elements of @var{ARRAY} along the dimension of @var{DIM}. If @var{DIM} is
+omitted it is taken to be @code{1}. @var{DIM} is a scalar of type
+@code{INTEGER} in the range of @math{1 \leq DIM \leq n)} where @math{n} is the
+rank of @var{ARRAY}. If the rank of @var{ARRAY} is one, then all elements of
+@var{ARRAY} are shifted by @var{SHIFT} places. If rank is greater than one,
+then all complete rank one sections of @var{ARRAY} along the given dimension are
+shifted. Elements shifted out one end of each rank one section are dropped. If
+@var{BOUNDARY} is present then the corresponding value of from @var{BOUNDARY}
+is copied back in the other end. If @var{BOUNDARY} is not present then the
+following are copied in depending on the type of @var{ARRAY}.
+
+@multitable @columnfractions .15 .80
+@item @emph{Array Type} @tab @emph{Boundary Value}
+@item Numeric @tab 0 of the type and kind of @var{ARRAY}.
+@item Logical @tab @code{.FALSE.}.
+@item Character(@var{len}) @tab @var{len} blanks.
+@end multitable
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = EOSHIFT(ARRAY, SHIFT [, BOUNDARY, DIM])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab May be any type, not scalar.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@item @var{BOUNDARY} @tab Same type as @var{ARRAY}.
+@item @var{DIM} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+Returns an array of same type and rank as the @var{ARRAY} argument.
+
+@item @emph{Example}:
+@smallexample
+program test_eoshift
+ integer, dimension(3,3) :: a
+ a = reshape( (/ 1, 2, 3, 4, 5, 6, 7, 8, 9 /), (/ 3, 3 /))
+ print '(3i3)', a(1,:)
+ print '(3i3)', a(2,:)
+ print '(3i3)', a(3,:)
+ a = EOSHIFT(a, SHIFT=(/1, 2, 1/), BOUNDARY=-5, DIM=2)
+ print *
+ print '(3i3)', a(1,:)
+ print '(3i3)', a(2,:)
+ print '(3i3)', a(3,:)
+end program test_eoshift
+@end smallexample
+@end table
+
+
+
+@node EPSILON
+@section @code{EPSILON} --- Epsilon function
+@fnindex EPSILON
+@cindex model representation, epsilon
+
+@table @asis
+@item @emph{Description}:
+@code{EPSILON(X)} returns the smallest number @var{E} of the same kind
+as @var{X} such that @math{1 + E > 1}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = EPSILON(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of same type as the argument.
+
+@item @emph{Example}:
+@smallexample
+program test_epsilon
+ real :: x = 3.143
+ real(8) :: y = 2.33
+ print *, EPSILON(x)
+ print *, EPSILON(y)
+end program test_epsilon
+@end smallexample
+@end table
+
+
+
+@node ERF
+@section @code{ERF} --- Error function
+@fnindex ERF
+@cindex error function
+
+@table @asis
+@item @emph{Description}:
+@code{ERF(X)} computes the error function of @var{X}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ERF(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL}, of the same kind as
+@var{X} and lies in the range @math{-1 \leq erf (x) \leq 1 }.
+
+@item @emph{Example}:
+@smallexample
+program test_erf
+ real(8) :: x = 0.17_8
+ x = erf(x)
+end program test_erf
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DERF(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node ERFC
+@section @code{ERFC} --- Error function
+@fnindex ERFC
+@cindex error function, complementary
+
+@table @asis
+@item @emph{Description}:
+@code{ERFC(X)} computes the complementary error function of @var{X}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ERFC(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} and of the same kind as @var{X}.
+It lies in the range @math{ 0 \leq erfc (x) \leq 2 }.
+
+@item @emph{Example}:
+@smallexample
+program test_erfc
+ real(8) :: x = 0.17_8
+ x = erfc(x)
+end program test_erfc
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DERFC(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node ERFC_SCALED
+@section @code{ERFC_SCALED} --- Error function
+@fnindex ERFC_SCALED
+@cindex error function, complementary, exponentially-scaled
+
+@table @asis
+@item @emph{Description}:
+@code{ERFC_SCALED(X)} computes the exponentially-scaled complementary
+error function of @var{X}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ERFC_SCALED(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} and of the same kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_erfc_scaled
+ real(8) :: x = 0.17_8
+ x = erfc_scaled(x)
+end program test_erfc_scaled
+@end smallexample
+@end table
+
+
+
+@node ETIME
+@section @code{ETIME} --- Execution time subroutine (or function)
+@fnindex ETIME
+@cindex time, elapsed
+
+@table @asis
+@item @emph{Description}:
+@code{ETIME(VALUES, TIME)} returns the number of seconds of runtime
+since the start of the process's execution in @var{TIME}. @var{VALUES}
+returns the user and system components of this time in @code{VALUES(1)} and
+@code{VALUES(2)} respectively. @var{TIME} is equal to @code{VALUES(1) + VALUES(2)}.
+
+On some systems, the underlying timings are represented using types with
+sufficiently small limits that overflows (wrap around) are possible, such as
+32-bit types. Therefore, the values returned by this intrinsic might be, or
+become, negative, or numerically less than previous values, during a single
+run of the compiled program.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@var{VALUES} and @var{TIME} are @code{INTENT(OUT)} and provide the following:
+
+@multitable @columnfractions .15 .70
+@item @code{VALUES(1)}: @tab User time in seconds.
+@item @code{VALUES(2)}: @tab System time in seconds.
+@item @code{TIME}: @tab Run time since start in seconds.
+@end multitable
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL ETIME(VALUES, TIME)}.
+@item @code{TIME = ETIME(VALUES)}, (not recommended).
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{VALUES}@tab The type shall be @code{REAL(4), DIMENSION(2)}.
+@item @var{TIME}@tab The type shall be @code{REAL(4)}.
+@end multitable
+
+@item @emph{Return value}:
+Elapsed time in seconds since the start of program execution.
+
+@item @emph{Example}:
+@smallexample
+program test_etime
+ integer(8) :: i, j
+ real, dimension(2) :: tarray
+ real :: result
+ call ETIME(tarray, result)
+ print *, result
+ print *, tarray(1)
+ print *, tarray(2)
+ do i=1,100000000 ! Just a delay
+ j = i * i - i
+ end do
+ call ETIME(tarray, result)
+ print *, result
+ print *, tarray(1)
+ print *, tarray(2)
+end program test_etime
+@end smallexample
+
+@item @emph{See also}:
+@ref{CPU_TIME}
+
+@end table
+
+
+
+@node EVENT_QUERY
+@section @code{EVENT_QUERY} --- Query whether a coarray event has occurred
+@fnindex EVENT_QUERY
+@cindex Events, EVENT_QUERY
+
+@table @asis
+@item @emph{Description}:
+@code{EVENT_QUERY} assignes the number of events to @var{COUNT} which have been
+posted to the @var{EVENT} variable and not yet been removed by calling
+@code{EVENT WAIT}. When @var{STAT} is present and the invocation was successful,
+it is assigned the value 0. If it is present and the invocation has failed,
+it is assigned a positive value and @var{COUNT} is assigned the value @math{-1}.
+
+@item @emph{Standard}:
+TS 18508 or later
+
+@item @emph{Class}:
+ subroutine
+
+@item @emph{Syntax}:
+@code{CALL EVENT_QUERY (EVENT, COUNT [, STAT])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{EVENT} @tab (intent(IN)) Scalar of type @code{EVENT_TYPE},
+defined in @code{ISO_FORTRAN_ENV}; shall not be coindexed.
+@item @var{COUNT} @tab (intent(out))Scalar integer with at least the
+precision of default integer.
+@item @var{STAT} @tab (optional) Scalar default-kind integer variable.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program atomic
+ use iso_fortran_env
+ implicit none
+ type(event_type) :: event_value_has_been_set[*]
+ integer :: cnt
+ if (this_image() == 1) then
+ call event_query (event_value_has_been_set, cnt)
+ if (cnt > 0) write(*,*) "Value has been set"
+ elseif (this_image() == 2) then
+ event post (event_value_has_been_set[1])
+ end if
+end program atomic
+@end smallexample
+
+@end table
+
+
+
+@node EXECUTE_COMMAND_LINE
+@section @code{EXECUTE_COMMAND_LINE} --- Execute a shell command
+@fnindex EXECUTE_COMMAND_LINE
+@cindex system, system call
+@cindex command line
+
+@table @asis
+@item @emph{Description}:
+@code{EXECUTE_COMMAND_LINE} runs a shell command, synchronously or
+asynchronously.
+
+The @code{COMMAND} argument is passed to the shell and executed (The
+shell is @code{sh} on Unix systems, and @code{cmd.exe} on Windows.).
+If @code{WAIT} is present and has the value false, the execution of
+the command is asynchronous if the system supports it; otherwise, the
+command is executed synchronously using the C library's @code{system}
+call.
+
+The three last arguments allow the user to get status information. After
+synchronous execution, @code{EXITSTAT} contains the integer exit code of
+the command, as returned by @code{system}. @code{CMDSTAT} is set to zero
+if the command line was executed (whatever its exit status was).
+@code{CMDMSG} is assigned an error message if an error has occurred.
+
+Note that the @code{system} function need not be thread-safe. It is
+the responsibility of the user to ensure that @code{system} is not
+called concurrently.
+
+For asynchronous execution on supported targets, the POSIX
+@code{posix_spawn} or @code{fork} functions are used. Also, a signal
+handler for the @code{SIGCHLD} signal is installed.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL EXECUTE_COMMAND_LINE(COMMAND [, WAIT, EXITSTAT, CMDSTAT, CMDMSG ])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{COMMAND} @tab Shall be a default @code{CHARACTER} scalar.
+@item @var{WAIT} @tab (Optional) Shall be a default @code{LOGICAL} scalar.
+@item @var{EXITSTAT} @tab (Optional) Shall be an @code{INTEGER} of the
+default kind.
+@item @var{CMDSTAT} @tab (Optional) Shall be an @code{INTEGER} of the
+default kind.
+@item @var{CMDMSG} @tab (Optional) Shall be an @code{CHARACTER} scalar of the
+default kind.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test_exec
+ integer :: i
+
+ call execute_command_line ("external_prog.exe", exitstat=i)
+ print *, "Exit status of external_prog.exe was ", i
+
+ call execute_command_line ("reindex_files.exe", wait=.false.)
+ print *, "Now reindexing files in the background"
+
+end program test_exec
+@end smallexample
+
+
+@item @emph{Note}:
+
+Because this intrinsic is implemented in terms of the @code{system}
+function call, its behavior with respect to signaling is processor
+dependent. In particular, on POSIX-compliant systems, the SIGINT and
+SIGQUIT signals will be ignored, and the SIGCHLD will be blocked. As
+such, if the parent process is terminated, the child process might not be
+terminated alongside.
+
+
+@item @emph{See also}:
+@ref{SYSTEM}
+@end table
+
+
+
+@node EXIT
+@section @code{EXIT} --- Exit the program with status.
+@fnindex EXIT
+@cindex program termination
+@cindex terminate program
+
+@table @asis
+@item @emph{Description}:
+@code{EXIT} causes immediate termination of the program with status. If status
+is omitted it returns the canonical @emph{success} for the system. All Fortran
+I/O units are closed.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL EXIT([STATUS])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STATUS} @tab Shall be an @code{INTEGER} of the default kind.
+@end multitable
+
+@item @emph{Return value}:
+@code{STATUS} is passed to the parent process on exit.
+
+@item @emph{Example}:
+@smallexample
+program test_exit
+ integer :: STATUS = 0
+ print *, 'This program is going to exit.'
+ call EXIT(STATUS)
+end program test_exit
+@end smallexample
+
+@item @emph{See also}:
+@ref{ABORT}, @gol
+@ref{KILL}
+@end table
+
+
+
+@node EXP
+@section @code{EXP} --- Exponential function
+@fnindex EXP
+@fnindex DEXP
+@fnindex CEXP
+@fnindex ZEXP
+@fnindex CDEXP
+@cindex exponential function
+@cindex logarithm function, inverse
+
+@table @asis
+@item @emph{Description}:
+@code{EXP(X)} computes the base @math{e} exponential of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = EXP(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or
+@code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_exp
+ real :: x = 1.0
+ x = exp(x)
+end program test_exp
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{EXP(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DEXP(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@item @code{CEXP(X)} @tab @code{COMPLEX(4) X} @tab @code{COMPLEX(4)} @tab Fortran 77 and later
+@item @code{ZEXP(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@item @code{CDEXP(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node EXPONENT
+@section @code{EXPONENT} --- Exponent function
+@fnindex EXPONENT
+@cindex real number, exponent
+@cindex floating point, exponent
+
+@table @asis
+@item @emph{Description}:
+@code{EXPONENT(X)} returns the value of the exponent part of @var{X}. If @var{X}
+is zero the value returned is zero.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = EXPONENT(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type default @code{INTEGER}.
+
+@item @emph{Example}:
+@smallexample
+program test_exponent
+ real :: x = 1.0
+ integer :: i
+ i = exponent(x)
+ print *, i
+ print *, exponent(0.0)
+end program test_exponent
+@end smallexample
+@end table
+
+
+
+@node EXTENDS_TYPE_OF
+@section @code{EXTENDS_TYPE_OF} --- Query dynamic type for extension
+@fnindex EXTENDS_TYPE_OF
+
+@table @asis
+@item @emph{Description}:
+Query dynamic type for extension.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = EXTENDS_TYPE_OF(A, MOLD)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be an object of extensible declared type or
+unlimited polymorphic.
+@item @var{MOLD} @tab Shall be an object of extensible declared type or
+unlimited polymorphic.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a scalar of type default logical. It is true if and only if
+the dynamic type of A is an extension type of the dynamic type of MOLD.
+
+
+@item @emph{See also}:
+@ref{SAME_TYPE_AS}
+@end table
+
+
+
+@node FDATE
+@section @code{FDATE} --- Get the current time as a string
+@fnindex FDATE
+@cindex time, current
+@cindex current time
+@cindex date, current
+@cindex current date
+
+@table @asis
+@item @emph{Description}:
+@code{FDATE(DATE)} returns the current date (using the same format as
+@ref{CTIME}) in @var{DATE}. It is equivalent to @code{CALL CTIME(DATE,
+TIME())}.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL FDATE(DATE)}.
+@item @code{DATE = FDATE()}.
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{DATE}@tab The type shall be of type @code{CHARACTER} of the
+default kind. It is an @code{INTENT(OUT)} argument. If the length of
+this variable is too short for the date and time string to fit
+completely, it will be blank on procedure return.
+@end multitable
+
+@item @emph{Return value}:
+The current date and time as a string.
+
+@item @emph{Example}:
+@smallexample
+program test_fdate
+ integer(8) :: i, j
+ character(len=30) :: date
+ call fdate(date)
+ print *, 'Program started on ', date
+ do i = 1, 100000000 ! Just a delay
+ j = i * i - i
+ end do
+ call fdate(date)
+ print *, 'Program ended on ', date
+end program test_fdate
+@end smallexample
+
+@item @emph{See also}:
+@ref{DATE_AND_TIME}, @gol
+@ref{CTIME}
+@end table
+
+
+@node FGET
+@section @code{FGET} --- Read a single character in stream mode from stdin
+@fnindex FGET
+@cindex read character, stream mode
+@cindex stream mode, read character
+@cindex file operation, read character
+
+@table @asis
+@item @emph{Description}:
+Read a single character in stream mode from stdin by bypassing normal
+formatted output. Stream I/O should not be mixed with normal record-oriented
+(formatted or unformatted) I/O on the same unit; the results are unpredictable.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+Note that the @code{FGET} intrinsic is provided for backwards compatibility with
+@command{g77}. GNU Fortran provides the Fortran 2003 Stream facility.
+Programmers should consider the use of new stream IO feature in new code
+for future portability. See also @ref{Fortran 2003 status}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL FGET(C [, STATUS])}
+@item @code{STATUS = FGET(C)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{C} @tab The type shall be @code{CHARACTER} and of default
+kind.
+@item @var{STATUS} @tab (Optional) status flag of type @code{INTEGER}.
+Returns 0 on success, -1 on end-of-file, and a system specific positive
+error code otherwise.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_fget
+ INTEGER, PARAMETER :: strlen = 100
+ INTEGER :: status, i = 1
+ CHARACTER(len=strlen) :: str = ""
+
+ WRITE (*,*) 'Enter text:'
+ DO
+ CALL fget(str(i:i), status)
+ if (status /= 0 .OR. i > strlen) exit
+ i = i + 1
+ END DO
+ WRITE (*,*) TRIM(str)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{FGETC}, @gol
+@ref{FPUT}, @gol
+@ref{FPUTC}
+@end table
+
+
+
+@node FGETC
+@section @code{FGETC} --- Read a single character in stream mode
+@fnindex FGETC
+@cindex read character, stream mode
+@cindex stream mode, read character
+@cindex file operation, read character
+
+@table @asis
+@item @emph{Description}:
+Read a single character in stream mode by bypassing normal formatted output.
+Stream I/O should not be mixed with normal record-oriented (formatted or
+unformatted) I/O on the same unit; the results are unpredictable.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+Note that the @code{FGET} intrinsic is provided for backwards compatibility
+with @command{g77}. GNU Fortran provides the Fortran 2003 Stream facility.
+Programmers should consider the use of new stream IO feature in new code
+for future portability. See also @ref{Fortran 2003 status}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL FGETC(UNIT, C [, STATUS])}
+@item @code{STATUS = FGETC(UNIT, C)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{UNIT} @tab The type shall be @code{INTEGER}.
+@item @var{C} @tab The type shall be @code{CHARACTER} and of default
+kind.
+@item @var{STATUS} @tab (Optional) status flag of type @code{INTEGER}.
+Returns 0 on success, -1 on end-of-file and a system specific positive
+error code otherwise.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_fgetc
+ INTEGER :: fd = 42, status
+ CHARACTER :: c
+
+ OPEN(UNIT=fd, FILE="/etc/passwd", ACTION="READ", STATUS = "OLD")
+ DO
+ CALL fgetc(fd, c, status)
+ IF (status /= 0) EXIT
+ call fput(c)
+ END DO
+ CLOSE(UNIT=fd)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{FGET}, @gol
+@ref{FPUT}, @gol
+@ref{FPUTC}
+@end table
+
+@node FINDLOC
+@section @code{FINDLOC} --- Search an array for a value
+@fnindex FINDLOC
+@cindex findloc
+
+@table @asis
+@item @emph{Description}:
+Determines the location of the element in the array with the value
+given in the @var{VALUE} argument, or, if the @var{DIM} argument is
+supplied, determines the locations of the elements equal to the
+@var{VALUE} argument element along each
+row of the array in the @var{DIM} direction. If @var{MASK} is
+present, only the elements for which @var{MASK} is @code{.TRUE.} are
+considered. If more than one element in the array has the value
+@var{VALUE}, the location returned is that of the first such element
+in array element order if the @var{BACK} is not present or if it is
+@code{.FALSE.}. If @var{BACK} is true, the location returned is that
+of the last such element. If the array has zero size, or all of the
+elements of @var{MASK} are @code{.FALSE.}, then the result is an array
+of zeroes. Similarly, if @var{DIM} is supplied and all of the
+elements of @var{MASK} along a given row are zero, the result value
+for that row is zero.
+
+@item @emph{Standard}:
+Fortran 2008 and later.
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = FINDLOC(ARRAY, VALUE, DIM [, MASK] [,KIND] [,BACK])}
+@item @code{RESULT = FINDLOC(ARRAY, VALUE, [, MASK] [,KIND] [,BACK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of intrinsic type.
+@item @var{VALUE} @tab A scalar of intrinsic type which is in type
+conformance with @var{ARRAY}.
+@item @var{DIM} @tab (Optional) Shall be a scalar of type
+@code{INTEGER}, with a value between one and the rank of @var{ARRAY},
+inclusive. It may not be an optional dummy argument.
+@item @var{MASK} @tab (Optional) Shall be of type @code{LOGICAL},
+and conformable with @var{ARRAY}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@item @var{BACK} @tab (Optional) A scalar of type @code{LOGICAL}.
+@end multitable
+
+@item @emph{Return value}:
+If @var{DIM} is absent, the result is a rank-one array with a length
+equal to the rank of @var{ARRAY}. If @var{DIM} is present, the result
+is an array with a rank one less than the rank of @var{ARRAY}, and a
+size corresponding to the size of @var{ARRAY} with the @var{DIM}
+dimension removed. If @var{DIM} is present and @var{ARRAY} has a rank
+of one, the result is a scalar. If the optional argument @var{KIND}
+is present, the result is an integer of kind @var{KIND}, otherwise it
+is of default kind.
+
+@item @emph{See also}:
+@ref{MAXLOC}, @gol
+@ref{MINLOC}
+
+@end table
+
+@node FLOOR
+@section @code{FLOOR} --- Integer floor function
+@fnindex FLOOR
+@cindex floor
+@cindex rounding, floor
+
+@table @asis
+@item @emph{Description}:
+@code{FLOOR(A)} returns the greatest integer less than or equal to @var{X}.
+
+@item @emph{Standard}:
+Fortran 95 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = FLOOR(A [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab The type shall be @code{REAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER(KIND)} if @var{KIND} is present
+and of default-kind @code{INTEGER} otherwise.
+
+@item @emph{Example}:
+@smallexample
+program test_floor
+ real :: x = 63.29
+ real :: y = -63.59
+ print *, floor(x) ! returns 63
+ print *, floor(y) ! returns -64
+end program test_floor
+@end smallexample
+
+@item @emph{See also}:
+@ref{CEILING}, @gol
+@ref{NINT}
+@end table
+
+
+
+@node FLUSH
+@section @code{FLUSH} --- Flush I/O unit(s)
+@fnindex FLUSH
+@cindex file operation, flush
+
+@table @asis
+@item @emph{Description}:
+Flushes Fortran unit(s) currently open for output. Without the optional
+argument, all units are flushed, otherwise just the unit specified.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL FLUSH(UNIT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{UNIT} @tab (Optional) The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Note}:
+Beginning with the Fortran 2003 standard, there is a @code{FLUSH}
+statement that should be preferred over the @code{FLUSH} intrinsic.
+
+The @code{FLUSH} intrinsic and the Fortran 2003 @code{FLUSH} statement
+have identical effect: they flush the runtime library's I/O buffer so
+that the data becomes visible to other processes. This does not guarantee
+that the data is committed to disk.
+
+On POSIX systems, you can request that all data is transferred to the
+storage device by calling the @code{fsync} function, with the POSIX file
+descriptor of the I/O unit as argument (retrieved with GNU intrinsic
+@code{FNUM}). The following example shows how:
+
+@smallexample
+ ! Declare the interface for POSIX fsync function
+ interface
+ function fsync (fd) bind(c,name="fsync")
+ use iso_c_binding, only: c_int
+ integer(c_int), value :: fd
+ integer(c_int) :: fsync
+ end function fsync
+ end interface
+
+ ! Variable declaration
+ integer :: ret
+
+ ! Opening unit 10
+ open (10,file="foo")
+
+ ! ...
+ ! Perform I/O on unit 10
+ ! ...
+
+ ! Flush and sync
+ flush(10)
+ ret = fsync(fnum(10))
+
+ ! Handle possible error
+ if (ret /= 0) stop "Error calling FSYNC"
+@end smallexample
+
+@end table
+
+
+
+@node FNUM
+@section @code{FNUM} --- File number function
+@fnindex FNUM
+@cindex file operation, file number
+
+@table @asis
+@item @emph{Description}:
+@code{FNUM(UNIT)} returns the POSIX file descriptor number corresponding to the
+open Fortran I/O unit @code{UNIT}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = FNUM(UNIT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{UNIT} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER}
+
+@item @emph{Example}:
+@smallexample
+program test_fnum
+ integer :: i
+ open (unit=10, status = "scratch")
+ i = fnum(10)
+ print *, i
+ close (10)
+end program test_fnum
+@end smallexample
+@end table
+
+
+
+@node FPUT
+@section @code{FPUT} --- Write a single character in stream mode to stdout
+@fnindex FPUT
+@cindex write character, stream mode
+@cindex stream mode, write character
+@cindex file operation, write character
+
+@table @asis
+@item @emph{Description}:
+Write a single character in stream mode to stdout by bypassing normal
+formatted output. Stream I/O should not be mixed with normal record-oriented
+(formatted or unformatted) I/O on the same unit; the results are unpredictable.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+Note that the @code{FGET} intrinsic is provided for backwards compatibility with
+@command{g77}. GNU Fortran provides the Fortran 2003 Stream facility.
+Programmers should consider the use of new stream IO feature in new code
+for future portability. See also @ref{Fortran 2003 status}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL FPUT(C [, STATUS])}
+@item @code{STATUS = FPUT(C)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{C} @tab The type shall be @code{CHARACTER} and of default
+kind.
+@item @var{STATUS} @tab (Optional) status flag of type @code{INTEGER}.
+Returns 0 on success, -1 on end-of-file and a system specific positive
+error code otherwise.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_fput
+ CHARACTER(len=10) :: str = "gfortran"
+ INTEGER :: i
+ DO i = 1, len_trim(str)
+ CALL fput(str(i:i))
+ END DO
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{FPUTC}, @gol
+@ref{FGET}, @gol
+@ref{FGETC}
+@end table
+
+
+
+@node FPUTC
+@section @code{FPUTC} --- Write a single character in stream mode
+@fnindex FPUTC
+@cindex write character, stream mode
+@cindex stream mode, write character
+@cindex file operation, write character
+
+@table @asis
+@item @emph{Description}:
+Write a single character in stream mode by bypassing normal formatted
+output. Stream I/O should not be mixed with normal record-oriented
+(formatted or unformatted) I/O on the same unit; the results are unpredictable.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+Note that the @code{FGET} intrinsic is provided for backwards compatibility with
+@command{g77}. GNU Fortran provides the Fortran 2003 Stream facility.
+Programmers should consider the use of new stream IO feature in new code
+for future portability. See also @ref{Fortran 2003 status}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL FPUTC(UNIT, C [, STATUS])}
+@item @code{STATUS = FPUTC(UNIT, C)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{UNIT} @tab The type shall be @code{INTEGER}.
+@item @var{C} @tab The type shall be @code{CHARACTER} and of default
+kind.
+@item @var{STATUS} @tab (Optional) status flag of type @code{INTEGER}.
+Returns 0 on success, -1 on end-of-file and a system specific positive
+error code otherwise.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_fputc
+ CHARACTER(len=10) :: str = "gfortran"
+ INTEGER :: fd = 42, i
+
+ OPEN(UNIT = fd, FILE = "out", ACTION = "WRITE", STATUS="NEW")
+ DO i = 1, len_trim(str)
+ CALL fputc(fd, str(i:i))
+ END DO
+ CLOSE(fd)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{FPUT}, @gol
+@ref{FGET}, @gol
+@ref{FGETC}
+@end table
+
+
+
+@node FRACTION
+@section @code{FRACTION} --- Fractional part of the model representation
+@fnindex FRACTION
+@cindex real number, fraction
+@cindex floating point, fraction
+
+@table @asis
+@item @emph{Description}:
+@code{FRACTION(X)} returns the fractional part of the model
+representation of @code{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{Y = FRACTION(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type of the argument shall be a @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as the argument.
+The fractional part of the model representation of @code{X} is returned;
+it is @code{X * RADIX(X)**(-EXPONENT(X))}.
+
+@item @emph{Example}:
+@smallexample
+program test_fraction
+ real :: x
+ x = 178.1387e-4
+ print *, fraction(x), x * radix(x)**(-exponent(x))
+end program test_fraction
+@end smallexample
+
+@end table
+
+
+
+@node FREE
+@section @code{FREE} --- Frees memory
+@fnindex FREE
+@cindex pointer, cray
+
+@table @asis
+@item @emph{Description}:
+Frees memory previously allocated by @code{MALLOC}. The @code{FREE}
+intrinsic is an extension intended to be used with Cray pointers, and is
+provided in GNU Fortran to allow user to compile legacy code. For
+new code using Fortran 95 pointers, the memory de-allocation intrinsic is
+@code{DEALLOCATE}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL FREE(PTR)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{PTR} @tab The type shall be @code{INTEGER}. It represents the
+location of the memory that should be de-allocated.
+@end multitable
+
+@item @emph{Return value}:
+None
+
+@item @emph{Example}:
+See @code{MALLOC} for an example.
+
+@item @emph{See also}:
+@ref{MALLOC}
+@end table
+
+
+
+@node FSEEK
+@section @code{FSEEK} --- Low level file positioning subroutine
+@fnindex FSEEK
+@cindex file operation, seek
+@cindex file operation, position
+
+@table @asis
+@item @emph{Description}:
+Moves @var{UNIT} to the specified @var{OFFSET}. If @var{WHENCE}
+is set to 0, the @var{OFFSET} is taken as an absolute value @code{SEEK_SET},
+if set to 1, @var{OFFSET} is taken to be relative to the current position
+@code{SEEK_CUR}, and if set to 2 relative to the end of the file @code{SEEK_END}.
+On error, @var{STATUS} is set to a nonzero value. If @var{STATUS} the seek
+fails silently.
+
+This intrinsic routine is not fully backwards compatible with @command{g77}.
+In @command{g77}, the @code{FSEEK} takes a statement label instead of a
+@var{STATUS} variable. If FSEEK is used in old code, change
+@smallexample
+ CALL FSEEK(UNIT, OFFSET, WHENCE, *label)
+@end smallexample
+to
+@smallexample
+ INTEGER :: status
+ CALL FSEEK(UNIT, OFFSET, WHENCE, status)
+ IF (status /= 0) GOTO label
+@end smallexample
+
+Please note that GNU Fortran provides the Fortran 2003 Stream facility.
+Programmers should consider the use of new stream IO feature in new code
+for future portability. See also @ref{Fortran 2003 status}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL FSEEK(UNIT, OFFSET, WHENCE[, STATUS])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{UNIT} @tab Shall be a scalar of type @code{INTEGER}.
+@item @var{OFFSET} @tab Shall be a scalar of type @code{INTEGER}.
+@item @var{WHENCE} @tab Shall be a scalar of type @code{INTEGER}.
+Its value shall be either 0, 1 or 2.
+@item @var{STATUS} @tab (Optional) shall be a scalar of type
+@code{INTEGER(4)}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_fseek
+ INTEGER, PARAMETER :: SEEK_SET = 0, SEEK_CUR = 1, SEEK_END = 2
+ INTEGER :: fd, offset, ierr
+
+ ierr = 0
+ offset = 5
+ fd = 10
+
+ OPEN(UNIT=fd, FILE="fseek.test")
+ CALL FSEEK(fd, offset, SEEK_SET, ierr) ! move to OFFSET
+ print *, FTELL(fd), ierr
+
+ CALL FSEEK(fd, 0, SEEK_END, ierr) ! move to end
+ print *, FTELL(fd), ierr
+
+ CALL FSEEK(fd, 0, SEEK_SET, ierr) ! move to beginning
+ print *, FTELL(fd), ierr
+
+ CLOSE(UNIT=fd)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{FTELL}
+@end table
+
+
+
+@node FSTAT
+@section @code{FSTAT} --- Get file status
+@fnindex FSTAT
+@cindex file system, file status
+
+@table @asis
+@item @emph{Description}:
+@code{FSTAT} is identical to @ref{STAT}, except that information about an
+already opened file is obtained.
+
+The elements in @code{VALUES} are the same as described by @ref{STAT}.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL FSTAT(UNIT, VALUES [, STATUS])}
+@item @code{STATUS = FSTAT(UNIT, VALUES)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{UNIT} @tab An open I/O unit number of type @code{INTEGER}.
+@item @var{VALUES} @tab The type shall be @code{INTEGER(4), DIMENSION(13)}.
+@item @var{STATUS} @tab (Optional) status flag of type @code{INTEGER(4)}. Returns 0
+on success and a system specific error code otherwise.
+@end multitable
+
+@item @emph{Example}:
+See @ref{STAT} for an example.
+
+@item @emph{See also}:
+To stat a link: @gol
+@ref{LSTAT} @gol
+To stat a file: @gol
+@ref{STAT}
+@end table
+
+
+
+@node FTELL
+@section @code{FTELL} --- Current stream position
+@fnindex FTELL
+@cindex file operation, position
+
+@table @asis
+@item @emph{Description}:
+Retrieves the current position within an open file.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL FTELL(UNIT, OFFSET)}
+@item @code{OFFSET = FTELL(UNIT)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{OFFSET} @tab Shall of type @code{INTEGER}.
+@item @var{UNIT} @tab Shall of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+In either syntax, @var{OFFSET} is set to the current offset of unit
+number @var{UNIT}, or to @math{-1} if the unit is not currently open.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_ftell
+ INTEGER :: i
+ OPEN(10, FILE="temp.dat")
+ CALL ftell(10,i)
+ WRITE(*,*) i
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{FSEEK}
+@end table
+
+
+
+@node GAMMA
+@section @code{GAMMA} --- Gamma function
+@fnindex GAMMA
+@fnindex DGAMMA
+@cindex Gamma function
+@cindex Factorial function
+
+@table @asis
+@item @emph{Description}:
+@code{GAMMA(X)} computes Gamma (@math{\Gamma}) of @var{X}. For positive,
+integer values of @var{X} the Gamma function simplifies to the factorial
+function @math{\Gamma(x)=(x-1)!}.
+
+@tex
+$$
+\Gamma(x) = \int_0^\infty t^{x-1}{\rm e}^{-t}\,{\rm d}t
+$$
+@end tex
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{X = GAMMA(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL} and neither zero
+nor a negative integer.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} of the same kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_gamma
+ real :: x = 1.0
+ x = gamma(x) ! returns 1.0
+end program test_gamma
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DGAMMA(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Logarithm of the Gamma function: @gol
+@ref{LOG_GAMMA}
+@end table
+
+
+
+@node GERROR
+@section @code{GERROR} --- Get last system error message
+@fnindex GERROR
+@cindex system, error handling
+
+@table @asis
+@item @emph{Description}:
+Returns the system error message corresponding to the last system error.
+This resembles the functionality of @code{strerror(3)} in C.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL GERROR(RESULT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{RESULT} @tab Shall be of type @code{CHARACTER} and of default kind.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_gerror
+ CHARACTER(len=100) :: msg
+ CALL gerror(msg)
+ WRITE(*,*) msg
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{IERRNO}, @gol
+@ref{PERROR}
+@end table
+
+
+
+@node GETARG
+@section @code{GETARG} --- Get command line arguments
+@fnindex GETARG
+@cindex command-line arguments
+@cindex arguments, to program
+
+@table @asis
+@item @emph{Description}:
+Retrieve the @var{POS}-th argument that was passed on the
+command line when the containing program was invoked.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. In new code, programmers should consider the use of
+the @ref{GET_COMMAND_ARGUMENT} intrinsic defined by the Fortran 2003
+standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL GETARG(POS, VALUE)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{POS} @tab Shall be of type @code{INTEGER} and not wider than
+the default integer kind; @math{@var{POS} \geq 0}
+@item @var{VALUE} @tab Shall be of type @code{CHARACTER} and of default
+kind.
+@end multitable
+
+@item @emph{Return value}:
+After @code{GETARG} returns, the @var{VALUE} argument holds the
+@var{POS}th command line argument. If @var{VALUE} cannot hold the
+argument, it is truncated to fit the length of @var{VALUE}. If there are
+less than @var{POS} arguments specified at the command line, @var{VALUE}
+will be filled with blanks. If @math{@var{POS} = 0}, @var{VALUE} is set
+to the name of the program (on systems that support this feature).
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_getarg
+ INTEGER :: i
+ CHARACTER(len=32) :: arg
+
+ DO i = 1, iargc()
+ CALL getarg(i, arg)
+ WRITE (*,*) arg
+ END DO
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+GNU Fortran 77 compatibility function: @gol
+@ref{IARGC} @gol
+Fortran 2003 functions and subroutines: @gol
+@ref{GET_COMMAND}, @gol
+@ref{GET_COMMAND_ARGUMENT}, @gol
+@ref{COMMAND_ARGUMENT_COUNT}
+@end table
+
+
+
+@node GET_COMMAND
+@section @code{GET_COMMAND} --- Get the entire command line
+@fnindex GET_COMMAND
+@cindex command-line arguments
+@cindex arguments, to program
+
+@table @asis
+@item @emph{Description}:
+Retrieve the entire command line that was used to invoke the program.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL GET_COMMAND([COMMAND, LENGTH, STATUS])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{COMMAND} @tab (Optional) shall be of type @code{CHARACTER} and
+of default kind.
+@item @var{LENGTH} @tab (Optional) Shall be of type @code{INTEGER} and of
+default kind.
+@item @var{STATUS} @tab (Optional) Shall be of type @code{INTEGER} and of
+default kind.
+@end multitable
+
+@item @emph{Return value}:
+If @var{COMMAND} is present, stores the entire command line that was used
+to invoke the program in @var{COMMAND}. If @var{LENGTH} is present, it is
+assigned the length of the command line. If @var{STATUS} is present, it
+is assigned 0 upon success of the command, -1 if @var{COMMAND} is too
+short to store the command line, or a positive value in case of an error.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_get_command
+ CHARACTER(len=255) :: cmd
+ CALL get_command(cmd)
+ WRITE (*,*) TRIM(cmd)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{GET_COMMAND_ARGUMENT}, @gol
+@ref{COMMAND_ARGUMENT_COUNT}
+@end table
+
+
+
+@node GET_COMMAND_ARGUMENT
+@section @code{GET_COMMAND_ARGUMENT} --- Get command line arguments
+@fnindex GET_COMMAND_ARGUMENT
+@cindex command-line arguments
+@cindex arguments, to program
+
+@table @asis
+@item @emph{Description}:
+Retrieve the @var{NUMBER}-th argument that was passed on the
+command line when the containing program was invoked.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL GET_COMMAND_ARGUMENT(NUMBER [, VALUE, LENGTH, STATUS])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NUMBER} @tab Shall be a scalar of type @code{INTEGER} and of
+default kind, @math{@var{NUMBER} \geq 0}
+@item @var{VALUE} @tab (Optional) Shall be a scalar of type @code{CHARACTER}
+and of default kind.
+@item @var{LENGTH} @tab (Optional) Shall be a scalar of type @code{INTEGER}
+and of default kind.
+@item @var{STATUS} @tab (Optional) Shall be a scalar of type @code{INTEGER}
+and of default kind.
+@end multitable
+
+@item @emph{Return value}:
+After @code{GET_COMMAND_ARGUMENT} returns, the @var{VALUE} argument holds the
+@var{NUMBER}-th command line argument. If @var{VALUE} cannot hold the argument, it is
+truncated to fit the length of @var{VALUE}. If there are less than @var{NUMBER}
+arguments specified at the command line, @var{VALUE} will be filled with blanks.
+If @math{@var{NUMBER} = 0}, @var{VALUE} is set to the name of the program (on
+systems that support this feature). The @var{LENGTH} argument contains the
+length of the @var{NUMBER}-th command line argument. If the argument retrieval
+fails, @var{STATUS} is a positive number; if @var{VALUE} contains a truncated
+command line argument, @var{STATUS} is -1; and otherwise the @var{STATUS} is
+zero.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_get_command_argument
+ INTEGER :: i
+ CHARACTER(len=32) :: arg
+
+ i = 0
+ DO
+ CALL get_command_argument(i, arg)
+ IF (LEN_TRIM(arg) == 0) EXIT
+
+ WRITE (*,*) TRIM(arg)
+ i = i+1
+ END DO
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{GET_COMMAND}, @gol
+@ref{COMMAND_ARGUMENT_COUNT}
+@end table
+
+
+
+@node GETCWD
+@section @code{GETCWD} --- Get current working directory
+@fnindex GETCWD
+@cindex system, working directory
+
+@table @asis
+@item @emph{Description}:
+Get current working directory.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL GETCWD(C [, STATUS])}
+@item @code{STATUS = GETCWD(C)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{C} @tab The type shall be @code{CHARACTER} and of default kind.
+@item @var{STATUS} @tab (Optional) status flag. Returns 0 on success,
+a system specific and nonzero error code otherwise.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_getcwd
+ CHARACTER(len=255) :: cwd
+ CALL getcwd(cwd)
+ WRITE(*,*) TRIM(cwd)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{CHDIR}
+@end table
+
+
+
+@node GETENV
+@section @code{GETENV} --- Get an environmental variable
+@fnindex GETENV
+@cindex environment variable
+
+@table @asis
+@item @emph{Description}:
+Get the @var{VALUE} of the environmental variable @var{NAME}.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. In new code, programmers should consider the use of
+the @ref{GET_ENVIRONMENT_VARIABLE} intrinsic defined by the Fortran
+2003 standard.
+
+Note that @code{GETENV} need not be thread-safe. It is the
+responsibility of the user to ensure that the environment is not being
+updated concurrently with a call to the @code{GETENV} intrinsic.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL GETENV(NAME, VALUE)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NAME} @tab Shall be of type @code{CHARACTER} and of default kind.
+@item @var{VALUE} @tab Shall be of type @code{CHARACTER} and of default kind.
+@end multitable
+
+@item @emph{Return value}:
+Stores the value of @var{NAME} in @var{VALUE}. If @var{VALUE} is
+not large enough to hold the data, it is truncated. If @var{NAME}
+is not set, @var{VALUE} will be filled with blanks.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_getenv
+ CHARACTER(len=255) :: homedir
+ CALL getenv("HOME", homedir)
+ WRITE (*,*) TRIM(homedir)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{GET_ENVIRONMENT_VARIABLE}
+@end table
+
+
+
+@node GET_ENVIRONMENT_VARIABLE
+@section @code{GET_ENVIRONMENT_VARIABLE} --- Get an environmental variable
+@fnindex GET_ENVIRONMENT_VARIABLE
+@cindex environment variable
+
+@table @asis
+@item @emph{Description}:
+Get the @var{VALUE} of the environmental variable @var{NAME}.
+
+Note that @code{GET_ENVIRONMENT_VARIABLE} need not be thread-safe. It
+is the responsibility of the user to ensure that the environment is
+not being updated concurrently with a call to the
+@code{GET_ENVIRONMENT_VARIABLE} intrinsic.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL GET_ENVIRONMENT_VARIABLE(NAME[, VALUE, LENGTH, STATUS, TRIM_NAME)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NAME} @tab Shall be a scalar of type @code{CHARACTER}
+and of default kind.
+@item @var{VALUE} @tab (Optional) Shall be a scalar of type @code{CHARACTER}
+and of default kind.
+@item @var{LENGTH} @tab (Optional) Shall be a scalar of type @code{INTEGER}
+and of default kind.
+@item @var{STATUS} @tab (Optional) Shall be a scalar of type @code{INTEGER}
+and of default kind.
+@item @var{TRIM_NAME} @tab (Optional) Shall be a scalar of type @code{LOGICAL}
+and of default kind.
+@end multitable
+
+@item @emph{Return value}:
+Stores the value of @var{NAME} in @var{VALUE}. If @var{VALUE} is
+not large enough to hold the data, it is truncated. If @var{NAME}
+is not set, @var{VALUE} will be filled with blanks. Argument @var{LENGTH}
+contains the length needed for storing the environment variable @var{NAME}
+or zero if it is not present. @var{STATUS} is -1 if @var{VALUE} is present
+but too short for the environment variable; it is 1 if the environment
+variable does not exist and 2 if the processor does not support environment
+variables; in all other cases @var{STATUS} is zero. If @var{TRIM_NAME} is
+present with the value @code{.FALSE.}, the trailing blanks in @var{NAME}
+are significant; otherwise they are not part of the environment variable
+name.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_getenv
+ CHARACTER(len=255) :: homedir
+ CALL get_environment_variable("HOME", homedir)
+ WRITE (*,*) TRIM(homedir)
+END PROGRAM
+@end smallexample
+@end table
+
+
+
+@node GETGID
+@section @code{GETGID} --- Group ID function
+@fnindex GETGID
+@cindex system, group ID
+
+@table @asis
+@item @emph{Description}:
+Returns the numerical group ID of the current process.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = GETGID()}
+
+@item @emph{Return value}:
+The return value of @code{GETGID} is an @code{INTEGER} of the default
+kind.
+
+
+@item @emph{Example}:
+See @code{GETPID} for an example.
+
+@item @emph{See also}:
+@ref{GETPID}, @gol
+@ref{GETUID}
+@end table
+
+
+
+@node GETLOG
+@section @code{GETLOG} --- Get login name
+@fnindex GETLOG
+@cindex system, login name
+@cindex login name
+
+@table @asis
+@item @emph{Description}:
+Gets the username under which the program is running.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL GETLOG(C)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{C} @tab Shall be of type @code{CHARACTER} and of default kind.
+@end multitable
+
+@item @emph{Return value}:
+Stores the current user name in @var{C}. (On systems where POSIX
+functions @code{geteuid} and @code{getpwuid} are not available, and
+the @code{getlogin} function is not implemented either, this will
+return a blank string.)
+
+@item @emph{Example}:
+@smallexample
+PROGRAM TEST_GETLOG
+ CHARACTER(32) :: login
+ CALL GETLOG(login)
+ WRITE(*,*) login
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{GETUID}
+@end table
+
+
+
+@node GETPID
+@section @code{GETPID} --- Process ID function
+@fnindex GETPID
+@cindex system, process ID
+@cindex process ID
+
+@table @asis
+@item @emph{Description}:
+Returns the numerical process identifier of the current process.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = GETPID()}
+
+@item @emph{Return value}:
+The return value of @code{GETPID} is an @code{INTEGER} of the default
+kind.
+
+
+@item @emph{Example}:
+@smallexample
+program info
+ print *, "The current process ID is ", getpid()
+ print *, "Your numerical user ID is ", getuid()
+ print *, "Your numerical group ID is ", getgid()
+end program info
+@end smallexample
+
+@item @emph{See also}:
+@ref{GETGID}, @gol
+@ref{GETUID}
+@end table
+
+
+
+@node GETUID
+@section @code{GETUID} --- User ID function
+@fnindex GETUID
+@cindex system, user ID
+@cindex user id
+
+@table @asis
+@item @emph{Description}:
+Returns the numerical user ID of the current process.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = GETUID()}
+
+@item @emph{Return value}:
+The return value of @code{GETUID} is an @code{INTEGER} of the default
+kind.
+
+
+@item @emph{Example}:
+See @code{GETPID} for an example.
+
+@item @emph{See also}:
+@ref{GETPID}, @gol
+@ref{GETLOG}
+@end table
+
+
+
+@node GMTIME
+@section @code{GMTIME} --- Convert time to GMT info
+@fnindex GMTIME
+@cindex time, conversion to GMT info
+
+@table @asis
+@item @emph{Description}:
+Given a system time value @var{TIME} (as provided by the @ref{TIME}
+intrinsic), fills @var{VALUES} with values extracted from it appropriate
+to the UTC time zone (Universal Coordinated Time, also known in some
+countries as GMT, Greenwich Mean Time), using @code{gmtime(3)}.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. In new code, programmers should consider the use of
+the @ref{DATE_AND_TIME} intrinsic defined by the Fortran 95
+standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL GMTIME(TIME, VALUES)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{TIME} @tab An @code{INTEGER} scalar expression
+corresponding to a system time, with @code{INTENT(IN)}.
+@item @var{VALUES} @tab A default @code{INTEGER} array with 9 elements,
+with @code{INTENT(OUT)}.
+@end multitable
+
+@item @emph{Return value}:
+The elements of @var{VALUES} are assigned as follows:
+@enumerate
+@item Seconds after the minute, range 0--59 or 0--61 to allow for leap
+seconds
+@item Minutes after the hour, range 0--59
+@item Hours past midnight, range 0--23
+@item Day of month, range 1--31
+@item Number of months since January, range 0--11
+@item Years since 1900
+@item Number of days since Sunday, range 0--6
+@item Days since January 1, range 0--365
+@item Daylight savings indicator: positive if daylight savings is in
+effect, zero if not, and negative if the information is not available.
+@end enumerate
+
+@item @emph{See also}:
+@ref{DATE_AND_TIME}, @gol
+@ref{CTIME}, @gol
+@ref{LTIME}, @gol
+@ref{TIME}, @gol
+@ref{TIME8}
+@end table
+
+
+
+@node HOSTNM
+@section @code{HOSTNM} --- Get system host name
+@fnindex HOSTNM
+@cindex system, host name
+
+@table @asis
+@item @emph{Description}:
+Retrieves the host name of the system on which the program is running.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL HOSTNM(C [, STATUS])}
+@item @code{STATUS = HOSTNM(NAME)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{C} @tab Shall of type @code{CHARACTER} and of default kind.
+@item @var{STATUS} @tab (Optional) status flag of type @code{INTEGER}.
+Returns 0 on success, or a system specific error code otherwise.
+@end multitable
+
+@item @emph{Return value}:
+In either syntax, @var{NAME} is set to the current hostname if it can
+be obtained, or to a blank string otherwise.
+
+@end table
+
+
+
+@node HUGE
+@section @code{HUGE} --- Largest number of a kind
+@fnindex HUGE
+@cindex limits, largest number
+@cindex model representation, largest number
+
+@table @asis
+@item @emph{Description}:
+@code{HUGE(X)} returns the largest number that is not an infinity in
+the model of the type of @code{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = HUGE(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL} or @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}
+
+@item @emph{Example}:
+@smallexample
+program test_huge_tiny
+ print *, huge(0), huge(0.0), huge(0.0d0)
+ print *, tiny(0.0), tiny(0.0d0)
+end program test_huge_tiny
+@end smallexample
+@end table
+
+
+
+@node HYPOT
+@section @code{HYPOT} --- Euclidean distance function
+@fnindex HYPOT
+@cindex Euclidean distance
+
+@table @asis
+@item @emph{Description}:
+@code{HYPOT(X,Y)} is the Euclidean distance function. It is equal to
+@math{\sqrt{X^2 + Y^2}}, without undue underflow or overflow.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = HYPOT(X, Y)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@item @var{Y} @tab The type and kind type parameter shall be the same as
+@var{X}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has the same type and kind type parameter as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_hypot
+ real(4) :: x = 1.e0_4, y = 0.5e0_4
+ x = hypot(x,y)
+end program test_hypot
+@end smallexample
+@end table
+
+
+
+@node IACHAR
+@section @code{IACHAR} --- Code in @acronym{ASCII} collating sequence
+@fnindex IACHAR
+@cindex @acronym{ASCII} collating sequence
+@cindex collating sequence, @acronym{ASCII}
+@cindex conversion, to integer
+
+@table @asis
+@item @emph{Description}:
+@code{IACHAR(C)} returns the code for the @acronym{ASCII} character
+in the first character position of @code{C}.
+
+@item @emph{Standard}:
+Fortran 95 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IACHAR(C [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{C} @tab Shall be a scalar @code{CHARACTER}, with @code{INTENT(IN)}
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+
+@item @emph{Example}:
+@smallexample
+program test_iachar
+ integer i
+ i = iachar(' ')
+end program test_iachar
+@end smallexample
+
+@item @emph{Note}:
+See @ref{ICHAR} for a discussion of converting between numerical values
+and formatted string representations.
+
+@item @emph{See also}:
+@ref{ACHAR}, @gol
+@ref{CHAR}, @gol
+@ref{ICHAR}
+@end table
+
+
+
+@node IALL
+@section @code{IALL} --- Bitwise AND of array elements
+@fnindex IALL
+@cindex array, AND
+@cindex bits, AND of array elements
+
+@table @asis
+@item @emph{Description}:
+Reduces with bitwise AND the elements of @var{ARRAY} along dimension @var{DIM}
+if the corresponding element in @var{MASK} is @code{TRUE}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = IALL(ARRAY[, MASK])}
+@item @code{RESULT = IALL(ARRAY, DIM[, MASK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER}
+@item @var{DIM} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with a value in the range from 1 to n, where n
+equals the rank of @var{ARRAY}.
+@item @var{MASK} @tab (Optional) shall be of type @code{LOGICAL}
+and either be a scalar or an array of the same shape as @var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type as @var{ARRAY}.
+
+If @var{DIM} is absent, a scalar with the bitwise ALL of all elements in
+@var{ARRAY} is returned. Otherwise, an array of rank n-1, where n equals
+the rank of @var{ARRAY}, and a shape similar to that of @var{ARRAY} with
+dimension @var{DIM} dropped is returned.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_iall
+ INTEGER(1) :: a(2)
+
+ a(1) = b'00100100'
+ a(2) = b'01101010'
+
+ ! prints 00100000
+ PRINT '(b8.8)', IALL(a)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{IANY}, @gol
+@ref{IPARITY}, @gol
+@ref{IAND}
+@end table
+
+
+
+@node IAND
+@section @code{IAND} --- Bitwise logical and
+@fnindex IAND
+@fnindex BIAND
+@fnindex IIAND
+@fnindex JIAND
+@fnindex KIAND
+@cindex bitwise logical and
+@cindex logical and, bitwise
+
+@table @asis
+@item @emph{Description}:
+Bitwise logical @code{AND}.
+
+@item @emph{Standard}:
+Fortran 90 and later, with boz-literal-constant Fortran 2008 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IAND(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER} or a boz-literal-constant.
+@item @var{J} @tab The type shall be @code{INTEGER} with the same
+kind type parameter as @var{I} or a boz-literal-constant.
+@var{I} and @var{J} shall not both be boz-literal-constants.
+@end multitable
+
+@item @emph{Return value}:
+The return type is @code{INTEGER} with the kind type parameter of the
+arguments.
+A boz-literal-constant is converted to an @code{INTEGER} with the kind
+type parameter of the other argument as-if a call to @ref{INT} occurred.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_iand
+ INTEGER :: a, b
+ DATA a / Z'F' /, b / Z'3' /
+ WRITE (*,*) IAND(a, b)
+END PROGRAM
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{IAND(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BIAND(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IIAND(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JIAND(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KIAND(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{IOR}, @gol
+@ref{IEOR}, @gol
+@ref{IBITS}, @gol
+@ref{IBSET}, @gol
+@ref{IBCLR}, @gol
+@ref{NOT}
+@end table
+
+
+
+@node IANY
+@section @code{IANY} --- Bitwise OR of array elements
+@fnindex IANY
+@cindex array, OR
+@cindex bits, OR of array elements
+
+@table @asis
+@item @emph{Description}:
+Reduces with bitwise OR (inclusive or) the elements of @var{ARRAY} along
+dimension @var{DIM} if the corresponding element in @var{MASK} is @code{TRUE}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = IANY(ARRAY[, MASK])}
+@item @code{RESULT = IANY(ARRAY, DIM[, MASK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER}
+@item @var{DIM} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with a value in the range from 1 to n, where n
+equals the rank of @var{ARRAY}.
+@item @var{MASK} @tab (Optional) shall be of type @code{LOGICAL}
+and either be a scalar or an array of the same shape as @var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type as @var{ARRAY}.
+
+If @var{DIM} is absent, a scalar with the bitwise OR of all elements in
+@var{ARRAY} is returned. Otherwise, an array of rank n-1, where n equals
+the rank of @var{ARRAY}, and a shape similar to that of @var{ARRAY} with
+dimension @var{DIM} dropped is returned.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_iany
+ INTEGER(1) :: a(2)
+
+ a(1) = b'00100100'
+ a(2) = b'01101010'
+
+ ! prints 01101110
+ PRINT '(b8.8)', IANY(a)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{IPARITY}, @gol
+@ref{IALL}, @gol
+@ref{IOR}
+@end table
+
+
+
+@node IARGC
+@section @code{IARGC} --- Get the number of command line arguments
+@fnindex IARGC
+@cindex command-line arguments
+@cindex command-line arguments, number of
+@cindex arguments, to program
+
+@table @asis
+@item @emph{Description}:
+@code{IARGC} returns the number of arguments passed on the
+command line when the containing program was invoked.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. In new code, programmers should consider the use of
+the @ref{COMMAND_ARGUMENT_COUNT} intrinsic defined by the Fortran 2003
+standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = IARGC()}
+
+@item @emph{Arguments}:
+None
+
+@item @emph{Return value}:
+The number of command line arguments, type @code{INTEGER(4)}.
+
+@item @emph{Example}:
+See @ref{GETARG}
+
+@item @emph{See also}:
+GNU Fortran 77 compatibility subroutine: @gol
+@ref{GETARG} @gol
+Fortran 2003 functions and subroutines: @gol
+@ref{GET_COMMAND}, @gol
+@ref{GET_COMMAND_ARGUMENT}, @gol
+@ref{COMMAND_ARGUMENT_COUNT}
+@end table
+
+
+
+@node IBCLR
+@section @code{IBCLR} --- Clear bit
+@fnindex IBCLR
+@fnindex BBCLR
+@fnindex IIBCLR
+@fnindex JIBCLR
+@fnindex KIBCLR
+@cindex bits, unset
+@cindex bits, clear
+
+@table @asis
+@item @emph{Description}:
+@code{IBCLR} returns the value of @var{I} with the bit at position
+@var{POS} set to zero.
+
+@item @emph{Standard}:
+Fortran 90 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IBCLR(I, POS)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{POS} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{IBCLR(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BBCLR(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IIBCLR(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JIBCLR(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KIBCLR(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{IBITS}, @gol
+@ref{IBSET}, @gol
+@ref{IAND}, @gol
+@ref{IOR}, @gol
+@ref{IEOR}, @gol
+@ref{MVBITS}
+@end table
+
+
+
+@node IBITS
+@section @code{IBITS} --- Bit extraction
+@fnindex IBITS
+@fnindex BBITS
+@fnindex IIBITS
+@fnindex JIBITS
+@fnindex KIBITS
+@cindex bits, get
+@cindex bits, extract
+
+@table @asis
+@item @emph{Description}:
+@code{IBITS} extracts a field of length @var{LEN} from @var{I},
+starting from bit position @var{POS} and extending left for @var{LEN}
+bits. The result is right-justified and the remaining bits are
+zeroed. The value of @code{POS+LEN} must be less than or equal to the
+value @code{BIT_SIZE(I)}.
+
+@item @emph{Standard}:
+Fortran 90 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IBITS(I, POS, LEN)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{POS} @tab The type shall be @code{INTEGER}.
+@item @var{LEN} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{IBITS(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BBITS(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IIBITS(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JIBITS(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KIBITS(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{BIT_SIZE}, @gol
+@ref{IBCLR}, @gol
+@ref{IBSET}, @gol
+@ref{IAND}, @gol
+@ref{IOR}, @gol
+@ref{IEOR}
+@end table
+
+
+
+@node IBSET
+@section @code{IBSET} --- Set bit
+@fnindex IBSET
+@fnindex BBSET
+@fnindex IIBSET
+@fnindex JIBSET
+@fnindex KIBSET
+@cindex bits, set
+
+@table @asis
+@item @emph{Description}:
+@code{IBSET} returns the value of @var{I} with the bit at position
+@var{POS} set to one.
+
+@item @emph{Standard}:
+Fortran 90 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IBSET(I, POS)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{POS} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{IBSET(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BBSET(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IIBSET(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JIBSET(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KIBSET(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{IBCLR}, @gol
+@ref{IBITS}, @gol
+@ref{IAND}, @gol
+@ref{IOR}, @gol
+@ref{IEOR}, @gol
+@ref{MVBITS}
+@end table
+
+
+
+@node ICHAR
+@section @code{ICHAR} --- Character-to-integer conversion function
+@fnindex ICHAR
+@cindex conversion, to integer
+
+@table @asis
+@item @emph{Description}:
+@code{ICHAR(C)} returns the code for the character in the first character
+position of @code{C} in the system's native character set.
+The correspondence between characters and their codes is not necessarily
+the same across different GNU Fortran implementations.
+
+@item @emph{Standard}:
+Fortran 77 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ICHAR(C [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{C} @tab Shall be a scalar @code{CHARACTER}, with @code{INTENT(IN)}
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+
+@item @emph{Example}:
+@smallexample
+program test_ichar
+ integer i
+ i = ichar(' ')
+end program test_ichar
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ICHAR(C)} @tab @code{CHARACTER C} @tab @code{INTEGER(4)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{Note}:
+No intrinsic exists to convert between a numeric value and a formatted
+character string representation -- for instance, given the
+@code{CHARACTER} value @code{'154'}, obtaining an @code{INTEGER} or
+@code{REAL} value with the value 154, or vice versa. Instead, this
+functionality is provided by internal-file I/O, as in the following
+example:
+@smallexample
+program read_val
+ integer value
+ character(len=10) string, string2
+ string = '154'
+
+ ! Convert a string to a numeric value
+ read (string,'(I10)') value
+ print *, value
+
+ ! Convert a value to a formatted string
+ write (string2,'(I10)') value
+ print *, string2
+end program read_val
+@end smallexample
+
+@item @emph{See also}:
+@ref{ACHAR}, @gol
+@ref{CHAR}, @gol
+@ref{IACHAR}
+@end table
+
+
+
+@node IDATE
+@section @code{IDATE} --- Get current local time subroutine (day/month/year)
+@fnindex IDATE
+@cindex date, current
+@cindex current date
+
+@table @asis
+@item @emph{Description}:
+@code{IDATE(VALUES)} Fills @var{VALUES} with the numerical values at the
+current local time. The day (in the range 1-31), month (in the range 1-12),
+and year appear in elements 1, 2, and 3 of @var{VALUES}, respectively.
+The year has four significant digits.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. In new code, programmers should consider the use of
+the @ref{DATE_AND_TIME} intrinsic defined by the Fortran 95
+standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL IDATE(VALUES)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{VALUES} @tab The type shall be @code{INTEGER, DIMENSION(3)} and
+the kind shall be the default integer kind.
+@end multitable
+
+@item @emph{Return value}:
+Does not return anything.
+
+@item @emph{Example}:
+@smallexample
+program test_idate
+ integer, dimension(3) :: tarray
+ call idate(tarray)
+ print *, tarray(1)
+ print *, tarray(2)
+ print *, tarray(3)
+end program test_idate
+@end smallexample
+
+@item @emph{See also}:
+@ref{DATE_AND_TIME}
+@end table
+
+
+@node IEOR
+@section @code{IEOR} --- Bitwise logical exclusive or
+@fnindex IEOR
+@fnindex BIEOR
+@fnindex IIEOR
+@fnindex JIEOR
+@fnindex KIEOR
+@cindex bitwise logical exclusive or
+@cindex logical exclusive or, bitwise
+
+@table @asis
+@item @emph{Description}:
+@code{IEOR} returns the bitwise Boolean exclusive-OR of @var{I} and
+@var{J}.
+
+@item @emph{Standard}:
+Fortran 90 and later, with boz-literal-constant Fortran 2008 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IEOR(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER} or a boz-literal-constant.
+@item @var{J} @tab The type shall be @code{INTEGER} with the same
+kind type parameter as @var{I} or a boz-literal-constant.
+@var{I} and @var{J} shall not both be boz-literal-constants.
+@end multitable
+
+@item @emph{Return value}:
+The return type is @code{INTEGER} with the kind type parameter of the
+arguments.
+A boz-literal-constant is converted to an @code{INTEGER} with the kind
+type parameter of the other argument as-if a call to @ref{INT} occurred.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{IEOR(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BIEOR(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IIEOR(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JIEOR(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KIEOR(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{IOR}, @gol
+@ref{IAND}, @gol
+@ref{IBITS}, @gol
+@ref{IBSET}, @gol
+@ref{IBCLR}, @gol
+@ref{NOT}
+@end table
+
+
+
+@node IERRNO
+@section @code{IERRNO} --- Get the last system error number
+@fnindex IERRNO
+@cindex system, error handling
+
+@table @asis
+@item @emph{Description}:
+Returns the last system error number, as given by the C @code{errno}
+variable.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = IERRNO()}
+
+@item @emph{Arguments}:
+None
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the default integer
+kind.
+
+@item @emph{See also}:
+@ref{PERROR}
+@end table
+
+
+
+@node IMAGE_INDEX
+@section @code{IMAGE_INDEX} --- Function that converts a cosubscript to an image index
+@fnindex IMAGE_INDEX
+@cindex coarray, @code{IMAGE_INDEX}
+@cindex images, cosubscript to image index conversion
+
+@table @asis
+@item @emph{Description}:
+Returns the image index belonging to a cosubscript.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Inquiry function.
+
+@item @emph{Syntax}:
+@code{RESULT = IMAGE_INDEX(COARRAY, SUB)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{COARRAY} @tab Coarray of any type.
+@item @var{SUB} @tab default integer rank-1 array of a size equal to
+the corank of @var{COARRAY}.
+@end multitable
+
+
+@item @emph{Return value}:
+Scalar default integer with the value of the image index which corresponds
+to the cosubscripts. For invalid cosubscripts the result is zero.
+
+@item @emph{Example}:
+@smallexample
+INTEGER :: array[2,-1:4,8,*]
+! Writes 28 (or 0 if there are fewer than 28 images)
+WRITE (*,*) IMAGE_INDEX (array, [2,0,3,1])
+@end smallexample
+
+@item @emph{See also}:
+@ref{THIS_IMAGE}, @gol
+@ref{NUM_IMAGES}
+@end table
+
+
+
+@node INDEX intrinsic
+@section @code{INDEX} --- Position of a substring within a string
+@fnindex INDEX
+@cindex substring position
+@cindex string, find substring
+
+@table @asis
+@item @emph{Description}:
+Returns the position of the start of the first occurrence of string
+@var{SUBSTRING} as a substring in @var{STRING}, counting from one. If
+@var{SUBSTRING} is not present in @var{STRING}, zero is returned. If
+the @var{BACK} argument is present and true, the return value is the
+start of the last occurrence rather than the first.
+
+@item @emph{Standard}:
+Fortran 77 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = INDEX(STRING, SUBSTRING [, BACK [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab Shall be a scalar @code{CHARACTER}, with
+@code{INTENT(IN)}
+@item @var{SUBSTRING} @tab Shall be a scalar @code{CHARACTER}, with
+@code{INTENT(IN)}
+@item @var{BACK} @tab (Optional) Shall be a scalar @code{LOGICAL}, with
+@code{INTENT(IN)}
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .35 .15 .17 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{INDEX(STRING,SUBSTRING)} @tab @code{CHARACTER} @tab @code{INTEGER(4)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{SCAN}, @gol
+@ref{VERIFY}
+@end table
+
+
+
+@node INT
+@section @code{INT} --- Convert to integer type
+@fnindex INT
+@fnindex IFIX
+@fnindex IDINT
+@cindex conversion, to integer
+
+@table @asis
+@item @emph{Description}:
+Convert to integer type
+
+@item @emph{Standard}:
+Fortran 77 and later, with boz-literal-constant Fortran 2008 and later.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = INT(A [, KIND))}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be of type @code{INTEGER},
+@code{REAL}, or @code{COMPLEX} or a boz-literal-constant.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+These functions return a @code{INTEGER} variable or array under
+the following rules:
+
+@table @asis
+@item (A)
+If @var{A} is of type @code{INTEGER}, @code{INT(A) = A}
+@item (B)
+If @var{A} is of type @code{REAL} and @math{|A| < 1}, @code{INT(A)}
+equals @code{0}. If @math{|A| \geq 1}, then @code{INT(A)} is the integer
+whose magnitude is the largest integer that does not exceed the magnitude
+of @var{A} and whose sign is the same as the sign of @var{A}.
+@item (C)
+If @var{A} is of type @code{COMPLEX}, rule B is applied to the real part of @var{A}.
+@end table
+
+@item @emph{Example}:
+@smallexample
+program test_int
+ integer :: i = 42
+ complex :: z = (-3.7, 1.0)
+ print *, int(i)
+ print *, int(z), int(z,8)
+end program
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{INT(A)} @tab @code{REAL(4) A} @tab @code{INTEGER} @tab Fortran 77 and later
+@item @code{IFIX(A)} @tab @code{REAL(4) A} @tab @code{INTEGER} @tab Fortran 77 and later
+@item @code{IDINT(A)} @tab @code{REAL(8) A} @tab @code{INTEGER} @tab Fortran 77 and later
+@end multitable
+
+@end table
+
+
+@node INT2
+@section @code{INT2} --- Convert to 16-bit integer type
+@fnindex INT2
+@cindex conversion, to integer
+
+@table @asis
+@item @emph{Description}:
+Convert to a @code{KIND=2} integer type. This is equivalent to the
+standard @code{INT} intrinsic with an optional argument of
+@code{KIND=2}, and is only included for backwards compatibility.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = INT2(A)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be of type @code{INTEGER},
+@code{REAL}, or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a @code{INTEGER(2)} variable.
+
+@item @emph{See also}:
+@ref{INT}, @gol
+@ref{INT8}
+@end table
+
+
+
+@node INT8
+@section @code{INT8} --- Convert to 64-bit integer type
+@fnindex INT8
+@cindex conversion, to integer
+
+@table @asis
+@item @emph{Description}:
+Convert to a @code{KIND=8} integer type. This is equivalent to the
+standard @code{INT} intrinsic with an optional argument of
+@code{KIND=8}, and is only included for backwards compatibility.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = INT8(A)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be of type @code{INTEGER},
+@code{REAL}, or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a @code{INTEGER(8)} variable.
+
+@item @emph{See also}:
+@ref{INT}, @gol
+@ref{INT2}
+@end table
+
+
+
+@node IOR
+@section @code{IOR} --- Bitwise logical or
+@fnindex IOR
+@fnindex BIOR
+@fnindex IIOR
+@fnindex JIOR
+@fnindex KIOR
+@cindex bitwise logical or
+@cindex logical or, bitwise
+
+@table @asis
+@item @emph{Description}:
+@code{IOR} returns the bitwise Boolean inclusive-OR of @var{I} and
+@var{J}.
+
+@item @emph{Standard}:
+Fortran 90 and later, with boz-literal-constant Fortran 2008 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IOR(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER} or a boz-literal-constant.
+@item @var{J} @tab The type shall be @code{INTEGER} with the same
+kind type parameter as @var{I} or a boz-literal-constant.
+@var{I} and @var{J} shall not both be boz-literal-constants.
+@end multitable
+
+@item @emph{Return value}:
+The return type is @code{INTEGER} with the kind type parameter of the
+arguments.
+A boz-literal-constant is converted to an @code{INTEGER} with the kind
+type parameter of the other argument as-if a call to @ref{INT} occurred.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{IOR(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BIOR(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IIOR(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JIOR(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KIOR(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{IEOR}, @gol
+@ref{IAND}, @gol
+@ref{IBITS}, @gol
+@ref{IBSET}, @gol
+@ref{IBCLR}, @gol
+@ref{NOT}
+@end table
+
+
+
+@node IPARITY
+@section @code{IPARITY} --- Bitwise XOR of array elements
+@fnindex IPARITY
+@cindex array, parity
+@cindex array, XOR
+@cindex bits, XOR of array elements
+
+@table @asis
+@item @emph{Description}:
+Reduces with bitwise XOR (exclusive or) the elements of @var{ARRAY} along
+dimension @var{DIM} if the corresponding element in @var{MASK} is @code{TRUE}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = IPARITY(ARRAY[, MASK])}
+@item @code{RESULT = IPARITY(ARRAY, DIM[, MASK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER}
+@item @var{DIM} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with a value in the range from 1 to n, where n
+equals the rank of @var{ARRAY}.
+@item @var{MASK} @tab (Optional) shall be of type @code{LOGICAL}
+and either be a scalar or an array of the same shape as @var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type as @var{ARRAY}.
+
+If @var{DIM} is absent, a scalar with the bitwise XOR of all elements in
+@var{ARRAY} is returned. Otherwise, an array of rank n-1, where n equals
+the rank of @var{ARRAY}, and a shape similar to that of @var{ARRAY} with
+dimension @var{DIM} dropped is returned.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_iparity
+ INTEGER(1) :: a(2)
+
+ a(1) = int(b'00100100', 1)
+ a(2) = int(b'01101010', 1)
+
+ ! prints 01001110
+ PRINT '(b8.8)', IPARITY(a)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{IANY}, @gol
+@ref{IALL}, @gol
+@ref{IEOR}, @gol
+@ref{PARITY}
+@end table
+
+
+
+@node IRAND
+@section @code{IRAND} --- Integer pseudo-random number
+@fnindex IRAND
+@cindex random number generation
+
+@table @asis
+@item @emph{Description}:
+@code{IRAND(FLAG)} returns a pseudo-random number from a uniform
+distribution between 0 and a system-dependent limit (which is in most
+cases 2147483647). If @var{FLAG} is 0, the next number
+in the current sequence is returned; if @var{FLAG} is 1, the generator
+is restarted by @code{CALL SRAND(0)}; if @var{FLAG} has any other value,
+it is used as a new seed with @code{SRAND}.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. It implements a simple modulo generator as provided
+by @command{g77}. For new code, one should consider the use of
+@ref{RANDOM_NUMBER} as it implements a superior algorithm.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = IRAND(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be a scalar @code{INTEGER} of kind 4.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of @code{INTEGER(kind=4)} type.
+
+@item @emph{Example}:
+@smallexample
+program test_irand
+ integer,parameter :: seed = 86456
+
+ call srand(seed)
+ print *, irand(), irand(), irand(), irand()
+ print *, irand(seed), irand(), irand(), irand()
+end program test_irand
+@end smallexample
+
+@end table
+
+
+
+@node IS_CONTIGUOUS
+@section @code{IS_CONTIGUOUS} --- Test whether an array is contiguous
+@fnindex IS_IOSTAT_EOR
+@cindex array, contiguity
+
+@table @asis
+@item @emph{Description}:
+@code{IS_CONTIGUOUS} tests whether an array is contiguous.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = IS_CONTIGUOUS(ARRAY)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of any type.
+@end multitable
+
+@item @emph{Return value}:
+Returns a @code{LOGICAL} of the default kind, which @code{.TRUE.} if
+@var{ARRAY} is contiguous and false otherwise.
+
+@item @emph{Example}:
+@smallexample
+program test
+ integer :: a(10)
+ a = [1,2,3,4,5,6,7,8,9,10]
+ call sub (a) ! every element, is contiguous
+ call sub (a(::2)) ! every other element, is noncontiguous
+contains
+ subroutine sub (x)
+ integer :: x(:)
+ if (is_contiguous (x)) then
+ write (*,*) 'X is contiguous'
+ else
+ write (*,*) 'X is not contiguous'
+ end if
+ end subroutine sub
+end program test
+@end smallexample
+@end table
+
+
+
+@node IS_IOSTAT_END
+@section @code{IS_IOSTAT_END} --- Test for end-of-file value
+@fnindex IS_IOSTAT_END
+@cindex @code{IOSTAT}, end of file
+
+@table @asis
+@item @emph{Description}:
+@code{IS_IOSTAT_END} tests whether an variable has the value of the I/O
+status ``end of file''. The function is equivalent to comparing the variable
+with the @code{IOSTAT_END} parameter of the intrinsic module
+@code{ISO_FORTRAN_ENV}.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IS_IOSTAT_END(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of the type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+Returns a @code{LOGICAL} of the default kind, which @code{.TRUE.} if
+@var{I} has the value which indicates an end of file condition for
+@code{IOSTAT=} specifiers, and is @code{.FALSE.} otherwise.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM iostat
+ IMPLICIT NONE
+ INTEGER :: stat, i
+ OPEN(88, FILE='test.dat')
+ READ(88, *, IOSTAT=stat) i
+ IF(IS_IOSTAT_END(stat)) STOP 'END OF FILE'
+END PROGRAM
+@end smallexample
+@end table
+
+
+
+@node IS_IOSTAT_EOR
+@section @code{IS_IOSTAT_EOR} --- Test for end-of-record value
+@fnindex IS_IOSTAT_EOR
+@cindex @code{IOSTAT}, end of record
+
+@table @asis
+@item @emph{Description}:
+@code{IS_IOSTAT_EOR} tests whether an variable has the value of the I/O
+status ``end of record''. The function is equivalent to comparing the
+variable with the @code{IOSTAT_EOR} parameter of the intrinsic module
+@code{ISO_FORTRAN_ENV}.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = IS_IOSTAT_EOR(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of the type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+Returns a @code{LOGICAL} of the default kind, which @code{.TRUE.} if
+@var{I} has the value which indicates an end of file condition for
+@code{IOSTAT=} specifiers, and is @code{.FALSE.} otherwise.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM iostat
+ IMPLICIT NONE
+ INTEGER :: stat, i(50)
+ OPEN(88, FILE='test.dat', FORM='UNFORMATTED')
+ READ(88, IOSTAT=stat) i
+ IF(IS_IOSTAT_EOR(stat)) STOP 'END OF RECORD'
+END PROGRAM
+@end smallexample
+@end table
+
+
+@node ISATTY
+@section @code{ISATTY} --- Whether a unit is a terminal device
+@fnindex ISATTY
+@cindex system, terminal
+
+@table @asis
+@item @emph{Description}:
+Determine whether a unit is connected to a terminal device.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = ISATTY(UNIT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{UNIT} @tab Shall be a scalar @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+Returns @code{.TRUE.} if the @var{UNIT} is connected to a terminal
+device, @code{.FALSE.} otherwise.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_isatty
+ INTEGER(kind=1) :: unit
+ DO unit = 1, 10
+ write(*,*) isatty(unit=unit)
+ END DO
+END PROGRAM
+@end smallexample
+@item @emph{See also}:
+@ref{TTYNAM}
+@end table
+
+
+
+@node ISHFT
+@section @code{ISHFT} --- Shift bits
+@fnindex ISHFT
+@fnindex BSHFT
+@fnindex IISHFT
+@fnindex JISHFT
+@fnindex KISHFT
+@cindex bits, shift
+
+@table @asis
+@item @emph{Description}:
+@code{ISHFT} returns a value corresponding to @var{I} with all of the
+bits shifted @var{SHIFT} places. A value of @var{SHIFT} greater than
+zero corresponds to a left shift, a value of zero corresponds to no
+shift, and a value less than zero corresponds to a right shift. If the
+absolute value of @var{SHIFT} is greater than @code{BIT_SIZE(I)}, the
+value is undefined. Bits shifted out from the left end or right end are
+lost; zeros are shifted in from the opposite end.
+
+@item @emph{Standard}:
+Fortran 90 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ISHFT(I, SHIFT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ISHFT(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BSHFT(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IISHFT(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JISHFT(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KISHFT(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{ISHFTC}
+@end table
+
+
+
+@node ISHFTC
+@section @code{ISHFTC} --- Shift bits circularly
+@fnindex ISHFTC
+@fnindex BSHFTC
+@fnindex IISHFTC
+@fnindex JISHFTC
+@fnindex KISHFTC
+@cindex bits, shift circular
+
+@table @asis
+@item @emph{Description}:
+@code{ISHFTC} returns a value corresponding to @var{I} with the
+rightmost @var{SIZE} bits shifted circularly @var{SHIFT} places; that
+is, bits shifted out one end are shifted into the opposite end. A value
+of @var{SHIFT} greater than zero corresponds to a left shift, a value of
+zero corresponds to no shift, and a value less than zero corresponds to
+a right shift. The absolute value of @var{SHIFT} must be less than
+@var{SIZE}. If the @var{SIZE} argument is omitted, it is taken to be
+equivalent to @code{BIT_SIZE(I)}.
+
+@item @emph{Standard}:
+Fortran 90 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = ISHFTC(I, SHIFT [, SIZE])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@item @var{SIZE} @tab (Optional) The type shall be @code{INTEGER};
+the value must be greater than zero and less than or equal to
+@code{BIT_SIZE(I)}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ISHFTC(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BSHFTC(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IISHFTC(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JISHFTC(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KISHFTC(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{ISHFT}
+@end table
+
+
+
+@node ISNAN
+@section @code{ISNAN} --- Test for a NaN
+@fnindex ISNAN
+@cindex IEEE, ISNAN
+
+@table @asis
+@item @emph{Description}:
+@code{ISNAN} tests whether a floating-point value is an IEEE
+Not-a-Number (NaN).
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{ISNAN(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Variable of the type @code{REAL}.
+
+@end multitable
+
+@item @emph{Return value}:
+Returns a default-kind @code{LOGICAL}. The returned value is @code{TRUE}
+if @var{X} is a NaN and @code{FALSE} otherwise.
+
+@item @emph{Example}:
+@smallexample
+program test_nan
+ implicit none
+ real :: x
+ x = -1.0
+ x = sqrt(x)
+ if (isnan(x)) stop '"x" is a NaN'
+end program test_nan
+@end smallexample
+@end table
+
+
+
+@node ITIME
+@section @code{ITIME} --- Get current local time subroutine (hour/minutes/seconds)
+@fnindex ITIME
+@cindex time, current
+@cindex current time
+
+@table @asis
+@item @emph{Description}:
+@code{ITIME(VALUES)} Fills @var{VALUES} with the numerical values at the
+current local time. The hour (in the range 1-24), minute (in the range 1-60),
+and seconds (in the range 1-60) appear in elements 1, 2, and 3 of @var{VALUES},
+respectively.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. In new code, programmers should consider the use of
+the @ref{DATE_AND_TIME} intrinsic defined by the Fortran 95
+standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL ITIME(VALUES)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{VALUES} @tab The type shall be @code{INTEGER, DIMENSION(3)}
+and the kind shall be the default integer kind.
+@end multitable
+
+@item @emph{Return value}:
+Does not return anything.
+
+
+@item @emph{Example}:
+@smallexample
+program test_itime
+ integer, dimension(3) :: tarray
+ call itime(tarray)
+ print *, tarray(1)
+ print *, tarray(2)
+ print *, tarray(3)
+end program test_itime
+@end smallexample
+
+@item @emph{See also}:
+@ref{DATE_AND_TIME}
+@end table
+
+
+
+@node KILL
+@section @code{KILL} --- Send a signal to a process
+@fnindex KILL
+
+@table @asis
+@item @emph{Description}:
+Sends the signal specified by @var{SIG} to the process @var{PID}.
+See @code{kill(2)}.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL KILL(PID, SIG [, STATUS])}
+@item @code{STATUS = KILL(PID, SIG)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{PID} @tab Shall be a scalar @code{INTEGER} with @code{INTENT(IN)}.
+@item @var{SIG} @tab Shall be a scalar @code{INTEGER} with @code{INTENT(IN)}.
+@item @var{STATUS} @tab [Subroutine](Optional)
+Shall be a scalar @code{INTEGER}.
+Returns 0 on success; otherwise a system-specific error code is returned.
+@item @var{STATUS} @tab [Function] The kind type parameter is that of
+@code{pid}.
+Returns 0 on success; otherwise a system-specific error code is returned.
+@end multitable
+
+@item @emph{See also}:
+@ref{ABORT}, @gol
+@ref{EXIT}
+@end table
+
+
+@node KIND
+@section @code{KIND} --- Kind of an entity
+@fnindex KIND
+@cindex kind
+
+@table @asis
+@item @emph{Description}:
+@code{KIND(X)} returns the kind value of the entity @var{X}.
+
+@item @emph{Standard}:
+Fortran 95 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{K = KIND(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{LOGICAL}, @code{INTEGER},
+@code{REAL}, @code{COMPLEX} or @code{CHARACTER}. It may be scalar or
+array valued.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a scalar of type @code{INTEGER} and of the default
+integer kind.
+
+@item @emph{Example}:
+@smallexample
+program test_kind
+ integer,parameter :: kc = kind(' ')
+ integer,parameter :: kl = kind(.true.)
+
+ print *, "The default character kind is ", kc
+ print *, "The default logical kind is ", kl
+end program test_kind
+@end smallexample
+
+@end table
+
+
+
+@node LBOUND
+@section @code{LBOUND} --- Lower dimension bounds of an array
+@fnindex LBOUND
+@cindex array, lower bound
+
+@table @asis
+@item @emph{Description}:
+Returns the lower bounds of an array, or a single lower bound
+along the @var{DIM} dimension.
+@item @emph{Standard}:
+Fortran 90 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = LBOUND(ARRAY [, DIM [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array, of any type.
+@item @var{DIM} @tab (Optional) Shall be a scalar @code{INTEGER}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+If @var{DIM} is absent, the result is an array of the lower bounds of
+@var{ARRAY}. If @var{DIM} is present, the result is a scalar
+corresponding to the lower bound of the array along that dimension. If
+@var{ARRAY} is an expression rather than a whole array or array
+structure component, or if it has a zero extent along the relevant
+dimension, the lower bound is taken to be 1.
+
+@item @emph{See also}:
+@ref{UBOUND}, @gol
+@ref{LCOBOUND}
+@end table
+
+
+
+@node LCOBOUND
+@section @code{LCOBOUND} --- Lower codimension bounds of an array
+@fnindex LCOBOUND
+@cindex coarray, lower bound
+
+@table @asis
+@item @emph{Description}:
+Returns the lower bounds of a coarray, or a single lower cobound
+along the @var{DIM} codimension.
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = LCOBOUND(COARRAY [, DIM [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an coarray, of any type.
+@item @var{DIM} @tab (Optional) Shall be a scalar @code{INTEGER}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+If @var{DIM} is absent, the result is an array of the lower cobounds of
+@var{COARRAY}. If @var{DIM} is present, the result is a scalar
+corresponding to the lower cobound of the array along that codimension.
+
+@item @emph{See also}:
+@ref{UCOBOUND}, @gol
+@ref{LBOUND}
+@end table
+
+
+
+@node LEADZ
+@section @code{LEADZ} --- Number of leading zero bits of an integer
+@fnindex LEADZ
+@cindex zero bits
+
+@table @asis
+@item @emph{Description}:
+@code{LEADZ} returns the number of leading zero bits of an integer.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LEADZ(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The type of the return value is the default @code{INTEGER}.
+If all the bits of @code{I} are zero, the result value is @code{BIT_SIZE(I)}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_leadz
+ WRITE (*,*) BIT_SIZE(1) ! prints 32
+ WRITE (*,*) LEADZ(1) ! prints 31
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{BIT_SIZE}, @gol
+@ref{TRAILZ}, @gol
+@ref{POPCNT}, @gol
+@ref{POPPAR}
+@end table
+
+
+
+@node LEN
+@section @code{LEN} --- Length of a character entity
+@fnindex LEN
+@cindex string, length
+
+@table @asis
+@item @emph{Description}:
+Returns the length of a character string. If @var{STRING} is an array,
+the length of an element of @var{STRING} is returned. Note that
+@var{STRING} need not be defined when this intrinsic is invoked, since
+only the length, not the content, of @var{STRING} is needed.
+
+@item @emph{Standard}:
+Fortran 77 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{L = LEN(STRING [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab Shall be a scalar or array of type
+@code{CHARACTER}, with @code{INTENT(IN)}
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{LEN(STRING)} @tab @code{CHARACTER} @tab @code{INTEGER} @tab Fortran 77 and later
+@end multitable
+
+
+@item @emph{See also}:
+@ref{LEN_TRIM}, @gol
+@ref{ADJUSTL}, @gol
+@ref{ADJUSTR}
+@end table
+
+
+
+@node LEN_TRIM
+@section @code{LEN_TRIM} --- Length of a character entity without trailing blank characters
+@fnindex LEN_TRIM
+@cindex string, length, without trailing whitespace
+
+@table @asis
+@item @emph{Description}:
+Returns the length of a character string, ignoring any trailing blanks.
+
+@item @emph{Standard}:
+Fortran 90 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LEN_TRIM(STRING [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab Shall be a scalar of type @code{CHARACTER},
+with @code{INTENT(IN)}
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+
+@item @emph{See also}:
+@ref{LEN}, @gol
+@ref{ADJUSTL}, @gol
+@ref{ADJUSTR}
+@end table
+
+
+
+@node LGE
+@section @code{LGE} --- Lexical greater than or equal
+@fnindex LGE
+@cindex lexical comparison of strings
+@cindex string, comparison
+
+@table @asis
+@item @emph{Description}:
+Determines whether one string is lexically greater than or equal to
+another string, where the two strings are interpreted as containing
+ASCII character codes. If the String A and String B are not the same
+length, the shorter is compared as if spaces were appended to it to form
+a value that has the same length as the longer.
+
+In general, the lexical comparison intrinsics @code{LGE}, @code{LGT},
+@code{LLE}, and @code{LLT} differ from the corresponding intrinsic
+operators @code{.GE.}, @code{.GT.}, @code{.LE.}, and @code{.LT.}, in
+that the latter use the processor's character ordering (which is not
+ASCII on some targets), whereas the former always use the ASCII
+ordering.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LGE(STRING_A, STRING_B)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING_A} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STRING_B} @tab Shall be of default @code{CHARACTER} type.
+@end multitable
+
+@item @emph{Return value}:
+Returns @code{.TRUE.} if @code{STRING_A >= STRING_B}, and @code{.FALSE.}
+otherwise, based on the ASCII ordering.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .34 .16 .17 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{LGE(STRING_A,STRING_B)} @tab @code{CHARACTER} @tab @code{LOGICAL} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{LGT}, @gol
+@ref{LLE}, @gol
+@ref{LLT}
+@end table
+
+
+
+@node LGT
+@section @code{LGT} --- Lexical greater than
+@fnindex LGT
+@cindex lexical comparison of strings
+@cindex string, comparison
+
+@table @asis
+@item @emph{Description}:
+Determines whether one string is lexically greater than another string,
+where the two strings are interpreted as containing ASCII character
+codes. If the String A and String B are not the same length, the
+shorter is compared as if spaces were appended to it to form a value
+that has the same length as the longer.
+
+In general, the lexical comparison intrinsics @code{LGE}, @code{LGT},
+@code{LLE}, and @code{LLT} differ from the corresponding intrinsic
+operators @code{.GE.}, @code{.GT.}, @code{.LE.}, and @code{.LT.}, in
+that the latter use the processor's character ordering (which is not
+ASCII on some targets), whereas the former always use the ASCII
+ordering.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LGT(STRING_A, STRING_B)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING_A} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STRING_B} @tab Shall be of default @code{CHARACTER} type.
+@end multitable
+
+@item @emph{Return value}:
+Returns @code{.TRUE.} if @code{STRING_A > STRING_B}, and @code{.FALSE.}
+otherwise, based on the ASCII ordering.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .34 .16 .17 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{LGT(STRING_A,STRING_B)} @tab @code{CHARACTER} @tab @code{LOGICAL} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{LGE}, @gol
+@ref{LLE}, @gol
+@ref{LLT}
+@end table
+
+
+
+@node LINK
+@section @code{LINK} --- Create a hard link
+@fnindex LINK
+@cindex file system, create link
+@cindex file system, hard link
+
+@table @asis
+@item @emph{Description}:
+Makes a (hard) link from file @var{PATH1} to @var{PATH2}. A null
+character (@code{CHAR(0)}) can be used to mark the end of the names in
+@var{PATH1} and @var{PATH2}; otherwise, trailing blanks in the file
+names are ignored. If the @var{STATUS} argument is supplied, it
+contains 0 on success or a nonzero error code upon return; see
+@code{link(2)}.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL LINK(PATH1, PATH2 [, STATUS])}
+@item @code{STATUS = LINK(PATH1, PATH2)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{PATH1} @tab Shall be of default @code{CHARACTER} type.
+@item @var{PATH2} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STATUS} @tab (Optional) Shall be of default @code{INTEGER} type.
+@end multitable
+
+@item @emph{See also}:
+@ref{SYMLNK}, @gol
+@ref{UNLINK}
+@end table
+
+
+
+@node LLE
+@section @code{LLE} --- Lexical less than or equal
+@fnindex LLE
+@cindex lexical comparison of strings
+@cindex string, comparison
+
+@table @asis
+@item @emph{Description}:
+Determines whether one string is lexically less than or equal to another
+string, where the two strings are interpreted as containing ASCII
+character codes. If the String A and String B are not the same length,
+the shorter is compared as if spaces were appended to it to form a value
+that has the same length as the longer.
+
+In general, the lexical comparison intrinsics @code{LGE}, @code{LGT},
+@code{LLE}, and @code{LLT} differ from the corresponding intrinsic
+operators @code{.GE.}, @code{.GT.}, @code{.LE.}, and @code{.LT.}, in
+that the latter use the processor's character ordering (which is not
+ASCII on some targets), whereas the former always use the ASCII
+ordering.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LLE(STRING_A, STRING_B)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING_A} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STRING_B} @tab Shall be of default @code{CHARACTER} type.
+@end multitable
+
+@item @emph{Return value}:
+Returns @code{.TRUE.} if @code{STRING_A <= STRING_B}, and @code{.FALSE.}
+otherwise, based on the ASCII ordering.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .34 .16 .17 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{LLE(STRING_A,STRING_B)} @tab @code{CHARACTER} @tab @code{LOGICAL} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{LGE}, @gol
+@ref{LGT}, @gol
+@ref{LLT}
+@end table
+
+
+
+@node LLT
+@section @code{LLT} --- Lexical less than
+@fnindex LLT
+@cindex lexical comparison of strings
+@cindex string, comparison
+
+@table @asis
+@item @emph{Description}:
+Determines whether one string is lexically less than another string,
+where the two strings are interpreted as containing ASCII character
+codes. If the String A and String B are not the same length, the
+shorter is compared as if spaces were appended to it to form a value
+that has the same length as the longer.
+
+In general, the lexical comparison intrinsics @code{LGE}, @code{LGT},
+@code{LLE}, and @code{LLT} differ from the corresponding intrinsic
+operators @code{.GE.}, @code{.GT.}, @code{.LE.}, and @code{.LT.}, in
+that the latter use the processor's character ordering (which is not
+ASCII on some targets), whereas the former always use the ASCII
+ordering.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LLT(STRING_A, STRING_B)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING_A} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STRING_B} @tab Shall be of default @code{CHARACTER} type.
+@end multitable
+
+@item @emph{Return value}:
+Returns @code{.TRUE.} if @code{STRING_A < STRING_B}, and @code{.FALSE.}
+otherwise, based on the ASCII ordering.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .34 .16 .17 .30
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{LLT(STRING_A,STRING_B)} @tab @code{CHARACTER} @tab @code{LOGICAL} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{LGE}, @gol
+@ref{LGT}, @gol
+@ref{LLE}
+@end table
+
+
+
+@node LNBLNK
+@section @code{LNBLNK} --- Index of the last non-blank character in a string
+@fnindex LNBLNK
+@cindex string, find non-blank character
+
+@table @asis
+@item @emph{Description}:
+Returns the length of a character string, ignoring any trailing blanks.
+This is identical to the standard @code{LEN_TRIM} intrinsic, and is only
+included for backwards compatibility.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LNBLNK(STRING)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab Shall be a scalar of type @code{CHARACTER},
+with @code{INTENT(IN)}
+@end multitable
+
+@item @emph{Return value}:
+The return value is of @code{INTEGER(kind=4)} type.
+
+@item @emph{See also}:
+@ref{INDEX intrinsic}, @gol
+@ref{LEN_TRIM}
+@end table
+
+
+
+@node LOC
+@section @code{LOC} --- Returns the address of a variable
+@fnindex LOC
+@cindex location of a variable in memory
+
+@table @asis
+@item @emph{Description}:
+@code{LOC(X)} returns the address of @var{X} as an integer.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = LOC(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Variable of any type.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER}, with a @code{KIND}
+corresponding to the size (in bytes) of a memory address on the target
+machine.
+
+@item @emph{Example}:
+@smallexample
+program test_loc
+ integer :: i
+ real :: r
+ i = loc(r)
+ print *, i
+end program test_loc
+@end smallexample
+@end table
+
+
+
+@node LOG
+@section @code{LOG} --- Natural logarithm function
+@fnindex LOG
+@fnindex ALOG
+@fnindex DLOG
+@fnindex CLOG
+@fnindex ZLOG
+@fnindex CDLOG
+@cindex exponential function, inverse
+@cindex logarithm function
+@cindex natural logarithm function
+
+@table @asis
+@item @emph{Description}:
+@code{LOG(X)} computes the natural logarithm of @var{X}, i.e. the
+logarithm to the base @math{e}.
+
+@item @emph{Standard}:
+Fortran 77 and later, has GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LOG(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or
+@code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} or @code{COMPLEX}.
+The kind type parameter is the same as @var{X}.
+If @var{X} is @code{COMPLEX}, the imaginary part @math{\omega} is in the range
+@math{-\pi < \omega \leq \pi}.
+
+@item @emph{Example}:
+@smallexample
+program test_log
+ real(8) :: x = 2.7182818284590451_8
+ complex :: z = (1.0, 2.0)
+ x = log(x) ! will yield (approximately) 1
+ z = log(z)
+end program test_log
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ALOG(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 or later
+@item @code{DLOG(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 or later
+@item @code{CLOG(X)} @tab @code{COMPLEX(4) X} @tab @code{COMPLEX(4)} @tab Fortran 77 or later
+@item @code{ZLOG(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@item @code{CDLOG(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node LOG10
+@section @code{LOG10} --- Base 10 logarithm function
+@fnindex LOG10
+@fnindex ALOG10
+@fnindex DLOG10
+@cindex exponential function, inverse
+@cindex logarithm function with base 10
+@cindex base 10 logarithm function
+
+@table @asis
+@item @emph{Description}:
+@code{LOG10(X)} computes the base 10 logarithm of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LOG10(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} or @code{COMPLEX}.
+The kind type parameter is the same as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_log10
+ real(8) :: x = 10.0_8
+ x = log10(x)
+end program test_log10
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{ALOG10(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DLOG10(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+@end table
+
+
+
+@node LOG_GAMMA
+@section @code{LOG_GAMMA} --- Logarithm of the Gamma function
+@fnindex LOG_GAMMA
+@fnindex LGAMMA
+@fnindex ALGAMA
+@fnindex DLGAMA
+@cindex Gamma function, logarithm of
+
+@table @asis
+@item @emph{Description}:
+@code{LOG_GAMMA(X)} computes the natural logarithm of the absolute value
+of the Gamma (@math{\Gamma}) function.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{X = LOG_GAMMA(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL} and neither zero
+nor a negative integer.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} of the same kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_log_gamma
+ real :: x = 1.0
+ x = lgamma(x) ! returns 0.0
+end program test_log_gamma
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{LGAMMA(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{ALGAMA(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DLGAMA(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Gamma function: @gol
+@ref{GAMMA}
+@end table
+
+
+
+@node LOGICAL
+@section @code{LOGICAL} --- Convert to logical type
+@fnindex LOGICAL
+@cindex conversion, to logical
+
+@table @asis
+@item @emph{Description}:
+Converts one kind of @code{LOGICAL} variable to another.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LOGICAL(L [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{L} @tab The type shall be @code{LOGICAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a @code{LOGICAL} value equal to @var{L}, with a
+kind corresponding to @var{KIND}, or of the default logical kind if
+@var{KIND} is not given.
+
+@item @emph{See also}:
+@ref{INT}, @gol
+@ref{REAL}, @gol
+@ref{CMPLX}
+@end table
+
+
+
+@node LSHIFT
+@section @code{LSHIFT} --- Left shift bits
+@fnindex LSHIFT
+@cindex bits, shift left
+
+@table @asis
+@item @emph{Description}:
+@code{LSHIFT} returns a value corresponding to @var{I} with all of the
+bits shifted left by @var{SHIFT} places. @var{SHIFT} shall be
+nonnegative and less than or equal to @code{BIT_SIZE(I)}, otherwise
+the result value is undefined. Bits shifted out from the left end are
+lost; zeros are shifted in from the opposite end.
+
+This function has been superseded by the @code{ISHFT} intrinsic, which
+is standard in Fortran 95 and later, and the @code{SHIFTL} intrinsic,
+which is standard in Fortran 2008 and later.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = LSHIFT(I, SHIFT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{See also}:
+@ref{ISHFT}, @gol
+@ref{ISHFTC}, @gol
+@ref{RSHIFT}, @gol
+@ref{SHIFTA}, @gol
+@ref{SHIFTL}, @gol
+@ref{SHIFTR}
+@end table
+
+
+
+@node LSTAT
+@section @code{LSTAT} --- Get file status
+@fnindex LSTAT
+@cindex file system, file status
+
+@table @asis
+@item @emph{Description}:
+@code{LSTAT} is identical to @ref{STAT}, except that if path is a
+symbolic link, then the link itself is statted, not the file that it
+refers to.
+
+The elements in @code{VALUES} are the same as described by @ref{STAT}.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL LSTAT(NAME, VALUES [, STATUS])}
+@item @code{STATUS = LSTAT(NAME, VALUES)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NAME} @tab The type shall be @code{CHARACTER} of the default
+kind, a valid path within the file system.
+@item @var{VALUES} @tab The type shall be @code{INTEGER(4), DIMENSION(13)}.
+@item @var{STATUS} @tab (Optional) status flag of type @code{INTEGER(4)}.
+Returns 0 on success and a system specific error code otherwise.
+@end multitable
+
+@item @emph{Example}:
+See @ref{STAT} for an example.
+
+@item @emph{See also}:
+To stat an open file: @gol
+@ref{FSTAT} @gol
+To stat a file: @gol
+@ref{STAT}
+@end table
+
+
+
+@node LTIME
+@section @code{LTIME} --- Convert time to local time info
+@fnindex LTIME
+@cindex time, conversion to local time info
+
+@table @asis
+@item @emph{Description}:
+Given a system time value @var{TIME} (as provided by the @ref{TIME}
+intrinsic), fills @var{VALUES} with values extracted from it appropriate
+to the local time zone using @code{localtime(3)}.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. In new code, programmers should consider the use of
+the @ref{DATE_AND_TIME} intrinsic defined by the Fortran 95
+standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL LTIME(TIME, VALUES)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{TIME} @tab An @code{INTEGER} scalar expression
+corresponding to a system time, with @code{INTENT(IN)}.
+@item @var{VALUES} @tab A default @code{INTEGER} array with 9 elements,
+with @code{INTENT(OUT)}.
+@end multitable
+
+@item @emph{Return value}:
+The elements of @var{VALUES} are assigned as follows:
+@enumerate
+@item Seconds after the minute, range 0--59 or 0--61 to allow for leap
+seconds
+@item Minutes after the hour, range 0--59
+@item Hours past midnight, range 0--23
+@item Day of month, range 1--31
+@item Number of months since January, range 0--11
+@item Years since 1900
+@item Number of days since Sunday, range 0--6
+@item Days since January 1, range 0--365
+@item Daylight savings indicator: positive if daylight savings is in
+effect, zero if not, and negative if the information is not available.
+@end enumerate
+
+@item @emph{See also}:
+@ref{DATE_AND_TIME}, @gol
+@ref{CTIME}, @gol
+@ref{GMTIME}, @gol
+@ref{TIME}, @gol
+@ref{TIME8}
+@end table
+
+
+
+@node MALLOC
+@section @code{MALLOC} --- Allocate dynamic memory
+@fnindex MALLOC
+@cindex pointer, cray
+
+@table @asis
+@item @emph{Description}:
+@code{MALLOC(SIZE)} allocates @var{SIZE} bytes of dynamic memory and
+returns the address of the allocated memory. The @code{MALLOC} intrinsic
+is an extension intended to be used with Cray pointers, and is provided
+in GNU Fortran to allow the user to compile legacy code. For new code
+using Fortran 95 pointers, the memory allocation intrinsic is
+@code{ALLOCATE}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{PTR = MALLOC(SIZE)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SIZE} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER(K)}, with @var{K} such that
+variables of type @code{INTEGER(K)} have the same size as
+C pointers (@code{sizeof(void *)}).
+
+@item @emph{Example}:
+The following example demonstrates the use of @code{MALLOC} and
+@code{FREE} with Cray pointers.
+
+@smallexample
+program test_malloc
+ implicit none
+ integer i
+ real*8 x(*), z
+ pointer(ptr_x,x)
+
+ ptr_x = malloc(20*8)
+ do i = 1, 20
+ x(i) = sqrt(1.0d0 / i)
+ end do
+ z = 0
+ do i = 1, 20
+ z = z + x(i)
+ print *, z
+ end do
+ call free(ptr_x)
+end program test_malloc
+@end smallexample
+
+@item @emph{See also}:
+@ref{FREE}
+@end table
+
+
+
+@node MASKL
+@section @code{MASKL} --- Left justified mask
+@fnindex MASKL
+@cindex mask, left justified
+
+@table @asis
+@item @emph{Description}:
+@code{MASKL(I[, KIND])} has its leftmost @var{I} bits set to 1, and the
+remaining bits set to 0.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = MASKL(I[, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER}.
+@item @var{KIND} @tab Shall be a scalar constant expression of type
+@code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER}. If @var{KIND} is present, it
+specifies the kind value of the return type; otherwise, it is of the
+default integer kind.
+
+@item @emph{See also}:
+@ref{MASKR}
+@end table
+
+
+
+@node MASKR
+@section @code{MASKR} --- Right justified mask
+@fnindex MASKR
+@cindex mask, right justified
+
+@table @asis
+@item @emph{Description}:
+@code{MASKL(I[, KIND])} has its rightmost @var{I} bits set to 1, and the
+remaining bits set to 0.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = MASKR(I[, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER}.
+@item @var{KIND} @tab Shall be a scalar constant expression of type
+@code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER}. If @var{KIND} is present, it
+specifies the kind value of the return type; otherwise, it is of the
+default integer kind.
+
+@item @emph{See also}:
+@ref{MASKL}
+@end table
+
+
+
+@node MATMUL
+@section @code{MATMUL} --- matrix multiplication
+@fnindex MATMUL
+@cindex matrix multiplication
+@cindex product, matrix
+
+@table @asis
+@item @emph{Description}:
+Performs a matrix multiplication on numeric or logical arguments.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = MATMUL(MATRIX_A, MATRIX_B)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{MATRIX_A} @tab An array of @code{INTEGER},
+@code{REAL}, @code{COMPLEX}, or @code{LOGICAL} type, with a rank of
+one or two.
+@item @var{MATRIX_B} @tab An array of @code{INTEGER},
+@code{REAL}, or @code{COMPLEX} type if @var{MATRIX_A} is of a numeric
+type; otherwise, an array of @code{LOGICAL} type. The rank shall be one
+or two, and the first (or only) dimension of @var{MATRIX_B} shall be
+equal to the last (or only) dimension of @var{MATRIX_A}.
+@var{MATRIX_A} and @var{MATRIX_B} shall not both be rank one arrays.
+@end multitable
+
+@item @emph{Return value}:
+The matrix product of @var{MATRIX_A} and @var{MATRIX_B}. The type and
+kind of the result follow the usual type and kind promotion rules, as
+for the @code{*} or @code{.AND.} operators.
+@end table
+
+
+
+@node MAX
+@section @code{MAX} --- Maximum value of an argument list
+@fnindex MAX
+@fnindex MAX0
+@fnindex AMAX0
+@fnindex MAX1
+@fnindex AMAX1
+@fnindex DMAX1
+@cindex maximum value
+
+@table @asis
+@item @emph{Description}:
+Returns the argument with the largest (most positive) value.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = MAX(A1, A2 [, A3 [, ...]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A1} @tab The type shall be @code{INTEGER} or
+@code{REAL}.
+@item @var{A2}, @var{A3}, ... @tab An expression of the same type and kind
+as @var{A1}. (As a GNU extension, arguments of different kinds are
+permitted.)
+@end multitable
+
+@item @emph{Return value}:
+The return value corresponds to the maximum value among the arguments,
+and has the same type and kind as the first argument.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{MAX0(A1)} @tab @code{INTEGER(4) A1} @tab @code{INTEGER(4)} @tab Fortran 77 and later
+@item @code{AMAX0(A1)} @tab @code{INTEGER(4) A1} @tab @code{REAL(MAX(X))} @tab Fortran 77 and later
+@item @code{MAX1(A1)} @tab @code{REAL A1} @tab @code{INT(MAX(X))} @tab Fortran 77 and later
+@item @code{AMAX1(A1)} @tab @code{REAL(4) A1} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DMAX1(A1)} @tab @code{REAL(8) A1} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{MAXLOC} @gol
+@ref{MAXVAL}, @gol
+@ref{MIN}
+@end table
+
+
+
+@node MAXEXPONENT
+@section @code{MAXEXPONENT} --- Maximum exponent of a real kind
+@fnindex MAXEXPONENT
+@cindex model representation, maximum exponent
+
+@table @asis
+@item @emph{Description}:
+@code{MAXEXPONENT(X)} returns the maximum exponent in the model of the
+type of @code{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = MAXEXPONENT(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the default integer
+kind.
+
+@item @emph{Example}:
+@smallexample
+program exponents
+ real(kind=4) :: x
+ real(kind=8) :: y
+
+ print *, minexponent(x), maxexponent(x)
+ print *, minexponent(y), maxexponent(y)
+end program exponents
+@end smallexample
+@end table
+
+
+
+@node MAXLOC
+@section @code{MAXLOC} --- Location of the maximum value within an array
+@fnindex MAXLOC
+@cindex array, location of maximum element
+
+@table @asis
+@item @emph{Description}:
+Determines the location of the element in the array with the maximum
+value, or, if the @var{DIM} argument is supplied, determines the
+locations of the maximum element along each row of the array in the
+@var{DIM} direction. If @var{MASK} is present, only the elements for
+which @var{MASK} is @code{.TRUE.} are considered. If more than one
+element in the array has the maximum value, the location returned is
+that of the first such element in array element order if the
+@var{BACK} is not present, or is false; if @var{BACK} is true, the location
+returned is that of the last such element. If the array has zero
+size, or all of the elements of @var{MASK} are @code{.FALSE.}, then
+the result is an array of zeroes. Similarly, if @var{DIM} is supplied
+and all of the elements of @var{MASK} along a given row are zero, the
+result value for that row is zero.
+
+@item @emph{Standard}:
+Fortran 95 and later; @var{ARRAY} of @code{CHARACTER} and the
+@var{KIND} argument are available in Fortran 2003 and later.
+The @var{BACK} argument is available in Fortran 2008 and later.
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = MAXLOC(ARRAY, DIM [, MASK] [,KIND] [,BACK])}
+@item @code{RESULT = MAXLOC(ARRAY [, MASK] [,KIND] [,BACK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER} or
+@code{REAL}.
+@item @var{DIM} @tab (Optional) Shall be a scalar of type
+@code{INTEGER}, with a value between one and the rank of @var{ARRAY},
+inclusive. It may not be an optional dummy argument.
+@item @var{MASK} @tab Shall be of type @code{LOGICAL},
+and conformable with @var{ARRAY}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@item @var{BACK} @tab (Optional) A scalar of type @code{LOGICAL}.
+@end multitable
+
+@item @emph{Return value}:
+If @var{DIM} is absent, the result is a rank-one array with a length
+equal to the rank of @var{ARRAY}. If @var{DIM} is present, the result
+is an array with a rank one less than the rank of @var{ARRAY}, and a
+size corresponding to the size of @var{ARRAY} with the @var{DIM}
+dimension removed. If @var{DIM} is present and @var{ARRAY} has a rank
+of one, the result is a scalar. If the optional argument @var{KIND}
+is present, the result is an integer of kind @var{KIND}, otherwise it
+is of default kind.
+
+@item @emph{See also}:
+@ref{FINDLOC}, @gol
+@ref{MAX}, @gol
+@ref{MAXVAL}
+@end table
+
+
+
+@node MAXVAL
+@section @code{MAXVAL} --- Maximum value of an array
+@fnindex MAXVAL
+@cindex array, maximum value
+@cindex maximum value
+
+@table @asis
+@item @emph{Description}:
+Determines the maximum value of the elements in an array value, or, if
+the @var{DIM} argument is supplied, determines the maximum value along
+each row of the array in the @var{DIM} direction. If @var{MASK} is
+present, only the elements for which @var{MASK} is @code{.TRUE.} are
+considered. If the array has zero size, or all of the elements of
+@var{MASK} are @code{.FALSE.}, then the result is @code{-HUGE(ARRAY)}
+if @var{ARRAY} is numeric, or a string of nulls if @var{ARRAY} is of character
+type.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = MAXVAL(ARRAY, DIM [, MASK])}
+@item @code{RESULT = MAXVAL(ARRAY [, MASK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER} or
+@code{REAL}.
+@item @var{DIM} @tab (Optional) Shall be a scalar of type
+@code{INTEGER}, with a value between one and the rank of @var{ARRAY},
+inclusive. It may not be an optional dummy argument.
+@item @var{MASK} @tab (Optional) Shall be of type @code{LOGICAL},
+and conformable with @var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+If @var{DIM} is absent, or if @var{ARRAY} has a rank of one, the result
+is a scalar. If @var{DIM} is present, the result is an array with a
+rank one less than the rank of @var{ARRAY}, and a size corresponding to
+the size of @var{ARRAY} with the @var{DIM} dimension removed. In all
+cases, the result is of the same type and kind as @var{ARRAY}.
+
+@item @emph{See also}:
+@ref{MAX}, @gol
+@ref{MAXLOC}
+@end table
+
+
+
+@node MCLOCK
+@section @code{MCLOCK} --- Time function
+@fnindex MCLOCK
+@cindex time, clock ticks
+@cindex clock ticks
+
+@table @asis
+@item @emph{Description}:
+Returns the number of clock ticks since the start of the process, based
+on the function @code{clock(3)} in the C standard library.
+
+This intrinsic is not fully portable, such as to systems with 32-bit
+@code{INTEGER} types but supporting times wider than 32 bits. Therefore,
+the values returned by this intrinsic might be, or become, negative, or
+numerically less than previous values, during a single run of the
+compiled program.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = MCLOCK()}
+
+@item @emph{Return value}:
+The return value is a scalar of type @code{INTEGER(4)}, equal to the
+number of clock ticks since the start of the process, or @code{-1} if
+the system does not support @code{clock(3)}.
+
+@item @emph{See also}:
+@ref{CTIME}, @gol
+@ref{GMTIME}, @gol
+@ref{LTIME}, @gol
+@ref{MCLOCK}, @gol
+@ref{TIME}
+@end table
+
+
+
+@node MCLOCK8
+@section @code{MCLOCK8} --- Time function (64-bit)
+@fnindex MCLOCK8
+@cindex time, clock ticks
+@cindex clock ticks
+
+@table @asis
+@item @emph{Description}:
+Returns the number of clock ticks since the start of the process, based
+on the function @code{clock(3)} in the C standard library.
+
+@emph{Warning:} this intrinsic does not increase the range of the timing
+values over that returned by @code{clock(3)}. On a system with a 32-bit
+@code{clock(3)}, @code{MCLOCK8} will return a 32-bit value, even though
+it is converted to a 64-bit @code{INTEGER(8)} value. That means
+overflows of the 32-bit value can still occur. Therefore, the values
+returned by this intrinsic might be or become negative or numerically
+less than previous values during a single run of the compiled program.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = MCLOCK8()}
+
+@item @emph{Return value}:
+The return value is a scalar of type @code{INTEGER(8)}, equal to the
+number of clock ticks since the start of the process, or @code{-1} if
+the system does not support @code{clock(3)}.
+
+@item @emph{See also}:
+@ref{CTIME}, @gol
+@ref{GMTIME}, @gol
+@ref{LTIME}, @gol
+@ref{MCLOCK}, @gol
+@ref{TIME8}
+@end table
+
+
+
+@node MERGE
+@section @code{MERGE} --- Merge variables
+@fnindex MERGE
+@cindex array, merge arrays
+@cindex array, combine arrays
+
+@table @asis
+@item @emph{Description}:
+Select values from two arrays according to a logical mask. The result
+is equal to @var{TSOURCE} if @var{MASK} is @code{.TRUE.}, or equal to
+@var{FSOURCE} if it is @code{.FALSE.}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = MERGE(TSOURCE, FSOURCE, MASK)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{TSOURCE} @tab May be of any type.
+@item @var{FSOURCE} @tab Shall be of the same type and type parameters
+as @var{TSOURCE}.
+@item @var{MASK} @tab Shall be of type @code{LOGICAL}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type and type parameters as @var{TSOURCE}.
+
+@end table
+
+
+
+@node MERGE_BITS
+@section @code{MERGE_BITS} --- Merge of bits under mask
+@fnindex MERGE_BITS
+@cindex bits, merge
+
+@table @asis
+@item @emph{Description}:
+@code{MERGE_BITS(I, J, MASK)} merges the bits of @var{I} and @var{J}
+as determined by the mask. The i-th bit of the result is equal to the
+i-th bit of @var{I} if the i-th bit of @var{MASK} is 1; it is equal to
+the i-th bit of @var{J} otherwise.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = MERGE_BITS(I, J, MASK)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER} or a boz-literal-constant.
+@item @var{J} @tab Shall be of type @code{INTEGER} with the same
+kind type parameter as @var{I} or a boz-literal-constant.
+@var{I} and @var{J} shall not both be boz-literal-constants.
+@item @var{MASK} @tab Shall be of type @code{INTEGER} or a boz-literal-constant
+and of the same kind as @var{I}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type and kind as @var{I}.
+
+@end table
+
+
+
+@node MIN
+@section @code{MIN} --- Minimum value of an argument list
+@fnindex MIN
+@fnindex MIN0
+@fnindex AMIN0
+@fnindex MIN1
+@fnindex AMIN1
+@fnindex DMIN1
+@cindex minimum value
+
+@table @asis
+@item @emph{Description}:
+Returns the argument with the smallest (most negative) value.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = MIN(A1, A2 [, A3, ...])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A1} @tab The type shall be @code{INTEGER} or
+@code{REAL}.
+@item @var{A2}, @var{A3}, ... @tab An expression of the same type and kind
+as @var{A1}. (As a GNU extension, arguments of different kinds are
+permitted.)
+@end multitable
+
+@item @emph{Return value}:
+The return value corresponds to the minimum value among the arguments,
+and has the same type and kind as the first argument.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{MIN0(A1)} @tab @code{INTEGER(4) A1} @tab @code{INTEGER(4)} @tab Fortran 77 and later
+@item @code{AMIN0(A1)} @tab @code{INTEGER(4) A1} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{MIN1(A1)} @tab @code{REAL A1} @tab @code{INTEGER(4)} @tab Fortran 77 and later
+@item @code{AMIN1(A1)} @tab @code{REAL(4) A1} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DMIN1(A1)} @tab @code{REAL(8) A1} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{MAX}, @gol
+@ref{MINLOC}, @gol
+@ref{MINVAL}
+@end table
+
+
+
+@node MINEXPONENT
+@section @code{MINEXPONENT} --- Minimum exponent of a real kind
+@fnindex MINEXPONENT
+@cindex model representation, minimum exponent
+
+@table @asis
+@item @emph{Description}:
+@code{MINEXPONENT(X)} returns the minimum exponent in the model of the
+type of @code{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = MINEXPONENT(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the default integer
+kind.
+
+@item @emph{Example}:
+See @code{MAXEXPONENT} for an example.
+@end table
+
+
+
+@node MINLOC
+@section @code{MINLOC} --- Location of the minimum value within an array
+@fnindex MINLOC
+@cindex array, location of minimum element
+
+@table @asis
+@item @emph{Description}:
+Determines the location of the element in the array with the minimum
+value, or, if the @var{DIM} argument is supplied, determines the
+locations of the minimum element along each row of the array in the
+@var{DIM} direction. If @var{MASK} is present, only the elements for
+which @var{MASK} is @code{.TRUE.} are considered. If more than one
+element in the array has the minimum value, the location returned is
+that of the first such element in array element order if the
+@var{BACK} is not present, or is false; if @var{BACK} is true, the location
+returned is that of the last such element. If the array has
+zero size, or all of the elements of @var{MASK} are @code{.FALSE.}, then
+the result is an array of zeroes. Similarly, if @var{DIM} is supplied
+and all of the elements of @var{MASK} along a given row are zero, the
+result value for that row is zero.
+
+@item @emph{Standard}:
+Fortran 90 and later; @var{ARRAY} of @code{CHARACTER} and the
+@var{KIND} argument are available in Fortran 2003 and later.
+The @var{BACK} argument is available in Fortran 2008 and later.
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = MINLOC(ARRAY, DIM [, MASK] [,KIND] [,BACK])}
+@item @code{RESULT = MINLOC(ARRAY [, MASK], [,KIND] [,BACK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER},
+@code{REAL} or @code{CHARACTER}.
+@item @var{DIM} @tab (Optional) Shall be a scalar of type
+@code{INTEGER}, with a value between one and the rank of @var{ARRAY},
+inclusive. It may not be an optional dummy argument.
+@item @var{MASK} @tab Shall be of type @code{LOGICAL},
+and conformable with @var{ARRAY}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@item @var{BACK} @tab (Optional) A scalar of type @code{LOGICAL}.
+@end multitable
+
+@item @emph{Return value}:
+If @var{DIM} is absent, the result is a rank-one array with a length
+equal to the rank of @var{ARRAY}. If @var{DIM} is present, the result
+is an array with a rank one less than the rank of @var{ARRAY}, and a
+size corresponding to the size of @var{ARRAY} with the @var{DIM}
+dimension removed. If @var{DIM} is present and @var{ARRAY} has a rank
+of one, the result is a scalar. If the optional argument @var{KIND}
+is present, the result is an integer of kind @var{KIND}, otherwise it
+is of default kind.
+
+@item @emph{See also}:
+@ref{FINDLOC}, @gol
+@ref{MIN}, @gol
+@ref{MINVAL}
+@end table
+
+
+
+@node MINVAL
+@section @code{MINVAL} --- Minimum value of an array
+@fnindex MINVAL
+@cindex array, minimum value
+@cindex minimum value
+
+@table @asis
+@item @emph{Description}:
+Determines the minimum value of the elements in an array value, or, if
+the @var{DIM} argument is supplied, determines the minimum value along
+each row of the array in the @var{DIM} direction. If @var{MASK} is
+present, only the elements for which @var{MASK} is @code{.TRUE.} are
+considered. If the array has zero size, or all of the elements of
+@var{MASK} are @code{.FALSE.}, then the result is @code{HUGE(ARRAY)} if
+@var{ARRAY} is numeric, or a string of @code{CHAR(255)} characters if
+@var{ARRAY} is of character type.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = MINVAL(ARRAY, DIM [, MASK])}
+@item @code{RESULT = MINVAL(ARRAY [, MASK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER} or
+@code{REAL}.
+@item @var{DIM} @tab (Optional) Shall be a scalar of type
+@code{INTEGER}, with a value between one and the rank of @var{ARRAY},
+inclusive. It may not be an optional dummy argument.
+@item @var{MASK} @tab Shall be of type @code{LOGICAL},
+and conformable with @var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+If @var{DIM} is absent, or if @var{ARRAY} has a rank of one, the result
+is a scalar. If @var{DIM} is present, the result is an array with a
+rank one less than the rank of @var{ARRAY}, and a size corresponding to
+the size of @var{ARRAY} with the @var{DIM} dimension removed. In all
+cases, the result is of the same type and kind as @var{ARRAY}.
+
+@item @emph{See also}:
+@ref{MIN}, @gol
+@ref{MINLOC}
+@end table
+
+
+
+@node MOD
+@section @code{MOD} --- Remainder function
+@fnindex MOD
+@fnindex AMOD
+@fnindex DMOD
+@fnindex BMOD
+@fnindex IMOD
+@fnindex JMOD
+@fnindex KMOD
+@cindex remainder
+@cindex division, remainder
+
+@table @asis
+@item @emph{Description}:
+@code{MOD(A,P)} computes the remainder of the division of A by P@.
+
+@item @emph{Standard}:
+Fortran 77 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = MOD(A, P)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be a scalar of type @code{INTEGER} or @code{REAL}.
+@item @var{P} @tab Shall be a scalar of the same type and kind as @var{A}
+and not equal to zero. (As a GNU extension, arguments of different kinds are
+permitted.)
+@end multitable
+
+@item @emph{Return value}:
+The return value is the result of @code{A - (INT(A/P) * P)}. The type
+and kind of the return value is the same as that of the arguments. The
+returned value has the same sign as A and a magnitude less than the
+magnitude of P. (As a GNU extension, kind is the largest kind of the actual
+arguments.)
+
+@item @emph{Example}:
+@smallexample
+program test_mod
+ print *, mod(17,3)
+ print *, mod(17.5,5.5)
+ print *, mod(17.5d0,5.5)
+ print *, mod(17.5,5.5d0)
+
+ print *, mod(-17,3)
+ print *, mod(-17.5,5.5)
+ print *, mod(-17.5d0,5.5)
+ print *, mod(-17.5,5.5d0)
+
+ print *, mod(17,-3)
+ print *, mod(17.5,-5.5)
+ print *, mod(17.5d0,-5.5)
+ print *, mod(17.5,-5.5d0)
+end program test_mod
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .25 .20 .31
+@headitem Name @tab Arguments @tab Return type @tab Standard
+@item @code{MOD(A,P)} @tab @code{INTEGER A,P} @tab @code{INTEGER} @tab Fortran 77 and later
+@item @code{AMOD(A,P)} @tab @code{REAL(4) A,P} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DMOD(A,P)} @tab @code{REAL(8) A,P} @tab @code{REAL(8)} @tab Fortran 77 and later
+@item @code{BMOD(A,P)} @tab @code{INTEGER(1) A,P} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IMOD(A,P)} @tab @code{INTEGER(2) A,P} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JMOD(A,P)} @tab @code{INTEGER(4) A,P} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KMOD(A,P)} @tab @code{INTEGER(8) A,P} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{MODULO}
+
+@end table
+
+
+
+@node MODULO
+@section @code{MODULO} --- Modulo function
+@fnindex MODULO
+@cindex modulo
+@cindex division, modulo
+
+@table @asis
+@item @emph{Description}:
+@code{MODULO(A,P)} computes the @var{A} modulo @var{P}.
+
+@item @emph{Standard}:
+Fortran 95 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = MODULO(A, P)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be a scalar of type @code{INTEGER} or @code{REAL}.
+@item @var{P} @tab Shall be a scalar of the same type and kind as @var{A}.
+It shall not be zero. (As a GNU extension, arguments of different kinds are
+permitted.)
+@end multitable
+
+@item @emph{Return value}:
+The type and kind of the result are those of the arguments. (As a GNU
+extension, kind is the largest kind of the actual arguments.)
+@table @asis
+@item If @var{A} and @var{P} are of type @code{INTEGER}:
+@code{MODULO(A,P)} has the value @var{R} such that @code{A=Q*P+R}, where
+@var{Q} is an integer and @var{R} is between 0 (inclusive) and @var{P}
+(exclusive).
+@item If @var{A} and @var{P} are of type @code{REAL}:
+@code{MODULO(A,P)} has the value of @code{A - FLOOR (A / P) * P}.
+@end table
+The returned value has the same sign as P and a magnitude less than
+the magnitude of P.
+
+@item @emph{Example}:
+@smallexample
+program test_modulo
+ print *, modulo(17,3)
+ print *, modulo(17.5,5.5)
+
+ print *, modulo(-17,3)
+ print *, modulo(-17.5,5.5)
+
+ print *, modulo(17,-3)
+ print *, modulo(17.5,-5.5)
+end program
+@end smallexample
+
+@item @emph{See also}:
+@ref{MOD}
+
+@end table
+
+
+
+@node MOVE_ALLOC
+@section @code{MOVE_ALLOC} --- Move allocation from one object to another
+@fnindex MOVE_ALLOC
+@cindex moving allocation
+@cindex allocation, moving
+
+@table @asis
+@item @emph{Description}:
+@code{MOVE_ALLOC(FROM, TO)} moves the allocation from @var{FROM} to
+@var{TO}. @var{FROM} will become deallocated in the process.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Pure subroutine
+
+@item @emph{Syntax}:
+@code{CALL MOVE_ALLOC(FROM, TO)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{FROM} @tab @code{ALLOCATABLE}, @code{INTENT(INOUT)}, may be
+of any type and kind.
+@item @var{TO} @tab @code{ALLOCATABLE}, @code{INTENT(OUT)}, shall be
+of the same type, kind and rank as @var{FROM}.
+@end multitable
+
+@item @emph{Return value}:
+None
+
+@item @emph{Example}:
+@smallexample
+program test_move_alloc
+ integer, allocatable :: a(:), b(:)
+
+ allocate(a(3))
+ a = [ 1, 2, 3 ]
+ call move_alloc(a, b)
+ print *, allocated(a), allocated(b)
+ print *, b
+end program test_move_alloc
+@end smallexample
+@end table
+
+
+
+@node MVBITS
+@section @code{MVBITS} --- Move bits from one integer to another
+@fnindex MVBITS
+@fnindex BMVBITS
+@fnindex IMVBITS
+@fnindex JMVBITS
+@fnindex KMVBITS
+@cindex bits, move
+
+@table @asis
+@item @emph{Description}:
+Moves @var{LEN} bits from positions @var{FROMPOS} through
+@code{FROMPOS+LEN-1} of @var{FROM} to positions @var{TOPOS} through
+@code{TOPOS+LEN-1} of @var{TO}. The portion of argument @var{TO} not
+affected by the movement of bits is unchanged. The values of
+@code{FROMPOS+LEN-1} and @code{TOPOS+LEN-1} must be less than
+@code{BIT_SIZE(FROM)}.
+
+@item @emph{Standard}:
+Fortran 90 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental subroutine
+
+@item @emph{Syntax}:
+@code{CALL MVBITS(FROM, FROMPOS, LEN, TO, TOPOS)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{FROM} @tab The type shall be @code{INTEGER}.
+@item @var{FROMPOS} @tab The type shall be @code{INTEGER}.
+@item @var{LEN} @tab The type shall be @code{INTEGER}.
+@item @var{TO} @tab The type shall be @code{INTEGER}, of the
+same kind as @var{FROM}.
+@item @var{TOPOS} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{MVBITS(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 90 and later
+@item @code{BMVBITS(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{IMVBITS(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JMVBITS(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KMVBITS(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{IBCLR}, @gol
+@ref{IBSET}, @gol
+@ref{IBITS}, @gol
+@ref{IAND}, @gol
+@ref{IOR}, @gol
+@ref{IEOR}
+@end table
+
+
+
+@node NEAREST
+@section @code{NEAREST} --- Nearest representable number
+@fnindex NEAREST
+@cindex real number, nearest different
+@cindex floating point, nearest different
+
+@table @asis
+@item @emph{Description}:
+@code{NEAREST(X, S)} returns the processor-representable number nearest
+to @code{X} in the direction indicated by the sign of @code{S}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = NEAREST(X, S)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL}.
+@item @var{S} @tab Shall be of type @code{REAL} and
+not equal to zero.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type as @code{X}. If @code{S} is
+positive, @code{NEAREST} returns the processor-representable number
+greater than @code{X} and nearest to it. If @code{S} is negative,
+@code{NEAREST} returns the processor-representable number smaller than
+@code{X} and nearest to it.
+
+@item @emph{Example}:
+@smallexample
+program test_nearest
+ real :: x, y
+ x = nearest(42.0, 1.0)
+ y = nearest(42.0, -1.0)
+ write (*,"(3(G20.15))") x, y, x - y
+end program test_nearest
+@end smallexample
+@end table
+
+
+
+@node NEW_LINE
+@section @code{NEW_LINE} --- New line character
+@fnindex NEW_LINE
+@cindex newline
+@cindex output, newline
+
+@table @asis
+@item @emph{Description}:
+@code{NEW_LINE(C)} returns the new-line character.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = NEW_LINE(C)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{C} @tab The argument shall be a scalar or array of the
+type @code{CHARACTER}.
+@end multitable
+
+@item @emph{Return value}:
+Returns a @var{CHARACTER} scalar of length one with the new-line character of
+the same kind as parameter @var{C}.
+
+@item @emph{Example}:
+@smallexample
+program newline
+ implicit none
+ write(*,'(A)') 'This is record 1.'//NEW_LINE('A')//'This is record 2.'
+end program newline
+@end smallexample
+@end table
+
+
+
+@node NINT
+@section @code{NINT} --- Nearest whole number
+@fnindex NINT
+@fnindex IDNINT
+@cindex rounding, nearest whole number
+
+@table @asis
+@item @emph{Description}:
+@code{NINT(A)} rounds its argument to the nearest whole number.
+
+@item @emph{Standard}:
+Fortran 77 and later, with @var{KIND} argument Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = NINT(A [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab The type of the argument shall be @code{REAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+Returns @var{A} with the fractional portion of its magnitude eliminated by
+rounding to the nearest whole number and with its sign preserved,
+converted to an @code{INTEGER} of the default kind.
+
+@item @emph{Example}:
+@smallexample
+program test_nint
+ real(4) x4
+ real(8) x8
+ x4 = 1.234E0_4
+ x8 = 4.321_8
+ print *, nint(x4), idnint(x8)
+end program test_nint
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return Type @tab Standard
+@item @code{NINT(A)} @tab @code{REAL(4) A} @tab @code{INTEGER} @tab Fortran 77 and later
+@item @code{IDNINT(A)} @tab @code{REAL(8) A} @tab @code{INTEGER} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{CEILING}, @gol
+@ref{FLOOR}
+@end table
+
+
+
+@node NORM2
+@section @code{NORM2} --- Euclidean vector norms
+@fnindex NORM2
+@cindex Euclidean vector norm
+@cindex L2 vector norm
+@cindex norm, Euclidean
+
+@table @asis
+@item @emph{Description}:
+Calculates the Euclidean vector norm (@math{L_2} norm)
+of @var{ARRAY} along dimension @var{DIM}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = NORM2(ARRAY[, DIM])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{REAL}
+@item @var{DIM} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with a value in the range from 1 to n, where n
+equals the rank of @var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type as @var{ARRAY}.
+
+If @var{DIM} is absent, a scalar with the square root of the sum of all
+elements in @var{ARRAY} squared is returned. Otherwise, an array of
+rank @math{n-1}, where @math{n} equals the rank of @var{ARRAY}, and a
+shape similar to that of @var{ARRAY} with dimension @var{DIM} dropped
+is returned.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_sum
+ REAL :: x(5) = [ real :: 1, 2, 3, 4, 5 ]
+ print *, NORM2(x) ! = sqrt(55.) ~ 7.416
+END PROGRAM
+@end smallexample
+@end table
+
+
+
+@node NOT
+@section @code{NOT} --- Logical negation
+@fnindex NOT
+@fnindex BNOT
+@fnindex INOT
+@fnindex JNOT
+@fnindex KNOT
+@cindex bits, negate
+@cindex bitwise logical not
+@cindex logical not, bitwise
+
+@table @asis
+@item @emph{Description}:
+@code{NOT} returns the bitwise Boolean inverse of @var{I}.
+
+@item @emph{Standard}:
+Fortran 90 and later, has overloads that are GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = NOT(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return type is @code{INTEGER}, of the same kind as the
+argument.
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{NOT(A)} @tab @code{INTEGER A} @tab @code{INTEGER} @tab Fortran 95 and later
+@item @code{BNOT(A)} @tab @code{INTEGER(1) A} @tab @code{INTEGER(1)} @tab GNU extension
+@item @code{INOT(A)} @tab @code{INTEGER(2) A} @tab @code{INTEGER(2)} @tab GNU extension
+@item @code{JNOT(A)} @tab @code{INTEGER(4) A} @tab @code{INTEGER(4)} @tab GNU extension
+@item @code{KNOT(A)} @tab @code{INTEGER(8) A} @tab @code{INTEGER(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+@ref{IAND}, @gol
+@ref{IEOR}, @gol
+@ref{IOR}, @gol
+@ref{IBITS}, @gol
+@ref{IBSET}, @gol
+@ref{IBCLR}
+@end table
+
+
+
+@node NULL
+@section @code{NULL} --- Function that returns an disassociated pointer
+@fnindex NULL
+@cindex pointer, status
+@cindex pointer, disassociated
+
+@table @asis
+@item @emph{Description}:
+Returns a disassociated pointer.
+
+If @var{MOLD} is present, a disassociated pointer of the same type is
+returned, otherwise the type is determined by context.
+
+In Fortran 95, @var{MOLD} is optional. Please note that Fortran 2003
+includes cases where it is required.
+
+@item @emph{Standard}:
+Fortran 95 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{PTR => NULL([MOLD])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{MOLD} @tab (Optional) shall be a pointer of any association
+status and of any type.
+@end multitable
+
+@item @emph{Return value}:
+A disassociated pointer.
+
+@item @emph{Example}:
+@smallexample
+REAL, POINTER, DIMENSION(:) :: VEC => NULL ()
+@end smallexample
+
+@item @emph{See also}:
+@ref{ASSOCIATED}
+@end table
+
+
+
+@node NUM_IMAGES
+@section @code{NUM_IMAGES} --- Function that returns the number of images
+@fnindex NUM_IMAGES
+@cindex coarray, @code{NUM_IMAGES}
+@cindex images, number of
+
+@table @asis
+@item @emph{Description}:
+Returns the number of images.
+
+@item @emph{Standard}:
+Fortran 2008 and later. With @var{DISTANCE} or @var{FAILED} argument,
+Technical Specification (TS) 18508 or later
+
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = NUM_IMAGES(DISTANCE, FAILED)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{DISTANCE} @tab (optional, intent(in)) Nonnegative scalar integer
+@item @var{FAILED} @tab (optional, intent(in)) Scalar logical expression
+@end multitable
+
+@item @emph{Return value}:
+Scalar default-kind integer. If @var{DISTANCE} is not present or has value 0,
+the number of images in the current team is returned. For values smaller or
+equal distance to the initial team, it returns the number of images index
+on the ancestor team which has a distance of @var{DISTANCE} from the invoking
+team. If @var{DISTANCE} is larger than the distance to the initial team, the
+number of images of the initial team is returned. If @var{FAILED} is not present
+the total number of images is returned; if it has the value @code{.TRUE.},
+the number of failed images is returned, otherwise, the number of images which
+do have not the failed status.
+
+@item @emph{Example}:
+@smallexample
+INTEGER :: value[*]
+INTEGER :: i
+value = THIS_IMAGE()
+SYNC ALL
+IF (THIS_IMAGE() == 1) THEN
+ DO i = 1, NUM_IMAGES()
+ WRITE(*,'(2(a,i0))') 'value[', i, '] is ', value[i]
+ END DO
+END IF
+@end smallexample
+
+@item @emph{See also}:
+@ref{THIS_IMAGE}, @gol
+@ref{IMAGE_INDEX}
+@end table
+
+
+
+@node OR
+@section @code{OR} --- Bitwise logical OR
+@fnindex OR
+@cindex bitwise logical or
+@cindex logical or, bitwise
+
+@table @asis
+@item @emph{Description}:
+Bitwise logical @code{OR}.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. For integer arguments, programmers should consider
+the use of the @ref{IOR} intrinsic defined by the Fortran standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = OR(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be either a scalar @code{INTEGER}
+type or a scalar @code{LOGICAL} type or a boz-literal-constant.
+@item @var{J} @tab The type shall be the same as the type of @var{I} or
+a boz-literal-constant. @var{I} and @var{J} shall not both be
+boz-literal-constants. If either @var{I} and @var{J} is a
+boz-literal-constant, then the other argument must be a scalar @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return type is either a scalar @code{INTEGER} or a scalar
+@code{LOGICAL}. If the kind type parameters differ, then the
+smaller kind type is implicitly converted to larger kind, and the
+return has the larger kind. A boz-literal-constant is
+converted to an @code{INTEGER} with the kind type parameter of
+the other argument as-if a call to @ref{INT} occurred.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_or
+ LOGICAL :: T = .TRUE., F = .FALSE.
+ INTEGER :: a, b
+ DATA a / Z'F' /, b / Z'3' /
+
+ WRITE (*,*) OR(T, T), OR(T, F), OR(F, T), OR(F, F)
+ WRITE (*,*) OR(a, b)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+Fortran 95 elemental function: @gol
+@ref{IOR}
+@end table
+
+
+
+@node PACK
+@section @code{PACK} --- Pack an array into an array of rank one
+@fnindex PACK
+@cindex array, packing
+@cindex array, reduce dimension
+@cindex array, gather elements
+
+@table @asis
+@item @emph{Description}:
+Stores the elements of @var{ARRAY} in an array of rank one.
+
+The beginning of the resulting array is made up of elements whose @var{MASK}
+equals @code{TRUE}. Afterwards, positions are filled with elements taken from
+@var{VECTOR}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = PACK(ARRAY, MASK[,VECTOR])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of any type.
+@item @var{MASK} @tab Shall be an array of type @code{LOGICAL} and
+of the same size as @var{ARRAY}. Alternatively, it may be a @code{LOGICAL}
+scalar.
+@item @var{VECTOR} @tab (Optional) shall be an array of the same type
+as @var{ARRAY} and of rank one. If present, the number of elements in
+@var{VECTOR} shall be equal to or greater than the number of true elements
+in @var{MASK}. If @var{MASK} is scalar, the number of elements in
+@var{VECTOR} shall be equal to or greater than the number of elements in
+@var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+The result is an array of rank one and the same type as that of @var{ARRAY}.
+If @var{VECTOR} is present, the result size is that of @var{VECTOR}, the
+number of @code{TRUE} values in @var{MASK} otherwise.
+
+@item @emph{Example}:
+Gathering nonzero elements from an array:
+@smallexample
+PROGRAM test_pack_1
+ INTEGER :: m(6)
+ m = (/ 1, 0, 0, 0, 5, 0 /)
+ WRITE(*, FMT="(6(I0, ' '))") pack(m, m /= 0) ! "1 5"
+END PROGRAM
+@end smallexample
+
+Gathering nonzero elements from an array and appending elements from @var{VECTOR}:
+@smallexample
+PROGRAM test_pack_2
+ INTEGER :: m(4)
+ m = (/ 1, 0, 0, 2 /)
+ ! The following results in "1 2 3 4"
+ WRITE(*, FMT="(4(I0, ' '))") pack(m, m /= 0, (/ 0, 0, 3, 4 /))
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{UNPACK}
+@end table
+
+
+
+@node PARITY
+@section @code{PARITY} --- Reduction with exclusive OR
+@fnindex PARITY
+@cindex Parity
+@cindex Reduction, XOR
+@cindex XOR reduction
+
+@table @asis
+@item @emph{Description}:
+Calculates the parity, i.e. the reduction using @code{.XOR.},
+of @var{MASK} along dimension @var{DIM}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = PARITY(MASK[, DIM])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{MASK} @tab Shall be an array of type @code{LOGICAL}
+@item @var{DIM} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with a value in the range from 1 to n, where n
+equals the rank of @var{MASK}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type as @var{MASK}.
+
+If @var{DIM} is absent, a scalar with the parity of all elements in
+@var{MASK} is returned, i.e. true if an odd number of elements is
+@code{.true.} and false otherwise. If @var{DIM} is present, an array
+of rank @math{n-1}, where @math{n} equals the rank of @var{ARRAY},
+and a shape similar to that of @var{MASK} with dimension @var{DIM}
+dropped is returned.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_sum
+ LOGICAL :: x(2) = [ .true., .false. ]
+ print *, PARITY(x) ! prints "T" (true).
+END PROGRAM
+@end smallexample
+@end table
+
+
+
+@node PERROR
+@section @code{PERROR} --- Print system error message
+@fnindex PERROR
+@cindex system, error handling
+
+@table @asis
+@item @emph{Description}:
+Prints (on the C @code{stderr} stream) a newline-terminated error
+message corresponding to the last system error. This is prefixed by
+@var{STRING}, a colon and a space. See @code{perror(3)}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL PERROR(STRING)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab A scalar of type @code{CHARACTER} and of the
+default kind.
+@end multitable
+
+@item @emph{See also}:
+@ref{IERRNO}
+@end table
+
+
+
+@node POPCNT
+@section @code{POPCNT} --- Number of bits set
+@fnindex POPCNT
+@cindex binary representation
+@cindex bits set
+
+@table @asis
+@item @emph{Description}:
+@code{POPCNT(I)} returns the number of bits set ('1' bits) in the binary
+representation of @code{I}.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = POPCNT(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the default integer
+kind.
+
+@item @emph{Example}:
+@smallexample
+program test_population
+ print *, popcnt(127), poppar(127)
+ print *, popcnt(huge(0_4)), poppar(huge(0_4))
+ print *, popcnt(huge(0_8)), poppar(huge(0_8))
+end program test_population
+@end smallexample
+@item @emph{See also}:
+@ref{POPPAR}, @gol
+@ref{LEADZ}, @gol
+@ref{TRAILZ}
+@end table
+
+
+
+@node POPPAR
+@section @code{POPPAR} --- Parity of the number of bits set
+@fnindex POPPAR
+@cindex binary representation
+@cindex parity
+
+@table @asis
+@item @emph{Description}:
+@code{POPPAR(I)} returns parity of the integer @code{I}, i.e. the parity
+of the number of bits set ('1' bits) in the binary representation of
+@code{I}. It is equal to 0 if @code{I} has an even number of bits set,
+and 1 for an odd number of '1' bits.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = POPPAR(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the default integer
+kind.
+
+@item @emph{Example}:
+@smallexample
+program test_population
+ print *, popcnt(127), poppar(127)
+ print *, popcnt(huge(0_4)), poppar(huge(0_4))
+ print *, popcnt(huge(0_8)), poppar(huge(0_8))
+end program test_population
+@end smallexample
+@item @emph{See also}:
+@ref{POPCNT}, @gol
+@ref{LEADZ}, @gol
+@ref{TRAILZ}
+@end table
+
+
+
+@node PRECISION
+@section @code{PRECISION} --- Decimal precision of a real kind
+@fnindex PRECISION
+@cindex model representation, precision
+
+@table @asis
+@item @emph{Description}:
+@code{PRECISION(X)} returns the decimal precision in the model of the
+type of @code{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = PRECISION(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL} or @code{COMPLEX}. It may
+be scalar or valued.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the default integer
+kind.
+
+@item @emph{Example}:
+@smallexample
+program prec_and_range
+ real(kind=4) :: x(2)
+ complex(kind=8) :: y
+
+ print *, precision(x), range(x)
+ print *, precision(y), range(y)
+end program prec_and_range
+@end smallexample
+@item @emph{See also}:
+@ref{SELECTED_REAL_KIND}, @gol
+@ref{RANGE}
+@end table
+
+
+
+@node PRESENT
+@section @code{PRESENT} --- Determine whether an optional dummy argument is specified
+@fnindex PRESENT
+
+@table @asis
+@item @emph{Description}:
+Determines whether an optional dummy argument is present.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = PRESENT(A)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab May be of any type and may be a pointer, scalar or array
+value, or a dummy procedure. It shall be the name of an optional dummy argument
+accessible within the current subroutine or function.
+@end multitable
+
+@item @emph{Return value}:
+Returns either @code{TRUE} if the optional argument @var{A} is present, or
+@code{FALSE} otherwise.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_present
+ WRITE(*,*) f(), f(42) ! "F T"
+CONTAINS
+ LOGICAL FUNCTION f(x)
+ INTEGER, INTENT(IN), OPTIONAL :: x
+ f = PRESENT(x)
+ END FUNCTION
+END PROGRAM
+@end smallexample
+@end table
+
+
+
+@node PRODUCT
+@section @code{PRODUCT} --- Product of array elements
+@fnindex PRODUCT
+@cindex array, product
+@cindex array, multiply elements
+@cindex array, conditionally multiply elements
+@cindex multiply array elements
+
+@table @asis
+@item @emph{Description}:
+Multiplies the elements of @var{ARRAY} along dimension @var{DIM} if
+the corresponding element in @var{MASK} is @code{TRUE}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = PRODUCT(ARRAY[, MASK])}
+@item @code{RESULT = PRODUCT(ARRAY, DIM[, MASK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER},
+@code{REAL} or @code{COMPLEX}.
+@item @var{DIM} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with a value in the range from 1 to n, where n
+equals the rank of @var{ARRAY}.
+@item @var{MASK} @tab (Optional) shall be of type @code{LOGICAL}
+and either be a scalar or an array of the same shape as @var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type as @var{ARRAY}.
+
+If @var{DIM} is absent, a scalar with the product of all elements in
+@var{ARRAY} is returned. Otherwise, an array of rank n-1, where n equals
+the rank of @var{ARRAY}, and a shape similar to that of @var{ARRAY} with
+dimension @var{DIM} dropped is returned.
+
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_product
+ INTEGER :: x(5) = (/ 1, 2, 3, 4 ,5 /)
+ print *, PRODUCT(x) ! all elements, product = 120
+ print *, PRODUCT(x, MASK=MOD(x, 2)==1) ! odd elements, product = 15
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{SUM}
+@end table
+
+
+
+@node RADIX
+@section @code{RADIX} --- Base of a model number
+@fnindex RADIX
+@cindex model representation, base
+@cindex model representation, radix
+
+@table @asis
+@item @emph{Description}:
+@code{RADIX(X)} returns the base of the model representing the entity @var{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = RADIX(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{INTEGER} or @code{REAL}
+@end multitable
+
+@item @emph{Return value}:
+The return value is a scalar of type @code{INTEGER} and of the default
+integer kind.
+
+@item @emph{Example}:
+@smallexample
+program test_radix
+ print *, "The radix for the default integer kind is", radix(0)
+ print *, "The radix for the default real kind is", radix(0.0)
+end program test_radix
+@end smallexample
+@item @emph{See also}:
+@ref{SELECTED_REAL_KIND}
+@end table
+
+
+
+@node RAN
+@section @code{RAN} --- Real pseudo-random number
+@fnindex RAN
+@cindex random number generation
+
+@table @asis
+@item @emph{Description}:
+For compatibility with HP FORTRAN 77/iX, the @code{RAN} intrinsic is
+provided as an alias for @code{RAND}. See @ref{RAND} for complete
+documentation.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{See also}:
+@ref{RAND}, @gol
+@ref{RANDOM_NUMBER}
+@end table
+
+
+
+@node RAND
+@section @code{RAND} --- Real pseudo-random number
+@fnindex RAND
+@cindex random number generation
+
+@table @asis
+@item @emph{Description}:
+@code{RAND(FLAG)} returns a pseudo-random number from a uniform
+distribution between 0 and 1. If @var{FLAG} is 0, the next number
+in the current sequence is returned; if @var{FLAG} is 1, the generator
+is restarted by @code{CALL SRAND(0)}; if @var{FLAG} has any other value,
+it is used as a new seed with @code{SRAND}.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. It implements a simple modulo generator as provided
+by @command{g77}. For new code, one should consider the use of
+@ref{RANDOM_NUMBER} as it implements a superior algorithm.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = RAND(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be a scalar @code{INTEGER} of kind 4.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of @code{REAL} type and the default kind.
+
+@item @emph{Example}:
+@smallexample
+program test_rand
+ integer,parameter :: seed = 86456
+
+ call srand(seed)
+ print *, rand(), rand(), rand(), rand()
+ print *, rand(seed), rand(), rand(), rand()
+end program test_rand
+@end smallexample
+
+@item @emph{See also}:
+@ref{SRAND}, @gol
+@ref{RANDOM_NUMBER}
+
+@end table
+
+
+@node RANDOM_INIT
+@section @code{RANDOM_INIT} --- Initialize a pseudo-random number generator
+@fnindex RANDOM_INIT
+@cindex random number generation, initialization
+
+@table @asis
+@item @emph{Description}:
+Initializes the state of the pseudorandom number generator used by
+@code{RANDOM_NUMBER}.
+
+@item @emph{Standard}:
+Fortran 2018
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL RANDOM_INIT(REPEATABLE, IMAGE_DISTINCT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .25 .70
+@item @var{REPEATABLE} @tab Shall be a scalar with a @code{LOGICAL} type,
+and it is @code{INTENT(IN)}. If it is @code{.true.}, the seed is set to
+a processor-dependent value that is the same each time @code{RANDOM_INIT}
+is called from the same image. The term ``same image'' means a single
+instance of program execution. The sequence of random numbers is different
+for repeated execution of the program. If it is @code{.false.}, the seed
+is set to a processor-dependent value.
+@item @var{IMAGE_DISTINCT} @tab Shall be a scalar with a
+@code{LOGICAL} type, and it is @code{INTENT(IN)}. If it is @code{.true.},
+the seed is set to a processor-dependent value that is distinct from th
+seed set by a call to @code{RANDOM_INIT} in another image. If it is
+@code{.false.}, the seed is set to a value that does depend which image called
+@code{RANDOM_INIT}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test_random_seed
+ implicit none
+ real x(3), y(3)
+ call random_init(.true., .true.)
+ call random_number(x)
+ call random_init(.true., .true.)
+ call random_number(y)
+ ! x and y are the same sequence
+ if (any(x /= y)) call abort
+end program test_random_seed
+@end smallexample
+
+@item @emph{See also}:
+@ref{RANDOM_NUMBER}, @gol
+@ref{RANDOM_SEED}
+@end table
+
+
+@node RANDOM_NUMBER
+@section @code{RANDOM_NUMBER} --- Pseudo-random number
+@fnindex RANDOM_NUMBER
+@cindex random number generation
+
+@table @asis
+@item @emph{Description}:
+Returns a single pseudorandom number or an array of pseudorandom numbers
+from the uniform distribution over the range @math{ 0 \leq x < 1}.
+
+The runtime-library implements the xoshiro256** pseudorandom number
+generator (PRNG). This generator has a period of @math{2^{256} - 1},
+and when using multiple threads up to @math{2^{128}} threads can each
+generate @math{2^{128}} random numbers before any aliasing occurs.
+
+Note that in a multi-threaded program (e.g. using OpenMP directives),
+each thread will have its own random number state. For details of the
+seeding procedure, see the documentation for the @code{RANDOM_SEED}
+intrinsic.
+
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL RANDOM_NUMBER(HARVEST)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{HARVEST} @tab Shall be a scalar or an array of type @code{REAL}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test_random_number
+ REAL :: r(5,5)
+ CALL RANDOM_NUMBER(r)
+end program
+@end smallexample
+
+@item @emph{See also}:
+@ref{RANDOM_SEED}, @gol
+@ref{RANDOM_INIT}
+@end table
+
+
+
+@node RANDOM_SEED
+@section @code{RANDOM_SEED} --- Initialize a pseudo-random number sequence
+@fnindex RANDOM_SEED
+@cindex random number generation, seeding
+@cindex seeding a random number generator
+
+@table @asis
+@item @emph{Description}:
+Restarts or queries the state of the pseudorandom number generator used by
+@code{RANDOM_NUMBER}.
+
+If @code{RANDOM_SEED} is called without arguments, it is seeded with
+random data retrieved from the operating system.
+
+As an extension to the Fortran standard, the GFortran
+@code{RANDOM_NUMBER} supports multiple threads. Each thread in a
+multi-threaded program has its own seed. When @code{RANDOM_SEED} is
+called either without arguments or with the @var{PUT} argument, the
+given seed is copied into a master seed as well as the seed of the
+current thread. When a new thread uses @code{RANDOM_NUMBER} for the
+first time, the seed is copied from the master seed, and forwarded
+@math{N * 2^{128}} steps to guarantee that the random stream does not
+alias any other stream in the system, where @var{N} is the number of
+threads that have used @code{RANDOM_NUMBER} so far during the program
+execution.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL RANDOM_SEED([SIZE, PUT, GET])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SIZE} @tab (Optional) Shall be a scalar and of type default
+@code{INTEGER}, with @code{INTENT(OUT)}. It specifies the minimum size
+of the arrays used with the @var{PUT} and @var{GET} arguments.
+@item @var{PUT} @tab (Optional) Shall be an array of type default
+@code{INTEGER} and rank one. It is @code{INTENT(IN)} and the size of
+the array must be larger than or equal to the number returned by the
+@var{SIZE} argument.
+@item @var{GET} @tab (Optional) Shall be an array of type default
+@code{INTEGER} and rank one. It is @code{INTENT(OUT)} and the size
+of the array must be larger than or equal to the number returned by
+the @var{SIZE} argument.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test_random_seed
+ implicit none
+ integer, allocatable :: seed(:)
+ integer :: n
+
+ call random_seed(size = n)
+ allocate(seed(n))
+ call random_seed(get=seed)
+ write (*, *) seed
+end program test_random_seed
+@end smallexample
+
+@item @emph{See also}:
+@ref{RANDOM_NUMBER}, @gol
+@ref{RANDOM_INIT}
+@end table
+
+
+
+@node RANGE
+@section @code{RANGE} --- Decimal exponent range
+@fnindex RANGE
+@cindex model representation, range
+
+@table @asis
+@item @emph{Description}:
+@code{RANGE(X)} returns the decimal exponent range in the model of the
+type of @code{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = RANGE(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{INTEGER}, @code{REAL}
+or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the default integer
+kind.
+
+@item @emph{Example}:
+See @code{PRECISION} for an example.
+@item @emph{See also}:
+@ref{SELECTED_REAL_KIND}, @gol
+@ref{PRECISION}
+@end table
+
+
+
+@node RANK
+@section @code{RANK} --- Rank of a data object
+@fnindex RANK
+@cindex rank
+
+@table @asis
+@item @emph{Description}:
+@code{RANK(A)} returns the rank of a scalar or array data object.
+
+@item @emph{Standard}:
+Technical Specification (TS) 29113
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = RANK(A)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab can be of any type
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the default integer
+kind. For arrays, their rank is returned; for scalars zero is returned.
+
+@item @emph{Example}:
+@smallexample
+program test_rank
+ integer :: a
+ real, allocatable :: b(:,:)
+
+ print *, rank(a), rank(b) ! Prints: 0 2
+end program test_rank
+@end smallexample
+
+@end table
+
+
+
+@node REAL
+@section @code{REAL} --- Convert to real type
+@fnindex REAL
+@fnindex REALPART
+@fnindex FLOAT
+@fnindex DFLOAT
+@fnindex FLOATI
+@fnindex FLOATJ
+@fnindex FLOATK
+@fnindex SNGL
+@cindex conversion, to real
+@cindex complex numbers, real part
+
+@table @asis
+@item @emph{Description}:
+@code{REAL(A [, KIND])} converts its argument @var{A} to a real type. The
+@code{REALPART} function is provided for compatibility with @command{g77},
+and its use is strongly discouraged.
+
+@item @emph{Standard}:
+Fortran 77 and later, with @var{KIND} argument Fortran 90 and later, has GNU extensions
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = REAL(A [, KIND])}
+@item @code{RESULT = REALPART(Z)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be @code{INTEGER}, @code{REAL}, or
+@code{COMPLEX}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+These functions return a @code{REAL} variable or array under
+the following rules:
+
+@table @asis
+@item (A)
+@code{REAL(A)} is converted to a default real type if @var{A} is an
+integer or real variable.
+@item (B)
+@code{REAL(A)} is converted to a real type with the kind type parameter
+of @var{A} if @var{A} is a complex variable.
+@item (C)
+@code{REAL(A, KIND)} is converted to a real type with kind type
+parameter @var{KIND} if @var{A} is a complex, integer, or real
+variable.
+@end table
+
+@item @emph{Example}:
+@smallexample
+program test_real
+ complex :: x = (1.0, 2.0)
+ print *, real(x), real(x,8), realpart(x)
+end program test_real
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{FLOAT(A)} @tab @code{INTEGER(4)} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DFLOAT(A)} @tab @code{INTEGER(4)} @tab @code{REAL(8)} @tab GNU extension
+@item @code{FLOATI(A)} @tab @code{INTEGER(2)} @tab @code{REAL(4)} @tab GNU extension (-fdec)
+@item @code{FLOATJ(A)} @tab @code{INTEGER(4)} @tab @code{REAL(4)} @tab GNU extension (-fdec)
+@item @code{FLOATK(A)} @tab @code{INTEGER(8)} @tab @code{REAL(4)} @tab GNU extension (-fdec)
+@item @code{SNGL(A)} @tab @code{REAL(8)} @tab @code{REAL(4)} @tab Fortran 77 and later
+@end multitable
+
+
+@item @emph{See also}:
+@ref{DBLE}
+
+@end table
+
+
+
+@node RENAME
+@section @code{RENAME} --- Rename a file
+@fnindex RENAME
+@cindex file system, rename file
+
+@table @asis
+@item @emph{Description}:
+Renames a file from file @var{PATH1} to @var{PATH2}. A null
+character (@code{CHAR(0)}) can be used to mark the end of the names in
+@var{PATH1} and @var{PATH2}; otherwise, trailing blanks in the file
+names are ignored. If the @var{STATUS} argument is supplied, it
+contains 0 on success or a nonzero error code upon return; see
+@code{rename(2)}.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL RENAME(PATH1, PATH2 [, STATUS])}
+@item @code{STATUS = RENAME(PATH1, PATH2)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{PATH1} @tab Shall be of default @code{CHARACTER} type.
+@item @var{PATH2} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STATUS} @tab (Optional) Shall be of default @code{INTEGER} type.
+@end multitable
+
+@item @emph{See also}:
+@ref{LINK}
+
+@end table
+
+
+
+@node REPEAT
+@section @code{REPEAT} --- Repeated string concatenation
+@fnindex REPEAT
+@cindex string, repeat
+@cindex string, concatenate
+
+@table @asis
+@item @emph{Description}:
+Concatenates @var{NCOPIES} copies of a string.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = REPEAT(STRING, NCOPIES)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab Shall be scalar and of type @code{CHARACTER}.
+@item @var{NCOPIES} @tab Shall be scalar and of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+A new scalar of type @code{CHARACTER} built up from @var{NCOPIES} copies
+of @var{STRING}.
+
+@item @emph{Example}:
+@smallexample
+program test_repeat
+ write(*,*) repeat("x", 5) ! "xxxxx"
+end program
+@end smallexample
+@end table
+
+
+
+@node RESHAPE
+@section @code{RESHAPE} --- Function to reshape an array
+@fnindex RESHAPE
+@cindex array, change dimensions
+@cindex array, transmogrify
+
+@table @asis
+@item @emph{Description}:
+Reshapes @var{SOURCE} to correspond to @var{SHAPE}. If necessary,
+the new array may be padded with elements from @var{PAD} or permuted
+as defined by @var{ORDER}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = RESHAPE(SOURCE, SHAPE[, PAD, ORDER])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SOURCE} @tab Shall be an array of any type.
+@item @var{SHAPE} @tab Shall be of type @code{INTEGER} and an
+array of rank one. Its values must be positive or zero.
+@item @var{PAD} @tab (Optional) shall be an array of the same
+type as @var{SOURCE}.
+@item @var{ORDER} @tab (Optional) shall be of type @code{INTEGER}
+and an array of the same shape as @var{SHAPE}. Its values shall
+be a permutation of the numbers from 1 to n, where n is the size of
+@var{SHAPE}. If @var{ORDER} is absent, the natural ordering shall
+be assumed.
+@end multitable
+
+@item @emph{Return value}:
+The result is an array of shape @var{SHAPE} with the same type as
+@var{SOURCE}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_reshape
+ INTEGER, DIMENSION(4) :: x
+ WRITE(*,*) SHAPE(x) ! prints "4"
+ WRITE(*,*) SHAPE(RESHAPE(x, (/2, 2/))) ! prints "2 2"
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{SHAPE}
+@end table
+
+
+
+@node RRSPACING
+@section @code{RRSPACING} --- Reciprocal of the relative spacing
+@fnindex RRSPACING
+@cindex real number, relative spacing
+@cindex floating point, relative spacing
+
+
+@table @asis
+@item @emph{Description}:
+@code{RRSPACING(X)} returns the reciprocal of the relative spacing of
+model numbers near @var{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = RRSPACING(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+The value returned is equal to
+@code{ABS(FRACTION(X)) * FLOAT(RADIX(X))**DIGITS(X)}.
+
+@item @emph{See also}:
+@ref{SPACING}
+@end table
+
+
+
+@node RSHIFT
+@section @code{RSHIFT} --- Right shift bits
+@fnindex RSHIFT
+@cindex bits, shift right
+
+@table @asis
+@item @emph{Description}:
+@code{RSHIFT} returns a value corresponding to @var{I} with all of the
+bits shifted right by @var{SHIFT} places. @var{SHIFT} shall be
+nonnegative and less than or equal to @code{BIT_SIZE(I)}, otherwise
+the result value is undefined. Bits shifted out from the right end
+are lost. The fill is arithmetic: the bits shifted in from the left
+end are equal to the leftmost bit, which in two's complement
+representation is the sign bit.
+
+This function has been superseded by the @code{SHIFTA} intrinsic, which
+is standard in Fortran 2008 and later.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = RSHIFT(I, SHIFT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{See also}:
+@ref{ISHFT}, @gol
+@ref{ISHFTC}, @gol
+@ref{LSHIFT}, @gol
+@ref{SHIFTA}, @gol
+@ref{SHIFTR}, @gol
+@ref{SHIFTL}
+
+@end table
+
+
+
+@node SAME_TYPE_AS
+@section @code{SAME_TYPE_AS} --- Query dynamic types for equality
+@fnindex SAME_TYPE_AS
+
+@table @asis
+@item @emph{Description}:
+Query dynamic types for equality.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = SAME_TYPE_AS(A, B)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be an object of extensible declared type or
+unlimited polymorphic.
+@item @var{B} @tab Shall be an object of extensible declared type or
+unlimited polymorphic.
+@end multitable
+
+@item @emph{Return value}:
+The return value is a scalar of type default logical. It is true if and
+only if the dynamic type of A is the same as the dynamic type of B.
+
+@item @emph{See also}:
+@ref{EXTENDS_TYPE_OF}
+
+@end table
+
+
+
+@node SCALE
+@section @code{SCALE} --- Scale a real value
+@fnindex SCALE
+@cindex real number, scale
+@cindex floating point, scale
+
+@table @asis
+@item @emph{Description}:
+@code{SCALE(X,I)} returns @code{X * RADIX(X)**I}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SCALE(X, I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type of the argument shall be a @code{REAL}.
+@item @var{I} @tab The type of the argument shall be a @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+Its value is @code{X * RADIX(X)**I}.
+
+@item @emph{Example}:
+@smallexample
+program test_scale
+ real :: x = 178.1387e-4
+ integer :: i = 5
+ print *, scale(x,i), x*radix(x)**i
+end program test_scale
+@end smallexample
+
+@end table
+
+
+
+@node SCAN
+@section @code{SCAN} --- Scan a string for the presence of a set of characters
+@fnindex SCAN
+@cindex string, find subset
+
+@table @asis
+@item @emph{Description}:
+Scans a @var{STRING} for any of the characters in a @var{SET}
+of characters.
+
+If @var{BACK} is either absent or equals @code{FALSE}, this function
+returns the position of the leftmost character of @var{STRING} that is
+in @var{SET}. If @var{BACK} equals @code{TRUE}, the rightmost position
+is returned. If no character of @var{SET} is found in @var{STRING}, the
+result is zero.
+
+@item @emph{Standard}:
+Fortran 90 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SCAN(STRING, SET[, BACK [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab Shall be of type @code{CHARACTER}.
+@item @var{SET} @tab Shall be of type @code{CHARACTER}.
+@item @var{BACK} @tab (Optional) shall be of type @code{LOGICAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_scan
+ WRITE(*,*) SCAN("FORTRAN", "AO") ! 2, found 'O'
+ WRITE(*,*) SCAN("FORTRAN", "AO", .TRUE.) ! 6, found 'A'
+ WRITE(*,*) SCAN("FORTRAN", "C++") ! 0, found none
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{INDEX intrinsic}, @gol
+@ref{VERIFY}
+@end table
+
+
+
+@node SECNDS
+@section @code{SECNDS} --- Time function
+@fnindex SECNDS
+@cindex time, elapsed
+@cindex elapsed time
+
+@table @asis
+@item @emph{Description}:
+@code{SECNDS(X)} gets the time in seconds from the real-time system clock.
+@var{X} is a reference time, also in seconds. If this is zero, the time in
+seconds from midnight is returned. This function is non-standard and its
+use is discouraged.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = SECNDS (X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{T} @tab Shall be of type @code{REAL(4)}.
+@item @var{X} @tab Shall be of type @code{REAL(4)}.
+@end multitable
+
+@item @emph{Return value}:
+None
+
+@item @emph{Example}:
+@smallexample
+program test_secnds
+ integer :: i
+ real(4) :: t1, t2
+ print *, secnds (0.0) ! seconds since midnight
+ t1 = secnds (0.0) ! reference time
+ do i = 1, 10000000 ! do something
+ end do
+ t2 = secnds (t1) ! elapsed time
+ print *, "Something took ", t2, " seconds."
+end program test_secnds
+@end smallexample
+@end table
+
+
+
+@node SECOND
+@section @code{SECOND} --- CPU time function
+@fnindex SECOND
+@cindex time, elapsed
+@cindex elapsed time
+
+@table @asis
+@item @emph{Description}:
+Returns a @code{REAL(4)} value representing the elapsed CPU time in
+seconds. This provides the same functionality as the standard
+@code{CPU_TIME} intrinsic, and is only included for backwards
+compatibility.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL SECOND(TIME)}
+@item @code{TIME = SECOND()}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{TIME} @tab Shall be of type @code{REAL(4)}.
+@end multitable
+
+@item @emph{Return value}:
+In either syntax, @var{TIME} is set to the process's current runtime in
+seconds.
+
+@item @emph{See also}:
+@ref{CPU_TIME}
+
+@end table
+
+
+
+@node SELECTED_CHAR_KIND
+@section @code{SELECTED_CHAR_KIND} --- Choose character kind
+@fnindex SELECTED_CHAR_KIND
+@cindex character kind
+@cindex kind, character
+
+@table @asis
+@item @emph{Description}:
+
+@code{SELECTED_CHAR_KIND(NAME)} returns the kind value for the character
+set named @var{NAME}, if a character set with such a name is supported,
+or @math{-1} otherwise. Currently, supported character sets include
+``ASCII'' and ``DEFAULT'', which are equivalent, and ``ISO_10646''
+(Universal Character Set, UCS-4) which is commonly known as Unicode.
+
+@item @emph{Standard}:
+Fortran 2003 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = SELECTED_CHAR_KIND(NAME)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NAME} @tab Shall be a scalar and of the default character type.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program character_kind
+ use iso_fortran_env
+ implicit none
+ integer, parameter :: ascii = selected_char_kind ("ascii")
+ integer, parameter :: ucs4 = selected_char_kind ('ISO_10646')
+
+ character(kind=ascii, len=26) :: alphabet
+ character(kind=ucs4, len=30) :: hello_world
+
+ alphabet = ascii_"abcdefghijklmnopqrstuvwxyz"
+ hello_world = ucs4_'Hello World and Ni Hao -- ' &
+ // char (int (z'4F60'), ucs4) &
+ // char (int (z'597D'), ucs4)
+
+ write (*,*) alphabet
+
+ open (output_unit, encoding='UTF-8')
+ write (*,*) trim (hello_world)
+end program character_kind
+@end smallexample
+@end table
+
+
+
+@node SELECTED_INT_KIND
+@section @code{SELECTED_INT_KIND} --- Choose integer kind
+@fnindex SELECTED_INT_KIND
+@cindex integer kind
+@cindex kind, integer
+
+@table @asis
+@item @emph{Description}:
+@code{SELECTED_INT_KIND(R)} return the kind value of the smallest integer
+type that can represent all values ranging from @math{-10^R} (exclusive)
+to @math{10^R} (exclusive). If there is no integer kind that accommodates
+this range, @code{SELECTED_INT_KIND} returns @math{-1}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = SELECTED_INT_KIND(R)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{R} @tab Shall be a scalar and of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program large_integers
+ integer,parameter :: k5 = selected_int_kind(5)
+ integer,parameter :: k15 = selected_int_kind(15)
+ integer(kind=k5) :: i5
+ integer(kind=k15) :: i15
+
+ print *, huge(i5), huge(i15)
+
+ ! The following inequalities are always true
+ print *, huge(i5) >= 10_k5**5-1
+ print *, huge(i15) >= 10_k15**15-1
+end program large_integers
+@end smallexample
+@end table
+
+
+
+@node SELECTED_REAL_KIND
+@section @code{SELECTED_REAL_KIND} --- Choose real kind
+@fnindex SELECTED_REAL_KIND
+@cindex real kind
+@cindex kind, real
+@cindex radix, real
+
+@table @asis
+@item @emph{Description}:
+@code{SELECTED_REAL_KIND(P,R)} returns the kind value of a real data type
+with decimal precision of at least @code{P} digits, exponent range of
+at least @code{R}, and with a radix of @code{RADIX}.
+
+@item @emph{Standard}:
+Fortran 90 and later, with @code{RADIX} Fortran 2008 or later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = SELECTED_REAL_KIND([P, R, RADIX])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{P} @tab (Optional) shall be a scalar and of type @code{INTEGER}.
+@item @var{R} @tab (Optional) shall be a scalar and of type @code{INTEGER}.
+@item @var{RADIX} @tab (Optional) shall be a scalar and of type @code{INTEGER}.
+@end multitable
+Before Fortran 2008, at least one of the arguments @var{R} or @var{P} shall
+be present; since Fortran 2008, they are assumed to be zero if absent.
+
+@item @emph{Return value}:
+
+@code{SELECTED_REAL_KIND} returns the value of the kind type parameter of
+a real data type with decimal precision of at least @code{P} digits, a
+decimal exponent range of at least @code{R}, and with the requested
+@code{RADIX}. If the @code{RADIX} parameter is absent, real kinds with
+any radix can be returned. If more than one real data type meet the
+criteria, the kind of the data type with the smallest decimal precision
+is returned. If no real data type matches the criteria, the result is
+@table @asis
+@item -1 if the processor does not support a real data type with a
+precision greater than or equal to @code{P}, but the @code{R} and
+@code{RADIX} requirements can be fulfilled
+@item -2 if the processor does not support a real type with an exponent
+range greater than or equal to @code{R}, but @code{P} and @code{RADIX}
+are fulfillable
+@item -3 if @code{RADIX} but not @code{P} and @code{R} requirements
+are fulfillable
+@item -4 if @code{RADIX} and either @code{P} or @code{R} requirements
+are fulfillable
+@item -5 if there is no real type with the given @code{RADIX}
+@end table
+
+@item @emph{Example}:
+@smallexample
+program real_kinds
+ integer,parameter :: p6 = selected_real_kind(6)
+ integer,parameter :: p10r100 = selected_real_kind(10,100)
+ integer,parameter :: r400 = selected_real_kind(r=400)
+ real(kind=p6) :: x
+ real(kind=p10r100) :: y
+ real(kind=r400) :: z
+
+ print *, precision(x), range(x)
+ print *, precision(y), range(y)
+ print *, precision(z), range(z)
+end program real_kinds
+@end smallexample
+@item @emph{See also}:
+@ref{PRECISION}, @gol
+@ref{RANGE}, @gol
+@ref{RADIX}
+@end table
+
+
+
+@node SET_EXPONENT
+@section @code{SET_EXPONENT} --- Set the exponent of the model
+@fnindex SET_EXPONENT
+@cindex real number, set exponent
+@cindex floating point, set exponent
+
+@table @asis
+@item @emph{Description}:
+@code{SET_EXPONENT(X, I)} returns the real number whose fractional part
+is that of @var{X} and whose exponent part is @var{I}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SET_EXPONENT(X, I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL}.
+@item @var{I} @tab Shall be of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}.
+The real number whose fractional part
+is that of @var{X} and whose exponent part if @var{I} is returned;
+it is @code{FRACTION(X) * RADIX(X)**I}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_setexp
+ REAL :: x = 178.1387e-4
+ INTEGER :: i = 17
+ PRINT *, SET_EXPONENT(x, i), FRACTION(x) * RADIX(x)**i
+END PROGRAM
+@end smallexample
+
+@end table
+
+
+
+@node SHAPE
+@section @code{SHAPE} --- Determine the shape of an array
+@fnindex SHAPE
+@cindex array, shape
+
+@table @asis
+@item @emph{Description}:
+Determines the shape of an array.
+
+@item @emph{Standard}:
+Fortran 90 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = SHAPE(SOURCE [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SOURCE} @tab Shall be an array or scalar of any type.
+If @var{SOURCE} is a pointer it must be associated and allocatable
+arrays must be allocated.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+An @code{INTEGER} array of rank one with as many elements as @var{SOURCE}
+has dimensions. The elements of the resulting array correspond to the extend
+of @var{SOURCE} along the respective dimensions. If @var{SOURCE} is a scalar,
+the result is the rank one array of size zero. If @var{KIND} is absent, the
+return value has the default integer kind otherwise the specified kind.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_shape
+ INTEGER, DIMENSION(-1:1, -1:2) :: A
+ WRITE(*,*) SHAPE(A) ! (/ 3, 4 /)
+ WRITE(*,*) SIZE(SHAPE(42)) ! (/ /)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{RESHAPE}, @gol
+@ref{SIZE}
+@end table
+
+
+
+@node SHIFTA
+@section @code{SHIFTA} --- Right shift with fill
+@fnindex SHIFTA
+@cindex bits, shift right
+@cindex shift, right with fill
+
+@table @asis
+@item @emph{Description}:
+@code{SHIFTA} returns a value corresponding to @var{I} with all of the
+bits shifted right by @var{SHIFT} places. @var{SHIFT} that be
+nonnegative and less than or equal to @code{BIT_SIZE(I)}, otherwise
+the result value is undefined. Bits shifted out from the right end
+are lost. The fill is arithmetic: the bits shifted in from the left
+end are equal to the leftmost bit, which in two's complement
+representation is the sign bit.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SHIFTA(I, SHIFT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{See also}:
+@ref{SHIFTL}, @gol
+@ref{SHIFTR}
+@end table
+
+
+
+@node SHIFTL
+@section @code{SHIFTL} --- Left shift
+@fnindex SHIFTL
+@cindex bits, shift left
+@cindex shift, left
+
+@table @asis
+@item @emph{Description}:
+@code{SHIFTL} returns a value corresponding to @var{I} with all of the
+bits shifted left by @var{SHIFT} places. @var{SHIFT} shall be
+nonnegative and less than or equal to @code{BIT_SIZE(I)}, otherwise
+the result value is undefined. Bits shifted out from the left end are
+lost, and bits shifted in from the right end are set to 0.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SHIFTL(I, SHIFT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{See also}:
+@ref{SHIFTA}, @gol
+@ref{SHIFTR}
+@end table
+
+
+
+@node SHIFTR
+@section @code{SHIFTR} --- Right shift
+@fnindex SHIFTR
+@cindex bits, shift right
+@cindex shift, right
+
+@table @asis
+@item @emph{Description}:
+@code{SHIFTR} returns a value corresponding to @var{I} with all of the
+bits shifted right by @var{SHIFT} places. @var{SHIFT} shall be
+nonnegative and less than or equal to @code{BIT_SIZE(I)}, otherwise
+the result value is undefined. Bits shifted out from the right end
+are lost, and bits shifted in from the left end are set to 0.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SHIFTR(I, SHIFT)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be @code{INTEGER}.
+@item @var{SHIFT} @tab The type shall be @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of the same kind as
+@var{I}.
+
+@item @emph{See also}:
+@ref{SHIFTA}, @gol
+@ref{SHIFTL}
+@end table
+
+
+
+@node SIGN
+@section @code{SIGN} --- Sign copying function
+@fnindex SIGN
+@fnindex ISIGN
+@fnindex DSIGN
+@cindex sign copying
+
+@table @asis
+@item @emph{Description}:
+@code{SIGN(A,B)} returns the value of @var{A} with the sign of @var{B}.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SIGN(A, B)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be of type @code{INTEGER} or @code{REAL}
+@item @var{B} @tab Shall be of the same type and kind as @var{A}.
+@end multitable
+
+@item @emph{Return value}:
+The kind of the return value is that of @var{A} and @var{B}.
+If @math{B \ge 0} then the result is @code{ABS(A)}, else
+it is @code{-ABS(A)}.
+
+@item @emph{Example}:
+@smallexample
+program test_sign
+ print *, sign(-12,1)
+ print *, sign(-12,0)
+ print *, sign(-12,-1)
+
+ print *, sign(-12.,1.)
+ print *, sign(-12.,0.)
+ print *, sign(-12.,-1.)
+end program test_sign
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .26 .20 .30
+@headitem Name @tab Arguments @tab Return type @tab Standard
+@item @code{SIGN(A,B)} @tab @code{REAL(4) A, B} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{ISIGN(A,B)} @tab @code{INTEGER(4) A, B} @tab @code{INTEGER(4)} @tab Fortran 77 and later
+@item @code{DSIGN(A,B)} @tab @code{REAL(8) A, B} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+@end table
+
+
+
+@node SIGNAL
+@section @code{SIGNAL} --- Signal handling subroutine (or function)
+@fnindex SIGNAL
+@cindex system, signal handling
+
+@table @asis
+@item @emph{Description}:
+@code{SIGNAL(NUMBER, HANDLER [, STATUS])} causes external subroutine
+@var{HANDLER} to be executed with a single integer argument when signal
+@var{NUMBER} occurs. If @var{HANDLER} is an integer, it can be used to
+turn off handling of signal @var{NUMBER} or revert to its default
+action. See @code{signal(2)}.
+
+If @code{SIGNAL} is called as a subroutine and the @var{STATUS} argument
+is supplied, it is set to the value returned by @code{signal(2)}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL SIGNAL(NUMBER, HANDLER [, STATUS])}
+@item @code{STATUS = SIGNAL(NUMBER, HANDLER)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NUMBER} @tab Shall be a scalar integer, with @code{INTENT(IN)}
+@item @var{HANDLER}@tab Signal handler (@code{INTEGER FUNCTION} or
+@code{SUBROUTINE}) or dummy/global @code{INTEGER} scalar.
+@code{INTEGER}. It is @code{INTENT(IN)}.
+@item @var{STATUS} @tab (Optional) @var{STATUS} shall be a scalar
+integer. It has @code{INTENT(OUT)}.
+@end multitable
+@c TODO: What should the interface of the handler be? Does it take arguments?
+
+@item @emph{Return value}:
+The @code{SIGNAL} function returns the value returned by @code{signal(2)}.
+
+@item @emph{Example}:
+@smallexample
+program test_signal
+ intrinsic signal
+ external handler_print
+
+ call signal (12, handler_print)
+ call signal (10, 1)
+
+ call sleep (30)
+end program test_signal
+@end smallexample
+@end table
+
+
+
+@node SIN
+@section @code{SIN} --- Sine function
+@fnindex SIN
+@fnindex DSIN
+@fnindex CSIN
+@fnindex ZSIN
+@fnindex CDSIN
+@cindex trigonometric function, sine
+@cindex sine
+
+@table @asis
+@item @emph{Description}:
+@code{SIN(X)} computes the sine of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SIN(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or
+@code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_sin
+ real :: x = 0.0
+ x = sin(x)
+end program test_sin
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{SIN(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DSIN(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@item @code{CSIN(X)} @tab @code{COMPLEX(4) X} @tab @code{COMPLEX(4)} @tab Fortran 77 and later
+@item @code{ZSIN(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@item @code{CDSIN(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{ASIN} @gol
+Degrees function: @gol
+@ref{SIND}
+@end table
+
+
+
+@node SIND
+@section @code{SIND} --- Sine function, degrees
+@fnindex SIND
+@fnindex DSIND
+@fnindex CSIND
+@fnindex ZSIND
+@fnindex CDSIND
+@cindex trigonometric function, sine, degrees
+@cindex sine, degrees
+
+@table @asis
+@item @emph{Description}:
+@code{SIND(X)} computes the sine of @var{X} in degrees.
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SIND(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or
+@code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}, and its value is in degrees.
+
+@item @emph{Example}:
+@smallexample
+program test_sind
+ real :: x = 0.0
+ x = sind(x)
+end program test_sind
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{SIND(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DSIND(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@item @code{CSIND(X)} @tab @code{COMPLEX(4) X} @tab @code{COMPLEX(4)} @tab GNU extension
+@item @code{ZSIND(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@item @code{CDSIND(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{ASIND} @gol
+Radians function: @gol
+@ref{SIN} @gol
+@end table
+
+
+
+@node SINH
+@section @code{SINH} --- Hyperbolic sine function
+@fnindex SINH
+@fnindex DSINH
+@cindex hyperbolic sine
+@cindex hyperbolic function, sine
+@cindex sine, hyperbolic
+
+@table @asis
+@item @emph{Description}:
+@code{SINH(X)} computes the hyperbolic sine of @var{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later, for a complex argument Fortran 2008 or later, has
+a GNU extension
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SINH(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_sinh
+ real(8) :: x = - 1.0_8
+ x = sinh(x)
+end program test_sinh
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{DSINH(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 90 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{ASINH}
+@end table
+
+
+
+@node SIZE
+@section @code{SIZE} --- Determine the size of an array
+@fnindex SIZE
+@cindex array, size
+@cindex array, number of elements
+@cindex array, count elements
+
+@table @asis
+@item @emph{Description}:
+Determine the extent of @var{ARRAY} along a specified dimension @var{DIM},
+or the total number of elements in @var{ARRAY} if @var{DIM} is absent.
+
+@item @emph{Standard}:
+Fortran 90 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = SIZE(ARRAY[, DIM [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of any type. If @var{ARRAY} is
+a pointer it must be associated and allocatable arrays must be allocated.
+@item @var{DIM} @tab (Optional) shall be a scalar of type @code{INTEGER}
+and its value shall be in the range from 1 to n, where n equals the rank
+of @var{ARRAY}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_size
+ WRITE(*,*) SIZE((/ 1, 2 /)) ! 2
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{SHAPE}, @gol
+@ref{RESHAPE}
+@end table
+
+
+@node SIZEOF
+@section @code{SIZEOF} --- Size in bytes of an expression
+@fnindex SIZEOF
+@cindex expression size
+@cindex size of an expression
+
+@table @asis
+@item @emph{Description}:
+@code{SIZEOF(X)} calculates the number of bytes of storage the
+expression @code{X} occupies.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{N = SIZEOF(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The argument shall be of any type, rank or shape.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type integer and of the system-dependent kind
+@var{C_SIZE_T} (from the @var{ISO_C_BINDING} module). Its value is the
+number of bytes occupied by the argument. If the argument has the
+@code{POINTER} attribute, the number of bytes of the storage area pointed
+to is returned. If the argument is of a derived type with @code{POINTER}
+or @code{ALLOCATABLE} components, the return value does not account for
+the sizes of the data pointed to by these components. If the argument is
+polymorphic, the size according to the dynamic type is returned. The argument
+may not be a procedure or procedure pointer. Note that the code assumes for
+arrays that those are contiguous; for contiguous arrays, it returns the
+storage or an array element multiplied by the size of the array.
+
+@item @emph{Example}:
+@smallexample
+ integer :: i
+ real :: r, s(5)
+ print *, (sizeof(s)/sizeof(r) == 5)
+ end
+@end smallexample
+The example will print @code{.TRUE.} unless you are using a platform
+where default @code{REAL} variables are unusually padded.
+
+@item @emph{See also}:
+@ref{C_SIZEOF}, @gol
+@ref{STORAGE_SIZE}
+@end table
+
+
+@node SLEEP
+@section @code{SLEEP} --- Sleep for the specified number of seconds
+@fnindex SLEEP
+@cindex delayed execution
+
+@table @asis
+@item @emph{Description}:
+Calling this subroutine causes the process to pause for @var{SECONDS} seconds.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL SLEEP(SECONDS)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SECONDS} @tab The type shall be of default @code{INTEGER}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+program test_sleep
+ call sleep(5)
+end
+@end smallexample
+@end table
+
+
+
+@node SPACING
+@section @code{SPACING} --- Smallest distance between two numbers of a given type
+@fnindex SPACING
+@cindex real number, relative spacing
+@cindex floating point, relative spacing
+
+@table @asis
+@item @emph{Description}:
+Determines the distance between the argument @var{X} and the nearest
+adjacent number of the same type.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SPACING(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type as the input argument @var{X}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_spacing
+ INTEGER, PARAMETER :: SGL = SELECTED_REAL_KIND(p=6, r=37)
+ INTEGER, PARAMETER :: DBL = SELECTED_REAL_KIND(p=13, r=200)
+
+ WRITE(*,*) spacing(1.0_SGL) ! "1.1920929E-07" on i686
+ WRITE(*,*) spacing(1.0_DBL) ! "2.220446049250313E-016" on i686
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{RRSPACING}
+@end table
+
+
+
+@node SPREAD
+@section @code{SPREAD} --- Add a dimension to an array
+@fnindex SPREAD
+@cindex array, increase dimension
+@cindex array, duplicate elements
+@cindex array, duplicate dimensions
+
+@table @asis
+@item @emph{Description}:
+Replicates a @var{SOURCE} array @var{NCOPIES} times along a specified
+dimension @var{DIM}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = SPREAD(SOURCE, DIM, NCOPIES)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SOURCE} @tab Shall be a scalar or an array of any type and
+a rank less than seven.
+@item @var{DIM} @tab Shall be a scalar of type @code{INTEGER} with a
+value in the range from 1 to n+1, where n equals the rank of @var{SOURCE}.
+@item @var{NCOPIES} @tab Shall be a scalar of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The result is an array of the same type as @var{SOURCE} and has rank n+1
+where n equals the rank of @var{SOURCE}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_spread
+ INTEGER :: a = 1, b(2) = (/ 1, 2 /)
+ WRITE(*,*) SPREAD(A, 1, 2) ! "1 1"
+ WRITE(*,*) SPREAD(B, 1, 2) ! "1 1 2 2"
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{UNPACK}
+@end table
+
+
+
+@node SQRT
+@section @code{SQRT} --- Square-root function
+@fnindex SQRT
+@fnindex DSQRT
+@fnindex CSQRT
+@fnindex ZSQRT
+@fnindex CDSQRT
+@cindex root
+@cindex square-root
+
+@table @asis
+@item @emph{Description}:
+@code{SQRT(X)} computes the square root of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = SQRT(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or
+@code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{REAL} or @code{COMPLEX}.
+The kind type parameter is the same as @var{X}.
+
+@item @emph{Example}:
+@smallexample
+program test_sqrt
+ real(8) :: x = 2.0_8
+ complex :: z = (1.0, 2.0)
+ x = sqrt(x)
+ z = sqrt(z)
+end program test_sqrt
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{SQRT(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DSQRT(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@item @code{CSQRT(X)} @tab @code{COMPLEX(4) X} @tab @code{COMPLEX(4)} @tab Fortran 77 and later
+@item @code{ZSQRT(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@item @code{CDSQRT(X)} @tab @code{COMPLEX(8) X} @tab @code{COMPLEX(8)} @tab GNU extension
+@end multitable
+@end table
+
+
+
+@node SRAND
+@section @code{SRAND} --- Reinitialize the random number generator
+@fnindex SRAND
+@cindex random number generation, seeding
+@cindex seeding a random number generator
+
+@table @asis
+@item @emph{Description}:
+@code{SRAND} reinitializes the pseudo-random number generator
+called by @code{RAND} and @code{IRAND}. The new seed used by the
+generator is specified by the required argument @var{SEED}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL SRAND(SEED)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SEED} @tab Shall be a scalar @code{INTEGER(kind=4)}.
+@end multitable
+
+@item @emph{Return value}:
+Does not return anything.
+
+@item @emph{Example}:
+See @code{RAND} and @code{IRAND} for examples.
+
+@item @emph{Notes}:
+The Fortran standard specifies the intrinsic subroutines
+@code{RANDOM_SEED} to initialize the pseudo-random number
+generator and @code{RANDOM_NUMBER} to generate pseudo-random numbers.
+These subroutines should be used in new codes.
+
+Please note that in GNU Fortran, these two sets of intrinsics (@code{RAND},
+@code{IRAND} and @code{SRAND} on the one hand, @code{RANDOM_NUMBER} and
+@code{RANDOM_SEED} on the other hand) access two independent
+pseudo-random number generators.
+
+@item @emph{See also}:
+@ref{RAND}, @gol
+@ref{RANDOM_SEED}, @gol
+@ref{RANDOM_NUMBER}
+@end table
+
+
+
+@node STAT
+@section @code{STAT} --- Get file status
+@fnindex STAT
+@cindex file system, file status
+
+@table @asis
+@item @emph{Description}:
+This function returns information about a file. No permissions are required on
+the file itself, but execute (search) permission is required on all of the
+directories in path that lead to the file.
+
+The elements that are obtained and stored in the array @code{VALUES}:
+@multitable @columnfractions .15 .70
+@item @code{VALUES(1)} @tab Device ID
+@item @code{VALUES(2)} @tab Inode number
+@item @code{VALUES(3)} @tab File mode
+@item @code{VALUES(4)} @tab Number of links
+@item @code{VALUES(5)} @tab Owner's uid
+@item @code{VALUES(6)} @tab Owner's gid
+@item @code{VALUES(7)} @tab ID of device containing directory entry for file (0 if not available)
+@item @code{VALUES(8)} @tab File size (bytes)
+@item @code{VALUES(9)} @tab Last access time
+@item @code{VALUES(10)} @tab Last modification time
+@item @code{VALUES(11)} @tab Last file status change time
+@item @code{VALUES(12)} @tab Preferred I/O block size (-1 if not available)
+@item @code{VALUES(13)} @tab Number of blocks allocated (-1 if not available)
+@end multitable
+
+Not all these elements are relevant on all systems.
+If an element is not relevant, it is returned as 0.
+
+This intrinsic is provided in both subroutine and function forms; however,
+only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL STAT(NAME, VALUES [, STATUS])}
+@item @code{STATUS = STAT(NAME, VALUES)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{NAME} @tab The type shall be @code{CHARACTER}, of the
+default kind and a valid path within the file system.
+@item @var{VALUES} @tab The type shall be @code{INTEGER(4), DIMENSION(13)}.
+@item @var{STATUS} @tab (Optional) status flag of type @code{INTEGER(4)}. Returns 0
+on success and a system specific error code otherwise.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_stat
+ INTEGER, DIMENSION(13) :: buff
+ INTEGER :: status
+
+ CALL STAT("/etc/passwd", buff, status)
+
+ IF (status == 0) THEN
+ WRITE (*, FMT="('Device ID:', T30, I19)") buff(1)
+ WRITE (*, FMT="('Inode number:', T30, I19)") buff(2)
+ WRITE (*, FMT="('File mode (octal):', T30, O19)") buff(3)
+ WRITE (*, FMT="('Number of links:', T30, I19)") buff(4)
+ WRITE (*, FMT="('Owner''s uid:', T30, I19)") buff(5)
+ WRITE (*, FMT="('Owner''s gid:', T30, I19)") buff(6)
+ WRITE (*, FMT="('Device where located:', T30, I19)") buff(7)
+ WRITE (*, FMT="('File size:', T30, I19)") buff(8)
+ WRITE (*, FMT="('Last access time:', T30, A19)") CTIME(buff(9))
+ WRITE (*, FMT="('Last modification time', T30, A19)") CTIME(buff(10))
+ WRITE (*, FMT="('Last status change time:', T30, A19)") CTIME(buff(11))
+ WRITE (*, FMT="('Preferred block size:', T30, I19)") buff(12)
+ WRITE (*, FMT="('No. of blocks allocated:', T30, I19)") buff(13)
+ END IF
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+To stat an open file: @gol
+@ref{FSTAT} @gol
+To stat a link: @gol
+@ref{LSTAT}
+@end table
+
+
+
+@node STORAGE_SIZE
+@section @code{STORAGE_SIZE} --- Storage size in bits
+@fnindex STORAGE_SIZE
+@cindex storage size
+
+@table @asis
+@item @emph{Description}:
+Returns the storage size of argument @var{A} in bits.
+@item @emph{Standard}:
+Fortran 2008 and later
+@item @emph{Class}:
+Inquiry function
+@item @emph{Syntax}:
+@code{RESULT = STORAGE_SIZE(A [, KIND])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{A} @tab Shall be a scalar or array of any type.
+@item @var{KIND} @tab (Optional) shall be a scalar integer constant expression.
+@end multitable
+
+@item @emph{Return Value}:
+The result is a scalar integer with the kind type parameter specified by KIND
+(or default integer type if KIND is missing). The result value is the size
+expressed in bits for an element of an array that has the dynamic type and type
+parameters of A.
+
+@item @emph{See also}:
+@ref{C_SIZEOF}, @gol
+@ref{SIZEOF}
+@end table
+
+
+
+@node SUM
+@section @code{SUM} --- Sum of array elements
+@fnindex SUM
+@cindex array, sum
+@cindex array, add elements
+@cindex array, conditionally add elements
+@cindex sum array elements
+
+@table @asis
+@item @emph{Description}:
+Adds the elements of @var{ARRAY} along dimension @var{DIM} if
+the corresponding element in @var{MASK} is @code{TRUE}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = SUM(ARRAY[, MASK])}
+@item @code{RESULT = SUM(ARRAY, DIM[, MASK])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array of type @code{INTEGER},
+@code{REAL} or @code{COMPLEX}.
+@item @var{DIM} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with a value in the range from 1 to n, where n
+equals the rank of @var{ARRAY}.
+@item @var{MASK} @tab (Optional) shall be of type @code{LOGICAL}
+and either be a scalar or an array of the same shape as @var{ARRAY}.
+@end multitable
+
+@item @emph{Return value}:
+The result is of the same type as @var{ARRAY}.
+
+If @var{DIM} is absent, a scalar with the sum of all elements in @var{ARRAY}
+is returned. Otherwise, an array of rank n-1, where n equals the rank of
+@var{ARRAY}, and a shape similar to that of @var{ARRAY} with dimension @var{DIM}
+dropped is returned.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_sum
+ INTEGER :: x(5) = (/ 1, 2, 3, 4 ,5 /)
+ print *, SUM(x) ! all elements, sum = 15
+ print *, SUM(x, MASK=MOD(x, 2)==1) ! odd elements, sum = 9
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{PRODUCT}
+@end table
+
+
+
+@node SYMLNK
+@section @code{SYMLNK} --- Create a symbolic link
+@fnindex SYMLNK
+@cindex file system, create link
+@cindex file system, soft link
+
+@table @asis
+@item @emph{Description}:
+Makes a symbolic link from file @var{PATH1} to @var{PATH2}. A null
+character (@code{CHAR(0)}) can be used to mark the end of the names in
+@var{PATH1} and @var{PATH2}; otherwise, trailing blanks in the file
+names are ignored. If the @var{STATUS} argument is supplied, it
+contains 0 on success or a nonzero error code upon return; see
+@code{symlink(2)}. If the system does not supply @code{symlink(2)},
+@code{ENOSYS} is returned.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL SYMLNK(PATH1, PATH2 [, STATUS])}
+@item @code{STATUS = SYMLNK(PATH1, PATH2)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{PATH1} @tab Shall be of default @code{CHARACTER} type.
+@item @var{PATH2} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STATUS} @tab (Optional) Shall be of default @code{INTEGER} type.
+@end multitable
+
+@item @emph{See also}:
+@ref{LINK}, @gol
+@ref{UNLINK}
+@end table
+
+
+
+@node SYSTEM
+@section @code{SYSTEM} --- Execute a shell command
+@fnindex SYSTEM
+@cindex system, system call
+
+@table @asis
+@item @emph{Description}:
+Passes the command @var{COMMAND} to a shell (see @code{system(3)}). If
+argument @var{STATUS} is present, it contains the value returned by
+@code{system(3)}, which is presumably 0 if the shell command succeeded.
+Note that which shell is used to invoke the command is system-dependent
+and environment-dependent.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+
+Note that the @code{system} function need not be thread-safe. It is
+the responsibility of the user to ensure that @code{system} is not
+called concurrently.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL SYSTEM(COMMAND [, STATUS])}
+@item @code{STATUS = SYSTEM(COMMAND)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{COMMAND} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STATUS} @tab (Optional) Shall be of default @code{INTEGER} type.
+@end multitable
+
+@item @emph{See also}:
+@ref{EXECUTE_COMMAND_LINE}, which is part of the Fortran 2008 standard
+and should considered in new code for future portability.
+@end table
+
+
+
+@node SYSTEM_CLOCK
+@section @code{SYSTEM_CLOCK} --- Time function
+@fnindex SYSTEM_CLOCK
+@cindex time, clock ticks
+@cindex clock ticks
+
+@table @asis
+@item @emph{Description}:
+Determines the @var{COUNT} of a processor clock since an unspecified
+time in the past modulo @var{COUNT_MAX}, @var{COUNT_RATE} determines
+the number of clock ticks per second. If the platform supports a
+monotonic clock, that clock is used and can, depending on the platform
+clock implementation, provide up to nanosecond resolution. If a
+monotonic clock is not available, the implementation falls back to a
+realtime clock.
+
+@var{COUNT_RATE} is system dependent and can vary depending on the kind of
+the arguments. For @var{kind=4} arguments (and smaller integer kinds),
+@var{COUNT} represents milliseconds, while for @var{kind=8} arguments (and
+larger integer kinds), @var{COUNT} typically represents micro- or
+nanoseconds depending on resolution of the underlying platform clock.
+@var{COUNT_MAX} usually equals @code{HUGE(COUNT_MAX)}. Note that the
+millisecond resolution of the @var{kind=4} version implies that the
+@var{COUNT} will wrap around in roughly 25 days. In order to avoid issues
+with the wrap around and for more precise timing, please use the
+@var{kind=8} version.
+
+If there is no clock, or querying the clock fails, @var{COUNT} is set
+to @code{-HUGE(COUNT)}, and @var{COUNT_RATE} and @var{COUNT_MAX} are
+set to zero.
+
+When running on a platform using the GNU C library (glibc) version
+2.16 or older, or a derivative thereof, the high resolution monotonic
+clock is available only when linking with the @var{rt} library. This
+can be done explicitly by adding the @code{-lrt} flag when linking the
+application, but is also done implicitly when using OpenMP.
+
+On the Windows platform, the version with @var{kind=4} arguments uses
+the @code{GetTickCount} function, whereas the @var{kind=8} version
+uses @code{QueryPerformanceCounter} and
+@code{QueryPerformanceCounterFrequency}. For more information, and
+potential caveats, please see the platform documentation.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Subroutine
+
+@item @emph{Syntax}:
+@code{CALL SYSTEM_CLOCK([COUNT, COUNT_RATE, COUNT_MAX])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .20 .65
+@item @var{COUNT} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with @code{INTENT(OUT)}.
+@item @var{COUNT_RATE} @tab (Optional) shall be a scalar of type
+@code{INTEGER} or @code{REAL}, with @code{INTENT(OUT)}.
+@item @var{COUNT_MAX} @tab (Optional) shall be a scalar of type
+@code{INTEGER} with @code{INTENT(OUT)}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_system_clock
+ INTEGER :: count, count_rate, count_max
+ CALL SYSTEM_CLOCK(count, count_rate, count_max)
+ WRITE(*,*) count, count_rate, count_max
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{DATE_AND_TIME}, @gol
+@ref{CPU_TIME}
+@end table
+
+
+
+@node TAN
+@section @code{TAN} --- Tangent function
+@fnindex TAN
+@fnindex DTAN
+@cindex trigonometric function, tangent
+@cindex tangent
+
+@table @asis
+@item @emph{Description}:
+@code{TAN(X)} computes the tangent of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later, for a complex argument Fortran 2008 or later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = TAN(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}, and its value is in radians.
+
+@item @emph{Example}:
+@smallexample
+program test_tan
+ real(8) :: x = 0.165_8
+ x = tan(x)
+end program test_tan
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{TAN(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DTAN(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{ATAN} @gol
+Degrees function: @gol
+@ref{TAND}
+@end table
+
+
+
+@node TAND
+@section @code{TAND} --- Tangent function, degrees
+@fnindex TAND
+@fnindex DTAND
+@cindex trigonometric function, tangent, degrees
+@cindex tangent, degrees
+
+@table @asis
+@item @emph{Description}:
+@code{TAND(X)} computes the tangent of @var{X} in degrees.
+
+This function is for compatibility only and should be avoided in favor of
+standard constructs wherever possible.
+
+@item @emph{Standard}:
+GNU extension, enabled with @option{-fdec-math}.
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = TAND(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}, and its value is in degrees.
+
+@item @emph{Example}:
+@smallexample
+program test_tand
+ real(8) :: x = 0.165_8
+ x = tand(x)
+end program test_tand
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{TAND(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab GNU extension
+@item @code{DTAND(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab GNU extension
+@end multitable
+
+@item @emph{See also}:
+Inverse function: @gol
+@ref{ATAND} @gol
+Radians function: @gol
+@ref{TAN}
+@end table
+
+
+
+@node TANH
+@section @code{TANH} --- Hyperbolic tangent function
+@fnindex TANH
+@fnindex DTANH
+@cindex hyperbolic tangent
+@cindex hyperbolic function, tangent
+@cindex tangent, hyperbolic
+
+@table @asis
+@item @emph{Description}:
+@code{TANH(X)} computes the hyperbolic tangent of @var{X}.
+
+@item @emph{Standard}:
+Fortran 77 and later, for a complex argument Fortran 2008 or later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{X = TANH(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab The type shall be @code{REAL} or @code{COMPLEX}.
+@end multitable
+
+@item @emph{Return value}:
+The return value has same type and kind as @var{X}. If @var{X} is
+complex, the imaginary part of the result is in radians. If @var{X}
+is @code{REAL}, the return value lies in the range
+@math{ - 1 \leq tanh(x) \leq 1 }.
+
+@item @emph{Example}:
+@smallexample
+program test_tanh
+ real(8) :: x = 2.1_8
+ x = tanh(x)
+end program test_tanh
+@end smallexample
+
+@item @emph{Specific names}:
+@multitable @columnfractions .20 .23 .20 .33
+@headitem Name @tab Argument @tab Return type @tab Standard
+@item @code{TANH(X)} @tab @code{REAL(4) X} @tab @code{REAL(4)} @tab Fortran 77 and later
+@item @code{DTANH(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)} @tab Fortran 77 and later
+@end multitable
+
+@item @emph{See also}:
+@ref{ATANH}
+@end table
+
+
+
+@node THIS_IMAGE
+@section @code{THIS_IMAGE} --- Function that returns the cosubscript index of this image
+@fnindex THIS_IMAGE
+@cindex coarray, @code{THIS_IMAGE}
+@cindex images, index of this image
+
+@table @asis
+@item @emph{Description}:
+Returns the cosubscript for this image.
+
+@item @emph{Standard}:
+Fortran 2008 and later. With @var{DISTANCE} argument,
+Technical Specification (TS) 18508 or later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{RESULT = THIS_IMAGE()}
+@item @code{RESULT = THIS_IMAGE(DISTANCE)}
+@item @code{RESULT = THIS_IMAGE(COARRAY [, DIM])}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{DISTANCE} @tab (optional, intent(in)) Nonnegative scalar integer
+(not permitted together with @var{COARRAY}).
+@item @var{COARRAY} @tab Coarray of any type (optional; if @var{DIM}
+present, required).
+@item @var{DIM} @tab default integer scalar (optional). If present,
+@var{DIM} shall be between one and the corank of @var{COARRAY}.
+@end multitable
+
+
+@item @emph{Return value}:
+Default integer. If @var{COARRAY} is not present, it is scalar; if
+@var{DISTANCE} is not present or has value 0, its value is the image index on
+the invoking image for the current team, for values smaller or equal
+distance to the initial team, it returns the image index on the ancestor team
+which has a distance of @var{DISTANCE} from the invoking team. If
+@var{DISTANCE} is larger than the distance to the initial team, the image
+index of the initial team is returned. Otherwise when the @var{COARRAY} is
+present, if @var{DIM} is not present, a rank-1 array with corank elements is
+returned, containing the cosubscripts for @var{COARRAY} specifying the invoking
+image. If @var{DIM} is present, a scalar is returned, with the value of
+the @var{DIM} element of @code{THIS_IMAGE(COARRAY)}.
+
+@item @emph{Example}:
+@smallexample
+INTEGER :: value[*]
+INTEGER :: i
+value = THIS_IMAGE()
+SYNC ALL
+IF (THIS_IMAGE() == 1) THEN
+ DO i = 1, NUM_IMAGES()
+ WRITE(*,'(2(a,i0))') 'value[', i, '] is ', value[i]
+ END DO
+END IF
+
+! Check whether the current image is the initial image
+IF (THIS_IMAGE(HUGE(1)) /= THIS_IMAGE())
+ error stop "something is rotten here"
+@end smallexample
+
+@item @emph{See also}:
+@ref{NUM_IMAGES}, @gol
+@ref{IMAGE_INDEX}
+@end table
+
+
+
+@node TIME
+@section @code{TIME} --- Time function
+@fnindex TIME
+@cindex time, current
+@cindex current time
+
+@table @asis
+@item @emph{Description}:
+Returns the current time encoded as an integer (in the manner of the
+function @code{time(3)} in the C standard library). This value is
+suitable for passing to @ref{CTIME}, @ref{GMTIME}, and @ref{LTIME}.
+
+This intrinsic is not fully portable, such as to systems with 32-bit
+@code{INTEGER} types but supporting times wider than 32 bits. Therefore,
+the values returned by this intrinsic might be, or become, negative, or
+numerically less than previous values, during a single run of the
+compiled program.
+
+See @ref{TIME8}, for information on a similar intrinsic that might be
+portable to more GNU Fortran implementations, though to fewer Fortran
+compilers.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = TIME()}
+
+@item @emph{Return value}:
+The return value is a scalar of type @code{INTEGER(4)}.
+
+@item @emph{See also}:
+@ref{DATE_AND_TIME}, @gol
+@ref{CTIME}, @gol
+@ref{GMTIME}, @gol
+@ref{LTIME}, @gol
+@ref{MCLOCK}, @gol
+@ref{TIME8}
+@end table
+
+
+
+@node TIME8
+@section @code{TIME8} --- Time function (64-bit)
+@fnindex TIME8
+@cindex time, current
+@cindex current time
+
+@table @asis
+@item @emph{Description}:
+Returns the current time encoded as an integer (in the manner of the
+function @code{time(3)} in the C standard library). This value is
+suitable for passing to @ref{CTIME}, @ref{GMTIME}, and @ref{LTIME}.
+
+@emph{Warning:} this intrinsic does not increase the range of the timing
+values over that returned by @code{time(3)}. On a system with a 32-bit
+@code{time(3)}, @code{TIME8} will return a 32-bit value, even though
+it is converted to a 64-bit @code{INTEGER(8)} value. That means
+overflows of the 32-bit value can still occur. Therefore, the values
+returned by this intrinsic might be or become negative or numerically
+less than previous values during a single run of the compiled program.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = TIME8()}
+
+@item @emph{Return value}:
+The return value is a scalar of type @code{INTEGER(8)}.
+
+@item @emph{See also}:
+@ref{DATE_AND_TIME}, @gol
+@ref{CTIME}, @gol
+@ref{GMTIME}, @gol
+@ref{LTIME}, @gol
+@ref{MCLOCK8}, @gol
+@ref{TIME}
+@end table
+
+
+
+@node TINY
+@section @code{TINY} --- Smallest positive number of a real kind
+@fnindex TINY
+@cindex limits, smallest number
+@cindex model representation, smallest number
+
+@table @asis
+@item @emph{Description}:
+@code{TINY(X)} returns the smallest positive (non zero) number
+in the model of the type of @code{X}.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = TINY(X)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{X} @tab Shall be of type @code{REAL}.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of the same type and kind as @var{X}
+
+@item @emph{Example}:
+See @code{HUGE} for an example.
+@end table
+
+
+
+@node TRAILZ
+@section @code{TRAILZ} --- Number of trailing zero bits of an integer
+@fnindex TRAILZ
+@cindex zero bits
+
+@table @asis
+@item @emph{Description}:
+@code{TRAILZ} returns the number of trailing zero bits of an integer.
+
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = TRAILZ(I)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab Shall be of type @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The type of the return value is the default @code{INTEGER}.
+If all the bits of @code{I} are zero, the result value is @code{BIT_SIZE(I)}.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_trailz
+ WRITE (*,*) TRAILZ(8) ! prints 3
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{BIT_SIZE}, @gol
+@ref{LEADZ}, @gol
+@ref{POPPAR}, @gol
+@ref{POPCNT}
+@end table
+
+
+
+@node TRANSFER
+@section @code{TRANSFER} --- Transfer bit patterns
+@fnindex TRANSFER
+@cindex bits, move
+@cindex type cast
+
+@table @asis
+@item @emph{Description}:
+Interprets the bitwise representation of @var{SOURCE} in memory as if it
+is the representation of a variable or array of the same type and type
+parameters as @var{MOLD}.
+
+This is approximately equivalent to the C concept of @emph{casting} one
+type to another.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = TRANSFER(SOURCE, MOLD[, SIZE])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{SOURCE} @tab Shall be a scalar or an array of any type.
+@item @var{MOLD} @tab Shall be a scalar or an array of any type.
+@item @var{SIZE} @tab (Optional) shall be a scalar of type
+@code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The result has the same type as @var{MOLD}, with the bit level
+representation of @var{SOURCE}. If @var{SIZE} is present, the result is
+a one-dimensional array of length @var{SIZE}. If @var{SIZE} is absent
+but @var{MOLD} is an array (of any size or shape), the result is a one-
+dimensional array of the minimum length needed to contain the entirety
+of the bitwise representation of @var{SOURCE}. If @var{SIZE} is absent
+and @var{MOLD} is a scalar, the result is a scalar.
+
+If the bitwise representation of the result is longer than that of
+@var{SOURCE}, then the leading bits of the result correspond to those of
+@var{SOURCE} and any trailing bits are filled arbitrarily.
+
+When the resulting bit representation does not correspond to a valid
+representation of a variable of the same type as @var{MOLD}, the results
+are undefined, and subsequent operations on the result cannot be
+guaranteed to produce sensible behavior. For example, it is possible to
+create @code{LOGICAL} variables for which @code{@var{VAR}} and
+@code{.NOT.@var{VAR}} both appear to be true.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_transfer
+ integer :: x = 2143289344
+ print *, transfer(x, 1.0) ! prints "NaN" on i686
+END PROGRAM
+@end smallexample
+@end table
+
+
+
+@node TRANSPOSE
+@section @code{TRANSPOSE} --- Transpose an array of rank two
+@fnindex TRANSPOSE
+@cindex array, transpose
+@cindex matrix, transpose
+@cindex transpose
+
+@table @asis
+@item @emph{Description}:
+Transpose an array of rank two. Element (i, j) of the result has the value
+@code{MATRIX(j, i)}, for all i, j.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = TRANSPOSE(MATRIX)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{MATRIX} @tab Shall be an array of any type and have a rank of two.
+@end multitable
+
+@item @emph{Return value}:
+The result has the same type as @var{MATRIX}, and has shape
+@code{(/ m, n /)} if @var{MATRIX} has shape @code{(/ n, m /)}.
+@end table
+
+
+
+@node TRIM
+@section @code{TRIM} --- Remove trailing blank characters of a string
+@fnindex TRIM
+@cindex string, remove trailing whitespace
+
+@table @asis
+@item @emph{Description}:
+Removes trailing blank characters of a string.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = TRIM(STRING)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab Shall be a scalar of type @code{CHARACTER}.
+@end multitable
+
+@item @emph{Return value}:
+A scalar of type @code{CHARACTER} which length is that of @var{STRING}
+less the number of trailing blanks.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_trim
+ CHARACTER(len=10), PARAMETER :: s = "GFORTRAN "
+ WRITE(*,*) LEN(s), LEN(TRIM(s)) ! "10 8", with/without trailing blanks
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{ADJUSTL}, @gol
+@ref{ADJUSTR}
+@end table
+
+
+
+@node TTYNAM
+@section @code{TTYNAM} --- Get the name of a terminal device
+@fnindex TTYNAM
+@cindex system, terminal
+
+@table @asis
+@item @emph{Description}:
+Get the name of a terminal device. For more information,
+see @code{ttyname(3)}.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL TTYNAM(UNIT, NAME)}
+@item @code{NAME = TTYNAM(UNIT)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{UNIT} @tab Shall be a scalar @code{INTEGER}.
+@item @var{NAME} @tab Shall be of type @code{CHARACTER}.
+@end multitable
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_ttynam
+ INTEGER :: unit
+ DO unit = 1, 10
+ IF (isatty(unit=unit)) write(*,*) ttynam(unit)
+ END DO
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{ISATTY}
+@end table
+
+
+
+@node UBOUND
+@section @code{UBOUND} --- Upper dimension bounds of an array
+@fnindex UBOUND
+@cindex array, upper bound
+
+@table @asis
+@item @emph{Description}:
+Returns the upper bounds of an array, or a single upper bound
+along the @var{DIM} dimension.
+@item @emph{Standard}:
+Fortran 90 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = UBOUND(ARRAY [, DIM [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an array, of any type.
+@item @var{DIM} @tab (Optional) Shall be a scalar @code{INTEGER}.
+@item @var{KIND}@tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+If @var{DIM} is absent, the result is an array of the upper bounds of
+@var{ARRAY}. If @var{DIM} is present, the result is a scalar
+corresponding to the upper bound of the array along that dimension. If
+@var{ARRAY} is an expression rather than a whole array or array
+structure component, or if it has a zero extent along the relevant
+dimension, the upper bound is taken to be the number of elements along
+the relevant dimension.
+
+@item @emph{See also}:
+@ref{LBOUND}, @gol
+@ref{LCOBOUND}
+@end table
+
+
+
+@node UCOBOUND
+@section @code{UCOBOUND} --- Upper codimension bounds of an array
+@fnindex UCOBOUND
+@cindex coarray, upper bound
+
+@table @asis
+@item @emph{Description}:
+Returns the upper cobounds of a coarray, or a single upper cobound
+along the @var{DIM} codimension.
+@item @emph{Standard}:
+Fortran 2008 and later
+
+@item @emph{Class}:
+Inquiry function
+
+@item @emph{Syntax}:
+@code{RESULT = UCOBOUND(COARRAY [, DIM [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{ARRAY} @tab Shall be an coarray, of any type.
+@item @var{DIM} @tab (Optional) Shall be a scalar @code{INTEGER}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+If @var{DIM} is absent, the result is an array of the lower cobounds of
+@var{COARRAY}. If @var{DIM} is present, the result is a scalar
+corresponding to the lower cobound of the array along that codimension.
+
+@item @emph{See also}:
+@ref{LCOBOUND}, @gol
+@ref{LBOUND}
+@end table
+
+
+
+@node UMASK
+@section @code{UMASK} --- Set the file creation mask
+@fnindex UMASK
+@cindex file system, file creation mask
+
+@table @asis
+@item @emph{Description}:
+Sets the file creation mask to @var{MASK}. If called as a function, it
+returns the old value. If called as a subroutine and argument @var{OLD}
+if it is supplied, it is set to the old value. See @code{umask(2)}.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL UMASK(MASK [, OLD])}
+@item @code{OLD = UMASK(MASK)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{MASK} @tab Shall be a scalar of type @code{INTEGER}.
+@item @var{OLD} @tab (Optional) Shall be a scalar of type
+@code{INTEGER}.
+@end multitable
+
+@end table
+
+
+
+@node UNLINK
+@section @code{UNLINK} --- Remove a file from the file system
+@fnindex UNLINK
+@cindex file system, remove file
+
+@table @asis
+@item @emph{Description}:
+Unlinks the file @var{PATH}. A null character (@code{CHAR(0)}) can be
+used to mark the end of the name in @var{PATH}; otherwise, trailing
+blanks in the file name are ignored. If the @var{STATUS} argument is
+supplied, it contains 0 on success or a nonzero error code upon return;
+see @code{unlink(2)}.
+
+This intrinsic is provided in both subroutine and function forms;
+however, only one form can be used in any given program unit.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Subroutine, function
+
+@item @emph{Syntax}:
+@multitable @columnfractions .80
+@item @code{CALL UNLINK(PATH [, STATUS])}
+@item @code{STATUS = UNLINK(PATH)}
+@end multitable
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{PATH} @tab Shall be of default @code{CHARACTER} type.
+@item @var{STATUS} @tab (Optional) Shall be of default @code{INTEGER} type.
+@end multitable
+
+@item @emph{See also}:
+@ref{LINK}, @gol
+@ref{SYMLNK}
+@end table
+
+
+
+@node UNPACK
+@section @code{UNPACK} --- Unpack an array of rank one into an array
+@fnindex UNPACK
+@cindex array, unpacking
+@cindex array, increase dimension
+@cindex array, scatter elements
+
+@table @asis
+@item @emph{Description}:
+Store the elements of @var{VECTOR} in an array of higher rank.
+
+@item @emph{Standard}:
+Fortran 90 and later
+
+@item @emph{Class}:
+Transformational function
+
+@item @emph{Syntax}:
+@code{RESULT = UNPACK(VECTOR, MASK, FIELD)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{VECTOR} @tab Shall be an array of any type and rank one. It
+shall have at least as many elements as @var{MASK} has @code{TRUE} values.
+@item @var{MASK} @tab Shall be an array of type @code{LOGICAL}.
+@item @var{FIELD} @tab Shall be of the same type as @var{VECTOR} and have
+the same shape as @var{MASK}.
+@end multitable
+
+@item @emph{Return value}:
+The resulting array corresponds to @var{FIELD} with @code{TRUE} elements
+of @var{MASK} replaced by values from @var{VECTOR} in array element order.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_unpack
+ integer :: vector(2) = (/1,1/)
+ logical :: mask(4) = (/ .TRUE., .FALSE., .FALSE., .TRUE. /)
+ integer :: field(2,2) = 0, unity(2,2)
+
+ ! result: unity matrix
+ unity = unpack(vector, reshape(mask, (/2,2/)), field)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{PACK}, @gol
+@ref{SPREAD}
+@end table
+
+
+
+@node VERIFY
+@section @code{VERIFY} --- Scan a string for characters not a given set
+@fnindex VERIFY
+@cindex string, find missing set
+
+@table @asis
+@item @emph{Description}:
+Verifies that all the characters in @var{STRING} belong to the set of
+characters in @var{SET}.
+
+If @var{BACK} is either absent or equals @code{FALSE}, this function
+returns the position of the leftmost character of @var{STRING} that is
+not in @var{SET}. If @var{BACK} equals @code{TRUE}, the rightmost
+position is returned. If all characters of @var{STRING} are found in
+@var{SET}, the result is zero.
+
+@item @emph{Standard}:
+Fortran 90 and later, with @var{KIND} argument Fortran 2003 and later
+
+@item @emph{Class}:
+Elemental function
+
+@item @emph{Syntax}:
+@code{RESULT = VERIFY(STRING, SET[, BACK [, KIND]])}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{STRING} @tab Shall be of type @code{CHARACTER}.
+@item @var{SET} @tab Shall be of type @code{CHARACTER}.
+@item @var{BACK} @tab (Optional) shall be of type @code{LOGICAL}.
+@item @var{KIND} @tab (Optional) An @code{INTEGER} initialization
+expression indicating the kind parameter of the result.
+@end multitable
+
+@item @emph{Return value}:
+The return value is of type @code{INTEGER} and of kind @var{KIND}. If
+@var{KIND} is absent, the return value is of default integer kind.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_verify
+ WRITE(*,*) VERIFY("FORTRAN", "AO") ! 1, found 'F'
+ WRITE(*,*) VERIFY("FORTRAN", "FOO") ! 3, found 'R'
+ WRITE(*,*) VERIFY("FORTRAN", "C++") ! 1, found 'F'
+ WRITE(*,*) VERIFY("FORTRAN", "C++", .TRUE.) ! 7, found 'N'
+ WRITE(*,*) VERIFY("FORTRAN", "FORTRAN") ! 0' found none
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+@ref{SCAN}, @gol
+@ref{INDEX intrinsic}
+@end table
+
+
+
+@node XOR
+@section @code{XOR} --- Bitwise logical exclusive OR
+@fnindex XOR
+@cindex bitwise logical exclusive or
+@cindex logical exclusive or, bitwise
+
+@table @asis
+@item @emph{Description}:
+Bitwise logical exclusive or.
+
+This intrinsic routine is provided for backwards compatibility with
+GNU Fortran 77. For integer arguments, programmers should consider
+the use of the @ref{IEOR} intrinsic and for logical arguments the
+@code{.NEQV.} operator, which are both defined by the Fortran standard.
+
+@item @emph{Standard}:
+GNU extension
+
+@item @emph{Class}:
+Function
+
+@item @emph{Syntax}:
+@code{RESULT = XOR(I, J)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{I} @tab The type shall be either a scalar @code{INTEGER}
+type or a scalar @code{LOGICAL} type or a boz-literal-constant.
+@item @var{J} @tab The type shall be the same as the type of @var{I} or
+a boz-literal-constant. @var{I} and @var{J} shall not both be
+boz-literal-constants. If either @var{I} and @var{J} is a
+boz-literal-constant, then the other argument must be a scalar @code{INTEGER}.
+@end multitable
+
+@item @emph{Return value}:
+The return type is either a scalar @code{INTEGER} or a scalar
+@code{LOGICAL}. If the kind type parameters differ, then the
+smaller kind type is implicitly converted to larger kind, and the
+return has the larger kind. A boz-literal-constant is
+converted to an @code{INTEGER} with the kind type parameter of
+the other argument as-if a call to @ref{INT} occurred.
+
+@item @emph{Example}:
+@smallexample
+PROGRAM test_xor
+ LOGICAL :: T = .TRUE., F = .FALSE.
+ INTEGER :: a, b
+ DATA a / Z'F' /, b / Z'3' /
+
+ WRITE (*,*) XOR(T, T), XOR(T, F), XOR(F, T), XOR(F, F)
+ WRITE (*,*) XOR(a, b)
+END PROGRAM
+@end smallexample
+
+@item @emph{See also}:
+Fortran 95 elemental function: @gol
+@ref{IEOR}
+@end table
+
+
+
+@node Intrinsic Modules
+@chapter Intrinsic Modules
+@cindex intrinsic Modules
+
+@menu
+* ISO_FORTRAN_ENV::
+* ISO_C_BINDING::
+* IEEE modules::
+* OpenMP Modules OMP_LIB and OMP_LIB_KINDS::
+* OpenACC Module OPENACC::
+@end menu
+
+@node ISO_FORTRAN_ENV
+@section @code{ISO_FORTRAN_ENV}
+@table @asis
+@item @emph{Standard}:
+Fortran 2003 and later, except when otherwise noted
+@end table
+
+The @code{ISO_FORTRAN_ENV} module provides the following scalar default-integer
+named constants:
+
+@table @asis
+@item @code{ATOMIC_INT_KIND}:
+Default-kind integer constant to be used as kind parameter when defining
+integer variables used in atomic operations. (Fortran 2008 or later.)
+
+@item @code{ATOMIC_LOGICAL_KIND}:
+Default-kind integer constant to be used as kind parameter when defining
+logical variables used in atomic operations. (Fortran 2008 or later.)
+
+@item @code{CHARACTER_KINDS}:
+Default-kind integer constant array of rank one containing the supported kind
+parameters of the @code{CHARACTER} type. (Fortran 2008 or later.)
+
+@item @code{CHARACTER_STORAGE_SIZE}:
+Size in bits of the character storage unit.
+
+@item @code{ERROR_UNIT}:
+Identifies the preconnected unit used for error reporting.
+
+@item @code{FILE_STORAGE_SIZE}:
+Size in bits of the file-storage unit.
+
+@item @code{INPUT_UNIT}:
+Identifies the preconnected unit identified by the asterisk
+(@code{*}) in @code{READ} statement.
+
+@item @code{INT8}, @code{INT16}, @code{INT32}, @code{INT64}:
+Kind type parameters to specify an INTEGER type with a storage
+size of 16, 32, and 64 bits. It is negative if a target platform
+does not support the particular kind. (Fortran 2008 or later.)
+
+@item @code{INTEGER_KINDS}:
+Default-kind integer constant array of rank one containing the supported kind
+parameters of the @code{INTEGER} type. (Fortran 2008 or later.)
+
+@item @code{IOSTAT_END}:
+The value assigned to the variable passed to the @code{IOSTAT=} specifier of
+an input/output statement if an end-of-file condition occurred.
+
+@item @code{IOSTAT_EOR}:
+The value assigned to the variable passed to the @code{IOSTAT=} specifier of
+an input/output statement if an end-of-record condition occurred.
+
+@item @code{IOSTAT_INQUIRE_INTERNAL_UNIT}:
+Scalar default-integer constant, used by @code{INQUIRE} for the
+@code{IOSTAT=} specifier to denote an that a unit number identifies an
+internal unit. (Fortran 2008 or later.)
+
+@item @code{NUMERIC_STORAGE_SIZE}:
+The size in bits of the numeric storage unit.
+
+@item @code{LOGICAL_KINDS}:
+Default-kind integer constant array of rank one containing the supported kind
+parameters of the @code{LOGICAL} type. (Fortran 2008 or later.)
+
+@item @code{OUTPUT_UNIT}:
+Identifies the preconnected unit identified by the asterisk
+(@code{*}) in @code{WRITE} statement.
+
+@item @code{REAL32}, @code{REAL64}, @code{REAL128}:
+Kind type parameters to specify a REAL type with a storage
+size of 32, 64, and 128 bits. It is negative if a target platform
+does not support the particular kind. (Fortran 2008 or later.)
+
+@item @code{REAL_KINDS}:
+Default-kind integer constant array of rank one containing the supported kind
+parameters of the @code{REAL} type. (Fortran 2008 or later.)
+
+@item @code{STAT_LOCKED}:
+Scalar default-integer constant used as STAT= return value by @code{LOCK} to
+denote that the lock variable is locked by the executing image. (Fortran 2008
+or later.)
+
+@item @code{STAT_LOCKED_OTHER_IMAGE}:
+Scalar default-integer constant used as STAT= return value by @code{UNLOCK} to
+denote that the lock variable is locked by another image. (Fortran 2008 or
+later.)
+
+@item @code{STAT_STOPPED_IMAGE}:
+Positive, scalar default-integer constant used as STAT= return value if the
+argument in the statement requires synchronisation with an image, which has
+initiated the termination of the execution. (Fortran 2008 or later.)
+
+@item @code{STAT_FAILED_IMAGE}:
+Positive, scalar default-integer constant used as STAT= return value if the
+argument in the statement requires communication with an image, which has
+is in the failed state. (TS 18508 or later.)
+
+@item @code{STAT_UNLOCKED}:
+Scalar default-integer constant used as STAT= return value by @code{UNLOCK} to
+denote that the lock variable is unlocked. (Fortran 2008 or later.)
+@end table
+
+The module provides the following derived type:
+
+@table @asis
+@item @code{LOCK_TYPE}:
+Derived type with private components to be use with the @code{LOCK} and
+@code{UNLOCK} statement. A variable of its type has to be always declared
+as coarray and may not appear in a variable-definition context.
+(Fortran 2008 or later.)
+@end table
+
+The module also provides the following intrinsic procedures:
+@ref{COMPILER_OPTIONS} and @ref{COMPILER_VERSION}.
+
+
+
+@node ISO_C_BINDING
+@section @code{ISO_C_BINDING}
+@table @asis
+@item @emph{Standard}:
+Fortran 2003 and later, GNU extensions
+@end table
+
+The following intrinsic procedures are provided by the module; their
+definition can be found in the section Intrinsic Procedures of this
+manual.
+
+@table @asis
+@item @code{C_ASSOCIATED}
+@item @code{C_F_POINTER}
+@item @code{C_F_PROCPOINTER}
+@item @code{C_FUNLOC}
+@item @code{C_LOC}
+@item @code{C_SIZEOF}
+@end table
+@c TODO: Vertical spacing between C_FUNLOC and C_LOC wrong in PDF,
+@c don't really know why.
+
+The @code{ISO_C_BINDING} module provides the following named constants of
+type default integer, which can be used as KIND type parameters.
+
+In addition to the integer named constants required by the Fortran 2003
+standard and @code{C_PTRDIFF_T} of TS 29113, GNU Fortran provides as an
+extension named constants for the 128-bit integer types supported by the
+C compiler: @code{C_INT128_T, C_INT_LEAST128_T, C_INT_FAST128_T}.
+Furthermore, if @code{_Float128} is supported in C, the named constants
+@code{C_FLOAT128} and @code{C_FLOAT128_COMPLEX} are defined.
+
+@multitable @columnfractions .19 .32 .34 .15
+@headitem Fortran Type @tab Named constant @tab C type @tab Extension
+@item @code{INTEGER}@tab @code{C_INT} @tab @code{int}
+@item @code{INTEGER}@tab @code{C_SHORT} @tab @code{short int}
+@item @code{INTEGER}@tab @code{C_LONG} @tab @code{long int}
+@item @code{INTEGER}@tab @code{C_LONG_LONG} @tab @code{long long int}
+@item @code{INTEGER}@tab @code{C_SIGNED_CHAR} @tab @code{signed char}/@code{unsigned char}
+@item @code{INTEGER}@tab @code{C_SIZE_T} @tab @code{size_t}
+@item @code{INTEGER}@tab @code{C_INT8_T} @tab @code{int8_t}
+@item @code{INTEGER}@tab @code{C_INT16_T} @tab @code{int16_t}
+@item @code{INTEGER}@tab @code{C_INT32_T} @tab @code{int32_t}
+@item @code{INTEGER}@tab @code{C_INT64_T} @tab @code{int64_t}
+@item @code{INTEGER}@tab @code{C_INT128_T} @tab @code{int128_t} @tab Ext.
+@item @code{INTEGER}@tab @code{C_INT_LEAST8_T} @tab @code{int_least8_t}
+@item @code{INTEGER}@tab @code{C_INT_LEAST16_T} @tab @code{int_least16_t}
+@item @code{INTEGER}@tab @code{C_INT_LEAST32_T} @tab @code{int_least32_t}
+@item @code{INTEGER}@tab @code{C_INT_LEAST64_T} @tab @code{int_least64_t}
+@item @code{INTEGER}@tab @code{C_INT_LEAST128_T}@tab @code{int_least128_t} @tab Ext.
+@item @code{INTEGER}@tab @code{C_INT_FAST8_T} @tab @code{int_fast8_t}
+@item @code{INTEGER}@tab @code{C_INT_FAST16_T} @tab @code{int_fast16_t}
+@item @code{INTEGER}@tab @code{C_INT_FAST32_T} @tab @code{int_fast32_t}
+@item @code{INTEGER}@tab @code{C_INT_FAST64_T} @tab @code{int_fast64_t}
+@item @code{INTEGER}@tab @code{C_INT_FAST128_T} @tab @code{int_fast128_t} @tab Ext.
+@item @code{INTEGER}@tab @code{C_INTMAX_T} @tab @code{intmax_t}
+@item @code{INTEGER}@tab @code{C_INTPTR_T} @tab @code{intptr_t}
+@item @code{INTEGER}@tab @code{C_PTRDIFF_T} @tab @code{ptrdiff_t} @tab TS 29113
+@item @code{REAL} @tab @code{C_FLOAT} @tab @code{float}
+@item @code{REAL} @tab @code{C_DOUBLE} @tab @code{double}
+@item @code{REAL} @tab @code{C_LONG_DOUBLE} @tab @code{long double}
+@item @code{REAL} @tab @code{C_FLOAT128} @tab @code{_Float128} @tab Ext.
+@item @code{COMPLEX}@tab @code{C_FLOAT_COMPLEX} @tab @code{float _Complex}
+@item @code{COMPLEX}@tab @code{C_DOUBLE_COMPLEX}@tab @code{double _Complex}
+@item @code{COMPLEX}@tab @code{C_LONG_DOUBLE_COMPLEX}@tab @code{long double _Complex}
+@item @code{COMPLEX}@tab @code{C_FLOAT128_COMPLEX} @tab @code{_Float128 _Complex} @tab Ext.
+@item @code{LOGICAL}@tab @code{C_BOOL} @tab @code{_Bool}
+@item @code{CHARACTER}@tab @code{C_CHAR} @tab @code{char}
+@end multitable
+
+Additionally, the following parameters of type @code{CHARACTER(KIND=C_CHAR)}
+are defined.
+
+@multitable @columnfractions .20 .45 .15
+@headitem Name @tab C definition @tab Value
+@item @code{C_NULL_CHAR} @tab null character @tab @code{'\0'}
+@item @code{C_ALERT} @tab alert @tab @code{'\a'}
+@item @code{C_BACKSPACE} @tab backspace @tab @code{'\b'}
+@item @code{C_FORM_FEED} @tab form feed @tab @code{'\f'}
+@item @code{C_NEW_LINE} @tab new line @tab @code{'\n'}
+@item @code{C_CARRIAGE_RETURN} @tab carriage return @tab @code{'\r'}
+@item @code{C_HORIZONTAL_TAB} @tab horizontal tab @tab @code{'\t'}
+@item @code{C_VERTICAL_TAB} @tab vertical tab @tab @code{'\v'}
+@end multitable
+
+Moreover, the following two named constants are defined:
+
+@multitable @columnfractions .20 .80
+@headitem Name @tab Type
+@item @code{C_NULL_PTR} @tab @code{C_PTR}
+@item @code{C_NULL_FUNPTR} @tab @code{C_FUNPTR}
+@end multitable
+
+Both are equivalent to the value @code{NULL} in C.
+
+
+
+@node IEEE modules
+@section IEEE modules: @code{IEEE_EXCEPTIONS}, @code{IEEE_ARITHMETIC}, and @code{IEEE_FEATURES}
+@table @asis
+@item @emph{Standard}:
+Fortran 2003 and later
+@end table
+
+The @code{IEEE_EXCEPTIONS}, @code{IEEE_ARITHMETIC}, and @code{IEEE_FEATURES}
+intrinsic modules provide support for exceptions and IEEE arithmetic, as
+defined in Fortran 2003 and later standards, and the IEC 60559:1989 standard
+(@emph{Binary floating-point arithmetic for microprocessor systems}). These
+modules are only provided on the following supported platforms:
+
+@itemize @bullet
+@item i386 and x86_64 processors
+@item platforms which use the GNU C Library (glibc)
+@item platforms with support for SysV/386 routines for floating point
+interface (including Solaris and BSDs)
+@item platforms with the AIX OS
+@end itemize
+
+For full compliance with the Fortran standards, code using the
+@code{IEEE_EXCEPTIONS} or @code{IEEE_ARITHMETIC} modules should be compiled
+with the following options: @code{-fno-unsafe-math-optimizations
+-frounding-math -fsignaling-nans}.
+
+
+
+@node OpenMP Modules OMP_LIB and OMP_LIB_KINDS
+@section OpenMP Modules @code{OMP_LIB} and @code{OMP_LIB_KINDS}
+@table @asis
+@item @emph{Standard}:
+OpenMP Application Program Interface v4.5,
+OpenMP Application Program Interface v5.0 (partially supported) and
+OpenMP Application Program Interface v5.1 (partially supported).
+@end table
+
+The OpenMP Fortran runtime library routines are provided both in
+a form of two Fortran modules, named @code{OMP_LIB} and
+@code{OMP_LIB_KINDS}, and in a form of a Fortran @code{include} file named
+@file{omp_lib.h}. The procedures provided by @code{OMP_LIB} can be found
+in the @ref{Top,,Introduction,libgomp,GNU Offloading and Multi
+Processing Runtime Library} manual,
+the named constants defined in the modules are listed
+below.
+
+For details refer to the actual
+@uref{https://www.openmp.org/wp-content/uploads/openmp-4.5.pdf,
+OpenMP Application Program Interface v4.5} and
+@uref{https://www.openmp.org/wp-content/uploads/OpenMP-API-Specification-5.0.pdf,
+OpenMP Application Program Interface v5.0}.
+
+@code{OMP_LIB_KINDS} provides the following scalar default-integer
+named constants:
+
+@table @asis
+@item @code{omp_allocator_handle_kind}
+@item @code{omp_alloctrait_key_kind}
+@item @code{omp_alloctrait_val_kind}
+@item @code{omp_depend_kind}
+@item @code{omp_lock_kind}
+@item @code{omp_lock_hint_kind}
+@item @code{omp_nest_lock_kind}
+@item @code{omp_pause_resource_kind}
+@item @code{omp_memspace_handle_kind}
+@item @code{omp_proc_bind_kind}
+@item @code{omp_sched_kind}
+@item @code{omp_sync_hint_kind}
+@end table
+
+@code{OMP_LIB} provides the scalar default-integer
+named constant @code{openmp_version} with a value of the form
+@var{yyyymm}, where @code{yyyy} is the year and @var{mm} the month
+of the OpenMP version; for OpenMP v4.5 the value is @code{201511}.
+
+The following derived type:
+
+@table @asis
+@item @code{omp_alloctrait}
+@end table
+
+The following scalar integer named constants of the
+kind @code{omp_sched_kind}:
+
+@table @asis
+@item @code{omp_sched_static}
+@item @code{omp_sched_dynamic}
+@item @code{omp_sched_guided}
+@item @code{omp_sched_auto}
+@end table
+
+And the following scalar integer named constants of the
+kind @code{omp_proc_bind_kind}:
+
+@table @asis
+@item @code{omp_proc_bind_false}
+@item @code{omp_proc_bind_true}
+@item @code{omp_proc_bind_primary}
+@item @code{omp_proc_bind_master}
+@item @code{omp_proc_bind_close}
+@item @code{omp_proc_bind_spread}
+@end table
+
+The following scalar integer named constants are of the
+kind @code{omp_lock_hint_kind}:
+
+@table @asis
+@item @code{omp_lock_hint_none}
+@item @code{omp_lock_hint_uncontended}
+@item @code{omp_lock_hint_contended}
+@item @code{omp_lock_hint_nonspeculative}
+@item @code{omp_lock_hint_speculative}
+@item @code{omp_sync_hint_none}
+@item @code{omp_sync_hint_uncontended}
+@item @code{omp_sync_hint_contended}
+@item @code{omp_sync_hint_nonspeculative}
+@item @code{omp_sync_hint_speculative}
+@end table
+
+And the following two scalar integer named constants are of the
+kind @code{omp_pause_resource_kind}:
+
+@table @asis
+@item @code{omp_pause_soft}
+@item @code{omp_pause_hard}
+@end table
+
+The following scalar integer named constants are of the kind
+@code{omp_alloctrait_key_kind}:
+
+@table @asis
+@item @code{omp_atk_sync_hint}
+@item @code{omp_atk_alignment}
+@item @code{omp_atk_access}
+@item @code{omp_atk_pool_size}
+@item @code{omp_atk_fallback}
+@item @code{omp_atk_fb_data}
+@item @code{omp_atk_pinned}
+@item @code{omp_atk_partition}
+@end table
+
+The following scalar integer named constants are of the kind
+@code{omp_alloctrait_val_kind}:
+
+@table @asis
+@code{omp_alloctrait_key_kind}:
+@item @code{omp_atv_default}
+@item @code{omp_atv_false}
+@item @code{omp_atv_true}
+@item @code{omp_atv_contended}
+@item @code{omp_atv_uncontended}
+@item @code{omp_atv_serialized}
+@item @code{omp_atv_sequential}
+@item @code{omp_atv_private}
+@item @code{omp_atv_all}
+@item @code{omp_atv_thread}
+@item @code{omp_atv_pteam}
+@item @code{omp_atv_cgroup}
+@item @code{omp_atv_default_mem_fb}
+@item @code{omp_atv_null_fb}
+@item @code{omp_atv_abort_fb}
+@item @code{omp_atv_allocator_fb}
+@item @code{omp_atv_environment}
+@item @code{omp_atv_nearest}
+@item @code{omp_atv_blocked}
+@end table
+
+The following scalar integer named constants are of the kind
+@code{omp_allocator_handle_kind}:
+
+@table @asis
+@item @code{omp_null_allocator}
+@item @code{omp_default_mem_alloc}
+@item @code{omp_large_cap_mem_alloc}
+@item @code{omp_const_mem_alloc}
+@item @code{omp_high_bw_mem_alloc}
+@item @code{omp_low_lat_mem_alloc}
+@item @code{omp_cgroup_mem_alloc}
+@item @code{omp_pteam_mem_alloc}
+@item @code{omp_thread_mem_alloc}
+@end table
+
+The following scalar integer named constants are of the kind
+@code{omp_memspace_handle_kind}:
+
+@table @asis
+@item @code{omp_default_mem_space}
+@item @code{omp_large_cap_mem_space}
+@item @code{omp_const_mem_space}
+@item @code{omp_high_bw_mem_space}
+@item @code{omp_low_lat_mem_space}
+@end table
+
+
+
+@node OpenACC Module OPENACC
+@section OpenACC Module @code{OPENACC}
+@table @asis
+@item @emph{Standard}:
+OpenACC Application Programming Interface v2.6
+@end table
+
+
+The OpenACC Fortran runtime library routines are provided both in a
+form of a Fortran 90 module, named @code{OPENACC}, and in form of a
+Fortran @code{include} file named @file{openacc_lib.h}. The
+procedures provided by @code{OPENACC} can be found in the
+@ref{Top,,Introduction,libgomp,GNU Offloading and Multi Processing
+Runtime Library} manual, the named constants defined in the modules
+are listed below.
+
+For details refer to the actual
+@uref{https://www.openacc.org/,
+OpenACC Application Programming Interface v2.6}.
+
+@code{OPENACC} provides the scalar default-integer
+named constant @code{openacc_version} with a value of the form
+@var{yyyymm}, where @code{yyyy} is the year and @var{mm} the month
+of the OpenACC version; for OpenACC v2.6 the value is @code{201711}.
--- /dev/null
+@c Copyright (C) 2004-2022 Free Software Foundation, Inc.
+@c This is part of the GNU Fortran manual.
+@c For copying conditions, see the file gfortran.texi.
+
+@ignore
+@c man begin COPYRIGHT
+Copyright @copyright{} 2004-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``Funding Free Software'', the Front-Cover
+Texts being (a) (see below), and with the Back-Cover Texts being (b)
+(see below). A copy of the license is included in the gfdl(7) man page.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@c Set file name and title for the man page.
+@setfilename gfortran
+@settitle GNU Fortran compiler.
+@c man begin SYNOPSIS
+gfortran [@option{-c}|@option{-S}|@option{-E}]
+ [@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
+ [@option{-W}@var{warn}@dots{}] [@option{-pedantic}]
+ [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
+ [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
+ [@option{-f}@var{option}@dots{}]
+ [@option{-m}@var{machine-option}@dots{}]
+ [@option{-o} @var{outfile}] @var{infile}@dots{}
+
+Only the most useful options are listed here; see below for the
+remainder.
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7),
+cpp(1), gcov(1), gcc(1), as(1), ld(1), gdb(1), dbx(1)
+and the Info entries for @file{gcc}, @file{cpp}, @file{gfortran}, @file{as},
+@file{ld}, @file{binutils} and @file{gdb}.
+@c man end
+@c man begin BUGS
+For instructions on reporting bugs, see
+@w{@value{BUGURL}}.
+@c man end
+@c man begin AUTHOR
+See the Info entry for @command{gfortran} for contributors to GCC and
+GNU Fortran.
+@c man end
+@end ignore
+
+@node Invoking GNU Fortran
+@chapter GNU Fortran Command Options
+@cindex GNU Fortran command options
+@cindex command options
+@cindex options, @command{gfortran} command
+
+@c man begin DESCRIPTION
+
+The @command{gfortran} command supports all the options supported by the
+@command{gcc} command. Only options specific to GNU Fortran are documented
+here.
+
+@xref{Invoking GCC,,GCC Command Options,gcc,Using the GNU Compiler
+Collection (GCC)}, for information
+on the non-Fortran-specific aspects of the @command{gcc} command (and,
+therefore, the @command{gfortran} command).
+
+@cindex options, negative forms
+All GCC and GNU Fortran options
+are accepted both by @command{gfortran} and by @command{gcc}
+(as well as any other drivers built at the same time,
+such as @command{g++}),
+since adding GNU Fortran to the GCC distribution
+enables acceptance of GNU Fortran options
+by all of the relevant drivers.
+
+In some cases, options have positive and negative forms;
+the negative form of @option{-ffoo} would be @option{-fno-foo}.
+This manual documents only one of these two forms, whichever
+one is not the default.
+@c man end
+
+@menu
+* Option Summary:: Brief list of all @command{gfortran} options,
+ without explanations.
+* Fortran Dialect Options:: Controlling the variant of Fortran language
+ compiled.
+* Preprocessing Options:: Enable and customize preprocessing.
+* Error and Warning Options:: How picky should the compiler be?
+* Debugging Options:: Symbol tables, measurements, and debugging dumps.
+* Directory Options:: Where to find module files
+* Link Options :: Influencing the linking step
+* Runtime Options:: Influencing runtime behavior
+* Code Gen Options:: Specifying conventions for function calls, data layout
+ and register usage.
+* Interoperability Options:: Options for interoperability with other
+ languages.
+* Environment Variables:: Environment variables that affect @command{gfortran}.
+@end menu
+
+@node Option Summary
+@section Option summary
+
+@c man begin OPTIONS
+
+Here is a summary of all the options specific to GNU Fortran, grouped
+by type. Explanations are in the following sections.
+
+@table @emph
+@item Fortran Language Options
+@xref{Fortran Dialect Options,,Options controlling Fortran dialect}.
+@gccoptlist{-fall-intrinsics -fallow-argument-mismatch -fallow-invalid-boz @gol
+-fbackslash -fcray-pointer -fd-lines-as-code -fd-lines-as-comments @gol
+-fdec -fdec-char-conversions -fdec-structure -fdec-intrinsic-ints @gol
+-fdec-static -fdec-math -fdec-include -fdec-format-defaults @gol
+-fdec-blank-format-item -fdefault-double-8 -fdefault-integer-8 @gol
+-fdefault-real-8 -fdefault-real-10 -fdefault-real-16 -fdollar-ok @gol
+-ffixed-line-length-@var{n} -ffixed-line-length-none -fpad-source @gol
+-ffree-form -ffree-line-length-@var{n} -ffree-line-length-none @gol
+-fimplicit-none -finteger-4-integer-8 -fmax-identifier-length @gol
+-fmodule-private -ffixed-form -fno-range-check -fopenacc -fopenmp @gol
+-freal-4-real-10 -freal-4-real-16 -freal-4-real-8 -freal-8-real-10 @gol
+-freal-8-real-16 -freal-8-real-4 -std=@var{std} -ftest-forall-temp
+}
+
+@item Preprocessing Options
+@xref{Preprocessing Options,,Enable and customize preprocessing}.
+@gccoptlist{-A-@var{question}@r{[}=@var{answer}@r{]}
+-A@var{question}=@var{answer} -C -CC -D@var{macro}@r{[}=@var{defn}@r{]}
+-H -P @gol
+-U@var{macro} -cpp -dD -dI -dM -dN -dU -fworking-directory
+-imultilib @var{dir} @gol
+-iprefix @var{file} -iquote -isysroot @var{dir} -isystem @var{dir} -nocpp
+-nostdinc @gol
+-undef
+}
+
+@item Error and Warning Options
+@xref{Error and Warning Options,,Options to request or suppress errors
+and warnings}.
+@gccoptlist{-Waliasing -Wall -Wampersand -Warray-bounds @gol
+-Wc-binding-type -Wcharacter-truncation -Wconversion @gol
+-Wdo-subscript -Wfunction-elimination -Wimplicit-interface @gol
+-Wimplicit-procedure -Wintrinsic-shadow -Wuse-without-only @gol
+-Wintrinsics-std -Wline-truncation -Wno-align-commons @gol
+-Wno-overwrite-recursive -Wno-tabs -Wreal-q-constant -Wsurprising @gol
+-Wunderflow -Wunused-parameter -Wrealloc-lhs -Wrealloc-lhs-all @gol
+-Wfrontend-loop-interchange -Wtarget-lifetime -fmax-errors=@var{n} @gol
+-fsyntax-only -pedantic @gol
+-pedantic-errors @gol
+}
+
+@item Debugging Options
+@xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
+@gccoptlist{-fbacktrace -fdump-fortran-optimized -fdump-fortran-original @gol
+-fdebug-aux-vars -fdump-fortran-global -fdump-parse-tree -ffpe-trap=@var{list} @gol
+-ffpe-summary=@var{list}
+}
+
+@item Directory Options
+@xref{Directory Options,,Options for directory search}.
+@gccoptlist{-I@var{dir} -J@var{dir} -fintrinsic-modules-path @var{dir}}
+
+@item Link Options
+@xref{Link Options,,Options for influencing the linking step}.
+@gccoptlist{-static-libgfortran -static-libquadmath}
+
+@item Runtime Options
+@xref{Runtime Options,,Options for influencing runtime behavior}.
+@gccoptlist{-fconvert=@var{conversion} -fmax-subrecord-length=@var{length} @gol
+-frecord-marker=@var{length} -fsign-zero
+}
+
+@item Interoperability Options
+@xref{Interoperability Options,,Options for interoperability}.
+@gccoptlist{-fc-prototypes -fc-prototypes-external}
+
+@item Code Generation Options
+@xref{Code Gen Options,,Options for code generation conventions}.
+@gccoptlist{-faggressive-function-elimination -fblas-matmul-limit=@var{n} @gol
+-fbounds-check -ftail-call-workaround -ftail-call-workaround=@var{n} @gol
+-fcheck-array-temporaries @gol
+-fcheck=@var{<all|array-temps|bits|bounds|do|mem|pointer|recursion>} @gol
+-fcoarray=@var{<none|single|lib>} -fexternal-blas -ff2c @gol
+-ffrontend-loop-interchange -ffrontend-optimize @gol
+-finit-character=@var{n} -finit-integer=@var{n} -finit-local-zero @gol
+-finit-derived -finit-logical=@var{<true|false>} @gol
+-finit-real=@var{<zero|inf|-inf|nan|snan>}
+-finline-matmul-limit=@var{n} @gol
+-finline-arg-packing -fmax-array-constructor=@var{n} @gol
+-fmax-stack-var-size=@var{n} -fno-align-commons -fno-automatic @gol
+-fno-protect-parens -fno-underscoring -fsecond-underscore @gol
+-fpack-derived -frealloc-lhs -frecursive -frepack-arrays @gol
+-fshort-enums -fstack-arrays
+}
+@end table
+
+@node Fortran Dialect Options
+@section Options controlling Fortran dialect
+@cindex dialect options
+@cindex language, dialect options
+@cindex options, dialect
+
+The following options control the details of the Fortran dialect
+accepted by the compiler:
+
+@table @gcctabopt
+@item -ffree-form
+@itemx -ffixed-form
+@opindex @code{ffree-form}
+@opindex @code{ffixed-form}
+@cindex options, Fortran dialect
+@cindex file format, free
+@cindex file format, fixed
+Specify the layout used by the source file. The free form layout
+was introduced in Fortran 90. Fixed form was traditionally used in
+older Fortran programs. When neither option is specified, the source
+form is determined by the file extension.
+
+@item -fall-intrinsics
+@opindex @code{fall-intrinsics}
+This option causes all intrinsic procedures (including the GNU-specific
+extensions) to be accepted. This can be useful with @option{-std=} to
+force standard-compliance but get access to the full range of intrinsics
+available with @command{gfortran}. As a consequence, @option{-Wintrinsics-std}
+will be ignored and no user-defined procedure with the same name as any
+intrinsic will be called except when it is explicitly declared @code{EXTERNAL}.
+
+@item -fallow-argument-mismatch
+@opindex @code{fallow-argument-mismatch}
+Some code contains calls to external procedures with mismatches
+between the calls and the procedure definition, or with mismatches
+between different calls. Such code is non-conforming, and will usually
+be flagged with an error. This options degrades the error to a
+warning, which can only be disabled by disabling all warnings via
+@option{-w}. Only a single occurrence per argument is flagged by this
+warning. @option{-fallow-argument-mismatch} is implied by
+@option{-std=legacy}.
+
+Using this option is @emph{strongly} discouraged. It is possible to
+provide standard-conforming code which allows different types of
+arguments by using an explicit interface and @code{TYPE(*)}.
+
+@item -fallow-invalid-boz
+@opindex @code{allow-invalid-boz}
+A BOZ literal constant can occur in a limited number of contexts in
+standard conforming Fortran. This option degrades an error condition
+to a warning, and allows a BOZ literal constant to appear where the
+Fortran standard would otherwise prohibit its use.
+
+@item -fd-lines-as-code
+@itemx -fd-lines-as-comments
+@opindex @code{fd-lines-as-code}
+@opindex @code{fd-lines-as-comments}
+Enable special treatment for lines beginning with @code{d} or @code{D}
+in fixed form sources. If the @option{-fd-lines-as-code} option is
+given they are treated as if the first column contained a blank. If the
+@option{-fd-lines-as-comments} option is given, they are treated as
+comment lines.
+
+@item -fdec
+@opindex @code{fdec}
+DEC compatibility mode. Enables extensions and other features that mimic
+the default behavior of older compilers (such as DEC).
+These features are non-standard and should be avoided at all costs.
+For details on GNU Fortran's implementation of these extensions see the
+full documentation.
+
+Other flags enabled by this switch are:
+@option{-fdollar-ok} @option{-fcray-pointer} @option{-fdec-char-conversions}
+@option{-fdec-structure} @option{-fdec-intrinsic-ints} @option{-fdec-static}
+@option{-fdec-math} @option{-fdec-include} @option{-fdec-blank-format-item}
+@option{-fdec-format-defaults}
+
+If @option{-fd-lines-as-code}/@option{-fd-lines-as-comments} are unset, then
+@option{-fdec} also sets @option{-fd-lines-as-comments}.
+
+@item -fdec-char-conversions
+@opindex @code{fdec-char-conversions}
+Enable the use of character literals in assignments and @code{DATA} statements
+for non-character variables.
+
+@item -fdec-structure
+@opindex @code{fdec-structure}
+Enable DEC @code{STRUCTURE} and @code{RECORD} as well as @code{UNION},
+@code{MAP}, and dot ('.') as a member separator (in addition to '%'). This is
+provided for compatibility only; Fortran 90 derived types should be used
+instead where possible.
+
+@item -fdec-intrinsic-ints
+@opindex @code{fdec-intrinsic-ints}
+Enable B/I/J/K kind variants of existing integer functions (e.g. BIAND, IIAND,
+JIAND, etc...). For a complete list of intrinsics see the full documentation.
+
+@item -fdec-math
+@opindex @code{fdec-math}
+Enable legacy math intrinsics such as COTAN and degree-valued trigonometric
+functions (e.g. TAND, ATAND, etc...) for compatability with older code.
+
+@item -fdec-static
+@opindex @code{fdec-static}
+Enable DEC-style STATIC and AUTOMATIC attributes to explicitly specify
+the storage of variables and other objects.
+
+@item -fdec-include
+@opindex @code{fdec-include}
+Enable parsing of INCLUDE as a statement in addition to parsing it as
+INCLUDE line. When parsed as INCLUDE statement, INCLUDE does not have to
+be on a single line and can use line continuations.
+
+@item -fdec-format-defaults
+@opindex @code{fdec-format-defaults}
+Enable format specifiers F, G and I to be used without width specifiers,
+default widths will be used instead.
+
+@item -fdec-blank-format-item
+@opindex @code{fdec-blank-format-item}
+Enable a blank format item at the end of a format specification i.e. nothing
+following the final comma.
+
+@item -fdollar-ok
+@opindex @code{fdollar-ok}
+@cindex @code{$}
+@cindex symbol names
+@cindex character set
+Allow @samp{$} as a valid non-first character in a symbol name. Symbols
+that start with @samp{$} are rejected since it is unclear which rules to
+apply to implicit typing as different vendors implement different rules.
+Using @samp{$} in @code{IMPLICIT} statements is also rejected.
+
+@item -fbackslash
+@opindex @code{backslash}
+@cindex backslash
+@cindex escape characters
+Change the interpretation of backslashes in string literals from a single
+backslash character to ``C-style'' escape characters. The following
+combinations are expanded @code{\a}, @code{\b}, @code{\f}, @code{\n},
+@code{\r}, @code{\t}, @code{\v}, @code{\\}, and @code{\0} to the ASCII
+characters alert, backspace, form feed, newline, carriage return,
+horizontal tab, vertical tab, backslash, and NUL, respectively.
+Additionally, @code{\x}@var{nn}, @code{\u}@var{nnnn} and
+@code{\U}@var{nnnnnnnn} (where each @var{n} is a hexadecimal digit) are
+translated into the Unicode characters corresponding to the specified code
+points. All other combinations of a character preceded by \ are
+unexpanded.
+
+@item -fmodule-private
+@opindex @code{fmodule-private}
+@cindex module entities
+@cindex private
+Set the default accessibility of module entities to @code{PRIVATE}.
+Use-associated entities will not be accessible unless they are explicitly
+declared as @code{PUBLIC}.
+
+@item -ffixed-line-length-@var{n}
+@opindex @code{ffixed-line-length-}@var{n}
+@cindex file format, fixed
+Set column after which characters are ignored in typical fixed-form
+lines in the source file, and, unless @code{-fno-pad-source}, through which
+spaces are assumed (as if padded to that length) after the ends of short
+fixed-form lines.
+
+Popular values for @var{n} include 72 (the
+standard and the default), 80 (card image), and 132 (corresponding
+to ``extended-source'' options in some popular compilers).
+@var{n} may also be @samp{none}, meaning that the entire line is meaningful
+and that continued character constants never have implicit spaces appended
+to them to fill out the line.
+@option{-ffixed-line-length-0} means the same thing as
+@option{-ffixed-line-length-none}.
+
+@item -fno-pad-source
+@opindex @code{fpad-source}
+By default fixed-form lines have spaces assumed (as if padded to that length)
+after the ends of short fixed-form lines. This is not done either if
+@option{-ffixed-line-length-0}, @option{-ffixed-line-length-none} or
+if @option{-fno-pad-source} option is used. With any of those options
+continued character constants never have implicit spaces appended
+to them to fill out the line.
+
+@item -ffree-line-length-@var{n}
+@opindex @code{ffree-line-length-}@var{n}
+@cindex file format, free
+Set column after which characters are ignored in typical free-form
+lines in the source file. The default value is 132.
+@var{n} may be @samp{none}, meaning that the entire line is meaningful.
+@option{-ffree-line-length-0} means the same thing as
+@option{-ffree-line-length-none}.
+
+@item -fmax-identifier-length=@var{n}
+@opindex @code{fmax-identifier-length=}@var{n}
+Specify the maximum allowed identifier length. Typical values are
+31 (Fortran 95) and 63 (Fortran 2003 and later).
+
+@item -fimplicit-none
+@opindex @code{fimplicit-none}
+Specify that no implicit typing is allowed, unless overridden by explicit
+@code{IMPLICIT} statements. This is the equivalent of adding
+@code{implicit none} to the start of every procedure.
+
+@item -fcray-pointer
+@opindex @code{fcray-pointer}
+Enable the Cray pointer extension, which provides C-like pointer
+functionality.
+
+@item -fopenacc
+@opindex @code{fopenacc}
+@cindex OpenACC
+Enable the OpenACC extensions. This includes OpenACC @code{!$acc}
+directives in free form and @code{c$acc}, @code{*$acc} and
+@code{!$acc} directives in fixed form, @code{!$} conditional
+compilation sentinels in free form and @code{c$}, @code{*$} and
+@code{!$} sentinels in fixed form, and when linking arranges for the
+OpenACC runtime library to be linked in.
+
+@item -fopenmp
+@opindex @code{fopenmp}
+@cindex OpenMP
+Enable the OpenMP extensions. This includes OpenMP @code{!$omp} directives
+in free form
+and @code{c$omp}, @code{*$omp} and @code{!$omp} directives in fixed form,
+@code{!$} conditional compilation sentinels in free form
+and @code{c$}, @code{*$} and @code{!$} sentinels in fixed form,
+and when linking arranges for the OpenMP runtime library to be linked
+in. The option @option{-fopenmp} implies @option{-frecursive}.
+
+@item -fno-range-check
+@opindex @code{frange-check}
+Disable range checking on results of simplification of constant
+expressions during compilation. For example, GNU Fortran will give
+an error at compile time when simplifying @code{a = 1. / 0}.
+With this option, no error will be given and @code{a} will be assigned
+the value @code{+Infinity}. If an expression evaluates to a value
+outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}],
+then the expression will be replaced by @code{-Inf} or @code{+Inf}
+as appropriate.
+Similarly, @code{DATA i/Z'FFFFFFFF'/} will result in an integer overflow
+on most systems, but with @option{-fno-range-check} the value will
+``wrap around'' and @code{i} will be initialized to @math{-1} instead.
+
+@item -fdefault-integer-8
+@opindex @code{fdefault-integer-8}
+Set the default integer and logical types to an 8 byte wide type. This option
+also affects the kind of integer constants like @code{42}. Unlike
+@option{-finteger-4-integer-8}, it does not promote variables with explicit
+kind declaration.
+
+@item -fdefault-real-8
+@opindex @code{fdefault-real-8}
+Set the default real type to an 8 byte wide type. This option also affects
+the kind of non-double real constants like @code{1.0}. This option promotes
+the default width of @code{DOUBLE PRECISION} and double real constants
+like @code{1.d0} to 16 bytes if possible. If @code{-fdefault-double-8}
+is given along with @code{fdefault-real-8}, @code{DOUBLE PRECISION}
+and double real constants are not promoted. Unlike @option{-freal-4-real-8},
+@code{fdefault-real-8} does not promote variables with explicit kind
+declarations.
+
+@item -fdefault-real-10
+@opindex @code{fdefault-real-10}
+Set the default real type to an 10 byte wide type. This option also affects
+the kind of non-double real constants like @code{1.0}. This option promotes
+the default width of @code{DOUBLE PRECISION} and double real constants
+like @code{1.d0} to 16 bytes if possible. If @code{-fdefault-double-8}
+is given along with @code{fdefault-real-10}, @code{DOUBLE PRECISION}
+and double real constants are not promoted. Unlike @option{-freal-4-real-10},
+@code{fdefault-real-10} does not promote variables with explicit kind
+declarations.
+
+@item -fdefault-real-16
+@opindex @code{fdefault-real-16}
+Set the default real type to an 16 byte wide type. This option also affects
+the kind of non-double real constants like @code{1.0}. This option promotes
+the default width of @code{DOUBLE PRECISION} and double real constants
+like @code{1.d0} to 16 bytes if possible. If @code{-fdefault-double-8}
+is given along with @code{fdefault-real-16}, @code{DOUBLE PRECISION}
+and double real constants are not promoted. Unlike @option{-freal-4-real-16},
+@code{fdefault-real-16} does not promote variables with explicit kind
+declarations.
+
+@item -fdefault-double-8
+@opindex @code{fdefault-double-8}
+Set the @code{DOUBLE PRECISION} type and double real constants
+like @code{1.d0} to an 8 byte wide type. Do nothing if this
+is already the default. This option prevents @option{-fdefault-real-8},
+@option{-fdefault-real-10}, and @option{-fdefault-real-16},
+from promoting @code{DOUBLE PRECISION} and double real constants like
+@code{1.d0} to 16 bytes.
+
+@item -finteger-4-integer-8
+@opindex @code{finteger-4-integer-8}
+Promote all @code{INTEGER(KIND=4)} entities to an @code{INTEGER(KIND=8)}
+entities. If @code{KIND=8} is unavailable, then an error will be issued.
+This option should be used with care and may not be suitable for your codes.
+Areas of possible concern include calls to external procedures,
+alignment in @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
+BOZ literal constant conversion, and I/O. Inspection of the intermediate
+representation of the translated Fortran code, produced by
+@option{-fdump-tree-original}, is suggested.
+
+@item -freal-4-real-8
+@itemx -freal-4-real-10
+@itemx -freal-4-real-16
+@itemx -freal-8-real-4
+@itemx -freal-8-real-10
+@itemx -freal-8-real-16
+@opindex @code{freal-4-real-8}
+@opindex @code{freal-4-real-10}
+@opindex @code{freal-4-real-16}
+@opindex @code{freal-8-real-4}
+@opindex @code{freal-8-real-10}
+@opindex @code{freal-8-real-16}
+@cindex options, real kind type promotion
+Promote all @code{REAL(KIND=M)} entities to @code{REAL(KIND=N)} entities.
+If @code{REAL(KIND=N)} is unavailable, then an error will be issued.
+The @code{-freal-4-} flags also affect the default real kind and the
+@code{-freal-8-} flags also the double-precision real kind. All other
+real-kind types are unaffected by this option. The promotion is also
+applied to real literal constants of default and double-precision kind
+and a specified kind number of 4 or 8, respectively.
+However, @code{-fdefault-real-8}, @code{-fdefault-real-10},
+@code{-fdefault-real-10}, and @code{-fdefault-double-8} take precedence
+for the default and double-precision real kinds, both for real literal
+constants and for declarations without a kind number.
+Note that for @code{REAL(KIND=KIND(1.0))} the literal may get promoted and
+then the result may get promoted again.
+These options should be used with care and may not be suitable for your
+codes. Areas of possible concern include calls to external procedures,
+alignment in @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
+BOZ literal constant conversion, and I/O and calls to intrinsic procedures
+when passing a value to the @code{kind=} dummy argument. Inspection of the
+intermediate representation of the translated Fortran code, produced by
+@option{-fdump-fortran-original} or @option{-fdump-tree-original}, is suggested.
+
+@item -std=@var{std}
+@opindex @code{std=}@var{std} option
+Specify the standard to which the program is expected to conform,
+which may be one of @samp{f95}, @samp{f2003}, @samp{f2008},
+@samp{f2018}, @samp{gnu}, or @samp{legacy}. The default value for
+@var{std} is @samp{gnu}, which specifies a superset of the latest
+Fortran standard that includes all of the extensions supported by GNU
+Fortran, although warnings will be given for obsolete extensions not
+recommended for use in new code. The @samp{legacy} value is
+equivalent but without the warnings for obsolete extensions, and may
+be useful for old non-standard programs. The @samp{f95},
+@samp{f2003}, @samp{f2008}, and @samp{f2018} values specify strict
+conformance to the Fortran 95, Fortran 2003, Fortran 2008 and Fortran
+2018 standards, respectively; errors are given for all extensions
+beyond the relevant language standard, and warnings are given for the
+Fortran 77 features that are permitted but obsolescent in later
+standards. The deprecated option @samp{-std=f2008ts} acts as an alias for
+@samp{-std=f2018}. It is only present for backwards compatibility with
+earlier gfortran versions and should not be used any more.
+
+@item -ftest-forall-temp
+@opindex @code{ftest-forall-temp}
+Enhance test coverage by forcing most forall assignments to use temporary.
+
+@end table
+
+@node Preprocessing Options
+@section Enable and customize preprocessing
+@cindex preprocessor
+@cindex options, preprocessor
+@cindex CPP
+@cindex FPP
+@cindex Conditional compilation
+@cindex Preprocessing
+@cindex preprocessor, include file handling
+
+Many Fortran compilers including GNU Fortran allow passing the source code
+through a C preprocessor (CPP; sometimes also called the Fortran preprocessor,
+FPP) to allow for conditional compilation. In the case of GNU Fortran,
+this is the GNU C Preprocessor in the traditional mode. On systems with
+case-preserving file names, the preprocessor is automatically invoked if the
+filename extension is @file{.F}, @file{.FOR}, @file{.FTN}, @file{.fpp},
+@file{.FPP}, @file{.F90}, @file{.F95}, @file{.F03} or @file{.F08}. To manually
+invoke the preprocessor on any file, use @option{-cpp}, to disable
+preprocessing on files where the preprocessor is run automatically, use
+@option{-nocpp}.
+
+If a preprocessed file includes another file with the Fortran @code{INCLUDE}
+statement, the included file is not preprocessed. To preprocess included
+files, use the equivalent preprocessor statement @code{#include}.
+
+If GNU Fortran invokes the preprocessor, @code{__GFORTRAN__}
+is defined. The macros @code{__GNUC__}, @code{__GNUC_MINOR__} and
+@code{__GNUC_PATCHLEVEL__} can be used to determine the version of the
+compiler. See @ref{Top,,Overview,cpp,The C Preprocessor} for details.
+
+GNU Fortran supports a number of @code{INTEGER} and @code{REAL} kind types
+in additional to the kind types required by the Fortran standard.
+The availability of any given kind type is architecture dependent. The
+following pre-defined preprocessor macros can be used to conditionally
+include code for these additional kind types: @code{__GFC_INT_1__},
+@code{__GFC_INT_2__}, @code{__GFC_INT_8__}, @code{__GFC_INT_16__},
+@code{__GFC_REAL_10__}, and @code{__GFC_REAL_16__}.
+
+While CPP is the de-facto standard for preprocessing Fortran code,
+Part 3 of the Fortran 95 standard (ISO/IEC 1539-3:1998) defines
+Conditional Compilation, which is not widely used and not directly
+supported by the GNU Fortran compiler. You can use the program coco
+to preprocess such files (@uref{http://www.daniellnagle.com/coco.html}).
+
+The following options control preprocessing of Fortran code:
+
+@table @gcctabopt
+@item -cpp
+@itemx -nocpp
+@opindex @code{cpp}
+@opindex @code{fpp}
+@cindex preprocessor, enable
+@cindex preprocessor, disable
+Enable preprocessing. The preprocessor is automatically invoked if
+the file extension is @file{.fpp}, @file{.FPP}, @file{.F}, @file{.FOR},
+@file{.FTN}, @file{.F90}, @file{.F95}, @file{.F03} or @file{.F08}. Use
+this option to manually enable preprocessing of any kind of Fortran file.
+
+To disable preprocessing of files with any of the above listed extensions,
+use the negative form: @option{-nocpp}.
+
+The preprocessor is run in traditional mode. Any restrictions of the
+file-format, especially the limits on line length, apply for
+preprocessed output as well, so it might be advisable to use the
+@option{-ffree-line-length-none} or @option{-ffixed-line-length-none}
+options.
+
+@item -dM
+@opindex @code{dM}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Instead of the normal output, generate a list of @code{'#define'}
+directives for all the macros defined during the execution of the
+preprocessor, including predefined macros. This gives you a way
+of finding out what is predefined in your version of the preprocessor.
+Assuming you have no file @file{foo.f90}, the command
+@smallexample
+ touch foo.f90; gfortran -cpp -E -dM foo.f90
+@end smallexample
+will show all the predefined macros.
+
+@item -dD
+@opindex @code{dD}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Like @option{-dM} except in two respects: it does not include the
+predefined macros, and it outputs both the @code{#define} directives
+and the result of preprocessing. Both kinds of output go to the
+standard output file.
+
+@item -dN
+@opindex @code{dN}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Like @option{-dD}, but emit only the macro names, not their expansions.
+
+@item -dU
+@opindex @code{dU}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Like @option{dD} except that only macros that are expanded, or whose
+definedness is tested in preprocessor directives, are output; the
+output is delayed until the use or test of the macro; and @code{'#undef'}
+directives are also output for macros tested but undefined at the time.
+
+@item -dI
+@opindex @code{dI}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Output @code{'#include'} directives in addition to the result
+of preprocessing.
+
+@item -fworking-directory
+@opindex @code{fworking-directory}
+@cindex preprocessor, working directory
+Enable generation of linemarkers in the preprocessor output that will
+let the compiler know the current working directory at the time of
+preprocessing. When this option is enabled, the preprocessor will emit,
+after the initial linemarker, a second linemarker with the current
+working directory followed by two slashes. GCC will use this directory,
+when it is present in the preprocessed input, as the directory emitted
+as the current working directory in some debugging information formats.
+This option is implicitly enabled if debugging information is enabled,
+but this can be inhibited with the negated form
+@option{-fno-working-directory}. If the @option{-P} flag is present
+in the command line, this option has no effect, since no @code{#line}
+directives are emitted whatsoever.
+
+@item -idirafter @var{dir}
+@opindex @code{idirafter @var{dir}}
+@cindex preprocessing, include path
+Search @var{dir} for include files, but do it after all directories
+specified with @option{-I} and the standard system directories have
+been exhausted. @var{dir} is treated as a system include directory.
+If dir begins with @code{=}, then the @code{=} will be replaced by
+the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
+
+@item -imultilib @var{dir}
+@opindex @code{imultilib @var{dir}}
+@cindex preprocessing, include path
+Use @var{dir} as a subdirectory of the directory containing target-specific
+C++ headers.
+
+@item -iprefix @var{prefix}
+@opindex @code{iprefix @var{prefix}}
+@cindex preprocessing, include path
+Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix}
+options. If the @var{prefix} represents a directory, you should include
+the final @code{'/'}.
+
+@item -isysroot @var{dir}
+@opindex @code{isysroot @var{dir}}
+@cindex preprocessing, include path
+This option is like the @option{--sysroot} option, but applies only to
+header files. See the @option{--sysroot} option for more information.
+
+@item -iquote @var{dir}
+@opindex @code{iquote @var{dir}}
+@cindex preprocessing, include path
+Search @var{dir} only for header files requested with @code{#include "file"};
+they are not searched for @code{#include <file>}, before all directories
+specified by @option{-I} and before the standard system directories. If
+@var{dir} begins with @code{=}, then the @code{=} will be replaced by the
+sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
+
+@item -isystem @var{dir}
+@opindex @code{isystem @var{dir}}
+@cindex preprocessing, include path
+Search @var{dir} for header files, after all directories specified by
+@option{-I} but before the standard system directories. Mark it as a
+system directory, so that it gets the same special treatment as is
+applied to the standard system directories. If @var{dir} begins with
+@code{=}, then the @code{=} will be replaced by the sysroot prefix;
+see @option{--sysroot} and @option{-isysroot}.
+
+@item -nostdinc
+@opindex @code{nostdinc}
+Do not search the standard system directories for header files. Only
+the directories you have specified with @option{-I} options (and the
+directory of the current file, if appropriate) are searched.
+
+@item -undef
+@opindex @code{undef}
+Do not predefine any system-specific or GCC-specific macros.
+The standard predefined macros remain defined.
+
+@item -A@var{predicate}=@var{answer}
+@opindex @code{A@var{predicate}=@var{answer}}
+@cindex preprocessing, assertion
+Make an assertion with the predicate @var{predicate} and answer @var{answer}.
+This form is preferred to the older form -A predicate(answer), which is still
+supported, because it does not use shell special characters.
+
+@item -A-@var{predicate}=@var{answer}
+@opindex @code{A-@var{predicate}=@var{answer}}
+@cindex preprocessing, assertion
+Cancel an assertion with the predicate @var{predicate} and answer @var{answer}.
+
+@item -C
+@opindex @code{C}
+@cindex preprocessing, keep comments
+Do not discard comments. All comments are passed through to the output
+file, except for comments in processed directives, which are deleted
+along with the directive.
+
+You should be prepared for side effects when using @option{-C}; it causes
+the preprocessor to treat comments as tokens in their own right. For example,
+comments appearing at the start of what would be a directive line have the
+effect of turning that line into an ordinary source line, since the first
+token on the line is no longer a @code{'#'}.
+
+Warning: this currently handles C-Style comments only. The preprocessor
+does not yet recognize Fortran-style comments.
+
+@item -CC
+@opindex @code{CC}
+@cindex preprocessing, keep comments
+Do not discard comments, including during macro expansion. This is like
+@option{-C}, except that comments contained within macros are also passed
+through to the output file where the macro is expanded.
+
+In addition to the side-effects of the @option{-C} option, the @option{-CC}
+option causes all C++-style comments inside a macro to be converted to C-style
+comments. This is to prevent later use of that macro from inadvertently
+commenting out the remainder of the source line. The @option{-CC} option
+is generally used to support lint comments.
+
+Warning: this currently handles C- and C++-Style comments only. The
+preprocessor does not yet recognize Fortran-style comments.
+
+@item -D@var{name}
+@opindex @code{D@var{name}}
+@cindex preprocessing, define macros
+Predefine name as a macro, with definition @code{1}.
+
+@item -D@var{name}=@var{definition}
+@opindex @code{D@var{name}=@var{definition}}
+@cindex preprocessing, define macros
+The contents of @var{definition} are tokenized and processed as if they
+appeared during translation phase three in a @code{'#define'} directive.
+In particular, the definition will be truncated by embedded newline
+characters.
+
+If you are invoking the preprocessor from a shell or shell-like program
+you may need to use the shell's quoting syntax to protect characters such
+as spaces that have a meaning in the shell syntax.
+
+If you wish to define a function-like macro on the command line, write
+its argument list with surrounding parentheses before the equals sign
+(if any). Parentheses are meaningful to most shells, so you will need
+to quote the option. With sh and csh, @code{-D'name(args...)=definition'}
+works.
+
+@option{-D} and @option{-U} options are processed in the order they are
+given on the command line. All -imacros file and -include file options
+are processed after all -D and -U options.
+
+@item -H
+@opindex @code{H}
+Print the name of each header file used, in addition to other normal
+activities. Each name is indented to show how deep in the @code{'#include'}
+stack it is.
+
+@item -P
+@opindex @code{P}
+@cindex preprocessing, no linemarkers
+Inhibit generation of linemarkers in the output from the preprocessor.
+This might be useful when running the preprocessor on something that
+is not C code, and will be sent to a program which might be confused
+by the linemarkers.
+
+@item -U@var{name}
+@opindex @code{U@var{name}}
+@cindex preprocessing, undefine macros
+Cancel any previous definition of @var{name}, either built in or provided
+with a @option{-D} option.
+@end table
+
+
+@node Error and Warning Options
+@section Options to request or suppress errors and warnings
+@cindex options, warnings
+@cindex options, errors
+@cindex warnings, suppressing
+@cindex messages, error
+@cindex messages, warning
+@cindex suppressing warnings
+
+Errors are diagnostic messages that report that the GNU Fortran compiler
+cannot compile the relevant piece of source code. The compiler will
+continue to process the program in an attempt to report further errors
+to aid in debugging, but will not produce any compiled output.
+
+Warnings are diagnostic messages that report constructions which
+are not inherently erroneous but which are risky or suggest there is
+likely to be a bug in the program. Unless @option{-Werror} is specified,
+they do not prevent compilation of the program.
+
+You can request many specific warnings with options beginning @option{-W},
+for example @option{-Wimplicit} to request warnings on implicit
+declarations. Each of these specific warning options also has a
+negative form beginning @option{-Wno-} to turn off warnings;
+for example, @option{-Wno-implicit}. This manual lists only one of the
+two forms, whichever is not the default.
+
+These options control the amount and kinds of errors and warnings produced
+by GNU Fortran:
+
+@table @gcctabopt
+@item -fmax-errors=@var{n}
+@opindex @code{fmax-errors=}@var{n}
+@cindex errors, limiting
+Limits the maximum number of error messages to @var{n}, at which point
+GNU Fortran bails out rather than attempting to continue processing the
+source code. If @var{n} is 0, there is no limit on the number of error
+messages produced.
+
+@item -fsyntax-only
+@opindex @code{fsyntax-only}
+@cindex syntax checking
+Check the code for syntax errors, but do not actually compile it. This
+will generate module files for each module present in the code, but no
+other output file.
+
+@item -Wpedantic
+@itemx -pedantic
+@opindex @code{pedantic}
+@opindex @code{Wpedantic}
+Issue warnings for uses of extensions to Fortran.
+@option{-pedantic} also applies to C-language constructs where they
+occur in GNU Fortran source files, such as use of @samp{\e} in a
+character constant within a directive like @code{#include}.
+
+Valid Fortran programs should compile properly with or without
+this option.
+However, without this option, certain GNU extensions and traditional
+Fortran features are supported as well.
+With this option, many of them are rejected.
+
+Some users try to use @option{-pedantic} to check programs for conformance.
+They soon find that it does not do quite what they want---it finds some
+nonstandard practices, but not all.
+However, improvements to GNU Fortran in this area are welcome.
+
+This should be used in conjunction with @option{-std=f95},
+@option{-std=f2003}, @option{-std=f2008} or @option{-std=f2018}.
+
+@item -pedantic-errors
+@opindex @code{pedantic-errors}
+Like @option{-pedantic}, except that errors are produced rather than
+warnings.
+
+@item -Wall
+@opindex @code{Wall}
+@cindex all warnings
+@cindex warnings, all
+Enables commonly used warning options pertaining to usage that
+we recommend avoiding and that we believe are easy to avoid.
+This currently includes @option{-Waliasing}, @option{-Wampersand},
+@option{-Wconversion}, @option{-Wsurprising}, @option{-Wc-binding-type},
+@option{-Wintrinsics-std}, @option{-Wtabs}, @option{-Wintrinsic-shadow},
+@option{-Wline-truncation}, @option{-Wtarget-lifetime},
+@option{-Winteger-division}, @option{-Wreal-q-constant}, @option{-Wunused}
+and @option{-Wundefined-do-loop}.
+
+@item -Waliasing
+@opindex @code{Waliasing}
+@cindex aliasing
+@cindex warnings, aliasing
+Warn about possible aliasing of dummy arguments. Specifically, it warns
+if the same actual argument is associated with a dummy argument with
+@code{INTENT(IN)} and a dummy argument with @code{INTENT(OUT)} in a call
+with an explicit interface.
+
+The following example will trigger the warning.
+@smallexample
+ interface
+ subroutine bar(a,b)
+ integer, intent(in) :: a
+ integer, intent(out) :: b
+ end subroutine
+ end interface
+ integer :: a
+
+ call bar(a,a)
+@end smallexample
+
+@item -Wampersand
+@opindex @code{Wampersand}
+@cindex warnings, ampersand
+@cindex @code{&}
+Warn about missing ampersand in continued character constants. The
+warning is given with @option{-Wampersand}, @option{-pedantic},
+@option{-std=f95}, @option{-std=f2003}, @option{-std=f2008} and
+@option{-std=f2018}. Note: With no ampersand given in a continued
+character constant, GNU Fortran assumes continuation at the first
+non-comment, non-whitespace character after the ampersand that
+initiated the continuation.
+
+@item -Warray-temporaries
+@opindex @code{Warray-temporaries}
+@cindex warnings, array temporaries
+Warn about array temporaries generated by the compiler. The information
+generated by this warning is sometimes useful in optimization, in order to
+avoid such temporaries.
+
+@item -Wc-binding-type
+@opindex @code{Wc-binding-type}
+@cindex warning, C binding type
+Warn if the a variable might not be C interoperable. In particular, warn if
+the variable has been declared using an intrinsic type with default kind
+instead of using a kind parameter defined for C interoperability in the
+intrinsic @code{ISO_C_Binding} module. This option is implied by
+@option{-Wall}.
+
+@item -Wcharacter-truncation
+@opindex @code{Wcharacter-truncation}
+@cindex warnings, character truncation
+Warn when a character assignment will truncate the assigned string.
+
+@item -Wline-truncation
+@opindex @code{Wline-truncation}
+@cindex warnings, line truncation
+Warn when a source code line will be truncated. This option is
+implied by @option{-Wall}. For free-form source code, the default is
+@option{-Werror=line-truncation} such that truncations are reported as
+error.
+
+@item -Wconversion
+@opindex @code{Wconversion}
+@cindex warnings, conversion
+@cindex conversion
+Warn about implicit conversions that are likely to change the value of
+the expression after conversion. Implied by @option{-Wall}.
+
+@item -Wconversion-extra
+@opindex @code{Wconversion-extra}
+@cindex warnings, conversion
+@cindex conversion
+Warn about implicit conversions between different types and kinds. This
+option does @emph{not} imply @option{-Wconversion}.
+
+@item -Wextra
+@opindex @code{Wextra}
+@cindex extra warnings
+@cindex warnings, extra
+Enables some warning options for usages of language features which
+may be problematic. This currently includes @option{-Wcompare-reals},
+@option{-Wunused-parameter} and @option{-Wdo-subscript}.
+
+@item -Wfrontend-loop-interchange
+@opindex @code{Wfrontend-loop-interchange}
+@cindex warnings, loop interchange
+@cindex loop interchange, warning
+Warn when using @option{-ffrontend-loop-interchange} for performing loop
+interchanges.
+
+@item -Wimplicit-interface
+@opindex @code{Wimplicit-interface}
+@cindex warnings, implicit interface
+Warn if a procedure is called without an explicit interface.
+Note this only checks that an explicit interface is present. It does not
+check that the declared interfaces are consistent across program units.
+
+@item -Wimplicit-procedure
+@opindex @code{Wimplicit-procedure}
+@cindex warnings, implicit procedure
+Warn if a procedure is called that has neither an explicit interface
+nor has been declared as @code{EXTERNAL}.
+
+@item -Winteger-division
+@opindex @code{Winteger-division}
+@cindex warnings, integer division
+@cindex warnings, division of integers
+Warn if a constant integer division truncates its result.
+As an example, 3/5 evaluates to 0.
+
+@item -Wintrinsics-std
+@opindex @code{Wintrinsics-std}
+@cindex warnings, non-standard intrinsics
+@cindex warnings, intrinsics of other standards
+Warn if @command{gfortran} finds a procedure named like an intrinsic not
+available in the currently selected standard (with @option{-std}) and treats
+it as @code{EXTERNAL} procedure because of this. @option{-fall-intrinsics} can
+be used to never trigger this behavior and always link to the intrinsic
+regardless of the selected standard.
+
+@item -Wno-overwrite-recursive
+@opindex @code{Woverwrite-recursive}
+@cindex warnings, overwrite recursive
+Do not warn when @option{-fno-automatic} is used with @option{-frecursive}. Recursion
+will be broken if the relevant local variables do not have the attribute
+@code{AUTOMATIC} explicitly declared. This option can be used to suppress the warning
+when it is known that recursion is not broken. Useful for build environments that use
+@option{-Werror}.
+
+@item -Wreal-q-constant
+@opindex @code{Wreal-q-constant}
+@cindex warnings, @code{q} exponent-letter
+Produce a warning if a real-literal-constant contains a @code{q}
+exponent-letter.
+
+@item -Wsurprising
+@opindex @code{Wsurprising}
+@cindex warnings, suspicious code
+Produce a warning when ``suspicious'' code constructs are encountered.
+While technically legal these usually indicate that an error has been made.
+
+This currently produces a warning under the following circumstances:
+
+@itemize @bullet
+@item
+An INTEGER SELECT construct has a CASE that can never be matched as its
+lower value is greater than its upper value.
+
+@item
+A LOGICAL SELECT construct has three CASE statements.
+
+@item
+A TRANSFER specifies a source that is shorter than the destination.
+
+@item
+The type of a function result is declared more than once with the same type. If
+@option{-pedantic} or standard-conforming mode is enabled, this is an error.
+
+@item
+A @code{CHARACTER} variable is declared with negative length.
+
+@item
+With @option{-fopenmp}, for fixed-form source code, when an @code{omx}
+vendor-extension sentinel is encountered. (The equivalent @code{ompx},
+used in free-form source code, is diagnosed by default.)
+@end itemize
+
+@item -Wtabs
+@opindex @code{Wtabs}
+@cindex warnings, tabs
+@cindex tabulators
+By default, tabs are accepted as whitespace, but tabs are not members
+of the Fortran Character Set. For continuation lines, a tab followed
+by a digit between 1 and 9 is supported. @option{-Wtabs} will cause a
+warning to be issued if a tab is encountered. Note, @option{-Wtabs} is
+active for @option{-pedantic}, @option{-std=f95}, @option{-std=f2003},
+@option{-std=f2008}, @option{-std=f2018} and
+@option{-Wall}.
+
+@item -Wundefined-do-loop
+@opindex @code{Wundefined-do-loop}
+@cindex warnings, undefined do loop
+Warn if a DO loop with step either 1 or -1 yields an underflow or an overflow
+during iteration of an induction variable of the loop.
+This option is implied by @option{-Wall}.
+
+@item -Wunderflow
+@opindex @code{Wunderflow}
+@cindex warnings, underflow
+@cindex underflow
+Produce a warning when numerical constant expressions are
+encountered, which yield an UNDERFLOW during compilation. Enabled by default.
+
+@item -Wintrinsic-shadow
+@opindex @code{Wintrinsic-shadow}
+@cindex warnings, intrinsic
+@cindex intrinsic
+Warn if a user-defined procedure or module procedure has the same name as an
+intrinsic; in this case, an explicit interface or @code{EXTERNAL} or
+@code{INTRINSIC} declaration might be needed to get calls later resolved to
+the desired intrinsic/procedure. This option is implied by @option{-Wall}.
+
+@item -Wuse-without-only
+@opindex @code{Wuse-without-only}
+@cindex warnings, use statements
+@cindex intrinsic
+Warn if a @code{USE} statement has no @code{ONLY} qualifier and
+thus implicitly imports all public entities of the used module.
+
+@item -Wunused-dummy-argument
+@opindex @code{Wunused-dummy-argument}
+@cindex warnings, unused dummy argument
+@cindex unused dummy argument
+@cindex dummy argument, unused
+Warn about unused dummy arguments. This option is implied by @option{-Wall}.
+
+@item -Wunused-parameter
+@opindex @code{Wunused-parameter}
+@cindex warnings, unused parameter
+@cindex unused parameter
+Contrary to @command{gcc}'s meaning of @option{-Wunused-parameter},
+@command{gfortran}'s implementation of this option does not warn
+about unused dummy arguments (see @option{-Wunused-dummy-argument}),
+but about unused @code{PARAMETER} values. @option{-Wunused-parameter}
+is implied by @option{-Wextra} if also @option{-Wunused} or
+@option{-Wall} is used.
+
+@item -Walign-commons
+@opindex @code{Walign-commons}
+@cindex warnings, alignment of @code{COMMON} blocks
+@cindex alignment of @code{COMMON} blocks
+By default, @command{gfortran} warns about any occasion of variables being
+padded for proper alignment inside a @code{COMMON} block. This warning can be turned
+off via @option{-Wno-align-commons}. See also @option{-falign-commons}.
+
+@item -Wfunction-elimination
+@opindex @code{Wfunction-elimination}
+@cindex function elimination
+@cindex warnings, function elimination
+Warn if any calls to impure functions are eliminated by the optimizations
+enabled by the @option{-ffrontend-optimize} option.
+This option is implied by @option{-Wextra}.
+
+@item -Wrealloc-lhs
+@opindex @code{Wrealloc-lhs}
+@cindex Reallocate the LHS in assignments, notification
+Warn when the compiler might insert code to for allocation or reallocation of
+an allocatable array variable of intrinsic type in intrinsic assignments. In
+hot loops, the Fortran 2003 reallocation feature may reduce the performance.
+If the array is already allocated with the correct shape, consider using a
+whole-array array-spec (e.g. @code{(:,:,:)}) for the variable on the left-hand
+side to prevent the reallocation check. Note that in some cases the warning
+is shown, even if the compiler will optimize reallocation checks away. For
+instance, when the right-hand side contains the same variable multiplied by
+a scalar. See also @option{-frealloc-lhs}.
+
+@item -Wrealloc-lhs-all
+@opindex @code{Wrealloc-lhs-all}
+Warn when the compiler inserts code to for allocation or reallocation of an
+allocatable variable; this includes scalars and derived types.
+
+@item -Wcompare-reals
+@opindex @code{Wcompare-reals}
+Warn when comparing real or complex types for equality or inequality.
+This option is implied by @option{-Wextra}.
+
+@item -Wtarget-lifetime
+@opindex @code{Wtargt-lifetime}
+Warn if the pointer in a pointer assignment might be longer than the its
+target. This option is implied by @option{-Wall}.
+
+@item -Wzerotrip
+@opindex @code{Wzerotrip}
+Warn if a @code{DO} loop is known to execute zero times at compile
+time. This option is implied by @option{-Wall}.
+
+@item -Wdo-subscript
+@opindex @code{Wdo-subscript}
+Warn if an array subscript inside a DO loop could lead to an
+out-of-bounds access even if the compiler cannot prove that the
+statement is actually executed, in cases like
+@smallexample
+ real a(3)
+ do i=1,4
+ if (condition(i)) then
+ a(i) = 1.2
+ end if
+ end do
+@end smallexample
+This option is implied by @option{-Wextra}.
+
+@item -Werror
+@opindex @code{Werror}
+@cindex warnings, to errors
+Turns all warnings into errors.
+@end table
+
+@xref{Warning Options,,Options to Request or Suppress Errors and
+Warnings, gcc,Using the GNU Compiler Collection (GCC)}, for information on
+more options offered by the GBE shared by @command{gfortran}, @command{gcc}
+and other GNU compilers.
+
+Some of these have no effect when compiling programs written in Fortran.
+
+@node Debugging Options
+@section Options for debugging your program or GNU Fortran
+@cindex options, debugging
+@cindex debugging information options
+
+GNU Fortran has various special options that are used for debugging
+either your program or the GNU Fortran compiler.
+
+@table @gcctabopt
+@item -fdump-fortran-original
+@opindex @code{fdump-fortran-original}
+Output the internal parse tree after translating the source program
+into internal representation. This option is mostly useful for
+debugging the GNU Fortran compiler itself. The output generated by
+this option might change between releases. This option may also
+generate internal compiler errors for features which have only
+recently been added.
+
+@item -fdump-fortran-optimized
+@opindex @code{fdump-fortran-optimized}
+Output the parse tree after front-end optimization. Mostly useful for
+debugging the GNU Fortran compiler itself. The output generated by
+this option might change between releases. This option may also
+generate internal compiler errors for features which have only
+recently been added.
+
+@item -fdump-parse-tree
+@opindex @code{fdump-parse-tree}
+Output the internal parse tree after translating the source program
+into internal representation. Mostly useful for debugging the GNU
+Fortran compiler itself. The output generated by this option might
+change between releases. This option may also generate internal
+compiler errors for features which have only recently been added. This
+option is deprecated; use @code{-fdump-fortran-original} instead.
+
+@item -fdebug-aux-vars
+@opindex @code{fdebug-aux-vars}
+Renames internal variables created by the gfortran front end and makes
+them accessible to a debugger. The name of the internal variables then
+start with upper-case letters followed by an underscore. This option is
+useful for debugging the compiler's code generation together with
+@code{-fdump-tree-original} and enabling debugging of the executable
+program by using @code{-g} or @code{-ggdb3}.
+
+@item -fdump-fortran-global
+@opindex @code{fdump-fortran-global}
+Output a list of the global identifiers after translating into
+middle-end representation. Mostly useful for debugging the GNU Fortran
+compiler itself. The output generated by this option might change
+between releases. This option may also generate internal compiler
+errors for features which have only recently been added.
+
+@item -ffpe-trap=@var{list}
+@opindex @code{ffpe-trap=}@var{list}
+Specify a list of floating point exception traps to enable. On most
+systems, if a floating point exception occurs and the trap for that
+exception is enabled, a SIGFPE signal will be sent and the program
+being aborted, producing a core file useful for debugging. @var{list}
+is a (possibly empty) comma-separated list of the following
+exceptions: @samp{invalid} (invalid floating point operation, such as
+@code{SQRT(-1.0)}), @samp{zero} (division by zero), @samp{overflow}
+(overflow in a floating point operation), @samp{underflow} (underflow
+in a floating point operation), @samp{inexact} (loss of precision
+during operation), and @samp{denormal} (operation performed on a
+denormal value). The first five exceptions correspond to the five
+IEEE 754 exceptions, whereas the last one (@samp{denormal}) is not
+part of the IEEE 754 standard but is available on some common
+architectures such as x86.
+
+The first three exceptions (@samp{invalid}, @samp{zero}, and
+@samp{overflow}) often indicate serious errors, and unless the program
+has provisions for dealing with these exceptions, enabling traps for
+these three exceptions is probably a good idea.
+
+If the option is used more than once in the command line, the lists will
+be joined: '@code{ffpe-trap=}@var{list1} @code{ffpe-trap=}@var{list2}'
+is equivalent to @code{ffpe-trap=}@var{list1},@var{list2}.
+
+Note that once enabled an exception cannot be disabled (no negative form).
+
+Many, if not most, floating point operations incur loss of precision
+due to rounding, and hence the @code{ffpe-trap=inexact} is likely to
+be uninteresting in practice.
+
+By default no exception traps are enabled.
+
+@item -ffpe-summary=@var{list}
+@opindex @code{ffpe-summary=}@var{list}
+Specify a list of floating-point exceptions, whose flag status is printed
+to @code{ERROR_UNIT} when invoking @code{STOP} and @code{ERROR STOP}.
+@var{list} can be either @samp{none}, @samp{all} or a comma-separated list
+of the following exceptions: @samp{invalid}, @samp{zero}, @samp{overflow},
+@samp{underflow}, @samp{inexact} and @samp{denormal}. (See
+@option{-ffpe-trap} for a description of the exceptions.)
+
+If the option is used more than once in the command line, only the
+last one will be used.
+
+By default, a summary for all exceptions but @samp{inexact} is shown.
+
+@item -fno-backtrace
+@opindex @code{fno-backtrace}
+@cindex backtrace
+@cindex trace
+When a serious runtime error is encountered or a deadly signal is
+emitted (segmentation fault, illegal instruction, bus error,
+floating-point exception, and the other POSIX signals that have the
+action @samp{core}), the Fortran runtime library tries to output a
+backtrace of the error. @code{-fno-backtrace} disables the backtrace
+generation. This option only has influence for compilation of the
+Fortran main program.
+
+@end table
+
+@xref{Debugging Options,,Options for Debugging Your Program or GCC,
+gcc,Using the GNU Compiler Collection (GCC)}, for more information on
+debugging options.
+
+@node Directory Options
+@section Options for directory search
+@cindex directory, options
+@cindex options, directory search
+@cindex search path
+@cindex @code{INCLUDE} directive
+@cindex directive, @code{INCLUDE}
+These options affect how GNU Fortran searches
+for files specified by the @code{INCLUDE} directive and where it searches
+for previously compiled modules.
+
+It also affects the search paths used by @command{cpp} when used to preprocess
+Fortran source.
+
+@table @gcctabopt
+@item -I@var{dir}
+@opindex @code{I}@var{dir}
+@cindex directory, search paths for inclusion
+@cindex inclusion, directory search paths for
+@cindex search paths, for included files
+@cindex paths, search
+@cindex module search path
+These affect interpretation of the @code{INCLUDE} directive
+(as well as of the @code{#include} directive of the @command{cpp}
+preprocessor).
+
+Also note that the general behavior of @option{-I} and
+@code{INCLUDE} is pretty much the same as of @option{-I} with
+@code{#include} in the @command{cpp} preprocessor, with regard to
+looking for @file{header.gcc} files and other such things.
+
+This path is also used to search for @file{.mod} files when previously
+compiled modules are required by a @code{USE} statement.
+
+@xref{Directory Options,,Options for Directory Search,
+gcc,Using the GNU Compiler Collection (GCC)}, for information on the
+@option{-I} option.
+
+@item -J@var{dir}
+@opindex @code{J}@var{dir}
+@opindex @code{M}@var{dir}
+@cindex paths, search
+@cindex module search path
+This option specifies where to put @file{.mod} files for compiled modules.
+It is also added to the list of directories to searched by an @code{USE}
+statement.
+
+The default is the current directory.
+
+@item -fintrinsic-modules-path @var{dir}
+@opindex @code{fintrinsic-modules-path} @var{dir}
+@cindex paths, search
+@cindex module search path
+This option specifies the location of pre-compiled intrinsic modules, if
+they are not in the default location expected by the compiler.
+@end table
+
+@node Link Options
+@section Influencing the linking step
+@cindex options, linking
+@cindex linking, static
+
+These options come into play when the compiler links object files into an
+executable output file. They are meaningless if the compiler is not doing
+a link step.
+
+@table @gcctabopt
+@item -static-libgfortran
+@opindex @code{static-libgfortran}
+On systems that provide @file{libgfortran} as a shared and a static
+library, this option forces the use of the static version. If no
+shared version of @file{libgfortran} was built when the compiler was
+configured, this option has no effect.
+@end table
+
+
+@table @gcctabopt
+@item -static-libquadmath
+@opindex @code{static-libquadmath}
+On systems that provide @file{libquadmath} as a shared and a static
+library, this option forces the use of the static version. If no
+shared version of @file{libquadmath} was built when the compiler was
+configured, this option has no effect.
+
+Please note that the @file{libquadmath} runtime library is licensed under the
+GNU Lesser General Public License (LGPL), and linking it statically introduces
+requirements when redistributing the resulting binaries.
+@end table
+
+
+@node Runtime Options
+@section Influencing runtime behavior
+@cindex options, runtime
+
+These options affect the runtime behavior of programs compiled with GNU Fortran.
+
+@table @gcctabopt
+@item -fconvert=@var{conversion}
+@opindex @code{fconvert=}@var{conversion}
+Specify the representation of data for unformatted files. Valid
+values for conversion on most systems are: @samp{native}, the default;
+@samp{swap}, swap between big- and little-endian; @samp{big-endian}, use
+big-endian representation for unformatted files; @samp{little-endian}, use
+little-endian representation for unformatted files.
+
+On POWER systems which suppport @option{-mabi=ieeelongdouble},
+there are additional options, which can be combined with others with
+commas. Those are
+@itemize @w{}
+@item @option{-fconvert=r16_ieee} Use IEEE 128-bit format for
+@code{REAL(KIND=16)}.
+@item @option{-fconvert=r16_ibm} Use IBM long double format for
+@code{REAL(KIND=16)}.
+@end itemize
+
+@emph{This option has an effect only when used in the main program.
+The @code{CONVERT} specifier and the GFORTRAN_CONVERT_UNIT environment
+variable override the default specified by @option{-fconvert}.}
+
+@item -frecord-marker=@var{length}
+@opindex @code{frecord-marker=}@var{length}
+Specify the length of record markers for unformatted files.
+Valid values for @var{length} are 4 and 8. Default is 4.
+@emph{This is different from previous versions of @command{gfortran}},
+which specified a default record marker length of 8 on most
+systems. If you want to read or write files compatible
+with earlier versions of @command{gfortran}, use @option{-frecord-marker=8}.
+
+@item -fmax-subrecord-length=@var{length}
+@opindex @code{fmax-subrecord-length=}@var{length}
+Specify the maximum length for a subrecord. The maximum permitted
+value for length is 2147483639, which is also the default. Only
+really useful for use by the gfortran testsuite.
+
+@item -fsign-zero
+@opindex @code{fsign-zero}
+When enabled, floating point numbers of value zero with the sign bit set
+are written as negative number in formatted output and treated as
+negative in the @code{SIGN} intrinsic. @option{-fno-sign-zero} does not
+print the negative sign of zero values (or values rounded to zero for I/O)
+and regards zero as positive number in the @code{SIGN} intrinsic for
+compatibility with Fortran 77. The default is @option{-fsign-zero}.
+@end table
+
+@node Code Gen Options
+@section Options for code generation conventions
+@cindex code generation, conventions
+@cindex options, code generation
+@cindex options, run-time
+
+These machine-independent options control the interface conventions
+used in code generation.
+
+Most of them have both positive and negative forms; the negative form
+of @option{-ffoo} would be @option{-fno-foo}. In the table below, only
+one of the forms is listed---the one which is not the default. You
+can figure out the other form by either removing @option{no-} or adding
+it.
+
+@table @gcctabopt
+@item -fno-automatic
+@opindex @code{fno-automatic}
+@cindex @code{SAVE} statement
+@cindex statement, @code{SAVE}
+Treat each program unit (except those marked as RECURSIVE) as if the
+@code{SAVE} statement were specified for every local variable and array
+referenced in it. Does not affect common blocks. (Some Fortran compilers
+provide this option under the name @option{-static} or @option{-save}.)
+The default, which is @option{-fautomatic}, uses the stack for local
+variables smaller than the value given by @option{-fmax-stack-var-size}.
+Use the option @option{-frecursive} to use no static memory.
+
+Local variables or arrays having an explicit @code{SAVE} attribute are
+silently ignored unless the @option{-pedantic} option is added.
+
+@item -ff2c
+@opindex ff2c
+@cindex calling convention
+@cindex @command{f2c} calling convention
+@cindex @command{g77} calling convention
+@cindex libf2c calling convention
+Generate code designed to be compatible with code generated
+by @command{g77} and @command{f2c}.
+
+The calling conventions used by @command{g77} (originally implemented
+in @command{f2c}) require functions that return type
+default @code{REAL} to actually return the C type @code{double}, and
+functions that return type @code{COMPLEX} to return the values via an
+extra argument in the calling sequence that points to where to
+store the return value. Under the default GNU calling conventions, such
+functions simply return their results as they would in GNU
+C---default @code{REAL} functions return the C type @code{float}, and
+@code{COMPLEX} functions return the GNU C type @code{complex}.
+Additionally, this option implies the @option{-fsecond-underscore}
+option, unless @option{-fno-second-underscore} is explicitly requested.
+
+This does not affect the generation of code that interfaces with
+the @command{libgfortran} library.
+
+@emph{Caution:} It is not a good idea to mix Fortran code compiled with
+@option{-ff2c} with code compiled with the default @option{-fno-f2c}
+calling conventions as, calling @code{COMPLEX} or default @code{REAL}
+functions between program parts which were compiled with different
+calling conventions will break at execution time.
+
+@emph{Caution:} This will break code which passes intrinsic functions
+of type default @code{REAL} or @code{COMPLEX} as actual arguments, as
+the library implementations use the @option{-fno-f2c} calling conventions.
+
+@item -fno-underscoring
+@opindex @code{fno-underscoring}
+@cindex underscore
+@cindex symbol names, underscores
+@cindex transforming symbol names
+@cindex symbol names, transforming
+Do not transform names of entities specified in the Fortran
+source file by appending underscores to them.
+
+With @option{-funderscoring} in effect, GNU Fortran appends one
+underscore to external names with no underscores. This is done to ensure
+compatibility with code produced by many UNIX Fortran compilers.
+
+@emph{Caution}: The default behavior of GNU Fortran is
+incompatible with @command{f2c} and @command{g77}, please use the
+@option{-ff2c} option if you want object files compiled with
+GNU Fortran to be compatible with object code created with these
+tools.
+
+Use of @option{-fno-underscoring} is not recommended unless you are
+experimenting with issues such as integration of GNU Fortran into
+existing system environments (vis-@`{a}-vis existing libraries, tools,
+and so on).
+
+For example, with @option{-funderscoring}, and assuming that @code{j()} and
+@code{max_count()} are external functions while @code{my_var} and
+@code{lvar} are local variables, a statement like
+@smallexample
+I = J() + MAX_COUNT (MY_VAR, LVAR)
+@end smallexample
+@noindent
+is implemented as something akin to:
+@smallexample
+i = j_() + max_count__(&my_var__, &lvar);
+@end smallexample
+
+With @option{-fno-underscoring}, the same statement is implemented as:
+
+@smallexample
+i = j() + max_count(&my_var, &lvar);
+@end smallexample
+
+Use of @option{-fno-underscoring} allows direct specification of
+user-defined names while debugging and when interfacing GNU Fortran
+code with other languages.
+
+Note that just because the names match does @emph{not} mean that the
+interface implemented by GNU Fortran for an external name matches the
+interface implemented by some other language for that same name.
+That is, getting code produced by GNU Fortran to link to code produced
+by some other compiler using this or any other method can be only a
+small part of the overall solution---getting the code generated by
+both compilers to agree on issues other than naming can require
+significant effort, and, unlike naming disagreements, linkers normally
+cannot detect disagreements in these other areas.
+
+Also, note that with @option{-fno-underscoring}, the lack of appended
+underscores introduces the very real possibility that a user-defined
+external name will conflict with a name in a system library, which
+could make finding unresolved-reference bugs quite difficult in some
+cases---they might occur at program run time, and show up only as
+buggy behavior at run time.
+
+In future versions of GNU Fortran we hope to improve naming and linking
+issues so that debugging always involves using the names as they appear
+in the source, even if the names as seen by the linker are mangled to
+prevent accidental linking between procedures with incompatible
+interfaces.
+
+@item -fsecond-underscore
+@opindex @code{fsecond-underscore}
+@cindex underscore
+@cindex symbol names, underscores
+@cindex transforming symbol names
+@cindex symbol names, transforming
+@cindex @command{f2c} calling convention
+@cindex @command{g77} calling convention
+@cindex libf2c calling convention
+By default, GNU Fortran appends an underscore to external
+names. If this option is used GNU Fortran appends two
+underscores to names with underscores and one underscore to external names
+with no underscores. GNU Fortran also appends two underscores to
+internal names with underscores to avoid naming collisions with external
+names.
+
+This option has no effect if @option{-fno-underscoring} is
+in effect. It is implied by the @option{-ff2c} option.
+
+Otherwise, with this option, an external name such as @code{MAX_COUNT}
+is implemented as a reference to the link-time external symbol
+@code{max_count__}, instead of @code{max_count_}. This is required
+for compatibility with @command{g77} and @command{f2c}, and is implied
+by use of the @option{-ff2c} option.
+
+@item -fcoarray=@var{<keyword>}
+@opindex @code{fcoarray}
+@cindex coarrays
+
+@table @asis
+@item @samp{none}
+Disable coarray support; using coarray declarations and image-control
+statements will produce a compile-time error. (Default)
+
+@item @samp{single}
+Single-image mode, i.e. @code{num_images()} is always one.
+
+@item @samp{lib}
+Library-based coarray parallelization; a suitable GNU Fortran coarray
+library needs to be linked.
+@end table
+
+
+@item -fcheck=@var{<keyword>}
+@opindex @code{fcheck}
+@cindex array, bounds checking
+@cindex bit intrinsics checking
+@cindex bounds checking
+@cindex pointer checking
+@cindex memory checking
+@cindex range checking
+@cindex subscript checking
+@cindex checking subscripts
+@cindex run-time checking
+@cindex checking array temporaries
+
+Enable the generation of run-time checks; the argument shall be
+a comma-delimited list of the following keywords. Prefixing a check with
+@option{no-} disables it if it was activated by a previous specification.
+
+@table @asis
+@item @samp{all}
+Enable all run-time test of @option{-fcheck}.
+
+@item @samp{array-temps}
+Warns at run time when for passing an actual argument a temporary array
+had to be generated. The information generated by this warning is
+sometimes useful in optimization, in order to avoid such temporaries.
+
+Note: The warning is only printed once per location.
+
+@item @samp{bits}
+Enable generation of run-time checks for invalid arguments to the bit
+manipulation intrinsics.
+
+@item @samp{bounds}
+Enable generation of run-time checks for array subscripts
+and against the declared minimum and maximum values. It also
+checks array indices for assumed and deferred
+shape arrays against the actual allocated bounds and ensures that all string
+lengths are equal for character array constructors without an explicit
+typespec.
+
+Some checks require that @option{-fcheck=bounds} is set for
+the compilation of the main program.
+
+Note: In the future this may also include other forms of checking, e.g.,
+checking substring references.
+
+@item @samp{do}
+Enable generation of run-time checks for invalid modification of loop
+iteration variables.
+
+@item @samp{mem}
+Enable generation of run-time checks for memory allocation.
+Note: This option does not affect explicit allocations using the
+@code{ALLOCATE} statement, which will be always checked.
+
+@item @samp{pointer}
+Enable generation of run-time checks for pointers and allocatables.
+
+@item @samp{recursion}
+Enable generation of run-time checks for recursively called subroutines and
+functions which are not marked as recursive. See also @option{-frecursive}.
+Note: This check does not work for OpenMP programs and is disabled if used
+together with @option{-frecursive} and @option{-fopenmp}.
+@end table
+
+Example: Assuming you have a file @file{foo.f90}, the command
+@smallexample
+ gfortran -fcheck=all,no-array-temps foo.f90
+@end smallexample
+will compile the file with all checks enabled as specified above except
+warnings for generated array temporaries.
+
+
+@item -fbounds-check
+@opindex @code{fbounds-check}
+@c Note: This option is also referred in gcc's manpage
+Deprecated alias for @option{-fcheck=bounds}.
+
+@item -ftail-call-workaround
+@itemx -ftail-call-workaround=@var{n}
+@opindex @code{tail-call-workaround}
+Some C interfaces to Fortran codes violate the gfortran ABI by
+omitting the hidden character length arguments as described in
+@xref{Argument passing conventions}. This can lead to crashes
+because pushing arguments for tail calls can overflow the stack.
+
+To provide a workaround for existing binary packages, this option
+disables tail call optimization for gfortran procedures with character
+arguments. With @option{-ftail-call-workaround=2} tail call optimization
+is disabled in all gfortran procedures with character arguments,
+with @option{-ftail-call-workaround=1} or equivalent
+@option{-ftail-call-workaround} only in gfortran procedures with character
+arguments that call implicitly prototyped procedures.
+
+Using this option can lead to problems including crashes due to
+insufficient stack space.
+
+It is @emph{very strongly} recommended to fix the code in question.
+The @option{-fc-prototypes-external} option can be used to generate
+prototypes which conform to gfortran's ABI, for inclusion in the
+source code.
+
+Support for this option will likely be withdrawn in a future release
+of gfortran.
+
+The negative form, @option{-fno-tail-call-workaround} or equivalent
+@option{-ftail-call-workaround=0}, can be used to disable this option.
+
+Default is currently @option{-ftail-call-workaround}, this will change
+in future releases.
+
+@item -fcheck-array-temporaries
+@opindex @code{fcheck-array-temporaries}
+Deprecated alias for @option{-fcheck=array-temps}.
+
+@item -fmax-array-constructor=@var{n}
+@opindex @code{fmax-array-constructor}
+This option can be used to increase the upper limit permitted in
+array constructors. The code below requires this option to expand
+the array at compile time.
+
+@smallexample
+program test
+implicit none
+integer j
+integer, parameter :: n = 100000
+integer, parameter :: i(n) = (/ (2*j, j = 1, n) /)
+print '(10(I0,1X))', i
+end program test
+@end smallexample
+
+@emph{Caution: This option can lead to long compile times and excessively
+large object files.}
+
+The default value for @var{n} is 65535.
+
+
+@item -fmax-stack-var-size=@var{n}
+@opindex @code{fmax-stack-var-size}
+This option specifies the size in bytes of the largest array that will be put
+on the stack; if the size is exceeded static memory is used (except in
+procedures marked as RECURSIVE). Use the option @option{-frecursive} to
+allow for recursive procedures which do not have a RECURSIVE attribute or
+for parallel programs. Use @option{-fno-automatic} to never use the stack.
+
+This option currently only affects local arrays declared with constant
+bounds, and may not apply to all character variables.
+Future versions of GNU Fortran may improve this behavior.
+
+The default value for @var{n} is 65536.
+
+@item -fstack-arrays
+@opindex @code{fstack-arrays}
+Adding this option will make the Fortran compiler put all arrays of
+unknown size and array temporaries onto stack memory. If your program uses very
+large local arrays it is possible that you will have to extend your runtime
+limits for stack memory on some operating systems. This flag is enabled
+by default at optimization level @option{-Ofast} unless
+@option{-fmax-stack-var-size} is specified.
+
+@item -fpack-derived
+@opindex @code{fpack-derived}
+@cindex structure packing
+This option tells GNU Fortran to pack derived type members as closely as
+possible. Code compiled with this option is likely to be incompatible
+with code compiled without this option, and may execute slower.
+
+@item -frepack-arrays
+@opindex @code{frepack-arrays}
+@cindex repacking arrays
+In some circumstances GNU Fortran may pass assumed shape array
+sections via a descriptor describing a noncontiguous area of memory.
+This option adds code to the function prologue to repack the data into
+a contiguous block at runtime.
+
+This should result in faster accesses to the array. However it can introduce
+significant overhead to the function call, especially when the passed data
+is noncontiguous.
+
+@item -fshort-enums
+@opindex @code{fshort-enums}
+This option is provided for interoperability with C code that was
+compiled with the @option{-fshort-enums} option. It will make
+GNU Fortran choose the smallest @code{INTEGER} kind a given
+enumerator set will fit in, and give all its enumerators this kind.
+
+@item -finline-arg-packing
+@opindex @code{finline-arg-packing}
+When passing an assumed-shape argument of a procedure as actual
+argument to an assumed-size or explicit size or as argument to a
+procedure that does not have an explicit interface, the argument may
+have to be packed, that is put into contiguous memory. An example is
+the call to @code{foo} in
+@smallexample
+ subroutine foo(a)
+ real, dimension(*) :: a
+ end subroutine foo
+ subroutine bar(b)
+ real, dimension(:) :: b
+ call foo(b)
+ end subroutine bar
+@end smallexample
+
+When @option{-finline-arg-packing} is in effect, this packing will be
+performed by inline code. This allows for more optimization while
+increasing code size.
+
+@option{-finline-arg-packing} is implied by any of the @option{-O} options
+except when optimizing for size via @option{-Os}. If the code
+contains a very large number of argument that have to be packed, code
+size and also compilation time may become excessive. If that is the
+case, it may be better to disable this option. Instances of packing
+can be found by using @option{-Warray-temporaries}.
+
+@item -fexternal-blas
+@opindex @code{fexternal-blas}
+This option will make @command{gfortran} generate calls to BLAS functions
+for some matrix operations like @code{MATMUL}, instead of using our own
+algorithms, if the size of the matrices involved is larger than a given
+limit (see @option{-fblas-matmul-limit}). This may be profitable if an
+optimized vendor BLAS library is available. The BLAS library will have
+to be specified at link time.
+
+@item -fblas-matmul-limit=@var{n}
+@opindex @code{fblas-matmul-limit}
+Only significant when @option{-fexternal-blas} is in effect.
+Matrix multiplication of matrices with size larger than (or equal to) @var{n}
+will be performed by calls to BLAS functions, while others will be
+handled by @command{gfortran} internal algorithms. If the matrices
+involved are not square, the size comparison is performed using the
+geometric mean of the dimensions of the argument and result matrices.
+
+The default value for @var{n} is 30.
+
+@item -finline-matmul-limit=@var{n}
+@opindex @code{finline-matmul-limit}
+When front-end optimization is active, some calls to the @code{MATMUL}
+intrinsic function will be inlined. This may result in code size
+increase if the size of the matrix cannot be determined at compile
+time, as code for both cases is generated. Setting
+@code{-finline-matmul-limit=0} will disable inlining in all cases.
+Setting this option with a value of @var{n} will produce inline code
+for matrices with size up to @var{n}. If the matrices involved are not
+square, the size comparison is performed using the geometric mean of
+the dimensions of the argument and result matrices.
+
+The default value for @var{n} is 30. The @code{-fblas-matmul-limit}
+can be used to change this value.
+
+@item -frecursive
+@opindex @code{frecursive}
+Allow indirect recursion by forcing all local arrays to be allocated
+on the stack. This flag cannot be used together with
+@option{-fmax-stack-var-size=} or @option{-fno-automatic}.
+
+@item -finit-local-zero
+@itemx -finit-derived
+@itemx -finit-integer=@var{n}
+@itemx -finit-real=@var{<zero|inf|-inf|nan|snan>}
+@itemx -finit-logical=@var{<true|false>}
+@itemx -finit-character=@var{n}
+@opindex @code{finit-local-zero}
+@opindex @code{finit-derived}
+@opindex @code{finit-integer}
+@opindex @code{finit-real}
+@opindex @code{finit-logical}
+@opindex @code{finit-character}
+The @option{-finit-local-zero} option instructs the compiler to
+initialize local @code{INTEGER}, @code{REAL}, and @code{COMPLEX}
+variables to zero, @code{LOGICAL} variables to false, and
+@code{CHARACTER} variables to a string of null bytes. Finer-grained
+initialization options are provided by the
+@option{-finit-integer=@var{n}},
+@option{-finit-real=@var{<zero|inf|-inf|nan|snan>}} (which also initializes
+the real and imaginary parts of local @code{COMPLEX} variables),
+@option{-finit-logical=@var{<true|false>}}, and
+@option{-finit-character=@var{n}} (where @var{n} is an ASCII character
+value) options.
+
+With @option{-finit-derived}, components of derived type variables will be
+initialized according to these flags. Components whose type is not covered by
+an explicit @option{-finit-*} flag will be treated as described above with
+@option{-finit-local-zero}.
+
+These options do not initialize
+@itemize @bullet
+@item
+objects with the POINTER attribute
+@item
+allocatable arrays
+@item
+variables that appear in an @code{EQUIVALENCE} statement.
+@end itemize
+(These limitations may be removed in future releases).
+
+Note that the @option{-finit-real=nan} option initializes @code{REAL}
+and @code{COMPLEX} variables with a quiet NaN. For a signalling NaN
+use @option{-finit-real=snan}; note, however, that compile-time
+optimizations may convert them into quiet NaN and that trapping
+needs to be enabled (e.g. via @option{-ffpe-trap}).
+
+The @option{-finit-integer} option will parse the value into an
+integer of type @code{INTEGER(kind=C_LONG)} on the host. Said value
+is then assigned to the integer variables in the Fortran code, which
+might result in wraparound if the value is too large for the kind.
+
+Finally, note that enabling any of the @option{-finit-*} options will
+silence warnings that would have been emitted by @option{-Wuninitialized}
+for the affected local variables.
+
+@item -falign-commons
+@opindex @code{falign-commons}
+@cindex alignment of @code{COMMON} blocks
+By default, @command{gfortran} enforces proper alignment of all variables in a
+@code{COMMON} block by padding them as needed. On certain platforms this is mandatory,
+on others it increases performance. If a @code{COMMON} block is not declared with
+consistent data types everywhere, this padding can cause trouble, and
+@option{-fno-align-commons} can be used to disable automatic alignment. The
+same form of this option should be used for all files that share a @code{COMMON} block.
+To avoid potential alignment issues in @code{COMMON} blocks, it is recommended to order
+objects from largest to smallest.
+
+@item -fno-protect-parens
+@opindex @code{fno-protect-parens}
+@cindex re-association of parenthesized expressions
+By default the parentheses in expression are honored for all optimization
+levels such that the compiler does not do any re-association. Using
+@option{-fno-protect-parens} allows the compiler to reorder @code{REAL} and
+@code{COMPLEX} expressions to produce faster code. Note that for the re-association
+optimization @option{-fno-signed-zeros} and @option{-fno-trapping-math}
+need to be in effect. The parentheses protection is enabled by default, unless
+@option{-Ofast} is given.
+
+@item -frealloc-lhs
+@opindex @code{frealloc-lhs}
+@cindex Reallocate the LHS in assignments
+An allocatable left-hand side of an intrinsic assignment is automatically
+(re)allocated if it is either unallocated or has a different shape. The
+option is enabled by default except when @option{-std=f95} is given. See
+also @option{-Wrealloc-lhs}.
+
+@item -faggressive-function-elimination
+@opindex @code{faggressive-function-elimination}
+@cindex Elimination of functions with identical argument lists
+Functions with identical argument lists are eliminated within
+statements, regardless of whether these functions are marked
+@code{PURE} or not. For example, in
+@smallexample
+ a = f(b,c) + f(b,c)
+@end smallexample
+there will only be a single call to @code{f}. This option only works
+if @option{-ffrontend-optimize} is in effect.
+
+@item -ffrontend-optimize
+@opindex @code{frontend-optimize}
+@cindex Front-end optimization
+This option performs front-end optimization, based on manipulating
+parts the Fortran parse tree. Enabled by default by any @option{-O} option
+except @option{-O0} and @option{-Og}. Optimizations enabled by this option
+include:
+@itemize @bullet
+@item inlining calls to @code{MATMUL},
+@item elimination of identical function calls within expressions,
+@item removing unnecessary calls to @code{TRIM} in comparisons and assignments,
+@item replacing @code{TRIM(a)} with @code{a(1:LEN_TRIM(a))} and
+@item short-circuiting of logical operators (@code{.AND.} and @code{.OR.}).
+@end itemize
+It can be deselected by specifying @option{-fno-frontend-optimize}.
+
+@item -ffrontend-loop-interchange
+@opindex @code{frontend-loop-interchange}
+@cindex loop interchange, Fortran
+Attempt to interchange loops in the Fortran front end where
+profitable. Enabled by default by any @option{-O} option.
+At the moment, this option only affects @code{FORALL} and
+@code{DO CONCURRENT} statements with several forall triplets.
+@end table
+
+@xref{Code Gen Options,,Options for Code Generation Conventions,
+gcc,Using the GNU Compiler Collection (GCC)}, for information on more options
+offered by the GBE
+shared by @command{gfortran}, @command{gcc}, and other GNU compilers.
+
+@c man end
+
+@node Interoperability Options
+@section Options for interoperability with other languages
+
+@table @asis
+
+@item -fc-prototypes
+@opindex @code{c-prototypes}
+@cindex Generating C prototypes from Fortran BIND(C) enteties
+This option will generate C prototypes from @code{BIND(C)} variable
+declarations, types and procedure interfaces and writes them to
+standard output. @code{ENUM} is not yet supported.
+
+The generated prototypes may need inclusion of an appropriate header,
+such as @code{<stdint.h>} or @code{<stdlib.h>}. For types which are
+not specified using the appropriate kind from the @code{iso_c_binding}
+module, a warning is added as a comment to the code.
+
+For function pointers, a pointer to a function returning @code{int}
+without an explicit argument list is generated.
+
+Example of use:
+@smallexample
+$ gfortran -fc-prototypes -fsyntax-only foo.f90 > foo.h
+@end smallexample
+where the C code intended for interoperating with the Fortran code
+then uses @code{#include "foo.h"}.
+
+@item -fc-prototypes-external
+@opindex @code{c-prototypes-external}
+@cindex Generating C prototypes from external procedures
+This option will generate C prototypes from external functions and
+subroutines and write them to standard output. This may be useful for
+making sure that C bindings to Fortran code are correct. This option
+does not generate prototypes for @code{BIND(C)} procedures, use
+@option{-fc-prototypes} for that.
+
+The generated prototypes may need inclusion of an appropriate
+header, such as @code{<stdint.h>} or @code{<stdlib.h>}.
+
+This is primarily meant for legacy code to ensure that existing C
+bindings match what @command{gfortran} emits. The generated C
+prototypes should be correct for the current version of the compiler,
+but may not match what other compilers or earlier versions of
+@command{gfortran} need. For new developments, use of the
+@code{BIND(C)} features is recommended.
+
+Example of use:
+@smallexample
+$ gfortran -fc-prototypes-external -fsyntax-only foo.f > foo.h
+@end smallexample
+where the C code intended for interoperating with the Fortran code
+then uses @code{#include "foo.h"}.
+@end table
+
+@node Environment Variables
+@section Environment variables affecting @command{gfortran}
+@cindex environment variable
+
+@c man begin ENVIRONMENT
+
+The @command{gfortran} compiler currently does not make use of any environment
+variables to control its operation above and beyond those
+that affect the operation of @command{gcc}.
+
+@xref{Environment Variables,,Environment Variables Affecting GCC,
+gcc,Using the GNU Compiler Collection (GCC)}, for information on environment
+variables.
+
+@xref{Runtime}, for environment variables that affect the
+run-time behavior of programs compiled with GNU Fortran.
+@c man end
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@setfilename gccgo.info
+@settitle The GNU Go Compiler
+
+@c Merge the standard indexes into a single one.
+@syncodeindex fn cp
+@syncodeindex vr cp
+@syncodeindex ky cp
+@syncodeindex pg cp
+@syncodeindex tp cp
+
+@include gcc-common.texi
+
+@c Copyright years for this manual.
+@set copyrights-go 2010-2022
+
+@copying
+@c man begin COPYRIGHT
+Copyright @copyright{} @value{copyrights-go} Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, the Front-Cover Texts being (a) (see below), and
+with the Back-Cover Texts being (b) (see below).
+A copy of the license is included in the
+@c man end
+section entitled ``GNU Free Documentation License''.
+@ignore
+@c man begin COPYRIGHT
+man page gfdl(7).
+@c man end
+@end ignore
+
+@c man begin COPYRIGHT
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@end copying
+
+@ifinfo
+@format
+@dircategory Software development
+@direntry
+* Gccgo: (gccgo). A GCC-based compiler for the Go language
+@end direntry
+@end format
+
+@insertcopying
+@end ifinfo
+
+@titlepage
+@title The GNU Go Compiler
+@versionsubtitle
+@author Ian Lance Taylor
+
+@page
+@vskip 0pt plus 1filll
+Published by the Free Software Foundation @*
+51 Franklin Street, Fifth Floor@*
+Boston, MA 02110-1301, USA@*
+@sp 1
+@insertcopying
+@end titlepage
+@contents
+@page
+
+@node Top
+@top Introduction
+
+This manual describes how to use @command{gccgo}, the GNU compiler for
+the Go programming language. This manual is specifically about
+@command{gccgo}. For more information about the Go programming
+language in general, including language specifications and standard
+package documentation, see @uref{https://golang.org/}.
+
+@menu
+* Copying:: The GNU General Public License.
+* GNU Free Documentation License::
+ How you can share and copy this manual.
+* Invoking gccgo:: How to run gccgo.
+* Import and Export:: Importing and exporting package data.
+* Compiler Directives:: Comments to control compilation.
+* C Interoperability:: Calling C from Go and vice-versa.
+* Index:: Index.
+@end menu
+
+
+@include gpl_v3.texi
+
+@include fdl.texi
+
+
+@node Invoking gccgo
+@chapter Invoking gccgo
+
+@c man title gccgo A GCC-based compiler for the Go language
+
+@ignore
+@c man begin SYNOPSIS gccgo
+gccgo [@option{-c}|@option{-S}]
+ [@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
+ [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
+ [@option{-o} @var{outfile}] @var{infile}@dots{}
+
+Only the most useful options are listed here; see below for the
+remainder.
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7), gcc(1)
+and the Info entries for @file{gccgo} and @file{gcc}.
+@c man end
+@end ignore
+
+@c man begin DESCRIPTION gccgo
+
+The @command{gccgo} command is a frontend to @command{gcc} and
+supports many of the same options. @xref{Option Summary, , Option
+Summary, gcc, Using the GNU Compiler Collection (GCC)}. This manual
+only documents the options specific to @command{gccgo}.
+
+The @command{gccgo} command may be used to compile Go source code into
+an object file, link a collection of object files together, or do both
+in sequence.
+
+Go source code is compiled as packages. A package consists of one or
+more Go source files. All the files in a single package must be
+compiled together, by passing all the files as arguments to
+@command{gccgo}. A single invocation of @command{gccgo} may only
+compile a single package.
+
+One Go package may @code{import} a different Go package. The imported
+package must have already been compiled; @command{gccgo} will read
+the import data directly from the compiled package. When this package
+is later linked, the compiled form of the package must be included in
+the link command.
+
+Go programs must generally be compiled with debugging information, and
+@option{-g1} is the default as described below. Stripping a Go
+program will generally cause it to misbehave or fail.
+
+@c man end
+
+@c man begin OPTIONS gccgo
+
+@table @gcctabopt
+@item -I@var{dir}
+@cindex @option{-I}
+Specify a directory to use when searching for an import package at
+compile time.
+
+@item -L@var{dir}
+@cindex @option{-L}
+When linking, specify a library search directory, as with
+@command{gcc}.
+
+@item -fgo-pkgpath=@var{string}
+@cindex @option{-fgo-pkgpath}
+Set the package path to use. This sets the value returned by the
+PkgPath method of reflect.Type objects. It is also used for the names
+of globally visible symbols. The argument to this option should
+normally be the string that will be used to import this package after
+it has been installed; in other words, a pathname within the
+directories specified by the @option{-I} option.
+
+@item -fgo-prefix=@var{string}
+@cindex @option{-fgo-prefix}
+An alternative to @option{-fgo-pkgpath}. The argument will be
+combined with the package name from the source file to produce the
+package path. If @option{-fgo-pkgpath} is used, @option{-fgo-prefix}
+will be ignored.
+
+Go permits a single program to include more than one package with the
+same name in the @code{package} clause in the source file, though
+obviously the two packages must be imported using different pathnames.
+In order for this to work with @command{gccgo}, either
+@option{-fgo-pkgpath} or @option{-fgo-prefix} must be specified when
+compiling a package.
+
+Using either @option{-fgo-pkgpath} or @option{-fgo-prefix} disables
+the special treatment of the @code{main} package and permits that
+package to be imported like any other.
+
+@item -fgo-relative-import-path=@var{dir}
+@cindex @option{-fgo-relative-import-path}
+A relative import is an import that starts with @file{./} or
+@file{../}. If this option is used, @command{gccgo} will use
+@var{dir} as a prefix for the relative import when searching for it.
+
+@item -frequire-return-statement
+@itemx -fno-require-return-statement
+@cindex @option{-frequire-return-statement}
+@cindex @option{-fno-require-return-statement}
+By default @command{gccgo} will warn about functions which have one or
+more return parameters but lack an explicit @code{return} statement.
+This warning may be disabled using
+@option{-fno-require-return-statement}.
+
+@item -fgo-check-divide-zero
+@cindex @option{-fgo-check-divide-zero}
+@cindex @option{-fno-go-check-divide-zero}
+Add explicit checks for division by zero. In Go a division (or
+modulos) by zero causes a panic. On Unix systems this is detected in
+the runtime by catching the @code{SIGFPE} signal. Some processors,
+such as PowerPC, do not generate a SIGFPE on division by zero. Some
+runtimes do not generate a signal that can be caught. On those
+systems, this option may be used. Or the checks may be removed via
+@option{-fno-go-check-divide-zero}. This option is currently on by
+default, but in the future may be off by default on systems that do
+not require it.
+
+@item -fgo-check-divide-overflow
+@cindex @option{-fgo-check-divide-overflow}
+@cindex @option{-fno-go-check-divide-overflow}
+Add explicit checks for division overflow. For example, division
+overflow occurs when computing @code{INT_MIN / -1}. In Go this should
+be wrapped, to produce @code{INT_MIN}. Some processors, such as x86,
+generate a trap on division overflow. On those systems, this option
+may be used. Or the checks may be removed via
+@option{-fno-go-check-divide-overflow}. This option is currently on
+by default, but in the future may be off by default on systems that do
+not require it.
+
+@item -fno-go-optimize-allocs
+@cindex @option{-fno-go-optimize-allocs}
+Disable escape analysis, which tries to allocate objects on the stack
+rather than the heap.
+
+@item -fgo-debug-escape@var{n}
+@cindex @option{-fgo-debug-escape}
+Output escape analysis debugging information. Larger values of
+@var{n} generate more information.
+
+@item -fgo-debug-escape-hash=@var{n}
+@cindex @option{-fgo-debug-escape-hash}
+A hash value to debug escape analysis. @var{n} is a binary string.
+This runs escape analysis only on functions whose names hash to values
+that match the given suffix @var{n}. This can be used to binary
+search across functions to uncover escape analysis bugs.
+
+@item -fgo-debug-optimization
+@cindex @option{-fgo-debug-optimization}
+@cindex @option{-fno-go-debug-optimization}
+Output optimization diagnostics.
+
+@item -fgo-c-header=@var{file}
+@cindex @option{-fgo-c-header}
+Write top-level named Go struct definitions to @var{file} as C code.
+This is used when compiling the runtime package.
+
+@item -fgo-compiling-runtime
+@cindex @option{-fgo-compiling-runtime}
+Apply special rules for compiling the runtime package. Implicit
+memory allocation is forbidden. Some additional compiler directives
+are supported.
+
+@item -fgo-embedcfg=@var{file}
+@cindex @option{-fgo-embedcfg}
+Identify a JSON file used to map patterns used with special
+@code{//go:embed} comments to the files named by the patterns. The
+JSON file should have two components: @code{Patterns} maps each
+pattern to a list of file names, and @code{Files} maps each file name
+to a full path to the file. This option is intended for use by the
+@command{go} command to implement @code{//go:embed}.
+
+@item -g
+@cindex @option{-g for gccgo}
+This is the standard @command{gcc} option (@pxref{Debugging Options, ,
+Debugging Options, gcc, Using the GNU Compiler Collection (GCC)}). It
+is mentioned here because by default @command{gccgo} turns on
+debugging information generation with the equivalent of the standard
+option @option{-g1}. This is because Go programs require debugging
+information to be available in order to get backtrace information. An
+explicit @option{-g0} may be used to disable the generation of
+debugging information, in which case certain standard library
+functions, such as @code{runtime.Callers}, will not operate correctly.
+@end table
+
+@c man end
+
+@node Import and Export
+@chapter Import and Export
+
+When @command{gccgo} compiles a package which exports anything, the
+export information will be stored directly in the object file. When a
+package is imported, @command{gccgo} must be able to find the file.
+
+@cindex @file{.gox}
+When Go code imports the package @file{@var{gopackage}}, @command{gccgo}
+will look for the import data using the following filenames, using the
+first one that it finds.
+
+@table @file
+@item @var{gopackage}.gox
+@item lib@var{gopackage}.so
+@item lib@var{gopackage}.a
+@item @var{gopackage}.o
+@end table
+
+The compiler will search for these files in the directories named by
+any @option{-I} options, in order in which the directories appear on
+the command line. The compiler will then search several standard
+system directories. Finally the compiler will search the current
+directory (to search the current directory earlier, use @samp{-I.}).
+
+The compiler will extract the export information directly from the
+compiled object file. The file @file{@var{gopackage}.gox} will
+typically contain nothing but export data. This can be generated from
+@file{@var{gopackage}.o} via
+
+@smallexample
+objcopy -j .go_export @var{gopackage}.o @var{gopackage}.gox
+@end smallexample
+
+For example, it may be desirable to extract the export information
+from several different packages into their independent
+@file{@var{gopackage}.gox} files, and then to combine the different
+package object files together into a single shared library or archive.
+
+At link time you must explicitly tell @command{gccgo} which files to
+link together into the executable, as is usual with @command{gcc}.
+This is different from the behavior of other Go compilers.
+
+@node Compiler Directives
+@chapter Compiler Directives
+
+The Go compiler supports a few compiler directives. A compiler
+directive uses a @code{//} comment at the start of a line. There must
+be no space between the @code{//} and the name of the directive.
+
+@table @code
+@item //line @var{file}:@var{line}
+The @code{//line} directive specifies that the source line that
+follows should be recorded as having come from the given file path and
+line number. Successive lines are recorded using increasing line
+numbers, until the next directive. This directive typically appears
+in machine-generated code, so that compilers and debuggers will show
+lines in the original input to the generator.
+
+@item //extern @var{extern_name}
+The @code{extern} directive sets the externally visible name of the
+next function declaration. See @ref{Function Names}.
+
+@item //go:compile @var{go_name} @var{extern_name}
+The @code{go:compile} directives sets the externally visible name of a
+function definition or declaration. See @ref{Function Names}.
+
+@item //go:noescape
+The @code{//go:noescape} directive specifies that the next declaration
+in the file, which must be a func without a body (meaning that it has
+an implementation not written in Go) does not allow any of the
+pointers passed as arguments to escape into the heap or into the
+values returned from the function. This information can be used during
+the compiler's escape analysis of Go code calling the function.
+
+@item //go:nosplit
+The @code{//go:nosplit} directive specifies that the next function
+declared in the file must not include a stack overflow check. This is
+most commonly used by low-level runtime sources invoked at times when
+it is unsafe for the calling goroutine to be preempted.
+
+@item //go:noinline
+The @code{//go:noinline} directive specifies that the next function
+defined in the file may not be inlined.
+
+@end table
+
+@node C Interoperability
+@chapter C Interoperability
+
+When using @command{gccgo} there is limited interoperability with C,
+or with C++ code compiled using @code{extern "C"}.
+
+This information is provided largely for documentation purposes. For
+ordinary use it is best to build programs with the go tool and then
+use @code{import "C"}, as described at
+@url{https://golang.org/cmd/cgo}.
+
+@menu
+* C Type Interoperability:: How C and Go types match up.
+* Function Names:: How Go functions are named.
+@end menu
+
+@node C Type Interoperability
+@section C Type Interoperability
+
+Basic types map directly: an @code{int} in Go is an @code{int} in C,
+etc. Go @code{byte} is equivalent to C @code{unsigned char}.
+Pointers in Go are pointers in C. A Go @code{struct} is the same as C
+@code{struct} with the same field names and types.
+
+@cindex @code{string} in C
+The Go @code{string} type is currently defined as a two-element
+structure:
+
+@smallexample
+struct __go_string @{
+ const unsigned char *__data;
+ int __length;
+@};
+@end smallexample
+
+You can't pass arrays between C and Go. However, a pointer to an
+array in Go is equivalent to a C pointer to the equivalent of the
+element type. For example, Go @code{*[10]int} is equivalent to C
+@code{int*}, assuming that the C pointer does point to 10 elements.
+
+@cindex @code{slice} in C
+A slice in Go is a structure. The current definition is:
+
+@smallexample
+struct __go_slice @{
+ void *__values;
+ int __count;
+ int __capacity;
+@};
+@end smallexample
+
+The type of a Go function with no receiver is equivalent to a C
+function whose parameter types are equivalent. When a Go function
+returns more than one value, the C function returns a struct. For
+example, these functions have equivalent types:
+
+@smallexample
+func GoFunction(int) (int, float)
+struct @{ int i; float f; @} CFunction(int)
+@end smallexample
+
+A pointer to a Go function is equivalent to a pointer to a C function
+when the functions have equivalent types.
+
+Go @code{interface}, @code{channel}, and @code{map} types have no
+corresponding C type (@code{interface} is a two-element struct and
+@code{channel} and @code{map} are pointers to structs in C, but the
+structs are deliberately undocumented). C @code{enum} types
+correspond to some integer type, but precisely which one is difficult
+to predict in general; use a cast. C @code{union} types have no
+corresponding Go type. C @code{struct} types containing bitfields
+have no corresponding Go type. C++ @code{class} types have no
+corresponding Go type.
+
+Memory allocation is completely different between C and Go, as Go uses
+garbage collection. The exact guidelines in this area are
+undetermined, but it is likely that it will be permitted to pass a
+pointer to allocated memory from C to Go. The responsibility of
+eventually freeing the pointer will remain with C side, and of course
+if the C side frees the pointer while the Go side still has a copy the
+program will fail. When passing a pointer from Go to C, the Go
+function must retain a visible copy of it in some Go variable.
+Otherwise the Go garbage collector may delete the pointer while the C
+function is still using it.
+
+@node Function Names
+@section Function Names
+
+@cindex @code{extern}
+@cindex external names
+Go code can call C functions directly using the @code{//extern} or
+@code{//go:linkname} compiler directives. An @code{//extern}
+directive must be at the beginning of the line and must start with
+@code{//extern}. This must be followed by a space and then the
+external name of the function. The function declaration must be on
+the line immediately after the comment. For example, here is how the
+C function @code{open} can be declared in Go:
+
+@smallexample
+//extern open
+func c_open(name *byte, mode int, perm int) int
+@end smallexample
+
+You can do the same thing using the @code{//go:linkname} compiler
+directive. The @code{//go:linkname} directive must be at the start of
+the line. It is followed by whitespace, the name of the Go function,
+more whitespace, and the external name of the function. Unlike
+@code{//extern}, @code{//go:linkname} does not need to appear
+immediately adjacent to the function definition or declaration.
+
+@smallexample
+//go:linkname c_open open
+func c_open(name *byte, mode int, perm int) int
+@end smallexample
+
+The C function naturally expects a nul terminated string, which in Go
+is equivalent to a pointer to an array (not a slice!) of @code{byte}
+with a terminating zero byte. So a sample call from Go would look
+like (after importing the @code{os} package):
+
+@smallexample
+var name = [4]byte@{'f', 'o', 'o', 0@};
+i := c_open(&name[0], os.O_RDONLY, 0);
+@end smallexample
+
+Note that this serves as an example only. To open a file in Go please
+use Go's @code{os.Open} function instead.
+
+The name of Go functions accessed from C is subject to change. At
+present the name of a Go function that does not have a receiver is
+@code{pkgpath.Functionname}. The @var{pkgpath} is set by the
+@option{-fgo-pkgpath} option used when the package is compiled; if the
+option is not used, the default is @code{go.@var{packagename}}. To
+call the function from C you must set the name using the @command{gcc}
+@code{__asm__} extension.
+
+@smallexample
+extern int go_function(int) __asm__ ("mypkgpath.Function");
+@end smallexample
+
+@node Index
+@unnumbered Index
+
+@printindex cp
+
+@bye
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+
+@c %**start of header
+@setfilename libgomp.info
+@settitle GNU libgomp
+@c %**end of header
+
+
+@copying
+Copyright @copyright{} 2006-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``Funding Free Software'', the Front-Cover
+texts being (a) (see below), and with the Back-Cover Texts being (b)
+(see below). A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@end copying
+
+@ifinfo
+@dircategory GNU Libraries
+@direntry
+* libgomp: (libgomp). GNU Offloading and Multi Processing Runtime Library.
+@end direntry
+
+This manual documents libgomp, the GNU Offloading and Multi Processing
+Runtime library. This is the GNU implementation of the OpenMP and
+OpenACC APIs for parallel and accelerator programming in C/C++ and
+Fortran.
+
+Published by the Free Software Foundation
+51 Franklin Street, Fifth Floor
+Boston, MA 02110-1301 USA
+
+@insertcopying
+@end ifinfo
+
+
+@setchapternewpage odd
+
+@titlepage
+@title GNU Offloading and Multi Processing Runtime Library
+@subtitle The GNU OpenMP and OpenACC Implementation
+@page
+@vskip 0pt plus 1filll
+@comment For the @value{version-GCC} Version*
+@sp 1
+Published by the Free Software Foundation @*
+51 Franklin Street, Fifth Floor@*
+Boston, MA 02110-1301, USA@*
+@sp 1
+@insertcopying
+@end titlepage
+
+@summarycontents
+@contents
+@page
+
+
+@node Top, Enabling OpenMP
+@top Introduction
+@cindex Introduction
+
+This manual documents the usage of libgomp, the GNU Offloading and
+Multi Processing Runtime Library. This includes the GNU
+implementation of the @uref{https://www.openmp.org, OpenMP} Application
+Programming Interface (API) for multi-platform shared-memory parallel
+programming in C/C++ and Fortran, and the GNU implementation of the
+@uref{https://www.openacc.org, OpenACC} Application Programming
+Interface (API) for offloading of code to accelerator devices in C/C++
+and Fortran.
+
+Originally, libgomp implemented the GNU OpenMP Runtime Library. Based
+on this, support for OpenACC and offloading (both OpenACC and OpenMP
+4's target construct) has been added later on, and the library's name
+changed to GNU Offloading and Multi Processing Runtime Library.
+
+
+
+@comment
+@comment When you add a new menu item, please keep the right hand
+@comment aligned to the same column. Do not use tabs. This provides
+@comment better formatting.
+@comment
+@menu
+* Enabling OpenMP:: How to enable OpenMP for your applications.
+* OpenMP Implementation Status:: List of implemented features by OpenMP version
+* OpenMP Runtime Library Routines: Runtime Library Routines.
+ The OpenMP runtime application programming
+ interface.
+* OpenMP Environment Variables: Environment Variables.
+ Influencing OpenMP runtime behavior with
+ environment variables.
+* Enabling OpenACC:: How to enable OpenACC for your
+ applications.
+* OpenACC Runtime Library Routines:: The OpenACC runtime application
+ programming interface.
+* OpenACC Environment Variables:: Influencing OpenACC runtime behavior with
+ environment variables.
+* CUDA Streams Usage:: Notes on the implementation of
+ asynchronous operations.
+* OpenACC Library Interoperability:: OpenACC library interoperability with the
+ NVIDIA CUBLAS library.
+* OpenACC Profiling Interface::
+* OpenMP-Implementation Specifics:: Notes specifics of this OpenMP
+ implementation
+* Offload-Target Specifics:: Notes on offload-target specific internals
+* The libgomp ABI:: Notes on the external ABI presented by libgomp.
+* Reporting Bugs:: How to report bugs in the GNU Offloading and
+ Multi Processing Runtime Library.
+* Copying:: GNU general public license says
+ how you can copy and share libgomp.
+* GNU Free Documentation License::
+ How you can copy and share this manual.
+* Funding:: How to help assure continued work for free
+ software.
+* Library Index:: Index of this documentation.
+@end menu
+
+
+@c ---------------------------------------------------------------------
+@c Enabling OpenMP
+@c ---------------------------------------------------------------------
+
+@node Enabling OpenMP
+@chapter Enabling OpenMP
+
+To activate the OpenMP extensions for C/C++ and Fortran, the compile-time
+flag @command{-fopenmp} must be specified. This enables the OpenMP directive
+@code{#pragma omp} in C/C++ and @code{!$omp} directives in free form,
+@code{c$omp}, @code{*$omp} and @code{!$omp} directives in fixed form,
+@code{!$} conditional compilation sentinels in free form and @code{c$},
+@code{*$} and @code{!$} sentinels in fixed form, for Fortran. The flag also
+arranges for automatic linking of the OpenMP runtime library
+(@ref{Runtime Library Routines}).
+
+A complete description of all OpenMP directives may be found in the
+@uref{https://www.openmp.org, OpenMP Application Program Interface} manuals.
+See also @ref{OpenMP Implementation Status}.
+
+
+@c ---------------------------------------------------------------------
+@c OpenMP Implementation Status
+@c ---------------------------------------------------------------------
+
+@node OpenMP Implementation Status
+@chapter OpenMP Implementation Status
+
+@menu
+* OpenMP 4.5:: Feature completion status to 4.5 specification
+* OpenMP 5.0:: Feature completion status to 5.0 specification
+* OpenMP 5.1:: Feature completion status to 5.1 specification
+* OpenMP 5.2:: Feature completion status to 5.2 specification
+@end menu
+
+The @code{_OPENMP} preprocessor macro and Fortran's @code{openmp_version}
+parameter, provided by @code{omp_lib.h} and the @code{omp_lib} module, have
+the value @code{201511} (i.e. OpenMP 4.5).
+
+@node OpenMP 4.5
+@section OpenMP 4.5
+
+The OpenMP 4.5 specification is fully supported.
+
+@node OpenMP 5.0
+@section OpenMP 5.0
+
+@unnumberedsubsec New features listed in Appendix B of the OpenMP specification
+@c This list is sorted as in OpenMP 5.1's B.3 not as in OpenMP 5.0's B.2
+
+@multitable @columnfractions .60 .10 .25
+@headitem Description @tab Status @tab Comments
+@item Array shaping @tab N @tab
+@item Array sections with non-unit strides in C and C++ @tab N @tab
+@item Iterators @tab Y @tab
+@item @code{metadirective} directive @tab N @tab
+@item @code{declare variant} directive
+ @tab P @tab @emph{simd} traits not handled correctly
+@item @emph{target-offload-var} ICV and @code{OMP_TARGET_OFFLOAD}
+ env variable @tab Y @tab
+@item Nested-parallel changes to @emph{max-active-levels-var} ICV @tab Y @tab
+@item @code{requires} directive @tab P
+ @tab complete but no non-host devices provides @code{unified_address},
+ @code{unified_shared_memory} or @code{reverse_offload}
+@item @code{teams} construct outside an enclosing target region @tab Y @tab
+@item Non-rectangular loop nests @tab Y @tab
+@item @code{!=} as relational-op in canonical loop form for C/C++ @tab Y @tab
+@item @code{nonmonotonic} as default loop schedule modifier for worksharing-loop
+ constructs @tab Y @tab
+@item Collapse of associated loops that are imperfectly nested loops @tab N @tab
+@item Clauses @code{if}, @code{nontemporal} and @code{order(concurrent)} in
+ @code{simd} construct @tab Y @tab
+@item @code{atomic} constructs in @code{simd} @tab Y @tab
+@item @code{loop} construct @tab Y @tab
+@item @code{order(concurrent)} clause @tab Y @tab
+@item @code{scan} directive and @code{in_scan} modifier for the
+ @code{reduction} clause @tab Y @tab
+@item @code{in_reduction} clause on @code{task} constructs @tab Y @tab
+@item @code{in_reduction} clause on @code{target} constructs @tab P
+ @tab @code{nowait} only stub
+@item @code{task_reduction} clause with @code{taskgroup} @tab Y @tab
+@item @code{task} modifier to @code{reduction} clause @tab Y @tab
+@item @code{affinity} clause to @code{task} construct @tab Y @tab Stub only
+@item @code{detach} clause to @code{task} construct @tab Y @tab
+@item @code{omp_fulfill_event} runtime routine @tab Y @tab
+@item @code{reduction} and @code{in_reduction} clauses on @code{taskloop}
+ and @code{taskloop simd} constructs @tab Y @tab
+@item @code{taskloop} construct cancelable by @code{cancel} construct
+ @tab Y @tab
+@item @code{mutexinoutset} @emph{dependence-type} for @code{depend} clause
+ @tab Y @tab
+@item Predefined memory spaces, memory allocators, allocator traits
+ @tab Y @tab Some are only stubs
+@item Memory management routines @tab Y @tab
+@item @code{allocate} directive @tab N @tab
+@item @code{allocate} clause @tab P @tab Initial support
+@item @code{use_device_addr} clause on @code{target data} @tab Y @tab
+@item @code{ancestor} modifier on @code{device} clause
+ @tab Y @tab See comment for @code{requires}
+@item Implicit declare target directive @tab Y @tab
+@item Discontiguous array section with @code{target update} construct
+ @tab N @tab
+@item C/C++'s lvalue expressions in @code{to}, @code{from}
+ and @code{map} clauses @tab N @tab
+@item C/C++'s lvalue expressions in @code{depend} clauses @tab Y @tab
+@item Nested @code{declare target} directive @tab Y @tab
+@item Combined @code{master} constructs @tab Y @tab
+@item @code{depend} clause on @code{taskwait} @tab Y @tab
+@item Weak memory ordering clauses on @code{atomic} and @code{flush} construct
+ @tab Y @tab
+@item @code{hint} clause on the @code{atomic} construct @tab Y @tab Stub only
+@item @code{depobj} construct and depend objects @tab Y @tab
+@item Lock hints were renamed to synchronization hints @tab Y @tab
+@item @code{conditional} modifier to @code{lastprivate} clause @tab Y @tab
+@item Map-order clarifications @tab P @tab
+@item @code{close} @emph{map-type-modifier} @tab Y @tab
+@item Mapping C/C++ pointer variables and to assign the address of
+ device memory mapped by an array section @tab P @tab
+@item Mapping of Fortran pointer and allocatable variables, including pointer
+ and allocatable components of variables
+ @tab P @tab Mapping of vars with allocatable components unsupported
+@item @code{defaultmap} extensions @tab Y @tab
+@item @code{declare mapper} directive @tab N @tab
+@item @code{omp_get_supported_active_levels} routine @tab Y @tab
+@item Runtime routines and environment variables to display runtime thread
+ affinity information @tab Y @tab
+@item @code{omp_pause_resource} and @code{omp_pause_resource_all} runtime
+ routines @tab Y @tab
+@item @code{omp_get_device_num} runtime routine @tab Y @tab
+@item OMPT interface @tab N @tab
+@item OMPD interface @tab N @tab
+@end multitable
+
+@unnumberedsubsec Other new OpenMP 5.0 features
+
+@multitable @columnfractions .60 .10 .25
+@headitem Description @tab Status @tab Comments
+@item Supporting C++'s range-based for loop @tab Y @tab
+@end multitable
+
+
+@node OpenMP 5.1
+@section OpenMP 5.1
+
+@unnumberedsubsec New features listed in Appendix B of the OpenMP specification
+
+@multitable @columnfractions .60 .10 .25
+@headitem Description @tab Status @tab Comments
+@item OpenMP directive as C++ attribute specifiers @tab Y @tab
+@item @code{omp_all_memory} reserved locator @tab Y @tab
+@item @emph{target_device trait} in OpenMP Context @tab N @tab
+@item @code{target_device} selector set in context selectors @tab N @tab
+@item C/C++'s @code{declare variant} directive: elision support of
+ preprocessed code @tab N @tab
+@item @code{declare variant}: new clauses @code{adjust_args} and
+ @code{append_args} @tab N @tab
+@item @code{dispatch} construct @tab N @tab
+@item device-specific ICV settings with environment variables @tab Y @tab
+@item @code{assume} directive @tab Y @tab
+@item @code{nothing} directive @tab Y @tab
+@item @code{error} directive @tab Y @tab
+@item @code{masked} construct @tab Y @tab
+@item @code{scope} directive @tab Y @tab
+@item Loop transformation constructs @tab N @tab
+@item @code{strict} modifier in the @code{grainsize} and @code{num_tasks}
+ clauses of the @code{taskloop} construct @tab Y @tab
+@item @code{align} clause/modifier in @code{allocate} directive/clause
+ and @code{allocator} directive @tab P @tab C/C++ on clause only
+@item @code{thread_limit} clause to @code{target} construct @tab Y @tab
+@item @code{has_device_addr} clause to @code{target} construct @tab Y @tab
+@item Iterators in @code{target update} motion clauses and @code{map}
+ clauses @tab N @tab
+@item Indirect calls to the device version of a procedure or function in
+ @code{target} regions @tab N @tab
+@item @code{interop} directive @tab N @tab
+@item @code{omp_interop_t} object support in runtime routines @tab N @tab
+@item @code{nowait} clause in @code{taskwait} directive @tab Y @tab
+@item Extensions to the @code{atomic} directive @tab Y @tab
+@item @code{seq_cst} clause on a @code{flush} construct @tab Y @tab
+@item @code{inoutset} argument to the @code{depend} clause @tab Y @tab
+@item @code{private} and @code{firstprivate} argument to @code{default}
+ clause in C and C++ @tab Y @tab
+@item @code{present} argument to @code{defaultmap} clause @tab N @tab
+@item @code{omp_set_num_teams}, @code{omp_set_teams_thread_limit},
+ @code{omp_get_max_teams}, @code{omp_get_teams_thread_limit} runtime
+ routines @tab Y @tab
+@item @code{omp_target_is_accessible} runtime routine @tab Y @tab
+@item @code{omp_target_memcpy_async} and @code{omp_target_memcpy_rect_async}
+ runtime routines @tab Y @tab
+@item @code{omp_get_mapped_ptr} runtime routine @tab Y @tab
+@item @code{omp_calloc}, @code{omp_realloc}, @code{omp_aligned_alloc} and
+ @code{omp_aligned_calloc} runtime routines @tab Y @tab
+@item @code{omp_alloctrait_key_t} enum: @code{omp_atv_serialized} added,
+ @code{omp_atv_default} changed @tab Y @tab
+@item @code{omp_display_env} runtime routine @tab Y @tab
+@item @code{ompt_scope_endpoint_t} enum: @code{ompt_scope_beginend} @tab N @tab
+@item @code{ompt_sync_region_t} enum additions @tab N @tab
+@item @code{ompt_state_t} enum: @code{ompt_state_wait_barrier_implementation}
+ and @code{ompt_state_wait_barrier_teams} @tab N @tab
+@item @code{ompt_callback_target_data_op_emi_t},
+ @code{ompt_callback_target_emi_t}, @code{ompt_callback_target_map_emi_t}
+ and @code{ompt_callback_target_submit_emi_t} @tab N @tab
+@item @code{ompt_callback_error_t} type @tab N @tab
+@item @code{OMP_PLACES} syntax extensions @tab Y @tab
+@item @code{OMP_NUM_TEAMS} and @code{OMP_TEAMS_THREAD_LIMIT} environment
+ variables @tab Y @tab
+@end multitable
+
+@unnumberedsubsec Other new OpenMP 5.1 features
+
+@multitable @columnfractions .60 .10 .25
+@headitem Description @tab Status @tab Comments
+@item Support of strictly structured blocks in Fortran @tab Y @tab
+@item Support of structured block sequences in C/C++ @tab Y @tab
+@item @code{unconstrained} and @code{reproducible} modifiers on @code{order}
+ clause @tab Y @tab
+@item Support @code{begin/end declare target} syntax in C/C++ @tab Y @tab
+@item Pointer predetermined firstprivate getting initialized
+to address of matching mapped list item per 5.1, Sect. 2.21.7.2 @tab N @tab
+@item For Fortran, diagnose placing declarative before/between @code{USE},
+ @code{IMPORT}, and @code{IMPLICIT} as invalid @tab N @tab
+@end multitable
+
+
+@node OpenMP 5.2
+@section OpenMP 5.2
+
+@unnumberedsubsec New features listed in Appendix B of the OpenMP specification
+
+@multitable @columnfractions .60 .10 .25
+@headitem Description @tab Status @tab Comments
+@item @code{omp_in_explicit_task} routine and @emph{explicit-task-var} ICV
+ @tab Y @tab
+@item @code{omp}/@code{ompx}/@code{omx} sentinels and @code{omp_}/@code{ompx_}
+ namespaces @tab N/A
+ @tab warning for @code{ompx/omx} sentinels@footnote{The @code{ompx}
+ sentinel as C/C++ pragma and C++ attributes are warned for with
+ @code{-Wunknown-pragmas} (implied by @code{-Wall}) and @code{-Wattributes}
+ (enabled by default), respectively; for Fortran free-source code, there is
+ a warning enabled by default and, for fixed-source code, the @code{omx}
+ sentinel is warned for with with @code{-Wsurprising} (enabled by
+ @code{-Wall}). Unknown clauses are always rejected with an error.}
+@item Clauses on @code{end} directive can be on directive @tab N @tab
+@item Deprecation of no-argument @code{destroy} clause on @code{depobj}
+ @tab N @tab
+@item @code{linear} clause syntax changes and @code{step} modifier @tab Y @tab
+@item Deprecation of minus operator for reductions @tab N @tab
+@item Deprecation of separating @code{map} modifiers without comma @tab N @tab
+@item @code{declare mapper} with iterator and @code{present} modifiers
+ @tab N @tab
+@item If a matching mapped list item is not found in the data environment, the
+ pointer retains its original value @tab N @tab
+@item New @code{enter} clause as alias for @code{to} on declare target directive
+ @tab Y @tab
+@item Deprecation of @code{to} clause on declare target directive @tab N @tab
+@item Extended list of directives permitted in Fortran pure procedures
+ @tab N @tab
+@item New @code{allocators} directive for Fortran @tab N @tab
+@item Deprecation of @code{allocate} directive for Fortran
+ allocatables/pointers @tab N @tab
+@item Optional paired @code{end} directive with @code{dispatch} @tab N @tab
+@item New @code{memspace} and @code{traits} modifiers for @code{uses_allocators}
+ @tab N @tab
+@item Deprecation of traits array following the allocator_handle expression in
+ @code{uses_allocators} @tab N @tab
+@item New @code{otherwise} clause as alias for @code{default} on metadirectives
+ @tab N @tab
+@item Deprecation of @code{default} clause on metadirectives @tab N @tab
+@item Deprecation of delimited form of @code{declare target} @tab N @tab
+@item Reproducible semantics changed for @code{order(concurrent)} @tab N @tab
+@item @code{allocate} and @code{firstprivate} clauses on @code{scope}
+ @tab Y @tab
+@item @code{ompt_callback_work} @tab N @tab
+@item Default map-type for @code{map} clause in @code{target enter/exit data}
+ @tab Y @tab
+@item New @code{doacross} clause as alias for @code{depend} with
+ @code{source}/@code{sink} modifier @tab Y @tab
+@item Deprecation of @code{depend} with @code{source}/@code{sink} modifier
+ @tab N @tab
+@item @code{omp_cur_iteration} keyword @tab Y @tab
+@end multitable
+
+@unnumberedsubsec Other new OpenMP 5.2 features
+
+@multitable @columnfractions .60 .10 .25
+@headitem Description @tab Status @tab Comments
+@item For Fortran, optional comma between directive and clause @tab N @tab
+@item Conforming device numbers and @code{omp_initial_device} and
+ @code{omp_invalid_device} enum/PARAMETER @tab Y @tab
+@item Initial value of @emph{default-device-var} ICV with
+ @code{OMP_TARGET_OFFLOAD=mandatory} @tab N @tab
+@item @emph{interop_types} in any position of the modifier list for the @code{init} clause
+ of the @code{interop} construct @tab N @tab
+@end multitable
+
+
+@c ---------------------------------------------------------------------
+@c OpenMP Runtime Library Routines
+@c ---------------------------------------------------------------------
+
+@node Runtime Library Routines
+@chapter OpenMP Runtime Library Routines
+
+The runtime routines described here are defined by Section 3 of the OpenMP
+specification in version 4.5. The routines are structured in following
+three parts:
+
+@menu
+Control threads, processors and the parallel environment. They have C
+linkage, and do not throw exceptions.
+
+* omp_get_active_level:: Number of active parallel regions
+* omp_get_ancestor_thread_num:: Ancestor thread ID
+* omp_get_cancellation:: Whether cancellation support is enabled
+* omp_get_default_device:: Get the default device for target regions
+* omp_get_device_num:: Get device that current thread is running on
+* omp_get_dynamic:: Dynamic teams setting
+* omp_get_initial_device:: Device number of host device
+* omp_get_level:: Number of parallel regions
+* omp_get_max_active_levels:: Current maximum number of active regions
+* omp_get_max_task_priority:: Maximum task priority value that can be set
+* omp_get_max_teams:: Maximum number of teams for teams region
+* omp_get_max_threads:: Maximum number of threads of parallel region
+* omp_get_nested:: Nested parallel regions
+* omp_get_num_devices:: Number of target devices
+* omp_get_num_procs:: Number of processors online
+* omp_get_num_teams:: Number of teams
+* omp_get_num_threads:: Size of the active team
+* omp_get_proc_bind:: Whether theads may be moved between CPUs
+* omp_get_schedule:: Obtain the runtime scheduling method
+* omp_get_supported_active_levels:: Maximum number of active regions supported
+* omp_get_team_num:: Get team number
+* omp_get_team_size:: Number of threads in a team
+* omp_get_teams_thread_limit:: Maximum number of threads imposed by teams
+* omp_get_thread_limit:: Maximum number of threads
+* omp_get_thread_num:: Current thread ID
+* omp_in_parallel:: Whether a parallel region is active
+* omp_in_final:: Whether in final or included task region
+* omp_is_initial_device:: Whether executing on the host device
+* omp_set_default_device:: Set the default device for target regions
+* omp_set_dynamic:: Enable/disable dynamic teams
+* omp_set_max_active_levels:: Limits the number of active parallel regions
+* omp_set_nested:: Enable/disable nested parallel regions
+* omp_set_num_teams:: Set upper teams limit for teams region
+* omp_set_num_threads:: Set upper team size limit
+* omp_set_schedule:: Set the runtime scheduling method
+* omp_set_teams_thread_limit:: Set upper thread limit for teams construct
+
+Initialize, set, test, unset and destroy simple and nested locks.
+
+* omp_init_lock:: Initialize simple lock
+* omp_set_lock:: Wait for and set simple lock
+* omp_test_lock:: Test and set simple lock if available
+* omp_unset_lock:: Unset simple lock
+* omp_destroy_lock:: Destroy simple lock
+* omp_init_nest_lock:: Initialize nested lock
+* omp_set_nest_lock:: Wait for and set simple lock
+* omp_test_nest_lock:: Test and set nested lock if available
+* omp_unset_nest_lock:: Unset nested lock
+* omp_destroy_nest_lock:: Destroy nested lock
+
+Portable, thread-based, wall clock timer.
+
+* omp_get_wtick:: Get timer precision.
+* omp_get_wtime:: Elapsed wall clock time.
+
+Support for event objects.
+
+* omp_fulfill_event:: Fulfill and destroy an OpenMP event.
+@end menu
+
+
+
+@node omp_get_active_level
+@section @code{omp_get_active_level} -- Number of parallel regions
+@table @asis
+@item @emph{Description}:
+This function returns the nesting level for the active parallel blocks,
+which enclose the calling call.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_active_level(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_active_level()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_level}, @ref{omp_get_max_active_levels}, @ref{omp_set_max_active_levels}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.20.
+@end table
+
+
+
+@node omp_get_ancestor_thread_num
+@section @code{omp_get_ancestor_thread_num} -- Ancestor thread ID
+@table @asis
+@item @emph{Description}:
+This function returns the thread identification number for the given
+nesting level of the current thread. For values of @var{level} outside
+zero to @code{omp_get_level} -1 is returned; if @var{level} is
+@code{omp_get_level} the result is identical to @code{omp_get_thread_num}.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_ancestor_thread_num(int level);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_ancestor_thread_num(level)}
+@item @tab @code{integer level}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_level}, @ref{omp_get_thread_num}, @ref{omp_get_team_size}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.18.
+@end table
+
+
+
+@node omp_get_cancellation
+@section @code{omp_get_cancellation} -- Whether cancellation support is enabled
+@table @asis
+@item @emph{Description}:
+This function returns @code{true} if cancellation is activated, @code{false}
+otherwise. Here, @code{true} and @code{false} represent their language-specific
+counterparts. Unless @env{OMP_CANCELLATION} is set true, cancellations are
+deactivated.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_cancellation(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{logical function omp_get_cancellation()}
+@end multitable
+
+@item @emph{See also}:
+@ref{OMP_CANCELLATION}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.9.
+@end table
+
+
+
+@node omp_get_default_device
+@section @code{omp_get_default_device} -- Get the default device for target regions
+@table @asis
+@item @emph{Description}:
+Get the default device for target regions without device clause.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_default_device(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_default_device()}
+@end multitable
+
+@item @emph{See also}:
+@ref{OMP_DEFAULT_DEVICE}, @ref{omp_set_default_device}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.30.
+@end table
+
+
+
+@node omp_get_device_num
+@section @code{omp_get_device_num} -- Return device number of current device
+@table @asis
+@item @emph{Description}:
+This function returns a device number that represents the device that the
+current thread is executing on. For OpenMP 5.0, this must be equal to the
+value returned by the @code{omp_get_initial_device} function when called
+from the host.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_device_num(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_device_num()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_initial_device}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.0}, Section 3.2.37.
+@end table
+
+
+
+@node omp_get_dynamic
+@section @code{omp_get_dynamic} -- Dynamic teams setting
+@table @asis
+@item @emph{Description}:
+This function returns @code{true} if enabled, @code{false} otherwise.
+Here, @code{true} and @code{false} represent their language-specific
+counterparts.
+
+The dynamic team setting may be initialized at startup by the
+@env{OMP_DYNAMIC} environment variable or at runtime using
+@code{omp_set_dynamic}. If undefined, dynamic adjustment is
+disabled by default.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_dynamic(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{logical function omp_get_dynamic()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_dynamic}, @ref{OMP_DYNAMIC}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.8.
+@end table
+
+
+
+@node omp_get_initial_device
+@section @code{omp_get_initial_device} -- Return device number of initial device
+@table @asis
+@item @emph{Description}:
+This function returns a device number that represents the host device.
+For OpenMP 5.1, this must be equal to the value returned by the
+@code{omp_get_num_devices} function.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_initial_device(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_initial_device()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_num_devices}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.35.
+@end table
+
+
+
+@node omp_get_level
+@section @code{omp_get_level} -- Obtain the current nesting level
+@table @asis
+@item @emph{Description}:
+This function returns the nesting level for the parallel blocks,
+which enclose the calling call.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_level(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_level()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_active_level}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.17.
+@end table
+
+
+
+@node omp_get_max_active_levels
+@section @code{omp_get_max_active_levels} -- Current maximum number of active regions
+@table @asis
+@item @emph{Description}:
+This function obtains the maximum allowed number of nested, active parallel regions.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_max_active_levels(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_max_active_levels()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_max_active_levels}, @ref{omp_get_active_level}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.16.
+@end table
+
+
+@node omp_get_max_task_priority
+@section @code{omp_get_max_task_priority} -- Maximum priority value
+that can be set for tasks.
+@table @asis
+@item @emph{Description}:
+This function obtains the maximum allowed priority number for tasks.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_max_task_priority(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_max_task_priority()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.29.
+@end table
+
+
+@node omp_get_max_teams
+@section @code{omp_get_max_teams} -- Maximum number of teams of teams region
+@table @asis
+@item @emph{Description}:
+Return the maximum number of teams used for the teams region
+that does not use the clause @code{num_teams}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_max_teams(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_max_teams()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_num_teams}, @ref{omp_get_num_teams}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.1}, Section 3.4.4.
+@end table
+
+
+
+@node omp_get_max_threads
+@section @code{omp_get_max_threads} -- Maximum number of threads of parallel region
+@table @asis
+@item @emph{Description}:
+Return the maximum number of threads used for the current parallel region
+that does not use the clause @code{num_threads}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_max_threads(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_max_threads()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_num_threads}, @ref{omp_set_dynamic}, @ref{omp_get_thread_limit}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.3.
+@end table
+
+
+
+@node omp_get_nested
+@section @code{omp_get_nested} -- Nested parallel regions
+@table @asis
+@item @emph{Description}:
+This function returns @code{true} if nested parallel regions are
+enabled, @code{false} otherwise. Here, @code{true} and @code{false}
+represent their language-specific counterparts.
+
+The state of nested parallel regions at startup depends on several
+environment variables. If @env{OMP_MAX_ACTIVE_LEVELS} is defined
+and is set to greater than one, then nested parallel regions will be
+enabled. If not defined, then the value of the @env{OMP_NESTED}
+environment variable will be followed if defined. If neither are
+defined, then if either @env{OMP_NUM_THREADS} or @env{OMP_PROC_BIND}
+are defined with a list of more than one value, then nested parallel
+regions are enabled. If none of these are defined, then nested parallel
+regions are disabled by default.
+
+Nested parallel regions can be enabled or disabled at runtime using
+@code{omp_set_nested}, or by setting the maximum number of nested
+regions with @code{omp_set_max_active_levels} to one to disable, or
+above one to enable.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_nested(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{logical function omp_get_nested()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_max_active_levels}, @ref{omp_set_nested},
+@ref{OMP_MAX_ACTIVE_LEVELS}, @ref{OMP_NESTED}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.11.
+@end table
+
+
+
+@node omp_get_num_devices
+@section @code{omp_get_num_devices} -- Number of target devices
+@table @asis
+@item @emph{Description}:
+Returns the number of target devices.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_num_devices(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_num_devices()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.31.
+@end table
+
+
+
+@node omp_get_num_procs
+@section @code{omp_get_num_procs} -- Number of processors online
+@table @asis
+@item @emph{Description}:
+Returns the number of processors online on that device.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_num_procs(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_num_procs()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.5.
+@end table
+
+
+
+@node omp_get_num_teams
+@section @code{omp_get_num_teams} -- Number of teams
+@table @asis
+@item @emph{Description}:
+Returns the number of teams in the current team region.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_num_teams(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_num_teams()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.32.
+@end table
+
+
+
+@node omp_get_num_threads
+@section @code{omp_get_num_threads} -- Size of the active team
+@table @asis
+@item @emph{Description}:
+Returns the number of threads in the current team. In a sequential section of
+the program @code{omp_get_num_threads} returns 1.
+
+The default team size may be initialized at startup by the
+@env{OMP_NUM_THREADS} environment variable. At runtime, the size
+of the current team may be set either by the @code{NUM_THREADS}
+clause or by @code{omp_set_num_threads}. If none of the above were
+used to define a specific value and @env{OMP_DYNAMIC} is disabled,
+one thread per CPU online is used.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_num_threads(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_num_threads()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_max_threads}, @ref{omp_set_num_threads}, @ref{OMP_NUM_THREADS}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.2.
+@end table
+
+
+
+@node omp_get_proc_bind
+@section @code{omp_get_proc_bind} -- Whether theads may be moved between CPUs
+@table @asis
+@item @emph{Description}:
+This functions returns the currently active thread affinity policy, which is
+set via @env{OMP_PROC_BIND}. Possible values are @code{omp_proc_bind_false},
+@code{omp_proc_bind_true}, @code{omp_proc_bind_primary},
+@code{omp_proc_bind_master}, @code{omp_proc_bind_close} and @code{omp_proc_bind_spread},
+where @code{omp_proc_bind_master} is an alias for @code{omp_proc_bind_primary}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{omp_proc_bind_t omp_get_proc_bind(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer(kind=omp_proc_bind_kind) function omp_get_proc_bind()}
+@end multitable
+
+@item @emph{See also}:
+@ref{OMP_PROC_BIND}, @ref{OMP_PLACES}, @ref{GOMP_CPU_AFFINITY},
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.22.
+@end table
+
+
+
+@node omp_get_schedule
+@section @code{omp_get_schedule} -- Obtain the runtime scheduling method
+@table @asis
+@item @emph{Description}:
+Obtain the runtime scheduling method. The @var{kind} argument will be
+set to the value @code{omp_sched_static}, @code{omp_sched_dynamic},
+@code{omp_sched_guided} or @code{omp_sched_auto}. The second argument,
+@var{chunk_size}, is set to the chunk size.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_get_schedule(omp_sched_t *kind, int *chunk_size);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_get_schedule(kind, chunk_size)}
+@item @tab @code{integer(kind=omp_sched_kind) kind}
+@item @tab @code{integer chunk_size}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_schedule}, @ref{OMP_SCHEDULE}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.13.
+@end table
+
+
+@node omp_get_supported_active_levels
+@section @code{omp_get_supported_active_levels} -- Maximum number of active regions supported
+@table @asis
+@item @emph{Description}:
+This function returns the maximum number of nested, active parallel regions
+supported by this implementation.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_supported_active_levels(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_supported_active_levels()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_max_active_levels}, @ref{omp_set_max_active_levels}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.0}, Section 3.2.15.
+@end table
+
+
+
+@node omp_get_team_num
+@section @code{omp_get_team_num} -- Get team number
+@table @asis
+@item @emph{Description}:
+Returns the team number of the calling thread.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_team_num(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_team_num()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.33.
+@end table
+
+
+
+@node omp_get_team_size
+@section @code{omp_get_team_size} -- Number of threads in a team
+@table @asis
+@item @emph{Description}:
+This function returns the number of threads in a thread team to which
+either the current thread or its ancestor belongs. For values of @var{level}
+outside zero to @code{omp_get_level}, -1 is returned; if @var{level} is zero,
+1 is returned, and for @code{omp_get_level}, the result is identical
+to @code{omp_get_num_threads}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_team_size(int level);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_team_size(level)}
+@item @tab @code{integer level}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_num_threads}, @ref{omp_get_level}, @ref{omp_get_ancestor_thread_num}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.19.
+@end table
+
+
+
+@node omp_get_teams_thread_limit
+@section @code{omp_get_teams_thread_limit} -- Maximum number of threads imposed by teams
+@table @asis
+@item @emph{Description}:
+Return the maximum number of threads that will be able to participate in
+each team created by a teams construct.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_teams_thread_limit(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_teams_thread_limit()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_teams_thread_limit}, @ref{OMP_TEAMS_THREAD_LIMIT}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.1}, Section 3.4.6.
+@end table
+
+
+
+@node omp_get_thread_limit
+@section @code{omp_get_thread_limit} -- Maximum number of threads
+@table @asis
+@item @emph{Description}:
+Return the maximum number of threads of the program.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_thread_limit(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_thread_limit()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_max_threads}, @ref{OMP_THREAD_LIMIT}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.14.
+@end table
+
+
+
+@node omp_get_thread_num
+@section @code{omp_get_thread_num} -- Current thread ID
+@table @asis
+@item @emph{Description}:
+Returns a unique thread identification number within the current team.
+In a sequential parts of the program, @code{omp_get_thread_num}
+always returns 0. In parallel regions the return value varies
+from 0 to @code{omp_get_num_threads}-1 inclusive. The return
+value of the primary thread of a team is always 0.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_get_thread_num(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function omp_get_thread_num()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_num_threads}, @ref{omp_get_ancestor_thread_num}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.4.
+@end table
+
+
+
+@node omp_in_parallel
+@section @code{omp_in_parallel} -- Whether a parallel region is active
+@table @asis
+@item @emph{Description}:
+This function returns @code{true} if currently running in parallel,
+@code{false} otherwise. Here, @code{true} and @code{false} represent
+their language-specific counterparts.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_in_parallel(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{logical function omp_in_parallel()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.6.
+@end table
+
+
+@node omp_in_final
+@section @code{omp_in_final} -- Whether in final or included task region
+@table @asis
+@item @emph{Description}:
+This function returns @code{true} if currently running in a final
+or included task region, @code{false} otherwise. Here, @code{true}
+and @code{false} represent their language-specific counterparts.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_in_final(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{logical function omp_in_final()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.21.
+@end table
+
+
+
+@node omp_is_initial_device
+@section @code{omp_is_initial_device} -- Whether executing on the host device
+@table @asis
+@item @emph{Description}:
+This function returns @code{true} if currently running on the host device,
+@code{false} otherwise. Here, @code{true} and @code{false} represent
+their language-specific counterparts.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_is_initial_device(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{logical function omp_is_initial_device()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.34.
+@end table
+
+
+
+@node omp_set_default_device
+@section @code{omp_set_default_device} -- Set the default device for target regions
+@table @asis
+@item @emph{Description}:
+Set the default device for target regions without device clause. The argument
+shall be a nonnegative device number.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_default_device(int device_num);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_default_device(device_num)}
+@item @tab @code{integer device_num}
+@end multitable
+
+@item @emph{See also}:
+@ref{OMP_DEFAULT_DEVICE}, @ref{omp_get_default_device}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.29.
+@end table
+
+
+
+@node omp_set_dynamic
+@section @code{omp_set_dynamic} -- Enable/disable dynamic teams
+@table @asis
+@item @emph{Description}:
+Enable or disable the dynamic adjustment of the number of threads
+within a team. The function takes the language-specific equivalent
+of @code{true} and @code{false}, where @code{true} enables dynamic
+adjustment of team sizes and @code{false} disables it.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_dynamic(int dynamic_threads);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_dynamic(dynamic_threads)}
+@item @tab @code{logical, intent(in) :: dynamic_threads}
+@end multitable
+
+@item @emph{See also}:
+@ref{OMP_DYNAMIC}, @ref{omp_get_dynamic}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.7.
+@end table
+
+
+
+@node omp_set_max_active_levels
+@section @code{omp_set_max_active_levels} -- Limits the number of active parallel regions
+@table @asis
+@item @emph{Description}:
+This function limits the maximum allowed number of nested, active
+parallel regions. @var{max_levels} must be less or equal to
+the value returned by @code{omp_get_supported_active_levels}.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_max_active_levels(int max_levels);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_max_active_levels(max_levels)}
+@item @tab @code{integer max_levels}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_max_active_levels}, @ref{omp_get_active_level},
+@ref{omp_get_supported_active_levels}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.15.
+@end table
+
+
+
+@node omp_set_nested
+@section @code{omp_set_nested} -- Enable/disable nested parallel regions
+@table @asis
+@item @emph{Description}:
+Enable or disable nested parallel regions, i.e., whether team members
+are allowed to create new teams. The function takes the language-specific
+equivalent of @code{true} and @code{false}, where @code{true} enables
+dynamic adjustment of team sizes and @code{false} disables it.
+
+Enabling nested parallel regions will also set the maximum number of
+active nested regions to the maximum supported. Disabling nested parallel
+regions will set the maximum number of active nested regions to one.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_nested(int nested);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_nested(nested)}
+@item @tab @code{logical, intent(in) :: nested}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_nested}, @ref{omp_set_max_active_levels},
+@ref{OMP_MAX_ACTIVE_LEVELS}, @ref{OMP_NESTED}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.10.
+@end table
+
+
+
+@node omp_set_num_teams
+@section @code{omp_set_num_teams} -- Set upper teams limit for teams construct
+@table @asis
+@item @emph{Description}:
+Specifies the upper bound for number of teams created by the teams construct
+which does not specify a @code{num_teams} clause. The
+argument of @code{omp_set_num_teams} shall be a positive integer.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_num_teams(int num_teams);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_num_teams(num_teams)}
+@item @tab @code{integer, intent(in) :: num_teams}
+@end multitable
+
+@item @emph{See also}:
+@ref{OMP_NUM_TEAMS}, @ref{omp_get_num_teams}, @ref{omp_get_max_teams}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.1}, Section 3.4.3.
+@end table
+
+
+
+@node omp_set_num_threads
+@section @code{omp_set_num_threads} -- Set upper team size limit
+@table @asis
+@item @emph{Description}:
+Specifies the number of threads used by default in subsequent parallel
+sections, if those do not specify a @code{num_threads} clause. The
+argument of @code{omp_set_num_threads} shall be a positive integer.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_num_threads(int num_threads);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_num_threads(num_threads)}
+@item @tab @code{integer, intent(in) :: num_threads}
+@end multitable
+
+@item @emph{See also}:
+@ref{OMP_NUM_THREADS}, @ref{omp_get_num_threads}, @ref{omp_get_max_threads}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.1.
+@end table
+
+
+
+@node omp_set_schedule
+@section @code{omp_set_schedule} -- Set the runtime scheduling method
+@table @asis
+@item @emph{Description}:
+Sets the runtime scheduling method. The @var{kind} argument can have the
+value @code{omp_sched_static}, @code{omp_sched_dynamic},
+@code{omp_sched_guided} or @code{omp_sched_auto}. Except for
+@code{omp_sched_auto}, the chunk size is set to the value of
+@var{chunk_size} if positive, or to the default value if zero or negative.
+For @code{omp_sched_auto} the @var{chunk_size} argument is ignored.
+
+@item @emph{C/C++}
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_schedule(omp_sched_t kind, int chunk_size);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_schedule(kind, chunk_size)}
+@item @tab @code{integer(kind=omp_sched_kind) kind}
+@item @tab @code{integer chunk_size}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_schedule}
+@ref{OMP_SCHEDULE}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.2.12.
+@end table
+
+
+
+@node omp_set_teams_thread_limit
+@section @code{omp_set_teams_thread_limit} -- Set upper thread limit for teams construct
+@table @asis
+@item @emph{Description}:
+Specifies the upper bound for number of threads that will be available
+for each team created by the teams construct which does not specify a
+@code{thread_limit} clause. The argument of
+@code{omp_set_teams_thread_limit} shall be a positive integer.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_teams_thread_limit(int thread_limit);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_teams_thread_limit(thread_limit)}
+@item @tab @code{integer, intent(in) :: thread_limit}
+@end multitable
+
+@item @emph{See also}:
+@ref{OMP_TEAMS_THREAD_LIMIT}, @ref{omp_get_teams_thread_limit}, @ref{omp_get_thread_limit}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.1}, Section 3.4.5.
+@end table
+
+
+
+@node omp_init_lock
+@section @code{omp_init_lock} -- Initialize simple lock
+@table @asis
+@item @emph{Description}:
+Initialize a simple lock. After initialization, the lock is in
+an unlocked state.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_init_lock(omp_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_init_lock(svar)}
+@item @tab @code{integer(omp_lock_kind), intent(out) :: svar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_destroy_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.1.
+@end table
+
+
+
+@node omp_set_lock
+@section @code{omp_set_lock} -- Wait for and set simple lock
+@table @asis
+@item @emph{Description}:
+Before setting a simple lock, the lock variable must be initialized by
+@code{omp_init_lock}. The calling thread is blocked until the lock
+is available. If the lock is already held by the current thread,
+a deadlock occurs.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_lock(omp_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_lock(svar)}
+@item @tab @code{integer(omp_lock_kind), intent(inout) :: svar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_init_lock}, @ref{omp_test_lock}, @ref{omp_unset_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.4.
+@end table
+
+
+
+@node omp_test_lock
+@section @code{omp_test_lock} -- Test and set simple lock if available
+@table @asis
+@item @emph{Description}:
+Before setting a simple lock, the lock variable must be initialized by
+@code{omp_init_lock}. Contrary to @code{omp_set_lock}, @code{omp_test_lock}
+does not block if the lock is not available. This function returns
+@code{true} upon success, @code{false} otherwise. Here, @code{true} and
+@code{false} represent their language-specific counterparts.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_test_lock(omp_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{logical function omp_test_lock(svar)}
+@item @tab @code{integer(omp_lock_kind), intent(inout) :: svar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_init_lock}, @ref{omp_set_lock}, @ref{omp_set_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.6.
+@end table
+
+
+
+@node omp_unset_lock
+@section @code{omp_unset_lock} -- Unset simple lock
+@table @asis
+@item @emph{Description}:
+A simple lock about to be unset must have been locked by @code{omp_set_lock}
+or @code{omp_test_lock} before. In addition, the lock must be held by the
+thread calling @code{omp_unset_lock}. Then, the lock becomes unlocked. If one
+or more threads attempted to set the lock before, one of them is chosen to,
+again, set the lock to itself.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_unset_lock(omp_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_unset_lock(svar)}
+@item @tab @code{integer(omp_lock_kind), intent(inout) :: svar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_lock}, @ref{omp_test_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.5.
+@end table
+
+
+
+@node omp_destroy_lock
+@section @code{omp_destroy_lock} -- Destroy simple lock
+@table @asis
+@item @emph{Description}:
+Destroy a simple lock. In order to be destroyed, a simple lock must be
+in the unlocked state.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_destroy_lock(omp_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_destroy_lock(svar)}
+@item @tab @code{integer(omp_lock_kind), intent(inout) :: svar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_init_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.3.
+@end table
+
+
+
+@node omp_init_nest_lock
+@section @code{omp_init_nest_lock} -- Initialize nested lock
+@table @asis
+@item @emph{Description}:
+Initialize a nested lock. After initialization, the lock is in
+an unlocked state and the nesting count is set to zero.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_init_nest_lock(omp_nest_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_init_nest_lock(nvar)}
+@item @tab @code{integer(omp_nest_lock_kind), intent(out) :: nvar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_destroy_nest_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.1.
+@end table
+
+
+@node omp_set_nest_lock
+@section @code{omp_set_nest_lock} -- Wait for and set nested lock
+@table @asis
+@item @emph{Description}:
+Before setting a nested lock, the lock variable must be initialized by
+@code{omp_init_nest_lock}. The calling thread is blocked until the lock
+is available. If the lock is already held by the current thread, the
+nesting count for the lock is incremented.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_set_nest_lock(omp_nest_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_set_nest_lock(nvar)}
+@item @tab @code{integer(omp_nest_lock_kind), intent(inout) :: nvar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_init_nest_lock}, @ref{omp_unset_nest_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.4.
+@end table
+
+
+
+@node omp_test_nest_lock
+@section @code{omp_test_nest_lock} -- Test and set nested lock if available
+@table @asis
+@item @emph{Description}:
+Before setting a nested lock, the lock variable must be initialized by
+@code{omp_init_nest_lock}. Contrary to @code{omp_set_nest_lock},
+@code{omp_test_nest_lock} does not block if the lock is not available.
+If the lock is already held by the current thread, the new nesting count
+is returned. Otherwise, the return value equals zero.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int omp_test_nest_lock(omp_nest_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{logical function omp_test_nest_lock(nvar)}
+@item @tab @code{integer(omp_nest_lock_kind), intent(inout) :: nvar}
+@end multitable
+
+
+@item @emph{See also}:
+@ref{omp_init_lock}, @ref{omp_set_lock}, @ref{omp_set_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.6.
+@end table
+
+
+
+@node omp_unset_nest_lock
+@section @code{omp_unset_nest_lock} -- Unset nested lock
+@table @asis
+@item @emph{Description}:
+A nested lock about to be unset must have been locked by @code{omp_set_nested_lock}
+or @code{omp_test_nested_lock} before. In addition, the lock must be held by the
+thread calling @code{omp_unset_nested_lock}. If the nesting count drops to zero, the
+lock becomes unlocked. If one ore more threads attempted to set the lock before,
+one of them is chosen to, again, set the lock to itself.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_unset_nest_lock(omp_nest_lock_t *lock);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_unset_nest_lock(nvar)}
+@item @tab @code{integer(omp_nest_lock_kind), intent(inout) :: nvar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_set_nest_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.5.
+@end table
+
+
+
+@node omp_destroy_nest_lock
+@section @code{omp_destroy_nest_lock} -- Destroy nested lock
+@table @asis
+@item @emph{Description}:
+Destroy a nested lock. In order to be destroyed, a nested lock must be
+in the unlocked state and its nesting count must equal zero.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_destroy_nest_lock(omp_nest_lock_t *);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_destroy_nest_lock(nvar)}
+@item @tab @code{integer(omp_nest_lock_kind), intent(inout) :: nvar}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_init_lock}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.3.3.
+@end table
+
+
+
+@node omp_get_wtick
+@section @code{omp_get_wtick} -- Get timer precision
+@table @asis
+@item @emph{Description}:
+Gets the timer precision, i.e., the number of seconds between two
+successive clock ticks.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{double omp_get_wtick(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{double precision function omp_get_wtick()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_wtime}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.4.2.
+@end table
+
+
+
+@node omp_get_wtime
+@section @code{omp_get_wtime} -- Elapsed wall clock time
+@table @asis
+@item @emph{Description}:
+Elapsed wall clock time in seconds. The time is measured per thread, no
+guarantee can be made that two distinct threads measure the same time.
+Time is measured from some "time in the past", which is an arbitrary time
+guaranteed not to change during the execution of the program.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{double omp_get_wtime(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{double precision function omp_get_wtime()}
+@end multitable
+
+@item @emph{See also}:
+@ref{omp_get_wtick}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 3.4.1.
+@end table
+
+
+
+@node omp_fulfill_event
+@section @code{omp_fulfill_event} -- Fulfill and destroy an OpenMP event
+@table @asis
+@item @emph{Description}:
+Fulfill the event associated with the event handle argument. Currently, it
+is only used to fulfill events generated by detach clauses on task
+constructs - the effect of fulfilling the event is to allow the task to
+complete.
+
+The result of calling @code{omp_fulfill_event} with an event handle other
+than that generated by a detach clause is undefined. Calling it with an
+event handle that has already been fulfilled is also undefined.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void omp_fulfill_event(omp_event_handle_t event);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine omp_fulfill_event(event)}
+@item @tab @code{integer (kind=omp_event_handle_kind) :: event}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.0}, Section 3.5.1.
+@end table
+
+
+
+@c ---------------------------------------------------------------------
+@c OpenMP Environment Variables
+@c ---------------------------------------------------------------------
+
+@node Environment Variables
+@chapter OpenMP Environment Variables
+
+The environment variables which beginning with @env{OMP_} are defined by
+section 4 of the OpenMP specification in version 4.5, while those
+beginning with @env{GOMP_} are GNU extensions.
+
+@menu
+* OMP_CANCELLATION:: Set whether cancellation is activated
+* OMP_DISPLAY_ENV:: Show OpenMP version and environment variables
+* OMP_DEFAULT_DEVICE:: Set the device used in target regions
+* OMP_DYNAMIC:: Dynamic adjustment of threads
+* OMP_MAX_ACTIVE_LEVELS:: Set the maximum number of nested parallel regions
+* OMP_MAX_TASK_PRIORITY:: Set the maximum task priority value
+* OMP_NESTED:: Nested parallel regions
+* OMP_NUM_TEAMS:: Specifies the number of teams to use by teams region
+* OMP_NUM_THREADS:: Specifies the number of threads to use
+* OMP_PROC_BIND:: Whether theads may be moved between CPUs
+* OMP_PLACES:: Specifies on which CPUs the theads should be placed
+* OMP_STACKSIZE:: Set default thread stack size
+* OMP_SCHEDULE:: How threads are scheduled
+* OMP_TARGET_OFFLOAD:: Controls offloading behaviour
+* OMP_TEAMS_THREAD_LIMIT:: Set the maximum number of threads imposed by teams
+* OMP_THREAD_LIMIT:: Set the maximum number of threads
+* OMP_WAIT_POLICY:: How waiting threads are handled
+* GOMP_CPU_AFFINITY:: Bind threads to specific CPUs
+* GOMP_DEBUG:: Enable debugging output
+* GOMP_STACKSIZE:: Set default thread stack size
+* GOMP_SPINCOUNT:: Set the busy-wait spin count
+* GOMP_RTEMS_THREAD_POOLS:: Set the RTEMS specific thread pools
+@end menu
+
+
+@node OMP_CANCELLATION
+@section @env{OMP_CANCELLATION} -- Set whether cancellation is activated
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+If set to @code{TRUE}, the cancellation is activated. If set to @code{FALSE} or
+if unset, cancellation is disabled and the @code{cancel} construct is ignored.
+
+@item @emph{See also}:
+@ref{omp_get_cancellation}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.11
+@end table
+
+
+
+@node OMP_DISPLAY_ENV
+@section @env{OMP_DISPLAY_ENV} -- Show OpenMP version and environment variables
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+If set to @code{TRUE}, the OpenMP version number and the values
+associated with the OpenMP environment variables are printed to @code{stderr}.
+If set to @code{VERBOSE}, it additionally shows the value of the environment
+variables which are GNU extensions. If undefined or set to @code{FALSE},
+this information will not be shown.
+
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.12
+@end table
+
+
+
+@node OMP_DEFAULT_DEVICE
+@section @env{OMP_DEFAULT_DEVICE} -- Set the device used in target regions
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Set to choose the device which is used in a @code{target} region, unless the
+value is overridden by @code{omp_set_default_device} or by a @code{device}
+clause. The value shall be the nonnegative device number. If no device with
+the given device number exists, the code is executed on the host. If unset,
+device number 0 will be used.
+
+
+@item @emph{See also}:
+@ref{omp_get_default_device}, @ref{omp_set_default_device},
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.13
+@end table
+
+
+
+@node OMP_DYNAMIC
+@section @env{OMP_DYNAMIC} -- Dynamic adjustment of threads
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Enable or disable the dynamic adjustment of the number of threads
+within a team. The value of this environment variable shall be
+@code{TRUE} or @code{FALSE}. If undefined, dynamic adjustment is
+disabled by default.
+
+@item @emph{See also}:
+@ref{omp_set_dynamic}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.3
+@end table
+
+
+
+@node OMP_MAX_ACTIVE_LEVELS
+@section @env{OMP_MAX_ACTIVE_LEVELS} -- Set the maximum number of nested parallel regions
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Specifies the initial value for the maximum number of nested parallel
+regions. The value of this variable shall be a positive integer.
+If undefined, then if @env{OMP_NESTED} is defined and set to true, or
+if @env{OMP_NUM_THREADS} or @env{OMP_PROC_BIND} are defined and set to
+a list with more than one item, the maximum number of nested parallel
+regions will be initialized to the largest number supported, otherwise
+it will be set to one.
+
+@item @emph{See also}:
+@ref{omp_set_max_active_levels}, @ref{OMP_NESTED}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.9
+@end table
+
+
+
+@node OMP_MAX_TASK_PRIORITY
+@section @env{OMP_MAX_TASK_PRIORITY} -- Set the maximum priority
+number that can be set for a task.
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Specifies the initial value for the maximum priority value that can be
+set for a task. The value of this variable shall be a non-negative
+integer, and zero is allowed. If undefined, the default priority is
+0.
+
+@item @emph{See also}:
+@ref{omp_get_max_task_priority}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.14
+@end table
+
+
+
+@node OMP_NESTED
+@section @env{OMP_NESTED} -- Nested parallel regions
+@cindex Environment Variable
+@cindex Implementation specific setting
+@table @asis
+@item @emph{Description}:
+Enable or disable nested parallel regions, i.e., whether team members
+are allowed to create new teams. The value of this environment variable
+shall be @code{TRUE} or @code{FALSE}. If set to @code{TRUE}, the number
+of maximum active nested regions supported will by default be set to the
+maximum supported, otherwise it will be set to one. If
+@env{OMP_MAX_ACTIVE_LEVELS} is defined, its setting will override this
+setting. If both are undefined, nested parallel regions are enabled if
+@env{OMP_NUM_THREADS} or @env{OMP_PROC_BINDS} are defined to a list with
+more than one item, otherwise they are disabled by default.
+
+@item @emph{See also}:
+@ref{omp_set_max_active_levels}, @ref{omp_set_nested}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.6
+@end table
+
+
+
+@node OMP_NUM_TEAMS
+@section @env{OMP_NUM_TEAMS} -- Specifies the number of teams to use by teams region
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Specifies the upper bound for number of teams to use in teams regions
+without explicit @code{num_teams} clause. The value of this variable shall
+be a positive integer. If undefined it defaults to 0 which means
+implementation defined upper bound.
+
+@item @emph{See also}:
+@ref{omp_set_num_teams}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.1}, Section 6.23
+@end table
+
+
+
+@node OMP_NUM_THREADS
+@section @env{OMP_NUM_THREADS} -- Specifies the number of threads to use
+@cindex Environment Variable
+@cindex Implementation specific setting
+@table @asis
+@item @emph{Description}:
+Specifies the default number of threads to use in parallel regions. The
+value of this variable shall be a comma-separated list of positive integers;
+the value specifies the number of threads to use for the corresponding nested
+level. Specifying more than one item in the list will automatically enable
+nesting by default. If undefined one thread per CPU is used.
+
+@item @emph{See also}:
+@ref{omp_set_num_threads}, @ref{OMP_NESTED}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.2
+@end table
+
+
+
+@node OMP_PROC_BIND
+@section @env{OMP_PROC_BIND} -- Whether theads may be moved between CPUs
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Specifies whether threads may be moved between processors. If set to
+@code{TRUE}, OpenMP theads should not be moved; if set to @code{FALSE}
+they may be moved. Alternatively, a comma separated list with the
+values @code{PRIMARY}, @code{MASTER}, @code{CLOSE} and @code{SPREAD} can
+be used to specify the thread affinity policy for the corresponding nesting
+level. With @code{PRIMARY} and @code{MASTER} the worker threads are in the
+same place partition as the primary thread. With @code{CLOSE} those are
+kept close to the primary thread in contiguous place partitions. And
+with @code{SPREAD} a sparse distribution
+across the place partitions is used. Specifying more than one item in the
+list will automatically enable nesting by default.
+
+When undefined, @env{OMP_PROC_BIND} defaults to @code{TRUE} when
+@env{OMP_PLACES} or @env{GOMP_CPU_AFFINITY} is set and @code{FALSE} otherwise.
+
+@item @emph{See also}:
+@ref{omp_get_proc_bind}, @ref{GOMP_CPU_AFFINITY},
+@ref{OMP_NESTED}, @ref{OMP_PLACES}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.4
+@end table
+
+
+
+@node OMP_PLACES
+@section @env{OMP_PLACES} -- Specifies on which CPUs the theads should be placed
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+The thread placement can be either specified using an abstract name or by an
+explicit list of the places. The abstract names @code{threads}, @code{cores},
+@code{sockets}, @code{ll_caches} and @code{numa_domains} can be optionally
+followed by a positive number in parentheses, which denotes the how many places
+shall be created. With @code{threads} each place corresponds to a single
+hardware thread; @code{cores} to a single core with the corresponding number of
+hardware threads; with @code{sockets} the place corresponds to a single
+socket; with @code{ll_caches} to a set of cores that shares the last level
+cache on the device; and @code{numa_domains} to a set of cores for which their
+closest memory on the device is the same memory and at a similar distance from
+the cores. The resulting placement can be shown by setting the
+@env{OMP_DISPLAY_ENV} environment variable.
+
+Alternatively, the placement can be specified explicitly as comma-separated
+list of places. A place is specified by set of nonnegative numbers in curly
+braces, denoting the hardware threads. The curly braces can be omitted
+when only a single number has been specified. The hardware threads
+belonging to a place can either be specified as comma-separated list of
+nonnegative thread numbers or using an interval. Multiple places can also be
+either specified by a comma-separated list of places or by an interval. To
+specify an interval, a colon followed by the count is placed after
+the hardware thread number or the place. Optionally, the length can be
+followed by a colon and the stride number -- otherwise a unit stride is
+assumed. Placing an exclamation mark (@code{!}) directly before a curly
+brace or numbers inside the curly braces (excluding intervals) will
+exclude those hardware threads.
+
+For instance, the following specifies the same places list:
+@code{"@{0,1,2@}, @{3,4,6@}, @{7,8,9@}, @{10,11,12@}"};
+@code{"@{0:3@}, @{3:3@}, @{7:3@}, @{10:3@}"}; and @code{"@{0:2@}:4:3"}.
+
+If @env{OMP_PLACES} and @env{GOMP_CPU_AFFINITY} are unset and
+@env{OMP_PROC_BIND} is either unset or @code{false}, threads may be moved
+between CPUs following no placement policy.
+
+@item @emph{See also}:
+@ref{OMP_PROC_BIND}, @ref{GOMP_CPU_AFFINITY}, @ref{omp_get_proc_bind},
+@ref{OMP_DISPLAY_ENV}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.5
+@end table
+
+
+
+@node OMP_STACKSIZE
+@section @env{OMP_STACKSIZE} -- Set default thread stack size
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Set the default thread stack size in kilobytes, unless the number
+is suffixed by @code{B}, @code{K}, @code{M} or @code{G}, in which
+case the size is, respectively, in bytes, kilobytes, megabytes
+or gigabytes. This is different from @code{pthread_attr_setstacksize}
+which gets the number of bytes as an argument. If the stack size cannot
+be set due to system constraints, an error is reported and the initial
+stack size is left unchanged. If undefined, the stack size is system
+dependent.
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.7
+@end table
+
+
+
+@node OMP_SCHEDULE
+@section @env{OMP_SCHEDULE} -- How threads are scheduled
+@cindex Environment Variable
+@cindex Implementation specific setting
+@table @asis
+@item @emph{Description}:
+Allows to specify @code{schedule type} and @code{chunk size}.
+The value of the variable shall have the form: @code{type[,chunk]} where
+@code{type} is one of @code{static}, @code{dynamic}, @code{guided} or @code{auto}
+The optional @code{chunk} size shall be a positive integer. If undefined,
+dynamic scheduling and a chunk size of 1 is used.
+
+@item @emph{See also}:
+@ref{omp_set_schedule}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Sections 2.7.1.1 and 4.1
+@end table
+
+
+
+@node OMP_TARGET_OFFLOAD
+@section @env{OMP_TARGET_OFFLOAD} -- Controls offloading behaviour
+@cindex Environment Variable
+@cindex Implementation specific setting
+@table @asis
+@item @emph{Description}:
+Specifies the behaviour with regard to offloading code to a device. This
+variable can be set to one of three values - @code{MANDATORY}, @code{DISABLED}
+or @code{DEFAULT}.
+
+If set to @code{MANDATORY}, the program will terminate with an error if
+the offload device is not present or is not supported. If set to
+@code{DISABLED}, then offloading is disabled and all code will run on the
+host. If set to @code{DEFAULT}, the program will try offloading to the
+device first, then fall back to running code on the host if it cannot.
+
+If undefined, then the program will behave as if @code{DEFAULT} was set.
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.0}, Section 6.17
+@end table
+
+
+
+@node OMP_TEAMS_THREAD_LIMIT
+@section @env{OMP_TEAMS_THREAD_LIMIT} -- Set the maximum number of threads imposed by teams
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Specifies an upper bound for the number of threads to use by each contention
+group created by a teams construct without explicit @code{thread_limit}
+clause. The value of this variable shall be a positive integer. If undefined,
+the value of 0 is used which stands for an implementation defined upper
+limit.
+
+@item @emph{See also}:
+@ref{OMP_THREAD_LIMIT}, @ref{omp_set_teams_thread_limit}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v5.1}, Section 6.24
+@end table
+
+
+
+@node OMP_THREAD_LIMIT
+@section @env{OMP_THREAD_LIMIT} -- Set the maximum number of threads
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Specifies the number of threads to use for the whole program. The
+value of this variable shall be a positive integer. If undefined,
+the number of threads is not limited.
+
+@item @emph{See also}:
+@ref{OMP_NUM_THREADS}, @ref{omp_get_thread_limit}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.10
+@end table
+
+
+
+@node OMP_WAIT_POLICY
+@section @env{OMP_WAIT_POLICY} -- How waiting threads are handled
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Specifies whether waiting threads should be active or passive. If
+the value is @code{PASSIVE}, waiting threads should not consume CPU
+power while waiting; while the value is @code{ACTIVE} specifies that
+they should. If undefined, threads wait actively for a short time
+before waiting passively.
+
+@item @emph{See also}:
+@ref{GOMP_SPINCOUNT}
+
+@item @emph{Reference}:
+@uref{https://www.openmp.org, OpenMP specification v4.5}, Section 4.8
+@end table
+
+
+
+@node GOMP_CPU_AFFINITY
+@section @env{GOMP_CPU_AFFINITY} -- Bind threads to specific CPUs
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Binds threads to specific CPUs. The variable should contain a space-separated
+or comma-separated list of CPUs. This list may contain different kinds of
+entries: either single CPU numbers in any order, a range of CPUs (M-N)
+or a range with some stride (M-N:S). CPU numbers are zero based. For example,
+@code{GOMP_CPU_AFFINITY="0 3 1-2 4-15:2"} will bind the initial thread
+to CPU 0, the second to CPU 3, the third to CPU 1, the fourth to
+CPU 2, the fifth to CPU 4, the sixth through tenth to CPUs 6, 8, 10, 12,
+and 14 respectively and then start assigning back from the beginning of
+the list. @code{GOMP_CPU_AFFINITY=0} binds all threads to CPU 0.
+
+There is no libgomp library routine to determine whether a CPU affinity
+specification is in effect. As a workaround, language-specific library
+functions, e.g., @code{getenv} in C or @code{GET_ENVIRONMENT_VARIABLE} in
+Fortran, may be used to query the setting of the @code{GOMP_CPU_AFFINITY}
+environment variable. A defined CPU affinity on startup cannot be changed
+or disabled during the runtime of the application.
+
+If both @env{GOMP_CPU_AFFINITY} and @env{OMP_PROC_BIND} are set,
+@env{OMP_PROC_BIND} has a higher precedence. If neither has been set and
+@env{OMP_PROC_BIND} is unset, or when @env{OMP_PROC_BIND} is set to
+@code{FALSE}, the host system will handle the assignment of threads to CPUs.
+
+@item @emph{See also}:
+@ref{OMP_PLACES}, @ref{OMP_PROC_BIND}
+@end table
+
+
+
+@node GOMP_DEBUG
+@section @env{GOMP_DEBUG} -- Enable debugging output
+@cindex Environment Variable
+@table @asis
+@item @emph{Description}:
+Enable debugging output. The variable should be set to @code{0}
+(disabled, also the default if not set), or @code{1} (enabled).
+
+If enabled, some debugging output will be printed during execution.
+This is currently not specified in more detail, and subject to change.
+@end table
+
+
+
+@node GOMP_STACKSIZE
+@section @env{GOMP_STACKSIZE} -- Set default thread stack size
+@cindex Environment Variable
+@cindex Implementation specific setting
+@table @asis
+@item @emph{Description}:
+Set the default thread stack size in kilobytes. This is different from
+@code{pthread_attr_setstacksize} which gets the number of bytes as an
+argument. If the stack size cannot be set due to system constraints, an
+error is reported and the initial stack size is left unchanged. If undefined,
+the stack size is system dependent.
+
+@item @emph{See also}:
+@ref{OMP_STACKSIZE}
+
+@item @emph{Reference}:
+@uref{https://gcc.gnu.org/ml/gcc-patches/2006-06/msg00493.html,
+GCC Patches Mailinglist},
+@uref{https://gcc.gnu.org/ml/gcc-patches/2006-06/msg00496.html,
+GCC Patches Mailinglist}
+@end table
+
+
+
+@node GOMP_SPINCOUNT
+@section @env{GOMP_SPINCOUNT} -- Set the busy-wait spin count
+@cindex Environment Variable
+@cindex Implementation specific setting
+@table @asis
+@item @emph{Description}:
+Determines how long a threads waits actively with consuming CPU power
+before waiting passively without consuming CPU power. The value may be
+either @code{INFINITE}, @code{INFINITY} to always wait actively or an
+integer which gives the number of spins of the busy-wait loop. The
+integer may optionally be followed by the following suffixes acting
+as multiplication factors: @code{k} (kilo, thousand), @code{M} (mega,
+million), @code{G} (giga, billion), or @code{T} (tera, trillion).
+If undefined, 0 is used when @env{OMP_WAIT_POLICY} is @code{PASSIVE},
+300,000 is used when @env{OMP_WAIT_POLICY} is undefined and
+30 billion is used when @env{OMP_WAIT_POLICY} is @code{ACTIVE}.
+If there are more OpenMP threads than available CPUs, 1000 and 100
+spins are used for @env{OMP_WAIT_POLICY} being @code{ACTIVE} or
+undefined, respectively; unless the @env{GOMP_SPINCOUNT} is lower
+or @env{OMP_WAIT_POLICY} is @code{PASSIVE}.
+
+@item @emph{See also}:
+@ref{OMP_WAIT_POLICY}
+@end table
+
+
+
+@node GOMP_RTEMS_THREAD_POOLS
+@section @env{GOMP_RTEMS_THREAD_POOLS} -- Set the RTEMS specific thread pools
+@cindex Environment Variable
+@cindex Implementation specific setting
+@table @asis
+@item @emph{Description}:
+This environment variable is only used on the RTEMS real-time operating system.
+It determines the scheduler instance specific thread pools. The format for
+@env{GOMP_RTEMS_THREAD_POOLS} is a list of optional
+@code{<thread-pool-count>[$<priority>]@@<scheduler-name>} configurations
+separated by @code{:} where:
+@itemize @bullet
+@item @code{<thread-pool-count>} is the thread pool count for this scheduler
+instance.
+@item @code{$<priority>} is an optional priority for the worker threads of a
+thread pool according to @code{pthread_setschedparam}. In case a priority
+value is omitted, then a worker thread will inherit the priority of the OpenMP
+primary thread that created it. The priority of the worker thread is not
+changed after creation, even if a new OpenMP primary thread using the worker has
+a different priority.
+@item @code{@@<scheduler-name>} is the scheduler instance name according to the
+RTEMS application configuration.
+@end itemize
+In case no thread pool configuration is specified for a scheduler instance,
+then each OpenMP primary thread of this scheduler instance will use its own
+dynamically allocated thread pool. To limit the worker thread count of the
+thread pools, each OpenMP primary thread must call @code{omp_set_num_threads}.
+@item @emph{Example}:
+Lets suppose we have three scheduler instances @code{IO}, @code{WRK0}, and
+@code{WRK1} with @env{GOMP_RTEMS_THREAD_POOLS} set to
+@code{"1@@WRK0:3$4@@WRK1"}. Then there are no thread pool restrictions for
+scheduler instance @code{IO}. In the scheduler instance @code{WRK0} there is
+one thread pool available. Since no priority is specified for this scheduler
+instance, the worker thread inherits the priority of the OpenMP primary thread
+that created it. In the scheduler instance @code{WRK1} there are three thread
+pools available and their worker threads run at priority four.
+@end table
+
+
+
+@c ---------------------------------------------------------------------
+@c Enabling OpenACC
+@c ---------------------------------------------------------------------
+
+@node Enabling OpenACC
+@chapter Enabling OpenACC
+
+To activate the OpenACC extensions for C/C++ and Fortran, the compile-time
+flag @option{-fopenacc} must be specified. This enables the OpenACC directive
+@code{#pragma acc} in C/C++ and @code{!$acc} directives in free form,
+@code{c$acc}, @code{*$acc} and @code{!$acc} directives in fixed form,
+@code{!$} conditional compilation sentinels in free form and @code{c$},
+@code{*$} and @code{!$} sentinels in fixed form, for Fortran. The flag also
+arranges for automatic linking of the OpenACC runtime library
+(@ref{OpenACC Runtime Library Routines}).
+
+See @uref{https://gcc.gnu.org/wiki/OpenACC} for more information.
+
+A complete description of all OpenACC directives accepted may be found in
+the @uref{https://www.openacc.org, OpenACC} Application Programming
+Interface manual, version 2.6.
+
+
+
+@c ---------------------------------------------------------------------
+@c OpenACC Runtime Library Routines
+@c ---------------------------------------------------------------------
+
+@node OpenACC Runtime Library Routines
+@chapter OpenACC Runtime Library Routines
+
+The runtime routines described here are defined by section 3 of the OpenACC
+specifications in version 2.6.
+They have C linkage, and do not throw exceptions.
+Generally, they are available only for the host, with the exception of
+@code{acc_on_device}, which is available for both the host and the
+acceleration device.
+
+@menu
+* acc_get_num_devices:: Get number of devices for the given device
+ type.
+* acc_set_device_type:: Set type of device accelerator to use.
+* acc_get_device_type:: Get type of device accelerator to be used.
+* acc_set_device_num:: Set device number to use.
+* acc_get_device_num:: Get device number to be used.
+* acc_get_property:: Get device property.
+* acc_async_test:: Tests for completion of a specific asynchronous
+ operation.
+* acc_async_test_all:: Tests for completion of all asynchronous
+ operations.
+* acc_wait:: Wait for completion of a specific asynchronous
+ operation.
+* acc_wait_all:: Waits for completion of all asynchronous
+ operations.
+* acc_wait_all_async:: Wait for completion of all asynchronous
+ operations.
+* acc_wait_async:: Wait for completion of asynchronous operations.
+* acc_init:: Initialize runtime for a specific device type.
+* acc_shutdown:: Shuts down the runtime for a specific device
+ type.
+* acc_on_device:: Whether executing on a particular device
+* acc_malloc:: Allocate device memory.
+* acc_free:: Free device memory.
+* acc_copyin:: Allocate device memory and copy host memory to
+ it.
+* acc_present_or_copyin:: If the data is not present on the device,
+ allocate device memory and copy from host
+ memory.
+* acc_create:: Allocate device memory and map it to host
+ memory.
+* acc_present_or_create:: If the data is not present on the device,
+ allocate device memory and map it to host
+ memory.
+* acc_copyout:: Copy device memory to host memory.
+* acc_delete:: Free device memory.
+* acc_update_device:: Update device memory from mapped host memory.
+* acc_update_self:: Update host memory from mapped device memory.
+* acc_map_data:: Map previously allocated device memory to host
+ memory.
+* acc_unmap_data:: Unmap device memory from host memory.
+* acc_deviceptr:: Get device pointer associated with specific
+ host address.
+* acc_hostptr:: Get host pointer associated with specific
+ device address.
+* acc_is_present:: Indicate whether host variable / array is
+ present on device.
+* acc_memcpy_to_device:: Copy host memory to device memory.
+* acc_memcpy_from_device:: Copy device memory to host memory.
+* acc_attach:: Let device pointer point to device-pointer target.
+* acc_detach:: Let device pointer point to host-pointer target.
+
+API routines for target platforms.
+
+* acc_get_current_cuda_device:: Get CUDA device handle.
+* acc_get_current_cuda_context::Get CUDA context handle.
+* acc_get_cuda_stream:: Get CUDA stream handle.
+* acc_set_cuda_stream:: Set CUDA stream handle.
+
+API routines for the OpenACC Profiling Interface.
+
+* acc_prof_register:: Register callbacks.
+* acc_prof_unregister:: Unregister callbacks.
+* acc_prof_lookup:: Obtain inquiry functions.
+* acc_register_library:: Library registration.
+@end menu
+
+
+
+@node acc_get_num_devices
+@section @code{acc_get_num_devices} -- Get number of devices for given device type
+@table @asis
+@item @emph{Description}
+This function returns a value indicating the number of devices available
+for the device type specified in @var{devicetype}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int acc_get_num_devices(acc_device_t devicetype);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{integer function acc_get_num_devices(devicetype)}
+@item @tab @code{integer(kind=acc_device_kind) devicetype}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.1.
+@end table
+
+
+
+@node acc_set_device_type
+@section @code{acc_set_device_type} -- Set type of device accelerator to use.
+@table @asis
+@item @emph{Description}
+This function indicates to the runtime library which device type, specified
+in @var{devicetype}, to use when executing a parallel or kernels region.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_set_device_type(acc_device_t devicetype);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_set_device_type(devicetype)}
+@item @tab @code{integer(kind=acc_device_kind) devicetype}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.2.
+@end table
+
+
+
+@node acc_get_device_type
+@section @code{acc_get_device_type} -- Get type of device accelerator to be used.
+@table @asis
+@item @emph{Description}
+This function returns what device type will be used when executing a
+parallel or kernels region.
+
+This function returns @code{acc_device_none} if
+@code{acc_get_device_type} is called from
+@code{acc_ev_device_init_start}, @code{acc_ev_device_init_end}
+callbacks of the OpenACC Profiling Interface (@ref{OpenACC Profiling
+Interface}), that is, if the device is currently being initialized.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_device_t acc_get_device_type(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{function acc_get_device_type(void)}
+@item @tab @code{integer(kind=acc_device_kind) acc_get_device_type}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.3.
+@end table
+
+
+
+@node acc_set_device_num
+@section @code{acc_set_device_num} -- Set device number to use.
+@table @asis
+@item @emph{Description}
+This function will indicate to the runtime which device number,
+specified by @var{devicenum}, associated with the specified device
+type @var{devicetype}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_set_device_num(int devicenum, acc_device_t devicetype);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_set_device_num(devicenum, devicetype)}
+@item @tab @code{integer devicenum}
+@item @tab @code{integer(kind=acc_device_kind) devicetype}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.4.
+@end table
+
+
+
+@node acc_get_device_num
+@section @code{acc_get_device_num} -- Get device number to be used.
+@table @asis
+@item @emph{Description}
+This function returns which device number associated with the specified device
+type @var{devicetype}, will be used when executing a parallel or kernels
+region.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int acc_get_device_num(acc_device_t devicetype);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{function acc_get_device_num(devicetype)}
+@item @tab @code{integer(kind=acc_device_kind) devicetype}
+@item @tab @code{integer acc_get_device_num}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.5.
+@end table
+
+
+
+@node acc_get_property
+@section @code{acc_get_property} -- Get device property.
+@cindex acc_get_property
+@cindex acc_get_property_string
+@table @asis
+@item @emph{Description}
+These routines return the value of the specified @var{property} for the
+device being queried according to @var{devicenum} and @var{devicetype}.
+Integer-valued and string-valued properties are returned by
+@code{acc_get_property} and @code{acc_get_property_string} respectively.
+The Fortran @code{acc_get_property_string} subroutine returns the string
+retrieved in its fourth argument while the remaining entry points are
+functions, which pass the return value as their result.
+
+Note for Fortran, only: the OpenACC technical committee corrected and, hence,
+modified the interface introduced in OpenACC 2.6. The kind-value parameter
+@code{acc_device_property} has been renamed to @code{acc_device_property_kind}
+for consistency and the return type of the @code{acc_get_property} function is
+now a @code{c_size_t} integer instead of a @code{acc_device_property} integer.
+The parameter @code{acc_device_property} will continue to be provided,
+but might be removed in a future version of GCC.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{size_t acc_get_property(int devicenum, acc_device_t devicetype, acc_device_property_t property);}
+@item @emph{Prototype}: @tab @code{const char *acc_get_property_string(int devicenum, acc_device_t devicetype, acc_device_property_t property);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{function acc_get_property(devicenum, devicetype, property)}
+@item @emph{Interface}: @tab @code{subroutine acc_get_property_string(devicenum, devicetype, property, string)}
+@item @tab @code{use ISO_C_Binding, only: c_size_t}
+@item @tab @code{integer devicenum}
+@item @tab @code{integer(kind=acc_device_kind) devicetype}
+@item @tab @code{integer(kind=acc_device_property_kind) property}
+@item @tab @code{integer(kind=c_size_t) acc_get_property}
+@item @tab @code{character(*) string}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.6.
+@end table
+
+
+
+@node acc_async_test
+@section @code{acc_async_test} -- Test for completion of a specific asynchronous operation.
+@table @asis
+@item @emph{Description}
+This function tests for completion of the asynchronous operation specified
+in @var{arg}. In C/C++, a non-zero value will be returned to indicate
+the specified asynchronous operation has completed. While Fortran will return
+a @code{true}. If the asynchronous operation has not completed, C/C++ returns
+a zero and Fortran returns a @code{false}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int acc_async_test(int arg);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{function acc_async_test(arg)}
+@item @tab @code{integer(kind=acc_handle_kind) arg}
+@item @tab @code{logical acc_async_test}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.9.
+@end table
+
+
+
+@node acc_async_test_all
+@section @code{acc_async_test_all} -- Tests for completion of all asynchronous operations.
+@table @asis
+@item @emph{Description}
+This function tests for completion of all asynchronous operations.
+In C/C++, a non-zero value will be returned to indicate all asynchronous
+operations have completed. While Fortran will return a @code{true}. If
+any asynchronous operation has not completed, C/C++ returns a zero and
+Fortran returns a @code{false}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int acc_async_test_all(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{function acc_async_test()}
+@item @tab @code{logical acc_get_device_num}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.10.
+@end table
+
+
+
+@node acc_wait
+@section @code{acc_wait} -- Wait for completion of a specific asynchronous operation.
+@table @asis
+@item @emph{Description}
+This function waits for completion of the asynchronous operation
+specified in @var{arg}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_wait(arg);}
+@item @emph{Prototype (OpenACC 1.0 compatibility)}: @tab @code{acc_async_wait(arg);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_wait(arg)}
+@item @tab @code{integer(acc_handle_kind) arg}
+@item @emph{Interface (OpenACC 1.0 compatibility)}: @tab @code{subroutine acc_async_wait(arg)}
+@item @tab @code{integer(acc_handle_kind) arg}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.11.
+@end table
+
+
+
+@node acc_wait_all
+@section @code{acc_wait_all} -- Waits for completion of all asynchronous operations.
+@table @asis
+@item @emph{Description}
+This function waits for the completion of all asynchronous operations.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_wait_all(void);}
+@item @emph{Prototype (OpenACC 1.0 compatibility)}: @tab @code{acc_async_wait_all(void);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_wait_all()}
+@item @emph{Interface (OpenACC 1.0 compatibility)}: @tab @code{subroutine acc_async_wait_all()}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.13.
+@end table
+
+
+
+@node acc_wait_all_async
+@section @code{acc_wait_all_async} -- Wait for completion of all asynchronous operations.
+@table @asis
+@item @emph{Description}
+This function enqueues a wait operation on the queue @var{async} for any
+and all asynchronous operations that have been previously enqueued on
+any queue.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_wait_all_async(int async);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_wait_all_async(async)}
+@item @tab @code{integer(acc_handle_kind) async}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.14.
+@end table
+
+
+
+@node acc_wait_async
+@section @code{acc_wait_async} -- Wait for completion of asynchronous operations.
+@table @asis
+@item @emph{Description}
+This function enqueues a wait operation on queue @var{async} for any and all
+asynchronous operations enqueued on queue @var{arg}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_wait_async(int arg, int async);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_wait_async(arg, async)}
+@item @tab @code{integer(acc_handle_kind) arg, async}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.12.
+@end table
+
+
+
+@node acc_init
+@section @code{acc_init} -- Initialize runtime for a specific device type.
+@table @asis
+@item @emph{Description}
+This function initializes the runtime for the device type specified in
+@var{devicetype}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_init(acc_device_t devicetype);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_init(devicetype)}
+@item @tab @code{integer(acc_device_kind) devicetype}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.7.
+@end table
+
+
+
+@node acc_shutdown
+@section @code{acc_shutdown} -- Shuts down the runtime for a specific device type.
+@table @asis
+@item @emph{Description}
+This function shuts down the runtime for the device type specified in
+@var{devicetype}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_shutdown(acc_device_t devicetype);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_shutdown(devicetype)}
+@item @tab @code{integer(acc_device_kind) devicetype}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.8.
+@end table
+
+
+
+@node acc_on_device
+@section @code{acc_on_device} -- Whether executing on a particular device
+@table @asis
+@item @emph{Description}:
+This function returns whether the program is executing on a particular
+device specified in @var{devicetype}. In C/C++ a non-zero value is
+returned to indicate the device is executing on the specified device type.
+In Fortran, @code{true} will be returned. If the program is not executing
+on the specified device type C/C++ will return a zero, while Fortran will
+return @code{false}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_on_device(acc_device_t devicetype);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{function acc_on_device(devicetype)}
+@item @tab @code{integer(acc_device_kind) devicetype}
+@item @tab @code{logical acc_on_device}
+@end multitable
+
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.17.
+@end table
+
+
+
+@node acc_malloc
+@section @code{acc_malloc} -- Allocate device memory.
+@table @asis
+@item @emph{Description}
+This function allocates @var{len} bytes of device memory. It returns
+the device address of the allocated memory.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{d_void* acc_malloc(size_t len);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.18.
+@end table
+
+
+
+@node acc_free
+@section @code{acc_free} -- Free device memory.
+@table @asis
+@item @emph{Description}
+Free previously allocated device memory at the device address @code{a}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_free(d_void *a);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.19.
+@end table
+
+
+
+@node acc_copyin
+@section @code{acc_copyin} -- Allocate device memory and copy host memory to it.
+@table @asis
+@item @emph{Description}
+In C/C++, this function allocates @var{len} bytes of device memory
+and maps it to the specified host address in @var{a}. The device
+address of the newly allocated device memory is returned.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a
+variable or array element and @var{len} specifies the length in bytes.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_copyin(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{void *acc_copyin_async(h_void *a, size_t len, int async);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_copyin(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_copyin(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_copyin_async(a, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_copyin_async(a, len, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.20.
+@end table
+
+
+
+@node acc_present_or_copyin
+@section @code{acc_present_or_copyin} -- If the data is not present on the device, allocate device memory and copy from host memory.
+@table @asis
+@item @emph{Description}
+This function tests if the host data specified by @var{a} and of length
+@var{len} is present or not. If it is not present, then device memory
+will be allocated and the host memory copied. The device address of
+the newly allocated device memory is returned.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a variable or
+array element and @var{len} specifies the length in bytes.
+
+Note that @code{acc_present_or_copyin} and @code{acc_pcopyin} exist for
+backward compatibility with OpenACC 2.0; use @ref{acc_copyin} instead.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_present_or_copyin(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{void *acc_pcopyin(h_void *a, size_t len);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_present_or_copyin(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_present_or_copyin(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_pcopyin(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_pcopyin(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.20.
+@end table
+
+
+
+@node acc_create
+@section @code{acc_create} -- Allocate device memory and map it to host memory.
+@table @asis
+@item @emph{Description}
+This function allocates device memory and maps it to host memory specified
+by the host address @var{a} with a length of @var{len} bytes. In C/C++,
+the function returns the device address of the allocated device memory.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a variable or
+array element and @var{len} specifies the length in bytes.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_create(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{void *acc_create_async(h_void *a, size_t len, int async);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_create(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_create(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_create_async(a, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_create_async(a, len, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.21.
+@end table
+
+
+
+@node acc_present_or_create
+@section @code{acc_present_or_create} -- If the data is not present on the device, allocate device memory and map it to host memory.
+@table @asis
+@item @emph{Description}
+This function tests if the host data specified by @var{a} and of length
+@var{len} is present or not. If it is not present, then device memory
+will be allocated and mapped to host memory. In C/C++, the device address
+of the newly allocated device memory is returned.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a variable or
+array element and @var{len} specifies the length in bytes.
+
+Note that @code{acc_present_or_create} and @code{acc_pcreate} exist for
+backward compatibility with OpenACC 2.0; use @ref{acc_create} instead.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_present_or_create(h_void *a, size_t len)}
+@item @emph{Prototype}: @tab @code{void *acc_pcreate(h_void *a, size_t len)}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_present_or_create(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_present_or_create(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_pcreate(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_pcreate(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.21.
+@end table
+
+
+
+@node acc_copyout
+@section @code{acc_copyout} -- Copy device memory to host memory.
+@table @asis
+@item @emph{Description}
+This function copies mapped device memory to host memory which is specified
+by host address @var{a} for a length @var{len} bytes in C/C++.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a variable or
+array element and @var{len} specifies the length in bytes.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_copyout(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{acc_copyout_async(h_void *a, size_t len, int async);}
+@item @emph{Prototype}: @tab @code{acc_copyout_finalize(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{acc_copyout_finalize_async(h_void *a, size_t len, int async);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_copyout(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_copyout(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_copyout_async(a, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_copyout_async(a, len, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_copyout_finalize(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_copyout_finalize(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_copyout_finalize_async(a, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_copyout_finalize_async(a, len, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.22.
+@end table
+
+
+
+@node acc_delete
+@section @code{acc_delete} -- Free device memory.
+@table @asis
+@item @emph{Description}
+This function frees previously allocated device memory specified by
+the device address @var{a} and the length of @var{len} bytes.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a variable or
+array element and @var{len} specifies the length in bytes.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_delete(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{acc_delete_async(h_void *a, size_t len, int async);}
+@item @emph{Prototype}: @tab @code{acc_delete_finalize(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{acc_delete_finalize_async(h_void *a, size_t len, int async);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_delete(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_delete(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_delete_async(a, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_delete_async(a, len, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_delete_finalize(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_delete_finalize(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_delete_async_finalize(a, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_delete_async_finalize(a, len, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.23.
+@end table
+
+
+
+@node acc_update_device
+@section @code{acc_update_device} -- Update device memory from mapped host memory.
+@table @asis
+@item @emph{Description}
+This function updates the device copy from the previously mapped host memory.
+The host memory is specified with the host address @var{a} and a length of
+@var{len} bytes.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a variable or
+array element and @var{len} specifies the length in bytes.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_update_device(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{acc_update_device(h_void *a, size_t len, async);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_update_device(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_update_device(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_update_device_async(a, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_update_device_async(a, len, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.24.
+@end table
+
+
+
+@node acc_update_self
+@section @code{acc_update_self} -- Update host memory from mapped device memory.
+@table @asis
+@item @emph{Description}
+This function updates the host copy from the previously mapped device memory.
+The host memory is specified with the host address @var{a} and a length of
+@var{len} bytes.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a variable or
+array element and @var{len} specifies the length in bytes.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_update_self(h_void *a, size_t len);}
+@item @emph{Prototype}: @tab @code{acc_update_self_async(h_void *a, size_t len, int async);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{subroutine acc_update_self(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @emph{Interface}: @tab @code{subroutine acc_update_self(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @emph{Interface}: @tab @code{subroutine acc_update_self_async(a, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@item @emph{Interface}: @tab @code{subroutine acc_update_self_async(a, len, async)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{integer(acc_handle_kind) :: async}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.25.
+@end table
+
+
+
+@node acc_map_data
+@section @code{acc_map_data} -- Map previously allocated device memory to host memory.
+@table @asis
+@item @emph{Description}
+This function maps previously allocated device and host memory. The device
+memory is specified with the device address @var{d}. The host memory is
+specified with the host address @var{h} and a length of @var{len}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_map_data(h_void *h, d_void *d, size_t len);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.26.
+@end table
+
+
+
+@node acc_unmap_data
+@section @code{acc_unmap_data} -- Unmap device memory from host memory.
+@table @asis
+@item @emph{Description}
+This function unmaps previously mapped device and host memory. The latter
+specified by @var{h}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_unmap_data(h_void *h);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.27.
+@end table
+
+
+
+@node acc_deviceptr
+@section @code{acc_deviceptr} -- Get device pointer associated with specific host address.
+@table @asis
+@item @emph{Description}
+This function returns the device address that has been mapped to the
+host address specified by @var{h}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_deviceptr(h_void *h);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.28.
+@end table
+
+
+
+@node acc_hostptr
+@section @code{acc_hostptr} -- Get host pointer associated with specific device address.
+@table @asis
+@item @emph{Description}
+This function returns the host address that has been mapped to the
+device address specified by @var{d}.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_hostptr(d_void *d);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.29.
+@end table
+
+
+
+@node acc_is_present
+@section @code{acc_is_present} -- Indicate whether host variable / array is present on device.
+@table @asis
+@item @emph{Description}
+This function indicates whether the specified host address in @var{a} and a
+length of @var{len} bytes is present on the device. In C/C++, a non-zero
+value is returned to indicate the presence of the mapped memory on the
+device. A zero is returned to indicate the memory is not mapped on the
+device.
+
+In Fortran, two (2) forms are supported. In the first form, @var{a} specifies
+a contiguous array section. The second form @var{a} specifies a variable or
+array element and @var{len} specifies the length in bytes. If the host
+memory is mapped to device memory, then a @code{true} is returned. Otherwise,
+a @code{false} is return to indicate the mapped memory is not present.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int acc_is_present(h_void *a, size_t len);}
+@end multitable
+
+@item @emph{Fortran}:
+@multitable @columnfractions .20 .80
+@item @emph{Interface}: @tab @code{function acc_is_present(a)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{logical acc_is_present}
+@item @emph{Interface}: @tab @code{function acc_is_present(a, len)}
+@item @tab @code{type, dimension(:[,:]...) :: a}
+@item @tab @code{integer len}
+@item @tab @code{logical acc_is_present}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.30.
+@end table
+
+
+
+@node acc_memcpy_to_device
+@section @code{acc_memcpy_to_device} -- Copy host memory to device memory.
+@table @asis
+@item @emph{Description}
+This function copies host memory specified by host address of @var{src} to
+device memory specified by the device address @var{dest} for a length of
+@var{bytes} bytes.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_memcpy_to_device(d_void *dest, h_void *src, size_t bytes);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.31.
+@end table
+
+
+
+@node acc_memcpy_from_device
+@section @code{acc_memcpy_from_device} -- Copy device memory to host memory.
+@table @asis
+@item @emph{Description}
+This function copies host memory specified by host address of @var{src} from
+device memory specified by the device address @var{dest} for a length of
+@var{bytes} bytes.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_memcpy_from_device(d_void *dest, h_void *src, size_t bytes);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.32.
+@end table
+
+
+
+@node acc_attach
+@section @code{acc_attach} -- Let device pointer point to device-pointer target.
+@table @asis
+@item @emph{Description}
+This function updates a pointer on the device from pointing to a host-pointer
+address to pointing to the corresponding device data.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_attach(h_void **ptr);}
+@item @emph{Prototype}: @tab @code{acc_attach_async(h_void **ptr, int async);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.34.
+@end table
+
+
+
+@node acc_detach
+@section @code{acc_detach} -- Let device pointer point to host-pointer target.
+@table @asis
+@item @emph{Description}
+This function updates a pointer on the device from pointing to a device-pointer
+address to pointing to the corresponding host data.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_detach(h_void **ptr);}
+@item @emph{Prototype}: @tab @code{acc_detach_async(h_void **ptr, int async);}
+@item @emph{Prototype}: @tab @code{acc_detach_finalize(h_void **ptr);}
+@item @emph{Prototype}: @tab @code{acc_detach_finalize_async(h_void **ptr, int async);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+3.2.35.
+@end table
+
+
+
+@node acc_get_current_cuda_device
+@section @code{acc_get_current_cuda_device} -- Get CUDA device handle.
+@table @asis
+@item @emph{Description}
+This function returns the CUDA device handle. This handle is the same
+as used by the CUDA Runtime or Driver API's.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_get_current_cuda_device(void);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+A.2.1.1.
+@end table
+
+
+
+@node acc_get_current_cuda_context
+@section @code{acc_get_current_cuda_context} -- Get CUDA context handle.
+@table @asis
+@item @emph{Description}
+This function returns the CUDA context handle. This handle is the same
+as used by the CUDA Runtime or Driver API's.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_get_current_cuda_context(void);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+A.2.1.2.
+@end table
+
+
+
+@node acc_get_cuda_stream
+@section @code{acc_get_cuda_stream} -- Get CUDA stream handle.
+@table @asis
+@item @emph{Description}
+This function returns the CUDA stream handle for the queue @var{async}.
+This handle is the same as used by the CUDA Runtime or Driver API's.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void *acc_get_cuda_stream(int async);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+A.2.1.3.
+@end table
+
+
+
+@node acc_set_cuda_stream
+@section @code{acc_set_cuda_stream} -- Set CUDA stream handle.
+@table @asis
+@item @emph{Description}
+This function associates the stream handle specified by @var{stream} with
+the queue @var{async}.
+
+This cannot be used to change the stream handle associated with
+@code{acc_async_sync}.
+
+The return value is not specified.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{int acc_set_cuda_stream(int async, void *stream);}
+@end multitable
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+A.2.1.4.
+@end table
+
+
+
+@node acc_prof_register
+@section @code{acc_prof_register} -- Register callbacks.
+@table @asis
+@item @emph{Description}:
+This function registers callbacks.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void acc_prof_register (acc_event_t, acc_prof_callback, acc_register_t);}
+@end multitable
+
+@item @emph{See also}:
+@ref{OpenACC Profiling Interface}
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+5.3.
+@end table
+
+
+
+@node acc_prof_unregister
+@section @code{acc_prof_unregister} -- Unregister callbacks.
+@table @asis
+@item @emph{Description}:
+This function unregisters callbacks.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void acc_prof_unregister (acc_event_t, acc_prof_callback, acc_register_t);}
+@end multitable
+
+@item @emph{See also}:
+@ref{OpenACC Profiling Interface}
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+5.3.
+@end table
+
+
+
+@node acc_prof_lookup
+@section @code{acc_prof_lookup} -- Obtain inquiry functions.
+@table @asis
+@item @emph{Description}:
+Function to obtain inquiry functions.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{acc_query_fn acc_prof_lookup (const char *);}
+@end multitable
+
+@item @emph{See also}:
+@ref{OpenACC Profiling Interface}
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+5.3.
+@end table
+
+
+
+@node acc_register_library
+@section @code{acc_register_library} -- Library registration.
+@table @asis
+@item @emph{Description}:
+Function for library registration.
+
+@item @emph{C/C++}:
+@multitable @columnfractions .20 .80
+@item @emph{Prototype}: @tab @code{void acc_register_library (acc_prof_reg, acc_prof_reg, acc_prof_lookup_func);}
+@end multitable
+
+@item @emph{See also}:
+@ref{OpenACC Profiling Interface}, @ref{ACC_PROFLIB}
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+5.3.
+@end table
+
+
+
+@c ---------------------------------------------------------------------
+@c OpenACC Environment Variables
+@c ---------------------------------------------------------------------
+
+@node OpenACC Environment Variables
+@chapter OpenACC Environment Variables
+
+The variables @env{ACC_DEVICE_TYPE} and @env{ACC_DEVICE_NUM}
+are defined by section 4 of the OpenACC specification in version 2.0.
+The variable @env{ACC_PROFLIB}
+is defined by section 4 of the OpenACC specification in version 2.6.
+The variable @env{GCC_ACC_NOTIFY} is used for diagnostic purposes.
+
+@menu
+* ACC_DEVICE_TYPE::
+* ACC_DEVICE_NUM::
+* ACC_PROFLIB::
+* GCC_ACC_NOTIFY::
+@end menu
+
+
+
+@node ACC_DEVICE_TYPE
+@section @code{ACC_DEVICE_TYPE}
+@table @asis
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+4.1.
+@end table
+
+
+
+@node ACC_DEVICE_NUM
+@section @code{ACC_DEVICE_NUM}
+@table @asis
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+4.2.
+@end table
+
+
+
+@node ACC_PROFLIB
+@section @code{ACC_PROFLIB}
+@table @asis
+@item @emph{See also}:
+@ref{acc_register_library}, @ref{OpenACC Profiling Interface}
+
+@item @emph{Reference}:
+@uref{https://www.openacc.org, OpenACC specification v2.6}, section
+4.3.
+@end table
+
+
+
+@node GCC_ACC_NOTIFY
+@section @code{GCC_ACC_NOTIFY}
+@table @asis
+@item @emph{Description}:
+Print debug information pertaining to the accelerator.
+@end table
+
+
+
+@c ---------------------------------------------------------------------
+@c CUDA Streams Usage
+@c ---------------------------------------------------------------------
+
+@node CUDA Streams Usage
+@chapter CUDA Streams Usage
+
+This applies to the @code{nvptx} plugin only.
+
+The library provides elements that perform asynchronous movement of
+data and asynchronous operation of computing constructs. This
+asynchronous functionality is implemented by making use of CUDA
+streams@footnote{See "Stream Management" in "CUDA Driver API",
+TRM-06703-001, Version 5.5, for additional information}.
+
+The primary means by that the asynchronous functionality is accessed
+is through the use of those OpenACC directives which make use of the
+@code{async} and @code{wait} clauses. When the @code{async} clause is
+first used with a directive, it creates a CUDA stream. If an
+@code{async-argument} is used with the @code{async} clause, then the
+stream is associated with the specified @code{async-argument}.
+
+Following the creation of an association between a CUDA stream and the
+@code{async-argument} of an @code{async} clause, both the @code{wait}
+clause and the @code{wait} directive can be used. When either the
+clause or directive is used after stream creation, it creates a
+rendezvous point whereby execution waits until all operations
+associated with the @code{async-argument}, that is, stream, have
+completed.
+
+Normally, the management of the streams that are created as a result of
+using the @code{async} clause, is done without any intervention by the
+caller. This implies the association between the @code{async-argument}
+and the CUDA stream will be maintained for the lifetime of the program.
+However, this association can be changed through the use of the library
+function @code{acc_set_cuda_stream}. When the function
+@code{acc_set_cuda_stream} is called, the CUDA stream that was
+originally associated with the @code{async} clause will be destroyed.
+Caution should be taken when changing the association as subsequent
+references to the @code{async-argument} refer to a different
+CUDA stream.
+
+
+
+@c ---------------------------------------------------------------------
+@c OpenACC Library Interoperability
+@c ---------------------------------------------------------------------
+
+@node OpenACC Library Interoperability
+@chapter OpenACC Library Interoperability
+
+@section Introduction
+
+The OpenACC library uses the CUDA Driver API, and may interact with
+programs that use the Runtime library directly, or another library
+based on the Runtime library, e.g., CUBLAS@footnote{See section 2.26,
+"Interactions with the CUDA Driver API" in
+"CUDA Runtime API", Version 5.5, and section 2.27, "VDPAU
+Interoperability", in "CUDA Driver API", TRM-06703-001, Version 5.5,
+for additional information on library interoperability.}.
+This chapter describes the use cases and what changes are
+required in order to use both the OpenACC library and the CUBLAS and Runtime
+libraries within a program.
+
+@section First invocation: NVIDIA CUBLAS library API
+
+In this first use case (see below), a function in the CUBLAS library is called
+prior to any of the functions in the OpenACC library. More specifically, the
+function @code{cublasCreate()}.
+
+When invoked, the function initializes the library and allocates the
+hardware resources on the host and the device on behalf of the caller. Once
+the initialization and allocation has completed, a handle is returned to the
+caller. The OpenACC library also requires initialization and allocation of
+hardware resources. Since the CUBLAS library has already allocated the
+hardware resources for the device, all that is left to do is to initialize
+the OpenACC library and acquire the hardware resources on the host.
+
+Prior to calling the OpenACC function that initializes the library and
+allocate the host hardware resources, you need to acquire the device number
+that was allocated during the call to @code{cublasCreate()}. The invoking of the
+runtime library function @code{cudaGetDevice()} accomplishes this. Once
+acquired, the device number is passed along with the device type as
+parameters to the OpenACC library function @code{acc_set_device_num()}.
+
+Once the call to @code{acc_set_device_num()} has completed, the OpenACC
+library uses the context that was created during the call to
+@code{cublasCreate()}. In other words, both libraries will be sharing the
+same context.
+
+@smallexample
+ /* Create the handle */
+ s = cublasCreate(&h);
+ if (s != CUBLAS_STATUS_SUCCESS)
+ @{
+ fprintf(stderr, "cublasCreate failed %d\n", s);
+ exit(EXIT_FAILURE);
+ @}
+
+ /* Get the device number */
+ e = cudaGetDevice(&dev);
+ if (e != cudaSuccess)
+ @{
+ fprintf(stderr, "cudaGetDevice failed %d\n", e);
+ exit(EXIT_FAILURE);
+ @}
+
+ /* Initialize OpenACC library and use device 'dev' */
+ acc_set_device_num(dev, acc_device_nvidia);
+
+@end smallexample
+@center Use Case 1
+
+@section First invocation: OpenACC library API
+
+In this second use case (see below), a function in the OpenACC library is
+called prior to any of the functions in the CUBLAS library. More specificially,
+the function @code{acc_set_device_num()}.
+
+In the use case presented here, the function @code{acc_set_device_num()}
+is used to both initialize the OpenACC library and allocate the hardware
+resources on the host and the device. In the call to the function, the
+call parameters specify which device to use and what device
+type to use, i.e., @code{acc_device_nvidia}. It should be noted that this
+is but one method to initialize the OpenACC library and allocate the
+appropriate hardware resources. Other methods are available through the
+use of environment variables and these will be discussed in the next section.
+
+Once the call to @code{acc_set_device_num()} has completed, other OpenACC
+functions can be called as seen with multiple calls being made to
+@code{acc_copyin()}. In addition, calls can be made to functions in the
+CUBLAS library. In the use case a call to @code{cublasCreate()} is made
+subsequent to the calls to @code{acc_copyin()}.
+As seen in the previous use case, a call to @code{cublasCreate()}
+initializes the CUBLAS library and allocates the hardware resources on the
+host and the device. However, since the device has already been allocated,
+@code{cublasCreate()} will only initialize the CUBLAS library and allocate
+the appropriate hardware resources on the host. The context that was created
+as part of the OpenACC initialization is shared with the CUBLAS library,
+similarly to the first use case.
+
+@smallexample
+ dev = 0;
+
+ acc_set_device_num(dev, acc_device_nvidia);
+
+ /* Copy the first set to the device */
+ d_X = acc_copyin(&h_X[0], N * sizeof (float));
+ if (d_X == NULL)
+ @{
+ fprintf(stderr, "copyin error h_X\n");
+ exit(EXIT_FAILURE);
+ @}
+
+ /* Copy the second set to the device */
+ d_Y = acc_copyin(&h_Y1[0], N * sizeof (float));
+ if (d_Y == NULL)
+ @{
+ fprintf(stderr, "copyin error h_Y1\n");
+ exit(EXIT_FAILURE);
+ @}
+
+ /* Create the handle */
+ s = cublasCreate(&h);
+ if (s != CUBLAS_STATUS_SUCCESS)
+ @{
+ fprintf(stderr, "cublasCreate failed %d\n", s);
+ exit(EXIT_FAILURE);
+ @}
+
+ /* Perform saxpy using CUBLAS library function */
+ s = cublasSaxpy(h, N, &alpha, d_X, 1, d_Y, 1);
+ if (s != CUBLAS_STATUS_SUCCESS)
+ @{
+ fprintf(stderr, "cublasSaxpy failed %d\n", s);
+ exit(EXIT_FAILURE);
+ @}
+
+ /* Copy the results from the device */
+ acc_memcpy_from_device(&h_Y1[0], d_Y, N * sizeof (float));
+
+@end smallexample
+@center Use Case 2
+
+@section OpenACC library and environment variables
+
+There are two environment variables associated with the OpenACC library
+that may be used to control the device type and device number:
+@env{ACC_DEVICE_TYPE} and @env{ACC_DEVICE_NUM}, respectively. These two
+environment variables can be used as an alternative to calling
+@code{acc_set_device_num()}. As seen in the second use case, the device
+type and device number were specified using @code{acc_set_device_num()}.
+If however, the aforementioned environment variables were set, then the
+call to @code{acc_set_device_num()} would not be required.
+
+
+The use of the environment variables is only relevant when an OpenACC function
+is called prior to a call to @code{cudaCreate()}. If @code{cudaCreate()}
+is called prior to a call to an OpenACC function, then you must call
+@code{acc_set_device_num()}@footnote{More complete information
+about @env{ACC_DEVICE_TYPE} and @env{ACC_DEVICE_NUM} can be found in
+sections 4.1 and 4.2 of the @uref{https://www.openacc.org, OpenACC}
+Application Programming Interface”, Version 2.6.}
+
+
+
+@c ---------------------------------------------------------------------
+@c OpenACC Profiling Interface
+@c ---------------------------------------------------------------------
+
+@node OpenACC Profiling Interface
+@chapter OpenACC Profiling Interface
+
+@section Implementation Status and Implementation-Defined Behavior
+
+We're implementing the OpenACC Profiling Interface as defined by the
+OpenACC 2.6 specification. We're clarifying some aspects here as
+@emph{implementation-defined behavior}, while they're still under
+discussion within the OpenACC Technical Committee.
+
+This implementation is tuned to keep the performance impact as low as
+possible for the (very common) case that the Profiling Interface is
+not enabled. This is relevant, as the Profiling Interface affects all
+the @emph{hot} code paths (in the target code, not in the offloaded
+code). Users of the OpenACC Profiling Interface can be expected to
+understand that performance will be impacted to some degree once the
+Profiling Interface has gotten enabled: for example, because of the
+@emph{runtime} (libgomp) calling into a third-party @emph{library} for
+every event that has been registered.
+
+We're not yet accounting for the fact that @cite{OpenACC events may
+occur during event processing}.
+We just handle one case specially, as required by CUDA 9.0
+@command{nvprof}, that @code{acc_get_device_type}
+(@ref{acc_get_device_type})) may be called from
+@code{acc_ev_device_init_start}, @code{acc_ev_device_init_end}
+callbacks.
+
+We're not yet implementing initialization via a
+@code{acc_register_library} function that is either statically linked
+in, or dynamically via @env{LD_PRELOAD}.
+Initialization via @code{acc_register_library} functions dynamically
+loaded via the @env{ACC_PROFLIB} environment variable does work, as
+does directly calling @code{acc_prof_register},
+@code{acc_prof_unregister}, @code{acc_prof_lookup}.
+
+As currently there are no inquiry functions defined, calls to
+@code{acc_prof_lookup} will always return @code{NULL}.
+
+There aren't separate @emph{start}, @emph{stop} events defined for the
+event types @code{acc_ev_create}, @code{acc_ev_delete},
+@code{acc_ev_alloc}, @code{acc_ev_free}. It's not clear if these
+should be triggered before or after the actual device-specific call is
+made. We trigger them after.
+
+Remarks about data provided to callbacks:
+
+@table @asis
+
+@item @code{acc_prof_info.event_type}
+It's not clear if for @emph{nested} event callbacks (for example,
+@code{acc_ev_enqueue_launch_start} as part of a parent compute
+construct), this should be set for the nested event
+(@code{acc_ev_enqueue_launch_start}), or if the value of the parent
+construct should remain (@code{acc_ev_compute_construct_start}). In
+this implementation, the value will generally correspond to the
+innermost nested event type.
+
+@item @code{acc_prof_info.device_type}
+@itemize
+
+@item
+For @code{acc_ev_compute_construct_start}, and in presence of an
+@code{if} clause with @emph{false} argument, this will still refer to
+the offloading device type.
+It's not clear if that's the expected behavior.
+
+@item
+Complementary to the item before, for
+@code{acc_ev_compute_construct_end}, this is set to
+@code{acc_device_host} in presence of an @code{if} clause with
+@emph{false} argument.
+It's not clear if that's the expected behavior.
+
+@end itemize
+
+@item @code{acc_prof_info.thread_id}
+Always @code{-1}; not yet implemented.
+
+@item @code{acc_prof_info.async}
+@itemize
+
+@item
+Not yet implemented correctly for
+@code{acc_ev_compute_construct_start}.
+
+@item
+In a compute construct, for host-fallback
+execution/@code{acc_device_host} it will always be
+@code{acc_async_sync}.
+It's not clear if that's the expected behavior.
+
+@item
+For @code{acc_ev_device_init_start} and @code{acc_ev_device_init_end},
+it will always be @code{acc_async_sync}.
+It's not clear if that's the expected behavior.
+
+@end itemize
+
+@item @code{acc_prof_info.async_queue}
+There is no @cite{limited number of asynchronous queues} in libgomp.
+This will always have the same value as @code{acc_prof_info.async}.
+
+@item @code{acc_prof_info.src_file}
+Always @code{NULL}; not yet implemented.
+
+@item @code{acc_prof_info.func_name}
+Always @code{NULL}; not yet implemented.
+
+@item @code{acc_prof_info.line_no}
+Always @code{-1}; not yet implemented.
+
+@item @code{acc_prof_info.end_line_no}
+Always @code{-1}; not yet implemented.
+
+@item @code{acc_prof_info.func_line_no}
+Always @code{-1}; not yet implemented.
+
+@item @code{acc_prof_info.func_end_line_no}
+Always @code{-1}; not yet implemented.
+
+@item @code{acc_event_info.event_type}, @code{acc_event_info.*.event_type}
+Relating to @code{acc_prof_info.event_type} discussed above, in this
+implementation, this will always be the same value as
+@code{acc_prof_info.event_type}.
+
+@item @code{acc_event_info.*.parent_construct}
+@itemize
+
+@item
+Will be @code{acc_construct_parallel} for all OpenACC compute
+constructs as well as many OpenACC Runtime API calls; should be the
+one matching the actual construct, or
+@code{acc_construct_runtime_api}, respectively.
+
+@item
+Will be @code{acc_construct_enter_data} or
+@code{acc_construct_exit_data} when processing variable mappings
+specified in OpenACC @emph{declare} directives; should be
+@code{acc_construct_declare}.
+
+@item
+For implicit @code{acc_ev_device_init_start},
+@code{acc_ev_device_init_end}, and explicit as well as implicit
+@code{acc_ev_alloc}, @code{acc_ev_free},
+@code{acc_ev_enqueue_upload_start}, @code{acc_ev_enqueue_upload_end},
+@code{acc_ev_enqueue_download_start}, and
+@code{acc_ev_enqueue_download_end}, will be
+@code{acc_construct_parallel}; should reflect the real parent
+construct.
+
+@end itemize
+
+@item @code{acc_event_info.*.implicit}
+For @code{acc_ev_alloc}, @code{acc_ev_free},
+@code{acc_ev_enqueue_upload_start}, @code{acc_ev_enqueue_upload_end},
+@code{acc_ev_enqueue_download_start}, and
+@code{acc_ev_enqueue_download_end}, this currently will be @code{1}
+also for explicit usage.
+
+@item @code{acc_event_info.data_event.var_name}
+Always @code{NULL}; not yet implemented.
+
+@item @code{acc_event_info.data_event.host_ptr}
+For @code{acc_ev_alloc}, and @code{acc_ev_free}, this is always
+@code{NULL}.
+
+@item @code{typedef union acc_api_info}
+@dots{} as printed in @cite{5.2.3. Third Argument: API-Specific
+Information}. This should obviously be @code{typedef @emph{struct}
+acc_api_info}.
+
+@item @code{acc_api_info.device_api}
+Possibly not yet implemented correctly for
+@code{acc_ev_compute_construct_start},
+@code{acc_ev_device_init_start}, @code{acc_ev_device_init_end}:
+will always be @code{acc_device_api_none} for these event types.
+For @code{acc_ev_enter_data_start}, it will be
+@code{acc_device_api_none} in some cases.
+
+@item @code{acc_api_info.device_type}
+Always the same as @code{acc_prof_info.device_type}.
+
+@item @code{acc_api_info.vendor}
+Always @code{-1}; not yet implemented.
+
+@item @code{acc_api_info.device_handle}
+Always @code{NULL}; not yet implemented.
+
+@item @code{acc_api_info.context_handle}
+Always @code{NULL}; not yet implemented.
+
+@item @code{acc_api_info.async_handle}
+Always @code{NULL}; not yet implemented.
+
+@end table
+
+Remarks about certain event types:
+
+@table @asis
+
+@item @code{acc_ev_device_init_start}, @code{acc_ev_device_init_end}
+@itemize
+
+@item
+@c See 'DEVICE_INIT_INSIDE_COMPUTE_CONSTRUCT' in
+@c 'libgomp.oacc-c-c++-common/acc_prof-kernels-1.c',
+@c 'libgomp.oacc-c-c++-common/acc_prof-parallel-1.c'.
+When a compute construct triggers implicit
+@code{acc_ev_device_init_start} and @code{acc_ev_device_init_end}
+events, they currently aren't @emph{nested within} the corresponding
+@code{acc_ev_compute_construct_start} and
+@code{acc_ev_compute_construct_end}, but they're currently observed
+@emph{before} @code{acc_ev_compute_construct_start}.
+It's not clear what to do: the standard asks us provide a lot of
+details to the @code{acc_ev_compute_construct_start} callback, without
+(implicitly) initializing a device before?
+
+@item
+Callbacks for these event types will not be invoked for calls to the
+@code{acc_set_device_type} and @code{acc_set_device_num} functions.
+It's not clear if they should be.
+
+@end itemize
+
+@item @code{acc_ev_enter_data_start}, @code{acc_ev_enter_data_end}, @code{acc_ev_exit_data_start}, @code{acc_ev_exit_data_end}
+@itemize
+
+@item
+Callbacks for these event types will also be invoked for OpenACC
+@emph{host_data} constructs.
+It's not clear if they should be.
+
+@item
+Callbacks for these event types will also be invoked when processing
+variable mappings specified in OpenACC @emph{declare} directives.
+It's not clear if they should be.
+
+@end itemize
+
+@end table
+
+Callbacks for the following event types will be invoked, but dispatch
+and information provided therein has not yet been thoroughly reviewed:
+
+@itemize
+@item @code{acc_ev_alloc}
+@item @code{acc_ev_free}
+@item @code{acc_ev_update_start}, @code{acc_ev_update_end}
+@item @code{acc_ev_enqueue_upload_start}, @code{acc_ev_enqueue_upload_end}
+@item @code{acc_ev_enqueue_download_start}, @code{acc_ev_enqueue_download_end}
+@end itemize
+
+During device initialization, and finalization, respectively,
+callbacks for the following event types will not yet be invoked:
+
+@itemize
+@item @code{acc_ev_alloc}
+@item @code{acc_ev_free}
+@end itemize
+
+Callbacks for the following event types have not yet been implemented,
+so currently won't be invoked:
+
+@itemize
+@item @code{acc_ev_device_shutdown_start}, @code{acc_ev_device_shutdown_end}
+@item @code{acc_ev_runtime_shutdown}
+@item @code{acc_ev_create}, @code{acc_ev_delete}
+@item @code{acc_ev_wait_start}, @code{acc_ev_wait_end}
+@end itemize
+
+For the following runtime library functions, not all expected
+callbacks will be invoked (mostly concerning implicit device
+initialization):
+
+@itemize
+@item @code{acc_get_num_devices}
+@item @code{acc_set_device_type}
+@item @code{acc_get_device_type}
+@item @code{acc_set_device_num}
+@item @code{acc_get_device_num}
+@item @code{acc_init}
+@item @code{acc_shutdown}
+@end itemize
+
+Aside from implicit device initialization, for the following runtime
+library functions, no callbacks will be invoked for shared-memory
+offloading devices (it's not clear if they should be):
+
+@itemize
+@item @code{acc_malloc}
+@item @code{acc_free}
+@item @code{acc_copyin}, @code{acc_present_or_copyin}, @code{acc_copyin_async}
+@item @code{acc_create}, @code{acc_present_or_create}, @code{acc_create_async}
+@item @code{acc_copyout}, @code{acc_copyout_async}, @code{acc_copyout_finalize}, @code{acc_copyout_finalize_async}
+@item @code{acc_delete}, @code{acc_delete_async}, @code{acc_delete_finalize}, @code{acc_delete_finalize_async}
+@item @code{acc_update_device}, @code{acc_update_device_async}
+@item @code{acc_update_self}, @code{acc_update_self_async}
+@item @code{acc_map_data}, @code{acc_unmap_data}
+@item @code{acc_memcpy_to_device}, @code{acc_memcpy_to_device_async}
+@item @code{acc_memcpy_from_device}, @code{acc_memcpy_from_device_async}
+@end itemize
+
+@c ---------------------------------------------------------------------
+@c OpenMP-Implementation Specifics
+@c ---------------------------------------------------------------------
+
+@node OpenMP-Implementation Specifics
+@chapter OpenMP-Implementation Specifics
+
+@menu
+* OpenMP Context Selectors::
+* Memory allocation with libmemkind::
+@end menu
+
+@node OpenMP Context Selectors
+@section OpenMP Context Selectors
+
+@code{vendor} is always @code{gnu}. References are to the GCC manual.
+
+@multitable @columnfractions .60 .10 .25
+@headitem @code{arch} @tab @code{kind} @tab @code{isa}
+@item @code{x86}, @code{x86_64}, @code{i386}, @code{i486},
+ @code{i586}, @code{i686}, @code{ia32}
+ @tab @code{host}
+ @tab See @code{-m...} flags in ``x86 Options'' (without @code{-m})
+@item @code{amdgcn}, @code{gcn}
+ @tab @code{gpu}
+ @tab See @code{-march=} in ``AMD GCN Options''
+@item @code{nvptx}
+ @tab @code{gpu}
+ @tab See @code{-march=} in ``Nvidia PTX Options''
+@end multitable
+
+@node Memory allocation with libmemkind
+@section Memory allocation with libmemkind
+
+On Linux systems, where the @uref{https://github.com/memkind/memkind, memkind
+library} (@code{libmemkind.so.0}) is available at runtime, it is used when
+creating memory allocators requesting
+
+@itemize
+@item the memory space @code{omp_high_bw_mem_space}
+@item the memory space @code{omp_large_cap_mem_space}
+@item the partition trait @code{omp_atv_interleaved}
+@end itemize
+
+
+@c ---------------------------------------------------------------------
+@c Offload-Target Specifics
+@c ---------------------------------------------------------------------
+
+@node Offload-Target Specifics
+@chapter Offload-Target Specifics
+
+The following sections present notes on the offload-target specifics
+
+@menu
+* AMD Radeon::
+* nvptx::
+@end menu
+
+@node AMD Radeon
+@section AMD Radeon (GCN)
+
+On the hardware side, there is the hierarchy (fine to coarse):
+@itemize
+@item work item (thread)
+@item wavefront
+@item work group
+@item compute unite (CU)
+@end itemize
+
+All OpenMP and OpenACC levels are used, i.e.
+@itemize
+@item OpenMP's simd and OpenACC's vector map to work items (thread)
+@item OpenMP's threads (``parallel'') and OpenACC's workers map
+ to wavefronts
+@item OpenMP's teams and OpenACC's gang use a threadpool with the
+ size of the number of teams or gangs, respectively.
+@end itemize
+
+The used sizes are
+@itemize
+@item Number of teams is the specified @code{num_teams} (OpenMP) or
+ @code{num_gangs} (OpenACC) or otherwise the number of CU
+@item Number of wavefronts is 4 for gfx900 and 16 otherwise;
+ @code{num_threads} (OpenMP) and @code{num_workers} (OpenACC)
+ overrides this if smaller.
+@item The wavefront has 102 scalars and 64 vectors
+@item Number of workitems is always 64
+@item The hardware permits maximally 40 workgroups/CU and
+ 16 wavefronts/workgroup up to a limit of 40 wavefronts in total per CU.
+@item 80 scalars registers and 24 vector registers in non-kernel functions
+ (the chosen procedure-calling API).
+@item For the kernel itself: as many as register pressure demands (number of
+ teams and number of threads, scaled down if registers are exhausted)
+@end itemize
+
+The implementation remark:
+@itemize
+@item I/O within OpenMP target regions and OpenACC parallel/kernels is supported
+ using the C library @code{printf} functions and the Fortran
+ @code{print}/@code{write} statements.
+@end itemize
+
+
+
+@node nvptx
+@section nvptx
+
+On the hardware side, there is the hierarchy (fine to coarse):
+@itemize
+@item thread
+@item warp
+@item thread block
+@item streaming multiprocessor
+@end itemize
+
+All OpenMP and OpenACC levels are used, i.e.
+@itemize
+@item OpenMP's simd and OpenACC's vector map to threads
+@item OpenMP's threads (``parallel'') and OpenACC's workers map to warps
+@item OpenMP's teams and OpenACC's gang use a threadpool with the
+ size of the number of teams or gangs, respectively.
+@end itemize
+
+The used sizes are
+@itemize
+@item The @code{warp_size} is always 32
+@item CUDA kernel launched: @code{dim=@{#teams,1,1@}, blocks=@{#threads,warp_size,1@}}.
+@end itemize
+
+Additional information can be obtained by setting the environment variable to
+@code{GOMP_DEBUG=1} (very verbose; grep for @code{kernel.*launch} for launch
+parameters).
+
+GCC generates generic PTX ISA code, which is just-in-time compiled by CUDA,
+which caches the JIT in the user's directory (see CUDA documentation; can be
+tuned by the environment variables @code{CUDA_CACHE_@{DISABLE,MAXSIZE,PATH@}}.
+
+Note: While PTX ISA is generic, the @code{-mptx=} and @code{-march=} commandline
+options still affect the used PTX ISA code and, thus, the requirments on
+CUDA version and hardware.
+
+The implementation remark:
+@itemize
+@item I/O within OpenMP target regions and OpenACC parallel/kernels is supported
+ using the C library @code{printf} functions. Note that the Fortran
+ @code{print}/@code{write} statements are not supported, yet.
+@item Compilation OpenMP code that contains @code{requires reverse_offload}
+ requires at least @code{-march=sm_35}, compiling for @code{-march=sm_30}
+ is not supported.
+@end itemize
+
+
+@c ---------------------------------------------------------------------
+@c The libgomp ABI
+@c ---------------------------------------------------------------------
+
+@node The libgomp ABI
+@chapter The libgomp ABI
+
+The following sections present notes on the external ABI as
+presented by libgomp. Only maintainers should need them.
+
+@menu
+* Implementing MASTER construct::
+* Implementing CRITICAL construct::
+* Implementing ATOMIC construct::
+* Implementing FLUSH construct::
+* Implementing BARRIER construct::
+* Implementing THREADPRIVATE construct::
+* Implementing PRIVATE clause::
+* Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses::
+* Implementing REDUCTION clause::
+* Implementing PARALLEL construct::
+* Implementing FOR construct::
+* Implementing ORDERED construct::
+* Implementing SECTIONS construct::
+* Implementing SINGLE construct::
+* Implementing OpenACC's PARALLEL construct::
+@end menu
+
+
+@node Implementing MASTER construct
+@section Implementing MASTER construct
+
+@smallexample
+if (omp_get_thread_num () == 0)
+ block
+@end smallexample
+
+Alternately, we generate two copies of the parallel subfunction
+and only include this in the version run by the primary thread.
+Surely this is not worthwhile though...
+
+
+
+@node Implementing CRITICAL construct
+@section Implementing CRITICAL construct
+
+Without a specified name,
+
+@smallexample
+ void GOMP_critical_start (void);
+ void GOMP_critical_end (void);
+@end smallexample
+
+so that we don't get COPY relocations from libgomp to the main
+application.
+
+With a specified name, use omp_set_lock and omp_unset_lock with
+name being transformed into a variable declared like
+
+@smallexample
+ omp_lock_t gomp_critical_user_<name> __attribute__((common))
+@end smallexample
+
+Ideally the ABI would specify that all zero is a valid unlocked
+state, and so we wouldn't need to initialize this at
+startup.
+
+
+
+@node Implementing ATOMIC construct
+@section Implementing ATOMIC construct
+
+The target should implement the @code{__sync} builtins.
+
+Failing that we could add
+
+@smallexample
+ void GOMP_atomic_enter (void)
+ void GOMP_atomic_exit (void)
+@end smallexample
+
+which reuses the regular lock code, but with yet another lock
+object private to the library.
+
+
+
+@node Implementing FLUSH construct
+@section Implementing FLUSH construct
+
+Expands to the @code{__sync_synchronize} builtin.
+
+
+
+@node Implementing BARRIER construct
+@section Implementing BARRIER construct
+
+@smallexample
+ void GOMP_barrier (void)
+@end smallexample
+
+
+@node Implementing THREADPRIVATE construct
+@section Implementing THREADPRIVATE construct
+
+In _most_ cases we can map this directly to @code{__thread}. Except
+that OMP allows constructors for C++ objects. We can either
+refuse to support this (how often is it used?) or we can
+implement something akin to .ctors.
+
+Even more ideally, this ctor feature is handled by extensions
+to the main pthreads library. Failing that, we can have a set
+of entry points to register ctor functions to be called.
+
+
+
+@node Implementing PRIVATE clause
+@section Implementing PRIVATE clause
+
+In association with a PARALLEL, or within the lexical extent
+of a PARALLEL block, the variable becomes a local variable in
+the parallel subfunction.
+
+In association with FOR or SECTIONS blocks, create a new
+automatic variable within the current function. This preserves
+the semantic of new variable creation.
+
+
+
+@node Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses
+@section Implementing FIRSTPRIVATE LASTPRIVATE COPYIN and COPYPRIVATE clauses
+
+This seems simple enough for PARALLEL blocks. Create a private
+struct for communicating between the parent and subfunction.
+In the parent, copy in values for scalar and "small" structs;
+copy in addresses for others TREE_ADDRESSABLE types. In the
+subfunction, copy the value into the local variable.
+
+It is not clear what to do with bare FOR or SECTION blocks.
+The only thing I can figure is that we do something like:
+
+@smallexample
+#pragma omp for firstprivate(x) lastprivate(y)
+for (int i = 0; i < n; ++i)
+ body;
+@end smallexample
+
+which becomes
+
+@smallexample
+@{
+ int x = x, y;
+
+ // for stuff
+
+ if (i == n)
+ y = y;
+@}
+@end smallexample
+
+where the "x=x" and "y=y" assignments actually have different
+uids for the two variables, i.e. not something you could write
+directly in C. Presumably this only makes sense if the "outer"
+x and y are global variables.
+
+COPYPRIVATE would work the same way, except the structure
+broadcast would have to happen via SINGLE machinery instead.
+
+
+
+@node Implementing REDUCTION clause
+@section Implementing REDUCTION clause
+
+The private struct mentioned in the previous section should have
+a pointer to an array of the type of the variable, indexed by the
+thread's @var{team_id}. The thread stores its final value into the
+array, and after the barrier, the primary thread iterates over the
+array to collect the values.
+
+
+@node Implementing PARALLEL construct
+@section Implementing PARALLEL construct
+
+@smallexample
+ #pragma omp parallel
+ @{
+ body;
+ @}
+@end smallexample
+
+becomes
+
+@smallexample
+ void subfunction (void *data)
+ @{
+ use data;
+ body;
+ @}
+
+ setup data;
+ GOMP_parallel_start (subfunction, &data, num_threads);
+ subfunction (&data);
+ GOMP_parallel_end ();
+@end smallexample
+
+@smallexample
+ void GOMP_parallel_start (void (*fn)(void *), void *data, unsigned num_threads)
+@end smallexample
+
+The @var{FN} argument is the subfunction to be run in parallel.
+
+The @var{DATA} argument is a pointer to a structure used to
+communicate data in and out of the subfunction, as discussed
+above with respect to FIRSTPRIVATE et al.
+
+The @var{NUM_THREADS} argument is 1 if an IF clause is present
+and false, or the value of the NUM_THREADS clause, if
+present, or 0.
+
+The function needs to create the appropriate number of
+threads and/or launch them from the dock. It needs to
+create the team structure and assign team ids.
+
+@smallexample
+ void GOMP_parallel_end (void)
+@end smallexample
+
+Tears down the team and returns us to the previous @code{omp_in_parallel()} state.
+
+
+
+@node Implementing FOR construct
+@section Implementing FOR construct
+
+@smallexample
+ #pragma omp parallel for
+ for (i = lb; i <= ub; i++)
+ body;
+@end smallexample
+
+becomes
+
+@smallexample
+ void subfunction (void *data)
+ @{
+ long _s0, _e0;
+ while (GOMP_loop_static_next (&_s0, &_e0))
+ @{
+ long _e1 = _e0, i;
+ for (i = _s0; i < _e1; i++)
+ body;
+ @}
+ GOMP_loop_end_nowait ();
+ @}
+
+ GOMP_parallel_loop_static (subfunction, NULL, 0, lb, ub+1, 1, 0);
+ subfunction (NULL);
+ GOMP_parallel_end ();
+@end smallexample
+
+@smallexample
+ #pragma omp for schedule(runtime)
+ for (i = 0; i < n; i++)
+ body;
+@end smallexample
+
+becomes
+
+@smallexample
+ @{
+ long i, _s0, _e0;
+ if (GOMP_loop_runtime_start (0, n, 1, &_s0, &_e0))
+ do @{
+ long _e1 = _e0;
+ for (i = _s0, i < _e0; i++)
+ body;
+ @} while (GOMP_loop_runtime_next (&_s0, _&e0));
+ GOMP_loop_end ();
+ @}
+@end smallexample
+
+Note that while it looks like there is trickiness to propagating
+a non-constant STEP, there isn't really. We're explicitly allowed
+to evaluate it as many times as we want, and any variables involved
+should automatically be handled as PRIVATE or SHARED like any other
+variables. So the expression should remain evaluable in the
+subfunction. We can also pull it into a local variable if we like,
+but since its supposed to remain unchanged, we can also not if we like.
+
+If we have SCHEDULE(STATIC), and no ORDERED, then we ought to be
+able to get away with no work-sharing context at all, since we can
+simply perform the arithmetic directly in each thread to divide up
+the iterations. Which would mean that we wouldn't need to call any
+of these routines.
+
+There are separate routines for handling loops with an ORDERED
+clause. Bookkeeping for that is non-trivial...
+
+
+
+@node Implementing ORDERED construct
+@section Implementing ORDERED construct
+
+@smallexample
+ void GOMP_ordered_start (void)
+ void GOMP_ordered_end (void)
+@end smallexample
+
+
+
+@node Implementing SECTIONS construct
+@section Implementing SECTIONS construct
+
+A block as
+
+@smallexample
+ #pragma omp sections
+ @{
+ #pragma omp section
+ stmt1;
+ #pragma omp section
+ stmt2;
+ #pragma omp section
+ stmt3;
+ @}
+@end smallexample
+
+becomes
+
+@smallexample
+ for (i = GOMP_sections_start (3); i != 0; i = GOMP_sections_next ())
+ switch (i)
+ @{
+ case 1:
+ stmt1;
+ break;
+ case 2:
+ stmt2;
+ break;
+ case 3:
+ stmt3;
+ break;
+ @}
+ GOMP_barrier ();
+@end smallexample
+
+
+@node Implementing SINGLE construct
+@section Implementing SINGLE construct
+
+A block like
+
+@smallexample
+ #pragma omp single
+ @{
+ body;
+ @}
+@end smallexample
+
+becomes
+
+@smallexample
+ if (GOMP_single_start ())
+ body;
+ GOMP_barrier ();
+@end smallexample
+
+while
+
+@smallexample
+ #pragma omp single copyprivate(x)
+ body;
+@end smallexample
+
+becomes
+
+@smallexample
+ datap = GOMP_single_copy_start ();
+ if (datap == NULL)
+ @{
+ body;
+ data.x = x;
+ GOMP_single_copy_end (&data);
+ @}
+ else
+ x = datap->x;
+ GOMP_barrier ();
+@end smallexample
+
+
+
+@node Implementing OpenACC's PARALLEL construct
+@section Implementing OpenACC's PARALLEL construct
+
+@smallexample
+ void GOACC_parallel ()
+@end smallexample
+
+
+
+@c ---------------------------------------------------------------------
+@c Reporting Bugs
+@c ---------------------------------------------------------------------
+
+@node Reporting Bugs
+@chapter Reporting Bugs
+
+Bugs in the GNU Offloading and Multi Processing Runtime Library should
+be reported via @uref{https://gcc.gnu.org/bugzilla/, Bugzilla}. Please add
+"openacc", or "openmp", or both to the keywords field in the bug
+report, as appropriate.
+
+
+
+@c ---------------------------------------------------------------------
+@c GNU General Public License
+@c ---------------------------------------------------------------------
+
+@include gpl_v3.texi
+
+
+
+@c ---------------------------------------------------------------------
+@c GNU Free Documentation License
+@c ---------------------------------------------------------------------
+
+@include fdl.texi
+
+
+
+@c ---------------------------------------------------------------------
+@c Funding Free Software
+@c ---------------------------------------------------------------------
+
+@include funding.texi
+
+@c ---------------------------------------------------------------------
+@c Index
+@c ---------------------------------------------------------------------
+
+@node Library Index
+@unnumbered Library Index
+
+@printindex cp
+
+@bye
--- /dev/null
+@c This file is designed to be included in manuals that use
+@c expandargv.
+
+@item @@@var{file}
+Read command-line options from @var{file}. The options read are
+inserted in place of the original @@@var{file} option. If @var{file}
+does not exist, or cannot be read, then the option will be treated
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+
+Options in @var{file} are separated by whitespace. A whitespace
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+backslash) may be included by prefixing the character to be included
+with a backslash. The @var{file} may itself contain additional
+@@@var{file} options; any such options will be processed recursively.
--- /dev/null
+@node Library Copying
+@appendixsec GNU LESSER GENERAL PUBLIC LICENSE
+
+@cindex LGPL, Lesser General Public License
+@center Version 2.1, February 1999
+
+@display
+Copyright @copyright{} 1991-2022 Free Software Foundation, Inc.
+51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA
+
+Everyone is permitted to copy and distribute verbatim copies
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+
+[This is the first released version of the Lesser GPL. It also counts
+as the successor of the GNU Library Public License, version 2, hence the
+version number 2.1.]
+@end display
+
+@appendixsubsec Preamble
+
+ The licenses for most software are designed to take away your
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+@iftex
+@appendixsubsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+@end iftex
+@ifinfo
+@center GNU LESSER GENERAL PUBLIC LICENSE
+@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
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+@enumerate 0
+@item
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+@end enumerate
+
+@iftex
+@heading END OF TERMS AND CONDITIONS
+@end iftex
+@ifinfo
+@center END OF TERMS AND CONDITIONS
+@end ifinfo
+
+@page
+@appendixsubsec How to Apply These Terms to Your New Libraries
+
+ If you develop a new library, and you want it to be of the greatest
+possible use to the public, we recommend making it free software that
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+
+ To apply these terms, attach the following notices to the library. It is
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+
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+@var{one line to give the library's name and an idea of what it does.}
+Copyright (C) @var{year} @var{name of author}
+
+This library is free software; you can redistribute it and/or modify it
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+
+This library is distributed in the hope that it will be useful, but
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+
+You should have received a copy of the GNU Lesser General Public
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+
+Also add information on how to contact you by electronic and paper mail.
+
+You should also get your employer (if you work as a programmer) or your
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+Yoyodyne, Inc., hereby disclaims all copyright interest in the library
+`Frob' (a library for tweaking knobs) written by James Random Hacker.
+
+@var{signature of Ty Coon}, 1 April 1990
+Ty Coon, President of Vice
+@end smallexample
+
+That's all there is to it!
--- /dev/null
+@c Automatically generated from *.c and others (the comments before
+@c each entry tell you which file and where in that file). DO NOT EDIT!
+@c Edit the *.c files, configure with --enable-maintainer-mode,
+@c run 'make stamp-functions' and gather-docs will build a new copy.
+
+@c alloca.c:26
+@deftypefn Replacement void* alloca (size_t @var{size})
+
+This function allocates memory which will be automatically reclaimed
+after the procedure exits. The @libib{} implementation does not free
+the memory immediately but will do so eventually during subsequent
+calls to this function. Memory is allocated using @code{xmalloc} under
+normal circumstances.
+
+The header file @file{alloca-conf.h} can be used in conjunction with the
+GNU Autoconf test @code{AC_FUNC_ALLOCA} to test for and properly make
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+manual for more); this header incorporates that logic and more, including
+the possibility of a GCC built-in function.
+
+@end deftypefn
+
+@c asprintf.c:32
+@deftypefn Extension int asprintf (char **@var{resptr}, const char *@var{format}, ...)
+
+Like @code{sprintf}, but instead of passing a pointer to a buffer, you
+pass a pointer to a pointer. This function will compute the size of
+the buffer needed, allocate memory with @code{malloc}, and store a
+pointer to the allocated memory in @code{*@var{resptr}}. The value
+returned is the same as @code{sprintf} would return. If memory could
+not be allocated, minus one is returned and @code{NULL} is stored in
+@code{*@var{resptr}}.
+
+@end deftypefn
+
+@c atexit.c:6
+@deftypefn Supplemental int atexit (void (*@var{f})())
+
+Causes function @var{f} to be called at exit. Returns 0.
+
+@end deftypefn
+
+@c basename.c:6
+@deftypefn Supplemental char* basename (const char *@var{name})
+
+Returns a pointer to the last component of pathname @var{name}.
+Behavior is undefined if the pathname ends in a directory separator.
+
+@end deftypefn
+
+@c bcmp.c:6
+@deftypefn Supplemental int bcmp (char *@var{x}, char *@var{y}, int @var{count})
+
+Compares the first @var{count} bytes of two areas of memory. Returns
+zero if they are the same, nonzero otherwise. Returns zero if
+@var{count} is zero. A nonzero result only indicates a difference,
+it does not indicate any sorting order (say, by having a positive
+result mean @var{x} sorts before @var{y}).
+
+@end deftypefn
+
+@c bcopy.c:3
+@deftypefn Supplemental void bcopy (char *@var{in}, char *@var{out}, int @var{length})
+
+Copies @var{length} bytes from memory region @var{in} to region
+@var{out}. The use of @code{bcopy} is deprecated in new programs.
+
+@end deftypefn
+
+@c bsearch.c:33
+@deftypefn Supplemental void* bsearch (const void *@var{key}, @
+ const void *@var{base}, size_t @var{nmemb}, size_t @var{size}, @
+ int (*@var{compar})(const void *, const void *))
+
+Performs a search over an array of @var{nmemb} elements pointed to by
+@var{base} for a member that matches the object pointed to by @var{key}.
+The size of each member is specified by @var{size}. The array contents
+should be sorted in ascending order according to the @var{compar}
+comparison function. This routine should take two arguments pointing to
+the @var{key} and to an array member, in that order, and should return an
+integer less than, equal to, or greater than zero if the @var{key} object
+is respectively less than, matching, or greater than the array member.
+
+@end deftypefn
+
+@c bsearch_r.c:33
+@deftypefn Supplemental void* bsearch_r (const void *@var{key}, @
+ const void *@var{base}, size_t @var{nmemb}, size_t @var{size}, @
+ int (*@var{compar})(const void *, const void *, void *), void *@var{arg})
+
+Performs a search over an array of @var{nmemb} elements pointed to by
+@var{base} for a member that matches the object pointed to by @var{key}.
+The size of each member is specified by @var{size}. The array contents
+should be sorted in ascending order according to the @var{compar}
+comparison function. This routine should take three arguments: the first
+two point to the @var{key} and to an array member, and the last is passed
+down unchanged from @code{bsearch_r}'s last argument. It should return an
+integer less than, equal to, or greater than zero if the @var{key} object
+is respectively less than, matching, or greater than the array member.
+
+@end deftypefn
+
+@c argv.c:138
+@deftypefn Extension char** buildargv (char *@var{sp})
+
+Given a pointer to a string, parse the string extracting fields
+separated by whitespace and optionally enclosed within either single
+or double quotes (which are stripped off), and build a vector of
+pointers to copies of the string for each field. The input string
+remains unchanged. The last element of the vector is followed by a
+@code{NULL} element.
+
+All of the memory for the pointer array and copies of the string
+is obtained from @code{xmalloc}. All of the memory can be returned to the
+system with the single function call @code{freeargv}, which takes the
+returned result of @code{buildargv}, as it's argument.
+
+Returns a pointer to the argument vector if successful. Returns
+@code{NULL} if @var{sp} is @code{NULL} or if there is insufficient
+memory to complete building the argument vector.
+
+If the input is a null string (as opposed to a @code{NULL} pointer),
+then buildarg returns an argument vector that has one arg, a null
+string.
+
+@end deftypefn
+
+@c bzero.c:6
+@deftypefn Supplemental void bzero (char *@var{mem}, int @var{count})
+
+Zeros @var{count} bytes starting at @var{mem}. Use of this function
+is deprecated in favor of @code{memset}.
+
+@end deftypefn
+
+@c calloc.c:6
+@deftypefn Supplemental void* calloc (size_t @var{nelem}, size_t @var{elsize})
+
+Uses @code{malloc} to allocate storage for @var{nelem} objects of
+@var{elsize} bytes each, then zeros the memory.
+
+@end deftypefn
+
+@c filename_cmp.c:201
+@deftypefn Extension int canonical_filename_eq (const char *@var{a}, const char *@var{b})
+
+Return non-zero if file names @var{a} and @var{b} are equivalent.
+This function compares the canonical versions of the filenames as returned by
+@code{lrealpath()}, so that so that different file names pointing to the same
+underlying file are treated as being identical.
+
+@end deftypefn
+
+@c choose-temp.c:45
+@deftypefn Extension char* choose_temp_base (void)
+
+Return a prefix for temporary file names or @code{NULL} if unable to
+find one. The current directory is chosen if all else fails so the
+program is exited if a temporary directory can't be found (@code{mktemp}
+fails). The buffer for the result is obtained with @code{xmalloc}.
+
+This function is provided for backwards compatibility only. Its use is
+not recommended.
+
+@end deftypefn
+
+@c make-temp-file.c:95
+@deftypefn Replacement const char* choose_tmpdir ()
+
+Returns a pointer to a directory path suitable for creating temporary
+files in.
+
+@end deftypefn
+
+@c clock.c:27
+@deftypefn Supplemental long clock (void)
+
+Returns an approximation of the CPU time used by the process as a
+@code{clock_t}; divide this number by @samp{CLOCKS_PER_SEC} to get the
+number of seconds used.
+
+@end deftypefn
+
+@c concat.c:24
+@deftypefn Extension char* concat (const char *@var{s1}, const char *@var{s2}, @
+ @dots{}, @code{NULL})
+
+Concatenate zero or more of strings and return the result in freshly
+@code{xmalloc}ed memory. The argument list is terminated by the first
+@code{NULL} pointer encountered. Pointers to empty strings are ignored.
+
+@end deftypefn
+
+@c argv.c:495
+@deftypefn Extension int countargv (char * const *@var{argv})
+
+Return the number of elements in @var{argv}.
+Returns zero if @var{argv} is NULL.
+
+@end deftypefn
+
+@c crc32.c:140
+@deftypefn Extension {unsigned int} crc32 (const unsigned char *@var{buf}, @
+ int @var{len}, unsigned int @var{init})
+
+Compute the 32-bit CRC of @var{buf} which has length @var{len}. The
+starting value is @var{init}; this may be used to compute the CRC of
+data split across multiple buffers by passing the return value of each
+call as the @var{init} parameter of the next.
+
+This is used by the @command{gdb} remote protocol for the @samp{qCRC}
+command. In order to get the same results as gdb for a block of data,
+you must pass the first CRC parameter as @code{0xffffffff}.
+
+This CRC can be specified as:
+
+ Width : 32
+ Poly : 0x04c11db7
+ Init : parameter, typically 0xffffffff
+ RefIn : false
+ RefOut : false
+ XorOut : 0
+
+This differs from the "standard" CRC-32 algorithm in that the values
+are not reflected, and there is no final XOR value. These differences
+make it easy to compose the values of multiple blocks.
+
+@end deftypefn
+
+@c argv.c:59
+@deftypefn Extension char** dupargv (char * const *@var{vector})
+
+Duplicate an argument vector. Simply scans through @var{vector},
+duplicating each argument until the terminating @code{NULL} is found.
+Returns a pointer to the argument vector if successful. Returns
+@code{NULL} if there is insufficient memory to complete building the
+argument vector.
+
+@end deftypefn
+
+@c strerror.c:572
+@deftypefn Extension int errno_max (void)
+
+Returns the maximum @code{errno} value for which a corresponding
+symbolic name or message is available. Note that in the case where we
+use the @code{sys_errlist} supplied by the system, it is possible for
+there to be more symbolic names than messages, or vice versa. In
+fact, the manual page for @code{perror(3C)} explicitly warns that one
+should check the size of the table (@code{sys_nerr}) before indexing
+it, since new error codes may be added to the system before they are
+added to the table. Thus @code{sys_nerr} might be smaller than value
+implied by the largest @code{errno} value defined in @code{<errno.h>}.
+
+We return the maximum value that can be used to obtain a meaningful
+symbolic name or message.
+
+@end deftypefn
+
+@c argv.c:352
+@deftypefn Extension void expandargv (int *@var{argcp}, char ***@var{argvp})
+
+The @var{argcp} and @code{argvp} arguments are pointers to the usual
+@code{argc} and @code{argv} arguments to @code{main}. This function
+looks for arguments that begin with the character @samp{@@}. Any such
+arguments are interpreted as ``response files''. The contents of the
+response file are interpreted as additional command line options. In
+particular, the file is separated into whitespace-separated strings;
+each such string is taken as a command-line option. The new options
+are inserted in place of the option naming the response file, and
+@code{*argcp} and @code{*argvp} will be updated. If the value of
+@code{*argvp} is modified by this function, then the new value has
+been dynamically allocated and can be deallocated by the caller with
+@code{freeargv}. However, most callers will simply call
+@code{expandargv} near the beginning of @code{main} and allow the
+operating system to free the memory when the program exits.
+
+@end deftypefn
+
+@c fdmatch.c:23
+@deftypefn Extension int fdmatch (int @var{fd1}, int @var{fd2})
+
+Check to see if two open file descriptors refer to the same file.
+This is useful, for example, when we have an open file descriptor for
+an unnamed file, and the name of a file that we believe to correspond
+to that fd. This can happen when we are exec'd with an already open
+file (@code{stdout} for example) or from the SVR4 @file{/proc} calls
+that return open file descriptors for mapped address spaces. All we
+have to do is open the file by name and check the two file descriptors
+for a match, which is done by comparing major and minor device numbers
+and inode numbers.
+
+@end deftypefn
+
+@c fopen_unlocked.c:49
+@deftypefn Extension {FILE *} fdopen_unlocked (int @var{fildes}, @
+ const char * @var{mode})
+
+Opens and returns a @code{FILE} pointer via @code{fdopen}. If the
+operating system supports it, ensure that the stream is setup to avoid
+any multi-threaded locking. Otherwise return the @code{FILE} pointer
+unchanged.
+
+@end deftypefn
+
+@c ffs.c:3
+@deftypefn Supplemental int ffs (int @var{valu})
+
+Find the first (least significant) bit set in @var{valu}. Bits are
+numbered from right to left, starting with bit 1 (corresponding to the
+value 1). If @var{valu} is zero, zero is returned.
+
+@end deftypefn
+
+@c filename_cmp.c:37
+@deftypefn Extension int filename_cmp (const char *@var{s1}, const char *@var{s2})
+
+Return zero if the two file names @var{s1} and @var{s2} are equivalent.
+If not equivalent, the returned value is similar to what @code{strcmp}
+would return. In other words, it returns a negative value if @var{s1}
+is less than @var{s2}, or a positive value if @var{s2} is greater than
+@var{s2}.
+
+This function does not normalize file names. As a result, this function
+will treat filenames that are spelled differently as different even in
+the case when the two filenames point to the same underlying file.
+However, it does handle the fact that on DOS-like file systems, forward
+and backward slashes are equal.
+
+@end deftypefn
+
+@c filename_cmp.c:183
+@deftypefn Extension int filename_eq (const void *@var{s1}, const void *@var{s2})
+
+Return non-zero if file names @var{s1} and @var{s2} are equivalent.
+This function is for use with hashtab.c hash tables.
+
+@end deftypefn
+
+@c filename_cmp.c:152
+@deftypefn Extension hashval_t filename_hash (const void *@var{s})
+
+Return the hash value for file name @var{s} that will be compared
+using filename_cmp.
+This function is for use with hashtab.c hash tables.
+
+@end deftypefn
+
+@c filename_cmp.c:94
+@deftypefn Extension int filename_ncmp (const char *@var{s1}, const char *@var{s2}, size_t @var{n})
+
+Return zero if the two file names @var{s1} and @var{s2} are equivalent
+in range @var{n}.
+If not equivalent, the returned value is similar to what @code{strncmp}
+would return. In other words, it returns a negative value if @var{s1}
+is less than @var{s2}, or a positive value if @var{s2} is greater than
+@var{s2}.
+
+This function does not normalize file names. As a result, this function
+will treat filenames that are spelled differently as different even in
+the case when the two filenames point to the same underlying file.
+However, it does handle the fact that on DOS-like file systems, forward
+and backward slashes are equal.
+
+@end deftypefn
+
+@c fnmatch.txh:1
+@deftypefn Replacement int fnmatch (const char *@var{pattern}, @
+ const char *@var{string}, int @var{flags})
+
+Matches @var{string} against @var{pattern}, returning zero if it
+matches, @code{FNM_NOMATCH} if not. @var{pattern} may contain the
+wildcards @code{?} to match any one character, @code{*} to match any
+zero or more characters, or a set of alternate characters in square
+brackets, like @samp{[a-gt8]}, which match one character (@code{a}
+through @code{g}, or @code{t}, or @code{8}, in this example) if that one
+character is in the set. A set may be inverted (i.e., match anything
+except what's in the set) by giving @code{^} or @code{!} as the first
+character in the set. To include those characters in the set, list them
+as anything other than the first character of the set. To include a
+dash in the set, list it last in the set. A backslash character makes
+the following character not special, so for example you could match
+against a literal asterisk with @samp{\*}. To match a literal
+backslash, use @samp{\\}.
+
+@code{flags} controls various aspects of the matching process, and is a
+boolean OR of zero or more of the following values (defined in
+@code{<fnmatch.h>}):
+
+@table @code
+
+@item FNM_PATHNAME
+@itemx FNM_FILE_NAME
+@var{string} is assumed to be a path name. No wildcard will ever match
+@code{/}.
+
+@item FNM_NOESCAPE
+Do not interpret backslashes as quoting the following special character.
+
+@item FNM_PERIOD
+A leading period (at the beginning of @var{string}, or if
+@code{FNM_PATHNAME} after a slash) is not matched by @code{*} or
+@code{?} but must be matched explicitly.
+
+@item FNM_LEADING_DIR
+Means that @var{string} also matches @var{pattern} if some initial part
+of @var{string} matches, and is followed by @code{/} and zero or more
+characters. For example, @samp{foo*} would match either @samp{foobar}
+or @samp{foobar/grill}.
+
+@item FNM_CASEFOLD
+Ignores case when performing the comparison.
+
+@end table
+
+@end deftypefn
+
+@c fopen_unlocked.c:39
+@deftypefn Extension {FILE *} fopen_unlocked (const char *@var{path}, @
+ const char * @var{mode})
+
+Opens and returns a @code{FILE} pointer via @code{fopen}. If the
+operating system supports it, ensure that the stream is setup to avoid
+any multi-threaded locking. Otherwise return the @code{FILE} pointer
+unchanged.
+
+@end deftypefn
+
+@c argv.c:93
+@deftypefn Extension void freeargv (char **@var{vector})
+
+Free an argument vector that was built using @code{buildargv}. Simply
+scans through @var{vector}, freeing the memory for each argument until
+the terminating @code{NULL} is found, and then frees @var{vector}
+itself.
+
+@end deftypefn
+
+@c fopen_unlocked.c:59
+@deftypefn Extension {FILE *} freopen_unlocked (const char * @var{path}, @
+ const char * @var{mode}, FILE * @var{stream})
+
+Opens and returns a @code{FILE} pointer via @code{freopen}. If the
+operating system supports it, ensure that the stream is setup to avoid
+any multi-threaded locking. Otherwise return the @code{FILE} pointer
+unchanged.
+
+@end deftypefn
+
+@c getruntime.c:86
+@deftypefn Replacement long get_run_time (void)
+
+Returns the time used so far, in microseconds. If possible, this is
+the time used by this process, else it is the elapsed time since the
+process started.
+
+@end deftypefn
+
+@c getcwd.c:6
+@deftypefn Supplemental char* getcwd (char *@var{pathname}, int @var{len})
+
+Copy the absolute pathname for the current working directory into
+@var{pathname}, which is assumed to point to a buffer of at least
+@var{len} bytes, and return a pointer to the buffer. If the current
+directory's path doesn't fit in @var{len} characters, the result is
+@code{NULL} and @code{errno} is set. If @var{pathname} is a null pointer,
+@code{getcwd} will obtain @var{len} bytes of space using
+@code{malloc}.
+
+@end deftypefn
+
+@c getpagesize.c:5
+@deftypefn Supplemental int getpagesize (void)
+
+Returns the number of bytes in a page of memory. This is the
+granularity of many of the system memory management routines. No
+guarantee is made as to whether or not it is the same as the basic
+memory management hardware page size.
+
+@end deftypefn
+
+@c getpwd.c:5
+@deftypefn Supplemental char* getpwd (void)
+
+Returns the current working directory. This implementation caches the
+result on the assumption that the process will not call @code{chdir}
+between calls to @code{getpwd}.
+
+@end deftypefn
+
+@c gettimeofday.c:12
+@deftypefn Supplemental int gettimeofday (struct timeval *@var{tp}, void *@var{tz})
+
+Writes the current time to @var{tp}. This implementation requires
+that @var{tz} be NULL. Returns 0 on success, -1 on failure.
+
+@end deftypefn
+
+@c hex.c:33
+@deftypefn Extension void hex_init (void)
+
+Initializes the array mapping the current character set to
+corresponding hex values. This function must be called before any
+call to @code{hex_p} or @code{hex_value}. If you fail to call it, a
+default ASCII-based table will normally be used on ASCII systems.
+
+@end deftypefn
+
+@c hex.c:42
+@deftypefn Extension int hex_p (int @var{c})
+
+Evaluates to non-zero if the given character is a valid hex character,
+or zero if it is not. Note that the value you pass will be cast to
+@code{unsigned char} within the macro.
+
+@end deftypefn
+
+@c hex.c:50
+@deftypefn Extension {unsigned int} hex_value (int @var{c})
+
+Returns the numeric equivalent of the given character when interpreted
+as a hexadecimal digit. The result is undefined if you pass an
+invalid hex digit. Note that the value you pass will be cast to
+@code{unsigned char} within the macro.
+
+The @code{hex_value} macro returns @code{unsigned int}, rather than
+signed @code{int}, to make it easier to use in parsing addresses from
+hex dump files: a signed @code{int} would be sign-extended when
+converted to a wider unsigned type --- like @code{bfd_vma}, on some
+systems.
+
+@end deftypefn
+
+@c safe-ctype.c:24
+@defvr Extension HOST_CHARSET
+This macro indicates the basic character set and encoding used by the
+host: more precisely, the encoding used for character constants in
+preprocessor @samp{#if} statements (the C "execution character set").
+It is defined by @file{safe-ctype.h}, and will be an integer constant
+with one of the following values:
+
+@ftable @code
+@item HOST_CHARSET_UNKNOWN
+The host character set is unknown - that is, not one of the next two
+possibilities.
+
+@item HOST_CHARSET_ASCII
+The host character set is ASCII.
+
+@item HOST_CHARSET_EBCDIC
+The host character set is some variant of EBCDIC. (Only one of the
+nineteen EBCDIC varying characters is tested; exercise caution.)
+@end ftable
+@end defvr
+
+@c hashtab.c:327
+@deftypefn Supplemental htab_t htab_create_typed_alloc (size_t @var{size}, @
+htab_hash @var{hash_f}, htab_eq @var{eq_f}, htab_del @var{del_f}, @
+htab_alloc @var{alloc_tab_f}, htab_alloc @var{alloc_f}, @
+htab_free @var{free_f})
+
+This function creates a hash table that uses two different allocators
+@var{alloc_tab_f} and @var{alloc_f} to use for allocating the table itself
+and its entries respectively. This is useful when variables of different
+types need to be allocated with different allocators.
+
+The created hash table is slightly larger than @var{size} and it is
+initially empty (all the hash table entries are @code{HTAB_EMPTY_ENTRY}).
+The function returns the created hash table, or @code{NULL} if memory
+allocation fails.
+
+@end deftypefn
+
+@c index.c:5
+@deftypefn Supplemental char* index (char *@var{s}, int @var{c})
+
+Returns a pointer to the first occurrence of the character @var{c} in
+the string @var{s}, or @code{NULL} if not found. The use of @code{index} is
+deprecated in new programs in favor of @code{strchr}.
+
+@end deftypefn
+
+@c insque.c:6
+@deftypefn Supplemental void insque (struct qelem *@var{elem}, @
+ struct qelem *@var{pred})
+@deftypefnx Supplemental void remque (struct qelem *@var{elem})
+
+Routines to manipulate queues built from doubly linked lists. The
+@code{insque} routine inserts @var{elem} in the queue immediately
+after @var{pred}. The @code{remque} routine removes @var{elem} from
+its containing queue. These routines expect to be passed pointers to
+structures which have as their first members a forward pointer and a
+back pointer, like this prototype (although no prototype is provided):
+
+@example
+struct qelem @{
+ struct qelem *q_forw;
+ struct qelem *q_back;
+ char q_data[];
+@};
+@end example
+
+@end deftypefn
+
+@c safe-ctype.c:45
+@deffn Extension ISALPHA (@var{c})
+@deffnx Extension ISALNUM (@var{c})
+@deffnx Extension ISBLANK (@var{c})
+@deffnx Extension ISCNTRL (@var{c})
+@deffnx Extension ISDIGIT (@var{c})
+@deffnx Extension ISGRAPH (@var{c})
+@deffnx Extension ISLOWER (@var{c})
+@deffnx Extension ISPRINT (@var{c})
+@deffnx Extension ISPUNCT (@var{c})
+@deffnx Extension ISSPACE (@var{c})
+@deffnx Extension ISUPPER (@var{c})
+@deffnx Extension ISXDIGIT (@var{c})
+
+These twelve macros are defined by @file{safe-ctype.h}. Each has the
+same meaning as the corresponding macro (with name in lowercase)
+defined by the standard header @file{ctype.h}. For example,
+@code{ISALPHA} returns true for alphabetic characters and false for
+others. However, there are two differences between these macros and
+those provided by @file{ctype.h}:
+
+@itemize @bullet
+@item These macros are guaranteed to have well-defined behavior for all
+values representable by @code{signed char} and @code{unsigned char}, and
+for @code{EOF}.
+
+@item These macros ignore the current locale; they are true for these
+fixed sets of characters:
+@multitable {@code{XDIGIT}} {yada yada yada yada yada yada yada yada}
+@item @code{ALPHA} @tab @kbd{A-Za-z}
+@item @code{ALNUM} @tab @kbd{A-Za-z0-9}
+@item @code{BLANK} @tab @kbd{space tab}
+@item @code{CNTRL} @tab @code{!PRINT}
+@item @code{DIGIT} @tab @kbd{0-9}
+@item @code{GRAPH} @tab @code{ALNUM || PUNCT}
+@item @code{LOWER} @tab @kbd{a-z}
+@item @code{PRINT} @tab @code{GRAPH ||} @kbd{space}
+@item @code{PUNCT} @tab @kbd{`~!@@#$%^&*()_-=+[@{]@}\|;:'",<.>/?}
+@item @code{SPACE} @tab @kbd{space tab \n \r \f \v}
+@item @code{UPPER} @tab @kbd{A-Z}
+@item @code{XDIGIT} @tab @kbd{0-9A-Fa-f}
+@end multitable
+
+Note that, if the host character set is ASCII or a superset thereof,
+all these macros will return false for all values of @code{char} outside
+the range of 7-bit ASCII. In particular, both ISPRINT and ISCNTRL return
+false for characters with numeric values from 128 to 255.
+@end itemize
+@end deffn
+
+@c safe-ctype.c:94
+@deffn Extension ISIDNUM (@var{c})
+@deffnx Extension ISIDST (@var{c})
+@deffnx Extension IS_VSPACE (@var{c})
+@deffnx Extension IS_NVSPACE (@var{c})
+@deffnx Extension IS_SPACE_OR_NUL (@var{c})
+@deffnx Extension IS_ISOBASIC (@var{c})
+These six macros are defined by @file{safe-ctype.h} and provide
+additional character classes which are useful when doing lexical
+analysis of C or similar languages. They are true for the following
+sets of characters:
+
+@multitable {@code{SPACE_OR_NUL}} {yada yada yada yada yada yada yada yada}
+@item @code{IDNUM} @tab @kbd{A-Za-z0-9_}
+@item @code{IDST} @tab @kbd{A-Za-z_}
+@item @code{VSPACE} @tab @kbd{\r \n}
+@item @code{NVSPACE} @tab @kbd{space tab \f \v \0}
+@item @code{SPACE_OR_NUL} @tab @code{VSPACE || NVSPACE}
+@item @code{ISOBASIC} @tab @code{VSPACE || NVSPACE || PRINT}
+@end multitable
+@end deffn
+
+@c lbasename.c:23
+@deftypefn Replacement {const char*} lbasename (const char *@var{name})
+
+Given a pointer to a string containing a typical pathname
+(@samp{/usr/src/cmd/ls/ls.c} for example), returns a pointer to the
+last component of the pathname (@samp{ls.c} in this case). The
+returned pointer is guaranteed to lie within the original
+string. This latter fact is not true of many vendor C
+libraries, which return special strings or modify the passed
+strings for particular input.
+
+In particular, the empty string returns the same empty string,
+and a path ending in @code{/} returns the empty string after it.
+
+@end deftypefn
+
+@c lrealpath.c:25
+@deftypefn Replacement {const char*} lrealpath (const char *@var{name})
+
+Given a pointer to a string containing a pathname, returns a canonical
+version of the filename. Symlinks will be resolved, and ``.'' and ``..''
+components will be simplified. The returned value will be allocated using
+@code{malloc}, or @code{NULL} will be returned on a memory allocation error.
+
+@end deftypefn
+
+@c make-relative-prefix.c:23
+@deftypefn Extension {const char*} make_relative_prefix (const char *@var{progname}, @
+ const char *@var{bin_prefix}, const char *@var{prefix})
+
+Given three paths @var{progname}, @var{bin_prefix}, @var{prefix},
+return the path that is in the same position relative to
+@var{progname}'s directory as @var{prefix} is relative to
+@var{bin_prefix}. That is, a string starting with the directory
+portion of @var{progname}, followed by a relative pathname of the
+difference between @var{bin_prefix} and @var{prefix}.
+
+If @var{progname} does not contain any directory separators,
+@code{make_relative_prefix} will search @env{PATH} to find a program
+named @var{progname}. Also, if @var{progname} is a symbolic link,
+the symbolic link will be resolved.
+
+For example, if @var{bin_prefix} is @code{/alpha/beta/gamma/gcc/delta},
+@var{prefix} is @code{/alpha/beta/gamma/omega/}, and @var{progname} is
+@code{/red/green/blue/gcc}, then this function will return
+@code{/red/green/blue/../../omega/}.
+
+The return value is normally allocated via @code{malloc}. If no
+relative prefix can be found, return @code{NULL}.
+
+@end deftypefn
+
+@c make-temp-file.c:173
+@deftypefn Replacement char* make_temp_file (const char *@var{suffix})
+
+Return a temporary file name (as a string) or @code{NULL} if unable to
+create one. @var{suffix} is a suffix to append to the file name. The
+string is @code{malloc}ed, and the temporary file has been created.
+
+@end deftypefn
+
+@c memchr.c:3
+@deftypefn Supplemental void* memchr (const void *@var{s}, int @var{c}, @
+ size_t @var{n})
+
+This function searches memory starting at @code{*@var{s}} for the
+character @var{c}. The search only ends with the first occurrence of
+@var{c}, or after @var{length} characters; in particular, a null
+character does not terminate the search. If the character @var{c} is
+found within @var{length} characters of @code{*@var{s}}, a pointer
+to the character is returned. If @var{c} is not found, then @code{NULL} is
+returned.
+
+@end deftypefn
+
+@c memcmp.c:6
+@deftypefn Supplemental int memcmp (const void *@var{x}, const void *@var{y}, @
+ size_t @var{count})
+
+Compares the first @var{count} bytes of two areas of memory. Returns
+zero if they are the same, a value less than zero if @var{x} is
+lexically less than @var{y}, or a value greater than zero if @var{x}
+is lexically greater than @var{y}. Note that lexical order is determined
+as if comparing unsigned char arrays.
+
+@end deftypefn
+
+@c memcpy.c:6
+@deftypefn Supplemental void* memcpy (void *@var{out}, const void *@var{in}, @
+ size_t @var{length})
+
+Copies @var{length} bytes from memory region @var{in} to region
+@var{out}. Returns a pointer to @var{out}.
+
+@end deftypefn
+
+@c memmem.c:20
+@deftypefn Supplemental void* memmem (const void *@var{haystack}, @
+ size_t @var{haystack_len} const void *@var{needle}, size_t @var{needle_len})
+
+Returns a pointer to the first occurrence of @var{needle} (length
+@var{needle_len}) in @var{haystack} (length @var{haystack_len}).
+Returns @code{NULL} if not found.
+
+@end deftypefn
+
+@c memmove.c:6
+@deftypefn Supplemental void* memmove (void *@var{from}, const void *@var{to}, @
+ size_t @var{count})
+
+Copies @var{count} bytes from memory area @var{from} to memory area
+@var{to}, returning a pointer to @var{to}.
+
+@end deftypefn
+
+@c mempcpy.c:23
+@deftypefn Supplemental void* mempcpy (void *@var{out}, const void *@var{in}, @
+ size_t @var{length})
+
+Copies @var{length} bytes from memory region @var{in} to region
+@var{out}. Returns a pointer to @var{out} + @var{length}.
+
+@end deftypefn
+
+@c memset.c:6
+@deftypefn Supplemental void* memset (void *@var{s}, int @var{c}, @
+ size_t @var{count})
+
+Sets the first @var{count} bytes of @var{s} to the constant byte
+@var{c}, returning a pointer to @var{s}.
+
+@end deftypefn
+
+@c mkstemps.c:60
+@deftypefn Replacement int mkstemps (char *@var{pattern}, int @var{suffix_len})
+
+Generate a unique temporary file name from @var{pattern}.
+@var{pattern} has the form:
+
+@example
+ @var{path}/ccXXXXXX@var{suffix}
+@end example
+
+@var{suffix_len} tells us how long @var{suffix} is (it can be zero
+length). The last six characters of @var{pattern} before @var{suffix}
+must be @samp{XXXXXX}; they are replaced with a string that makes the
+filename unique. Returns a file descriptor open on the file for
+reading and writing.
+
+@end deftypefn
+
+@c pexecute.txh:278
+@deftypefn Extension void pex_free (struct pex_obj @var{obj})
+
+Clean up and free all data associated with @var{obj}. If you have not
+yet called @code{pex_get_times} or @code{pex_get_status}, this will
+try to kill the subprocesses.
+
+@end deftypefn
+
+@c pexecute.txh:251
+@deftypefn Extension int pex_get_status (struct pex_obj *@var{obj}, @
+ int @var{count}, int *@var{vector})
+
+Returns the exit status of all programs run using @var{obj}.
+@var{count} is the number of results expected. The results will be
+placed into @var{vector}. The results are in the order of the calls
+to @code{pex_run}. Returns 0 on error, 1 on success.
+
+@end deftypefn
+
+@c pexecute.txh:261
+@deftypefn Extension int pex_get_times (struct pex_obj *@var{obj}, @
+ int @var{count}, struct pex_time *@var{vector})
+
+Returns the process execution times of all programs run using
+@var{obj}. @var{count} is the number of results expected. The
+results will be placed into @var{vector}. The results are in the
+order of the calls to @code{pex_run}. Returns 0 on error, 1 on
+success.
+
+@code{struct pex_time} has the following fields of the type
+@code{unsigned long}: @code{user_seconds},
+@code{user_microseconds}, @code{system_seconds},
+@code{system_microseconds}. On systems which do not support reporting
+process times, all the fields will be set to @code{0}.
+
+@end deftypefn
+
+@c pexecute.txh:2
+@deftypefn Extension {struct pex_obj *} pex_init (int @var{flags}, @
+ const char *@var{pname}, const char *@var{tempbase})
+
+Prepare to execute one or more programs, with standard output of each
+program fed to standard input of the next. This is a system
+independent interface to execute a pipeline.
+
+@var{flags} is a bitwise combination of the following:
+
+@table @code
+
+@vindex PEX_RECORD_TIMES
+@item PEX_RECORD_TIMES
+Record subprocess times if possible.
+
+@vindex PEX_USE_PIPES
+@item PEX_USE_PIPES
+Use pipes for communication between processes, if possible.
+
+@vindex PEX_SAVE_TEMPS
+@item PEX_SAVE_TEMPS
+Don't delete temporary files used for communication between
+processes.
+
+@end table
+
+@var{pname} is the name of program to be executed, used in error
+messages. @var{tempbase} is a base name to use for any required
+temporary files; it may be @code{NULL} to use a randomly chosen name.
+
+@end deftypefn
+
+@c pexecute.txh:161
+@deftypefn Extension {FILE *} pex_input_file (struct pex_obj *@var{obj}, @
+ int @var{flags}, const char *@var{in_name})
+
+Return a stream for a temporary file to pass to the first program in
+the pipeline as input.
+
+The name of the input file is chosen according to the same rules
+@code{pex_run} uses to choose output file names, based on
+@var{in_name}, @var{obj} and the @code{PEX_SUFFIX} bit in @var{flags}.
+
+Don't call @code{fclose} on the returned stream; the first call to
+@code{pex_run} closes it automatically.
+
+If @var{flags} includes @code{PEX_BINARY_OUTPUT}, open the stream in
+binary mode; otherwise, open it in the default mode. Including
+@code{PEX_BINARY_OUTPUT} in @var{flags} has no effect on Unix.
+@end deftypefn
+
+@c pexecute.txh:179
+@deftypefn Extension {FILE *} pex_input_pipe (struct pex_obj *@var{obj}, @
+ int @var{binary})
+
+Return a stream @var{fp} for a pipe connected to the standard input of
+the first program in the pipeline; @var{fp} is opened for writing.
+You must have passed @code{PEX_USE_PIPES} to the @code{pex_init} call
+that returned @var{obj}.
+
+You must close @var{fp} using @code{fclose} yourself when you have
+finished writing data to the pipeline.
+
+The file descriptor underlying @var{fp} is marked not to be inherited
+by child processes.
+
+On systems that do not support pipes, this function returns
+@code{NULL}, and sets @code{errno} to @code{EINVAL}. If you would
+like to write code that is portable to all systems the @code{pex}
+functions support, consider using @code{pex_input_file} instead.
+
+There are two opportunities for deadlock using
+@code{pex_input_pipe}:
+
+@itemize @bullet
+@item
+Most systems' pipes can buffer only a fixed amount of data; a process
+that writes to a full pipe blocks. Thus, if you write to @file{fp}
+before starting the first process, you run the risk of blocking when
+there is no child process yet to read the data and allow you to
+continue. @code{pex_input_pipe} makes no promises about the
+size of the pipe's buffer, so if you need to write any data at all
+before starting the first process in the pipeline, consider using
+@code{pex_input_file} instead.
+
+@item
+Using @code{pex_input_pipe} and @code{pex_read_output} together
+may also cause deadlock. If the output pipe fills up, so that each
+program in the pipeline is waiting for the next to read more data, and
+you fill the input pipe by writing more data to @var{fp}, then there
+is no way to make progress: the only process that could read data from
+the output pipe is you, but you are blocked on the input pipe.
+
+@end itemize
+
+@end deftypefn
+
+@c pexecute.txh:286
+@deftypefn Extension {const char *} pex_one (int @var{flags}, @
+ const char *@var{executable}, char * const *@var{argv}, @
+ const char *@var{pname}, const char *@var{outname}, const char *@var{errname}, @
+ int *@var{status}, int *@var{err})
+
+An interface to permit the easy execution of a
+single program. The return value and most of the parameters are as
+for a call to @code{pex_run}. @var{flags} is restricted to a
+combination of @code{PEX_SEARCH}, @code{PEX_STDERR_TO_STDOUT}, and
+@code{PEX_BINARY_OUTPUT}. @var{outname} is interpreted as if
+@code{PEX_LAST} were set. On a successful return, @code{*@var{status}} will
+be set to the exit status of the program.
+
+@end deftypefn
+
+@c pexecute.txh:237
+@deftypefn Extension {FILE *} pex_read_err (struct pex_obj *@var{obj}, @
+ int @var{binary})
+
+Returns a @code{FILE} pointer which may be used to read the standard
+error of the last program in the pipeline. When this is used,
+@code{PEX_LAST} should not be used in a call to @code{pex_run}. After
+this is called, @code{pex_run} may no longer be called with the same
+@var{obj}. @var{binary} should be non-zero if the file should be
+opened in binary mode. Don't call @code{fclose} on the returned file;
+it will be closed by @code{pex_free}.
+
+@end deftypefn
+
+@c pexecute.txh:224
+@deftypefn Extension {FILE *} pex_read_output (struct pex_obj *@var{obj}, @
+ int @var{binary})
+
+Returns a @code{FILE} pointer which may be used to read the standard
+output of the last program in the pipeline. When this is used,
+@code{PEX_LAST} should not be used in a call to @code{pex_run}. After
+this is called, @code{pex_run} may no longer be called with the same
+@var{obj}. @var{binary} should be non-zero if the file should be
+opened in binary mode. Don't call @code{fclose} on the returned file;
+it will be closed by @code{pex_free}.
+
+@end deftypefn
+
+@c pexecute.txh:34
+@deftypefn Extension {const char *} pex_run (struct pex_obj *@var{obj}, @
+ int @var{flags}, const char *@var{executable}, char * const *@var{argv}, @
+ const char *@var{outname}, const char *@var{errname}, int *@var{err})
+
+Execute one program in a pipeline. On success this returns
+@code{NULL}. On failure it returns an error message, a statically
+allocated string.
+
+@var{obj} is returned by a previous call to @code{pex_init}.
+
+@var{flags} is a bitwise combination of the following:
+
+@table @code
+
+@vindex PEX_LAST
+@item PEX_LAST
+This must be set on the last program in the pipeline. In particular,
+it should be set when executing a single program. The standard output
+of the program will be sent to @var{outname}, or, if @var{outname} is
+@code{NULL}, to the standard output of the calling program. Do @emph{not}
+set this bit if you want to call @code{pex_read_output}
+(described below). After a call to @code{pex_run} with this bit set,
+@var{pex_run} may no longer be called with the same @var{obj}.
+
+@vindex PEX_SEARCH
+@item PEX_SEARCH
+Search for the program using the user's executable search path.
+
+@vindex PEX_SUFFIX
+@item PEX_SUFFIX
+@var{outname} is a suffix. See the description of @var{outname},
+below.
+
+@vindex PEX_STDERR_TO_STDOUT
+@item PEX_STDERR_TO_STDOUT
+Send the program's standard error to standard output, if possible.
+
+@vindex PEX_BINARY_INPUT
+@vindex PEX_BINARY_OUTPUT
+@vindex PEX_BINARY_ERROR
+@item PEX_BINARY_INPUT
+@itemx PEX_BINARY_OUTPUT
+@itemx PEX_BINARY_ERROR
+The standard input (output or error) of the program should be read (written) in
+binary mode rather than text mode. These flags are ignored on systems
+which do not distinguish binary mode and text mode, such as Unix. For
+proper behavior these flags should match appropriately---a call to
+@code{pex_run} using @code{PEX_BINARY_OUTPUT} should be followed by a
+call using @code{PEX_BINARY_INPUT}.
+
+@vindex PEX_STDERR_TO_PIPE
+@item PEX_STDERR_TO_PIPE
+Send the program's standard error to a pipe, if possible. This flag
+cannot be specified together with @code{PEX_STDERR_TO_STDOUT}. This
+flag can be specified only on the last program in pipeline.
+
+@end table
+
+@var{executable} is the program to execute. @var{argv} is the set of
+arguments to pass to the program; normally @code{@var{argv}[0]} will
+be a copy of @var{executable}.
+
+@var{outname} is used to set the name of the file to use for standard
+output. There are two cases in which no output file will be used:
+
+@enumerate
+@item
+if @code{PEX_LAST} is not set in @var{flags}, and @code{PEX_USE_PIPES}
+was set in the call to @code{pex_init}, and the system supports pipes
+
+@item
+if @code{PEX_LAST} is set in @var{flags}, and @var{outname} is
+@code{NULL}
+@end enumerate
+
+@noindent
+Otherwise the code will use a file to hold standard
+output. If @code{PEX_LAST} is not set, this file is considered to be
+a temporary file, and it will be removed when no longer needed, unless
+@code{PEX_SAVE_TEMPS} was set in the call to @code{pex_init}.
+
+There are two cases to consider when setting the name of the file to
+hold standard output.
+
+@enumerate
+@item
+@code{PEX_SUFFIX} is set in @var{flags}. In this case
+@var{outname} may not be @code{NULL}. If the @var{tempbase} parameter
+to @code{pex_init} was not @code{NULL}, then the output file name is
+the concatenation of @var{tempbase} and @var{outname}. If
+@var{tempbase} was @code{NULL}, then the output file name is a random
+file name ending in @var{outname}.
+
+@item
+@code{PEX_SUFFIX} was not set in @var{flags}. In this
+case, if @var{outname} is not @code{NULL}, it is used as the output
+file name. If @var{outname} is @code{NULL}, and @var{tempbase} was
+not NULL, the output file name is randomly chosen using
+@var{tempbase}. Otherwise the output file name is chosen completely
+at random.
+@end enumerate
+
+@var{errname} is the file name to use for standard error output. If
+it is @code{NULL}, standard error is the same as the caller's.
+Otherwise, standard error is written to the named file.
+
+On an error return, the code sets @code{*@var{err}} to an @code{errno}
+value, or to 0 if there is no relevant @code{errno}.
+
+@end deftypefn
+
+@c pexecute.txh:145
+@deftypefn Extension {const char *} pex_run_in_environment (struct pex_obj *@var{obj}, @
+ int @var{flags}, const char *@var{executable}, char * const *@var{argv}, @
+ char * const *@var{env}, int @var{env_size}, const char *@var{outname}, @
+ const char *@var{errname}, int *@var{err})
+
+Execute one program in a pipeline, permitting the environment for the
+program to be specified. Behaviour and parameters not listed below are
+as for @code{pex_run}.
+
+@var{env} is the environment for the child process, specified as an array of
+character pointers. Each element of the array should point to a string of the
+form @code{VAR=VALUE}, with the exception of the last element that must be
+@code{NULL}.
+
+@end deftypefn
+
+@c pexecute.txh:301
+@deftypefn Extension int pexecute (const char *@var{program}, @
+ char * const *@var{argv}, const char *@var{this_pname}, @
+ const char *@var{temp_base}, char **@var{errmsg_fmt}, @
+ char **@var{errmsg_arg}, int @var{flags})
+
+This is the old interface to execute one or more programs. It is
+still supported for compatibility purposes, but is no longer
+documented.
+
+@end deftypefn
+
+@c strsignal.c:541
+@deftypefn Supplemental void psignal (int @var{signo}, char *@var{message})
+
+Print @var{message} to the standard error, followed by a colon,
+followed by the description of the signal specified by @var{signo},
+followed by a newline.
+
+@end deftypefn
+
+@c putenv.c:21
+@deftypefn Supplemental int putenv (const char *@var{string})
+
+Uses @code{setenv} or @code{unsetenv} to put @var{string} into
+the environment or remove it. If @var{string} is of the form
+@samp{name=value} the string is added; if no @samp{=} is present the
+name is unset/removed.
+
+@end deftypefn
+
+@c pexecute.txh:312
+@deftypefn Extension int pwait (int @var{pid}, int *@var{status}, int @var{flags})
+
+Another part of the old execution interface.
+
+@end deftypefn
+
+@c random.c:39
+@deftypefn Supplement {long int} random (void)
+@deftypefnx Supplement void srandom (unsigned int @var{seed})
+@deftypefnx Supplement void* initstate (unsigned int @var{seed}, @
+ void *@var{arg_state}, unsigned long @var{n})
+@deftypefnx Supplement void* setstate (void *@var{arg_state})
+
+Random number functions. @code{random} returns a random number in the
+range 0 to @code{LONG_MAX}. @code{srandom} initializes the random
+number generator to some starting point determined by @var{seed}
+(else, the values returned by @code{random} are always the same for each
+run of the program). @code{initstate} and @code{setstate} allow fine-grained
+control over the state of the random number generator.
+
+@end deftypefn
+
+@c concat.c:160
+@deftypefn Extension char* reconcat (char *@var{optr}, const char *@var{s1}, @
+ @dots{}, @code{NULL})
+
+Same as @code{concat}, except that if @var{optr} is not @code{NULL} it
+is freed after the string is created. This is intended to be useful
+when you're extending an existing string or building up a string in a
+loop:
+
+@example
+ str = reconcat (str, "pre-", str, NULL);
+@end example
+
+@end deftypefn
+
+@c rename.c:6
+@deftypefn Supplemental int rename (const char *@var{old}, const char *@var{new})
+
+Renames a file from @var{old} to @var{new}. If @var{new} already
+exists, it is removed.
+
+@end deftypefn
+
+@c rindex.c:5
+@deftypefn Supplemental char* rindex (const char *@var{s}, int @var{c})
+
+Returns a pointer to the last occurrence of the character @var{c} in
+the string @var{s}, or @code{NULL} if not found. The use of @code{rindex} is
+deprecated in new programs in favor of @code{strrchr}.
+
+@end deftypefn
+
+@c setenv.c:22
+@deftypefn Supplemental int setenv (const char *@var{name}, @
+ const char *@var{value}, int @var{overwrite})
+@deftypefnx Supplemental void unsetenv (const char *@var{name})
+
+@code{setenv} adds @var{name} to the environment with value
+@var{value}. If the name was already present in the environment,
+the new value will be stored only if @var{overwrite} is nonzero.
+The companion @code{unsetenv} function removes @var{name} from the
+environment. This implementation is not safe for multithreaded code.
+
+@end deftypefn
+
+@c setproctitle.c:31
+@deftypefn Supplemental void setproctitle (const char *@var{fmt}, ...)
+
+Set the title of a process to @var{fmt}. va args not supported for now,
+but defined for compatibility with BSD.
+
+@end deftypefn
+
+@c strsignal.c:348
+@deftypefn Extension int signo_max (void)
+
+Returns the maximum signal value for which a corresponding symbolic
+name or message is available. Note that in the case where we use the
+@code{sys_siglist} supplied by the system, it is possible for there to
+be more symbolic names than messages, or vice versa. In fact, the
+manual page for @code{psignal(3b)} explicitly warns that one should
+check the size of the table (@code{NSIG}) before indexing it, since
+new signal codes may be added to the system before they are added to
+the table. Thus @code{NSIG} might be smaller than value implied by
+the largest signo value defined in @code{<signal.h>}.
+
+We return the maximum value that can be used to obtain a meaningful
+symbolic name or message.
+
+@end deftypefn
+
+@c sigsetmask.c:8
+@deftypefn Supplemental int sigsetmask (int @var{set})
+
+Sets the signal mask to the one provided in @var{set} and returns
+the old mask (which, for libiberty's implementation, will always
+be the value @code{1}).
+
+@end deftypefn
+
+@c simple-object.txh:96
+@deftypefn Extension {const char *} simple_object_attributes_compare @
+ (simple_object_attributes *@var{attrs1}, simple_object_attributes *@var{attrs2}, @
+ int *@var{err})
+
+Compare @var{attrs1} and @var{attrs2}. If they could be linked
+together without error, return @code{NULL}. Otherwise, return an
+error message and set @code{*@var{err}} to an errno value or @code{0}
+if there is no relevant errno.
+
+@end deftypefn
+
+@c simple-object.txh:81
+@deftypefn Extension {simple_object_attributes *} simple_object_fetch_attributes @
+ (simple_object_read *@var{simple_object}, const char **@var{errmsg}, int *@var{err})
+
+Fetch the attributes of @var{simple_object}. The attributes are
+internal information such as the format of the object file, or the
+architecture it was compiled for. This information will persist until
+@code{simple_object_attributes_release} is called, even if
+@var{simple_object} itself is released.
+
+On error this returns @code{NULL}, sets @code{*@var{errmsg}} to an
+error message, and sets @code{*@var{err}} to an errno value or
+@code{0} if there is no relevant errno.
+
+@end deftypefn
+
+@c simple-object.txh:49
+@deftypefn Extension {int} simple_object_find_section @
+ (simple_object_read *@var{simple_object} off_t *@var{offset}, @
+ off_t *@var{length}, const char **@var{errmsg}, int *@var{err})
+
+Look for the section @var{name} in @var{simple_object}. This returns
+information for the first section with that name.
+
+If found, return 1 and set @code{*@var{offset}} to the offset in the
+file of the section contents and set @code{*@var{length}} to the
+length of the section contents. The value in @code{*@var{offset}}
+will be relative to the offset passed to
+@code{simple_object_open_read}.
+
+If the section is not found, and no error occurs,
+@code{simple_object_find_section} returns @code{0} and set
+@code{*@var{errmsg}} to @code{NULL}.
+
+If an error occurs, @code{simple_object_find_section} returns
+@code{0}, sets @code{*@var{errmsg}} to an error message, and sets
+@code{*@var{err}} to an errno value or @code{0} if there is no
+relevant errno.
+
+@end deftypefn
+
+@c simple-object.txh:27
+@deftypefn Extension {const char *} simple_object_find_sections @
+ (simple_object_read *@var{simple_object}, int (*@var{pfn}) (void *@var{data}, @
+ const char *@var{name}, off_t @var{offset}, off_t @var{length}), @
+ void *@var{data}, int *@var{err})
+
+This function calls @var{pfn} for each section in @var{simple_object}.
+It calls @var{pfn} with the section name, the offset within the file
+of the section contents, and the length of the section contents. The
+offset within the file is relative to the offset passed to
+@code{simple_object_open_read}. The @var{data} argument to this
+function is passed along to @var{pfn}.
+
+If @var{pfn} returns @code{0}, the loop over the sections stops and
+@code{simple_object_find_sections} returns. If @var{pfn} returns some
+other value, the loop continues.
+
+On success @code{simple_object_find_sections} returns. On error it
+returns an error string, and sets @code{*@var{err}} to an errno value
+or @code{0} if there is no relevant errno.
+
+@end deftypefn
+
+@c simple-object.txh:2
+@deftypefn Extension {simple_object_read *} simple_object_open_read @
+ (int @var{descriptor}, off_t @var{offset}, const char *{segment_name}, @
+ const char **@var{errmsg}, int *@var{err})
+
+Opens an object file for reading. Creates and returns an
+@code{simple_object_read} pointer which may be passed to other
+functions to extract data from the object file.
+
+@var{descriptor} holds a file descriptor which permits reading.
+
+@var{offset} is the offset into the file; this will be @code{0} in the
+normal case, but may be a different value when reading an object file
+in an archive file.
+
+@var{segment_name} is only used with the Mach-O file format used on
+Darwin aka Mac OS X. It is required on that platform, and means to
+only look at sections within the segment with that name. The
+parameter is ignored on other systems.
+
+If an error occurs, this functions returns @code{NULL} and sets
+@code{*@var{errmsg}} to an error string and sets @code{*@var{err}} to
+an errno value or @code{0} if there is no relevant errno.
+
+@end deftypefn
+
+@c simple-object.txh:107
+@deftypefn Extension {void} simple_object_release_attributes @
+ (simple_object_attributes *@var{attrs})
+
+Release all resources associated with @var{attrs}.
+
+@end deftypefn
+
+@c simple-object.txh:73
+@deftypefn Extension {void} simple_object_release_read @
+ (simple_object_read *@var{simple_object})
+
+Release all resources associated with @var{simple_object}. This does
+not close the file descriptor.
+
+@end deftypefn
+
+@c simple-object.txh:184
+@deftypefn Extension {void} simple_object_release_write @
+ (simple_object_write *@var{simple_object})
+
+Release all resources associated with @var{simple_object}.
+
+@end deftypefn
+
+@c simple-object.txh:114
+@deftypefn Extension {simple_object_write *} simple_object_start_write @
+ (simple_object_attributes @var{attrs}, const char *@var{segment_name}, @
+ const char **@var{errmsg}, int *@var{err})
+
+Start creating a new object file using the object file format
+described in @var{attrs}. You must fetch attribute information from
+an existing object file before you can create a new one. There is
+currently no support for creating an object file de novo.
+
+@var{segment_name} is only used with Mach-O as found on Darwin aka Mac
+OS X. The parameter is required on that target. It means that all
+sections are created within the named segment. It is ignored for
+other object file formats.
+
+On error @code{simple_object_start_write} returns @code{NULL}, sets
+@code{*@var{ERRMSG}} to an error message, and sets @code{*@var{err}}
+to an errno value or @code{0} if there is no relevant errno.
+
+@end deftypefn
+
+@c simple-object.txh:153
+@deftypefn Extension {const char *} simple_object_write_add_data @
+ (simple_object_write *@var{simple_object}, @
+ simple_object_write_section *@var{section}, const void *@var{buffer}, @
+ size_t @var{size}, int @var{copy}, int *@var{err})
+
+Add data @var{buffer}/@var{size} to @var{section} in
+@var{simple_object}. If @var{copy} is non-zero, the data will be
+copied into memory if necessary. If @var{copy} is zero, @var{buffer}
+must persist until @code{simple_object_write_to_file} is called. is
+released.
+
+On success this returns @code{NULL}. On error this returns an error
+message, and sets @code{*@var{err}} to an errno value or 0 if there is
+no relevant erro.
+
+@end deftypefn
+
+@c simple-object.txh:134
+@deftypefn Extension {simple_object_write_section *} simple_object_write_create_section @
+ (simple_object_write *@var{simple_object}, const char *@var{name}, @
+ unsigned int @var{align}, const char **@var{errmsg}, int *@var{err})
+
+Add a section to @var{simple_object}. @var{name} is the name of the
+new section. @var{align} is the required alignment expressed as the
+number of required low-order 0 bits (e.g., 2 for alignment to a 32-bit
+boundary).
+
+The section is created as containing data, readable, not writable, not
+executable, not loaded at runtime. The section is not written to the
+file until @code{simple_object_write_to_file} is called.
+
+On error this returns @code{NULL}, sets @code{*@var{errmsg}} to an
+error message, and sets @code{*@var{err}} to an errno value or
+@code{0} if there is no relevant errno.
+
+@end deftypefn
+
+@c simple-object.txh:170
+@deftypefn Extension {const char *} simple_object_write_to_file @
+ (simple_object_write *@var{simple_object}, int @var{descriptor}, int *@var{err})
+
+Write the complete object file to @var{descriptor}, an open file
+descriptor. This writes out all the data accumulated by calls to
+@code{simple_object_write_create_section} and
+@var{simple_object_write_add_data}.
+
+This returns @code{NULL} on success. On error this returns an error
+message and sets @code{*@var{err}} to an errno value or @code{0} if
+there is no relevant errno.
+
+@end deftypefn
+
+@c snprintf.c:28
+@deftypefn Supplemental int snprintf (char *@var{buf}, size_t @var{n}, @
+ const char *@var{format}, ...)
+
+This function is similar to @code{sprintf}, but it will write to
+@var{buf} at most @code{@var{n}-1} bytes of text, followed by a
+terminating null byte, for a total of @var{n} bytes.
+On error the return value is -1, otherwise it returns the number of
+bytes, not including the terminating null byte, that would have been
+written had @var{n} been sufficiently large, regardless of the actual
+value of @var{n}. Note some pre-C99 system libraries do not implement
+this correctly so users cannot generally rely on the return value if
+the system version of this function is used.
+
+@end deftypefn
+
+@c spaces.c:22
+@deftypefn Extension char* spaces (int @var{count})
+
+Returns a pointer to a memory region filled with the specified
+number of spaces and null terminated. The returned pointer is
+valid until at least the next call.
+
+@end deftypefn
+
+@c splay-tree.c:305
+@deftypefn Supplemental splay_tree splay_tree_new_with_typed_alloc @
+(splay_tree_compare_fn @var{compare_fn}, @
+splay_tree_delete_key_fn @var{delete_key_fn}, @
+splay_tree_delete_value_fn @var{delete_value_fn}, @
+splay_tree_allocate_fn @var{tree_allocate_fn}, @
+splay_tree_allocate_fn @var{node_allocate_fn}, @
+splay_tree_deallocate_fn @var{deallocate_fn}, @
+void * @var{allocate_data})
+
+This function creates a splay tree that uses two different allocators
+@var{tree_allocate_fn} and @var{node_allocate_fn} to use for allocating the
+tree itself and its nodes respectively. This is useful when variables of
+different types need to be allocated with different allocators.
+
+The splay tree will use @var{compare_fn} to compare nodes,
+@var{delete_key_fn} to deallocate keys, and @var{delete_value_fn} to
+deallocate values. Keys and values will be deallocated when the
+tree is deleted using splay_tree_delete or when a node is removed
+using splay_tree_remove. splay_tree_insert will release the previously
+inserted key and value using @var{delete_key_fn} and @var{delete_value_fn}
+if the inserted key is already found in the tree.
+
+@end deftypefn
+
+@c stack-limit.c:28
+@deftypefn Extension void stack_limit_increase (unsigned long @var{pref})
+
+Attempt to increase stack size limit to @var{pref} bytes if possible.
+
+@end deftypefn
+
+@c stpcpy.c:23
+@deftypefn Supplemental char* stpcpy (char *@var{dst}, const char *@var{src})
+
+Copies the string @var{src} into @var{dst}. Returns a pointer to
+@var{dst} + strlen(@var{src}).
+
+@end deftypefn
+
+@c stpncpy.c:23
+@deftypefn Supplemental char* stpncpy (char *@var{dst}, const char *@var{src}, @
+ size_t @var{len})
+
+Copies the string @var{src} into @var{dst}, copying exactly @var{len}
+and padding with zeros if necessary. If @var{len} < strlen(@var{src})
+then return @var{dst} + @var{len}, otherwise returns @var{dst} +
+strlen(@var{src}).
+
+@end deftypefn
+
+@c strcasecmp.c:15
+@deftypefn Supplemental int strcasecmp (const char *@var{s1}, const char *@var{s2})
+
+A case-insensitive @code{strcmp}.
+
+@end deftypefn
+
+@c strchr.c:6
+@deftypefn Supplemental char* strchr (const char *@var{s}, int @var{c})
+
+Returns a pointer to the first occurrence of the character @var{c} in
+the string @var{s}, or @code{NULL} if not found. If @var{c} is itself the
+null character, the results are undefined.
+
+@end deftypefn
+
+@c strdup.c:3
+@deftypefn Supplemental char* strdup (const char *@var{s})
+
+Returns a pointer to a copy of @var{s} in memory obtained from
+@code{malloc}, or @code{NULL} if insufficient memory was available.
+
+@end deftypefn
+
+@c strerror.c:675
+@deftypefn Replacement {const char*} strerrno (int @var{errnum})
+
+Given an error number returned from a system call (typically returned
+in @code{errno}), returns a pointer to a string containing the
+symbolic name of that error number, as found in @code{<errno.h>}.
+
+If the supplied error number is within the valid range of indices for
+symbolic names, but no name is available for the particular error
+number, then returns the string @samp{Error @var{num}}, where @var{num}
+is the error number.
+
+If the supplied error number is not within the range of valid
+indices, then returns @code{NULL}.
+
+The contents of the location pointed to are only guaranteed to be
+valid until the next call to @code{strerrno}.
+
+@end deftypefn
+
+@c strerror.c:608
+@deftypefn Supplemental char* strerror (int @var{errnoval})
+
+Maps an @code{errno} number to an error message string, the contents
+of which are implementation defined. On systems which have the
+external variables @code{sys_nerr} and @code{sys_errlist}, these
+strings will be the same as the ones used by @code{perror}.
+
+If the supplied error number is within the valid range of indices for
+the @code{sys_errlist}, but no message is available for the particular
+error number, then returns the string @samp{Error @var{num}}, where
+@var{num} is the error number.
+
+If the supplied error number is not a valid index into
+@code{sys_errlist}, returns @code{NULL}.
+
+The returned string is only guaranteed to be valid only until the
+next call to @code{strerror}.
+
+@end deftypefn
+
+@c strncasecmp.c:15
+@deftypefn Supplemental int strncasecmp (const char *@var{s1}, const char *@var{s2})
+
+A case-insensitive @code{strncmp}.
+
+@end deftypefn
+
+@c strncmp.c:6
+@deftypefn Supplemental int strncmp (const char *@var{s1}, @
+ const char *@var{s2}, size_t @var{n})
+
+Compares the first @var{n} bytes of two strings, returning a value as
+@code{strcmp}.
+
+@end deftypefn
+
+@c strndup.c:23
+@deftypefn Extension char* strndup (const char *@var{s}, size_t @var{n})
+
+Returns a pointer to a copy of @var{s} with at most @var{n} characters
+in memory obtained from @code{malloc}, or @code{NULL} if insufficient
+memory was available. The result is always NUL terminated.
+
+@end deftypefn
+
+@c strnlen.c:6
+@deftypefn Supplemental size_t strnlen (const char *@var{s}, size_t @var{maxlen})
+
+Returns the length of @var{s}, as with @code{strlen}, but never looks
+past the first @var{maxlen} characters in the string. If there is no
+'\0' character in the first @var{maxlen} characters, returns
+@var{maxlen}.
+
+@end deftypefn
+
+@c strrchr.c:6
+@deftypefn Supplemental char* strrchr (const char *@var{s}, int @var{c})
+
+Returns a pointer to the last occurrence of the character @var{c} in
+the string @var{s}, or @code{NULL} if not found. If @var{c} is itself the
+null character, the results are undefined.
+
+@end deftypefn
+
+@c strsignal.c:383
+@deftypefn Supplemental {const char *} strsignal (int @var{signo})
+
+Maps an signal number to an signal message string, the contents of
+which are implementation defined. On systems which have the external
+variable @code{sys_siglist}, these strings will be the same as the
+ones used by @code{psignal()}.
+
+If the supplied signal number is within the valid range of indices for
+the @code{sys_siglist}, but no message is available for the particular
+signal number, then returns the string @samp{Signal @var{num}}, where
+@var{num} is the signal number.
+
+If the supplied signal number is not a valid index into
+@code{sys_siglist}, returns @code{NULL}.
+
+The returned string is only guaranteed to be valid only until the next
+call to @code{strsignal}.
+
+@end deftypefn
+
+@c strsignal.c:448
+@deftypefn Extension {const char*} strsigno (int @var{signo})
+
+Given an signal number, returns a pointer to a string containing the
+symbolic name of that signal number, as found in @code{<signal.h>}.
+
+If the supplied signal number is within the valid range of indices for
+symbolic names, but no name is available for the particular signal
+number, then returns the string @samp{Signal @var{num}}, where
+@var{num} is the signal number.
+
+If the supplied signal number is not within the range of valid
+indices, then returns @code{NULL}.
+
+The contents of the location pointed to are only guaranteed to be
+valid until the next call to @code{strsigno}.
+
+@end deftypefn
+
+@c strstr.c:6
+@deftypefn Supplemental char* strstr (const char *@var{string}, const char *@var{sub})
+
+This function searches for the substring @var{sub} in the string
+@var{string}, not including the terminating null characters. A pointer
+to the first occurrence of @var{sub} is returned, or @code{NULL} if the
+substring is absent. If @var{sub} points to a string with zero
+length, the function returns @var{string}.
+
+@end deftypefn
+
+@c strtod.c:27
+@deftypefn Supplemental double strtod (const char *@var{string}, @
+ char **@var{endptr})
+
+This ISO C function converts the initial portion of @var{string} to a
+@code{double}. If @var{endptr} is not @code{NULL}, a pointer to the
+character after the last character used in the conversion is stored in
+the location referenced by @var{endptr}. If no conversion is
+performed, zero is returned and the value of @var{string} is stored in
+the location referenced by @var{endptr}.
+
+@end deftypefn
+
+@c strerror.c:734
+@deftypefn Extension int strtoerrno (const char *@var{name})
+
+Given the symbolic name of a error number (e.g., @code{EACCES}), map it
+to an errno value. If no translation is found, returns 0.
+
+@end deftypefn
+
+@c strtol.c:33
+@deftypefn Supplemental {long int} strtol (const char *@var{string}, @
+ char **@var{endptr}, int @var{base})
+@deftypefnx Supplemental {unsigned long int} strtoul (const char *@var{string}, @
+ char **@var{endptr}, int @var{base})
+
+The @code{strtol} function converts the string in @var{string} to a
+long integer value according to the given @var{base}, which must be
+between 2 and 36 inclusive, or be the special value 0. If @var{base}
+is 0, @code{strtol} will look for the prefixes @code{0} and @code{0x}
+to indicate bases 8 and 16, respectively, else default to base 10.
+When the base is 16 (either explicitly or implicitly), a prefix of
+@code{0x} is allowed. The handling of @var{endptr} is as that of
+@code{strtod} above. The @code{strtoul} function is the same, except
+that the converted value is unsigned.
+
+@end deftypefn
+
+@c strtoll.c:33
+@deftypefn Supplemental {long long int} strtoll (const char *@var{string}, @
+ char **@var{endptr}, int @var{base})
+@deftypefnx Supplemental {unsigned long long int} strtoull (@
+ const char *@var{string}, char **@var{endptr}, int @var{base})
+
+The @code{strtoll} function converts the string in @var{string} to a
+long long integer value according to the given @var{base}, which must be
+between 2 and 36 inclusive, or be the special value 0. If @var{base}
+is 0, @code{strtoll} will look for the prefixes @code{0} and @code{0x}
+to indicate bases 8 and 16, respectively, else default to base 10.
+When the base is 16 (either explicitly or implicitly), a prefix of
+@code{0x} is allowed. The handling of @var{endptr} is as that of
+@code{strtod} above. The @code{strtoull} function is the same, except
+that the converted value is unsigned.
+
+@end deftypefn
+
+@c strsignal.c:502
+@deftypefn Extension int strtosigno (const char *@var{name})
+
+Given the symbolic name of a signal, map it to a signal number. If no
+translation is found, returns 0.
+
+@end deftypefn
+
+@c strverscmp.c:25
+@deftypefun int strverscmp (const char *@var{s1}, const char *@var{s2})
+The @code{strverscmp} function compares the string @var{s1} against
+@var{s2}, considering them as holding indices/version numbers. Return
+value follows the same conventions as found in the @code{strverscmp}
+function. In fact, if @var{s1} and @var{s2} contain no digits,
+@code{strverscmp} behaves like @code{strcmp}.
+
+Basically, we compare strings normally (character by character), until
+we find a digit in each string - then we enter a special comparison
+mode, where each sequence of digits is taken as a whole. If we reach the
+end of these two parts without noticing a difference, we return to the
+standard comparison mode. There are two types of numeric parts:
+"integral" and "fractional" (those begin with a '0'). The types
+of the numeric parts affect the way we sort them:
+
+@itemize @bullet
+@item
+integral/integral: we compare values as you would expect.
+
+@item
+fractional/integral: the fractional part is less than the integral one.
+Again, no surprise.
+
+@item
+fractional/fractional: the things become a bit more complex.
+If the common prefix contains only leading zeroes, the longest part is less
+than the other one; else the comparison behaves normally.
+@end itemize
+
+@smallexample
+strverscmp ("no digit", "no digit")
+ @result{} 0 // @r{same behavior as strcmp.}
+strverscmp ("item#99", "item#100")
+ @result{} <0 // @r{same prefix, but 99 < 100.}
+strverscmp ("alpha1", "alpha001")
+ @result{} >0 // @r{fractional part inferior to integral one.}
+strverscmp ("part1_f012", "part1_f01")
+ @result{} >0 // @r{two fractional parts.}
+strverscmp ("foo.009", "foo.0")
+ @result{} <0 // @r{idem, but with leading zeroes only.}
+@end smallexample
+
+This function is especially useful when dealing with filename sorting,
+because filenames frequently hold indices/version numbers.
+@end deftypefun
+
+@c timeval-utils.c:43
+@deftypefn Extension void timeval_add (struct timeval *@var{a}, @
+ struct timeval *@var{b}, struct timeval *@var{result})
+
+Adds @var{a} to @var{b} and stores the result in @var{result}.
+
+@end deftypefn
+
+@c timeval-utils.c:67
+@deftypefn Extension void timeval_sub (struct timeval *@var{a}, @
+ struct timeval *@var{b}, struct timeval *@var{result})
+
+Subtracts @var{b} from @var{a} and stores the result in @var{result}.
+
+@end deftypefn
+
+@c tmpnam.c:3
+@deftypefn Supplemental char* tmpnam (char *@var{s})
+
+This function attempts to create a name for a temporary file, which
+will be a valid file name yet not exist when @code{tmpnam} checks for
+it. @var{s} must point to a buffer of at least @code{L_tmpnam} bytes,
+or be @code{NULL}. Use of this function creates a security risk, and it must
+not be used in new projects. Use @code{mkstemp} instead.
+
+@end deftypefn
+
+@c unlink-if-ordinary.c:27
+@deftypefn Supplemental int unlink_if_ordinary (const char*)
+
+Unlinks the named file, unless it is special (e.g. a device file).
+Returns 0 when the file was unlinked, a negative value (and errno set) when
+there was an error deleting the file, and a positive value if no attempt
+was made to unlink the file because it is special.
+
+@end deftypefn
+
+@c fopen_unlocked.c:31
+@deftypefn Extension void unlock_std_streams (void)
+
+If the OS supports it, ensure that the standard I/O streams,
+@code{stdin}, @code{stdout} and @code{stderr} are setup to avoid any
+multi-threaded locking. Otherwise do nothing.
+
+@end deftypefn
+
+@c fopen_unlocked.c:23
+@deftypefn Extension void unlock_stream (FILE * @var{stream})
+
+If the OS supports it, ensure that the supplied stream is setup to
+avoid any multi-threaded locking. Otherwise leave the @code{FILE}
+pointer unchanged. If the @var{stream} is @code{NULL} do nothing.
+
+@end deftypefn
+
+@c vasprintf.c:47
+@deftypefn Extension int vasprintf (char **@var{resptr}, @
+ const char *@var{format}, va_list @var{args})
+
+Like @code{vsprintf}, but instead of passing a pointer to a buffer,
+you pass a pointer to a pointer. This function will compute the size
+of the buffer needed, allocate memory with @code{malloc}, and store a
+pointer to the allocated memory in @code{*@var{resptr}}. The value
+returned is the same as @code{vsprintf} would return. If memory could
+not be allocated, minus one is returned and @code{NULL} is stored in
+@code{*@var{resptr}}.
+
+@end deftypefn
+
+@c vfork.c:6
+@deftypefn Supplemental int vfork (void)
+
+Emulates @code{vfork} by calling @code{fork} and returning its value.
+
+@end deftypefn
+
+@c vprintf.c:3
+@deftypefn Supplemental int vprintf (const char *@var{format}, va_list @var{ap})
+@deftypefnx Supplemental int vfprintf (FILE *@var{stream}, @
+ const char *@var{format}, va_list @var{ap})
+@deftypefnx Supplemental int vsprintf (char *@var{str}, @
+ const char *@var{format}, va_list @var{ap})
+
+These functions are the same as @code{printf}, @code{fprintf}, and
+@code{sprintf}, respectively, except that they are called with a
+@code{va_list} instead of a variable number of arguments. Note that
+they do not call @code{va_end}; this is the application's
+responsibility. In @libib{} they are implemented in terms of the
+nonstandard but common function @code{_doprnt}.
+
+@end deftypefn
+
+@c vsnprintf.c:28
+@deftypefn Supplemental int vsnprintf (char *@var{buf}, size_t @var{n}, @
+ const char *@var{format}, va_list @var{ap})
+
+This function is similar to @code{vsprintf}, but it will write to
+@var{buf} at most @code{@var{n}-1} bytes of text, followed by a
+terminating null byte, for a total of @var{n} bytes. On error the
+return value is -1, otherwise it returns the number of characters that
+would have been printed had @var{n} been sufficiently large,
+regardless of the actual value of @var{n}. Note some pre-C99 system
+libraries do not implement this correctly so users cannot generally
+rely on the return value if the system version of this function is
+used.
+
+@end deftypefn
+
+@c waitpid.c:3
+@deftypefn Supplemental int waitpid (int @var{pid}, int *@var{status}, int)
+
+This is a wrapper around the @code{wait} function. Any ``special''
+values of @var{pid} depend on your implementation of @code{wait}, as
+does the return value. The third argument is unused in @libib{}.
+
+@end deftypefn
+
+@c argv.c:289
+@deftypefn Extension int writeargv (char * const *@var{argv}, FILE *@var{file})
+
+Write each member of ARGV, handling all necessary quoting, to the file
+named by FILE, separated by whitespace. Return 0 on success, non-zero
+if an error occurred while writing to FILE.
+
+@end deftypefn
+
+@c xasprintf.c:31
+@deftypefn Replacement char* xasprintf (const char *@var{format}, ...)
+
+Print to allocated string without fail. If @code{xasprintf} fails,
+this will print a message to @code{stderr} (using the name set by
+@code{xmalloc_set_program_name}, if any) and then call @code{xexit}.
+
+@end deftypefn
+
+@c xatexit.c:11
+@deftypefun int xatexit (void (*@var{fn}) (void))
+
+Behaves as the standard @code{atexit} function, but with no limit on
+the number of registered functions. Returns 0 on success, or @minus{}1 on
+failure. If you use @code{xatexit} to register functions, you must use
+@code{xexit} to terminate your program.
+
+@end deftypefun
+
+@c xmalloc.c:38
+@deftypefn Replacement void* xcalloc (size_t @var{nelem}, size_t @var{elsize})
+
+Allocate memory without fail, and set it to zero. This routine functions
+like @code{calloc}, but will behave the same as @code{xmalloc} if memory
+cannot be found.
+
+@end deftypefn
+
+@c xexit.c:22
+@deftypefn Replacement void xexit (int @var{code})
+
+Terminates the program. If any functions have been registered with
+the @code{xatexit} replacement function, they will be called first.
+Termination is handled via the system's normal @code{exit} call.
+
+@end deftypefn
+
+@c xmalloc.c:22
+@deftypefn Replacement void* xmalloc (size_t)
+
+Allocate memory without fail. If @code{malloc} fails, this will print
+a message to @code{stderr} (using the name set by
+@code{xmalloc_set_program_name},
+if any) and then call @code{xexit}. Note that it is therefore safe for
+a program to contain @code{#define malloc xmalloc} in its source.
+
+@end deftypefn
+
+@c xmalloc.c:53
+@deftypefn Replacement void xmalloc_failed (size_t)
+
+This function is not meant to be called by client code, and is listed
+here for completeness only. If any of the allocation routines fail, this
+function will be called to print an error message and terminate execution.
+
+@end deftypefn
+
+@c xmalloc.c:46
+@deftypefn Replacement void xmalloc_set_program_name (const char *@var{name})
+
+You can use this to set the name of the program used by
+@code{xmalloc_failed} when printing a failure message.
+
+@end deftypefn
+
+@c xmemdup.c:7
+@deftypefn Replacement void* xmemdup (void *@var{input}, @
+ size_t @var{copy_size}, size_t @var{alloc_size})
+
+Duplicates a region of memory without fail. First, @var{alloc_size} bytes
+are allocated, then @var{copy_size} bytes from @var{input} are copied into
+it, and the new memory is returned. If fewer bytes are copied than were
+allocated, the remaining memory is zeroed.
+
+@end deftypefn
+
+@c xmalloc.c:32
+@deftypefn Replacement void* xrealloc (void *@var{ptr}, size_t @var{size})
+Reallocate memory without fail. This routine functions like @code{realloc},
+but will behave the same as @code{xmalloc} if memory cannot be found.
+
+@end deftypefn
+
+@c xstrdup.c:7
+@deftypefn Replacement char* xstrdup (const char *@var{s})
+
+Duplicates a character string without fail, using @code{xmalloc} to
+obtain memory.
+
+@end deftypefn
+
+@c xstrerror.c:7
+@deftypefn Replacement char* xstrerror (int @var{errnum})
+
+Behaves exactly like the standard @code{strerror} function, but
+will never return a @code{NULL} pointer.
+
+@end deftypefn
+
+@c xstrndup.c:23
+@deftypefn Replacement char* xstrndup (const char *@var{s}, size_t @var{n})
+
+Returns a pointer to a copy of @var{s} with at most @var{n} characters
+without fail, using @code{xmalloc} to obtain memory. The result is
+always NUL terminated.
+
+@end deftypefn
+
+@c xvasprintf.c:38
+@deftypefn Replacement char* xvasprintf (const char *@var{format}, va_list @var{args})
+
+Print to allocated string without fail. If @code{xvasprintf} fails,
+this will print a message to @code{stderr} (using the name set by
+@code{xmalloc_set_program_name}, if any) and then call @code{xexit}.
+
+@end deftypefn
+
+
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+@c %**start of header
+@setfilename libiberty.info
+@settitle @sc{gnu} libiberty
+@c %**end of header
+
+@syncodeindex fn cp
+@syncodeindex vr cp
+@syncodeindex pg cp
+
+@finalout
+@c %**end of header
+
+@dircategory GNU libraries
+@direntry
+* Libiberty: (libiberty). Library of utility functions which
+ are missing or broken on some systems.
+@end direntry
+
+@macro libib
+@code{libiberty}
+@end macro
+
+@ifinfo
+This manual describes the GNU @libib library of utility subroutines.
+
+Copyright @copyright{} 2001-2022 Free Software Foundation, Inc.
+
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, with no Front-Cover Texts, and with no
+ Back-Cover Texts. A copy of the license is included in the
+ section entitled ``GNU Free Documentation License''.
+
+@ignore
+Permission is granted to process this file through TeX and print the
+results, provided the printed document carries a copying permission
+notice identical to this one except for the removal of this paragraph
+(this paragraph not being relevant to the printed manual).
+
+@end ignore
+@end ifinfo
+
+
+@titlepage
+@title @sc{gnu} libiberty
+@author Phil Edwards et al.
+@page
+
+
+@vskip 0pt plus 1filll
+Copyright @copyright{} 2001-2022 Free Software Foundation, Inc.
+
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, with no Front-Cover Texts, and with no
+ Back-Cover Texts. A copy of the license is included in the
+ section entitled ``GNU Free Documentation License''.
+
+@end titlepage
+@contents
+@page
+
+@ifnottex
+@node Top,Using,,
+@top Introduction
+
+The @libib{} library is a collection of subroutines used by various
+GNU programs. It is available under the Library General Public
+License; for more information, see @ref{Library Copying}.
+
+@end ifnottex
+
+@menu
+* Using:: How to use libiberty in your code.
+
+* Overview:: Overview of available function groups.
+
+* Functions:: Available functions, macros, and global variables.
+
+* Licenses:: The various licenses under which libiberty sources are
+ distributed.
+
+* Index:: Index of functions and categories.
+@end menu
+
+@node Using
+@chapter Using
+@cindex using libiberty
+@cindex libiberty usage
+@cindex how to use
+
+@c THIS SECTION IS CRAP AND NEEDS REWRITING BADLY.
+
+To date, @libib{} is generally not installed on its own. It has evolved
+over years but does not have its own version number nor release schedule.
+
+Possibly the easiest way to use @libib{} in your projects is to drop the
+@libib{} code into your project's sources, and to build the library along
+with your own sources; the library would then be linked in at the end. This
+prevents any possible version mismatches with other copies of libiberty
+elsewhere on the system.
+
+Passing @option{--enable-install-libiberty} to the @command{configure}
+script when building @libib{} causes the header files and archive library
+to be installed when @kbd{make install} is run. This option also takes
+an (optional) argument to specify the installation location, in the same
+manner as @option{--prefix}.
+
+For your own projects, an approach which offers stability and flexibility
+is to include @libib{} with your code, but allow the end user to optionally
+choose to use a previously-installed version instead. In this way the
+user may choose (for example) to install @libib{} as part of GCC, and use
+that version for all software built with that compiler. (This approach
+has proven useful with software using the GNU @code{readline} library.)
+
+Making use of @libib{} code usually requires that you include one or more
+header files from the @libib{} distribution. (They will be named as
+necessary in the function descriptions.) At link time, you will need to
+add @option{-liberty} to your link command invocation.
+
+
+@node Overview
+@chapter Overview
+
+Functions contained in @libib{} can be divided into three general categories.
+
+
+@menu
+* Supplemental Functions:: Providing functions which don't exist
+ on older operating systems.
+
+* Replacement Functions:: These functions are sometimes buggy or
+ unpredictable on some operating systems.
+
+* Extensions:: Functions which provide useful extensions
+ or safety wrappers around existing code.
+@end menu
+
+@node Supplemental Functions
+@section Supplemental Functions
+@cindex supplemental functions
+@cindex functions, supplemental
+@cindex functions, missing
+
+Certain operating systems do not provide functions which have since
+become standardized, or at least common. For example, the Single
+Unix Specification Version 2 requires that the @code{basename}
+function be provided, but an OS which predates that specification
+might not have this function. This should not prevent well-written
+code from running on such a system.
+
+Similarly, some functions exist only among a particular ``flavor''
+or ``family'' of operating systems. As an example, the @code{bzero}
+function is often not present on systems outside the BSD-derived
+family of systems.
+
+Many such functions are provided in @libib{}. They are quickly
+listed here with little description, as systems which lack them
+become less and less common. Each function @var{foo} is implemented
+in @file{@var{foo}.c} but not declared in any @libib{} header file; more
+comments and caveats for each function's implementation are often
+available in the source file. Generally, the function can simply
+be declared as @code{extern}.
+
+
+
+@node Replacement Functions
+@section Replacement Functions
+@cindex replacement functions
+@cindex functions, replacement
+
+Some functions have extremely limited implementations on different
+platforms. Other functions are tedious to use correctly; for example,
+proper use of @code{malloc} calls for the return value to be checked and
+appropriate action taken if memory has been exhausted. A group of
+``replacement functions'' is available in @libib{} to address these issues
+for some of the most commonly used subroutines.
+
+All of these functions are declared in the @file{libiberty.h} header
+file. Many of the implementations will use preprocessor macros set by
+GNU Autoconf, if you decide to make use of that program. Some of these
+functions may call one another.
+
+
+@menu
+* Memory Allocation:: Testing and handling failed memory
+ requests automatically.
+* Exit Handlers:: Calling routines on program exit.
+* Error Reporting:: Mapping errno and signal numbers to
+ more useful string formats.
+@end menu
+
+@node Memory Allocation
+@subsection Memory Allocation
+@cindex memory allocation
+
+The functions beginning with the letter @samp{x} are wrappers around
+standard functions; the functions provided by the system environment
+are called and their results checked before the results are passed back
+to client code. If the standard functions fail, these wrappers will
+terminate the program. Thus, these versions can be used with impunity.
+
+
+@node Exit Handlers
+@subsection Exit Handlers
+@cindex exit handlers
+
+The existence and implementation of the @code{atexit} routine varies
+amongst the flavors of Unix. @libib{} provides an unvarying dependable
+implementation via @code{xatexit} and @code{xexit}.
+
+
+@node Error Reporting
+@subsection Error Reporting
+@cindex error reporting
+
+These are a set of routines to facilitate programming with the system
+@code{errno} interface. The @libib{} source file @file{strerror.c}
+contains a good deal of documentation for these functions.
+
+@c signal stuff
+
+
+@node Extensions
+@section Extensions
+@cindex extensions
+@cindex functions, extension
+
+@libib{} includes additional functionality above and beyond standard
+functions, which has proven generically useful in GNU programs, such as
+obstacks and regex. These functions are often copied from other
+projects as they gain popularity, and are included here to provide a
+central location from which to use, maintain, and distribute them.
+
+@menu
+* Obstacks:: Stacks of arbitrary objects.
+@end menu
+
+@c This is generated from the glibc manual using contrib/make-obstacks-texi.pl
+@include obstacks.texi
+
+@node Functions
+@chapter Function, Variable, and Macro Listing.
+@include functions.texi
+
+@node Licenses
+@appendix Licenses
+
+@menu
+
+* Library Copying:: The GNU Library General Public License
+* BSD:: Regents of the University of California
+
+@end menu
+
+@c This takes care of Library Copying. It is the copying-lib.texi from the
+@c GNU web site, with its @node line altered to make makeinfo shut up.
+@include copying-lib.texi
+
+@page
+@node BSD
+@appendixsec BSD
+
+Copyright @copyright{} 1990 Regents of the University of California.
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+
+@enumerate
+
+@item
+Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+
+@item
+Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+
+@item
+[rescinded 22 July 1999]
+
+@item
+Neither the name of the University nor the names of its contributors
+may be used to endorse or promote products derived from this software
+without specific prior written permission.
+
+@end enumerate
+
+THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
+
+@node Index
+@unnumbered Index
+
+@printindex cp
+
+@bye
+
--- /dev/null
+@node Obstacks
+@subsection Obstacks
+@cindex obstacks
+
+An @dfn{obstack} is a pool of memory containing a stack of objects. You
+can create any number of separate obstacks, and then allocate objects in
+specified obstacks. Within each obstack, the last object allocated must
+always be the first one freed, but distinct obstacks are independent of
+each other.
+
+Aside from this one constraint of order of freeing, obstacks are totally
+general: an obstack can contain any number of objects of any size. They
+are implemented with macros, so allocation is usually very fast as long as
+the objects are usually small. And the only space overhead per object is
+the padding needed to start each object on a suitable boundary.
+
+@menu
+* Creating Obstacks:: How to declare an obstack in your program.
+* Preparing for Obstacks:: Preparations needed before you can
+ use obstacks.
+* Allocation in an Obstack:: Allocating objects in an obstack.
+* Freeing Obstack Objects:: Freeing objects in an obstack.
+* Obstack Functions:: The obstack functions are really macros.
+* Growing Objects:: Making an object bigger by stages.
+* Extra Fast Growing:: Extra-high-efficiency (though more
+ complicated) growing objects.
+* Status of an Obstack:: Inquiries about the status of an obstack.
+* Obstacks Data Alignment:: Controlling alignment of objects in obstacks.
+* Obstack Chunks:: How obstacks obtain and release chunks;
+ efficiency considerations.
+* Summary of Obstacks::
+@end menu
+
+@node Creating Obstacks
+@subsubsection Creating Obstacks
+
+The utilities for manipulating obstacks are declared in the header
+file @file{obstack.h}.
+@pindex obstack.h
+
+@comment obstack.h
+@comment GNU
+@deftp {Data Type} {struct obstack}
+An obstack is represented by a data structure of type @code{struct
+obstack}. This structure has a small fixed size; it records the status
+of the obstack and how to find the space in which objects are allocated.
+It does not contain any of the objects themselves. You should not try
+to access the contents of the structure directly; use only the macros
+described in this chapter.
+@end deftp
+
+You can declare variables of type @code{struct obstack} and use them as
+obstacks, or you can allocate obstacks dynamically like any other kind
+of object. Dynamic allocation of obstacks allows your program to have a
+variable number of different stacks. (You can even allocate an
+obstack structure in another obstack, but this is rarely useful.)
+
+All the macros that work with obstacks require you to specify which
+obstack to use. You do this with a pointer of type @code{struct obstack
+*}. In the following, we often say ``an obstack'' when strictly
+speaking the object at hand is such a pointer.
+
+The objects in the obstack are packed into large blocks called
+@dfn{chunks}. The @code{struct obstack} structure points to a chain of
+the chunks currently in use.
+
+The obstack library obtains a new chunk whenever you allocate an object
+that won't fit in the previous chunk. Since the obstack library manages
+chunks automatically, you don't need to pay much attention to them, but
+you do need to supply a function which the obstack library should use to
+get a chunk. Usually you supply a function which uses @code{malloc}
+directly or indirectly. You must also supply a function to free a chunk.
+These matters are described in the following section.
+
+@node Preparing for Obstacks
+@subsubsection Preparing for Using Obstacks
+
+Each source file in which you plan to use obstacks
+must include the header file @file{obstack.h}, like this:
+
+@smallexample
+#include <obstack.h>
+@end smallexample
+
+@findex obstack_chunk_alloc
+@findex obstack_chunk_free
+Also, if the source file uses the macro @code{obstack_init}, it must
+declare or define two macros that will be called by the
+obstack library. One, @code{obstack_chunk_alloc}, is used to allocate
+the chunks of memory into which objects are packed. The other,
+@code{obstack_chunk_free}, is used to return chunks when the objects in
+them are freed. These macros should appear before any use of obstacks
+in the source file.
+
+Usually these are defined to use @code{malloc} via the intermediary
+@code{xmalloc} (@pxref{Unconstrained Allocation, , , libc, The GNU C Library Reference Manual}). This is done with
+the following pair of macro definitions:
+
+@smallexample
+#define obstack_chunk_alloc xmalloc
+#define obstack_chunk_free free
+@end smallexample
+
+@noindent
+Though the memory you get using obstacks really comes from @code{malloc},
+using obstacks is faster because @code{malloc} is called less often, for
+larger blocks of memory. @xref{Obstack Chunks}, for full details.
+
+At run time, before the program can use a @code{struct obstack} object
+as an obstack, it must initialize the obstack by calling
+@code{obstack_init} or one of its variants, @code{obstack_begin},
+@code{obstack_specify_allocation}, or
+@code{obstack_specify_allocation_with_arg}.
+
+@comment obstack.h
+@comment GNU
+@deftypefun int obstack_init (struct obstack *@var{obstack-ptr})
+Initialize obstack @var{obstack-ptr} for allocation of objects. This
+macro calls the obstack's @code{obstack_chunk_alloc} function. If
+allocation of memory fails, the function pointed to by
+@code{obstack_alloc_failed_handler} is called. The @code{obstack_init}
+macro always returns 1 (Compatibility notice: Former versions of
+obstack returned 0 if allocation failed).
+@end deftypefun
+
+Here are two examples of how to allocate the space for an obstack and
+initialize it. First, an obstack that is a static variable:
+
+@smallexample
+static struct obstack myobstack;
+@dots{}
+obstack_init (&myobstack);
+@end smallexample
+
+@noindent
+Second, an obstack that is itself dynamically allocated:
+
+@smallexample
+struct obstack *myobstack_ptr
+ = (struct obstack *) xmalloc (sizeof (struct obstack));
+
+obstack_init (myobstack_ptr);
+@end smallexample
+
+@comment obstack.h
+@comment GNU
+@deftypefun int obstack_begin (struct obstack *@var{obstack-ptr}, size_t chunk_size)
+Like @code{obstack_init}, but specify chunks to be at least
+@var{chunk_size} bytes in size.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun int obstack_specify_allocation (struct obstack *@var{obstack-ptr}, size_t chunk_size, size_t alignment, void *(*chunkfun) (size_t), void (*freefun) (void *))
+Like @code{obstack_init}, specifying chunk size, chunk
+alignment, and memory allocation functions. A @var{chunk_size} or
+@var{alignment} of zero results in the default size or alignment
+respectively being used.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun int obstack_specify_allocation_with_arg (struct obstack *@var{obstack-ptr}, size_t chunk_size, size_t alignment, void *(*chunkfun) (void *, size_t), void (*freefun) (void *, void *), void *arg)
+Like @code{obstack_specify_allocation}, but specifying memory
+allocation functions that take an extra first argument, @var{arg}.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@defvar obstack_alloc_failed_handler
+The value of this variable is a pointer to a function that
+@code{obstack} uses when @code{obstack_chunk_alloc} fails to allocate
+memory. The default action is to print a message and abort.
+You should supply a function that either calls @code{exit}
+(@pxref{Program Termination, , , libc, The GNU C Library Reference Manual}) or @code{longjmp} (@pxref{Non-Local
+Exits, , , libc, The GNU C Library Reference Manual}) and doesn't return.
+
+@smallexample
+void my_obstack_alloc_failed (void)
+@dots{}
+obstack_alloc_failed_handler = &my_obstack_alloc_failed;
+@end smallexample
+
+@end defvar
+
+@node Allocation in an Obstack
+@subsubsection Allocation in an Obstack
+@cindex allocation (obstacks)
+
+The most direct way to allocate an object in an obstack is with
+@code{obstack_alloc}, which is invoked almost like @code{malloc}.
+
+@comment obstack.h
+@comment GNU
+@deftypefun {void *} obstack_alloc (struct obstack *@var{obstack-ptr}, size_t @var{size})
+This allocates an uninitialized block of @var{size} bytes in an obstack
+and returns its address. Here @var{obstack-ptr} specifies which obstack
+to allocate the block in; it is the address of the @code{struct obstack}
+object which represents the obstack. Each obstack macro
+requires you to specify an @var{obstack-ptr} as the first argument.
+
+This macro calls the obstack's @code{obstack_chunk_alloc} function if
+it needs to allocate a new chunk of memory; it calls
+@code{obstack_alloc_failed_handler} if allocation of memory by
+@code{obstack_chunk_alloc} failed.
+@end deftypefun
+
+For example, here is a function that allocates a copy of a string @var{str}
+in a specific obstack, which is in the variable @code{string_obstack}:
+
+@smallexample
+struct obstack string_obstack;
+
+char *
+copystring (char *string)
+@{
+ size_t len = strlen (string) + 1;
+ char *s = (char *) obstack_alloc (&string_obstack, len);
+ memcpy (s, string, len);
+ return s;
+@}
+@end smallexample
+
+To allocate a block with specified contents, use the macro @code{obstack_copy}.
+
+@comment obstack.h
+@comment GNU
+@deftypefun {void *} obstack_copy (struct obstack *@var{obstack-ptr}, void *@var{address}, size_t @var{size})
+This allocates a block and initializes it by copying @var{size}
+bytes of data starting at @var{address}. It calls
+@code{obstack_alloc_failed_handler} if allocation of memory by
+@code{obstack_chunk_alloc} failed.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun {void *} obstack_copy0 (struct obstack *@var{obstack-ptr}, void *@var{address}, size_t @var{size})
+Like @code{obstack_copy}, but appends an extra byte containing a null
+character. This extra byte is not counted in the argument @var{size}.
+@end deftypefun
+
+The @code{obstack_copy0} macro is convenient for copying a sequence
+of characters into an obstack as a null-terminated string. Here is an
+example of its use:
+
+@smallexample
+char *
+obstack_savestring (char *addr, size_t size)
+@{
+ return obstack_copy0 (&myobstack, addr, size);
+@}
+@end smallexample
+
+@noindent
+Contrast this with the previous example of @code{savestring} using
+@code{malloc} (@pxref{Basic Allocation, , , libc, The GNU C Library Reference Manual}).
+
+@node Freeing Obstack Objects
+@subsubsection Freeing Objects in an Obstack
+@cindex freeing (obstacks)
+
+To free an object allocated in an obstack, use the macro
+@code{obstack_free}. Since the obstack is a stack of objects, freeing
+one object automatically frees all other objects allocated more recently
+in the same obstack.
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_free (struct obstack *@var{obstack-ptr}, void *@var{object})
+If @var{object} is a null pointer, everything allocated in the obstack
+is freed. Otherwise, @var{object} must be the address of an object
+allocated in the obstack. Then @var{object} is freed, along with
+everything allocated in @var{obstack} since @var{object}.
+@end deftypefun
+
+Note that if @var{object} is a null pointer, the result is an
+uninitialized obstack. To free all memory in an obstack but leave it
+valid for further allocation, call @code{obstack_free} with the address
+of the first object allocated on the obstack:
+
+@smallexample
+obstack_free (obstack_ptr, first_object_allocated_ptr);
+@end smallexample
+
+Recall that the objects in an obstack are grouped into chunks. When all
+the objects in a chunk become free, the obstack library automatically
+frees the chunk (@pxref{Preparing for Obstacks}). Then other
+obstacks, or non-obstack allocation, can reuse the space of the chunk.
+
+@node Obstack Functions
+@subsubsection Obstack Functions and Macros
+@cindex macros
+
+The interfaces for using obstacks are shown here as functions to
+specify the return type and argument types, but they are really
+defined as macros. This means that the arguments don't actually have
+types, but they generally behave as if they have the types shown.
+You can call these macros like functions, but you cannot use them in
+any other way (for example, you cannot take their address).
+
+Calling the macros requires a special precaution: namely, the first
+operand (the obstack pointer) may not contain any side effects, because
+it may be computed more than once. For example, if you write this:
+
+@smallexample
+obstack_alloc (get_obstack (), 4);
+@end smallexample
+
+@noindent
+you will find that @code{get_obstack} may be called several times.
+If you use @code{*obstack_list_ptr++} as the obstack pointer argument,
+you will get very strange results since the incrementation may occur
+several times.
+
+If you use the GNU C compiler, this precaution is not necessary, because
+various language extensions in GNU C permit defining the macros so as to
+compute each argument only once.
+
+Note that arguments other than the first will only be evaluated once,
+even when not using GNU C.
+
+@code{obstack.h} does declare a number of functions,
+@code{_obstack_begin}, @code{_obstack_begin_1},
+@code{_obstack_newchunk}, @code{_obstack_free}, and
+@code{_obstack_memory_used}. You should not call these directly.
+
+@node Growing Objects
+@subsubsection Growing Objects
+@cindex growing objects (in obstacks)
+@cindex changing the size of a block (obstacks)
+
+Because memory in obstack chunks is used sequentially, it is possible to
+build up an object step by step, adding one or more bytes at a time to the
+end of the object. With this technique, you do not need to know how much
+data you will put in the object until you come to the end of it. We call
+this the technique of @dfn{growing objects}. The special macros
+for adding data to the growing object are described in this section.
+
+You don't need to do anything special when you start to grow an object.
+Using one of the macros to add data to the object automatically
+starts it. However, it is necessary to say explicitly when the object is
+finished. This is done with @code{obstack_finish}.
+
+The actual address of the object thus built up is not known until the
+object is finished. Until then, it always remains possible that you will
+add so much data that the object must be copied into a new chunk.
+
+While the obstack is in use for a growing object, you cannot use it for
+ordinary allocation of another object. If you try to do so, the space
+already added to the growing object will become part of the other object.
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_blank (struct obstack *@var{obstack-ptr}, size_t @var{size})
+The most basic macro for adding to a growing object is
+@code{obstack_blank}, which adds space without initializing it.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_grow (struct obstack *@var{obstack-ptr}, void *@var{data}, size_t @var{size})
+To add a block of initialized space, use @code{obstack_grow}, which is
+the growing-object analogue of @code{obstack_copy}. It adds @var{size}
+bytes of data to the growing object, copying the contents from
+@var{data}.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_grow0 (struct obstack *@var{obstack-ptr}, void *@var{data}, size_t @var{size})
+This is the growing-object analogue of @code{obstack_copy0}. It adds
+@var{size} bytes copied from @var{data}, followed by an additional null
+character.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_1grow (struct obstack *@var{obstack-ptr}, char @var{c})
+To add one character at a time, use @code{obstack_1grow}.
+It adds a single byte containing @var{c} to the growing object.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_ptr_grow (struct obstack *@var{obstack-ptr}, void *@var{data})
+Adding the value of a pointer one can use
+@code{obstack_ptr_grow}. It adds @code{sizeof (void *)} bytes
+containing the value of @var{data}.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_int_grow (struct obstack *@var{obstack-ptr}, int @var{data})
+A single value of type @code{int} can be added by using
+@code{obstack_int_grow}. It adds @code{sizeof (int)} bytes to
+the growing object and initializes them with the value of @var{data}.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun {void *} obstack_finish (struct obstack *@var{obstack-ptr})
+When you are finished growing the object, use
+@code{obstack_finish} to close it off and return its final address.
+
+Once you have finished the object, the obstack is available for ordinary
+allocation or for growing another object.
+@end deftypefun
+
+When you build an object by growing it, you will probably need to know
+afterward how long it became. You need not keep track of this as you grow
+the object, because you can find out the length from the obstack
+with @code{obstack_object_size}, before finishing the object.
+
+@comment obstack.h
+@comment GNU
+@deftypefun size_t obstack_object_size (struct obstack *@var{obstack-ptr})
+This macro returns the current size of the growing object, in bytes.
+Remember to call @code{obstack_object_size} @emph{before} finishing the object.
+After it is finished, @code{obstack_object_size} will return zero.
+@end deftypefun
+
+If you have started growing an object and wish to cancel it, you should
+finish it and then free it, like this:
+
+@smallexample
+obstack_free (obstack_ptr, obstack_finish (obstack_ptr));
+@end smallexample
+
+@noindent
+This has no effect if no object was growing.
+
+@node Extra Fast Growing
+@subsubsection Extra Fast Growing Objects
+@cindex efficiency and obstacks
+
+The usual macros for growing objects incur overhead for checking
+whether there is room for the new growth in the current chunk. If you
+are frequently constructing objects in small steps of growth, this
+overhead can be significant.
+
+You can reduce the overhead by using special ``fast growth''
+macros that grow the object without checking. In order to have a
+robust program, you must do the checking yourself. If you do this checking
+in the simplest way each time you are about to add data to the object, you
+have not saved anything, because that is what the ordinary growth
+macros do. But if you can arrange to check less often, or check
+more efficiently, then you make the program faster.
+
+@code{obstack_room} returns the amount of room available
+in the current chunk.
+
+@comment obstack.h
+@comment GNU
+@deftypefun size_t obstack_room (struct obstack *@var{obstack-ptr})
+This returns the number of bytes that can be added safely to the current
+growing object (or to an object about to be started) in obstack
+@var{obstack} using the fast growth macros.
+@end deftypefun
+
+While you know there is room, you can use these fast growth macros
+for adding data to a growing object:
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_1grow_fast (struct obstack *@var{obstack-ptr}, char @var{c})
+@code{obstack_1grow_fast} adds one byte containing the
+character @var{c} to the growing object in obstack @var{obstack-ptr}.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_ptr_grow_fast (struct obstack *@var{obstack-ptr}, void *@var{data})
+@code{obstack_ptr_grow_fast} adds @code{sizeof (void *)}
+bytes containing the value of @var{data} to the growing object in
+obstack @var{obstack-ptr}.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_int_grow_fast (struct obstack *@var{obstack-ptr}, int @var{data})
+@code{obstack_int_grow_fast} adds @code{sizeof (int)} bytes
+containing the value of @var{data} to the growing object in obstack
+@var{obstack-ptr}.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun void obstack_blank_fast (struct obstack *@var{obstack-ptr}, size_t @var{size})
+@code{obstack_blank_fast} adds @var{size} bytes to the
+growing object in obstack @var{obstack-ptr} without initializing them.
+@end deftypefun
+
+When you check for space using @code{obstack_room} and there is not
+enough room for what you want to add, the fast growth macros
+are not safe. In this case, simply use the corresponding ordinary
+growth macro instead. Very soon this will copy the object to a
+new chunk; then there will be lots of room available again.
+
+So, each time you use an ordinary growth macro, check afterward for
+sufficient space using @code{obstack_room}. Once the object is copied
+to a new chunk, there will be plenty of space again, so the program will
+start using the fast growth macros again.
+
+Here is an example:
+
+@smallexample
+@group
+void
+add_string (struct obstack *obstack, const char *ptr, size_t len)
+@{
+ while (len > 0)
+ @{
+ size_t room = obstack_room (obstack);
+ if (room == 0)
+ @{
+ /* @r{Not enough room. Add one character slowly,}
+ @r{which may copy to a new chunk and make room.} */
+ obstack_1grow (obstack, *ptr++);
+ len--;
+ @}
+ else
+ @{
+ if (room > len)
+ room = len;
+ /* @r{Add fast as much as we have room for.} */
+ len -= room;
+ while (room-- > 0)
+ obstack_1grow_fast (obstack, *ptr++);
+ @}
+ @}
+@}
+@end group
+@end smallexample
+
+@cindex shrinking objects
+You can use @code{obstack_blank_fast} with a ``negative'' size
+argument to make the current object smaller. Just don't try to shrink
+it beyond zero length---there's no telling what will happen if you do
+that. Earlier versions of obstacks allowed you to use
+@code{obstack_blank} to shrink objects. This will no longer work.
+
+@node Status of an Obstack
+@subsubsection Status of an Obstack
+@cindex obstack status
+@cindex status of obstack
+
+Here are macros that provide information on the current status of
+allocation in an obstack. You can use them to learn about an object while
+still growing it.
+
+@comment obstack.h
+@comment GNU
+@deftypefun {void *} obstack_base (struct obstack *@var{obstack-ptr})
+This macro returns the tentative address of the beginning of the
+currently growing object in @var{obstack-ptr}. If you finish the object
+immediately, it will have that address. If you make it larger first, it
+may outgrow the current chunk---then its address will change!
+
+If no object is growing, this value says where the next object you
+allocate will start (once again assuming it fits in the current
+chunk).
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun {void *} obstack_next_free (struct obstack *@var{obstack-ptr})
+This macro returns the address of the first free byte in the current
+chunk of obstack @var{obstack-ptr}. This is the end of the currently
+growing object. If no object is growing, @code{obstack_next_free}
+returns the same value as @code{obstack_base}.
+@end deftypefun
+
+@comment obstack.h
+@comment GNU
+@deftypefun size_t obstack_object_size (struct obstack *@var{obstack-ptr})
+This macro returns the size in bytes of the currently growing object.
+This is equivalent to
+
+@smallexample
+((size_t) (obstack_next_free (@var{obstack-ptr}) - obstack_base (@var{obstack-ptr})))
+@end smallexample
+@end deftypefun
+
+@node Obstacks Data Alignment
+@subsubsection Alignment of Data in Obstacks
+@cindex alignment (in obstacks)
+
+Each obstack has an @dfn{alignment boundary}; each object allocated in
+the obstack automatically starts on an address that is a multiple of the
+specified boundary. By default, this boundary is aligned so that
+the object can hold any type of data.
+
+To access an obstack's alignment boundary, use the macro
+@code{obstack_alignment_mask}.
+
+@comment obstack.h
+@comment GNU
+@deftypefn Macro size_t obstack_alignment_mask (struct obstack *@var{obstack-ptr})
+The value is a bit mask; a bit that is 1 indicates that the corresponding
+bit in the address of an object should be 0. The mask value should be one
+less than a power of 2; the effect is that all object addresses are
+multiples of that power of 2. The default value of the mask is a value
+that allows aligned objects to hold any type of data: for example, if
+its value is 3, any type of data can be stored at locations whose
+addresses are multiples of 4. A mask value of 0 means an object can start
+on any multiple of 1 (that is, no alignment is required).
+
+The expansion of the macro @code{obstack_alignment_mask} is an lvalue,
+so you can alter the mask by assignment. For example, this statement:
+
+@smallexample
+obstack_alignment_mask (obstack_ptr) = 0;
+@end smallexample
+
+@noindent
+has the effect of turning off alignment processing in the specified obstack.
+@end deftypefn
+
+Note that a change in alignment mask does not take effect until
+@emph{after} the next time an object is allocated or finished in the
+obstack. If you are not growing an object, you can make the new
+alignment mask take effect immediately by calling @code{obstack_finish}.
+This will finish a zero-length object and then do proper alignment for
+the next object.
+
+@node Obstack Chunks
+@subsubsection Obstack Chunks
+@cindex efficiency of chunks
+@cindex chunks
+
+Obstacks work by allocating space for themselves in large chunks, and
+then parceling out space in the chunks to satisfy your requests. Chunks
+are normally 4096 bytes long unless you specify a different chunk size.
+The chunk size includes 8 bytes of overhead that are not actually used
+for storing objects. Regardless of the specified size, longer chunks
+will be allocated when necessary for long objects.
+
+The obstack library allocates chunks by calling the function
+@code{obstack_chunk_alloc}, which you must define. When a chunk is no
+longer needed because you have freed all the objects in it, the obstack
+library frees the chunk by calling @code{obstack_chunk_free}, which you
+must also define.
+
+These two must be defined (as macros) or declared (as functions) in each
+source file that uses @code{obstack_init} (@pxref{Creating Obstacks}).
+Most often they are defined as macros like this:
+
+@smallexample
+#define obstack_chunk_alloc malloc
+#define obstack_chunk_free free
+@end smallexample
+
+Note that these are simple macros (no arguments). Macro definitions with
+arguments will not work! It is necessary that @code{obstack_chunk_alloc}
+or @code{obstack_chunk_free}, alone, expand into a function name if it is
+not itself a function name.
+
+If you allocate chunks with @code{malloc}, the chunk size should be a
+power of 2. The default chunk size, 4096, was chosen because it is long
+enough to satisfy many typical requests on the obstack yet short enough
+not to waste too much memory in the portion of the last chunk not yet used.
+
+@comment obstack.h
+@comment GNU
+@deftypefn Macro size_t obstack_chunk_size (struct obstack *@var{obstack-ptr})
+This returns the chunk size of the given obstack.
+@end deftypefn
+
+Since this macro expands to an lvalue, you can specify a new chunk size by
+assigning it a new value. Doing so does not affect the chunks already
+allocated, but will change the size of chunks allocated for that particular
+obstack in the future. It is unlikely to be useful to make the chunk size
+smaller, but making it larger might improve efficiency if you are
+allocating many objects whose size is comparable to the chunk size. Here
+is how to do so cleanly:
+
+@smallexample
+if (obstack_chunk_size (obstack_ptr) < @var{new-chunk-size})
+ obstack_chunk_size (obstack_ptr) = @var{new-chunk-size};
+@end smallexample
+
+@node Summary of Obstacks
+@subsubsection Summary of Obstack Macros
+
+Here is a summary of all the macros associated with obstacks. Each
+takes the address of an obstack (@code{struct obstack *}) as its first
+argument.
+
+@table @code
+@item int obstack_init (struct obstack *@var{obstack-ptr})
+Initialize use of an obstack. @xref{Creating Obstacks}.
+
+@item int obstack_begin (struct obstack *@var{obstack-ptr}, size_t chunk_size)
+Initialize use of an obstack, with an initial chunk of
+@var{chunk_size} bytes.
+
+@item int obstack_specify_allocation (struct obstack *@var{obstack-ptr}, size_t chunk_size, size_t alignment, void *(*chunkfun) (size_t), void (*freefun) (void *))
+Initialize use of an obstack, specifying intial chunk size, chunk
+alignment, and memory allocation functions.
+
+@item int obstack_specify_allocation_with_arg (struct obstack *@var{obstack-ptr}, size_t chunk_size, size_t alignment, void *(*chunkfun) (void *, size_t), void (*freefun) (void *, void *), void *arg)
+Like @code{obstack_specify_allocation}, but specifying memory
+allocation functions that take an extra first argument, @var{arg}.
+
+@item void *obstack_alloc (struct obstack *@var{obstack-ptr}, size_t @var{size})
+Allocate an object of @var{size} uninitialized bytes.
+@xref{Allocation in an Obstack}.
+
+@item void *obstack_copy (struct obstack *@var{obstack-ptr}, void *@var{address}, size_t @var{size})
+Allocate an object of @var{size} bytes, with contents copied from
+@var{address}. @xref{Allocation in an Obstack}.
+
+@item void *obstack_copy0 (struct obstack *@var{obstack-ptr}, void *@var{address}, size_t @var{size})
+Allocate an object of @var{size}+1 bytes, with @var{size} of them copied
+from @var{address}, followed by a null character at the end.
+@xref{Allocation in an Obstack}.
+
+@item void obstack_free (struct obstack *@var{obstack-ptr}, void *@var{object})
+Free @var{object} (and everything allocated in the specified obstack
+more recently than @var{object}). @xref{Freeing Obstack Objects}.
+
+@item void obstack_blank (struct obstack *@var{obstack-ptr}, size_t @var{size})
+Add @var{size} uninitialized bytes to a growing object.
+@xref{Growing Objects}.
+
+@item void obstack_grow (struct obstack *@var{obstack-ptr}, void *@var{address}, size_t @var{size})
+Add @var{size} bytes, copied from @var{address}, to a growing object.
+@xref{Growing Objects}.
+
+@item void obstack_grow0 (struct obstack *@var{obstack-ptr}, void *@var{address}, size_t @var{size})
+Add @var{size} bytes, copied from @var{address}, to a growing object,
+and then add another byte containing a null character. @xref{Growing
+Objects}.
+
+@item void obstack_1grow (struct obstack *@var{obstack-ptr}, char @var{data-char})
+Add one byte containing @var{data-char} to a growing object.
+@xref{Growing Objects}.
+
+@item void *obstack_finish (struct obstack *@var{obstack-ptr})
+Finalize the object that is growing and return its permanent address.
+@xref{Growing Objects}.
+
+@item size_t obstack_object_size (struct obstack *@var{obstack-ptr})
+Get the current size of the currently growing object. @xref{Growing
+Objects}.
+
+@item void obstack_blank_fast (struct obstack *@var{obstack-ptr}, size_t @var{size})
+Add @var{size} uninitialized bytes to a growing object without checking
+that there is enough room. @xref{Extra Fast Growing}.
+
+@item void obstack_1grow_fast (struct obstack *@var{obstack-ptr}, char @var{data-char})
+Add one byte containing @var{data-char} to a growing object without
+checking that there is enough room. @xref{Extra Fast Growing}.
+
+@item size_t obstack_room (struct obstack *@var{obstack-ptr})
+Get the amount of room now available for growing the current object.
+@xref{Extra Fast Growing}.
+
+@item size_t obstack_alignment_mask (struct obstack *@var{obstack-ptr})
+The mask used for aligning the beginning of an object. This is an
+lvalue. @xref{Obstacks Data Alignment}.
+
+@item size_t obstack_chunk_size (struct obstack *@var{obstack-ptr})
+The size for allocating chunks. This is an lvalue. @xref{Obstack Chunks}.
+
+@item void *obstack_base (struct obstack *@var{obstack-ptr})
+Tentative starting address of the currently growing object.
+@xref{Status of an Obstack}.
+
+@item void *obstack_next_free (struct obstack *@var{obstack-ptr})
+Address just after the end of the currently growing object.
+@xref{Status of an Obstack}.
+@end table
+
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+
+@c %**start of header
+@setfilename libitm.info
+@settitle GNU libitm
+@c %**end of header
+
+
+@copying
+Copyright @copyright{} 2011-2022 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+A copy of the license is included in the section entitled ``GNU
+Free Documentation License''.
+@end copying
+
+@ifinfo
+@dircategory GNU Libraries
+@direntry
+* libitm: (libitm). GNU Transactional Memory Library
+@end direntry
+
+This manual documents the GNU Transactional Memory Library.
+
+@insertcopying
+@end ifinfo
+
+
+@setchapternewpage odd
+
+@titlepage
+@title The GNU Transactional Memory Library
+@page
+@vskip 0pt plus 1filll
+@comment For the @value{version-GCC} Version*
+@sp 1
+@insertcopying
+@end titlepage
+
+@summarycontents
+@contents
+@page
+
+
+@node Top
+@top Introduction
+@cindex Introduction
+
+This manual documents the usage and internals of libitm, the GNU Transactional
+Memory Library. It provides transaction support for accesses to a process'
+memory, enabling easy-to-use synchronization of accesses to shared memory by
+several threads.
+
+
+@comment
+@comment When you add a new menu item, please keep the right hand
+@comment aligned to the same column. Do not use tabs. This provides
+@comment better formatting.
+@comment
+@menu
+* Enabling libitm:: How to enable libitm for your applications.
+* C/C++ Language Constructs for TM::
+ Notes on the language-level interface supported
+ by gcc.
+* The libitm ABI:: Notes on the external ABI provided by libitm.
+* Internals:: Notes on libitm's internal synchronization.
+* GNU Free Documentation License::
+ How you can copy and share this manual.
+* Library Index:: Index of this documentation.
+@end menu
+
+
+@c ---------------------------------------------------------------------
+@c Enabling libitm
+@c ---------------------------------------------------------------------
+
+@node Enabling libitm
+@chapter Enabling libitm
+
+To activate support for TM in C/C++, the compile-time flag @option{-fgnu-tm}
+must be specified. This enables TM language-level constructs such as
+transaction statements (e.g., @code{__transaction_atomic}, @pxref{C/C++
+Language Constructs for TM} for details).
+
+@c ---------------------------------------------------------------------
+@c C/C++ Language Constructs for TM
+@c ---------------------------------------------------------------------
+
+@node C/C++ Language Constructs for TM
+@chapter C/C++ Language Constructs for TM
+
+Transactions are supported in C++ and C in the form of transaction statements,
+transaction expressions, and function transactions. In the following example,
+both @code{a} and @code{b} will be read and the difference will be written to
+@code{c}, all atomically and isolated from other transactions:
+
+@example
+__transaction_atomic @{ c = a - b; @}
+@end example
+
+Therefore, another thread can use the following code to concurrently update
+@code{b} without ever causing @code{c} to hold a negative value (and without
+having to use other synchronization constructs such as locks or C++11
+atomics):
+
+@example
+__transaction_atomic @{ if (a > b) b++; @}
+@end example
+
+GCC follows the @uref{https://sites.google.com/site/tmforcplusplus/, Draft
+Specification of Transactional Language Constructs for C++ (v1.1)} in its
+implementation of transactions.
+
+The precise semantics of transactions are defined in terms of the C++11/C11
+memory model (see the specification). Roughly, transactions provide
+synchronization guarantees that are similar to what would be guaranteed when
+using a single global lock as a guard for all transactions. Note that like
+other synchronization constructs in C/C++, transactions rely on a
+data-race-free program (e.g., a nontransactional write that is concurrent
+with a transactional read to the same memory location is a data race).
+
+@c ---------------------------------------------------------------------
+@c The libitm ABI
+@c ---------------------------------------------------------------------
+
+@node The libitm ABI
+@chapter The libitm ABI
+
+The ABI provided by libitm is basically equal to the Linux variant of Intel's
+current TM ABI specification document (Revision 1.1, May 6 2009) but with the
+differences listed in this chapter. It would be good if these changes would
+eventually be merged into a future version of this specification. To ease
+look-up, the following subsections mirror the structure of this specification.
+
+@section [No changes] Objectives
+@section [No changes] Non-objectives
+
+@section Library design principles
+@subsection [No changes] Calling conventions
+@subsection [No changes] TM library algorithms
+@subsection [No changes] Optimized load and store routines
+@subsection [No changes] Aligned load and store routines
+
+@subsection Data logging functions
+
+The memory locations accessed with transactional loads and stores and the
+memory locations whose values are logged must not overlap. This required
+separation only extends to the scope of the execution of one transaction
+including all the executions of all nested transactions.
+
+The compiler must be consistent (within the scope of a single transaction)
+about which memory locations are shared and which are not shared with other
+threads (i.e., data must be accessed either transactionally or
+nontransactionally). Otherwise, non-write-through TM algorithms would not work.
+
+For memory locations on the stack, this requirement extends to only the
+lifetime of the stack frame that the memory location belongs to (or the
+lifetime of the transaction, whichever is shorter). Thus, memory that is
+reused for several stack frames could be target of both data logging and
+transactional accesses; however, this is harmless because these stack frames'
+lifetimes will end before the transaction finishes.
+
+@subsection [No changes] Scatter/gather calls
+@subsection [No changes] Serial and irrevocable mode
+@subsection [No changes] Transaction descriptor
+@subsection Store allocation
+
+There is no @code{getTransaction} function.
+
+@subsection [No changes] Naming conventions
+
+@subsection Function pointer encryption
+
+Currently, this is not implemented.
+
+
+@section Types and macros list
+
+@code{_ITM_codeProperties} has changed, @pxref{txn-code-properties,,Starting a
+transaction}.
+@code{_ITM_srcLocation} is not used.
+
+
+@section Function list
+
+@subsection Initialization and finalization functions
+These functions are not part of the ABI.
+
+@subsection [No changes] Version checking
+@subsection [No changes] Error reporting
+@subsection [No changes] inTransaction call
+
+@subsection State manipulation functions
+There is no @code{getTransaction} function. Transaction identifiers for
+nested transactions will be ordered but not necessarily sequential (i.e., for
+a nested transaction's identifier @var{IN} and its enclosing transaction's
+identifier @var{IE}, it is guaranteed that @math{IN >= IE}).
+
+@subsection [No changes] Source locations
+
+@subsection Starting a transaction
+
+@subsubsection Transaction code properties
+
+@anchor{txn-code-properties}
+The bit @code{hasNoXMMUpdate} is instead called @code{hasNoVectorUpdate}.
+Iff it is set, vector register save/restore is not necessary for any target
+machine.
+
+The @code{hasNoFloatUpdate} bit (@code{0x0010}) is new. Iff it is set, floating
+point register save/restore is not necessary for any target machine.
+
+@code{undoLogCode} is not supported and a fatal runtime error will be raised
+if this bit is set. It is not properly defined in the ABI why barriers
+other than undo logging are not present; Are they not necessary (e.g., a
+transaction operating purely on thread-local data) or have they been omitted by
+the compiler because it thinks that some kind of global synchronization
+(e.g., serial mode) might perform better? The specification suggests that the
+latter might be the case, but the former seems to be more useful.
+
+The @code{readOnly} bit (@code{0x4000}) is new. @strong{TODO} Lexical or dynamic
+scope?
+
+@code{hasNoRetry} is not supported. If this bit is not set, but
+@code{hasNoAbort} is set, the library can assume that transaction
+rollback will not be requested.
+
+It would be useful if the absence of externally-triggered rollbacks would be
+reported for the dynamic scope as well, not just for the lexical scope
+(@code{hasNoAbort}). Without this, a library cannot exploit this together
+with flat nesting.
+
+@code{exceptionBlock} is not supported because exception blocks are not used.
+
+@subsubsection [No changes] Windows exception state
+@subsubsection [No changes] Other machine state
+
+@subsubsection [No changes] Results from beginTransaction
+
+@subsection Aborting a transaction
+
+@code{_ITM_rollbackTransaction} is not supported. @code{_ITM_abortTransaction}
+is supported but the abort reasons @code{exceptionBlockAbort},
+@code{TMConflict}, and @code{userRetry} are not supported. There are no
+exception blocks in general, so the related cases also do not have to be
+considered. To encode @code{__transaction_cancel [[outer]]}, compilers must
+set the new @code{outerAbort} bit (@code{0x10}) additionally to the
+@code{userAbort} bit in the abort reason.
+
+@subsection Committing a transaction
+
+The exception handling (EH) scheme is different. The Intel ABI requires the
+@code{_ITM_tryCommitTransaction} function that will return even when the
+commit failed and will have to be matched with calls to either
+@code{_ITM_abortTransaction} or @code{_ITM_commitTransaction}. In contrast,
+gcc relies on transactional wrappers for the functions of the Exception
+Handling ABI and on one additional commit function (shown below). This allows
+the TM to keep track of EH internally and thus it does not have to embed the
+cleanup of EH state into the existing EH code in the program.
+@code{_ITM_tryCommitTransaction} is not supported.
+@code{_ITM_commitTransactionToId} is also not supported because the
+propagation of thrown exceptions will not bypass commits of nested
+transactions.
+
+@example
+void _ITM_commitTransactionEH(void *exc_ptr) ITM_REGPARM;
+void *_ITM_cxa_allocate_exception (size_t);
+void _ITM_cxa_free_exception (void *exc_ptr);
+void _ITM_cxa_throw (void *obj, void *tinfo, void (*dest) (void *));
+void *_ITM_cxa_begin_catch (void *exc_ptr);
+void _ITM_cxa_end_catch (void);
+@end example
+
+The EH scheme changed in version 6 of GCC. Previously, the compiler
+added a call to @code{_ITM_commitTransactionEH} to commit a transaction if
+an exception could be in flight at this position in the code; @code{exc_ptr} is
+the address of the current exception and must be non-zero. Now, the
+compiler must catch all exceptions that are about to be thrown out of a
+transaction and call @code{_ITM_commitTransactionEH} from the catch clause,
+with @code{exc_ptr} being zero.
+
+Note that the old EH scheme never worked completely in GCC's implementation;
+libitm currently does not try to be compatible with the old scheme.
+
+The @code{_ITM_cxa...} functions are transactional wrappers for the respective
+@code{__cxa...} functions and must be called instead of these in transactional
+code. @code{_ITM_cxa_free_exception} is new in GCC 6.
+
+To support this EH scheme, libstdc++ needs to provide one additional function
+(@code{_cxa_tm_cleanup}), which is used by the TM to clean up the exception
+handling state while rolling back a transaction:
+
+@example
+void __cxa_tm_cleanup (void *unthrown_obj, void *cleanup_exc,
+ unsigned int caught_count);
+@end example
+
+Since GCC 6, @code{unthrown_obj} is not used anymore and always null;
+prior to that, @code{unthrown_obj} is non-null if the program called
+@code{__cxa_allocate_exception} for this exception but did not yet called
+@code{__cxa_throw} for it. @code{cleanup_exc} is non-null if the program is
+currently processing a cleanup along an exception path but has not caught this
+exception yet. @code{caught_count} is the nesting depth of
+@code{__cxa_begin_catch} within the transaction (which can be counted by the TM
+using @code{_ITM_cxa_begin_catch} and @code{_ITM_cxa_end_catch});
+@code{__cxa_tm_cleanup} then performs rollback by essentially performing
+@code{__cxa_end_catch} that many times.
+
+
+
+@subsection Exception handling support
+
+Currently, there is no support for functionality like
+@code{__transaction_cancel throw} as described in the C++ TM specification.
+Supporting this should be possible with the EH scheme explained previously
+because via the transactional wrappers for the EH ABI, the TM is able to
+observe and intercept EH.
+
+
+@subsection [No changes] Transition to serial--irrevocable mode
+@subsection [No changes] Data transfer functions
+@subsection [No changes] Transactional memory copies
+
+@subsection Transactional versions of memmove
+
+If either the source or destination memory region is to be accessed
+nontransactionally, then source and destination regions must not be
+overlapping. The respective @code{_ITM_memmove} functions are still
+available but a fatal runtime error will be raised if such regions do overlap.
+To support this functionality, the ABI would have to specify how the
+intersection of the regions has to be accessed (i.e., transactionally or
+nontransactionally).
+
+@subsection [No changes] Transactional versions of memset
+@subsection [No changes] Logging functions
+
+@subsection User-registered commit and undo actions
+
+Commit actions will get executed in the same order in which the respective
+calls to @code{_ITM_addUserCommitAction} happened. Only
+@code{_ITM_noTransactionId} is allowed as value for the
+@code{resumingTransactionId} argument. Commit actions get executed after
+privatization safety has been ensured.
+
+Undo actions will get executed in reverse order compared to the order in which
+the respective calls to @code{_ITM_addUserUndoAction} happened. The ordering of
+undo actions w.r.t. the roll-back of other actions (e.g., data transfers or
+memory allocations) is undefined.
+
+@code{_ITM_getThreadnum} is not supported currently because its only purpose
+is to provide a thread ID that matches some assumed performance tuning output,
+but this output is not part of the ABI nor further defined by it.
+
+@code{_ITM_dropReferences} is not supported currently because its semantics and
+the intention behind it is not entirely clear. The
+specification suggests that this function is necessary because of certain
+orderings of data transfer undos and the releasing of memory regions (i.e.,
+privatization). However, this ordering is never defined, nor is the ordering of
+dropping references w.r.t. other events.
+
+@subsection [New] Transactional indirect calls
+
+Indirect calls (i.e., calls through a function pointer) within transactions
+should execute the transactional clone of the original function (i.e., a clone
+of the original that has been fully instrumented to use the TM runtime), if
+such a clone is available. The runtime provides two functions to
+register/deregister clone tables:
+
+@example
+struct clone_entry
+@{
+ void *orig, *clone;
+@};
+
+void _ITM_registerTMCloneTable (clone_entry *table, size_t entries);
+void _ITM_deregisterTMCloneTable (clone_entry *table);
+@end example
+
+Registered tables must be writable by the TM runtime, and must be live
+throughout the life-time of the TM runtime.
+
+@strong{TODO} The intention was always to drop the registration functions
+entirely, and create a new ELF Phdr describing the linker-sorted table. Much
+like what currently happens for @code{PT_GNU_EH_FRAME}.
+This work kept getting bogged down in how to represent the @var{N} different
+code generation variants. We clearly needed at least two---SW and HW
+transactional clones---but there was always a suggestion of more variants for
+different TM assumptions/invariants.
+
+The compiler can then use two TM runtime functions to perform indirect calls in
+transactions:
+@example
+void *_ITM_getTMCloneOrIrrevocable (void *function) ITM_REGPARM;
+void *_ITM_getTMCloneSafe (void *function) ITM_REGPARM;
+@end example
+
+If there is a registered clone for supplied function, both will return a
+pointer to the clone. If not, the first runtime function will attempt to switch
+to serial--irrevocable mode and return the original pointer, whereas the second
+will raise a fatal runtime error.
+
+@subsection [New] Transactional dynamic memory management
+
+@example
+void *_ITM_malloc (size_t)
+ __attribute__((__malloc__)) ITM_PURE;
+void *_ITM_calloc (size_t, size_t)
+ __attribute__((__malloc__)) ITM_PURE;
+void _ITM_free (void *) ITM_PURE;
+@end example
+
+These functions are essentially transactional wrappers for @code{malloc},
+@code{calloc}, and @code{free}. Within transactions, the compiler should
+replace calls to the original functions with calls to the wrapper functions.
+
+libitm also provides transactional clones of C++ memory management functions
+such as global operator new and delete. They are part of libitm for historic
+reasons but do not need to be part of this ABI.
+
+
+@section [No changes] Future Enhancements to the ABI
+
+@section Sample code
+
+The code examples might not be correct w.r.t. the current version of the ABI,
+especially everything related to exception handling.
+
+
+@section [New] Memory model
+
+The ABI should define a memory model and the ordering that is guaranteed for
+data transfers and commit/undo actions, or at least refer to another memory
+model that needs to be preserved. Without that, the compiler cannot ensure the
+memory model specified on the level of the programming language (e.g., by the
+C++ TM specification).
+
+For example, if a transactional load is ordered before another load/store, then
+the TM runtime must also ensure this ordering when accessing shared state. If
+not, this might break the kind of publication safety used in the C++ TM
+specification. Likewise, the TM runtime must ensure privatization safety.
+
+
+
+@c ---------------------------------------------------------------------
+@c Internals
+@c ---------------------------------------------------------------------
+
+@node Internals
+@chapter Internals
+
+@section TM methods and method groups
+
+libitm supports several ways of synchronizing transactions with each other.
+These TM methods (or TM algorithms) are implemented in the form of
+subclasses of @code{abi_dispatch}, which provide methods for
+transactional loads and stores as well as callbacks for rollback and commit.
+All methods that are compatible with each other (i.e., that let concurrently
+running transactions still synchronize correctly even if different methods
+are used) belong to the same TM method group. Pointers to TM methods can be
+obtained using the factory methods prefixed with @code{dispatch_} in
+@file{libitm_i.h}. There are two special methods, @code{dispatch_serial} and
+@code{dispatch_serialirr}, that are compatible with all methods because they
+run transactions completely in serial mode.
+
+@subsection TM method life cycle
+
+The state of TM methods does not change after construction, but they do alter
+the state of transactions that use this method. However, because
+per-transaction data gets used by several methods, @code{gtm_thread} is
+responsible for setting an initial state that is useful for all methods.
+After that, methods are responsible for resetting/clearing this state on each
+rollback or commit (of outermost transactions), so that the transaction
+executed next is not affected by the previous transaction.
+
+There is also global state associated with each method group, which is
+initialized and shut down (@code{method_group::init()} and @code{fini()})
+when switching between method groups (see @file{retry.cc}).
+
+@subsection Selecting the default method
+
+The default method that libitm uses for freshly started transactions (but
+not necessarily for restarted transactions) can be set via an environment
+variable (@env{ITM_DEFAULT_METHOD}), whose value should be equal to the name
+of one of the factory methods returning abi_dispatch subclasses but without
+the "dispatch_" prefix (e.g., "serialirr" instead of
+@code{GTM::dispatch_serialirr()}).
+
+Note that this environment variable is only a hint for libitm and might not
+be supported in the future.
+
+
+@section Nesting: flat vs. closed
+
+We support two different kinds of nesting of transactions. In the case of
+@emph{flat nesting}, the nesting structure is flattened and all nested
+transactions are subsumed by the enclosing transaction. In contrast,
+with @emph{closed nesting}, nested transactions that have not yet committed
+can be rolled back separately from the enclosing transactions; when they
+commit, they are subsumed by the enclosing transaction, and their effects
+will be finally committed when the outermost transaction commits.
+@emph{Open nesting} (where nested transactions can commit independently of the
+enclosing transactions) are not supported.
+
+Flat nesting is the default nesting mode, but closed nesting is supported and
+used when transactions contain user-controlled aborts
+(@code{__transaction_cancel} statements). We assume that user-controlled
+aborts are rare in typical code and used mostly in exceptional situations.
+Thus, it makes more sense to use flat nesting by default to avoid the
+performance overhead of the additional checkpoints required for closed
+nesting. User-controlled aborts will correctly abort the innermost enclosing
+transaction, whereas the whole (i.e., outermost) transaction will be restarted
+otherwise (e.g., when a transaction encounters data conflicts during
+optimistic execution).
+
+
+@section Locking conventions
+
+This section documents the locking scheme and rules for all uses of locking
+in libitm. We have to support serial(-irrevocable) mode, which is implemented
+using a global lock as explained next (called the @emph{serial lock}). To
+simplify the overall design, we use the same lock as catch-all locking
+mechanism for other infrequent tasks such as (de)registering clone tables or
+threads. Besides the serial lock, there are @emph{per-method-group locks} that
+are managed by specific method groups (i.e., groups of similar TM concurrency
+control algorithms), and lock-like constructs for quiescence-based operations
+such as ensuring privatization safety.
+
+Thus, the actions that participate in the libitm-internal locking are either
+@emph{active transactions} that do not run in serial mode, @emph{serial
+transactions} (which (are about to) run in serial mode), and management tasks
+that do not execute within a transaction but have acquired the serial mode
+like a serial transaction would do (e.g., to be able to register threads with
+libitm). Transactions become active as soon as they have successfully used the
+serial lock to announce this globally (@pxref{serial-lock-impl,,Serial lock
+implementation}). Likewise, transactions become serial transactions as soon as
+they have acquired the exclusive rights provided by the serial lock (i.e.,
+serial mode, which also means that there are no other concurrent active or
+serial transactions). Note that active transactions can become serial
+transactions when they enter serial mode during the runtime of the
+transaction.
+
+@subsection State-to-lock mapping
+
+Application data is protected by the serial lock if there is a serial
+transaction and no concurrently running active transaction (i.e., non-serial).
+Otherwise, application data is protected by the currently selected method
+group, which might use per-method-group locks or other mechanisms. Also note
+that application data that is about to be privatized might not be allowed to be
+accessed by nontransactional code until privatization safety has been ensured;
+the details of this are handled by the current method group.
+
+libitm-internal state is either protected by the serial lock or accessed
+through custom concurrent code. The latter applies to the public/shared part
+of a transaction object and most typical method-group-specific state.
+
+The former category (protected by the serial lock) includes:
+@itemize @bullet
+@item The list of active threads that have used transactions.
+@item The tables that map functions to their transactional clones.
+@item The current selection of which method group to use.
+@item Some method-group-specific data, or invariants of this data. For example,
+resetting a method group to its initial state is handled by switching to the
+same method group, so the serial lock protects such resetting as well.
+@end itemize
+In general, such state is immutable whenever there exists an active
+(non-serial) transaction. If there is no active transaction, a serial
+transaction (or a thread that is not currently executing a transaction but has
+acquired the serial lock) is allowed to modify this state (but must of course
+be careful to not surprise the current method group's implementation with such
+modifications).
+
+@subsection Lock acquisition order
+
+To prevent deadlocks, locks acquisition must happen in a globally agreed-upon
+order. Note that this applies to other forms of blocking too, but does not
+necessarily apply to lock acquisitions that do not block (e.g., trylock()
+calls that do not get retried forever). Note that serial transactions are
+never return back to active transactions until the transaction has committed.
+Likewise, active transactions stay active until they have committed.
+Per-method-group locks are typically also not released before commit.
+
+Lock acquisition / blocking rules:
+@itemize @bullet
+
+@item Transactions must become active or serial before they are allowed to
+use method-group-specific locks or blocking (i.e., the serial lock must be
+acquired before those other locks, either in serial or nonserial mode).
+
+@item Any number of threads that do not currently run active transactions can
+block while trying to get the serial lock in exclusive mode. Note that active
+transactions must not block when trying to upgrade to serial mode unless there
+is no other transaction that is trying that (the latter is ensured by the
+serial lock implementation.
+
+@item Method groups must prevent deadlocks on their locks. In particular, they
+must also be prepared for another active transaction that has acquired
+method-group-specific locks but is blocked during an attempt to upgrade to
+being a serial transaction. See below for details.
+
+@item Serial transactions can acquire method-group-specific locks because there
+will be no other active nor serial transaction.
+
+@end itemize
+
+There is no single rule for per-method-group blocking because this depends on
+when a TM method might acquire locks. If no active transaction can upgrade to
+being a serial transaction after it has acquired per-method-group locks (e.g.,
+when those locks are only acquired during an attempt to commit), then the TM
+method does not need to consider a potential deadlock due to serial mode.
+
+If there can be upgrades to serial mode after the acquisition of
+per-method-group locks, then TM methods need to avoid those deadlocks:
+@itemize @bullet
+@item When upgrading to a serial transaction, after acquiring exclusive rights
+to the serial lock but before waiting for concurrent active transactions to
+finish (@pxref{serial-lock-impl,,Serial lock implementation} for details),
+we have to wake up all active transactions waiting on the upgrader's
+per-method-group locks.
+@item Active transactions blocking on per-method-group locks need to check the
+serial lock and abort if there is a pending serial transaction.
+@item Lost wake-ups have to be prevented (e.g., by changing a bit in each
+per-method-group lock before doing the wake-up, and only blocking on this lock
+using a futex if this bit is not group).
+@end itemize
+
+@strong{TODO}: Can reuse serial lock for gl-*? And if we can, does it make
+sense to introduce further complexity in the serial lock? For gl-*, we can
+really only avoid an abort if we do -wb and -vbv.
+
+
+@subsection Serial lock implementation
+@anchor{serial-lock-impl}
+
+The serial lock implementation is optimized towards assuming that serial
+transactions are infrequent and not the common case. However, the performance
+of entering serial mode can matter because when only few transactions are run
+concurrently or if there are few threads, then it can be efficient to run
+transactions serially.
+
+The serial lock is similar to a multi-reader-single-writer lock in that there
+can be several active transactions but only one serial transaction. However,
+we do want to avoid contention (in the lock implementation) between active
+transactions, so we split up the reader side of the lock into per-transaction
+flags that are true iff the transaction is active. The exclusive writer side
+remains a shared single flag, which is acquired using a CAS, for example.
+On the fast-path, the serial lock then works similar to Dekker's algorithm but
+with several reader flags that a serial transaction would have to check.
+A serial transaction thus requires a list of all threads with potentially
+active transactions; we can use the serial lock itself to protect this list
+(i.e., only threads that have acquired the serial lock can modify this list).
+
+We want starvation-freedom for the serial lock to allow for using it to ensure
+progress for potentially starved transactions (@pxref{progress-guarantees,,
+Progress Guarantees} for details). However, this is currently not enforced by
+the implementation of the serial lock.
+
+Here is pseudo-code for the read/write fast paths of acquiring the serial
+lock (read-to-write upgrade is similar to write_lock:
+@example
+// read_lock:
+tx->shared_state |= active;
+__sync_synchronize(); // or STLD membar, or C++0x seq-cst fence
+while (!serial_lock.exclusive)
+ if (spinning_for_too_long) goto slowpath;
+
+// write_lock:
+if (CAS(&serial_lock.exclusive, 0, this) != 0)
+ goto slowpath; // writer-writer contention
+// need a membar here, but CAS already has full membar semantics
+bool need_blocking = false;
+for (t: all txns)
+ @{
+ for (;t->shared_state & active;)
+ if (spinning_for_too_long) @{ need_blocking = true; break; @}
+ @}
+if (need_blocking) goto slowpath;
+@end example
+
+Releasing a lock in this spin-lock version then just consists of resetting
+@code{tx->shared_state} to inactive or clearing @code{serial_lock.exclusive}.
+
+However, we can't rely on a pure spinlock because we need to get the OS
+involved at some time (e.g., when there are more threads than CPUs to run on).
+Therefore, the real implementation falls back to a blocking slow path, either
+based on pthread mutexes or Linux futexes.
+
+
+@subsection Reentrancy
+
+libitm has to consider the following cases of reentrancy:
+@itemize @bullet
+
+@item Transaction calls unsafe code that starts a new transaction: The outer
+transaction will become a serial transaction before executing unsafe code.
+Therefore, nesting within serial transactions must work, even if the nested
+transaction is called from within uninstrumented code.
+
+@item Transaction calls either a transactional wrapper or safe code, which in
+turn starts a new transaction: It is not yet defined in the specification
+whether this is allowed. Thus, it is undefined whether libitm supports this.
+
+@item Code that starts new transactions might be called from within any part
+of libitm: This kind of reentrancy would likely be rather complex and can
+probably be avoided. Therefore, it is not supported.
+
+@end itemize
+
+@subsection Privatization safety
+
+Privatization safety is ensured by libitm using a quiescence-based approach.
+Basically, a privatizing transaction waits until all concurrent active
+transactions will either have finished (are not active anymore) or operate on
+a sufficiently recent snapshot to not access the privatized data anymore. This
+happens after the privatizing transaction has stopped being an active
+transaction, so waiting for quiescence does not contribute to deadlocks.
+
+In method groups that need to ensure publication safety explicitly, active
+transactions maintain a flag or timestamp in the public/shared part of the
+transaction descriptor. Before blocking, privatizers need to let the other
+transactions know that they should wake up the privatizer.
+
+@strong{TODO} Ho to implement the waiters? Should those flags be
+per-transaction or at a central place? We want to avoid one wake/wait call
+per active transactions, so we might want to use either a tree or combining
+to reduce the syscall overhead, or rather spin for a long amount of time
+instead of doing blocking. Also, it would be good if only the last transaction
+that the privatizer waits for would do the wake-up.
+
+@subsection Progress guarantees
+@anchor{progress-guarantees}
+
+Transactions that do not make progress when using the current TM method will
+eventually try to execute in serial mode. Thus, the serial lock's progress
+guarantees determine the progress guarantees of the whole TM. Obviously, we at
+least need deadlock-freedom for the serial lock, but it would also be good to
+provide starvation-freedom (informally, all threads will finish executing a
+transaction eventually iff they get enough cycles).
+
+However, the scheduling of transactions (e.g., thread scheduling by the OS)
+also affects the handling of progress guarantees by the TM. First, the TM
+can only guarantee deadlock-freedom if threads do not get stopped. Likewise,
+low-priority threads can starve if they do not get scheduled when other
+high-priority threads get those cycles instead.
+
+If all threads get scheduled eventually, correct lock implementations will
+provide deadlock-freedom, but might not provide starvation-freedom. We can
+either enforce the latter in the TM's lock implementation, or assume that
+the scheduling is sufficiently random to yield a probabilistic guarantee that
+no thread will starve (because eventually, a transaction will encounter a
+scheduling that will allow it to run). This can indeed work well in practice
+but is not necessarily guaranteed to work (e.g., simple spin locks can be
+pretty efficient).
+
+Because enforcing stronger progress guarantees in the TM has a higher runtime
+overhead, we focus on deadlock-freedom right now and assume that the threads
+will get scheduled eventually by the OS (but don't consider threads with
+different priorities). We should support starvation-freedom for serial
+transactions in the future. Everything beyond that is highly related to proper
+contention management across all of the TM (including with TM method to
+choose), and is future work.
+
+@strong{TODO} Handling thread priorities: We want to avoid priority inversion
+but it's unclear how often that actually matters in practice. Workloads that
+have threads with different priorities will likely also require lower latency
+or higher throughput for high-priority threads. Therefore, it probably makes
+not that much sense (except for eventual progress guarantees) to use
+priority inheritance until the TM has priority-aware contention management.
+
+
+@c ---------------------------------------------------------------------
+@c GNU Free Documentation License
+@c ---------------------------------------------------------------------
+
+@include fdl.texi
+
+@c ---------------------------------------------------------------------
+@c Index
+@c ---------------------------------------------------------------------
+
+@node Library Index
+@unnumbered Library Index
+
+@printindex cp
+
+@bye
--- /dev/null
+\input texinfo @c -*-texinfo-*-
+
+@c %**start of header
+@setfilename libquadmath.info
+@settitle GCC libquadmath
+@c %**end of header
+
+@copying
+Copyright @copyright{} 2010-2022 Free Software Foundation, Inc.
+
+@quotation
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with the Front-Cover Texts being ``A GNU Manual,''
+and with the Back-Cover Texts as in (a) below. A copy of the
+license is included in the section entitled ``GNU Free Documentation
+License.''
+
+(a) The FSF's Back-Cover Text is: ``You have the freedom to
+copy and modify this GNU manual.
+@end quotation
+@end copying
+
+@ifinfo
+@dircategory GNU Libraries
+@direntry
+* libquadmath: (libquadmath). GCC Quad-Precision Math Library
+@end direntry
+
+This manual documents the GCC Quad-Precision Math Library API.
+
+Published by the Free Software Foundation
+51 Franklin Street, Fifth Floor
+Boston, MA 02110-1301 USA
+
+@insertcopying
+@end ifinfo
+
+
+@setchapternewpage odd
+
+@titlepage
+@title The GCC Quad-Precision Math Library
+@page
+@vskip 0pt plus 1filll
+@comment For the @value{version-GCC} Version*
+@sp 1
+Published by the Free Software Foundation @*
+51 Franklin Street, Fifth Floor@*
+Boston, MA 02110-1301, USA@*
+@sp 1
+@insertcopying
+@end titlepage
+
+@summarycontents
+@contents
+@page
+
+
+@node Top
+@top Introduction
+@cindex Introduction
+
+This manual documents the usage of libquadmath, the GCC Quad-Precision
+Math Library Application Programming Interface (API).
+
+
+@comment
+@comment When you add a new menu item, please keep the right hand
+@comment aligned to the same column. Do not use tabs. This provides
+@comment better formatting.
+@comment
+@menu
+* Typedef and constants:: Defined data types and constants
+* Math Library Routines:: The Libquadmath math runtime application
+ programming interface.
+* I/O Library Routines:: The Libquadmath I/O runtime application
+ programming interface.
+* GNU Free Documentation License::
+ How you can copy and share this manual.
+* Reporting Bugs:: How to report bugs in GCC Libquadmath.
+@c * Index:: Index of this documentation.
+@end menu
+
+
+@c ---------------------------------------------------------------------
+@c Defined macros
+@c ---------------------------------------------------------------------
+
+@node Typedef and constants
+@chapter Typedef and constants
+
+The following data type has been defined via @code{typedef}.
+
+@table @asis
+@item @code{__complex128}: @code{__float128}-based complex number
+@end table
+
+The following macros are defined, which give the numeric limits of the
+@code{__float128} data type.
+
+@table @asis
+@item @code{FLT128_MAX}: largest finite number
+@item @code{FLT128_MIN}: smallest positive number with full precision
+@item @code{FLT128_EPSILON}: difference between 1 and the next larger
+ representable number
+@item @code{FLT128_DENORM_MIN}: smallest positive denormalized number
+@item @code{FLT128_MANT_DIG}: number of digits in the mantissa (bit precision)
+@item @code{FLT128_MIN_EXP}: maximal negative exponent
+@item @code{FLT128_MAX_EXP}: maximal positive exponent
+@item @code{FLT128_DIG}: number of decimal digits in the mantissa
+@item @code{FLT128_MIN_10_EXP}: maximal negative decimal exponent
+@item @code{FLT128_MAX_10_EXP}: maximal positive decimal exponent
+@end table
+
+The following mathematical constants of type @code{__float128} are defined.
+
+@table @asis
+@item @code{M_Eq}: the constant e (Euler's number)
+@item @code{M_LOG2Eq}: binary logarithm of 2
+@item @code{M_LOG10Eq}: common, decimal logarithm of 2
+@item @code{M_LN2q}: natural logarithm of 2
+@item @code{M_LN10q}: natural logarithm of 10
+@item @code{M_PIq}: pi
+@item @code{M_PI_2q}: pi divided by two
+@item @code{M_PI_4q}: pi divided by four
+@item @code{M_1_PIq}: one over pi
+@item @code{M_2_PIq}: one over two pi
+@item @code{M_2_SQRTPIq}: two over square root of pi
+@item @code{M_SQRT2q}: square root of 2
+@item @code{M_SQRT1_2q}: one over square root of 2
+@end table
+
+
+@c ---------------------------------------------------------------------
+@c Math routines
+@c ---------------------------------------------------------------------
+
+@node Math Library Routines
+@chapter Math Library Routines
+
+The following mathematical functions are available:
+
+@table @asis
+@item @code{acosq}: arc cosine function
+@item @code{acoshq}: inverse hyperbolic cosine function
+@item @code{asinq}: arc sine function
+@item @code{asinhq}: inverse hyperbolic sine function
+@item @code{atanq}: arc tangent function
+@item @code{atanhq}: inverse hyperbolic tangent function
+@item @code{atan2q}: arc tangent function
+@item @code{cbrtq}: cube root function
+@item @code{ceilq}: ceiling value function
+@item @code{copysignq}: copy sign of a number
+@item @code{coshq}: hyperbolic cosine function
+@item @code{cosq}: cosine function
+@item @code{erfq}: error function
+@item @code{erfcq}: complementary error function
+@item @code{exp2q}: base 2 exponential function
+@item @code{expq}: exponential function
+@item @code{expm1q}: exponential minus 1 function
+@need 800
+@item @code{fabsq}: absolute value function
+@item @code{fdimq}: positive difference function
+@item @code{finiteq}: check finiteness of value
+@item @code{floorq}: floor value function
+@item @code{fmaq}: fused multiply and add
+@item @code{fmaxq}: determine maximum of two values
+@item @code{fminq}: determine minimum of two values
+@item @code{fmodq}: remainder value function
+@item @code{frexpq}: extract mantissa and exponent
+@item @code{hypotq}: Eucledian distance function
+@item @code{ilogbq}: get exponent of the value
+@item @code{isinfq}: check for infinity
+@item @code{isnanq}: check for not a number
+@item @code{issignalingq}: check for signaling not a number
+@item @code{j0q}: Bessel function of the first kind, first order
+@item @code{j1q}: Bessel function of the first kind, second order
+@item @code{jnq}: Bessel function of the first kind, @var{n}-th order
+@item @code{ldexpq}: load exponent of the value
+@item @code{lgammaq}: logarithmic gamma function
+@item @code{llrintq}: round to nearest integer value
+@item @code{llroundq}: round to nearest integer value away from zero
+@item @code{logbq}: get exponent of the value
+@item @code{logq}: natural logarithm function
+@item @code{log10q}: base 10 logarithm function
+@item @code{log1pq}: compute natural logarithm of the value plus one
+@item @code{log2q}: base 2 logarithm function
+@need 800
+@item @code{lrintq}: round to nearest integer value
+@item @code{lroundq}: round to nearest integer value away from zero
+@item @code{modfq}: decompose the floating-point number
+@item @code{nanq}: return quiet NaN
+@item @code{nearbyintq}: round to nearest integer
+@item @code{nextafterq}: next representable floating-point number
+@item @code{powq}: power function
+@item @code{remainderq}: remainder function
+@item @code{remquoq}: remainder and part of quotient
+@item @code{rintq}: round-to-nearest integral value
+@item @code{roundq}: round-to-nearest integral value, return @code{__float128}
+@item @code{scalblnq}: compute exponent using @code{FLT_RADIX}
+@item @code{scalbnq}: compute exponent using @code{FLT_RADIX}
+@item @code{signbitq}: return sign bit
+@item @code{sincosq}: calculate sine and cosine simultaneously
+@item @code{sinhq}: hyperbolic sine function
+@item @code{sinq}: sine function
+@item @code{sqrtq}: square root function
+@item @code{tanq}: tangent function
+@item @code{tanhq}: hyperbolic tangent function
+@need 800
+@item @code{tgammaq}: true gamma function
+@item @code{truncq}: round to integer, towards zero
+@item @code{y0q}: Bessel function of the second kind, first order
+@item @code{y1q}: Bessel function of the second kind, second order
+@item @code{ynq}: Bessel function of the second kind, @var{n}-th order
+@item @code{cabsq} complex absolute value function
+@item @code{cargq}: calculate the argument
+@item @code{cimagq} imaginary part of complex number
+@item @code{crealq}: real part of complex number
+@item @code{cacoshq}: complex arc hyperbolic cosine function
+@item @code{cacosq}: complex arc cosine function
+@item @code{casinhq}: complex arc hyperbolic sine function
+@item @code{casinq}: complex arc sine function
+@item @code{catanhq}: complex arc hyperbolic tangent function
+@item @code{catanq}: complex arc tangent function
+@item @code{ccosq} complex cosine function:
+@item @code{ccoshq}: complex hyperbolic cosine function
+@item @code{cexpq}: complex exponential function
+@need 800
+@item @code{cexpiq}: computes the exponential function of ``i'' times a
+ real value
+@item @code{clogq}: complex natural logarithm
+@item @code{clog10q}: complex base 10 logarithm
+@item @code{conjq}: complex conjugate function
+@item @code{cpowq}: complex power function
+@item @code{cprojq}: project into Riemann Sphere
+@item @code{csinq}: complex sine function
+@item @code{csinhq}: complex hyperbolic sine function
+@item @code{csqrtq}: complex square root
+@item @code{ctanq}: complex tangent function
+@item @code{ctanhq}: complex hyperbolic tangent function
+@end table
+
+
+@c ---------------------------------------------------------------------
+@c I/O routines
+@c ---------------------------------------------------------------------
+
+@node I/O Library Routines
+@chapter I/O Library Routines
+
+@menu
+* @code{strtoflt128}: strtoflt128, Convert from string
+* @code{quadmath_snprintf}: quadmath_snprintf, Convert to string
+@end menu
+
+
+@node strtoflt128
+@section @code{strtoflt128} --- Convert from string
+
+The function @code{strtoflt128} converts a string into a
+@code{__float128} number.
+
+@table @asis
+@item Syntax
+@code{__float128 strtoflt128 (const char *s, char **sp)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{s} @tab input string
+@item @var{sp} @tab the address of the next character in the string
+@end multitable
+
+The argument @var{sp} contains, if not @code{NULL}, the address of the
+next character following the parts of the string, which have been read.
+
+@item Example
+@smallexample
+#include <quadmath.h>
+
+int main ()
+@{
+ __float128 r;
+
+ r = strtoflt128 ("1.2345678", NULL);
+
+ return 0;
+@}
+@end smallexample
+@end table
+
+
+@node quadmath_snprintf
+@section @code{quadmath_snprintf} --- Convert to string
+
+The function @code{quadmath_snprintf} converts a @code{__float128} floating-point
+number into a string. It is a specialized alternative to @code{snprintf}, where
+the format string is restricted to a single conversion specifier with @code{Q}
+modifier and conversion specifier @code{e}, @code{E}, @code{f}, @code{F}, @code{g},
+@code{G}, @code{a} or @code{A}, with no extra characters before or after the
+conversion specifier. The @code{%m$} or @code{*m$} style must not be used in
+the format.
+
+@table @asis
+@item Syntax
+@code{int quadmath_snprintf (char *s, size_t size, const char *format, ...)}
+
+@item @emph{Arguments}:
+@multitable @columnfractions .15 .70
+@item @var{s} @tab output string
+@item @var{size} @tab byte size of the string, including trailing NUL
+@item @var{format} @tab conversion specifier string
+@end multitable
+
+@item Note
+On some targets when supported by the C library hooks are installed
+for @code{printf} family of functions, so that @code{printf ("%Qe", 1.2Q);}
+etc.@: works too.
+
+@item Example
+@smallexample
+#include <quadmath.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+int main ()
+@{
+ __float128 r;
+ int prec = 20;
+ int width = 46;
+ char buf[128];
+
+ r = 2.0q;
+ r = sqrtq (r);
+ int n = quadmath_snprintf (buf, sizeof buf, "%+-#*.20Qe", width, r);
+ if ((size_t) n < sizeof buf)
+ printf ("%s\n", buf);
+ /* Prints: +1.41421356237309504880e+00 */
+ quadmath_snprintf (buf, sizeof buf, "%Qa", r);
+ if ((size_t) n < sizeof buf)
+ printf ("%s\n", buf);
+ /* Prints: 0x1.6a09e667f3bcc908b2fb1366ea96p+0 */
+ n = quadmath_snprintf (NULL, 0, "%+-#46.*Qe", prec, r);
+ if (n > -1)
+ @{
+ char *str = malloc (n + 1);
+ if (str)
+ @{
+ quadmath_snprintf (str, n + 1, "%+-#46.*Qe", prec, r);
+ printf ("%s\n", str);
+ /* Prints: +1.41421356237309504880e+00 */
+ @}
+ free (str);
+ @}
+ return 0;
+@}
+@end smallexample
+
+@end table
+
+
+@c ---------------------------------------------------------------------
+@c GNU Free Documentation License
+@c ---------------------------------------------------------------------
+
+@include fdl.texi
+
+@c ---------------------------------------------------------------------
+@c Reporting Bugs
+@c ---------------------------------------------------------------------
+
+@c For BUGURL
+@include libquadmath-vers.texi
+
+@node Reporting Bugs
+@chapter Reporting Bugs
+
+Bugs in the GCC Quad-Precision Math Library implementation should be
+reported via @value{BUGURL}.
+
+
+@c ---------------------------------------------------------------------
+@c Index
+@c ---------------------------------------------------------------------
+
+@c @node Index
+@c @unnumbered Index
+@c
+@c @printindex cp
+
+@bye
projects / platform / upstream / gcc.git / commitdiff